Akitake Tamura

Using electrostatic repulsion to prevent adhesion of infinitesimal particles

The miniaturization of semiconductor devices has been proceeding rapidly in recent years. With that progress, the size of particulate contamination that must be controlled is also decreasing. Infinitesimal particles of diameters less than 50 nm cannot be controlled by conventional air flow control and filtering, so new control methods are required. We evaluated a new particle control method that uses the repulsive electrostatic force to prevent the adhesion of particles. We confirmed that the method suppressed the adhesion of particles by about 92%.

Contamination control of particles smaller than 40 nm by thermophoretic force

As the miniaturization of semiconductor devices increases, the size of contamination particles that must be controlled becomes smaller. The effects of diffusion are stronger for smaller particles, so control becomes more difficult. We therefore evaluated the use of thermophoretic force in a new control technique. We confirmed that particle adhesion could be mostly prevented by simply heating the wafer to 5degC above the temperature of the air flow. Furthermore, we established a model of adhesion prevention behavior which predicts that the adhesion prevention effect of thermophoretic force is adequate, even for particles less than 40 nm in diameter. In addition, we actually confirmed that thermophoresis prevents adhesion even for 20 nm PSL particles.