Ultraclean surface treatment device

The present invention provides a novel porous polymeric device (101) (103) (105) (107) (109) (111) (113), e.g., an ultraclean brush. The device includes an elongated foam member (101, 103), which has an outer surface for removing residual particles from a surface of a substrate. Among other features, the elongated foam member includes a polyvinyl alcohol bearing compound, where the elongated foam member has a calcium ion impurity concentration of less than about 1 part per million. Accordingly, the present device is much cleaner than conventional devices.

BACKGROUND OF THE INVENTION
 The present invention relates to the manufacture of objects. More
 particularly, the present invention provides a technique including a
 system for manufacturing an ultraclean "scrubbing" brush or surface
 treatment device for the manufacture of integrated circuits, for example.
 Merely by way of example, the present invention is applied to a scrubbing
 device for the manufacture of integrated circuits. But it will be
 recognized that the invention has a wider range of applicability; it can
 also be applied to the manufacture of semiconductor substrates, hard
 disks, flat panel displays, and the like.
 In the manufacture of electronic devices such as integrated circuits, the
 presence of particulate contamination, trace metals, and mobile ions on a
 wafer is a serious problem. Particulate contamination can cause a wide
 variety of problems such as electrical "opens" or "shorts" in the
 integrated circuit. These opens and shorts often lead to reliability and
 functional problems in the integrated circuit that has the opens or
 shorts. Mobile ion and trace metal contaminants can also lead to
 reliability and functional problems in the integrated circuit. The
 combination of these factors is the main source of lower device yields on
 a wafer, thereby increasing the cost of an average functional device on
 the wafer. In the manufacture of highly integrated devices, planarizing
 techniques have been used.
 Chemical-mechanical polishing ("CMP") is a commonly used technique for
 planarizing a film on the wafer prior to subsequent processing of the
 wafer. CMP often requires an introduction of a polishing slurry onto a
 surface of a film on the semiconductor wafer as the wafer is being
 mechanically polished against a rotating polishing pad. The slurries
 typically are water based and can contain fine abrasive particles such as
 silica, alumina, and other abrasive materials. After polishing is
 complete, the processed wafers must be cleaned to completely remove
 residual slurry and other residue from the polishing process in order that
 the surface is ready for other processing steps such as etching,
 photolithography, and others.
 To clean residual slurry material from the surface of the polished surface,
 cleaning brushes have been used. These cleaning brushes are often a member
 that is cylindrical in shape, which generally rotates along a center axis
 of the cylindrical shaped member. The cleaning brushes are also often made
 of a foam or porous polymeric material such as polyvinyl alcohol ("PVA").
 A combination of rotational movement of the brush and force or pressure
 placed on the brush against the wafer causes residual slurry materials to
 be removed from the surface of the wafer. Unfortunately, it has been found
 that the brushes themselves often contain residual materials from the
 brush manufacturing process. These residual materials include, among
 others, residual particles and impurities such as ions and particulate
 contamination. Given that brushes are often "dirty" from a manufacturer,
 it is often difficult to maintain cleanliness of an integrated circuit
 manufacturing process by using such dirty brushes.
 From the above, it is seen that an improved technique for cleaning a
 surface treatment device is highly desired.
 SUMMARY OF THE INVENTION
 According to the present invention, a technique including a treatment
 device for cleaning surfaces is provided. In an exemplary embodiment, the
 present invention provides an ultraclean or microclean surface treatment
 device which includes a scrubbing brush for the manufacture of substrates
 for the electronics industry.
 In a specific embodiment, the present invention provides a novel porous
 polymeric device, e.g., an ultraclean brush. The device includes an
 elongated porous polymeric member, which has an outer surface for removing
 residual particles from a surface of a substrate. Among other features,
 the member includes a polyvinyl alcohol bearing compound, where the
 elongated member has a calcium ion impurity concentration of less than
 about 1 part per million. Accordingly, the present device is much cleaner
 than conventional devices.
 In an alternative embodiment, the present invention provides a surface
 treatment device. The device is a porous polymeric member including an
 outer surface for removing residual particles from a surface of a
 substrate such as a wafer or hard disk. The porous polymeric member is
 made of at least a polyvinyl alcohol bearing compound, which may be known
 as PVA, but is not limited. The porous polymeric member also has a calcium
 ion impurity concentration of less than about 1 part per million, and a
 sodium ion concentration of less than about 0.1 part per million. The
 porous polymeric member is substantially free from loose portions (e.g.,
 un-cross-linked) of the porous polymeric member greater than about 1
 micron in size, or greater than about 0.5 micron in size, or greater than
 about 0.1 micron in size.
