JP4394631B2 - Defect inspection method and apparatus - Google Patents

Description

  The present invention is a defect that inspects defects such as foreign matter generated in a manufacturing process in which a circuit pattern is formed on a substrate to manufacture an object, such as a semiconductor manufacturing process, a liquid crystal display element manufacturing process, and a printed circuit board manufacturing process. The present invention relates to an inspection apparatus and method.

  For example, in the semiconductor manufacturing process, if foreign matter is present on the semiconductor substrate (wafer), it may cause a failure such as a wiring insulation failure or a short circuit. Further, the semiconductor element is miniaturized and fine foreign matter exists in the semiconductor substrate. In addition, the foreign matter may cause defective insulation of the capacitor and destruction of the gate oxide film. These foreign substances are various due to various causes such as those generated from the moving part of the transfer device, those generated from the human body, those generated by reaction in the processing apparatus by the process gas, those mixed in chemicals and materials, etc. It is mixed in the state of. Similarly, in the liquid crystal display element manufacturing process, if foreign matters are mixed on the pattern or some kind of defect occurs, the liquid crystal display element cannot be used as a display element. The situation is the same in the manufacturing process of the printed circuit board, and the inclusion of foreign matter causes a short circuit of the pattern and a defective connection.

As described above, conventional techniques relating to a defect inspection apparatus and method for foreign matters and the like are disclosed in JP-A-1-250847 (Prior Art 1), JP-A-6-258239 (Prior Art 2), and JP-A-6-324003. JP-A-8-210989 (conventional technique 4) and JP-A-8-271437 (conventional technique 5) are known.
Prior art 1 includes a storage means for storing desired characteristics of the surface of the substrate, an illumination means for illuminating a certain area of the surface of the substrate to be inspected substantially uniformly, and an area of the substrate illuminated by the illumination means. An inspection apparatus for inspecting the surface characteristics of a substrate, comprising: TDI sensor means for imaging; and comparison means for comparing the imaging area of the substrate with the stored desired characteristics of the substrate in response to the storage means and the sensor means. Are listed.

Further, the conventional technique 2 is obtained through a transport means for transporting a substrate having a repetitive pattern with different pitches, an illumination system for irradiating a plane wave light in a straight line on the substrate, a spatial filter, and a spatial filter. , A detector for detecting a light image formed by the imaging optical system, and signals generated based on a repetitive pattern with a large pitch on the substrate obtained through a spatial filter among signals detected by the detector. There is described a defect detection apparatus comprising an erasing means for comparing and erasing and a defect detecting means for detecting a defect such as a minute foreign substance on a substrate based on a signal obtained from the erasing means.
Prior art 3 includes a detection head composed of an illumination means, a detection optical system, a spatial filter unit, a detector, an operational amplifier, and an A / D converter, a pitch detection means, an operator processing system, and foreign matter data. There is described a foreign matter inspection apparatus including a memory, a large foreign matter data memory, a pattern memory, a software processing system, parameter transmission means, foreign matter memory, coordinate data creation means, and a microcomputer.

Further, in the prior art 4, laser light emitted from a semiconductor laser oscillator is converted into a plurality of non-interfering light beams so as to smooth or average the intensity of reflected light generated from a thin film formed on a substrate. Then, the light is condensed and irradiated onto a substrate on which a light transmitting thin film is formed at the same time at different incident angles T1 to Tn, and 0.3 to 0.8 [mu] m existing on the substrate by the illumination light or the same. The following describes a micro defect detection apparatus that collects scattered light generated from micro defects such as micro foreign matters with a condenser lens and detects the light with a detector such as a TDI sensor.
Further, in the prior art 5, a linear longitudinal direction is obtained by making the phase distribution substantially the same in the linear width direction by a shading correction plate in which a plurality of curved transmission portions are formed with respect to the intensity distribution of the light emitted from the light source. The illumination optical system for correcting the illumination intensity so that the illumination intensity is substantially uniform and repeatedly collecting and irradiating the sample on the sample on which the chip is repeatedly formed by the condensing optical system from the oblique direction, and the illumination optical system The detection optical system that receives the scattered reflected light from the sample irradiated by (1) with a linear image sensor and converts it into a signal, and the chip that repeats the signal converted from the linear image of the detection optical system are compared between the chips and due to mismatch A foreign matter inspection apparatus including an interchip comparing means for inspecting as a foreign matter on a sample is described.

JP-A-1-250847 JP-A-6-258239 JP-A-6-324003 JP-A-8-210989 JP-A-8-271437

  However, in the above prior art, it is not possible to easily detect defects such as extremely small foreign matters of about 0.1 μm or less on a substrate in which repeated patterns and non-repeated patterns are mixed with high sensitivity and high speed. . That is, in the above prior art, as the MTF decreases as the distance from the optical axis in the detection optical system decreases, the illumination illuminance is insufficient at the periphery of the detection area on the substrate, and both high-sensitivity inspection and high-speed inspection are achieved. I could not.

The object of the present invention is to effectively use the light amount of a Gaussian beam emitted from a normal inexpensive light source in order to solve the above-mentioned problems, and to detect defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity. It is another object of the present invention to provide a defect inspection apparatus and method capable of performing inspection at high speed.
Another object of the present invention is to effectively use the light quantity of a Gaussian beam emitted from a normal inexpensive light source, and in addition, in the detection optical system, the MTF decreases as the distance from the optical axis decreases. A defect inspection apparatus and method capable of solving a shortage of illuminance at the periphery of a detection region on a substrate and inspecting defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity and high speed. It is to provide.

Another object of the present invention is to inspect defects such as extremely small foreign objects of about 0.1 μm or less so that an optical image based on DUV laser light obtained from a substrate to be inspected can be received by a TDI image sensor. It is an object of the present invention to provide a defect inspection apparatus and method that can be used.
Another object of the present invention is to effectively use the amount of light generated from a lamp light source, and in the detection optical system, as the MTF decreases with increasing distance from the optical axis, An object of the present invention is to provide a defect inspection apparatus that eliminates shortage of illuminance in the peripheral area and can inspect defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity and at high speed.

In order to achieve the above object, the present invention realizes illumination that maximizes the illuminance in a region where the illuminance is minimum in the illumination illuminance distribution within the illumination range, and maximizes the signal S / N. Thus, improvement in detection sensitivity and improvement in throughput are realized.
That is, according to the present invention, a Gaussian beam light beam shaped so as to obtain the maximum illuminance (illuminance of about 60% with respect to the illuminance at the center) on the outermost periphery (peripheral portion) of the detection region is applied to the inspection target substrate. By illuminating the detection area, it is possible to improve the sensitivity (S / N) at the peripheral part in the detector and to inspect defects such as minute foreign matter existing in the detection area with high sensitivity and high speed. It is characterized by doing so.

Further, the present invention is based on a Gaussian distribution in which the length from the optical axis of the detection region to the peripheral portion is substantially standard deviation by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. Illuminated with a Gaussian beam light beam shaped to have an illuminance distribution, and a light image obtained from the detection region on the inspection target substrate illuminated with the shaped Gaussian beam light beam is applied to the detection region by a detection optical system. An image formed on the light receiving surface of a detector having a corresponding light receiving surface to detect an image signal corresponding to the detection region from the detector, and a foreign object existing in the detection region based on the detected image signal This is a defect inspection method characterized by inspecting defects.
Further, according to the present invention, the ratio of the illuminance at the periphery of the detection region to the illuminance at the center of the detection region is 0.46 by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. Shaped by adapting the diameter or long axis length to the length between the peripheral parts around the optical axis of the detection region so that it is about 0.73 (more preferably about 0.54 to 0.67). A detector having a light-receiving surface corresponding to the detection region by a detection optical system for illuminating with the shaped Gaussian beam and detecting a light image obtained from the detection region on the inspection target substrate illuminated with the shaped Gaussian beam An image signal corresponding to the detection area is detected from the detector, and a defect such as a foreign substance existing in the detection area is inspected based on the detected image signal. Defect inspection method .

