Dual Etch Stop Layer for Thin SOI Uniformity
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Solution Overview
Problem
The existing methods for manufacturing Extremely Thin SOI (ETSOI) devices face challenges in achieving uniformity and preventing dopant diffusion and relaxation defects during the etching process, particularly when using boron-doped or SiGe etch stop layers, which affect the quality and thickness of the thin silicon film.
Innovation Solution
A method involving two distinct etch stop layers is employed, where the first etch stop layer, potentially boron-doped, is used for splitting after bonding, and the second etch stop layer, such as SiGe with a high Ge content, serves as a diffusion barrier and is selectively etched post-transfer, ensuring accurate control and minimizing under-etching and relaxation defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a boron-doped etch stop layer is used, then splitting control is improved, but dopant diffusion into the thin silicon film occurs deteriorating quality
Solution Approach 1:
The patent divides the etch stop function into two separate layers: a first etch stop layer (boron-doped) dedicated to splitting control, and a second etch stop layer (undoped or low-doped) that contacts the thin silicon film. This segmentation allows each layer to specialize in its primary function without compromising the other, preventing boron diffusion while maintaining splitting accuracy.
Solution Approach 2:
The second etch stop layer acts as an intermediary barrier between the boron-doped first etch stop layer and the thin silicon film. This intermediate layer prevents direct contact and diffusion of boron dopants into the silicon film, while still allowing the splitting process to occur in the first layer.
2Manufacturing precision
If an SiGe layer is used as etch stop layer, then etching selectivity is improved, but relaxation defects occur due to high Ge concentration
Solution Approach 1:
The patent segments the etch stop functionality between two layers, allowing the SiGe material to be used in the second layer with optimized Ge concentration that provides sufficient etching selectivity without exceeding the threshold that would cause relaxation defects. The first layer handles splitting without Ge-related issues.
Solution Approach 2:
The patent optimizes the Ge concentration parameter in the SiGe etch stop layer to achieve the desired etching selectivity while staying below the critical concentration that triggers relaxation defects. This parameter optimization allows the beneficial selectivity of SiGe without the harmful relaxation effects.
3Ease of manufacture
If splitting is performed in the bulk substrate, then detachment is achieved, but under-etching of the thin silicon film occurs at edges
Solution Approach 1:
The patent segments the splitting process to occur specifically in the first etch stop layer rather than the bulk substrate. This localized splitting in the dedicated first layer prevents the under-etching problem that occurs when splitting propagates through the bulk substrate and affects the thin silicon film edges.
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 enables the production of ETSOI devices with unprecedented uniformity and thickness control of the thin silicon film, up to 20 nm, while preventing dopant contamination and relaxation defects, thereby enhancing the manufacturing process for microchip fabrication.
Implementation Method 1
detaching the donor substrate by splitting initiated in the first etch stop layer
Implementation Method 2
the second etch stop layer, such as SiGe with a high Ge content, serves as a diffusion barrier
Data Source
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AI summary
The present invention relates to a method comprising forming a structure by steps comprising a) forming a first etch stop layer on a donor substrate; b) forming a second etch stop layer on the first etch stop layer, wherein the material of the second etch stop layer differs from the material of the first etch stop layer; c) forming a thin silicon film on the second etch stop layer; and bonding the structure to a target substrate; and detaching the donor substrate by splitting initiated in the first etch stop layer.