Cleaner composition, method for making and using same

A cleaning solution composition for use on electronic component and equipment employed in the cleaning of these components. The cleaning solution comprises ultrapure water containing carbonic acid plus an oxidizing agent selected from hydrogen peroxide, ozone, and combinations thereof. The invention includes a method of removing contaminants from electronic components, containers and associated equipment using the cleaning solution of novel composition. Further, the invention includes a method of preparing the novel cleaning solution composition by contacting carbon dioxide gas with ultrapure water and adding an oxidizing agent, or by contacting carbon dioxide gas with an ultrapure water solution of oxidizing agent.

CROSS-REFERENCE TO RELATED APPLICATIONS, IF ANY
 Not applicable.
 STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 Not applicable.
 REFERENCE TO A MICROFICHE APPENDIX, IF ANY
 Not applicable.
 BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates, generally, to a cleaning solution
 composition and a method of making and using the cleaning solution
 composition. More particularly, the invention relates to an acidic
 cleaning solution composition containing an oxidizing agent, and a method
 of making and using the acidic oxidizing cleaning solution.
 2. Background Information
 The semiconductor industry employs extensive cleaning regimens in the
 production of various electronic components, such as printed circuit
 boards and devices, as well as the precursors therefor, such as chips and
 wafers. Various cleaning and rinsing steps are used to remove contaminants
 from these components during fabrication, since even minute contaminants
 can interfere with the operation of the electronic components. The
 materials used to clean the components include ultrapure water, and
 aqueous solutions of various cleaning agents, including acidic, neutral,
 and basic substances, as well as organic solvents, both polar and
 nonpolar. The contaminants targeted for removal from the electronic
 components include inorganic compounds, such as metal salts, organic
 substances, such as grease or oil, and particulate material. Particles can
 cause open or short circuits and non-integral dielectric films in
 semiconductor devices. Organic and inorganic contaminants, both metallic
 and nonmetallic, can result in poor dielectric film quality with decreased
 device performance and reliability. Metallic contaminants can be
 especially damaging. Taken as a whole, contaminants result in a large
 portion of yield loss in the manufacture of electronic components.
 In addition, the purity of the cleaning and rinsing substances used to
 remove the contaminants must be controlled to prevent contamination of the
 electrical component being treated. Also, the containers and equipment
 used in the cleaning and rinsing processes must not contribute
 contaminants to the system. For instance, the present total allowable
 metal ion concentration in chemicals used for the semiconductor industry
 is 5 parts per billion (ppb). It is estimated that the purity of chemicals
 must improve 10-fold approximately every 6 years. Thus, both the chemicals
 used and the equipment employed to handle the chemicals must be
 extensively free from contaminants.
 Since metal ions are particularly undesirable semiconductor contaminants,
 metallic containers are generally avoided for cleaning liquids. Plastic
 containers, and, in particular, perfluorinated organic polymer based
 containers, are widely used for this purpose. These containers are subject
 to both surface and bulk contamination where contaminants are desorbed
 from the surface or bulk of the perfluorinated polymer based container.
 There are numerous approaches to cleaning components and many issues which
 must be considered in selecting the best approach. Safety and
 environmental concerns must be addressed, as well as the effectiveness of
 the cleaning technology for providing clean components. Cleaning
 effectiveness considerations need to include the ability to remove
 particles, inorganic materials, and organic materials. Cleaning agents
 should be easily removed from the component and not leave a substantial
 residue. In addition, components must dry without "spotting".
 Safety concerns include cleaning agent toxicity and flammability.
 Environmental concerns include the release of hazardous air pollutants
 (HAPs), volatile organic compounds (VOCs), ozone depleting solvents (ODSs)
 and compounds which have a high global warming potential (GWP).
 The major variables which control cleaning effectiveness are the solution
 chemistry (including temperature) and the use of mechanical energy.
 Chemistries which are commonly used include aqueous solutions (with and
 without surfactants), semiaqueous solutions (water and organic solvent
 mixtures), organic solvents, hydrofluorocarbons and co-solvent systems.
 Mechanical energy can be imparted to the cleaning solution using
 ultrasonic transducers, megasonic transducers, carbon dioxide snow, high
 pressure spray, and the like.
 The state of the art generally includes various devices, methods and
 compositions for removing contaminants from components and material used
 to clean these components. The complexity of the selection process is
 described in a paper by Kanegsberg and Seelig entitled "Precision Cleaning
 Options for the '90s" published in Precision Cleaning '96 Proceedings, pp.
