JPH0450732B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention effectively adjusts the bias conditions of an electron gun made of a single crystal chip such as lanthanum hexaboride in an aperture image projection type electron beam device using Keller illumination. This invention relates to an electron beam device that can be optimized for.

[Prior Art] A tungsten hairpin type electron gun has conventionally been generally used in an aperture image projection type electron beam device using Keller illumination, but recently there has been a demand for improved performance such as higher brightness. Various attempts have been made to use single crystal chip type materials such as lanthanum hexaboride (LaB ₆ ). As shown in Fig. 1, this type of single crystal chip has a shape in which the tip of a rectangular parallelepiped chip is machined into a conical shape with a half-vertical angle θ, and the top of the cone is machined into a spherical shape with a radius of curvature r. It is used by applying a predetermined bias voltage between the single crystal chip and Wehnelt in a heated state. The electron beam is emitted centering on the tip of the single crystal chip, and the characteristics of the electron beam generally depend on the crystal axis orientation of the single crystal chip, the radius of curvature r of the tip of the chip, its half-vertex angle θ, and the like.

FIG. 2 shows the relationship between the bias voltage V applied between a <100> single crystal LaB ₆ chip and Wehnelt and the electron beam brightness B, using the chip temperature T as a parameter. Note that the chip temperature T is adjusted by the heater current. As shown in this characteristic, the maximum brightness B _nax of the electron beam is
The higher the chip temperature T (T1<T2<T3), the higher the value, but it can be obtained with a constant bias voltage V2. Further, when the bias voltage is increased to V4 (>V2), the brightness converges to a constant brightness B _cpost although there are some differences depending on the chip temperature T.

Figures 3 a to d show that the bias voltage mentioned above is V1 ~
This is a schematic diagram of the electron beam emission pattern (intensity distribution) in V4. As shown in this schematic diagram, when the bias voltage applied to a single-crystal chip is as low as V1, V2 (<V3), its emitters will change as shown in Figure a and b, respectively, reflecting the crystal orientation of the chip. The pattern appears as a 4-fold symmetrical pattern. Furthermore, when the bias voltage exceeds V3, which is approximately the intermediate value between the voltage V2 that obtains the maximum brightness B _nax and the voltage V4 that obtains the constant brightness B _cpost , the current intensity at the center increases as shown in Figure 3c. This results in an emission pattern that exhibits a slightly low but approximately uniform intensity distribution. When the bias voltage exceeds V4, the emission pattern exhibits Gaussian distribution characteristics as shown in d of the same figure. Incidentally, the relationship between this bias voltage V and the emission pattern hardly depends on the above-mentioned chip axis direction, r, and θ.

However, the bias voltage V applied between the single crystal chip and Wehnelt is normally provided by passing an emission current through a bias resistor inserted between the single crystal chip and Wehnelt. And the adjustment of the bias voltage V is
This is done by varying the bias resistor R mentioned above.

However, when the bias resistor R is varied in this manner, it is undeniable that the emission current changes considerably. Therefore, when the bias resistance is varied to adjust the bias voltage V, the electron beam brightness B changes differently depending on the chip temperature T at that time, as shown in FIG. 4 due to the change in the bias voltage. Show characteristics. In other words, the control value of the bias resistor R for setting an appropriate bias voltage V largely depends on the chip temperature T, and even when the same control value is given,
The electron beam brightness becomes completely different depending on the chip temperature T at that time.

Incidentally, the bias resistors R1 to R4 shown in FIG. 4 when the chip temperature is T3 correspond to the bias voltages V1 to V4 shown in FIG. 2 described above, respectively. In this case, the electron beam emission patterns for the bias resistors R1 to R4 are as shown in FIGS. 3a to 3d, respectively.

