USH952H - Method of preparing a quartz surface for sweeping - Google Patents
Method of preparing a quartz surface for sweeping Download PDFInfo
- Publication number
- USH952H USH952H US07/405,822 US40582289A USH952H US H952 H USH952 H US H952H US 40582289 A US40582289 A US 40582289A US H952 H USH952 H US H952H
- Authority
- US
- United States
- Prior art keywords
- metal
- quartz
- openings
- sweeping
- electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 239000010453 quartz Substances 0.000 title claims abstract description 40
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000010408 sweeping Methods 0.000 title claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 41
- 239000002184 metal Substances 0.000 claims abstract description 41
- 238000000151 deposition Methods 0.000 claims abstract description 9
- 230000000737 periodic effect Effects 0.000 claims abstract description 8
- 238000004140 cleaning Methods 0.000 claims abstract description 5
- 230000001464 adherent effect Effects 0.000 claims description 9
- 239000011651 chromium Substances 0.000 claims description 9
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 7
- 239000010931 gold Substances 0.000 claims description 7
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 5
- 229910052737 gold Inorganic materials 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 238000005530 etching Methods 0.000 claims description 4
- 238000003754 machining Methods 0.000 claims description 3
- 239000010953 base metal Substances 0.000 claims description 2
- 239000011159 matrix material Substances 0.000 claims description 2
- RZVXOCDCIIFGGH-UHFFFAOYSA-N chromium gold Chemical compound [Cr].[Au] RZVXOCDCIIFGGH-UHFFFAOYSA-N 0.000 claims 1
- 238000009792 diffusion process Methods 0.000 description 4
- 239000002585 base Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 206010040925 Skin striae Diseases 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 229910021332 silicide Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- UOCLXMDMGBRAIB-UHFFFAOYSA-N 1,1,1-trichloroethane Chemical compound CC(Cl)(Cl)Cl UOCLXMDMGBRAIB-UHFFFAOYSA-N 0.000 description 1
- 229910018512 Al—OH Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 238000004566 IR spectroscopy Methods 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/04—Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/06—Forming electrodes or interconnections, e.g. leads or terminals
Definitions
- This invention relates in general to a method of treating a quartz surface and in particular to a method of preparing a quartz surface for sweeping.
- Quartz is swept generally to render it largely insensitive to radiation. Sweeping generally involves subjecting a quartz crystal in air to an electric field of at least 250V/cm at a temperature of at least 400° C. for a period of at least 12 hours. Such air-swept quartz in resonators commonly yields frequency offsets of no greater than 0.1 ppm after a cumulative exposure of 10 6 to 10 7 rad.
- Many methods have been tried to improve the contact. For example, one method has been to sputter or evaporate the metal onto the quartz surface. This improves the contact, but if the metal is too strongly adherent, then hydrogen species including H 2 , H + , and H 2 O cannot diffuse interfacially fast enough to cover the entire surface between the quartz and the metallic electrode. On the other hand, if the metal is weakly adherent, then metal recession results in loss of electrode contact during the prolonged sweeping times at high temperatures.
- the general object of this invention is to provide a method of treating a quartz surface.
- a more particular object of the invention is to provide a method of preparing a quartz surface for sweeping wherein there will be a good electrical contact between the quartz surface and a metallic electrode.
- a still further object of the invention is to provide a method of preparing quartz for sweeping wherein the quartz will be homogeneously swept assuring production of resonators with predictable performance.
- the periodic openings created in the electrode insure that hydrogen species H 2 , H + and H 2 O will be present at three phase points between electrode, quartz, and atmosphere and will spread interfacially to two phase points between the electrode and quartz.
- the periodic openings either in stripe form or dot matrix or other geometric arrangement can be made by photolithography, photolithographic etching, or lasing machining.
- the quartz material being prepared for sweeping can have different sizes, shapes, and dimensions.
- the quartz surface used is first cleaned using conventional cleaning techniques such as trichloroethane, hot detergent, alcohol, and distilled water. As a final step, samples are cleaned in an oxygen plasma for 2 minutes.
