Hakaru Kyuragi

Synchrotron radiation‐excited chemical‐vapor deposition and etching

Photoexcited chemical‐vapor deposition (CVD) and etching using synchrotron radiation as an exciting light source were experimentally demonstrated. CVD of silicon nitride film and etching of Si and SiO2 by SF6+O2 gases are described in detail. In several reaction systems, it was found that the surface photoexcitation was an important mechanism. Reaction models for gas‐phase excitation and surface excitation were proposed.

Synchrotron radiation stimulated semiconductor processes: Chemical vapor deposition and etching

A synchrotron radiation beamline and reaction chamber were constructed for the study of synchrotron radiation excited photochemical reactions, especially for their application to semiconductor processes. Characteristics of this experiment and experimental results with chemical vapor deposition and etching in this beamline are described. The potential of this new application is discussed.

Application of x‐ray lithography with a single‐layer resist process to subquartermicron large scale integrated circuit fabrication

The applicability of synchrotron radiation x‐ray lithography to future ultralarge scale integrated circuit fabrication processes is demonstrated by the test fabrication of subquartermicron bipolar‐ complementary metaloxide semiconductor devices (SRAM, gate arrays, and several test element groups) with a total size of two‐million transistors. Synchrotron radiation lithography is used at four critical levels: gate poly, first metal, via hole, and second metal. Both negative and positive chemically amplified resists are used with a single‐layer resist system to simplify the resist process. An overview of the lithography process is presented with emphasis on patterning and overlay performance.

Tungsten–beryllium multilayer mirrors for soft x rays

Multilayer structures of tungsten and beryllium were synthesized onto flat silicon single-crystal substrates by the neutral atom beam sputtering technique. Structures of constituent tungsten and beryllium thin films were evaluated. The standard deviation of the interface roughness of the multilayer was estimated to be ~2.5 A. Reflectivities of multilayer mirrors were measured at a grazing incidence of 5.0 degrees . The observed reflectivity of 30% at 1055 eV was in good agreement with the calculated value considering the interface roughness and oxygen contamination for a tungsten-beryllium structure having a period of 77.0 A.

Spatial period division with synchrotron radiation bandwidth control by W/Be multilayer mirror

Submicrometer periodic patterns were fabricated by spatial period division (SPD) using synchrotron radiation. The spectrum bandwidth was controlled to nearly the optimum width by using a W/Be multilayer mirror. This reduces the influence of gap variations between the x‐ray mask and the Si wafer.

A novel method of selective SiO2 formation on Mo electrodes

A novel technique of selective SiO2 formation called the interfacial oxidation method is proposed and proved feasible by experiment. By this technique, a poly‐Si/MoO2/Mo structure (poly‐Si on MoO2 on Mo) can be converted to a poly‐Si/SiO2/Mo structure by annealing in an H2 atmosphere so that SiO2 is selectively formed on only Mo electrodes. The SiO2 film formed by this method is shown to have almost the same properties as thermally grown SiO2 film; the Si(2p) binding energy peak, etching rate for diluted HF(H2O:HF=100:3), and average breakdown strength were 102.9 eV, 102 A/min, and 3.6×106 V/cm, respectively. In addition, most diodes of 500×500 u2009μm2 area showed a leakage current of less than 10−12 A.

Characterization of silicon nitride films formed by synchrotron radiation‐excited chemical vapor deposition

From a standpoint of physical, chemical, and electrical properties, silicon nitride films formed by synchrotron radiation‐excited chemical vapor deposition with SiH4+N2 gas mixture are characterized. These properties are compared with the properties of films deposited by other low‐temperature processes. It is found that the present film has such features as lower hydrogen content (<4×1021 cm−3), higher film density (2.9–3.05 g/cm3), lower etching rate against BHF (<10 nm/min), and potentially improved electrical properties considering that deposition was performed at substrate temperatures as low as 200u2009°C. Deposition kinetics, the effect of bias on film properties, and ways to improve the electrical properties are also discussed.