利用电阻场板提高SOILIGBT的性能英文.docx

1、利用电阻场板提高SOILIGBT的性能英文第23卷第10期半导体学报Vol. 23,N o. 102002年10月CHI NESE JOURNA L OF SE MIC ONDUCT ORSOct. , 20023Projcet supported by National Natural Science F oundation of China (N o. 69776041Y ang H ongqiang male ,was born in 1974,PhD candidate. H is research lies in the field of S OI ,power device ,an

2、d power ICs. Han Lei male ,was born in 1968,PhD candidate. He is interested in power device and smart power IC.Chen X ingbi male ,was born in 1931,academician of The Chinese Academy of Sciences. H is current research includes power devices ,smart power ICs and de 2vice physics.Received 8February 200

3、2,revised manuscript received 26April 2002c 2002The Chinese Institute of E lectronics Improvement of E lectrical Perform ance of SOI 2LIGBTby R esistive Field Plate 3Y ang H ongqiang , Han Lei and Chen Xingbi(Institute o f Micro 2Electronics and Solid 2Electronics , Univer sity o f Electronic Scienc

4、e and Technology , Chengdu 610054, China Abstract :The electrical performance including breakdown v oltage and turn 2off speed of S OI 2LIG BT is improved by incorporating a resistive field plate (RFP and a p 2M OSFET. The p 2M OSFET is controlled by a signal detected from a point of the RFP. During

5、 the turning 2off of the IG BT ,the p 2M OSFET is turned on ,which provides a channel for the excessive carriers to flow out of the drift re 2gion and prevents the carriers from being injected into the drift region. At the same time ,the electric field affected by the RFP makes the excessive carrier

6、s flow through a wider region ,which alm ost eliminates the second phase of the turning 2off of the S OI 2LIG BT caused by the substrate bias. Faster turn 2off speed is achieved by above tw o factors. During the on state of the IG BT ,the p 2M OSFET is off ,which leads to an on 2state performance li

7、ke normal one. At least ,the increase of the breakdown v oltage for 25%and the decrease of the turn 2off time for 65%can be achieved by this structure as can be verified by the numerical simulation re 2sults.K ey w ords :resistive field plate ; dynamic controlled anode 2short ; turn 2off time ; brea

8、kdown v oltage ; forward v oltage drop EEACC :1210; 2560CLC number :T N386Document code :A Article I D :025324177(2002 10210142051I ntroductionP ower device is widely used in different fields. But the contradictive relationship am ong the on 2state power dissipation , breakdown v oltage , and switch

9、ing speed re 2stricts its use in m ost situations. F or exam ple ,it is always a problem that the long time taken to turn off an IG BT can not be reduced without affecting the other characteristics significantly. S ome s olutions ,for exam ple ,anode 2short ,mi 2nority 2carrier 2lifetime 2control ,

10、etc , have been put forwardto res olve the problem of IG BT. The technique of anode 2short is the m ost effective one. It can reduce the turn 2off time by preventing the injection of the carriers and provid 2ing a way for the excessive carriers to disappear m ore quickly. But there is still a drawba

11、ck that the anode 2short structure will decrease the efficiency of carrier injection during on 2state , which causes the forward v oltage drop much lower. Finding a new structure that can im prove the whole performance of IG BT will be great valuable.Different s olutions for above problem are descri

12、bed based on the dynamic controlled anode 2short. Neverthe 2less ,am ong these methods , s ome are un fit for sustaining high v oltage 1, s ome need com plicated driving cir 2cuits 2,3, and s ome can only be used in a special cir 2cuits 4. S ome new structures yielding better performance with the sa

13、me driving circuits of a conventional IG BT are expected. That is the purpose of this paper.2Theoretical analysisThe m ost im portant parts of the new structure of IG 2BT proposed are the RFP and the p 2M OSFET , whose s ource and drain are connected to the anode and bu ffer re 2gion of the IG BT ,r

14、espectively. The p 2M OSFET acts as a dynamic anode 2short structure and is controlled by the signal detected from a point of the RFP ,in other w ords , controlled by the anode v oltage indirectly since the RFP is connected to the cathode and anode. A schematic diagram of the new structure of S OI 2

15、LIG BT is shown in Fig. 1,in which K,G and A are the electrodes of cathode ,gate and anode of a conventional LIG BT. G 1is the gate used for dynamic controlled anode 2short. R L is the load resistor ofFig. 1Schematic diagram of the new structure IG BT (shadow region stands for oxide or RFP IG BT. C

16、om pared to a normal IG BT ,an additional p 2M OS 2FET is in this structure. When the IG BT is in the onstate , the difference of the electrical potential between the anode and the cathode takes the minimum value ,which causes minimum gate v oltage of G 1. Then the p 2M OSFET will be off ,and the an

