JP7214262B2 - Charged particle beam device, sample processing method - Google Patents

Description

The present invention relates to a charged particle beam apparatus for processing a sample using a charged particle beam and a sample processing method using a charged particle beam.

For example, as one of the methods for analyzing the internal structure of a sample such as a semiconductor device and performing three-dimensional observation, a charged particle beam (Focused Ion Beam; FIB) lens barrel and an electron beam (Electron Beam; EB) are used. A cross-sectional processing observation method is known in which a charged particle beam composite apparatus equipped with a lens barrel is used to form a cross-section by FIB and the cross-section is observed by a scanning electron microscope (SEM) (for example, , see Patent Document 1).

As for this cross-section processing and observation method, a method of constructing a three-dimensional image by repeating cross-section formation processing by FIB and cross-section observation by SEM is known. In this method, the three-dimensional shape of the target sample can be analyzed in detail from various directions from the reconstructed three-dimensional image. Furthermore, it has an advantage over other methods in that any cross-sectional image of the target sample can be reproduced.

On the other hand, in principle, SEM has a limit to high-magnification (high-resolution) observation, and the information obtained is limited to the vicinity of the sample surface. For this reason, an observation method using a transmission electron microscope (TEM), in which electrons are transmitted through a sample processed into a thin film, is also known for observation with higher magnification and higher resolution. The above-described FIB-based cross-section forming process is also effective for the preparation of thin-film fine samples (hereinafter sometimes referred to as fine sample pieces) used for such TEM observations.

Conventionally, when preparing a micro sample piece for use in TEM observation, a charged particle beam is irradiated along the thickness direction of the sample, for example, the tip portion of the sample, thereby reducing the thickness of the sample and thinning it. I was making a sample piece.
For example, when thinning a sample in which a plurality of devices are laminated along the thickness direction in a semiconductor substrate, an SEM image of a processed cross section is observed while irradiating a charged particle beam, and the number of devices exposed in the processed cross section is determined. By counting the desired processing end point was grasped.

On the other hand, in order to reduce the processing stripe pattern (curtain effect) along the irradiation direction of the charged particle beam, which is caused by processing using the charged particle beam, the charged particle beam is irradiated from the direction inclined to the thickness direction of the sample. (see, for example, Patent Document 2).

Japanese Unexamined Patent Application Publication No. 2008-270073 JP-A-9-186210

However, in the sample processing method (thinning method) described above, the portion of the sample to be thinned is etched, and the portion adjacent to the portion is not etched, resulting in a step bent at 90°. In order to prevent the curtain effect as described above, if a charged particle beam is irradiated from a direction inclined with respect to the processing surface of the portion to be thinned, the charged particle beam is blocked by the above-mentioned adjacent portion. There is a shadow area that does not hit. For this reason, the processing width must be determined in consideration of the shadow area which is not hit by the charged particle beam, and it becomes necessary to irradiate the processing range larger than the desired processing width with the charged particle beam. For this reason, the processing time of the sample becomes long, and there is also a possibility that a micro sample piece having a desired shape cannot be produced.

Also, when thinning a sample in which a plurality of devices are laminated along the thickness direction in a semiconductor substrate, when counting the number of devices exposed by processing in order to grasp the processing end point, the above-mentioned shadow region As a result, the contrast of the machined surface is lowered, the number of devices cannot be accurately counted, and there is a possibility that the machined end point cannot be accurately grasped.

The present invention has been made in view of the circumstances described above, and is capable of uniformly irradiating a charged particle beam to the entirety of a micro sample piece having a reduced sample thickness, and furthermore, providing a processing end point during processing. It is an object of the present invention to provide a charged particle beam apparatus and a sample processing method capable of clearly grasping the

