JP2007193030A - Focusing device, microscope, and focusing processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically change focusing height without releasing tracking control to track a sample. <P>SOLUTION: The focusing device 100 is equipped with: a focusing means for changing a relative distance between a sample S having a level difference on its surface and an objective 3a; a chromatic aberration correction lens 9 for forming a spot image by spot light projected to the sample S on an image forming surface IP; an optical element moving means for moving the chromatic aberration correction lens 9; a spot image detection means for receiving and detecting the spot image; a correction lens position storage table 26b for storing the disposing positions of the chromatic aberration correction lens 9 in association with each of a plurality of surfaces to be observed set in the predetermined height of the level difference; and a control part 25 successively performing control to move the chromatic aberration correction lens 9 to the disposing position associated with the surface to be observed, and to change a relative distance between the sample S and the objective 3a on the basis of the result of detection by the spot image detection means so as to focus the focal plane of the objective 3a on the surface to be observed for each of the plurality of surfaces to be observed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a focusing device, a microscope, and a focusing processing program for focusing a specimen having a step on a surface on a focal plane of an objective lens.

  Conventionally, a microscope capable of automatically capturing and recording an observation image has been used in an automatic inspection process of a wafer on which a fine circuit pattern is formed. Such a microscope is equipped with a focusing device that automatically focuses a specimen such as a wafer on the focal plane of the objective lens, thereby focusing (observing) the observation image. In recent years, many techniques for improving the operability, functionality, etc. of the focusing device that automatically performs focusing have been proposed (see, for example, Patent Documents 1 to 3).

  As shown in FIG. 18, the focusing device described in Patent Document 1 includes infrared light emitting elements 122 and 123 such as a laser diode, minute lenses 120 and 121, a prism 119, a beam splitter 116, and an infrared light spot projection. Lens 115, reduction lens 114, detection lens 117, and PSD 118 as a light receiving element.

  Infrared light emitted from the infrared light emitting elements 122 and 123 is transmitted through the minute lenses 120 and 121, reflected by the prism 119, transmitted through the beam splitter 116, and projected on the imaging plane IP by the projection lens 115. Projected on. Further, each projected infrared light is projected as a light spot on the specimen S via the reduction lens 114, the dichroic mirror 113, the prism 124, the λ / 4 plate 162, the lens barrel lens 112, and the objective lens 111. The Thereafter, each infrared light reflected on the specimen S follows the optical path in the opposite direction, is reflected by the beam splitter 116, and is collected on the light receiving surface of the PSD 118 by the detection lens 117, thereby forming a light spot image. Imaged.

  Here, each infrared light emitted from the infrared light emitting elements 122 and 123 is alternately emitted at a predetermined time difference so as not to be simultaneously received by the PSD 118. Each infrared light is projected obliquely on the specimen S through the off-axis of the objective lens 111. For this reason, when the surface of the specimen S is not focused on the focal plane of the objective lens 111, each infrared light forms a light spot image at a different position on the light receiving surface of the PSD 118. It is detected that the upper light spot image moves in accordance with the switching of the emission of each infrared light. Further, when the surface of the specimen S is focused on the focal plane of the objective lens 111, each infrared light forms a light spot image at the same position on the light receiving surface of the PSD 118, and the PSD 118 receives the light. It cannot be detected that the light spot image on the surface moves.

  In other words, the focusing device described in Patent Document 1 can focus the specimen S with respect to the objective lens 111 by moving the specimen S to a position where the movement of the light spot image cannot be detected by the PSD 118. Further, the magnitude and direction of the defocus of the sample S can be detected from the relative positional relationship between the light spot images detected by the PSD 118. In this focusing apparatus, the sample S is moved up and down together with the stage 131 by rotationally driving a pinion 134 engaged with a rack 132 attached to the stage 131 by a motor 133.

  On the other hand, as shown in FIG. 19, the focusing device described in Patent Document 2 includes a reference light source 204, a collimation lens 205, a light shielding plate 206, a polarization beam splitter (PBS) 207, a condensing lens 208, and a chromatic aberration correction lens 209. , A λ / 4 plate 210, a light shielding plate 212, an imaging lens 213, and a light receiving element 214.

  Invisible light such as infrared light emitted from the reference light source 204 is converted into a parallel light beam centered on the optical axis by the collimation lens 205, and then a half of the light beam cross section is shielded by the light shielding plate 206. The light beam has a cross section. The invisible light is reflected by the PBS 207, relayed by the condenser lens 208 and the chromatic aberration correction lens 209, then reflected by the dichroic prism 211 via the λ / 4 plate 210, and by the objective lens 203 a attached to the revolver 202. , And projected as a light spot on the specimen S. Thereafter, the invisible light reflected on the specimen S follows the optical path on the opposite side of the projection with the optical axis of the objective lens 203a interposed therebetween, passes through the PBS 207, and then is received by the light receiving element 214 by the imaging lens 213. It is condensed on the surface and formed as a light spot image.

  Here, the light receiving surface of the light receiving element 214 is arranged so as to coincide with the focal plane of the imaging lens 213, and is further arranged so as to be conjugate with the focal plane of the objective lens 203a. For this reason, the invisible light forms a minimal light spot image on the light receiving surface of the light receiving element 214 when the surface of the specimen S is focused on the focal plane of the observation light through the objective lens 3 a.

  Further, when the surface of the sample S is not focused on the focal plane of the observation light through the objective lens 3a and is in the near focus position (position approaching the objective lens 3a from the focal plane), The invisible light is collected on the far side (rear side) of the light receiving element 214, and forms a light spot image having a half-moon-like spread on the light receiving surface in the drawing and on the upper side. On the contrary, when the surface of the sample S is at the far focus position (position far from the objective lens 3a from the focal plane), the invisible light is condensed on the near side (front side) of the light receiving element 214. Then, a light spot image having a half-moon-like spread is formed on the upper and lower sides of the figure on the light receiving surface.

  That is, the focusing device described in Patent Document 2 moves the sample S to a position where the spot diameter is detected as being minimal by the light receiving element 214, thereby focusing the sample S on the objective lens 3a. Can do. Further, the magnitude and direction of the defocus of the sample S can be detected from the size and spreading direction of the light spot image detected by the light receiving element 214. In this focusing apparatus, the sample S is moved up and down together with the stage 201 by the motor 216 driven by the focusing motor driving unit 219.

  Further, as shown in FIG. 20, the focusing device described in Patent Document 3 includes a diffraction grating DG between the collimation lens 205 and the light shielding plate 206 in addition to the configuration of the focusing device described in Patent Document 2. Is provided. In FIG. 20, the same components as those in the focusing device of Patent Document 2 are denoted by the same reference numerals.

