JPH0378951A - Image photographing type ion micro-analyzer - Google Patents

Abstract

PURPOSE:To accomplish an ion micro-analyzer in a simple construction, in which the energy scope can be restricted to a certain extent, by putting the track for the primary ion beam coaxially with the track of secondary ion beam and opposite to the direction of this secondary ion beam. CONSTITUTION:The track for the primary ion beam I1 is coaxial with the track of secondary ion beam I2 and opposite to the direction of this secondary ion beam I2. The secondary ion beam I2 emitted from the surface of a specimen 20 hops out coaxially with the primary ion beam I1 and in the direction oppositely thereto, passes through a drawout slit 21 and drawout lens L1, is deflected by a deflector D1 with the track bent, passes No.1 enlarging lens system 11, and is introduced to a mass spectral system 12. The mass spectral system 12 is formed from a superposition field where magnetic field and electric field are formed in the same region, and the secondary ion beam I2 mass-separated by this mass spectral system 12 is introduced to a sensing system 13 composed of No.2 enlarging lens system 26, ion multiplier 27, anode 28, and focusing plane 29. This simplifies the configuration and allows reduction of the energy aberration on the image surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion microanalyzer (hereinafter referred to as IMA), and particularly relates to a mapping type IMA.

[Prior art] IMA is used as a device for elemental analysis of minute parts on the surface of a sample.
It has been known. IMA performs elemental analysis by mass spectrometry of secondary ions of sample atoms emitted from the sample surface by irradiation with a primary ion beam (ion microprobe), and its main feature is high sensitivity. ing. IMA is broadly divided into scanning type, which scans with a narrowly focused primary ion beam, and mapping type, which irradiates with a relatively thick primary ion beam without scanning and directly obtains an ion image, and various configurations have been proposed for each. However, the present applicant previously proposed a mapping type IMA that has a superimposed field in which the electric field and magnetic field forming the mass spectrometry system exist in the same region (see Japanese Patent Application No. 82-234130). .

Figure 11 shows its configuration. In the figure, IS is the ion source, I+ is the primary ion beam, and S is the sample N I2.
is the secondary ion beam, To is the connecting optical system, SL is the entrance slit, 0 is the center orbit of the ion, 1 is the uniform magnetic field 2 in the direction perpendicular to the paper, and the direction perpendicular to the -like magnetic field on the paper. LP is a projection lens, SL is a mass selection slit, F is a superimposed field in which a toroidal electric field 3 with
S indicates a fluorescent screen.

In FIG. 11, regarding the ion image, the connecting optical system T
An ion image F1 on the sample surface is formed by the ion image F1 on the sample surface, and an ion image F2 converted by the superimposed field is projected as F3 at the position of the fluorescent screen FS.

The projection lens Lp is used to increase the magnification of the image and can be omitted if unnecessary.

Regarding crossover, the crossover CI of ions emitted from the sample surface by the connecting optical system TO
is formed at the position of the inlet slit SL+, and a crossover C is formed at the position of the mass selection slit SL, , due to the superimposed field.
2 is formed. At this time, mass selection slit SL,! Only mass dispersion is occurring above, and an ion image of the sample surface is formed on the fluorescent screen FS by only ions of the mass selected by the mass selection slit SL0. By changing the strength of the magnetic field 2 of the superimposed field 1, the mass number of ions passing through the mass selection slit SLo can be changed, and ion images of ions with different mass numbers can be obtained.

In the configuration shown in Fig. 11 described above, in order to increase the mass selectivity of the ion image and minimize the distortion of the ion image, distortion-free and double convergence must be established for both the crossover and the ion image at the same time. It is important to satisfy the conditions for steric convergence.

Here, as mentioned above, ions flying in a superimposed field in which an electric field that causes the center orbit of the ion beam to exist on an equipotential surface and a magnetic field that is approximately perpendicular to this electric field exist simultaneously. The motion is expressed in cylindrical coordinates (r+
This will be explained using φ+2).

FIG. 12 is a diagram showing a schematic configuration of the superimposed field generating means,
A uniform magnetic field is formed between the pair of pole pieces 4, 4' in a direction perpendicular to each pole piece. Furthermore, a pair of electric field generating substrates 5.5' on which a large number of linear electrodes are arranged concentrically is attached to the surface of each magnetic pole piece 4, 4'.
By applying an appropriate potential to these linear electrodes, an electric field having a direction substantially perpendicular to the magnetic field is generated between the magnetic pole pieces.