Here, between the bias resistor R and the bias voltage V, if the emission current is I, then V=IR
However, when the bias resistance R is changed, the emission current I also changes, and the emission current also changes depending on the chip temperature T. Therefore,
When the chip temperature T changes, the bias resistance adjustment value changes.
This means that the above-mentioned relationship between R1 to R4 and the emission pattern no longer holds true. Therefore, when the bias voltage V applied to the single crystal chip is variably set by adjusting the bias resistor, it is necessary to change the adjustment conditions each time the chip temperature T changes. For this reason, in an electron beam device incorporating a single-crystal chip as an electron gun, it is extremely difficult to adjust the bias resistance R to properly set the bias conditions for the single-crystal chip. It was difficult to optimize.

Note that the data in FIGS. 2 and 4 are obtained when the acceleration power source (high-voltage power source 3) is held constant in an electron optical system as shown in FIG. 5, which will be described later.
The brightness was measured when the bias resistance R was varied (bias resistance circuit 5 was adjusted). More specifically, the data in FIG. 4 is obtained by measuring the brightness when the bias resistor R is varied while the chip temperature is held constant (for example, T1) by controlling the heater current. Furthermore, the chip temperature is T2, T3,
Perform the above measurements by changing T4 sequentially. The change in brightness with respect to the bias resistance R is plotted. The data shown in FIG. 2 was measured in the same manner as above, and the change in brightness versus bias voltage V was plotted.

[Problems to be Solved by the Invention] In an electron beam device incorporating a single crystal chip as an electron gun, it is necessary to appropriately set the bias conditions for the single crystal chip that determine the electron beam characteristics. It was extremely difficult.

The present invention was made in consideration of these circumstances, and its purpose is to provide a single crystal incorporated as an electron gun in order to provide the uniformity of electron beam intensity and brightness necessary for Keller illumination. It is an object of the present invention to provide a highly practical electron beam device in which bias conditions for a chip can be easily set.

[Example] Hereinafter, an example of an electron beam apparatus according to the present invention will be described with reference to the drawings.

FIG. 5 schematically shows the electron optical system and measurement control system of this apparatus. Referring to FIG. 5, the general configuration of this device will first be described.

Electron gun 1 is lanthanum hexaboride (LaB ₆ )
It is composed of a single crystal chip 1a and a Wehnelt chip 1b, and is arranged opposite to the anode 2. This electron gun 1 is energized by applying a high voltage between it and the anode 2 by a high voltage power source 3. However, the above electron gun 1
The single crystal chip 1a is electrically heated by a heater power supply 4 to set the chip temperature, and the bias conditions (bias voltage, bias resistance) is set. In this manner, the electron gun 1 is driven and an electron beam is emitted from the single crystal chip 1a. In addition, a current detector 6 inserted between the high voltage power supply 3 and the ground
is for detecting the emission current I _R of the electron gun 1. The driving state of the electron gun 1 is monitored by this emission current I _R.

A blanking plate 7 is disposed opposite to the position of the first crossover image A of the electron beam emitted by the electron gun 1, and blanking control of the electron beam for the electron optical system described below is performed.

This first crossover image A is focused on the deflection center position of the shaping deflector 11 by an illumination lens 9 having an anti-scattering aperture 8, and a second crossover image C is created. A deflection electrode 11 for beam shape variable control provided at the position of the second crossover image C controls the deflection of the first aperture image B formed on the aperture 10. The controlled first aperture image B is transmitted to a second beam shaping aperture 1 through a projection lens 13 having an aperture 12.
Projected to 4. The aperture image B projected onto the second beam shaping aperture 14 overlaps with the aperture 14 to form a second aperture image D having a variable beam cross-sectional shape.

Further, the projection lens 13 has the aperture 1
A third crossover image E is formed at a position below 4. Reduction lens 16 with aperture 15
The image F of the third crossover E is transferred to the anti-scattering objective aperture 1 included in the objective lens 17.
At the same time, a third aperture image G, which is a reduced aperture image D formed on the second beam shaping aperture 14, is formed on the sample surface through the objective lens 17. 19 as a fourth aperture image H.