  The invisible light emitted from the reference light source 204 is converted into a parallel light beam centered on the optical axis by the collimation lens 205, and a plurality of parallel light beams whose propagation directions are slightly different from each other in the direction perpendicular to the drawing surface by the diffraction grating DG. It is divided into. Thereafter, the divided light beams are relayed in the same manner as the focusing device described in Patent Document 2, and are projected onto the specimen S to form a plurality of light spots arranged in a straight line. Further, each light beam reflected by the sample S is traced on the opposite side across the optical axis, and travels backward through the optical path, passes through the PBS 207, and then collects on the light receiving surface of the light receiving element 214 by the imaging lens 213. It is illuminated and imaged as a light spot image. The respective light spot images on the light receiving surface are linearly arranged in a direction perpendicular to the paper surface in the drawing.

  Here, the specimen S is focused on the objective lens 3a by an operation similar to that of the focusing device described in Patent Document 2. For example, the specimen S has steps at a plurality of locations on the surface. When a plurality of light spots are projected at various positions, the average height surface of the plurality of steps is focused on the focal plane of the objective lens 3a. On the other hand, in the focusing devices described in Patent Documents 1 and 2, since there is one light spot to be projected, when there is a step on the surface of the sample S, the surface of the step on which the spot light is projected is Focused. When the height projected is changed according to the movement of the sample S or the like, the surface of the step to be focused is also changed.

Japanese Patent No. 2614843 Japanese Patent Laid-Open No. 11-249027 JP 2001-296469 A

  By the way, in the focusing device according to the prior art, since spot light is projected into the observation field of the objective lens, infrared light having a wavelength different from observation light such as visible light or ultraviolet light is used. . However, in this case, the focal plane due to the observation light of the objective lens and the focal plane due to the infrared light deviate according to the axial chromatic aberration between the observation light and the infrared light. In other words, due to chromatic aberration in the objective lens, the focusing surface by the focusing device deviates from the surface observed by the observation light (observed surface), and a focusing error corresponding to the amount of deviation occurs. . Further, the amount of focusing error changes when the objective lens is replaced with an objective lens having a different chromatic aberration characteristic.

  For this reason, in the focusing device described in Patent Document 1, the reduction lens 114 is provided, the chromatic aberration of the focal plane of the objective lens 111 is reduced on the imaging plane IP, and the focusing caused by the slight remaining chromatic aberration. The focus error is corrected by an electrical offset generated by the correction circuit. Furthermore, this offset amount is set in advance for each replaceable objective lens, and is changed in accordance with the switching of the objective lens, so that a focusing error does not occur even when the objective lens has a different chromatic aberration characteristic. ing. Note that the objective lens switching is recognized by detecting the rotational position of the revolver.

  On the other hand, in the focusing device described in Patent Document 2, a chromatic aberration correction lens 209 is provided, the chromatic aberration correction lens 209 is moved in the optical axis direction, and the chromatic aberration of the focal plane of the objective lens 203a is reduced. By correcting on the image plane, the focusing error caused by chromatic aberration is corrected. Further, the hole position of the revolver 202 set on the specimen S is detected, and the chromatic aberration correction lens 209 is moved to the arrangement position stored in association with the hole position of the revolver, so that the objective lens having a different chromatic aberration characteristic is replaced. In this case, the focusing error is prevented from occurring.

  However, although the focusing devices described in Patent Documents 1 and 2 can correct the focusing error due to chromatic aberration as described above, only one light spot is projected on the sample S. There has been a problem that the focusing error that occurs due to the step on the surface cannot be eliminated. Specifically, for example, when this focusing device is applied to an automatic defect extraction device such as a semiconductor wafer, there are the following problems.

  That is, first, focusing is performed at a location including a defect on the wafer, and an image including the defect (defect image) is captured and acquired. Next, the wafer is moved sideways, focusing is performed at the same address location in the adjacent die in the wafer, and a reference image (golden image) for defect extraction is taken. At this time, it is uncertain whether the light spot is projected on the convex portion of the step formed on the surface of the sample S or the concave portion due to uncertain factors such as the movement accuracy of the stage for moving the wafer. Therefore, the in-focus state of the golden image may be different from the in-focus state of the defect image. As a result, when the golden image is subtracted from the defect image, there is a problem in that a background component difference caused by a difference in focus state is detected as a false defect.

  On the other hand, the focusing device described in Patent Document 3 projects a plurality of light spots on the surface of the specimen S, so that the average height surface of the step on the surface is always focused on the objective lens. The defect image and the golden image can be captured in the same in-focus state. As a result, only the defect component can be satisfactorily extracted by subtraction processing of each image.

  Specifically, for example, as shown in FIG. 21A, when a defect image of the specimen S having the defects DA and DB in the convex portions and the concave portions of the step is picked up, a plurality of spot projections are performed on the region including the defects DA and DB. The average height surface AP can be focused on the objective lens by projecting the light SR. At this time, a defect image PI1 including defect images DAI and DBI as shown in FIG. Similarly, a golden image PI2 as shown in FIG. 22-2 can be acquired by focusing on the average height plane AP as shown in FIG. Then, by subtracting the golden image PI2 from the defect image PI1, as shown in FIG. 23, it is possible to obtain a defect extraction image PI3 in which only the defect images DAI and DBI are extracted with the background components removed satisfactorily.

  However, in such a focusing device, since the average height surface is always stably focused, there are the following problems. That is, as shown in FIG. 23, since the defect images DAI and DBI are extracted in a blurred state, when the operator visually observes the defect images DAI and DBI and performs state inspection, sufficient observation is performed. There was a problem that it could not be done.

  On the other hand, it is conceivable that the convex part and the concave part of the step where the defects DA and DB exist are respectively focused and the defect images DAI and DBI are captured clearly. However, in this case, the tracking control as the tracking operation of the sample in the continuous focusing process needs to be temporarily canceled and the operator needs to move the sample S up and down, and when returning to the tracking control, the sample S There is a problem that the initial setting process such as searching needs to be re-executed and the tact time increases.

  The present invention has been made in view of the above, and can adjust the average height surface of the step formed on the surface of the specimen to the focal plane of the objective lens and perform tracking control for tracking the specimen. It is an object of the present invention to provide a focusing device, a microscope, and a focusing processing program capable of automatically changing a focusing height without canceling the focusing.

  In order to solve the above-described problems and achieve the object, a focusing apparatus according to claim 1 is a projecting apparatus for focusing on the surface of the specimen having a step on the surface and a focusing means for changing a relative distance between the objective lens and the specimen. An imaging optical element that forms a spot image of the spot light formed on a predetermined imaging surface, an optical element moving unit that moves the imaging optical element in an optical axis direction of the imaging optical element, and the spot Spot image detection means for receiving and detecting an image; and a storage table for storing the arrangement position of the imaging optical element for each of a plurality of observation surfaces set within a predetermined height of the step. The optical element moving means moves the imaging optical element to the arrangement position associated with the surface to be observed, and based on the detection result of the spot image detection means, the focusing means Changing relative distance The focuses control the focal plane of the observation target surface said objective lens, characterized in that and a focusing control unit sequentially performed for each of the plurality of the observed surface.

