JP6974820B2 - Charged particle beam device, sample processing method - Google Patents

Description

The present invention relates to a charged particle beam device 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 or performing three-dimensional observation, a charged particle beam (FIB) lens barrel and an electron beam (EB) are used. A cross-section processing observation method is known in which a cross-section forming process is performed by FIB and the cross section is observed by a scanning electron microscope (SEM) using a charged particle beam composite device equipped with a lens barrel (for example,). , Patent Document 1).

As this cross-section processing observation method, a method of constructing a three-dimensional image by repeating cross-section forming 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. Further, it has an advantage that other methods do not have, that is, it is possible to reproduce an arbitrary cross-sectional image of the target sample.

On the other hand, in principle, SEM has a limit in observation at high magnification (high resolution), and the information obtained is also limited to the vicinity of the sample surface. For this reason, an observation method using a transmission electron microscope (TEM) that allows electrons to pass through a sample processed into a thin film is also known for observation with higher magnification and higher resolution. The cross-section forming process by FIB as described above is also effective for producing a thin filmed fine sample (hereinafter, may be referred to as a minute sample piece) used for observation by TEM.

Conventionally, when preparing a minute sample piece used for observation by TEM, for example, the tip portion of the sample is irradiated with a charged particle beam along the thickness direction of the sample, and the thickness of the sample is reduced to make a thin film. I was making a sample piece.
For example, when thinning a sample in which a plurality of devices are laminated in a semiconductor substrate along the thickness direction, the number of devices exposed on the processed cross section is observed by observing an SEM image of the processed cross section while irradiating a charged particle beam. By counting, the desired machining 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 caused by the processing using the charged particle beam, the charged particle beam is irradiated from a direction inclined with respect to the thickness direction of the sample. (See, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2008-270734 Japanese Unexamined Patent Publication No. 9-186210

However, in the above-mentioned sample processing method (thinning method), the portion of the sample to be thinned is etched, and the portion adjacent to the portion is not etched, so that a step that bends at 90 ° occurs. Then, when the charged particle beam is irradiated from an inclined direction to the machined surface of the fragmented portion as a measure against the curtain effect as described above, the above-mentioned adjacent portion shields the charged particle beam, so that the charged particle beam There is a shadow area that does not hit. Therefore, the processing width must be determined in consideration of the shadow region where the charged particle beam does not hit, and it becomes necessary to irradiate the charged particle beam to a processing range larger than the desired processing width. Therefore, the processing time of the sample becomes long, and there is a possibility that a minute sample piece having a desired shape cannot be produced.

Further, 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 Due to the influence, the contrast of the machined surface is lowered, the number of devices cannot be counted accurately, and there is a possibility that the end point of the machine cannot be accurately grasped.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to uniformly irradiate the entire small sample piece with a reduced sample thickness with a charged particle beam, and the processing end point at the time of processing. It is an object of the present invention to provide a charged particle beam device capable of clearly grasping the above, and a sample processing method.

In order to solve the above problems, the embodiment of the present embodiment provides the following charged particle beam device and sample processing method.
That is, the charged particle beam device of the present invention irradiates a charged particle beam toward a sample formed by stacking a plurality of embedded layers inside a base material along the thickness direction to create a minute sample piece. An apparatus having a charged particle beam lens barrel capable of irradiating a charged particle beam toward the sample, a sample chamber accommodating the charged particle beam lens barrel, and a sample piece holder capable of holding the sample. When the charged particle beam is used to form a micro sample piece in which the thickness of a part of the sample is reduced, the portion adjacent to the flaked portion of the micro sample piece is inclined with respect to the flaked portion. The inclined portion is formed , the processing thickness and the processing width are determined with reference to the SEM image of the inclined portion, and the processing end point is the buried layer exposed to the inclined portion with reference to the SEM image of the inclined portion. characterized in that it have a computer for controlling so as to determine a count of.

According to the charged particle beam apparatus of the present invention, the cross-sectional shape of the device exposed to the inclined portion by forming an inclined portion in which the portion adjacent to the sliced portion of the minute sample piece is inclined with respect to the sliced portion. Looks larger and clearer than the cross-sectional shape in a cross section perpendicular to the extension of the device, so the number of devices can be accurately counted. Thereby, the processing end point of the sample by the charged particle beam can be easily and surely determined.