Further, the present invention provides the defect inspection method, wherein the shaped Gaussian beam is in a slit shape, and the substrate to be inspected is relative to the direction intersecting the longitudinal direction of the slit-shaped Gaussian beam. It is made to move to.
In the defect inspection method, the present invention is characterized in that the detector is a TDI image sensor.
The present invention is also characterized in that, in the defect inspection method, the shaped Gaussian beam is illuminated from an oblique direction with respect to an illumination area on the substrate to be inspected.

Further, according to the present invention, the ratio of the illuminance at the periphery of the detection region to the illuminance at the center of the detection region is 0.46 by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. The diameter or major axis length is adapted to the length between the peripheral parts around the optical axis of the detection area so that it falls within the range of about ~ 0.73 (more preferably about 0.54 to 0.67). And detecting a light image obtained from a detection region on the inspection target substrate illuminated with the shaped beam beam by a detection optical system having a light receiving surface corresponding to the detection region. Forming an image on the light receiving surface of the detector, detecting an image signal corresponding to the detection area from the detector, and inspecting a defect such as a foreign substance existing in the detection area based on the detected image signal. This is a feature defect inspection method.
Further, the present invention illuminates a detection region on a substrate to be inspected on which a circuit pattern is formed with a DUV beam light beam by an illumination optical system, and detects on the substrate to be inspected illuminated with the DUV beam light beam. A light image obtained from the region is imaged on the light receiving surface of a TDI image sensor having a light receiving surface corresponding to the detection region by a detection optical system and sensitive to DUV light, and the TDI image sensor is applied to the detection region. A defect inspection method characterized by detecting a corresponding image signal and inspecting a defect such as a foreign substance existing in the detection region based on the detected image signal.

Further, the present invention is based on a Gaussian distribution in which the length from the optical axis of the detection region to the peripheral portion is substantially standard deviation by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. Illuminating with a Gaussian beam of a DUV beam shaped so as to have an illuminance distribution, and detecting optical images obtained from a detection area on the inspection target substrate illuminated with the Gaussian beam of the shaped DUV beam A system having a light receiving surface corresponding to the detection region and forming an image on the light receiving surface of a TDI image sensor sensitive to DUV light to detect an image signal corresponding to the detection region from the TDI image sensor; A defect inspection method characterized by inspecting a defect such as a foreign substance existing in the detection area based on a detected image signal.
The present invention also provides an illuminance distribution comprising a Gaussian distribution having a standard deviation of the length from the optical axis of the detection area to the peripheral portion of the detection area on the substrate to be inspected on which the circuit pattern is formed. An illumination optical system (including an illumination light source) that illuminates with a Gaussian beam light beam shaped to have a light image obtained from a detection region on the inspection target substrate that is illuminated with the Gaussian beam light beam by the illumination optical system. A detection optical system that forms an image on the light receiving surface of a detector having a light receiving surface corresponding to the detection region and detects an image signal corresponding to the detection region from the detector, and is detected from the detector of the detection optical system. And a signal processing system for determining the presence or absence of a defect such as a foreign substance existing in the detection region based on the image signal.

In the present invention, the ratio of the illuminance at the periphery of the detection area to the illuminance at the center of the detection area is 0.46 to 0.73 with respect to the detection area on the substrate to be inspected on which the circuit pattern is formed. Illumination optical system (including an illumination light source) that illuminates with a Gaussian beam light beam that is shaped by adapting the diameter or major axis length to the length between the peripheral parts centering on the optical axis of the detection region And an optical image obtained from a detection area on the substrate to be inspected illuminated with a Gaussian beam by the illumination optical system, formed on a light receiving surface of a detector having a light receiving surface corresponding to the detection area by the detection optical system A detection optical system for detecting an image signal corresponding to the detection area from the detector, and the presence or absence of a defect such as a foreign substance existing in the detection area based on the image signal detected from the detector of the detection optical system. Signal processing system A defect inspection apparatus comprising the.
In the defect inspection apparatus according to the present invention, the illumination optical system includes an optical element that forms a Gaussian beam light beam in a slit shape, and further, the substrate to be inspected is arranged in a longitudinal direction of the slit Gaussian beam light beam. It is characterized by comprising a moving means for moving relatively in the direction intersecting with.
According to the present invention, in the defect inspection apparatus, the detector in the detection optical system is configured by a TDI image sensor.
Further, the present invention is characterized in that, in the defect inspection apparatus, the illumination optical system is configured to illuminate a Gaussian beam light beam from an oblique direction with respect to an illumination area on the substrate to be inspected.

Further, according to the present invention, the ratio of the illuminance at the periphery of the detection region to the illuminance at the center of the detection region is 0.46 by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. Illumination optical system for illuminating with a beam beam shaped by adapting the diameter or major axis length to the length between the peripheral parts centering on the optical axis of the detection region so as to be in a range of about 0.73 (Including an illumination light source), and a light receiving surface corresponding to the detection region is detected by a detection optical system for a light image obtained from a detection region on the inspection target substrate illuminated with a Gaussian beam light beam shaped by the illumination optical system. A detection optical system that forms an image on the light receiving surface of the detector and detects an image signal corresponding to the detection region from the detector, and the detection based on the image signal detected from the detector of the detection optical system Such as foreign objects present in the area A defect inspection apparatus characterized by comprising a determining signal processing system the presence or absence of Recessed.
The present invention also provides an illumination optical system that illuminates a detection region on a substrate to be inspected on which a circuit pattern is formed with a DUV beam light beam by an illumination optical system, and a DUV beam light beam that is illuminated by the illumination optical system. A TDI image sensor having a light receiving surface corresponding to the detection region by a detection optical system and having sensitivity to DUV light (for example, thinning the substrate from the back side) And a detection optical system that detects an image signal corresponding to the detection area from the TDI image sensor and an image detected from a detector of the detection optical system. A defect inspection apparatus comprising: a signal processing system that determines whether a defect such as a foreign substance existing in the detection region is present based on a signal.

Further, the present invention is based on a Gaussian distribution in which the length from the optical axis of the detection region to the peripheral portion is substantially standard deviation by the illumination optical system with respect to the detection region on the inspection target substrate on which the circuit pattern is formed. And an illumination optical system that illuminates with a Gaussian beam of a DUV beam shaped so as to have an illuminance distribution, and a detection area on a substrate to be inspected that is illuminated with the Gaussian beam of a DUV beam by the illumination optical system. An optical signal is formed on the light receiving surface of a TDI image sensor having a light receiving surface corresponding to the detection region by a detection optical system and sensitive to DUV light, and an image signal corresponding to the detection region from the TDI image sensor. And a signal for determining the presence / absence of a defect such as a foreign substance existing in the detection region based on an image signal detected from a detector of the detection optical system A defect inspection apparatus is characterized in that a science.
The present invention also provides a lamp light source and a lot lens that emits a light beam by increasing the illuminance at the periphery of the detection region compared to the illuminance at the center using the alignment characteristics of the light generated from the lamp light source. And an illumination optical system that illuminates a detection region on a substrate to be inspected on which a circuit pattern is formed with a beam beam emitted from the lot lens, and an object that is illuminated with the beam beam by the illumination optical system. An optical image obtained from the detection area on the inspection target substrate is formed on the light receiving surface of a detector having a light receiving surface corresponding to the detection area by a detection optical system, and an image signal corresponding to the detection area is output from the detector. And a signal processing system for determining the presence or absence of a defect such as a foreign substance existing in the detection region based on an image signal detected from a detector of the detection optical system. That is a defect inspection apparatus.

As described above, according to the above configuration, the amount of the Gaussian beam emitted from a normal inexpensive light source is effectively used, and a minute foreign matter of about 0.1 to 0.5 μm is about 0.1 μm or less. It is possible to inspect defects such as extremely small foreign matter with high sensitivity and at high speed.
Further, according to the above configuration, the amount of Gaussian beam emitted from a normal inexpensive light source is effectively used, and the MTF (Modulation Transfer Function) decreases with increasing distance from the optical axis in the detection optical system. The lack of illuminance at the periphery of the detection area on the substrate to be inspected is resolved, and the fine foreign matter of 0.1 to 0.5 μm is highly sensitive to defects such as extremely fine foreign matters of 0.1 μm or less. And can be inspected at high speed.