  In the focusing device according to claim 2, in the above invention, the storage table is provided with the imaging optical element on each of the plurality of surfaces to be observed for each of the plurality of replaceable objective lenses. The position is stored in association with each other.

  According to a third aspect of the present invention, in the above-described invention, the focusing device includes a lens switching mechanism that switches the plurality of objective lenses, and the focusing control unit causes the lens switching mechanism to switch the objective lens, and Control is performed to sequentially move the imaging optical element to each arrangement position stored in the storage table in association with the switched objective lens.

  In the focusing device according to a fourth aspect of the present invention, in the above invention, the storage table has the plurality of arrangement positions for correcting a focusing error caused by a transparent film formed on the surface of the specimen. It is characterized in that it is stored in association with each surface to be observed.

  Further, in the focusing device according to claim 5, in the above invention, the storage table, as an arrangement position for correcting the focusing error, the arrangement position with respect to the specimen in which the transparent film is not formed, The arrangement position correction amount for correcting the focusing error is individually stored.

  In the focusing device according to claim 6, in the above invention, the storage table may be provided with an arrangement position for correcting the focusing error for each of the plurality of transparent films that can be formed on the specimen. It is characterized by being stored in association with each of the surfaces to be observed.

  Further, in the focusing device according to claim 7, in the above invention, the storage table is configured such that the storage table has the plurality of steps set within the predetermined height for each predetermined height of the steps of the plurality of samples. Each observation surface is stored with the arrangement position of the imaging optical element associated therewith.

  In the focusing device according to claim 8, in the above invention, the storage table is configured to set the arrangement position for correcting chromatic aberration generated based on chromatic aberration characteristics of the objective lens for each of the plurality of observation surfaces. The information is stored in association with each other.

  In the focusing device according to claim 9, in the above invention, the storage table is provided for each of an upper end surface, a lower end surface, and an average height surface set within the predetermined height as the plurality of observation surfaces. The arrangement position of the imaging optical element is stored in association with each other.

  According to a tenth aspect of the present invention, in the above invention, the spot image detection means includes a relay optical system that optically relays the spot image formed linearly on the imaging surface. A light receiving means for receiving the spot image relayed by the relay optical system, and detecting whether or not the total spot area of the spot image is minimal based on an output value from the light receiving means. The focusing control unit performs control to change the relative distance based on the detection result of the spot image detection unit so that the total spot area of the spot image is minimized.

  According to an eleventh aspect of the present invention, a microscope includes the focusing device according to any one of the above.

  A focusing processing program according to a twelfth aspect forms a spot image of a spot light projected on a sample having a step on the surface, detects the spot image on a predetermined image plane, and detects a predetermined height of the step. For each of the plurality of observation planes set within the range, the focusing plane that stores the arrangement position of the imaging optical element that forms the spot image in association with the observation plane is used as the focal plane of the objective lens. A focus processing program for moving the imaging optical element to the arrangement position associated with the surface to be observed, and a detection result of the spot image Based on the control, the relative distance between the sample and the objective lens is changed so that the sum of the spot areas of the spot image is minimized, and the control is performed to focus the surface to be observed on the focal plane of the objective lens. For each of the plurality of surfaces to be observed Characterized in that to execute sequentially performing focus control procedure.

  According to a thirteenth aspect of the present invention, there is provided the focusing processing program according to the above-described invention, wherein the focusing device is configured so that the imaging optical element is provided on each of the plurality of observation surfaces for each of the plurality of replaceable objective lenses. An arrangement position is stored in association with each other, and the focusing control procedure switches the plurality of objective lenses, and the imaging optical element is stored in each arrangement position stored in association with the switched objective lens. It is characterized by performing control to move sequentially.

  According to the focusing device, the microscope, and the focusing processing program according to the present invention, the average height surface of the step formed on the surface of the sample can be focused on the focal plane of the objective lens, and the sample is tracked. The focus height can be automatically changed without canceling the tracking control, and when applied to a defect extraction device, it is possible to clearly image defects on the specimen without increasing the tact time. To do.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a focusing device, a microscope, and a focusing processing program according to the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment. In the description of the drawings, the same parts are denoted by the same reference numerals.

(Embodiment)
FIG. 1 is a diagram showing a main configuration of a focusing device 100 and a microscope according to the present embodiment. As shown in FIG. 1, the focusing device 100 is a focus detection optical system that detects the in-focus state of the sample S, and a reference light source 4 and a collimation lens 5 that converts light emitted from the light source into a parallel light beam. A diffraction grating DG that diffracts a light beam and divides the light beam into a plurality of light beams, and a light shielding plate 6 that shields a part of the light beam. Here, the reference light source 4 is a laser light source that emits, for example, infrared light as visible light. In addition, it includes a PBS 7 that reflects a predetermined linearly polarized light beam, a condensing lens 8 and a chromatic aberration correction lens 9 that optically relay the light beam, and a λ / 4 plate 10 that converts linearly polarized light into circularly polarized light. A condensing lens 13 that collects a light beam to form a light spot image, a light shielding plate 12 that prevents flare, ghost, and the like, and a two-divided sensor 14 as a light receiving element that receives the light spot image are provided.

  Here, the light receiving surface 14 c of the two-divided sensor 14 is disposed so as to coincide with the focal plane of the condensing lens 13, and a predetermined imaging surface IP (virtual surface) is formed by the condensing lenses 8 and 13. It arrange | positions so that it may become conjugate. The imaging plane IP is set at a position conjugate with the focal plane of the objective lens 3a by the chromatic aberration correction lens 9 as an imaging optical element and the objective lens 3a. In addition, the focal plane of the objective lens in the present invention is not limited to the focal plane, but includes a focus plane with respect to the imaging observation system provided in the microscope.

  In the focus detection optical system having such a configuration, the infrared light emitted from the reference light source 4 is converted into a parallel light beam by the collimation lens 5 and is slightly propagated in the direction perpendicular to the paper surface in the figure by the diffraction grating DG. Are divided into a plurality of parallel light beams. Each of the divided parallel light beams is shielded by the light-shielding plate 6 by a half of the light beam cross section, and is formed into a parallel light beam having a half-moon shaped cross section. Each parallel light beam that has passed through the light shielding plate 6 is reflected by the PBS 7 in the left direction as S-polarized light, relayed by the condenser lens 8 and the chromatic aberration correction lens 9, and then passes through the λ / 4 plate 10 to be circularly polarized. Is converted to

  Each of the parallel luminous fluxes that have been circularly polarized is reflected downward in the drawing by the dichroic prism 11 provided in the microscope, and forms a plurality of light spots on the surface Sa of the sample S by the objective lens 3 a attached to the revolver 2. Projected. Each projected light spot is linearly arranged in a direction perpendicular to the paper surface in the figure. Specifically, as shown in FIG. 2A which is a side view from the AA direction in FIG. 1 and FIG. 2B which is a plan view of the sample S, for example, five spot projection lights SR are included. It is projected on the surface Sa, and five light spots SP are linearly arranged at predetermined intervals. Note that the number of light spots SP projected on the sample S is not limited to five, and may be any plural number.