17、ode 2short structure will stop w orking. Theon 2state power dissipation of the IG BT maintains a very small value. During the course of turning 2off ,the potential difference between the anode and the cathode increases with the increase of anode v oltage. When the anode v olt 2age reaches a critical

18、 value ,the p 2M OSFET will be turned on ,which prevents the injection of the carriers and makes the excessive carriers of the base region disappear m ore quickly. Then a faster turn 2off speed is achieved.It is necessary to point out that there are three phas 2es in the turning 2off of a normal S O

19、I 2LIG BT ,and the sec 2ond phase caused by the substrate bias is an additional part com pared to a normal IG BT 5. In our new structure , the electric field affected by the RFP makes the excessive carriers flow through a wider region ,which alm ost elimi 2nates the second phase. Faster turn 2off sp

20、eed is achieved.It is im portant to decide the point from which the gate v oltage of G 1is detected ,in other w ords ,the ratio of the length of the RFP at the right of this point to that of the total ,since either the on 2or off 2state of the p 2M OS 2FET is decided by it. A too large value of the

21、ratio leads to a higher v oltage than the threshold v oltage of the p 2M OSFET all the time ,which makes the p 2M OSFET be al 2ways in its on 2state. Then 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

22、 not turn on the p 2M OSFET during the turning 2off of the IG BT , which leads to a turn 2off time just like the normal one. S o ,the com promise between the forward power dissipation and the turn 2off time should be considered.3Simulation analysisT M A/ME DICI 7is used for simulation to verify the

23、validation of the theoretical analysis in the part tw o. The new structure for simulation is shown in Fig. 1,which in 2dicates the dimensional parameters. The other parameters are given in T able 1. Different values of L 1are given to achieve the optimum result by considering the tradeoff of the tur

24、n 2on performance and the turn 2off speed. The nor 2mal IG BT is just the same as the new structure without the510110期Y ang H ongqing et al. :Im provement of E lectrical Performance of S OI 2LIG BT RFP and the p 2M OSFET ,and the parameters are the opti 2mum ones for the normal IG BT. Both of the ne

25、w and the normal structure are simulated.T able 1Parameters for simulationParametersValues Unit C oncentration of n substrate 15-3C oncentration of n 2drift 15-3C oncentration of n 2bu ffer 17-3+20-3C oncentration of channel region 17-3Threshold v oltage of p 2M OSFET6VThickness of the gate oxide011

26、m Distance from the detected point to the right of the RFP (L 115,2,215m T otal length of the RFP 30m R L2 M /mV 250V G ate v oltage V G 15VH igh injection lifetime20sThe curves of the turn 2on and turn 2off corresponding to different values of L 1by simulation are shown in Figs. 2and 3. From the fi

27、gures ,the conclusion can be drawn that larger L 1leads to poorer turn 2on performance butfaster turning 2off. The case of L 1=2m is taken as an ex 2am ple to give the explanation of the turn 2on and turn 2off mechanism.Fig. 2Turn 2on curves S olid line :new structure ;Dash line :normalIG BTThe pote

28、ntial difference between the gate G 1and the an 2ode A ,the s ource of the p 2M OSFET ,versus time during the turning 2on and turning 2off is shown in Fig. 4(a andFig. 3Turn 2off curves S olid line :new structure ;Dash line :normalIG BTFig. 4(a P otential difference between the gate G 1and the an 2o

29、de during the course of turning 2on ; (b P otential difference be 2tween the gate G 1and the anode during the course of turning 2off(b . According to Fig. 4(a , the potential difference is larger than the threshold v oltage of the p 2M OSFET before the time of 715ns ,which turns on the p 2M OSFET ,s

30、 o the IG BT w orks in anode 2short m ode ,and the anode current is smaller than that of a normal IG BT. A fter that ,the v oltage added on G 1decreases ,the p 2M OSFET is not in its on 2state any m ore ,which makes the anode current rise to the level as normal. The degradation of the turn 2on perfo

31、r 2mance can be neglected since the difference between the6101半导体学报23卷turning on of the new structure and that of the normal IG 2BT is very small (in Fig. 1,the curves of the normal caseand that of L 1=115m alm ost overlap .A fter the turning on ,the IG BT reaches its on 2state. According to the res

32、ults of simulation ,the values of the forward v oltage drop for the new structure and the normal IG BT are the same ,which are 1143V ,while the values of the anode current both equal to 112429A/m. This is the precondition for com paring the turn 2off course of the tw o structures of IG BT.Figure 4(b shows the potential difference between the gate G 1and the anode during the course of turning 2off. During the period of 0to 112s ,the v oltage added on G 1is smaller than the threshold v oltage