 224-235.
 These devices and methods are believed to have significant limitations and
 shortcomings. Specifically, cleaning solutions may contain corrosive,
 toxic and difficult to dispose of materials. An ideal cleaning solution
 should be easy to prepare on-site, comparatively safe and nontoxic in use,
 and conveniently decomposed to innocuous products for disposal.
 Applicant's invention provides a cleaning solution composition, as well as
 a method of making and using the cleaning solution, which are believed to
 constitute an improvement over the prior art.
 BRIEF SUMMARY OF THE INVENTION
 The present invention provides a cleaning solution composition for use on
 electronic components and equipment employed in the cleaning of these
 components. The cleaning solution comprises ultrapure water containing
 carbonic acid plus an oxidizing agent selected from hydrogen peroxide,
 ozone, and combinations thereof. The invention includes a method of
 removing contaminants from electronic components, containers and
 associated equipment using the cleaning solution of novel composition.
 Further, the invention includes a method of preparing the novel cleaning
 solution composition by contacting carbon dioxide gas with ultrapure water
 and adding an oxidizing agent, or by contacting carbon dioxide gas with an
 ultrapure water solution of oxidizing agent.
 The features, benefits and objects of this invention will become clear to
 those skilled in the art by reference to the following description, claims
 and drawings.

DETAILED DESCRIPTION
 The present invention comprises a cleaning solution composition for
 removing contaminants from electrical components, as well as from
 containers and associated equipment employed in the cleaning process for
 these components. In addition, the invention includes a method of removing
 contaminants from components, containers or associated equipment using the
 cleaning solution of novel composition. Finally, the invention includes a
 method of preparing the novel cleaning solution composition.
 1. Cleaning Solution Composition
 The cleaning solution composition of the present invention comprises a
 solution of ultrapure water plus carbonic acid and an oxidizing agent. The
 oxidizing agent is selected from the group consisting of hydrogen
 peroxide, ozone and a combination of hydrogen peroxide plus ozone. Each of
 these components is commercially available in high purity form, or is
 easily prepared from high purity materials so as to produce a material
 suitable for use in cleaning electrical components and associated
 equipment.
 Carbonic acid is formed in situ by contacting ultrapure water with carbon
 dioxide gas. Carbon dioxide reacts with water to form carbonic acid
 according to equation 1.
EQU CO.sub.2 +H.sub.2 O.fwdarw.H.sub.2 CO.sub.3 (1)
 Carbonic acid is a weak acid and, in water, dissociates to form hydronium
 ions and bicarbonate ions according to equation 2.
EQU H.sub.2 CO.sub.3 +H.sub.2 O.fwdarw.H.sub.3 O.sup.+ +HCO.sub.3.sup.- (2)
 Thus, an aqueous carbonic acid solution will exhibit an acidic pH, that is,
 a pH less than 7.0. Bicarbonate ion does not dissociate to hydronium ions
 and carbonate ions to any measurable extent unless the pH of the aqueous
 solution is made quite basic, a pH greater than 7.0, by addition of a
 strong base that provides hydroxide ions. The carbonic acid concentration
 of such solutions can be indirectly determined by measuring the pH of the
 these solutions. As additional carbon dioxide reacts to produce additional
 carbonic acid, equation 2 is driven to form higher concentrations of
 reaction products, hydronium ions and bicarbonate ions. Since pH measures
 solution hydronium ion concentration, carbonic acid solution content is
 indirectly measured. The more acidic (lower pH) the carbonic acid
 solution, the higher the concentration of carbonic acid contained therein.
 The measured ionization constant for an aqueous solution of carbonic acid
 is K.sub.1 =4.45.times.10.sup.-7. Using this ionization constant value,
 aqueous solutions containing 0.1, 1.0 or 10 moles/liter of carbonic acid
 are calculated to have a pH of 3.7, 3.2 or 2.7 respectively. Thus, the
 most acidic pH attainable for an aqueous carbonic acid solution alone is
 2.0 or higher.
 Carbon dioxide is commercially available in high purity with the material
 available in pressurized cylinders ranging in size from hand carried
 lecture bottles to rail car sized pressure vessels.
