JP5668113B2 - Defect inspection equipment - Google Patents

Description

The present invention relates to a defect inspection apparatus that inspects minute defects existing on the surface and end face of a sample such as a semiconductor substrate or a thin film substrate with high sensitivity and high speed.

In a production line for semiconductor substrates, thin film substrates, and the like, in order to maintain and improve product yield, inspection of defects existing on the surface of semiconductor substrates, thin film substrates, and the like is performed.

As a prior art of the defect inspection apparatus and method, Japanese Patent Laid-Open No. 9-304289 (
Patent Document 1), Japanese Patent Application Laid-Open No. 2003-240730 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2008-3.
Japanese Patent No. 2621 (Patent Document 3) is known.

In Patent Document 1, a low-angle light receiving system having an elevation angle of 30 degrees or less with respect to the surface of the wafer and a high-angle light receiving system having an elevation angle larger than this are provided, and the wafer is scanned with laser light at a low angle. The light receiving system and the high-angle light receiving system receive the scattered light of the laser light and detect the foreign matter corresponding to the scanning,
A wafer surface inspection apparatus is described in which a defect detected only by the high-angle light receiving system at the same scanning position is regarded as a crystal defect, and a foreign matter detected by the low-angle light receiving system is used.

Further, in Patent Document 2, scattered light from the edge portion of the wafer is distributed with strong directivity from the edge portion in the normal direction, and scattered light from a defect such as a foreign substance existing on the edge portion of the wafer is Using one or more detection optical systems avoiding scattered light from the edge portion (disengaged from the normal direction) by utilizing a characteristic that does not show remarkable directivity; or There is described a surface inspection apparatus in which scattered light from an edge portion is shielded by a spatial filter disposed on a Fourier transform plane, thereby detecting scattered light from the defect with a detector.

Further, in Patent Document 3, in a surface inspection apparatus that irradiates a surface of an inspection object while scanning with a light beam and detects scattered light from the inspection object, the inspection object with respect to the irradiation position of the light beam is disclosed. A position detection means for detecting a relative movement position of the body, and to the detector for detecting scattered light before the irradiation position of the light beam detected by the position detection means reaches the edge of the object to be inspected; Detector shielding means for blocking incident scattered light, or an optical path for blocking the optical path of the light beam irradiated before the irradiation position of the light beam detected by the position detecting means reaches the edge portion of the object to be inspected A detector control means for stopping the function of the detector for detecting scattered light before the irradiation position of the light beam detected by the blocking mechanism or the position detection means reaches the edge of the object to be inspected; , It is described that reduce the degradation of the detector to be triggered scattered light. Further, Patent Document 3 scans the light beam in a direction in which scattered light generated from the edge portion does not increase toward the detector when the light beam hits the edge portion of the inspection object. It is described.

JP-A-9-304289 JP 2001-255278 A JP 2008-32621 A

Particularly in the manufacture of semiconductor substrates and the like, the vicinity of the outer peripheral edge of the substrate (hereinafter referred to as the edge portion)
Defects are likely to occur due to adhesion of foreign matter and film peeling. In order to deal with such a defect occurring at the edge portion early / in advance, a defect inspection at the edge portion is required. In addition, by maximizing the total area of chips that can be secured as good products out of the total area of the substrate,
Improving manufacturing yield is an issue.

  However, Patent Document 1 does not consider defect inspection at the edge portion.

In the case of the surface inspection apparatus described in Patent Document 2, the detection optical system is arranged so as not to receive diffracted light having strong directivity generated from the edge part, or directivity generated from the edge part. The strong diffracted light is shielded by a spatial filter and is not detected by a detector. Further, in the case of the surface inspection apparatus described in Patent Document 3, before the irradiation position of the light beam detected by the position detection means reaches the edge portion of the object to be inspected, the light is scattered to the detector for detecting scattered light. It is configured not to detect the scattered light (diffracted light) from the edge part by blocking the incidence of light (diffracted light), blocking the optical path of the light beam, or stopping the detector function for detecting scattered light. Yes.

However, Patent Documents 2 and 3 do not sufficiently consider inspecting the vicinity of the edge portion of the substrate at high speed and with high sensitivity, as in the surface inspection of the substrate.

An object of the present invention is to provide a defect inspection apparatus capable of inspecting minute defects present on the surface and end face of a substrate such as a semiconductor substrate or a thin film substrate with high sensitivity and high speed.

The present invention also provides an illumination optical system that illuminates the illumination light by guiding the light emitted from the light source onto the sample, and the light generated on the sample by the illumination field illuminated by the illumination optical system from a plurality of directions. comprising a plurality of detecting optical system for obtaining a detection signal for each direction of the plurality of condenses, and determining the signal processor of the presence of defects by processing a plurality of detection signals obtained by the plurality of detecting optical system A defect inspection apparatus for processing a detection signal obtained from a detection optical system in which diffracted light generated from the edge grip portion of the sample is not incident in the signal processing portion when inspecting the vicinity of the edge grip portion of the sample. A defect inspection apparatus characterized by determining the presence of a defect.

In addition, the present invention provides an illumination optical system that illuminates a sample by guiding light emitted from a light source onto the sample, and light generated on the sample from a plurality of directions by the illumination field illuminated by the illumination optical system. A plurality of detection optical systems that collect light and obtain detection signals in a plurality of directions, and a signal processing unit that processes a plurality of detection signals obtained from the plurality of detection optical systems to determine the presence of a defect. A detection optical system for detecting defects in the vicinity of the edge portion of the sample and the vicinity of the edge grip portion of the sample so that diffracted light generated from the vicinity of the edge portion of the sample and the edge grip portion of the sample is not incident on the signal processing unit The detection signal obtained from the above is processed to determine the presence of a defect .

