JPH05215519A - Optical film thickness monitor - Google Patents
Optical film thickness monitorInfo
- Publication number
- JPH05215519A JPH05215519A JP24467491A JP24467491A JPH05215519A JP H05215519 A JPH05215519 A JP H05215519A JP 24467491 A JP24467491 A JP 24467491A JP 24467491 A JP24467491 A JP 24467491A JP H05215519 A JPH05215519 A JP H05215519A
- Authority
- JP
- Japan
- Prior art keywords
- light
- intensity
- film thickness
- interference
- monochromatic
- 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
Landscapes
- Length Measuring Devices By Optical Means (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
(57)【要約】
【目的】 高精度で成膜時の膜厚計測が可能な膜厚モニ
タを提供する。
【構成】 光源１より発した白色光Ｌ1 はモニタ用薄膜
２３により干渉を受ける。その反射光Ｌ2 はハーフミラ
ー３により二分割される。一方の白色光Ｌ3 の強度は第
１の受光器５により検出され、他方の白色光Ｌ4 は光学
フィルタ４に入射し、所望の膜厚に対応した波長の単色
光が取り出される。そしてこの単色光の強度が第１の受
光器６により検出され、その検出信号Ｖ2 と第１の受光
器５の検出信号Ｖ1 との差分が差動増幅器７により求め
られ、出力Ｖ3 がチャートレコーダ８に入力される。従
って、チャートレコーダ８では、干渉によって起こる周
期的な強度変化のみが出力される。
(57) [Summary] [Purpose] To provide a film thickness monitor capable of highly accurately measuring film thickness during film formation. [Structure] The white light L 1 emitted from the light source 1 is interfered by the monitor thin film 23. The reflected light L 2 is split into two by the half mirror 3. The intensity of the one white light L 3 is detected by the first light receiver 5, and the other white light L 4 is incident on the optical filter 4 to extract monochromatic light having a wavelength corresponding to a desired film thickness. The intensity of the monochromatic light is detected by the first light receiver 6, the difference between the detection signal V 2 and the detection signal V 1 of the first light receiver 5 is obtained by the differential amplifier 7, the output V 3 It is input to the chart recorder 8. Therefore, the chart recorder 8 outputs only the periodic intensity change caused by the interference.
Description
【０００１】[0001]
【産業上の利用分野】この発明は、真空蒸着による成膜
装置等に適用される光学式膜厚モニタであって、特に薄
膜との干渉作用を利用したものに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film thickness monitor applied to a film forming apparatus or the like by vacuum vapor deposition, which particularly utilizes an interference action with a thin film.
【０００２】[0002]
【従来の技術】従来、薄膜との干渉作用を利用して成膜
時の膜厚を計測する光学式膜厚モニタにおいては、単色
光の強度変化を利用していた。即ち、白色光を真空チャ
ンバ内で形成されつつある薄膜に照射し、形成すべき膜
厚に対応した波長の単色光を干渉フィルタを用いて干渉
光より取り出す。その後、この単色光の強度変化を受光
器により測定していた。この場合、単色光の強度変化は
成膜時間とともに周期的に変化するため、操作者は強度
変化の最大値を尺度として形成された膜厚を知ることが
可能となる。2. Description of the Related Art Conventionally, in an optical film thickness monitor for measuring a film thickness during film formation by utilizing an interference action with a thin film, a change in intensity of monochromatic light has been used. That is, white light is applied to the thin film being formed in the vacuum chamber, and monochromatic light having a wavelength corresponding to the film thickness to be formed is extracted from the interference light using an interference filter. After that, the change in the intensity of the monochromatic light was measured by a light receiver. In this case, since the intensity change of the monochromatic light changes periodically with the film formation time, the operator can know the formed film thickness with the maximum value of the intensity change as a scale.
【０００３】[0003]
【発明が解決しようとする課題】上記した通り、従来の
技術は原理的には精度の良い膜厚モニタとして機能する
ものであるが、実際には以下の問題点により計測精度は
良いものではなかった。As described above, the conventional technique theoretically functions as an accurate film thickness monitor, but in reality the measurement accuracy is not good due to the following problems. It was
【０００４】即ち、白色光源の強度揺らぎ，真空ポンプ
の振動に伴う光学系の振動やモニタガラスの振動及びモ
ニタガラス自身の配置精度等の影響により観測光の強度
が変動し、このため計測精度が悪化するという問題点が
生じていた。That is, the intensity of the observation light fluctuates due to the fluctuation of the intensity of the white light source, the vibration of the optical system due to the vibration of the vacuum pump, the vibration of the monitor glass, and the arrangement accuracy of the monitor glass itself, which causes the measurement accuracy to change. There was a problem of getting worse.
