1. Wet chemical etching has the following etch profile:

Anisotropic
Isotropic

2. Highly anisotropic or directional profiles can be obtained by:

Wet etching
Dry etching

3. The thermal oxide film thickness is 4000°A. After 50 seconds of plasma etch the thickness becomes 2000°A. What is the etch rate?

30°A/sec
40°A/sec
50°A/sec
35°A/sec

4. Wet etch has poor selectivity and slow etch rate:

True
False

5. Wet etch is very useful for critical dimensions less than 3 microns.

True
False

6. Which of the following is most commonly used to etch silicon nitride:

Mixture of nitric acid and HF acid
Hot phosphoric acid
Acetic acid

7. Titanium can be wet etched while keeping silicon oxide and titanium silicide intact by the following:

A mixture of phosphoric acid, acetic acid, nitric acid and water
Mixture of hydrogen peroxide and sulfuric acid
Hydrofluoric acid

8. What is the degree of anisotropy of an isotropic etching?

1
0
0.5

9. Mean free path increases with increasing pressure:

True
False

10. The barrel and downstream etch system are designed for:

Anisotropic etch
Isotropic etch