RF Phase Control in Plasma Chambers for Uniform CVD Deposition
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Solution Overview
Problem
Parasitic plasma formation in semiconductor process chambers reduces the stability and power efficiency of capacitively coupled plasmas used in chemical vapor deposition, leading to non-uniform film deposition and reduced deposition rates.
Innovation Solution
The implementation of an annular grounding bowl and a phase control circuit coupled to the faceplate and RF mesh in the process chamber, which adjusts the phase difference between the faceplate and RF mesh to minimize parasitic plasma formation and enhance plasma uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If RF power is applied to generate capacitively coupled plasma, then plasma is formed for CVD process, but parasitic plasma is generated under the pedestal reducing plasma stability and power efficiency
Solution Approach 1:
A dielectric layer is introduced between the pedestal and the grounding bowl to prevent direct electrical contact. This dielectric intermediary blocks the formation of parasitic plasma while maintaining the grounding function, thereby improving plasma stability and power efficiency without compromising the CVD process
Solution Approach 2:
The harmful parasitic plasma generation path is extracted by separating the grounding function from direct contact with the pedestal. The grounding bowl is positioned to ground the chamber wall while the dielectric layer prevents plasma formation in the gap, removing the source of instability
2Reliability
If grounding bowl is positioned close to pedestal to prevent parasitic plasma, then plasma stability improves, but plasma uniformity deteriorates
Solution Approach 1:
The dielectric layer provides localized electrical isolation only where needed (at the pedestal-grounding bowl interface) while maintaining overall plasma uniformity. This localized quality change prevents parasitic plasma without affecting the broader plasma distribution across the substrate
Solution Approach 2:
The electrical properties of the system are changed by introducing the dielectric material with specific permittivity and thickness. This parameter change modifies the electric field distribution locally to prevent parasitic plasma while maintaining uniform plasma conditions in the process volume
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 reduces parasitic plasma occurrence, increases plasma density and stability, and improves the uniformity of film deposition, thereby enhancing the efficiency and uniformity of the chemical vapor deposition process.
Implementation Method 1
The RF power source provides RF power to the pedestal and to the gas distribution assembly to generate capacitively coupled plasma
Implementation Method 2
A parasitic plasma may be generated in a lower volume of the process chamber under the pedestal. The parasitic plasma reduces the density and stability of the capacitively coupled plasma
Implementation Method 3
The RF power source provides RF power to the pedestal and to the gas distribution assembly to generate capacitively coupled plasma between the pedestal and the gas distribution assembly
Data Source
AI summary
Embodiments described herein relate to apparatus and techniques for radio frequency (RF) phase control in a process chamber. A process volume is defined in the process chamber by a faceplate electrode and a support pedestal. A grounding bowl is disposed within the process chamber about the support pedestal opposite the process volume. The grounding bowl substantially fills a volume other than the process volume below the support pedestal. A phase tuner circuit is coupled to an RF mesh disposed in the support pedestal and the faceplate electrode. The tuner circuit adjusts a phase difference between a phase of the faceplate electrode and a phase of the RF mesh.