WO2021019136A1

WO2021019136A1 - Device for inspecting a surface of an object

Info

Publication number: WO2021019136A1
Application number: PCT/FR2020/051135
Authority: WO
Inventors: Philippe Gastaldo
Original assignee: Unity Semiconductor
Priority date: 2019-07-31
Filing date: 2020-06-30
Publication date: 2021-02-04
Also published as: FR3099569A1

Abstract

A device (1) for inspecting a surface (S) of an object, the device comprising a polychromatic light source (20) for projecting an inspection beam onto the surface (S); a confocal mask (6a, 6b) intercepting the inspection beam and a beam reflected by the surface, having a plurality of chromatic filtering openings; a chromatic system (3) spatially spreading the focusing of the inspection beam over focusing planes along an optical axis (AO) in a depth of field, intercepting the reflected beam so as to project it onto a conjugated detection plane (P) of the focusing planes; a movable support (4) for positioning the surface (S) in the depth of field; a timed integration image sensor (5) synchronised with the movement of the surface, the image sensor (5) comprising a matrix of photodetectors disposed in the detection plane (P), the chromatic filtering openings of the confocal mask illuminating part of the photodetectors.

Description

DESCRIPTION

TITLE: DEVICE FOR INSPECTING THE SURFACE OF AN OBJECT

FIELD OF THE INVENTION

The present invention relates to a device for inspecting a surface of an object. A device according to the invention allows the inspection of the surface of the object when the latter comprises strong variations in height and makes it possible to generate at high rates intensity images representative of the reflectivity of this surface with a depth. wide field of view and high lateral resolution. In general, the invention relates to the field of imaging for the inspection and control of objects, such as substrates for the semiconductor industry or for integrated optics (semiconductor wafers or substrates in all forms, during or at the end of the manufacture of semiconductor devices), or other objects in the fields of mechanics or the manufacturing industry for example (micro mechanisms, parts or assembly of watchmaking , assembled systems).

TECHNOLOGICAL BACKGROUND OF THE INVENTION

In the field of the semiconductor industry, the increase in the production rates of semiconductor device wafers and the reduction in the size of the patterns create a growing need for high-speed imaging inspection. The methods for imaging these platelets must thus allow the rapid localization of defects, structures and patterns over the entire surface of the platelets. Moreover, due to the curvature of the platelets in particular, or due to the height of the structures to be imaged (wafer edges, etc.), it is necessary to be able to take clear images in an area of extended depth of field. In other fields, such as those of micromechanics or watchmaking, the objects to be inspected may have significant relief or height differences, also requiring extended depths of field.

Optical imaging systems such as conventional microscopes are known. These systems are generally limited in depth of field: the optical diffraction limit makes it very difficult to have both a high magnification and a great depth of field. This is particularly penalizing when checking remote surfaces or structures with significant heights or depths. This problem is generally solved by keeping the objective at a desired distance from the measured surface, by an autofocus type system. This results in reduced displacement speeds and more complex systems, or even the need to perform several passes to acquire the images.

Document US Pat. No. 8,654,324 implements a method for increasing the depth of field by exploiting the chromatic dispersion of a chromatic lens. Light transmitted through a slit is projected onto an object through a chromatic lens. The light reflected from the inspected surface is returned to the chromatic objective and then transmitted through a slit placed in front of a linear detector. The chromatic objective used in this configuration makes it possible to increase the measurement depth of field by exploiting the fact that different wavelengths are focused at different distances on the object. However, this system is not suitable for the formation of intensity images in two dimensions and with high lateral resolution. This is because of its slot configuration which does not meet the criteria of confocal detection in one dimension and thus generates crosstalk or cross-talk between measurement channels.

Document US Pat. No. 9,739,600 B1 describes a system making it possible to locate patterns in two dimensions with an extended depth of field obtained by a chromatic lens. The profile or the distance of the identified structures can be measured by the same instrument while respecting the criteria of a detection confocal, with a minimum of cross-talk between measurement channels. The acquisition speed of the system is however directly limited by the quantity of light collected by the photodetector and above all by the number of measurement channels that it is possible to implement.

