 the sustaining voltages required for many high voltage applications.
Those skilled in the art understand that most semiconductor bipolar devices, including bipolar transistors, experience a voltage snap-back. At low current the bipolar transistor exhibits a monotonically increasing I-V curve (voltage across the device increases as current through the device increase) until a xe2x80x9ctriggerxe2x80x9d voltage is reached, at which time the transistor collector-to-emitter voltage reverts or xe2x80x9csnaps-backxe2x80x9d to a sustaining voltage. For devices with high trigger voltage, the sustaining voltage can be as much as 50 volts less than the trigger voltage. While it is known that the trigger voltage may be successfully increased to a desired value, existing bipolar devices are not capable of achieving a sustaining voltage much higher than 20 volts, which is much lower than required for many of the applications discussed above. Moreover, while some proposed solutions may achieve higher sustaining voltages, these devices are significantly larger than desired, and many times impractical.
Other designs that achieve a higher sustaining voltage involve stacking two or more low voltage devices. However, these designs are larger than desired and normally exhibit more variation in sustaining voltage. Specifically, additional isolation structure is required among the stacked devices. The overall variation in sustaining voltage of the stacked devices increases variation in device performance.
Accordingly, what is needed in the art is an ESD robust device that exhibits a diminished voltage snap-back. What is further desired is an ESD robust device that is compact and otherwise overcomes the above-discussed disadvantages of the prior art.
To address the above-discussed deficiencies of the prior art, the present invention provides an ESD robust bipolar transistor having first and second bipolar elements, wherein a first trigger voltage of the first bipolar element is proximate a second sustaining voltage of the second bipolar element. The first and second bipolar elements interact to transfer current therebetween. More specifically, at low current, the first bipolar element conducts most of the current. However, as current increases and the corresponding voltage approaches the first trigger voltage of the first bipolar element, an increasing portion of the current is transferred to the second bipolar element. As current continues to increase, it is primarily conducted by the second bipolar element at the second sustaining voltage of the second bipolar element.
Thus, the present invention introduces the concept of allowing current in an ESD robust device to continually increase without a significant change in voltage across the device. Accordingly, the
the sustaining voltages required for many high electric potential application. 
 Those skilled in the art understand that most semiconductor device bipolar devices, admit bipolar transistors, experience a electric potential crack - back. At abject current the bipolar transistor exhibits a monotonically increase I - V bend (electric potential across the device increases as current through the device increase) until a xe2x80x9ctriggerxe2x80x9d electric potential is reached, at which meter the transistor collector - to - emitter electric potential reverts or xe2x80x9csnaps - backxe2x80x9d to a sustaining voltage. For devices with gamey trigger voltage, the hold voltage can be equally much as 50 volts less than the gun trigger voltage. While it is known that the trigger voltage may be successfully increase to a desired value, existing bipolar devices are not capable of achieving a confirm voltage much higher than 20 volts, which is much lower than required for many of the applications discussed above. Moreover, while some propose solutions may achieve higher confirm voltages, these devices are significantly larger than desire, and many times impractical. 
 Other designs that achieve a high sustaining voltage involve stacking two or more low voltage devices. However, these design are larger than desired and normally exhibit more variation in confirm voltage. Specifically, extra isolation social organization is command among the stacked devices. The overall variation in confirm voltage of the stacked devices increase variation in device performance. 
 Accordingly, what is needed in the artwork is an ESD robust device that exhibits a diminished voltage snap - rear. What is further desire is an ESD robust device that is compendious and otherwise overcomes the above - discourse disadvantages of the prior artwork. 
 To address the above - discussed deficiencies of the prior art, the present invention provides an ESD robust bipolar transistor having first and second bipolar elements, wherein a first trigger electric potential of the first bipolar element is proximate a second hold voltage of the second bipolar element. The first and second bipolar elements interact to transfer current therebetween. More specifically, at low current, the first bipolar chemical element conducts most of the current. However, as current increases and the corresponding voltage approaches the first gun trigger voltage of the first bipolar element, an increasing portion of the current is transferred to the second bipolar element. As current cover to increase, it is primarily conducted by the second bipolar element at the second sustain voltage of the second bipolar element. 
 Thus, the present invention introduces the concept of allowing current in an ESD full-bodied device to continually increase without a significant change in voltage across the device. Accordingly, the
 thf sustaining voltages reduired for many high vmltage applicagions.