 To produce the cleaning solution, sufficient carbon dioxide is contacted
 with the ultrapure water to produce a carbonic acid solution of pH in the
 range 2.0 to about 6.0. Preferably, sufficient carbon dioxide is contacted
 with the ultrapure water to produce a carbonic acid solution of pH in the
 range 2.0 to about 5.0. Most preferably, sufficient carbon dioxide is
 contacted with the ultrapure water to produce a carbonic acid solution of
 pH in the range 2.0 to about 4.5.
 The oxidizing agent added to the carbonic acid solution is selected from
 the group consisting of hydrogen peroxide, ozone and hydrogen peroxide
 plus ozone. Hydrogen peroxide is available as electronic grade high purity
 material, in the form of aqueous solutions up to about 70% hydrogen
 peroxide by weight. Sufficient hydrogen peroxide is added to the above
 described carbonic acid solution to produce a hydrogen peroxide
 concentration of about 1% to 10% by weight. Preferably hydrogen peroxide
 is added to produce a hydrogen peroxide concentration of about 4% to 6% in
 the carbonic acid solution. Most preferably hydrogen peroxide is added to
 produce a hydrogen peroxide concentration of about 5% in the carbonic acid
 solution.
 Alternatively, hydrogen peroxide solution can first be added to ultrapure
 water and the resulting solution contacted with carbon dioxide gas to
 generate carbonic acid in solution, thus producing a cleaning solution
 having the desired pH range.
 Ozone is another oxidizing agent which can be added to the carbonic acid
 solution to produce a suitable cleaning solution composition. Ozone is a
 gas at ambient conditions and is an extremely powerful oxidizing agent.
 The high reactivity of ozone necessitates that ozone be generated at the
 point of use. Ozone is routinely produced on site by commercially
 available ozone generator devices. Air, oxygen-enriched air, or pure
 oxygen is subjected to a corona discharge in the ozone generator to
 produce a gas containing up to about 10% ozone. The ozone-containing gas
 is contacted with the carbonic acid aqueous solution to dissolve all or a
 portion of the ozone in that solution. Preferably, the resulting cleaning
 solution contains at least about 1 mg/l of dissolved ozone as the
 oxidizing agent. Most preferably, the carbonic acid solution is saturated
 with ozone.
 Alternatively, ozone can first be added to ultrapure water and the
 resulting solution contacted with carbon dioxide gas to generate carbonic
 acid in solution, thus producing a cleaning solution having the desired pH
 range.
 In a further embodiment of the invention, a combination of hydrogen
 peroxide and ozone is employed as the oxidizing agent of the cleaning
 solution composition. Preferably, the hydrogen peroxide is added to
 produce a hydrogen peroxide concentration of about 4% to 6% in the
 carbonic acid solution, and ozone is added to produce an aqueous solution
 saturated with ozone. Again, the carbonic acid may be generated in
 solution before or after addition of the oxidizing agent or agents.
 The combination of an aqueous solution of carbonic acid and an oxidizing
 agent selected from hydrogen peroxide, ozone and hydrogen peroxide plus
 ozone, has been found to be a highly effective composition for cleaning
 electrical components, as well as containers and other equipment employed
 in the electronics industry. Not only is the cleaning solution composition
 effective in removing contaminants, but the spent cleaning solution is
 easily and economically treated to render it innocuous. Solutions of
 carbonic acid and hydrogen peroxide can be neutralized by simply
 maintaining the solution at an elevated temperature. Heat will readily
 decompose hydrogen peroxide to oxygen and water and convert carbonic acid
 to carbon dioxide gas. Carbonic acid and ozone can also be removed from
 solution by sparging with an inert gas, such as nitrogen. Ozone can easily
 be decomposed by either heating the solution or by treating the solution
 with UV radiation.
 2. Method of Making and Using Cleaning Solution
 Several methods of making the novel composition cleaning solution have been
 briefly mentioned above. In one embodiment, carbon dioxide gas is
 contacted with ultrapure water to produce a solution of carbonic acid of
 the desired solution pH. Preferably carbon dioxide gas is sparged into
 water to bring about carbonic acid formation. Next, an oxidizing agent is
 added to the carbonic acid solution to produce the novel cleaning
 solution. The oxidizing agent may be hydrogen peroxide, ozone or a
 combination of hydrogen peroxide plus ozone. Hydrogen peroxide is added in
 the form of an aqueous solution while ozone is generated in a gaseous
 mixture with air or oxygen, and the mixture is contacted with the carbonic
 acid solution. Preferably, the gas mixture is sparged into the carbonic
 acid solution to dissolve the ozone therein. A combination of hydrogen
 peroxide plus ozone requires separate addition steps for each oxidant.
