JP2005302600A - Fine processing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine processing method and apparatus for forming a thin film work with high processing accuracy.
After a workpiece 6 is sputter-etched by irradiating an ion beam 12, an electron beam 16 is irradiated so as to reach the inside of the workpiece 6 using a scanning electron microscope. An image of a reference portion set in advance at a position deeper than the reference plane inside the workpiece 6 is acquired. In the repetition step, the subsequent ion beam 12 is irradiated with an output smaller than that of the preceding ion beam 12. The subsequent electron beam 16 is irradiated with an acceleration voltage smaller than that of the preceding electron beam 16. The repetition process is performed until the acceleration voltage falls to the reference acceleration voltage. The reference acceleration voltage is a minimum value at which the electron beam 16 can enter the work 6 by a distance from the reference surface to the reference portion.
[Selection] Figure 2

Description

  The present invention relates to a fine processing method and an apparatus therefor.

  In recent years, the processing method using the focused ion beam method has become the mainstream in the creation of workpieces for transmission electron microscopes, but it is also possible to observe the cross-section while processing with an apparatus equipped with a scanning electron microscope in the focused ion beam method Has attracted attention. In these techniques, it is necessary to make the processing width as small as possible so that the electron beam can pass through the workpiece when observing the workpiece with a transmission electron microscope.

As a technique for measuring the processing width for thinning a workpiece of a transmission electron microscope, the processing width of the workpiece can be easily reduced by irradiating the workpiece being processed with an energy beam different from the focused ion beam method of the processing device. It is known that it can be measured with high accuracy. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 7-273087

  However, a method for clarifying the distance to the reference portion to be observed with a transmission electron microscope is not provided. In other words, how far the reference part to be observed with the transmission electron microscope is located from the surface of the workpiece is basically when the target spot is seen with the scanning electron microscope, and that spot is used as the end point detection of processing. .

  An object of the present invention is to provide a fine processing method and apparatus for forming a thin film workpiece with high processing accuracy.

(1) A micromachining method according to the present invention is a micromachining method in which a workpiece is sputter-etched so as to stop at a reference surface at a preset depth,
After the workpiece is sputter-etched by irradiating an ion beam by a focused ion beam method, the reference inside the workpiece is irradiated by irradiating the workpiece with an electron beam using a scanning electron microscope. Obtaining an image of a reference portion preset in a position deeper than the surface;
Including repeated steps of
In the repetition step, the subsequent ion beam is irradiated with an output smaller than the preceding ion beam, the subsequent electron beam is irradiated with an acceleration voltage smaller than the preceding electron beam,
The repeating step is performed until the acceleration voltage drops to a reference acceleration voltage,
The reference acceleration voltage is a minimum value at which the electron beam can enter the work by a distance from the reference surface to the reference portion. According to the present invention, the distance to the reference portion can be measured on a scale called the acceleration voltage of the scanning electron microscope, and the reference portion is not cut too much. This makes it possible to create a thin film workpiece with high processing accuracy.
(2) A micromachining apparatus according to the present invention includes an ion beam irradiator that irradiates an ion beam by a focused ion beam method in order to perform sputter etching of a workpiece by performing an ion beam irradiation step;
An ion beam output controller for controlling the output of the ion beam;
A scanning electron microscope including an electron beam irradiator for irradiating an electron beam, and performing an observation step including an electron beam irradiation step and an image acquisition step using the electron beam irradiator;
An electron beam acceleration voltage controller for controlling the acceleration voltage of the electron beam;
A drive controller that controls the ion beam irradiator and the scanning electron microscope so that the ion beam irradiation step and the observation step are alternately repeated;
The image determination as to whether or not the image acquired in the image acquisition step is to display a preset reference portion at a position deeper than a reference plane at a preset depth inside the work is the observation An image determination unit that outputs an image display result or an image non-display result after the start of the step and before the start of the ion beam irradiation step;
Accelerating voltage determination as to whether or not the accelerating voltage has reached a value below a reference accelerating voltage, which is a minimum value that allows the electron beam to enter the workpiece by a distance from the reference surface to the reference portion. Accelerating voltage determination device that outputs the acceleration voltage arrival result or the acceleration voltage non-reaching result after the step start and before the ion beam irradiation step starts,
A central processing unit;
Have
The central processing unit is
In response to the input of the image display result, the acceleration voltage determination unit performs the acceleration voltage determination,
Corresponding to the input of the acceleration voltage non-reaching result, the ion beam output control unit so that the output of the ion beam is lower than the immediately preceding ion beam irradiation step in the ion beam irradiation step immediately after the acceleration voltage determination. And controlling the electron beam acceleration voltage control unit so that the acceleration voltage of the electron beam is lower than the immediately preceding electron beam irradiation step in the electron beam irradiation step immediately after the acceleration voltage determination. According to the present invention, the distance to the reference portion can be measured on a scale called the acceleration voltage of the scanning electron microscope, and the reference portion is not cut too much. Thereby, the fine processing apparatus which can produce a thin film workpiece | work with high processing precision can be provided.
(3) This fine processing device
In response to the input of the image non-display result, the central processing unit performs the ion beam irradiation step immediately after the image determination so that the output of the ion beam is the same as the previous ion beam irradiation step. The ion beam output control unit may be controlled.
(4) This microfabrication device
The central processing unit may control the drive control unit so as to stop the repetition of the ion beam irradiation step and the observation step in response to the input of the acceleration voltage arrival result.
(5) This fine processing device
The central processing unit performs the final ion beam irradiation step in response to the input of the acceleration voltage arrival result, and does not perform the subsequent ion beam irradiation step and the observation step. In the final ion beam irradiation step, the ion beam output control unit may be controlled so that the output of the ion beam is lower than the previous ion beam irradiation step.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart for explaining a microfabrication method according to the present embodiment. FIG. 2 is a diagram for explaining the microfabrication apparatus according to the present embodiment.

