Plasma Processing Apparatus Impedance Control for Etching Uniformity
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Solution Overview
Problem
Conventional plasma processing apparatuses face challenges in controlling the ratio between input powers during pulse-on and pulse-off periods when pulse-modulating high frequency powers, leading to instability and inefficiencies in plasma etching processes, particularly in reducing charging damage and micro-loading effects.
Innovation Solution
A plasma processing apparatus with a matching device that uses a weighted average of load impedance measurements during pulse-on and pulse-off periods to control the input power ratio, allowing for optimized power modulation and stable plasma generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high frequency power is pulse-modulated to reduce charging damage, then reliability is improved, but manufacturing precision deteriorates due to inability to control input power ratio
Solution Approach 1:
The invention changes the parameter of load impedance measurement by introducing a weighted average calculation that combines measurements from both pulse-on and pulse-off periods. By adjusting the weight coefficient, the system can control the input power ratio during pulse modulation, thereby maintaining etching uniformity while reducing charging damage through pulse modulation.
Solution Approach 2:
The invention implements a feedback mechanism where the load impedance is measured during both pulse-on and pulse-off periods, processed through weighted average calculation, and used to control the input power ratio. This closed-loop feedback system enables precise control of plasma generation while maintaining manufacturing precision during pulse-modulated operation.
2Productivity
If pulse modulation is applied to reduce micro-loading effects, then productivity is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The invention makes the existing load impedance measurement system multi-functional by enabling it to perform both traditional continuous measurement and pulse-modulated measurement with weighted average calculation. This universal approach allows the same hardware to support both continuous and pulse-modulated operation modes, improving etching efficiency without proportionally increasing device complexity.
Solution Approach 2:
The invention introduces a weight coefficient parameter that can be adjusted to optimize the balance between productivity and device complexity. By changing this parameter, the system can adapt the degree of pulse modulation and corresponding control complexity, enabling flexible optimization of etching efficiency while managing control system complexity.
3Manufacturing precision
If weighted average of load impedance is used to control input power ratio, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The invention performs preliminary action by measuring and storing load impedance values during both pulse-on and pulse-off periods before calculating the weighted average. This pre-measurement and storage approach allows the system to process impedance data efficiently and control the input power ratio with high precision, improving etching selectivity while managing the complexity through structured data preparation.
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 approach enables precise control of input power ratios, enhancing the stability and effectiveness of plasma etching processes by reducing charging damage and micro-loading effects, thereby improving etching uniformity and selectivity.
Implementation Method 1
high frequency power having a frequency (typically, 13.56 MHz or higher) suitable for plasma generation is applied to the upper electrode or the lower electrode. Electrons are accelerated in a high frequency electric field generated between the two facing electrodes by applying the high frequency power, and plasma is generated as a result of ionization by collision between the electrons and a processing gas.
Implementation Method 2
a first matching device, having a variable reactance element provided on the first high frequency transmission line and a first impedance sensor configured to measure a load impedance on the first high frequency transmission line with respect to the first high frequency power supply, configured to control a reactance of the variable reactance element such that a load impedance measurement value outputted from the first impedance sensor is equal to or approximate to a matching point corresponding to an output impedance of the first high frequency power supply
Data Source
AI summary
A plasma processing apparatus can control a ratio between an input power during a pulse-on period and an input power during a pulse-off period by a matching operation of a matching device provided on a high frequency transmission line for supplying the high frequency power as a continuous wave without a power modulation. An impedance sensor 96A provided in a matching device of a plasma generation system includes a RF voltage detector 100; a voltage-detection-signal generating circuit 102; an arithmetic-average-value calculating circuit 104; a weighted-average-value calculating circuit 106; and a moving-average-value calculating unit 108 of a voltage sensor system, and also includes a RF electric current detector 110; an electric current-detection-signal generating circuit 112; an arithmetic-average-value calculating circuit 114; a weighted-average-value calculating circuit 116; a moving-average-value calculating unit 118; and an impedance calculating circuit 120 of an electric current sensor system.