JPH06180280A - Particle counting method - Google Patents
Particle counting methodInfo
- Publication number
- JPH06180280A JPH06180280A JP4334099A JP33409992A JPH06180280A JP H06180280 A JPH06180280 A JP H06180280A JP 4334099 A JP4334099 A JP 4334099A JP 33409992 A JP33409992 A JP 33409992A JP H06180280 A JPH06180280 A JP H06180280A
- Authority
- JP
- Japan
- Prior art keywords
- laser pulse
- cell
- particle
- sample
- plasma emission
- 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
- 239000002245 particle Substances 0.000 title claims abstract description 31
- 238000000034 method Methods 0.000 title claims description 11
- 239000013074 reference sample Substances 0.000 claims abstract description 17
- 238000005259 measurement Methods 0.000 claims abstract description 16
- 239000000523 sample Substances 0.000 claims abstract description 10
- 230000002123 temporal effect Effects 0.000 claims description 10
- 230000015556 catabolic process Effects 0.000 claims description 3
- 230000035945 sensitivity Effects 0.000 claims description 3
- 238000001514 detection method Methods 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 230000001678 irradiating effect Effects 0.000 abstract description 3
- 238000005286 illumination Methods 0.000 abstract 5
- 230000005494 condensation Effects 0.000 abstract 2
- 238000009833 condensation Methods 0.000 abstract 2
- 239000012535 impurity Substances 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 4
- 238000012937 correction Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 239000004793 Polystyrene Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 1
- 238000012850 discrimination method Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、半導体製造のように、
水，薬液，反応ガスなど製造プロセスで利用する各種の
気体又は液体中への粒子状不純物の混入を極力抑制する
必要がある分野において利用される粒子モニタに関す
る。BACKGROUND OF THE INVENTION The present invention, like semiconductor manufacturing,
The present invention relates to a particle monitor used in a field in which it is necessary to suppress as much as possible the mixing of particulate impurities into various gases or liquids used in manufacturing processes such as water, chemicals, and reaction gases.
【０００２】[0002]
【従来の技術】特願平2−225331号や特願平2−205036号
明細書に記載されているように、レーザブレイクダウン
法では粒子の検出感度がレーザパルス出力密度の時間的
空間的分布に依存するので、レーザパルス出力密度の変
動に起因する計数誤差を補正するため、原理的には出力
密度をモニタする必要がある。しかし、従来手法では、
出力密度の時間的空間的分布をモニタして粒子計数を補
正する装置が高額化・大型化するためにレーザパルスエ
ネルギをモニタして代用しているが、レーザブレイクダ
ウンによるプラズマ発光強度はレーザパルスエネルギと
線形関係にないので、この手法では必ずしも高精度に補
正できない問題があった。2. Description of the Related Art As described in Japanese Patent Application No. 2-225331 and Japanese Patent Application No. 2-205036, in the laser breakdown method, the detection sensitivity of particles is the temporal and spatial distribution of the laser pulse power density. , It is necessary to monitor the power density in principle in order to correct the counting error due to the fluctuation of the laser pulse power density. However, in the conventional method,
The device that corrects the particle count by monitoring the temporal and spatial distribution of the power density is using the laser pulse energy as a substitute in order to increase the cost and size, but the plasma emission intensity due to laser breakdown is the laser pulse intensity. Since it is not in a linear relationship with the energy, there is a problem that this method cannot always correct it with high accuracy.
【０００３】[0003]
【発明が解決しようとする課題】本発明の目的は、レー
ザパルス出力密度のモニタ及び補正機構を特別に付加す
ることなく比較的簡便な装置でレーザパルス出力密度の
揺らぎによる計数誤差を高精度で補正する手段を提供す
ることにある。SUMMARY OF THE INVENTION An object of the present invention is to provide a highly accurate counting error due to fluctuations in laser pulse power density with a relatively simple device without specially adding a laser pulse power density monitor and correction mechanism. It is to provide a means for correction.
【０００４】[0004]
【課題を解決するための手段】本発明では、レーザパル
スを分割してその一つを参照試料に照射し、そこからの
プラズマ発光を観測してレーザパルスの揺らぎを定量化
することにより、上記目的を達成する。According to the present invention, by dividing a laser pulse, irradiating one of them on a reference sample, and observing the plasma emission from the reference sample to quantify the fluctuation of the laser pulse, Achieve the purpose.
