JPS62259006A - Interference film thickness measuring instrument - Google Patents
Interference film thickness measuring instrumentInfo
- Publication number
- JPS62259006A JPS62259006A JP10095686A JP10095686A JPS62259006A JP S62259006 A JPS62259006 A JP S62259006A JP 10095686 A JP10095686 A JP 10095686A JP 10095686 A JP10095686 A JP 10095686A JP S62259006 A JPS62259006 A JP S62259006A
- Authority
- JP
- Japan
- Prior art keywords
- spectrum
- light source
- light
- interference
- normal distribution
- 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.)
- Pending
Links
- 238000001228 spectrum Methods 0.000 claims abstract description 37
- 230000003287 optical effect Effects 0.000 claims abstract description 30
- 230000005540 biological transmission Effects 0.000 claims abstract description 7
- 230000035945 sensitivity Effects 0.000 claims abstract description 3
- 230000003595 spectral effect Effects 0.000 claims description 6
- 238000000411 transmission spectrum Methods 0.000 claims description 4
- 230000001131 transforming effect Effects 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 6
- 239000013307 optical fiber Substances 0.000 abstract description 3
- 230000009466 transformation Effects 0.000 abstract description 3
- 239000010408 film Substances 0.000 description 14
- 238000010586 diagram Methods 0.000 description 6
- 238000012937 correction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 230000010355 oscillation Effects 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 101150069512 RHO1 gene Proteins 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Length Measuring Devices By Optical Means (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は膜厚計測に係り、特に半導体産゛業、有機高分
子産業などの各種膜厚計測に好適な干渉図形方式の膜厚
測定装置に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to film thickness measurement, and in particular to an interferometric film thickness measurement device suitable for various film thickness measurements in the semiconductor industry, organic polymer industry, etc. Regarding.
従来の干渉を用いた膜厚測定装置は、特公昭５４−３６
５１５号公報及び特開昭５９−１０５５０８号公報に記
載されている如く、白色光を用いているが、その白色光
の光源スペクトルの形状に関しては配慮されておらず、
記述もされていなかった。A conventional film thickness measuring device using interference was developed by
As described in Japanese Patent No. 515 and Japanese Patent Application Laid-Open No. 59-105508, white light is used, but no consideration is given to the shape of the light source spectrum of the white light.
It wasn't even described.
上記従来技術では、光源スペクトルの形状を補正する手
段を備えておらず、干渉図形の振動波形が大きな光路差
のところまで継続し、干渉図形中に含まれる副極大の光
路差位置の検出に支障を来たす場合もあった。The above-mentioned conventional technology does not have a means for correcting the shape of the light source spectrum, and the oscillation waveform of the interferogram continues up to a large optical path difference, which hinders the detection of the sub-maximal optical path difference position included in the interferogram. In some cases, this occurred.
本発明の目的は、干渉図形の振動波形を比較的小光路差
内に減衰させ、特に薄膜の膜厚測定に際し生ずる干渉図
形の主極大による副極大の隠ぺいを除去し、膜厚測定の
下限を引下げることのできる干渉膜厚測定装置を提供す
ることにある。The purpose of the present invention is to attenuate the oscillation waveform of an interferogram within a relatively small optical path difference, eliminate the concealment of sub-maximum by the main maximum of the interferogram that occurs especially when measuring the thickness of a thin film, and lower the lower limit of film thickness measurement. An object of the present invention is to provide an interference film thickness measuring device that can be pulled down.
上記目的は、白色光の光源スペクトルを波数軸に関し正
規分布（ガウシアン）図形状に補正する事により達成さ
れる。The above object is achieved by correcting the light source spectrum of white light into a normal distribution (Gaussian) diagram shape with respect to the wave number axis.
これは、急岐なピークスペクトルを有し又はピークがス
ペクトルの一方の端近くにずれている光の干渉図形の振
動波形の減衰が緩やかであるのに対し、波数スペクトル
のほぼ中央に緩やかなピークを有する正規分布形スペク
トルの光の干渉図形では、その振動波形が比較的速やか
である事に着目したものである。This is because the vibration waveform of an optical interferogram that has a sharply diverging peak spectrum or whose peak is shifted near one end of the spectrum has a gradual attenuation, but a gradual peak near the center of the wavenumber spectrum. This study focuses on the fact that in the interference pattern of light with a normal distribution spectrum, the oscillation waveform is relatively rapid.
