Adsorption and desorption kinetics for SiCl4 on Si(111)7×7

Abstract

The adsorption and desorption kinetics for SiCl 4 on Si ( 111 ) 7 X 7 were studied using laserinduced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. TPD experiments monitored SiCl 2 as the desorption product at approximately 950 K using a heating rate of {3 = 9 Kls. SiCl 2 was also observed as the desorption product in the LITO yield at all surface coverages. LITO measurements determined the initial reactive sticking coefficient (So) ofSiCl 4 on Si( 111)7 X 7 versus surface temperatu"e. The sticking coefficient was observed to decrease with surface temperature from So z 0.18 at 160 K to SozO.03 at 600 K. TPO experiments revealed that the chlorine surface coverage saturated after large SiCl 4 exposures and the saturation coverage was independent of surface temperature. Isothermal LITO studies enabled the surface chlorine coverage to be monitored as a function of time during SiCl 2 desorption. These studies revealed second-order desorption kinetics for SiCl 2 with a desorption activation barrier of Ed = 67 ± 5 kcallmol and preexponential OfVd = 3.2X lO o ±o.1 cm 2 /s. Experiments with preadsorbed hydrogen demonstrated that the initial sticking coefficient of SiCl 4 was reduced as a function of increasing hydrogen coverage. This behavior indicated that the adsorption of SiCl 4 on Si ( 111 ) 7 X 7 requires free surface dangling bonds. LITO techniques were also used to study the surface diffusion of the chlorine on Si( 111 )7X 7 after SiCl 4 adsorption. No evidence of significant surface chlorine mobility (D<2 X 10 ~ II cm 2 Is) was found for surface temperatures as high as 825 K..

Selective epitaxial growth of boron- and phosphorus-doped Si and SiGe for raised sources and drains

“…Meanwhile, the 97 kcal mol À1 activation energy found for F(HCl)/F(H 2 )=0.0021, quite similar to the 93 kcal mol À1 one found by Bodnar et al [17] (also in RP-CVD), is characteristic of the desorption of chlorine atoms from the silicon surface. Indeed, the silicon-chlorine bond strength is of 90 kcal mol À1 [24]. Finally, the 79 kcal mol À1 intermediary activation energy found for F(HCl)/ F(H 2 )=0.0011 would indicate that we are faced with a desorption of both H and Cl atoms from the surface in this case.…”

Low temperature growth kinetics of high Ge content SiGe in reduced pressure-chemical vapor deposition

“…Meanwhile, the LT activation energies monotonously decrease from 57 down to 41 kcal mol À1 as the 600 1C Ge concentration increases from 18.2% up to 44.3%. Those LT values can quite instructively be compared to the Si-H bond strength (47 kcal mol À1 [33]), the Ge-H bond strength (37 kcal mol À1 [34,35]), the Si-Cl bond strength (90 kcal mol À1 [36]) and the Ge-Cl bond strength (51 kcal mol À1 [37]). For 18% of Ge at 600 1C, it is mainly the desorption of H from Si surface atoms and of Cl from Ge surface atoms that frees sites and governs the SiGe growth rate increase with the growth temperature (E a (Si-H) ¼ 47 kcal mol À1 oE a (Ge-Cl) ¼ 51 kcal mol À1 oE a (18%) ¼ 57 kcal mol À1 5E a (Si-Cl) ¼ 90 kcal mol À1 ).…”

Epitaxial growth of Si and SiGe at temperatures lower than 500°C with disilane and germane

“…200°C below those typically used in more conventional processes). To that end, we have adopted a hydrogenated chemistry based on disilane (Si 2 H 6 ), which decomposes at temperatures lower than silane and especially dichlorosilane (the Si-Si bond energy is indeed lower than the Si-H and Si-Cl ones; 1.45 eV versus 2.0 eV and 3.9 eV respectively [7,8]), with, for SiGe, the addition of germane (GeH 4 ). Disilane is however intrinsically non-selective versus dielectrics commonly used as spacer (Si 3 N 4 ) or isolation (SiO 2 ).…”