New pesticidal compositions which comprise

The present invention relates to novel compositions for controlling harmful insects and representatives of the order Acarina, a process for the preparation of these compositions, and their use in agriculture, forestry and horticulture.
When controlling phytophagous animal pests with the aid of pesticides, one attempts to minimize contamination of the plants to be protected and their environment, including the soil in which they grow. Moreover, beneficial animals and warm-blooded species are to be adversely affected by the pesticidally active compounds as little as possible. However, in contrast, the pests to be controlled are to be exposed to the pesticidally active compounds as much as possible so that the pests can take up sufficient amounts of the active compounds by contact action, as stomach poisons or via the gas phase.
When controlling insects, the abovementioned conditions can be met for example by combining signal substances such as pheromones, kairomones or attractants, which have an attractant action on insects, with insecticidally active compounds and applying the resulting mixtures to the stand to be protected not in such a way that the entire area is covered, but only locally to sharply defined individual sites. Since the signal substances are released at the treated sites, the pests migrate to these sites, become contaminated with the pesticidally active compounds and are destroyed. This type of insect control is termed the xe2x80x9cattract-and-killxe2x80x9d method.
In contrast, it is also possible to control insects with the aid of the so-called xe2x80x9cconfusionxe2x80x9d strategy. When using this method, the amount of pheromones introduced into the plant stand to be protected is so large that the male insects are no longer capable of locating the female insects. This prevents the pests from breeding.
For the compositions used in the two control strategies to develop a sufficiently long-term action, the formulations in question must comprise the attractants in such a form that, on the one hand, they can be released in a controlled manner but, on the other hand, are protected against environmental factors such as light, oxygen and the weather.
A large number of preparations based on the above-described principles of controlling animal pests have already been disclosed. One attempts to protect the sensitive active compounds against undesirable degradation by means of a variety of measures.
For example, EP-A 0 055 475 discloses that male insects of the species Cossus cossus can be controlled with the aid of (Z)-5-dodecen-1-yl acetate, if appropriate in the form of a mixture with (Z)-3-decen-1-yl acetate, (Z)-3-dodecen-1-yl acetate and/or (E)-5-dodecen-1-yl acetate. The attractant, or the mixtures of the active components, are applied in solvents which have a low vapour pressure, such as oils or fats, or else, if appropriate, as a mixture with antioxidants and UV stabilizers in the form of an adsorbate on inert solids.
Furthermore, GB-PA 2 064 323 describes insecticides based on pheromones in which the signal :substances and UV stabilizers and additional additives such as antioxidants are fixed onto a combination of absorbing and adsorbing solids. However, the disadvantage of these preparations is their relatively poor resistance to weathering despite the stabilizing additives which they comprise and the fact that the active compounds are therefore decomposed or leached out after a relatively short time.
Furthermore, it has already been disclosed to employ combinations of attractants and insecticides for pest control in microencapsulated form or bound in water-soluble polymers (cf. JP-A 59-7101 and xe2x80x9cAdvances in Pesticide Formulation Technologyxe2x80x9d 1984, Chapter 11, pages 151-162). In the preparation of these microcapsules, a procedure is followed in which the active compounds are dissolved in an oil phase, the resulting mixture is emulsified in water and the emulsion is subsequently encapsulated. Controlled release of the attractant and, in addition, its protection against environmental factors are thereby achieved. The disadvantage of this process is, however, the complicated microencapsulation process. Moreover, the attractants are not always sufficiently stabilized against environmental factors, despite the encapsulation, because the thin capsule wall does not provide sufficient protection against photochemical degradation.
According to GB-A 2 141 932, preparations which comprise pheromones, if appropriate as a mixture with UV absorbers and other additives, in liquid or semi-liquid, liquid, water-resistant polymers which protect against UV radiation, can be used as pesticides. While the active components remain stable over a sufficiently long period in these formulations, the amount of active compound which diffuses out does not always guarantee a sufficiently high degree of efficacy.
EP-A 0 376 888 discloses that formulations which are composed mostly of one or more permanently liquid UV absorbers, besides insecticides and attractants and customary additives, and which are present in viscous form which remains permanently uncured are also suitable for controlling pests. The very high content of UV-absorbing substances protects the attractants in these formulations against photodegradation over a prolonged period. However, the use under realistic conditions causes problems since the UV absorbers are, as a rule, highly stable and are not degraded, or are degraded only very slowly. If the formulation is applied regularly over several years, it is therefore accumulated in the area under cultivation which has been treated.
Furthermore, WO 87-04 591 discloses compositions for controlling spider mites. The formulations are composed of a substrate which comprises attractants such as Nerodiol and Farnesol, furthermore insecticidally active compounds and also oils which are added in the form of emulsions. The attractants are released from these substrates in a controlled manner. However, the disadvantage is that no long-term action is achieved when using these compositions. Rather, achieving satisfactory control requires regular subsequent treatments.
J. Entomol. Sci. Vol. 25, No. 4, 581-586, (1990) describes pheromonexe2x80x94and insecticidexe2x80x94comprising preparations for controlling the cotton boll weevil (Anthonomus grandis). As an essential component, the compositions comprise cotton seed oil, which promotes feeding of the pest and therefore has a beneficial effect on the uptake of active compound. However, the fact that this vegetable oil does not contribute to stabilizing the formulation against environmental effects is unfavourable.
Finally, it has been disclosed that oils in attractant-comprising preparations can act as solvents for active compounds (cf. WO 87-04 591, EP-A 0 055 475 and xe2x80x9cAdvances in Pesticide Formulation Technology 1984, Chapter 11, pages 151 to 162). The active compounds, however, are not stabilized against undesirable degradation.
There have now been found new pesticidal compositions which comprise
at least one signal substance,
at least one UV absorber which is only sparingly miscible with water,
at least one unsaturated oil which is only sparingly miscible with water and
if appropriate, pesticidally active compounds and/or additives.
Furthermore, it has been found that compositions according to the invention can be prepared by
a) dispersing at least one signal substance, at least one UV absorber which is only sparingly miscible with water and, if appropriate, pesticidally active compounds and/or additives in at least one unsaturated oil which is only sparingly miscible with water and
b) if appropriate, emulsifying this premix in water while adding surface-active substances.
Finally, it has been found that the compositions according to the invention are highly suitable for controlling harmful insects and undesirable representatives from the order Acarina in agriculture, forestry and horticulture.
It must be considered as extremely surprising that the compositions according to the invention, which comprise a mixture of UV absorber and unsaturated oil, protect the signal substances which are present and the pesticidally active compounds which may also be present, better against environmental degradation than prior-art compositions which comprise either only the unsaturated vegetable oil or merely the UV absorber.
The compositions according to the invention are distinguished by a series of advantages. For example, they allow specific and environmentally friendly pest control over a prolonged period. Furthermore, the attractants in these preparations are extremely stable even under unfavourable weather conditions.
