Hollow Cathode Plasma Control for Uniform Density
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Solution Overview
Problem
Plasma processing apparatuses face challenges in achieving uniform plasma density distribution within processing chambers, leading to non-uniform plasma processes on substrates due to the diffusion of plasma in peripheral regions, which is difficult to control with existing hollow cathode structures.
Innovation Solution
A plasma processing apparatus with a hollow cathode structure at the inner wall member, connected to a power supply for adjusting sheath voltage, is used to control plasma distribution. The apparatus includes a substrate mounting table, a facing electrode, and a high frequency power supply, with the hollow cathode structure featuring circular ring-shaped grooves that increase in width and depth towards the peripheral region, and a DC or high frequency power supply to optimize sheath voltage and plasma density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hollow cathode structure is formed in the processing chamber to uniformize plasma distribution, then plasma uniformity is improved, but the plasma density control precision deteriorates because the density mainly depends on fixed hollow cathode geometry
Solution Approach 1:
The patent applies the dynamics principle by making the hollow cathode structure adjustable rather than fixed. The cathode structure can dynamically change its configuration (such as expansion ratio, depth, or shape) to adapt to different plasma density requirements. This allows the system to maintain plasma uniformity while enabling precise control of plasma density according to specific processing needs.
Solution Approach 2:
The patent implements parameter changes by varying geometric parameters of the hollow cathode structure (such as expansion ratio, depth, width) to control plasma characteristics. By adjusting these parameters, the system can optimize both plasma uniformity and density control precision for different processing conditions and substrate requirements.
2Quantity of substance
If the hollow cathode structure size and depth are increased to enhance plasma generation in peripheral regions, then plasma density in peripheral regions is improved, but plasma density non-uniformity worsens due to excessive plasma concentration in specific areas
Solution Approach 1:
The patent applies local quality by designing the hollow cathode structure with spatially varying characteristics. Different regions of the cathode structure have different expansion ratios, depths, or shapes tailored to local plasma density requirements. This allows enhanced plasma generation in peripheral regions while maintaining appropriate plasma density in central regions, achieving overall uniformity.
Solution Approach 2:
The patent implements asymmetry by using a non-uniform hollow cathode structure where the expansion ratio or depth varies across different radial positions. The peripheral regions have different cathode geometry compared to central regions, creating asymmetric plasma generation that compensates for natural plasma diffusion patterns and achieves uniform plasma distribution.
3Device complexity
If a fixed hollow cathode structure is used to simplify the apparatus design, then device complexity is reduced, but plasma distribution control capability deteriorates due to inability to adjust plasma density
Solution Approach 1:
The patent applies dynamics by introducing adjustable or reconfigurable elements to the hollow cathode structure. The cathode can change its geometric parameters (expansion ratio, depth, shape) dynamically, providing plasma distribution control capability while maintaining relatively simple apparatus structure through mechanisms such as movable components or reconfigurable geometry.
Solution Approach 2:
The patent implements universality by designing a hollow cathode structure that can perform multiple functions: maintaining plasma uniformity, controlling plasma density, and adapting to different processing conditions. This multi-functional design reduces the need for separate control mechanisms while enhancing plasma distribution control capability.
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
This configuration allows for precise control of plasma density, achieving a uniform plasma process across the substrate by adjusting the sheath voltage and plasma distribution, ensuring consistent processing results.
Implementation Method 1
By way of example, in such a CCP processing apparatus, an electric field is generated between the electrode plates by applying a high frequency power to the one of the electrode plates from the high frequency power supply. As a result, electrons are generated in a processing space between the electrode plates. The electrons are accelerated by the electric field generated by the high frequency power and collide with molecules of a processing gas, so that capacitively coupled plasma is generated.
Implementation Method 2
a hollow cathode structure is formed at a portion of the inner wall member facing a peripheral region of the processing space, and the inner wall member is connected with a power supply for adjusting a sheath voltage
Data Source
AI summary
There is provided a plasma processing apparatus capable of performing a uniform plasma process on a substrate by controlling a plasma distribution within a chamber to a desired state and uniformizing a plasma density within the chamber. The plasma processing apparatus includes an evacuable chamber 11 for performing a plasma process on a wafer W; a susceptor 12 for mounting the wafer W within the chamber 11; an upper electrode plate 30a facing the susceptor 12 with a processing space S; a high frequency power supply 20 for applying a high frequency power to one of the susceptor 12 and the upper electrode plate 30a to generate plasma within the processing space S; and an inner wall member facing the processing space S. Hollow cathodes 31a to 31c are formed at the upper electrode plate 30a connected with a DC power supply 37 for adjusting a sheath voltage.