Tungsten Etching via Cyclic Plasma and Thermal Treatment
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Solution Overview
Problem
Current tungsten etching technologies face challenges in achieving high uniformity and controllability in atomic layer level etching, particularly in the wafer in-plane and pattern depth directions, due to non-uniform distribution of reactive species and pattern collapse issues during the etching of high aspect ratio patterns in semiconductor manufacturing.
Innovation Solution
The method involves generating a surface reaction layer on the tungsten film using fluorine radicals in plasma and then removing it by heating to a boiling point temperature, with both processes having self-limiting properties, allowing for precise control of the etching amount through cyclic repetition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching is used to achieve high etching speed, then productivity is improved, but manufacturing precision deteriorates due to non-uniform reactive species distribution
Solution Approach 1:
The continuous etching process is segmented into discrete cyclic steps: plasma treatment for a first predetermined time to form a surface reaction layer, followed by heating treatment for a second predetermined time to remove the layer. This segmentation allows precise control of etching amount per cycle, achieving atomic layer level precision while maintaining high overall etching speed through multiple cycles.
Solution Approach 2:
The etching process uses periodic cyclic treatment alternating between plasma treatment and heating treatment. Each cycle consists of plasma treatment for a first predetermined time followed by heating treatment for a second predetermined time. This periodic action ensures uniform reactive species distribution and consistent etching amount per cycle, resolving the uniformity issue while maintaining productivity.
2Manufacturing precision
If wet chemical solution is used for isotropic etching, then manufacturing precision is improved, but object-generated harmful factors worsen due to pattern collapse from surface tension
Solution Approach 1:
The wet chemical etching process is replaced with a plasma-based process combined with thermal treatment. Instead of using liquid chemical solutions that cause surface tension and pattern collapse, the invention uses plasma treatment to form a surface reaction layer followed by heating to remove it. This substitution eliminates the harmful surface tension effect while maintaining isotropic etching capability and high manufacturing precision.
Solution Approach 2:
The process changes the physical state and parameters of the etching environment from liquid wet chemical solution to gaseous plasma followed by thermal treatment. By controlling plasma treatment time, heating temperature, and cycle repetitions, the invention achieves isotropic etching without the pattern collapse issues associated with wet chemical methods.
3Productivity
If continuous plasma treatment is used to increase productivity, then etching speed is improved, but manufacturing precision deteriorates due to inability to control etching amount at atomic layer level
Solution Approach 1:
The etching process is segmented into discrete cyclic steps with predetermined times: plasma treatment for a first predetermined time to form a surface reaction layer, followed by heating treatment for a second predetermined time to remove it. This segmentation creates self-limiting reactions that produce a fixed etching amount per cycle, enabling atomic layer level precision while maintaining high throughput through multiple cycles.
Solution Approach 2:
The plasma treatment step performs a preliminary action by forming a surface reaction layer on the tungsten film before the actual removal step. This preliminary layer formation is controlled to occur for a first predetermined time, creating a consistent starting point for the subsequent heating treatment that removes a fixed amount of material, thereby achieving precise dimension control.
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 isotropic atomic layer level etching with high uniformity and controllability, improving processing dimension accuracy and yield by ensuring a fixed etching amount per cycle, regardless of the wafer position or depth.
Implementation Method 1
generating a surface reaction layer of the tungsten film on a surface of the tungsten film by supplying a reactive species including fluorine which is generated in plasma onto the surface of the tungsten film
Implementation Method 2
removing the surface reaction layer that is generated on the surface of the tungsten film by heating the surface reaction layer to a boiling point temperature or higher of the tungsten fluoride
Implementation Method 3
removing the surface reaction layer that is generated on the surface of the tungsten film by heating the surface reaction layer to a boiling point temperature or higher of the tungsten fluoride
Implementation Method 4
supplying a reactive species including fluorine which is generated in plasma
Implementation Method 5
supplying a reactive species including fluorine which is generated in plasma
Data Source
AI summary
In an etching method of etching a tungsten film, the method is provided to execute a generating a surface reaction layer on a tungsten film that is formed on a surface of a base material by supplying a reactive species including fluorine which is generated in plasma onto the base material for a first predetermined time in a state where the base material of which the tungsten film is formed on at least a portion of the surface is cooled to a melting point temperature or lower of a tungsten fluoride, and a removing the surface reaction layer that is generated on the tungsten film by heating the base material of which the surface reaction layer is generated on the tungsten film to a boiling point temperature or higher of the tungsten fluoride for a second predetermined time.