JPH05232040A - External appearance inspecting floodlight device - Google Patents

Abstract

PURPOSE:To provide an external appearance inspecting floodlight device in a simple low cost constitution, by which the whole of a large substrate can be illuminated uniformly and which has an excellent foreign material detecting capacity capable of detecting a foreign material on the substrate and by which an external appearance inspection on the substrate can be carried out efficiently. CONSTITUTION:A floodlight device is provided with a light collecting fresnel lens 18 to regulate illumination light emitted from a light source 28 into a parallel light flux, a floodlighting fresnel lens 20 constituted to be connected to/disconnected from the parallel light flux introduced through this light collecting fresnel lens 18 so as to regulate the introduced parallel light flux into a convergent light flux and a transmission type liquid crystal plate 24 constituted to be connected to/disconnected from the convergent light flux introduced through this floodlighting fresnel lens 20 so as to illuminate the surface of a large substrate 22 by giving optical characteristics to the introduced convergent light flux. The transmission type liquid crystal plate 24 is opaque usually, and has a function of being transformed into a transparent shape by voltage impression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light projecting device for inspecting the appearance on a substrate such as a wafer or a liquid crystal glass substrate.

[0002]

2. Description of the Related Art Conventionally, in order to inspect the appearance on a board,
For example, a light projecting device as shown in FIGS. 4 to 8 is used.

The light projecting device shown in FIG. 4 illuminates diffused light emitted from a light source 2 onto a substrate, for example, a wafer 4, and scatters light from foreign matter 6 such as dust or scratches on the surface of the wafer 4. The appearance of the surface of the wafer 4 is inspected by the difference in the intensity of the light directly reflected from the surface of the wafer 4.

However, in such a light projecting device, the scattered light and the direct reflected light are simultaneously incident on the eyes 8 of the observer and are dazzling, so that it is difficult to judge the foreign matter 6 such as dust or scratches on the wafer surface. There is a problem that becomes. Therefore, in the apparatus shown in FIG. 5, the reflected light is prevented from directly entering the observer's eyes 8.
A light shielding plate 10 is arranged.

Further, the light projecting device shown in FIG. 6 is configured to illuminate the surface of the wafer 4 with a converged light flux through the lens 12 to perform a visual inspection. Further, the light projecting device shown in FIG.
It is configured to illuminate the surface of and to perform a visual inspection.

Although the irradiation range of the light flux illuminated on the wafer surface through the light projecting device of FIGS. 6 and 7 is relatively narrow,
Since strong light can be applied and the eyes 8 of the observer can be brought close to the observation optical axis, it becomes easy to observe scattered light from the foreign matter 6 such as dust and scratches. Further, as shown in FIG. 8, a method of illuminating the entire wafer surface using a plurality of optical fibers 16 is also known.

[0007]

However, in the apparatus shown in FIG. 5, the light-shielding plate 10 also blocks the observation field of view, and in order to observe the entire wafer 4, the light-shielding plate 10 must be moved or the wafer must be moved. There is a problem in that the angle between the light source 2 and the light source 2 has to be changed, and complicated work is required.

Further, since the apparatus shown in FIGS. 6 and 7 cannot illuminate the entire wafer without unevenness, when inspecting the appearance of a large wafer, a plurality of apparatuses of this type are required, which results in cost reduction. There is a problem that it is disadvantageous. Further, the apparatus shown in FIG. 8 has a problem that it becomes difficult to determine the foreign matter 6 such as dust and scratches on the wafer surface because the scattered light is aggregated.

The present invention has been made in order to solve such a problem, and its purpose is to illuminate a large-sized substrate as a whole with a simple and low-priced structure and to detect foreign substances on the substrate. Another object of the present invention is to provide a visual inspection light projecting device capable of efficiently performing visual inspection of a substrate.

[0010]

In order to achieve such an object, the present invention is a light projecting device for illuminating a surface of a substrate to inspect the appearance of the substrate, which guides light in an illumination optical path. First optical means for regulating the converted light into a parallel light flux,

It is constructed so that it can be inserted into and removed from the parallel luminous flux guided through the first optical means, and it can illuminate the entire surface of the substrate by giving predetermined optical characteristics to the parallel luminous flux. Second optical means.

[0012]

In the projector of the present invention, the second optical means is allowed to escape from the illumination optical path and only the first optical means is disposed in the illumination optical path, so that the parallel light flux is illuminated on the entire surface of the substrate. Visual inspection is performed. Further, by inserting the first and second optical means into the illumination optical path, the illumination light having predetermined optical characteristics is illuminated on the entire surface of the substrate and a predetermined visual inspection is performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A visual inspection light projecting apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the appearance inspection light projecting apparatus of this embodiment is provided with a Fresnel lens for condensing 18 (thickness: 5 mm) which is arranged in the illumination optical path and regulates incident light into a parallel light flux.
A light projecting Fresnel lens 20 (thickness: 5 mm) configured to be insertable into and removable from a parallel light beam guided through the light collecting Fresnel lens 18, and restricting the guided light beam to a convergent light beam. An observation sample, such as an observation sample, which is configured to be attachable / detachable to / from the convergent light flux guided through the Fresnel lens 20 for projecting light and gives optical characteristics to the convergent light flux guided
And a scattering plate 24 that illuminates a large substrate 22 having a diagonal of 500 mm or more.

