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Method for Placing Capacitance Proximity Sensor on a TSV Backside Grind

IP.com Disclosure Number: IPCOM000234583D
Publication Date: 2014-Jan-20
Document File: 2 page(s) / 93K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method is disclosed for placing a sensor based on capacitance on a rotating grind wheel via shock absorbing attachment pads. The sensor assists in determining approach of TSV during backside grinding in a wafer finish.

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Method for Placing Capacitance Proximity Sensor on a TSV Backside Grind

Typically, use of through-Si vias (TSV's) in Silicon chips to transport power and signals from one side of a chip to other side has increased the need to develop thin wafers in order to contact the TSV's. For some TSV's, deep holes or trenches are etched into the Si and filled with metal (e.g., copper or tungsten). However, the depth capability of the etch processes for the diameter or width of the TSV's is not sufficient to reach entirely through the wafer, and in some cases is less than 10% of the wafer thickness. In order to expose bottoms of TSVs, up to 90% of the backside of the wafer needs to be removed. This removal is typically accomplished by "backside grind" operations. Present endpoint detection for backside grind on wafers with tungsten TSV's includes noting the change in grind rate that occurs when the grinder encounters the tungsten, and chemical detection schemes that can detect traces of the TSV metal in the grind slurry. But TSV depth can vary somewhat across the wafer, and some variability exists in the uniformity of the backside grind process. In addition, it is sometimes desirable to stop Si removal before the TSV is actually revealed, in order to use other processes, such as slower chemical etches or polishes, for exposing the TSV's. Hence a better endpoint detection method is needed.

Disclosed is a system and method of placing a sensor based on capacitance on a rotating...