In order to solve the above problems, aspects of the present embodiment provide the following charged particle beam apparatus and sample processing method.
That is, a charged particle beam apparatus according to the present invention is a charged particle beam apparatus for irradiating a sample with a charged particle beam to prepare a micro sample piece, wherein the charged particle beam is capable of irradiating the sample with a charged particle beam. a beam column, the sample chamber accommodating the charged particle beam column, and a sample piece holder capable of holding the sample, wherein the charged particle beam reduces the thickness of a partial region of the sample. When forming the micro sample piece, the portion adjacent to the thinned portion of the micro sample piece is an inclined portion inclined at an angle range of 10° or more and less than 90° with respect to the thickness direction of the thinned portion The inclined portion is provided up to the root portion of the thinned portion of the micro sample piece, so that the argon ion beam is used to reduce processing fringes generated when the micro sample piece is formed by the charged particle beam. is formed so that the argon ion beam is not blocked even at the base of the micro sample when the micro sample is irradiated with the argon ion beam from a direction intersecting with the charged particle beam and parallel to the inclined portion and a computer that controls such that processing stripes are reduced in the entire area of the micro sample piece by irradiating the micro sample piece.

According to the charged particle beam apparatus of the present invention, the portion adjacent to the thinned portion of the micro-specimen forms an inclined portion inclined with respect to the thinned portion. are larger and clearer than the cross-sectional shape in the cross section perpendicular to the direction of extension of the device, so the number of devices can be accurately counted. This makes it possible to easily and reliably determine the processing end point of the sample by the charged particle beam.

Further, according to the present invention, the inclined portion is formed with reference to an SEM image of the inclined portion obtained by a scanning electron microscope .

A sample processing method according to the present invention is a method for fabricating a sample by irradiating a sample with a charged particle beam to prepare a minute sample piece by reducing the thickness of a partial region of the sample. , forming a plurality of removal regions with a predetermined processing thickness along the thickness direction of the sample and a processing width along the width direction perpendicular to the thickness direction, overlapping the removal region along the thickness direction; an inclined portion forming step of forming an inclined portion inclined with respect to the thinned portion in a portion adjacent to the thinned portion of the micro sample piece by gradually reducing the processing width with each overlapping region; The inclined portion is provided up to the root portion of the micro-sample, so that the argon ion beam is directed to the micro-specimen in order to reduce processing fringes generated when the micro-specimen is formed by the charged particle beam. The argon ion beam is formed so that the argon ion beam is not blocked even at the base of the micro sample piece when irradiating the micro sample piece with the argon ion beam from a direction intersecting with the charged particle beam and parallel to the inclined portion. and an argon ion beam irradiation step in which processing stripes are reduced in the entire area of the micro sample piece by irradiating the micro sample piece with an argon ion beam .

According to the sample processing method of the present invention, it is possible to form an inclined portion inclined with respect to the thinned portion in the portion adjacent to the thinned portion of the micro sample piece. When irradiating the reprocessing beam with an irradiation angle different from that of the charged particle beam used in the above, it is possible to eliminate the shadow area where the argon ion beam is not irradiated at the base of the micro-specimen. can be irradiated with an argon ion beam. As a result, processing stripes are reduced in the entire area of the micro-specimen, and a micro-specimen can be formed from which a clear observation image can be obtained.

Further, the present invention is characterized in that the processing thickness and the processing width of each removed region in the sloped portion forming step are determined with reference to an SEM image of the sloped portion obtained by a scanning electron microscope. and

In the sloped portion forming step, the thinned portion and the sloped portion adjacent to the thinned portion are inclined with respect to each other within a range of 10° or more and less than 90°.

According to the present invention, it is possible to evenly irradiate a charged particle beam to the entire micro sample piece with reduced sample thickness, and to clearly grasp the end point of processing during processing. A beam device and a sample processing method can be provided.

1 is a configuration diagram of a charged particle beam device according to an embodiment of the present invention; FIG. FIG. 4 is an explanatory diagram showing a sample processing method step by step; FIG. 4 is an explanatory diagram showing a sample processing method step by step; FIG. 10 is an explanatory diagram showing another example of the sample processing method;

A charged particle beam apparatus according to an embodiment of the present invention and a sample processing method using the same will be described below with reference to the drawings. It should be noted that each embodiment shown below is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make it easier to understand the features of the present invention, there are cases where the main parts are enlarged for convenience, and the dimensional ratio of each component is the same as the actual one. not necessarily.

FIG. 1 is a schematic configuration diagram showing a charged particle beam device according to an embodiment of the present invention.
As shown in FIG. 1, a charged particle beam apparatus 10 according to an embodiment of the present invention includes a sample chamber 11 whose interior can be maintained in a vacuum state, and a bulk sample V and a sample piece S in the sample chamber 11. and a stage driving mechanism 13 for driving the stage 12 .

