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Hafnium Oxide HfO2 Notes


Hafnium Oxide (HfO2) General Information

Hafnium oxide is an inorganic compound with a chemical formula of HfO2. It has a density of 9.68 g/cc, a melting point of 2,758°C, and a vapor pressure of 10-4 Torr at 2,500°C. It is off-white in color and generally considered to be one of the more stable hafnium compounds. Hafnium oxide has been utilized significantly in recent years as an addition to computer chips as a way to improve the speed and efficiency of processors. It is also evaporated under vacuum for optical coatings and semiconductor fabrication.

Hafnium Oxide HfO2 Specifications

Material TypeHafnium Oxide
SymbolHfO2
Color/AppearanceWhite, Crystalline Solid
Melting Point (°C)2,758
Theoretical Density (g/cc)9.68
SputterRF, RF-R
Max Power Density
(Watts/Square Inch)
20*
Type of BondIndium, Elastomer
Z Ratio**1.00
E-BeamFair
E-Beam Crucible Liner MaterialDirect in Hearth
Temp. (°C) for Given Vap. Press. (Torr) 10-4:  ~2,500
Export Control (ECCN) 1C231
CommentsFilm HfO.

** The z-ratio is unknown. Therefore, we recommend using 1.00 or an experimentally determined value. Please click here for instructions on how to determine this value.

* This is a recommendation based on our experience running these materials in KJLC guns. The ratings are based on unbonded targets and are material specific. Bonded targets should be run at lower powers to prevent bonding failures. Bonded targets should be run at 20 Watts/Square Inch or lower, depending on the material.

Z-Factors

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

  • Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
  • Place a new substrate adjacent to the used quartz sensor.
  • Set QCM Density to the calibrated value; Tooling to 100%
  • Zero thickness
  • Deposit approximately 1000 to 5000 A of material on the substrate.
  • Use a profilometer or interferometer to measure the actual substrate film thickness.
  • Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.

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