Wafer Grinding Angle Control for Edge Chipping Prevention

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Solution Overview

Problem

Existing wafer processing methods face challenges in maintaining wafer rigidity and preventing chipping during grinding, especially when slanting the inner side surface of the outer circumferential portion, which can lead to reduced device space and edge chipping.

Innovation Solution

A method involving a grinding process that forms a first portion with devices and an annular second portion, where the angle between the reverse side of the first portion and the inner side surface of the second portion is between 45° and 75°, preferably 55° to 70°, using a grinding wheel smaller in diameter than the wafer, to prevent chipping while maintaining a wide area for device formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the reverse side of the central portion of the wafer is ground to thin it, then the wafer can be thinned to a desired thickness, but the rigidity of the wafer is greatly reduced making it difficult to handle

Engineering Contradiction:

Improvewafer thicknessVSAvoidwafer rigidity

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The wafer is divided into two functional zones: a central first portion that is thinned for device formation and an outer annular second portion that maintains original thickness for structural support. This segmentation allows different regions to serve different purposes - the thinned central area enables device fabrication while the thicker outer ring preserves wafer rigidity and handleability during processing

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different thickness profiles are applied to different regions of the wafer. The central portion is locally thinned to the desired thickness for device formation, while the outer circumferential portion maintains its original thickness to provide mechanical strength. This local quality differentiation resolves the contradiction between needing thin areas for devices and thick areas for rigidity

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the inner side surface of the outer circumferential portion is made perpendicular to the reverse side of the central portion, then the grinding process is simple, but the edge of the inner side surface tends to be chipped off during subsequent handling

Engineering Contradiction:

Improvegrinding process simplicityVSAvoidedge integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Instead of creating a sharp perpendicular corner between the inner side surface and the reverse side, the invention introduces a curved transition surface with a specific angle (45°-75°) between these surfaces. This curvature eliminates the stress concentration at sharp corners that causes chipping, while still maintaining a relatively simple grinding process. The rounded transition protects the edge integrity during subsequent handling and processing steps

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Reliability

If the inner side surface of the outer circumferential portion is slanted with respect to the reverse side of the central portion to prevent chipping, then edge integrity is improved, but the central portion is reduced so much that sufficient space for device formation is lost

Engineering Contradiction:

Improveedge integrityVSAvoiddevice formation area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The invention optimizes the angle parameter between the inner side surface and the reverse side of the central portion to be within 45°-75°. This specific angular range prevents edge chipping by eliminating stress concentration, while simultaneously ensuring that the central portion retains sufficient area for device formation. The controlled angle parameter balances edge protection with adequate device space

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

This approach prevents wafer chipping and maintains a sufficient space for device formation by controlling the angle between the grinding wheel and the wafer surfaces, ensuring the wafer remains rigid and functional during subsequent handling and processing steps.

Implementation Method 1

the reverse side of the wafer is ground using a grinding wheel that is smaller in diameter than the wafer, thinning the central portion of the wafer

Methodology Applied

Scientific EffectAbrasion: Abrasion

Data Source

PatentUS10115578B2Wafer and method of processing wafer

Publication Date: 2018.10.30 DISCO CORP

AI summary

A method of processing a wafer having on a face side thereof a device area with a plurality of devices formed therein and an outer circumferential excess area surrounding the device area includes a grinding step for grinding a reverse side of the wafer corresponding to the device area with a grinding wheel that is smaller in diameter than the wafer, thereby forming a first portion corresponding to the device area and an annular second portion surrounding the first portion, the annular second portion being thicker and more protrusive toward a reverse side thereof than the first portion. In the grinding step, the grinding wheel and the wafer are moved relatively to each other so that the angle formed between the reverse side of the first portion and an inner side surface of the annular second portion is larger than 45° and smaller than 75°.