JPS6050850A - Scanning electron microscope - Google Patents

Abstract

PURPOSE:To prevent any variation of a position irradiated by an electron ray caused by a beam locking by making the position of a minimum confusion circle formed when an electron ray is subjected to locking in a scanned image observation mode, to coincide with the corresponding position of a sample surface, based upon a signal representing an electron ray locking angle. CONSTITUTION:Providing an electron gun 1, a focusing lens 2, an objective lens 3, deflectors 6, 7 to deflect the electron ray, means 11-13 to supply scanning signals to the deflectors 6, 7, a detector 20 to detect a signal obtained from a sample 4 by the electron ray irradiating the sample 4, and a display device 14 synchronously scanned with the above-mentioned electron ray scanning to display a picture in response to an output signal from the detector 20, an ovservation can be performed by making changeover between a scanned picture and an electron channeling pattern by the electron ray locking. In such a device, a means is provided to make a position Cm of a minimum confusion circle formed when an electron ray is subjected to locking in a scanned image observation mode, to coincide with the corresponding position of the sample surface S based upon a signal representing the electron ray locking angle alpha.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application IA'fF, light uses the beam 11x4 function (excellent scanning electron microscope!).

[Prior art 1; H111,'I, By observing the bunneling pattern using a scanning electron microscope, it was found that the crystal Vfl41't on the surface of the bulk wiping r1 was wide <t'r
'/'r has been. Electron channeling pattern (using a good electron beam with 4 rows of 1η) (, r++tl l t
;-,,t; lJru'rN 了fu'/)it(t'
JJ 411M While fixing the electron beam at one point, scan the incident angle θ and azimuth angle φ of the electron beam to perform so-called beam locking, and also measure the anti-0.1 electron beam, secondary electrons, etc. obtained with this scanning. -C is obtained by supplying the detection signal to a display means such as a cathode ray tube which is scanned in synchronization with this scanning.

Figures 1 (a) and (, b) are for showing ray diagrams when obtaining a normal scanning image and an electron channeling pattern in a scanning electron microscope, respectively. In both figures, 1 is an electron gun; 2 is a focusing lens, 3 is an objective lens, and 4 is a trial lens. 6 is a first stage deflector consisting of a pair of deflection planes for the X and Y directions; similarly, 7 is a second stage deflector consisting of a pair of deflection planes J: FB; Shows an electron beam. As is clear from these figures, in the scanning image observation mode, a crossover image 5 of the electron gun 1 is formed by the focusing lens 2, and this image 5 is projected onto the sample surface S by the objective lens 3. Deflectors 6 and 7
This projected point is scanned on the sample surface S0. On the other hand, in the electron channeling pattern observation mode, the focusing lens 2 is excited so that the electron gun ``one bar image is formed on the front focal plane E3 of the objective lens 3'', and the descending electron beam is sampled. J, sea urchin irradiated to $41/l. Right there, the 1st stage f1mi device 61 layers 1,') 7t
7 ” r-ray 1:: r'3 Total deflection - J-rot, crossover image 5' is obtained by shifting the focal plane 8 of the objective lens 3 ÷ 1
1? In order to pass the test, the electron beam that enters the test t'l 'I is
13 is a person who has a trial talent ≧ 17I! J・I r: State where X is fixed () at one point on optical axis C 0 person 0・1 angle 0 and chi☆angle φ
You can avoid burning. However, this J,
In conventional equipment H, the electron beam is However, the irradiation position of the electron beam on the sample actually moved several iQf1m, which made it possible to analyze the minute part of the sample. J
, In order to solve such drawbacks, for example, an auxiliary 1-nons is placed near the objective 1-non, and the excitation strength f of this auxiliary lens is
α is determined according to the deflection angle of the electron beam. It is conceivable that the entry point of the electron beam into the sample is fixed, but since the equipment is large-scale, the production cost is very high.
<rru.

3- [Objective of the Invention] The present invention has been made to solve these conventional drawbacks, and has a relatively simple structure that can prevent beam locking (-the fluctuation of the electron beam irradiation position caused by the electron beam). The purpose is to provide a device that is inexpensive to manufacture.

[Structure of the Invention] The present invention includes an electron gun, a focusing lens, an objective lens, a deflector for deflecting an electron beam, a means for supplying a scanning signal to the deflector, and an electron beam sample. A scanning device comprising: a detector for detecting a signal obtained from the sample by irradiating the electron beam; and a display device that is scanned in synchronization with the scanning of the electron beam to display an image based on the output signal from the detector. In a device that enables observation by switching between an image and an electron channeling pattern based on electron beam locking, the minimum confusion formed when the electron beam is locked in scanning image observation mode is determined based on a signal representing the electron beam rocking angle α. It is characterized by comprising a means for matching the position of the circle with the position of the sample surface 4-a).

[Credit for the Invention] The basic idea of the present invention will be explained below with reference to FIGS. 2 and 3, in which the same components as in FIG. 1 are denoted by the same numbers.

