JPH025337A - Charged particle beam device and sample observing method thereby - Google Patents

Abstract

PURPOSE:To improve resolution and image quality and enable stable operation by providing an objective lens formed from an einzel lens and a single pole magnetic lens and means for irradiating with ions and electrons along the same axis. CONSTITUTION:A composite electromagnetic lens 12 is formed from an einzel- type static lens 10 and a magnetic lens 11 and functions as an objective lens. The top face 13 of the magnetic lens 11 and the central axis of the static lens 10 is disposed coaxially, and an opening 33 is formed in that portion to pass an electron beam or electron beam flux 22. The ion or electron beam selectively irradiates a sample 5 along the same particle beam axis 25. Generated secondary electrons 24 are constrained in the vicinity of the particle beam axis 25 by the magnetic lens 11 and pass through the opening 23, then after moved along a spiral path by means of the static lens 10 enter a secondary electron detector 15 where they are detected efficiently. Stable operation is possible because positive ions and electrons can be focused at the same point by the electromagnetic field with the same polarity and the same strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focused charged particle beam device using an objective lens consisting of an electrostatic lens and a magnetic field type lens, and a sample observation method using this device.

[Summary of the invention]

Using an animal lens consisting of an electrostatic lens and a magnetic field type lens, the spherical aberration coefficient and chromatic aberration coefficient of the electron probe irradiation system are reduced, and the generated secondary electrons are efficiently detected by passing through the hole of the electrostatic lens. I decided to do so. In addition, in a charged particle beam device that can selectively irradiate a sample with positive ions and electrons, an objective lens consisting of an electrostatic lens and a magnetic field type lens is used to focus the electron flux onto the sample, while the positive ion flux and By the action of the electric field of the electrostatic lens, which maintains the same polarity as when focusing the electrons, positive ions and electrons can be focused on the same sample position while maintaining the focus on the sample.

[Conventional technology]

Some charged particle beam devices such as electron microscopes use an electrostatic lens as an objective lens.

In terms of -II, such an electrostatic lens can shorten the electronic probe control time compared to a magnetic field type lens, makes it easier to achieve an ultra-high vacuum, and makes it possible to make the device more compact. However, it also has disadvantages, such as increased spherical aberration coefficients and chromatic aberration coefficients, which tend to reduce resolution, and electrical insulation problems when applying high voltage to the electrodes. Regarding the electrical insulation problem, in recent years, in the field of scanning electron microscopes, low acceleration devices with an acceleration voltage of 5 KV (kilovolts) or less have been attracting attention, and the above problem has been significantly alleviated.

A conventional example of an electrostatic lens with such characteristics is shown in Fig. 8. This electrostatic lens is called an Einzel lens, and has a central electrode l and pairs of electrodes on both sides of the central electrode l. It is generally composed of ground electrodes 2 and 3 arranged. Insulation is provided between the center electrode 1 and each ground electrode 2.3 so that a high voltage can be applied thereto.

In such an electrostatic lens, a negative (deceleration mode for electrons) or positive (acceleration mode for electrons) voltage is applied to the central electrode l, and the ground electrode 2.3
is grounded and held at ground potential. -Finally, the deceleration mode is often used in electrostatic lenses.

An electron beam flux 4 irradiated from an electron beam source is focused on a sample 5 located at a distance of WD (this is referred to as a working distance) from the lower ground electrode 3.

Regarding this Einzel lens, as values for each part, the thickness T of the central electrode is T-0 (am), the distance S between the central electrode 1 and the upper and lower electrodes 2 and 3 is 5 = 4 (n), and the central electrode 1 The hole diameter and the hole diameter of the upper and lower electrodes are D+ =02 =4
(1) m+), spherical aberration coefficient Cs and chromatic aberration coefficient C
The value of c is shown in FIG. 9.

