JP3978307B2 - Ultraviolet laser beam generator, defect inspection apparatus and method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultraviolet laser beam generator for generating an ultraviolet laser beam used for inspection and observation of fine pattern defects and foreign matters represented by semiconductor device manufacturing and flat panel display manufacturing, and defect inspection capable of high-resolution detection. The present invention relates to an apparatus and a method thereof.
[0002]
[Prior art]
For example, as semiconductors are highly integrated, circuit patterns are becoming increasingly finer. Among these, masks and reticles used when manufacturing semiconductor elements in a photolithography process, and pattern defects on a wafer onto which circuit patterns formed on these are transferred by exposure are increasingly required to be detected with high resolution. As a technique for increasing the resolution, it is possible to shorten the wavelength of illumination light from visible light to ultraviolet light. Conventionally, as a light source, for example, a mercury lamp, an Xe lamp, or the like is used, and only a necessary wavelength is optically selected from various bright lines of the lamp.
[0003]
However, the bright line of the lamp has a wide emission spectrum width and it is difficult to correct the chromatic aberration of the optical system, and the light source becomes large in order to obtain sufficient illuminance, resulting in poor efficiency. In recent years, an exposure apparatus equipped with a KrF excimer laser device having a wavelength of 248 nm has been developed as a light source for an exposure apparatus in semiconductor manufacturing. However, the excimer laser light source is large and uses a fluorine gas. There are issues such as the need for safety measures. Therefore, as another ultraviolet laser light source, the wavelength of solid YAG laser light is converted by a nonlinear optical crystal to obtain the third harmonic (355 nm) or the fourth harmonic (266 nm) of the YAG laser light.
[0004]
As described above, wavelength conversion apparatuses for obtaining UV laser light are disclosed in JP-A-8-6082 (conventional technology 1), JP-A-7-15061 (conventional technology 2), and JP-A-11-64902 (conventional technology). Technique 3) and Japanese Patent Laid-Open No. 11-87814 (conventional technique 4) are known.
[0005]
Prior art 1 has a resonance frequency corresponding to the resonance length, which is disposed on the emission side of the light emitting means for emitting light of the fundamental wavelength, and has an optical path length of light passing through the inside as a resonance length. Resonance means having a plurality of reflection means for reflecting the light, and disposed on an optical path of light passing through the resonance means, having optical anisotropy and incident light, and the light A nonlinear optical material that emits at least one conversion wavelength light having a wavelength different from that of light; and an electric field application that applies an electric field to the nonlinear optical material so that a resonance frequency of the resonance means is tuned to the light of the fundamental wavelength. And a wavelength conversion device for generating UV laser light.
[0006]
Further, in the prior art 2, a light source that supplies laser light, an optical resonator that resonates laser light generated from the light source, and a wavelength that is shorter than the wavelength of the laser light are disposed in the optical resonator. In the laser light wavelength conversion device comprising: a nonlinear optical material that converts the light wave into a light wave; and an optical system that returns the laser light emitted from the optical resonator to the light source through the optical resonator again, the optical resonator, It describes that the nonlinear optical material and the optical system are arranged in a vacuum chamber.
[0007]
Further, in the prior art 3, in an external resonance type wavelength conversion device, an optical element is provided in a space between a wavelength conversion element (for example, a nonlinear optical crystal) and a laser beam separation optical member (for example, a mirror having wavelength selectivity). By providing a transparent material, filling with air or an inert gas, or substantially in a vacuum state, and blocking between the wavelength conversion element and the laser beam separation optical member from the outside, dust and gas It is described that the components are prevented from adhering to and depositing on the laser light emitting surface of the wavelength conversion element, the light receiving surface of the laser light separating optical member, and the like.
[0008]
Further, in the prior art 4, before using the laser resonator, contaminants such as oil adhering to the mirror and non-linear crystal components constituting the laser resonator are substantially removed to remove the laser resonator. It is described to extend the life.
[0009]
[Problems to be solved by the invention]
By the way, in the wavelength converter, when the surface of all optical members such as mirrors and non-linear optical crystals installed in the optical resonator is irradiated with ultraviolet light, and ultraviolet light is applied to the residual suspended matter in the optical resonator. There was a problem that a slight reaction gas generated when irradiated later adhered to the surfaces of all optical members such as mirrors and non-linear optical crystals in the optical resonator, leading to problems such as a decrease in transmittance.
[0010]
In order to solve this problem, in the prior art 2, the optical resonator, the nonlinear optical material, and the optical system are arranged in the vacuum chamber. However, in the prior art 2, since the optical resonator, the nonlinear optical material, and the optical system are arranged in the vacuum chamber, the optical resonator, the nonlinear optical material, and the optical system can be prevented from being contaminated. Although it is possible, even if atmospheric pressure is applied to the vacuum chamber, the vacuum chamber is made strong and a seal structure so that the optical resonator, nonlinear optical material, and optical system are not deformed due to internal stress. Therefore, there is a problem that the structure of the vacuum chamber including the seal structure becomes complicated. Furthermore, in the prior art 2, as described in Japanese Patent Laid-Open No. 7-15061, it is necessary to control the temperature of the nonlinear optical crystal, so that heat is generated in the vacuum chamber and other mirrors are used. It has the subject that it will affect optical members, such as.
[0011]
Moreover, in the said prior art 3, by blocking | interrupting between a wavelength conversion element and a laser beam separation optical member from the outside, dust and a gas component are the laser beam emission surface of the said wavelength conversion element, or the said laser beam separation optical member. Although consideration is given to preventing adhesion and deposition on the light-receiving surface, etc., consideration is not given to prevention of adhesion of contaminants to the entire optical resonator including the nonlinear optical crystal.
[0012]
As described above, in any of the prior arts 1 to 4, an optical resonator including a nonlinear optical crystal with a simplified structure without being greatly affected by temperature rise control of the nonlinear optical element (nonlinear optical crystal). No consideration is given to the prevention of contamination from the whole.
[0013]
In order to solve the above problems, the object of the present invention is to reduce the contamination of the entire optical resonator including the nonlinear optical element by simplifying the structure without being greatly affected by the heat generated from the nonlinear optical element. It is an object of the present invention to provide an ultraviolet laser light generating device that prevents the attachment of an object and efficiently converts the wavelength of incident laser light and extends the lifetime without reducing the output intensity of the ultraviolet laser light.
Another object of the present invention is to provide an ultraviolet laser light generation device that facilitates maintenance by easily investigating the cause when the output intensity of ultraviolet laser light is reduced in the wavelength conversion device. It is in.
Further, another object of the present invention is to detect a fine inspection pattern formed on an inspection object such as a semiconductor wafer with high resolution by illumination with a stable intensity by ultraviolet laser light, and to detect the fine inspection pattern on the fine inspection pattern. It is an object of the present invention to provide a defect inspection apparatus and method capable of inspecting defects.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention focuses on suppressing the generation potential of a chemical reaction gas with residual organic matter by irradiation with ultraviolet light inside an optical resonator in a wavelength conversion device that generates ultraviolet laser light. The structure is such that residual organic matter does not float inside the optical resonator. Specifically, an optical resonator and a non-linear optical element are installed in the container to form a sealed structure, and the inside of the container is replaced with an inert gas in a state in which an organic substance is prevented from entering from the outside, thereby making it difficult to oxidize. At the same time, it is intended to prevent the heat trapping based on the constant temperature control of the nonlinear optical element to prevent the influence of heat on other optical members.
