JPH10221227A - Sample for transmission electron microscope and method for preparing sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a sample in thin form easily and quickly in the condition that the damage of a place to undergo a section observation remains lesser. SOLUTION: A place to undergo a section observation 3 made by a transmission electron microscope is provided in a semiconductor device pattern 2 formed on a Si substrate 1. Centering on this place to be observed 3, a notch in stepped shape symmetrical to the left and right is formed using a dicing saw in the peripheral part of the place 3, followed by cutting out to provide a sample for observation. Then the extreme periphery of the place 3 is subjected to a sputter etching process to generate a thin form by means of low angle ion beam irradiation in which Ar is used as ion seed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a sample for a transmission electron microscope and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as the pattern of a semiconductor device has been miniaturized, the importance of a technique for observing and evaluating a specific minute portion of the semiconductor device by a transmission electron microscope (hereinafter abbreviated as TEM) has been increasing. However, in order to observe a specific minute part by TEM, the specific minute part is 0.3 μm
It has to be thinned to the following thickness, which is very difficult.

Conventionally, as a method for solving this problem, mechanical processing using a dicing saw apparatus and sputter etching processing using a focused ion beam (hereinafter abbreviated as FIB) processing apparatus are used in combination for cross-sectional observation. The most common method is to prepare a sample and observe a specific minute portion with a TEM.

[0004] Hereinafter, a method for manufacturing a sample for cross-sectional observation using the above-mentioned conventional dicing saw apparatus and FIB processing apparatus will be described with reference to the drawings. 11 to 15 show a method of manufacturing a sample for cross-sectional observation using a dicing saw device, and FIG. 16 shows an arrangement for processing a sample processed by a dicing saw device using a FIB processing device.
FIG. 17 is a perspective view showing an arrangement for TEM observation of the prepared sample.

As shown in FIG. 11, a semiconductor device pattern 2 is formed on a rectangular silicon (hereinafter abbreviated as Si) substrate 1, and a cross-sectional observation by TEM is performed in the semiconductor device pattern 2. Point 3 is marked. In preparing a sample, first, the Si substrate 1 configured as described above is fixed on a Si-based dummy chip 13 as shown in FIG. Next, as shown in FIG. 13, a pair of parallel cuts 18 for shaving off the periphery of the cross-section observation point 3 are formed by using a dicing saw device. Further, as shown in FIG. 14, the TEM is provided next to the cut 18 so that the dummy chip 13 can be cut.
The notch 19 for cutting out the sample is processed. Then, as shown in FIG. 15, a pair of cuts 20 are processed in a direction perpendicular to the cuts 18 and 19, and a TEM sample including the cross-section observation point 3 is completely cut out. Thereafter, the outer periphery of the cross-section observation point 3 is sputter-etched by the ion beam 21 using Ga of FIB as an ion species so as to have a configuration as shown in FIG.

The sample manufactured by the above method is arranged on a grid 8 in a state where a cross section can be observed by a TEM as shown in FIG.
Observed by irradiating a transmitted electron beam 17 from an electron gun and transmitting the transmitted electron beam.

[0007]

However, in the above-mentioned conventional method for manufacturing a sample for cross-sectional observation, in the method for manufacturing a sample for cross-sectional observation, the ion beam
It takes a lot of time, the skill of the worker,
It is essential to maintain the FIB processing device in a stable operation state. For this reason, there is a disadvantage that the cost for manufacturing the TEM sample increases, and there is a disadvantage that the cross-section observation portion 3 is damaged by sputter etching using Ga as an ion species.

In view of the above problems, an object of the present invention is to
It is an object of the present invention to provide a sample for a transmission electron microscope and a method for manufacturing the same, which can be easily and quickly cut in a short time and with little damage to an observation portion.

[0009]

In order to achieve this object, the present invention is to form a step-shaped inclined portion which is inclined with respect to the surface of a sample, around a section to be observed.

