JP2004309154A

JP2004309154A - Infrared analyzer

Info

Publication number: JP2004309154A
Application number: JP2003098915A
Authority: JP
Inventors: Tsukasa Satake; 司佐竹; Kazuyuki Ikemoto; 和幸池本; Satoyuki Onishi; 智行大西
Original assignee: Horiba Ltd
Current assignee: Horiba Ltd
Priority date: 2003-04-02
Filing date: 2003-04-02
Publication date: 2004-11-04
Anticipated expiration: 2023-04-02
Also published as: JP4176535B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared analyzer used for both measurement and calibration even in cases where a gas for calibration which is a specific constituent gas is a type of gas not easily supplied by gas containers. <P>SOLUTION: This infrared analyzer is equipped with a means for detecting a wavelength for measurement of a gas 1 and a wavelength undergoing only absorption which is negligible order of absorption, and a comparison wavelength detection means. As a comparison gas 2, one is selected having an absorption wavelength as close as possible to the wavelength for measurement. The analyzer is equipped with a calculation part having the function of calculating a measurement signal of the gas 1 obtained by removing a factor affecting detection sensitivity by subtracting a signal from the means for the comparison wavelength detection from what is obtained by multiplying a signal from the comparison wavelength detection means by measurement gain when introducing the gas 1 into a cell while calculating a concentration comparing signal of a gas 2 obtained by removing a factor affecting the detection sensitivity by subtracting a comparison wavelength signal from what is obtained by multiplying a measurement wavelength signal by calibration gain when introducing the gas 2 of known concentration into the cell, and the function of switching between the introduction of the gas 1 and that of the gas 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、赤外線分析装置に関する。
【０００２】
【従来の技術】
