MOS is in charge of working principle animation

 

The grid that insulation field effect is in charge of and source extremely, grid is mixed segregation of SiO2 insulation layer all is used between leakage pole, get a name because of this. It is metallic aluminium because of grid again, reason calls MOS canal again. Its grid – the resistor between source pole is gotten greatly than canal of knot field effect much, can amount to 1010Ω above, because it compares knot field effect,still provide temperature stability good, compositive the temperature when changing is simple, and apply extensively at large-scale with VLSI in.

 

 

As identical as canal of knot field effect, sketch map of animation of principle of MOS canal job also has N raceway groove and P raceway groove two kinds, but each kinds are divided again to increase model and extinct model two kinds, 4 kinds of kinds that accordingly MOS provides are: N raceway groove increases model raceway groove of canal, N is extinct model raceway groove of canal, P increases model raceway groove of canal, P is extinct model canal. Every grid – UGS of source pole voltage is zero hour leakage pole electric current all also is belonged to for the pipe of 0 increase model canal, every grid – UGS of source pole voltage is zero hour leakage pole electric current all is not belonged to for the pipe of 0 extinct model canal.

 

 

According to electric means different, MOSFET is divided again increase model, extinct model. Alleged increase model it is to point to: When VGS=0 pipe is to show off-state, after adding correct VGS, majority carries stream child be attracted grid, thereby “ enhances ” of this area carry stream child, form electric raceway groove.

 

 

 

N raceway groove increases model the develop that MOSFET basically is a kind of or so semmetry attacks structure, it is layer of insulation of film of a SiO2 is built on P semiconductor, diffuse with photoetching craft next the N of two tall adulteration area, from N area derivative electrode, one is leakage pole D, one is source pole S. source pole is mixed aluminium of a metal regards the plating on the insulation layer between leakage pole as grid G.

 

When VGS ＝ 0 V, two back-to-back diode comparatives between leakage source, electrify pressing is added to won’t form electric current between D, S between D, S.

 

Add when grid when having voltage, when be like VGS(th) of ＜ of 0 ＜ VGS, carry the action of capacitance electric field that forms between grid and underlay, in the P that will approach grid lower part semiconductor much child hole repels to lower part, appeared the depletion layer of one layer anion; Will attract at the same time among them little child move to surface layer, but the amount is limited, can’t form electric raceway groove, will leakage pole is mixed source pole is communicated, still can’t form ID of leakage pole electric current so.

 

Increase VGS further, when VGS ＞ VGS(th) (VGS(th) calls open voltage) , had compared as a result of right now grid voltage strong, more electron gathers in surface layer of the P that approachs grid lower part semiconductor, can form raceway groove, will leakage pole is mixed source pole is communicated. If increase tension of source having leakage right now, can form ID of leakage pole electric current. The electron in the electric raceway groove that forms in grid lower part, because of with P semiconductor carry stream child hole polarity is contrary, reason is called instead model layer. Increase as VGS continuity, ID will increase ceaselessly. In ＝ of the ID when VGS ＝ 0V 0, just can appear after VGS ＞ VGS(th) only leakage pole electric current, so, canal of this kind of MOS is called increase model MOS canal.

 

VGS is right the control relation of leakage pole electric current can use ID ＝ F(VGS(th)) | This one curve describes VDS=const, call move character curve, animation of principle of MOS canal job sees a picture 1. .

 

The size of the slope Gm that transfers characteristic curve mirrorred bar source voltage to be opposite the control action of leakage pole electric current. The dimension of Gm is MA/V, so Gm also is called cross guide. Cross guide.

 

Graph 1. Transfer characteristic curve

 

2—54 of animation of principle of MOS canal job (A) increase for N raceway groove model graph of animation of principle of MOS canal job, its circuit symbol is like graph 2—54 (B) be shown. It is to use the P with an impure inferior chroma silicon chip to serve as underlay, use diffusion technique to diffuse on underlay N of two tall impure pH indicator area (express with N+ ) , go up in this N area derivative electrode of two ohmic contacts, call source pole respectively (express with S) with leakage extremely (express with D) . The underlay surface between source area, leakage area enclothes silicon of a 2 oxidation (SiO2) insulation layer, on this insulation layer deposit gives metallic aluminous layer and derivative electrode serves as grid (express with G) . From underlay derivative electrode of an ohmic contact calls underlay electrode (express with B) . Because be of mutual insulation between grid and other electrode, say it is in charge of for effect of insulation bar field so. 2—54 of graph of animation of principle of MOS canal job (A) medium L is raceway groove length, w is raceway groove width.