 Numerous advantages are achieved using the present invention over
 conventional techniques. For example, the present invention provides an
 ultraclean or microclean brush product in some embodiments. The present
 brush product is cleaner and tends to introduce fewer particles or
 impurities onto a substrate to be processed. Additionally, the present
 brush product is cleaner "out of the box." That is, the present brush
 product is much cleaner on delivery than conventional products, which are
 now on the market at the filing date of this present application.
 Accordingly, the present brush product is easier to use and provides for a
 more efficient manufacturing process, which is important in the
 manufacture of integrated circuits, for example. The present invention can
 also be applied to other porous polymeric products. These and other
 advantages or benefits are described throughout the present specification
 and are described more particularly below.
 These and other embodiments of the present invention, as well as its
 advantages and features are described in more detail in conjunction with
 the text below and attached Figs.

DESCRIPTION OF SPECIFIC EMBODIMENTS
 FIG. 1 is a simplified diagram of surface treatment devices according to
 embodiments of the present invention. This Fig. is merely an illustration
 and should not limit the scope of the claims herein. One of ordinary skill
 in the art would recognize other variations, modifications, and
 alternatives. As shown, the devices or porous polymeric products (e.g.,
 foam or sponge products) can range in size and shape, depending upon the
 application. According to an embodiment, the device can be shaped as brush
 rollers 101, which have protrusions thereon, or brush rollers 103 that
 have smooth surfaces. These brush rollers have shapes and sizes to meet
 the particular cleaning application for devices such as semiconductor
 wafers, hard disks, and other applications. The device can also be in the
 form of wipes 105, disks 107, and custom applications 109. Additionally,
 the device can be in the form of puck brushes 111 and plugs 113.
 Furthermore, the device can be in other shapes and sizes depending upon
 the application.
 In a specific embodiment, the devices are made using a suitable material
 that is firm, porous, elastic, and has certain abrasion resistiveness. In
 most embodiments, the main raw starting material for the device is
 polyvinyl alcohol, but can be others. As merely an example, polyvinyl
 alcohol is used to form a polyvinyl acetal porous elastic material. The
 porous material varies in characteristic depending upon cleanliness, type
 of pore forming agent or process, type of aldehyde employed for the
 conversion of a polyvinyl alcohol to a polyvinyl acetal, and other
 factors. These factors also include the relative proportions of reactants,
 reaction temperature and time, and the general condition and starting
 materials in the manufacturing process. Cleanliness of the manufacturing
 process is also important in the manufacture of these devices.
 Cleaning effectiveness of the device also depends upon a porosity and pore
 size of the device. In most embodiments, the porosity can be more than
 about 85%. In devices where porosity is less than 85% polyvinyl acetal
 porous elastic material may have poor flexibility. In most embodiments,
 the porosity is less than about 95%, since a greater porosity value may
 provide poor strength. Other characteristics include a desirable average
 pore size or opening. The pore size opening in some embodiments ranges
 from about 10 micron to about 200 micron. In devices where the average
 pore opening is less than 10 micron, the porous elastic material may have
 poor elasticity and/or flow properties, thus making the performance of the
 cleaning roll unsatisfactory. Alternatively, the average pore opening of
 more than 200 microns can be unsuitable for a cleaning roll because of
 inconsistent pore configuration. Of course, the selected pore size and
 porosity depend upon the application.
 The polyvinyl acetal porous elastic material usable for the present
 invention can be produced in a known manner, for example, by dissolving at
 least one polyvinyl alcohol having an average degree of polymerization of
 300 to 3,000 and a degree of saponification of not less than 80% in water
 to form a 5% to 30% aqueous solution, adding a pore forming agent to the
 solution, and subjecting the solution to reaction with an aldehyde such as
 formaldehyde or acetaldehyde until the device becomes water-insoluble. The
 polymer is 50 to 70 mole % of acetal units. In some embodiments, where the
 polymer has less than 50 mole % of acetal units, the retained polyvinyl
 alcohol may ooze out from the product upon use and undesirably contaminate
 the article to be cleaned. Where the polymer has more than 70 mole % of
 acetal units, the device may have poor elasticity and flexibility in other
 embodiments.