With such an optical system, the electron beam is emitted from the electron gun 1 and the first and second beam shaping apertures 1
An aperture image of the electron beam whose cross-sectional shape has been shaped by 0 and 14 is formed on the sample surface 19 via the objective lens 17, thereby forming a Keller illumination system for the electron beam on the sample surface 19. .

Therefore, the reduction lens 15 and the objective lens 17
The deflection electrode plate 20 is arranged oppositely between D/
It is driven by an inverting amplifier 22 and a non-inverting amplifier 23 which operate upon receiving the output of the A converter 21. By this deflection electrode plate 20, the third
The aperture image G is deflected, and the position of electron beam irradiation on the sample surface 19 by the objective lens 17 is variably set. By variable control of the electron beam irradiation position on the sample surface 19, for example, scanning of the electron beam irradiation position is performed.

Now, an electron beam intensity distribution measuring device (first measuring system) is provided at the position of the sample surface 19 of this apparatus configured with the Keller illumination system as described above. This electron beam intensity distribution measuring device uses, for example, a thin gold wire 24 stretched in a cross shape for measuring the intensity distribution and beam size of an electron beam, and electrons scattered by this thin wire 24 with a large scattering angle. an aperture 25 that absorbs the beam, and a Faraday cup (second measurement system) 26 that detects the electron beam current that is not blocked by the thin gold wire 24.
It is composed of However, the electron beam current detected by the lever measuring device (Faraday cup 26) is amplified by the sense amplifier 27, then converted into digital information via the A/D converter 28, and then sent to the interface 33, which will be described later. It is given to the computer 34 via the computer 34.

Further, the projection lens 13 and the reduction lens 16
Each of the apertures 12 and 15 detects the current of the electron beam blocked by the aperture as information on the axis deviation of the electron beam. The beam currents detected by these apertures 12 and 15 are amplified by sense amplifiers 29 and 30, respectively, and then amplified by A/D converters 31 and 3.
2 is converted into digital information and provided to the computer 34 via the interface 33.

The computer 34 via the interface 33
Information on the axis deviation of the electron beam detected by the apertures 12 and 15 and output from the A/D converters 31 and 32, and the Faraday cup 2
6 and output from the A/D converter 28, and information on the emission current of the electron gun 1 detected by the current detector 6 are respectively taken in, and the information is applied to the electron optical system described above. Perform a series of control actions.

That is, this computer 34 controls and drives the blanking plate 7 and deflection plate 11 described above in accordance with preset program information to perform blanking control and beam shape shaping control. Further, the computer 34 outputs electron beam scanning control information to the D/A converter 21 via the interface 33, energizes the deflection electrode plate 20, and controls exposure by a series of electron beam deflection scans. conduct.

Further, the computer 34 controls the operating conditions of the variable bias resistance circuit 5 and the heater power source 4, as described later, in accordance with the various information input as described above. By controlling the bias resistance variable circuit 5 and the heater power source 4, the operating conditions of the electron gun 1 are controlled to obtain sufficient electron beam characteristics for Keller illumination of the electron optical system, and the optimum settings thereof are performed.

Further, the computer 34 connects the D/A converters 35 and 3 via the interface 33 according to the information (information on axis deviation) obtained from the apertures 12 and 15.
Control data is given to 6, 37, 38, and 39, respectively. These D/A converters 35, - 39 are connected to the blanking plate 7 of the electron optical system, the first beam shaping aperture 10, and the projection lens 13 via drive amplifiers 40, 41, 42, 43, and 44, respectively. , the second beam shaping aperture 14, and the deflection coil 4 provided at each position of the reduction lens 15.
5, 46, 47, 48, and 49. These deflection coils 45, 46, 47, 4
By driving 8 and 49, the center axis of the electron beam is aligned with respect to the optical system.

Next, the basic principle of setting the bias conditions for the single crystal chip 1a in the apparatus thus constructed will be explained.

