Wafer Bonding Chuck with Variable Height Ribs

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Solution Overview

Problem

Conventional wafer bonding processes result in significant post-bond distortion, particularly near the center and edge of the bonded wafer pair, due to variations in pre-bond wafer shapes and mechanical performance differences, leading to lateral misalignment issues.

Innovation Solution

The implementation of a wafer bonding apparatus with modified chuck designs featuring variable surface heights and temperature regulation elements to pre-distort the wafers before bonding, reducing distortion by compensating for shape variations and mechanical differences through inclined or declined mounting surfaces and radial zones.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional wafer bonding process is used, then bonding is achieved, but post-bond distortion occurs due to pre-bond wafer shape variations

Engineering Contradiction:

Improvebonding qualityVSAvoidpost-bond distortion

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-distorting the wafer mounting surface before bonding occurs. The lower chuck mounting surface is designed with a predetermined distortion pattern that compensates for expected post-bond distortion, so that when the wafer is bonded, the distortion is already locked in at a controlled level rather than occurring uncontrollably after bonding

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies local quality by creating non-uniform height distribution across the chuck mounting surface. Radial ribs are positioned at specific radii with different heights, and the mounting surface has varying heights in different radial zones, allowing different regions of the wafer to experience different pre-distortion levels tailored to local requirements

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If uniform chuck mounting surface is used, then manufacturing is simple, but post-bond distortion is significant near center and edge

Engineering Contradiction:

Improvechuck manufacturing simplicityVSAvoidwafer alignment precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent implements local quality by designing the chuck mounting surface with spatially varying properties. The mounting surface has different heights in different radial zones, with radial ribs at specific radii having predetermined heights. This localized variation in mounting surface geometry allows precise control of wafer distortion in different regions while maintaining a relatively simple overall chuck structure

Inventive Principle:

Principle #3Local quality

3Productivity

If mechanical force is applied to center for bonding, then bonding initiates, but upward bending occurs near edge

Engineering Contradiction:

Improvebonding process efficiencyVSAvoidwafer edge curvature

Core Design Contradiction:

ProductivityVSShape

Solution Approach 1:

The patent applies preliminary anti-action by pre-distorting the mounting surface to counteract the harmful upward bending that occurs at the wafer edge during bonding. The mounting surface is designed with specific height variations that create opposing forces to the edge upward bending, effectively canceling out the distortion before it fully develops during the bonding process

Inventive Principle:

Principle #9Preliminary anti-action

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 significantly reduces post-bond distortion, minimizing lateral misalignment between wafers by 'locking in' distortion during the bonding process, thereby improving the accuracy and reliability of the wafer bonding process.

Implementation Method 1

vacuum pressure may be used to hold the wafers on the chucks

Methodology Applied

Scientific EffectVacuum pressure: Vacuum

Implementation Method 2

a mechanical force applied to the center of the upper wafer 16, which causes the upper wafer to bow or bend

Methodology Applied

Scientific EffectMechanical force: Mechanical Force

Implementation Method 3

temperature regulation elements to pre-distort the wafers before bonding

Methodology Applied

Scientific EffectTemperature regulation: Heating

Implementation Method 4

variable surface heights and temperature regulation elements to pre-distort the wafers before bonding, reducing distortion by compensating for shape variations

Methodology Applied

Scientific EffectGeometric deformation: Geometry

Data Source

PatentUS11594431B2Wafer bonding apparatus and methods to reduce post-bond wafer distortion

Publication Date: 2023.02.28 TOKYO ELECTRON LTD

AI summary

Various embodiments of wafer bonding apparatuses and methods are described herein for reducing distortion in a post-bonded wafer pair. More specifically, the present disclosure provides embodiments of wafer bonding apparatuses and methods to reduce post-bond wafer distortion that occurs primarily within the center and/or the edge of the post-bonded wafer pair. In the present disclosure, post-bonded wafer distortion is reduced by correcting for variations in the pre-bond wafer shapes. Variations in pre-bond wafer shape are corrected, or compensated for, by making hardware modifications to the wafer chuck. Such modifications may include, but are not limited to, modifications to the surface height and/or the temperature of the wafer chuck. Although hardware modifications are disclosed herein for reducing post-bond wafer distortion near the center and/or the edge of the post-bonded wafer pair, similar modifications can be made to reduce post-bond wafer distortion within other areas or zones of the post-bonded wafer pair.