JPH07248203A - Laser scanning microscope having combined measuring function - Google Patents

Laser scanning microscope having combined measuring function

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Publication number
JPH07248203A
JPH07248203A JP3839094A JP3839094A JPH07248203A JP H07248203 A JPH07248203 A JP H07248203A JP 3839094 A JP3839094 A JP 3839094A JP 3839094 A JP3839094 A JP 3839094A JP H07248203 A JPH07248203 A JP H07248203A
Authority
JP
Japan
Prior art keywords
light
reflected light
reflected
beam splitter
function
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
JP3839094A
Other languages
Japanese (ja)
Other versions
JP3411364B2 (en
Inventor
Hiroo Fujita
宏夫 藤田
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.)
Citizen Watch Co Ltd
Original Assignee
Citizen Watch Co Ltd
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Filing date
Publication date
Application filed by Citizen Watch Co Ltd filed Critical Citizen Watch Co Ltd
Priority to JP03839094A priority Critical patent/JP3411364B2/en
Publication of JPH07248203A publication Critical patent/JPH07248203A/en
Application granted granted Critical
Publication of JP3411364B2 publication Critical patent/JP3411364B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Instruments For Measurement Of Length By Optical Means (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Microscoopes, Condenser (AREA)

Abstract

PURPOSE:To obtain a microscope having combined measuring functions capable of confocal detection and non-confocal detection etc., by detecting reflection light from a measuring object with two light receivers placed in different positions and in different forms. CONSTITUTION:An X-direction scanner 12 and a Y-direction scanner 14 are respectively controlled the scan with signals supplied from an X-direction scan driver 120 and a Y-direction scan driver 140. The laser light 102 scanned two- dimensionally with the scanners 12, 14 is focused on a small spot with an object lens 104 and casted on a measuring object 106 of which shape and dimensions are measured. For confocal detection, the reflection light from the measuring object 106 is reflected with a beam splitter 11 and detected with a light receiver 15 by way of a focus lens 112. For non-confocal detection, the reflection light from the measuring object 106 is reflected with a beam splitter 13 and detected with a light receiver 11 by way of a focus lens 132. Data processors 16 and 18 respectively process the reflection light intensity data detected with the light receivers 15 and 17 and obtain the shape and the dimensions.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は表面形状、寸法などを光
学的に測定するとき使用される、レーザ走査顕微鏡の構
成に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a laser scanning microscope used for optically measuring surface shape, size and the like.

【0002】[0002]

【従来の技術】ミクロンからサブミクロン領域の微細パ
ターンの3次元形状、寸法などの測定にレーザ走査顕微
鏡(LSM)が使用されている。LSMは微小スポット
に集光したレーザ光を走査光学系を用いて物体面上で2
次元走査し、物体面からの反射光強度、あるいは透過光
強度を走査の各点で検出し、反射光、透過光の強度変化
をデータ処理してパターン像を得る光学装置である。以
下に示す説明は物体面からの反射光を検出する例である
が、透過光を検出する場合も同様である。LSMは反射
光の検出法により、非共焦点型LSMと共焦点型LSM
の2種類に大別される。非共焦点型は単一の受光面を持
つ面検出器で反射光の全体強度を検出する方式である。
その分解能は、試料上に集光されたレーザスポット径で
決まり、白色光を照明する従来の顕微鏡と同等である。
しかし、反射光に付随したコヒーレント雑音などのノイ
ズは面検出器で積分されるため、従来の顕微鏡よりは像
のコントラスト特性が良い、S/N比が高いなどの特徴
がある。共焦点型は同じく単一の受光面を持つ点検出器
で反射光を検出する。共焦点型は、実用的にはスリッ
ト、ピンホール等を用いて点検出機能を持たせ、反射光
に付随する各種のノイズ光が受光面に入らないようにカ
ットし、反射光の強度分布のエアリーディスク内の強度
のみを検出する。その結果として、従来の顕微鏡、非共
焦点型LSMよりも空間分解能が高く、回折限界を超え
た測定が可能になる。したがって、面内方向に関して高
分解能の測定を行うには共焦点型が適している。そのた
め、LSMといえば共焦点型の構成になっているのが一
般的である。
2. Description of the Related Art A laser scanning microscope (LSM) is used for measuring the three-dimensional shape and size of a fine pattern in the micron to sub-micron region. LSM uses a scanning optical system to scan a laser beam focused on a small spot on the object plane.
It is an optical device that performs two-dimensional scanning, detects the intensity of reflected light from the object surface or the intensity of transmitted light at each point of scanning, and processes the intensity changes of reflected light and transmitted light to obtain a pattern image. The following description is an example of detecting the reflected light from the object surface, but the same applies to the case of detecting the transmitted light. LSM is a non-confocal type LSM and a confocal type LSM depending on the detection method of reflected light.
There are two types. The non-confocal type is a method for detecting the total intensity of reflected light with a surface detector having a single light receiving surface.
The resolution is determined by the diameter of the laser spot focused on the sample and is equivalent to that of a conventional microscope that illuminates white light.
However, since noise such as coherent noise accompanying the reflected light is integrated by the surface detector, it has characteristics such as better image contrast characteristics and a higher S / N ratio than conventional microscopes. The confocal type also detects reflected light with a point detector having a single light receiving surface. The confocal type is practically provided with a point detection function using slits, pinholes, etc., and cuts various types of noise light that accompany the reflected light so that it does not enter the light receiving surface. Only the intensities in the Airy disc are detected. As a result, the spatial resolution is higher than that of the conventional microscope and the non-confocal type LSM, and the measurement exceeding the diffraction limit becomes possible. Therefore, the confocal type is suitable for performing high-resolution measurement in the in-plane direction. Therefore, LSM generally has a confocal configuration.

【0003】図3に従来の共焦点型LSMの構成を示
す。30はレーザ光源、31、32はX方向走査器、Y
方向走査器で、レーザ光300を2次元走査する。一般
には、X方向走査器31は音響光学素子、Y方向走査器
32はガルバノミラーが用いられている。33はビーム
スプリッターである。2次元走査されるレーザ光310
は対物レンズ34で微小なスポットに集光され、被測定
物35の面上に照射される。被測定物35からの反射光
はビームスプリッター33で反射され、集光レンズ36
を介して、多数の画素が1次元的に配置されたCCDイ
メージセンサーから成る受光器37で検出される。受光
器37の各画素は紙面に平行なX方向に並んでいるとす
る。受光器37への反射光365の入射において、被測
定物35への照射光が紙面に垂直なY方向へ走査を行っ
ているときは、反射光365は受光器37のY方向の一
定位置に入射するため、Y方向には走査の定点位置検出
となる。しかし、照射光がX方向へ走査を行っていると
きは、反射光365は受光器37の面上をX方向に移動
するため、X方向には走査の定点位置検出にはならな
い。このとき、受光器37の各画素はX方向には多分割
されているため、反射光365のビームスポット径が受
光器37の各画素の幅よりも大きければ、画素の大きさ
に応じた領域の反射光強度が順次検出される。そのた
め、X方向の走査に対しては共焦点検出、Y方向には非
共焦点検出と同等の効果を持つことになる。そこで、反
射光365が受光器37の各画素上を移動することによ
って得られた反射光強度信号から、被測定物35の形
状、寸法などを測定する。
FIG. 3 shows the configuration of a conventional confocal LSM. 30 is a laser light source, 31 and 32 are X-direction scanners, Y
The directional scanner scans the laser light 300 two-dimensionally. In general, an acousto-optic device is used for the X-direction scanning device 31, and a galvanometer mirror is used for the Y-direction scanning device 32. 33 is a beam splitter. Two-dimensionally scanned laser light 310
Is condensed into a minute spot by the objective lens 34, and is irradiated onto the surface of the DUT 35. The reflected light from the DUT 35 is reflected by the beam splitter 33, and the condenser lens 36
A large number of pixels are detected by a light receiver 37 which is a one-dimensionally arranged CCD image sensor. It is assumed that the pixels of the light receiver 37 are arranged in the X direction parallel to the paper surface. When the reflected light 365 is incident on the light receiver 37 and the irradiation light on the DUT 35 is scanning in the Y direction perpendicular to the paper surface, the reflected light 365 is at a fixed position in the Y direction on the light receiver 37. Since the light is incident, the fixed point position for scanning is detected in the Y direction. However, when the irradiation light is scanning in the X direction, the reflected light 365 moves in the X direction on the surface of the light receiver 37, so that the fixed point position for scanning is not detected in the X direction. At this time, since each pixel of the light receiver 37 is multi-divided in the X direction, if the beam spot diameter of the reflected light 365 is larger than the width of each pixel of the light receiver 37, an area corresponding to the pixel size is obtained. The reflected light intensities are sequentially detected. Therefore, it has the same effect as the confocal detection for the scanning in the X direction and the non-confocal detection for the Y direction. Therefore, the shape, size, etc. of the DUT 35 are measured from the reflected light intensity signal obtained by the reflected light 365 moving on each pixel of the light receiver 37.

