Mutsuo Yamashita

Effect of substrate bias voltage on the thermal stability of Cu/Ta/Si structures deposited by ion beam deposition

The interfacial reactions of the Cu (100 nm)/Ta (50 nm)/Si structures and their relationship with the microstructure of Ta diffusion barrier are investigated. Ta films were deposited on Si (100) substrates using a non-mass separated ion beam deposition system at various bias voltages ranging from 0 to -200 V. An optimum applied substrate bias voltage of -125 V was found to yield a dominant α-Ta film with a noncolumnar structure, low electrical resistivity (about 40 µΩcm) and smooth surface. A Ta diffusion barrier which was deposited at the optimum bias voltage prevented Cu–Si interaction up to 600°C for 60 min in flowing purified H2, whereas a Ta layer with a columnar structure, deposited at zero bias voltage, degraded at 300°C. Two different reactions of the Cu/Ta (0 V)/Si and the Cu/Ta (-125 V)/Si structures concerning the thermal stability were investigated and discussed on the basis of the experimental results.

Preparation of high-purity Cu films by non-mass separated ion beam deposition

Cu films were deposited on Si(1 0 0) substrates by applying a negative substrate bias voltage using non-mass separated ion beam deposition (IBD) method. By the SIMS results with Cs þ ion beam, the Cu film deposited at VS ¼ 0 V was found to contain more impurities than the Cu film deposited at VS ¼� 50 V. On the other hand, from the SIMS results with O þ ion beam, it was found that elements which are easy to be positive ions such as B, Mg, Na, Al, K, Ca and Fe seem to be increased slightly as compared to the those of the Cu film deposited at VS ¼ 0 V. As a result, higher-purity Cu film deposited at VS ¼� 50 V could be obtained in comparison with the film deposited at VS ¼ 0 V. The purification effect of the Cu film deposited at VS ¼� 50 V was described in details. � 2003 Elsevier Science B.V. All rights reserved.

High purity RF-sputter type metal ion source for non-mass-separated ion beam deposition

High purity RF-sputter type metal ion source has been developed for non-mass separated ion beam deposition. An Fe or Cu rod target of purity 99.999% or 99.9999%, respectively, was DC-sputtered inside an RF inductively generated Ar plasma. Optical emission spectroscopy from the plasma region (Fe case) indicated that emission from Fe* becomes larger than that of Ar* when DC bias voltage of -1 kV was applied. This result agreed with our previous mass spectroscopic results that Fe/sup +/ ion intensity overcomes that of Ar/sup +/ because of an efficient Penning ionization of sputtered and evaporated Fe particles. Cu films deposited on Si substrate at RT with the ion source showed non-columnar structure at a substrate bias voltage of -150 V, whereas only columnar structure was obtained with no bias voltage. This tendency qualitatively agreed with the case of Fe film formation obtained in our mass separated IBD.

Ion bombardment-type high frequency metal ion source for compact ion beam deposition apparatus

A novel metal ion source has been developed for a compact nonmass-separated ion beam deposition apparatus. To produce a dense plasma, a high frequency (hf) antenna coil made of Cu was mounted inside the metallic ionization chamber and a hf power of 300 W (13.56 MHz) was applied to this coil. A Cr rod target 10 mm in diameter was fitted at the center of the hf coil and a dc bias voltage of −600 V was applied to it. The temperature of a tip of the Cr rod target increased locally by means of ion bombardment; the Cr target material vaporized vigorously by sublimation and effectively ionized in the high density plasma. A pure Cr ion current of 400 μA was obtained at an energy of 100 eV without mass separation. Circular Cr thin films of 10 mm in diameter and 500 nm in thickness were deposited on Si substrates at a deposition rate of 30 nm/min at an ion energy of 100 eV. No contamination due to a sputtering of Cu antenna coil was detected by X-ray fluorescence analysis.

The effect of a magnetic field on the plasma characteristics of a sputter-type hf ion source

Abstract The effect of a superimposed dc magnetic field on the plasma characteristics of a sputter-type hf ion source with a built-in high-frequency (hf) coil was examined. Both the plasma density and the electron temperature at the central portion of the hf coil were decreased with an increase in the parallel magnetic field which is parallel to the axis of the hf coil. The target current, which is closely related to the total ion density and the sputtering rate, also decreased. On the contrary, sputtered source atoms were highly ionized and were guided along the axis of the hf coil, and its density increased with an increase in parallel magnetic field. The result of the mass analysis of the ion beam extracted from the central portion of the plasma region was as follows: When a Cu target was used and the applied parallel magnetic field was varied from 0 to 70 G, the Cu + ion current increased from 250 μA to 360 μA, but the Ar + ion current decreased from 100 μA to 40 μA, at a discharge gas pressure of 1 × 10 −1 Torr.