JP2015176685A - Charged particle beam irradiation device and charged particle beam irradiation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide charged particle beam irradiation device and method that can shorten the time required for sample processing and observation.SOLUTION: A controller 20 controls an irradiation unit for irradiating an electron beam B1 so that the irradiation current amount of the electron beam B1 to be applied to a processing target area is larger than the irradiation current amount of the electron beam B1 to be applied to a non-processing area, and a pulse having a predetermined pulse duty ratio is output. A detection signal amplifier 18 sets the gain of a detection signal during an irradiation time of the charged particle beam to the processing target area to be lower than the gain of a detection signal during an irradiation time of the electron beam B1 to the non-processing area, and amplifies the detection signal. An image constructing unit 30 constructs an observation image for observing the state of a powder sample 13 by using the amplified detection signal.

Description

  The present invention relates to a charged particle beam irradiation apparatus and a charged particle beam irradiation method used when a sample is irradiated with a charged particle beam.

  2. Description of the Related Art An optical modeling apparatus that forms a three-dimensional object by irradiating a laser beam onto a powder layer made of a resin powder spread on a stage to melt the resin powder and stacking layers obtained by solidifying the resin powder is widely known. In recent years, charged particles are applied to a specific region of the surface of a powder sample (hereinafter referred to as “sample surface”) spread on a stage by various apparatuses such as an electron beam exposure apparatus, an electron beam processing apparatus, and a focused ion beam apparatus. A three-dimensional additive manufacturing apparatus that forms a three-dimensional object by stacking layers obtained by melting and solidifying a powder sample by irradiating a beam to process and modify the sample is used.

  In such a three-dimensional additive manufacturing apparatus, in order to achieve the two purposes of (1) processing of the sample surface and (2) observation of the sample surface, irradiation conditions of charged particle beams generated from the same source are used. Control to switch is performed.

  For example, when processing the sample surface, a processing mode that defines irradiation conditions of a charged particle beam that can optimally process the sample is set. In the processing mode, the surface of the sample can be melted by irradiating a charged particle beam having a sufficient irradiation current amount to a processing target region or pattern position designated in advance. The non-processing target area is irradiated with blinking charged particle beams so as not to melt the non-processing target area.

  On the other hand, when the operator observes the sample surface, an observation mode that defines the irradiation conditions of the charged particle beam that does not process the sample is set. In the observation mode, a charged particle beam with a reduced amount of irradiation current is raster-scanned over the entire area to be observed. Then, secondary electrons, reflected electrons, and the like generated from the sample surface irradiated with the charged particle beam are detected, the detection signal is imaged, and the sample surface is displayed on the display unit.

  As an example of such a three-dimensional additive manufacturing apparatus, one disclosed in Patent Document 1 is known. This patent document 1 discloses a technique for forming a hardened layer by irradiating a powder material with a light beam and stacking the hardened layer to produce a shaped article having a desired three-dimensional shape.

JP 2001-152204 A

  By the way, the observation mode is used for the operator to change and adjust the processing conditions if necessary while confirming the processing state of the sample surface. For this reason, it is desirable to observe the sample surface as often as possible while minimizing the time difference required between the processing and observation processes of the sample.

  However, conventionally, after performing the scanning for processing, the raster scanning for observation is performed, so it takes time to perform observation after processing the sample surface. In addition, if the time required for scanning the sample surface during processing becomes long, the state of the sample surface cannot be accurately grasped from the image displayed on the display unit during observation, and the charged particle beam can be adjusted according to the processing state. was difficult.

  The present invention has been made in view of such a situation, and an object thereof is to shorten the time required for processing and observing a sample.

In the present invention, the control unit irradiates the non-processed region of the sample with the irradiation current amount of the charged particle beam that irradiates the processing region of the sample to be processed to the irradiation unit that irradiates the charged particle beam. The pulse output is made to be larger than the beam irradiation current amount and at a predetermined pulse duty ratio.
Next, the secondary electron detector detects the secondary electrons excited by the charged particle beam irradiated on the sample, and outputs a detection signal.
Next, the detection signal amplifying unit lowers the gain of the detection signal during the period in which the charged particle beam is irradiated onto the processing region, lower than the gain of the detection signal during the period in which the charged particle beam is irradiated onto the non-processing region, Amplify the detection signal.
And an image structure part comprises the observation image for observing the state of a sample using the amplified detection signal.

