1. Which of the following has no role in selecting the type of growth technique?
a) Thickness of the film
b) Stress on the film
c) Temperature of the film
d) Purity of the film
Explanation: There are some important _lm parameters, which need to be controlled and these decide the type of growth technique that is adopted.
(1) Thickness and uniformity
(2) Roughness
(3) Composition control
(4) Stress
(5) Purity
(6) Film integrity.
2. In case of deep holes/grooves the choice of technique plays an important role.
a) True
b) False
Explanation: In most cases, the underlying substrate is not at. The choice of technique becomes especially important when depositing in deep trenches/holes, with a high aspect ratio (depth/width) that needs to be maintained.
3. For which of the following physical deposition technique is not suitable?
a) Deep trenches
b) Flat surfaces
c) Wafer of very reactive material
d) Rough surfaces
Explanation: In case of deep trenches/holes, aspect ratio (depth/width) needs to be maintained. In such cases, physical deposition techniques will not work since they will cover the hole before filling it.
4. In chemical vapour deposition, chemicals containing the desired film/layer are used.
a) True
b) False
Explanation: the basic principle is that chemicals containing the desired film/layer are introduced into a reactor (where the wafer is held at high temperature) in the form of a vapour. These chemicals react on the wafer surface to form the film on the wafer.
5. Low pressure chemical vapour deposition (LPCVD) is used to_____
a) increase the purity of the film
b) to reduce the roughness of the film
c) to form thick films
d) to reduce stress on the film
Explanation: CVD process can be in atmospheric conditions or under low pressure (LPCVD). LPCVD is usually used for growing silicon nitride, to reduce the comprehensive stress on the film. For growing atomically thin films, a layer by layer growth process, called atomic layer deposition (ALD), is used
6. Morphology of μpSi and mpSi can be defined by a concrete spatial distribution.
a) True
b) False
Explanation: The sponge-like morphology of μpSi and mpSi cannot be defined by a concrete spatial distribution because of the complex structure of their porous network.
7. The resulting pore structure in pSi is intrinsically dependent on the doping level of the Si wafer.
a) True
b) False
Explanation: MpSi is produced by electrochemical etching of n-type wafers. The etching of p- and n-type Si wafers with a high or moderate level of doping yields mpSi structures and μpSi structures
8. Why the pore characteristics of the resulting pSi structures depend upon the doping type? Choose the most correct option.
a) Processing time depends on doping
b) The manufacturing process is selected on the basis of doping
c) The pore formation mechanism relies on doping
d) Atomic size of doping atom affects the final structure
Explanation: The reason why the pore characteristics of the resulting pSi structures depend upon the doping type and its level of the silicon wafer is that the pore formation mechanism relies on these parameters.
9. _____ mechanism is associated with the pore formation in μpSi structures.
a) Enhanced electric field
b) Tunnelling
c) Quantum confinement
d) Space-charge limited mechanism
Explanation: The space-charge limited mechanism is associated with the pore formation in μpSi structures, which results when n-type silicon wafers are electrochemically etched in HF solutions.
10.The enhanced electric field and tunnelling mechanisms are associated with the formation of _____ structures.
a) mpSi
b) npSi
c) μpSi
d) pSi
Explanation: The enhanced electric field and tunnelling mechanisms are associated with the formation of mpSi structures when highly or moderately doped Si wafers are electrochemically etched in HF solutions.