JPH0479137A - Electron beam apparatus and electron beam automatic alignment method - Google Patents

Abstract

PURPOSE:To automatically align electron beam with the optical axis with good reproducibility by returning and putting out a plurality of alignment controlling data to an alignment means based on the electron beam which reaches to a region where beam is radiated after starting and secondary electrons and reflected electrons from the ragion where beam is radiated. CONSTITUTION:A controlling means 15 to return and put out a plurality of alignment controlling data ATX, ATY, ASX, ASY to an alignment means 12 based on electron beam 11a which reaches a region A where beam is radiated after starting and secondary electrons and reflected electrons 11b from the region A where beam is radiated is installed. For this, even in the case that the inner conditions of an electron-optical system vary due to overhauling of an apparatus, etc., practical circumstancial conditions are controlled by feed- back without depending on manual adjustment of an alignment coil immediate after starting of the apparatus and the electron beam is thus aligned with the optical axis automatically with good reproducibility. Consequently, manual adjustment of the alignment coil by a skilled man becomes unnecessary and complete automation is achieved.

Description

[Detailed description of the invention] (Table of contents) Overview Industrial field of application Conventional technology (Figures 10 and 11) Problems to be solved by the invention Means for solving the problems (Figures 1 and 2) Figure) Example of operation (Figures 3 to 9) Effects of the invention [Summary] The central axis of the electron beam immediately after starting up of an electron beam device, especially a scanning electron microscope or an electron beam tester, etc. is aligned with the light of the electron optical system. Regarding the full automation of the alignment adjustment process to match the axis, even if the internal conditions of the electron optical system change due to an overhaul of the device, the alignment coil will not have to be manually adjusted immediately after the device starts up. The purpose of the invention is to automatically align the electron beam to the optical axis with good reproducibility without causing the beam to irradiate. and a first detection means for detecting the electron beam that has reached the beam irradiation area;
a second detection means for detecting secondary electrons or reflected electrons from the beam irradiation area; and a control means for controlling input and output of the electron gun, alignment means, first detection means, and second detection means. fc, the control means returns a plurality of alignment control data to the alignment means based on the electron beam that reaches the beam irradiation area after activation and secondary electrons or reflected electrons from the beam irradiation area. Contains and configures output.

[Industrial application field]

The present invention relates to an electron beam device and an automatic electron beam alignment method, and more specifically, the present invention relates to an electron beam device and an automatic electron beam alignment method. This relates to the full automation of the alignment adjustment process.

In recent years, scanning electron microscopes and electron beam testers have been used in the manufacturing process of LSIs and the like. In the electron guns used in these electron beam devices, the emission current does not become stable immediately due to temperature changes or the like. For this reason, the measurer or the control system frequently performs alignment adjustment to align the central axis of the electron beam with the optical axis of the electron optical system.

In addition, the present inventors have previously filed a patent application (Japanese Patent Application No. 1-5119
9) According to the electron beam alignment method that introduces the semi-automatic adjustment method described above, the measurer aligns the electron beam with the optical axis of the optical coordinate system in advance, obtains optimal alignment adjustment data, and then calculates the adjustment data. Based on this, the alignment adjustment of the electron beam is automatically corrected immediately after the start-up of the device, and the adjustment is automated.

However, if an electron beam device is continuously used, the alignment conditions of the electron optical system change due to the influence of dirt, floating charges, etc. inside the device.

Furthermore, environmental conditions may change due to an overhaul of the electron beam device, and previously acquired adjustment data may no longer be usable.

Therefore, manual adjustment of the alignment coil by a skilled person is required, which poses a problem of hindering complete automation.

Therefore, even if the internal conditions of the electron optical system change due to an overhaul of the device, the alignment coil can be adjusted with high reproducibility without relying on manual adjustment immediately after the device starts up. A device and an automatic alignment method that can automatically align the optical axis are desired.

[Conventional technology]

10th. FIG. 11 is an explanatory diagram of a conventional example.

FIG. 10 shows a configuration diagram of a conventional electron beam device.

In the figure, the inventors filed a patent application (Japanese Patent Application No. 1-5
1199) is an electron gun 1. Alignment coil 2. Faraday Katsub 3. A/D converter 4
．． Control circuit 5. D/A converter6. It consists of a secondary electron detector 71, a manual regulator 8, a monitor 9, and an electron gun control circuit 10.

The electron beam alignment function of the device is as follows: First, when an electron gun 1 emits an electron beam 1a, an alignment coil 2 adjusts the alignment of the electron beam 1a. In this alignment adjustment, when creating correction data, the measurer adjusts the alignment coil 2 using the manual adjuster 8. Furthermore, when the correction data is created, the control circuit 5 outputs automatic adjustment, automatic control data, etc. to the D/A converter 6 based on the correction data. Note that during alignment adjustment, the electron beam 1a is detected by the Faraday tube 3, and the A/
The D converter 4 A/D converts the beam current IB.

