Apparatus for Preparing Cross-Sectional Specimen Using Ion Beam

Abstract

There is disclosed a cross-sectional specimen preparation apparatus. The milling position can be modified or corrected in a short time. Also, the internal structure of the specimen can be known. The apparatus has an optical observation device for observing a cross section of the specimen milled by the ion beam. During ion beam irradiation or when the irradiation is interrupted, a shutter is opened. The cross section of the specimen can be observed while maintaining the vacuum inside a processing chamber. The apparatus further includes an adjusting mechanism for varying the relative position between the specimen and the shielding material. Whenever one sectioning operation ends, an image of the cross section is accepted and the milling position is moved an incremental distance. A three-dimensional image of the specimen is constructed from obtained plural images.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1b show schematic side elevations showing the structure of a prior art cross-sectional specimen preparation apparatus;

FIGS. 2 a, 2b, and 2c show schematic views illustrating the manner in which a cross section is milled with a cross section polisher;

FIG. 3 is a schematic block diagram of the structure of a cross-sectional specimen preparation apparatus according to one embodiment of the present invention;

FIG. 4 illustrates the concept of the present invention;

FIG. 5 is a flowchart illustrating a procedure for making an observation of a section during milling in accordance with one embodiment of the present invention; and

FIG. 6 is a flowchart illustrating another procedure performed when plural cross-sectional images are accepted in accordance with one embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are hereinafter described with reference to the accompanying drawings. Like components are indicated by like reference numerals in various figures including FIGS. 1a and 1b already referenced. Those components that are already described will not be described below to avoid repeated description. A structure added by the present invention is described hereinafter. It is to be noted that the technical scope of the present invention is not limited to exemplary embodiments shown below.

An example of the structure of a cross-sectional specimen preparation apparatus embodying the present invention is schematically shown in FIG. 3. In this figure, actuators 30 and 31 drive the specimen position-adjusting mechanism 5 and the shielding material position-adjusting mechanism 10, respectively. Each actuator 30 and 31 is controlled by each controller 32 and 33, respectively. Another controller 34 controls the ion beam emitted from the ion gun 2. An optical observation device 40 constituting a cross section observation device sends image data to an arithmetic and control unit 36 via an image acceptance device 42. A shutter 41 having an opening-closing mechanism is mounted to prevent the optical observation device from being contaminated by particles flying off from the specimen 6 and shielding material 12 due to ion beam irradiation. The shutter 41 is opened and closed under control of a controller 43. The controllers 32, 33, 34, and 43 are connected with the arithmetic and control unit 36 via an interface 35. A display device 37 is made of a CRT (cathode-ray tube) or liquid crystal monitor. An input device 38 is made of a computer mouse or a keyboard.

Although not shown in FIG. 3, the specimen position-adjusting mechanism 5 and the shielding material position-adjusting mechanism 10 are disposed on the specimen stage 4 together with the actuators 30 and 31 and mounted to the vacuum chamber 1 such that the mechanisms 5 and 10 can be opened and closed by the specimen stage pullout mechanism 3 in the same way as in the related-art apparatus shown in FIGS. 1a and 1b.

To permit the relative position between the specimen 6 and the shielding material 12 to be changed accurately, one of a linear scale, a linear encoder, and an optical encoder is preferably built in at least one of the specimen position-adjusting mechanism 5 and the shielding material position-adjusting mechanism 10. The incorporation of the digital control device makes it possible to accurately recognize and control the amount of movement of the relative position between the specimen 6 and the shielding material 12 when the relative position is varied minutely.

The arithmetic and control unit 36 controls the controllers, which, in turn, control the cross-sectional specimen preparation apparatus. The unit 36 is loaded with a software program for creating a three-dimensional image from plural two-dimensional images. The software program constitutes an image-processing device. The image processing can be performed by a dedicated device separated from the arithmetic and control unit 36.

FIG. 4 schematically illustrates the concept of the present invention. A pattern “A” appears on the cross section of the specimen 6 milled by an ion beam B. During the ion beam irradiation or when the irradiation is interrupted, image data obtained by the optical observation device 40 constituting the cross section observation device is sent to the display device 37. The cross section of the specimen 6 can be observed at all times. Information about the three-dimensional structure of “A” present inside the specimen 6 can be obtained by varying the relative position between the shielding material 12 and the specimen 6 in steps of d, collecting image data whenever milling is completed at each position, and constructing a three-dimensional image from the image data about the plural images.