In the graph shown here, Csd and Ccd are the spherical aberration coefficient and chromatic aberration coefficient, respectively, in the deceleration mode, and Csa and Cca are the spherical aberration coefficient and the chromatic aberration coefficient, respectively, in the acceleration mode. As can be seen from this graph, each aberration coefficient Csa in acceleration mode,
Cca is considered to be on the same level as the aberration coefficient in a normal magnetic field type lens, but each aberration coefficient Csd in deceleration mode
, Ccd has a value several times larger than the aberration coefficient in the acceleration mode of the electrostatic lens or the aberration coefficient in the magnetic field type lens. Therefore, it can be seen that the resolution tends to decrease in the electrostatic lens in the normal deceleration mode.

(Problems to be Solved by the Invention) On the other hand, although such conventional electrostatic lenses have advantages in terms of aberration coefficients as described above in acceleration mode, when operated in this acceleration mode, However, there is a problem in that the secondary electron capture efficiency tends to decrease.

That is, in this case, since a positive voltage is applied to the center electrode 1, a part of the secondary electrons are drawn into the electrostatic lens hole, especially when the working distance WD is small. For this reason,
With the usual method of installing the detector at a lateral position between the sample 5 and the electrostatic lens, it is difficult to capture all the secondary electrons. Therefore, in the case of acceleration mode, it is desirable to extract the secondary electrons above the electrostatic lens and detect them with a detector installed above this. However, in this case, the secondary electron capture rate is determined by the hole diameter of the lens. , varies greatly depending on the voltage applied to the electrostatic lens, etc. (for example, Autumn 1987, Japan Society of Applied Physics, 20a-G-9, NTT, Ken Saito et al.). Therefore,
In particular, it has been difficult to put it into practical use when the working distance WD or acceleration voltage changes significantly.

Also, for magnetic field type lenses, if the working distance WD is small, a secondary electron detector is installed above the magnetic field type lens, and if WD is large, a secondary electron detector is installed on the side of the sample. It was complicated, such as having to use it.

Furthermore, when secondary electrons are detected with a single secondary electron detector installed on the side of the sample, the sample must be illuminated obliquely, and for example, when observing a VLSI pattern, the line profile may change. This had the disadvantage that it became asymmetrical and the length measurement became inaccurate.

Furthermore, in sample observation devices that use ions as charged particles, such as an ion focusing device (FIB), magnetic field type lenses are not used because the quality of the ions is large.
The electrostatic lens shown in FIG. 8 is used for C. In recent years, G.
Generate positive ions and electrons such as a from the same particle source,
There is an attempt to focus ions and electrons on the sample 5 using a lens barrel that shares the particle beam axis. For example, in Fig. 8, for monovalent positive ions, a positive voltage with an accelerating voltage of U is applied to the central electric scraper 1, and for electrons, a negative voltage of the same magnitude is applied. When applied, the light is focused at a position with the same working distance WD and has the same optical constant.

However, since the polarity of the applied voltage must be switched, there are problems in terms of stability and operability of the device's operation.

The present invention was made in view of these conventional problems, and its first purpose is to reduce the aberration coefficient, increase the secondary electron capture efficiency, and improve the resolution of scanning charged particle beam devices. , to improve image quality.

The second object of the present invention is to make it possible to focus positive ions and electrons on the same sample position without changing the polarity of the objective lens and to make the intensity almost the same, thereby improving the stability and operability of the charged particle FA device. The objective is to provide improved sample observation methods.

[Means to solve the problem]

In order to achieve the above object, the present invention configures an objective lens with an electrostatic lens and a monopolar magnetic field type lens arranged coaxially with the electrostatic lens, and focuses a charged particle beam onto a sample using the objective lens. In addition, a secondary electron detector was installed above the objective lens, and the secondary electrons were restrained near the particle beam axis by the objective lens, passed through the electrostatic lens hole, and detected by the secondary electron detector. This is the main point.

Moreover, the invention of this application is a particle that generates ions and electrons!
l/jIa, means for selectively irradiating the sample with these ions or electrons along the same particle beam axis, an objective lens composed of an electrostatic lens and a magnetic field type lens arranged coaxially with each other, and this objective. The main gist is a charged particle beam device having a secondary electron detector placed above a lens.

