JP6762608B2 - Three-dimensional shape measurement method using a scanning white interference microscope - Google Patents

Three-dimensional shape measurement method using a scanning white interference microscope Download PDF

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JP6762608B2
JP6762608B2 JP2016173995A JP2016173995A JP6762608B2 JP 6762608 B2 JP6762608 B2 JP 6762608B2 JP 2016173995 A JP2016173995 A JP 2016173995A JP 2016173995 A JP2016173995 A JP 2016173995A JP 6762608 B2 JP6762608 B2 JP 6762608B2
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coherence length
dimensional shape
inclination angle
interference
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JP2018040644A (en
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有吾 小野田
有吾 小野田
栄広 佐藤
栄広 佐藤
晶一 長谷川
晶一 長谷川
香織 柳川
香織 柳川
石橋 清隆
清隆 石橋
輝雄 加藤
輝雄 加藤
林太郎 中谷
林太郎 中谷
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Hitachi High Tech Science Corp
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00Measuring arrangements characterised by the use of optical techniques
    • G01B11/24Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/2441Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00Measuring instruments characterised by the use of optical techniques
    • G01B9/02Interferometers

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  • Length Measuring Devices By Optical Means (AREA)
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Description

本発明は、白色光源を用いた干渉計測により三次元形状計測を行う方法に関する。 The present invention relates to a method of performing three-dimensional shape measurement by interference measurement using a white light source.

走査型白色干渉顕微鏡は、白色光を試料に照射し、得られる干渉信号を高さ情報に変換することで三次元計測を行う装置であり、得られる干渉信号から各種計算をして表面形状、高さ、段差、膜厚、表面粗さ、同種材・異種材等の判定をする。 A scanning white interference microscope is a device that performs three-dimensional measurement by irradiating a sample with white light and converting the obtained interference signal into height information, and performs various calculations from the obtained interference signal to obtain the surface shape. Judge height, step, film thickness, surface roughness, similar material / dissimilar material, etc.

例えば、特許文献1では、走査型白色干渉顕微鏡の参照面ミラーを傾斜させることにより、計測対象物の傾斜角を求める方法が記載されている。特許文献2では、薄膜が存在する場合に、走査型白色干渉顕微鏡により得られた干渉パターンが重なり合って歪め合う現象を、テンプレートを用いることでピーク分離する方法が記載されている。 For example, Patent Document 1 describes a method of obtaining an inclination angle of an object to be measured by inclining a reference plane mirror of a scanning white interference microscope. Patent Document 2 describes a method of peak separation by using a template for a phenomenon in which interference patterns obtained by a scanning white interference microscope overlap and distort in the presence of a thin film.

国際公開第2014/185133号International Publication No. 2014/185133 特開2011−221027号公報Japanese Unexamined Patent Publication No. 2011-2221027

走査型白色干渉顕微鏡を用いた三次元計測においては、光線光学で与えられる対物レンズの開口数NA(numerical aperture)に応じて定められる角度より内側での計測では、見かけ上のコヒーレンス長は顕著に変化しない。よって、このような条件でのコヒーレンス長には、これまで特に注意が払われていない。 In three-dimensional measurement using a scanning white interference microscope, the apparent coherence length is remarkable in the measurement inside the angle determined by the numerical aperture NA (numerical aperture) of the objective lens given by photooptics. It does not change. Therefore, no particular attention has been paid to the coherence length under such conditions.

ただし、開口数NAを越えた高傾斜面計測において、測定される見かけ上のコヒーレンス長は大きくなる。このような状況下では、傾斜角度を求める際に特許文献1では、参照面ミラーの傾斜を大きくする、例えば開口数NA以上に参照面ミラーを傾けると戻り光が少なくなるため暗くなってしまい、開口数NA以上における傾斜角度の計測は難しかった。 However, the apparent coherence length measured becomes large in the measurement of a high inclined surface exceeding the numerical aperture NA. Under such a situation, in Patent Document 1, when the tilt angle is obtained, if the tilt of the reference plane mirror is increased, for example, if the reference plane mirror is tilted beyond the numerical aperture NA, the return light is reduced and the reference plane mirror becomes dark. It was difficult to measure the tilt angle when the numerical aperture was NA or more.

また、試料に膜が形成されている場合、高傾斜面の計測においては、観測されるコヒーレンス長の延びが、膜による影響なのか高傾斜面による影響なのかの区別および着眼はされてこなかった。 In addition, when a film is formed on the sample, it has not been possible to distinguish and focus on whether the observed coherence length extension is due to the film or the high-inclined surface in the measurement of the high-inclined surface. ..

本発明は、計測対象物の表面における傾斜角度の大きい高傾斜面の適切な計測を実現し得る走査型白色干渉顕微鏡を用いた三次元形状計測方法を提供する。 The present invention provides a three-dimensional shape measurement method using a scanning white interference microscope that can realize appropriate measurement of a highly inclined surface having a large inclination angle on the surface of an object to be measured.

本発明は、走査型白色干渉顕微鏡を用いた三次元形状計測方法であって、計測対象物に対し照射した光源からの光の干渉信号の包絡線を取得し、前記包絡線の半値幅に基づき、観測される見かけ上のコヒーレンス長である観測コヒーレンス長lc'を取得し、前記観測コヒーレンス長に基づき、前記計測対象物の表面の傾斜角度を計測する。 The present invention is a three-dimensional shape measurement method using a scanning white coherence microscope, in which an envelope of an interference signal of light from a light source irradiating an object to be measured is acquired and based on the half width of the envelope. , The observed coherence length lc', which is the apparent coherence length observed, is acquired, and the inclination angle of the surface of the object to be measured is measured based on the observed coherence length.

本発明によれば、干渉信号の包絡線の半値幅に基づき、観測コヒーレンス長を取得した上で、計測対象物(試料)の表面の傾斜角度を計測することができる。よって、計測対象物の表面における傾斜角度の大きい高傾斜面でも適切に傾斜角度を計測することができ、表面の形状、特性を把握することができる。 According to the present invention, it is possible to measure the inclination angle of the surface of the object to be measured (sample) after obtaining the observed coherence length based on the half width of the envelope of the interference signal. Therefore, the inclination angle can be appropriately measured even on a highly inclined surface having a large inclination angle on the surface of the object to be measured, and the shape and characteristics of the surface can be grasped.