【０００５】[0005]
【作用】参照試料の成分及び濃度、並びに参照試料に含
まれる参照粒子の成分，粒径及び濃度が既知かつ一定で
あれば、参照試料で生じるプラズマ発光現象（発光強
度，レーザパルスからの発光遅れ時間，発光位置等）の
揺らぎの原因は全てレーザパルス出力密度の時間的空間
的揺らぎに帰着でき、上記の種々の測定パラメータの揺
らぎからレーザパルス出力密度の揺らぎを定量的に評価
することが可能である。したがって、測定試料に対し
て、レーザパルス出力密度の時間的空間的揺らぎによっ
て生じる粒子計数感度の時間的変動を補正でき、粒子計
数精度を向上できる。Function: If the components and concentrations of the reference sample and the components, particle size and concentration of the reference particles contained in the reference sample are known and constant, the plasma emission phenomenon (emission intensity, emission delay from the laser pulse) that occurs in the reference sample The causes of fluctuations in time, light emission position, etc.) can all be attributed to the temporal and spatial fluctuations in the laser pulse power density, and it is possible to quantitatively evaluate the fluctuations in the laser pulse power density from the fluctuations in the above various measurement parameters. Is. Therefore, with respect to the measurement sample, it is possible to correct the temporal fluctuation of the particle counting sensitivity caused by the temporal and spatial fluctuation of the laser pulse output density, and improve the particle counting accuracy.
【０００６】[0006]
【実施例】本発明の一実施例を図１を用いて説明する。
パルスレーザ１からのレーザパルス２はビームスプリッ
タ３で分割し、一方のパルスはレンズ４を通して測定セ
ル５に入射し、測定試料６内で集光する。セルを透過し
たレーザパルスはビームモニタ７によりエネルギ値を測
定する。他方のパルスはミラー８で光路を偏向した後、
レンズ４を通して参照セル９に入射し、参照試料１０内
で集光する。セルを透過したパルスは同様にビームモニ
タ７によりエネルギ値を測定する。両セル内でのレーザ
パルス集光条件を同一にするため、ビームスプリッタか
ら両セル手前のレンズまでの光路長が等しくなるように
光学系を設置する。両分割パルスのエネルギ測定値は、
レーザパルスエネルギの安定度の確認に利用する。両セ
ルで生じるプラズマ発光はそれぞれ光検出器１１で受光
し、測定回路１２により発光強度を測定する。光検出器
は、プラズマ発光強度のみを測定するならば通常の光ダ
イオードや光電子増倍管でよいが、粒径の弁別法によっ
てはプラズマ発光位置を測定するならばアレイセンサを
用いる必要があり、また、プラズマ発光の遅れ時間を測
定するならば、高速の光ダイオードや光電子増倍管を用
いる必要がある。参照試料には粒子状不純物をほぼ完全
に取り除いた媒質を利用し、予めレーザパルス出力密度
の時間的空間的分布とプラズマ発光強度との関係を求め
てデータ処理装置１３に記憶しておく。したがって、参
照セルからのプラズマ発光強度を測定回路からデータ処
理装置に取り込むと、レーザパルス出力密度の時間的空
間的分布をパターン分類できるので、測定セルからのプ
ラズマ発光の計数率を、レーザパルス出力密度の時間的
空間的分布のパターン分類ごとの換算係数を用いて粒子
濃度に高精度で換算することができる。パターン分類法
としては、例えば、時間的にはパルスの半値幅を５分
類、空間的にはパルスの１／ｅ径（ガウス分布の場合）
を５分類程度にすれば実用上は充分である。なお、図１
には明示していないが、粒径の弁別には、従来法のプラ
ズマ発光強度，プラズマ発光遅れ時間及びプラズマ発光
位置等のパラメータそれぞれの粒径依存性やこれら複数
パラメータの同時測定などを利用する。上記の手順でデ
ータ処理装置で粒径及び濃度が測定できるので、この情
報をプロセス制御装置１４に送ると、これらの情報に応
じてプロセスの制御情報を送り出し、例えば、一定の粒
径以上の不純物の濃度が一定値を越えると警報を発した
り、プロセスを停止したりする。DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
The laser pulse 2 from the pulse laser 1 is split by the beam splitter 3, one pulse of which is incident on the measurement cell 5 through the lens 4 and is condensed in the measurement sample 6. The energy value of the laser pulse transmitted through the cell is measured by the beam monitor 7. After the other pulse deflects the optical path by the mirror 8,
The light enters the reference cell 9 through the lens 4 and is condensed in the reference sample 10. Similarly, the energy value of the pulse transmitted through the cell is measured by the beam monitor 7. In order to make the laser pulse focusing conditions the same in both cells, the optical system is installed so that the optical path lengths from the beam splitter to the lenses in front of both cells are equal. The energy measurements of both split pulses are
It is used to confirm the stability of laser pulse energy. The plasma emission generated in both cells is received by the photodetector 11, and the emission intensity is measured by the measuring circuit 12. The photodetector may be an ordinary photodiode or photomultiplier if only the plasma emission intensity is measured, but if the plasma emission position is to be measured depending on the particle size discrimination method, it is necessary to use an array sensor, Further, when measuring the delay time of plasma emission, it is necessary to use a high-speed photodiode or a photomultiplier tube. As the reference sample, a medium from which the particulate impurities are almost completely removed is used, and the