JP2005274155A - Flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw inspection device capable of easily setting the center wavelength and wavelength width of illumination light at the time of inspection to desired values. <P>SOLUTION: The flaw inspection device is constituted of an illumination means for converting the illumination light from a light source to almost parallel light flux to illuminate a specimen; an image forming means for forming the image of the specimen by the reflected light from the specimen in the parallel light flux from the imaging means; an imaging means for taking the image formed by the image forming means; the wavelength selecting means arranged in the light path between the light source and the imaging means to indently and selectively set the center wavelength and wavelength width of the light flux in the light path; and a flaw detection means for detecting the flaw of the specimen on the basis of the image taken by the imaging means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a defect inspection apparatus for detecting a defect of an object to be inspected.

  Conventionally, when a semiconductor substrate is manufactured, defects may be formed on the substrate due to various causes. For example, variations in the thickness of the resist applied to the substrate surface in the photolithography process and dust adhering to the resist cause defects. Examples of the defect include a disconnection of the pattern on the substrate after etching, a reduction in line width, and a pinhole in the pattern. Further, the in-focus defect in the exposure of the wiring pattern to the resist causes a defect of defective formation of the cross-sectional shape of the resist after development. This defect can cause a defect in a later process.

  For this reason, the wafer and the substrate are subjected to defect detection and defect correction. A defect inspection apparatus is generally used for detecting the defect.

  For example, Patent Documents 1 and 2 show the conventional defect inspection apparatus. The defect inspection apparatus disclosed in Patent Document 1 will be described with reference to FIG. 11, and the defect inspection apparatus disclosed in Patent Document 2 will be described with reference to FIG.

  The defect inspection apparatus disclosed in Patent Document 1 is an apparatus that observes a light beam regularly reflected by the object 101 such as the wafer or the substrate having at least one periodic pattern and detects a defect on the object 101. . Specifically, the defect inspection apparatus includes a lamp house 5. The lamp house 5 includes a halogen lamp 6, a condenser lens 7, and a heat ray absorption filter 8. The light from the halogen lamp 6 enters the condenser lens 7 through the heat ray absorption filter 8 and is converted into a parallel light beam.

  The defect inspection apparatus further includes a rotating holder 9 having a plurality of interference filters and a white light illumination hole. The rotation holder 9 is configured such that any interference filter or the hole can be arranged on the optical path of the light beam that has passed through the condenser lens 7 by rotating. Each interference filter is configured to transmit only a light beam in a predetermined band centered on a predetermined wavelength. For this reason, the rotation holder 9 can change the wavelength width of the light beam to pass by changing the interference filter. In the present specification, in the light flux having a predetermined wavelength width, the center wavelength of the wavelength width is referred to as a center wavelength.

  Further, the defect inspection apparatus includes a condenser lens 10, an optical fiber bundle 11, a diffusion plate 12, a diaphragm 13, a collimator lens 14, and a half mirror 15. The light beam from the light source unit enters the collimator lens 14 via the half mirror 15, is converted into a parallel light beam, and is irradiated on the subject 101.

  The defect inspection apparatus further includes an imaging lens 16 and a CCD 17. The light beam regularly reflected by the subject 101 enters the imaging lens 16 through the collimating lens 14 and the half mirror 15. The imaging lens 16 forms an image of the subject 101 on the CCD 17 with the incident light beam. The CCD 17 captures an image of the subject 101 that has been formed.

  As described above, the defect inspection apparatus captures an image of the reflected light of the light beam irradiated on the subject 101 with the CCD 17 and observes the film thickness variation of the subject 101 as interference fringes. Moreover, this defect inspection apparatus can also capture an image of diffracted light from the subject by tilting the optical axis of the illumination system or imaging system.

  As shown in FIG. 12, the defect inspection apparatus of Patent Document 2 includes an illumination unit 802 having a light source, and a collimator lens 803 that converts a light beam emitted from the illumination unit 802 into a parallel light beam. The illumination unit 802 and the collimator lens 803 illuminate the subject 101 at an incident angle θi with respect to the normal of the surface of the subject 101.

  The defect inspection apparatus further includes a collimating lens 804, an imaging lens 806, and a line image sensor 807. The collimating lens 804 converges the light reflected, diffracted and scattered by the subject 101 at the inspection angle θd with respect to the normal line of the surface of the subject 101. The imaging lens 806 focuses the light beam from the collimating lens 804 on the line image sensor 807.

  This defect inspection apparatus moves the subject 101 relative to the defect inspection apparatus in a direction orthogonal to the width direction of the line image sensor 807 (indicated by an arrow AA in FIG. 11). By this movement, the defect inspection apparatus images the entire subject 101 and acquires an inspection image.

  In this inspection image, the defect is observed by light and darkness of light reflected by the subject 101 (reflected light). Specifically, defects such as film thickness unevenness appear as the brightness of the regular reflection light. In addition, defects due to poor focusing are observed as the brightness of the diffracted light. Thus, since the defect is detected by the brightness of the specularly reflected light and the diffracted light, the object 101 is imaged at a plurality of inspection angles θd so that the object 101 can be imaged at the inspection angle θd with the clearest contrast. Take an image.

