3D Protruding Channel Transistors for DRAM Peripheral Circuits
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Solution Overview
Problem
The performance of dynamic random access memory (DRAM) is limited by the transistors in peripheral circuits, which have not evolved significantly despite advancements in memory cell transistors, becoming a weak link in improving DRAM performance.
Innovation Solution
The implementation of a memory device with a peripheral circuit featuring three-dimensional transistors that include a protruding channel structure, where the upper part of the channel has a top width smaller than the bottom width, and a gate structure covering the channel, enhancing the gate coupling area without increasing the transistor dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional planar transistors are used in peripheral circuits, then manufacturing process is simple, but transistor performance is limited and cannot keep up with memory cell transistor advancements
Solution Approach 1:
The patent transitions from traditional planar (2D) transistor channels to three-dimensional protruding channel structures that extend vertically from the substrate. This dimensional change increases the effective channel area and gate coupling without proportionally increasing the lateral footprint, thereby improving transistor performance while managing structural complexity.
Solution Approach 2:
The gate structure is positioned to surround and cover the protruding channel structure, creating a nested configuration where the gate envelops the channel. This nesting arrangement enhances gate control and coupling area without requiring a proportional increase in the overall transistor footprint, addressing the performance-complexity tradeoff.
2Reliability
If transistor dimensions are increased to improve performance, then gate coupling area increases, but device area increases and density decreases
Solution Approach 1:
By extending the channel structure vertically into a protruding three-dimensional form, the patent increases the effective gate coupling area without proportionally increasing the lateral device footprint. This dimensional transition allows performance improvement while maintaining high device density.
Solution Approach 2:
The patent modifies the geometric parameters of the transistor structure by creating a protruding channel with specific width variations along its length. The channel has a first width at the substrate interface and a second, narrower width at the top, optimizing the gate coupling area while controlling the overall device area.
3Reliability
If three-dimensional protruding channel structure is implemented, then gate coupling area increases and performance improves, but manufacturing complexity increases
Solution Approach 1:
The patent implements three-dimensional protruding channel structures by extending channels vertically from the substrate and positioning gates to surround them. This dimensional change increases gate coupling area and performance while the manufacturing process integrates these structures through sequential formation steps.
4Ease of manufacture
If peripheral circuit transistors are kept simple for easy manufacturing, then manufacturing cost is low, but they become a weak link in improving overall DRAM performance
Solution Approach 1:
The patent applies three-dimensional protruding channel structures specifically to peripheral circuit transistors, transitioning them from simple planar designs to enhanced 3D structures. This dimensional change improves their performance to match memory cell transistor advancements while integrating them into the existing manufacturing framework.
Data Source
AI summary
A memory device includes an array of memory cells and a peripheral circuit disposed around the memory cells. The memory cells each include an access transistor with a trench gate structure and a storage capacitor coupled to the access transistor. The peripheral circuit includes a first transistor with a protruding channel structure and a gate structure covering the protruding channel structure. The protruding channel structure has a bottom part and an upper part, and the upper part has a top width and a bottom width smaller the top width.