JPH07288096A - Electrification detecting method for sample and scanning electron microscope - Google Patents
Electrification detecting method for sample and scanning electron microscopeInfo
- Publication number
- JPH07288096A JPH07288096A JP6081538A JP8153894A JPH07288096A JP H07288096 A JPH07288096 A JP H07288096A JP 6081538 A JP6081538 A JP 6081538A JP 8153894 A JP8153894 A JP 8153894A JP H07288096 A JPH07288096 A JP H07288096A
- Authority
- JP
- Japan
- Prior art keywords
- sample
- electron beam
- signal
- scanning
- electron
- 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.)
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、走査電子顕微鏡におい
て絶縁物や半導体などの試料を観察する場合に用いて好
適な試料の帯電量検出方法および走査電子顕微鏡に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a charge amount of a sample and a scanning electron microscope which are suitable for observing a sample such as an insulator or a semiconductor in a scanning electron microscope.
【０００２】[0002]
【従来の技術】走査電子顕微鏡では、試料に電子ビーム
を細く集束すると共に、試料上で電子ビームを２次元的
に走査している。そして、試料への電子ビームの照射に
ともなって発生した２次電子や反射電子を検出し、その
検出信号を電子ビームの走査と同期した陰極線管に供給
し、試料の走査像を得るようにしている。2. Description of the Related Art A scanning electron microscope finely focuses an electron beam on a sample and scans the sample two-dimensionally with the electron beam. Then, secondary electrons and backscattered electrons generated by the irradiation of the sample with the electron beam are detected, and the detection signal is supplied to a cathode ray tube synchronized with the scanning of the electron beam to obtain a scan image of the sample. There is.
【０００３】通常、試料としては導電性のものが多く用
いられるが、絶縁物や半導体材料などの導電性でない試
料の場合には、試料への電子ビームの照射により試料が
帯電する。この帯電を防止するため、事前に試料表面に
カーボンや金属などの導電性物質をコーティング処理す
るようにしている。しかしながら、コーティング処理し
た試料はその表面が実質的にコーティング材料で汚染さ
れることになり、試料の生の表面状態の観察が不可能と
なる。また、半導体デバイスの中間検査などの場合に
は、そもそも金属のコーティングなどはできない。Generally, a conductive sample is often used, but in the case of a non-conductive sample such as an insulator or a semiconductor material, the sample is charged by irradiation of an electron beam. In order to prevent this charging, the sample surface is previously coated with a conductive substance such as carbon or metal. However, the surface of the coated sample is substantially contaminated with the coating material, making it impossible to observe the raw surface state of the sample. In the case of intermediate inspection of semiconductor devices, metal coating cannot be performed in the first place.
【０００４】このようなことから、絶縁物試料などの観
察をコーティング処理なしで行う手法が開発されてい
る。その手法としては、試料室の圧力を高くし、帯電し
た試料表面の電荷を試料周辺のガスイオンによって中和
する、試料に照射する電子ビームの電流量を減少させ
る、試料に照射する電子ビームの加速電圧を低くするな
どがある。Under these circumstances, a method for observing an insulator sample or the like without coating treatment has been developed. The technique is to increase the pressure in the sample chamber, neutralize the charges on the charged sample surface by gas ions around the sample, reduce the current amount of the electron beam irradiating the sample, and change the electron beam irradiating the sample. For example, lower the acceleration voltage.
【０００５】[0005]
【発明が解決しようとする課題】上記した絶縁物試料を
観察する手法の一つとして、試料室の圧力を高くした場
合、考慮すべきは、試料に到達する電子ビーム量とその
プローブ径が試料室の圧力に依存することである。すな
わち、より高い試料室内の圧力は試料の帯電を解消する
ことに効果が高いが、その反面、試料に到達する電子ビ
ームの量が減少する。その結果、高い倍率での像の観察
が困難となり、また、Ｘ線分析を行う場合には、微小領
域の分析を困難とする。従って、試料室の圧力を高くし
て観察する場合には、帯電を解消する最も低い圧力に試
料室内圧力を設定する操作が重要となる。As one of the methods for observing the above-described insulator sample, when the pressure in the sample chamber is increased, it should be considered that the amount of electron beam reaching the sample and its probe diameter are It depends on the pressure in the chamber. That is, the higher pressure in the sample chamber is highly effective in eliminating the charge on the sample, but on the other hand, the amount of the electron beam reaching the sample is reduced. As a result, it becomes difficult to observe an image at a high magnification, and when performing X-ray analysis, it becomes difficult to analyze a minute area. Therefore, when observing with increasing the pressure in the sample chamber, it is important to set the pressure in the sample chamber to the lowest pressure that eliminates electrostatic charge.
