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    • 专利摘要:
    The invention comprises a method for inspecting a wafer (2) for electronics, optics or optoelectronics, comprising: - rotating the wafer (2) about a perpendicular axis of symmetry to a main surface (S) of said wafer, - the emission, from at least one light source (20), of at least two pairs of incident coherent light beams, each pair being arranged to form, at least one intersection between the two beams, a respective measurement volume containing interference fringes having a distance interfranges different from that of another measurement volume, at least a portion of the main surface (S) of the wafer passing through each said measuring volumes during the rotation of the wafer, - the collection of a light beam scattered by the surface of the wafer, - the acquisition of the collected light and the emission of an electrical signal representing the variation of intensity light of the light collected as a function of time, - the detection, in said signal, of a frequency component, said frequency being the time signature of the passage of a fault in a respective measurement volume, - for each detected signature, the determination of a parameter, said visibility of the defect, dependent on the interfrange distance of the respective measuring volume and the size of the defect, - starting from the visibility determined for each measurement volume, obtaining respective information on the size of the said defect, - the overlapping of the information obtained for each measurement volume in order to determine the size of the defect.
    公开号:FR3026485A1
    申请号:FR1459172
    申请日:2014-09-29
    公开日:2016-04-01
    发明作者:De Gevigney Mayeul Durand；Philippe Gastaldo
    申请人:Altatech Semiconductor；
    IPC主号:
    专利说明:

    [0001] TECHNICAL FIELD OF THE INVENTION The present invention relates to a method and system for inspecting wafers for electronics, optics or the like. optoelectronics. BACKGROUND OF THE INVENTION In the manufacture and use of wafers for electronics, optics or optoelectronics, it is customary to carry out an inspection of the surface of each wafer to detect any defects. Due to the very small size of the defects to be detected, a visual inspection by an operator is not sufficient.
    [0002] Furthermore, the inspection is generally not only intended to detect the presence or absence of defects, but also to provide qualitative and / or quantitative information on such defects, such as their location, size and / or nature, for example . Inspection systems have therefore been developed to detect smaller and smaller defects and to provide all required information on the nature, size, location, etc. said defects. These systems must also allow a duration of inspection of each wafer which is short enough not to penalize production rates. The document VVO 2009/112704 describes a semiconductor wafer inspection system using laser velocimetry Doppler effect (LDV, acronym for the English term "Laser Doppler Velocimetry"). As can be seen in FIG. 1, this system comprises a light source 20 and an interferometer device 30 coupled to the light source arranged facing the surface S of the wafer 2 to be inspected, which is animated by a movement. Said interferometric device comprises a light guide whose input is coupled to the light source and comprising two branches for dividing the beam from the light source into two incident beams. At the exit of the light guide, the two branches are oriented relative to each other so as to form, at the intersection between the two beams, a measurement volume comprising a plurality of parallel fringes. The system furthermore comprises an optical fiber 40 arranged between the surface of the wafer and a detection module 50, so as to guide the detection module with the light retro-diffused by the surface of the wafer.
    [0003] VVO 02/39099 discloses another semiconductor wafer inspection system based on Doppler laser velocimetry. The presence of a defect on the surface of the wafer is translated, when this fault crosses the interference fringes, by the diffusion of a Doppler puff measured by the detection module. A Doppler burst is a signal with a dual frequency component: a low frequency component, forming the signal envelope, corresponding to the average light intensity scattered by the defect, and a high frequency component corresponding to the Doppler frequency containing information on the speed of the fault. The Doppler frequency fp is related to the speed v of displacement of the defect in the direction perpendicular to the fringes and to the distance A between the interference fringes (or interfringe distance) by the relation: y = f * A. FIG. a Doppler burst due to the passage of a fault in the interference zone, expressed in the form of a voltage (in Volts) at the output of the detection module as a function of time.
    [0004] From such a Doppler burst, it is possible to determine the size of the defects detected on the surface of the wafer. In this regard, see WM Farmer's publication "Measurement of Particle Size, Number Density, and Velocity Using a Laser Interferometer," which presents a model of particle visibility based on particle size. . Thus, for a figure of given interference fringes, the relation between the size of a defect assimilated to a sphere, which is defined as the diameter of the sphere, and the visibility determined according to the formula above, is given by a curve of the type of that illustrated in FIG.
