利用电阻场板提高SOI-LIGBT的性能英文.

1、第23卷第10期半导体学报Vol. 23,N o. 10 2002 年 10 月CHI NESE JOURNA L OF SE MIC ONDUCT ORSOct. , 20023P rojcet supp orted by Nati onal Natural Scie nee F oun datio n of China (N o.69776041Y ang H on gqia ng male ,was born in 1974, PhD can didate. H is research lies inthe field of S OI ,po wer device ,and po wer

2、 ICs. Han Lei male ,was born in 1968 ,PhD can didate. He is in terested in po wer device and smart po wer IC.Chen X in gbimale ,was born in 1931,academicia n of The Chin ese Academy ofScie nces. H is curre nt research in cludes po wer devices ,smart po wer ICs and de 2vice p hysics.Received 8Februar

3、y 2002,revised manu scri pt received 26A pril 2002c 2002The Chin ese In stitute of E lectro nics Impro veme nt of E lectrical P erform ance of SOI 2LIGBTby R esistive Field P late 3Y ang H on gqia ng , Han Lei and Chen Xingbi(In stitute o f Micro 2Electr onics and Solid 2Electr onics , Uni ver sity

4、o f Electr onicScie nee and Tech no logy , Che ngdu 610054, Chi naAbstract :The electrical p erforma nee in cludi ng breakdow n v oltage and turn 2off sp eed of S OI 2LIG BT is imp roved by incorpo rati ng a resistive field plate (RFP and a p2M OSFET. The p 2M OSFET is con trolled by a sig nal detec

5、ted from a poi nt of the RFP.Duri ng the turni ng 2off of the IG BT ,the p 2M OSFET is turned on ,which p rovides a cha nnel for the excessive carriers to flow out of the drift re 2gi on and p reve nts the carriers from being injected into the drift regi on. At the same time ,the electric field affe

6、cted by the RFP makes the excessive carriers flow through a wider regi on ,which alm ost elim in ates the sec ond p hase of the turni ng 2off of the S OI 2LIG BT caused by the substrate bias. Faster turn 2off sp eed is achieved by above tw o factors. During the on state of the IG BT ,the p 2M OSFET

7、is off ,which leads to an on 2state p erforma nee like no rmal one. At least ,the in crease of the breakdow n v oltage for 25%a nd the decrease of the turn 2off time for 65%ca n be achieved by this structure as can be verified by the nu merical simulati on re 2sults.K ey w ords :resistive field plat

8、e ; dyn amic con trolled anode 2short ; tur n 2off time ;breakdow n v oltage ; forward v oltage drop EEACC :1210; 2560CLC number :T N386Docume nt code :AArticle ID :025324177(2002 10210142051 I n troduct ionP ower device is widely used in differe nt fields. But the con tradictive relatio nship am on

9、g the on 2state po wer diss ip ati on , breakdow n v oltage , and switchi ng sp eed re 2stricts its use in m ost situati ons. F or exam pie ,it is always a p roblem that the long time take n to turn off an IG BT can not be reduced without affect ing the other characteristics sig nifica ntly. S ome s

10、 oluti ons ,for exam pie ,anode 2short ,mi 2no rity 2carrier 2lifetime 2con trol , etc , have bee n put forwardto res olve the p roblem of IG BT. The tech nique of anode 2short is the m ost effective on e. It can reduce the turn 2off time by p reve nti ng the injectio n of the carriers and p rovid 2

11、ing a way for the excessive carriers to disa pp ear m ore quickly. But there is still a drawback that the anode 2short structure will decrease the efficie ncy of carrier injectio n duri ng on 2state , which causes the forward v oltage drop much lower. Finding a new structure that can im prove the wh

12、ole p erforma nee of IG BT will be great valuable.Differe nt s oluti ons for above p roblem are described based on the dyn amic con trolled anode 2short. Neverthe 2less ,am ong these methods , s ome are un fit for susta ining high v oltage 1, s ome n eed com p licated driv ing cir 2cuits 2,3, and s

13、ome can only be used in a sp ecial cir 2cuits 4. S ome new structures yieldi ng better p erforma nee with the same driv ing circuits of a conven ti onal IG BT are exp ected. That is the purp ose of this paper.2 Theoretical an alysisThe m ost im p orta nt p arts of the new structure of IG 2BT prop os

14、ed are the RFP and the p 2M OSFET , whose s ource and drain are conn ected to the anode and bu ffer re 2gi on of the IG BT ,res pectively. The p 2M OSFET acts as a dyn amic anode 2short structure and is con trolled by the sig nal detected from a point of the RFP ,in other w ords , con trolled by the