Further, according to the above configuration, a light image based on UVD (far ultraviolet) laser light such as excimer laser light obtained from the substrate to be inspected can be received by the TDI image sensor and is about 0.1 to 0.5 μm. The minute foreign matter can be inspected for defects such as a very small foreign matter of about 0.1 μm or less from the solid.
Further, according to the above configuration, the peripheral portion of the detection region on the substrate to be inspected as the MTF decreases as the distance from the optical axis in the detection optical system effectively uses the amount of light generated from the lamp light source. Insufficient illuminance deficiency can be eliminated, and defects such as extremely small foreign matters of about 0.1 μm or less existing in the detection region can be inspected with high sensitivity and at high speed. The detection area is moved on the substrate to be inspected.

According to the present invention, a substrate to be inspected, such as an LSI wafer, using an inexpensive light source by increasing the illuminance at the periphery of a detection region detected by a detector such as a TDI image sensor to improve the efficiency of illumination. The above fine foreign matter of about 0.1 to 0.5 μm has the effect of being able to detect even extremely fine foreign matters and defects of about 0.1 μm or less from the solid with high sensitivity and high throughput.
In addition, according to the present invention, the illumination efficiency is increased by increasing the illuminance at the periphery of the detection region detected by a detector such as a TDI image sensor so that the MTF decreases as the distance from the optical axis in the detection optical system increases. By using an inexpensive light source by improving, a fine foreign matter of about 0.1 to 0.5 μm on a substrate to be inspected such as an LSI wafer has a very small foreign matter or defect of about 0.1 μm or less. There is an effect that detection can be performed with high sensitivity and high throughput.

In addition, according to the present invention, an optical image based on UVD (far ultraviolet) laser light such as excimer laser light obtained from the substrate to be inspected can be received by the TDI image sensor and is about 0.1 to 0.5 μm. The minute foreign matter has an effect of being able to inspect even a defect such as a very small foreign matter of about 0.1 μm or less from the solid.
In addition, according to the present invention, the peripheral portion of the detection region on the substrate to be inspected is used as the MTF decreases as the distance from the optical axis in the detection optical system effectively uses the amount of light generated from the lamp light source. Insufficient illuminance is eliminated, and defects such as extremely small foreign matters of about 0.1 μm or less can be inspected with high sensitivity and at high speed.

Embodiments of a defect inspection apparatus and method according to the present invention will be described with reference to the drawings.
While semiconductor devices are increasingly miniaturized, it is required to further improve the yield. Accordingly, a semiconductor substrate such as a semiconductor wafer for manufacturing such a semiconductor element is present on the semiconductor substrate because a very fine circuit pattern of 0.3 to 0.2 μm or less is formed. Even if there are defects such as foreign matter that are extremely small molecules of about 0.1 μm or less or those close to the atomic level, this causes a malfunction of the semiconductor device.
Because of this situation, the defect inspection apparatus and method according to the present invention exist on a semiconductor substrate such as a semiconductor wafer on which an extremely miniaturized circuit pattern of about 0.3 to 0.2 μm or less exists. It has been demanded that defects such as extremely small foreign matter can be inspected with high sensitivity and at high speed.

First, a first embodiment of a defect inspection apparatus for foreign matter or the like according to the present invention will be described.
FIG. 1 is a diagram showing a schematic configuration of a first embodiment of a defect inspection apparatus for foreign matter or the like according to the present invention. FIG. 2 is a diagram showing an example of the illumination optical system.
That is, a defect inspection apparatus for foreign matters includes a stage 201 on which a substrate pattern 1 to be inspected on which an extremely fine circuit pattern is formed, such as a semiconductor wafer (semiconductor substrate), a semiconductor laser, an argon laser, An illumination light source 101 composed of a laser light source such as a YAG-SHG laser or an excimer laser, a discharge tube such as a xenon lamp or a mercury lamp, or a filament light source such as a halogen lamp, and the high luminance emitted from the illumination light source 101 The illumination optical system 102 that illuminates the target substrate 1 with a slit-shaped Gaussian beam (illumination region 2) 107 having a substantially Gaussian distribution as shown in FIG. A detection optical system 301 that includes an imaging lens system including a lens and forms an image of light reflected, diffracted, or scattered from the detection region 3; Comparing the detector 302 having a light receiving surface corresponding to the detection area 3 and the image signals of the same circuit pattern detected from the detector 302, which are composed of a TDI (Time Delay Integration) image sensor, a CCD image sensor, and the like. The signal processing system 401 detects a defect such as a foreign substance due to a mismatch. This defect inspection apparatus includes an automatic focus control system so that the surface of the inspection target substrate 1 is imaged on the light receiving surface of the detector 302. Further, as the detection optical system 301, as described in JP-A-6-258239 and JP-A-6-324003, a repetitive pattern having a small pitch formed on a Fourier transform lens and a substrate to be inspected. A spatial filter unit that shields diffracted light from the light and a Fourier transform lens may be used.

  As shown in FIG. 2, a specific configuration of the illumination light source 101 and the illumination optical system 102 includes, for example, a concave lens or convex lens 103 that expands the beam diameter of the laser beam 106 emitted from the illumination light source 101, and a concave or convex lens 103. As shown in FIG. 3, the collimating lens 104 that converts the expanded beam into a substantially parallel light beam, and the substantially parallel light beam converted by the collimating lens 104 are converged in the y-axis direction on the substrate 1 to be inspected. A cylindrical lens (an optical system having a focusing function in the y-axis direction) 105 that irradiates with a slit-shaped Gaussian beam (illumination region 2) 107 having a substantially Gaussian distribution as illuminance. The concave or convex lens 103 and the collimating lens 104 constitute a beam expander that expands the beam diameter. As the illumination optical system 102, as described in JP-A-6-258239 and JP-A-6-324003, a beam expander including a collimator lens, a concave lens, and a receiver lens, and the beam expander The converted substantially parallel light beam is focused in the y-axis direction and irradiated on the substrate 1 to be inspected with a slit-shaped Gaussian beam light beam (illumination region 2) 107 having a substantially Gaussian distribution as shown in FIG. A cylindrical lens (an optical system having a focusing function in the y-axis direction) 105 and a mirror that reflects the slit-shaped Gaussian beam 107 obtained by the cylindrical lens 105 and irradiates the inspection target substrate 1 from an oblique direction. Can be configured.

  By the way, with this configuration, the distance b between the concave or convex lens 103 and the collimating lens 104 or the distance between the concave lens and the receiver lens is variably set, so that the illuminance in the x direction has a substantially Gaussian distribution. The illumination width can be set variably. That is, by adjusting the beam expander, it is possible to variably set the length Lx in the x direction of the illumination area (slit-shaped light beam 107) 2 having a substantially Gaussian distribution as illuminance. Further, by changing the distance between the cylindrical lens 105 and the substrate 1 to be inspected, the width Ly in the y direction of the focused illumination region (slit-shaped Gaussian beam 107) can be variably set. .

  A detection area 3 shown in FIG. 3 indicates a detection area by a TDI image sensor or a CCD image sensor on the inspection target substrate 1. For example, in the case of a TDI image sensor, each pixel size is, for example, 27 μm × 27 μm, and is configured by, for example, 64 rows in the time delay integration (TDI) direction, for example, 64 rows and 64 × 4096 CCD image sensors in the MUX direction that operates in the TDI mode. The That is, the TDI image sensor 302a has n (for example, 64) stages of line sensors as shown in FIG. The line rate, which is the amount of information output from the sensor, is the same as that of the line sensor, but for each line rate rt, the accumulated charges are sequentially transferred to the lines 1, 2,. By synchronizing the feed rate of the stage 201 that moves the inspection target substrate 1 in the y-axis direction with the line rate, for example, the optical image 6 based on the scattered light or diffracted light from the minute foreign material 5 reaches the line n. Accumulation over a long period of time makes it possible to detect with high sensitivity even defects such as extremely small foreign matter. This image sensor basically detects the sum of scattered light or diffracted light intensity until an image of a defect such as a minute foreign substance reaches line 1 to line n. Scattered light or diffracted light from the same point on the target substrate is completely incoherent in time.

