JPH0321810A - Pattern inspecting device - Google Patents

Abstract

PURPOSE:To observe various charts by the use of one device by switching an illuminating system before using the system or combining plural illuminating systems before using the system. CONSTITUTION:A projection part 20 is provided with a housing 21, a screen 30, a projecting lens 40, a projection system mirror which guides a luminous flux from the lens 40 to the screen 30, a vertical reflection illuminating means 60, and an obliquely illuminating unit 70 being an oblique reflection illuminating means. The illuminating means 60 illuminates the chart placed on a table 11 through the lens 40. The unit 70 is made rotatable centering around the optical axis of the lens 40, so that it can be observed with illumination from various directions even though the chart is not rotated. A transmission illuminating means 80 for illuminating the chart from a side opposite to the lens 40 is provided with a halogen lamp 81, a parabolic mirror 82, a heat absorbing filter 83 and a shutter 84. Therefore, the countermeasure to the various charts is facilitated by selecting one or plural illuminating systems by which the chart is easy to be viewed and using it or them in accordance with the kind and the direction of a flaw on the chart.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to the W! Regarding the projection device used for viewing,
In particular, it relates to inspection equipment that has multiple illumination means. [Prior art] Traditionally, in applications such as finding scratches on printed circuit boards, which are opaque charts, the printed circuit board placed on a table is illuminated from above, and the reflected light from the printed board is imaged. Inspection by forming an image on a screen using a lens
An illumination type pattern inspection device is used.

In addition, when inspecting a transparent chart such as a mask printed with an exposure pattern for semiconductor manufacturing or printed circuit board manufacturing, illumination light is projected from below the mask, and the light beam that has passed through the mask is captured by an imaging lens. Transmitted illumination type pattern inspection equipment is used, which performs inspection by forming an image on a screen. [Problems to be Solved by the Invention] However, in the conventional single inspection device described above, different devices must be used when inspecting an opaque chart and when inspecting a transparent chart. On the other hand, depending on the type of chart, it may be possible to perform a good inspection by switching between reflected illumination and transmitted illumination, or by using both at the same time.However, conventional inspection equipment cannot handle such applications. I couldn't do it. [5? ! [Object of the present invention] This invention was made in view of the above problems, and
The purpose of the present invention is to provide a pattern inspection device that can inspect both transparent charts and opaque charts, and can inspect by switching a plurality of illuminations. [Means for Solving the Problems] A pattern inspection device according to the present invention includes a projection lens that projects a luminous flux from an illuminated chart onto a screen;
At least one of vertical reflective illumination means that illuminates the chart through a projection lens, oblique reflective illumination means that illuminates the chart on the projection lens side and from outside the lens, and transmitted illumination means that illuminates the chart from the opposite side of the projection lens. It is characterized by having an illumination means for selectively illuminating. [Function] According to the above configuration, the illumination method can be switched or used in combination depending on the type of chart,
You can inspect a wider variety of charts. [Example] This invention will be explained below based on the drawings. 1 to 10 show an embodiment of this invention. As shown in FIG. 1, this pattern inspection device consists of a base portion 10 having a table 11 for placing a chart on its upper surface.
and a projection section 20 that is supported by the base section 10 via a column 12 on the left side in the figure. The projection part is
A box 2l that houses an optical system, a screen 30 vertically provided on the front side of the box 21 on the right side in the figure, and a projection lens 40 that projects the light beam from the illuminated chart onto the screen 30. , a projection system mirror that guides a light flux from the projection lens 40 to the screen 30, vertical reflection illumination means, and oblique reflection illumination means.

Rollers are provided at the four corners of the lower surface of the base, and a transmitted illumination means, which will be described later, is provided below the table l1. The table 11 is provided so as to be slidable in two horizontal directions with respect to the base portion 10, and a portion of the table 11 is transparent so that the illumination light from the transmitted illumination means is transmitted to the projection lens 40 side.

The projection system mirrors include a first mirror mark, a second mirror 5l, and a third mirror.
It is +*a from the three mirrors of mirror 52. 1st
1 The second mirror 50.51 is a plane mirror, and the third
The mirror 52 is a roof mirror that is laminated to intersect perpendicularly with the optical axis of the projection lens as a boundary. Note that the roof mirror may be provided not only at the position of the third mirror 52 but also at the positions of the first and second mirrors 50 and 51.

