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

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Acceptance test for TiO2 deposition:

. Acceptance Criteria

Acceptance Results recipe 1

Acceptance Results recipe 2 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
  • 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

TiO2

Deposition thickness
  • 147nm
  • ~184 nm
  • 121 nm
  • 43.3nm in 10min 2013-10-07
Deposition rate
  • 2.8 nm/min
  • 3.54nm/min +- 0.03nm/min

One stdev - wafer to wafer

  • 3.03nm/min

Only done once

  • 4.33 nm/min 2013-10-07
Thickness uniformity
  • <+-1%
  • <+-1.00%
  • <+-0.90%
  • Not tested
Reproducibility
  • <+-1.5%
  • +-0.9% on 5 wafers in a row
  • not tested
  • not tested
Stress
  • <500MPa
  • ~300MPa
  • Not measured expect ~300MPa
  • Not tested
Refractive index .
  • 2.451+-0.004 (stddev wafer to wafer)
  • 2.437+-0.005 (stddev on wafer)
  • 2.108 test done shortly after pump down


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


Repetitions of the accpetance test

Test1-3 were done without a bakeout. 1 Hour after a user had run several hours of runs with the same recipe. Test4-6 were done after a bakeout. Several hours after the system ad been used and with out heat-up recipe and conditioning run.

Acceptance recipe TiO2 2 Deposition thickness (0,0) Deposition thickness average Deposition time Deposition rate (0,0) Refrative index@632.8nm
2014-06-16 test1 60.7 nm 58.4 nm 20min 3.04nm/min 2.42679
2014-06-16 test2 59.4 nm 59.6 nm 20min 2.97nm/min 2.42651
2014-06-16 test3 59.3 nm 59.2 nm 20min 2.97nm/min 2.4249
2014-06-19 test4 60.62/60.51 59.49/59.38 20min 2.97nm/min 2.42776/2.43090
2014-06-19 test5 59.92/59.84 59.80/59.73 20min 2.99nm/min 2.42776/2.42983
2014-06-19 test6 60.31 59.53 20min 2.98nm/min 2.42776

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 Ionfab 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.