 

The MOSFET that graph 2—54 place shows, mix when grid G any tension are not increased between source pole S, namely UGS=0

 

When, because leakage pole is mixed,the interval of two N+ area has source pole P underlay, be equivalent to two back carrying connective PN on the back to written guarantee, the resistor between them is as high as the quantitative class of 1012W, electric raceway groove is not had between D, S that is to say, why to no matter be added between leakage, source pole,plant so the voltage of polarity, won’t produce ID of leakage pole electric current.

 

When underlay B and source extremely S weak point is received, mix in grid G positive electricity is added to press between source pole S, namely UGS ﹥ 0 when, 2—55 of graph of animation of principle of MOS canal job (A) be shown, produce an electric field that points to underlay by grid between grid and underlay. Below the action of this electric field, the cavity near P underlay surface will is down square motion by repulsion, the attraction that the electron gets electric field moves to underlay surface, the cavity with underlay surface is compound, formed a depletion layer. If heighten UGS tension further, when making UGS achieves some voltage UT, the cavity in layer of P underlay surface is repelled entirely and extinct, and free electron abundantly is attracted exterior layer, arrive by quantitative change qualitative change, make exterior layer became free electron to be much child N layer, call “ to turn over model layer ” , 2—55 of graph of animation of principle of MOS canal job (B) be shown. Instead model the layer will leak extremely D is mixed source pole S photograph of two N+ area connects, formed the N between leakage, source pole electric raceway groove. Call the UGS value that begins to form place of electric raceway groove to need threshold value voltage or open voltage, express with UT. Apparent, only the ability when UGS ﹥ UT has raceway groove, and UGS is bigger, raceway groove is thicker, of raceway groove guide electrify block is jumped over small, electric capability is stronger. Why do this call it namely increase model cause.

 

Below the condition of UGS ﹥ UT, if be in,leakage pole D is mixed positive electricity is added to press UDS between source pole S, electric raceway groove can have electricity current. Leakage pole electric current flows to source area by leakage area, because raceway groove has certain resistance, produce voltage drop along raceway groove so, the potential edge raceway groove that makes raceway groove is nodded each is chased to source area by leakage area reduce gradually, the voltage UGD that nears leakage area one end is the smallest, its value is UGD=UGS – UDS, corresponding raceway groove is the thinnest; The voltage that nears source area one end is the biggest, be equal to UGS, corresponding raceway groove is the thickest. Make so raceway groove ply is even no longer, whole raceway groove is shown tilt shape. As the accretion of UDS, the raceway groove that nears leakage area one end is thinner and thinner.

 

 

 

 

 

Increase some when UDS critical value, make when UGD≤UT, the raceway groove that leakage carries disappears, go depletion layer only, call this kind of situation raceway groove “ places ” beforehand, 2—56 of graph of animation of principle of MOS canal job (A) be shown. Continue to increase UDS(namely UDS ＞ UGS – UT) , place breakpoint direction of Xiang Yuan pole is mobile, 2—56 of graph of animation of principle of MOS canal job (B) be shown. Although place breakpoint to be in,move, but raceway groove area (source pole S arrives clip breakpoint) voltage drop keeps changeless, still be equal to UGS – UT. Accordingly, voltage of UDS spare part [UDS – (UGS – UT)] falls to place an area to go up entirely, break in clip stronger electric field is formed inside the area. At this moment electronic edge raceway groove from the source extremely flow direction places an area, when the electron arrives at clip to break area brim, suffer the effect that places area strong electric field, very can fast drift arrives leakage pole.

 

Extinct model. Extinct model it is to point to, form raceway groove namely when VGS=0, when adding correct VGS, can make majority carries stream child pour out of raceway groove, “ is consequently extinct ” carry stream child, make pipe changes direction end.