  The microfabrication method according to the present embodiment is a method in which a workpiece (for example, a sample or a sample) 6 is sputter-etched so as to be stopped at a reference surface 8 (see FIG. 3) at a preset depth. First, in step 100, in order to sputter-etch the workpiece 6 by irradiating the ion beam 12 of the focused ion beam method, the output (current) of the ion beam 12 is output at a high output (for example, 20000 pA) by the ion beam output control unit 14. ). Further, the acceleration voltage of the electron beam 16 is set to a high acceleration voltage (for example, 15 kV) by the electron beam acceleration voltage controller 18.

  Next, in step 110, the electron beam irradiator 20 of the scanning electron microscope is used to irradiate the workpiece 6 with the electron beam 16 having the acceleration voltage value set in step 100. As a result, the captured image is displayed on the CRT 22 and stored in the image storage unit 24. FIG. 3 shows the relationship between the incident direction of the workpiece 6 and the electron beam 16.

  Next, in step 120, the workpiece 6 is processed by irradiating the workpiece 6 with the ion beam 12 using the ion beam irradiator 26, and sputter etching the workpiece 6 with the ion beam 12. FIG. 3 shows the relationship between the incident direction of the workpiece 6 and the ion beam 12.

  Next, in step 130, after the workpiece 6 is sputter-etched in step 120, the electron beam 16 is irradiated so as to reach the inside of the workpiece 6 using the electron beam irradiator 20 of the scanning electron microscope. As a result, the captured image is displayed on the CRT 22 and stored in the image storage unit 24.

