Buffer Layer Protects Epitaxial Layer from Etchant Damage
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Solution Overview
Problem
During the fabrication of CMOS devices, the epitaxial layer adjacent to the gate structure in NMOS and PMOS regions is often damaged by etchants, leading to degraded device performance.
Innovation Solution
A method involving the formation of a buffer layer on the gate structure and a contact etch stop layer (CESL) is implemented to protect the epitaxial layer, which includes forming a substrate with defined regions, creating fin-shaped structures, forming gate structures, spacers, and epitaxial layers, and applying a buffer layer and CESL to prevent damage from etchants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polysilicon gate is used, then the gate structure can be formed, but boron penetration and depletion effect occur which degrade device performance
Solution Approach 1:
The patent extracts and removes the problematic polysilicon gate material that causes boron penetration and depletion effects. Instead of using conventional polysilicon gates, the invention employs alternative gate structures or materials that eliminate these harmful effects while maintaining the necessary gate functionality for device operation.
Solution Approach 2:
The patent changes the material parameters and compositional characteristics of the gate structure. By transitioning from polysilicon to alternative materials or composite structures, the invention modifies the electrical and chemical properties to prevent boron penetration and reduce depletion effects, thereby improving device performance.
2Reliability
If high-k metal gate structures are fabricated, then gate control is improved, but the epitaxial layer adjacent to the gate structure is damaged by etchants
Solution Approach 1:
The patent introduces an intermediary protective layer between the etchant and the epitaxial layer adjacent to the gate structure. This intermediate layer acts as a barrier that prevents direct contact between the etchant and the sensitive epitaxial regions, thereby protecting the epitaxial layer from damage while allowing the etching process to proceed for other structures.
Solution Approach 2:
The patent applies preliminary protective measures to the epitaxial layer before the etching process. By pre-forming protective coatings or modifying the epitaxial layer structure in advance, the invention creates resistance against etchant attack before the harmful etching action occurs, preventing damage to the gate-adjacent epitaxial regions.
3Productivity
If the epitaxial layer is exposed during etching, then the etching process can be completed, but the epitaxial layer performance is degraded
Solution Approach 1:
The patent employs an intermediary protective layer that allows the etching process to proceed while shielding the epitaxial layer from direct etchant exposure. This mediator layer enables complete etching of necessary structures without compromising the integrity and performance of the epitaxial layer, as the protective layer can be removed or integrated afterward.
Solution Approach 2:
The patent performs preliminary protection of the epitaxial layer before the etching process begins. By pre-applying protective coatings or forming protective structures, the invention ensures that the epitaxial layer is safeguarded during the entire etching sequence, allowing productive etching while maintaining epitaxial layer performance.
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
The buffer layer and CESL effectively protect the epitaxial layers from etchant damage, enhancing the performance and reliability of semiconductor devices by maintaining the integrity of the epitaxial layers during the etching process.
Implementation Method 1
The buffer layer and CESL effectively protect the epitaxial layers from etchant damage, enhancing the performance and reliability of semiconductor devices by maintaining the integrity of the epitaxial layers during the etching process.
Data Source
AI summary
A method for fabricating semiconductor device includes the steps of: providing a substrate having a first region and a second region; forming a first gate structure on the first region and a second gate structure on the second region; forming a first spacer around the first gate structure; forming a first epitaxial layer adjacent to two sides of the first spacer; forming a buffer layer on the first gate structure; and forming a contact etch stop layer (CESL) on the buffer layer on the first region and the second gate structure on the second region.