図1は、本発明の実施の形態に係る走査型白色干渉顕微鏡の全体構成図である。FIG. 1 is an overall configuration diagram of a scanning white interference microscope according to an embodiment of the present invention. 図2は、試料の表面の傾斜角度θの定義を示す図である。FIG. 2 is a diagram showing the definition of the inclination angle θ of the surface of the sample. 図3は、走査型白色干渉顕微鏡により観測される一般的な干渉信号を示すグラフである。FIG. 3 is a graph showing a general interference signal observed by a scanning white interference microscope. 図4は、計測対象物の表面における、低傾斜面および高傾斜面のそれぞれにおいて、カメラの1ピクセル(1画素)に相当する領域を拡大して示す図である。FIG. 4 is an enlarged view showing a region corresponding to one pixel (one pixel) of the camera on each of the low-inclined surface and the high-inclined surface on the surface of the measurement object. 図5は、カメラの1ピクセルにおける高さ差分を示す図である。FIG. 5 is a diagram showing a height difference in one pixel of the camera. 図6は、傾斜角度に対応した高さ差分をプロットしたグラフを示す。FIG. 6 shows a graph plotting the height difference corresponding to the tilt angle. 図7は、計測対象物の表面の局所曲率半径を求める方法を説明する概念図である。FIG. 7 is a conceptual diagram illustrating a method of obtaining the local radius of curvature of the surface of the object to be measured. 図8は、計測対象物の表面における、低傾斜面および高傾斜面のそれぞれにおいて、カメラの1ピクセルに相当する領域に発生する干渉縞を拡大して示す図である。FIG. 8 is an enlarged view showing interference fringes generated in a region corresponding to one pixel of the camera on each of the low-inclined surface and the high-inclined surface on the surface of the measurement object. 図9は、広範囲での干渉縞と1ピクセルの関係を示す模式図であり、(a)は低傾斜面における関係を示し、(b)は高傾斜面における関係を示す。9A and 9B are schematic views showing the relationship between the interference fringes over a wide range and one pixel, in which FIG. 9A shows the relationship on a low slope surface and FIG. 9B shows the relationship on a high slope surface. 図10は、所定の傾斜角度において、1ピクセルに入力される輝度の振幅値を表す式(12)をプロットしたグラフである。FIG. 10 is a graph in which the equation (12) representing the amplitude value of the luminance input to one pixel at a predetermined tilt angle is plotted. 図11は、膜を有する計測対象物において、高傾斜面の計測を行う状況を説明する概念図である。FIG. 11 is a conceptual diagram illustrating a situation in which a highly inclined surface is measured in a measurement object having a film. 2つの輝点の干渉縞の分離の可否を説明する概念図であり、(a)は観測される干渉縞の包絡線の中心がコヒーレンス長lcの半分となったときを分離できる上限と仮定した場合の説明図であり、(b)は見かけ上の延びΔzの補正後の説明図である。It is a conceptual diagram explaining whether or not the interference fringes of two bright spots can be separated, and (a) is assumed to be the upper limit of separation when the center of the envelope of the observed interference fringes becomes half of the coherence length lc. It is explanatory drawing of the case, and (b) is explanatory drawing after correction of the apparent extension Δz. 図13は、式(5)および式(13)を所定の条件においてプロットして得られるグラフである。FIG. 13 is a graph obtained by plotting equations (5) and (13) under predetermined conditions.

以下、本発明に係る走査型白色干渉顕微鏡を用いた三次元形状計測方法の好適な実施形態を、図1〜図13に基づいて詳述する。 Hereinafter, a preferred embodiment of the three-dimensional shape measuring method using the scanning white interference microscope according to the present invention will be described in detail with reference to FIGS. 1 to 13.

図1は、本発明の実施の形態に係る走査型白色干渉顕微鏡の全体構成図である。走査型白色干渉顕微鏡100は、装置本体10と、計測対象の試料S(計測対象物)が載置されたステージ20と、得られたデータを処理するコンピュータ(プロセッサ)30とを含む。装置本体10は、白色光源11と、フィルタ12と、ビームスプリッタ13と、二光束干渉対物レンズ(対物レンズ)14と、カメラ15と、ピエゾアクチュエータ16と、を含む。 FIG. 1 is an overall configuration diagram of a scanning white interference microscope according to an embodiment of the present invention. The scanning white interference microscope 100 includes an apparatus main body 10, a stage 20 on which a sample S (measurement target) to be measured is placed, and a computer (processor) 30 that processes the obtained data. The apparatus main body 10 includes a white light source 11, a filter 12, a beam splitter 13, a two-luminous flux interference objective lens (objective lens) 14, a camera 15, and a piezo actuator 16.

矢印Aで示すように白色光源11から出射された光(白色光)は、フィルタ(例えば波長フィルタ、偏光フィルタなど)12を通過した後、ビームスプリッタ13で二光束干渉対物レンズ14へ導かれる(矢印B)。光は二光束干渉対物レンズ14内のビームスプリッタで、計測対象物(試料S自体およびその内部の物質を含む)側へ向かう第1の光と、図示せぬ参照ミラー側へ向かう第2の光の2つに分割される。計測対象物に対して対向して配置される二光束干渉対物レンズ14内のビームスプリッタから計測対象物までの光学距離と、当該ビームスプリッタから参照ミラーまでの光学距離が等しくなった時に、計測信号が2つの光の干渉信号の形態で観測可能となり、カメラ15がこの干渉信号を干渉縞(干渉パターン)として撮像し、干渉信号がコンピュータ30に保持、格納される。また、図1の実施形態では、ビームスプリッタ13から図示せぬ参照ミラーまでの距離が固定されているため、ピエゾアクチュエータ16を用いて掃引させることにより(矢印Cの動き)、計測対象物との距離を変化させている。走査型白色干渉顕微鏡100はコヒーレンス長の短い白色光源を用いるため(コヒーレンス長〜1μm)、干渉信号が得られた位置が、計測対象物が存在するZ位置(深さ位置)となる。 As shown by the arrow A, the light (white light) emitted from the white light source 11 passes through the filter (for example, wavelength filter, polarizing filter, etc.) 12 and then is guided to the diluminous flux interference objective lens 14 by the beam splitter 13. Arrow B). The light is a beam splitter in the two-luminous flux interference objective lens 14, and the first light toward the measurement target (including the sample S itself and the substance inside the sample S) side and the second light toward the reference mirror side (not shown). It is divided into two parts. A measurement signal when the optical distance from the beam splitter to the measurement object in the two-beam interference objective lens 14 arranged to face the measurement object and the optical distance from the beam splitter to the reference mirror become equal. Is observable in the form of two light interference signals, the camera 15 images the interference signal as an interference fringe (interference pattern), and the interference signal is held and stored in the computer 30. Further, in the embodiment of FIG. 1, since the distance from the beam splitter 13 to the reference mirror (not shown) is fixed, by sweeping with the piezo actuator 16 (movement of arrow C), the distance to the object to be measured The distance is changing. Since the scanning white interference microscope 100 uses a white light source having a short coherence length (coherence length ~ 1 μm), the position where the interference signal is obtained is the Z position (depth position) where the object to be measured exists.

図2は、測定対象物である試料Sの表面の傾斜角度θの定義を示す図であり、図1の走査型白色干渉顕微鏡の全体構成図の一部を用いている。測定対象物に対して鉛直方向におろした線から、測定対象物の表面の接線に対する法線に見込んだ角度を傾斜角度θと定義している。図2の例では、点Pにおける傾斜角度はθであり、点Pにおける傾斜角度はθである。 FIG. 2 is a diagram showing the definition of the inclination angle θ of the surface of the sample S which is the measurement target, and a part of the overall configuration diagram of the scanning white interference microscope of FIG. 1 is used. The angle from the line drawn vertically to the object to be measured to the normal to the tangent to the surface of the object to be measured is defined as the inclination angle θ. In the example of FIG. 2, the tilt angle at the point P 1 is θ 1 , and the tilt angle at the point P 2 is θ 2 .

