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The Difference Between Chemical And Physical Plasma Systems



Plasma cleaning, a surface cleaning process that employs plasma, a partially ionized gas, has become a valuable method for removing contaminants and unwanted substances. The plasma is created by energizing a gas, resulting in a mixture of ions, electrons, and neutral species.


Through physical and/or chemical mechanisms, the reactive species in the plasma interact with the surface, effectively eliminating organic and inorganic residues, thin films, oxides, oils, particles, and more. In this article, we will break down the key differences between physical and chemical plasma systems.


What Is Plasma Cleaning?

Plasma cleaning refers to a surface cleaning process that utilizes plasma, which is a partially ionized gas, to remove contaminants and unwanted substances from a surface. Plasma is created by applying energy to a gas, causing it to ionize and generate a mixture of ions, electrons, and neutral species. These highly reactive species in the plasma interact with the surface being cleaned, leading to the removal of contaminants through physical and/or chemical mechanisms.


Plasma cleaning offers several advantages over traditional cleaning methods. It can effectively remove organic and inorganic residues, thin films, oxides, oils, particles, and other unwanted substances from various materials, including metals, semiconductors, glass, plastics, and ceramics. The cleaning process is typically performed in a vacuum chamber or a controlled environment to maintain the plasma conditions.


What Is Physical Plasma Cleaning?

Physical plasma cleaning, also known as plasma etching or sputter cleaning, relies on the physical bombardment of the surface with energetic ions. It involves creating a plasma, which is a partially ionized gas, and exposing the surface to this plasma. In this case, the plasma includes electrons, ions, and neutral. The ions in the plasma have high energy and can physically sputter away contaminants or material from the surface being cleaned.


The bombardment of ions causes physical etching of the surface, effectively removing organic or inorganic contaminants, thin films, oxides, or other unwanted materials. Physical plasma cleaning is commonly used to remove organic residues, improve the adhesion of coatings, clean semiconductor wafers, and modify surface properties.


What Technology Is Physical Plasma Cleaning Used for?

Physical plasma cleaning finds applications in diverse technologies and industries. It is extensively used in semiconductor fabrication for removing contaminants and unwanted films from semiconductor surfaces before subsequent manufacturing steps.


Physical plasma cleaning is crucial in preparing surfaces before the thin film deposition processes, ensuring optimal film adhesion and quality. It is also employed for surface modification purposes, enhancing the adhesion of coatings and paints onto different materials.


In microfabrication and microengineering, physical plasma cleaning plays a vital role in cleaning and activating surfaces for high-quality microstructures. Additionally, it is utilized in the aerospace and defense industries for cleaning and preparing critical components.


Overall, physical plasma cleaning is a versatile technique used in technologies requiring precise surface cleaning, patterning, or modification.


What Is Chemical Plasma Cleaning?

Chemical plasma cleaning, also known as plasma activation or plasma functionalization, involves using reactive species in the plasma to chemically interact with the surface. In this method, the plasma is created using a gas mixture containing reactive gases such as oxygen, hydrogen, nitrogen, or other chemicals. The reactive species present in the plasma can chemically react with the contaminants or the surface, altering their properties or removing them.


Chemical plasma cleaning can enhance surface wettability, promote bonding, remove organic substances, or activate surfaces for subsequent processes like coating, bonding, or printing. It is commonly used in industries such as microelectronics, biotechnology, and materials science.


What Technology Is Chemical Plasma Cleaning Used for?

Chemical plasma cleaning is utilized in various technologies and industries, such as microelectronics, biotechnology, optics, PCB manufacturing, and the automotive industry. In the microelectronics and semiconductor industry, it is used for surface preparation and removal of contaminants before device fabrication.


In biotechnology and medical devices, chemical plasma cleaning helps clean and activate surfaces of implants and medical equipment, enhancing biocompatibility. In optics and photonics, it is employed to clean optical components and improve surface quality for better performance.


In PCB manufacturing, chemical plasma cleaning ensures clean and activated surfaces for subsequent processes. In the automotive industry, it assists in cleaning, activating, and improving surface adhesion for painting or bonding applications. These examples highlight the diverse applications of chemical plasma cleaning in different technological fields.


