Gate Structure Capping Oxide Layer Against Metal Penetration
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Solution Overview
Problem
As semiconductor device scaling-down continues, existing manufacturing processes have been inadequate in preventing metal penetration into the substrate and maintaining optimal oxygen levels in gate dielectric layers, leading to performance issues such as high threshold voltage and poor uniformity.
Innovation Solution
The implementation of a capping oxide layer formed over a capping layer in the semiconductor structure, which serves as an oxygen source for the gate dielectric layer and a barrier to prevent metal penetration from the gate electrode into the substrate, thereby reducing oxygen vacancies and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal gate electrode is formed directly over gate dielectric layer, then device scaling is achieved, but metal penetration into substrate occurs and oxygen vacancies increase
Solution Approach 1:
A capping oxide layer is introduced as an intermediary between the metal gate electrode and gate dielectric layer. This intermediate layer prevents direct contact between metal and dielectric, blocking metal penetration into the substrate while also serving as an oxygen source to fill oxygen vacancies in the gate dielectric layer, thereby resolving the reliability issues associated with direct metal-dielectric contact in scaled devices.
Solution Approach 2:
The gate structure is segmented into multiple functional layers: gate dielectric layer, capping layer, capping oxide layer, and metal gate electrode layer. This segmentation allows each layer to perform its specific function - the capping oxide layer specifically addresses metal penetration and oxygen vacancy issues without interfering with the primary functions of the gate dielectric and metal electrode.
2Ease of manufacture
If conventional gate structure is used, then manufacturing process is simple, but oxygen vacancies in gate dielectric layer cause high threshold voltage and poor uniformity
Solution Approach 1:
The capping oxide layer serves a dual function: it acts as a barrier to metal penetration and simultaneously serves as an oxygen source that diffuses into the gate dielectric layer to fill oxygen vacancies. This self-service mechanism improves threshold voltage uniformity and reduces defects without requiring additional complex manufacturing steps beyond the standard layer deposition process.
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 enhances the uniformity and performance of semiconductor devices by reducing oxygen vacancies in the gate dielectric layer and preventing metal penetration, thus maintaining optimal threshold voltage and device reliability.
Implementation Method 1
The capping oxide layer may be used as an oxygen source for the gate dielectric layer
Implementation Method 2
a barrier layer to prevent the metal formed over it from penetrating to the substrate
Data Source
AI summary
Semiconductor structures and methods for forming the same are provided. The method includes forming a dummy gate structure over a substrate and forming a sealing layer surrounding the dummy gate structure. The method includes forming a spacer covering the sealing layer and removing the dummy gate structure to form a trench. The method further includes forming an interfacial layer and a gate dielectric layer. The method further includes forming a capping layer over the gate dielectric layer and partially oxidizing the capping layer to form a capping oxide layer. The method further includes forming a work function metal layer over the capping oxide layer and forming a gate electrode layer over the work function metal layer. In addition, a bottom surface of the capping oxide layer is higher than a bottom surface of the spacer.