In addition, in order to create optimal correction data, the electron beam
A crossover image of a is displayed on the monitor 9. At this time, secondary electrons 1b are detected by the secondary electron detector 7, signal processed by the control circuit 5, and the secondary electron acquired image is displayed on the monitor 9.

Thereby, in the control circuit 5, alignment data is created based on the beam current data D1 so that the beam current IB becomes maximum.

Thereafter, the alignment data is read out from the memory every time the device is started, and the correction data is sent to the D/A converter 6, and the alignment coil 2 consisting of tilt coils TX, TY and shift coils SX, SY. is automatically adjusted and controlled.

FIG. 11 is a flowchart of a conventional method for automatically aligning an electron beam.

In the figure, the present inventors first discovered patent ratio II (patent application No.
According to the electron beam alignment method that introduces the semi-automatic adjustment method described in 51199), correction data AD for optimal alignment adjustment is obtained in advance in steps PI and P2, and in step P3, the electron beam device performs the observation and measurement on that day. When activated for step P4. At P5, the alignment coil 2 is automatically adjusted and controlled based on the correction data AD.

That is, in step P1, the alignment coil 2 is manually adjusted at every arbitrary elapsed time from the start of activation of the electron gun 1.

Next, optimal control information for the alignment coil 2 is acquired and correction data AD is created.

Next, in step P3, the device is activated for that day.

Furthermore, in step P4, the tilt coils TX and TY of the alignment coil 2 are automatically controlled based on the correction data AD. In parallel with this, in step P5, shift coil 5XSY of alignment coil 2 is
Automatic adjustment is performed based on the beam current data BD of the electron beam 1a that reaches the electron beam 1a.

First, when the electron gun power source 4 is turned on, the electron beam 1a emitted from the electron gun 1 passes through the alignment coil 2 and other electron optical deflection systems and reaches the Faraday tube 3.

Next, the beam current IB captured by the Faraday tube 3 is converted from analog to digital by an A/D converter, and the beam current data BD is taken into the control circuit 5. Further, the secondary electrons 1b emitted from the Faraday tube 3 are detected by a secondary electron detector, and the detection data D2 is taken into the control circuit.

Next, in the control circuit 5, alignment data is created based on the detection data D1 so that the beam current IB is maximized. The alignment data is sent to the D/A converter 6, and alignment coils including tilt coils TX and TY and shift coils SX and SY are automatically adjusted.

Thereby, the electron beam 1a of a scanning electron microscope, electron beam tester, etc. is aligned with the optical axis 0 of the optical coordinate system XY.

[Problems to be Solved by the Invention] By the way, according to a conventional electron beam alignment method that introduces a semi-automatic adjustment method, which the present inventors have previously applied for a patent (Japanese Patent Application No. 1-51199), it is possible to The measurer aligns the electron beam with the optical axis of the optical coordinate system, obtains optimal alignment adjustment data, and automatically corrects the electron beam alignment adjustment immediately after starting the device based on the adjustment data. , we are trying to automate it.

Therefore, if you continue to use an electron beam device, the alignment conditions of the electron optical system may change due to the influence of dirt or floating charges inside the device, or the environmental conditions may change due to overhaul of the electron beam device, etc. If it changes, the previously acquired correction data AD for alignment adjustment may become unusable. This is because the control circuit 5 automatically adjusts the alignment coils 2 such as the pair of tilt coils TX and TY and the pair of shift coils SX and SY based on the correction data AD in an unstable state immediately after the start of filament heating. This is because if this happens, the electron beam 1a may converge at a local point deviating from the optical axis 0 of the electron optical system due to the influence of dirt, floating charges, etc. inside the device.

This necessitates manual adjustment of the alignment coil by a skilled person, which poses a problem of hindering complete automation.

The present invention was created in view of the problems of the conventional method, and even if the internal conditions of the electron optical system change due to an overhaul of the device, the alignment coil can be changed immediately after starting the device. An electron beam device and an automatic electron beam alignment method that enable automatic alignment of the electron beam to the optical axis with good reproducibility through feedback control of actual environmental conditions without relying on manual adjustment processing. The purpose is to provide.

[Means for Solving the Problems] FIG. 1 is a diagram showing the principle of an electron beam apparatus according to the present invention, and FIG. 2 is a diagram showing the principle of an automatic electron beam alignment method according to the present invention.