[0015]
That is, the present invention relates to a laser excitation light source that emits and emits laser fundamental wave light, an ultraviolet light that is composed of an incident window that receives the laser fundamental wave light emitted from the laser excitation light source, and a multiplied harmonic light of the laser fundamental wave light. Provided in a hermetically sealed container with an exit window that exits to the outside, an optical resonator comprising a plurality of optical members that resonate with the laser fundamental wave light incident from the entrance window, and provided inside the optical resonator A wavelength converter that includes a nonlinear optical element that generates a multiplied harmonic light of the laser fundamental wave light, and that emits an ultraviolet laser light composed of the multiplied harmonic light in the emission window, and further includes a wavelength converter in the container. It is an ultraviolet laser beam generator configured to include a wavelength conversion device provided with a cleaning means for cleaning by filling with an active gas.
[0016]
Further, in the ultraviolet laser beam generator according to the present invention, the cleaning means of the wavelength converter connects the exhaust means for exhausting the gas in the container and the supply means for supplying the inert gas into the container. It is characterized by comprising.
Moreover, the present invention is characterized in that, in the ultraviolet laser beam generator, the cleaning means of the wavelength converter includes an adhesive material that fixes the contaminants floating in the container to the wall surface in the container.
Further, the present invention is characterized in that in the ultraviolet laser beam generator, the wavelength conversion device has a double or triple structure, and a gap filled with an inert gas is provided between the containers.
[0017]
The present invention also provides a laser excitation light source that emits and emits a laser fundamental wave light, an ultraviolet laser beam comprising an incident window that receives the laser fundamental wave light emitted from the laser excitation light source, and a harmonic wave multiplied by the laser fundamental wave light. An exit window that exits to the outside is provided in a sealed container, and is provided in an optical resonator composed of a plurality of optical members that resonate with the fundamental laser light incident from the entrance window, and the optical resonator. A non-linear optical element that generates a multiplied harmonic light of the laser fundamental wave light, and a wavelength converter that emits an ultraviolet laser light composed of the multiplied harmonic light in the emission window, and further, a contamination in the container It is an ultraviolet laser beam generator configured to include a wavelength converter provided with an optical detection means for optically detecting the state.
Moreover, the present invention is characterized in that, in the ultraviolet laser beam generator, the optical detection means is configured by installing a plurality of photoelectric conversion means in a container.
[0018]
Further, the present invention is characterized in that the ultraviolet laser beam generator further comprises a detecting means for detecting an output intensity of the ultraviolet laser beam emitted from the wavelength converter.
[0019]
In the ultraviolet laser beam generator according to the present invention, the laser excitation light source is a light source that emits a second harmonic wave of the Nd YAG laser beam.
[0020]
The present invention also provides the ultraviolet laser light generation device, an illumination optical system that illuminates an inspection target object with the ultraviolet laser light emitted from the ultraviolet laser light generation device, and an inspection object illuminated by the illumination optical system. Based on a detection optical system that collects reflected light from an object, a photoelectric converter that receives reflected light collected by the detection optical system and converts it into a signal, and a signal obtained from the photoelectric converter A defect inspection apparatus comprising a defect detection circuit for detecting a defect on the inspection object.
[0021]
The present invention also provides a plurality of ultraviolet laser light generators installed with coaxial optical paths of the emitted laser light, and an ultraviolet laser light emitted from any one or a plurality of the ultraviolet laser light generators. An illumination optical system that illuminates the object to be inspected, a detection optical system that collects reflected light from the object to be inspected illuminated by the illumination optical system, and reflected light that is collected by the detection optical system A defect inspection apparatus comprising: a photoelectric converter that receives light and converts it into a signal; and a defect detection circuit that detects a defect on the inspection target based on a signal obtained from the photoelectric converter. is there.
Further, the invention is characterized in that at least one of the plurality of ultraviolet laser light generators is a spare ultraviolet laser light generator.
In the present invention, the illumination optical system includes a selection optical system that illuminates an object to be inspected by selecting ultraviolet laser light emitted from any one or a plurality of ultraviolet laser light generators. It is characterized by that.
Further, the present invention is characterized in that the illumination optical system includes a combining optical system that combines the ultraviolet laser light emitted from each of the plurality of ultraviolet laser generators to illuminate the object to be inspected.
In addition, the present invention is characterized in that the ultraviolet laser beam generator is configured to emit an ultraviolet laser beam by continuously oscillating it.
Further, the present invention is characterized in that the defect inspection apparatus has a coherence reduction optical system as an illumination optical system.
Further, the present invention includes an objective lens as the illumination optical system and a detection optical system, and further, as the illumination optical system, ultraviolet laser light emitted from the ultraviolet laser light generator is passed over the pupil of the objective lens. A coherence reduction optical system that reduces the coherence by scanning in two dimensions is provided.
[0022]
The present invention further includes an objective lens as the illumination optical system and a detection optical system, and further, as the illumination optical system, ultraviolet laser light emitted from the ultraviolet laser light generator is passed through the objective lens to be inspected. It is characterized in that it is configured to illuminate an object with an annular illumination.
[0023]
In the defect inspection apparatus according to the present invention, the illumination optical system and the detection optical system include a polarizing beam splitter and a deflecting element group.
[0024]
Further, the present invention illuminates the object to be inspected with the ultraviolet laser light emitted from the ultraviolet laser light generator, condenses the reflected light from the illuminated object to be inspected, and collects the light. In this defect inspection method, reflected light is received by a photoelectric converter and converted into a signal, and a defect on the inspection object is detected based on the converted signal.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a high-resolution optical system, a defect inspection apparatus, and a method thereof according to the present invention will be described with reference to FIGS.
[0026]
A first embodiment of a defect inspection apparatus according to the present invention will be described with reference to FIG. In the present invention, in order to perform high-luminance illumination in the DUV region, an ultraviolet laser light source (ultraviolet laser light generator) 3 that emits DUV laser light is used. The stage 2 has degrees of freedom in the X, Y, Z, and θ directions, and a semiconductor wafer (an object to be inspected), which is an example in which an inspection pattern is formed, is placed as the sample 1. The ultraviolet laser light (DUV laser light) L2 emitted from the ultraviolet laser light source 3 is transmitted to the objective lens 11 via the beam expander 6, the coherence reduction optical system 7, the lens 8, the polarizing beam splitter 9, and the polarizing element group 10. Incident light is irradiated onto an inspection object (for example, a semiconductor wafer) 1 on which an inspection pattern is formed. The beam expander 6 expands the ultraviolet laser light to a certain size, and is a so-called Koehler illumination that is focused on the vicinity 11 a of the pupil of the objective lens 11 by the lens 8 and then irradiates the sample 1. .