 Although the above devices are generally described in selected shapes and
 sizes, alternative configurations can also be used. As merely an example,
 the polymeric product can have a gear-like configuration, which has
 numerous parallel grooves formed at an angle to the roll. Additionally,
 protrusions or projections on the surface of the foam product can include
 a variety of shapes, e.g., circular, ellipsoidal, rectangular, diamond, or
 the like. The total surface area occupied by the projections can range in
 value from about 10% and greater, or about 15% to 65%, or greater than
 about 65%. Of course, the particular shape and size of the foam product
 depends upon the application.
 Other techniques can also be used to manufacture porous polymeric devices
 used for surface treatment applications. These techniques include, among
 others, an air injected foam or sponge product as well as others. The
 device can also be made of polyurethane, and others.
 The present devices have fewer impurities and/or particulates than
 conventional foam products. In a preferred embodiment, the concentration
 ranges of the impurities are shown in, for example, Table 1A. These
 impurity concentrations compare a conventional brush with the present
 brush. Concentrations are noted in parts per million and were derived
 using ion chromatography or ICPMS.
 TABLE 1A
 Impurity Levels in Present Foam Product
 Conventional Brush Present Brush
 Impurity (PPM) (PPM)
 Fluoride 13.0 &lt;.1
 Chloride 5.0 &lt;1.0
 Nitrite &lt;0.5 &lt;0.01
 Bromide &lt;1.0 &lt;0.05
 Nitrate &lt;1.0 &lt;0.05
 Phosphate &lt;1.0 &lt;0.05
 Sulfate 9.5 &lt;0.20
 Lithium &lt;0.1 &lt;0.1
 Calcium 7.3 &lt;0.05
 Magnesium 3.2 &lt;0.01
 Potassium 2.33 &lt;0.05
 Sodium 243 &lt;0.10
 Based upon Table 1A, it is clear that the present invention provides a much
 cleaner device that conventional ones. In particular, the concentration of
 sodium, for example, which is detrimental to integrated circuits, is less
 than about 0.10 parts per million ("PPM") from a conventional value of
 about 243 PPM. Additionally, the other impurities also have been
 substantially reduced by way of the present invention.
 In an alternative embodiment, the present devices would have fewer
 impurities and/or particulates than conventional foam products. In this
 embodiment, the concentration ranges of the impurities are shown in, for
 example, Table 1B. These impurity concentrations compare a conventional
 brush with the present brush. Concentrations are noted in parts per
 million and were derived using ICPMS.
 TABLE 1B
 Impurity Levels in Present Foam Product
 Impurity Standard Brush (PPM) Present Brush (PPM)
 Aluminum 0.116 &lt;0.01
 Barium 0.0032 &lt;0.01
 Beryllium Not detected &lt;0.004
 Bismuth Not detected &lt;0.004
 Boron 0.0407 &lt;0.01
 Cadmium Not detected &lt;0.003
 Calcium 7.3 &lt;0.1
 Cesium Not detected &lt;0.002
 Chromium 0.0165 &lt;0.01
 Cobalt 0.0004 &lt;0.0002
 Copper 0.0553 &lt;0.01
 Gallium Not detected &lt;0.0004
 Indium Not detected &lt;0.0002
 Iron 0.32 &lt;0.1
 Lead 0.0184 &lt;0.01
 Lithium 0.001 &lt;0.0003
 Magnesium 3.2 &lt;0.1
 Manganese Not detected &lt;0.0005
 Molybdenum Not detected &lt;0.0005
 Nickel Not detected &lt;0.0005
 Potassium 2.33 &lt;0.1
 Rubidium Not detected &lt;0.0001
 Silicon 12 &lt;1
 Silver Not detected &lt;0.0003
 Sodium 242 &lt;10.0
 Strontium 0.0359 &lt;0.0001
 Thallium Not detectable &lt;0.0005
 Thorium Not detected &lt;0.0002
 Tin 0.0107 &lt;0.0017
 Titanium 0.0048 &lt;0.0005
 Tungsten Not detected &lt;0.0002
 Vanadium Not detected &lt;0.008
 Zinc 0.064 &lt;0.02
 Table 1B: Impurity Levels in Present Foam Product
 Based upon Table 1B, it is clear that the present invention provides a
 cleaner device that conventional ones. In particular, the concentration of
 calcium, for example, which is detrimental to integrated circuits, is less
 than about 0.10 parts per million ("PPM") from a conventional value of
 about 7.3 PPM. Additionally, the other impurities also have been
 substantially reduced by way of the present invention. The present
 invention achieves these results by way of a novel cleaning procedure,
 which is described below in more detail.