relationship between the temporal and spatial distribution of the laser pulse output density and the plasma emission intensity is obtained in advance and stored in the data processing device 13. Therefore, when the plasma emission intensity from the reference cell is taken into the data processing device from the measurement circuit, the temporal and spatial distribution of the laser pulse output density can be classified into patterns, and the count rate of the plasma emission from the measurement cell can be calculated as the laser pulse output. It is possible to convert the particle concentration with high accuracy by using the conversion coefficient for each pattern classification of the temporal and spatial distribution of the density. As the pattern classification method, for example, the half-value width of the pulse is classified into five in terms of time, and the spatial 1 / e diameter of the pulse (in the case of Gaussian distribution)
It is practically sufficient to classify into 5 categories. Note that FIG.
Although it is not specified in the above, the particle size dependence of each parameter such as plasma emission intensity, plasma emission delay time, plasma emission position, etc. of the conventional method and simultaneous measurement of these multiple parameters are used for discriminating the particle size. . Since the particle size and the concentration can be measured by the data processing device according to the above procedure, when this information is sent to the process control device 14, process control information is sent out according to this information, for example, impurities having a certain particle size or more. When the concentration of exceeds a certain value, an alarm is issued or the process is stopped.
【０００７】本実施例によれば、レーザパルスを分割し
て粒子状不純物を含まない参照試料に照射してプラズマ
発光強度を測定し、予め記憶してあるレーザパルス出力
密度とプラズマ発光強度との関係を利用してレーザパル
ス出力密度の時間的空間的分布をパターン分類すること
により、測定試料からのプラズマ発光の計数率を高精度
で粒子濃度に換算できる利点がある。According to the present embodiment, the laser pulse is divided and irradiated on the reference sample containing no particulate impurities to measure the plasma emission intensity, and the laser pulse output density and the plasma emission intensity stored in advance are compared. By patterning the temporal and spatial distribution of the laser pulse power density using the relationship, there is an advantage that the count rate of plasma emission from the measurement sample can be converted into the particle concentration with high accuracy.
【０００８】参照試料は、測定試料と同一媒質を用いる
のが一般的であるが、測定試料が液体の場合であって
も、気体を用いてもよい。気体は液体に比べて粒子状不
純物の除去が容易であり、媒質以外によるプラズマ発光
の可能性は無視できる。また圧力も制御しやすいので、
参照セルからのプラズマ発光信号を検出しやすいように
圧力を調整できる利点がある。例えば、レーザの出力に
余裕がなく、参照セル側に大きなエネルギを分割できな
い場合に、気体の種類及び圧力を適当に調整することが
できる。The reference sample generally uses the same medium as the measurement sample, but a gas may be used even when the measurement sample is a liquid. Compared to liquid, gas is easier to remove particulate impurities, and the possibility of plasma emission other than medium can be ignored. Also, pressure is easy to control,
There is an advantage that the pressure can be adjusted so that the plasma emission signal from the reference cell can be easily detected. For example, when the laser output has no margin and a large amount of energy cannot be divided to the reference cell side, the type and pressure of the gas can be adjusted appropriately.
【０００９】参照試料は必ずしも粒子状不純物を取り除
いたものである必要はなく、一定の濃度のポリスチレン
標準粒子等の参照粒子を含んでいてもよい。比較的高濃
度の参照粒子を混入しておけばレーザパルスの出力密度
が低くても安定にプラズマ発光を生じることができる。
ポリスチレン標準粒子は粒径が揃っているので媒質によ
るプラズマ発光と同様に参照信号として適切である。The reference sample does not necessarily have to have particulate impurities removed, and may contain a certain concentration of reference particles such as polystyrene standard particles. If reference particles having a relatively high concentration are mixed, plasma emission can be stably generated even if the laser pulse output density is low.