フーリエ理論に於ては、正規分布図形のフーリエ変換は
再び正規分布図形となり、矩形のフーリエ変換は５ＩＮ
Ｃ関数図形となる事が知られている。In Fourier theory, the Fourier transform of a normal distribution figure becomes a normal distribution figure again, and the Fourier transform of a rectangle is 5IN
It is known that it becomes a C function figure.
又、基準図形をフーリエ変換の原点から移動させてフー
リエ変換すると、いわゆる遷移則により、基準図形のフ
ーリエ変換を包絡線とし、移動量に比例した周波数を持
った減衰する振動波形となる事も知られている。It is also known that when a reference figure is moved from the origin of the Fourier transform and Fourier transform is performed, the Fourier transform of the reference figure becomes an envelope and a damping vibration waveform with a frequency proportional to the amount of movement occurs due to the so-called transition law. It is being
光のスペクトル図形と、その光を干渉されて得られる干
渉図形の関係は１両者がフーリエ変換及びフーリエ逆変
換して相互に求められ、上記のフーリエ理論宴適用され
ることになる。The relationship between the spectral figure of light and the interference figure obtained by interfering the light is mutually determined by Fourier transform and inverse Fourier transform, and the above-mentioned Fourier theory equation is applied.
可視域、又は近赤外域で透明な膜物質を測定するには、
可視域から近赤外域に広がる白色光源が必要となるが、
通常低波移域の光エネルギが微弱で、光源スペクトルは
帯域状となるから振動波形は必然的に存在する。To measure transparent film materials in the visible or near infrared range,
A white light source that extends from the visible region to the near-infrared region is required,
Normally, the light energy in the low wave transition range is weak and the light source spectrum is band-like, so a vibration waveform inevitably exists.
従って帯域スペクトルの形状を正規分布形にする事によ
り、干渉図形に′おける振動波形の包路線の形状を正規
分布形にする事が可能で、その結果振動波形の振幅も急
速にＯに近づけることが出来る。Therefore, by making the shape of the band spectrum into a normal distribution shape, it is possible to make the shape of the envelope of the vibration waveform in the interferogram into a normal distribution shape, and as a result, the amplitude of the vibration waveform can also rapidly approach O. I can do it.
以下１本発明の実施例について説明する。 An embodiment of the present invention will be described below.
第１図には１本発明の一実施例が示されている。FIG. 1 shows an embodiment of the present invention.
図において、白色光源１．コリメータレンズ２゜半透膜
５．対物レンズ６から成る照射光学系により、白色光ｇ
１からの光は、移動台８上の試料７の表面に点状に集光
照射される。試料７の表面に存在する透光膜の表面と裏
面から反射する膜干渉光は、対物レンズ６を経て、半透
膜５に到りそこで反射して干渉計１立に導入される。干
渉計３０は偏光子１０．ウォラストンプリズム１２．検
光子１４から構成された波面傾斜型の偏光干渉計である
。偏光子１０．検光子１４は、ウォラストンプリズム１
２の結晶光軸に対し４５°回転させて置かれた直線偏光
板である。ウォラストンプリズム１２は水晶の如き複属
析性物質の、互に光軸が直交する２個のプリズムから構
成されており、偏光子１０を通過した直線偏光は、ウォ
ラストンプリズム１２中で互に直交する２個の直流偏光
に分解し、ウォラストンプリズム１２の通過位置に依っ
て異なる位相遅延を与えられ、検光子１４で合成されて
、干渉光束となる。この時中心軸に対して波面の進行方
向が傾斜した２個の波面が生ずる事になり、この波面の
分離はウォラストンプリズム１２の内部で生ずる。その
結果、いわゆる等５干渉縞がプリズム１２の内部に観測
され、結像レンズ１５により、光ダイオードアレイ１７
上に。In the figure, white light source 1. Collimator lens 2゜semi-permeable membrane 5. The irradiation optical system consisting of the objective lens 6 produces white light
The light from 1 is focused and irradiated onto the surface of the sample 7 on the moving stage 8 in the form of a point. The film interference light reflected from the front and back surfaces of the transparent film existing on the surface of the sample 7 passes through the objective lens 6, reaches the semi-transparent film 5, is reflected there, and is introduced into an interferometer. The interferometer 30 has a polarizer 10. Wollaston Prism 12. This is a wavefront tilting type polarization interferometer composed of an analyzer 14. Polarizer 10. Analyzer 14 is Wollaston prism 1
This is a linear polarizing plate rotated by 45 degrees with respect to the optical axis of the second crystal. The Wollaston prism 12 is composed of two prisms made of a multimetallic material such as quartz and whose optical axes are perpendicular to each other. The light is separated into two orthogonal DC polarized lights, given different phase delays depending on the passing position of the Wollaston prism 12, and combined by the analyzer 14 to form an interference light beam. At this time, two wavefronts are generated whose traveling directions are inclined with respect to the central axis, and separation of these wavefronts occurs inside the Wollaston prism 12. As a result, so-called equal 5 interference fringes are observed inside the prism 12, and the imaging lens 15 causes the photodiode array 17 to
above.
