JPS62174608A - Pattern detector - Google Patents

Abstract

PURPOSE:To keep flatness and to fix an object to be inspected with good accuracy even in case of detecting transmitted light by using a transparent flexible films and vacuum-sucking the object to be inspected to a table keeping the flatness. CONSTITUTION:A frame part 14 is provided surrounding a base plate 12 and the plate 12 and the transparent flexible films 13 are fitted airtightly and a channel for vacuum suction is formed. Then, the thin films 13 such as the Mylar films are laid in layers on the upper part of the object 2 to be inspected held on the plate 12 and vacuum-sucked by a sucker 4 connected with a suction port of a frame part 14. When the films 13 are vacuum-sucked in this way, the films 13 are stuck to the object 12 to be inspected and fixed uniformly by the air pressure. On this occasion, the air is impressed on the plate 12 from the vertical directions and the deformation is extremely small. Further, when the base plate is constituted of a transparent member such as a glass plate, and optical path is maintained extending over the whole area to be inspected by it and an optical axis is not changed because the deformation is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pattern detection device, and particularly to a pattern detection device used for objects such as photomasks that are easily bent and require transmitted light detection.

[Background of the invention]

In a pattern detection apparatus that detects a pattern using an optical method and performs image processing of the detection signal to inspect for defects, it is generally necessary to mount an object within the depth of focus of the optical system while maintaining flatness. For example, in optical automatic inspection equipment for printed circuit boards, photomasks, and other circuit boards, patterns are often detected at the same magnification or magnification due to the detection resolution, and the focal depth and d depth may be approximately 0.2 tays. There are many, but the target printed circuit boards and photomasks are warped.

There is twisting and bending, so it is necessary to maintain flatness when installing. For this reason, in the past, they were fixed by vacuum suction on a flat table, or held down with a glass plate or the like.

What is shown in Fig. 6 is a cross-sectional view of the fixing device used for vacuum suction and attachment, in which 1 is a stage part in which a hole 3 for vacuum suction is provided on the surface that holds the inspection object 2, and 4 is a suction The device is shown.

This fixing device is often used when detecting a pattern by illuminating it from above. The stage section 1 on which the inspection object 2 is placed has an internal chamber and is connected to a suction bag [4] such as a vacuum pump or suction blower. The object to be inspected is suctioned and fixed through a large number of holes 3 provided on the top surface. This fixing device has ribs inside to prevent deformation due to its own weight and negative pressure, and if the flatness of the top surface is ensured, the inspection object 2 will be fixed along this, so it can be fixed by suction. At the same time, flatness can be obtained. However, it is clear that it cannot be used when performing transmitted light detection. Furthermore, when attempting to detect an inspection object such as a transparent film mask using a reflected light method, the influence of the suction holes cannot be ignored.

However, there are various objects to be inspected by the pattern detection apparatus, and each has its own optimal illumination method and detection method. In other words, a method that detects transmitted light is suitable for objects that are clearly transparent or opaque, such as a photomask, but the conventional method of vacuum suction and fixing the object on a table is incompatible because the suction is performed at the illumination part. The method of placing a glass plate, etc., had the disadvantage of poor flatness.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern detection device that can maintain flatness and accurately fix an object to be inspected even when detecting transmitted light.

[Summary of the invention]

The present invention provides a pattern detection device that uses an optical method to detect a pattern of an object to be inspected, which is attached to a fixing device by suction with negative pressure while maintaining flatness, in which the fixing device is connected to a base member that holds the object to be inspected. , a transparent flexible membrane covering the inspection object on the base member, and a flow path for negative pressure suction provided surrounding the base member, the base member and the transparent flexible membrane being airtightly attached. It is characterized in that it consists of a frame member that is formed.

The present invention was made with the focus on the fact that by using a transparent flexible membrane to vacuum suction the test object onto a table that maintains its flatness, suction ports can be placed around the test object.

[Embodiments of the invention]

Examples will be described below.

FIG. 5 is an explanatory diagram showing the concept of one embodiment of the pattern detection device of the present invention, and FIG. 1 is an explanatory diagram of the fixing device of FIG. 5. In addition, in FIG. 5, details of the fixing device to be inspected are omitted. In the pattern detection device shown in FIG. 5, the inspection object 2 to be inspected is fixed at a predetermined position by the fixing device 5, but at this time, the inspection object 2 is kept flat with respect to the detection optical system 6. It is necessary to be sagging. When the pattern of the inspection object 2 is to be detected using transmitted light, the illumination optical system 7 is arranged to sandwich the detection optical system 6 and the inspection object 2. The optical systems 6 and 7 and the inspection object 2 must be moved relatively within the inspection range, and in this example, the fixed bag [5 is moved by the drive mechanism 8. Therefore, when detecting transmitted light.

The fixing device 5 must not block the optical axis even if it moves within the inspection range, and must have the same optical characteristics. In other words, when the inspection object 2 is fixed by sandwiching it between glass plates, etc. The optical axis and focal position must not change due to changes in deflection or thickness. The inspection device generally includes a binarization circuit 9 that digitizes the electrical signal obtained by the detection optical system 6, a defect determination section 10 that extracts defective parts from the image signal, and a control that controls the operation of the entire device. Consisting of 11 parts.

