JP2732123B2 - Pattern inspection equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection apparatus used for observing a pattern on, for example, a film mask, a printed circuit board, etc. is there.

2. Description of the Related Art Conventionally, for applications such as finding scratches on a printed board, which is an opaque chart, a printed board mounted on a table is illuminated from above, and reflected light from the printed board is used as an imaging lens. There is used a reflection illumination type pattern inspection apparatus that forms an image on a screen for inspection.

When inspecting a transparent chart such as a mask on which an exposure pattern for manufacturing a semiconductor or a printed circuit board is printed, illuminating light is projected from below the mask, and a light flux transmitted through the mask is formed by an imaging lens. 2. Description of the Related Art A transmission illumination type pattern inspection apparatus that forms an image on a screen and inspects the screen is used.

[Problems to be Solved by the Invention] However, in the conventional inspection apparatus described above, different apparatuses must be used for inspecting an opaque chart and for inspecting a transparent chart.

On the other hand, depending on the type of chart, there is a case where a good inspection can be performed by performing an inspection while switching or simultaneously using the reflection illumination and the transmission illumination, but a conventional inspection apparatus is compatible with such an application. I couldn't.

Conventionally, the chart itself had to be rotated to illuminate the chart from outside the projection lens by means of the oblique reflection illuminating means and to reliably find the flaws on the chart. It was difficult to find the wounds.

[Object of the Invention] Accordingly, a first object has been made in view of the above problem, and it is possible to inspect both a transparent chart and an opaque chart, and to inspect by switching a plurality of illuminations. To provide a pattern inspection apparatus capable of performing the above.

The second purpose is to illuminate the chart obliquely from all directions without rotating the chart itself,
It is an object of the present invention to provide a pattern inspection device capable of finding a flaw on a chart.

[Means for Solving the Problems] To achieve the first object, the invention of claim 1 is
A projection lens for projecting a light beam from the illuminated chart onto a screen, vertical reflection illumination means for illuminating the chart via the projection lens, and oblique reflection illumination for illuminating the chart from the projection lens side and from outside the lens Means for illuminating the chart by selecting at least one of transmission illumination means for illuminating the chart from the opposite side of the projection lens, wherein the vertical reflection illumination means comprises: a light source; and the projection lens. A reflection member that is inserted into an optical path from the light source to the screen and causes a light beam from the light source to enter a projection lens; and a retracting unit that retracts the reflective member from the optical path when the vertical reflection illumination unit is not used. It is an inspection device.

According to another aspect of the present invention, there is provided a projection lens for projecting a light beam from an illuminated chart onto a screen, and a vertical reflection illumination means for illuminating the chart via the projection lens. An oblique reflection illumination means for illuminating the chart from the projection lens side and from outside the lens, and an illumination means for selecting and illuminating at least one of the transmission illumination means for illuminating the chart from the opposite side of the projection lens. In the pattern inspection apparatus having the above, the vertical reflection illumination means has a light source, and a reflecting member that is inserted into an optical path from the projection lens to the screen and causes a light beam from the light source to enter the projection lens, and In the optical path from the light source to the reflecting member, the light beam has a parallel light beam portion that travels substantially in the direction of the optical axis of the projection lens as a parallel light beam. And characterized in that a pattern inspection apparatus having a focusing mechanism for moving the optical element to the projection lens together.

Further, in order to achieve the above-mentioned second object, the invention according to claim 3 provides a projection lens for projecting a light beam from an illuminated chart onto a screen, and illuminating the chart from the projection lens side and from outside the lens. The oblique reflection illuminating means, wherein the oblique reflection illuminating means includes a means for changing an illumination direction capable of illuminating the chart from an arbitrary position around the projection lens. And a pattern inspection apparatus having the same.

[Operation] In the inventions according to the first and second aspects, a variety of charts are inspected by switching or combining illumination methods according to the type of chart.

In addition, when the chart is illuminated by the light source of the vertical reflection illuminating means in the first aspect of the present invention, the reflecting member is inserted into the optical path by the retracting means. When the reflection member is not used for the vertical reflection illumination means, that is, when the oblique reflection illumination means or the transmission illumination means is used, the reflection member is retracted from the optical path by the retracting means. As a result, there is no reflecting member for reducing the light amount in the optical path from the chart to the screen, so that the reflected light reflected from the chart or the transmitted light transmitted through the chart reaches the screen without a light amount reduction.