Then, the plurality of inspection images captured as described above are compared with a reference image that is an image obtained by capturing an image of a subject that does not have a defect, and portions with different luminance between the reference image and the inspection image are defective. Extract as
Japanese Patent Laid-Open No. 7-27709 JP-A-9-61365

  In general, a multilayer pattern is formed on the surface of the object 101 by a photolithography process, and a resist layer is formed on these patterns. The defect inspection apparatus inspects defects in the upper resist layer of the multilayer object 101. Although the conventional defect inspection apparatus is intended to detect defects in the upper resist layer, there is a problem in that defects in which the lower layer pattern or resist layer is not regarded as a problem are detected at the same time.

  In order to suppress defects such as film thickness variations in the lower layer that appear in the inspection image at this time, it may be possible to widen the wavelength width of the narrowband light used for imaging, but the brightness of the defect formation of the resist layer is reduced and imaging is performed. The problem becomes difficult to do.

  For this reason, it is necessary to adjust the center wavelength and wavelength width of the light used for the illumination to appropriate values according to the type of the subject and the defect to be detected. Conventional defect inspection apparatuses such as those disclosed in Patent Documents 1 and 2 selectively change the wavelength width by exchanging the interference filter. However, since the center wavelength and the wavelength width that the interference filter passes are fixed for each interference filter, the center wavelength and the wavelength width cannot be adjusted to optimum values.

  For this reason, adjusting the center wavelength and the wavelength width to optimum values can be achieved by preparing a large number of interference filters having different center wavelengths and wavelength widths. However, in order to make it possible to finely adjust the center wavelength and the wavelength width, a large number of interference filters are required, which is not practical, and even if a large number of interference filters are prepared, substantially fine adjustment is not possible. Is possible.

  In view of the above problems, an object of the present invention is to provide a defect inspection apparatus that can easily set the center wavelength and wavelength width of illumination light at the time of inspection to desired values and remove the influence of lower layers to improve the accuracy of defect detection. Is to provide.

  In order to solve the above problems, the defect inspection apparatus of the present invention has the following configuration.

    The present invention forms an image of the subject by illuminating means for illuminating the subject with illumination light from a light source as a substantially parallel luminous flux, and reflected light from the subject out of the parallel luminous flux from the illuminating means. An imaging means for imaging, an imaging means for taking an image formed by the imaging means, and an optical path between the light source and the imaging means, and a center wavelength and a wavelength of a light beam in the optical path Provided is a defect inspection apparatus comprising wavelength selection means for selectively setting the widths independently, and defect detection means for detecting a defect of the subject from an image picked up by the image pickup means.

  Furthermore, the present invention provides an illuminating unit that illuminates the subject with illumination light from a light source as a substantially parallel light beam, and an image of the subject by reflected light from the subject out of the parallel light beam from the illuminating unit. An image forming means for forming an image, an image pickup device array arranged along the width direction, a plurality of image pickup devices arranged along a longitudinal direction orthogonal to the width direction, an image pickup means for picking up an image by each image pickup unit, the light source and the image pickup A spectroscopic unit that is arranged on an optical path between the optical unit and splits a light beam in the optical path along the longitudinal direction; and a defect detection that detects a defect of the subject by an image captured by the imaging unit. And a defect inspection apparatus for forming an image by adding the imaging results obtained by the imaging element array corresponding to the designated wavelength range.

  The present invention can provide a defect inspection apparatus that can easily set the center wavelength and wavelength width of illumination light at the time of inspection to desired values and remove the influence of lower layers to improve the accuracy of defect detection.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the defect inspection apparatus 1 according to the first embodiment will be described with reference to FIGS. FIG. 1 is a schematic side view showing a defect inspection apparatus 1 according to the present embodiment. FIG. 2 is a schematic side view showing a wavelength selection unit of the defect inspection apparatus 1 in FIG. FIG. 3 is a schematic block diagram showing a control system of the defect inspection apparatus 1 in FIG. The defect inspection apparatus 1 according to the present embodiment inspects the subject 101 that is a multilayer substrate. In the subject 101, a resist layer having a plurality of periodic patterns is formed on the uppermost layer.

  The defect inspection apparatus 1 includes a stage 20, an illumination unit 30, an imaging unit 40, a wavelength selection unit 50, an imaging unit 70, and a control system 200. The defect inspection apparatus 1 irradiates the subject 101 disposed on the stage 20 with illumination light from the illumination unit 30, and the imaging unit 40 collects reflected light from the subject 101 and forms an image. Then, the imaging unit 70 captures an image from the imaging unit 40 and inspects the object 101 for defects. In the present embodiment, a wavelength selection unit 50 is disposed in the optical path of the illumination unit 30. Below, each structure of the defect inspection apparatus 1 is demonstrated in detail.