Here, in the plane of z=O, on the circumference of r=a, that is, on the center orbit of the ion beam, the electric field has a constant strength and points toward the center, and the magnetic field points in two directions. shall be.

In order to handle the electromagnetic field near z = (L r = a, r = a (1 + ρ) ... (1) r = aζ ... (2) However, if ρ and ζ are sufficiently smaller than 1, then do.

If the equation that determines the trajectory of an ion in a superimposed field is expressed as a first-order approximation based on such a premise, the equations for the r direction and the two directions are as follows.

The above coefficients Kr' and □2 are constants determined by the electric field and magnetic field, and when a uniform magnetic field is used as the magnetic field, d and Kr''=3+J!-31+ (-2q)2 ・ (5
) consecutive K −” = −(]7+1) ・・
・It is expressed as (6). In addition, γ and β are the relative change rates of mass and velocity, respectively, and when the mass and velocity of the ion passing through the central orbit are respectively m- and v8, the mass m and velocity V of the ion of interest are m = m @ (1 + γ) ... (7) v = va (1 + β) ・ (8) It is given by the following relationship. Furthermore, a and a are the radii of the central orbit of the ion assuming that the magnetic field and electric field exist independently, respectively, and between a and a, 1/a=1/as +1
/am...(9) There is a relationship.

In the above equations (5) and (6), `` is the first-order expansion coefficient when the electric field is tiller expanded around the central orbit, and is the first-order expansion coefficient of the equipotential line that coincides with the central orbit in the central orbit plane of the ion beam. The ratio C of the radius of curvature a to the radius of curvature R0 of the equipotential line passing through its central orbit in the plane containing the z-axis, that is, c, = a/Rs... By (10), ノ:=-(L+c )...(11).

The above Kr'' determines the primary ion convergence characteristics in the r direction, and K determines the primary ion convergence characteristics in the two directions.
2, the relation between the position of the crossover in front of the superimposed field and its imaging position can be summarized as the following simple equation:

(,i”-g) X (J!“-g)=f”
...(12) However, in equation (12), ``' is the distance between the position where the crossover is formed and the incident end surface of the superimposed field, and ``'' is the imaging position of the crossover due to the superimposed field and the exit of the superimposed field. The distance from the end surface, f is the focal length of the superimposed field, f = (a/K) (1/s inKφ)
・It is expressed as (13), where g is the distance between the input/output end face of the superimposed field and the focal point, and it is expressed as g=(a/K)co tKφ ・(14).

The image magnification at this time or X=f/()'-g)=()"-g)/f...-(15).

The above equations (12) to (15) are common to the r direction and the two directions; if ni = is set, the relational expressions are for the r direction, and when K= is set, the relational equations are for the two directions.

Furthermore, the dispersion at the image position in the r direction is D=aδ(1+X) ・(1B)δ=(γ+(
2--; )β)/ is expressed as '...(17).

Considering this dispersion, ■When a/am = 2, equation (17) becomes δ = 7/, which becomes 2, and only mass dispersion occurs; if the mass is the same, no dispersion due to ion speed or energy occurs. Therefore, the condition for double convergence holds as it is.

■a / a m = O1, that is, a, = ■, and when the magnetic field is zero, equation (17) becomes δ = (γ + 2β) /, I, and at this time, the ions receive only the force due to the electric field, and all ions causes dispersion only by its own kinetic energy. That is, energy separation occurs.

By the way, from equations (5), (6) and (8), K
rt+Kx2=1+ (a/a,)"...(
1B) is obtained.

Also, from formula (9), a/am=2 in ■ above means a/a*=-1...(19), and a/am=O in ■ is a/a
It can be seen that it means a = + 1 (20).

Therefore, in both cases (1) and (2) mentioned above, the above equation (17) becomes: Kμ+A2=2 (21). That is,
As a condition for steric convergence, in both cases of ■ and ■,
It can be seen that it is sufficient to make 2= and 1=1.

