JP3981895B2

JP3981895B2 - Automatic macro inspection device

Info

Publication number: JP3981895B2
Application number: JP23450597A
Authority: JP
Inventors: 俊昭北村
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 1997-08-29
Filing date: 1997-08-29
Publication date: 2007-09-26
Anticipated expiration: 2017-08-29
Also published as: JPH1172443A

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶製造用ガラス基板や、ＩＣ製造用のウエハ等の表面検査を行う装置に関し、特に、いわゆるマクロ検査と称される被検査物の表面全体の検査を行う装置に関する。
【０００２】
【従来の技術】
液晶製造用ガラス基板や、ＩＣ製造用のウエハ等（以下、これらを被検査物とも称する）の表面のマクロ検査は、基板、ウエハ等の表面のキズ、レジスト塗布むら、フォトリソグラフィー工程における欠陥などを、被検査物の表面全体を観察して検査を行うものである。従来のマクロ検査は、スポットライト状の白色拡散光源を用いて、被検査物を回転させながら検査員が目視判断して検査していた。
【０００３】
しかしながら、検査員による目視検査では、検査員毎の技術レベル差、および検査員の体調等による検査レベルのばらつきがあり、安定した検査結果が得にくい、効率が良くない等という問題がある。また、液晶製造用ガラス基板、ＩＣ製造用のウエハ等の製造に際しては微細な異物の付着等による表面汚染を避けなければならいなので、発塵要因となる人間による検査工程はできるかぎり避けるべきである。
【０００４】
このようなことから、マクロ検査工程を自動化することが提案されており、このようなものとして、特公平６−８７８９号公報に開示の装置がある。この装置では、ウエハ表面に光を照射し、この表面からの反射光をＩＴＶカメラで受光して、被検査物の表面全体の反射光画像を取得し、このようして得られた反射光画像を予め測定した正常検査物の反射光画像と比較する画像処理を行って被検査物のマクロ検査を行うようになっている。この装置においては、ウエハ表面に対する光の照射角度を種々変更して検査できるように、ＩＴＶカメラは固定したままで、ウエハ表面角度および照明角度を可変設定できるようになっている。
【０００５】
【発明が解決しようとする課題】
しかしながら、このような自動マクロ検査装置の場合には、ウエハ表面角度および照明角度を可変設定させる機構が必要であり、このような機構の作動に際して可動部分からの発塵が生じて被検査物表面を汚染する可能性があるという問題がある。なお、上記公報に開示の装置は、被検査物の表面から直接反射される光を用いてマクロ検査を行うようになっており、被検査物表面への照射光の入射角度と反射光の反射角度が等しくなる位置にカメラが配設される。
【０００６】
しかし、最近においては、被検査物の表面の繰り返しパターンに応じて発生する回折光や、散乱光等を検査対象とすることが考えられている。このような場合には、検査対象となる反射光の反射角度は、被検査物のパターンピッチ等に応じて変化するため、これら各種の角度に対応できるように、照明装置の照明角度、撮像カメラの受光角度を調整する必要がある。このため、この場合にも角度調整機構が必要であり、この機構からの発塵による被検査物表面の汚染等が問題となる。
【０００７】
本発明はこのような問題に鑑みたもので、照明角度、被検査物の表面角度、受光装置もしくは撮像装置の受光角度等を可変調整することなく、すなわち、照明装置、撮像装置等を固定したまま、さまざまな被検査物のマクロ検査を効率よく行うことができるような自動マクロ検査装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
このような目的達成のため、本発明に係る自動マクロ検査装置は、被検査物に対して第１の所定角度で固定配設され、被検査物の被検査面に向かってほぼ平行な光束を有した照明光を照射する照明装置と、被検査物に対して第２の所定角度で固定配設され、被検査物から照明光の照射により発生する回折光を受光して被検査物の像を撮像する撮像手段と、この撮像手段により得られた画像信号を取り込み、画像処理を行って被検査物のマクロ検査を行う画像処理手段と、照明装置からの照明光の波長を、照明装置が第１の所定角度で固定配設され、且つ、撮像手段が第２の所定角度で固定配設された状態で回折光が撮像手段に入射する波長に設定する照明波長設定手段とを備えて構成される。
【０００９】
このような構成の自動マクロ検査装置の場合には、照明波長設定手段により照明光の波長を設定することができるので、被検査物から射出される回折光の方向を撮像手段の受光方向に合致するように波長を設定すれば、効率の良いマクロ検査が行える。このため、このマクロ検査装置の場合には、照明装置および撮像手段を固定することができ、従来の装置のようにこれらの向きを変える可動機構が不要であるので、余計な発塵源がなくなり、被検査物の汚染が抑えられる。
【００１０】
なお、照明装置を、拡散光源およびこれからの光をほぼ平行な光速に変換する平行変換手段から構成するのが好ましく、この場合、平行変換手段を、拡散光源が焦点位置になるようにして配設された凹面鏡から構成するのが好ましい。このように凹面鏡を用いることにより白色光を用いた照明の場合でも色収差発生の問題がなくなる。また、同様な理由から、撮像手段を、被検査物からの回折光を収束させる凹面鏡と、この凹面鏡により収束された光から被検査物の像を撮影するカメラ手段とから構成するのが好ましい。さらに、照明装置が、被検査物の被検査面全体を同時に照明可能に構成するのが好ましく、これにより被検査物の被検査面全体を一度に照明して検査することができるため、効率の良いマクロ検査が可能となる。
【００１１】
また、照明装置を、ライン状の拡散光源と、このライン状拡散光源のラインに沿って対向配設されたシリンドリカルレンズとから構成することもでき、この場合には、シリンドリカルレンズによりライン状拡散光源からの光を少なくとも一方向にほぼ平行となる光束を作り出して被検査物を照明する。
【００１２】
ここで、照明波長設定手段による波長設定は、次のようにして行われる。すなわち、上記第１の所定角度が被検査物の表面に直角な線に対して角度θiであり、上記第２の所定角度が前記被検査物の表面に直角な線に対して角度θdであるときに、照明光の波長λが、次式（１）を満足するように設定される。
【００１３】
【数１】