  In the present embodiment, the stage 20 is configured to hold the subject 101 and move it along two predetermined axes that are orthogonal to each other. In this specification, one axis is defined as the X axis, and the other axis is defined as the Y axis. In this specification, an axis perpendicular to the X and Y axes is taken as a Z axis. Therefore, the Z axis substantially coincides with the normal direction of the surface of the subject 101 supported by the stage 20. In addition, the defect inspection apparatus is provided with a not-shown subject transport unit provided with a substrate transport robot for transporting a semiconductor wafer substrate or FPD glass substrate to be inspected onto the stage 20. The subject transport unit includes a stocker that stores the subject 101 before the examination and a stocker that stores the subject 101 after the examination. The illumination unit 30 is an illumination unit that illuminates the subject 101, and includes a lamp house 31, an optical fiber 35, a diffusion plate 36, a diaphragm 37, a half mirror 38, and a collimator lens 39.

The lamp house 31 includes, for example, a halogen lamp 32 that emits white light, a heat ray absorption filter 33, and a condenser lens 34 as light sources. The condenser lens 34 converts the light from the halogen lamp 32 into a parallel light flux and makes it incident on the wavelength selection unit 50. The optical fiber 35 has an incident end 35 a connected to the wavelength selector 50 and an output end 35 b connected to the diffusion plate 36.
The diffuser plate 36 and the diaphragm 37 constitute a secondary light source that averages the intensity distribution of the light beam incident from the light source and adjusts the cross section of the light after passing through to an optimum size. 38.

  The half mirror 38 reflects the light flux from the diffusing plate 36 and the diaphragm 37 toward the collimating lens 39 and transmits the reflected light from the subject 101 to enter the imaging unit 40.

  The collimating lens 39 shapes the light beam reflected by the half mirror 38 into a parallel light beam and irradiates the subject 101. In the present embodiment, the half mirror 38 and the collimating lens 39 are arranged so that the light beam illuminated toward the subject 101 is vertically incident. Further, the focal position of the collimating lens 39 exists on the light source side reflected by the half mirror 38 and on the imaging side that has been transmitted. The focal position on the light source side of the collimator lens 39 is set to the position of the diffusion plate 36, and the focal position on the imaging side is set to the position of the imaging unit 40.

  The imaging unit 40 includes an imaging lens, and is an imaging unit that collects the light from the half mirror 38 and forms an image of the surface of the subject 101 on the imaging surface of the imaging unit 70. is there. The imaging unit 70 is an imaging unit that captures an image by the imaging unit 40 and is an area sensor such as a CCD that can capture an image of a predetermined region of the subject 101 at a time.

  As shown in FIG. 2, the wavelength selection unit 50 is a monochromator whose transmission wavelength width is variable. The wavelength selection unit 50 receives light from the lamp house 31 and can independently and continuously adjust the center wavelength and wavelength width of the incident light. The light enters the optical fiber 35. The wavelength selector 50 includes an entrance slit 50a, lenses 50b and 50d, a prism 50c, and an exit slit 50e. The light beam from the lamp house 31 enters the lens 50b through the incident slit 50a, is shaped into a parallel light beam, and enters this prism 50c.

  The prism 50c splits the incident light beam by a spectroscopic element that splits the incident light beam, with different wavelengths along the width direction d1 of the opening of the exit slit 50e, as indicated by a solid line and a broken line. The light beam split by the prism 50c enters the lens 50d and converges on the exit slit 50e. The light beam that has passed through the opening of the exit slit 50 e enters the incident end 35 a of the optical fiber 35. The exit slit 50e is configured such that the width of the opening can be changed along the width direction d1 by a movable device (not shown). By changing the width of the opening, the wavelength width can be arbitrarily set with respect to the result of spectral separation by the prism 50c. Can be set.

  Further, the prism 50c is configured to be rotated by a rotation driving device (not shown), and is emitted from the emission slit 50e by rotating the prism 50c about an axis orthogonal to the paper surface in FIG. The center wavelength of the light beam can be arbitrarily selected.

  Next, the control system 200 will be described with reference to FIG.

  The control system 200 includes a stage control unit 201, a drive circuit 202, an optical system control unit 203, a subject transport control unit 204, an image interface (image I / F) 205, an image processing device 206, and a monitor 207. 210, image storage device 208, host computer 209, keyboard 211, memory 212, and sequencer 213.

The stage control unit 201 is connected to the stage 20 and controls driving of the stage 20.
The drive circuit 202 is connected to the imaging unit 70 and controls driving of the imaging unit 70.

  The optical system control unit 203 is connected to the illumination unit 30, the imaging unit 40, and the calculation selection unit 50, and controls the driving thereof. More specifically, the optical system control unit 203 controls the amount of illumination light of the illumination unit 30, the wavelength width of the wavelength selection unit 50, and the center wavelength.