In addition, the present invention is generated on the sample by the illumination optical system that illuminates the illumination light by the polarized illumination by guiding the light emitted from the light source onto the sample and the illumination field illuminated by the illumination optical system. A plurality of detection optical systems that collect light from a plurality of directions and obtain detection signals in the plurality of directions, and a plurality of detection signals obtained from the plurality of detection optical systems are processed to determine the presence of a defect. A defect inspection apparatus including a signal processing unit, and when inspecting the vicinity of the edge portion of the sample and the vicinity of the edge grip portion of the sample , the signal processing unit generates at least from the vicinity of the edge portion of the sample and the edge grip portion of the sample. The present invention is characterized in that a detection signal obtained from a detection optical system in which diffracted light does not enter is processed to determine the presence of a defect .

According to the present invention, it is possible to inspect the vicinity of the edge portion of the substrate with high sensitivity, similarly to the surface inspection of the substrate.

1 is an overall schematic configuration diagram showing an embodiment of a defect inspection apparatus according to the present invention. It is a schematic diagram which shows the scanning method of the illumination field on the sample which concerns on this invention. It is a figure which shows schematic structure of each detection optical system which concerns on this invention. (A) is explanatory drawing which shows the angle range which each detection optical system which concerns on this invention detects scattered light, (b1) and (b2) are schematic diagrams which show arrangement | positioning of the several detection optical system which concerns on this invention It is. (A) (b) is a schematic diagram which shows the illuminance distribution control method which concerns on this invention, (c)-(e) is a figure which shows the structure of the illuminance distribution control element which concerns on this invention. It is a figure which shows the illumination intensity distribution implement | achieved by the illumination optical system which concerns on this invention. It is a block diagram which shows the structure of the analog processing part which comprises the signal processing part which concerns on this invention. The block diagram which shows the structure of the digital processing part which comprises the signal processing part which concerns on this invention It is the cross section and top view explaining the scattered light and diffracted light which generate | occur | produce in the edge part of a wafer when the illumination field which concerns on this invention is scanned in the edge part vicinity of a wafer. (A) is a figure which shows the detection optical system in which the edge diffracted light which generate | occur | produces from the edge part of the wafer which concerns on this invention injects, (b) (c) is a haze process part of the digital processing part which concerns on this invention. It is a figure which shows the intensity | strength signal waveform of the edge diffracted light to monitor corresponding to the illumination intensity distribution of illumination light. It is a block diagram which shows one Embodiment of the light-shielding means which shields the edge diffracted light in the detection optical system in which the edge diffracted light which concerns on this invention injects. (A) is sectional drawing which shows the edge grip which hold | maintains the wafer which concerns on this invention, (b) is a top view explaining the diffracted light which generate | occur | produces from the edge grip which concerns on this invention, (c) (d) is this It is a top view which shows the detection optical system into which the diffracted light generated from the edge grip which concerns on this invention injects. (A) is a figure which shows the analysis (polarization filter) of the diffracted light which generate | occur | produces in the edge and edge grip at the time of P polarization illumination based on this invention, (b) is the case at the time of S polarization illumination concerning this invention It is a figure which shows the analysis (polarization filter) of the diffracted light which generate | occur | produces in an edge and an edge grip. It is a block diagram which shows one Example of the illumination field position shift measurement means (wafer cross-sectional shape profile measurement means) based on this invention. It is a block diagram which shows one Example of the illumination field position correction means which concerns on this invention.

The configuration of the embodiment of the present invention will be described with reference to FIG. Illumination optical system 101, detection optical system 102a,
102b, a stage 103 on which the wafer 1 can be placed, a signal processing unit 105, an overall control unit 53,
The display unit 54 is configured.

The illumination optical system 101 includes a laser light source 2, an attenuator 3, a polarizing element 4, a beam expander 7, an illuminance distribution control element 5, reflection mirrors m 1 and m 2, and a condensing optical system (condensing lens) 6. The laser light emitted from the laser light source 2 is adjusted to a desired beam intensity by the attenuator 3, adjusted to a desired polarization state by the polarization element 4, adjusted to a desired beam diameter by the beam expander 7, and the reflection mirror m. Then, the inspection area of the wafer 1 is illuminated via the condenser lens 6. The illuminance distribution control element 5 is used to control the intensity distribution of illumination on the wafer 1. Although FIG. 1 shows a configuration in which the illumination optical system 101 irradiates light from an oblique direction with respect to the normal line of the wafer 1, the illumination optical system 101 is directed to the surface of the wafer 1 via another optical path not shown in FIG. It is also possible to irradiate light vertically, and the angle of illumination can be switched according to the inspection object.

As the laser light source 2, in order to detect a minute defect near the wafer surface, a laser beam that emits a short wavelength ultraviolet or vacuum ultraviolet laser beam and has a high output of 1 W or more is used.
In order to detect defects inside the wafer, those that emit a visible or infrared laser beam are used.

The stage 103 includes a stage control unit 55, a translation stage 11, a rotary stage 10, and a Z stage (not shown). FIG. 2 shows the relationship between the illumination area (illumination field 20) on the wafer 1 and the scanning direction due to the movement of the rotary stage 10 and the translation stage 11, and the locus of the illumination field 20 drawn on the wafer 1 thereby. FIG. 2 shows the shape of the illumination field 20 formed in an elliptical shape that is long in one direction and short in a direction perpendicular to it by illumination distribution control in the illumination optical system 101 or illumination from an oblique direction. Teruno 20 is driven by the rotational movement of the rotary stage 10.
The stage 11 is scanned in the translational direction S2 by the translational motion of the stage 11 in the circumferential direction S1 of the circle around the rotation axis of the rotary stage 10. The longitudinal direction of the illumination field 20 is the scanning direction S2.
The illumination optical system 101 is configured so that the illumination field 20 passes through the rotation axis of the rotary stage 10 by scanning in the scanning direction S2. The movement of the Z stage corresponds to the height of the wafer 1, that is, the movement of the surface of the wafer 1 in the normal direction. In the above configuration, the scanning direction S
While the wafer is rotated once by one scan, scanning in the scanning direction S2 is performed for a distance equal to or shorter than the length in the longitudinal direction of the illumination field 20, thereby drawing a spiral trajectory T on the entire surface of the wafer 1. Are scanned.