 

Extinct model canal of MOS field effect, it is to be in production process, enter in the mix into in SiO2 insulation layer beforehand many ionic, accordingly, when UGS=0, these the electric field of ionic generation also can give enough electron in ” of induction of the “ in P underlay, form N electric raceway groove.

 

When UDS>0, will produce bigger leakage extremely voltaic ID. If make UGS<0, criterion it will be weakened the electric field that ionic place forms, make narrow of N raceway groove, make ID is reduced thereby. When UGS more negative, the raceway groove when reaching some numerical value disappears, ID=0. Make we also call the UGS of ID=0 clip breaks tension, still express with UP. UGS

 

N raceway groove is extinct model the structure of MOSFET and increase model MOSFET structure is similar, differred only, it is N raceway groove extinct model MOSFET is when grid voltage UGS=0, raceway groove has existed. This N raceway groove is to making law of infuse of ion of the application in the process be in beforehand the surface of underlay, make between D, S, say for initiative raceway groove. N raceway groove is extinct model the structure of MOSFET and symbol are in charge of working principle animation like MOS 1. (A) be shown, it is the SiO2 in grid lower part the mix into in insulation layer entered many metal ionic. Become so VGS ＝ 0 when, these ionic already the induction goes out instead model layer, formed raceway groove. Then, want to have leakage source voltage only, leakage pole electric current exists. When VGS ＞ 0 when, will make ID increases further. VGS ＜ 0 when, as VGS reduce leakage pole electric current gradually, till ID ＝ 0. The VGS of 0 calls corresponding ID ＝ clip breaks tension, express with symbolic VGS(off) , also express with VP sometimes. N raceway groove is extinct model if the move character curve of MOSFET pursues 1. (B) be shown.

 

Graph 1. N raceway groove is extinct model the structure of MOSFET and move character curve

 

As a result of extinct model MOSFET is when UGS=0, the raceway groove between leakage source has existed, want to add UDS only so, have ID current. If increase to pressing UGS to bar, the electric field between grid and underlay will make raceway groove medium induction more electrons, raceway groove thickening, the conductance of raceway groove increases.

 

If negative tension is increased in grid (namely UGS ＜ 0 ＝ , can be in corresponding underlay surface induction gives positive electrical charge, these positive electrical charge are quits the electron in N raceway groove, produce a depletion layer in underlay surface thereby, make raceway groove narrow, raceway groove conductance is reduced. When losing bar pressing to increase some voltage Up, extinct area expands whole raceway groove, raceway groove is broken completely by clip (extinct) , although UDS still is put,be in at this moment, also won’t produce leakage pole electricity, namely ID=0. UP calls clip to break voltage or threshold value tension, its value is normally between –1V–10V N raceway groove is extinct model the output character curve of MOSFET and move character curve are like graph 2—60 respectively (A) , (B) be shown.

 

Inside alterable resistance area, the relation of ID and UDS, UGS still is

 

 

In constant current area, the relation of ID and UGS still satisfies type (2—81) , namely

 

 

If consider the impact of UDS, ID can is approximately

 

 

Right extinct model for field effect canal, type (2—84) also can express to be

 

 

 

In type, IDSS calls the saturated leakage current when UGS=0, its value is

 

 

The working principle of MOSFET of P raceway groove and MOSFET of N raceway groove are identical, just carry electricly stream child different, polarity of power supply voltage is different just. This as ambipolar model dynatron has NPN model with PNP model same.

 

 

3 main parameter

 

(1) sheds parameter continuously

 

Point to extinct model MOS places voltage UGS=UGS(off) , increase model MOS canal is open voltage UGS(th) , extinct model the saturation of field effect dynatron leaks extremely the leakage of correspondence of the place when voltaic IDSS(UGS=0 extremely electric current) , input resistor RGS.

 

(2) low frequency is crossed guide Gm

 

Gm can be in move is begged on characteristic curve take, the unit is MS(fine long hair Xi Menzi) .

 

(3) is the biggest IDM of leakage pole electric current