  Next, in step 140, whether or not the image acquired in step 130 is to display the preset reference portion 10 at a position deeper than the reference plane 8 at the preset depth inside the workpiece 6. Image judgment is performed. This image determination is performed after the observation step 130 is started and before the next ion beam irradiation step 120 is started, and an image display result or an image non-display result is output. That is, at the first time, the image acquired in step 110 and the image acquired in step 130 are compared, and an image display result or an image non-display result is output. After the second time, the subsequent image acquired in step 130 is compared with the preceding image, and an image display result or an image non-display result is output. The comparison method compares an initial or subsequent image with a preceding image, and extracts a difference image of the image with respect to the preceding image showing different portions of the two images. This difference image is binarized to obtain a binarized difference image of the image. Obtaining this binarized difference image is the image display result. Further, when this binarized difference image cannot be obtained, an image non-display result is obtained. The binarization process binarizes a difference image of an image composed of several gradations of light and dark into black and white with a predetermined threshold value. The threshold varies depending on conditions such as the material of the reference portion 10, the material of the obstruction, and the state of the secondary electron detector 54.

  Next, step 150 is a determination process for repeating the processing from step 120 to step 140 until the image display result is output in step 140. The determination content is “YES” in which the image display result is output in step 140. In this case, the process proceeds to step 160. Alternatively, the state in which the image non-display result is output in step 140 is set to “NO”. In this case, the process proceeds to step 120. At this time, in the ion beam irradiation step 120 immediately after the image determination, the ion beam output control unit 14 is controlled so that the output of the ion beam 12 is the same as that in the previous ion beam irradiation step 120.

  Next, step 160 is a determination process for repeating step 170 and the processing steps from step 130 to step 150 when it is determined “YES” in step 150 until the acceleration voltage drops to the reference acceleration voltage. . The reference acceleration voltage is a minimum acceleration voltage value (for example, 1 kV) at which the electron beam 16 can enter the work 6 by a distance from the reference surface 8 to the reference portion 10. The determination content is “YES” when the acceleration voltage of the electron beam 16 is 1 kV or less. In this case, the process proceeds to step 180. Alternatively, a state where the acceleration voltage of the electron beam 16 is 1 kV or higher is set to “NO”. In this case, the process proceeds to step 170.

  Next, in step 170, if “NO” is determined in step 160, the ion beam output control unit 14 is controlled to irradiate the subsequent ion beam 12 with an output smaller than the preceding ion beam 12. The output of the ion beam 12 is further reduced. In addition, the acceleration voltage of the electron beam 16 is reduced by controlling the electron beam acceleration voltage control unit 18 in order to irradiate the subsequent electron beam 16 with an acceleration voltage smaller than that of the preceding electron beam 16. For example, the ion beam output controller 14 is controlled by the ion beam irradiator 26 so that the workpiece 6 is irradiated with the ion beam 12 having a current of 5000 pA, and the current of the ion beam 12 is lowered to 5000 pA. Further, the electron beam irradiator 20 controls the electron beam acceleration voltage control unit 18 so that the workpiece 6 is irradiated with the electron beam 16 accelerated at an acceleration voltage of 3 kV, and the acceleration voltage of the electron beam 16 is lowered to 3 kV. .

  Next, in step 180, when it is determined “YES” in step 160, the drive control unit is configured to stop the repetition of the ion beam irradiation step 120 and the observation step 130 in response to the input of the acceleration voltage arrival result. 28 is controlled. Further, the drive controller 28 is controlled so that the final ion beam irradiation step 180 is performed and the subsequent ion beam irradiation step 120 and observation step 130 are not performed. In the final ion beam irradiation step 180, the ion beam output control unit is controlled so that the output of the ion beam 12 is lower than that of the previous ion beam irradiation step 120. For example, the workpiece 6 is processed by irradiating the workpiece 6 with the ion beam 12 having a current of 500 pA by the ion beam irradiator 26 and sputter-etching the workpiece 6 with the ion beam 12.

  As shown in FIG. 3, the workpiece 6 is irradiated with the ion beam 12 and is processed by a set processing amount by sputter etching. If the workpiece 6 is machined from the side opposite to the machining surface using the ion beam 12, a reference portion thin film workpiece having a predetermined thickness can be obtained. Machining of the workpiece 6 from the opposite side is performed in the same manner as the first machining (machining from the front side). The thin film work thus obtained is observed with a transmission electron microscope or the like, and further analyzed if necessary.

