Curved Word Line Geometry for DRAM On-Current and GIDL
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Solution Overview
Problem
Dynamic random-access memories (DRAMs) require periodic refreshing to maintain stored voltage, and there is a need to improve on-current and gate-induced drain leakage (GIDL) to enhance performance.
Innovation Solution
The memory structure incorporates specific geometries and arrangements of word lines and capacitors, with angled and curved configurations that increase contact areas and reduce electric fields, thereby enhancing on-current and reducing GIDL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If straight word lines are used in conventional DRAM structures, then the layout is simple and manufacturing is easier, but the on-current is insufficient and GIDL is high
Solution Approach 1:
The patent applies curvature to the word line structure by introducing bending portions that form acute angles (less than 180 degrees) instead of straight lines. This curved geometry increases the contact area between the word line and the memory cell, thereby improving on-current and reducing GIDL effects while maintaining manufacturability through standard photolithography processes.
Solution Approach 2:
The patent implements local quality by creating specific bending portions at strategic locations along the word line where acute angles are formed. These localized geometric modifications concentrate the beneficial effects (increased contact area, reduced electric field) at critical interfaces with memory cells, while the rest of the word line maintains a simpler structure for ease of manufacture.
2Reliability
If word lines are positioned far from capacitors, then manufacturing alignment is easier, but the contact area is reduced and on-current decreases
Solution Approach 1:
The bent word line configuration allows the structure to reach closer to the capacitor regions without requiring precise straight-line alignment. The curvature provides manufacturing tolerance by accommodating slight positional variations while still achieving adequate contact area, thus improving on-current without proportionally increasing alignment difficulty.
3Reliability
If straight word lines are used, then the electric field distribution is uniform, but GIDL is high due to insufficient field modulation
Solution Approach 1:
The patent creates localized regions of high electric field concentration at the bending portions where acute angles are formed. This non-uniform field distribution is intentional and beneficial, as it reduces GIDL effects at critical interfaces while maintaining overall device functionality. The field modulation is concentrated where it provides maximum benefit for leakage reduction.
Data Source
AI summary
A memory structure includes a first memory cell, a first word line and a second word line. The first word line includes a first portion, a second portion and a third portion. The first portion extends from an end of the second portion along a first direction, and the third portion extends from an another end of the second portion along a second direction. An angle between the first direction and the second direction is less than 180°. The second word line includes a forth portion, a fifth portion and a sixth portion. The forth portion extends from an end of the fifth portion along a third direction, and the sixth portion extends from an another end of the fifth portion along a forth direction. An angle between the third direction and the forth direction is less than 180°.