【０００５】この発明はこの様な問題点を克服すべくな
されたものであり、その目的とするところは、干渉作用
以外の好ましくない強度変動要因が存在していてもその
影響を受けること無く高精度で、成膜時の膜厚を計測す
ることができる膜厚モニタを提供することにある。The present invention has been made in order to overcome such problems, and an object of the present invention is not to be influenced by an undesired intensity fluctuation factor other than the interference action, and to be high. An object of the present invention is to provide a film thickness monitor capable of accurately measuring the film thickness during film formation.
【０００６】[0006]
【課題を解決するための手段】単色光では薄膜による干
渉の影響を受けてその強度が大きく変化するのに対し
て、複合光では薄膜による干渉の影響は各波長の平均と
して現れるため、成膜中に於けるその強度は殆ど変化し
ないものと考えられる。Means for Solving the Problems In monochromatic light, the intensity of the light changes greatly under the influence of thin film interference, whereas in composite light, the influence of thin film interference appears as an average of each wavelength. It is considered that its strength in the inside hardly changes.
【０００７】一方、光源の強度揺らぎ等の干渉以外の強
度変動要因は、単色光や複合光に係わらず、一律に同様
の強度変化をもたらす。従って、干渉作用後の複合光の
強度と単色光の強度との差分を求めることにより不要な
強度変動をキャンセルし、計測精度の向上を図ることが
できると考えられる。On the other hand, factors of intensity variation other than interference, such as intensity fluctuations of the light source, cause similar intensity changes regardless of whether they are monochromatic light or composite light. Therefore, it is considered that unnecessary difference in intensity can be canceled and the measurement accuracy can be improved by obtaining the difference between the intensity of the composite light after the interference action and the intensity of the monochromatic light.
【０００８】この発明は係る観点に着眼してなされたも
のであり、本光学式膜厚モニタは次の様な構成を有する
ものである。即ち、（ａ）薄膜との干渉作用を受けた複
合光を第１及び第２の複合光に分波する分波手段と、
（ｂ）第１の複合光の強度を検出する第１の受光手段
と、（ｃ）第２の複合光から所定の波長の単色光を抽出
するフィルタ手段と、（ｄ）抽出された所定の波長の単
色光の強度を検出する第２の受光手段と、（ｅ）第１の
受光手段の出力信号と第２の受光手段の出力信号との差
分を検出する検出手段とを備える様にしたものである。The present invention has been made in view of this point of view, and the present optical film thickness monitor has the following configuration. That is, (a) demultiplexing means for demultiplexing the composite light that has received the interference action with the thin film into the first and second composite light,
(B) first light receiving means for detecting the intensity of the first composite light; (c) filter means for extracting monochromatic light of a predetermined wavelength from the second composite light; (d) predetermined extracted light. Second light receiving means for detecting the intensity of monochromatic light of a wavelength, and (e) detection means for detecting the difference between the output signal of the first light receiving means and the output signal of the second light receiving means are provided. It is a thing.
【０００９】[0009]
【作用】複合光自身は薄膜との干渉による影響を受けな
いが、外因的要因による強度変化を受ける。その様な強
度変化を受けた複合光は、分波手段により第１の複合光
と第２の複合光とに分波される。更に第２の複合光はフ
ィルタ手段を透過し、その結果、所定の波長の単色光が
得られる。従って、複合光から抽出された当該単色光
は、上記強度変化の情報のみならず薄膜との干渉による
強度変化の情報をも含んでいる。The composite light itself is not affected by the interference with the thin film, but is affected by the intensity change due to external factors. The composite light that has undergone such an intensity change is split into the first composite light and the second composite light by the branching means. Further, the second composite light passes through the filter means, and as a result, monochromatic light having a predetermined wavelength is obtained. Therefore, the monochromatic light extracted from the composite light includes not only the information on the intensity change but also the information on the intensity change due to the interference with the thin film.
