JPH10307009A - Optical film-thickness measuring apparatus for multilayer thin film - Google Patents

Optical film-thickness measuring apparatus for multilayer thin film

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Publication number
JPH10307009A
JPH10307009A JP11564597A JP11564597A JPH10307009A JP H10307009 A JPH10307009 A JP H10307009A JP 11564597 A JP11564597 A JP 11564597A JP 11564597 A JP11564597 A JP 11564597A JP H10307009 A JPH10307009 A JP H10307009A
Authority
JP
Japan
Prior art keywords
film thickness
film
wavelength
thickness
reflectance
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
Application number
JP11564597A
Other languages
Japanese (ja)
Inventor
Makoto Hashimoto
誠 橋本
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.)
Sony Corp
Original Assignee
Sony Corp
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Filing date
Publication date
Application filed by Sony Corp filed Critical Sony Corp
Priority to JP11564597A priority Critical patent/JPH10307009A/en
Publication of JPH10307009A publication Critical patent/JPH10307009A/en
Pending legal-status Critical Current

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  • Length Measuring Devices By Optical Means (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

PROBLEM TO BE SOLVED: To obtain an optical film-thickness measuring apparatus by which a film thickness can be measured by stably and with high accuracy by a method wherein a measuring wavelength range is set at the cycle or higher of the reflection dependence of a reflectance based on a substrate on which at least only a lower-layer film is formed. SOLUTION: A light source 101 emits a luminous flux 101a. An optical-intensity detector 107 captures reflected light 106a from a wafer 106 to be measured. An A/D converter 21 converts a reflected-light intensity output into a digital value. A system control means M1 controls a system as a whole, and a measuring-wavelength-range control means M2 controls a diffraction-grating driving device 103. A film-thickness capturing means M8 captures a film thickness based on a reflectance. A measuring- wavelength range is set at the cycle or higher of the wavelength dependence of a reflectance based on a substrate on which at least only a lower-layer film is formed. Consequently, even when a little irregularity in the film thickness of the lower-layer film is generated, an optimum film-thickness computing wavelength can be selected easily out of one measured result, and the film thickness can be measured with good accuracy.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、二層膜構造試料に
おける上層薄膜膜厚を光学的に測定する膜厚測定装置に
関し、とりわけ既知として予め入力される下層膜厚と実
際の下層膜厚との誤差が上層膜厚測定に及ぼす影響を自
動的に抑制する機能をもつ、膜厚測定プログラムを備え
た膜厚測定装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring device for optically measuring the thickness of an upper thin film in a sample having a two-layer film structure. The present invention relates to a film thickness measuring apparatus provided with a film thickness measuring program and having a function of automatically suppressing the influence of the error of the thickness on the measurement of the upper layer thickness.

【０００２】[0002]

【従来の技術】半導体製造プロセスにおいては、基板上
に形成された薄膜の膜厚を非接触で測定する必要が生じ
る場合がある。従来、このような膜厚の測定には、基板
からの光反射率の測定結果に基づき膜厚を算出する光学
的測定法が適用されてきた。図９は、このような従来の
膜厚測定装置のブロック構成図である。2. Description of the Related Art In a semiconductor manufacturing process, it may be necessary to measure the thickness of a thin film formed on a substrate in a non-contact manner. Conventionally, an optical measurement method for calculating the film thickness based on the measurement result of the light reflectance from the substrate has been applied to such measurement of the film thickness. FIG. 9 is a block diagram of such a conventional film thickness measuring apparatus.

【０００３】図９において、符号１０１は光源、符号１
０２は回折格子、符号１０３は回折格子駆動装置、符号
１０４は光学系、符号１０５はウエハーステージ、符号
１０６は被測定ウエハー、符号１０７は光強度検出器、
符号１０８は制御／演算部、符号１０９は出力部であ
る。In FIG. 9, reference numeral 101 denotes a light source, and reference numeral 1 denotes a light source.
02 is a diffraction grating, 103 is a diffraction grating driving device, 104 is an optical system, 105 is a wafer stage, 106 is a wafer to be measured, 107 is a light intensity detector,
Reference numeral 108 denotes a control / arithmetic unit, and reference numeral 109 denotes an output unit.

【０００４】光源１０１から出た光は、回折格子１０２
によって単色光とされた後、レンズ等の光学系１０４を
透過して、被測定ウエハー１０６表面にほぼ垂直に入射
される。ウエハー１０６を保持するステージ１０５は可
動となっており、測定者は着目する部分に入射光をあて
ることが可能にされている。ウエハー１０６表面から反
射された光は再度光学系を通った後、ＣＣＤ等の光強度
検出器１０７に導かれる。The light emitted from the light source 101 is
After being converted into monochromatic light, the light passes through an optical system 104 such as a lens and is incident on the surface of the wafer 106 to be measured almost perpendicularly. The stage 105 for holding the wafer 106 is movable, so that the measurer can direct incident light to a portion of interest. The light reflected from the surface of the wafer 106 passes through the optical system again, and is guided to a light intensity detector 107 such as a CCD.

【０００５】光強度検出器１０７による反射光の強度の
測定結果は、制御／演算部１０８に送られる。また、制
御／演算部１０８は回折格子駆動装置１０３も制御す
る。したがって制御／演算部１０８は測定された反射率
を測定波長の関数として処理できる。この結果から薄膜
の膜厚値を算出し、この膜厚値がディスプレイなどの出
力部１０９に出力される。また図示されていないが、こ
のような測定装置系は一般に入力部を有し、測定開始指
示、測定プログラム選択などが可能となっている。The result of the measurement of the intensity of the reflected light by the light intensity detector 107 is sent to a control / arithmetic unit 108. The control / calculation unit 108 also controls the diffraction grating driving device 103. Therefore, the control / calculation unit 108 can process the measured reflectance as a function of the measured wavelength. The thickness value of the thin film is calculated from the result, and the thickness value is output to the output unit 109 such as a display. Although not shown, such a measuring device system generally has an input unit, and can perform a measurement start instruction, a measurement program selection, and the like.

