JP2000074848A - Method and device for inspecting ununiformity of light transmittive material - Google Patents

Method and device for inspecting ununiformity of light transmittive material

Info

Publication number
JP2000074848A
JP2000074848A JP24204698A JP24204698A JP2000074848A JP 2000074848 A JP2000074848 A JP 2000074848A JP 24204698 A JP24204698 A JP 24204698A JP 24204698 A JP24204698 A JP 24204698A JP 2000074848 A JP2000074848 A JP 2000074848A
Authority
JP
Japan
Prior art keywords
light
uniformity
leaked
substance
transmitting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP24204698A
Other languages
Japanese (ja)
Other versions
JP3673649B2 (en
Inventor
Masaru Tanabe
勝 田辺
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hoya Corp
Original Assignee
Hoya Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hoya Corp filed Critical Hoya Corp
Priority to JP24204698A priority Critical patent/JP3673649B2/en
Publication of JP2000074848A publication Critical patent/JP2000074848A/en
Application granted granted Critical
Publication of JP3673649B2 publication Critical patent/JP3673649B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/88Investigating the presence of flaws or contamination
    • G01N21/95Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/958Inspecting transparent materials or objects, e.g. windscreens

Abstract

PROBLEM TO BE SOLVED: To surely and quickly detect optical ununiformity of a light transmissive material with high sensitivity even when an inexpensive imaging optical system having a low number of apertures. SOLUTION: A laser beam L from a laser 2 is introduced into a transparent substrate 1 from an introducing face using mirrors 31, 32. The beam L introduced into the substrate 1 repeats total reflection on a surface of the substrate 1 (a main surface and an end face) to be brought substantially into a confined condition within the substrate 1. When ununiform part such as a flaw exists in the surface of the substrate 1, a total reflection condition is not satisfied, and the beam is leaked from the ununiform part. All the leaked beams are scattered by ground glass 6, and the scattered beam from the ground glass 6 is image-formed on a CCD 4 via an imaging lens 5 to be detected.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明は、フォトマスク用透
明基板や情報記録媒体用透明基板であるガラスサブスト
レートなどの透光性物質の光学的な不均一性(欠陥)を
検査する方法及びその検査装置に係り、特に、鏡面仕上
げされた透光性物質表面での全反射の性質を利用するこ
とによって、透光性物質の不均一性を高感度、高速度に
検出できるようにした透光性物質の不均一性検査方法及
びその検査装置に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting optical non-uniformity (defect) of a transparent material such as a transparent substrate for a photomask or a transparent substrate for an information recording medium, such as a glass substrate. Regarding the inspection device, in particular, the use of the property of total reflection on the mirror-finished surface of the light-transmitting material allows the light-transmitting material to detect the non-uniformity of the light-transmitting material with high sensitivity and high speed. TECHNICAL FIELD The present invention relates to a method for inspecting non-uniformity of a conductive substance and an inspection apparatus therefor.

【0002】[0002]

【従来の技術】半導体集積回路、フォトマスク等の製造
工程において、微細パターンの形成には、フォトリソグ
ラフィー法が用いられている。例えば、半導体集積回路
を製造する際には、高精度に研磨され、鏡面仕上げされ
た透明基板上に遮光性膜(例えばクロム膜)によりパタ
ーンが形成されたフォトマスクを用いてパターンを転写
している。このパターンの原盤とも言えるフォトマスク
についての検査方法は、特開昭58―162038号公
報に記載の面状態検査装置にみられるように、パターン
面の微小な領域に光を集め、パターン面からの反射出
力、透過出力を比較する方法が知られている。
2. Description of the Related Art In a process of manufacturing a semiconductor integrated circuit, a photomask, or the like, a photolithography method is used for forming a fine pattern. For example, when manufacturing a semiconductor integrated circuit, a pattern is transferred by using a photomask in which a pattern is formed by a light-shielding film (for example, a chromium film) on a highly polished and mirror-finished transparent substrate. I have. An inspection method for a photomask, which can be said to be a master of this pattern, involves collecting light in a small area of the pattern surface, as seen in a surface state inspection apparatus described in Japanese Patent Application Laid-Open No. 58-162038. A method of comparing a reflection output and a transmission output is known.

【0003】[0003]

【発明が解決しようとする課題】しかしながら、近年に
おいてはパターンの高密度化に伴い、上記方法のように
パターン面の検査のみならず、高精度に研磨されて鏡面
仕上げされた透明基板そのものの微細な欠陥も欠陥検出
の対象となっている。また、上述した方法では、パター
ン面の微小な領域に光を集めることから、検査領域が広
い範囲にわたっている場合には何らかの手段を用いて光
を走査する必要があり、検査領域の面積に比例して検査
時間がかかることと、欠陥の有無によってパターン自体
及び透明基板に対する反射光・透過光の光量の変化があ
まり大きくなく、透明基板の微細な欠陥検出への適用は
困難であった。
However, in recent years, with the increase in the density of patterns, not only the inspection of the pattern surface as in the above method, but also the fineness of the highly polished and mirror-finished transparent substrate itself. Defects are also targets for defect detection. Further, in the above-described method, since light is collected in a minute area on the pattern surface, it is necessary to scan the light by using some means when the inspection area covers a wide range, which is proportional to the area of the inspection area. And the amount of reflected light and transmitted light with respect to the pattern itself and the transparent substrate does not change much depending on the presence or absence of a defect, and it is difficult to apply the method to the detection of fine defects on the transparent substrate.

【0004】そこで、本発明者は、鏡面仕上げされた表
面を有する透光性物質(透明基板など)の不均一部分の
有無を検査する方法であって、前記透光性物質の光路が
光学的に均一の場合には、前記表面で全反射が起こるよ
うに透光性物質内に光を導入し、透光性物質内に導入さ
れ伝播する光の光路中に不均一部分が存在するときに、
前記表面から光が漏出することから透光性物質の不均一
性を検出する方法を見出した。
Therefore, the present inventor provides a method for inspecting the presence or absence of a non-uniform portion of a light-transmitting substance (such as a transparent substrate) having a mirror-finished surface, wherein the light path of the light-transmitting substance is optically In the case of uniformity, light is introduced into the translucent material so that total reflection occurs on the surface, and when there is a non-uniform part in the optical path of the light introduced and propagated in the translucent material. ,
A method for detecting non-uniformity of a light-transmitting substance from light leaking from the surface has been found.

【0005】この方法によれば、透光性物質の表面に
傷、付着異物による汚れ等の不均一部分がなければ、透
光性物質内に導入した光は表面で全反射して外部へは漏
出しないが、不均一部分があると全反射条件が満足され
ず、透光性物質表面から光が漏れ出す。また、透光性物
質表面の不均一性のみならず、内部の異物、不純物等の
欠陥、あるいはガラスの脈理等に特徴的な、透過率は同
じで屈折率だけが違う欠陥の検出に関しても、異物や屈
折率の違うところでは本来均一ならば通る光路(経路)
を外れ、透光性物質外部へ漏れ出すことになるため検出
可能になる。このように、物理的な臨界現象である幾何
光学的な全反射を利用しているため、被検査対象である
透光性物質の不均一部分と均一部分とにおける検査光に
対する応答も臨界的であり、暗い均一部分の背景に漏出
光として不均一部分が劇的なコントラストで現れる。
[0005] According to this method, if there is no uneven portion such as a flaw or dirt due to attached foreign matter on the surface of the light-transmitting material, the light introduced into the light-transmitting material is totally reflected by the surface and transmitted to the outside. Although it does not leak, if there is an uneven portion, the condition for total reflection is not satisfied, and light leaks from the surface of the light transmitting material. Not only non-uniformity of the surface of the translucent material, but also detection of defects such as foreign matter and impurities inside, or defects having the same transmittance but different refractive indexes characteristic of glass striae. Optical path (path) that passes if it is originally uniform at the place where foreign matter or refractive index is different
And leaks out of the light-transmitting substance, so that detection becomes possible. As described above, since the geometrical total reflection, which is a physical critical phenomenon, is used, the response to the inspection light in the nonuniform portion and the uniform portion of the translucent material to be inspected is also critical. There is a non-uniform part with dramatic contrast as leakage light on the background of a dark uniform part.

