Time-of-flight ion scattering and recoil spectroscopy (TOF-ISARS) enables the characterization of the composition and structure of surfaces with 1–2 monolayer specificity. It will be shown that surface analysis is possible at ambient pressures greater than 3 mTorr using TOF-ISARS techniques; allowing for real-time, in situ studies of film growth processes. TOF-ISARS comprises three analytical techniques: ion scattering spectroscopy (ISS), which detects the backscattered primary ion beam; direct recoil spectroscopy (DRS), which detects the surface species recoiled into the forward scattering direction; and mass spectroscopy of recoiled ions (MSRI), which is a variant of DRS capable of isotopic resolution for all surface species - including H and He. The advantages and limitations of each of these techniques will be discussed.

The use of the three TOF-ISARS methods for real-time, in situ film growth studies at high ambient pressures will be illustrated. It will be shown that MSRI analysis is possible during sputter deposition. It will be also be demonstrated that the analyzer used for MSRI can also be used for time of flight secondary ion mass spectroscopy (TOF-SIMS) under high vacuum conditions. The use of a single analyzer to perform the complimentary surface analytical techniques of MSRI and SIMS is unique. The dual functionality of the MSRI analyzer provides surface information not obtained when either MSRI or SIMS is used independently.

In-situ real time characterization of chemically and structurally complex thin films is becoming important as complex materials are finding more applications in electronic devices. To this end, a unique thin film growth and deposition system was constructed combining a multi-target sputter deposition system with spectroscopic ellipsometry and time-of-flight ion scattering and recoil spectroscopy. This system is demonstrated with studies on YBa2Cu3O7−δand BaSrTiO3 films.

A dual beam experiment has been set up combining real-time depth profiling and low energy ion implantation in order to study the kinetics of ion nitriding. The choice of low energy ion implantation allows precise and independent control of the important ion nitriding parameters ion energy, ion current density, temperature and residual gas composition. Real-time depth profiling is achieved by Elastic Recoil Detection (ERD) using an angle resolving ionization chamber telescope detector. A large solid angle (5.4 msr) allows a fast data acquisition and hence real-time depth profiling with a time resolution of about 30 s combined with a depth resolution of about 10 nm. The capabilities of the setup and its limitations will be discussed. Measurements revealing the role of mechanisms relevant for the nitrogen transport during ion nitriding of stainless steel i.e. diffusion, sputtering, adsorption of oxygen from the residual gas will be presented.

When alpha-particles pass through thin films they lose an amount of energy proportional to the film thickness with the proportionality constant depending on the film composition. Thus, by measuring this energy loss one can determine the film thickness. We have applied this technique to measurements of the etch rate of various III-V semiconductor layers grown by molecular beam epitaxy. Prior to film growth, GaAs substrates were recoil-implanted with the alpha-emitting 224Ra isotope by exposure to a 5µCi source of 228Th. The implanted isotope decays with a half-life of 3.7 days, which allows measurements to be done for up to about two weeks after implantation. Following growth, the samples were etched in an electron cyclotron resonance etcher using a Cl2/BCl3/Ar gas mixture. As the film is etched the energy of the alpha-particles emitted from the surface increases. By introducing a high resolution Si detector into the etcher we are able to measure changes in the alpha-emission spectrum without removing the sample from the etcher. Thickness changes with an uncertainty of 5–10nm are obtained in 5 minute measurements at the end of each etch step. Some of the samples were also measured by SEM, yielding results in good agreement with values obtained by the alpha-particle measurements. As an example of an application of the technique we will describe measurements of the temperature dependence of the etch rate of GaAs in the 15–150 °C temperature range using optical bandgap thermometry to determine the substrate temperature. In a second example, we explore the application of the technique to etch rate of short pitch (250–500nm) grating. In this case the shape of the alpha-spectrum is sensitive to the profile of the etched trenches.

The layered structure of oxides, like the high-T, cuprates, has been topic of research for some years now. The possibility to control thin film deposition on an atomic level has made fabrication of artificial structures and junctions accessible by depositing atomic layers or molecular blocks sequentially. Perfectly smooth substrate surfaces are hereby a prerequisite.

Using Pulsed Laser Deposition (PLD), different perovskite oxide materials have been deposited on SrTiO3 substrates. With in situ high pressure Reflection High Energy Electron Diffraction we studied growth at different temperatures and oxygen pressures. Ex situ XRD and AFM have been used to study the morphology after deposition.

Here we applied a new approach in obtaining layer-by-layer growth implied by the way of depositing the material, almost regardless of the deposition conditions. By alternating intervals of high supersaturation depositing one unit cell layer with intervals of lower supersaturation, one is able to force a layer-by-layer growth mode, which is in principle only feasible with PLD. We applied this technique to fabricate the layered infinite structure (Ba,Sr,Ca)CuO2 with artificial layered modulation, which have been characterized by XRD and AFM.