The light collecting Fresnel lens 18, the light projecting Fresnel lens 20, and the scattering plate 24 have a larger diameter (about 500 to 600 mm) than the large-sized substrate 22. Therefore, the large-sized substrate 22 is uniformly illuminated over the entire area.

Further, the scattering plate 24 used in the apparatus of this embodiment is connected to a power source 26 through a transparent electrode (not shown) and is capable of applying a voltage to a transmission type liquid crystal plate (hereinafter, this liquid crystal plate will be referred to as a liquid crystal plate). Reference numeral 24) is used. In the dimming liquid crystal sheet (not shown) applied to the transmissive liquid crystal plate 24, since the liquid crystal (not shown) is usually random in the liquid droplets, the incident light is scattered at the interface or inside. Although it is in an opaque state, the liquid crystal is aligned in the direction of the electric field by applying a voltage so that incident light is not scattered and has a function of changing to transparent.

Further, as shown in FIGS. 1 to 3, for example, a metal halide lamp (150 to 250 W) is applied to the light source 28 used in the light projecting device of this embodiment. In such a light source 28, the light emitting point is positioned at the first focal point of the elliptical rotary surface mirror 30, and the second focal point of the elliptical rotary mirror 30 is provided with the scattering plate.
It is configured to be 2. Further, the distance between the gate 32 and the converging Fresnel lens 18 matches the focal length (f) of the converging Fresnel lens 18.

Between the light source 28 and the gate 32,
A heat ray absorption filter 34 is provided. The scattering plate arranged in the gate 32 has a size of 20 to 30 mm and has a function of emitting uniform illumination light from the gate 32. Hereinafter, the operation of the appearance inspection light projecting apparatus of the present embodiment having such a configuration will be described with reference to FIGS.

Illumination light emitted from the light source 28 passes through an elliptical rotation mirror 30, a heat ray absorption filter 34, and a gate 32, and a filter (green, yellow, polarizing plate, etc.) 36.
And is irradiated onto the mirror 38. The illumination light applied to the mirror 38 is reflected by the mirror 38, applied to the converging Fresnel lens 18, and regulated into a parallel light flux.

In the apparatus shown in FIG. 1, since the convergent light flux is used as the illumination light, the projection Fresnel lens 20 and the transmissive liquid crystal plate 24 which is transparent when a voltage is applied are provided in the illumination light path. Has been inserted. Therefore, the convergent light flux from the light-projecting Fresnel lens 20 passes through the transmissive liquid crystal plate 24 as it is and illuminates the entire surface of the large-sized substrate 22 without spots.

The reflected illumination light reflected from the large substrate 22 is
An image is formed at a position S near the eyes 40 of the observer. At this time,
When a foreign matter 42 such as dust or scratches is present on the surface of the large-sized substrate 22, scattered light is generated from the foreign matter 42 and no image is formed at the near position S. As a result, the observer can confirm the presence of the foreign matter 42 on the surface of the large substrate 22 by visually observing the minute scattered light from outside the optical axis. The vicinity position S
It is also preferable to dispose a light shielding plate (not shown), for example, so that the reflected light directly reflected from the substrate surface does not enter the eye 40.

Such a convergent light flux is particularly suitable for inspection of irregularities and spots of a pattern printed on the substrate, dust and scratches on the substrate surface, and the illuminance on the surface of the large substrate 22 is extremely bright. Therefore, not only is it easy to confirm the foreign matter 42, but since the light source image is not incident on the eye 40, it does not become dazzling and does not hinder observation.

Next, when a surface light source is selected as the illumination light, as shown in FIG. 2, the voltage applied from the power source 26 is cut off to make the transmissive liquid crystal plate 24 opaque.
The convergent light flux formed by passing through the light-projecting Fresnel lens 20 becomes a Sharkusten illumination light by the transmissive liquid crystal plate 24, and is uniformly illuminated on the entire surface of the large-sized substrate 22.

Such a surface light source is particularly suitable for inspecting unevenness of the film thickness of the resist or the like on the substrate, pinholes on the transparent conductive film (ITO), dust under the film, and the like. The illuminance is uniform over the entire surface and the interference pattern formed by the foreign matter 42 existing on the substrate surface is clearly visible.

In the light projecting device of the present embodiment, the transmissive liquid crystal plate 24 is applied as the scattering plate, and the converged light flux or the surface light source can be appropriately selected only by applying or blocking the voltage to the transmissive liquid crystal plate 24. It is not necessary to insert and remove the scattering plate in the illumination optical path, and the observation work efficiency can be improved.

