Micro/Nano Fabrication Technology, Homework Question 1 A layer of SiO2 is processed as discussed…

Micro/Nano Fabrication Technology, Homework Assignment 1
A layer of SiO2 is processed as discussed in class (See Figure 1). The photolithography mask is shown in Figure 2. Assuming the SiO2 is etched with a perfectly selective (i.e., it only etches SiO2 and nothing else), perfectly anisotropic (i.e., etched sidewalls are vertical) etchant, consider the following situations:
(a) Positive photoresist is exposed using a 4x projection lithography system with an Arf laser a = 193 nm). The numerical aperture of the lens system is 0.6, the resolution coefficient kl = 0.8, and the depth of focus coefficient k2 = 0.5.
Calculate the depth of focus for this system. What constraints does this DOF place on processing parameters?
What is the minimum resolvable feature size?
Draw the cross-section along the dotted line in Figure 2 of the etched SiO2 layer, given the following dimensions, as measured on the reticle: A = 20 um B = 1.348 um C = 516 nm D=772 nm E = 20 um F = 2.316 um. All unspecified dimensions are much larger than the largest specified dimension.
(b) Negative photoresist is exposed via a proximity lithography system utilizing the Mercury I-line (a = 365.4 nm). The gap between the reticle and the sample is 50um, about half the diameter of a human hair.
What is the minimum resolvable feature size?
Draw the cross-section along the dotted line in Figure 2 of the etched SiO2 layer, given the following dimensions, as measured on the reticle: A = 10 um B = 1.9 um C = 730.8 nm D=5 um E = 10 um F = 3 um. All unspecified dimensions are much larger than the largest specified dimension.
Figure 1: Fabrication process for problem 2
Figure 2: Lithography mask for problem 2