[0027]
The reflected light from the sample 1 is detected by the image sensor 13 from above the sample 1 through the objective lens 11, the polarizing element group 10, the polarizing beam splitter 9, and the imaging lens 12. The image sensor 13 needs to be able to detect DUV light and can be composed of a TDI image sensor. When a TDI sensor is used as the image sensor 13 as described above, as shown in FIG. 20, a cylindrical lens is included as the lens 8 in order to make the illumination light flux into a slit shape 140 that matches the shape of the light receiving surface 130 of the TDI sensor. Such a configuration is preferable in terms of illumination efficiency.
[0028]
The polarizing beam splitter 9 has a function of reflecting when the polarization direction of the laser beam is parallel to the reflecting surface and transmitting when the laser beam is perpendicular. The ultraviolet laser light used as the ultraviolet laser light source 3 is originally a polarized laser, and the polarizing beam splitter 9 is installed so that the ultraviolet laser light L2 emitted from the coherence reduction optical system 7 is totally reflected. Since the inspection pattern formed on the inspection object 1 such as a wafer by the process has various shapes, the reflected light from the pattern has various polarization directions. The polarizing element group 10 controls the polarization direction of the laser illumination light and the reflected light, and sets the polarization ratio of the illumination light so that the reflected light due to the pattern shape and density difference does not reach the image sensor 13 due to uneven brightness. For example, a half-wave plate 10a and a quarter-wave plate 10b are incorporated for changing the phase of the illumination wavelength by 45 degrees or 90 degrees. Therefore, the light illuminated from the polarizing element group 10 onto the inspection object 1 becomes, for example, circularly polarized illumination light, and all of the light reflected from the inspection object 1 is reflected by the polarizing element group 10. It becomes perpendicular to the surface and passes through the polarization beam splitter 9. Thus, since the resolution of the optical system 70 changes depending on the illumination or detection polarization state, the mirror 86, the lens 87, and the detection provided in the optical path from the polarization beam splitter 9 to the image sensor 13 are provided. Based on the spatial image of the pupil plane of the objective lens 11 detected by the device 88, the polarization elements 10a and 10b are controlled to rotate relatively around the optical axis, and the circuit pattern formed on the object 1 to be inspected. The performance (resolution) of the optical system 70 can be improved by controlling the polarization state of the reflected light that changes according to the density and detecting it with the image sensor 13.
[0029]
The image sensor 13 is formed of, for example, a storage type sensor (TDI sensor) that can detect ultraviolet light, and depends on the brightness (lightness) of reflected light from the pattern to be inspected formed on the object 1 to be inspected. The grayscale image signal is output. That is, brightness information (grayscale image signal) of the inspection pattern formed on the inspection object 1 is detected by the image sensor 13 while the inspection object 1 is moved at a constant speed by scanning the stage 2. . The grayscale image signal 13a obtained from the image sensor 13 is input to the signal processing circuit 60 and subjected to defect inspection including foreign matter on the inspection target. The signal processing circuit 60 includes an A / D converter 14, a gradation converter 15, a delay memory 16, a comparator 17, a CPU 19, and the like. The A / D converter 14 converts the grayscale image signal 13a obtained from the image sensor 13 into a digital image signal.
[0030]
The focus detection optical system 71 detects the displacement of the stage 2 in the Z direction. Then, the focus detection circuit 72 processes the displacement in the Z direction of the stage 2 detected by the focus detection optical system 71, and, for example, based on the drive control command from the drive circuit 73 corresponding to this process, the Z of the stage 2 By driving and controlling the displacement in the direction, the image sensor 13 can detect the brightness information of the pattern in a focused state with high accuracy with respect to the pattern to be inspected formed on the object 1 to be inspected. become.
[0031]
The gradation converter 15 is composed of, for example, an 8-bit gradation converter, and a gradation as described in JP-A-8-320294 is applied to the digital image signal output from the A / D converter 14. Conversion is performed. That is, the gradation converter 15 performs logarithm, exponent, polynomial conversion, and the like, and the brightness of the image generated by the interference between the thin film formed on the inspection object 1 such as a semiconductor wafer and the laser beam in the process. Unevenness is corrected.
[0032]
The delay memory 16 stores the output image signal from the gradation converter 15 for one cell, one chip, or one shot constituting the object 1 to be inspected, such as a semiconductor wafer, according to the scanning width of the image sensor 13. It is something to be made.
[0033]
The comparator 17 compares the image signal output from the gradation converter 15 with the image signal obtained from the delay memory 16 and detects a mismatched portion as a defect. That is, the comparator 17 compares the detected image with the image delayed by an amount corresponding to the cell pitch or the like output from the delay memory 16. Accordingly, the CPU 19 inputs coordinates such as array data on the inspection object 1 such as a semiconductor wafer obtained based on the design information using the input means 18 constituted by a keyboard, a recording medium, a network, and the like. Thus, based on the inputted coordinates such as array data on the semiconductor wafer 1, defect inspection data is created based on the comparison inspection result by the comparator 17 and stored in the storage device 20. This defect inspection data can be displayed on the display means 21 such as a display as required, and can also be output to the output means 22 so that the defect location can be observed with, for example, another review device.
[0034]
The details of the comparator 17 may be those disclosed in Japanese Patent Application Laid-Open No. 61-212708. For example, the image alignment circuit, the difference image detection circuit for the aligned image, and the difference image are binarized. The non-coincidence detection circuit is configured by a feature extraction circuit that extracts an area, length, coordinates, and the like from the binarized output.
[0035]
Next, an embodiment of the ultraviolet laser light source (ultraviolet laser light generator) 3 will be described. In order to obtain high resolution, it is necessary to shorten the wavelength, and high brightness illumination is necessary to improve the inspection speed. In the past, a discharge lamp such as mercury xenon was used, and the visible spectrum was widely used in the emission spectrum (bright line) of the lamp. Compared with these light intensities, the bright line in the ultraviolet and deep ultraviolet regions is visible. Compared with light, it is about several percent, and a large light source is required to secure desired luminance. When the size of the light source is increased in this way, there is a limit in moving away from the optical system so as not to be affected by heat generation. From such a viewpoint, in the present invention, an ultraviolet laser beam (DUV light (Deep Ultraviolet ray)) that can easily secure a short wavelength is used as the light source 3. As the ultraviolet laser light, laser light having a wavelength of about 100 nm to 400 nm is shown, and as the DUV laser light, laser light having a wavelength of about 100 nm to 314 nm is shown.
[0036]
As shown in FIG. 2, the ultraviolet laser light source (ultraviolet laser light generator) 3 includes, for example, a solid-state laser device (laser excitation light source) 4 that emits and emits laser fundamental light having a wavelength of 532 nm and a wavelength converter 5. . The solid-state laser device 4 emits a Nd: YAG laser beam having an oscillation wavelength of 1064 nm through a nonlinear optical crystal to be a double wave, and a laser beam having a wavelength of 532 nm, which is controlled so as to be output at a constant intensity. It is. That is, the solid-state laser device 4 that outputs the second harmonic wave of the Nd: YAG laser beam controls the current of the laser power source in accordance with the monitored output, so that the output of the laser beam L1 having a certain intensity is emitted. Configured to be The laser beam L 1 having a wavelength of 532 nm emitted from the solid-state laser device 4 is single-mode oscillation and is incident on the wavelength conversion device 5.