The charged particle beam apparatus 10 includes a focused ion beam irradiation optical system 14 that irradiates a charged particle beam, such as a focused ion beam (FIB), onto an irradiation target within a predetermined irradiation area (that is, scanning range) inside the sample chamber 11. ing. The charged particle beam apparatus 10 includes an electron beam irradiation optical system 15 that irradiates an irradiation target within a predetermined irradiation area inside the sample chamber 11 with an electron beam (EB). The charged particle beam device 10 includes a detector 16 that detects secondary charged particles (secondary electrons, secondary ions) R generated from an irradiation target by irradiation with a charged particle beam or an electron beam.

The charged particle beam apparatus 10 includes a gas ion beam optical system 18 that irradiates a gas ion beam (GB) onto an irradiation target within a predetermined irradiation area inside the sample chamber 11 .
These focused ion beam irradiation optical system 14, electron beam irradiation optical system 15, and gaseous ion beam optical system 18 are arranged so that their beam irradiation axes can intersect substantially at one point on the stage 12. . That is, when the sample chamber 11 is viewed from the side, the focused ion beam optical system 14 is arranged along the vertical direction, and the electron beam irradiation optical system 15 and the gas ion beam optical system 18 are arranged, for example, with respect to the vertical direction. It is arranged along a direction inclined by 45°. Due to this arrangement layout, when the sample chamber 11 is viewed from the side, the beam irradiation axis of the gas ion beam (GB) is oriented with respect to the beam irradiation axis of the electron beam (EB) irradiated from the electron beam irradiation optical system 15. , for example, perpendicular to each other.

The charged particle beam device 10 includes a gas supply unit 17 that supplies gas G to the surface of the object to be irradiated. Specifically, the gas supply unit 17 is a nozzle 17a having an outer diameter of about 200 μm.
The charged particle beam device 10 includes a gas supply unit 17 that supplies gas G to the surface of the object to be irradiated. Specifically, the gas supply unit 17 is a nozzle 17a having an outer diameter of about 200 μm.

The charged particle beam apparatus 10 picks up the sample piece S from the sample V fixed on the stage 12, holds the sample piece S, and drives the needle 19a to move the sample piece S to the sample piece holder P, and the needle 19a to move the sample piece S. A specimen transfer means 19 consisting of a needle driving mechanism 19b for transporting, and an absorption current detector which detects the inflow current (also called absorption current) of the charged particle beam flowing into the needle 19a and sends the inflow current signal to a computer for imaging. 20 and.

The charged particle beam apparatus 10 includes a display device 21 that displays image data based on the secondary charged particles R detected by the detector 16, a computer 22, and an input device 23.

The irradiation targets of the focused ion beam irradiation optical system 14 and the electron beam irradiation optical system 15 are the sample V and the sample piece S fixed to the stage 12, and the needle 19a and the sample piece holder P existing within the irradiation area. be.

The charged particle beam device 10 scans and irradiates the surface of the object to be irradiated with the charged particle beam, thereby imaging the irradiated portion, performing various processes (excavation, trimming, etc.) by sputtering, and forming a deposition film. etc. is feasible. The charged particle beam device 10 cuts out a sample piece S from a sample V, and cuts out a micro sample piece Q (see FIG. 3: for example, a thin piece sample, a needle-like sample, etc.) used for TEM observation from the cut sample piece S, or uses an electron beam. can be performed to form analytical specimen strips.

The charged particle beam apparatus 10 thins, for example, the tip portion of the sample piece S transferred to the sample piece holder P to a desired thickness (eg, 5 to 100 nm) suitable for transmission observation by a transmission electron microscope, It is possible to obtain a micro sample piece Q for observation. The charged particle beam device 10 can observe the surface of an irradiation target by scanning and irradiating the surface of the irradiation target such as the sample S and the needle 19a with a charged particle beam or an electron beam.

Absorbed current detector 20 includes a preamplifier to amplify the needle's incoming current and send it to computer 22 . An absorbed current image of the shape of the needle can be displayed on the display device 21 by a needle inflow current detected by the absorbed current detector 20 and a signal synchronized with scanning of the charged particle beam, and the needle shape and tip position can be specified.