The signal substances which may be present in the compositions according to the invention are all customary substances which have an attractant action on the pests to be controlled and which alter the behaviour of the latter. Signal substances which are preferably suitable are pheromones, kairomones and attractants. Examples of such substances which may be mentioned are the following:
Z-5-Decenyl acetate, dodecanyl acetate, Z-7-dodecenyl acetate, E-7-dodecenyl acetate, Z-8-dodecenyl acetate, E-8-dodecenyl acetate, Z-9-dodecenyl acetate, E-9-dodecenyl acetate, E-10-dodecenyl acetate, 11-dodecenyl acetate, Z-9,11-dodecadienyl acetate, E-9,11-dodecadienyl acetate, Z-11-tridecenyl acetate, E-11-tridecenyl acetate, tetradecenyl acetate, E-7-tetradecenyl acetate, Z-8-tetradecenyl acetate, E-8-tetradacenyl acetate, Z-9-tetradecenyl acetate, E-9-tetradecenyl acetate, Z-10-tetradecenyl acetate, E-10-tetradecenyl acetate, Z-11-tetradecenyl acetate, E-11-tetradecenyl acetate, Z-12-pentadecenyl acetate, E-12-pentadecenyl acetate, hexadecanyl acetate, Z-7-hexadecenyl acetate, Z-11-hexadecenyl acetate, E-11-hexadecenyl acetate, octadecanyl acetate, E,Z-7,9-dodecadienyl acetate, Z,E-7,9-dodecadienyl acetate, E,E-7,9-dodecadienyl acetate, Z,Z-7,9-dodecadienyl acetate, E,E-8,10-dodecadienyl acetate, E,Z-9,12-dodecadienyl acetate, E,Z-4,7-tri-decadienyl acetate, 4-methoxy-cinnamaldehyde, xcex2-ionone, estragol, eugenol, indole, 8-methyl-2-decyl propanoate, E,E-9,11-tetradecadienyl acetate, Z,Z-9,12-tetradecadienyl acetate, Z,Z-7,11-hexadecadienyl acetate, E,Z-7,11-hexadecadienyl acetate, Z,E-7,11-hexadecadienyl acetate, E,E-7,11-hexadecadienyl acetate, Z,E-3,13-octadecadienyl acetate, E,Z-3,13-octadecadienyl acetate, E,E-3,13-octadecadienyl acetate, ethanol, hexanol, heptanol, octanol, decanol, Z-6-nonenol, E-6-nonenol, dodecanol, 11-dodecenol, Z-7-dodecenol, E-7-dodecenol, Z-8-dodecenol, E-8-dodecenol, E-9-dodecenol, Z-9-dodecenol, E-9,11-dodecadienol, Z-9,11-dodecadienol, Z,E-5,7-dodecadienol, E,E-5,7-dodecadienol, E,E-8,10-dodecadienol, E,Z-8,10-dodecadienol, Z,Z-8,10-dodecadienol, Z,E-8,10-dodecadienol, E,Z-7,9-dodecadienol, Z,Z-7,9-dodecadienol, E-5-tetradecenol, Z-8-tetradecenol, Z-9-tetradecenol, E-9-tetradecenol, Z-10-tetradecenol, Z-11-tetradecenol, E-11-tetradecenol, Z-11-hexadecenol, Z,E-9,11-tetradecadienol, Z,E-9,12-tetradecadienol, Z,Z-9,12-tetradecadienol, Z,Z-10,12-tetradecadienol, Z,Z-7,11-hexadecadienol, Z,E-7,11-hexadecadienol, (E)-14-methyl-8-hexadecen-1-ol, (Z)-14-methyl-8-hexadecen-1-ol, E,E-10,12-hexadecadienol, E,Z-10,12-hexadecadienol, dodecanal, Z-9-dodecenal, tetradecanal, Z-7-tetradecenal, Z-9-tetradecenal, Z-11-tetradecenal, E-11-tetradecenal, E-11,13-tetradecadienal, E,E-8,10-tetradecadienal, Z,E-9,11-tetradecadienal, Z,E-9,12-tetradecadienal, hexadecanal, Z-8-hexadecenal, Z-9-hexadecenal, Z-10-hexadecenal, E-10-hexadecenal, Z-11-hexadecenal, E-11-hexadecenal, Z-12-hexadecenal, Z-13-hexadecenal, (Z)-14-methyl-8-hexadecenal, (E)-14-methyl-8-hexadecenal, Z,Z-7,11-hexadecadienal, Z,E-7,11-hexadecadienal, Z,E-9,11-hexadecadienal, E,E-10,12-hexadecadienal, E,Z-10,12-hexadecadienal, Z,E-10,12-hexadecadienal, Z,Z-10,12-hexadecadienal, Z,Z-11,13-hexadecadienal, octadecanal, Z-11-octadecenal, E-13-octadecenal, Z-13-octadecenal, Z-5-decenyl-3-methyl butanoate disparlure: (+) cis-7,8-epoxy-2-methyloctadecane, seudenol: 3-methyl-2-cyclohexen-1-ol, sulcatol: 6-methyl-5-hepten-2-ol, ipsenol: 2-methyl-6-methylene-7-octen-4-ol, ipsdienol: 2-methyl-6-methylene-2,7-octadien-4-ol, grandlure I: cis-2-isopropenyl-1-methylcyclobutane-ethanol, grandlure II: Z-3,3-dimethyl-1-cyclohexane-ethanol, grandlure III: Z-3,3-dimethyl-1-cyclohexane-acetalde-hyde, grandlure IV: E-3,3-dimethyl-1-cyclohexane-acetaldehyde, cis-2-ver-benol: cis-4,6,6-trimethylbicyclo[3,1,1]hept-3-en-2-ol cucurbitacin, 2-methyl-3-buten-2-ol, 4-methyl-3-heptanol, cucurbitacin, 2-methyl-3-buten-2-ol, 4-methyl-3-heptanol, xcex1-pinene: 2,6,6-trimethylbicyclo[3,1,1]hepten-2-ene, xcex1-caryophyllene: 4,11,11-trimethyl-8-methylene-bicyclo[7,2,0]undecane, Z-9-tricosene, (xcex1-multistriatin, 2-(2-endo,4-endo)-5-ethyl-2,4-dimethyl-6,8-dioxabicyclo[3,2,1]octane, methyleugenol: 1,2-dimethoxy-4-(2-propenyl)phenol, lineatin: 3,3,7-trimethyl-2,9-dioxatricyclo[3,3,1,0]nonane, chalcogran: 2-ethyl-1,6-dioxaspiro[4,4]nonane, frontalin: 1,5-dimethyl-6,8-dioxabicyclo[3,2,1]octane, endo-brevicomin: endo-7-ethyl-5-methyl-6,8-dioxabicyclo[3,2,1]octane, exo-brevicomin: exo-7-ethyl-5-methyl-6,8-dioxabicyclo[3,2,1]octane, (Z)-5-(1-decenyl)dihydro-2-(3H)-furanone, farnesol: 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol, nerolidol 3,7-11-trimethyl-1,6,10-dodecatrien-3-ol, 3-methyl,6-(1-methylethenyl)-9-decen-1-ol acetate, (Z)-3-methyl-6-(1-methylethenyl)-3,9-decadien-1-ol acetate, (E)-3,9-methyl-6-(1-methyl-ethenyl)-5,8-decadien-1-ol acetate, 3-methylene-7-methyl-octen-1-ol propionate, (Z)-3,7-dimethyl-2,7-octadien-1-ol propionate, (Z)-3,9-dimethyl-6-(1-methyl-ethenyl)-3,9-decadlien-1-ol propionate.
The compositions according to the invention comprise at least one UV absorber which is only sparingly miscible with water. These are to be understood as meaning substances which are capable of absorbing UV light, preferably UV radiation from surlight in a wavelength range of from 270 to 400 nm. Suitable substances are preferably liquid UV absorbers, such as
2-(2-hydroxyphenyl)-benzotriazoles of the formula
xe2x80x83in which
a R1 represents hydrogen or chlorine,
R2 represents hydrogen, alkyl, phenylalkyl or phenyl and
R3 represents alkyl, phenylalkyl, phenyl or xe2x80x94(CH2)2xe2x80x94COO-alkyl,
2-hydroxy-4-alkoxy-benzophenones of the formula
xe2x80x83in which
R4 represents hydrogen, alkyl or alkoxy and
R5 represents alkyl, preferably isooctyl or dodecyl,
oxalanilides of the formula
xe2x80x83in which
R6 represents alkyl,
cinnamic acid derivatives of the formula
xe2x80x83in which
R7 represents alkyl, preferably n-butyl, or
xe2x80x83in which
xe2x80x83R8 and R9 represent alkyl, or
xe2x80x83in which
R10 represents alkyl, preferably butyl or the radical
and
triazine derivatives of the formula
xe2x80x83in which
R11 represents hydrogen or hydroxyl,
R12 represents alkyl having 1 to 18 carbon atoms,
R13 represents alkyl having 1 to 18 carbon atoms or alkoxy having 1 to 18 carbon atoms,
R14 represents alkyl having 1 to 18 carbon atoms and
m and n represent the numbers 0, 1 or 2.
Examples of 2-(2-hydroxyphenyl)-benzotriazoles of the formula (I) which may be mentioned are the substances listed in Table 1 below:
The compositions according to the invention comprise at least one unsaturated oil which is sparingly miscible with water. These are to be understood as meaning all straight-chain or branched oily liquids of synthetic or natural origin which optionally contain functional groups and which have one or more unsaturated bonds between two carbon atoms and whose solubility in water is  less than 1 g/l.
