JP5191842B2 - Carbon deposition equipment - Google Patents

Description

  The present invention relates to a carbon vapor deposition apparatus for forming a conductive carbon thin film on a sample surface by evaporating and heating carbon (carbon).

  For example, when a sample is observed or analyzed using a charged particle beam apparatus such as a scanning electron microscope (SEM) or an electron probe microanalyzer (EPMA), Au (gold atomic symbol) or Pt (platinum element symbol) is used for the sample. In some cases, the sample is coated with a metal such as Pd (elemental symbol of palladium), an alloy thereof, or carbon.

  One of the purposes of coating metals such as Au, Pt, Pd and their alloys is to form a conductive thin film on the surface of a non-conductive sample, thereby preventing charge-up (charging) and thermal damage caused by irradiation of charged particles. Is to prevent. Another object is to obtain a high-quality secondary electron image by improving the generation efficiency of secondary electrons generated from the sample surface by irradiation with an electron beam, particularly when observing a secondary electron image with an SEM or the like. .

  On the other hand, when conducting elemental analysis of a non-conductive sample using EPMA, the conductive thin film coated on the sample is prioritized to be a substance that does not affect the analysis as much as possible. For this reason, it is necessary to avoid metals such as Au, Pt, and Pd and alloys thereof as much as possible, and to coat a material that has a small interaction with the electron beam irradiated on the sample. For the purpose of analyzing non-conductive samples, vacuum deposition apparatuses that coat carbon conductive thin films are widely used.

  Japanese Utility Model Laid-Open No. 5-756 of Patent Document 1 discloses a technique of an integrated carbon holder that allows a carbon rod used for vacuum deposition to be easily and quickly attached to a carbon holder. In addition, in Japanese Utility Model Publication No. 7-30674 of Patent Document 2, a large current is applied to carbon for a short time, and after a cooling time, a large current is applied again to evaporate the carbon. In other words, a technique for obtaining a high-quality carbon film with a low degree of vacuum by performing sputter deposition is disclosed.

Japanese Utility Model Publication No. 5-756 Japanese Utility Model Publication No. 7-30664 JP-A 52-62138

  In order to obtain a high-quality carbon film, there is a problem different from the case of coating a metal such as Au, Pt, Pd or an alloy thereof.

  For example, since carbon is more easily oxidized than metals such as Au, Pt, and Pd, a high vacuum is required during energization heating. In order to create a high vacuum in the vacuum chamber of the carbon deposition apparatus, it is necessary to provide an oil diffusion pump and a turbo molecular pump. Therefore, the apparatus is inevitably expensive, it usually takes about 30 minutes to obtain a high vacuum, the structure and operation of the vacuum system is complicated, the installation area and weight are increased, and high vacuum measurement is required. Therefore, there is a problem that an expensive vacuum gauge is required.

  In addition, when carbon is heated and evaporated in a high vacuum, the mean free path is long, and therefore, in the case of an uneven sample, there is a problem that uneven deposition of the vapor deposition material occurs due to the shadow effect. In order to solve the problem of the shadow effect, if the metal is Au, Pt, Pd or the like, as disclosed in Japanese Patent Laid-Open No. 52-62138 of Patent Document 3, the degree of vacuum is reduced and vapor deposition is performed. A method of causing vapor deposition without unevenness by causing wraparound of atoms (particles) is possible. However, as described above, since carbon is easily oxidized, it is difficult to form a high-quality conductive carbon film when vapor deposition is performed in an atmosphere with a low degree of vacuum. In order to solve the problem of the shadow effect when performing carbon deposition in a high vacuum, a method has been used in which the sample stage is tilted and rotated to uniformly change the direction of the sample and eliminate unevenness. However, the apparatus for tilting and rotating the sample stage is expensive, and there is a problem that it takes time and effort to operate.

  In addition, since carbon is heated to a high temperature, when a sample that is weak against heat is coated, the sample may be deformed or thermally damaged. Furthermore, since strong light is generated from high-temperature carbon, a protective jig such as sunglasses is required.

  Furthermore, as described in Japanese Utility Model Laid-Open No. 5-756 of Patent Document 1, the portion of the carbon rod that is evaporated by energization heating must be finely cut. A tool for that purpose is necessary, and there is a problem that it takes time and labor to prepare a carbon rod to be used.

  The present invention has been made to solve the above-described problems, and its object is to provide a carbon deposition apparatus capable of forming a high-quality conductive carbon film without unevenness in a short time with a simple operation. Is to provide.