一方、光線光学下においては、図2の傾斜角度θによって定められる対物レンズ14の臨界角度(対物レンズの中心を通過する軸上の1点から出て対物レンズに入る光のうち最も外側の光の角度)がΘの場合、対物レンズ14の開口数NA(numerical aperture)は、下記の式(1)に求められる。尚、nは屈折率(測定対象物側の空間の物質の屈折率)であり、通常、空気の場合1である。対物レンズ14の開口数NAが高いほど水平分解能は高くなり、また、焦点深度が小さくなるため垂直分解能も高くなる。 On the other hand, under ray optics, the outermost light among the light emitted from one point on the axis passing through the center of the objective lens and entering the objective lens, which is the critical angle of the objective lens 14 determined by the tilt angle θ in FIG. When Θ), the numerical aperture NA (numerical aperture) of the objective lens 14 is obtained by the following equation (1). Note that n is the refractive index (refractive index of the substance in the space on the side of the object to be measured), which is usually 1 in the case of air. The higher the numerical aperture NA of the objective lens 14, the higher the horizontal resolution, and the smaller the depth of focus, the higher the vertical resolution.

Figure 0006762608
Figure 0006762608

図3は、走査型白色干渉顕微鏡100により観測される一般的な干渉信号、すなわち計測対象物(試料S)に対し、白色光源11から照射した光(白色光)の干渉信号を示すグラフである。走査型白色干渉顕微鏡100のカメラ15で観測される信号強度Iは、式(2)で示すように、参照光強度のIおよび測定試料からの反射光強度Iのオフセット項(第1項および第2項)、および干渉信号である第3項からなる。第3項中のΔpは光路長差(OPD:Optical Path Difference)であり、図1で説明した二光束干渉対物レンズ14内の図示せぬビームスプリッタから計測対象物(試料S自体およびその内部の物質を含む)側までの光学距離と図示せぬビームスプリッタから図示せぬ参照ミラー側までの光学距離の差である。 FIG. 3 is a graph showing a general interference signal observed by the scanning white interference microscope 100, that is, an interference signal of light (white light) emitted from a white light source 11 with respect to a measurement object (sample S). .. The signal intensity I observed by the camera 15 of the scanning white interference microscope 100 is the offset term (first term) of the reference light intensity I 1 and the reflected light intensity I 2 from the measurement sample, as shown in the equation (2). And the second term), and the third term which is an interference signal. Δp in the third term is an optical path length difference (OPD), which is an object to be measured (sample S itself and its inside) from a beam splitter (not shown) in the two-beam interference objective lens 14 described with reference to FIG. It is the difference between the optical distance to the side (including the substance) and the optical distance from the beam splitter (not shown) to the reference mirror side (not shown).

Figure 0006762608
Figure 0006762608

式(2)の干渉項である第3項は図3の実線で示す干渉信号に相当し、破線で表す干渉信号の包絡線は、式(3)の3つの因子から構成される。3つの因子は、光源、すなわち白色光源11の波長スペクトル特性f(λ)、波長フィルタ(フィルタ12に含まれる)のスペクトル特性f(λ)、カメラ15の感度であるスペクトル特性f(λ)である。λは光源の波長である。 The third term, which is the interference term of the equation (2), corresponds to the interference signal shown by the solid line in FIG. 3, and the envelope of the interference signal represented by the broken line is composed of the three factors of the equation (3). Three factors, a light source, i.e. wavelength spectrum characteristic f 1 of the white light source 11 (lambda i), the spectral characteristics f 2 (lambda i) of the wavelength filter (included in the filter 12), the spectral characteristics f is the sensitivity of the camera 15 3i ). λ i is the wavelength of the light source.

Figure 0006762608
Figure 0006762608

これらから決まる図3の包絡線の半値幅はコヒーレンス長として観測される。コヒーレンス長lcは式(4)で与えられるが、式(4)は、傾斜角度θ=0°(0度)における式であり、計測対象物の表面の性状による影響を受けていない光源のコヒーレンス長の値である。式(4)において、λ:光源の中心波長、Δλ:光源の波長の半値幅、c:光速、Δf:光源の周波数の半値幅である。また、この式は、傾斜角度θ=0°を前提とした状態において、白色光源11とフィルタ12の波長フィルタの特性(白色光源の波長や波長フィルタの透過波長等)によって決まる一義的な値を示すものであり、基本となるコヒーレンス長である基本コヒーレンス長lcとして定義される。 The half width of the envelope in FIG. 3 determined from these is observed as the coherence length. The coherence length lc is given by the equation (4), and the equation (4) is an equation at an inclination angle θ = 0 ° (0 degree), and the coherence of the light source is not affected by the surface properties of the object to be measured. The length value. In equation (4), λ c : the center wavelength of the light source, Δλ: the half width of the wavelength of the light source, c: the speed of light, and Δf: the half width of the frequency of the light source. Further, this equation sets a unique value determined by the characteristics of the wavelength filters of the white light source 11 and the filter 12 (wavelength of the white light source, transmission wavelength of the wavelength filter, etc.) on the assumption that the inclination angle θ = 0 °. It is shown and is defined as the basic coherence length lc, which is the basic coherence length.

Figure 0006762608
Figure 0006762608

図4は、計測対象物である試料Sの表面における、低傾斜面Sおよび高傾斜面Sのそれぞれにおいて、カメラ15の1ピクセル(1画素)に相当する領域を拡大して示すものである。ここでの1ピクセルに相当する領域は、計測対象物の断面を示しており(横軸が半径方向のx座標、縦軸が高さ方向のz座標)、それぞれの領域における表面が表れている。本図における表面は、1ピクセルにおいて変化する表面の状態を概念的に示したものであり、実際に記録される信号ではない。 4, the surface of the sample S is a measurement object, in each of the low inclined surfaces S 1 and the high-tilt surfaces S 2, shows an enlarged view of the region corresponding to one pixel of the camera 15 (1 pixel) is there. The area corresponding to one pixel here shows the cross section of the object to be measured (the horizontal axis is the x-coordinate in the radial direction, the vertical axis is the z-coordinate in the height direction), and the surface in each area appears. .. The surface in this figure conceptually shows the state of the surface that changes in one pixel, and is not a signal that is actually recorded.

掃引時に得られる干渉信号は、計測対象物の表面に対して得られるが、低傾斜面Sでは1ピクセルの横方向(x方向)に渡って表面の位置は高さ方向(z方向)で大きく変動しない。よって、1ピクセルに入力される、表面ごとに得られる複数のフレームごとの干渉信号SGはそれぞれ近い高さのものが得られ、それぞれ重なり合う度合いが大きくなり、干渉して強め合う。従って半値幅が小さく高さの大きい合成された干渉信号、すなわち山型の包絡線ECが得られる。 Interference signal obtained at the time of the sweep is obtained for the surface of the measurement object, at the position of the surface over the lower inclined surface S 1 in one pixel in the lateral direction (x direction) the height direction (z-direction) It does not fluctuate significantly. Therefore, the interference signals SG 1 for each of a plurality of frames, which are input to one pixel and are obtained for each surface, are obtained at similar heights, and the degree of overlap is increased, and they interfere with each other and strengthen each other. Therefore, a combined interference signal having a small half width and a large height, that is, a mountain-shaped envelope EC 1 , can be obtained.