[0037]
Further, the oscillation mode of the solid-state laser device 4 of the ultraviolet laser light source 3 may be continuous oscillation or pulse oscillation. However, the stage 2 is continuously scanned and an image from the object 1 to be inspected is an image sensor such as a TDI sensor. Because of the relationship detected at 13, continuous oscillation is desirable.
[0038]
The ultraviolet laser light source 3 is a device that generates a third harmonic (355 nm) or a fourth harmonic (266 nm) of the fundamental wave by converting the wavelength of a solid YAG laser (1064 nm) with a nonlinear optical crystal or the like. It may be configured. Furthermore, if it exists as the ultraviolet laser light source 3, it may be 100 nm or less.
[0039]
Next, the wavelength converter 5 that is an element of the present invention will be described. FIG. 2 is a view of the ultraviolet laser light source 3 in FIG. 1 as viewed from the Z direction, and shows a schematic structure (cross section) of the wavelength conversion device 5. Mirrors M1 to M4 are arranged inside the container of the wavelength conversion device 5, and the laser light L1 emitted from the solid-state laser device 4 and incident from the transparent window 35 of the incident port 39 provided in the containers 41 and 45 is , Passes through the mirror M1 and reaches the mirror M2. The mirror M2 transmits part of the incident light and reflects the rest. The laser beam reflected by the mirror M2 reaches the mirror M3. The nonlinear optical crystal 30 is disposed in the optical path between the mirror M3 and the mirror M4, and the laser light totally reflected by the mirror M3 passes through the nonlinear optical crystal 30 and reaches the mirror M4. And an optical resonator is comprised by the optical member which has these mirrors M1-M4 and which has a high reflectance. Furthermore, since the nonlinear optical crystal 30 is disposed at an appropriate position calculated optically, the incident light is converted into a second harmonic having a wavelength of 266 nm by the crystal 30. In the mirror M4, only the second harmonic ultraviolet laser light L2 is emitted outside the wavelength converter 5 through the transparent window 35 of the emission port 40 provided in the containers 41 and 45. That is, the mirror M4 is coated so as to transmit the second harmonic and reflect other wavelengths. The laser light L3 that has not been converted by the nonlinear optical crystal 30 is reflected by the mirror M4 and reaches the mirror M1, and again follows the same optical path as the laser light L1 that has passed through the mirror M1. Here, a part of incident light that has passed through the mirror M2 is detected by detecting means (not shown) to detect an error between the frequency of the incident light and the resonance frequency of the wavelength converter, and is tuned so that both are always in a resonance state. Therefore, the resonator length is controlled with high accuracy by, for example, finely moving the mirror M3 at high speed by a servo mechanism (for example, a piezoelectric element) not shown. By controlling the resonator length with high accuracy in this way, an optical resonator is constituted by an optical member having a high reflectance composed of the mirrors M1 to M4. A wavelength converter 50 is configured by the optical resonator and the nonlinear optical crystal 30 provided inside the containers 41 and 42.
[0040]
Therefore, the ultraviolet laser beam L2 having a wavelength of 266 nm emitted from the wavelength conversion device 5 has coherence (has coherence), and when the circuit pattern on the inspection object 1 is illuminated with the laser beam, the spec Cause the occurrence of Therefore, it is necessary to reduce the coherence in the illumination with the ultraviolet laser beam L2. In order to reduce coherence, either temporal or spatial coherence may be reduced. Therefore, in the present invention, the spatial coherence is reduced by the coherence reduction optical system 7.
[0041]
FIG. 3 is a schematic diagram showing an embodiment of an illumination optical system including the coherence reduction optical system 7 according to the present invention. The laser light L2 emitted from the transparent window 35 of the emission port 40 of the wavelength conversion device 5 is converted into a parallel light beam expanded to a certain size by the beam expander 6, and is condensed at the focal position of the lens 24. Thereafter, the light is condensed on the pupil 11 a of the objective lens 11 through the lens 25, the lens 8, and the polarization beam splitter 9. Incidentally, the focal position 28 of the lens 24 is also the focal position of the lens 25, and the focal position 28 is conjugate with the position of the pupil 11a of the objective lens 11.
[0042]
As shown in FIG. 4, the coherence reduction optical system 7 has, for example, a circular diffuser plate 26 disposed at a focal position 28 in the optical path and rotated at high speed by a motor 27. That is, as shown in FIG. 5, a diffusion plate 26 whose surface is processed to an appropriate roughness is disposed at the focal position of the lens 24 (and the lens 25), and the pupil 11 a of the objective lens 11 is rotated by the rotation of the motor 27. Spatial coherence is reduced by scanning a laser spot that is focused on, thereby reducing coherence. The laser beam spreads to some extent on the diffusion plate 26. The lens 25 is selected as a lens having a numerical aperture that covers this, and the detailed specifications of the diffusion plate 26 are determined by experiments. Further, the coherence reduction optical system 7 is not limited to the method described above, and a polyhedral rotating mirror, a rotating vibration mirror, or the like may be used as another means.
[0043]
By the way, the laser light source 3 used for illumination uses the mirrors M1 to M4 and the nonlinear optical crystal 30 in which the excitation light L1 having a wavelength of 532 nm by the solid-state laser is disposed in the container of the wavelength conversion device 5 to be a double wave. As described above, it is necessary to tune the internal optical system so that the frequency of the incident light and the resonant frequency of the wavelength converter 50 are always in a resonant state, as described above. For example, the inside of the container of the wavelength conversion device 5 is very delicate. Among them, the nonlinear optical crystal 30 has deliquescence and dislikes moisture. Therefore, in order to stably obtain ultraviolet laser light, it is necessary to always keep the surfaces of the mirrors M1 to M4 and the nonlinear optical crystal 30 installed in the optical resonator in a clean state.
[0044]
In addition, there is a thermostat (not shown) for keeping the temperature of the nonlinear optical crystal 30 constant in order to emit a constant ultraviolet laser beam from the wavelength converter 50 installed inside the container of the wavelength converter 5. It is installed in a fine movement mechanism 45 that supports the nonlinear optical crystal 30.
[0045]
Here, when the inside of the containers 41 and 45 of the wavelength conversion device 5 cannot be kept in a clean state, a chemical reaction occurs by irradiating with ultraviolet laser light, and adheres to and cures the internal optical element surface. As a result, the output intensity of the ultraviolet laser beam is reduced. Therefore, when the output intensity of the ultraviolet laser light is reduced, it is assumed that the surface of the nonlinear optical crystal 30 is burned by readjustment of the optical members M1 to M4 such as mirrors inside the container of the wavelength conversion device 5 and laser irradiation. This can be dealt with by changing the position of the laser irradiation to 30 little by little, but both require a lot of labor and time.
