Specific Process Knowledge/Thin film deposition/Deposition of ZnO/ZnO deposition in Sputter System (Lesker)

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ZnO Sputtering

This page presents the results of ZnO deposition using RF sputtering in Sputter-System Lesker, now commonly known as "Old Lesker". The deposition target is ZnO, and a small fraction of O2 as reactive gas has been added to improve the stoichiometry. Source #5 (RF) was used. Target #5.

The fabrication and characterization described below were conducted in 2021 by Evgeniy Shkondin, DTU Nanolab. The prepared samples were investigated by the X-ray Reflectivity method. The focus of the study was the deposition conditions.


The process recipe in a Sputter-System (Lesker) is following:


  • Deposition type: RF, RF-R
  • Power: 60 W.
  • Pressure: 3 mTorr
  • Gas: Ar, 10% of O2 in Ar
  • Deposition time: 3600s which corresponds to 1 hour.
  • Temperature: 20°C (no heating)
  • Measured DC bias: 253V


  • Deposition Rate: 0.0143 nm/s for deposition in pure Ar
  • Deposition Rate: 0.0165 nm/s for deposition in 10%O2 in Ar



XRR-measurement


X-ray reflectivity (XRR) profiles for ZnO films at two different deposition conditions (pure Ar and 10% of O2 in Ar) has been obtained using Rigaku XRD SmartLab equipment. The voltage and current settings for the Cu X-ray tube were standard 40kV and 30mA. The incident optics contained a IPS (incident parallel slit) adaptor with 5 ° Soller slit. Other slits: IS=0.03mm RS1=0.03mm and RS2=0.075mm. Step size: 0.01 and measurement time - 5s for each point. Fitting procesure was performed using commercial GlobalFit software assuming the model based on Si substrate with native oxide followed by the deposited ZnO film with moisture surfaces. The results are summarized in a tables below.


Deposition of ZnO using RF, RF-R Sputtering in Sputter-System (Lesker)
Deposition in Pure Ar
Layer name Thickness (nm) Density (g/cm3) Rougness (nm) Delta Beta
Moisture 2.2 5.22 1.25 1.6993e-5 3.9459e-7
ZnO (sputtered)

51.39

 5.74 2.20 1.6519e-5 3.2241e-7
SiO2 (native oxide) 2.23 2.22 0.42 7.2451e-6 1.6824e-7
Si (wafer) 2.328 0.03 7.5795e-6 1.7601e-7
Deposition in 10% O2 in Ar
Layer name Thickness (nm) Density (g/cm3) Rougness (nm) Delta Beta
Moisture 2.40 2.53 1.96 8.2439e-6 1.9144e-7
ZnO (sputtered)

59.38

 5.66 1.93 1.6283e-5 3.1781e-7
SiO2 (native oxide) 0.51 1.89 0.41 5.9327e-6 1.3777e-7
Si (wafer) 2.328 0.01 7.5795e-6 1.7601e-7



  • XRR analysis of ZnO thin film.

  • X-ray reflectivity. Measurement and Fit. ZnO deposition in pure Ar

  • X-ray reflectivity. Measurement and Fit. ZnO deposition in 10% O2 in Ar

Spectroscopic ellipsometry

The results in this section (uniformity, thickness, refractive index) has been obtained using Ellipsometer VASE. ZnO thin film on Si has been fitted using Tauc-Lorentz model with severeal additional Lorentz oscillators.


  • Thickness uniformity for ZnO sputtered thin fims.

  • Thickness uniformity measured by spectroscopic ellipsometry. ZnO deposition in pure Ar.

  • Thickness uniformity measured by spectroscopic ellipsometry. ZnO deposition in 10% O2 in Ar

The uniformity is clearly better for the film deposited in pure Ar!


  • ZnO sputtered thin film. Optical functions.

  • Refractive index of sputtered ZnO.

  • Absorption coefficient of sputtered ZnO.

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