Abstract: Quality control of a periodic structure is performed using the damping rate of acoustic waves generated in the periodic structure. In this technique, an excitation light beam illuminates the first layer in the periodic structure to excite an acoustic wave. Possible irregularities in the periodic structure can scatter the acoustic wave, thereby increasing the damping rate of the acoustic wave. A sequence of probe light beams illuminates the periodic structure to measure the acoustic wave as a function of time to generated a temporal signal representing the damping rate of the acoustic signal. The acquired damping rate is employed to evaluate the quality of the periodic structure.

Abstract: Quality control of a periodic structure is performed using the damping rate of acoustic waves generated in the periodic structure. In this technique, an excitation light beam illuminates the first layer in the periodic structure to excite an acoustic wave. Possible irregularities in the periodic structure can scatter the acoustic wave, thereby increasing the damping rate of the acoustic wave. A sequence of probe light beams illuminates the periodic structure to measure the acoustic wave as a function of time to generated a temporal signal representing the damping rate of the acoustic signal. The acquired damping rate is employed to evaluate the quality of the periodic structure.

Abstract: The invention represents an improved method of measuring trenches on semiconductor wafers with optical spectroscopy. According to the described method, it is possible to characterize not only depth but also shape of the trench. The advancement is achieved by improved Effective Medium Approximation-based modeling of the optical response of trench structures.

Abstract: The invention represents an improved method of measuring trenches on semiconductor wafers with optical spectroscopy. According to the described method, it is possible to characterize not only depth but also shape of the trench. The advancement is achieved by improved Effective Medium Approximation-based modeling of the optical response of trench structures.

Abstract: The present invention uses ISTS to measure trenches with near- or sub-micron width. The trenches can be etched in a thin film on in a silicon substrate. One step of the method is exciting the structure by irradiating it with a spatially periodic laser intensity pattern in order to generate surface acoustic waves. Other steps are diffracting a probe laser beam off the thermal grating to form a signal beam; detecting the signal beam as a function of time to generate a signal waveform; determining surface acoustic wave phase velocity from the waveform; and determining at least one property of the trench structures based on the dependence of surface acoustic wave phase velocity on the parameters of the structure.

Abstract: The present invention uses ISTS to measure trenches with near- or sub-micron width. The trenches can be etched in a thin film on in a silicon substrate. One step of the method is exciting the structure by irradiating it with a spatially periodic laser intensity pattern in order to generate surface acoustic waves. Other steps are diffracting a probe laser beam off the thermal grating to form a signal beam; detecting the signal beam as a function of time to generate a signal waveform; determining surface acoustic wave phase velocity from the waveform; and determining at least one property of the trench structures based on the dependence of surface acoustic wave phase velocity on the parameters of the structure.

Abstract: The present invention measures a structure including multiple narrow metallic regions, each being disposed between neighboring regions comprising a second, non-metallic material. One step of the method is exciting the structure by irradiating it with a spatially periodic excitation field made up of excitation stripes in order to generate a thermal grating. Other steps are diffracting a probe laser beam off the thermal grating to form a signal beam; detecting the signal beam as a function of time to generate a signal waveform; and determining at least one property of the structure based on a thermal component of the signal waveform.

Abstract: Structures are characterized by exposing a sample to optical radiation, measuring a spectrum associated with the exposure, detecting at least one characteristic parameter in the measured spectrum, and computing at least one structural parameter based on the at least one characteristic parameter.

Abstract: In an opto-acoustic measuring device for thin films and solid surfaces, the probe beam is split into a first probe beam portion and a second reference beam portion. The splitting of the probe beam is achieved using a phase mask that also splits the excitation beam. The probe beam is aligned using a retro-reflector on a motorized stage to control the beam angle. Excitation and probe/reference beams are overlapped at the sample surface. The first probe beam portion gets diffracted by material disturbances generated by excitation beams. The diffracted part of the first probe beam portion is collinear with the second reference beam portion, resulting in heterodyning. The heterodyne signal measured by the detector is analyzed in order to determine thickness and/or other properties of a thin film or solid surface. The invention improves magnitude and reproducibility of the opto-acoustic signal which results in enhanced precision of measurements.

Abstract: The present invention provides a new method of laser-based metrology of very thin solid films (22) based on the generation of the refractive index grating in the gas or liquid medium in contact with the film (22). In a primary embodiment, excited acoustic waves (25) in the gas or liquid medium modulate an intensity of the diffracted probe beam resulting in a low-frequency component of the signal compared to the frequencies of the acoustic modes excited in the solid sample. Amplitude of this low-frequency component is correlated with the amount of energy absorbed by the film (22), and, consequently, with the film thickness, which provides a method for film thickness measurement as well as for a detection of a metal film on a dielectric underlayer.

Abstract: A method for measuring the thickness of a film is based on monitoring a transient change of the reflectivity of the film following an impulsive heating. The method includes the steps of impulsively irradiating a surface of the film with an excitation pulse to cause a rise in temperature in the film; irradiating the surface of the film with a probe beam, such that it reflects off the surface of the film to generate a reflected probe beam; detecting a time-dependent variation in intensity of the reflected probe beam; generating a signal waveform based on the measured variations in intensity; and determining the thickness of the film based on the signal waveform.

Abstract: The present invention measures a structure including multiple narrow metallic regions, each being disposed between neighboring regions comprising a second, non-metallic material. One step of the method is exciting the structure by irradiating it with a spatially periodic excitation field made up of excitation stripes in order to generate a thermal grating. Other steps are diffracting a probe laser beam off the thermal grating to form a signal beam; detecting the signal beam as a function of time to generate a signal waveform; and determining at least one property of the structure based on a thermal component of the signal waveform.

Abstract: In an opto-acoustic measuring device for thin films and solid surfaces, the probe beam is split into a first probe beam portion and a second reference beam portion. The splitting of the probe beam is achieved using a phase mask that also splits the excitation beam. The probe beam is aligned using a retro-reflector on a motorized stage to control the beam angle. Excitation and probe/reference beams are overlapped at the sample surface. The first probe beam portion gets diffracted by material disturbances generated by excitation beams. The diffracted part of the first probe beam portion is collinear with the second reference beam portion, resulting in heterodyning. The heterodyne signal measured by the detector is analyzed in order to determine thickness and/or other properties of a thin film or solid surface. The invention improves magnitude and reproducibility of the opto-acoustic signal which results in enhanced precision of measurements.

Abstract: An apparatus for measuring a property of a structure comprising at least one layer, the appratus including a light source that produces an optical pulse having a duration of less than 10 ps; a diffractive element that receives the optical pulse and diffracts it to generate at least two excitation pulses; an optical system that spatially and temporally overlaps at least two excitation pulses on or in the structure to form an excitation pattern, containing at least two light regions, that launches an acoustic wave having an out-of-plane component that propagates through the layer, reflects off a lower boundary of the layer, and returns to a surface of the structure to modulate a property of the structure; a light source that produces a probe pulse that diffracts off the modulated property to generate at least one signal pulse; a detector that receives at least one signal pulse and in response generates a light-induced electrical signal; and an analyzer that analyzes the light-induced electrical signal to measur