Contact Etch Stop Layer Stack for Strain Engineering
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Solution Overview
Problem
Conventional techniques for creating strain in transistor channel regions are inefficient, leading to reduced stress transfer and increased production costs, while maintaining metal silicide integrity and enhancing transistor performance.
Innovation Solution
The use of differently stressed contact etch stop layers, where one transistor type is directly in contact with the contact etch stop layer, allowing for selective etching and maintaining high integrity of metal silicide regions, while enhancing stress transfer mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etch stop layer techniques are used, then transistor strain is created, but stress transfer efficiency is reduced and metal silicide integrity is compromised
Solution Approach 1:
The patent divides the etch stop layer into two separate layers: a first etch stop layer (silicon nitride) and a second etch stop layer (silicon oxide). This segmentation allows each layer to perform its function independently - the silicon nitride layer provides stress transfer to the channel region while the silicon oxide layer protects the metal silicide regions during etching, thereby resolving the contradiction between stress transfer efficiency and metal silicide integrity.
Solution Approach 2:
The patent introduces an intermediary layer (silicon oxide etch stop layer) between the stress-inducing layer (silicon nitride) and the metal silicide regions. This intermediary acts as a protective barrier during selective etching processes, preventing direct contact between the etchant and metal silicide regions, thus maintaining metal silicide integrity while allowing the silicon nitride layer to effectively transfer stress to the channel region.
2Reliability
If strain engineering is implemented to improve transistor performance, then charge carrier mobility increases, but process complexity and production costs increase
Solution Approach 1:
The patent makes the contact etch stop layer structure multi-functional by combining stress transfer and selective etching protection functions into a single integrated layer system. The first etch stop layer (silicon nitride) serves both as a stress-inducing layer for strain engineering and as part of the etch stop structure, while the second etch stop layer (silicon oxide) provides both etching protection and stress transfer. This multi-functionality reduces process complexity compared to separate strain engineering and etch protection processes.
Solution Approach 2:
The patent utilizes parameter changes in the etch stop layer materials (different etch selectivities of silicon nitride and silicon oxide) to achieve both strain engineering and protective functions. By selecting materials with contrasting etch properties, the process enables selective removal of the silicon oxide layer to expose metal silicide regions while retaining the silicon nitride layer for stress transfer, thereby simplifying the overall process through material property optimization rather than adding complex process steps.
3Manufacturing precision
If selective etching is used to remove contact etch stop layer portions, then transistor-specific strain is achieved, but material erosion and device damage occur
Solution Approach 1:
The patent applies beforehand cushioning by forming a protective silicon oxide layer over the metal silicide regions before performing selective etching of the silicon nitride layer. This pre-formed protective layer acts as a cushion or barrier that prevents the etchant from directly attacking and eroding the metal silicide regions during the selective etching process, thereby enabling precise strain engineering without causing material erosion or device damage.
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 enables effective strain engineering in transistor channel regions, improving transistor performance by enhancing stress transfer efficiency while maintaining device integrity and reducing material erosion.
Implementation Method 1
the first contact etch stop layer has a first specified intrinsic stress... the second contact etch stop layer has a second intrinsic stress that differs from the first intrinsic stress
Data Source
AI summary
By partially removing an etch stop layer prior to the formation of a first contact etch stop layer, a superior stress transfer mechanism may be provided in an integration scheme for generating strain by means of contact etch stop layers. Thus, a semiconductor device having different types of transistors may be provided, in which a high degree of metal silicide integrity as well as a highly efficient stress transfer mechanism is achieved.