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Message ID: 395     Entry time: Tue Aug 8 09:58:34 2017
Author: Gabriele 
Type: General 
Category: Measurements 
Subject: Effect of assist beam on tantala coatings - no post deposition annealing  

ntroduction

A set of substrates have been coated by the Colorado State University Fort Collins group, with ~500 nm tantala and various ion assist beam parameters. Here's a table summarizing the depositions parameter, by Le Yang

 

substrate

main ion source voltage / V

main ion source current / mA

main ion source Ar flow / sccm

target oxygen flow / sccm

assist ion source voltage / V

assist ion source current / mA

assist ion source gas/sccm

thickness / nm

abs

/ ppm

notes

Ar

O2

s1600525 1250 600 18 49 100 100 12.5 0 480    

s1600535

1250

600

18

49

100

100

12.5

0

541

7.2

 

s1600536

1250

600

18

49

100

100

3.5

9

532

20.2

 

s1600537

1250

600

18

49

100

100

6.5

6

534

 

damaged

by

holder

s1600538

1250

600

18

49

100

100

6.5

6

524

 

scratch

s1600547

1250

600

18

49

100

100

6.5

6

528

15.4

 

s1600532

1250

600

18

49

200

100

12.5

0

518

17.8

 

s1600539

1250

600

18

49

200

100

3.5

9

541

17.7

 

s1600533

1250

600

18

49

200

100

6.5

6

539

11.6

 

s1600530

1250

600

18

49

100

200

12.5

0

537

10.3

 

s1600550

1250

600

18

49

100

200

3.5

9

519

19.9

 

s1600548

1250

600

18

49

100

200

6.5

6

532

17.2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Coating losses before annealing

The plot below shows the measured loss angle for all modes of all samples, before annealing. The error bars for the datapoints are from the 95% confidence intervals computed from 8 measurements each. The red line is the average value over frequencies, and the shaded red area gives the 95% confidence interval of the mean value. The loss angle seems reasonably indipendent of frequency.

The following pot then shows the averaged loss angle as a function of the serial number, for reference

There are three main parameters that are changed in the deposition: the assist beam voltage, the assist beam current and the content of oxygen in the assist beam. The plots below show the losses as a function of those parameters. The x axis changes in each of the four panels, and for each plot, the color code is linked to one of the process variables:

Conclusions

Quoting Le Yang and Carmen Menoni

  1. under certain conditions as oxygen flow increase and Ar flow decrease, the loss angle becomes worse
  2. with existence of oxygen ions the loss is mitigated by increase of beam voltage
  3. relatively small particle size of oxygen compared with argon the caused the less effective interaction between assist ions and coating adatoms on the surface
  4. with increase of ion dose, the mechanical loss drops
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