  According to the present invention, since the observation image of the processed region and the non-processed region of the sample can be acquired by one scanning of the charged particle beam, the time required for processing and observing the sample can be shortened.

1 is a block diagram illustrating a configuration example of a three-dimensional additive manufacturing apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the example of the process target pattern which concerns on one embodiment of this invention. It is explanatory drawing which shows the example of a change of the extraction electric potential which concerns on the example of 1 embodiment of this invention. It is explanatory drawing which shows the example of a change of the irradiation current which concerns on one embodiment of this invention. It is explanatory drawing which shows the example of a change of the detection gain which concerns on the example of 1 embodiment of this invention. It is explanatory drawing which shows the example of a change of the detection gain which concerns on the modification of one embodiment of this invention.

Hereinafter, an electron gun and a three-dimensional additive manufacturing apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.
In the present specification and drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant description is omitted.

[1. Example of embodiment]
<Configuration example of three-dimensional additive manufacturing apparatus>
FIG. 1 is a configuration diagram of a three-dimensional additive manufacturing apparatus 1.
The three-dimensional additive manufacturing apparatus 1 is used as an example of a charged particle beam irradiation apparatus. The three-dimensional additive manufacturing apparatus 1 uses an electron beam B1 (an example of a charged particle beam) based on CAD data created by a three-dimensional CAD (Computer Aided Design) to perform high-speed and high-accuracy complex parts. It is possible to make a model. Moreover, the three-dimensional additive manufacturing apparatus 1 can create a high-strength metal part that has been difficult with the conventional method.

  The three-dimensional layered manufacturing apparatus 1 includes an electron gun 2 that emits an electron beam B1, a deflection unit 6, a lens 7, a powder sample storage 9, a powder stack arm 10, a Z-axis stage 11, a detection current control electrode 14, a switch 15, and a terminal. 16a, 16b, a secondary electron detection unit 17, and a detection signal amplification unit 18. The three-dimensional additive manufacturing apparatus 1 includes a control unit 20, an extraction potential generation unit 24, a scanning drive unit 25, an image configuration unit 30, and a display unit 33.

  A field emission type electron gun 2 installed in a modeling chamber (not shown) has a three-pole configuration including an emitter 3, an extraction electrode 4 and an acceleration electrode 5, and is applied to a powder sample 13 spread on a Z-axis stage 11. The electron beam B1 is emitted.

  The deflecting unit 6 deflects the electron beam B1 emitted from the electron gun 2 to a predetermined position on the Z-axis stage 11. The lens 7 focuses the electron beam B1 by electromagnetic action, and forms an image on the Z-axis stage 11 with the electron beam B1. The electron gun 2, the deflection unit 6, and the lens 7 are used as an “irradiation unit” for irradiating the powder sample 13 with the electron beam B 1.

  The interior of the modeling chamber is evacuated to prevent the powder sample 13 from deteriorating. The Z-axis stage 11 is movable in the Z-axis direction (vertical direction) in units of one layer of the powder sample 13. On the Z-axis stage 11, the powder sample 13 is spread at a predetermined height (for example, the diameter of one particle of the powder sample 13) by the powder stacking arm 10 that can move in the horizontal direction. Then, the sample surface of the Z-axis stage 11 is irradiated with the electron beam B1 based on the processing target pattern 40 shown in FIG.

Here, the processing target pattern 40 will be described.
FIG. 2 shows an example of the processing target pattern 40.
An English letter “A” shown as an example of the processing target pattern 40 is a figure formed on the powder sample 13 spread on the Z-axis stage 11 and is created based on CAD data. The portions other than the processing target pattern 40 are non-processing regions a1 and a2 where the processing by the electron beam B1 is not performed, and the processing target pattern 40 is a processing region b1 where the processing by the electron beam B1 is performed. Then, the processing target pattern 40 is displayed on the display unit 33 as an observation image.

