Study of an Ellipsometer.

1. STUDY of an ELLIPSOMETER
Summer Internship work
By CHION Romain
Under the guidance of Professor Kimani Toussaint

2. Synopsis
Basic information about Ellipsomettry
Possible causes of defect
Testing the optical components
Polarizer
Compensator
Analyzer
Testing the electronic components
Logic board
Jacks
Photodetector
Software
Samples data
Acknowledgment
2

3. Basic information (1/4)
• The ellipsometry allows us, by studying the
polarization of the reflexion of a LASER beam
on a sample, to know the thickness of the
different layer of this sample as well as their
refraction index or composition…
Synopsis
3

4. Basic information (2/4)
• The ellipsometer studied (4) is from
here
Gaertner Scientific Corporation
(3)
(1)
• It be here
Shouldis composed of:
• Input:
• LASER (1)(2)
• Polarizer (1)
• Compensator or QWP (ON or OFF) (1)
• Sample stage (2)
• Output:
• Analizer (3)
• Motor (4)
• Photodetector (4)
Synopsis
4

5. Basic information (3/4)
• The ellipsometry measurement consists in two
series of measure:
• For the first one, the compensator
is OFF, the incoming light beam is
therefore lineary polarized and is
reflected elliptically
• Then, the compensator is ON,
the incoming light beam is circularly
polarized by rotating the analyzer
we can then get two series of data
Synopsis
5

6. Basic information (4/4)
• The data measured is then processed
through an original software that gives us
the information required.
• The user manual describes perfectly the
methods to make the ellipsometer and the
software work properly.
Synopsis
6

7. Possible problems
• The different problems that can occure with an
ellipsometer can be divided among the different types of
components:
• Mechanical: not much to do, it's broken. Though some small
problems and mistakes are listed in the user manual.
• Optical: Problems with the path of the beam, with it's
polarization, with the input wavelength…
• Electric & Electronic: Photodetector giving a wrong output, row
data are not processed well, computer and ellipsometer not
talking the right way…
• Software
• While many problems can be detected easily, some of them
need an accurate checking through tests.
Synopsis
7

8. Optical Components
•Polarizer
•Compensator
•Analyzer
Synopsis

9. Polarizer (1/3)
• The polarizer is part of the income device, we
can't dismantle it without decreasing the
acuracy of the ellipsometer.
• Therefore to test it we have to use the whole
income of the ellipsometer.
Synopsis
9

10. Polarizer (2/3)
• Hypothesis: If a light beam passing through the polarizer is
linearly polarized then this polarizer is working.
• Method:
• Dismantle all the output (explained in user's manual)
• Put back the lense
• Put the two arms of the ellipsometer on 90°
• Put a second polarizer (analyzer) and a powermeter instead of
the missing output in the light beam path.
• By rotating the analyzer search for the highest intensity
• Measure the intensity for a set of angles of polarization for the
analyzer
• Compare the experiment data with Malus Law theory
Synopsis
10

11. Polarizer (3/3)
Rotation (°)
Rotation (°)
140 Measured Intensity (µA) Malus Law (µA)
0 114,6 114,6
Results: 120
15
30
109,9
96,9
106,9232556
85,95
• Maximum intensity 100
45 69,7 57,3
60 35 28,65
every 180° 75 7 7,676744363
80
90 0,015 0
Measured Intensity (µA)
105 7,7 7,676744363
• Near to zero intensity 60 120 34,1 28,65
135 71,1 Malus Law (µA)
57,3
90° after each maximum
40 150 96,3 85,95
165 107,9 106,9232556
• Average distance 20 180 114,3 114,6
195 109 106,9232556
of 5% 0 210 96,8 85,95
0 50 225
100 150 200 70,3 250 300 57,3
240 35,4 28,65
• Linearly polarized 255 7,9 7,676744363
270 0 0
Synopsis
11

12. Compensator (1/3)
• The compensator is activated thanks to the
little spring above the polarizer.
• The method is the same than for the former
experience.
Synopsis
12

13. Compensator (2/3)
• Hypothesis: If a light beam passing through the working polarizer
with compensator (Quarter Wave Plate) is circularly polarized then
the compensator is working.
• Method:
• Dismantle all the output (explained in user's manual)
• Put back the lense
• Put the two arms of the ellipsometer on 90°
• Put a second polarizer (analyzer) and a powermeter instead of the
missing output in the light beam path.
• Maintain the spring of the compensator ON
• Measure the intensity for a set of angles of polarization for the
analyzer
• The data should be constant
Synopsis
13

