DRAM FinFET Peripheral Circuitry for Ferroelectric Read Stability
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Solution Overview
Problem
Current DRAM circuitry using ferroelectric capacitors faces challenges in maintaining data retention due to the reversal of polarization states during memory read operations, requiring immediate rewriting of memory cells after reading.
Innovation Solution
The implementation of finFET transistors with conductively-doped epitaxial semiconductor material for wordline-driver and sense-line-amplifier circuitry, where the gate insulator thickness differs between the two, and the formation of these transistors with specific doping and masking processes to optimize the structure and functionality of memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferroelectric capacitors are used in memory cells, then non-volatile data storage is achieved, but polarization state reversal during read operations requires immediate rewriting of memory cells
Solution Approach 1:
The patent applies parameter changes by modifying the gate insulator thickness to different values for wordline-driver transistors versus sense-line-amplifier transistors. This differentiation in electrical parameters optimizes the performance of each transistor type, enabling better control over polarization state stability and reducing the frequency of required rewrites, thereby improving both data retention and operational efficiency
2Ease of manufacture
If uniform gate insulator thickness is used in all transistors, then manufacturing simplicity is maintained, but optimized performance for different transistor functions is not achieved
Solution Approach 1:
The patent implements local quality by assigning different gate insulator thicknesses to different transistor locations and functions. Specifically, wordline-driver transistors have one gate insulator thickness while sense-line-amplifier transistors have a different gate insulator thickness. This localized differentiation optimizes the electrical characteristics and performance of each transistor type for its specific function within the memory circuit
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 data retention and reduces the need for immediate rewriting of memory cells by stabilizing the polarization states, improving the overall performance and reliability of DRAM circuitry.
Implementation Method 1
A capacitor has two electrical conductors separated by electrically insulating material. Energy as an electric field may be electrostatically stored within such material.
Data Source
AI summary
DRAM circuitry comprises a memory array comprising memory cells individually comprising a transistor and a charge-storage device. The transistors individually comprise two source/drain regions having a gate there-between that is part of one of multiple wordlines of the memory array. One of the source/drain regions is electrically coupled to one of the charge-storage devices. The other of the source/drain regions is electrically coupled to one of multiple sense lines of the memory array. Peripheral circuitry comprises wordline-driver transistors having gates which individually comprise one of the wordlines and comprises sense-line-amplifier transistors having gates which individually comprise one of the sense lines. The sense-line-amplifier transistors and the wordline-driver transistors individually are a finFET having at least one fin comprising a channel region of the respective finFET. The sense-line-amplifier transistors and the wordline-driver transistors individually comprise two source/drain regions that individually comprise conductively-doped epitaxial semiconductor material that is adjacent one of two laterally-opposing sides of the at least one fin in a vertical cross-section. Methods are also disclosed.