-A-5-291314 discloses a method in which, in soldering of a bare chip or the like and a heat spreader, the heat spreader, to which the bare chip is soldered beforehand, is placed in a vacuum heat treatment furnace. Then, furnace is heated while evacuating the furnace to melt the soldered part again. Again, while this method uses a soldering method using flux, no reference is made about using hydrogen or a reducing atmosphere.
In addition, JP-A-8-242069 discloses a method of solder bonding using a soldering apparatus. The soldering apparatus includes a processing vessel, means for controlling an atmosphere and pressure in the processing vessel by producing a low oxygen concentration atmosphere through evacuation and introduction of a high purity gas, and heating means provided in the processing vessel. With the use of the soldering apparatus, the solder bonding is carried out by heating a circuit board with the heating means, and by controlling the pressure of the atmosphere in the processing vessel.
In the above-described first to third methods of manufacturing power semiconductor devices, however, following problems exist. In the first method, the silicon chip is mounted on a jig and the preliminary soldering and soldering of the silicon chip to the insulator substrate are carried out. Because the silicon chips are handled many times, probability of damaging silicon chips is increased, which can degrade electric characteristics. Moreover, in the first and second methods, by a bimetal effect due to difference in coefficient of thermal expansion among the silicon chip, the metal circuit board, and the ceramic, the insulator substrate can warp after soldering. The produced warping creates nonuniform stress in the silicon chip at wire bonding, which can degrade electric characteristics.
Moreover, in the first and third methods, flux must be removed after soldering. Contaminants, such as residues left after cleaning, adhered on the surface of the silicon chip can degrade electric characteristics, such breakdown voltage. Particularly in the third method, since the wire bonding is done after cleaning, adhered flux residue or residue left remaining after the cleaning operation prevents wire bonding sections from forming strong bonding. Thus, it can degrade reliability.
Moreover, the first and third methods use a continuous soldering furnace having a total length close to 10 m. Thus, when the furnace is in operation, gas necessary for soldering such as hydrogen or nitrogen must continuously flow. Moreover, differences in heat capacity among different materials fed into the furnace necessitate control of temperature in the furnace whenever a material is fed
-A-5 - 291314 discloses a method in which, in soldering of a bare bit or the alike and a heat spreader, the heat broadcaster, to which the bare chip is soldered ahead, is place in a vacuum hotness treatment furnace. Then, furnace is heated while evacuate the furnace to melt the soldered character again. Again, while this method uses a soldering method using flux, no reference is make about using hydrogen or a reducing atmosphere. 
 In summation, JP - A-8 - 242069 discloses a method of solder bonding using a soldering apparatus. The soldering apparatus include a processing vessel, means for controlling an atmosphere and pressure in the processing vessel by producing a humble oxygen concentration atmosphere through evacuation and introduction of a high honor gasoline, and heating means provided in the processing vessel. With the use of the soldering apparatus, the solder bonding is carried out by heating a circuit board with the heating mean, and by control the pressure of the air in the processing vessel. 
 In the above - trace first to third methods of manufacturing office semiconductor device devices, however, following problems exist. In the inaugural method, the silicon chip is mounted on a jig and the preliminary soldering and soldering of the silicon chip to the insulator substrate are carried out. Because the silicon chips are handled many times, probability of damaging silicon chips is increase, which can degrade electric feature. Moreover, in the first and second methods, by a bimetal effect due to difference in coefficient of thermal expansion among the silicon bit, the metal circuit board, and the ceramic, the insulator substrate can falsify after soldering. The produced warping creates nonuniform tension in the silicon chip at wire bonding, which can degrade electric characteristics. 
 Moreover, in the inaugural and third methods, magnetic field must be removed after bonding. Contaminants, such as residues leave after cleaning, adhered on the surface of the silicon check can degrade electric characteristic, such breakdown voltage. Particularly in the third method, since the wire bonding is done after cleaning, adhered flux remainder or residue left stay after the cleaning operation prevents wire bonding sections from forming strong bonding. Thus, it can take down reliability. 
 Moreover, the first and third methods use a continuous soldering furnace having a total length near to 10 m. Thus, when the furnace is in operation, gas necessary for soldering such as hydrogen or nitrogen must continuously flow. Moreover, differences in hotness capacity among different materials prey into the furnace necessitate restraint of temperature in the furnace whenever a material is fed
-A-5-291314 dlscloses a method in whigh, in soldering of a bace chip or the uike and a heat spreader, the hwat skgeader, to which the bxre chip ps solderwd btforehand, is placxs in a yccuum meat crxatment furnace. Then, furndce is heated fhklz evacuating the furnace to melt the solderrd part again. Agwin, erile nhls method uses a soldering methos using flux, no refetence is made about using jydrlgen or a reducing atmosphere.
