Source/Drain Contact Structure With Directional Sidewall Metal Removal
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Solution Overview
Problem
As semiconductor devices continue to shrink, reducing structural defects such as voids and contact resistance in source/drain contacts becomes increasingly challenging, with existing methods being only partially effective.
Innovation Solution
The method involves forming a semiconductor device with a fin-like structure, where a directional deposition process is used to form a metal layer over the source/drain feature, followed by a directional treatment process to form a barrier layer, and then a series of coating and etching processes to selectively remove sidewall portions of the metal layer, thereby forming a source/drain contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition processes are used to form metal layers in contact openings, then complete coverage is achieved, but voids form and contact resistance increases
Solution Approach 1:
The patent applies different deposition conditions to different regions of the contact opening. The directional deposition process deposits metal at different thicknesses on horizontal surfaces versus vertical sidewalls, creating local quality variations that prevent void formation while ensuring complete coverage and low contact resistance.
Solution Approach 2:
The patent transitions from conventional isotropic deposition to anisotropic directional deposition, adding a directional dimension to the deposition process. This allows differential metal layer formation based on surface orientation (horizontal vs. vertical), resolving the contradiction between complete coverage and void prevention.
2Manufacturing precision
If material layers are removed from sidewalls to reduce defects, then structural quality improves, but material loss occurs at the bottom
Solution Approach 1:
The selective removal process targets only sidewall portions of the metal layer while preserving the bottom portion. This local quality differentiation ensures that defect reduction through sidewall removal does not compromise the integrity of the bottom contact region.
Solution Approach 2:
The patent segments the metal layer into distinct portions (sidewall vs. bottom) and applies different treatment to each. The sidewall portions are selectively removed while the bottom portions are retained, achieving defect reduction without material loss at critical interfaces.
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 reduces the total thickness of material layers on the sidewalls of the contact opening, allowing for more complete removal of these layers without losing material from the bottom, thus reducing structural defects and contact resistance.
Implementation Method 1
depositing a first metal layer in the contact opening, the first metal layer having a first portion over the source/drain feature and a second portion along a sidewall of the contact opening
Implementation Method 2
performing a directional treatment process to form a barrier layer in the metal layer
Data Source
AI summary
A semiconductor structure includes a source/drain feature in the semiconductor layer. The semiconductor structure includes a dielectric layer over the source/drain feature. The semiconductor structure includes a silicide layer over the source/drain feature. The semiconductor structure includes a barrier layer over the silicide layer. The semiconductor structure includes a seed layer over the barrier layer. The semiconductor structure includes a metal layer between a sidewall of the seed layer and a sidewall of the dielectric layer, a sidewall of each of the silicide layer, the barrier layer, and the metal layer directly contacting the sidewall of the dielectric layer. The semiconductor structure includes a source/drain contact over the seed layer.