Conditions for ■, a / a a = 2+ a /
Substituting as=-1 into equations (5) and (6), we get Kr"=no+1, K-=1-7!, and when J=0, we make ■=1 for K,'= It turns out that you can do it.

In order to satisfy ノ=0, from formula (11), C=-
1. Therefore, from equation (10), it is necessary to set R*=-a. This means that, as shown in FIG. 13, a curvature of radius a is given in the opposite direction to that in FIG.

On the other hand, by substituting the conditions for ■, a/am=o, a/aS=1, into equations (5) and (6), K12=30,
K, R=-(1+1), and when J=-2, 2=
It turns out that 2 = 1 can be established. In order to satisfy 1=-2, c=
1. Therefore, from equation (10), it is necessary to set R@ = a. This can be done by making Ro in FIG. 12 match a.

From the above, ■ Set the magnetic field strength and electric field strength so that a/am = 2 + a/as = -1 holds, and set the electric field distribution as shown in Figure 13 so that J = 0 holds. Furthermore, the cross-over formed at the position of the entrance slit SL+ in FIG. 11 is imaged at the position of the mass selection slit SLo. , f are selected and the fluorescent screen FS is placed at the imaging position of the ion image, three-dimensional convergence is established, and an ion image with minimal distortion can be obtained on the screen FS. The magnification of this ion image can be adjusted by changing the conditions of the connecting optical system and by changing the size of the crossover formed at the SL+ position.
It can be set arbitrarily without changing the conditions of the superimposed field.

Furthermore, by changing the strength of the electric field of the superimposed field, ions of different masses will pass through the mass selection slits SL, so that ion images of different ions can be obtained.

■, i'', ,g''+f settings are the same as in case ■, the magnetic field strength is set to zero so that a/am = O holds, and the electric field strength is set so that a/ae = 1 holds. If you leave it as is and set it in the opposite direction to ■, and set the electric field distribution so that J=1 holds, then the mass selection slit SL□
A crossover image in which energy dispersion has occurred is formed at the position, and an energy image is obtained on the fluorescent screen FS by the ions having the same energy that have passed through the slit. This energy image is likely to appear as an image even if the sample surface is composed of different materials, as ions of different masses can contribute to image formation if they have a specified energy. It is possible to understand the overall appearance of the sample surface better than with an ion image in which only ions appear in the image.

Note that a/a is the area between ■ and ■, that is, -1 × a/a,
When set to <1, an image with both mass dispersion and energy dispersion mixed is obtained. However, in this intermediate region, 2. Since the value of 2 is smaller than 1 and the convergence power becomes small, it is necessary to add a distortion-free lens in order to form images at the same image position.

[Problems to be Solved by the Invention] However, the conventional mapping type MA having superimposed fields has the following problems.

The primary ion beam axis and the secondary ion beam extraction axis are separate, and the primary ion beam axis is inclined about 30'' with respect to the secondary ion beam axis.In addition, in order to extract the secondary ion beam, , an extraction slit 5Ls1 and/or an extraction lens shown as SLs in FIG. Therefore, the structure of the pull-out slit 5Ls1 and/or the pull-out lens becomes complicated, and high precision is required for processing and assembly, making the work extremely complicated.

Further, although the configuration shown in FIG. 11 allows double convergence and steric convergence to be achieved, this also means that energy separation is not performed over a very wide range of energies.

However, if proper energy separation is not performed,
Another problem has arisen in that the ion image formed on the imaging plane becomes blurred due to chromatic aberration of the lens system disposed in the trajectory of the secondary ion beam.

The present invention solves the above-mentioned problems, and aims to provide a mapping type ion microanalyzer that has a simple structure and can limit the energy range to a certain degree.

[Means for Solving the Problems] In order to achieve the above object, the mapping type ion microanalyzer of the present invention is provided with a mapping type ion microanalyzer having a mass spectrometry system, in which the trajectory of the primary ion beam is the same as that of the secondary ion beam. is coaxial with the orbit of the secondary ion beam and opposite to the direction of the secondary ion beam,
Furthermore, it is characterized by comprising a deflection electric field for deflecting the primary ion beam and the secondary ion beam, a deceleration electric field on the side where the secondary ion beam enters the deflection electric field, and an accelerating electric field on the exit side of the deflection electric field. be.

