JP2009042202A - Wafer inspection equipment and wafer inspection method - Google Patents

Wafer inspection equipment and wafer inspection method Download PDF

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JP2009042202A
JP2009042202A JP2007229537A JP2007229537A JP2009042202A JP 2009042202 A JP2009042202 A JP 2009042202A JP 2007229537 A JP2007229537 A JP 2007229537A JP 2007229537 A JP2007229537 A JP 2007229537A JP 2009042202 A JP2009042202 A JP 2009042202A
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defect
light
wafer
illumination
inspection
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Yuzo Taniguchi
雄三 谷口
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TANIGUCHI CONSULTING ENGINEERS
TANIGUCHI CONSULTING ENGINEERS CO Ltd
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TANIGUCHI CONSULTING ENGINEERS
TANIGUCHI CONSULTING ENGINEERS CO Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein the inspection equipment for detecting defects in the edge region of a wafer there are no means for classifying the kinds of the defects or determination of mortality. <P>SOLUTION: In this invention, lighting systems from different angles are used. The wavelength band of light source used for each lighting system is separated respectively. Thus, the reflection light and scattered light to be used for imaging can be discriminated from which light source the light comes. The intensity performance of the reflected light or scattered light by the illuminations of various directions varies, depending on the kinds of defects; and thus, the kinds of the defects can be classified, on the basis of these performance. Moreover, by combining the information of the detection size or the existing position with these classification, determination of mortality becomes possible. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、半導体ウエハの端部の欠陥を検出する検査方法および装置に関するものであるThe present invention relates to an inspection method and apparatus for detecting defects at the edge of a semiconductor wafer.

図2に半導体ウエハの端面の部分断面図の例を示す。半導体ウエハの端面断面が同図(a)のように矩形状であると端部が傷付き、クラックが発生しやすく、同図(b)に示すように、面取り、及び又は、球面加工されるようになってきている。ウエハ端面の検査対象領域は、例えば、端面部、面取り部、周辺の平坦部に大別される。ウエハ製造メーカにおけるウエハ端面加工後の検査は主に端面部や面取り部が検査対象であり、ウエハ加工時に発生する傷、クラック、異物などを検出する。特に傷、クラックは致命欠陥となるので不良として除去しなければならない。半導体製造メーカの製造工程中では端面部、面取り部、周辺の平坦部が検査対象領域となり、傷、クラックのほか、フォトレジスト残り、膜残り、異物などを検出する。傷、クラックなどはどの工程でも致命欠陥となりうるが、他の欠陥はその大きさ、存在場所、種類により致命か非致命かが異なる。例えば、端面や面取り部の小さな異物やレジスト残りは致命にはならないが、周辺の平坦部に存在するレジスト残り、膜残りや大きな異物は工程によっては致命不良となりうる。したがって、検査終了後に、欠陥を目視確認して分類しなければならないが、特に、ウエハ端面部には非致命の小さい異物が多数付着しており、これを1個ずつ目視で他の欠陥と分類して致命性判定するのでは検査効率が低下する。また、レジスト残りや膜残りも場所や大きさにより致命になる場合も非致命になる場合もあり、これらも欠陥検出時に確度の高い分類ができることが望まれている。一般に、人は欠陥をその形状、色、濃度などの情報と過去の知識をもとに分類している。FIG. 2 shows an example of a partial cross-sectional view of the end face of the semiconductor wafer. If the cross section of the end face of the semiconductor wafer is rectangular as shown in FIG. 1A, the end is easily damaged and cracks are likely to occur, and chamfering and / or spherical processing is performed as shown in FIG. It has become like this. The inspection target area on the wafer end surface is roughly classified into, for example, an end surface portion, a chamfered portion, and a peripheral flat portion. In the inspection after the wafer end surface processing in the wafer manufacturer, the end surface portion and the chamfered portion are mainly inspection targets, and scratches, cracks, foreign matters and the like generated during the wafer processing are detected. In particular, scratches and cracks become fatal defects and must be removed as defects. During the manufacturing process of the semiconductor manufacturer, the end face part, the chamfered part, and the peripheral flat part become inspection target areas, and in addition to scratches and cracks, the remaining photoresist, remaining film, and foreign matter are detected. Scratches, cracks, etc. can be fatal defects in any process, but other defects are fatal or non-fatal depending on their size, location, and type. For example, a small foreign substance or a resist residue on the end face or chamfered portion is not fatal, but a resist residue, a film residue or a large foreign substance existing on the peripheral flat portion can be fatally defective depending on the process. Therefore, after inspection, defects must be visually confirmed and classified. In particular, a large number of non-fatal foreign substances are adhered to the wafer end surface, and these are classified as other defects visually. In this case, the inspection efficiency decreases when the criticality is determined. In addition, the resist residue and the film residue may be fatal or non-fatal depending on the location and size, and it is desired that these can be classified with high accuracy when a defect is detected. In general, people classify defects based on information such as shape, color, density, and past knowledge.

