GB2294217A

GB2294217A - Ultra clean nozzle

Info

Publication number: GB2294217A
Application number: GB9515688A
Authority: GB
Inventors: Tadamoto Tamai
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 1994-10-19
Filing date: 1995-07-31
Publication date: 1996-04-24
Anticipated expiration: 2015-07-31
Also published as: KR100267268B1; GB9515688D0; JPH08117644A; JP2809995B2; TW362996B; DE19531780A1; KR960013477A; GB2294217B

Description

4 ULTRA CLEAN NOZZLE 2294217 The present invention relates to a nozzle and

a method of manufacturing the same, andmore particularly to a ultra clean nozzle to be used at a ultra low temperature for jetting out ultra low temperature fluid containing droplets towards a vorkpiece placed in a clean atmosphere and cleaning it.

In this specification, a "ultra low Xemperature" means a temperature of about 120 K or lower, particularly a temperature of about 85 to 110 K.

As a method of cleaning a workpiece such as a semiconductor wafer which is required to be ultra clean, it has been proposed to blow ultra low temperature argon gas to a workpiece. With this method, argon gas or mixture gas containing argon gas is cooled to a ultra low temperature, and is jetted out of a nozzle to the surface of a workpiece placed in a vacuum chamber in a low pressure atmosphere.

Gas jetted out of the nozzle and released in the low pressure atmosphere is adiabatically expanded rapidly to lower its temperature. This lowered temperature generates argon fine solid particles which collide with the workpiece surface.

For example, argon-containing gas under a pressured state is cooled to a temperature slightly higher than the -liquefaction temperature of argon gas under the pressure applied thereto, and jetted out of the nozzle into a vacuum chamber. Part of the expanded argon gas is changed to argon sol'id fine particles and collides with the surface of a workpiece.

Blowing argon fine particles is performed for the purpose of 'cleaning, and contamination of a workpiece to be cleaned should be avoided as much as possible. Solid or liquid particles in argon-containing gas can be removed by a filter prior to blowing them. Impurity gas having a higher liquefaction temperature than argon can be removed by precooling the gas at the position upstream of the nozzle.

There are a limited number of gases having a lower liquefaction point than argon gas, such as nitrogen, hydrogen, and helium gases. Particles of these gases attached to the surface of a workpiece, can be easily dissociated by heating the workpiece or by other methods.

it is an object of the present invention to provide a nozzle capable of jetting out ultra low temperature gas into a ultra clean atmosphere while preventing the generation of particles of foreign substances.

It is another object of the present invention to provide a method of manufacturing a nozzle to be used at a ultra low temperature, capable of preventing the generation of particles of-foreign substances as much as possible.

According to one aspect of the present invention, there is provided a nozzle to be used at a ultra low temperature having nozzle apertures defined by pure metal members, the nozzle jetting out ultra low temperature fluid containing droplets to a workpiece placed in a clean atmosphere.

According to another aspect of the present invention, there is provided a method of manufacturing a nozzle to be used at a ultra-low temperature, comprising the steps of: preparing a solid member of pure metal material; machining the pure metal solid member and forming a nozzle header of a tubular shape having a hollow and nozzle apertures communicating an outside of the nozzle header with the hollow; performing chemical mechanical polishing for the hollow; and performing ultrasonic cleaning for the nozzle apertures.

The pure metal is preferably pure aluminum.

According to the experiments made by the inventor, a number of particles of foreign substances not negligible were observed while argon gas is jetted out of a nozzle into a vacuum chamber. One of the causes, of generating these particles may be the generation of particles during the machining work of making the nozzle. That the number of foreign particles reduces with the time of using the nozzle, may be considered as resulting from removing attached foreign particles off the nozzle. It has been found, however, that the number of foreign particles is not reduced more than a certain level even if the nozzle is used for a long time period.

Stainless steel or high tensile aluminum alloy has been used as the material of a nozzle to be used at a ultra low temperature. However, it has been found that if a nozzle is manufactured by using these materials, the number of foreign particles during Ar gas blowing is not reduced even after a long time period.

It has been found that if a nozzle-header is made of pure aluminum material,.the number of generated particles reduces rapidly as the used time increases..

