Recess Channel Fabrication via Mandrel Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for fabricating semiconductor devices with recess channel structures face issues such as excessive extension of the recess, leading to short current problems and complexity due to the requirement of multiple layers and potential misalignment during the patterning process, which results in uneven divot sizes and depths.
Innovation Solution
A method that forms a recess in a substrate, followed by a filling layer and a liner, then removes the filling layer and liner to expose the substrate, allowing for the formation of divots around the recess channel region, which prevents excessive recess extension and ensures uniform divot sizes and depths without the need for a sandwich structure with a liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etching process is used to form a recess channel structure, then the recess channel can be formed in the substrate, but the recess tends to extend excessively outwardly, causing short current problems
Solution Approach 1:
A mandrel structure is introduced as an intermediary element during the recess formation process. The mandrel is positioned within the recess and controls the etching depth and lateral extension, preventing the recess from extending excessively outwardly. After the recess is formed, the mandrel is removed, leaving a precisely defined recess channel structure without short current problems.
Solution Approach 2:
The mandrel structure is prepared and positioned in advance before the recess etching process. This preliminary action establishes the boundaries and depth control for the recess formation, ensuring that the recess channel is formed with accurate dimensions and position before any etching occurs.
2Manufacturing precision
If multiple layers including a sandwich structure with liner are used to prevent excessive recess extension, then the recess extension problem can be controlled, but the manufacturing process becomes complex and misalignment may occur during patterning
Solution Approach 1:
The complex sandwich structure with liner is replaced by extracting only the essential function - depth control. The mandrel structure provides the necessary depth and lateral control through its physical presence during etching, eliminating the need for multiple layered structures and reducing process complexity while maintaining precision.
Solution Approach 2:
Instead of using multiple layers to control recess extension from the top down, the mandrel structure controls the etching process from the bottom up by being positioned within the recess during etching. This inverted approach simplifies the structure while achieving the same control function.
3Reliability
If ion implantation dosage is increased to solve short channel length effects, then the OFF leakage current can be reduced, but the leakage current in storage node junction increases and data retention time shortens
Solution Approach 1:
The recess channel structure creates local quality variations in the channel region. By forming a recess, the channel length is effectively increased in specific locations without requiring increased ion implantation dosage throughout the entire device. This localized structural modification reduces OFF leakage current while avoiding the adverse effects of excessive ion implantation on storage node junctions.
Data Source
AI summary
A method of fabricating a semiconductor device having a recess channel structure is provided. A first recess is formed in a substrate. A liner and a filling layer are formed in the first recess. A portion of the substrate adjacent to the first recess and a portion of the liner and the filling layer are removed to form trenches. An insulation layer fills the trenches to form isolation structures. The filling layer is removed, using the liner as an etching stop layer, to expose the insulation layer. A portion of the exposed insulation layer is removed to form a second recess having divots adjacent to the sidewalls of the substrate. The liner is removed. A dielectric layer and a gate are formed over the substrate covering the second recess. Source and drain regions are formed in the substrate adjacent to the second recess.