Buried Gate Structure Layout to Prevent DRAM Layer Bending
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Solution Overview
Problem
In DRAM devices, the formation of a buried gate structure can lead to adjacent layers being bent due to compressive or tensile stress, resulting in non-uniform electrical characteristics.
Innovation Solution
A gate structure is designed with a first gate electrode extending in a first direction, a second gate electrode with a larger grain size on a portion of the first gate electrode, a gate mask, and a gate insulation pattern covering the lower surface and sidewalls of the gate electrodes. This configuration allows the gate structure to extend straightly and maintain uniform electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gate electrode is formed to fill a recess in a DRAM device, then the gate structure can be properly formed, but adjacent layers (pad layer, active pattern, isolation pattern) may be bent due to compressive or tensile stress
Solution Approach 1:
The gate electrode is divided into two distinct segments: a first gate electrode at the lower portion and a second gate electrode at the upper portion. Each segment can be independently formed with different materials and properties, allowing stress management while maintaining proper gate structure formation.
Solution Approach 2:
Different regions of the gate electrode are assigned different qualities - the first gate electrode uses one material composition while the second gate electrode uses another. This local differentiation allows optimization of stress characteristics in specific regions to prevent bending of adjacent layers.
2Reliability
If adjacent layers are bent due to stress during gate electrode formation, then manufacturing becomes complicated, but the electrical characteristics become non-uniform
Solution Approach 1:
By segmenting the gate electrode into first and second gate electrodes with different materials, the patent achieves uniform electrical characteristics while managing the complexity of layer formation. Each segment contributes to overall electrical performance consistency.
Solution Approach 2:
The gate electrode structure uses composite materials - the first gate electrode and second gate electrode are formed from different materials with complementary properties. This composite approach ensures uniform electrical characteristics across the gate structure.
3Shape
If a single-material gate electrode is used, then the structure is simple, but it cannot prevent bending of adjacent layers due to stress
Solution Approach 1:
The gate electrode is segmented into first and second gate electrodes positioned at lower and upper portions respectively. This segmentation enables straight extension of the gate structure by distributing stress across different material regions.
Solution Approach 2:
Composite materials are used in the dual gate electrode structure, with each material selected for its stress characteristics. This composite approach maintains structural straightness while managing the increased device complexity.
Data Source
AI summary
A gate structure may include a first gate electrode extending in a first direction, a second gate electrode on a portion of the first gate electrode, a gate mask on the first and second gate electrodes, and a gate insulation pattern on a lower surface and a sidewall of the first gate electrode and sidewalls of the second gate electrode and the gate mask. The gate structure is in an upper portion of a substrate. A grain size of the second gate electrode is greater than a grain size of the first gate electrode.