Field-Effect Transistor Without Punch-Through Stopper
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional field effect transistors face issues with underneath-channel leakage current and process-related problems due to the formation of punch-through stoppers, which degrade performance and reliability.
Innovation Solution
A field effect transistor is designed without a punch-through stopper, featuring first insulating films embedded in the substrate and second insulating films on the gate side surfaces, with source and drain regions formed on these films, eliminating the need for impurity implantation and heat treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a punch-through stopper is formed to prevent underneath-channel leakage current, then leakage current is reduced, but interface states appear on the substrate surface during STI deposition and thermal annealing processes, degrading device performance and reliability
Solution Approach 1:
An insulating film is formed on the substrate surface before STI deposition to prevent interface state formation. This preliminary protective action ensures that subsequent thermal processes do not create harmful interface states, resolving the contradiction between preventing leakage and maintaining reliability.
Solution Approach 2:
The insulating film acts as an intermediary layer between the substrate and the STI region. This intermediate structure prevents direct interaction between the substrate surface and STI materials during deposition and annealing, eliminating interface state formation while still blocking leakage current.
2Object-affected harmful factors
If a punch-through stopper is formed through impurity implantation and heat treatment, then underneath-channel leakage current is prevented, but the manufacturing process becomes complex and productivity is reduced
Solution Approach 1:
The complex punch-through stopper formation process involving impurity implantation and heat treatment is completely removed from the manufacturing process. The insulating film formation replaces the punch-through stopper function, extracting the harmful complex steps while maintaining the essential leakage prevention capability.
Solution Approach 2:
The manufacturing approach changes from impurity implantation and thermal processing to simple insulating film deposition. This parameter change in the formation method eliminates multiple process steps, thereby improving productivity while achieving the same electrical isolation function.
3Object-affected harmful factors
If a punch-through stopper is formed through impurity implantation, then underneath-channel leakage current is prevented, but impurities diffuse into the channel during thermal processes, lowering carrier mobility
Solution Approach 1:
Instead of using impurity implantation which causes harmful diffusion, the invention uses insulating film formation which provides beneficial electrical isolation without introducing impurities. This converts the harmful impurity diffusion effect into a beneficial pure isolation mechanism, preserving carrier mobility while preventing leakage.
Solution Approach 2:
The insulating film serves as an intermediary barrier that prevents leakage current without introducing impurities into the channel. This intermediate structure achieves electrical isolation through physical separation rather than chemical doping, eliminating impurity diffusion while maintaining high carrier mobility.
Data Source
AI summary
Disclosed is a field effect transistor including an insulating film disposed between a source/drain region and a substrate. Since the insulating film prevents current leakage under a channel, it is not necessary to form a punch-through stopper. Further disclosed is a method of forming a field effect transistor.