【0006】ところで、透明基板のより微細な傷等の欠
陥検出が求められているが、欠陥が微細になるほど、透
明基板の表面から漏出する光は、四方八方に拡散された
光ではなく、ある特定方向に向かう偏った強度分布の光
となる傾向がある。ところが、透明基板の欠陥部分から
の漏出光を結像光学系として顕微鏡用対物レンズを用い
てCCD素子などに結像して検出する場合、市販されて
いる顕微鏡用の対物レンズは、例えば、倍率2倍、開口
数0.055(株式会社ミツトヨ製)程度であるので、
結像できる漏出光は、透明基板の表面に於ける法線とな
す角が3.15°以下の一部のわずかな漏出光に限られ
てしまう。
By the way, detection of defects such as fine scratches on the transparent substrate is required. However, as the defect becomes finer, the light leaking from the surface of the transparent substrate is not light diffused in all directions, but rather light. There is a tendency that the light has a biased intensity distribution toward a specific direction. However, when light leaking from a defective portion of a transparent substrate is imaged and detected on a CCD element or the like using a microscope objective lens as an imaging optical system, a commercially available microscope objective lens has, for example, a magnification. Since it is about twice and the numerical aperture is about 0.055 (manufactured by Mitutoyo Corporation),
The leaked light that can form an image is limited to a part of the leaked light having an angle of 3.15 ° or less with the normal to the surface of the transparent substrate.

【0007】このことは、欠陥検出において、検出手段
のCCD撮像素子などにより多くの露光蓄積時間を必要
としたり、欠陥の程度をその微弱な光の強度から少なめ
に見積もったりしてしまうことになる。また、露光蓄積
時間を長くすると、単純に検査時間が増えるだけでな
く、透明基板自体のレイリー散乱光も検出手段にかなり
入射してしまうこととなり、透明基板の欠陥部分のコン
トラストを低下させることにもなる。
[0007] This means that, in the detection of a defect, more exposure and accumulation time is required for the CCD image pickup device or the like of the detecting means, and the degree of the defect is estimated to be lower based on the weak light intensity. . In addition, if the exposure accumulation time is lengthened, not only does the inspection time simply increase, but also the Rayleigh scattered light of the transparent substrate itself is considerably incident on the detecting means, and the contrast of a defective portion of the transparent substrate is reduced. Also.

【0008】開口数が0.8以上である高開口数結像光
学系を用いれば、透明基板の表面に於ける法線と53.
13°以上の角度をなす漏出光も結像可能である。とこ
ろが、このような高開口数の結像光学系は、視野が狭
く、検査時間が膨大となってしまう(欠陥検査の迅速化
を図るために、一回の検査領域を10mm□(角)程度
確保したい)。しかしながら、高開口数(0.4以上)
で、なおかつ広い視野(数10mm□)を持つ結像光学
系の市販品は存在せず、特注品は収差補正の点などから
製造が難しく、かつ非常に高価であって検査装置のコス
トが高くなってしまうという問題があった。
When a high numerical aperture imaging optical system having a numerical aperture of 0.8 or more is used, the normal to the surface of the transparent substrate and the 53.
Leakage light having an angle of 13 ° or more can be imaged. However, such an imaging optical system having a high numerical aperture has a narrow field of view and requires an enormous amount of inspection time. (In order to speed up defect inspection, a single inspection area is about 10 mm square (square). Want to secure). However, high numerical aperture (0.4 or more)
In addition, there is no commercially available imaging optical system having a wide field of view (several tens of mm square), and specially ordered products are difficult to manufacture from the point of aberration correction, and are very expensive, and the cost of the inspection apparatus is high. There was a problem that would be.

【0009】本発明は、上記問題点を解決するためにな
されたものであり、低開口数である結像光学系を使用し
ても透光性物質の光学的な不均一性を高感度・高速度で
確実に検出でき、且つ低コストで実現できる透光性物質
の不均一性検査方法及び検査装置を提供することを目的
とする。
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has high sensitivity and high optical nonuniformity of a translucent substance even when an imaging optical system having a low numerical aperture is used. An object of the present invention is to provide a method and an apparatus for inspecting non-uniformity of a light-transmitting substance which can be reliably detected at a high speed and can be realized at low cost.

【0010】[0010]

【課題を解決するための手段】上記目的を達成するため
に、本発明は、鏡面仕上げされた表面を有する透光性物
質の不均一性を検査する方法であって、前記透光性物質
の光路が光学的に均一の場合には、前記表面で全反射を
繰り返して透光性物質内に閉じ込められるようにレーザ
ー光を導入し、前記表面から全反射することなく漏出し
た光を散乱させた後、低開口数の結像光学系を介して前
記散乱光を検出することで、透光性物質の不均一性を検
査するようにしたことを特徴とする。
According to the present invention, there is provided a method for inspecting non-uniformity of a light-transmitting material having a mirror-finished surface, comprising the steps of: When the optical path is optically uniform, laser light was introduced so as to be confined within the translucent material by repeating total reflection on the surface, and scattered light leaked without total reflection from the surface. Thereafter, the non-uniformity of the light-transmitting substance is inspected by detecting the scattered light through an imaging optical system having a low numerical aperture.

【0011】透光性物質に表面の傷等の不均一部分がな
ければ、透光性物質内に導入したレーザー光は表面で全
反射を繰り返して透光性物質内にレーザー光が閉じ込め
られ、外部へは漏出しないが、不均一部分があると全反
射条件が満足されず、透光性物質表面から光が漏れ出
す。即ち、透光性物質表面に傷、クラック、付着異物に
よる汚れ等の不均一部分がある場合、光路が均一であれ
ば全反射面となる表面から光が漏出することになる。ま
た、透光性物質表面の不均一のみならず、内部のクラッ
ク、気泡、不純物等の欠陥、あるいはガラスの脈理等に
特徴的な、透過率は同じで屈折率だけが違う欠陥の検出
に関しても、異物や屈折率の違うところでは本来均一な
らば通る光路(経路)を外れ、表面での全反射条件が満
足されず、透光性物質外部へ漏れ出すことになるため検
出可能になる。
If there is no non-uniform part such as a scratch on the surface of the light-transmitting substance, the laser light introduced into the light-transmitting substance repeats total reflection on the surface and is confined in the light-transmitting substance. Although it does not leak to the outside, if there is an uneven portion, the condition of total reflection is not satisfied, and light leaks from the surface of the light-transmitting material. That is, when there is a non-uniform portion such as a scratch, a crack, or a stain due to an adhered foreign substance on the surface of the light-transmitting material, light leaks from the surface that is the total reflection surface if the optical path is uniform. In addition to detecting irregularities on the surface of the translucent material, defects such as internal cracks, bubbles and impurities, or defects that have the same transmittance but differ only in the refractive index, which are characteristic of glass striae, etc. However, if a foreign substance or a part having a different refractive index is originally uniform, the optical path (path) through which the light is passed is deviated, the condition of total reflection on the surface is not satisfied, and the substance leaks out of the light-transmitting substance, so that detection becomes possible.

【0012】透光性物質の傷からの漏出光は、四方八方
に拡散された光ではなく、ある特定方向に向かう偏った
強度分布の光(方向性の強い光)となる場合が多く、傷
等の欠陥が微細になるほどその傾向が強い。従って、方
向性の強い傷等の欠陥からの漏出光は、低開口数の結像
光学系には入射されず検出されない欠陥が出てきてしま
う。そこで、この発明では、透光性物質表面から全反射
することなく漏出した光を、一旦散乱させ散乱光として
検出するようにしているので、方向性を強く示す傷や微
細欠陥による漏出光に対しても、低開口数(例えば、
0.4以下)の結像光学系にて確実に結像できるように
している。このため、高性能な透光性物質の不均一性検
査を低コストにて行うことができる。
Light leaked from a wound of a light-transmitting substance is often not a light diffused in all directions but a light having a biased intensity distribution toward a specific direction (light having a strong directivity). This tendency is stronger as defects such as defects become finer. Therefore, light leaked from a defect such as a highly directional flaw may enter a low numerical aperture imaging optical system, and a defect may not be detected. Therefore, in the present invention, light leaked without being totally reflected from the surface of the translucent material is once scattered and detected as scattered light. Even low numerical aperture (for example,
(Less than 0.4). Therefore, a high-performance non-uniformity inspection of a light-transmitting substance can be performed at low cost.

【0013】上記発明において、透光性物質の表面が互
いに平行な平面を有し、導入したレーザー光がこれら平
面で全反射を繰り返して透光性物質内に閉じ込められる
ようにすると、レーザー光が透光性物質内に行き渡るよ
うになり、透光性物質の広範囲な領域の検査を、実際上
同時に行うことができ、高速検査が可能となる。
In the above invention, when the surface of the light-transmitting substance has planes parallel to each other and the introduced laser light is confined in the light-transmitting substance by repeating total reflection in these planes, the laser light As a result, a wide area of the light-transmitting material can be inspected at the same time, and the high-speed inspection can be performed.

