JPH09183064A - System and method for polishing surface of soft metal using carbon dioxide snow - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and a method for polishing the surface of a soft metal such as gold into a sub-angstrom surface roughness. SOLUTION: This polishing system includes a processing chamber 12, having both a processing space 23 and a means for purging the processing space 23 by causing recirculation of gas, a tank 14 holding liquid carbon dioxide, a carbon dioxide jet spray system 11 having a nozzle-and-orifice device 17 generating solid carbon dioxide gas snow, and a robot arm 30 on which an element 32 placed within the processing space 23 and polished is installed and which moves and positions the nozzle-and-orifice device 17 with respect to the surface 20 of the element 32 in order to polish the surface 20. The nozzle-and-orifice device 17 is designed to polish metal surfaces by the mechanical action of the solid carbon dioxide gas snow generated by the controlled expansion of the liquid carbon dioxide passing through its nozzle and orifice.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to systems and methods for polishing soft metal surfaces, and more particularly to a system for polishing soft metal surfaces such as gold mirrors using CO ₂ snow that achieves sub-angstrom surface roughness. Regarding the method.

[0002]

Heretofore, there have been no systems and methods for polishing soft metal surfaces, such as gold mirror surfaces, to achieve sub-Angstrom surface roughness. Presently effective techniques use wet polishing to treat the substrate to Angstrom roughness or better, after which gold is provided using a thin film deposition process. The resulting gold surface is so soft that it cannot be mechanically or chemically polished to the same smoothness as the underlying substrate. Further, there is currently no effective polishing system for soft metal surfaces using a gas / solid jet spray polishing system using CO ₂ snow in an ultra-clean treatment environment room. Heretofore, these two separate techniques have not been combined to provide a polishing system for soft metal surfaces. In practice, conventional systems cause dust contamination and precipitation of the metal surface being polished due to the nature of the conventional polishing process used.
As a result, conventional polishing systems could not be used in ultra-clean processing environments.

[0003]

Accordingly, it is an object of the present invention to provide a system and method for polishing soft metal surfaces to sub-Angstrom surface roughness. Another object of the present invention is to provide a system and method for polishing soft metal surfaces using CO ₂ snow.

[0004]

To achieve the above and other objectives, the present invention is a system that can be used to polish metal surfaces, such as gold mirror surfaces, using CO ₂ snow. And provide a method. The system and method achieves sub-angstrom order surface roughness of polished metal surfaces. Generally, the system includes a processing chamber holding an element having a metal surface to be polished. A CO ₂ jet spray system is provided to generate solid CO ₂ gas snow. An operator controllable robot arm is mounted in the process chamber for locating an element having a metal surface to be polished and for moving and locating a CO ₂ jet spray system with respect thereto for polishing the surface of the element. . The CO ₂ jet spray system polishes metal surfaces using the mechanical action obtained from solid CO ₂ gas snow produced by the controlled expansion of liquid CO ₂ .

The present invention uses a gas / solid jet spray device located in a process chamber such as an ultraclean process chamber.
The processing chamber contains precision processing tools for inspecting, testing and polishing soft metal coatings, including gold mirror coatings and the like. Jet spray polishing system is optimal for CO ₂
It includes a CO ₂ gas supply system used to emit snow and a combined orifice nozzle device. The combined jet spray orifice and nozzle device is configured to polish metal surfaces by mechanical action derived from solid gas snow produced by the controlled expansion of liquid CO ₂ .

Polishing is performed in an ultraclean room. Ambient dust and precipitates scratch soft metal surfaces, especially gold surfaces. Ultra clean room is a large enclosed room or treatment space with pre-filter to reduce humidity, high capacity blower, high flow rate and high efficiency particulate removal (HEPA) filter, return pipe system, and dry gas purification Includes system. A dry and clean environment is provided in the ultra-clean chamber, which is necessary to avoid deposits that interfere with the polishing process.

The solid / gas jet spray polishing system is intended to be used as the final step required to produce ultra-low scattering gold mirrors, especially for use in optics made by the applicant of the present invention. Designed However, the system and method of the present invention can also be used to treat other soft metal surfaces used in metrology and other fields where high quality surfaces, such as Angstroms, are required.