【0004】共焦点型LSMは、従来の顕微鏡や非共焦
点型LSMに比べて、高さ方向の分解能が高いという特
徴もあり、3次元形状計測にも有効である。共焦点型は
焦点の合っていない面からの反射光はピンホール、スリ
ットなどによりカットされるため、焦点の合っている面
からの反射光だけが検出される。そのため、結果的には
照射されている面に対しては焦点深度が浅くなり、高さ
分解能が向上する。この場合の分解能は、対物レンズの
NA値で決まる照射レーザ光の焦点深度、及び対物レン
ズあるいは物体面を焦点方向に移動するときの移動のス
テップ距離に依存する。一般にはレーザ光の焦点深度の
制約が主であるが、NA値が0.8程度の対物レンズを
用いたときは、分解能は0.1μm程度である。しか
し、この分解能よりも細かい分解能で高さ形状を測定す
るには別の測定方法が必要になる。この目的のためには
光ヘテロダイン干渉法が適している。光ヘテロダイン干
渉法は、周波数の異なる二つの光ビームを干渉させて、
差の周波数を持つビート信号を作成し、ビート信号の位
相変化を検出して高さ形状を測定する技術である。高さ
の凹凸までも含めて形状を測定するときは、レーザ光の
波長の1/4までの高さを、1/1000波長程度の分
解能で測定することが可能である。
The confocal LSM has a feature that the resolution in the height direction is higher than that of a conventional microscope or a non-confocal LSM, and is effective for three-dimensional shape measurement. In the confocal type, since the reflected light from the out-of-focus surface is cut by the pinhole, slit, etc., only the reflected light from the in-focus surface is detected. Therefore, as a result, the depth of focus becomes shallow with respect to the illuminated surface, and the height resolution is improved. The resolution in this case depends on the focal depth of the irradiation laser light determined by the NA value of the objective lens and the step distance of movement when moving the objective lens or the object plane in the focal direction. Generally, the restriction of the depth of focus of the laser beam is mainly, but when an objective lens having an NA value of about 0.8 is used, the resolution is about 0.1 μm. However, another measurement method is required to measure the height profile with a resolution smaller than this resolution. Optical heterodyne interferometry is suitable for this purpose. Optical heterodyne interferometry causes two light beams with different frequencies to interfere with each other,
This is a technique for creating a beat signal having a difference frequency, detecting the phase change of the beat signal, and measuring the height shape. When measuring the shape including the unevenness of the height, it is possible to measure the height up to ¼ of the wavelength of the laser light with a resolution of about 1/1000 wavelength.

【0005】光ヘテロダイン干渉法は、周波数の異なる
2ビーム光の作成方法に応じて各種の方式があるが、図
4には、一個の音響光学素子(以下にAODと略記す
る)を用いたビーム走査型の例を示す。図4の図番にお
いて、図3と同じものは説明を省略する。41はAOD
で、図3のX方向走査器31に相当するが、X方向への
ビーム走査のみならず、周波数の異なる2ビーム光を発
生する。この2ビーム光の発生と走査は、AOD41の
走査ドライバー42で2周波数成分を持つ信号を作成
し、その信号によりAOD41を駆動することで可能に
なる。AOD41から発せられた2ビーム光の一部をビ
ームスプリッター33で反射し、集光レンズ43を介し
て受光器44で検出して参照光ビート信号を作成する。
ビームスプリッター33を透過した2ビーム光はY方向
走査器32でY方向に走査され、対物レンズ34を介し
て被測定物35に照射されて2次元走査する。被測定物
35から反射された2ビーム光はビームスプリッター3
3で反射され、集光レンズ36を介して受光器45で検
出されて反射光ビート信号を作成する。ここで、受光器
44、45はいずれも単一の受光面である。46は位相
比較器で、参照光ビート信号と反射光ビート信号の間の
位相差を検出し、位相変化から高さ形状を測定する。以
上に示した光ヘテロダイン干渉法は、2ビーム光が照射
された2点間の光路長差を電気信号の位相差から検出す
る差動検出型である。この構成については本願発明者に
よる特許公報平3−39563号“光ヘテロダイン干渉
法による微小角度測定方法”に詳細に述べている。
There are various optical heterodyne interferometry methods depending on the method of producing two-beam light having different frequencies. In FIG. 4, a beam using one acousto-optic device (hereinafter abbreviated as AOD) is used. An example of a scanning type is shown. In the drawing numbers of FIG. 4, the description of the same parts as those in FIG. 3 will be omitted. 41 is AOD
3 corresponds to the X-direction scanner 31 in FIG. 3, but not only beam scanning in the X-direction but also two-beam light with different frequencies is generated. The generation and scanning of the two-beam light can be performed by generating a signal having two frequency components by the scanning driver 42 of the AOD 41 and driving the AOD 41 with the signal. A part of the two-beam light emitted from the AOD 41 is reflected by the beam splitter 33 and is detected by the light receiver 44 via the condenser lens 43 to create a reference light beat signal.
The two-beam light that has passed through the beam splitter 33 is scanned in the Y direction by the Y-direction scanner 32, and is irradiated onto the object 35 to be measured through the objective lens 34 to perform two-dimensional scanning. The two-beam light reflected from the DUT 35 is beam splitter 3
The reflected light beat signal is generated by being reflected by 3 and detected by the light receiver 45 through the condenser lens 36. Here, each of the light receivers 44 and 45 is a single light receiving surface. A phase comparator 46 detects the phase difference between the reference light beat signal and the reflected light beat signal, and measures the height shape from the phase change. The optical heterodyne interferometry described above is a differential detection type that detects the optical path length difference between two points irradiated with two beams of light from the phase difference of electrical signals. This configuration is described in detail in Japanese Patent Laid-Open No. 3-39563, "Method for measuring minute angle by optical heterodyne interferometry" by the present inventor.

【0006】[0006]

【発明が解決しようとする課題】従来の共焦点型LSM
は、反射光を画素が分離されたCCDイメージセンサで
検出しているため、レーザ光を連続に走査しても反射光
強度変化が不連続的に検出されて検出感度が低下すると
いう問題点、また、反射光を検出するときに、イメージ
センサーの画素のスペーシング部分により干渉縞が発生
し、出力信号にノイズが重畳されるという問題点、さら
には、実質的にはスリット検出と同等なため、X方向走
査には共焦点検出となっても、Y方向走査には非共焦点
検出となって、2次元共に高分解能の検出ができないと
いう問題点がある。また、共焦点型検出は、面内分解能
が向上すると共に、焦点深度が浅くなって高さ分解能が
向上するという利点があるが、被測定物によってはこれ
らの特性が逆に欠点になる場合がある。すなわち、下面
と上面の間の段差が大きい微細パターンの寸法を測定す
るような場合、焦点深度が短くなると下面と上面からの
反射光強度が異なるために一度の走査で適正な反射光強
度が検出されず、複数回の走査を必要とすることがあ
る。このように、被測定物に応じては必ずしも共焦点型
検出が有利になるとは限らず、非共焦点検出が適してい
る場合もある。図2に示した従来の共焦点LSMは共焦
点検出だけができる単一機能であるため、非共焦点検出
を行うためには別のLSMが必要になる。
Conventional confocal LSM
Since the reflected light is detected by a CCD image sensor in which pixels are separated, a change in reflected light intensity is discontinuously detected even when the laser light is continuously scanned, and the detection sensitivity is lowered. In addition, when detecting reflected light, interference fringes are generated due to the spacing of the pixels of the image sensor, and noise is superimposed on the output signal. Furthermore, it is substantially equivalent to slit detection. , There is a problem that even if confocal detection is performed in the X-direction scanning, non-confocal detection is performed in the Y-direction scanning, and high-resolution detection cannot be performed in two dimensions. Further, confocal detection has an advantage that the in-plane resolution is improved, and the depth of focus is reduced to improve the height resolution. However, depending on the DUT, these characteristics may be disadvantages. is there. That is, when measuring the size of a fine pattern with a large step between the lower surface and the upper surface, the reflected light intensity from the lower surface differs from the upper surface when the depth of focus becomes shorter, so the appropriate reflected light intensity can be detected with one scan. Instead, it may require multiple scans. As described above, the confocal detection is not always advantageous depending on the object to be measured, and the non-confocal detection may be suitable in some cases. Since the conventional confocal LSM shown in FIG. 2 has a single function capable of only confocal detection, another LSM is required to perform non-confocal detection.

