SiC Bonded Substrate Heat Treatment for Back-Grinding Warp Control
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Solution Overview
Problem
Substrate warping during back grinding occurs in SiC bonded substrates, exceeding 1 mm, leading to transport errors and processing issues in semiconductor device manufacturing.
Innovation Solution
A substrate structure comprising a SiC polycrystal support substrate bonded to a SiC single crystal substrate, with a ground surface warping of 1.0 mm or less, achieved through a manufacturing method involving film formation, separation, heat treatment, and grinding/polishing processes, including a heat treatment at 1600 °C to 2000 °C to reduce internal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a SiC bonded substrate is used to reduce manufacturing cost, then the manufacturing cost is reduced, but the substrate warping exceeds 1 mm during back grinding
Solution Approach 1:
The patent applies preliminary action by performing heat treatment at 1600-2000°C on the SiC polycrystal support substrate before back grinding. This pre-treatment reduces internal stress and prevents excessive warping during subsequent grinding operations, enabling the substrate to maintain warping of 1 mm or less while still using the cost-effective bonded substrate structure
Solution Approach 2:
The patent changes the thermal parameter by heating the SiC polycrystal support substrate to 1600-2000°C and holding it for 1 hour or more. This parameter change modifies the internal stress state of the substrate, reducing its tendency to warp during back grinding and enabling precise processing of the bonded substrate
2Productivity
If back grinding is performed to thin the support substrate by 40-50%, then manufacturing efficiency is improved, but substrate warping increases beyond acceptable limits
Solution Approach 1:
The patent performs heat treatment as a preliminary action before back grinding. By reducing internal stress through heating at 1600-2000°C prior to grinding, the substrate maintains stability during the 40-50% thickness reduction, achieving both high manufacturing efficiency and acceptable warping control of 1 mm or less
3Manufacturing precision
If a SiC single crystal substrate is used instead of bonded substrate, then substrate quality is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent segments the substrate into two functional parts: a SiC polycrystal support substrate that provides mechanical strength and cost-effectiveness, and a SiC single crystal layer that provides the necessary electrical properties for device fabrication. This segmentation allows each material to fulfill its optimal function while balancing cost and quality requirements
Solution Approach 2:
The patent uses a composite material structure by bonding a SiC single crystal layer to a SiC polycrystal support substrate. This composite approach combines the advantages of both materials: the single crystal provides superior electrical properties for semiconductor devices, while the polycrystal support provides mechanical strength and cost-effectiveness
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
The method effectively suppresses substrate warping to 1.0 mm or less, preventing transport and processing errors, enhancing manufacturing efficiency and reducing costs by optimizing the back grinding process.
Implementation Method 1
fixing it to a support substrate (a material having strength, heat resistance, and cleanliness that can withstand the device manufacturing process: for example, SiC polycrystal) using a bonding method that does not involve the formation of an oxide film at the bonding interface
Implementation Method 2
achieved through a manufacturing method involving film formation, separation, heat treatment, and grinding/polishing processes, including a heat treatment at 1600 °C to 2000 °C to reduce internal stress
Implementation Method 3
the surface of the support substrate that is not bonded to the SiC single crystal substrate is a ground surface, and wherein the amount of warping of the ground surface is 1.0 mm or less
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~4
AI summary
Provided is a substrate for a SiC semiconductor device, a SiC bonded substrate, a SiC polycrystal substrate, and a SiC polycrystal substrate manufacturing method, which can suppress an amount of warping of the substrate after back grinding to 1.0 mm or less in the substrate for a SiC semiconductor device having a structure in which the SiC polycrystal substrate and a SiC single crystal substrate are bonded. A substrate for a SiC semiconductor device, wherein the substrate is formed by stacking a support substrate made of SiC polycrystal, a SiC single crystal substrate bonded to the surface of the support substrate, a SiC single crystal epitaxial layer formed on the surface of the SiC single crystal substrate, and a component of a semiconductor element formed on the SiC single crystal epitaxial layer, in this sequence, wherein the surface of the support substrate that is not bonded to the SiC single crystal substrate is a ground surface, and wherein the amount of warping of the ground surface is 1.0 mm or less.