Hafnium oxide deposition (CVD)

The equipment required for this process are a CVD and a plasma cleaner for removing impurities after the Hafnium oxide deposition

Since HfCl₄ is a solid salt at room temperature, we need to first create a liquid precursor which can be turned into a vapor.

The process is based on a Japanese paper and requires a complex precursor.

The synthesis of the Hf precursor TDEAH (Hf(NEt2)4) is so complex, that it needs its own page.

Precursor injection

Vapor pressure

Introduce TDEAH gas into the deposition chamber using a bubbling system, use N₂ as the carrier gas.

To prevent liquefaction of the source before it enters the deposition chamber, maintain the line from the bubbler to the chamber at a temperature of 85°C.

Heat the bubbling system chamber to 80°C.

The flow rate into the CVD chamber should be 40 sccm.

Oxidizer injection

CVD setup

Have O₂ in N₂ in a ration 1:99 and feed it into the chamber through a separate nozzle, because otherwise the O₂ decomposes the TDEAH before it can reach the substrate.

The flow rate can be varied between 0 and 20 sccm, for obvious reasons you want it higher than zero, because without oxygen you won't get any oxide.

Substrate/CVD chamber temperature

Set a temperature between 300°C and 450°C, in order to control deposition speed.

CVD chamber pressure

Set the pressure within the CVD chamber to 1 torr

Equipment

• Potential CVD furnaces:
  • https://www.digiqualsystems.com/products/furnaces/tubular-furnace/horizontal-tubular-furnace/
  • https://www.mtixtl.com/ThreeZonesTubeFurnaceHighVacuumMFCGas-OTF-1200X-III-HVC-UL.aspx

• Bubblers:
  • https://www.mtixtl.com/Bubbler/Evaporatorforliquidsourcesandchemicalprecursors-BL-SS.aspx

• Mass flow meters
  • https://www.mtixtl.com/Liquid-delivery-system.aspx