【０００６】前記のようにして測定される単層膜の反射
率には、図１０の線図に示されるような、波長依存の周
期性がある。すなわち、下層のみの構成（単層膜）によ
る反射率カーブ１１０は膜内での干渉に対応した長周期
のうねりを示す。The reflectance of the single-layer film measured as described above has a wavelength-dependent periodicity as shown in the diagram of FIG. That is, the reflectance curve 110 due to the configuration of only the lower layer (single-layer film) shows a long-period undulation corresponding to the interference in the film.

【０００７】ところで従来、前記のような薄膜測定は単
層膜中心に行われてきたが、近年、二層以上の薄膜が堆
積された多層膜構造基板において同様の測定をおこなう
必要が多くなってきた。ＳＯＩ基板のような、Ｓｉ／酸
化膜／Ｓｉ基板構造の試料について上層のＳｉ膜厚を測
定する場合などがその典型的な例である。このような、
多層膜構造基板の上層の膜厚を測定する一般的な測定方
法として、下層の膜厚を既知として上層の膜厚を光学的
に算出する方法が知られている。Conventionally, the above-mentioned thin film measurement has been mainly performed on a single-layer film. In recent years, however, it has become increasingly necessary to perform the same measurement on a multi-layer structure substrate on which two or more thin films are deposited. Was. A typical example is measurement of the upper Si film thickness of a sample having a Si / oxide film / Si substrate structure such as an SOI substrate. like this,
As a general measuring method for measuring the thickness of the upper layer of the multilayer film-structured substrate, there is known a method of optically calculating the thickness of the upper layer with the thickness of the lower layer being known.

【０００８】図２には、Ｓｉ（１．５μｍ）／ＳｉＯ2
（０．７μｍ）／Ｓｉ基板積層構造の試料における反射
率特性の曲線Ａｂｐ２が示されている。図示されるよう
に反射率特性の曲線Ａｂｐ２は、反射率の波長依存性を
示す。すなわち、曲線Ａｂｐ２は上層シリコン層内での
干渉に対応した短周期成分と、下層酸化膜内での干渉に
対応した長周期のうねり成分から主に構成される。FIG. 2 shows Si (1.5 μm) / SiO 2
The curve Abp2 of the reflectance characteristic of the sample having the (0.7 μm) / Si substrate laminated structure is shown. As shown, the curve Abp2 of the reflectance characteristic indicates the wavelength dependence of the reflectance. That is, the curve Abp2 mainly includes a short-period component corresponding to the interference in the upper silicon layer and a long-period swell component corresponding to the interference in the lower oxide film.

【０００９】したがって、曲線Ａｂｐ２の極大点の包絡
線Ｅｖ２は、酸化膜のみの単層構造試料による反射率カ
ーブＡｂｐ１と同様の波長依存性を示す。すなわち、包
絡線Ｅｖ２は単層構造試料による反射率カーブＡｂｐ１
における長周期のうねりと同様の長周期のうねりを示
す。上層の膜厚算出は包絡線Ｅｖ２のピーク付近のデー
タを用いて行われるので、従来では測定波長範囲を下層
酸化膜の膜厚によって異なる範囲に設定していた。Therefore, the envelope Ev2 of the maximum point of the curve Abp2 shows the same wavelength dependence as the reflectance curve Abp1 of the single layer structure sample having only the oxide film. That is, the envelope Ev2 is a reflectance curve Abp1 of the single-layer structure sample.
5 shows a long-period undulation similar to that of FIG. Since the calculation of the film thickness of the upper layer is performed using data near the peak of the envelope Ev2, conventionally, the measurement wavelength range is set to a different range depending on the film thickness of the lower oxide film.

【００１０】[0010]

【発明が解決しようとする課題】しかしながら、前記の
ような上層の膜厚測定には、以下の問題点が存在する。
上層膜の膜厚算出においては、埋め込み下層膜の膜厚を
既知として使用している。ところが一般的に、半導体製
造過程において薄膜を成膜する際には、膜厚ばらつきの
発生が避けられない。このため、前述のように上層膜膜
厚測定において、既知の値として入力された下層膜厚
と、現実の下層膜厚とは一致することが少ない。However, measuring the thickness of the upper layer as described above has the following problems.
In calculating the thickness of the upper film, the thickness of the buried lower film is used as known. However, in general, when a thin film is formed in a semiconductor manufacturing process, occurrence of film thickness variation is inevitable. For this reason, in the upper layer film thickness measurement as described above, the lower layer thickness input as a known value rarely matches the actual lower layer thickness.

【００１１】下層膜厚が変化すると、反射率の波長依存
性も変化する。例えば図１１は、埋込み酸化膜厚が前記
図２におけるものと異なる場合の、反射率の波長依存性
を示す線図である。この積層構造は、Ｓｉ（１．５μ
ｍ）／ＳｉＯ2 （６００ｎｍ）／Ｓｉ基板であり、図２
の構成よりも下層酸化膜が１００ｎｍだけ薄くなってい
る。As the thickness of the lower layer changes, the wavelength dependence of the reflectance also changes. For example, FIG. 11 is a diagram showing the wavelength dependence of the reflectance when the buried oxide film thickness is different from that in FIG. This laminated structure has a Si (1.5 μ
m) / SiO 2 (600 nm) / Si substrate, and FIG.
The lower oxide film is thinner by 100 nm than that of the structure.

