JP2003036118A - Appearance inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an appearance inspection device which can perform focusing operation fast and shorten a tact time for capturing the enlarged image of a substrate to be inspected. SOLUTION: The device is equipped with an optical unit 30 equipped with an objective 43 for observing the object to be inspected with specific magnification and a stage 20 for inspection which supports the object to be inspected and can control the position of the object to be inspected about the objective 43 with a specific movement quantity, and the optical unit 30 has a piezoelectric element 46 which can control the position of the objective 43 about the object to be inspected with a movement quantity smaller than the movement quantity by a Z stage 23 of the stage 20 for inspection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection apparatus for performing visual inspection of an object to be inspected such as a semiconductor wafer.

[0002]

2. Description of the Related Art Semiconductor devices are manufactured by forming a fine device pattern on a semiconductor wafer. In the manufacturing process of this semiconductor device, for example,
When a foreign substance is attached, a pattern defect is generated, or a dimensional abnormality is generated, a device pattern is defective. A semiconductor device in which such a defect has occurred becomes a defective device, which reduces the yield in the manufacturing process.

Therefore, in order to stabilize the yield in the manufacturing process at a high level, defects caused by such foreign matters, pattern defects, abnormal dimensions, etc. are found early,
It is necessary to identify the cause and take effective measures for the manufacturing process. By thus quickly identifying the cause of the defect, taking countermeasures in the manufacturing process, and improving the yield, for example, a new process can be started up quickly, and high profit can be obtained in the process.

Therefore, when a defect occurs in a semiconductor device, the defect is detected using a microscope apparatus for inspecting a semiconductor, the cause of the defect is sought, and the equipment or process for producing the defect from the result is detected. I try to identify.

This semiconductor inspection microscope apparatus is capable of magnifying and observing a defect on a semiconductor wafer, or is capable of capturing an image of the magnified defect and displaying the image on a monitor, a so-called optical microscope. It is a device like. By using this semiconductor inspection microscope apparatus, it is possible to identify what the defect of the defective device is.

As for the design rule of the semiconductor process, a line width of 0.18 μm is currently the mainstream, and further miniaturization is progressing, and the introduction of processes such as 0.15 μm and 0.13 μm is also progressing. With the progress of miniaturization of the design rule of such a semiconductor process, minute defects that have been negligible up to now also become a problem, and the size of defects to be detected is becoming smaller.

Therefore, in the microscope apparatus for inspecting semiconductors, an objective lens having a high magnification is required to observe such minute defects.

However, the objective lens capable of obtaining high magnification has a very short depth of focus. For example, if the numerical aperture (NA) is 0.9 and the magnification is 100 times, the depth of focus is ± 0.5 μm or less. It is very difficult to manually adjust the focus position with such a short depth of focus, for example, at each inspection. Therefore, a semiconductor inspection microscope apparatus requires a mechanism for performing automatic focusing accurately and at high speed without manual work.

A conventional semiconductor inspection microscope apparatus detects a distance between a semiconductor wafer and an objective lens by making laser light or LED light incident on an objective lens by a measuring optical probe and detecting the reflected light. A distance detection mechanism was provided. The conventional semiconductor inspection microscope apparatus generally controls the distance between the objective lens and the semiconductor wafer based on the distance information detected by the distance detection mechanism so that the focal position of the objective lens coincides with the observation surface of the semiconductor wafer. I was doing automatic focusing.

There are various types of inspection microscopes for semiconductors equipped with the above-mentioned automatic focusing mechanism and inspection devices using the microscopes, and they are roughly classified into the following three configurations.

As a first configuration, there is one in which a microscope is fixedly installed above a substrate to be inspected, and an XYZ drive stage having a table for supporting and fixing the substrate to be inspected is installed below the substrate to be inspected. .

As a second configuration, an XY is provided in which a microscope and a stage for driving the microscope in the Z direction are installed above the substrate to be inspected, and a table for supporting and fixing the substrate to be inspected is provided below the substrate to be inspected. Some have a stage.

As a third structure, a microscope and a stage for driving the microscope in the Z direction are installed above the substrate to be inspected on a stage for driving in the X (or Y) direction.
There is one in which a table for supporting and fixing the substrate to be inspected is installed below.

[0014]

In the first configuration, since the driving mechanism for the microscope does not exist, it is suitable when a precise optical system is adopted. For the Z drive system of the table that supports the substrate to be inspected, it is conceivable to employ a mechanism that uses a piezoelectric element or a mechanism that drives a wedge-shaped moving body with a ball screw or the like as shown in Utility Model Registration Publication No. 2592572. .

However, when the objective lens having an extremely shallow depth of focus is adopted, the former piezoelectric element is very effective, but when the inspection target is a large substrate, it is difficult to obtain a piezoelectric element suitable for this.

In addition, the drive by the former piezoelectric element is also limited in the transportable weight. Further, when a Z movement stroke is required to have a length equal to or longer than the focusing distance, there is a problem that it is difficult to adopt because the stroke of the piezoelectric element is very short.

The latter mechanical drive using a wedge-shaped moving body can solve the transport weight to some extent, but the resolution is finer according to the depth of focus, vibration countermeasures at the time of driving, and static at the time of stopping. The waiting time to the fixed time becomes a problem.

In the second configuration, since the microscope itself is vertically driven, the rigidity of the drive system and the mechanism supporting the drive system is required when the optical system configuration requires high precision or when the optical system is a heavy object. It is necessary to pay great attention to vibration countermeasures.
The above-mentioned mechanical drive or drive using a piezoelectric element can be considered as the vertical drive of the microscope, but these also have the problems described in the first configuration.

