Phosphide or Arsenide MOSFET Contacts for Thermal Resistance Stability
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Solution Overview
Problem
Metal contacts to MOSFET source/drain regions are thermally unstable, leading to increased resistance due to dopant diffusion and deactivation during high-temperature processing steps in semiconductor manufacturing, affecting transistor performance.
Innovation Solution
Incorporating a phosphide or arsenide metal compound layer between the n-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, thereby forming thermally stable low-resistance contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contacts are formed directly to source/drain regions, then contact resistance is initially low, but resistance increases after high-temperature processing due to dopant diffusion and deactivation
Solution Approach 1:
A phosphide or arsenide metal compound layer is introduced as an intermediary between the n-type source/drain region and the contact metal layer. This intermediate layer acts as a diffusion barrier that prevents dopant diffusion and maintains dopant activation during high-temperature processing, thereby ensuring thermal stability of contact resistance without significantly increasing structural complexity
Solution Approach 2:
The contact structure employs a composite material approach by combining the phosphide or arsenide metal compound with the contact metal layer. This composite structure leverages the beneficial properties of both materials: the phosphide/arsenide compound provides diffusion barrier functionality while the metal layer provides electrical conductivity, achieving both low resistance and thermal stability
2Reliability
If dopant concentration is increased in source/drain regions to reduce contact resistance, then contact resistance decreases, but dopant diffusion during high-temperature processing increases
Solution Approach 1:
The phosphide or arsenide metal compound layer serves as an intermediary that decouples the relationship between dopant concentration and diffusion. It allows high dopant concentration to be maintained in the source/drain region for low contact resistance while the intermediate layer prevents this dopant from diffusing during high-temperature processing, thus stabilizing the dopant concentration profile
Solution Approach 2:
The phosphide or arsenide metal compound layer is formed in advance before high-temperature processing to preemptively block dopant diffusion pathways. This preliminary protective action prevents the harmful effect of dopant diffusion that would otherwise occur during subsequent high-temperature processing steps
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 phosphide or arsenide metal compound layer reduces contact resistance and maintains dopant activation, resulting in improved transistor performance by preventing dopant diffusion and limiting silicide formation at the source/drain interface.
Implementation Method 1
Incorporating a phosphide or arsenide metal compound layer between the n-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
Data Source
AI summary
Contacts to n-type source/drain regions comprise a phosphide or arsenide metal compound layer. The phosphide or arsenide metal compound layers can aid in forming thermally stable low resistance contacts. A phosphide or arsenide metal compound layer is positioned between the source/drain region and the contact metal layer of the contact. A phosphide or arsenic metal compound layer can be used in contacts contacting n-type source/drain regions comprising phosphorous or arsenic as the primary dopant, respectively. The phosphide or arsenide metal compound layers prevent diffusion of phosphorous or arsenic 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. Phosphide and arsenide metal contact layers can also reduce the amount of silicide that forms in source/drain regions during processing by limiting the amount of contact metal that diffuses into source/drain regions.