Nitride Barrier Layer in Semiconductor Memory Cells
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Solution Overview
Problem
The introduction of carbon atoms from organic materials in the block film during thermal treatment in semiconductor memory cells leads to fixed charges, causing increased variation in threshold voltage and reverse narrow channel effects, which deteriorate device properties.
Innovation Solution
A semiconductor device configuration with a tunnel insulating film, a charge storing layer comprising a first nitride film, a block film to prevent charge transfer, and a barrier layer containing a second nitride film between the element isolation insulating film and the block film, which minimizes the introduction of unwanted elements and reduces threshold voltage variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the block film contains organic material and is thermally treated, then charge storage capability is improved, but carbon atoms are introduced into the active area causing fixed charges and threshold voltage variation
Solution Approach 1:
A nitride film is introduced as an intermediary barrier layer between the element isolation insulating film and the block film. This nitride film prevents carbon atoms from the organic block film from diffusing into the active area during thermal treatment, while still allowing the block film to perform its charge storage function. The intermediary layer thus resolves the contradiction by blocking the harmful carbon diffusion path without compromising the charge storage capability.
Solution Approach 2:
The patent employs a composite structure combining the element isolation insulating film, the nitride barrier film, and the organic block film. This multi-material composite approach allows each layer to perform its specific function: the element isolation film provides electrical isolation, the nitride film prevents carbon diffusion, and the block film stores charge. The composite structure thus achieves both charge storage capability and prevention of threshold voltage variation.
2Reliability
If the block film contains organic material, then charge transfer prevention is enhanced, but reverse narrow channel effect occurs at corners due to fixed charges
Solution Approach 1:
The nitride film serves as a protective intermediary between the organic block film and the active area. It allows the block film to maintain its charge transfer prevention function while blocking the diffusion of carbon atoms that would otherwise create fixed charges causing reverse narrow channel effect at channel corners.
3Productivity
If thermal treatment is applied to the block film, then charge storage efficiency is improved, but carbon atom diffusion into the active area increases
Solution Approach 1:
The nitride film acts as a thermal and diffusion barrier during the thermal treatment process. It allows the block film to undergo thermal treatment for improved charge storage efficiency while preventing carbon atoms from diffusing into the active area, thus resolving the contradiction between processing effectiveness and material loss.
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 configuration effectively reduces threshold voltage variance and improves device properties by preventing the introduction of fixed charges and enhancing charge storage efficiency.
Implementation Method 1
a barrier layer containing a second nitride film formed between the element isolation insulating film and the block film
Implementation Method 2
the charge trap layer comprises a nitride film and electrons are stored in isolated traps
Data Source
AI summary
A semiconductor storage device including a semiconductor substrate including an upper surface having a plurality of trenches formed into the upper surface; a plurality of element isolation insulating films filled in each of the trenches so as to protrude upward from the upper surface of the semiconductor substrate, the element isolation insulating films containing an oxide material; a tunnel insulating film formed on the semiconductor substrate situated between the element isolation insulating films; a charge storing layer comprising a first nitride film and being formed on the tunnel insulating film; a block film formed across an upper surface of the charge storing layer and an upper surface of the element isolation insulating film to prevent charge transfer; a gate electrode formed on the block film; and a barrier layer containing a second nitride film formed between the element isolation insulating film and the block film.