The detection optical systems 102a and 102b are configured to collect and detect scattered light or diffracted light generated in different directions and angles. FIG. 3 shows the configuration of the detection optical system 102a. Since the components of the detection optical system 102b are the same as those of the detection optical system 102a, description thereof is omitted. FIG.
As will be described later with reference to (b), in order to detect scattered light in a wide angular range, a plurality of different detection optical systems (not shown in FIG. 1) other than the two detection optical systems 102a and 102b are arranged. The

The detection optical system 102 a includes a condensing imaging system 8, a polarization filter 13, and a sensor (detector) 9.
Consists of The polarizing filter 13 can be attached to and detached from the optical axis A of the condensing imaging system 8 and can rotate the detection direction, and reduces scattered light components due to wafer roughness and the like, and diffraction / scattered light components due to edges, which cause noise. Use for purposes.

The image of the illumination field 20 is formed on the sensor 9 by the condensing image forming system 8. In order to enable detection of weak foreign matter scattered light, a photomultiplier tube, an avalanche photodiode, a semiconductor photodetector combined with an image intensifier, or the like is used as the sensor 9.

Next, the relationship between the angle components of the scattered light detected by the plurality of detection optical systems 102a and 102b according to the present invention will be described with reference to FIG. FIG. 4A is an explanatory diagram showing an angular range in which each detection optical system detects scattered light. The equatorial plane corresponds to the wafer surface, and is shown as a hemisphere with the normal direction of the wafer surface as the zenith, and the scanning direction ( (Translation direction) An azimuth angle (longitude) of the optical axis of the detection optical system 102 with reference to S2 is φ, and an angle from the zenith is θ. The angle range detected by the detection optical system 102 is indicated by the hemispherical region R, and these are shown by being projected in parallel on a plane parallel to the equator plane, as shown in FIGS. 4 (b1) and 4 (b2) each detection optical system 1
The angle range detected by 02 is indicated by hatching. As shown in FIGS. 4 (b1) and 4 (b2), it is possible to detect various types of defects by providing a plurality of detection optical systems 102 and covering a wide angle range. In addition, since the angle distribution of the defect scattered light varies depending on the defect type and the defect size, the scattered light intensities at various angles are simultaneously detected by the plurality of detection optical systems 102 and processed by the signal processing unit 105 described later. It is possible to classify various defect types and estimate defect dimensions with high accuracy.

FIG. 4 (b1) is a diagram showing an embodiment in which a detection optical system 102 suitable for inspecting a foreign matter having a minute dimension on the order of several tens of nm to a large dimension on the order of several hundred nm is arranged. The scattered light of the minute foreign matter is strongly emitted at a low angle when P-polarized illumination is performed. Therefore, by detecting the low-angle scattered light component in all directions by the plurality of detection optical systems 102, it is possible to detect a very small defect. Furthermore, the detection optical system 102 detects a scattered light component that is emitted at a high elevation angle, thereby causing a crystal defect (COP: Crystal Originated Particle) in which scattered light at a high angle is strongly emitted.
) Etc. can be inspected with high sensitivity. FIG. 4B2 is a diagram showing an embodiment in which the detection optical system 102 that increases the NA of each detection optical system is arranged. In this way, by increasing the NA of each detection optical system, it is possible to detect even weaker scattered light, which is suitable for detecting a defect having a smaller size.

In any configuration, by capturing scattered light in a wide angle range by the plurality of detection optical systems 102, scattered light having different directions emitted by defects can be detected, and various types of defects can be detected robustly. Furthermore, by detecting the scattered light components of low elevation angle and high elevation angle individually, it is possible to simultaneously detect and classify convex defects such as foreign substances and concave defects such as COP and scratch.

Next, the configuration of the illuminance distribution control element 5 and the illuminance distribution control method in the illumination optical system 101 according to the present invention will be described with reference to FIGS. FIG. 5A is a diagram showing a configuration when a transmission optical element is used as the illuminance distribution control element 5. That is, the light emitted from the laser light source 2
The laser light 41 adjusted to have a desired intensity, polarization, and beam diameter by the configuration of the illumination optical system 101 passes through the illuminance distribution control element 5 and is guided onto the wafer 1 via the condensing optical system 6. The illuminance distribution control element 5 is controlled by the controller 14 that receives a signal from the overall control unit 53. FIG. 5B is a diagram showing a configuration when a reflective optical element is used as the illuminance distribution control element 5. Further, the illuminance distribution control element 5 is two-dimensional (shown in FIG. 5C) or one-dimensional (shown in FIG. 5D) in a plane perpendicular to the optical axis of the transmitted light. For each position, an optical element having a function of changing the intensity or phase of transmitted light is used. Then, by forming an image of the light transmission surface of the illuminance distribution control element 5 on the wafer 1 by the condensing optical system 6, the similar shape of the light intensity distribution modulated by the illuminance distribution control element 5 is obtained. Projected onto the wafer 1.
The distance from the condensing optical system 6 to the intersection of the optical axis and the upper surface of the wafer 1 and the distance from the condensing optical system 6 to the transmission surface of the illuminance distribution control element 5 are both equal to the focal length of the condensing optical system 6. As a result, a Fourier transform image of the light amplitude distribution on the light transmission surface of the illuminance distribution control element 5 is projected onto the wafer 1. With this configuration, an illuminance distribution corresponding to the transmittance and phase distribution given by the illuminance distribution control element 5 is formed on the wafer 1. Further, by using a cylindrical lens as the condensing optical system 6, the above-described action is applied to only one axis, and the laser light (illumination light) is condensed in the other axial direction, so that the scanning direction (translation direction) S2 Is given an illuminance distribution according to the transmittance and phase distribution given by the illuminance distribution control element 5, and only a short region can be illuminated in the scanning direction (circumferential direction) S1. Incidentally, since the illuminance distribution of the laser light emitted from the laser light source 2 is substantially Gaussian distribution, the Gaussian distribution whose shape is determined by the beam expander 7 and the condenser lens 6 when the illuminance distribution control element 5 is not particularly actuated. Laser beam is projected onto the wafer.

