Grounded Shield Geometry for Low-Sputter PVD Plasma Boundaries
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Solution Overview
Problem
In physical vapor deposition (PVD) chambers, the high plasma density and frequency of the RF source lead to undesirable sputtering of the grounded shield, causing contamination and affecting plasma geometry, as the plasma potential difference results in sputtering of the grounded shield.
Innovation Solution
The design includes a grounded shield with a specific ratio of surface area to height and diameter, and the incorporation of waves on the shield to increase surface area while maintaining the same height, reducing the plasma potential difference and preventing sputtering, along with optimized RF frequencies and pressures to achieve high deposition rates without shield contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high frequency RF power source is used to increase plasma density, then deposition rate is improved, but sputtering of grounded shield increases causing contamination
Solution Approach 1:
The grounded shield is designed with specific geometric ratios (surface area to height ratio of 2-3, diameter ratio of target to shield height of 4-4.3) to equalize the plasma potential distribution across the shield surface. This equipotential design reduces the potential difference between plasma and shield, thereby minimizing ion bombardment and sputtering while allowing high frequency RF operation for high deposition rates
Solution Approach 2:
The invention changes the geometric parameters of the grounded shield (surface area, height, diameter ratios) to optimize plasma confinement and potential distribution. By adjusting these parameters, the system achieves high plasma density for fast deposition while controlling the sheath region to prevent excessive ion bombardment of the shield
2Productivity
If high plasma density is achieved through increased RF frequency, then deposition rate increases, but plasma geometry at boundary deteriorates
Solution Approach 1:
The grounded shield with optimized surface area to height ratio (2-3) creates an equipotential boundary that maintains uniform plasma potential distribution at the plasma edge. This prevents plasma leakage and maintains well-defined plasma geometry even at high frequencies where plasma density is high
Solution Approach 2:
By optimizing the diameter ratio of target to shield height (4-4.3) and surface area to height ratio (2-3), the invention controls the plasma boundary shape and confinement. These parameter adjustments ensure that high plasma density does not compromise the geometric integrity of the plasma region
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 or eliminates sputtering of the grounded shield, allowing for increased deposition rates with high ionization levels and minimized contamination, while maintaining target to substrate spacing and plasma geometry.
Implementation Method 1
an RF power source to form a plasma within the chamber body
Implementation Method 2
A typical PVD chamber may use a radio frequency (RF) power source to form the plasma. As the frequency of the RF source increases, the plasma density increases
Implementation Method 3
This potential difference coupled with the high plasma-ion density can cause undesirable sputtering of the grounded shield
Implementation Method 4
the plasma potential can be in the region of a few tens to a few hundred volts positive with respect to the grounded shield
Implementation Method 5
Methods and apparatus for physical vapor deposition are provided herein
Data Source
AI summary
Methods and apparatus for physical vapor deposition are provided herein. In some embodiments, a process kit shield for use in a physical vapor deposition chamber may include an electrically conductive body having one or more sidewalls defining a central opening, wherein the body has a ratio of a surface area of inner facing surfaces of the one or more sidewalls to a height of the one or more sidewalls of about 2 to about 3.