【００１４】
このように照明光の波長λを設定すれば、撮像手段により効率良くｎ次の回折光を捉えて、この回折光を用いたマクロ検査を効率良く行うことができる。
【００１８】
【発明の実施の形態】
以下、本発明の好ましい実施形態について説明する。図１に本発明に係る自動マクロ検査装置の第１の実施例に係る概略構成を示しており、この装置は、ウエハ（被検査物）３の表面に平行光束の照明光を照射する照明光学系１００と、ウエハ３からの回折光、散乱光等を受光する受光系１０１と、撮像素子（撮像カメラ）６と、画像処理装置７とから構成される。
【００１９】
照明光学系１００は、光源部１と凹面鏡２によって構成される。光源部１は凹面鏡２の焦点位置に配設されており、光源部１からの拡散光は凹面鏡２により平行光束に変換されてウエハ３に向かって照射される。このとき凹面鏡２はウエハ３の全面を照明可能な口径を有し、平行光束の照明光によりウエハ３の全面が同時に照明される。光源部１は白色光源であるハロゲンランプと、照明波長域を制限する干渉フィルタとを有する。この干渉フィルタは所定の波長域の光を透過するバンドパスフィルタとして機能し、異なる波長域の光を透過させる複数の干渉フィルタを外部から手動ないし遠隔操作により切り替え、光源部１から照射される光の波長選択が可能となっている。
【００２０】
受光系１０１は、上記のようにしてウエハ３に照射されたときにウエハ３から発生する回折光もしくは散乱光を受光するもので、ウエハ３の全面からの回折光もしくは散乱光を取り込むに十分な口径を有した凹面鏡４と、この凹面鏡４に入射して集光された光を結像させる受光レンズ５とを有する。このとき受光レンズ５は撮像素子６に結像させるようになっており、撮像素子６によりウエハ３の回折光もしくは散乱光の像が撮影される。
【００２１】
このようにして撮像素子６により撮影されたウエハの像は、画像処理装置７に送られ、ここに予め撮影されて記憶されている正常ウエハの像と比較して、表面欠陥検査等のマクロ検査が行われる。
【００２２】
この例においては、光源部１は凹面鏡の前側焦点位置付近に配設され、ウエハ３は凹面鏡４の後側焦点面付近に配設されており、これにより、凹面反射鏡を用いた反射型のテレセントリック光学系としている。このように光学系に凹面鏡を用いているために色収差の問題がなく、精度の高い検査が可能である。
【００２３】
このような構成の自動マクロ検査装置を用いてウエハ３のマクロ検査を行う例を説明する。まず、図示しない搬送機構により図２に示す検査位置にウエハ３が搬送される。そして、上記のような配置に対応するとともに検査の種類に対応して光源部１の干渉フィルタを選択する。この例では、照明光学系１００および受光系１０１は固定配設されており、照明光学系１００からウエハ３への照明光の入射角度は常に一定であり、且つ受光系１０１へ入射される回折光の回折角度も常に一定であるため、所望の検査光が受光系１０１に入射するように干渉フィルタの選択を行うものである。
【００２４】
この点について図３および図４を参照して詳しく説明する。図３に示すように、ウエハ３の表面に基本ピッチｐで繰り返しパターンが設けられている場合には、照明光の入射角度θｉと、回折光の射出角度θｄとの関係は、次式（４）のようになる。
【００２５】
【数３】

