Multi-Slope Gate Spacer for Semiconductor Trench Stability
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Solution Overview
Problem
The challenge in semiconductor device fabrication is to maintain the integrity and functionality of interlayer insulation films during the formation of replacement metal gate electrodes, particularly as the size of MOS transistors decreases, leading to issues with gate electrode height changes and potential loss of insulation.
Innovation Solution
A semiconductor device design featuring a gate spacer with specific angled surfaces and a replacement metal gate electrode that fills a trench, accompanied by a capping pattern to maintain insulation and support self-aligned contacts, ensuring the integrity of the interlayer insulation film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate electrode is formed to fill the trench completely, then the gate electrode height is maximized for better device performance, but the interlayer insulation film may be lost or damaged during the formation process
Solution Approach 1:
The gate spacer is divided into multiple parts (first part, second part, and optionally third part) with different slope characteristics. The first part has a gentle slope to prevent insulation film loss, while the second part has a steeper slope to maximize gate electrode height. This segmentation allows each part to serve its specific function without compromising the other.
Solution Approach 2:
Different regions of the gate spacer are given different local qualities in terms of slope angle. The first part (closer to the substrate) has a gentler slope angle, while the second part (higher up) has a steeper slope angle. This local differentiation optimizes both insulation film preservation and gate electrode height in their respective regions.
2Ease of manufacture
If the gate spacer has a uniform slope, then the manufacturing process is simplified, but the gate electrode height cannot be optimized while preventing insulation film loss
Solution Approach 1:
The gate spacer formation process is segmented into multiple stages, with each stage creating a specific slope section. This can be achieved through multiple deposition and etching steps, or by using a multi-layer spacer structure where each layer contributes to a different slope section, thereby simplifying the overall control of the complex shaping process.
Solution Approach 2:
The gate spacer is formed with preliminary slope characteristics that guide the subsequent gate electrode formation. The multi-part structure with different slopes is prepared in advance, allowing the gate electrode to be deposited conformally and then planarized to achieve the desired height while maintaining insulation film integrity.
3Area of stationary object
If the gate spacer slope is made steeper to reduce area, then the device integration density increases, but the interlayer insulation film is more likely to be lost
Solution Approach 1:
The gate spacer is segmented vertically with the first part having a gentler slope and the second part having a steeper slope. This segmentation allows the lower section to preserve the insulation film while the upper section reduces the overall area footprint, achieving both goals simultaneously.
Solution Approach 2:
Different slope angles are applied locally to different height regions of the gate spacer. The lower region (first part) uses a gentler slope to protect the insulation film, while the upper region (second part) uses a steeper slope to minimize area occupation, optimizing both protection and density locally.
Data Source
AI summary
A semiconductor device includes a gate spacer defining a trench. The trench includes a first part and a second part sequentially positioned on a substrate. An inner surface of the first part has a slope of an acute angle and an inner surface of the second part has a slope of a right angle or obtuse angle with respect to the substrate. A gate electrode fills at least a portion of the trench.