It is now assumed that the central axis of the electron beam from the electron gun 1 is aligned with the electron optical system, and that the axis within the optical system is also aligned. Under these conditions, the electron beam is deflected and scanned to form an aperture image H as shown in FIG.
For example, if the change in beam current at this time is detected by Faraday cup 26,
A detection result of the electron beam current I as shown in FIG. b is obtained. In Fig. 6a, in order to avoid unnecessary complication in the explanation, the electron beam is scanned only in the x direction, and the electron beam current is Although an example is shown in which the beam current I is measured, the beam current I is similarly detected when the electron beam is deflected and scanned in the y direction. Further, here, a portion of the fourth aperture image H where the current intensity is high is schematically shown as a region K, and the aperture image H is shown assuming the largest size.

Here, FIG. 6b shows the aperture image H of the electron beam.
As the electron beam deflects and scans, the aperture image H of the electron beam is The state is shown in which the aperture image H is gradually blocked by the thin gold wire 24 until the entire aperture image H is blocked by the thin gold wire 24.

Therefore, if the aperture image H of the electron beam is of the emission pattern under the condition of the bias voltage V2 that obtains the maximum brightness B _nax described above, then the portion of the aperture image H that is blocked by the thin gold wire 24 is Due to the difference in current intensity, as the thin gold line 24 of the aperture image H traverses, a beam current I is detected that shows uneven changes as shown by the solid line in FIG. 6b. By the way, if the beam intensity distribution of the aperture image H is uniform, the thin gold wire 2
Since there is a proportional relationship between the cross-sectional area of the electron beam blocked by 4 and the current intensity there, Figure 6b
A linear change characteristic of the beam current I as shown by the broken line is detected.

Next, in order to evaluate the beam intensity distribution from the beam current I detected in this way, the beam current I detected as described above is used by the computer 34.
The change in is differentiated by the scanning movement distance x of the electron beam, and the information [dI/dX] is calculated as intensity distribution information as shown in FIG. 6c. Furthermore, this information [dI/
dX] is differentiated to calculate the information [d ² I/dX ² ] as shown in d of the figure.

In this calculation, if the deflection speed of the electron beam is υ, the scanning movement distance x is υt (t: time)
Needless to say, this is shown in . Therefore, in the calculator 34, the deflection scanning speed υ is made constant, and the time t
Alternatively, differential calculation processing may be performed regarding .
In addition, such signal calculation processing is performed not only in the x direction but also in the y direction, and [dI/dy]
and [d ² I/dy ² ] information is also obtained.

Next, the unevenness of the characteristic [dI/dX] ([dI/dy] in the y direction) is compared and determined.
If this characteristic has an uneven structure, this means that crystal plane anisotropy appears in the emission pattern as shown in Figures 3a and b, which is caused by the work function of the LaB ₆ single crystal chip 1a. It is shown that. Therefore, in this case, by increasing the bias voltage to the electron gun 1 (single crystal chip 1a), the current intensity of the emission pattern can be made approximately uniform as shown in FIGS. 3c and 3d. I understand that it is necessary.

For example, if the beam intensity distribution of the aperture image H is uniform and there is no unevenness in the [dI/dX] characteristic as described above, the differential characteristic [d ² I/dx ² ] is shown in Figure 6 d.
It becomes zero in the region x0 to x1 as shown by the middle broken line. On the other hand, if there are irregularities in the [dI/dX] characteristic, the differential characteristic [d ² I/dx ² ] will have large irregularities whose polarity changes between positive and negative within the above range.
Therefore, find the functional form of [d ² I/dx ² ] above, and calculate the area
By controlling the bias resistance variable circuit 5 and adjusting the bias resistance R so that [d ² I/dx ² ] becomes zero in x0 to x1, unevenness in the [dI/dX] characteristic can be eliminated, and the above-mentioned Faraday cup It is possible to make the change in the electron beam intensity I detected at 26 linear, thereby making it possible to make the intensity distribution of the electron beam substantially uniform. In addition, the above x0 is [d ²
I/dx ² ] is the position where a zero value is detected second from the first (left side in the figure), and x1 is the position where a zero value is detected second from the last (right side in the figure).

