Plasma Etching Nitrogen Radical Suppression
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Solution Overview
Problem
Conventional plasma processing methods for forming holes of different depths in multilayer films with oxide layers and tungsten etching stop layers face challenges in miniaturization and clogging, as the thickness of etching stop layers must be adjusted according to depth differences, leading to reduced selection ratios and hole shape quality.
Innovation Solution
A plasma processing method using a gas mixture of fluorocarbon-based gases, rare gases, oxygen, and nitrogen, where nitrogen reduces CF and CF3 radicals, minimizing clogging and allowing for the formation of protective films on etching stop layers, thereby maintaining a high selection ratio and preventing excessive etching of protective films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of etching stop layers is adjusted according to depth differences to form holes of different depths, then holes with different depths can be formed, but the selection ratio decreases and hole shape quality deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the processing gas by introducing nitrogen (5-50 sccm) to suppress CF and CF3 radical generation. This parameter change in gas composition enables simultaneous formation of holes with different depths while maintaining high selection ratio (≥5) and preventing clogging, without requiring adjustment of etching stop layer thicknesses
Solution Approach 2:
Nitrogen acts as an intermediary substance in the processing gas that suppresses the formation of harmful CF and CF3 radicals. This intermediary component mediates between the etching process and clogging prevention, allowing holes of different depths to be formed while maintaining protective films on etching stop layers
2Productivity
If conventional plasma processing is used to etch oxide layers, then etching can be performed, but clogging occurs and protective films are excessively etched
Solution Approach 1:
The patent converts the harmful effect of CF and CF3 radicals (which cause clogging) into a beneficial process by using nitrogen to suppress their generation. The same fluorocarbon-based gas that could cause clogging is now used effectively for etching oxide layers without forming excessive protective films or causing clogging, when combined with nitrogen suppression
3Length of moving object
If etching stop layers are made thinner to enable miniaturization, then device size is reduced, but etching resistance decreases leading to loss of stop layer integrity
Solution Approach 1:
By changing the processing gas composition to include nitrogen, the patent achieves high etching resistance with thinner etching stop layers. The nitrogen suppression of CF and CF3 radicals prevents excessive protective film formation, allowing thin tungsten layers (50-200 nm) to maintain sufficient etching resistance for miniaturized devices
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
This approach enables the simultaneous formation of holes with different depths while suppressing clogging and maintaining the integrity of etching stop layers, resulting in high-quality hole shapes and improved etching resistance.
Implementation Method 1
a plasma processing method uses a gas mixture of fluorocarbon-based gases, rare gases, oxygen, and nitrogen, where nitrogen reduces CF and CF3 radicals
Implementation Method 2
nitrogen reduces CF and CF3 radicals, minimizing clogging and allowing for the formation of protective films on etching stop layers
Implementation Method 3
allowing for the formation of protective films on etching stop layers, thereby maintaining a high selection ratio and preventing excessive etching of protective films
Data Source
AI summary
Provided are a plasma processing method and a plasma processing apparatus which may form a protective film on the surface of an etching stop layer and suppress clogging of openings of holes when etching an oxide layer are provided. The plasma processing method forms a plurality of holes having different depths in multi-layered films that include an oxide layer, a plurality of etching stop layers made of tungsten, and a mask layer. The plasma processing method includes an etching process in which a processing gas is supplied to generate plasma such that etching is performed from the top surface of the oxide layer to the plurality of etching stop layers so as to form hole having different depths in the oxide layer. Here, the processing gas includes a fluorocarbon-based gas, a rare gas, oxygen, and nitrogen.