 In another embodiment, the novel cleaning solution is prepared by first
 adding the oxidizing agent or agents to ultrapure water to produce a
 solution of oxidizing agent, and then contacting carbon dioxide gas with
 the oxidizing agent solution to produce carbonic acid therein, and thus
 produce the desired cleaning solution.
 The invention also includes a method of removing contaminants from
 contaminated items using the novel cleaning solution. The steps include
 providing the cleaning solution of ultrapure water, carbonic acid and
 oxidizing agent, contacting contaminated items with the cleaning solution
 for a selected time period to remove contaminants, and removing the items
 from contact with the cleaning solution to produce items with reduced
 contaminants. Preferably, the items are contacted with the cleaning
 solution by immersion of the items in the solution. In a further
 embodiment of the process, the cleaning solution is heated to a selected
 temperature during the item contacting step. The duration of the
 contacting step is approximately one hour, and preferably at least one
 hour, although shorter times may be desirable. The duration of the
 contacting step may be in excess of twenty-four hours in certain
 applications. The selected temperature to which the cleaning solution is
 heated during the contacting step is preferably about 50 degrees C., and
 most preferably is about 80 degrees C.
 The following examples should be interpreted in the illustrative and not
 the limited sense with regard to the present invention.
 EXAMPLE I
 It is imperative to minimize the contaminants that enter the chemical
 cleaning reagents which are used to clean electronic components. A
 significant source of contaminants is the containers and associated
 equipment used in handling the chemical cleaning reagents. In order to
 assess the efficiency of various cleaning compositions and contacting
 regimens, samples of plastic parts used in semiconductor fluid handling
 systems were subjected to a variety of cleaning compositions and the
 effectiveness of each determined. Techniques were developed to measure
 inorganic, organic and particulate contaminants in parts made from
 different polymers with different geometries and fabrication histories.
 Polymers investigated included polytetrafluoroethylene (PTFE),
 perfluoroalkoxy (PFA) and polyvinylidenedifluoride (PVDF). Geometries
 examined include large, flat surfaces and various small complex parts. The
 parts were fabricated by machining or injection molding.
 The cleaning methods initially evaluated are described in Table 1.
 TABLE 1
 Cleaning Methods Evaluated
 Cleaning Chemical Temp, Time,
 procedure Description Composition .degree. C. minutes
 None Ambient --
 Carbonated A mixture of 5% H.sub.2 O.sub.2 in Ambient 60
 peroxide hydrogen peroxide UPW
 and carbon dioxide in pH = 4.5
 ultrapure water in a
 circulating bath.
 Hot A heated mixture of 5% H.sub.2 O.sub.2 80.degree. C. 60
 carbonated hydrogen peroxide UPW
 peroxide and carbon dioxide in pH = 4.5
 ultrapure water in a
 circulating bath.
 QDR Ultrapure water in a 100% UPW Ambient 10
 quick dump rinse
 station
 Megasonic + Ultrapure water in a 100% UPW Ambient 5
 QDR megasonic cleaning
 station
 Surfactant An aqueous 0.1% TX400 Ambient 60
 surfactant solution in in UPW
 a circulating bath.
 HFE + hot Hydrofluoroether in a 100% Ambient 120
 UPW circulating bath. HFE7100 and
 80.degree. C.
 Piranha A mixture of sulfuric 80% H.sub.2 SO.sub.4 80.degree. C. 5
 acid and hydrogen 20% H.sub.2 O.sub.2
 peroxide in a (30% in
 stagnant bath water)
 Hot UPW Heated ultrapure 100% UPW 80.degree. C. 60
 water in a circulating
 bath.
 Proprietary A commercial -- -- --
 cleaner cleaner used to purify
 fluoropolymer parts
 Process Effectiveness Test Methods
 Tests to determine the effectiveness of various cleaning methods were
 performed in two steps. First, a variety of common cleaning solutions were
 used to clean two types of plastic semiconductor equipment components. In
 addition, one type of plastic component that had been heavily contaminated
 by handling was included. All of these initial-cleaning tests were run
 under the same conditions using multi-contaminant dynamic extraction
 (MCDE). The amounts of inorganic, organic and particulate contamination
 remaining after each cleaning process that could be extracted into water
 were measured. These results were the basis of a comparison of cleaning
 solution effectiveness. The more contaminant remaining, the less effective
 the cleaning method.