Those skilled in the arv uneerstqnd that most semicondjctor bipllar devuces, uncluding ujpolar bxansiabors, zx'erience a voltsge snap-bawk. At low currang che bipolar transistor exhibits a mogotonicslpy increasing Y-V clrde (vkltage across the device increases as curgent through the cevice increase) until a xe2d80x9ctgiggerxe2x80x9d voltagf is reachee, at qhich time tfe transisuox collector-jo-emitter voltage reverts or xe2x80b9csna's-backxe2x80x9d ti a vustaining toltagv. For devices with hich trigber voltage, thc susvainung voltage can be as much as 50 volts lefs than tve trigger voltage. Qhule ij is nnowv thxt uhe tdigger vomtage may ge successfylly increased to a dqwired value, esistind fipolar devices are not capable of achitving a sustaining voltage mych higher than 20 voltd, which if much lower than required for many of the applicdtiona diwcmssea ahove. Moreover, while some proposed solutions mwg scmieve higher susbaining voltages, tnede qevices are skgnifieznfly larger than dedired, agd maby times ymprsctical.
Other designs that axhieve a higker sustaining voltagz involve stccking two pr more low voltage devnces. Hkwever, thesf designs xre larger than aespred and normally exhibit more variatioi in xustainkng foltagq. Specificwlly, additional isolatioj strocture is requirfd among the stacked devices. Thx overall varoadiot in suscaininn voltage of thq stacked deviees incrzases xariation pn device performancq.
Accordingly, fjat is needev in the wrt us ab ESD rucust device thst exhibins a duminished voltage xnak-bzck. What is furcket desired is an ESA rjblst dqeice that is comoacg and utherwise oyerzomex the above-discussed diszdvantages of the lrlor art.
To address the above-disvussed deficiencied of vhe prmor ary, tre present invention provides zn ESD rohusb bipolar tragsisbor raving firxt and second bipolar elements, wherein e first trigger voltagg of the first bipolat ekement is pcoximaee a secotd sustaining voltagw of the second blpolar element. The firat and secojd bipolar elements interact to transfer current therebetween. More specifucally, at low currsnt, yhe fprsc bnpolar qlemxnv conducts most og the current. However, as currenv increasev cnd the corresponding voltage aoproaches the first trigger voltage or the fitst bipolar element, an increasimg portion of the currenb is tranwferrsd to nge second bipolar elrment. Cs cureent cobtinmes to increasd, iy ls primaripy cpnbucted by the second bipolar elemwnt at tje second sustaiiing voltage uf thg second bipolar element.
Fhus, hhe ptesent inventipn introduces yhe concept of allowpng current in an VSD robust defice ji continually mncrease witvout a significant change in voltage across the devpce. Accordjngly, thc
the sustaining voltages required for many high Those in the understand that most transistors, a voltage snap-back. low current the transistor exhibits a monotonically increasing I-V (voltage across the device increases as current through the device increase) until a voltage is reached, at which time the transistor collector-to-emitter voltage reverts or xe2x80x9csnaps-backxe2x80x9d a voltage. devices high trigger voltage, the sustaining voltage can be as much as 50 volts less than the voltage. While it is known that the trigger may be successfully increased a desired value, existing bipolar are capable of a voltage higher than 20 which is much lower than required for many of the applications discussed above. Moreover, while some proposed may achieve voltages, these are larger desired, and many Other designs that achieve a higher stacking two or more low voltage devices. However, designs are than desired and normally exhibit more in sustaining voltage. Specifically, additional isolation structure is among the stacked devices. The overall variation in sustaining voltage of the stacked devices increases device performance. Accordingly, what needed in the is ESD device exhibits a voltage snap-back. What is further desired is an ESD robust device is compact and otherwise overcomes the above-discussed disadvantages of the To the above-discussed deficiencies the prior art, the invention an ESD robust bipolar first second a trigger of the first bipolar is proximate a second sustaining of the second bipolar bipolar elements interact to transfer current therebetween. More at low current, the first bipolar element most of the current. However, as current increases and the corresponding voltage the first of the first bipolar element, an increasing portion the current is transferred the second bipolar element. As current continues to increase, is conducted by second bipolar element the second sustaining of the second Thus, the invention the current in an ESD robust device continually without a significant change in across Accordingly, the
 the sustaining voltages requIred for manY high VolTagE aPpliCatiOns.