  Returning to the description of FIG. 1, the detection current control electrode 14 limits the detection current generated by the secondary electrons excited from the powder sample 13 irradiated with the electron beam B1. The detection current is limited by switching the switch 15 having one end connected to the detection current control electrode 14 to either the positive potential terminal 16a or the negative potential terminal 16b. When the other end of the switch 15 is connected to the positive potential terminal 16a, a positive potential is applied to the detection current control electrode 14, and the number of secondary electrons attracted to the detection current control electrode 14 increases. On the other hand, when the other end of the switch 15 is connected to the negative potential terminal 16b, a negative potential is applied to the detection current control electrode 14, so that secondary electrons attracted to the detection current control electrode 14 are reduced.

The secondary electron detector 17 outputs a detection signal by detecting secondary electrons excited by the electron beam B <b> 1 irradiated to the powder sample 13 via the detection current control electrode 14.
The detection signal amplification unit 18 outputs the amplified detection signal to the image construction unit 30.

  The control unit 20 controls the operation of each unit in the three-dimensional additive manufacturing apparatus 1. As control performed by the control unit 20 on the irradiation unit, the extraction potential generation unit 24 generates an extraction potential generation signal for generating the extraction potential. Here, the control unit 20 increases the irradiation current amount of the electron beam B1 irradiated to the processing region b1 of the powder sample 13 more than the irradiation current amount of the electron beam B1 irradiated to the non-processing regions a1 and a2 of the powder sample 13. In addition, the irradiation unit is caused to output a pulse with a predetermined pulse duty ratio.

  Then, the control unit 20 changes the mode set in the extraction potential generating unit 24 in the non-processed regions a1 and a2 and the processed region b1 when the irradiating unit raster scans the entire surface of the sample surface with the electron beam B1. In the non-processed areas a1 and a2, an observation mode is set, and an electron beam B1 with a low extraction potential is continuously output. However, in the processing region b1, the processing mode is set, and the electron beam B1 in which the extraction potential in the observation mode is increased by a predetermined pulse duty ratio is output as a pulse.

The control unit 20 includes a scanning signal generation unit 21, a processing region generation unit 22, and a processing region storage unit 23.
The scanning signal generator 21 generates a scanning signal for driving the scan driver 25.
The machining area generation unit 22 generates a machining area b1 and non-machining areas a1 and a2 from the machining target pattern 40.
The processing area storage unit 23 stores the processing target pattern 40 generated by the processing area generation unit 22 as processing target pattern data.

The extraction potential generator 24 generates a positive extraction potential to be applied to the extraction electrode 4 based on the extraction potential generation signal received from the control unit 20. At this time, the extraction potential generator 24 switches the extraction potential at a high speed according to the processing mode or observation mode set by the control unit 20.
The scanning drive unit 25 controls the operation of the deflecting unit 6 based on the scanning signal received from the scanning signal generating unit 21, and causes the electron beam B1 to be raster scanned on the sample surface.

  The image constructing unit 30 constructs an observation image for observing the state of the powder sample 13 using the amplified detection signal received from the detection signal amplifying unit 18. The image construction unit 30 includes an image generation unit 31 and an image memory 32.

The image generation unit 31 generates an observation image based on the detection signal input from the detection signal amplification unit 18.
The image memory 32 (an example of a storage unit) is configured by, for example, an on-memory that can be accessed hard. The image memory 32 stores the observation image generated by the image generation unit 31.
The display unit 33 displays the observation image configured by the image configuration unit 30. The operator can observe the state of the surface of the powder sample 13 from the observation image displayed on the display unit 33.

<Operation example of 3D additive manufacturing equipment>
Here, the operation of the three-dimensional additive manufacturing apparatus 1 will be described.
First, after the inside of the modeling chamber is evacuated by a vacuum pump (not shown), the powder sample storage 9 supplies the powder sample 13 to the Z-axis stage 11. Then, the powder sample 13 is uniformly spread on the Z-axis stage 11 so that the powder lamination arm 10 has a predetermined height. Thereafter, an electron beam B 1 is irradiated from the electron gun 2 toward the powder sample 13 on the Z-axis stage 11.

