JP5540908B2 - Manufacturing method of probe for focused ion beam processing apparatus and probe for focused ion beam processing apparatus - Google Patents

Description

  The present invention relates to a probe for a focused ion beam processing apparatus and a method for manufacturing the probe, which are used when a sample is separated and processed, particularly when an arbitrary part is extracted from a local region and measured and analyzed.

  A technique for observing a fine structure by detecting secondary charged particles generated when a sample is irradiated with a charged particle beam is well known. In particular, recently, a technique for observing surface roughness, composition change, crystal orientation change, etc. by using Ga ions as a charged particle beam and detecting electrons as secondary charged particles generated at that time has been reported. Yes. This method is also well known as a method (focused ion beam processing method) for producing a thin specimen for a transmission electron microscope using the sputtering effect of Ga ions, and a typical method is disclosed in Patent Literature. 1 is disclosed.

  This focused ion beam processing apparatus basically includes an ion beam optical system for irradiating a focused Ga ion beam and a secondary electron generated from an irradiation target of the Ga ion beam. A detector and an image display device that forms a secondary electron image based on secondary electrons obtained by the detector are provided. The basic principle of producing a specimen for a transmission electron microscope with the focused ion beam utilizes a sputtering phenomenon. At this time, a Ga ion beam can be arbitrarily and easily scanned, and a sample for a transmission electron microscope can be processed in a submicron order. As a result, the sample preparation technology for transmission electron microscopes that require ultra-thin samples of submicron thickness using the focused ion beam processing method has been dramatically improved. The current focused ion beam processing method is not only used for failure analysis of early semiconductor manufacturing equipment, but also as a sample preparation method when observing with a transmission electron microscope in material development and product development of magnetic materials and metal materials. That position has been established.

  The technical progress of the focused ion beam processing apparatus is remarkable, and a non-patent document 1 reports a micro-sampling technique for extracting a cross-sectional tissue in a local region more pinpointly. Further, a method for extracting not only the cross-sectional structure but also a plane parallel to the sample surface is disclosed in Patent Document 2, and the microsampling method for driving the manipulator in the apparatus at the time of the focused ion beam processing operation has already been widely applied not only in the semiconductor field. As an analysis method in the field of material development, it has become a general-purpose technology. The point of the microsampling method technique is to introduce a probe device having a manipulation function into a vacuum region in the focused ion beam processing apparatus, and the present invention relates to a tip portion of the probe apparatus. There are various kinds of focused ion beam processing apparatuses having similar functions at present, and they are not necessarily called micro-sampling methods but may be called lift-out methods or other names. In the case where a part having a manipulating function is introduced into the vacuum apparatus, all are applicable.

  Various improvements have been made to the tip shape of a probe device for extracting a local region. However, it is basically oriented to microfabrication, and the development so far assumes a needle shape with a thick base and a thin tip. As the probe manufacturing technique, the electrolytic polishing method is mainly used, and various methods using the electric field polishing technique are disclosed in, for example, Patent Document 3, Patent Document 4, and the like.

  In the microsampling process, it is necessary to attach the probe tip to the sample many times. At this time, tungsten gas or carbon gas is injected to the sample position and irradiated with a Ga ion beam, which is a kind of chemical vapor. A phase reaction is caused to form a deposited film having an amorphous structure and an adhesive force spreading in an arbitrary shape. This is called a gas deposition method. At this time, in a semiconductor device or the like, local sample contamination due to gas spreading may be a problem. Therefore, Patent Literature 5 discloses a needle-like probe that can separate and extract a sample from a base material in a form that sandwiches the sample without using a gas. Again, the premise is a needle shape with a thick root and a thin tip. Similarly, as a method capable of omitting the gas deposition step, Patent Document 6 discloses a method in which the tip of the probe is cracked and the sample is extracted while holding the sample piece for extraction while holding the sample by elastic force. ing. However, it is difficult to sandwich a large region, and the holding becomes unstable depending on the sample shape.