Further, the present invention is characterized in that an argon ion beam is irradiated so as to be parallel to the inclined portion.

The sample processing method of the present invention is a sample preparation method in which a charged particle beam is irradiated toward a sample to prepare a micro sample piece in which the thickness of a part of the sample is reduced, and the sample is irradiated by the charged particle beam. A plurality of removal areas 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 in a plurality of layers along the thickness direction to remove the sample. 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 each time the region is overlapped. In the sample, a plurality of embedded layers are formed inside the base material along the thickness direction, and the processed thickness and the processed width of each of the removed areas in the inclined portion forming step are scan type. Determined with reference to the SEM image of the tilted portion obtained by an electron microscope, the tilted portion forming step uses the SEM image to count the number of buried layers exposed on the tilted portion. It is characterized by determining the processing end point.

According to the sample processing method of the present invention, an inclined portion inclined with respect to the sliced portion can be formed in a portion adjacent to the sliced portion of the minute sample piece, so that the sample can be processed in a subsequent step. When irradiating a reprocessed beam with an irradiation angle different from that of the charged particle beam used in, it is possible to eliminate the shadow area where the argon ion beam is not irradiated at the base of the micro sample piece, and the entire area of the micro sample piece is surely covered. Can be irradiated with an argon ion beam. As a result, the processed fringe pattern is reduced in the entire area of the minute sample piece, and the minute sample piece capable of obtaining a clear observation image can be formed.

The inclined portion forming step is characterized in that the flaked portion and the inclined portion which is a portion adjacent to the flaked portion are inclined in a range of 10 ° or more and less than 90 ° with respect to each other.

Further, the present invention is further provided with an argon beam irradiation step of irradiating the minute sample piece with an argon ion beam so as to be parallel to the inclined portion.

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

It is a block diagram of the charged particle beam apparatus which concerns on embodiment of this invention. It is explanatory drawing which showed the sample processing method step by step. It is explanatory drawing which showed the sample processing method step by step. It is explanatory drawing which showed another example of the sample processing method.

Hereinafter, a charged particle beam device according to an embodiment of the present invention and a sample processing method using the charged particle beam device will be described with reference to the drawings. It should be noted that each of the embodiments shown below is specifically described in order to better understand the gist of the invention, and is not limited to the present invention unless otherwise specified. In addition, the drawings used in the following description may be shown by enlarging the main parts for convenience in order to make the features of the present invention easy to understand, and the dimensional ratios of each component are the same as the actual ones. It is not always the case.

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, the charged particle beam device 10 according to the embodiment of the present invention has a sample chamber 11 that can maintain the inside in a vacuum state, and a bulk sample V and a sample piece S inside the sample chamber 11. It is provided with a stage 12 capable of fixing the sample piece holder P for holding the sample piece holder P, and a stage drive mechanism 13 for driving the stage 12.

The charged particle beam device 10 includes a focused ion beam irradiation optical system 14 that irradiates an irradiation target in a predetermined irradiation region (that is, a scanning range) inside the sample chamber 11 with a charged particle beam, for example, a focused ion beam (FIB). ing. The charged particle beam device 10 includes an electron beam irradiation optical system 15 that irradiates an electron beam (EB) on an irradiation target in a predetermined irradiation region inside the sample chamber 11. 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 device 10 includes a gas ion beam optical system 18 that irradiates an irradiation target in a predetermined irradiation region inside the sample chamber 11 with a gas ion beam (GB).
The focused ion beam irradiation optical system 14, the electron beam irradiation optical system 15, and the gas ion beam irradiation optical system 18 are arranged so that their respective beam irradiation axes can intersect at substantially one point on the stage 12. .. That is, when the sample chamber 11 is viewed from the side in a plan view, 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 in the vertical direction, for example. It is arranged along a direction inclined by 45 °. Due to such an arrangement layout, when the sample chamber 11 is viewed from the side in a plan view, the beam irradiation axis of the gas ion beam (GB) is opposed to the beam irradiation axis of the electron beam (EB) irradiated from the electron beam irradiation optical system 15. For example, the direction of intersection is at right angles.