 Multi-Contaminant Dynamic Extraction (MCDE)
 The multi-contaminant dynamic extraction procedure (MCDE) is an on-line
 procedure for simultaneously measuring extractable organic and inorganic
 levels as well as particle shedding from a component with time. This
 technique measures the rate at which contaminants are extracted. This
 method has been developed with two main goals in mind: (1) to determine
 component cleanliness levels and (2) to evaluate various
 component-cleaning techniques to improve the cleanliness of the
 components. This technique has been used to evaluate the cleanliness of a
 variety of PFA resins and injection molded PFA parts as well as filters,
 valves, and machined fluoropolymer parts.
 The method provides simultaneous on-line measurements of the current level
 of inorganics, organics, and particulate contaminants. The length of the
 test can be varied based on the cleanliness of the components being
 tested. The method gives a quick indication (&lt;1 day) of whether a part
 is clean or contaminated. Although secondary sample analysis is not
 required to obtain information on the cleanliness of the part, samples may
 be drawn from the system at any time during testing to provide additional
 information about the chemical nature of the contamination. No hazardous
 chemicals are required since the system operates with ultrapure water.
 MCDE Test System
 The MCDE test setup is shown in FIG. 1. Components to be tested are placed
 in a loop of circulating ultrapure water (UPW). The resistivity, total
 organic carbon (TOC), and particle concentrations in the system are
 monitored to determine if inorganics, organics, and particles are
 extracted from the components over time. The test system consists of an
 UPW reservoir, pump, filter, parts chamber, a Thornton resistivity probe
 (to measure inorganics), PMS M65 laser particle counter, and an Anatel
 A-100 TOC analyzer to measure organics.
 MCDE Test Procedure
 The following description outlines the process of flushing and installing
 components in the system to begin a test. The test system is initially
 flushed with ultrapure water until the resistivity of the water in the
 system reaches 18.3 Mohm-cm. N.sub.2 is slowly metered into the top of the
 reservoir and allowed to vent from the reservoir. The N.sub.2 flow
 provides a nitrogen blanket for the system so that the resistivity of the
 UPW is not inadvertently degraded due to absorption of carbon dioxide from
 the ambient atmosphere.
 The incoming UPW flow is then stopped. At this point, components are
 installed into the system. To do so, the pump is stopped and closing the
 isolation valve between the filter and the parts chamber isolates the
 parts chamber. Opening the sample/drain valve and closing the reservoir
 vent drains the parts chamber. The parts chamber is then removed to
 install components in the test chamber. The low N.sub.2 flow into the
 reservoir blankets the UPW in the reservoir while the components are
 installed in the test chamber.
 Alternatively, for flow-through components such as valves, the parts
 chamber is replaced by a spool piece during system flush up. Then, the
 spool piece is removed so that the flow-through component may be installed
 in its place. After the components have been installed, the parts chamber
 is purged with 10 l/min. of N.sub.2 for several minutes through the
 blow-down port on the parts chamber to remove CO.sub.2 added to the
 chamber during component installation.
 Once the chamber or flow-through part has been purged, the isolation valve
 is opened and the pump is turned on to circulate water through the system
 at a flow rate of 1.01 l/min. If necessary, UPW is added until the
 reservoir is nearly full. Once all gag bubbles have been removed from the
 TOC analyzer and particle counter lines, testing is started. During all
 tests, the N.sub.2 blanket is maintained to eliminate absorption of
 CO.sub.2 by the water in the system. Both the particle counter and Anatel
 instrument return the sampled water to the reservoir so that all water and
 most contaminants are kept in the system. Tests were performed over 20-24
 hours, but this time may vary depending on the cleanliness of the parts.
 MCDE Data Analysis/System Background
 To maintain a closed system and still be able to make measurements of TOC
 requires the return of UPW that had been sampled by the Anatel instrument
 back to the reservoir. Each time the Anatel instrument takes a sample, a
 valve closes, isolating the 7-ml sample volume. The ultraviolet radiation
 of the lamp breaks down the organics in the UPW thereby forming dissolved
 C.sub.2 in the UPW in the form of carbonic acid. The TOC in the sample is
 determined by measuring the change in resistivity. After the measurement
 process is complete, the valve opens and the sample chamber is flushed.
