Shinji Suganomata

Mass Spectrometry of Discharge Products at 13.56 MHz in SF6 Gas

Discharge products in SF6 RF plasma were measured by means of direct sampling using a quadrupole mass spectrometer. In the plasma, the neutral dissociative species SF2 and SF4 are present. The positive ion SF3+ is predominant, and SF5+, SF2+, SF+ and F+ are also present. The concentration of each neutral and ion product depends on RF power, gas flow rate and area of the silicon wafer set on the grounded electrode. When SF, SF2, SF+ and SF2+ increase to certain amounts, S2F+, SF2+ and S+ can be observed.

Ionic Species in 13.56 MHz Discharges in CF 4 Gas and Mixtures of It with Ar and O 2

Signal intensities of positive ions were measured in situ by direct sampling from parallel-plate discharges in CF 4 /Ar and CF 4 /O 2 mixtures using a quadrupole mass spectrometer. Major positive ions in CF 4 /Ar discharge are CF x + (x = 3, 2, 1) and Ar + . Some of the production of CF 2 + and CF + is considered to be due to the contribution of Ar + . Major positive ions in CF 4 /O 2 discharge are CF 3 + , O y + and F y + (y = 2, 1). The signal intensity of CO 2 + is of the same order as that of F y + . The signal intensities of F y + and O + in CF 4 /O 2 discharge are higher than those in pure CF 4 and O 2 discharges, respectively. Intensity ratios of the ions vary with the gas mixing ratios.

Positive Ions in C 4F 8 RF Discharge in a Planar Diode

Positive ions were measured in situ by direct sampling from C4F8 discharge at 13.56 MHz using a quadrupole mass spectrometer. Major positive ions in the discharge plasma are CF+, CF2+, CF3+, C2F4+, C2F5+ and C3F5+. When the gas flow rate increases, the signal intensity of C2F4+ increases. The intensity variation of C3F5+ is similar to that of C2F4+. However, those of CF3+ and C2F5+ decrease with increasing gas flow rate, and those of CF+ and CF2+ are almost constant. The difference in intensity variations is considered to result from the production processes of ions.

Positive and negative ions in RF plasmas of SF6/N2and SF6/Ar mixtures in a planar diode

Ionic species in 13.56 MHz discharge of SF6/N2 and SF6/Ar mixtures were measured by means of direct sampling using a quadrupole mass spectrometer. Dominant negative ions in the SF6/N2 discharge are F-, SF5- and SF6-, while the positive ions are SF3+, SF5+ and N2+. In the SF6/Ar discharge the major ions are the same as in the SF6/N2 discharge except that N2+ is replaced by Ar+. The signal intensity ratios of these ionic species depend on the ratio of N2 or Ar to SF6 in the discharge. In particular, the ratio of Ar to SF6 in the SF6/Ar discharge increases, the signal intensity ratio of SF3+ to SF5+ shows a concave variation, and the total intensity of negative ions decreases rapidly in the SF6/Ar discharge. These results in the SF6/Ar discharge are different from the variations in the SF6/N2 discharge, and seem to be based on the effects of the metastable atom Ar* on both production of SF3+ and extinction of negative ions.

Optical Properties of LiNbO3 Implanted with Ag+ Ions

Ag+ ions were implanted into LiNbO3 held at room temperatures with the energy of 25 keV in the range of 2×1015 to 8×1016 ions/cm2. Absorption in the visible range was measured. LiNbO3 implanted with Ag+ ions shows brilliant reddish-violet and a large absorption peak at about 520 nm. Ag atoms aggregate during implantation and form very small flat particles of the size of about 0.3 to a few micrometers in surface layers of depths up to 16 nm.

Coloration of Sapphire by Metal-Ion Implantation

Relations between the coloration of synthetic sapphire and impure elements introduced by ion implantation were investigated. Ion species used for implantation were Nb+, Fe+, Cu+, Co+, Ti+, Cr+. Doses of metal ions were 1 ×1017 ∼3 ×1017 ions/cm2. The color of the parts implanted with Fe+ or Co+ and subsequently annealed at 1000°C for 3 h was yellowish-brown or light blue, respectively. Transparencies in the visible range and the depth profiles of Fe and Co of the parts implanted with Fe+ or Co+ ions were measured.

Positive Ions in RF Discharge Plasma of CF_4 Gas in a Planar Diode

Positive ions were measured in situ by direct sampling from CF4 discharge space at 13.56 MHz using a quadrupole mass spectrometer. CF3+ is observed predominantly with smaller amounts of CF2+ and CF+. With increasing RF power, both CF2+ and CF+ shift to the lower energy side of CF3+, and their intensities tend to increase. Such a phenomenon is also observed as controlling the potential of a sampling tip externally. These seem to suggest that CF2+ and CF+ are produced mainly in the sheath region.

Negative Ions in 13.56 MHz Discharge of SF6 Gas in a Planar Diode

Mass spectra of negative ions were measured in situ by direct sampling from SF6 discharges at 13.56 MHz separately in the two cases of the grounded electrode attached with and without Si wafer. In both cases, F- is observed dominantly, with smaller amounts of SF-5 and SF-6. In the case with Si wafer, however, all these intensities decrease overall. Positive ions SF+2 and SF+3 are predominant in the cases with and without Si wafer, respectively. Negative ions SF-2 and SF-3, however, are hardly observed regardless of whether Si wafer is present or not.

Metal ion source using rf discharge combined with sputtering

An ion source capable of producing a wide variety of ion species from elemental materials is described. Ion beams of metals can be produced by sputtering a disk, made of the materials to be ionized, placed on the cathode. In order to raise the rate of ionization of the sputtered materials an rf discharge is superimposed on the dc sputtering. Ions of refractory metals, such as Nb, can be easily produced without using halides.

Mass spectrometric observation of decomposition products SFx (x=1,2) in SF6 discharge at 13.56 MHz

The presence of a smaller mass fragment SF2 was indicated from the output signal of a quadrupole mass spectrometer by means of direct sampling from an SF6 discharge space at a pressure of 50 or 100 mTorr. Its intensity was observed to increase with the discharge power according to the degree of fragmentation of SF6.