According to this, the processing for cutting out the sample for the transmission electron microscope and the step of forming the inclined portion around the cross-section observation point can be performed in parallel, and it is easy and in a short time. Sample can be manufactured. In addition, since the inclined portion is formed, it is possible to thin the cross-section observation portion by sputter etching the outer periphery of the cross-section observation portion at a small angle by an ion beam using Ar as an ion species,
Therefore, thinning can be performed with little damage to the observation site.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a semiconductor device pattern is formed on a silicon substrate, and a cross-sectional observation point observed by a transmission electron microscope is provided in the semiconductor device pattern. In the sample for an electron microscope, a step-shaped inclined portion inclined with respect to the sample surface is formed around the cross-section observation point.

According to this, the processing for cutting out the sample for the transmission electron microscope and the step of forming the inclined portion around the cross-section observation point can be performed in parallel, so that it can be performed easily and in a short time. Since the sample can be manufactured and the inclined portion is formed, it is possible to make the cross-section observation portion thin by sputter etching the outer periphery of the cross-section observation portion at a small angle with an ion beam using Ar as an ion species. Therefore, thinning can be performed at a low cost and with little damage to the observation site.

According to a second aspect of the present invention, the semiconductor device pattern is covered with a surface protecting glass. According to this, the surface of the semiconductor device pattern is reliably protected.

According to a third aspect of the present invention, when the sample is rotated around a central axis in a direction orthogonal to the normal line, the step-shaped inclined portion extends over the entire circumference during the rotation. The ion beam is formed so as to be able to irradiate a cross-section observation point from a direction having an angle with respect to a normal line.

According to this method, an ion beam using Ar as an ion species can be irradiated at a small angle with respect to the normal line of the sample over the entire circumference of the rotation of the sample, thereby enabling sputter etching. By using a sputter etching apparatus that is clearly less expensive than the processing using the FIB apparatus, the cost for manufacturing a sample can be reduced and a sample with less damage can be manufactured.

According to a fourth aspect of the present invention, there is provided a sample for a transmission electron microscope, wherein a semiconductor device pattern is formed on a silicon substrate, and a cross-sectional observation position observed by a transmission electron microscope is provided in the semiconductor device pattern. When manufacturing a sample, a step-shaped inclined portion that is inclined with respect to the sample surface is formed around the cross-section observation point.

This makes it possible to perform the processing for cutting out the sample for the transmission electron microscope and the step of forming the inclined portion around the cross-section observation point in parallel, and therefore, the sample can be easily and quickly obtained. Since the inclined portion was formed, the outer peripheral portion of the cross-section observation point could be sputter-etched at a small angle with an ion beam using Ar as an ion species to thin the cross-section observation point, Therefore, thinning can be performed at a low cost and with little damage to the observation site.

According to a fifth aspect of the present invention, the processing for forming the inclined portion is performed in parallel with the processing for cutting out the sample from the material. In this case, the sample can be manufactured easily and in a short time.

According to a sixth aspect of the present invention, the sample has a rectangular shape in plan view, and a short side of the rectangular sample is cut out with a certain thickness remaining at the bottom of the sample, and then the sample is inclined. A process for forming a portion is performed, and then the long side of the sample is completely cut out of the material.

By cutting out the short side of the sample while leaving a certain thickness at the bottom of the sample, the sample is prevented from falling off during processing.

According to a seventh aspect of the present invention, the semiconductor device pattern is covered with a surface protecting glass, and then the inclined portion is processed together with the surface protecting glass.
This prevents the sample surface from being damaged during processing. In addition, damage to the sample surface when the cross-section observation site is thinned by sputter etching the outer periphery of the cross-section observation site at a small angle with an ion beam using Ar as an ion species is prevented.

According to an eighth aspect of the present invention, an inclined portion is processed by using a dicing saw device. With this configuration, it is possible to specifically realize that the processing for cutting out the sample and the step of forming the inclined portion around the cross-section observation point are performed in parallel.

According to a ninth aspect of the present invention, the method comprises rotating the sample, on which the stepped inclined portion is formed, around a central axis in a direction perpendicular to the normal line, and rotating the sample over the entire circumference during the rotation. By irradiating an ion beam to a section observation point from a direction having an angle with respect to the line, an extremely peripheral portion of the section observation point is removed.