[0046]
Thus, first, a first embodiment of the wavelength conversion device 5 according to the present invention will be described. In this first embodiment, as shown in FIGS. 6 and 7, a wavelength converter 50 composed of an optical resonator composed of optical members M1 to M4 and a nonlinear optical crystal 30 is blocked from outside air by a container 41. The structure was hermetically sealed. FIG. 7 shows a state where the lid 31 is removed. That is, a transparent window 35 is provided at the laser beam incident port 39 and the emission port 40 formed in the container 41 and shielded by using, for example, an O-ring 36 or the like, for example, an inert gas storage container (not shown) for cleaning. A supply valve 32 provided with a filter 37 at the tip for supplying, for example, an inert gas gas for cleaning into the container 41, and an exhaust for exhausting residual gas in the container 41 connected to an exhaust pump The detector for observing the state of the gas in the valve | bulb 33 and the container 41, especially that the inert gas was filled was provided. Thus, as the cleaning means for cleaning the inside of the container 41, for example, the supply valve 32 provided with the filter 37 at the tip connected to an inert gas storage container (not shown) and the exhaust pump are connected. The exhaust valve 33 and a detector 34 for observing that the inert gas is filled, for example, are configured. With this configuration, after the adjustment of the optical system in the container of the wavelength conversion device 5 is completed, the lid 31 is attached and an exhaust pump (not shown) is connected to the exhaust valve 33 as shown in FIG. The residual gas in the container 41 is exhausted. Next, an inert gas is supplied from the supply valve 32. The detector 34 is, for example, a barometer, and monitors the atmospheric pressure in the container 41. The supply of the inert gas is completed when the atmospheric pressure in the container 41 reaches 1 atm. As the inert gas, a gas that does not chemically react with the laser beam in the wavelength converter 50 is preferable, and examples thereof include nitrogen gas and argon gas. In addition, a filter 37 is provided at the tip of the supply valve 32, and this serves to control the flow rate when supplying the inert gas and to prevent impurities such as foreign matters from being mixed.
[0047]
In particular, the exhaust valve 33 is connected to the exhaust pump 33 to exhaust the residual gas in the container 41, and then the inert gas is supplied from the supply valve 32 into the container 41 and is supplied in a state of being filled to about 1 atm. The container 32 may be sealed by closing the valve 32 and the exhaust valve 33. Alternatively, the inert gas may be supplied from the supply valve 32 into the container 41 to be filled to about 1 atmosphere, and then the inert gas may be flown in a small amount so that the laser beam does not fluctuate.
[0048]
According to the first embodiment described above, new foreign matter can be prevented from entering the container 41, and as a result, the surfaces of the mirrors M1 to M4 and the crystal 30 installed in the optical resonator. Can always be kept in a clean state, and the output intensity of the ultraviolet laser light can be prevented from being lowered.
[0049]
Next, a second embodiment of the wavelength conversion device 5 according to the present invention will be described. In the second embodiment, as shown in FIG. 9, the wavelength converter 50 is shut off from the outside air by a double structure of a container 42 and a casing (container) 45 and sealed. In the case of the second embodiment, it is possible to prevent mechanical stress from being generated on the wavelength converter 50 by closing the lid 31. That is, the outer casing 45 is provided with transparent windows 35 at the entrance port 39 and the exit port 40, shielded by using, for example, an O-ring 36, etc., and the valves 32 and 33 for supplying and discharging the gas, A detector 34 for observing the state of the gas was provided. The container 42 containing the wavelength converter 50 was supported by a support member 43 in a casing (container) 45 to have a double structure. The inner container 42 is formed with an incident port 46 for entering laser light incident through the transparent window 35 of the incident port 39 and an exit port 47 for emitting the ultraviolet laser light L2 to the transparent window 35 of the exit port 40, An intake hole 48, an exhaust hole 49, and a pressure hole 51 communicating with the inside and outside of the container 42 are formed. In particular, by making a large number of the intake holes 48 and the exhaust holes 49 small, even if a small amount of inert gas continues to flow, it functions as a buffer between the outside of the container 42 and the inside of the casing 45, It is possible to eliminate the flow of the inert gas in 42 and eliminate the fluctuation of the laser beam. Naturally, the exhaust valve 33 is connected to the exhaust pump 33 to exhaust the residual gas in the casing 45 including the inside of the container 42, and then the inert gas is supplied from the supply valve 32 into the casing 45 to reach about 1 atm. In a filled state, the exhaust valve 33 and the supply valve 32 may be closed to seal the casing 45. Thus, according to the second embodiment of the wavelength converter 5, the generation of mechanical stress on the wavelength converter 50 is prevented, and an inert gas that does not chemically react with the laser beam, such as nitrogen gas, By supplying the gas so as to be filled with argon gas or the like, it is possible to prevent a new foreign substance from entering the container 42. As a result, the surfaces of the mirrors M1 to M4 and the crystal 30 installed in the optical resonator. Can always be kept in a clean state, and the output intensity of the ultraviolet laser light can be prevented from being lowered.
[0050]
In the second embodiment, the wavelength converter 50 is shut off from the outside air by the double structure of the container 42 and the casing (container) 45, and is sealed, but the structure is somewhat complicated. You may comprise a container with a triple structure. If the container has a triple structure in this way, even when a small amount of inert gas continues to flow, a gap serving as a buffer can be formed between the containers, so that the fluctuation of the laser beam can be eliminated more and more. Become.
[0051]
Next, a third embodiment of the wavelength conversion device 5 according to the present invention will be described. In the third embodiment, an adhesive material 38 is applied to the inner wall of the container 41 in the first embodiment as shown in FIG. Of course, in the third embodiment, the adhesive material 38 may be applied to the inner wall of the container 42 in the second embodiment. According to the third embodiment, it is possible to prevent the foreign matter 39 remaining in the containers 41 and 42 from flying up by the wind pressure and adhering to the internal optical components when the inert gas is supplied. In addition, when the gas in the containers 41 and 42 is exhausted, the floating foreign material 39 in contact with the adhesive material 38 can be caught and held semipermanently.
