SiC Composite Substrate Bonding to Suppress Wafer Warpage
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Solution Overview
Problem
The manufacturing process of SiC bonded substrates faces challenges such as warpage in repeatedly used SiC single-crystalline substrates, leading to conveying errors and bonding defects, particularly during surface activation and bonding steps, due to the stress from hydrogen ion implantation layers.
Innovation Solution
A composite substrate is created by directly bonding a SiC single-crystalline substrate to a first SiC polycrystalline substrate with a volume resistivity of 10 Ω·cm or less, using covalent bonds at normal temperature, and employing fast atomic beams for activation, followed by side surface polishing to remove recesses and facilitate electrostatic chucking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a SiC single-crystalline substrate is repeatedly used in the manufacturing process of SiC bonded substrates, then manufacturing efficiency is improved, but warpage occurs due to stress from hydrogen ion implantation layers
Solution Approach 1:
The substrate is divided into two parts: a SiC single-crystalline substrate layer and a SiC polycrystalline support substrate layer. The support substrate acts as a separate structural component that provides mechanical strength and suppresses warpage, while the single-crystalline layer maintains the desired electrical properties. This segmentation allows the single-crystalline substrate to be repeatedly used without suffering permanent deformation.
Solution Approach 2:
A composite substrate structure is created by bonding a SiC single-crystalline substrate to a SiC polycrystalline substrate. The composite structure combines the advantages of both materials: the single-crystalline layer provides high electrical quality and the polycrystalline layer provides mechanical robustness and warpage suppression. The covalent bonding at normal temperature creates a strong interface that maintains structural integrity during repeated processing.
2Ease of manufacture
If hydrogen ion implantation is performed to create separation layers, then substrate separation is enabled, but stress is generated causing warpage and conveying errors
Solution Approach 1:
The SiC polycrystalline support substrate serves as an intermediary that absorbs the stress generated by hydrogen ion implantation. Instead of the stress acting on the single-crystalline substrate directly, the support substrate acts as a buffer that accommodates the dimensional changes, preventing warpage that would otherwise cause conveying errors.
3Manufacturing precision
If surface activation and bonding are performed under vacuum conditions, then bonding quality is improved, but electrostatic chucking becomes difficult due to lack of adhesion
Solution Approach 1:
The bonding process utilizes parameter changes in the vacuum environment. Under vacuum conditions, the surfaces are activated and bonded through covalent bonding mechanisms that are enhanced by the vacuum atmosphere. The low oxygen environment prevents oxidation and allows direct bonding, while the vacuum pressure provides the necessary force for intimate contact between surfaces.
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 method suppresses warpage and bonding defects, enabling stable handling and processing of SiC single-crystalline substrates, improving manufacturing efficiency and reducing defects in the SiC bonded substrate production.
Implementation Method 1
irradiating a first bonding target surface of the SiC single-crystalline substrate and a bonding target surface of the first SiC polycrystalline substrate with a fast atomic beam to activate these bonding target surfaces
Implementation Method 2
bonding the first bonding target surface of the SiC single-crystalline substrate and the bonding target surface of the first SiC polycrystalline substrate to each other at normal temperature such that these bonding target surfaces are directly bonded to each other by covalent bonds
Implementation Method 3
implanting hydrogen ions into a second bonding target surface of the SiC single-crystalline substrate in the composite substrate for transferring a SiC single crystal to form a hydrogen ion implantation layer inside the SiC single-crystalline substrate
Implementation Method 4
the composite substrate for transferring a SiC single crystal and the second SiC polycrystalline substrate are held by an electrostatic chuck
Data Source
AI summary
Provided are: a composite substrate for transferring a SiC single crystal; a method for manufacturing the composite substrate for transferring a SiC single crystal; and a method for manufacturing a SiC bonded substrate, in which warpage in a SiC single-crystalline substrate repeatedly used in a process for manufacturing a SiC bonded substrate is improved such that errors in conveying the SiC single-crystalline substrate or a problem of not being able to hold the SiC single-crystalline substrates on a processing table can be suppressed, the SiC single-crystalline substrate can be held on the processing table using an electrostatic chuck during a surface activation step or a bonding step, and the occurrence of bonding defects can be suppressed.A composite substrate for transferring a SiC single crystal includes a SiC single-crystalline substrate and a first SiC polycrystalline substrate having a volume resistivity of 10 Ω·cm or less, in which one surface of the SiC single-crystalline substrate is directly bonded to one surface of the first SiC polycrystalline substrate by covalent bonds.