Rounded Gate Electrode Silicide Stress Management
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Solution Overview
Problem
Conventional semiconductor devices with silicide layers on gate electrodes face challenges in achieving uniform thickness and low resistance due to film stresses and uneven silicide distribution, especially at gate widths of 150 nm or less, leading to unstable operation and increased resistance.
Innovation Solution
A semiconductor device with a gate electrode having a silicide layer featuring an upward-convex, approximately circular arc shape in cross-section, where the bottom and top surfaces of the silicide layer are curved, ensuring a uniform thickness and reduced film stresses, achieved through specific manufacturing processes including etching and rounding of the gate electrode ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional salicide process is used with a rectangular gate electrode, then the silicide layer formation is simplified, but the silicide layer thickness becomes uneven and resistance increases
Solution Approach 1:
The gate electrode top surface is modified from a rectangular shape to have rounded corners with a specific radius of curvature (10-50 nm). This curvature prevents the concentration of film stresses at the corners during silicidation, enabling uniform silicide layer thickness across the entire gate electrode surface including the corners, thereby resolving the thickness uniformity issue while maintaining process simplicity
2Device complexity
If the gate electrode has sharp corners, then the manufacturing process is simpler, but film stresses concentrate at the corners causing uneven silicide distribution
Solution Approach 1:
Rounded corners with radius of curvature 10-50 nm are formed on the gate electrode top surface. This curvature distributes film stresses uniformly during the silicidation process, preventing stress concentration at corners and ensuring even silicide layer formation, thereby improving reliability without significantly increasing device complexity
Solution Approach 2:
The radius of curvature parameter of the gate electrode corners is specifically controlled within 10-50 nm range. This parameter change optimizes the stress distribution during silicidation, preventing both stress concentration (which causes uneven silicide) and excessive rounding (which would reduce gate width). The precise parameter control ensures uniform silicide layer and stable device operation
3Productivity
If gate width is reduced for miniaturization, then device density increases, but resistance becomes unstable and signal delays increase
Solution Approach 1:
Rounded corners on the gate electrode top surface prevent stress concentration during silicidation, ensuring uniform silicide layer thickness even in narrow gates. This uniformity maintains stable resistance characteristics and prevents signal delays, enabling continued miniaturization without sacrificing reliability
Solution Approach 2:
The corner radius of curvature is optimized to 10-50 nm, which is sufficiently large to distribute stresses uniformly but small enough to maintain the required gate width for miniaturization. This parameter optimization enables stable resistance and signal integrity even at reduced gate widths, supporting higher device density
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 solution results in a stable and low-resistance silicide layer with reduced variation in resistance across the gate electrode, preventing signal delays and unstable operation even at smaller gate widths.
Implementation Method 1
A silicide process which uses silicide, a compound of silicon and metal, is known as a technology for reducing these resistances
Implementation Method 2
The surface portion of the gate electrode and the respective surface portions of the source/drain regions are then silicided in a self-aligned manner by heat treatment
Implementation Method 3
refractory metal expands to a large degree by heat treatment, whereas silicon does not expand very much. Moreover, the sidewall which is formed from a silicon oxide film, a silicon nitride film, a lamination thereof, or the like is less likely to expand by heat treatment as compared to silicon
Data Source
AI summary
In order that a top surface of a gate electrode does not have sharp portions, ends of the top surface of the gate electrode are rounded before refractory metal is deposited for silicidation. This reduces intensive application of film stresses which are generated in heat treatment, enabling formation of a silicide layer with a uniform, sufficient thickness.