Hysteresis in adhesion through biasing in semiconductor surfaces

Adhesion is crucial in semiconductor production as it affects the positioning precision and lifespan of contacting components such as silicon wafers and wafer stages. Electrical grounding or biasing are conventional methods to regulate the electrostatic interaction between components. An applied bias voltage, especially if it is greater than the band gap of a semiconductor material, can induce charges and counter-charges between surfaces in/near contact, thereby significantly increasing electrostatic adhesion. However, provisionally applied electric field may lead to, for example, charge/hole trapping and electrowetting at or close to the surfaces of interacting solids. Trapped charges or water adsorption can remain even after removing electrical bias, which may lead to hysteresis in the adhesion behavior. Our experiments indicate that the adhesion between nano-asperities remains significantly higher even minutes after a bias voltage is applied to one of the surfaces. Improved understanding of history-dependent adhesion can lead to concrete strategies towards (1) eliminating charge traps and electrowetting already in the manufacturing process of materials and coatings and (2) avoiding their adverse effects on adhesion, friction, and wear.