  Next, a micromachining apparatus that creates a thin film workpiece by the micromachining method according to the present embodiment will be described.

  The microfabrication apparatus according to the present embodiment is an apparatus that sputter-etches the workpiece 6 so as to stop at the reference surface 8 at a preset depth.

  The micromachining apparatus according to the present embodiment has a machining chamber 30. The processing chamber 30 arranges the workpiece 6.

  The microfabrication apparatus according to the present embodiment has an ion beam irradiator 26. The ion beam irradiator 26 irradiates the ion beam 12 by the focused ion beam method. The ion beam irradiator 26 performs the sputter etching of the workpiece 6 by performing the ion beam irradiation step 120.

  The microfabrication apparatus according to the present embodiment has an ion beam output control unit 14. The ion beam output control unit 14 controls the output of the ion beam 12 of the ion beam irradiator 26.

  The microfabrication apparatus according to the present embodiment has an electron beam irradiator 20. The electron beam irradiator 20 irradiates the electron beam 16. The electron beam irradiator 20 is mounted on the scanning electron microscope 4. The scanning electron microscope 4 performs observation steps 110 and 130 including an electron beam irradiation step using the electron beam irradiator 20 and an image acquisition step.

  The microfabrication apparatus according to the present embodiment has an electron beam acceleration voltage control unit 18. The electron beam acceleration voltage control unit 18 controls the acceleration voltage of the electron beam 16 of the electron beam irradiator 20.

  The microfabrication apparatus according to the present embodiment has a drive control unit 28. The drive control unit 28 controls the ion beam irradiator 26 and the scanning electron microscope 4 so that the ion beam irradiation step 120 and the observation step 130 are alternately repeated.

  The microfabrication apparatus according to the present embodiment has an image determination device 32. Whether or not the image determination unit 32 displays the reference portion 10 set in advance at a position deeper than the reference plane 8 at the preset depth inside the workpiece 6 in the image acquisition step. Image judgment is performed. The image determination unit 32 performs image determination after the observation step 130 is started and before the next ion beam irradiation step 120 is started, and outputs an image display result or an image non-display result.

  The microfabrication apparatus according to the present embodiment has an acceleration voltage determination unit 34. The acceleration voltage determination unit 34 determines whether or not the acceleration voltage has reached a reference acceleration voltage or less, which is the minimum value at which the electron beam 16 can enter the workpiece 6 by a distance from the reference plane 8 to the reference portion 10. Make a voltage decision. The acceleration voltage determination unit 34 performs the acceleration voltage determination after the observation step 130 is started and before the next ion beam irradiation step 120 is started, and outputs an acceleration voltage arrival result or an acceleration voltage non-arrival result.

  The microfabrication apparatus according to the present embodiment has a central processing unit 36. The central processing unit 36 causes the acceleration voltage determiner 34 to make an acceleration voltage determination in response to the input of the image display result. In response to the input of the image non-display result, the central processing unit 36 outputs the ion beam so that the output of the ion beam 12 is the same as the previous ion beam irradiation step 120 in the ion beam irradiation step 120 immediately after the image determination. The control unit 14 is controlled. In response to the input of the acceleration voltage non-reaching result, the central processing unit 36 performs an ion beam irradiation so that the output of the ion beam 12 is lower than that of the immediately preceding ion beam irradiation step 120 in the ion beam irradiation step 120 immediately after the acceleration voltage determination. The output control unit 14 is controlled. In response to the input of the acceleration voltage non-reaching result, the central processing unit 36 performs the electron beam irradiation step 130 immediately after the acceleration voltage determination so that the acceleration voltage of the electron beam 16 is lower than the immediately preceding electron beam irradiation step 130. The beam acceleration voltage control unit 18 is controlled. The central processing unit 36 controls the drive control unit 28 so as to stop the repetition of the ion beam irradiation step 120 and the observation step 130 in response to the input of the acceleration voltage arrival result. The central processing unit 36 performs the final ion beam irradiation step 180 in response to the input of the acceleration voltage arrival result, and sets the drive control unit 28 so as not to perform the subsequent ion beam irradiation step 120 and the observation step 130. Control. In the final ion beam irradiation step 180, the central processing unit 36 controls the ion beam output control unit 14 so that the output of the ion beam 12 is lower than that of the previous ion beam irradiation step 120.

