Plasma immersion ion implantation (PIII) is a cluster compatible doping and processing tool offering many inherent advantages over conventional beamline ion implantation. When first introduced in the late 1980s, the technique was primarily used to enhance the surface mechanical properties of metals. Recently, a substantial amount of research activities have focused on microelectronics and have led to a number of very interesting applications, such as the formation of shallow junction, synthesis of silicon-on-insulator, large area implantation, trench doping, conformal deposition, and so on. In this paper, we will review the principles of PIII, the dynamic sheath model for various kinds of plasma, reactor designs, recent applications in the area of microelectronics, as well as the future of PIII pertaining to semiconductor materials and processing.

Plasma immersion ion implantation—a fledgling technique for semiconductor processing

The effect of ambient oxygen pressure on the synthesis of epitaxial YBa2Cu3O7−x films on (100) SrTiO3 substrates by post‐deposition annealing of amorphous precursor films was studied for oxygen partial pressures pO2 between 1.0 and 8.0×10−5 atm and annealing temperatures between 890 and 650 °C. A pO2−1/T diagram containing recent literature data regarding YBa2Cu3O7−x oxygen stoichiometry, phase stability, and liquid‐phase formation was compiled to provide guidance for the selection and interpretation of annealing conditions. The results evidence a strong dependency of growth properties on the oxygen pressure with enhanced c‐oriented epitaxy at lower pO2 values. A particularly interesting result is the formation of predominantly c‐oriented films at 740 °C and pO2=2.6×10−4 atm (0.2 Torr). Similar to YBa2Cu3O7−x films produced by in situ laser ablation at the same temperature and oxygen pressure, the films exhibited low ion channeling yields (χmin<0.1) and a dense (smooth) surface morphology, while critical ...

Effect of oxygen pressure on the synthesis of YBa2Cu3O7-x thin films by post-deposition annealing

High quality superconducting films of YBa 2 Cu 3 O 7− x were deposited in situ using single target 90° off-axis sputtering. We have investigated their superconducting DC and RF properties, their normal state properties, and their microstructures. These films are distinctly different from bulk crystals and post-deposition annealed films. Sharp superconducting transition temperatures can be reproducibly obtained by control of deposition parameters. The T c can be varied from 75 to 89 K. The optimization of properties other than T c and the control of film texture occur under conditions different from those for which the highest T c is obtained. Normal state conductivities are as high as or higher than those of single crystals. Critical current densities reach 6 × 10 7 A/cm 2 at 4.2 K. All the above properties are relatively insensitive to compositional variations. The T c 's have a much weaker dependence on the c -axis lattice parameters than do those of bulk samples. The measured low-temperature penetration depth is 1400 A and surface resistance at 4.2 K and 10 GHz is as low as 16 μΩ. Microstructural studies show sharp interfaces between films and their substrates and a variety of defect structures. Many of the properties of in situ films can be explained by clean grain boundaries and the characteristics of the surface growth occuring during in situ deposition.

Synthesis and properties of YBa2Cu3O7 thin films grown in situ by 90° off-axis single magnetron sputtering

High-T c
 superconductivity has generated a great deal of interest because of the challenges it presents in the fields of material science, condensed matter physics, and electrical engineering, and because of the potential applications which may result from these research efforts. Thin-film passive microwave components may become the first high-temperature superconducting (HTS) devices available for widespread use and commercialization. In this article, we review aspects of material science, physics, and engineering which directly impact high-T

 c
 superconducting microwave devices and discuss issues which determine the performance of these devices. Methods of growing HTS thin films on large-area substrates, techniques for fabricating single-level HTS passive microwave components, and the relevant properties of high-T

 c
 superconducting films are discussed, with a focus on thin films of the HTS material YBa2Cu3O7−δ. Several known mechanisms for microwave loss in both the superconductor and the dielectric substrate are presented. An overview of the general classes of superconducting passive microwave devices is given, and representative microwave devices which have been recently demonstrated are described in detail. Examples of a select few HTS active microwave components are also presented. Potential microwave applications are illustrated with comparisons to current technology.