    [0005] It is observed that, for a visibility greater than 0.15, the curve of FIG. 3 provides a single defect size corresponding to a given visibility value. However, for a visibility of less than 0.15, the curve has rebounds, reflecting the fact that the same visibility value can correspond to several sizes of defects. Thus, in the example of FIG. 3, a visibility of 0.1 corresponds to three sphere radii: 0.83 μm, 1.12 μm and 1.45 μm. In such a case, there is therefore the problem of determining, among these different possible sizes, the actual size of the defect present on the wafer. In particular, this technique does not make it possible to measure the size of defects whose sizes are very different. Indeed, as seen in Figure 3, it is not possible to determine the size of defects whose size is greater than 0.9 pm (corresponding to visibility less than 0.15).
    [0006] However, the size of defects that can be detected on a wafer extends over a wide range of dimensions, typically from a few tens of nanometers to a few hundred micrometers. Another disadvantage of the curve-based technique of FIG. 3 is that, for certain defect sizes (for example a radius of 0.95 pm), the visibility is zero, ie no flush Doppler does not occur. Therefore, a fault of this size can not be detected. BRIEF DESCRIPTION OF THE INVENTION An object of the invention is to overcome the aforementioned drawbacks and to define a system and a method of inspection of wafers which make it possible to detect any defects possibly present on the wafer and having a size greater than a few tens of nanometers, and to determine in a certain way the size of each defect detected. This system and method should further exhibit improved detection dynamics over existing systems and methods, ie greater ability to detect a large number of defects and evaluate their size in a short time. over a wide range of defects. According to the invention, there is provided a method of inspecting a wafer for electronics, optics or optoelectronics, comprising: - rotating the wafer about an axis of symmetry perpendicular to a main surface of said wafer, - the emission, from at least one light source, of at least two pairs of incident coherent light beams, each pair being arranged to form, at the intersection between the two beams, a respective measurement volume containing interference fringes having a distance interfranges different from that of another measurement volume, at least a portion of the main surface of the wafer passing in each of said measuring volumes during the rotation of the wafer, - the collection of a light beam scattered by the surface of the wafer, - the acquisition of the collected light and the emission of an electrical signal representing the variation of the intensity the luminous frequency of the light collected as a function of time, the detection, in said signal, of a frequency component in the variation of the intensity of said collected light, said frequency being the time signature of the passage of a defect in a respective measurement volume, - for each detected signature, the determination of a parameter, called visibility of the defect, dependent on the interfrange distance of the respective measurement volume and the size of the defect, - from the visibility determined for each volume measuring, obtaining a respective information on the size of said defect, - the cross-checking of the information obtained for each measurement volume to determine the size of the defect.
    [0007] Particularly advantageously, obtaining information on the size of the defect comprises: - calculating the visibility of the defect in each measurement volume, - for each measurement volume, from a reference curve of the visibility according to the size of the defect for the respective interframe distance, the determination of one or more possible sizes for the defect. Preferably, said method comprises filtering the signal with a bandpass filter whose bandwidth integrates the Doppler frequency associated with each measurement volume. According to one embodiment, said measurement volumes are at least partially superimposed. According to another embodiment, said measurement volumes follow one another along the rotational path of the wafer. Particularly advantageously, the method further comprises a radial displacement of said measurement volumes relative to the wafer. As a general rule, the fringes of each measurement volume are oriented transversely to the rotational path of the wafer. According to a particularly advantageous embodiment, the interferometric device is an integrated optical device comprising a light guide whose input is coupled to the light source and which is divided into two pairs of branches whose output is oriented to form a volume respective measurement at the intersection of the two beams of each pair. According to one embodiment of the invention, the wafer is at least partially transparent vis-à-vis the wavelength of the light source and each measurement volume extends in a region of the wafer having a thickness less than 30 the thickness of said wafer. Another object relates to a platelet inspection system for electronics, optics or optoelectronics, comprising: - a device for driving a wafer in rotation about an axis of symmetry perpendicular to a main surface of said wafer, at least one light source, at least one interferometric device coupled to the light source for dividing the beam emitted by said source into two beams and for forming, at the intersection between the two beams, a volume of respective measurement containing interference fringes having a distance interfranges different from that of another measurement volume. a device for collecting light scattered by the wafer; a device for acquiring the collected light configured to emit an electrical signal representing the variation of the light intensity of said light collected as a function of time; processing configured to: * detect, in said signal, a frequency component in the variation of the intensity of said collected light, said frequency being the time signature of the passage of a fault in a respective measurement volume, * for each detected signature , the determination of a parameter, said visibility of the defect, depending on the interfrange distance of the respective measuring volume and the size of the defect, * obtain, from the visibility determined for each measuring volume, respective information on the size of said defect, and * cross-check the information obtained for each measurement volume to determine the size of the defect aut. According to an advantageous embodiment, said system comprises a single light source and a single interferometric device to form all the measurement volumes. According to a preferred embodiment, the interferometric device is in the form of an integrated optical device comprising a light guide whose input is coupled to the light source and which is divided into two pairs of branches whose output is oriented to form a respective measurement volume at the intersection of the two beams of each pair. Particularly advantageously, said system further comprises an arm for moving the interferometric device and the device for collecting the diffusively diffused beam in a radial direction.