これらクラックや傷のような欠陥を検査するウエハ端部の欠陥検査装置としては、例えば、特許第2999712号公報(以下、公知例1とよぶ)や特許公開第2003−287412号(以下、公知例2とよぶ)に掲載された構造のものがある。これらはともにレーザ光をウエハ端面部に照射して、端面部のクラックや傷などから反射や散乱されるレーザ光を検出しようとするものである。しかし、これらは単にレーザ光の反射光を検出するだけであるので、欠陥の形状や色、濃淡などの情報は取れないので、異物とクラック、傷などの分類を行うことは原理上難しい。また、詳細は不明であるがカラー画像処理により欠陥検査を行う装置も公表されている。As a defect inspection apparatus for a wafer edge portion for inspecting defects such as cracks and scratches, for example, Japanese Patent No. 2999712 (hereinafter referred to as well-known example 1) and Japanese Patent Publication No. 2003-287712 (hereinafter, well-known example). 2). Both of these are intended to detect a laser beam reflected or scattered from a crack or a flaw on the end face by irradiating the end face with a laser beam. However, since these only detect the reflected light of the laser beam, information such as the shape, color, and shading of the defect cannot be obtained. Therefore, it is difficult in principle to classify foreign objects, cracks, scratches, and the like. In addition, although details are unknown, an apparatus for performing defect inspection by color image processing has been announced.

図4に、現在市販されている端面の欠陥検査装置の基本構成を示す。ウエハはウエハチャックに固定され、ウエハ端部の表面の欠陥を検出する光学系、裏面の欠陥を検出する光学系、端面を検出する光学系から構成される。検出はレーザを走査して欠陥信号を撮像するもの、一般的な照明で画像を撮像するものなどがあるが詳細は公表されていない。前記のごとくレーザ照射方式では異物とクラック、傷などの分類を行うことは原理上難しく、高角度の照明では細い筋状のクラックは検出困難である。また、半導体製造工程におけるウエハ端面の欠陥検査装置において、欠陥分類が可能であると公表している装置はない。FIG. 4 shows a basic configuration of an end face defect inspection apparatus currently on the market. The wafer is fixed to a wafer chuck, and includes an optical system that detects a defect on the front surface of the wafer end, an optical system that detects a defect on the back surface, and an optical system that detects the end surface. The detection includes scanning the laser to pick up a defect signal and picking up an image with general illumination, but details are not disclosed. As described above, it is difficult in principle to classify foreign objects, cracks, scratches, and the like with the laser irradiation method, and it is difficult to detect thin streak-like cracks with high-angle illumination. In addition, there is no device that has been announced that defect classification is possible in the defect inspection device for the wafer end face in the semiconductor manufacturing process.

発明が解決しようとする課題Problems to be solved by the invention

本発明は従来の技術において問題となっている課題を解決するために考案されたものであり、その課題は、端面検査において検出が要求される、傷、クラック、フォトレジスト残り、膜残り、異物など多種の欠陥を検出すると同時に、これら検出欠陥の種類や致命性を確度高く分類するウエハ端面の欠陥検査方法および欠陥検査装置を提供することにある。The present invention has been devised in order to solve the problems that are a problem in the prior art, and the problems include scratches, cracks, photoresist residue, film residue, foreign matter that are required to be detected in end face inspection. Another object of the present invention is to provide a defect inspection method and a defect inspection apparatus for a wafer end face that can detect various types of defects and classify the types and criticality of these detected defects with high accuracy.

課題を解決するための手段Means for solving the problem

本発明における請求項1記載のウエハ端部の欠陥検査方法および欠陥検査装置は、光照明手段および光撮像手段を有し半導体ウエハの端面領域の欠陥を検出する検査装置において、前記光照明手段として被検査面に対して低角度で光を照射する照明手段と被検査面に対して高角度で光を照射する手段を具備し、高角度照明により得られた画像信号をもとにした欠陥検出処理と低角度照明により得られた画像信号をもとにした欠陥検出処理を個別に行い、各照明により得られる欠陥信号強度の特徴の差異をもとに欠陥分類を行うことを特徴とするものである。According to the present invention, there is provided a defect inspection method and a defect inspection apparatus for a wafer edge, wherein the light illumination means and the optical imaging means have an optical illumination means and an optical imaging means for detecting defects in an end face region of a semiconductor wafer. Defect detection based on image signals obtained by high-angle illumination, with illumination means for irradiating light at a low angle to the surface to be inspected and means for irradiating light at a high angle to the surface to be inspected Defect classification based on the difference in feature of defect signal intensity obtained by each illumination by performing defect detection processing based on image signal obtained by processing and low-angle illumination individually It is.

本発明における請求項2記載のウエハ端部の欠陥検査方法および欠陥検査装置は、前記、高角度の照明手段と低角度の照明手段の照明光として、異なる帯域の波長を用い波長帯域別に欠陥検出処理することにより、どちらの照明による欠陥信号かを識別可能とすることを特徴とするものである。According to a second aspect of the present invention, there is provided a defect inspection method and a defect inspection apparatus for a wafer edge, wherein different wavelengths are used as the illumination light of the high-angle illumination means and the low-angle illumination means. By processing, it is possible to identify which illumination signal is a defect signal.

