Flash Memory Gate Stack With Stepped Dielectric for Metal Gate Integration
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Solution Overview
Problem
Existing semiconductor technologies face challenges in efficiently manufacturing high-density flash memory devices with improved performance and reliability, particularly in the transition from polysilicon to metal gate electrodes, where process complexities and material interactions affect device integrity and functionality.
Innovation Solution
A method for fabricating semiconductor devices involving the formation of recessed regions on a substrate, followed by the sequential deposition and patterning of gate stacks and isolation features, utilizing dielectric and conductive layers to enhance device performance and reliability, including the use of metal gate electrodes for improved conductivity and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon gate electrode is replaced with metal gate electrode, then device performance and conductivity are improved, but process complexity and manufacturing difficulty increase
Solution Approach 1:
The gate electrode structure is segmented into multiple functional layers including metal gate electrode, dielectric layer, and polysilicon layer, allowing each layer to perform specific functions and be optimized independently while reducing overall process complexity
Solution Approach 2:
The gate structure uses composite materials combining metal (for conductivity), dielectric (for insulation), and polysilicon (for control), leveraging the advantages of each material to achieve improved device performance while managing manufacturing complexity
2Productivity
If feature size is decreased, then functional density is increased, but manufacturing precision and material interaction control become more difficult
Solution Approach 1:
Different regions of the gate structure have different thicknesses and material compositions optimized for local requirements, with the metal gate electrode and dielectric layer thicknesses specifically tailored for high-density applications while maintaining manufacturing precision
Solution Approach 2:
The solution moves from controlling only horizontal feature size to also controlling vertical layer thicknesses, using multi-layer stacking to achieve high functional density while maintaining manufacturable feature dimensions
3Productivity
If gate dielectric layer thickness is decreased, then device scaling is improved, but gate-induced drain leakage increases
Solution Approach 1:
The gate dielectric structure uses composite materials including oxide layer and nitride layer, where the nitride layer provides superior leakage blocking properties while the oxide layer enables thinning for scaling, thus reducing gate-induced drain leakage while maintaining device scaling
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a control gate, a select gate, a charge trapping structure, a dielectric structure, and a spacer. The control gate and the select gate are over a channel region of the semiconductor substrate and separated from each other. The charge trapping structure is between the control gate and the semiconductor substrate. The dielectric structure is between the select gate and the semiconductor substrate. The dielectric structure has a first part and a second part, the first part is between the charge trapping structure and the second part, and the second part is thicker than the first part. The select gate is between the spacer and the control gate, and the select gate is separated from the spacer by the second part of the dielectric structure.