The method of the present invention places an element having a metal surface to be polished in a chamber. Solid CO ₂ gas snow is generated indoors using a CO ₂ jet spray system. The CO ₂ jet spray system is moved to move solid CO ₂ gas snow with respect to the surface of the device to polish metal surfaces. Solid CO ₂ gas snow polishes metal surfaces using the mechanical action produced by the controlled expansion of liquid CO ₂ .

The polishing system and method of the present invention can polish delicate surfaces such as gold without causing scratches or mechanical contact that occurs when an abrasive is used. The polishing system and method of the present invention are clean and do not produce waste residues or chemical debris in the form of liquid slurries. The jet spray produced by the polishing system is environmentally friendly and the snow produced sublimes and is exhausted to the atmosphere. The jet spray polishing system and method of the present invention is currently the only effective technique capable of polishing gold or other soft metal surfaces without damaging the surface. However, this system and method for polishing gold and other soft metal surfaces is relatively slower than chemical or mechanical polishing methods.

[0010]

Various features and advantages of the present invention will be readily understood by reference to the following detailed description and the accompanying drawings. Note that the same reference numerals indicate the same elements. Referring to FIG. 1, there is shown a gas / solid jet spray polishing system 10 and method 40 according to the present invention used to polish a soft metal surface 20 to a sub-Angstrom surface roughness. The gas / solid jet spray polishing system 10 may be, for example, a jet spray device manufactured by the applicant of the present invention,
It may include the trade name ECO-SNOW and is comprised of a jet spray system 11 mounted within an ultraclean process chamber 12. The jet spray system 11 comprises a gas supply system 13 having a tank 14 and a pipe 15 for storing liquid CO ₂ , one or more valve devices 16, and a solid C 2
It includes a nozzle-orifice device 17 containing various nozzle and orifice combinations used to produce O ₂ gas snow 18. The jet spray nozzle-orifice combination forming the nozzle-orifice device 17 comprises the solids produced by the controlled expansion of the liquid CO ₂ 21 through the selected nozzle-orifice combination used. It is configured to polish the metal surface 20 by mechanical action obtained from the gas snow 18.
A typical orifice device 17 is described in US patent application Ser. No. 08 / 356,606 filed October 15, 1995 and December 12, 1995.
No. 08 / 356,607, filed 14th March.

The ultra-clean treatment chamber 12 is a front entrance door that allows the elements to be placed in the laminar internal treatment space 23 of the chamber 12.
Load lock passage with 22a and rear exit door 22b
It has 22. A high efficiency particulate removal (HEPA) filter 24 is provided to filter nitrogen gas 25 or dry air 25 supplied from a nitrogen or dry air tank 26. A floor 31 of stainless steel mesh is provided within the ultraclean treatment chamber 12 that allows filtered nitrogen gas 25 or dry air 25 to pass therethrough and be recirculated. The nitrogen gas 25 or the dry air 25 is fed to the inlet filter 35 and the second
Filter 27 or pre-filter 27 and the pre-filtered nitrogen gas 25 or dry air 25 is passed through the internal treatment space 23 using a high scfm (standard cubic feet per minute) capacity recirculation blower 28. Be recycled.
The heater 33 controlled by the temperature controller 29 is the second
Surrounding the filter 27. The HEPA filter 24, the blower 28, the stainless steel mesh floor 31 and the internal processing space 23 form a nitrogen gas 25 or dry air 25 purification system. Operator controllable XYZ used to move and position nozzle and orifice device 17 and move and position element 32 to the position to be polished.
A robot arm is mounted in the internal processing space 23.

The ultraclean process chamber 12 also includes a temperature controller (not shown) that is part of the temperature controller 29. In addition to the jet spray system 11 of the present invention, the ultra-clean treatment chamber 12 is equipped with precision process inspection and test tools (not shown). The inspection and test tool and jet spray system 11 provide a complete system 10 for polishing soft metal surfaces 20 and coatings, including gold mirror surfaces and coatings and the like.