This makes it possible to irradiate the ion beam using Ar as an ion species at a small angle along the inclined portion. Can be

According to a tenth aspect of the present invention, the ion species of the ion beam is Ar. This makes it possible to produce a sample in a short time and easily by using sputter etching using Ar as an ion species, and to produce a sample at a low cost by using a sputter etching apparatus that is less expensive than a conventional FIB apparatus. Can be.

Hereinafter, an embodiment of a TEM sample according to the present invention will be described with reference to the drawings. FIG.
FIG. 3 shows a cross-sectional view of a TEM sample according to the present invention, which is manufactured using a dicing saw apparatus. Here, the Si substrate 1
A semiconductor device pattern 2 is formed thereon, and a cross-section observation point 3 is marked in the semiconductor device pattern 2. A very thin surface protection glass 4 (such as a cover glass) is fixed on the semiconductor device pattern 2 including the cross-section observation point 3 with an epoxy resin. S
The i-substrate 1 is processed into a symmetrical step-like shape having a configuration in which both sides thereof are inclined with the portion of the semiconductor device pattern 2 in which the cross-section observation point 3 is described as an apex. Reference numeral 5 denotes a surface indicating the flat portion of the staircase shape, 6 denotes a surface indicating the height of the staircase shape, and 7 denotes a surface indicating the lowest flat portion of the staircase shape.

This step-like shape can be formed, for example, by processing with a dicing saw device. The dimensions of each part will be described below.
Is 6 μm, and the height 6 of the stepped shape is 30 μm. Only the top of the staircase shape including the section observation point 3 has a width of 1
The height is set to 30 μm plus the thickness of the surface protection glass 4. The flat portions 5 and 7 having the stepped shape have seven steps except for the surface portion of the top surface protection glass 4. The sample shape is symmetrical about the cross-section observation point 3 as described above, and the height from the surface of the semiconductor device pattern 2 to the lowermost flat portion 7 of the stepped shape is 210 μm. Is about 1/3 of the height of the entire sample excluding the surface protection glass 4 (in the case of a 6-inch wafer).

After the above processing by the dicing saw device, the obtained TEM sample is fixed laterally to the single-hole grid 8 as shown in FIG. 2, and is perpendicular to the normal N of the surface of the semiconductor device pattern 2. In addition, it is rotatable about a central axis 9 corresponding to the section observation point 3. 10
Is an ion gun using Ar as an ion species, and irradiates an ion beam 11 in an oblique direction along a stepwise shape of a TEM sample. Reference numeral 12 denotes an incident angle of the ion beam 11 with respect to the normal line N. In this manner, the ion beam 11 emitted from the ion gun 10 enables the extreme peripheral portion of the cross-section observation point 3 in the semiconductor device pattern 2 to be sputter-etched.

It should be noted that the above-mentioned numerical values for the stepped shape in the periphery of the cross-section observation point 3 shown in FIG. 1 indicate that the incident angle 12 of the ion beam 11 shown in FIG. On the other hand, when it is 12 degrees, it is a numerical value obtained by a trigonometric function.

In the above description, the numerical values of the stepped shape were calculated based on the case where the incident angle 12 of the ion beam in the sputter etching using Ar as the ion species was 12 degrees. It is needless to say that the same effect can be obtained by using a numerical value as required in consideration of a sputter etching rate due to a difference in a material, an ion species, and a configuration between an ion gun and a sample position.

Hereinafter, a method for producing the above TEM sample using a dicing saw will be described with reference to the drawings. 3 to 10 show the procedure of processing using a dicing saw device.

FIG. 3 shows an example of a material for forming a sample for cross-sectional observation, and the structure is the same as that of FIG. That is, a semiconductor device pattern 2 is formed on a rectangular Si substrate 1, and a cross-section observation point 3 is marked in the semiconductor device pattern 2.

First, as shown in FIG. 4, a glass 4 for surface protection is fixed with an epoxy resin on the semiconductor device pattern 2 including the section 3 for observation. The surface protecting glass 4 is necessary to prevent the sample surface from being damaged when processed by a dicing saw device and from being damaged by sputter etching using Ar as an ion species. Next, the sample processed in this manner is fixed on the dummy chip 13 as shown in FIG. 5, and further fixed on the sample table of the dicing saw device.

