in situ stokes ellipsometer L104ST




in situ stokes ellipsometer L104ST description
The Stokes In Situ Ellipsometer permits real-time in-process monitoring of growing or etched films.  Early film growth on a bare substrate can be precisely measured in milliseconds to within 1 angstrom with the model L104ST. The measured DEL and PSI values also clearly determine the end point during an etch so tight control can be achieved over your process.

The model L104ST is a super fast, highly reliable, no moving parts laser ellipsometer which is ideal for measuring rapidly growing films in-process and in situ. Mounts onto CVD, electron-beam evaporation, MBE, sputtering as well as other chambers that have an entry and exit window port for the measuring beam.

The L104ST replaces complex optics and mechanisms with new StokesMeter™ technology. The advanced StokesMeter ™(see below) completes a measurement in milliseconds by sampling the laser beam intensity at 4 detectors followed by a computer calculation. Since the compact 4" x 4" measurement head has no moving parts, it is rugged, trouble-free and clean.


  • Fastest possible instrument for thin film measurement.
  • Trouble-free, no moving parts advanced StokesMeter™ measurement head.
  • Measures complete state of polarization useful for rough,scattering samples.
  • Accurate, stable measurements using spectrally precise laser ellipsometry.
  • Simple, compact component instrument - competitively priced.

The adjustable polarizer and analyzer modules mount onto window flanges outside your reactor or chamber. The polarizer module emits a continuous low power laser beam, which passes thru the chamber window onto a sample which must be precisely located. The beam then reflects from the sample passing out of the chamber into the analyzer module which reads the polarization. An alignment prism is supplied so that the user can position the sample together with the polarizer and analyzer modules which have provision for fine angular adjustment. The angle of incidence, measured with respect to the sample, is determined by the two chamber ports and can be between 30 and 85 degrees although 70 degrees is most commonly used.

A unique feature is the Stokes Ellipsometer's ability to compensate for small deviations in the measuring beam caused by sample misalignment, sample out-of-flatness and small changes in sample thickness. This important characteristic enables the Stokes Ellipsometer to be quickly installed onto your chamber, ready for fast , accurate measurement.



A photopolarimeter for the simultaneous measurement of all four Stokes parameters of light. The light beam, the state of polarization of which is to be determined, strikes, at oblique angles of incidence, three photodetector surfaces in succession, each of which is partially spectrally reflecting and each of which generates an electrical signal proportional to the fraction of the radiation it absorbs. A fourth photodetector is substantially totally light absorptive and detects the remainder of the light. The four outputs thus developed form a 4x1 signal vector I which is linearly related, I=AS, to the input Stokes vector S. Consequently, S is obtained by S=A(-1)I. The 4x4 instrument matrix A must be nonsingular, which requires that the planes of incidence for the first three detector surfaces are all different. For a given arrangement of four detectors, A can either be computed or determined by calibration.


software measures:

  • One, two, three and four layer transparent films
  • Contaminants on bare substrates
  • PSI and DELTA for user characterization of films and substrates.

optional accessories

Single Angle Ex situ Support Base for In situ Ellipsometer L104SB
Support frame for alternately mounting the L104ST polarizer and analyzer modules at a fixed 70 degree angle of incidence for ex situ measuring. 

Variable Angle Ex situ Support L104SA
Support frame for alternately mounting the L104ST polarizer and analyzer modules for ex situ measuring. Includes a combination Viewing Scope/Tilt Monitor and Tiltable Stage.  Incidence angles can be easily set to 30, 45, 50, 60 70,75,80,and 90 degrees. This support converts the model L104ST into the table-top L116S Stokes Ellipsometer.

Calibration Kit L118-KIT
Stokes Calibration Kit permits re-calibration of any Stokes Ellipsometer quickly and easily. Kit consists of calibration software and 4 calibration samples.

L104ST can be equipped with the following laser options:


LS405    Substitutes 405 nm  Blue laser diode in place of 633 nm HeNe Gas Laser  $13K
LS544    Substitutes 544 nm Green HeNe Gas laser in place of 633 nm HeNe Laser  $4K
LS830    Substitutes 830 nm laser diode in place of 633 nm HeNe Gas Laser $9K


L2W405    Adds 405 nm Blue Laser Diode to 633 nm ellipsometer $21K
L2W544    Adds 544 nm Green HeNe Gas Laser to 633 nm ellipsometer $15K
L2W830    Adds 830 nm laser diode to 633 nm ellipsometer  $18K 


L3W405.544   Adds 405 Laser Diode and 544 Green Gas Laser to 633 nm ellipsometer $26K
L3W405.830   Adds 405 Laser Diode and 830nm laser diode to 633 nm ellipsometer $29K          
L3W544.830   Adds 544 Green Gas Laser and 830nm laser diode to 633 nm ellipsometer $23K


Rough scattering samples common in the solar cell industry are difficult to measure accurately with most ellipsometers because of the loss of signal strength and depolarization of the measurement beam. Although there are ways to boost the signal strength and capture more scattered light, dealing with depolarization is much more difficult and requires the determination of the complete state of polarization namely the measurement of the 4 stokes parameters S0, s1, s2, s3. Gaertner Stokes Ellipsometers do this naturally as our StokesMeterä polarimeter is used as the ellipsometer analyzer. This gives Stokes Ellipsometers the unique ability to instantly separate the polarized from the unpolarized components of the measuring beam thereby delivering a highly accurate measurement of film thickness and index based only on the totally polarized component of light. The L-SCAT scatter option includes a hardware modification to capture more of the scattered light from rough, textured surfaces and a program display of the degree of polarization P.


in situ stokes ellipsometer L104ST specifications

Angle of Incidence: Fixed by user at a single incidence angle from 85° to 30° using an alignment prism
Alignment Adjustments: ± 1/4 inch lateral shift both polarizer/analyzer
± 6° angular adjustment which is diminished by the amount of ± 1/4 inch lateral adjustment used.
Sample/Specimen: Must be precisely located
Light Source: HeNe 632.8 gas laser 
Light Beam Size: 1mm beam diameter
Measurement Time: 1 millisecond 
Computer(not included): Windows 10/7/VISTA/XP PC with USB port required
Precision: Thickness: sub-angstrom
Index: ± .001 over most of the measurement range
Electrical Power (VAC): 100V, 115V, 220V, 230V, 240V
Electronic Unit: Outline Dimensions: 14 x 33 x 43 cm
Weight: 17 lbs.
Interface cable to computer: 6.5 ft.
Laser/Polarizer Module: Weight: 12 lbs. for L104ST 
Interface cable to electronic unit: 6 ft.
Analyzer Module: Weight: 12 lbs.
Interface cable to electronic unit: 6 ft.
CE Compliance: S series Ellipsometers comply with European safety directives and carry the CE mark.

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