【0007】光ヘテロダイン干渉は、レーザ光の波長の
1/4までの段差測定には適しているが、1/2波長程
度の段差がある場合は測定できないという問題点があ
る。それは、位相角度の検出において、位相角度がπr
adを超えると、位相角度の絶対値が不明になるためで
ある。1/4波長以上の段差を測定する場合に共焦点型
LSMを用いたときは、分解能が0.1μmであるた
め、測定精度が悪くなる。そのため、1/2波長程度の
段差を数10nmの精度で測定する有効な手段がないと
いう問題点があった。さらには、光ヘテロダイン干渉計
測の場合、従来は光ヘテロダイン干渉の単一機能だけの
構成であるため、主として高さ方向の形状測定だけを行
い、2次元的な面内形状、寸法の測定には応用されてい
なかった。したがって、従来の方法では、共焦点型と非
共焦点型による形状、寸法の測定、及び光ヘテロダイン
干渉による高さ形状測定は一つの測定機で実現できず、
測定目的に応じて別々の測定装置が必要であり、測定コ
ストの増大、測定効率の低下が起こるという問題点があ
った。本発明は上記問題点を解決し、一つの測定装置で
共焦点検出、非共焦点検出、及び光ヘテロダイン干渉検
出が可能な複合計測機能を持つ新規な構成のレーザ走査
顕微鏡を実現することを目的とする。
The optical heterodyne interference is suitable for measuring a step difference up to ¼ of the wavelength of the laser beam, but has a problem that it cannot be measured when there is a step difference of about ½ wavelength. It is because the phase angle is πr in the detection of the phase angle.
This is because the absolute value of the phase angle becomes unknown when it exceeds ad. When a confocal LSM is used to measure a step difference of ¼ wavelength or more, the resolution is 0.1 μm, and therefore the measurement accuracy becomes poor. Therefore, there is a problem that there is no effective means for measuring a step of about 1/2 wavelength with an accuracy of several tens of nm. Further, in the case of the optical heterodyne interferometry, the conventional configuration has only a single function of the optical heterodyne interferometry, so that mainly the shape measurement in the height direction is performed and the two-dimensional in-plane shape and dimension measurement is performed. It was not applied. Therefore, in the conventional method, the confocal and non-confocal shapes, the dimension measurement, and the height shape measurement by the optical heterodyne interference cannot be realized by one measuring machine,
Different measuring devices are required according to the purpose of measurement, and there are problems that the measurement cost increases and the measurement efficiency decreases. It is an object of the present invention to solve the above problems and to realize a laser scanning microscope having a novel configuration having a combined measurement function capable of confocal detection, non-confocal detection, and optical heterodyne interference detection with a single measuring device. And

【0008】[0008]

【課題を解決するための手段】上記の課題を解決するた
めに本発明は以下の構成をなす。レーザ光源から放射さ
れたレーザ光を第一のビームスプリッターを透過させ、
該透過光をX方向走査器に入射してX方向に走査し、該
X方向に走査されるレーザ光を第二のビームスプリッタ
ーを透過させ、該透過光をY方向走査器に入射してY方
向に走査して2次元走査を行わせ、該2次元走査される
レーザ光を対物レンズで微小なスポットに集光して被測
定物に照射し、該被測定物からの反射光を前記第二のビ
ームスプリッターで反射させて前記反射光の全体強度を
第二の受光器で検出する非共焦点検出機能と、前記被測
定物からの反射光を前記第一のビームスプリッターで反
射させ、該反射光の強度分布の中央部を含む一部の範囲
の強度を第一の受光器で検出する共焦点検出機能を設け
たレーザ走査顕微鏡であって、前記第一のビームスプリ
ッターで反射される光路と、前記第二のビームスプリッ
ターで反射される光路を選択する切り替え手段を設け、
前記非共焦点検出機能と共焦点検出機能を測定目的に応
じて選択して使用する構成である。
In order to solve the above problems, the present invention has the following constitution. The laser beam emitted from the laser light source is transmitted through the first beam splitter,
The transmitted light is incident on the X-direction scanner to scan in the X-direction, the laser light scanned in the X-direction is transmitted through the second beam splitter, and the transmitted light is incident on the Y-direction scanner to Y Direction, two-dimensional scanning is performed, the two-dimensionally scanned laser light is focused on a minute spot by an objective lens and irradiated onto the object to be measured, and reflected light from the object to be measured is reflected by the first object. A non-confocal detection function of detecting the total intensity of the reflected light with a second light receiver by reflecting with a second beam splitter, and the reflected light from the DUT is reflected by the first beam splitter, A laser scanning microscope provided with a confocal detection function for detecting the intensity of a part of the range including the central portion of the intensity distribution of reflected light with a first light receiver, the optical path reflected by the first beam splitter. And is reflected by the second beam splitter A switching means for selecting a road provided,
The non-confocal detection function and the confocal detection function are selected and used according to the purpose of measurement.

【0009】さらには、レーザ光源から放射されたレー
ザ光を第一のビームスプリッターを透過させ、該透過光
をX方向走査器に入射してX方向に走査し、該X方向に
走査されるレーザ光を第二のビームスプリッターを透過
させ、該透過光をY方向走査器に入射してY方向に走査
して2次元走査を行わせ、該2次元走査されるレーザ光
を対物レンズで微小なスポットに集光して被測定物に照
射し、該被測定物からの反射光を前記第二のビームスプ
リッターで反射させて前記反射光の全体強度を第二の受
光器で検出する非共焦点検出機能と、前記被測定物から
の反射光を前記第一のビームスプリッターで反射させ、
該反射光の強度分布の中央部を含む一部の範囲の強度を
第一の受光器で検出する共焦点検出機能と、前記被測定
物からの反射光を前記第二のビームスプリッターで反射
させて、該反射光を前記第二の受光器で検出し、該第二
の受光器で検出された反射光の位相変化を検出する光ヘ
テロダイン干渉機能を設けたレーザ走査顕微鏡であっ
て、測定目的に応じて前記X方向走査器あるいはY方向
走査器を駆動する電気信号のスペクトルを制御してレー
ザ光の周波数と光強度分布を変化させると共に、前記第
一のビームスプリッターで反射される光路と、前記第二
のビームスプリッターで反射される光路を選択する切り
替え手段を設け、前記非共焦点検出機能と共焦点検出機
能と光ヘテロダイン干渉機能を測定目的に応じて選択し
て使用する構成である。
Further, the laser light emitted from the laser light source is transmitted through the first beam splitter, the transmitted light is incident on the X-direction scanner, scanned in the X-direction, and is scanned in the X-direction. The light is transmitted through the second beam splitter, the transmitted light is incident on the Y-direction scanner, and is scanned in the Y-direction to perform two-dimensional scanning. A non-confocal light that is focused on a spot and irradiates an object to be measured, and the reflected light from the object to be measured is reflected by the second beam splitter and the total intensity of the reflected light is detected by a second light receiver. Detection function, reflected light from the DUT is reflected by the first beam splitter,
A confocal detection function of detecting the intensity of a part of the range including the central portion of the intensity distribution of the reflected light by the first light receiver, and the reflected light from the DUT is reflected by the second beam splitter. A laser scanning microscope provided with an optical heterodyne interference function for detecting the reflected light with the second light receiver and detecting a phase change of the reflected light detected with the second light receiver. According to the control of the spectrum of the electric signal for driving the X-direction scanner or the Y-direction scanner to change the frequency and the light intensity distribution of the laser light, and the optical path reflected by the first beam splitter, A configuration is provided in which a switching unit that selects an optical path reflected by the second beam splitter is provided, and the non-confocal detection function, the confocal detection function, and the optical heterodyne interference function are selected and used according to the measurement purpose. .

【0010】さらには、前記光ヘテロダイン干渉機能と
前記共焦点検出機能を用いて被測定物の段差を測定する
とき、光ヘテロダイン干渉機能で検出された位相φと共
に、共焦点検出機能で検出された反射光強度の変化から
前記位相角度がπ(rad)を超える回数nを計測し
て、位相角度nπ+φ(rad)から前記の段差を測定
する構成である。
Furthermore, when the step difference of the object to be measured is measured by using the optical heterodyne interference function and the confocal detection function, the phase φ detected by the optical heterodyne interference function and the confocal detection function are detected. The number n of times the phase angle exceeds π (rad) is measured from the change in reflected light intensity, and the step is measured from the phase angle nπ + φ (rad).