【００１２】両図の包絡線Ｅｖ３（図１１参照）と包絡
線Ｅｖ２（図２参照）を比較すると明らかなように、下
層酸化膜の膜厚の僅かな変動によって、反射率特性が大
きく変化する。これによる測定膜厚値への影響の例を、
図１２にしたがって説明する。As is apparent from a comparison between the envelope Ev3 (see FIG. 11) and the envelope Ev2 (see FIG. 2) in both figures, a slight change in the thickness of the lower oxide film greatly changes the reflectance characteristic. . An example of the effect of this on the measured film thickness is
This will be described with reference to FIG.

【００１３】図１２は、シリコン膜厚測定値への埋込み
酸化膜厚のバラツキによる影響を示す線図である。すな
わち、Ｓｉ（１．５μｍ）／ＳｉＯ2 ／Ｓｉ基板による
積層構造における下層酸化膜厚入力値と、上層シリコン
膜厚算出値の関係を示している。ここで下層酸化膜厚の
入力値（プログラム中で設定入力される酸化膜厚）は７
００ｎｍに設定されている。FIG. 12 is a diagram showing the influence of the variation of the buried oxide film thickness on the measured value of the silicon film thickness. That is, the relationship between the input value of the lower oxide film thickness and the calculated value of the upper silicon film thickness in the stacked structure of the Si (1.5 μm) / SiO 2 / Si substrate is shown. Here, the input value of the lower oxide film thickness (the oxide film thickness set and input in the program) is 7
It is set to 00 nm.

【００１４】同図に示されるように、この例では実際の
下層酸化膜厚が６４０ｎｍ前後を境に、膜厚測定値が大
きく変動する。すなわち、下層酸化膜厚の入力値と実際
値との差が６０ｎｍの時点で、上層シリコン膜厚算出値
が厚い方向にジャンプしている。この程度の膜厚ばらつ
きは、現在の半導体プロセス技術ではしばしば発生する
ものであり、よって測定膜厚に誤差が発生するという問
題があった。As shown in FIG. 1, in this example, the measured value of the film thickness fluctuates greatly when the actual lower oxide film thickness is around 640 nm. That is, when the difference between the input value and the actual value of the lower oxide film thickness is 60 nm, the calculated upper silicon film thickness value jumps in the direction of increasing thickness. Such a film thickness variation often occurs in the current semiconductor process technology, and there is a problem that an error occurs in the measured film thickness.

【００１５】さらに、本発明者は、例えば図１１に示さ
れるように測定波長範囲Ｚλｔの中に包絡線Ｅｖ３の極
小点Ａが含まれていると、上層膜厚算出値が実際の値よ
りも大きく演算されるという不都合が生じることを見出
した。これは極小点Ａが上層Ｓｉ層内での干渉とは関係
のない、いわば偽のピークであることに起因する。こう
した偽のピークを用いた演算によって、従来技術では測
定膜厚値に看過しえない誤差が発生するおそれがあっ
た。Further, the present inventor has found that when the minimum point A of the envelope Ev3 is included in the measurement wavelength range Zλt as shown in FIG. 11, for example, the calculated upper layer thickness is smaller than the actual value. It has been found that the problem of large calculation occurs. This is because the minimum point A is a false peak which has nothing to do with interference in the upper Si layer. The calculation using such a false peak may cause an error that cannot be overlooked in the measured film thickness value in the related art.

【００１６】本発明は、前記のような従来技術の有する
課題や欠点を解決するためなされたもので、その目的は
二層膜試料における上層膜厚の光学的測定において下層
膜厚入力値と実際膜厚とのずれに起因する誤差発生を抑
制し、安定かつ高精度の測定を実現するとともに、測定
時間が短く実用的なプログラムを備える膜厚測定装置を
提供することにある。The present invention has been made to solve the above-mentioned problems and disadvantages of the prior art. The purpose of the present invention is to provide an optical measurement of the upper layer thickness in a two-layer film sample, and to compare the input value of the lower layer thickness with the actual value. An object of the present invention is to provide a film thickness measuring apparatus which suppresses the occurrence of an error due to a deviation from the film thickness, realizes stable and accurate measurement, and has a short measuring time and a practical program.

【００１７】[0017]

【課題を解決するための手段】前記従来技術の課題を解
決するため、本発明に係る膜厚測定装置は、基板表面か
らの光反射率の波長依存性を計測し、下層膜種及び膜厚
と上層膜厚を既知として、該測定結果から基板表面に形
成された上層薄膜膜厚を算出する光学的二層膜の膜厚測
定装置であって、測定波長範囲を、少なくとも下層膜の
みが形成された基板に基づく反射率の波長依存性の周期
以上とする制御手段を備えることを特徴とする。In order to solve the above-mentioned problems of the prior art, a film thickness measuring apparatus according to the present invention measures the wavelength dependence of the light reflectance from the substrate surface, and determines the type and thickness of the lower layer film. And an upper-layer film thickness is known, an optical double-layer film thickness measuring apparatus that calculates the upper-layer thin film thickness formed on the substrate surface from the measurement result, and the measurement wavelength range is at least formed only by the lower-layer film. And a control unit for setting a period of the wavelength dependence of the reflectance based on the substrate to be set.

【００１８】前記の構成により、下層膜に若干の膜厚ば
らつきが生じる場合でも、一度の測定結果のうちから最
適の膜厚算出波長の選定が容易になる。According to the above configuration, even when a slight thickness variation occurs in the lower layer film, it is easy to select an optimum thickness calculation wavelength from a single measurement result.