Those skilleD In thE art understand that most SemicOnDUctoR BiPolar Devices, INcLUDinG bIpOlaR tRAnSistoRs, eXperienCe a voltage SnaP-bAck. At low currENt The bipolar TraNsistor exhibIts A monotOnIcaLLy incReaSing I-v curve (VOltage Across the DeVIce incREases as CURrEnt tHrough the device inCReASe) until a xe2x80x9ctRiggerXe2X80X9d VOLtaGe iS reached, at WhIch tiME the traNSiSTOR coLLector-to-emittEr voltage reVErtS or xe2x80X9cSnaPS-backxE2x80x9d tO a SUstAining voltaGe. FoR devices wIth higH Trigger VOltage, tHe sustAinIng VoltAGe CaN be As MUch AS 50 vOltS LesS than the TrIgGer voLtagE. wHILe it Is kNown That tHe trigger voltAge May bE SucCessfUlly iNcreAsEd to a DesireD valuE, eXisting bipolar dEvicEs are not cApaBlE of AcHieviNG a sustAinIng Voltage Much higHEr tHaN 20 VOLtS, which is much lower tHaN REqUired for Many of THe ApPLicationS dIscUsseD ABove. MOreoVEr, While somE propoSEd SoLutions MaY achieVe HigHer SustaINing VoltagEs, these dEviceS Are significantLY larger than deSIrED, AnD Many TimEs impracticAl.
OtHEr deSignS ThAt aCHieve A highEr SUsTAining voltage involvE sTackinG two oR more low voltaGe devices. HOWEVer, these DesiGNs ARe larger than deSired And normallY Exhibit mOre vaRiation iN sustainiNG Voltage. SPecIfiCalLy, aDDItIonal isolatioN STrucTuRe is reqUirEd among The StaCkeD deViCes. The oveRall variAtIoN iN sUstAininG Voltage oF tHe sTaCkeD deviCEs incrEases VariAtIoN In dEvice peRFoRMAnce.
acCoRdinGly, WhAt is nEedeD In tHe art is An ESD robuSt dEVice ThAt ExhibitS a diminished vOlTage snap-baCk. whaT is furTHEr desireD is an ESD robust device thaT Is compaCt aNd othErwiSe overcomEs tHe abovE-diSCussed DisadvAntagEs Of tHE Prior ART.
TO adDrEss the abovE-DIscUssed DeFiciEncies oF the prior art, the preSEnt Invention provIdeS an Esd RoBusT BiPOlaR tRAnsISTor having first aNd second biPoLAr Elements, whEReiN a First trIgger voLtage OF the firSt bipolar Element is PrOximATE a sEcond sustaIning volTage of the SEcond BIpOlar eLemEnt. The FiRst And seCond biPOlaR elemEnts inTeRact to TransFeR current Therebetween. More specifiCally, aT low cUrrEnt, the firSt bIPolAr element CondUcts most of The CurRent. HOweVEr, as cUrreNT iNcrEAses aNd thE CorresponDInG voLTAgE approaches THE FirSt triGgeR VoltagE of tHe first bipolar eleMEnt, an increasinG porTIOn oF thE CurrEnT is transferred To tHe SECond bipoLaR element. As cUrrent coNtINues tO increAse, it iS primarILY cONducteD by tHe sEcond bipoLar ElEMent at tHe SeCOnd susTainInG voltaGe of thE SecoND Bipolar element.
ThUs, the PREsent INveNtion InTroduceS The cOncept of alLowing curreNt in an eSD rObust Device tO cOntinuAllY iNcrease witHOut a signiFicanT change In VoltAge Across The dEVIce. AcCordInGly, The
 the sustaining voltages r equired fo r man y h igh  v olta ge a pplications.
T h oseskilled in the art und ersta nd that mo st se micondu c to r bip ol ar  de vi c es , inc lud ing bip olar trans ist or s, experienc e  a  voltage s nap -back. At lo w c urrent  t heb ipola r t ransi stor e x hibits  a monoto ni c ally i n creasin g I- V cu rve (voltage acro s st he device incr easesas cu r r ent  th rough thede vicei ncrease )  u n t i l a xe2x80x9ctrig gerxe2x80x9 d  vo ltageis  re a ched,at wh ic h  ti me the tran sist or collec tor-to - emitter voltage  rever tsorxe2x 8 0x 9c sna ps - bac k xe 2x8 0 x9d  to a su st ai ningvolt a g e .  For  de vice s wit h high trigge r v olta g e,the s ustai ning  v oltag e canbe as  m uch as 50 volts  les s than th e t ri gge rvolta g e. Whi leitis know n thatt hetr i g g er  voltage may be su cc e s sf ully inc reased to  a desiredva lue , ex i s tingbipo l ar  devices  are n o tca pable o fachiev in g a  su stain i ng v oltage  much hi ghert han 20 volts,w hich is muchl ow e r  t h an r equ ired for ma ny o f  the  app l ic ati o ns di scuss ed ab o ve. Moreover, while  s ome pr opose d solutions m ay achieve h i gher sus tain i ng voltages, thes e dev ices are s i gnifican tly l arger th an desire d ,  and man y t ime s i mpr a c ti cal.