紙面に垂直の干渉縞を結像する。この干渉縞を電気信号
に変換したものが、干渉図形であって、アレイ１７の中
心から両側に遠ざかるに従い、干渉光路差が（正及び負
に）増加する。Image interference fringes perpendicular to the plane of the paper. The interference pattern converted into an electrical signal is an interference pattern, and the interference optical path difference increases (positively and negatively) as it moves away from the center of the array 17 on both sides.
アレイ１７は駆動電源１８からのクロックパルス列で走
引され、アレイ１７からの電流信号は増幅器１９で増幅
され電圧信号となり、Ａ−Ｄ変換器２０でディジタル化
されて演算処理袋４Ｉ！ｉ４０に入力する。The array 17 is driven by a clock pulse train from the drive power supply 18, and the current signal from the array 17 is amplified by the amplifier 19 to become a voltage signal, which is digitized by the A/D converter 20 and sent to the processing bag 4I! Enter into i40.
通常の白熱ランプと、シリコン、光ダイオードアレイを
組み合せた時の干渉図形は第３図（ｂ）の如くであり、
これをフーリエ変換したスペクトルは同図Ｃａ）に示さ
れる。スペクトル図形４１は低波数側１２，５００ａｍ
−″１（波長８００ｎｍ）に、ピーク４２を有しており
、干渉図形４３は減衰光路差４４として約７μｍの大き
さを持っている。一方、第４図（ａ）は正規分布図形の
スペクトル４５であって、そのピーク波数４６は１６，
１００ロー１（波是６２０ｎｍ）である、同図（ｂ）は
スペクトル４５のフーリエ変換であり、干渉図形４７の
減衰波数４８は約１．８μｍで充分に小さい。The interference pattern when a normal incandescent lamp is combined with silicon and a photodiode array is as shown in Figure 3(b).
The spectrum resulting from Fourier transformation is shown in Figure Ca). Spectrum figure 41 is on the low wave number side 12,500 am
-"1 (wavelength 800 nm), and the interference pattern 43 has a size of about 7 μm as the attenuation optical path difference 44. On the other hand, FIG. 4(a) shows the spectrum of the normal distribution pattern. 45, and its peak wave number 46 is 16,
100 rho1 (wave length: 620 nm), FIG. 12(b) is a Fourier transform of the spectrum 45, and the attenuation wave number 48 of the interference pattern 47 is approximately 1.8 μm, which is sufficiently small.
本発明の骨子は、第３図（ａ）の光源スペクトルを第４
図（ａ）のスペクトルに補正する手段を光学系中に設け
るところにある。そのため、第１図に於ては光ｇｌ側に
透過型の光学フィルタ３１を設けている。この光学フィ
ルタは、フィルタ３２の位置に配置してもよいし、光源
１とアレイ１７の間の適当な位置に設けてもよい。The gist of the present invention is to convert the light source spectrum of FIG. 3(a) into a fourth
A means for correcting the spectrum shown in Figure (a) is provided in the optical system. Therefore, in FIG. 1, a transmission type optical filter 31 is provided on the light GL side. This optical filter may be placed at the position of the filter 32 or at an appropriate position between the light source 1 and the array 17.