As described above, the beam emitted from the illumination light source 101 is converted into a slit-shaped Gaussian beam 107 by the illumination optical system (irradiation optical system) 102, and the converted slit-shaped beam 107 is used on the stage 201. For example, irradiation is performed from an oblique direction so that the illumination region 2 is formed on the surface of the substrate 1 to be inspected. The detector 302a constituted by a TDI image sensor or the like moves each stage 201 in the y-axis direction by moving the stage 201 in the y-axis direction, and moves each pixel at a line rate rt synchronized with the feed speed. By sequentially transferring the charges accumulated in the detection optical system 301, scanning is performed with the width H of the detection region 3 while capturing a light image of the detection region 3 on the inspection target substrate 1 imaged by the detection optical system 301. By detecting each pixel (element) and processing the detected signal by the signal processing system 401, a defect such as a minute foreign substance existing in the detection region 3 is inspected with high sensitivity and high speed. Can do.
In this manner, by using the TDI image sensor 302a, the total illuminance of scattered light or diffracted light (light quantity = illuminance × time) generated from defects such as minute foreign matters can be obtained, and the sensitivity can be improved. Further, the TDI image sensor irradiates the irradiation region 2 with the slit-shaped light beam 107 at a time and moves the substrate 1 to be inspected in the y-axis direction in synchronization with the line rate rt of the TDI image sensor 302a. By receiving light with respect to 3, it is possible to inspect for defects such as minute foreign matter existing in the detection region 3 having a wide width H at high speed.

Next, a description will be given of an embodiment according to the present invention for inspecting defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity and at high speed. That is, if a defect such as a very small foreign substance of about 0.1 μm or less is to be detected with high sensitivity, the intensity of scattered light or diffracted light from the defect such as a very small foreign object received at each pixel of the TDI image sensor 302a. And the size of each pixel on the substrate 1 to be inspected must be about 1 μm × 1 μm or less.
Thus, in order to make each pixel size on the substrate 1 to be inspected about 1 μm × 1 μm or less, when each pixel size of the TDI image sensor is 27 μm × 27 μm, for example, the detection optical system 301 such as an objective lens The imaging magnification M may be about 27 times or more, and can be realized. If the TDI image sensor 302a is configured with a 26 × 4096 CCD image sensor, the detection area 3 has W = 26 μm or less and H = 4096 μm or less.

  In addition, the detection optical system 301 that forms an optical image of scattered light or diffracted light obtained from the surface of the substrate 1 to be inspected on the light receiving surface of the TDI image sensor 302a is constituted by an objective lens or the like, and thus lens aberration. And MTF (Modulation Transfer Function) (change in contrast of sinusoidal pattern image as a function of spatial frequency) decreases toward the periphery of the lens as compared to the center of the lens (optical axis 303). Have. Therefore, the pixel 302ae at the end (periphery) where the MTF is most distant from the optical axis 303 on the light receiving surface of the TDI image sensor 302a shown in FIG. 4A, that is, the optical axis of the detection region 3 shown in FIG. It is necessary to increase the intensity of scattered light or diffracted light from a defect such as a very small foreign substance located at the end (periphery) at the farthest distance from 303 and where the MTF decreases most.

  Incidentally, the illuminance of the slit-shaped Gaussian beam 107 irradiated on the surface of the substrate 1 to be inspected by the illumination light source 101 and the illumination optical system 102 in the irradiation region 2 has a normal Gaussian distribution as shown in FIG. Thus, illumination outside the detection area 3 is wasted, but it is necessary to illuminate the illumination area 2 wider than the detection area 3.

Therefore, from such a state, the present invention effectively uses the light amount emitted from the illumination light source 101 without increasing the illuminance emitted from the illumination light source 101, and is farthest from the optical axis 303 of the detection region 3. In other words, the illuminance located at the end (periphery) where the MTF is most decreased is increased to detect defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity. That is, an inexpensive illumination light source that emits the minimum necessary illuminance (laser light source such as semiconductor laser, argon laser, YAG-SHG laser, and excimer laser, discharge tube such as xenon lamp and mercury lamp, filament light source such as halogen lamp, etc. 101), the illumination optical system 102 increases the illuminance located farthest from the optical axis 303 of the detection region 3 and at the end (periphery) where the MTF is the lowest by the illumination optical system 102, thereby providing highly efficient illumination. It is to be realized.
Specifically, the present invention specifically detects the detection region 3 when the illumination light source 101 and the illumination optical system 102 irradiate the irradiation region 2 of the substrate 1 to be inspected with the slit beam 107 having a Gaussian illuminance. The illumination optical system 102 is adjusted (controlled) so as to maximize the illuminance at the peripheral part of the illumination. Here, when the illuminance of the slit beam 107 is a Gaussian distribution, the following (Equation 1) is used as shown in FIG. 3, and the illuminance is maximized at the outermost periphery of the illumination area. (Equation 2) shown below.

この場合、ＴＤＩイメージセンサ３０２ａの受光面が対応する検出領域３のｘ軸方向の最外周（端部）での照度ｆ(ｘ_０)は、中心部ｆ(０)の約６０．７％で最大となる。即ち、（数２）式において、ｘ_０＝σ（σ＝１で、ｘ_０＝１）のとき、最大値ｆ(ｘ_０)＝０．６０７ｆ(０)となる。なお、上記（数１）式において、ｘ_０＝０．８σ〜１．２σ（σ＝１で、ｘ_０＝０．８〜１．２（ガウスビーム光束１０７について照明光学系１０２による±２０％程度の整形誤差を許容する。））のとき、ｆ（ｘ_０）＝０．４９ｆ(０)〜０．７３ｆ(０)となる。また、上記（数１）式において、０．８ｘ_０〜１．２ｘ_０＝σ（σ＝０．８〜１．２（ガウスビーム光束１０７について照明光学系１０２による±２０％程度の整形誤差を許容する。）で、ｘ_０＝１）のとき、ｆ（ｘ_０）＝０．４６ｆ(０)〜０．７１ｆ(０)となる。従って、照明光学系１０２によるガウスビーム光束１０７のｘ_０＝σ（σ＝１で、ｘ_０＝１）にする整形誤差として±２０％程度許容すると、検出領域３において中心部（光軸３０３）の照度ｆ(０)に対する周辺部（外周部）の照度ｆ（ｘ_０）の比は、０．４６〜０．７３（ｆ（ｘ_０）＝０．４６ｆ(０)〜０．７３ｆ(０)）となる。なお、照明光学系１０２によるガウスビーム光束１０７のｘ_０＝σ（σ＝１で、ｘ_０＝１）にする整形誤差として±１０％程度許容すると、検出領域３において中心部（光軸３０３）の照度ｆ(０)に対する周辺部（外周部）の照度ｆ（ｘ_０）の比は、０．５４〜０．６７（ｆ（ｘ_０）＝０．５４ｆ(０)〜０．６７ｆ(０)）となる。
いずれにしても、検出領域３において中心部（光軸３０３）の照度ｆ(０)に対する周辺部（外周部）の照度ｆ（ｘ_０）の比が、０．４６〜０．７３になるようにガウスビーム光束１０７を照明光学系１０２によって整形することによって、照明光源１０１から出射されるビームを有効に活用して検出領域３の周辺部における照度を最大に近づけることが可能となる。