According to the second aspect of the present invention, the optical element from the parallel light beam portion to the projection lens is moved integrally by the focusing mechanism, thereby focusing on the chart while securing the telecentricity of the vertical reflection illumination. Will be.

Further, in the invention according to claim 3, the chart is illuminated from an arbitrary position around the projection lens by means for changing the illumination position without rotating the chart itself.

[Example] Hereinafter, the present invention will be described with reference to the drawings. Fig. 1 ~
FIG. 10 shows an embodiment of the present invention.

As shown in FIG. 1, the pattern inspection apparatus includes a base unit 10 having a chart mounting table 11 on the upper surface.
And a projection unit 20 supported on the base unit 10 via a support 12 on the left side in the figure.

The projection unit includes a box 21 that houses the optical system, a screen 30 provided in the vertical direction on the front side of the box 21 on the right side in the drawing, and a light beam from the illuminated chart.
Lens, a projection mirror for guiding a light beam from the projection lens 40 to the screen 30, a vertical reflection illumination unit, and an oblique reflection illumination unit.

Rollers are provided at the four corners on the lower surface of the base portion, and below the table 11, a transmission illumination means described later is provided. The table 11 is provided so as to be slidable in two horizontal directions with respect to the base unit 10, and a part of the table 11 is partially transparent so that illumination light from the transmission illumination unit is transmitted toward the projection lens 40.

The projection system mirror includes a first mirror 50, a second mirror 51, and a third mirror.
The mirror 52 includes three mirrors. The first and second mirrors 50 and 51 are plane mirrors, and the third mirror 52 is a roof mirror which is vertically crossed and bonded with the optical axis of the projection lens as a boundary. The Dach mirror is the third mirror 52
May be provided at the position of the first and second mirrors 50 and 51 as well as the position of the first mirror.

FIG. 2 shows an optical path of the projection optical system. After passing through the projection lens 40, the reflected light beam from the chart becomes erect by being reflected three times in the up-down direction, becomes a left-right erect image by the third mirror 52, and is projected on the screen as an erect image.

The screen 30 is composed of two acrylic plates 31 and 32 and a light diffusing film 3 sandwiched between them, as shown in an enlarged manner in FIG.
And a frame 22 having an inner flange.
And is fixed from outside by a contact piece 23. The light-diffusing film 33 has a light-diffusing layer formed on one side and can focus the chart image projection on this light-diffusing layer, so that the image can be accurately focused even when performing observation at a high magnification. Can be matched.

A vertical reflection illuminating means 60 for illuminating a chart placed on the table 11 via the projection lens 40 includes a xenon lamp 61 as a light source, and a parabolic mirror 62 for converting illumination light from the xenon lamp 61 into a substantially parallel light beam. A vertical reflection illumination system first and second mirrors 63 and 64 provided in parallel with each other to guide illumination light toward the projection lens 40; an illumination system field stop 65 for regulating the diameter of the illumination light flux; and a xenon lamp. Heat ray absorption filter 66 that absorbs infrared components contained in the luminous flux of 61
ON / O of xenon lamp 61 when vertical reflection lighting is not used
A shutter 67 for turning on / off the illumination light regardless of the FF, a Fresnel lens 68 for condensing the illumination light, and a vertical reflection illumination system half-size mirror 53 for allowing the illumination light from the xenon lamp 61 to enter the projection lens. doing.

A portion between the first mirror 63 and the second mirror 64 is a parallel light beam portion where the light beam travels in the direction of the optical axis of the projection lens as a substantially parallel light beam.

Inspection equipment using conventional vertical reflection illumination is provided with a half mirror in the optical path from the chart to the screen, and guides the luminous flux from the light source to the chart by this half mirror, and transmits the reflected light from the chart to the screen side. I have.

However, in such a configuration, only 25% of the amount of light emitted from the light source is utilized for projection, even if the reflectivity of the chart is 100%, and there is a problem that the loss is large. Was.

Therefore, in this apparatus, a half-size mirror 53 that covers half of the optical path with respect to the diameter of the projection lens 40 is provided at a position that becomes the exit pupil of the projection light beam of the chart image.

Thus, all light beams from the light source can be made incident on the projection lens 40. At this time, if the projection lens 40 is telecentric on the chart side, the vertical reflection illumination system is also telecentric on the chart side.

