Two-Piece Ceramic Showerhead for Rapid Gas Switching
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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 and uniformity, primarily because of the periodic etch/deposition scheme and gas distribution inefficiencies.
Innovation Solution
A ceramic showerhead for an inductively coupled plasma processing apparatus that rapidly switches between etching and deposition gases within 200 milliseconds, using a two-piece design with specific gas passage configurations to enhance gas distribution and plasma processing efficiency, allowing for faster and more uniform etching of silicon substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the Bosch process uses periodic etch/deposition steps to etch deep features, then deep structures can be defined in silicon substrate, but sidewall roughness and scalloping occur
Solution Approach 1:
The patent implements dynamic control of the etch process by continuously adjusting process parameters such as gas flow rates, RF power, and pressure during the etching cycle. This dynamic adjustment allows optimization of the etch rate and sidewall profile throughout the deep etching process, reducing scalloping while maintaining high aspect ratio features
Solution Approach 2:
The patent employs periodic pulsed plasma etching cycles with alternating etch and deposition steps. By optimizing the duration and frequency of these periodic cycles, the process achieves deep etching while controlling sidewall roughness through precise timing of polymer deposition during each cycle
2Manufacturing precision
If the Bosch process shortens etch/deposition step duration to reduce scalloping, then sidewall roughness decreases, but overall etch rate reduces
Solution Approach 1:
The patent maintains continuous etching action by optimizing the cycle frequency and duration of etch/deposition steps. The process ensures that etching continues effectively throughout the entire wafer surface without interruption, maximizing material removal rate while controlling sidewall quality through continuous plasma exposure
Solution Approach 2:
The patent dynamically changes process parameters including gas composition, flow rates, RF power levels, and pressure during different phases of the etching cycle. These parameter adjustments optimize both the etch rate and sidewall profile, achieving high productivity with controlled roughness
3Device complexity
If conventional gas distribution systems are used in plasma processing, then simple device structure is maintained, but gas distribution uniformity and switching speed are insufficient
Solution Approach 1:
The gas distribution system is segmented into multiple independent gas delivery channels with individual control valves and flow meters. This segmentation allows precise control of gas flow to different regions of the plasma chamber, achieving uniform gas distribution and rapid switching between process gases
Solution Approach 2:
The patent introduces intermediate gas distribution manifolds and flow control components between the gas sources and plasma chamber. These intermediary elements enable precise regulation and uniform distribution of process gases, improving switching speed and distribution homogeneity
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 achieves higher etch rates of at least 10 μm/minute with improved uniformity, significantly reducing sidewall roughness and increasing the overall etch rate by enabling rapid and uniform gas switching in the plasma processing chamber.
Implementation Method 1
an inductively coupled plasma (ICP) source
Implementation Method 2
radio frequency (RF) biased substrate electrode
Data Source
AI summary
A two piece ceramic showerhead includes upper and lower plates which deliver process gas to an inductively coupled plasma processing chamber. The upper plate overlies the lower plate and includes radially extending gas passages which extend inwardly from an outer periphery of the upper plate, axially extending gas passages in fluid communication with the radially extending gas passages and an annular recess forming a plenum between the upper and lower plates. The lower plate includes axially extending gas holes in fluid communication with the plenum. The upper plate can include eight radially extending gas passages evenly spaced around the periphery of the upper plate and the lower plate can include inner and outer rows of gas holes. The two piece ceramic showerhead forms a dielectric window of the chamber through which radiofrequency energy generated by an antenna is coupled into the chamber. A gas delivery system delivers process gas to a plenum between the upper and lower plates having a gas volume of no greater than 500 cm3. The gas holes in the lower plate extend between the plenum and a plasma exposed yttria coated surface of the lower plate. The gas delivery system is operable to supply an etching gas and a deposition gas into the processing chamber such that the etching gas in the plenum can be replaced with the deposition gas within about 200 milliseconds and vice versa.