JP5105281B2 - Sample processing method and apparatus - Google Patents

Description

  The present invention relates to a sample processing method and apparatus. For example, the present invention relates to a sample processing method and apparatus suitable for processing a sample from a plurality of directions, such as processing of a TEM sample used for observation with a transmission electron microscope.

Conventionally, for example, when preparing a TEM sample for observation with a transmission electron microscope (TEM), the sample is processed by irradiating the sample with a focused ion beam.
In sample processing with a focused ion beam, as the processing continues, the processing region of the sample is charged by the charge of the focused ion beam, so that the focused ion beam that is subsequently irradiated onto the processing region is bent and accurate processing is performed. Is known to be impossible.
For this reason, a sample processing method is performed in which a position reference mark is formed on a part of a sample, and the position reference mark is irradiated with a processing focused ion beam to correct a positional deviation of the focused ion beam with respect to the sample. ing.
As such a sample processing method and apparatus, for example, in Patent Document 1, in a pattern film processing apparatus, a pattern film formed on a substrate is irradiated with a focused ion beam in a dot shape to ion-etch the pattern film. The reference pattern is formed, and the secondary charged particle detector is detected by the secondary charged particle detector while scanning the focused ion beam, and is displayed on the image display device and the image position of the reference pattern position is stored. In order to process the pattern film, the scanning range of the focused ion beam is limited, a predetermined position on the surface of the sample is scanned a predetermined number of times, and then the focused ion beam is scanned over the range including the reference pattern for reference A pattern is detected, compared with a stored reference position, the amount of movement of the reference position is calculated, and a pattern film repair that corrects a predetermined position based on the amount of movement is performed. The method has been described.
In Patent Document 2, in a focused ion beam processing method of processing a sample using a focused ion beam, a scanning ion microscope image of the sample is acquired every predetermined time, and the (nth) acquired in this step. -1) Image data D [n-1] of a specific area in the nth scanning ion microscope image and image data D [n] of a specific area in the nth scanning ion microscope image (where n = 1, 2) , 3,...), And a method for correcting the processing position by shifting the irradiation position of the focused ion beam by the determined displacement amount, and for performing this method. A focused ion beam processing apparatus is described.
In the specific region of Patent Document 2, a cross-shaped mark is formed to refer to the position on the sample.
Japanese Patent Publication No. 5-4660 JP 2000-21347 A

However, the conventional sample processing method and apparatus as described above have the following problems.
In the technique described in Patent Document 1, an image of a reference pattern on a sample is obtained by irradiating a focused ion beam for processing on the reference pattern, so that the reference pattern is processed each time it is referenced. The reference pattern deteriorates. As a result, there is a problem that the accuracy of the position correction amount calculated from the reference pattern image deteriorates with time.
In the technique described in Patent Document 2, similarly to the technique described in Patent Document 1, since the focused ion beam is repeatedly irradiated to the specific area, the specific area is processed, and the image of the mark formed in the specific area changes. However, since the amount of position correction of the focused ion beam is obtained by comparing the amount of movement of the latest image of the specific area with respect to the image of the specific area immediately before, the influence of deterioration of the mark shape over time due to processing is reduced. Be able to.
However, when processing by switching the irradiation direction of the focused ion beam, the error of the position correction amount is large because the focused ion beam irradiated in an oblique direction with respect to the mark changes the shape of the mark asymmetrically. There is a problem of becoming.

  The present invention has been made in view of the above problems, and provides a sample processing method and apparatus capable of improving the processing accuracy of a sample when the sample is processed using a focused ion beam. For the purpose.

In order to solve the above problems, a sample processing method according to the present invention forms a position reference mark on a sample, scans the position reference mark with a focused ion beam, and obtains position information of the position reference mark in the sample. A sample processing method for processing the sample by acquiring and correcting an irradiation position of the focused ion beam on the sample based on the position information, wherein the processing of the sample is performed on the focused ion beam on the sample Irradiating the focused ion beam from a direction substantially along one of the plurality of irradiation directions on the sample , and switching the position reference mark to the position reference mark. a mark forming process of forming a substantially along the uneven shape on one of the plurality of illumination directions, the focused ion beam is irradiated along the one of the plurality of radiation directions Te scans the position reference mark having substantially along uneven shape to one of said plurality of radiation directions, and mark position information acquisition step of acquiring position information of the position reference mark, the mark position information acquisition based on the position information before Symbol position location reference mark obtained in step corrects the irradiation position with respect to the sample of the focused ion beam, said focused ion beam along one of said plurality of radiation directions A sample processing step of processing the sample by irradiating , wherein the mark forming step, the mark position information acquisition step, and the sample processing step are performed for each of the plurality of irradiation directions. .
According to the present invention, a plurality of position reference marks are formed on the sample, and any one of the plurality of position reference marks is scanned by the focused ion beam to obtain position information of any of the plurality of position reference marks. To do. Then, based on the position information of any of the acquired plurality of position reference marks, the irradiation position of the focused ion beam on the sample is corrected, and the sample is processed.
For this reason, in the processing of the sample, in order to correct the irradiation position, the irradiation amount of the focused ion beam per position reference mark is reduced, so that the shape deterioration of the position reference mark can be reduced.
In addition, when scanning the position reference mark, the position reference mark in which the concavo-convex shape is formed in the direction substantially along the irradiation direction of the focused ion beam is selected. , The shape deterioration of the position reference mark is reduced.

In the sample processing method according to the present invention, wherein the position reference mark for scanning the focused ion beam is a position processing mark that has a concavo-convex shape formed in a direction substantially along the irradiation direction of the focused ion beam. Is preferably formed by a focused ion beam used for processing before processing the sample.
In this case, since the position reference mark is formed by the focused ion beam for processing the sample before the sample is processed, the position reference mark having the uneven shape formed in the direction along the irradiation direction of the focused ion beam can be easily obtained. Can be formed.