 However, 7 ml of water with a reduced resistivity is added to the 4-liter
 system. The resistivity of the sample water exiting the Anatel instrument
 is related to the TOC in the system. For example, a TOC sample of 50 ppb
 would release about 7 ml of 2 Mohm-cm water into the system. The addition
 of this 7-ml of water reduces the resistivity of the system from 18.3 to
 about 18.0 Mohm-cm. The nitrogen blanket of the system may remove the
 carbonic acid, thereby eliminating the resistivity degradation problem due
 to the Anatel instrument. To reduce the effect of the Anatel instrument,
 the instrument is configured to sample only once per hour.
 By breaking down the organic compounds each time a TOC measurement is made
 and returning the 7 ml of water back into the 4-liter system, the TOC in
 the system is reduced by about 0.2% per sample. This results in a
 reduction in TOC of 4.7% (7.0) in 24 hours and 28.6% (39.4) in 1 week.
 System background tests are performed periodically to ensure that
 contamination is not being introduced by the components that make up the
 test system. Background tests are performed using the same procedure,
 except no parts are installed in the system. System water samples are
 analyzed for cations, anions, and trace metals.
 Cleaning Effectiveness
 MCDE test results: The amount of inorganic, organic and particulate
 contaminants removed in the MCDE tests by each cleaning solution was
 measured. Surface contaminants are shown in Tables 2 through 4; inorganic
 and organic contaminants in the bulk material are shown in Tables 5 and 6.
 The highlighted numbers in the tables indicate the cleaning solutions with
 the better performances. Blank cells in the table indicate that the part
 was not tested. Hot carbonated peroxide was among the most effective
 processes in most instances.
 TABLE 2
 Inorganic surface contamination remaining after cleaning
 as measured by MCDE
 Surface contamination, ng (as NaCl)/cm.sup.2
 Clean New Part A New Part B Handled Part A
 MCDE background 8 8 8
 None 185 450 750
 Carbonated peroxide 175
 QDR 75
 Megasonic 75 45 65
 Surfactant 110
 Piranha 70 50
 Hot UPW 70 80
 Hot carbonated 75 45 150
 peroxide
 Megasonic plus hot 65
 carbonated peroxide
 Proprietary 70
 commercial cleaner
 HFE plus hot UPW 85
 TABLE 2
 Inorganic surface contamination remaining after cleaning
 as measured by MCDE
 Surface contamination, ng (as NaCl)/cm.sup.2
 Clean New Part A New Part B Handled Part A
 MCDE background 8 8 8
 None 185 450 750
 Carbonated peroxide 175
 QDR 75
 Megasonic 75 45 65
 Surfactant 110
 Piranha 70 50
 Hot UPW 70 80
 Hot carbonated 75 45 150
 peroxide
 Megasonic plus hot 65
 carbonated peroxide
 Proprietary 70
 commercial cleaner
 HFE plus hot UPW 85
 TABLE 4
 Particulate contamination remaining after cleaning
 as measured by MCDE
 Time (in minutes) to achieve specified addition rate
 of particles .gtoreq.0.1 .mu.m
 Clean &lt;10/mL &lt;1/ml
 None 90 320
 Proprietary 120 500
 commercial cleaner
 Megasonic 25 65
 HFE+ Hot UPW 10 35
 Hot carbonated 5 30
 peroxide
 TABLE 4
 Particulate contamination remaining after cleaning
 as measured by MCDE
 Time (in minutes) to achieve specified addition rate
 of particles .gtoreq.0.1 .mu.m
 Clean &lt;10/mL &lt;1/ml
 None 90 320
 Proprietary 120 500
 commercial cleaner
 Megasonic 25 65
 HFE+ Hot UPW 10 35
 Hot carbonated 5 30
 peroxide
 TABLE 6
 Organic bulk contamination remaining after cleaning
 as measured by 24 hour MCDE tests
 Bulk contamination, ng (as TOC)/cm.sup.2
 Clean New Part A New Part B Handled Part A
 Background 20 2.5 20
 None 135 5 &lt;5
 Carbonated peroxide 75
 QDR 80
 Megasonic 65 &lt;5
 Surfactant &lt;5
 Piranha &lt;5
 Hot UPW 100 5
 Hot carbonated 60 &lt;5 5
 peroxide
 Megasonic plus hot &lt;5
 carbonated peroxide
 HFE plus hot UPW 10
 Proprietary &lt;5
 commercial cleaner
 In almost all cases the carbonated peroxide and hot carbonated peroxide
 cleaning solutions were as effective or more effective than the other
 cleaners evaluated.
