P-Type MOSFET Contacts With Boride Barrier for Thermal Stability
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Solution Overview
Problem
Metal contacts to MOSFET source/drain regions are thermally unstable, leading to increased contact resistance due to dopant diffusion and deactivation during high-temperature processing steps in semiconductor manufacturing, affecting transistor performance.
Innovation Solution
Incorporating a boride, indium, or gallium metal compound layer between the p-type source/drain region and the contact metal layer, which acts as a diffusion barrier and maintains a dopant concentration gradient to prevent dopant diffusion and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal contact layer is formed directly on the source/drain region, then contact resistance is initially low, but the contact becomes thermally unstable and resistance increases during high-temperature processing
Solution Approach 1:
A boride, indium, or gallium metal compound layer is introduced as an intermediary layer between the contact metal layer and the source/drain region. This intermediate layer acts as a diffusion barrier that prevents dopant diffusion during high-temperature processing, thereby maintaining thermal stability while preserving low contact resistance.
Solution Approach 2:
The contact structure is formed as a composite material system consisting of multiple layers: the contact metal layer, the boride/indium/gallium metal compound layer, and the source/drain region. This composite structure combines the advantages of each material to achieve both low resistance and thermal stability.
2Productivity
If high-temperature processing steps are performed to complete semiconductor manufacturing, then device fabrication is completed, but dopant diffusion and deactivation occur leading to increased contact resistance
Solution Approach 1:
The boride, indium, or gallium metal compound layer is formed preliminarily before the high-temperature processing steps. This preliminary action establishes a protective diffusion barrier in advance, preventing dopant diffusion and deactivation during subsequent high-temperature manufacturing processes.
Solution Approach 2:
The high-temperature processing steps, which normally cause harmful dopant diffusion and deactivation, are converted into a beneficial process by the presence of the metal compound layer. The layer allows the necessary thermal processing to complete manufacturing while preventing the harmful effects, effectively using the heat for both fabrication and protection.
3Ease of manufacture
If dopant diffusion is allowed during processing, then manufacturing steps can be completed, but contact resistance increases and transistor performance deteriorates
Solution Approach 1:
The metal compound layer serves as an intermediary diffusion barrier that allows manufacturing processes to proceed with necessary thermal steps while controlling dopant diffusion. This enables processing flexibility without sacrificing contact resistance control.
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 use of boride, indium, or gallium metal compound layers results in thermally stable, low-resistance contacts with a 'pile-up' of p-type dopants at the contact-source/drain interface, enhancing transistor performance by reducing contact resistance and silicide formation.
Implementation Method 1
Incorporating a boride, indium, or gallium metal compound layer between the p-type source/drain region and the contact metal layer, which acts as a diffusion barrier and maintains a dopant concentration gradient to prevent dopant diffusion
Implementation Method 2
acts as a diffusion barrier and maintains a dopant concentration gradient to prevent dopant diffusion and reduce contact resistance
Data Source
AI summary
Contacts to p-type source/drain regions comprise a boride, indium, or gallium metal compound layer. The boride, indium, or gallium metal compound layers can aid in forming thermally stable low resistance contacts. A boride, indium, or gallium metal compound layer is positioned between the source/drain region and the contact metal layer. A boride, indium, or gallium metal compound layer can be used in contacts contacting p-type source/drain regions comprising boron, indium, or gallium as the primary dopant, respectively. The boride, indium, or gallium metal compound layers prevent diffusion of boron, indium, or gallium from the source/drain region into the metal contact layer and dopant deactivation in the source/drain region due to annealing and other high-temperature processing steps that occur after contact formation. Boride, indium, or gallium metal contact layers can also reduce the amount of silicide that forms in source/drain regions during processing by limiting contact metal diffusion into source/drain regions.