In this case, the illuminance f (x ₀ ) at the outermost periphery (end) in the x-axis direction of the detection region 3 corresponding to the light receiving surface of the TDI image sensor 302a is about 60.7% of the central portion f (0). Maximum. That is, in the formula (2), when x ₀ = σ (σ = 1, x ₀ = 1), the maximum value f (x ₀ ) = 0.607f (0). In the above equation (1), x ₀ = 0.8σ to 1.2σ (σ = 1, x ₀ = 0.8 to 1.2 (± 20% by the illumination optical system 102 for the Gaussian beam 107). When a degree of shaping error is allowed))), f (x ₀ ) = 0.49f (0) to 0.73f (0). Further, in the above formula (1), 0.8x _{0 to} 1.2x ₀ = σ (σ = 0.8 to 1.2 (the shaping error of about ± 20% by the illumination optical system 102 for the Gaussian beam 107). If x ₀ = 1), f (x ₀ ) = 0.46 f (0) to 0.71f (0). Accordingly, if a shaping error of about ± 20% is allowed as a shaping error to make x ₀ = σ (σ = 1, x ₀ = 1) of the Gaussian beam 107 by the illumination optical system 102, the center portion (optical axis 303) in the detection region 3 is allowed. The ratio of the illuminance f (x ₀ ) of the peripheral part (outer peripheral part) to the illuminance f ( ₀ ) of 0.46 to 0.73 (f (x ₀ ) = 0.46f (0) to 0.73f (0) )). In addition, if about ± 10% is allowed as a shaping error to make x ₀ = σ (σ = 1, x ₀ = 1) of the Gaussian beam 107 by the illumination optical system 102, the center portion (optical axis 303) in the detection region 3 is allowed. The ratio of the illuminance f (x ₀ ) of the peripheral part (outer peripheral part) to the illuminance f ( ₀ ) of 0.54 to 0.67 (f (x ₀ ) = 0.54f (0) to 0.67f (0 )).
In any case, the ratio of the illuminance f (x ₀ ) of the peripheral part (outer peripheral part) to the illuminance f ( ₀ ) of the central part (optical axis 303) in the detection region 3 is 0.46 to 0.73. In addition, by shaping the Gaussian beam 107 with the illumination optical system 102, it is possible to effectively utilize the beam emitted from the illumination light source 101 and bring the illuminance at the periphery of the detection region 3 close to the maximum.

In the graph shown in FIG. 5, the x-axis direction of the detection region 3 when changing the illumination width in the x-axis direction, that is, the standard deviation σ, without changing the amount of light that is the sum of the illuminances emitted from the illumination light source 101. The change in the illuminance (light quantity per unit area) f (x ₀ = 1) at the outer peripheral portion (x ₀ = 1) of FIG.
In the graph shown in FIG. 6, the illumination width, that is, the standard deviation σ is set to σ = 0.5, σ = 1, σ = 2 without changing the amount of light that is the sum of the illuminances emitted from the illumination light source 101. The change of the illuminance (light quantity per unit area) f (x ₀ ) at the coordinate x ₀ in the x-axis direction of the detection region 3 when changed to is shown.

As apparent from FIGS. 5 and 6, in order to maximize the illuminance at the outer peripheral portion (x ₀ = 1) in the x-axis direction of the detection region 3, x based on the Gaussian distribution by the illumination optical system 102 is used. It suffices to illuminate so that the axial illumination width is approximately σ = 1 (standard deviation σ = x ₀ ). That is, as shown in FIG. 3, when the length from the optical axis center of the detection region 3 to the outer peripheral portion in the x-axis direction is x ₀ , the illumination optical system 102 causes the standard deviation σ = x ₀ (detection). The illumination region 2 (with respect to the substrate 1 to be inspected) is shaped into a slit-shaped light beam 107 having a Gaussian distribution of illuminance, which is the length from the center that is the optical axis of the region 3 to the outer periphery in the x-axis direction). Lx and Ly indicate areas where the illuminance f is 0.2 or more where f (0).)
Actually, when a TDI image sensor or a two-dimensional linear image sensor is used as the detector 302, the pixel farthest away from the optical axis 303 and having the lowest MTF is the corner of the detection region 3 (in the case of a TDI image sensor). since the pixel 302ac is located in the corner portion shown in 4 is to be located in the corresponding.), as the _{x 0,} it is desirable to ^{√ ((H / 2) 2} + (W / 2) 2) . If W can be ignored, x ₀ = (H / 2). H and W indicate the width (length) in the x-axis direction and the width in the y-axis direction of the detection region 3 on the substrate to be inspected. The width in the x-axis direction of the light receiving area (imaging area) in the TDI image sensor or the two-dimensional linear image sensor is indicated by (H × M), and the width in the y-axis direction is indicated by (W × M). Note that M represents an imaging magnification by the imaging optical system 301.

As described above, the outer peripheral portion of the detection region 3 in the x-axis direction (when using a TDI image sensor or a two-dimensional linear image sensor, the pixel farthest from the optical axis 303) is represented by x ₀ (= √ ((H / 2 ) ² + (W / 2) ² ) or (H / 2)), the illumination optical system 102 shapes the light beam 107 into a slit-like light beam 107 having a Gaussian illuminance of approximately σ = x _0. By illuminating the inspection target substrate 1 as an illumination area 2 (Lx and Ly are areas where the illuminance f is 0.2 or more with f (0)), a special illumination light source with high power is not used. Inexpensive ordinary illumination light sources (semiconductor lasers, argon lasers, YAG-SHG lasers, excimer lasers and other laser light sources, xenon lamps, mercury lamps and other discharge tubes, halogen lamps and other filament light sources, etc. 101) can be used to realize efficient illumination, and as a result, scattered light from defects such as minute foreign matters received by pixels in the periphery of the detector 302 where the MTF is most lowered by the detection optical system 301. Alternatively, the intensity of the diffracted light can be increased, and a minute foreign matter of about 0.1 to 0.5 μm can detect defects such as a very small foreign matter of about 0.1 μm or less from a solid with high sensitivity and high speed (high Can be detected). It should be noted that the illuminance differs in the relationship of (f (x ₀ ) = 0.46f (0) to 0.73f (0)), particularly between the central portion and the peripheral portion of the detection region 3 in the x-axis direction. However, in the signal processing system 401, image signals obtained from the same pixel column in the x-axis direction in the detection region detected by the detector 302 such as a TDI image sensor by moving the inspection object 1 in the y-axis direction. Therefore, there is almost no influence of the difference in illuminance between the central part and the peripheral part. Then, in the signal processing system 401, each chip or cell is repeated with the same circuit pattern based on the image signal detected from the detector 302 such as a TDI image sensor by moving the inspection object 1 in the y-axis direction. By extracting the difference image signal of each other and determining the extracted difference image signal with a desired determination criterion, it is possible to detect and inspect a defect such as a foreign object.
Here, what is important is that the illuminance (light quantity) at the periphery of the detection region 3 is substantially maximized. The means for that purpose is to change the illumination width in the illumination optical system 102 in the above embodiment. However, other means, such as changing the shape of the secondary light source of illumination by the illumination optical system 102 or changing the size at the position of the Fourier transform forming the secondary light source, may be used. good.

Although the embodiment described above has been described for the case of defect inspection of foreign matter or the like adhering to the surface of the substrate 1 to be inspected, it can also be applied to the defect inspection of circuit patterns on the substrate 1 to be inspected. Normally, in the case of a circuit pattern defect inspection, the light is transmitted or reflected by a polarizing beam splitter disposed on an objective lens constituting the detection optical system 301 and converted from P-polarized light or S-polarized light to circularly polarized light by a λ / 4 plate. Then, the circularly polarized slit-shaped light beam 107 is incident on the illumination area 2 of the inspection object 1 through the objective lens and reflected, diffracted or scattered from the detection area 3 of the inspection object 1. Light is converted into S-polarized light or P-polarized light by a λ / 4 plate through an objective lens, and reflected or transmitted by the polarizing beam splitter, and imaged on a detector 302 composed of a TDI image sensor or the like by a paired Fourier transform lens. To be configured. Then, in the signal processing system 401, each chip or cell is repeated with the same circuit pattern based on the image signal detected from the detector 302 such as a TDI image sensor by moving the inspection object 1 in the y-axis direction. It is possible to detect and inspect a defect present in the circuit pattern by extracting a difference image signal of each other and determining the extracted difference image signal based on a desired determination criterion. Also in the defect inspection of this circuit pattern, the outer periphery of the detection region 3 in the x-axis direction (when using a TDI image sensor or a two-dimensional linear image sensor, the pixel farthest from the optical axis 303) is represented by x ₀ (= √ (( H / 2) ² + (W / 2) ² ) or (H / 2)), the illumination optical system 102 shapes the light beam 107 into a slit-like beam having an illuminance with a Gaussian distribution of approximately σ = x _0. Then, by subjecting the substrate 1 to be inspected to the incident illumination 2 as an illumination area 2, an inexpensive ordinary illumination light source (semiconductor laser, argon laser, YAG-SHG laser, (Equipped with laser light source such as excimer laser, discharge tube such as xenon lamp and mercury lamp, filament light source such as halogen lamp, etc.) As a result, the scattered light or the diffracted light intensity from the defect of the circuit pattern received by the pixel in the peripheral portion of the detector 302 where the MTF is most lowered by the detection optical system 301 can be increased. A minute foreign matter of about 1 to 0.5 μm can detect a very small defect of about 0.1 μm or less from a solid with high sensitivity and high speed (with high throughput).