The optical path of the vertical reflection illumination is as shown in FIG.
In FIG. 4, the bending of the optical path by the first and second mirrors of the vertical reflection illumination system is omitted.

The divergent light emitted from the xenon lamp 61 is converted into a substantially parallel light beam by the parabolic mirror 62, and the two mirrors 63, 64 and the aperture 6
5. The light is condensed on the half-size mirror 53 by the Fresnel lens 68 via the filter 66 and the shutter 67. The Fresnel lens 68 forms a secondary light source image on the half-size mirror 53.

The entire amount of the illuminating light beam is reflected toward the chart side by the half-size mirror 53, and the specular reflection component of the light beam reaching the chart via the projection lens 40 passes through the projection lens 40 again, and the half-size mirror 53 Transmit on the side not provided.

The transmitted light flux forms a chart image with high contrast on the screen 30 via the projection system mirrors 50, 51, 52.

The vertical reflection illumination is bright-field illumination in which a part having no flaw appears bright on a screen because a specularly reflected component returns to a projection lens to form a chart image.

According to the above configuration, the light amount loss in the chart is 0 for the specular reflection component, and the light amount can be effectively used. Also in the experiment, the illuminance on the screen was about twice as large as that of a conventional apparatus using a half mirror when other conditions were the same, showing improvement. In this embodiment, a half-size mirror is used for the purpose of increasing the amount of light. However, the scope of the present invention is not limited to this, and a half mirror similar to a conventional one can be used.

By the way, in order to focus the chart image on the screen 30, it is necessary to move the projection lens 40 in the direction of its optical axis. Telecentricity is lost.

Therefore, in this apparatus, the vertical reflection illumination system second mirror 64 is used.
, The half-size mirror 53 and the projection lens 40 are attached to the slide base 24, and the optical axis Ax1 of the projection lens 40 with respect to the box 21 of the projection unit 20.
It is configured to be able to move in the direction. The part that is integrally moved as the focusing mechanism is the part surrounded by the broken line in FIG.

Since the light flux is substantially parallel between the first mirror 63 and the second mirror 64, even when the slide base 24 moves, the focus can be adjusted while securing the telecentricity of the vertical reflection illumination system. .

Next, the oblique reflection illumination means for illuminating the chart from the projection lens side and from outside the lens will be described. The oblique illumination unit 70 is attached below the projection lens 40.

The oblique reflection illumination unit provided in the conventional inspection apparatus is of a fixed type in which the illumination direction cannot be changed. Therefore, depending on the direction of the flaw on the chart, it may be difficult to find the flaw while the chart is fixed, and the oversight of the flaw is prevented by rotating the chart.

However, when the chart is rotated, the chart image on the screen is also rotated, so that it is difficult to perform the inspection. In addition, since the rotation must be performed about the optical axis of the projection lens, the operation is troublesome. There was such a problem.

Therefore, this apparatus enables the oblique reflection illumination unit 70 to be rotatable around the optical axis Ax1 of the projection lens 40, and makes it possible to find a scratch in any direction without rotating the chart itself.

Hereinafter, the configurations of the projection lens 40 and the oblique illumination unit will be described with reference to FIG.

The lens barrel 41 to which each lens of the projection lens 40 is fixed is fixed in a cylindrical lens holder 42 fixed to the slide base 24 in the projection unit 20, and this lens holder 42
A rotation holder 44 is rotatably provided on the outer periphery of the device via a bearing 43. The rotation of the rotation holder 44 is restricted by tightening the fixing screw 45, and the rotation of the lens holder 42 is prevented.
Fixed to

The oblique illumination unit 70 includes a halogen lamp 71, a heat ray absorption filter 72, and a shutter 73, and a pair is fixed to the rotary holder 44 with the projection lens 40 interposed therebetween. Accordingly, the oblique illumination unit 70 is rotatable around the optical axis Ax1 of the projection lens, and can perform observation by illumination from various directions without rotating the chart.

The optical path at the time of the oblique reflection illumination is as shown in FIG.

That is, the illumination light emitted from the oblique illumination unit 70 is reflected on the chart. At this time, the regular reflection component in the chart does not enter the projection lens, and only the irregular reflection component due to a flaw or the like enters the projection lens and is projected on the screen.

As described above, in the oblique reflection illumination, the specular reflection component deviates from the projection lens, and a part of the irregular reflection component at the damaged portion is guided to the screen by the projection lens. Only bright darkfield illumination.