 EXAMPLE II
 A second set of tests was performed to verify the MCDE results. The
 cleaning process that the MCDE tests deemed most effective were subjected
 to a DyconE.sup.X.SM. dynamic extraction procedure. The DyconE.sup.X
 procedure measures the contaminants extracted by 35% HCl, a far more
 powerful extractant than water. The amount of residual HCl-extractable
 contaminants following each of the cleaning procedures was used as a
 second measure of the effectiveness of each cleaning solution. Again, the
 more contaminants seen in the DyconE.sup.X procedure, the less effective
 the cleaning solution.
 DyconE.sup.X.SM.
 DyconE.sup.X.SM. is a dynamic extraction procedure patented by FSI
 International (U.S. Pat. No. 5,641,895). It is a dynamic batch procedure
 designed to measure the accumulated mass of various metallic elements
 extracted from a test component by a semiconductor process fluid as a
 function of time. The extraction data are typically normalized to the
 surface area of the component that was in contact with chemical solution
 during the test. The rate of extraction, in terms of ng/cm.sup.2 -day, is
 determined by calculating the derivative of the curve obtained by plotting
 the normalized mass extracted as a function of time. The measured rates of
 extraction of individual metallic elements and the sum of all metallic
 elements at day 7 are compared to the requirements for the component. For
 example, FSI International's 1998 specification for total extractables at
 7 days is less than or equal to 0.5 nanograms/cm.sup.2 /day.
 The concept of DyconE.sup.X arose in response to the difficulty associated
 with evaluating data from conventional methods used to determine the
 extraction of metallic components. These methods typically involved
 contacting the component with the fluid for a given period of time and
 analyzing samples of the fluid before the test was initiated and after the
 test was completed (i.e. a 2-point test method). Due to stringent purity
 requirements, changes in metal concentrations on the order of the
 detection limits of the analytical procedure can be significant, and
 errors in sampling and analysis can easily confuse interpretation of
 results. These problems have been well documented in the literature. Data
 collected over time in the DyconE.sup.X procedure are well suited to
 regression analysis, which provides a statistical counterbalance to the
 errors associated with sampling and analysis. The reliability of the
 evaluation is greatly improved over two-point test methods.
 The DyconE.sup.X procedure can be conducted quite simply in a static mode
 or, most advantageously, in a flow mode. Flow mode minimizes the liquid
 diffusion barrier to extraction. The DyconE.sup.X apparatus (flow mode) is
 typically configured to extract only the wetted surface of the component
 by connecting that component into a loop of circulating chemical in the
 same manner as the component would be used in the manufacturing facility.
 However, a fluid reservoir can also be inserted into the test apparatus
 and used to submerge a component for chemical extraction of all interior
 and exterior surfaces. Since the circulated chemical, typically
 concentrated hydrochloric acid, is highly corrosive, the system should be
 placed in a secondary containment enclosure.
 DyconE.sup.X Test Procedure
 The test apparatus is shown in FIG. 2. The procedure employs a
 pre-extracted, closed-loop test system that continuously circulates the
 extracting chemical through the test unit. The main components of the
 apparatus include a PFA chemical leachate reservoir and a circulation pump
 with a PTFE pump head. PFA tubing, fitting, and valves are used
 exclusively in the apparatus. Since the residence time in the chemical
 reservoir is on the order of minutes whereas the characteristic time
 required to detect measurable changes in concentration is on the order of
 hours, the system can be considered well mixed. The test is normally run
 for 10 days, and samples of circulating chemical are taken at several
 times throughout the test. Samples are analyzed by ICP-MS (inductively
 coupled plasma-mass spectroscopy) and GFAAS (graphite furnace atomic
 absorption spectroscopy) for the 20 metallic elements: Al, Ba, Be, B, Cd,
 Ca, Cr, Cu, Au, Fe, Pb, Li, Mg, Mn, Ni, K, Na, Sn, Ti and Zn.
