Dummy Wafer Distortion Compensation in Wafer Bonding

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Solution Overview

Problem

Wafer-to-wafer bonding techniques often result in undesirable in-plane distortions and stress between wafers, complicating subsequent patterning steps and device layer formation.

Innovation Solution

The use of one or more dummy wafers during the bonding process to compensate for and reduce in-plane distortions by imparting a selected distortion signature on the target wafer, which is then superimposed with additional distortions from subsequent bonding, resulting in minimized overall distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If wafer-to-wafer bonding is performed by locally deforming wafers to make contact, then bonding is achieved without adhesive, but undesirable in-plane distortions and stress are introduced between wafers

Engineering Contradiction:

Improvebonding processVSAvoidin-plane distortion

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The method applies preliminary deformation to a dummy wafer before bonding to the target wafer. This preliminary action creates a distortion signature in the dummy wafer that will be transferred to the target wafer, preparing the system in advance to counteract subsequent bonding-induced distortions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy wafer is pre-deformed to create a distortion that is opposite to the expected bonding-induced distortion. When bonded to the target wafer, this preliminary anti-action counteracts the harmful distortions that would otherwise be introduced during subsequent wafer bonding operations.

Inventive Principle:

Principle #9Preliminary anti-action

2Manufacturing precision

If dummy wafers are used to compensate for distortions, then in-plane distortion is reduced by 2× or more, but process complexity increases due to additional bonding and removal steps

Engineering Contradiction:

Improvein-plane distortionVSAvoidbonding process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The dummy wafer is treated as a disposable component that is bonded to the target wafer, serves its distortion-compensation function, and then removed. This approach accepts the temporary addition of process steps in exchange for using a simple, sacrificial component rather than modifying the main bonding process.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The dummy wafer acts as an intermediary element between the bonding process and the target wafer. It mediates the distortion forces by absorbing and transferring controlled deformations, protecting the target wafer from direct exposure to harmful bonding-induced stresses.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If local deformation is applied to initiate bonding, then full bonding propagates across the wafer interface, but stress accumulates between the bonded wafers

Engineering Contradiction:

Improvebond strengthVSAvoidinter-wafer stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The method changes the physical state and mechanical properties of the dummy wafer through controlled deformation. By altering the dummy wafer's shape and stress distribution before bonding, the parameter changes enable stress relief in the final bonded structure while maintaining strong bonding interfaces.

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 effectively reduces in-plane distortions by 2× or more, as demonstrated by simulation analysis, and can be combined with tool setting changes for further reduction, leading to smaller distortion magnitudes in the final device layer.

Implementation Method 1

bonding may be initiated by locally deforming one or both of the wafers to make local contact between the wafers

Methodology Applied

Scientific EffectDeformation: Deformation

Implementation Method 2

allowing the plural wafer arrangement to relax to shift distortion into the other of the first and second wafers

Methodology Applied

Scientific EffectStress Relaxation: Stress Relaxation

Implementation Method 3

The wafers then bond to one another via propagation of the local contact to full bonding of the wafers. In particular, the wafers may remain attached due to interfacial surface adhesion (e.g., a van der Waals bond)

Methodology Applied

Scientific EffectVan der Waals force: Van der Waals Force

Data Source

PatentUS11195719B2Reducing in-plane distortion from wafer to wafer bonding using a dummy wafer

Publication Date: 2021.12.07 INTEL CORP

AI summary

Embodiments of the present disclosure describe techniques for reducing in-plane distortion from wafer to wafer bonding using a dummy wafer. One embodiment is an apparatus formed using a dummy wafer, the apparatus comprising: a device layer fusion bonded to a first side of a carrier wafer, wherein the dummy wafer comprises a first wafer and the carrier wafer comprises a second wafer that is different than the first wafer; wherein the device layer comprise a portion of a third wafer that is different than the second wafer; and wherein a second opposite side of the carrier wafer includes: a removal process artifact, wherein a distortion signature present in the portion of the second wafer is indicative of the use of the dummy wafer fusion bonded to the second side of the carrier wafer, or a remainder of the dummy wafer. Other embodiments may be disclosed and/or claimed.