In the third configuration, the footprint of the inspection apparatus can be made close to the size of the substrate to be inspected, which is effective in a small space. However, like the second configuration, the microscope itself is moved up and down. In order to drive the optical system, when the structure of the optical system is required to be highly precise or the optical system is a heavy object, it is necessary to pay great attention to the rigidity of the drive system and the mechanism supporting it, and measures against vibration. In addition, it is equipped with a horizontal movement mechanism, and it is necessary to pay greater attention to the vibration and rigidity associated with the movement of the optical system.

It can be said that the piezoelectric element is effective for fine movement, but it is difficult to limit the size of the member, the limit of the loadable weight, and the large stroke. Is. Also, the mechanical drive method is
This means that there will be problems of finer resolution corresponding to the depth of focus, countermeasures against vibration during driving, and waiting time until settling time when stopped.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform a focusing operation at a high speed and to reduce a time tact for capturing an enlarged image of a substrate to be inspected. It is to provide a visual inspection device that can perform.

[0022]

In order to achieve the above-mentioned object, the appearance inspection apparatus of the present invention comprises an observation means having a magnifying lens for observing an object to be inspected at a predetermined magnification, and the object to be inspected. Supporting means for controlling the position of the object to be inspected with respect to the magnifying lens with a predetermined movement amount, and the observing means supports the position of the magnifying lens with respect to the object to be inspected. The driving means is controllable with a movement amount smaller than the movement amount of the means.

Preferably, the driving means has a piezoelectric element that expands and contracts by a predetermined amount according to the applied voltage and moves the magnifying lens by a predetermined amount according to the expansion and contraction.

Preferably, the supporting means has a supporting member for supporting the object to be inspected, and second driving means for moving the supporting member in the direction of the magnifying lens.

For example, the second driving means moves in a direction perpendicular to the moving direction of the support member and has a wedge-shaped moving body having a predetermined inclined surface with respect to the moving direction, and the wedge-shaped moving body. And an abutting member that is in contact with the supporting member on the surface opposite to the inclined surface.

The observing means has an objective lens for ultraviolet light as the magnifying lens, and first distance detecting means for detecting the amount of positional deviation of the object to be inspected from the focal length of the objective lens for ultraviolet light. And first control means for controlling the movement amount of the drive means according to the amount of positional deviation from the focal length detected by the first distance detection means.

The first control means is arranged such that the amount of positional deviation from the focal length detected by the first distance detection means is
When it is smaller than the predetermined threshold value, the movement amount of the drive means is controlled according to the positional deviation amount.

When the amount of positional deviation from the focal length detected by the first distance detecting means is larger than a predetermined threshold value, the moving amount of the supporting means is controlled according to the positional deviation amount. It further has a second control means.

The observing means includes an objective lens for visible light,
It further comprises a second distance detecting means for detecting a positional deviation amount of the inspection object from the focal length of the visible light objective lens, wherein the second control means is the second distance detecting means. The amount of movement of the support means is controlled according to the amount of positional deviation from the focal length detected by.

In the above appearance inspection apparatus of the present invention, first,
The object to be inspected is mounted on the supporting means, and the supporting means is moved by a predetermined movement amount so that the position of the object to be inspected with respect to the magnifying lens comes close to the focal position of the magnifying lens.
When the object to be inspected comes close to the focal position of the magnifying lens, the driving means moves the magnifying lens by a predetermined amount so that the position of the object to be inspected comes to the focal position of the magnifying lens. Then, after the focusing of the magnifying lens on the object to be inspected is completed, the observation unit observes an enlarged image of the object to be inspected, and within the observation visual field,
A visual inspection is performed to determine whether the inspection target has a defect or the like. As described above, first, the long-distance focusing operation is performed.
The board to be inspected is moved by the supporting means with a large movement amount,
After the amount of displacement of the board to be inspected from the focus position of the magnifying lens is reduced, the final adjustment to the focus position is performed by the driving means with a small movement amount so that the focus of the magnifying lens can be performed accurately and at high speed. Be seen.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the appearance inspection apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the appearance inspection apparatus according to this embodiment, and FIG. 2 is a perspective view of the essential parts of the appearance inspection apparatus according to this embodiment.

As shown in FIG. 1, a visual inspection apparatus 1 includes a vibration isolation table 10, an inspection stage 20 installed on the vibration isolation table 10, and an optical unit installed on the vibration isolation table 10. Three
0, the image processing unit 50, the control unit 60, and the input unit 70.
And a display unit 80.

The vibration isolation table 10 is for suppressing vibrations from the floor and vibrations generated when the inspection stage 20 is moved and scanned. In order to inspect substrates such as semiconductor wafers with fine device patterns formed,
Vibration isolation table 10
To suppress the vibration.

The vibration isolation table 10 is preferably a so-called active vibration isolation table. The active vibration isolation table is a vibration isolation table that detects vibrations and operates in a direction of canceling the vibrations to quickly remove the vibrations, and has an excellent vibration isolation effect.

In this appearance inspection apparatus 1, since the inspection is performed at a high resolution by using ultraviolet light as described later, the influence of vibration is likely to appear largely, but the appearance inspection of the active vibration isolation table excellent in the vibration isolation effect is performed. By using it as the vibration isolation table 10 of the apparatus 1, it is possible to suppress the influence of vibration and improve the inspection capability when performing inspection with high resolution using ultraviolet light.

