SiC Substrate Stack for Low-Deformation Active Layer Bonding
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Solution Overview
Problem
The assembly of a 4H type polycrystalline SiC active layer and a polycrystalline SiC support substrate in semiconductor structures is hindered by discontinuities in crystalline quality and structure, leading to thermal deformation and loss of electrical conductivity due to differences in thermal expansion and crystalline alignment.
Innovation Solution
A method involving the formation of a polycrystalline SiC support substrate with a stack of layers, comprising a first layer of polytype 3C and a second layer of polytype 4H and/or 6H, allowing for the bonding of a monocrystalline SiC active layer of polytype 4H or 6H, thereby separating interfaces of different crystalline qualities and polytypes to minimize performance-degrading issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a 4H type polycrystalline SiC active layer is assembled with a polycrystalline SiC support substrate, then the structure can be manufactured, but thermal deformation occurs due to difference in coefficient of thermal expansion between hexagonal and cubic polytypes
Solution Approach 1:
The invention changes the polytype parameter of the support substrate from cubic (3C) to hexagonal (4H or 6H) to match the active layer polytype, thereby eliminating thermal expansion mismatch and preventing thermal deformation during manufacturing and operation
Solution Approach 2:
The invention creates homogeneity in crystalline structure by using matching polytypes (both hexagonal) for the active layer and support substrate, ensuring uniform thermal and electrical properties throughout the structure
2Ease of manufacture
If a 4H type polycrystalline SiC active layer is assembled with a polycrystalline SiC support substrate, then the structure can be manufactured, but electrical conductivity is lost at the interface due to misalignment of crystalline grains
Solution Approach 1:
The invention changes the polytype parameter of the support substrate to hexagonal (4H or 6H) to match the active layer, enabling proper alignment of crystalline grains and restoring electrical conductivity at the bonding interface
Solution Approach 2:
The invention creates homogeneity in crystalline orientation by using matching hexagonal polytypes, allowing continuous electron transport across the interface and maintaining reliable electrical conductivity
3Strength
If a bonding layer such as doped silicon is used to bond the donor substrate to the support substrate, then bonding can be achieved, but a stabilizing anneal at high temperature (around 1700°C) is required which increases energy consumption
Solution Approach 1:
The invention changes the polytype parameter of the support substrate to match the active layer, enabling direct bonding without requiring high-temperature stabilizing anneal, thereby significantly reducing energy consumption while maintaining bonding strength
Solution Approach 2:
The invention extracts the bonding layer (doped silicon) from the structure by enabling direct bonding between the donor substrate and support substrate through polytype matching, eliminating the need for additional bonding materials and high-temperature processing
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 reduces thermal deformation and enhances electrical conductivity by aligning hexagonal structures at the interface, improving the mechanical strength and electrical properties of the semiconductor structure.
Implementation Method 1
the difference in coefficient of thermal expansion can generate deformation of the structure when it is subjected to a high thermal budget
Implementation Method 2
the bonding of a donor substrate comprising an active layer of monocrystalline SiC of polytype 4H or 6H on one face of the polytype 4H and/or 6H of the support substrate
Data Source
Figure 1~3A
Figure 3B~3D
Figure 4A~4C
AI summary
The invention relates to a process for the manufacture of a semiconductor structure comprising a support substrate (1) of polycrystalline silicon carbide (SiC) and an active layer (2) of single-crystal silicon carbide, comprising: - the formation of a support substrate comprising a stack of a first layer (11) of polycrystalline SiC mainly of polytype 3C and of a second layer (12) of polycrystalline SiC mainly of polytype 4H and/or 6H, - the bonding of a donor substrate (20) comprising an active layer (2) of single-crystal SiC of polytype 4H or 6H to a face of polytype 4H and/or 6H of the support substrate, - the transfer of the active layer (2) onto the support substrate.