Dielectric Cap Structure for VTFET Hardmask Erosion Prevention
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Solution Overview
Problem
During the fabrication of vertical transport field-effect transistor (VTFET) devices, substantial erosion of fin hardmasks occurs during etch processes, exposing underlying layers and compromising the integrity of the device structure.
Innovation Solution
A dielectric cap structure is introduced to protect the fin hardmasks by selectively forming caps on top of the fin hardmasks and liners, preventing erosion during etch processes such as the OPL open and pre-epi clean stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etch processes are performed to open OPL material over fins, then the OPL material is successfully removed, but substantial erosion of fin hardmasks occurs exposing underlying layers
Solution Approach 1:
A dielectric cap structure is formed on top of the fin hardmask before the etch process. This cap structure serves as a protective layer that prevents erosion of the underlying fin hardmask during subsequent etch operations to open the OPL material.
Solution Approach 2:
The dielectric cap structure acts as an intermediary protective layer between the etch process and the fin hardmask. It absorbs the erosive effect of the etch, allowing the OPL to be opened while preserving the fin hardmask integrity.
2Reliability
If pre-epi clean etch is performed prior to epitaxial growth, then the substrate surface is cleaned, but further erosion of fin hardmasks occurs especially when underlying layers are already exposed
Solution Approach 1:
The dielectric cap structure is formed in advance before the pre-epi clean etch process. This pre-formed cap protects the fin hardmask from erosion during the cleaning etch that would otherwise expose underlying layers when they are already vulnerable from previous OPL opening.
Solution Approach 2:
The dielectric cap structure provides beforehand protection against the harmful erosive effect of the pre-epi clean etch. It acts as a cushioning layer that prevents the etch from reaching and eroding the fin hardmask and underlying layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dielectric cap structure effectively prevents hardmask erosion, ensuring the fin hardmasks remain intact and functional throughout subsequent processing steps, enhancing the reliability and precision of VTFET device fabrication.
Implementation Method 1
A dielectric cap structure is introduced to protect the fin hardmasks by selectively forming caps on top of the fin hardmasks and liners, preventing erosion during etch processes
Data Source
AI summary
A novel dielectric cap structure for VTFET device fabrication is provided. In one aspect, a method of forming a VTFET device includes: patterning fins in a substrate using fin hardmasks, including a first fin(s) and a second fin(s); depositing a liner over the fins and the fin hardmasks; selectively forming first hardmask caps on top of the fin hardmasks/liner over the first fin(s); forming first bottom source and drain at a base of the first fin(s) while the fin hardmasks/liner over the first fin(s) are preserved by the first hardmask caps; selectively forming second hardmask caps on top of the fin hardmasks/liner over the second fin(s); and forming second bottom source and drains at a base of the second fin(s) while the fin hardmasks/liner over the second fin(s) are preserved by the second hardmask caps. A device structure is also provided.