JP7127883B2 - Composite charged particle beam system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite charged particle beam apparatus for preparing thin specimens with ion beams.

2. Description of the Related Art Conventionally, it is known to prepare a thin sample for observation with a transmission electron microscope (TEM) using a focused ion beam (FIB) apparatus. It is also known that gallium, which is an ion species, is implanted into a thin sample by irradiation with a focused ion beam to form a damaged layer.

In recent years, as a means for removing the damaged layer, a finishing process has been proposed in which a thin sample is irradiated with a gas ion beam (GIB) to remove the damaged layer (see Cited Document 1). According to such means, it is possible to form a thin sample with a less damaged layer.

Japanese Patent Application Laid-Open No. 2007-066710

However, in the conventional means, when a structure such as a semiconductor device is exposed on the observation surface of the thin sample, the etching rate of the gaseous ion beam differs depending on the presence or absence of the structure, so that unevenness is formed on the observation surface. A phenomenon that appears as streaks, a so-called curtain effect, occurs. For this reason, there is a problem that streaks formed by ion beam processing appear in the observation image of the observation surface in addition to the original device structure.

In particular, various types of materials are used in advanced devices in recent years. Therefore, there are cases where the difference in etching rate becomes significant.

In addition, since the advanced device has a fine structure, the object to be observed is also fine. Therefore, even if the unevenness appearing on the observation surface is small, it affects the observation.

The present invention provides a composite charged particle beam apparatus capable of suppressing the curtain effect and obtaining an observation image with few streaks.

The composite charged particle beam device of the present invention comprises:
a first charged particle beam column for irradiating a thin sample with a first charged particle beam;
a second charged particle beam column for irradiating a second charged particle beam onto the first charged particle beam irradiation position of the thin sample;
a sample holder;
a sample stage on which the sample holder is placed,
The sample holder is
a base placed on the sample table;
a rotary drive driven by a motor;
a rotating table that rotates about a flip axis by driving the rotation driving unit;
A composite charged particle beam apparatus, wherein the TEM grid holding the thin sample is rotated in a plane perpendicular to the observation plane of the thin sample by reciprocating driving around the flip axis together with the rotating table.

As one aspect of the present invention, for example, the sample stage can be tilted about the tilt axis,
The eucentric positions of the tilt axis and the flip axis coincide.

As one aspect of the present invention, for example, the sample stage can move, tilt, and rotate the sample holder in three axial directions of XYZ.

According to the composite charged particle beam apparatus according to the present invention, it is possible to suppress the curtain effect and obtain an observation image with few streaks even for a thin sample having a structure such as a semiconductor device.

1 is an overall configuration diagram of a composite charged particle beam device according to an embodiment of the present invention; FIG. FIG. 4 is a configuration diagram of the main parts of the composite charged particle beam apparatus of the embodiment, showing the arrangement relationship between the operation of the sample stage and each lens barrel. FIG. 4 is a perspective view of a sample holder placed on a sample stage; FIG. 4 is an enlarged view of a portion P in FIG. 3, and is a view mainly showing an enlarged perspective view of a worm wheel; FIG. 4 is a diagram showing the movement of the TEM grid attached to the top of the worm wheel in the sample holder, (a) is a schematic diagram showing the movement of the TEM grid accompanying rotation of the worm wheel, and (b) is rotation It is a schematic diagram which shows a motion of a TEM grid accompanying rotation of a stand. FIG. 2 is a schematic diagram of a thin section sample as an object to be processed and observed.

An embodiment of a composite charged particle beam device according to the present invention will be described below. FIG. 1 shows the overall configuration of a composite charged particle beam device 100 of this embodiment. A composite charged particle beam device 100 includes an FIB lens barrel (first charged particle beam lens barrel) 1 for irradiating a focused ion beam (FIB) as a first charged particle beam, and a second charged particle beam Equipped with an EB column (second charged particle beam column) 2 for irradiating an electron beam (EB) as a beam, and a GIB column 3 for irradiating a gas ion beam (GIB). ing.

The FIB column 1 has a liquid metal ion source. Further, the GIB column 3 has a PIG type gas ion source. A gaseous ion source uses helium, argon, xenon, oxygen, etc. as the ion source gas.

