Source/Drain Epitaxial Layer Structure for Lattice Defect Suppression
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Solution Overview
Problem
The increasing demand for high-performance, high-speed, and multifunctional semiconductor devices has led to challenges in integrating semiconductor devices effectively, particularly in achieving reliable electrical characteristics and preventing lattice mismatch and defects in source/drain regions.
Innovation Solution
The semiconductor device incorporates a multi-epitaxial layer structure with a first epitaxial layer including silicon-germanium and boron, and a second epitaxial layer with silicon-germanium, boron, and carbon, where the second epitaxial layer covers the end portions of the first epitaxial layer, reducing lattice mismatch and defects, and a third epitaxial layer with varying thicknesses to enhance etching selectivity and prevent damage during sacrificial layer removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-epitaxial layer structure is used in the source/drain region, then lattice mismatch and defects are reduced, but device complexity increases
Solution Approach 1:
The source/drain region is divided into multiple epitaxial layers (first epitaxial layer, second epitaxial layer, and third epitaxial layer) with different compositions and functions. Each layer is segmented to perform specific tasks: the first layer provides lattice matching, the second layer suppresses defect formation, and the third layer controls etching selectivity. This segmentation resolves the contradiction by organizing complexity into functional modules that collectively improve reliability.
Solution Approach 2:
The patent employs composite material structures where different epitaxial layers contain varying compositions of silicon, germanium, and impurities (boron, carbon). The first epitaxial layer may contain silicon-germanium with specific Ge concentration, while the second and third layers have different compositions optimized for their respective functions. This composite approach allows each material component to contribute its unique properties, reducing lattice mismatch while managing the overall structural complexity.
2Reliability
If the second epitaxial layer covers end portions of the first epitaxial layer, then etching selectivity is enhanced and damage is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The second epitaxial layer is formed to preliminarily cover the end portions of the first epitaxial layer before the etching process occurs. This preliminary coverage action ensures that when etchants are applied to remove sacrificial layers, the critical regions are already protected. The design anticipates potential etching damage and prevents it in advance, though it requires precise control during the epitaxial growth process to achieve proper alignment.
Solution Approach 2:
The second epitaxial layer is not uniformly distributed but specifically positioned to cover only the end portions of the first epitaxial layer where etching damage is most likely to occur. This localized quality approach concentrates the protective function where it is most needed, enhancing etching selectivity and damage prevention while minimizing the overall complexity compared to a complete uniform coverage structure.
3Reliability
If multiple impurities are included in epitaxial layers, then electrical characteristics are improved, but impurity diffusion control becomes more difficult
Solution Approach 1:
The second epitaxial layer acts as an intermediary barrier between regions containing different impurities. It includes carbon as a diffusion barrier element that prevents unwanted impurity diffusion while allowing the first and third epitaxial layers to maintain their respective impurity profiles (such as boron in the first layer). This intermediary layer mediates the interaction between different impurity-containing regions, enabling improved electrical characteristics without excessive diffusion control complexity.
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 configuration improves the reliability and electrical characteristics of semiconductor devices by suppressing lattice defects and impurity diffusion, maintaining resistance, and preventing damage from etchants, thereby enhancing the overall performance and integration of semiconductor devices.
Implementation Method 1
a first epitaxial layer covering an inner wall of the recessed region of the active region; and a second epitaxial layer on the first epitaxial layer... reducing lattice mismatch and defects
Implementation Method 2
the first epitaxial layer and the second epitaxial layer include silicon-germanium (SiGe) having different compositions... enhance etching selectivity
Implementation Method 3
each of the first epitaxial layer and the second epitaxial layer includes a first impurity including boron (B), the second epitaxial layer further includes a second impurity including carbon (C)... suppressing lattice defects and impurity diffusion
Data Source
AI summary
A semiconductor device including an active region extending in a first direction on a substrate; channel layers vertically spaced apart on the active region; a gate structure extending in a second direction and intersecting the active region, the gate structure surrounding the channel layers; a source/drain region on the active region in contact with the channel layers; and a contact plug connected to the source/drain region, wherein the source/drain region includes a first epitaxial layer on side surfaces of the channel layers and including a first impurity; a second epitaxial layer on the first epitaxial layer and including the first impurity and a second impurity; and a third epitaxial layer on the second epitaxial layer and including the first impurity, and in a horizontal sectional view, the second epitaxial layer includes a peripheral portion having a thickness in the first direction that increases along the second direction.