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In-Situ Endpoint Detection Method for Chemical Mechanical Polishing of Dielectrics.

IP.com Disclosure Number: IPCOM000033055D
Original Publication Date: 2004-Nov-23
Included in the Prior Art Database: 2004-Nov-23
Document File: 4 page(s) / 32K

Publishing Venue

Motorola

Related People

Kevin Cooper: AUTHOR [+3]

Abstract

Chemical mechanical planarization (CMP) is frequently used in semiconductor processing to remove material and planarize the surface of a wafer. A key challenge of many CMP processes is determining the endpoint. Prior inventions detect endpoints at interfaces of metals and dielectrics by sensing differences in reflectivity of the polished metal and the underlying dielectric. These methods rely on the detection of the reflected or transmitted radiation. Other inventions use differences in friction (temperature or mechanical force sensors) to determine polishing endpoints. Since reflection signals or frictional forces do not change significantly with dielectric thickness; these techniques are typically ineffective for stopping at a particular thickness within the dielectric layer. The invention proposed is based on detection of radiation scattered at an interface. Due to the strong position dependence of scattered radiation (at the total internal reflection interface), the proposed method can precisely control the dielectric thickness and allows in-situ or ex-situ measurements. This is particularly useful for high frequency transistor applications using high dielectric constant materials (e.g. Al2O3, HfO2, etc…) for the gate dielectric. These materials are difficult to etch; however, they may be chemically mechanically polished to form very thin (<50 nm) and uniform films.

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In-Situ Endpoint Detection Method for Chemical Mechanical Polishing of Dielectrics.

Kevin Cooper, John Flake, and Yuri Solomentsev

Abstract

Chemical mechanical planarization (CMP) is frequently used in semiconductor processing to remove material and planarize the surface of a wafer.  A key challenge of many CMP processes is determining the endpoint. Prior inventions detect endpoints at interfaces of metals and dielectrics by sensing differences in reflectivity of the polished metal and the underlying dielectric.  These methods rely on the detection of the reflected or transmitted radiation.  Other inventions use differences in friction (temperature or mechanical force sensors) to determine polishing endpoints. Since reflection signals or frictional forces do not change significantly with dielectric thickness; these techniques are typically ineffective for stopping at a particular thickness within the dielectric layer.  The invention proposed is based on detection of radiation scattered at an interface.  Due to the strong position dependence of scattered radiation (at the total internal reflection interface), the proposed method can precisely control the dielectric thickness and allows in-situ or ex-situ measurements.  This is particularly useful for high frequency transistor applications using high dielectric constant materials (e.g. Al2O3, HfO2, etc…) for the gate dielectric.  These materials are difficult to etch; however, they may be chemically mechanically polished to form very thin (<50 nm) and uniform films.

Description of Problem:

There are several integration schemes where it is desired to conclude with a planar dielectric film of pre-determined thickness.  Common ways to accomplish this are timed polishes or timed etches.  However, timed processes are subject to internal process variation and to external deviations from up stream processes.  These variances may result in a larger than desired spread in film thickness.  What would be more ideal would be an endpoint detection method to determine when one has reached the desired thickness.  Current CMP equipment’s endpoint systems for dielectric materials are based on detected changes in either optical or mechanical properties.  These changes only occur at interfaces, not within film layers.  Therefore, they can not be used to accurately stop within a film. 

Description of Solution

The invention proposed is based on detection of radiation scattered at an interface.  Due to the strong position dependence of scattered radiation (at the total internal reflection interface), the proposed method can pre...