【００２６】
このため、ウエハ３に対して、入射角度が角度θｉとなる方向から平行光束照明が行われるように照明光学系１００を配設し、回折光の反射角度θｄに対向して凹面鏡４が位置するように受光系１０１を配設すると、照明光の波長がλのときに、受光系１０１によりｎ次の回折光を最も効率よく受光できることがわかる。本例では、照明光学系１００および受光系１０１を固定配設しており、その配設位置に対して、ｎ次の回折光が最も効率良く受光系１０１により受光されるような波長λとなるように干渉フィルタが選択される。
【００２７】
一方、受光系１０１により散乱光を受光してマクロ検査を行う場合もある。この場合には、図４に示すように、ｎ次の回折光の射出角度θｄ’と、（ｎ＋１）次の回折光の射出角度θｄ”との間の位置に、受光系１０１の凹面鏡４が位置するように、照明光の波長λが設定される。具体的には、ｎ次の回折光の射出角度θｄ’は次式（５）で決まり、（ｎ＋１）次の回折光の射出角度θｄ”は次式（６）で決まるため、受光系１０１の凹面鏡４に入射する回折光の角度θｄが、 θｄ’＜θｄ＜θｄ” となるような照明光の波長λが照明波長設定手段により設定される。
【００２８】
【数４】
（ｓｉｎθi − ｓｉｎθd’）＝ｎ・λ／ｐ・・・（５）
（ｓｉｎθi − ｓｉｎθd”）＝（ｎ＋１）・λ／ｐ・・・（６）
【００２９】
上記のように波長λの選択を行うと、この波長の照明光がウエハ３に照射されたときに、図４に示すように、ｎ次の回折光は角度θｄ’の方向に射出され、（ｎ＋１）次の回折光はθｄ”の方向に射出され、これらの間に受光系１０１の凹面鏡４が位置するため、受光系１０１には回折光は入射せず、散乱光のみが受光され、散乱光を用いた効率の良いマクロ検査が行われる。
【００３０】
ここで元に戻って、上記のようにして受光系１０１により受光された回折光もしくは散乱光は、凹面鏡４により受光レンズ５に集光されるとともに受光レンズ４により撮像素子６の上に結像される。このようにして撮像素子６により撮影された画像情報は、画像処理装置６に送られ、正常ウエハの画像と対比されてマクロ検査が自動的に行われる。
【００３１】
なお、ウエハ３を検査位置で支持する装置に回転支持機構を設け、ウエハ３の回転位置調整を行えるようにしても良い。このようにした場合、ウエハ３のパターン方向、キズ欠陥等のように、照明光と、回折光強度、散乱光の発生方向が回転位置に応じて異なるときに、ウエハ３を回転させて最も検査効率の良い方向に設定することができる。
【００３２】
なお、上記実施例では、凹面鏡を用いたが、これに変えて反射型のフレネルゾーンプレートを用いても良い。さらに、レンズを用いた屈折光学系で色収差補正を行ったものを用いることもできる。
【００３３】
次に、本発明に係る自動マクロ検査装置の第２の実施例について図２を参照して説明する。なお、この例の装置において、上記第１の実施例の装置と同一部分には同一の符号を付して説明する。この装置は、照明光学系１０２、受光系１０１、撮像素子６および画像処理装置７から構成され、照明光学系１０２のみが第１の実施例の装置と異なるだけである。
【００３４】
照明光学系１０２は、光源部１０と、光ファイバ送光系１１およびシリンドリカルレンズ１２によって構成され、ウエハ３の全面を照明可能な光束をウエハ３に照射する。光源部１０は白色光源光であるハロゲンランプと、照明波長域を制限する干渉フィルタとからなる。これについては、第１の実施例と同一構成である。
【００３５】
光ファイバ送光系１１は、一端側（入射端）が光源部１０に対向して光源部１０からの照明光を受光し、他端側（出射端）は一次元のライン状に配列されて構成されている。このため、光ファイバ送光系１１の他端側からの射出光束は、図２の紙面と平行な面内では角度θの広がり角度を持つ拡散光であり、紙面に垂直な方向へのファイバのライン長分の奥行きを持つ光源となる。
【００３６】
この光ファイバ送光系１１の他端は、シリンドリカルレンズ１２の後側焦点となる位置に位置しており、光ファイバ送光系１１の他端側から射出された拡散光はシリンドリカルレンズ１２により紙面に平行な面内では平行光束に近い光束に変換される。これにより、少なくとも図２の紙面に平行な面内では上記第１実施例で示したテレセントリック光学系と同等な平行光束がウエハ３の全面に照射される。
【００３７】
このようにウエハ３に照明光が照射されると、これにより生じる回折光もしくは散乱光が受光系１０１により受光され、撮像素子６により撮像され、画像処理装置７において画像処理がなされてマクロ検査が行われるのであるが、これについては第１実施例と同じなのでその説明は省略する。
【００３８】
このような構成のマクロ検査装置の場合には、照明光学系の構成が小型、コンパクト化でき、且つ低コスト化できる。
【００３９】
なお、上記第１および第２実施例において、光源部を、白色光源と分光器を組み合わせて構成することも可能である。
【００４０】
【発明の効果】
以上説明したように、本発明によれば、第１の所定角度で固定配設された照明装置と、第２の所定角度で固定配設されて回折光による検査物の像を撮像する撮像手段と、この撮像手段により得られた画像から被検査物のマクロ検査を行う画像処理手段とを有し、さらに、証明波長設定手段により照明光の波長を可変設定できるように構成されているので、被検査物から射出される回折光の方向を撮像手段の受光方向に合致するように波長を設定すれば、効率の良いマクロ検査が行える。このため、このマクロ検査装置の場合には、照明装置および撮像手段を固定することができ、従来の装置のようにこれらの向きを変える可動機構が不要であり、余計な発塵源がなくなり、被検査物の汚染が抑えられる。
【００４１】
なお、照明装置を、拡散光源およびこれからの光をほぼ平行な光束に変換する平行変換手段から構成するのが好ましく、この場合、平行変換手段を、拡散光源が焦点位置になるようにして配設された凹面鏡から構成するのが好ましい。このように凹面鏡を用いることにより白色光を用いた照明の場合でも色収差発生の問題がなくなる。また、同様な理由から、撮像手段を、被検査物からの回折光もしくは散乱光を収束させる凹面鏡と、この凹面鏡により収束された光から被検査物の像を撮影するカメラ手段とから構成するのが好ましい。
【００４２】
また、照明装置を、ライン状の拡散光源と、このライン状拡散光源のラインに沿って対向配設されたシリンドリカルレンズとから構成することもでき、この場合には、シリンドリカルレンズによりライン状拡散光源からの光を少なくとも一方向にほぼ平行となる光束を作り出して被検査物を照明する。このようにすれば、照明装置を小型、コンパクト化して、低コスト化を図ることができる。
【００４３】
なお、回折光を用いたマクロ検査を行うときには、照明波長設定手段による波長設定は、前述の式（１）を満足するようになされる。この式（１）は回折光が受光系（撮像手段）の方に射出されるための条件であり、これにより、撮像手段により効率良くｎ次の回折光を捉えて、この回折光を用いたマクロ検査を効率良く行うことができる。
【図面の簡単な説明】
【図１】本発明の第１実施例に係る自動マクロ検査装置を示す概略図である。
【図２】本発明の第２実施例に係る自動マクロ検査装置を示す概略図である。
【図３】ウエハに照射される照明光と回折光との関係を示す説明図である。
【図４】ウエハに照射される照明光とｎ次および（ｎ＋１）次の回折光と受光系の凹面鏡位置との関係を示す説明図である。
【符号の説明】
１，１０光源部
２，４凹面鏡
３ウエハ
５受光レンズ
６撮像素子
７画像処理装置
１１光ファイバ送光系
１２シリンドリカルレンズ
１００，１０２照明光学系
１０１受光系[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for inspecting the surface of a glass substrate for liquid crystal production, a wafer for IC production, and the like, and more particularly, to an apparatus for inspecting the entire surface of an object to be inspected called so-called macro inspection.
[0002]
[Prior art]