The composite charged particle beam device 100 further comprises a secondary electron detector 4 for detecting secondary electrons generated from the thin sample 7 by EB, FIB or GIB irradiation. A backscattered electron detector for detecting backscattered electrons generated from the thin sample 7 by EB irradiation may be provided.

The composite charged particle beam device 100 further includes a sample holder 6 for holding and fixing the thin sample 7 and a sample table 5 for mounting the sample holder 6 thereon. The sample stage 5 is movable in three axial directions of XYZ (not shown). Furthermore, the sample table 5 can be tilted and rotated as described later.

The composite charged particle beam device 100 further includes a sample stage controller 15 . The sample table control unit 15 controls a drive mechanism (not shown) to move the sample table 5 in the three axial directions of XYZ. Further, the sample table control unit 15 controls the tilt driving unit 8 to tilt the sample table 5 and controls the rotation driving unit 10 to rotate the sample table 5 .

The composite charged particle beam device 100 further comprises a sample holder controller 60 . The sample holder control unit 60 drives the sample holder 6 placed on the sample table 5 to set the direction of the thin sample 7 in a desired direction. Details of the configuration and operation of the sample holder 6 will be described later.

The composite charged particle beam apparatus 100 further includes an FIB controller 11 , an EB controller 12 , a GIB controller 13 , an image forming unit 14 and a display unit 18 . An EB control unit 12 controls EB irradiation from the EB lens barrel 2 . The FIB controller 11 controls FIB irradiation from the FIB lens barrel 1 . A GIB control unit 13 controls GIB irradiation from the GIB lens barrel 3 . The image forming unit 14 forms an SEM image from the signal for scanning the EB and the signal of the secondary electrons detected by the secondary electron detector 4 . The display unit 18 can display observation images such as SEM images, various control conditions of the apparatus, and the like. The image forming unit 14 also forms a SIM image from the signal for scanning the FIB and the signal of the secondary electrons detected by the secondary electron detector 4 . The display unit 18 can display a SIM image.

The composite charged particle beam device 100 further comprises an input section 16 and a control section 17 . The operator inputs the conditions for device control to the input section 16 . The input unit 16 transmits the input information to the control unit 17 . The control unit 17 transmits control signals to the FIB control unit 11, the EB control unit 12, the GIB control unit 13, the image forming unit 14, the sample stage control unit 15, the display unit 18, and the sample holder control unit 60, and controls the entire apparatus. to control.

Regarding the control of the device, for example, the operator sets the FIB and GIB irradiation regions based on observation images such as SEM images and SIM images displayed on the display unit 18 . The operator uses the input unit 16 to input a processing frame for setting an irradiation area on the observation image displayed on the display unit 18 . Further, when the operator inputs a processing start instruction to the input unit 16, the control unit 17 transmits an irradiation area and a processing start signal to the FIB control unit 11 or the GIB control unit 13, and the FIB control unit 11 transmits the FIB, or The GIB from the GIB control unit 13 is applied to the designated irradiation area of the thin sample 7 . As a result, the irradiation area input by the operator can be irradiated with FIB or GIB.

The composite charged particle beam apparatus 100 also includes a gas gun 19 that supplies an etching gas to the vicinity of the EB, FIB, or GIB irradiation area of the thin sample 7 . Halogen gas such as chlorine gas, fluorine-based gas (xenon fluoride, fluorine carbide, etc.), and iodine gas is used as an etching gas. By using an etching gas that reacts with the material of the thin sample 7, gas-assisted etching by EB, FIB, or GIB can be performed. In particular, gas-assisted etching by EB can perform etching processing without giving damage to the thin sample 7 due to ion sputtering.

FIG. 2 shows the essential part of the composite charged particle beam system 100, showing the positional relationship between the operation of the sample table 5 and each column. For SEM observation of the thin sample 7 being processed by the FIB 1b or GIB 3b, the FIB irradiation axis 1a of the FIB barrel 1 and the EB irradiation axis 2a of the EB barrel 2, and the EB irradiation axis 2a of the EB barrel 2 and the GIB The GIB irradiation axis 3a of the lens barrel 3 is arranged so as to intersect above the thin sample 7 whose position is adjusted by moving the sample stage 5. As shown in FIG. That is, the irradiation position of FIB1b of FIB lens barrel 1, the irradiation position of EB2b of EB lens barrel 2, and the irradiation position of GIB3b of GIB lens barrel 3 coincide on thin sample .

