History of SIMOX Material
- PDF / 6,378,184 Bytes
- 5 Pages / 576 x 777.6 pts Page_size
- 59 Downloads / 176 Views
Watanabe and Tooi first reported on the formation of silicon oxide by oxygenion implantation into silicon in 1966.' Further investigations of such oxygenimplanted oxide layers have been carried out by several workers, with the result that the oxide has equivalent isolation characteristics to those for thermally grown silicon oxide.2"5 Practical applications of the oxygen-implanted oxide to semiconductor devices have been reported by only a few workers, with a suggestion of their usefulness.2 Unfortunately Watanabe and Tooi's work has not been followed by additional silicon-on-insulator (SOI) studies. In 1978 Izumi, Doken, and Ariyoshi succeeded in fabricating a complementarymetal-oxide-semiconductor (CMOS) ring oscillator using a buried SiO2 layer formed by oxygen-ion (16O+) implantation into silicon.6 They named the new SOI technology "SIMOX," which is short for separation by implanted oxygen.6 Since then Izumi and his research group have continued their study of SIMOX technology. Separation by implanted oxygen was originally developed to solve the aluminum autodoping and crystalline defect problems in silicon on sapphire (SOS). There are three key points in SIMOX technology. First the buried SiO2 layer must be formed with adequate dielectric isolation characteristics. Second the top silicon layer on the SIMOX wafer must maintain sufficient monocrystallinity. Third the thermally oxidized SiO2 layer, which covers the mesatype island of a metaloxide semiconductor field-effect transistor (MOSFET), and the buried SiO2 layer must be sufficiently continuous at the bottom edge of the mesatype island. Separation -by- implanted - oxygen technology met these three key points. However it still faced other serious difficulties. The synthesis of SiO2 by oxygen-ion implantation into silicon requires a huge oxygen dose. Simple calculations indicate that the synthesis of stoichiometric SiO2 requires a high density of oxygen atoms 20
22
3
of 4.48 X 10 cm . With an oxygen-ion acceleration energy of 150 keV, the necessary oxygen dose is of the order of 1018 c m 2 . In other words, the oxygen dose is 100-1,000 times higher than the impurity-ion dose employed in conventional silicon-fabrication processes. This was beyond the capabilities of a conventional ion implanter in the 1970s. A conventional ion implanter used in the late 1970s with an oxygen-ion beam current of about 100 μA required approximately 65 h to form the buried SiO2 layer by oxygen-ion implantation into a 100-mm silicon wafer.7 Only after the joint development of a 100-mA-class oxygen-ion implanter (NV-200) by Eaton Corporation and NTT in 1986 was SIMOX considered to be one of the most practical and attractive SOI technologies.8 In addition the development of the low-dose SIMOX wafer by Nakashima and Izumi in 1990 and of the internal thermal oxidation (ITOX) process by Nakashima et al. in 1994 put SIMOX wafer technology into a dominant position among SOI materials, accelerating the practical use of SIMOX 910 wafers.
0+
Initial Stage
16
+
For SOI the SiO2 layer
Data Loading...
