Semiconductor Die Stack Lattice Offset for Wafer Bond Stress Relief
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Solution Overview
Problem
Semiconductor packages with wafers bonded in the same lattice direction are prone to warpage and fracture due to insufficient stress resistance, leading to defects and fragmentation during high-temperature processes.
Innovation Solution
Orienting the crystal lattices of bonded semiconductor wafers in different directions, with an angle greater than 0.5 degrees, to reduce stress accumulation and enhance stress resistance in the wafer-to-wafer bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semiconductor wafers are bonded in the same lattice direction, then the bonding process is simple and alignment is easy, but the stress resistance is insufficient leading to warpage and fracture
Solution Approach 1:
The patent applies asymmetry by intentionally misaligning the crystal lattice directions of bonded wafers. Instead of bonding wafers with identical lattice orientations (symmetric approach), the invention bonds wafers with different lattice directions (e.g., <100> with <110>, or <100> with <111>), creating an asymmetric configuration that distributes stress more evenly and prevents warpage and fracture during high-temperature processing.
2Reliability
If wafers are bonded with different lattice directions, then stress resistance is improved, but alignment precision and bonding complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-establishing lattice direction markers and alignment references on the wafers before bonding. The method includes preparing the wafers with known lattice orientations, determining the appropriate angular offset (greater than 0.5 degrees) in advance, and using these pre-determined parameters to guide the bonding alignment process, thereby achieving both high reliability and manufacturing precision.
Data Source
AI summary
A semiconductor die stack includes a first semiconductor die having a first lattice direction, and a second semiconductor die bonded to the first semiconductor die and having a second lattice direction different than the first lattice direction.