More particularly, the inspection rates depend on the optimization of the filling factor of the measurement points on the wafers inspected and defining the density of points measured at each instant. The fill factor is defined as the ratio between the diameter of the measurement points (diameter of the light beam projected onto the wafer at the focal point) and the separation between two measurement points. Thus, the use of optical fibers or integrated optical circuits poses a physical limitation on the possibility of bringing the measurement channels closer together.

One of the objectives of the invention is to provide a device for rapidly imaging a surface of an object over an extended depth of field.

Another objective of the invention is to provide such a device allowing a high density of measurement points (high spatial resolution) while minimizing the light coupling (cross-talk) between the detection channels.

Another objective of the invention is to allow localization and inspection of structures and patterns of a surface of an object such as a semiconductor substrate.

BRIEF DESCRIPTION OF THE INVENTION

With a view to achieving one of these aims, the invention provides a device for inspecting a surface of an object, the device comprising:

- at least one polychromatic light source for projecting an inspection beam onto the surface; at least one confocal mask intercepting the inspection beam and a beam reflected from the surface, the confocal mask having a plurality of chromatic filtering apertures;

- a chromatic system spatially spreading the focus of the inspection beam as a function of present wavelengths, according to focusing planes along an optical axis in a depth of field, and intercepting the beam reflected by the surface to project it onto a detection plane combined with the focusing planes;

a mobile support for receiving the object and positioning the surface in the depth of field of the chromatic system, the support being controllable to move the surface relative to the chromatic system at least in an inspection direction;

- a timed integration image sensor synchronized with the displacement of the surface in the direction of inspection, the image sensor comprising a matrix of photodetectors arranged in the detection plane, the chromatic filtering openings of the confocal mask illuminating a part. photodetectors.

According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination:

• the chromatic filtering openings are arranged on the confocal mask to illuminate a plurality of photodetectors arranged on a column of the matrix corresponding to a plurality of measurement points arranged according to the inspection direction;

• the chromatic filtering openings are distributed in a complementary manner over at least two lines of the confocal mask to illuminate a plurality of photodetectors corresponding to a plurality of measurement points arranged along at least two lines arranged in a direction perpendicular to the inspection direction ; • the confocal mask comprises a plurality of groups of at least two lines comprising chromatic filtering apertures distributed in a complementary manner over said at least two lines;

• the device comprises a confocal illumination mask arranged in the inspection beam and a confocal detection mask arranged in the reflected beam, the confocal illumination mask and the confocal detection mask being respectively placed in a conjugate plane of the planes. of focusing vis-à-vis the chromatic system;

• the confocal detection mask is produced by depositing at least one material on the surface of the image sensor;

• the inspection device comprises a single confocal mask, arranged in a jointly conjugated plane of the detection plane and of the focusing planes with respect to the chromatic system;

• the polychromatic light source comprises a halogen lamp or an array of electroluminescent diodes, associated with a diffusion device to homogenize the intensity of the inspection beam;

• the chromatic system includes a chromatic lens;

• the chromatic objective comprises a lens or a combination of lenses, at least one diffraction lens and / or at least one metal lens;

• the chromatic system includes a separator element;

• the separator element is a separator cube or a semi-reflecting plate;

• the photodetectors are fitted with a color filter; • the chromatic filtering openings are arranged to each illuminate a plurality of photodetectors provided with different color filters.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will emerge from the detailed description of the invention which will follow with reference to the appended figures in which:

[Fig. 1] Figure 1 shows an inspection device according to a first embodiment of the invention;

[Fig. 2] FIG. 2 represents a block diagram of the confocal chromatic operation implemented by the device of FIG. 1;

[Fig. 3] FIG. 3 represents a front view of a detection mask illuminated by a reflected beam;

[Fig. 4] Figure 4 shows an opening arrangement on a confocal mask in alignment with a photodetection array;

[Fig. 5] Figure 5 shows two inspection fields on the surface of a surface to be inspected.

DETAILED DESCRIPTION OF THE INVENTION

For the sake of simplification of the description to come, the same references are used for elements which are identical or perform the same function in the state of the art or in the various embodiments disclosed of the device. FIG. 1 represents a first embodiment of an inspection device according to the present invention.