Figure 2 shows the optical path of the projection optical system. After the reflected light flux from the chart passes through the projection lens 40, it is reflected three times in the vertical direction and becomes erect, and is turned into a left and right erect image by the third mirror 52, and is projected on the screen as an erect image. As shown enlarged in FIG. 3, the screen 30 is composed of two acrylic plates 31 and 32 and a light diffusion film 33 sandwiched between them. It is inserted and fixed from the outside by the contact piece 23. The light diffusing film 33 has a light diffusing layer formed on one side, and the chart image projection can be focused on this light diffusing layer, so the image can be focused accurately even when observing at high magnification. It can be matched. The vertical reflection illumination means 60 that illuminates the chart placed on the table 11 through the projection lens 40 includes a xenon lamp 6l as a light source and a parabolic mirror 62 that converts the illumination light from the xenon lamp 6l into a substantially parallel light beam. , vertical reflective illumination system first and second mirrors 63 and 64 that are arranged parallel to each other and guide the illumination light toward the projection lens 40 side, an illumination system field stop 65 that regulates the diameter of the illumination light beam, and a xenon lamp. A heat ray absorption filter 66 that absorbs infrared components contained in the luminous flux of 61 and a heat ray absorption filter 66 that turns on the illumination light regardless of whether the xenon lamp 6l is ON or OFF when vertical reflection illumination is not used.
/OFF, a Fresnel lens 68 that condenses illumination light, and a vertical reflection illumination system half-size mirror 53 that allows illumination light from the xenon lamp 6l to enter the projection lens. The space between the first mirror 63 and the second mirror 64 is a parallel light flux section in which the light beam travels in the direction of the optical axis of the projection lens as a substantially parallel light flux. Conventional inspection equipment using vertical reflected illumination has a half mirror installed in the optical path from the chart to the screen, and this half mirror guides the light flux from the light source to the chart, and also transmits the reflected light from the chart to the screen side. There is. However, in such a configuration, only 25% of the light emitted from the light source is utilized for projection even if the reflectance of the chart is 100x.
The problem was that the loss was large. Therefore, in this device, a half-size mirror 53 that covers half of the optical path with the diameter of the projection lens 40 as the boundary is provided at a position that becomes the exit pupil of the projection light beam of the chart image. Thereby, all the light beams from the light source can be made to enter the projection lens 40. Also, at this time, the projection lens 40
If is telecentric to the chart side, the vertical reflection illumination system will also be telecentric to the chart side. The optical path of vertically reflected illumination is as shown in Figure 4.
In addition, in FIG. 4, the bending of the optical path by the first and second mirrors of the vertical reflection illumination system is omitted. The diverging light emitted from the xenon lamp 61 is made into a nearly parallel beam by a parabolic mirror 62, and is transmitted through a Fresnel lens 68 via two mirrors 63, an aperture section, a filter 66, and a shutter 67.
The light is focused onto the half-size mirror 53. The Fresnel lens 68 forms a secondary light source image on the half-size mirror 53. The entire amount of the illumination light flux is reflected toward the chart side by the half-size mirror 53, and the specularly reflected component of the light flux that has reached the chart via the projection lens 40 passes through the projection lens 40 again and is reflected by the half-size mirror 53. Transmits through the side that is not provided. The transmitted light flux forms a chart image with high contrast on the screen 30 via the projection system mirrors 50, 51, and 52. Vertically reflected illumination is bright-field illumination in which the specularly reflected component returns to the projection lens and forms a chart image, so the unblemished areas appear bright on the screen. According to the above configuration,
The light amount loss on the chart is 0 for the specular reflection component, allowing effective use of the light amount. In experiments, the illuminance on the screen was significantly improved by about twice that of a conventional device using a half mirror, with other conditions being the same. In addition, in this example,
Although a half-size mirror is used for the purpose of increasing the amount of light, the scope of application of the present invention is not limited to this, and it is also possible to use a half-size mirror similar to the conventional one. 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 forward axis direction, but if only the projection lens is moved in the above configuration, the vertical reflection illumination system Telecentricity is broken. Therefore, in this device, the optical elements from the second mirror 64 of the vertical reflection illumination system to the Fresnel lens 68, the half-size mirror 53, and the projection lens 40 are attached to the slide base 24, and the projection is projected onto the box body 21 of the projection section 20. The lens 40 is configured to be movable in the direction of the optical axis Ax1. The portion surrounded by the broken line in FIG. 5 is moved as a focusing mechanism. Since the light beams are almost parallel between the first mirror 63 and the second mirror 64, even if the slide base 24 moves, the focus can be adjusted while ensuring the telecentricity of the vertical reflection illumination system. can. Next, we will explain the oblique reflection illumination means that illuminates the chart on the projection lens side and from outside the lens. The oblique illumination unit 70 is attached below the projection lens 40. The oblique reflective illumination unit installed in conventional inspection equipment is
It was a fixed type that could not change the lighting direction. Therefore,
Depending on the direction of the flaw on the chart, it may be difficult to detect it if the chart is fixed, so rotating the chart prevents the flaw from being overlooked. However, when the chart is rotated, the chart image on the screen also rotates, making inspection difficult to perform.Also, the rotation must be performed around the optical axis of the projection lens, which requires a lot of effort. There was a problem with this. Therefore, this device makes the oblique reflection illumination unit 70 rotatable around the optical axis Ax1 of the projection lens 40, making it possible to detect flaws in any direction without rotating the chart itself. The configurations of the projection lens 40 and the oblique illumination unit will be explained below based on FIG. 6. A lens barrel 4l to which each lens of the projection lens 40 is fixed is fixed in a cylindrical lens holder 42 fixed to a slide base 24 in the projection section 20, and a bearing is provided on the outer periphery of the lens holder 42. A rotary holder 44 is rotatably provided via 43. The rotation of the rotating holder 44 is restricted by tightening the fixing screw 45, and the rotating holder 44 is fixed to the lens holder 42. The oblique lighting unit 70 includes a halogen lamp 71. It consists of a heat ray absorption filter 72 and a shutter 73, and the pair is fixed to a rotating holder 44 with the projection lens 40 in between. As a result, the oblique illumination unit 70 is rotatable around the optical axis Axl of the projection lens, and observation by illumination from various directions can be performed without rotating the chart. The optical path for oblique reflective illumination is
As shown in Figure 7. That is, the illumination light emitted from the oblique illumination unit 70 is reflected by the chart. At this time, the regular reflection component on the chart does not enter the projection lens, and only the diffuse reflection component due to scratches etc. enters the projection lens and is reflected on the screen. It will be projected. In this way, with oblique reflection illumination, the specular reflection component is removed from the projection lens, and part of the diffuse reflection component at the scratched area is guided to the screen by the projection lens, so the area without scratches is dark and the scratches are dark. Only part of the image is illuminated using dark-field illumination. Note that the above-mentioned oblique reflection illumination rotation mechanism may be operated manually or may be operated automatically using a motor. Furthermore, the irradiation direction of the oblique illumination light can be changed not only by rotating two independent light sources as described above, but also by the following modifications. First, a ring-shaped light source is provided around the projection lens 40, and a cover with a slit that exposes only a portion of the light source to irradiate the chart with light from a predetermined direction is provided, and this cover is rotated. A configuration in which the irradiation direction can be changed is considered. Second, a configuration may be considered 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 transmitted illumination stage 80 that illuminates the chart from the opposite side of the projection lens includes a halogen lamp 8l as a light source and a parabolic mirror that converts the illumination light from the halogen lamp 81 into a substantially parallel beam. 82, a heat ray absorption filter 83 and a sitter 84. Note that the reference numeral 85 in the figure is a cooling fan that releases hot air inside the light source device. Although not shown, cooling fans are similarly provided for other light sources. The optical path when using transmitted illumination is as shown in Figure 8. Transmitted illumination is used to illuminate a transparent chart, which cannot be observed with reflected illumination, from below and form an image using transmitted light. Since this pattern inspection device has the three types of illumination means described above, it can be used to inspect various charts by selecting and using one or more illumination methods that are easy to see depending on the type and direction of the scratches that occur on the chart. It is possible to respond. When observing while switching the illumination method, turn on the illumination light source.
If the illumination method is switched by /OFF, the inspection work efficiency will deteriorate if the light source takes a long time to rise. For example, halogen lamps are connected to slow starters that take about 10 seconds to reach a predetermined output to prevent overcurrent, and xenon lamps are connected to a slow starter that takes about 10 seconds to reach a predetermined output to prevent overcurrent; It is necessary to take some time. In addition, in general, the lifespan of a light source will be shortened if the light source is repeatedly turned on and off, so it is not desirable to turn the light source itself on and off when switching lighting. Therefore, in this device, a shutter is provided between each light source and the chart, and the light source itself can be turned on and off, or at least the illumination luminous flux can be switched. For example, the shutter 67 provided in the vertical reflection illumination system is a known five-blade shutter as shown in FIG. It can be opened and closed. It is also possible to open the shutter using a solenoid and use a spring, etc. to open the shutter. By using the above shutter, it is possible to switch the type of illumination without depending on the rise time of the light source and without shortening the life of the light source. Next, a retraction mechanism for the half-size mirror 53 will be explained based on FIG. As described above, when observing with reflective vertical illumination, the light beam that is specularly reflected by the chart and directed toward the screen 30 is transmitted through the side where the half-size mirror 53 is not provided, so it does not cause a loss in light amount. ．． however,
When inspection is performed using transmitted illumination or oblique reflected illumination, the half-size mirror 53 is disposed so as to block half of the optical path of the projection light beam, which causes a loss in the amount of light.