  At that time, the emitter 3 included in the irradiation unit is heated by a heating power source (not shown) to emit electrons. The extraction potential generator 24 changes the extraction potential in accordance with the timing of irradiating the processing region b1 or the non-processing regions a1 and a2 of the powder sample 13 with the electron beam B1. The extraction electrode 4 extracts electrons from the emitter 3 when a positive extraction potential generated by the extraction potential generator 24 is applied. Further, the acceleration electrode 5 causes the electron beam B1 obtained by accelerating electrons emitted from the emitter 3 to be directed to the deflecting unit 6 by the acceleration potential applied by the acceleration power supply 26.

  The electron beam B1 is deflected by the deflecting unit 6, passes through the lens 7, and melts the powder sample 13 spread on the Z-axis stage 11 at a high temperature. The melted powder sample 13 is solidified after the electron beam B1 passes through it. The two-dimensional structure formed by the solidified powder sample 13 after being melted layer by layer by the electron beam B1 is obtained by cutting the three-dimensional structure in a plane at the same height as one powder layer.

  When a predetermined shape is formed on the Z-axis stage 11 by the electron beam B1, the Z-axis stage 11 is lowered every time the scanning period of the electron beam B1 elapses, and the powder sample 13 is spread again. Then, again, the three-dimensional additive manufacturing apparatus 1 irradiates the electron beam B1 for each layer of the powder sample 13, repeats melting and solidification of the powder sample 13, and finally forms a desired model 12 .

  When irradiating the electron beam B1, the scanning signal generation unit 21 adjusts an appropriate repetition frequency for performing raster scanning according to the time during which the electron beam B1 is stopped, and sets this repetition frequency in the deflection unit 6. Then, the control unit 20 uses the electron gun 2 by setting either the observation mode without the metal melting effect or the processing mode with the metal melting effect capable of melting the metal powder in the extraction potential generating unit 24. Is possible.

  In the observation mode, the extraction potential generator 24 applies an extraction potential of, for example, several kV to the extraction electrode 4. At this time, the irradiation current of the electron beam B1 is a small current. For this reason, the electron beam B1 obtained in the observation mode does not melt the sample surface.

  On the other hand, the extraction potential generator 24 applies a pulsed extraction potential exceeding 10 kV to the extraction electrode 4 in the processing mode, for example. Thereby, the irradiation current of the electron beam B1 becomes a large current. The extraction electrode 4 to which a pulsed extraction potential is applied can increase the electric field intensity around the emitter 3 without destroying the emitter 3, extract electrons from the emitter 3, and increase the brightness of the electron beam B <b> 1. . Also, the sample surface can be processed by irradiating the powder sample 13 with the pulsed electron beam B1 having an irradiation current increased by about three digits without increasing the beam diameter of the electron beam B1.

  Secondary electrons are emitted from the sample surface irradiated with the electron beam B1. The amount of secondary electrons (detection current) that reaches the secondary electron detector 17 is controlled by the detection current control electrode 14. Then, the secondary electron detector 17 outputs a detection signal based on the detected secondary electrons.

  The detection signal amplifier 18 lowers the gain of the detection signal during the period in which the processing region b1 is irradiated with the electron beam B1 in accordance with a predetermined pulse duty ratio determined in the processing mode. Conversely, the detection signal amplification unit 18 increases the gain of the detection signal during a period in which the non-processed regions a1 and a2 are irradiated with the electron beam B1 in accordance with a predetermined pulse duty ratio. The gain of the detection signal is changed based on the timing at which the extraction potential received by the detection signal amplification unit 18 from the extraction potential generation unit 24 increases or decreases.