The subject transport control unit 204 is connected to the above-described subject transport unit, and controls the driving of the subject transport unit.
The image processing device 206 is connected to the imaging unit 70 and the host computer 209, and the drive is controlled by the host computer 209. The image processing apparatus 206 has a defect detection function that performs image processing on the inspection image acquired by the imaging unit 70 and extracts defects such as film thickness variation and dust. In addition, the image processing apparatus 206 sends data such as the type, number, position, and area of defects related to the extracted defects to the host computer 209. The image processing device 206 is further connected to a monitor 207 and an image storage device 208. A monitor 207 is an image display device that displays an image or the like created by the image processing device 206.
The image storage device 208 is a data storage device for storing the inspection image obtained and processed by the image processing device 206. The image storage device 208 is an inspection image of the subject 101, an extracted defect image, and a non-defective non-defective subject. A reference image obtained by imaging 101 is stored.

  The host computer 209 is connected to the image processing device 206, the monitor 210, the keyboard 211, the memory 212, and the sequencer 213. The host computer 209 controls driving of the image processing apparatus 206 and the sequencer 213 and displays necessary settings for this control on the monitor 210 as a control menu.

  The keyboard 211 is an input device for inputting commands selectable from the control menu and / or other commands and information necessary for control to the host computer 209.

  The memory 212 is connected to the host computer 209 and stores control information necessary for the control. The control information includes, for example, inspection conditions for each type of subject (optical system setting, inspection area, image processing conditions, acceptance criteria for determining pass / fail of defects, etc.), inspection data, and the like. This control information can be stored in the storage unit in advance before inspection, or can be input by the keyboard 211 or the like at the time of inspection and stored in the storage unit.

  The sequencer 213 is connected to the stage control unit 201, the drive circuit 202, the optical system control unit 203, and the subject transport control unit 204, and sends control target drive sequences controlled by them. Also, the sequencer 213 sends a drive command from the host computer 209 to them.

  Below, operation | movement of the defect inspection apparatus 1 of the said structure is demonstrated. When performing an inspection using the defect inspection apparatus 1, first, the operator instructs the type of the subject 101 and the start of the inspection using the keyboard 211. In response to this instruction, the host computer 209 searches for and reads the examination conditions corresponding to the type of the input subject 101 from the examination conditions stored in advance in the memory 212.

  Then, the host computer 209 controls the optical system control unit 203 via the sequencer 213 based on the inspection condition, and sets the illumination unit 30. Specifically, the light amount of the halogen lamp 32 and the center wavelength and wavelength width of the light beam passing through the wavelength selection unit 50 are set. More specifically, the wavelength selection unit 50 drives the rotation driving device so as to set the angle of the prism 50c according to the set center wavelength. At the same time, the wavelength selector 50 changes the opening width of the exit slit 50e in accordance with the set wavelength width.

  Subsequently, the host computer 209 issues a drive command to the subject transport control unit 204 and the stage control unit 201 via the sequencer 213. Upon receiving this drive command, the subject transport control unit 204 drives the subject transport unit to take out one subject 101 from the stocker and place it on the stage 20.

  The stage 20 adsorbs and holds the subject 101 and then positions the subject 101 so as to be in the center of the observation field.

  After positioning the subject 101, the host computer 209 causes the imaging unit 70 to image the surface of the subject 101. The imaging unit 70 acquires an inspection image and sends the inspection image to the image processing device 206.

  The image processing device 206 performs image processing on the inspection image and extracts defects from, for example, the difference between the inspection image and the reference image. The image processing apparatus 206 sends data such as the extracted defect position and area to the host computer 209. The host computer 209 compares the number of defects, the area, and the like with the acceptance criteria of the subject 101 and makes a pass / fail determination. When the examination is completed, the subject 101 is classified as good or bad and is transported to a stocker for storing the subject after the examination (not shown). In this way, the examination of one subject 101 is completed.

  As described above, the wavelength selection unit 50 according to the present embodiment can continuously change the center wavelength of the illumination light by rotating the prism 50c. Therefore, unlike the case where the center wavelength is changed by the interference filter, the wavelength selection unit 50 according to the present embodiment can finely adjust the center wavelength. At the same time, the wavelength selection unit 50 according to the present embodiment can finely adjust the center wavelength without increasing the number of components such as interference filters according to the number of selected center wavelengths.

  In addition, the wavelength selection unit 50 of the present embodiment can continuously change the wavelength width of the illumination light by changing the opening width of the exit slit. Therefore, unlike the case where the wavelength width is changed by the interference filter, the wavelength selection unit 50 according to the present embodiment can finely adjust the wavelength width. At the same time, the wavelength selection unit 50 of the present embodiment can finely adjust the wavelength width without increasing the number of components such as interference filters according to the number of selected wavelength widths. Therefore, the defect inspection apparatus 1 according to the present embodiment can suppress the detection of the defect in the lower layer and detect the defect in the target layer more clearly with the illumination light having the center wavelength and the wavelength width set appropriately.