A procedure for quickly and easily judging the progress of a sectioning process performed by the cross-sectional specimen preparation apparatus shown in FIG. 3 and according to the present invention and quickly modifying the position at which a cross section is created is next described by referring to the flowchart of FIG. 5.

In step S1, the specimen stage pullout mechanism 3 is opened. Under this condition, the operator attaches a specimen from which a section is created onto the specimen holder 7. The position at which the cross section is created is adjusted. After completion of the adjustment, the stage pullout mechanism 3 is closed. The processing chamber 18 is evacuated to a degree of vacuum necessary for ion beam irradiation by the pumping system 17.

In step S2, the operator sets processing conditions including the accelerating voltage of the ion beam IB, ion current, and processing time by entering instructions regarding them from the input device 38.

In step S3, the arithmetic and control unit 36 closes the shutter 41 via the controller 43 to prevent contamination of the optical observation device.

In step S4, the arithmetic and control unit 36 directs the ion beam IB at the portion of the specimen 6 not shielded by the shielding material 12 via the controller 34.

In step S5, the irradiation by the ion beam IB is continued until the specified processing time has passed or an instruction for stopping the processing is given from the operator.

In step S6, the irradiation by the ion beam IB is continued until an instruction for interrupting the processing is given from the operator.

In step S7, if an instruction for interrupting the irradiation is given, the arithmetic and control unit 36 stops the ion gun 2 from emitting the ion beam IB via the controller 34 and opens the shutter 41 via the controller 43.

In step S8, the operator observes the milled surface of the specimen 6 displayed on the display device 37 using the optical observation device 40. The milled surface of the specimen 6 is illuminated with light by lighting (not shown).

In step S9, the operator makes a decision based on the results of observation of the milled surface as to whether or not the milling of the section is continued. If the decision is affirmative (the milling is continued intact), control returns to step S3.

In step S10, if the milling is not continued, the operator makes a decision as to whether or not the milling position is changed. If the milling position is not varied, the process is terminated intact.

In step S11, if the milling position is varied, the specimen position-adjusting mechanism 5 or shielding material position-adjusting mechanism 10 is controlled by the input device 38 to slightly move the relative position between the specimen 6 and the shielding material 12. Then, control returns to step S3.

In the above-described procedure, the shutter 41 is always closed during ion beam irradiation. Alternatively, the shutter 41 may be opened according to the need even during the ion beam irradiation to permit observation of the milled surface.

A procedure for obtaining plural cross-sectional images to obtain information about the internal structure of the specimen 6 by the cross-sectional specimen preparation apparatus shown in FIG. 3 is next described by referring to the flowchart of FIG. 6.

In step S21, when the specimen stage pullout mechanism 3 is open, the operator attaches a specimen to be cross-sectioned onto the specimen holder 7 and adjusts the position where the cross section is prepared. After completion of the adjustment, the stage pullout mechanism 3 is closed. The processing chamber 18 is evacuated by the pumping system 17 to a degree of vacuum necessary for ion beam irradiation.

In step S22, the operator enters processing conditions such as the accelerating voltage of the ion beam IB, ion current, and milling time to create one cross section from the input device 38 and sets these conditions.

In step S23, the operator specifies the magnitude d of each incremental movement, the number of times the position is varied, and mechanism to be controlled for position movement (specimen 6 or shielding material 12) by entering them from the input device 38 to collect plural cross-sectional images.

In step S24, the arithmetic and control unit 36 closes the shutter 41 via the controller 43 to prevent contamination of the optical observation device.

In step S25, the arithmetic and control unit 36 instructs the controller 34 to direct the ion beam IB at the portion of the specimen 6 not shielded by the shielding material 12.

In step S26, if an instruction for ending the process is given from the operator, the irradiation by the ion beam IB is stopped. The operation for collecting cross-sectional images is ended.

