JP4937775B2 - Micro sample table, method for producing the same, micro sample table assembly, and sample holder - Google Patents

Description

  The present invention relates to a micro sample stage for fixing a micro sample for use in electron microscope observation and the like and a sample holder having a micro sample stage.

  In order to observe a flaky micro sample collected from a semiconductor wafer or semiconductor device with a transmission electron microscope (TEM), it is necessary to make the electron beam irradiation region (observation region) of the micro sample as thin as possible. As such a thinning technique, for example, a technique described in Patent Document 1 is known. In the technique of Patent Document 1, a micro sample is set up and fixed on the upper surface of a sample stage, and the side surface of the sample stage is attached to the surface of a thin half-cut mesh. In this state, focused ions are substantially parallel to the surface of the micro sample. The sample is thinned by irradiating the beam. When TEM observation is performed on a thin sample, the half-cut mesh portion is grasped with tweezers or the like and is carried to the TEM observation stage for attachment.

JP 2006-226970 A

  In Patent Document 1, since the side surface of the sample table is attached to the surface of the half-cut mesh, the thickness of the sample table is the same as that increased by the thickness of the half-cut mesh. Therefore, when irradiating with a charged particle beam and performing removal processing for thinning, not only the micro sample but also the cut end surface of the half cut mesh is irradiated, and the micro sample is obtained by reverse sputtering of the half cut mesh. The problem of contamination.

  In addition, when the micro sample is moved while holding the half-cut mesh portion with tweezers or the like, there is a problem that the micro sample is damaged by being brought into contact with another member or dropped.

(1) A sample table according to the invention of claim 1 is a micro sample table for fixing a micro sample to be processed , a base having an upper surface and a bottom surface parallel to the upper surface, and an upper surface of the base . spaced to stand so as to protrude from a plurality of fixing portions which minute sample is fixed, apart from upright so as to protrude from the upper surface of the base portion, a plurality of high projection height than the fixed part The plurality of columnar guard portions are arranged such that the fixed portion is sandwiched between the pair of columnar guard portions, and the fixed portions and the columnar guard portions are arranged alternately and spaced apart from each other. It is characterized by that.
(2) According to the invention of claim 2, in the micro sample table according to claim 1, the thickness of the fixed part and the guard part in the width direction of the upper surface is set to be thicker in the guard part than in the fixed part. It is characterized by that.
(3) The invention of claim 3 is the micro sample stage according to claim 1 or 2, wherein the stacking direction of the base portion and the fixing portion is the thickness direction of the silicon wafer, and the silicon wafer is integrally manufactured from the silicon wafer by micromachining technology. It is characterized by being.
(4) A fourth aspect of the present invention, in the micro sample table according to any one of claims 1 to 3, processing is characterized by flaking process der Rukoto by the charged particle beam.
(5) The method for producing a micro sample table according to the invention of claim 5 is the method for manufacturing the micro sample table according to claim 3 , wherein a groove is formed by etching or dicing from the surface of the silicon wafer. base and, characterized that you form a fixing portion, and the columnar guard portion.
(6) A micro sample table assembly according to the invention of claim 6 is a micro sample table assembly including a plurality of micro sample tables according to claim 3, wherein the plurality of micro sample tables are formed on a common base substrate. It is characterized that you have become integrally.
(7) A sample holder according to the invention of claim 7 comprises the micro sample table according to claim 4, and a pedestal on which the base of the micro sample table is fixed and supports the micro sample table, To do.
(8) The invention according to claim 8 is the sample holder according to claim 7, wherein the pedestal has a thin plate shape, the bottom surface of the base is fixed to the end surface of the thin plate, and the thickness of the thin plate is thinner than the thickness of the base. It is characterized by being set .

According to the sample holder of the present invention, it is possible to prevent a minute sample from being contaminated by the reverse sputtering of the pedestal.
According to the micro sample table of the present invention, since the guard portion is provided, it is possible to prevent the micro sample from being damaged.
According to the method for producing a micro sample table of the present invention, a large number of micro sample tables can be created in a lump.
According to the micro sample table assembly of the present invention, it becomes easy to handle a large number of micro sample tables that have been created in one batch.