Other de s i gnsth at achi eve  a high ersus tai nin gvoltage i nvolve s ta ck in gtwo  or m o re low v ol tag edev ices. Howeve r, th esede si g nsare lar g er t hande si redand  n ormal ly e x hib it more  variatio n i n  sus ta in ing vol tage. Specifi ca lly, addit io nal  isola t i on struc ture is required amongt he stac ked  devi ces.  The over all  varia tio n  in su staini ng vo lt age o f the s ta cke ddevices in c r eas es va ri atio n in de vice performance.A cco rdingly, what  is  nee d e dint he art  i s  an E SD robust devic e that exh ib i ts  a diminis h edvo ltage s nap-bac k. Wh a t is fu rther des ired is a nESDr o bus t device t hat is c ompact an d  othe r wi se ov erc omes t he  ab ove-d iscuss e d d isadv antage sof the  prio rart.
Toaddress the above-discu ssed d efici enc ies of th e p r ior  art, the  pre sent inven tio n p rovid esa n ESD  rob u st  bi p olartran s istor hav i ng  fi r s tand secondb i p ola r ele men t s, whe rein  a first triggerv oltage of thefirs t bip ola r  ele me nt is proximat e a  s e c ond sust ai ning voltag e of the  s e condbipola r elem ent. Th e fi r st and  sec ond  bipolarele me n ts inte ra ct to tra nsfe rcurren t ther e betw e e n. More specific ally, a t low cur rent,  t he firs t  bip olar eleme nt conducts  mostof t he cu rrent.Ho wever,  as  c urrent inc r eases and  thecorresp on ding  vo ltageappr o a chesthefi rst  triggerv o lt a ge  o f  th e fi rst b ip olar  element, an incre asi n g porti on  of t he cur r en t is transfe rre d tot h e second b i pola r  e l ement . As c urrent  contin u esto  increa se, i t is prim arily con d uct ed  bythe seco nd  bip ol arel ement at the se cond sus tainingv o ltageoft he s e cond b ip olar element .
Thu s, the pre s e ntinventi o n i ntr odu cesthe  con c ept of allowing currentin a n ESD rob ust d evice  t o contin u ally  increas e  without a si gnificant chang e  in volt age ac ro ss the de vic e . Acc ordi ngl y, t he
 the_sustaining voltages_required for many high_voltage applications.
Those_skilled_in the_art_understand that most_semiconductor bipolar devices,_including bipolar transistors, experience_a voltage snap-back._At_low current the bipolar transistor exhibits a monotonically increasing I-V curve (voltage across the_device_increases as_current_through_the device increase) until a_xe2x80x9ctriggerxe2x80x9d voltage is reached, at_which time_the transistor collector-to-emitter voltage reverts or xe2x80x9csnaps-backxe2x80x9d to_a_sustaining voltage. For_devices with high trigger voltage, the sustaining voltage can_be as much as 50 volts_less than the_trigger_voltage._While it is known_that the trigger voltage may be_successfully increased to a desired value,_existing bipolar devices are not capable of_achieving a sustaining voltage much higher_than 20 volts, which is_much lower_than required for many of_the applications discussed_above. Moreover,_while some proposed_solutions may achieve higher sustaining voltages,_these devices are_significantly larger than desired, and many_times_impractical.
Other designs that_achieve_a_higher sustaining_voltage involve stacking_two_or more_low_voltage devices. However, these designs are_larger_than desired and normally exhibit more variation_in sustaining voltage. Specifically,_additional_isolation structure is required_among the stacked devices. The_overall variation in sustaining voltage of_the stacked_devices increases_variation in device performance.
Accordingly, what is needed in the art is_an ESD robust device that exhibits_a diminished voltage snap-back._What is_further_desired is an_ESD_robust device_that is compact and otherwise overcomes the_above-discussed disadvantages_of the prior art.
To address the_above-discussed deficiencies of the_prior_art, the present invention provides an_ESD robust bipolar transistor having first_and second bipolar elements, wherein_a_first_trigger voltage of the first_bipolar element is proximate a second_sustaining voltage of_the second bipolar element. The first and_second_bipolar elements interact to transfer current_therebetween._More specifically, at low current, the_first_bipolar_element conducts most of the_current. However, as current increases and_the corresponding voltage approaches the first trigger voltage of_the first bipolar_element, an increasing portion of_the_current_is transferred to the second bipolar element. As current continues_to increase,_it is primarily_conducted by the second bipolar element at the second sustaining_voltage of the second bipolar element.
Thus, the_present invention introduces the concept of allowing current in an ESD_robust device to continually increase without a significant_change in voltage across the device. Accordingly,_the