In order to solve the above problem, an invention according to claim 1 is directed to an airtight container, an exhaust pump for exhausting the inside of the airtight container, a carbon member disposed in the airtight container so as to be electrically heated, A sample stage for holding the sample so that the surface of the sample can be seen through the carbon member in the hermetic container; and a gas supply means for filling the inert gas in the hermetic container, and the inert gas is contained in the hermetic container. By filling and exhausting with the exhaust pump, the carbon member is energized and heated in a state where the pressure in the hermetic container is set to 0.5 Pa to 5 Pa, and carbon is deposited on the surface of the sample held on the sample stage. It is characterized by doing.

The invention according to claim 2 is characterized in that the exhaust pump is a rotary pump.

The invention described in claim 3 is characterized in that the inert gas is argon gas.

  According to the present invention, it is not necessary to set the chamber of the vacuum deposition apparatus to a high vacuum, so that the deposition can be performed in a short time, the apparatus can be reduced in size and weight, the cost and the maintenance cost can be reduced, and the operation is facilitated. There is. Further, since an inert gas is present in the vacuum chamber, carbon particles can wrap around and a carbon vapor deposition film can be formed without unevenness. In addition, since the temperature rise of carbon due to electric heating is smaller than that in the conventional high vacuum method, deformation and thermal damage of a sample that is sensitive to heat can be significantly reduced. Since it is only necessary to simply attach the prefabricated carbon rod without any special processing, the labor and time required for preparation can be greatly reduced. Despite being produced in a low vacuum and in a short time, a high-quality carbon film equivalent to a carbon film produced under a conventional high vacuum can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited by this illustration.

  FIG. 1 is a diagram for explaining a schematic configuration example of a carbon deposition apparatus for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a basic body of a carbon vapor deposition apparatus, on which a power source, an operation panel and the like (not shown) are arranged. 2 is an airtight container, and a transparent material having vacuum resistance such as hard glass is usually used. A space surrounded by the airtight container 2 is defined as a sample chamber 2a. An O-ring 11 is disposed between the hermetic container 2 and the basic body 1, and the hermeticity of the sample chamber 2a can be maintained. When the leak valve (not shown) is opened to bring the sample chamber 2a to atmospheric pressure, the airtight container 2 can be removed from the basic body 1. A vacuum gauge (not shown) for monitoring the degree of vacuum in the sample chamber 2a is provided.

  S is a sample for carbon deposition, 4 is a sample stage for placing the sample S, and 3 is a carbon rod. 5a and 5b are electrodes for energizing the carbon rod 3, and 7a and 7b are electrode rods. It is. Both ends of the carbon rod 3 are fixed to the electrodes 5a and 5b by holding plates 6a and 6b, respectively. In FIG. 1, the holding plate is shown to be on the sample S side, but it is not necessary to limit to this position. It is sufficient that at least both ends of the carbon rod are attached so as to contact each electrode.

  Moreover, it is preferable that the distance between the carbon rod 3 and the sample S can be changed. For example, the distance between the carbon rod 3 and the sample S can be made variable by attaching the electrodes 5a and 5b to the electrode rods 7a and 7b by screwing and changing the screwing position.

  It is desirable to provide a shutter mechanism between the carbon rod 3 and the sample S. If there is a shutter mechanism, a preliminary operation such as baking out can be performed while the sample is placed on the sample stage.

  8 is a supply pipe for supplying argon gas (Ar) from an argon gas cylinder (not shown) to the sample chamber 2a, 8a is an argon gas flow rate adjusting valve, and 9 is an exhaust pipe for exhausting air and argon gas in the sample chamber 2a. , 9a is an exhaust pipe opening / closing valve, and 10 is a rotary pump (RP).

Next, a procedure for performing carbon vapor deposition using the carbon vapor deposition apparatus configured as shown in FIG. 1 will be described.
Step 1: With the on-off valve 9a and the flow rate adjustment valve 8a closed, the atmosphere is introduced into the sample chamber 2a and the airtight container 2 is removed.
Step 2: A sample S to be subjected to carbon deposition is placed on the sample table 4.

  Step 3: Both ends of the carbon rod 3 are attached to the electrodes 5a and 5b, respectively, and fixed with the pressing plates 6a and 6b. The carbon rod 3 preferably has a diameter of about 0.5 mm to 1 mm. The carbon rod marketed for the conventional carbon vapor deposition apparatus can be used as it is. Although it is possible to use a mechanical pencil lead, in this case, it is preferable to have an operation mode in which the binder contained in the lead is baked out before being used for vapor deposition.

