azu_td_1349475_sip1_... - Arizona Campus Repository

Photoresist Thickness (|xm)
50
Speed (rpm) Experimental Values Manufacturer's Values
3000 1.2 1.23
4000 1.09 1.06
5000 0.94 0.93
Table 4-1 Speed vs. thickness values for Shipley 1811 photoresist.
baked again. This stage of the process is known as the soft-bake and it occurs
for thirty minutes at 90° C.
4.4 Exposure and Development
A Karl Suss MJB3 mask aligner with a 325 nm UV light source was used
to expose the mask onto the substrates. The mask aligner was used in a
constant intensity mode at 15 mW/cm 2 . The exposure time setting varied as a
function of photoresist thickness. The thicker the photoresist layer, the longer
the exposure time necessary to expose the mask pattern all the way through the
photoresist to the glass substrate. To determine the necessary exposure time, a
mask with linear gratings was exposed to a number of substrates, each for a
different exposure time. The substrates were then examined using the stylus
profiler to determine the proper exposure time. The proper exposure time was
determined by examining the square well pattern formed in the photoresist by
the mask exposure. If the height of the square well features in the photoresist
was not equal to the known height of the photoresist, the exposure time used
was insufficient. Figure 4-2 is an example of the output from the stylus profiler
used to determine the appropriate exposure times. Using this experimental