JP2754301B2 - How to make a sample for electron microscope observation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a sample for electron microscopic observation (hereinafter simply referred to as "sample"), and more particularly to a method for preparing a sample suitable for observing a very small specific region.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional sample preparation method. This method will be described. FIG. 2A shows a silicon wafer 5 in which an IC is formed. In the manufacturing process, first, a silicon wafer 5 or a diamond pen 6 is used to make a scratch, cleave a small piece, and cut out a silicon wafer piece 51. The silicon wafer piece 51 has a shape as shown in FIG.
× 1.5mm × thickness.

As shown in FIG. 2 (C), the 1.5 mm × 1.
Adhere 5mm x thickness silicon wafer pieces 51 to each other with adhesive (the upper silicon wafer piece is 51 ')
. As shown in FIG. 2 (D), the bonded silicon wafer pieces
Put 51 and 51 'on the bottom surface of the weight 72 of the polishing jig 71. Then, polishing is performed thinly on the polishing plate 73 using the polishing agent 74. The surface to be polished is the surface 511 shown in FIG.

The polished silicon wafer pieces 51, 51 'are taken out of a polishing jig 71, and as shown in FIG.
The silicon wafer pieces 51 and 51 'are attached to the rotating sample table 81, and the surface 511 is further polished. In this case, since the silicon wafer piece is simultaneously rotated using the polishing jig 82 while rotating the silicon wafer piece, the surface to be polished has a mortar shape.

As shown in FIG. 2F, in order to further thin the mortar-shaped silicon wafer piece, the charged particle beam 91 is directed at a shallow angle, for example, θ = 10-45 degrees with respect to the silicon wafer piece. While irradiating with the degree, rotate the silicon wafer piece, and proceed to thinning in a mortar shape,
A part of the hole was polished to the extent that the hole was opened, and the extremely thin part around the hole was observed using a transmission electron microscope.

[0006]

In the prior art, the positioning accuracy of sample preparation for observing a specific area is about ± 0.5 mm, and a specific area such as less than 1 μm can be observed. It was impossible to produce a perfect sample. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a sample which can be observed with an electron microscope with a specific extremely high alignment accuracy.

[0007]

According to the present invention, in order to achieve the above object, first, a process for leaving a very small part of a surface layer including a specific observation region is aligned while observing with a high-performance microscope. Processing is performed using a high-speed rotating peripheral blade processing device.

[0008] In this case, the above-mentioned processing is performed so that the work time is short in final thinning with the converged charged particle beam, which is the next step, and the processing is hardly broken during processing such as cutting. Processing is performed only on the surface layer portion as narrow as possible and as shallow as possible.

Further, in order to cut into a size that can be mounted in the body of an electron microscope in a state including a specific observation area, a predetermined high-speed rotating outer edge processing device is used while observing with a high-performance microscope. Cut to thickness. Thereafter, the sample including the specific observation region and formed by the above processing is further sliced using a focused charged particle beam.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a drawing showing one embodiment of the present invention.
, (B) and (C) show the state of the first stage of machining with the high-speed rotating peripheral cutting machine, and (D) shows the thinning FIB machining with the convergent charged particle beam machine. (E) shows a diagram observed by an electron microscope.

First, as shown in FIG. 1 (A), a high-speed rotating outer peripheral cutting device having a width of thickness a which can be attached to an electron microscope including a specific place (a part indicated by a cross in the figure) requiring observation. (However, only the outer peripheral blade 2 is shown), and the sample 11 is cut out.

At this time, a high-performance optical microscope (magnification of 1000 or more as an example) is attached to the high-speed rotating outer peripheral edge processing apparatus to be able to observe a specific observation place (not shown in the figure). A hairline is used to position a specific place to be observed, and a cut is made at a specific place with the blade 2 of the high-speed rotating peripheral blade processing device.

The width a is set to 100 μm in the embodiment and is a thickness that can be mounted on an electron microscope, and the thicker the film is, the harder it is to be damaged. Selection is made in consideration of the shape of the part and the ease of handling of the sample. In FIG. 1 (A), b is a cutting width when cutting by the rotating outer peripheral blade. Next, as shown in FIG. 1B, a specific observation place is marked. Including this inscription, a cut is made with a width of c and a depth of d, and only the surface layer is thinned so that the cross section of the sample 11 becomes convex. In the embodiment, processing is performed with c = 10 μm and d = 30 μm.

[0014] The specific observation place (the place of the cross) is 10
Since it may be difficult to observe even a microscope with a high magnification of 00 or more, the laser processing device (omitted in the figure) is provided by excluding the specific place by several μm in order to distinguish the specific place (x mark) in the embodiment. In order to distinguish it from other places, a few traces of machining were provided as inscriptions with a diameter of 0.1 μm.

The laser processing apparatus uses a laser oscillator mounted on an optical microscope, and is basically the same as the optical microscope mounted on a high-speed rotating peripheral blade processing apparatus. The object may be small.
In that case, a microscope of a convergent charged particle beam processing apparatus can be used to make the marking more accurate.