  Further, since the detection signal amplification unit 18 outputs a detection signal whose gain is changed according to the observation mode or the processing mode of the electron beam B1, the signal intensity of the entire observation image generated by the image generation unit 31 based on the detection signal is substantially increased. It can be kept uniform. In addition, the image generation unit 31 samples the detection signal in synchronization with the entire raster scan of the electron beam B <b> 1 and stores it in the image memory 32. For this reason, the image generation unit 31 can generate an observation image from the detection signal read from the image memory 32 and output the observation image to the display unit 33.

<Pulse control of extraction potential>
Next, the pulse control method of the extraction potential will be described with reference to FIGS. In the following description, the extraction potential, irradiation current, and detection gain in the non-processed areas a1 and a2 are referred to as “base part”, and the extraction potential, irradiation current, and detection gain in the processing area b1 are referred to as “pulse part”.

FIG. 3 shows an example of changes in the extraction potential.
The extraction potential generator 24 applies a low extraction potential E1 (base portion) to the extraction electrode 4 during the time t1 to t2 when the electron beam B1 scans the non-processed area a1. During the time t2 to t3 when the electron beam B1 scans the processing region b1, a pulsed extraction potential E2 (pulse part) higher than the extraction potential E1 is extracted while applying the extraction potential E1 to the extraction electrode 4. Apply to electrode 4. After time t3 when the electron beam B1 scans the non-processed area a2, the extraction potential E2 is not applied, and a low extraction potential E1 is applied to the extraction electrode 4.

FIG. 4 shows an example of change in irradiation current.
In the electron gun 2, the irradiation current I1 (base part) by the electron beam B1 is reduced in order to observe the sample surface during the time t1 to t2 when the electron beam B1 scans the non-processed area a1.

  On the other hand, since the electron gun 2 processes the sample surface during the time t2 to t3 when the electron beam B1 scans the processing region b1, the irradiation current I2 (pulse part) by the electron beam B1 is pulsed more than the irradiation current I1. The shape is enlarged. At time t3, the irradiation current I1 is restored.

FIG. 5 shows a change example of the detection gain.
The detection signal amplification unit 18 increases the detection gain G1 (base unit) during the time t1 to t2 when the electron beam B1 scans the non-processed area a1. Then, during the time t2 to t3 when the electron beam B1 scans the processing region b1, the detection gain G2 (pulse part) is lowered in accordance with the timing at which the irradiation current is increased in a pulse shape. Thereafter, at time t3 when the electron beam B1 scans the non-processed area a2, the detection gain G1 is restored.

  According to the three-dimensional additive manufacturing apparatus 1 according to the embodiment described above, the processing of the sample surface and the configuration of the observation image are performed almost simultaneously by performing one full raster scan on the sample surface. be able to. For this reason, the time required for processing and observation of the powder sample 13 can be shortened. The display unit 33 displays the processing result of the processing target pattern 40 for each raster scan by the electron beam B1. Therefore, the operator can efficiently check and set the processing conditions.

  Further, when the powder sample 13 is irradiated with the pulsed electron beam B1 in the processing mode, a large amount of secondary electrons are generated and the detection signal is increased by irradiating the electron beam B1 with a large current. For this reason, in the processing region b1, a negative potential is applied to the detection current control electrode 14 so that a large amount of secondary electrons are not attracted to the detection current control electrode 14. In the non-processed regions a1 and a2, a positive potential is applied to the detection current control electrode 14 to attract many secondary electrons to the detection current control electrode 14. In this way, switching between the processing mode and the observation mode is performed at the boundary between the non-processing regions a1 and a2 and the processing region b1. Then, the detection signal amplification unit 18 reduces the gain of the detection signal when the electron beam B1 is pulsed in synchronization with the extraction potential applied in a pulsed manner to the extraction electrode 4. For this reason, by using the processing mode and the observation mode together in one raster scan, it is possible to obtain detection signals continuously, and it is possible to construct a normal image in which no whiteout occurs.

[2. Modified example]
In the embodiment described above, the gain is changed in accordance with the pulse application of the extraction potential E2 as shown in FIG. 5, but the present invention is not limited to this.