An inspection stage 20 is installed on the vibration isolation table 10. The inspection stage 20 is a stage for supporting a substrate to be inspected such as a semiconductor wafer. The inspection stage 20 has a function of supporting the substrate to be inspected and moving the substrate to be inspected to a predetermined inspection target position.

Specifically, the inspection stage 20 includes an X stage 21 installed on the vibration isolation table 10, a Y stage 22 installed on the X stage 21, and a Y stage 2.
Z stage 23 installed on the second stage, and Z stage 23
And a suction plate 24 installed on the.

The X stage 21 and the Y stage 22 are
The stage moves horizontally, and the X stage 21 and the Y stage 22 move in directions orthogonal to each other. When inspecting a substrate to be inspected, the substrate to be inspected is moved to the inspection target position by the X stage 21 and the Y stage 22.

The X stage 21 includes, for example, as shown in FIG. 2, an X servo motor 211 and an X servo motor 211.
The X stage 21 has an X screw shaft 212 connected to the X screw shaft 212 and an X guide rail 213 as a drive mechanism.
It is screwed to 2 and can be moved in the X direction along the X guide rail 213 by the rotation of the X servo motor 211. Although not shown in FIG. 2, the Y stage installed on the X stage 21 also has a similar drive mechanism and can be driven in the Y direction.

The Z stage 23 is a stage which moves in the vertical direction, and is for adjusting the height of the stage, as will be described later. At the time of inspecting the substrate to be inspected, the Z stage 23 adjusts the height of the stage so that the inspection surface of the substrate to be inspected has an appropriate height.

The suction plate 24 is for sucking and fixing the substrate to be inspected.

A drive mechanism for moving the Z stage 23 in the vertical direction will be described with reference to FIG. Z stage 2
The drive mechanism 3 is roughly classified into a base body 230, a servo motor 231, a wedge-shaped moving body 232, and an abutting member 2.
33.

The servo motor 231 is held by the base body 230, and the screw shaft 236 is connected thereto.

The wedge-shaped moving body 232 is a wedge body 234.
And a main body 235 to which this is fixed.
A screw bush 237 having a female screw that is screwed onto the screw shaft 236 is fixed by a screw 238.

In the main body 235 of the wedge-shaped moving body 232,
A sliding member 239 such as a linear ball bearing that is reciprocally provided on the bottom surface of the base body 230 is provided, and a guide hole 235a is provided.

The wedge body 234 is formed with an inclined surface 234a having a predetermined angle with respect to the axial direction of the screw shaft 236. With the above structure, when the servo motor 231 is rotated, the wedge-shaped moving body 232 moves in the axial direction of the screw shaft 263, and the inclined surface 234a also moves in that direction.

The contact member 233 is composed of a block body,
On one end surface side thereof, the inclined surface 23 that is in close contact with the inclined surface 234a
3a is formed, and a flat surface 233b parallel to the axis of the screw shaft 236 is formed on the other end surface side opposite to the inclined surface 233a. The Z stage 23 is installed in contact with the flat surface 233. Further, the contact member 233 is arranged at a position substantially facing the wedge body 234 in a state where the side surface thereof is slidably supported by the base body 230 in the Z direction.

A protrusion preventing means 240 for preventing the contact member 233 from protruding sideways in the drawing is provided. The pop-out prevention means 240 is used for the wedge-shaped moving body 23.
2 of the piston 241 slidably supported in the second guide hole 235a and the head of the piston 241 and the abutting member 23.
3 and a spring 243 housed in the guide hole 235a to press the contact member 242 toward the contact member 233.

Although not shown, for example, the Z stage 23 can be smoothly moved in the vertical direction, that is, the direction orthogonal to the axial direction of the screw shaft 236 by the vertical movement of the contact member 233. A guide member 23 is slidably installed on the base body 230.

The movement operation of the Z stage 23 in the vertical direction by the drive mechanism having the above configuration will be described. In the present embodiment, since the Z stage 23 is moved mechanically in the vertical direction with good control, the wedge-shaped moving body 2 is moved as described above.
It is configured to move 32.

That is, for example, when the screw shaft 236 is rotated by the servo motor 231, the wedge-shaped moving body 232 is moved according to the screw pitch of the screw shaft 236.
It will move in the axial direction of 36.

The inclined surface 2 of the wedge-shaped moving body 232.
The contact member 233 that is in contact with 34 a is the wedge-shaped moving body 23.
Along with the movement of 2, a predetermined amount of vertical movement is required. At this time, the amount of movement of the contact member 233 in the vertical direction with respect to the amount of movement of the wedge-shaped moving body 232 in the axial direction is as follows. 233a), it becomes smaller by a predetermined ratio.

Therefore, although the servo motor 231 is constructed so as to be able to accurately rotate in units of less than 1 degree, compared with the case where the contact member 233 is directly moved by the servo motor 231, the servo motor 231 is The number of rotations of the servo motor required to move a fixed amount can be increased, and the resolution in fine movement is improved. As described above, Z
Mechanical drive of the stage has been realized.

An inspection stage 20 is mounted on the vibration isolation table 10.
The optical unit 30 is installed so as to be located above. The optical unit 30, as shown in FIG.
It is installed in a column 12, which is supported by a support member 11 installed on the upper surface of the zero, and is made of a member having high precision and high rigidity for suppressing vibration. Optical unit 30
Has both a function of capturing an image of a substrate to be inspected with visible light at low resolution and a function of capturing an image of the substrate to be inspected with high resolution using ultraviolet light.

Next, the optical system of the optical unit will be described in detail with reference to FIG.

