Paper PS-TuP15
The Analysis of ZrO₂ Thin Films Etching in BCl₃/Cl₂ Inductively Coupled Plasma

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

As feature size of CMOS device has been decreased 100 nm, the new material has required to substitute for SiO₂ as gate dielectric material. The silicon oxide for gate reached a physical limit owing to very high gate leakage current of 10 A/cm² for very thin gate SiO₂ of below 1nm. Therefore, high dielectric constant materials, such as HfO₂, ZrO₂, and Al2O3 have attracted a great attention. Among them, ZrO₂ is the most candidate because of its high dielectric constant of 20 ~ 25, wide bandgap of 5~7 eV, and thermal stability with Si. In order to obtain a small feature accurate pattern transfer, development of plasma etching process for ZrO₂ thin film is important problem to be solved. There are few papers on the etch of ZrO₂ thin films with using helical resonator plasma and electron cyclotron plasma in Cl₂/BCl₃. They reported that etch rate of ZrO₂ is limited by the low volatile etch by product such as ZrCl₂, but the etch rate can be accelerated by the addition BCl₃ which can be effectively remove oxygen from the surface of ZrO₂. However, there is no relationships between input parameters and plasma chemistry as well as surface reactions. In present work, the etching characteristics of ZrO₂ thin film was investigated with using inductively coupled BCl₃/Cl₂ plasma. ZrO₂ thin film was deposited on Si substrate by atomic layer deposition (ALD). The variation of etch rate and selectivity was monitored while additive gases was varied in BCl₃/Cl₂ plasma. Simultaneously, the etch behavior of ZrO₂ was investigated with variation of RF power, DC bias voltage, and pressure. To understand the influence of additive O₂, He or N₂ into BCl₃/Cl₂ on the electron temperature and the density of radicals, Langmuir probe (LP), optical emission spectroscopy (OES), quadrupole mass spectromter (QMS) was used during etching process.