The above-described oblique reflection illumination rotation mechanism may be manually operated, or may be automatically performed by a motor. In addition, the change of the irradiation direction of the oblique illumination light is not limited to the configuration in which the two independent light sources are rotated as described above, but may be modified as follows.

First, a ring-shaped light source is provided around the projection lens 40, and a cover with a slit for exposing only a part of the light source to irradiate the chart with light from a predetermined direction is provided. It is conceivable to change the irradiation direction.

Secondly, a configuration is also conceivable in which a large number of oblique illumination units 70 are provided around the projection lens, and the irradiation direction is changed by switching ON / OFF of these units.

As shown in FIG. 1, the transmission illumination means 80 for illuminating the chart from the opposite side of the projection lens includes a halogen lamp 81 as a light source, and a parabolic mirror 82 that makes the illumination light from the halogen lamp 81 a substantially parallel light beam. And a heat ray absorption filter 83 and a shutter 84.

Reference numeral 85 in the drawing denotes a cooling fan that emits hot air in the light source device. Although not shown, the cooling fan is similarly provided for other light sources.

The optical path when using the transmitted illumination is as shown in FIG.

The transmitted illumination is used when a transparent chart that cannot be observed by the above-described reflected illumination is illuminated from below to form an image with transmitted light.

Since this pattern inspection apparatus has the above-described three types of illumination means, one or a plurality of easy-to-see illumination methods are selected and used depending on the type and direction of the flaw generated on the chart, so that various charts can be obtained. Can respond.

When performing observation while switching the illumination method, turn on the illumination light source
If the illumination method is switched by / OFF, the work efficiency of the inspection is deteriorated when the rise time of the light source is long. For example, a slow starter is connected to a halogen lamp so that it takes about 10 seconds to reach a predetermined output to prevent overcurrent. You need to wait for time.

Further, in general, the life of the light source is shortened when the ON / OFF operation is repeated, so that a configuration in which the light source itself is turned ON / OFF for switching the illumination is not preferable.

Therefore, in this device, a shutter is provided between each light source and the chart, and the illumination light flux can be switched without turning on / off the light source itself.

For example, a shutter 67 provided in a vertical reflection illumination system,
A known five-blade shutter as shown in FIG.
By operating the shutter lever 67a with the shutter opening / closing solenoid 67b, the shutter blade 67c can be driven to open / close. The shutter can be opened by a solenoid and closed by a spring or the like.

By using the shutter, the type of illumination can be switched without depending on the rise time of the light source and without shortening the life of the light source.

Next, the retracting mechanism of the half-size mirror 53 will be described with reference to FIG.

As described above, when the observation is performed by the reflected vertical illumination, specular reflection is performed on the chart, and the luminous flux toward the screen 30 passes through the side where the half-size mirror 53 is not provided, and thus does not cause a light amount loss. . However, when the inspection is performed by the transmission illumination or the oblique reflection illumination, the half-size mirror 53 is arranged so as to half block the optical path of the projection light beam, which causes a light amount loss.

Therefore, the half-size mirror 53 is configured to be able to retreat from the optical path of the projection light beam by the retreat mechanism 90 shown in FIG. The retracting mechanism 90 includes a mirror base 91 fixed to the slide base 24, a rotating member 92 to which the half-size mirror 53 is attached and rotatably attached to the mirror base 91, and a rotating member 92. And a direct-acting solenoid 93 that is connected to one end of the solenoid to turn the turning member 92. The rotating member 92 is urged to rotate in a counterclockwise direction in the figure by urging means (not shown), and the mirror base 91 is provided with a stopper 95 having a damper 94 on the surface.

When the vertical reflection illumination is used, the rotating member 92 is fixed at a position where it contacts the stopper 95 as shown by the solid line in the drawing by the urging force of the urging means, and positions the half-size mirror 53 in the optical path. When the oblique reflection illumination and the transmission illumination are used, the rod of the direct acting solenoid 93 is protruded to rotate the rotating member 92 against the urging force, and the half-size mirror 53 is shown by a two-dot chain line in the figure. Fix at the position indicated by.

Thus, no matter which lighting means is selected,
The amount of light reaching the screen can be increased without hindering the light flux emitted from the projection lens toward the screen.