Sample processing apparatus of the present invention, a focused ion beam irradiating unit for irradiating a focused ion beam specimen, with respect to the irradiation center axis of the focused ion beam irradiated from said population bundle ion beam irradiation part, the position of the sample And holding the variably held posture to change the irradiation direction of the focused ion beam on the sample between a plurality of irradiation directions during processing of the sample, and the focused ion beam is irradiated to the sample A secondary charged particle detector that detects the intensity of the secondary charged particles emitted by the light source, and a beam that controls the sample holding unit and the focused ion beam irradiation unit to scan the focused ion beam on the sample a scanning control unit, and the mark position information storage unit for each store a plurality of formation position information of a position reference mark formed on the sample, the beam scanning system The scanning region of scanning the focused ion beam by parts, the focusing in the plurality of location reference mark reader scanning area setting set in a region including the mark portion, the scanning area set by the mark reader scanning area setting unit An image acquisition unit that acquires an image of an area including the position reference mark by acquiring the intensity of the secondary charged particle detected by the secondary charged particle detector in synchronization with scanning of the ion beam; A position information calculation unit that calculates the position of the position reference mark in the image by performing image processing on the image acquired by the image acquisition unit, and information on the position reference mark calculated by the position information calculation unit Is compared with the formation position information of the position reference mark stored in advance, the irradiation position correction amount of the focused ion beam is calculated, and the irradiation position correction amount is calculated based on the irradiation position correction amount. The a position correction control section for changing the scanning reference position in the beam scan control unit, the beam scanning control unit of the sample by irradiating the focused ion beam along one of said plurality of radiation directions Prior to performing the processing, the sample is irradiated with the focused ion beam from a direction substantially along one of the plurality of irradiation directions on the sample, and has the uneven shape substantially along one of the plurality of irradiation directions. When performing control of forming a reference mark and processing the sample by irradiating the focused ion beam along one of the plurality of irradiation directions, the scanning region set by the mark reading scanning region setting unit is set. is configured to perform control for switching to realm including the position reference mark having substantially along uneven shape to one of said plurality of radiation directions.
According to the present invention, the sample is held in the sample holding unit, and the sample is positioned so that the processing surface is orthogonal to the irradiation center axis of the focused ion beam irradiated from the focused ion beam irradiation unit. Next, the mark reading / scanning area setting unit selects one of a plurality of position reference marks whose formation position information is stored in the storage unit, sets an area including the position reference mark as a scanning area, and The scanning control unit causes the focused ion beam from the focused ion beam irradiation unit to scan the scanning region.
Then, the image acquisition unit acquires the image of the region including the position reference mark by acquiring the intensity of the secondary charged particle detected by the secondary charged particle detector in synchronization with the scanning of the focused ion beam.
Next, the image is processed by the position information calculation unit, and the position of the position reference mark is calculated.
The position correction control unit calculates the irradiation position correction amount of the focused ion beam by comparing the position of the position reference mark calculated by the position information calculation unit with the position reference mark formation position information stored in the storage unit. The scanning reference position in the beam scanning control unit is changed according to the irradiation position correction amount.
Thus, by repeating the irradiation of the focused ion beam onto the sample, the irradiation position can be corrected based on the image of the position reference mark even if the irradiation position of the focused ion beam on the sample is shifted.
Since the region including the position reference mark set in the scanning region is selectively switched between a plurality of regions corresponding to the plurality of position reference marks, focused ions per one position reference mark are used. Since the irradiation amount of the beam is reduced, the shape deterioration of the position reference mark can be reduced.
In addition, since the region including the position reference mark can be selectively switched according to the irradiation direction of the focused ion beam, the position reference mark can be degraded by selecting the position reference mark that is less deteriorated by the irradiation direction. Can be reduced.
In addition, the sample processing apparatus of this invention is an apparatus which can be used in order to perform the sample processing method of this invention.

  According to the sample processing method and apparatus of the present invention, the shape deterioration of the position reference mark can be reduced, so that the processing accuracy of the sample can be improved when the sample is processed using the focused ion beam. There is an effect.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

[First Embodiment]
First, the sample processing apparatus according to the first embodiment of the present invention will be described.
FIG. 1 is a schematic perspective view showing a schematic configuration of a sample processing apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a schematic configuration of the sample processing apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic perspective view showing an example of a sample processed by the sample processing method according to the first embodiment of the present invention. FIG. 4A is a partially enlarged view of A view (B view) of FIG. FIG. 4B is a cross-sectional view taken along the line CC of FIG. FIG. 5 is a functional block diagram of the control unit of the sample processing apparatus according to the first embodiment of the present invention.
Note that the XYZ coordinate system and the xyz coordinate system described in the figures are provided in common in each figure for the convenience of direction reference. The XYZ coordinate system is a coordinate system fixed to the apparatus installation surface, and the positive Z-axis direction indicates the upper side of the vertical direction, and the XY plane indicates the horizontal plane. The xyz coordinate system is a coordinate system fixed to the sample, and a machining surface 1a, which will be described later, is parallel to the xy plane, and the direction from the z-axis positive direction to the z-axis negative direction is orthogonal to the machining surface 1a. In the case of the focused ion beam irradiation direction.

As shown in FIGS. 1 and 2, the sample processing apparatus 100 of the present embodiment includes a vacuum chamber 13, an ion beam irradiation system 20 (focused ion beam irradiation unit), a sample table 14 that holds the sample 1, and a sample table. 14 is provided with a sample stage 16 for moving and holding 14, a secondary charged particle detector 18, a gas gun 11, a control unit 30, and a display unit 38.
The inside of the vacuum chamber 13 can be depressurized to a predetermined degree of vacuum, and a part or all of the components other than the control unit 30 and the display unit 38 are arranged in the vacuum chamber 13. .

  The sample processing apparatus 100 having such a configuration processes, for example, a sample 1 made of a semiconductor wafer, a semiconductor chip, or the like by an ion beam 20A (focused ion beam) emitted from an ion beam irradiation system 20. The type of processing is not particularly limited, but is particularly suitable for processing the sample 1 from a plurality of directions. For example, a cross section is formed on the sample 1 to observe the cross section with a scanning electron microscope (SEM) or the like. It can be suitably used for processing and processing for cutting out a TEM sample from the sample 1 for observation with a transmission electron microscope.

