Revolutionizing Plasma Processes: The Power of Impedans Plasma Measurement Solutions 

RFEA

Introduction 

Accurate plasma measurements are crucial for industries leveraging plasma’s potential, providing key insights into parameters like electron density and temperature that enhance process optimization and product quality. Real-time understanding of plasma behavior enables precise circuit patterns in semiconductor manufacturing and controlled modifications in surface treatments to improve material properties. As a guide for efficiency and innovation, plasma measurements drive advancements across various sectors.  

Importance of Plasma Measurements 

Plasma plays a pivotal role in diverse industries, from semiconductor manufacturing, surface treatments to medical industry and space applications etc. shaping the course of modern technology and innovation. Precise measurements of plasma parameters are crucial for process optimization and enhanced product quality. 

In semiconductor manufacturing, accurate plasma measurements facilitate the creation of intricate circuitry through processes like plasma etching, where parameters like ion energy distribution and ion flux are vital for consistency and quality. Similarly, in thin film deposition, controlling plasma parameters ensures uniform, high-quality coatings that are critical for device performance. 

Accurate measurements also guide surface treatments, improving material adhesion and resulting in durable outcomes. By measuring plasma characteristics such as plasma potential, density, electron temperature, ion energy and flux, industries can optimize processes for efficiency and yield. Real-time data allows engineers to adjust conditions, reducing defects, minimizing waste and maximizing output. 

Overview of Plasma Measurement Techniques 

The study of plasma requires an array of measurement techniques to piece together its behaviour. From optical spectroscopy to VI probes, each technique offers a unique window into the complex world of plasma, contributing to diagnostics and process monitoring across various industries.   

Optical Spectroscopy: Optical spectroscopy involves analyzing the light emitted or absorbed by plasma. By breaking down this light into its component wavelengths, researchers can deduce the composition, temperature, and density of plasma. This technique finds applications in fusion research, astrophysics, and industrial plasma processes also. 

Langmuir Probes: Langmuir probes consist of electrodes immersed in plasma that measure the current flowing to or from the electrode. This allows for a localised determination of key plasma parameters, such as the plasma potential, plasma density, electron temperature and many more. Langmuir probes are the most widely used plasma diagnostic and have been proven to work in many different plasma chambers set ups and processes.  

Laser-Based Diagnostics: Laser-based techniques use laser light to interact with plasma, providing information about particle behaviour. Laser-Induced Fluorescence (LIF) detects emissions from excited particles, revealing details about composition and temperature. Thomson scattering uses scattered light to measure particle velocities and temperatures. These techniques are pivotal in fusion research and high-energy plasma physics.  

Faraday Cups: Faraday cups are devices that collect charged particles, measuring their quantity and energy. By quantifying the number of particles and their energy distribution, researchers can analyse the plasma’s ion composition and energy states. Faraday cups are crucial tools for determining plasma characteristics in research and industrial applications.  

Retarding Field Energy Analysers: Retarding Field Energy Analysers measure the ion energy distribution of ions. They work by applying an electric field that retards the motion of charged particles, allowing a measurement of the ion energy and flux to a substrate. These devices are essential for understanding ion energies within plasma, which are crucial in driving processes such as ion etching, deposition techniques and surface treatments. 

VI Probes: Voltage-Current (VI) probes measure the electrical properties of the plasma power delivery network by assessing the current, voltage, and phase of the RF power. They can determine forward and reflected power, as well as total power delivered to the plasma, aiding in matchbox performance monitoring. Additionally, VI probes can directly capture electrical signals from the plasma, offering a non-invasive way to monitor plasma processes.  

Introducing Impedans Plasma Diagnostic Solutions  

Impedans Ltd offers a wide range of plasma diagnostic instruments and systems designed to address the specific needs of plasma researchers and process engineers. These advanced tools provide precise measurements of plasma parameters, enabling a deep understanding of plasma behaviour and facilitating process improvement.  

Langmuir Probes: Impedans’ Langmuir probes are invaluable tools for in-situ plasma characterization. They have been used in over 100 scientific publications, demonstrating their reliability and wide range of compatibility with different plasma tools. Plato probe is a unique Langmuir probe capable of plasma measurements in deposition environment as well. Purchase of an Impedans Langmuir probe comes with free unlimited use of their advanced software, which performs complex analysis on raw current – voltage data to output key values for plasma parameters. The combination of the software, installation and use of Impedans’ dedicated support team make Impedans’ Langmuir probes accessible to all users.  

  

Figure 1 Impedans Langmuir Probe installed in a plasma chamber 

Octiv VI Probes: Impedans’ range of Ocitv VI probes offer precise monitoring of RF power and impedance during plasma processes. These can be connected for 24/7 monitoring using Impedans software connecter over USB or Ethernet or controlled using an API connection. Their wide range of products give research options of measuring calibrated RF parameters both in the 50 Ohm region before the matchbox and in the non 50 Ohm region. It can be used to monitor the forward and reflected RF power to ensure stable and controlled plasma generation, whilst latter can be used for direct monitoring of the plasma load itself, and how the capacitance and impedance changes over the course of a plasma process. These tools have demonstrated the detection of both clean and etch endpoint detection, and wafer misplacement in a wide range of tools by directly monitoring the voltage, current and phase of the plasma load. Impedans also offer a Moduli RF Spectrometer for measuring uncalibrated RF parameters, by measuring RF fields wherever there is leakage, for example at a window port or at the fans at the matchbox. This provides a useful tool to monitor RF parameters where the installation of an inline sensor is not feasible.   

 

Figure 2 Impedans Octiv VI probe for RF measurements 

Semion RFEA Systems: Impedans’ Semion RFEAs (Retarding Field Energy Analysers) systems deliver comprehensive substrate level plasma diagnostics, measuring key parameters such as the ion energy distribution function (IEDF) and ion flux to a substrate. These systems serve as electronic dummy wafers that are situated in the plasma in place of a substrate in a plasma process. Semion RFEAs have been used in a wide variety of tool types to give reliable measurements of key parameters in etching, deposition and surface treatment processes. Impedans include added options of ion angle/aspect ratio measurements (Vertex RFEA), deposition rate of ions and neutrals (Quantum RFEA) or a high time resolution RFEA to measure the evolution of the IEDF and ion flux over the course of a pulsed DC or HiPIMS signal applied to a plasma (Semion pDC). Advanced software and a devoted support team of experienced plasma engineers make using Impedans Semion RFEAs accessible for process control, scaling and matching.  


Figure 3 Impedans Semion RFEA installed in a plasma chamber 

Conclusion 

Plasma measurement techniques play a crucial role in understanding and optimizing plasma processes. The precise measurement of plasma parameters allows for better understanding and control of plasma behaviour, resulting in improved process repeatability, reduced downtime, and enhanced product quality.  

Impedans Ltd offers a comprehensive range of plasma diagnostic solutions that enable researchers and engineers to gain precise insights into plasma behaviour. By leveraging Impedans instruments, plasma researchers and process engineers can enhance their process understanding, improve productivity, and drive innovation. Explore the Impedans website to view the range of Impedans products and solutions and unlock the full potential of your plasma processes.   

 To learn more about our plasma measurement products contact us at info@impedans.com