OTS Memory Cell Electrode Stack for Clearer Threshold Voltage States
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in achieving reliable differentiation between threshold voltages for different logic states due to small differences in threshold voltages, affecting accuracy in reading and writing operations.
Innovation Solution
Incorporating a high-concentration electrode between the OTS film and an electrode, with varying nitrogen concentrations, and adjusting the dimensions of the OTS film and electrodes to enhance the difference in threshold voltages for logic states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional memory cell structure without high-concentration electrode is used, then the device complexity is lower, but the threshold voltage differentiation between logic states is insufficient
Solution Approach 1:
The memory cell is segmented into multiple functional layers: first electrode, OTS film, high-concentration electrode, and second electrode. This segmentation allows each layer to perform its specific function, with the high-concentration electrode specifically responsible for enhancing threshold voltage differentiation through its position and material properties.
Solution Approach 2:
The high-concentration electrode acts as an intermediary element between the OTS film and the second electrode. It mediates the electrical field distribution and enhances the threshold voltage difference by concentrating charge carriers in its region, thereby improving the reliability of logic state differentiation without requiring fundamental structural redesign.
2Measurement precision
If the OTS film dimension is increased to enhance threshold voltage difference, then the reading accuracy improves, but the manufacturing precision requirement increases
Solution Approach 1:
Instead of uniformly increasing the entire OTS film dimension, the invention applies local quality enhancement by introducing a high-concentration electrode at a specific location. This localized approach concentrates the electric field and charge carriers in the critical region, enhancing threshold voltage differentiation without requiring proportional increases in the overall OTS film dimensions, thereby reducing manufacturing precision requirements.
3Reliability
If nitrogen concentration in the electrode is increased to improve threshold voltage distinction, then the logic state differentiation improves, but the material composition control difficulty increases
Solution Approach 1:
The invention utilizes parameter changes by varying the nitrogen concentration in the high-concentration electrode material. By adjusting this specific parameter (nitrogen concentration) in a localized region, the threshold voltage differentiation is enhanced. The patent provides specific concentration ranges (e.g., 1-10 at%) to guide material synthesis, making the parameter change manageable and reproducible in manufacturing.
Data Source
AI summary
A method of manufacturing a semiconductor memory device includes forming a first conductive line extending in a first direction on a substrate, forming a second conductive line extending in a second direction on the first conductive line, and forming a first memory cell between the first conductive line and the second conductive line by sequentially stacking a first electrode, a first high-concentration electrode, a first ovonic threshold switch (OTS) film, and a second electrode, wherein a concentration of nitrogen (N) contained in the first high-concentration electrode is greater than a concentration of nitrogen (N) contained in the first electrode.