The development of multichannel ellipsometers with photodiode array-based detection systems has enabled real time spectroscopic ellipsometry (SE), a technique now being used widely to study surface modification and thin film growth. Multichannel ellipsometers based on the rotating-element design acquire spectroscopic data in parallel and thus offer advantages over other designs. The simplest rotating-element multichannel ellipsometers are constructed using a rotating polarizer or analyzer for polarization state modulation or detection. These configurations have a number of drawbacks, in particular, their insensitivity when measuring samples that reflect linearly polarized light and their susceptibility to errors when measuring samples having unrecognized non-idealities (e.g., macroscopic inhomogeneities) that generate a mixture of polarization states in the reflected beam. In this review, we describe recent advances in multichannel ellipsometry including (i) enhancement of the spectral range of the rotating-polarizer multichannel ellipsometer to 1.5–6.5 eV, (ii) adaptation of the rotating-compensator configuration to multichannel ellipsometry for studies of weakly absorbing and macroscopically inhomogeneous materials, and (iii) development of a dual rotating-compensator multichannel ellipsometer design for real time studies of optically anisotropic materials. As a recent example of the application of rotating-compensator multichannel ellipsometry, we describe analyses of (i) a macroscopically-rough (textured) tin-oxide (Sno2) film on a glass substrate and (ii) the fabrication of the p-layer component of an amorphous silicon-based p-i-n solar cell on the textured SnO2 film surface at a temperature of 200°C.

The purpose of this paper is to review modeling and real-time monitoring by robust methods of reflectance spectroscopy of organometallic chemical vapor deposition processes in extreme regimes of pressure. The merits of p-polarized reflectance spectroscopy under the conditions of chemical beam epitaxy (CBE) and of internal transmission spectroscopy and principal angle spectroscopy at high pressure are assessed. In order to extend OMCVD to materials that exhibit large thermal decomposition pressure at their optimum growth temperature we have designed and built a differentially-pressure-controlled (DCP) OMCVD reactor for use at pressures ≤ 6 atm. We also describe a compact hard-shell (CHS) reactor for extending the pressure range to 100 atm. At such very high pressure the decomposition of source vapors occurs in the vapor phase, and is coupled to flow dynamics and transport. Rate constants for homogeneous gas phase reactions can be predicted based on a combination of first principles and semi-empirical calculations. The pressure dependence of unimolecular rate constants is described by RRKM theory, but requires variational and anharmonicity corrections not included in presently available calculations with the exception of ammonia decomposition. Commercial codes that include chemical reactions and transport exist, but do not adequately cover at present the kinetics of heteroepitaxial crystal growth.

In this article, we report the results of a successful effort to extend rotating-polarizer multichannel ellipsometry into the ultraviolet (uv) spectral region above 5 eV. Key modifications over previous system designs include (i) incorporation of a see-through deuterium (D2) lamp that allows a tandem Xe/D2 source configuration for a usable spectral output from 1.5 to 6.5 eV, (ii) MgF 2 Rochon polarizers for high transmission in the uv without the need for optical activity corrections, and (iii) a spectrograph with a concave grating blazed at 2500 A and internally mounted order-sorting filters. With these modifications, we can collect 132-point ellipsometric spectra over the range from 1.5 to 6.5 eV with a minimum acquisition time of 24.5 ms (one optical cycle). For averages over two and eighty optical cycles (requiring 49 ms and 1.96 s, respectively), the standard deviations in (Ψ, Δ) are (0.04°, 0.08°) and (0.008°, 0.015°), respectively, measured on a thermally-oxidized silicon wafer at a photon energy of 6 eV. In this first report, we briefly describe problems faced in the development of the new instrument. As an example of the applications of the instrument, we present the results of a real time study of the growth of a hexagonal boron nitride (BN) thin film by rf magnetron sputtering on a Si wafer substrate at a temperature of 250°C. The instrument is expected to be useful in BN film growth studies since the additional data in the uv assist in discriminating the wide band gap (Eg) hexagonal (4 < Eg < 5.8 eV) and cubic (Eg > 6 eV) phases of this material.

The optical absorption peak at 4. leV associated with oxygen deficiency in YBa2Cu3O7−x thin films was monitored by spectroscopic ellipsometry (SE) in real time during the growth process. Two regimes dominated by oxygen out- and in-diffusion have been observed during deposition by ion beam sputtering at 700°C.The effect of oxygen partial pressure during the post-deposition cooling process on the oxidation of deposited films has also been investigated. The thermodynamic stability of the grown films was examined by real time SE during post annealing process. In-situ SE measurements have been performed to obtain the dielectric function of oxygen deficient YBa2Cu3O6 films in the temperature range from 27°C to 700°C. It has been demonstrated that real time SE is a sensitive and useful technique for in-situ diagnostics of the dynamics of YBa2Cu3O7−x thin film processes.

