Non-Linear FinFET Gate Profile for Source/Drain Spacing
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Solution Overview
Problem
The semiconductor industry faces challenges in implementing advanced IC fabrication processes, particularly in forming gate structures with desired profiles for FinFET devices, which is crucial for maintaining the desired distance to nearby structures like source/drain structures.
Innovation Solution
The method involves forming a dummy gate structure with different profiles at its top and bottom portions, where the bottom portion has a non-linear surface, such as a hyperbolic surface, to create a wider process window and maintain the desired distance between the gate structure and nearby source/drain structures during the replacement gate process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy gate structure with a non-linear surface (hyperbolic profile) is formed, then the process window for source/drain structure growth is widened and the distance to nearby structures is maintained, but the device complexity and fabrication difficulty increase
Solution Approach 1:
The dummy gate structure is divided into two distinct portions: a top portion with a first profile and a bottom portion with a second (hyperbolic) profile. This segmentation allows each portion to serve different functions - the top portion maintains gate control while the bottom portion provides the necessary spacing and process window for source/drain structure formation, thereby resolving the contradiction between reliability and device complexity.
Solution Approach 2:
Different profiles are applied to different portions of the dummy gate structure based on local requirements. The bottom portion near the source/drain regions has a hyperbolic profile to maintain distance and prevent current leakage, while the top portion has a different profile optimized for gate control. This local differentiation resolves the contradiction by tailoring the structure to specific functional needs.
2Productivity
If the gate structure is formed closer to source/drain structures to increase device density, then productivity and device density improve, but current leakage and electrical defects increase
Solution Approach 1:
The solution moves from considering only horizontal spacing to incorporating vertical dimensionality through the non-linear profile. The hyperbolic profile of the bottom portion creates a three-dimensional configuration that maintains adequate distance from source/drain structures while allowing higher device density in the planar direction, thus resolving the contradiction between productivity and reliability.
Solution Approach 2:
The dummy gate structure with its non-linear profile acts as an intermediary element between the gate electrode and source/drain structures. It provides the necessary spacing and control to prevent current leakage while enabling close proximity for high device density, thereby resolving the contradiction between productivity and electrical performance.
3Ease of manufacture
If a standard linear gate structure is used, then fabrication is simpler and device complexity is reduced, but the process window for source/drain structure growth is limited and desired distance cannot be maintained
Solution Approach 1:
The dummy gate structure with its pre-formed non-linear profile is created before source/drain structure formation. This preliminary action establishes the correct geometric configuration and spacing requirements in advance, providing a wider process window for subsequent source/drain structure growth and preventing fabrication errors, thus resolving the contradiction between ease of manufacture and manufacturing precision.
Data Source
AI summary
Semiconductor device structures with a gate structure having different profiles at different portions of the gate structure may include a fin structure on a substrate, a source/drain structure on the fin structure, and a gate structure over the fin structure and along a sidewall of the fin. The source/drain structure is proximate the gate structure. The gate structure has a top portion having a first sidewall profile and a bottom portion having a second sidewall profile different from the first sidewall profile.