Stress Measurement
C-1
C
S
TRESS
M
EASUREMENT
NOTE –
Stress Measurement is an optional feature that must be installed in the Dektak
software prior to use.
The Dektak 150 stress measurement function calculates tensile or compressive stress on processed
wafers. Its algorithm creates a curve comprising stress values for every data point on the scan trace. If
a pre-stress (pre-deposition) scan data file is saved, the calculation proceeds (on all the scan data
points) as follows:
1
A running average with a window size of 1/10 the scan length loads and smooths the pre-stress scan data.
2
The smoothed data is further smoothed using a segmented third order polynomial interpolation technique.
3
The first and second derivatives of the smoothed data trace derives the curvature trace.
4
Steps 1 - 3 are also applied to the post-stress scan data, producing a curvature trace for the post-stress
scan data.
5
The stress curve computes from the comparison of the two curvature traces.
6
The maximum and average compressive and tensile stresses are calculated from the stress curve, and
displayed in the
Analytical Results
window (see
The Dektak stress formula appears in
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