 The test procedure involves first filling the leachate reservoir with
 chemical. A typical chemical used for dynamic extraction is ultra-high
 purity, 35% hydrochloric acid, such as BASELINE Hydrochloric Acid from
 Seastar Chemicals, Inc. A control sample of chemical is taken directly
 from the reagent bottle for analysis. The circulation pump is started and
 the chemical solution is circulated through the system, which contains a
 clean pre-leached spool piece in place of the test component, for an hour
 before the pump is stopped. At this time a second control sample of
 chemical is taken from the reservoir for analysis as the system blank. The
 spool piece is then replaced with the test component and the pump is
 started to initiate the test. The first sample is taken at about 40
 minutes to estimate surface contamination of the component, and serves as
 the initial or baseline sample for evaluation of the extraction of metals
 from this component. Subsequent samples, which represent extraction of
 metallic species from the bulk material of the component being tested, are
 taken at approximately 0.08, 0.4, 2 and 10 days from the time the first
 sample is drawn. The initial volume of chemical that is added, and the
 volumes of all samples withdrawn from the system, are recorded to ensure
 an accurate evaluation of the mass of metallics extracted, based on the
 analysis of samples from the system over time.
 DyconE.sup.X Data Analysis
 Metal extraction from the bulk material can be predicted from diffusion
 theory, which suggests that a reasonable approximation to the mass
 extracted as a function of time is provided by equation (3):
EQU m=k.multidot.t.sup.n (3)
 where:
 t=time (days)
 m=normalized cumulative mass extracted (ng/cm.sup.2) at time t
 k=proportionality constant
 n=exponent
 Taking the log of both sides of equation (3) gives:
EQU Log(m)=log(k)+n.multidot.log(t) (4)
 The parameters in equation (3) for the metallic elements are obtained from
 a linear regression analysis of the normalized extraction data as a
 function of time plotted in log/log format. In this case, n is the slope
 and log k is the intercept as shown in equation (4).
 This mathematical model assumes the extraction process can be approximated
 by diffusion from planar material with uniformly distributed contaminants,
 and is valid until most of the mass is extracted. The theory also predicts
 that the slopes of the extraction curves, plotted on log/log scale, should
 be 0.5. In many cases, the experimentally determined slopes can vary
 significantly from 0.5. The difference between prediction and observation
 may be due to the fact that the assumptions inherent in the theory are not
 met in practice.
 The values for the constants k and n can be used to calculate the total
 mass extracted (for the 20 elements analyzed) from the test piece at
 different times by substituting these values into equation (3). In
 addition, the rate of extraction, expressed as ng/cm.sup.2 -day, can be
 determined by calculating the derivative of equation (3), as shown in
 equation (5):
EQU Rate of extraction=dm/dt=n.multidot.k.multidot.t.sup.n-1 (5)
 The rate of extraction at any time can be calculated by substituting the
 values for the constants and the time into equation (5). A more detailed
 description of the data analysis procedure is given in the original
 patent.
 DyconE.sup.x Test Results
 As a second measure of cleanliness some of the cleaning solutions that were
 deemed effective by MCDE were tested using the DyconE.sup.x procedure. The
 results of this testing showed that the parts cleaned with hot carbonated
 peroxide contained the lowest levels of residual HCl-extractable
 contaminants (Table 7). The major metal ions detected were iron and
 aluminum.
 If the contaminants on the exterior of a component are soluble in a
 cleaning solution, they are quickly removed. In this study, the
 contaminants removed in the first hour of the tests were considered to be
 surface contamination. Contaminants within the bulk material of the
 component require more time for extraction; thus, contaminants that are
 extracted after one hour are considered bulk contaminants.
 TABLE 7
 Residual contaminants of the new Part B extracted by the
 DyconE.sup.X procedure
 Bulk Total
 Surface Major Metal Ex- Mass Major
 Metal Surface traction in Extracted Bulk
 Cleaning Extraction Contamin- 10 days in 10 days Contamin-
 Technique (ng/cm.sup.2) ants (ng/cm.sup.2) (ng/cm.sup.2) ants
 None 22.3 Fe, Al 3.5 25.8 Fe, Al, Cr
 Proprietary 15.4 Fe, Al, 10.7 26.1 Fe, Cr,
 Commercial Cu, Na Ca, Ni,
 Cleaner Mg
 Hot 5.5 Fe 1.7 7.2 Fe
 carbonated
 peroxide
 The descriptions above and the accompanying drawings should be interpreted
 in the illustrative and not the limited sense. While the invention has
 been disclosed in connection with the preferred embodiment or embodiments
 thereof, it should be understood that there may be other embodiments which
 fall within the scope of the invention as defined by the following claims.
 Where a claim, if any, is expressed as a means or step for performing a
 specified function it is intended that such claim be construed to cover
 the corresponding structure, material, or acts described in the
 specification and equivalents thereof, including both structural
 equivalents and equivalent structures, material-based equivalents and
 equivalent materials, and act-based equivalents and equivalent acts.