Macro inspection of the surface of glass substrates for liquid crystal production, wafers for IC production, etc. (hereinafter also referred to as inspected objects), surface scratches on substrates, wafers, etc., resist coating unevenness, defects in the photolithography process, etc. Are inspected by observing the entire surface of the object to be inspected. In the conventional macro inspection, a spotlight-like white diffused light source is used to inspect the visual inspection by an inspector while rotating the inspection object.
[0003]
However, the visual inspection by the inspector has a problem in that there is a difference in the inspection level depending on the technical level of each inspector and the physical condition of the inspector, and it is difficult to obtain a stable inspection result and the efficiency is not good. In addition, when manufacturing glass substrates for liquid crystal manufacturing, wafers for IC manufacturing, etc., surface contamination due to the attachment of fine foreign matters must be avoided, so inspection processes by humans that cause dust generation should be avoided as much as possible. .
[0004]
For this reason, it has been proposed to automate the macro inspection process. As such, there is an apparatus disclosed in Japanese Patent Publication No. 6-8789. In this apparatus, the wafer surface is irradiated with light, reflected light from the surface is received by an ITV camera, a reflected light image of the entire surface of the object to be inspected is obtained, and the reflected light image thus obtained is obtained. Is subjected to image processing for comparison with a reflected light image of a normal inspection object, which has been measured in advance, to perform a macro inspection of the inspection object. In this apparatus, the wafer surface angle and the illumination angle can be variably set while the ITV camera remains fixed so that the inspection can be performed by changing the irradiation angle of light on the wafer surface.
[0005]
[Problems to be solved by the invention]
However, in the case of such an automatic macro inspection apparatus, a mechanism for variably setting the wafer surface angle and the illumination angle is required, and when such a mechanism is operated, dust is generated from the movable part and the surface of the object to be inspected. There is a problem that it may contaminate. Note that the apparatus disclosed in the above publication performs a macro inspection using light directly reflected from the surface of the object to be inspected, and the incident angle of the irradiation light on the surface of the object to be inspected and the reflection of the reflected light. Cameras are arranged at positions where the angles are equal.
[0006]
However, recently, it has been considered to use diffracted light, scattered light, or the like generated according to a repetitive pattern on the surface of the object to be inspected. In such a case, since the reflection angle of the reflected light to be inspected changes according to the pattern pitch of the object to be inspected, the illumination angle of the illuminating device, the imaging camera so as to be able to cope with these various angles. It is necessary to adjust the light receiving angle. For this reason, also in this case, an angle adjusting mechanism is necessary, and contamination of the surface of the object to be inspected due to dust generation from this mechanism becomes a problem.
[0007]
The present invention has been made in view of such a problem, and without variably adjusting the illumination angle, the surface angle of the inspection object, the light receiving angle of the light receiving device or the imaging device, that is, the lighting device, the imaging device, etc. are fixed. An object of the present invention is to provide an automatic macro inspection apparatus that can efficiently perform macro inspection of various inspection objects.
[0008]
[Means for Solving the Problems]