Unsaturated oils are preferably of vegetable or animal origin and are distinguished by a high content of unsaturated fatty acids. Examples of such oils are linseed oil, palm oil, groundnut oil, cotton oil, soya oil, sunflower oil, colza oil, castor oil and fish oil. Castor oil is particularly preferred. However, the fatty acids contained in the abovementioned oils, or compounds which are obtained by chemically modifying the fatty acids such as, for example, fatty acid ethoxylates, can also be used to prepare the compositions according to the invention. Examples of such fatty acids which can be employed individually or in the form of a mixture are myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinoleic acid, linoleic acid, linolenic acid, arachidonic acid and clupanodonic acid.
The compositions according to the invention can comprise one or more pesticidally active compounds. These are to be understood as meaning all customary substances which are suitable for controlling harmful insects and undesirable representatives of the order Acarina. The following are preferably suitable: carbamates, organophosphorus compounds, nitrophenols and their derivatives, nitromethylenes, nicotinoids, formamidines, ureas, phenylbenzoylureas, pyrethroids, chlorinated hydrocarbons and Bacillus thuringiensis preparations. Examples which may be mentioned are the following substances:
Abamectin, AC 303 630, acephate, acrinathrin, alanycarb, aldicarb, alphamethrin, amitraz, avermectin, AZ 60541, azadirachtin, azinphos A, azinphos M, azocyclotin,
Bacillus thuringiensis, bendiocarb, benfuracarb, bensultap, betacyfluthrin, bifenthrin, BPMC, bromfenprox, bromophos A, bufencarb, buprofezin, butocarboxim, butylpyridaben,
cadusafos, carbaryl, carbofuran, carbophenothion, carbosulfan, cartap, CGA 157 419, CGA 184699, chloethocarb, chlorethoxyfos, chlorfenvinphos, chlorfluazuron, chlormephos, chlorpyrifos, chlorpyrifos M, cis-resmethrin, clocythrin, clofentezine, cyanophos, cycloprothrin, cyfluthrin, cyhalothrin, cyhexatin, cypermethrin, cyromazin,
deltamethrin, demeton M, demeton S, demeton-S-methyl, diafenthiuron, diazinon, dichlofenthion, dichlorvos, dicliphos, dicrotophos, diethion, diflubenzuron, dimethoate, dimethylvinphos; dioxathion, disulfoton,
edifenphos, emainectin, esfenvalerate, ethiofencarb, ethion, ethofenprox, ethoprophos, etrimphos,
fenamiphos, fenazaquin, fenbutatin oxide, fenitrothion, fenobucarb, fenothiocarb, fenoxycarb, fenpropathrin, fenpyrad, fenpyroximate, fenthion, fenvalerate, fipronil, fluazinam, flucycl.oxuron, flucythrinate, flufenoxuron, flufenprox, fluvalinate, fonophos, formothion, fosthiazate, fubfenprox, furathiocarb,
HCH, heptenophos, hexaflumuron, hexythiazox, imidacloprid, iprobenfos, isazophos, isofenphos, isoprocarb, isoxathion, ivermectin, lambda-cyhalothrin., lufenuron,
malathion, mecarbam, mevinphos, mesulfenphos, metaldehyde, methacrifos, methamidophos, rnethidathion, methiocarb, methomyl, metolcarb, milbemectin, monocrotophos, mnxidectin,
naled, NC 184, NI 25, nitenpyram
omethoate, oxamyl, oxydemethon M, oxydeprofos,
parathion A, parathion M, permethrin, phenthoate, phorate, phosalone, phosmet, phosphamidon, phoxim, pirimicarb, pirimiphos M, pirimiphos A, profenofos, promecarb, propaphos, propoxur, prothiofos, prothoate, pymetrozin, pyrachlophos, pyridaphenthion, pyresmethrin, pyrethrum, pyridaben, pyrimidifen, pyriproxifen, quinalphos,
RH 5992,
salithion, sebufos, silafluofen, sulfotep, sulprofos,
tebufenozid, tebu:Fenpyrad, tebupirimiphos, teflubenzuron, tefluthrin, temephos, terbam, terbufos, tetrachlorvinphos, thiafenox, thiodicarb, thiofanox, thiomethon, thionazin, thuringiensin, tralomethrin, triarathene, triazophos, triazuron, trichlorfon, triflumuron, trimelthacarb,
vamidothion, XMC, xylylcarb, zetamethrin.
Suitable additives which may be present in the compositions according to the invention are all those substances which can conventionally be employed as additives in plant treatment products. They include polymers, surface-active substances, colourants, antioxidants, thickeners, fillers, antifreeze agents and solvents. Moreover, the compositions according to the invention can also contain water.
Suitable polymers which can be present in the compositions according to the invention are all customary polymers or copolymers which are soluble or dispersible in water. Preferably suitable are polymers which are accessible by synthesis by means of anionic or non-ionic polymerization of suitable monomers, for example by emulsion polymerization or bead polymerization with the aid of free-radical formers or other initiator systems. Other polymers which can preferably be employed are those based on natural-rubber latices.
Examples of particularly prefered polymers which may be mentioned are the following substances:
Polyvinyl acetate (Mowilith(copyright)), polyvinyl alcohols with different degrees of hydrolysis (Mowiol(copyright)), polyvinylpyrrolidones (Lewiskod K(copyright), Agrimer(copyright)), polyacrylates (Carbopol(copyright)), acrylate-, polyol- or polyester-based paint system binders which are soluble or dispersible in water (Desmophen(copyright), Roskydal(copyright), Bayhydrol(copyright) polyraers which may be mentioned are the following substances:), moreover copolymers of two or more monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, vinylpyrrolidone, ethylenically unsaturated monomers such as ethylene, butadiene, isoprene, chloroprene, styrene, divinylbenzene, ot-methylstyrene or p-methylstyrene, further vinyl halides such as vinyl chloride and vinylidene chloride, additionally vinyl esters such as vinyl acetate, vinyl propionate or vinyl stearate, moreover vinyl methyl ketone or esters of acrylic acid or methacrylic acid with monohydric alcohols or polyols such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethylene methacrylate, lauryl acrylate, lauryl methacrylate, decyl acrylate, N,N-dimethylamino-ethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate or glycidyl methacrylate, furthermore diethyl esters or monoesters of unsaturated dicarboxylic acids, furthermore (meth)acrylamido-N-methylol methyl ether, amides or nitriles such as acrylamide, methacrylamide, N-methylol(meth)acrylamide, acrylonitrile, methacrylonitrile, and also N-substituted maleiraides and ethers such as vinyl butyl ether, vinyl isobutyl ether or vinyl phenyl ether.
Suitable surface-active substances which can be present in the compositions according to the invention are all those substances which have surface-active properties and which are conventionally used in plant treatment products. Preferably suitable are non-ionic and anionic emulsifiers such as polyoxyethylene fatty acid esters, polyoxyethylene fatty alcohol ethers, alkylaryl polyglycol ethers, fatty amine ethoxylates, alkylsulphonates, alkyl sulphates, alkylarylsulphonates, aryl sulphates and silicone surfactants. Examples of such surface-active substances are listed in McCutcheon""s xe2x80x9cEmulsifiers and Detergentsxe2x80x9d 1982 North America Edit, MC Publishing Co., 175 Rock Road, Glen Rock, N.J. 07 452, USA.
Suitable colourants are soluble or sparingly soluble colour pigments such as, for example, titanium dioxide, colour black or zinc oxide.
Suitable antioxidants are all substances which can usually be employed for this purpose in plant treatment products. Sterically hindered phenols and alkyl-substituted hydroxyanisoles and hydroxytoluenes are preferred.
Suitable thickeners are all substances which can usually be employed for this purpose in plant treatment products. The following are preferably suitable: organic polymers such as partially or fully neutralized polyacrylic acids (Carbopol(copyright)), polyvinylpyrrolidone homo- or copolymers (Luviskol K(copyright) or Luviskol VA(copyright)), polyethylene glycols (Polyox(copyright)), ethylene oxide/propylene oxide copolymers (Pluronic(copyright)), polyvinyl alcohols and non-ionically or ionically modified celluloses (Tylose(copyright)), thixotropic xanthan-based thickeners (Kelzan(copyright)), and moreover inorganic disperse thickeners such as precipitated or pyrogenic silicas, kaolins, bentonites, aluminium/silicon mixed oxides, and silicates.
