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1、258 C H A P T E R 6 Fundamentals of the Metal-Oxide-Semiconductor Field-Effect TransistorTEST YOUR UNDERSTANDINGTYU6.2 The silicon impurity doping concentration in an aluminum-silicon dioxide-silicon MOS structure is .Using the parameters in Example 6.3, determine the metal-semiconductor work functi
2、on differenceTYU6.3 Consider an n+ polysilicon gate in an MOS structure with a retype silicon substrate. The doping concentration of the silicon is . Using . Equation (6.19), find the value of TYU6.4 Repeat Exercise TYU6.3 for a p+ polysilicon gate using Equation (6.20).TYU6.5 An MOS device has the
3、following parameters: aluminum gate, p-type substrate with , , and .Determine the threshold voltage. TYU6.6 Consider an MOS device with the following parameters: p+ polysilicon gate, n-type substrate with , , and . (Use Figure 6.21.3 Determine the threshold voltage. TYU6.7 The device described in Ex
4、ercise TYU6.6 is to be redesigned by changing the n-type doping concentration such Mat the threshold voltage is in the range All other parameters remain the same. For example,forand6.4|CAPACITANCE-VOLTAGE CHARACTERISTICSObjective: Describe and analyze the capacitance-voltage characteristics of a MOS
5、 capacitor.The MOS capacitor structure is the heart of the MOSFET. A great deal of information about the MOS device and the oxide-semiconductor interface can be obtained from the capacitance versus voltage or C-V characteristics of the device. The capacitance of a device is defined as (6.39)where d
6、Q is the magnitude of the differential change in charge on one plate as a function of the differential change in voltage dV across the capacitor. The capacitance is a small-signal or ac parameter and is measured by superimposing a small ac voltage on an applied dc gate voltage. The capacitance, then
7、, is measured as a function of the applied dc gate voltage.6.4.1 Ideal C-V CharacteristicsFirst we will consider the ideal C-V characteristics of the MOS capacitor and then discuss some of the deviations that occur from these idealized results. We will initially 259Figure 6.34| (a) Energy-band diagr
8、am through an MOS capacitor for the accumulation mode. (b) Differential charge distribution at accumulation for a differential change in gate voltage.assume that there is zero charge trapped in the oxide and also that there is no charge trapped at the oxide-semiconductor interface.There are three op
9、erating conditions of interest in the MOS capacitor: accumulation, depletion, and inversion. Figure 6.34a shows the energy-band diagram of an MOS capacitor with a p-type substrate for the case when a negative voltage is applied to the gate, inducing an accumulation layer of holes in the semiconducto
10、r at the oxide-semiconductor interface. A small differential change in voltage across the MOS structure will cause a differential change in charge on the metal gate and also in the hole accumulation charge, as shown in Figure 6.34b. The differential changes in charge density occur at the edges of th
11、e oxide, as in a parallel-plate capacitor. The capacitance C per unit area of the MOS capacitor for this accumulation mode is just the oxide capacitance, or (6.40) Capacitance in accumulaton mode Figure 6.35a shows the energy-band diagram of the MOS device when a small positive voltage is applied to
12、 the gate, inducing a space charge region in the semi-conductor; Figure 6.35b shows the charge distribution through the device for this condition The oxide capacitance and the capacitance of the depletion region are in series. A small differential change in voltage across the capacitor will cause a
13、differential change in the space charge width. The corresponding differential changes In charge densities are shown in the figure. The total capacitance of the series combination is (6.41a) (6.41b) Capacitance in Depletion mode第六章对基础知识的金属氧化物半导体场效应电晶体测试您的理解TYU6.2 硅掺杂杂质在铝二氧化硅硅MOS结构浓度为，采用在例6.3中的参数，确定了金
14、属半导体的功函数的区别。TYU6.3 考虑在同一个硅衬底MOS结构重新输入n +多晶硅栅。的硅掺杂浓度为。使用。方程（6.19），求价值所）TYU6.4 6.20重复练习TYU6.3的p+多晶硅栅采用公式。TYU6.5 的MOS器件具有以下参数：与铝栅，P型基板16立方公分，弓形体，并具有。确定阈值电 TYU6.6 考虑以下参数MOS器件的使用：对+多晶硅栅厘米- 3，弓形体，N型基板用 ，并具有。 （使用图6.21.3确定阈值电压。TYU6.7 对锻炼TYU6.6描述的设备是通过改变n型掺杂浓度等席子下面的阈值电压范围为重新设计。所有其他参数保持不变。For example,forand6.4 |电容电压特性目的：描述和分析特性的MOS电容器的电容电压。MOS电容结构是MOSFET的心。一本关于MOS器件和氧化物半导体界面的大量信息，可从与该设备的电压或电容的CV特性。该器件的电容定义为 （6.39）其中d Q为电压幅度在负责一个板块的鉴别变化改变一个函数的微分电容上的DV。电容是一个小信号或交流电参数，并叠加一个小门上施加直流电压的交流电压测量。电容，那么，是衡量一所施加直流栅极电压的函
