Epitaxial Wafer Susceptor Temperature Control
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Solution Overview
Problem
The existing methods for manufacturing epitaxial wafers face challenges with warpage-induced thermal stress in silicon wafers, leading to particle generation and scratches due to friction with the susceptor, which are difficult to address without complex and costly apparatus modifications, especially for larger diameter wafers.
Innovation Solution
Adjusting the susceptor temperature based on the resistivity of the silicon wafer to remedy warpage within a fixed time frame, using specific temperature ranges for different resistivity levels (775±25°C for 0.005 to 0.020 Ω·cm and 825±25°C for 8 to 12 Ω·cm) to prevent friction and scratches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the silicon wafer is carried into a reactor with high-temperature atmosphere by using a carrier blade, then the epitaxial layer can be formed on the silicon wafer, but elastic deformation (warpage) is produced in the silicon wafer due to thermal stress
Solution Approach 1:
The susceptor is preheated to a specific temperature range (400-800°C) before the silicon wafer is transferred onto it. This preliminary heating action ensures that when the wafer enters the high-temperature reactor atmosphere, the temperature difference between the front and back surfaces is minimized, preventing thermal stress-induced warpage while allowing epitaxial growth to proceed
2Shape
If the silicon wafer is loaded on a susceptor in a state where warpage is produced, then the warpage can be remedied, but the back surface edge portion and the susceptor graze each other to generate particles and extraneous materials
Solution Approach 1:
The susceptor is preheated before wafer transfer, and the wafer is transferred directly onto the preheated susceptor without intermediate warpage remediation steps. This preliminary preparation eliminates the need for post-transfer warpage correction, preventing contact between the wafer back surface edge and susceptor that would otherwise generate particles and extraneous materials
Solution Approach 2:
The invention converts the potential harm of warpage into a benefit by preheating the susceptor to match the reactor temperature profile. This ensures the wafer undergoes uniform thermal expansion from the beginning, and any warpage that occurs is minimal and does not require corrective actions that would cause particle generation
3Shape
If a control unit is used to confirm warpage shape and transfer the silicon wafer after restoration, then warpage can be remedied, but the apparatus becomes complicated and time loss occurs
Solution Approach 1:
The susceptor performs the function of both heating and warpage prevention simultaneously through preheating. The system uses the existing thermal field without adding separate monitoring and control units, allowing the wafer to maintain proper shape through self-regulation in the controlled thermal environment
Solution Approach 2:
The invention changes the temperature parameter of the susceptor (heating it to 400-800°C before transfer) to prevent warpage formation in the first place. This parameter adjustment eliminates the need for complex shape monitoring and correction systems, simplifying the overall apparatus while maintaining wafer integrity
4Shape
If heating is controlled to reduce temperature difference between front and back surfaces, then warpage can be avoided, but the apparatus becomes complicated and cost increases
Solution Approach 1:
The susceptor serves dual purposes: it provides mechanical support for the wafer and simultaneously controls the thermal environment through preheating. This eliminates the need for separate heating control systems, achieving uniform temperature distribution and preventing warpage through the susceptor's inherent thermal mass and preheating capability
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 effectively reduces particle generation and scratches on the silicon wafer surface without requiring a complex apparatus, ensuring uniform temperature distribution and correcting warpage in a timely manner for various resistivity levels, including larger diameter wafers.
Implementation Method 1
elastic deformation, i.e., so-called warpage is produced in the silicon wafer due to a thermal stress
Implementation Method 2
when a silicon wafer is carried into a reactor having a high-temperature atmosphere by using a carrier blade of an epitaxial growth apparatus having an automatic carriage function, elastic deformation, i.e., so-called warpage is produced in the silicon wafer due to a thermal stress
Data Source
AI summary
In a method for manufacturing an epitaxial wafer by which an epitaxial layer is formed on a surface of a silicon wafer arranged in a reactor by distributing a raw material gas in the reactor, a temperature of a susceptor at the time of carrying the silicon wafer into the reactor is adjusted in accordance with a resistivity of the silicon wafer. There is provided the method for manufacturing an epitaxial wafer, the method enabling reduction in generation of particles from friction of a back surface edge portion and the susceptor due to warpage of the wafer caused at the time of carriage into the reactor and occurrence of scratches on the silicon wafer back surface edge portion without requiring a complicated apparatus.