【００１９】あるいは、本発明に係る膜厚測定装置は、
前記において測定された各波長に対する反射率の極大点
から構成される包絡線を求める演算手段を有することを
特徴とする。この構成により、包絡線を求める演算が自
動化され、連続測定動作が可能になる。Alternatively, the film thickness measuring device according to the present invention
It is characterized by having an arithmetic means for obtaining an envelope composed of the maximum points of the reflectance for each wavelength measured in the above. With this configuration, the calculation for obtaining the envelope is automated, and the continuous measurement operation can be performed.

【００２０】あるいは、本発明に係る膜厚測定装置は、
前記包絡線の極小点の抽出手段を備えることを特徴とす
る。この構成により、包絡線の極小点を求める演算が自
動化され、連続測定動作が可能になる。Alternatively, the film thickness measuring apparatus according to the present invention comprises:
It is characterized by comprising means for extracting a minimum point of the envelope. With this configuration, the calculation for finding the minimum point of the envelope is automated, and a continuous measurement operation becomes possible.

【００２１】あるいは、本発明に係る膜厚測定装置は、
前記包絡線極小点を含まない波長範囲の反射率データか
ら上層膜厚を算出する演算手段を備えることを特徴とす
る。Alternatively, the film thickness measuring device according to the present invention
An arithmetic unit for calculating an upper layer thickness from reflectance data in a wavelength range not including the minimum point of the envelope is provided.

【００２２】前記の構成を有する本発明にかかる膜厚測
定装置によれば、下層膜厚入力値と実際膜厚とのずれに
起因する測定誤差発生が抑制される。According to the film thickness measuring apparatus of the present invention having the above-described configuration, the occurrence of a measurement error due to a deviation between the input value of the lower layer thickness and the actual film thickness is suppressed.

【００２３】[0023]

【発明の実施の形態】以下、この発明の好適な実施形態
を添付図を参照して詳細に説明する。なお、以下に述べ
る実施形態は、この発明の好適な具現例の一部であり、
技術構成上好ましい種々の限定が付されているが、この
発明の範囲は、以下の説明において特にこの発明を限定
する旨の記載がない限り、これらの形態に限られるもの
ではない。Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiment described below is a part of a preferred embodiment of the present invention,
Although various limitations that are preferable in terms of the technical configuration are given, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

【００２４】図１は、本発明に係る膜厚測定装置の一実
施形態におけるブロック構成図である。同図に示される
ように、本発明に係る膜厚測定装置ＡＰは、光束１０１
ａを発する光源１０１、光束１０１ａを回折した照射光
１０２ａを発する回折格子１０２、回折格子１０２を回
動駆動する回折格子駆動装置１０３、照射光１０２ａお
よび反射光１０６ａを通過させる光学系１０４、照射光
１０２ａによって照射される被測定ウエハー１０６を載
置するステージ１０５、被測定ウエハー１０６からの反
射光１０６ａを捕捉する光強度検出器１０７、光強度検
出器１０７からの反射光強度出力をデジタル値に変換す
るＡ／Ｄコンバータ２１を備える。FIG. 1 is a block diagram showing an embodiment of a film thickness measuring apparatus according to the present invention. As shown in FIG.
a, a diffraction grating 102 that emits irradiation light 102a obtained by diffracting the light beam 101a, a diffraction grating driving device 103 that rotationally drives the diffraction grating 102, an optical system 104 that passes the irradiation light 102a and the reflected light 106a, and irradiation light. The stage 105 on which the wafer 106 to be measured irradiated by the wafer 102a is mounted, the light intensity detector 107 for capturing the reflected light 106a from the wafer 106 to be measured, and the reflected light intensity output from the light intensity detector 107 are converted into digital values. A / D converter 21 is provided.

【００２５】さらに、系全体を制御する系制御手段Ｍ
１、回折格子駆動装置１０３を制御する測定波長範囲制
御手段Ｍ２、Ａ／Ｄコンバータ２１からの出力に基づき
原データを編成する原データ編成手段Ｍ３、原データ編
成手段Ｍ３が編成した原データの極大値を演算する原デ
ータの極大値演算手段Ｍ４、原データの極大値演算手段
Ｍ４によって得られた極大値に基づき包絡線を演算する
包絡線演算手段Ｍ５、包絡線演算手段Ｍ５によって得ら
れた包絡線の極大・極小値を抽出する包絡線の極大・極
小値抽出手段Ｍ６、包絡線の極大・極小値抽出手段Ｍ６
によって得られた極小点を除外して演算用波長領域を設
定する演算用波長領域設定手段Ｍ７、演算用波長領域設
定手段Ｍ７によって得られた演算用波長領域内で膜厚演
算を行う、反射率に基づく膜厚演算手段Ｍ８を備える。Further, system control means M for controlling the entire system
1. Measuring wavelength range control means M2 for controlling the diffraction grating driving device 103, original data organizing means M3 for organizing original data based on the output from the A / D converter 21, and the maximum of the original data organized by the original data organizing means M3. The maximum value calculation means M4 of the original data for calculating the value, the envelope calculation means M5 for calculating the envelope based on the maximum value obtained by the maximum value calculation means M4 of the original data, and the envelope obtained by the envelope calculation means M5 Envelope maximum / minimum value extraction means M6 for extracting the maximum / minimum value of the line, maximum / minimum value extraction means M6 of the envelope
Wavelength region setting means M7 for setting the wavelength region for calculation excluding the minimum point obtained by the calculation, the film thickness calculation is performed in the wavelength region for calculation obtained by the wavelength region setting device for calculation M7, the reflectance And a film thickness calculating means M8 based on.

【００２６】前記の系制御手段Ｍ１〜膜厚演算手段Ｍ８
は、いずれもＣＰＵ（不図示）によって実行可能なプロ
グラムとして構成され、例えばＲＯＭ（不図示）に格納
されている。これらプログラムは必要に応じて順次、Ｃ
ＰＵにより実行される。The system control means M1 to the film thickness calculating means M8
Are each configured as a program executable by a CPU (not shown), and are stored in, for example, a ROM (not shown). These programs are executed sequentially as necessary.
Performed by the PU.