光源からの赤外線が、特定成分ガスを含む試料ガスが導入されたセルを通過するようにして、そのとき得られる特定成分ガスの固有吸収波長の赤外線のエネルギーに比例した信号（測定信号）と、特定成分ガスによる吸収がないかあるいは無視できる程度の吸収しかない波長の赤外線のエネルギーに比例した信号（比較信号）との差を増幅して、測定用波長（固有吸収波長）の赤外線の吸収量から特定成分ガスの濃度を求めるようにした赤外線分析装置においては、定期的にゼロ校正とスパン校正とを行う必要がある。
【０００３】
そして、上記赤外線分析装置においてゼロ校正とスパン校正とを行うのに、従来は、セル内にゼロガスを導入して指示が安定した後、ゼロ点調整を行い、次いで、ガスボンベで供給されるスパンガス（所定の既知濃度の特定成分ガス）をセル内に導入して指示が安定した後、スパン調整を行っている。
【０００４】
【発明が解決しようとする課題】
しかしながら、半導体プロセスのガス供給側に導入され、半導体装置の製造に用いられるガスの多くは、ガスボンベで容易に供給されないものであり、その場合には校正手段がない。
【０００５】
この発明は、前記の点に留意してなされたものであり、その目的は、特定成分ガスの校正用ガスが、ガスボンベで容易に供給されないガス種である場合において、測定とともに校正も行える赤外線分析装置を提供することである。
【０００６】
【課題を解決するための手段】
前記課題を解決するために、この発明の赤外線分析装置は、特定成分ガスの測定用波長、および、特定成分ガスによる吸収がないかあるいは無視できる程度の吸収しかない比較用波長の二種類を、それぞれ検知する測定用波長検知手段、および、比較用波長検知手段を備えており、前記比較用波長のうち、前記測定用波長にできるだけ近い吸収波長を有するものが比較ガスとして選択されており、更に、特定成分ガスを赤外線分析計のセルに導入したときには、前記比較用波長検知手段より出力される比較波長信号に測定時ゲインを乗じたものから前記測定用波長検知手段より出力される測定波長信号を引き算して光源光量等の赤外線分析計の検出感度に影響する要素を除去した特定成分ガスの濃度測定信号を演算する一方、既知濃度の前記比較ガスを前記セルに導入したときには、前記測定波長信号に校正時ゲインを乗じたものから前記比較波長信号を引き算して光源光量等の赤外線分析計の検出感度に影響する要素を除去した前記比較ガスの濃度比較信号を演算する機能と、特定成分ガスと前記比較ガスの前記セルへの導入を相互に切換える信号切換処理機能とを有する演算部を備えたことを特徴とする。
【０００７】
【発明の実施の形態】
以下にこの発明の実施の形態について説明する。なお、この発明はそれによって限定されるものではない。
【０００８】
図１〜図４は、この発明の一実施形態を示す。
【０００９】
図１は、いわゆる１光源１セルタイプの赤外線分析計２０を備えた赤外線分析装置の概略構成を示している。図２は、赤外線分析装置の使用環境を示す。また、図３（Ａ）は、半導体プロセスにおけるガスの供給状態を示し、図３（Ｂ）は、その拡大部分を示している。
【００１０】
図４は、校正用ガスが容易に供給できない、例えば１３５０ｃｍ^−１〜１４００ｃｍ^−１の測定用波長を有する特定成分ガス（測定対象ガス）Ａ_１の赤外線吸収スペクトルＱと、前記特定成分ガスＡ_１による吸収がないかあるいは無視できる程度の吸収しかなく、かつ、前記測定用波長にできるだけ近い吸収波長（例えば８８０ｃｍ^−１〜９２０ｃｍ^−１）を有する比較ガスＡ_２の赤外線吸収スペクトルＰとを示す。この実施形態では、半導体装置に用いられる成膜の原料となる粉体のＰｂ（ＤＰＭ）_２を昇華させて特定成分ガスＡ_１を発生させている。また、この実施形態では、上記条件に当てはまる比較ガスＡ_２としてＮＦ_３ガスを用いている。
【００１１】
図１において、１は、赤外線分析計２０のセルで、ガス導入口２、ガス導出口３を備え、両端部に赤外線透過性のセル窓４，５が形成されている。６は、このセル１の一方のセル窓４の外方に設けられた赤外線を発する光源で、この光源６からの赤外線はセル１内を通過して後述する検出部８に入射するようにしてある。図５には、用いる光源６の光量特性が示されている。Ｌは、光量特性曲線である。なお、赤外線分析計２０として、非分散型赤外線分析計を用いている。
【００１２】
７は、セル１と検出部８との間に設けられた変調用のチョッパで、図外の駆動機構によって回転するように構成されている。なお、変調用のチョッパ７をセル１と光源６との間に設けてもよい。
【００１３】
