EE415/515 Fundamentals of Semiconductor Devices Fall 2012

Transcription

1 090 EE4555 Fudaetals of Seicoductor evices Fall 0 ecture : MOSFE hapter 0.3, J. E. Morris Reider: Here is what the MOSFE looks like

2 090 N-chael MOSFEs: Ehaceet & epletio odes 090 J. E. Morris 3 P-chael MOSFEs: Ehaceet & epletio odes 090 J. E. Morris 4

3 090 riode operatio at sall : Space chare reios arrier ijectio duced iversio oducti chael = as 0 =µ Q 090 J. E. Morris J. E. Morris 6 3

4 090 creasi : Oset of saturatio 090 J. E. Morris 7 creasi : Oset of saturatio At the saturatio poit: - sat= i.e. sat= - Note space chare reio at drai i saturatio. E-field sweeps carriers across. Appriatio: Assue << sat costat. 090 J. E. Morris 8 4

5 090 N-chael MOSFE characteristics: Note o-liear triode reio See later : where k k ad K saturatio : 090 J. E. Morris 9 k K is the process coductio paraeter is the coductio paraeter N-chael depletio ode 090 J. E. Morris 0 5

6 090 - haracteristics Oh's aw :, E J E y z E e e E J dydz Q E y y dy costat alo chael 090 J. E. Morris - haracteristics: hare eutrality Q Q ss Q Q S a J. E. Morris 6

7 090 - haracteristics: Gauss s aw E ds E s Q i. e. E Q ss Q ss Q Q d Q S Q a d S a 090 J. E. Morris 3 - haracteristics: Oide field is chael potetial wrt S at 090 J. E. Morris 4 7

8 haracteristics: Oide field 090 J. E. Morris 5 for iversio usi s s s F Fp e E e e E E S ss S ss s d d d d Q E Q Q Q Q Q t t E So a a Hece : - haracteristics: Fial equatios 090 J. E. Morris 6, sat sat sat sat For whe 0 & sat Ma where sat ad for d d d d

9 090 E 0.7 N-chael Si MOSFE: µ =650c -s, t =8, =, =0.40. Fid the drai curret for a =0.8, b =., & c =.6, if the trasistor is biased i the saturatio reio. 090 J. E. Morris 7 & 090 J. E. Morris 8 9

10 090 E 0.8 N-chael Si MOSFE: =6µ, =.5µ, t =8. he the trasistor is biased i the saturatio reio, the drai curret is sat=0.3a at =.0 ad sat=0.95a at =.5. eterie the electro obility ad threshold voltae. 090 J. E. Morris 9 P-chael p for 0 sat p sat for sat S S S S SG SG S S 090 J. E. Morris 0 0

11 090 rascoductaces 090 J. E. Morris : : reio Saturatio riode reio

12 090 How about i saturatio? sat= G - Sae idea, but we ow use sat eq is?? is quadratic fuctio of G Z sat i sat Z sat i sat by plotti vs. G we should et a straiht lie see fi hat does itersectio of this lie with G ais ive? Slope of the curve k N Proble: saturatio values of ad k N ot the sae as liear reio values! Substrate bias effect So far assued substrate at zero source potetial SB 0 B < 0 Space chare reio width icreases. cr -ve chare icr +ve ate chare icrease. 090 J. E. Morris 4

13 090 Q SB SB S 0 Q 0 Q Q e N e N S s S S s a a Substrate bias effect: Body effect coefficiet a en en SB where is the body effect coefficiet a d SB SB a d e N s e N a s a SB 090 J. E. Morris 5 E 0.9 N-chael Si MOSFE: N a =0 6 c 3, t =. Fid a body effect coefficiet, & b the chae i for a SB = & b SB =. 090 J. E. Morris 6 3

14 090 Hih frequecy effects 090 J. E. Morris 7 4

15 090 Sall sial equivalet circuit d = ds + dsp s = s + sp 090 J. E. Morris 9 Siplified sall-sial odels r s, r d elected r ds elected s = s + s r s =+ r s s 090 J. E. Morris 30 5

16 090 6 utoff frequecy hael trasit tie v sat ot usual liitatio 090 J. E. Morris 3 d s d s s d d s i s d d s d d s d s s i R R j R j R j j R j j for 0 : Output : put utoff frequecymiller capacitace 090 J. E. Morris 3 G M s M s i s M s i j d s d at d M s M s s d s i R j R j where d f So & 0 saturatio : G s

17 090 E 0.0 N-chael Si MOSFE: µ =40c -s, t =8, =.µ, =4µ, =0.40. Fid the cutoff frequecy if the trasistor is biased i the saturatio reio at = J. E. Morris 33 MOS structures 090 J. E. Morris 34 7

18 090 MOS iverter Note p + p + structure 090 J. E. Morris 35 MOS p + p + structure: atch-up 090 J. E. Morris 36 8

19 090 Gate ide tueli ie-depedet dielectric breakdow 9