Suitable antifreeze agents are all substances which can usually be employed for this purpose in plant treatment products. Urea, glycerol or propylene glycol are preferably suitable.
Suitable fillers are, again, all inert materials which can usually be employed for this purpose in plant treatment products. The following are preferably suitable: ground minerals, calcium carbonate, ground quartz and aluminium/silicon mixed oxides or mixed hydroxides.
Suitable solvents are all inert, organic solvents which can usually be employed for this purpose in plant treatment products. Preferred substances are glycols such as propylene glycol and polyethylene glycols having various molecular weights; ketones such as methyl isobutyl ketone, methyl isopropyl ketone and cyclohexanone; amides such as dimethyl- or diethyl formamide; N,N-dialkylated carboxamides (for example Hallcomid(copyright)); alkyllactams such as substituted pyrrolidones (for example N-methylpyrrolidone and Surfadone(copyright)) and caprolactams (for example Azone(copyright)); hydrocarbons, n-paraffins and isoparaffins having various boiling ranges as can be obtained, for example, under the trade names Exxol(copyright), Norpar(copyright) and Isopar(copyright); aromatic hydrocarbons such as xylene and aromatic distillation fractions (for example Solvesso(copyright)); esters such as propylene glycol monomethyl ether acetate, dibutyl adipate and di-n-butyl phthalate; ethers such as propylene glycol methyl ether or propylene glycol butyl ether; alcohols such as ethanol, n- and i-propanol, n- and i-butanol, n- and i-amyl alcohol, benzyl alcohol, tetrahydrofurfuryl alcohol, 1-methoxy-2-propanol, and higher alcohols, furthermore liquid carriers which have been obtained by modifying vegetable oils, such as, for example, rapeseed oil methyl ester and 2-ethylhexyl laurate; and furthermore dimethyl sulphoxide, dioxane and tetrahydrofuran. The solvents can be employed in the form of individual components or in the form of mixtures. Particularly preferred are those which are miscible with the UV stabilizer or the unsaturated oil and which are not unduly volatile.
The concentrations of individual components in the compositions according to the invention can be varied within a wide range. For example, after deducting the water which is optionally present in the compositions according to the invention, the concentrations
of signal substances are generally between 0.01 and 1% by weight, preferably between 0.05 and 0.3% by weight,
of UV absorbers are generally between 1 and 40% by weight, preferably between 5 and 20% by weight,
of unsaturated oils are between 10 and 90% by weight, preferably between 40 and 85% by weight,
of pesticidally active compounds are generally between 0 and 10% by weight, preferably between 0 and 5% by weight,
of additives are between 0 and 70% by weight, preferably between 0 and 60% by weight.
Besides, the compositions according to the invention can also comprise water. The water content prior to drying varies within a wide range. It is generally between 0 and 80% by weight.
When preparing the compositions according to the invention, a procedure is generally followed in which a premix is first prepared by dissolving or dispersing at least one signal substance, at least one UV absorber and, if appropriate, one or more pesticidally active compounds in at least one unsaturated oil with stirring at temperatures between 20xc2x0 C. and 70xc2x0 C., preferably at room temperature, and, if appropriate, additives are added. However, a different procedure may also be followed when preparing compositions according to the invention. For example, the premix can be dispersed in a solution of at least one surface-active substance in water with stirring at temperatures between 20xc2x0 C. and 70xc2x0 C., preferably at room temperature. The dispersing process can be carried out in such a way that an oil-in-water emulsion is formed in which the average particle size is generally between 0.5 and 50 xcexcm, but preferably between 1 and 20 xcexcm. The resulting emulsion can subsequently be treated with a solution or dispersion of at least one polymer in water and, if appropriate, additives with stirring at temperatures between 20xc2x0 and 70xc2x0 C., but preferably at room temperature.
However, a different procedure may be followed when preparing the compositions according to the invention. In principle, it is possible to mix the components in any order. All stirring and mixing apparatus which is customary for this purpose is suitable for preparing the compositions according to the invention.
The compositions according to the invention are obtained from the preparation in a fluid or viscous state. Depending on the preparation process, they remain viscous after application or else form a non-flowable coating.
The compositions according to the invention are highly suitable for controlling harmful insects and undesirable representatives of the order Acarina which are found in agriculture, in forests and in horticulture, including viticulture. For example, they can be employed against the pests mentioned below.
From the order of the Isopoda, for example, Oniscus asellus, Armadillidium vulgare and Porcellio scaber.
From the order of the Diplopoda, for example, Blaniulus guttulatus.
From the order of the Chilopoda, for example, Geophilus carpophagus and Scutigera spec.
From the order of the Symphyla, for example, Scutigerella immaculata.
From the order of the Thysanura, for example, Lepisma saccharina.
From the order of the Collembola, for example, Onychiurus armatus.
From the order of the Orthoptera, for example, Blatta orientalis, Periplaneta americana, Leucophaea maderae, Blattella germanica, Acheta domesticus, Gryllotalpa spp., Locusta migratoria migratorioides, Melanoplus differentialis and Schistocerca gregaria.
From the order of the Dermaptera, for example, Forficula auricularia.
From the order of the Isoptera, for example, Reticulitermes spp.
From the order of the Anoplura, for example, Phylloxera vastatrix, Pemphigus spp., Pediculus humanus corporis, Haematopinus spp. and Linognathus spp.
From the order cf the Mallophaga, for example, Trichodectes spp. and Damalinea spp.
From the order of the Thysanoptera, for example, Hercinothrips femoralis and Thrips tabaci.
From the order of the Heteroptera, for example, Eurygaster spp., Dysdercus intermedius, Piesma quadrata, Cimex lectularius, Rhodnius prolixus and Triatoma spp.
From the order of the Homoptera, for example, Aleurodes brassicae, Bemisia tabaci, Trialeurodes vaporariorum, Aphis gossypii, Brevicoryne brassicae, Cryptomyzus ribis, Aphis fabae, Doralis pomi, Eriosoma lanigerum, Hyalopterus arundinis, Macrosiphum avenae, Myzus spp., Phorodon humuli, Rhopalosiphum padi, Empoasca spp., Euscelis bilobatus, Nephotettix cincticeps, Lecanium corni, Saissetia oleae, Laodelphax striatellus, Nilaparvata lugens, Aonidiella aurantii, Aspidiotus hederae, Pseudococcus spp. and Psylla spp.
From the order of the Lepidoptera, for example, Pectinophora gossypiella, Bupalus piniarius, Cheimatobia brumata, Lithocolletis blancardella, Hyponomeuta padella, Plutella maculipennis, Malacosoma neustria, Euproctis chrysorrhoea, Lymantria spp., Bucculatrix thurberiella, Phyllocnistis citrella, Agrotis spp., Euxoa spp., Feltia spp., Earias insulana, Heliothis spp., Spodoptera exigua, Mamestra brassicae, Panolis flammea, Prodenia litura, Spodoptera spp., Trichoplusia ni, Carpocapsa pomonella, Pieris spp., Chilo spp., Pyrausta nubilalis, Ephestia kuehniella, Galleria mellonella, Tineola bisselliella, Tinea pellionella, Hofmannophila pseudospretella, Cacoecia podana, Capua reticulana, Choristoneura fumiferana, Clysia ambiguella, Homona magnanima and Tortrix viridana.
From the order of the Coleoptera, for example, Anobium punctatum, Rhizopertha dominica, Acanthoscelides obtectus, Bruchidius obtectus, Hylotrupes bajulus, Agelastica alni, Leptinotarsa decemlineata, Phaedon cochleariae, Diabrotica spp., Psylliodes chrysocephala, Epilachna varivestis, Atomaria spp., Oryzaephilus surinamensis, Anthonomus spp., Sitophilus spp., Otiorrhynchus sulcatus, Cosmopolites sordidus, Ceuthorrhynchus assimilis, Hypera postica, Dermestes spp., Trogoderma spp., Anthrenus spp., Attagenus spp., Lyctus spp., Meligethes aeneus, Ptinus spp., Niptus hololeucus, Gibbium psylloides, Tribolium spp., Tenebrio molitor, Agriotes spp., Conoderus spp., Melolontha melolontha, Amphimallon solstitialis and Costelytra zealandica.