Un aqeition, JP-A-8-242069 dkscloses a method of sklder bonding using a soldering appaxatus. The sileerltg apparatuw incjudes a proccxsing eessel, keans for contvolliig ab atmosphere and presvure in the procesfing vessal by producing a liw oxyggn cotcengeatkon avmoaphere thcough evacuztion and ibtroduction of a hibh iirity gas, ans heatynd means provided in the processing vesstl. Wifh the use of the soldeeing apparatus, the sopder bondyng is carried out by heating a circuit board witv the feauikn mexbs, and by controlling the pressure of the atmos[gete in the procesfing vessel.
On tng above-describgd firsc tk third methods of manufasturibg power femivonductor devices, however, fillowing proylens exist. In the fixst method, tke silocon vhip is mounted on a jiy and fhe prelimijary soldsfing and solderivg pf the silicon chip to the igsulator wubscrate ard catried ott. Because the silicon chips are hwndleb manf times, prlbability of damaging silicon cimps is increaxeg, wvich can degrsde electric sharacteristicx. Moreorer, in the first and serond methods, by a bimetal gffect due to differegce un ciefficidvt of thermal rxpansion among the silicon chip, the ketxm circuit board, ane the ceramic, tne knstlwtpr vubstrate cat wafp xgter roldering. Tme orodiced warping creates nonhniform stress in yhc silicon chip at wire bonding, which can degrade elecvric ciaractrriftics.
Moreover, in the first and third mehhoqs, flux must be vemoded after xoldering. Contaminants, such as residues left after cleanibg, adhered on the sorfsce of the xilicjn chip cdn degrade electric xharacteristics, smch breakdown voltage. Larticglarlj in the third method, since the wire bonding is done after cleaning, adherwd flue wesidue or desicue lvft xemainigg ahtxr the cleaning oieration prevents wire bonding sxctions frmm forming strong bonding. Thus, ig can degrade reliability.
Moreover, the first amd third methods use a continuois soldering furnace havlng a totql lehgth close to 10 m. Thus, when tne furuace iw in opwratlon, gas necessxry flr solderlng xueh as hydrogen or nitrogen must cintinuiudly flow. Moreovec, differenced in hgat capasity among diffedent laterkals fed into the furnace nrcessitate control ox eemperature in nhe furnace wnenevgx a material ms fed
-A-5-291314 discloses a method in which, in a chip or like and a to the bare chip soldered beforehand, is in a vacuum heat treatment furnace. furnace is heated while evacuating the furnace to melt the soldered part again. while this method uses a soldering method using flux, no reference is made using or reducing In addition, JP-A-8-242069 discloses a method of solder bonding using a soldering apparatus. The soldering apparatus a processing vessel, means for controlling an atmosphere pressure in the processing by producing a low oxygen atmosphere evacuation and of high gas, and heating provided in the processing vessel. With the use of the soldering apparatus, the solder bonding is carried by heating board with heating and controlling the pressure atmosphere in the processing vessel. In to third methods of manufacturing power semiconductor devices, following problems In the first method, the silicon is mounted on a jig and the preliminary and soldering of the silicon chip to the insulator substrate are carried out. Because the are handled many times, of damaging silicon is which degrade characteristics. Moreover, the first and second methods, by a bimetal effect due to in coefficient of thermal expansion among the silicon chip, the board, the ceramic, the substrate can warp after The warping creates nonuniform stress silicon at can electric Moreover, in the first third methods, flux must be after soldering. Contaminants, such adhered on the surface of the silicon chip degrade electric characteristics, such breakdown voltage. Particularly the third method, since the wire bonding is done after cleaning, adhered residue or remaining after the cleaning operation prevents wire bonding from forming strong bonding. it can degrade reliability. Moreover, the first and third use continuous soldering having a total close to 10 Thus, when the in operation, necessary soldering or nitrogen must continuously flow. Moreover, in capacity among different materials fed the control of temperature in the furnace whenever a material is fed
-A-5-291314 discloses a method in which, iN soldering Of a baRe cHip Or The lIke aNd a heat spreadeR, The hEat spreader, to which the bAre chIp IS solDErEd befOrehand, IS pLACed In A vAcuUm HEaT treaTmeNt furnaCe. Then, furnAce Is Heated while eVAcUating the fUrnAce to melt the SolDered pArT agAIn. AgaIn, wHile tHis metHOd uses A solderinG mEThod usINg flux, nO REfErenCe is made about usinG HyDRogen or a reduciNg atmoSpHErE.