  The workpiece 6 is mounted on a workpiece holder 38 that can move in two directions (X and Y orthogonal to the ion beam direction and orthogonal to each other). The movement of the workpiece 6 is performed by the workpiece fine movement device 40, and the control thereof is performed by the workpiece fine movement control unit 42. The workpiece 6 is transported into the processing chamber 30 by a workpiece introduction system (not shown) and loaded into the workpiece holder 38. The workpiece holder 38 is appropriately set by a workpiece fine movement device 40 of a stage drive system incorporated in a housing of the micromachining device. It is configured to be driven. The work fine movement device 40 is connected to the central processing unit 36 via the work fine movement control unit 42.

  The ion beam 12 irradiated from the ion beam irradiator 26 that sputter-etches the workpiece 6 by irradiating the ion beam 12 by the focused ion beam method passes through the condenser lens 44, the diaphragm 46, and the objective lens 48, and then onto the workpiece 6. Converge. A scanning coil 50 that deflects the ion beam 12 irradiated to the workpiece 6 and thereby scans the workpiece 6 and a deflection signal controller 52 for controlling the scanning coil 50 are arranged. The scanning coil 50 is connected to a deflection signal control unit 52 that controls the processing region. The deflection signal control unit 52 is connected to the central processing unit 36 in order to obtain beam position data.

  The scanning electron microscope 4 includes an electron beam irradiator 20, a secondary electron detector 54, a signal amplifier 56, a condenser lens 58, a scanning coil 60, and a scanning power source 62. The electron beam irradiator 20 irradiates the electron beam 16 so as to reach the inside of the workpiece 6. The electron beam 16 is focused in a spot shape on the surface of the workpiece 6 by the condenser lens 58, and the surface of the workpiece 6 is scanned by the scanning coil 60 that deflects the electron beam 16 disposed between the condenser lens 58 and the workpiece 6. A scanning power source 62 is connected to the scanning coil 60. Between the workpiece 6 and the scanning coil 60, the secondary is disposed on the wall surface of the processing chamber 30 so as to face the workpiece 6 and receives the secondary electrons 64 from the workpiece 6 and detects the amount of current of the secondary electrons 64. An electronic detector 54 is incorporated. The secondary electron detector 54 is connected to the central processing unit 36 through a signal amplifier 56. The secondary electron detector 54 detects the secondary electrons 64 emitted from the work 6 when the work 6 is irradiated by the electron beam 16, and the signal amplifier 56 amplifies the secondary electron signal to the central processing unit 36. send. The central processing unit 36 displays the image on the CRT 22 and acquires an image of the reference portion 10 set in advance at a position deeper than the reference surface 8 inside the workpiece 6.

  According to the present embodiment, the distance to the reference portion can be measured on a scale called the acceleration voltage of the scanning electron microscope, and the reference portion is not cut too much. This makes it possible to create a thin film workpiece with high processing accuracy.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment. Furthermore, the present invention includes contents that exclude any of the technical matters described in the embodiments in a limited manner. Or this invention includes the content which excluded the well-known technique limitedly from embodiment mentioned above.