In general, the inspection device 1 projects an inspection light beam onto a surface S of an inspected object. The beam is reflected on this surface S to project onto a detection plane P of an image sensor 5.

The inspected object, such as a semiconductor substrate, is placed on a movable support 4 of the inspection device 1, for example a table whose movement can be controlled. The mobile support 4 makes it possible to move the surface in at least one inspection direction I under the inspection beam.

The inspection device 1 comprises a lighting system 2 comprising a polychromatic light source 20 to form the inspection beam. The source 20 therefore emits several wavelengths which may for example be included in the visible spectrum, in a range of wavelengths between 380 nm to 700 nm, or in the infrared beyond 700 nm.

In general, the wavelengths making up the emission spectrum of the source 20 are chosen according to the nature of the object inspected and the layers which are likely to cover it. The wavelengths of the polychromatic source 20 will be chosen so that the inspection beam is reflected by the surface S of the object to be inspected. In addition, when a covering layer is present, the wavelengths of the polychromatic source 20 can be chosen so that they are included in the transparency spectrum of this covering layer.

By way of example, the polychromatic light source 20 can be formed from a halogen lamp or from an array of light-emitting diodes.

In general, we seek to form an inspection beam of large transverse dimension so as to illuminate a large portion of the inspected surface S, designated “inspection field” in the remainder of this description. In an application in the field of semiconductors, the inspection field can have a dimension of between a few hundred microns and a side of a few millimeters. To this end, it is possible to provide, as is the case in the embodiment shown in FIG. 1, a diffusion device 21 for homogenizing the intensity of the inspection light beam produced by the lighting system. 2. The diffusion device 21 can for example be produced by a ground glass or by an optical guiding element ensuring a mixture of the propagation modes of the radiation produced by the polychromatic source 20 so as to make the intensity of the beam homogeneous. inspection.

It is also possible to provide optical fibers 22 or any other form of guide for light radiation, to conduct the light beam produced by the source 20 as far as the injection zone of the inspection beam into the device 1, here occupied by the distribution device 21.

Of course, the lighting system 20 is not limited to that described of this mode of implementation. For example, it can be envisaged that it is composed of a polychromatic super-continuum light source, the radiation of which is guided by at least one optical guide to the injection zone.

Continuing the description of FIG. 1, the inspection device 1 also comprises a chromatic system 3 arranged on the optical path of the inspection beam and of the reflected beam. The chromatic system 3 generates a chromatic dispersion of the light which passes through it and thus spatially spreads the focus of the polychromatic inspection beam, as a function of the wavelengths present, according to focusing planes distributed along an optical axis AO in a depth of field of the chromatic system 3 extended with respect to the depth of field obtained for an individual wavelength. For this purpose, the chromatic system 3 comprises a chromatic objective 3a leading to focusing the different wavelengths of the inspection beam, over its entire transverse extent, at different distances from the objective. The chromatic objective 3 can be achieved in multiple ways, for example by means of a lens or a combination of lenses. These lenses can intercept the entire transverse extent of the inspection beam, or be respectively dedicated to portions of this beam constituting measurement channels. They can also be diffraction lenses or holographic devices. They can also be metal lenses, that is to say reflective or transmissive optical elements having structured reflection or transmission surfaces. The patterns constituting this surface structuring have dimensions smaller than the wavelengths of the inspection light beam and affect the phase of the radiation of this beam and therefore its shape and its propagation. The patterns on the surface of the optical elements can be produced by known methods of photolithography and etching.

Whatever the nature of the chromatic objective 3a, the latter is chosen to present a significant chromatic aberration, leading to spatially spreading the inspection beam, according to the wavelengths which compose it, according to arranged focusing planes. in the depth of field of the chromatic system 3. This depth of field can for example extend over a distance of 100 to 200 microns.

During a measurement, the surface S of the inspected object is placed in the depth of field of the chromatic system 3. For this purpose, provision can be made for the mobile support 4 to be able to adjust the position of the surface S by moving the inspected object. in the direction of the axis AO of the chromatic system 3, so as to maintain the surface S of the object in the depth of field. This characteristic is particularly advantageous when the surface S has significant reliefs in elevation or depression.