The sample chamber 11 can be evacuated to a desired vacuum state by an exhaust device (not shown) and can maintain the desired vacuum state.
A stage 12 holds a sample V. FIG. The stage 12 has a holder fixing base 12a that holds the sample piece holder P. As shown in FIG. The holder fixing table 12a may have a structure capable of mounting a plurality of sample piece holders P thereon.

The stage driving mechanism 13 is housed inside the sample chamber 11 while being connected to the stage 12 , and displaces the stage 12 along a predetermined axis according to control signals output from the computer 22 . The stage drive mechanism 13 includes a movement mechanism 13a that moves the stage 12 in parallel at least along the X-axis and the Y-axis that are parallel to the horizontal plane and perpendicular to each other, and the vertical Z-axis that is perpendicular to the X-axis and the Y-axis. ing. The stage drive mechanism 13 includes a tilt mechanism 13b that tilts the stage 12 around the X-axis or the Y-axis, and a rotation mechanism 13c that rotates the stage 12 around the Z-axis.

The focused ion beam irradiation optical system 14 has a beam emission part (not shown) inside the sample chamber 11 facing the stage 12 at a position vertically above the stage 12 in the irradiation area, and the optical axis is vertically oriented. They are fixed in the sample chamber 11 in parallel. As a result, it is possible to irradiate the charged particle beam vertically downward from above to the object to be irradiated, such as the sample V and the sample piece S placed on the stage 12, and the needle 19a existing within the irradiation area.

Also, the charged particle beam device 10 may be provided with another ion beam irradiation optical system instead of the focused ion beam irradiation optical system 14 as described above. The ion beam irradiation optical system is not limited to an optical system that forms a focused beam as described above. The ion beam irradiation optical system may be, for example, a projection type ion beam irradiation optical system in which a stencil mask having a regular aperture is placed in the optical system to form a shaped beam in the shape of the aperture of the stencil mask. According to such a projection-type ion beam irradiation optical system, a shaped beam having a shape corresponding to the processing region around the sample piece S can be formed with high accuracy, and the processing time can be shortened.

The focused ion beam irradiation optical system 14 includes an ion source 14a that generates ions, and an ion optical system 14b that focuses and deflects ions extracted from the ion source 14a. The ion source 14a and the ion optical system 14b are controlled according to control signals output from the computer 22, and the computer 22 controls the irradiation position and irradiation conditions of the charged particle beam.

The ion source 14a is, for example, a liquid metal ion source using liquid gallium or the like, a plasma ion source, a gas electric field ion source, or the like. The ion optical system 14b includes, for example, a first electrostatic lens such as a condenser lens, an electrostatic deflector, a second electrostatic lens such as an objective lens, and the like. When a plasma type ion source is used as the ion source 14a, high-speed processing can be achieved with a large current beam, which is suitable for extracting a large-sized sample piece S. For example, by using argon ions as the gas field ionization ion source, the focused ion beam irradiation optical system 14 can irradiate an argon ion beam.

The electron beam irradiation optical system 15 has a beam emission part (not shown) inside the sample chamber 11, which is inclined at a predetermined angle (for example, 60°) with respect to the vertical direction of the stage 12 in the irradiation area. It is fixed in the sample chamber 11 so as to face the sample chamber 11 with its optical axis parallel to the direction of inclination. This makes it possible to irradiate the electron beam downward in the tilt direction on the irradiation target such as the sample V and the sample piece S fixed to the stage 12 and the needle 19a present in the irradiation area.

The electron beam irradiation optical system 15 includes an electron source 15a that generates electrons, and an electron optical system 15b that focuses and deflects the electrons emitted from the electron source 15a. The electron source 15a and the electron optical system 15b are controlled according to control signals output from the computer 22, and the computer 22 controls the irradiation position and irradiation conditions of the electron beam. The electron optical system 15b includes, for example, an electromagnetic lens and a deflector.