本発明における請求項3記載のウエハ端部の欠陥検査方法および欠陥検査装置は、前記高角度照明系と画像検出系に各1枚の偏光フィルタを互いに偏光方向が直交する方向に配置することにより透明膜や半透明膜の検出および他の欠陥との識別を可能とすることを特徴とするものである。According to a third aspect of the present invention, there is provided a defect inspection method and defect inspection apparatus for a wafer edge by disposing one polarization filter in each of the high angle illumination system and the image detection system in directions in which the polarization directions are orthogonal to each other. It is characterized in that it can detect a transparent film or a translucent film and distinguish it from other defects.

本発明における請求項4記載のウエハ端部の欠陥検査方法および欠陥検査装置は、前記欠陥の種類の分類結果、欠陥の存在箇所情報および欠陥の寸法をもとに欠陥の致命性判定を行うことを特徴とするものである。According to a fourth aspect of the present invention, there is provided a defect inspection method and a defect inspection apparatus for a wafer edge, wherein the defect fatality determination is performed based on the classification result of the defect type, the information on the existence of the defect, and the size of the defect. It is characterized by.

以下、本発明の実施の形態を具体的に説明するが、この実施の形態は、本発明の趣旨をより良く理解させるため具体的に説明するものであり、特に指定のない限り、発明内容を限定するものではない。Hereinafter, embodiments of the present invention will be described in detail. These embodiments are specifically described for better understanding of the gist of the present invention, and unless otherwise specified, the contents of the invention are described. It is not limited.

〔光学系の構成〕図1に本発明の光学系の構成例を示す。図の例ではウエハ1の表面のエッジ領域と面取り部を検出する光学系1、ウエハ1の裏面のエッジ領域と面取り部を検出する光学系2およびウエハ1の端面部を検出する光学系の3軸の光学系3を配置している。前記3式の光学系の構成は略同一である。各光学系の照明系は低角度照明系、高角度照明系からなる。ここで、本発明では、高角度照明と低角度照明の区別は、照明光を平坦なウエハ面に照明したとき、その反射光が対物レンズ7に入射するかどうかの臨界角とする。この角度は対物レンズ7の開口数により定まる。なお、装置の基本構成は図4と同様である。[Configuration of Optical System] FIG. 1 shows a configuration example of the optical system of the present invention. In the example shown in the figure, the optical system 1 detects the edge region and the chamfered portion of the front surface of the wafer 1, the optical system 2 detects the edge region and the chamfered portion of the back surface of the wafer 1, and the optical system 3 detects the end surface portion of the wafer 1. An axial optical system 3 is arranged. The three optical systems have substantially the same configuration. The illumination system of each optical system consists of a low angle illumination system and a high angle illumination system. Here, in the present invention, the distinction between high-angle illumination and low-angle illumination is a critical angle as to whether or not the reflected light is incident on the objective lens 7 when the illumination light is illuminated onto a flat wafer surface. This angle is determined by the numerical aperture of the objective lens 7. The basic configuration of the apparatus is the same as that shown in FIG.

低角度照明系は、狭帯域波長照明光源2を有し、斜方からウエハ面を照射する。光源としては、例えばレーザ、LEDあるいは広帯域波長の照明光を光学フィルタを通して狭帯域波長としたものなどを用いる。狭帯域波長照明光源2の照明光は集光レンズ3にてウエハ面に集光する。高角度照明系は図1の例では同軸落射照明であるが、高角度からのリング照明でもよい。照明光は広帯域波長照明光源4、例えば、ハロゲンランプ、キセノンランプ、水銀灯、白色LEDなどを用いる。広帯域波長の高角度照明はハーフミラー6、対物レンズ7を通してウエハ面に集光する。光学フィルタ5は挿入無しの状態と挿入状態を切り替え可能とするのが好ましい。低角度照明光の波長帯域を遮断する光学フィルタ5を挿入すれば低角度照明光と高角度照明光を分離できる。また、フォトレジスト残り、透明膜や半透明膜残りの欠陥検出を行う場合には光学フィルタ5を偏光フィルタにし、撮像素子9の前に偏光フィルタを光学フィルタ8として挿入する。ここで、光学フィルタ5と光学フィルタ8の偏光フィルタは互いに直交する方向に配置する。欠陥からの散乱光の散乱方向はその照射角に依存するので、低角度照明系は複数の照射角θ1の照明系の組み合わせ、例えばθ1が10度以下の照明と数10度の照明の組み合わせなどでもよく、これにより欠陥からの散乱光の照射角依存性の影響が低減する。The low-angle illumination system has a narrow-band wavelength illumination light source 2 and irradiates the wafer surface from an oblique direction. As the light source, for example, a laser, an LED, or illumination light having a broadband wavelength that has a narrow band wavelength through an optical filter is used. The illumination light from the narrow-band wavelength illumination light source 2 is condensed on the wafer surface by the condenser lens 3. The high-angle illumination system is coaxial epi-illumination in the example of FIG. 1, but may be ring illumination from a high angle. As the illumination light, a broadband wavelength illumination light source 4, for example, a halogen lamp, a xenon lamp, a mercury lamp, a white LED or the like is used. High-angle illumination with a broadband wavelength is focused on the wafer surface through the half mirror 6 and the objective lens 7. It is preferable that the optical filter 5 can be switched between a non-inserted state and an inserted state. If the optical filter 5 that blocks the wavelength band of the low-angle illumination light is inserted, the low-angle illumination light and the high-angle illumination light can be separated. Further, in the case of detecting defects in the remaining photoresist, transparent film, and semi-transparent film, the optical filter 5 is a polarizing filter, and the polarizing filter is inserted as an optical filter 8 in front of the image sensor 9. Here, the polarizing filters of the optical filter 5 and the optical filter 8 are arranged in directions orthogonal to each other. Since the scattering direction of the scattered light from the defect depends on the irradiation angle, the low-angle illumination system is a combination of illumination systems having a plurality of irradiation angles θ1, for example, a combination of illumination having θ1 of 10 degrees or less and illumination of several tens of degrees. However, this may reduce the influence of the irradiation angle dependence of the scattered light from the defect.