As shown in FIGS. 1 and 4, the optical unit 30 has a halogen lamp 31, a visible light optical system 32, and a visible light as a mechanism for capturing an image of a substrate to be inspected with visible light. The objective lens 33, the visible light CCD camera 34, and the distance detector 35 are provided. Note that the description of the distance detection unit 35 is omitted here because it will be described later, and the optical system that illuminates the substrate to be inspected and the optical system that images the substrate to be inspected will be described.

First, when capturing an image of the substrate to be inspected with visible light, the halogen lamp 31 is turned on, and the visible light from the halogen lamp 31 is guided to the visible light optical system 32 by the optical fiber 310. Here, the visible light optical system 32 includes an illumination optical system 320 composed of two lenses 321, 322, and the visible light guided to the visible light optical system 32 by the optical fiber 310 is first ,
It is incident on the illumination optical system 320.

Then, the visible light incident on the visible light optical system 32 passes through the illumination optical system 320 and the half mirror 32.
3 and is reflected by the half mirror 323 toward the visible light objective lens 33.
It is incident on the substrate to be inspected via. As a result, the substrate to be inspected is illuminated with visible light.

Then, the reflected light from the substrate to be inspected illuminated with the visible light enters the visible light CCD camera 34 through the visible light objective lens 33, the half mirror 323 and the imaging lens 324, whereby An enlarged image of the substrate to be inspected is captured by the visible light CCD camera 34. Then, the image of the inspected substrate taken by the visible light CCD camera 34 is sent to the image processing unit 50.

Inside the optical unit 30, a mechanism for picking up an image of the substrate to be inspected with ultraviolet light is provided.
An ultraviolet laser source 41, an ultraviolet optical system 42, an ultraviolet objective lens 43, an ultraviolet CCD camera 44,
A distance sensor 45 and a piezoelectric element 46 are arranged. Note that the distance sensor 45 and the piezoelectric drive element 46 are also used here.
A description of focus control using is omitted since it will be described later, and an optical system that illuminates the substrate to be inspected and an optical system that images the substrate to be inspected will be described.

When capturing an image of the substrate to be inspected with ultraviolet light, the ultraviolet laser light source 41 is turned on, and the ultraviolet light from the ultraviolet laser light source 41 is transmitted to the ultraviolet optical system 42 by the optical fiber 410. Be guided. Here, the ultraviolet light optical system 42 includes an illumination optical system 420 composed of two lenses 421 and 422, and the ultraviolet light guided to the ultraviolet light optical system 42 by the optical fiber 410 is first ,
It enters the illumination optical system 420.

Then, the ultraviolet light incident on the illumination optical system 420 passes through the illumination optical system 420 and the half mirror 42.
3 and is reflected by the half mirror 423 toward the ultraviolet light objective lens 43.
It is incident on the substrate to be inspected via. As a result, the substrate to be inspected is illuminated with ultraviolet light.

Then, the reflected light from the substrate to be inspected illuminated with the ultraviolet light enters the ultraviolet CCD camera 44 through the ultraviolet objective lens 43, the half mirror 423, and the imaging lens 424, and As a result, an enlarged image of the substrate to be inspected is captured by the CCD camera 44 for ultraviolet light. Then, the image of the substrate to be inspected captured by the ultraviolet CCD camera 44 is sent to the image processing unit 50.

The visible light objective lens 33 and the ultraviolet light objective lens 43 are specifically installed on the suction plate 24 as shown in FIG. That is, FIG.
As shown in, the ultraviolet objective lens 43 is supported by the base plate 40 via the piezoelectric element 46. The piezoelectric element 46 has a connecting member 45a as described later.
A distance sensor 45 is provided via the. As the visible light objective lens 33, various types of high-to-low-magnification visible light objective lenses 33 a, 33 b, and 33 c are supported by a revolver 330 installed on the base plate 40.

As described above, the appearance inspection apparatus 1 has both an optical system for visible light and an optical system for ultraviolet light, and is capable of inspecting a substrate to be inspected at low resolution using visible light. It is possible to perform both high resolution inspection of a substrate to be inspected using ultraviolet light.

In order to control the optical unit 30 and the inspection stage 20 and perform image analysis processing, an image processing section 50 and a control section 60 are provided in connection with the respective devices of the optical unit 30 and the inspection stage 20. In addition, an input unit 70 and a display unit 80 are provided.

When inspecting a substrate to be inspected, the image processing section 50 takes in an image of the substrate to be inspected by the CCD cameras 34 and 44 installed inside the optical unit 30, and is necessary for the inspection. Perform predetermined processing.

As will be described later, the control unit 60 determines that the inspection target area of the inspection target substrate is
CCD camera 3 installed inside the optical unit 30
The inspection stage 2 as imaged by 4, 44
0, each device of the optical unit 30 is controlled.

The input section 70 is connected to the image processing section 50 and the control section 60. For example, the input section 70 inputs instructions to the image processing section 50 necessary for analysis of images captured from the CCD cameras 34 and 44, The control unit 60 is for inputting an instruction necessary for controlling each device inside the inspection stage 20 and the optical unit 30, and includes, for example, a pointing device such as a mouse and a keyboard.

The display section 80 is connected to the image processing section 50 and the control section 60. For example, the CCD camera 34,
The image processing unit 50 displays the analysis result and the like of the image captured from the image processing unit 44, and the control unit 60 displays various conditions at the time of inspecting the substrate to be inspected.
It consists of a T display and a liquid crystal display.