Consequently, and advantageously, the movable support 4 can consist of a table provided with means capable of controlling its movement in a plane perpendicular to the inspection beam in order to move the surface in the inspection direction I, and complementary means ensuring a displacement in a direction perpendicular to this plane in order to maintain the surface S in the depth of field of the chromatic system 3. However, insofar as the depth of field of the chromatic system 3 is extended, the constraints to maintain there the surface S are relaxed relative to an achromatic system.

The displacement in space of the surface S during a measurement sequence can be controlled by an electronic control unit 7. The latter can also collect the trajectory made during the measurement sequence in order to be able to reconstitute a faithful image of the inspected surface S.

Continuing the description of the embodiment shown in Figure 1, the chromatic system 3 is also provided with a splitter element 3b, for example a splitter cube or a reflecting plate, to intercept the beam reflected by the surface S and the project onto a detection plane P of an image sensor 5. The splitter element 3b is placed on the optical path of the reflected beam, downstream from the chromatic optic 3a, so that the reflected beam passes through this objective 3a before projecting onto the detection plane P.

Other optical parts of the chromatic system 3 can be placed on the optical path between the separator element 3b and the detection plane of the image sensor 5, but in all cases the detection plane P is arranged in a plane conjugate, with respect to the chromatic system 3, of the focusing planes. According to the invention, the image sensor 5 is a timed integration image sensor (designated by “image sensor” in the rest of this description for the sake of simplicity). The detailed operation of such a sensor is for example described in document EP2088763. It comprises a matrix of photodetectors arranged in a plurality of rows and columns. The charges generated by the photodetectors are moved from one row to another, in a direction of columns synchronously with the displacement of the imaged object. The last line of the matrix is moved in a shift register, or any other form of electronic component making it possible to extract the charges from this line, in order to constitute an image line of the object.

In the inspection device 1, the matrix of photodetectors of the image sensor 5 is arranged in the detection plane P onto which the reflected beam is projected. In other words, the image sensor 5 is arranged in the inspection device 1 to image the inspection field. Such a matrix can have a very large number of rows and columns, for example more than 10,000 columns and several hundred rows.

The image sensor 5 is connected to the electronic control unit 7 in order to synchronize it with the displacement of the surface S according to the inspection direction I, and to repeatedly recover the lines of charges extracted from the matrix of end photodetectors. of columns. In this configuration, and in the absence of any masking, a point of the surface S which moves in the inspection direction I is successively imaged on the photodetectors of a column of the matrix, that is to say on successive rows of the column. Simultaneously, the electric charge generated by a photodetector is moved synchronously from one row to another, in a column direction, so that the charge accumulated at the end of this scanning, at the end of the column, is representative. of the light reflected by the point of the surface S during the entire duration of its displacement, in the conjugate plane of the image sensor 5, along of the corresponding column of the sensor according to the inspection direction I.

The inspection device shown in Figure 1 also includes two confocal masks 6a, 6b arranged in conjugate planes of the surface S of the object vis-à-vis the chromatic system 3, and respectively placed in the optical path of the beam inspection and reflected beam.

A first confocal illumination mask 6a is here arranged on the diffusion device 21. The mask has a plurality of illumination openings. These openings can be crossed by the inspection beam coming from the lighting system, and the confocal lighting mask blocks the beam outside these openings. The inspection beam therefore consists of a plurality of lighting channels defined by the lighting openings, projecting onto the surface S at the level of a plurality of measurement points distributed in the inspection field of the device. 1, according to focal planes as a function of the wavelengths in the depth of field of the chromatic system 3.

A second confocal detection mask 6b is here arranged on the detection plane of the image sensor 5. Similar to the first confocal illumination mask 6a, the confocal detection mask 6b comprises a plurality of chromatic filtering openings (or confocal chromatic), conjugates of the lighting apertures of the confocal lighting mask 6a. More precisely, the lighting apertures and the chromatic filtering apertures are combined from the same measurement points by the chromatic system 3.

The confocal detection mask 6b and the image sensor 5 are arranged relative to one another so that the chromatic filtering openings of the confocal mask 6b are respectively placed opposite a photodetector or a group of photodetectors and illuminate part of the photodetectors of the array. For this, the confocal detection mask 6b can be plated, glued, or produced directly on the surface of the image sensor 5. It can in particular be produced by selective deposits of layers of dielectric or metallic materials on the surface of the sensor 5. .

