Imaging 300mm stokes waferskan™ ellipsometer
The model LSE-WS Stokes WAFERSKAN Ellipsometer is a high speed film thickness mapping system measuring one site per second including stage travel! It uses patented StokesMeter™ technology to give tilt-free, focus free, 2D/3D color thickness and index images on any size wafer up to 300mm. Based on advanced StokesMeter™ technology (winner of Photonics Spectra and R&D 100 best new products awards). The units' elegant design offers unprecedented ease of use and instantaneous measurement at a cost much lower than conventional production control metrology systems. Affordably priced under $50K in the USA, the LSE-WS is a outstanding value in a high precision imaging ellipsometer. 

features

• Tilt-free, focus free, hands-off operation for similar wafers.

• Fastest possible instrument for thin film measurement.

• Trouble-free, no moving parts patented StokesMeter™ measurement head.

• Accurate, stable measurements using spectrally precise laser ellipsometry.

• Simple, compact tabletop instrument - affordably priced.

• Measures complete state of polarization useful for rough,scattering samples.
• Accurate, stable measurements using spectrally precise laser ellipsometry.
• Simple, compact tabletop instrument - competitively priced.

high accuracy and performance
The model LSE-WS builds on the production proven Gaertner WAFERSKAN™ line of ellipsometers in widespread use throughout the world. From thin gate oxides only tens of angstroms thick to thick polyimides and photoresists Gaertner has earned a reputation for providing precise, reliable results. The model LSE-WS sets an even higher performance standard to meet today's more demanding metrology applications.

Single Layer films such as oxides, nitrides and photoresists can be measured to sub-angstrom precision. Two, three and four layer films, with know bottom layers such as poly on oxide and oxide on poly on oxide can be measured for the thickness and refractive index of the top layer or for both thicknesses. New Windows software enhances ease of use and understanding.

great graphics 
The measurement results are displayed on the computer monitor and can be sent to a printer. Results stored in a text data file are displayed in a 2D contour or 3D Map images. The images can be rotated, tilted, reduced or enlarged for immediate viewing and interpretation.

 
2D contour image of film thickness

 
3D contour image of film thickness

 
Main Screen

easy to use
The LSE-WS Stokes WAFERSKAN™ is simple to operate. The user interacts with a single main program screen so the set up is easy to understand and the measurement can be quickly made. Stored recipes are readily accessed for scanning different films and patterns. Similar wafers are automatically scanned with a single mouse click. The operator can chose 1, 5, 9, or 49 point circular measurement,  X-Y grid, diameter, or Polar Scans with up to 1000 measurement points and set the wafer edge exclusion. 

high precision stages
High quality stepping motor stages provide precise and repeatable positions. The wafer is held on the optically flat table by vacuum. The stages move automatically in rapid yet precise steps under programmed computer control. Measurement time is less that one second per point including stage travel. Step precision is better than 10 microns, with the area of coverage and points within that area easily set for automatic scanning.

speed and stability
The LSE-WS Ellipsometer measures by reflecting a polarized laser beam from the sample surface at a 70° incident angle and determines the change in polarization caused by the sample virtually instantaneously. Since there are no moving parts in the StokesMeter™ measuring head the measurements are accurate and repeatable even after many months of continuous use. Precision of measurement is further enhanced by the use of a stable, spectrally precise, high signal to noise HeNe laser light source.

description of stokesmeter™ technology
This patented device uses no moving parts and no modulators to quickly and accurately determine the complete polarization state of the measuring beam.

The diagram above shows the StokesMeter™ 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.

technological advantage
The clean, compact StokesMeter™ replaces a typical rotating analyzer assembly consisting of a drum, prism, encoders, switches, motor and detector and their associated electronics. In addition, the waveplate mechanism on the polarizer arm, is eliminated. This results in a fast, precise, stable no moving parts ellipsometer.

An outstanding feature is the Stokes Ellipsometer's compensation for small changes in angular beam deviation caused by sample out-of-flatness. This permits fast, uninterrupted scanning over the entire wafer surface without the need to pause to correct for focus and tilt. When scanning similar wafers, tilt-free, focus-free, hands-off operation at tremendous speed is the obvious benefit.

LSE-WS can be equipped with the following laser options:

 LASER SUBSTITUTION

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 Gas Laser  $4K
LS830    Substitutes 830 nm laser diode in place of 633 nm HeNe Gas Laser $9K

ADD ADDITIONAL LASER FOR A 2 WAVELENGTH ELLIPSOMETER 

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 

ADD TWO ADDITIONAL LASERS FOR A 3 WAVELENGTH ELLIPSOMETER  

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

L-SCAT SOLAR CELL / SCATTERING SAMPLE MEASUREMENT OPTION  $2K

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 software display of the degree of polarization P.

stokes waferskan™ ellipsometer LSE-WS specifications

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