[Operations and Effects of the Invention] According to the present invention, firstly, the primary ion beam is irradiated coaxially with the secondary ion beam and substantially perpendicular to the sample, and the deflection electric field is a field capable of three-dimensional focusing. , the configuration is simple, and the energy of the secondary ions can be selected by the slit placed at the entrance of the mass spectrometry system.

Secondly, in the deflection electric field that deflects the primary ion beam and the secondary ion beam, a deceleration electric field is placed on the incident side of the secondary ion beam, and an accelerating electric field is placed on the exit side, so energy dispersion is further improved. It is possible to increase the size of the slit, thereby eliminating the imbalance of the slit system.
Furthermore, it is possible to vary the image magnification of the ion image over a wide range.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the overall configuration of a mapping type ion microanalyzer according to the present invention, in which 10 is an ion extractor, 11 is a first magnifying lens system, 12 is a mass spectrometry system, and 13 10 is a detection system, 10 is a sample, 21 is an extraction slit, 22 is an extraction lens, 26 is a second magnifying lens system, 27 is an ion multiplier, 28 is an anode, 2
9 is the imaging plane, I+ is the primary ion beam, Ie is the secondary ion beam, LI is the extraction lens, I) + + D
2 is a deflector, L2 is a lens, So is an entrance slit, SC
indicates the exit slit.

In FIG. 1, the configuration of the mapping type ion microanalyzer according to the present invention is roughly divided into an ion extraction section 10, a first magnifying lens system 11, a mass spectrometry system 12, and a detection system 13. The ion extractor 10 is connected to the sample 20. Drawer slit 21, drawer lens Lh Deflector D+
, D2, a lens L2, and an entrance slit S0, the primary ion beam I is first deflected by a deflector D+, which is also composed of an electric field. , the extraction lens L+ and the extraction slit 21, and is irradiated almost perpendicularly to the surface of the sample 20. The secondary ion beam E 2 emitted from the surface of the sample 20 is coaxial with the primary ion beam I, flies out in the opposite direction, passes through an extraction slit 21 and an extraction lens L, is deflected by a deflector D+, and is deflected into a trajectory. The lens L2 is bent, the entrance slit SO% is bent, and the first magnifying lens system 11 is composed of a plurality of lenses.
is introduced into the mass spectrometry system 12 through the. Mass spectrometry system 12
is formed by a superimposed field in which a magnetic field and an electric field are formed in the same area, similar to that shown in FIG. The secondary ion beam I2 mass-separated by the mass spectrometry system 12 is passed through a second magnifying lens system 26, an ion multiplier 27, an anode 28,
The light is introduced into a detection system 13 that includes an imaging plane 29 . Note that the detection system 13 is the same as the conventional one, so a detailed explanation will be omitted. Thus, in the present invention, the primary ion beam axis is coaxial with the extraction axis of the secondary ion beam (2). Note that the acceleration energy of the primary ion beam 2 irradiated onto the sample 20 can be varied over a wide range, and in some cases, an ion beam with a polarity opposite to that of the secondary ion beam 2 is required. Therefore, it is natural that measures must be taken to meet these demands.

FIG. 2 is a diagram showing the trajectory of the primary ion beam 11 in the ion extraction section 10.
When the polarity is the same as that of the secondary ion beam A2, and the acceleration energy is low acceleration of 10 keV or less, the trajectory will be as shown by 30 in the figure, and when the acceleration energy is high acceleration of 20 keV or more, the trajectory will be as shown in the figure. When the polarity of the primary ion beam I is different from the polarity of the secondary ion beam I2, the trajectory is as shown by the broken line 32 in the figure.

FIG. 3 shows an example of a specific configuration of the ion extractor 10, and the dimensions in the figure are standardized to be D (=5 mm). In FIG. 3, the electrode of the extraction lens L on the sample 20 side also serves as the extraction slit 21.

Further, Oct in the figure indicates an octopole.

FIG. 4 shows the secondary ion beam I2 in the configuration shown in FIG.
2 is a diagram illustrating an example of a Raybus showing a first-order α convergence characteristic, where the solid line indicates the convergence characteristic of the crossover point formed by the secondary ion beam from the surface of the sample 200, and the convergence characteristic of the cross-over point formed by the secondary ion beam The convergence characteristics of the image point or object point (hereinafter referred to as image point) on the plane are shown by broken lines, respectively.