  In this way, sample extraction technology from a minute region has progressed mainly in the field of semiconductor technology, but the size of the target sample there is a volume region having a width of 10 μm, a thickness of 2 μm and a height of about 10 μm. On the other hand, in the field of material research, for example, as in steel material research, if the crystal grain size of the extracted specific region is about 30 μm to 100 μm, a specific position extraction technique including a wide region of 50 μm or more is desired. However, it is difficult to freely manipulate a manipulator having a large shape in a vacuum apparatus, and simple technical development has been desired.

Japanese Patent Laid-Open No. 5-180739 JP-A-5-52721 JP-A-4-184848 JP-A-6-128800 JP 2006-292766 A JP 2000-2630 A

T. Ohnishi et al., Proc. 25th International Symposium for Testing and Failure Analysis, California, (1999) p.449

  The present invention has been made in view of the above-described situation, and a probe device for a manipulator for a focused ion beam processing apparatus has a simple structure, a low cost, and a versatile apparatus configuration, from a wide specific area. It aims to realize the extraction of.

In order to achieve the above object, the gist of the present invention is as follows.
(1) Using a focused ion beam processing apparatus, beam processing is performed on a comb-shaped probe portion having a tip branched into n pieces (n ≧ 2) from a metal thin plate having a thickness of 30 μm or less and a branching interval of 20 μm or more and 200 μm or less. A step of forming a groove in the center of the probe support for manipulating, a step of joining the probe support and the comb-shaped portion by a gas deposition method, and the comb-shaped portion as a first step. A probe for a focused ion beam processing apparatus comprising: a step of separating from a thin metal plate and integrating with the probe support portion; and a step of processing the tip portion of the comb-shaped portion into a width of 1 μm to 3 μm. Manufacturing method .
(2) In a focused ion beam processing apparatus, a probe for a focused ion beam processing apparatus used as a tip member of a probe apparatus for manipulating a sample, and having a comb-shaped tip portion branched into n (n ≧ 2) A probe for a focused ion beam processing apparatus , characterized in that a branch interval of the tip is 20 μm or more and 200 μm or less, and the length of the needle at the tip is changed .
(3) The probe for a focused ion beam processing apparatus according to (2), wherein an angle formed by the tip portion and a probe support portion that supports the tip portion is not less than 100 ° and not more than 130 ° .

  According to the present invention, it is possible to extract a large sample having a size of 50 μm or more, which has been difficult in the past, in the process of the micro sampling method in the focused ion beam processing operation.

It is a schematic block diagram which shows a focused ion beam processing apparatus. It is a perspective view which shows an example of the sample extraction method of the large volume area | region containing the specific area | region by the microsampling method using the comb-shaped probe of this invention. It is a front view which shows an example of the manufacturing method of the comb-shaped probe of this invention. It is a side view explaining the positional relationship of a probe and a sample, (a) shows a prior art example, (b) shows the example of this invention. It is a photograph which shows the example of the sample extraction procedure by the comb-shaped probe of this invention. It is an Example of this invention, and is a photograph which shows the manufacturing process of the comb-shaped probe which the probe front-end | tip part branched into three. It is a different Example of this invention, (a) is a photograph which shows a manufacturing process, (b) is a front view which shows a usage example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  An outline of the focused ion beam processing apparatus is shown in FIG. A target sample 6 and a probe device tip 10 which is a microsampling manipulator are arranged in a vacuum chamber 1. In the ion beam optical system 2 connected by a vacuum system, Ga ions as a liquid radiation source are converted into an ion beam, accelerated to 30 to 40 kV, and irradiated to the sample 6 through a focusing lens system (not shown). Secondary electrons are generated from the portion irradiated with the ion beam. The secondary electrons are received by the secondary electron detector 5 and imaged by the image display device 3. A scanning ion microscope image is obtained by synchronizing the secondary electron intensity generated with respect to the scanned Ga ion beam through a secondary electron detector 5 that converts the intensity into an electric quantity. Further, the probe device 9 is introduced into the vacuum chamber 1 by a manipulation function. The probe device 9 secures a vacuum through the bellows 8 with the housing of the vacuum chamber 1 in order to perform a microsampling method for extracting a specific portion 7 to be observed as a sample preparation method for a transmission electron microscope. To be installed. A probe 11 for extracting the specific portion 7 of the sample 6 is attached to the tip of the probe device tip 10. In general, the probe 11 has an angle of 20 to 30 ° with respect to the vertical direction, and is designed to be inclined toward the surface of the sample 6. In the micro-sampling method, the probe device tip 10 is adhered to or separated from the sample 6 many times, and the extracted specific portion 7 of the sample 6 is mounted on another support for a transmission electron microscope and fixed. As an adhesion method between the sample 6 and the object in these series of operations, there is a method of forming an amorphous deposited film by a chemical vapor deposition method. For this purpose, tungsten or carbon gas is used. A gas deposition mechanism 4 is mounted.