Illuminance distribution control element 5 having a fixed transmittance distribution or phase distribution given as described above includes a diffractive optical element (DOE), a homogenizer (aspheric lens, microlens array, optical fiber bundle, or inner surface of a hollow pipe). Reflective coating (Fig. 5
(Shown in (e))). Further, the illuminance distribution control element 5 is controlled by the controller 14 connected to the overall control unit 53, and is dynamically changed to a spatial light modulation element (SLM: Spatial).
With the light modulator, the illumination field 20 is dynamically controlled and adjusted so that the illuminance distribution becomes an arbitrary shape before and after scanning the wafer 1 or during the scanning. Dynamically variable spatial light modulation elements include transmissive types such as liquid crystal elements and magneto-optic spatial light modulation elements, and reflective types include digital micromirror devices (DMD) and grating valves (GLV). And reflective liquid crystal elements such as LCOS.

Next, an example of the illuminance distribution formed by the above configuration will be described with reference to FIG. FIG. 6A shows a Gaussian distribution substantially reflecting the illuminance distribution of the laser light source 2, and FIG.
) Shows a case where a uniform illuminance distribution is formed using a homogenizer or the like as the illuminance distribution control element 5. The uniform illuminance distribution shown in FIG. 6B is suitable for realizing high-sensitivity inspection by maximizing the amount of scattered light from the defect while suppressing thermal damage to the wafer due to high-illuminance laser irradiation. FIG. 6C shows a distribution in which the central illuminance is reduced with respect to the uniform illuminance distribution. The temperature rise generated when the uniform illuminance distribution is maximized at the center of the illuminance distribution, which may cause thermal damage to the wafer. Therefore, the illuminance distribution shown in FIG. The distribution is suitable for realizing high sensitivity.

Next, according to the present invention, it is possible to accurately classify various defect types and estimate defect dimensions based on scattered light intensity signals at various angles simultaneously detected by a plurality of detection optical systems covering a wide angle range. The signal processing unit 105 to be performed will be described.

First, the analog processing unit 51 constituting the signal processing unit 105 will be described with reference to FIG. Here, for the sake of simplicity, the configuration of the analog processing unit 51 when two detection optical systems, that is, the detection optical systems 102a and 102b are provided will be described. The signal current output from each of the sensors (detectors) 9a and 9b is converted into a voltage and amplified by the preamplifier units 501a and 501b. The amplified analog signal is further filtered with high-frequency noise components by low-pass filters 511a and 511b, and then an analog-to-digital conversion unit having a sampling rate sufficiently higher than the cutoff frequency of the low-pass filters 511a and 511b (
(A / D converters) 502a and 502b are converted into digital signals and output.

Next, the digital processing unit 52 constituting the signal processing unit 105 will be described with reference to FIG. Each output signal from the analog processing unit 51 is extracted in the digital processing unit 52 by the high-pass filters 604a and 604b, and the defect signals 603a and 603b are extracted and input to the defect determination unit 605. Since the defect is scanned in the S1 direction by the illumination field 20,
The waveform of the defect signal is obtained by enlarging or reducing the illuminance distribution profile of the illumination field 20 in the S1 direction. Therefore, each of the high-pass filters 604a and 604b passes through the frequency band including the defect signal waveform and cuts the frequency band and the DC component including relatively much noise, thereby reducing the S / N of the defect signals 603a and 603b. Will improve. Each high-pass filter 6
As 04a and 604b, a high-pass filter that has a specific cutoff frequency and is designed to cut off components above that frequency, a band-pass filter, or an FIR filter that is similar to the waveform of a defect signal is used. The defect determination unit 605 performs threshold processing on the input of the signal including the defect waveform output from each of the high pass filters 604a and 604b, and determines the presence / absence of a defect. That is, since defect signals based on detection signals from a plurality of detection optical systems are input to the defect determination unit 605, the defect determination unit 605 performs threshold processing on the sum or weighted average of the plurality of defect signals. OR for a group of defects extracted by threshold processing for a plurality of defect signals in the same coordinate system set on the wafer surface
By taking the AND or the like, it becomes possible to perform a highly sensitive defect inspection as compared with the defect detection based on a single defect signal.

Further, the defect determination unit 605 calculates defect coordinates and defect size estimation values indicating defect positions in the wafer, which are calculated based on the defect waveform and the sensitivity information signal, for the portions determined to have defects. This is provided to the overall control unit 53 as 607 and output to the display unit 54 or the like. The defect coordinates are calculated based on the center of gravity of the defect waveform. The defect size is calculated based on the integrated value of the defect waveform.

Further, each output signal from the analog processing unit 51 is supplied to the low-pass filters 601a and 601 in addition to the high-pass filters 604a and 604b constituting the digital processing unit 52.
Each of the low-pass filters 601a and 601b outputs a low-frequency component and a direct current component corresponding to the amount of scattered light (haze) from minute roughness in the illumination field 20 on the wafer. As described above, the outputs from each of the low-pass filters 601a and 601b are input to the haze processing unit 606, and the processing of the haze information is performed. That is, the haze processing unit 605 outputs a signal corresponding to the magnitude of the haze for each location on the wafer as a haze signal from the magnitude of the input signal obtained from each of the low-pass filters 601a and 601b. Further, since the angular distribution of the amount of scattered light from the roughness changes according to the spatial frequency distribution of the minute roughness, as shown in FIG. 8, each detector of the plurality of detection optical systems 102 installed at mutually different azimuths and angles. By using the haze signal from (each sensor) 9 as an input to the haze processing unit 606, the haze processing unit 606 can obtain information on the spatial frequency distribution of minute roughness from the intensity ratio thereof.

