Contact Plug Formation Using Masked Opening Widening
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, the integration density of electronic components increases, leading to challenges in forming contact plugs with minimal defects and reduced resistance, particularly due to pattern loading effects and voids during the manufacturing process.
Innovation Solution
The process involves patterning openings in dielectric layers to expose underlying features, depositing an adhesion layer, and using a mask layer to widen the upper portions of these openings, allowing for improved gap filling with conductive materials like cobalt, which reduces defects and resistance, and repeated deposition and etch-back processes to mitigate pattern loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is reduced to increase integration density, then more components can be integrated into a given area, but manufacturing precision deteriorates due to pattern loading effects and void formation
Solution Approach 1:
The contact opening formation process is segmented into multiple steps: first forming a mandrel pattern, then using it to define the final contact opening. This segmentation allows the opening to be formed with precise dimensions while avoiding pattern loading effects that occur in direct single-step patterning at scaled dimensions.
Solution Approach 2:
A mandrel structure is introduced as an intermediary element to facilitate the formation of contact openings. The mandrel serves as a template that enables precise opening formation without directly experiencing the pattern loading effects, thereby improving manufacturing precision while maintaining high integration density.
2Device complexity
If conventional contact opening formation is used, then process simplicity is maintained, but gap filling deteriorates leading to voids and defects in conductive material deposition
Solution Approach 1:
The mandrel structure is formed in advance before the contact opening is created. This preliminary action establishes a precise geometric template that ensures proper gap filling during subsequent conductive material deposition, preventing voids and defects while maintaining reasonable process complexity.
Solution Approach 2:
The geometric parameters of the contact opening are controlled through the mandrel dimensions. By adjusting the mandrel size and shape, the opening dimensions are precisely controlled to optimize gap filling during conductive material deposition, thereby improving reliability without significantly increasing process complexity.
3Productivity
If opening dimensions are reduced for higher density, then integration density improves, but adhesion between conductive and dielectric layers deteriorates
Solution Approach 1:
The mandrel-based approach enables local optimization of opening dimensions and geometry. The opening can be designed with specific dimensional characteristics at different locations to ensure adequate adhesion surface area for the conductive layer while maintaining high overall integration density.
Solution Approach 2:
The mandrel structure serves as a template that is replicated across the substrate. This copying approach ensures uniform, optimized opening geometry throughout the device, maintaining consistent adhesion quality across all contact points while achieving high integration density.
Data Source
AI summary
An embodiment method includes patterning an opening through a dielectric layer, depositing an adhesion layer along sidewalls and a bottom surface of the opening, depositing a first mask layer in the opening over the adhesion layer, etching back the first mask layer below a top surface of the dielectric layer, and widening an upper portion of the opening after etching back the first mask layer. The first mask layer masks a bottom portion of the opening while widening the upper portion of the opening. The method further includes removing the first mask layer after widening the upper portion of the opening and after removing the first mask layer, forming a contact in the opening by depositing a conductive material in the opening over the adhesion layer.