Specific Process Knowledge/Thin film deposition/Deposition of Titanium

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Titanium deposition

Titanium can be deposited by e-beam evaporation or sputtering. In the chart below you can compare the different deposition equipment. The following sections tell about some properties of evaporated Ti films and the use of Ti as an adhesion layer.

	E-beam evaporation (Temescal)	E-beam evaporation (Wordentec)	E-beam evaporation (Physimeca)	Sputter deposition (Wordentec)	Sputter deposition (Lesker)	Sputter deposition (Cluster-based sputter system)
General description	E-beam deposition of Titanium	E-beam deposition of Titanium	E-beam deposition of Titanium	Sputter deposition of Titanium	Sputter deposition of Titanium	Sputter deposition of Titanium
Pre-clean	Ar ion beam	RF Ar clean		RF Ar clean	RF Ar clean	RF Ar clean
Layer thickness	10Å to 1 µm*	10Å to 1 µm*	10Å to 1000Å	.	.	.
Deposition rate	0.5Å/s to 10Å/s	10Å/s to 15Å/s	About 10Å/s	Depending on process parameters, see here.	Depending on process parameters, about 1 Å/s.	Depending on process parameters
Batch size	Up to 4x6" wafers Up to 3x8" wafers (ask for holder) smaller pieces	24x2" wafers or 6x4" wafers or 6x6" wafers	1x 2" wafer or 1x 4" wafers or Several smaller pieces	24x2" wafers or 6x4" wafers or 6x6" wafers	Smaller pieces Up to 1x6" wafers	Up to 10x4" or 6" wafers Many smaller pieces
Allowed substrates	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers	III-V materials Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers	Almost any as long as they do not degas at the substrate temperature used for your process. See cross-contamination sheets.	Almost any as long as they do not degas at the substrate temperature used for your process. See cross-contamination sheets.
Allowed materials	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Almost any as noted above	Almost any as noted above
Comment

* For thicknesses above 600 nm please write to metal@nanotech.dtu.dk to ensure that there is enough material available.

Comments: Adhesion layer

Ti as an adhesion layer

Titanium is most often used as a adhesion layer for other metals, like for example gold. Gold does not stick very well to Si, and to prevent it to come off in future process steps or in the final application, a layer of Ti (or Cr) is often deposited onto the wafer.

The most common thickness of the Ti adhesion layer is 10 nm. Also layers with a thickness of 5 nm is used. Read more about gold adhesion layers.

Very thin adhesion layers

If it is important to have a very thin Ti layer, it is possible to use even thinner adhesion layers. There is some experience in using a 3 nm Ti as adhesion layer for a 200 nm thick gold layer. In this case a Si wafer was dipped in buffer and rinsed in water immediately before being placed in the PVD equipment (Wordentec). After an RF clean process of the wafer, 3nm of Ti and 200 nm of Au was deposited, and this worked fine during futher processing.