【００２７】さらに、符号２２は膜厚値表示部であり、
具体的にはＣＲＴやＬＣＤによるディスプレイモニター
装置である。符号２３は膜厚値出力部であり、具体的に
はプリンタ装置である。Reference numeral 22 denotes a film thickness value display unit.
Specifically, it is a display monitor device using a CRT or an LCD. Reference numeral 23 denotes a film thickness value output unit, specifically, a printer device.

【００２８】前記の光源１０１から光強度検出器１０７
までの動作は、前記図９におけると同様であり、説明は
省略される。From the light source 101 to the light intensity detector 107
The operations up to this point are the same as those in FIG. 9 and the description is omitted.

【００２９】本発明の要部は、系制御手段Ｍ１〜膜厚演
算手段Ｍ８にある。以下、添付のフローチャートにした
がい、各手段の動作を説明する。The main part of the present invention is the system control means M1 to the film thickness calculation means M8. The operation of each means will be described below according to the attached flowchart.

【００３０】図３は、本発明の一実施形態である膜厚測
定装置ＡＰの備える、測定波長範囲制御手段Ｍ２および
原データ編成手段Ｍ３による、サンプリング測定及び原
データ編成動作のフローチャートである。同図におい
て、ステップＳ１では下層膜（埋め込み酸化膜）のみの
構造において測定された反射率波長依存性の周期以上で
あるような、サンプリング測定波長範囲が設定される。
とりわけ、このサンプリング測定波長範囲は好適には、
下層膜のみが形成された場合の基板からの反射率波長依
存性の周期の２倍程度の測定波長範囲にすることが好ま
しい。FIG. 3 is a flowchart of the sampling measurement and original data organization operations by the measurement wavelength range control means M2 and the original data organization means M3 provided in the film thickness measuring apparatus AP according to one embodiment of the present invention. In FIG. 5, in step S1, a sampling measurement wavelength range is set such that it is equal to or longer than the period of the reflectance wavelength dependence measured in the structure of only the lower layer film (buried oxide film).
In particular, this sampling measurement wavelength range is preferably
It is preferable to set the measurement wavelength range to about twice the period of the reflectance wavelength dependency from the substrate when only the lower layer film is formed.

【００３１】前記のようにしてサンプリング測定波長範
囲が設定されると、ついでステップＳ２で最初のサンプ
リングのための波長が設定され、照射光がこの開始波長
となるよう、ステップＳ３で回折格子が回動制御され
る。このようにして設定波長の照射光が発せられ、被測
定ウエハーからの反射光が光強度検出器によって検出さ
れると、この反射光強度に基づいてステップＳ４で反射
率が測定される。After the sampling measurement wavelength range is set as described above, the wavelength for the first sampling is set in step S2, and the diffraction grating is turned in step S3 so that the irradiation light has this start wavelength. Dynamic control. The irradiation light of the set wavelength is emitted in this manner, and when the reflected light from the wafer to be measured is detected by the light intensity detector, the reflectance is measured in step S4 based on the reflected light intensity.

【００３２】前記のようにして一個のサンプリング測定
値が得られた後に、ステップＳ５でサンプリング波長が
増加・更新され、ステップＳ３に戻って次のサンプリン
グ測定動作が継続される。このように波長を漸増させつ
つ測定を反復し、設定されたサンプリング測定波長範囲
の全域にわたって測定が為され、原データが編成され
る。測定の終了はステップＳ６により判定がなされる。After one sampling measurement value is obtained as described above, the sampling wavelength is increased and updated in step S5, and the process returns to step S3 to continue the next sampling measurement operation. As described above, the measurement is repeated while gradually increasing the wavelength, the measurement is performed over the entire set sampling measurement wavelength range, and the original data is organized. The end of the measurement is determined in step S6.

【００３３】前記のようにして得られた原データは、図
２に示されるような反射率曲線Ａｂｐ２を形成する。The original data obtained as described above forms a reflectance curve Abp2 as shown in FIG.

【００３４】図４は、本発明の一実施形態である膜厚測
定装置ＡＰの備える、原データの極大値演算手段Ｍ４に
よる、原データの極大値演算動作のフローチャートであ
る。また図５は、原データの極大値演算原理の説明図で
ある。FIG. 4 is a flowchart of the operation of calculating the maximum value of the original data by the maximum value calculating means M4 of the original data provided in the film thickness measuring apparatus AP according to one embodiment of the present invention. FIG. 5 is an explanatory diagram of the principle of calculating the maximum value of the original data.

【００３５】図５に示されるように、原データφｎはサ
ンプリング間隔Δλ毎に、すなわち波長がλ２０、λ２
１、λ２２、λ２３と離散的なサンプリングポイント毎
に得られているから、反射率の極大値は一般的にサンプ
リングポイント間に存することになる。As shown in FIG. 5, the original data φn is provided at every sampling interval Δλ, that is, when the wavelength is λ20, λ2
Since 1, λ22 and λ23 are obtained for each discrete sampling point, the maximum value of the reflectance generally exists between the sampling points.

【００３６】そこで各原データφｎを載せる部分フィッ
ティング曲線Ｐｃｖを編成すると、この部分フィッティ
ング曲線Ｐｃｖの極大値Ｐｍｘを算出することができ
る。図４はこのような動作の流れを示すものであり、ス
テップＳ１１で原データに基づき、部分フィッティング
曲線を編成する。Therefore, when a partial fitting curve Pcv on which each original data φn is placed is organized, a maximum value Pmx of the partial fitting curve Pcv can be calculated. FIG. 4 shows the flow of such an operation. In step S11, a partial fitting curve is formed based on the original data.