[0052]
Next, a fourth embodiment of the wavelength conversion device 5 according to the present invention will be described. As shown in FIG. 10, in the fourth embodiment, a plurality of optical sensors S1 to S6 are arranged inside the container of the wavelength converter 5 in the third embodiment, and the plurality of optical sensors S1 to S6 are used to store the container. It is possible to monitor the contamination state of the optical members M1 to M4 and the non-linear optical element 30 by detecting scattered light from the contaminants generated in 41 and 42 and detecting the degree of contamination in the container, that is, the contamination state. Is. That is, the plurality of optical sensors S1 to S6 constitute an optical contaminant detection unit that detects scattered light from contaminants generated in the containers 41 and 42. The contaminant is usually an organic substance, and the optical sensors S1 to S6 detect fluorescent scattered light generated from the organic substance. Each of the plurality of optical sensors S1 to S6 includes a condenser lens and a photoelectric conversion element (not shown), and detects, for example, the contamination state of the surfaces of the mirrors M1 to M4 and the surface of the nonlinear optical crystal 30. To do. Since the photoelectric conversion element generates an electromotive force according to the amount of received light, a threshold value is provided for this, and when the threshold value is exceeded, it is determined that the surfaces of the mirrors M1 to M4 and the surface of the nonlinear optical crystal 30 are contaminated. For example, if there is an output signal from the optical sensor S2, it can be seen that the contaminant 40 has adhered to the surface of the mirror M2. Since the wavelength of the laser beam is known, by using an optical sensor having high sensitivity only in a specific wavelength band as the optical sensors S1 to S6, the influence of disturbance light can be prevented and the detection threshold can be set low, so that the mirrors M1 to M4 In addition, slight contamination on the surface of the crystal 30 can be detected with high sensitivity. In the defect inspection apparatus shown in FIG. 1, a detection means (not shown) comprising a photoelectric converter or the like provided by branching the output intensity of the ultraviolet laser light L2 emitted from the wavelength converter 5 from the illumination optical path. If the output intensity decreases as a result of monitoring, the cause is that the surfaces of the optical members M1 to M4 and 30 to be detected by any of the optical sensors S1 to S6 are contaminated with contaminants. Therefore, the surface of the optical member is cleaned or replaced with an uncontaminated optical member. As a method for monitoring the ultraviolet laser light L2 emitted from the wavelength converter 5, the output of the beam expander 6 or the coherence reduction optical system 7 may be monitored. Naturally, when the output of the beam expander 6 or the coherence reduction optical system 7 is monitored, a decrease in output intensity due to contamination of the optical system 6 or 7 is also included.
[0053]
Further, when there is no output signal based on contamination from the optical sensors S1 to S6, and the output intensity of the ultraviolet laser light L2 emitted from the wavelength converter 5 is lowered by monitoring with the detection means (not shown) as described above. Is considered to be caused by the nonlinear optical crystal 30. In this case, since there is a high possibility that the inside of the crystal 30 is burned by the laser irradiation, the nonlinear optical crystal 30 is moved in the YZ direction by the fine adjustment mechanism 45 so that the output intensity of the ultraviolet laser light L2 is increased. Is done. Of course, the fourth embodiment can be applied to the second embodiment shown in FIG.
[0054]
As described above, by monitoring the contamination state in the wavelength conversion device, it is possible to easily and appropriately determine whether or not the wavelength conversion device needs to be maintained. It is possible to eliminate extra time for adjusting the optical system.
[0055]
According to the embodiment of the present invention described above, a long-lived laser light source, i.e., a wavelength converter, can be extended for a long time without lowering the light output of the ultraviolet laser light. Oscillation can be obtained, and as a result, a fine pattern formed on the inspection object 1 can be detected with high resolution, and defects generated in the fine pattern can be inspected with high reliability.
[0056]
Next, a second embodiment of the defect inspection apparatus according to the present invention will be described with reference to FIG. 11, FIG. 18, and FIG. This second embodiment differs from the first embodiment shown in FIG. 1 in that a solid-state laser device (laser excitation light source) 4 and a wavelength conversion device 5 are first provided as shown in FIG. A plurality of ultraviolet laser light sources (ultraviolet laser light generators) 3 provided are installed so that the ultraviolet laser light emitted from the ultraviolet laser light source 3 is coaxial, and only one is provided as shown in FIG. May be used by switching them when others fail, and as shown in FIG. 19A, all of them may be oscillated and used at low output. That is, in the second embodiment, a plurality of ultraviolet laser light sources 3a, 3b, and 3c including the solid-state laser device 4 and the wavelength conversion device 5 are provided, and emitted from each of the ultraviolet laser light sources 3a, 3b, and 3c. The ultraviolet laser light is folded in the Z direction, for example, in each of the mirrors 81 a, 81 b, 81 c, coaxially input, and input to the beam expander 6. In particular, as shown in FIG. 19B, by switching and selecting each mirror (selection optical system) 81a to 81c, it is possible to switch and select the outputs of the ultraviolet laser light sources 3a to 8c. As a result, the ultraviolet laser light is always emitted from the normal ultraviolet laser light source provided as a reserve and irradiated onto the inspection object 1, and the fine pattern formed on the inspection object 1 has a high resolution. It is possible to detect and detect defects generated in the fine pattern with high reliability. Thus, while using a normal ultraviolet laser light source, it is possible to adjust the wavelength converter 5 of the abnormal ultraviolet laser light source that has failed or deteriorated, or to replace it with a normal wavelength converter 5. Become.
[0057]
In addition, as shown to Fig.19 (a), when combining and using the ultraviolet laser beam radiate | emitted from several ultraviolet laser light source 3a-3c with the synthetic | combination optical systems 81a-81c, the whole output is TV camera 85, for example. For example, the output of the solid laser device 4 in a normal ultraviolet laser light source is adjusted in place of the deteriorated ultraviolet laser light source so that a predetermined value is obtained for the entire output to be monitored. It can be increased and automatically adjusted. Further, the wavelength conversion device 5 of the deteriorated ultraviolet laser light source is adjusted so as to increase the output intensity of the ultraviolet laser light L2 by moving the nonlinear optical crystal 30 in the YZ direction by the fine adjustment mechanism 45. Is also possible.
[0058]
Further, as shown in FIG. 18, an ultraviolet laser light source 3 composed of a plurality of light sources 3a and 3b is installed separately from the optical system 70, propagation of mechanical vibrations emitted from the stage and the like to the ultraviolet laser light source 3, and ultraviolet laser The heat conduction from the light source 3 to the optical system 70 is blocked. In the present embodiment shown in FIG. 18, a case where the ultraviolet laser light source 3 is installed below the vibration isolation platen 80 is shown. In this case, although not shown, the exhaust is locally performed so that the heat generated by the ultraviolet laser light source 3 is not transmitted to the upper surface plate 80. The laser beams L2 emitted from the ultraviolet laser light sources 3a to 3c are folded back in the Z direction by the mirrors 81a to 81c and reach the optical system 70 via the mirror 90 and the beam expander 6. In the pattern inspection of the surface of the semiconductor wafer 1, the stage 2 on which the wafer 1 is mounted is scanned in the X and Y directions and the entire surface is inspected. During the inspection, the position of the center of gravity changes as the stage moves. Tilts. In this case, the surface plate 80 is returned to the horizontal state by an air servo or the like, but the ultraviolet laser light L2 emitted from the ultraviolet laser light source 3 has a beam diameter of about 1 mm or less, and the optical system 70 and the ultraviolet laser light L2 It is expected that the optical axis is temporarily off the optical axis. Therefore, in the present invention, the mirror 90, the lens 91, and the position detector 92 are installed on the surface plate 80, thereby detecting the amount of movement of the ultraviolet laser light L2, and the mirror 81 is moved using an actuator such as a piezo. The optical path of the off-axis ultraviolet laser beam L2 is corrected at high speed. Here, the mirror 90 is coated with a reflective film so as to reflect a slight amount of the ultraviolet laser light L2, and the lens 91 projects the reflected light on the position detector 92 in an enlarged manner. The position detector 92 is configured, for example, by dividing the light receiving element in the XZ direction, and detects a movement amount of the laser light by calculating a detection signal of the light receiving element by an electric circuit (not shown). Thereby, the ultraviolet laser light emitted from each of the ultraviolet laser light sources 3a and 3b can be stably incident on the optical system 70.
