title: Fabrication of buckling free ultrathin silicon membranes by direct bonding with thermal difference.
abstract: An innovative method to fabricate large area (up to several squared millimeters) ultrathin (100 nm) monocrystalline silicon (Si) membranes is described. This process is based on the direct bonding of a silicon-on-insulator wafer with a preperforated silicon wafer. The stress generated by the thermal difference applied during the bonding process is exploited to produce buckling free silicon nanomembranes of large areas. The thermal differences required to achieve these membranes (≥1 mm(2)) are estimated by analytical calculations. An experimental study of the stress achievable by direct bonding through two specific surface preparations (hydrophobic or hydrophilic) is reported. Buckling free silicon nanomembranes secured on a 2 × 2 cm(2) frame with lateral dimensions up to 5 × 5 mm(2) are successfully fabricated using the optimized direct bonding process. The stress estimated by theoretical analysis is confirmed by Raman measurements, while the flatness of the nanomembranes is demonstrated by optical interferometry. The successful fabrications of high resolution (50 nm half pitch) tungsten gratings on the silicon nanomembranes and of focused ion beam milling nanostructures show the promising potential of the Si membranes for X-ray optics and for the emerging nanosensor market.
authors: †Université de Montréal, C.P. 6128, Montréal, Québec H3C 3J7, Canada.|‡CEA-LETI, 17 rue des Martyrs, Grenoble F-38054, France.
authors: Florian
authors: F
authors: Delachat
authors: ‡CEA-LETI, 17 rue des Martyrs, Grenoble F-38054, France.
authors: Christophe
authors: C
authors: Constancias
authors: ‡CEA-LETI, 17 rue des Martyrs, Grenoble F-38054, France.
authors: Frank
authors: F
authors: Fournel
authors: ‡CEA-LETI, 17 rue des Martyrs, Grenoble F-38054, France.
authors: Christophe
authors: C
authors: Morales
authors: §INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada.
authors: Boris
authors: B
authors: Le Drogoff
authors: §INRS-EMT, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada.
authors: Mohamed
authors: M
authors: Chaker
authors: †Université de Montréal, C.P. 6128, Montréal, Québec H3C 3J7, Canada.
authors: Joelle
authors: J
authors: Margot
mesh_terms: D017097:Electric Impedance; D057927:Hydrophobic and Hydrophilic Interactions; D055595:Mechanical Phenomena; D008567:Membranes, Artificial; D036103:Nanotechnology / Q000379:methods*; D055620:Optical Phenomena; D012825:Silicon / Q000737:chemistry*; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D012825:Silicon
keywords: direct bonding; nanofabrication; nanomembranes; nanotechnology; silicon