Heterogeneous recombination of atomic bromine and fluorine

Abstract

Recombination coefficients (γ) of Br and F atoms have been measured for crystalline Si, quartz, photoresist, anodized aluminum, poly-Si, WSix, tungsten and stainless steel surfaces for a range of temperatures. The γBr and γF values are compared to our previously reported measurements of γCl [G. P. Kota, J. W. Coburn, and D. B. Graves, J. Vac. Sci. Technol. A 16, 270 (1998)]. In general, the Br-, Cl- and F-atom recombination coefficients decrease as the surface temperature increases. The γBr values are similar to the γCl values for the various surfaces. At room temperature, γBr is highest (>0.4) for stainless steel and tungsten, moderate (0.1–0.4) for poly-Si, WSix and anodized Al, and lowest (<0.05) for c-Si, quartz and photoresist. However, γF, at room temperature, is no greater than 0.05 for all the surfaces. γF increases slightly as the temperature is decreased to 80 K but is still below 0.1 for all the surfaces. The recombination coefficient data as a function of temperature for all surfaces are fit to a phenomenological model developed previously for γCl (see the above reference). The model assumes that the incident halogen atoms physisorb on a surface that is saturated with chemisorbed halogen atoms. The physisorbed atoms are assumed to diffuse on the surface and either desorb before recombining or recombine and then desorb. The recombination rate is assumed to be first order in physisorbed atom coverage.

Etching mechanisms of (Ba,Sr)TiO3 thin films in CF4/Ar inductively coupled plasma

“…where c F is the probability of heterogeneous recombination for fluorine atoms (c F % 0:05 from [22]), D F the effective diffusion coefficient and k is the effective diffusion length. Effective diffusion coefficients are represented by the combination of free diffusion coefficient and inter-diffusion coefficient, calculated using the Chapman-Enscog equation [10,21] while the effective diffusion length is determined by the given reactor axial and radial sizes [16].…”

Etching Characteristics of In2O3 and SnO2 Thin Films in an Inductively Coupled HBr/Ar Plasma: Effects of Gas Mixing Ratio and Bias Power

“…The rate coefficients of heterogeneous recombination for H and Br atoms were obtained using k S ¼ ½ðà 2 =DÞ þ ð2r=v T Þ, 13) where D is the effective diffusion coefficient, 14,15) is the recombination probability, à À2 ¼ ð2:405=rÞ 2 þ ð=lÞ 2 is the effective diffusion length, 15) and v T ¼ ð8k B T=mÞ 1=2 . Since the recombination probabilities of both Br and H atoms in the HBr plasma are not known, we used the values recommended for pure Br 2 and H 2 gases ( Br % 0:2 16) and H % 0:05 17) ). When writing the kinetic equations for positive ions, we used k S ¼ v=d c , where d c ¼ 0:5rl=ðrh l þ lh r Þ.…”

Influence of Oxygen Addition and Wafer Bias Voltage on Bromine Atom Surface Reaction in a HBr/Ar Inductively Coupled Plasma

“…17,59) This suggests that the etching rates of Al 2 O 3 and SiO 2 are similar in HBr/Ar plasma and that the Br surface loss originating from the etching process is similar for these two materials. Kota et al have reported that the recombination coefficient of Br radicals on Al 2 O 3 is larger than that on SiO 2 , 60) and the difference in the Br radical density between Si and Al 2 O 3 wafers in the present study might be understood by the difference in the Br radical surface recombination probability. Figure 8 shows the dependence of the Br radical density on the bias voltage applied to the blanket Si wafer at O 2 flow rates of 0, 6, and 24 sccm.…”