Edge Ring Self-Bias Estimation for Stable Ion Sheath Alignment
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Solution Overview
Problem
In plasma processing, the thickness reduction of the edge ring leads to a misalignment of the ion sheath, causing ions to incident on the substrate edge at an improper angle, which affects processing quality.
Innovation Solution
A plasma processing apparatus that includes a controller to adjust the negative DC voltage applied to the edge ring by estimating the self-bias voltage based on real-time voltage measurements, ensuring the ion sheath remains properly aligned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the edge ring is reduced, then the plasma processing can be performed, but the upper end position of the sheath above the edge ring becomes lower than the upper end position of the sheath above the substrate, causing the incident direction of ions upon the substrate edge to become sloped
Solution Approach 1:
The patent applies a negative DC voltage to the edge ring to change the electrical parameter of the edge ring, which adjusts the sheath position and corrects the ion incident direction from sloped to vertical, resolving the shape distortion caused by edge ring thickness reduction
Solution Approach 2:
The negative DC voltage is applied in advance to the edge ring to prevent the sheath misalignment before it occurs, maintaining proper ion incident direction throughout the plasma processing operation
2Shape
If a negative DC voltage is applied to the edge ring to correct the ion incident direction, then the ion sheath alignment is improved, but the self-bias voltage of the edge ring becomes difficult to measure accurately
Solution Approach 1:
The patent periodically switches between applying the negative DC voltage to the edge ring and stopping the application, creating periodic action that allows measurement of the self-bias voltage during the stop period while maintaining correction during the application period
Solution Approach 2:
The self-bias voltage is measured in advance during the period when the negative DC voltage application is stopped, before the correction is applied, allowing accurate measurement without interference from the negative DC voltage
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 solution effectively maintains the alignment of the ion sheath, ensuring consistent and high-quality plasma processing by adjusting the negative DC voltage in real-time based on the estimated self-bias voltage.
Implementation Method 1
a radio frequency power is supplied from a radio frequency power supply
Implementation Method 2
a negative DC voltage to be applied to the edge ring
Implementation Method 3
an estimate of a self-bias voltage of the edge ring generated by a supply of the radio frequency power
Implementation Method 4
a current measurement value indicating a current flowing between the edge ring and the DC power supply
Implementation Method 5
A plasma processing apparatus is used in a plasma processing upon a substrate
Data Source
AI summary
In a plasma processing apparatus, a controller specifies a time point when a current starts to flow between an edge ring and a DC power supply after beginning an application of a negative DC voltage to the edge ring from the DC power supply. The controller specifies, from a voltage measurement value indicating a voltage of the edge ring at the time point, an estimate of a self-bias voltage of the edge ring generated by a supply of a radio frequency power. The controller sets a sum of an absolute value of the estimate of the self-bias voltage and a set value as an absolute value of the negative DC voltage to be applied to the edge ring by the DC power supply.