【０００６】従来の試料室圧力の設定操作は、まず試料
室内の圧力を任意の高さにし、試料上の所定領域で電子
ビームの走査を行う。この走査に基づく反射電子や２次
電子を検出し検出信号を陰極線管に供給して走査像を表
示し、その像の観察を行う。この像を直接観察したりあ
るいは像を写真撮影した上で得られた像から試料の帯電
の影響の有無をオペレータの判断によって行う。この判
断に基づき、帯電の影響があれば、試料室にガスを供給
するガス源と接続されたニードル弁を操作し、試料室内
により多くのガスを供給して圧力を高める。逆に帯電の
影響が全くない場合には、ニードル弁を操作してガスの
供給量を減らし、試料室内圧力を低くする。しかしなが
ら、このような操作は、オペレータの勘や経験によるも
ので、正確ではなく、また、時間も多く要することにな
る。In the conventional setting operation of the sample chamber pressure, first, the pressure in the sample chamber is set to an arbitrary height, and the electron beam is scanned in a predetermined region on the sample. Reflected electrons and secondary electrons based on this scanning are detected and a detection signal is supplied to the cathode ray tube to display a scanned image, and the image is observed. Whether or not the image is directly observed or the image obtained by photographing the image is influenced by the charging of the sample is judged by the operator. Based on this judgment, if there is an influence of electrification, a needle valve connected to a gas source that supplies gas to the sample chamber is operated to supply more gas to the sample chamber and increase the pressure. On the contrary, when there is no influence of charging, the needle valve is operated to reduce the gas supply amount and lower the sample chamber pressure. However, such an operation is not accurate and requires a lot of time because of the intuition and experience of the operator.
【０００７】本発明は、このような点に鑑みてなされた
もので、その目的は、試料の帯電の状態を自動的に簡単
に検出することができる試料の帯電検出方法および走査
電子顕微鏡を実現するにある。The present invention has been made in view of the above circumstances, and an object thereof is to realize a sample charge detection method and a scanning electron microscope capable of automatically and easily detecting the charge state of a sample. There is.
【０００８】[0008]
【課題を解決するための手段】本発明に基づく試料の帯
電検出方法は、試料上を繰り返し電子ビームによって所
定時間走査し、この所定時間の電子ビームの走査に伴っ
て得られた信号の変動分を検出するようにしたことを特
徴としている。According to a method of detecting electrostatic charge of a sample based on the present invention, a sample is repeatedly scanned with an electron beam for a predetermined time, and a fluctuation amount of a signal obtained by the electron beam scanning for the predetermined time is detected. Is characterized in that
【０００９】本発明に基づく走査電子顕微鏡は、電子銃
と、電子銃からの電子ビームを試料上に集束する集束レ
ンズと、電子ビームを試料上で２次元的に走査する走査
手段と、試料への電子ビームの照射に応じて得られた信
号を検出する検出器と、検出器の出力信号が供給される
試料像表示手段と、検出器からの信号に基づいて所定時
間内における検出信号の変動分を求める手段と、求めら
れた変動分に基づいて試料周辺の圧力、試料への電子ビ
ームの照射量、電子ビームの加速電圧のいずれかを制御
するための制御手段とを備えたことを特徴としている。A scanning electron microscope according to the present invention includes an electron gun, a focusing lens for focusing an electron beam from the electron gun on a sample, a scanning means for two-dimensionally scanning the electron beam on the sample, and a sample. Detector for detecting the signal obtained in response to the irradiation of the electron beam, sample image display means to which the output signal of the detector is supplied, and fluctuation of the detection signal within a predetermined time based on the signal from the detector And a control means for controlling any of the pressure around the sample, the irradiation amount of the electron beam on the sample, and the acceleration voltage of the electron beam based on the calculated variation. I am trying.
【００１０】[0010]
【作用】本発明では、試料上を繰り返し電子ビームによ
って所定時間走査し、この所定時間の電子ビームの走査
に伴って得られた信号の変動分を検出し、試料の帯電の
状態を判定する。According to the present invention, the sample is repeatedly scanned with the electron beam for a predetermined time, and the fluctuation of the signal obtained by the scanning of the electron beam for the predetermined time is detected to determine the charged state of the sample.