The positions of the electron beam irradiation optical system 15 and the focused ion beam irradiation optical system 14 are exchanged so that the electron beam irradiation optical system 15 is tilted in the vertical direction and the focused ion beam irradiation optical system 14 is tilted in the vertical direction by a predetermined angle. can be placed in

The gas ion beam optical system 18 irradiates a gas ion beam (GB) such as an argon ion beam. The gas ion beam optical system 18 can ionize argon gas and irradiate it at a low acceleration voltage of about 1 kV. Since such a gaseous ion beam (GB) has a lower focusability than a focused ion beam (FIB), the etching rate for the sample piece S and the minute sample piece Q is low. Therefore, it is suitable for precise finishing of the sample piece S and the minute sample piece Q.

The detector 16 detects secondary charged particles (secondary electrons, secondary ions) R emitted from an irradiation target such as a sample V, a sample piece S, and a needle 19a when a charged particle beam or an electron beam is irradiated to the irradiation target. (that is, the amount of secondary charged particles) is detected, and information on the detected amount of secondary charged particles R is output. The detector 16 is arranged at a position where the amount of the secondary charged particles R can be detected inside the sample chamber 11, for example, at a position obliquely above the irradiation target such as the sample V or the sample piece S in the irradiation area. , are fixed in the sample chamber 11 .

The gas supply unit 17 is fixed to the sample chamber 11 , has a gas injection unit (also referred to as a nozzle) inside the sample chamber 11 , and is arranged facing the stage 12 . The gas supply unit 17 supplies an etching gas for selectively promoting etching of the sample V and the sample piece S by a charged particle beam (focused ion beam) according to their materials, and an etching gas for the sample V and the sample piece S. It is possible to supply the sample V and the sample piece S with a deposition gas or the like for forming a deposition film of deposits such as metals or insulators on the surface.

The needle driving mechanism 19b constituting the sample piece transfer means 19 is accommodated inside the sample chamber 11 with the needle 19a connected thereto, and displaces the needle 19a according to the control signal output from the computer 22. The needle driving mechanism 19b is provided integrally with the stage 12, and moves integrally with the stage 12 when the stage 12 is rotated around the tilting axis (that is, the X axis or the Y axis) by the tilting mechanism 13b, for example.

The needle driving mechanism 19b includes a moving mechanism (not shown) that moves the needle 19a in parallel along each of the three-dimensional coordinate axes, and a rotating mechanism (not shown) that rotates the needle 19a around the central axis of the needle 19a. I have. This three-dimensional coordinate axis is independent of the orthogonal three-axis coordinate system of the sample stage, and is an orthogonal three-axis coordinate system with two-dimensional coordinate axes parallel to the surface of the stage 12. When in rotation, this coordinate system tilts and rotates.

The computer 22 controls at least the stage drive mechanism 13, the focused ion beam irradiation optical system 14, the electron beam irradiation optical system 15, the gas supply unit 17, and the needle drive mechanism 19b.

The computer 22 is arranged outside the sample chamber 11, and is connected to a display device 21 and an input device 23 such as a mouse or a keyboard that outputs a signal according to an operator's input operation. The computer 22 comprehensively controls the operation of the charged particle beam system 10 based on signals output from the input device 23 or signals generated by preset automatic operation control processing.

The computer 22 converts the detected amount of the secondary charged particles R detected by the detector 16 while scanning the irradiation position of the charged particle beam into a luminance signal associated with the irradiation position. Image data representing the shape of the irradiation target is generated from the two-dimensional positional distribution of the detected amount. In the absorption current image mode, the computer 22 detects the absorption current flowing through the needle 19a while scanning the irradiation position of the charged particle beam, thereby obtaining the shape of the needle 19a from the two-dimensional positional distribution of the absorption current (absorption current image). to generate the absorption current image data shown.

The computer 22 causes the display device 21 to display a screen for executing operations such as enlargement, reduction, movement and rotation of each image data together with the generated image data. The computer 22 causes the display device 21 to display a screen for performing various settings such as mode selection and processing settings in automatic sequence control.

A sample processing method of the present invention using the charged particle beam device 10 configured as above will be described.
2 and 3 are explanatory diagrams showing the sample processing method step by step.
In the following embodiments, as a sample processing method, a sample piece S supported by a sample piece holder P is thinned by a charged particle beam to form a minute sample piece Q for TEM observation. . Further, as shown in FIG. 2(a), the sample piece S is assumed to be, for example, a region in which a plurality of devices 31, 31, . . . , devices 31, 31, . A direction perpendicular to the thickness direction T and the width direction W is called a processing direction D. As shown in FIG.

