Wafer Gettering Layer Formation Using Ultrasonic Abrasive Grains

The patent applies ultrasonic vibration to the free abrasive grains in the water bath, causing them to vibrate at high frequency and maintain continuous contact with the wafer reverse side. This mechanical vibration enables the abrasive grains to effectively create microcracks and gettering sites while significantly reducing the processing time compared to static methods.

The patent ensures continuous contact between the ultrasonically vibrating abrasive grains and the wafer surface throughout the processing period. The ultrasonic vibration maintains constant dynamic interaction, eliminating idle periods where grains would otherwise settle away from the wafer, thereby achieving continuous useful action for gettering layer formation.

The patent performs gettering layer formation by ultrasonic vibration of abrasive grains immediately after grinding the wafer reverse side, before any polishing or etching operations that would remove the strain layer. This preliminary action ensures the gettering effect is established while the processing strain layer is still present, subsequently protecting the wafer without compromising the gettering function.

The patent utilizes the processing strain layer created by grinding, which would normally be considered a defect requiring removal, and instead leverages it as a beneficial foundation for gettering site formation. The ultrasonic vibration of abrasive grains transforms the strained region into effective gettering sites that trap impurities, converting a harmful factor into a useful function.