  As shown in FIG. 1, each light beam projected and reflected on the sample S traces the optical path on the opposite side of the projection across the optical axis OA1 of the objective lens 3a, and is reflected by the dichroic prism 11. After passing through the λ / 4 plate 10 and converted into linearly polarized light again, it is relayed by the chromatic aberration correction lens 9 and the condenser lens 8 and passes through the PBS 7 as P-polarized light in the right direction in the figure. Each transmitted light beam passes through the light shielding plate 12 and is then condensed on the light receiving surface 14c of the two-divided element 14 by the condenser lens 13 to form a light spot image. Here, each light spot image is formed by being arranged on a two-divided line of the two-divided sensor 14, and is received by the respective light receiving units 14a and 14b included in the two-divided sensor 14.

  In such a focus detection optical system, the reference light source 4 is not limited to the laser light source, and may be an LED, for example. Further, although the condensing lenses 8 and 13 and the chromatic aberration correcting lens 9 are shown as single lenses in FIG. 1, it is preferable that the condensing lenses 8 and 13 and the chromatic aberration correcting lens 9 are lenses composed of lens groups in which spherical aberration and the like are corrected favorably.

  On the other hand, the focusing device 100 has a laser driving unit 22 that oscillates and drives the reference light source 4 and a chromatic aberration correction lens 9 in the direction of the optical axis OA2 as a mechanism for controlling the above-described focusing detection optical system and each part of the microscope. A chromatic aberration correction lens motor 17 and a chromatic aberration correction lens motor drive unit 20 as optical element moving means for moving the chromatic aberration correction lens 9, and a limit detection unit 33 for limiting the movement range of the chromatic aberration correction lens 9.

  Further, the focusing device 100 switches the objective lens 3a to another objective lens 3b attached to the revolver 2, etc., so that the revolver motor 15 and the revolver motor drive unit 18 as a lens switching mechanism for rotating the revolver 2 are used. And a revo hole position detector 21 for detecting a mounting hole (revo hole) in the revolver 2 of the objective lens arranged opposite to the sample S, and the sample S in the direction of the optical axis OA1 of the objective lens arranged opposite to the sample S. A focusing motor 16 and a focusing motor drive unit 19 are provided as focusing means for movement. Here, the focusing motor 16 moves the stage 1 holding the sample S up and down in the drawing and moves the sample S in the direction of the optical axis OA1, thereby changing the relative distance between the sample S and the objective lens 3a. The revolver 2 can simultaneously hold an objective lens (not shown) in addition to the objective lenses 3a and 3b. Further, the mechanism for changing the relative distance between the specimen S and the objective lens 3a as the focusing means is not limited to the specimen S, and the objective lens 3a may be moved up and down.

  Further, the focusing device 100 includes an amplifier 23 that amplifies the current signals SA1 and SB1 output from the light receiving units 14a and 14b of the two-divided sensor 14 in accordance with the received light intensity after current / voltage conversion, and an amplified voltage. And an A / D converter 24 that performs A / D conversion on the signals SA2 and SB2 and outputs the signals as detection signals SA3 and SB3.

  In addition, the focusing device 100 is realized using a ROM and a RAM, and includes a storage unit 26 that stores various processing programs, processing parameters, processing data, and the like, and a CPU that executes the processing program stored in the storage unit 26. And a control unit 25 that controls processing and operation of each part that is realized and electrically connected. In addition, the storage unit 26, in particular, for each of the focusing processing program 26a that defines the focusing processing procedure performed by the focusing device 100 and a plurality of observation surfaces set within the height of the step on the surface of the specimen S. A correction lens position storage table 26b that stores an arrangement position of the chromatic aberration correction lens 9 in the direction of the optical axis OA2 is stored.

  The control unit 25 includes a revolver motor drive unit 18, a focusing motor drive unit 19, a chromatic aberration correction lens motor drive unit 20, a laser drive unit 22, an A / D conversion unit 24, a storage unit 26, and a limit detection unit. 33 is electrically connected.

  The specimen S as a target to be focused by the focusing device 100 has a step with a predetermined height on the surface, and has a plurality of step portions Sb with a height H as shown in FIG. The height H of the stepped portion Sb is set to a predetermined value such as the height of a circuit pattern or the like formed on the surface of the wafer or the like as the specimen S. A plurality of observation surfaces OP1 to OP3 can be arbitrarily set in advance. Here, the surface to be observed OP1 is a standard height surface for observing the average height of the stepped portion Sb, and the surfaces to be observed OP2 and OP3 are for observing the convex portion and the concave portion of the stepped portion Sb, respectively. An upper offset surface and a lower offset surface. Note that the number of observation surfaces to be set need not be limited to three, but may be two or four or more.

  For example, as shown in FIG. 4, the correction lens position storage table 26b sets the lens position as the arrangement position of the chromatic aberration correction lens 9 in the optical axis OA2 direction for each of the observation surfaces OP1 to OP3 set in this way. It is stored in association. Further, the correction lens position storage table 26b stores the correspondence between the observed surfaces OP1 to OP3 and the respective lens positions in association with the revolver numbers “1” to “4” of the revolver 2. Yes.

  Each lens position to be stored in the correction lens position storage table 26b is obtained based on the design value of the focus detection optical system or the like, or obtained by adjusting in advance with an actual machine using a reference wafer having a stepped portion Sb. It is done. Then, it is input by an input means (not shown) and recorded in advance in the correction lens position storage table 26b.

  The control unit 25 refers to the correction lens position storage table 26b and, for example, when the objective lens attached to the rebo hole number “1” is disposed to face the sample S, the lens associated with the observation surface OP1. The chromatic aberration correction lens 9 is moved to the position 11A, the specimen S is moved in the direction of the optical axis OA1, and control is performed so that the observed surface OP1 is focused on the focal plane of the objective lens. Furthermore, the control unit 25 performs control so that the same processing is sequentially performed on the observation surfaces OP2 and OP3. Details of focusing processing control by the control unit 25 will be described later.

  The association between each objective lens 3a, 3b, etc. attached to the revolver 2 and the rebo hole number is recorded in advance in the storage unit 26, and the control unit 25 performs this recording and the rebo hole position detection unit 21. The objective lens disposed to face the specimen S is specified based on the revo hole number detected by the.

  Here, with reference to FIGS. 5-1 to 5-3, the detection principle of the in-focus state using the above-described focus detection optical system will be described. 5A to 5C show the optical path from the light shielding plate 12 to the two-dividing element 14 in the focus detection optical system, and each figure (b) shows the light reception of the two-dividing element 14. The front view of the surface 14c is shown. FIGS. 5A to 5C illustrate the case where the specimen S is focused on the focal plane of the objective lens, the far focus position, and the near focus position.