【００１１】[0011]
【実施例】以下、図面を参照して本発明の実施例を詳細
に説明する。図１は本発明に基づく走査電子顕微鏡の一
例を示しており、１は電子ビームカラム、２は試料室で
ある。電子ビームカラム１の上部には電子銃３が設けら
れており、電子銃３から発生し加速された電子ビームは
集束レンズ４、対物レンズ５によって試料室２内の試料
６上に細く集束される。試料６に照射される電子ビーム
は、垂直偏向コイル７，水平偏向コイル８によって２次
元的に走査される。垂直偏向コイル７には、走査信号発
生回路９からの垂直偏向信号がゲート回路１０を介して
供給され、水平偏向コイル８には走査信号発生回路９か
らの水平偏向信号が供給される。Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an example of a scanning electron microscope according to the present invention, in which 1 is an electron beam column and 2 is a sample chamber. An electron gun 3 is provided above the electron beam column 1, and the electron beam generated and accelerated by the electron gun 3 is finely focused on a sample 6 in a sample chamber 2 by a focusing lens 4 and an objective lens 5. . The electron beam with which the sample 6 is irradiated is two-dimensionally scanned by the vertical deflection coil 7 and the horizontal deflection coil 8. The vertical deflection coil 7 is supplied with the vertical deflection signal from the scanning signal generation circuit 9 through the gate circuit 10, and the horizontal deflection coil 8 is supplied with the horizontal deflection signal from the scanning signal generation circuit 9.
【００１２】試料室２内部は図示していないが適宜な真
空ポンプによって排気されている。また、試料室２内部
には、窒素ガス源１１からニードル弁１２を介して窒素
ガスが供給されるように構成されている。その結果、試
料室２内部の圧力は、ニードル弁１２を駆動機構１３に
よって操作し、試料室２内部に供給する窒素ガスの量を
制御することによって調整が可能となる。試料室２内部
の圧力は、真空計１４によって測定され、その圧力に応
じた信号は、圧力判定回路１５に供給される。Although not shown, the inside of the sample chamber 2 is evacuated by an appropriate vacuum pump. Further, the inside of the sample chamber 2 is configured to be supplied with nitrogen gas from a nitrogen gas source 11 via a needle valve 12. As a result, the pressure inside the sample chamber 2 can be adjusted by operating the needle valve 12 by the drive mechanism 13 and controlling the amount of nitrogen gas supplied into the sample chamber 2. The pressure inside the sample chamber 2 is measured by the vacuum gauge 14, and a signal corresponding to the pressure is supplied to the pressure determination circuit 15.
【００１３】試料６への電子ビームの照射によって発生
した反射電子は、反射電子検出器１６によって検出され
る。検出器１６からの検出信号は、増幅器１７によって
増幅された後、陰極線管１８に供給される。また、検出
器１６からの検出信号はローパスフィルタ１９とハイパ
スフィルタ２０に供給される。ローパスフィルタ１９は
所定周波数以下の信号を通過させ、ハイパスフィルタ２
０は所定の周波数以上の信号を通過させる。The backscattered electrons generated by the irradiation of the sample 6 with the electron beam are detected by the backscattered electron detector 16. The detection signal from the detector 16 is amplified by the amplifier 17 and then supplied to the cathode ray tube 18. The detection signal from the detector 16 is supplied to the low pass filter 19 and the high pass filter 20. The low-pass filter 19 allows signals of a predetermined frequency or lower to pass therethrough, and the high-pass filter 2
0 allows signals of a predetermined frequency or higher to pass through.
【００１４】ローパスフィルタ１９の出力信号は変動分
検出回路２１に供給され、また、ハイパスフィルタ２０
の出力信号は、変動分検出回路２２に供給される。２種
の変動分検出回路２１，２２の出力は、演算回路２３に
供給され、その比が演算される。演算回路２３で求めら
れた比の信号は、メータ２４によって表示されると共
に、制御回路２５に供給される。このような構成の動作
を図２のタイムチャートも参考にして以下説明する。The output signal of the low-pass filter 19 is supplied to the fluctuation detecting circuit 21, and the high-pass filter 20 is also supplied.
The output signal of is supplied to the fluctuation detecting circuit 22. The outputs of the two types of fluctuation amount detection circuits 21 and 22 are supplied to the arithmetic circuit 23 and the ratio thereof is calculated. The ratio signal obtained by the arithmetic circuit 23 is displayed by the meter 24 and is supplied to the control circuit 25. The operation of such a configuration will be described below with reference to the time chart of FIG.