From the order of the Hymenoptera, for example, Diprion spp., Hoplocampa spp., Lasius spp., Monomorium pharaonis and Vespa spp.
From the order of the Diptera, for example, Aedes spp., Anopheles spp., Culex spp., Drosophila melanogaster, Musca spp., Fannia spp., Calliphora erythrocephala, Lucilia spp., Chrysomyia spp., Cuterebra spp., Gastrophilus spp., Hyppobosca spp., Stomoxys spp., Oestrus spp., Hypoderma spp., Tabanus spp., Tannia spp., Bibio hortulanus, Oscinella frit, Phorbia spp., Pegomyia hyoscyami, Ceratitis capitata, Dacus oleae and Tipula paludosa.
From the order of the Siphonaptera, for example, Xenopsylla cheopis and Ceratophyllus spp.
From the order of the Arachnida, for example, Scorpio maurus and Latrodectus mactans.
From the order of the Acarina, for example, Acarus siro, Argas spp., Ornithodoros spp., Dermanyssus gallinae, Eriophyes ribis, Phyllocoptruta oleivora, Boophilus spp., Rhipicephalus spp., Amblyomma spp., Hyalomma spp., Ixodes spp., Psoroptes spp., Chorioptes spp., Sarcoptes spp., Tarsonemus spp., Bryobia praetiosa, Panonivchus spp. and Tetranychus spp.
Using conventional devices as they are known to those skilled in the art the compositions according to the invention can be applied to, and distributed on, the areas under cultivation or plants to be treated in the form of droplets, the drop-size range or thin limited layers. Particularly suitable for the treatment of orchard crops or grape vines is a process in which a defined amount of the formulations according to the invention is applied to the stems of the plants with the aid of dosing dispensers, pipettes or syringes, it being possible for the application device also to be provided with a spreading device or a broad-jet nozzle so as to apply the compositions broadly over a relatively large area. It is also possible to spread the formulations according to the invention on a solid support, where they are allowed to dry.
The amounts in which the compositions according to the invention are applied can vary within a substantial range. They are in general in the order of magnitude which is conventionally used for xe2x80x9cattract-and-killxe2x80x9d formulations.

Abstract: at least one signal substance,

Abstract: at least one unsaturated oil which is only sparingly miscible with water and,

Abstract: if desired, pesticidally active compounds and/or additives,

Abstract: a process for the preparation of the new compositions, and their use for controlling insects and undesirable representatives of the order Acarina.


A light-transmitting building component, as wall roof or ceiling component etc. is formed with a technical membrane, in the form of a textile tissue on the outward-facing side and, furthermore, by a sound-insulation layer arranged at a distance to the outer layer of the technical membrane, and by and infrared-impeding, light-transmitting layer on the inward-facing side. In this manner, a building component is created which features low surface weight and still meets stringent requirements not only in terms of resistance to climatic influences but also with regard to heat and sound insulation.

The present invention involves a light-transmitting, specifically a translucent building component, for use as a wall, roof or ceiling component, etc., featuring a technical membrane.
Technical membranes are textile surface structures which consist, for example, of systems of threads, warp threads and weft yarns, crossing at right angles, but which can also be made up of foils. Such technical membranes used as building materials serve mainly for primary load reduction for wide-span roof support structures. For such buildings, technical membranes are particularly suitable, due to their low surface weight in conjunction with high tensile strength. Currently, their use is limited to serving as protection against external influences, such as humidity, wind, snow and radiation. If special coatings are planned, these soft bending materials feature behavior which is, for example, anti-adhesive to dirt and highly resistant to decomposition. If there are plans to use this material not only as a bearing element but also as a room-closing component, this will involve requirements in terms of heat and sound insulation, in addition to mechanical properties. However, technical membranes generally have poor heat insulation properties, which raises problems of warming and cooling, together with the corresponding energy cost, as well as heat accumulation and accumulation of condensed water as a result of temperature fluctuations. Due to the influence of manifold internal and external noise sources on the structure or the component, rooms can generally only be used if this noise energy is absorbed by room-closing components of great mass. As a result of their low surface weight, the above-mentioned technical membranes by definition feature poor sound-insulating properties.
Construction designs of room-closing components using technical membranes usually try to solve these problems by using insulating materials in connection with arranging the membrane sometimes in 3 to 5 layers. As a result of the low mass of such a construction, satisfactory results can only be achieved by using very thick sound insulation layers, if at all. It is another disadvantage of such a design that it will admit only very little light transmission or none at all, therefore making the introduction of artificial light necessary, with all its well-known disadvantages in terms of energy cost and loss of comfort.
It is the purpose of the present invention to provide a light-transmitting, specifically a translucent building component, such as for wall, roof or ceiling components, etc of the type mentioned at the beginning, featuring low surface weight while still meeting stringent requirements not only in terms of resistance to climatic influences but also in terms of heat and sound insulation properties.
To solve this task, a light-transmitting, specifically a translucent building component, serving as a wall, roof or ceiling component, etc. of the type mentioned earlier features the an infrared-impeding, light and sound transmitting layer on the side facing inward.
The steps according to the present invention will achieve such a light-transmitting building component, which is structured in three layers and combines all the essential functions for such a light-transmitting component. The technical membrane on the outward-facing side has the primary purpose of load reduction as well as serving as protection against climatic effects, radiation and humidity. Furthermore, this technical membrane also ensures a high degree of light-transmission. The sound insulation layer acts effectively against both external and internal sources of noise. The inward-facing room-closing layer with infrared-inhibiting effect serves to suppress most of the exchange of long-wave radiation between the room and this layer. Since this layer renders the transmission of infrared rays negligible, the heat radiation hitting this layer from the room is reflected back to the room. In other words, due to the reflection of infrared rays to this inner layer, the thermal comfort in the room is significantly improved and the outward-facing technical membrane is heated up. It is not the outward-facing technical membrane, which absorbs solar rays and heats up as a result, which is reflected but rather the temperature in the room. This lowers the calculated mean temperature of the room-closing surfaces. Thermal comfort, of which, according to Fanger, the calculated mean temperature of the enclosing surfaces is a contributing factor, in addition to the atmospheric temperature, is significantly enhanced. If the inward-facing layer is heated up by short-wave solar radiation, only a small portion of this heat is transmitted into the room. Consequently, in addition to improved comfort, the cooling charge to be evacuated from the room is also considerably reduced.
This infrared-inhibiting, light-transmitting layer could for instance be provided directly at the surface of the sound-insulating layer facing inward toward the room. However, the preferred design for the infrared-inhibiting, light-transmitting layer would be as an inward-facing layer of a plastic foil. It is beneficial if the inward-facing layer of plastic foil is arranged at a distance from the sound-insulation layer.
With the spaces between the individual layers, which are preferably of about equal size, connected to the air in the room or to ambient air, appropriate ventilation openings make possible the ventilation of the three-layered construction of the building component from behind, in conjunction with the thermal lift of the warming air column. This avoids physical construction problems in such intermediate spaces, such as the accumulation of condensation and damage resulting from humidity.
The surface of the plastic foil with the infrared-impeding coating is joined to a support featuring preferably regular perforation and/or the thickness of the plastic foil being significantly smaller than that of the support and that the support features perforations over a significant portion of its surface, preferably about 40 to 60%, ensures that the plastic foil provided with an infrared-inhibiting layer in combination with the perforated support, for instance, permits sound waves generated in the room to pass almost without attenuation, so that these sound waves will then be absorbed by the sound-insulation layer located over it. The passage of sound is consequently minimized to the reflection of the room noise back into the room.
The most advantageous designs for the support, the plastic foil and the infrared-inhibiting layer are those based on fiberglass tissue, non-flammable material and abrasion-resistant, respectively, so that light transmission as well as safety considerations are taken into account, as well as the fact that the layer can be cleaned with non-abrasive cleaning agents without losing its function.
The most advantageous design of the sound-insulating layer is based on the feature of hollow bodies of light-transmitting material which are arranged in a direction against each other and offset with the direction of other arrangements of hollow bodies. The hollow bodies have an approximately rectangular shape and are of a roughly trapezoidal cross-section, with the volume of the inner hollow bodies being small and the material of the hollow bodies being mode of UV-resistant material, which is fire-resistant material. The surfaces of the hollow bodies which face the outer or inner layer of the technical membrane, and are parallel to them, have irregular shapes. The acoustic effectiveness is achieved via the bending resilience of the hollow acoustic bodies or their impact surfaces. With appropriate geometry, these hollow absorber bodies can be installed in a self-supporting manner. For structures of a bigger span, it may be necessary to use auxiliary constructions on which the hollow absorber bodies can then be mounted.
