Semiconductor Structure with Graded SiGe Stack for Selective Etching
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Solution Overview
Problem
In semiconductor manufacturing, the etching process for gate-all-around transistor structures composed of Si and SiGe stacks faces challenges with inter-diffusion issues, where high germanium concentration leads to material loss in silicon layers and low germanium concentration results in ineffective etching selectivity, making it difficult to remove the SiGe layer effectively.
Innovation Solution
A SiGe stack with varying germanium concentrations is used, where a higher germanium concentration is placed in the middle and lower concentrations are at the interfaces with silicon layers, allowing for controlled etching rates to facilitate the removal of the SiGe layer while minimizing material loss, by employing a method that includes forming a first silicon germanium layer with a lower germanium concentration, a second with a higher concentration, and a third with an intermediate concentration, and adjusting their thicknesses to optimize etching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high germanium concentration is used in SiGe layer, then etching selectivity is improved, but material loss in silicon layer increases
Solution Approach 1:
The patent applies local quality by creating a SiGe stack with non-uniform germanium concentration distribution. The intermediate SiGe layer has higher germanium concentration (30-60%) to provide etching selectivity, while the first and third SiGe layers have lower germanium concentration (5-20%) to minimize inter-diffusion and material loss to adjacent silicon layers. This spatial variation in composition resolves the contradiction between achieving etching selectivity and preventing material loss.
Solution Approach 2:
The patent uses composite materials by constructing a multi-layer SiGe stack where each layer has different germanium concentration. This composite structure combines the benefits of high germanium concentration (etching selectivity) and low germanium concentration (reduced inter-diffusion) within a single integrated structure, allowing both requirements to be satisfied simultaneously.
2Loss of substance
If low germanium concentration is used in SiGe layer, then material loss in silicon layer is reduced, but etching selectivity deteriorates
Solution Approach 1:
The patent applies local quality by creating a SiGe stack with non-uniform germanium concentration distribution. The intermediate SiGe layer has higher germanium concentration (30-60%) to provide etching selectivity, while the first and third SiGe layers have lower germanium concentration (5-20%) to minimize inter-diffusion and material loss to adjacent silicon layers. This spatial variation in composition resolves the contradiction between achieving etching selectivity and preventing material loss.
Solution Approach 2:
The patent uses composite materials by constructing a multi-layer SiGe stack where each layer has different germanium concentration. This composite structure combines the benefits of high germanium concentration (etching selectivity) and low germanium concentration (reduced inter-diffusion) within a single integrated structure, allowing both requirements to be satisfied simultaneously.
3Device complexity
If single-layer SiGe structure is used, then device complexity is reduced, but ability to control etching rate distribution deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the SiGe layer into multiple sub-layers (first, second, and third SiGe layers) with different germanium concentrations. This segmentation allows independent optimization of each layer's properties: the intermediate layer provides etching selectivity while the outer layers minimize inter-diffusion, achieving better etching rate control than a single-layer structure.
Solution Approach 2:
The patent uses composite materials by constructing a multi-layer SiGe stack where each layer has different germanium concentration. This composite structure combines the benefits of high germanium concentration (etching selectivity) and low germanium concentration (reduced inter-diffusion) within a single integrated structure, allowing both requirements to be satisfied simultaneously.
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 effective removal of the SiGe layer with reduced material loss to the silicon layer, improving etching selectivity and facilitating subsequent operations by creating a necking structure in the etched profile that alleviates inter-diffusion issues and supports the formation of semiconductor structures.
Implementation Method 1
high germanium concentration leads to material loss in silicon layers and low germanium concentration results in ineffective etching selectivity
Implementation Method 2
inter-diffusion issues, where high germanium concentration leads to material loss in silicon layers
Data Source
AI summary
The present disclosure provides a semiconductor structure, including a substrate having a front surface, a first semiconductor layer proximal to the front surface, a second semiconductor layer over the first semiconductor layer, a gate having a portion between the first semiconductor layer and the second semiconductor layer, a spacer between the first semiconductor layer and the second semiconductor layer, contacting the gate, and a source/drain (S/D) region, wherein the S/D region is in direct contact with a bottom surface of the second semiconductor layer, and the spacer has an upper surface interfacing with the second semiconductor layer, the upper surface including a first section proximal to the S/D region, a second section proximal to the gate, and a third section between the first section and the second section.