MOSFET Cap Layer Structure for Flicker Noise Reduction
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Solution Overview
Problem
Metal-oxide-semiconductor field-effect transistors (MOSFETs) face flicker noise issues due to charge carrier trapping at defect states in the gate dielectric and shallow trench isolation (STI) corners, which are exacerbated by the outgassing of noise-reducing materials during anneal processes, reducing their effectiveness.
Innovation Solution
A patterned outgas prevention layer is formed over the gate electrode and semiconductor substrate to prevent the noise-reducing material from escaping during subsequent anneal processes, maintaining its effectiveness in reducing flicker noise by acting as a capping layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If noise-reducing material is introduced to reduce flicker noise, then flicker noise is reduced, but the material outgasses during anneal processes reducing its effectiveness
Solution Approach 1:
A cap layer is introduced as an intermediary component between the noise-reducing material and the external environment. This cap layer prevents the noise-reducing material from outgassing during anneal processes while allowing the material to remain in place and continue reducing flicker noise. The cap layer acts as a mediator that resolves the conflict between maintaining material effectiveness and preventing material loss.
Solution Approach 2:
The cap layer is formed over the gate electrode before the anneal process occurs. This preliminary action ensures that when the anneal process is subsequently performed, the noise-reducing material is already protected from outgassing. By preparing the protective structure in advance, the effectiveness of the noise-reducing material is preserved without requiring modifications to the anneal process itself.
2Loss of substance
If a cap layer is added to prevent material outgassing, then material retention is improved, but device structure becomes more complex
Solution Approach 1:
The cap layer is designed to serve multiple functions: it prevents noise-reducing material outgassing during anneal processes, and it can also serve as a foundation for subsequent processing steps such as forming contact holes or depositing additional layers. By making the cap layer multi-functional, the added structural complexity is justified by the multiple benefits it provides, rather than being a single-purpose addition.
Data Source
AI summary
In some embodiments, a semiconductor device is provided. The semiconductor device includes a gate electrode disposed on a substrate. Source/drain regions are disposed on or within the substrate along opposing sides of the gate electrode. A noise reducing component is arranged along an upper surface of the gate electrode and/or along an upper surface of the substrate over the source/drain regions. A cap layer covers the upper surface of the gate electrode and/or the upper surface of the substrate over the source/drain regions. An inter-level dielectric (ILD) is disposed over and along one or more sidewalls of the cap layer.