８はセル１の他方のセル窓５の外方に設けられた検出部で、互いに並列に配置された比較波長検出器１０と測定波長検出器（測定用波長検知手段）９とより主としてなる。測定波長検出器９は、特定成分ガスＡ_１が吸収する１３５０ｃｍ^−１〜１４００ｃｍ^−１の測定用波長の赤外線を透過させるバンドパスフィルタ１１を備えており、透過した赤外線エネルギーに比例した測定波長信号（以下Ｓ信号という）を出力する。また、比較波長検出器１０は、特定成分ガスＡ_１による吸収がないかあるいは無視できる程度の吸収しかなく、かつ、前記測定用波長にできるだけ近い８８０ｃｍ^−１〜９２０ｃｍ^−１の比較用波長の赤外線を通過させるバンドパスフィルタ１２を備えており、透過した赤外線エネルギーに比例した比較波長信号（以下Ｃ信号という）を出力する。そして、比較波長検出器１０とバンドパスフィルタ１２とから、比較用波長を検知する比較用波長検知手段が構成され、また、測定波長検出器９とバンドパスフィルタ１１とから、測定用波長を検知する測定用波長検知手段が構成される。
【００１４】
ところで、一般に赤外線分析計などの各種分析計は、検出部、増幅部などの温度ドリフトあるいは経時変化によって生ずる誤差を補正するために、測定を行うに際してはその測定作業に先立って、分析計のゼロ調整およびスパン校正を行う必要がある。そして、所定の既知濃度の特定成分ガス（測定対象ガス）の校正用ガスをガスボンベ等からセルに供給することでスパン校正が行われる。
【００１５】
しかし、上述したように、校正用ガスがガスボンベによって容易に供給されないガスである場合は、校正手段がない。この発明は、特定成分ガスＡ_１の校正用ガスを容易に供給できない場合の近似波長を有する校正用ガスが収容されているガスボンベを使って校正できるようにしたものである。
【００１６】
すなわち、この発明は、校正用ガスがガスボンベによって容易に供給されない、例えばＰｂ（ＤＰＭ）_２を昇華させてなるガスＡ_１を測定対象とする赤外線分析計を持つ赤外線分析装置であって、この赤外線分析装置は、例えば１３５０ｃｍ^−１〜１４００ｃｍ^−１の測定用波長と、例えば８８０ｃｍ^−１〜９２０ｃｍ^−１の比較用波長の二種類を検知する手段として、前記測定用波長検知手段、比較用波長検知手段を持っている。
【００１７】
そして、この発明では、測定用波長と比較用波長の二波長を用いて、特定成分ガスＡ_１の濃度測定信号Ｃと比較ガスの濃度比較信号Ｄを演算するよう構成されている。
【００１８】
１５は、その演算部で、特定成分ガス〔Ｐｂ（ＤＰＭ）_２を昇華させてなるガス〕Ａ_１の濃度測定信号を演算するとともに、前記比較ガス（ＮＦ_３）Ａ_２の濃度比較信号を演算する機能を有し、また、特定成分ガスＡ_１と前記比較ガスＡ_２の前記セル１への導入を例えば三方電磁弁３３によって相互に切換える信号切換処理機能を有し、更に、信号切換を数回繰り返して得られた前記濃度測定信号Ｃおよび濃度比較信号Ｄに基づいて特定成分ガスＡ_１と前記比較ガスＡ_２の濃度検量線を作成する機能を有し、また、測定作業時において既知濃度Ｄの前記比較ガスＡ_２を前記セル１に導入して得られる前記濃度比較信号Ｄ’と前記濃度検量線とに基づいて赤外線分析計２０の校正の要否を判断する機能を有する。
【００１９】
更に、濃度測定信号Ｃの演算は、特定成分ガスＡ_１を赤外線分析計２０のセル１に導入した状態で、前記比較用波長検知手段１０，１２より出力されるＣ信号に測定時ゲインＧ_Ｘを乗じたものから前記測定用波長検知手段９，１１より出力されるＳ信号を引き算するよう行われる。

【００２０】
また、濃度比較信号Ｄの演算は、既知濃度の前記比較ガスＡ_２を前記セル１に導入した状態で、前記Ｓ信号に校正時ゲインＧ_Ｃを乗じたものから前記Ｃ信号を引き算するよう行われる。

【００２１】
そして、これら演算にあたり、演算前に予め、特定成分ガスＡ_１と比較ガスＡ_２の信号強度比を求め、測定時ゲインＧ_Ｘおよび校正時ゲインＧ_Ｃを最適化しておくのが好ましい。
【００２２】
なお、測定用波長と比較用波長の二波長を用いて、特定成分ガスＡ_１の濃度測定信号Ｃと比較ガスの濃度比較信号Ｄを演算するのは、光源６から発せられる赤外線光量が、図５に示すように、特定成分ガスＡ_１による吸収信号量５０、ならびに、比較ガスＡ_２による吸収信号量５１の１０〜１００倍と極端に大きいことから、測定用波長帯として例えば１３５０ｃｍ^−１〜１４００ｃｍ^−１を選択するとともに、そのときの光量検出用波長を例えば８８０ｃｍ^−１〜９２０ｃｍ^−１に選択性を持つバンドパスフィルタ１１で検出し、かつ、前記（１），（２）式に示したように差をとることによって、光源光量等の赤外線分析計の検出感度に影響する要素を除去できるからである。