15、 anode v oltage in directly since the RFP is conn ected to the cathode and ano de. A schematic diagram of the new structure of S OI 2LIG BT is show n in Fig. 1,i n which K,G and A are the electrodes of cathode ,gate and anode of a conven ti onal LIG BT.G 1is the gate used for dyn amic con trolled an

16、ode 2short. R L is the load resistor5RlG110 3040p-niGnmndofFig. 1 Schematic diagram of the new structure IG BT (shadow regi on sta nds for oxide or RFPIG BT. C om pared to a normal IG BT ,a n additio nal p 2M OS 2FET is in this structure. Whe n the IG BT is in the on state , the differe nee of the e

17、lectrical poten tial betwee n the anode and the cathode takes the mi nimum value ,which causes mi nimum gate v oltage of G 1. The n the p 2M OSFET will be off ,and the anode 2short structure will sto p w orking. Theon 2state po wer diss ip ati on of the IG BT mai ntai ns a very small value. During t

18、he course of turning 2off ,the poten tial differe nee betwee n the anode and the cathode in creases with the in crease of anode v oltage. Whe n the anode v olt 2age reaches a critical value ,the p 2M OSFET will be turned on ,which p reve nts the injectio n of the carriers and makes the excessive car

19、riers of the base regi on disa pp ear m ore quickly.The n a faster turn 2off sp eed is achieved.It is n ecessary to point out that there are three p has 2es in the turning 2off of a no rmal S 01 2LIG BT ,and the sec 2ond p hase caused by the substrate bias is an additi onal part com p ared to a no r

20、mal IG BT 5. In our new structure , the electric field affected by the RFP makes the excessive carriers flow through a wider regi on ,which alm ost elimi 2n ates the sec ond p hase. Faster turn 2off sp eed is achieved.It is im p orta nt to decide the point from which the gate v oltage of G 1is detec

21、ted ,in other w ords ,the ratio of the len gth of the RFP at the right of this point to that of the total ,si nee either the on 2or off 2state of the p 2M OS 2FET is decided by it. A too large value of the ratio leads to a higher v oltage tha n the threshold v oltage of the p 2MOSFET all the time ,w

22、hich makes the p 2M OSFET be al 2ways in its on 2state. The n the anode 2short structure always w orks ,and the IG BT has a higher forward v oltage drop.On the other hand ,too small a value of the ratio can not turn on the p 2M OSFET duri ng the turni ng 2off of the IG BT , which leads to a turn 2of

23、f time just like the no rmal one. S o ,the com pro mise betwee n the forward po wer diss ip ati on and the turn 2off time should be con sidered.3 Simulatio n an alysisT M A/ME DICI 7is used for simulatio n to verify the validation of the theoretical an alysis in the part tw o. The new structure for

24、simulati on is show n in Fig. 1,which in 2dicates the dime nsional p arameters. The other p arameters are give n in T able 1.Differe nt values of L 1are give n to achieve the op timum result by con sideri ng the tradeoff of the turn 2on p erforma nee and the turn 2off sp eed. The nor 2mal IG BT is j

25、ust the same as the new structure without the10110 期 Y ang H ongqing et al. : Im provement of E lectrical Performanee of S 01 2LIG BTRFP and the p 2M OSFET ,and the p arameters are the opti 2mum ones for the no rmal IG BT. Both of the new and the no rmal structure are simulated.T able 1 P arameters

26、for simulati onP arametersValues Unit C oncen trati on of n substrate 15-3C oncen tratio n of n 2drift 15-3C oncen tratio n of n 2bu ffer 17-3+20-3C oncen trati on of cha nnel regi on 17-3Threshold v oltage of p2M OSFET6VThick ness of the gate oxide011 卩 m Distanee from the detected point to the rig

27、ht of the RFP (L115,2,215卩 m T otal length of the RFP 302V 250V G ate v oltage V G 15VH igh injeetio n lifetime20The curves of the turn 2on and turn 2off corres ponding to differe nt values of L 1by simulati on are show n in Figs. 2and 3. From the figures ,the con clusi on can be draw n thatlarger L

28、 1leads to poorer turn 2on p erforma nee but explan ati on of the turn 2on and turn 2off mecha nism.faster turning 2off. The case of L 1=2卩 m is taken as an ex 2am pie to give theFig. 2 Turn 2on curves S olid line :new structure ;Dash line :nor mallG BTThe poten tial differe nee betwee n the gate G

29、land the an 2ode A ,the s ource of the p 2M OSFET ,versus time duri ng the turni ng 2on and turni ng 2off is show n in Fig. 4(a andFig. 3 Turn 2off curves S olid line :new structure ;Dash line :normallG BTFig. 4 (a P ote ntial differe nee betwee n the gate G land the an 2ode duri ng the course of tu

