JPS6027790A - Cryopump - Google Patents

Abstract

PURPOSE:To improve corrosion resistance, by depositing molybdenum or a molybdenum silicide compound on the surface of a cryopanel or condensing plate, and blackening it. CONSTITUTION:Molybdenum or a molybdenum silicide compound is deposited on the surface of a cryopanel or condensing plate and is blackened. For example, a chromium film 2-1 is deposited on a copper plate 1-2 by vacuum deposition or the like. Then similarly Mo-Si 3-1 is deposited by sputtering or the like. The reason for the application of the chromium is to make the adhesion of the Mo-Si favorable. Thereafter, when plasma etching is carried out by using a Freon type gas, the surface of the Mo-Si 3-2 is roughened and blackened. As a result, the life of a pump can be prolonged, and as the absorption area is increased due to the roughened surface to improve the exhaustion speed.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to improvements in cryopumps.

[Prior art and its problems] In recent years, the application of vacuum technology has been widely used in semiconductor manufacturing processes, including sputtering equipment, vapor deposition equipment, low-pressure vapor deposition equipment for forming thin films, and dry etching for microfabrication. Vacuum systems are frequently used in equipment, etc. These devices are operated in the pressure range from 10'Tow to 110-1To. As vacuum pumps, oil rotary pumps, mechanical booster pumps, etc. are mainly used to maintain pressure during auxiliary exhaust wax or film formation and etching, while oil diffusion pumps, turbo molecular pumps, cryopumps, etc. exhaust residual gas in the system. It is used for high vacuum and in some cases for film formation in high vacuum or for maintaining pressure during etching.

Taking etching in the semiconductor manufacturing process as an example, miniaturization,
Dynamic random access MOS memory (256K DRAM)
) is required to be 2 μm or less.

The materials to be etched include silicon oxide film (8i02), polycrystalline silicon (pOV-81), high melting point metals such as W, Mo, their silicide compounds, and aluminum (A
There are many materials such as J). In particular, for M, if K H2O is present in the etching atmosphere, etching may not proceed, so it is necessary to reduce H2O as much as possible. For this reason, cryopumps with high pumping speed have been introduced for H2O. The principle of the cryopump is to adsorb gas onto a metal panel cooled to an absolute temperature of 150 degrees or less to perform vacuum evacuation.

FIG. 1 shows a schematic configuration diagram of a cryopump apparatus. 0 1 is a stainless steel container of the cryopump, and 2 is an irradiation shield plate for preventing heat radiation to the container 1.

Helium gas (
He) is introduced from the helium supply port 3, and the helium gas adiabatically expands in the first stage cylinder 4 and second stage cylinder 5 to directly cool the cryopanel 6 made of copper (Cu).
Its temperature will be below 150°C. The condensing plate 7 is cooled by heat radiation to a temperature of about 800 ℃. The adiabatically expanded helium is returned to the refrigerator again through the helium return port 8. 9 is the crankcase, which has a built-in drive unit to drive the cylinders. A hydrogen vapor pressure gauge is installed to measure the pressure within the system. 11 and 12 are called the second stage and first stage cold station, respectively, and have the function of constantly generating refrigeration to maintain the temperature within the set temperature range.
0, 12 te 7K ~100K (7)? l [There is. Helium, H2 (hydrogen), and argon (A') are condensed in the charcoal inside the adsorption cylinder 13.Since the cryopump uses an adsorption method, once a certain amount of gas is adsorbed, it must be regenerated by releasing the gas. At this time, a safety valve 14 is provided to prevent the pressure inside the container 2 from becoming abnormally high, and the gas is released from there to the outside.The cryopanel 6 has a black surface to prevent heat from being released to the surroundings. However, as mentioned above (sometimes the condensing plate 7 is also evaporated), when it has recently been used in semiconductor etching equipment, these gases become black when regenerated by halogen gas. A problem arises in that the surface of the cryopanel 6 and the condensing plate 7 deteriorate due to corrosion, which significantly reduces the characteristics of the pump.

[Purpose of the Invention] The present invention improves the above-mentioned drawbacks of the conventional device, and improves the method of blackening the cryopanel and condensation plate to improve corrosion resistance and provide a highly reliable cryo pump. The purpose is to provide.

[Summary of the Invention] Conventional blackening treatment involves coating the copper or stainless steel surfaces of cryopanels and condensation plates with an organic paint using molybdenum (MO) or its silicide compound (
Mogi) is deposited by vapor deposition or sputtering, and then a portion of the deposit is isotropically dry-etched with Freon gas to blacken the surface.

[Effects of the Invention] The present invention significantly improves the life of cryopanels and condensing plates, and is particularly effective for halogen gases.

[Embodiments of the invention] Embodiments of the present invention will be described in detail using the drawings.

FIG. 2(a) is a partial sectional view of a conventional cryo panel or condensing plate. That is, the constituent material, for example, a copper plate (1
-1) Paint 2 is coated on top. Figure 2(b),
(C) shows an embodiment of the present invention, in which the copper plate 1-
A chromium (Cr) film 2-1 is deposited on 2 by vapor deposition or the like to a thickness of several hundred angstroms. Next, Mo8i 3-1 is similarly deposited by about 4000X using a sunomi-shita method. Chromium is Mo
8 It is attached to improve the adhesion of i. Rio
After depositing MoSi (3-1) on the copper plate 1-2, plasma etching is performed using Freon gas, which is often used in semiconductor manufacturing processes, as shown in Figure 2 (C
), unevenness occurs on the Mo5i3-2 surface and the surface becomes black. The reason for this is that when Mo and Mo8i are deposited by evaporation or sputtering, they tend to form columnar crystals, and when they are then plasma etched with Freon-based gas, the grain boundaries are etched faster than the inside of the grain boundaries, so if the etching is stopped midway through, There is a height difference γ between the grain boundaries and inside the grain boundaries, which absorbs light and is blackened.

When the cryopump of the present invention is used in a dry etching device, the life of the stone and pump is increased by more than 10 times, and the suction area is increased due to the unevenness of the surface, and the pumping speed is increased by about 20 cm. Furthermore, since the film thickness of the C' and Mo8i films was 1 μm or less, there was no temperature difference between the blackened surface and the cryopanel surface.

When using halogen-based gases, it is necessary to take great care to ensure that the etching depth of grain boundaries is not less than the film thickness when etching Mo3i so that these gases do not penetrate into the cryopanel, but dry etching technology has significantly advanced. In particular, it has been confirmed that machining can be performed with sufficient precision. From the viewpoint of corrosion resistance, it is desirable to use Mo or pMosi, but MO may also be used when used in vapor deposition or sputtering equipment.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a cryo pump, and Figure 2 is a partial sectional view of a cryo panel condensing plate, with (a) showing a conventional example, and (b) and (C) showing examples of the present invention. There is. 7... Condensation plate, 6... Cryo panel, 11.
・・Second stage cold stage code, 12...i 1st stage code 1)' Stage code. 14...Safety valve, 13...Adsorption tube. (7317) Patent attorney Kensuke Norichika (and 1 other person) Figure 1 Figure 2

Claims (3)

[Claims] (1) Depositing molybdenum or a molybdenum silicide compound on the surface of the cryopanel or condensing plate in the cryopump, and then subjecting the cryopanel or condensing plate to plasma etching treatment with a halogen-based gas to blacken the surface. A cryopump device featuring: (2) The halogen gas is freon-14 (CF
14) and oxygen. (3) The etching depth D) of the grain boundaries of the molybdenum oxide or molybdenum silicide compound has a relationship of D ) Do with respect to the film thickness (DO) of the thin film before etching. The cryopump device according to item 1.