Vacuum Chuck Pad Segmentation for Wafer Polishing

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Solution Overview

Problem

Existing vacuum chucks for silicon wafers suffer from defects like contact marks and particle quality degradation due to inadequate followability and contact issues during beveling and polishing, particularly in the outer circumferential region, where the vacuum pad separates from the wafer, allowing polishing slurry to enter and cause scratches.

Innovation Solution

A vacuum chuck design featuring a vacuum protection pad with through holes and an annular or arc-shaped concave portion, where the pad is bonded only at the central region, allowing it to flex and maintain contact with the wafer, reducing slurry entry and enhancing vacuum holding stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the vacuum pad is bonded across the entire vacuum surface including the outer circumferential region, then the vacuum holding force is strengthened, but the pad cannot follow wafer flexion during polishing, causing separation and defect generation

Engineering Contradiction:

Improvevacuum holding stabilityVSAvoidfollowability to wafer flexion

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The vacuum surface is divided into a central region and an outer circumferential region by an annular concave portion. The vacuum pad is bonded only to the central region, leaving the outer circumferential region unbonded. This segmentation allows the pad to maintain vacuum holding in the central area while remaining flexible and adaptable in the outer region to follow wafer flexion during polishing, preventing separation and defect generation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the vacuum pad have different bonding characteristics: the central region is bonded to provide stable vacuum holding, while the outer circumferential region is left unbonded to provide flexibility and adaptability. This local differentiation of bonding quality resolves the contradiction between holding stability and followability.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the vacuum pad is made flexible to follow wafer flexion, then defect generation is reduced, but vacuum holding stability in the outer circumferential region deteriorates

Engineering Contradiction:

Improvedefect generationVSAvoidvacuum holding stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The vacuum surface is segmented into central and outer circumferential regions. The central region provides stable vacuum holding through bonding, while the outer circumferential region provides flexibility to follow wafer flexion without bonding, thus preventing defects while maintaining overall vacuum stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The vacuum pad transitions from a static, fully-bonded structure to a dynamic structure where the outer circumferential region can move independently. This dynamic capability allows the pad to adapt to wafer flexion during polishing, reducing defect generation while the central bonded region maintains vacuum holding stability.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If polishing slurry is supplied during beveling/polishing, then polishing quality is improved, but slurry enters the gap between pad and wafer, causing contact marks and particle quality degradation

Engineering Contradiction:

Improvepolishing qualityVSAvoidcontact marks and particle quality degradation

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

By segmenting the vacuum surface into bonded central region and unbonded outer circumferential region, the design allows the outer region to maintain continuous contact with the wafer during polishing. This prevents slurry from entering gaps and causing defects, while still enabling effective polishing in the central region where slurry is supplied.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The unbonded outer circumferential region acts as a cushion that compensates for wafer flexion before slurry can enter the interface between pad and wafer. This prior cushioning effect prevents slurry infiltration and subsequent defect generation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This design significantly reduces defects in the outer circumferential region by maintaining a tight contact and minimizing slurry entry, ensuring stable wafer holding and improved polishing accuracy.

Implementation Method 1

a silicon wafer W is placed on a vacuum chuck 2 of a beveling/polishing device 1. The silicon wafer W is held by a vacuum to be sucked and held on the vacuum chuck 2.

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentUS10460975B2Vacuum chuck, beveling/polishing device, and silicon wafer beveling/polishing method

Publication Date: 2019.10.29 SUMCO CORP

AI summary

A vacuum chuck includes: a vacuum chuck stage having a circular vacuum surface; a vacuum protection pad provided to the vacuum surface; an annular or arc-shaped concave portion dividing the vacuum surface into a central region located closer to a center of the vacuum surface and an outer circumferential region located on an outer circumferential side; and radially-extending concave portions formed in the central region. The vacuum protection pad has through holes in communication with the radially-extending concave portions, and the vacuum protection pad is bonded to the vacuum surface at the central region excluding the radially-extending concave portions.