Similarly, the bias resistance R is adjusted in the y direction according to the characteristic (functional form) of [d ² I/dy ² ]. By adjusting the bias resistor R in this manner, the electron beam intensity distribution (brightness) can be made uniform.

By the way, as mentioned above, when the intensity distribution is made uniform by adjusting the bias resistor R and the electron beam is irradiated onto the sample surface 19, the brightness β of the electron beam at the shaping aperture 10 is determined by the brightness β at the Faraday cup 26 at that time. The detected electron beam current (the beam current when the entire electron beam is detected by the Faraday cup 26 without being blocked by the thin gold wire 24) _{is Inax} , the cross-sectional area of the electron beam is S, and the objective lens 17 is When the half apex angle of the converged electron beam is α, it is expressed by the following equation.

β=I _nax /{(πα) ² S} Therefore, the beam area S is kept constant, for example, the maximum area
If it is fixed at S _nax , the brightness of the electron beam at the aperture 10 and the beam current I _nax will be in a proportional relationship, so the electron beam current measured at the Faraday cup 26 instead of the brightness β
It is possible to adjust the brightness β of the electron beam at the aperture 10 by manipulating the bias voltage V using I _nax as a control variable.

Therefore, the brightness β under the above conditions is calculated from the beam current I (=I _nax ) detected by the Faraday cup 26 using the calculator 34 according to the above-mentioned relational expression.
Find it at After that, a comparison calculation is made with the brightness β _oeed desired for electron beam irradiation, and when a relationship such as [β>β _oeed ] is obtained, the bias voltage V is increased to obtain the above-described relationship [β=β _oeed ]. The bias voltage V is variably controlled. In other words, since the intensity distribution of the electron beam has already been made uniform, the bias voltage at that time is set higher than the bias voltage V2 that obtains the maximum brightness B _nax (state of V3 in Figure 2). . Therefore, the bias voltage is further increased so that the electron beam brightness decreases (converges) toward a constant brightness B _cpost , and the aperture 10
The brightness β at is adjusted to the desired brightness β _oeed .

Conversely, if the relationship [β<β _oeed ] is obtained, the temperature T of the single crystal chip 1a is increased by variably controlling the heater power source 4, and the intensity B of the electron beam itself is increased. β=β _oeed ]. That is, in this state, the intensity distribution of the electron beam is made uniform, and the bias voltage at this time is the bias voltage V2 that obtains the maximum brightness B _nax .
It is in a state where it is set higher than . Therefore,
Increasing the brightness by adjusting the bias voltage means that the uniform intensity distribution of the electron beam is disrupted. Therefore, after raising the chip temperature itself and increasing its bias voltage so as to obtain the maximum brightness B _nax , the above-mentioned adjustment procedure for making the intensity distribution of the electron beam uniform is repeatedly executed. >β _oeed ], and then adjust the bias voltage to obtain the desired brightness B _oeed .

By adjusting the bias voltage in this manner, it becomes possible to obtain from the electron gun 1 the brightness β _oeed necessary for electron beam exposure.

Incidentally, instead of directly monitoring the bias voltage V applied to the single crystal chip 1a and varying the bias resistor R, thereby adjusting the bias voltage, The bias voltage V may be monitored from the emission current I _R of the crystal chip 1a, and the bias voltage V may be adjusted by variably setting the bias resistor R in accordance with the monitoring result.

By the way, the bias condition settings for the electron gun 1 mentioned above are explained under the assumption that the central axis of the electron beam is aligned with the electron optical system, and that the axis is also aligned within the optical system. did.
However, even if the intensity distribution of the electron beam emitted from the single crystal chip 1a is uniform, if the central axis of the electron beam is misaligned with respect to the electron optical system, the beam current detected from the Faraday cup 26 as described above. Information on the intensity distribution represented by the differential characteristic of I [dI/dx] loses its axial symmetry as shown in FIG. 7a, and a slope occurs in [dI/dx]. In this case,
Figure 7b shows the differential characteristic [d ² I/dx] of the above [dI/dx].
dx ² ], the zero value positions x0 and x1 described above are the same point. In other words, the range in which [d ² I/dx ² ], indicated by the above zero value positions x0 and x1, is zero is itself zero.