As shown in FIG. 1, the apparatus includes at least an electron gun 11 that emits an electron beam 11a onto a beam irradiation area A, an alignment means 12 that adjusts the irradiation direction of the electron beam 11a, and the beam irradiation area A. A first detection means 13 for detecting the electron beam 11a that has reached A, and secondary electrons or reflected electrons 11b from the beam irradiation area A.
a second detection means 14 for detecting the electron gun 11. Alignment means 12. a control means 15 for controlling input and output of the first detection means 13 and the second detection means 14; It is characterized by feedback-outputting a plurality of alignment control data AT×, ATY, ASXASY to the alignment means 12 based on the secondary electrons or reflected electrons 11b from the irradiated area A, and the method thereof is shown in FIG. As shown, first, in step P1, the electron beam 11a is deflected to the beam irradiated area A, and then, in step P2, the electron beam 11a is deflected based on the secondary electrons or reflected electrons 11b from the beam irradiated area A. 11a is performed, and further, in step P3, an alignment adjustment process is performed for the electron beam 11a to an optical axis reference point 0 of the electron optical system based on the image acquisition process, In the alignment method, after performing the image acquisition processing in step P2, irradiation adjustment processing of the electron beam 11a is performed in step P4, and then, in step P5, the electron beam 11a is adjusted based on the irradiation adjustment processing and image acquisition processing. A first alignment adjustment process is performed to align the electron optical system near the optical axis reference point O, and then, in step P6, a re-irradiation adjustment process of the electron beam 11a is performed based on the first alignment adjustment process. , further characterized in that, in step P7, a second alignment adjustment process is performed to align the electron beam 11a with the optical axis reference point ○ of the electron optical system based on the re-irradiation adjustment process, thereby achieving the above object. do.

[Function] According to the device of the present invention, the electron beam 1) a that reaches the beam irradiation area A after startup and the beam irradiation area A
Based on the secondary electrons or reflected electrons 11b from the alignment means 12, a plurality of alignment control chips 9 AT
X, ATL ASX, ASY (7) Control means 15 for feedback output is provided.

Therefore, even if the internal conditions of the electron optical system change due to an overhaul of the device, the alignment coil can be fed back the actual environmental conditions immediately after the device starts up, without relying on manual adjustment processing. control,
It is possible to automatically align the electron beam to the optical axis with good reproducibility.

This eliminates the need for manual adjustment of the alignment coil by a skilled person, making it possible to achieve complete automation.

Further, according to the alignment method of the present invention, step P
Based on the image acquisition process of the irradiation shape image of the electron beam 11a in step 3, the alignment adjustment process is performed on the irradiation shape image of the electron beam 11a to the optical axis reference point O of the electron optical system, or after the image acquisition process of step P2, step P5 performs a first alignment adjustment process based on the irradiation adjustment process and image acquisition process,
After that, a second alignment adjustment process is performed in step P7.

Therefore, compared to the conventional electron beam alignment method that introduced a semi-automatic adjustment method that the present inventors previously applied for a patent (Japanese Patent Application No. 1-51199), it is possible to perform alignment H [alignment processing] using a so-called learning function. can do.

That is, the measurer aligns the electron beam 11a with the optical axis of the electron optical system in advance, obtains optimal alignment adjustment data, and then adjusts the position of the pair of tilt coils TX and TY and the pair of shift coils SX and SY. Compared to the method of automatically adjusting the alignment coil 2 based on the correction data AD, etc., due to the influence of dirt and floating charges inside the device,
The pair of tilt coils TX, TY and Pair of shift coils SX,
Alignment control data ATX, ATY, etc. for SY, etc.
It becomes possible to perform automatic adjustment processing based on ASX and ASY.

This makes it possible to adjust the alignment of the electron beam 11a to the optical axis reference point of the electron optical system with good reproducibility based on the environmental conditions immediately after startup on the day the device is used.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

3 to 9 are diagrams for explaining an electron beam device and an automatic electron beam alignment method according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a configuration of an electron beam device according to an embodiment of the present invention. It shows.

In the figure, 21 is an electron gun that emits an electron beam 21a. For example, the electron gun 21 may be a tungsten hairpin filament or a lanthanum hexaporide (L).
aBa) Consists of filaments, etc.

Reference numerals 22A and 22B are an alignment coil and an alignment coil drive circuit, which are one embodiment of the alignment means 12. The alignment coil 22A includes a pair of tilt coils TX and TY and a pair of shift coils SX and SY. Note that the functions of each coil will be explained in detail in FIG. 4. The alignment coil drive circuit 22B includes 4
Two registers RTXRTY, R3X, RTY and 4-
) (7) D/A converter DTX, DTY, DSX,
Consists of DTY. Further, the function of the drive circuit 22B is to hold the tilt X data ATX, tilt Y data ATY, shift X data ASX, and shift X data ASW (hereinafter referred to as alignment control data) from the control computer 25D and to D/A converter DTX, DT
Output to Y DSX, DTY, and output the data to ATX,
ATY, ASX, and ASY are digital/analog converted and output to a pair of tilt coils TX and TY and a pair of shift coils sx and sy.

Reference numerals 23A and 23B are Faraday cubes and A/D converters, which are examples of the first detection means 13. The Faraday tube 23A detects the electron beam 21a that reaches the beam irradiation area A. In the embodiment of the present invention, the Faraday tube 23 is movable, and has a mechanism that moves it above the sample 26 as necessary. Further, the A/D converter 23B performs A/D conversion of the beam current IB from the Faraday tube 23A, and outputs it to the control computer 25A as beam current data BD.