Then, as shown in FIG. 6, a pair of cut grooves 14 are formed at intervals of 2.5 mm around the cross-section observation point 3.
To form At this time, the depth of the cut groove 14 is Si
It should be about 50 μm above the boundary between the substrate 1 and the dummy chip 13. That is, 50 μm
The cut groove 14 is formed while leaving a thickness of the order of magnitude.
This is because the width of the rectangular TEM sample needs to be reduced from １ ／ to 比 べ as compared with the processing using the conventional dicing saw device, so that the bonding area between the Si substrate 1 and the dummy chip 13 is reduced. This is for the purpose of improving the adhesion durability between the TEM sample and the dummy chip 13 because the TEM sample tends to fall off and drop off. 50μ
If it is more than m, the sample is easily damaged when the sample is removed from the dummy chip 13, and if it is less than 50 μm, the sample for TEM tends to drop off.

Next, as shown in FIG. 7, the cut grooves 14 machined at 2.5 mm intervals as described above
A pair of cut grooves 15 are machined in the direction of degree at intervals of 10 μm around the cross-section observation point 3. The depth of the cut groove 15 is 30 μm from the surface of the semiconductor device pattern 2.

Further, as shown in FIG. 8, a step-like cutting is performed. In detail, following the cut groove 15,
A pair of cut grooves are formed in a direction away from the cross-section observation point 3 to the left and right with a width of 6 μm in parallel with the cut grooves 15 and a depth of 60 μm from the surface of the semiconductor device pattern 2. Then, the number of cuts is set to one, and the same cut grooves are repeated 7 times in total including the cut grooves 15 by increasing the groove width to 6 μm and increasing the groove depth by 30 μm. The seventh depth of cut is 210 μm from the surface of the semiconductor device pattern 2.

Finally, as shown in FIG. 9, on both sides of the seventh cut position, up to a position 50 μm below the boundary between the Si substrate 1 and the dummy chip 13, that is, up to a position where it enters the inside of the dummy chip 13. , Cut groove 1
6 is formed.

By processing using the above dicing saw device, a TEM sample having a step-like shape as shown in FIG. 1 can be processed. The TEM sample thus manufactured is detached from the dummy chip 13, and sliced around the cross-section observation point 3 by sputter etching using Ar as an ion species in a configuration as shown in FIG. Then, with a configuration as shown in FIG. 10, the sample is placed in a state where a cross-section can be observed by a TEM, and the cross-section observation portion 3 of this sample is irradiated with a transmission electron beam 17 from an electron gun of the TEM and transmitted therethrough. Observe.

Here, Ar was used as an ion species when calculating the numerical values of the positions and depths of the cut grooves by the dicing saw device in correspondence with the numerical values of the stepped shape of the TEM sample shown in FIG. Although the case where the incident angle 12 of the ion beam 11 in the sputter etching was set to 12 degrees was applied, similarly, the sputter etching speed due to the difference between the sample material, the ion species, and the configuration of the ion gun and the sample position was considered, It goes without saying that the same effect can be obtained by using a numerical value as required.

[0040]

As described above, according to the present invention, a stepped inclined portion which is inclined with respect to the sample surface is formed around the cross-section observation point, so that processing for cutting out the sample for the transmission electron microscope can be performed. In addition, the step of forming an inclined portion around the cross-section observation point can be performed in parallel. Therefore, not only can the sample be manufactured easily and in a short time, but also since the inclined portion is formed, Ar By using the ion beam as the ion species, the cross-section observation point can be thinned by sputter etching the outer periphery of the cross-section observation point at a small angle. By using a sputter etching apparatus that is clearly cheaper than the conventional FIB apparatus, the manufacturing cost of the TEM sample can be reduced, and an ion using Ar as an ion species can be obtained. Beam, it is possible to obtain a less optimum TEM sample of damage by sputter etching.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a sample for a transmission electron microscope according to an embodiment of the present invention.