【００１０】そこで第１の受光手段は第１の複合光の強
度を検出し、その結果を検出手段に出力する。又、第２
の受光手段は当該単色光の強度を検出し、同じくその結
果を検出手段に出力する。そして、検出手段は両結果を
受けて両者の差分を求める。これにより、薄膜との干渉
により受けた当該単色光の強度変化の情報のみが取り出
されることになる。Therefore, the first light receiving means detects the intensity of the first composite light and outputs the result to the detecting means. Also, the second
The light receiving means detects the intensity of the monochromatic light and outputs the result to the detecting means. Then, the detecting means receives both results and obtains the difference between the two. As a result, only the information on the intensity change of the monochromatic light received by the interference with the thin film is extracted.
【００１１】[0011]
【実施例】図１は成膜時の膜厚計測の主要構成部を模式
的に示した概念図であり、この発明の一実施例である光
学式膜厚モニタ１０を用いたものである。同図に於い
て、光源１は、例えばハロゲン電球等より成る白色光源
である。そして、光源１より放出される光の波長領域
（波長λ）内の一波長λ0 の単色光が形成すべき膜厚と
関係づけられている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram schematically showing the main components for film thickness measurement during film formation, which uses an optical film thickness monitor 10 which is an embodiment of the present invention. In the figure, the light source 1 is a white light source such as a halogen bulb. Then, it is related to the film thickness of the monochromatic light of one wavelength λ 0 within the wavelength region (wavelength λ) of the light emitted from the light source 1.
【００１２】又、真空チャンバ２の一部分にはガラス窓
２４が設けられており、真空チャンバ２内には、蒸着源
２１やモニタガラス２２が所定の位置に配置されてい
る。そしてモニタガラス２２の一方の面上には、蒸着源
２１より蒸発した蒸着物質が堆積し、モニタ用薄膜２３
が形成される。Further, a glass window 24 is provided in a part of the vacuum chamber 2, and a vapor deposition source 21 and a monitor glass 22 are arranged at predetermined positions in the vacuum chamber 2. The vapor deposition material evaporated from the vapor deposition source 21 is deposited on one surface of the monitor glass 22, and the monitor thin film 23 is formed.
Is formed.
【００１３】一方、光学式膜厚モニタ１０は、ハーフミ
ラー３，光学フィルタ４，第１の受光器５，第２の受光
器６，差動増幅器７及びミラーＭ3 を有している。ここ
に光学フィルタ４は干渉フィルタを利用したバンドパス
フィルタであり、その帯域中心波長は波長λ0 である。
又、第１及び第２の受光器５，６としては、光電管やフ
ォトダイオード等が利用されるが、共に同一特性を有す
る様に調整されている。そして、第１の受光器５の出力
Ｖ1 は差動増幅器７のマイナス端子に印加されており、
第２の受光器６の出力Ｖ2 は差動増幅器７のプラス端子
に印加される。尚、光学フィルタ４としては干渉フィル
タの他に、例えば、モノクロメータを用いることも可能
である。On the other hand, the optical film thickness monitor 10 has a half mirror 3, an optical filter 4, a first light receiver 5, a second light receiver 6, a differential amplifier 7 and a mirror M 3 . Here, the optical filter 4 is a bandpass filter using an interference filter, and its band center wavelength is the wavelength λ 0 .
As the first and second light receivers 5 and 6, photoelectric tubes, photodiodes and the like are used, but they are adjusted so as to have the same characteristics. The output V 1 of the first light receiver 5 is applied to the negative terminal of the differential amplifier 7,
The output V 2 of the second light receiver 6 is applied to the positive terminal of the differential amplifier 7. As the optical filter 4, for example, a monochromator can be used instead of the interference filter.
【００１４】又、差動増幅器７の出力Ｖ3 はチャートレ
コーダ８に入力されており、出力Ｖ3 の周期的変化が本
図に例示されている。Further, the output V 3 of the differential amplifier 7 is input to the chart recorder 8, and the periodical change of the output V 3 is illustrated in this figure.
【００１５】次に以上の構成を基に、光学式膜厚モニタ
１０の動作について述べる。Next, the operation of the optical film thickness monitor 10 will be described based on the above configuration.
