Planar Plasma Sensor Layout for Real-Time Wafer Density Measurement
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Solution Overview
Problem
Conventional plasma diagnosis methods face challenges in accurately measuring plasma density due to structural interference and low signal intensity, particularly when using electrostatic probes and planar ring-type or conical plasma diagnosis apparatuses, which result in unreliable measurements and resonance issues.
Innovation Solution
A planar-type plasma diagnosis apparatus with a transmission antenna and a reception antenna, both having planar shapes, are insulated from each other and positioned to face each other, increasing capacitive coupling and signal intensity, and are buried in a wafer-shaped circular member or electrostatic chuck to minimize structural changes and enable real-time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bar-shaped probe or loop-shaped reception antenna is inserted into the plasma to measure plasma density, then the reception rate is increased, but structural interference with the plasma is caused and measurement accuracy is reduced due to perturbation of surrounding plasma density
Solution Approach 1:
The invention extracts the antennas from the plasma environment and embeds them in the electrostatic chuck instead. The transmission antenna and reception antenna are positioned on opposite sides of the chuck, allowing microwave transmission through the plasma without inserting any structural elements into the plasma itself, thereby eliminating structural interference while maintaining measurement capability
Solution Approach 2:
The electrostatic chuck serves as an intermediary structure that holds both the transmission and reception antennas. This mediator allows the antennas to be positioned in optimal locations for microwave transmission through the plasma without direct contact with the plasma, thus enabling accurate measurement while avoiding plasma perturbation
2Measurement precision
If a planar ring-type ultra-high frequency plasma diagnosis apparatus is used with concentric transmission and reception antennas, then plasma density measurement is enabled, but resonance signals attributed to structural characteristics cause unreliable measurements
Solution Approach 1:
The invention changes from a symmetric concentric ring structure to an asymmetric configuration where the transmission antenna and reception antenna are positioned on opposite sides of the electrostatic chuck. This asymmetric arrangement disrupts the structural symmetry that causes resonance signals, thereby eliminating the harmful resonance effects while maintaining the plasma diagnosis function
Solution Approach 2:
Instead of placing the reception antenna surrounding the transmission antenna (concentric structure), the invention inverts the arrangement by placing the transmission antenna on one side of the chuck and the reception antenna on the opposite side, with microwaves transmitted through the plasma. This inverted configuration eliminates the resonance problems inherent in concentric structures
3Measurement precision
If conventional plasma diagnosis methods are used, then plasma parameters can be measured, but high electric potential from electrostatic probes changes the plasma and makes accurate plasma density measurement difficult
Solution Approach 1:
The invention replaces the electrostatic probe method (which uses high electric potential) with a microwave-based electromagnetic measurement system. By using microwave transmission and reception through the plasma, the system can measure plasma density without applying high electric potential that would alter the plasma state, thus eliminating the measurement error caused by plasma modification
Solution Approach 2:
The invention changes the measurement parameter from direct electric potential measurement to microwave frequency transmission measurement. By measuring the change in microwave transmission characteristics through the plasma, the system can infer plasma density without directly interacting with the plasma through high electric potential, thereby avoiding plasma state changes
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 allows for reliable and real-time plasma density measurement by preventing structural interference and resonance signals, enhancing the measurement of plasma uniformity at a lower cost, especially during plasma processes near wafers.
Implementation Method 1
a transmission antenna and a reception antenna which are insulated from each other and face each other, and emit and receive electromagnetic waves, respectively
Implementation Method 2
When a frequency of the microwave is smaller than a plasma frequency, the microwave does not pass through the plasma, and when the frequency of the microwave is greater than the plasma frequency, the microwave passes through the plasma, and a frequency at this point is called a cut-off frequency, and plasma density can be obtained from this cut-off frequency
Implementation Method 3
both having planar shapes, are insulated from each other and positioned to face each other, increasing capacitive coupling and signal intensity
Data Source
AI summary
The present invention relates to a planar-type plasma diagnosis apparatus comprising: a transmission antenna for applying a frequency-variable microwave to plasma; a reception antenna for receiving the microwave from the plasma; and a body part encompassing the transmission antenna and the reception antenna so that same are insulated from each other, wherein the upper surface of the transmission antenna for applying the microwave and the upper surface of the reception antenna for receiving the microwave are planar, and side surfaces of the upper surfaces of the transmission antenna and the reception antenna face each other.