Hereinafter, a micro sample table and a sample holder according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram schematically showing a sample holder according to an embodiment of the present invention. FIG. 1 (a) is a front view, FIG. 1 (b) is a cross-sectional view taken along the line II, and FIG. It is the elements on larger scale of FIG.1 (b). FIG. 2A is a perspective view schematically showing the structure of the micro sample table according to the embodiment. FIGS. 2B and 2C are diagrams for explaining the effects of the conventional example and the embodiment. In FIG. 1 and FIG. 2A, directions are represented by XYZ orthogonal coordinates.

  Referring to FIG. 1, the sample holder 1 has a structure in which a micro sample table 10 is fixed to a pedestal mesh 100. For example, the micro sample table 10 is mounted on the cut end surface 100A of the substantially semi-disc-shaped pedestal mesh 100 and fixed thereto. That is, as shown in FIG. 1B, the micro sample table 10 and the base mesh 100 are fixed up and down. The minute sample piece S is fixed upright on the upper surface which is the top of the fixing portion 12. The minute sample piece S may be fixed to the side surface of the fixing portion 12. Since the micro sample stage 10 and the pedestal mesh 100 are fixed vertically, the micro sample piece S can be prevented from being contaminated during the thinning preparation of the micro sample piece S, as will be described later. Fewer observations and measurements are possible.

  The micro sample stage 10 holds a rectangular parallelepiped block-shaped micro sample piece S collected from a semiconductor wafer or a semiconductor device by bonding or the like, and uses it for transmission electron microscope (TEM) observation or Auger electron spectroscopy (AES). It is used as a work table for preparing a thin sample piece S. The sample holder 1 carries the pedestal mesh 100 with tweezers or the like while holding the micro sample piece S on the micro sample stage 10 and carries the micro sample piece S to the microscope apparatus or the spectroscopic device during microscopic observation or spectroscopic analysis. And set on the stage.

  The micro sample stage 10 will be described in detail with reference to FIGS. 1 and 2A. The micro sample table 10 is made of silicon, and has a rectangular parallelepiped base portion 11, a fixed portion 12 that is erected on the upper surface of the base portion 11 and is thinner than the base portion 11, and a guard portion 13 that is sandwiched between the fixed portions 12. The micro sample table 10 has an integrated structure in which two fixing portions 12 and three guard portions 13 are alternately projected on the upper surface 11A of the base portion 11. From the viewpoint of maintaining strength, the thickness of the base portion 11 (the length in the Y direction) is made thicker than the fixed portion 12 and the guard portion 13. Further, the guard portion 13 is made thicker than the fixed portion 12, and the height of the guard portion 13 (length in the Z direction) is made higher than that of the fixed portion 12. It is preferable to make the top of the guard part 13 higher than the top of the minute sample piece S standing on the fixing part 12.

  As shown in the partial cross-sectional view of FIG. 1 (c), an inclination angle θ formed by a line segment connecting the edge 12e of the fixed portion 12 and the edge 11e of the base portion 11 with the vertical axis falls within 5 to 30 °. The thickness of the base part 11 and the thickness and height of the fixing part 12 are adjusted.

  The width (the length in the X direction) and the thickness (the length in the Y direction) of the fixing portion 12 can be arbitrarily formed according to the dimensions of the minute sample piece S and the like. For example, the thickness can be fixed to 5 μm, and the width can be arbitrarily changed within a range of 5 to 500 μm. The micro sample piece S is fixed upright on the fixing unit 12 so that the surface thereof, that is, the plane on which the thinning preparation is performed is parallel to the XZ plane.

  In the sample holder 1 described above, the pedestal mesh 100 has a thin plate shape, and a notch end surface (fixed surface) 100A for fixing the micro sample table 10 is provided on the upper end surface of the thin plate. Then, the bottom surface of the micro sample table 10 is fixed to the cut end surface 100A so that the standing direction of the micro sample piece S coincides with the surface direction of the thin plate.