【００１６】先ず、光源１より放出された白色光Ｌ1 は
ミラーＭ1 にて反射され、ガラス窓２４を介してモニタ
ガラス２２の一方の表面に入射する。モニタガラス２２
の他方の表面には、モニタ用薄膜２３が形成されつつあ
る。このとき白色光Ｌ1 は、モニタガラス２２の両面や
モニタ用薄膜２３の表面においてそれぞれ反射され、各
反射光は干渉しあう結果、白色光Ｌ2 が反射光として生
じる。First, the white light L 1 emitted from the light source 1 is reflected by the mirror M 1 and enters one surface of the monitor glass 22 through the glass window 24. Monitor glass 22
A thin film for monitoring 23 is being formed on the other surface of the. At this time, the white light L 1 is reflected on both surfaces of the monitor glass 22 and the surface of the monitor thin film 23, and the reflected lights interfere with each other, so that the white light L 2 is generated as the reflected light.
【００１７】この際生じる白色光Ｌ2 の強度変化ΔＩ2
は、既述した通り、振動や光源１の揺らぎ等の影響によ
り生じた変化分ΔＩexだけであると考えられる（ΔＩ2
＝ΔＩex）。即ち、白色光Ｌ1 内の個々の単色光は成長
時にあるモニタ用薄膜２３との干渉によりその膜厚値に
応じた強度変化をきたすが、それらの合成波である白色
光Ｌ2 としてみた場合には、個々の単色光の干渉による
強度変化は平均化される結果、白色光Ｌ1 の干渉による
強度変化は殆ど無視できる程度であると判断できる。The intensity change ΔI 2 of the white light L 2 generated at this time
As described above, is considered to be only the change amount ΔI ex caused by the influence of vibration or fluctuation of the light source 1 (ΔI 2
= ΔI ex ). That is, the individual monochromatic light in the white light L 1 causes an intensity change according to the film thickness value due to the interference with the monitoring thin film 23 at the time of growth, but when viewed as white light L 2 which is a composite wave thereof. Therefore, it can be determined that the intensity changes due to the interference of the individual monochromatic lights are averaged, and the intensity changes due to the interference of the white light L 1 are almost negligible.
【００１８】この白色光Ｌ2 はその後、ガラス窓２４を
介してミラーＭ2 により反射されるとともに、ハーフミ
ラー３により白色光Ｌ3 と白色光Ｌ4 とに２分割され
る。そして白色光Ｌ3 はミラーＭ3 にて反射され、第１
の受光器５によりその強度が検出される。Thereafter, the white light L 2 is reflected by the mirror M 2 through the glass window 24, and is split into the white light L 3 and the white light L 4 by the half mirror 3. Then, the white light L 3 is reflected by the mirror M 3 and
The intensity is detected by the light receiver 5 of.
【００１９】他方、白色光Ｌ4 は光学フィルタ４に入射
し、波長λ0 の単色光が抽出されるとともに、その強度
が第２の受光器６により検出される。ここで検出される
波長λ0 の単色光の強度Ｉ0 には、当該単色光とモニタ
用薄膜２３との干渉により生じた強度変化ΔＩ0 に関す
る情報と振動等の影響による強度変化ΔＩ01に関する情
報とが含まれている。そして上記強度変化ΔＩ01は波長
に依存しないものと考えられるため、白色光Ｌ2 の強度
変化ΔＩexに相等しい。On the other hand, the white light L 4 is incident on the optical filter 4, and the monochromatic light of the wavelength λ 0 is extracted, and the intensity thereof is detected by the second light receiver 6. The intensity I 0 of the monochromatic light of the wavelength λ 0 detected here includes information about the intensity change ΔI 0 caused by the interference between the monochromatic light and the monitoring thin film 23 and information about the intensity change ΔI 01 due to the influence of vibration or the like. And are included. Since the intensity change ΔI 01 is considered to be independent of wavelength, it is equal to the intensity change ΔI ex of the white light L 2 .
【００２０】そこで強度変化ΔＩexに対応する第１の受
光器５の出力Ｖ1 をＶexとし、強度変化ΔＩ0 に対応す
る第２の受光器６の出力Ｖ2 の成分をＶ0 として表すな
らば、各出力Ｖ1 ，Ｖ2 は、Ｖ1 ＝Ｖex，Ｖ2 ＝Ｖ0 ＋
Ｖexの式で表される。従って、差動増幅器７の出力Ｖ3
はＶ3 ＝ｋ（Ｖ2 −Ｖ1 ）＝ｋＶ0 となり（ｋ：増幅
率）、干渉による強度変化ΔＩ0 の情報のみが増幅され
チャートレコーダ８に入力される。Represents [0020] Therefore the output V 1 of the first light-receiving device 5 corresponding to the intensity change [Delta] I ex and V ex, the component of the output V 2 of the second photodetector 6 which corresponds to the intensity change [Delta] I 0 as V 0 Then, the respective outputs V 1 and V 2 are V 1 = V ex and V 2 = V 0 +
It is represented by the formula of V ex . Therefore, the output V 3 of the differential amplifier 7
Becomes V 3 = k (V 2 −V 1 ) = kV 0 (k: amplification factor), and only the information of the intensity change ΔI 0 due to interference is amplified and input to the chart recorder 8.