【0011】[0011]

【作用】本発明は、複合計測化が可能なLSMを実現す
るもので、単一の計測機能しか持たなかった従来のLS
Mに対して、二つあるいは三つの異なる計測機能を一つ
の光学装置に統合し、測定目的に応じて使用する機能を
選択するものである。第一の複合化は共焦点検出と非共
焦点検出に関するもので、被測定物からの反射光の検出
に際して、異なる位置に設けた二つの受光器で、二つの
異なる形態の検出を行う。非共焦点検出は、2次元走査
の一方の走査に対しては走査定点、他方の走査に対して
は走査非定点となる位置に設けた受光器で反射光の全体
強度を検出する。共焦点検出は、2次元走査の両方の走
査に対して走査定点となる位置で、反射光の強度分布の
中央部を含む一部の範囲の反射光強度を検出する。二つ
の受光器はいずれも単一の受光面を持つ構成である。こ
のとき、共焦点検出と非共焦点検出のいずれも、単一の
強度ピークを持った照射ビームを、同一の走査光学系を
用いて走査するが、反射光検出の選択は、反射光の検出
光路を切り換えることによって行う。
The present invention realizes an LSM capable of complex measurement, and is a conventional LS having only a single measurement function.
For M, two or three different measurement functions are integrated into one optical device, and the function to be used is selected according to the measurement purpose. The first combination relates to confocal detection and non-confocal detection. When detecting reflected light from the object to be measured, two light receivers provided at different positions detect two different forms. In non-confocal detection, the total intensity of reflected light is detected by a light receiver provided at a scanning fixed point for one of the two-dimensional scanning and a scanning non-fixed point for the other scanning. The confocal detection detects the reflected light intensity in a part of the range including the central portion of the intensity distribution of the reflected light at a position that is a scanning fixed point for both two-dimensional scanning. Each of the two light receivers has a single light receiving surface. At this time, in both confocal detection and non-confocal detection, the irradiation beam having a single intensity peak is scanned using the same scanning optical system, but the reflected light detection is selected. This is done by switching the optical path.

【0012】第二の複合化は共焦点検出、非共焦点検
出、光ヘテロダイン干渉検出を一つの光学装置に統合す
るもので、2次元面内の形状、寸法計測と共に高さ形状
計測を一つの測定機で行う。この三つの機能の複合化
は、反射光の検出受光器を複数個設置し、音響光学素子
の駆動信号を変調すること、及び反射光の検出光路を切
り替えることにより実現する。音響光学素子は、それを
駆動する電気信号のスペクトルを制御することで、物体
面への照射レーザ光の光強度分布、光周波数を自在に変
換する。共焦点検出と非共焦点検出は通常の単一の強度
ピークを持つレーザ光を走査し、前述の方法で反射光を
検出する。光ヘテロダイン干渉検出では、異なる周波数
を持ち、二つの強度ピークを持つ2ビーム光を作成して
走査する。このとき、反射光の検出は非共焦点検出用の
受光器と兼用するが、反射光強度ではなく、ビート信号
の位相を検出する。
The second combination is to integrate confocal detection, non-confocal detection, and optical heterodyne interference detection into a single optical device, and to measure height and shape along with two-dimensional shape and dimension measurement. Use a measuring machine. The combination of these three functions is realized by providing a plurality of photodetectors for detecting reflected light, modulating the drive signal of the acoustooptic device, and switching the detection optical path of reflected light. The acousto-optic element controls the spectrum of an electric signal for driving the acousto-optic element, thereby freely converting the light intensity distribution and the optical frequency of the laser light emitted to the object plane. In the confocal detection and the non-confocal detection, a laser beam having a normal single intensity peak is scanned and the reflected light is detected by the above method. In optical heterodyne interference detection, two beams of light having different frequencies and two intensity peaks are created and scanned. At this time, the reflected light is also used as a photodetector for non-confocal detection, but not the reflected light intensity but the phase of the beat signal is detected.

【0013】第二の複合化の場合、光ヘテロダイン干渉
機能を単独で用いるときは、1/4波長以下の段差測定
に応用する。1/4波長以上の段差を測定するときは、
光ヘテロダイン干渉機能と共焦点検出機能の両方を用い
る。光ヘテロダイン干渉機能では、1/4波長以上の段
差では位相角度がπ(rad)を超えてしまい、位相と
段差の関係が不明になる。共焦点検出機能は焦点位置ズ
レに対して反射光強度が大きく変化する特徴がある。そ
こで、共焦点検出機能により、段差による焦点位置ズレ
によって生じる反射光強度の低下を検出する。その強度
低下から段差の概略を決定して、前記位相角度がπ(r
ad)を超える回数nを計測する。こうして得られたπ
(rad)からの回転数による位相角度nπと、光ヘテ
ロダイン干渉機能で検出した位相角度の和から段差を測
定する。
In the case of the second combination, when the optical heterodyne interference function is used alone, it is applied to the step measurement of ¼ wavelength or less. When measuring the step difference of 1/4 wavelength or more,
Both optical heterodyne interference function and confocal detection function are used. In the optical heterodyne interference function, the phase angle exceeds π (rad) at a step of ¼ wavelength or more, and the relationship between the phase and the step becomes unclear. The confocal detection function is characterized in that the intensity of reflected light changes greatly with respect to the focal position shift. Therefore, the confocal detection function detects a decrease in reflected light intensity caused by a focus position shift due to a step. From the decrease in strength, the outline of the step is determined, and the phase angle is π (r
The number of times n which exceeds ad) is measured. Π thus obtained
The step is measured from the sum of the phase angle nπ based on the rotation speed from (rad) and the phase angle detected by the optical heterodyne interference function.

【0014】[0014]

【実施例】以下に図面を用いて本発明の実施例を詳細に
説明する。図1は本発明の第一の実施例である、共焦点
検出と非共焦点検出の二つの機能を一つの光学装置に持
たせた例を示すシステムブロック図である。10はレー
ザ光源で、例えば半導体レーザ、He−Neレーザなど
から成り、レーザ光100を放射する。11は第一のビ
ームスプリッター(以下に第一のBSと略記する)で、
反射光検出の際の光路変換を行う。12はX方向への走
査を行うX方向走査器で、例えば音響光学素子からな
り、X方向走査ドライバー120から供給される信号に
より走査を制御する。13は第二のビームスプリッター
(以下に第二のBSと略記する)で、反射光検出の際の
光路変換を行う。14はY方向への走査を行うY方向走
査器で、例えばガルバノミラーからなり、Y方向走査ド
ライバー140から供給される信号で走査を制御する。
X方向走査器12とY方向走査器14で2次元走査され
るレーザ光102を対物レンズ104で微小なスポット
に集光し、形状、寸法などが測定される被測定物106
に照射する。被測定物106からの反射光の検出に際し
てつぎの二つの検出方法を用いる。第一の検出は第一の
BS11で反射光検出を行う場合で、共焦点検出を行
う。第二の検出は第二のBS13で反射光検出を行う場
合で、非共焦点検出を行う。これら二つの異なる反射光
検出は反射光の検出光路を切り換えることによって行
う。
Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a system block diagram showing an example in which one optical device has two functions of confocal detection and non-confocal detection, which is a first embodiment of the present invention. Reference numeral 10 denotes a laser light source, which is composed of, for example, a semiconductor laser or a He-Ne laser, and emits a laser beam 100. Reference numeral 11 is a first beam splitter (hereinafter abbreviated as a first BS),
The optical path is changed when the reflected light is detected. Reference numeral 12 denotes an X-direction scanning device that performs scanning in the X-direction, and is composed of, for example, an acousto-optic device, and controls scanning by a signal supplied from the X-direction scanning driver 120. A second beam splitter 13 (hereinafter abbreviated as a second BS) 13 converts the optical path when detecting reflected light. Reference numeral 14 is a Y-direction scanning device that performs scanning in the Y-direction, and is composed of, for example, a galvanometer mirror, and controls scanning by a signal supplied from a Y-direction scanning driver 140.
An object to be measured 106 whose shape and dimensions are measured by condensing a laser beam 102 which is two-dimensionally scanned by the X-direction scanner 12 and the Y-direction scanner 14 into a minute spot by an objective lens 104.
To irradiate. The following two detection methods are used when detecting the reflected light from the DUT 106. The first detection is when the reflected light is detected by the first BS 11, and confocal detection is performed. The second detection is a case where reflected light is detected by the second BS 13, and non-confocal detection is performed. These two different reflected light detections are performed by switching the detection light path of the reflected light.