 FIG. 2 is a simplified diagram of a cleaning system 200 according to an
 embodiment of the present invention. This Fig. is merely an illustration
 and should not limit the scope of the claims herein. One of ordinary skill
 in the art would recognize other variations, modifications, and
 alternatives. The simplified diagram shows a system 200, used to clean
 porous polymeric products (e.g., foam, sponge) to microclean or ultraclean
 levels. System 200 includes a variety of features such as a chemical
 source region 201, and a chemical metering region 203. A variety of
 chemicals used for cleaning are available in the chemical source region
 201. These chemicals include, among others, acids, bases, solvents, and
 chelating agents. The chemicals preferably include hydrochloric acid (HCl)
 223, ammonium hydroxide (NH.sub.4 OH) 225, isopropyl alcohol (IPA) 227,
 and ethylenediaminetetraacetic acid (EDTA) 229, but are not limited to
 these. Each of these chemical sources is coupled to a metering pump 221
 through one of a plurality of lines 222, 224, 226, and 228. Line 222
 connects metering pump 221 (P-1) to the HCl source, line 224 connects
 metering pump 221 (P-2) to the NH.sub.4 OH source, line 226 connects
 metering pump 221 (P-3) to the IPA source, and line 228 connects metering
 pump 221 (P-4) to the EDTA source. All of these lines combine at a
 manifold, which directs the chemical or fluid to line 213, which connects
 to the washer/extraction unit 209. In other embodiments, the lines may be
 kept apart to be separate from each other.
 The chemical source region is made of a suitable enclosure for preventing
 chemicals from escaping into the environment or plant floor. In some
 embodiments, the source region is made by a chemically non-reactive
 material such as polypropylene, Kynar.TM., Teflon.TM., polyvinyl chloride,
 or others. In most embodiments, the source region is double contained.
 That is, chemicals escaping from any of the sources are trapped and drain
 out of the source region without escaping to the plant floor or
 environment. In other embodiments, the chemical source region is triple
 contained. Of course, the type of source unit used depends upon the nature
 and types of chemicals.
 Pumps (P-1, P-2, P-3, P-4) are commonly controlled by a chemical
 distribution controller 205, which is electrically connected by line 219.
 Line 219 separates into a plurality of lines to control each of the pumps
 for metering purposes. As merely an example, the metering pumps are
 capable of handling a wide variety of corrosive chemicals and solvents.
 These pumps are often units made by a company called Nova Systems, but can
 be others.
 Chemical distribution controller 205 communicates to the pumps through line
 219 that separates into independent lines to metering pumps. Chemical
 distribution controller 205 can be any suitable unit for metering
 chemicals from one of a plurality of chemical sources through one of a
 plurality of metering pumps. Alternatively, multiple pumps can be
 actuating to bring in more than one chemical source into the
 washer/extraction unit. The controller has input/output modules, which
 receive and transmit signals to and from selected system elements. The
 controller is sufficiently chemical resistant and is durable for
 manufacturing operations. As merely an example, the controller is a
 product called Novalink, which is made by a company called Nova Systems.
 Of course, other controllers can also be used.
 To oversee the operation of the system including the washer/extraction
 unit, a washer/extraction unit controller 207 couples to controller 205
 through line 217, and couples to washer/extraction unit 209 through line
 215. The controller has a variety of input and output modules. These
 modules are used to interface with sensors, motors, pumps, and the like
 from the washer/extraction unit, as well as other apparatus or devices.
 The controller is a microprocessor based unit which is coupled to memory,
 including dynamic random access memory, and program storage devices. A
 variety of process recipes can be stored in memory of the controller. The
 controller is also sufficiently chemical resistant and is durable for
 manufacturing operations. As merely an example, the controller from the
 Dubix machine. Of course, other controllers can also be used.
 Also shown is a waste stream 211 from the washer/extraction unit. The waste
 stream removes used fluids or undesirable fluids from the washer
 extraction unit. In preferred embodiments, the waste fluid stream is
 chemically balanced and is safe to health, environment, and property. In
 some embodiments, washer/extraction unit uses a specific process recipe
 that produces an environmentally safe waste stream. Alternatively, the
 waste stream must be treated before returning fluids back to the
 environment. Preferably, the waste stream is balanced or pH balanced to
 meet environmental specifications.