  As described above, since the micro sample stage 10 is provided with the guard portions 13 on both sides in the vicinity of the fixed portion 12, even when the sample holder 1 is brought into contact with other members during transportation or dropped. The damage of the minute sample piece S can be avoided by the guard effect of the guard part 13. In particular, since the guard portion 13 is provided close to the fixed portion 12 with respect to another member having a sharp tip, the guard effect of the guard portion 13 works effectively.

In the state shown in FIG. 1, the micro sample piece S is fixed to the micro sample stage 10 having the above-described structure and dimensions, and the micro sample piece S is prepared to be thinned, and then the TEM observation of the micro sample piece S or the AES micro In order to carry out the analysis, it is set in these devices and used. For the thinning preparation, a method of processing with a focused ion beam (FIB) is used. In the FIB processing method, for example, the fine sample piece S is irradiated with a finely focused Ga ⁺ beam at a shallow angle with respect to the −Z direction, so that it is thinned to a level of 0.1 μm. At this time, the fixing portion 12 is also processed to be thin at the same time. Therefore, the thickness of the fixed portion 12 is limited also from the incident angle of the Ga ⁺ beam. Similarly, the thickness of the base 11 is also limited.

In the FIB processing stage, foreign matter or the like may adhere to the surface of the minute sample piece S due to reverse sputtering by irradiation with a Ga ⁺ beam. The generation source is the micro sample stage 10 and the base mesh 100. In particular, since the pedestal mesh 100 is made of a metal such as molybdenum, it is necessary to avoid Ga ⁺ beam irradiation to the pedestal mesh 100 as much as possible. For this purpose, a structure in which the micro sample table 10 is placed on the cut-out end surface 100A of the base mesh 100 is very effective.

  As shown in FIG. 2 (c), when the micro sample table 10 is fixed to the side surface of the pedestal mesh 100, a charged particle beam such as an ion beam is irradiated to the cut end surface 100 A of the pedestal mesh 100, and the pedestal mesh 100 is reversed. Sputter. In this regard, as in the embodiment of FIG. 2B, the charged particle beam can reverse-sputter the pedestal mesh 100 by installing the micro sample stage 10 on the upper surface of the cut end surface 100A of the pedestal mesh 100. Absent. In addition, in the micro sample stand which obtains such an effect, the guard part 13 is not an essential structure.

In addition, as a method of removing the foreign matter adhering to the surface of the micro sample piece S, for example, ion milling that irradiates the micro sample piece S from below the micro sample stage 10 with an Ar ⁺ beam at a low angle with respect to the YZ plane. A technique is used.

Next, the process from the process A to the process R shown in FIGS. 3 to 5, directions are represented by XYZ orthogonal coordinates corresponding to FIGS.
A large number of micro sample tables 10 of the present embodiment are manufactured by micro machining using a single crystal silicon wafer as a material, and the vertical direction (Z direction) of the micro sample table 10 is the thickness direction of the single crystal silicon wafer. It is formed.

  FIG. 3 is a diagram for explaining the manufacturing steps A to F of the micro sample stage 10, and FIGS. 3A1 to 3A6 are partial plan views of the single crystal silicon wafer on which the micro sample stage 10 is formed as viewed from above. 3 and FIGS. 3B1 to 3B6 are partial cross-sectional views taken along lines II-II in FIGS. 3A1 to 3A6, respectively.

  In step A, the single crystal silicon wafer 101 is bonded to the base substrate 102 with a thermosetting resin. In the bonding operation, a thermosetting resin paste is applied onto the base substrate 102 by a spin coater, the single crystal silicon wafer 101 is attached, and then heated with a hot plate. The base substrate 102 is for preventing a large number of minute sample bases 10 from being separated at the end of the manufacturing process, and any material may be used as long as it does not interfere with the manufacturing process. It is preferable to use the same material or a material with a small difference in thermal expansion coefficient.

In step B, a SiO ₂ film 103 is formed on the single crystal silicon wafer 101 by sputtering.
In step C, a resist 104 is applied to the surface of the SiO ₂ film 103 by a spin coater and prebaked using a hot plate.

