Optical Plasma Monitoring of Y-Ba-Cu-O Sputter Target Transients
- PDF / 427,672 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 93 Downloads / 159 Views
OPTICAL PLASMA MONITORING OF Y-Ba-Cu-O SPUTTER TARGET TRANSIENTS J. D. KLEIN AND A. YEN EIC Laboratories, Norwood, MA 02062 ABSTRACT Plasma emission spectra resulting from rf sputtering Y-Ba-Cu-O targets were observed as a function of time using an optical multichannel analyser. Although most lines of the observed spectra are not attributable to target species, peaks associated with each cation element were resolved. The Ba and Cu peaks can be used as tracking indicators of process conditions. For example, switching from an O2/Ar sputter atmosphere to pure Ar enhanced the Ba peak more than those associated with CuO. The emission spectra from a newly fabricated target exhibited a first-order transient response in seeking equilibrium with the rf plasma. The transient response of a previously sputtered target is also first-order but with a shorter time constant. INTRODUCTION There has been a high degree of interest in the sputter deposition of high-T, copper oxide superconductor films from a single oxide target [1-6]. However, the sputter deposition of high T, superconducting thin films is often hindered by poor cation stoichiometry. Two major contributors to poor stoichiometry are sensitivity to process variables [1-5] and aging of the target [6]. Significant changes in the color of the rf plasma have been observed upon initial sputtering of both new and previously sputtered targets [1]. This suggests that direct optical monitoring of the rf plasma may provide a sensitive means of tracking rf plasma transients important in determining cation stoichiometry. Emission spectra from laser ablation deposition of high-T. superconductors have been obtained in the Y-Ba-Cu-O [7-10], Bi-Ca-Sr-Cu-O [11], and TI-Ca-Ba-Cu-O [8] systems. However, the use of this emerging technique in monitoring rf sputter plasmas seems to have been restricted to permalloy magnetic films [12]. This work demonstrates real-time optical monitoring of the plasmas generated during rf sputtering of nonstoichiometric yttrium-barium-copper-oxide (YBCO), Cu, BaO, and Y targets. EXPERIMENTAL All deposition runs were performed in a Microscience IBEX-2000 deposition chamber evacuated by a diffusion pump fitted with a liquid nitrogen trap and backed by a mechanical pump. A 5 cm Ion Tech, Ltd. B315 planar magnetron sputter source was used in the sputter-up configuration with either O2/Ar or Ar atmospheres. The sputter targets were fabricated by a multiple-step reactive sintering process in which powders of Y20 3, CuO, and BaCO3 of 99.999% nominal purity are mixed with mortar and pestle before being compacted in a 3.8 cm diameter die and sintered in an air atmosphere at 950°C. The rf plasma spectra were acquired with an EG&G Princeton Applied Research Model 1460 Optical Multichannel Analyzer (OMA) diode array spectrophotometer fitted with an adjustable spectrometer and an intensified detector. Light emitted by the plasma passed through a UV-transmissive window before being collected by a collimating lens and routed to the detector by a fiber optic cable. The diode
Data Loading...
