Question 1)a) Explain how the chemical vapor deposition techniques are utilized to deposit thin films of various materials in MEMS. Compare these techniques with those of PVD.
b) Determine desired viscosity to density ratio of a photoresist solution to be prepared for the spin coating technique. The allowed time of rotation of chunk within production process is 2 minutes and desired height of photoresist is 50 μm. The rotor rotates at a speed of 10, 000 rpm. Assume original height is 500 μm.
c) Explain a process to produce variable resistivity (through depth) semiconductors.
Question 2)a) Determine size of the mask opening that after anisotropic etching will yield a flat rectangular area which results in a volume of 100 X 200 X80 μm3.
b) Explain photolithography process steps to fabricate micro feature of SiO2 on Si using positive as well as negative photoresist.
c) Explain LIGA process to fabricate MEMS structures.
Question 3)a) What are the effects of diffraction phenomenon on designing of high resolution optical microscope?
b) The optical system has numerical aperture (NA) of 0.3 and operates with light of wavelength of 0.365 μm. The resist in use requires an MTF of 0.5 or greater for adequate pattern reproduction. Process needs a focus tolerance of ±2 μm.
i) Calculate the resolution, assuming incoherent illumination
ii) What will be the change in resolution if NA is increased to 0.42.