Nitride Passivation Layer for Blister-Free FinFET Threshold Control
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Solution Overview
Problem
During the fabrication of semiconductor devices, etchants penetrate through anti-reflective coating layers, causing chemical reactions with oxide-based hardmask layers, leading to the formation of water-soluble by-products that result in blisters, which adversely impact the controllability of threshold voltage in semiconductor structures.
Innovation Solution
A nitride-based passivation layer is used to replace or be formed over the oxide-based hardmask layer, limiting chemical reactions with etchants and preventing blister formation by firmly attaching the anti-reflective coating, thus ensuring accurate control of the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an oxide-based hardmask layer is used, then the fabrication process can proceed with standard materials, but etchants penetrate through the anti-reflective coating and cause chemical reactions that generate water-soluble by-products leading to blister formation
Solution Approach 1:
A nitrogen-containing passivation layer is introduced as an intermediary between the anti-reflective coating and the oxide-based hardmask layer. This passivation layer acts as a mediator that prevents direct contact between etchants and the oxide-based hardmask layer, thereby eliminating the chemical reactions that produce water-soluble by-products and blisters, while still allowing the fabrication process to use standard oxide-based hardmask materials
Solution Approach 2:
The nitrogen-containing passivation layer serves as a temporary protective layer that is intentionally designed to be removed after serving its protective function. This disposable layer prevents blister formation during critical fabrication steps, then is selectively removed to allow subsequent processing to continue, effectively solving the blister problem without permanently altering the structure
2Productivity
If the anti-reflective coating is removed to access the hardmask layer, then etching can proceed, but etchants directly contact the oxide-based hardmask layer causing unwanted chemical reactions
Solution Approach 1:
The nitrogen-containing passivation layer serves as a protective intermediary that remains in place during etching operations. When etchants contact the structure, they react with or are blocked by the passivation layer rather than the oxide-based hardmask layer, preventing the formation of water-soluble by-products while allowing the etching process to proceed efficiently
Solution Approach 2:
The passivation layer is applied in advance to prevent the harmful chemical reactions between etchants and the oxide-based hardmask layer before the reactions can occur. This preliminary protective action ensures that when etching takes place, the unwanted chemical reactions have already been prevented, maintaining etching efficiency without generating blisters
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 use of a nitride-based passivation layer significantly reduces blister formation and enhances the controllability of the threshold voltage in semiconductor structures, improving the fabrication process by minimizing defects and maintaining etchant effectiveness.
Implementation Method 1
limiting chemical reactions with etchants
Implementation Method 2
firmly attaching the anti-reflective coating
Data Source
AI summary
A method for making a semiconductor structure includes forming a first fin and a second fin over a substrate. The method includes forming one or more work function layers over the first and second fins. The method includes forming a nitride-based metal film over the one or more work function layers. The method includes covering the first fin with a patternable layer. The method includes removing a second portion of the nitride-based metal film from the second fin, while leaving a first portion of the nitride-based metal film over the first fin substantially intact.