一方、高傾斜面Sでは、1ピクセルの横方向(x方向)に渡って表面の位置は高さ方向(z方向)で大きく変動する。よって、1ピクセルに入力される、表面ごとに得られる複数のフレームごとの干渉信号SGは様々な高さに応じたものが得られ、重なり合う度合いが小さくなり、干渉して強め合いにくい。従って半値幅が大きく高さの小さい合成された干渉信号、すなわち台形のような形状をした包絡線ECが得られる。すなわち見かけ上、基本コヒーレンス長lcがあたかも延びたように観測される。 On the other hand, the high-tilt surfaces S 2, the position of the surface over the lateral direction (x direction) of one pixel varies greatly in the height direction (z direction). Therefore, the interference signals SG 2 for each of a plurality of frames obtained for each surface, which are input to one pixel, can be obtained according to various heights, the degree of overlap is small, and it is difficult to interfere and strengthen each other. Therefore, a synthesized interference signal having a large half-value width and a small height, that is, an envelope EC 2 having a trapezoidal shape can be obtained. That is, apparently, the basic coherence length lc is observed as if it were extended.

図5は、カメラ15の1ピクセルに着目したものであり、カメラ15のピクセルサイズ(画素サイズ;1ピクセルの1辺)がWc、対物レンズ14の倍率がXの場合、実際に1ピクセルにおいて観測される領域は、Wc/Xを1辺とする正方形の領域になる。そして、1ピクセルにおける一端と他端では、異なる高さ情報(異なる表面の位置情報)が入力されると仮定する(図5ではZおよびZ)。このとき、一端と他端を結ぶ表面の角度をθ、すなわち傾斜角度とすると、1ピクセルに入力される表面の位置の変動量に相当する高さ差分であるΔz(=Z−Z)は、式(5)で与えられることとなる。 FIG. 5 focuses on one pixel of the camera 15, and when the pixel size (pixel size; one side of one pixel) of the camera 15 is Wc and the magnification of the objective lens 14 is X, it is actually observed at one pixel. The region to be created is a square region having Wc / X as one side. Then, it is assumed that different height information (position information of different surfaces) is input at one end and the other end of one pixel (Z 1 and Z 2 in FIG. 5). At this time, if the angle of the surface connecting one end and the other end is θ, that is, the inclination angle, Δz (= Z 2 −Z 1 ), which is a height difference corresponding to the amount of variation in the position of the surface input to one pixel. Will be given by equation (5).

Figure 0006762608
Figure 0006762608

図6は、式(5)で得られる高さ差分Δzを、傾斜角度θに応じてグラフ上にプロットしたものであり、1ピクセルに入力される高さ差分は、表面の傾斜角度θが0°であれば(例えば図4の低傾斜面S付近)、0であることは自明である。また、式(5)より、傾斜角度θが増大するにつれ、1ピクセルに入力される高さ差分Δzは増大することも自明である。すなわち、傾斜角度0°においては、見かけ上、コヒーレンス長の伸長の影響は0であり、式(4)の基本コヒーレンス長lcがそのまま観測される。一方、傾斜角度θが大きくなるにつれ、高さ差分Δzは、式(5)に従い増大する。このようにして実際に、走査型白色干渉顕微鏡100を用いた観測により取得される観測コヒーレンス長(見かけ上のコヒーレンス長)lc'は傾斜角度に従って変化し、式(6)で与えられる。すなわち、高さ差分Δzは、傾斜角度θに応じて基本コヒーレンス長lcが延びる値であるコヒーレンス長の延びに相当する。そして、観測コヒーレンス長lc'は、走査型白色干渉顕微鏡100の白色光源11およびフィルタ12の波長フィルタによって定められる基本コヒーレンス長lcと、傾斜角度θに応じて基本コヒーレンス長lcが延びる値である延びΔzの和である。 FIG. 6 is a graph obtained by plotting the height difference Δz obtained by the equation (5) according to the inclination angle θ, and the height difference input to one pixel has a surface inclination angle θ of 0. if ° (e.g. low inclined surface S around 1 in FIG. 4), it is obvious that it is zero. Further, from the equation (5), it is obvious that the height difference Δz input to one pixel increases as the inclination angle θ increases. That is, at an inclination angle of 0 °, the influence of the extension of the coherence length is apparently 0, and the basic coherence length lc of the equation (4) is observed as it is. On the other hand, as the inclination angle θ increases, the height difference Δz increases according to the equation (5). In this way, the observed coherence length (apparent coherence length) lc', which is actually obtained by observation using the scanning white interference microscope 100, changes according to the tilt angle and is given by the equation (6). That is, the height difference Δz corresponds to the extension of the coherence length, which is the value at which the basic coherence length lc is extended according to the inclination angle θ. The observed coherence length lc'is a value obtained by extending the basic coherence length lc determined by the wavelength filters of the white light source 11 and the filter 12 of the scanning white interference microscope 100 and the basic coherence length lc according to the inclination angle θ. It is the sum of Δz.

基本コヒーレンス長lc、カメラ15のピクセルサイズWc、および対物レンズの倍率Xは既知であり、観測されるコヒーレンス長lc'を計測することにより、式(5)および式(6)を用いて、傾斜角度θ(tanθ)、高さ差分Δzを求めることができる。このようにして、計測対象物の表面の形状、すなわち計測対象物の表面の傾斜角度を計測することができる。 The basic coherence length lc, the pixel size Wc of the camera 15, and the magnification X of the objective lens are known, and by measuring the observed coherence length lc', the tilt is used using equations (5) and (6). The angle θ (tan θ) and the height difference Δz can be obtained. In this way, the shape of the surface of the object to be measured, that is, the inclination angle of the surface of the object to be measured can be measured.

Figure 0006762608
Figure 0006762608

図7は、図4および図5で説明した、カメラの1ピクセル内で捉えられた表面の位置変化を利用し、当該ピクセルにおける計測対象物の表面の局所曲率半径を求める方法を説明する概念図である。ピクセルにおける両端の点をP、Pとし、点P、Pを通る半径rの円が点P、Pそれぞれでの半径r、rの間の中心を通る半径(半径r、rの各々から角度θ’ずれた半径)が、表面上の任意の仮想点Pに位置すると仮定する。すなわち、1ピクセル内で計測された時の局所曲率半径は同じと想定できるため、r=r=rが成立し、代表点は、両端の半径r、rを均等な角度θ’で分割する半径rが通過する点Pである。この仮想点Pにおける半径rが、局所曲率半径であると仮定すると、式(7)で表される関係が成立することとなる。 FIG. 7 is a conceptual diagram illustrating a method of obtaining the local radius of curvature of the surface of the object to be measured in the pixel by utilizing the position change of the surface captured within one pixel of the camera described with reference to FIGS. 4 and 5. Is. The points at both ends at the pixel and P 1, P 2, the radius (radius circle of radius r passing through the points P 1, P 2 passes through the center between the radius r 1, r 2 at point P 1, P 2, respectively It is assumed that the radius (radius offset by an angle θ'from each of r 1 and r 2 ) is located at an arbitrary virtual point P on the surface. That is, since it can be assumed that the local radius of curvature when measured within one pixel is the same, r = r 1 = r 2 holds, and the representative points are the radii r 1 and r 2 at both ends at equal angles θ'. It is a point P through which the radius r divided by is passed. Assuming that the radius r at the virtual point P is the local radius of curvature, the relationship represented by the equation (7) is established.

