tft-lcd原理

1、IVO CONFIDENTIAL,,,TFT-LCD & TFT Device,Array INT,IVO CONFIDENTIAL,Contents,TFT-LCD Introduction -- TFT-LCD Structure(構(gòu)成) -- Operation(操作) of T

2、FT-LCD -- CF & Array Structure -- TFT-LCD Key Parameters(參數(shù))TFT Device Introduction -- Semiconductor Basic -- TFT Structure & Operation -- TFT characteristic & Drive,TFT—Thin Film Tr

3、ansistor 薄膜電晶體LCD—Liquid Crystal Display液晶顯示器由于TFT-LCD具有體積小，重量輕，低輻射，低耗電量，全彩化等優(yōu)點(diǎn)，因此在各類顯示器件上得到了廣泛的應(yīng)用。,TFT-LCD,IVO CONFIDENTIAL,TFT-LCD Structure,TFT ArrayColor FilterLCD CellLCM : Polarizer film, TAB or COG, Back-

4、light,IVO CONFIDENTIAL,TFT-LCD Structure,IVO CONFIDENTIAL,,Principle of TFT-LCD,LCD SystemTFT ArrayLCD CellColor FilterLCM,Normally White Mode,,IVO CONFIDENTIAL,,,a-Si,p-Si,c-Si,Function of TFT,TFT acts as a switch,I

5、VO CONFIDENTIAL,,Equivalent Circuit of a Panel,TFT,Storage capacitor,LC capacitor,Data bus,Scan bus,Operation of TFT-LCD,IVO CONFIDENTIAL,Electrical potential ? Water levelTFT ? Water faucetInt

6、erconnections ? Water pipesCapacitors ? Water tanks,Operation of TFT-LCD,,,,,,,,,,,,,,,,Operation of TFT-LCD,IVO CONFIDENTIAL,,,,,,,,,,,,,,,,Operation of TFT-LCD,IVO CONFIDENTIAL,每個(gè)畫素具有一個(gè) TFT ，其閘極連接至掃描線，源極連

7、接至資料線，而汲極連接至液晶電極。顯示器依次起動(dòng)每條掃描線，以將畫素中的TFT 打開，而資料線送入對(duì)應(yīng)的視訊信號(hào)，對(duì)液晶電極充電至適當(dāng)?shù)碾妷骸．?dāng) TFT關(guān)閉後，到下次重新寫入信號(hào)前，儲(chǔ)存電容可將電荷保存，以提供液晶電極適當(dāng)?shù)碾妷?。接著起?dòng)下一條水平掃描線，並送入對(duì)應(yīng)的視訊信號(hào)。在整個(gè)畫面的視訊資料寫入後，再自第一條重新寫入信號(hào)，此重覆的頻率一般為60~70 Hz。對(duì)每個(gè)畫素而言，液晶上所跨的電壓和穿透度具有一定的關(guān)係。因此，

8、只要能控制所寫入的電壓，即可顯示想要的畫面。,Pixel ComponentsT：Switching TFTCLC：Liquid CrystalCs：Storage Capacitor,AMLCD Driving,IVO CONFIDENTIAL,Color Filter Structure,IVO CONFIDENTIAL,Pixel Structure,IVO CONFIDENTIAL,,,,,L,,,,,W,Array Pi

9、xel Structure,IVO CONFIDENTIAL,Storage capacitance,IVO CONFIDENTIAL,IVO Array Pixel Structure,Common線,Gate線,BM線,a-Si island,Data線,ITO,IVO CONFIDENTIAL,TFT,Cs,IVO Array Structure,IVO CONFIDENTIAL,有效顯示區(qū)域(Active Area)的對(duì)角線尺寸

10、LCD Panel 的有效顯示區(qū)域，即可顯示文字圖形的總面積。 參考下圖，白色區(qū)域即此片Panel 的有效顯示區(qū)域。 In the viewing area of the LCD glass, the dimensions of the perimeter of the conductive area.[(337.9mm)2 + (270.3mm)2](1/2) / 2

11、5.4(inch/mm) = 17.0 inch,Size,IVO CONFIDENTIAL,Resolution,IVO CONFIDENTIAL,Resolution,ppi means pixel per inch,IVO CONFIDENTIAL,Gray levelsNumber of Colors = [Gray levels of R] x [Gray levels of G] x [Gray levels

12、of B]◆ 4-bit x 3 ? 24 x 24 x 24 = 4096◆ 5-bit + 6-bit + 5-bit (total 16-bit)? 25 x 26 x 25 = 65,536 (64K)◆ 6-bit x 3? 26 x 26 x 26 = 262,144◆ 8-bit x 3? 28 x 28 x 28 = 16,777,216 (16.7M),Number