【0015】共焦点検出は、被測定物106からの反射
光を第一のBS11で反射し、集光レンズ112を介し
て第一の受光器15で検出することによって実現する。
この反射光検出では、第一の受光器15での反射光検出
効率を上げるために、第二のBS13を切り換えレバー
等の切り替え手段を用いて光路外に移動させる。このと
き、光学長を一定に保つために、第二のBS13の光学
長に等しい光学長を持つガラスブロックを第二のBS1
3の位置に挿入して光学長を一定に保ち、被測定物10
6からの反射光が直接にX方向走査器12に再入射され
るようにする。反射光114はY方向走査器14とX方
向走査器12を再通過するため、照射レーザ光が被測定
物106の2次元面内のどの位置を走査していても、反
射光114は常に第一の受光器15の一定位置に入射す
る。すなわち、2次元走査の定点位置で反射光検出を行
うことになる。そのため、第一の受光器15は単一の受
光面だけを持つ単一受光器でよく、その受光面にピンホ
ールなどを直接に張り付けた構成とすることができる。
このとき、反射光の強度分布の中央部をピンホールの中
心位置に設定して、反射光の中央部を含む一部の範囲の
強度のみを検出すれば、2次元の両方に対して共焦点検
出が可能になる。また、第一の受光器15にスリットな
どを直接に張り付け、反射光の強度分布の中央部をスリ
ットの中心位置に設定し、反射光の中央部を含む一部の
範囲の強度のみを検出すれば、スリット短軸方向に関し
ては共焦点検出、スリットの長軸方向に対しては非共焦
点検出となる。この共焦点型検出では、2次元走査に応
じて連続的に反射光を検出することが可能で、反射光強
度の変化を感度よく検出することができる。また、単一
の受光面で反射光114を検出するため、干渉性ノイズ
などが発生せず、S/N比のよい反射光を検出すること
ができる。16は第一のデータ処理部で、共焦点検出さ
れた反射光強度データを処理し、面内分解能が向上する
という特徴を生かして、サブミクロンオーダの寸法計測
などを行う。
The confocal detection is realized by reflecting the reflected light from the object to be measured 106 by the first BS 11 and detecting it by the first light receiver 15 via the condenser lens 112.
In this reflected light detection, the second BS 13 is moved out of the optical path using a switching means such as a switching lever in order to increase the efficiency of detecting the reflected light at the first light receiver 15. At this time, in order to keep the optical length constant, a glass block having an optical length equal to that of the second BS 13 is attached to the second BS 1
Inserted at position 3 to keep the optical length constant,
The reflected light from 6 is directly incident on the X-direction scanner 12 again. Since the reflected light 114 passes through the Y-direction scanner 14 and the X-direction scanner 12 again, the reflected light 114 is always reflected by the irradiation laser light at any position in the two-dimensional plane of the DUT 106. It is incident on a fixed position of one light receiver 15. That is, the reflected light is detected at the fixed point position of the two-dimensional scanning. Therefore, the first light receiver 15 may be a single light receiver having only a single light receiving surface, and a pinhole or the like may be directly attached to the light receiving surface.
At this time, if the central part of the intensity distribution of the reflected light is set to the center position of the pinhole and only the intensity of a part of the range including the central part of the reflected light is detected, the confocal point will be confocal for both two dimensions. It becomes possible to detect. Further, a slit or the like is directly attached to the first light receiver 15, the central portion of the intensity distribution of the reflected light is set at the central position of the slit, and only the intensity of a partial range including the central portion of the reflected light is detected. For example, confocal detection is performed in the minor axis direction of the slit, and non-confocal detection is performed in the major axis direction of the slit. In this confocal type detection, reflected light can be continuously detected according to two-dimensional scanning, and a change in reflected light intensity can be detected with high sensitivity. Further, since the reflected light 114 is detected by a single light receiving surface, coherent noise is not generated, and the reflected light having a good S / N ratio can be detected. Reference numeral 16 denotes a first data processing unit, which processes the reflected light intensity data detected by confocal detection and utilizes the feature that the in-plane resolution is improved to perform dimension measurement on the order of submicrons.

【0016】非共焦点検出は、被測定物106からの反
射光を第二のBS13で反射し、集光レンズ132を介
して第二の受光器17で検出する。この反射光検出では
第二のBS13の左側の光路に反射光が入射しないよう
に、レーザ光の偏光軸の調整を行い、反射光検出の効率
を上げる。反射光134はY方向走査器14を再通過す
るため、照射レーザ光のY方向の走査に対しては走査定
点となる。しかし、反射光はX方向走査器12を再通過
しないために、X方向の走査に対しては走査定点とはな
らず、第二の受光器17の面上をX方向(紙面に平行な
方向)に移動する。そのため、非共焦点検出では第二の
受光器17として、その受光面上での移動距離よりも広
い幅の受光面を持つ単一受光器の構成にし、反射光13
4の全体強度を検出する。この非共焦点検出でも、2次
元走査に応じて連続的に反射光の強度変化を検出するこ
とができる。18は第二のデータ処理部で、非共焦点検
出された反射光強度データを処理し、数10μm程度の
部材の形状、寸法などを測定する。以上のように、本発
明の第一の実施例では、一つの光学装置内に共焦点検出
と非共焦点検出という二つの異なる機能を持たせ、測定
目的に応じて反射光の検出光路を切り替えることで機能
を選択する。
In the non-confocal detection, the reflected light from the object to be measured 106 is reflected by the second BS 13 and detected by the second light receiver 17 via the condenser lens 132. In this reflected light detection, the polarization axis of the laser light is adjusted so that the reflected light does not enter the optical path on the left side of the second BS 13, and the efficiency of reflected light detection is increased. Since the reflected light 134 passes through the Y-direction scanner 14 again, it becomes a scanning fixed point for the scanning of the irradiation laser light in the Y-direction. However, since the reflected light does not pass through the X-direction scanner 12 again, it does not serve as a scanning fixed point for scanning in the X-direction, and the surface of the second light receiver 17 is moved in the X-direction (direction parallel to the paper surface). ) Move to. Therefore, in the non-confocal detection, the second light receiver 17 is configured as a single light receiver having a light receiving surface having a width wider than the moving distance on the light receiving surface, and the reflected light 13
4. Detect the overall intensity of 4. Even with this non-confocal detection, it is possible to continuously detect the intensity change of the reflected light in accordance with the two-dimensional scanning. A second data processing unit 18 processes the reflected light intensity data detected by the non-confocal focus, and measures the shape, size, etc. of the member having a size of several tens of μm. As described above, in the first embodiment of the present invention, two different functions of confocal detection and non-confocal detection are provided in one optical device, and the detection optical path of reflected light is switched according to the measurement purpose. To select the function.

【0017】図2に本発明の第二の実施例のシステムブ
ロック図を示して動作を説明する。第二の実施例は、共
焦点検出、非共焦点検出と共に光ヘテロダイン干渉機能
を付加し、一つの光学装置に三つの計測機能を持たせた
例である。図2の説明では図1と同じ図番の説明は省略
する。レーザ走査顕微鏡で光ヘテロダイン干渉機能を実
現するには、図4に示したような周波数の異なる2ビー
ム光の発生と2ビーム光の走査が必要である。2ビーム
光の発生と走査を同時に満足するデバイスとしては音響
光学素子(以下にAODと略記する)が適している。そ
こで、X方向走査器12にAODを用いた例を説明す
る。AODを駆動するX方向走査ドライバー120が、
2周波数成分fa±fmの信号を出力する構成であると
き、単一の強度ピークのレーザ光がAODに入射したと
き、二つの強度ピークを持ち異なる方向に進行する2ビ
ーム光が得られる。このとき、2ビーム光は互いに周波
数が異なり、2ビーム光の間の周波数差は2fmであ
る。周波数faはビーム走査を制御し、周波数fmは2
ビーム光の分離を制御する。AODによる2ビーム光の
発生と走査の詳細は本願発明者による特許公報平3−4
4243号“光ヘテロダイン干渉法による表面形状測定
装置”に詳細に述べられているので、本願明細書では省
略する。なお、AODは単一周波数のfa成分を持つ信
号で駆動すれば、入射光と同じ単一の強度ピークを持っ
た通常のビームが発生し、図1に示した共焦点検出、非
共焦点検出を行う。したがって、本発明の第二の実施例
ではAODから発せられる走査ビームの周波数、強度分
布の切り換え制御も行う。
The operation will be described with reference to the system block diagram of the second embodiment of the present invention shown in FIG. The second embodiment is an example in which an optical heterodyne interference function is added together with confocal detection and non-confocal detection, and one optical device has three measurement functions. In the description of FIG. 2, the description of the same figure numbers as in FIG. 1 will be omitted. In order to realize the optical heterodyne interference function with the laser scanning microscope, it is necessary to generate two-beam light having different frequencies and to scan the two-beam light as shown in FIG. An acousto-optic device (hereinafter abbreviated as AOD) is suitable as a device that simultaneously satisfies the generation and scanning of two beams of light. Therefore, an example in which the AOD is used for the X-direction scanner 12 will be described. The X-direction scanning driver 120 that drives the AOD
When the configuration is such that signals of two frequency components fa ± fm are output, two-beam light having two intensity peaks and traveling in different directions can be obtained when laser light having a single intensity peak is incident on the AOD. At this time, the two beam lights have different frequencies from each other, and the frequency difference between the two beam lights is 2 fm. The frequency fa controls the beam scanning and the frequency fm is 2
Controls the separation of beam light. Details of generation and scanning of two-beam light by AOD are described in Japanese Patent Application Laid-Open No. 3-4.
Since it is described in detail in No. 4243 “Surface shape measuring apparatus by optical heterodyne interferometry”, it is omitted in the present specification. When the AOD is driven by a signal having a fa component of a single frequency, a normal beam having the same single intensity peak as the incident light is generated, and the confocal detection and non-confocal detection shown in FIG. 1 are performed. I do. Therefore, in the second embodiment of the present invention, switching control of the frequency and intensity distribution of the scanning beam emitted from the AOD is also performed.