  First, when the sample S is focused, the surface Sa of the sample S and the light receiving surface 14c of the two-divided sensor 14 are conjugate. For this reason, as shown in FIG. 5A, the plurality of light beams LF1 that have passed through the light shielding plate 12 are each condensed by the condenser lens 13 onto the two-divided line 14d of the two-divided sensor 14, and have a small spot diameter. A plurality of light spot images SI are formed.

  On the other hand, when the sample S is at the far focus position, the conjugate surface of the surface Sa is positioned on the near side of the light receiving surface 14c. For this reason, as shown in FIG. 5B, the plurality of light beams LF2 that have passed through the light shielding plate 12 are each condensed by the condensing lens 13 on the near side of the light receiving surface 14c and on the light receiving portion 14b side on the light receiving surface 14c. Are formed as a plurality of light spot images SI ′ having a half-moon shape.

  On the other hand, when the sample S is in the near focus position, the conjugate surface of the surface Sa is positioned on the far side of the light receiving surface 14c. Therefore, as shown in FIG. 5C, the plurality of light beams LF3 that have passed through the light shielding plate 12 are received on the light receiving surface 14c so as to be condensed on the far side of the light receiving surface 14c by the condenser lens 13, respectively. The light is formed as a plurality of light spot images SI ″ having a half-moon shape on the side of the portion 14a.

  That is, in the focusing apparatus 100, the surface Sa of the sample S is objectively detected by detecting whether or not the spot diameters of the plurality of light spot images formed on the light receiving surface 14c are minimal by the two-divided sensor 14. Whether or not the lens is focused can be detected. Furthermore, the direction of defocusing of the surface Sa can be detected by detecting the spreading direction of the light spot image. In the focusing apparatus 100, such a focused state is detected by performing arithmetic processing on the detection signals SA3 and SB3 acquired by the control unit 25 from the A / D conversion unit 24.

  By the way, in FIGS. 5A to 5C, it is assumed that a plurality of light spots projected on the specimen S are projected on the flat end of the surface Sa, and each light in the light spot images SI, SI ′, SI ″. The spot images are shown to have the same size, whereas when each of a plurality of light spots projected onto the specimen S is projected at various positions on the surface Sa, it is on the light receiving surface 14c. Each of the light spot images formed on the light has different sizes depending on the height of the projected step as shown in Fig. 6. In this case, the control unit 25 is formed on the light receiving surface 14c. It is detected whether the sum of the spot intensities received by the light receiving part 14a of the plurality of light spot images is equal to the sum of the spot intensities received by the light receiving part 14b, and the average height surface of the steps on the surface Sa matches the objective lens. Check if you are in focus And thus to.

  Further, in the focusing apparatus 100, as shown in FIG. 1, since the light receiving surface 14c is conjugate with the image forming surface IP, the image is formed when the total of the plurality of light spot areas on the light receiving surface 14c is minimal. The sum of the plurality of light spot areas formed as intermediate images on the surface IP is minimal. That is, the focusing device 100 detects whether the total of a plurality of light spot areas imaged on the imaging plane IP is minimal in the optical system from the condenser lens 8 to the two-dividing element 14. It can be said that it is provided as spot image detection means. Whether or not the surface Sa of the sample S is focused on the objective lens by detecting whether or not the sum of the plurality of light spot areas imaged on the imaging surface IP is minimal. It can be said that this is detected.

  Note that the spot image detection means is not limited to the configuration of the optical system from the condenser lens 8 to the two-dividing element 14, and various forms of detection means can be applied. For example, an imaging device or the like can be used instead of the two-divided sensor 14. Further, the two-divided sensor 14 or the imaging device may be arranged directly on the imaging plane IP. However, in this case, it is necessary to introduce the light beam from the diffraction grating DG in the optical path from the chromatic aberration correction lens 9 to the λ / 4 plate 10.

  Next, with reference to FIGS. 7-1 to 7-3, the focusing operation when the surface to be observed to be focused on the focal plane of the objective lens is switched will be described. FIGS. 7-1 to 7-3 are diagrams showing the optical path from the sample S to the two-divided sensor 14 in the focusing apparatus 100, omitting the dichroic prism 11, and linearly. Here, the specimen S is assumed to have a step formed by an upper step surface Sc and a lower step surface Sd on the surface thereof.

  First, as shown in FIG. 7A, when the upper surface Sc of the sample S is focused on the focal plane FS of the objective lens 3a as the surface to be observed, the chromatic aberration correction lens 9 is associated with the upper surface Sc. It is arranged at the lens position P1. In this state, the total sum of the plurality of light spot areas imaged on the imaging surface IP and the light receiving surface 14c is minimized.

  Subsequently, when the lower surface Sd of the sample S is focused on the focal plane FS as the observation surface, the control unit 25 corresponds to the lower surface Sd by the chromatic aberration correction lens motor 17 and the chromatic aberration correction lens motor drive unit 20. Control is performed to move the chromatic aberration correction lens 9 to the attached lens position P2. As a result, as shown in FIG. 7-2, each light spot projected from the objective lens 3a onto the specimen S is condensed on the near focus surface NFS, and has a half-moon shape on the upper step surface Sc in the lower side in the figure. An image is formed as a light spot having a spread. Each light spot image formed on the imaging surface IP and the light receiving surface 14c is also formed as a half-moon shaped light spot image having a spread on the upper side and the lower side in the drawing, respectively.

  Further, the control unit 25 causes the focusing motor 16 and the focusing motor drive unit 19 to move the specimen S to the near focus plane NFS so that the sum of the plurality of light spot areas formed on the light receiving surface 14c is minimized. Control to move to. As a result, each light spot projected from the objective lens 3a onto the specimen S is condensed on the upper surface Sc and imaged on the imaging surface IP and the light receiving surface 14c, as shown in FIG. 7-3. Each light spot image is formed as a light spot image in which the total area is minimized. In this state, the lower surface Sd is focused on the focal plane FS.

  Thus, in the focusing apparatus 100, the chromatic aberration correction lens 9 is moved to a lens position previously associated with the surface to be observed of the sample S, and this surface to be observed is focused on the focal plane FS of the objective lens 3a. be able to. Further, by associating lens positions with each of a plurality of observation surfaces having different heights, each observation surface can be automatically focused as appropriate. Furthermore, by associating the lens position with each surface to be observed for each of a plurality of replaceable objective lenses attached to the revolver 2, even when the objective lens is switched, each surface to be observed is automatically and appropriately Can be focused.

  The lens positions associated with each observation surface and each objective lens in this way are stored in the correction lens position storage table 26b. In addition, each lens position is a lens capable of correcting chromatic aberration generated based on the chromatic aberration characteristics of the objective lens, particularly axial chromatic aberration of observation light (visible light or ultraviolet light) and infrared light on the focal plane of the objective lens. Stored as a position. For this reason, in the focusing apparatus 100, each surface to be observed can be focused on the focal plane of the observation light. In addition, as a lens position where chromatic aberration can be corrected, a lens position corresponding to the offset of the surface to be observed and a correction amount of the lens position for correcting chromatic aberration in the objective lens may be stored separately.