  The above configuration shown in FIG. 1 is called a focused ion beam device or a focused ion beam device, and is a widely used device.

  The probe tip shape in the conventional microsampling method is a fine needle shape, and when the tip is bonded to one end of the sample piece to be extracted and picked up, it becomes a cantilever needle shape, so the size that can be picked up is at most The maximum width was about 20 μm. In picking up a sample larger than that, since the other end side is easily shaken at the time of separation, there is a difficulty in work such as re-adhesion in a surrounding groove.

  Therefore, FIG. 2 schematically shows a pickup using the comb-shaped probe according to the present invention. In order to observe the cross-sectional structure in the vicinity of the specific part 7 of the sample 6 shown in FIG. 2A with a transmission electron microscope, a procedure for extracting the sample with the comb-shaped probe 20 of the present invention will be described. At this time, the structure of the actual material including the steel material is irregular, and it is necessary to extract it including a large region of 50 μm or more. First, as shown in FIG. 2B, a groove is formed by Ga ion beam processing around the specific portion 7 to be extracted. Then, as shown in FIG. 2C, a large volume region is extracted by the comb-shaped tip portion 13 attached to the probe support portion 12. What is shown in a dotted circle is a conventional microsampling probe 22. When extracting the specific part 7 of the sample 6, the comb-shaped tip 13 and the specific part 7 are bonded and lifted by the gas deposition method. After the specific portion 7 taken out is adhered and fixed to the mount base 14 having a semicircular front shape suitable for a transmission electron microscope stage prepared separately by the gas deposition method, as shown in FIG. The tip portion of the shaped tip portion 13 is cut with a Ga ion beam. By such a series of methods, the specific part 7 having a large volume of 50 μm or more can be extracted while being positioned.

  Next, an example of the manufacturing method of the comb-shaped probe of the present invention will be described with reference to FIG. This can be fabricated in a focused ion beam processing apparatus. First, a thin plate 15 of Mo material having a thickness of 15 μm is prepared, and a comb-shaped portion 16 as shown in FIG. Here, the number of needles of the probe tip 17 branched into a comb shape is n = 2, the length of the comb-shaped portion 16 is 200 μm, and the branch interval is about 20 μm. The comb-shaped portion 16 is still connected to the thin plate 15 at this point. The material of the thin plate 15 is not limited to Mo, and there is no problem with other metal materials such as Cu and Ni. However, since Ni is ferromagnetic, it may have an adverse effect during electron microscope observation, and is preferably a non-magnetic metal material thin plate. Moreover, considering that the thickness of the specific portion 7 of the sample 6 to be extracted is several μm to several tens of μm, a metal thin plate having a thickness of 30 μm or less is preferable. When it is thicker than 30 μm, it is too thick as compared with the thickness of the specific portion 7 of the sample 6 to be extracted, and this adversely affects the operability. Moreover, since the thinner one can reduce ion beam processing time, it is more preferable if it is a metal thin plate thinner than 30 μm, and FIG. 3 shows an example of a thickness of 15 μm.

  Next, as shown in a schematic diagram of FIG. 3B, the center of the tip 18 of the microsampling probe support 12 is grooved. Then, the upper part of the comb-shaped portion 16 processed in FIG. 3A and the tip 18 of the probe support 12 are combined as shown in FIG. 12) and the comb-shaped part 16 are integrated. The figure is viewed from the front, and the comb-shaped portion 16 is parallel to the paper surface, but the probe support portion 12 for microsampling is attached at an angle of about 80 ° to the paper surface. Therefore, the joint portion between the tip portion 18 of the probe support portion 12 and the upper portion of the comb-shaped portion 16 has a three-dimensional structure, which is bonded by a gas deposition method to form the bonding portion 19.

