Bulb-Type Recess Gate With Separated Isolation Edge
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Solution Overview
Problem
The misalignment between recess and gate structures in semiconductor devices leads to leakage current and degraded electric characteristics due to the narrow contact area, which is exacerbated by the bulb-type recess formation process causing damage to the semiconductor substrate during chemical dry etching.
Innovation Solution
An exposure mask with specific recess patterns having varying line widths is used to form a bulb-type recess gate, ensuring a given distance separation from the active region edge, preventing substrate damage and misalignment during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the recess line width is narrowed to prevent misalignment between recess and gate, then leakage current is reduced, but the effective contact area is reduced and manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The recess pattern is designed with different line widths in different regions: a first line width in the region adjacent to the active region and a second line width in other regions. This local variation allows the recess to maintain adequate width for manufacturing precision while having a narrowed portion near the active region to prevent leakage current, thus resolving the contradiction between reliability and manufacturing precision
Solution Approach 2:
The recess pattern is segmented into multiple regions with different line width characteristics. The pattern includes a first region adjacent to the active region with a first line width, and a second region with a second line width. This segmentation allows different portions of the recess to serve different functions: preventing leakage where needed and maintaining manufacturability where not critical
2Area of moving object
If the recess is formed closer to the active region edge to increase contact area, then gate channel length is increased, but misalignment occurs and leakage current is generated
Solution Approach 1:
The recess pattern applies local quality by having a specific line width configuration in the region adjacent to the active region. The first line width in this critical region is carefully controlled to maintain adequate contact area while preventing misalignment-induced leakage, thus optimizing both contact area and reliability locally rather than using a uniform width throughout
3Area of moving object
If the bulb-type recess is formed by chemical dry etching to increase contact area, then gate effectiveness is improved, but substrate damage occurs during the etching process
Solution Approach 1:
The exposure mask is designed with a pre-calculated and optimized recess pattern configuration before the etching process. The pattern includes specific line width variations that anticipate and prevent substrate damage by controlling the etching profile, thus performing a preliminary protective action that prevents harmful effects during the actual etching process
Solution Approach 2:
The invention converts the potential harm of chemical dry etching into a benefit by designing a recess pattern that utilizes the etching process to create the desired bulb-type structure while the specific line width configuration prevents substrate damage. The controlled narrow portion of the recess pattern protects the substrate during etching while still achieving the necessary contact area
Data Source
AI summary
When a recess of a bulb-type recess gate is formed, the recess formed in a device isolation region is formed to be separated from an edge of an active region. This structure thereby prevents damage of a semiconductor substrate of the edge of the active region and a defect during a Self Alignment Contact (SAC) process. As a result, characteristics and yield of devices improve.