The confocal detection mask 6b can also be produced in the form of an element distinct from the sensor 5, positioned in an optical plane conjugated to the sensor by a lens or an imaging system.

In the inspection device 1 thus configured, the lighting paths of the inspection beam pass through the chromatic objective 3a. The beam is focused, according to the different wavelengths which constitute it, in focusing planes distributed over the very wide depth of field by the effect of the chromatic objective 3a. The radiation from each illumination channel is reflected by the inspected surface S, arranged in the depth of field, at the measurement points, again passes through the chromatic objective 3a, and is projected onto the confocal detection mask 6b by the intermediate of the separator element 3b.

There is thus shown in Figure 2 a block diagram of the confocal chromatic operation implemented by the device of Figure 1. In this figure, the illumination mask 6a has an illumination opening defining an inspection beam comprising here a single lighting channel. By the effect of the chromatic objective 3a placed on its optical path, the inspection beam is focused, as a function of the optical wavelengths present, on an extended depth of field. In Figure 2, there is shown a first wavelength lo of the beam which is focused in a focusing plane PfO and a second wavelength l _± of the beam which focuses on a second focusing plane Pfl, quite distinct in the foreground.

The surface S to be inspected was placed at the level of the first focusing plane PfO, so that the illumination aperture of the mask illumination there image for the first wavelength. The light at the first wavelength lo coming from the illumination opening is therefore reflected on the surface S in order to focus on the detection plane P of the image sensor 5, in the chromatic filtering opening of the mask detection 6b. Thus, this light at the first wavelength lo reaches in all or almost all of its intensity the detection plane P through the opening of the mask.

On the contrary, the light at the second wavelength l _± is not perfectly focused on the first focusing plane PfO in which the surface S resides. Consequently, this light is reflected diffusely, up to the mask of detection 6b which largely blocks it, so that little of its intensity reaches the detection plane P.

FIG. 3 shows a front view of the detection mask 6b, which here has 12 chromatic filtering openings O arranged in 4 columns and 3 rows. The mask 6b is illuminated by the reflected beam in an assembly similar to that shown in FIG. 2. Also shown in FIG. 3 is the outline of the light halo H corresponding to the projection onto the mask of radiation at wavelengths. reflected outside their focal planes on the inspected surface S.

To limit the phenomenon of coupling between different detection channels, it is important that the openings of the masks 6a, 6b are sufficiently far from each other, so that the diffuse halo associated with an opening does not cover too much of an area. neighboring opening.

For example, the centers of two adjacent openings on the illumination mask 6a or on the detection mask 6b can be separated by a distance greater than twice the dimension of these openings (their diameters if these openings are circular). However, moving the openings of the masks 6a, 6b away from one another leads to a reduction in the filling factor of the measurement points in the inspection field. As noted in the introduction, a reduction in the fill factor affects the inspection rate and the density of the measurement points.

To solve this problem, the openings of the illumination and detection masks are cleverly arranged vis-à-vis the photodetectors of the image sensor 5.

Thus, FIG. 4 shows part of the photodetector matrix in the form of a grid G. Each cell of the grid symbolizes a photodetector or a group of photodetectors. The part of the matrix shown is composed of 5 columns (referenced C1 to C5) and 5 rows (referenced L1 to L5). The openings of the masks 6a, 6b are represented by circles, here arranged in alignment with the photodetectors of the camera. These openings are capable of causing the reflected beam to pass, which is then projected onto the exposed photodetectors to be measured by the image sensor 5. It is noted that these are either the openings of the illumination mask 6a or of the optical mask. detection 6b, these two masks being optically conjugated to each other when the photodetectors are exposed.