    [0008] BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings in which: FIG. 1 is a block diagram of an inspection system based on the Doppler laser velocimetry, as described in document VVO 2009/112704, - FIG. 2 illustrates an exemplary Doppler burst, - FIG. 3 is a diagram illustrating the visibility (unitless quantity) of a defect equated with a sphere according to its size (in this case the radius of the sphere expressed in micrometers), - Figure 4 is a block diagram of the inspection system according to one embodiment of the invention, - Figures 5A and 5B are schematic diagrams of the interferometric device according to two embodiments of the invention; FIG. 6 is a diagram illustrating the visibility (without unit) of a defect likened to a sphere as a function of its size (radius of the sphere in μm), for an inspection system according to the invention; FIG. 7 illustrates the principle of detection of defects using a number N greater than or equal to two of measurement volumes.
    [0009] To facilitate the reading of the figures, they are not necessarily made to scale. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION In the present invention, we are interested in any wafer intended to be used in the field of electronics, optics or optoelectronics. In particular, the wafer may comprise at least one of the following materials: Si, Ge, GaN, SiC, glass, Quartz, Sapphire, GaAs (non-limiting list). Furthermore, the wafer material may or may not be at least partially transparent to the wavelength of the light source of the inspection system. Indeed, according to a particularly advantageous embodiment which will be described in detail below, the inspection system provides a controlled depth of field to control the position of the measurement volume with respect to the wafer, ensuring that the region of the wafer in which the measurement volume extends has a thickness less than the thickness of the wafer. This ensures that the detected defects are on the surface to be inspected or close to it, and not on the opposite surface. To allow unambiguous determination of the size of a detected defect and make each defect visible regardless of its size in a range of about ten nanometers to a few hundred micrometers, the invention proposes forming at least two measurement volumes. containing interference fringes and each having a different interfringe distance. The measurement volumes are arranged relative to one another so that a defect of the wafer passes in each of the measurement volumes and generates, if necessary, a respective Doppler burst.
    [0010] Figure 4 is a block diagram of an inspection system 1 implementing such measurement volumes. The system comprises a support 10 intended to receive a wafer 2 to be inspected and to rotate it about an axis of symmetry X of the wafer perpendicular to a main surface S of said wafer. In general, the wafer is circular but the invention can be applied to any other form. The wafer 2 is held on the support 10 by any appropriate means, such as electrostatic means, mechanical means, etc.
    [0011] The mechanism for rotating the support is known per se and will therefore not be described in detail. The support 10 comprises one or more encoders (not shown) to know at any time the angular position of the wafer. The inspection system 1 further comprises a light source 20.