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

The charged particle beam device 10 takes out the sample piece S from the sample V fixed to the stage 12, holds the sample piece S, and drives the needle 19a and the needle 19a to be transferred to the sample piece holder P to drive the sample piece S. An absorption current detector that detects the inflow current (also called absorption current) of the charged particle beam flowing into the needle 19a and the sample piece transfer means 19 including the needle drive mechanism 19b to be conveyed, and sends the inflow current signal to a computer for imaging. 20 and.

The charged particle beam device 10 includes a display device 21 for displaying image data and the like 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 fixed to the stage 12, the sample piece S, the needle 19a existing in the irradiation region, the sample piece holder P, and the like. be.

The charged particle beam device 10 irradiates the surface of the irradiation target with the charged particle beam while scanning the image, various processes (excavation, trimming, etc.) by sputtering and imaging of the irradiated portion, and formation of a deposition film. Etc. are feasible. The charged particle beam device 10 cuts out a sample piece S from the sample V, and uses a minute sample piece Q (see FIG. 3: for example, a thin piece sample, a needle-shaped sample, etc.) or an electron beam used for observation by TEM from the cut out sample piece S. It is possible to carry out the processing to form the analysis sample piece.

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

The absorption current detector 20 includes a preamplifier, amplifies the inflow current of the needle, and sends it to the computer 22. The needle inflow current detected by the absorption current detector 20 and the signal synchronized with the scanning of the charged particle beam can display the absorption current image of the needle shape on the display device 21, and the needle shape and the tip position can be specified.

The sample chamber 11 is configured so that the inside can be exhausted to a desired vacuum state by an exhaust device (not shown) and the desired vacuum state can be maintained.
The stage 12 holds the sample V. The stage 12 includes a holder fixing base 12a for holding the sample piece holder P. The holder fixing base 12a may have a structure in which a plurality of sample piece holders P can be mounted.

The stage drive mechanism 13 is housed inside the sample chamber 11 in a state of being connected to the stage 12, and displaces the stage 12 with respect to a predetermined axis according to a control signal output from the computer 22. The stage drive mechanism 13 includes a moving mechanism 13a that moves the stage 12 in parallel along at least the X-axis and the Y-axis that are parallel to the horizontal plane and orthogonal to each other and the Z-axis in the vertical direction that is orthogonal to the X-axis and the Y-axis. ing. The stage drive mechanism 13 includes a tilting mechanism 13b that tilts the stage 12 around the X-axis or the Y-axis, and a rotating mechanism 13c that rotates the stage 12 around the Z-axis.

In the focused ion beam irradiation optical system 14, the beam emitting portion (not shown) inside the sample chamber 11 faces the stage 12 at a position vertically above the stage 12 in the irradiation region, and the optical axis is oriented in the vertical direction. It is fixed in the sample chamber 11 in parallel. As a result, it is possible to irradiate the irradiation target such as the sample V, the sample piece S, and the needle 19a existing in the irradiation region with the charged particle beam from the upper side to the lower side in the vertical direction.

Further, the charged particle beam device 10 may include 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 the optical system that forms the 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 fixed opening is installed in the optical system to form a molded beam having an opening shape of the stencil mask. According to such a projection type ion beam irradiation optical system, it is possible to accurately form a molded beam having a shape corresponding to the machining region around the sample piece S, and the machining time is shortened.

The focused ion beam irradiation optical system 14 includes an ion source 14a for generating ions and an ion optical system 14b for focusing and deflecting ions drawn from the ion source 14a. The ion source 14a and the ion optical system 14b are controlled according to a control signal output from the computer 22, and the irradiation position and irradiation conditions of the charged particle beam are controlled by the computer 22.

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

In the electron beam irradiation optical system 15, the beam emitting portion (not shown) inside the sample chamber 11 is inclined to the stage 12 at a predetermined angle (for example, 60 °) with respect to the vertical direction of the stage 12 in the irradiation region. It is fixed to the sample chamber 11 with the optical axis parallel to the tilt direction while facing the sample chamber 11. As a result, it is possible to irradiate the irradiation target such as the sample V fixed to the stage 12, the sample piece S, and the needle 19a existing in the irradiation region from the upper side to the lower side in the tilt direction with an electron beam.