Advantageous design of the outward-facing technical membrane can be achieved on the basis of the outer technical membrane being a textile tissue with a plastic coating, and specifically a fiberglass tissue with a PTFE coating, and with the outer technical member being prestressed and the individually layers being mounted firmly in a frame component and kept at a distance from each other. For example, to prevent long-term damage from humidity, fiberglass threads or siliconised PVC threads are used as base material for weaving the technical membrane. To meet strict requirements in terms of anti-dirt adhesion behavior and decomposition resistance, the bearer tissue of the technical membrane is coated with PVC, PTFE or silicone. One main benefit of this design is that it continues to permit a high degree of light transmission.
Further details about the present invention can be seen in the following description, which explains and describes the invention in more detail, based on the sample design represented in the drawing. This includes the following:

Light-transmitting building construction element


A graphics processor may be operated in a reduced power mode to render frames at rate equal to or less than the rate at which frames are presented on an interconnected display. Graphics processor clock speeds are controlled to reduce the time during which the graphics processor is idle between rendering frames. The graphics processor clock speed may thus be slowed without impacting the quality of rendered images. At the same time the voltage applied to power the graphics processor may be reduced. Optionally, a back bias voltage may further be applied to the processor substrate to reduce power consumption. Clock speed and voltage levels may be adjusted using closed-loop control.

Modern computing device design strives to reduce the electrical power consumed by individual computing components, and subsystems. Reduced power consumption, in turn allows the computing device to operate at reduced temperatures and higher speeds. Moreover, it allows the computing device to operate for longer periods of time using battery or similar energy sources. This in turn, allows the devices to be more portable.
Known power reduction techniques include shutting down components and subsystems, and reducing operating frequencies of clocked circuits during times of no operation. Computer graphics adapters, for example, are shut down or operated at reduced frequency when not in use.
These conventional power management techniques, however, are mainly focused on a usage model that requires portions of the computing device to become fully idle for periods of time.
Newer computer operating systems, such as Microsoft's next generation desktop operating system (VISTA), are expected to extensively use 3D rendering as a normal part of the creation of a standard desktop view. In addition, it is expected that 2D and 3D rendering in the form of animations will run continuously even without user interaction.
In the presence of continuous rendering, the utility of existing power techniques is reduced drastically. Specifically, the continuous rendering may prevent the graphics processor from ever being idle, thus inhibiting the majority of the current power management features.
Clearly then, continuous high speed rendering in the absence of user interaction is wasteful. Accordingly, improved power management methods and components are desirable.

Dynamically controlled power reduction method and circuit for a graphics processor


A process for manufacturing of a semiconductor device comprising a blocking pn junction, a source zone of a first conductivity type connected to a first electrode and bordering on a zone forming the blocking pn junction of a second conductivity type complementary to the first conductivity type, and a drain zone of the first conductivity type connected to a second electrode, the side of the zone of the second conductivity type facing the drain zone forming a first surface, and in the region between the first surface and a second surface located between the first surface and the drain zone, areas of the first and second conductivity type nested in one another, comprises the step of:

The present invention concerns a semiconductor device with a semiconductor body having a blocking pn-junction, a first zone of a first conductivity type, which is connected to a first electrode and abuts one of the zones of a second conductivity type opposite the first conductivity type forming the blocking pn-junction, and with a second zone of the first conductivity type, which is connected to a second electrode, whereby the side of the zone of the second conductivity type facing the second zone forms a first surface and in the region between the first surface and a second surface, which lies between the first surface and the second zone, areas of the first and of the second conductivity type are nested.
Such semiconductor devices are also known as compensation devices. Such compensation devices are, for example, n- or p-channel MOS field effect transistors, diodes, thyristors, GTOs, or other components. In the following, however, a field effect transistor (also referred to briefly as xe2x80x9ctransistorxe2x80x9d) is assumed as an example.
There have been various theoretical investigations spread over a long period of time concerning compensation devices (cf. U.S. Pat. Nos. 4,754,310 and 5,216,275) in which, however, specifically, improvements of the on-resistance RDS(on) but not of stability under current load, such as, in particular, robustness with regard to avalanche and short circuit in the high-current operation with high source-drain voltage, are sought.
Compensation devices are based on mutual compensation of the charge of n- and p-doped areas in the drift region of the transistor. The areas are spatially arranged such that the line integral above the doping along a line running vertical to the pn-junction in each case remains below the material-specific breakdown voltage (silicon: approximately 2xc3x971012 cmxe2x88x922). For example, in a vertical transistor, as is customary in power electronics, p- and n-columns or plates, etc. may be arranged in pairs. In a lateral structure, p- and n-conductive layers may be stacked on each other laterally alternating between a groove with a p-conductive layer and a groove with an n-conductive layer (cf. U.S. Pat. No. 4,754,310).
By means of the extensive compensation of the p- and n-doping, the doping of the current-carrying region (for n-channel transistors, the n-region; for p-channel transistors, the p-region) can be significantly increased, whereby, despite the loss in current-carrying area, a clear gain in on-resistance RDS(on) results. The blocking capability of the transistor depends substantially on the difference between the two dopings. Since, because of the reduction of the on-resistance, a doping higher by at least one order of magnitude of the current-carrying area is desirable, control of the blocking voltage requires controlled adjustment of the compensation level, which can be defined for values in the range xe2x89xa6xc2x110%. With a greater gain in on-resistance, the range mentioned becomes even smaller. The compensation level is then definable by
(p-dopingxe2x88x92n-doping)/n-doping
or by
charge difference/charge of one doping area.
Other definitions are, however, possible.
It is an object of the present invention to provide a robust semiconductor component of the kind initially mentioned, to be firstly distinguished by a high xe2x80x9cavalanchexe2x80x9d ruggedness and high current load capacity before and/or during breakdown and secondly simple to produce with reproducible properties in view of technological latitudes of fluctuation of manufacturing processes.
This object is accomplished according to the invention, in a semiconductor component of the kind initially mentioned, in that the regions of the first and second types of conductivity are so doped that charge carriers of the second conductivity type predominate in regions near the first surface and charge carriers of the first conductivity type in regions near the second surface.
Preferably, the regions of the second conductivity type do not extend as far as up to the second zone, so that between said second surface and the second zone, a weakly doped region of the first conductivity type remains. It is possible, however, to allow the width of this region to go to xe2x80x9czero.xe2x80x9d The weakly doped region, however, provides certain advantages, such as enhancement of the barrier voltage, xe2x80x9csmoothxe2x80x9d profile of the electrical field strength, or improvement of commutation properties of the inverse diode.
In another refinement of the invention, it is provided that between the first and second surfaces, a degree of compensation effected by the doping is so varied that atomic residues of the second conductivity type dominate near the first surface and atomic residues of the first conductivity type near the second surface. In other words, there are sequences of p, pxe2x88x92, nxe2x88x92, n or n, nxe2x88x92, pxe2x88x92, p layers between the two surfaces.
Advantageous improvements of the semiconductor device according to the invention (hereinafter also referred to as xe2x80x9ccompensation devicexe2x80x9d) are disclosed by the other dependent claims.
The effect of the areas nested in each other, alternating different conductivity types, on the electrical field, is, in contrast to a conventional DMOS transistor, for example, as follows (xe2x80x9clateralxe2x80x9d and xe2x80x9cverticalxe2x80x9d refer in the following to a vertical transistor):
(a) There is a cross-field, xe2x80x9clateralxe2x80x9d to the direction of the connection between the electrodes, the strength of which depends on the proportion of the lateral charge (line integral perpendicular to the lateral pn-junction) relative to the breakdown charge. This field leads to the separation of electrons and holes and to a reduction in the current-carrying cross-section along the current paths. This fact is of primary significance for the understanding of the processes in avalanche, of the breakdown characteristic curve, and of the saturation region of the output characteristics diagram.