By the way, when a part of the laser beam is applied to the convex shape of the edge portion of the wafer, very strong diffracted light is generated, and the generated very strong diffracted light covers the wide solid angle detector 9. , The detector 9 is saturated and the inspection becomes impossible. Further, the detector 9 may be deteriorated or damaged due to excessive light input. Strong diffracted light is also generated by the shape of the grip that holds the wafer at the edge.

Therefore, according to the present invention, in the defect inspection near the edge portion of the wafer, the edge diffracted light intensity in the vicinity of the edge portion is monitored by the detection optical system 41 and the signal processing unit 105 to detect the detection optical system 41 on which the edge diffracted light is incident. Other detection optical system 1 that shields only the detector and does not need to be shielded
The maximum area of the chip that can be secured as a non-defective product out of the total area of the wafer by performing high-sensitivity defect detection up to the vicinity of the edge portion where defects due to adhesion of foreign matter, film peeling, etc. easily occur using the detector 9 of 02 To improve the yield. Next, an embodiment having a configuration characteristic of the present invention will be described with reference to the drawings.

First, how the diffracted light and scattered light are emitted from the edge portion of the wafer when the illumination field 20 according to the present invention scans the vicinity of the edge portion of the wafer will be described with reference to FIG. FIG. 9A is a view of the wafer as viewed from above, and shows a state in which the illumination field 20 is scanned sequentially from the center of the wafer by scanning S1 and S2 and approaches (approaches) the vicinity of the edge portion of the wafer. FIG. 9B shows 1 (cross section) of the wafer in which the illumination field 20 approaches the vicinity of the edge portion of the wafer. Generally, the inclined portion 31 of the wafer edge is called a bevel, and the end face 32 is called an apex. Here, the illuminance distribution 21 of the laser light is assumed to be a Gaussian distribution and is schematically shown. When the bottom of the illuminance distribution reaches the edge portion, strong diffracted light and scattered light 22 are generated at the edge portion, particularly at the corner portion of the bevel boundary, compared with the minute roughness scattered light on the surface other than the edge portion. This is because the scale of the irregularities at the corners of the bevel boundary is very large, on the order of microns, compared with the nano- to angstrom-order micro roughness. The angular distribution of diffracted light and scattered light generated at the edge portion is schematically shown in FIG. FIG. 9 follows the direction and angle display method of the detection optical system described in FIG. The bevel boundary line is always perpendicular to the illumination direction due to the helical scanning by the circumferential scanning S1 and the translational scanning S2. Therefore, as shown in FIG. 9C, edge diffracted light 24 is generated in the incident direction of the illumination light, the outgoing direction 23 of the specularly reflected light, and the in-plane direction passing through the zenith. Further, since roughness and surface roughness are present at the bevel boundary and the bevel, scattered light 25 appears around the diffracted light 24 as shown in FIG.

However, since the edge diffracted light 24 has a high intensity, the sensor (detector) 9 of the detection optical system 102 is used.
If the light is directly incident on the sensor 9, the sensor 9 may be deteriorated or broken.

Therefore, an embodiment of a method for avoiding deterioration or failure of the sensor 9 which is a feature of the present invention will be described with reference to FIGS.

First, the edge diffracted light intensity monitoring means will be described with reference to FIG. Detection optical system 1
As the arrangement of 02, the case of the arrangement shown in FIG. 4B1 will be described. FIG. 10 (a)
As shown in FIG. 4, the edge diffracted light 24 is incident on a part (a detection optical system on which the edge diffracted light enters is referred to as an edge diffracted light detecting optical system 41) 41 among the plurality of detection optical systems. As a result, the detection signal detected by the detector 9 of the edge diffracted light detection optical system 41 passes through the analog processing unit 51 constituting the signal processing unit 105 and passes through the low-pass filter 601 of the digital processing unit 52 from FIG.
(B) The edge diffracted light intensity signal shown in (c) is obtained. FIG. 10B shows a case where the illuminance distribution of the illumination light (laser light) shown in FIG. 6A is a Gaussian distribution, and FIG.
FIG. 6B shows a case where the illuminance distribution of the illumination light (laser light) shown in FIG. 6B is a uniform illuminance distribution (and a distribution in which the illuminance drops steeply away from the center). The edge diffracted light intensity signal shown in FIG. 10B becomes stronger as the illumination field 20 approaches the edge portion because the illuminance distribution of the illumination light is a Gaussian distribution. On the other hand, in the edge diffracted light intensity signal shown in FIG. 10C, the illuminance distribution of the illumination light is a uniform illuminance distribution. In addition, since the scanning speed S2 in the radial direction (translation direction) is slower than the scanning speed S1 in the circumferential direction, the time change of the edge diffracted light intensity signal is gradual. For example, the haze processing unit 606 uses the haze of the detection optical system 41. By observing the signal, that is, the signal after passing through the low-pass filter 601, the edge diffracted light intensity signal can be observed. Therefore, for example, the haze processing unit 606 includes the detection optical system 41.
It is determined whether or not the intensity of the haze signal exceeds a predetermined light shielding start threshold value, and when the intensity exceeds, the strong edge diffracted light is incident on the sensor 9 of the detection optical system 41 by the light shielding means shown in FIG. By shielding the light, it is possible to avoid damage to the sensor 9 due to edge diffracted light.

When the illuminance distribution of the illumination light shown in FIG. 10C is a uniform illuminance distribution, FIG.
) The illuminance distribution of the illumination light shown in FIG. 3 is smaller than the Gaussian distribution (indicated by a one-dot chain line), and the illuminance at a position away from the beam center is small (the illuminance distribution has a short skirt), so
In e, diffracted light and scattered light generated from the edge portion are weakly suppressed. For this reason, when the illuminance distribution of the illumination light is a uniform illuminance distribution, the high sensitivity inspection similar to the wafer surface can be performed also in the edge vicinity region Re.