Real-time spectroscopic ellipsometry (RTSE) method was applied to study thermal cleaning process of silicon surfaces for epitaxial growth by ultra-high vacuum chemical vapor deposition (UHV-CVD). For the first time, in-situ observation of oxide decomposition process under Si2H6 ambience was carried out. The substrates with thin oxide formed by wet chemical treatment were heated up by infrared heater under UHV or under Si2H6 ambience in an UHV-CVD chamber and the oxide decomposition processes were observed by RTSE. Ellipsometric parameters Psi and Delta increase with the progress of oxide decomposition process and become constant with the completion of the decomposition. It was found that the oxide decomposition process consists of two phases and rate-determing processes are different in each phase. It was also found that Si2H6 lowers the activation energies of oxide decomposition process in each phase.

Electron cyclotron resonance (ECR) CF4/ 02 plasma etching of silicon nitride (SixNy) deposited by plasma enhanced chemical vapor deposition (PECVD) has been examined in-situ by means of spectroscopic ellipsometry (SE) and optical emission (OE). The observed real-time etchrate and the relative intensity of emission of atomic fluorine at 703.7 nm are measured simultaneously and both are found to change with time during the etch in a reproducible manner. The evolution of the real-time etch rate and the fluorine emission intensity depends on the machine input settings and the extent to which the chamber has been exposed to CF4/ 02 plasma prior to sample introduction. In general the initial 10 to 40 seconds of etching reveal a rapid increase in the etch rate, the remainder of the etch exhibiting an etch rate which typically increases gradually until the etch is stopped. This variation in etch behavior with time during the etch process complicates the task of precisely and reliably etching ultrathin (< 50 nm) films, necessitating real-time control based upon in-situ sensors, the end objective of this work. The dependence of the evolution of the SixNy etch rate on microwave power, chamber pressure, and gas in-flow rate is presented and the implications of these dependencies on the implementation of real-time feedback control are discussed.

The interaction of ethene with silicon (111) surfaces at different process temperatures (580°C, 680°C, 780°C) was monitored in situ by spectroscopic ellipsometry. It is shown that spectroscopic ellipsometry is a reliable method to monitor the carbonization process of silicon surfaces. Different SiC formation stages (incubation time, (√3×√3)R30° reconstruction, 2D growth and 3D growth) were observed using complimentary analyzing techniques. The change of the ellipsometric signal as a function of process time is related to these stages and was interpreted using an optical model which consists of four layers (surface roughness, SiC layer, interface layer, Si substrate).

Initial oxidation process of silicon in UV/ozone ambient has been monitored using a multi-wavelength, in-situ spectroscopic ellipsometry. Ozone gas was chemically formed by photochemical reaction of oxygen under ulUmviolet illuimination. The oxide growth was monitored for hydrogenated silicon surfaces as functions of oxygen gas flow rate, gas pressure and wafer temperature. Initial oxidation rates were very high at almost all the temperatures. The oxidation rate was 0.2 nm/min about ten times higher than that for thermal oxidation without UV light at low temperatures. The accelerated oxidation was probably due to an electric field effect on the oxidation of back-bond silicon by active oxygen atoms included in the ozone gas.

A series of AlGaAs/GaAs depositions were monitored in-situ by spectroscopic ellipsometry and desorption mass spectroscopy, under various substrate temperatures (890 K - 990 K) where non-unity sticking conditions occur. An upper bound on the temperature where AlGaAs/GaAs heterostructures may be grown was determined. Ex-situ cross-sectional transmission electron microscopy verified that the AlGaAs/GaAs layer thicknesses grown by molecular beam epitaxy were accurately determined by spectroscopic ellipsometry at these elevated temperatures. The substrate temperature dependence on Ga desorption rates was consistent with Monte Carlo simulation where desorption from both physisorbed and chemisorbed states were included.

Titanium Nitride (TiNx) thin films were deposited on Si(100) by reactive magnetron sputtering. The varied deposition conditions were the substrate temperature (Td) (27 - 650 °C) and the negative bias voltage (Vb) applied to the substrate (0 - 200 V) in order to produce TiNx films with various compositions and structural characteristics. The deposition process was monitored in-situ by Spectroscopic Ellipsometry in the spectral range 1.5–5.5 eV. Determination of the film composition was made through the measured screened plasma energy ωps while the electrical resistivity of TiNx was studied in terms of the unscreened plasma energy ωpu. ωpu was calculated by an optical model including a Drude term and Lorentz oscillator terms and their dependence on Td and Vb was studied. The ωpu was found to increase with Vb until a saturation value was obtained. The saturation value of ωpu depends on the Td.ωpu describes better the TiNx films, since it is directly correlated with their metallic character in terms of the electrical resistivity.

