Showerhead Dielectric Layer Stack to Suppress Parasitic Plasma
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Solution Overview
Problem
In semiconductor processing chambers, parasitic plasma formation occurs due to RF fields penetrating regions between the substrate and the showerhead, leading to inefficiencies and potential damage during plasma-enhanced chemical vapor deposition (PECVD) processes.
Innovation Solution
A plasma reducing system is implemented, featuring a plurality of dielectric layers arranged between an electrode and a grounded conducting structure. These dielectric layers create gaps that attenuate RF fields, preventing parasitic plasma formation while maintaining a high impedance path to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a solid dielectric layer is used between ground and the electrode to prevent excessive RF coupling to ground, then RF coupling is reduced, but the required thickness is generally not practical
Solution Approach 1:
The patent divides a single thick dielectric layer into multiple thinner dielectric layers separated by gaps. This segmentation achieves the same RF blocking function as a thick layer while using less total material and providing a more practical structure. The gaps between layers further reduce RF coupling through multiple air interfaces that reflect and attenuate RF fields.
Solution Approach 2:
The patent introduces air gaps as intermediary spaces between dielectric layers. These air gaps act as additional mediators that reflect RF fields due to the impedance mismatch between dielectric materials and air, thereby enhancing RF coupling prevention without requiring increased dielectric thickness.
2Object-affected harmful factors
If an RF shield is used to reduce parasitic plasma, then parasitic plasma is reduced, but if not designed properly it can give rise to a low RF impedance path to ground
Solution Approach 1:
The RF shield is segmented into multiple dielectric layers with gaps between them. This segmentation disrupts continuous RF field paths that would otherwise create low impedance ground paths, while still providing RF shielding to suppress parasitic plasma in the processing chamber.
Solution Approach 2:
The patent creates a composite structure alternating between dielectric materials and air gaps. This composite configuration provides both RF shielding functionality to reduce parasitic plasma and high RF impedance to prevent excessive coupling to ground, combining benefits that neither material alone could provide.
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 system effectively reduces parasitic plasma density by a factor of about 5, improving the efficiency and reliability of PECVD processes by minimizing plasma-related issues and preventing excessive RF coupling to ground.
Implementation Method 1
a plurality of dielectric layers that are arranged between an electrode and the first surface
Implementation Method 2
These dielectric layers create gaps that attenuate RF fields, preventing parasitic plasma formation
Data Source
AI summary
A system includes an electrode. The electrode includes a showerhead having a first stem portion and a head portion. A plurality of dielectric layers is vertically stacked between the electrode and a first surface of a conducting structure. The plurality of dielectric layers includes M dielectric layers arranged adjacent to the head portion and P dielectric portions arranged around the first stem portion. The plurality of dielectric layers defines a first gap between the electrode and one of the plurality of dielectric layers, a second gap between adjacent ones of the plurality of dielectric layers, and a third gap between a last one of the plurality of dielectric layers and the first surface. A number of the plurality of dielectric layers and sizes of the first gap, the second gap, and the third gap are selected to prevent parasitic plasma between the first surface and the electrode.