The electron beam irradiation optical system 15 includes an electron source 15a for generating electrons and an electron optical system 15b for focusing and deflecting electrons emitted from the electron source 15a. The electron source 15a and the electron optical system 15b are controlled according to a control signal output from the computer 22, and the irradiation position and irradiation conditions of the electron beam are controlled by the computer 22. The electro-optical system 15b includes, for example, an electromagnetic lens, a deflector, and the like.

The arrangement of the electron beam irradiation optical system 15 and the focused ion beam irradiation optical system 14 is exchanged, and 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. It may 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 with a low acceleration voltage of about 1 kV. Since such a gas ion beam (GB) has a lower focusing property 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 precision finishing of the sample piece S and the minute sample piece Q.

The detector 16 is a secondary charged particle (secondary electron, secondary ion) R emitted from the irradiation target when the irradiation target such as the sample V, the sample piece S, and the needle 19a is irradiated with the charged particle beam or the electron beam. (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 inside the sample chamber 11 at a position where the amount of the secondary charged particles R can be detected, for example, a position diagonally above the irradiation target such as the sample V and the sample piece S in the irradiation region. , 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 so as to face the stage 12. The gas supply unit 17 includes an etching gas for selectively promoting etching of the sample V and the sample piece S by the charged particle beam (focused ion beam) according to these materials, and 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 made of deposits such as metal or an insulator on the surface.

The needle drive mechanism 19b constituting the sample piece moving means 19 is housed inside the sample chamber 11 in a state where the needle 19a is connected, and the needle 19a is displaced according to a control signal output from the computer 22. The needle drive mechanism 19b is provided integrally with the stage 12, for example, when the stage 12 is rotated around the tilt axis (that is, the X axis or the Y axis) by the tilt mechanism 13b, the needle drive mechanism 19b moves integrally with the stage 12.

The needle drive mechanism 19b includes a movement mechanism (not shown) that moves the needle 19a in parallel along each of the three-dimensional coordinate axes, and a rotation mechanism (not shown) that rotates the needle 19a around the central axis of the needle 19a. I have. It should be noted that 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 having a two-dimensional coordinate axis parallel to the surface of the stage 12, and the surface of the stage 12 is in an inclined state. When in a rotating state, 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.

Further, the computer 22 is arranged outside the sample chamber 11 and is connected to the display device 21 and an input device 23 such as a mouse or a keyboard that outputs a signal corresponding to the input operation of the operator. The computer 22 integrally controls the operation of the charged particle beam device 10 by a signal output from the input device 23 or a signal generated by a preset automatic operation control process.

The computer 22 converts the detected amount of the secondary charged particles R detected by the detector 16 into a luminance signal associated with the irradiation position while scanning the irradiation position of the charged particle beam, and converts the detection amount of the secondary charged particles R into a brightness signal associated with the irradiation position. Image data showing the shape of the irradiation target is generated by the two-dimensional position 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, and thereby obtains the shape of the needle 19a by the two-dimensional position distribution (absorption current image) of the absorption current. Generates the indicated absorption current image data.

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

The sample processing method of the present invention using the charged particle beam device 10 having the above configuration will be described.
2 and 3 are explanatory views showing the sample processing method step by step.
In the following embodiment, as a sample processing method, an example of forming a micro sample piece Q for TEM observation by thinning the sample piece S supported by the sample piece holder P with a charged particle beam will be described. .. Further, as shown in FIG. 2A, it is assumed that the sample piece S is, for example, a sample V made of a semiconductor substrate (see FIG. 1) cut out from a region in which a plurality of devices 31, 31 ... Are formed. The direction in which the devices 31, 31 ... Are arranged is referred to as a thickness direction T, and the direction perpendicular to the thickness direction T and the extension direction of the device 31 is referred to as a width direction W. Further, the direction perpendicular to the thickness direction T and the width direction W is referred to as a processing direction D.

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

Next, as shown in FIG. 2C, a position overlapping the first removal region E1 along the thickness direction T, that is, a position shifted from the first removal region E1 along the thickness direction T by a predetermined processing thickness. Is irradiated with FIB to form a second removal region 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 end portion E2e on the root side of the second removal region E2 is displaced from the end portion E1e on the root side of the first removal region E1 toward the center side in the width direction W.