NiSi, with its low resistivity and wide processing window (350 - 750°C), is an attractive candidate for use as a gate contact material. In order to follow the interface reaction that leads to the formation of NiSi in real time, ellipsometry and atomic force microscopy (AFM) were used to study changes on the surface resulting from the reaction between Ni and Si for various times and temperatures, and Rutherford Backscattering spectrometry (RBS) to determine compositional changes in the forming silicides. We report that ellipsometry can be used to monitor the various Ni-Si phases forming in real time, and we have observed agglomeration of the silicide, which has been reported to occur at 1000°C, at temperatures, as low as 550°C for long time anneals.

Manufacturable, sputtered, device-quality, CdS thin films are reported for high efficiency solar cell applications. The sputtering plasma is monitored during deposition using optical emission spectroscopy. Optical emission spectroscopy (OES) is commonly used as an end point detector in plasma etching processes, where the disappearance of the etch product wavelength signature provides an unambiguous indication of completion. OES is only now beginning to be examined for controlling deposition processes, primarily because the dependence between OES signal and film properties can frequently be a quite complex function of the electron and gas densities, the emitting species concentration, the electron impact excitation cross section, the electron energy distribution function, and the probability of inelastic collisions between plasma species. OES monitoring during CdS sputtering allows accurate determination of deposition rate. Both Cd and S emission peaks can be identified, allowing tracking of the results of preferential sputtering. The OES output has been tied directly into the chamber controls, resulting in automatic closed-loop control of deposition rate. The resulting CdS films are device-quality and well-suited to large-scale manufacturing. A photovoltaic efficiency of 12.1 % was obtained from sputtered CdS on CIGS absorber, compared to 12.9% for the traditional, but less manufacturable, chemical bath deposited CdS on the same batch of CIGS. The sputtering technique has many advantages over other deposition techniques, such as easy scaleablity to large areas, simple process control, compatibility with in-line manufacturing of layered devices and low cost. RF, or lower-cost pulsed DC, sputtering power supplies can be used with comparable deposition rates. The structure, optical, and electrical properties of the sputtered CdS thin films have been characterized.

The pseudo-binary NdBa2Cu3O-Ba3Cu10O13phase diagrams and the crystallization of NdBa2Cu3Ox have been in-situ observed using high-temperature optical microscopy in air and under three different reduced oxygen atmospheres namely, 1%, 0.1% and 0.0097% oxygen in argon. The liquidus line was found to become narrower both in composition and temperature with reducing oxygen content in the atmosphere. These results suggested that while in air NdBa2Cu3Ox can be crystallized from both high-temperature solution and peritectic melt; under reduced oxygen atmospheres the crystallization of NdBa2Cu3Ox is only possible from a peritectic melt. The in-situ observations of crystallization of NdBa2Cu3Ox from high-temperature solutions revealed that the growth mechanism changes from 3D via 2D layer-by-layer to continuos dendritic growth with increasing cooling rate. On the other hand, the NdBa2Cu3Ox crystallization from a peritectic melt involved two distinct steps (i) conversion of Nd4Ba2Cu2Ox into NdBa2Cu3Ox and (ii) nucleation and growth of NdBa2Cu3Ox The growth morphology in this case was independent of the cooling rate. This result and the direct observation of the dissolution of Nd4Ba2Cu2Ox into the liquid suggested that the solute diffusion is the rate-limiting factor.

Microelectromechanical systems (MEMS) can be regarded as advanced film-based devices. Although the dimensions of a MEMS are in the range of micrometers to millimeters, due to low mass and contact area the interaction of the micro parts is confined to the upper monolayers of the material. To achieve a good performance as well as a long lifetime it is necessary to control the adsorbate coverage of the micro parts. Besides the tools of surface science (XPS, HREELS, AES, … ) a precise characterization of the adsorbate film with respect to mechanical properties (adhesion, friction, mechanically induced desorption) is required. Those needs are met with a new generation of test equipment comprising of sensors and actuators, thus, rendering the instruments also a MEMS. Force sensing devices made of glass are introduced to measure ultra low deflections caused by the interaction of the micro parts via the adsorbate layer. The devices combine precisely etched glass structures (bending beams,) with fiber optics.

The formation of Pt silicide (PtSi) by the thermally activated reaction of a 23 nm Pt layer on Si was monitored in situ by ellipsometry. Characteristic changes in the ellipsometric angles as a function of temperature signal the approach of two reaction fronts to the surface: one belonging to the Pt/Pt2Si and the other to the Pt2Si/PtSi interface. An analysis of the evolution of the ellipsometric angles as a function of temperature for different heating rates allows the accurate determination of the average activation energies of the two reactions. From a modeling of the optical data in terms of a specific reaction model further kinetic parameters such as the reaction rate constants and the actual distribution of activation energies have been deduced.