The image processing section 50 and the control section 60 are respectively provided with memory interfaces 50a and 6a.
They are connected to each other via 0a, and data can be exchanged with each other.

Here, the control unit 60 is the stage control unit 6
1, a light source controller 62, and a piezoelectric element controller 63.

The stage controller 61 controls the X stage 21,
It is connected to the Y stage 22, the Z stage 23, and the suction plate 24, and outputs a control signal to the X stage 21, the Y stage 22, the Z stage 23, and the suction plate 24 when inspecting a substrate to be inspected. Then, based on the control signal, the substrate to be inspected is fixed by the suction plate 24, and the X stage 21, the Y stage 22, and the Z stage 23 are operated so that the substrate to be inspected has a predetermined position and height. The stage controller 61 is connected to the distance sensor 45 and the distance detector 35,
As will be described later, a distance detection signal indicating a shift amount from the focus position is input from the distance sensor 45 and the distance detection unit 35, and a control signal for controlling the movement amount of the Z stage 23 is set to Z according to the distance detection signal. Output to the drive mechanism of the stage 23.

The light source controller 62 is connected to the driving source of the halogen lamp 31 and the ultraviolet laser light source 41,
The halogen lamp 31 and the ultraviolet laser light source 41 are turned on and off based on a control signal from the light source control unit 62.

The piezoelectric element control section 63 is connected to the distance sensor 45 and the piezoelectric element 46, and inputs a distance detection signal indicating the positional deviation of the substrate to be inspected with respect to the focal position of the objective lens 45 from the distance sensor 45, A control signal is output so that the piezoelectric element 46 has a desired expansion / contraction amount according to the detection distance.

Next, the structure of the distance detecting section 35 of the visual inspection apparatus 1 will be described with reference to FIG. It should be noted that FIG. 6 shows only an optical system required for automatic focus position adjustment of the visible light objective lens 33 in the optical unit 30. However, the optical system required for this automatic focusing is
It is provided in the optical unit 30 so as not to cause mechanical interference with the illumination and imaging optical system of the substrate to be inspected shown in FIG.

As shown in FIG. 6, the distance detector 35 includes a visible light objective lens 33, a laser diode 351 for emitting a laser beam, a photodetector 352 for receiving the laser beam reflected by the substrate to be inspected, A half mirror 353 that separates the optical paths of the emitted light from the laser diode 351 and the reflected light from the inspected substrate 2, a knife edge 354 provided between the laser diode 351 and the half mirror 353, and a half mirror 353. Collimator lens 35 provided between the objective lens 33 for visible light
5 and a preamplifier 356.

The laser diode 351 emits visible laser light. The laser light emitted from the laser diode 351 is made into a semicircular spot shape by the knife edge 354, and is incident on the half mirror 353. The half mirror 353 reflects the laser light emitted from the laser diode 351, and the laser light reflected by the half mirror 353 is collimated by the collimator lens 355 and then enters the visible light objective lens 33. The visible light objective lens 33 condenses the parallel laser light and irradiates the inspected substrate 2.

Since the laser spot formed on the substrate 2 to be inspected has the knife edge 354, its shape becomes a semicircular shape, and its barycentric position linearly moves according to the shift amount of the focal position. I will do it.

That is, the shape of the laser spot formed on the substrate 2 to be inspected is semicircular due to the influence of the knife edge 354. As shown in FIG. 7, the laser spot LS formed on the substrate 2 to be inspected has the smallest spot size when the focal point F and the reflecting surface coincide with each other. The spot size increases as the reflecting surface moves away from the focus position F, and the semicircular shape is symmetrical before and after the focus position around the spot position at the time of focusing.

In this way, the center of gravity G of the laser spot formed on the substrate 2 to be inspected moves linearly according to the amount of deviation from the focus position F.

The laser light collected by the visible light objective lens 33 is reflected by the substrate 2 to be inspected, passes through the visible light objective lens 33 and the collimator lens 355 again, and enters the half mirror 353. Half mirror 35
3 transmits the reflected light from the substrate to be inspected, and the reflected light transmitted through the half mirror 353 is applied to the photodetector 352.

In the photodetector 352, for example, the photodetection region is divided into a plurality of regions so that the barycentric position G of the received laser spot can be detected, and the reflected light from the substrate to be inspected is received and received. It is converted into an electric signal according to the amount of light, and the electric signal is supplied to the preamplifier 356. Like the laser spot LS formed on the substrate 2 to be inspected, the laser spot formed on the photodetection region of the photodetector 352 has a linear center of gravity position according to the amount of deviation from the focus position. Move to.

The preamplifier 356 obtains the position of the center of gravity of the laser spot by obtaining the difference signal of the electric signals from the respective photodetection regions of the photodetector, and the deviation amount of the substrate to be inspected from the focus position of the visible light objective lens 33. To generate a distance detection signal.

The stage controller 61 obtains the distance between the visible light objective lens 33 and the substrate 2 to be inspected from the distance detection signal, so that the distance matches the focal length of the visible light objective lens 33. The Z stage 23 is moved to control the height position of the substrate to be inspected.

The focus position control of the visible optical system is controlled as described above.

Next, the focusing mechanism for ultraviolet light of the visual inspection apparatus 1 will be described.

As described above, the distance sensor 45 is provided in the optical unit 30 in a fixed relative positional relationship with respect to the ultraviolet light objective lens 43. That is, as shown in FIG. 5, the distance sensor 45 includes the piezoelectric element 4
6 is fixed via a connecting member 45a, and its height position (position in the vertical direction) is substantially the same as that of the ultraviolet objective lens 43.