Furthermore, the invention of the present application provides the above-mentioned ion and electron focusing type charged particle beam device, in which, by the action of the electromagnetic field of the objective lens,
While focusing the electron beam on the sample, the polarity of the electrostatic lens is kept the same as when the electric and magnetic fields are applied, and the ion flux is focused on the sample mainly due to the electric field of the objective lens, and the generated two The main gist is a sample observation method in which secondary electrons are confined near the optical axis, passed forward through an objective lens hole, and then detected by a secondary electron detector.

[Effect]

An electron beam emitted from a particle beam source is subjected to electric and magnetic field effects by an objective lens and is focused onto a sample.

This focusing of the electron beam causes an excitation effect on the sample surface and generates secondary electrons. This secondary electron is captured by the electric field and magnetic field of the objective lens, is restrained near the particle beam axis, and passes through the objective lens hole. Then, it is detected by a secondary electron detector placed above the objective lens. In addition, in devices where the particle beam source emits both electrons and positive ions, it is possible to focus each particle on the same sample position without switching the lens polarity for positive ions and electrons, and to maintain almost the same intensity, resulting in stability. , improves operability.

〔Example〕

FIG. 1 is a diagram showing a first embodiment of a charged particle beam device according to the first invention of the present application. The charged particle beam device according to this embodiment includes an electrostatic lens 10 placed in front of a sample 5 installed in a sample chamber 14, and a top surface 13 placed between the sample 5 and the electrostatic lens lO. , a magnetic field type lens 1) which constitutes an objective lens 12 together with the electrostatic lens IO, and a secondary electron detector 15 disposed in front of the objective lens 12. The electrostatic lens 10 is arranged in pairs with a Middle East type i16 on both sides above and below the central electrode 16.
6 is constituted by an Einzel lens having an upper electrode 18 and a lower electrode I9 insulated by an insulating member 17 such as an insulator. A positive voltage of ■ (volts) is applied to the center electrode 16, and the upper and lower electrodes 18 and 19 are grounded. A single-pole magnetic field lens is used as the magnetic field lens 1), and this magnetic field lens has a magnetic pole top surface 13 disposed close to the electrostatic lens 10, and a yoke 20 made of a magnetic material, and this yoke. 20 and an excitation coil 21 wound around the electrostatic lens, and is installed coaxially with the electrostatic lens. Also, the top surface 13 and each mold 4m16.18.
A hole 23 through which the electron beam or electron beam bundle 22 passes is formed in the central axis portion of the electron beam 19 .

Further, the sample chamber 14 is made of a non-magnetic material, and the excitation coil 21 and the yoke portion 20a surrounding it are installed outside the vacuum and can be taken out when baking out the lens barrel.

In such a configuration, the magnetic field type lens 1) has a magnetomotive force J(
AT (ampere turns) is applied.

The electron beam flux 22 is focused on the sample 5 by the electric field created by the electrostatic lens 10 and the magnetic field created by the magnetic field type lens 11. This electron probe is scanned onto the sample 5 by a two-stage scanning means (not shown) provided above the objective lens 12. The secondary electrons 24 generated by this are a magnetic field type lens! The particle beam is restrained near the axis 25 (hereinafter referred to as the optical axis for convenience) by the magnetic field created by (2), enters the lens hole 23, and is further restrained near the optical axis 25 by the action of the electrostatic field by the electrostatic lens IO. It is detected by a secondary electron detector 15 provided above the electrostatic lens 10.

FIG. 2 is a diagram showing a second embodiment in which the structure of the charged particle beam device according to the first embodiment is partially modified. In this example, the magnetic pole top surface 1 of the monopolar magnetic field type lens 1)
3 constitutes the lower electrode of the electrostatic lens lO. The configuration of other parts is the same as that of the first embodiment. The same applies to the action. Note that since the lower electrode of the electrostatic lens 10 and the top surface of the magnetic pole of the magnetic field type lens 1) have a common structure, the structure is more compact than that of the first embodiment. Sample 5
Since the distance between the objective lens 12 and the objective lens 12 becomes smaller, the optical characteristics of the objective lens 12 are further improved.