As shown in Figure 2, in the scanning image observation mode -C:
The objective lens 3 is excited as shown in the optical path 1-1 to form an image of the bar image 5 on the sample surface S. Therefore, the electron channeling pattern can be observed. If the magnetic field of the objective lens 3 remains the same when the mode is shifted to the first mode, the deflection plane 9 of the first deflector 6 is located below the crossover image 5, so When rocking is performed by the first deflector 6, the electron beam is directed to the sample plane SJ, at a point 1 below Δ1°, as shown in the optical path 1-2.
0 as the center, and therefore the incidence of the electron beam on the sample plane S varies. Furthermore, although the spherical aberration of the objective lens 3 is not taken into account in FIG. 2, in reality there is spherical aberration, so the fluctuation of <2 in the human fish due to rocking becomes even larger.

That is, as shown in FIG. 3, the deflection plane 9 of the first deflector 6 emits a paraxial ray 12° 12 from the intersection with the optical axis O.
' is focused on the point 10 on the LEET from the sample surface S, but the rays on higher-order trajectories L3 and 13' are affected by 1 of the spherical aberration of the objective lens 30.
It focuses on the white Cm above the sample surface S, and irradiates this point Cm during rocking.A) A point with the least movement (circle of least confusion) of "7" ¥1 is created. If the position can be included in this +:, tcm, 11 to 1 of the electron beam irradiation position. C is to minimize the change 1 due to

Now, the point Cm where the minimum 11 random circle is formed with the 11th surface S
ΔF is the distance from
,z,)
, zi - is the distance between the objective lens 3 and the sample 1'+1S, and the distance between the objective lens 3 and the image 10 of the deflection principal surface 90, and d is the v1 diameter of the minimum 11 random circle, then 1 /Zo
+1/Z+ =1/7o -+1/Z+Zi ”-Zi
-8f -puj Δ1-1 Δf-3/4 - Cs -a2d=1/2
Since there is When the excitation strength 1α of the objective lens 3 is increased by 1↓, the spherical aberration coefficient C5 is negligibly small. Therefore, when switching the east mode from the scanning recording mode to the lightning channeling pattern upper mode, the focus of objective 1 and nons 3 can be changed. If we change the distance -1 between the planes of the 1st plane S by an amount corresponding to Δ] - given by the equation (1) above, the electron beam irradiation point will be 11 Embodiment 1 The present invention is based on the idea that it is possible to analyze a minute area by suppressing movement to a line width. Details) Ho.

7- FIG. 4 is for showing one embodiment of the present invention, and in FIG. 4, the same components as in FIG. 1 are given the same numbers.

In the figure, 11 is a scanning signal generation circuit, and the scanning signals from this circuit 111 can be supplied to the first and second deflectors 6 and 7 via variable gain amplifiers 12 and 13, respectively. , are supplied to the deflection coil D of the cathode ray tube 14. 15 controls the supply of the scanning signal to the second deflector 7 as the observation mode is switched between the scanning image observation mode and the electron channeling pattern observation mode.
l-! This is a switch circuit for 16t, L
When observing the channeling pattern, a signal is generated to specify the locking angle of the electron beam. The signal is supplied to the amplifier 12. 1
7 and 18 are excitation power sources for the focusing and objective lenses 2.3, respectively. Objective lens aid 1 power supply 18 is excitation control circuit 19
-C is controlled based on the control signal from The excitation control circuit 19 includes a first circuit 19a that generates an excitation designation signal 11 for observing a scanning image, and a second circuit 19b that generates an excitation designation signal for observing an electronic channeling pattern. The circuit 19c includes a switch circuit 19c for switching the output signal of the circuit between the output signals of these two circuits 19a and 19b. The circuit 19b is supplied with the locking angle α from the rocking angle designation signal generation circuit 16 (above), and this circuit 16b is supplied with the rocking angle α from the rocking angle designation signal bow generation circuit 16, and this circuit 16b receives the designation signal 1 from the circuit 16J.
The circuit 19a generates a signal that excites the objective lens 3 so as to form a minimum 811 random circle Orn at a position distant from the specified position by ΔF of equation (1). Further, the switch circuit 15 and the switch 19C are interlocked.
It's becoming a sea urchin. 20 is the illumination 01 of the electron beam FB on sample 4
The output signal of this detector 20J is sent to the cathode ray tube 14 via an amplifier 21 to increase the luminance. ] How is it supplied?

In this J, u/l-configuration, first observe the scanned image and
, when dozing off, switch circuits 15 and 19C are
When connected as shown by the dotted line in the figure, the excitation power supply 17 is switched to Jlj, and the image of the electron gun 1 is transferred to the focusing lens 2 as shown in Fig. 1 (
J formed at point 5 of a>.

Therefore, the objective lens 3 is excited so that the image of the A-bar image 5 is focused on L i'ri'1S-1. Further, the amplification factors of the variable amplification factor amplifiers 12 and 13 are switched to a predetermined value for scanning image observation by a control means not shown.

