7AF Version 5.02 Features
9/10/99 Steve Jacobson
Purpose
Software version 5.02 introduces a new grinding mode to treat the situation where a customer’s wafers are
attached to a substrate with a wax layer, forming a kind of sandwich. The difficulty is that the wax layer,
although smooth, may vary in thickness from sandwich to sandwich. The customer wants to grind the wafer
(the top layer) to a particular target thickness, but the varying wax layer prevents him from being able to
request grinding the entire sandwich to a particular target thickness. The 7AF measuring probe measures the
entire sandwich, not the top layer.
Other new features help with topflush/backflush and work chuck coolant.
Measurement Data File
The solution to the sandwich problem requires the customer to measure each wafer (each top layer) and to
provide a data file of these measurements. The 7AF software will then use the data file to calculate a
separate grinding recipe for each sandwich so that its top layer is ground to the desired target thickness.
Because the recipe is changed for each wafer, the grinding mode will be called IND(ividual) WAFER.
There is a danger here that the wrong data file might inadvertently be used for the wrong cassette of wafers.
A great deal of responsibility will fall on those gathering data on the wafers, preparing the wafers and data
for submission to the machine, and operating the grinding process.
The data file will be ASCII, with one line for each slot in the cassette. Missing wafers will be represented by
an entry of zero. Anything in the file beyond the last line will be ignored. The number of lines will default to
25, but will actually correspond to machine variable 81, Wafers Per Cassette. The top line in the file
corresponds to the bottom slot of the send cassette. The second line corresponds to the next slot from the
bottom, and so on. Note that this is the opposite order from what might be expected, but it is the order in
which wafers are processed. Each line contains an integer that is the input thickness of the wafer (the top
layer) in microns.
As an example, suppose the cassette has 12 slots and that the top four slots are filled. Suppose the GaAs
wafer in the top slot is 567 microns thick, the next wafer is 678, the next is 500, and the lowest one is 600.
The measurement file looks like this. Any additional lines are ignored.
0
0
0
0
0
0
0
0
600
500
678
567
The name of the file is MEASUR1.INP for the wafers in Send Cassette 1 and MEASUR2.INP for the wafers
in Send Cassette 2. This file will be searched for first on the hard drive, in the directory c:\7af\execode,
where it can be downloaded from GEM. If it is not found there, it will be searched for in the top level
directory of the floppy disk. An error will be generated if it is not found in either place
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