【0014】前記漏出光の散乱には、例えば、透光性物
質の少なくとも被検査領域の表面から漏出した光を全て
散乱できるように、表面の外側に散乱体を設ける。散乱
体としては、拡散板(すりガラスなど)、回折格子(例
えば、超音波により形成される周期的な屈折率変化を有
する媒体)、蛍光板または浮遊する微粒子などが挙げら
れる。
In the scattering of the leaked light, for example, a scatterer is provided outside the surface so as to be able to scatter all light leaked from at least the surface of the region to be inspected of the translucent substance. Examples of the scatterer include a diffusion plate (eg, ground glass), a diffraction grating (eg, a medium having a periodic change in refractive index formed by ultrasonic waves), a fluorescent plate, and floating fine particles.

【0015】散乱光を検出した後に、前記散乱光を解析
することで透光性物質の不均一性に関するデータを収集
するのが好ましい。これにより、透光性物質の不均一性
の形状・種類等を確認することができる。
After detecting the scattered light, it is preferable to collect data on the non-uniformity of the translucent substance by analyzing the scattered light. Thereby, the shape, type, and the like of the non-uniformity of the translucent substance can be confirmed.

【0016】また、本発明の透光性物質の不均一性検査
装置は、鏡面仕上げされた表面を有する透光性物質の不
均一性の検査を行う検査装置であって、前記透光性物質
の光路が光学的に均一の場合には前記表面で全反射を繰
り返して透光性物質内に閉じ込められるように透光性物
質内にレーザー光を導入する照射手段と、前記透光性物
質の表面から全反射することなく漏出した光を散乱させ
る漏出光散乱手段と、低開口数の結像光学系を介して前
記散乱光を検出する検出手段と、を有することを特徴と
する。
Further, the present invention provides an apparatus for inspecting non-uniformity of a light-transmitting substance, the inspection apparatus for inspecting non-uniformity of a light-transmitting substance having a mirror-finished surface. When the optical path is optically uniform, irradiation means for introducing laser light into the translucent material so as to be confined within the translucent material by repeating total reflection on the surface, and It is characterized by having leaked light scattering means for scattering light leaked without being totally reflected from the surface, and detecting means for detecting the scattered light via a low numerical aperture imaging optical system.

【0017】このように、透光性物質の表面からの漏出
光を漏出光散乱手段で散乱させ、散乱光を低開口数の結
像光学系を介して検出手段により検出するように構成し
ているので、方向性の強い漏出光も確実に検出すること
ができ、しかも、低コストの検査装置を実現することが
できる。
As described above, light leaking from the surface of the translucent material is scattered by the leaking light scattering means, and the scattered light is detected by the detecting means via an imaging optical system having a low numerical aperture. Therefore, it is possible to reliably detect leaked light having high directivity, and to realize a low-cost inspection apparatus.

【0018】上記検査装置において、漏出光散乱手段
は、透光性物質の表面と結像光学系との間に配置され、
透光性物質の少なくとも被検査領域の表面からの漏出光
が全て漏出光散乱手段に入射されるように設けるのが好
ましい。このようにすると、透光性物質に存在する傷等
の不均一部分から漏出する、通常とらえにくい方向性を
有する漏出光も確実にとらえることができ、不均一性検
査を高感度にて行うことができる。
In the above inspection apparatus, the leaked light scattering means is disposed between the surface of the translucent substance and the imaging optical system,
It is preferable that at least the light leaking from the surface of the region to be inspected of the light-transmitting substance be incident on the leaked light scattering means. By doing so, it is possible to reliably detect leaked light having a direction that is difficult to catch normally, which leaks from a non-uniform portion such as a scratch existing in the light-transmitting material, and performs a non-uniformity inspection with high sensitivity. Can be.

【0019】漏出光散乱手段としては、例えば、漏出光
を散乱する拡散板を用いる。透光性物質からの漏出光を
拡散板により拡散ないし散乱することにより、方向性の
強い漏出光も容易に結像光学系にも向かわせることがで
きる。拡散板には、透明基板表面に拡散性の凹凸を有す
るすりガラスなどや、透明基板内に散乱粒子等が一様に
分散された状態のオパールガラスのようなものが挙げら
れる。
As the leaked light scattering means, for example, a diffusion plate for scattering leaked light is used. By diffusing or scattering the light leaked from the translucent material by the diffusion plate, the leaked light having a strong directivity can be easily directed to the imaging optical system. Examples of the diffusion plate include frosted glass having diffusive irregularities on the transparent substrate surface, and opal glass in which scattering particles are uniformly dispersed in the transparent substrate.

【0020】また、漏出光散乱手段は、超音波発生器
と、超音波発生器より発生した超音波が伝播される媒体
とを具備するものでもよい。超音波により媒体中には周
期的な屈折率の変化が生じ、これが回折格子のように作
用し、透光性物質からの漏出光の一部が回折あるいは屈
折を受けて散乱ないし偏向される。媒体としては、例え
ば、気体(透光性物質の周囲の空気など)又はガラス
(透明ガラス板など)を用いる。この場合、超音波の発
生を停止すると、透光性物質からの漏出光を、散乱させ
ずに、直接に観測することもできる。
The leaked light scattering means may include an ultrasonic generator and a medium through which ultrasonic waves generated by the ultrasonic generator propagate. The ultrasonic wave causes a periodic change in the refractive index in the medium, which acts like a diffraction grating, and a part of the light leaked from the translucent substance is diffracted or refracted and scattered or deflected. As the medium, for example, a gas (such as air around a translucent substance) or glass (such as a transparent glass plate) is used. In this case, when the generation of the ultrasonic wave is stopped, the leaked light from the translucent substance can be directly observed without scattering.

【0021】また、漏出光散乱手段として、蛍光板を設
け、透光性物質からの漏出光を一旦蛍光板で受けて、蛍
光板から発した蛍光(散乱光)を結像光学系を介して検
出手段で検出する構成とする。照射手段には、蛍光板の
蛍光物質を励起可能な光を発生するレーザーを用いる。
このレーザーには、蛍光板に用いられる蛍光物質の励起
に好適な波長域、例えば、紫外域や紫外に近い可視域の
レーザー、具体的には、紫外線レーザ、アルゴンブルー
レーザー、アルゴングリーンレーザーなどが好ましい。
Further, a fluorescent plate is provided as a leaked light scattering means, and the light leaked from the translucent substance is once received by the fluorescent plate, and the fluorescent light (scattered light) emitted from the fluorescent plate is detected by the detecting means via the imaging optical system. It is configured to detect. As the irradiation means, a laser that generates light capable of exciting the fluorescent substance of the fluorescent plate is used.
The laser preferably has a wavelength range suitable for exciting the fluorescent substance used for the fluorescent plate, for example, a laser in a visible range near ultraviolet or ultraviolet, specifically, an ultraviolet laser, an argon blue laser, an argon green laser, or the like is preferable. .

【0022】漏出光散乱手段は、透光性物質の表面と結
像光学系との間に分散させた状態で存在する微粒子でも
よく、漏出光は散乱体としての微粒子に照射されて散乱
され、散乱光が検出手段で検出される。漏出光の散乱が
一様になされるように、微粒子の粒径は、ほぼ均一とす
るのがよく、また、微粒子の粒径は、0.03〜100
μmが好ましい。
The leaked light scattering means may be fine particles existing in a state of being dispersed between the surface of the light-transmitting substance and the imaging optical system. Scattered light is detected by the detection means. The particle size of the fine particles is preferably substantially uniform so that scattering of the leaked light is uniform, and the particle size of the fine particles is 0.03 to 100.
μm is preferred.

【0023】検出手段は、画像処理装置と接続されてい
るものであって、画像処理装置は入カされたデータに基
づいて不均一性の解析を行う解析部を有するものが好ま
しい。解析部を設けることにより、透光性物質における
不均一性の解析を検査時に行うことができ、透光性物質
の製造工程における欠陥発生原因の追求等を容易に実施
でき、検査効率を向上することができる。
Preferably, the detecting means is connected to an image processing apparatus, and the image processing apparatus preferably has an analyzing section for analyzing non-uniformity based on input data. By providing the analysis unit, it is possible to analyze the non-uniformity of the light-transmitting material at the time of inspection, and to easily pursue a cause of a defect occurrence in the manufacturing process of the light-transmitting material, thereby improving the inspection efficiency. be able to.