低角度照明による画像と高角度照明による画像は撮像素子9に同時に結像される。撮像素子9は、カラーCCDカメラなど広波長域の画像信号を波長帯域別に、例えばR(赤の波長帯域)G(緑の波長帯域)B(青の波長帯域)を分離して検出できるものとする。このことにより、例えば、狭帯域照明光源2を赤色とすると、低角度照明により欠陥に照射および反射散乱された光はCCDカメラの赤信号に変換される。高角度照明により欠陥に照射および反射散乱された光はRGBの画像信号に変換される。ここで、前記のように高角度照明系の光学フィルタ5を低角度照明光の波長帯域を遮断するフィルタ、すなわちこの例では赤色の波長帯域だけを遮断するフィルタにすると高角度照明系からえられる画像信号はGBのみの信号に変換される。撮像素子9のRGB出力は、帯域別画像処理回路10にて各帯域個別に並列信号処理する。The image by the low angle illumination and the image by the high angle illumination are simultaneously formed on the image sensor 9. The image sensor 9 can detect an image signal in a wide wavelength range, such as a color CCD camera, by separating, for example, R (red wavelength range) G (green wavelength range) B (blue wavelength range) by wavelength range. To do. Thus, for example, when the narrow-band illumination light source 2 is red, the light irradiated and reflected / scattered on the defect by the low-angle illumination is converted into a red signal of the CCD camera. The light irradiated on the defect and reflected and scattered by the high-angle illumination is converted into RGB image signals. Here, as described above, when the optical filter 5 of the high angle illumination system is a filter that blocks the wavelength band of the low angle illumination light, that is, a filter that blocks only the red wavelength band in this example, the optical filter 5 can be obtained from the high angle illumination system. The image signal is converted into a GB-only signal. The RGB output of the image sensor 9 is subjected to parallel signal processing for each band individually by the image processing circuit 10 for each band.

[欠陥信号の特徴と分類判定処理]次に、検出対象の欠陥の種類と各照明系による反射光、散乱光の一般的な性質について説明する。図5に異物と反射光、散乱光の関係を示す。一般に異物は図示のように異形をしたものや比較的丸い形状のものが多い。これらに、低角度照明光を照射すると、ウエハ表面での反射光は対物レンズ7には入射しない。一方異物からの散乱光は各方向に散乱してその一部が対物レンズに入射し撮像素子9上に結像検出される、すなわち低角度照明では異物はウエハ面に比して明るく観察される。高角度照明光を照射すると、ウエハ面からの反射光はそのまま正反射して対物レンズ7に入射するが、異物からの散乱光は各方向に散乱するので対物レンズ7に入射する光量は少なくなる、すなわち、高角度照明では一般に異物はウエハ面に比して暗く観察される。このように、照射角が異なる照明により得られる信号強度の特徴は大きく異なる。[Defect Signal Characteristics and Classification Determination Processing] Next, the types of defects to be detected and general properties of reflected light and scattered light from each illumination system will be described. FIG. 5 shows the relationship between a foreign substance, reflected light, and scattered light. In general, foreign substances are often irregularly shaped as shown in the drawing or relatively round. When these are irradiated with low-angle illumination light, the reflected light on the wafer surface does not enter the objective lens 7. On the other hand, the scattered light from the foreign matter is scattered in each direction, and a part of the scattered light enters the objective lens and is imaged and detected on the image sensor 9. In other words, the foreign matter is observed brighter than the wafer surface in low-angle illumination. . When high-angle illumination light is irradiated, the reflected light from the wafer surface is specularly reflected and enters the objective lens 7, but the scattered light from the foreign matter is scattered in each direction, so that the amount of light incident on the objective lens 7 is reduced. That is, in general, foreign objects are observed darker than the wafer surface in high-angle illumination. Thus, the characteristics of the signal intensity obtained by illumination with different illumination angles are greatly different.