Here, the beam irradiation area A refers to the Faraday tube 2
When 3A is extended to the optical axis of the electron beam 21a,
This is the reach area, and when the Faraday tube 23 is not extended to the optical axis, the top surface of the sample 26 is tilted.

Reference numerals 24A to 24C are a secondary electron detector, a signal processing circuit, and an image memory, which are one embodiment of the second detection means 14.

The secondary electron detector 24A detects secondary electrons and reflected electrons 11b from the beam irradiated area A. The signal processing circuit 24B performs analog/digital conversion processing on the detection signal from the secondary electron detector 24A and outputs image acquisition data.

The image memory 24C stores image acquisition data.

Reference numerals 25A and 25B are a control computer and an electron gun control circuit, which are an embodiment of the control means 15. Control computer 25A
are the electron gun control circuit 25B and the alignment drive circuit 22.
It controls input and output of the B1 image memory 24C, A/D conversion circuit 23B, and monitor 27. In particular, in the embodiment of the present invention, the control calculation 11125A calculates the alignment drive circuit based on the electron beam 21a that reaches the beam irradiation area A after startup and the secondary electrons or reflected electrons 21b from the beam irradiation area A. It is characterized by feedback outputting a plurality of alignment control data ATX, ATY, ASX, and ASY to 22B.

Reference numeral 26 is a sample, and the voltage waveform and SEM (Scanni
ng Electron Microscope) images are observed.

Reference numeral 27 denotes a monitor, which displays the crossover image, SEM image, etc. of the electron beam 21a based on the image acquisition data from the secondary electron detector 24A on a CRT (Cathode Ray).
Tube) This is what is displayed on the screen. Note that the crossover image will be explained with reference to FIG.

FIGS. 4(a) and 4(b) are explanatory diagrams of an alignment coil according to an embodiment of the present invention, and FIG. 4(a) shows a functional diagram of Tχ and TY of the tilt coil.

In the same figure (a), the alignment coil is the electron gun 21
The center axis of the electron beam is aligned with a straight line connecting the centers of a pre-lens and a condenser lens (not shown), which are provided directly under the anode of It is a coil. The alignment coil 22A includes a pair of tilt coils Tx and TV and a pair of shift coils sx and sy. The tilt coils TX and TV have the function of changing the direction of the electron beam 21a without changing the position of the electron gun 21.

Thereby, the electron beam 21a that has deviated from the optical axis O can be returned to the optical axis O.

FIG. 4B is a functional diagram of the shift coils SX and SY, which have the function of virtually changing the position of the electron gun 21 using the pre-aperture 21c as a fulcrum.

51F (a) to (c) are crossover images of the electron beam according to the embodiment of the present invention, in which the crossover image of the electron beam 21a reaching the beam irradiation area A and the electron gun 2 are shown.
The relationship with the filament current of 1 is shown.

FIG. 5A shows a crossover image of the electron beam 21a when the filament current of the electron gun 21 is maximized. In the crossover image, secondary electrons and reflected electrons 1b from the beam irradiation area A are detected by the secondary electron detector 24A, the detection signal is subjected to analog/digital conversion processing, and the monitor 27 is generated based on the image acquisition data. This is an image of the irradiation shape of the electron beam 21a.

Note that (b) and (c) of the same figure show the electron beam 21 when the filament current of the electron gun 21 is adjusted and gradually decreased.
The cross-over image of a is shown.

The crossover image shows that when the filament current is reduced,
Crystal structures such as tungsten hairpin filaments and lanthanum hexapolide (LaB) filaments appear. For example, it is a quincunx cross section. By determining the coordinates of the center of gravity of this quincunx-shaped irradiation position, alignment adjustment processing can be performed from the start of activation of the device.

In this manner, according to the electron beam device according to the embodiment of the present invention, the electron beam 21a that reaches the beam irradiation area A after the device is started, and the secondary electrons or reflected electrons 21b from the beam irradiation area A. Based on this, the alignment drive circuit 22B is provided with a control calculation 1!125A that outputs a plurality of alignment control '17B theta ATX, ATY, ASX, ASY+7) feedback.

Therefore, even if the internal conditions of the electron optical system change due to an overhaul of the device, the alignment coil 22A can be adjusted to the actual environmental conditions immediately after starting the device without relying on manual adjustment processing. Feedbank control enables automatic alignment adjustment of the electron beam to the optical axis with good reproducibility.

This eliminates the need for manual adjustment of the alignment coil by a skilled person, making it possible to achieve complete automation.

Next, an automatic electron beam alignment method according to an embodiment of the present invention will be described with supplementary explanation of the operation of the apparatus.

6 to 8 are flowcharts of an electron beam automatic alignment method according to an embodiment of the present invention, and FIG. 9 shows an explanatory diagram supplementing the automatic alignment method.

FIG. 6 shows a tilt coil TX according to an embodiment of the present invention,
A flowchart of coarse adjustment control by TY is shown.

