NONON Gate Insulator Segmentation for Charge Leakage
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Solution Overview
Problem
The use of NONON stacked film structures as inter-gate insulating films in semiconductor devices leads to increased charge transportation between neighboring floating gate electrodes, causing issues such as threshold voltage changes and data errors due to differing charge accumulation states.
Innovation Solution
A semiconductor device structure is implemented where the second gate insulating film layer includes a NONON stacked film structure with a separated silicon nitride film layer at the lowermost position interposing neighboring floating gate electrodes, and a thicker silicon oxide film is formed across the element isolation insulating film to prevent charge transportation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NONON stacked film structure is employed for inter-gate insulating film, then TDDB is reduced and bird's beak occurrence is prevented, but charge transportation between neighboring floating gate electrodes increases
Solution Approach 1:
The patent divides the lowermost silicon nitride film layer into separated portions positioned only under individual floating gate electrodes, with gaps between neighboring gate electrodes. This segmentation prevents continuous charge transportation paths while maintaining the protective benefits of the NONON structure under each gate electrode.
Solution Approach 2:
The patent applies different structural configurations to different regions: the NONON stacked film structure is maintained under individual floating gate electrodes to provide local protection and prevent bird's beak, while the silicon nitride film is removed from regions between neighboring gates to eliminate charge transportation pathways. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Manufacturing precision
If NONON stacked film structure is employed for inter-gate insulating film, then manufacturing precision is improved by preventing bird's beak, but data accuracy deteriorates due to charge transportation
Solution Approach 1:
The silicon nitride film layer is segmented into discrete portions under each floating gate electrode rather than forming a continuous layer. This segmentation maintains manufacturing precision benefits (preventing bird's beak at gate edges) while eliminating the continuous charge transportation pathway that would compromise data accuracy between neighboring gates.
Solution Approach 2:
The patent implements local quality by maintaining the full NONON stacked structure only where needed under individual gate electrodes for manufacturing precision, while removing the potentially harmful continuous nitride layer in inter-gate regions to preserve data accuracy. Each region is optimized for its specific requirement.
3Reliability
If continuous silicon nitride film is used in NONON structure, then insulation between gate and substrate is improved, but charge leakage between neighboring gates increases
Solution Approach 1:
The patent segments the silicon nitride film layer into separate portions positioned only under individual floating gate electrodes, creating gaps between neighboring gates. This maintains the insulation function under each gate while eliminating the charge leakage pathway between gates that would occur with a continuous film.
Solution Approach 2:
The patent applies different film configurations to different locations: continuous NONON stacked films are maintained under individual gate electrodes to provide local insulation and prevent bird's beak, while the film is removed from inter-gate regions to prevent charge leakage. This local differentiation resolves the contradiction between insulation and leakage prevention.
Data Source
AI summary
A semiconductor device including a semiconductor substrate; a first gate insulating film formed on the semiconductor substrate; a first gate electrode layer formed on the first gate insulating film; an element isolation insulating film formed so as to isolate a plurality of the first gate electrode layers; a second gate insulating film layer formed so as to cover upper surfaces of the plurality of first gate electrode layers and the element isolation insulating films; and a second gate electrode layer formed on the second gate insulating film layer; and the second gate insulating film layer includes a NONON stacked film structure and a nitride film layer contacting the first gate electrode layer and constituting a lowermost layer of the NONON stack film structure is separated at a portion interposing the plurality of neighboring first gate electrode layers.