JP3117687B2 - Aperture plate and processing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aperture plate and a processing method therefor, and more particularly to a high-precision aperture plate suitable for an electron beam application apparatus such as an electron microscope and a processing method therefor.

[0002]

2. Description of the Related Art Conventionally, in an electron beam application apparatus such as an electron microscope, an aperture plate has been used to adjust a beam diameter of an electron beam. This aperture plate is, for example, as described in JP-A-04-206244,
It is a high melting point metal plate made of molybdenum or the like with minute through holes, and its surface is coated with platinum or platinum-palladium to prevent charging and contamination.

[0003]

In the conventional aperture plate as described above, etching is used as a method for making holes in the aperture plate. However, the resist used for etching a molybdenum metal plate is as follows. Unlike resists used in ordinary semiconductor manufacturing and the like, those having high heat resistance, corrosion resistance, and acid resistance are used. However, the resist used during etching is not completely removed,
If the aperture plate remains on the surface of the aperture plate, the surface of the residual resist, which is an insulator, will be charged and affect the electron beam when the aperture plate is attached to an electron microscope and used.
There is a problem that contamination (impurity source) and the like occur, and the resolution cannot be improved.

[0004] Further, even when coating with platinum or the like, the coated metal is evaporated by repeated heating by passing an electron beam in a portion where the resist remains,
There has been a problem of thermal damage that peeling is easy.
Then, a resist as an insulator appears on the surface due to the evaporation, and there is a problem that the above-described problem is reproduced. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an aperture plate capable of achieving and maintaining a high resolution and a processing method thereof.

[0005]

SUMMARY OF THE INVENTION The present invention is characterized by a cleaning step capable of completely removing the residual resist from the aperture plate, or a coating step of coating the surface of the aperture plate with osmium. According to the present invention, the residual resist on the aperture plate after the hole drilling by etching is more completely removed as compared with the conventional method,
Problems such as charging, contamination, and peeling of the coating are reduced, and the resolution is improved. Further, the coated osmium forms a hard bond film layer, and a uniform conductive amorphous thin film at the molecular level is formed on the surface of the aperture plate, so that deterioration of resolution can be prevented.

[0006]

Embodiments of the present invention will be described below in detail. FIG. 1 is an explanatory view showing a part of a process of processing an aperture plate to which the present invention is applied. For example, the process of manufacturing an aperture plate for an electron microscope can be roughly divided into three processes. First, the first step is a step of making a hole of a predetermined size by etching a molybdenum metal plate. The molybdenum plate, which is a material, is first fired in a vacuum furnace, finished to a predetermined thickness and surface by a rolling roller, and then heat-treated in a hydrogen furnace in a state of leaning against it. Thereafter, a hole having a predetermined diameter is formed by etching by a known method.

The photoresist used at this time is, for example, a mixture of xylene, ethylbenzene, cyclized polyisobrene and the like. Unlike a resist usually used for semiconductor production, heat resistance of 1000 ° C. or more, corrosion resistance, and sulfuric acid Rich in acid resistance to HF and hydrofluoric acid. Therefore, after drilling, for example, the well-known RIE (reactive ion etching)
Although the resist is removed to some extent by the apparatus, the resist is not sufficient as an aperture plate, and the resist still remains on the surface of the aperture plate 10 subjected to the resist removal processing.

In the method according to the embodiment of the present invention, a cleaning step is performed to remove the resist. FIG. 1 shows this cleaning step. In the cleaning step, first, ten aperture plates (10) in which drilling is completed are prepared. And
"UGR sulfuric acid" (concentration 97%, for precision analysis) 50cc (1
1) was placed in a beaker, and this was placed in a known heating device 1
2 to 80-120 degrees Celsius. Then, put 10 squeezing plates in the heated UGR sulfuric acid 11,
Maintain the temperature for 10-20 minutes.

Thereafter, only the UGR sulfuric acid 11 is discarded,
Inject 50 cc (14) of the "EL mixture" heated to 30 to 70 degrees Celsius into the beaker containing the diaphragm plate 10.
EL mixture is EL sulfuric acid (concentration 96%, for electronics industry)
And EL hydrogen peroxide solution (concentration 30%, for electronics industry)
The mixture was mixed at a ratio of 1 to 6 to 1. The beaker is set in the ultrasonic cleaning device 15 for about 40 seconds to 1 minute to clean the aperture plate 13. After the washing, the EL mixture 14 is discarded.

