Semiconductors are the foundation of modern electronic information technology, and the level of their manufacturing process has a direct impact on electronic products. Surface cleaning is a very important part of the semiconductor manufacturing process, which can remove impurities and contaminants from the surface and improve the reliability and stability of the device. However, the traditional wet cleaning technology has been difficult to meet the development needs of semiconductor process, because it has problems such as water residue, secondary pollution, and low cleaning efficiency.
In order to solve these problems, dry cleaning technology has been developed to effectively clean the surface of objects without the need for liquid media.
Application background of dry cleaning technology
In the semiconductor manufacturing process, the cleanliness of the surface of a device directly affects the performance and quality of the device. If there are organic pollutants, impurities or harmful gases on the surface, it may cause changes in the electrical characteristics of the device, structural defects, poor contact, short circuit, open circuit and other faults, resulting in the reduction of the reliability and appearance quality of the device, the shortening of the service life, and the increase of the failure rate and cost of the product. Therefore, removing contaminants from the surface of the device is a first and foremost critical step.
The traditional cleaning technology is mainly based on wet cleaning, that is, the use of liquid media such as water or solvent to clean the surface of the object through immersion, spraying, ultrasonic, etc. However, with the continuous development of semiconductor technology, the size of devices is getting smaller and smaller, the surface structure is becoming more and more complex, and the requirements for cleaning are also increasing. Wet cleaning technology has struggled to adapt to this change, and some problems have been encountered in the production process, such as:
Water Stain Residue:Due to the surface tension and capillary action of the liquid, it is difficult to completely dry the surface of the cleaned device, and it is easy to produce water stains or water droplets, which may contain impurities or contaminants, causing secondary pollution or damage to the device.
Cleaning agent contamination:The cleaning agent itself may contain contaminants such as organic matter or metal ions, or may chemically react with the surface of the device during the cleaning process, resulting in harmful by-products that may remain on the surface of the device and affect 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 of cleaning is longer, the cost of cleaning is higher, the efficiency of cleaning is lower, and it is not suitable for high-volume production.
Environmental Issues:Wet cleaning consumes a lot of water and also produces a lot of wastewater, which can contain harmful chemicals and require specialized treatment, otherwise it can be harmful to the environment and human health.
In order to overcome the shortcomings of wet cleaning technology, dry cleaning technology came into being, which refers to the technology of cleaning the surface of objects by means of gas, plasma or solid particles in the absence of liquid media. Dry cleaning technology can effectively remove impurities and contaminants on the surface of the device, and improve the reliability and stability of the deviceAt the same time, it can also save water resources and reduce wastewater discharge, which is in line with the concept of environmental protection.
Dry cleaning technology is widely used in the semiconductor manufacturing process, and its main role is to treat the surface of the material, improve the surface properties of the material, improve the adhesion and affinity of the material, and prepare for the subsequent process steps.
Classification and characteristics of dry cleaning technology
Dry cleaning technology can be divided into the following four types according to the different cleaning media:
· Plasma cleaning
Plasma is a fourth-state substance composed of charged particles with a balance of positive and negative charges, which hasHigh energy, high activity, high selectivityand other features. Plasma cleaning is a technology that uses plasma to ionize and accelerate gases, and cleans the surface of objects with high-energy electrons, ions, atoms, molecules, free radicals and other particles.
Plasma cleaning can:It can effectively remove organic matter, oxides, metal ions and other pollutants on the surface, and at the same time, it can also activate, modify, etch the surface to improve the adhesion and affinity of the surface.
Pros:Yes: fast cleaning speed, good cleaning effect, controllable cleaning process, no residue after cleaning, no secondary pollution or damage. Therefore, it is suitable for surface cleaning of various materials, especially for sensitive materials.
· Electron beam cleaning
An electron beam is a beam composed of electrons moving at high speed, which has the characteristics of high energy, high brightness, and high directionality. Electron beam cleaning is a technique in which a concentrated electron beam is applied to the surface of an object, subjecting it to heat and removing contaminants. Electron beam cleaning is mainly suitable for the surface treatment of metal materials.
· UV light cleaning
UV light refers to electromagnetic radiation with a wavelength between 10-400 nanometers, which has the characteristics of high energy, high activity and high penetration. 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 suitable for the surface treatment of organic materials.
· Mechanical cleaning
Mechanical cleaning is a technique that uses high-velocity air currents or solid particles to impact the surface of an object to remove contaminants. Although the cleaning process is also quite efficient, it is not suitable for the semiconductor manufacturing process due to the strong physical cleaning will cause obvious damage to the surface of the material, but is often used for the cleaning of some non-sensitive material surfaces.
The development prospect of plasma cleaning technology
Among the dry cleaning technologies, plasma cleaning technology is recognized by the industry as a more efficient cleaning technology that will have great application value in the future.
Is it "strong"?
Compared with the other three cleaning methods, plasma cleaning is special in that it is -
Higher efficiency efficacy:It can complete the cleaning task of a large number of devices in a short time, which greatly improves the production efficiency; Achieve a high degree of cleaning and thoroughly remove impurities and contaminants from the device surface, improving package reliability.
High controllability:The plasma cleaning machine is a kind of high-tech equipment with strong controllability. By adjusting the gas type, pressure, power and other parameters, the cleaning process can be accurately controlled to ensure the stability and consistency of the cleaning effect.
Avoid damage and contamination:It is not easy to cause physical damage or chemical corrosion, and the adverse effects of cleaning are minimal, which is conducive to maintaining the original performance of the device.
Wide range of applications:Plasma cleaning is suitable for surface cleaning of various materials, including surface treatment of sensitive materials, and has strong versatility.
With the continuous development of plasma cleaning technology, there have been many successful cases in the application of plasma cleaning technology. Previously, we also introduced the real effect of the microwave plasma cleaning machine MWD-80 in the cleaning experiment.
Read the original article carefully
What is the effect of microwave plasma cleaning on the surface of DBC substrates? (Application examples).
Optimization of microwave plasma cleaning for die bond and wire bond (including process introduction).
Conclusion: Dry cleaning technology has important application value and outstanding advantages in the field of semiconductors. That's why dry cleaning has been heavily promoted in recent years, despite the fact that traditional wet cleaning is cheaper and more economical. In particular, plasma cleaning is one of the most representative and promising technologies in dry cleaning technology. With the gradual demand for high performance and high reliability of semiconductor packaging, the process difficulty is further improved, and plasma dry cleaning will usher in a broader application space.