Self-Aligned Contact Patterning Using Dual Masks
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Solution Overview
Problem
The miniaturization of integrated circuits (ICs) has led to challenges in forming contact areas over active regions, where existing techniques struggle to achieve precise alignment and efficient filling of spaces between spacers, affecting the performance and yield of semiconductor devices.
Innovation Solution
A patterning technique using a combination of clear tone and dark tone masks to form self-aligned contact areas, where the boundaries are defined by the masks and spacers, allowing the contact areas to fill the spaces between adjacent spacers, thereby improving alignment and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing patterning techniques are used to form contact areas, then the manufacturing process is simpler, but the alignment precision and filling efficiency deteriorate
Solution Approach 1:
The patterning process is segmented into multiple steps using different mask types (clear tone mask for first contact areas, dark tone mask for second contact areas). This segmentation allows each mask to be optimized for specific contact area requirements, achieving precise alignment and efficient filling without compromising overall process manageability
Solution Approach 2:
Spacer structures serve as intermediaries that define the boundaries of contact areas and enable self-alignment. The spacers are formed first, then contact areas are patterned relative to these spacers, ensuring precise alignment without requiring direct alignment between multiple contact areas
2Area of moving object
If contact areas are made smaller to increase density, then the device functionality is improved, but the filling efficiency and contact resistance deteriorate
Solution Approach 1:
Different contact areas are assigned different local qualities through selective patterning. First contact areas (clear tone) and second contact areas (dark tone) have different boundary definitions and filling characteristics, allowing each to be optimized for its specific functional requirements while maintaining overall device density
Solution Approach 2:
The contact area boundaries are defined not only in the lateral dimension but also in the vertical dimension through spacer height control. This multi-dimensional approach allows precise control of contact area dimensions and filling efficiency independently, enabling small contact areas with good filling efficiency and low contact resistance
3Manufacturing precision
If photolithography techniques are updated for advanced nodes, then the manufacturing precision is improved, but the equipment cost and process complexity increase
Solution Approach 1:
Spacer structures are formed in advance before contact area patterning. These pre-formed spacers serve as alignment references and boundary definitions for subsequent contact area formation, enabling precise patterning at advanced nodes while using existing photolithography equipment and processes
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming a first masking layer and second masking layer over a substrate. The first masking layer includes an opening over an active area and a spacer in the substrate, and the second masking layer blocks a portion of the opening in the first masking layer. The method includes performing an etching process, using the first masking layer and the second masking layer as an etching mask, to form a contact opening which exposes a portion of the active area and a portion of the spacer, and forming a contact plug in the contact opening and over the exposed portion of the active area and the exposed portion of the spacer.