【００１５】まず、通常の走査電子顕微鏡像の観察につ
いて説明する。電子銃３からの電子ビームを集束レンズ
４、対物レンズ５によって試料６上に細く集束し、更
に、走査信号発生回路９からの垂直走査信号と水平走査
信号を偏向コイル７，８に供給し、試料上で電子ビーム
を２次元的に走査する。試料６への電子ビームの照射に
よって発生した反射電子は、反射電子検出器１６によっ
て検出される。検出器１６の検出信号は増幅器１７によ
って増幅された後、走査信号発生回路１９からの走査信
号に同期した陰極線管１８に供給されることから、陰極
線管１８には試料の電子ビームの走査領域の反射電子像
が得られる。First, the observation of a normal scanning electron microscope image will be described. The electron beam from the electron gun 3 is finely focused on the sample 6 by the focusing lens 4 and the objective lens 5, and the vertical scanning signal and the horizontal scanning signal from the scanning signal generating circuit 9 are supplied to the deflection coils 7 and 8. The electron beam is two-dimensionally scanned on the sample. The backscattered electrons generated by the irradiation of the sample 6 with the electron beam are detected by the backscattered electron detector 16. The detection signal of the detector 16 is amplified by the amplifier 17 and then supplied to the cathode ray tube 18 synchronized with the scanning signal from the scanning signal generating circuit 19, so that the cathode ray tube 18 is provided with a scanning region of the electron beam of the sample. A backscattered electron image is obtained.
【００１６】さて、試料６が絶縁物試料や半導体試料の
場合、試料室２内の圧力は高められる。この場合、試料
室２には窒素ガス源１１からのガスがニードル弁１２を
介して供給されるように構成されており、ニードル弁１
２を駆動機構１３によってより開放するように駆動する
ことにより、試料室２内の圧力は高められる。この試料
室２内の圧力は試料６の帯電の状態に応じて最適に制御
しなければならない。このため帯電状態の検出動作が実
行されるが、その場合、電子ビームの試料上の走査は、
特定の垂直位置で繰り返し水平方向に行われる。When the sample 6 is an insulator sample or a semiconductor sample, the pressure inside the sample chamber 2 is increased. In this case, the sample chamber 2 is configured so that the gas from the nitrogen gas source 11 is supplied through the needle valve 12, and the needle valve 1
By driving 2 to be more open by the drive mechanism 13, the pressure in the sample chamber 2 is increased. The pressure in the sample chamber 2 must be optimally controlled according to the charged state of the sample 6. Therefore, the operation of detecting the charged state is executed, but in that case, the scanning of the electron beam on the sample is
Repeated horizontally in a particular vertical position.
【００１７】図３は試料上での電子ビームの走査モード
を説明するための図であるが、図３（ａ）は通常の像観
察状態における走査の様子を示しており、試料６上の特
定の範囲Ｓで２次元的に電子ビームのラスター走査が行
われる。図３（ｂ）は帯電検出モードの時の電子ビーム
の走査状態を示しており、走査領域Ｓの特定の垂直位置
Ｖにおいて電子ビームは繰り返し水平方向に走査され
る。FIG. 3 is a diagram for explaining a scanning mode of the electron beam on the sample, but FIG. 3A shows a scanning state in a normal image observation state, and the scanning on the sample 6 is performed. The raster scanning of the electron beam is two-dimensionally performed in the range S of. FIG. 3B shows a scanning state of the electron beam in the charge detection mode, and the electron beam is repeatedly scanned in the horizontal direction at a specific vertical position V in the scanning region S.
【００１８】図２（ａ）は垂直偏向信号を示しており、
制御回路２５、あるいは、図示しないキーボードなどか
らゲート回路１０に対して帯電検出スタート信号が供給
されると、まず、ゲート回路１０からは時間Ｔの間、垂
直位置Ｖ1で電子ビームが水平方向に走査されるように
一定強度の信号を垂直偏向コイル７に供給する。この時
間Ｔの間、図２（ｂ）の示すように、水平走査信号は繰
り返し水平偏向コイル８に供給される。この走査によ
り、試料６からは反射電子が発生し、この反射電子は検
出器１６によって検出される。図２（ｃ）は反射電子検
出信号波形を示している。この図から明らかなように、
試料上での電子ビームの繰り返し走査に伴い、試料が徐
々に帯電することから、検出信号は全体としては徐々に
高くなり、その間、試料の凹凸に応じて信号強度は急俊
に変化する。FIG. 2A shows the vertical deflection signal,
When a charge detection start signal is supplied to the gate circuit 10 from the control circuit 25 or a keyboard (not shown) or the like, the gate circuit 10 first causes the electron beam to move horizontally at the vertical position V 1 for a time T. A signal having a constant intensity is supplied to the vertical deflection coil 7 so as to be scanned. During this time T, the horizontal scanning signal is repeatedly supplied to the horizontal deflection coil 8 as shown in FIG. By this scanning, reflected electrons are generated from the sample 6, and the reflected electrons are detected by the detector 16. FIG. 2C shows a reflected electron detection signal waveform. As you can see from this figure,
Since the sample is gradually charged as the electron beam is repeatedly scanned on the sample, the detection signal as a whole gradually increases, and during that period, the signal intensity rapidly changes according to the unevenness of the sample.
