Thin film deposition procedure

Similar to the procedure for Si micromachining, micromachining for glass also includes thin-film deposition, photolithography, etching, and bonding (see Figure 2.3) [102],... 

Solution-phase synthetic methods, as they were described for synthetic organic libraries, can also be applied to materials science and are devoid of the diffusion problems encountered in thin-film deposition. The reagent solutions are mixed and incubated following an appropriate procedure, and the final products are usually isolated by precipitation or crystallization. Automated liquid dispensing units with extreme precision and high rehabiUty can be used in synthetic protocols. No major differences are presented in respect to solution-phase organic library synthesis (see Section 8.2.4). Several examples are briefly illustrated below to provide a quick overview of the currently reported synthetic methods in solution for materials libraries. 

A study of dielectric characteristics of alumina thin films deposited on silicon substrates from Al(acac)3 dissolved in dmf by spray pyrolysis between 450 and 650 °C was recently reported by Falcony and coworkers. The addition of water vapor significantly improved the dielectric characteristics and smoothness of the deposits. In comparison to the CVD technique described above (see Section m.A.l) this procedure lead to considerable carbon impurities in the films. The overall resisfivify of fhe alumina layers decreases, when both the concentration of the solution and the deposition temperature increase, which is explainable with the increase of carbon residues in the films. 

In the grafting from approach, a surface, that was previously activated e.g. by plasma treatment, is exposed to a monomer solution (Huang et al. 2003). A more simple, one-step procedure is to inadiate a polymeric surface like TCP, which is covered with the monomer solution, by an electron beam (Yamada et al. 1990). Alternatively, ultraviolet light and a photosensitiser can be utilised to initiate polymerisation and cross-linking (Curti et al. 2005). A completely different route to prepare thin SRP coatings with good adhesion to solid substrates is plasma polymerisation (Biederman and Osada 1992). In this case, NIPAAm is used as a precursor in a plasmachemical thin film deposition process (Cheng et al. 2005 Pan et al. 2001). 

The basic cleaning procedure is quite simple. The thick lacquer coating is applied to the precleaned surface with a brush or by dipping. The parts are then allowed to dry completely. In a subsequent operation, performed in a laminar flow box to prevent recontamination, the lacquer film is stripped off. Stripping is easier if a wire loop is embedded in the coating. Attempts to strip off the film in vacuum prior to thin-film deposition were only partly successful because of the difficulty in detecting surface residues inside the evacuated system. 

The electrochemical performances of self-organized Ti02 nanotube obtained from Ti foils (references [26, 28] provide examples of the fabrication process) and Ti thin films deposited onto Si substrates have been examined according to a procedure described in reference [34]. Layers of nanotubular titania (ntTi02) are directly produced by the anodization of Ti in fluoride-containing medium and without the use of any template. We... 

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

The chemical and electronic properties of elements at the interfaces between very thin films and bulk substrates are important in several technological areas, particularly microelectronics, sensors, catalysis, metal protection, and solar cells. To study conditions at an interface, depth profiling by ion bombardment is inadvisable, because both composition and chemical state can be altered by interaction with energetic positive ions. The normal procedure is, therefore, to start with a clean or other well-characterized substrate and deposit the thin film on to it slowly at a chosen temperature while XPS is used to monitor the composition and chemical state by recording selected characteristic spectra. The procedure continues until no further spectral changes occur, as a function of film thickness, of time elapsed since deposition, or of changes in substrate temperature. 

A procedure involving (a) the deposition of nearly stoichiometric films of copper and indium on suitable substrates using vacuum evaporation or electrodeposition and (b) the heat treatment of Cu-In films in a hydrogen-selenium atmosphere at temperatures above 630 °C was reported to yield large grain (several mm in size), stoichiometric thin films of chalcopyrite CIS with a preferred 112 orientation [167]. 

The tltanla-based thin film catalyst models were constructed by first oxidizing the titanium surface In 5 x 10 torr of O2 for approximately 30 minutes at 775 K. This produced an AES llneshape consistent with fully oxidized TIO2. The metal was then vapor deposited onto the oxide support with the latter held at 130 K. The thickness of the metal overlayer and Its cleanliness were verified by AES. After various annealing and adsorption procedures, these thin films were further characterized using SSIMS, AES and TDS. For comparison, some work was done with Pt on Al20s. In this case a Mo foil covered with AI2O3 replaced the Tl(OOOl) substrate. 

Chemical solution deposition (CSD) procedures have been widely used for the production of both amorphous and crystalline thin films for more than 20 years.1 Both colloidal (particulate) and polymeric-based processes have been developed. Numerous advances have been demonstrated in understanding solution chemistry, film formation behavior, and for crystalline films, phase transformation mechanisms during thermal processing. Several excellent review articles regarding CSD have been published, and the reader is referred to Refs. 5-12 for additional information on the topic. Recently, modeling of phase transformation behavior for control of thin-film microstructure has also been considered, as manipulation of film orientation and microstructure for various applications has grown in interest.13-15... 

Tolstoy, V. P. 1997. The peroxide route of the successive ionic layer deposition procedure for synthesizing nanolayers of metal oxides, hydroxides and peroxides. Thin Solid Films 307 10-13. 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

---