ISAT 436 – Micro/Nanofabrication and Applications Spring 2002
Homework #5: Photolithography
Due: 27 March 2002
Guidelines:
Clearly label each problem.
Clearly label the answer to each problem. For example, put a box around the number and its
units.
Show all your work, even if it is only scratch work.
Problems:
1. Jaeger problem 2.1 on page 40.
2. Jaeger problem 2.3 on pages 41-42. Your drawing should be “to scale”. Also, mark
the feature dimensions on your drawing.
Also add parts (c) and (d) as follows:
(c) Sketch the cross section of the mask if positive photoresist was used to make the
pattern shown.
(d) Sketch the cross section of the mask if negative photoresist was used to make the
pattern shown
3. Jaeger problem 2.4(a) on page 42.
4. Many “experts” believe that the maximum numerical aperture for large-field, high-
throughput optics in projection photolithography systems is between 0.7 and 0.8.
The theoretical limit for the photolithography process parameter k is about 0.25, but
in practical systems it is typically around 0.50 to 0.75.
Calculate the minimum feature size and the depth of focus for projection photo-
lithographic processes using light of the following wavelengths:
436 nm “g-line” of Hg lamp
365 nm “i-line” of Hg lamp
248 nm KrF laser
193 nm ArF laser
157 nm F2 laser
For this calculation, assume that you are considering a future photolithography tool
for which the numerical aperture of the lens is 0.75 and that the photolithography
process parameter k is 0.4.
5. What are some advantages of “direct step-on-wafer” over contact printing? What are
some advantages of contact printing over direct step-on-wafer?