13、of Colors,IVO CONFIDENTIAL,屏幕像素接受到信號(hào)后，由白轉(zhuǎn)黑(Tr)及由黑轉(zhuǎn)白(Tf)所需 的轉(zhuǎn)變時(shí)間。所需轉(zhuǎn)變時(shí)間越短越好。較短的反應(yīng)時(shí)間使 畫面轉(zhuǎn)化更為順暢。Response time = Tr + Tf Time interval between 10%(on) to 90%(on) or 90%(off) to 10%(off) of brightness.,Response

14、 Time,IVO CONFIDENTIAL,The difference in luminance between all-white divided by the brightness of an all blackAt normal direction,Contrast Ratio,IVO CONFIDENTIAL,面對(duì)屏幕，往其上、下、左、右四方觀測，調(diào)整此屏幕直到 其無法由此看到屏幕畫面的角度。 Viewin

15、g angle depends on its statement about “Contrast Ratio” A cone perpendicular to the LCD in which minimum contrast can be seen.,View Angle (U/D/L/R),IVO CONFIDENTIAL,IVO CONFIDENTIAL,Contents,TFT-LCD Introduction

16、 -- TFT-LCD Structure -- Operation of TFT-LCD -- CF & Array Structure -- TFT-LCD Key ParametersTFT Device Introduction --

17、Semiconductor Basic -- TFT Structure & Operation -- TFT characteristic & Drive,Orbital and Energy Band Structure of an Atom,,,,,,,,,,Valence band, Ev,,Band gap, Eg,,Valence shells,,Nuclei,Conducting ban

18、d, Ec,Atom Description,,,IVO CONFIDENTIAL,Band Gap and Resistivity,,,,,,,,,,Eg = 1.1 eV,,Eg = 8 eV,Aluminum2.7 mW?cm,Sodium4.7 mW?cm,Silicon~ 1010 mW?cm,Silicon dioxide> 1020 mW?cm,Conductors,Semiconductor,Insulat

19、or,IVO CONFIDENTIAL,Crystal Structure of Single Crystal Silicon,Pure Silicon,IVO CONFIDENTIAL,N-type (Arsenic) Doped Silicon and Its Donor Energy Band,Electron,,,Valence band, Ev,,Eg = 1.1 eV,Conducting band, Ec,,,,Ed ~

20、 0.05 eV,,,,Doped Silicon,IVO CONFIDENTIAL,P-type (Boron) Doped Silicon and Its Donor Energy Band,,,Valence band, Ev,,Eg = 1.1 eV,Conducting band, Ec,,,,Ea ~ 0.05 eV,,,,Electron,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,-,,,,,,,

21、,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Si,,,,Si,,,,Si,,,,Si,,,,Si,,,,Si,,,,Si,,,,Si,,,,B,,,,,Hole,,Doped Silicon,IVO CONFIDENTIAL,ResistorCapacitorDiodeBipolar TransistorMOS Transistor,Basic Devices,IVO CONFIDENTIAL,Metal-Ox

22、ide-SemiconductorAlso called MOSFET (MOS Field Effect Transistor)Simple, symmetric structureSwitch, good for digital, logic circuitMost commonly used devices in the semiconductor industry,MOS Transistor,IVO CONFIDENT

23、IAL,IVO CONFIDENTIAL,MOSFET,,,,,,,,VG,VD,Vs,,,,,,,,,,,,+,,,“Metal” Gate,,SiO,2,,Source,,Drain,,,p-Si,,,,,n,,+,,,,,,,,,,,,,V,,D,,> 0,,,,,V,,G,,> V,,T,,> 0,,,+ + + + + + +,,,- - - - - - -,,,,,,,,,,,,,Electron flow

24、,,,,Positive charges,,Negative charges,No current,,,,,,,,,,n,,+,,,,SiO,,2,,,Source,,,Drain,,,p-Si,,,,,n,,+,,,,,,,,,,,,,V,,D,,,,,V,,G,,= 0,n,,,,,NMOS Device & TFT Operation,“Metal” Gate,IVO CONFIDENTIAL,TFT Work princ

25、iple,,,,,,,,,,,+,,,“Metal” Gate,,SiO,2,,Source,,Drain,,,n-Si,,,,,p,,+,,,,,,,,,,,,,V,,D,,> 0,,,,,V,,G,,< V,,T,,< 0,,,+ + + + + + +,,- - - - - - -,,,Hole flow,,,,Positive charges,,Negative charges,No current,,,,,