 The washer/extraction unit is used with a variety of process recipes to
 clean and remove impurities from the foam product or products. The unit
 can be any suitable washing machine-type unit with a variety of cleaning
 and rinsing cycles, which are programmable. As merely an example, the unit
 is a product made by a company known as Dubix, but can be others. The unit
 is made of a suitable material to be chemically resistant and clean to
 reduce any possibility of particulate contamination or the introduction of
 impurities onto the foam products. In preferred embodiments, the unit is a
 spin/rinse unit, which rotates a basket in a circular manner, to clean and
 remove impurities from the foam product. The spin/rinse unit is preferably
 made of stainless steel or another relatively non-reactive material that
 does not introduce impurities into the porous polymeric product.
 In an alternative embodiment, the present invention provides a ware washing
 machine according to an embodiment of the present invention. The ware
 washing machine can be in the form of commercial dish washing machines and
 the like, which are to be used to carry out the techniques of the present
 invention. Among ware washing machines, the present invention uses door
 loading and/or conveyor type machines. Door loading machines operate on a
 "batch" basis in which articles (e.g., porous polymeric or sponge
 products) are loaded into the machine, the articles are placed through
 various cycles such as wash, rinse, and others. After completing the
 cycles, the articles are removed. In conveyor type machines, for example,
 the articles including the sponge or porous polymeric products are placed
 in one end of the machine, passed through the device, and subjected to
 various operations based on their location in the device. The ware washing
 machine can use any suitable control systems. These control systems base
 chemical charge on the article based upon timing. For example, certain
 control systems have often dispensed chemicals when the article is in a
 rinse cycle.
 Although the above is generally described in terms of a washer/extraction
 unit, the present system can also include other types of washing and/or
 rinsing units. These units can be a batch-type unit, which include a
 plurality of washing and rinsing tanks. Alternatively, the units can
 include sprayers, misters, atomizers, sonic generators, and the like. The
 system should have sufficient mechanical forces to remove liquid from the
 products in an efficient manner. The system also should be able to fully
 displace the products if desired. Of course, the type of unit used depends
 upon the application.
 A process according to the present invention can be briefly outlined as
 follows:
 (1) Provide products from manufacturer;
 (2) Insert products into washer;
 (3) Perform pre-wash with clean water;
 (4) Perform solvent wash;
 (5) Perform acid wash;
 (6) Perform caustic wash;
 (7) Perform chelation wash;
 (8) Perform rinse;
 (9) Spin extract;
 (10) Perform additional steps, as required; and
 (11) Remove cleaned products.
 The above sequence of steps are used to substantially remove all
 particulate contamination and impurities from the porous polymeric
 devices. These devices are often "dirty" from the manufacturing process
 and should be substantially cleaned before use in a manufacturing
 operation, e.g., semiconductor fabrication. The above sequence of steps
 removes or substantially reduces quantities of ionic contamination, trace
 metals, particulates, and other forms of contamination. Although complex,
 the above sequence of steps is easily used in a washer unit with a
 programmable control unit. Depending upon the embodiment or embodiments, a
 rinse cycle or cycles may follow any of the above washes. Accordingly, the
 present method can be easily implemented using conventional technology in
 a cost effective manner. Details of the above method are illustrated by
 way of FIG. 3, which illustrates a simplified flow diagram 300 of a
 cleaning method according to an embodiment of the present invention. This
 Fig. is merely an illustration and should not limit the scope of the
 claims herein. One of ordinary skill in the art would recognize other
 variations, modifications, and alternatives.
 As merely an example, a process according to the present invention begins
 at step 301. The process has a step (step 302) of providing a plurality of
 porous polymeric devices, which require cleaning. These devices are
 generally from a manufacturer of polymeric devices or foam products. An
 example of this device is a product made by a company called Kanebo
 Limited of Japan. Other companies also have similar devices. These
 companies include, among others, Cupps Industrial Inc., Merocel Scientific
 Products, Perfect and Glory Enterprise Co., Ltd. In generally all of the
 present embodiments, the polymeric devices include a variety of impurities
 that can be detrimental to the manufacture of integrated circuits, for
 example. These impurities should be removed or reduced in concentration
 before use in a clean or sensitive environment.
 The devices are loaded (step 305) into a washer/extraction unit which can
 be programmed with a variety of process recipes to clean and remove
 impurities from the devices. The unit can be any suitable washing
 machine-type unit with a variety of cleaning and rinsing cycles, which are
 programmable. As merely an example, the unit is a product made by a
 company called Dubix, but can be others. The unit is made of a suitable
 material to be chemically resistant and clean to reduce any possibility of
 particulate contamination or the introduction of impurities onto the
 devices to be cleaned. In preferred embodiments, the unit is a spin/rinse
 unit, which rotates a basket in a circular manner, to clean and remove
 impurities from the devices. The rotational action provides mechanical
 agitation to fluids that tend to loosen and remove impurities and
 particulate from the devices.
