Butt Contact for Semiconductor Fin Structures
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Solution Overview
Problem
The narrow width of fin structures in MOSFET transistors makes it difficult to establish good electrical contact between conductive contacts and source or drain regions, hindering effective connection to adjacent gate structures.
Innovation Solution
The process involves removing a spacer on the side of a metal replacement gate to create a larger exposed area, allowing for a conductive material to be etched into a trench and form a butt contact that directly contacts both the sidewall and top of the metal replacement gate, enhancing contact with the doped region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional contact structure is used with a narrow fin structure, then the transistor density is improved, but the electrical contact between the contact and the source or drain region deteriorates
Solution Approach 1:
The contact structure transitions from a planar surface contact to a three-dimensional structure that contacts both the top surface and the sidewall of the gate. By etching the contact hole through the interlayer dielectric and having the conductive material contact the gate sidewall, the contact area is effectively increased from two dimensions to three dimensions, improving electrical connection while maintaining the narrow fin structure for high transistor density
Solution Approach 2:
The gate structure itself serves as an intermediary element that facilitates the electrical connection. Instead of the contact directly reaching the source/drain region through a long path in the narrow fin, the conductive material contacts the gate sidewall and top, using the gate as a conductive pathway to reach the source/drain region more effectively
2Productivity
If the fin structure width is reduced to increase transistor density, then the number of transistors per area is improved, but the difficulty of establishing good electrical contact increases
Solution Approach 1:
The gate structure is formed first as a reference feature, and then the contact hole is etched and the conductive material is deposited in relation to this pre-formed gate. This preliminary formation of the gate provides a reliable alignment reference, making it easier to position the contact correctly even when the fin structure width is reduced for higher transistor density
Solution Approach 2:
The gate structure serves its dual function as both the transistor control element and as the alignment reference for contact formation. The same gate that controls the transistor also provides the geometric reference that automatically guides the contact positioning, eliminating the need for separate alignment markers or complex alignment processes
Data Source
AI summary
A semiconductor device includes a substrate, a fin structure on the substrate, the fin structure comprising a doped region, a first gate over the fin structure, the first gate positioned adjacent the doped region, the first gate having a spacer on a first side and having no spacer on a second side between the gate and the doped region, and a conductive plug that contacts the doped region and a top of the gate.