Analysis of Köhler illumination for 193 nm scatterfield microscope

Sohn, Yeung Joon; Quintanilha, R.; Howard, Lowell P.; Silver, Richard M.

doi:10.1117/12.816624

Cited by 5 publications

(6 citation statements)

References 2 publications

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“…Recently, several results have been reported from scatterfield microscopes featuring angular illumination control through a scanned aperture in the CBFP. [5][6][7][8] These demonstrations establish the potential of scatterfield microscopy for semiconductor metrology in many applications. There are three aspects of this microscopy technique that can be optimized.…”

Section: Introductionmentioning

confidence: 90%

193 nm angle-resolved scatterfield microscope for semiconductor metrology

et al. 2009

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An angle-resolved scatterfield microscope (ARSM) featuring 193 nm excimer laser light was developed for measuring critical dimension (CD) and overlay of nanoscale targets as used in semiconductor metrology. The microscope is designed to have a wide and telecentric conjugate back focal plane (CBFP) and a scan module for resolving Köhler illumination in the sample plane. Angular scanning of the sample plane was achieved by linearly scanning an aperture across the 12 mm diameter CBFP, with aperture size as small as 0.4 mm for some scans. For each aperture, the sample was illuminated over a range of angles from 12° to 48°, corresponding to a numerical aperture of 0.2 to 0.74. Angleresolved measurement results are presented for grating targets with nominal linewidths down to 50 nm.

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Section: Introductionmentioning

confidence: 90%

193 nm angle-resolved scatterfield microscope for semiconductor metrology

et al. 2009

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“…The optical path is purged during operation to prevent ozone generation and optical component damage. The new 193 nm instrument has been described elsewhere in detail [8,9]. The main features include an angular scan mode and a full-field illumination modification mode.…”

Section: Nm Defect Inspection Tool: Design and Datamentioning

confidence: 99%

The limits and extensibility of optical patterned defect inspection

et al. 2010

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New techniques recently developed at the National Institute of Standards and Technology using bright-field optical tools are applied to signal-based defect analysis of features with dimensions well below the measurement wavelength. A key to this approach is engineering the illumination as a function of angle and analysis of the entire scattered field. In this paper we demonstrate advantages using this approach for die-to-die defect detection metrology. This methodology, scatterfield optical microscopy (SOM), is evaluated for defect inspection of several defect types defined by Sematech on the Defect Metrology Advisory Group (DMAG) intentional defect array (IDA) wafers. We also report the systematic evaluation of defect sensitivity as a function of illumination wavelength.Theoretical simulations are reported that were carried out using a fully three-dimensional finite difference time domain (FDTD) electromagnetic simulation package. Comprehensive modeling was completed investigating angle-resolved illumination to enhance the detection of several defect types from the IDA wafer designs. The defect types covered a variety of defects from the IDA designs. The simulations evaluate the SOM technique on defect sizes ranging from those currently measurable to those the industry considers difficult to measure. The simulations evaluated both the 65 nm IDA metal-1 M1 trench and the polysilicon stack and more recent 13 nm linewidth logic cells.

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“…The angular scanning mode has a fiber illuminator configuration to improve the angular and intensity illumination homogeneity as compared to aperture scanning the CBFP. 2 The scatterfield microscope can be arranged in many different configurations for measurement in the Fourier plane, yielding combinations of the Jones reflection matrix components. By scanning the CBFP with an aperture, the reflected intensity of the specular and the intensity of the higher diffraction orders can be measured as function of the incident angles and polarization noted by I Φ P,A (θ).…”

Section: Nm Scatterfield Microscopementioning

confidence: 99%

“…By reducing the wavelength we expect to improve the resolution on linewidth measurements. 2 The goal of this preliminary study is to evaluate the possibility in measuring and calibrating future SRM mask using this new microscope. We will first present our new 193 nm scatterfield microscope, then our first results on full-field Fourier imaging for optical indexes measurements.…”

Section: Introductionmentioning

confidence: 99%

“…The CBFP is uniquely designed to be telecentric so that the optical axis of the optical fiber system coincides with the chief optical rays while being scanned. 2 The illumination beam at the sample plane has a defined NA from 0.12 to 0.74 (≈ 6˚to ≈ 48˚), limited by the catadioptric infinity-corrected objective lens. A pellicle beam splitter splits off the collected light from the objective to one of two Charge-Coupled Device (CCD) sensors.…”

Section: Introductionmentioning

confidence: 99%

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Photomask metrology using a 193nm scatterfield microscope

et al. 2009

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The current photomask linewidth Standard Reference Material (SRM) supplied by the National Institute of Standards and Technology (NIST), SRM 2059, is the fifth generation of such standards for mask metrology. The calibration of this mask has been usually done using an in house NIST ultra-violet transmission microscope and an Atomic Force Microscope (AFM). Recently, a new optical reflection scatterfield microscope has been developed at NIST for wafer inspection, Critical Dimension (CD) and overlay metrology purposes. Scatterfield microscopy relies on illumination engineering at a sufficiently large Conjugate Back Focal Plane (CBFP) of the microscope. 1 Our new scatterfield reflection microscope uses 193 nm excimer laser light as well as sophisticated configurations to allow measurement of both the image plane and the Fourier plane using full-field and angle-resolved illumination. By reducing the wavelength compared to many current metrology tools that work in the visible light and near ultra-violet range, we have made substantial improvements in image resolution 2 and commensurate gains in sensitivity to geometrical parameters. We present a preliminary study on the use of this new microscope to calibrate and measure features of this SRM photomask. The 193 nm scatterfield microscope is used in full-field mode with a NA range from 0.12 to 0.74 using our scatterfield imaging method. Experimental results obtained on isolated lines for different polarization states of the illumination are presented and discussed. Pitch measurements are compared to the measurements done on our NIST Ultra-Violet (UV) transmission microscope.

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Analysis of Köhler illumination for 193 nm scatterfield microscope

Cited by 5 publications

References 2 publications

193 nm angle-resolved scatterfield microscope for semiconductor metrology

193 nm angle-resolved scatterfield microscope for semiconductor metrology

The limits and extensibility of optical patterned defect inspection

Photomask metrology using a 193nm scatterfield microscope

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