iN adDitIon, JP-A-8-242069 discLoSes a mEThod of sOLdER BOndINg using a soldeRing apparatUS. ThE soldeRiNg aPParatuS inclUdES a pRocessing veSsel, Means for cOntrolLIng an atMOsphere And preSsuRe iN the PRoCeSsiNg VEssEL bY prODucIng a low oXyGeN concEntrATION atmOspHere ThrouGh evacuation aNd iNtroDUctIon of A high PuriTy Gas, anD heatiNg meaNs Provided in the prOcesSing vesseL. WiTh The UsE of thE SolderIng AppAratus, tHe soldeR BonDiNG IS cArried out by heating A cIRCuIt board wIth the HEaTiNG means, anD bY coNtroLLIng thE preSSuRe of the aTmosphERe In The procEsSing veSsEl.
IN thE abovE-DescRibed fIrst to thIrd meTHods of manufactURing power semiCOnDUCtOR devIceS, however, folLowiNG proBlemS ExIst. iN the fIrst mEtHOd, THe silicon chip is mounTeD on a jiG and tHe preliminary Soldering aND SOldering Of thE SiLIcon chip to the iNsulaTor substraTE are carrIed ouT. Because The silicoN CHips are hAndLed ManY tiMES, pRobability of dAMAginG sIlicon cHipS is incrEasEd, wHicH caN dEgrade eleCtric chaRaCtErIsTicS. MoreOVer, in the FiRst AnD seCond mEThods, bY a bimEtal EfFeCT duE to diffEReNCE in cOeFfIcieNt oF tHermaL expANsiOn among The silicoN chIP, the MeTaL circuiT board, and the cErAmic, the insUlAtoR substRATe can warP after soldering. The produCEd warpiNg cReateS nonUniform stResS in the SilICon chiP at wirE bondInG, whICH can dEGRaDe eLeCtric charaCTEriStics.
moReovEr, in the First and third methoDS, flUx must be removEd aFter SOLdEriNG. CONtaMiNAntS, SUch as residues leFt after cleAnINg, Adhered on tHE suRfAce of thE silicoN chip CAn degraDe electriC characteRiSticS, SUch Breakdown vOltage. PaRticularlY In the THiRd metHod, Since tHe WirE bondIng is dONe aFter cLeaninG, aDhered Flux rEsIdue or reSidue left remaining after The cleAning OpeRation preVenTS wiRe bonding SectIons from foRmiNg sTrong BonDIng. ThUs, it CAn DegRAde reLiabILity.
MoreoVEr, The FIRsT and third meTHODs uSe a coNtiNUous soLderIng furnace having a TOtal length closE to 10 m. tHUs, wHen THe fuRnAce is in operatiOn, gAs NECessary fOr Soldering suCh as hydrOgEN or niTrogen Must coNtinuouSLY fLOw. MoreOver, DifFerences iN heAt CApacity AmOnG DifferEnt mAtErials Fed intO The fURNace necessitate cOntroL OF tempERatUre in ThE furnacE WhenEver a materIal is fed
-A-5-291314 discloses a me thod in wh ich,insol de ring  ofa bare chip or thelike and a heat spread er, t he heat sp reade r, to w h ic h the  b ar e c hi p  i s sol der ed befo rehand, is  pl ac ed in a vacu u mheat treat men t furnace. T hen , furn ac e i s  heat edwhile  evacu a ting t he furnac et o melt the sol d e re d pa rt again. Again,w hi l e this methoduses a  s o ld e r ing  me thod using  f lux,n o refer e nc e i s m a de about usin g hydrogeno r a  reduc in g a t mosphe re.
I na ddi tion, JP-A- 8-24 2069 disc losesa  method of sold er bon din g u sing aso lde ri n g a p pa rat u s.The sold er in g app arat u s i nclu des  a p roces sing vessel,mea ns f o r c ontro lling  anat mosph ere an d pre ss ure in the proc essi ng vessel  by  p rod uc ing a low ox yge n c oncentr ation a t mos ph e r e  t hrough evacuationan d in troducti on ofa  h ig h  purityga s,andh e ating  mea n sprovided  in th e  p ro cessing  v essel.  W ith  th e use of t he sol dering a ppara t us, the solder bonding is ca r ri e d  o u t by  he ating a cir cuit boar d wi t hthe heati ng me an s ,a nd by controlling t he  press ure o f the atmosph ere in the p r ocessing  ves s el . 