Therefore, the half-size mirror 53 is provided with a bridge so that it can be retreated from the optical path of the projection light beam by a retreat mechanism 90 shown in FIG. Evacuation machine side 90 has slide base 2
4, 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 connected to one end of the rotating member 92. It has a direct acting solenoid 93 that rotates the rotating member 92. The rotating member 92 is biased to rotate counterclockwise in the drawing by a biasing means (not shown), and a stopper 95 having a damper 94 on its surface is attached to the mirror base 9l. When using the vertical anti-q.1 illumination, the rotating member 92 is moved by the urging force of the urging means to the stopper 9 as shown by the solid line in the figure.
It is fixed at the position where it abuts on the half-size mirror 53.
is placed in the optical path. When using oblique reflected illumination or transmitted illumination, by protruding the rod of the direct acting solenoid 93, the rotating member 92 is rotated against the biasing force, and the half-size mirror 53 is moved as indicated by the chain double-dashed line in the figure. Fix it at the position shown. As a result, no matter which illumination means is selected, the amount of light reaching the screen can be increased without interfering with the light flux that exits the projection lens and heads towards the screen. [Effects] As explained above, according to the present invention, it is possible to observe various charts with one device by switching the illumination method or using a combination of multiple illumination methods. can. Further, according to the configuration of claim 2, it is possible to prevent loss of light amount when performing observation using oblique reflected illumination or transmitted illumination. According to the configuration of claim 3, focusing can be performed while ensuring the telecentricity of the vertically reflected illumination. Furthermore, according to the fourth aspect of the present invention, by changing the direction of illumination, it is possible to detect flaws in any direction without rotating the chart itself.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the entire device showing one embodiment of the pattern inspection device according to the present invention, FIG. 2 is an optical path diagram of the projection optical system,
Figure 3 is a partially enlarged view of Figure 1 showing the screen configuration;
Fig. 4 is an explanatory diagram showing the optical path during vertical reflected illumination, Fig. 5 is an explanatory diagram showing the integral movement configuration during focusing, and Fig. 6 is an explanatory diagram showing the optical path during vertical reflected illumination.
The figure is an explanatory diagram showing the configuration of a projection lens and an oblique reflection illumination unit, FIG. ((Explanatory diagram showing the optical path in bright light,
FIG. 9 is an explanatory diagram showing the structure of the shutter, and FIG. 10 is an explanatory diagram of the retraction mechanism of the half-size mirror. In addition, in FIG. 4, FIG. 5, and FIG. 8, the parabolic mirror is shown as a lens having a similar function. 30... Screen 40... Projection lens 53... Half size mirror (reflection member) 60...
Vertical reflective illumination means 61...・・・
・Halogen lamp 73...Shutter 80...Transmission illumination means 81...Halogen lamp 82...Parabolic mirror 84...Shutter 90...Retreat Jf! Mechanism funeral 2 Fig. 5 Fig. 4 Fig. 6 Fig. Possible Ax1 No. 7 Fig. 9 Fig. 67 1)/C Fig. 8 Fig. 10