First, an example of the processing shape of the sample 1 in the sample processing of this embodiment will be described.
By etching the processing surface 1a on the upper side in the figure (z axis positive direction side) from the sample 1 of this embodiment to the z axis negative direction side (see arrow A in the figure), as shown in FIG. A wall 1d parallel to the zx plane sandwiched between 1B and the holes 1A and 1B is formed, and the TEM sample 2 including the observation cross section is cut out from the middle of the wall 1d.
In the present embodiment, the mark portion 3 that is a position reference mark for correcting the irradiation position on the xy plane of the ion beam 20A is formed.
Further, when the TEM sample 2 is cut out from the wall 1d, etching is performed by changing the irradiation direction of the ion beam 20A in the direction of the arrow B shown in the drawing. Before performing this processing, a mark portion 4 that is a position reference mark for correcting the irradiation position in the direction orthogonal to the irradiation direction of the ion beam 20A is formed on the marking surface 1c on the side of the cut-out position of the TEM sample 2. Like to do.

The shape of the mark portion 3 (4) is a shape that allows each image to be acquired from the intensity of the secondary charged particles 23 generated by scanning the ion beam 20A on the mark portion 3 (4). Any shape can be used as long as each fixed position of the mark portion 3 (4) can be specified. In this embodiment, as shown in FIGS. 4A and 4B, the diameter D ₁ (D ₂ ), a cylindrical hole of depth h ₁ (h ₂ ) is adopted. Here, the position of the mark portion 3 (4) is acquired as the position of the center O ₁ (O ₂ ) of the circle at the upper end or the lower end of the cylindrical hole.

Hereinafter, each configuration of the sample processing apparatus 100 will be described.
In the present embodiment, the ion beam irradiation system 20 includes a focused ion beam column whose optical axis is disposed along the vertical direction, and is disposed above the sample stage 14 in the vacuum chamber 13. Therefore, by irradiating the sample 1 placed on the sample stage 14 with the ion beam 20A vertically upward (Z-axis positive direction in the figure), the sample 1 is directed vertically downward (Z-axis negative direction in the figure). It can be etched.
The ion beam irradiation system 20 is electrically connected to the control unit 30, and the irradiation position and irradiation conditions of the ion beam 20A are controlled by the control signal of the control unit 30.

  The ion beam irradiation system 20 forms a ion beam 20A, which is a focused ion beam, and a gas field ion source 21 that generates and discharges ions in the focused ion beam column and ions extracted from the gas field ion source 21. The ion optical system 25 is provided.

Although not particularly shown, the gas field ion source 21 has, for example, an ion generation chamber that is maintained in a high vacuum state, a pyramid shape whose tip is sharpened at an atomic level, and a needle-like base material made of tungsten or molybdenum. , An emitter coated with a noble metal such as platinum, palladium, iridium, rhodium, and gold, a gas supply source for supplying a trace amount of rare gas (eg, Ar gas) to the ion chamber, an extraction electrode, and a cooling device. .
With such a configuration, the gas field ion source 21 generates a rare gas ion by applying a voltage between the emitter and the extraction electrode (field ionization), and the ion optical system 25 generates an ion beam by the rare gas ion. It can be injected towards.

  The ion optical system 25 includes, for example, a condenser lens that focuses the ion beam from the gas field ion source 21 toward the vacuum chamber 13 from the gas field ion source 21 side, an aperture that narrows the ion beam, and an optical axis of the ion beam. , An objective lens that focuses the ion beam on the sample, and a deflector that scans the ion beam on the sample are arranged in this order.

As shown in FIG. 2, the sample stage 16 includes a tilt mechanism 16a that performs tilt movement about the X axis and the Y axis, an XYZ movement mechanism 16b that performs parallel movement along the X axis, the Y axis, and the Z axis, and a Z axis. The sample stage 14 is held on the tilt mechanism 16a.
Further, the tilt mechanism 16a, the XYZ movement mechanism 16b, and the rotation mechanism 16c are each connected to the control unit 30 so as to be communicable, and the movement amount is controlled by a control signal from the control unit 30.
For this reason, the sample stage 14 and the sample stage 16 constitute a sample holding unit that variably holds the position and posture of the sample 1 with respect to the irradiation center axis of the ion beam 20A irradiated from the ion beam irradiation system 20. ing.

  The secondary charged particle detector 18 detects the intensity of the secondary charged particles 23 emitted from the sample 1 when the sample 1 is scanned with the ion beam 20 </ b> A, and the control unit 30 detects the intensity of the secondary charged particles 23. This information is sent out. The arrangement position of the secondary charged particle detector 18 is not particularly limited as long as the intensity of the secondary charged particle 23 can be detected. In the present embodiment, as shown in FIGS.

The gas gun 11 is a gas such as a gas for increasing the etching rate for increasing the etching rate of the etching with the ion beam 20A in the vicinity of the sample 1 and a gas for depositing when a mark portion to be described later is formed by deposition. Supply.
If the sample 1 is irradiated with the ion beam 20 </ b> A while supplying the deposition gas from the gas gun 11, gas-assisted deposition can be performed, and a deposit or a film of a metal or an insulator is deposited on the sample 1. Can be formed.

The control unit 30 performs overall control of the sample processing apparatus 100. For example, the control unit 30 is electrically connected to each part of the sample processing apparatus 100 such as the ion beam irradiation system 20, the sample stage 16, and the secondary charged particle detector 18. It is connected.
Further, the control unit 30 displays an image of the scanning range of the ion beam 20A based on the intensity information of the secondary charged particles sent from the secondary charged particle detector 18, or displays, for example, a fracture surface in the image. A display unit 38 comprising a monitor for superimposing and displaying characters and symbols such as position information is connected.