A nozzle structure of pure aluminum material is f irst formed by machining works. AfVr the nozzle structure is made, cleaning is required for removing particles formed during mechanical processing. It is preferable to perform cleaning through chemical mechanical polishing (CMP) for the mechanical part having a large diameter. However, CMP is difficult to be performed for the nozzle apertures having a small diameter. The nozzle apertures can be cleaned by ultrasonic washing.

In the above manner, the number of particles contained in the gas jetted out of the nozzle can be reduced. Therefore, the cleaning effects of jetted-out Ar gas can be enhanced.

-4 Figs.1A to 1C are schematic cross sectional views showing the structure of a nozzle to be used at a ultra low temperature according to an embodiment of the invention.

Figs.2A and 2B are schematic cross sectional views illustrating a cleaning process for the nozzle to be used at a ultra low temperature according to the embodiment of the invention.

Vig..3 is a schematic diagram showing the structure of an argon cleaning system according to the embodiment of the invention.

Fig.4 is a graph showing a time-dependent change in temperature and pressure in a nozzle header.

Fig-S is a graph showing the relationship between a cooled temperature and flow rate of mixture gas containing argon.

Fig-6 is a schematic plan view showing another example of the structure of a cooling means of a cleaning system.

Fig.7 is a schematic diagram partially in section of the cooling means of the cleaning system shown in Fig.6.

Fig.8 is a partially enlarged view of the nozzle shown in Fig.1A.

Fig.9 is a graph showing the measurement results of the number of particles residual on the surface of cleaned wafers, when a nozzle header mad-e of aluminum alloy is used.

Fig.10 is a graph showing the measurement results of the number of particles residual on the surface of cleaned wafers, when a nozzle header of an embodiment of,the invention is used.

Figs.1A to 1C show the structure of a nozzle according to an embodiment of the invention. As shown in Fig.1A, a rrbzzle header 1 is made of a tubular pure aluminum member, and is hermetically coupled to a heat exchanger 2 through a metal gasket S. The nozzle header 1 has a connector portion 8 having a large diameter or thick wall for the connection to the heat exchanger 2. A thread 9 is formed in the outer circumferential portion of the connector 8.

A connector portion 11 of the heat exchanger 2 has the same diameter as the connector 8 of the nozzle header 1, for the -connection to the nozzle header 1. A fastener 3 engages with the connector 11 of the heat exchanger 2 through a bearing 6 which provides a smooth slide of the fastener 3. A thread 13 formed in the inner circumferential portion of the fastener 3 meshes with the thread 9 of the connector 8 of the nozzle header 1.

The nozzle header 1 is pushed against the heat exchanger 2 through the meshing between the threads 9 and 13 upon rotation of the fastener 3, and is hermetically sealed by the metal gasket S.

-6 The other end of the nozzle header 1 is terminated by a member such as shown in Figs.1B and 1C. Fig.1B shows a structure that a terminating member or stopper 4a serving as a blanking lid closes the opening of the nozzle header 1. A thermocouple Tc is embedded in the terminating member 4a. The coupling between constituent parts is similar to that at the heat exchanger 2.

F'ig.1C shows a structure that a terminating member 4b having a small diameter sleeve is coupled to the opening of the nozzle header 1. A thermocouple or pressure gage is inserted into the sleeve. The sleeve is sealed by any of the well-known means.

A cylindr.ical hollow 15 is formed centrally of the nozzle header 1. A plurality of nozzle apertures 16 are formed in the wall of the nozzle header 1, communicating the hollow 15 with the outside of the nozzle header 1. Each nozzle aperture 16 is cylindrical. The hollow 15 has an. inner diameter of, for example, about 4 to 12 mm, and the nozzle aperture 16 has an inner diameter of, for example, 0.15 to 0.3 mm. The diameter of each nozzle aperture and the number of nozzle apertures are determined basing upon a desired pressure difference to be maintained in the nozzle header 1 relative to the outside of the nozzle header.

A pitch between adjacent nozzle apertures 16 is made equal to a lateral scan width of a stage on which a workpiece to be cleaned is placed. For example, it is set to about 10 to 30 mm. A width of an area where nozzle apertures is distributively formed matches the width of the workpiece. For example, in the case of cleaning 6-inch wafers, twelve nozzle apertures are distributively formed at a pitch of 12.5 mm in the width of 137.5 mm.

