Semiconductor Device Spacer Segmentation for Stress and Protection
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Solution Overview
Problem
In semiconductor manufacturing, reducing the width of spacers to increase stress between epitaxial layers and channel regions can impair the protective effect for NMOS transistors, potentially exposing them during the formation of epitaxial layers, which reduces their reliability.
Innovation Solution
The method involves forming second openings by etching the side walls of first openings with an etching gas, expanding them underneath adjacent spacers, and filling these openings with epitaxial layers, which increases stress between epitaxial layers and channel regions without reducing spacer width, thus enhancing transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the width of spacers is reduced to increase stress between epitaxial layers and channel regions, then the stress effect is improved, but the protective effect for NMOS transistors is impaired
Solution Approach 1:
The spacer structure is divided into two distinct parts: a first spacer that provides protection for NMOS transistors, and a second spacer that provides stress effect on PMOS transistors. This segmentation allows each spacer to be optimized for its specific function without compromising the other, resolving the contradiction between protective effect and stress effect.
Solution Approach 2:
Different regions of the device are provided with different spacer configurations tailored to their specific requirements. PMOS regions receive narrow second spacers for maximum stress effect, while NMOS regions maintain wide first spacers for protective coverage. This local differentiation allows simultaneous optimization of stress and protection in different areas of the same substrate.
2Productivity
If the width of spacers is reduced to increase stress effect, then transistor performance is improved, but the risk of NMOS exposure increases
Solution Approach 1:
The unified spacer structure is segmented into function-specific spacers, allowing the second spacer to be narrowed for performance enhancement while the first spacer maintains adequate width for reliability protection. This eliminates the need to compromise between performance and reliability in a single spacer design.
Solution Approach 2:
Performance-critical PMOS regions are provided with narrow spacers for maximum stress effect, while reliability-critical NMOS regions are provided with wide spacers for protection. This localized quality differentiation enables simultaneous achievement of high performance and high reliability in different transistor types.
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 enhances carrier migration rates and response speed of semiconductor devices by increasing compressive or tensile stresses between epitaxial layers and channel regions without compromising the protective effect of spacers on NMOS transistors.
Implementation Method 1
forming second openings by etching the side walls of first openings with an etching gas
Implementation Method 2
forming epitaxial layers in the first openings and the second openings
Implementation Method 3
By forming the SiGe epitaxial layers, a compressive stress is formed because of lattice mismatch between Si and Ge
Data Source
AI summary
A semiconductor device and a method for forming the same are provided. The method includes: providing a substrate having a gate structure and first spacers on both sidewalls of the gate structure formed on a top surface of the substrate; forming first openings in the substrate by using the first spacers as a mask, wherein the first openings are located on both sides of the gate structure; forming second openings by etching the first openings with an etching gas, wherein each of the second openings is an expansion of a corresponding one of the first openings toward the gate structure and extends to underneath an adjacent first spacer; and forming epitaxial layers in the first openings and the second openings.