Learning Unit Two
Quiz 2
Test what you have learned by answering the following questions:


1. Diffusion is used (please choose the most accurate answer):
To form bases, emitters, and resistors in bipolar device technology
To dope polysilicon in MOS device
To form source and drain regions
All of the above
2. When impurity concentrations are low which of the following apply:
Fick's diffusion equation with a constant diffusivity
Fick's diffusion equation with concentration dependent diffusivity
3. The units of the diffusion constant D are:
4. When a host atom leaves the lattice site creating a vacancy it becomes self-interstitial:
5. Occasionally a host atom acquires sufficient energy to leave the lattice site creating a vacancy. When an impurity atom migrates to the vacancy site it is called:

Diffusion by vacancy
Impurity diffusion
All of the above
6. Impurity atoms with larger radii would diffuse faster:
7. Fick's second law of diffusion is derived from:
Law of conservation of energy
Law of conservation of momentum
Law of conservation of matter
8. What factors does sheet resistance depend on (please choose the most accurate answer)?
Junction depth
The carrier mobility
Impurity distribution
All of the above
9. If the surface concentration is maintained constant throughout the diffusion process, then the following distribution is obtained:
A gaussian diffusion profile
A complementary error function profile
10. Given, sheet resistance=50 ohms per square, length=120 microns, width=20 microns of a resistor what is its resistance?

250 ohms
300 ohms
500 ohms
600 ohms