No abstract

No abstract

In recent years, fluorinated silicon oxide (SiOF) film prepared by plasma enhanced chemical vapor deposition (PECVD) has attracted much attention because of its easy implementation of low-k dielectric. In PECVD SiOF film, the incorporation of fluorine causes changes in the Si-O network to a less polarizable geometry resulting in a reduction of the dielectric constant. 1 However, it has been known that the PECVD SiOF film is susceptible to moisture absorption by the reaction, SiF ϩ H 2 O r SiOH ϩ HF F. 2 In case this reaction takes place, a degradation of film quality and increase of dielectric constant may be observed. Although it has been suggested that the SiOF film capped with a thin layer of undoped oxide film could reduce the instability due to the moisture adsorption, 3 there have been few reports about improving the bulk quality of the SiOF film. In this report, the improvement of the bulk quality of the PECVD SiOF film was demonstrated by adding Ar during deposition process of SiOF film. It is supposed that 4 metastable Ar atoms can transfer their energy to other reactant gases, thus, the formation of the SiOF network was promoted. As the result, moisture absorption was reduced and accordingly the stability of the SiOF film was improved. The results of Fourier transform infrared (FTIR) spectroscopy and ramp current-voltage (I-V) measurement are reported.Experimental The deposition of the SiOF films was made in a parallel plate Plasma Therm model VII-70 PECVD system. One side polished, boron doped silicon wafers with (100) orientation were used as the substrates. The substrates were cleaned by RCA procedure 5 before they were loaded into the reactor. The SiOF films were deposited by flowing 50 and 100 standard cubic centimeters per minute (sccm) of Ar, respectively, into the deposition process of SiOF film using 40 sccm of Si 2 H 6 (5% in He), 100 sccm of N 2 O, and 30 sccm of CF 4 . The radio frequency (rf) power, process pressure, and substrate temperature were maintained at 50 W, 700 mT, and 180ЊC, respectively. The thickness of the film was measured using an Applied Materials ellipsometer model II. The films were dipped into boiling deionized (DI) water for 30 min for moisture absorption. The FTIR spectra for the film were monitored by Perkin Elmer model 1600 spectrometer. Metal oxide semiconductor (MOS) capacitors were fabricated by standard photolithography, then were subjected to postmetallization anneal (PMA) in N 2 ambient at 400ЊC for 30 min to make electrical measurements. The capacitance-voltage (C-V) measurements were performed by superimposing a 25 mV ac signal at 1 MHz on a dc voltage with a sweep rate of 20 mV/s using a HP 4275A LCR meter. The I-V characteristics were obtained using a HP 4140B pA meterdc voltage source. All measurements were carried out at room temperature. Figure 1 displays the FTIR spectra for the SiOF film, which has the dielectric constant of ϳ3.51. The spectrum for the film after a 10 month aging test was compared with the spectra for the film 6 asdeposited and with po...

A phase-shifted (PS) distributed-feedback (DFB) laser with linearly chirped grating (CG) was analyzed using the coupled-mode equations and rate equations. It was found that the mode instability of a DFB laser was caused by both the lasing-mode movement and the deterioration of the effective reflectivity spectrum of the corrugated-grating waveguide caused by the nonuniform carrier distribution under the injection. By suitable arrangement of the chirped factor of the PS-CG-DFB laser and the phase-shift value, PS-CG-DFB laser can overcome the effective reflectivity spectrum-deterioration problem and make the mode more stable under injection.