Dry etching characteristics of TiN film using Ar/CHF3, Ar/Cl2, and Ar/BCl3 gas chemistries in an inductively coupled plasma

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Dry etching characteristics of TiN film have been studied in the case of using Ar/CHF3, Ar/Cl2, and Ar/BCl3 chemistries in an inductively coupled plasma. The TiN film was not etched at all without the addition of CHF3, BCl3, or Cl2 to the Ar gas flow. On the other hand, it was found that the TiN film was etched with one of the earlier additional gases. It was also found that a nontapered profile of etched TiN is obtained by Cl2 addition and a tapered profile by CHF3 or BCl3 addition. Moreover, a lower taper angle is obtained by increasing the amount of additional BCl3. X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses for the etched samples of TiN show that TiF3 exists on the etched surface of TiN in the case of CHF3 addition and that BOxNy exists in the case of BCl3 addition. On the basis of these results, the effect of the gas addition to Ar on the characteristics of TiN reactive ion etching is considered as follows; under the Ar/CHF3 condition, although N in the TiN film is removed by evaporation in the form of NFx, Ti is fluorinated to form TiFx having low vapor pressure, which results in the low etching rate. Under the Ar/Cl2 condition, since NClx and TiClx have high vapor pressures, TiN is easily etched off, resulting in the highest etching rate with a nontapered profile. Under the Ar/BCl3 condition, although Cl plays the same role as it does under the Ar/Cl2 condition, B is likely to form a nonvolatile compound such as BOxNy, resulting in the deposition of the nonvolatile films on both the upper surface and sidewall of the TiN, which leads to a lower etching rate than that in the case of Cl2 addition and a lower taper angle of the etched profile.