After the secondary ion beam I2 exits the sample surface, it is deflected only by the deflection electric field created by the deflector. As can be easily understood by comparing FIG. 3 and FIG. 4, in this configuration, the image point 11 of the image point is located at the midpoint of the deflection electric field, so no energy dispersion occurs regarding the image point. , regarding the crossover point, due to the deflection electric field, 02 in Fig. 4
Energy dispersion occurs at the position. In this case, the energy dispersion yδ, occurring at the position of the crossover point C2, is
The energy is V, and the energy width of the secondary ion beam is Δ.
When V, y6, :8.9ΔV/V (+*
m ), and assuming ■ = 5kv1 Δv = 50v, yδa: 0. A dispersion of approximately Imm is generated. Therefore, by arranging the entrance slit So at the crossover point C2, the energy of the secondary ion beam A2 introduced into the mass spectrometry system 12 can be limited.

In this way, the secondary ion beam I2 can be selected depending on the energy it has, and at the same time, by limiting the energy width to some extent, energy aberrations on the image plane can be reduced.

Further, the energy of the secondary ion beam I2 is limited by the extraction lens L1 and the lens L2 at the crossover point C2 located at the entrance slit 5o17) position. Furthermore, the image I2 is enlarged approximately 10 times by the action of the extraction lens L1 and the lens L2. This image Is is further magnified by about 10 times by the first magnifying lens system 11. The first magnifying lens system 11 uses, for example, an Elnzel lens with the same structure, and as shown in FIG.
It is composed of three stages of lenses: TI+ LT2 r LT3, and the lens LT2 is movable along the secondary ion beam axis as shown by the arrow so that the magnification can be varied. Then, by the first magnifying lens system 11, the image of the crossover point C2 at the position of the entrance slit So is moved to the position of the superimposed field entrance slit So', and the enlarged image I3 of the sample mechanism 2 is It is designed so that it can be varied independently of the image Cs of the crossover point,
The image I8 is focused at a suitable position within the superimposed field. now,
Assuming that the dimensions of each part are as shown in FIG. 5, the crossover magnification Me in the first magnifying lens system 11 is
and image magnification MI are respectively expressed by the following formulas.

Me = (a/d)X (e/b)=n a/b”1
22) M+ = 1/Me = b/n a
...(23) However, O<n<1.

The image of the crossover point C3 is generated by the superimposed field of the mass spectrometry system 12, and is formed from the exit of the superimposed field (=30D: see Figure 1).
The cross-over point C4 is moved to the position of the exit slit Sc, which is located at a distance of 1. Then, the mass separation of the ions is performed at the position of the exit slit Sc.

The mechanism 3 of the sample surface imaged at an appropriate position within the superimposed field is
The final image is further enlarged 4 to 5 times by the second magnifying lens system 26! p occurs on the imaging plane 29.

Next, the configuration of the deflectors D+ and D2 will be explained with reference to FIG. FIG. 6(a) is a plan view of the deflector, and FIG. 6(b) is a side view taken from AA in FIG. 6(a), where O indicates the secondary ion beam axis.

An upper resistive film electrode 40 and a lower resistive film electrode 41 are arranged above and below the secondary ion beam axis O, respectively, and are arranged at a predetermined interval by an inner electrode 42 and an outer electrode 43. Upper resistive film electrode 4-O and lower resistive film electrode 4
1, wire electrodes made of platinum and having a width of, for example, 0.2 m+s are formed on the resistive film at a pitch of, for example, 2.5 ms+. Therefore, for example, if a predetermined negative potential is applied to the inner electrode 42 and a positive potential is applied to the outer electrode 43,
The equipotential surface formed between the upper resistive film electrode 40 and the lower resistive film electrode 41 is as shown by 46 in FIG. 6(b), and therefore the electric field is in the direction shown by arrow 47 in the figure. from,
The secondary ion beam carrying a positive charge is bent in the opposite direction to the arrow 47, that is, toward the inner electrode 42.

In FIG. 6(a), shunt plates 44 and 45 are arranged at a predetermined distance d at the entrance and exit of the deflector, respectively.

