Apparatus and method for measuring the gripping strength of a vacuum wand

An apparatus for measuring the gripping strength of a wafer holder, such as a vacuum wand or an automated robotic arm, is used to periodically test wafer holders during manufacture of wafers, and thereby eliminate the damage caused to wafers by worn wafer holders. The apparatus includes a hold tester to be held by the wafer holder and a gauge coupled to the hold tester that indicates the force applied by the wafer holder to the hold tester. The wafer holder is coupled to a predetermined region on the hold tester, and the wafer holder gauge is pulled away from the hold tester until the wafer holder becomes separated from the hold tester. The maximum force applied by the wafer holder on the hold tester is measured by the gauge and the above described process is repeated to obtain a second measurement of the force. If the difference in the two force measurements is less than a predetermined deviation, and if one of the two measured forces is below a predetermined gripping strength, the wafer holder is considered defective and a correction process is used to find and fix correctable defects. In the correction process, the defects can be corrected, for example, by replacing the wafer holder's tip, or checking the hold tester for abrasions.

Abstract

An apparatus for measuring the gripping strength of a wafer holder, such as a vacuum wand or an automated robotic arm, is used to periodically test wafer holders during manufacture of wafers, and thereby eliminate the damage caused to wafers by worn wafer holders. The apparatus includes a hold tester to be held by the wafer holder and a gauge coupled to the hold tester that indicates the force applied by the wafer holder to the hold tester. The wafer holder is coupled to a predetermined region on the hold tester, and the wafer holder gauge is pulled away from the hold tester until the wafer holder becomes separated from the hold tester. The maximum force applied by the wafer holder on the hold tester is measured by the gauge and the above described process is repeated to obtain a second measurement of the force. If the difference in the two force measurements is less than a predetermined deviation, and if one of the two measured forces is below a predetermined gripping strength, the wafer holder is considered defective and a correction process is used to find and fix correctable defects. In the correction process, the defects can be corrected, for example, by replacing the wafer holder's tip, or checking the hold tester for abrasions.

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