【００２３】
而して、赤外線分析装置を介して半導体プロセスにおけるＣＶＤチャンバー内に特定成分ガスＡ_１を流す測定作業に先立って、特定成分ガスＡ_１と前記比較ガスＡ_２の濃度検量線を作成する。
【００２４】
この場合、粉体のＰｂ（ＤＰＭ）_２が収容された容器５２をヒータで加熱することにより、Ｐｂ（ＤＰＭ）_２を昇華させて特定成分ガスＡ_１を発生させながら、三方電磁弁３３を測定ライン７０の側に切換えた状態でセル１内に、Ａｒをキャリアガスとして特定成分ガスＡ_１を導入し、これに光源６からの赤外線を投射してチョッパ７によって変調を行う。
【００２５】
特定成分ガスＡ_１を流しているので、前記（１）式から濃度測定信号Ｃを得ることができる。
【００２６】
その後、セル１のパージを行って三方電磁弁３３を測定ライン７０から比較ガス供給ライン８０の側に切換える。これら二つの切換えは、演算部１５が行う。
【００２７】
切換後セル１内に、既知濃度の比較ガスＡ_２を導入し、これに光源６からの赤外線を投射してチョッパ７によって変調を行う。
【００２８】
比較ガスＡ_２を流しているので、前記（２）式から濃度測定信号Ｄを得ることができる。
【００２９】
信号切換を数回繰り返して得られた濃度測定信号Ｃ，Ｄから特定成分ガスＡ_１と前記比較ガスＡ_２の濃度検量線を作成できる。
【００３０】
次に、赤外線分析装置を介してＣＶＤチャンバー内に特定成分ガスＡ_１を流す測定作業を行う。
【００３１】
セル１内に特定成分ガスＡ_１を導入し、これに光源６からの赤外線を投射してチョッパ７によって変調を行う。
【００３２】
特定成分ガスＡ_１を流しているので、前記（１）式から濃度測定信号Ｃを得る。
【００３３】
その後、セル１のパージを行って三方電磁弁３３を測定ライン７０から比較ガス供給ライン８０の側に切換える。これら二つの切換えは、演算部１５が行う。
【００３４】
切換後セル１内に、既知濃度の比較ガスＡ_２を導入し、これに光源６からの赤外線を投射してチョッパ７によって変調を行う。
【００３５】
比較ガスＡ_２を流しているので、前記（２）式から濃度測定信号Ｄ’を得ることができる。
【００３６】
前記セル１に導入して得られた濃度測定信号Ｄ’と濃度測定信号Ｄを前記濃度検量線とに基づいて赤外線分析計の校正の要否を判断する。
【００３７】
そして、校正が必要な場合は、（Ｄ’／Ｄ）×Ｃのスパン校正を行ってＣＶＤチャンバー内に流された特定成分ガスＡ_１の濃度Ｃ’が計測できる。
【００３８】
以上、半導体プロセスにおけるガスは、その校正用ガス（比較ガス）Ａ_２がガスボンベ等によって容易に供給されないものである場合が多いが、上述したように、可能な限り測定用波長に近い比較用波長を有するガスを用い、測定用波長と比較用波長の二波長を検知する測定用波長検知手段９，１１、比較用波長検知手段１０，１２を設け、また、特定成分ガスＡ_１濃度測定時は前記（１）式を用い、比較ガスＡ_２濃度測定時は前記（２）式を用いることにより、簡単な構成で構成機能および測定機能を有する赤外線分析装置を得ることができる。
【００３９】
なお、前記Ｓ信号またはＣ信号は、それぞれが光学系の全体光量を表しているが、例えば光路の汚れによる光量低下（図５においてＬ’で示す）を前記Ｓ信号またはＣ信号の出力信号で確認できるように構成し、更に、例えば光路の汚れにより初期光量から所定の光量（アラームレベル）に低下した時点でアラーム信号を発するように構成してもよい。
【００４０】
【発明の効果】
以上この発明では、特定成分ガスの校正用ガスが、ガスボンベで容易に供給されないガス種である場合において、測定とともに校正も行える赤外線分析装置を提供することができる効果がある。
【図面の簡単な説明】
【図１】この発明の一実施形態を示す全体構成説明図である。
【図２】上記実施形態における使用環境を示す構成説明図である。
【図３】（Ａ）は、半導体プロセスにおけるガスの供給状態を示す図である。（Ｂ）は、図３（Ａ）における一部を拡大して示す図である。
【図４】特定成分ガス（測定対象ガス）と比較ガスの赤外線吸収スペクトルを示す特性図である。
【図５】特定成分ガスによる吸収信号量、ならびに、比較ガスによる吸収信号量を示す図である。
【符号の説明】
１…セル、９，１１…測定用波長検知手段、１０，１２…比較用波長検知手段、１５…演算部、２０…赤外線分析計、Ａ_１…特定成分ガス、Ａ_２…比較ガス。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an infrared analyzer.