In operation, the operator of system 10 operates on an element having a metal surface 20 or coating to be polished.
32 is disposed in the internal processing chamber 23 through the load lock passage 22. This may be done by opening the front entrance door 22a to initially place the element in the load lock passage 22. Rear door 22b when element 32 is placed in passage 22
Is opened and the robot arm 30 is operated by the operator to pick up the element 32. The robot arm 30 is used to move the element 32 into the processing space 23 for cleaning, testing and polishing.

The temperature of the internal processing space 23 is maintained above ambient temperature and is regulated by a feedback controller (not shown) on the heater 33 surrounding the second filter 27. The nitrogen gas 25 or the air 25 flowing into the internal processing space 23 is filtered three times by the inlet filter 35, the second filter 27, and the high-velocity HEPA filter 24. Nitrogen gas 25 or air 25 is sucked by a high capacity blower 28,
It is pushed into the internal processing space 23 by the HEPA filter 24. The gas flow during the polishing process is collected by the return pipe 34 and recirculated through the internal processing space 23.

The high velocity spray of solid gas particles forming the solid gas snow 18 is directed onto the surface 20 of the element 32 to be polished. The solid gas particles contact the surface 20 and remove the protruding portions of the surface, one atom at a time. This removal produces a very fine sub-Angstrom polished surface 20.

Atomic force microscopy confirms the polishing of the gold mirror surface 20 by CO ₂ gas jet spraying.
FIG. 2 is a graph showing the surface roughness of the gold surface 20 measured prior to use of the system 10 and method 40 of the present invention,
3 is a graph showing the surface roughness of the gold surface 20 measured after using the system 10 and method 40 of the present invention.

A WYCO surface engraver supporting atomic force microscopy data for the polished and tested element 32 was used to measure the surface roughness of the polished element 32. The gold surface 20 has a root mean square (R) of 9.83 angstroms before polishing.
MS) roughness and after polishing with solid CO ₂ such as Snow 18 the RMS roughness was 6.13 Å. The peak-to-valley value was 4.48 angstroms before polishing to 2.65 angstroms after polishing, and a device using CO ₂ gas / solid jet spray system 10 32
The effect of sub-Angstrom polishing on surface 20 was shown.

The polishing process using system 10 and method 40 of the present invention is performed in ultraclean room 12. The dust and precipitation of the surrounding environment damages the metal surface 20, especially the gold surface. Second filter 27, high capacity blower 28, H
The EPA filter 24, the return pipe 34 and the dry gas cleaning system reduce humidity. The dry and clean environment provided within the ultraclean chamber 12 avoids sedimentation that interferes with the polishing process.

Solid / Gas Jet Spray Polishing System
10 was specifically designed to be used as the final step needed to produce an ultra-low scattering gold mirror used in an optical system manufactured by the applicant of the present invention. However, the system 10 and method 40 of the present invention can also be used to treat other metal or soft metal surfaces 20 in metrology and other fields where high quality surfaces 20 on the order of Angstroms are required.

The polishing system 10 and method 40 of the present invention comprises:
The delicate surface 20 of gold or the like can be polished without causing scratches or mechanical contact that occurs when an abrasive is used. The process is clean and does not produce waste or chemical residues in the form of liquid slurries. The gas / solid jet spray 18 is environmentally friendly and the snow produced sublimes and is exhausted to the atmosphere. Gas of the invention /
The solid jet spray polishing system 10 and method 40
It is the only effective technique that can polish the gold surface 20 without damaging the surface 20. The system 10 and method 40 of the present invention polishes gold and other soft metal surfaces 20 to sub-angstrom surface roughness, but at a relatively slow rate compared to conventional chemical or mechanical polishing methods.

