
Calibration Plate I85
The Calibration Plate I85 B (5"x5") is a mask made
of HEBSglass and written with test patterns useful for calibrating photoresist
thickness vs. mask optical density (OD). The mask is written with
an ebeam writer with a 0.1 µm addressing grid size and consists
of the following three parts:
Part I: 
This part helps
users to match photoresist heights with specific optical densities in the
mask to build a calibration curve. The pattern exhibits 200 gray
levels that are identified with labels of (i + 1), ranging from 1 to 200.
Each gray level consists of 3 test strips, each test strip being 204.8µm
x 819.2µm
in size. The gray levels are designated optical density values according
to the equation D = 0.152 + 0.009286i, where i = 0, 1, 2 . . . 199.
Thus, by using the equation, the minimum and maximum OD can be determined
to be 0.152 and 2.0 respectively. 
Part II: 
This section can be utilized
to determine the number of gray levels needed to fabricate a smooth surface
figure for a 3dimensional microdevice. The pattern consists of
two sets of 31 gratings, one set of 31 gratings having a constant delta
T between adjacent gray levels and the other with constant delta OD, where
OD = D = log (1/T) and T is transmittance. The OD range of each of
the 62 gratings is 0.12 to 1.12. As the width of a grating pitch
increases from 2µm to 500µm, the number of gray levels is increased
from 10 to 20 to 100. The two sets of 31 gratings are divided into
the following 6 groups: 
Group1: 
19 blaze gratings having periods
of 2µm, 3µm… to 20µm: Each grating has 10 periods,
and has 10 gray levels in each period. T = 0.759  0.0759i,
where i = 0, 1, 2 . . . . . 9. This range in transmission values
corresponds to an OD range of 0.12 to 1.12. 
Group 2: 
6 blaze gratings having periods
of 10µm, 20µm… to 60µm: Each grating has 4 periods,
and has 20 gray levels in each period. T = 0.759  0.03595i,
where i = 0, 1, 2 . . . . . 19. This range in transmission values
corresponds to an OD range of 0.12 to 1.12. 
Group 3: 
6 blaze gratings having periods
of 50µm, 100µm, 200µm, 300µm, 400µm, and
500µm: Each grating has 4 periods, and has 100 gray levels
in each period. T = 0.759  0.0069i, where i = 0, 1, 2 . . . . . 99.
This range in transmission values corresponds to an OD range of 0.12 to
1.12. 
Group 4: 
19 blaze gratings having periods of 2µm,
3µm…
to 20µm:
Each grating has 10 periods, and has 10 gray levels in each period.
D = 0.12 + 0.111i, where i = 0, 1, 2 . . . . . 9. 
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