Figure 0006762608
Figure 0006762608

高さ差分Δzを観測した後、図6のグラフおよび式(5)から傾斜角度θを求めることができ、式(7)には未知の変数θ、θ、局所曲率半径rの3つが残ることになる。よって、式(7)の3つの連立方程式を解くことで、局所曲率半径r、ひいては局所曲率1/rを算出することが可能となる。すなわち、高さ差分Δzである延びΔzと、傾斜角度θから、計測対象物の表面の局所曲率半径rを算出することが可能である。なお、局所曲率半径(局所曲率)は、表面の高さzが検出できれば、光線光学の分野で周知の式(8)より求めることができるが、高さであるzの2階微分が分母にあるためノイズが大きい。それに対して式(7)は傾斜角度θから局所曲率半径を求めているため、ノイズに強い計測手法といえる。 After observing the height difference Δz, the inclination angle θ can be obtained from the graph of FIG. 6 and equation (5). In equation (7), there are three unknown variables θ 1 , θ 2 , and the local radius of curvature r. It will remain. Therefore, by solving the three simultaneous equations of the equation (7), it is possible to calculate the local radius of curvature r and, by extension, the local curvature 1 / r. That is, it is possible to calculate the local radius of curvature r of the surface of the object to be measured from the extension Δz which is the height difference Δz and the inclination angle θ. The radius of curvature (local curvature) can be obtained from the equation (8) well known in the field of photooptics if the height z of the surface can be detected, but the second derivative of z, which is the height, is the denominator. There is a lot of noise. On the other hand, the equation (7) is a noise-resistant measurement method because the local radius of curvature is obtained from the inclination angle θ.

Figure 0006762608
Figure 0006762608

次に、適切な基本コヒーレンス長lcを設定するための手法について説明する。図4における高傾斜面Sの如き高傾斜面を計測する場合、傾斜角度90度(90°)まで測ると仮定すると、傾斜角度90°の点から所定の傾斜角度θcをとる点において、カメラの1ピクセルの距離に相当する長さは、式(9)で与えられる。x90は傾斜角度90°の点におけるピクセルのx座標の値、xθcは所定の傾斜角度θcをとる点におけるピクセルのx座標の値である。 Next, a method for setting an appropriate basic coherence length lc will be described. When measuring high inclined surface such as a high-tilt surfaces S 2 in FIG. 4, assuming that measure to the inclined position of 90 degrees (90 °), in that has a predetermined inclination angle θc in terms of tilt angle 90 °, Camera The length corresponding to the distance of 1 pixel of is given by the equation (9). x 90 is the x-coordinate value of the pixel at a point with an inclination angle of 90 °, and x θc is the x-coordinate value of the pixel at a point with a predetermined inclination angle θc.

Figure 0006762608
Figure 0006762608

式(9)より、傾斜角度90°からカメラ1ピクセル分ずれた傾斜角度θcは、式(10)で与えられる。式(6)において基本コヒーレンス長lcをむやみに大きくし過ぎると、見かけ上延びたコヒーレンス長(観測コヒーレンス長)lc'に対するΔzの影響度が小さくなり、傾斜角度の計測精度が落ちてしまうため、基本コヒーレンス長lcは所定の大きさに抑えることが望ましい。しかしながら、基本コヒーレンス長lcが短すぎると光量不足や干渉縞の出現時間の極小化などの弊害が生じ得る。 From the equation (9), the inclination angle θc deviated from the inclination angle of 90 ° by one pixel of the camera is given by the equation (10). If the basic coherence length lc is made too large in the equation (6), the influence of Δz on the apparently extended coherence length (observed coherence length) lc'is reduced, and the measurement accuracy of the tilt angle is lowered. It is desirable that the basic coherence length lc be suppressed to a predetermined size. However, if the basic coherence length lc is too short, adverse effects such as insufficient light intensity and minimization of the appearance time of interference fringes may occur.

そこで、傾斜角度90°まで計測できることを前提条件とし、カメラ1ピクセル分ずれた傾斜角度θc(88°付近等)の表面の位置において延びΔzが基本コヒーレンス長lcと等しくなれば、計測可能な全傾斜角度において分解能を保ちつつ計測ができる。よって、傾斜角度θcにおける見かけ上延びるΔzを、光源および波長フィルタから設定可能な基本コヒーレンス長lcの最大値の目安とすることができ、式(11)を条件として基本コヒーレンス長lcを設定する。すなわち、基本コヒーレンス長lcは、傾斜角度90°に対応する計測対象物の表面から、カメラの1画素分に相当する傾斜角度θcだけずれた表面における延びΔz以下になるように設定されることが望ましい。基本コヒーレンス長lcは最大でカメラ1ピクセル分ずれた傾斜角度θcにおいてlc:Δz=1:1(lc=Δz)となる。ここでは傾斜角度90°まで計測できることを前提条件としたが、既に測定試料の傾斜角度が分かっており傾斜角度90°までの計測が不要であるときには、例えば傾斜角度60°でも同様に計算することが可能であり、基本コヒーレンス長lcも小さくできることから、計測できる傾斜角度は犠牲になるものの、z分解能が高くなる。 Therefore, assuming that the tilt angle can be measured up to 90 °, if the extension Δz becomes equal to the basic coherence length lc at the surface position of the tilt angle θc (near 88 °, etc.) deviated by 1 pixel of the camera, all measurable. Measurement can be performed while maintaining resolution at the tilt angle. Therefore, the apparently extending Δz at the inclination angle θc can be used as a guideline for the maximum value of the basic coherence length lc that can be set from the light source and the wavelength filter, and the basic coherence length lc is set under the condition of the equation (11). That is, the basic coherence length lc is set so as to extend Δz or less on the surface deviated by the tilt angle θc corresponding to one pixel of the camera from the surface of the measurement object corresponding to the tilt angle 90 °. desirable. The basic coherence length lc is lc: Δz = 1: 1 (lc = Δz) at an inclination angle θc deviated by one pixel of the camera at the maximum. Here, it is assumed that the tilt angle can be measured up to 90 °, but when the tilt angle of the measurement sample is already known and the measurement up to the tilt angle of 90 ° is unnecessary, for example, the tilt angle of 60 ° can be calculated in the same manner. Since this is possible and the basic coherence length lc can be reduced, the z-resolution is increased at the expense of the measurable tilt angle.

