7AF Software Version 6.05.0 Features
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7AF Version “6.05” Features
04/21/2004 Steven Jacobson
Purpose
Version 6.05.0 adds several small improvements and corrections to the software.
Approach to the Wafer in the Grind Cycle
As the grind wheel descends towards the wafer at the start of a grind cycle, it descends rapidly until reaching an
intermediate height. Then it switches to an intermediate speed of descent. When it touches the wafer, the speed
changes to the recipe speed. The intermediate height and intermediate speed had been constant. Now they can
be adjusted using Machine Variables 28 and 29, named Coarse Approach Params and Fine Approach
Parameters. However, adjusting them requires considerable care.
Warning: Grind results can be adversely affected by poorly chosen values.
The form of these variables is the decimal value nnn.nn where the whole number part gives the intermediate
height in microns and the fractional part gives the intermediate speed in microns per second. Note that three
digits can be used for the height and two digits for the speed.
The value 50.40 represents height 50 and speed 40, which are the default values for coarse grind approach.
The value 10.20 represents height 10 and speed 20, which are the default values for fine grind approach.
Zero or invalid height or invalid speed is treated as the default.
Timers For Testing Work Chuck Vacuum
Machine Variables 90 and 91, called LT Chuck Min Vac “hg and RT Chuck Min Vac “hg, now contain
additional information. The integer part still gives the minimum vacuum for the work chuck. The fractional
part, limited to two digits, tells how many seconds to tolerate vacuum below the minimum. Vacuum may build
slowly when first turned on, or there may be momentary fluctuation. Use this timer to avoid unnecessary error
messages. If the timer is not set it will default to its old value of 4.1 seconds.
Example 1: 10.08 allows vacuum below 10 inches for up to 8 sec.
Example 2: 10 allows vacuum below 10 inches for up to 4.1 sec.
Preventing a Wafer in the Bottom Slot of the Send Cassettes
In some cases, there is no room for the robot end effector to pick up a wafer from the bottom slot of the send
cassette. When this happens, the solution has been to train the robot for the second slot instead of the bottom
slot, and to declare the cassette to hold one less wafer, e.g., 24 instead of 25. But that still does not stop a
human operator from placing a wafer in that bottom slot, where it can be broken by the robot.
To prevent this, set Machine Variable 82, called Cassette Flags, to 1. Train the robot for the bottom slot and
declare the correct number of slots for the cassette, e.g., 25. If variable 82 is set, and the robot scanner finds a
wafer in the bottom slot, it will declare a cross-slot error, preventing the grind cycle from using the cassette.
When the operator removes that wafer and the cassette is re-scanned, grinding will proceed.
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