Hokkaido University Research Profiles

Manufacturing Technology

Steam/Water Mixture Spray Cleaning Method with an Ultra-low Impact on the Environment

An ultraprecise and safe cleaning method making use of the physical action of steam and water and no chemicals.

We have developed an innovative cleaning method using a completely new vapor-water multiphase spray method, whereby water and steam are mixed and sprayed at high speed from a nozzle. This method is especially notable for not using any chemicals and minimizing the burden on the environment.
We have confirmed that the specified performance can be achieved with ultra-precision cleaning during semiconductor manufacturing processes, etc.

Content of research

Based on our previous research results, we have discovered that when a droplet hits a solid surface in a condensable gas (not air), splashing is suppressed and a thin liquid film (lamella) spreads on the solid surface at high speed. Since the high-speed lamellae may generate a strong fluid shear force, it seemed possible to use a mixed jet of steam and water to realize an environmentally friendly cleaning method.
Based on our previous research results, we have confirmed that this cleaning method, which uses only water and steam, can achieve the specified cleaning performance for ultra-precision cleaning required in the manufacturing processes of semiconductors, LEDs, and solar cells. This cleaning method is also safe both for the human body and the environment, because it uses only water and steam instead of detergents or other chemicals that are harmful to the human body.

  • Schematic diagram of this cleaning method

  • Cleaning example: photoresist stripping

  • (a) in air (b) in saturated steam
    Principle of physical action generation: Collision of alcohol droplets

  • (a) Initial state (b) Steam/water spray (c) Air/water spray
    Cleaning example: difference in spray conditions for residue removal after dry etching

Potential for social implementation

  • ・Semiconductor manufacturing process
  • ・Manufacturing process of LEDs and other electronic devices
  • ・Sterilization and cleaning processes in food production
  • ・Cleaning processes for overall living environments

Appealing points to industry and local governments

We ourselves are greatly surprised to realize that we can obtain the cleaning effect by using only the physical action of the steam and water mixed spray. We will continue our research to find new possibilities of fluid mechanics and deepen our understanding of this cleaning method to make it available in various situations in society and to realize an environmentally friendly recycling society.