  In step D, pattern exposure and development of the resist 104 are performed using a photomask using a mask aligner. An unnecessary resist layer outside the pattern is removed by development. As shown in FIG. 3 (a4), since the region including the three patterns formed in the X direction is a unit constituting one micro sample table 10, two units are shown in FIG. 3 (a4). Has been.

In step E, the SiO ₂ film 103 is wet-etched with buffered hydrofluoric acid using the resist 104 as a mask, and the portion of the SiO ₂ film 103 not covered with the resist 104 is removed.
In step F, the resist 104 used as a mask is removed by a remover.

  4A and 4B are diagrams for explaining the manufacturing steps G to L of the micro sample table 10, and FIGS. 4A1 to 4A6 are partial plan views of the single crystal silicon wafer as viewed from above, and FIGS. (B6) is a fragmentary sectional view which followed the II-II line | wire of Fig.4 (a1)-(a6), respectively.

In step G, an Al film 105 is formed by sputtering on the surface of the silicon wafer 101 on which the SiO ₂ film 103 is formed.
In step H, a resist 106 is applied to the surface of the Al film 105 by a spin coater, and prebaking is performed using a hot plate.

  In step I, a photomask is used and pattern exposure of the resist 106 is performed using a mask aligner. An unnecessary resist layer outside the pattern is removed by development. As shown in FIG. 4A3, one unit pattern formed in the X direction includes three large resist patterns 106b and two small resist patterns 106a.

In step J, the Al film 105 is wet-etched with a mixed acid P solution using the resist patterns 106a and 106b as a mask, and the Al film 105 not covered with the resist patterns 106a and 106b is removed. As a result, as shown in FIG. 4 (b4), on the single crystal silicon wafer 101, a large three-layer pattern composed of the SiO ₂ film 103b, the Al film 105b, and the resist 106b, and 2 composed of the Al film 105a and the resist 106a. A small pattern of layers remains.

In step K, the remaining resist patterns 106a and 106b are removed with a remover.
In step L, a resist 107 is applied to the surface on which the pattern is formed by a spin coater, and prebaking is performed using a hot plate.

  FIG. 5 is a diagram for explaining manufacturing steps M to R of the micro sample table 10, and FIGS. 5A1 to 5A6 are partial plan views of the single crystal silicon wafer as viewed from above, and FIGS. (B6) is a fragmentary sectional view which followed the II-II line | wire of Fig.5 (a1)-(a6), respectively.

  In step M, pattern exposure of the resist 107 is performed using a photomask using a mask aligner. An unnecessary resist layer outside the pattern is removed by development. Reference numeral 107A denotes a mask shielding area where the resist 107 remains. This remaining region is a region including the three large patterns 106b and the two small patterns 106a described in step I.

  In step N, the silicon wafer 101 is dry-etched in the thickness direction (−Z direction) by ICP-RIE (inductively coupled plasma-reactive ion etching) using the pattern of the resist 107 as a mask. As a result, a step is formed in the silicon wafer 101 as shown in FIG.

  In step O, the resist 107 used as a mask is removed with a remover. Thereby, the pattern of the Al films 105a and 105b is exposed.

  In step P, the silicon wafer 101 is dry-etched in the thickness direction (−Z direction) by ICP-RIE using the pattern of the Al films 105a and 105b as a mask. As a result, a step structure is formed in the silicon wafer 101 as shown in FIG. That is, 101a that becomes the fixing part 12 of the micro sample stage 10, 101b that becomes the guard part 13, and 101c that becomes the base part 11 are formed. Reference numerals 101 a, 101 b and 101 c are integrally formed from the single crystal silicon wafer 101.

In step Q, the pattern of the Al films 105a and 105b is removed by wet etching with a mixed acid P solution. As a result, the patterned SiO ₂ film 103b is exposed.

In step R, the silicon wafer 101 is dry-etched in the thickness direction (−Z direction) by ICP-RIE using the exposed pattern of the SiO ₂ film 103b as a mask. By this dry etching, the region of the silicon wafer 101 where the pattern of the SiO ₂ film 103b does not exist is uniformly reduced in thickness. As a result, the height of the 101a serving as the fixed portion 12 is lower than the thickness of 101b serving as the guard portion 13 by a uniform reduction in thickness. After the step R is completed, the remaining SiO ₂ film 103b is removed by wet etching with buffered hydrofluoric acid.

