SOI Wafer Thickness Tuning With Two-Step Wet Etching
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Solution Overview
Problem
Existing methods for manufacturing SOI wafers face challenges in precisely controlling the etching removal amount and achieving excellent in-plane uniformity of the SOI film thickness, particularly due to variations in oxidation rates and chemical liquid application, leading to inconsistent film thickness.
Innovation Solution
A method involving a two-step etching process using an SC1 solution followed by ozone water and HF-containing aqueous solution, where the first etching step has a smaller removal amount than the second, performed in a single wafer spin etching machine, to achieve precise control and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single etching step is used to adjust SOI film thickness, then the process is simple and fast, but the in-plane uniformity of film thickness deteriorates due to temperature variations and centrifugal force effects
Solution Approach 1:
The etching process is divided into multiple sequential etching steps, each removing a portion of the SOI film thickness. This segmentation allows the total etching removal amount to be distributed across multiple operations, reducing the etching removal amount per step and thereby improving in-plane uniformity while maintaining overall productivity
Solution Approach 2:
The patent changes the etching parameters by controlling the etching removal amount in each step to be within a specific range (0.1-10 nm per step). This parameter control ensures that temperature variations and centrifugal force effects do not cause excessive in-plane non-uniformity in any single etching step
2Manufacturing precision
If oxidation is used to thin the SOI film, then film thinning can be achieved, but the oxidation rate varies with atmospheric pressure fluctuations making accurate thickness control difficult
Solution Approach 1:
The patent implements a feedback mechanism where the SOI film thickness is measured after oxidation, and based on the measured value, the etching removal amount is determined to achieve the target thickness. This closed-loop control compensates for oxidation rate variations and achieves precise thickness control
Solution Approach 2:
The patent performs preliminary oxidation to form an oxide layer, then measures the resulting SOI film thickness before proceeding to etching. This preliminary action allows the subsequent etching parameters to be optimized based on actual film thickness, improving final thickness control accuracy
3Productivity
If batch cleaning is used for oxide film removal, then the process is efficient, but the SOI film thickness variations within the batch cannot be corrected
Solution Approach 1:
The patent segments the film thickness adjustment process into batch oxide film removal followed by individual wafer etching steps. This allows efficient batch processing for bulk oxide removal while enabling subsequent precise individual wafer adjustments to correct thickness variations
Solution Approach 2:
The patent applies different processing approaches to different stages: batch cleaning for uniform oxide removal, then individual wafer etching for localized thickness correction. This local quality approach tailors the processing method to the specific requirements of each stage
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 method allows for precise control of the etching removal amount and achieves excellent in-plane uniformity of the SOI film thickness, enabling the SOI wafer to be manufactured with a thinned film closer to the target value.
Implementation Method 1
a first etching step of etching a surface of the SOI layer using an SC1 solution
Implementation Method 2
a second etching step of etching the surface of the SOI layer by bringing the SOI layer into contact with ozone water to form an oxide film on the surface of the SOI layer
Implementation Method 3
bringing the formed oxide film into contact with an HF-containing aqueous solution to remove the oxide film
Data Source
AI summary
A method for manufacturing an SOI wafer including a step of performing an adjustment to a film thickness of an SOI layer of the SOI wafer by wet etching. In the step of performing the adjustment to the film thickness of the SOI layer, a first etching step of etching a surface of the SOI layer using an SC1 solution; and a second etching step of etching the surface of the SOI layer by bringing the SOI layer into contact with ozone water to form an oxide film on the surface of the SOI layer and then bringing the formed oxide film into contact with an HF-containing aqueous solution to remove the oxide film, are performed in combination. The etchings are performed such that a removal amount of the SOI layer in the first etching step is smaller than that in the second etching step.