[0059]
As described above, since a plurality of ultraviolet laser light sources 3 including the solid-state laser device 4 and the wavelength conversion device 5 are installed, the output of the ultraviolet laser light source can be switched and selected. Therefore, it is always possible to ensure a normal ultraviolet laser light source, and it is possible to continuously inspect a fine pattern using the ultraviolet laser light with high reliability.
[0060]
Next, another embodiment of the coherence reduction optical system 7 will be described. In this embodiment, the coherence is spatially reduced by two-dimensionally scanning the laser beam by an on-pupil scanning mechanism composed of two orthogonal scanning mirrors 61 and 64 as shown in FIG. I have to. FIG. 13 is a schematic diagram of an illumination system. The ultraviolet laser light L2 emitted from the ultraviolet laser light source 3 and enlarged to a certain size by the beam expander 6 is reflected by the mirror 61 as a parallel light beam, condensed by the lens 62, and then again by the lens 63. Then, the light is condensed on the pupil 11 a of the objective lens 11 by the lens 8. Reference numerals 67 and 69 denote laser beam reflection positions at the scanning mirrors 61 and 64, respectively, and are in a positional relationship conjugate with the surface of the inspection object 1. Reference numeral 68 denotes a first pupil conjugate plane conjugate with the pupil 11a of the objective lens 11. Accordingly, by rotating or swinging the scanning mirrors 61 and 63 with an electric signal, the ultraviolet laser light L2 can be scanned two-dimensionally on the pupil 11a of the objective lens 11. The electrical signals input to the scanning mirrors 61 and 64 include, for example, a triangular wave and a sine wave. By changing the frequency and amplitude of the input electrical signal, the ultraviolet laser light L2 on the pupil 11a of the objective lens 11 is changed. Various shapes can be scanned. In particular, the scanning mirrors 61 and 64 are controlled to scan the ultraviolet laser spot on the pupil 11a of the objective lens 11 in a ring shape as shown in FIG. It becomes possible to reduce the coherence on 1 and perform ring-shaped illumination. Further, as will be described later, even when the illumination light is an ultraviolet multi-slit spot beam corresponding to the TDI sensor, it is possible to completely emit light by placing a diffusion plate after the on-pupil scanning mechanism composed of the scanning mirrors 61 and 64. Interference can be eliminated.
[0061]
By the way, a mirror 82 that branches an illumination light amount that does not interfere with the illumination of the object 1 to be inspected is arranged in the illumination optical path, and a part of the illumination laser beam is branched by the mirror 82 so that it can be observed by the TV camera 85. Configured. That is, since the light branched by the mirror 82 is ultraviolet laser light, a screen 83 that emits fluorescence when the ultraviolet laser light is incident is placed at a position conjugate with the pupil 11 a of the objective lens 11. As a result, the fluorescent image generated on the screen 83 (when the ultraviolet laser beam is scanned two-dimensionally in a ring shape) 92 is enlarged by the lens 84, whereby an image 91 as shown in FIG. Observation with the camera 85 is possible. Reference numeral 93 denotes the outer diameter of the pupil 11a of the objective lens 11. Then, in the signal processing circuit 60 shown in FIG. 18, by processing the image 91 output from the TV camera 85, for example, the amount of deviation of the illumination light 92 from the center of the pupil 11a can be obtained. By feeding back to the control circuit 95, scanning by the scanning mirrors 61 and 64 of the coherence reduction optical system 7 can be controlled.
[0062]
Further, the signal processing circuit 60 binarizes the image received by the TV camera 85 and adds the pixels having a certain brightness or higher to obtain the illumination area, thereby optimizing the illumination condition (illumination σ). Is also possible.
[0063]
Needless to say, the scanning of the ultraviolet laser light by the scanning mirrors 61 and 64 is performed within the accumulation time of the image sensor 13.
[0064]
Next, another embodiment of illumination conditions will be described. That is, in this embodiment, the ultraviolet laser light is illuminated by multi-spot illumination on the pupil of the objective lens 11. By performing multi-spot illumination in this way, the illumination σ can be increased, so that the scanning time by the scanning mirrors 61 and 64 can be delayed. FIG. 15 is a three-dimensional view in which the multi-lens array 65 and the lens 66 are arranged in the coherence reduction optical system 7, and FIG. 16 is a schematic diagram of an illumination system using the same. That is, the multi-lens array 65 and the lens 66 are added to the incident ultraviolet laser light L2, thereby creating a multi-imaginary ultraviolet laser light source and condensing it on the pupil 11a of the objective lens 11. Configure. Note that reference numeral 110 shown in FIG. 16A denotes a mask for forming multi-spot light. 110b shown in FIG. 16B is a mask for forming multi-spot light, and 110b shown in FIG. 16C is a mask for forming multi-slit spot light. Reference numerals 112a and 112b denote portions that transmit light, and reference numerals 111a and 111b denote portions that shield light. As a means 65 for creating a virtual ultraviolet laser light source, for example, as shown in FIG. 17A, a lens array 114 in which two cylindrical lens arrays 113 are arranged orthogonally, or as shown in FIG. This is achieved by arranging a lot lens array 115 in which two convex lenses are two-dimensionally arranged in the optical path. However, when an accumulation type TDI sensor is used as the image sensor 13, as shown in FIG. 20, it is necessary to use multi-slit spot light 140 as multi-spot light so as to correspond to the light receiving surface 130 of the TDI sensor. . Therefore, as the means 65, for example, an elongated lot lens array 116 shown in FIG.
[0065]
And the scanning state of the multi-spot light used as the annular illumination on the pupil 11a of the objective lens 11 is shown in FIG. Even with multi-slit spot light corresponding to the TDI sensor, scanning is performed on the pupil 11a of the objective lens 11 in the same manner. The pitch 120 of the laser condensing point on the pupil 11a of the objective lens 11 can be freely changed by changing the focal length of the lens 66 and other lenses.
[0066]
【The invention's effect】
According to the present invention, in the wavelength converter, the structure is simplified and contamination of the entire optical resonator including the nonlinear optical element is prevented without being greatly affected by the heat generated from the nonlinear optical element. There is an effect that it is possible to realize an ultraviolet laser light generation device that achieves a long life without efficiently converting the wavelength of incident laser light and reducing the output intensity of the ultraviolet laser light.
[0067]
Further, according to the present invention, when the output intensity of the ultraviolet laser beam is reduced in the wavelength conversion device, the cause can be easily investigated to facilitate maintenance including determination of necessity of maintenance. There is an effect that can be done.
