Dry Etching Characteristics of Pb(Zr,Ti)O3 Films in CF4 and Cl2/CF4 Inductively Coupled Plasmas

Authors:
  • JJJin-Ki Jung
    Jin-Ki Jung
  • WLWon-Jong Lee
    Won-Jong Lee
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Abstract
The dry etching mechanism of lead zirconate titanate (PZT) films was studied in high density CF4 and Cl2/CF4 inductively coupled plasmas. The concentrations of atomic Cl and F as well as the flux and energy of bombarding ions were monitored as a function of etching parameters such as etching gas ratio, substrate bias voltage (Vs), induction coil power and process pressure. The compositions and chemical bonding states of etched PZT films were examined by X-ray photoelectron spectroscopy (XPS). The etching of PZT films in CF4-based plasma is chemically assisted sputter etching, and the dominant step of the overall etching process is either the formation or the removal of the etch by-products, depending on the etching conditions. The etching of PZT films in Cl2/CF4 mixed plasma is mainly dominated by the formation of metal chlorides which depends on the concentration of the atomic Cl and the bombarding ion energy. The PZT film shows a maximum etch rate in 90% Cl2/(Cl2+CF4) plasma where the concentration of atomic Cl is maximum. The etch selectivity of PZT to Pt is less than 1.3 in CF4-based plasma, where as more than 2 in Cl2/CF4 mixed plasma. The amount of sidewall residue is greatly reduced in Cl2/CF4 mixed plasma compared with in CF4 plasma. A more vertical etch profile of PZT films can be obtained by lowering the process pressure and increasing the substrate bias voltage.

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