In step S27, after a lapse of the milling time to prepare one cross section, the arithmetic and control unit 36 instructs the controller 34 to stop the ion gun 2 from emitting the ion beam IB. The arithmetic and control unit 36 opens the shutter 41 via the controller 43.

In step S28, the image acceptance device 42 accepts cross-sectional images of the specimen 6 from the optical observation device 40 and sends them to the arithmetic and control unit 36.

In step S29, control returns to step S24 until the specified number of position changes and acceptance of the cross-sectional images at those positions are completed. The milling operation and the operation for acquiring cross-sectional images are continued.

In the above-described procedure, the shutter 41 is always closed during ion beam irradiation. According to the need, the shutter 41 may be opened even during ion beam irradiation to permit one to observe the milled surface. Furthermore, the work may be terminated before it is completed according to an operator's instruction without previously specifying the number of position changes. In addition, the magnitudes d of the specified incremental movements may not be always required to be uniform.

In the embodiment of the present invention described so far, cross sections of a specimen are observed with the optical observation device. It is to be noted that the observation device for observing cross sections of specimens are not restricted to optical observation devices. For example, a small-sized electron gun, a secondary electron detector and/or a backscattered electron detector are built into the processing chamber. When the ion beam irradiation is interrupted, the secondary, electron image and/or backscattered electron image may be observed. Additionally, infrared detectors, for example, may be incorporated and an infrared radiation distribution map (infrared thermography image) may be observed. Further, plural ones of optical image, secondary electron image, backscattered electron image, and infrared radiation distribution map may be made simultaneously observable.

As described so far, when a cross section is created using a cross section polisher, the progress of sectioning can be quickly and easily judged by providing the function of adjusting the positions of the specimen and shielding material when the cross section is being milled or when the milling is interrupted, as well as the observation function. Consequently, the milling position can be modified or corrected in a short time. Additionally, information about the three-dimensional structure inside the specimen can be obtained by providing the two functions (i.e., the function of adjusting the positions of the specimen and shielding material when the cross section is being milled or when the milling is interrupted and the observation function) and by acquiring cross-sectional images of plural large cross sections of more than hundreds of micrometers which are difficult to mill by FIB.

Having thus described our invention with the detail and particularity required by the Patent Laws, what is desired protected by Letters Patent is set forth in the following claims.

Claims

1. A cross-sectional specimen preparation apparatus for preparing a cross section of a specimen by covering a part of the specimen with a shielding material and directing an ion beam at the specimen from a side of the shielding material including an edge portion of the shielding material to mill away the unshielded portion of the specimen with the ion beam, said cross-sectional specimen preparation apparatus comprising: (i) ion beam irradiation means mounted in a vacuum chamber and acting to direct the ion beam at the specimen;(ii) a position-adjusting mechanism housed inside the vacuum chamber and acting to adjust a relative position between the edge portion of the shielding material and the specimen; and(iii) motion control means permitting one to control movement of the position of the position-adjusting mechanism from outside the vacuum chamber.

2. A cross-sectional specimen preparation apparatus as set forth in claim 1, wherein said position-adjusting mechanism has at least one of a shielding material position-adjusting mechanism for moving the position of the shielding material relative to the specimen to adjust the position where the cross section is prepared and a specimen-moving mechanism for moving the position of a specimen holder carrying the specimen thereon relative to the shielding material.

3. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein said movement control means has position recognition means capable of recognizing amounts of variation in the relative position between the specimen and the shielding material.

4. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein said position recognition means has at least one of a linear scale, a linear encoder, and an optical encoder.

5. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein there is further provided cross section observation means capable of observing a cross section of the specimen when the sample is being irradiated with the ion beam for sectioning or when the irradiation is interrupted.

6. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein said cross section observation means has at least one of optical image observation means, secondary electron image observation means, backscattered electron image observation means, and infrared radiation distribution map observation means.

7. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein a shutter designed to be capable of being opened and closed from outside vacuum is mounted between the observation means and the cross section of the specimen.

8. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 7, wherein there is further provided image acceptance means capable of accepting a cross-sectional image obtained by the observation means as two-dimensional digital data.

9. A cross-sectional specimen preparation apparatus as set forth in claims 1 and 2, wherein there is further provided image processing means for building a three-dimensional image from plural images accepted by the image acceptance means.