JPS63178523A - Automatic focusing method - Google Patents
Automatic focusing methodInfo
- Publication number
- JPS63178523A JPS63178523A JP62009020A JP902087A JPS63178523A JP S63178523 A JPS63178523 A JP S63178523A JP 62009020 A JP62009020 A JP 62009020A JP 902087 A JP902087 A JP 902087A JP S63178523 A JPS63178523 A JP S63178523A
- Authority
- JP
- Japan
- Prior art keywords
- waveform
- focusing
- information
- value
- current
- 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
- 238000000034 method Methods 0.000 title claims abstract description 15
- 230000001186 cumulative effect Effects 0.000 claims abstract description 15
- 238000010894 electron beam technology Methods 0.000 claims abstract description 7
- 230000003111 delayed effect Effects 0.000 claims abstract description 4
- 239000002245 particle Substances 0.000 claims abstract description 3
- 230000005284 excitation Effects 0.000 claims description 5
- 238000000605 extraction Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims 1
- 238000010586 diagram Methods 0.000 description 5
- 230000006870 function Effects 0.000 description 2
- 101100481408 Danio rerio tie2 gene Proteins 0.000 description 1
- 101100481410 Mus musculus Tek gene Proteins 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 238000012887 quadratic function Methods 0.000 description 1
Landscapes
- Electron Beam Exposure (AREA)
Abstract
Description
【発明の詳細な説明】
〔発明の目的〕
（産業上の利用分野）
本発明は、 ＬＳＩパター・ンを試料に描画する荷電
ビーム抽画装置に於いてレンズ焦点を自動的に合わせる
方法に関する。DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for automatically focusing a lens in a charged beam extraction device for drawing an LSI pattern on a sample.
（従来の技術）
従来、焦点合わせの自動化には以下のような方法が考案
されている。まず１段差マーク波形の立ち上り時間をカ
ウントして、このカウント値を最小にする電流値を励磁
電流とする方法がある。この方法の問題点は波形のノイ
ズを十分低減させないと糖室が悪化する０別の方法とし
ては、段差マーク波形を２回計算機で微分計算し、その
計算結果を最大にする電流値を計算する方法がある。こ
の方法では、波形の質によって微分条件を決定する手間
が必要で、しかも処理時間を多く必要とするＯ
（発明が解決しようとする問題点）
本発明は、上述しｔ欠点を除く定めになさ１．念もので
、処理速度が速く、ノイズの影響を大きく受けずに自動
焦点合わせができる方法を提供することを目的とする。(Prior Art) Conventionally, the following methods have been devised for automating focusing. First, there is a method of counting the rise time of the one-level difference mark waveform and setting the current value that minimizes this count value as the excitation current. The problem with this method is that if the waveform noise is not sufficiently reduced, the sugar chamber deteriorates.Another method is to differentiate the step mark waveform twice using a computer, and then calculate the current value that maximizes the calculated result. There is a way. This method requires a lot of effort to determine the differential conditions depending on the quality of the waveform, and also requires a lot of processing time. 1. The purpose of this invention is to provide a method that has high processing speed and can perform automatic focusing without being significantly affected by noise.
Ｃ問題点を解決するための手段】
本発明では、ｉｔ子ビーム抽画装置において、レンズ用
のコイルに流れる電流を一定に増加させながら、試料上
に作らｎｔマークのエツジを電子ビームで走査し、検出
される反射電子信号ｉＡ／Ｄ変換し、得られ友波形デー
タとこれを遅延させたデータとの差（差信号）′ｆ：計
算し、すでに設定さルているスレッシ１−ルドレベル以
上の差信号データを累積加算する。電流値と累積加算値
のデータから、両者の関係を２次関数に最小２乗法であ
てはめ、この関数から累積加算値を最大にする電流値を
計算し、この電流値をコイルの励磁電流とする。Means for Solving Problem C] In the present invention, the edge of the nt mark made on the sample is scanned with an electron beam while the current flowing through the lens coil is constantly increased in the electron beam extraction device. , the detected backscattered electron signal iA/D converted, and the difference (difference signal) between the obtained waveform data and the delayed data (difference signal)'f: Calculated, and the difference (difference signal) between Cumulatively add difference signal data. From the data of the current value and cumulative addition value, apply the relationship between the two to a quadratic function using the least squares method, calculate the current value that maximizes the cumulative addition value from this function, and use this current value as the excitation current of the coil. .