Therefore, the computer 34 compares the positions of x0 and x1, and if the positions are the same, it is determined that the central axis of the electron beam has shifted with respect to the electron optical system. In this case, the deflection coil 45 is driven by the energization of the D/A converter 35 by the computer 34, and the [d ² I/dx ² ]
The center axis alignment of the electron beam is controlled so that the distance between zero value points |x0−x1| in is maximized. By maximizing this distance |x0−x1|, the deviation of the central axis of the electron beam emitted from the single crystal chip 1a with respect to the electron optical system is corrected.
The aperture 10 of will receive uniform intensity illumination of the electron beam.

Furthermore, if the alignment within the optical system is poor, the proportion of the electron beam that is blocked by the apertures 12 and 15 in the projection lens 13 and the reduction lens 16 increases. Therefore, as shown in FIG. 8, the computer 34 performs control to maximize (dI/dx) _nax and aligns the optical system in order to correct the axis deviation within the optical system. By this alignment, the electron beam current I measured by the Faraday cup 26 is maximized, and the electron beam current I measured under this condition is equal to the brightness β at the aperture 10 described above.
It is used as the beam current I _nax when calculating.

That is, if the axis alignment in the optical system is poor, the first aperture image B will become the second
will not be correctly projected onto the beam shaping aperture 14 of the projection lens 13, and a portion of it will be blocked by the aperture 12 of the projection lens 13. As a result, the aperture 12 detects the electron beam current equivalent to the amount of electron beam intercepted.
Therefore, in order to make the beam current detected by this aperture 12 zero or minimize it, the deflection coils 46 and 47 are driven and controlled in relation to each other, and the beam current detected by the aperture 12 is adjusted between the first and second beam shaping apertures 10 and 14. The axis of the electron beam is aligned.

Further, if the axis alignment of the objective lens 17 with respect to the second aperture image D is poor, the electron beam current is detected at the aperture 15 in the reduction lens 16 because the aperture 15 blocks the electron beam. Since this electron beam current is not what should originally be obtained if the alignment is perfect, alignment is achieved by driving the deflection coil 48 so that the electron beam current detected by the aperture 15 is zero.

In this manner, the optical system is aligned by driving the deflection coils 46, 47, 48 so as to minimize the electron beam current flowing into the apertures 12, 15.

After the central axis of the electron beam is aligned with the electron optical system and the axis inside the optical system is completed, preparations for setting the bias conditions are completed, and the bias for the electron gun 1 described above is completed. Optimizing adjustments to conditions will be made.

If the bias condition setting for the electron gun 1 described above is summarized including the preparatory processing described above, the processing procedure will be as shown in FIG. 10.

In this processing procedure, first, the single crystal chip 1a is driven under a certain bias condition, the electron beam at that time is deflected and scanned in the x direction, and the Faraday cup 2 is
The process starts with detecting the beam current I of the electron beam at step 6 (step a). Note that although the case where the electron beam is deflected and scanned in the x direction will be described here, the processing procedure is similarly carried out in the y direction.

Next, from the characteristics of the electron beam current I measured in this processing procedure, the computer 34 calculates its differential characteristic [dI/dx] and the characteristic obtained by further differentiating this differential characteristic [dI/dx] [d ² I/dx]. dx ² ] (step b). Then, from this characteristic [d ² I/dx ² ], find the two positions x0 and x1 that take the aforementioned zero value (step c), and determine whether these positions x0 and x1 are the same position. (Step d). Through this determination process, it is determined whether or not the central axis of the electron beam is aligned with the electron optical system as described above. And the above two positions
If x0 and x1 are at the same position and it is determined that the center axis of the electron beam is misaligned with respect to the electron optical system, the distance |x0−x1| is changed by driving the deflection coil 45 as described above. The center axes are aligned so that the center axis is maximized (step e). The alignment of the central axis of this electron beam with respect to the electron optical system is
While repeating the processes of steps a and b described above, the two positions x0 and x0 detected at that time are
This is done by sequentially calculating the distance |x0−x1| from x1.