An example of the magnetic field distribution (B / B zo) in the optical axis Z direction due to the single magnetic field type lens in this example and an example of the potential distribution (V / V, ) on the optical axis due to the electrostatic Einzel lens are shown in the 10th example. As shown in the figure.

However, Be and Vo indicate their respective maximum values, and ■ indicates that the ground potential is 0 volts.

As shown in Fig. 10, the magnetic field distribution of the unipolar magnetic field type distribution gradually attenuates in the direction of 2>0 (the direction of the sample in Fig. 2), and decreases in the direction of Z<0 (in the direction of the sample in Fig. 2). The magnetic field of the monopolar magnetic field type lens and the electric field created by the electrostatic Einzel lens hardly overlap.

Therefore, the charged particles are not affected by the combined electromagnetic field, but are affected by the electric field and the magnetic field separately. This is also a feature of the objective lens of the present invention.

FIG. 3 explains the trajectory of the secondary electrons in the above two examples, in which a positive voltage was applied to the electrostatic lens 10 of the objective lens 12, and the magnetomotive force of the magnetic field type lens 1) was set to 0. The orbits of the secondary electrons in this case are shown in Figure 3 fal.

In this case, the secondary electrons 24 emitted from the sample 5 at a large angle
travels almost straight and collides with the magnetic pole without passing through the hole 23 of the electrostatic lens 10. In Fig. 3 fbl, the voltage applied to the electrostatic lens 10 is O, and the magnetomotive force of the magnetic field type lens is several hundreds (AT
) The secondary electrons 24 are restrained near the optical axis, but when the hole diameter of the magnetic field type lens 1) is small, they hit the hole wall and the secondary electrons are detected. Vessel 1
It may not reach 5. Figure 3 [C1 shows the movement of the secondary electrons 24 when a positive magnetomotive force is applied to the electrostatic lens 10 and an appropriate magnetomotive force is applied to the magnetic field type lens 1).The secondary electrons 24 are restrained near the optical axis 25 by the magnetic field. It is further subjected to the restraining action of an electric field within the electrostatic lens 10, and is taken out above the electrostatic lens 10 through the lens hole 23.

Approximate conditions for the magnetomotive force of the magnetic field type lens for allowing secondary electrons to enter the lens hole 23 are as follows.

An electron with velocity Q entering a uniform magnetic field B at an angle θ has a radius of moυsinθ e make a spiral movement.

Therefore, in the embodiment shown in FIGS. 1 and 2,
In order for the secondary electrons 24 to enter the lens hole 23, it is necessary to satisfy the following condition: (1) 2γ≦DO at the sample 5 position (ie, the distance from the top surface 13 to the WD). Here, DO is the diameter of the top surface 13 of the magnetic field type lens 1). Furthermore, (2) it is necessary to satisfy the condition 2T≦DI at the position of the top surface 13 of the magnetic field type lens 1). Here DI is the top surface 13
This is the diameter of the hole provided in the hole.

Of the above two conditions, condition (1) is a condition for restraining the secondary electrons 24 near the optical axis 25, and condition (2) is a condition for the secondary electrons 24 to enter the lens hole 23. be.

When each of the above conditions is determined using the second equation regarding the distribution of magnetic flux density B, WD holds true as condition fl), and DI holds true as condition (2).

Furthermore, if the focus excitation force of only the magnetic field type lens 1) at the sample position (that is, the WD) is 30, then
In order to perform focus control using the electrostatic lens 10, the magnetomotive force J to be applied to the magnetic field type lens 1) needs to satisfy the following equation: J<JO-...-(31).

By applying a magnetomotive force J that satisfies the above three conditions to the magnetic field type lens 1), most of the secondary electrons 24 are always guided upward through the lens hole 23 regardless of the working distance WD, and the secondary electrons Detection can be performed by the detector 15, and focus control can be performed by an electrostatic lens. This eliminates the inconvenience of having to provide a plurality of secondary electron detectors depending on the WD when conventional magnetic field type lenses are used.