【0024】また、本発明の透光性物質の不均一性検査
装置は、鏡面仕上げされた表面を有する透光性物質の不
均一性の検査を行う検査装置であって、前記透光性物質
の光路が光学的に均一の場合には前記表面で全反射を繰
り返して透光性物質内に閉じ込められるように透光性物
質内にレーザー光を導入する照射手段と、前記透光性物
質の表面から全反射することなく漏出した光を撮像手段
に導くイメージガイドとを有し、このイメージガイド
は、その入射端面側から出射端面側に向かって漸次縮径
された光ファイバーが束ねられたものであって、入射端
面側が前記透光性物質の表面に近接して設けられ、出射
端面側が前記撮像手段に直接的に接続されていることを
特徴とする。
Further, the present invention provides an apparatus for inspecting non-uniformity of a light-transmitting substance, which inspects the non-uniformity of a light-transmitting substance having a mirror-finished surface. When the optical path is optically uniform, irradiation means for introducing laser light into the translucent material so as to be confined within the translucent material by repeating total reflection on the surface, and An image guide that guides light leaked to the imaging means without being totally reflected from the surface, and the image guide is a bundle of optical fibers whose diameters are gradually reduced from the incident end face side to the output end face side. The incident end face is provided close to the surface of the translucent substance, and the emission end face is directly connected to the imaging means.

【0025】この発明では、透光性物質表面からの漏出
光を散乱させずに、漏出光(画像)をそのままテーパ状
の光ファイバーを束ねたイメージガイドで撮像手段に導
いて検出している。イメージガイドの入射端面を透光性
物質の表面に近接させているので、漏出光の逃げが少な
く、また、透光性物質表面(入射端面)側が広く撮像手
段(出射端面)側が狭いテーパ状の光ファイバーを束ね
たイメージガイドなので、一度に透光性物質表面の広範
囲な検査を実施できる。
According to the present invention, the leaked light (image) is guided to the image pickup means by an image guide in which tapered optical fibers are bundled without scattering light leaked from the surface of the translucent substance, and detected. Since the incident end face of the image guide is close to the surface of the translucent material, there is little escape of leaked light, and the tapered shape has a wide translucent material surface (incident end face) side and a narrow imaging means (emission end face) side. Since the image guide is a bundle of optical fibers, it can perform a wide range of inspections on the surface of the translucent material at once.

【0026】[0026]

【発明の実施の形態】以下に、本発明の実施の形態を図
面を用いて説明する。
Embodiments of the present invention will be described below with reference to the drawings.

【0027】(実施形態1)図1は本発明の透光性物質
の不均一性検査装置の一実施形態を示す概略構成図であ
る。図1において、1は被検査対象である光学ガラス等
からなる矩形状の透明基板である。透明基板1は、図2
に示すように、主表面(表面及び裏面)Hと端面(T面
及び面取り部のC面からなる)とで区画され、いずれの
面も鏡面研磨した後、洗浄処理されている。なお、例え
ば、レーザー光が導入される導入面となるC面が鏡面研
磨されていない場合には、導入面となるC面(粗面)に
透明基板1とほぼ同一の屈折率を有するマッチングオイ
ル等を塗布し、マッチングオイルの自由表面等によって
疑似鏡面を形成するようにしてもよい。透明基板1は、
後述の基板1表面での全反射が阻害されず且つ漏出光の
検査を容易とするために、3点支持など図示省略のフォ
ルダーによってできるだけ接触部分を少なくして水平に
保持される。
(Embodiment 1) FIG. 1 is a schematic structural view showing one embodiment of the apparatus for inspecting non-uniformity of a light-transmitting substance according to the present invention. In FIG. 1, reference numeral 1 denotes a rectangular transparent substrate made of optical glass or the like to be inspected. The transparent substrate 1 is shown in FIG.
As shown in (1), the main surface (front surface and back surface) H and an end surface (consisting of a T surface and a C surface of a chamfered portion) are defined, and both surfaces are mirror-polished and then cleaned. In addition, for example, when the C surface serving as the introduction surface into which the laser beam is introduced is not mirror-polished, a matching oil having a refractive index substantially equal to that of the transparent substrate 1 is provided on the C surface (rough surface) serving as the introduction surface. Or the like, and a pseudo mirror surface may be formed by the free surface of the matching oil or the like. The transparent substrate 1
In order that the total reflection on the surface of the substrate 1 described later is not hindered and the inspection of the leaked light is facilitated, the holder is horizontally held with a contact portion as small as possible by a folder (not shown) such as a three-point support.

【0028】この透明基板1に対して、不均一性を検査
するためのレーザー光を透明基板のC面から導入するた
めの照射手段が設けられている。照射手段は、レーザー
光を発光するレーザー2と、レーザー光を透明基板1の
C面の所定位置・角度で照射するためのミラー31、32
とを有する。なお、ミラー31、32は光の入射角度等を
微調整するためのものであり、ミラー31、32を用いず
に、レーザー2から直接に基板1にレーザー光を照射す
るようにしてもよい。また、透明基板1内に導入された
レーザー光が全反射を起こす範囲内で入射角度を変動さ
せて入射できるように、入射角度変動手段をミラー
1、32などに設けてもよい。レーザー2として、ビー
ム径0.7mm、ビームの広がり角1mrad、レーザーパ
ワー0.5mW、波長543.5nmのHe―Neレーザ
ーを使用した。
Irradiation means for introducing a laser beam for inspecting non-uniformity from the C surface of the transparent substrate to the transparent substrate 1 is provided. The irradiating means includes a laser 2 for emitting laser light, and mirrors 3 1 , 3 2 for irradiating the laser light at a predetermined position and angle on the C surface of the transparent substrate 1.
And The mirrors 3 1 and 3 2 are for finely adjusting the incident angle of light and the like. The laser 2 is directly irradiated from the laser 2 to the substrate 1 without using the mirrors 3 1 and 3 2. You may. Further, incident angle changing means may be provided on the mirrors 3 1 , 3 2, etc. so that the laser beam introduced into the transparent substrate 1 can be incident with the incident angle changed within a range where total reflection occurs. As the laser 2, a He-Ne laser having a beam diameter of 0.7 mm, a beam divergence angle of 1 mrad, a laser power of 0.5 mW, and a wavelength of 543.5 nm was used.

【0029】また、透明基板1の上方には、透明基板1
から漏出する光を検出するための検出手段としてのCC
D(ないしCCDカメラ)4が設けられると共に、透明
基板1からの漏出光をCCD4に結像する、低開口数
(0.045)の結像レンズ(ないし結像レンズ系)5
が設けられている。なお、透明基板1から漏出した光を
検出する検出手段としては、CCDに限らず、フォトマ
ルチプライヤー等を用いてもよい。
The transparent substrate 1 is provided above the transparent substrate 1.
As detection means for detecting light leaking from
A D (or CCD camera) 4 is provided, and an imaging lens (or imaging lens system) 5 having a low numerical aperture (0.045) for imaging light leaked from the transparent substrate 1 onto the CCD 4.
Is provided. The detecting means for detecting the light leaked from the transparent substrate 1 is not limited to the CCD, but may be a photomultiplier or the like.

【0030】透明基板1と結像レンズ5との間には、漏
出光散乱手段として、この実施形態1では、すりガラス
6が配置されている。すりガラス6は、透明基板1表面
で全反射せずに漏れ出た漏出光が全て入射されるよう
に、透明基板1に近接させて基板1を覆うように設けら
れる。従って、透明基板1表面の傷等から方向性の強い
光が漏出し、透明基板1表面における法線とのなす角
が、例えば60〜70°の漏出光であっても、すりガラ
ス6にとらえられ、すりガラス6で多くの方向に拡散な
いし散乱され、結像レンズ5の方向にも散乱光が到達し
て検出されるように構成されている。
In the first embodiment, a frosted glass 6 is disposed between the transparent substrate 1 and the imaging lens 5 as leakage light scattering means. The frosted glass 6 is provided so as to cover the substrate 1 close to the transparent substrate 1 so that all of the leaked light leaking without being totally reflected on the surface of the transparent substrate 1 is incident. Therefore, light having a strong directivity leaks from a scratch or the like on the surface of the transparent substrate 1, and even if the angle formed by the normal to the surface of the transparent substrate 1 is, for example, 60 to 70 °, the light is captured by the ground glass 6. The scattered light is diffused or scattered in many directions by the frosted glass 6, and the scattered light also reaches the direction of the imaging lens 5 and is detected.

【0031】次に、図1の検査装置を用いて行った具体
的な検査方法を述べる。検査対象として、152.4×
152.4×6.35mmの大きさで、C面の幅が0.4
mmのフォトマスク用ガラス基板(ガラスサブストレー
ト)を検査した。このガラス基板のC面から、図2に示
すように、ガラス基板内に入射してから最初に当たる主
表面Hへの入射角θiが臨界角θcよりも大きくなるよう
にレーザ光を入射した。ガラス基板の屈折率は1.46
で、臨界角度θcが約43°なので、入射角θiを44.
1°とした。
Next, a specific inspection method performed using the inspection apparatus of FIG. 1 will be described. 152.4 × for inspection
152.4 × 6.35mm, C-plane width 0.4
A glass substrate for a photomask (glass substrate) having a thickness of 2 mm was inspected. As shown in FIG. 2, laser light was incident from the C surface of the glass substrate such that the incident angle θi to the main surface H, which first hit the glass substrate after entering the glass substrate, was larger than the critical angle θc. The refractive index of the glass substrate is 1.46
Since the critical angle θc is about 43 °, the incident angle θi is 44.
1 °.

