UNIBOND Wafers: Smart Cut Technology

The production of UNIBOND wafers uses both ion implantation and wafer bonding technologies. Starting with two wafers, the silicon surface of one wafer is first oxidized to form what will become the buried oxide layer of the SOI structure. An ion implantation step, using hydrogen ions, is then executed through the oxide layer by a standard high-current ion implanter to form the Smart Cut layer, which is then annealed and polished. The surface silicon of the finished wafer has very low defect levels approaching those in bulk silicon; the oxide layer is pin-hole free. The remaining wafer, which is still within SEMI standards for thickness specifications, is reclaimed and polished. It is then used as the support wafer for the production of the next UNIBOND wafer.

The two limitations of conventional bonding are solved by this technology. The uniformity for thin SOI layers is obtained as ion implantation is used; and, since the second wafer is saved, the traditional wafer bonding cost barrier caused by the consumption of two starting wafers to produce one SOI wafer, is eliminated.

SOITEC has successfully developed proprietary process technologies to create a thin monocrystalline film of silicon on quartz or glass wafers. The process produces wafers with electrical characteristics superior to polysilicon films. Wafers with a monocrystalline film of silicon-on-quartz or glass are used for manufacturing liquid crystal displays (LCDs) of small dimension and high resolution, a process which has traditionally used polysilicon. Drivers can be processed on the same wafers, making the connections of the thin-film transistor (TFT) matrix easier. Applications include thin-film transistor liquid crystal displays (TFT-LCDs), charge coupled device (CCD) detectors, virtual reality devices and high definition television (HDTV) projection systems.

SOITEC USA Inc., 2 Centennial Drive, Peabody, MA 01960. Tel: 978-5312222; Fax: 978-531-2758.