Also, if you do not want to increase the magnetic flux density B at the sample position,
It is convenient when a fixed magnetic flux density is desired (for example, when observing a magnetic material). That is, the condition fil~(
By selecting the magnetomotive force J that satisfies 3), the required magnetic flux density B above the sample 5 can be obtained. At this time, the focus is adjusted by controlling the voltage applied to the electrostatic lens 10.

FIG. 4 is a diagram showing a third embodiment of the charged particle beam device according to the present invention. The charged particle beam device according to this example is
An electrostatic lens 10 is provided above the sample 5, a magnetic field type lens 26 is provided below the sample 5 coaxially with the electrostatic lens 1o, and constitutes an objective lens 27 together with the electrostatic lens 1O; A secondary electron detector 15 is provided north of the lens 10.

The electrostatic lens 10 has the same configuration as described above. A unipolar magnetic field lens is used as the magnetic field lens 26, and this unipolar magnetic field lens consists of a yoke 28 having a magnetic pole top surface at the center, and an excitation coil 29 wound around the yoke 28. It is installed at a distance l below the lower ground electrode 19 of the electrostatic lens 10.

In this configuration, a high voltage is applied to the center electrode 16 of the electrostatic lens 10, and a magnetomotive force J is applied to the magnetic field type lens 26.
(AT) is applied. As a result, the electron beam 22 is focused on the sample 5 by the action of the electromagnetic field, as in the first and second embodiments. Secondary electron 24 emitted from sample 5
passes through the lens hole 23 while being affected by the magnetic field created by the unipolar magnetic field type lens 26, and is further focused by the action of the electrostatic field created by the electrostatic lens, and then passes through the secondary electron detector 1.
Detected by 5.

The orbits of the secondary electrons can be explained using the same theoretical formula as described above for the first and second embodiments. Therefore, in order to allow the secondary electrons 24 to enter the lens hole 23, it is sufficient to satisfy the conditions (1) and (2). In this third embodiment, when the diameter of the lens hole 23 is D, the conditions for the magnetomotive force J of the magnetic field type lens 26 for the secondary electrons to enter this lens hole 23 (the above-mentioned condition ( 2)) is D t D .

becomes. Here, Do is the diameter of the top surface 28.

In addition, the condition corresponding to the above condition (1) at the sample position is the above equation (4) because in the arrangement in this example, the magnetic flux density B on the sample 5 is larger than the magnetic flux density B in the lens hole 23. If you are satisfied, you will be satisfied automatically.

Furthermore, also in this embodiment, it is necessary to satisfy the condition of the above-mentioned formula (3).

By satisfying each of the above conditions, the secondary electrons 24 emitted from the sample 5 can be guided above the objective lens 27 through the lens hole 23 and detected by the secondary electron detector 15.

Next, the first. Second. Spherical aberration coefficient C5 and chromatic aberration coefficient C of objective lens 12.27 shown as the third example
Let's talk about c.

The paraxial orbit of an electron in an axisymmetric electromagnetic field is expressed by the following equation.

, and M, N, and G are expressed by the following formula, where y: Displacement from optical axis 2 φ; Potential Bz: Magnetic flux density in two directions of optical axis e: Electron charge mo: Rest mass of electron It is.

The spherical aberration coefficient Cs and the chromatic aberration coefficient Cc of the electromagnetic lens are respectively expressed by the following equations.

Here, zo: object plane position z,: image plane position φ0: potential at the object plane U: acceleration voltage - φ”' −B z B' z ] −−(8
) N= FT I FIG. 5 shows the equation (5) ~at+ for the second embodiment.
2 is a graph showing the values of Cs and Cc determined by 2. However, in this case, the dimensions of the electrostatic lens 10 are T = 4 (n) S = 4 (n) DI = oz = 4 (dragon), and for the magnetic field type lens 1), o, -t2 (m). Moreover, the magnetomotive force J of the magnetic field type lens 1) is J/,
A constant value of r100 = 5 (AT/V7) was set.