Next, a second embodiment of the defect inspection apparatus according to the present invention will be described.
FIG. 5 is a diagram showing a schematic configuration of a second embodiment of the defect inspection apparatus according to the present invention. In the second embodiment, the illumination optical system is configured by epi-illumination. The illumination light source 701 uses a DUV (far ultraviolet) laser (eg, excimer laser KrF = 248 nm, excimer laser ArF = 193 nm). As described above, since the DUV (far ultraviolet) laser has a short wavelength, it has a high resolution and can obtain an optical image based on scattered light or diffracted light from defects such as extremely small foreign matters of about 0.1 μm or less. become. Therefore, the illumination optical system 702 includes an illumination light source 701 such as a DUV laser, a polarization control optical system 703 for setting the polarization of illumination light, and pupil scanning illumination optics that scans laser light on the pupil 717 of the objective lens 711. The system 704 and the half mirror (1) 705 are configured. The basic configuration of the detection optical system 710 includes an objective lens 711, an imaging lens 712, an enlargement optical system 713, a polarization detection optical system 714 for setting the polarization of detection light before the image sensor, and a DUV quantum efficiency. Is configured with an image sensor 715 of about 10% or more. Further, a half mirror (2) 721 is installed in the middle of the detection optical path, and an autofocus system 722 for aligning the surface of the sample 1 with the focus of the objective lens 711 is disposed. Further, a half mirror (3) 731 is provided so that the pupil position of the objective lens 711 can be observed by the lens (1) 732 and the pupil observation optical system 733. Further, a half mirror (4) 741 is installed so that the pattern on the sample can be observed and aligned by the lens (2) 742 and the alignment optical system 743.

  Accordingly, the DUV laser beam emitted from the illumination light source 701 is converted into linearly polarized light by the polarization control optical system 703, and irradiated onto the pupil 717 of the objective lens 711 in two dimensions by the pupil scanning illumination optical system 704. Will be. The reflected light from the sample 1 is transmitted through the half mirror (1) 705 through the pupil 717 of the objective lens 711, and the optical image of the sample is imaged on the image sensor 715 by the imaging lens 712 and the magnifying optical system 713. It should be noted that by blocking the linearly polarized light component illuminated on the sample 1 by the polarization detection optical system 714, the image sensor 715 generates a light image formed by the scattered light or diffracted light component obtained from the surface of the sample 1. It will receive light.

By the way, in the second embodiment of the present invention, since a DUV laser light source is used as the illumination light source 701, it is necessary to use an image sensor 715 that is sensitive to DUV. However, when the surface irradiation type TDI image sensor shown in FIG. 8A is used as the image sensor 715, incident light is transmitted through the cover glass 805, and an oxide film (SiO ₂ ) in the gate 801 between the metal films 802. Since it passes through 803 and enters the CCD formed on the Si substrate 804, short-wavelength incident light attenuates and has almost no sensitivity to wavelengths of 400 nm or less, and DUV light cannot be detected as it is. Therefore, in order to obtain DUV sensitivity with a front-illuminated image sensor, there is a method in which the oxide film 803 in the gate 801 is thinned to reduce the short wavelength attenuation. As another method, an organic thin film coating is applied to the cover glass 805 so that when DUV light is incident, visible light is emitted accordingly, so that DUV light can be emitted by an image sensor that is sensitive only to visible light. There is a way to detect.

  On the other hand, as the image sensor 715, as shown in FIG. 8B, a back-illuminated TDI image sensor configured such that the thickness of the Si substrate 804 is thinned and light is incident from the thinned back side is used. By making light incident from the back side without the gate structure, the DVD quantum efficiency can be increased to about 10% or more, the quantum efficiency can be increased, the dynamic range can be increased, and the sensitivity can be obtained even at a wavelength of 400 nm or less. Further, the sensitivity can be increased by making the image sensor 715 TDI (Time Delay Integration) as described above.

  Next, the signal processing system 401 will be specifically described with reference to FIG. In other words, the signal processing system 401 indicates the grayscale values accumulated for each column pixel obtained in synchronization with the movement of the inspected substrate 1 in the y-axis direction from the image sensors 302 and 715 constituted by TDI image sensors and the like. An AD conversion circuit 402 that AD converts an image signal to be converted, and a digital image signal output from the AD conversion circuit corresponds to, for example, one pitch of circuit patterns repeated in the y-axis direction (may be a plurality of pitches). The delay memory 403 that delays by the amount of deviation, the digital detection image signal 408 obtained from the AD conversion circuit 402 and the digital reference image signal 409 delayed from the delay memory 403, for example by one pitch, are compared, for example, a difference image A signal is extracted, and the extracted difference image signal is binarized with a predetermined threshold value to detect a defect candidate such as a foreign object or a circuit pattern defect. A comparison circuit 404 that forms a binary image signal to be shown, and a binarized image signal that shows a defect candidate such as a foreign substance obtained from the comparison circuit 404, the area, position coordinates, and maximum length for each defect candidate For example, a defect candidate feature quantity extraction circuit 405 that extracts feature quantities such as a projection length (maximum length) in the x-axis direction and the y-axis direction and a moment, and the defect candidate feature quantity extraction circuit 405 extract the feature quantities. A defect determination circuit 406 that determines a defect when a feature amount of a defect candidate to be exceeded exceeds a predetermined determination criterion. As the feature amount, a three-dimensional feature amount may be extracted by adding a gray value based on the digital detection image signal obtained from the AD conversion circuit 402 at a point specified as a defect candidate. In particular, in order to detect a defect such as a very small foreign matter of about 0.1 μm or less, it is necessary to prevent a false detection by excluding a noise component based on delicate unevenness on the surface of the substrate 1 to be inspected. For this purpose, a difference image signal that exceeds a predetermined threshold is once extracted as a defect candidate such as a foreign substance, and whether the defect is a defect such as a foreign substance from the feature amount of each extracted defect candidate is due to subtle unevenness on the surface. It is necessary to find a defect such as a true minute foreign object by discriminating the object.

  That is, since the circuit pattern to be inspected is repeatedly formed on the substrate 1 to be inspected, in the comparison circuit 404, the digital detection image signal 408 of the circuit pattern obtained from the AD conversion circuit 402 and, for example, one pitch obtained from the delay memory 403 For example, a difference image signal (difference signal of pixel values of two image signals) is obtained by comparing with the digital reference image signal 409 of the adjacent circuit pattern delayed by the minute amount, and the obtained difference image signal is extracted as a defect candidate. A defect candidate point such as a foreign object is extracted by converting it into a binary image signal with a threshold for use. As an example of setting the binarization threshold, the entire difference image signal is binarized using a preset threshold or a threshold obtained from the brightness of the image to be inspected. As another example of threshold setting, a method may be considered in which a threshold is calculated for each coordinate or brightness of the difference image signal and binarized with a different threshold at each point of the difference image signal. In any case, the threshold for the difference image signal must be set low so that defects such as extremely small foreign matter can be detected, and false information based on subtle irregularities on the surface of the substrate 1 to be inspected is also detected. It will end up.

