Microwave Plasma Source Frequency Control for Density Uniformity
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Solution Overview
Problem
Conventional RLSA® microwave plasma processing apparatuses face challenges in precisely controlling plasma density distribution due to variations caused by microwave power and gas conditions, making it difficult to achieve uniform plasma treatment for large semiconductor wafers.
Innovation Solution
A microwave plasma processing apparatus equipped with a frequency controller that adjusts the oscillation frequency of the microwave oscillator based on temperature detection signals from multiple positions on the antenna part, allowing for precise control of plasma density distribution by modulating the microwave frequency and electric field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a slot antenna with a predetermined slot pattern is used to generate microwave plasma, then the plasma density distribution is determined accordingly, but the plasma density distribution varies depending on microwave power and gas conditions, making it difficult to control with high precision
Solution Approach 1:
The patent introduces a variable impedance element that can be dynamically adjusted to change the impedance distribution along the slot antenna. This dynamic adjustment capability allows the system to adapt to different microwave power levels and gas conditions, maintaining precise plasma density distribution control despite varying operating conditions.
Solution Approach 2:
The patent changes the electrical parameter (impedance) of the antenna by introducing a variable impedance element. By adjusting the impedance distribution along the slot antenna, the system can control the microwave field distribution and consequently control the plasma density distribution with high precision under various operating conditions.
2Productivity
If microwave power is increased to improve plasma generation efficiency, then plasma density increases, but plasma density distribution becomes harder to control uniformly
Solution Approach 1:
The patent applies local quality by creating different impedance sections along the slot antenna. Each section has a specific impedance value that locally controls the microwave field strength, allowing different regions of the plasma to have optimized density distributions. This enables uniform plasma generation across the entire processing area even at high power levels.
Solution Approach 2:
The variable impedance element provides dynamic control capability, allowing the system to adjust impedance distribution in real-time based on operating conditions. This dynamic adjustment ensures that plasma density uniformity is maintained across different power levels, optimizing both productivity and precision.
3Manufacturing precision
If the slot pattern is fixed to provide desired plasma density distribution, then initial plasma distribution is optimized, but adjustments become difficult when microwave power or gas conditions change
Solution Approach 1:
The patent transforms the fixed slot pattern into a dynamically adjustable structure by incorporating a variable impedance element. This allows the electrical characteristics of the antenna to be changed without modifying the physical slot pattern, providing both optimal initial plasma distribution and the ability to adjust to changing operating conditions.
Solution Approach 2:
The patent changes the electrical parameter (impedance) rather than the physical structure. By adjusting the impedance of the variable impedance element, the system can modify the microwave field distribution and plasma density distribution without changing the slot pattern, maintaining both optimization and adaptability.
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
Enables high-precision control of plasma density distribution, ensuring uniform plasma treatment even with variations in microwave power and gas conditions, thereby improving the processing of large semiconductor wafers.
Implementation Method 1
a microwave oscillator configured to oscillate the microwave and vary an oscillation frequency of the microwave
Implementation Method 2
an antenna part including a slot antenna and a microwave-transmitting plate, the slot antenna being configured to radiate the microwave propagating through the waveguide into the chamber
Implementation Method 3
the microwave-transmitting plate constituting a ceiling plate of the chamber and being made of a dielectric material through which the microwave radiated from the slots transmits
Implementation Method 4
a plurality of temperature detectors configured to detect temperatures at a plurality of positions of the antenna part outside the chamber
Implementation Method 5
a frequency controller configured to receive detection signals obtained by the plurality of temperature detectors and control the oscillation frequency of the microwave oscillator so that a plasma density distribution inside the chamber becomes a desired distribution, based on the detection signals
Implementation Method 6
a microwave plasma source for generating a microwave plasma inside a chamber by radiating a microwave into the chamber
Data Source
AI summary
A microwave plasma source for generating a microwave plasma inside a chamber by radiating a microwave into the chamber, includes: a microwave oscillator for oscillating the microwave and vary an oscillation frequency thereof; a waveguide through which the microwave propagates; an antenna part including a slot antenna for radiating the microwave into the chamber and having a predetermined pattern of slots, and a microwave-transmitting plate constituting a ceiling plate of the chamber and made of a dielectric material through which the microwave radiated from the slots transmits; temperature detectors for detecting temperatures at plural positions of the antenna part outside the chamber when the microwave plasma is generated; and a frequency controller for receiving detection signals obtained by the temperature detectors and controlling the oscillation frequency of the microwave oscillator so that a plasma density distribution inside the chamber becomes a desired distribution based on the detection signals.