When the alignment of the central axis of the electron beam with respect to the electron optical system is completed, or because the two positions x0 and x1 are different in the determination process shown in step d described above, the central axis of the electron beam is aligned with the electron optical system. If it is confirmed that the optical system is aligned, then the alignment within the optical system is performed as described above (step f). That is, the deflection coils 46 and 47 are driven so that the electron beam current detected by the apertures 12 and 15 becomes zero or minimum, thereby aligning the axis within the optical system.

Through the above processing procedure, alignment of the central axis of the electron beam with respect to the electron optical system and alignment within the optical system are completed. When this preparatory process is completed, a process for optimizing the bias conditions of the electron gun 1 is started.

This process begins with the steps a, to c described above.
The electron beam is
The beam current I of the electron beam is detected by the Faraday cup 26 in a state where all of the above-mentioned axis alignments have been completed, and from the characteristics of this electron beam current I, the computer 34 calculates its differential. The process starts by calculating the characteristic [dI/dx] and the characteristic [d ² I/dx ² ] obtained by further differentiating this differential characteristic [dI/dx] (step g). Next, it is determined from the above characteristic [d ² I/dx ² ] whether or not there is any unevenness in the characteristic [dI/dx] indicating the intensity distribution of the electron beam (step h), and it is determined whether the intensity distribution of the electron beam is approximately uniform. Check whether it is the same or not.

If this judgment shows that there are irregularities in the characteristic [dI/dx], the bias resistor R is adjusted as described above (step i), and the differential characteristic [d ² I/dx ² ] is The two zero value positions mentioned above
Adjustment is made so that the value of [d ² I/dx ² ] within the range indicated by x0 and x1 becomes zero.

Therefore, when the intensity distribution of the electron beam is made approximately uniform by adjusting the bias resistor R, or when there is no unevenness in the characteristic [dI/dx], it is confirmed that the intensity distribution of the electron beam is approximately uniform. After that, the computer 34 calculates the brightness β of the electron beam at that time from the electron beam current I determined by the Faraday cup 26 (the measurement beam current I _nax in a state where it is not blocked by the thin gold wire 24). Calculate (step j). Then, this calculated brightness β of the electron beam is compared with the brightness β _oeed required for Keller illumination (step k), and if [β>β _oeed ], the bias voltage V is increased to reduce the brightness β to β _oed
(Step 1). And conversely [β<
β _oeed ], the heater power is adjusted to raise the chip temperature T and adjust the brightness β to β _oeed (step m).

Through this series of processing procedures, the bias conditions for the electron gun 1 are optimized, the brightness β _oeed necessary for electron beam exposure is obtained, and the processing procedure is completed (step n).

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the sample surface 1
9, the beam current I of the electron beam was detected and its intensity distribution was determined, but it is not necessarily specific to the sample surface. For example, as shown in Figure 9,
Near the mask edge of the first beam shaping aperture 10 provided below the illumination lens 9
A 100 μm hole 10a may be provided, and a Faraday cup 26 may be provided opposite the hole 10a to detect the beam current I. When such a structure is adopted, the electron beam illuminated on the aperture 10 is two-dimensionally scanned, and the electron beam on the aperture 10 is determined based on the magnitude of the deflection current at that time and the value of the beam current detected by the Faraday cup 26. Beam intensity distribution can be determined. in this case,
[d ² I/dxdy] is the amount detected by the faraday cup 26, so if the bias voltage V is adjusted so that the above [d ² I/dxdy] is constant within the opening of the aperture 10, good.