In this arrangement, the chromatic filtering openings are arranged on the confocal mask (6a, 6b) to respectively illuminate a plurality of photodetectors, or a plurality of groups of photodetectors, arranged on a column (C1-C5) of the matrix. The image sensor 5 is synchronized with the movement of the surface to be inspected so that the plurality of photodetectors of a column under the openings is in correspondence with a plurality of measurement points arranged according to the inspection direction (I) . When the surface S is moved along the inspection direction I, the photodetectors of the column under the openings of the mask are successively exposed to the light coming from a measurement point. At the end of the column, a charge is recovered corresponding to the quantity of light reflected by the measurement point during an extended exposure time, corresponding to the exposure time of each photodetector multiplied by the number of openings in the column. In this way, it is possible to produce a high intensity image of the inspected surface and / or to increase the inspection rate.

In this arrangement also, the chromatic filtering openings are distributed over the confocal mask 6b in a complementary manner over at least two rows, that is to say for example only for a given column, if one row does not include an aperture of chromatic filtering, another line includes one. In particular, such a complementary distribution makes it possible to ensure that, for a group of rows which each include a chromatic filtering opening, for a sub-part of the columns, each column comprises the same number of chromatic filtering openings (for example example a) for the group of lines. In this way, a plurality of photodetectors are exposed, also distributed in a complementary manner over at least two rows of the matrix. In the example of FIG. 4, the photodetectors of lines L1 and L2, and of lines L3 and L4 are thus arranged in a complementary manner on these two lines. In other words, two contiguous photodetectors in row or in column are not simultaneously exposed under an opening of the mask. In this way, the openings are sufficiently separated from one another to limit the parasitic coupling between several detection channels. The image sensor 5 is synchronized with the movement of the surface S to be inspected so that the photodetectors distributed over the lines correspond to a plurality of measurement points arranged similarly along lines arranged in a direction perpendicular to the inspection direction. (I). Thanks to the complementary distribution of the chromatic filtering openings between the lines, when the surface S is moved in the inspection direction I, the measurement points imaged on the detector combine very densely in the inspection field. Thus, FIG. 5 shows a first inspection field C11 as well as the measurement points (in dotted lines) imaged on the image sensor 5 of this inspection field. The surface has been moved in the direction of inspection and a second inspection field CI2 has been shown as well as the measurement points in this field (in solid line). The distribution on several complementary lines of the openings allows as the movement of the object to proceed to dense measurements in the inspection field.

Of course, the openings can be distributed in a complementary manner over a larger number of lines, which makes it possible to separate these openings even further from each other and to limit the coupling phenomenon even more. For a given dimension of the photodetector matrix, this amounts to placing fewer photodetectors on a column, and therefore affecting the quality of intensity of the image.

Advantageously, the confocal mask (6a, 6b) can comprise a plurality of groups of lines with a complementary distribution of the chromatic filtering openings. These groups of lines may for example comprise a distribution of identical chromatic filtering openings. Thus each measurement point of the object is imaged on the detector in a plurality of chromatic filtering apertures, sequentially, which makes it possible to accumulate more intensity or charges and to fully exploit the number of lines of the array of photodetectors.

The device as described makes it possible to obtain images in intensity, or in gray level, of the surface of the object, or in other words of its reflectivity.

Insofar as the chromatic system performs an encoding of the height of the object in wavelength, it is also possible to obtain depth information. This requires determining the wavelength of the radiation detected by the photodetectors. This can be implemented by employing a color image sensor, thus returning color information in addition to the intensity information of the detected radiation.

This approach can be implemented in different ways.

According to a first approach, a plurality of photodetectors are placed under the openings of the mask, respectively provided with color filters, for example RGB. Each measurement point is then characterized by the intensity measurement in each of the spectra defined by these filters.

According to another approach, the photodetector (or the photodetectors) under an opening is provided with a single color filter, but the nature of this filter varies from one column to another, along the row. The radiation emitted by adjacent measurement points of the surface S, corresponding to adjacent columns of the detector, is therefore detected by photodetectors respectively dedicated to a color.

The color information, even coarse, obtained using an RGB type filter, can advantageously be used by the electronic control unit 7 to estimate the elevation of the measurement points, and more specifically the distance separating the point. for measuring a reference plane of the device. The control unit 7 can therefore estimate an average distance separating the surface S from this reference plane. It can control the displacement along the optical axis AO of the mobile support 4 on this average distance estimate to maintain the inspection surface S in the depth of field of the chromatic system 3 while moving this surface S along the inspection direction. I, during a measurement sequence.