The sample table 5 is driven to tilt about a tilting axis 8a which is perpendicular to the FIB irradiation axis 1a and which is positioned within a first plane 21 defined by the FIB irradiation axis 1a and the GIB irradiation axis 3a. The portion 8 allows tilting. That is, the tilt driving section 8 as a tilting mechanism is driven under the control of the control section 17 and the sample table control section 15 to tilt the sample table 5 as indicated by the arrow A. FIG.

In addition, the sample table 5 can be rotated by a rotary drive unit 10 to rotate the thin sample 7 within a plane. That is, the rotation driving section 10 as a rotating mechanism is driven under the control of the control section 17 and the sample table control section 15 to rotate the sample table 5 in the plane as indicated by the arrow B. FIG. Various devices such as a servomotor can be used for the rotation drive unit 10 as a rotation mechanism, and the type thereof is not particularly limited.

Next, the configuration, operation and function of the sample holder 6 placed on the sample stage 5 will be described. As shown in FIG. 3, the sample holder 6 includes a base 61 arranged directly on the sample table 5, a holder shaft 62, a rotating table 63 as a second rotating unit, and a first rotating unit. and a worm wheel 64 as a rotating unit. The holder shaft 62 is rotated by power supply from a motor (not shown) driven by power supply from the outside. The plate-shaped rotating base 63 is connected to the holder shaft 62 in the space above the base 61 via a reduction gear or the like, and as the holder shaft 62 rotates, the F axis (flip axis) as a shaft axis is rotated. It rotates (oscillates) in the FR1 direction as the central axis of rotation.

FIG. 4 is an enlarged view of part P in FIG. The worm wheel 64 is accommodated in a recess 63a formed in the rotating base 63. As shown in FIG. An arc-shaped guide groove 66 is formed in the worm wheel 64 . A roller 65 that is provided on the rotating table 63 and driven independently of the rotating table 63 is fitted in the guide groove 66 in a rotatable state while sliding in the guide groove 66 . When the roller 65 rotates, it rotates while sliding along the guide groove 66 without idle rotation. It rotates (oscillates) in the SR1 direction. Therefore, the worm wheel 64 is rotatable (swingable) independently of the rotating base 63 .

A TEM grid 67 is provided on the top of the worm wheel 64 as a sample holder to which the thin sample 7 can be directly attached. The TEM grid 67 is made of a thin plate, and has a sample holding table 67a formed in the center, and five columns 67b1, 67b2, 67b3, 67b4, and 67b5 formed on the sample holding table 67a. The thin sample 7 is attached to the pillars 67b1-67b5.

The TEM grid 67 moves as shown in FIG. 5 as the rotating table 63 and the worm wheel 64 rotate, and the thin sample 7 attached to the TEM grid 67 also moves. FIG. 5(a) shows the movement of the TEM grid 67 as the worm wheel 64 rotates. The TEM grid 67 rotates in the direction of the arrow SR2 linked with the motion arrow SR1 of the worm wheel 64 in FIG. FIG. 5(b) shows the movement of the TEM grid 67 accompanying the rotation of the rotation table 63. FIG. The TEM grid 67 rotates in the direction of an arrow FR2 interlocked with the motion arrow FR1 of the rotating table 63 in FIG.

As shown in FIG. 5(a), in this embodiment, the worm wheel 64 and thus the TEM grid 67 are placed on the sample table 5, and the thin sample 7 is moved around the first rotation axis A1 extending in the direction perpendicular to the plane of the paper. It is possible to rotate the thin sample 7 in a plane parallel to the observation plane. The first rotation axis A1 here is parallel to the S axis in FIG. 4, and is a virtual axis around which the TEM grid 67 rotates about the first rotation axis A1. The observation surface of the thin sample 7 spreads in the direction parallel to the paper surface, that is, the direction perpendicular to the first rotation axis A1, and the thin sample 7 rotates in the paper surface, that is, in the plane parallel to the observation surface. move. Also, the first rotation axis A1 coincides with the position of the central column 67b3 among the columns 67b1 to 67b5.

