深圳大学-数字集成电路(中文)第三章

1、Digital Integrated CircuitsDevices Digital Integrated CircuitsDevices q定性了解定性了解MOS器件器件 q介绍器件的基本公式介绍器件的基本公式 q介绍用于手工分析的简单模型介绍用于手工分析的简单模型 q介绍用于介绍用于SPICE模拟的器件模型模拟的器件模型 q工艺偏差的影响工艺偏差的影响 Digital Integrated CircuitsDevices n p p n BA SiO2 Al A B Al A B 一维表示 二极管符号 IC工艺中PN结截面图 Digital Integrated CircuitsDevic

2、es hole diffusion electron diffusion pn hole drift electron drift Charge Density Distance x+ - Electrical x Field x Potential V W2-W1 (a) Current flow. (b) Charge density. (c) Electric field. (d) Electrostatic potential. Digital Integrated CircuitsDevices x pn0 np0 -W1W2 0 pn(W2) n-region p-region L

3、p diffusion Typically avoided in Digital ICs Digital Integrated CircuitsDevices x pn0 np0 -W1W2 0 n-region p-region diffusion The Dominant Operation Mode Digital Integrated CircuitsDevices Digital Integrated CircuitsDevices VD ID = IS(eVD/T 1) + VD + + VDon ID (a) Ideal diode model(b) First-order di

4、ode model Digital Integrated CircuitsDevices Digital Integrated CircuitsDevices 25.015.05.05.0 VD (V) 0.1 ID (A) 0.1 0 0 雪崩击穿雪崩击穿 Avalanche Breakdown Digital Integrated CircuitsDevices ID RS CD + - VD Digital Integrated CircuitsDevices VGS VT Ron S D A Switch! |VGS| An MOS Transistor Digital Integra

5、ted CircuitsDevices Polysilicon Aluminum Digital Integrated CircuitsDevices D S G G S DD S G NMOS 三端器件三端器件 B NMOS 四端器件四端器件 PMOS 三端器件三端器件PMOS 四端器件四端器件 Digital Integrated CircuitsDevices n+n+ p-substrate DS G B VGS + - Depletion Region n-channel Digital Integrated CircuitsDevices Digital Integrated Ci

6、rcuitsDevices -2.5-2-1.5-1-0.50 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 VBS (V) VT (V) Digital Integrated CircuitsDevices 平 方 关 系 VGS= 2.5 V VGS= 2.0 V VGS= 1.5 V VGS= 1.0 V 电阻区 饱和区 VDS = VGS - VT VDS IDS 0 0.5 11.522.5 01 23456 Digital Integrated CircuitsDevices n+n+ p-substrate D S G B VG

7、S x L V(x) + VDS ID MOS transistor and its bias conditions Digital Integrated CircuitsDevices oxGSTH dq(x)= -C Wdxv-v(x)-V 边界条件边界条件:V(x)|x=0=0, V(x)|x=L=VDS Digital Integrated CircuitsDevices 三极管区三极管区(线性区线性区) 每条曲线在每条曲线在VDSVGSVTH时时 取最大值，且大小为：取最大值，且大小为： 2 2 nox DGSTH CW I=(V- V ) L VDSVGSVTH时沟道刚好被夹断时沟

8、道刚好被夹断 W 称为过驱动电压； 称为宽长比 L GSTH V- V Digital Integrated CircuitsDevices n+n+ S G VGS D VDS VGS - VT VGS - VT + - Pinch-off Digital Integrated CircuitsDevices IDnCox W L (VGSVTH)VDS 1 2 VDS2 ID nCox 2 W L (VGSVTH) 2 V DSVGSVTH (Pinchoff) Qd(x)WCox(VGSV(x)VTH) 当当V(x)接近接近VGS-VT， Qd(x)接近于接近于0，即反，即反 型层将在型

9、层将在XL处终止处终止 ，沟道被夹断。，沟道被夹断。 Digital Integrated CircuitsDevices Digital Integrated CircuitsDevices Linear Relationship -4 VDS (V) 00.511.522.5 0 0.5 1 1.5 2 2.5 x 10 ID (A) VGS= 2.5 V VGS= 2.0 V VGS= 1.5 V VGS= 1.0 V Early Saturation Digital Integrated CircuitsDevices (V/m) c = 1.5 un (m/s) usat = 105

10、 Constant mobility (slope = ) Constant velocity Digital Integrated CircuitsDevices ID Long-channel device Short-channel device VDS VDSAT VGS - VT VGS = VDD Digital Integrated CircuitsDevices 00.511.522.5 0 1 2 3 4 5 6x 10 -4 VGS (V) ID (A) 00.511.522.5 0 0.5 1 1.5 2 2.5x 10 -4 VGS (V) ID (A) quadrat

11、ic quadratic linear Long ChannelShort Channel Digital Integrated CircuitsDevices -4 VDS (V) 00.511.522.5 0 0.5 1 1.5 2 2.5x 10 ID (A) VGS= 2.5 V VGS= 2.0 V VGS= 1.5 V VGS= 1.0 V 00.511.522.5 0 1 2 3 4 5 6x 10 -4 VDS (V) ID (A) VGS= 2.5 V VGS= 2.0 V VGS= 1.5 V VGS= 1.0 V Resistive Saturation VDS = VG

12、S - VT Long ChannelShort Channel Digital Integrated CircuitsDevices S D G B Digital Integrated CircuitsDevices 00.511.522.5 0 0.5 1 1.5 2 2.5 x 10 -4 VDS (V) ID (A) Velocity Saturated Linear Saturated VDSAT=VGT VDS=VDSAT VDS=VGT Digital Integrated CircuitsDevices -2.5-2-1.5-1-0.50 -1 -0.8 -0.6 -0.4

13、-0.2 0 x 10 -4 VDS (V) ID (A) Assume all variables negative! VGS = -1.0V VGS = -1.5V VGS = -2.0V VGS = -2.5V Digital Integrated CircuitsDevices VGS VT Ron S D ID VDS VGS = VDD VDD/2VDD R0 Rmid Digital Integrated CircuitsDevices 0.511.522.5 0 1 2 3 4 5 6 7 x 10 5 VDD (V) Req (Ohm) Digital Integrated

14、CircuitsDevices Digital Integrated CircuitsDevices D S G B CGDCGS CSBCDB CGB Digital Integrated CircuitsDevices S D G CGC S D G CGC S D G CGC Cut-off ResistiveSaturation 在数字电路设计时最重要的工作区: 饱和区、截至区 Digital Integrated CircuitsDevices WLCox WLCox 2 2WLCox 3 CGC CGCS VDS/(VGS-VT) CGCD 01 CGC CGCS = CGCD CGCB WLCox WLCox 2 VGS CGC和和 VGS的关系的关系(with VDS = 0)CGC与与饱和程度的关系饱和程度的关系 Digital Integrated Cir