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Prevent Wafer Flatness Degradation Due to Laser Induced Damage

IP.com Disclosure Number: IPCOM000050114D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Gabarino, PL: AUTHOR [+4]

Abstract

This method of generating laser-induced damage (LID) on the backside of a silicon wafer, in conjunction with the modified chuck design, provides improved control over the flatness of ultraflat wafers. Ultraflat wafers when measured in the chucked or clamped state typically measure from less than 1 to 3 Mum in flatness.

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Prevent Wafer Flatness Degradation Due to Laser Induced Damage

This method of generating laser-induced damage (LID) on the backside of a silicon wafer, in conjunction with the modified chuck design, provides improved control over the flatness of ultraflat wafers. Ultraflat wafers when measured in the chucked or clamped state typically measure from less than 1 to 3 Mum in flatness.

The LID process produces spalling as a side effect; i.e., material accumulates around the contact area of the laser beam. In Fig. 1, the LID pattern is a straight line pattern across the wafer, from edge to edge, and channels for a loss of vacuum are generated. The wafer flatness will degrade. In Figs. 2A and 2B, two LID patterns that do not intersect the wafer edge are shown, and there is no easy path for loss of vacuum, and true flatness will be maintained. Due to the spalling, inherent in the LID process, the back of the wafer is still not in intimate contact with the surface of the vacuum chuck. A potential loss of vacuum can be further reduced by constructing a lip (as shown in Fig. 3) on the vacuum chuck which is, in turn, in contact with the untreated outer rim of the wafer backside. The contact area between the outer rim of the untreated wafer backside and the vacuum chuck effectively provides a seal to avoid loss of vacuum. True wafer flatness in the ultraflat region is maintained.

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