Nonvolatile Memory Film Stack with Selective Insulation
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Solution Overview
Problem
Conventional trap type memory devices face challenges in miniaturization, initial threshold value uniformity, and retention properties due to issues with charge accumulation efficiency, leakage current, and defects in the manufacturing process.
Innovation Solution
A nonvolatile storage device with a semiconductor substrate and a film stack including a charge accumulating layer and tunnel insulating film, where the film stack extends onto the surface of the gate electrode on the first impurity diffusion region side, reducing charge loss and enhancing writing efficiency, and a method for manufacturing this device involving specific steps for forming impurity diffusion regions and gate electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the insulating film is completely removed from the first impurity diffusion region to reduce leakage current, then leakage current is reduced, but charge accumulation efficiency deteriorates
Solution Approach 1:
The insulating film is selectively removed only from specific regions where leakage current occurs (such as regions not overlapping with the gate electrode), while being retained in regions where charge accumulation is needed. This local differentiation allows the structure to simultaneously reduce leakage current and maintain charge accumulation efficiency by applying different properties to different spatial locations.
2Area of stationary object
If the cell area is reduced for miniaturization, then device density increases, but manufacturing precision requirements worsen
Solution Approach 1:
The insulating film removal is performed as a preliminary self-aligned process before subsequent manufacturing steps. By removing the insulating film in advance using the gate electrode and other structures as alignment references, the process establishes precise positional relationships early in the manufacturing sequence, which facilitates miniaturization while maintaining alignment precision through self-alignment mechanisms.
3Productivity
If the insulating film thickness is reduced to improve writing efficiency, then writing efficiency improves, but data retention properties worsen
Solution Approach 1:
The insulating film thickness is locally optimized by being completely removed only in specific regions where thinning would harm data retention, while being retained at appropriate thickness in regions where charge accumulation and data storage are critical. This spatially differentiated approach allows writing efficiency to be improved through selective thinning without compromising overall data retention properties.
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 solution enables miniaturization of trap type memory devices with improved initial threshold value uniformity, high writing efficiency, and reduced leakage current, while maintaining charge retention properties.
Implementation Method 1
a film stack including a charge accumulating layer and tunnel insulating film sequentially from the gate electrode side
Implementation Method 2
tunnel insulating film sequentially from the gate electrode side
Data Source
AI summary
Provided is an excellent nonvolatile storage device having advantageous in miniaturization and less variation in initial threshold value, and exhibiting a high writing efficiency, without an erasing failure and a retention failure. The nonvolatile storage device is characterized by including a film stack extending from between a semiconductor substrate and a gate electrode onto at least a surface of the gate electrode lying on a first impurity diffusion region side, the film stack including a charge accumulating layer and a tunnel insulating film sequentially from a gate electrode side.