Figure 0006762608
Figure 0006762608

Figure 0006762608
Figure 0006762608

次に、高傾斜面における干渉信号の劣化対策について説明する。図8は、図4と同様に、計測対象物である試料Sの表面における、低傾斜面Sおよび高傾斜面Sのそれぞれにおいて、カメラ15の1ピクセル(1画素)に相当する領域を拡大して示すものである。ただし、図4とは異なり、ここでの1ピクセルに相当する領域は、図4で得られた計測対象物の断面である1ピクセルに垂直なxy平面上で、表面の形状が干渉縞によって表れたものを示したものであり、実際に1ピクセルにおいて記録される信号である(横軸が半径方向のx座標、縦軸がx座標およびz座標に直交するy座標)。従来、開口数NA以内での観察(低傾斜面Sの観察)では発生しなかった現象であるが、高傾斜面Sのように開口数NAから求まる傾斜角度よりも大きな領域では、1ピクセル内に多数の干渉縞が入力されるため、干渉信号は打ち消し合って弱め合う現象が発生する。 Next, measures against deterioration of the interference signal on a highly inclined surface will be described. Figure 8 is similar to FIG. 4, the surface of the sample S is a measurement object, in each of the low inclined surfaces S 1 and the high-tilt surfaces S 2, a region corresponding to one pixel of the camera 15 (1 pixel) It is shown in an enlarged scale. However, unlike FIG. 4, the region corresponding to 1 pixel here is on the xy plane perpendicular to 1 pixel, which is the cross section of the object to be measured obtained in FIG. 4, and the shape of the surface appears by interference fringes. It is a signal that is actually recorded in one pixel (the horizontal axis is the x-coordinate in the radial direction, and the vertical axis is the y-coordinate orthogonal to the x-coordinate and the z-coordinate). Conventionally, observation of within the numerical aperture NA is a (lower inclined surface S 1 of the observation) phenomenon in did not occur in an area larger than the inclination angle obtained from the numerical aperture NA as high inclined surface S 2 is 1 Since a large number of interference fringes are input in the pixel, the interference signals cancel each other out and weaken each other.

図9は図8の表現を変えたものであり、広範囲での干渉縞と1ピクセルの関係を示す模式図である。干渉縞の明から明の幅および暗から暗の幅が1波長(λ)分に相当し、明から暗の幅が半波長λ/2に相当する。図9(a)に示すように、低傾斜面Sでは、干渉縞の各明暗の信号の幅に相当する高さ差分Δzは、光源の波長λの半分に相当するλ/2より小さい。この結果、Δzがλ/2より小さいという条件を満たすような低傾斜面Sでは、図8でも示したように、1ピクセル内で干渉縞の信号が打ち消し合い難い。 FIG. 9 is a modified representation of FIG. 8 and is a schematic diagram showing the relationship between interference fringes over a wide range and one pixel. The width of light to light and the width of dark to dark of the interference fringes correspond to one wavelength (λ), and the width of light to dark corresponds to half wavelength λ / 2. As shown in FIG. 9 (a), the low-inclined surface S 1, the height difference Δz corresponding to the width of each light and dark signals of the interference fringes is equivalent to half of the wavelength lambda of the light source lambda / 2 less. As a result, the low inclined surface S 1 as Δz satisfies the condition that lambda / 2 is less than, as also shown in FIG. 8, hardly canceled signal of the interference fringes within one pixel.

一方、図9(b)に示すように、Δzがλ/2より大きいという条件を満たすような高傾斜面Sでは、1ピクセル内に複数の明暗の干渉縞が入り打ち消し合ってしまう。この打消し合いは1ピクセルの領域内で発生するため、傾斜角度が大きくなり干渉縞の本数が多くなるにつれ、得られる干渉信号の強度も徐々に小さくなる。 On the other hand, as shown in FIG. 9 (b), the high-tilt surfaces S 2 as Δz satisfies the condition that is greater than lambda / 2, thus cancel each other contains the interference fringes of a plurality of light and dark in 1 pixel. Since this cancellation occurs within the region of 1 pixel, the intensity of the obtained interference signal gradually decreases as the inclination angle increases and the number of interference fringes increases.

図10は、所定の傾斜角度において、1ピクセルに入力される輝度の振幅値(任意単位)を表す式(12)をプロットしたグラフである。式(12)は、1ピクセルに入力される高さ差分Δzを波長λで割り波数とし、さらに干渉次数mを用いて、カメラ1ピクセルに入ってくる干渉縞の本数が多くなるにつれ、輝度の振幅値、すなわち干渉信号が弱くなっていくことを表現している。そして、図10は、干渉信号の強度が大きくなる極大値における干渉縞の参考事例をも示すものである。このグラフが示す輝度の振幅値はいわば干渉信号の強度であり、計測する傾斜角度が二光束干渉対物レンズの開口数NAから定まる臨界角度を越えた角度領域において、干渉信号が弱め合ってしまう傾斜角度が式(12)で決まる周期性をもって存在することが直感的に理解される。 FIG. 10 is a graph in which the equation (12) representing the amplitude value (arbitrary unit) of the luminance input to one pixel at a predetermined tilt angle is plotted. In the equation (12), the height difference Δz input to one pixel is divided by the wavelength λ and the wave number is used, and the interference order m is used to increase the number of interference fringes entering one pixel of the camera. It expresses that the amplitude value, that is, the interference signal becomes weaker. Further, FIG. 10 also shows a reference example of the interference fringes at the maximum value at which the intensity of the interference signal becomes large. The amplitude value of the brightness shown in this graph is, so to speak, the intensity of the interference signal, and the interference signal weakens each other in the angle region where the measured tilt angle exceeds the critical angle determined by the numerical aperture NA of the two-luminous flux interference objective lens. It is intuitively understood that the angle exists with the periodicity determined by the equation (12).

Figure 0006762608
Figure 0006762608

干渉信号の強度が小さいということは、観測される信号強度が小さくなる、すなわち信号ノイズ比S/Nが悪化するため、その傾斜角度においてばらつきが大きくなり、正確な形状計測ができなくなるおそれがある。このような潜在的な課題に対応するため、計測された見かけ上延びた観測コヒーレンス長lc'から計測した傾斜角度を求める(式(5)および式(6)を参照)。そこからその傾斜角度(干渉信号の弱い傾斜角度)の近傍での平均化処理や、フーリエ解析を用いた当該傾斜角度に対応する周期成分の除去等の方法により、信号ノイズ比S/Nを上げることにより、形状計測の信頼性を向上させることができる。 If the strength of the interference signal is low, the observed signal strength is low, that is, the signal-to-noise ratio S / N is deteriorated, so that the inclination angle becomes large and there is a risk that accurate shape measurement cannot be performed. .. In order to deal with such a potential problem, the measured tilt angle is obtained from the measured apparently extended observation coherence length lc'(see equations (5) and (6)). From there, the signal-to-noise ratio S / N is increased by averaging in the vicinity of the tilt angle (weak tilt angle of the interference signal) and removing the periodic component corresponding to the tilt angle using Fourier analysis. As a result, the reliability of shape measurement can be improved.

次に膜を有する計測対象物の計測方法について説明する。図11は膜fを有する計測対象物の試料Sにおいて、高傾斜面Sの計測を行う状況を説明する概念図である。xy座標上において、試料Sの最外表面の座標が(x,z)、膜fの内側に相当する内表面の座標が(x,z)であると仮定する。傾斜角度0°における膜の膜厚tは、任意の傾斜角度においてはz−zとして表現され、式(13)で与えられる。この式は、鉛直方向より観測した時の膜fの膜厚tを示す。局所曲率半径rは、座標(x,z)における局所曲率半径である(すなわち、座標(x,z)での局所曲率半径は、r+t)。尚、膜fは試料Sの表面に存在することは必須ではなく、試料Sの内部に存在する層のようなものであってもよい。また、膜fは単層膜であっても多層膜であってもよい。 Next, a method for measuring an object to be measured having a film will be described. Figure 11 is the sample S of a measurement object having a film f, it is a conceptual diagram illustrating a situation in which to measure the high-tilt surfaces S 2. It is assumed that the coordinates of the outermost surface of the sample S are (x 1 , z 2 ) and the coordinates of the inner surface corresponding to the inside of the film f are (x 1 , z 1 ) on the xy coordinates. Thickness t of the membrane in the inclination angle of 0 °, at any inclination angle is expressed as z 2 -z 1, given by equation (13). This formula shows the film thickness t of the film f when observed from the vertical direction. The local radius of curvature r is the local radius of curvature at the coordinates (x 1 , z 1 ) (that is, the local radius of curvature at the coordinates (x 1 , z 2 ) is r + t). The film f is not essential to be present on the surface of the sample S, and may be a layer existing inside the sample S. Further, the film f may be a single-layer film or a multilayer film.

