Showerhead Suppressor for Plasma Isolation in Substrate Processing
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Solution Overview
Problem
Substrate processing systems face issues with parasitic plasma formation behind showerheads in PEALD and PECVD systems, leading to unwanted deposition, which existing purging and plasma suppression methods either fail to isolate the volume effectively or disrupt process conditions.
Innovation Solution
A suppressor assembly is introduced above the showerhead to partition the volume behind it, increasing pressure relative to the reaction volume and using dielectric materials to control the flow of purge gases, thereby suppressing parasitic plasma formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If purging is used to prevent process gases from getting behind the showerhead, then unwanted deposition is reduced, but the required flow rates increase and process conditions are disrupted
Solution Approach 1:
The processing chamber is segmented into two distinct volumes: a reaction volume below the showerhead and a partitioned volume above the showerhead. The suppressor assembly creates a physical barrier that divides the chamber, allowing independent control of gas flows in each region. This segmentation enables low purge gas flow rates in the partitioned volume while maintaining proper process conditions in the reaction volume.
Solution Approach 2:
Different gas flow conditions are applied to different regions of the processing chamber. The partitioned volume above the showerhead receives low flow rates of purge gas, while the reaction volume below the showerhead maintains its required process gas flow rates. This local differentiation eliminates the need for high purge gas flows throughout the entire chamber.
2Object-affected harmful factors
If high purge gas flow is used to purge the volume behind the showerhead, then parasitic plasma is reduced, but plasma impedance shifts and light up behind the showerhead occurs
Solution Approach 1:
By segmenting the chamber into partitioned and reaction volumes, the suppressor assembly allows independent management of plasma conditions in each region. The partitioned volume can be purged at low flow rates sufficient to prevent parasitic plasma, while the reaction volume maintains stable plasma conditions without disruption from high purge flows.
Solution Approach 2:
The suppressor assembly acts as an intermediary barrier between the reaction volume and the partitioned volume. It allows low flow rates of purge gas to effectively suppress parasitic plasma in the partitioned volume without allowing high flow rates that would disrupt plasma impedance and cause light up in the reaction volume.
3Device complexity
If volume isolation is not implemented, then the system structure is simpler, but higher purge gas flow rates are required
Solution Approach 1:
The suppressor assembly introduces a moderate level of structural complexity by segmenting the chamber into two volumes. This segmentation is justified by the significant reduction in purge gas flow rates required, as the partitioned volume can be purged independently at low flow rates rather than requiring high flows to clear the entire chamber.
Solution Approach 2:
The suppressor assembly enables a change in the purge gas flow rate parameter from high values (required without isolation) to low values (sufficient with isolation). The partitioned volume configuration allows effective parasitic plasma suppression at low purge gas flows, representing a beneficial parameter change that offsets the added structural complexity.
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 effectively isolates the volume behind the showerhead, reducing parasitic plasma and unwanted deposition by maintaining process gas flow integrity and plasma impedance, enhancing the overall substrate processing efficiency.
Implementation Method 1
A plasma suppression apparatus is disclosed for purging and plasma suppression in a substrate processing system. The plasma suppression apparatus includes a suppressor that defines a partitioned volume behind a showerhead and that is arranged to generate increased pressure in the partitioned volume relative to a reaction volume in front of the showerhead.
Implementation Method 2
The increased pressure is arranged to suppress radio frequency (RF) energy in the partitioned volume to limit the generation of unwanted or unintended plasma behind the showerhead (referred to herein as parasitic plasma).
Implementation Method 3
The suppressor is arranged to define a partitioned volume behind the showerhead and to control a flow of purge gases through the partitioned volume. In some examples, the suppressor is made of dielectric material.
Data Source
AI summary
A substrate processing system includes a showerhead including a stem portion and a head portion. The stem portion is in fluid communication with a process gas source, and the head portion is arranged to provide process gases from the process gas source to a reaction volume of a processing chamber below the showerhead to generate plasma in the reaction volume. A suppressor is arranged above the head portion of the showerhead, extends from the stem portion toward sidewalls of the processing chamber, and is sealed against the sidewalls of the processing chamber or sealed against an enclosure surrounding the suppressor. The suppressor, the sidewalls, and a top surface of the processing chamber, the suppressor and the enclosure, or the suppressor, the enclosure, and the top surface define a partitioned volume of the processing chamber above the showerhead. The partitioned volume is in fluid communication with a purge gas source.