As shown in FIG. 5, the functional configuration of the control unit 30 includes an image capture unit 31 (image acquisition unit), a storage unit 32, a position information calculation unit 33, a position correction control unit 34, a mark reading scanning area setting unit 36, And a beam scanning control unit 35.
The image capturing unit 31 captures the detection output of the intensity of the secondary charged particles 23 from the secondary charged particle detector 18 as luminance data for each scanning position (irradiation position) of the ion beam 20A, and obtains two-dimensional image data. It is generated and sent to the storage unit 32. The scanning position information of the ion beam 20A is acquired from the beam scanning control unit 35.

The storage unit 32 stores the image data captured by the image capturing unit 31, and the calculation and control by the position information calculation unit 33, the position correction control unit 34, the beam scanning control unit 35, and the mark reading scanning region setting unit 36. It stores information necessary for the operation and calculation results.
For example, the position information of the cut-out range of the TEM sample 2 on the sample 1, the information of the processing procedure for scanning the ion beam 20A to cut out the TEM sample 2, the mark portion 3 that is the position information of the position reference mark, 4 and information on the scanning area of the ion beam 20A set as an area including the mark portions 3 and 4 for acquiring images of the mark portions 3 and 4 are stored.

The position information calculation unit 33 performs image processing on the image data stored in the storage unit 32, detects the mark portions 3 and 4 previously formed on the sample 1 in the image data, and scans the image with the ion beam 20A. The positions of the mark portions 3 and 4 based on the data are calculated. In the present embodiment, for example, the positions of the centers O ₁ and O ₂ can be obtained by extracting and binarizing the circular images of the mark portions 3 and 4 and then obtaining the center of gravity of the circular image.
The position correction control unit 34 compares the positions of the mark units 3 and 4 calculated by the position information calculation unit 33 with the formation position information of the mark units 3 and 4 stored in the storage unit 32 in advance, and thereby compares the position of the ion beam 20A. The irradiation position correction amount is calculated and sent to the beam scanning control unit 35.

The mark reading / scanning area setting unit 36 sets the position information of the scanning area so that the scanning area of the ion beam 20 </ b> A is any area including the mark parts 3 and 4, and sends it to the beam scanning control unit 35. Is.
This scanning region can scan a range in which the position information of the mark portions 3 and 4 can be specified even when the irradiation position of the ion beam 20A is shifted due to a charge generated by processing of the sample 1 using the ion beam 20A. Set to
In the present embodiment, as shown in FIG. 4A, W ₁ that covers the mark portion 3 (4) with a margin around the center O ₁ (O ₂ ) of the mark portion 3 (4). The scanning area 3A (4A), which is a square area of × W ₁ (W ₂ × W ₂ ) (W ₁ > D ₁ , W ₂ > D ₂ ), is set. In this case, Δ ₁ = (W ₁ −D ₁ ) / 2 and Δ ₂ = (W ₂ −D ₂ ) / 2 are margins for the irradiation position deviation of the ion beam 20A.

The beam scanning control unit 35 controls the sample stage 16 and the ion beam irradiation system 20 to scan the ion beam 20A on the sample 1.
That is, based on the processing procedure information stored in the storage unit 32, the sample stage 16 is controlled so that the position and orientation of the sample 1 held on the sample stage 14 are relative to the irradiation axis of the ion beam irradiation system 20. The sample 1 is moved so as to be in a predetermined position and posture, and the ion beam 20A irradiated from the ion beam irradiation system 20 is raster-scanned within a certain scanning region. As a result, the raster scanning range is etched.
Similarly, raster scanning is performed in any of the scanning areas 3A and 3B based on the position information of the scanning area from the mark reading / scanning area setting unit 36. Thereby, it is possible to acquire an image of any of the mark portions 3 and 4 by the secondary charged particles 23 generated in the raster scanning range.

  For the device configuration of the control unit 30, dedicated hardware may be used, but in this embodiment, a computer for calculation and control is executed by a computer having a CPU, a memory, an external storage device, an input / output interface, and the like. It is realized by executing.

Next, the operation of the sample processing apparatus 100 will be described.
FIG. 6 is a schematic perspective view explaining the step of forming the position reference mark in the sample processing method according to the first embodiment of the present invention. FIG. 7 is a schematic perspective view illustrating a step of processing a sample following the step shown in FIG. FIG. 8A is a schematic plan view showing an example of the temporal change of the position reference mark according to the first embodiment of the present invention. FIG.8 (b) is DD sectional drawing of Fig.8 (a). FIG. 9A is a schematic plan view showing an example of the change with time of the position reference mark when the irradiation direction of the focused ion beam is oblique. FIG. 9B is an EE cross-sectional view of FIG. FIG. 10 is a schematic perspective view explaining the step of forming another position reference mark following the step shown in FIG. FIG. 11 is a schematic perspective process explanatory diagram illustrating a process of cutting out a TEM sample following the process illustrated in FIG. 10.

  The sample processing method of the present embodiment using the sample processing apparatus 100 includes a mark forming process for forming the mark portions 3 and 4 on the sample 1 according to the irradiation direction of the ion beam 20A, and the positions of the mark portions 3 and 4 and the like. A mark position information acquisition step for acquiring reference mark position information, and a processing of the sample 1 by correcting the irradiation position of the ion beam 20A on the sample 1 based on the position reference mark position information acquired in the mark position information acquisition step. A sample processing step of performing

First, the sample 1 is held at the reference position on the sample stage 14. And according to the information of the processing procedure memorize | stored in the memory | storage part 32, the sample 1 is processed as follows.
First, the sample stage 16 is driven by the beam scanning control unit 35 so that the irradiation axis of the ion beam irradiation system 20 coincides with the normal direction of the processing surface 1a. At this time, the z axis in FIG. 6 coincides with the Z axis in FIGS. An arbitrary position on the machining surface 1a parallel to the xy plane is described by coordinates (X, Y, Z ₀ ) in the XYZ coordinate system (where Z ₀ is a constant).