In order to achieve such an object, the automatic macro inspection apparatus according to the present invention is fixedly disposed at a first predetermined angle with respect to the inspection object, and emits a substantially parallel light beam toward the inspection surface of the inspection object. An illuminating device for irradiating the illuminating light and an object to be inspected and fixedly arranged at a second predetermined angle with respect to the object to be inspected, and receiving the diffracted light generated by the illumination light irradiation from the object to be inspected. An illuminating device that captures the wavelength of illumination light from an illuminating device, an image processing unit that captures an image signal obtained by the imaging unit, performs image processing, and performs macro processing of the inspection object. fixed arranged at a first predetermined angle, and, with an illumination wavelength setting means imaging means diffracted light while being fixed arranged at a second predetermined angle is set to wavelength incident on the image pickup means Composed.
[0009]
In the case of the automatic macro inspection apparatus having such a configuration, the wavelength of the illumination light can be set by the illumination wavelength setting means, so that the direction of the diffracted light emitted from the inspection object matches the light receiving direction of the imaging means. If the wavelength is set in such a way, efficient macro inspection can be performed. For this reason, in the case of this macro inspection device, the illumination device and the imaging means can be fixed, and there is no need for a movable mechanism that changes their orientation as in the conventional device, so there is no extra dust generation source. , Contamination of the inspection object is suppressed.
[0010]
The illuminating device is preferably composed of a diffusion light source and parallel conversion means for converting light from the light source into a substantially parallel light speed. In this case, the parallel conversion means is arranged so that the diffusion light source is at the focal position. It is preferable that the concave mirror is formed. By using a concave mirror in this way, the problem of chromatic aberration is eliminated even in the case of illumination using white light. For the same reason, the imaging means is preferably composed of a concave mirror for converging diffracted light from the object to be inspected and camera means for taking an image of the object to be inspected from the light converged by the concave mirror. Furthermore, it is preferable that the illumination device is configured to be able to illuminate the entire inspection surface of the inspection object at the same time. This enables the entire inspection surface of the inspection object to be illuminated and inspected at a time. Good macro inspection is possible.
[0011]
In addition, the illumination device can also be composed of a line-shaped diffused light source and a cylindrical lens arranged oppositely along the line of the line-shaped diffused light source. In this case, the line-shaped diffused light source is formed by the cylindrical lens. A light beam that is substantially parallel to at least one direction is emitted from the light from the light to illuminate the object to be inspected.
[0012]
Here, the wavelength setting by the illumination wavelength setting means is performed as follows. That is, the first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the inspection object, and the second predetermined angle is an angle θd with respect to a line perpendicular to the surface of the inspection object. Sometimes, the wavelength λ of the illumination light is set so as to satisfy the following expression (1).
[0013]
[Expression 1]

