Low-Temperature Graphene Synthesis via Diffusion-Couple Wafer Stacking
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Solution Overview
Problem
Existing methods for synthesizing graphene at the back-end-of-line (BEOL) stage in semiconductor manufacturing face challenges in achieving high throughput and scalability while adhering to a low thermal budget of <500°C to avoid damaging underlying devices and materials.
Innovation Solution
A diffusion-couple synthesis method using a graphene synthesis tool that applies pressure and temperature simultaneously to a substrate load, comprising a carbon source and sacrificial diffusion layers, allowing graphene formation at controlled interfaces without a transfer step, utilizing commercially available tools like wafer bonding tools and hot isostatic presses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional graphene synthesis methods are used at BEOL stage, then device compatibility is maintained, but throughput and scalability are limited
Solution Approach 1:
The patent combines multiple substrates into a single substrate load for simultaneous processing. The method stacks multiple prepared substrates with carbon sources and sacrificial diffusion layers in alternating fashion, allowing all substrates to undergo graphene synthesis in one continuous process run, thereby dramatically increasing throughput without requiring separate processing steps for each substrate.
Solution Approach 2:
The invention uses commercially available wafer bonding tools and hot isostatic presses for graphene synthesis, making existing multi-functional equipment perform the specialized function of low-temperature graphene formation. This approach leverages the universality of retasked tools to handle both traditional semiconductor processing and emerging 2D material synthesis without requiring entirely new dedicated equipment.
2Manufacturing precision
If high temperature synthesis is used, then graphene quality improves, but underlying devices and materials are damaged
Solution Approach 1:
The patent fundamentally changes the temperature parameter from conventional high-temperature CVD methods (>1000°C) to low-temperature solid-phase diffusion conditions (400-500°C). This parameter change enables graphene synthesis that is compatible with BEOL thermal budgets, preventing damage to underlying devices and materials while still producing high-quality graphene through controlled carbon diffusion.
Solution Approach 2:
The invention replaces the thermal field dominance of conventional CVD with a combined thermal-mechanical field approach. By applying mechanical pressure (e.g., 1-10 GPa) alongside moderate heating (400-500°C), the method enables carbon diffusion and graphene formation at temperatures that would be insufficient for conventional thermal processes, thereby avoiding thermal damage to devices.
3Productivity
If multiple substrates are processed individually, then process control is maintained, but machine utilization and throughput decrease
Solution Approach 1:
The patent merges multiple individual substrate processing operations into a single integrated process. By stacking multiple substrate-carbon source-sacrificial layer assemblies in alternating fashion within one substrate load, all substrates undergo synthesis simultaneously under uniform conditions, maximizing machine utilization while maintaining consistent process parameters across all substrates.
Solution Approach 2:
The invention segments the substrate load into repeating units of substrate-carbon source-sacrificial layer assemblies. This segmentation allows each unit to be independently prepared and characterized, ensuring process uniformity, while the entire segmented load is processed together in one batch, achieving high throughput and optimal machine utilization.
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
Enables high-quality graphene synthesis on large-area substrates with uniformity and efficiency, compatible with CMOS technology, enhancing throughput and reducing capital asset depreciation by optimizing machine utilization.
Implementation Method 1
Solid-phase diffusion of atoms in a 'material stack' forming a 'diffusion-couple' can be leveraged to synthesize high-quality thin-films at relatively low temperatures
Implementation Method 2
mechanisms to apply relatively large and uniform mechanical pressures (e.g., up to 1000 psi, etc.) to the diffusion-couple
Data Source
AI summary
A diffusion-couple synthesis method using a graphene synthesis tool(GST) including: providing a substrate-load(SL) which includes first-prepared substrate(fPS) and second-prepared- substrate(sPS), where fPS includes a first-carbon-source(fCS), a first-sacrificial-diffusion layer(fSDL), and a first-device-level(fDL), where a first-dielectric-layer(fDiLy) is disposed atop fDL, where fSDL is disposed directly atop fDiLy, where fCS is disposed directly atop the fSDL, and where the sPS includes a secondCS, a secondSDL, and a secondDL, where secondDL is disposed atop the secondDL, where the secondSDL is disposed atop secondDiLy, where secondCS is disposed atop secondSDL; providing a GST capable of applying pressure and temperature to SL within a process chamber(PC); placing SL within PC; applying the pressure and the temperature to SL, where sPS is inverted and disposed above fPS, where fCS is in direct contact with secondCS; forming graphene at a first interface between the fDiLy and the fSDL and at a second interface between secondDiLy and secondSDL.