SiC Substrate Bow Control for Photolithography Stability
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is the deterioration of processing accuracy due to substrate bending, which affects the flatness and stability of the substrate during photolithography, leading to uneven suction and exposure variations in the pattern formation process.
Innovation Solution
A method is developed to control the bending of the substrate by maintaining a moderate bow and warp within specific ranges, ensuring the substrate is moderately bent convexly upward, allowing for stable suction and reducing exposure variations during photolithography, using techniques like epitaxial growth and CMP polishing to achieve a flat surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is made flat to improve processing accuracy, then dimension accuracy and form accuracy of the pattern are enhanced, but the substrate may bend when an epitaxial layer or thin film is formed due to heat or stress
Solution Approach 1:
The substrate is pre-formed with a specific bow shape (convex upward) before epitaxial growth or thin film formation. This preliminary shaping compensates for the expected bending that will occur during subsequent processing, ensuring the substrate remains sufficiently flat for photolithography after the epitaxial layer or thin film is added.
Solution Approach 2:
The invention controls the bow value within a specific range (0 mm to +150 mm, preferably +10 mm to +50 mm) to optimize the balance between initial flatness and post-processing stability. By adjusting this geometric parameter, the substrate maintains adequate flatness for photolithography while accommodating thermal and stress-induced changes during epitaxial growth or thin film formation.
2Reliability
If the substrate is sucked by vacuum chuck for photolithography, then the substrate is held stable, but uneven suction occurs when the substrate is bent, causing exposure variation
Solution Approach 1:
The substrate is pre-shaped with a moderate bow (convex upward) before photolithography. This preliminary shaping ensures that when vacuum is applied through the chuck, the substrate makes uniform contact across its surface, enabling even suction and stable positioning during the photolithography process, thereby preventing exposure variation.
3Manufacturing precision
If the substrate has strong flatness to maintain processing accuracy, then photolithography can be performed stably, but the substrate cannot accommodate thermal expansion or stress during epitaxial growth
Solution Approach 1:
The invention optimizes the bow value parameter within a specific range (0 mm to +150 mm) to achieve a balance between maintaining sufficient flatness for photolithography and providing adequate compliance to accommodate thermal expansion and stress during epitaxial growth or thin film formation. This parameter optimization allows the substrate to adapt to processing conditions while maintaining manufacturing precision.
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 enhances the processing accuracy of semiconductor devices by maintaining a stable substrate shape, reducing exposure variations, and improving the electrical characteristics of the semiconductor devices formed.
Implementation Method 1
the substrate is sucked by vacuum chuck of a back surface of the semiconductor substrate
Implementation Method 2
an epitaxial layer made of a semiconductor material is initially formed on one main surface of a semiconductor substrate
Implementation Method 3
using techniques like epitaxial growth and CMP polishing to achieve a flat surface
Data Source
Figure 1(A)~1(C)
Figure 2~5
Figure 6~7
AI summary
A method of manufacturing a semiconductor device, comprising the steps of: preparing a substrate (1) composed of silicon carbide and having a main surface (1a, 1 b) having a diameter of 2 inches or greater; forming a thin film (4) composed of silicon carbide on one said main surface of said substrate (1); and forming a thin film (5) composed of a material other than silicon carbide on a main surface of said thin film (4), which is not opposed to said substrate (1), in said step of preparing a substrate, said substrate being prepared such that a value for bow at said main surface (1a, 1b) is not smaller than -40 µm and not greater than 0 µm and a value for warp at said main surface (1a, 1b) is not smaller than 0 µm and not greater than 40 µm, in said step of forming a thin film (4) composed of silicon carbide, said thin film (4) composed of silicon carbide being formed such that a value for bow at said main surface is not smaller than -40 µm and not greater than 0 µm and a value for warp at said main surface is not smaller than 0 µm and not greater than 40 µm, and in said step of forming a thin film (5) composed of a material other than silicon carbide, said thin film (5) composed of a material other than silicon carbide being formed such that a value for bow at said main surface is not smaller than 0 µm and not greater than 150 µm and a value for warp at said main surface is not smaller than 0 µm and not greater than 150 µm.