図6に傷のようにウエハ面が凹状に削られた場合の例を示す。低角度照明による散乱光は凹部の端部で各方向に散乱してその一部が対物レンズ7に入射する。一方、凹部の内部には光が入射しないので、この部分からの散乱光は少ない。すなわち凹部の端部はウエハ面よりも明るく、凹部の内部は端部よりも暗く観察される。一方、高角度照明による反射光散乱光は、ウエハ面からは正反射して明るい検出信号に、凹部端部では散乱してその一部が対物レンズ7に入射する。この凹部端面からの光強度は端部の凹凸の程度と照射角度により強度は異なるがウエハ表面よりは暗くなり、凹部内部からの反射散乱光は少ないので凹部内部からの散乱光強度は暗くなる。すなわち、凹部の内部はウエハ面よりも暗く観察される。図7に示す、極めて細い筋状のクラックの場合、低角度照明による散乱光により細い筋状の欠陥として検出されるが、高角度照明の場合このような細い欠陥による散乱光強度は極めて小さいので、高角度照明での検出感度は低くなる。なお、傷やクラックは一般に細長くかつ直線状の形状を示すものが多い。FIG. 6 shows an example in which the wafer surface is cut into a concave shape like a scratch. Scattered light by low-angle illumination is scattered in each direction at the end of the recess, and a part of the light enters the objective lens 7. On the other hand, since light does not enter the inside of the recess, the scattered light from this portion is small. That is, the end of the recess is observed brighter than the wafer surface, and the interior of the recess is observed darker than the end. On the other hand, the reflected light scattered light by the high-angle illumination is regularly reflected from the wafer surface to be a bright detection signal, scattered at the end of the concave portion, and part of it is incident on the objective lens 7. The light intensity from the end face of the recess differs depending on the degree of unevenness and the irradiation angle at the end, but becomes darker than the wafer surface, and the scattered light intensity from the inside of the recess becomes dark because there is little reflected scattered light from the inside of the recess. That is, the inside of the recess is observed darker than the wafer surface. In the case of the extremely thin streak-shaped crack shown in FIG. 7, it is detected as a thin streak-like defect by scattered light by low-angle illumination, but in the case of high-angle illumination, the scattered light intensity due to such a thin defect is extremely small. The detection sensitivity at high angle illumination is low. In many cases, scratches and cracks generally have an elongated and linear shape.

図8にフォトレジスト残りや透明または半透明の膜残りの不良の例を示す。これらの欠陥は一般に膜厚が1μm程度あるいはそれより極めて薄い欠陥であり、表面が滑らかであるという特徴をもっている。低角度照明では、ウエハ表面や欠陥表面での反射光は対物レンズ7に入射されず、欠陥端部からの散乱光だけが明るく検出される。すなわち欠陥の周囲だけが明るく観察される。高角度照明では、ウエハ面からの光は正反射し、欠陥である膜部では膜表面からの反射光と膜下面からの反射光が干渉を引き起こす。干渉は膜厚、膜の屈折率、光の波長の関係で光の濃淡差が発生することであるが、広帯域波長の照明光の場合は干渉色を呈する場合が多い。なお、特定の波長を吸収する特性を有する膜の場合は色変化を起こす。また、欠陥の端部は図のように散乱されて暗くなる。すなわち、欠陥の端部は暗く、内部は暗くまたは色変化を起こす。なお、透明や半透明欠陥を検出するには、図1の光学フィルタ5と光学フィルタ8を偏光フィルタとし、各偏光フィルタの方向を直交させると、偏光顕微鏡の原理で欠陥部のみを鮮明に検出できる。また、有機物欠陥を弁別検出するには、例えば高角度照明として紫外線を含むものを用い、光学フィルタ5として紫外線だけを透過させるフィルタ、光学フィルタ8として紫外線を遮光するフィルタを用いると、紫外線照射により有機物から励起された蛍光を検出できる。このことにより、異物が有機物か無機物か、膜残りがフォトレジストか無機膜か、などを弁別可能となる。不透明な金属膜、例えば銅の膜が残っている場合は、反射光、散乱光が銅色になるという特徴を利用することができる。欠陥の形状が直線状かどうかは、欠陥の各画素の座標を回帰分析し、回帰式の回りの分散値の大小により評価できる。また、細線かどうかは、例えば欠陥の周囲長(輪郭の長さ)と欠陥の面積をもとに評価できる。FIG. 8 shows an example of a defect in a photoresist residue or a transparent or translucent film residue. These defects are generally defects having a film thickness of about 1 μm or extremely thinner than that, and are characterized by a smooth surface. In the low-angle illumination, the reflected light from the wafer surface or the defect surface is not incident on the objective lens 7 and only the scattered light from the defect end is detected brightly. That is, only the periphery of the defect is observed brightly. In high-angle illumination, the light from the wafer surface is regularly reflected, and the reflected light from the film surface and the reflected light from the lower surface of the film cause interference in the defective film portion. Interference is a difference in light density due to the relationship between the film thickness, the refractive index of the film, and the wavelength of light. In the case of illumination light with a wide-band wavelength, an interference color is often exhibited. In the case of a film having a characteristic of absorbing a specific wavelength, color change occurs. Moreover, the edge part of a defect is scattered and becomes dark like a figure. That is, the edge of the defect is dark and the interior is dark or undergoes a color change. In order to detect a transparent or translucent defect, if the optical filter 5 and the optical filter 8 in FIG. 1 are used as polarizing filters and the directions of the polarizing filters are orthogonal to each other, only the defective portion is clearly detected by the principle of a polarizing microscope. it can. In addition, in order to discriminate and detect organic defects, for example, a high-angle illumination that includes ultraviolet rays is used, a filter that transmits only ultraviolet rays is used as the optical filter 5, and a filter that blocks ultraviolet rays is used as the optical filter 8. Fluorescence excited from organic matter can be detected. This makes it possible to discriminate whether the foreign matter is organic or inorganic, and whether the film residue is a photoresist or inorganic film. In the case where an opaque metal film, for example, a copper film remains, the feature that reflected light and scattered light become copper color can be used. Whether or not the shape of the defect is a straight line can be evaluated by regression analysis of the coordinates of each pixel of the defect and the magnitude of the variance around the regression equation. Whether the line is a thin line can be evaluated based on, for example, the peripheral length of the defect (contour length) and the area of the defect.