Claims (4)

[Claims] (1) A projection lens that projects the luminous flux from the illuminated chart onto a screen; a vertical reflection illumination means that illuminates the chart via the projection lens; and an oblique illumination means that illuminates the chart from outside the lens on the side of the projection lens. 1. A pattern inspection apparatus comprising: an illumination means for selectively illuminating at least one of a lateral reflection illumination means and a transmissive illumination means for illuminating a chart from the opposite side of the projection lens. (2) The vertical reflection illumination means includes a light source, a reflection member that is inserted into an optical path from the projection lens to the screen and makes the light beam from the light source enter the projection lens, and a reflection member that illuminates the reflection member with vertical reflection. 2. The pattern inspection apparatus according to claim 1, further comprising a retracting means for retracting the means from the optical path when the means is not in use. (3) The vertical reflection illumination means includes a light source and a reflection member that is inserted into an optical path from the projection lens to the screen and makes the light beam from the light source enter the projection lens, and A focusing mechanism that has a parallel light beam section in which the light beam travels as a parallel light beam substantially in the optical axis direction of the projection lens in the optical path reaching the reflecting member, and moves the optical elements from the parallel light beam section to the projection lens as one unit. The pattern inspection apparatus according to claim 1, characterized in that it has: (4) The pattern inspection apparatus according to claim 1, wherein the oblique reflection illumination means includes a light source and a rotation mechanism that rotatably holds the light source around the projection lens.