    [0012] The light source 20 is typically a DFB laser (acronym for the English term "Distributed Feed Back"). The light source is coupled to an interferometric device 30 which will be described in detail with reference to FIG. 5. The interferometric device 30 is designed to form at least two measurement volumes (of which only one is shown diagrammatically in FIG. 4 under the reference V ) with different interfringe distances. These measurement volumes can be totally or partially in the same space. As will be explained below with reference to FIG. 6, the interfringe distances are chosen so that the visibility curves associated with each of these measurement volumes are sufficiently different from one another that a non-visible defect in one of the measuring volumes is visible in the other measurement volume, and to remove any ambiguities concerning the size of the detected defects. It is conceivable that the inspection system comprises several interferometric devices each coupled to a light source to form a respective measurement volume, but this embodiment is less advantageous in terms of size and cost. Therefore, preferably, the inspection system comprises a single light source and a single interferometric device adapted to form the different measurement volumes. The inspection system further comprises a device 40 for collecting the light retro-diffused by the surface of the wafer. This device 40 may comprise an optical fiber, preferably of large core diameter (that is to say, typically between 100 and 1000 μm in diameter), the input of which is arranged opposite the surface of the wafer, in the vicinity measuring volumes, and whose output is coupled to a device 50 for collecting the collected light to emit an electrical signal representing the variation of the light intensity of the collected light as a function of time. Said device 50 typically comprises a photodetector. Preferably, the interferometric device 30 and the device 40 for collecting the backscattered light are rigidly secured to one another. Indeed, the input of the collection device 40 must be positioned appropriately with respect to the measurement volumes to receive the light backscattered by the wafer. Finally, the inspection system 1 comprises a processing device 60 configured to detect, in said signal, a frequency component corresponding to the Doppler frequency. The processing device 60 is advantageously coupled to an interface (not shown) allowing a user to access the results in order to view, save and / or print them. In the case where the wafer is at least partially transparent vis-à-vis the wavelength of the light source, it ensures that the region in which each measurement volume extends has a thickness less than that of the wafer. The thickness of said region is preferably less than or equal to 90% of the thickness of the wafer. For example, for a wafer of 500 μm to 1 mm thickness, the measurement volumes are made to extend in a region of the wafer having a thickness less than or equal to 100 μm. The dimension of the measurement volume is characteristic of the interferometric device and is defined by the angle between the two branches of the light guide in which propagates the light beam emitted by the source and the numerical aperture of said branches. In this respect, it should be noted that the inspection systems presently on the market do not make it possible to satisfactorily inspect transparent wafers. Indeed, in the case of systems based on the dark field inspection technique ("dark field"), the incident beam passes through the thickness of the wafer and any defect, whether present on the surface to be inspected, on the opposite surface or in the thickness of the substrate, generates diffused light. It is therefore not possible, with such a system, to know if each detected defect is on the surface to be inspected or not. In addition, KLA-Tencor offers a transparent plate inspection system called Candela TM, dark field illumination and confocal detection. However, this system is particularly difficult to develop because of the positioning accuracy required for confocal detection, and thus does not provide repeatable results. The system used in the invention eliminates the constraints related to the "dark field" technique and the confocal detection technique by detecting the defects 35 by a frequency signature, which can only be transmitted by faults crossing a measurement volume. In such a system, the positioning of the interferometric device must therefore be precisely adjusted with respect to the surface of the wafer to be inspected, but the device for collecting the backscattered light does not require such a high positioning accuracy since it is by the Doppler frequency that is carried out the restriction of the measurement volume and thus the detection. Furthermore, to inspect transparent wafers, the preferred embodiment of the interferometric device is an integrated optical device as described below. Such a device makes it possible to control the depth of field of the inspection system. On the other hand, the size measurement by a visibility calculation is independent of the position of the fault in the measurement volume. To inspect a wafer, said wafer 2 is placed on the support 10 and the support is rotated at a controlled angular speed w. Thanks to the encoders present on the support 10, one knows at every moment the angular position of a given point of the wafer. The speed of rotation of the wafer is typically of the order of 5000 revolutions / min. In the inspection system 1, the interferometer device 30 is arranged facing a main surface of the wafer 2, on an arm (not shown) adapted to move said device 30 in a radial direction. Thus, taking into account the rotation of the wafer, one can successively scan the entire surface of the wafer with the measurement volumes by radially translating the interferometric device and the collection device of the backscattered light. The two measurement volumes are formed on the same side of the wafer, to ensure that a fault passes in all the measurement volumes. The interference fringes of each measurement volume are oriented transversely to the rotational path of the wafer, so that the defects are traversed. The inclination between the fringes and the rotational path of the wafer may be perpendicular or at another non-zero angle.