Further, as shown in FIG. 3A, the position overlapping the nth removal region En formed immediately before along the thickness direction T, that is, only a predetermined processing thickness from the nth removal region En along the thickness direction T. The shifted position is irradiated with FIB to form the (n + 1) th removal region 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 nth removal region En by a predetermined reduction width ΔW. In this way, the sample piece S is irradiated with FIB along the processing direction D, and a large number of removal areas in which the processing width is gradually reduced are formed so as to overlap in the thickness direction T, thereby forming the sample piece S. A minute sample piece Q having a reduced thickness along the thickness direction T is formed.

By forming a large number of removal areas in which the processing width is gradually reduced, the thinned portion Qs whose thickness is reduced is formed in the minute sample piece Q. 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 in which the end portions on the root side of each removal area are connected (inclined portion formation). Process). The inclined portion C is, for example, an inclined surface inclined in a 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 suffices if it has been done. 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. Here, by incident the beam at a small incident angle of less than 90 ° in the range of 10 ° or more and less than 90 °, the damage layer to the sample due to the beam incident can be made shallow. As a result, since the damage layer is shallow, it is possible to clearly grasp the processing end point at the time of processing even if the sample has fine device dimensions.

In the embodiment shown in FIGS. 2 and 3, the FIB is scanned and irradiated so that the processing width Wn along the width direction W of the sample piece S is gradually reduced, so that the inclined portion (thin section portion) is irradiated. The portion adjacent to) C is formed, but the scanning method of the FIB is not limited to this.

For example, in the example of the FIB scan shown in FIG. 4, the processing width Wn of the removal region En along the width direction W of the sample piece S to be the sliced portion Qs is made constant. Then, the FIB is continuously scanned from the root side of each removal region En in the direction of inclination in the range of 10 ° or more and less than 90 ° with respect to the thickness direction T. As a result, the inclined portion C is formed in the region scanned in the direction in which the FIB is inclined with respect to the thickness direction T. The processing width Wn along the inclined portion C is gradually increased in stages. Here, as the FIB scanning method, a vector scan is used in which the scanning direction of the FIB is changed from the width direction of the sample piece S to the direction inclined with respect to the thickness direction T.
Further, 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 the direction inclined with respect to the thickness direction T, and a raster scan or a bitmap scan is set in each irradiation area. May be used.

In addition to this, the scanning direction of the FIB in the trapezoidal region partitioned by the sliced portion Qs of the minute sample piece Q and the inclined portion C which is a portion adjacent to the sliced portion Qs is not particularly limited. If the inclined portion C, which is a portion adjacent to the flaked portion Qs, can be formed, the FIB may be scanned in any direction to form a removal area.

In the process of forming a large number of removal regions in which the processing width is 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. Then, by observing the obtained SEM image and counting the number of devices 31, 31 ... Exposed on the inclined portion C, the processing end point in the thickness direction T by the FIB can be determined. Since the cross-sectional shape of the devices 31, 31 ... Exposed on the inclined portion C looks larger and clearer than, for example, the cross-sectional shape of the device exposed on the cross section along the thickness direction T, the device 31, 31 ... The number can be counted accurately.

It should be noted that the process from the acquisition of the SEM image to the counting of the devices 31, 31 ... Exposed on the inclined portion C is automatically performed by, for example, the computer 22, and the result is fed back to the irradiation condition of the FIB for the sample piece S. Therefore, it is possible to automate the formation of the minute sample piece Q to which the inclined portion C is connected to the root side.

As a specific example of the method of detecting the machining end point by such automation, the number of design devices 31, 31 ... Appearing up to the observation target position (exposed to the inclined portion C) is input to the computer 22 in advance. The planned number of appearances of such a device 31 can be grasped from the design data of the integrated circuit formed on the sample V and the like.

Then, the number of devices 31 appearing in the inclined portion C by repeating the formation of the removal area by the irradiation of the FIB and the acquisition of the irradiation SEM image is counted by the image comparison software executed by the computer 22 or the like. Then, when the planned number of appearances of the device 31 input in advance to the computer 22 and the number of the devices 31 appearing in the inclined portion C by acquiring the actual SEM image match, this is recognized as the processing end point and the FIB is irradiated. To end.

