Annealing influences on phosphorus-ion-implanted vicinal Si(111) studied by reflective second-harmonic generation Kuang Yao Lo* and Yi Jen Huang Department of Applied Physics, National Chia Yi University, Chia Yi, Taiwan 600, Republic of China and Institute of Optoelectronics and Solid State Electronics, National Chia Yi University, Chia Yi, Taiwan 600, Republic of China Received 21 August 2006; published 3 July 2007 Annealing effects on the implanted vicinal Si111 were analyzed by reflective second-harmonic generation RSHG. The phenomena of impurity diffusion and precipitation were observed through the anisotropic con- tribution of the C 3V component in the RSHG rotational anisotropy experiments for a series of rapid thermal annealing RTA times. The surface reconstruction of the implanted vicinal Si111 was clearly observed due to the contribution of the C 1V symmetry which is raised from the step structure on the vicinal surface. The enhanced value of the C 1V component originates because P atoms participate in the surface reconstruction. The phase difference between the C 3V and C 1V components has large variations at lower RTA temperature because the reconstruction situation near the surface was not completed until the RTA time of 30 s and was influenced by the precipitation of P atoms. With the assistance of step structure on vicinal Si111, the reconstruction of the implanted Si111 reveals more physical information. DOI: 10.1103/PhysRevB.76.035302 PACS numbers: 78.20.-e, 42.65.-k, 61.72.Tt I. INTRODUCTION Optically reflected second-harmonic generation RSHG has proven to be a sensitive tool for obtaining information on the structural and electronic properties of metal and semicon- ductor surfaces. 1,2 The symmetrical group of the silicon sur- face differs from that of the silicon bulk, which is a cen- trosymmetrical media. 3 RSHG is forbidden within the electric-dipole approximation in centrosymmetrical media and only allowed on the surface and interfaces, where the bulk symmetry is broken. Therefore, the RSHG signal is very strongly influenced by the surface layer of these mate- rials, where the reduced symmetry enables the SHG process. Anisotropic contributions to RSHG intensity have been used for studies of the phenomenological theory and analysis from Si. 1,4 SHG rotational anisotropy RA-SHG is indeed highly sensitive to the microscopic structure and symmetrical prop- erties of the silicon interface structure. 5 To obtain the higher performance of very large scale in- tegration, it is necessary to deeply understand the mechanism of thin film growth. One of the chief issues the silicon device industry faces for miniaturization is the production of ul- trashallow doped layers, 6 since the formation of ultrashallow layers is important for the fabrication of nanosemiconductor devices. In particular, variations in the interface of the ul- trashallow layer during the thermal process will influence the device performance. 7 A high degree of reproducibility and control of dopant purity, dosage, and spatial distribution for the requirement in the ultrashallow doped layers can be achieved by low-energy ion implantation techniques and rapid thermal annealing RTA processes. RTA technology is an efficient technique to remove the ion implantation dam- age, activate dopant impurities, and produce a surface with crystal quality and sheet resistance equal to or greater than those obtained by conventional furnace annealing, but with the advantage of reduced impurity redistribution. 8 The results of the low-energy implanted silicon dealt with the RTA process have been successfully diagnosed by the RA-SHG method, 9 and theoretical analyses have been pre- sented to explain the actual phenomena in the RTA process. 10 This nondestructive method presented an illustration of the recrystallization degree in the shallow region that was not explained by traditional x-ray diffraction. Our previous re- sults showed that the RTA temperature is a key factor in recrystallizing the dosed range and diffusing the impurities within the expected range. After a suitable RTA process, the destroyed region of Si is recrystallized and implanted impu- rities enter the Si sites in the pattern of a well-ordered sub- lattice with polar bond behavior. Govorkov et al. 11 pointed out that the inhomogeneous strain-induced contribution to the second-order nonlinear susceptibility tensor would have the same nonvanishing components as the surface-dipole nonlinear susceptibility tensor. The residual electrical dipoles are formed along the surface symmetry during the RTA pro- cess, since implanted impurities enter the Si sites with enough activation energy. These are additional SHG sources from the implanted silicon. 10 Accordingly, Lo presented the potential of identifying the recrystallized condition during the RTA treatment by analyzing RSHG patterns. 10 However, the analysis results of the RSHG method are integrated over the surface region, which is limited by the penetration depth of the incident light. Thus, further formations on the top surface layers of implanted silicon would be hidden in the bulklike surface region layer. Recently, vicinal Si111, which is cut with a small offset angle towards the 112 ¯  direction, was used in the SHG stud- ies for the surface adsorption and buried interface since vici- nal Si111 surface reflects a onefold symmetry originating from the surface steps in the 112 ¯  direction. 11–13 Except for the contribution of threefold symmetry C 3V  from the 111 terraces, the appearance of steps on the vicinal Si111 sur- face gives a strong effect in observing RA-SHG and this result is consistent with the regular step structure having C 1V symmetry. RA-SHG studies of Si-O bondings on vicinal Si111 and H-atom termination have suggested that the one- fold contribution to the SHG signal comes primarily from Si atoms at or in the immediate vicinity of the surface steps. 12–14 These studies revealed that the step structures on a PHYSICAL REVIEW B 76, 035302 2007 1098-0121/2007/763/0353027 ©2007 The American Physical Society 035302-1