Polishing Pad Light-Transmitting Region Scratch Prevention

Solution Overview

Problem

Conventional CMP polishing pads struggle to prevent scratches on the wafer surface during polishing and fail to accurately detect the end-point of polishing, leading to inefficiencies and increased costs due to the need for separate test wafers and uncertainty in processing results.

Innovation Solution

A polishing pad with a light-transmitting region having a surface layer and a soft layer, where the soft layer is laminated under the surface layer with a hardness difference of 5 degrees or more, providing cushioning properties to reduce scratches and maintain transparency for accurate optical end-point detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a hard transparent material is used for the window to maintain structural integrity, then the window can withstand polishing pressure, but scratches occur on the wafer surface

Engineering Contradiction:

Improvestructural integrity of windowVSAvoidscratches on wafer surface

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The window is divided into multiple layers with different hardness characteristics. The outer layer has higher hardness to resist scratching, while the inner layer has lower hardness to provide cushioning and absorb polishing pressure, preventing transmission of harmful forces to the wafer surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The window is constructed as a composite structure combining materials with different mechanical properties. The outer layer uses a harder transparent material for scratch resistance, while the inner layer uses a softer transparent material for pressure absorption, creating a composite that simultaneously achieves both protective functions.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a soft material is used for the window to reduce scratches, then the wafer surface is protected, but the window cannot withstand polishing pressure and structural integrity is compromised

Engineering Contradiction:

Improvescratches on wafer surfaceVSAvoidstructural integrity of window

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The window is divided into multiple layers with different hardness characteristics. The outer layer has higher hardness to resist scratching, while the inner layer has lower hardness to provide cushioning and absorb polishing pressure, preventing transmission of harmful forces to the wafer surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The window is constructed as a composite structure combining materials with different mechanical properties. The outer layer uses a harder transparent material for scratch resistance, while the inner layer uses a softer transparent material for pressure absorption, creating a composite that simultaneously achieves both protective functions.

Inventive Principle:

Principle #40Composite materials

3Measurement precision

If the window material is made translucent for optical detection, then end-point detection is enabled, but polishing pressure transmission is reduced affecting polishing uniformity

Engineering Contradiction:

Improveend-point detection accuracyVSAvoidpolishing uniformity

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The optical properties and mechanical properties of the window material are optimized by selecting appropriate materials and controlling their physical parameters. The window material is chosen to have sufficient transparency for optical detection while maintaining adequate mechanical strength and pressure transmission characteristics for uniform polishing.

Inventive Principle:

Principle #35Parameter changes

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 polishing pad effectively minimizes scratches on the wafer surface and enables in-situ detection of the desired surface properties, improving processing efficiency and reducing waste by allowing real-time monitoring of polishing progress.

Implementation Method 1

the soft layer has a hardness lower than that of the surface layer, so the light-transmitting region has cushioning properties

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

detecting the end-point of polishing by irradiating a wafer via a polishing pad through a window (light-transmitting region) with light beam, and monitoring interference signal generated by reflection of the light beam

Methodology Applied

Scientific EffectOptical interference: Interference

Data Source

PatentUS9737972B2Polishing pad

Publication Date: 2017.08.22 DUPONT ELECTRONIC MATERIALS HLDG INC

AI summary

The purpose of the present invention is to provide a polishing pad that hardly generates scratches on a surface of a subject to be polished. This polishing pad is characterized in that: the polishing pad is provided with a polishing layer having a polishing region and a light-transmitting region; the light-transmitting region includes a surface layer positioned on the pad surface side, and at least one soft layer laminated under the surface layer, and the soft layer has a hardness lower than that of the surface layer.