First, a sample piece S, which is a small region including an observation target, is cut out by FIB processing from a sample V (see FIG. 1) made of a semiconductor substrate. Then, using the needle 19a (see FIG. 1), the sample piece S to be processed is supported on the sample piece holder P (see FIG. 1) so that the thickness direction of the semiconductor substrate is in the vertical direction (processing direction D). . Then, as shown in FIG. 2B, an irradiation area is set for the sample piece S, and the FIB is irradiated along the processing direction D from the focused ion beam irradiation optical system 14 (see FIG. 1). Then, a first removal area E1 having a predetermined processing thickness along the thickness direction T of the sample piece S and a processing width W1 along the width direction W is formed. As a result, for example, the end surface of one device 31 is exposed at the root side end E1e of the first removal area E1.

Next, as shown in FIG. 2C, a position overlapping the first removal area E1 along the thickness direction T, that is, a position shifted by a predetermined processing thickness along the thickness direction T from the first removal area E1 is irradiated with the FIB to form a second removal area E2. At this time, the processing width W2 along the width direction W is set to a width shorter than the processing width W1 by a predetermined reduction width ΔW. As a result, the root-side end E2e of the second removal area E2 is shifted toward the center in the width direction W from the root-side end E1e of the first removal area E1.

Furthermore, as shown in FIG. 3( a ), a position overlapping the n-th removal region En formed immediately before along the thickness direction T, that is, along the thickness direction T from the n-th removal region En, a predetermined processing thickness The shifted position is irradiated with FIB to form the (n+1)-th removal area E(n+1). At this time, the processing width W(n+1) along the width direction W is set to a width shorter than the processing width Wn of the immediately preceding n-th removal area En by a predetermined reduction width ΔW. In this manner, the sample piece S is irradiated with the FIB along the processing direction D, and a large number of removed regions with gradually reduced processing widths are formed in the thickness direction T, thereby forming the sample piece S. A minute sample piece Q with a reduced thickness along the thickness direction T is formed.

By forming a large number of removal areas with such a stepwise reduction in processing width, the micro sample piece Q is formed with a thinned portion Qs with a reduced thickness. Then, an inclined portion (a portion adjacent to the thinned portion) C is formed in a portion adjacent to the thinned portion Qs, that is, a portion where the root side end portions of the respective removed regions are connected. process). The inclined portion C is, for example, an inclined surface inclined in the range of 10° or more and less than 90° with respect to the thickness direction T. For example, the surface of the inclined portion C is formed so as to be parallel to the irradiation angle of the argon ion beam. It is good if it is. As an example, in the present embodiment, the inclined portion C forms an inclined surface inclined at 20° with respect to the thickness direction T. As shown in FIG. Here, in the range of 10° or more and less than 90°, by irradiating the beam at a small incident angle of less than 90°, the layer of damage to the sample due to beam incidence can be made shallow. As a result, since the damage layer is shallow, it is possible to clearly grasp the processing end point during processing even for a sample with a fine device dimension.

In the embodiment shown in FIGS. 2 and 3, the FIB scans and irradiates so that the processing width Wn along the width direction W of the sample piece S becomes smaller step by step. ) C, but the scanning method of the FIB is not limited to this.

For example, in the example of FIB scanning shown in FIG. 4, the processing width Wn of the removal area En along the width direction W of the sample piece S, which becomes the thinned portion Qs, is constant. Further, the FIB scans continuously in a direction inclined in the range of 10° or more and less than 90° with respect to the thickness direction T from the root side of each removal area En. As a result, an inclined portion C is formed in a region scanned by the FIB in a direction inclined with respect to the thickness direction T. As shown in FIG. The machining width Wn along the inclined portion C gradually increases step by step. Here, the FIB scanning method uses vector scanning in which the FIB scanning direction is changed from the width direction of the sample S to a direction inclined with respect to the thickness direction T. FIG.
In addition, a first rectangular irradiation area is set in the width direction of the sample piece S, and a second rectangular irradiation area is set in a direction inclined with respect to the thickness direction T, and raster scanning or bitmap scanning is performed in each irradiation area. may be used.