【００１９】図２（ｃ）の信号はローパスフィルタ１９
とハイパスフィルタ２０に供給される。ローパスフィル
タ１９は図２（ｃ）の信号の内低周波成分を通過させ、
ハイパスフィルタ２０は高周波成分のみを通過させる。
図２（ｄ）はローパスフィルタ１９を通過した信号を示
しており、また、図２（ｅ）はハイパスフィルタ２０を
通過した信号を示している。この低周波成分は試料の帯
電に応じた信号であり、高周波成分は試料表面の凹凸に
応じた信号である。ローパスフィルタ１９を通過した信
号は、変動分検出回路２１に供給され、時間Ｔ内での低
周波成分の変動分ΔＤLが検出される。また、ハイパス
フィルタ２０を通過した信号は、変動分検出回路２２に
供給され、時間Ｔ内での高周波成分の変動分（ピークツ
ーピーク値）ΔＤHが検出される。The signal shown in FIG. 2C has a low-pass filter 19
Is supplied to the high pass filter 20. The low-pass filter 19 passes the internal low frequency component of the signal of FIG.
The high pass filter 20 passes only high frequency components.
2 (d) shows the signal passed through the low-pass filter 19, and FIG. 2 (e) shows the signal passed through the high-pass filter 20. The low frequency component is a signal according to the charging of the sample, and the high frequency component is a signal according to the unevenness of the sample surface. The signal that has passed through the low-pass filter 19 is supplied to the fluctuation amount detection circuit 21, and the fluctuation amount ΔD L of the low frequency component within the time T is detected. Further, the signal that has passed through the high-pass filter 20 is supplied to the fluctuation detection circuit 22 and the fluctuation (peak-to-peak value) ΔD H of the high frequency component within the time T is detected.
【００２０】変動分検出回路２１，２２によって得られ
た変動分信号ΔＤL，ΔＤHは、演算回路２３に供給さ
れ、その比Ｒ（＝ΔＤL／ΔＤH）が求められる。この比
は試料の帯電状態を示したものであり、演算回路２３の
出力はメータ２４に供給されて表示され、オペレータに
現状の試料の帯電状態を正確に知らせることができる。
更に、図１の実施例では比の信号Ｒは制御回路２５に供
給される。制御回路２５は、Ｒの絶対値と予め定めた許
容値ｋとの比較を行う。許容値ｋは、試料の観察や分析
に支障のない値とされている。The fluctuation amount signals ΔD L and ΔD H obtained by the fluctuation amount detecting circuits 21 and 22 are supplied to the arithmetic circuit 23, and the ratio R (= ΔD L / ΔD H ) is obtained. This ratio shows the charged state of the sample, and the output of the arithmetic circuit 23 is supplied to the meter 24 and displayed, so that the operator can be informed accurately of the current charged state of the sample.
Further, in the embodiment of FIG. 1, the ratio signal R is supplied to the control circuit 25. The control circuit 25 compares the absolute value of R with a predetermined allowable value k. The allowable value k is a value that does not hinder the observation and analysis of the sample.