    [0013] According to the principle of the method of WM Farmer mentioned above, the visibility of a defect detected by the formula is calculated for each measurement volume: - / mi, / m '+ / mi, - 2 * Offset where lmax and Imin (in V) define the minimum voltage and the maximum voltage defining the peak of the Doppler burst, and Offset (in V) is the shift between the average value of the signal and the abscissa axis corresponding to a zero voltage ( see Figure 2). This shift, which does not appear in W.M. Farmer's formula, is related to the measurement conditions and takes into account the fact that, even in the absence of a fault, a small amount of light scattered by the surface can be detected. Moreover, a plurality of reference curves of the type of FIG. 3 are recorded in a memory of the processing device, each reference curve defining the visibility of a defect in a respective measurement volume according to the size of the defect. .
    [0014] In one embodiment of the invention, the measurement volumes follow each other along the rotational path of the wafer, at the same radial distance from the axis of rotation of the wafer. Thus, the defects successively pass through the different measurement volumes during the rotation of the wafer.
    [0015] According to another embodiment of the invention, the measurement volumes are at least partly superimposed. Indeed, subject to implementing bandpass filtering integrating the Doppler frequency associated with each interfringe distance and therefore with each measurement volume, the signal emitted by the photodetector contains only the information related to these measurement volumes and makes it possible to to distinguish them. By "integrating" is meant here that the bandwidth of the filter comprises the Doppler frequency and a low frequency range around this Doppler frequency. FIGS. 5A and 5B are schematic diagrams of two embodiments of an interferometric device making it possible to form two measurement volumes containing interference fringes and each having a different interfrange distance.
    [0016] In the case of Figure 5A, the measurement volumes are adjacent; in the case of Figure 5B, the measurement volumes are at least partially superimposed. This device 30 comprises a light guide 31 whose input 32 is coupled to the light source 20 and comprising two main branches 33, 34 symmetrical to divide the beam from the light source into two incident beams.
    [0017] Each branch 33, 34 divides itself into two symmetrical secondary branches 33a, 33b and 34a, 34b respectively. At its end, each secondary branch has an enlarged portion intended to widen the beam while retaining a Gaussian profile. At the exit of the light guide, the secondary branches of each pair are oriented relative to each other so as to form, at the intersection between the two beams, a measurement volume containing parallel interference fringes . As shown diagrammatically in FIG. 5A, the pair 33a, 33b forms a measurement volume whose interfrange distance has a value M and the pair 34a, 34b forms a measuring volume whose interfrange distance has a value 32 different from M.
    [0018] The device of FIG. 5B obeys the same principle as that of FIG. 5A but the fringes have not been represented to simplify the figure. In this embodiment, the different branches are nested symmetrically so that the measurement volumes created at the output of said branches substantially coincide. Particularly advantageously, the interferometric device is in the form of an integral sensor consisting of a single piece and ensuring both the separation of the beam emitted by the light source and the transmission of the pairs of branches of the beam to form the interference volumes at the sensor output. It is recalled that an integrated optical device is an optical device manufactured by microelectronics techniques. The article "Integrated Laser Doppler Velocimeter for Fluid Velocity and Wall Friction Measurements" by P. Lemaitre-Auger et al. describes such a sensor (which comprises in this case a single main branch and two secondary branches, so as to form a single measurement volume). Such a sensor is manufactured in particular by the company A2 Photonic Sensor and marketed under the reference lLDATM. The same manufacturing method as that described in the aforementioned article can be implemented to integrate within the sensor several light guides to form several measurement volumes. By way of example, the integrated optical device can be manufactured by ion exchange on a glass substrate. This method generally comprises: providing a glass substrate; depositing a metal masking layer on said glass substrate; depositing a polymer layer on the metal layer; photolithographic transfer of a pattern defining the shape of the light guide on the polymer layer; - the chemical etching of the metal masking layer by means of a chemical process in the areas left exposed by the polymer mask; removal of the polymer mask, - immersion of the substrate covered with the metal masking layer etched in an ion bath (for example a potassium nitrate bath), - exchange of ions present in the bath (for example potassium ions) and ions contained in the glass (eg sodium ions) through areas of the substrate not covered by the metal masking layer, the latter blocking the passage of ions. Due to the difference in size between the ions present in the bath and the ions present in the glass, the ion exchange generates in the glass substrate local mechanical stresses which increase the refractive index of the glass. This gives the light guide mentioned above. The masking layer is then removed and a protective layer, for example SiO 2, is optionally deposited. Finally, the edges of the substrate are cut and finely polished. There are other methods of manufacturing integrated optical devices and the skilled person can choose from the microelectronics technologies at his disposal to design the integrated optical device. Optionally, the integrated optical device may be further associated with an optical fiber for collecting the backscattered light.