[0002]
[Prior art]
A signal (measurement signal) proportional to the energy of the infrared light having a specific absorption wavelength of the specific component gas obtained by passing infrared light from the light source through the cell into which the sample gas containing the specific component gas has been introduced, Amplifies the difference from the signal (comparison signal) proportional to the energy of infrared light of a wavelength that has no or negligible absorption by the specific component gas, and absorbs infrared light at the measurement wavelength (specific absorption wavelength). In the infrared analyzer which determines the concentration of the specific component gas from the above, it is necessary to periodically perform zero calibration and span calibration.
[0003]
Conventionally, in order to perform zero calibration and span calibration in the infrared analyzer, conventionally, zero gas is introduced into the cell, and after the indication is stabilized, zero point adjustment is performed, and then span gas (supplied by a gas cylinder) is supplied. After the indication is stabilized by introducing a specific component gas having a predetermined known concentration into the cell, the span is adjusted.
[0004]
[Problems to be solved by the invention]
However, most of the gases introduced into the gas supply side of the semiconductor process and used for manufacturing semiconductor devices are not easily supplied by gas cylinders, in which case there is no calibration means.
[0005]
The present invention has been made in consideration of the above points, and an object of the present invention is to provide an infrared spectrometer capable of performing calibration together with measurement when a gas for calibration of a specific component gas is a gas type that is not easily supplied by a gas cylinder. It is to provide a device.
[0006]
[Means for Solving the Problems]
In order to solve the problem, the infrared analyzer of the present invention has two types of wavelengths for measurement of a specific component gas, and comparison wavelengths that have no or negligible absorption by the specific component gas, Each of which has a measuring wavelength detecting means for detecting, and a comparative wavelength detecting means, and among the comparative wavelengths, one having an absorption wavelength as close as possible to the measuring wavelength is selected as a comparative gas. When the specific component gas is introduced into the cell of the infrared spectrometer, the measurement wavelength signal output from the measurement wavelength detection means is obtained by multiplying the comparison wavelength signal output from the comparison wavelength detection means by the gain at the time of measurement. While calculating the concentration measurement signal of the specific component gas by removing the factors that affect the detection sensitivity of the infrared analyzer such as the light source light amount by subtracting When the comparison gas is introduced into the cell, the comparison wavelength signal is subtracted from the measurement wavelength signal multiplied by the gain at the time of calibration to remove an element such as a light source amount that affects the detection sensitivity of the infrared analyzer. An arithmetic unit having a function of calculating a gas concentration comparison signal and a signal switching processing function of mutually switching the introduction of the specific component gas and the comparison gas into the cell is provided.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited thereby.
[0008]
1 to 4 show one embodiment of the present invention.
[0009]
FIG. 1 shows a schematic configuration of an infrared analyzer provided with an infrared analyzer 20 of a so-called one light source and one cell type. FIG. 2 shows a use environment of the infrared analyzer. FIG. 3A shows a gas supply state in a semiconductor process, and FIG. 3B shows an enlarged portion thereof.
[0010]
4, it can not be easily supplied calibration gas, for example an infrared absorption spectrum Q of the specific component gas (measurement target gas) _{A 1} having a measurement wavelength of ^1350cm ^-1 ^~1400cm -1, the specific component gas _{A 1} ₂ shows an infrared absorption spectrum P of a comparative gas A2 that has no or negligible absorption due to and has an absorption wavelength (for example, 880 cm ^{−1 to} 920 cm ⁻¹ ) as close to the measurement wavelength as possible. In this embodiment, by generating a specific component gas A ₁ was sublimed powder of Pb (DPM) ₂ as a raw material for film formation used in a semiconductor device. In this embodiment, the NF ₃ gas is used as the comparative gas A ₂ satisfying the above conditions.
