JP3531323B2 - Ion beam processing method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam projection method and apparatus for subjecting a sample to microfabrication using an ion beam formed by a mask.

[0002]

2. Description of the Related Art An ion beam projection apparatus projects an aperture pattern on a mask illuminated with an ion beam onto a sample by reducing it with a lens and utilizing physical or chemical changes on the sample. This is a device for processing fine patterns on the.

As a conventional example, an ion projection lithographic apparatus that exposes a stencil mask pattern with an ion beam onto a wafer coated with a photoresist as a sample,
Proceedings Microelectronics Engineering,
Volume 17 (1992) pp. 229-240 (Mic
roelectronic Engineering, 17 (1992) 229-2
40).

The structure of this ion projection lithography apparatus will be described with reference to FIG. The stencil mask 24 is exposed by the irradiation lens 23 with the ion beam 22 extracted from the ion source 21. In this case, in order to form a pattern as fine as possible on the photoresist, a light element hydrogen or helium ion is emitted using a duoplasmatron type ion source. The stencil mask 24 held on the mask stage 25 is provided with an opening pattern 24 ′, and the ion beam 22 passing through the stencil mask 24 is projected onto a sample 28 by a projection lens 27 via a focusing lens 26. At this time, the projection lens 27 reduces the image of the opening pattern 24 ′ provided on the stencil mask 24 onto the sample 28 and exposes it. The sample 28 is held by the sample stage 29, and when one ion beam projection is completed, the sample stage 29 is sequentially moved to expose the same pattern image at different positions on the sample surface. By this ion beam projection and movement of the step-and-repeat type sample stage, it is possible to expose a large number of the same pattern on the entire sample surface. Further, these ion optical systems are installed in the vacuum container 30.

As described above, after exposing the resist to the pattern by the ion beam, the sample is developed and the resist in the ion beam projection portion is removed to form a resist pattern in which the opening pattern 24 'on the stencil mask 24 is reduced. Many can be formed.

[0006]

In the ion projection lithography apparatus as described above, the pattern formed on the sample surface is determined by the opening pattern provided in advance on the stencil mask. A plurality of patterns formed on the sample are repeated with the same pattern by intermittent projection of the ion beam and sequential movement of the sample stage.

When the pattern ion beam having a high current density is continuously projected onto the sample using the projection type ion beam optical system, the substrate is sputtered into the opening pattern shape of the mask. By utilizing this, for example, if the rectangular opening is provided in the stencil mask most easily, a rectangular concave portion can be formed in the sample. By observing the side surface of this recess,
The sectional structure of the substrate can be known. That is, the cross section of the sample can be formed using the projection type ion beam optical system.

Even if the number of patterns provided on the stencil mask is small, it is desired to form a sharp image with less distortion and blur. In addition, there are many needs for using the beam to perform processing such as etching and deposition on the sample surface. However, when a pattern is projected using a projection-type ion beam optical system, the image has large distortion and blurring in the peripheral part away from the optical axis, and it is difficult to obtain a sharp shape to the peripheral part. Is large and not always sharp. This can be explained as follows.

FIG. 3 is a graph schematically showing the relationship between the distance from the optical axis and the magnitude of distortion generated in the beam. The beam reaching the sample surface has the smallest distortion on the optical axis and the best resolution of the formed image, but it sharply increases with distance from the optical axis and the image resolution deteriorates. When a sample is processed by sputter etching with a projected ion beam, the sharpness of the processed part and the non-processed part, that is, the boundary between the ion beam projection part and the non-projection part is affected by the beam distortion and aberration. If the aberration is large, the sharpness of the boundary becomes worse. Particularly, in the processing method for forming the cross section of the sample, the boundary surface between the processed portion and the non-processed portion must be sharp. However, if the side of the opening pattern provided in the mask that determines the cross section to be formed in the sample is far from the optical axis, distortion and aberration occur as described above at the boundary surface of the pattern beam, and the result is obtained. It should not be possible to form a sharp cross section.

