Si-Rich Silicon Nitride Charge Film for Non-Volatile Memory
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Solution Overview
Problem
The challenge in non-volatile semiconductor storage devices using hot electrons for writing and hot holes for erasure is the deterioration of the film quality, particularly the bottom Si oxide film, which reduces the data holding characteristic and limits the number of rewrites due to increased electric charge injection amounts and subthreshold coefficient deterioration.
Innovation Solution
A manufacturing method for non-volatile semiconductor storage devices involves forming an Si nitride film (SRN film) stoichiometrically excessively containing silicon using physical vapor deposition or chemical vapor deposition, which acts as an electric charge holding film to suppress local presence of electric charges, thereby reducing the injection amounts and improving rewriting durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hot electrons and hot holes are injected into the electric charge holding film for writing and erasure, then low-voltage and high-speed programming is achieved, but the film quality deteriorates and the number of rewrites is limited
Solution Approach 1:
The patent changes the compositional parameters of the electric charge holding film by using an Si-rich Si nitride film instead of a stoichiometric Si3N4 film. This parameter change in film composition reduces trap density and suppresses local charge accumulation, thereby improving rewriting durability while maintaining low-voltage and high-speed programming capabilities
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers including Si oxide films and Si-rich Si nitride film. This composite material structure allows the device to achieve both low-voltage/high-speed operation and improved rewriting durability by distributing stress and charge accumulation across different material layers
2Quantity of substance
If the electric charge holding film uses a stoichiometric Si3N4 film, then the trap density is high, but the local presence of electric charges increases and rewriting durability decreases
Solution Approach 1:
The patent changes the compositional parameter of the Si nitride film from stoichiometric Si3N4 to Si-rich composition. This parameter change reduces the trap density and suppresses local charge accumulation, thereby improving charge distribution uniformity and rewriting durability while maintaining sufficient charge holding capability
3Device complexity
If the bottom Si oxide film is used as potential barrier film, then the device structure is simple, but the film quality deteriorates due to increased electric charge injection amounts
Solution Approach 1:
The patent employs a composite insulating film structure consisting of Si oxide films and Si-rich Si nitride film layers. This composite structure reduces the burden on the bottom Si oxide film by providing additional charge holding capacity in the Si-rich Si nitride layer, thereby preventing film quality deterioration while maintaining structural simplicity
Solution Approach 2:
The patent uses Si-rich Si nitride film which excessively contains silicon beyond the stoichiometric ratio. This excessive silicon content creates a film composition that is optimized for reducing trap density and suppressing local charge accumulation, thereby protecting the bottom Si oxide film from deterioration
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 SRN film enhances rewriting durability by reducing electric charge injection amounts and suppressing subthreshold coefficient deterioration, leading to improved data holding characteristics and increased number of rewrites without compromising film quality.
Implementation Method 1
forming an Si nitride film (SRN film) stoichiometrically excessively containing silicon using physical vapor deposition or chemical vapor deposition
Implementation Method 2
forming an Si nitride film (SRN film) stoichiometrically excessively containing silicon using physical vapor deposition or chemical vapor deposition
Implementation Method 3
acts as an electric charge holding film to suppress local presence of electric charges, thereby reducing the injection amounts
Data Source
AI summary
Performance of a non-volatile semiconductor storage device which performs electron writing by hot electrons and hole erasure by hot holes is improved. A non-volatile memory cell which performs a writing operation by electrons and an erasure operation by holes has a p-type well region, isolation regions, a source region, and a drain region provided on an Si substrate. A control gate electrode is formed via a gate insulating film between the source region and the drain region. In a left-side side wall of the control gate electrode, a bottom Si oxide film, an electric charge holding film, a top Si oxide film, and a memory gate electrode are formed. The electric charge holding film is formed from an Si nitride film stoichiometrically excessively containing silicon.