    [0019] An advantage of this integrated device is its robustness and stability. In particular, unlike a system made by other techniques such as micro optics or optical fibers, the compactness of the integrated device and the integration of the various components make it insensitive to vibration and temperature gradients.
    [0020] Advantageously, when it is desired to inspect wafers at least partially transparent to the wavelength of the light source, the thickness of the region of the wafer in which the measurement volume extends is made less than the thickness of the wafer (this region including a portion of the surface to be inspected). The thickness of said region is preferably less than or equal to 90% of the thickness of the wafer. For example, for a wafer of 500 μm to 1 mm thickness, the measurement volume is made to extend in a region of the wafer having a thickness less than or equal to 100 μm. The dimension of the measurement volume is characteristic of the interferometric device and is defined by the angle between the two branches of the light guide in which propagates the light beam emitted by the source and the numerical aperture of said branches. These characteristics are therefore fixed during the manufacture of the integrated optical device, which ensures a good control of system performance during its production series. Thus, it is possible to limit this measurement volume to the surface of the wafer or to a region of the vicinity of said surface. This ensures that the detected defects are on the surface to be inspected or close to it, and not on the opposite surface of the wafer. An integrated optical device has an additional advantage in this context, since its stability makes it possible to avoid a drift of the depth of field. The control of the depth of field allowed by the integrated device thus facilitates the inspection of transparent platelets by Doppler laser velocimetry. It will be noted that, in contrast, the control of the depth of field is of less importance for the inspection of an opaque wafer insofar as the measurement volume does not penetrate into the thickness of such a wafer, it is sufficient for a part of the surface of the wafer to pass into the measurement volume to allow the inspection of said surface. As indicated in the aforementioned article, the interfringe distance depends on the wavelength of the light source, the optical index of the light guide and the angle between the two secondary branches. For a given wavelength of the light source, the interfringe distance is thus fixed during the manufacture of the integrated optical device. Figure 6 shows two examples of visibility curves according to the size of the fault for two different interfringe distances.
    [0021] Curve (a) corresponds substantially to the curve of FIG. 3. It can be observed that curve (b) has fewer "rebounds" corresponding to zero visibility than curve (a), and that said points of zero visibility do not coincide. not with the points of zero visibility of the curve (a).
    [0022] Thus, if a defect has zero visibility in the measurement volume corresponding to the curve (a), it is not detectable via the curve (a); on the other hand, since it has a non-zero visibility in the measurement volume corresponding to the curve (b), it is detectable by means of said curve (b). For example, a defect of 1.7 pm radius has zero visibility on the curve (a) but a visibility of about 0.22 on the curve (b) and will be detectable on the curve (b). Moreover, this shift of the visibility curves makes it possible to remove the ambiguities on the size of the defects detected by cross-checking the information provided by the two curves. Indeed, by choosing visibility curves sufficiently distant from each other, a visibility corresponding to several possible fault sizes on one of the curves will only correspond to one defect size on the other curve. For example, a defect of 1.5 μm has a visibility of 0.07 on curve (a). However, a visibility of 0.07 corresponds, on curve (a), to four defect sizes: 0.8 μm, 1 μm, 1.5 μm and 2 μm; this single visibility value does not allow us to conclude on the size of the detected defect. On the other hand, this same defect of 1.5 pm of radius has, on the curve (b), a visibility of 0.33. Therefore, knowing the visibilities of 0.07 and 0.33 makes it possible to conclude unambiguously that the radius of the detected defect is 1.5 μm. Those skilled in the art are able to determine the interfringe distance of each measurement volume to allow the determination of the size of a defect throughout the size range to be detected. Based on curves of the type of that of Figure 3, which can be obtained by simulation according to the method described by WM Farmer, the skilled person will seek to have sufficiently large visibility for each measurement volume and avoid cases where the combination of the information collected from each measurement volume can correspond to several sizes of defects. Although the embodiments have been described so far with two measurement volumes having distinct interfrange distances, the invention can more generally be implemented with an integer number N greater than or equal to two of measurement volumes each having a specific interfringe distance. With three or more measurement volumes, the accuracy of determining the size of the defects is indeed further increased. FIG. 7 is a logic diagram illustrating the fault detection chain with a number N of measurement volumes greater than two.
