Surface plasma treatments enabling low temperature direct bonding

Plasma activations for wafer bonding have been investigated for their ability to induce strong bonding even at low temperature treatment. Generally occurring with plasma treatment, revelation of many bonding defects (e.g. bubbles, voids....) during (200-500 degrees C) low temperature annealing is an important issue. In this paper, we will focus on bonding energy and quality enhancement obtained after reactive ion etch or microwave plasma treatment, under various atmospheres. Effects of a short plasma treatment on Si and SiO2 surfaces are highlighted hereafter. Low-density layers around bonding interfaces have been characterized by interfacial X-ray reflectivity. Evolution of these layers through subsequent annealing are discussed to help in understanding mechanisms involved through such plasma treatments.