Nonvolatile Memory Block Insulating Film Defect Reduction
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Solution Overview
Problem
The finer cells in MONOS nonvolatile semiconductor memory devices are prone to charge leakage due to defects in the block insulating film made of lanthanum aluminate, leading to degradation in charge holding characteristics.
Innovation Solution
The use of LaxAlyOz and LaxAlySizOw films with higher dielectric constants for the block and second element isolation insulating films, respectively, reduces defects and enhances the charge storage layer's ability to retain charges by increasing the Si concentration in the second element isolation insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lanthanum aluminate is used for the block insulating film, then the dielectric constant is increased to prevent charge leakage, but the material exhibits deliquescence causing defects and charge leakage to adjacent cells
Solution Approach 1:
The patent changes the material composition parameters by introducing silicon-containing oxide materials (such as silicon oxide, silicon oxynitride) to replace or supplement lanthanum aluminate in the block insulating film. This parameter change eliminates deliquescence while maintaining high dielectric constant, thereby resolving the contradiction between reliability and material defects.
Solution Approach 2:
The patent employs composite insulating film structures combining multiple materials (e.g., silicon oxide layer + silicon nitride layer, or silicon-containing oxide with high dielectric constant material). This composite approach maintains the high dielectric constant needed for charge retention while avoiding the deliquescence problem of pure lanthanum aluminate, thus resolving the technical contradiction.
2Quantity of substance
If cells are made finer to increase storage density, then the memory capacity is improved, but charge leakage from the charge storage layer increases
Solution Approach 1:
The patent changes the dielectric constant parameter of the block insulating film by using silicon-containing oxide materials with higher dielectric constants. This allows finer cell dimensions to be used for increased storage density while the enhanced dielectric property prevents charge leakage, thus resolving the contradiction between storage density and charge retention.
3Volume of moving object
If the block insulating film is made thinner to reduce cell size, then the storage density is improved, but the leakage of charges increases
Solution Approach 1:
The patent changes the material composition parameter of the block insulating film to use silicon-containing oxide materials with higher dielectric constants. This allows the film thickness to be reduced for smaller cell size while the superior dielectric properties maintain effective charge isolation, resolving the contradiction between cell size and charge isolation reliability.
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 suppresses charge leakage and degradation in charge holding characteristics by reducing defects in the insulating films between cells, improving the overall performance of the nonvolatile semiconductor memory device.
Implementation Method 1
The use of LaxAlyOz and LaxAlySizOw films with higher dielectric constants for the block and second element isolation insulating films, respectively
Data Source
AI summary
In one embodiment, a nonvolatile semiconductor memory device includes a substrate; a tunnel insulating film on the substrate; a charge storage layer on the tunnel insulating film; a block insulating film on the charge storage layer; a first element isolation insulating film in an element isolation trench in the substrate, having a bottom surface lower than an interface between the substrate and the tunnel insulating film, and having a top surface lower than an interface between the charge storage layer and the block insulating film; a second element isolation insulating film on the first element isolation insulating film, protruding to a top surface of the block insulating film, in contact with a side surface of the block insulating film, and having a higher Si concentration than the block insulating film; and a control gate electrode on the block insulating film and on the second element isolation insulating film.