Semiconductor Bonding Metal Layer Interdiffusion Control
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Solution Overview
Problem
When transferring a semiconductor element with a recess to a supporting substrate using an alloy layer, existing methods often result in gaps at the bonded portion, leading to insufficient mechanical strength due to reduced fluidity of the metal layers during the alloying process.
Innovation Solution
The method involves disposing a metal layer to impede alloying between the outermost metal layers at the semiconductor and supporting substrate sides, allowing for reduced fluidity deterioration in the early stages of bonding, thereby minimizing the formation of gaps at the recessed areas by controlling the interdiffusion of metal layers through specific layer configurations and heating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple metal layers are alloyed together by heating to firmly bond the semiconductor element to the supporting substrate, then the bonding strength is improved, but the fluidity of the metal layers deteriorates in the early stages, leading to gap formation at the recess
Solution Approach 1:
The metal layer is divided into multiple sub-layers (first metal layer, second metal layer, third metal layer) with different functions. The first metal layer provides bonding strength, the second metal layer maintains fluidity during early bonding, and the third metal layer prevents excessive interdiffusion. This segmentation allows each layer to optimize its specific function without compromising the others.
Solution Approach 2:
The second metal layer acts as an intermediary between the first and third metal layers. It maintains fluidity during early bonding stages to fill gaps, while the third metal layer acts as a barrier to prevent excessive interdiffusion. This intermediary structure resolves the contradiction between needing fluidity for gap filling and preventing excessive mixing.
2Strength
If the metal layers are heated to allow interdiffusion and alloying, then the bonding is strengthened, but the recess area experiences insufficient metal flow to fill gaps
Solution Approach 1:
Different regions of the metal layer structure have different properties tailored to local needs. The second metal layer has high fluidity specifically in regions where gap filling is needed, while the third metal layer has low interdiffusion characteristics in regions where excessive mixing should be prevented. This local quality optimization ensures both gap filling and bonding strength are achieved.
3Strength
If the metal layers are alloyed together to form a firm bond, then the mechanical strength is improved, but the uniformity of the alloy layer is reduced due to gap formation
Solution Approach 1:
The alloy layer is segmented into multiple functional sub-layers that maintain compositional uniformity within each layer while providing different functions. The second metal layer ensures uniform distribution in gap regions, while the third metal layer maintains uniform composition by preventing excessive interdiffusion boundaries, resulting in an overall uniform alloy structure with enhanced mechanical strength.
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 the likelihood of gaps at the bonded portion, enhancing the mechanical strength and uniformity of the alloy bonding layer, ensuring a more robust bond between the semiconductor element and the supporting substrate.
Implementation Method 1
heating the first metal layer and the fourth metal layer facing each other to allow the first and fourth metal layers to be interdiffused
Implementation Method 2
allow the first and fourth metal layers to be interdiffused with the second metal layer and to be alloyed
Implementation Method 3
bonding the first member and the second member together by heating the first metal layer and the fourth metal layer
Implementation Method 4
The third metal layer impedes interdiffusion between the second metal layer and the fourth metal layer
Data Source
AI summary
A method of manufacturing a semiconductor device includes: providing a first member comprising: a first substrate, a semiconductor layer disposed on the first substrate and defining a first recess, and a first metal layer disposed above at least a portion other than the first recess, the first member defining a second recess in a region of a surface of the first member including a region directly above the first recess; providing a second member comprising: a second substrate, a second metal layer on or above the second substrate, a third metal layer on the second metal layer, and a fourth metal layer on the third metal layer; and bonding the first member and the second member together by heating the first metal layer and the fourth metal layer while facing each other. The third metal layer impedes interdiffusion between the second metal layer and the fourth metal layer.