In the figure, first, step P1 is started when the device is started.
Shift coils sx, sy and tilt coils TX, T
V alignment control data AT, ATY, ASX,
Initial value of ASY=ASX4. ．． iL, ASY,,i
, ATXi11+t, ATYt, ltt, AS
X-1la, ASY-, la, ATX
,I, ,ATY, ,are set. At this time, the control computer 25A outputs the beam control signal BS to the electron gun control circuit 25B, and the four registers RTX, RTY, R3X,
RTYtm applicable data ATX, ATY, ASX, A
Set SY. Furthermore, the contents of the beam control signal BS are as follows:
It controls the electron gun control circuit 25B so that the filament current of the electron gun 21 is maximized.

Next, an alignment scan is started in step P2. At this time, four D/A converters DTXDTY DS
From X, DTY, 80 data ATX, ATY
ASX and ASY are digital/analog converted, and a pair of tilt coils TX and TY and a pair of shift coils SX
, SY are driven, and the electron beam 21a moves on a straight line connecting the centers of the Brilens and the condenser lens.

Next, in step P3, the initial value=ASXi-;z.

ASY6-=t, ATXL, 14z, ATY11l
it, ASX-a ASV41Il, , ATX
, l, a, An image of the electron beam 21a is acquired by ATV-+. At this time, secondary electrons and reflected electrons ib from the beam irradiation area A are detected by the secondary electron detector 24A, and the detection signal is subjected to analog/digital conversion processing by the signal processing circuit 24B. and is stored in the image memory 24C.

Next, in step P4, calculation processing of the center of gravity position of calculation of the peripheral distribution is performed. Here, the control computer 25A reads image acquisition data from the image memory 24C and displays on the monitor 27 a crossover image of the electron beam 21a that has reached the beam irradiation area A (see FIG. 9(a)). In FIG. 9(b), the control computer 25A calculates the coordinates of the center of gravity of the electron beam 21a from the crossover image. At this time, the barycenter coordinate value calculation process is performed, for example, by adding the luminance of each pixel of the image acquisition data acquired from the beam irradiation area A in the X direction and the Y direction, and calculates the peripheral distribution data PREF (x). , PIIIEF (y)
given as. In the embodiment of the present invention, the X-axis peripheral distribution data of the electron optical system PREF (x) −250
, Y-axis peripheral distribution data PREF (:V) = 2
The center of gravity of the electron beam 21a is located at the intersection of the electron beams 20 and 20.

This data PREF (x), PREF ()
') to represent the coordinates of the center of gravity of the electron beam 21a, the center of gravity position of the electron beam 21a on the Y axis is given by, and the center of gravity position of the electron beam 21a on the Y axis is given by, respectively.

Furthermore, in step P5, the difference numerator (ATV) between the center position of the CRT screen and the center of gravity position of the crossover image is calculated. At this time, set the center coordinates of the CRT screen (Xo, Yo
), the evaluation of the difference numerator (ATV) between the center position of the CRT screen and the center of gravity position of the crossover image is T (ATX, ATV) = (Xo-PREF
(x) ) ”+ (Yo-PREF (y) )t
It is carried out based on.

The difference numerator (ATV) in this case is the amount by which the central axis of the electron beam 21a deviates from the straight line connecting the centers of the Brilens and the condenser lens due to the environmental conditions inside the lens barrel of the device. .

Furthermore, the evaluation amount T (ATV) when no crossover image appears on the CR7 screen is set in advance at the position farthest from the center position of the CRT screen.

Next, in step P6, the alignment control data ATV is updated. In this update step, the initial value of alignment control data ATV -ATYi,it, ATV・96
The interval is updated in a predetermined step of 1/n, and this n
Please set in advance (.

After that, in step P7, the alignment control data ATV
>ATY, performs the determination process of 11a. At this time, the updated alignment control data ATV is the initial value ATY,
, d (No), the process moves to step P8 and continues the image acquisition process. If it is larger than the initial jlJ value ATV-a (YES), step P9 is performed one more time.

In step P9, the evaluation value Tsav (ATX, ATV) -T (AT
Compute the minimum value of V). The evaluation value Tsav at which the difference numerator (ATV) between the center position of the CRT screen and the center of gravity position of the crossover image is the smallest is set as the optimum value.

In addition, alignment control data AT at step PIO
Performs update processing of X. In this update step, the initial value of alignment control data ATX=ATXi, 1tATX-
-a is updated in a predetermined step of 1/n, and this n is set in advance.

Then, the alignment control data AT at step pH
Compare X>ATX-a. At this time, alignment control data A? If x is smaller than the initial value ATX-y (NO), the process moves to step P8 and the image acquisition process is continued. If it is larger than the initial value ATX--a (YES), the process moves to step P12.

In step P12, the minimum value Tl of the evaluation value Tssv (ATX, ATV) of the alignment control data ATX is determined.
1lin and alignment control data ATX and ATV.

