Radial Force Control for Polishing Pad Dressing

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Solution Overview

Problem

Polishing pads used in semiconductor wafer polishing degrade over time, leading to non-uniformity and roughness, which affects the quality of polished wafers, necessitating a method to dress the polishing surface effectively.

Innovation Solution

A system comprising a rotatable polishing pad, a wafer measurement device for obtaining radial profiles, and a dressing apparatus with a radially movable and force-adjustable dressing member, controlled by pre-programmed recipes based on the wafer profiles, to ensure uniformity and smoothness of the polishing surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the polishing pad is used repeatedly over time, then productivity is improved through continuous operation, but the polishing surface becomes rough and non-uniform, degrading wafer quality

Engineering Contradiction:

Improvecontinuous polishing operationVSAvoidwafer surface uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system performs preliminary measurement of wafer thickness uniformity before dressing, and pre-programs appropriate dressing recipes based on predicted pad conditions. This allows the dressing process to be optimized in advance rather than reactively, maintaining precision while minimizing interruption to continuous production.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback loop where wafer thickness measurements are continuously monitored, and this data feeds back to determine when and how the pad should be dressed. The feedback mechanism enables dynamic adjustment of dressing parameters based on actual pad degradation, resolving the contradiction between continuous operation and maintaining precision.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If the polishing pad surface is dressed frequently to maintain uniformity, then wafer quality is improved, but production time is lost due to frequent interruptions

Engineering Contradiction:

Improvewafer surface uniformityVSAvoidproduction interruption time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The system enables self-service dressing by automatically determining pad degradation levels through wafer measurement feedback and autonomously selecting and executing appropriate dressing recipes. This reduces the need for operator intervention and minimizes production interruption time while maintaining wafer quality standards.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system uses multiple pre-programmed dressing recipes with different parameters (dressing force, speed, duration) that can be selected based on the measured pad condition. By changing parameters rather than always performing full dressing cycles, the system maintains precision while minimizing time loss.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a uniform dressing force is applied across the entire polishing pad surface, then the dressing process is simple to control, but it cannot address radial non-uniformity in the pad surface

Engineering Contradiction:

Improvedressing control simplicityVSAvoidradial surface uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The system applies local quality by using pre-programmed recipes that specify different dressing forces for different radial zones of the pad. The controller automatically adjusts the dressing force based on the radial position, allowing targeted treatment of specific non-uniform areas while maintaining overall process simplicity through automated control.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system transitions from static uniform force application to dynamic force adjustment based on radial position and measured pad conditions. The controller dynamically modifies dressing parameters during operation, enabling precise correction of radial non-uniformity while keeping the operator interface simple through pre-programmed recipes.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system effectively dresses the polishing pad by adjusting force application radially, resulting in wafers with improved thickness uniformity, smoothness, and flatness, maintaining high quality throughout the pad's life.

Implementation Method 1

One way to dress a polishing pad is by smoothing the polishing surface of the pad using an abrasive dressing element

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

The mounting system is adapted to change the first amount of force to thereby change the second amount of force applied on the polishing surface

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentUS7846006B2Dressing a wafer polishing pad

Publication Date: 2010.12.07 GLOBALWAFERS CO LTD

AI summary

A dressing apparatus for dressing a polishing pad includes a dressing member engageable with the polishing pad. The dressing apparatus is adapted to change the amount of force exerted by the dressing member on the polishing pad as the dressing member moves radially along the polishing pad. A controller for controlling the dressing apparatus has pre-programmed recipes that are selectable based on the radial profile of a measured polished wafer.