EE 330 Exam 1 Spring 2011 If reference to a semiconductor processes is needed be
ID: 1925621 • Letter: E
Question
EE 330Exam 1
Spring 2011
If reference to a semiconductor processes is needed beyond what is given in a specific problem or question, assume a CMOS process is available with the following key process parameters; UnCOX=100uA/v2, UpCOX=UnCOX/3 ,VTNO=0.5V, VTPO= - 0.5V,
COX=2fFu2,? = 0, r=0, If reference to a diode is made, assume the process parameter JS=10-17A/u2. If any other process parameters for MOS devices are needed, use the process parameters associated with the process described on the attachment to this exam. Specify clearly what process parameters you are using in any solution requiring process parameters.
1. (2pts) What is the minimum gate length in a state of the art CMOS process such as those used by Intel in making current generation microprocessors?
2. (2pts) The pn junction was reported in the early 40’s but it was several years later until the operation was well understood and a model of the IV characteristics was developed. Who developed the model of the pn junction?
3. (2pts) Why is the effective length of a MOS transistor a little bit less than the drawn length of the transistor?
4. (2pts) If the thickness of gate oxide for a MOS transistor is about 70A, about how many SiO2 molecules, on average, are stacked on top of each other to form the gate oxide?
5. (2 pts) What is the difference in concept between hard yield and soft yield in a semiconductor device?
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6. (2pts) Why is it not practical to make large resistors in most basic semiconductor processes?
7. (2pts) How does Polysilicon differ from the silicon that is used to form the substrate of a wafer?
8. (2pts) Why is the major difference between an n+ layer of silicon that is created by deposition/diffusion and an n+ layer that is formed with an epitaxial process?
9. (2pts) The capacitance of a VARACTOR varies with the dc voltage across the device. What is happening in this device that causes the capacitance to be voltage dependent?
10.(2pts) The a-law model does a better job of modeling a short-channel MOSFET than the square-law model yet is seldom used in analytical calculations of electronic circuits. Why is this model seldom used for analytical calculations?
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