Wafer Aligner Test

During many stages of Ion Implantation, the silicon wafer has to be precisely aligned. This test was necessary because a supplier quality gear defect resulted in 11.5° deviation per revolution of the wafer on this drive train assembly. The incorrect gears escaped to multiple customer sites risking wafer-scrap issues. Manufacturing had to test and contain stock and WIP.

Solution:
• Use a Sensor to detect a notch in a mock wafer to ensure the gear tooth ratio is correct, and that the wafer is revolving the correct amount.
• Rotate the wafer until the notch comes into alignment with the sensor. Pause, and then rotate a specific amount of motor counts which should correspond to 360°. If the notch is not in alignment after this rotation, then the drive train fails the test.

Mechanical Design: 3d printing
• Designed and printed a bracket to mount sensor on the existing aligner fixture.
• Designed and printed an adjustment plate to keep bracket level and allow for bracket adjustment.
• Fabricated two types of mock wafers with notch for sensor detection.

Test Outcomes:
• Easier for operator. The technician just has to place mock wafer on chuck, press start, and follow a few LabVIEW instructions.
• More precise than containment solution. Containment involved measuring all gears with calipers to determine if they had the correct number of teeth.
• Standardizes testing process and gathers LabVIEW data for each test run.
• Other issues in the drive train that could result in a wafer misalignment will also cause this test to fail.