30、rni ng 2on ; (b P ote ntial differe nee be 2twee n the gate G land the anode duri ng the course of turning 2off(b . Accord ing to Fig. 4(a , the poten tial differe nee is larger tha n the threshold v oltage of the p 2M OSFET before the time of 715 ns ,which turns on the p 2M OSFET ,s o the IG BT w o

31、rks in anode 2short m ode ,and the anode curre nt is smaller tha n that of a normal IG BT. A fter that ,the v oltage added on G Idecreases ,the p 2M OSFET is not in its on 2state any m ore ,which makes the anode curre nt rise to the level as no rmal. The degradati on of the turn 2on p erfor 2ma nee

32、can be n eglected since the differe nee betwee n the6101半导体学报23卷turning on of the new structure and that of the no rmal IG 2BT is very small (in Fig.1,the curves of the no rmal caseand that of L 1=115 卩 m alm ost overlap .A fter the turni ng on ,the IG BT reaches its on 2state. Accord ing to the res

33、ults ofsimulatio n ,the values of the forward v oltage drop for the new structure and the normalIG BT are the same ,which are 1143V ,while the values of the anode curre nt both equal to112429A/ 卩 m. This is the precondition for com paring the turn 2off course of the tw ostructures of IG BT.Figure 4(

34、b shows the poten tial differe nee betwee n the gate G 1and the anode duri ngthe course of turning 2off. Duri ng the period of 0to 112卩 s ,the v oltage added on G 1is smaller than the threshold v oltage of the p 2M OS2FET. The excessive carriers of the drift regi on disa pp ear in the no rmal way. T

35、he newstructure does not affect the turning 2off. But after that ,the gate v oltage of G 1is higherthan the threshold v oltage ,and g oes on in creas ing with the time. The cha nnel of the p2M OSFET is gen erated ,which acts as an anode 2short structure of the IG BT. S o ,fromthe n on ,the excessive

36、 carriers disa pp ear faster ,and the anode curre nt will decrease tozero s oon. There is no m ore a long tail in the turn 2off curve ,which makes the turn 2offtime of the device decrease sig nifica ntly.As it is well 2known the in troduci ng of an RFP can im prove the breakdow n v oltageof the LIG

37、BT. The break 2dow n v oltage of 320V is achieved for the new structure whileon ly 257V for the no rmal structure.4 Discussi on and con clusi onI f there is no dielectric in sulator betwee n the IG BT and the p 2M OSFET ,in otherw ords ,the anode of the IG BT and the s ource of the p 2M OSFET are co

38、rres ponding tothe same p +2regi on ,and the drain of the p 2M OSFET lies in the n 2bu ffer regi on ,thep arasitic tran sistor p +(a node n(n 2bu ffer p +(the additi onal p +2regi on will w ork as a recomb in ati oncen ter ,which reduces the concen trati on of the excessive carriers of the n 2bu ffe

39、rregi on ,the n leads to a higher forward v oltage drop while it is in on 2state. I f theabove drawback is acce pted , the new structure can be used in bulk silic on device aswell as in S 01 device ,and fewer additi onal requireme nts for the fabricati on are n eed 2ed.The p arameters for simulatio

40、n are the op timum ones for the no rmal IG BT asdescribed in part 3,a nd it is m ore im pers onal to show the adva ntage by com paring thenew structure with an op timized no rmal IG BT. A great im 2pro veme nt of thep erforma nee of the IG BT was achieved accord ing to the results of simulatio n. Tu

41、rn 2offtime de 2creases for about 65%a nd breakdow n v oltage in crease for 25%,while on 2statep erforma nee is alm ost the same as the no rmal.In order to con sider the p erforma nee of the new structure once the p arameters arecha nged ,tw o situati ons are simulated :(1 Decrease the im p urity co

42、ncen tratio n of thedrift regi on and the injectio n efficie ncy ; (2 In crease both of them. When the values of theconcen trati on of the drift regi on and the anode regi on are 21014cm -3a nd 1 Xxi019cm -3, the values of the breakdow n v oltage are 212V and 299V for theno rmal IG BT and new struct

43、ure , res pectively ,in creas ing about 40%,a nd the values oftheturn 2off time are 0145卩 s and 0115 卩 s , decreasing about 66%.When the values of the concentration of thedrift re 2gi on ,the anode regi on and the bu ffer regi on are 51015,1X1020a nd 1 W16cm -3,the values of the breakdow n v oltage

44、are 70 V and430V ,in creasi ng about 500%,a ndthe values of the turn 2off time are 30 卩 s and 1 卩 s ,decreas 2ing about 96%.Obviously ,the im provement of thsr perf2ma nee is m ore sig nifica ntly after vary ing the p arameters , while the p erforma nee of theno rmal IG BT degrades much. R efere nce

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