Massachusetts Institute of Technology
3.155J / 6.152J Microelectronics Processing Technology
Fall Term 2003
Problem Set,Lithography
Out,October 8,2003 Due,October 15,2003
1) Plot resolution and depth of field as a function of exposure wavelength for a projection
aligner with 100nm < λ < 500nm,Assume NA = 0.26,Recalculate on the same plot for NA =
0.41,Discuss the implication of these plots for the technologist that must manufacture
transistors with 0.5 μm features,
2) A 0.6 μm thick layer of resist has Q
0
= 40 mJ/cm
2
and Q
f
= 160 mJ/cm
2
,Calculate the resist
contrast and CMTF,If the resist thickness is cut in half,Q
f
reduces to 70 mJ/cm
2
while Q
0
is
unchanged,Assuming NA = 0.4,use the figure below to determine the minimum linewidth
for an aligner with S = 1.0 using both resist thicknesses with a source of 365 nm,The figure
below plots MTF of the aligner for a set of lines and spaces,The lines and spaces are of equal
width (W),and the spatial frequency is normalized by the Rayleigh criteria,R,In other
words,a normalized spatial frequency of 0.5,corresponds to a linewidth W equal to R (since
the equivalent source spacing of the lines is 2W,
3) Estimate the diffraction-limited resolution for an X-Ray exposure system using photons with
an energy of 1 keV and a mask to wafer separation of 20 microns,