As is clear from Fig. 5, at WDχ5 (mW), C3χ75 (ms), Ccχ9.5 (1m)
, and a sufficiently small aberration coefficient is obtained. Also, W.D.
It can be seen that where the value of is large, the spherical aberration coefficient Cs is particularly small compared to the conventional case.

Note that calculations were made here using equations (5) to 00 for the case where the electric field and magnetic field exist in combination, but in the embodiments of the present invention, especially in FIG. 4, the electric field and the magnetic field exist almost independently. Therefore, similar values can be obtained by calculating and combining the dimensions for the electric field and magnetic field.

Furthermore, for any other combination of the voltage applied to the electrostatic lens 10 and the magnetomotive force of the magnetic field type lens 1), it is possible to obtain the values of Cs and Cc in the same manner as described above. The values of Cs and Cc can be determined in the same manner for the third embodiment.

In the charged particle beam apparatuses according to the first to third embodiments, when changing the acceleration voltage while keeping the sample position the same, the magnetic field type lens 1). The magnetomotive force j of 26 is the above il
The focus can be controlled by changing the voltage applied to the electrostatic lens 10 with a constant value that satisfies equations 1 to (4).

Furthermore, in the first to third embodiments, if a voltage is weakly applied to the electrostatic lens and the unipolar magnetic field lens is strongly excited, or if a voltage is strongly applied to the electrostatic lens and the unipolar magnetic field lens is weakly excited, each Produces a special effect.

Now, in the example of Fig. 2, T-4m++, S=4wm, thickness of monopolar lens pole piece 4fl, D+ =Dz =D+ =4taφ, Do =12
For the case of mmφ, find Cs and Cc.

Fig. 1) shows Cs with respect to WD, and Fig. 12 shows Cc with respect to WD.

In Figure 1), Cs represents Cs when only the electrostatic lens (acceleration mode) is operated, and Csm represents Cs when only the unipolar magnetic field type lens is operated.

Cse shows the change in C3 with respect to WD when the electrostatic lens strength is maintained at a value that focuses the WD at 10 m using only the electrostatic lens, and the magnetomotive force T of the monopolar magnetic field type lens is increased (at point E, J =0).

Csm indicates the change in Cc with respect to WD when the monopolar magnetic field type lens strength is maintained at a value that allows focusing on WD = 10 fins only with this lens, and the electrostatic lens strength is increased. Applied voltage of lens center electrode■
1 = 0 volts).

FIG. 12 similarly shows the chromatic aberration coefficient Cc.

From Figure 1) and Figure 12, C5 with only a single-pole magnetic field type lens
It can be seen that Cc is the smallest, but this lens alone has the disadvantage that secondary electrons cannot be detected effectively as described above.

Therefore, in order to eliminate this inconvenience, a weak voltage is applied to the electrostatic Einzel lens. For example, a voltage of +50 volts is applied. This voltage has an extremely weak effect on the primary electron beam of -500 volts or more, and its C3, CC
is no different from that of a single-pole magnetic field lens.

However, it has a strong lens effect on secondary electrons (approximately -5V), and due to its focusing effect, the secondary electrons are taken out above the electrostatic lens and detected.

In this case, it is suitable for high-resolution observation and high-precision length measurement by detecting secondary electrons from above, but it is not suitable for high-speed automatic length measurement due to the hysteresis peculiar to magnetic field type lenses.

Therefore, in order to achieve high-speed automatic length measurement, the magnetomotive force of the single magnetic field lens should be small, and the applied voltage V of the electrostatic lens should be large (for example, WD - 10 m, J = 60 AT. The magnetomotive force acts only extremely weakly on primary electron beams of 1,500 mm or more, but acts as a strong magnetic field lens on secondary electrons, confining them near the optical axis.C5Cc It is no different from Cs and 'Cc with only electrostatic lenses.

