SURFACE PLASMA ACTIVATION BEFORE DIRECT WAFER BONDING : A SHORT REVIEW AND RECENT RESULTS

摘要

Plasma activations for wafer bonding have been investigated for their ability to induce strong bonding even at low temperature treatment. In this paper, a short review presents state of the art and focus is made on bonding energy and quality enhancement obtained after reactive ion etch (RIE) or microwave (MW) plasma treatment, under various atmospheres. Effects of a short plasma treatment on Si and SiO_2 surfaces are highlighted hereafter. In Si-Si bonded structures the main issue with plasma treatment, is the occurrence of many bonding defects (e.g. bubbles, voids...) during [200℃-500℃] low temperature annealing. Low-density layers around bonding interfaces have been characterized by interfacial X-ray reflectivity. Evolution of these layers versus subsequent annealing are discussed for better understanding of the mechanisms involved in such plasma treatments and for bonding defect issue resolution.