Here, as shown in FIG. 2, the sample stage 5 can be tilted about the tilting axis 8a. matches. That is, the reference line E shown in FIGS. 5(a) and 5(b) indicates the eucentric position, on which the tilt axis 8a and the first rotation axis A1 are positioned. Here, the eucentric position corresponds to the irradiation position of FIB1b and EB2b (and GIB3b) on the thin section sample 7 . With such a configuration, even if the tilting of the sample stage 5 and the rotation of the TEM grid 67 shown in FIG. Observation becomes possible.

In FIG. 5(a), the direction in which the first rotation axis A1 extends is fixed to the direction perpendicular to the plane of the paper, but the direction in which the tilt axis 8a extends changes according to the rotation of the sample table 5 by the rotation drive unit 10. Therefore, it is not fixed in FIG. 5(a).

In addition, as shown in FIG. 5B, in this embodiment, the rotating table 63 and the TEM grid 67 are mounted on the sample table 5 so as to rotate about the second rotating shaft A2 extending in the direction perpendicular to the plane of the paper. It is possible to rotate the thin sample 7 within a plane perpendicular to the observation surface of the sample 7 . The second rotation axis A2 here corresponds to the F axis in FIG. 3, and is a virtual axis around which the TEM grid 67 rotates about the second rotation axis A2. The observation surface of the thin sample 7 spreads in a direction perpendicular to the paper surface, that is, in a direction parallel to the second rotation axis A2, and the thin sample 7 is rotated within the paper surface, that is, a plane perpendicular to the observation surface. move. The eucentric position of the tilting axis 8a of the sample table 5 and the second rotation axis A2 also coincide.

In FIGS. 5A and 5B, three TEM grids 67 at different rotational positions are shown separated in the horizontal direction in order to clearly show the movement of the TEM grids 67 . However, in an actual device, the three TEM grids 67 at different positions are not separated because they rotate about the first and second rotation axes A2.

FIG. 6 is a schematic diagram of a thin sample 7 obtained by cutting out a part of a semiconductor device. The thin sample 7 has device structures 31 , 32 , 33 . Structures 31 and 33 are exposed on the cross section 7a as an observation surface. FIB1b, EB2b, and GIB3b are irradiated from the upper surface 7c side.

When a charged particle beam is irradiated from one direction to such a cross section, the etching rate differs between a portion with a structure and a portion without a structure, so unevenness is formed on the cross section. When a cross section on which unevenness is formed is observed with an SEM, the observed image includes streaks caused by the unevenness. Since this streak is formed by ion beam processing, it is not a structure or defect of the semiconductor device. If streaks appear in the observed image, they may be indistinguishable from semiconductor device structures and defects.

In the composite charged particle beam apparatus 100 of this embodiment, the sample table 5 can be tilted about the tilt axis 8a by the action of the tilt drive section 8, and can be rotated by the action of the rotation drive section 10, The relative position (orientation) of the thin sample 7 with respect to the FIB barrel 1, EB barrel 2, and GIB barrel 3 can be changed. Furthermore, the sample holder 6 on the sample table 5 can change the relative position (orientation) of the thin sample 7 with respect to the FIB lens barrel 1, EB lens barrel 2, and GIB lens barrel 3 by the action shown in FIG. can. By combining the movements of the sample stage 5 and the sample holder 6, for example, the irradiation direction of the GIB 3b from the GIB lens barrel 3 to the thin sample 7 can be finely set. Therefore, it is possible to freely etch the unevenness generated in the cross section 7a as an observation surface of the thin sample 7 by etching with the GIB 3b from one direction with the GIB 3b from the other direction. It is possible to suppress the formation of unevenness due to the structure of the device exposed to the surface. In addition, since the relative position (orientation) of the thin sample 7 with respect to the FIB barrel 1, EB barrel 2, and GIB barrel 3 can be changed at the eucentric position, for example, By continuously reciprocating the TEM grid during beam irradiation, the thin sample 7 is uniformly irradiated with the beam. As a result, it is possible to suppress the formation of irregularities due to the structure of the device. As a result, it is possible to suppress the generation of unnecessary streaks in the obtained observation image of the observation surface, and it is possible to perform observation with high accuracy.

