ELEC9703 -Tutorial
Thursday, March 13rd, 2025
A/Prof. Aron Michael
School of Electrical Engineering and Telecommunications
Problem 1
Show that the angle formed by the intersection between the (100) plane and the (111) plane
is 54.7o
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Problem 2
Show that the angle formed by the intersection between the (110) plane and the (111) plane
is 35.6o
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Problem 3
A square diaphragm structure, 1mmx 1mm, is to be fabricated out of (100) silicon for a
pressure sensor. The wafer thickness is 450um. The diaphragm thickness should be 10um.
a. What should be the feature size of the mask opening to achieve desired diaphragm size?
b. What etchant and masking layer would you use?
c. Sketch the mask orientation relative to the wafer flat.
d. How would you achieve repeatable wafer thickness?
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Problem 4
A mask feature shown Figure 2 is patterned on the Si3N4 layer on a (100) silicon surface so that the
Si3N4 is removed inside the pattern. The wafer thickness is 300 m. After a long anisotropic etch in KOH,
what would be the final shape of the micromachined cavity?
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Problem 5
What etchants and silicon wafer orientations will allow you to create the following cross-sectional profiles?
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Problem 6
What would be the possible bevel plane formed from (100) wafer if Ɵ = 45o, 48.2o, 54.7o and 90o ? What
would be the possible bevel planes formed from (110) wafer if Ɵ = 90o and 35.6o
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(100)
Ɵ
Problem 7
The figure 7 below shows the fabrication steps for condenser microphone. Explain each process step,
which the structures are fabricated, what material used as structure and mask, and etchant.
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Figure 7
Problem 8
Figure 8 is an air-gap insulated microstructure produced by a technique called “near-surface
micromachining”. The structural height is 20µm, lateral dimensions 60 x 60 µm2 and supporting bridge
width 2µm. The supporting bridges are SiO2 films with Aluminium conducting paths. Develop a simple
production process that would enable you to manufacture this structure. You have at your disposal the
latest processing technology tools including deep reactive ion etching capability.
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Figure 8
Problem 9
Figure 9 is the schematics of a scratch drive actuator – using surface micromachining techniques from
multi-poly (POLY-MUMPS). Describe how the actuator may be fabricated.
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Figure 9
Problem 10
Figure 10 is the schematics of the scratch drive actuate rotating mirror – using surface micromachining
techniques from multi-poly (POLY-MUMPS). Describe how the switch may be fabricated.
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Figure 10

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