In forming the nozzle header 1, an aluminum material for sputtering target use, having a purity of 5N (99-999 %) and vacuum cas'Ved is machined into a solid rod. This solid rod is machined to have-a predetermined outer'dimension by lathe machining. Next, a through hollow 15 is formed by.gun drill machining. After the hollow 15 is formed, nozzle apertures 16 are formed by drill machining.

After the structure of the nozzle header 1 is formed by machining works, the hollow 15 is polished through chemical mechanical polishing (CMP) to remove particles formed during machining. CMP is a combination of chemical etching by acid and mechanical polishing.

Fig.2A illustrates a CMP process. A rod or string type polishing member 17 with adhered abrasive particles is inserted into and passed through the hollow 15 to perform CMP while etchant 18 is flowed.

Next, the nozzle apertures 16 are cleaned. If a diameter of a nozzle aperture is about 0.3 mm or larger, CMP which jets out etchant liquid containing diamond particles can be performed. However, if a diameter is about 0.25 mm or smaller, it is very difficult to perform CMP. In this embodiment, each nozzle aperture 16 has a diameter of 0.18 mm and CMP is difficult to be performed.

Fig.2B illustrates a process of cleaning nozzle apertures.. Pure water is filled in a vessel 19 and the nozzle header 1 is immersed in the pure water. A ultrasonic vibrator or transducer 20 is dipped in the pure water and toe tip of the transducer 20 is placed near to the nozzle header 1.

The.transducer 20 is sequentially moved just above each nozzle aperture 16 to ultrasonically wash it. It is possible to efficiently remove particles formed during machining and residual on the wall of each nozzle aperture 16.

This nozzle header constructed as above may be used with an argon cleaning system described in US patent application Serial No.8/185,184, filed on January 21, 1994, which is herein incorporated by reference.

Fig.3 shows an argon -cleaning system using the abovedescribed pure aluminum nozzle. Ar gas and N2 gas are regulated by respective mass flow controllers 91 and 92 to have constant flow rates, and mixed together. This mixture gas is supplied from a pipe 21 to a filter 25 which removes foreign particles from the mixture gas and supplies the gas through a pipe 22 to a double-tube heat exchanger 77.

Liquid nitrogen is supplied from a pipe 86 into intermediate cylindrical hollow of the double-tube heat exchanger 77. The liquid nitrogen cools the mixture gas -g- supplied through the pipe 22 into the central hollow of the double-tube 77 to a liquefaction point of Ar gas under the pressure applied thereto, or to a temperature lower than the liquefaction point. Part or all of the liquid nitrogen in the intermediate cylindrical hollow is vaporized and exhausted from a pipe 87. A flow rate controller 82 is coupled to the pipe 87 to regulate the flow rates of exhausted nitrogen gas and liquid nitrogen to have-desired values.

The. mixture gas supplied through the pipe 22 is cooled to.a liquefaction point of Ar gas under the pressure applied thereto, or lower. At least part of the Ar gas is changed to liquid and supplied to the nozzle header 1 disposed in a vacuum chamber 24. A pipe interconnecting the double-tube heat exchanger 77 and nozzle header 1 is preferably.straight. The nozzle header 1 is made of pure aluminum as described already. The nozzle header 1 is coupled to a terminating member as shown in Fig.1C.

If a pipe has a bending portion, mirror surface polishing and electrolytic polishing.of the inner wall -of the pipe are difficult. It is therefore.difficult to prevent the generation of particles from the irregular surface of the inner wall of the pipe. A great amount of concavity and convexity is formed at the inner'wall of the bending portion, and becomes a cause of generating particles. A plurality of nozzle apertures are formed in the nozzle header 1. Cooled mixture gas as well as argon droplets are jetted out of the nozzle apertures into the vacuum chamber 24.

The nozzle header 1 is coupled to an external pressure gage 78 through a pipe 75 to measure a pressure in the nozzle header 1. A thermocouple 76 is inserted into the nozzle header 1 through the pipe 75 to measure a temperature in the nozzle header 1.