【００３７】ついで、ステップＳ１２で部分フィッティ
ング曲線の極大値を演算する。このようなプログラムと
しては例えば、波長λにおける反射率Ｒ（λ）と、次の
波長λ＋Δλにおける反射率 Ｒ（λ＋Δλ） の差 Ｚ＝Ｒ（λ）−Ｒ（λ＋Δλ） が負から正へと符号が変化したときのＲ（λ）を選択し
て極大値とする。以上は増分の変化により極大値を求め
るアルゴリズムであるが、これ以外にも例えば、微係数
がゼロを示す位置により極大値を求めるアルゴリズムも
適用可能である。Next, in step S12, the maximum value of the partial fitting curve is calculated. As such a program, for example, the difference Z = R (λ) -R (λ + Δλ) between the reflectance R (λ) at the wavelength λ and the reflectance R (λ + Δλ) at the next wavelength λ + Δλ is changed from negative to positive. Is changed and R (λ) is selected as the maximum value. The above is the algorithm for obtaining the maximum value by the change in the increment. However, for example, an algorithm for obtaining the maximum value from the position where the differential coefficient is zero can be applied.

【００３８】この部分フィッティングと極大値演算を全
部分につき実行すべく、ステップＳ１３〜ステップＳ１
１間でループによる反復がなされる。In order to execute the partial fitting and the local maximum value calculation for all parts, steps S13 to S1 are executed.
A loop is repeated between the two.

【００３９】つぎに、得られた各極大値を包む包絡線の
演算がなされる。図６は、本発明の一実施形態である膜
厚測定装置ＡＰの備える、包絡線演算手段Ｍ５による包
絡線演算動作のフローチャートである。ステップＳ１４
において、演算によって極大値Ｐｍｘの包絡線Ｅｖ２が
作成される。なお前記のようにして得られた包絡線Ｅｖ
２は、図２のように示すことができる。Next, the calculation of the envelope enclosing the obtained local maximum values is performed. FIG. 6 is a flowchart of an envelope calculating operation by the envelope calculating means M5 included in the film thickness measuring apparatus AP according to one embodiment of the present invention. Step S14
, An envelope Ev2 of the local maximum value Pmx is created. Note that the envelope Ev obtained as described above is used.
2 can be shown as in FIG.

【００４０】つぎに、得られた包絡線Ｅｖ２の極値の演
算がなされる。図７は、本発明の一実施形態である膜厚
測定装置ＡＰの備える、包絡線の極大・極小値抽出手段
Ｍ６による包絡線の極値抽出動作と、膜厚演算用波長領
域設定手段Ｍ７による波長領域設定動作のフローチャー
トである。Next, the extremum of the obtained envelope Ev2 is calculated. FIG. 7 shows an extreme value extraction operation of the envelope by the maximum value / minimum value extraction means M6 of the envelope included in the film thickness measuring apparatus AP according to one embodiment of the present invention, and a wavelength region setting means M7 for film thickness calculation. 5 is a flowchart of a wavelength region setting operation.

【００４１】同図において、ステップＳ１５で包絡線Ｅ
ｖ２の極大値と極小値が、それらを実現する波長λＭと
ともに抽出され、ついでステップＳ１６で、極小値を排
除した演算用波長領域Ｚλ（図２参照）が設定される。
このように、原反射率データ列から前述の偽のピークに
相当する測定データのみを抽出し、これを排除する波長
範囲を決定することができる。Referring to FIG. 5, an envelope E is obtained in step S15.
The maximum value and the minimum value of v2 are extracted together with the wavelength λM that realizes them, and then, in step S16, the calculation wavelength region Zλ (see FIG. 2) excluding the minimum value is set.
As described above, it is possible to extract only the measurement data corresponding to the above-mentioned false peak from the original reflectance data sequence and determine the wavelength range in which the measurement data is excluded.

【００４２】すなわち、 まず偽のピークに相当する測
定データ近傍の適当に定められた数の反射率データを削
除し、原測定反射率データ列を分割する。つぎに分割さ
れた各反射率データ列のうちの一つを選択する。これは
例えば各データ列のデータ数を算出し、データ数の最も
多いものを選択することで実行される。That is, first, an appropriately determined number of pieces of reflectance data near the measurement data corresponding to the false peak are deleted, and the original measured reflectance data sequence is divided. Next, one of the divided reflectance data strings is selected. This is performed, for example, by calculating the number of data in each data string and selecting the one with the largest number of data.

【００４３】図８は、本発明の一実施形態である膜厚測
定装置ＡＰの備える、反射率に基づく膜厚演算手段Ｍ８
による膜厚演算動作のフローチャートである。同図にお
いて、ステップＳ２１で、先ず下層のみの反射率データ
から前記演算用波長領域Ｚλ内の波長λＭにおける反射
率データφ’Ｍが読み込まれ、ステップＳ２２で反射率
データφ’Ｍ及び、波長領域Ｚλ内の波長λＭにおける
包絡線の極大値φＭに基づいて、膜厚が算出される。FIG. 8 shows a reflectance-based film thickness calculating means M8 provided in a film thickness measuring apparatus AP according to an embodiment of the present invention.
6 is a flowchart of a film thickness calculation operation according to FIG. In the figure, in step S21, first, the reflectance data φ'M at the wavelength λM in the operation wavelength region Zλ is read from the reflectance data of only the lower layer, and in step S22, the reflectance data φ'M and the wavelength region The film thickness is calculated based on the maximum value φM of the envelope at the wavelength λM in Zλ.

【００４４】算出された膜厚は、膜厚値表示部２２によ
り表示されるか、あるいは／および膜厚値出力部２３に
よりプリントアウトされる。The calculated film thickness is displayed on the film thickness display unit 22 or / and printed out by the film thickness output unit 23.

