Quartz Window Twist-and-Lock Gas Injector Mounting
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Solution Overview
Problem
Dielectric windows in plasma processing chambers, typically made of brittle materials like quartz, are prone to chipping due to the machining of bayonet openings for gas injector assemblies, leading to mounting issues and damage during installation.
Innovation Solution
A dielectric window with a central bore and an upper recess for an annular insert with a bayonet opening, made from materials with higher tensile strength than quartz, such as plastic or ceramic, which is securely attached to the window using bolts or bonding, and a gas injector assembly with an RF shield and faceplate that engages the insert in a twist-and-lock fashion to avoid direct pressure on the window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bayonet opening is machined directly into the dielectric window for gas injector assembly, then the gas injector can be mounted securely, but the brittle window material is prone to chipping and damage
Solution Approach 1:
The mounting structure is divided into separate components: the dielectric window and the annular insert. The insert contains the bayonet opening and is attached to the window, separating the mounting function from the window itself. This prevents stress concentration on the brittle window material while maintaining secure gas injector mounting.
Solution Approach 2:
The annular insert acts as an intermediary element between the gas injector assembly and the dielectric window. It absorbs the mechanical stress of mounting and provides the bayonet opening, protecting the window from direct stress and chipping while enabling secure injector attachment.
2Device complexity
If the gas injector assembly is mounted directly to the dielectric window, then the structure is simple, but the mounting stress concentrates on the window causing potential damage
Solution Approach 1:
The mounting structure is segmented into the window, annular insert, and gas injector assembly. This segmentation distributes the mounting stress across multiple components rather than concentrating it on the window, reducing the risk of window damage while maintaining structural integrity.
Solution Approach 2:
The annular insert serves as a mediator that interfaces between the gas injector assembly and the window. It provides a mounting interface with the bayonet opening while protecting the window from direct mechanical stress, effectively distributing the load.
3Reliability
If quartz material is used for the dielectric window, then the window has good dielectric properties, but the material has low tensile strength and is prone to chipping
Solution Approach 1:
The annular insert acts as a protective intermediary that compensates for the low tensile strength of quartz. It provides the mechanical strength needed for mounting operations while the quartz window maintains its dielectric properties for plasma generation.
Solution Approach 2:
The system effectively creates a composite structure combining the dielectric window (quartz) with the annular insert (higher strength material). This composite approach allows each material to perform its optimal function: quartz for dielectric performance and the insert for mechanical strength and mounting.
Data Source
AI summary
An improved gas injection assembly for mounting in a central bore of a dielectric window of an inductively coupled plasma chamber includes a window having a central bore and cylindrical recess configured to receive an annular insert having a bayonet opening. The gas injector assembly includes a gas injector, an RF shield surrounding the gas injector, and a faceplate surrounding the RF shield, the faceplate including projections at the bottom thereof for engaging the bayonet opening in the annular insert. The window and gas injection assembly are designed to avoid chipping of the window which is typically made of quartz and in prior mounting arrangements the window has a bayonet opening machined therein. Due to the brittle nature of the quartz material, the machined bayonet opening was subject to chipping when the gas injector assembly was inserted into the bayonet opening.