  Next, an observation image of the specimen S is obtained each time a plurality of observation surfaces stored in the correction lens position storage table 26b are sequentially focused and focused by the microscope according to the present embodiment including the focusing device 100. A focusing processing procedure for capturing an image will be described. Here, as an example, a processing procedure when the microscope shown in FIG. 1 is applied to an automatic defect extraction apparatus will be described.

  FIG. 8 is a flowchart showing a defect extraction process performed by the microscope according to the present embodiment based on the focusing process executed by the control unit 25 executing the focusing process program 26a stored in the storage unit 26. . As shown in FIG. 8, first, the control unit 25 drives the revolver motor 15 by the revolver motor drive unit 18, rotates the revolver 2, and switches the objective lens (step S101).

  Subsequently, the control unit 25 performs a standard height surface focusing process for focusing the observed surface OP1 as the standard height surface on the focal plane of the objective lens after switching (step S102). In this step S102, the control unit 25 detects the revo hole number of the objective lens arranged opposite to the sample S by the rebo hole position detection unit 21, and associates it with the observed surface OP1 in the detected rebo hole number. The read lens position is read from the correction lens position storage table 26b.

  Then, the control unit 25 drives the chromatic aberration correction lens motor 17 by the chromatic aberration correction lens motor drive unit 20 to move the chromatic aberration correction lens 9 to the read lens position. Further, based on the detection signals SA3 and SB3 from the A / D conversion unit 24, the focusing motor drive unit 19 causes the focusing motor 16 so that the sum of the plurality of light spot areas on the two-divided sensor 14 is minimized. , And the specimen S is moved together with the stage 1 to focus the observation surface OP1. In step S102, the control unit 25 refers to the detection signal from the limit detection unit 33 and confirms the completion of movement of the chromatic aberration correction lens 9.

  Thereafter, an imaging observation system (not shown) provided in the microscope takes an observation image of the focused observation surface OP1 and records it as a standard height image (step S103). In this step S103, for example, as shown in FIG. 9A, when the sample S has defects DA and DB on the convex portion and the concave portion of the stepped portion Sb, respectively, the defect that is out of focus as shown in FIG. A standard height image OPI1 as a defect image including the images DAI1 and DBI1 is captured and recorded. Here, the height of the stepped portion Sb is larger than the focal depth DOF of the objective lens, and the defects DA and DB are located outside the focal depth DOF on the observation surface OP1.

  Subsequently, the control unit 25 performs an upper offset surface focusing process for focusing the observed surface OP2 as the upper offset surface on the focal plane of the objective lens (step S104). In step S104, as in step S102, the control unit 25 reads the lens position associated with the observed surface OP2 at the detected rebo hole number from the correction lens position storage table 26b, and adds chromatic aberration to the read lens position. The correction lens 9 is moved. Further, the specimen S is moved so that the sum of the plurality of light spot areas in the two-divided sensor 14 is minimized, and the observed surface OP2 is focused.

  After that, the imaging observation system of the microscope takes an observation image of the focused observation surface OP2 and records it as an upper offset image (step S105). In this step S105, for example, as shown in FIG. 10-1, the observation surface OP2 having the same height as the defect DA is focused, so that the defect image DAI2 is clearly captured as shown in FIG. 10-2. The upper offset image OPI2 is recorded as the defective image. The defect image DBI2 is imaged in a state where the focus is out of focus because the defect DB is located outside the focal depth DOF on the observation surface OP2.

  Subsequently, the control unit 25 performs a lower offset surface focusing process for focusing the observation surface OP3 as the lower offset surface on the focal plane of the objective lens (step S106), and the imaging observation system of the microscope is focused. The observed image of the observed surface OP3 is captured and recorded as a lower offset image (step S107).

  In step S106, the control unit 25 reads the lens position associated with the observation surface OP3 from the correction lens position storage table 26b, and then focuses the observation surface OP3 by the same process as in step S104. In step S107, for example, as shown in FIG. 11-1, the observation surface OP3 having the same height as the defect DB is focused, so that the defect image DBI3 becomes clear as shown in FIG. 11-2. A lower offset image OPI3 is recorded as a captured defect image. The defect image DAI3 is captured in a state where the focus is out of focus because the defect DA is located outside the depth of focus DOF on the observation surface OP3.

  Thereafter, the control unit 25 drives the stage 1 by an unillustrated XY stage driving motor drive unit to move the specimen S laterally to a predetermined reference observation position (step S108), and the surface to be observed by the same processing as step S102. A standard height surface focusing process for focusing OP1 is performed (step S109). In addition, the imaging observation system of the microscope takes an observation image of the focused observation surface OP1 and records it as a standard height image (step S110). In this step S110, for example, as shown in FIG. 12-1, an area having no defect in the stepped portion Sb is observed as the reference observation position, and therefore, as shown in FIG. A standard height image OPI4 is recorded.

  Further, the image processing unit (not shown) of the microscope subtracts the standard height image OPI4 as the golden image from the standard height image OPI1 as the defect image acquired in step S103, and extracts only the defect images DAI1 and DBI1. An extracted image OPI5 is generated and recorded (step S111).

  In this way, the microscope according to the present embodiment executes the series of processes in steps S101 to S111 as the defect extraction process, and executes the process for the predetermined number of times until a predetermined process end instruction is received. Until this, the series of defect extraction processes is repeated.

  In the focusing apparatus 100, the control unit 25 sums up the light spot areas on the two-divided sensor 14 so as to always maintain the focused state with respect to the observed surfaces OP1 to OP3 in each of steps S102 to S111. Is always calculated, and tracking control is performed so that the focusing motor driving unit 19 drives the focusing motor 16 so that the difference between the total light spot area in the light receiving unit 14a and the total light spot area in the light receiving unit 14b is minimized. It is carried out. Further, the control unit 25 performs control so that the chromatic aberration correction lens 9 is gradually moved in steps S102, S104, S106, and S109 so that the tracking control is not released.

  As described above, the focusing apparatus 100 according to the present embodiment has the average height surface of the stepped portion Sb formed on the surface Sa of the sample S based on the focusing processing program 26a and the correction lens position storage table 26b. Can be focused on the focal plane of the objective lens, and the focus heights are automatically changed without canceling the tracking control so that the observed planes OP2 and OP3 are successively focused. be able to.

  As a result, when the microscope according to the present embodiment equipped with the focusing device 100 is applied as a defect extraction device, it can acquire a defect extraction image obtained by imaging and extracting a defect on the specimen S, and can reduce the tact time. It is possible to acquire a defect image in which defects are clearly imaged without increasing. Then, the operator of the microscope according to the present embodiment uses the standard height image OPI1, the upper offset image OPI2, the lower offset image OPI3, the golden image OPI4, and the defect extraction image as defect images recorded in the defect extraction process. The OPI 5 can be displayed on a display device provided in the microscope or an external display device, and appropriately observed.