A wafer table 79 is disposed under the nozzle header 1. Mixture gas containing argon fine particles jetted out of the nozzle apeetures are blown to the workpiece placed on the wafer table 79 to clean the surface of the workpiece.

The vacuum chamber 24 is coupled through a pipe 83 and an oil trap 84 to an evacuating system 85 which evacuates the inside of the vacuum chamber 24. - The oil trap 84 prevents a back flow of oil from the evacuating system 85. A dry pump may be used in order to reduce a back flow of oil.

Data measured by the pressure gage 78 and thermocouple 76 is sent in the form of electric signals to a controller 81 which controls the flow rate controller 82 to regulate the flow rate of the liquid nitrogen and set the pressure in the nozzle header, 1 to a desired value.

Fig.4 is a graph showing a change in the pressure and temperature in the nozzle header 1. The abscissa represents time. and the ordinate represents temperature and pressure. As the mixture gas is cooled by the double-tube heat exchanger 77, the temperature in the nozzle header 1 lowers. After the temperature reaches a liquefaction point TO of Ar gas under the pressure applied thereto, it hardly lowers..

The pressure lowers as the temperature falls. At the temperature To. the pressure becomes Po. As the mixture gas is further cooled, Ar gas is liquefied. Therefore. the speed of reducing the pressure becomes high and the desired Pressure P1 preset to the controller 81 is obtained.

When the controller 81 detects that the pressurain the nozzle header 1 has reached PiL, it controls the flow rate controller 'b2 to regulate the flow rate and maintain the pressure constant. A difference between Po and Pil corresponds to an amount of.liquefied Ar gas. From this difference, it is therefore possible to estimate the amount of. liquefied Ar gas. As a result, it is possible to liquefy a desired amount of Ar gas by setting the pressure P, to a desired value. It.is also possible to control the amount of liquefied Ar gas with a small error, because the pressure changes greatly with the amount of liquefied Ar gas.

It can be considered that if the amount,of liquefied Ar gas is constant, the number of argon fine particles jetted out of the nozzle apertures is also constant. A desired number of argon fine particles can therefore be blown to the workpiece surface. Trade-off between damages on the workpiece surface and cleaning ability can be properly settled during cleaning.

In the description with reference to Fig.4, the cooling quantity is controlled by detecting a change in the pressure in the nozzle header 1 while maintaining the flow rate

12- of mixture gas constant. The flow rate of mixture gas may be controlled by maintaining the pressure in the nozzle header 1 at a desired constant value.

Fig.5 is a graph showing the relationship between a temperature of cooled mixture gas and a.flow rate, when the flow rate is increased while maintaining the pressure in the nozzle header 1 constant. The abscissa represents a temperature of cooled mixture gas in the unit.of absolute temperature K,.and the ordinate represents a total flow rate of argon gas and nitrogen gas before cooling in the unit of slm.

As the flow rate is gradually increased. the pressure in the nozzle header 1 rises. Since the pressure is maintained constant,..the controller 81 operates to increase the cooling,quantity and lower the temperature of the mixture gas. As the.flow rate is gradually increased. the temperature of the cooled mixture gas gradually lowers.

When the temperature.of the.cooled mixture gas reaches a liquefaction point of Ar gas under the pressure applied thereto, Ar starts being liquefied. The temperature and flow rate of the mixture gas at the time when liquefaction starts were about 106 K and about 12 slm under the conditions of this embodiment, although they changes with the pressure, shape, and the like of the nozzle header 1.

As the flow rate is further increased, the controller 81 operates to increase the cooling quantity and Ar gas is changed more into droplets. The, temperature of the mixture gas is maintained generally constant at the liquefaction point of Ar.. As a result, after the mixture gas is once cooled to the liquefaction point of Ar, the temperature of the mixture gas scarcely lowers and,only the flow rate Increases abruptly, as shown in Fig.S. This increase of the flow rate corresponds to the amount of liquefied argon.

The amount of liquefied argon can therefore be obtained from a difference between the flow rate of mixture gas during.cleahipg and the flow rate when argon liquefaction starts. In,order to obtain the,high cleaning effects without damaging the cleaning surface toomuch, it is preferable to set the flow rate of mixture gas during cleaning to about 1.2 to 4 times the flow rate when argon liquefaction starts.

