Strasbaugh Mechanical Maintenance Procedures
Version 1.2 - April 18, 1996 7 - 23
Since wheel wear compensation is dependent on many
variables, most of which are process related, compensation
data must be determined empirically. To measure coarse
wheel wear zero out the coarse wheel compensation and
coarse wear limit data. Initialize the machine to eliminate any
previous compensation. After initializing grind enough wafers
so that any initial error compensation is eliminated and
measure the compensation amount. (Compensation is the
difference between the "actual" and "offset" coordinates for the
coarse wheel.) After grinding many wafers the accumulated
correction for the coarse wheel represents wheel wear. By
comparing this compensation amount to the total amount of
stock removed the ratio of wheel wear to stock removal can be
determined. This should be normalized as microns ground per
1 micron of wheel wear to minimize the compensation
increment (1 micron).
To measure finish wheel compensation requires essentially the
same procedure. However, to best simulate actual production
conditions it is best to first grind all wafers to the coarse grind
thickness with a single grind cycle using the coarse wheel.
These wafers can then be used in the dual grind cycle to
measure finish wheel wear. This will eliminate any interaction
from the coarse wheel performance during testing.
Since wheel wear is minimal it may require extensive grinding
of many wafers to accumulate measurable wheel wear for
accurate wheel wear data.
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