Furthermore, in the above embodiment, an electron gun using a single crystal LaB ₆ chip was explained, but the single crystal chip has a structure as shown in FIG. 1, and the work function of the chip material has plane anisotropy. If so, it will have the characteristics shown in Figures 2 and 3 a to d, so
For example, single-crystal chips such as tantalum carbide (Ta C), titanium carbide (Ti C), zirconium carbide (Zr C), and La ₀₃ Nd ₀₇ B ₆ in which part of the lanthanum in LaB ₆ is replaced with ndiumium. Can be applied. In addition, the intensity distribution of the electron beam is measured by coating a heavy metal fine powder smaller than the beam shape on a substrate with a low atomic density such as beryllium, and detecting the reflected electrons obtained by scanning the fine powder with the electron beam. You may also do so.

Further, although the control value of the bias condition based on the measurement information was determined by the computer 34, it goes without saying that a dedicated arithmetic processing circuit may be configured to perform the arithmetic operation. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, it is very easy to calculate the electron beam intensity according to the electron beam intensity distribution, the electron beam brightness at the aperture, or the boom current under the condition that the beam size is constant. By obtaining a control value for the bias resistor or bias voltage, it is possible to adjust the bias conditions to equalize the beam intensity and provide sufficient brightness necessary for exposure, making it possible to create a simple and highly practical electron beam device. can be provided.

[Brief explanation of the drawing]

The figures show an electron beam device according to an embodiment of the present invention. Fig. 1 is a perspective view showing the structure of a single crystal chip used in an electron gun, and Fig. 2 is a diagram showing the relationship between bias voltage and brightness. , FIGS. 3a to 3d are diagrams schematically showing emission patterns, FIG. 4 is a diagram showing the relationship between bias resistance and brightness, FIG. 5 is a diagram showing the overall configuration of the embodiment device, and FIG. Figures a to d are diagrams for explaining the measurement principle of boom strength distribution, Figure 7 a,
b and Fig. 8 are diagrams showing the beam intensity distribution, and Fig. 9 is a diagram showing the beam intensity distribution.
Figure 1 shows another example of beam intensity distribution measurement.
FIG. 0 is a diagram showing the flow of the overall adjustment processing procedure in this apparatus. DESCRIPTION OF SYMBOLS 1... Electron gun, 3... High voltage power supply, 4... Heater power supply, 5... Bias resistance variable circuit, 10... First beam shaping aperture, 14... Second beam shaping aperture, 17... Objective Lens, 20...
... Deflection electrode plate, 26 ... Faraday cup, 34
……calculator.

Claims (1)

[Claims] 1. An electron gun using a single-crystal chip, an aperture image projection type electron optical system that projects an electron beam emitted from the electron gun with Keller illumination, and a variable shaping aperture for the electron beam. a lens system for controlling the illumination of the electron beam, a first measurement system for measuring the intensity distribution of the electron beam, a second measurement system for measuring the electron beam current of the electron beam; and a control system that varies the bias voltage or bias resistance of the electron gun based on the measurement results obtained by the second measurement system, wherein the control system performs the measurement using the first measurement system. a first means for making the intensity distribution of the electron beam uniform by varying the bias voltage or bias resistance of the electron gun based on the intensity distribution of the electron beam; Measure the electron beam current with the given electron beam dimensions under the specified conditions using the second measurement system, and compare the electron beam current measured by the second measurement system with the desired electron beam current. and third means for varying the bias voltage or bias resistance of the electron gun to match the electron beam current with a desired value according to the comparison result obtained by the second means. An electron beam device comprising: 2. The uniformity of the intensity distribution of the electron beam based on the measurement results from the first measurement system is performed by keeping the dimensions of the electron beam constant.
Electron beam device described in Section 1. 3. The electron beam device according to claim 1, wherein the single crystal chip constituting the electron gun is a lanthanum hexaboride (LaB ₆ ) single crystal. 4. Claims in which the control system variably controls the bias voltage or bias resistance of the electron gun in order to uniformize the intensity distribution of the electron beam and provide a predetermined brightness necessary for Keller illumination in the electron optical system. The electron beam device according to item 1.