26、,,,,,p,,+,,,,SiO,,2,,,Source,,,Drain,,,n-Si,,,,,p,,+,,,,,,,,,,,,,V,,D,,,,,V,,G,,= 0,p,,,,,,,,,,,PMOS Device,“Metal” Gate,IVO CONFIDENTIAL,Structures of TFT,IVO CONFIDENTIAL,What is a-Si, poly-Si and c-Si ?,,IVO CONFIDENT

27、IAL,a-Si vs. p-Si TFT,,a-Si TFT,LTPS TFT,LDD,,,,,,,,Staggered,Coplanar,Normal,Inverted,,BCE, E/S,Structures of TFT,IVO CONFIDENTIAL,,,,,,Type,FeatureandDrawback,Back Channel Etch (BCE),,Channel Protect (Tri-layer),Gate

28、Insulator,,,Active Layer,,,N+ Ohmic Contact,,Etching Stopper,,Better active to n+ contactHave the less PEP processBetter shrinkage roomHigher photo sensitivity due to thicker active layerLow active growth through pu

29、t,Thinner active layer, which lower photo sensitivity and higher growth through putThe etching stopper provides larger process marginGenerally need one more PEPCritical n+ to active contact,Structures of TFT,IVO CONFI

30、DENTIAL,,,,,,Type,Feature and Drawback,MIS,,MIM,Cuint = Cunit (7PEP) * 0.85Yield killer is: (1). Metal protrusion, (2). Oxide particleCan minimum the yielding loss caused by PR pin hole,,Metal,ITO,,,Insulator,Passivati

31、on,,,,,Cuint = Cunit (7PEP) * 0.72Yield killer is: (1). PR pinhole, (2). Metal protrusion, (3). Oxide particleCan minimum the yielding loss caused by (2) and (3) via the double insulators,Cs structure in TFT Pixel,IVO

32、CONFIDENTIAL,What kind of function does TFT play ? A perfect switch !!!,,Gate,Source,Display data,TFT,CLC,CST,,,Write & Hold,What is a GOOD TFT?,IVO CONFIDENTIAL,High linear mobilityHigh Ion/Ioff

33、ratio (> 5 orders)Uniform Vth distributionRigid to BTS (bias temperature stress),Requirements of a GOOD TFT,on/off current ratiothreshold voltagefield effect mobilityleakage current,Transfer characteristic of T

34、FT,Transfer characteristic of TFT,IVO CONFIDENTIAL,Transfer characteristic of TFT,Operating Point of TFT,Linear region (VGS>VTH, VGD>VTH),IDS ≒ (W/L)μCI[(VGS-VTH)VDS-1/2(VDS)2],,Transfer characteristic of TFT,Satur

35、ation region (VGS>VTH, VGD<VTH),,IDS ≒ (W/2L)μCI(VGS-VTH)²,Transfer characteristic of TFT,Transfer characteristic of TFT,Transfer characteristic of TFT,Transfer characteristic of TFT,Transfer characteristic of

36、 TFT,,,Vds<<(Vg-Vth),gain Threshold Voltage--Vth,Linear region,gain Mobility--u,Saturation region,Linear region,,,,,,,VD,VS,,,,,,,,,,,,VG,,TFT Current Path,,,Log(IDS),VGS,,Current Components,Current Leakage,A half

37、of channel charge and a overlap capacitance,Leakage currentand photo-current,,,,,,,,,,,,,,Drain,Source,Gate,Current,ON State,Channel,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Transient State ON to OFF,OFF State,,,,Channel Charge,,Le

38、akage Current, Photo Current,Overlap Capacitance,,,,Detailed Electrical Model of a Pixel,Feedthrough voltage bychannel charge and aparasitic capacitance,Voltage drop due to the leakage currentand photo-current,These

39、voltage shift cause DC voltage,Flicker, Image Sticking, Low Contrast Ratio,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,VG,V i,t = 0,t = Tf,V drop,VD,Vc,VLC(t),ON,OFF,,,,,,,,V com,Active Matrix Driving,?Vp = pixel voltage offsetCgs

40、 = gate-source capacitanceCLC = Liquid Crystal capacitanceCST = storage capacitance?Vg = gate voltage swing Vs = drain voltage Vp = pixel voltage Vg = gate voltage Vcom= common

41、 voltage,Pixel Voltage Off-set,TFT Design TFT Structure W/L & TFT Size Electrode Overlap,K = (1/2) x ?eff x Cg x (W/L),?eff: Field-Effect Electron Mobility 0.5~1.0 cm2/V-sec, Typ.Cg : Gate Capacitance

42、per Unit Area,Fab. Process Parameter,,,Mask Design,,,Design of a-Si TFT,,,,,,,,,,,,VD,VG,Vp(t),Large K,Small K,,,,,ID (t),,,,Large K,Small K,,,Time (t),0,Tf,Design of the current gain (K),Performance of a-Si TFT,IVO CONF