Next, a mark forming process for forming the mark portion 3 when the processed surface 1a is processed in the negative z-axis direction is performed.
Beam scanning control unit 35, storage unit 32 obtains the information of the shape and forming position of the mark portion 3, based on the information, the ion beam 20A is a circle having a diameter D ₁ about the point O ₁ scanning a range, etching a range of depth h ₁ from the processing surface 1a. Thereby, the mark part 3 as shown in FIG. 4 is formed.
The depth h ₁ may be any depth that allows the secondary charged particles 23 to acquire an identifiable image when the ion beam 20 </ b> A is scanned to read the mark portion 3. For this reason, since the processing amount of the mark portion 3 is small, the influence of the charge of the sample 1 during processing can be almost ignored.

Next, the beam scanning control unit 35 acquires information for forming the holes 1A and 1B from the storage unit 32, and performs etching by scanning the ion beam 20A in the scanning regions 5A and 5B in FIG. . That is, shapes such as the inclined surface 1b, the marking surface 1c, and the wall portion 1d in FIG. 3 are formed.
At this time, as the processing progresses, the sample 1 is charged and the ion beam 20A is bent, and the irradiation position of the ion beam 20A shifts from the target position. For this reason, in this method, after performing the mark position information acquisition step, the sample processing step is performed, and the holes 1A and 1B are processed while repeating these as necessary. The timing for performing the mark position information acquisition step can be set as appropriate. However, when the position accuracy may be rough, it is performed at a low frequency, and processing of a portion requiring position accuracy, for example, the side surface of the wall 1d is formed. In processing or the like, it is preferable to carry out at high frequency.

In the mark position information acquisition step, the mark reading / scanning area setting unit 36 sends the position information of the scanning area 3 </ b> A to the beam scanning control unit 35. In the beam scanning control unit 35, the scanning region 3A is raster scanned. Further, the intensity of the secondary charged particles 23 released at that time is detected by the secondary charged particle detector 18 and sent to the image capturing unit 31 together with the information of the scanning position.
In the image capturing unit 31, the detection output of the secondary charged particle detector 18 is captured as luminance data for each scanning position, and two-dimensional image data of the scanning region 3 </ b> A is generated and stored in the storage unit 32. Since the scanning area 3 </ b> A is an area including the mark portion 3, the image data includes a circular image of the edge portion of the mark portion 3 or the bottom surface of the mark portion 3.
Next, the position information calculation unit 33 calculates the position of the center O ₁ of the mark unit 3 from the image data. For example, in this embodiment, a circular image in the scanning region 3A is extracted and binarized by image processing, and then the center of gravity of the circular image is obtained, and relative position information with respect to the scanning region 3A is sent to the position correction control unit 34. .
The mark position information acquisition process for the mark unit 3 is thus completed.

Next, the beam scanning control unit 35 moves the scanning region to a region to be processed on the processing surface 1a, and performs the sample processing step by irradiating the ion beam 20A.
At that time, first, the position correction control unit 34 stores the relative position information of the center O ₁ acquired by the position information calculation unit 33 with respect to the scanning region 3A in the storage unit 32 in advance. When the position of the center O ₁ calculated by the position information calculation unit 33 is deviated from the formation position information of the mark unit 3, the irradiation position correction amount of the ion beam 20A is calculated from this deviation amount. It is sent to the beam scanning control unit 35.
In the present embodiment, not generated bends the ion beam 20A, if the deviation in the irradiation position is not generated, the scan region 3A corresponds to the intersection of diagonal lines of the center O ₁ and the scanning region 3A of the mark portion 3. If the irradiation position of the ion beam 20A is deviated, the position of the scanning region 3A on the sample 1 moves, so that the center O ₁ of the mark portion 3 is displaced with respect to the center of the scanning region 3A.
The beam scanning control unit 35 scans the ion beam irradiation system 20 at a position where the processing position information stored in the storage unit 32 is corrected by the irradiation position correction amount sent from the position correction control unit 34.

In this manner, the processing surface 1a is processed in the z-axis direction by repeating the mark position information acquisition step and the sample processing step. Then, as shown in FIG. 7, a wall 1d for cutting out the TEM sample 2, two inclined surfaces 1b and a TEM sample 2 whose depth gradually increases from the outer edge of the processed surface 1a toward the wall 1d. The marking surface 1c for forming the mark portion 4 and the side surface in the x-axis direction of the TEM sample 2 are formed on the side surface on the negative side in the y-axis direction of the wall portion 1d located on the side of the cutting position (x-axis negative direction). Two cut grooves 1e are formed.
In this embodiment, when cutting the base end portion of the wall portion 1d to cut out the TEM sample 2, the marking surface is used to irradiate the ion beam 20A from the direction substantially along the inclination of the wall portion 1d in the yz plane. 1c is a plane which has an inclination which protrudes in the y-axis negative direction side toward the base end side from the processing surface 1a side with respect to the side surface of the wall portion 1d.

When the mark position information acquisition process and the sample processing process are repeated, the scanning region 3A is also etched by the ion beam 20A. For example, when the depth h is etched, as shown in FIGS. 8A and 8B, the scanning region 3A is processed from the processing surface 1a to the square hole portion 6A having the depth h, and the mark portion 3 is The hole 6B is processed from the bottom surface of the hole to a depth h ₁ (depth (h ₁ + h) from the processing surface 1a).
In this case, since the mark portion 3 is formed by etching in the irradiation direction of the ion beam 20A, the position on the xy plane does not change even if the etching depth h changes. For this reason, the reference position mark for correcting the position parallel to the processed surface 1a is stable over time.

Here, a case where the irradiation direction of the ion beam 20A for acquiring the image of the mark unit 3 is tilted with respect to the z axis will be described.
In this case, as shown in FIGS. 9A and 9B, the mark portion 3 is etched obliquely along the inclination in the irradiation direction, and the scanning region 3A and the mark portion 3 are inclined hole portions 7A and 7B, respectively. To change. Thus, the processability asymmetrically proceeds with respect to the center O _1, as shown in FIG. 9 (a), the edge of the oblique hole 7A becomes oval, the corner edges of the bottom surface of the oblique hole 7B is When the center is obtained from each of the circles, the positions of the points Q and R are obtained, and any of them is shifted from the center O ₁ of the mark portion 3 in the x-axis direction.
Therefore, in this case, the irradiation position correction amount is shifted with time.
Therefore, in this embodiment, when the sample processing is performed by changing the irradiation direction of the ion beam 20A, the irradiation position correction of the ion beam 20A is performed using another mark portion etched in the irradiation direction.

