3.5 Transistor Nonvolatile Memory Cell Using Gate Oxide Breakdown
Solution Overview
Problem
Nonvolatile memory cells require specialized manufacturing processes that are not compatible with CMOS logic processes, leading to lag in technological advancements compared to standard CMOS logic processes.
Innovation Solution
A 3.5 transistor memory cell design using CMOS logic processes, incorporating a breakdown transistor that can be programmed using gate oxide breakdown, eliminating the need for additional mask steps and allowing for smaller transistor sizes, thereby increasing memory density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If specialized manufacturing processes are used for nonvolatile memory cells, then nonvolatile memory functionality is achieved, but manufacturing complexity increases and compatibility with CMOS logic processes is lost
Solution Approach 1:
The patent applies universality by designing a nonvolatile memory cell that uses standard CMOS logic processes, allowing the same manufacturing infrastructure to produce both logic circuits and nonvolatile memory. The 3.5 transistor cell structure utilizes conventional CMOS components (transistors, capacitors, interconnects) and process steps, eliminating the need for specialized non-CMOS fabrication lines while maintaining nonvolatile memory functionality through gate oxide breakdown mechanisms that can be integrated into standard CMOS flow.
2Reliability
If specialized manufacturing processes are used for nonvolatile memory cells, then nonvolatile memory functionality is achieved, but technological advancement lags behind CMOS logic processes
Solution Approach 1:
By making the memory cell compatible with standard CMOS processes, the invention enables the memory technology to advance at the same pace as CMOS logic processes. Each new CMOS process generation (scaling, new materials, improved techniques) can be directly applied to the memory cell without requiring separate process development, ensuring synchronized technological advancement.
3Reliability
If additional mask steps are added for specialized structures, then nonvolatile memory functionality is achieved, but manufacturing complexity and production time increase
Solution Approach 1:
The memory cell structure is designed to be formed using standard CMOS mask sets and process steps. The breakdown transistor and storage node are created using conventional transistor fabrication techniques already present in the CMOS process flow, eliminating the need for additional dedicated mask steps for memory-specific structures.
4Ease of manufacture
If larger transistor sizes are used for nonvolatile memory cells, then manufacturing is easier, but memory density decreases
Solution Approach 1:
The invention utilizes parameter changes by exploiting the gate oxide breakdown phenomenon, which occurs at specific voltage thresholds. By controlling the breakdown voltage and threshold characteristics through standard CMOS process parameters (oxide thickness, doping profiles, transistor dimensions), the design achieves compact transistor sizes suitable for high density while maintaining manufacturability through conventional process control.
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
Enables the fabrication of nonvolatile memory cells that are compatible with CMOS logic processes, advancing memory technology by increasing density and reducing manufacturing complexity, with the ability to produce larger memory arrays using conventional CMOS processes.
Implementation Method 1
incorporating a breakdown transistor that can be programmed using gate oxide breakdown
Data Source
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AI summary
A programmable memory cell formed useful in a memory array having column bitlines and row wordlines is disclosed. The memory cell comprises a breakdown transistor having its gate connected to a program wordline and a write transistor connected in series at a sense node to said breakdown transistor. The gate of the write transistor is connected to a write wordline. Further, a first sense transistor has its gate connected to the sense node. A second sense transistor is connected in series to the first sense transistor and has its gate connected to a read wordline. The second sense transistor has its source connected to a column bitline.