Further, as another specific example of the method of detecting 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, the 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 executed by the computer 22 or the like. Alternatively, on the design of the cut out portion of the sample piece S based on the number of devices 31 exposed on the cut end surface of the sample V after the sample piece S is cut out, the design data of the integrated circuit formed on the sample V, and the like. You may count the number of devices 31.

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

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

In this argon beam irradiation step, the argon gas is ionized from the gas ion beam optical system 18 (see FIG. 1), and the entire area of the minute sample piece Q is irradiated with an argon ion beam at a low acceleration voltage of, for example, about 1 kV. At this time, it is preferable to irradiate the minute sample piece Q with EB from the electron beam irradiation optical system 15 and finish the minute sample piece Q with an argon ion beam based on the obtained SEM image. For the detection of the machining end point at this time, the machining end point detection procedure at the time of machining the minute sample piece Q by the above-mentioned FIB can be applied. This makes it possible to automate the argon beam irradiation process.

In such an argon beam irradiation step, 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 minute sample piece Q. The entire area of the minute sample piece Q, which has been thinned by reducing the thickness of the sample piece S, can be uniformly irradiated with the argon ion beam.

That is, as shown in FIG. 1, when the sample chamber 11 is viewed from the side in a plan view, the gas ion beam (GB) with respect to the beam irradiation axis of the electron beam (EB) irradiated from the electron beam irradiation optical system 15. The gas ion beam optical system 18 is arranged so that the beam irradiation axes intersect at right angles, for example. Therefore, if the thickness direction T is, for example, a right angle to the width direction W of the minute sample piece Q, a shadow region where the argon ion beam is not irradiated is generated at the base portion of the minute sample piece Q.

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

As shown in FIG. 3C, a large number of removal areas are formed in which the processing width along the width direction W is gradually reduced even from the direction opposite to the processing direction along the thickness direction T described above. , It is possible to form a micro sample piece Q having a thinned portion Qs whose thickness is reduced from both sides.

Although embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

10 ... charged particle beam device, 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 stand, 34 ... Column part, C ... Inclined part, P ... Sample piece holder, Q ... Micro sample piece, R ... Secondary charge Particles, S ... sample pieces, V ... samples.

Claims (5)

It is a charged particle beam device that creates a minute sample piece by irradiating a sample formed by stacking a plurality of embedded layers inside a substrate along the thickness direction with a charged particle beam.
A charged particle beam lens barrel capable of irradiating a charged particle beam toward the sample,
The sample chamber for accommodating the charged particle beam lens barrel and
With a sample piece holder capable of holding the sample,
When a micro sample piece in which the thickness of a part of the sample is reduced is formed by the charged particle beam, a portion adjacent to the flaked portion of the micro sample piece is inclined with respect to the flaked portion. The processing thickness and processing width are determined with reference to the SEM image of the inclined portion, and the processing end point is the number of the buried layers exposed to the inclined portion with reference to the SEM image of the inclined portion. a charged particle beam apparatus characterized in that it have a computer for controlling so counted to determine. The charged particle beam apparatus according to claim 1, wherein an argon ion beam is irradiated so as to be parallel to the inclined portion. It is a sample preparation method of irradiating a sample with a charged particle beam to prepare a minute sample piece in which the thickness of a part of the sample is reduced.
By irradiating the charged particle beam, a plurality of removal areas of 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 forming them in layers and gradually reducing the processing width each time the removal areas 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. With a step of forming an inclined portion to be formed ,
The sample is formed by stacking a plurality of embedded layers inside the base material along the thickness direction.
In the inclined portion forming step, the processed thickness and the processed width of each of the removed areas are determined with reference to the SEM image of the inclined portion obtained by the scanning electron microscope.
The sample processing method is characterized in that the inclined portion forming step determines a processing end point by counting the number of the buried layers exposed on the inclined portion using the SEM image. The third aspect of the present invention is characterized in that, in the inclined portion forming step, the thinned portion and the inclined portion which is a portion adjacent to the thinned portion are inclined in a range of 10 ° or more and less than 90 ° with respect to each other. Sample processing method. The sample processing method according to claim 3 or 4, further comprising an argon beam irradiation step of irradiating the minute sample piece with an argon ion beam so as to be parallel to the inclined portion.

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