以上述べた、広帯域波長の高角度照明による各種欠陥からの反射光や散乱光の波長別の信号特性と、狭帯域波長の低角度照明により各種欠陥から得られる信号特性の一般的な特性を表1にまとめる。The general characteristics of the signal characteristics according to the wavelength of the reflected light and scattered light from various defects by the wide-angle high-angle illumination and the signal characteristics obtained from the various defects by the narrow-angle low-angle illumination are described above. Put it together.

表1内の明暗の記載は特記ない時は、下地であるウエハ表面から得られる信号強度に比しての明るさの相対値であり、欠陥部とウエハ表面部の信号の差分をとり、差分値が正の場合を明、負の場合を暗とする。また、差分値の絶対値をコントラストとし、コントラストがあらかじめ設定したしきい値以上かどうかでしきい値判定処理する。欠陥の端部領域か内部領域かの区別は、検出した欠陥形状の外周輪郭領域を端部領域、輪郭領域の内部に包含される領域を内部領域とする。なお、微細な欠陥には内部領域が存在しないので、端部領域の情報をもとに分類処理を行う。このように、表1をもとに論理的に判断することにより、各種の欠陥を高い確率で分類することが可能となる。また、一般に素子形成工程のウエハはその処理工程により致命欠陥の種類や大きさが異なる。したがって、致命性の判定しきい値は工程別に欠陥の存在箇所と欠陥の種類別にあらかじめ定めておく。例えば、端面部や面取り部の異物の致命性判定欠陥サイズは表面や裏面の平坦部の判定サイズよりも大きくし、平坦部の金属性の膜残りの致命性判定欠陥サイズは異物やフォトレジストや透明膜残り欠陥の致命性判定サイズよりも小さくする、などにより的確な致命性判定を行うことが可能となる。このように、非致命の欠陥を無視し、検出が必要な欠陥だけを分離検出することにより、検査後の欠陥確認作業が大幅に削減され、さらに不良ウエハと良品ウエハを自動選別することも可能となる。Unless otherwise stated in Table 1, the brightness is a relative value of brightness compared to the signal intensity obtained from the underlying wafer surface, and the difference between the signal of the defective portion and the wafer surface portion is taken as the difference. Light if the value is positive, dark if negative. Further, the absolute value of the difference value is set as contrast, and threshold value determination processing is performed depending on whether the contrast is equal to or higher than a preset threshold value. The distinction between the end region and the internal region of the defect is defined as the outer peripheral contour region of the detected defect shape as the end region and the region included in the contour region as the internal region. In addition, since an internal area does not exist in a fine defect, the classification process is performed based on the information on the edge area. Thus, by logically judging based on Table 1, various defects can be classified with high probability. In general, a wafer in an element formation process has different types and sizes of critical defects depending on the processing process. Therefore, the criticality determination threshold is determined in advance for each defect location and defect type for each process. For example, the criticality determination defect size of the foreign material on the end face portion or the chamfered portion is larger than the determination size of the flat portion on the front surface or the back surface, and the criticality determination defect size of the metal film remaining on the flat portion is the foreign material, photoresist or It becomes possible to make an accurate determination of criticality by making the size smaller than the criticality determination size of the transparent film remaining defect. In this way, by ignoring non-fatal defects and separating and detecting only the defects that need to be detected, the defect confirmation work after inspection is greatly reduced, and it is also possible to automatically sort defective and non-defective wafers. It becomes.