 A program according to this embodiment is selected from the
 washer/extraction unit. The program is often loaded into controller such
 as a unit made by a company called Nova, as well as others. This program
 can carry out a variety of cleaning processes. This program removes a
 substantial amount of impurities and particulate contamination from the
 devices. After the process, the devices are substantially free from
 impurities. As merely an example the impurities would be less than those
 noted in Table 1, but can be others depending upon the application and
 needs. The cleaned or microcleaned devices are removed (step 311) from the
 washer/extraction unit in a clean room environment before packaging. The
 clean room environment is generally at least a Class 100 or Class 10 clean
 room, which prevents additional contamination from attaching onto the
 devices. The process stops at step 313, but additional steps can be
 performed as desired.
 A process according to an alternative embodiment of the present invention
 can be briefly outlined as follows:
 (1) Provide products from manufacturer;
 (2) Insert products into washer;
 (3) Perform pre-wash with clean water;
 (4) Perform solvent wash;
 (5) Rinse solvent wash;
 (6) Perform first acid wash;
 (7) Perform second acid wash;
 (8) Rinse acid washes;
 (9) Perform first caustic wash;
 (10) Perform EDTA wash;
 (11) Perform second caustic wash;
 (12) Rinse caustic washes;
 (13) Spin extract;
 (14) Perform additional steps, as required; and
 (15) Remove cleaned products.
 The above sequence of steps are used to substantially remove all
 particulate contamination and impurities from the porous polymeric
 devices. These devices are often "dirty" from the manufacturing process
 and should be substantially cleaned before use in a manufacturing
 operation, e.g., semiconductor fabrication. The above sequence of steps
 removes or substantially reduces quantities of ionic contamination and
 particulate. Although complex, the above sequence of steps is easily used
 in a washer unit with a programmable control unit. Depending upon the
 embodiment or embodiments, a rinse cycle or cycles may follow any of the
 above washes. Accordingly, the present method can be easily implemented
 using conventional technology in a cost effective manner. Details of the
 above method are illustrated by way of FIG. 3A, which illustrates a
 simplified flow diagram 330 of a cleaning method according to an
 embodiment of the present invention. This Fig. is merely an illustration
 and should not limit the scope of the claims herein. One of ordinary skill
 in the art would recognize other variations, modifications, and
 alternatives.
 As merely an example, a process according to the present invention begins
 at step 331. The process has a step (step 332) of providing a plurality of
 porous polymeric devices, which require cleaning. These devices are
 generally from a manufacturer of polymeric devices or foam products. An
 example of this device is a product made by a company called Kanebo
 Limited of Japan. Other companies also have similar devices. These
 companies include, among others, Cupps Industrial Inc., Merocel Scientific
 Products, Perfect and Glory Enterprise Co., Ltd. In generally all of the
 present embodiments, the polymeric devices include a variety of impurities
 that can be detrimental to the manufacture of integrated circuits, for
 example. These impurities should be removed or reduced in concentration
 before use in a clean or sensitive environment.
 The devices are loaded (step 335) into a washer/extraction unit which can
 be programmed with a variety of process recipes to clean and remove
 impurities from the devices. The unit can be any suitable washing
 machine-type unit with a variety of cleaning and rinsing cycles, which are
 programmable. As merely an example, the unit is a product made by a
 company called Dubix, but can be others. The unit is made of a suitable
 material to be chemically resistant and clean to reduce any possibility of
 particulate contamination or the introduction of impurities onto the
 devices to be cleaned. In preferred embodiments, the unit is a spin/rinse
 unit, which rotates a basket in a circular manner, to clean and remove
 impurities from the devices. The rotational action provides mechanical
 agitation to fluids that tend to loosen and remove impurities and
 particulate from the devices.
 A program according to this embodiment is selected from the
 washer/extraction unit. The program is often loaded into controller such
 as a unit made by a company called Nova, as well as others. This program
 can carry out a variety of cleaning processes. This program removes a
 substantial amount of impurities and particulate contamination from the
 devices. The program can include a variety of process steps to selectively
 remove impurities from the product.
 In a specific embodiment, the present method uses a step of performing a
 pre-wash (step 336) with clean water or ultra-clean deionized water. The
 pre-wash step removes loose particulate contamination from the product.