（作用）
本発明によれば、波形のノイズに大きく依存しないで、
高速に焦点を合わせることができる０又、処理が容易で
ある友め、専用のハードウェアを取り付けなくても、Ｅ
Ｂ装置に不可欠なマーク位置検出装置の波形記憶回路を
使って計算機で処理可能で、速く処理できる。(Function) According to the present invention, without depending greatly on waveform noise,
It is easy to focus, has fast focusing, and is easy to process.
It can be processed by a computer using the waveform memory circuit of the mark position detection device, which is essential to the B device, and can be processed quickly.
（実施例）
第１図は１本発明の実施例で用いられる装置の配置図で
ある。１は電子ビーム露光装置、２は偏向器、３は対物
レンズ、４は反射電子検出器、５は試料、６は電子銃で
ある。計算機６から、焦点合わせ用のコイル３を駆動す
るアンプ７のＤＡｃ８にデータを設定する０試料５の凸
型段差マークのエツジを電子ビームで走査し１反射電子
信号？Ａ／Ｄ変換して２回路１ｏで平均加算処理して波
形記憶メモＩＪＩＩへ畜き込む。このときの波形データ
’ｔｉＥ２図に示す。この波形データ（ａ） ｅ波形記
憶メモリから読み出し、こｆ′Ｌを遅延させ定データ（
ｂ）との差（差信号データ）（Ｃ）を計算する０最大値
と最小値から差信号波形のエツジを交差するように、適
当な値をスレッシ習ルドレベルに設定し固定する。スレ
ッシミルドレベル以上の差信号データを回路１５で累積
加算ｆｉｌ ′１に求める。(Embodiment) FIG. 1 is a layout diagram of an apparatus used in an embodiment of the present invention. 1 is an electron beam exposure device, 2 is a deflector, 3 is an objective lens, 4 is a backscattered electron detector, 5 is a sample, and 6 is an electron gun. Data is set from the computer 6 to the DAc 8 of the amplifier 7 that drives the focusing coil 3.0 The edge of the convex step mark on the sample 5 is scanned with an electron beam to obtain a reflected electron signal? The data is A/D converted, averaged and added in two circuits 1o, and stored in the waveform storage memory IJII. The waveform data at this time is shown in figure 'tiE2. This waveform data (a) e is read from the waveform storage memory, and the constant data (
b) Calculate the difference (difference signal data) (C) 0 An appropriate value is set and fixed at the threshold learned level so that the edge of the difference signal waveform crosses between the maximum value and the minimum value. Difference signal data above the threshold level is obtained by a circuit 15 as a cumulative addition fil'1.
ただし、ｙ土（ｉ＝Ｑｍｔ２）
（Ｃ）は焦点が合っている時、（ｄ）はぼかし九時の差
信号波形である。However, y (i=Qmt2) (C) is the difference signal waveform when the image is in focus, and (d) is the difference signal waveform when the image is blurred.
つまり焦点が合っている（Ｃ）の波形の場＠−は累積加
算値が大きく、ぼかした波形（ｄ）の場会は累積加算値
が小さくなる。この特性を利用して、スレッシールドレ
ペル１７を設定してから、焦点合わせ用■コイルの電流
値を一定に増加させながら、上記した累積７ＪＯ′に、
値を計算する。電流値と累積加算値のデータから両者の
関係は；ｇ４図で示しｔ特性が得らｎる。この特性から
２式ｙ ＝ ａｘ２＋ｂｘ＋ｃ （ｙ ：累積加算値、
ｘ：電流値〕に最小二乗法であてはめる。データから係
数ａ、ｂ、ｃが決定されると累積加算値を最大にする電
流値ｘ＝−Ｉ「が計算さｎ、この電流値を励磁電流に設
定すれば焦点を合わせられる。In other words, the cumulative addition value is large in the case of the in-focus waveform (C) @-, and the cumulative addition value is small in the case of the blurred waveform (d). Utilizing this characteristic, after setting the threshold level 17, while constantly increasing the current value of the focusing coil, to the cumulative 7JO' mentioned above,
Calculate the value. From the data of the current value and the cumulative addition value, the relationship between the two is shown in the diagram G4 and the t characteristic can be obtained. From this characteristic, the following equation y = ax2 + bx + c (y: cumulative addition value,
x: current value] using the least squares method. When the coefficients a, b, and c are determined from the data, the current value x=-I' that maximizes the cumulative addition value is calculated, and by setting this current value as the excitation current, focusing can be achieved.