〔画像処理システム構成例〕図9の破線部に囲まれた部分に帯域別画像処理回路10のシステム構成例を示す。撮像素子9のRGB各出力は3本の並列画像処理回路に分離して入力される。本画像処理回路の動作機能をR画像信号の処理回路を例にとって説明する。R画像信号は画像補正回路11にてシェーディング補正、ガンマ変換などを行う。その後信号は分離され、一方が例えばFIFOメモリからなる画像遅延回路12に入力され、予め定められたCCDの走査ライン数信号を遅延させる。この遅延画像出力と遅延させていない信号の差分信号を差分器13でもとめる。差分器13の信号をしきい値レジスタ14の設定値と比較器15で比較して欠陥出力を得る。欠陥出力信号は欠陥メモリ17の制御信号として使用され、本図では省略するが、欠陥部のXY各座標を欠陥メモリ17に入力する。一方、画像遅延回路11の出力と差分器13の出力(差分画像)はさらに画像遅延回路16により遅延させる。これは欠陥出力のタイミングと各画像信号を同期させるためである。画像遅延回路16の出力も欠陥部のXY各座標と同時に欠陥メモリ17に入力する。このことにより、欠陥座標と欠陥部近傍の画像信号および差分画像信号を同時に記録することができる。なお、同様にG信号、B信号も並列に画像処理される。各欠陥メモリ17の内容はCPU18に入力され、欠陥サイズの抽出、欠陥分類および致命性判定を行う。本帯域別画像処理回路10は撮像素子9の出力画像信号を連続でパイプライン処理する高速欠陥検出回路であり、検査の高速化に有効である。撮像素子9としては、一次元ラインセンサによるラインカメラ、二次元のエリアカメラともに本システムで適用可能である。[Image Processing System Configuration Example] A system configuration example of the image processing circuit 10 for each band is shown in a portion surrounded by a broken line in FIG. The RGB outputs of the image sensor 9 are separately input to three parallel image processing circuits. The operation function of the image processing circuit will be described by taking an R image signal processing circuit as an example. The R image signal is subjected to shading correction, gamma conversion and the like by the image correction circuit 11. Thereafter, the signals are separated, and one of them is input to an image delay circuit 12 made of, for example, a FIFO memory, and delays a predetermined CCD scanning line number signal. The difference signal between the delayed image output and the undelayed signal is also stopped by the differencer 13. The signal of the differentiator 13 is compared with the set value of the threshold register 14 by the comparator 15 to obtain a defect output. The defect output signal is used as a control signal for the defect memory 17 and is omitted in this drawing, but the XY coordinates of the defect portion are input to the defect memory 17. On the other hand, the output of the image delay circuit 11 and the output of the differentiator 13 (difference image) are further delayed by the image delay circuit 16. This is for synchronizing the timing of defect output and each image signal. The output of the image delay circuit 16 is also input to the defect memory 17 simultaneously with the XY coordinates of the defective portion. Thus, the defect coordinates, the image signal near the defect portion, and the difference image signal can be recorded simultaneously. Similarly, the G signal and the B signal are processed in parallel. The contents of each defect memory 17 are input to the CPU 18 to perform defect size extraction, defect classification, and criticality determination. This band-by-band image processing circuit 10 is a high-speed defect detection circuit that continuously pipelines the output image signal of the image sensor 9 and is effective in increasing the inspection speed. As the image sensor 9, both a line camera using a one-dimensional line sensor and a two-dimensional area camera can be applied in this system.

発明の効果The invention's effect

以上述べたように、本発明によれば、ウエハ端部に存在する各種欠陥を確度高く検出、分類しさらに致命性の判定を行うことができ、ウエハ端面検査装置の検査効率が大幅に向上し、その結果半導体ウエハの品質向上に大きく貢献できることは明らかである。As described above, according to the present invention, it is possible to detect and classify various defects existing at the wafer edge with high accuracy and to further determine the criticality, thereby greatly improving the inspection efficiency of the wafer edge inspection apparatus. As a result, it is obvious that the quality of the semiconductor wafer can be greatly improved.

産業上の応用分野Industrial application fields

本発明は、半導体ウエハの端部の欠陥検査方法および欠陥検査装置に適用でき、半導体ウエハの製造メーカにおける品質管理、出荷検査、半導体製造メーカにおけるウエハの受入検査、品質管理、不良対策用途などにも適用できる。ウエハの種類としてはシリコンウエハだけでなく、化合物半導体、石英ウエハなどに適用できることは言うまでもない。INDUSTRIAL APPLICABILITY The present invention can be applied to a defect inspection method and a defect inspection apparatus for an edge portion of a semiconductor wafer, and is used for quality control, shipment inspection, wafer acceptance inspection, quality control, defect countermeasure use in a semiconductor manufacturer. Is also applicable. Needless to say, the types of wafers can be applied not only to silicon wafers but also to compound semiconductors and quartz wafers.

本発明における欠陥検出系の説明図である。It is explanatory drawing of the defect detection system in this invention. 半導体ウエハの端部の断面の説明図である。It is explanatory drawing of the cross section of the edge part of a semiconductor wafer. ウエハの断面方向からみた欠陥の種類の説明図であるIt is explanatory drawing of the kind of defect seen from the cross-sectional direction of the wafer. ウエハの断面方向からみた端面の欠陥検査装置の基本構成の説明図である。It is explanatory drawing of the basic composition of the defect inspection apparatus of the end surface seen from the cross section direction of the wafer. ウエハの断面方向からみた異物からの反射光、散乱光の説明図である。It is explanatory drawing of the reflected light and scattered light from the foreign material seen from the cross-sectional direction of the wafer. ウエハの断面方向からみた傷からの反射光、散乱光の説明図である。It is explanatory drawing of the reflected light and the scattered light from the damage | wound seen from the cross-sectional direction of the wafer. ウエハの断面方向からみた細いクラックからの反射光、散乱光の説明図である。It is explanatory drawing of the reflected light from the thin crack seen from the cross-sectional direction of the wafer, and scattered light. ウエハの断面方向からみたフォトレジストや透明、半透明膜残りの欠陥からの反射光、散乱光の説明図である。It is explanatory drawing of the reflected light and scattered light from the photoresist which looked at the cross section direction of the wafer, and the defect of transparent and semi-transparent film | membrane. 帯域別画像処理回路のシステム構成例である。2 is a system configuration example of an image processing circuit for each band.