 The clean water also dissolves any water soluble contaminates from the
 product. The water has a resistivity of greater than 18 megohm about
 ninety percent (or greater) of the time with a 17.6 megohm minimum.
 Additionally, the pre-wash step is often maintained at room temperature or
 a temperature of less than about 60.degree. C. The temperature is
 maintained at these temperature ranges to prevent any deformation of the
 product, which is often sensitive to high temperatures.
 A solvent wash is performed (step 337) to the product. The solvent wash
 preferably introduces a relatively concentrated isopropyl alcohol (i.e.,
 IPA) or any other solvent (e.g., reagent alcohol, ethyl alcohol) into the
 washer/extraction unit, which is often filled with clean water or other
 fluid. The solvent is suitable for dissolving any loose particulate
 contamination from the product. The loose particulate contamination can
 include any un-cross-linked polymers from the product. Additionally, the
 contamination can include any small and loose portions of the polymeric
 product. It is generally believed that the solvent dissolves portions of
 loose polymers from the product and washes them away. The IPA solvent is
 often maintained at a concentration of about 0.5% and less, but not lower
 than 0.05%, which reduces efficiency of the solvent wash process. A higher
 concentration than about 8%, however, may dissolve the product itself,
 which causes damage to such product. The solvent is preferably aqueous. In
 some embodiments, the solvent wash occurs in an agitation cycle of the
 washer/extraction unit. The agitation cycle is generally performed in a
 "gentle" mode, which reduces a possibility of excessive foaming. An
 aggressive cycle is generally not used since excessive foaming can occur
 in some embodiments.
 A rinse step 338 can follow the solvent wash step. The rinse step generally
 removes any solvent along with any residual organic contaminants from the
 product. It occurs by draining the solvent from the product, filling the
 washer/extraction unit with clean water, agitating the product, draining
 the product, and using centrifugal force to extract residual liquid from
 the product. Of course, the exact sequence of steps depends upon the
 application. The rinse step is often maintained at a temperature of about
 20.degree. C. or less than about 60.degree. C. to prevent any damage or
 deformation of the product. In a preferred embodiment, the rinse step
 occurs using "cold" water, which is either at about room temperature or
 slightly less than room temperature.
 An acid wash (step 339) takes place to remove, for example, to remove any
 trace metals (e.g., iron, aluminum, copper) from the product. In
 particular, a liquid or gas including acid is introduced into the
 washer/extraction unit. In most embodiments, the acid is mixed with water
 for proper dilution. The acid wash can occur using a single or multiple
 steps. The acid wash is generally maintained at a concentration level
 between 0.3 and 0.6 weight ("wt") percent. A concentration level below
 0.04 wt percent will not maintain the target pH of less than two. A
 concentration above 2 wt percent may cause degradation of the product. The
 acid wash does not generally have any incidental limitations such as
 foaming or the like. Accordingly, it generally occurs using an aggressive
 or "high" wash cycle in some embodiments. The acid wash also occurs at a
 temperature of less than about 60.degree. C. or about room temperature.
 Preferably, the acid can be any suitable compound such as hydrochloric
 acid (e.g., HCl), sulfuric acid, citric acid, and others. However, strong
 oxidizing acids, such as nitric acid, typically cannot be used because
 they may damage the product. The acid, however, is generally free from
 calcium and other elements, which may cause damage to, for example, and
 integrated circuit process or the like.
 A rinse step 340 or steps follow each of all of the acid washes. The rinse
 step generally removes any acid and trace metals from the product. It
 occurs by draining the acid from the product, filling the
 washer/extraction unit with clean water, agitating the product, draining
 the product, and using centrifugal force to extract residual liquid from
 the product. Of course, the exact sequence of steps depends upon the
 application. The rinse step is often maintained at a temperature of about
 20.degree. C. or less than about 60.degree. C. to prevent any damage or
 deformation of the product. In a preferred embodiment, the rinse step
 occurs using "cold" water, which is either at about room temperature or
 slightly less than room temperature.
 A sequence of caustic washes (step 341) follows the acid wash according to
 an embodiment of the present invention. In a multi-step caustic wash
 method, a first caustic wash occurs to the product using a solution
 containing ammonium hydroxide. The ammonium hydroxide is at a
 concentration ranging from about 0.05% to about 5.0%, but can also be at
 other concentrations. High concentrations, however, are generally not
 desirable due to noxious fumes and the like. Extremely low concentrations
 generally reduce the effectiveness of the washing step. The caustic
 washing step removes a portion of negative ions or particles with a
 negative zeta potential from the product according to some embodiments.