The distance sensor 45 is the objective lens 4 for ultraviolet light.
The distance between the substrate 3 and the substrate 2 to be inspected is detected, and this distance detection signal is output to the piezoelectric element controller 63. As the distance sensor 45, for example, a capacitance type sensor is used. The capacitance sensor can measure the distance between the sensor and the object to be measured without contacting the object to be measured by measuring the capacitance between the sensor and the object to be measured. This distance detection signal serves as an index of the amount of displacement of the substrate to be inspected with respect to the focus position of the ultraviolet light objective lens 43 by calculating the electrostatic capacitance when the focus position is in advance as a target value.

Upon receiving the distance detection signal, the piezoelectric element control section 63 outputs a desired voltage to the piezoelectric element 46 so as to approach the target value calculated in advance, and expands and contracts the piezoelectric element 46 so as to expand and contract. The surface to be inspected of the inspection substrate 2 is made to match the focal point of the ultraviolet light objective lens 43.

Next, an inspection method using the above appearance inspection apparatus 1 will be described with reference to the flowchart shown in FIG. First, in step ST1, as a pre-operation adjustment, one of the high-magnification visible light objective lenses 33 mounted on the revolver 330 is used to inspect the substrate 2 to be inspected.
The suction plate 24 that supports the lens is subjected to a focusing operation using the Z stage 23, and the focal position is fixed as a reference position. Then, at this reference position, the supporting position of the piezoelectric element 46 is adjusted in the vertical direction so that the piezoelectric element 46 is located at the center of its stroke.

Next, in step ST2, the stage controller 61 controls the X stage 21 and the Y stage 22.
Are driven to move the substrate 2 to be inspected XY to the observation position so that the region to be inspected of the substrate 2 to be inspected is within the field of view of the objective lens 33 for visible light.

Next, in step ST3, the Z stage 23 is controlled by the stage controller 61 in response to the distance detection signal from the distance detector 35 indicating the amount of deviation from the focus position.
Is driven to automatically focus the visible light objective lens 33.

Next, in step ST4, an image of the substrate 2 to be inspected is picked up by the visible light CCD camera 34,
The captured visible image is sent to the image processing unit 50.

Next, in step ST5, the image processing section 50 performs a predetermined process to inspect whether the substrate 2 to be inspected has a defect. It should be noted that the processing here includes various kinds of processing, for example, by performing comparison with a reference image in the case where there is no defect in advance. When a defect can be detected, the defect is stored in a storage device (not shown) connected to the image processing unit 50 or the control unit 60,
The process here is terminated.

On the other hand, if the defect cannot be detected in step ST5, the process proceeds to step ST6 and subsequent steps to detect the defect by performing imaging with high resolution using ultraviolet light having a shorter wavelength than visible light. I do.

In this case, first, in step ST6, the automatic focusing of the ultraviolet light objective lens 43 is performed.
Based on the distance detection signal from the distance sensor 45, a predetermined voltage is applied to the piezoelectric element by the piezoelectric element control unit 63 to expand and contract the piezoelectric element.

Next, in step ST7, an image of the substrate to be inspected is picked up by the ultraviolet CCD camera 44, and the picked-up ultraviolet image is sent to the image processing section 50.

Next, in step ST8, the image processing section 50 performs a predetermined process to inspect whether the substrate 2 to be inspected has a defect. It should be noted that the processing here includes various kinds of processing, for example, by performing comparison with a reference image in the case where there is no defect in advance. When a defect can be detected, the defect is stored in a storage device (not shown) connected to the image processing unit 50 or the control unit 60,
The process ends. If no defect is detected in step ST8, information indicating that there is no defect is stored in a storage device (not shown) connected to the image processing unit 50 or the control unit 60, and the process ends. .

According to the procedure as described above, first, the image picked up by the visible light CCD camera 34 is processed and analyzed to inspect the substrate to be inspected at a low resolution to detect defects in the visible light. If it is not possible, then, the substrate 2 to be inspected is inspected with high resolution by processing and analyzing the image captured by the ultraviolet CCD camera 44. By doing so, it is possible to detect finer defects as compared with the case of inspecting defects using only visible light.

However, when the image is picked up with visible light at a low resolution, the area that can be picked up at one time is wider. Therefore, when the defect is sufficiently large, the visible light is used to take a low resolution image of the substrate to be inspected. It is more efficient to carry out an inspection. Therefore, it is possible to more efficiently inspect the substrate 2 to be inspected by first inspecting the defect using visible light instead of inspecting the defect using ultraviolet light from the beginning.

Further, it is also possible to perform a trace operation in which focusing operations are performed in parallel with the XY movement to the inspection position. A trace operation using the above appearance inspection apparatus 1 will be described with reference to the flowchart shown in FIG. In the example described above, the focusing operation by the CCD camera for ultraviolet light 44 is performed using only the piezoelectric element, but in the tracing operation, the focusing operation using the Z stage 23 and the piezoelectric element 46 are used. Focusing operation is also used.

As the adjustment before the operation, the revolver 33
The suction plate 2 that supports the substrate 2 to be inspected by using the high-magnification visible light objective lens 33
4 performs the focusing operation using the Z stage 23,
The focal position is fixed as the reference position. Then, at this reference position, the supporting position of the piezoelectric element 46 is adjusted in the vertical direction so that the piezoelectric element 46 is located at the center of its stroke.

Then, the stage controller 61 drives the X stage 21 and the Y stage 22 and performs the following operation.