  The imaging unit 70 of the present embodiment is an area image sensor such as a CCD. However, the image pickup unit 70 of the present embodiment can use a line image sensor as in the conventional defect inspection apparatus in FIG. In this case, the stage 20 can move the subject 101 relative to the imaging unit 70 in the length direction of the imaging region of the line image sensor and in a direction substantially orthogonal to the length direction. Composed. With this configuration, the defect inspection apparatus 1 according to the present embodiment can reliably image the entire surface of the subject 101 by driving the stage 20 as the moving unit and the imaging unit 70 as the imaging unit in synchronization. It is.

  The defect inspection apparatus according to the second embodiment will be described below. The defect inspection apparatus according to the present embodiment is different from the wavelength selection section 50 according to the first embodiment only in the configuration of the wavelength selection section 51. Therefore, in this embodiment, the same components as those in the defect inspection apparatus 1 of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  As shown in FIG. 4, the wavelength selector 51 includes an entrance slit 50a, a concave diffraction grating 51a, and an exit slit 50e. The concave diffraction grating 51a is a spectroscopic element that splits an incident light beam. Specifically, the concave diffraction grating 51a splits the light beam from the entrance slit 50a and converges it on the exit slit 50e. Similar to the prism 50c, the concave diffraction grating 51a is spectrally divided into different wavelengths along the width direction d1 of the opening of the exit slit 50e by rotating the concave diffraction grating 51a in the direction of the arrow shown by a rotary drive device (not shown). Can be selected for any given center wavelength. Therefore, similarly to the wavelength selection unit 50 of the first embodiment, the wavelength selection unit 51 of the present embodiment can set the center wavelength and the wavelength width continuously and independently.

  The defect inspection apparatus according to the third embodiment will be described below. The defect inspection apparatus of the present embodiment is also different from the wavelength selection section 50 of the first embodiment only in the configuration of the wavelength selection section 52. Therefore, in this embodiment, the same components as those in the defect inspection apparatus 1 of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

As shown in FIG. 5, the wavelength selector 52 includes an entrance slit 50a, lenses 52a and 52b, an acoustooptic device 52c, and an oscillator 52d. The light beam from the entrance slit 50a enters the lens 52a, is converged by the lens 52a, and enters the acoustooptic device 52c.
In the present embodiment, the oscillator 52d is an oscillator that outputs RF power to the acoustooptic device 52c.
The acousto-optic element 52c is of a type called an acousto-optic tunable filter (AOTF), which diffracts only a light beam having a wavelength corresponding to the frequency of the RF power input from the oscillator 52d in the direction of the primary light, Is transmitted in the direction of the zero-order light. The acoustooptic device 52c causes the diffracted light beam to enter the lens 52b.

The lens 52b converges the incident light beam and makes it incident on the incident end 35a.
AOTF can arbitrarily select the center wavelength of the primary light, but the wavelength width is generally a fixed value and is about 0.1 to 10 nanometers (nm). Accordingly, in order to freely select the wavelength width, the acoustooptic device 52c of the present embodiment is configured as follows.

  As the oscillator 52d of the present embodiment, a multi-channel RF oscillator capable of outputting a plurality of oscillation frequencies is used. As shown in FIG. 6A, the oscillator 52d inputs drive signals having a plurality of oscillation frequencies f such as frequencies f1 and f2 to the acoustooptic device 52c. FIG. 6A is a diagram illustrating a drive signal input to the acousto-optic element 52c when the vertical axis represents the amplitude a of the compression pressure and the horizontal axis represents the frequency f.

  The acoustooptic device 52c diffracts the incident light beam in the primary light direction at each oscillation frequency when a plurality of drive signals having different oscillation frequencies f are input. This diffracted light beam is set to a specific wavelength width of the acoustooptic device 52c and a center wavelength corresponding to the input oscillation frequency f. For example, when two drive signals having frequencies f1 and f2 are input, the acoustooptic device 52c has center wavelengths λ1 and λ2 corresponding to the frequencies f1 and f2, as shown in FIG. Diffracts the light beam.

  When the wavelengths of the diffracted light corresponding to the respective frequencies are close to each other, the spectrum of the primary light is synthesized as indicated by a broken line in FIG. Thereby, the acoustooptic device 52c can form first-order diffracted light having a wider wavelength width than the intrinsic wavelength width. Note that the wavelength width of the first-order diffracted light after synthesis can be arbitrarily set by adjusting the number of drive signals input to the acoustooptic device 52c and the interval of the oscillation frequency f between the input drive signals. Of course, by changing the center wavelength of each primary diffracted light to be synthesized, the center wavelength of the primary diffracted light after synthesis can also be changed. That is, the wavelength selector 52 having the above configuration can arbitrarily select the center wavelength and wavelength width of the light beam incident on the incident end 35a via the lens 52b.