【００２１】Ｒ＞ｋの場合、帯電の量が多いことであ
り、この場合、制御回路２５はニードル弁１２の駆動機
構１３を制御し、より多くの窒素ガスを試料室２内部に
導入するようにし、試料室の圧力を高める。図２（ｆ）
はニードル弁１２の開き量、図２（ｇ）は試料室２の圧
力変化を示しており、時間Ｔ経過後にニードル弁１２が
制御され試料室２の圧力が上昇する。試料室２の圧力の
変化は真空計１４によって監視されており、真空計の信
号は圧力判定回路１５に供給される。圧力判定回路１５
は試料室２内の圧力が、所定の値で平衡状態となったこ
とを判定し、その信号を制御回路２５に供給する。When R> k, it means that there is a large amount of electrification. In this case, the control circuit 25 controls the drive mechanism 13 of the needle valve 12 so that more nitrogen gas is introduced into the sample chamber 2. And increase the pressure in the sample chamber. Figure 2 (f)
Shows the opening amount of the needle valve 12, and FIG. 2 (g) shows the pressure change in the sample chamber 2. After the time T, the needle valve 12 is controlled and the pressure in the sample chamber 2 rises. The change in the pressure of the sample chamber 2 is monitored by the vacuum gauge 14, and the signal of the vacuum gauge is supplied to the pressure determination circuit 15. Pressure determination circuit 15
Determines that the pressure in the sample chamber 2 has reached an equilibrium state at a predetermined value, and supplies the signal to the control circuit 25.
【００２２】なお、試料室２内の圧力を変化させ平衡状
態となるまで、制御回路２５はゲート回路１０を制御
し、電子ビームの走査を図３（ｃ）に示すように、試料
の観察領域Ｓの外側の放電ポジションＶ2で行うよう
に、垂直偏向コイルに垂直走査信号を供給する。試料室
２内の圧力が平衡状態になると、制御回路２５は、圧力
判定回路１５からの信号に応じてゲート回路１０を制御
し、再び帯電検出モードでの電子ビームの走査を行う。
なお，圧力判定回路１５は、図２（ｈ）に示すように、
試料室２内の圧力が安定している期間にはハイレベルの
信号を出力し、逆に非安定の期間はローレベルの信号を
出力する。The control circuit 25 controls the gate circuit 10 until the pressure in the sample chamber 2 is changed to the equilibrium state, and the scanning of the electron beam is performed in the observation region of the sample as shown in FIG. 3 (c). A vertical scanning signal is supplied to the vertical deflection coil as is done at the discharge position V 2 outside S. When the pressure in the sample chamber 2 reaches an equilibrium state, the control circuit 25 controls the gate circuit 10 according to the signal from the pressure determination circuit 15 to scan the electron beam again in the charging detection mode.
The pressure determination circuit 15 is, as shown in FIG.
A high-level signal is output while the pressure in the sample chamber 2 is stable, and conversely, a low-level signal is output during an unstable period.
【００２３】再び時間Ｔの間、垂直位置Ｖ1で電子ビー
ムが水平方向に走査されるように一定強度の信号を垂直
偏向コイル７に供給する。この時間Ｔの間、図２（ｂ）
に示すように、水平走査信号は繰り返し水平偏向コイル
８に供給される。このモードでの電子ビームの走査によ
り、前記したように反射電子検出信号の高周波成分と低
周波成分の変動分が検出され、それらの比Ｒが求められ
る。この求められた比Ｒが、Ｒ≦ｋであると、試料の帯
電が像観察や分析に支障のない程度であり、その後（時
刻ｔ後）、制御回路２５はゲート回路１０を制御し、走
査信号発生回路９からの通常の２次元走査のための垂直
走査信号を垂直偏向コイル７に供給する。この状態で試
料６の所望領域Ｓは電子ビームによって２次元的に走査
され、帯電の影響の極めて少ない像観察や分析が行われ
る。During the time T again, a signal having a constant intensity is supplied to the vertical deflection coil 7 so that the electron beam is horizontally scanned at the vertical position V 1 . During this time T, FIG.
The horizontal scanning signal is repeatedly supplied to the horizontal deflection coil 8 as shown in FIG. By scanning the electron beam in this mode, the fluctuations of the high frequency component and the low frequency component of the backscattered electron detection signal are detected as described above, and their ratio R is obtained. If the obtained ratio R is R ≦ k, the charging of the sample does not hinder the image observation and analysis. After that (after time t), the control circuit 25 controls the gate circuit 10 to perform scanning. A vertical scanning signal for normal two-dimensional scanning from the signal generating circuit 9 is supplied to the vertical deflection coil 7. In this state, the desired region S of the sample 6 is two-dimensionally scanned by the electron beam, and image observation and analysis with extremely little influence of charging are performed.