That is, first, in step ST11, it is detected from the distance detection signal from the distance sensor 45 whether the substrate 2 to be inspected is at the focal position of the objective lens 43 for ultraviolet light, and if it is at the focal position. Is step S
Proceeding to T15, an image of the substrate to be inspected is captured by the objective lens 43 for ultraviolet light, and the captured ultraviolet image is processed by the image processor 50.
Then, the image processing unit 50 performs a predetermined process to inspect whether the substrate 2 to be inspected has a defect (step S).
T16).

If the focus position is not reached in step ST11, the process proceeds to step ST12 and the distance sensor 45
The deviation from the focus position detected from the distance detection signal is compared with a preset threshold value. If the deviation from the focus position is equal to or larger than the threshold value, the process proceeds to step ST13 and the stage controller 61 Thus, the Z stage 23 is driven according to the distance detection signal input from the distance sensor 45, and the Z stage 23 is brought closer to the focal position of the ultraviolet light objective lens 43.

When the deviation from the focus position is less than or equal to the threshold value, or when the deviation from the focus position is less than or equal to the threshold value by driving the Z stage 23,
Proceeding to step ST14, the piezoelectric element control unit 63 applies a predetermined voltage to the piezoelectric element to expand or contract the automatic focus position of the ultraviolet light objective lens 43 based on the distance detection signal from the distance sensor 45. By doing.

The subsequent steps include step ST1.
5, an image of the substrate to be inspected is picked up by the CCD camera 44 for ultraviolet light, and the picked-up ultraviolet image is processed by the image processing unit 50.
Then, the image processing unit 50 performs a predetermined process to inspect whether the substrate 2 to be inspected has a defect (step S).
T16).

As described above, in the trace operation in which the focusing operation is performed in parallel with the XY operation to the inspection position, the signal indicating the deviated state from the focus position is used to switch the drive by the Z stage 23 or the piezoelectric element 46. Thresholds are set for each stage control unit 61
By switching between the focusing operation using the Z stage 23 according to the method described above and the focusing operation using the piezoelectric element 46 performed by the piezoelectric element control unit 63, a high-speed XY operation can be followed even for an inspected object having irregularities. It is possible to perform highly accurate focusing.

In the appearance inspection apparatus 1 according to the present embodiment described above, as described above, the focusing operation using ultraviolet light, which requires extremely low vibration and high resolution minute movement, and
It also has a focusing operation by moving with low magnification and relatively coarse resolution using visible light.

That is, when the suction plate 24 is moved in the vertical direction by driving the Z stage 23, the wedge-shaped moving body 232 described above is moved to mechanically relatively accurately drive the Z stage 23. . In this mechanical drive, the resolution is coarse compared to the drive of the piezoelectric element, but a long stroke can be moved at high speed. Also,
By using the mechanical drive, even if the suction plate 24 and the like have an area and weight capable of mounting a large area substrate, there is almost no limitation to this.

On the other hand, for the focusing operation of the ultraviolet objective lens 43 having a very shallow depth of focus, the objective lens 43 is
The piezoelectric element 46 having a stroke of about 0.5 to 1.0 mm is incorporated between the base plate 40 and the base plate 40. Therefore, it is difficult to limit the size of the member, the limit of the loadable weight, and the large stroke, but it is effective for the fine movement of the piezoelectric element 4.
By using 6 for driving a small and lightweight object such as the objective lens 43, it is possible to perform high-resolution fine movement that cannot be achieved by the above mechanical drive resolution.

As described above, the fine movement mechanism by the piezoelectric element 46 having a small stroke but high resolution and the mechanical driving mechanism by the wedge-shaped moving body 232 which has a coarse resolution but can move a long stroke at a high speed are provided. By doing so, a long-distance focusing operation can be performed at high speed, and the settling time can be set to 0 without limit.
Therefore, the time tact for capturing the target image can be significantly shortened.

Since the two types of drive mechanisms described above are provided, the suction plate 24 supporting the substrate to be inspected is
It is not necessary to dispose directly under the objective lenses 33 and 43, and a sufficient distance may be maintained. Therefore, the degree of freedom in designing the inspection device can be improved.

Furthermore, as described above, if the projections and depressions are within the observation visual field, it is possible to perform the XY operation and the trace operation for performing the focusing operation. In this case, the objective lens will not be damaged.

The appearance inspection apparatus of the present invention is not limited to the above description of the embodiment. For example, in the present embodiment, a piezoelectric element is used as a drive mechanism that achieves extremely low vibration and high resolution minute movement, and a wedge-shaped moving body is used as a drive mechanism that moves a relatively long coarse stroke at high speed. Although the mechanical drive used is adopted, the present invention is not limited to this, and any other drive capable of achieving a similar function can be substituted.

Further, in the present embodiment, description has been made of the case where two kinds of optical systems, that is, an optical system for ultraviolet light and an optical system for visible light are mounted, but for example, only a single optical system is mounted and a piezoelectric element is mounted. You may move up and down at. In the present embodiment, only the ultraviolet light objective lens 43 is driven by the piezoelectric element 46. However, for example, a piezoelectric element is also provided between the revolver 330 and the base plate 40, and the visible light objective lens 33 is provided. Also, the piezoelectric element may be vertically driven. Further, although an example of the inspection method using the appearance inspection apparatus according to the present embodiment has been described, it is also possible to adopt another inspection method such as performing a defect inspection using only ultraviolet light. Besides, various modifications can be made without departing from the scope of the present invention.

