Ceramic Showerhead Gas Ring Segmentation for Plasma Etch Uniformity
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Solution Overview
Problem
The Bosch process for plasma etching in the semiconductor industry results in roughened sidewalls due to sidewall 'scalloping' and has limitations in achieving high etch rates, primarily because of the periodic etch/deposition scheme and non-uniform gas distribution across the substrate.
Innovation Solution
A gas delivery system for an inductively coupled plasma processing apparatus featuring a ceramic showerhead with radially extending gas inlets and fast-switching valves, allowing for rapid and uniform switching between etching and deposition gases, reducing scalloping and enhancing etch rates by ensuring consistent gas distribution across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional side gas injection is used, then device complexity is reduced, but manufacturing precision deteriorates due to non-uniform gas distribution and scalloping
Solution Approach 1:
The gas delivery system is segmented into multiple independent gas inlets distributed around the showerhead periphery, with each inlet receiving gas through separate flow paths. This segmentation enables uniform gas distribution across the substrate surface, eliminating the non-uniformity caused by conventional side injection and reducing scalloping effects.
Solution Approach 2:
A ceramic showerhead structure serves as an intermediary component between the gas supply system and the substrate. The showerhead with its radially extending gas inlets acts as a mediator that transforms the gas flow from the source into a uniform distribution pattern across the processing chamber, improving sidewall uniformity without requiring direct complex injection systems.
2Productivity
If periodic etch/deposition steps are used, then manufacturing precision is maintained through polymer protection, but productivity decreases due to dead time between steps
Solution Approach 1:
The gas delivery system enables continuous and uniform gas distribution throughout the etching process, eliminating dead time between etch and deposition steps. The uniform gas flow ensures consistent plasma generation and etching action across the entire substrate surface, maintaining high etch rates without the need for periodic interruption for polymer deposition.
Solution Approach 2:
The system changes the gas distribution parameters from non-uniform side injection to uniform radial distribution through the showerhead. This parameter change allows the process to maintain protective polymer formation while achieving continuous high-rate etching, as the uniform gas flow ensures both etching and polymer protection occur simultaneously across the substrate.
3Manufacturing precision
If shorter etch/deposition steps are used, then manufacturing precision improves with reduced scalloping, but productivity decreases due to increased cycle frequency requirements
Solution Approach 1:
The uniform gas distribution system enables continuous high-rate etching without periodic interruption, eliminating the need for frequent short cycles. The consistent gas flow maintains both protective polymer formation and high etch rates simultaneously, achieving smooth sidewalls through continuous action rather than repeated short cycles.
Solution Approach 2:
The invention changes the fundamental process parameters by enabling sustained high etch rates through uniform gas distribution. This allows the use of longer etching steps without increasing scalloping, as the uniform gas flow ensures consistent polymer protection throughout the extended etching duration, thereby improving productivity while maintaining precision.
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 solution significantly increases etch rates and achieves greater uniformity, with etch rates exceeding 10 μm/min and complete gas switching within milliseconds, compared to conventional side gas injection methods which achieve about 3 μm/min.
Implementation Method 1
fast-switching valves, allowing for rapid and uniform switching between etching and deposition gases, reducing scalloping and enhancing etch rates by ensuring consistent gas distribution across the substrate
Implementation Method 2
ceramic showerhead with radially extending gas inlets and fast-switching valves, allowing for rapid and uniform switching between etching and deposition gases
Implementation Method 3
The Bosch process can be carried out in a plasma processing apparatus configured with a high-density plasma source, such as an inductively coupled plasma (ICP) source
Implementation Method 4
During an etching step, SF6 facilitates spontaneous and isotropic etching of silicon (Si)
Implementation Method 5
during a deposition step, C4F8 facilitates the deposition of a protective polymer layer onto sidewalls as well as bottoms of the etched structures
Implementation Method 6
Upon energetic and directional ion bombardment, which is present in the etching steps, any polymer film coated in the bottoms of etched structures from the previous deposition step will be removed to expose the silicon surface for further etching
Data Source
AI summary
A gas delivery system for a ceramic showerhead includes gas connection blocks and a gas ring, the gas connection blocks mounted on the gas ring such that gas outlets in the blocks deliver process gas to gas inlets in an outer periphery of the showerhead. The gas ring includes a bottom ring with channels therein and a welded cover plate enclosing the channels. The gas ring can include a first channel extending ½ the length of the gas ring, two second channels connected at midpoints thereof to downstream ends of the first channel, and four third channels connected at midpoints thereof to downstream ends of the second channels. the cover plate can include a first section enclosing the first channel, two second sections connected at midpoints thereof to ends of the first section, and third sections connected at midpoints thereof to ends of the second sections. The channels are arranged such that the process gas travels equal distances for a single gas inlet in the gas ring to eight outlets in the cover ring allowing equal gas flow.