In FIG. 1, 2 is an object to be inspected, 12 is a base plate that holds the object to be inspected, 13 is a transparent flexible film that covers the object 2 to be inspected on the base plate 12, and 14 is provided surrounding the base plate 12. A frame portion 4 indicates a suction device to which the plate 12 and the transparent flexible membrane 13 are airtightly attached to form a flow path for negative pressure suction. In this fixing device, a thin transparent flexible film 13 such as Mylar film is placed on top of the inspection object 2 held on a base plate 12, and the film is sucked into negative pressure by a suction device 4 connected to a suction port in a frame part 14. be done. When suctioned to negative pressure in this manner, the transparent flexible membrane 13 comes into close contact with the inspection object 2 and is uniformly fixed at atmospheric pressure. At this time, the base plate 12
Since the atmosphere is applied from above and below, deformation is extremely small.

FIG. 2 is an explanatory diagram of a fixing device of a pattern detection device for detecting transmitted light according to another embodiment, and the same parts as in FIGS. 5 and 1 are given the same reference numerals. In this embodiment, the base plate 15
is made of a transparent member such as a glass plate, which ensures an optical path over the entire area to be inspected, and because there is little deformation, there is no change in the optical axis.

FIG. 3 is an explanatory diagram of a fixing device of a pattern detection device having a detection system for upward illumination according to still another embodiment.

The same parts as in FIG. 5 and FIG. 1 are given the same reference numerals. When a pattern is formed on a transparent material, if the reflectance of the pattern is low, the base plate 12 is made to have a high reflectance surface, and conversely, if the pattern has a high reflectance such as metal vapor deposition, the base plate 12 is made to have a low reflectance. By using a reflectance surface, pattern detection with good contrast becomes possible.

FIG. 4 is an explanatory diagram of a fixing device of a pattern detection device applied to inspection objects having different thicknesses according to still another embodiment, and the same parts as in FIGS. 5 and 1 are given the same reference numerals. When the thicknesses of the objects to be inspected differ in this way, by placing the sheet 17 corresponding to the thickness between the object to be inspected 2 and the base plate, the pattern surface can always be fixed at the same position. There is no need to adjust the focus of the detection system.

These embodiments have the following effects.

(1) The upper and lower parts of the inspection object can be made of transparent materials, and there is no need to arrange other mechanisms at positions that block the optical path from the illumination section to the detection section, so it can be applied to transmitted light detection.

(2) During suction, atmospheric pressure acts from above and below, so
There is no deformation of the mechanism due to vacuum suction, and the structure can be made smaller.

(3) Since there is no deformation due to vacuum suction, the inspection object can be fixed along the flatness of the base part.

(4) If the base part has a highly reflective surface or a sheet with a highly reflective surface is laid, the surface of the transparent material will have low reflection (for example, black color).
It is possible to detect an object to be inspected having a pattern of parts using reflected light.

(5) By making the base part a low-reflection surface or by laying a sheet with a low-reflection surface, an object to be inspected having a pattern of highly reflective (for example, metal vapor deposited) parts on the surface of the transparent material can be detected by reflected light.

(6) By placing a sheet on the base that corresponds to the thickness of the object to be inspected, the pattern surface can always be kept at the same height, so no special adjustment mechanism is required even for objects of different thickness. Become.

〔Effect of the invention〕

INDUSTRIAL APPLICATION This invention makes it possible to provide a pattern detection device that can maintain flatness and accurately fix an inspection target even when detecting transparent light, and has great industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a fixing device of an embodiment of the pattern detection device of the present invention, FIGS. 2, 3, and 4 are explanatory diagrams of fixing devices of different embodiments, and FIG. Explanatory diagram showing the concept of one embodiment of the pattern detection device of the invention, No. 6
The figure is an explanatory diagram of a fixing device of a conventional pattern detection device. Optical system, 8...
・Kaku! l! IJ mechanism, 12... base plate, 13...
Transparent flexible film, 14...frame part. Agent: Patent attorney Hiroo Nagasaki 81. ．． ：、、、：、e"
ly-+- (1 other person) Potato January 4th... Uta 1 table! 14... Tsum-AH #3 Mouth bud 4 eyes

Claims (1)

[Scope of Claims] 1. In a pattern detection device that uses an optical method to detect a pattern of an inspection target that is attached to a fixing device while maintaining flatness by suctioning with negative pressure, the fixing device a base member that holds a base member, a transparent flexible film that covers the test object on the base member, and a transparent flexible film that surrounds the base member, and that the base member and the transparent flexible film are airtightly attached to each other, and that the base member and the transparent flexible film are attached to each other in a negative pressure state. 1. A pattern detection device comprising a frame member forming a suction channel. 2. The pattern detection device according to claim 1, wherein the base member is made of a transparent material. 3. The surface of the base member that holds the inspection object,
The pattern detection device according to claim 1, which has a high reflectance. 4. The surface of the base member that holds the inspection object,
The pattern detection device according to claim 1, which has a low reflectance. 5. The pattern detection device according to claim 1, wherein the base member has a sheet inserted on its surface to make the height of the surface of the object to be inspected constant.