Therefore, in the defect candidate feature quantity extraction circuit 405, the defect candidate signal given by the binarized image signal contains a false report, and thus the binarized image signal and / or AD at the detected defect candidate point. Based on the digital detection image signal obtained from the conversion circuit 402, the feature amount such as the area, position coordinate, maximum length (projection length in the x-axis direction and y-axis direction), moment, gray value, etc. for each defect candidate point is obtained. Extract. Then, the defect determination circuit 406 determines whether the defect candidate point is a defect or a false report from the extracted feature amount, and finds a true defect.
As described above, in the signal processing system 401, defects such as extremely small foreign matters of about 0.1 μm or less can be discriminated from the false alarms and inspected.

  Next, an embodiment different from the above-described embodiment of the illumination optical system used in the defect inspection apparatus according to the present invention will be described with reference to FIGS. In this embodiment of the illumination optical system, an illumination light source 501 including a filament light source 502 such as a halogen lamp and an elliptical mirror 503 that condenses light generated from the light source 502 and the illumination light source 501 are condensed and emitted. A collimator lens 504 that converts the light to be substantially parallel light, and a lot lens (glass) that forms a secondary light source consisting of a spot beam at the exit end 505a by transmitting the substantially parallel light converted by the collimator lens 504 504), a pair of Fourier transform lenses 506 for condensing the spotted beam emitted from the exit end 505a, which is a secondary light source, on the pupil 507a of the objective lens 507, and the objective lens 507. The exit end 505a of the lot lens 505 and the surface of the substrate 1 to be inspected are configured in an optically conjugate relationship. By the way, using the orientation characteristic of the lamp 502 as shown in FIG. 11, a light beam with high emission intensity of the lamp 502 reaches the periphery of the detection region 3 ′, which is the peripheral portion of the illumination region 2 ′, as shown in FIG. The amount of light around the detection region (detection visual field) 3 ′ can be improved. In this case, it is possible to increase the illuminance by effectively utilizing the light amount generated from the lamp light source 502 rather than using the fly-eye lens. Further, in the case of this illumination optical system, the detection region 3 ′ has an illuminance distribution (pseudo annular illumination with increased ambient illuminance) shown in FIG. 12 corresponding to a decrease in MTF as the distance from the optical axis in the objective lens 507 increases. Can be illuminated.

  The slit-shaped light beam 107 described in the first embodiment of the defect inspection apparatus can be obtained by disposing the cylindrical lens 105 in the Fourier transform lens 506 or somewhere before or after the Fourier transform lens. The illuminance at the periphery of the detection region 3 can be increased, and as a result, the intensity of scattered light or diffracted light from a defect such as a foreign substance received by a pixel at the periphery of the detector 302 where the MTF decreases most by the detection optical system 301 It is possible to detect defects such as extremely small foreign matters of about 0.1 μm or less with high sensitivity and at high speed.

It is a figure which shows schematic structure of the 1st Example of the defect inspection apparatus which concerns on this invention. It is a figure which shows concretely the structure of one Example of the illumination optical system used for the 1st Example of the defect inspection apparatus shown in FIG. It is a figure for demonstrating the basic idea which shapes a slit-shaped Gaussian beam light beam with an illumination optical system, and improves illumination efficiency. It is a figure for demonstrating the method to receive and image the optical image of the detection area | region on a to-be-inspected board | substrate at the time of using a TDI image sensor as a detector. When varying the standard deviation σ a (corresponding to the width of the illumination) in the Gaussian beam flux is a diagram illustrating a change in the illuminance f (x ₀₎ in the peripheral portion of the detection area (x 0 _{= 1).} When irradiated with Gaussian beam flux when the standard deviation σ to 0.5, 1, 2, is a graph showing changes in intensity f (x ₀₎ to the length of the optical axis (x ₀₎ of the detection area . It is a figure which shows the structure of the 2nd Example of the defect inspection apparatus which concerns on this invention. It is a figure for demonstrating the Example of the TDI image sensor which enabled it to receive DUV light. It is a block diagram which shows one Example of the signal processing system which enabled it to discriminate | determine defects, such as a very small foreign material of about 0.1 micrometer or less, from a false report. It is a figure which shows the structure of the other Example of the illumination optical system used for the 1st Example of the defect inspection apparatus shown in FIG. In order to explain that the illumination optical system shown in FIG. 10 effectively uses the amount of light generated from the lamp light source and increases the illuminance at the periphery of the detection region using the orientation of the light generated from the lamp light source. FIG. It is a figure which shows the illumination intensity distribution with respect to the detection area | region obtained by the illumination optical system shown in FIG. 10 and FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate to be inspected, 2, 2 '... Illumination area 3, 3' ... Detection area, 5 ... Fine foreign material, 101 ... Illumination light source, 102 ... Illumination optical system, 103 ... Concave or convex lens, 104 ... Collimator lens, DESCRIPTION OF SYMBOLS 105 ... Cylindrical lens, 106 ... Laser beam, 107 ... Slit-shaped Gaussian beam, 201 ... Stage, 301 ... Detection optical system, 302 ... Detector, 302a ... TDI image sensor, 302ae ... Peripheral pixel (outer peripheral pixel) , 302ac ... corner pixels, 303 ... optical axis, 401 ... signal processing system, 402 ... AD converter circuit, 403 ... delay memory, 404 ... comparison circuit, 405 ... feature quantity extraction circuit for defect candidates, 406 ... defect determination circuit, 501 ... illumination light source, 502 ... lamp light source, 503 ... elliptical mirror, 504 ... collimator lens, 505 ... rod lens (glass rod), 50 ... Fourier transform lens, 507 ... objective lens, 701 ... DUV laser light source, 702 ... illumination optical system, 703 ... polarization control optical system, 704 ... pupil scanning illumination optical system, 705 ... half mirror (1), 711 ... objective lens, 712 ... Imaging lens, 713 ... Magnification optical system, 714 ... Polarization detection optical system, 715 ... TDI image sensor, 722 ... Automatic focus system, 733 ... Pupil observation optical system, 743 ... Alignment optical system.

Claims (10)