[0011]
In FIG. 1, reference numeral 1 denotes a cell of an infrared spectrometer 20, which has a gas inlet 2 and a gas outlet 3, and has infrared-transparent cell windows 4 and 5 formed at both ends. Reference numeral 6 denotes a light source that emits infrared light provided outside one cell window 4 of the cell 1. The infrared light from the light source 6 passes through the cell 1 and enters a detection unit 8 described later. is there. FIG. 5 shows the light amount characteristics of the light source 6 used. L is a light amount characteristic curve. In addition, a non-dispersive infrared analyzer is used as the infrared analyzer 20.
[0012]
Reference numeral 7 denotes a modulation chopper provided between the cell 1 and the detection unit 8, and is configured to be rotated by a driving mechanism (not shown). Note that a modulation chopper 7 may be provided between the cell 1 and the light source 6.
[0013]
Reference numeral 8 denotes a detection unit provided outside the other cell window 5 of the cell 1, and is mainly composed of a comparison wavelength detector 10 and a measurement wavelength detector (measurement wavelength detection means) 9 arranged in parallel with each other. The measurement wavelength detector 9 includes a bandpass filter 11 that transmits infrared light having a measurement wavelength of 1350 cm ⁻¹ to 1400 cm ⁻¹ absorbed by the specific component gas A ₁ , and a measurement wavelength signal proportional to the transmitted infrared energy. (Hereinafter referred to as an S signal). The comparison wavelength detector 10 is not only the extent of absorption absorption is no or negligible due to the specific component gas _{A 1,} and infrared comparative wavelength as close as possible ^880cm ^-1 ^~920cm -1 in the measuring wavelength , And outputs a comparison wavelength signal (hereinafter, referred to as a C signal) proportional to the transmitted infrared energy. The comparison wavelength detector 10 and the bandpass filter 12 constitute comparison wavelength detection means for detecting the comparison wavelength, and the measurement wavelength detector 9 and the bandpass filter 11 detect the measurement wavelength. The measuring wavelength detecting means is configured.
[0014]
By the way, in general, various analyzers such as an infrared analyzer are required to perform zero measurement prior to the measurement work in order to correct an error caused by a temperature drift or a change with time of a detection unit and an amplification unit. Adjustment and span calibration must be performed. Then, span calibration is performed by supplying a gas for calibration of a specific component gas (gas to be measured) having a predetermined known concentration to the cell from a gas cylinder or the like.
[0015]
However, as described above, when the calibration gas is a gas that is not easily supplied by the gas cylinder, there is no calibration means. This invention has to be able to calibrate using the gas cylinder in which the calibration gas having an approximate wavelength when not readily supply the calibration gas of the specific component gas A ₁ is housed.
[0016]
That is, this invention is not easily supplied calibration gas by gas cylinder, an infrared spectrometer with an infrared spectrometer to be measured the gas A ₁ comprising subliming, for example Pb (DPM) _2, the infrared analyzer, for example a measuring wavelength of ^1350cm ^-1 ^~1400cm -1, for example, as a means for detecting the two kinds of comparative wavelength of ^880cm ^-1 ^~920cm -1, the measuring wavelength detector, a wavelength detection comparator Have the means.
[0017]
And, in this invention, using a two-wavelength of the comparison wavelength and measuring wavelength, it is configured for calculating a density comparison signal D of the comparator gas concentration measurement signal C of a specific component gas A _1.
[0018]
Reference numeral 15 denotes a calculation unit for calculating a concentration measurement signal of the specific component gas [gas obtained by sublimating Pb (DPM) ₂ ] A ₁ and calculating a concentration comparison signal of the comparison gas (NF ₃ ) A _2. has a function of, also has a signal switching processing function for switching from one another by a specific component gas a ₁ and the reference gas a introduced for example three-way electromagnetic valve 33 to the cell 1 of _2, further, the number of the signal switching It has the ability to create concentration calibration curve of the specific component gas a ₁ and the reference gas a ₂ based on the concentration measurement signals C and concentration comparison signal D obtained repeated times, also known concentration during measurement operation It has a function to determine the necessity of calibration of the infrared gas analyzer 20 based on the reference gas a ₂ of D to said density calibration curve and the concentration comparison signal D 'obtained by introducing to the cell 1.
