Split-Gate Nonvolatile Memory Gate Insulating Film Structure
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Solution Overview
Problem
Current semiconductor devices with split-gate nonvolatile memory technologies face challenges in enhancing electric performance and reliability, particularly in the structure and manufacturing methods used for the gate insulating films and charge storage regions.
Innovation Solution
A semiconductor device with a specific laminated structure of silicon oxide and silicon nitride films in the gate insulating film, where a silicon nitride film is interposed between silicon oxide films, serving as a charge storage portion, and a silicon oxide film without nitride is used between the gate electrodes, improving the charge storage efficiency and reducing voltage requirements for write/erase operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ONO film structure is used in split-gate nonvolatile memory, then the device can store charges, but the electric performance and reliability are insufficient
Solution Approach 1:
The gate insulating film is segmented into distinct functional regions: a first ONO film structure (with silicon oxide-silicon nitride-silicon oxide layers) in the charge storage region, and a second silicon oxide film structure in the region between gate electrodes. This segmentation allows each region to be optimized independently for its specific function, improving overall device reliability while maintaining manageable structural complexity
Solution Approach 2:
Different regions of the gate insulating film are assigned different material compositions and structures tailored to local requirements: the silicon nitride layer is positioned specifically where charge storage is needed, while pure silicon oxide regions are used where electrical isolation is prioritized. This local optimization enhances both data retention reliability and electric performance without requiring complete structural redesign
2Use of energy by moving object
If oxide film thicknesses are reduced to improve write/erase voltage, then voltage requirements decrease, but data retention reliability may be compromised
Solution Approach 1:
The gate insulating film employs a composite structure combining silicon oxide and silicon nitride materials in specific configurations. The silicon nitride layer provides superior charge trapping capability with thinner effective thickness compared to pure oxide structures, enabling reduced write/erase voltages while maintaining data retention reliability through the complementary properties of the composite material system
3Reliability
If a silicon nitride film is added to the gate insulating film for charge storage, then charge storage capability improves, but the manufacturing process becomes more complex
Solution Approach 1:
The silicon nitride layer is incorporated into the gate insulating film structure during the initial film formation process, before subsequent electrode and interlayer structure fabrication. This preliminary integration of the charge storage layer into the base insulating film process minimizes additional manufacturing steps and reduces overall process complexity while ensuring proper alignment and integration
Solution Approach 2:
The silicon nitride charge storage layer is nested within the silicon oxide layers to form an ONO (oxide-nitride-oxide) sandwich structure. This nested configuration allows the charge storage functionality to be embedded within the existing gate insulating film architecture, adding capability while maintaining a compact, integrated structure that does not significantly increase manufacturing complexity
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 enhances the electric performance and reliability of semiconductor devices by optimizing the charge storage capability and reducing the thickness of oxide films, while allowing for lower voltage operations, thus improving data retention and operational efficiency.
Implementation Method 1
a first silicon nitride film functions as a charge storage portion of the memory cell
Data Source
AI summary
An improvement is achieved in the performance of semiconductor device including a nonvolatile memory. In a split-gate nonvolatile memory, between a memory gate electrode and a p-type well and between a control gate electrode and the memory gate electrode, an insulating film is formed. Of the insulating film, the portion between the lower surface of the memory gate electrode and the upper surface of a semiconductor substrate has silicon oxide films, and a silicon nitride film interposed between the silicon oxide films. Of the insulating film, the portion between a side surface of the control gate electrode and a side surface of the memory gate electrode is formed of a silicon oxide film, and does not have the silicon nitride film.