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The ALD window for titanium dioxide (TiO₂) ranges from 120 ^oC to 350 ^oC.

A low temperatures between 120 ^oC and 150 ^oC an anatase TiO₂ layer is grow in the ALD, and at higher temperatures between 300 ^oC and 350 ^oC and amorphous TiO₂ layer is grown in the ALD. At temperatures between 150 ^oC and 300 ^oC the TiO₂ layer will be a mixture of both anatase and amorphous TiO₂.

SEM images of both anatase and amorphous TiO₂ are shown below.

For Si wafers, anatase TiO₂ is best grown wafers without native oxide (do an BHF etch), and amorphous TiO₂ is best grown on wafers with native oxide.

XPS measurements shows that at temperaturs below 120 ^oC the TiO₂ layer will be contaminated with about 1-3 % chlorine molecules from the TiCl₄ precursor.

All results shown on this page have been obtained using the "TiO2" recipe on new Si(100) wafers with native oxide:

Recipe: TiO2

Temperature: 150 ^oC - 350 ^oC

	TMA	H₂O
Nitrogen flow	150 sccm	200 sccm
Pulse time	0.1 s	0.1 s
Purge time	3.0 s	4.0 s

In the graphs below the TiO₂ thickness as function of number of cycles for deposition temperatures between 150 ^oC and 350 ^oC can be seen. From the equations the number of cycles required for a certain thickess can be calculated.

Titanium oxide thickness as function of number of cycles
Temperature 150 ^oC.
Temperature 200 ^oC.
Temperature 250 ^oC.

Below some SEM images of anatase TiO₂ deposited on trenches are shown.

Anatase TiO<sub

Below some SEM images of amorphous TiO₂ deposited on trenches are shown

Amorphous TiO<sub

Evgeniy Shkondin, DTU Danchip, 2014.