Properties of SiO2 Grown in the Presence of HCl or Cl2

Abstract

Effects associated with the incorporation of chlorine during the thermal growth of SiO2 (500-1400A) on <lU0> Si are investigated as a function of additive species (HC1, C12), additive concentration, and oxidation temperature (900~176 Chlorine profiles are measured mainly by nuclear backscattering spectroscopy, and oxide thicknesses and refractive, index changes by ellipsometry. The highest chlorine concentrations in unannealed oxides always occur at the Si-SiO2 interface. Under otherwise similar conditions, the use of C12 results in higher, more evenly distributed chlorine levels (up to 1.2 • 1021 at era-3). The incorporated chlorine is gradually removed by annealing at temperatures in excess of II00~ as well as under conditions where further oxide growth takes place without the presence, of HCI or Cl2. Additional oxide formation in steam effectively removes all the incorporated chlorine. MOS capacitors made from oxides grown in HCI or Cl2 show fixed charge levels lower than 10 n cm -2 and mobile charge levels less than 1O l~ cm -2. When biased at high fields (>6 MV/cm) signihcant shifts in the flatband potential of Si were observed. Chlorine-grown oxides exhibit positive and negative shifts attributed to a mobile species; the smaller negative shifts in HCI oxides are attributed to interface states. Other electrical data of intentionally Na-contaminated HCI oxides suggest that only a constant fraction of the Na is trapped.

Thermal Oxidation Kinetics of Silicon in Pyrogenic H 2 O and 5% HCl / H 2 O Mixtures

“…Recent investigations concerning the oxidation kinetics of silicon in dry oxygen containing small additions of HC1 or C12 have been reported (1)(2)(3)(4). These and other studies have indicated that such chlorine additions provide certain benefits to the resulting device structures, such as alkali ion passivation, higher and more uniform oxide dielectric strength, and improved junction properties due to lower leakage (5)(6)(7)(8). Coincidentally increased oxidation rates have been observed with increasing chlorine concentration in the oxygen ambient (1)(2)(3)(4).…”

Chlorine Concentration Profiles in O 2 / HCl and H 2 O / HCl Thermal Silicon Oxides Using SIMS Measurements

“…These chlorine concentration profiles in oxides prepared in O2/HC1 ambients can be compared with results reported by other investigators. Most of the previously reported profiles have been carried out using Rutherford backscattering of alpha particles, such as Meek (7), van der Meulen et al (9), and Butler et al (10). Kriegler et al (8) have used the SIMS technique to determine C1 profiles at 1150~ as a function of percent HC1 in O2 (2.5-4.0%), although their chlorine concentrations in the oxide are reported only in arbitrary units.…”

“…If the exact oxide preparation procedures are considered, all these results are in reasonable agreement with those reported here. For instance, van der Meulen et al (9) report chlorine concentrations for 0.1 ~m oxides prepared at temperatures ranging from 900 ~ to 1150~ which are similar to the present values, in that peak concentrations increase from <3 • 1019 "to 8.4 • 1020/cm 3 for 9 v/o HCI in O~. All these profiles indicate a pileup of the chlorine in the oxide near the Si-SiO2 interface, and of peak concentration half-widths of less than 200A.…”

Computer Aided Design of Integrated Circuit Fabrication Processes for VLSI Devices

“…Further models of dopant distribution should account for this segregation, and include its dependence on processing parameters such as oxidation time, temperature, and bulk doping level.Similarly large amounts of chlorine, an additive in the oxidation ambient, are found at the Si-SiO 2 interface (seeFig. 22).Past studies of chlorine distributions in SiO 2 grown in 0 2 /HCl mixtures[26][27][28][29] showed high levels of chlorine residing in the oxide near the interface with much lower levels of chlorine in the bulk oxide. These results have been compiled largely from SIMS and RBS data, and show the FWHM of the a chlorine pile-up to be typically 150-200 A.…”