Next, the base end portion of the wall portion 1d formed in the above process is cut, and sample processing for cutting out the TEM sample 2 is performed. In the present embodiment, an irradiation direction is an oblique direction orthogonal to the x-axis direction and approximately along the inclination of the inclined surface 1b in the yz plane.
First, the beam scanning control unit 35 drives the tilt mechanism 16a of the sample stage 16, tilts the irradiation axis of the ion beam irradiation system 20 with respect to the processing surface 1a, and the irradiation direction of FIG. Set to match the negative Z-axis direction.

From this state, a mark forming step for forming the mark portion 4 is performed.
The beam scanning control unit 35 acquires information on the shape and formation position of the mark unit 4 from the storage unit 32, drives the sample stage 16 based on the information, and the ion beam 20A is obtained as shown in FIG. scans the range of circle of diameter D ₂ about the point O _2, to etch the range of depth h ₂ from the marking surface 1c. Thereby, the mark part 4 as shown in FIG. 4 is formed.

Next, a mark position information acquisition process for the mark unit 4 is performed. That is, the beam scanning control unit 35 acquires the position information of the scanning region 4A from the mark reading scanning region setting unit 36 in substantially the same manner as described above, raster scans the scanning region 4A, the secondary charged particle detector 18, The image capturing unit 31 acquires the image data of the mark unit 4. Then, the position information calculation unit 33 calculates the position of the center O ₂ of the mark unit 4 on the marking surface 1 c from this image data, and sends it to the position correction control unit 34.
Thus, the mark position information acquisition process for the mark portion 4 is completed.

Next, as shown in FIG. 11, a sample processing step for cutting the cutting region 8 at the base end portion of the wall portion 1d sandwiched between the two cutting grooves 1e is performed.
First, the position correction control unit 34 compares the position information of the center O ₂ acquired by the position information calculation unit 33 with the formation position information of the mark unit 4 stored in the storage unit 32 in advance, and the position information calculation unit 33 When the calculated position of the center O ₂ is deviated from the formation position information of the mark portion 4, the irradiation position correction amount of the ion beam 20 A is calculated from this deviation amount and sent to the beam scanning control unit 35.
The beam scanning control unit 35 scans the ion beam irradiation system 20 at a position where the position information of the cutting region 8 stored in the storage unit 32 is corrected by the irradiation position correction amount sent from the position correction control unit 34. Go.
Then, if necessary, the mark position information acquisition step and the sample processing step are repeated to etch the cut region 8 in the irradiation direction, and the TEM sample 2 is cut out as shown in FIG.
In this sample processing step, when the scanning region 4A is repeatedly scanned, the scanning region 4A and the mark portion 4 are etched in the irradiation direction as described in the case of the scanning region 3A. Moreover, since the position of the center O ₂ of the mark portion 4 on the plane parallel to the marking surface 1c is stable over time, accurate irradiation position correction can be performed.
The sample processing for cutting out the TEM sample 2 from the sample 1 is thus completed.

  According to the sample processing method using the sample processing apparatus 100 of the present embodiment, when the sample processing is performed by changing the irradiation direction of the ion beam 20A on the sample 1, the ion beam 20A is changed according to the irradiation direction. Since the mark portions 3 and 4 are provided as position reference marks for correcting the irradiation position, even if the mark position information acquisition process is repeated for them, the shape deterioration related to the position information to be acquired by the mark portions 3 and 4 is prevented. Therefore, when the sample is processed using the ion beam 20A, the processing accuracy of the sample can be improved.

[Second Embodiment]
Next, a sample processing method according to the second embodiment of the present invention will be described.
FIG. 12 is a schematic perspective view showing an example of a sample processed by the sample processing method according to the second embodiment of the present invention.

  The sample processing method of this embodiment can be performed using the sample processing apparatus 100 according to the first embodiment, and corresponds to one irradiation direction of the ion beam 20A as shown in FIG. Thus, a sample processing is performed by providing mark portions 51 and 52 which are a plurality of position reference marks. Hereinafter, a description will be given centering on differences from the first embodiment.

The sample processing method of the present embodiment will be described using an example in which the hole 50A is processed in the sample 50 shown in FIG.
The sample 50 is a rectangular parallelepiped member similar to the sample 1, and the processed surface 50 a is provided in parallel to the xy plane of the xyz coordinate system fixed to the sample 50.
The hole 50A is a rectangular hole etched to a certain depth from the processing surface 50a in a rectangular range in which the long side extends in the x-axis direction and the short side extends in the y-axis direction. A side surface 50B (y-axis positive direction side), 50b, 50c, 50d and a bottom surface 50e are formed.
Here, the inner side surface 50 </ b> B is a cross section for observing a cross section of the sample 50. For this reason, the formation position and the processing surface accuracy of the inner side surface 50B are required to be higher than the inner side surfaces 50b, 50c, and 50d.

In the present embodiment, first, a mark forming step for forming the mark portions 51 and 52 as position reference marks on the processed surface 50a is performed.
The mark parts 51 and 52 are provided in parallel at positions where the scanning areas 51A and 51B do not overlap each other in the vicinity where the hole part 50A is formed.
In this embodiment, as shown in FIG. 4, the mark portions 51 and 52 are circular holes similar in shape to the mark portions 3 and 4 of the first embodiment, each having a center O ₃ , O ₄ , diameters D ₃ and D ₄ , and depths h ₃ and h ₄ . The size of the scanning areas 51A and 51B is a square area with a margin as in the first embodiment, and W ₃ × W ₃ and W ₄ × W ₄ according to each diameter. Set to
The conditions of the ion beam 20A for forming the mark parts 51 and 52 are such that the irradiation direction coincides with the irradiation direction of the roughing process and the finishing process described later, and the mark parts 51 and 52 are formed with good shape accuracy. If possible, they may be different or may be common conditions. Further, the mark portions 51 and 52 may be formed sequentially or simultaneously.