【００４５】[0045]

【発明の効果】以上説明したように、本発明の請求項１
に係る膜厚測定装置は、測定波長範囲を、少なくとも下
層膜のみが形成された基板に基づく反射率の波長依存性
の周期以上とする制御手段を備えて構成するものであ
る。したがって、下層膜に若干の膜厚ばらつきが生じる
場合でも、一度の測定結果のうちから最適の膜厚算出波
長の選定が容易にでき、よって良好な精度の膜厚測定が
可能になる。As described above, according to the first aspect of the present invention,
The film thickness measuring apparatus according to the above is provided with a control means for setting the measurement wavelength range to at least the wavelength-dependent period of the reflectance based on the substrate on which only the lower layer film is formed. Therefore, even when a slight thickness variation occurs in the lower layer film, an optimum thickness calculation wavelength can be easily selected from a single measurement result, so that good accuracy of the thickness measurement can be achieved.

【００４６】本発明の請求項２に係る膜厚測定装置は、
前記請求項１の構成において、測定された各波長に対す
る反射率の極大点から構成される包絡線を求める演算手
段を有して構成するものである。したがって、包絡線を
求める演算を自動化でき、よって連続測定動作が可能に
なる。The film thickness measuring apparatus according to claim 2 of the present invention
In the configuration of the first aspect, there is provided an arithmetic unit for obtaining an envelope composed of a maximum point of the reflectance for each measured wavelength. Therefore, the calculation for obtaining the envelope can be automated, and the continuous measurement operation can be performed.

【００４７】本発明の請求項３に係る膜厚測定装置は、
前記請求項２の構成において、前記包絡線の極小点の抽
出手段を備えて構成するものである。したがって、包絡
線の極小点を求める演算を自動化でき、よって連続測定
動作が可能になる。The film thickness measuring apparatus according to claim 3 of the present invention
In the configuration of the second aspect, there is provided a means for extracting a minimum point of the envelope. Therefore, the calculation for finding the minimum point of the envelope can be automated, and thus a continuous measurement operation can be performed.

【００４８】本発明の請求項４に係る膜厚測定装置は、
前記請求項３の構成において、前記包絡線極小点を含ま
ない波長範囲の反射率データから上層膜厚を算出する演
算手段を備えて構成するものである。したがって、下層
膜厚入力値と実際膜厚とのずれに起因する測定誤差発生
を抑制でき、高精度で安定した測定を実現することがで
きる。The film thickness measuring apparatus according to claim 4 of the present invention
In the configuration of the third aspect, there is provided an arithmetic unit for calculating an upper layer thickness from reflectance data in a wavelength range not including the minimum point of the envelope. Therefore, it is possible to suppress the occurrence of a measurement error due to the difference between the input value of the lower layer thickness and the actual film thickness, and it is possible to realize highly accurate and stable measurement.

【００４９】このように本発明の膜厚測定装置は、前記
プログラムを備えることにより、二層膜構造試料におけ
る上層薄膜膜厚の光学的測定に関して、既知として予め
入力される下層膜厚と実際の下層膜厚との誤差が上層膜
厚測定に及ぼす影響を自動的に抑制する機能を実現した
ものである。As described above, the film thickness measuring apparatus of the present invention is provided with the above-mentioned program, so that the optical measurement of the upper layer thin film thickness in the two-layer film structure sample can be performed by comparing the lower layer film thickness previously input as known with the actual value. This realizes a function of automatically suppressing the influence of an error with the lower layer thickness on the measurement of the upper layer thickness.

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

【図１】本発明に係る膜厚測定装置の一実施形態におけ
るブロック構成図である。FIG. 1 is a block diagram of a film thickness measuring apparatus according to an embodiment of the present invention.

【図２】シリコン／酸化シリコン／シリコン基板積層構
造の反射率の波長依存性を示す線図である。FIG. 2 is a diagram showing the wavelength dependence of the reflectance of a silicon / silicon oxide / silicon substrate stacked structure.

【図３】本発明に係る膜厚測定装置の一実施形態におけ
るサンプリング測定及び原データ編成動作のフローチャ
ートである。FIG. 3 is a flowchart of a sampling measurement and original data organization operation in one embodiment of the film thickness measuring apparatus according to the present invention.

【図４】本発明に係る膜厚測定装置の一実施形態におけ
る原データの極大値演算動作のフローチャートである。FIG. 4 is a flowchart of an operation of calculating a local maximum value of original data in an embodiment of the film thickness measuring apparatus according to the present invention.

【図５】原データの極大値演算原理の説明図である。FIG. 5 is an explanatory diagram of a principle of calculating a maximum value of original data.

【図６】本発明に係る膜厚測定装置の一実施形態におけ
る包絡線演算動作のフローチャートである。FIG. 6 is a flowchart of an envelope calculation operation in one embodiment of the film thickness measuring apparatus according to the present invention.

【図７】本発明に係る膜厚測定装置の一実施形態におけ
る包絡線の極値抽出動作のフローチャートである。FIG. 7 is a flowchart of an envelope extreme value extracting operation in the embodiment of the film thickness measuring apparatus according to the present invention.

【図８】本発明に係る膜厚測定装置の一実施形態におけ
る膜厚演算動作のフローチャートである。FIG. 8 is a flowchart of a film thickness calculating operation in one embodiment of the film thickness measuring device according to the present invention.

【図９】従来の膜厚測定装置のブロック構成図である。FIG. 9 is a block diagram of a conventional film thickness measuring apparatus.

【図１０】反射率の波長依存周期性を示す線図である。FIG. 10 is a diagram showing the wavelength-dependent periodicity of the reflectance.