Chemical and Physical Factors in Plasma Systems

When it comes to plasma cleaning systems, there are several chemical and physical factors that play a significant role in the cleaning process. These factors influence the efficiency, selectivity, and effectiveness of plasma cleaning. Here are the key chemical and physical factors in plasma systems:


Physical Factors

Electric Field and Voltage

An electric field is created in the plasma system using electrodes and applied voltage. The strength of the electric field affects the ionization and acceleration of charged species in the plasma. It determines the energy of the ions bombarding the surface, thereby influencing the physical sputtering effect.


Plasma Uniformity

Uniform plasma distribution across the surface being cleaned is important for consistent and effective cleaning. Non-uniform plasma can result in uneven cleaning and surface modification. The design of the plasma system, electrode configuration, gas distribution, and chamber geometry play a role in achieving plasma uniformity.


Substrate Temperature

The temperature of the substrate or surface being cleaned can influence the plasma cleaning process. In some cases, elevated temperatures can enhance cleaning by increasing the reactivity of the contaminants or promoting desorption. However, for temperature-sensitive materials, maintaining a low substrate temperature is necessary to prevent damage.


Exposure Time

The duration of exposure to the plasma influences the extent of cleaning. Longer exposure times allow more interactions between the reactive species and contaminants, resulting in better cleaning. However, the exposure time needs to be optimized to avoid overexposure or damage to the surface.


Chemical Factors

Gas Composition

The choice of gas composition in the plasma system is crucial as it determines the reactive species present in the plasma. Different gases, such as oxygen, nitrogen, hydrogen, argon, or mixtures thereof, can be used to create the desired chemical environment for cleaning. The reactive species in the plasma, such as ions, radicals, and excited atoms/molecules, chemically react with the contaminants on the surface.


Gas Flow Rate

The flow rate of the gas into the plasma chamber affects the transport of reactive species to the surface. Proper gas flow rate control ensures a sufficient supply of reactive species to interact with the contaminants and facilitate their removal.


Pressure

The pressure inside the plasma chamber impacts the plasma characteristics and cleaning process. Low-pressure plasmas can enhance ion bombardment and physical sputtering, while high-pressure plasmas favor chemical reactions. The pressure is adjusted to optimize the cleaning process for specific applications.


Power and Energy Density

The power supplied to the plasma system determines the energy of the ions and electrons in the plasma. Higher power levels lead to more energetic species, increasing the physical bombardment and sputtering effects. Energy density, which is the power per unit area, influences the intensity of cleaning and can be adjusted to suit the requirements of the surface being cleaned.


Different Types of Plasma Cleaning Products

Plasma cleaning products encompass various types of machines designed to cater to specific cleaning needs. Some common types include plasma etchers, used for precise material removal in semiconductor fabrication; plasma ashers, which remove organic residues and photoresist films; plasma surface activators, promoting surface wettability and bonding; plasma cleaners or sterilizers, removing contaminants and sterilizing surfaces; plasma ashing systems, preparing samples for analysis; plasma cleaners for optics, ensuring optimal performance of optical components; and plasma surface modification systems, enabling customized surface treatments.


These diverse plasma cleaning products offer solutions for industries such as semiconductor, biotechnology, optics, PCB manufacturing, and automotive, among others, meeting various cleaning requirements and ensuring efficient surface cleaning and preparation.


Plasma Cleaning and SCI

In conclusion, plasma cleaning has emerged as a powerful technique for surface cleaning, providing effective removal of contaminants and unwanted substances. Whether through physical plasma cleaning or chemical plasma cleaning, these methods offer distinct advantages and find applications in various industries.


There are many different varieties of plasma cleaning products, such as Batch Plasma, Inline Plasma, and Strip Plasma. To break down the important differences between each machine and how they are used, one should contact the experts at SCI Plasma.

SCI Plasma is a respected organization comprising a team of skilled specialists who are experts in delivering exceptional plasma cleaning solutions. With their vast expertise and experience, they are invaluable partners for individuals and organizations in need of assistance with plasma cleaning.


If you need assistance with plasma cleaning, clarification in choosing the right equipment, or customized solutions for your specific cleaning requirements, the dedicated experts at SCI Plasma are fully committed to helping you.


 

Mr Davide Zonca is the CEO of SCI Automation, a leading plasma cleaning, etching and surface treatment equipment manufacturer. SCI Automation has been in the plasma cleaning business since 2000 with experience in advanced semiconductor packaging and assembly.

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