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GAERTNER L116S300 STOKES ELLIPSOMETER

The model L116S300 for up to 300mm wafers builds on the production proven Gaertner 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 L116S300 model sets a new and 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. Windows LGEMP and optional LMOD modeling software permits multiparameter measurements utilizing the manually selectable angles of incidence.

The Ellipsometer measures by reflecting a polarized laser beam from the sample surface at one of eight available incident angles 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.

Features


The L116S300, based on advanced StokesMeter™ technology, offers instantaneous measurement at a low cost and is upgradeable to the Imaging Waferskan, Two or Three Wavelength ellipsometers.

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

  • Fastest possible instrument for thin film measurement.

  • Variable angle useful for difficult to measure films.

  • 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 tabletop instrument - competitively priced.

An outstanding feature is the Stokes Ellipsometer's compensation for small changes in angular beam deviation caused by sample thickness changes. This permits fast, uninterrupted measurement over the entire wafer surface without the need to pause to correct for focus and tilt. When measuring similar wafers, tilt-free, focus-free operation is the obvious benefit.

This advanced 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.

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.