(Modification)
Next, modifications of the focusing device and the microscope according to the present embodiment will be described. In the above-described embodiment, the correction lens position storage table 26b stores the lens position of the chromatic aberration correction lens 9 on the assumption that the light spot SP is directly projected onto the stepped portion Sb of the sample S. Then, a transparent film such as an anti-oxidation film having a high reflectance is formed on the stepped portion Sb, and the lens position is stored on the assumption that the light spot SP is projected on the formed transparent film. .

  When a transparent film having a high reflectivity is formed on the specimen S, the projected spot projection light SR is reflected by the surface of the transparent film, so that the focusing device 100 is used instead of the observation surfaces OP1 to OP3. In addition, the surface of the transparent film is focused on the focal plane of the objective lens, resulting in a focusing error. For this reason, the correction lens position storage table 26b according to the present modification, for example, as shown in FIG. 14, is the lens position for correcting the focusing error caused by the transparent film, that is, the film thickness, refractive index, and surface reflection of the transparent film. A lens position that can correct the focus offset amount as a focus error that occurs based on the rate or the like is stored in association with each of the observation surfaces OP1 to OP3.

  Thereby, the focusing apparatus 100, for example, when the chromatic aberration correction lens 9 is moved to the lens position 11B associated with the observation surface OP1, the sum of the plurality of light spot areas imaged on the two-divided sensor 14. As shown in FIG. 15A, the average height surface OPtf of the surface of the transparent film TF is focused on the focal plane of the focusing device 100. However, for the imaging observation system of the microscope, the focusing error is As a result, the in-focus offset amount ΔHT1 can be corrected to focus the observed surface OP1 on the focal plane of the observation light.

  Similarly, when the chromatic aberration correction lens 9 is moved to the lens position 12B associated with the observation surface OP2, for example, the focusing device 100, as shown in FIG. The amount ΔHT2 can be corrected, and the observed surface OP2 can be focused on the focal plane of the observation light. As a result, the imaging observation system can clearly capture the defect image of the defect DA.

  Further, for example, when the chromatic aberration correction lens 9 is moved to the lens position 13B associated with the surface to be observed OP3, the focusing device 100, as shown in FIG. ΔHT3 can be corrected, and the observed surface OP3 can be focused on the focal plane of the observation light. Thereby, the imaging observation system can clearly capture a defect image of the defect DB.

  Here, the correction lens position storage table 26b has been described as storing the lens position including the lens position correction amount for correcting the focusing error caused by the transparent film. For example, as shown in FIG. As the lens position for correcting the focusing error due to the transparent film, the lens position with respect to the specimen S on which the transparent film is not formed, that is, the lens position shown in FIG. 4 and the thin film correction amount as the lens position correction amount are individually stored. You may make it do. Thereby, the focusing device 100 can read the lens position from the correction lens position storage table 26b regardless of whether or not the transparent film is formed, and can automatically focus the observed surfaces OP1 to OP3. .

  Further, the focusing device 100 may include the storage table shown in FIG. 14 or 16 for each of the plurality of transparent films that can be formed on the specimen S as the correction lens position storage table 26b. Thus, even when the transparent film formed on the specimen S is changed, the focusing device 100 reads the lens position according to the transparent film and automatically aligns the observation surfaces OP1 to OP3. Can be burnt.

  Further, the correction lens position storage table 26b described above has been described as storing the lens position in association with each of the observed surfaces OP1 to OP3 as the standard height surface, the upper offset surface, and the lower offset surface. As shown in FIG. 17, the offset amount of the lens position corresponding to the offset amount of the surface to be observed may be stored in association with the standard position as the lens position corresponding to the standard height surface. In this case, the control unit 25 can acquire lens positions corresponding to the upper and lower offset surfaces by adding and subtracting the offset amount to and from the standard position. Accordingly, the correction lens position storage table 26b can easily store the offset surfaces having different offset amounts for the respective rebo holes in association with the standard height surfaces. In FIG. 17, the correction lens position storage table 26b stores the lens position correction amount for correcting the focusing error due to the transparent film in association with each standard position.

  Up to this point, the best mode for carrying out the present invention has been described as the embodiment and the modification. However, the present invention is not limited to the embodiment and the modification, and is within the scope of the present invention. Various modifications are possible. For example, in the embodiment and the modification described above, the focusing device 100 has been described as sequentially focusing the observation surfaces OP1 to OP3 stored in advance in the correction lens position storage table 26b. The surface to be observed that is instructed to be input may be appropriately focused.

  Further, the focusing device 100 described above has the chromatic aberration correction lens 9 on each of a plurality of observation surfaces set within each predetermined height for each predetermined height of the step determined according to the plurality of specimens S. The lens positions may be stored in association with each other. That is, a storage table as shown in FIGS. 4, 14, 16 and 17 may be provided for each of the plurality of steps. Accordingly, the focusing device 100 can automatically focus a plurality of observation surfaces sequentially regardless of the level difference of the sample S.

  In addition, the focusing device 100 described above is configured to collect light so that a plurality of spots are linearly arranged on the sample S via the diffraction grating DG. However, the present invention is not limited thereto, and for example, the diffraction grating DG. It is good also as a structure which condenses a line spot on the sample S linearly using a cylindrical lens (toric lens) or a slit instead of. In this case, it goes without saying that the same effect as that of the focusing device 100 can be obtained.