【0018】光ヘテロダイン干渉では、AODで発せら
れた2ビーム光の一部の強度を第二のBS13で反射さ
せ、集光レンズ202を介して第三の受光器21で検出
して参照光信号22を作成する。2ビーム光を被測定物
106の面上で走査したときの反射光は第二のBS13
で反射させ、集光レンズ132を介して第二の受光器1
7で検出する。このときは反射光信号23を作成する。
参照光信号22と反射光信号23は共に周波数が2fm
のビート信号である。第二の受光器17は前述の非共焦
点検出と共用するが、非共焦点検出は1ビーム光走査、
光ヘテロダイン検出は2ビーム光走査で検出する点が異
なる。参照光信号22、反射光信号23の間の位相差
を、位相比較器24で検出する。参照光信号22の位相
は一定であるが、反射光信号23の位相は被測定物10
6の表面の段差などによって変化するため、参照光信号
22の位相を基準として反射光信号23の位相変化を検
出する。上述した光ヘテロダイン干渉は2ビーム光の間
の位相差を検出すると差動型の構成である。25は第三
のデータ処理部で、位相比較器24からの位相データを
演算して被測定物106の高さ形状を測定する。本実施
例で各機能を個別に使用するときは、光ヘテロダイン干
渉機能は2ビーム光の間の光路長差が1/4波長以下と
なる段差測定などに応用する。なお、上述の光ヘテロダ
イン干渉では、参照光信号22を第三の受光器21で光
学的に作成した例を示したが、前記の方法を用いないで
電気的に参照光信号を作成することもできる。それに
は、AODを駆動する信号の周波数fmを2倍した周波
数を作成すればよい。この場合の光学系は、図1に示し
た光学系とまったく同一となる。
In the optical heterodyne interference, the intensity of a part of the two-beam light emitted from the AOD is reflected by the second BS 13, and is detected by the third photodetector 21 via the condenser lens 202 to detect the reference optical signal. Create 22. The reflected light when the two-beam light is scanned on the surface of the DUT 106 is the second BS13.
Second light receiver 1 through the condenser lens 132.
Detect at 7. At this time, the reflected light signal 23 is created.
Both the reference light signal 22 and the reflected light signal 23 have a frequency of 2 fm.
Is the beat signal of. The second light receiver 17 is also used for the above-mentioned non-confocal detection, but the non-confocal detection is one beam light scanning,
Optical heterodyne detection is different in that it is detected by two-beam optical scanning. The phase difference between the reference light signal 22 and the reflected light signal 23 is detected by the phase comparator 24. The phase of the reference light signal 22 is constant, but the phase of the reflected light signal 23 is constant.
6 changes due to a step or the like on the surface, the phase change of the reflected light signal 23 is detected based on the phase of the reference light signal 22. The above-mentioned optical heterodyne interference has a differential structure when the phase difference between the two beam lights is detected. A third data processing unit 25 calculates the phase data from the phase comparator 24 to measure the height shape of the DUT 106. When each function is used individually in the present embodiment, the optical heterodyne interference function is applied to the step measurement in which the optical path length difference between the two beam lights is ¼ wavelength or less. In the above-described optical heterodyne interference, an example in which the reference light signal 22 is optically created by the third light receiver 21 is shown, but the reference light signal may be electrically created without using the above method. it can. To this end, a frequency that is twice the frequency fm of the signal that drives the AOD may be created. The optical system in this case is exactly the same as the optical system shown in FIG.

【0019】図5に第一の実施例(図1)を具体化する
ときの光学系の構成例を示す。レーザ光源10から放射
されたレーザ光は第一のBS11を透過し、シリンドリ
カルレンズ50と凸レンズ51の組合せで、紙面に平行
な面内に広がりを持つシートビームに変換されて、X方
向走査器(AOD)12に照射される。AOD12から
は回折1次光が発生し、X方向への走査を行う。AOD
12を出射した回折光は、凸レンズ52、シリンドリカ
ルレンズ53を経て再び円形ビームに変換される。位置
540が円形ビームへの変換点である。発散光として進
行するビームは第二のBS13を透過し、凸レンズ55
でコリメートされ、Y方向走査器(ガルバノミラー)1
4でY方向に走査される。この走査ビームはリレーレン
ズ56、57を経由(その間に反射ミラー560を設け
る)し、対物レンズ104で微小スポットに集光されて
被測定物106の面上を2次元走査する。被測定物10
6からの反射光は、第一のBS11で反射させ、第一の
受光器15で検出して共焦点検出を行い、また、第二の
BS13で反射させ、第二の受光器17で検出して非共
焦点検出を行う。以上の構成において、レーザ光100
が直線偏光である場合は、第一と第二のBS11、13
は偏光ビームスプリッターの構成とし、例えばレンズ5
7と対物レンズ106の間に1/4波長板を設置して偏
光軸を調整すれば、反射光の検出効率を高めることがで
きる。
FIG. 5 shows an example of the configuration of an optical system when the first embodiment (FIG. 1) is embodied. Laser light emitted from the laser light source 10 passes through the first BS 11, is converted into a sheet beam having a spread in a plane parallel to the paper surface by the combination of the cylindrical lens 50 and the convex lens 51, and the X-direction scanner ( AOD) 12 is irradiated. First-order diffracted light is generated from the AOD 12, and scanning is performed in the X direction. AOD
The diffracted light emitted from 12 passes through the convex lens 52 and the cylindrical lens 53, and is converted into a circular beam again. Position 540 is the conversion point to a circular beam. The beam that travels as divergent light passes through the second BS 13 and has a convex lens 55.
Collimated by Y direction scanner (galvano mirror) 1
4 is scanned in the Y direction. This scanning beam passes through relay lenses 56 and 57 (a reflection mirror 560 is provided between them), is focused on a minute spot by the objective lens 104, and two-dimensionally scans the surface of the DUT 106. DUT 10
The reflected light from 6 is reflected by the first BS 11, detected by the first light receiver 15 for confocal detection, and reflected by the second BS 13 and detected by the second light receiver 17. Non-confocal detection. In the above configuration, the laser light 100
Is linearly polarized light, the first and second BSs 11 and 13
Is a polarization beam splitter configuration, for example lens 5
If a quarter-wave plate is installed between the objective lens 106 and the objective lens 106 to adjust the polarization axis, the detection efficiency of reflected light can be increased.

【0020】図6で本発明の第一の実施例の具体的応用
例について説明する。図6(a)の曲線61は共焦点系
の偏向特性、図6(b)の曲線62は非共焦点系の偏向
特性を表す図である。各々の横軸はX方向走査器12に
よる走査位置、縦軸は反射光強度(相対強度)を表す。
曲線61の共焦点検出の場合は、走査位置の変化に対し
て反射光強度の変動が大きい。それは被測定物106か
らの反射光が再度X方向走査器(AOD)12に入射す
るため、走査の両端付近での回折効率が低下するためで
ある。したがって、反射光強度が大きい範囲610が実
際の測定に有効な範囲となり、一般には全走査距離の1
/3程度である。範囲610の両側では反射光強度の低
下が大きくなり、反射光強度信号のS/N比が低下して
測定の信頼性が低下する。曲線62の非共焦点検出の場
合、反射光がAOD12に再入射しないため、回折効率
の低下が少なく、ほぼ走査の全域にわたって反射光強度
が一定となる。そのために測定に有効な範囲が全走査範
囲までに広がるという特徴がある。例えば、全走査距離
を10μmに設定した場合、〜3μm以下の寸法測定、
特に、サブミクロン領域の回折限界を超えた寸法測定に
は共焦点検出を用いればよく、〜3μm以上の大きな寸
法測定の場合には非共焦点検出を用いればよい。したが
って、本発明の構成により、共焦点検出型LSMだけを
用いる場合に比べて、寸法測定に有効な範囲が3倍程度
まで拡大できる。
A specific application example of the first embodiment of the present invention will be described with reference to FIG. A curve 61 in FIG. 6A shows the deflection characteristic of the confocal system, and a curve 62 in FIG. 6B shows the deflection characteristic of the non-confocal system. The horizontal axis represents the scanning position by the X-direction scanner 12, and the vertical axis represents the reflected light intensity (relative intensity).
In the case of the confocal detection of the curve 61, the fluctuation of the reflected light intensity is large with respect to the change of the scanning position. This is because the reflected light from the object to be measured 106 is incident on the X-direction scanner (AOD) 12 again, so that the diffraction efficiency near the both ends of scanning is reduced. Therefore, the range 610 in which the reflected light intensity is large is an effective range for actual measurement, and generally, it is 1 of the total scanning distance.
It is about / 3. On both sides of the range 610, the reduction of the reflected light intensity becomes large, the S / N ratio of the reflected light intensity signal decreases, and the measurement reliability decreases. In the case of the non-confocal detection of the curve 62, the reflected light does not re-enter the AOD 12, so that the diffraction efficiency is less deteriorated and the reflected light intensity is almost constant over the entire scanning area. Therefore, there is a feature that the range effective for measurement extends to the entire scanning range. For example, when the total scanning distance is set to 10 μm, dimension measurement of ˜3 μm or less,
In particular, confocal detection may be used for dimension measurement exceeding the diffraction limit in the submicron region, and non-confocal detection may be used for large dimension measurement of ˜3 μm or more. Therefore, with the configuration of the present invention, the effective range for dimension measurement can be expanded up to about 3 times as compared with the case where only the confocal detection type LSM is used.