【図１１】埋込み酸化膜厚が異なる場合の反射率の波長
依存性を示す線図である。FIG. 11 is a graph showing the wavelength dependence of the reflectance when the buried oxide film thickness is different.

【図１２】シリコン膜厚測定値への埋込み酸化膜厚のバ
ラツキによる影響を示す線図である。FIG. 12 is a diagram showing an influence of a variation in a buried oxide film thickness on a measured value of a silicon film thickness.

【符号の説明】[Explanation of symbols]

ＡＰ…本発明に係る膜厚測定装置、Ｍ１…系制御手段、
Ｍ２…測定波長範囲制御手段、Ｍ３…原データ編成手
段、Ｍ４…原データの極大値演算手段、Ｍ５…包絡線演
算手段、Ｍ６…包絡線の極大・極小値抽出手段、Ｍ７…
演算用波長領域設定手段、Ｍ８…反射率に基づく膜厚演
算手段、２１…Ａ／Ｄコンバータ、２２…膜厚値表示
部、２３…膜厚値出力部、１０１…光源、１０１ａ…光
束、１０２…回折格子、１０２ａ…照射光、１０３…回
折格子駆動装置、１０４…光学系、１０５…ステージ、
１０６…被測定ウエハー、１０６ａ…反射光、１０７…
光強度検出器。AP: a film thickness measuring apparatus according to the present invention, M1: system control means,
M2: measurement wavelength range control means, M3: original data organization means, M4: maximum value calculation means of original data, M5: envelope calculation means, M6: maximum / minimum value extraction means of envelope, M7 ...
Calculation wavelength region setting means, M8: Film thickness calculation means based on reflectance, 21: A / D converter, 22: Film thickness display section, 23: Film thickness output section, 101: Light source, 101a: Light flux, 102 ... Diffraction grating, 102a ... Irradiation light, 103 ... Diffraction grating driving device, 104 ... Optical system, 105 ... Stage,
106: wafer to be measured, 106a: reflected light, 107:
Light intensity detector.

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 基板表面からの光反射率の波長依存性を
計測し、下層膜種及び膜厚と上層膜厚を既知として、該
測定結果から基板表面に形成された上層薄膜膜厚を算出
する光学的二層膜の膜厚測定装置であって、 測定波長範囲を、少なくとも下層膜のみが形成された基
板に基づく反射率の波長依存性の周期以上とする制御手
段を備えることを特徴とする膜厚測定装置。1. A method for measuring the wavelength dependence of the light reflectance from the substrate surface, and calculating the thickness of the upper thin film formed on the substrate surface from the measurement results, assuming that the type and thickness of the lower film and the upper film thickness are known. An optical double-layer film thickness measuring apparatus, comprising: a control unit that sets a measurement wavelength range to at least a wavelength-dependent period of reflectance based on a substrate on which only the lower layer film is formed. Film thickness measuring device. 【請求項２】 測定された各波長に対する反射率の極大
点から構成される包絡線を求める演算手段を有すること
を特徴とする請求項１記載の膜厚測定装置。2. The film thickness measuring apparatus according to claim 1, further comprising an arithmetic unit for obtaining an envelope composed of a maximum point of the reflectance for each measured wavelength. 【請求項３】 前記包絡線の極小点の抽出手段を備える
ことを特徴とする請求項２記載の膜厚測定装置。3. The apparatus according to claim 2, further comprising means for extracting a minimum point of the envelope. 【請求項４】 前記包絡線極小点を含まない波長範囲の
反射率データから上層膜厚を算出する演算手段を備える
ことを特徴とする請求項３記載の膜厚測定装置。4. The film thickness measuring apparatus according to claim 3, further comprising an arithmetic unit for calculating an upper layer thickness from reflectance data in a wavelength range not including the minimum point of the envelope.
JP11564597A 1997-05-06 1997-05-06 Optical film-thickness measuring apparatus for multilayer thin film Pending JPH10307009A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP11564597A JPH10307009A (en) 1997-05-06 1997-05-06 Optical film-thickness measuring apparatus for multilayer thin film

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP11564597A JPH10307009A (en) 1997-05-06 1997-05-06 Optical film-thickness measuring apparatus for multilayer thin film

Publications (1)

Publication Number Publication Date
JPH10307009A true JPH10307009A (en) 1998-11-17

Family

ID=14667778

Family Applications (1)

Application Number Title Priority Date Filing Date
JP11564597A Pending JPH10307009A (en) 1997-05-06 1997-05-06 Optical film-thickness measuring apparatus for multilayer thin film

Country Status (1)

Country Link
JP (1) JPH10307009A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000311334A (en) * 1999-04-27 2000-11-07 Victor Co Of Japan Ltd Magnetic recording medium and method for evaluating characteristic of the same
JP2002323303A (en) * 2001-04-26 2002-11-08 Denso Corp Diafragm thickness measurement method, its device, and manufacturing method for semiconductor device
CN111486794A (en) * 2019-01-29 2020-08-04 大塚电子株式会社 Optical measurement system and optical measurement method

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000311334A (en) * 1999-04-27 2000-11-07 Victor Co Of Japan Ltd Magnetic recording medium and method for evaluating characteristic of the same
JP2002323303A (en) * 2001-04-26 2002-11-08 Denso Corp Diafragm thickness measurement method, its device, and manufacturing method for semiconductor device
CN111486794A (en) * 2019-01-29 2020-08-04 大塚电子株式会社 Optical measurement system and optical measurement method
JP2020122680A (en) * 2019-01-29 2020-08-13 大塚電子株式会社 Optical measuring system and optical measurement method
CN111486794B (en) * 2019-01-29 2024-02-13 大塚电子株式会社 Optical measurement system and optical measurement method

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