Preparation and Properties of Sputtered Hafnium and Anodic HfO[sub 2] Films

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Abstract
Hafnium films sputtered at high voltages (4 kV) had a density of 98% of the bulk, specific resistivities as low as 50 µmhm‐cm and TCR as high as 1580 ppm/°C. Films with a density of 50% of that of the bulk, a specific resistivity of 815 µohm‐cm, and TCR of 800 ppm/°C were obtained at the lower sputtering voltages (1.5 kV). High‐ and low‐density films had Hall coefficients of and , respectively. All the sputtered films had the same hexagonal close‐packed structure as the bulk material, although the high‐ and low‐density films had different preferred orientation. The oxide density, anodization constant, and dielectric constant for hafnium oxide were found to be 7.9 g/cm3, 20 Aå/V, and 18, respectively. The anodized hafnium oxide had a monoclinic polycrystalline structure with some preferred orientation, or (001) plus . Test capacitors with anodic oxides formed to 100V at 1 mA/cm2 had capacitance density values of 0.085 µf/cm2, dissipation factors below 0.01 at 1 kHz, and a frequency dependence of capacitance of ±1% in the range of 0.1–100 kHz relative to the 1 kHz value. Temperature coefficient of capacitance values varied from 300 to 600 ppm/°C.

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