Semiconductor Contact Liner Diffusion for Fill Resistance
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Solution Overview
Problem
In p-type field effect transistors (PFETs) for 14/10 nm silicon-on-insulator technologies, the use of a Ti-based silicide liner with a NiPt bilayer poses challenges due to the requirement for a thick metal layer, leading to incomplete contact fill issues as semiconductor devices shrink, affecting contact opening fill and overall contact resistance.
Innovation Solution
A method involving the formation of a contact opening in a dielectric layer over a semiconductor substrate, where a first liner layer is deposited to conformally coat the opening and diffuse into the substrate, forming an intermix region, followed by a refractory metal layer and metal deposition to fill the contact, without increasing the metal thickness, thereby improving contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ti-based silicide liner with NiPt bilayer is used to improve workfunction in PFET source and drain, then the workfunction is improved, but the contact opening fill becomes incomplete due to the thick metal layer required
Solution Approach 1:
The contact structure is segmented into multiple functional layers: a thin intermix region (5-10 nm) providing workfunction improvement, a refractory metal layer (TiN or TaN) providing low resistance, and a tungsten fill providing structural support and electrical connection. This segmentation allows each layer to be optimized independently, resolving the conflict between thick metal requirements for workfunction and thin metal requirements for complete contact fill.
Solution Approach 2:
The invention changes the material composition and thickness parameters of the contact layers. Specifically, it uses a thin intermix region (5-10 nm) instead of a thick bilayer, adjusts the refractory metal layer thickness (5-20 nm), and optimizes the tungsten fill dimensions. These parameter changes enable complete contact opening fill while maintaining the required workfunction improvement for PFET operation.
2Reliability
If a thick bilayer is deposited to improve workfunction, then the workfunction is improved, but contact opening fill issues occur such as incomplete contact fill
Solution Approach 1:
The contact structure is segmented into multiple functional layers: a thin intermix region (5-10 nm) providing workfunction improvement, a refractory metal layer (TiN or TaN) providing low resistance, and a tungsten fill providing structural support and electrical connection. This segmentation allows each layer to be optimized independently, resolving the conflict between thick metal requirements for workfunction and thin metal requirements for complete contact fill.
Solution Approach 2:
The invention changes the material composition and thickness parameters of the contact layers. Specifically, it uses a thin intermix region (5-10 nm) instead of a thick bilayer, adjusts the refractory metal layer thickness (5-20 nm), and optimizes the tungsten fill dimensions. These parameter changes enable complete contact opening fill while maintaining the required workfunction improvement for PFET operation.
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 avoids contact opening fill issues and enhances overall contact resistance by forming a thin, conformal intermix region at the substrate interface, allowing for effective contact formation without the need for thick metal layers.
Implementation Method 1
causing a portion of the first liner layer to diffuse into the upper portion of the semiconductor substrate to form a first intermix region
Implementation Method 2
depositing a refractory metal layer over the first intermix region; and depositing a metal in the contact opening
Data Source
AI summary
An aspect of the invention includes a method for forming a contact in a dielectric layer over a semiconductor substrate. The method may comprise: forming a contact opening in a dielectric layer over the semiconductor substrate to expose an upper portion of the semiconductor substrate; depositing a first liner layer to conformally coat the contact opening; causing a portion of the first liner layer to diffuse into the upper portion of the semiconductor substrate to form a first intermix region at the upper portion of the semiconductor substrate; depositing a refractory metal layer over the first intermix region; and depositing a metal in the contact opening thereby forming the contact.