It is a figure which shows the principal part structure of the focusing apparatus and microscope concerning embodiment of this invention. It is an enlarged view of the sample and objective lens shown in FIG. It is a figure which shows the level | step difference which a sample has, and the to-be-observed surface set within the height of this level | step difference. It is a figure which shows an example of the correction | amendment lens position storage table shown in FIG. It is a figure explaining the detection principle of the focus state by the focus detection optical system shown in FIG. It is a figure explaining the detection principle of the focus state by the focus detection optical system shown in FIG. It is a figure explaining the detection principle of the focus state by the focus detection optical system shown in FIG. It is a figure which shows the light spot image when a several light spot is projected on the various positions of the level | step difference on a sample. It is a figure explaining the focusing operation | movement which switches the to-be-observed surface focused on a focal plane. It is a figure explaining the focusing operation | movement which switches the to-be-observed surface focused on a focal plane. It is a figure explaining the focusing operation | movement which switches the to-be-observed surface focused on a focal plane. It is a flowchart which shows the defect extraction process procedure which the microscope concerning embodiment of this invention performs. It is a figure which shows the height relationship between the level | step difference and defect on a sample, and a standard height surface. It is a figure which shows the observation image of the standard height surface shown to FIGS. It is a figure which shows the height relationship between the level | step difference and defect on a sample, and an upper offset surface. It is a figure which shows the observation image of the upper offset surface shown to FIGS. It is a figure which shows the height relationship between the level | step difference on a sample, a defect, and a lower offset surface. It is a figure which shows the observation image of the lower offset surface shown to FIGS. It is a figure which shows the height relationship between the level | step difference on a sample, and a standard height surface. It is a figure which shows the observation image of the standard height surface shown to FIGS. It is a figure which shows the defect extraction image which extracted the defect image shown to FIGS. 9-2. It is a figure which shows the modification of a correction lens position storage table. It is a figure which shows the height relationship between the level | step difference on a sample, a defect, and a transparent film, and a standard height surface. It is a figure which shows the height relationship between the level | step difference on a sample, a defect, and a transparent film, and an upper offset surface. It is a figure which shows the height relationship between the level | step difference on a sample, a defect, and a transparent film, and a lower offset surface. It is a figure which shows the modification of a correction lens position storage table. It is a figure which shows the modification of a correction lens position storage table. It is a figure which shows the principal part structure of the focusing apparatus concerning a prior art, and a microscope. It is a figure which shows the principal part structure of the focusing apparatus concerning a prior art, and a microscope. It is a figure which shows the principal part structure of the focusing apparatus concerning a prior art, and a microscope. It is a figure which shows the height relationship between the level | step difference and defect on a sample observed with the microscope shown in FIG. 20, and a to-be-observed surface. It is a figure which shows the observation image of the to-be-observed surface shown to FIGS. It is a figure which shows the height relationship between the level | step difference on the sample observed with the microscope shown in FIG. 20, and a to-be-observed surface. It is a figure which shows the observation image of the to-be-observed surface shown to FIGS. It is a figure which shows the defect extraction image which extracted the defect image shown to FIGS. 21-2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stage 2 Revolver 3a, 3b Objective lens 4 Reference light source 5 Collimation lens 6,12 Light-shielding plate 7 PBS
8, 13 Condensing lens 9 Chromatic aberration correction lens 10 λ / 4 plate 11 Dichroic prism 14 Dividing element 14a, 14b Light receiving portion 14c Light receiving surface 14d Dividing line 15 Revolver motor 16 Focusing motor 17 Chromatic aberration correcting lens motor 18 Revolver Motor drive unit 19 Focusing motor drive unit 20 Chromatic aberration correction lens motor drive unit 21 Revo hole position detection unit 22 Laser drive unit 23 Amplifier 24 A / D converter 25 Control unit 26 Storage unit 26a Focus processing program 26b Correction lens position Storage table 33 Limit detection unit 100 Focusing device DA, DB Defect DAI, DAI1, DAI2, DAI3, DBI, DBI1, DBI2, DBI3 Defect image DG Diffraction grating DOF Depth of focus FS Focal plane IP Imaging plane NFS Near focus plane OA 1, OA2 Optical axis OP1 to OP3 Observation surface OPI1, OPI4 Standard height image OPI2 Upper offset image OPI3 Lower offset image OPI5 Defect extraction image S Sample Sa Surface Sb Stepped portion Sc Upper section Sd Lower step surface SI, SI ', SI " Light spot image SP Light spot SR Spot projection light TF Transparent film

Claims (13)

Focusing means for changing the relative distance between the sample having a step on the surface and the objective lens;
An imaging optical element that forms a spot image of the spot light projected on the specimen on a predetermined imaging plane;
Optical element moving means for moving the imaging optical element in the optical axis direction of the imaging optical element;
Spot image detecting means for receiving and detecting the spot image;
A storage table that stores the arrangement positions of the imaging optical elements in association with each other for each of the plurality of observation surfaces set within a predetermined height of the step,
The optical element moving means moves the imaging optical element to the arrangement position associated with the surface to be observed, and based on the detection result of the spot image detecting means, the focusing means moves the relative A focus control means for sequentially changing the distance and focusing the observation surface on the focal plane of the objective lens for each of the plurality of observation surfaces;
A focusing device characterized by comprising:   The storage table stores, for each of a plurality of replaceable objective lenses, an arrangement position of the imaging optical element in association with each of the plurality of observation surfaces. Focusing device. A lens switching mechanism for switching the plurality of objective lenses;
The focusing control unit causes the lens switching mechanism to switch the objective lens, and sequentially moves the imaging optical element to each arrangement position stored in the storage table in association with the switched objective lens. The focusing apparatus according to claim 2, wherein control is performed.   The storage table stores the arrangement position for correcting a focusing error caused by a transparent film formed on the surface of the specimen in association with each of the plurality of observation surfaces. The focusing device according to any one of 1 to 3.   In the storage table, as the arrangement position for correcting the focusing error, the arrangement position for the specimen on which the transparent film is not formed and the arrangement position correction amount for correcting the focusing error are individually set. The focusing device according to claim 4, wherein the focusing device is stored in the focusing device.   The storage table stores, for each of a plurality of transparent films that can be formed on the specimen, an arrangement position for correcting the focusing error in association with each of the plurality of observation surfaces. Item 6. The focusing device according to Item 4 or 5.   The storage table has an arrangement position of the imaging optical element on each of the plurality of observation surfaces set within the predetermined height for each predetermined height of the steps of the plurality of specimens. The focusing device according to any one of claims 1 to 6, wherein the focusing device is stored in association with each other.   The storage table stores the arrangement position for correcting chromatic aberration generated based on chromatic aberration characteristics of the objective lens in association with each of the plurality of observation surfaces. A focusing device according to any one of the above.   The storage table stores the arrangement position of the imaging optical element in association with each of an upper end surface, a lower end surface, and an average height surface set as the plurality of observation surfaces within the predetermined height. The focusing device according to any one of claims 1 to 8. The spot image detecting means includes a relay optical system that optically relays the spot image formed linearly on the imaging surface, and a light receiving means that receives the spot image relayed by the relay optical system. And based on the output value from the light receiving means, it is detected whether or not the sum of the spot areas of the spot image is minimal,
2. The focus control unit performs control to change the relative distance based on a detection result of the spot image detection unit so that a total spot area of the spot image is minimized. The focusing device according to any one of? 9.   A microscope comprising the focusing device according to claim 1. A spot image of spot light projected on a specimen having a step on the surface is imaged and detected on a predetermined imaging surface, and for each of a plurality of observation surfaces set within a predetermined height of the step And a focusing processing program for focusing the observation surface on the focal plane of the objective lens in a focusing device that stores the arrangement position of the imaging optical element that forms the spot image in association with each other. ,
In the focusing device,
The sample optical element is moved to the arrangement position associated with the surface to be observed, and the sample is adjusted so that the total spot area of the spot image is minimized based on the detection result of the spot image. And a focus control procedure for sequentially performing the control for changing the relative distance between the object lens and the object surface to the focal plane of the object lens for each of the object surfaces. Focusing processing program. The focusing device stores, for each of the plurality of replaceable objective lenses, the arrangement position of the imaging optical element in association with each of the plurality of observation surfaces,
The focusing control procedure is characterized in that the plurality of objective lenses are switched, and the imaging optical element is sequentially moved to each arrangement position stored in association with the switched objective lenses. The focusing processing program according to claim 12.

Images