Therefore, the resolution is lower than when a single-pole magnetic field type lens is operated strongly, but by combining it with a field emission electron gun, it is possible to obtain a resolution of, for example, about 20 degrees even at a low accelerating voltage, and submicron Highly accurate length measurement of patterns is possible. The value of J-60AT is determined by the constraint condition formula [1],
! 2], it effectively enters the electrostatic lens hole and is detected after being focused by the electrostatic lens.

If this magnetomotive force J=60AT is fixed regardless of the accelerating voltage, there will be no problem of hysteresis due to changes in the accelerating voltage, and the device will work well for the above purpose.

Furthermore, if you want to observe a magnetic material such as a magnetic disk without a magnetic field, the magnetomotive force of the unipolar magnetic field type lens should be J = O, but in this case, a secondary electron detector is installed on the side of the sample. There is a need.

It is also possible to modify the third embodiment and replace the excitation coil 29 with a permanent magnet. FIG. 6 is a diagram showing an example of such a change.

In this modified example, the outer part of the yoke 31 of the magnetic field type lens 30 is constituted by a permanent magnet 32 magnetized to N and S poles, and the action of this permanent magnet 32 causes the top surface 33 of the single magnetic field type lens to move forward. A magnetic field is created. Note that the arrangement and configuration 1 function of the sample 5, electrostatic lens 10, and secondary electron detector 15 above this magnetic field type lens 30 are the same as described above for the third embodiment, and the magnetic field type lens The same applies to the point that 30 constitutes the objective lens 34 together with the electrostatic lens IO.

Regarding the charged particle beam devices according to the first to third embodiments (including modified examples) having the configuration and operation as described above, the particle beam source is improved, and the sample 5 is irradiated with electrons and positive ions. If this is possible, the functionality of this charged particle beam device will be further expanded.

Figure 7 shows the voltage of the electrostatic lens 10 and the magnetomotive force of the monopolar magnetic field type lens 1) in a charged particle beam device that can selectively irradiate the sample 5 with electrons or positive ions from the particle beam source side. FIG. 3 is a diagram showing that the positive ion beam 35 and the electron beam 22 are focused on the same sample position (that is, the same WD), assuming that the positive ion beam 35 and the electron beam 22 are the same. A positive applied voltage V (
#0.6 l IJ 1) (Volt) A magnetomotive force J (=7 xE■) (AT) is applied to the magnetic field type lens 1). Although this is not applied to the positive ions 35, the positive applied voltage V acts as a deceleration electric field, and the ions are focused at the position of the WDζ15 fin at a relatively low voltage.

On the other hand, for negatively charged electrons 22, a positive applied voltage V having the same magnitude as that for positive ions acts as an accelerating electric field, and the voltage is sufficient to focus them on the same sample position. However, it is sufficiently large compared to the case where □ is an ion, and it can be focused to the electric field and I=I15). In these cases, the aberration coefficient for the ion trajectory is, for example, Csd in FIG.

The aberration coefficient for the electron trajectory is shown as Cs and Cc in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, small spherical aberration coefficients and chromatic aberration coefficients can be obtained by using an objective lens constituted by an electrostatic lens and a magnetic field type lens. The secondary electrons are confined and guided near the optical axis of the composite electromagnetic lens, and can be efficiently detected by the secondary electron detector, which improves resolution.

Image quality improves.

Furthermore, during VLSI observation, the line profile of the pattern can be obtained symmetrically, and the length measurement accuracy is improved. Furthermore, when observing a sample, the excitation of the magnetic field type lens is fixed and the focus can be controlled using only the electrostatic lens.
The response speed is improved compared to magnetic field type lens control, which is advantageous for automated measurements.