Besides this, the scanning direction of the FIB in the trapezoidal region defined by the thinned portion Qs of the micro sample piece Q and the inclined portion C adjacent to the thinned portion Qs is not particularly limited. , and an inclined portion C adjacent to the thinned portion Qs can be formed, the FIB may be scanned in any direction to form the removal area.

In the process of forming a large number of removal areas with the processing width gradually reduced as described above, EB is irradiated from the electron beam irradiation optical system 15 at an arbitrary timing, and an SEM image of the inclined portion C is acquired. By observing the obtained SEM image and counting the number of devices 31, 31 . . . The cross-sectional shape of the devices 31, 31 . Able to count numbers accurately.

In addition, from the acquisition of the SEM image to the counting of the devices 31, 31 . . . Thus, it is possible to automate the formation of the micro sample piece Q having the inclined portion C connected to the root side.

As a specific example of such an automatic processing end point detection method, the number of designed devices 31, 31 . The planned appearance number of such devices 31 can be grasped from the design data of the integrated circuit formed on the sample V or the like.

Then, the number of devices 31 appearing on the inclined portion C is counted by image comparison software or the like executed by the computer 22 by repeating the formation of the removed area by FIB irradiation and the acquisition of the irradiation SEM image. Then, when the planned number of devices 31 input in advance to the computer 22 matches the number of devices 31 that have appeared in the inclined portion C obtained by acquiring the actual SEM image, this is recognized as the processing end point and the FIB is irradiated. terminate.

Further, as another specific example of the detection method of the processing end point by automation, when the sample piece S is cut out from the sample (semiconductor substrate) V (see FIG. 1) by FIB, an SEM image of the side wall of the sample piece S is acquired. . Then, the number of devices 31 exposed on the side wall of the sample piece S is counted by image comparison software or the like executed by the computer 22 . Alternatively, the number of devices 31 exposed on the cut end surface of the sample V after cutting the sample piece S, the design data of the integrated circuit formed on the sample V, etc. The number of devices 31 may be counted.

From the total number of devices 31 on the sample piece S recognized by the computer 22 in this way, the actual number of devices 31 appearing on the inclined portion C by repeating the formation of the removed area by FIB irradiation and the acquisition of the irradiation SEM image is calculated. When the number of devices 31 to be left on the sample piece S, which is input in advance to the computer 22, matches the number of the devices 31 to be left on the sample piece S, this is recognized as the processing end point and the FIB irradiation is terminated.

Next, as shown in FIG. 3(b), for example, at an angle parallel to the surface of the inclined portion C, the micro sample piece Q was irradiated with a gas ion beam, for example, an argon ion beam, and an FIB was used. Reduces processing stripes (curtain effect) caused by processing (argon beam irradiation process).

In this argon beam irradiation step, the gas ion beam optical system 18 (see FIG. 1) ionizes argon gas and irradiates the entire area of the micro sample Q with a low acceleration voltage of about 1 kV, for example. At this time, it is preferable to irradiate the micro sample Q with EB from the electron beam irradiation optical system 15 and finish the micro sample Q with an argon ion beam based on the obtained SEM image. For the detection of the processing end point at this time as well, the processing end point detection procedure for processing the micro sample piece Q by the FIB described above can be applied. Thereby, the argon beam irradiation process can be automated.

In such an argon beam irradiation process, an inclined portion C inclined in an angle range of 10° or more and less than 90° with respect to the thickness direction T is formed as a portion adjacent to the root portion of the micro sample piece Q. The argon ion beam can be evenly applied to the entire area of the micro sample piece Q, which is thinned by reducing the thickness of the sample piece S.

That is, as shown in FIG. 1, when the sample chamber 11 is viewed from the side, the gas ion beam (GB) is aligned with the beam irradiation axis of the electron beam (EB) irradiated from the electron beam irradiation optical system 15. A gas ion beam optical system 18 is arranged so that the beam irradiation axis is, for example, in a direction that intersects at right angles. For this reason, if the thickness direction T is, for example, perpendicular to the width direction W of the micro sample piece Q, a shadow region where the argon ion beam is not irradiated is generated at the base of the micro sample piece Q. FIG.