  In the wavelength selection unit 52 configured as described above, the oscillator 52d can be replaced with a voltage controlled oscillator (VCO). The VCO is an oscillator that inputs RF power having a frequency corresponding to an input voltage (input voltage) to the acoustooptic device 52c as a drive signal. Accordingly, when the input voltage is continuously changed, the VCO can continuously change the frequency of the drive signal input to the acoustooptic device 52c in response to the change. For example, as shown by a triangular wave in FIG. 6C, the oscillator 52d can continuously change the frequency of the drive signal to be output when the input voltage is continuously changed. FIG. 6C shows the input voltage to the VCO when the horizontal axis is time t and the vertical axis is voltage V. In FIG. 6C, the triangular wave changes between the voltages V1 and V2.

  When the frequency of the drive signal continuously changes, the acousto-optic element 52c can continuously change the center wavelength of the diffracted light beam. In other words, the acoustooptic device 52c scans the center wavelength between the wavelength widths corresponding to the range in response to the input of the frequency continuously changed within the predetermined range.

  Note that the imaging unit 70 captures an image using a light beam received during a predetermined image accumulation time. For this reason, when the center wavelength is scanned for a predetermined wavelength width within the image accumulation time, the imaging unit 70 can capture an image using a light flux for the predetermined wavelength width. Accordingly, the wavelength selection unit 52 configured as described above is operated so that the center wavelength scans the desired wavelength width within the image accumulation time in order to select a light flux having a desired wavelength width at the time of imaging. For example, when the input voltage indicated by the triangular wave is applied to the VCO, by setting the triangular wave period T to be shorter than the image accumulation time, the wavelength selection unit 52 scans the center wavelength corresponding to the desired wavelength width. Can be completed within the image storage time. In the present embodiment, the period T is set, for example, in the range of about 1 μsec to about 100 μsec, but can be arbitrarily set according to the image accumulation time of the imaging unit 70. Thus, even when a VCO is used as the oscillator 52d, the acoustooptic device 52c can arbitrarily set the wavelength width of the diffracted light beam. It goes without saying that the center wavelength can be arbitrarily selected also in the wavelength selector 52 of this configuration.

  With the above configuration, the wavelength selection unit 52 of the present embodiment can also set the center wavelength and the wavelength width continuously and independently, similarly to the wavelength selection unit 50 of the first embodiment. In addition, since the acousto-optic element 52c has an effective angle opening of about 10 degrees, it can be disposed immediately before the imaging unit 70 between the optical paths of the illumination unit 30 and the imaging unit 70. It is not limited in.

  The defect inspection apparatus according to the fourth embodiment will be described below. The defect inspection apparatus according to the present embodiment is different from the wavelength selection section 50 according to the first embodiment only in the configuration of the wavelength selection section 53. Therefore, in this embodiment, the same components as those in the defect inspection apparatus 1 of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  As shown in FIG. 7, the wavelength selector 53 includes an entrance slit 50a, lenses 50b and 50d, a driver 53a, and a liquid crystal tunable filter (LCTF) 53b. The lens 50b converts the light flux from the entrance slit 50a into a parallel light flux and makes it incident on the LCTF 53b. The driver 53a is a device that applies a drive voltage to the LCTF 53b.

  The LCTF 53b is an element having a crossed Nicols polarizing plate and a liquid crystal filter disposed between these polarizing plates and capable of arbitrarily changing the retardation of the transmitted polarized light (Noboru Noboru, “VariSpec liquid crystal tunable filter”). "Optical Alliance, 7 (1995) P49-52,"). A voltage from the driver 53a is applied to the liquid crystal filter. The LCTF 53b configured as described above can arbitrarily set the center wavelength of transmitted light by changing the voltage applied to the liquid crystal filter by the driver 53a. The LCTF 53b is configured such that the wavelength width of transmitted light can be selected from a plurality of values within a range of about 5 to 20 nm. The light that has passed through the LCTF 53b enters the lens 50d.

  The lens 50 d converges the light beam from the LCTF 53 b and makes it incident on the incident end 35 a of the optical fiber 35.

  As described above, the wavelength selection unit 53 according to the present embodiment can set the center wavelength and the wavelength width continuously and independently, similarly to the wavelength selection unit 50 according to the first embodiment.

  Further, since the LCTF 53b has an effective angle opening of about 10 degrees to about 20 degrees, it can be disposed immediately before the imaging unit 70 between the optical paths of the illumination unit 30 and the imaging unit 70. There is no limitation in arrangement.

  The defect inspection apparatus 1 ′ according to the present embodiment is a defect inspection apparatus of the type that images a subject by the line image sensor shown in FIG. 12 of the first background art, instead of the spectroscopic unit 60 and the line image sensor 7a. It is a device that combines area image sensors. In the present embodiment, the same configurations as those of the defect inspection apparatus 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 8, the defect inspection apparatus 1 ′ of the present embodiment includes a stage 20, an illumination unit 30a, an imaging unit 40a, a spectroscopic unit 60, an imaging unit 70a, and a control system 200. It has.

