Curved Substrate Holder Geometry for Void-Free Wafer Bonding
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Solution Overview
Problem
Existing substrate bonding technologies experience void formation issues at the circumferential portions of stacked substrates due to inadequate retention and alignment, leading to malfunction and reduced bonding strength.
Innovation Solution
The substrate bonding apparatus employs a substrate holder with a circumferential support portion that curves the substrate's circumferential portion toward the holder, creating a wider space for gas and liquid escape, and uses a bonding unit with precise alignment and activation processes to minimize void occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a substrate holder with annular wall portion and support pins is used to retain substrates by vacuum adsorption, then substrate retention is achieved, but numerous voids occur in the circumferential portion of the stacked substrate
Solution Approach 1:
The substrate holder is designed with different structural characteristics in different regions: the annular wall portion provides circumferential support while the support pins provide localized retention points. This local differentiation allows the holder to maintain substrate retention functionality while preventing void formation at critical circumferential areas.
Solution Approach 2:
The substrate holder is configured in advance with specifically positioned support pins and an annular wall structure that pre-establishes proper substrate support geometry before bonding occurs. This preliminary configuration ensures that substrates are held in the correct position and orientation, preventing void formation during the bonding process.
2Productivity
If substrates are directly bonded after activation, then bonding process efficiency is improved, but voids occur reducing bonding strength
Solution Approach 1:
The substrate holder acts as an intermediary device between substrate retention and direct bonding. It maintains substrate position and prevents void formation during the bonding process, enabling direct bonding to proceed efficiently while ensuring bonding strength is not compromised by void defects.
3Device complexity
If the circumferential portion of the substrate is not properly supported, then device complexity is reduced, but adiabatic expansion voids occur
Solution Approach 1:
The annular wall portion of the substrate holder provides curved circumferential support that naturally accommodates and supports the circumferential portion of the substrate. This curved structure prevents the formation of adiabatic expansion voids by maintaining proper substrate geometry without requiring overly complex support mechanisms.
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 configuration significantly reduces the occurrence of voids and adiabatic expansion voids, enhancing the bonding strength and yield of the stacked substrates by maintaining a consistent contact region and reducing pressure differences.
Implementation Method 1
a substrate holder configured to retain, by vacuum adsorption, a substrate that is placed on a retaining surface formed by a wall portion continuing in an annular form on an outer peripheral side and multiple support pins arranged on an inside of the wall portion
Data Source
AI summary
A substrate holder includes a central support portion configured to support a central portion of a substrate, and an circumferential support portion arranged on an outside of the central support portion and configured to support a circumferential portion on an outside of the central portion, and the circumferential support portion is configured to support the circumferential portion so that at least a partial region of the circumferential portion is curved toward the substrate holder with a curvature greater than that of the central portion.