However, as in the present embodiment, in response to the argon ion beam irradiated at an angle inclined with respect to the thickness direction T, the inclined portion inclined in the range of, for example, 10° or more and less than 90° By forming C, it is possible to eliminate the shadow region where the argon ion beam is not irradiated at the base of the micro sample piece Q, so that the entire area of the micro sample piece Q can be reliably irradiated with the argon ion beam. As a result, the processed stripe pattern is reduced in the entire area of the minute sample piece Q, and a sample piece for TEM observation that can obtain a clear observation image can be formed.

In addition, as shown in FIG. 3C, a large number of removal areas are formed by gradually reducing the processing width along the width direction W from the direction opposite to the processing direction along the thickness direction T described above. , a micro sample piece Q having thinned portions Qs whose thickness is reduced from both sides can be formed.

While embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Charged particle beam apparatus, 11... Sample chamber, 12... Stage (sample stage), 13... Stage drive mechanism, 14... Focused ion beam irradiation optical system (charged particle beam irradiation optical system), 15... Electron beam irradiation optical system (Charged particle beam irradiation optical system) 16... Detector 17... Gas supply unit 18... Gas ion beam irradiation optical system (charged particle beam irradiation optical system) 19a... Needle 19b... Needle drive mechanism 20... Absorption Current detector, 21... Display device, 22... Computer, 23... Input device, 33... Sample table, 34... Columnar part, C... Inclined part, P... Sample piece holder, Q... Micro sample piece, R... Secondary charging Particles, S... sample piece, V... sample.

Claims (5)

A charged particle beam device that irradiates a charged particle beam toward a sample to create a micro sample piece,
a charged particle beam column capable of irradiating a charged particle beam toward the sample;
the sample chamber containing the charged particle beam column;
a specimen holder capable of holding the specimen,
When the charged particle beam is used to form a micro sample piece in which the thickness of a partial region of the sample is reduced, a portion of the micro sample piece adjacent to the thinned portion is 10 mm thick with respect to the thickness direction of the thinned portion. and less than 90°, and the inclined portion is provided up to the root portion of the thinned portion of the micro sample, so that the charged particle beam can tilt the micro sample. The argon ion beam is formed so that the argon ion beam is not obstructed even at the root portion of the micro sample piece when the micro sample piece is irradiated with the argon ion beam in order to reduce processing stripes generated during formation,
a computer that irradiates the micro-specimen with an argon ion beam in a direction intersecting with the charged particle beam and in a direction parallel to the inclined portion, thereby controlling the micro-specimen so that processing stripes are reduced in the entire area of the micro-specimen; A charged particle beam device, comprising: 2. A charged particle beam apparatus according to claim 1, wherein said inclined portion is formed with reference to an SEM image of said inclined portion obtained by a scanning electron microscope. A specimen preparation method for producing a micro specimen by irradiating a specimen with a charged particle beam to reduce the thickness of a partial region of the specimen, comprising:
By irradiating the charged particle beam, a plurality of removal regions having a predetermined processing thickness along the thickness direction of the sample and a processing width along the width direction perpendicular to the thickness direction are formed along the thickness direction. By overlappingly forming and gradually reducing the processing width each time the removal regions are overlapped, an inclined portion inclined with respect to the thinned portion is formed in a portion adjacent to the thinned portion of the micro sample piece. An inclined portion forming step is provided,
The inclined portion is provided up to the root portion of the micro sample piece, so that the micro sample piece is irradiated with the argon ion beam in order to reduce processing stripes generated when the micro sample piece is formed by the charged particle beam. formed so that the argon ion beam is not obstructed even at the base of the micro sample piece when performing
An argon ion beam irradiation step for reducing processing stripes over the entire area of the micro sample by irradiating the micro sample with an argon ion beam in a direction intersecting with the charged particle beam and parallel to the inclined portion. A sample processing method characterized by: 4. The processing thickness and the processing width of each removed area in the sloped portion forming step are determined with reference to an SEM image of the sloped portion obtained by a scanning electron microscope. The described sample processing method. 6. In the sloped portion forming step, the thinned portion and the sloped portion adjacent to the thinned portion are mutually inclined within a range of 10° or more and less than 90°. The sample processing method according to any one of claims 1 to 3.

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