EE245 Homework 2
Due 9/13/00
First Name:
Last Name:
Here is a
paper
written by Kirt Williams and Richard Muller on etch rates for micromachining processes.
What is the actual composition (by weight) of "concentrated HF"?
"5:1 BHF"?
Is phosphoric acid a solid, liquid, or gas at room temperature?
At what temperature do we typically etch with it?
What two pieces of equipment were used to measure the etch rates?
Find two MEMS-related journal and give their names here:
20# Xerox paper (letter size) is about 100 microns thick. If you were to scale a sheet of Xerox paper down to 2 microns thick how big would it be?
Draw the cross-section of the following process flow, along the dash-line direction in the picture. Assume a bare {100} silicon starting substrate. If I release theis cantilever, how will it curl?
1. LPCVD PSG, 2 micron
2. spin negative photoresist, expose using mask1, develop
3. timed HF etch with 50% overetch (how long will this take?)
4. strip resist in acetone
5. LPCVD polysilicon, 2 microns, anneal at 900C for 30 minutes
6. spin positive resist, expose using mask 2, develop
7. plasma poly etch, 50% overetch (what machine should I use? how long will this take?)
Note: For both masks, the area outside of box is considered to be transparent.
Draw a cross-section of the same process as in question 2, but assume that positive resist is used for both lithography steps.
(K. Pister)