符号の説明Explanation of symbols

1 半導体ウエハ 2 狭帯域波長照明光源 3 集光レンズ
4 広帯域波長照明光源 5 光学フィルタ 6 ハーフミラー
7 対物レンズ 8 光学フィルタ 9 撮像素子
10 帯域別画像処理回路 11 画像補正回路 12 画像遅延回路
13 差分器 14 しきい値レジスタ 15 比較器
16 画像遅延回路 17 欠陥メモリ 18 CPU
DESCRIPTION OF SYMBOLS 1 Semiconductor wafer 2 Narrow-band wavelength illumination light source 3 Condensing lens 4 Wide-band wavelength illumination light source 5 Optical filter 6 Half mirror 7 Objective lens 8 Optical filter 9 Image sensor 10 Image processing circuit according to zone 11 Image correction circuit 12 Image delay circuit 13 Differentiator 14 Threshold Register 15 Comparator 16 Image Delay Circuit 17 Defective Memory 18 CPU

Claims (4)

光照明手段および光撮像手段を有し半導体ウエハの端面領域の欠陥を検出する検査装置において、前記光照明手段として被検査面に対して低角度で光を照射する照明手段と被検査面に対して光を高角度で照射する手段を具備し、高角度照明により得られた画像信号をもとにした欠陥検出処理と低角度照明により得られた画像信号をもとにした欠陥検出処理を個別に行い、前記各照明により得られる欠陥信号強度の特徴の差異をもとに欠陥分類を行うことを特徴とする、ウエハ端部の欠陥検査方法および欠陥検査装置。In an inspection apparatus having a light illuminating means and a light imaging means for detecting a defect in an end face region of a semiconductor wafer, the illuminating means for irradiating light at a low angle with respect to the surface to be inspected as the light illuminating means and the surface to be inspected In this way, the defect detection process based on the image signal obtained by the high angle illumination and the defect detection process based on the image signal obtained by the low angle illumination are individually provided. And a defect inspection method and a defect inspection apparatus for a wafer edge, wherein the defect classification is performed based on the difference in characteristic of the defect signal intensity obtained by each illumination. 前記、高角度の照明手段と低角度の照明手段の照明光として、異なる帯域の波長を用い、波長帯域別に欠陥検出処理することを特徴とする請求項1記載のウエハ端部の欠陥検査方法および欠陥検査装置。2. The defect inspection method for a wafer edge according to claim 1, wherein a defect detection process is performed for each wavelength band using wavelengths of different bands as illumination light of the high-angle illumination means and the low-angle illumination means. Defect inspection equipment. 前記高角度照明系と画像検出系に各1枚の偏光フィルタを互いの偏光方向を直交する方向に配置することを特徴とする請求項1または請求項2のいずれかに記載のウエハ端部の欠陥検査方法および欠陥検査装置。3. The wafer end portion according to claim 1, wherein one polarization filter is disposed in each of the high-angle illumination system and the image detection system in a direction orthogonal to each other. 4. Defect inspection method and defect inspection apparatus. 前記欠陥の種類の分類結果、欠陥の存在箇所情報および欠陥の寸法をもとに欠陥の致命性判定を行うことを特徴とする請求項1ないし請求項3のいずれかに記載のウエハ端部の欠陥検査方法および欠陥検査装置。4. The wafer end portion according to claim 1, wherein the defect fatality determination is performed based on the classification result of the defect type, defect location information, and defect size. 5. Defect inspection method and defect inspection apparatus.
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013053904A (en) * 2011-09-02 2013-03-21 Fujitsu Semiconductor Ltd Surface inspection method and surface inspection device
CN105277574A (en) * 2014-07-22 2016-01-27 牧德科技股份有限公司 Method for inspection of multiple exposure image mixing using overlapping exposure
JP2016102724A (en) * 2014-11-28 2016-06-02 日立金属株式会社 Appearance inspection method of flat enameled wire and visual inspection apparatus of flat enameled wire
CN108604880A (en) * 2015-10-26 2018-09-28 应用材料公司 Detect the method and system of the gap in solar wafer
JP2018197695A (en) * 2017-05-24 2018-12-13 株式会社カネカ Electronic component exterior appearance inspection method and exterior appearance inspection device
JP2020009924A (en) * 2018-07-09 2020-01-16 株式会社Sumco Silicon wafer inspection method, inspection apparatus, and manufacturing method

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013053904A (en) * 2011-09-02 2013-03-21 Fujitsu Semiconductor Ltd Surface inspection method and surface inspection device
CN105277574A (en) * 2014-07-22 2016-01-27 牧德科技股份有限公司 Method for inspection of multiple exposure image mixing using overlapping exposure
JP2016024185A (en) * 2014-07-22 2016-02-08 牧徳科技股▲ふん▼有限公司 Inspection method of multiple exposure image mixing utilizing overlapping exposure
JP2016102724A (en) * 2014-11-28 2016-06-02 日立金属株式会社 Appearance inspection method of flat enameled wire and visual inspection apparatus of flat enameled wire
CN108604880A (en) * 2015-10-26 2018-09-28 应用材料公司 Detect the method and system of the gap in solar wafer
JP2018197695A (en) * 2017-05-24 2018-12-13 株式会社カネカ Electronic component exterior appearance inspection method and exterior appearance inspection device
JP2020009924A (en) * 2018-07-09 2020-01-16 株式会社Sumco Silicon wafer inspection method, inspection apparatus, and manufacturing method

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