[0014]
If the wavelength λ of the illumination light is set in this way, it is possible to efficiently capture the nth-order diffracted light by the image pickup means and perform a macro inspection using this diffracted light efficiently.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 shows a schematic configuration according to a first embodiment of an automatic macro inspection apparatus according to the present invention. This apparatus illuminates the surface of a wafer (inspected object) 3 with illumination light of a parallel light beam. The system 100 includes a light receiving system 101 that receives diffracted light, scattered light, and the like from the wafer 3, an image sensor (imaging camera) 6, and an image processing device 7.
[0019]
The illumination optical system 100 includes a light source unit 1 and a concave mirror 2. The light source unit 1 is disposed at the focal position of the concave mirror 2, and the diffused light from the light source unit 1 is converted into a parallel light beam by the concave mirror 2 and irradiated onto the wafer 3. At this time, the concave mirror 2 has a diameter capable of illuminating the entire surface of the wafer 3, and the entire surface of the wafer 3 is simultaneously illuminated by the illumination light of the parallel light flux. The light source unit 1 includes a halogen lamp that is a white light source and an interference filter that limits the illumination wavelength range. This interference filter functions as a bandpass filter that transmits light of a predetermined wavelength range, and switches a plurality of interference filters that transmit light of different wavelength ranges from the outside by manual or remote operation, and is emitted from the light source unit 1 Wavelength selection is possible.
[0020]
The light receiving system 101 receives diffracted light or scattered light generated from the wafer 3 when irradiated on the wafer 3 as described above, and is sufficient to capture diffracted light or scattered light from the entire surface of the wafer 3. It has a concave mirror 4 having a diameter and a light receiving lens 5 that forms an image of light that has entered the concave mirror 4 and is condensed. At this time, the light receiving lens 5 forms an image on the image sensor 6, and the image of the diffracted light or scattered light of the wafer 3 is taken by the image sensor 6.
[0021]
The wafer image photographed by the image pickup device 6 in this way is sent to the image processing apparatus 7, and compared with the normal wafer image photographed and stored in advance here, a macro inspection such as a surface defect inspection is performed. Is done.
[0022]
In this example, the light source unit 1 is disposed in the vicinity of the front focal position of the concave mirror, and the wafer 3 is disposed in the vicinity of the rear focal plane of the concave mirror 4, whereby a reflective type using a concave reflector is used. It is a telecentric optical system. As described above, since the concave mirror is used in the optical system, there is no problem of chromatic aberration, and high-precision inspection is possible.
[0023]
An example of performing a macro inspection of the wafer 3 using the automatic macro inspection apparatus having such a configuration will be described. First, the wafer 3 is transferred to the inspection position shown in FIG. 2 by a transfer mechanism (not shown). Then, the interference filter of the light source unit 1 is selected corresponding to the above arrangement and corresponding to the type of inspection. In this example, the illumination optical system 100 and the light receiving system 101 are fixedly arranged, and the incident angle of the illumination light from the illumination optical system 100 to the wafer 3 is always constant, and the diffracted light incident on the light receiving system 101. Since the diffraction angle is always constant, the interference filter is selected so that desired inspection light enters the light receiving system 101.
[0024]
This point will be described in detail with reference to FIG. 3 and FIG. As shown in FIG. 3, when a repetitive pattern is provided at the basic pitch p on the surface of the wafer 3, the relationship between the incident angle θi of the illumination light and the emission angle θd of the diffracted light is expressed by the following equation (4 )become that way.
[0025]
[Equation 3]