【0032】実施形態1では、一例として、砂番#80
0、基板サイズ250mm×250mm×3mmのすり
ガラスを使用した。また、すりガラスと被検査物である
透明ガラス基板との距離は、小さいほど漏出光を確実に
とらえることが可能であるという観点から、たとえば、
透明ガラス表面から0.5mmの距離に、すりガラスを
配置した。漏出光散乱手段であるすりガラスは、すべて
の漏出光をとらえる必要があり、つまり、上述したよう
に、ガラス基板表面とのなす角が小さい漏出光もとらえ
る必要があるので、すりガラスは、ガラス基板と同等も
しくは大きいサイズで、ガラス基板からの漏出光が完全
にとらえられるように、ガラス基板の上方(検出手段
側)に近接して配置するのがよい。
In the first embodiment, as an example, sand number # 80
0, ground glass having a substrate size of 250 mm × 250 mm × 3 mm was used. Further, from the viewpoint that the smaller the distance between the ground glass and the transparent glass substrate to be inspected is, the smaller the leakage light can be reliably captured, for example,
Ground glass was placed at a distance of 0.5 mm from the transparent glass surface. Ground glass, which is a leaked light scattering means, needs to catch all leaked light, that is, as described above, it is necessary to catch leaked light whose angle with the glass substrate surface is small. It is preferable to arrange the same size or a large size in close proximity to the upper side (detection means side) of the glass substrate so that light leaked from the glass substrate can be completely captured.

【0033】ガラス基板内に入射した光は、ガラス基板
の主表面及び端面で全反射を繰り返し、ガラス基板内に
ほぼ閉じ込められたような状態となるが、ガラス基板の
表面に研磨時の異物混入等による傷や、あるいはガラス
基板の内部に気泡、脈理などがあると、全反射条件が満
足されず、その部分から光が漏れ出る。この漏れ出た光
が全て、すりガラスに入射され、その凹凸面により光が
散乱される。したがって、ガラス基板からの漏出光が結
像レンズとは異なる方向に向かう偏った光であっても、
結像レンズ外へ逃げてしまうことなく、すりガラスによ
って散乱されるので、その散乱光の一部が結像レンズに
も入射し、検出手段によって検出される。つまり、微細
な傷等の欠陥から漏出する、いかなる方向性を有する光
も、安価な低開口数の結像レンズで確実に検出すること
が可能になる。また、漏出光をすりガラスで散乱してい
るので、結像レンズに入射する光量は全体的としては減
少するが、1秒程度の露光時間で、微細な傷等の欠陥か
ら漏出する光を確実にとらえることができ、高感度で実
用的な不均一性の検査装置を実現できる。
The light that has entered the glass substrate repeats total reflection on the main surface and the end surface of the glass substrate, and becomes substantially confined in the glass substrate. If the glass substrate is damaged by bubbles, striae, or the like, the total reflection condition is not satisfied, and light leaks out of the portion. All of the leaked light is incident on the frosted glass, and the light is scattered by the uneven surface. Therefore, even if the leaked light from the glass substrate is biased light directed in a different direction from the imaging lens,
Since the light is scattered by the frosted glass without escaping out of the imaging lens, a part of the scattered light also enters the imaging lens and is detected by the detecting means. That is, light having any direction that leaks from a defect such as a fine scratch can be reliably detected by an inexpensive imaging lens having a low numerical aperture. In addition, since the leaked light is scattered by frosted glass, the amount of light incident on the imaging lens is reduced as a whole, but with an exposure time of about 1 second, the light leaked from defects such as minute scratches can be surely reduced. Therefore, a highly sensitive and practical non-uniformity inspection apparatus can be realized.

【0034】(実施形態2)実施形態2においては、漏
出光散乱手段として、超音波によって形成される回折格
子を用いた例について説明する。すなわち、実施形態2
においては、透明基板と結像レンズとの間に超音波を導
く媒体を配置し、超音波を前記媒体へと導き、媒体に回
折格子の機能を与えて透明基板からの漏出光を散乱させ
ている。
(Embodiment 2) In Embodiment 2, an example in which a diffraction grating formed by ultrasonic waves is used as the leaked light scattering means will be described. That is, the second embodiment
In, a medium for guiding ultrasonic waves is disposed between the transparent substrate and the imaging lens, the ultrasonic waves are guided to the medium, and the medium is given a function of a diffraction grating to scatter light leaked from the transparent substrate. I have.

【0035】実施形態2に係る不均一性の検査装置を図
3に示し、実施形態1と異なる箇所について説明する。
低開口数である結像レンズ5と透明基板1との間の空間
に存在する空気を超音波の伝播媒体とし、この空気に対
して超音波ビームBを導入するためにトランスデューサ
7を配置する。トランスデューサ7は、これに接続され
た図示しないドライバ(高周波発振器)からの高周波電
圧の入力により、超音波ビームBを出射する。超音波ビ
ームBは、透明基板1上面の全域と接触している空気に
対して導入される。
FIG. 3 shows a non-uniformity inspection apparatus according to the second embodiment, and portions different from the first embodiment will be described.
Air existing in the space between the imaging lens 5 having a low numerical aperture and the transparent substrate 1 is used as an ultrasonic wave propagation medium, and a transducer 7 is arranged to introduce the ultrasonic beam B into the air. The transducer 7 emits an ultrasonic beam B by inputting a high-frequency voltage from a driver (high-frequency oscillator) (not shown) connected thereto. The ultrasonic beam B is introduced to air in contact with the entire area of the upper surface of the transparent substrate 1.

【0036】この超音波ビームBの導入によって、結像
レンズ5と透明基板1との間の空間に存在する空気に、
超音波の波長を周期とした屈折率変動が生じ、これが回
折格子の作用をする。この超音波による回折格子に対し
て透明基板1からの漏出光が入射すると、回折を受けず
に直進する0次光の他に、ブラッグ回折による1次回折
光が生じ、漏出光の進行方向が変えられる。(あるい
は、屈折率の変動部分で漏出光が屈折されて偏向され
る。)このように、透明基板1から出射された漏出光が
散乱されるため、低開口数の結像レンズ5を用いても、
透明基板1の傷等の微細欠陥による方向性の強い漏出光
も、実施形態1と同様な理由で、確実に結像レンズ5に
入射させることができ、透明基板1の表面に於ける法線
となす角の大きい漏出光もとらえることができる。
By introducing the ultrasonic beam B, the air existing in the space between the imaging lens 5 and the transparent substrate 1
A change in the refractive index occurs with the wavelength of the ultrasonic wave as a period, which acts as a diffraction grating. When the leaked light from the transparent substrate 1 is incident on the diffraction grating by the ultrasonic waves, the first-order diffracted light due to the Bragg diffraction is generated in addition to the 0th-order light which goes straight without receiving the diffraction, and the traveling direction of the leaked light is changed. Can be (Alternatively, the leaked light is refracted and deflected at the portion where the refractive index fluctuates.) Since the leaked light emitted from the transparent substrate 1 is scattered, the imaging lens 5 having a low numerical aperture is used. Also,
Leakage light having a strong directivity due to minute defects such as scratches on the transparent substrate 1 can be surely incident on the imaging lens 5 for the same reason as in the first embodiment, and the normal line on the surface of the transparent substrate 1 The leaked light having a large angle can be captured.

【0037】超音波を導く媒体としては、空気に限定さ
れず、ガラス板を使用することもできる。この場合、図
1のすりガラス6に代えて透明なガラス板を配置し、こ
のガラス板に接触させてトランスデューサを設け、ガラ
ス板に超音波を導入して回折格子を形成する。このよう
にすると、空気を媒体とした場合に比べ、減衰も少なく
超音波が広がることがないので、より効率良く漏出光を
散乱させることができる。
The medium for guiding the ultrasonic waves is not limited to air, but may be a glass plate. In this case, a transparent glass plate is disposed in place of the frosted glass 6 of FIG. 1, a transducer is provided in contact with the glass plate, and ultrasonic waves are introduced into the glass plate to form a diffraction grating. By doing so, the leakage light can be scattered more efficiently because the attenuation is small and the ultrasonic wave does not spread as compared with the case where air is used as the medium.

