Pass Transistor Body Effect Compensation in 3D Non-Volatile Memory
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Solution Overview
Problem
Non-volatile memory devices with three-dimensional structures face challenges in process complexity and unintentional noise due to variations in the threshold voltage of pass transistors caused by the body effect of semiconductor substrates, leading to low output voltages compared to input voltages.
Innovation Solution
A non-volatile memory device design that includes a semiconductor substrate with doped regions and well regions of varying doping concentrations, insulated by an implant region, where pass transistors on different regions are connected to specific selection lines and word lines, and voltage is applied to the well regions to minimize threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a three-dimensional structure is used to increase memory cell density, then the number of memory cells per chip area is improved, but process difficulty and unintentional noise increase due to body effect variations
Solution Approach 1:
The semiconductor substrate is divided into multiple independently controllable regions (first region, second region, third region) with separate well regions and implant regions. Each region can have its threshold voltage independently adjusted by applying different voltages to its well region, allowing precise control of pass transistor characteristics in each segment to compensate for body effect variations while maintaining high density 3D structure.
Solution Approach 2:
Different regions of the substrate are doped with different doping concentrations and types (first type and second type) to create locally optimized conditions. The first region has a first doping concentration while the second region has a second doping concentration, allowing each region to be tailored for specific operational requirements and reducing unwanted interactions between adjacent structures.
2Reliability
If pass transistor threshold voltage varies due to body effect, then output voltage becomes considerably low compared to input voltage, but increasing doping concentration to stabilize threshold voltage increases process complexity
Solution Approach 1:
The well regions are designed to receive dynamically adjustable voltages (first voltage for first well region, second voltage for second well region) that can be changed during operation. This dynamic voltage adjustment allows the threshold voltage of pass transistors to be actively controlled and optimized for different operational modes, compensating for body effect variations without requiring fixed high doping concentrations that would increase process complexity.
Solution Approach 2:
The invention changes the electrical parameters (voltage levels, doping concentrations) of different regions to optimize pass transistor performance. By applying different voltages to different well regions and using different doping concentrations in different regions, the threshold voltage can be precisely controlled to maintain stable output voltage levels without oversimplifying the overall device structure.
3Object-affected harmful factors
If implant regions are used to insulate different doped regions, then unintentional noise is reduced, but the number of manufacturing steps increases
Solution Approach 1:
The implant regions serve dual functions: they provide electrical insulation between differently doped regions to prevent noise and unwanted interactions, and they act as isolation structures that define the boundaries of active regions. By combining these functions into a single structural element, the invention reduces the need for separate insulation layers or additional processing steps that would otherwise be required.
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
The design effectively reduces threshold voltage variations and enhances the efficiency of output voltages in pass transistors, improving the operational stability and performance of non-volatile memory devices.
Implementation Method 1
The threshold voltage of the pass transistor may be varied under particular conditions due to a body effect of a semiconductor substrate itself
Implementation Method 2
the peripheral circuit region includes a first region and a second region which are doped to a predetermined or alternatively, desired depth at an upper portion of the semiconductor substrate
Data Source
AI summary
A non-volatile memory device comprises a memory cell region including a plurality of cell transistors, a first-type semiconductor substrate including a peripheral circuit region including circuits configured to control the plurality of cell transistors, and a plurality of pass transistors on the peripheral circuit region of the semiconductor substrate, wherein the peripheral circuit region includes a first region and a second region which are doped to a depth at an upper portion of the semiconductor substrate while being insulated from each other by an implant region, wherein the first region is a second type different from the first type, and includes a first doped region, and a first well region beneath the first doped region and configured to have a higher doping concentration than the first doped region, wherein the second region is the first type, and includes a second doped region, and a second well region beneath the second doped region and configured to have a higher doping concentration than the second doped region, wherein a first pass transistor on the first region from among the plurality of pass transistors is connected to a string selection line or a ground selection transistor, wherein a second pass transistor on the second region from among the plurality of pass transistors is connected to a word line, wherein a positive voltage or a negative voltage is configured to be applied to the second well region during operation of the second pass transistor.