High-temperature superconducting microwave devices: Fundamental issues in materials, physics, and engineering

We measure the relative permittivitye
r and dielectric loss tangent tanδ of substrate materials for high-T
c superconducting films at 18–300 K and at 5–10 GHz using the cavity-resonator method. The materials measured are single crystals of MgO, LaAlO3, YAlO3, LaSrGaO4, NdGaO3, sapphire, and ZrO2 ceramic. Thee
r values are 10–30 and become almost constant below about 50 K. The tanδ values decrease with decreasing temperature and are below 1×10−5 at 77 K except for those of NdGaO3 and ZrO2 ceramic. This suggests that the tanδ values of MgO, LaAlO3, YAlO3, LaSrGaO4, and sapphire do not limit the quality factors of microwave passive components fabricated using high-T
c superconducting films. It is also demonstrated that the tanδ of the substrate material is strongly affected by impurities.

Relative permittivity and dielectric loss tangent of substrate materials for high-Tc superconducting film

We have performed intra‐ and extra‐cavity microwave frequency (1–100 GHz) measurements on high quality Y1Ba2Cu3O7−x superconducting thin films on (100) LaAlO3 substrates. The ∼0.3 μm thin films fabricated by the pulsed laser deposition technique exhibit superconducting transition temperatures >90 K, as determined by resistivity and ac susceptibility measurements, and critical current densities of 5×106 A/cm2 at 77 K. Moreover, ion beam channeling minimum yields of ∼3% were measured, indicating the extremely high crystalline quality of films grown on the LaAlO3 substrate. Microwave surface resistance values at 77 K for these films are found to be more than one to two orders of magnitude lower than for copper at 77 K for almost the entire frequency range explored. We postulate that the reason we observe such low surface resistances in these films is the virtual absence of grain and phase boundaries coupled with the high degree of crystallinity. Furthermore, we believe that the residual resistance measured b...

Microwave properties of highly oriented YBa2Cu3O7−x thin films

We report measurements of the temperature dependence of the surface resistivity of highquality Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ crystals at 5.95 GHz. A narrow transition with 89-K onset is observed. Resistivity in the normal state is found to be ${R}_{\mathrm{norm}}=126\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ \ensuremath{\Omega}. We establish an upper limit for the resistivity at 77 K of 1.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ \ensuremath{\Omega} and at 2 K of 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ \ensuremath{\Omega}. The dissipation in four crystals with a total area of about 20 ${\mathrm{mm}}^{2}$ is measured to be nearly independent of peak microwave magnetic field over the range of 0.5 to 93 G in sharp contrast to the strong field dependence observed in bulk sintered samples.

Observation of a narrow superconducting transition at 6 GHz in crystals of YBa2Cu3O7.

To achieve luminosities of 30-100 times CESR, 1-2 A of current must be stored. A CESR B-factory parameter list calls for 50 MV for two rings, to be supplied by 16 cells operating at 10 MV/m gradient. With a new cell shape, the impedances of the dangerous higher order modes (HOM) are drastically reduced. All HOMs propagate out of the cavity via the beam pipe, which is specially shaped. This allows HOM power couplers to be placed completely outside the cryostat. A ferrite absorber on the beam pipe lowers all Qs to approximately 100, which is sufficient to avoid multibunch instabilities without feedback systems. A waveguide input coupler on the beam-pipe provides Qext as low as 5*10/sup 4/, with a C- slot shaped iris that has a negligible effect on the cavity loss parameter.<<ETX>>

Accelerating cavity development for the Cornell B factory CESR-B

To achieve luminosities of 30-100 times CESR, 1-2 A of current must be stored. A CESR B-factory parameter list calls for 50 MV for two rings, to be supplied by 16 cells operating at 10 MV/m gradient. With a new cell shape, the impedances of the dangerous higher order modes (HOM) are drastically reduced. All HOMs propagate out of the cavity via the beam pipe, which is specially shaped. This allows HOM power couplers to be placed completely outside the cryostat. A ferrite absorber on the beam pipe lowers all Qs to approximately 100, which is sufficient to avoid multibunch instabilities without feedback systems. A waveguide input coupler on the beam-pipe provides Qext as low as 5*10/sup 4/, with a C- slot shaped iris that has a negligible effect on the cavity loss parameter. >

https://epaper.kek.jp/p91/pdf/pac1991_0786.pdf

J. Kirchgessner

Papers

Microwave properties of highly oriented YBa2Cu3O7−x thin films

Observation of a narrow superconducting transition at 6 GHz in crystals of YBa2Cu3O7.

Accelerating cavity development for the Cornell B factory CESR-B

Accelerating cavity development for the Cornell B-factory, CESR-B

CESR-B: Conceptual design for a B factory based on CESR