[0019]
Further, the calculation of the concentration measurement signal C is performed by measuring the measurement gain G _{X with the} C signal output from the comparison

wavelength detecting means

10 or 12 while the specific component gas A ₁ is introduced into the cell 1 of the infrared spectrometer 20. Is subtracted from the S signal output from the measuring wavelength detecting means 9 and 11 from the product of the above.

[0020]
Further, the calculation of the density comparison signal D, and the reference gas A ₂ of known concentration in a state introduced into the cell 1, so as to subtract the C signal from which the multiplied calibration during gain G _C to S signal line Is

[0021]
Then, when these operations, in advance before operation, obtains the signal intensity ratio of reference gas A ₂ and the specific component gas A _1, preferably keep optimizing measurement time gain G _X and calibration during gain G _C.
[0022]
Incidentally, by using a dual wavelength of the comparison wavelength and measuring wavelength, for calculating the concentration comparison signal D of the comparator gas concentration measurement signal C of a specific component gas A _1, infrared light intensity emitted from the light source 6 is, FIG. as shown in 5, the absorption signal of 50 by a particular component gas _{a 1,} and, since the extremely and 10 to 100 times the absorption signal amount 51 according to comparative gas _{a 2} large, as the measurement wavelength band for example 1350 cm ^-1 ~ with selecting 1400 cm ^-1, detected by the band-pass filter 11 having a selective light quantity detection wavelength at that time for example, ^880cm ^-1 ^~920cm -1, and wherein (1), shown in equation (2) By taking the difference as described above, it is possible to remove factors that influence the detection sensitivity of the infrared analyzer, such as the light source light amount.
[0023]
And Thus, prior to the measurement operation to flow a specific component gas A ₁ into the CVD chamber in a semiconductor process through an infrared analyzer, to create a concentration calibration curve of the specific component gas A ₁ and the reference gas A _2.
[0024]
In this case, by heating the container 52 to which the particles of Pb _{(DPM) 2} is accommodated in the heater, while generating a specific component gas _{A 1} by sublimating Pb _{(DPM) 2,} measuring a three-way solenoid valve 33 in the cell 1 in a state where switching to the side of the line 70, to introduce a specific component gas a ₁ Ar as carrier gas, performs modulation by chopper 7 thereto by projecting infrared radiation from the light source 6.
[0025]
Since flowing the specific component gas A _1, wherein (1) can be obtained concentration measurement signal C from the equation.
[0026]
Thereafter, the cell 1 is purged, and the three-way solenoid valve 33 is switched from the measurement line 70 to the comparison gas supply line 80. The arithmetic unit 15 switches between these two.
[0027]
After the switching, a comparative gas A ₂ having a known concentration is introduced into the cell 1, an infrared ray from the light source 6 is projected on the gas, and modulation is performed by the chopper 7.
[0028]
Since flowing the reference gas A _2, it is possible to obtain a density measurement signal D from the equation (2).
[0029]
Concentration measurement signal obtained by repeating several times the signal switching C, can create concentration calibration curve of the specific component gas A ₁ and the reference gas A ₂ from D.
[0030]
Next, the measurement operation performed by flowing a specific component gas A ₁ to the CVD chamber via an infrared analyzer.
[0031]
A specific component gas A ₁ is introduced into the cell 1, and infrared rays from a light source 6 are projected on the gas A ₁ for modulation by a chopper 7.
[0032]
Since flowing the specific component gas A _1, to obtain a density measurement signal C from the equation (1).
[0033]
Thereafter, the cell 1 is purged, and the three-way solenoid valve 33 is switched from the measurement line 70 to the comparison gas supply line 80. The arithmetic unit 15 switches between these two.
[0034]
After the switching, a comparative gas A ₂ having a known concentration is introduced into the cell 1, an infrared ray from the light source 6 is projected on the gas, and modulation is performed by the chopper 7.
[0035]
Since flowing the reference gas A _2, wherein (2) can be obtained concentration measurement signal D 'from the equation.