【００２４】以上本発明の一実施例を詳述したが、本発
明はこの実施例に限定されない。例えば、反射電子を検
出したが、２次電子やＸ線を検出する場合にも本発明を
用いることができる。また、試料室内の圧力が平衡状態
となるまで、電子ビームの走査を試料の観察領域から外
れた位置で行うようにしたが、その間、電子ビームのブ
ランキングを行い、試料上の走査は行わないようにして
も良い。Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment. For example, although the backscattered electrons are detected, the present invention can be used when detecting secondary electrons or X-rays. The electron beam was scanned at a position outside the observation region of the sample until the pressure inside the sample chamber reached an equilibrium state, but during that time, the electron beam was blanked and the sample was not scanned. You may do it.
【００２５】更に、帯電の影響を少なくするために試料
室内の圧力を制御するようにしたが、帯電の影響は試料
に照射する電子ビームの電流量や加速電圧によっても少
なくすることができるため、帯電の状況を示す信号によ
り、電子ビームの電流量や加速電圧を制御するように構
成しても良い。また、帯電の状態を、像のコントラスト
も考慮して、検出信号の低周波成分と高周波成分の変動
分の比によって判断するようにしたが、例えば、低周波
成分の変動分のみによって行っても良い。Further, the pressure in the sample chamber is controlled in order to reduce the influence of the charging, but the influence of the charging can be reduced by the current amount of the electron beam irradiating the sample and the accelerating voltage. The current amount of the electron beam and the accelerating voltage may be controlled by a signal indicating the charging status. Further, the charging state is determined by the ratio of the fluctuation components of the low-frequency component and the high-frequency component of the detection signal in consideration of the image contrast. good.
【００２６】[0026]
【発明の効果】以上説明したように、本発明では、試料
上を繰り返し電子ビームによって所定時間走査し、この
所定時間の電子ビームの走査に伴って得られた信号の変
動分を検出し、試料の帯電の状態を判定するようにし
た。その結果、オペレータの勘や経験に頼らず、正確に
短時間に試料の帯電の状態を検出できる。As described above, according to the present invention, the sample is repeatedly scanned with the electron beam for the predetermined time, and the variation of the signal obtained by the scanning of the electron beam for the predetermined time is detected to detect the sample. The state of charge of is determined. As a result, the charged state of the sample can be accurately detected in a short time without depending on the intuition and experience of the operator.
【図１】本発明の一実施例である走査電子顕微鏡を示す
図である。FIG. 1 is a diagram showing a scanning electron microscope which is an embodiment of the present invention.
【図２】図１の実施例を説明するためのタイムチャート
である。FIG. 2 is a time chart for explaining the embodiment of FIG.
【図３】試料上の電子ビームの走査位置を説明するため
の図である。FIG. 3 is a diagram for explaining a scanning position of an electron beam on a sample.
１ 電子光学カラム ２ 試料室 ３ 電子銃 ４ 集束レンズ ５ 対物レンズ ６ 試料 ７，８ 偏向コイル ９ 走査信号発生回路 １０ ゲート回路 １１ ガス源 １２ ニードル弁 １３ 駆動機構 １４ 真空計 １５ 圧力判定回路 １６ 反射電子検出器 １７ 増幅器 １８ 陰極線管 １９ ローパスフィルタ ２０ ハイパスフィルタ ２１，２２ 変動分検出器 ２３ 演算回路 ２４ メータ ２５ 制御回路 DESCRIPTION OF SYMBOLS 1 Electron optical column 2 Sample chamber 3 Electron gun 4 Focusing lens 5 Objective lens 6 Sample 7,8 Deflection coil 9 Scanning signal generating circuit 10 Gate circuit 11 Gas source 12 Needle valve 13 Driving mechanism 14 Vacuum gauge 15 Pressure determination circuit 16 Reflection electron Detector 17 Amplifier 18 Cathode ray tube 19 Low-pass filter 20 High-pass filter 21 and 22 Fluctuation detector 23 Calculation circuit 24 Meter 25 Control circuit
Claims (4)
定時間走査し、この所定時間の電子ビームの走査に伴っ
て得られた信号の変動分を検出するようにした試料の帯
電検出方法。1. A method for detecting electrostatic charge of a sample, wherein a sample is repeatedly scanned with an electron beam for a predetermined time, and a fluctuation of a signal obtained by scanning the electron beam for the predetermined time is detected.
定時間走査し、この所定時間の電子ビームの走査に伴っ
て得られた信号の低周波成分の変動分と高周波成分の変
動分を検出し、それらの比を求めるようにした試料の帯
電検出方法。2. A sample is repeatedly scanned with an electron beam for a predetermined period of time, and fluctuations of a low frequency component and a high frequency component of a signal obtained by the scanning of the electron beam for the predetermined time are detected. The method for detecting the charge of a sample so as to obtain the ratio.
