SiC Wafer Thermal Oxidation Layout for Uniform Oxide Thickness
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Solution Overview
Problem
Existing methods for forming thermal oxide films on silicon carbide wafers fail to adequately suppress variations in film thickness across multiple wafers, leading to non-uniformity and inconsistencies in semiconductor device manufacturing.
Innovation Solution
The method involves forming first inorganic films on the lower surfaces of silicon carbide wafers, followed by etching to ensure a minimum thickness of 750 nm, and then performing thermal oxidation treatment with a batch type vertical diffusion furnace, where wafers are aligned with a dummy wafer and monitor wafer to control the oxidation reaction and uniformity of oxide film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal oxidation treatment is performed on multiple SiC wafers without special arrangement, then the manufacturing process is simple, but the oxide film thickness varies significantly among wafers
Solution Approach 1:
A dummy wafer is introduced as an intermediary element to absorb excess oxygen and control the oxidation atmosphere. The dummy wafer is placed at a specific position (second position from the top) among the SiC wafers during thermal oxidation treatment, acting as a mediator to uniformize the oxide film thickness across all wafers by regulating oxygen distribution in the stacking direction.
Solution Approach 2:
The dummy wafer is created as a copy of the SiC wafer structure but without the critical device regions. It replicates the substrate material and surface properties to interact with the oxidation environment in the same way, allowing it to effectively control the oxidation atmosphere without affecting the functional devices on the actual SiC wafers.
2Productivity
If wafers are stacked closely to maximize space utilization, then productivity increases, but oxygen distribution becomes non-uniform causing thickness variation
Solution Approach 1:
The dummy wafer serves as an oxygen-absorbing intermediary positioned at the second location from the top in the wafer stack. This placement creates an optimized oxygen distribution pattern that penetrates through all wafers uniformly, enabling close stacking for high productivity while maintaining precise thickness control across the batch.
Solution Approach 2:
The position of the dummy wafer within the stack is optimized as a critical parameter. By placing it at the second position from the top rather than at the bottom or top, the oxygen diffusion path and distribution pattern are optimized to achieve uniform oxidation across all wafers even when stacked closely for high throughput processing.
3Manufacturing precision
If no dummy wafer is used, then the manufacturing process is simpler, but oxide film thickness varies due to oxygen distribution issues
Solution Approach 1:
The dummy wafer acts as an oxygen-regulating intermediary that simplifies the overall process by enabling uniform oxidation without requiring complex oxygen flow control systems or post-processing adjustments. Its presence naturally balances oxygen distribution, making the manufacturing process more robust and easier to control.
Solution Approach 2:
The dummy wafer is a sacrificial element that can be reused for multiple batches but ultimately serves a temporary function. It is a simple, inexpensive component compared to the valuable SiC wafers containing devices, and can be discarded or regenerated after serving its purpose of controlling oxygen distribution during oxidation.
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 suppresses variations in oxide film thickness among silicon carbide wafers, ensuring uniformity and improving the manufacturing process for semiconductor devices like MOSFETs, by controlling the oxidation reaction and reducing gas generation, thereby enhancing in-plane uniformity and reducing thickness differences.
Implementation Method 1
Oxide films are formed on upper surfaces of the plurality of silicon carbide wafers by performing thermal oxidation treatment
Implementation Method 2
etching of the plurality of silicon carbide wafers is performed after the formation of the first inorganic films
Data Source
AI summary
Provided is a method of manufacturing a semiconductor device capable of suppressing variation in thickness of oxide films among a plurality of SiC wafers. Forming first inorganic films on lower surfaces of a plurality of SiC wafer, and then performing etching of the plurality of SiC wafers so that 750 nm or more of the first inorganic film is left in thickness, and then forming oxide films on upper surfaces of the plurality of SiC wafers by performing thermal oxidation treatment in a state in which a first SiC wafer of the plurality of SiC wafers is placed directly below any one of at least one wafer, including at least one of a dummy wafer and a monitor wafer, and a second SiC wafer of the plurality of SiC wafers is placed directly below a third SiC wafer of the plurality of SiC wafers.