4 and 5 show the relationship between the position of the opening pattern on the mask and the processed shape formed on the sample.
FIG. 4A shows a part of the mask 40 having an opening pattern 42 for forming a rectangular recess in the sample, and the mask 40 has a rectangular opening pattern 42 centered on the optical axis 41.
Is provided. Reference numerals 43 and 43 ′ are two straight lines that are orthogonal to each other through the optical axis 41 shown to clarify the positional relationship between the optical axis 41 and the rectangular opening pattern 42. When the rectangular opening pattern 42 is very small, each side of the rectangular opening pattern 42 (for example, point A in FIG. 3) is close to the optical axis 41, so that the distortion C is sufficiently small. However, the rectangular opening pattern 4
When 2 becomes large, each side of the rectangular aperture pattern 42 (for example, point B in FIG. 3) is separated from the optical axis 41, so that the beam passing near each side and reaching the sample has a large distortion D. become. FIG. 4B is a cross section of the recess 45 obtained by projecting such a beam onto the sample 44 and subjecting the sample 44 to sputter etching. The desired vertical (sharp) cross section cannot be obtained due to sagging on the boundary surfaces (cross sections) 46, 46 'of the processed and non-processed portions formed on each side of the opening pattern on the mask. For these reasons, there has been a demand for an ion beam processing method and a processing apparatus capable of forming a sharp processed surface.

In view of the above-mentioned problems, the first object of the present invention is to provide a pattern ion beam formed by passing an ion beam through an opening pattern of a mask to form a sharp cross section, particularly a cross section substantially perpendicular to the sample surface. And a second object of the present invention is to provide an ion beam processing apparatus for realizing the first object.

[0012]

In order to solve the above problems, the opening pattern provided in the mask is formed in the cross section to be formed in the opening pattern 51 provided in the mask 50 as shown in FIG. The corresponding side 52 is arranged so as to be orthogonal to each other through the optical axis 53 (reference numeral 53 ′ indicates the optical axis 53).
A straight straight line through). FIG. 5B shows the concave portion 5 formed in the sample 54 by passing through the opening pattern 51 of FIG.
5 is a sectional view of FIG. Since the ion beam irradiated to the mask 50 has the smallest distortion and aberration around the optical axis 53, the cross-section 56 formed by the side 52 has very good sharpness and becomes nearly vertical. The above-mentioned problem can be solved by such an opening pattern.

Specifically, it is realized by the following configuration.

(1) An ion source, a mask having an opening pattern through which an ion beam passes, an irradiation optical system for irradiating the mask with an ion beam extracted from the ion source, a sample stage for holding a sample, and the above In an ion beam processing apparatus including a projection optical system that projects a pattern ion beam that has passed through a mask onto the sample to form an image of the aperture pattern on the sample, in particular, the aperture pattern has a side intersecting an optical axis. An ion beam processing device that has a graphic.

(2) In (1), particularly, the ion beam processing apparatus in which the mask has only one opening pattern.

(3) An ion source, a mask section having an opening pattern through which the ion beam passes, an irradiation optical system for irradiating the mask section with the ion beam extracted from the ion source, and a sample stage for holding a sample. And a projection optical system that projects a patterned ion beam that has passed through the mask portion onto the sample to form an image of the aperture pattern on the sample, in particular,
The above-mentioned mask portion is composed of two masks that are overlapped with each other with a gap, and one of the two masks has an opening pattern having one side that intersects the optical axis.

(4) In (3), in particular, the mask portion has a first mask fixed with an opening pattern having at least one side orthogonal to the optical axis, and an opening or notch. And an ion beam processing apparatus including a second mask movable in a direction perpendicular to the optical axis.

(5) In the ion beam processing apparatus according to (4), in particular, the first mask is a rectangular flat plate.

(6) In (4) or (5), in particular, an ion beam processing apparatus in which there are two types of substantial apertures through which the ion beam passes by the movement of the second mask: a large aperture and a minute aperture. .

(7) In (1) to (6), in particular,
An ion beam processing apparatus having a secondary electron detector near the sample.

(8) In (7), particularly, an ion beam processing apparatus having a beam scanning means between the mask and the sample.

(9) In (1) to (8), in particular,
An ion beam processing apparatus further comprising a means for displaying a secondary electron image of the sample.

(10) The ion beam extracted from the ion source is applied to a mask having an opening pattern of a figure having one side orthogonal to the optical axis, and the patterned ion beam passing through the mask is sampled by a projection optical system. An ion beam processing method for processing the sample by projecting onto the sample.