    [0023] The light source 20 is coupled to the input of the interferometric device which comprises N pairs of secondary branches, each pair being designed to have a different interfrange distance A1, A2, ..., AN. The device 40 for collecting the backscattered light is common to all the measuring volumes, as is the acquisition device 50 and the processing device 60. In the processing device 60, the signal supplied by the acquisition device 50 is filtered by N bandpass filters each having a different bandwidth Bi, B2, BN, integrating the Doppler frequency associated with a respective interframe distance. filtered therefore provides N information Si, S2, ... SN on the size of detected faults. In the case where a fault is not visible in one of the measurement volumes, the corresponding information is an absence of a fault. In the case where a defect has a visibility associated with different possible sizes, the corresponding information is the set of possible sizes. The set of information Si, S2,..., SN is then combined to allow, by overlapping, the unambiguous determination of the size of each detected defect (step shown schematically by block C). The sensing device then provides a report R on the detected defects, indicating the size and position of each defect. VVO REFERENCES 2009/112704 VVO 02/39099 25 Measurement of Particle Size, Number Density, and Velocity Using a Laser Interferometer, W. M. Farmer, Applied Optics, Vol. 11, No. 11, Nov. 1972, pp. 2603-2612 Integrated Laser Doppler Velocimeter for Fluid Velocity and Wall Friction Measurements, P. Lemaitre-Auger, A. Cartellier, P. Benech and Schanen Duport, Sensors, 2002, Proceedings of IEEE (Vol: 1), pp. 78-82 30
    权利要求:
    Claims (13)
    [0001]
    REVENDICATIONS1. A method of inspecting a wafer (2) for electronics, optics or optoelectronics, comprising: - rotating the wafer (2) about an axis (X) of symmetry perpendicular to a main surface (S) of said wafer, - the emission, from at least one light source (20) coupled to an interferometric device (30), of at least two pairs of incident coherent light beams, each pair being arranged to form, at the intersection between the two beams, a respective measurement volume containing interference fringes having a different interfringe distance from that of another measurement volume, at least a part of the main surface (S) of the wafer passing in each of said measuring volumes during the rotation of the wafer, - the collection of at least a portion of the light diffused by said portion of the surface of the wafer, - the acquisition of the light collected and the broadcast of an electrical signal representing the variation of the light intensity of the light collected as a function of time, - the detection, in said signal, of a frequency component in the variation of the light intensity of said collected light, said frequency being the time signature of the passage of a fault in a respective measurement volume, - for each detected signature, the determination of a parameter, called visibility of the fault, depending on the interfringe distance of the respective measurement volume and the size of the fault, - From the visibility determined for each measurement volume, obtaining a respective information on the size of the defect, - the cross-checking of the information obtained for each measurement volume to determine the size of the defect.
    [0002]
    2. The method according to claim 1, wherein obtaining information on the size of the defect comprises: calculating the visibility of the defect in each measurement volume, for each measurement volume, starting from a reference curve of the visibility according to the size of the defect for the respective interframe distance, the determination of one or more possible sizes for the defect.
    [0003]
    3. Method according to one of claims 1 or 2, comprising filtering the signal with a bandpass filter whose bandwidth includes the Doppler frequency associated with each measurement volume.
    [0004]
    4. Method according to one of claims 1 to 3, wherein said measurement volumes are at least partially superimposed.
    [0005]
    5. Method according to one of claims 1 to 3, wherein said measuring volumes follow one another along the path of rotation of the wafer.
    [0006]
    6. Method according to one of claims 1 to 5, comprising a radial displacement of said measurement volumes relative to the wafer.
    [0007]
    7. Method according to one of claims 1 to 6, wherein the fringes of each measurement volume are oriented transversely to the rotational path of the wafer.
    [0008]
    8. Method according to one of claims 1 to 7, wherein the interferometric device (30) is an integrated optical device comprising a light guide whose input is coupled to the light source and which is divided into two pairs of branches whose output is oriented to form a respective measurement volume at the intersection of the two beams of each pair.
