Rotatable Offner imaging system for ellipsometric measurement

Abstract

To realize high spatial resolution imaging ellipsometric measurement with large field of view, we developed a rotatable Offner system with unit magnification. When the conventional Offner imaging system is tilted relative to the sample plane for the ellipsometric measurement, only a small region of plane is in focus. The rotatable Offner system developed here renders the entire object in focus through all rotations. The performance of the prototype of the Offner system and imaging ellipsometer is tested by generating maps of the ellipsometric parameters Δ and Ψ for samples such as a silicon wafer and a resolution target made of chromium film evaporated on a glass substrate.

Reflection and transmission ellipsometry measurement under incoherent superposition of light

“…For the Si thin film / quartz (Si/SiO2) sample, the reflection and transmission ellipsometric parameters were acquired with a home-built ellipso-microscope, which can be used in either reflection or transmission configurations. Figures 1 illustrates the optical arrangement of the ellipso-microscope, which was built based on our previous work [13][14][15][16]. The light from the Xenon lamp passes through an optical filter (=5905 nm), a convergence lens system (NAc=0.0088), a linear Gran-Thompson polarizer, and a compensator (a quarter wave-plate).…”

“…The light from the Xenon lamp passes through an optical filter (=5905 nm), a convergence lens system (NAc=0.0088), a linear Gran-Thompson polarizer, and a compensator (a quarter wave-plate). The reflected light from the sample surface (in reflection mode) and transmitted light through the sample (in transmission mode) pass through an analyzer and an Offner imaging catoptrics system [13,17] (NAi=0.07), and then is collected by a complementary metal-oxide-semiconductor (CMOS) device (2592×1944 pixels, pixel size 2.2 m, 12 Bit). The incidence angle is adjustable from 45° to 65°.…”

“…To receive the entire image in focus for oblique illumination and observation system, at each incidence angle, the CMOS device was reconfigured and aligned to keep the planes of image (the detection plane of the CMOS) and object (sample surface) parallel, so that the imaging system fulfils the Scheimpflug condition [17]. The Offner imaging system is telecentric in both object and image spaces, and possesses unit magnification [13,17]. The traditional ellipsometric parameters  and  were obtained by using the rotating compensator method [19,20,21].…”

Characterization of thin films from reflection and transmission ellipsometric parameters

“…2,3) Single point measurement spectroscopic ellipsometry [4][5][6] is currently the mainstream of the instrumentation. Some ellipsometry like phase-modulated ellipsometry 7) and imaging ellipsometry [8][9][10] have the need for wavelength-by-wavelength measurements to obtain ellipsometric parameters spectra. The necessity of wavelength-bywavelength measurements, by scanning incident or output lights with an optical filter or monochromator, drags down the speed of the whole data acquirement.…”

Lateral ellipsometry resolution for imaging ellipsometry measurement

“…The prototype imaging ellipsometer was built based on our previous work. 9,15) Figure 1(a) illustrates the optical arrangement of the instrument. The light from the Xenon lamp passes through an optical filter (λ = 650 ± 10 nm), a convergence lens system (NA c = 0.0088), a linear Gran-Thompson polarizer, and a compensator.…”