Plasma Etch Tool High Aspect Ratio Ion Control
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Solution Overview
Problem
Conventional plasma etching techniques face challenges in effectively etching high aspect ratio features due to inefficient control of etch directionality and profile, leading to issues such as wide ion energy and angular distributions, slow diffusion of neutral species, and charge buildup on masks, which limits their effectiveness for advanced semiconductor devices.
Innovation Solution
The plasma etching apparatus separates the plasma-generation space, ionization space, and acceleration space with biased grids, alternating between electron attachment ionization to form negative ions and Penning ionization to form positive ions, allowing for the selective acceleration of ions and neutral species to achieve precise etching of high aspect ratio features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching techniques are used, then etching can be performed, but etch directionality and profile control are inefficient
Solution Approach 1:
The plasma etching apparatus is divided into three distinct functional zones: a plasma generation region, an ionization region, and an acceleration region. Each region performs a specific function - plasma generation creates reactive species, ionization converts neutrals to ions, and acceleration directs ions toward the substrate. This segmentation allows independent optimization of each function, improving etch directionality and profile control while maintaining manageable system complexity.
Solution Approach 2:
A grid structure serves as an intermediary component between the plasma generation region and the substrate. The grid applies controlled electric fields to guide ion trajectories, acting as a mediator that translates plasma generation into directed ion bombardment. This intermediary enables precise control of ion directionality without requiring direct contact between the plasma source and substrate.
2Manufacturing precision
If conventional plasma etching is used, then etching proceeds, but ion energy distribution is wide and uncontrolled
Solution Approach 1:
Different regions of the apparatus provide different local conditions: the plasma generation region provides high electron density, the ionization region provides controlled electric fields for ion formation, and the acceleration region provides focused electric fields for ion energy control. This local differentiation allows precise control of ion energy distribution at the substrate while simplifying overall operation through regional specialization.
Solution Approach 2:
The apparatus dynamically controls electric field distribution through independently biased grids and electrodes. By adjusting bias voltages on different grids, the system can dynamically optimize ion energy distribution for different etching requirements. This dynamic control capability improves manufacturing precision while maintaining ease of operation through programmable bias control.
3Productivity
If conventional plasma etching is used, then etching occurs, but neutral species diffusion is slow
Solution Approach 1:
The apparatus replaces reliance on slow neutral species diffusion with electric field-driven ion transport. By converting neutral species to ions in the ionization region and then accelerating them through electric fields, the system achieves much faster transport speeds compared to neutral diffusion. This substitution dramatically increases etch rate while maintaining directional control.
Solution Approach 2:
The system changes the physical state and motion mechanism of etching species from neutral diffusion to ion acceleration. By applying electric fields in the ionization and acceleration regions, species are transported at velocities determined by electric field strength rather than by thermal diffusion limits. This parameter change enables significantly higher etch rates.
4Manufacturing precision
If conventional plasma etching is used, then etching proceeds, but charge buildup occurs on masks
Solution Approach 1:
The apparatus extracts and separates charged species (ions) from neutral species through the ionization region and grid structures. By removing ions from the neutral plasma flow and directing them separately through electric fields, the system prevents charge accumulation on masks while maintaining clean neutral species flow. This extraction resolves the charge buildup problem.
Solution Approach 2:
The grid structures serve as intermediaries that selectively interact with charged species while allowing neutral species to pass through. The grids apply electric fields that guide ions away from mask surfaces, preventing charge buildup, while maintaining the neutral species flux needed for etching. This intermediary function solves the charge control problem.
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 efficient and precise etching of high aspect ratio features by separating and controlling ion and neutral species, reducing charge buildup and re-deposition of etch byproducts, and improving etch rate and directionality, thus addressing the limitations of conventional plasma etching methods.
Implementation Method 1
a plasma generating source, an ionization space coupled to the plasma generating source and configured to generate ions
Implementation Method 2
accelerate negative ions of a reactive species to the substrate in the acceleration space by introducing the reactive species into the ionization space and applying a positive bias to the substrate support
Implementation Method 3
accelerate positive ions of a non-reactive species to the substrate in the acceleration space by introducing the non-reactive species into the ionization space and applying a negative bias to the substrate support
Implementation Method 4
extract electrons from the plasma to the ionization space to ionize the reactive species and form the negative ions of the reactive species in the ionization space
Implementation Method 5
cause diffusion of metastable species from the plasma to the ionization space to ionize the non-reactive species and form the positive ions of the non-reactive species in the ionization space
Data Source
AI summary
High aspect ratio features are etched using a plasma etching apparatus that can alternate between accelerating negative ions of reactive species at a low energy and accelerating positive ions of inert gas species at a high energy. The plasma etching apparatus can be divided into at least two regions that separate a plasma-generating space from an ionization space. Negative ions of the reactive species can be generated by electron attachment ionization in the ionization space when a plasma is ignited in the plasma-generating space. Positive ions of the inert gas species can be generated by Penning ionization in the ionization space when the plasma is quenched in the plasma-generating space.