T-Shaped Bilayer Cap Structure for Semiconductor Gate Protection
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Solution Overview
Problem
As semiconductor processes scale down, it becomes challenging to fabricate back end of the line (BEOL) and middle of the line (MOL) metallization features due to critical dimension scaling and process limitations, leading to erosion of low-k dielectric spacer material during etching, which can result in shorts between metal gate and source/drain contacts.
Innovation Solution
A T-shaped bilayer cap structure composed of materials like nitride and SiOC is implemented over the gate structure and sidewall spacers, which acts as an etch stop layer to protect the low-k spacer during downstream etching processes, preventing metal gate shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If etching process is used to remove dielectric material adjacent to gate structures, then dielectric material is removed to form openings for drain and source contacts, but spacer material of the gate structure is eroded away exposing the metal material
Solution Approach 1:
A capping material is deposited over the gate structure and sidewall spacers before the etching process to protect the spacer material. This preliminary protective action prevents erosion of the low-k dielectric spacer during subsequent etching operations to form source and drain contacts.
Solution Approach 2:
The capping material serves as an intermediary protective layer between the etching process and the spacer material. This intermediate layer absorbs the harmful effects of the etching process, preventing direct contact with and erosion of the vulnerable low-k dielectric spacer.
2Productivity
If spacer material is eroded away during etching, then dielectric material is removed, but metal material of the gate structure is exposed resulting in a short
Solution Approach 1:
The capping material is applied in advance before contact formation etching to prevent exposure of the metal gate material. This preliminary protection ensures that while dielectric removal proceeds efficiently, the metal gate remains covered and shorting is prevented.
Solution Approach 2:
The capping material provides beforehand cushioning protection to the gate structure during the contact formation process. This prior protective measure cushions against the harmful effects of over-etching that would otherwise expose the metal gate and create shorts.
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a cap structure and methods of manufacture. The structure includes: a gate structure composed of conductive gate material; sidewall spacers on the gate structure, extending above the conductive gate material; and a capping material on the conductive gate material and extending over the sidewall spacers on the gate structure.