Specific Process Knowledge/Thin film deposition/Deposition of Titanium Oxide/IBSD of TiO2

Acceptance test for TiO2 deposition:

.	Acceptance Criteria	Acceptance Results recipe 1	Acceptance Results recipe 2
Substrate information	50 mm SSP Si wafer 525 µm thick Supplied by Danchip	100 mm SSP Si wafer 525+-25 µm thick	100 mm SSP Si wafer 525+-25 µm thick
Material to be deposited	TiO2 The purpose of the TiO2 is to be part of a mirror: <br\> 5 quarterwavelength pairs of <br\> SiO2 <br\> TiO2 <br\> Extra quarterwavelength layer of <br\> TiO2 <br\> 5 quarterwavelength pairs of <br\> SiO2 <br\> TiO2 <br\> Design wavelength (for refractive indices and layer thicknesses):1300nm <br\> The acceptance criteria is set up for the single SiO2 and TiO2 layers. <br\> Five runs in a row for each material.	TiO2	TiO2
Deposition thickness	147nm	~184 nm	121 nm
Deposition rate	2.8 nm/min	3.54nm/min +- 0.03nm/min One stdev - wafer to wafer	3.03nm/min Only done once
Thickness uniformity	<+-1%	<+-1.00%	<+-0.90%
Reproducibility	<+-1.5%	+-0.9% on 5 wafers in a row	not tested
Stress	<500MPa	~300MPa	Not measured expect ~300MPa
Refractive index	.	2.451+-0.004 (stddev wafer to wafer)	2.437+-0.005 (stddev on wafer)

	Recipe 1	Recipe 2
Platen angle	50 degrees	30 degrees
Platen rotation speed	20rpm	20rpm
Ar(N) flow	4 sccm	4 sccm
Ar(dep. source) flow	9 sccm	9 sccm
O2(dep. source) flow	2 sccm	2 sccm
O2(etch source) flow	8 sccm	8 sccm
I(N)	459mA	450mA
Power	875W	875W
I(B)	390mA	390mA
V(B)	1300V	1300V
Vacc(B)	400V	400V
Deposition time	52min	40min

Other results

Roughness of the surface

Measured with the Optical profiler - PSI mode (on one sample from the acceptace test): Sa= ~1nm

How to pattern TiO2

TiO2 can be difficult to pattern since TiO2 is a very hand material that is also difficult to etch wet. Hot sulfuric acid can remove it (not allowed at Danchip without special permission). HF will etch it at a very low etch rate. It can be sputtered by IBE but also at a very low etch rate and there is no masking material with a resonable selectivity to TiO2. If you want to pattern a TiO2 that you deposite in the IBSD Iondab then we advice you to do it with a lift-off process. Make your resist pattern, deposite TiO2 on top and do the lift-off in an apropriate solvent depending on the resist chosen.