Plasma Edge Ring Voltage Control for Etching Shape
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Solution Overview
Problem
In plasma processing apparatuses, the etching shape of semiconductor wafers near the edge collapses in the radial direction, resulting in elliptical holes and tilting due to the consumption of the edge ring, which affects the uniformity and roundness of the etching process.
Innovation Solution
A plasma processing apparatus with a controller that applies a negative DC voltage to the edge ring, periodically alternating between two voltage states, synchronized with the electrode potential, to control the sheath thickness and prevent tilting, ensuring a complete circular hole shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional plasma processing apparatus uses an edge ring at the periphery of the wafer, then the in-plane uniformity of processing is improved, but the etching shape near the edge collapses in the radial direction resulting in elliptical holes and tilting
Solution Approach 1:
The patent applies periodic action by alternating the DC voltage applied to the edge ring between a first voltage value (during plasma generation) and a second voltage value (during non-plasma periods). This periodic voltage alternation prevents continuous ion bombardment at the wafer edge, thereby preventing the collapse of etching shape and maintaining roundness while preserving in-plane uniformity during plasma processing periods.
Solution Approach 2:
The patent changes the voltage parameter applied to the edge ring by switching between two distinct voltage states. During plasma generation, a first DC voltage is applied to control sheath thickness and ion incidence; during non-plasma periods, the voltage is changed to a second value to allow relaxation and prevent cumulative damage. This parameter change resolves the contradiction by dynamically adjusting the electrical conditions to maintain both uniformity and shape integrity.
2Manufacturing precision
If DC voltage is continuously applied to the edge ring, then sheath thickness is controlled and ion incidence angle is maintained, but the edge ring consumption causes tilting and loss of roundness
Solution Approach 1:
The patent implements periodic action by intermittently applying DC voltage to the edge ring only during plasma generation periods rather than continuously. This periodic application reduces cumulative ion bombardment and material consumption from the edge ring, extending its service life while maintaining precise control of sheath thickness and ion incidence angle during the actual processing periods when plasma is present.
Solution Approach 2:
The patent ensures continuity of useful action by applying DC voltage to the edge ring during every plasma generation period, maintaining consistent sheath thickness control and ion incidence angle control precisely when needed for processing. The voltage is discontinued only during non-plasma periods where no processing occurs, thus maintaining continuous useful action during productive periods while reducing overall consumption.
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 solution effectively prevents tilting and maintains the roundness of the etching shape at the wafer edge, improving the precision and uniformity of the etching process by controlling the sheath thickness and ion incidence angle.
Implementation Method 1
a DC power supply configured to supply a DC voltage to the edge ring; and a controller configured to execute a first control procedure in which the DC voltage periodically repeats a first state having a first voltage value and a second state having a second voltage value higher than the first voltage value
Implementation Method 2
a plasma generation source configured to supply plasma into the processing container; an etching process is performed with plasma generated from a gas by a radio-frequency power
Implementation Method 3
a bias power supply configured to supply a bias power to the electrode
Data Source
AI summary
A plasma processing apparatus includes a container; a stage disposed in the container and including an electrode; a plasma source that generates plasma in the container; a bias power supply that periodically supplies a pulsed negative DC voltage to the electrode; an edge ring disposed to surround a substrate placed on the stage; and a DC power supply that supplies a DC voltage to the edge ring. The DC power supply supplies a first DC voltage in a first time period when the pulsed negative DC voltage is not supplied to the electrode, and supplies a second DC voltage in a second time period when the pulsed negative DC voltage is supplied to the electrode.