【0038】(実施形態3)次に、漏出光散乱手段とし
て、微粒子を適用した例を述べる。すなわち、透明基板
と結像レンズとの間に、浮遊状態で微粒子を介在させ、
漏出光を散乱体としての微粒子によって散乱し、漏出光
を散乱光として確実に低開口数である結像レンズに導
き、CCDカメラに結像させるようにしている。
(Embodiment 3) Next, an example in which fine particles are applied as leaked light scattering means will be described. That is, fine particles are interposed in a floating state between the transparent substrate and the imaging lens,
The leaked light is scattered by fine particles as scatterers, and the leaked light is surely guided as a scattered light to an imaging lens having a low numerical aperture to form an image on a CCD camera.

【0039】このとき、散乱体としての微粒子には、数
10μmの径のもので、粒径が揃っているものを使用す
るのがよい。具体的には、研磨剤、ラテックス粒子、ガ
ラス粒子、蛍光粒子などの微粒子を使用することができ
る。また、このとき、結像レンズと透明基板との間を微
粒子が一方向に流れる微粒子流を形成する。このため
に、例えば、透明基板にマイナスの電荷を帯電させ、か
つ微粒子にもマイナスの電荷を帯電させると共に、透明
基板の両側に設置した電極間に1V程度の電位差を与え
て、一方の電極から他方の電極へと透明基板に沿って微
粒子が流れるようにする。
At this time, it is preferable to use fine particles having a diameter of several tens of μm and having a uniform particle diameter as the scatterers. Specifically, fine particles such as an abrasive, latex particles, glass particles, and fluorescent particles can be used. At this time, a fine particle flow in which the fine particles flow in one direction between the imaging lens and the transparent substrate is formed. For this purpose, for example, a transparent substrate is charged with a negative charge, and a fine particle is also charged with a negative charge, and a potential difference of about 1 V is applied between electrodes provided on both sides of the transparent substrate, so that one of the electrodes is Fine particles are caused to flow along the transparent substrate to the other electrode.

【0040】また、結像レンズと透明基板との間に、光
透過性をもつ中空の管などを設置し、その管などの中の
微粒子を、電場やガス流などを用いて、流動化させるよ
うにしてもよい。ただし、いずれの方法においても、分
散状態の微粒子(ないし微粒子流)が透明基板の上方に
且つ透明基板上面を覆うような領域に存在するようにす
る。
A hollow tube or the like having a light transmitting property is provided between the imaging lens and the transparent substrate, and the fine particles in the tube or the like are fluidized by using an electric field or a gas flow. You may do so. However, in any of the methods, the dispersed fine particles (or fine particle flow) are present above the transparent substrate and in a region that covers the upper surface of the transparent substrate.

【0041】以上、漏出光散乱手段を用いて透明基板内
の不均一性検査を行う方法及び装置について説明した
が、上記実施形態1〜3においては、透明基板の不均一
部分の像を直接的に明瞭に確認できないものである。す
なわち、すりガラス、超音波による回折格子、微粒子等
の漏出光散乱手段の存在により、CCDカメラを通して
みると、透明基板中の傷等の像がぼやけ、シャープな直
接像をみることができない。このため、透明基板の不均
一部分の形状・種類・大きさ等の詳細データまで確認す
ることができない。次に記載の実施形態4では、直接的
に不均一部分の像を確認できるとともに、それに関する
データを収集できる不均一部分の検査方法及び検査装置
について説明する。
While the method and apparatus for inspecting non-uniformity in the transparent substrate using the leaked light scattering means have been described above, in the first to third embodiments, the image of the non-uniform portion of the transparent substrate is directly reflected. Cannot be clearly identified. That is, due to the presence of frosted glass, a diffraction grating by ultrasonic waves, and leakage light scattering means such as fine particles, when viewed through a CCD camera, an image such as a scratch in the transparent substrate is blurred, and a sharp direct image cannot be seen. For this reason, it is not possible to confirm detailed data such as the shape, type, and size of the non-uniform portion of the transparent substrate. In a fourth embodiment described below, a method and an apparatus for inspecting a non-uniform portion which can directly confirm an image of the non-uniform portion and collect data relating to the non-uniform portion will be described.

【0042】(実施形態4)実施形態4は、漏出光散乱
手段として蛍光板を適用した例であり、上記実施形態1
〜3と相違する点を主に説明する。すなわち、実施形態
4においては、入射光(透明基板1からの漏出光)の波
長に対して蛍光を示す蛍光板8を、透明基板1と低開口
数の結像レンズ5との間に、図4に示すように配置す
る。蛍光板8は、すべての漏出光をとらえることができ
るように、実施形態1のすりガラス6と同様に、透明基
板1に近接させ、かつ透明基板1の主表面を覆うように
配置される。蛍光板8には、例えば、ガラス板に紫外線
の照射により蛍光を発する硫化亜鉛などの物質をコーテ
ィングしたものを用い(あるいは、紫外線の照射により
蛍光を発する、重金属を含む通常のガラス板を用いても
よい。)、一方、検査光源となるレーザー2には、紫外
線レーザーを用いる。なお、蛍光板の蛍光物質として
は、可視光により蛍光を発生するものでも勿論よく、蛍
光板に用いられる蛍光物質を励起して蛍光を発生できる
レーザーを選択する。
(Embodiment 4) Embodiment 4 is an example in which a fluorescent plate is applied as the leaked light scattering means.
Points different from the first to third aspects will be mainly described. That is, in the fourth embodiment, a fluorescent plate 8 that shows fluorescence with respect to the wavelength of incident light (light leaking from the transparent substrate 1) is provided between the transparent substrate 1 and the imaging lens 5 having a low numerical aperture. Arrange as shown. The fluorescent plate 8 is arranged close to the transparent substrate 1 and so as to cover the main surface of the transparent substrate 1 like the ground glass 6 of the first embodiment so as to capture all leaked light. As the fluorescent plate 8, for example, a glass plate coated with a substance such as zinc sulfide which emits fluorescence by irradiation of ultraviolet rays is used (or a normal glass plate containing a heavy metal which emits fluorescence by irradiation of ultraviolet rays may be used). On the other hand, an ultraviolet laser is used as the laser 2 serving as the inspection light source. The fluorescent substance of the fluorescent plate may be a substance that generates fluorescence by visible light, and a laser capable of generating fluorescent light by exciting the fluorescent substance used for the fluorescent plate is selected.

【0043】透明基板1に紫外線域のレーザー光を入射
させ、透明基板1の不均一部分から漏出する紫外域の光
を蛍光板8で受ける。そして、蛍光板8が発する蛍光の
散乱光を低開口数の結像レンズ5で集光し、CCD4に
て蛍光波長の光を検出する。CCD4には画像処理装置
9が接続されており、画像処理装置9は、検出した情報
(光量、強度分布等)を解析して、透明基板1における
不均一性の種類(表面部の傷やクラック、内部の脈理や
気泡)や不均一部分の大きさ、位置等を出力することを
可能とする。画像処理装置9の画像解析を行う解析部
は、例えば、コンピュータに画像データ処理プログラム
を格納させた画像処理システムであり、それを用いて検
査を行うことにより、欠陥検出のみにとどまらず、上述
したように欠陥解析をも行うことが可能となる。
Laser light in the ultraviolet region is incident on the transparent substrate 1, and ultraviolet light leaking from the non-uniform portion of the transparent substrate 1 is received by the fluorescent plate 8. Then, the scattered light of the fluorescent light emitted from the fluorescent plate 8 is condensed by the imaging lens 5 having a low numerical aperture, and the light having the fluorescent wavelength is detected by the CCD 4. An image processing device 9 is connected to the CCD 4. The image processing device 9 analyzes the detected information (light quantity, intensity distribution, etc.) and determines the type of non-uniformity (scratch or crack on the surface) of the transparent substrate 1. , Internal striae and bubbles) and the size and position of non-uniform portions. The analysis unit that performs image analysis of the image processing apparatus 9 is, for example, an image processing system in which a computer stores an image data processing program, and performs inspection using the image processing system to perform not only defect detection but also the above-described processing. As described above, the defect analysis can be performed.

【0044】検出される画像は、均一部分の暗い背景に
傷等がある不均一部分が線状、点状などに輝いてみえる
もので、得られた画像から傷等の不均一部分を明瞭に判
別できた。この輝いてみえた箇所は、従来の通常照明下
での光学顕微鏡によっては確認できなかったが、原子間
力顕微鏡を用いて測定したところ、たとえば、幅が0.
13μmで、深さが約0.13μmの傷であることが確
認された。
In the detected image, the non-uniform portion having a scratch or the like on the dark background of the uniform portion appears to shine like a line or a dot, and the non-uniform portion such as a scratch is clearly seen from the obtained image. I was able to determine. This bright spot could not be confirmed by a conventional optical microscope under normal illumination, but when measured using an atomic force microscope, for example, the width was 0.1 mm.
It was confirmed that the scratch was 13 μm and had a depth of about 0.13 μm.

