Semiconductor is the basis of modern electronic information technology, the level of its manufacturing process has a direct impact on the existence of electronic products. In the semiconductor manufacturing process, surface cleaning is a very important link, it can remove surface impurities and pollutants, improve the reliability and stability of the device. However, the traditional wet cleaning technology has been difficult to meet the development needs of the semiconductor process, because it has a water residue, secondary pollution, low cleaning efficiency and other problems. In order to solve these problems, dry cleaning technology came into being, which uses gas, plasma or solid particles, etc., without the need for liquid media, it can effectively clean the surface of the object.

I. Background of the application of dry cleaning technology

In the semiconductor manufacturing process, the cleanliness of the device surface directly affects the performance and quality of the device. The presence of organic contaminants, impurities or harmful gases on the surface may cause changes in the electrical characteristics of the device, structural defects, poor contacts, short circuits, open circuits and other faults, resulting in lower reliability and appearance quality of the device, shorter service life, and an increase in the failure rate and cost of the product. Therefore, removing contaminants from the device surface is a primary and critical step.

Traditional cleaning technology is mainly based on wet cleaning, that is, the use of liquid media such as water or solvent, through immersion, spray, ultrasonic and other ways to clean the surface of the object. However, with the continuous development of semiconductor technology, the size of the device is getting smaller and smaller, the structure of the surface is getting more and more complex, and the cleaning requirements are getting higher and higher. Wet cleaning technology has been difficult to adapt to this change, and encountered some problems in the production process, such as:

Water residue: Due to the surface tension and capillary effect of the liquid, it is difficult to completely dry the surface of the device after cleaning, and it is easy to produce water stains or water droplets, which may contain impurities or pollutants, causing secondary pollution or damage to the device.

Cleaning agent pollution: the cleaning agent itself may contain organic or metal ions and other pollutants, or in the cleaning process and the device surface chemical reaction, resulting in harmful by-products, these pollutants or by-products may remain on the surface of the device, affecting the performance and stability of the device.

Low cleaning efficiency: wet cleaning usually requires multiple steps, such as pretreatment, cleaning, drying, etc., each step requires a certain amount of time and equipment, the total time for cleaning is longer, the cost of cleaning is higher, the efficiency of cleaning is lower, and it is not suitable for high output production.

Environmental issues: Wet cleaning consumes a large amount of water and also generates a large amount of wastewater, which may contain hazardous chemicals and require specialised treatment, otherwise it can be harmful to the environment and the health of personnel.

In order to overcome the defects of wet cleaning technology, dry cleaning technology came into being, which refers to the technology of cleaning the surface of the object through gas, plasma or solid particles in the absence of liquid medium. Dry cleaning technology can effectively remove impurities and pollutants on the surface of the device, improve the reliability and stability of the device, but also save water resources, reduce wastewater discharge, in line with the concept of environmental protection. Dry cleaning technology is widely used in the semiconductor manufacturing process, the main role is to carry out surface treatment of the material, improve the surface properties of the material, improve the adhesion and affinity of the material, for the subsequent process steps to prepare.

II. Classification and characteristics of dry cleaning technology

Dry cleaning technology can be divided into the following four types depending on the cleaning medium:

Plasma Cleaning: Plasma is a fourth state material composed of charged particles with balanced positive and negative charges, which has the characteristics of high energy, high activity and high selectivity. Plasma cleaning is a technology that uses plasma to ionise and accelerate gases to clean the surface of objects with high-energy electrons, ions, atoms, molecules, free radicals and other particles. Plasma cleaning can effectively remove organic matter, oxides, metal ions and other pollutants on the surface, but also to activate the surface, modification, etching and other treatments to improve the adhesion and affinity of the surface. The advantages of plasma cleaning are fast cleaning speed, good cleaning effect, controllable cleaning process, no residue after cleaning, will not cause secondary pollution or damage, applicable to a variety of materials surface cleaning, especially for sensitive materials surface treatment.

E-beam cleaning: E-beam is a beam of electrons moving at high speed, which is characterised by high energy, high brightness and high directionality. E-beam cleaning is a technology that irradiates the surface of an object with a gathered beam of electrons to heat it and remove contaminants. E-beam cleaning is mainly suitable for surface treatment of metal materials.

UV light cleaning: UV light refers to electromagnetic radiation with a wavelength between 10-400 nm, which has the characteristics of high energy, high activity, high penetrability, etc. UV light cleaning is a technology that uses ultraviolet light to irradiate the surface of an object to decompose and remove organic pollutants.UV light cleaning is mainly applicable to the surface treatment of organic materials.

Mechanical Cleaning: Mechanical cleaning is a technique that uses high-speed airflow or solid particles to impact the surface of an object to remove contaminants. Although the cleaning process is also still considered efficient, but due to the stronger physical cleaning will cause significant damage to the material surface, so it is not suitable for use in the semiconductor manufacturing process, but commonly used in some non-sensitive material surface cleaning.

III. Prospects for the development of plasma cleaning technology

In the dry cleaning technology, plasma cleaning technology is recognised as more efficient and will have great application value in the future. Where exactly is it "strong"?

Plasma cleaning is special compared to the other three cleaning methods:

Higher efficiency and effectiveness: able to complete a large number of device cleaning tasks in a shorter period of time, significantly improving production efficiency; to achieve a high degree of cleaning effect, completely remove impurities and contaminants on the surface of the device, and improve the reliability of the package.

Highly controllable: plasma cleaner is a high-tech equipment with strong controllability. By adjusting the gas type, pressure, power and other parameters, precise control of the cleaning process can be achieved, ensuring the stability and consistency of the cleaning effect.

Avoid damage and pollution: not easy to cause physical damage or chemical corrosion, cleaning caused by the adverse effects of minimal, conducive to maintaining the original performance of the device.

Wide range of application: plasma cleaning is suitable for surface cleaning of various materials, including surface treatment of sensitive materials, with strong versatility.

With the continuous development of plasma cleaning technology, the application in the field of semiconductor has had many successful cases. Previously, we have also introduced the real effect of Microwave Plasma Cleaner MWD-80 of Zhongke Guangzhi in the cleaning experiment.

IV. Conclusion

Dry cleaning technology in the semiconductor field has an important application value and outstanding advantages. This is also despite the traditional wet cleaning cost is lower, more economical, in recent years the industry is still vigorously promote dry cleaning technology. Especially plasma cleaning, it is the most representative of dry cleaning technology and development prospects of a technology. With the semiconductor packaging gradually to high-performance, high-reliability demand, process difficulty further enhancement, plasma dry cleaning will also usher in a broader application space.

Opto-Intel Technologies Co., Ltd. is an innovative enterprise specialising in the research, development, production and sales of high-reliability semiconductor packaging equipment, with more than dozens of invention patents and independent intellectual property rights, providing high-quality, cost-effective microwave plasma system for the semiconductor industry. If you are interested in our products or technology, welcome to contact us, we will be happy to provide you with the best quality solutions.