  6A and 6B are diagrams schematically showing the micro sample stage 10 created by the process of the above-described embodiment. FIG. 6A is a partial plan view seen from above, and FIG. 6B is FIG. It is a fragmentary sectional view in alignment with the II-II line of (a). As shown in FIG. 6, two micro sample tables 10 are formed by sequentially performing the manufacturing steps A to R described above. Finally, the individual micro sample table 10 is separated from the base substrate 102 used as a base, and the micro sample table 10 is completed.

  In the above manufacturing process, a series of manufacturing procedures for the two micro sample tables 10 has been described. However, the actual manufacturing process is a so-called batch process performed in units of silicon wafers. In this batch processing, a large number of minute sample bases 10 can be manufactured at once from one silicon wafer by micromachining mainly using photolithography, and a significant reduction in manufacturing cost can be expected. Furthermore, since the processing is performed so that the height direction of the micro sample table 10 is the thickness direction of the silicon wafer, the material can be used without waste.

  As described above, the plurality of micro sample tables simultaneously manufactured on the silicon wafer are integrated with the wafer on the bottom surfaces thereof. This is called a micro sample table assembly. That is, a large number of micro sample bases 10 created in a lump are connected by the base substrate 102 on the bottom surface thereof. Therefore, the handling and workability of the micro sample stage when singulated are improved.

  As shown in FIG. 1, the individually separated micro sample bases 10 are bonded and fixed to the cut end surface 100 </ b> A of the base mesh 100, and the sample holder 1 is completed. That is, in the sample holder 1 of the present embodiment, the side surface 11B of the micro sample table 10 is not fixed to the side surface 100B of the pedestal mesh 100, but as shown in FIG. The base mesh 100 is fixed up and down. Since the cut-out end surface 100A does not protrude from the side surface of the micro sample table 10, as shown in FIG. 2B, FIB is not irradiated during the thinning preparation of the micro sample piece S by FIB processing. . Therefore, contamination of the small sample piece S can be prevented, and observation and measurement with less background noise can be performed.

  In the micro sample table 10 of the present embodiment, for example, the guard part 13 is disposed in the vicinity of the fixing part 12 with the fixing part 12 interposed therebetween, so that the sample holder 1 is brought into contact with other members during transportation. Even if it is dropped, damage to the minute sample piece S can be avoided by the guard effect of the guard portion 13. In particular, since the guard portion 13 is provided close to the fixed portion 12 with respect to another member having a sharp tip, the guard effect of the guard portion 13 works effectively.

  In addition, since a large number of micro sample tables 10 can be manufactured simultaneously from a silicon wafer by a micromachining technique, the manufacturing cost per unit can be greatly reduced. Moreover, since the height direction of the micro sample stage 10 is the thickness direction of the silicon wafer, it is advantageous for material removal. Even in the micro sample bases 10, since the parts of the base 11, the fixing part 12, and the guard part 13 are integrally manufactured, variations in strength and dimensional accuracy are small.

  Various modifications are also conceivable for the micro sample stage 10 of the present embodiment. The arrangement and number of the fixing portions 12 and the guard portions 13 and the relative heights of the fixing portions 12 and the guard portions 13 can be arbitrarily changed. For example, a sample stage 10A having a multistage structure having a symmetrical shape as shown in FIG. 7A may be used, or a sample stage 10B having an asymmetric shape as shown in FIG. 7B may be used. Further, as shown in FIG. 7C, a sample stage 10C in which the fixing part 12A and the guard part 13A are integrated may be used. Further, as shown in FIG. 7D, a sample stage 10D provided with guard portions 13B on both sides of the plurality of fixing portions 12B1 to 12B3 may be used.

  In the above, the sample stage is created by photolithography, but in particular, the sample stage may be created by replacing steps P to R with dicing. Note that processing by photolithography processing and processing by photolithography processing and dicing processing can be called processing by micromachining technology.

