Showerhead Upper Electrode Structure to Suppress Abnormal Discharge
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Solution Overview
Problem
Abnormal discharges in upper electrodes of capacitively-coupled plasma processing apparatuses occur due to secondary electron emission when electrons or positive ions collide with dielectric materials, leading to instability and inefficiency in plasma processing.
Innovation Solution
The upper electrode design incorporates a dielectric third member forming a gas diffusion chamber, connected with first and second gas holes, and sealing members to minimize secondary electron emission and friction, thereby suppressing abnormal discharges by stabilizing the gas flow and fixing the relative position of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dielectric material is used to form the gas diffusion chamber in the upper electrode, then the gas diffusion function is improved, but abnormal discharge occurs due to secondary electron emission when electrons or positive ions collide with the dielectric
Solution Approach 1:
The upper electrode is divided into multiple members (first member, second member, third member) with the dielectric third member forming the gas diffusion chamber. This segmentation allows the dielectric to perform its gas diffusion function while being isolated from direct electron/positive ion collision paths, preventing abnormal discharge.
Solution Approach 2:
The dielectric third member acts as an intermediary component that facilitates gas diffusion from the first member to the second member through controlled pores, while its positioning and design prevent it from being directly struck by high-energy electrons or positive ions that would cause secondary electron emission and abnormal discharge.
2Ease of manufacture
If the upper electrode components are designed with multiple members and gas holes, then the gas diffusion control is improved, but friction between components increases leading to particle generation
Solution Approach 1:
The patent employs sealing members (such as O-rings or flexible sealing films) between the first member, second member, and third member to eliminate friction contacts. These flexible sealing elements provide gas-tight seals without requiring rigid mechanical contact, thereby preventing friction-induced particle generation while maintaining proper gas diffusion control through the structured gas holes in each member.
3Ease of operation
If the relative position of components is not fixed, then assembly and adjustment are easier, but abnormal discharge occurs due to position instability
Solution Approach 1:
The patent incorporates positioning structures (such as positioning holes, positioning protrusions, or fixed configurations of the first member, second member, and third member) that pre-establish the correct relative positions of components during assembly. This preliminary positioning action ensures stable spatial relationships are achieved automatically, preventing abnormal discharge caused by position instability while maintaining ease of assembly through straightforward alignment features.
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 reduces abnormal discharges in the upper electrode, enhancing the stability and efficiency of plasma processing by minimizing secondary electron emission and frictional particle generation.
Implementation Method 1
Abnormal discharges in upper electrodes of capacitively-coupled plasma processing apparatuses occur due to secondary electron emission when electrons or positive ions collide with dielectric materials
Implementation Method 2
A gas diffusion chamber into which a processing gas is introduced from a gas introduction port is defined inside the upper electrode
Data Source
AI summary
An upper electrode disclosed forms a shower head in a capacitively-coupled plasma processing apparatus. The upper electrode includes a first member, a second member, and a third member. The first member is formed of a conductor. The first member provides a first gas hole. The first gas hole penetrates the first member. The second member is formed of a conductor. The second member is provided on the first member. The second member provides a second gas hole. The third member is formed of a dielectric. The third member is provided between the first member and the second member. The third member defines the gas diffusion chamber. The first gas hole and the second gas hole are connected to the gas diffusion chamber.