[0026]
For this reason, the illumination optical system 100 is arranged so that the parallel beam illumination is performed on the wafer 3 from the direction in which the incident angle is the angle θi, and the concave mirror 4 is positioned facing the reflection angle θd of the diffracted light. When the light receiving system 101 is arranged as described above, it can be seen that the nth-order diffracted light can be received most efficiently by the light receiving system 101 when the wavelength of the illumination light is λ. In this example, the illumination optical system 100 and the light receiving system 101 are fixedly arranged, and the wavelength λ is such that the nth-order diffracted light is most efficiently received by the light receiving system 101 with respect to the arrangement position. The interference filter is selected as follows.
[0027]
On the other hand, scattered light is received by the light receiving system 101 to perform a macro inspection. In this case, as shown in FIG. 4, the concave mirror 4 of the light receiving system 101 is located at a position between the exit angle θd ′ of the nth-order diffracted light and the exit angle θd ″ of the (n + 1) th-order diffracted light. The wavelength λ of the illumination light is set so as to be positioned, specifically, the exit angle θd ′ of the nth-order diffracted light is determined by the following equation (5), and the exit angle θd of the (n + 1) th-order diffracted light. Since “is determined by the following equation (6), the wavelength λ of the illumination light is set by the illumination wavelength setting means so that the angle θd of the diffracted light incident on the concave mirror 4 of the light receiving system 101 satisfies θd ′ <θd <θd”. Is done.
[0028]
[Expression 4]
(Sin θi−sin θd ′) = n · λ / p (5)
(Sin θi−sin θd ″) = (n + 1) · λ / p (6)
[0029]
When the wavelength λ is selected as described above, when the illumination light of this wavelength is irradiated onto the wafer 3, as shown in FIG. 4, the nth-order diffracted light is emitted in the direction of the angle θd ′, n + 1) The next diffracted light is emitted in the direction of θd ″, and the concave mirror 4 of the light receiving system 101 is positioned between them. Therefore, no diffracted light is incident on the light receiving system 101 and only scattered light is received and scattered. Efficient macro inspection using light is performed.
[0030]
Here, returning to the original, the diffracted light or scattered light received by the light receiving system 101 as described above is condensed on the light receiving lens 5 by the concave mirror 4 and imaged on the image sensor 6 by the light receiving lens 4. Is done. The image information photographed by the image sensor 6 in this way is sent to the image processing device 6, and a macro inspection is automatically performed in comparison with an image of a normal wafer.
[0031]
Note that a rotation support mechanism may be provided in the apparatus that supports the wafer 3 at the inspection position so that the rotation position of the wafer 3 can be adjusted. In such a case, when the illumination light, the diffracted light intensity, and the generation direction of the scattered light are different depending on the rotation position, such as the pattern direction of the wafer 3 and a flaw defect, the wafer 3 is rotated for the most inspection. It can be set in an efficient direction.
[0032]
In the above embodiment, the concave mirror is used, but a reflective Fresnel zone plate may be used instead. Further, it is also possible to use a refracting optical system that uses a lens and has been subjected to chromatic aberration correction.
[0033]
Next, a second embodiment of the automatic macro inspection apparatus according to the present invention will be described with reference to FIG. In the apparatus of this example, the same parts as those of the apparatus of the first embodiment are denoted by the same reference numerals. This apparatus includes an illumination optical system 102, a light receiving system 101, an image sensor 6, and an image processing apparatus 7. Only the illumination optical system 102 is different from the apparatus of the first embodiment.
[0034]
The illumination optical system 102 includes a light source unit 10, an optical fiber transmission system 11, and a cylindrical lens 12, and irradiates the wafer 3 with a light beam that can illuminate the entire surface of the wafer 3. The light source unit 10 includes a halogen lamp that is white light source light and an interference filter that limits the illumination wavelength range. This is the same configuration as in the first embodiment.
[0035]
In the optical fiber transmission system 11, one end side (incident end) faces the light source unit 10 to receive illumination light from the light source unit 10, and the other end side (outgoing end) is arranged in a one-dimensional line. It is configured. For this reason, the light beam emitted from the other end of the optical fiber transmission system 11 is diffused light having a spread angle of an angle θ in a plane parallel to the paper surface of FIG. 2, and the fiber in a direction perpendicular to the paper surface. The light source has a depth equivalent to the line length.
[0036]
The other end of the optical fiber transmission system 11 is located at a position that becomes the rear focal point of the cylindrical lens 12, and the diffused light emitted from the other end side of the optical fiber transmission system 11 is made by the cylindrical lens 12 on the paper surface. Is converted into a light beam close to a parallel light beam. Thereby, at least in the plane parallel to the paper surface of FIG. 2, the entire surface of the wafer 3 is irradiated with a parallel light beam equivalent to the telecentric optical system shown in the first embodiment.
[0037]
When the illumination light is irradiated onto the wafer 3 in this way, the diffracted light or scattered light generated thereby is received by the light receiving system 101, picked up by the image pickup device 6, and subjected to image processing in the image processing device 7 for macro inspection. Although this is done, since this is the same as in the first embodiment, its description is omitted.
[0038]
In the case of the macro inspection apparatus having such a configuration, the configuration of the illumination optical system can be reduced in size and size, and the cost can be reduced.
[0039]
In the first and second embodiments, the light source unit can be configured by combining a white light source and a spectroscope.
[0040]
【The invention's effect】
As described above, according to the present invention, an imaging for imaging an illumination device fixed arranged at a first predetermined angle, an image of the inspected object by a fixed arranged has been diffracted light at a second predetermined angle And an image processing means for performing a macro inspection of the inspection object from the image obtained by the imaging means, and further, the wavelength of the illumination light can be variably set by the certification wavelength setting means. If the wavelength is set so that the direction of the diffracted light emitted from the inspection object matches the light receiving direction of the imaging means, an efficient macro inspection can be performed. For this reason, in the case of this macro inspection apparatus, it is possible to fix the illumination device and the imaging means, and there is no need for a movable mechanism that changes their orientation as in the conventional apparatus, and there is no extra dust generation source, Contamination of the inspection object is suppressed.
[0041]
The illuminating device is preferably composed of a diffusion light source and parallel conversion means for converting the light from the light into a substantially parallel light beam. In this case, the parallel conversion means is arranged so that the diffusion light source is at the focal position. It is preferable that the concave mirror is formed. By using a concave mirror in this way, the problem of chromatic aberration is eliminated even in the case of illumination using white light. For the same reason, the imaging means is composed of a concave mirror for converging diffracted light or scattered light from the object to be inspected, and camera means for taking an image of the object to be inspected from the light converged by the concave mirror. Is preferred.
[0042]
In addition, the illumination device can also be composed of a line-shaped diffused light source and a cylindrical lens arranged oppositely along the line of the line-shaped diffused light source. In this case, the line-shaped diffused light source is formed by the cylindrical lens. A light beam that is substantially parallel to at least one direction is emitted from the light from the light to illuminate the object to be inspected. In this way, it is possible to reduce the cost by reducing the size and size of the lighting device.
[0043]
When performing a macro inspection using diffracted light, the wavelength setting by the illumination wavelength setting means is made to satisfy the above-described equation (1). This equation (1) is a condition for the diffracted light to be emitted toward the light receiving system (imaging means). With this, the n-th order diffracted light is efficiently captured by the imaging means, and this diffracted light is used. Macro inspection can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an automatic macro inspection apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic view showing an automatic macro inspection apparatus according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a relationship between illumination light and diffracted light irradiated on a wafer.
FIG. 4 is an explanatory diagram showing a relationship between illumination light irradiated on a wafer, n-order and (n + 1) -order diffracted light, and a concave mirror position of a light receiving system.
[Explanation of symbols]
DESCRIPTION OF