Next, the light shielding means of the edge detection optical system 41 will be described with reference to FIG. The edge detection optical system 41 includes a light shielding shutter 15 in addition to the configuration of the detection optical system 120. The light shielding shutter 15 is operated by an electrical switching signal obtained from the light shielding shutter controller 16 based on a signal determined that the edge diffracted light intensity signal observed by the digital processing unit 52 exceeds a predetermined light shielding start threshold. Switching between light shielding and light transmission is performed. As the light shielding shutter 15, a mechanical shutter, a liquid crystal filter, an electro-optic element, an acousto-optic element, or the like is used. Based on the processing shown in FIG. 10, the light-shielding shutter controller 16 receives a determination signal as to whether or not the edge diffracted light intensity output from the digital processing unit 52 exceeds a certain intensity, and the edge diffracted light intensity exceeds a certain intensity. A signal that switches the light-shielding shutter 15 to the light-shielding state is output. As described above, light shielding for sensor protection can be performed only in a situation where excessive light incidence due to edge diffracted light in the vicinity of the edge portion becomes a problem.

Next, an embodiment of an edge grip for holding a wafer according to the present invention will be described with reference to FIG. That is, in order to avoid contamination on the back surface of the wafer and adhesion of foreign matter, an edge chuck that holds the edge portion while pressing it from the outside is used. The portion that contacts the edge of the wafer and holds the edge in the edge chuck is called an edge grip 81. FIG. 12A shows a schematic diagram of a state and a cross section of the edge grip 81 viewed from directly above. In the shape of the edge grip 81, an edge (ridge) in a direction substantially equal to the scanning direction S1, that is, the wafer circumferential direction (shown by a thick line in FIG. 12A) is an edge grip ridge 83, and the scanning direction S2, that is, the wafer diameter direction. A side (ridge) in a direction substantially equal to the edge grip is defined as an edge grip ridge 82. An angle formed between the edge grip surface to which the illumination light hits and the wafer surface, that is, an angle formed between the edge grip ridge 82 and the wafer surface is defined as φe. As shown in FIG. 12A, since the edge grip 81 protrudes inward from the apex 32, the diffracted light and scattered light generated at the edge grip 81 are also highly sensitive when inspecting the vicinity of the edge portion. It becomes a factor that hinders inspection.

By the way, when the illumination field 20 approaches the vicinity of the edge portion of the wafer, scattered light and diffracted light are generated from the edge grip 81 as well as the edge portion. Here, if the surface of the edge grip 81 to which a part of the illumination light hits and the edge grip ridges 82 and 83 are polished so that the unevenness is reduced, the intensity of the scattered light becomes weaker than the diffracted light, and the edge grip Of the light generated from the portion 81, the diffracted lights 85 and 86 from the edge grip ridges 82 and 83 are dominant. FIG. 12B shows the emission directions of the diffracted lights 85 and 86 by the edge grip ridges 82 and 83, and FIG.
This is shown by the direction and angle display method of the detection optical system described in (a). Since the edge grip ridge 83 is in the same direction as the edge boundary of the wafer, the edge grip diffracted light 86 from the edge grip ridge 83 is similar to the edge diffracted light 24 as shown in FIG. The light is emitted in the incident direction, the emission direction 23 'of the edge grip surface regular reflection light, and the in-plane direction passing through the zenith. On the other hand, since the edge grip ridge 82 is a direction orthogonal to the edge grip ridge 83, the edge grip diffracted light 85 passes through the emission direction 23 ′ of the edge grip surface regular reflection light as shown in FIG. It is emitted in a shape orthogonal to the grip diffracted light 86. Therefore, the emission direction of the edge grip diffracted light 85 is the center of the circle (the zenith direction = the zenith direction = the display in FIG. 12B).
It is determined by the value of k corresponding to the position in the emission direction 23 ′ of the edge grip surface regular reflection light when the distance from the wafer normal direction (corresponding to 90 ° from the zenith) to the circumference (corresponding to 90 ° from the zenith) is 1. This value is obtained by the following calculation. If the incident angle of the illumination light is φi, the emission angle of the edge grip surface regular reflection light 23 ′ is φi−2φe. From the definition shown in FIG.
k = sin (φi−2φe). From the above, the shape of the edge grip 81 (for example, φe
Etc.) and the exit angle k of the edge grip diffracted light 85 by selecting the incident angle φi of the illumination light.
Can be selected.

FIG. 12C shows k1 that minimizes the number of detection optical systems on which the edge grip diffracted light is incident.
The example which selected the value of is shown. When the value of k1 is selected as shown in FIG.
The edge grip diffracted light 85 is incident only on the detection optical system 87. That is, the detection optical system 87 is in the direction in which the edge diffracted light 24 shown in FIG. 9C and the edge grip diffracted light 86 shown in FIG. 12B are also incident (the edge diffracted light detection optical system 41 is the edge grip diffracted light. Detection optical system 8
7 is included. ). Therefore, in the vicinity of the edge portion and the edge grip, the edge diffracted light detection optical system 41 is selectively shielded by the means shown in FIGS. 10 and 11, thereby causing damage to the sensor of the edge diffracted light detection optical system 41. It is possible to avoid the defect and detect the defect by using another detection optical system.

FIG. 12D shows that the edge grip diffracted light 85 does not enter any detection optical system.
The example which selected the value of is shown. In this embodiment, the incident angle φi of the illumination light is increased (that is, illumination with a low elevation angle is performed), and φe is decreased (that is, the angle of the edge grip ridge is made parallel to the wafer surface). It is valid. Therefore, in order to prevent the edge grip diffracted light 85 from entering any of the detection optical systems, for example, k2> 0.95 needs to be set, and for that purpose, (φi−2φe)> 72 degrees needs to be set. Therefore, an edge grip having a shape such that φe <−1 degree when φi = 70 degrees and φe <4 degrees when φi = 80 degrees is used. Of course, the incident angle φi of the illumination light may be set based on the edge grip shape.

As described above, damage to the sensor of the edge diffracted light detection optical system 41 is avoided and high-sensitivity defect detection is performed over a wide area up to the vicinity of the edge portion and the vicinity of the edge grip by another detection optical system. It is possible to improve the yield by maximizing the total area of chips that can be secured as non-defective products out of the total area of the wafer.