Further, when the parallel light flux is selected as the illumination light, as shown in FIG. 3, the light-collecting Fresnel lens 20 and the transmissive liquid crystal plate 24 are avoided outside the illumination optical path to thereby condense the Fresnel lens 18. The parallel light flux formed by transmitting the light is uniformly illuminated on the large-sized substrate 22.

Such a parallel light flux is particularly suitable for a batch inspection of a large-sized substrate and an inspection for dust and scratches on the surface of the substrate, and since it is possible to collectively illuminate the entire surface of the large-sized substrate 22, the substrate appearance. The inspection efficiency can be improved.

As described above, in the appearance inspection light projecting apparatus of this embodiment, the transmissive liquid crystal plate 24 is applied as the scattering plate, and the voltage is applied while the transmissive liquid crystal plate 24 is placed in the illumination optical path. It is possible to easily select a desired convergent light flux or surface light source by applying / blocking. As a result, the efficiency of the work of inspecting the appearance of the substrate can be improved. Further, since the floodlighting device of the present embodiment is configured to illuminate the entire surface of a large-sized substrate without unevenness, it has excellent foreign matter detection ability over the entire surface of the substrate and can efficiently perform visual inspection of the substrate. it can.

The present invention is not limited to the configuration of the above-mentioned embodiment, and for example, the Fresnel lens 2 for projecting light is used.
It is needless to say that the desired convergent light flux or surface light source can be appropriately selected by inserting and removing the 0 and the transmissive liquid crystal plate 24 in the illumination optical path.

Further, by arranging a glass plate on which a film-shaped polarizing film is formed as an analyzer at a position where the illumination light guided from the filter 36 in which the polarizing plate is inserted can be received, the polarization of the large substrate 22 is polarized. It is also possible to make an observation. The polarized light observation can also be performed by an observer wearing glasses or the like provided with a polarizing plate and placing the eyes 40 at the light source image position. Further, in the above-described embodiment, the visual inspection by the observer has been described, but the visual inspection of the substrate may be performed via the image processing apparatus.

[0031]

EFFECTS OF THE INVENTION The floodlighting device for appearance inspection according to the present invention uses a transmissive liquid crystal plate as a scattering plate, and the transmissive liquid crystal plate is placed in the illumination optical path while the voltage is applied or cut off. A desired convergent light flux or surface light source can be easily selected. As a result, the efficiency of the work of inspecting the appearance of the substrate can be improved. Furthermore, since the floodlighting device of the present invention is configured to illuminate the entire surface of a large substrate without spots,
The foreign matter detection ability over the entire surface of the substrate is excellent, and the appearance inspection of the substrate can be efficiently performed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an appearance inspection light projecting apparatus according to an embodiment of the present invention, showing a state in which an entire surface of a substrate is observed using a converged light flux.

FIG. 2 is a diagram showing a state in which the entire surface of the substrate is observed by a surface light source using the apparatus shown in FIG.

FIG. 3 is a diagram showing a state in which the entire surface of the substrate is observed by a parallel light flux using the apparatus shown in FIG.

FIG. 4 is a schematic view of a conventional light projecting device, showing a state where the substrate surface is observed by diffused light.

5 is a diagram showing a state in which a light shielding plate is provided in the apparatus shown in FIG. 4 and the surface of the substrate is being observed.

FIG. 6 is a schematic view of a conventional light projecting device, showing a state where the substrate surface is observed by a convergent light beam.

FIG. 7 is a schematic view of a conventional light projecting device, showing a state in which a substrate surface is observed by a parallel light beam.

FIG. 8 is a schematic view of a conventional light projecting device, showing a state in which the substrate surface is observed using a plurality of optical fibers.

[Explanation of symbols]

Reference numeral 18 ... Condensing Fresnel lens, 20 ... Projecting Fresnel lens, 22 ... Large substrate, 24 ... Transmissive liquid crystal plate, 28 ... Light source.

Claims (4)

[Claims] 1. A light projecting device for illuminating a surface of a substrate to inspect the appearance of the substrate, comprising: first optical means for regulating light guided in an illumination optical path into a parallel light flux; The second light beam is configured to be insertable into and removable from the parallel light flux guided through the first optical means, and to impart predetermined optical characteristics to the parallel light flux to illuminate the entire surface of the substrate. An optical projection device for visual inspection, comprising: an optical unit. 2. The light projecting apparatus for appearance inspection according to claim 1, wherein the first optical means is a first Fresnel lens. 3. The second optical means is configured to be insertable into and removable from the parallel light flux guided through the first optical means, and regulates the parallel light flux into a convergent light flux. Two
Of the Fresnel lens and the converging light beam guided through the second Fresnel lens, and is configured to be removable from the converging light beam to give a predetermined optical characteristic to the entire surface of the substrate. The light projection device for appearance inspection according to claim 1 or 2, further comprising: a scattering plate. 4. The appearance inspection projection device according to claim 3, wherein the scattering plate is an opaque light control liquid crystal sheet to which a voltage can be applied, and the transparent plate changes to be transparent when a voltage is applied. Light equipment.