(11) In (10), in particular, an ion beam processing method for forming a recess in the sample by the patterned ion beam projection.

(12) In the method of (11), in particular, the recess formed in the sample has at least one surface substantially perpendicular to the surface of the sample.

(13) Ions for processing the sample by irradiating the mask part having the opening pattern with the ion beam extracted from the ion source and projecting the patterned ion beam passing through the mask part onto the sample by the projection optical system. A beam processing method, in particular, the opening pattern is formed by a plurality of masks overlapping with each other with a gap, and
An ion beam processing method for forming one side orthogonal to the sample through the optical axis by at least one of the masks.

(14) In the method of (13), particularly, the pattern of the pattern formed on the sample forms a recess having at least one surface substantially perpendicular to the surface of the sample.

(15) In (13), in particular, by moving one of the plurality of masks to change the shape of the substantial passage portion of the ion beam, and to use the pattern beams having different cross-sectional shapes. An ion beam processing method for forming a desired processing shape on the sample by the method.

(16) In (13), in particular, the pattern ion beam that has passed through the large opening is formed by forming a large opening in the mask portion where the ion beam substantially passes.
An ion beam processing method in which a substantially aperture portion of the mask portion is formed into a minute opening, and the sample is processed using the patterned ion beam that has passed through the minute opening.

(17) An ion beam processing method according to (16), which particularly includes a step of processing the sample by scanning the patterned ion beam that has passed through the minute aperture.

(18) An ion beam processing method according to (16), which particularly includes a step of scanning the patterned ion beam passing through the minute aperture and observing the surface of the sample with secondary electrons from the sample.

(19) In (16), in particular, a step of roughly processing the sample with the patterned ion beam that has passed through the large opening, and a step of finishing the sample with the patterned ion beam that has passed through the minute opening. Ion beam processing method including.

In (20) and (16), in particular, the step of observing the sample with the ion beam that has passed through the minute opening, the step of subjecting the sample to rough processing with the ion beam that has passed through the large opening, and An ion beam processing method comprising a step of finishing the sample with an ion beam that has passed through a minute opening.

[0034]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG. This example is an ion beam processing apparatus for forming a cross section on a semiconductor element.

In FIG. 1, 2 is an ion source, 3 is an irradiation lens, 4 is a mask portion, 5 is a focusing lens, 6 is a projection lens, and 7 is a sample. The ion source 2 is an argon point ion source. The ion beam 8 emitted from the ion source 2 is substantially vertically incident on the mask portion 4 by the irradiation lens 3. The mask portion 4 has a variable aperture pattern 4 ′, and a fixed mask 10 where one side of the aperture pattern 4 ′ intersects the optical axis 9.
And a movable mask 11 that substantially determines the ion beam passage region. The fixed mask 10 is fixed to the supporting portion 12 via a fixing portion 10 '. Further, the movable mask 11 is fixed to the support portion 12 via a support 13 and a fine movement means 14. The amount of expansion and contraction of the fine moving means 14 determines the substantial ion beam passage area. The ion beam 8 that has passed through the mask portion 4 is once focused by the focusing lens 5,
It is projected onto the sample 7 by the projection lens 6. At this time, a reduced image of the shape of the opening pattern 4'formed by the mask portion 4 can be formed on the surface of the sample 7. The greatest feature of this apparatus is that one side of the opening pattern 4'in the mask portion 4 is provided so as to intersect the optical axis 9 at right angles.

The sample stage 15 is capable of XY fine movement, and a plurality of processed portions can be formed on the sample 7 by sequentially moving the sample stage 15 and pattern ion beam projection. Further, a secondary electron detector 16 is installed near the sample 7 so that secondary electrons generated during beam projection can be detected. The opening pattern 4'of the mask portion 4 is made minute,
A fine ion beam is made to reach the sample, the fine ion beam is scanned and swept on the sample by the scanner 17, and the secondary electrons emitted from the sample 7 are captured, so that the secondary electron image on the sample surface can be viewed. All of the above optical components are provided in the vacuum container 18.