【0045】(実施形態5)上記実施形態1〜4では、
透明基板から漏出した光を漏出光散乱手段で散乱し、散
乱された光を検出していたが、この実施形態5では、漏
出光を直接的に検出している。すなわち、図5に示すよ
うに、透明基板1とその漏出光を検出する撮像手段とし
てのCCD4との間には、イメージガイド10が設けら
れている。このイメージガイド10は、その入射端面部
10aから出射端面部10bに向かって漸次縮径された
光ファイバーが束ねられたものであって、全体として円
形断面のテーパ形状となっている。イメージガイド10
の入射端面は、透明基板1表面に近接され、かつCCD
4による一回の検査領域(視野領域)11を覆うことが
できるように設けられる。また、イメージガイド10の
出射端面はCCD4のCCD面に直接接続されている。
(Embodiment 5) In Embodiments 1 to 4,
Although the light leaked from the transparent substrate is scattered by the leaked light scattering means and the scattered light is detected, in the fifth embodiment, the leaked light is directly detected. That is, as shown in FIG. 5, an image guide 10 is provided between the transparent substrate 1 and the CCD 4 as an image pickup means for detecting the leaked light. The image guide 10 is formed by bundling optical fibers whose diameters are gradually reduced from the incident end face 10a toward the emission end face 10b, and has a tapered shape with a circular cross section as a whole. Image Guide 10
Is incident on the surface of the transparent substrate 1 and the CCD
4 is provided so as to cover one inspection area (viewing area) 11. The exit end face of the image guide 10 is directly connected to the CCD surface of the CCD 4.

【0046】この実施形態では、透明基板1からの漏出
光を散乱させずに、透明基板1表面の漏出光(画像)を
イメージガイド10でそのまま縮小してCCD4に導い
て検出しているため、効率よくCCD4に結像でき、高
感度の検出が可能となる。更に、イメージガイド10の
入射端面を透明基板1表面に近接させると共に、出射端
面をCCD面に直接接続しているので、漏出光の逃げや
漏れがなく、また、入射端面部10aが広く出射端面部
10bが狭いテーパ状のイメージガイド10なので、一
度に広範囲な検査領域11を検査することができる。な
お、上記実施形態4のように、CCD4に画像処理装置
9を接続して、透明基板の不均一性の形状・種類等を解
析させるようにしてもよい。また、イメージガイドの断
面は円形ではなく、矩形断面などでもよい。
In this embodiment, the leakage light (image) on the surface of the transparent substrate 1 is reduced as it is by the image guide 10 and guided to the CCD 4 for detection without scattering the leakage light from the transparent substrate 1. An image can be efficiently formed on the CCD 4 and high-sensitivity detection can be performed. Further, since the incident end face of the image guide 10 is close to the surface of the transparent substrate 1 and the output end face is directly connected to the CCD surface, there is no escape or leakage of leaked light, and the incident end face portion 10a has a wide exit end face. Since the portion 10b is a narrow tapered image guide 10, a wide inspection area 11 can be inspected at a time. As in the fourth embodiment, the image processing device 9 may be connected to the CCD 4 to analyze the shape and type of the non-uniformity of the transparent substrate. The cross section of the image guide is not limited to a circle, but may be a rectangular cross section.

【0047】上述した実施形態の検査方法を用いること
によって、欠陥を持ったガラス基板を迅速・適切に排除
することができ、ガラス基板の生産性を向上することが
できた。なお、欠陥を持ったガラス基板を再度精密に鏡
面研磨、洗浄処理を行うことによって、仕様の範囲に入
るフォトマスク用ガラス基板とすることができる。
By using the inspection method of the above-described embodiment, a glass substrate having a defect can be quickly and appropriately eliminated, and the productivity of the glass substrate can be improved. Note that a glass substrate for a photomask that falls within the range of specifications can be obtained by precisely again performing mirror polishing and cleaning processing on a glass substrate having a defect.

【0048】また、上記実施の形態では、鏡面仕上げさ
れた表面を有する透光性物質として、ガラス製の透明基
板を挙げたが、ガラスに限らず、アクリル樹脂等の光学
プラスチック、水晶等の光学結晶など、検査光が通過で
きる材質ならばどのようなものでもよい。
In the above embodiment, a transparent substrate made of glass is used as the light-transmitting substance having a mirror-finished surface. However, the light-transmitting substance is not limited to glass. Any material, such as a crystal, can be used as long as it can transmit the inspection light.

【0049】また、透光性物質の形状は、矩形、円形、
円環状等の基板に限らず、ブロック形状や曲面を有する
ものでもよい。更に、透明基板としては、フォトマスク
(位相シフトマスク)用基板、液晶用ガラス基板、情報
記憶用ガラス基板(磁気デイスク、光デイスク等)等各
種基板の検査に適用可能である。
The shape of the translucent substance is rectangular, circular,
The substrate is not limited to an annular substrate and may have a block shape or a curved surface. Further, as the transparent substrate, it is applicable to inspection of various substrates such as a substrate for a photomask (phase shift mask), a glass substrate for a liquid crystal, and a glass substrate for information storage (a magnetic disk, an optical disk, etc.).

【0050】また、レーザーとしては、気体レーザーに
限らず半導体レーザー等の可視領域のレーザーあるい
は、透光性物質に対して吸収が少ないものであれば、紫
外線領域のエキシマレーザーや、赤外領域のND−YA
Gレーザ、CO2レーザー等を検査用光源として使用す
ることができる。
The laser is not limited to a gas laser, but may be a laser in the visible region such as a semiconductor laser or an excimer laser in the ultraviolet region or an excimer laser in the infrared region as long as it has little absorption for a translucent substance. ND-YA
A G laser, a CO2 laser or the like can be used as a light source for inspection.

【0051】[0051]

【発明の効果】以上説明したように、本発明によれば、
透光性物質表面から全反射することなく漏出した漏出光
を、一旦散乱させ散乱光を低開口数の結像光学系にて確
実に結像させて検出し、又は漏出光をイメージガイドで
導いて検出するようにしているので、透光性物質の傷や
微細欠陥による方向性を強く示す漏出光に対しても、確
実に検出でき、高感度・高速度な透光性物質の不均一性
検査を低コストにて実現できる。
As described above, according to the present invention,
The leaked light that has leaked without being totally reflected from the surface of the translucent material is scattered once, and the scattered light is surely imaged and detected by an imaging optical system with a low numerical aperture, or the leaked light is guided by an image guide. , Which can reliably detect even leaked light that strongly indicates directionality due to scratches or minute defects in the light-transmitting material, and provides high-sensitivity, high-speed non-uniformity of the light-transmitting material. Inspection can be realized at low cost.

【図面の簡単な説明】[Brief description of the drawings]

【図1】本発明に係る透光性物質の不均一性検査装置の
一実施形態を示す概略構成図である。
FIG. 1 is a schematic configuration diagram showing an embodiment of a non-uniformity inspection apparatus for a translucent substance according to the present invention.

【図2】図1の透明基板及びすりガラスを拡大した断面
図である。
FIG. 2 is an enlarged sectional view of a transparent substrate and ground glass of FIG. 1;

【図3】本発明に係る透光性物質の不均一性検査装置の
他の実施形態を示す概略構成図である。
FIG. 3 is a schematic configuration diagram showing another embodiment of the non-uniformity inspection apparatus for a translucent substance according to the present invention.

【図4】本発明に係る透光性物質の不均一性検査装置の
他の実施形態を示す概略構成図である。
FIG. 4 is a schematic configuration diagram showing another embodiment of the non-uniformity inspection apparatus for a translucent substance according to the present invention.

【図5】本発明に係る透光性物質の不均一性検査装置の
他の実施形態を示すもので、漏出光検出系の概略構成を
示す斜視図である。
FIG. 5 is a perspective view showing another embodiment of the apparatus for inspecting non-uniformity of a light-transmitting substance according to the present invention, showing a schematic configuration of a leaked light detection system.