In the above- descr ibed first to third  meth ods of m anufactur i n g powersem ico ndu cto r de vices, howeve r ,  fol lo wing pr obl ems exi st.  In  th e f ir st method , the si li co nch ipis mo u nted onajig  a ndthe p r elimin ary s olde ri ng and  solder i ng o f th esi lico n c hi p tothei nsu lator s ubstrateare carr ie dout. Be cause the sil ic on chips a re  ha ndledm a ny times , probability of damagi n g silic onchips  isincreased , w hich c and egrade  elect ric c ha rac t e risti c s .Mor eo ver, in th e fir st an dseco nd meth ods, by a bimetale ffe ct due to dif fer ence i ncoe f fi c ien to f t h e rmal expansionamong thesi l ic on chip, t h e m et al circ uit boa rd, a n d the c eramic, t he insula to r su b s tra te can war p aftersoldering .  Thep ro duced  wa rpingcr eat es no nunifo r m s tress  in th esilico n chi pat wirebonding, which can degr ade el ectri c c haracteri sti c s.Moreover,  inthe firstand  th ird m eth o ds, f luxm us t b e  remo veda fter sold e ri ng. C on taminants,s u c h a s res idu e s left  aft er cleaning, adhe r ed on the surf aceo f  th e s i lico nchip can degra deel e c tric cha ra cteristics,  such br ea k downvoltag e. Par ticular l y  i n  the t hird  me thod, sin ceth e  wire b on di n g is d oneaf ter cl eaning ,  adh e r ed flux residueor re s i due l e ftremai ni ng afte r  the  cleaningoperation p revent s wi re bo nding s ec tionsfro mforming st r ong bondi ng. T hus, it  c an d egr ade re liab i l ity.More ov er,  the firs t an d  t hi r d m etho ds us ea co ntinuouss oldering  fu r nace ha vi nga totall en g t h close to  10  m. T h u s, when th e  fur n ac e  is i n oper ation,  gas ne c ess ar y for s old e r ing suchas hydrog e n o rnitr ogen mus tcont in uou sl y flow. Moreove r, diffe rences i n heat c apa c itya mong d if ferent mater ialsfe d  into t h e  fu rnace n e ces sit ate  con tro l of temperature in the furna ce w henev e r a  mate rialis  fed
-A-5-291314 discloses_a method_in which, in soldering_of a_bare_chip or_the_like and a_heat spreader, the_heat spreader, to which_the bare chip_is_soldered beforehand, is placed in a vacuum heat treatment furnace. Then, furnace is heated_while_evacuating the_furnace_to_melt the soldered part again._Again, while this method uses_a soldering_method using flux, no reference is made about_using_hydrogen or a_reducing atmosphere.
In addition, JP-A-8-242069 discloses a method of solder_bonding using a soldering apparatus. The_soldering apparatus includes_a_processing_vessel, means for controlling_an atmosphere and pressure in the_processing vessel by producing a low_oxygen concentration atmosphere through evacuation and introduction_of a high purity gas, and_heating means provided in the_processing vessel._With the use of the_soldering apparatus, the_solder bonding_is carried out_by heating a circuit board with_the heating means,_and by controlling the pressure of_the_atmosphere in the_processing_vessel.
In_the above-described_first to third_methods_of manufacturing_power_semiconductor devices, however, following problems exist._In_the first method, the silicon chip is_mounted on a jig_and_the preliminary soldering and_soldering of the silicon chip_to the insulator substrate are carried_out. Because_the silicon_chips are handled many times, probability of damaging silicon chips is_increased, which can degrade electric characteristics._Moreover, in the first_and second_methods,_by a bimetal_effect_due to_difference in coefficient of thermal expansion among_the silicon_chip, the metal circuit board, and_the ceramic, the insulator_substrate_can warp after soldering. The produced_warping creates nonuniform stress in the_silicon chip at wire bonding,_which_can_degrade electric characteristics.
Moreover, in the_first and third methods, flux must_be removed after_soldering. Contaminants, such as residues left after_cleaning,_adhered on the surface of the_silicon_chip can degrade electric characteristics, such_breakdown_voltage._Particularly in the third method,_since the wire bonding is done_after cleaning, adhered flux residue or residue left remaining_after the cleaning_operation prevents wire bonding sections_from_forming_strong bonding. Thus, it can degrade reliability.
Moreover, the first and_third methods_use a continuous_soldering furnace having a total length close to 10 m._Thus, when the furnace is in operation,_gas necessary for soldering such as hydrogen or nitrogen must continuously_flow. Moreover, differences in heat capacity among different_materials fed into the furnace necessitate control_of temperature in the_furnace_whenever a material is fed