The ion source 2, the irradiation lens 3, the focusing lens 5 and the projection lens 6 are respectively provided with power supplies 2 ', 3', 5'and 6'for supplying voltage, and their outputs are signal processor 19 respectively. Controlled by. Also, the fine movement means 1
4, the sample stage 15 and the scanner 17 are also controlled by the signal processor 19. Further, a signal from the secondary electron detector 16 can be taken in and the beam shape and the surface shape of the sample can be displayed on the image display device 19 'as required. By paying attention to the size, distortion and blurring of the beam shape displayed on the image display device 19 ', the strength of each lens can be adjusted and the position of the variable mask 11 can be adjusted.

In the present embodiment, one type of ion beam optical system has been described as an example, but it goes without saying that the above effects can be obtained with other configurations having different numbers and positions of irradiation lenses and projection lenses. . Further, although an argon point ion source is used as the ion source in this example, an ion source using a metal or semiconductor such as gallium or silicon as an ion species may be used.

As described above, the ion beam processing apparatus according to the present invention is effective for forming a vertical processing region of a processing cross section. Furthermore, the sample can be observed with a micro aperture pattern ion beam. Further, the opening pattern may be formed by one mask or may be formed by a larger number of plural masks.

(Second Embodiment) Here, a specific example of the mask portion 4 will be described in detail with reference to FIGS. 6 to 8.

In the ion beam processing apparatus according to the present invention,
The mask that determines the beam shape reaching the sample differs from the stencil mask used in the conventional projection type ion beam apparatus as shown in FIG. 6 in the following points.

While the conventional stencil mask has a structure in which aperture patterns are scattered around the optical axis, the mask used in the ion beam processing apparatus according to the present invention has the optical axis as shown in FIG. The opening pattern may be a combination of a plurality of members, which has a pattern opening pattern having one side orthogonal to each other.

7 and 8 show a structure in which the opening pattern is determined by a plurality of masks, and the mask portion 60 is a fixed mask 6
1 and a movable mask 62. Fixed mask 6
1 is fixedly installed so that its end sides are orthogonal to each other including the optical axis 63 and shield half of the irradiation ion beam 64. The movable mask 62 is installed with a slight gap from the fixed mask 61 and has an opening 65 having a shape to be projected. In this embodiment, in particular, the opening 65 is composed of a large opening 66 and a minute opening 67.

The movable mask 62 is parallel to the fixed mask 61, and can be finely moved in the direction perpendicular to the end side of the fixed mask 61. The position of the movable mask 62 substantially determines the shape of the beam passage opening, and the passed pattern. Ion beam 6
The sectional shape 69 of 8 is determined. In the present example, the stop positions of the movable mask 62 are set at two positions, and the shape of the substantial beam passage opening can be of two types, a large opening and a minute opening. With this mechanism, the large area pattern beam 68 and the minute area pattern beam 70 shown in FIG. 8 can be formed. The large area pattern beam 68 is used to process a sample in a short time, and the minute area pattern beam 70 is used to process a minute portion. You can use them as you like. The fine movement means for driving the movable mask 62 may be mechanical, or electric parts such as a piezoelectric element may be used.

With the mask portion 60 having such a structure, the irradiation ion beam 64 having a substantially circular cross section can be shaped into the patterned ion beams 68 and 70 having a polygonal cross section. Since the mask portion 60 is installed at the focal position of the irradiation lens, an image of the opening pattern of the mask portion 60 can be accurately formed on the sample surface by the projection lens. In the above example, there are two cases of substantial beam passage areas, large and small, but the substantial beam passage area can be variously controlled by minutely controlling the moving amount of the movable mask.

FIG. 9 shows another example of the movable mask. The notch 92 of the movable mask 91 is tapered. A straight line 80 that is orthogonal to the optical axis 97 indicates the movable direction of the movable mask 91, and a straight line 81 indicates the end side of the fixed mask 93. Further, reference numeral 98 is an irradiation region of the irradiation ion beam. By controlling the position of the movable mask 91, the substantial beam passage region formed with the fixed mask 93 can be controlled. The figure (a) is a minute opening 94, the figure (b) is a middle opening 95, and the figure (c) is large. The case of the opening 96 is shown. Further, in the case of the present embodiment, the processing area is variable, and the end side of the fixed mask 83 orthogonal to the optical axis 98 does not move and the length of the side that effectively forms the processing surface (E in the figure). , F) can be changed,
The length of the cross section formed on the sample can be variously controlled by the movable mask shown in FIG.

