Steven A. Voight

Epitaxial PbZr.52Ti.48O3 films on SrTiO3/(001)Si substrates deposited by sol–gel method

We report on the sol–gel deposition and characterization of high-quality, epitaxial films of PbZr.52Ti.48O3 (PZT) on (001)Si substrates, with a thickness range of 400 A to 1 μm. The epitaxial growth of PZT on (001)Si is achieved using a thin template layer of SrTiO3, grown by molecular-beam epitaxy. The sol–gel PZT films have a typical surface roughness of 5 A and exhibit well defined reflective high-energy electron diffraction patterns characteristic of smooth, epitaxial films. Using high-resolution transmission electron microscopy and double-crystal x-ray diffraction, we find that the PZT films are oriented with the c axis normal to the (001)Si plane and with the a axis lying along 〈110〉Si direction. Finally, we measure the electromechanical coupling coefficients and the surface acoustic wave velocities for our films as a function of thickness and compare our experimental data to previously published theoretical values for this system.

Nitrogen-doped plasma enhanced chemical vapor deposited (PECVD) amorphous carbon: processes and properties

In this work we discuss thin film amorphous carbon, which is deposited in a dual frequency, plasma enhanced chemical vapor deposition (PECVD) system in such a manner that it contains a small amount of nitrogen. Unlike most carbon films deposited using PECVD, the films in this study were deposited on the grounded electrode and therefore, subject to little energetic bombardment during growth. Methane was used as the carbon-containing precursor. We illustrate some potential applications for this type of film and discuss the effect of various process parameters on resultant film properties such as optical constants, resistivity, stoichiometry, and chemical bonding and structure.

Effect of annealing temperature on physical properties of thin epitaxial PZT films on STO/Si substrates

In this work, we report the effect of annealing temperature on the properties of epitaxial PbZr0.52Ti0.48O3 (PZT) films deposited using sol-gel techniques on (001) Si substrates with a thin, epitaxial SrTiO3 (STO) interlayer. The STO is grown on silicon using molecular beam epitaxy (MBE) and acts as the template for PZT growth. We report the values for stress, density, thickness, and refractive index vs. anneal temperatures for a thin PZT film. AFM surface roughness values of less than 0.4 nm are typical for this film. XRD patterns show the film to be c-axis orientated, with PHI scans demonstrating that the [100] PZT is orientated along the [110] Si direction. SEM cross-sections show the film morphology is free of gain boundaries and are clear of interfacial layers from the multiple spin/bake/anneal deposition technique, thereby making this material an excellent candidate for electro-optic applications.

Improved adhesion of photoresist to III-V substrates using PECVD carbon films

Amorphous PECVD carbon films have been investigated as a means to prepare III-V compound semiconductor substrates for improved photoresist adhesion. Results show that significant improvements in adhesive durability of patterned photoresist occurred for carbon primed GaAs and InGaAs wafers used in conjunction with both i-line and DUV lithography processes. These carbon layers, were 50-100 Angstrom in thickness, and varied in composition and morphology from a nitrogen-doped, diamond-like material (DLC), to a more hydrogen rich, polymer-like material (PLC). Adhesion durability tests performed in baths of ammonium hydroxide (NH4OH) and hydrochloric acid (HCl) in general showed superior performance compared to non-primed substrates. The sole exception was a failure of PLC priming on GaAs wafers used with a DUV anti-reflective coating. This same system, however, was shown to work extremely well when a DLC coating was substituted. Characterization of PLC and DLC films included use of AES, XPS, FTIR, AFM, and contact angle analysis. Results indicate that carbon films passivate III-V oxides, creating a stable, hydrophobic surface. This factor is proposed as a key reason for the improved resistance to aggressive aqueous environments. AFM results show that carbon films are extremely smooth and actually decrease surface roughness, indicating that mechanical adhesion is unlikely.

Nitrogen-doped plasma-enhanced CVD amorphous carbon: processes and properties

In this work we discuss thin film amorphous carbon which is deposited in a dual frequency plasma enhanced CVD system with a nitrogen-containing ambient. Unlike most carbon films deposited using PECVD, the films in this study were deposited on the grounded electrode and therefore subject to little energetic bombardment during growth. Methane was used as the carbon-containing precursor. We illustrate some potential applications for this type of film and discuss the effect of various process parameters on resulting film properties, such as optical constants, stoichiometry, and chemical bonding and structure.