[0036]
Based on the concentration measurement signal D ′ and the concentration measurement signal D obtained by being introduced into the cell 1, the calibration of the infrared analyzer is determined based on the concentration calibration curve.
[0037]
When calibration is required, it can be measured is (D '/ D) × concentration of a specific component gas A ₁ which flowed into the CVD chamber by performing a span calibration of the C C'.
[0038]
Above, the gas in the semiconductor process, but the calibration gas (reference gas) A ₂ is often one that is not easily supplied by a gas cylinder or the like, as described above, comparative wavelength close to the measuring wavelength as possible using a gas having a measuring wavelength detection means 9, 11 for detecting the two wavelengths of the comparison wavelength and measuring wavelength, the comparison wavelength detection means 10, 12 provided, also, the time of the specific component gas a ₁ concentration measurement using the equation (1), when compared gas a ₂ concentration measurement by using the equation (2) can be obtained infrared analysis device having a structure function and measurement functions with a simple structure.
[0039]
Each of the S signal and the C signal represents the total light amount of the optical system. For example, a decrease in the light amount (indicated by L ′ in FIG. 5) due to contamination of the optical path is indicated by the output signal of the S signal or the C signal. The configuration may be such that confirmation is possible, and furthermore, an alarm signal may be generated at the time when the amount of light decreases from the initial light amount to a predetermined light amount (alarm level) due to, for example, contamination of the optical path.
[0040]
【The invention's effect】
As described above, according to the present invention, when the calibration gas of the specific component gas is a gas type that is not easily supplied by the gas cylinder, it is possible to provide an infrared analyzer that can perform calibration together with measurement.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an overall configuration showing an embodiment of the present invention.
FIG. 2 is a configuration explanatory diagram showing a use environment in the embodiment.
FIG. 3A is a diagram showing a gas supply state in a semiconductor process. FIG. 3B is an enlarged view of a part of FIG.
FIG. 4 is a characteristic diagram showing infrared absorption spectra of a specific component gas (gas to be measured) and a comparative gas.
FIG. 5 is a diagram showing an absorption signal amount by a specific component gas and an absorption signal amount by a comparative gas.
[Explanation of symbols]
1 ... cell, 9,11 ... measuring wavelength detection means, 10, 12 ... comparison wavelength detection means, 15 ... operation unit, 20 ... infrared spectrometer, A 1 _... specific component gas, A 2 _... reference gas.

Claims

Measurement wavelength detection means for detecting two types of wavelengths for measurement of the specific component gas, and comparison wavelengths having no or negligible absorption by the specific component gas, and comparison wavelength detection means Among the comparison wavelengths, those having an absorption wavelength as close as possible to the measurement wavelength are selected as the comparison gas, and further, when a specific component gas is introduced into the cell of the infrared spectrometer, The measurement wavelength signal output from the measurement wavelength detection means is subtracted from the product of the comparison wavelength signal output from the comparison wavelength detection means multiplied by the gain at the time of measurement to affect the detection sensitivity of the infrared analyzer such as the light source light quantity. While calculating the concentration measurement signal of the specific component gas from which the element to be removed is removed, when the reference gas having a known concentration is introduced into the cell, the measurement wavelength signal A function of calculating the concentration comparison signal of the comparison gas by subtracting the comparison wavelength signal from the product obtained by multiplying the gain at the time of calibration and removing elements that affect the detection sensitivity of the infrared analyzer such as the light source light amount, and a specific component gas. An infrared analyzer comprising: a calculation unit having a signal switching processing function of mutually switching the introduction of the comparison gas into the cell.

Prior to the measurement operation of introducing the specific component gas to the gas supply side of the semiconductor process, the calculation unit performs the specific component gas and the specific component gas based on the concentration measurement signal and the concentration comparison signal obtained by repeating the signal switching several times. A function of creating a concentration calibration curve of a comparison gas, and calibration of an infrared analyzer based on the concentration comparison signal and the concentration calibration curve obtained by introducing the reference gas having a known concentration into the cell during a measurement operation. The infrared analyzer according to claim 1, further comprising a function of determining necessity.