  Thereafter, the comb-shaped portion 16 is cut with a Ga ion beam and cut off from the Mo thin plate 15 as shown in FIG. And the shape of the front-end | tip part 21 used as a probe of the comb-shaped probe 20 is further finely processed, respectively, and is trimmed as shown in FIG.3 (f). If the width of one needle of the tip portion 21 at this time is larger than 3 μm, the operability when the comb-shaped probe 20 is bonded to or detached from the sample is deteriorated, and the yield for successfully extracting a specific portion is 50. %, And the width is 3 μm or less. Although the lower limit of the width is not particularly defined, if it is smaller than about 1 μm, the strength when lifting the sample is insufficient, and the yield for successful extraction of a specific part is lowered. Therefore, the width of about 1 μm or more is actually required. . A comb-shaped probe 20 having a shape as shown in FIG. 3G is finally manufactured by a machining operation that satisfies such conditions. Both can be manufactured in a focused ion beam processing apparatus in a vacuum. At this time, the branching interval is shown as 20 μm in FIG. 3 (f). However, if it is less than 20 μm, the processing interval is too narrow, and it is difficult to maintain the branch by adsorbing each other when a fresh surface comes out during ion beam processing. Therefore, the branch interval is set to 20 μm or more. In addition, the maximum value of the branching interval was set to 200 μm so that the time for the FIB ion beam processing was within a few hours and within a realistic working time. Further, in consideration of a steady processing time, it is desirable that the interval is 100 μm or less. In the present specification, the branch interval is the dimension of the gap between the needles at the probe tip.

  Next, the three-dimensional structure of the comb-shaped probe 20 will be described. As shown in FIG. 4 (a), in the conventional microsampling method, the probe 22 is introduced into the sample at an angle of 20 to 30 °, for example, 30 ° as shown in the figure, and the specific portion 7 of the sample and the gas degasser are introduced. Bonded by the position method. On the other hand, the tip 13 of the comb-shaped probe 20 of the present invention is introduced substantially parallel to the sample surface, and the probe support 12 is 90 ° or more, for example, as shown in FIG. Will have an angle of 115 °. In general, the introduction angle of the probe support portion is related to the manipulation operation range in the apparatus. However, as a result of investigations by the present inventors, it can be confirmed that scanning is possible if the introduction angle is in the range of 10 to 40 °. It was. In order to achieve a more stable operation, the introduction angle is preferably 20 to 30 °. On the other hand, the tip portion 13 of the comb-shaped probe 20 of the present invention is attached at an angle with respect to the probe support portion 12 and is therefore introduced substantially parallel to the sample surface. If the angle between the tip 13 and the probe support 12 is 100 to 130 °, scanning is possible. Further, in consideration of operability, when the tip end portion 13 is attached to the probe support portion 12 in an angle range of 110 to 120 °, a more stable operation becomes possible.

  Depending on the sample, it may be desired to observe the structure in the vicinity of the surface layer portion. In such a case, it may be desired to avoid attaching a pickup probe to the outermost layer from the viewpoint of damage. In such a case, it is necessary to adhere a probe around the sample to be extracted, and as shown in FIG. 5A, a comb in which the length of the needle at the tip 25 is intentionally changed. Shape probes are effective. Thus, the sample can be extracted by adhering the needle of the tip 25 around the specific range 7 to be extracted as shown in FIG. 5B while avoiding damage to the target sample surface layer.

  As shown in the above series of explanations, a comb-shaped probe suitable for extracting a large volume region of 50 μm or more can be produced by processing in the focused ion beam apparatus. It is possible to increase the number of needles at the tip of the comb-shaped probe to two, three, and four arbitrarily including the interval according to the sample site, and the length of the tip can also be adjusted. However, if the number of needles is large, the probe processing time becomes longer, and considering the extraction of a sample for electron microscope observation, it is practical to extract a sample having a size of about 1 mm at the maximum, and the number of needles n Is preferably 10 or less. Furthermore, by using the conventional probe support portion and adhering the tip of the comb-shaped probe at an angle of 100 to 130 °, sampling in a state almost parallel to the sample surface to be extracted has become possible.

