Pulsed ion beam surface analysis as a means of in situ real-time analysis of thin films during growth

Abstract

Low-energy (5–15 keV) pulsed ion beam surface analysis comprises several different surface spectroscopies which possess the ability to provide a remarkably wide range of information directly relevant to the growth of single and multicomponent semiconductor, metal and metal-oxide thin films and layered structures. Ion beam methods have not however, been widely used as anin situ monitor of thin film growth because existing commercial instrumentation causes excessive film damage, physically conflicts with the deposition equipment, and requires a chamber pressure ∼10−7–10−8 Torr, i.e., much lower than that associated with most deposition processes (≥10−4 Torr). We have developed time-of-flight ion scattering and recoil spectroscopy (TOF-SARS) as a nondestructive, insitu, real-time probe of thin film composition and structure which does not physically interfere with the deposition process. Several TOF-SARS implementations are exceptionally surface specific, yet in a properly designed system can yield high-resolution data at ambient pressures well in excess of 10 mTorr (4–6 orders of magnitude higher than conventional surface analytic methods). Because of the exceptional surface specificity of these methods, TOF-SARS is ideally suited as a means of studying ultrathin layers and atomically abrupt interfaces. TOF-SARS instrumentation designed specifically for use as an in situ, real-time monitor of growth processes for single and multicomponent thin films and layered structures is described here. Representative data are shown for in situ analysis of Pb and Zr layers at room temperature and high vacuum, as well as under conditions appropriate to the growth of Pb(ZrxTi1−x)O3 (PZT) perovskite films on MgO and RuO2 substrates.

Pulsed Laser Deposition (PLD)

“…Typically connected to the PLD chamber, RHEED systems are often equipped with a differentiated vacuum pumping unit for in situ observations during thin-film deposition under a gaseous ambience [10]. Several other in situ characterization techniques, including low-energy electron diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy, coaxial impact collision ion scattering spectroscopy, scanning probe microscope, and optical measurements, such as spectroscopic ellipsometry, have also been implemented in PLD systems [13][14][15][16][17]. Laser molecular beam epitaxy (MBE) (Figure 8.2) [11,12], which couples in situ RHEED observation with PLD for epitaxial growth, has proved to enable real-time growth control at an atomic-layer scale.…”

“…The crystal orientation of the films depended on the background and nitrogen partial pressures as well as growth temperature. TEM observations also revealed that in-plane AlN jj [11][12][13][14][15][16][17][18][19][20] sapphire and [11][12][13][14][15][16][17][18][19][20] AlN jj [11][12][13][14][15][16][17][18][19][20] 6H-SiC were epitaxial relationships between AlN and substrate materials, respectively. Figure 8.17 shows X-ray diffraction scans of AlN films grown on sapphire (0001) and 6H-SiC (0001).…”

“…15 Combinatorial libraries of transition-metal-doped ZnO grown by pulsed laser deposition (PLD)[73].…”

TOF-LEIS spectra of Ga/Si: Peak shape analysis

“…However, the shape of TOF-LEIS spectra is far more complicated than in 'electrostatic' LEIS since a large amount of multiply scattered particles is detected even for scattering angle h larger than 90°. The group of Krauss [1,2] was the first one to relate the shapes of peaks in TOF-LEIS spectra to the sample morphology when studying Pb, Zr and Ru growth on MgO and RuO 2 substrates. For layers with thicknesses below 1 ML they claim that the Gaussian shape of the LEIS peak indicates 2D growth of the film.…”

In Situ, Real-Time Studies of Film Growth Processes Using Ion Scattering and Direct Recoil Spectroscopy Techniques

“…)03 (PZT) [29,31], Sr13iATaz09(SET) [29,32], B~5Sro,sTi03 @ST) [29], and YBazCu3@.X(YBCO) [4].~n a DRS study of S13Tdeposition onto Pt, it was demonstrated that although Pt and Bi differ in mass by 14 amu, the resolution of DRS was not sufficient to separate these two species [32]. More recently, MSRI was used to study SBT deposition onto Pt and it was shown that the resolution of MSRI was sufilcient to separate Bi (in the deposited film) from Pt (the underlying substrate) [29].…”