- a metal electrode is then deposited on the cleaned quartz surface by first depositing a strongly adherent metal as a base, followed by a mixture of the base metal with a surface metal followed by the deposition of the surface metal alone.
- a very desirable metal electrode can be formed using chromium as the base or strongly adherent metal and gold as the surface metal. More particularly, the metal electrode can be formed by first depositing by sputtering or evaporation deposition about 100 angstroms of chromium followed by about 50 angstroms of a mixture of chromium and gold followed by about 1000 angstroms of gold.
- vanadium, aluminum, hafnium, zirconium, titanium or niobium as the strongly adherent base film and either platinum, nickel, copper, manganese or cobalt as the surface film.
- Periodic openings are then created intentionally within an electroded surface of the quartz sample to be swept.
- the openings or holes should be spaced such that the surface density of openings assures complete coverage of the surface through the interfacial diffusional spread of H-species. In short, any geometrical design that creates openings in the metal electrode will suffice.
- the metal should not be disconnected by the arrangement of openings, that is, all the metal should be at one potential. In this connection, unintentional electrode openings are referred to as porous films. If porosity is insufficient, color centers will form. If porosity is extensive, loss of electrical contact can result.
- Intentional opening designs will maintain physical and electrical contact and allow penetration of atmospheric water vapor at 3-phase points (electrode-quartz-atmosphere) and interfacial diffusion to 2-phase points for the purpose of electrochemical conversion of H 2 O and H 2 into protons (H + ).
- the proton entry sites will probably be at dislocation and damaged regions on the quartz surface.
- the invention will insure that a quartz surface will be air-swept homogeneously, that is, alkali-metal compensators for A1 impurities will be replaced by H + , eliminating or drastically reducing any non-uniformity of Q or radiation sensitivity created by the formation of competing hole-compensated aluminum impurities.
- a quartz y-bar is cleaned and its Z surfaces electroded by evaporating, first 100 ⁇ of Cr, then 50 ⁇ Cr/Au mixture followed by 1000 ⁇ of Au. Periodic openings are then created in the electrodes using a photolithographic etching or lift-off technique.
- H-species diffuse interfacially to entry points in the quartz for sweeping the interfacial diffusivity in the case of chromium on quartz has been determined to be 7 ⁇ 10 -9 cm 2 /sec, with the H-diffusant being drained into the quartz for volume diffusion or sweeping. Stripes running in any direction is the preferred geometry as openings are created such that H-species can diffuse interfacially from each of the openings. If the metal stripe width is less than 2 times the diffusion length for the isothermal sweeping period, it will be assured that H-species will diffuse over the entire quartz surface.
- the open-quartz stripe width should be kept under 0.5 mm as it has been found that H can be introduced in regions as close as 0.5 mm to an anode boundary.
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Physical Vapour Deposition (AREA)
Abstract
A quartz surface is prepared for sweeping by a method including the steps : f
(A) cleaning the quartz surface,
(B) depositing a metal electrode onto the cleaned quartz surface, and
(C) creating periodic openings in the metal electrode in such a manner that the metal is not disconnected by the arrangement of openings and all the metal is at one potential.
Description
The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.
This invention relates in general to a method of treating a quartz surface and in particular to a method of preparing a quartz surface for sweeping.
Quartz is swept generally to render it largely insensitive to radiation. Sweeping generally involves subjecting a quartz crystal in air to an electric field of at least 250V/cm at a temperature of at least 400° C. for a period of at least 12 hours. Such air-swept quartz in resonators commonly yields frequency offsets of no greater than 0.1 ppm after a cumulative exposure of 106 to 107 rad.
Sweeping only occurs when there is good electrical contact between the quartz and a metallic electrode. Many methods have been tried to improve the contact. For example, one method has been to sputter or evaporate the metal onto the quartz surface. This improves the contact, but if the metal is too strongly adherent, then hydrogen species including H2, H+, and H2 O cannot diffuse interfacially fast enough to cover the entire surface between the quartz and the metallic electrode. On the other hand, if the metal is weakly adherent, then metal recession results in loss of electrode contact during the prolonged sweeping times at high temperatures.