In this example, the irradiation direction of the thin sample 7 of the GIB 3b is changed, but it is also possible to change the irradiation direction of the thin sample 7 of the FIB 1b and EB2b.

Although the FIB lens barrel 1 is arranged in the vertical direction in the above description, the FIB lens barrel 1 and the EB lens barrel 2 may be exchanged.

Further, although the thin sample 7 is generally finished by GIB 3b, gas-assisted etching by EB 2b or FIB 1b may be used instead of GIB 3b. When using the FIB 1b, it is desirable to change the beam energy of the FIB 1b between the processing for forming the cross section 7a of the thin sample 7 and the finishing processing. That is, in the processing for forming the cross section 7a of the thin sample 7, the FIB 1b accelerated at an acceleration voltage of 30 to 40 kV is used to form a steep cross section at high speed with a beam having a small beam diameter. By using a low-acceleration FIB 1b with a voltage of about 1 kV to 10 kV and using a beam with a small penetration depth into the thin sample 7, processing with little damage is performed. As a result, finishing with less damage can be performed.

Details such as the size of the sample holder 6 and the mounting method of the thin sample 7 are not particularly limited, and an optimum one can be selected according to the observation. Moreover, by exchanging the front surface and the back surface of the thin sample 7, it becomes possible to process both the front surface and the back surface.

Note that the detailed configuration of the sample holder 6 is shown in the above embodiment. However, the configuration of the sample holder 6 is not limited to that of the embodiment. That is, it is sufficient if the sample holder 6 is placed on the sample table 5 and the thin sample 7 can be rotated about the first rotation axis A1 in a plane parallel to the observation surface of the thin sample 7. , the worm wheel 64 of the embodiment is not an essential component. Further, the sample holder 6 is placed on the sample stage 5, and the thin sample 7 is rotated in a plane perpendicular to the observation surface of the thin sample 7 around the second rotating shaft A2 substantially perpendicular to the first rotating shaft A1. 7 can be rotated, and the rotation table 63 of the embodiment is not an essential component.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified, improved, etc. as appropriate. In addition, the material, shape, size, numerical value, form, number, location, etc. of each component in the above-described embodiment are arbitrary and not limited as long as the present invention can be achieved.

The composite charged particle beam apparatus according to the present invention can finely set the irradiation direction of various beams to a thin sample, so that the curtain effect can be suppressed and an observation image with few streaks can be obtained. can.

1: FIB lens barrel 1a: FIB irradiation axis 1b: FIB
2: EB barrel 2a: EB irradiation axis 2b: EB
3: GIB lens barrel 3a: GIB irradiation axis 3b: GIB
4: Secondary electron detector 5: Sample table 6: Sample holder 7: Thin piece sample 7a: Cross section 7c: Upper surface 8: Tilt drive unit 8a: Tilt shaft 10: Rotation drive unit 11: FIB control unit 12: EB control unit 13 : GIB control unit 14: image forming unit 15: sample table control unit 16: input unit 17: control unit 18: display unit 19: gas gun 21: first surfaces 31, 32, 33: structure 60: sample holder control Part 61: base 62: holder shaft 63: rotation base (second rotation unit)
64: Worm wheel (first rotating unit)
65: Roller 66: Guide groove 67: TEM grid (sample holder)
100: Composite charged particle beam device A1: First rotation axis A2: Second rotation axis

Claims (2)

a first charged particle beam column for irradiating a thin sample with a first charged particle beam;
a second charged particle beam column for irradiating a second charged particle beam onto the first charged particle beam irradiation position of the thin sample;
a sample holder;
a sample stage on which the sample holder is placed,
The sample stage can be tilted about a tilt axis,
The sample holder is
a base placed on the sample table;
a rotary drive driven by a motor;
a rotating table that rotates independently of the sample table around a flip axis driven by the rotating drive unit;
rotating the TEM grid that holds the thin sample so as to be arranged on the flip axis together with the rotating table in a plane perpendicular to the observation plane of the thin sample by reciprocating driving about the flip axis ;
eucentric positions of the tilt axis and the flip axis coincide;
Composite charged particle beam device. A composite charged particle beam device according to claim 1 ,
The composite charged particle beam apparatus, wherein the sample table is capable of moving, tilting, and rotating the sample holder in three axial directions of XYZ.

Images