[0068]
In addition, according to the present invention, a fine inspection pattern formed on an inspection target such as a semiconductor wafer is detected with high resolution by illumination with a stable intensity by ultraviolet laser light, and defects on the fine inspection pattern are detected. There is an effect that can be inspected with high reliability.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a defect inspection apparatus according to the present invention.
FIG. 2 is a diagram showing a schematic configuration of an ultraviolet laser light generating apparatus according to the present invention.
3 is a schematic diagram showing an example of an illumination optical system including the coherence reduction optical system shown in FIG. 1. FIG.
FIG. 4 is a perspective view showing an embodiment of a coherence reduction optical system.
FIG. 5 is a front view of FIG. 4;
FIG. 6 is a perspective view showing an external appearance of a wavelength converter according to the present invention.
FIG. 7 is a cross-sectional view showing a first embodiment of a wavelength converter according to the present invention.
FIG. 8 is a cross-sectional view showing a third embodiment of the wavelength converter according to the present invention.
FIG. 9 is a cross-sectional view showing a second embodiment of the wavelength converter according to the present invention.
FIG. 10 is a cross-sectional view showing a fourth embodiment of the wavelength converter according to the present invention.
FIG. 11 is a block diagram showing a second embodiment of the defect inspection apparatus according to the present invention.
FIG. 12 is a perspective view showing another embodiment of the coherence reduction optical system.
13 is a schematic diagram of the optical system shown in FIG.
FIG. 14 is a diagram showing a state (annular illumination state) in which an ultraviolet laser spot light is scanned on a pupil of an objective lens to reduce spatial coherence.
FIG. 15 is a perspective view showing an embodiment of an optical system that reduces spatial coherence using multi-spots.
FIG. 16 is a schematic diagram showing an illumination optical system using multi-spots.
FIG. 17 is a diagram illustrating an example of an optical element that forms a multi-spot.
FIG. 18 is a front view showing a second embodiment of the defect inspection apparatus according to the present invention.
FIG. 19 is an explanatory diagram of an ultraviolet laser light source used in a second embodiment according to the present invention.
FIG. 20 is a diagram showing a slit illumination light beam used when a TDI sensor is used as an image sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Test object (sample), 2 ... Stage 3, 3a, 3b, 3c ... Ultraviolet laser light source (ultraviolet laser light generator), 4 ... Solid laser device (laser excitation light source), 5 ... Wavelength converter, DESCRIPTION OF SYMBOLS 6 ... Beam expander, 7 ... Coherence reduction optical system, 9 ... Polarizing beam splitter, 10 ... Polarizing element group, 11 ... Objective lens, 12 ... Imaging lens, 13 ... Image sensor (photoelectric converter), 14 ... A / D converter, 15 ... gradation converter, 16 ... delay memory, 17 ... comparator, 19 ... CPU, 24, 25 ... lens, 26 ... diffuser plate, 30 ... nonlinear optical element (nonlinear optical crystal), 32 ... supply Valves 33: Exhaust valves 34 ... Detectors 35 ... Transparent windows 36 ... O-rings 37 ... Filters 39 ... Incident ports 40 ... Emission ports 41, 42 ... Containers 45 ... Casings (containers) 46 ... the entrance, 7 ... Exit port, 48 ... Intake hole, 49 ... Exhaust hole, 50 ... Wavelength converter, 51 ... Pressure hole, 60 ... Signal processing circuit, 61, 64 ... Scanning mirror (upper pupil scanning mechanism), 62, 63, 66 ... lens, 65 ... multi-lens array, 71 ... focus detection optical system, 81, 81a, 81b, 81c ... mirror (selection optical system, synthesis optical system), 130 ... light receiving surface of TDI sensor, 140 ... slit spot illumination light beam, M1 to M4: mirrors constituting an optical resonator.

Claims (7)

A laser excitation light source that emits and emits laser fundamental light; and
An incident window for entering the laser fundamental wave light emitted from the laser excitation light source and an emission window for emitting the ultraviolet laser light composed of the multiplied harmonic light of the laser fundamental wave light to the outside are provided in a sealed container, and incident from the incident window. An optical resonator composed of a plurality of optical members that resonate with respect to the laser fundamental wave light, and a non-linear optical element that is provided inside the optical resonator and generates a multiplied harmonic light of the laser fundamental light, and The window is provided with a wavelength converter for emitting ultraviolet laser light composed of the multiplied harmonic light in the window, and the container is further filled with an inert gas so that a trace amount that does not cause fluctuation of the laser light flows in and out. And comprising a wavelength conversion device equipped with a cleaning means for cleaning ,
Furthermore, the wavelength conversion device container has a double or triple structure, and there is a gap filled with an inert gas between the containers .   2. The cleaning means of the wavelength conversion device is configured by connecting an exhaust means for exhausting the gas in the container and a supply means for supplying an inert gas into the container to the container. Ultraviolet laser beam generator.   2. The ultraviolet laser beam generator according to claim 1, wherein the cleaning means of the wavelength conversion device includes an adhesive material for fixing contaminants floating in the container to the wall surface in the container. A laser excitation light source that emits and emits laser fundamental light; and
An incident window for entering the laser fundamental wave light emitted from the laser excitation light source and an emission window for emitting the ultraviolet laser light composed of the multiplied harmonic light of the laser fundamental wave light to the outside are provided in a sealed container, and incident from the incident window. An optical resonator composed of a plurality of optical members that resonate with respect to the laser fundamental wave light, and a non-linear optical element that is provided inside the optical resonator and generates a multiplied harmonic light of the laser fundamental light, and The window is provided with a wavelength converter for emitting ultraviolet laser light composed of the multiplied harmonic light in the window, and the container is further filled with an inert gas so that a trace amount that does not cause fluctuation of the laser light flows in and out. A wavelength converting device including a cleaning means for cleaning and an optical detection means for optically detecting a contamination state in the container ,
Furthermore, the wavelength conversion device container has a double or triple structure, and there is a gap filled with an inert gas between the containers . The laser excitation light source, ultraviolet laser light generating apparatus according to any one of claims 1-4, characterized in that it consists of a light source for emitting a second harmonic light of the YAG laser beam of Nd. The ultraviolet laser beam generator according to any one of claims 1 to 4 ,
An illumination optical system for illuminating an object to be inspected with ultraviolet laser light emitted from the ultraviolet laser light generator;
A detection optical system for collecting the reflected light from the object to be inspected illuminated by the illumination optical system;
A photoelectric converter that receives reflected light collected by the detection optical system and converts it into a signal;
A defect inspection apparatus comprising: a defect detection circuit that detects a defect on the inspection object based on a signal obtained from the photoelectric converter. An ultraviolet laser beam emitted from the ultraviolet laser beam generator according to any one of claims 1 to 4 is illuminated on an object to be inspected, and reflected light from the illuminated object to be inspected is collected. A defect inspection method characterized in that the collected reflected light is received by a photoelectric converter and converted into a signal, and a defect on the inspection object is detected based on the converted signal.

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