In this way, by forming a deflection electric field using a multi-wire electrode formed on a parallel plate, we can create a field that produces three-dimensional convergence equivalent to a spherical electric field, that is, a field that converges with equal convergence accuracy in the vertical and horizontal directions. It is something that can be obtained.

As described above, according to the above embodiment, ■ The configuration is simplified because the primary bio-ion beam and the secondary ion beam can be made coaxial and perpendicular to the sample surface. ■ The deflection electric field Entrance slit S of superimposed field of mass spectrometry system
It is possible to obtain the effect that the energy of the ion can be selected at the position o.

Next, another embodiment of the present invention will be described with reference to FIG.

In FIG. 7, a reduction group lens 50 is disposed before the deflector D1, that is, on the side where the secondary ion beam is incident, and an accelerating lens 51 is disposed after the deflector D1. Both the deceleration lens 50 and the acceleration lens 51 are composed of two cylindrical lenses V+ and Va, where the cylindrical lens VI is at ground potential and the cylindrical lens v2 is at a predetermined positive potential, for example 4k.
V, is done. Therefore, if the energy of the secondary ion beam is now 5 keV, the secondary ion beam is decelerated to 1 keV by the deceleration lens 50, and the deflector D
After being deflected by +, it is again 5keV by the acceleration lens 51.
is accelerated to

The reason for adopting such a configuration is to increase the energy dispersion of the secondary ion beam, and the specific reason is as follows. In the configuration shown in Figure 1, the primary ion beam is coaxial with the secondary ion beam and is incident on the sample at approximately right angles, and the energy width of the secondary ion beam is limited by the deflection electric field of the deflector D. Although steric convergence is performed by convergence, there is a problem in that unbalance may occur in the slit system due to low energy dispersion. That is, as mentioned above, the energy dispersion yδ at the position of the crossover point C2 in FIG.
The energy is V=5keV.

If the energy width ΔV=50eV, approximately 0.1 vI
At this time, if the height of the slit is 1 mil, the aberration called the circle of least confusion on the sample surface that occurs when extracting the secondary ion beam is 24 μm, which limits the spatial resolution. It turns out.

Therefore, in order to improve the spatial resolution, it is necessary to limit the energy width ΔV and therefore the width of the slit or the height of the slit. On the other hand, the required mass resolution is R=M/ΔM= If it is 300,
The required slit width is approximately 1.0 mm, and the slit height is approximately 2.0 mm, which causes an imbalance in the slit system. This is because the configuration shown in FIG. 1 has a small energy dispersion, and therefore, in order to maintain a balance between mass resolution and spatial resolution, it is necessary to increase the energy dispersion.

Furthermore, the configuration shown in FIG. 1 has a problem in that the magnification of the ion image is too large. That is, in the case of the Raybus shown in FIG. 4, the image magnification is approximately 12 times, and a large magnification is already obtained before the first magnifying lens system 11. However, in the mass spectrometry system 12, aberrations occur when the magnification factor of the incident ion beam is large, so it is not necessarily preferable that the magnification factor becomes large at the front stage of the mass spectrometry system 12. Of course, as mentioned above,
Lens L arranged in the middle of the first magnifying lens system 11
Although it is possible to reduce the image by moving the TI appropriately, it is not efficient to reduce the image that has been enlarged.
The range of magnification adjustment that can be done with 2 is not that wide.

The configuration shown in FIG. 7 improves energy dispersion by decelerating the secondary ion beam before the deflection electric field, and also allows the magnification of the ion image to be changed arbitrarily. This system solves the problem of the configuration shown in FIG. 8, and its operation will be explained using an example of a ray pass shown in FIG. Note that, hereinafter, Dll indicates the diameter of the cylindrical lens constituting the deceleration lens and the acceleration lens. In FIG. 7, the primary ion beam enters the deflector D+ from direction A in the opposite direction and coaxially with the secondary ion beam, passes through the deceleration lens 50, and enters the sample 20 at approximately right angles. It is designed to irradiate.

