Direct Graphene Formation on Semiconductor Substrates
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Solution Overview
Problem
Current methods for producing graphene on large diameter silicon substrates face challenges such as low yield, film stress, chemical residues, bonding defects, and wrinkles due to the transfer process from metal foils, which are not scalable for volume manufacturing.
Innovation Solution
A method involving the deposition of a metal film on a semiconductor substrate, followed by exposure to a carbon source, allowing carbon atoms to in-diffuse and precipitate into a graphene layer directly on the substrate, eliminating the need for transfer steps and enabling large area graphene formation without film transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If graphene is transferred from metal foil to silicon substrate using conventional methods, then graphene can be formed on large area, but the transfer process causes film stress, chemical residues, bonding defects, and wrinkles
Solution Approach 1:
The invention extracts and eliminates the problematic transfer step from the process. By growing graphene directly on the silicon substrate using a metal catalyst layer that is subsequently removed, the method takes out the intermediate metal foil transfer step that causes stress, residues, and defects, while still achieving large area coverage
Solution Approach 2:
The metal catalyst layer is deposited and prepared in advance on the silicon substrate before carbon source introduction. This preliminary action establishes the growth environment directly on the final substrate, preventing transfer-related defects while enabling subsequent graphene formation in the desired location
2Reliability
If conventional transfer methods are used, then graphene formation is achievable, but the process is complex and not suitable for volume manufacturing
Solution Approach 1:
The invention merges the graphene growth step with the substrate preparation step by growing graphene directly on the silicon substrate. This combines what were previously separate operations (transfer to foil, then transfer to substrate) into a single integrated process, reducing complexity and improving reliability for manufacturing
Solution Approach 2:
The silicon substrate serves dual purposes: as the final device substrate and as the support during graphene growth. The substrate itself participates in the growth process by providing mechanical support and thermal management, eliminating the need for separate transfer operations and simplifying the overall process
3Area of stationary object
If metal foil transfer method is used, then large sheets of graphene can be produced, but film stress and bonding defects occur during transfer
Solution Approach 1:
The invention extracts the intermediate metal foil that causes stress and bonding issues. By growing graphene directly on the silicon substrate with a removable metal catalyst layer, the method eliminates the need for PMMA bonding and metal foil dissolution steps that introduce stress and defects, while maintaining large sheet production capability
Solution Approach 2:
The metal catalyst layer is deposited and prepared in advance on the silicon substrate before carbon source introduction. This preliminary action establishes the growth environment directly on the final substrate, preventing transfer-related defects while enabling subsequent graphene formation in the desired location
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 allows for the direct coating of large diameter semiconductor wafers with single or multi-layer graphene, reducing defects and improving yield by integrating graphene formation on silicon substrates without transfer processes, enabling scalable production.
Implementation Method 1
contacting the front metal film surface with a carbon-containing gas in a reducing atmosphere at a temperature sufficient to in-diffuse carbon atoms into the bulk metal region of the metal film
Implementation Method 2
precipitating carbon atoms to thereby form a layer of graphene between the front semiconductor substrate surface and the back metal film surface
Data Source
AI summary
The invention generally related to a method for preparing a layer of graphene directly on the surface of a semiconductor substrate. The method includes forming a carbon-containing layer on a front surface of a semiconductor substrate and depositing a metal film on the carbon layer. A thermal cycle degrades the carbon-containing layer, which forms graphene directly upon the semiconductor substrate upon cooling. In some embodiments, the carbon source is a carbon-containing gas, and the thermal cycle causes diffusion of carbon atoms into the metal film, which, upon cooling, segregate and precipitate into a layer of graphene directly on the semiconductor substrate.