【００２１】この様に振動等の影響による強度変化はキ
ャンセルされるため、チャートレコーダ８では干渉によ
って起こる周期的な強度変化ΔＩ0 がノイズなく出力さ
れる。その結果、蒸着作業者はチャートレコーダ８の出
力を見ることによって、精度良く所定の膜厚の薄膜を蒸
着させることができる。Since the intensity change due to the influence of vibration is canceled in this way, the chart recorder 8 outputs the periodic intensity change ΔI 0 caused by interference without noise. As a result, the vapor deposition operator can accurately deposit a thin film having a predetermined thickness by looking at the output of the chart recorder 8.
【００２２】[0022]
【発明の効果】以上説明した通りこの発明によれば、光
源の揺らぎや光学系の振動等が原因となって生じるノイ
ズをキャンセルすることができ、極めて精度の良い膜厚
モニタを実現することができる効果がある。As described above, according to the present invention, it is possible to cancel the noise caused by the fluctuation of the light source, the vibration of the optical system, etc., and it is possible to realize the film thickness monitor with extremely high accuracy. There is an effect that can be done.
【図１】成膜時の膜厚計測の主要構成部を模式的に示し
た概念図である。FIG. 1 is a conceptual diagram that schematically shows the main components of film thickness measurement during film formation.
１ 光源 ３ ハーフミラー ４ 光学フィルタ ５ 第１の受光器 ６ 第２の受光器 ７ 差動増幅器 １０ 光学式膜厚モニタ ２２ モニタガラス ２３ モニタ用薄膜 1 Light Source 3 Half Mirror 4 Optical Filter 5 First Light Receiver 6 Second Light Receiver 7 Differential Amplifier 10 Optical Film Thickness Monitor 22 Monitor Glass 23 Thin Film for Monitor
Claims (1)
との干渉を利用した光学式膜厚モニタであって、 （ａ） 前記薄膜との干渉作用を受けた前記複合光を第
１及び第２の複合光に分波する分波手段と、 （ｂ） 前記第１の複合光の強度を検出する第１の受光
手段と、 （ｃ） 前記第２の複合光から前記所定の波長の単色光
を抽出するフィルタ手段と、 （ｄ） 抽出された前記所定の波長の単色光の強度を検
出する第２の受光手段と、 （ｅ） 前記第１の受光手段の出力信号と前記第２の受
光手段の出力信号との差分を検出する検出手段とを、備
えた光学式膜厚モニタ。1. An optical film thickness monitor utilizing interference between a composite light including a monochromatic light having a predetermined wavelength and a thin film, wherein: (a) the composite light subjected to an interference action with the thin film is first And demultiplexing means for demultiplexing into the second composite light, (b) first light receiving means for detecting the intensity of the first composite light, and (c) the predetermined wavelength from the second composite light. Filter means for extracting the monochromatic light, (d) second light receiving means for detecting the intensity of the extracted monochromatic light of the predetermined wavelength, and (e) an output signal of the first light receiving means and the first light receiving means. An optical film thickness monitor comprising: a detecting unit that detects a difference between the output signal of the second light receiving unit and the output signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24467491A JPH05215519A (en) | 1991-08-28 | 1991-08-28 | Optical film thickness monitor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24467491A JPH05215519A (en) | 1991-08-28 | 1991-08-28 | Optical film thickness monitor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05215519A true JPH05215519A (en) | 1993-08-24 |
Family
ID=17122263
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24467491A Pending JPH05215519A (en) | 1991-08-28 | 1991-08-28 | Optical film thickness monitor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05215519A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5684574A (en) * | 1994-11-01 | 1997-11-04 | Matsushita Electric Industrial Co., Ltd. | In-process film thickness monitoring system |
-
1991
- 1991-08-28 JP JP24467491A patent/JPH05215519A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5684574A (en) * | 1994-11-01 | 1997-11-04 | Matsushita Electric Industrial Co., Ltd. | In-process film thickness monitoring system |
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