Reinforced Gate Cap and Spacer Divots for Self-Aligned Contact Etch
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Solution Overview
Problem
In semiconductor fabrication, self-aligned contacts face issues with gate cap and spacer loss due to limited etch selectivity during plasma etch processes, which can misalign and damage the contact formation.
Innovation Solution
A method is introduced where divots are created in the top portions of spacers and gate caps, filled with etch-stop material having better etch-stop ability than the spacer and gate cap materials, to reduce or eliminate loss during the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hard mask gate cap is used as an etch-stop in self-aligned contacts, then misalignment due to size reduction is addressed, but gate cap and spacer loss occurs due to limited etch selectivity during plasma etch
Solution Approach 1:
The gate cap structure is segmented into multiple portions with different etch-stop capabilities. A first gate cap portion with better etch-stop ability is positioned at the top where it is most needed to prevent loss during plasma etch, while a second gate cap portion extends downward to provide structural support. This segmentation allows the gate cap to simultaneously achieve precision alignment and resist material loss.
Solution Approach 2:
Different portions of the gate cap are assigned different material properties tailored to their specific functional requirements. The top portion uses material with superior etch-stop characteristics to prevent loss during contact etching, while lower portions may use materials optimized for structural integrity or other process requirements. This local differentiation resolves the contradiction between precision and material loss.
2Manufacturing precision
If plasma etch is used for contact formation, then self-aligned contact precision is achieved, but gate cap and spacer loss occurs due to limited etch selectivity
Solution Approach 1:
The gate cap structure is pre-configured with enhanced etch-stop portions before the plasma etch process begins. By预先 positioning material with superior etch-stop ability at the top of the gate cap, the structure is prepared in advance to resist the plasma etch, preventing loss and maintaining structural integrity throughout the contact formation process.
Solution Approach 2:
The gate cap is constructed as a composite structure combining materials with different properties. The top portion uses material with excellent etch-stop characteristics against plasma, while other portions may use materials optimized for structural support or electrical properties. This composite approach allows the gate cap to simultaneously achieve precision alignment and maintain reliability during plasma etch.
Data Source
AI summary
A method includes providing a starting structure, the starting structure including a semiconductor substrate, sources and drains, a hard mask liner layer over the sources and drains, a bottom dielectric layer over the hard mask liner layer, metal gates between the sources and drains, the metal gates defined by spacers, gate cap openings between corresponding spacers and above the metal gates, and a top dielectric layer above the bottom dielectric layer and in the gate cap openings, resulting in gate caps. The method further includes removing portions of the top dielectric layer, the removing resulting in contact openings and divot(s) at a top portion of the spacers and/or gate caps, and filling the divot(s) with etch-stop material, the etch-stop material having an etch-stop ability better than a material of the spacers and gate cap. A resulting semiconductor structure is also disclosed.