  Step 3: The airtight container 2 is attached, the on-off valve 9a is opened, and the atmosphere in the sample chamber 2a is exhausted by the rotary pump 10. When the degree of vacuum in the sample chamber 2a becomes about 1 Pa, the argon gas is introduced so that the flow rate adjusting valve 8a is opened to introduce argon gas, and the vacuum in the sample chamber 2a is maintained at about 2 Pa while being evacuated by the rotary pump 10. Adjust the flow rate. The required flow rate of argon gas varies somewhat depending on the surface condition of the sample to be deposited, but if the argon gas in the sample chamber 2a is too small, the effect of wraparound is not sufficient, and conversely if too much, the carbon evaporation is hindered. It is done. Therefore, it is desirable that the degree of vacuum of the sample chamber 2a is set between approximately 0.5 Pa and 5 Pa when the carbon is heated by current.

  Step 4: A current of about 50 A is passed through the carbon rods through the electrode rods 7a and 7b and the electrodes 5a and 5b. When energized, the carbon rod becomes red hot and the carbon evaporates.

  Step 5: Stop energization when the carbon rod becomes thinner. The time required from the start of exhausting the atmosphere of the sample chamber 2a to the end of carbon deposition is about 5 minutes.

Step 6: The on-off valve 9a and the flow rate adjusting valve 8a are closed to introduce the atmosphere into the sample chamber 2a, the airtight container 2 is removed, and the sample S is taken out.
The above is description of the procedure which performs carbon vapor deposition using the carbon vapor deposition apparatus of this invention. In the above example, argon gas is used as the inert gas, but the same effect can be obtained with other inert gases. In step 3 above, the sample chamber 2a is maintained at a degree of vacuum necessary for carbon deposition while being evacuated by the rotary pump 10. However, if the degree of vacuum necessary for heating and heating the carbon can be maintained, the rotary chamber 10a is not necessarily rotary. There is no need to continue exhausting with the pump 10.
FIG. 2 is a transmission electron micrograph of a cross section of the carbon film taken to evaluate the film quality and film thickness of the carbon film produced by the carbon deposition apparatus of the present invention. A carbon film was deposited on a silicon substrate by the carbon deposition apparatus of the present invention, and Cr was coated on the carbon film in order to confirm the thickness of the carbon film accurately. In order to produce a thin film having a cross section of this sample, Ion Slicer (registered trademark) (trade name of JEOL Ltd., an apparatus for producing a thin film sample for transmission electron microscope observation by irradiating ions) was used.
From the transmission electron micrograph of FIG. 2, it can be confirmed that the carbon film has a thickness of about 13 nm and has a good amorphous structure.
As described above, by using the carbon vapor deposition apparatus of the present invention, it is possible to obtain a very good carbon film equivalent to a carbon film formed over time in a conventional high vacuum atmosphere in a short time.

The figure for demonstrating the schematic structural example of the carbon vapor deposition apparatus which implements this invention. The transmission electron microscope photograph image | photographed in order to confirm the film quality and film thickness of the carbon film produced with the carbon vapor deposition apparatus of this invention.

Explanation of symbols

S ... Sample 1 ... Basic body 2 ... Airtight container 2a ... Sample chamber 3 ... Carbon rod 4 ... Sample stand 5a, 5b ... Electrodes 6a, 6b ... Presser plates 7a, 7b ... Electrode rod 8 ... Supply pipe 8a ... Flow rate adjusting valve 9 ... Exhaust pipe 9a ... Open / close valve 10 ... Rotary pump (RP)
11 ... O-ring

Claims (3)

An airtight container, an exhaust pump for exhausting the inside of the airtight container, a carbon member arranged to be electrically heated in the airtight container, and a sample held in the airtight container so that the surface of the sample can be seen through the carbon member A sample stage and a gas supply means for filling the gas tight container with an inert gas, filling the gas tight container with the inert gas, and exhausting the gas with the exhaust pump; A carbon vapor deposition apparatus characterized in that the carbon member is energized and heated in a state set to 5 Pa to 5 Pa to deposit carbon on the surface of the sample held on the sample stage. The carbon vapor deposition apparatus according to claim 1, wherein the exhaust pump is a rotary pump. The carbon deposition apparatus according to claim 1, wherein the inert gas is an argon gas.

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