Semiconductor Die Stack Lattice Misalignment for Stress Resistance
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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
1Ease of manufacture
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 deliberately 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 effectively and prevents warpage and fracture during high-temperature processing.
2Reliability
If the angle between lattice directions is increased to reduce stress, then stress resistance improves, but alignment precision and manufacturing complexity increase
Solution Approach 1:
The patent applies parameter changes by specifying discrete, standardized lattice direction angles between wafers. Rather than requiring precise continuous alignment, the invention defines specific angular relationships between crystal orientations (such as 45 degrees between <100> and <110>, or 54.7 degrees between <100> and <111>), which are achievable with conventional semiconductor manufacturing tolerances while still providing effective stress distribution.
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.