  The present invention is not limited to the embodiments described above as long as the characteristics are not impaired. For example, the guard part 13 may not be integrally formed of silicon, but the guard part 13 made of a different kind of material may be added to the micro sample table 10 after the base part 11 and the fixing part 12 are formed.

It is a figure which shows typically the sample holder which concerns on embodiment of this invention, Fig.1 (a) is a front view, FIG.1 (b) is a II sectional view, FIG.1 (c) is FIG. It is the elements on larger scale of b). 2A is a perspective view schematically showing the structure of a micro sample table according to the embodiment, FIG. 2B is a diagram for explaining the effect of the embodiment, and FIG. 2C is a diagram for explaining a conventional problem. It is. It is a figure explaining manufacturing process AF of the micro sample stand which concerns on embodiment, FIG.3 (a1)-(a6) is a partial top view, FIG.3 (b1)-(b6) is FIG. It is a fragmentary sectional view along the II-II line of a1)-(a6). It is a figure explaining the manufacturing process GL of the micro sample stand concerning embodiment, FIG.4 (a1)-(a6) is a partial top view, FIG.4 (b1)-(b6) is FIG. It is a fragmentary sectional view along the II-II line of a1)-(a6). FIGS. 5A to 5A are partial plan views, and FIGS. 5B1 to 5B6 are views illustrating the manufacturing steps M to R of the micro sample table according to the embodiment, respectively. It is a fragmentary sectional view along the II-II line of a1)-(a6). It is a figure which shows typically the micro sample stand which concerns on embodiment, FIG. 6 (a) is a fragmentary top view, FIG.6 (b) is a fragmentary sectional view along the II-II line of Fig.6 (a). is there. It is a figure which shows the modification of the micro sample stand by this invention.

Explanation of symbols

1: specimen holder 10: the micro sample stage 11: base portion 12: fixing portion 13: guard portion 100: base mesh 100A: notch end surface (fixing surface) 101: silicon wafer 102: base substrate 103: SiO ₂ film 105: Al film S: Small sample piece

Claims (8)

A micro sample stage for fixing a micro sample to be processed,
A base having a top surface and a bottom surface parallel to the top surface ;
A plurality of fixing portions which are vertically provided so as to protrude from the upper surface of the base portion and to which the micro sample is fixed;
A plurality of columnar guard portions that are vertically provided so as to protrude from the upper surface of the base portion and have a protruding height higher than the fixed portion ;
The plurality of columnar guard portions are arranged such that the fixing portion is sandwiched between a pair of the columnar guard portions, and the fixing portions and the columnar guard portions are spaced apart and arranged alternately. Characteristic micro sample stage. In the micro sample stand according to claim 1,
A thickness of the fixed part and the guard part in the width direction of the upper surface is set so that the guard part is thicker than the fixed part . In the micro sample stand according to claim 1 or 2 ,
A micro sample stage, wherein the stacking direction of the base portion and the fixing portion is the thickness direction of a silicon wafer, and the silicon wafer is integrally manufactured from the silicon wafer by a micromachining technique. In the micro sample stand as described in any one of Claims 1 thru | or 3 ,
A micro sample stage, wherein the processing is a thinning process using a charged particle beam. It is a manufacturing method of the micro sample stand according to claim 3 ,
A method of manufacturing a micro sample table, wherein a groove is formed by etching or dicing from the surface of the silicon wafer to form the base portion, the fixing portion, and the columnar guard portion. A micro sample table assembly comprising a plurality of the micro sample tables according to claim 3,
A plurality of micro sample tables are formed on a common base substrate and integrated with each other . A micro sample stage according to claim 4 ,
Wherein the micro sample stage of the base is fixed, the sample holder and a base for supporting the micro sample stage. The sample holder according to claim 7 ,
The pedestal has a thin plate shape,
The bottom surface of the base is fixed to the end surface of the thin plate,
The thickness of the said thin plate is set thinner than the thickness of the said base, The sample holder characterized by the above-mentioned .

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