The general object of this invention is to provide a method of treating a quartz surface. A more particular object of the invention is to provide a method of preparing a quartz surface for sweeping wherein there will be a good electrical contact between the quartz surface and a metallic electrode. A still further object of the invention is to provide a method of preparing quartz for sweeping wherein the quartz will be homogeneously swept assuring production of resonators with predictable performance.
It has now been found that the aforementioned objects can be attained by a method including the steps of:
(A) cleaning the quartz surface,
(B) depositing a metal electrode onto the cleaned quartz surface, and
(C) creating periodic openings in the metal electrode in such a manner that the metal electrode is not disconnected by the arrangement of the openings and all the metal is at one potential.
The periodic openings created in the electrode insure that hydrogen species H2, H+ and H2 O will be present at three phase points between electrode, quartz, and atmosphere and will spread interfacially to two phase points between the electrode and quartz. The periodic openings, either in stripe form or dot matrix or other geometric arrangement can be made by photolithography, photolithographic etching, or lasing machining.
The quartz material being prepared for sweeping can have different sizes, shapes, and dimensions. For example, there can be Y-bars, SC-bars, AT-cut and SC-cut resonator blanks, etc. Since, apparently 1 mm of material should be removed from the cathode side of the swept piece, the thickness of the piece to be swept should be adjusted in order to produce the required final dimensions of finished resonator blanks.
The quartz surface used is first cleaned using conventional cleaning techniques such as trichloroethane, hot detergent, alcohol, and distilled water. As a final step, samples are cleaned in an oxygen plasma for 2 minutes.
A metal electrode is then deposited on the cleaned quartz surface by first depositing a strongly adherent metal as a base, followed by a mixture of the base metal with a surface metal followed by the deposition of the surface metal alone. A very desirable metal electrode can be formed using chromium as the base or strongly adherent metal and gold as the surface metal. More particularly, the metal electrode can be formed by first depositing by sputtering or evaporation deposition about 100 angstroms of chromium followed by about 50 angstroms of a mixture of chromium and gold followed by about 1000 angstroms of gold. In lieu of chromium and gold, one might use vanadium, aluminum, hafnium, zirconium, titanium or niobium as the strongly adherent base film and either platinum, nickel, copper, manganese or cobalt as the surface film.
Periodic openings are then created intentionally within an electroded surface of the quartz sample to be swept. The openings or holes should be spaced such that the surface density of openings assures complete coverage of the surface through the interfacial diffusional spread of H-species. In short, any geometrical design that creates openings in the metal electrode will suffice. The metal should not be disconnected by the arrangement of openings, that is, all the metal should be at one potential. In this connection, unintentional electrode openings are referred to as porous films. If porosity is insufficient, color centers will form. If porosity is extensive, loss of electrical contact can result. Intentional opening designs will maintain physical and electrical contact and allow penetration of atmospheric water vapor at 3-phase points (electrode-quartz-atmosphere) and interfacial diffusion to 2-phase points for the purpose of electrochemical conversion of H2 O and H2 into protons (H+). The proton entry sites will probably be at dislocation and damaged regions on the quartz surface.
The invention will insure that a quartz surface will be air-swept homogeneously, that is, alkali-metal compensators for A1 impurities will be replaced by H+, eliminating or drastically reducing any non-uniformity of Q or radiation sensitivity created by the formation of competing hole-compensated aluminum impurities.
A quartz y-bar is cleaned and its Z surfaces electroded by evaporating, first 100 Å of Cr, then 50 Å Cr/Au mixture followed by 1000 Å of Au. Periodic openings are then created in the electrodes using a photolithographic etching or lift-off technique.