As described above, according to the convergent charged particle beam apparatus, it is possible to observe at a higher magnification than an optical microscope, and it is also possible to imprint by fixing the converged charged particle beam at one place. Therefore, if the engraving process performed by the laser processing device is performed using a convergent charged particle beam, an engraving that can be observed with an optical microscope at a high magnification of several thousand to 10,000 times is provided, It is possible to process only the surface layer including the specific position with the width C and the depth d while checking the engraved mark that can be observed with the optical microscope attached to the apparatus.

Note that the high-speed rotating outer peripheral edge machining apparatus has a positioning accuracy of 0.1 μm invented to enhance the positioning accuracy.
(This high-speed rotating outer peripheral edge processing device has applied for a patent. Japanese Patent Application No. 03-119441).

The cutting width b shown in FIG. 1A is the same as that of FIG.
In this case, as shown by b ', the material 1' and the material 1 'are prevented from tilting during the processing of (B).
This is because 1 ″ is brought close to the sample 11 and the sample 11 is fixed. The sample 11 is fixed to the processing stage (omitted in the figure) using a heat-soluble wax, and as shown in FIG. Heats the stage to melt the wax and sample material 1'1 "
11 and the wax wraps around the minute gap,
The sample 11 is firmly fixed with the material 1 "1".

Next, as shown in FIG. 1C, FIG.
A cut is made at right angles to the processing direction shown in (B), so that it can be mounted on an electron microscope. In the embodiment, the dimension in the longitudinal direction is set to about 1.5 mm. As shown in FIG. 1 (D), the sample 11 is etched by scanning the focused particle beam 3 in the longitudinal direction of the sample (the direction of the arrow). That is, the upper surface of the sample 11 having the convex cross section is etched to be more convex. In the embodiment, e = 0.1 μm in FIG. In order to observe the image of the electron microscope well, it is better to finish it thinner. At the time of thinning, a metal such as tungsten is preferably deposited on the surface in order to protect the surface portion.

FIG. 1E conceptually shows a state where the electron beam 4 penetrates after the sample shown in FIG. It is a drawing. It is better that the unprocessed width is small in order to transmit the electron beam. Although the unprocessed width e changes depending on the acceleration voltage of the electron microscope, an electron microscope image which is better when finished is thinner is obtained.

The observation sample shown in FIG. 1E is actually placed on an electron microscope sample support called a mesh and placed on an electron microscope sample stage so that the sample can be easily fixed. Is done.

[0022]

According to the method for preparing a sample for electron microscopic observation of the present invention, a specific observation site can be selectively sliced, and the positioning accuracy, which was about 0.5 mm in the prior art, is plus or minus. It can be dramatically improved to 0.1 μm or more. This accuracy is restricted by the degree of convergence of the focused charged particle beam. If the convergence of the focused charged particle beam is improved, the accuracy can be further increased.

Further, by using and manufacturing the high-speed rotating outer peripheral edge processing apparatus, the time required for thinning by the final convergent charged particle beam apparatus, particularly the time required for the step of roughly etching and removing the periphery of a specific observation place, is reduced. Can be shortened. That is, it is possible to shorten the sample preparation time as a whole.

From the viewpoint of work efficiency, in the prior art, a slice preparation place is often shifted from a specific position where observation is required, and sample preparation is often repeated. According to the present invention, since the thinning operation is performed while observing the secondary electron detection image of the optical microscope and the converged charged particle beam device at a high magnification, it is possible to substantially eliminate the necessity of redoing and the like, which is very convenient. It is.

[Brief description of the drawings]

FIG. 1 is a drawing according to the present invention, wherein (A), (B), (C)
Is a diagram showing the first stage of processing using a high-speed rotating outer edge processing device, and FIG. (D) is a thinning FIB using a convergent charged particle beam device.
The figure in which processing is being performed, and the figure (E) is a figure observed with an electron microscope.

FIG. 2 is a drawing related to the prior art, showing a method of preparing a sample.

[Explanation of symbols]

 11 Specimen 1, 1 'Material 2 High-speed rotating peripheral cutting machine blade 3 Convergent charged particle beam

──────────────────────────────────────────────────続 き Continued on the front page (72) Isao Watanabe, Inventor 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Kenji 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-1-219536 (JP, A) JP-A-2-132345 (JP, A) JP-A 64-84730 (JP, A) JP-A-4-763737 (JP, A) JP-A-4-361132 (JP, A) JP-A-4-322442 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 1/28 G01N 1/32 H01J 37/20

Claims (2)

(57) [Claims] 1. A material requiring observation with an electron microscope is observed with the optical microscope using a high-speed rotating peripheral blade processing apparatus equipped with a high-magnification optical microscope, and the width is set to a width that can be mounted on the electron microscope. A step of cutting the material, a step of imprinting a specific observation place, a step of processing the cut material into a convex or L-shaped cross section while leaving the mark, and etching with a focused charged particle beam Thinning the upper surface of the convex or L-shape into a convex or L-shape by using the method described above. 2. The method according to claim 1, wherein the engraving is performed by a laser processing device or a focused charged particle beam device.