Measurement of pad thickness and control of conditioning

Abstract

A conditioning process includes rotating a polishing pad about an axis of rotation, conditioning the polishing pad by sweeping an abrasive disk in a path across a surface of the polishing pad between an inner radial distance from the axis of rotation and an outer radial distance from the axis of rotation, sweeping a sensor across the polishing pad while conditioning the polishing pad, measuring a thickness of the polishing pad at a plurality of positions between the inner radial distance and the outer radial distance with the sensor, and adjusting at least one of a dwell time or a pressure of the abrasive disk against the polishing pad for a portion of the path based on measurements of the thickness by the sensor such that the polishing pad wears to a more uniform thickness than without such adjustment.

Description

TECHNICAL FIELD The present disclosure relates to control of conditioning during chemical mechanical polishing.BACKGROUND[0001]An integrated circuit is typically formed on a substrate by the sequential deposition of conductive, semiconductive, or insulative layers on a silicon wafer. One fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. A conductive filler layer, for example, can be deposited on a patterned insulative layer to fill the trenches or holes in the insulative layer. After planarization, the portions of the conductive layer remaining between the raised pattern of the insulative layer form vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized until a predetermined thickness is lef...

AI Technical Summary

Benefits of technology

[0012]Certain implementations can include one or more of the following advantages. The thickness of the polishing pad can be measured without halting of the polishing operation, thus improving throughput. The polishing pad can be maintained with a uniform thickness, thus improving polishing uniformity and reducing within-wafer non-uniformity (WIWNU). Air bubbles between the polishing pad and the platen can be detected, and the polishing pad can be replaced as a precautionary measure.

Problems solved by technology

Since conditioning abrades the polishing pad surface, it can gradually wear away the polishing pad.

One problem is that wearing of the polishing pad from conditioning can be non-uniform, e.g., more pad material can removed from an annular region between the center and edge of the polishing pad.

This non-uniform wear results in non-uniformity in the polishing pad thickness, which can lead to non-uniformity in the polishing rate.

Another unrelated problem is that if a polishing pad is not properly installed on the platen, air bubbles can be trapped between the polishing pad and platen.

These air bubbles can create bumps in the pad surface that can lead to polishing non-uniformity or defects.

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