On subsequent sweeping, the samples exhibit a uniformity of replacement of alkali compensators (for A1 impurities) with protons resulting in Al-OH centers. Infrared absorption spectroscopy reveals a uniform increase of the room temperature A1-OH band at 3378 cm-1 with respect to spatial variations of an IR analysis beam propagating in the X-direction. There is no indication of color-center striae in the Z-direction. Color-center striae are an indication that sweeping has proceeded nonuniformly. Color centers are created when H+ is unavailable at the anode for entry into the quartz by electrochemical processes. This unavailability will occur if thick strongly adherent metallizations are applied. Openings in the metallization avoids this occurrence. Strongly adherent films result from the formation of metal silicides when metals react with the SiO2 surface. These strongly adherent films are required to insure that the electrode is not removed in subsequent handling, cleaning, or during the sweeping process itself which causes metal recession. The formation of metal silicides in the metal quartz interface inhibits the interfacial diffusion of H-species. Electrode films containing openings insure that H-species can be introduced at three-phase points or points where the atmosphere, electrode and quartz meet. From these linear regions, H-species diffuse interfacially to entry points in the quartz for sweeping the interfacial diffusivity in the case of chromium on quartz has been determined to be 7×10-9 cm2 /sec, with the H-diffusant being drained into the quartz for volume diffusion or sweeping. Stripes running in any direction is the preferred geometry as openings are created such that H-species can diffuse interfacially from each of the openings. If the metal stripe width is less than 2 times the diffusion length for the isothermal sweeping period, it will be assured that H-species will diffuse over the entire quartz surface. The open-quartz stripe width should be kept under 0.5 mm as it has been found that H can be introduced in regions as close as 0.5 mm to an anode boundary. In the case of chromium and a 36 hour maximum temperature sweeping time, the metal stripe width is made to be <2 times the mean free diffusional path ×=(Dt)1/2
I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.
Claims (9)
1. Method of preparing a quartz surface for sweeping, said method including the steps of:
(A) cleaning the quartz surface,
(B) depositing a metal electrode onto the cleaned quartz surface, and
(C) creating periodic openings in the metal electrode in such a manner that the metal electrode is not disconnected by the arrangement of the openings and all the metal is at one potential, and so that H species including H2, H+ and H2 O between the metal and the quartz, from each of the openings.
2. Method according to claim 1 wherein the metal electrode is formed by first depositing a strongly adherent metal as a base followed by a mixture of the base metal with a surface metal followed by the surface metal.
3. Method according to claim 2 wherein the metal electrode is formed by first depositing about 100 angstroms of chromium as the base followed by about 50 angstroms of a chromium-gold mixture followed by about 1000 angstroms of gold.
4. Method according to claim 1 wherein the periodic openings are created in the metal electrodes through the use of a method selected from the group consisting of photolithographic lift off, photolithographic etching, and laser machining.
5. Method according to claim 4 wherein the method used is photolithographic lift off.
6. Method according to claim 4 wherein the method used is photolithographic etching.
7. Method according to claim 4 wherein the method used is laser machining.
8. Method according to claim 1 wherein the openings are created in a stripe arrangement.
9. Method according to claim 1 wherein the openings are created in a dot-matrix arrangement.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/405,822 USH952H (en) | 1989-09-11 | 1989-09-11 | Method of preparing a quartz surface for sweeping |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/405,822 USH952H (en) | 1989-09-11 | 1989-09-11 | Method of preparing a quartz surface for sweeping |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| USH952H true USH952H (en) | 1991-08-06 |
Family
ID=23605393
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/405,822 Abandoned USH952H (en) | 1989-09-11 | 1989-09-11 | Method of preparing a quartz surface for sweeping |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | USH952H (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5086549A (en) * | 1990-10-01 | 1992-02-11 | The United States Of America As Represented By The Secretary Of The Army | Method of preparing a lumbered quartz bar for sweeping and then sweeping said lumbered quartz bar |
-
1989
- 1989-09-11 US US07/405,822 patent/USH952H/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5086549A (en) * | 1990-10-01 | 1992-02-11 | The United States Of America As Represented By The Secretary Of The Army | Method of preparing a lumbered quartz bar for sweeping and then sweeping said lumbered quartz bar |
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