Next, rough machining is performed to form a square hole composed of an inner side surface 50C (see the two-dot chain line in the drawing), inner side surfaces 50b, 50c, and 50d, and a bottom surface 50e located on the negative side in the y direction of the position of the inner side surface 50B. The process and the finishing process of etching the inner side surface 50C to the position of the inner side surface 50B and finishing the inner side surface 50B into an observable cross section are performed in this order. That is, in this embodiment, it is an example in the case of providing two types of processing steps with the same irradiation direction.
In these processing steps, the irradiation direction is constant and is the normal direction of the processing surface 50a (see arrow a in FIG. 12). In these roughing process and finishing process, the mark position information acquisition process and the sample processing process are sequentially repeated in the same manner as in the first embodiment.

In the roughing process, in order to improve the processing efficiency, conditions such as the beam diameter and output of the ion beam 20A are made larger than those in the finishing process, or a gas for increasing the etching rate is supplied from the gas gun 11. Then, the etching is performed at a high etching rate, and the processing is performed under a condition that gives priority to the processing speed.
In the present embodiment, in this roughing process, the mark reading / scanning area setting unit 36 selects the scanning area 51A to perform the mark position information acquisition process with reference to the mark part 51, thereby correcting the irradiation position. The amount is calculated and the sample processing step is performed.

Next, in the finishing process, in order to improve the processing accuracy, conditions such as the beam diameter and output of the ion beam 20A are made smaller than those in the roughing process, and the irradiation position accuracy is prioritized over the processing speed. Processing with.
In the present embodiment, in this finishing process, the mark reading / scanning area setting unit 36 selects the scanning area 52A to perform the mark position information acquisition process with reference to the mark part 52, thereby correcting the irradiation position. The amount is calculated and the sample processing step is performed.

According to the sample processing method of the present embodiment, in the rough processing step, the scanning region 51A is scanned by the ion beam 20A in which processing speed is prioritized, so that the substantial beam diameter of the ion beam 20A is large. . For this reason, the edge part of the mark part 51 tends to deteriorate over time. In addition, when the irradiation direction is slightly shifted due to the bending of the ion beam 20A, the center position of the mark portion 51 is easily shifted.
Such a change in the irradiation position correction amount due to the deterioration of the mark portion 51 is as small as is acceptable in the roughing process because the depth direction of the mark portion 51 matches the irradiation direction of the ion beam 20A. It is. On the other hand, in the finishing process performed after the roughing process, there is a possibility of unacceptable deterioration.
In the present embodiment, in the finishing process, since the mark part 52 that is not referred to in the roughing process is referred to, the irradiation position correction of the ion beam 20A in the roughing process can be performed satisfactorily. Even if it has deteriorated in the processing step, the inner side surface 50B can be processed with good positional accuracy.

Next, a modification of this embodiment will be described.
Regardless of whether the processing of the sample 50 is a roughing processing step, a finishing processing step, or a plurality of processing steps, the present modified example uses a plurality of mark reading / scanning region setting units 36 to perform a plurality of processing steps. The mark portions 51 and 52, which are position reference marks, are selectively switched over time for reference.
For example, the processing proceeds while the mark portions 51 and 52 are referred to alternately. Alternatively, when the reference count of the mark unit 51 exceeds a certain number, the mark unit 52 is referred to.
According to this modification, even if the mark portions 51 and 52 are deteriorated, it is possible to refer to the mark portions 51 and 52 with little progress of deterioration, and therefore processing with good position accuracy can be performed.

In the above description, the example in which the position reference mark is etched in the direction that coincides with the irradiation direction of the focused ion beam that scans the position reference mark at the time of processing the sample has been described. If the deterioration is within an allowable range, the etching direction of the position reference mark may be different from the irradiation direction of the focused ion beam that scans the position reference mark. That is, it is only necessary that the etching direction of the position reference mark and the irradiation direction of the focused ion beam that scans the position reference mark substantially coincide with each other.
For example, as shown in FIG. 12, in the processing of the sample 50, when the irradiation direction is switched between two directions of the arrow a and the arrow b, the mark portions 51 and 52 are deteriorated by the processing of the arrow b. If it is within the allowable range, the mark portions 51 and 52 may be used as position reference marks at the time of processing of the arrow b.

In the above description, the position reference mark is described as an example of a hole formed by etching with a focused ion beam. However, the position reference mark may be formed by a recess such as a linear groove. For example, the position reference mark may have a circular shape in the scanning region in the above description, but the planar shape of the position reference mark is limited to this. Not. For example, an appropriate shape that can specify a certain position in a planar shape, such as an X shape in a plan view, a cross shape, a V shape, or a polygonal shape, can be employed.

  In the above description, the position reference mark is described as an example where the concave portion is formed by etching with a focused ion beam. However, the position reference mark including the convex portion may be formed by deposition. That is, as the position reference mark, an appropriate uneven shape formed by at least one of etching and deposition can be adopted.

  In the description of the first embodiment, the mark portion 4 is described as an example in which the mark portion 4 is formed after forming the marking surface 1c substantially orthogonal to the irradiation direction. However, the depth at which the mark portion 4 is etched is described. Can be ensured, the inclination of the marking surface 1c may intersect the irradiation direction. For example, the side surface of the wall portion 1d or the side surface of the wall portion 1d may be formed on the surface by protruding in the negative direction in the y-axis direction.

In the description of the first embodiment, the mark portion 4 has been described as an example in the case where the mark portion 4 is provided after forming the hole portion 1A. However, if processing is possible, the hole portion 1A is formed before the hole portion 1A is formed. The sample 1 corresponding to the portion 1A may be formed so as to penetrate, and then the hole portion 1A may be formed.
In this case, since it is not necessary to remove the charge when forming the hole 1A, the machining process is simplified as compared with the case where the charge is removed.

