Semiconductor Memory Device Using Resistance-Change Select Switch
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Solution Overview
Problem
The existing semiconductor memory devices with resistance-change memory elements face a significant challenge in maintaining a small cell size and reducing the number of manufacturing processes, particularly in three-dimensional structures where multiple memory elements are stacked, due to the need for additional select elements like transistors.
Innovation Solution
The implementation of a semiconductor memory device that uses a second resistance-change memory element as a select switch, eliminating the need for transistors by employing a diode or other resistance-change memory elements to control the resistance states, thereby maintaining the same manufacturing process dimensions and reducing the overall process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor is used as a select element for each resistance-change memory element, then the select function is achieved, but the cell size and number of manufacturing processes increase significantly
Solution Approach 1:
The patent merges the select function with a resistance-change memory element by using one resistance-change memory element to control another. Specifically, a first resistance-change memory element is used as a select switch to control access to a second resistance-change memory element, eliminating the need for separate transistor select elements. This combining approach reduces cell size while maintaining the necessary select functionality.
Solution Approach 2:
The patent makes resistance-change memory elements serve multiple functions: they act as both storage elements and select switches. The first resistance-change memory element functions as a select switch, while the second resistance-change memory element serves as the storage element. This multi-functionality reduces the overall device complexity and cell size by eliminating dedicated transistor select elements.
2Reliability
If a transistor is used as a select element for each resistance-change memory element, then the select function is achieved, but the number of manufacturing processes increases
Solution Approach 1:
The patent combines the select function with the resistance-change memory element structure, using the same manufacturing process to create both the storage element and the select switch. This merging eliminates the need for additional transistor fabrication processes, thereby reducing the total number of manufacturing steps while maintaining selective access functionality.
Solution Approach 2:
The patent uses homogeneous materials and structures for both the select switch and the storage element - both are resistance-change memory elements with similar or identical structures. This homogeneity allows for simplified manufacturing processes, as the same fabrication techniques can be applied to create both functional elements without requiring additional process steps for transistor fabrication.
3Quantity of substance
If multiple resistance-change memory elements are stacked in three-dimensional structure, then the storage capacity is increased, but the cell size and manufacturing complexity increase significantly
Solution Approach 1:
The patent transitions from a two-dimensional planar structure to a three-dimensional stacked structure, where multiple resistance-change memory elements are vertically stacked. This dimensional change allows for increased storage capacity within a smaller footprint area. The select switch structure extends vertically to control multiple stacked memory elements, enabling high-density storage without proportionally increasing the cell footprint.
4Quantity of substance
If multiple resistance-change memory elements are stacked in three-dimensional structure, then the storage capacity is increased, but the number of manufacturing processes increases
Solution Approach 1:
The patent implements vertical stacking of resistance-change memory elements in the third dimension, allowing multiple storage elements to be integrated within a single cell footprint. This three-dimensional arrangement increases storage capacity without requiring additional planar manufacturing processes, as the stacking can be achieved through vertical deposition and patterning techniques that extend the existing manufacturing process to the vertical dimension.
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 approach allows for efficient data storage and retrieval without increasing cell size or manufacturing processes, effectively serving as a switch with a resistance ratio of 100:1000, and prevents signal disturbance by controlling the resistance states of non-selected cells.
Implementation Method 1
a rectifier element of a two-terminal type
Implementation Method 2
phase-change memories (PRAM, PCM) and resistance-change memories (PRAM, ReRAM) are suggested
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes a plurality of first resistance-change memory elements of a two-terminal type, a second resistance-change memory element of a two-terminal type, a rectifier element of a two-terminal type, a local bit line connected to ends of the first resistance-change memory elements, an end of the second resistance-change memory element and an end of the rectifier element, and a global bit line connected to the other end of the second resistance-change memory element.