SYMBOLS

1,10 Light source part 2,4 Concave mirror 3 Wafer 5 Light receiving lens 6 Image pick-up element 7 Image processing apparatus 11 Optical fiber light transmission system 12

Cylindrical lenses

100, 102 Illumination optical system 101 Light receiving system

Claims

An illuminating device that is fixedly disposed facing the object to be inspected at a first predetermined angle and that emits illumination light having a substantially parallel light beam toward the surface to be inspected of the object;
Imaging that is fixedly disposed opposite to the inspection object at a second predetermined angle and that receives diffracted light generated by irradiation of the illumination light from the inspection object and captures an image of the inspection object Means,
Image processing means for capturing an image signal obtained by the imaging means, performing image processing, and performing macro inspection of the inspection object; and
The wavelength of the illuminating light from the illuminating device is diffracted in a state where the illuminating device is fixedly disposed at the first predetermined angle and the imaging means is fixedly disposed at the second predetermined angle. automatic macro inspection apparatus characterized by light is an illumination wavelength setting means for setting the wavelength incident on the imaging means.

2. The automatic macro inspection apparatus according to claim 1, wherein the illuminating device includes a diffusing light source and parallel conversion means for converting light from the diffusing light source into a substantially parallel light beam.

The automatic macro inspection apparatus according to claim 2, wherein the parallel conversion unit includes a concave mirror disposed so that the diffused light source is in a focal position.

Said imaging means comprises a said concave mirror for converging the diffracted light from the object to be inspected, said by forming an image of converged said diffracted light or al the inspection object by the concave mirror and the camera means for capturing The automatic macro inspection apparatus according to any one of claims 1 to 3.

5. The automatic macro inspection apparatus according to claim 1, wherein the illumination apparatus can simultaneously illuminate the entire inspection surface of the inspection object.

The illuminating device includes a line-shaped diffused light source and a cylindrical lens disposed so as to face the line-shaped diffused light source. The automatic macro inspection apparatus according to claim 1, wherein a light beam that is substantially parallel to a direction is generated to illuminate the inspection object.

When the first predetermined angle is an angle θi with respect to a line perpendicular to the surface of the inspection object, and the second predetermined angle is an angle θd with respect to a line perpendicular to the surface of the inspection object Further, the wavelength λ of the illumination light set by the illumination wavelength setting means is expressed by the following equation (sin θi−sin θd) = n · λ / p
Where n is the order of the diffracted light to be imaged
The automatic macro inspection apparatus according to claim 1, wherein p is set so as to satisfy a pattern pitch on the surface of the inspection object.