The secondary ion beam extracted from the surface of the sample 20 is
The ion image is made into a parallel beam by the lens L+, and the crossover point is imaged as 01 by the lens L1 at a position 4.4D away from the lens L1, that is, at the position of LDI, which is the center of the deceleration lens 60. be done. The parallel beam of the ion image is decelerated by the deceleration lens 50, and is bent at the position of its second principal surface PP+a by the converging action of the deceleration lens 50, and the focal length f
2, the image is formed as shown by 11 in the figure, but this position is the 7th
As shown in the figure, it is positioned at the center of the deflection electric field. With respect to the center of the deflection electric field, the accelerating lens 51
It has a position and structure symmetrical to the deceleration lens 50. Therefore,
The ion image is bent by the second principal surface PP12 of the accelerating lens 51 to become a parallel beam again, and exits from the accelerating lens 51 at the same height as when it enters the decelerating lens 50. Therefore, no energy dispersion occurs regarding the beam ray of the ion image.

On the other hand, the crossover point is made parallel to the first principal surface PP,+ of the deceleration lens 50, and is further bent by the first principal surface PP21 of the accelerating lens 51 and exits. 5 from the center LD2 position
．． The image is formed as 02 at a position 0D@ apart. Here, crossover point C for crossover point c1
The image magnification Me of 2 is set to approximately 1.0.

Also, the image magnification M+ of the ion image becomes a parallel beam between the lens L1 and the lens L2, so M+ = f L
2/ f t+, where fLl=7D/
3, and f+,2 is the focal length d1 of the lens L2.
Therefore, the total magnification up to ion image position ■2 is M +2 = (2/3)X (3/7)
X (d+/D).

The first magnifying lens system 11 is composed of three L/7 lenses L/7 lenses L2+Lt3 as shown in FIG. 5, and the fourth crossover point is imaged at the position of the lens Lts. . The fourth crossover point c4 is an object point of the mass spectrometry system 12, and the ion image I is focused as 14 at the center position of the superimposed field by the lens Lta.

The image magnification and energy dispersion of the ion image in the ray path shown in FIG. 8 are as follows. Now, if the distance from the crossover point C4 to the center of the superimposed field of the mass spectrometry system 12 is g=eon, the image magnification M+ of the total ion image up to the ion image I4 is M+:M+2XM+t=(2/3 )X(3/7)X(d
+/d2)X (60b/a) = 17.14X(d+/d2)X (b/a)
”(24). However, M+τ is the image magnification regarding the ion image of the first magnifying lens system 11, and M+y=
It is expressed as (b/d2)X(GOD/a).

Also, the energy dispersion yδ, can be found as follows, but now, y/θ@ = f + D 1
1=3.59Ds, U=1kev1 U11=
5kev1 Then, the angle of the deflection electric field of the deflector D1 is φ
=30' (=0°5236 rad), then yδ. =4G, 24Dsδ, (,,)
...(26). Here, δ is a ratio indicating how much energy width can be taken with respect to the energy possessed by the ion beam. For example, if the energy is 5 k e VN and the energy width is 50 V, 5015000 = 1/ 1000 to value:
Naru. Mata, D.

is a value measured in cm.

On the other hand, the image magnification M + ' of the ion image in the ray path shown in FIG. 4 and the energy dispersion yδ,
' is calculated from the ray path, M+': 47.24
b/a...(27)y
δ,' = 9.31 δ − (mu)
... (
28), and it can be seen that the energy dispersion shown by equation (2G) is improved by about five times compared to the ray path shown in FIG. In addition, the image magnification parameter is al
In addition to b, d+ and a2 are added, resulting in d + / d
By changing the ratio *, it can be arbitrarily changed from a minimum of about 10 times, so the range of change in image magnification can be increased.

As described above, according to the configuration shown in FIG. 7, the ray path of the ion image can enter and exit the deceleration lens system as a parallel beam, so the position of the crossover point C1 with respect to the deceleration lens system can be calculated using equation (24) and Equation (26) can be freely changed while maintaining it.

In the embodiments shown in FIGS. 7 and 8, the crossover point C1 is located at the center Lo+ of the deceleration lens 50, but it may also be located at the front focal point of the deceleration lens 50. Figure 9 shows the ray path at that time. The ion image is made into a parallel beam by the lens L+, bent by the second principal surface PP+a of the deceleration lens 50, and formed into an image as 11 at the center position of the deflection electric field, and further parallelized by the second principal surface PP22 of the acceleration lens 51. What is done with the beam is the same as the ray path shown in FIG. 8, and the crossover point is similarly
The beam is made into a parallel beam by the first principal surface PP++ of the accelerating lens 51, and is bent again by the first principal surface PPe+ of the accelerating lens 51.