FIG. 2 is a layout diagram showing a relationship between the transmission electron microscope sample of FIG. 1 and a sputter etching process using an ion beam.

FIG. 3 is a perspective view of a material for manufacturing the sample of FIG. 1;

FIG. 4 is a perspective view illustrating a process for manufacturing the same sample.

FIG. 5 is a perspective view illustrating a process at the next stage of FIG. 4;

FIG. 6 is a perspective view illustrating a process at the next stage of FIG. 5;

FIG. 7 is a perspective view illustrating a process at the next stage of FIG. 6;

FIG. 8 is a perspective view illustrating a process at the next stage of FIG. 7;

FIG. 9 is a perspective view illustrating a process at the next stage of FIG. 8;

FIG. 10 is a layout diagram showing a relationship between a cross-sectional observation sample of the present invention and an electron beam of a transmission electron microscope.

FIG. 11 is a perspective view of a conventional material for manufacturing a cross-sectional observation sample.

FIG. 12 is a perspective view illustrating a step for manufacturing the same sample.

FIG. 13 is a perspective view illustrating a process at a next stage of FIG. 12;

FIG. 14 is a perspective view illustrating a step in the next stage of FIG. 13;

FIG. 15 is a perspective view illustrating a step in the next stage of FIG. 14;

FIG. 16 is a perspective view illustrating a step in the next stage of FIG. 15;

FIG. 17 is a layout diagram showing a relationship between a conventional cross-sectional observation sample and an electron beam of a transmission electron microscope.

[Description of Signs] 1 Si substrate 2 Semiconductor device pattern 3 Cross-section observation point 4 Glass for surface protection

Claims (10)

[Claims] 1. A sample for a transmission electron microscope in which a semiconductor device pattern is formed on a silicon substrate, and a cross-sectional observation position observed by a transmission electron microscope is a sample for a transmission electron microscope provided in the semiconductor device pattern. A sample for a transmission electron microscope, characterized in that a step-shaped inclined portion inclined with respect to the sample surface is formed around a portion. 2. The sample for a transmission electron microscope according to claim 1, wherein the semiconductor device pattern is covered with glass for surface protection. 3. The step-shaped inclined portion has an angle with respect to the normal over the entire circumference when the sample is rotated around a central axis in a direction orthogonal to the normal. The ion beam is formed so as to be able to irradiate a section observation point from a set direction.
The sample for a transmission electron microscope according to the above. 4. A semiconductor device pattern is formed on a silicon substrate, and a cross-sectional observation point observed by a transmission electron microscope is used for manufacturing a transmission electron microscope sample provided in the semiconductor device pattern. A method for manufacturing a sample for a transmission electron microscope, comprising forming a stepped inclined portion with respect to the surface of a sample around an observation point. 5. The method for manufacturing a sample for a transmission electron microscope according to claim 4, wherein the processing for forming the inclined portion is performed in parallel with the processing for cutting out the sample from the material. 6. The sample is rectangular in plan view,
After cutting out the short side of this rectangular sample with a certain thickness remaining at the bottom of the sample, processing for forming the inclined portion is performed, and then the long side of the sample is completely cut out of the material. The method for producing a sample for a transmission electron microscope according to claim 4 or 5, wherein: 7. The transmission according to claim 4, wherein the semiconductor device pattern is covered with a surface protection glass, and the inclined portion is processed together with the surface protection glass. A method for manufacturing a sample for an electron microscope. 8. The method for producing a sample for a transmission electron microscope according to claim 4, wherein the inclined portion is machined by using a dicing saw device. 9. While rotating a sample having a stepped inclined portion formed around a central axis in a direction perpendicular to the normal line, the sample has an angle with respect to the normal line over the entire circumference during the rotation. 9. A method for manufacturing a sample for a transmission electron microscope according to claim 4, wherein an extremely peripheral portion of the cross-section observation point is removed by irradiating the cross-section observation point with an ion beam from the set direction. . 10. The method for producing a sample for a transmission electron microscope according to claim 9, wherein the ion species of the ion beam is Ar.