SiC Epitaxial Substrate Flatness via Back Surface Grinding
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Solution Overview
Problem
The existing methods for manufacturing SiC epitaxial substrates often result in uneven epitaxial film thickness due to fluctuations in source gas distribution, leading to substrate flatness issues, which can cause misalignment in photolithography and reduce semiconductor chip yield.
Innovation Solution
A method involving the epitaxial growth of silicon carbide on a silicon carbide substrate, followed by forming a protective film on the epitaxial film, grinding or polishing the back surface to match the front surface shape, and removing the protective film, ensuring the Site Back Surface Referenced Ideal Ranges (SBIR) and Site Front side least sQuares focal plane Range (SFQR) are within specific ranges for excellent flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a protective film is formed on the back surface before epitaxial growth to prevent protrusions, then protrusion formation is suppressed, but the flatness of the epitaxial substrate is deteriorated due to source gas fluctuations
Solution Approach 1:
The back surface of the substrate is ground or polished before epitaxial growth to establish a reference flatness. This preliminary action ensures that when the protective film is formed and subsequent processing occurs, the substrate maintains excellent flatness despite source gas fluctuations during epitaxial growth.
Solution Approach 2:
The patent replaces chemical etching methods with mechanical grinding or polishing to remove protrusions and establish flatness. This mechanical approach provides more precise control over surface flatness compared to chemical methods, enabling the substrate to maintain excellent flatness through the epitaxial growth process.
2Ease of manufacture
If the substrate has original flatness variations with taper shape, then manufacturing is easier, but the epitaxial film inherits the poor flatness
Solution Approach 1:
The substrate back surface is ground or polished before epitaxial growth to correct any original flatness variations or taper shapes. This preliminary mechanical processing establishes a reference flatness that prevents the epitaxial film from inheriting poor flatness, while still allowing ease of manufacture in subsequent steps.
3Device complexity
If no protective film is used during epitaxial growth, then the process is simpler, but SiC protrusions form on the back surface requiring complex removal operations
Solution Approach 1:
The back surface is ground or polished before epitaxial growth to create a flat reference surface. This preliminary action, combined with using the substrate itself as a protective barrier, prevents protrusion formation without requiring additional protective film materials or complex removal operations, thus simplifying the overall process.
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 results in SiC epitaxial substrates with improved flatness, reducing vertical misalignment in photolithography and enhancing semiconductor chip manufacturing yield by maintaining the desired flatness and alignment of mask patterns.
Implementation Method 1
having an epitaxial film obtained by epitaxially growing silicon carbide on a front surface of a silicon carbide substrate
Implementation Method 2
grinding or polishing an opposite surface to the first main surface of the silicon carbide substrate
Implementation Method 3
grinding or polishing an opposite surface to the first main surface of the silicon carbide substrate
Data Source
AI summary
A new substrate manufacturing method of obtaining a SiC epitaxial substrate having excellent flatness and a SiC epitaxial substrate having excellent flatness are provided. In a SiC epitaxial substrate having an epitaxial film obtained by epitaxially growing silicon carbide on a front surface of a silicon carbide substrate, the SiC epitaxial substrate has a first main surface made of the epitaxial film and a second main surface opposite to the first main surface. A maximum value of SBIR on the second main surface based on a 10 mm square site satisfies a condition of 0.1 µm or more and 1.5 µm or less.