For completeness, the polishing method 40 of the present invention will now be described with reference to FIG. FIG. 4 is a flow diagram illustrating one embodiment of the method of the present invention. In its most general form, the method 40 of the present invention includes the step 41 of placing in the chamber 12 an element having a metal surface to be polished. In step 42, the solid CO ₂ gas snow 18 becomes C
Produced in chamber 12 using O ₂ jet spray system 11. In step 43, the CO ₂ jet spray system 11 is moved to move the solid CO ₂ gas snow 18 with respect to the surface 20 of the element 32 to polish the metal surface 20. Solid CO ₂ gas snow 18 polishes the metal surface 20 using the mechanical action produced by the controlled expansion of liquid CO ₂ 21.

The foregoing has described a system and method for polishing soft metal surfaces using CO ₂ snow that achieves sub-Angstrom surface roughness. It should be understood that the described embodiments are merely some examples of numerous specific embodiments that represent applications of the principles of the invention. Obviously, those skilled in the art can easily recognize various other structures without departing from the technical scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a gas / solid jet spray polishing system according to the present invention.

FIG. 2 is a graph showing the surface roughness of gold measured before using the system of FIG.

FIG. 3 is a graph showing the surface roughness of gold measured after using the system of FIG.

FIG. 4 is a flow diagram showing one embodiment of the method of the present invention.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Herbert Sea Bitting Rolling Hills Estates, 90274, California, USA Silver Spring Drive 25

Claims (10)

[Claims] 1. A treatment space, means for moving an element having a metal surface to be polished into the treatment space, and means for recirculating gas through the treatment space to purify the treatment space. A processing chamber, a tank containing liquid carbon dioxide, a nozzle and an orifice device for producing solid carbon dioxide gas snow, and a nozzle and orifice device for producing solid carbon dioxide gas snow, and the nozzle and orifice device. A carbon dioxide jet spray system coupled to the processing chamber, comprising a pipe for transferring liquid carbon dioxide to the device, and arranged in the processing space, installing an element to be polished,
An operator-controllable robot arm that moves and positions a nozzle and orifice device with respect to the surface to polish the surface of the element, the nozzle and orifice device controlling controlled flow of liquid carbon dioxide through the nozzle and orifice. A polishing system for a metal surface, which is configured to polish a metal surface by a mechanical action obtained from solid carbon dioxide gas snow generated by the expansion. 2. The system of claim 1, wherein the carbon dioxide jet spray system further comprises a valve device. 3. The system according to claim 1, wherein the processing chamber constitutes an ultra-clean processing chamber. 4. The system of claim 1, wherein the processing chamber comprises a load lock passage having a front entrance door and a rear exit door that allows placement of elements within its interior processing space. 5. The system according to claim 1, wherein the processing chamber comprises a temperature controller connected to a heater to control the temperature of the processing space. 6. The means for recirculating gas through the processing space comprises a blower, a high-efficiency particulate removal filter for filtering the gas, and a stainless steel which allows the filtered gas to pass therethrough for recirculation. The system of claim 1, comprising a steel mesh surface. 7. A processing chamber for holding an element having a metal surface to be polished, a carbon dioxide jet spray system for producing solid carbon dioxide gas snow, and a metal surface to be polished placed in the processing chamber. A carbon dioxide jet spray system for locating the element and for moving and positioning the carbon dioxide jet spray system with respect to the surface to polish the surface of the element, the carbon dioxide jet spray system comprising liquid carbon dioxide A polishing system for metal surfaces, which uses a mechanical action obtained from solid carbon dioxide gas snow produced by controlled expansion to polish metal surfaces. 8. A device having a metal surface to be polished is placed in a process chamber, and a carbon dioxide jet spray system is used to generate solid carbon dioxide gas snow in the process chamber. Moving the carbon dioxide jet spray system to move the carbon dioxide gas snow to polish the metal surface, wherein the solid carbon dioxide gas snow is mechanically produced by the controlled expansion of liquid carbon dioxide. A method for polishing a metal surface, which comprises polishing the metal surface using an action. 9. The method of claim 8, further comprising the step of recirculating gas through the process chamber to clean the process chamber. 10. The step of moving the carbon dioxide jet spray system uses an operator-controllable robot arm located within the process chamber to move the solid carbon dioxide gas snow with respect to the surface of the device. The method described.