Bottom-Side Source-Drain Regrowth for Low-Resistance Contacts
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Solution Overview
Problem
Existing approaches to achieving high dopant activation in semiconductor contact regions result in high contact resistance due to thermal degradation during back-end processing, leading to poor device performance in terms of speed and power consumption.
Innovation Solution
The process involves fabricating transistor assemblies using traditional semiconductor processing techniques from the top-side of the wafer, followed by amorphization of the bottom-side contact region using an implant, and subsequent recrystallization with a fast anneal technique to achieve highly active metastable dopants, thereby reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If contact structures are formed in front-end processing operations during transistor fabrication, then contact structures are created early in the process, but thermal operations during back-end processing result in high contact resistance
Solution Approach 1:
The patent applies preliminary action by forming the contact structures during front-end processing operations before the thermal operations occur. The contact structures are created early in the fabrication process, and then a subsequent thermal annealing operation is performed to activate dopants and reduce contact resistance after the thermal operations that would otherwise degrade the contact regions.
Solution Approach 2:
The patent utilizes parameter changes by performing a thermal annealing operation that changes the temperature and dopant activation parameters of the contact structures. This thermal processing step modifies the electrical properties of the contact regions, transforming them from a high-resistance state to a low-resistance state with high dopant activation.
2Reliability
If high dopant activation is achieved in contact regions, then contact resistance is lowered and power consumption is reduced, but thermal operations during back-end processing degrade the contact structures
Solution Approach 1:
The contact structures are prepared in advance during front-end processing with dopant implantation or diffusion, positioning them in an optimal state before exposure to thermal operations. This preliminary doping creates a foundation that can withstand subsequent thermal processing while maintaining high dopant activation.
Solution Approach 2:
The patent employs a rapid thermal annealing process that quickly heats and cools the contact regions, rushing through the thermal operation before significant degradation can occur. This fast thermal processing activates dopants and reduces contact resistance while minimizing the time exposure to conditions that would cause thermal degradation.
3Productivity
If thermal operations are performed during back-end processing, then subsequent processing steps are completed, but contact resistance increases degrading device performance
Solution Approach 1:
Contact structures are formed and pre-positioned during front-end processing before back-end operations begin. This preliminary formation ensures that contact regions are ready to withstand the thermal operations of back-end processing without degrading, allowing full productivity of back-end steps while preserving device performance.
Solution Approach 2:
The contact structures are pre-conditioned during front-end processing with dopant introduction and initial annealing, creating a resilient structure that can withstand the thermal stress of back-end processing. This beforehand cushioning protects the contact regions from thermal degradation, ensuring low contact resistance is maintained throughout subsequent 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
This approach significantly reduces contact resistance, leading to improved device performance characterized by increased drive current, faster switching speeds, and reduced power consumption.
Implementation Method 1
amorphization of the bottom-side contact region using an implant
Implementation Method 2
subsequent recrystallization with a fast anneal technique
Data Source
AI summary
A device is disclosed. The device includes a channel, a first source-drain region adjacent a first portion of the channel, the first source-drain region including a first crystalline portion that includes a first region of metastable dopants, a second source-drain region adjacent a second portion of the channel, the second source-drain region including a second crystalline portion that includes a second region of metastable dopants. A gate conductor is on the channel.