SOI Thin Silicon Etching with Variable Bath Speeds and Etch Gradients
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Solution Overview
Problem
Achieving uniformity in the thickness of very thin silicon layers on SOI substrates is challenging due to manufacturing steps that introduce non-concentric symmetry variations, leading to electrical issues and performance degradation in digital and photonic devices.
Innovation Solution
A wet etching process involving immersion in a chemical bath with controlled insertion and exit speeds to create non-uniform etching profiles, using an SC1 solution, to compensate for thickness non-uniformities, particularly reducing exit speeds to generate a gradient of at least 0.15 nm in the thin silicon layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If localized etching is performed using plasma or cluster ion beam processes to correct thickness inconsistencies, then thickness uniformity is improved, but surface roughness increases and amorphous silicon is created
Solution Approach 1:
The patent replaces plasma or ion beam etching processes with a wet chemical etching process using an aqueous solution. This substitution eliminates the creation of amorphous silicon and reduces surface roughness while still achieving thickness uniformity correction through controlled non-uniform etching profiles generated by varying substrate immersion speeds
Solution Approach 2:
The patent changes the etching parameters by using a wet chemical process instead of plasma/ion beam, and by controlling the etching profile through variable immersion speeds (introduction velocity and exit velocity). This allows correction of thickness non-uniformities while maintaining surface quality
2Manufacturing precision
If sacrificial thermal oxidation is used to correct thickness inconsistencies, then local thickness correction is achieved, but temperature gradients are difficult to introduce and resolution is limited
Solution Approach 1:
The patent replaces the complex thermal oxidation process with a simpler wet chemical etching process. Instead of requiring temperature gradient control equipment and dealing with thermal management complexity, the patent uses controlled immersion speeds in a chemical bath to achieve the same thickness correction goal with simpler equipment and process control
3Productivity
If conventional fast immersion speeds are used in wet etching, then productivity is maintained, but thickness non-uniformities cannot be compensated
Solution Approach 1:
The patent applies dynamic control to the immersion process by varying the introduction and exit velocities during substrate immersion. This dynamic approach allows the system to achieve both high productivity (through optimized overall cycle time) and high precision (through non-uniform etching profiles that compensate for thickness variations)
Solution Approach 2:
The patent changes the velocity parameters during the etching process, using different introduction and exit velocities to create controlled non-uniform etching profiles. This parameter variation enables simultaneous achievement of productivity and precision by matching the etching pattern to the specific thickness non-uniformities present
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 process effectively reduces non-uniformity in the thin silicon layer, improving the uniformity and reducing surface roughness, thereby enhancing the performance of SOI structures by compensating for non-concentric symmetry contributions.
Implementation Method 1
immersing the substrate in an etching bath so as to expose the principal surface to an etching agent
Data Source
Figure 1(a)~2(c)
Figure 3~4a
Figure 4b~5a
AI summary
The invention relates to a method for etching a main surface (1a) of a thin layer (11) of a substrate (1), which comprises immersing the substrate (1) in an etching bath so as to expose the main surface (1a) to an etching agent, the substrate (1) being oriented relative to the bath (100) such that: - when it is introduced into the bath (100), the main surface (1a) is gradually immersed from an initial introduction point (PII) to an end introduction point (PFI), at an introduction speed, and - when it exits the bath (100), the main surface (1a) gradually emerges from an initial exit point (PIS) to an end exit point (PFS), at an exit speed, the method being characterised in that: - the introduction speed is chosen in such a way as to etch the main surface (1a) according to a first non-uniform profile between the initial introduction point (PII) and the end introduction point (PFI), and/or - the exit speed is chosen in such a way as to etch the main surface (1a) according to a second non-uniform profile between the initial exit point (PIS) and the end exit point (PFS), in order to compensate for non-uniformities in the thickness of the thin layer (11).