【0021】さらには、非共焦点検出は焦点深度が長
く、共焦点検出は焦点深度が短いという特徴を生かした
応用も可能である。対物レンズのNAが0.5であると
き、非共焦点検出では焦点深度が〜1.5μm程度であ
るため、段差が1.5μm程度あるパターンの寸法測定
に応用できる。共焦点検出では焦点深度が〜0.3μm
程度であるため、段差が0.3μm以下であるパターン
の寸法測定に応用する。このように、焦点深度の違いを
利用すれば、測定対象に応じて最適な測定ができるた
め、測定の信頼性が向上し、測定対象が広がる。以上の
測定では、いずれの測定にも単一型受光器を用いている
ため、走査に応じて反射光の強度変化が連続的に検出さ
れ、従来のLSMに比べて感度の高い測定が可能であ
る。
Further, the non-confocal detection has a long depth of focus, and the confocal detection has a short depth of focus. When the NA of the objective lens is 0.5, the depth of focus is about 1.5 μm in non-confocal detection, and therefore, it can be applied to the dimension measurement of a pattern having a step difference of about 1.5 μm. Depth of focus is ~ 0.3μm in confocal detection
Therefore, it is applied to the dimension measurement of a pattern having a step difference of 0.3 μm or less. As described above, if the difference in the depth of focus is used, the optimum measurement can be performed according to the measurement target, so that the reliability of the measurement is improved and the measurement target is expanded. In the above measurement, since the single type light receiver is used for all the measurements, the intensity change of the reflected light is continuously detected according to the scanning, and the measurement with higher sensitivity than the conventional LSM is possible. is there.

【0022】図7に本発明の第二の実施例の具体的な応
用例として、共焦点検出と光ヘテロダイン干渉の複合計
測例を示す。レーザ光源に波長が633nmのHe−N
eレーザ光を使用したとき、一度の2ビーム光の照射で
測定できる段差は±1/4波長(±0.158μm)以
下である。段差が1/4波長を超える場合には、共焦点
検出系による反射光強度検出と、光ヘテロダイン干渉計
測による位相角度検出の組み合わせればよい。図7
(a)は基板70とパターン部71の間の段差を測定す
るとき、段差発生部へ2ビーム光を照射した状態図であ
る。本例での光ヘテロダイン干渉法は2ビーム光の間の
光路差を検出する差動型の構成であるため、基板70と
パターン部71の両方に2ビーム光を照射する。パター
ン71の段差がhのとき、hに応じて位相角度が変化す
る。図7(b)は位相角度の検出を示す図である。λを
レーザ光の波長としたとき、h<λ/4のときに対応す
る位相角度がφa(0<φa<π)であれば、φaから
直接に段差hが測定できる。しかし、λ/4<h<λ/
2になれば、位相角度はφo+πとなる。この場合は位
相角度が負である。さらに、λ/2<h<3λ/4とな
れば、位相角度はφp+2πとなる。このように、hが
λ/4を超えるときは、πを超える回数nによって位相
角度nπが付加されるが、位相角度の測定からはnπが
決定されない。
FIG. 7 shows an example of composite measurement of confocal detection and optical heterodyne interference as a specific application example of the second embodiment of the present invention. He-N with wavelength of 633 nm for laser light source
When the e-laser light is used, the level difference that can be measured by irradiating two beams of light once is ± 1/4 wavelength (± 0.158 μm) or less. When the step exceeds ¼ wavelength, the reflected light intensity detection by the confocal detection system and the phase angle detection by the optical heterodyne interferometry may be combined. Figure 7
(A) is a state diagram in which two-beam light is irradiated to the step generation portion when measuring the step between the substrate 70 and the pattern portion 71. Since the optical heterodyne interferometry in this example has a differential type configuration for detecting an optical path difference between two beam lights, both the substrate 70 and the pattern portion 71 are irradiated with the two beam lights. When the step of the pattern 71 is h, the phase angle changes according to h. FIG. 7B is a diagram showing the detection of the phase angle. When λ is the wavelength of the laser light, if h <λ / 4 and the corresponding phase angle is φa (0 <φa <π), the step h can be measured directly from φa. However, λ / 4 <h <λ /
When it becomes 2, the phase angle becomes φo + π. In this case, the phase angle is negative. Further, if λ / 2 <h <3λ / 4, the phase angle becomes φp + 2π. Thus, when h exceeds λ / 4, the phase angle nπ is added by the number of times n that exceeds π, but nπ is not determined from the measurement of the phase angle.

【0023】図7(c)の曲線75は共焦点検出を行う
場合の、焦点位置の変化に対する反射光強度の変化を示
す図である。一般には焦点ズレが大きくなるほど反射光
の強度低下が大きくなる。上述したnπを決定するため
に、最初に基板70に照射光の焦点を合わせておき、次
にパターン部71に照射して強度の変化を測定する。曲
線75において、範囲750は段差がλ/4までの場合
の反射光強度範囲、範囲760は段差がλ/4以上でλ
/2までの反射光強度範囲、範囲770は段差がλ/2
以上で3λ/4までの反射光強度範囲である。共焦点検
出では焦点ズレに対する反射光強度の変化が大きいた
め、基板70に対するパターン部71の強度変化を測定
することにより、付加される位相角度nπのnの値を決
定することができる。そこで、前述のnπと検出した位
相角度φの和から、hがλ/4を超えた場合でも段差を
正確に測定することが可能である。
A curve 75 in FIG. 7C is a diagram showing a change in reflected light intensity with respect to a change in focus position when confocal detection is performed. Generally, the greater the focus shift, the greater the decrease in the intensity of the reflected light. In order to determine nπ, the irradiation light is first focused on the substrate 70, and then the pattern portion 71 is irradiated to measure the change in intensity. In the curve 75, a range 750 is a reflected light intensity range when the step is up to λ / 4, and a range 760 is λ / 4 when the step is λ / 4 or more.
Range of reflected light intensity up to / 2, range 770 has a step difference of λ / 2
With the above, the reflected light intensity range is up to 3λ / 4. In the confocal detection, since the change in the reflected light intensity with respect to the focus shift is large, the value of n of the added phase angle nπ can be determined by measuring the change in the intensity of the pattern portion 71 with respect to the substrate 70. Therefore, it is possible to accurately measure the step difference from the sum of nπ and the detected phase angle φ, even when h exceeds λ / 4.

【0024】[0024]

【発明の効果】上記のごとく本発明は一つのレーザ走査
顕微鏡の光学装置に、共焦点機能、非共焦点機能、光ヘ
テロダイン干渉機能という三つの機能のうち、二つある
いは三つの機能を設けた構成で、一つの装置で面内、面
外の形状、寸法の多様な測定が可能になる。機能の選択
は、機構的には反射光を検出する光路の切り換え、電気
的には駆動信号のスペクトルの制御で行うため、簡単な
操作で選択できる。本装置は、被測定物に応じては複数
の機能を用いて相補的な測定ができるため、測定範囲の
拡大、測定の信頼性の向上に有効である。また、従来は
測定目的に応じて個別の測定機を必要としていたが、一
つの測定機でよいため、計測効率の向上、測定コストの
低減が可能で、生産ラインでのインライン計測に有効で
ある。
As described above, the present invention provides two or three of the three functions of the confocal function, the non-confocal function, and the optical heterodyne interference function in the optical device of one laser scanning microscope. With the configuration, one device can perform various measurements of in-plane and out-of-plane shapes and dimensions. The function is mechanically selected by switching the optical path for detecting the reflected light and electrically by controlling the spectrum of the drive signal, so that the function can be selected by a simple operation. Since this device can perform complementary measurement using a plurality of functions depending on the object to be measured, it is effective in expanding the measurement range and improving the reliability of measurement. In the past, an individual measuring machine was required according to the purpose of measurement, but since only one measuring machine is required, it is possible to improve the measurement efficiency and reduce the measurement cost, which is effective for in-line measurement on the production line. .

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

【図1】本発明の第一の実施例の構成と動作を説明する
ブロック図である。
FIG. 1 is a block diagram illustrating the configuration and operation of a first embodiment of the present invention.

【図2】本発明の第二の実施例の構成と動作を説明する
ブロック図である。
FIG. 2 is a block diagram illustrating the configuration and operation of a second embodiment of the present invention.

【図3】従来のレーザ走査顕微鏡の構成と動作を説明す
るブロック図である。
FIG. 3 is a block diagram illustrating the configuration and operation of a conventional laser scanning microscope.