【符号の説明】[Explanation of symbols]

1 透明基板 2 レーザー 31、32 ミラー 4 CCD 5 結像レンズ 6 すりガラス 7 トランスデューサ 8 蛍光板 9 画像処理装置 10 イメージガイド 11 検査領域 L レーザー光 B 超音波ビームDESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Laser 3 1 , 3 2 mirror 4 CCD 5 Imaging lens 6 Ground glass 7 Transducer 8 Fluorescent plate 9 Image processing device 10 Image guide 11 Inspection area L Laser light B Ultrasonic beam

Claims (17)

【特許請求の範囲】[Claims] 【請求項1】 鏡面仕上げされた表面を有する透光性物
質の不均一性を検査する方法において、 前記透光性物質の光路が光学的に均一の場合には、前記
表面で全反射を繰り返して透光性物質内に閉じ込められ
るようにレーザー光を導入し、前記表面から全反射する
ことなく漏出した光を散乱させた後、低開口数の結像光
学系を介して前記散乱光を検出することで、透光性物質
の不均一性を検査するようにしたことを特徴とする透光
性物質の不均一性検査方法。
1. A method for inspecting non-uniformity of a light-transmitting material having a mirror-finished surface, wherein, if the light path of the light-transmitting material is optically uniform, total reflection is repeated on the surface. After introducing laser light so as to be confined in the translucent material and scattering the leaked light without total reflection from the surface, the scattered light is detected through an imaging optical system having a low numerical aperture. A method for inspecting non-uniformity of a light-transmitting substance.
【請求項2】 前記透光性物質の表面が互いに平行な平
面を有し、前記導入したレーザー光がこれら平面で全反
射を繰り返して透光性物質内に閉じ込められることを特
徴とする請求項1に記載の透光性物質の不均一性検査方
法。
2. The light-transmitting material according to claim 2, wherein the surfaces of the light-transmitting material have planes parallel to each other, and the introduced laser light is confined in the light-transmitting material by repeating total reflection on these planes. 2. The method for inspecting non-uniformity of a translucent substance according to 1.
【請求項3】 前記透光性物質の少なくとも被検査領域
の前記表面から漏出した光を全て散乱できるように、前
記表面の外側に散乱体が存在することを特徴とする請求
項1又は2に記載の透光性物質の不均一性検査方法。
3. The apparatus according to claim 1, wherein a scatterer is present outside the surface so as to scatter all light leaked from at least the surface of the region to be inspected of the translucent substance. The method for inspecting non-uniformity of a translucent substance according to the above.
【請求項4】 前記散乱体は、拡散板、回折格子、蛍光
板または浮遊する微粒子であることを特徴とする請求項
3に記載の透光性物質の不均一性検査方法。
4. The method according to claim 3, wherein the scatterer is a diffusion plate, a diffraction grating, a fluorescent plate, or floating fine particles.
【請求項5】 前記散乱光を検出した後に、前記散乱光
を解析することで前記透光性物質の不均一性に関するデ
ータを収集することを特徴とする請求項1乃至4のいず
れかに記載の透光性物質の不均一性検査方法。
5. The method according to claim 1, wherein after detecting the scattered light, the scattered light is analyzed to collect data on non-uniformity of the light-transmitting substance. Inspection method for non-uniformity of translucent material.
【請求項6】 鏡面仕上げされた表面を有する透光性物
質の不均一性の検査を行う検査装置において、 前記透光性物質の光路が光学的に均一の場合には前記表
面で全反射を繰り返して透光性物質内に閉じ込められる
ように透光性物質内にレーザー光を導入する照射手段
と、前記透光性物質の表面から全反射することなく漏出
した光を散乱させる漏出光散乱手段と、低開口数の結像
光学系を介して前記散乱光を検出する検出手段と、を有
することを特徴とする透光性物質の不均一性検査装置。
6. An inspection apparatus for inspecting non-uniformity of a light-transmitting substance having a mirror-finished surface, wherein when the light path of the light-transmitting substance is optically uniform, total reflection is performed on the surface. Irradiating means for introducing laser light into the light-transmitting material so as to be repeatedly confined in the light-transmitting material; and leaked light scattering means for scattering light leaking without being totally reflected from the surface of the light-transmitting material. And a detecting means for detecting the scattered light via an imaging optical system having a low numerical aperture.
【請求項7】 前記漏出光散乱手段は、前記透光性物質
の表面と前記結像光学系との間に配置され、前記透光性
物質の少なくとも被検査領域の前記表面からの漏出光が
全て漏出光散乱手段に入射されるように設けられている
ことを特徴とする請求項6に記載の透光性物質の不均一
性検査装置。
7. The leakage light scattering means is disposed between a surface of the light-transmitting substance and the imaging optical system, and leaks light of the light-transmitting substance from at least a surface of a region to be inspected of the light-transmitting substance. 7. The apparatus for inspecting non-uniformity of a translucent substance according to claim 6, wherein the apparatus is provided so as to be all incident on the leaked light scattering means.
【請求項8】 前記漏出光散乱手段として、前記漏出光
を散乱する拡散板が設けられていることを特徴とする請
求項6又は7に記載の透光性物質の不均一性検査装置。
8. The apparatus according to claim 6, wherein a diffuser plate for scattering the leaked light is provided as the leaked light scattering means.
【請求項9】 前記漏出光散乱手段は、超音波発生器
と、超音波発生器より発生した超音波が伝播される媒体
とを具備することを特徴とする請求項6又は7に記載の
透光性物質の不均一性検査装置。
9. The translucent light according to claim 6, wherein said leaked light scattering means comprises an ultrasonic generator and a medium through which ultrasonic waves generated by the ultrasonic generator are propagated. Non-uniformity inspection device for light-sensitive substances.
【請求項10】 前記媒体は、気体又はガラスであるこ
とを特徴とする請求項9に記載の透光性物質の不均一性
検査装置。
10. The apparatus according to claim 9, wherein the medium is gas or glass.
【請求項11】 前記漏出光散乱手段として、蛍光板が
設けられていることを特徴とする請求項6又は7に記載
の透光性物質の不均一性検査装置。
11. The apparatus according to claim 6, wherein a fluorescent screen is provided as the leaked light scattering means.
【請求項12】 前記照射手段には、前記蛍光板の蛍光
物質を励起可能な光を発生するレーザーが用いられるこ
とを特徴とする請求項11に記載の不均一性検査装置。
12. The non-uniformity inspection apparatus according to claim 11, wherein a laser that generates light capable of exciting a fluorescent substance of the fluorescent plate is used as the irradiation unit.
【請求項13】 前記漏出光散乱手段は、前記透光性物
質の表面と前記結像光学系との間に分散させた状態で存
在する微粒子であることを特徴とする請求項6又は7に
記載の透光性物質の不均一性検査装置。
13. The apparatus according to claim 6, wherein said leaked light scattering means is fine particles which are present in a state of being dispersed between the surface of said translucent material and said imaging optical system. A non-uniformity inspection device for a light-transmitting substance as described in the above.
【請求項14】 前記微粒子の粒径は、ほぼ均一である
ことを特徴とする請求項13に記載の透光性物質の不均
一性検査装置。
14. The apparatus according to claim 13, wherein the particle diameter of the fine particles is substantially uniform.
【請求項15】 前記微粒子の粒径は、0.03〜10
0μmであることを特徴とする請求項13又は14に記
載の透光性物質の不均一性検査装置。
15. The particle size of the fine particles is 0.03-10.
The non-uniformity inspection apparatus for a light-transmitting substance according to claim 13, wherein the thickness is 0 μm.
【請求項16】 前記検出手段は、画像処理装置と接続
されているものであって、前記画像処理装置は入カされ
たデータに基づいて不均一性の解析を行う解析部を有す
ることを特徴とする請求項6乃至15のいずれかに記載
の透光性物質の不均一性検査装置。
16. The detection means is connected to an image processing apparatus, wherein the image processing apparatus has an analysis unit for analyzing non-uniformity based on input data. The non-uniformity inspection device for a light-transmitting substance according to any one of claims 6 to 15.
【請求項17】 鏡面仕上げされた表面を有する透光性
物質の不均一性の検査を行う検査装置において、 前記透光性物質の光路が光学的に均一の場合には前記表
面で全反射を繰り返して透光性物質内に閉じ込められる
ように透光性物質内にレーザー光を導入する照射手段
と、前記透光性物質の表面から全反射することなく漏出
した光を撮像手段に導くイメージガイドとを有し、この
イメージガイドは、その入射端面側から出射端面側に向
かって漸次縮径された光ファイバーが束ねられたもので
あって、入射端面側が前記透光性物質の表面に近接して
設けられ、出射端面側が前記撮像手段に直接的に接続さ
れていることを特徴とする透光性物質の不均一性検査装
置。
17. An inspection apparatus for inspecting non-uniformity of a light-transmitting material having a mirror-finished surface, wherein when the light path of the light-transmitting material is optically uniform, total reflection is performed on the surface. Irradiating means for introducing laser light into the light-transmitting material so as to be repeatedly confined in the light-transmitting material; and an image guide for guiding light leaked from the surface of the light-transmitting material without being totally reflected from the surface to the imaging means. This image guide is a bundle of optical fibers that are gradually reduced in diameter from the incident end face side to the emission end face side, and the incident end face side is close to the surface of the translucent material. A light-transmitting substance non-uniformity inspection apparatus, wherein the light-emitting end face side is directly connected to the imaging means.
JP24204698A 1998-08-27 1998-08-27 Non-uniformity inspection method and inspection apparatus for translucent material Expired - Fee Related JP3673649B2 (en)

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