(b) The xe2x80x9cverticalxe2x80x9d electrical field parallel to the direction of the connection between the electrodes is determined locally by the difference between the adjacent dopings. This means that with an excess of donors (n-loaded distribution: the charge in the n-conductive areas exceeds the charge of the p-areas) on the one hand, a DMOS-like field distribution (maximum of the field on the blocking pn junction, decreasing field in the direction of the opposing back of the device) appears, whereby the gradient of the field is, however, clearly less than would correspond to the doping of the n-area alone. On the other hand, however, by overcompensation of the n-conductive area with acceptors, a field distribution rising in the direction of the back is possible (p-loaded distribution: excess of acceptors compared to the donors). In such a design, the field maximum lies at the bottom of the p-area. If the two dopings are exactly compensated, there is a horizontal field distribution.
With an exact horizontal field distribution, the maximum of the breakdown voltage is obtained. If the acceptors or the donors predominate, the breakdown voltage drops in each case. If the breakdown voltage is then plotted as a function of the degree of compensation, a parabolic characteristic is obtained.
Constant doping in the p- and n-conductive areas or even a locally varying doping with periodic maxima of equal height results in a comparatively sharply pronounced maximum of the xe2x80x9ccompensation parabolaxe2x80x9d. For the benefit of a xe2x80x9cproduction windowxe2x80x9d (including the fluctuations of all relevant individual processes), a comparatively high breakdown voltage must be steered for in order to obtain reliable yields and production reliability. Consequently, the objective must be to make the compensation parabola as flat and as broad as possible.
When the blocking voltage is applied to the device, the drift region, i.e., the region of the areas of opposite doping arranged in pairs, is cleared of mobile charge carriers. The positively charged donor cores and the negatively charged acceptor cores remain in the spreading space charge region. They then determine the course of the field.
The flow of current through the space charge region causes a change in the electric field when the concentration of the charge carrier associated with the flow of current comes into the region of the background doping. Electrons compensate donors; holes compensate acceptors. For the stability of the device, it is also very important which doping predominates locally, where charge carriers are generated, and how their concentrations result along their current paths.
For the following embodiments, for an understanding of the basic mechanism, initially a constant doping of the p- and n-conductive areas is assumed.
In the on-state and especially in the saturation region of the output characteristics of a MOS transistor, a pure stream of electrons flows from the channel into an n-doped area, also referred to as a xe2x80x9ccolumnxe2x80x9d in a vertical transistor, whereby in the base an increasing focusing of the flow of current occurs because of the electrical cross-field. High-current stability is promoted by dominance of the n-doping; however, since the channel region with its positive temperature coefficient eliminates inhomogeneous current distribution in a cell field, this mode of operation is rather uncritical. Reduction in the current density is obtained through partial shadowing of the channel connection (cf. DE 198 08 348 A1).
With regard to the breakdown characteristic or its course, the following must be taken into consideration: The generation of electrons and holes occurs in the region of maximum field strength. The separation of the two types of charge carriers is performed by the electrical cross-field. Along the two current paths in the p- and n-area, respectively, focusing and further multiplication occurs. Ultimately, also no effect of a partial channel shadowing occurs. Stability is present only when the mobile charge carriers cause a rise in the electrical field outside their source and thus a rise in the breakdown voltage of the respective cell. For compensation devices this means stability in the p- and n-loaded region, but not in the maximum of the compensation parabola. In the p-loaded region, the breakdown occurs at the xe2x80x9cbottomxe2x80x9d of the column. The electrons flow out of the drift region and thus do not affect the field. The holes are pulled through the longitudinal electrical field to the top source contact. In the process, the hole current is focused along its path by the electrical cross-field: The current density rises here. Thus, the longitudinal electrical field is initially affected near the surface. As a result of compensation of the excess acceptor cores (p-loaded distribution), a reduction in the gradient of the electrical field and a rise in the breakdown voltage occur. This situation is stable as long as the field there remains clearly below the critical field strength (for silicon: approximately 270 kV/cm for a charge carrier concentration of approximately 1015 cmxe2x88x923).
In the n-loaded region with an excess of donors, the breakdown is near the surface. The holes flow to the source contact and still affect the field on their path from their source to the p-well. The objective must consequently be to place the breakdown location as near as possible to the p-well. This can be accomplished, for example, by a local elevation in the n-doping. The electrons flow through the complete drift zone to the back and likewise affect the field along their current path. Stability is obtained when the effect of the electron current prevails over that of the hole current. Since the geometry of the cell arrangement plays an important role here, there is a region of stable and instable characteristic curves especially near the maximum of compensation parabola.
The conditions in the avalanche are very similar to those of a breakdown. The currents are, however, clearly higher and have with a rated current as much as twice the rated current of the transistor. Since the electrical cross-field always causes a clear focusing of the current, in compensation devices the stability range is left at comparatively low current loads. Physically, this means that the current-induced rise in the field has already advanced so much that locally the breakdown field strength has been reached. The longitudinal electrical field can then not rise further locally; the curvature of the longitudinal electrical field, however, increases which results in a drop in the breakdown voltage of the cell in question. In the characteristic curve of an individual cell and also in the simulation, this is reflected by a negative differential resistance; i.e., the voltage drops as the current rises. In a large transistor with more than 10,000 cells this results in a very rapid inhomogeneous redistribution of the current. A filament is formed, and the transistor melts locally.
This yields the following consequences for the stability of compensation devices:
(a) Due to the separation of electrons and holes there is no xe2x80x9cauto-stabilizationxe2x80x9d as with IGBTs and diodes. Instead, the degree of compensation, field distribution, and breakdown location must be set exactly.
(b) On the compensation parabola, with constant doping of the p- and n-areas or xe2x80x9ccolumnsxe2x80x9d, there are stable regions in the clearly p- and in the clearly n-charged regions. The two regions are not contiguous. Thus, there is only an extremely small production window. With constant doping of the p- and n-areas or columns, the compensation parabola is extremely steep. The breakdown location moves within a few percent from the bottom of the p-column in the direction of the surface.
(c) For each compensation device, there is a current destruction threshold in the avalanche which is directly coupled with the degree of compensation. The degree of compensation, on the other hand, determines the achievable breakdown voltage and effects the RDS(on) gain.
(d) With constant doping of the p- and n-areas, the devices arexe2x80x94as mentioned abovexe2x80x94instable near the maximum of the compensation parabola. This results in the fact that the devices with the highest blocking voltage are destroyed in the avalanche test.
As explained above, to prevent the disadvantages, the degree of compensation is varied along the doping areas, i.e., in a vertical structure from the top in the direction of the back of the transistor, such that the atomic cores of the second conductivity type dominate near the surface and the atomic cores of the first conductivity type dominate near the back.
The resultant field distribution has a xe2x80x9chump-shapedxe2x80x9d curve with a maximum at approximately one-half of the depth(cf. FIG. 6). Thus, both the electrons and holes affect the field distribution in the breakdown and in the avalanche. Both types of charge carriers have a stabilizing effect, since in each case they run from their source into areas in which they compensate the dominating excess background doping. There is thus a continuous stability range from p-loaded to n-loaded degrees of compensation.
A variation of the degree of compensation due to production fluctuations shifts the breakdown location only slightly in the vertical direction and continuously back and forth, as long as this variation is less than the technically adjusted variation of the degree of compensation. The size of this modification of the degree of compensation also determines the limits of the stability range. Thus, the production window becomes freely selectable.
The focusing of the currents is clearly less pronounced since both types of charge carriers travel only one-half the path in the region of the compressing electrical cross-field. Thus, the devices can be stressed with clearly higher currents in the avalanche.
Since in a variation of the degree of compensation, e.g., in the direction toward xe2x80x9cn-loadingxe2x80x9d, the electrical field increases in each case in the upper area of the drift region, but simultaneously decreases in the lower area (vice versa with variations toward p-loaded distribution), the breakdown voltage varies only relatively little as a function of the degree of compensation. Thus, the compensation parabola becomes preferably flat and wide.
The vertical variation of the degree of compensation can be effected by variation of the doping in the p-region or by variation of the doping in the n-region or by variation of the doping in both regions. The variation of the doping along the column may have a constant rise or be in a plurality of steps. In principle, the variation increases monotonically from a p-loaded degree of compensation to an n-loaded degree of compensation.
