Gate Contact Structure With Helmet Layer for Alignment Margin
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Solution Overview
Problem
In CMOS fabrication, the shrinking technology nodes pose challenges such as misalignment of contacts leading to source/drain regions shorting to metal gate structures, exacerbated by decreasing gate length and spacing, which complicates the implementation of high-dielectric-constant gate dielectric layers and metal gate electrodes.
Innovation Solution
A method for fabricating semiconductor devices involves forming a helmet layer over the gate electrode, followed by a bottom conductive feature and contact etch stop layer, with a via hole filled with conductive material, and the use of high-k dielectric layers and metal gate electrodes to reduce gate leakage and maintain performance with decreased dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If technology nodes are shrunk to improve device density and performance, then device integration is improved, but misalignment of contacts occurs leading to source/drain regions shorting to metal gate structures
Solution Approach 1:
The helmet layer is formed over the gate electrode before contact formation, establishing a protective structure in advance that defines the contact formation window and prevents misalignment issues that would otherwise occur during subsequent processing steps
Solution Approach 2:
The helmet layer acts as an intermediary protective structure between the gate electrode and the contact formation process, providing a defined interface that prevents direct contact between source/drain regions and metal gate structures while allowing proper contact alignment
2Productivity
If gate length and spacing are decreased to improve device density, then device integration is improved, but the processing window for contact plug formation is reduced
Solution Approach 1:
The helmet layer is formed in advance over the gate electrode, establishing a protective structure that defines the contact formation window before contact holes are etched, thereby maintaining adequate processing margins even as gate dimensions are reduced
Solution Approach 2:
The helmet layer extends the protective function into the vertical dimension, providing side wall coverage that compensates for reduced lateral spacing and maintains processing robustness in scaled devices
3Reliability
If high-dielectric-constant gate dielectric layers are used to reduce gate leakage, then electrical performance is improved, but device complexity increases
Solution Approach 1:
The helmet layer is formed before contact formation, establishing a protective structure that simplifies subsequent contact processing by providing a defined etch stop and protection layer, thereby reducing overall process complexity despite the use of high-k dielectric materials
Data Source
AI summary
A method includes forming a gate stack over a substrate and a gate spacer on a sidewall of the gate stack; forming a source/drain region in the substrate and adjacent to the gate spacer; forming a first interlayer dielectric layer over the source/drain region; forming a protective layer over the gate stack and in contact with a top surface of the gate spacer; removing the first interlayer dielectric layer after forming the protective layer; forming an etch stop layer over the protective layer; forming a second interlayer dielectric layer over the etch stop layer; etching the second interlayer dielectric layer and the etch stop layer to form an opening that exposes a top surface of the protective layer; and forming a contact plug in the opening.