Next, the detection optical system 41 (detection optics) is generated from the edge diffracted light 24 generated from the vicinity of the edge portion of the wafer according to the present invention and incident on the detection optical system 41 and the edge grip 81 that holds and holds the edge portion. An embodiment in which the edge grip diffracted light 86 incident on the system 87 (including the system 87) is removed by analysis (polarization filter) will be described with reference to FIG.

That is, when detecting minute defects on fine roughness, P-polarized illumination is incident on the wafer 1 from an oblique direction by the illumination optical system 101 shown in FIG. When viewed from the illumination light incident surface (the surface including the illumination light incident direction and the wafer normal), the electric field vibration caused by the P-polarized oblique illumination is only in the direction parallel to the incident surface. The vibration direction of the scattered light and diffracted light emitted from the light beam is also parallel to the incident surface (lateral direction in FIG. 13A). For this reason, in the detection optical system 41 (including the detection optical system 87) to which the edge diffracted light 24 and the edge grip diffracted light 86 are incident, the polarization filter 13 that blocks the polarized light in this direction is used. The diffracted light 24 and the edge grip diffracted light 86 can be shielded.

On the other hand, when detecting a defect on a relatively rough roughness, S-polarized oblique illumination is used as illumination light by the illumination optical system 101 shown in FIG. In this case, the edge diffracted light 24 generated from the vicinity of the edge portion of the wafer and the edge grip diffracted light 86 generated from the edge grip 81 are used.
Is the direction orthogonal to the polarization direction of the edge diffracted light 24 and the edge grip diffracted light 86 by the P-polarized oblique illumination (the vertical direction in FIG. 13B). Therefore, the detection optical system 41 (detection optical system 87) on which the edge diffracted light 24 and the edge grip diffracted light 86 are incident.
By using a polarizing filter 13 that blocks the polarization in this direction,
The edge diffracted light 24 and the edge grip diffracted light 86 can be shielded.

As described above, the detection optical system 41 (including the detection optical system 87) in each of the case of detecting a minute defect on fine roughness and the case of detecting a defect on relatively rough roughness.
Further, the edge diffracted light 24 and the edge grip diffracted light 86 can be selectively shielded by arranging the analyzer (polarizing filter) 13 so as to be crossed Nicol with the illumination polarization.
At this time, in the detection optical system 41 (including the detection optical system 87), the scattered light from the defect is detected by being transmitted through the polarization filter 13 because the polarization state is disturbed by the shape and material of the defect.
Of course, since the analyzer 13 is not disposed in the other detection optical systems, it is possible to detect defects with high sensitivity over a wide area up to the vicinity of the edge portion and the vicinity of the edge grip.

Next, the illumination field is displaced from the field of view of the detection optical system by correcting the displacement of the illumination field due to the wafer surface displacement (tilt angle deviation and height deviation), which is a feature of the present invention. The illuminating position displacement measuring means (edge cross-sectional shape profile measuring means) and illuminating position correction means to be prevented will be described with reference to FIGS. FIG. 14 is a schematic configuration diagram showing an embodiment of the illumination field position deviation measuring means (wafer cross-sectional shape profile measuring means) according to the present invention, and FIG. 15 is an embodiment of the illumination field position correcting means according to the present invention. It is a schematic block diagram which shows a form. By the way, the emission angle and the emission position (for example, 23 and 23 ′) of the regular reflection light by the illumination light change depending on the change in the inclination angle and height of the wafer surface (including the vicinity of the edge). Therefore, the illumination field misalignment measuring means (wafer cross-sectional shape profile measuring means) according to the present invention is:
As shown in FIG. 14, the condenser lens 203 having a focal length f, a position detector 204, a half mirror 201, a position detector 202, and a processing circuit 205 are provided. The condenser lens 203 is installed at a position where the distance from the wafer surface is sufficiently larger than f on the optical path through which the regular reflection light of the illumination light passes. The position detector 204 is separated from the condenser lens 203 by a distance f.
A detection surface is installed at the position of, and an angle change (angle shift) of specular reflection light due to a change in the tilt angle and height of the wafer surface is detected as a change in position. The position detector 202 is installed on the optical path of the specularly reflected light reflected by the half mirror 201, and the angular deviation of the specularly reflected light and the deviation of the emission position of the specularly reflected light on the wafer (that is, the illumination field 20). (Position displacement) is also detected. The processing circuit 205 performs a process of subtracting the angular deviation of the regular reflection light detected by the position detector 204 from the angular deviation of the regular reflection light detected by the position detector 202 and the positional deviation of the illumination field 20. Thus, the positional deviation amount of the illumination field 20 is calculated. Then, the displacement signal of the illumination field 20 obtained by the processing circuit 205 is input to the overall control unit 53 and sin (φ
By dividing by i), it is converted into the amount of change in the height of the wafer surface. The overall control unit 53 further records the amount of change in the wafer surface height for each scanning position R in the scanning direction (translation direction) S2, thereby obtaining a wafer cross-sectional profile from the wafer surface to the edge portion. Thus, the wafer cross-sectional profile obtained by the overall control unit 53 is displayed on the display unit 54 as a graph, for example.

