Nonvolatile Memory Switch Circuit Segmentation
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Solution Overview
Problem
Conventional semiconductor memory devices face challenges in increasing storage capacity due to physical limitations and high costs associated with miniaturization, particularly with three-dimensional memory cell configurations, which lead to difficulties in accurate read operations due to increased current flow in unselected memory strings.
Innovation Solution
A nonvolatile semiconductor memory device is designed with a plurality of first memory strings, each comprising electrically rewritable first memory transistors connected in series, a select transistor, and a switch circuit that controls electrical connections between bit lines, featuring a columnar semiconductor layer and charge storage layer to reduce current flow in unselected memory strings during read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory cells are disposed three-dimensionally to increase storage capacity, then the degree of integration is improved, but the current flow in unselected memory strings increases making accurate read operations difficult
Solution Approach 1:
The bit line is divided into multiple segments with individual switch circuits controlling each segment. This segmentation allows selective connection of only the required memory string to the bit line, preventing current flow through unselected memory strings and enabling accurate read operations in three-dimensional memory configurations
Solution Approach 2:
Switch circuits are introduced as intermediary components between the bit line and memory strings. These switch circuits act as controllable connectors that can selectively establish or break electrical connections, allowing precise control over which memory strings are active during read operations and thereby eliminating interference from unselected strings
2Quantity of substance
If the number of memory strings connected to one bit line is increased, then storage capacity is improved, but the sum total of current flowing in unselected memory strings increases
Solution Approach 1:
The bit line is segmented into multiple independent sections, each capable of connecting to a specific memory string through its own switch circuit. This allows the system to support a large total number of memory strings while activating only one segment at a time, thereby maintaining low current flow even as the overall capacity increases
Solution Approach 2:
The switch circuits provide dynamic control over the connection state between bit lines and memory strings. By dynamically switching connections based on read/write operations, the system can efficiently manage multiple memory strings without incurring the penalty of continuous current flow through all strings
Data Source
AI summary
A nonvolatile semiconductor memory device comprises: a plurality of first memory strings; a first select transistor having one end thereof connected to one end of the first memory strings; a first line commonly connected to the other end of a plurality of the first select transistors; a switch circuit having one end thereof connected to the first line; and a second line commonly connected to the other end of a plurality of the switch circuits. The switch circuit controls electrical connection between the second line and the first line.