What Is Cleaning System?
A Cleaning System is a device that uses chemical and physical properties to remove unwanted substances from the surface of materials.
It is used in the manufacturing process of precision equipment, semiconductors, displays, among others. When not used correctly, Cleaning Systems can lead to an increased incidence of defective products and reduced yields!
Cleaning methods vary from ultrasonic cleaning, spray cleaning, brush cleaning, dry cleaning, and solvent cleaning. In the case of semiconductor manufacturing, there are more than 500 manufacturing processes, of which the cleaning process is said to account for 30% to 40%.
Applications of Cleaning System
Examples of specific uses of Cleaning System are as follows:
- Cleaning silicon wafers in the semiconductor process.
- Cleaning of dirt adhering to metal filter mesh.
- Removing metal dust adhering to metal surfaces after cutting.
Cleaning System is selected based on the type of contamination, size of the cleaning target, cleaning time, and cleaning accuracy. Also important are the cleaning method, cleaning agent used, and drying method.
Principle of Cleaning System
In the case of semiconductor processes, the role of cleaning is to remove contamination from wafers. Contaminants include small invisible debris called particles, organic matter contained in human grime and dandruff, oil and grease such as sweat, and contamination from metals used in the factory.
Cleaning System washes these contaminants away with solvent or pure water. However, the process doesn’t conclude with cleaning alone. An essential step is drying, commonly referred to as “dry-in/dry-out.” Wafers must undergo thorough drying before being removed from the equipment.
Typical Cleaning Systems include ultrasonic cleaning, spray cleaning, brush cleaning, dry cleaning, and solvent cleaning.
1.Ultrasonic Cleaning System
Ultrasonic Cleaning Systems are used to clean wafers by placing the object to be cleaned in a chemical solution and vibrating the inside of the object with ultrasonic waves. The magnitude and frequency of the vibration are selected according to the object to be cleaned.
2.Spray Cleaning System
Spray Cleaning System is a method of cleaning objects by spraying gas or liquid from a nozzle. Handheld Cleaning Systems are also available and can be used for cleaning large objects.
3. Brush Cleaning System
Brush Cleaning System uses brushes to remove contaminants, and then rinses them away with a solution or spray washer. Since brushes are used as a physical method of cleaning, they can clean difficult-to-remove contaminants.
4. Dry Cleaning System
Dry Cleaning System irradiates UV (ultraviolet) light onto the object to be cleaned to generate ozone and active oxygen, which react with the contaminant to remove it. This method is mainly used in the manufacturing of semiconductors and displays.
5. Solvent Cleaning System
Solvent Cleaning System dissolves and removes contaminants by utilizing the dissolving power of solvents. Care must be taken because extremely hazardous solvents may be used.
Structure of Cleaning System
The basic structure of a Cleaning System consists of a conveyor system, a processing tank, a pure water tank, and a drying stage. The conveyor system is used to carry in and out objects, and the cleaning system cleans the objects in the processing tank. The pure water tank is used to wash away the chemicals adhering to the object, and the drying stage is used to dry the object.
In principle, only one type of contamination can be cleaned with one type of treatment solution, and multiple treatment tanks and pure water tanks are required when multiple types of contamination are to be cleaned. In the semiconductor manufacturing process, two types of equipment are used: batch-type equipment that processes multiple wafers at once, and single-wafer equipment that processes wafers one at a time.
In the batch type, wafers are placed together in a case called a carrier, and each carrier is placed in a processing layer for cleaning. The single-wafer type performs spray cleaning while rotating the wafers one by one.
Other Information on Cleaning System
Cleaning Agents Used in Cleaning System
Cleaning semiconductors involves the use of multiple processing liquids. Each treatment solution removes different contaminants. Each treatment is followed by rinsing with pure water.
SPM
A mixture of sulfuric acid and hydrogen peroxide for removal of organic matter.
APM
A mixture of ammonia and hydrogen peroxide to remove particles and organic matter. In addition, ultrasonic waves are added to increase the particle removal rate.
DHF
A mixture of hydrofluoric acid and pure water to remove metals and oxide films. Since hydrofluoric acid is a strong acid and dissolves silicon, it is diluted with pure water and used to treat only the wafer surface.
HPM
A mixture of hydrochloric acid and hydrogen peroxide is used to remove any remaining metal and oxides, creating a passivation layer on the surface to prevent re-deposition of contaminants.
Finally, the wafers are rinsed with pure water and undergo a drying process.