Drain Select Transistor Threshold Voltage Control
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Solution Overview
Problem
Current semiconductor memory devices face challenges in achieving an optimal threshold voltage distribution for drain select transistors, leading to difficulties in controlling these transistors effectively, which affects the overall performance and efficiency of the memory device.
Innovation Solution
The implementation of a method that involves ion implantation to set the threshold voltage of some drain select transistors and a programming method to adjust the threshold voltage of others, allowing for a more precise and narrowed distribution, thereby improving control over the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion implantation is used to set threshold voltage of drain select transistors, then manufacturing precision is improved, but device complexity increases due to additional process steps
Solution Approach 1:
The patent applies different threshold voltage setting methods to different drain select transistors based on their specific requirements. Some transistors receive ion implantation for precise threshold control, while others use standard programming methods, creating local quality differentiation to optimize overall device performance
Solution Approach 2:
The patent segments the drain select transistor population into different groups based on their threshold voltage requirements. By dividing transistors into those needing ion implantation and those using standard programming, the method achieves precise control over threshold voltage distribution while managing process complexity through structured segmentation
2Ease of operation
If programming operation is performed on drain select transistors, then ease of operation is improved, but manufacturing precision deteriorates due to broader threshold voltage distribution
Solution Approach 1:
The patent changes the physical state and parameters of selected drain select transistors through ion implantation before programming. This pre-modification of transistor parameters creates a narrower initial threshold voltage distribution, which then allows programming operations to achieve precise final threshold values with reduced spread
3Device complexity
If uniform threshold voltage setting method is used for all drain select transistors, then device complexity is reduced, but reliability deteriorates due to insufficient control over threshold voltage distribution
Solution Approach 1:
The patent implements local quality by applying different threshold voltage setting approaches to different drain select transistors. Selected transistors receive ion implantation for enhanced control, while others use standard methods, creating localized optimization that improves overall device reliability without requiring complete uniformity across all transistors
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 enhances the control over drain select transistors, leading to improved performance and efficiency in semiconductor memory devices by allowing for better selection and programming of cell strings.
Implementation Method 1
The threshold voltage of the first drain select transistor may be set through an ion implantation process
Data Source
AI summary
A semiconductor memory device includes a first cell string, a second cell string, a peripheral circuit, and a control logic. The first cell string includes first and second drain select transistors. The second cell string includes third and fourth drain select transistors. The peripheral circuit performs a program operation on the fourth drain select transistor included in the second cell string. The threshold voltage of the first drain select transistor is set through an ion implantation process. The threshold voltage of the fourth drain select transistor is set through the program operation.