[0119]

According to the appearance inspection apparatus of the present invention, the focusing operation can be performed at high speed, and therefore, the time tact for capturing an enlarged image of the substrate to be inspected can be shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an appearance inspection device according to an embodiment.

FIG. 2 is a perspective view of a main part of the appearance inspection device according to the present embodiment.

FIG. 3 is a sectional view showing details of a drive mechanism of a Z stage.

FIG. 4 is a diagram showing a configuration example of an optical system of an optical unit of an appearance inspection device.

FIG. 5 is a diagram showing a configuration example of a visible light objective lens and an ultraviolet light objective lens.

FIG. 6 is a diagram showing a configuration example of a distance detection unit of the appearance inspection device.

FIG. 7 is a diagram for explaining the principle of distance detection by the distance detector of the visual inspection device.

FIG. 8 is a flowchart illustrating an example of a procedure for inspecting a substrate to be inspected by the appearance inspection device according to the present embodiment.

FIG. 9 is a flowchart of another example of a procedure for inspecting a substrate to be inspected by the appearance inspection device according to the present embodiment.

[Explanation of symbols]

1 ... Appearance inspection device, 2 ... Inspected substrate, 10 ... Vibration isolation table, 1
1 ... Support member, 12 ... Column, 20 ... Inspection stage,
21 ... X stage, 22 ... Y stage, 23 ... Z stage, 24 ... Suction plate, 30 ... Optical unit, 31 ...
Halogen lamp, 32 ... Optical system for visible light, 33, 33
a, 33b, 33c ... Objective lens for visible light, 34 ... CCD camera for visible light, 35 ... Distance detection unit, 40 ... Base plate, 41 ... UV light source, 42 ... UV optical system, 43 ... UV light Objective lens, 44 ... CCD for UV light
Camera, 45 ... Distance sensor, 45a ... Connecting member, 46 ...
Piezoelectric element, 50 ... Image processing section, 50a ... Memory link interface, 60 ... Control section, 60a ... Memory link interface, 61 ... Stage control section, 62 ... Light source control section, 63 ... Piezoelectric element control section, 70 ... Input section, 80 ...
Display unit, 211 ... X servo motor, 212 ... X screw shaft,
213 ... X guide rail, 230 ... Base body, 231 ... Servo motor, 232 ... Wedge-shaped moving body, 233 ... Abutting member, 233a ... Sloping surface, 233b ... Flat surface, 234 ... Wedge body, 234a ... Sloping surface, 235 ... Main body, 235a ...
Guide hole, 236 ... Screw shaft, 237 ... Screw bush, 2
38 ... Screws, 239 ... Sliding body, 240 ... Protrusion prevention means, 241 ... Piston, 242 ... Contact member, 243 ... Spring, 310 ... Optical fiber, 320 ... Illumination optical system, 321, 322 ... Lens, 323 ... Half mirror ,
324 ... Imaging lens, 330 ... Revolver, 351 ... Laser diode, 352 ... Photodetector, 353 ...
Half mirror, 354 ... Knife edge, 355 ... Collimator lens, 356 ... Preamplifier, 410 ... Optical fiber, 420 ... Illumination optical system, 421, 422 ... Lens,
423 ... Half mirror, 424 ... Imaging lens.

Claims (8)

[Claims] 1. An observing device having a magnifying lens for observing an object to be inspected at a predetermined magnification, and a position for moving the object to be inspected with respect to the magnifying lens by a predetermined amount of movement. And a supporting means controllable by means of a visual inspection, wherein the observing means has a driving means capable of controlling the position of the magnifying lens with respect to the object to be inspected with a movement amount smaller than the movement amount of the supporting means. apparatus. 2. The appearance inspection apparatus according to claim 1, wherein the drive means has a piezoelectric element that expands and contracts by a predetermined amount according to an applied voltage and moves the magnifying lens by a predetermined amount according to the expansion and contraction. 3. A supporting member for supporting the object to be inspected, and a second moving member for moving the supporting member in the direction of the magnifying lens.
The visual inspection apparatus according to claim 1, further comprising: 4. The wedge-shaped moving body that moves in a direction perpendicular to the moving direction of the support member and has a predetermined inclined surface with respect to the moving direction, and the wedge-shaped moving body. 4. The appearance inspection apparatus according to claim 3, further comprising an inclined surface that is in contact with the inclined surface, and an abutting member that is in contact with the support member on a surface opposite to the inclined surface. 5. The observing means has an ultraviolet light objective lens as the magnifying lens, and a first distance for detecting a positional deviation amount of the inspection object from a focal length of the ultraviolet light objective lens. The external appearance according to claim 1, further comprising: a detection unit; and a first control unit that controls a movement amount of the drive unit according to a position shift amount from a focal length detected by the first distance detection unit. Inspection device. 6. The first control means is characterized in that the amount of positional deviation from the focal length detected by the first distance detection means is:
The appearance inspection apparatus according to claim 5, wherein when the difference is smaller than a predetermined threshold value, the movement amount of the drive unit is controlled according to the positional deviation amount. 7. When the amount of positional deviation from the focal length detected by the first distance detecting means is larger than a predetermined threshold value, the moving amount of the supporting means is changed according to the positional deviation amount. 7. The second control means for controlling is further provided.
Appearance inspection device described. 8. The observation means includes an objective lens for visible light,
It further comprises a second distance detecting means for detecting a positional deviation amount of the inspection object from the focal length of the visible light objective lens, wherein the second control means is the second distance detecting means. The visual inspection apparatus according to claim 7, wherein the movement amount of the supporting means is controlled according to the amount of positional deviation from the focal length detected by.