【図4】従来の光ヘテロダイン干渉計の構成と動作を説
明するブロック図である。
FIG. 4 is a block diagram illustrating the configuration and operation of a conventional optical heterodyne interferometer.

【図5】本発明に適用する光学系の構成の一実施例を示
す図である。
FIG. 5 is a diagram showing an example of a configuration of an optical system applied to the present invention.

【図6】本発明の第一の実施例の応用を説明する図で、
(a)は共焦点検出による偏向特性を示す図、(b)は
非共焦点検出による偏向特性を示す図である。
FIG. 6 is a diagram illustrating an application of the first embodiment of the present invention,
(A) is a figure which shows the deflection characteristic by confocal detection, (b) is a figure which shows the deflection characteristic by non-confocal detection.

【図7】本発明の第二の実施例の応用を説明する図で、
(a)は段差のあるパターンへの2ビーム光の照射を示
す図、(b)は位相角度の検出を示す図、(c)は焦点
位置に応じて反射光強度が変化する様子を表す図であ
る。
FIG. 7 is a diagram for explaining an application of the second embodiment of the present invention,
(A) is a diagram showing irradiation of two-beam light on a stepped pattern, (b) is a diagram showing detection of a phase angle, and (c) is a diagram showing how reflected light intensity changes depending on a focal position. Is.

【符号の説明】[Explanation of symbols]

10 レーザ光源 11 第一のビームスプリッター 12 X方向走査器 13 第二のビームスプリッター 14 Y方向走査器 15 第一の受光器 16 第一のデータ処理部 17 第二の受光器 18 第二のデータ処理部 21 第三の受光器 24 位相比較器 25 第三のデータ処理部 10 Laser Light Source 11 First Beam Splitter 12 X-Direction Scanner 13 Second Beam Splitter 14 Y-Direction Scanner 15 First Light Receiver 16 First Data Processing Section 17 Second Light Receiver 18 Second Data Processing Part 21 Third light receiver 24 Phase comparator 25 Third data processing unit

Claims (3)

【特許請求の範囲】[Claims] 【請求項1】 レーザ光源から放射されたレーザ光を第
一のビームスプリッターを透過させ、該透過光をX方向
走査器に入射してX方向に走査し、該X方向に走査され
るレーザ光を第二のビームスプリッターを透過させ、該
透過光をY方向走査器に入射してY方向に走査して2次
元走査を行わせ、該2次元走査されるレーザ光を対物レ
ンズで微小なスポットに集光して被測定物に照射し、該
被測定物からの反射光を前記第二のビームスプリッター
で反射させて前記反射光の全体強度を第二の受光器で検
出する非共焦点検出機能と、前記被測定物からの反射光
を前記第一のビームスプリッターで反射させ、該反射光
の強度分布の中央部を含む一部の範囲の強度を第一の受
光器で検出する共焦点検出機能を設けたレーザ走査顕微
鏡であって、前記第一のビームスプリッターで反射され
る光路と、前記第二のビームスプリッターで反射される
光路を選択する切り替え手段を設け、前記非共焦点検出
機能と共焦点検出機能を測定目的に応じて選択して使用
することを特徴とする複合計測機能を有するレーザ走査
顕微鏡。
1. Laser light emitted from a laser light source is transmitted through a first beam splitter, the transmitted light is made incident on an X-direction scanner and scanned in the X-direction, and the laser light is scanned in the X-direction. Through the second beam splitter, the transmitted light is made incident on the Y-direction scanner and scanned in the Y-direction to perform two-dimensional scanning, and the two-dimensionally scanned laser light is made into a minute spot by the objective lens. Non-confocal detection in which the object is measured by irradiating the object to be measured, reflected light from the object to be measured is reflected by the second beam splitter, and the total intensity of the reflected light is detected by the second light receiver. Function and confocal for reflecting the reflected light from the DUT by the first beam splitter and detecting the intensity of a partial range including the central portion of the intensity distribution of the reflected light by the first light receiver A laser scanning microscope provided with a detection function, A switching means for selecting an optical path reflected by one beam splitter and an optical path reflected by the second beam splitter is provided, and the non-confocal detection function and the confocal detection function are selected according to the measurement purpose. A laser scanning microscope having a composite measuring function characterized by being used.
【請求項2】 レーザ光源から放射されたレーザ光を第
一のビームスプリッターを透過させ、該透過光をX方向
走査器に入射してX方向に走査し、該X方向に走査され
るレーザ光を第二のビームスプリッターを透過させ、該
透過光をY方向走査器に入射してY方向に走査して2次
元走査を行わせ、該2次元走査されるレーザ光を対物レ
ンズで微小なスポットに集光して被測定物に照射し、該
被測定物からの反射光を前記第二のビームスプリッター
で反射させて前記反射光の全体強度を第二の受光器で検
出する非共焦点検出機能と、前記被測定物からの反射光
を前記第一のビームスプリッターで反射させ、該反射光
の強度分布の中央部を含む一部の範囲の強度を第一の受
光器で検出する共焦点検出機能と、前記被測定物からの
反射光を前記第二のビームスプリッターで反射させて、
該反射光を前記第二の受光器で検出し、該第二の受光器
で検出された反射光の位相変化を検出する光ヘテロダイ
ン干渉機能を設けたレーザ走査顕微鏡であって、測定目
的に応じて前記X方向走査器あるいはY方向走査器を駆
動する電気信号のスペクトルを制御してレーザ光の周波
数と光強度分布を変化させると共に、前記第一のビーム
スプリッターで反射される光路と、前記第二のビームス
プリッターで反射される光路を選択する切り替え手段を
設け、前記非共焦点検出機能と共焦点検出機能と光ヘテ
ロダイン干渉機能を測定目的に応じて選択して使用する
ことを特徴とする複合計測機能を有するレーザ走査顕微
鏡。
2. Laser light emitted from a laser light source is transmitted through a first beam splitter, the transmitted light is made incident on an X-direction scanner and scanned in the X-direction, and the laser light is scanned in the X-direction. Through the second beam splitter, the transmitted light is made incident on the Y-direction scanner and scanned in the Y-direction to perform two-dimensional scanning, and the two-dimensionally scanned laser light is made into a minute spot by the objective lens. Non-confocal detection in which the object is measured by irradiating the object to be measured, reflected light from the object to be measured is reflected by the second beam splitter, and the total intensity of the reflected light is detected by the second light receiver. Function and confocal for reflecting the reflected light from the DUT by the first beam splitter and detecting the intensity of a partial range including the central portion of the intensity distribution of the reflected light by the first light receiver Detecting function, the reflected light from the DUT to the second Reflect it with a beam splitter,
A laser scanning microscope provided with an optical heterodyne interference function for detecting the reflected light by the second light receiver and detecting a phase change of the reflected light detected by the second light receiver, depending on a measurement purpose. Control the spectrum of the electric signal for driving the X-direction scanner or the Y-direction scanner to change the frequency and the light intensity distribution of the laser light, and the optical path reflected by the first beam splitter, A switching means for selecting an optical path reflected by the second beam splitter is provided, and the non-confocal detection function, the confocal detection function, and the optical heterodyne interference function are selected and used according to the measurement purpose. Laser scanning microscope with measuring function.
【請求項3】 前記の光ヘテロダイン干渉機能と前記の
共焦点検出機能を用いて被測定物の段差を測定すると
き、光ヘテロダイン干渉機能で検出された位相角度φと
共に、共焦点検出機能で検出された反射光強度の変化か
ら前記位相角度がπ(rad)を超える回数nを計測し
て、位相角度nπ+φ(rad)から前記の段差を測定
することを特徴とする請求項2に記載の複合計測機能を
有するレーザ走査顕微鏡。
3. When measuring a step of an object to be measured using the optical heterodyne interference function and the confocal detection function, the confocal detection function detects the phase angle φ detected by the optical heterodyne interference function. 3. The composite according to claim 2, wherein the step count is measured from the phase angle nπ + φ (rad) by measuring the number n of times the phase angle exceeds π (rad) from the change in reflected light intensity. Laser scanning microscope with measuring function.
JP03839094A 1994-03-09 1994-03-09 Laser scanning microscope with compound measurement function Expired - Fee Related JP3411364B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP03839094A JP3411364B2 (en) 1994-03-09 1994-03-09 Laser scanning microscope with compound measurement function

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP03839094A JP3411364B2 (en) 1994-03-09 1994-03-09 Laser scanning microscope with compound measurement function

Publications (2)

Publication Number Publication Date
JPH07248203A true JPH07248203A (en) 1995-09-26
JP3411364B2 JP3411364B2 (en) 2003-05-26

Family

ID=12523961

Family Applications (1)

Application Number Title Priority Date Filing Date
JP03839094A Expired - Fee Related JP3411364B2 (en) 1994-03-09 1994-03-09 Laser scanning microscope with compound measurement function

Country Status (1)

Country Link
JP (1) JP3411364B2 (en)

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