Since the polystyrene standard particles have uniform particle diameters, they are suitable as a reference signal as in the case of plasma emission by a medium.
【００１０】[0010]
【発明の効果】本発明は、レーザパルスを分割して参照
試料に照射してプラズマ発光強度を測定し、予め評価し
てあるレーザパルス出力密度と参照試料のプラズマ発光
強度との関係を利用してレーザパルス出力密度の揺らぎ
を定量化できるので、レーザパルス出力密度のモニタ及
び補正機構を特別に付加することなく、測定試料からの
プラズマ発光の計数率のレーザパルス出力密度依存性を
高精度で補正して粒子濃度に換算できる利点がある。INDUSTRIAL APPLICABILITY The present invention utilizes the relationship between the laser pulse power density and the plasma emission intensity of the reference sample, which has been evaluated in advance, by measuring the plasma emission intensity by irradiating the reference sample with the laser pulse divided. Since the fluctuation of the laser pulse power density can be quantified by using the laser pulse power density, the laser pulse power density dependence of the plasma emission count rate from the measurement sample can be accurately measured without adding a special laser pulse power density monitor and correction mechanism. There is an advantage that it can be corrected and converted into particle concentration.
【図１】本発明の一実施例の装置のブロック図。FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.
１…パルスレーザ、４…レンズ、５…測定セル、９…参
照セル、１１…光検出器、１２…測定回路、１３…デー
タ処理装置。DESCRIPTION OF SYMBOLS 1 ... Pulse laser, 4 ... Lens, 5 ... Measuring cell, 9 ... Reference cell, 11 ... Photodetector, 12 ... Measuring circuit, 13 ... Data processing device.
Claims (3)
マを生成し、プラズマ発光を検出して粒子計数するレー
ザブレイクダウン法において、前記レーザパルスを分割
して一方のパルスを測定試料に照射して前記測定試料中
の粒子を計数し、他方のパルスを参照試料に照射してプ
ラズマ発光を検出して前記レーザパルスの出力密度の時
間的空間的分布の揺らぎに起因する粒子検出感度の変動
を補正することを特徴とする粒子計数方法。1. A laser breakdown method in which a plasma having a particle as a nucleus is generated by a laser pulse, and the plasma emission is detected to count the particle, the laser pulse is divided, and one pulse is irradiated to a measurement sample. Particles in the measurement sample are counted, the other sample is irradiated to the reference sample to detect plasma emission, and the fluctuation of the particle detection sensitivity due to the fluctuation of the temporal and spatial distribution of the power density of the laser pulse is corrected. A method of counting particles, comprising:
気体である粒子計数方法及び装置。2. The particle counting method and apparatus according to claim 1, wherein the medium of the reference sample is a gas.
粒径及び濃度が既知の参照粒子を含む粒子計数方法及び
装置。3. The method according to claim 1, wherein the reference sample is a component,
A particle counting method and apparatus including reference particles of known particle size and concentration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4334099A JPH06180280A (en) | 1992-12-15 | 1992-12-15 | Particle counting method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4334099A JPH06180280A (en) | 1992-12-15 | 1992-12-15 | Particle counting method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06180280A true JPH06180280A (en) | 1994-06-28 |
Family
ID=18273519
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4334099A Pending JPH06180280A (en) | 1992-12-15 | 1992-12-15 | Particle counting method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06180280A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100408155B1 (en) * | 2001-08-10 | 2003-12-01 | (주)다산알앤디 | Dust measuring instrument |
| JP2009109197A (en) * | 2007-10-26 | 2009-05-21 | Sony Corp | Measuring method of microparticle |
-
1992
- 1992-12-15 JP JP4334099A patent/JPH06180280A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100408155B1 (en) * | 2001-08-10 | 2003-12-01 | (주)다산알앤디 | Dust measuring instrument |
| JP2009109197A (en) * | 2007-10-26 | 2009-05-21 | Sony Corp | Measuring method of microparticle |
| JP4509163B2 (en) * | 2007-10-26 | 2010-07-21 | ソニー株式会社 | Measuring method of fine particles |
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