Shaped into a long slit shape in one direction by the beam shaping means of the laser beam emitted from the laser light source, irradiating the slit-shaped laser beam shaped by the beam shaping means from an oblique direction with respect to the slit-shaped illumination area on the specimen Then, the reflected scattered light from the detection area on the sample in the slit-shaped illumination area on the sample due to the irradiation is imaged through an objective lens, and reflected from the imaged detection area on the sample. An image of scattered light is captured by a linear image sensor, and a detection image obtained by capturing the image is compared with a reference image obtained by capturing from the reference region corresponding to the detection region on the sample by the linear image sensor. A method for detecting defects,
Substantially standard deviation longitudinal length between the two ends of the (H) half (x ₀₎ of the laser beam of the slit shaped intensity distribution of the slit-shaped longitudinal detection areas on the sample and (sigma) to have a Gaussian distribution, the longitudinal direction of the detection area on the specimen to be imaged and the slit-shaped laser beam in the linear image sensor when irradiating from the oblique direction with respect to the slit-like illumination area on the specimen both end portions _(x 0) illumination intensity f _(x 0) is the longitudinal direction of the illumination of the slit-shaped laser beam in the range of 0.46 to 0.73 with respect to the illumination intensity f (0) of the central portion of the defect inspection method characterized by distribution is set to shape. A laser beam emitted from a laser light source is shaped into a slit shape that is long in one direction, and the shaped slit-shaped laser beam is irradiated from an oblique direction to a slit-shaped illumination area on the sample, linear image sensor an image of the reflected scattered light of the reflected scattered light is imaged through the objective lens, the detection region on the specimen obtained by said imaging from the detection area on the specimen of the illumination region of slit-like in imaging, the detection image obtained by imaging, a method of detecting defects as compared to a reference image obtained by imaging by the linear image sensor from a reference area corresponding to the detection area on the specimen ,
Substantially standard deviation longitudinal length between the two ends of the (H) half (x ₀₎ of the laser beam of the slit shaped intensity distribution of the slit-shaped longitudinal detection areas on the sample and (sigma) to have a Gaussian distribution, the longitudinal length of the slit-shaped illumination area on Sai該sample irradiated with the slit-shaped laser beam from the oblique direction with respect to the slit-shaped illumination area on the specimen (Lx ) Is variable, and the illumination intensity f (x ₀ ) at both ends (x ₀ ) in the longitudinal direction of the detection region on the sample imaged by the linear image sensor is larger than the illumination intensity f ( ₀ ) at the center. A defect inspection method characterized in that the illuminance distribution in the longitudinal direction of the slit-shaped laser beam is shaped and set within a range of 0.46 to 0.73 . A laser beam emitted from a laser light source is shaped into a slit shape that is long in one direction, and the shaped slit-shaped laser beam is irradiated from an oblique direction to a slit-shaped illumination area on the sample, The reflected and scattered light from the detection area on the sample in the slit-shaped illumination area is imaged through the objective lens, and the image of the reflected and scattered light is imaged with a linear image sensor. the detected image obtained, a method of detecting defects as compared to a reference image obtained by imaging by the linear image sensor from a reference area corresponding to the detection area on the specimen,
Substantially standard deviation longitudinal length between the two ends of the (H) half (x ₀₎ of the laser beam of the slit shaped intensity distribution of the slit-shaped longitudinal detection areas on the sample and (sigma) A longitudinal direction of the detection region on the sample imaged by the linear image sensor when the slit-shaped laser beam is irradiated from the oblique direction to the slit-shaped illumination region on the sample. both end portions _{(x 0)} illumination intensity f _{(x 0)} is the longitudinal direction of the illumination of the slit-shaped laser beam in the range of 0.46 to 0.73 with respect to the illumination intensity f (0) of the central portion of the distribution is set to shape, the said detected image obtained by imaging the detection area on the sample by the linear image sensor, and imaging from the reference area corresponding to the detection region on the sample by the linear image sensor Obtained Defect inspection method characterized by detecting defects without being affected by the illuminance distribution in the longitudinal direction of the slit-shaped laser beam by comparing with the reference image. Defect inspection method according to any one of claims 1 to 3, wherein the laser beam emitted from the laser light source is a DUV laser beam. Slit-shaped laser beam irradiated onto the specimen, a defect inspection method according to any one of claims 1 to 3, wherein the polarized light is controlled slit-shaped laser beam. A laser light source for emitting a laser beam, a beam shaping means for shaping the laser beam emitted from the laser light source into a long slit-shaped laser beam in one direction, a slit-shaped laser beam shaped by the beam shaping means Irradiation means for irradiating the slit-shaped illumination area on the sample from an oblique direction, and a detection area on the sample among the slit-shaped illumination areas on the sample irradiated with the slit-shaped laser beam by the irradiation means Imaging means for forming an image of reflected and scattered light from the image through an objective lens, and imaging means for taking an image of the reflected and scattered light from the detection region on the sample imaged by the imaging means with a linear image sensor When the detection image imaged by the imaging means, a reference area corresponding to the detection area on the sample as compared to a reference image obtained by imaging by the imaging means The defect inspection apparatus and an image processing means for detecting Recessed,
The beam shaping means is configured such that the intensity distribution in the longitudinal direction of the laser beam emitted from the laser light source is approximately half (x ₀ ) of the length (H) between both ends in the longitudinal direction of the detection region on the sample. deviation (sigma) that is shaped into a long slit-shaped laser beam in the one direction with a Gaussian distribution, and the imaging time of irradiating a slit-shaped laser beam said shaped into slit-like illumination area on the specimen The illumination intensity f (x ₀ ) at both ends (x ₀ ) in the longitudinal direction of the detection region on the sample imaged by the linear image sensor of the means is 0.46 to the illumination intensity f (0) at the center. A defect inspection apparatus characterized in that the illuminance distribution in the longitudinal direction of the slit-shaped laser beam is shaped and set within a range of 0.73 . A laser light source for emitting a laser beam, a beam shaping means for shaping the laser beam emitted from the laser light source into a long slit-shaped laser beam in one direction, a slit-shaped laser beam shaped by the beam shaping means Irradiation means for irradiating the slit-shaped illumination area on the sample from an oblique direction, and a detection area on the sample among the slit-shaped illumination areas on the sample irradiated with the slit-shaped laser beam by the irradiation means Imaging means for forming an image of reflected and scattered light from the image through an objective lens, and imaging means for taking an image of the reflected and scattered light from the detection region on the sample imaged by the imaging means with a linear image sensor When the detection image imaged by the imaging means, a reference area corresponding to the detection area on the sample as compared to a reference image obtained by imaging by the imaging means The defect inspection apparatus and an image processing means for detecting Recessed,
The beam shaping means is configured such that the intensity distribution in the longitudinal direction of the laser beam emitted from the laser light source is approximately half (x ₀ ) of the length (H) between both ends in the longitudinal direction of the detection region on the sample. When the laser beam is shaped into a slit-shaped laser beam having a Gaussian distribution with a deviation (σ) and long in one direction, and the slit-shaped laser beam thus shaped is irradiated to the sample from the oblique direction. The length (Lx) in the longitudinal direction of the slit-shaped illumination area on the sample is variable, and the illumination intensity f (at the longitudinal ends (x ₀ ) of the detection area on the sample imaged by the linear image sensor. x ₀ ) is an illumination width setting means in which the illuminance distribution in the longitudinal direction of the slit-shaped laser beam is shaped and set within the range of 0.46 to 0.73 with respect to the illumination intensity f (0) at the center. this, including the Defect inspection apparatus according to claim. A laser light source for emitting a laser beam, a beam shaping means for shaping the emitted laser beam to the laser beam slit in one direction has a length from the laser light source, the beam shaping means by the shaped slit-shaped laser beam Irradiating means for irradiating the slit-shaped illumination area on the sample from an oblique direction, and detection on the sample among the slit-shaped illumination areas on the sample irradiated with the slit-shaped laser beam by the irradiation means Imaging means for forming an image of reflected and scattered light from a region through an objective lens, and imaging of reflected and scattered light from a detection region on the sample imaged by the imaging means by a linear image sensor and means, the detection image imaged by the imaging means, as compared to a reference image obtained by imaging by the imaging means from the reference area corresponding to the detection area on the specimen The defect inspection apparatus and an image processing means for detecting Recessed,
The beam shaping means is configured such that the intensity distribution in the longitudinal direction of the laser beam emitted from the laser light source is approximately half (x ₀ ) of the length (H) between both ends in the longitudinal direction of the detection region on the sample. The laser beam is shaped into a slit-like laser beam having a Gaussian distribution with a deviation (σ) and long in one direction, and the shaped slit-like laser beam is obliquely formed with respect to the slit-like illumination area on the sample. When illuminating, the illumination intensity f (x ₀ ) at both ends (x ₀ ) in the longitudinal direction of the detection region on the sample imaged by the linear image sensor of the imaging means is compared to the illumination intensity f (0) at the center. The illuminance distribution in the longitudinal direction of the slit-shaped laser beam is shaped and set within a range of 0.46 to 0.73,
The image processing means images the detection area on the sample irradiated with the slit-shaped laser beam set by shaping the illuminance distribution in the longitudinal direction by the beam shaping means with a linear image sensor of the imaging means. By comparing the detected image obtained in this way with the reference image obtained by imaging with the imaging means from a reference area corresponding to the detection area on the sample , the longitudinal illuminance distribution of the slit-shaped laser beam can be obtained . A defect inspection apparatus characterized by detecting defects without being affected. The laser light source, the defect inspection apparatus according to any one of claims 6 to 8, characterized in that fire the DUV laser beam. Defect inspection apparatus according to any one of claims 6 to 8, further comprising a polarization control means for controlling the state of polarization of the laser beam emitted from the laser light source.

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