Next, distilled water 17 heated to 40 ° C. to 50 ° C. is poured into a beaker containing a diaphragm plate 16 and poured and washed, and this is repeated twice. Furthermore, take the squeezing plate into a net basket, put the basket in a beaker,
Add 150 cc of distilled water heated to 0 degree, set in the ultrasonic cleaning device 15, and perform ultrasonic cleaning for 1-2 minutes. This ultrasonic cleaning is repeated several times. Finally, the squeezing plates are taken out one by one, inserted into a microtube, and dried by heating at about several hundred degrees Celsius. The inventor has confirmed that the dry resist remaining after the etching step by the above-described cleaning step is almost completely removed by checking the aperture plate after the cleaning step processing with an electron microscope.

Next, the coating step will be described.
FIG. 2 is an explanatory diagram showing the coating step of the present invention. In the coating process, first, the gas in the vacuum vessel 21 of the coating device 20 is exhausted. A rotary pump is generally used for evacuation in a commercially available coating apparatus 20, but a rotary pump can obtain only a degree of vacuum of about 10 −2 Torr. When a metal diaphragm plate is coated at such a low vacuum, a uniform film thickness can be formed on the surface of the diaphragm plate, unlike the film formation on the insulator surface, which is the purpose of a commercial coating device. Experiments have shown that it is difficult and uneven. Although the reason for the unevenness is not clear, it is presumed that the unevenness is caused not only by the fat component remaining on the surface of the diaphragm plate but also by the effect of oxygen and water vapor remaining in the vacuum vessel.

Therefore, in the embodiment of the present invention in which the surface of the metal diaphragm plate is coated, the cleaning process, which is a pretreatment, is sufficiently performed.
By using a well-known oil diffusion (diffusion) pump as an exhaust pump, for example, 10 minus 4
Ensure a vacuum of ~ 5 torr. Further, by injecting an inert gas such as an argon gas, a helium gas, a nitrogen gas or the like after the evacuation and evacuating again, the concentrations of oxygen and water vapor can be further reduced. The injection of the inert gas and the exhaust may be repeated a plurality of times. In the present invention, since the concentration of the impurity gas is reduced by the above-described method, unevenness of the coating film thickness is eliminated, and uniform film formation can be stably performed.

As the metal to be coated, osmium tetroxide is used. When the aperture plate is coated with platinum or platinum-palladium, the metal is crystallized (granulated) and the coating surface is not uniform and smooth, but in the case of osmium according to the present invention, it is uniform and hard. It becomes an amorphous thin film, and has better conductivity than conventional metals. The melting point of osmium is 270 degrees Celsius.
Since it is as high as 0 degrees and there is no damage due to the electron beam irradiation of the electron microscope, it is possible to irradiate a sufficiently focused strong electron beam at a high accelerating voltage, and to bring out the resolution of the electron microscope to the limit.

For the coating treatment, a commercially available coating apparatus can be applied. For example, a plasma coating apparatus (NL-OPC80N) manufactured by Nippon Laser Electronics Co., Ltd. may be applied. This plasma coating apparatus introduces a small amount of osmium tetroxide crystal placed in a sublimation tube into a small-capacity gas reactor equipped with an anode plate and a cathode plate, and sets the selected sublimation gas pressure to a selected DC glow discharge. Glow discharge is generated by voltage. Then, the space between the electrodes is instantaneously turned into a plasma state to emit light. At this time, ionized osmium molecules are instantaneously adhered and deposited on the surface of the diaphragm plate 18 placed in the negative glow phase region on the cathode plate to form an amorphous osmium thin film. The film thickness to be coated is about several nanometers to several tens of nanometers. Through the above process, the resist remaining on the diaphragm plate is completely removed, and the coating is coated with an amorphous thin film of osmium, which is hard and has good conductivity. Can be

Although the embodiment of the present invention has been disclosed above, the present invention may have the following modifications. In the embodiment, the combination of the cleaning step and the coating step is disclosed.For example, only the cleaning step or the coating step alone has an effect of improving the resolution as compared with the conventional aperture plate. May be. For example, in addition to etching, the holes in the aperture plate can be formed by electric discharge machining, machining, laser machining, electron beam machining, etc., and even in such a case, the effects described above can be obtained by applying osmium coating. Can be expected.