14. Compensator (3/3)
Rotation (°) Intensity (µA)
Results:
60
0 52
50
15 52
40
30 51
• Almost always the same 30 45 50,5
Measured Intensity
(µA)
value 20 60 51
10 75 49
0 90 52
• Independent of the angle 0 50
105 150
100 200
51,5
of polarization 120 50
135 50,5
150 51
• Circularly polarized. 165 51
180 52
Synopsis
14

15. Analyzer
• The analyzer is the output polarizer of the
ellipsometer. It can't be took apart from the
motor.
• The method is the same as before but the only
part taken off shall be the photodetector.
• The results are similar to those before.
Synopsis
15

16. Electronic Components
•Logic board
•Jacks
•Photodetector
Synopsis

17. Logic board
• The logic board, counter, and PCI board are
accessible through manipulations explained in
the "Logic board upgrade" manual
• They all can be tested through the side jacks
Synopsis
17

18. Jacks (1/2)
• The ECE store did not have the compatible male
jacks so we used a simple voltmeter to measure
the different output of the jacks:
• Red: Photodetector output
• Orange: Reference pulse at the begining of the
automatic measurement
• Yellow: Count pulse each 5°
• Black: Ground
• Green: Signal that a reading is ready for the computer
• Blue: Signal that the computer is ready for the reading
• Brown: Count pulse but for the motor
Synopsis
18

19. Jacks (2/2)
Jacks AS Mode (mV) AM Mode N/M (mV) AM Mode W/M (mV)
• Results: Red 70 72 ~ 120 75 ~ 121
Orange 51 55 55 ~ 225
Yellow 50 1600 1600
Green 55 49 1600
Blue 56 45 1600
Brown 56 1600 1600
• Finally pulse appears only boardsthe with the
Count notice that the output vary ready
The measurement pulse when only while
We canthe computer andappears areoutput
part while taking well
taking rotating asmeasurements.
analyzer rotating whether we take pulse
only is measurements as for motormeasures
or not, the logical board therefore receive
data
Synopsis
19

20. Photodetector (1/3)
• The photodetector is part of a photodetector
board. It's easy to take it off thanks to the
user's manual instructions
• By looking at the different components
datasheets we have been able to create a
dynamic map of the board
Synopsis
20

21. Photodetector (2/3)
• Hypothesis: Following the datasheet of the
photodetector we can follow a similar patern
with the intensity curves in function of the
wavelength and our measures.
• Method:
• Dismantle the photodetector
• Connect the power supply (V+ on PIN, V- on PIN)
• Take measurement of the different outputs (row
output on PIN, amplified output on PIN)
• Repeat for different wavelength LASER
Synopsis
21

22. Photodetector (3/3)
• Results: PIN
H
White light (mV) Green Laser (mV) Red Laser (mV) Ellipsometer (mV)
260 7200 ? 9300
O 250 6300 ? 7900
• If we compare
experimental and
theoretical data we find
the same ratios
between green and
red lights
Synopsis
22

23. Software
•Datas
Synopsis

24. Data (1/2)
• The data are collected after different samples
with the ellipsometer.
• With enough data, an offset might be found.
We can then calculate the true values from
the results given by the software
Synopsis
24

25. Datas (2/2)
Samples Expected (Å et Ø) Calculated (Å et Ø)
SiO2 1156,6 1155,3
• If we compare the Substrate: 2,5 1,437 1,469
expected and measured SiN 4060 3038
Substrate: 3,6 1,754 1,753
data, we find similare
SiN 4060 3038
results, which is good, Substrate: 3,4 1,754 1,753
But the acuracy is not Training * 2 490 ±5% 927
Substrate: 3,4 ? 1,71
enough for such a
complex device as an No LASER 0 0
10000 9172
ellipsometer Substrate: 1 1 1,001
LASER alone 0 0
10000 9172
Substrate: 1 1 1,001
Synopsis
25

26. Acknoledgement
• I would like to thank Santosh Tripathi for all the
help he gave me this summer
• I thank also the whole ProbeLab for their support
and company.
• Finally I thank Professor Toussaint for the
opportunity he gave me to work here and for the
experience it gave me.
Synopsis
26

27. THANKS FOR YOUR ATTENTION