In this way, by forming the mask with the fixed mask 93 having one side orthogonal to the optical axis and the movable mask having the tapered notch, a patterned ion beam with very small aberration and distortion is formed. A sharp cross section can be formed by projecting the patterned ion beam onto the sample, and the length of the cross section can be controlled.

(Embodiment 3) This embodiment uses an ion beam processing apparatus equipped with the mask portion shown in FIGS. 7 and 8 and has a sectional structure without cleaving a sample having a structure in which different materials are laminated. This is an ion beam processing method for knowing. This will be described with reference to FIG.

As described above, in the mask of this embodiment, the substantial beam passage opening is determined by the setting position of the movable mask.
It can be set in two stages, a large opening and a small opening that are close to a pentagon. It has a substantially pentagonal shape with sides of about 200 μm and about 100 μm at the time of large opening, and has a semicircular shape with a radius of 5 μm at the time of minute opening. In the present embodiment, the reduction ratio of the image formed on the sample with respect to the opening pattern on the mask is designed to be about 1/20 depending on the lens position and the focal length of the ion beam optical system, so that the beam reaching the sample 100 is about 10 μm. And about 5
A substantially pentagonal large aperture pattern beam having a side of μm and a semicircular fine pattern beam having a radius of 0.25 μm at a minute aperture.

First, as shown in FIG. 10A, the recess 102 is roughly processed in a short time by the large aperture pattern beam 101. The depth was about 3 μm, and the processing time was about 200 seconds. The surface 103 in the figure is the cross section to be noted. Next, as shown in FIG. 2B, a minute pattern beam 104 is projected. At this time, the beam 10 is projected along the cross section 103 by a scanner (not shown) installed between the mask and the sample.
The cross-section 103 can be finished by scanning 4 (the arrow in the figure indicates the scanning direction of the ion beam). As a result, a smooth cross section 103 could be obtained in about 300 seconds including roughing and finishing. When a rectangular hole having the same shape is processed by a focused ion beam (FIB), the processing time is about 10 to 500 times as long as that of the present method. That is,
The use of this method brings about an effect that the time is reduced by two to three digits.

The processing time by the patterned ion beam is
If the processing area is large to some extent, it does not depend on the processing area but on the processing depth. On the other hand, in the processing by FIB, the processing time depends on the processing area and the depth. Therefore, if the processing depth is the same, the processing by the patterned ion beam can be accelerated as the processing area becomes larger. Here, with a patterned ion beam and FIB, for example, 50 μm × 1 on a silicon substrate.
The time for forming a rectangular parallelepiped recess having a depth of 0 μm and a depth of 5 μm is compared. Shape of patterned ion beam 50μm × 1
0 μm, current density 10 mA / cm ² , FIB diameter 10
Assuming that the current density at 0 nm is 5 A / cm ² and the sputtering yield of the sample is 2, in the case of FIB, it is about 1.0 × 10.
^It takes ⁵ (seconds) (about 28 hours), whereas the patterned ion beam completes the processing in only about 260 seconds (about 4.3 minutes). The processing time is reduced to about 1/400. In this way, large area rough processing is performed with a large aperture pattern beam, and a large area cross section can be formed in a short time by finishing the cross section with a fine cross section pattern beam. By making the surface including the axis a cross section, a smooth cross section with little sagging can be obtained.

(Embodiment 4) This embodiment is an example in which a process region search or observation step is added prior to the cross-section forming process.

The apparatus used here is the ion beam processing apparatus shown in FIG. 1, and the mask shown in FIG. 9 is used. In order to search for and confirm a desired processing area prior to the rough processing with a pattern beam having a large opening, the substantial beam passage area of the mask portion is set to a fine opening to obtain a fine bundle beam. This fine-bundle beam is scanned and swept on the sample surface by the scanner 17 installed between the mask and the sample surface, the secondary electrons emitted from the sample are captured by the secondary electron detector 16, and transmitted to the signal processor 19. By synchronizing the deflection voltage of the scanner 17 with the secondary electron intensity, a secondary electron image on the sample surface can be displayed on the image display unit 19 '. Here, a desired processing area is set.

