FinFET Source/Drain Epitaxy with Semiconductor Etch Stop Layer
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in integrating more components into a given area, including issues with etching losses and contact resistance in FinFETs, which affect performance and integration density.
Innovation Solution
A multi-layered epitaxial source/drain region is grown with an intermediate epitaxial layer acting as a semiconductor contact etch stop layer (CESL) to protect underlying layers and control etching during source/drain contact formation, increasing contact area and reducing etching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is reduced to increase integration density, then more components can be integrated into a given area, but etching losses and contact resistance increase
Solution Approach 1:
The source/drain structure is segmented into multiple epitaxial layers with different materials and doping concentrations. The first epitaxial layer has lower doping concentration while the second epitaxial layer has higher doping concentration, creating distinct functional zones that optimize both contact resistance and etching control
Solution Approach 2:
Different regions of the source/drain structure are assigned different material compositions and doping concentrations. The first epitaxial layer uses one material composition optimized for low contact resistance, while the second epitaxial layer uses a different material composition optimized for etching stop functionality, allowing each region to perform its specific function optimally
2Productivity
If feature size is reduced to increase integration density, then more components can be integrated into a given area, but etching losses increase
Solution Approach 1:
The first epitaxial layer is formed as a preliminary protective structure before the etching process. This layer acts as a pre-established barrier that prevents excessive etching into the underlying substrate, allowing the etch process to be performed with controlled material removal
Solution Approach 2:
The first epitaxial layer serves as an intermediary between the etching process and the underlying substrate. It absorbs and controls the etching action, preventing direct and excessive etching of the substrate while still allowing the etch process to proceed effectively
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 improves the performance of FinFETs by enhancing contact area and reducing etching losses, thereby increasing operating current and integration density.
Implementation Method 1
A multi-layered epitaxial source/drain region is grown with an intermediate epitaxial layer acting as a semiconductor contact etch stop layer (CESL)
Data Source
AI summary
In an embodiment, a device includes: a semiconductor substrate; a first fin extending from the semiconductor substrate; a second fin extending from the semiconductor substrate; an epitaxial source/drain region including: a main layer in the first fin and the second fin, the main layer including a first semiconductor material, the main layer having an upper faceted surface and a lower faceted surface, the upper faceted surface and the lower faceted surface each being raised from respective surfaces of the first fin and the second fin; and a semiconductor contact etch stop layer (CESL) contacting the upper faceted surface and the lower faceted surface of the main layer, the semiconductor CESL including a second semiconductor material, the second semiconductor material being different from the first semiconductor material.