Multi-Spacer Gate Structure for Wet Etch Dielectric Protection
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Solution Overview
Problem
Existing semiconductor fabrication processes often damage gate dielectric layers during etching and cleaning processes, leading to reduced device yield and potential device failure.
Innovation Solution
A multi-spacer structure is introduced, comprising a first spacer on the sidewalls of the gate stack, a second spacer with a wedge-shaped lower portion on the substrate, and a third spacer on the second spacer. This structure provides a protective seal against wet etchants, preventing damage to the gate dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-spacer structures are used, then the fabrication process is simple, but the gate dielectric layer is damaged during etching and cleaning processes
Solution Approach 1:
The single spacer structure is divided into multiple spacers (first spacer, second spacer, and third spacer) with different materials and positions. Each spacer serves a specific protective function: the first spacer protects the gate dielectric, the second spacer provides structural support, and the third spacer protects during source/drain formation. This segmentation allows comprehensive protection while maintaining clear functional differentiation.
Solution Approach 2:
The multi-spacer structure uses different materials for each spacer layer. The first spacer is made of silicon nitride, the second spacer uses a different material composition, and the third spacer employs yet another material. This composite approach allows each spacer to be optimized for its specific protective function against different chemical etchants and processing conditions.
2Productivity
If multiple spacers are introduced to protect gate dielectric, then device yield improves, but fabrication process complexity increases
Solution Approach 1:
The first spacer is formed on the gate stack sidewalls before any etching or cleaning processes occur. This preliminary protective layer is in place before the gate dielectric is exposed to potential damage, preventing etchant penetration and chemical damage during subsequent fabrication steps.
Solution Approach 2:
The multi-spacer structure acts as a protective cushion before the gate dielectric is exposed to harmful etchants. The spacers are positioned and formed in advance to create a protective barrier that absorbs and deflects the harmful effects of chemical etching processes.
Data Source
AI summary
The present disclosure relates to a semiconductor device including a substrate having a top surface and a gate stack. The semiconductor device also includes a multi-spacer structure. The multi-spacer includes a first spacer formed on a sidewall of the gate stack, a second spacer, and a third spacer. The second spacer includes a first portion formed on a sidewall of the first spacer and a second portion formed on the top surface of the substrate. The second portion of the second spacer has a thickness in a first direction that gradually decreases. The third spacer is formed on the second portion of the second spacer and on the top surface of the substrate. The semiconductor device further includes a source/drain region formed in the substrate, and a portion of the third spacer abuts the source/drain region and the second portion of the second spacer.