It is a flowchart explaining the fine processing method which concerns on this Embodiment. It is a figure explaining the fine processing apparatus which concerns on this Embodiment. It is a figure explaining the workpiece | work which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 ... Scanning electron microscope 6 ... Work piece 8 ... Reference plane 10 ... Reference part 12 ... Ion beam 14 ... Ion beam output control part 16 ... Electron beam 18 ... Electron beam acceleration voltage control part 20 ... Electron beam irradiator 22 ... CRT 24 ... Image storage unit 26 ... Ion beam irradiator 28 ... Drive control unit 30 ... Processing chamber 32 ... Image judgment unit 34 ... Acceleration voltage judgment unit 36 ... Central processing unit 38 ... Work holder 40 ... Work fine movement device 42 ... Work fine movement control unit 44 ... Condenser lens 46 ... Aperture 48 ... Objective lens 50 ... Scanning coil 52 ... Deflection signal controller 54 ... Secondary electron detector 56 ... Signal amplifier 58 ... Condenser lens 60 ... Scanning coil 62 ... Scanning power supply 64 ... Secondary electron

Claims (5)

A micromachining method for sputter etching a workpiece so as to stop at a reference surface at a preset depth,
After the workpiece is sputter-etched by irradiating an ion beam by a focused ion beam method, the reference inside the workpiece is irradiated by irradiating the workpiece with an electron beam using a scanning electron microscope. Obtaining an image of a reference portion preset in a position deeper than the surface;
Including repeated steps of
In the repetition step, the subsequent ion beam is irradiated with an output smaller than the preceding ion beam, the subsequent electron beam is irradiated with an acceleration voltage smaller than the preceding electron beam,
The repeating step is performed until the acceleration voltage drops to a reference acceleration voltage,
The micro-machining method, wherein the reference acceleration voltage is a minimum value at which the electron beam can enter the workpiece by a distance from the reference surface to the reference portion. An ion beam irradiator that irradiates an ion beam by a focused ion beam method in order to perform sputter etching of a workpiece by performing an ion beam irradiation step;
An ion beam output controller for controlling the output of the ion beam;
A scanning electron microscope including an electron beam irradiator for irradiating an electron beam, and performing an observation step including an electron beam irradiation step and an image acquisition step using the electron beam irradiator;
An electron beam acceleration voltage controller for controlling the acceleration voltage of the electron beam;
A drive controller that controls the ion beam irradiator and the scanning electron microscope so that the ion beam irradiation step and the observation step are alternately repeated;
The image determination as to whether or not the image acquired in the image acquisition step is to display a preset reference portion at a position deeper than a reference plane at a preset depth inside the work is the observation An image determination unit that outputs an image display result or an image non-display result after the start of the step and before the start of the ion beam irradiation step;
Accelerating voltage determination as to whether or not the accelerating voltage has reached a value below a reference accelerating voltage, which is a minimum value that allows the electron beam to enter the workpiece by a distance from the reference surface to the reference portion. Accelerating voltage determination device that outputs the acceleration voltage arrival result or the acceleration voltage non-reaching result after the step start and before the ion beam irradiation step starts,
A central processing unit;
Have
The central processing unit is
In response to the input of the image display result, the acceleration voltage determination unit performs the acceleration voltage determination,
Corresponding to the input of the acceleration voltage non-reaching result, the ion beam output control unit so that the output of the ion beam is lower than the immediately preceding ion beam irradiation step in the ion beam irradiation step immediately after the acceleration voltage determination. And the electron beam accelerating voltage control unit controls the electron beam accelerating voltage control unit so that the accelerating voltage of the electron beam is lower than the immediately preceding electron beam irradiating step in the electron beam irradiating step immediately after the acceleration voltage determination. . The microfabrication apparatus according to claim 2, wherein
In response to the input of the image non-display result, the central processing unit performs the ion beam irradiation step immediately after the image determination so that the output of the ion beam is the same as the previous ion beam irradiation step. A fine processing device that controls the ion beam output controller. In the microfabrication apparatus according to claim 2 or claim 3,
The central processing unit controls the drive control unit so as to stop the repetition of the ion beam irradiation step and the observation step in response to an input of the acceleration voltage arrival result. The microfabrication apparatus according to claim 4, wherein
The central processing unit performs the final ion beam irradiation step in response to the input of the acceleration voltage arrival result, and does not perform the subsequent ion beam irradiation step and the observation step. In the final ion beam irradiation step, the ion beam output control unit is controlled so that the output of the ion beam is lower than the previous ion beam irradiation step.

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