By the way, if the position of the illumination field 20 is shifted due to a height shift of the wafer surface and deviates from the field of view of the detection optical system, the inspection sensitivity is lowered. In order to prevent this, the position of the illumination field is corrected by the illumination field position correction means shown in FIG. 15 based on the measured displacement value of the illumination field 20 obtained by the illumination field position deviation measurement means (wafer cross-sectional shape profile measurement means). There is a need. That is, the illumination field position correction means provided in the illumination optical system 101 is configured by installing the beam deflection element 211, the condenser lens 212, and the mirror 213 (m2) in the optical path of the illumination optical system 101. The illumination light is subjected to angle control by the beam deflecting element 211, reflected by the mirror 213 (m 2), and guided onto the wafer 1. The illumination position correction controller 214 controls the beam position by controlling the magnitude of deflection by the beam deflection element 211. That is, the illumination field position correction controller 214 restores the illumination field position based on the displacement amount (position displacement measurement value) of the illumination field 20 obtained from the processing circuit 205 (including the overall control unit 53). By controlling the beam deflection element 211, the illumination field 2 for the scattered light detection angle range of each detection optical system
The position of 0, that is, the emission angle and the emission position (for example, 23, 23 ′) of the specularly reflected light is corrected so as to match the change in the inclination angle and height of the wafer surface (including the vicinity of the edge). In the system 41 (including the detection optical system 87), the edge diffracted light 24 and the edge grip diffracted light 86 are shielded, and in the other detection optical systems, the incidence of the edge diffracted light 24 and the edge grip diffracted lights 85 and 86 is eliminated. It is possible to inspect the vicinity of the edge portion of the wafer with high sensitivity in the same manner as the wafer surface inspection by detecting scattered light in a wide angle range.

As described above, according to the embodiment of the present invention, the edge shape profile measuring means and the illumination field position correcting means are provided, and the illumination field position deviation due to the wafer surface deviation (tilt angle deviation and height deviation). That is, by correcting the deviation of the emission angle and the emission position (for example, 23, 23 ′) of the specularly reflected light, the edge detection light and the edge grip diffraction light are shielded in the specific detection optical system, and the other detection optical system In this case, it is possible to widen the angle range covered by the detector and increase the inspection sensitivity by increasing the spatial resolution and resolution with a trade-off of shallow depth of focus. In other words, according to the embodiment of the present invention, the scanning of the minute laser beam spot by the illumination optical system 101 and the detection of scattered light with high light collection efficiency with a wide solid angle by the plurality of detection optical systems 102 are performed. Simultaneously with the surface inspection, a high-sensitivity inspection capable of detecting defects on the order of several hundred nm to several tens of nm near the edge of the wafer is realized.

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Laser light source, 3 ... Attenuator, 4 ... Polarizing element, 5 ... Illuminance distribution control element, 6 ... Condensing lens, 7 ... Beam expander, 8 ... Condensing imaging system, 9 ... Sensor, 10 DESCRIPTION OF SYMBOLS ... Translation stage, 11 ... Rotary stage, 13 ... Polarizing filter, 14 ... Controller, 15 ... Light-shielding shutter, 16 ... Shutter controller, 20 ... Teruno, 31 ... Bevel, 32 ... Apex, 41 ... Edge diffraction light detection optical system, 51 ... Analog processing unit, 52 ... Digital processing unit, 53
DESCRIPTION OF SYMBOLS ... Whole control part 54 ... Display part 81 ... Edge grip 101 ... Illumination optical system 102 ... Detection optical system 103 ... Stage 105 ... Signal processing part 202 ... Position detector 203 ... Condensing lens 204 DESCRIPTION OF SYMBOLS ... Position detector, 205 ... Processing circuit, 211 ... Beam deflector, 212 ... Condensing lens, 214 ... Field position correction controller, 501a, b ... Preamplifier unit, 502a,
b: A / D conversion unit, 511a, b ... low pass filter, 601a, b ... low pass filter, 604a, b ... high pass filter, 605 ... defect determination unit, 606 ... haze processing unit, S1 ... scanning direction, S2 ... scanning direction , Re: Edge vicinity region.

Claims (4)

An illumination optical system that guides light emitted from the light source onto the sample and illuminates it as an illumination field;
A plurality of detection optical systems for collecting light generated on the sample by the illumination field illuminated by the illumination optical system from a plurality of directions and obtaining detection signals in the plurality of directions;
A defect inspection apparatus comprising a signal processing unit that processes a plurality of detection signals obtained by the plurality of detection optical systems and determines the presence of a defect,
When inspecting the vicinity of the edge grip portion of the sample, the detection signal obtained from the detection optical system in which diffracted light generated from the edge grip portion of the sample is not incident is processed in the signal processing portion to determine the presence of a defect. Defect inspection device characterized by. An illumination optical system that guides light emitted from the light source onto the sample and illuminates it as an illumination field;
A plurality of detection optical systems for collecting light generated on the sample by the illumination field illuminated by the illumination optical system from a plurality of directions and obtaining detection signals in the plurality of directions;
A defect inspection apparatus comprising a signal processing unit that processes a plurality of detection signals obtained from the plurality of detection optical systems and determines the presence of a defect,
When inspecting the vicinity of the edge portion of the sample and the vicinity of the edge grip portion of the sample, the signal processing unit is obtained from a detection optical system in which diffracted light generated from the vicinity of the edge portion of the sample and the edge grip portion of the sample is not incident. A defect inspection apparatus characterized in that a detection signal is processed to determine the presence of a defect. The illumination optical system further includes an illumination field misalignment measuring unit that measures the amount of misalignment of the illumination field illuminated on the sample by the illumination optical system, and the illumination optical system includes an illumination field measured by the illumination field misalignment measuring unit. 3. The defect inspection apparatus according to claim 1, further comprising an illumination field position correction unit that corrects the position of the illumination field illuminated on the sample based on an amount of field displacement. An illumination optical system that guides the light emitted from the light source onto the sample and illuminates it as an illumination field by polarized illumination;
A plurality of detection optical systems for collecting light generated on the sample from a plurality of directions by an illumination field illuminated by the polarized illumination illuminated by the illumination optical system and obtaining detection signals in the plurality of directions;
A defect inspection apparatus comprising a signal processing unit that processes a plurality of detection signals obtained from the plurality of detection optical systems and determines the presence of a defect,
When inspecting the vicinity of the edge portion of the sample and the vicinity of the edge grip portion of the sample, from the detection optical system in which diffracted light generated at least near the edge portion of the sample and the edge grip portion of the sample is not incident in the signal processing unit A defect inspection apparatus that processes a detection signal obtained to determine the presence of a defect.

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