Figure 0006762608
Figure 0006762608

光学の分野では2つの輝点を分離できる定義として、例えばレイリーの分解能(0.61*λ/NA)で知られるような式が存在する。ここでは単純に観測される干渉縞の包絡線の中心がコヒーレンス長lcの半分となったときを分離できる上限と仮定したものを図12(a)に、また、後述の見かけ上の延びΔzの補正後を図12(b)に示す。そして、式(6)をもとに次式(14)を実際に分離できる高さδとして議論する。 In the field of optics, as a definition capable of separating two bright spots, for example, there is an equation known as Rayleigh's resolution (0.61 * λ / NA). Here, it is assumed in FIG. 12 (a) that the center of the envelope of the observed interference fringes is half the coherence length lc as the upper limit that can be separated, and the apparent extension Δz described later is shown. The corrected state is shown in FIG. 12 (b). Then, based on the equation (6), the following equation (14) is discussed as a height δ that can be actually separated.

Figure 0006762608
Figure 0006762608

図13は式(13)および式(14)を所定の条件(ピクセルサイズWc、対物レンズの倍率X、膜の膜厚t、局所曲率半径r等を適宜設定)においてプロットして得られるグラフである。式(14)をプロットして得られるグラフが、実線で示した「実際に分離できる高さ」であり、式(13)をプロットして得られるグラフが、破線で示した「鉛直方向より観測した時の膜厚」である。 FIG. 13 is a graph obtained by plotting equations (13) and (14) under predetermined conditions (pixel size Wc, objective lens magnification X, film thickness t, local radius of curvature r, etc. are appropriately set). is there. The graph obtained by plotting equation (14) is the "actually separable height" shown by the solid line, and the graph obtained by plotting equation (13) is "observed from the vertical direction" shown by the broken line. It is the film thickness at the time of

この図から、傾斜角度0°を中心とした所定幅の低傾斜面の領域においては、鉛直方向より観察した時の膜fの膜厚よりも、観測されるコヒーレンス長、すなわち実際に分解できる高さの方が小さいために、観測される干渉縞は重ならないため、膜でも干渉信号を試料から分離して、当該膜の有無の判別を行うことが可能であることを示している。そして、約±23°において、鉛直方向より観察した時の膜厚よりもコヒーレンス長の延び、すなわち分離できる高さδが上回っていることが分かる。このことは、±23°以上の傾斜角度においては観測される干渉縞が重なり出すため、膜の有無の判断を行うことが困難であることを意味する。そこで式(5)および図6より把握可能なコヒーレンス長の延びΔzを観測コヒーレンス長lc’から差し引きする補正を行う。すなわち、補正後の分離できる高さδ’は、式(14)からΔzを差し引いた下記の式(15)により与えられる。 From this figure, in the region of the low slope surface with a predetermined width centered on the tilt angle of 0 °, the observed coherence length, that is, the height that can be actually decomposed, is larger than the film thickness of the film f when observed from the vertical direction. Since the size is smaller, the observed interference fringes do not overlap, indicating that it is possible to separate the interference signal from the sample even with the film and determine the presence or absence of the film. Then, at about ± 23 °, it can be seen that the extension of the coherence length, that is, the separable height δ, exceeds the film thickness when observed from the vertical direction. This means that it is difficult to determine the presence or absence of the film because the observed interference fringes start to overlap at an inclination angle of ± 23 ° or more. Therefore, correction is performed by subtracting the coherence length extension Δz, which can be grasped from Eq. (5) and FIG. 6, from the observed coherence length lc'. That is, the corrected height δ'that can be separated is given by the following equation (15) obtained by subtracting Δz from the equation (14).

Figure 0006762608
Figure 0006762608

この結果、補正後の分離できる高さδ’は見かけ上延びることがなくなり傾斜角度依存性をもたなくなるため、図13の一点鎖線で示すように補正後の分離できる高さδ’は傾斜角度に対して依存しなくなり光源のコヒーレンス長、すなわち基本コヒーレンス長lcのみで決まるようになり、計測対象物の膜の有無を低傾斜面のみならず高傾斜面(本例では±23°を超える領域)においても判断することが可能となる。図13の一点鎖線で示す「補正後の分離できる高さδ’」に示すように、その傾斜角度における計算上求まる半値幅の干渉縞の信号と差分をとった後の干渉縞波形から、膜の膜厚を求めることが可能である。そして高傾斜面においても膜の傾斜角度の計測が可能となる。 As a result, the corrected height δ'that can be separated does not apparently extend and has no inclination angle dependence. Therefore, as shown by the alternate long and short dash line in FIG. 13, the height δ'that can be separated after correction is the inclination angle. The coherence length of the light source, that is, the basic coherence length lc, is no longer dependent on the light source. ) Can also be judged. As shown in "Corrected separable height δ'" shown by the alternate long and short dash line in FIG. 13, the film is obtained from the interference fringe waveform after taking the difference from the signal of the interference fringe having the half-value width calculated at the inclination angle. It is possible to obtain the film thickness of. Then, the inclination angle of the film can be measured even on a highly inclined surface.

本発明によれば、干渉信号の包絡線の半値幅に基づき、観測コヒーレンス長を取得した上で、計測対象物(試料)の表面の傾斜角度を計測することができる。よって、計測対象物の表面における傾斜角度の大きい高傾斜面でも適切に傾斜角度を計測することができ、表面の形状、特性を把握することができる。 According to the present invention, it is possible to measure the inclination angle of the surface of the object to be measured (sample) after obtaining the observed coherence length based on the half width of the envelope of the interference signal. Therefore, the inclination angle can be appropriately measured even on a highly inclined surface having a large inclination angle on the surface of the object to be measured, and the shape and characteristics of the surface can be grasped.

特に本発明によれば、光源および波長フィルタを含む走査型白色干渉顕微鏡から定まる、傾斜角度θ=0°における基本コヒーレンス長と、干渉縞波形の変化、特にその半値幅に相当する観測コヒーレンス長を計測することで、計測対象物(試料)の表面の傾斜角度を計測することができる。 In particular, according to the present invention, the basic coherence length at an inclination angle θ = 0 ° and the change in the interference fringe waveform, particularly the observed coherence length corresponding to the half width thereof, determined from a scanning white interference microscope including a light source and a wavelength filter. By measuring, the inclination angle of the surface of the object to be measured (sample) can be measured.