Therefore, circuit 11J is activated to generate the running signal, flr: +!
When a scanning signal like this is generated, the electron beam scans the physical sample two-dimensionally, and along with this scanning, the detector 20j is detected at 4T.

The detection signal obtained is supplied to the cathode ray tube 14.
A normal scanned image is displayed on the cathode ray tube 14. Next time you go to observe the electron channeling pattern,
When the switch circuit 190 is connected as shown by the solid line in FIG. 4, the switch circuit 15 is turned off. Further, the focusing lens 2 is excited so that a beam A-bar image of the electron gun 1 is formed on the front focal plane 8 of the objective lens, as shown in FIG. 1(b). In addition, the b11 magnetic power source 18 of the objective lens is connected to the second excitation designation circuit 19.
Toyo, I + Ia designation (1'7 >'3 +, - early encouragement (to be married, objective 1 nonce: '3 is fA
/Is t:'+Inner circle Cm In the case shown in Fig. 1, j, front 1. +1△1 (J far (1'/ coming to Vr'l),
If a scanning signal is supplied to the 11 circuit 1J, then this scanning (ijr3 is supplied to the first deflector 6, and the Song Dynasty, electric gun 1 beam [1 sover image 1) ゛ in front of objective 1 nons/] In order to scan the jiao-gyo surface, the electron beam test 1M'l was fixed at 80.1 point. In this state, the position angle φ of the large sword f (10 and j) is scanned. is displayed, but the focus of objective lens J3 is
:,! The distance 11111 is J in the case of the scanning image observation mode, and is equal to the previous ijLΔi−tc (°): v), the point Cm where the II4 small 1i random circle is formed. It also happens that Δ[datJ move 1) C1-1-1σ trial judgment is equal to the digit 1m of S. Therefore, it is possible to reduce the electron beam entrance and the transfer of 1 beam on the test surface S to 1 small.

It should be noted that this embodiment is merely one embodiment of the present invention; it may be implemented in numerous other embodiments.

For example, in the lJ embodiment (2), the objective lens 1
1) Change the focusing distance of the 1st point by 1↓, and when switching the 7th point, on the contrary, automatically move the /] of the sample in the direction of the optical axis 1. It is structured and bestowed.

[Effect 1 It is clear from the above explanation', 't J: Sea urchin, 1. According to the reddening device, the comparative inner surface is 111th -)! 1
1! One-piece construction: With a one-stroke, inexpensive configuration, it is possible to lock the electron beam without moving the electron beam and detect the electron channeling pattern in a minute area.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) show the scanning image observation mode and suspended image mode (1) in the conventional apparatus, respectively. A ray diagram of the tunneling pattern observation mode, Figures 2 and 3 are diagrams for explaining the basic idea of the present invention, and Figure C is a diagram for explaining an embodiment of the present invention. . 1: Electron gun, 2: Focusing lens, 3: Objective lens, 4: Sample, 5: Scanning image observation mode (-J crossover image of electron gun, 5-: Electron channeling 12- Bakun i11.! 11: Scanning signal generation circuit, 12.13: Variable gain amplifier, 14:
Cathode ray tube, Ih, 19 (C: switch circuit, 16: lower angle + CI designated fFisj 41 circuit, 17.18
: Excitation power supply, 19: 1ijl lit system 911 circuit, 19a, 19b: Excitation 1 effect i'i '3 R11
'I! 'l k'FI, 20: M output, C: Optical axis, C
rr): Minimum 111 random circles (f I 1 reel ■;, Mi, S
: Sample surface. Bt K'l Applicant 11 Electronics Co., Ltd. Representative Imu - Dai

Claims (3)

[Claims] (1) An electron gun, a focusing lens, an objective lens, a deflector for deflecting an electron beam, a means for supplying a scanning signal to the deflector, and a sample to be removed by irradiating the sample with an electron beam. It is equipped with a detector for detecting the obtained signal, and a display which is scanned in synchronization with the scanning of the electron beam in order to display an image based on the output signal from the detector. Finished! In an apparatus that enables observation by switching the electron channeling pattern by fAn tracking, the minimum circle of confusion formed when the electron beam is locked in the scanning image observation mode based on the J signal, which represents the electron beam rocking angle α. 1. A scanning electron microscope characterized by comprising a means for testing and matching the position of the object with the position of the object. (2) The position of the minimum ♀j1 random circle formed when the electron beam 1] is set to the scanning image observation mode and the electron beam is turned 11 on the basis of the tucking angle α to the bending signal. Trial 1
1.Means to achieve 't if'7 1.1,
A scanning electron microscope according to claim 1, comprising means for reducing the focal distance #f of the objective lens to 1L. (3) Testing the minimum ♦11100 position formed when lowering the electron beam in the scanning image observation mode based on the signal without showing the electron beam 11 tuning angle α. a) "111" I (2) The means for aligning the sample along the optical axis (111) (2) The scanning electron beam according to claim (1), which comprises one mechanically moved stage of 1L. microscope.