It is also possible to use a metal other than molybdenum, for example, a metal having a lower melting point than molybdenum, as the material of the aperture plate. Even in such a case, by applying the osmium coating, the surface of the aperture plate is covered with the conductive thin film having a high melting point, so that the above-described effects can be expected. In the embodiment, the case where the aperture plate is newly manufactured is disclosed.
For example, when the aperture plate is mounted on an electron microscope and used, impurities adhere or the coating is peeled off. Therefore, as the regeneration process of the used aperture plate, only the cleaning process and / or the coating process of the present invention are performed. May be. In the embodiment, the example in which the present invention is applied to the aperture plate in the electron microscope is disclosed. However, the present invention is not limited to the aperture plate of the electron microscope, and can be applied to processing of parts of an apparatus that handles an arbitrary electron beam. is there.

[0017]

As described above, in the present invention,
By performing a cleaning process that can more completely remove the residual resist on the aperture plate, or a coating process that coats the surface of the aperture plate with osmium, the residual resist on the aperture plate after drilling by etching can be reduced by the conventional method. Compared with the above, the removal is more complete, so that problems such as charging, contamination, and peeling of the coating are reduced, and the resolution is improved. Furthermore, since the coated osmium becomes a hard amorphous conductive film, there is an effect that deterioration of resolution can be prevented. Since osmium has a higher melting point than platinum, performance can be further improved by further coating osmium on a conventional platinum-coated aperture plate. Therefore, the aperture plate of the present invention can achieve high resolution and maintain the performance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a cleaning step of a diaphragm plate to which the present invention is applied.

FIG. 2 is an explanatory view showing a coating process of a diaphragm plate to which the present invention is applied.

[Explanation of symbols]

, 10, 13, 16, 18, 30, ... aperture plate, 11
... concentrated sulfuric acid, 12 ... heating device, 14 ... mixed solution of concentrated sulfuric acid and hydrogen peroxide solution, 15 ... ultrasonic cleaning device, 17 ... distilled water,
20: plasma coating device, 21: vacuum vessel, 2
5 ... oil diffusion pump, 26 ... argon gas

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 37/09 C23C 30/00 H01J 9/14

Claims (5)

(57) [Claims] (1) Dozens of nanometers are formed on a metal plate having minute holes.
Adjusting the beam diameter of an electron beam in an electron beam application apparatus, including a coating step of coating an amorphous osmium thin film with a film thickness of less than Torr.
Of the aperture plate for the processing method. By wherein washing by concentrated sulfuric acid and the hydrogen peroxide solution was heated molybdenum plate spaced a small hole by etching, the cleaning step of removing the remaining resist, the washed the plate, several tens of the electron beam apparatus which comprises a coating step of applying a coating of amorphous thin male <br/> Miumu a thickness of nm or less
A method of processing an aperture plate for adjusting the beam diameter of an electron beam . 3. The cleaning step includes a first cleaning step of cleaning with concentrated sulfuric acid heated to 80 to 120 degrees Celsius, and mixing of concentrated sulfuric acid and hydrogen peroxide at a ratio of 3: 1 to 7: 1. 3. The electronic device according to claim 2 , further comprising: a second cleaning step of performing ultrasonic cleaning with a mixed liquid heated to 30 to 70 degrees Celsius; and a third cleaning step of cleaning with distilled water. 4. A method of processing an aperture plate for adjusting a beam diameter of an electron beam in a beam application apparatus. 4. The first coating step of exhausting an impurity gas in a vessel for performing plasma coating using a pump and an inert gas capable of achieving a degree of vacuum of 10 −4 Torr or more. If, osmium a to the plate by plasma coating
Electronic according to claim 1 or 2, characterized in that it comprises a second coating step of applying a coating of Amorphous thin film, the
An aperture plate processing method for adjusting a beam diameter of an electron beam in a beam application apparatus . 5. An electron beam application apparatus processed by the processing method described in any one of 1 to 4 above .
A diaphragm plate for adjusting the beam diameter of the electron beam .