この光源スペクトルの形状を補正する光学フィルタの透
過率特性は、例えば第５図の様であれば良い。透過スペ
クトル５１は、波数１７．７００ａｍ−’にビーク５２
を有する帯域透過型である。The transmittance characteristics of the optical filter for correcting the shape of the light source spectrum may be as shown in FIG. 5, for example. The transmission spectrum 51 has a peak 52 at a wave number of 17.700 am-'.
It is a band transmission type with
透過スペクトル５１は、正規分布図形スペクトル４５を
光源スペクトル４１で、波数について送次除したスペク
トル比に比例する。従って、光源の干渉図形４３をフー
リエ変換する事により、光ｇ１のスペクトル特性、アレ
イ１７の検知器感度特性、光学系中の光学部品の透過特
性などを可法した総合スペクトルを容易に得る事ができ
る。The transmission spectrum 51 is proportional to the spectral ratio obtained by dividing the normal distribution pattern spectrum 45 by the light source spectrum 41 with respect to the wave number. Therefore, by Fourier transforming the interference pattern 43 of the light source, it is possible to easily obtain a comprehensive spectrum that takes into account the spectral characteristics of the light g1, the sensitivity characteristics of the detector of the array 17, the transmission characteristics of the optical components in the optical system, etc. can.
又、光学フィルタ３１又は３２は、半透膜５にスペクト
ル補正効果を持たせるならば、即ち半透膜５の斜め透過
率と斜め反射率の積が、前記光学フィルタの透過率にス
ペクトル領域全体にわたって比例する様とすれば、不要
となる。Furthermore, if the optical filter 31 or 32 is to have a spectral correction effect on the semi-transparent film 5, that is, the product of the oblique transmittance and the oblique reflectance of the semi-transparent film 5 will be equal to the transmittance of the optical filter over the entire spectral region. If it were to be proportional across the range, it would be unnecessary.
第２図は別の一実施例であって、第１図と同一部品は同
じ符号を付して説明する。第１図の半透膜５は、光ファ
イバ３５に置き換わり、Ｙ字状に分岐した一方より光源
１の光を入射し、共通端で試料７に照光と受光を行わせ
、他端が干婢計旦へのコリメータレンズ３６に対向して
いる。FIG. 2 shows another embodiment, and the same parts as those in FIG. 1 will be described with the same reference numerals. The semi-transparent membrane 5 in FIG. 1 is replaced by an optical fiber 35, which is branched into a Y-shape and receives the light from the light source 1 from one end, illuminates and receives the sample 7 at the common end, and uses the other end to enter the light from the light source 1. It faces the collimator lens 36 to the meter.
本例では第１図実施例に比べて、試料７上の光スポット
の大きさを小さく出来ないが、照射光学系が簡単化され
る。In this example, the size of the light spot on the sample 7 cannot be made smaller than in the example shown in FIG. 1, but the irradiation optical system is simplified.
以上説明したように１本発明によれば、干渉図形の減衰
特性が大幅に改善され、主極大の両側に派生する振動波
形の数も少く、小さな光路差速しか存在しない、従って
、従来計測不可能であった、薄い膜に対しても充分高い
精度をもって、膜干渉の結果生ずる副極大の光路差位置
を検出する事が出来るから、膜厚測定の下限を低める効
果がある。As explained above, according to the present invention, the attenuation characteristics of the interferogram are greatly improved, the number of vibration waveforms derived on both sides of the main maximum is small, and only a small optical path difference velocity exists. Since it is possible to detect the sub-maximal optical path difference position resulting from film interference with sufficiently high accuracy even for thin films, this method has the effect of lowering the lower limit of film thickness measurement.
また１本発明によれば、照射光学系即ち光ファイバの出
口と、試料との間の作動距離の変動の影響をあまり受け
ないから、従来必要とした自動点機構など繁雑な手段が
不要となる効果がある。Furthermore, according to the present invention, since it is not affected much by fluctuations in the working distance between the irradiation optical system, that is, the exit of the optical fiber, and the sample, complicated means such as an automatic point mechanism that were conventionally required are not required. effective.