Furthermore, the sample is irradiated with positive ions and electrons,
When obtaining an image, positive ions and electrons can be focused on the same point by using electric and magnetic fields of the same polarity and the same magnitude, improving stability and operability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of a charged particle beam device according to the present invention, FIG. 2 is a diagram showing a second embodiment of a charged particle beam device according to the present invention, and FIGS. cl is a diagram showing secondary electron trajectories accompanying changes in the operation of the objective lens in the above two embodiments, FIG. 4 is a diagram showing a third embodiment of the charged particle beam device according to the present invention, and FIG. 5 is a diagram showing the above embodiment. A graph showing the spherical aberration coefficient and chromatic aberration coefficient of the objective lens in FIG. 6 is a diagram of a modification of the third embodiment in which a permanent magnet is used for the magnetic field type lens, and FIG. 7 is a graph showing the irradiation by switching between ions and electrons. Fig. 8 is a schematic configuration diagram showing an example of a conventional electrostatic lens, and Fig. 9 shows the spherical aberration and chromatic aberration of a conventional electrostatic lens and a magnetic field type lens, respectively. These are graphs. Figure 1O is a diagram showing an example of the potential distribution on the optical axis in an electrostatic lens and the magnetic field distribution on the optical axis in a monopolar magnetic field type lens.
s, a diagram showing Cs with only a single-pole magnetic field type lens, and Cs when both lenses are operated simultaneously, and FIG. 12 is a diagram similar to the first) diagram for Cc. 10... Electrostatic lens 1). 26.30...Magnetic field type lens 12.27.34...Objective lens 13...Top surface 15...Secondary electron detector and above Applicant: Seiko Electronics Co., Ltd. Agent Patent attorney Keiyuki Hayashi Explanation of the orbit of secondary electrons Figure 1 Figure 3 (α) Orbit of two missing electrons Figure 13 □ W edition Figure 6 Figure 3 (b) D, ZV thousand orbits 1 beak Fig. 3 (C) shows the permanent downy hair and the heather is shown in Fig. 6 (F)! ! IJ・1's Natsumimen da matari L i brutality r (Cs), color da 7 difference i series r (Cc ri Hōkiguzuzukihigashi's sparse side Sakai and f
! ! Figure 9 of Sakai's late death (1111 marriage to -m-)

Claims (7)

[Claims] (1) An electrostatic lens installed in front of the sample, and a monopolar magnetic field coaxial with the electrostatic lens and with the top surface of the magnetic pole placed close to the electrostatic lens between the electrostatic lens and the sample. A charged particle beam device comprising: an objective lens constituted by a mold lens; and a secondary electron detector disposed in front of the objective lens. (2) The charged particle beam device according to claim (1), wherein the electrostatic lens is an Einzel lens, and the lower electrode thereof is constituted by the top surface of a magnetic pole of a monopolar magnetic field type lens. (3) An objective lens consisting of an electrostatic lens placed in front of the sample, a unipolar magnetic field type lens coaxial with the electrostatic lens and with the top surface of the magnetic pole placed behind the sample, and an electrostatic lens. A charged particle beam device equipped with a secondary electron detector placed in front of the lens. (4) Claims (1) to (3) comprising a particle beam source that generates ions and electrons, and means for selectively irradiating the sample with these ions or electron beams along the same particle beam axis.
The charged particle beam device described. (5) The electron beam is focused on the sample by the electric and magnetic fields of the objective lens, and the ion flux is focused by keeping the polarity of the electrostatic lens the same as when the electric and magnetic fields are applied. The electric field of the objective lens is used to focus the secondary electrons on the sample, and the resulting secondary electrons are restrained near the particle beam axis, passed through the objective lens hole, and then detected by a secondary electron detector. Claim (4)
Sample observation method using the charged particle beam device described. (6) A weak voltage is applied to the electrostatic lens, and the unipolar magnetic field lens is strongly excited, so that the electron beam flux is focused on the sample mainly by the magnetic field action of the unipolar magnetic field type lens. A charged particle beam device according to any one of claims (1) to (3). (7) A strong voltage is applied to the electrostatic lens, a monopolar magnetic field lens is weakly excited, and the charged particle beam is focused on the sample mainly by the action of the electric field of the electrostatic lens. A charged particle beam device according to any one of claims (1) to (3).