  The illumination unit 30a includes a light source 31a that outputs white light and a collimator lens 31b that converts the light beam emitted from the illumination unit 30a into a parallel light beam. The light source 31 a and the collimator lens 31 b illuminate the subject 101 at an incident angle θi with respect to the normal line of the surface of the subject 101. The illumination unit 30a illuminates a linear region extending along the width direction of the subject 101. In other words, the illumination unit 30a illuminates a linear region along the Y axis. In the present embodiment, an area illuminated by the illumination unit 30a is an illumination area. The linear illumination area is an imaging area that is imaged by the imaging unit 70a. The imaging unit 70 a captures the entire imaging area 101 by sequentially imaging the imaging area along the longitudinal direction of the imaging object 101.

  The imaging unit 40 a includes a collimating lens 41 and an imaging lens 42. The collimating lens 41 converges the light reflected, diffracted and scattered by the subject 101 at the inspection angle θd with respect to the normal of the surface of the subject 101 among the light beams irradiated through the collimating lens 31b. Then, the light is incident on the imaging lens 42.

  The imaging lens 42 collects the light flux from the collimating lens 41 and forms an image. Thereby, the imaging lens 42 forms an image of the illumination area. The spectroscopic unit 60 is a spectroscopic unit that is disposed at the image forming position of the image forming lens 42 and separates the light beam from the image forming lens 42.

  Hereinafter, the spectroscopic unit 60 will be described in detail with reference to FIG. As shown in FIG. 9, the spectroscopic unit 60 includes an entrance slit 50a, lenses 50b and 50d, and a prism 50c, similarly to the configuration of the wavelength selection unit 50 of the first embodiment. The light beam incident from the entrance slit 50 a is split in the same manner as the wavelength selector 50. The spectroscopic unit 60 is different from the wavelength selection unit 50 in that the exit slit 50e is omitted. Note that the spectroscopic unit 60 performs spectroscopic analysis so that different wavelengths are distributed along a predetermined spectroscopic direction d2. The split light beam enters the lens 50d, is converged by the lens 50d, and enters the area image sensor 70a.

  The area image sensor 70a is a two-dimensional CCD in which pixels are arranged in a row direction axis along the spectral direction d2 and in a column direction orthogonal to the row direction axis. The column direction is indicated by the reference sign d3 in FIG. In the imaging unit 70a, a row of CCD image pickup elements arranged in the column direction is referred to as an image pickup element row. In FIG. 10A and FIG. 10B, the imaging element array is indicated by reference numeral 71a and extends in the left-right direction. Accordingly, the area image sensor 70a is configured by arranging a plurality of line-shaped imaging element arrays 71a along the column direction along the spectral direction d2. In the present embodiment, as shown in FIG. 10A, the area image sensor 70a is composed of, for example, 10 image sensor element rows 71a. As described above, the light beam incident on the area image sensor 70a via the spectroscopic unit 60 is split along the spectral direction d2. Accordingly, light beams having different wavelengths are distributed along the spectral direction d2 on the imaging surface of the area image sensor 70a. In other words, the area image sensor 70a receives light beams having different wavelengths along the arrangement direction of the imaging element array 71a. That is, the wavelength of the received light beam is different for each imaging element array 71a. Therefore, the imaging unit 70a images the imaging region with light beams having a plurality of wavelengths by the plurality of imaging element arrays 71a. For this reason, the area image sensor 70a can acquire the imaging data imaged with the light flux of each wavelength within a predetermined wavelength width by imaging the imaging area with the plurality of imaging element arrays 71a arranged continuously. .

  The imaging unit 70a is connected to the control system 200 via the horizontal transfer register 72a. The horizontal transfer register 72a is a unit that acquires imaging data (charge of each pixel of the CCD) acquired by the imaging unit 70a and transfers it to the image processing device 206 of the control system 200. In the present embodiment, the horizontal transfer register 72a reads imaging data by binning. Binning is a data reading method in which the charge accumulated in each pixel of the CCD is added by the amount corresponding to the pixel along a specified direction and read. Specifically, as shown in FIG. 10B, the horizontal transfer register 72a sequentially reads imaging data for each imaging element array 71a. Note that the horizontal transfer register 72a can select whether to add or discard the read image data for each image sensor array 71a. Then, the horizontal transfer register 72a adds only the image data of the designated image sensor row 71a, and sends the addition result data (added row data) to the control system 200 after addition of all the designated image sensor rows 71a. . In the present embodiment, the horizontal transfer register 72a is connected to the control system 200, and is controlled according to a drive command of the control system 200. The control system 200 controls the horizontal transfer register 72a so as to add only the imaging element array 71a corresponding to the designated center wavelength and wavelength width. The horizontal transfer register 72a forms imaging data similar to that obtained by imaging with the designated center wavelength and wavelength width based on the imaging data for each imaging element array 71a by addition. In this manner, the defect inspection apparatus 1 ′ of the present embodiment arbitrarily sets the imaging conditions (center wavelength and wavelength width) of the inspection image to be acquired by selecting the number and position of the imaging element arrays 71a to be added. Can be selected. Therefore, also in the defect inspection apparatus 1 ′ of the present embodiment, the center wavelength and the wavelength width of the illumination light at the time of inspection can be easily set to desired values as in the first embodiment. Therefore, the defect inspection apparatus 1 ′ can suppress detection of defects in the lower layer and more clearly detect defects in the target layer by using illumination light having an appropriately set center wavelength and wavelength width.