    [0009]
    9. Method according to one of claims 1 to 8, wherein the wafer is at least partially transparent vis-à-vis the wavelength of the light source and each measuring volume extends in a region of the wafer having a thickness less than the thickness of said wafer.
    [0010]
    10. A wafer inspection system for electronics, optics or optoelectronics, comprising: - a device (10) for driving a wafer in rotation about an axis of symmetry perpendicular to a main surface of said wafer, - at least one light source (20), - at least one interferometric device (30) coupled to the light source (20) for dividing the beam emitted by said source into two pairs of beams and for forming, at intersection between two beams of each pair, a respective measurement volume containing interference fringes having a distance interfranges different from that of another measurement volume. a device (40) for collecting at least a portion of the light diffused by the surface of the wafer; a device (50) for acquiring the collected light configured to emit an electrical signal representing the variation of the light intensity of said collected light as a function of time, - a processing device (60) configured to: detect, in said signal, a frequency component in the variation of the intensity of said collected light, said frequency being the time signature the passage of a fault in a respective measurement volume, * for each detected signature, the determination of a parameter, called visibility of the fault, depending on the interfrange distance of the respective measurement volume and the size of the fault, * obtain from the visibility determined for each measurement volume, a respective information on the size of said defect, and * cross-refer the information obtained for each v Measurement olume to determine the size of the defect.
    [0011]
    11. System according to claim 10, comprising a single light source (20) and a single interferometric device (30) to form all the measurement volumes.
    [0012]
    12. System according to one of claims 10 or 11, wherein the interferometric device (30) is in the form of an integrated optical device comprising a light guide whose input is coupled to the light source and which is divides into two pairs of branches whose output is oriented to form a respective measurement volume at the intersection of the two beams of each pair
    [0013]
    13. System according to one of claims 10 to 12, further comprising an arm for moving the interferometric device (30) and the device (40) for collecting the light diffused in translation in a radial direction.
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    同族专利:
    公开号 | 公开日
    WO2016050735A1|2016-04-07|
    US9857313B2|2018-01-02|
    FR3026485B1|2016-09-23|
    SG11201701774SA|2017-04-27|
    CN107076547B|2018-09-14|
    KR20170066366A|2017-06-14|
    US20170219496A1|2017-08-03|
    JP2017533421A|2017-11-09|
    EP3201609B1|2018-11-07|
    CN107076547A|2017-08-18|
    EP3201609A1|2017-08-09|
    JP6530063B2|2019-06-12|
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    法律状态:
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    2018-05-04| CA| Change of address|Effective date: 20180330 |
    2018-05-04| CD| Change of name or company name|Owner name: UNITY SEMICONDUCTOR, FR Effective date: 20180330 |
    2018-09-24| PLFP| Fee payment|Year of fee payment: 5 |
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    2021-09-27| PLFP| Fee payment|Year of fee payment: 8 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1459172A|FR3026485B1|2014-09-29|2014-09-29|METHOD AND SYSTEM FOR INSPECTING PLATELETS FOR ELECTRONICS, OPTICS OR OPTOELECTRONICS|FR1459172A| FR3026485B1|2014-09-29|2014-09-29|METHOD AND SYSTEM FOR INSPECTING PLATELETS FOR ELECTRONICS, OPTICS OR OPTOELECTRONICS|
    US15/515,227| US9857313B2|2014-09-29|2015-09-29|Method and system for inspecting wafers for electronics, optics or optoelectronics|
    EP15770915.5A| EP3201609B1|2014-09-29|2015-09-29|Method and system for inspecting wafers for electronics, optics or optoelectronics|
    KR1020177008386A| KR20170066366A|2014-09-29|2015-09-29|Method and system for inspecting wafers for electronics, optics or optoelectronics|
    CN201580052310.0A| CN107076547B|2014-09-29|2015-09-29|Method and system for examining the chip for being used for electricity, optics or photoelectricity|
    SG11201701774SA| SG11201701774SA|2014-09-29|2015-09-29|Method and system for inspecting wafers for electronics, optics or optoelectronics|
    PCT/EP2015/072364| WO2016050735A1|2014-09-29|2015-09-29|Method and system for inspecting wafers for electronics, optics or optoelectronics|
    JP2017518137A| JP6530063B2|2014-09-29|2015-09-29|Method and system for inspecting a wafer for electronics, optics or optoelectronics|
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