An example of the configuration for obtaining the ray path shown in FIG.
As shown in Figure (a), in this case, the crossover point C
Since the slits can be placed at both positions 1 and C2, the energy width of the secondary ion beam can be restricted, and the resolution can therefore be improved. In addition, in Fig. 10(a), the deflection angle of the deflector DI is set to 30@, and if the energy of the secondary ions is 1 keV, the radius of rotational curvature of the deflection electric field is as small as 50i as shown in the figure. Therefore, the device can be configured compactly. In addition, in the above explanation, deceleration is performed at the connection point of the metal cylindrical electrode (Mld focus
Although the case where the deceleration is performed discretely at 1 point) has been described, it is clear to those skilled in the art that the deceleration may be performed in several stages or may be performed continuously. Further, as shown in FIG. 9, the configuration for placing the crossover point CI at the front focal point of the deceleration lens is as shown in FIG. 10 (b), (c), or (d).
It is also possible to adopt a configuration as shown in FIG. 10(a), and in these cases as well, slits can be placed at both the crossover points C8 and C2, similar to the configuration shown in FIG. 10(a). Therefore, the energy width of the secondary ion beam can be limited, and the resolution can therefore be improved.

As described above, for the secondary ion beam, by placing a deceleration lens in the front stage of the deflection electric field and an acceleration lens in the rear stage, the ray path of the ion image is caused to enter and exit parallel to this system. ■It is possible to eliminate and optimize the imbalance required in the width and height of the slit, which regulates both the energy aberration of the ion image spatial resolution and the mass resolution.■It is possible to optimize the image magnification for the ion image. Since the magnification can be changed smoothly from low magnification to high magnification, it is possible to obtain the effect that the image magnification of the ion image can be optimized.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments (various modifications are possible, and in particular, the dimensions of each part can take various values). It will be obvious to those skilled in the art that

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of one embodiment of the mapping type ion microanalyzer according to the present invention, Fig. 2 is a diagram showing the trajectories of the primary ion beam and secondary ion beam in the deflection electric field, and Fig. 3 is a diagram showing the specific FIG. 4 is a diagram showing a ray path in the configuration shown in FIG. 3, FIG. 5 is a diagram showing an example of the configuration of the first magnifying lens system, and FIG. 8 is a diagram showing a specific example of the deflector. 7 is a diagram showing a second embodiment of the mapping type ion microanalyzer according to the present invention, FIG. 8 is a diagram showing an example of a ray path in the configuration shown in FIG. 7, and FIG. 9 is a diagram showing another ray path. FIG. 10 is a diagram showing an example of the configuration for achieving the ray path shown in FIG. Figure 12 is a diagram showing an outline of the superimposed field generation means, and Figure 13 is! FIG. 3 is a diagram for explaining the distribution of a toroidal electric field of =0. DESCRIPTION OF SYMBOLS 10... Ion extraction part, 11... First magnifying lens system, 12... Mass spectrometry system, 13... Detection system, 10
...Sample, 21...Drawer slit, 22...
Pull-out lens, 26...Second magnifying lens system, 27.
...Ion multiplier, 28...Anode, 29
...Imaging plane, 11...Primary ion beam, Ill.
・Secondary ion beam, LI ・Extractor lens,
D+ s Da... Deflector, L2... Lens, So
...Entrance slit, Sc...Exit slit. Applicant: JEOL Ltd.

Claims (2)

[Claims] (1) A mapping type ion microanalyzer having a mass spectrometry system, characterized in that the trajectory of the primary ion beam is coaxial with the trajectory of the secondary ion beam, and in the opposite direction to the direction of the secondary ion beam. Mapping type ion microanalyzer. (2) A claim characterized in that a deflection electric field is provided for deflecting the primary ion beam and the secondary ion beam, and a deceleration electric field is provided on the side of the deflection electric field where the secondary ion beam enters, and an acceleration electric field is provided on the side from which the secondary ion beam exits. The mapping type ion microanalyzer according to item 1.