The speed of movement of the surface S, depending on the inspection direction, can for example reach a value of the order of 100 mm / second. Of course, the invention is not limited to the embodiments described and it is possible to provide variant embodiments without departing from the scope of the invention as defined by the claims.

Thus, the two opaque illumination and detection masks 6a, 6b can be replaced by a single mask, arranged in this case under the separator element 3b. The mask can for example be fixed directly under a splitter cube or a reflecting plate, for example by depositing an opaque material on this optical part. In this alternative configuration, the apertures of the single mask perform both the function of the illumination and color filtering apertures. The openings of this mask are then optically conjugated from the surface S of the object by the chromatic system 3, and optically conjugated from the image sensor 5.

Claims

1. Device for inspecting (1) a surface (S) of an object, the device comprising:

- at least one polychromatic light source (20) for projecting an inspection beam onto the surface (S); at least one confocal mask (6a, 6b) intercepting the inspection beam and a beam reflected from the surface (S), the confocal mask (6a, 6b) having a plurality of chromatic filtering apertures;

- a chromatic system (3) spatially spreading the focusing of the inspection beam as a function of present wavelengths, according to focusing planes along an optical axis (AO) in a depth of field, and intercepting the beam reflected by the surface (S) to project it onto a detection plane (P) combined with the focusing planes;

- a mobile support (4) for receiving the object and positioning the surface (S) in the depth of field of the chromatic system (3), the support (4) being able to be controlled to move the surface (S) relative to the chromatic system (3) at least according to an inspection direction (I);

- a timed integration image sensor (5) synchronized with the displacement of the surface (S) in the inspection direction (I), the image sensor (5) comprising a matrix of photodetectors arranged in the detection plane (P), the chromatic filtering openings of the confocal mask (6a, 6b) illuminating part of the photodetectors.

2. Inspection device according to the preceding claim wherein the chromatic filtering openings are arranged on the confocal mask (6a, 6b) to illuminate a plurality of photodetectors arranged on a column of the matrix corresponding to a plurality of measurement points arranged. according to the inspection direction (I).

3. Inspection device according to one of the preceding claims wherein the filter openings chromaticity are distributed in a complementary manner on at least two lines of the confocal mask (6a, 6b) to illuminate a plurality of photodetectors corresponding to a plurality of measurement points arranged along at least two lines arranged in a direction perpendicular to the inspection direction (I).

4. Inspection device according to the preceding claim wherein the confocal mask (6a, 6b) comprises a plurality of groups of at least two lines comprising chromatic filtering openings distributed in a complementary manner on said at least two lines.

5. Device according to one of the preceding claims comprising a confocal illumination mask (6a) arranged in the inspection beam and a confocal detection mask (6b) arranged in the reflected beam, the confocal illumination mask (6a). ) and the confocal detection mask (6b) being respectively placed in a plane conjugate of the focusing planes with respect to the chromatic system (3).

6. Device according to the preceding claim wherein the confocal detection mask (6b) is produced by depositing at least one material on the surface of the image sensor (5).

7. Inspection device according to one of claims 1 to 4 comprising a single confocal mask, arranged in a jointly conjugated plane of the detection plane (P) and of the focusing planes with respect to the chromatic system (3). .

8. Inspection device according to one of the preceding claims wherein the polychromatic light source

(20) comprises a halogen lamp or an array of light-emitting diodes, associated with a diffusion device

(21) to homogenize the intensity of the inspection beam.

9. Inspection device according to one of the preceding claims wherein the chromatic system (3) comprises a chromatic lens (3a).

10. Inspection device according to the preceding claim wherein the chromatic objective (3a) comprises a lens or a combination of lenses, at least one diffraction lens and / or at least one metal lens.

11. Inspection device according to one of the preceding claims wherein the chromatic system (3) comprises a separator element (3b).

12. Inspection device according to the preceding claim wherein the separator element (3b) is a separator cube or a semi-reflecting blade.

13. Inspection device according to one of the preceding claims wherein the photodetectors are provided with a color filter.

14. Inspection device according to the preceding claim, wherein the chromatic filtering openings are arranged to each illuminate a plurality of photodetectors provided with different color filters.