Metal Gate Isolation Features for Flat S/D Contact Landing
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Solution Overview
Problem
Existing trench-filling materials for metal gate electrodes in semiconductor manufacturing often have different etch selectivity than the inter-layer dielectric layer, leading to hillocks in the source/drain contact landing area, which increase contact resistance and reduce yield.
Innovation Solution
The introduction of oxygen-free dielectric isolation features in the trench between newly-cut metal gate segments and within the inter-layer dielectric adjacent to source/drain features, using materials like silicon nitride and silicon carbide nitride, to prevent oxidation and improve etching rates, thereby reducing hillocks and contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing trench-filling materials are used for metal gate electrodes, then the filling process can be completed, but hillocks form in the source/drain contact landing area due to different etch selectivity than the inter-layer dielectric layer
Solution Approach 1:
The patent segments the trench-filling process into multiple steps: first forming a mandrel structure, then depositing dielectric material around it, and finally removing the mandrel. This segmentation allows precise control of the filling process and prevents hillock formation by ensuring uniform material distribution and etch selectivity management.
Solution Approach 2:
The patent performs preliminary actions by forming a mandrel structure and depositing a first dielectric material before final trench filling. This preliminary structure serves as a template that guides subsequent material deposition and prevents direct contact between the trench-filling material and the source/drain contact landing area, thereby preventing hillocks.
2Productivity
If trench-filling material with different etch selectivity than ILD layer is used, then the metal gate cut process can be completed, but contact resistance increases due to hillocks in the S/D contact landing area
Solution Approach 1:
The patent introduces an intermediary first dielectric material that is deposited around the mandrel structure. This intermediary material acts as a buffer between the trench-filling material and the source/drain contact landing area. It has controlled etch selectivity that prevents hillock formation while allowing the metal gate cut process to proceed efficiently, thereby maintaining low contact resistance.
Solution Approach 2:
The patent applies local quality by using different dielectric materials in different regions: the first dielectric material is deposited specifically around the mandrel in the trench region, while the second dielectric material fills the remaining trench space. This localized material differentiation ensures that the contact landing area remains free of hillocks while maintaining overall process efficiency.
3Ease of manufacture
If conventional dielectric materials are used in the trench, then the metal gate electrode can be formed, but oxidation occurs and etching rates are reduced
Solution Approach 1:
The patent employs an inert environment approach by selecting dielectric materials with high oxidation resistance for the trench region. The first dielectric material deposited around the mandrel and the second dielectric material used for trench filling are specifically chosen to resist oxidation, creating a stable, inert environment that protects the metal gate electrode from oxidative degradation while maintaining ease of manufacture.
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 enhances contact resistance in the source/drain contact landing area, improving the yield and performance of semiconductor devices by preventing hillocks and ensuring better gate control.
Implementation Method 1
an oxygen-free dielectric material, such as silicon nitride and silicon carbide nitride, is deposited in the trench to form an isolation feature
Implementation Method 2
a metal layer deposition followed by a subsequent metal layer cut process
Implementation Method 3
an oxygen-free dielectric material, such as silicon nitride and silicon carbide nitride, is deposited in the trench
Data Source
AI summary
Semiconductor devices and methods of fabricating semiconductor devices are provided. The present disclosure provides a semiconductor device that includes a first fin structure and a second fin structure each extending from a substrate; a first gate segment over the first fin structure and a second gate segment over the second fin structure; a first isolation feature separating the first and second gate segments; a first source/drain (S/D) feature over the first fin structure and adjacent to the first gate segment; a second S/D feature over the second fin structure and adjacent to the second gate segment; and a second isolation feature also disposed in the trench. The first and second S/D features are separated by the second isolation feature, and a composition of the second isolation feature is different from a composition of the first isolation feature.