Thereafter, in step P13, a process is performed to determine whether the convergence value TSo>Twin. At this time, the convergence value TSo is the evaluation value T S
If it is larger than the minimum value Tm1n of AV (NO),
The process moves to step P14. Also, it is the evaluation value TsA
If it is smaller than the minimum value T111n of v (YES), the process moves to step P17.

Therefore, in step P14, the alignment control data AT
X. A process is performed to reduce the update step of the ATV, and the minimum step is determined in step P15. At this time, if the update step of alignment control data ATX, ATV is not the minimum value (No), step P1
6, the alignment control data ATX, AT
Initial value = ATX, centered on V, 1. , ATV=-i
t, ATX-11a, and ATV-1,a, and narrow the search range.

Moreover, if it is the minimum value (YES), proceed to step P3 and initial value=ATχ;,,tt ATY
An image of the electron beam 21a is acquired at r-rt, ATX, I, a, ATY, y.

Note that in step P13, the convergence value Tso is changed to the evaluation value TSA
If it is smaller than the minimum value TVin of V (YES),
In step P17, optimal alignment control data ATXSAV = AT is supplied to the tilt coils TX and TY.
X, ATYsAv-ATV can be obtained.

As a result, the data ATXsav = ATX,
ATYSAV = Save ATV and shift coil SX, S
Y alignment control data ASXsAv = ASX
, ASYsAv=ASW search processing is started.

FIG. 7 shows shift coils SX and S according to an embodiment of the present invention.
12 shows a coarse adjustment control flowchart according to Y.

In the figure, step P continues from the previous step P17.
At step 18, an irradiation process is performed to gradually lower the filament current to a specified value. At this time, alignment control data ATXSAV" = ATX, A is provided to the tilt coils TX and TY.
By supplying TYSAV'=ATV, a crossover image of the electron beam 21a appears on the surface of the monitor 27 (see FIG. 5(a)). The content of the beam control signal BS is to control the electron gun control circuit 25B so as to gradually lower the filament Eft flow of the electron gun 21.

Next, in step P19, initial value = ASX, □, AS
Yt-iz, ATX;+1;t, ATYtIl=t
, ASX-a, ASY--a, ATX
--a, an image of the electron beam 21a is acquired by ATY a fla.

Next, in step P20, calculation processing of the center of gravity position of calculation of the peripheral distribution is performed. At this time, similarly to step P4, the control computer 25A reads the image acquisition data from the image memory 24C, and the electron beam 2 that has reached the beam irradiation area A
The crossover image 1a is displayed on the monitor 27 (see FIG. 9(a)). Further, in FIG. 9(b), the control calculation 1125A calculates the barycentric coordinates of the electron beam 21a from the crossover image. At this time, the barycentric coordinate value calculation process is performed using, for example, the value obtained by adding the luminance of each pixel of the image acquisition data acquired from the beam irradiation area A between the X direction and the X direction, using the peripheral distribution data PREF ( X)PR
Given as EF (y). This data PREF
Using (X) and PREF (y) to indicate the coordinates of the center of gravity of the electron beam 21a, the center of gravity position of the electron beam 21a on the Y axis and the center of gravity position of the electron beam 21a on the Y axis are given by, respectively. .

Furthermore, in step P21, a difference S (ASY) between the center position of the CRT screen and the center of gravity position of the crossover image is calculated. The calculation process at this time is similar to step P5, and the center coordinates of the CRT screen are set to (X.

Yo), then CRTi! The evaluation of the difference numerator (ASY) between the center position of the ii plane and the center of gravity position of the crossover image is as follows: S (ASX, ASY) = (Xo-PREF
(x))”+ (Yo-PI?EF (y))”
It is carried out based on.

In addition, in step P22, alignment control data ASY
Update. In this update step, the initial value of alignment control data ASY = ASYi, , iL, ASY
l, - shall be updated in a predetermined step of 1/n,
This n is set in advance.

Next, in step P23, ASY>ASY, □ is determined.

At this time, if the updated alignment control data Asy is smaller than the initial value Asy, □ (NO), the process moves to step P24 and the image acquisition process is continued. If it is larger than the initial value AS'i-a (YES), the process moves to step P25.

In step P25, the evaluation value 5sAv (ASX, ASY) of the alignment control data Asy = S (A
SY) is calculated. The evaluation value s sAv at which the difference S (ASY) between the center position of the CRT screen and the center of gravity position of the crossover image is the smallest is set as the optimum value.

Next, in step P26, alignment control data ASX
Update processing. In this update step, the initial value of alignment control data ASχ=ASX,□,.

It is assumed that the interval between ASX- and a is updated in a predetermined step of 1/n, and this n is set in advance.

Furthermore, in step P27, alignment control data A
SX > A SX, 1m comparison processing is performed. At this time, the alignment control data Asχ is the initial value ASX, .
If it is smaller than 4 (No), the process moves to step P24 and the image acquisition process is continued. That is the initial value ASX
If it is larger than ,A, (YES), then Ste, 7BP
Move to 2B.