FIG. 6 shows a change example of the detection gain.
In this example, the detection gain G2 is maintained during the time t2 to t3 when the electron beam B1 scans the processing region b1. As a result, even if the extraction potential increases in a pulse shape, the detection gain is kept low, so that the amplification of the detection signal due to the application of the large extraction potential to the extraction electrode 4 can be suppressed.

  Further, the pulse potential ratio of the extraction potential, the irradiation current, and the detection gain can be arbitrarily changed according to the diameter of the powder sample 13, the shape of the processing target pattern 40, and the like.

  In the three-dimensional layered manufacturing apparatus 1, an example in which the electron beam B <b> 1 using negatively charged electrons is used as an example of the charged particle beam, but positively charged particles may be used for the charged particle beam.

Moreover, it is also possible to set the observation mode and the processing mode independently as in the prior art.
In addition to the powder sample 13, a molten resin or the like can also be used.

The present invention is not limited to the above-described embodiments, and various other application examples and modifications can of course be taken without departing from the gist of the present invention described in the claims.
For example, the above-described embodiments are detailed and specific descriptions of the configuration of the apparatus and the system in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Absent. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  DESCRIPTION OF SYMBOLS 1 ... Three-dimensional additive manufacturing apparatus, 2 ... Electron gun, 3 ... Emitter, 4 ... Extraction electrode, 5 ... Acceleration electrode, 6 ... Deflection part, 7 ... Lens, 13 ... Powder sample, 14 ... Detection current control electrode, 15 ... Switch, 16a, 16b ... terminal, 17 ... secondary electron detector, 18 ... detection signal amplifier, 20 ... controller, 25 ... scan driver, 26 ... acceleration power source, 30 ... image composing unit, 33 ... display unit

Claims (5)

An irradiation unit for irradiating a charged particle beam;
The amount of irradiation current of the charged particle beam that irradiates the processing region of the sample to be processed is larger than the amount of irradiation current of the charged particle beam that irradiates the non-processing region of the sample, and has a predetermined pulse duty ratio. A control unit for causing the irradiation unit to perform pulse output;
A secondary electron detector that outputs a detection signal by detecting secondary electrons excited by the charged particle beam applied to the sample;
The detection signal has a gain lower than that of the detection signal during a period in which the charged particle beam is irradiated onto the non-processed region. A detection signal amplification unit for amplifying
A charged particle beam irradiation apparatus comprising: an image constructing unit that constructs an observation image for observing the state of the sample using the amplified detection signal. The charged particle beam irradiation apparatus according to claim 1, wherein the detection signal amplifying unit lowers the gain of the detection signal during a period in which the charged particle beam is irradiated onto the processing region in accordance with the predetermined pulse duty ratio. . The charged particle beam is an electron beam,
The irradiation unit is
An emitter that emits electrons;
An extraction potential generated by an extraction potential generation unit is applied, and an extraction electrode that extracts the electrons from the emitter;
An accelerating potential is applied, and an acceleration electrode that accelerates the electrons emitted from the emitter to form the electron beam, and
The charged particle according to claim 1, wherein the control unit changes the extraction potential generated by the extraction potential generation unit in accordance with a timing of irradiating the processing region or non-processing region of the sample with the electron beam. Beam irradiation device. The image configuration unit includes a storage unit that stores the observation image,
The charged particle beam irradiation apparatus according to claim 1, wherein the observation image is output to a display unit that displays the observation image. The charged particle beam that irradiates the non-processed region of the sample with an irradiation current amount of the charged particle beam that is applied to the processing region of the sample to be processed by the control unit to the irradiation unit that irradiates the charged particle beam. A step of causing the pulse output to be larger than the irradiation current amount and having a predetermined pulse duty ratio;
A step of outputting a detection signal by detecting a secondary electron excited by the charged particle beam applied to the sample by the secondary electron detector;
The detection signal amplification unit lowers the gain of the detection signal during a period in which the charged particle beam is irradiated onto the processing region, and is lower than the gain of the detection signal in a period during which the charged particle beam is irradiated onto the non-processing region. Amplifying the detection signal;
And a step of forming an observation image for observing the state of the sample using the amplified detection signal. The charged particle beam irradiation method.

Images