  In the observation of the structure in the vicinity of the grain boundary in a steel material having an average grain size of about 20 μm, a large volume sample was extracted including a plurality of grain boundaries by a microsampling method having a comb-shaped probe. That is, in order to extract a region having a width of about 60 μm, as shown in FIG. 6, a comb-shaped probe having a tip portion 26 composed of three needles having a branch interval of about 20 μm is manufactured from a thin Mo plate having a thickness of 15 μm. did. As shown in the drawing, the length of the entire comb-shaped portion is about 200 μm. The portion 28 to be bonded to the probe support portion is 3 μm square, and the coupling portion 27 with the Mo thin plate is finally cut off, so that a comb-shaped probe having a tip portion 26 composed of three needles can be obtained. As a result, it is possible to extract a specific region including two or more crystal grains in the deformed portion, and it is possible to observe a structure in which dislocations gather due to stress concentration at the grain boundary. In structural analysis of a specific part where deformation is concentrated, observation of a dislocation structure including a plurality of grain boundaries is indispensable. For the first time, the present invention enables sample extraction for an electron microscope from such a large volume.

  Next, as an application of a further comb-shaped probe, considering the correspondence to the recent focused ion beam processing method capable of arbitrary shape processing, as shown in FIG. 7, the number of needles forming the tip portion is n = 5, In addition, a comb-shaped probe was manufactured in which the needles were not necessarily parallel and the needles at both ends were inclined. The machining process is shown in FIG. Similar to the manufacturing method described above, the Mo thin plate was used to secure the connection portion 29 with the thin plate, and finally the connection portion 29 was cut by ion beam processing. Connection to the probe support was made at the top 30. As shown in the schematic diagram of FIG. 6B, the L-shaped specific region 32 is bonded to the one inclined portion 31 and the other two needles of the needles at both ends by the bonding portion 33. By extracting such an L-shaped specific region 32, it is possible to perform final flake processing for observation with a transmission electron microscope from two directions, the vertical direction and the horizontal direction. In contrast to the fact that microscopic observation was possible only from one direction of a specific region, it was possible to observe the structure from different directions. In other words, two-sided observation is possible even with a transmission electron microscope, and crystal structure analysis technology has made significant progress.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Ion beam optical system 3 Image display apparatus 4 Gas deposition mechanism 5 Secondary electron detector 6 Sample 7 Specific site | part 9 Probe apparatus 10 Probe apparatus front-end | tip part 11 Probe 12 Probe support part 13 (of comb-shaped probe) front-end | tip Part 14 mount base 15 thin plate 16 comb-shaped part 17 probe tip 18 (probe support part) tip 19 adhesive part 20 comb-shaped probe 21 tip 22 (in the conventional microsampling method) probe 26 tip 27 Mo thin plate Bonding part 28 Part to be bonded to the probe support part 29 Connection part 30 to the thin plate Upper part 31 Inclined part 32 L-shaped specific area 33 Adhering part

Claims (3)

Using a focused ion beam processing apparatus, a step of forming a comb-shaped probe portion having a tip branching into n pieces (n ≧ 2) from a metal thin plate having a thickness of 30 μm or less and having a branch interval of 20 μm or more and 200 μm or less is formed by beam processing. When,
Grooving the center of the probe support for manipulating;
Bonding the probe support and the comb-shaped portion by a gas deposition method;
Separating the comb-shaped portion from the first thin metal plate and integrating with the probe support;
Processing the tip portion of the comb-shaped portion into a width of 1 μm or more and 3 μm or less;
A method for manufacturing a probe for a focused ion beam processing apparatus, comprising: In a focused ion beam processing apparatus, a probe for a focused ion beam processing apparatus used as a tip member of a probe apparatus for manipulating a sample,
It has a comb-shaped tip portion branched into n (n ≧ 2), the branch interval of the tip portion is 20 μm or more and 200 μm or less, and the length of the needle at the tip portion is changed. Probe for focused ion beam processing equipment. The probe for a focused ion beam processing apparatus according to claim 2, wherein an angle formed by the tip portion and a probe support portion that supports the tip portion is 100 ° or more and 130 ° or less .