料上に集束する集束レンズと、電子ビームを試料上で２
次元的に走査する走査手段と、試料への電子ビームの照
射に応じて得られた信号を検出する検出器と、検出器の
出力信号が供給される試料像表示手段と、検出器からの
信号に基づいて所定時間内における検出信号の変動分を
求める手段と、求められた変動分に基づいて試料周辺の
圧力、試料への電子ビームの照射量、電子ビームの加速
電圧のいずれかを制御するための制御手段とを備えた走
査電子顕微鏡。3. An electron gun, a focusing lens for focusing an electron beam from the electron gun on the sample, and an electron beam 2 on the sample.
Scanning means for dimensionally scanning, a detector for detecting a signal obtained according to irradiation of an electron beam on a sample, sample image display means to which an output signal of the detector is supplied, and a signal from the detector Means for obtaining the fluctuation amount of the detection signal within a predetermined time based on the above, and controlling any of the pressure around the sample, the electron beam irradiation amount to the sample, and the accelerating voltage of the electron beam based on the calculated fluctuation amount. And a scanning electron microscope.
における検出信号の変動分を求める手段は、検出信号の
低周波成分を通過させるローパスフィルタと、検出信号
の高周波成分を通過させるハイパスフィルタと、ローパ
スフィルタを通過した信号の所定時間内の変動分を検出
する第１の変動分検出手段と、ハイパスフィルタを通過
した信号の所定時間内の変動分を検出する第２の変動分
検出手段と、第１と第２の変動分検出手段からの信号の
比を求める手段とより成る請求項３記載の走査電子顕微
鏡。4. A low-pass filter that passes a low-frequency component of the detection signal and a high-pass filter that passes a high-frequency component of the detection signal are provided as means for obtaining the fluctuation amount of the detection signal within a predetermined time based on the signal from the detector. A first fluctuation amount detecting means for detecting a fluctuation amount of the signal passed through the low pass filter within a predetermined time, and a second fluctuation amount detecting means for detecting a fluctuation amount of the signal passing through the high pass filter within a predetermined time period. 4. The scanning electron microscope according to claim 3, further comprising: and a means for obtaining a ratio of signals from the first and second fluctuation amount detecting means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6081538A JPH07288096A (en) | 1994-04-20 | 1994-04-20 | Electrification detecting method for sample and scanning electron microscope |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6081538A JPH07288096A (en) | 1994-04-20 | 1994-04-20 | Electrification detecting method for sample and scanning electron microscope |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH07288096A true JPH07288096A (en) | 1995-10-31 |
Family
ID=13749082
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6081538A Withdrawn JPH07288096A (en) | 1994-04-20 | 1994-04-20 | Electrification detecting method for sample and scanning electron microscope |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07288096A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6618850B2 (en) | 2000-02-22 | 2003-09-09 | Hitachi, Ltd. | Inspection method and inspection system using charged particle beam |
| JP2009043936A (en) * | 2007-08-09 | 2009-02-26 | Hitachi High-Technologies Corp | Electron microscope |
| JP2014146526A (en) * | 2013-01-30 | 2014-08-14 | Hitachi High-Technologies Corp | Electron beam device, and electron beam observation method |
-
1994
- 1994-04-20 JP JP6081538A patent/JPH07288096A/en not_active Withdrawn
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6618850B2 (en) | 2000-02-22 | 2003-09-09 | Hitachi, Ltd. | Inspection method and inspection system using charged particle beam |
| US6931620B2 (en) | 2000-02-22 | 2005-08-16 | Hitachi, Ltd. | Inspection method and inspection system using charged particle beam |
| US7526747B2 (en) | 2000-02-22 | 2009-04-28 | Hitachi, Ltd. | Inspection method and inspection system using charged particle beam |
| JP2009043936A (en) * | 2007-08-09 | 2009-02-26 | Hitachi High-Technologies Corp | Electron microscope |
| US7989768B2 (en) | 2007-08-09 | 2011-08-02 | Hitachi High-Technologies Corporation | Scanning electron microscope |
| US8481935B2 (en) | 2007-08-09 | 2013-07-09 | Hitachi High-Technologies Corporation | Scanning electron microscope |
| JP2014146526A (en) * | 2013-01-30 | 2014-08-14 | Hitachi High-Technologies Corp | Electron beam device, and electron beam observation method |
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