Sonos-NAND Trench Structure for Charge Isolation
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Solution Overview
Problem
Conventional semiconductor devices with charge storage layers face challenges in separating electrical charges between memory cells, leading to interference and difficulties in storing data efficiently, particularly due to complementary bit disturb (CBD) effects and influence on threshold voltages.
Innovation Solution
A semiconductor device with a trench structure and insulating films, where a charge storage layer is separated in the direction of a word line and under both ends of the word line, allowing for self-alignment and effective separation between memory cells, using different materials for insulating films to prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the charge storage layer is connected between adjacently arranged memory cells, then the device complexity is reduced, but the threshold voltages of the adjacently arranged memory cells are influenced as electrical charges move around
Solution Approach 1:
The charge storage layer is divided into separate segments for each memory cell by introducing trenches between adjacently arranged memory cells. This segmentation prevents electrical charges from moving between cells while maintaining individual cell functionality, thus stabilizing threshold voltages without significantly increasing overall device complexity.
Solution Approach 2:
Insulating films are introduced as intermediary materials filling the trenches between memory cells. These insulating films act as barriers that prevent charge migration between adjacent cells while allowing each cell to maintain its own charge storage capability, thereby ensuring threshold voltage stability.
2Reliability
If the charge storage layer is separated in a channel direction in a memory cell, then electrical charges can be separated, but the manufacturing precision requirements increase due to the need for precise trench formation and alignment
Solution Approach 1:
Trenches are formed in advance before the charge storage layer is fully processed, creating predetermined separation regions. This preliminary action establishes the charge separation structure early in the manufacturing process, reducing the precision requirements for subsequent steps while ensuring proper charge isolation between cells.
Solution Approach 2:
The trench structure and insulating films are designed to automatically provide charge separation functionality without requiring additional complex processing steps. The self-aligned nature of the trench formation and insulating film deposition simplifies manufacturing while ensuring reliable charge separation between adjacent memory cells.
Data Source
AI summary
The present invention is a semiconductor device including a semiconductor substrate having a trench, a first insulating film provided on side surfaces of the trench, a second insulating film of a material different from the first insulating film provided to be embedded in the trench, a word line provided extending to intersect with the trench above the semiconductor substrate, a gate insulating film of a material different from the first insulating film separated in an extending direction of the word line by the trench and provided under a central area in a width direction of the word line, and a charge storage layer separated in the extending direction of the word line by the trench and provided under both ends in the width direction of the word line to enclose the gate insulating film, and a method for manufacturing the same.