また、本発明によれば、計測位置における表面の局所曲率半径を求めることも可能となる。従来の計測対象物のZ位置(高さ位置)から局所曲率半径を求める方法によれば、計算式の分母に2階微分がくるためノイズが大きかったが、本発明によれば傾斜角度から求めるためノイズは小さくなる。 Further, according to the present invention, it is also possible to obtain the local radius of curvature of the surface at the measurement position. According to the conventional method of obtaining the radius of curvature from the Z position (height position) of the object to be measured, noise is large because the second derivative comes to the denominator of the calculation formula. Therefore, the noise becomes small.

また、本発明によれば、適切な基本コヒーレンス長を設定することが可能であり、観測コヒーレンス長に対する基本コヒーレンス長の影響を抑えることができるため、正確な観測コヒーレンス長が得られ、ひいては正確な傾斜角度を計測することが可能となる。 Further, according to the present invention, an appropriate basic coherence length can be set, and the influence of the basic coherence length on the observed coherence length can be suppressed, so that an accurate observed coherence length can be obtained, and thus an accurate observed coherence length can be obtained. It is possible to measure the tilt angle.

また、本発明によれば、膜を有する計測対象物に関しても、所定の傾斜角度に対する観測コヒーレンス長が分かっているため、コヒーレンス長の延びを差し引く補正により高傾斜面の計測においても膜の計測が可能となる。例えば、計算上求まる半値幅以上の干渉縞が観測された際に、膜体の有無の判別ができるようになる。また、その時、その角度における計算上求まる半値幅の干渉縞の信号と差分をとった後の干渉縞波形から膜厚を求めることも可能である。 Further, according to the present invention, since the observed coherence length with respect to a predetermined inclination angle is known also for the measurement object having the film, the film can be measured even in the measurement of the high inclination surface by the correction by subtracting the extension of the coherence length. It will be possible. For example, when an interference fringe having a half-value width or more obtained by calculation is observed, the presence or absence of a film body can be determined. At that time, it is also possible to obtain the film thickness from the interference fringe waveform after taking the difference from the signal of the interference fringe having a half-value width calculated at that angle.

尚、本発明は、上述した実施形態に限定されるものではなく、適宜、変形、改良、等が可能である。その他、上述した実施形態における各構成要素の材質、形状、寸法、数値、形態、数、配置箇所、等は本発明を達成できるものであれば任意であり、限定されない。 The present invention is not limited to the above-described embodiment, and can be appropriately modified, improved, and the like. In addition, the material, shape, size, numerical value, form, number, arrangement location, etc. of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

本発明によれば、走査型白色干渉顕微鏡を用いた三次元形状計測方法にあたって、傾斜角度の大きな試料の表面についても適切な計測を可能とすることができる。 According to the present invention, in the three-dimensional shape measuring method using a scanning white interference microscope, it is possible to appropriately measure the surface of a sample having a large inclination angle.

10 装置本体
11 白色光源(光源)
12 フィルタ(波長フィルタを含む)
13 ビームスプリッタ
14 二光束干渉対物レンズ(対物レンズ)
15 カメラ
16 ピエゾアクチュエータ
20 ステージ
30 コンピュータ
100 走査型白色干渉顕微鏡
S 試料(計測対象物)
f 膜
10 Device body 11 White light source (light source)
12 filters (including wavelength filter)
13 Beam splitter 14 Two-luminous flux interference objective lens (objective lens)
15 Camera 16 Piezo actuator 20 Stage 30 Computer 100 Scanning white interference microscope S Sample (measurement object)
f film

Claims (6)

走査型白色干渉顕微鏡を用いた三次元形状計測方法であって、
計測対象物に対し照射した光源からの光の干渉信号の包絡線を取得し、
前記包絡線の半値幅に基づき、観測される見かけ上のコヒーレンス長である観測コヒーレンス長lc'を取得し、
前記観測コヒーレンス長lc'に基づき、前記計測対象物の表面の傾斜角度を計測する、三次元形状計測方法。
A three-dimensional shape measurement method using a scanning white interference microscope.
Obtain the envelope of the interference signal of the light from the light source that irradiates the object to be measured.
Based on the half width of the envelope, the observed coherence length lc', which is the observed apparent coherence length, is obtained.
A three-dimensional shape measuring method for measuring the inclination angle of the surface of the object to be measured based on the observed coherence length lc'.
請求項1に記載の三次元形状計測方法であって、
前記観測コヒーレンス長lc'が、前記走査型白色干渉顕微鏡の前記光源および波長フィルタによって定められる基本コヒーレンス長lcと、前記傾斜角度に応じて前記基本コヒーレンス長lcが延びる値である延びΔzの和である、三次元形状計測方法。
The three-dimensional shape measuring method according to claim 1.
The observed coherence length lc'is the sum of the basic coherence length lc determined by the light source and the wavelength filter of the scanning white interference microscope and the extension Δz, which is a value at which the basic coherence length lc extends according to the tilt angle. There is a three-dimensional shape measurement method.
請求項2に記載の三次元形状計測方法であって、
前記延びΔzと前記傾斜角度から、前記計測対象物の表面の局所曲率半径を算出する、三次元形状計測方法。
The three-dimensional shape measuring method according to claim 2.
A three-dimensional shape measuring method for calculating the local radius of curvature of the surface of the object to be measured from the extension Δz and the inclination angle.
請求項3に記載の三次元形状計測方法であって、
前記基本コヒーレンス長lcは、傾斜角度90度に対応する前記計測対象物の表面から、前記干渉信号を捉えるカメラの1画素分に相当する傾斜角度θcだけずれた表面における前記延びΔz以下になるように設定される、三次元形状計測方法。
The three-dimensional shape measuring method according to claim 3.
The basic coherence length lc is set to be equal to or less than the extension Δz on a surface deviated from the surface of the measurement object corresponding to the tilt angle of 90 degrees by a tilt angle θc corresponding to one pixel of the camera that captures the interference signal. Three-dimensional shape measurement method set to.
請求項1に記載の三次元形状計測方法であって、
前記走査型白色干渉顕微鏡が、前記計測対象物に対して対向して配置される対物レンズと、前記干渉信号を捉えるカメラとを有し、
前記対物レンズの開口数から定まる臨界角度を越える傾斜角度において、前記カメラの1画素内において干渉信号が打消し合う近傍の傾斜角度では平均化処理、またはフーリエ解析を用いた当該傾斜角度に対応する周期成分の除去により、信号ノイズ比S/Nを向上させる、三次元形状計測方法。
The three-dimensional shape measuring method according to claim 1.
The scanning white interference microscope has an objective lens arranged so as to face the measurement object and a camera that captures the interference signal.
At an inclination angle exceeding the critical angle determined by the numerical aperture of the objective lens, an inclination angle in the vicinity where interference signals cancel each other within one pixel of the camera corresponds to the inclination angle using averaging processing or Fourier analysis. A three-dimensional shape measurement method that improves the signal-to-noise ratio S / N by removing periodic components.
請求項2に記載の三次元形状計測方法であって、
前記観測コヒーレンス長lc'から前記延びΔzを差し引きすることで、前記計測対象物の膜の有無を判断する、三次元形状計測方法。
The three-dimensional shape measuring method according to claim 2.
A three-dimensional shape measuring method for determining the presence or absence of a film of the measurement object by subtracting the extension Δz from the observed coherence length lc'.
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