In step P28, the minimum value S of the evaluation value 5sav CASX, ASY) of the alignment control data ATX is determined.
Perform value calculation processing for win, ASX, and ASY.

Thereafter, in step P29, it is determined whether the convergence value Sso>5w1n. At this time, the convergence value Sso is the evaluation value S S
If it is larger than the minimum value S+++in of AW (No), the process moves to step P30. Also, it is the evaluation value S
If it is smaller than the minimum SAV value S win (YES
), the process moves to step P33.

Therefore, in step P30, the alignment control data AS
Processing is performed to reduce the update steps of X and ASY, and the minimum step is determined in step P31. At this time, if the update step of alignment control data ASX, ASY is not the minimum value (NO), step P
32 and alignment control data J) ASX, A
Initial value = ASX, centered on SY, 11. , ASYH,
Update lHz, ASX,y, ASY-na, and narrow the search range.

If it is the minimum value (YES), proceed to step P19 and set the initial value -ASX,..., ASY+-
+t, ASX,,,a, An image of the electron beam 21a is acquired with ASY-R4.

Note that in step P29, the convergence value Tso is the evaluation value S SA
If it is smaller than the minimum value S win of V (YES), in step P33, the optimum alignment control data ASXsAv =A to be supplied to the shift coils SX and SY4 is
SX, ASYsav = ASY can be obtained.

As a result, the data ASXSAv=ASX, AS
Y.S.A.

= Save ASY and set each coil TX, TV, SX SY
, alignment control data ATXsAv -ATXA
TYSAV=ATY, ASXsAv=ASX,
Using ASYsAv=ASY, the process proceeds to fine adjustment processing.

FIG. 8 shows a fine adjustment control flowchart according to an embodiment of the present invention.

In the figure, step P continues from the previous step P33.
At step 34, the filament current is returned to its original value. At this time, the control computer 25A outputs a beam control signal BS to the electron gun control circuit 25B. The content of the beam control signal BS is to control the electron gun control circuit 25B so that the filament current of the electron gun 21 is maximized (or rated value).

Furthermore, the alignment scan is finished in step P35, and the initial values for the fine algorithm are set as ATXsav, ATYSAV, ASXs in step P36.
Set as avASYs□.

After that, the fine adjustment algorithm is started in step P37. At this time, alignment control data ATX
sav −ATX, ATYsav = ATY,
Fine alignment adjustment processing is performed on each coil TXTY, SX, and SY based on ASXSAV-ASX, ASYsiv =A5Y. Further, the electron beam 21a reaching the beam irradiation area A is detected by the Faraday tube 23A, and the beam current IB is detected by the A/D converter 23B.
is A/D converted and outputted to the control computer 25A as beam current data BD. This allows the electron gun control circuit 2 to reach the maximum number of electron beams 21a.
5B is controlled.

In addition, the inventors of the present invention first issued a patent for Stenbu P37.
(Japanese Patent Application No. 1-51199), the process is continued like the electron beam alignment method using the semi-automatic adjustment method disclosed in Japanese Patent Application No. 1-51199, and the process moves on to measurement operations, etc.

In this way, according to the automatic alignment method according to the embodiment of the present invention, as shown in FIGS. 6 and 7, first, in step PI, the electron beam 21a is deflected to the beam irradiation area A, and In step P3, the beam irradiation area A
A crossover image (irradiation shape image) of the electron beam 21a is image acquired based on the secondary electrons or reflected electrons 11b from the tilt coil TX in steps P4 to P17.
, TY alignment control data ATXSAV = A
TX, AT'l'5AV=ATV is required.

Further, in step P18, the filament current of the t-hanging beam 21a is reduced through control processing (irradiation adjustment processing), and in steps P19 to P33, alignment control data ASXsaw -ASX of shift coils sx and sy is performed based on the irradiation adjustment processing and image acquisition processing. , ASYsAv = ASY
is determined, and rough alignment adjustment processing (first alignment 1M adjustment processing) is performed to align the electron beam 21a near the optical axis reference point 0 of the electron optical system. Thereafter, in step P34, the filament current of the electron beam 21a is increased based on the first alignment adjustment process (re-irradiation adjustment process), and further, in step P3
5 to P37, fine alignment adjustment processing (second alignment adjustment processing) is performed to align the electron beam 21a with the optical axis reference point O of the electron optical system.

Therefore, compared to the conventional electron beam alignment method in which a semi-automatic adjustment method was introduced as previously patented by the present inventors (Japanese Patent Application No. 1-51199), alignment adjustment processing is performed using a so-called learning function. be able to.

That is, in advance, the measurer aligns the electron beam 21a with the optical axis of the electron optical system, obtains optimal alignment adjustment data, and aligns the pair of tilt coils TX TY and 1.
Alignment coil 2 such as a pair of shift coils SX and SY
Compared to the method of automatically adjusting 2A based on correction data AD, the electron beam 21a may be moved to a local point off the optical axis O of the electron optical system due to the influence of dirt or floating charges inside the device. Actual environmental conditions such as when there is a risk of convergence of the electron beam 21a are controlled to feed a pair of tilt coils TX, TY, a pair of shift coils SX, SY, etc. using alignment control data ATχ, A.
Automatic adjustment processing can be performed based on TY, ASχ, and ASY.

