Semiconductor Substrate Bonding With Mechanical Self-Alignment
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Solution Overview
Problem
Current methods for aligning semiconductor substrates in Wafer-on-Wafer processes face challenges due to stress-induced misalignment caused by thermal and mechanical processes, leading to weaker bonds and potential assembly failure.
Innovation Solution
Mechanical self-alignment and slip-resistance are achieved through topographically inverse surface structures with etched protrusions and grooves on the substrates, which inter-fit to reduce misalignment and form slanted bonding regions, enhancing the bonding strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical alignment methods are used to align substrates, then initial alignment is achieved, but stress-induced misalignment occurs during thermal and mechanical processes
Solution Approach 1:
The patent applies preliminary action by creating mechanical interlocking structures (protrusions and grooves) on the substrate surfaces before bonding. These structures are pre-formed to mechanically self-align the substrates during the bonding process, compensating for any initial misalignment that occurs during optical alignment and subsequent thermal/mechanical processing.
Solution Approach 2:
The patent implements self-service through mechanical self-alignment structures that automatically adjust and correct alignment deviations without external intervention. The interlocking protrusions and grooves enable the substrates to self-correct misalignment through mechanical interfitting, eliminating the need for additional alignment correction steps after optical alignment.
2Ease of manufacture
If substrates are bonded without mechanical self-alignment structures, then bonding process is simpler, but lateral slippage occurs under thermal and mechanical stresses
Solution Approach 1:
The patent applies asymmetry by creating non-symmetric interlocking structures with protrusions on one substrate and corresponding grooves on the other substrate. This asymmetric design provides directional mechanical interlocking that prevents lateral slippage while maintaining bonding simplicity, as the structures naturally guide alignment during the bonding process.
Solution Approach 2:
The patent utilizes curved or angled surfaces in the mechanical interlocking structures, where the grooves and protrusions have slanted walls that facilitate self-alignment through mechanical interfitting. This curvature enables the structures to guide substrates into proper alignment and resist lateral forces during thermal and mechanical processing.
3Strength
If topographically inverse surface structures are etched to enable mechanical self-alignment, then slip-resistance and bonding strength are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the bonding interface into discrete mechanical interlocking elements (multiple protrusions and grooves distributed across the substrate surfaces). This segmentation provides cumulative bonding strength through multiple contact points while keeping each individual structure element relatively simple to manufacture using standard etching processes.
Solution Approach 2:
The patent implements inversion by creating topographically inverse structures where one substrate has protrusions and the other has corresponding grooves. This inverse relationship enables mechanical interlocking and self-alignment, enhancing bonding strength while the complementary nature of the inverse structures allows for efficient manufacturing through paired etching processes.
Data Source
AI summary
A method for mechanical self-alignment and slip-resistance in bonding semiconductor substrates is provided. The method includes providing a first semiconductor substrate with a first surface and a second semiconductor substrate with a second surface. Next, the method includes etching a first mechanical alignment structure into the first surface and then etching a second mechanical alignment structure into the second surface, such that the first and second mechanical alignment structures are topographically inverse. What follows is optically aligning the first substrate to the second substrate, such that the first and second surface face one another, and then bringing the substrate surfaces into contact. Next, the substrates mechanically self-align, such that the topographically inverse structures inter-fit. Finally, the method includes bonding both substrates, such that planar bonding regions form between the surfaces and slanted bonding regions form between the mechanical alignment structures.