Abstract: The subject invention discloses a method and apparatus for evaluating both the thickness and compositional variables in a layered or thin film sample. Two independent detection systems are provided for measuring thermal waves generated in a sample by a periodic, localized heating. One detection system is of the type that generates output signals that are primarily a function of the surface temperature of the sample. The other detection system generates signals that are primarily a function of the integral of the temperature beneath the sample surface. The two independent thermal wave measurements permit analysis of both thickness and compositional variables. An apparatus is disclosed wherein both detection systems can be implemented efficiently within one apparatus.

Abstract: An apparatus and method is disclosed for evaluating surface conditions on a sample. The system is particularly suited for detecting thin residues encountered in semiconductor lithographic and etching processes. The system is also capable of measuring ion implanted dopant concentrations prior to annealing. The apparatus includes an intensity modulated laser beam which is focused on the surface of the sample to generate periodic heating. A second light beam is focused onto the periodically heated area of the sample in a manner such that it is reflected to a detector. The intensity changes in the probe beam, resulting from the temperature induced changes of reflectivity at the surface of the sample, are measured and evaluated to determine the absence or presence of residues, or to measure the concentrations of ion implanted dopants.

Abstract: A method and apparatus is disclosed for detecting thermal waves. This system is based on the measurement of the change in reflectivity at the sample surface which is a function of the changing surface temperature. The apparatus includes a radiation probe beam that is directed on a portion of the area which is being periodically heated. A photodetector is aligned to sense the intensity changes in the reflected radiation probe beam which results from the periodic heating. These signals are processed to detect the presence of thermal waves.

Abstract: A method and apparatus is disclosed for evaluating surface and subsurface features in a sample by detecting scattering of a probe beam. More particularly, the subject invention relates to the detection of thermal and/or plasma waves through the phenomenon of optical scattering. The apparatus includes a periodic excitation source for supplying energy to the surface of the sample to generate thermal and/or plasma waves. A radiation probe is directed to the surface of the sample within the area that is being periodically excited and in a manner that the probe beam is scattered from the excited area. Variations of the intensity of the scattered probe beam are detected and processed to evaluate surface and subsurface characteristics of the sample.

Abstract: A method and apparatus for thin film thickness measurements with thermal waves in which heating and detection laser beams are focused onto the film, normal to the surface of the film, with the two beams parallel and non-coaxial.

Abstract: A method for measuring thermal waves in a sample is disclosed. More particularly, thermal waves, which may be used for imaging, are generated in a sample through local periodic heating as, for example, by impinging an intensity modulated beam of energy on the surface of the sample. A laser probe is focused on a portion of the heated area on the surface of the sample in a manner such that the beam is reflected from the surface. The angular displacement of the reflected beam, resulting from the local angular change in surface conditions of the sample due to the thermal waves are monitored. By this arrangement, the displacement of the reflected beam can be used to detect the thermal waves.

Abstract: The subject invention discloses a method for non-destructively determining the thickness of layers deposited on a substrate by analyzing thermal waves generated in a sample. The methods are particularly suited for use with integrated circuit manufacturing. In the subject method, the sample is subjected to a focused periodic heat source which generates thermal waves. Either the magnitude or phase of the thermal waves generated in the sample are measured. The values obtained are normalized relative to a reference sample. The normalized values are analyzed with respect to a theoretical model of the sample to calculate the thickness of the unknown layers. In an alternate embodiment, thermal characteristics can be determined in a sample as a function of depth. The latter approach is useful for nondestructively determining dopant concentrations or lattice defects in semiconductor devices as a function of depth beneath the surface.

Abstract: The subject invention relates to a method of evaluating the quality of the bond achieved between two members utilizing thermoacoustic microscopy. More particularly, thermoacoustic microscopy is used to detect and/or image the plate-mode resonant signature of bonded members to determine the quality of the bond therebetween. The method is particularly suited for analyzing the integrity of a bond between an integrated circuit die and a substrate. The subject method takes advantage of the fact that the plate-mode signature of a securely bonded die and substrate combination and a poorly bonded combination will be different. Accordingly, by detecting and/or imaging the plate-mode resonant signature of the sample the integrity of the bond can be assessed. Two techniques for carrying out the subject method are disclosed.