In the case of this embodiment, a desired cross section forming portion is designated from the image display portion 19 '. The XY movement of the sample stage is controlled so that the midpoint of the entire length of the cross section coincides with the optical axis, and the movable mask is finely moved so that the cross section length becomes as specified. When the processing position is determined, the substantial beam passage region of the mask is made to have a large opening, and the patterned ion beam is projected. When the high-speed rough machining by the patterned ion beam is completed, the substantial beam passage region of the mask is returned to the fine aperture to form the fine aperture pattern beam, and the desired cross-section portion is scanned at low speed to perform the finishing process. By a series of these operations, a cross section can be formed at a desired position on the sample.

[0055]

With the ion beam processing method and the ion beam processing apparatus according to the present invention, the sample can be sharply processed with less distortion by the patterned ion beam that has passed through the opening pattern formed in the mask.

[Brief description of drawings]

FIG. 1 is a block diagram of an ion beam processing apparatus according to the present invention.

FIG. 2 is a block diagram of a conventional projection type ion beam device.

FIG. 3 is an explanatory diagram showing a general relationship between a distance from an optical axis of a projection beam and distortion.

FIG. 4 is an explanatory view of a processed shape of the sample when the center of the opening pattern and the optical axis are aligned with each other.

FIG. 5 is an explanatory view of a processed shape according to the method of the present invention.

FIG. 6 is a plan view showing an example of a stencil mask used in a conventional projection type ion beam apparatus.

FIG. 7 is a perspective view showing a relationship between a mask configuration and an ion beam according to an embodiment of the present invention.

FIG. 8 is a perspective view showing a relationship between a mask structure and an ion beam according to an embodiment of the present invention.

FIG. 9 is a plan view of a mask unit according to an embodiment of the present invention.

FIG. 10 is an explanatory view of a cross-section forming processing procedure using the mask portion shown in FIGS.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion beam processing apparatus, 2 ... Ion source, 3 ... Irradiation lens, 4 ... Mask part, 4 '... Substantial beam passage area, 5
Focusing lens, 6 Projection lens, 7 Sample, 9 Optical axis, 10 Fixed mask, 11 Movable mask, 14 Fine movement means, 16 Secondary electron detector, 19 Signal processing device.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A 8-162389 (JP, A) JP-A 5-315212 (JP, A) JP-A 62-63425 (JP, A) JP-A 52- 143776 (JP, A) JP-A-6-295055 (JP, A) Actual development Sho 63-131060 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7 / 20

Claims (5)

(57) [Claims] 1. An ion source, a mask having an opening pattern through which an ion beam passes, an irradiation optical system for irradiating the mask with the ion beam extracted from the ion source, a sample stage for holding a sample, In an ion beam processing apparatus including a projection optical system that projects a patterned ion beam that has passed through a mask onto the sample to form an image of the aperture pattern on the sample, the aperture pattern has a side orthogonal to an optical axis. An ion beam processing device characterized by being a figure. 2. An ion source, a mask section having an opening pattern through which an ion beam passes, an irradiation optical system for irradiating the mask section with the ion beam extracted from the ion source, and a sample stage for holding a sample. An ion beam processing apparatus including a projection optical system for projecting the patterned ion beam that has passed through the mask portion onto the sample to form an image of the aperture pattern on the sample, the mask portion is overlapped with a gap. An ion beam processing apparatus comprising two masks, one of the two masks having an opening pattern having one side orthogonal to the optical axis. 3. An ion beam for processing a sample by irradiating a mask portion having an opening pattern with an ion beam extracted from an ion source and projecting the patterned ion beam passing through the mask portion onto the sample by a projection optical system. A method of processing, wherein the opening pattern is formed by a plurality of masks overlapping with each other with a gap, and at least one of the masks forms one side orthogonal to the sample through the optical axis. Beam processing method. 4. The patterned ion beam according to claim 3, wherein the substantial passing portion of the ion beam in the mask portion is formed with a large opening, and the substantial passing portion of the mask portion is formed with a minute opening. An ion beam processing method for processing the sample using a patterned ion beam. 5. The ion beam processing method according to claim 4, including a step of scanning the sample with a patterned ion beam that has passed through the minute aperture, and observing the sample surface with secondary electrons from the sample. .