[Effects] As described above, according to the first to third aspects of the present invention,
By switching between illumination methods or using a combination of a plurality of illumination methods, it is possible to observe various charts with one apparatus.

Further, according to the configuration of the first aspect, it is possible to prevent a light amount loss when performing observation by oblique reflection illumination and transmission illumination.

According to the configuration of the second aspect, focusing can be performed while securing the telecentricity of the vertical reflection illumination.

Furthermore, according to the configuration of the third aspect, by changing the illumination direction, it is possible to find scratches in all directions without rotating the chart itself.

According to the fourth aspect of the present invention, the oblique reflection illuminating means is rotated around the projection lens, so that the direction of illumination on the chart can be easily performed steplessly, and the illumination on the chart can be easily performed. The structure for changing the direction can be simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an entire apparatus showing an embodiment of a pattern inspection apparatus according to the present invention, FIG. 2 is an optical path diagram of a projection optical system,
FIG. 3 is a partially enlarged view of FIG. 1 showing the structure of the screen,
FIG. 4 is an explanatory view showing an optical path at the time of vertical reflection illumination, FIG. 5 is an explanatory view showing an integral moving structure at the time of focusing, and FIG.
FIG. 7 is an explanatory diagram showing the configuration of the projection lens and the oblique reflection illumination unit, FIG. 7 is an explanatory diagram showing an optical path in oblique reflection illumination, FIG. FIG. 9 is an explanatory view showing the structure of the shutter, and FIG. 10 is an explanatory view of a retracting mechanism of the half-size mirror. In FIGS. 4, 5, and 8, the parabolic mirror is shown as a lens having a similar function. 30 Screen 40 Projection lens 53 Half-size mirror (reflective member) 60 Vertical reflection illumination means 61 Xenon lamp 62 Parabolic mirror 63, 64 Mirror 67 Shutter 68 Fresnel lens 70 Oblique illumination unit (oblique illumination means) 71 Halogen lamp 73 Shutter 80 Transmission illumination means 81 Halogen lamp 82 Parabolic mirror 84 Shutter 90 Evacuation mechanism

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masaaki Aoyama 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Asahi Optical Industry Co., Ltd. (56) References JP-A-62-70824 (JP, A) 26-8676 (JP, Y1) Yoshio Morimoto, "Projector", Nikkan Kogyo Shimbun, December 25, 1967, p.82

Claims (4)

(57) [Claims] 1. A projection lens for projecting a light beam from an illuminated chart onto a screen, vertical reflection illuminating means for illuminating the chart via the projection lens, and illuminating the chart from the projection lens side and from outside the lens An oblique reflection illuminating means, and a illuminating means for selecting and illuminating at least one of a transmission illuminating means for illuminating the chart from the opposite side of the projection lens, wherein the vertical reflection illuminating means comprises a light source A reflecting member inserted into an optical path from the projection lens to the screen to allow a light beam from the light source to enter the projection lens, and retracting the reflecting member from the optical path when the vertical reflection illumination means is not used A pattern inspection apparatus comprising a retreat means. 2. A projection lens for projecting a light beam from an illuminated chart onto a screen, vertical reflection illumination means for illuminating the chart via the projection lens, and illuminating the chart from the projection lens side and from outside the lens. An oblique reflection illuminating means, and a illuminating means for selecting and illuminating at least one of a transmission illuminating means for illuminating the chart from the opposite side of the projection lens, wherein the vertical reflection illuminating means comprises a light source And a reflecting member that is inserted into the optical path from the projection lens to the screen and causes the light beam from the light source to enter the projection lens, and the light beam is parallel to the optical path from the light source to the reflecting member. It has a parallel light beam portion that travels substantially in the optical axis direction of the projection lens as a light beam, and moves the optical element from the parallel light beam portion to the projection lens integrally Pattern inspection apparatus characterized by having a focusing mechanism for. 3. A pattern inspection apparatus comprising: a projection lens for projecting a light beam from an illuminated chart onto a screen; and an oblique reflection illumination means for illuminating the chart from the projection lens side and from outside the lens. A pattern inspection apparatus characterized in that the oblique reflection illuminating means has a means for changing an illumination direction capable of illuminating the chart from an arbitrary position around the projection lens. 4. The pattern inspection apparatus according to claim 3, wherein said oblique reflection illumination means includes a light source and a rotation mechanism for holding said light source rotatably around said projection lens.