In the above embodiment, the.cooling quantity.is controlled by regulating the flow rate of N2 gas at the outlet port of the double-tube heat exchanger 77. The cooling quantity may be controller by other methods. For example, the cooling quantity may be controlled by regulating the flow rate of liquid nitrogen by changing the pressure of a liquid nitrogen supply bomb.

In the above embodiment, the double-tube heat exchanger using liquid nitrogen is used as the cooling means. Other cooling means may also be used. For example, a cryosystem such as a GiffordMcMahon (GM) refrigerator, a Stirling refrigerator, and a turbo refrigerator may be used.

Figs.6 and 7 show cooling means using GM refrigerators. Fig.6 is a plan view of the cooling means, and Fig.7 is the side view thereof. As shown in Fig.6, mixture gas of Ar gas and N2 gas with foreign particles removed by a filter is supplied to a bending point 88 of a pipe 22. The pipe 22 extending from the bending point 88 to a vacuum chamber 24 contacts a cooling plate 89 of GM refrigerators with good heat conduction. A heater 90 is disposed around the pipe 22. The pipe 22 extending from the. bending.point 88 to a nozzle header i straight. timilar to the embodiment shown in Fig.3, the straight pipe is effective for preventing the generation of particles. The pipe 22, cooling plate 89, and heater 90 are housed in a vacuum chamber 94 for heat insulation.

As shown in Fig.7, GM refrigerators 95a and 95b installed under the cooling plate 89 cool the plate 89. In Fig.7, although two GM refrIgerators are serially Installed relative to the pipe 22, a single GM refrigerator may be used if it can provide a sufficient cooling abil-ity. if insufficient, cooling by liquid nitrogen illustrated in Fig.3 may be used in combination. Three or more refrigerators may also be used.

The calorific power of the heater 90 is controlled by a controller 93 connected to the heater 90. The cooling quantity of Ar gas can be controlled by regulating the calorific power of the heater 90. The controller 91 is supplied with data of the pressure in the nozzle header in the form of electric signal. The controller 93 regulates the calorific power of the heater 90 so as to set the pressure to a desired value.

The pipe 22 shown in Figs.3 and 7, particularly the portion of -the pipe 22 downstream of the heat exchanger, is preferably made of pure aluminum.

Fig.8 illustrates the relationship between a hollow 15 of a nozzle header 1 and a nozzle aperture 16. -Ar-containing -gas is supplied at a velocity of v1 into the hollow 15, and jetted out 'bf the nozzle aperture 16 at a velocity of v2. The velocity v1 in the hollow,15 is considerably slow as compared to the velocity v2 in the nozzle aperture 16.

Ar-containing gas passing through the nozzle aperture 16 has-a high flow velocity. If there is a particle source in the wall of the nozzle aperture, particles are blown out when.the Ar-containing gas is jetted out. Therefore, the nozzle aperture.16 is required to have at least the structure which makes particles be generated as less as possible.

The inventor first formed nozzle headers 1 by stainless steel and high tensile aluminum alloy. By using these nozzle headers, argon-containing gas was jetted out to the surface of an Si wafer in a vacuum atmosphere, and particles on the Si wafer picked up from the vacuum chamber were observed. It can be considered that the number of particles residual on the wafer reflects the number of particles.contained in the gas jetted out of nozzle apertures.

Fig.9 shows the measurement results of particles on a 6-inch Si wafer when a nozzle header 1 made of Al alloy QISA6061) was used. The abscissa represents a cumulative number of test runs after the nozzle header was first used. and the ordinate represents the number of particles on a cleaned 6-inch Si wafer.

The nozzle header had the structure described with Fig.1 and Was.used with the system shown in Fig.7. One test run took about 30 minutes. Of 30 minutes, Ar-containing gas was Jetted out of the nozzle header for about 10 minutes. The nozzle header was first cooled from a room temperature to about 100 K. The flow rate of the Ar mixture gas was set to 42 slm (Ar: 38 slm, N2: 4 sIm). The gage pressure in the nozzle header was 3 to 3.5 kg, and the pressure in the vacuum chamber was about 0.3 atmospheric pressure.