なお、焦点会わせに使用するマークは、上述した実施例
のような凸型の段差マークに限られない〇例えばＶ突起
、金粒子でも対応可能で、反射電子検出器アンプを反転
させれば■溝、凹型段差マークでもよい。ま之反射電子
に代えて２次電子を検出してもよい。Note that the mark used for focusing is not limited to the convex step mark as in the above-mentioned embodiment; for example, V protrusions or gold particles can also be used, and if the backscattered electron detector amplifier is reversed, ■ A groove or a concave step mark may also be used. Secondary electrons may be detected instead of the reflected electrons.
本発明によれば処理速度が速く、ノイズの影響を受けに
くい。According to the present invention, the processing speed is fast and it is less susceptible to noise.
第１図は本発明の実施例で用いら１．る自動焦点合わせ
装置を示す配胃図、第２図は焦点と差信号波形の関係を
表わす波形図、第３図は数式を説明する友めの図、に４
図は励磁電流と累積加算値との関係を表わす波形図であ
る。
ｌ・・・電子ビーム露光装置、３・・・焦点合わせ用コ
イル（対物レンズ）、６・・・計算機。
代理人 弁理士 則 近 憲 佑
同 竹 花 喜久男
第２図
第４図FIG. 1 shows 1. used in the embodiment of the present invention. Figure 2 is a waveform diagram showing the relationship between the focal point and the difference signal waveform, and Figure 3 is a companion diagram to explain the mathematical formula.
The figure is a waveform diagram showing the relationship between exciting current and cumulative addition value. l... Electron beam exposure device, 3... Focusing coil (objective lens), 6... Computer. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana Figure 2 Figure 4
Claims (2)
ルに流す電流を設定した後、試料上に作られたマークを
荷電ビームで走査し、検出される反射もしくは２次荷電
粒子信号をＡ／Ｄ変換して得られた波形データと、これ
を遅延させたデータとの差（差信号）を計算し、すでに
設定されているスレッシヨールドレベル以上の該差信号
データを累積加算し、該累積加算値を最大にする電流を
レンズの励磁電流とすることを特徴とする自動焦点合わ
せ方法。(1) In the charged electron beam extraction device, after setting the current flowing through the lens coil, the mark made on the sample is scanned with the charged beam, and the detected reflection or secondary charged particle signal is The difference (difference signal) between the waveform data obtained by D-conversion and the delayed data is calculated, and the difference signal data above the threshold level that has already been set is cumulatively added. An automatic focusing method characterized in that a current that maximizes the added value is used as a lens excitation current.
関係を多項式関数で近似し、該関数から累積加算値を最
大にする電流値を計算し、得られた電流値をレンズの励
磁電流とすることを特徴とする特許請求の範囲第１項記
載の自動焦点合わせ方法。(2) Obtain multiple points of current value and cumulative addition value data, approximate the relationship between the two using a polynomial function, calculate the current value that maximizes the cumulative addition value from the function, and use the obtained current value to 2. The automatic focusing method according to claim 1, wherein an excitation current is used.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62009020A JPS63178523A (en) | 1987-01-20 | 1987-01-20 | Automatic focusing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62009020A JPS63178523A (en) | 1987-01-20 | 1987-01-20 | Automatic focusing method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS63178523A true JPS63178523A (en) | 1988-07-22 |
Family
ID=11708971
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62009020A Pending JPS63178523A (en) | 1987-01-20 | 1987-01-20 | Automatic focusing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63178523A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01283831A (en) * | 1988-05-10 | 1989-11-15 | Fujitsu Ltd | Charged beam exposing method |
| EP0507627A2 (en) * | 1991-04-03 | 1992-10-07 | Sharp Kabushiki Kaisha | Automatic focusing device and method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56138923A (en) * | 1980-03-31 | 1981-10-29 | Jeol Ltd | Adjusting method for focussing |
| JPS5897609A (en) * | 1981-12-07 | 1983-06-10 | Toshiba Corp | Mark position detector |
-
1987
- 1987-01-20 JP JP62009020A patent/JPS63178523A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56138923A (en) * | 1980-03-31 | 1981-10-29 | Jeol Ltd | Adjusting method for focussing |
| JPS5897609A (en) * | 1981-12-07 | 1983-06-10 | Toshiba Corp | Mark position detector |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01283831A (en) * | 1988-05-10 | 1989-11-15 | Fujitsu Ltd | Charged beam exposing method |
| EP0507627A2 (en) * | 1991-04-03 | 1992-10-07 | Sharp Kabushiki Kaisha | Automatic focusing device and method |
| US5337084A (en) * | 1991-04-03 | 1994-08-09 | Sharp Kabushiki Kaisha | Automatic focusing device utilizing a trend of variation and degree of reliability of a focusing evaluation value signal to improve image focusing |
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