The invention can be readily applied even with p-channel transistors. In that case, an appropriately altered course of the semiconductor regions occurs: A (p, p-dominated, n-dominated, n) course is replaced by an (n, n-dominated, p-dominated, p) course.
The stability limits are reached on the n-loaded side when the field runs horizontally near the surface over an appreciable part of the drift region. On the p-loaded side the stability limits are reached when the field runs horizontally near the bottom of the compensating column region over a noticeable part of the drift region.
In general, the compensation parabola becomes flatter and wider the greater the gradient of the degree of compensation. The breakdown voltage in the maximum of the compensation parabola drops accordingly.
Another important limitation of the variation of the degree of compensation results from the requirement to remain below the breakdown charge. In addition, with greater elevation of the p-column doping near the surface, current pinch-off effects occur near the surface (lateral JFET effect).
For 600 V devices, a variation of the degree of compensation lengthwise of the p- and n-areas of 50%, for example, is advantageous.
Although above the starting point has been primarily a vertical transistor, the semiconductor device according to the invention can, in principle, have a vertical or even a lateral structure. With a lateral structure, n- and p-conductive plate-shaped areas are, for example, arranged laterally stacked in each other.
Applications for such lateral transistors are, for example, found in the smart power sector or in microelectronics; vertical transistors are, in contrast, produced primarily in power electronics.
The vertical modification of the degree of compensation is very simple to implement since in the individual epitaxial planes, only the implantation dose must be altered. The xe2x80x9crealxe2x80x9d compensation dose is then implanted in the middle epitaxial layer; below that, for example, 10% less in each case, above that, for example, 10% more in each case. However, instead of the implantation dose, it is possible to alter the epitaxial doping.
By means of the more manageable variation, it is possible to reduce the production costs. The number of necessary epitaxial layers can be reduced, and the openings for the compensation implantation can be reduced as a result of greater variation of the implanted dose due to the greater relative variation of the resist dimension with simultaneously prolonged subsequent diffusion for the merging of the individual p-regions into the xe2x80x9ccolumnxe2x80x9d.
The structure according to the invention is produced by the following individual steps:
First, a multi-xcexcm-thick, n-doped epitaxial layer is applied to a semiconductor substrate. The p-doping ions are introduced into this epitaxial layer via a resist mask by means of ion implantation. Next, the entire process is repeated as often as necessary until there is an adequately thick n-multi epitaxial layer with embedded p-centers aligned with each other and stacked. The production of the actual device then occurs, by means of, for example, the processing of the base zones, the source zones, the front metalization, and the gate electrodes in a field effect transistor. By thermal diffusion, the p-doped centers merge into a rippled vertical column. Due to intrinsic compensation, the concentration of the p- or n-doping material is always substantially higher than the resultant electrically active doping.
The ripple of the vertical column is expressed in a varying acceptor-donor ratio ke(z) per horizontal plane. The electrical compensation varies accordingly in each horizontal plane in the semiconductor body. The ripple of the column causes no significant change in the horizontal field. Consequently, in the first approximation, the contribution UBh is considered unaffected by the ripple.
In the vertical direction, layers with non-horizontally compensated p- and n-charges alternate. An epitaxial layer corresponds to a complete ripple period and, consequently, corresponds to two adjacent pn-junctions. Due to the production fluctuations in the epitaxy cycles, the charge balance is not equalized over the entire volume of a pn-junction such that the degree of compensation does not equal 0.
In a semiconductor device according to the present invention, the voltage consumed in the blocked state in the cell field between anodes and cathodes or in a field effect transistor vertically between source and drain must also be discharged laterally on the edge of the semiconductor device. Semiconductor devices are often operated up to a breakdown. In this case, a very high current flows through the impact ionization which occurs. In order not to destroy the semiconductor device, no excessively high current densities may occur, i.e., the breakdown current must be distributed as uniformly as possible over the entire semiconductor device. However, this requirement can be fulfilled only if the cell field carries the majority of this current. If the semiconductor device breaks down in the edge structure at a smaller blocking voltage than the cell field, this results in most cases in irreversible thermal damage to the semiconductor device. The semiconductor device must, consequently, be avalanche-rugged. Avalanche-rugged semiconductor devices, especially vertical transistors, reduce the safety distance necessary to manage overvoltages, whereby in many applications comparatively low-blocking transistors may be used, which require at the same RDS(on) a comparatively small semiconductor device surface and are thus more economical. With conventional high-voltage MOSFETs, this is very significant since the RDS(on) of these transistors rises disproportionately with the breakdown voltage. With conventional power devices, expensive surface-mounted structures or structures near the surface usually result in the situation that the semiconductors device edge can block more voltage than the cell field. The lower-lying semiconductor device volume is homogeneously doped so low that it withstands the necessary voltage without structuring. With the semiconductor devices according to the present invention, which use the production process of intrinsic compensation, the demands with regard to the edge structure are intensified because here even the lower-lying volumes under the edge must be processed. The material actually accommodating the blocking voltage, i.e., the epitaxial layer above the highly doped semiconductor substrate, is relatively low ohmic and will only block a fraction of the required voltage. The blocking capability for the cell field is achieved only with the introduction of the counter doped columns.
For the volume below the edge, there are, in principle, two different processing methods:
1. The semiconductor edge may be processed separately from the cell field, i.e., in additional steps. An overall counter doping of the substrate on the semiconductor edge, e.g., by means of overall edge implantation and diffusion, is conceivable. Thus, an overall intrinsically compensated and thus highly blocking edge can be produced. Such a procedure is, however, associated with very high costs.
2. The column structure in the cell field is continued into the edge, whereby the substrate is also built up to basically the same blocking voltages as in the cell field. A minimal increase, for example, in the dielectric strength of the edge may be obtained in many cases by means of a suitable variation of the deep compensation profile of the columns, as this has been described on the preceding pages for the cell field, whereby, however, the tolerance range compared to the cell field and thus the tolerance range of the entire semiconductor device becomes smaller. Additionally, additional effects may provoke breakdown on the edge of the semiconductor device.
On the one hand, the surface-mounted edge structures or structures near the surface cause additional field distortions and generate centers of high field strength.
On the other hand, it may be necessary to apply an expedient negative xe2x80x9cerror chargexe2x80x9d to the edge, which causes a curvature of the equipotential lines toward the semiconductor device surface, whereby these can be picked up and carried by the surface structure. This corresponds to a field discharge on the semiconductor device edge. This error charge condition may also cause a voltage-induced premature breakdown of the semiconductor device edge compared to the cell field.
Accordingly, it is best to reduce the horizontal components of electric field and simultaneously the vertical ripple of the compensation profile on the edge. Both result in higher blocking voltages on the semiconductor device edge. To implement this, the local separation must be eliminated or at least weakened in the charge centers of opposing polarity, i.e., an intrinsic compensation must be undertaken.
Thus, a high-voltage resistant edge structure is created, which consists of a plurality of floating zones of the second conductivity type, which are separated by intermediate zones of the first conductivity type, whereby the width of the intermediate zones and width of the floating zones are smaller than the width of the areas of the first and of the second conductivity type, which are nested in each other inside the cell fields. These floating zones and intermediate zones are doped such that the charge carriers of floating zones and of intermediate zones are completely cleared with the application of blocking voltage.
Thus, preferably, the edge volume is processed in one and the same operation, whereby both the thickness of an individual epitaxial layer and the cell grid is reduced in size in the edge region, yielding at the end of the process homogeneous dopant distribution for both types of charge carriers for each edge cell. With regard to the ratio of unmasked surface per cell to the total cell surface in the edge region, the charge applied by implantation can be ideally adapted to the charge which is defined by the epitaxy. In order to achieve ideal blockability, a charge balance, i.e., intrinsically compensated condition, is sought.
Preferably, the thickness of the individual epitaxial layers will be designed according to specifications which the cell field defines. This again yields a vertically rippled compensation profile on the semiconductor edge, but in a substantially weaker form than in the cell field. A reduction in the cell grid results in the fact that the resolution of the doping material source is reduced, whereby the boundaries of the individual diffusion fronts become blurred.
An additional advantage of the edge design described is the coupling between the production defects in the edge and in the cell field since error mechanisms act in both regions in the same direction.

Abstract: varying in individual semiconductor layers, by doping, the degree of compensation in the regions of the second conductivity type.