Each time a cleaning test was finished, the Ar mixture gas.was stopped and the vacuum chamber was evacuated. Thereafter, the Si wafer was picked up and particles on the wafer were counted. After the measurement, the wafer was placed in the vacuum chamber and the vacuum chamber was evacuated. Thereafter, the Ar mixture gas blowing system was cooled to perform the next cleaning process.

Particles of 0.28 um or larger were measured at four channels CH1 to CH4. The total number of particles is indicated by a solid line, and the number of particles of 1.5 gm or larger is indicated by a broken line. The abscissa represents the number of test runs and test date.

Residual particles had a tendency of reducing its number as a whole. This tendency coincides with the assumption that if particles are residual on the surface of the nozzle header and removed or peeled off.as the Ar mixture gas is jetted out, the number of residual particles gradually reduces.

The number of residual particles at the first test run of eacl test day is larger than-that- of the immediately preceding test run. The absolute value thereof has a tendency of reducing its-value. This may be considered as resulting. from that the system is heated to a room temperature in night, and it is cooled to about 100 K in day.

As seen from.the measurement results on May 16 and 17 and some other days, the number of particles increases at some test runs during the day.. As seen from the measurement results on May 23, a large number of residual particles is observed which cannot be expected from the measurement results at the preceding days.

After the test runs were repeated 70 times, the number of residual particles was about 200 to 300.

Fig.10 shows the measurement results of particles on an Si wafer when the embodiment nozzle header 1 made of pure aluminum was used.

The same measurement conditions as the nozzle header made of Al alloy were introduced except the different nozzle header material. The number of residual particles at the initial stage reduced from 1000 or over of Al alloy to about 300.

The average number of particles reduced to about 20 which is approximately a practical level, in ten days after the nozzle header was used (exclusive of the.days when the test was.not made).. In each day, the number of particles reduced generally monotonously. The number of residual particles at the. first test run in each day also reduced generally monotonousl.. In-other words,-.the number of particles rarely increased like mutation.

The nozzle header of Al alloy reduced the number of residual particles to about 200 to 300 after 70 test runs. whereas the nozzle header of pure A1 reduced the number of residual particles.to about 20 after 70 test runs.

The phenomenon that use of pure alufflinum reduces the number of particles may be considered as in the following.

A1 alloy is an.alloy containing a plurality of compositions. It is considered from the microscopic viewpoint that A1 alloy hasn't a uniform composition, but locally contains non-metal inclusions having impurity nuclei. Nonmetal inclusions in A1 alloy underwent a heat cycle between a room temperature and a ultra low temperature have thermal expansion different from adjacent compositions and have higher brittleness.

After the nozzle header undergoes a large heat cycle, strains are generated in the non-metal inclusions in Al alloy because of a difference between thermal expansion coefficients, and fine slides and cracks are considered to be generated. If even a small part of such non-metal inclusions is exposed to the, surface of the nozzle header, decomposition of the inclusions is enhanced by a stress exerted by a high speed gas flow on the exposed surface, so that fine powders are peeled off and blown along the jet gas flow. If decomposition occurs at a new region, the number of residual particles-may increase greatly.

Genpration of fine powders by a heat cycle is considered to be inevitable if the nozzle header material is alloy. Therefore, even if stainless steel is used, similar fine powders may be generated.

In contrast, if the nozzle header I is made of pure aluminum, it can be expected that fine powders are hard to be generated because the material has a uniform composition withless impurities and a local stress. by thermal expansion is not generated. In the above embodiment, aluminum of a purity of 5N is used. The advantages of using pure material are expected by using aluminum having at least a purity of 2N (99 %). It is preferable to use aluminum of a purity of 3N, or more preferably a-purity of 4N.

Even if fine powders are generated, it is considered that these fine powders are not conveyed by a jet gas flow if the gas flow velocity is low at the region where the powders are formed. It is therefore considered that of the nozzle header 1, the nozzle apertures 16 become the outstanding cause of particle generation because the gas flow velocity is maximum at these regions. It is therefore considered that the number of particles contained in a jet gas reduces if at least the region of the nozzle apertures 16 is made of pure aluminum. It is obvious that apossibility of generating fine powders is further lowered if the whole nozzle header is made of pure aluminum. In the measurement of the number of particles, the heat exchanger made of stainless steel is used. If the gas passage of 'the heat exchange is also made of pure aluminum, it is expected that a probability of particle generation is further lowered.