  In the present embodiment, the prism 50c is used as the spectroscopic element. However, the spectroscopic element can be replaced with another spectroscopic element such as the concave diffraction grating 51a. In other words, any known spectroscopic means can be used for the spectroscopic element of the present embodiment as long as the spectroscopic element can be dispersed along a predetermined spectroscopic direction d2.

It is a schematic side view which shows the defect inspection apparatus according to 1st Embodiment. It is a schematic side view which shows the wavelength selection part shown in FIG. It is a block diagram which shows the control system shown in FIG. It is a schematic side view which shows the wavelength selection part according to 2nd Embodiment. It is a schematic side view which shows the wavelength selection part according to 3rd Embodiment. 6A is a diagram illustrating a drive signal output from the oscillator, FIG. 6B is a diagram illustrating a wavelength of a light beam diffracted by the acoustooptic device, and FIG. It is a figure which shows the input voltage input into a voltage controlled oscillator. It is a schematic side view which shows the wavelength selection part according to 3rd Embodiment. It is a schematic perspective view which shows the defect inspection apparatus of 5th Embodiment. It is a schematic side view which shows the spectroscopy part shown in FIG. FIG. 10A is a schematic diagram illustrating the imaging unit 70a, and FIG. 10B is a schematic diagram illustrating the imaging unit 70a at the time of addition. It is a schematic side view which shows the conventional defect inspection apparatus. It is a schematic perspective view which shows another conventional defect inspection apparatus.

Explanation of symbols

f, f1, f2 ... frequency, 1 ... defect inspection device, d1 ... opening width direction, d2 ... spectral direction, d3 ... width direction axis, V1, V2 ... voltage, 10 ... condensing lens, 101 ... subject, DESCRIPTION OF SYMBOLS 20 ... Stage, 200 ... Control system, 201 ... Stage control part, 202 ... Drive circuit, 203 ... Optical system control part, 204 ... Subject conveyance control part, 206 ... Image processing apparatus, 207 ... Monitor, 208 ... Image storage apparatus 209 ... Host computer 210 ... Monitor 211 ... Keyboard 212 ... Memory 213 ... Sequencer 30 ... Illumination unit 31 ... Lamp house 32 ... Halogen lamp 33 ... Heat absorption filter 34 ... Condenser lens 35 ... Optical fiber, 35a ... incident end, 35b ... outgoing end, 36 ... diffuser plate, 37 ... stop, 38 ... half mirror, 39 ... collimating lens, 40, 40 Image forming unit, 41 ... Collimating lens, 42 ... Imaging lens, 49 ... P, 50 ... Wavelength selection unit, 50a ... Incident slit, 50b, 50d ... Lens, 50c ... Prism, 50e ... Output slit, 51 ... Wavelength selection Part, 51a ... concave diffraction grating, 52 ... wavelength selection part, 52a, 52b ... lens, 52c ... acousto-optic element, 52d ... oscillator, 53 ... wavelength selection part, 53a ... driver, 53b ... LCTF, 6 ... halogen lamp, 60 ... Spectroscopic part, 70 ... Imaging part, 70a ... Imaging part, 70b ... Imaging surface, 71a ... Imaging element row, 72 ... Polychromator, 72a ... Horizontal transfer register, [theta] d ... Inspection angle, [theta] i ... Incident angle, [lambda] 1 ... Center wavelength .

Claims (2)

Illuminating means for illuminating the subject with illumination light from the light source as a substantially parallel light beam;
Imaging means for forming an image of the subject by reflected light from the subject out of the parallel luminous flux from the illumination means;
Imaging means for capturing an image formed by the imaging means;
A wavelength selection unit that is disposed in an optical path between the light source and the imaging unit, and that selectively selectively sets a center wavelength and a wavelength width of a light beam in the optical path;
Defect detection means for detecting a defect of the subject from an image captured by the imaging means;
A defect inspection apparatus comprising: Illuminating means for illuminating the subject with illumination light from the light source as a substantially parallel light beam;
Imaging means for forming an image of the subject by reflected light from the subject out of the parallel luminous flux from the illumination means;
An imaging unit that arranges a plurality of imaging element arrays arranged along the width direction along a longitudinal direction orthogonal to the width direction, and images by each imaging unit;
A spectroscopic unit that is disposed on an optical path between the light source and the imaging unit, and that splits a light beam in the optical path along the longitudinal direction;
Defect detection means for detecting a defect of the subject from an image captured by the imaging means;
Comprising
The defect inspection apparatus for forming an image by adding the imaging results of the imaging element array corresponding to the designated wavelength range.

Images