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Video of How to Operate the Gaertner Ellipsometer with the new software and hardware installed 11/12/21;

/wiki/spaces/BNCWiki/pages/6239184

iLab Name: Cleanroom Ellipsometer
iLab Kiosk: BRK Metrology Core
FIC: Shared
Owner: Rich Harlan
Location: Cleanroom - Q Bay
Maximum Wafer Size: 6"/150 mm

Overview

General Description

The cleanroom Ellipsometer can measure the thickness and refractive index of thin films on reflective substrates, as well as the optical properties of bare substrates.

Specifications

Manual tilt alignment and table height using computer table adjust screen
Light source: HeNe laser, 632.8 nm, 1 mW output.
Advanced StokesMeter™ determines beam polarization
Incidence angles: 70° (default), 50°, 30°.
Maximum sample thickness: 1/2 inch.
Maximum sample diameter: 5 inch.
Film thickness range: 0-60,000 Angstroms on substrate (or on 1, 2 or 3 other known sublayers).
Accuracy: ±3 Angstroms (manufacturer claimed over most of measurement range)
Repeatability: ±1 Angstrom (manufacturer claimed over most of measurement range)
Spot size is approximately 1mm by 3mm
Your substrate must be polished and must not rough to diffract the laser

Technology Overview

Ellipsometry measures the thickness of an optically transparent film based on a change in polarization of an incident laser. This change is compared to a model, and values for thickness and refractive index are calculated. The values PSI (psi, Ψ) and DEL (delta, Δ).

The software uses the following abbreviations:

Thick1: Thickness of film being measured
Nf: Real value of refractive index for film being measured
Kf: Imaginary value of refractive index for film being measured
ω (OMEGA): Thickness period; used for determination of thick film thickness
Ns: Real value of refractive index for substrate
Ks: Imaginary value of refractive index for substrate
Φ (PHI): Angle of incidence
ψ (PSI): Amplitude ratio as determined by measurement
Δ (DELTA): Phase difference as determined by measurement
λ (LAMBDA): Wavelength of incident light; fixed at 632.8 nm for HeNe laser

Sample Requirements and Preparation

Backside must be free of contaminants that may transfer to the stage. The area of measurement should be clean to be measured properly.

Standard Operating Procedure

Written SOP, Click here to expand...

This instruction covers the set-up and safe use of the Gaertner Ellipsometer L116A measurement system. The ellipsometer measures the thickness of an optically transparent film based on a change in polarization of an incident laser. This change is compared to a model and returns a calculated thickness and refractive index value. The accuracy of the thickness value can be greatly increased if the known refractive index is entered. The film thickness range is between 0Å and 60,000Å. The sample must have a polished surface free of rough defects that will cause the laser to diffract.

1. SAFETY REQUIREMENTS

a. Safety glasses must be worn whenever in the clean room, except when using a microscope or when wearing protective goggles.

b. Do NOT look directly into the Helium-Neon laser or at the reflection of the laser from the sample stage as noted on the laser caution label. The laser shutter should remain closed unless a measurement is being taken.

2. EQUIPMENT

a. Gaertner Ellipsometer Model L116A

i. 6-inch Wafer Stage

ii. Light Source: HeNe laser, 632.8nm, 1mW output

iii. Stokes Meter

iv. CRT Monitor for User Interface

3. TOOL CONFIGURATION

Caption	Figure
Figure 1
Figure 2

4. CYCLE OF OPERATION

a. User time must be scheduled through iLab prior to using the system.

b. Verify the Laser Shutter is closed. The shutter should be slid over the laser opening shown in Figure 1. This

will prevent accidental laser exposure.

c. Turn on the ellipsometer laser power by rotating the Laser Power (key) Switch (clockwise) shown in Figure1.

NOTE: Allow the laser to warm up for 15 minutes to ensure reliable measurements

d. Turn on the computer and monitor, if not already on.

e. Double click the “GEMP_SP” icon if the Gaertner Ellipsometer Measurement Program (GEMP) isn’t already running.

f. Verify the laser shutter is closed before placing sample in the center of the stage.

g. Look through the eyepiece on the front of the ellipsometer (Figure3). The stage pitch must be adjusted so the center

of the two “X” images are aligned (Figure2). If the thicker cross is missing, verify the overlay knob (Figure3) is turned

full counterclockwise.

NOTE: There are 3 knobs that adjust the stage. One pitches the stage left and right, one pitches the stage
fore and aft, and one moves the entire stage up and down. For this step use the left-right and fore-aft
knobs.

h. Verify the angle of incident is set to 70°
NOTE: This measurement angle is generally already set to 70°, but can be adjusted by releasing the set
screw on the back and lifting the arms. Lifting by the laser tube arm or stokes
meter arm will cause the system to be misaligned.

i. Open the Laser Shutter by sliding the lever towards you.

j. Click on the “Measurement and Calculation” button at the top of the GEMP screen.

k. Click on the “F9 Adjust Sample Table” button or press the F9 key on the keyboard.

l. Adjust the stage height up or down (Figure2) to move the bar to the maximum power and the click “OK”

m. Press the “Load File” button in the upper right area of the Measurement and Calibration window to select a file or
use the “0default.tfm” for a thin oxide on silicon film
NOTE: The value displayed next to “Thickness 1” must be close to the expected value for film to be measured.
The Nf default value of 1.46 is for thermally grown silicon oxide.

n. Click on the “F8 Measure & Calculate” button or press the F8 key on the keyboard.

o. The measured data will be displayed in the “Measured Data” on the lower right area of the Measurement and
Calibration window

p. For multiple measurements, press the “F5 Start” button or the F5 button on the keyboard. Click on the F6 Stop
button or press the F6 key on the keyboard when the desired number of measurements have been reached.
NOTE: The “F10 Stats” button must be locked down to display the Measurement Statistics
It should be noted the system is measuring for two unknown values (thickness and refractive index)
and may introduce some error in one or both of the values

q. The “Print Stats” button in the Measurement Statistics window will display the information in then main GEMP window.
The “Clear Stats” button will clear the values in the “Measurement Statistics” window.

r. Press the “Return” button in the lower right corner (or the X in the upper right corner) when finished taking measurements

s. Close the Laser Shutter

t. Turn off the Laser and Lamp Power (key) Switch

u. Remove sample from stage.

v. Log out of iLab

5. SUPPLEMENTAL DATA

a. Definition

i. Ns – Refractive index for the substrate

ii. Nf – Refractive index for the film

iii. Ks – Extinction value of refractive index for substrate

iv. WL – Laser wavelength

v. N – Refractive index

vi. PHI (Φ) – Angle of Incidence

vii. POL – Polarization angle

viii. PSI (Ψ) – Amplitude ratio as determined by measurement

ix. DEL (Δ) – Phase difference as determined by measurement

x. DELc (Δc) – Phase difference as calculated

xi. Default silicon refractive Index = 3.850

xii. Default film refractive index = 1.460

xiii. Default extinction value of refractive index = -0.0200

xiv. Default laser wavelength = 6328

xv. Default angle of incident =70.00

xvi. Default polarization angle = 45.00

6. STARTUP and SHUTDOWN

a. Startup

i. Press the power button on the computer box

ii. Press the power button on the monitor

iii. If the monitor displays “C:\GSC>”, type “menu” and press “ENTER”.

b. Shutdown

i. At the main menu type “99” and then “ENTER”

ii. The computer is now safe to power down

Questions & Troubleshooting

Process Library

References

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