The-same effects are expected even if pure metals other than aluminum are used.

As described above, the number of particles mixed with a gas flow jetted out of the nozzle header can be reduced if the nozzle header is made of pure metal material, particularly pure aluminum material.

The present invention has-been described in connection with the preferred embodiments.

The invention is not limited only to the above embodiments. It is apparent to those skilled in the art that various modifications, improvements, combinations and the like can be made without departing from the scope of the appended claims.

Claims

CLAIMS:

1. A nozzle to be used at an ultra low temperature having nozzle apertures defined by pure metal members, the nozzle jetting out ultra low temperature fluid containing droplets to a workpiece placed in a clean atmosphere.

2. A nozzle to be used at an ultra low temperature, according to claim 1. wherein said pure metal member is pure aluminum meinber.

3. A nozzle to be used at an ultra low temperature according to claim 2, wherein said pure aluminum members have a purity of 99 % or higher.

4. A nozzle to be used at an ultra low temperature according to claim 2, wherein said pure aluminum members have a purity of 99.9 % or higher.

5. A nozzle to be used at an ultra low temperature according to claim 2, wherein said pure aluminum members have a purity of 99.99 % or higher.

6. A nozzle to be used at an ultra low temperature according to any one of claims 2 to 5, wherein said pure aluminum members are vacuum casted.

7. A surface cleaning system comprising:

gas supplying means for supplying a gas containing argon liquid; a nozzle device made of pure metal for being supplied with at least said gas containing argon liquid, said nozzle device having a plurality of nozzles for jetting out said gas containing said argon liquid; susceptor means for supporting a cleaning object by facing said cleaning object toward the gas jetting direction of said nozzle device; a hermetically sealed chamber for accommodating said nozzle device and said susceptor means; and exhausting means for exhausting a gas in said hermetically sealed chamber.

8. A surface cleaning system according to claim 7, wherein said pure metal is pure aluminum.

A surface cleaning system according to claim 7 or claim 8, wherein said gas supplying means comprises:

an argon gas source for supplying a gas containing at least an argon gas; and cooling means for cooling said gas supplied from said argon gas source to the liquefying temperature of argon gas specific to the pressure of said argon gas. said cooling means capable of controlling the,cooling power, and further comprises:

temperature gauge for measuring a temperature of the inside of said nozzle device; pressure gauge for measuring a pressure of the inside of said nozzle device; and controlling means for receiving a temperature value measured by said temperature gauge and a pressure value measured by said pressure gauge and controlling the cooling PO 'to set said p ressure value to a wer of sa:id. cooling mepLns predetermined value.

10. A surface cleansing system according to claim 9, further comprising argon flow regulating means mounted at the upstream of said cooling means for regulating the flow of said argon-containing gas to have a predetermined mol flow.

A surface cleaning system according to claim 9 or claim 10, wherein said cooling means includes a heat exchanger and cooling medium flow regulating means for regulating the flow of liquid nitrogen flowing through said heat exchanger.

12. A surface cleaning:system according to any one of claims 9, 10 or 11 wherein said cooling means includes a cryo-system and heating means.

13.

A method of manufactuning a nozzle to be used at an ultra low temperature, comprising the steps of: preparing a solid member of pure metal material; machining the pure metal solid member and forming a nozzle header of a tubular shape having a hollow and nozzle apertures communicating an outside of the nozzle header with the hollow; performing chemical mechanical polishing for the hollow; and performing ultrasonic cleaning for the nozzle apertures. 1

14. A method of manufacturing a nozzle to be used at an ultra low temperature according to claim 13, wherein said pure metal is pure aluminum.

15. A nozzle to be used at an ultra low temperature substantially as described herein with reference to and as shown in the accompanying figures.

16. A surface cleaning system substantially as described herein with reference to and as shown in the accompanying figures.

17. A method of manufacturing a nozzle to be used at an ultra low temperature substantially as described herein with reference to and as shown in the accompanying figures.