Low Ohmic Contacts via Laser-Induced Vacancy Defects
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Solution Overview
Problem
As semiconductor devices are scaled down, dopant diffusion during annealing processes leads to increased device dimensions and contact resistance issues, particularly at the silicide junction, degrading device performance.
Innovation Solution
The introduction of vacancy defects in the substrate, created by laser irradiation, which aligns with the depth of a metal-based contact, reduces contact resistance by enhancing dopant activation and acting as a diffusion barrier, thereby maintaining dopant concentration at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If annealing processes are used to electrically activate dopants, then dopant activation is improved, but dopant diffusion increases leading to increased device dimensions
Solution Approach 1:
The patent introduces vacancy defects by changing the physical state of the substrate through laser irradiation, creating a new parameter (vacancy concentration) that modifies the diffusion behavior of dopants during annealing, allowing activation while controlling dimensional spread
Solution Approach 2:
Vacancy defects act as an intermediary mechanism that facilitates dopant activation while simultaneously serving as a barrier to uncontrolled diffusion, mediating between the need for electrical activation and the need for dimensional precision
2Productivity
If transistors are scaled down to improve device density, then productivity is improved, but contact resistance at the silicide junction increases
Solution Approach 1:
The patent applies local quality by creating vacancy defects specifically at the contact region interface, concentrating the beneficial effect where needed to reduce contact resistance without affecting other parts of the scaled device
Solution Approach 2:
The vacancy defects are formed before the metal contact is deposited, preparing the substrate in advance to facilitate lower resistance contact formation when the metal is subsequently applied
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 effectively reduces contact resistance and maintains dopant concentration at the interface, improving device performance by controlling dopant diffusion and activation.
Implementation Method 1
Vacancy defects are formed in the substrate. The vacancy defects have a peak concentration at a depth DV
Implementation Method 2
Vacancy defects are formed in the substrate through laser irradiation
Implementation Method 3
dopants have a tendency to diffuse or expand both laterally and vertically away from the profile as-introduced during annealing
Implementation Method 4
The metal based contact has a depth DC which is equal to about DV. The vacancy defects lower the resistance of the metal based contact with the substrate
Data Source
AI summary
A method for forming a device is disclosed. A substrate with a contact region is provided. Vacancy defects are formed in the substrate. The vacancy defects have a peak concentration at a depth DV. A metal based contact is formed in the contact region. The metal based contact has a depth DC which is equal to about DV. The vacancy defects lower the resistance of the metal based contact with the substrate.