Curved Support Ring for Silicon Wafer Thermal Treatment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thermal treatment of monocrystalline silicon semiconductor wafers using existing support rings leads to stress-induced slip and deterioration of nanotopography, causing defects and defocusing issues during electronic component fabrication.
Innovation Solution
A monocrystalline silicon support ring with a curved surface and specific roughness and flatness criteria, designed to minimize stress on the wafer, along with a thermal treatment method involving controlled heating and nitrogen concentration, ensures reduced defect density and improved nanotopography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional support ring with a horizontal or slightly curved surface is used during thermal treatment, then the wafer can be supported stably, but stress-induced slip and deterioration of nanotopography occur due to the intrinsic weight of the wafer pressing onto the support ring
Solution Approach 1:
The support ring features a curved support surface with a specific radius of curvature (R ≥ 150 mm for 300 mm wafers, R ≥ 225 mm for 450 mm wafers) that matches the natural sag of the wafer under its own weight. This curvature distributes the wafer weight evenly across the support surface, preventing localized stress concentrations that would cause slip and nanotopography deterioration, while maintaining stable wafer support during thermal treatment.
2Productivity
If high heating rates are used in the temperature range above 900°C to reduce treatment time, then productivity increases, but stress-induced slip occurs due to temperature gradients in the crystal lattice
Solution Approach 1:
The patent optimizes the heating rate parameter to ≤ 10°C/min in the critical temperature range above 900°C. This controlled heating rate prevents excessive temperature gradients within the crystal lattice that would induce thermal stress and slip, while still achieving productive thermal treatment cycles. The curved support surface works in conjunction with this controlled heating rate to minimize overall stress on the wafer.
3Manufacturing precision
If the support ring surface is made very smooth to improve nanotopography, then slip is reduced, but the support ring becomes more sensitive to surface defects and contamination
Solution Approach 1:
The support ring surface is engineered with specific local quality characteristics: a controlled roughness profile with Ra ≤ 0.8 μm and Rz ≤ 4.0 μm. This optimized surface quality provides sufficient smoothness to prevent slip and maintain nanotopography, while the controlled Rz parameter ensures the surface remains robust against contamination and surface defects. The curved geometry further enhances this by distributing stresses that would otherwise concentrate on surface irregularities.
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 solution significantly reduces stress-induced defects and improves the nanotopography of thermally treated semiconductor wafers, preventing slip and enhancing the quality of the front side for electronic component integration.
Implementation Method 1
A monocrystalline silicon support ring with a curved surface and specific roughness and flatness criteria, designed to minimize stress on the wafer
Implementation Method 2
Thermal treatment of silicon wafers is generally carried out in a vertical furnace. In such a furnace, a multiplicity of semiconductor wafers are simultaneously heated to high temperatures over a relatively long time period.
Implementation Method 3
Temperature gradients, relative movements of semiconductor wafer and support ring owing to different coefficients of thermal expansion of silicon and silicon carbide
Implementation Method 4
rapid cooling of the single crystal prevents vacancies from remaining mobile long enough to be able to agglomerate into comparatively large COP defects
Implementation Method 5
doping the single crystal with nitrogen has the effect that during cooling of the single crystal, vacancy supersaturation is delayed
Data Source
AI summary
A support ring for supporting a monocrystalline silicon semiconductor wafer during a thermal treatment of the semiconductor wafer has outer and inner lateral surfaces and a curved surface extending from the outer lateral surface to the inner lateral surface, this curved surface serving for the placement of the semiconductor wafer. The curved surface has a radius of curvature of not less than 6000 mm and not more than 9000 mm for 300 mm diameter wafers, or a radius of curvature of not less than 9000 mm and not more than 14,000 mm for 450 mm diameter wafers. Use of the support ring during thermal treatment reduces slip and improves wafer nanotopography.