第１図は本発明の一実施例の構成図、第２図は別の一実
施例の構成図、第３図は補正前の光源スペクトルと干渉
図形、第４図は本発明による補正後の光源スペクトルと
干渉図形、第５図は補正中の光学フィルタの透過スペク
トルを示す図、第６図は光学フィルタを用いた結果観測
される薄膜干渉図である。
１・・・白色光源、２，６．１５・・・レンズ、５・・
・半透膜、７・・・試料、８・・・移動台、３０・・・
偏光干渉計。
３１．３２・・・光学フィルタ、１７・・・光ダイオー
ドプレイ、１８・・・駆！Ｍ電源、１９・・・増幅器、
２０・・・ＡＤ変換器、４０・・・演算処理装置、４１
，４５゜５１・・・スペクトル、４３，４７．５３・・
・干渉図形。Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of another embodiment, Fig. 3 is a light source spectrum and interference pattern before correction, and Fig. 4 is a diagram after correction according to the present invention. Light source spectrum and interference pattern; FIG. 5 is a diagram showing the transmission spectrum of an optical filter during correction; FIG. 6 is a thin film interference diagram observed as a result of using the optical filter. 1...White light source, 2,6.15...Lens, 5...
・Semipermeable membrane, 7...sample, 8...movement table, 30...
Polarization interferometer. 31.32...Optical filter, 17...Photodiode play, 18...Drive! M power supply, 19... amplifier,
20... AD converter, 40... Arithmetic processing unit, 41
,45°51...spectrum,43,47.53...
・Interference figure.
Claims (1)
反射光によつて生じる膜干渉光を干渉計に導き、該干渉
計で得られる干渉図形から膜厚を測定するものにおいて
、上記干渉計の検知器の感度特性を含めた白色光の分光
スペクトルの形状が、波数軸で表わした有限の正規分布
に近似するように補正する光学フィルタを有する干渉膜
厚測定装置。 ２、特許請求の範囲第１項記載のものにおいて、上記光
学フィルタは、白色光源光を干渉計に導いて得られた干
渉図形をフーリエ変換して光源スペクトルを求め、該光
源スペクトル領域の略中央に頂点を有する正規分布スペ
クトルを定め、該正規分布スペクトルを前記光源スペク
トルで除して得られたスペクトル比が、透過フィルタの
透過率スペクトルにほぼ一致するものであることを特徴
とする干渉膜厚測定装置。[Claims] 1. Apply white light to the film to be measured, guide the film interference light generated by the light reflected from the front and back surfaces of the film to an interferometer, and calculate the film thickness from the interference pattern obtained by the interferometer. An interference film thickness that has an optical filter that corrects the shape of the spectrum of white light, including the sensitivity characteristics of the detector of the interferometer, to approximate a finite normal distribution expressed on the wave number axis. measuring device. 2. In the optical filter according to claim 1, the optical filter obtains a light source spectrum by Fourier transforming an interference pattern obtained by guiding white light source light to an interferometer, and obtains a light source spectrum, and An interference film thickness characterized in that a normal distribution spectrum having an apex is determined, and a spectral ratio obtained by dividing the normal distribution spectrum by the light source spectrum almost matches the transmittance spectrum of the transmission filter. measuring device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10095686A JPS62259006A (en) | 1986-05-02 | 1986-05-02 | Interference film thickness measuring instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10095686A JPS62259006A (en) | 1986-05-02 | 1986-05-02 | Interference film thickness measuring instrument |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS62259006A true JPS62259006A (en) | 1987-11-11 |
Family
ID=14287805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10095686A Pending JPS62259006A (en) | 1986-05-02 | 1986-05-02 | Interference film thickness measuring instrument |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62259006A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008233063A (en) * | 2007-02-21 | 2008-10-02 | Canon Inc | Surface profile measuring apparatus, exposure device, and computer |
| US8619263B2 (en) | 2010-01-06 | 2013-12-31 | Panasonic Corporation | Film thickness measuring apparatus using interference and film thickness measuring method using interference |
-
1986
- 1986-05-02 JP JP10095686A patent/JPS62259006A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008233063A (en) * | 2007-02-21 | 2008-10-02 | Canon Inc | Surface profile measuring apparatus, exposure device, and computer |
| US8619263B2 (en) | 2010-01-06 | 2013-12-31 | Panasonic Corporation | Film thickness measuring apparatus using interference and film thickness measuring method using interference |
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