Impressive advances in vapor-phase deposition and photolithographic patterning techniques have been fueling the silicon microelectronics revolution over the last 40 years. However, for many interesting classes of materials, including biological materials or functional synthetic polymers, vacuum deposition and photolithography are not the techniques of choice for producing ordered structures and devices. Many of these materials selfassemble into well-ordered microstructures when deposited from solution, and patterning may be more readily achieved by solution-based selective deposition and direct-printing techniques. It is appealing to consider novel ways of manufacturing functional circuits and devices based on techniques that are similar to printing visual information onto paper.

A solution to the thin film silicon transistor gate metallization problem in active matrix liquid crystal displays is demonstrated in the form of a self-passivation process for copper. Bottom-level copper (Cu) lines are passivated by a self-aligned CrOx encapsulation formed by surface segregation of chromium (Cr) from dilute Cu1-xCrx alloys (x=0.1–2.3) at 400°C. The encapsulation is an efficient barrier for Cu diffusion into the SiNx gate insulator during the plasma deposition and transistor processing, and solves the problems of oxidation and adhesion to the glass substrate. Gate line resistivities are 4.5 to 7.5μΩcm depending on the initial Cr concentration. The performance of self-passivated Cu-gate thin film transistors is comparable to that of transistors with refractory metal gates.

We discuss the properties of semiconducting iron silicides, grown epitaxially on Si(001) and Si(111) by molecular beam epitaxy. The growth on Si (111) involves phase transitions from epitaxially stabilized metallic phases, leading to larger epitaxial β-FeSi2 grains than most other deposition procedures. The structural and electric properties of β-FeSi2/Si(001) are improved considerably for growth temperatures above 650 °C. Hall mobilities of p—conducting films reach values up to 600 cm2/Vsec at 100 K, at carrier densities below 1017 cm−3. Despite of the high majority carrier mobility and low carrier density, the photoelectric response of p-β-FeSi2/n-Si(001) diodes does not yield any significant contribution from the silicide, however, in accordance with the expected band structure diagram.

Pseudomorphic Fe1-x Si films have been grown on Si(111) by molecular beam epitaxy (MBE) at room temperature (RT). Structural investigations revealed that the phase crystallizes in the cubic CsCl structure with a lattice constant close to half that of Si. Upon annealing, films thicker than 15Å undergo a phase transition to the stable bulk ε-FeSi, either in epitaxial or in polycrystalline form at temperatures around 300°C. Thinner films do not transform to the ε-FeSi phase. Instead they exhibit a continuous increase of the Si content up to the stoichiometry of FeSi2 The CsCl symmetry persists, exept for prolonged annealing close to the transition to βFeSi2, where γ-FeSi2 (CaF2 ) forms as an intermediate phase.

The first magneto—transport data taken on thin pseudomorphic FeSi films with the CsCl structure are presented. FeSi appears to be a Kondo system with a Kondo temperature of TK ∼ 15 K. On air-exposed films which have not been protected by a Si-cap an ultrathin magnetic oxide is formed leading to large anomalies in the Hall effect and the magnetoresistance as the film thickness approaches 20 Å.

Epitaxial single-domain CoSi2(100) layers were grown on Si(100) by use of a template technique. In-situ scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED) were used for a detailed surface study. The (√2×√2)R45 reconstruction of the Co-rich “C-surface” and the (3√2×√2)R45 as well as a newly discovered (√2×√2)R45 of the Si-rich “S-surface” were resolved in real space and are discussed in detail. The transition from the C- to the S-surface above 500 °C is related to a (2×2) reconstruction.