This makes it possible to adjust the alignment of the electron beam 21a to the optical axis reference point of the electron optical system with good reproducibility based on the environmental conditions immediately after startup on the day the device is used.

In the embodiment of the present invention, the method of performing the second alignment adjustment process based on the first alignment adjustment process has been described, but after performing the image processing of the crossover image of the electron beam 21a, Even if the electron beam 21a is aligned to the optical axis reference point O of the electron optical system, it is possible to automatically control it at the same time as the start of the device. According to the apparatus of the invention, the control means is provided for feedback-outputting a plurality of alignment control data to the alignment means based on the electron beam that reaches the beam irradiation area after activation and the secondary electrons or reflected electrons from the area. It is being

Therefore, even if the internal conditions of the electron optical system change due to an overhaul of the device, the actual environmental conditions can be grasped immediately after the device starts up, without relying on manual adjustment of the alignment coil. The feedback can be controlled.

Further, according to the alignment method of the present invention, the first. Second alignment adjustment processing is being performed.

Therefore, compared to the conventional electron beam alignment method that introduced a semi-automatic adjustment method that the present inventors previously applied for a patent (Japanese Patent Application No. 1-51199), it is possible to perform alignment adjustment processing using a so-called learning function. I can do it.

This eliminates the need for manual adjustment of the alignment coils by a skilled person, and automatically adjusts a pair of tilt coils, a pair of shift coils, etc. based on alignment control data with good reproducibility immediately after starting the device. becomes possible.

This makes it possible to completely automate the alignment adjustment process, which greatly contributes to improving the functionality of scanning electron microscopes, electron beam testers, and the like.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of an electron beam device according to the present invention, Fig. 2 is a principle diagram of an electron beam automatic alignment method according to the present invention, and Fig. 3 is a principle diagram of an electron beam device according to an embodiment of the present invention. FIG. 4 is an explanatory diagram of an alignment coil according to an embodiment of the present invention; FIG. 5 is a plan view of a crossover image according to an embodiment of the present invention; FIG. 6 is a diagram of a cross-over image according to an embodiment of the present invention; Tilt coil TX according to the embodiment
FIG. 7 is a flowchart of coarse adjustment control using shift coils sx sy according to an embodiment of the present invention; FIG. 8 is a flowchart of fine adjustment control according to an embodiment of the present invention; FIG. is a supplementary explanatory diagram for determining barycentric coordinates from a crossover image according to an embodiment of the present invention, FIG. 10 is a configuration diagram of an electron beam device according to a conventional example, and FIG. 11 is an alignment diagram of an electron beam according to a conventional example. 3 is a flowchart of the method. (Explanation of symbols) 11... Electron gun, 11a... Electron beam, 11b... Secondary electron or reflected electron, 12... Alignment means, 13... First detection means, 14... - Second detection means, 15... Control means, A... Beam irradiation area, ATχ, ATY, ASX, ASY... Alignment control data, 0... Optical axis reference point.

Claims (3)

[Claims] (1) At least an electron gun (11) that emits an electron beam (11a) to the beam irradiation area (A), an alignment means (12) that adjusts the irradiation direction of the electron beam (11a), and the beam irradiation area (A). First detection means (13) for detecting the electron beam (11a) that has reached the irradiation area (A)
, a second detection means (14) for detecting secondary electrons or reflected electrons (11b) from the beam irradiation area (A), the electron gun (11), an alignment means (12), a first A control means (15) for controlling input/output of the detection means (13) and the second detection means (14) is provided, and the control means (15) controls the beam irradiation area (A) after activation.
A plurality of alignment control data (ATX, ATY, ASX , ASY)
An electron beam device characterized by outputting feedback. (2) Electron beam (11a) to beam irradiation area (A)
an output deflection process, and an image acquisition process of an irradiation shape image of the electron beam (11a) based on the secondary electrons or reflected electrons (11b) from the beam irradiation area (A); 1. An automatic electron beam alignment method, characterized in that the electron beam (11a) is aligned to an optical axis reference point (O) of an electron optical system based on the alignment adjustment process. (3) In the automatic electron beam alignment method according to claim 2, after the image acquisition process, an irradiation adjustment process of the electron beam (11a) is performed, and the electron beam (11a) is adjusted based on the irradiation adjustment process and the image acquisition process. Beam (11a)
A first alignment adjustment process is performed to align the electron beam near the optical axis reference point (O) of the electron optical system, and a re-irradiation adjustment process for the electron beam (11a) is performed based on the first alignment adjustment process. , based on the re-irradiation adjustment process, the electron beam (11a) is directed to the optical axis reference point (O
) A method for automatically aligning an electron beam, the method comprising performing a second alignment adjustment process for positioning the electron beam.