  In the above description, the example in which the number of position reference marks is two has been described. However, two or more appropriate number of position reference marks may be provided as necessary. For example, a plurality according to the irradiation direction of the focused ion beam at the time of processing, a plurality according to the number of processes at the time of processing, a plurality according to the lifetime of the position reference mark, and the like can be provided as necessary.

  In addition, all the constituent elements described in the above-described embodiments and modifications are implemented by being replaced or combined within the scope of the technical idea of the present invention, if technically possible. be able to.

It is a typical perspective view showing a schematic structure of a sample processing device concerning a 1st embodiment of the present invention. It is typical sectional drawing which shows schematic structure of the sample processing apparatus which concerns on the 1st Embodiment of this invention. It is a typical perspective view showing an example of a sample processed by a sample processing method concerning a 1st embodiment of the present invention. It is the elements on larger scale of the A view (B view) of FIG. 3, and CC sectional drawing of this partial enlarged view. It is a functional block diagram of the control unit of the sample processing apparatus which concerns on the 1st Embodiment of this invention. It is a typical perspective view explanatory drawing explaining the process of forming the position reference mark in the sample processing method which concerns on the 1st Embodiment of this invention. FIG. 7 is a schematic perspective view illustrating a step of processing a sample following the step shown in FIG. 6. It is the typical top view which shows an example of the time-dependent change of the position reference mark of the 1st Embodiment of this invention, and its DD sectional drawing. It is a typical top view which shows an example of a time-dependent change of a position reference mark when the irradiation direction of a focused ion beam becomes a diagonal direction, and its EE sectional drawing. FIG. 8 is a schematic perspective process explanatory diagram illustrating a process of forming another position reference mark following the process shown in FIG. 7. FIG. 11 is a schematic perspective view illustrating a step of cutting out a TEM sample following the step illustrated in FIG. 10. It is a typical perspective view showing an example of a sample processed by a sample processing method concerning a 2nd embodiment of the present invention.

Explanation of symbols

1, 50 Sample 1a Processing surface 1c Marking surface 2 TEM samples 3, 4, 51, 52 Mark part (position reference mark)
3A, 4A, 51A, 52A Scanning region 11 Gas gun 14 Sample stage (sample holder)
16 Sample stage (sample holder)
18 Secondary charged particle detector 20 Ion beam irradiation system (focused ion beam irradiation unit)
20A ion beam 20A (focused ion beam)
30 Control unit 31 Image capture unit (image acquisition unit)
32 Storage unit 33 Position information calculation unit 34 Position correction control unit 35 Beam scanning control unit 36 Mark reading scanning region setting unit

Claims (3)

A position reference mark is formed on the sample, the position reference mark is scanned by a focused ion beam, position information of the position reference mark in the sample is obtained, and the focused ion beam with respect to the sample is acquired based on the position information A sample processing method for correcting the irradiation position and processing the sample,
The processing of the sample is processing performed by switching the irradiation direction of the focused ion beam on the sample between a plurality of irradiation directions,
Mark formation for irradiating the focused ion beam on the sample from a direction substantially along one of the plurality of irradiation directions to form the position reference mark as an uneven shape substantially along one of the plurality of irradiation directions. Process,
Wherein a plurality of said focused ion beam irradiated along one illumination direction, by scanning the position reference mark having substantially along uneven shape to one of said plurality of radiation directions, the position reference mark a mark position information acquisition step of acquiring position information of
Based on the position information before Symbol position location reference mark obtained by said mark position information obtaining step, by correcting the irradiation position with respect to the sample of the focused ion beam, along one of the plurality of radiation directions A sample processing step of processing the sample by irradiating the focused ion beam ;
With
The sample processing method , wherein the mark formation step, the mark position information acquisition step, and the sample processing step are performed for each of the plurality of irradiation directions . The plurality of position reference marks are
2. The sample processing method according to claim 1 , wherein the sample is formed by a focused ion beam used for processing before processing the sample. A focused ion beam irradiating unit for irradiating a focused ion beam specimen,
Irradiation of the focused ion beam to the sample during processing of the sample by variably holding the position and orientation of the sample with respect to the irradiation central axis of the focused ion beam irradiated from the focused ion beam irradiation unit A sample holder for switching the direction between a plurality of irradiation directions ;
A secondary charged particle detector for detecting the intensity of secondary charged particles emitted by irradiating the sample with the focused ion beam;
A beam scanning control unit that controls the sample holding unit and the focused ion beam irradiation unit to scan the focused ion beam on the sample;
A mark position information storage unit for storing formation position information of a plurality of position reference marks formed on the sample;
Said scan region to scan the focused ion beam by the beam scan control unit, the mark is set in an area including a plurality of position reference mark reader scanning area setting unit,
By acquiring the intensity of the secondary charged particles detected by the secondary charged particle detector in synchronization with the scanning of the focused ion beam in the scanning area set by the mark reading scanning area setting unit, An image acquisition unit for acquiring an image of an area including the position reference mark;
A position information calculation unit that calculates the position of the position reference mark in the image by performing image processing on the image acquired by the image acquisition unit;
The position reference mark information calculated by the position information calculation unit is compared with the position reference mark formation position information stored in advance to calculate the irradiation position correction amount of the focused ion beam and to correct the irradiation position correction. A position correction control unit that changes a scanning reference position in the beam scanning control unit according to the amount,
The beam scanning control unit
Prior to processing the sample by irradiating the focused ion beam along one of the plurality of irradiation directions, the focused ion beam is applied onto the sample from a direction substantially along one of the plurality of irradiation directions. And performing control to form the position reference mark having a concavo-convex shape substantially along one of the plurality of irradiation directions,
When processing the sample by irradiating the focused ion beam along one of the plurality of irradiation directions, the scanning region set by the mark reading scanning region setting unit is set as one of the plurality of irradiation directions. sample processing apparatus according to claim <br/> performing control to switch the realm including the position reference mark having a concavo-convex shape substantially along.

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