 Negative ions are also removed from the product by way of a concentration
 gradient according to some embodiments. The caustic wash step is
 maintained at a temperature of about 15.degree. C.-20.degree. C. and less
 than about 60.degree. C. to prevent any damage to the product, which is
 temperature sensitive. The caustic wash step also can occur using a gentle
 cycle or an aggressive cycle, depending upon the application. In some
 embodiments, the caustic wash step does not allow for any introduction of
 a sodium bearing compound such as sodium hydroxide or a potassium bearing
 compound such as potassium hydroxide. These compounds are generally
 detrimental to electronic devices such as integrated circuits, hard disks,
 and the like.
 A chelating step (step 342) occurs to remove additional trace metals from
 the product. The chelating step uses a compound such as EDTA to remove
 trace metals from a caustic solution from the first caustic wash. The
 chelating step "grabs" trace metals from the basic solution. By way of the
 basic solution, these metals do not precipitate out. The second caustic
 wash, which is noted above, removes or "scavenges" any remaining
 impurities such as calcium, magnesium, and others. In a preferred
 embodiment, the EDTA solution concentration ranges from about 5 ppm to
 about 500 ppm, but can be others. Additionally, the solution temperature
 ranges from about 17.degree. C. to about 40.degree. C. and is less than
 about 60.degree. C. to prevent a possibility of damage to the product.
 A rinse step 343 can follow the caustic wash step. The rinse step generally
 removes any caustic with impurities from the product. It occurs by
 draining the caustic solution from the product, filling the
 washer/extraction unit with clean water, agitating the product, draining
 the product, and using centrifugal force to extract residual liquid from
 the product. Of course, the exact sequence of steps depends upon the
 application. The rinse step is often maintained at a temperature of about
 20.degree. C. or less than about 60.degree. C. to prevent any damage or
 deformation of the product. In a preferred embodiment, the rinse step
 occurs using "cold" water, which is either at about room temperature or
 slightly less than room temperature.
 The method performs a step of drying or removing a substantial portion of
 moisture (step 344) from the product. In a specific embodiment, the method
 uses a step of mechanical "spinning" to accelerate the product to high
 speeds, which are often desirable to remove moisture from the product. In
 particular, the rinse water is drained from the product, the
 washer/extraction unit is spun, and moisture is thereby removed from the
 product. After the process, the devices are substantially free from
 impurities. As merely an example the impurities would be less than those
 noted in Table 1, but can be others depending upon the application and
 needs. The cleaned or microcleaned devices are removed (step 341) from the
 washer/extraction unit in a clean room environment before packaging. The
 clean room environment is generally at least a Class 100 or Class 10 clean
 room, which prevents additional contamination from attaching onto the
 devices.
 The process stops at step 343, but additional steps can be performed as
 desired.
 The above process is merely an example of a technique that can be performed
 to provide ultra clean surface treatment devices according to an
 embodiment of the present invention. The present invention can also be
 performed in a "batch" type process, where various cleaning solutions are
 applied to the devices in a sequential manner. This batch type process
 would include immersion of the devices in tanks, sprays, and other
 techniques. Additionally, the sequence of steps is not intended to be
 limiting. It will be recognized that the steps can be performed in another
 order without departing from the scope of the claims herein. Furthermore,
 a step or steps can be removed, a step or steps can be combined or even
 added in some embodiments.
 Although the above techniques have been generally described in terms of
 system hardware and software, it would be recognized that other variations
 can exist. As merely an example, the present invention can be implemented
 by combining further aspects in hardware. Alternatively, the present
 invention can be implemented by combining further aspects in software. The
 hardware can be integrated more fully or even separated. Alternatively,
 the software can be integrated more fully or even separated. Depending
 upon the application, the present invention uses hardware, software, or a
 combination of both hardware and software to carry out elements as recited
 by the claims herein.
 FIG. 4 is a simplified diagram of a scrubbing process according to an
 embodiment of the present invention. This Fig. is merely an illustration
 and should not limit the scope of the claims herein. One of ordinary skill
 in the art would recognize other variations, modifications, and
 alternatives. The scrubbing process uses the cleaned devices according to
 the present invention. As shown in the Fig., a semiconductor product wafer
 cleaning system 401 has two brush stations, a first comprising cylindrical
 PVA brushes 402 and 403, and a second comprising cylindrical PVA brushes
 404 and 405. On each of the brushes, there are projections 406 also made
 of PVA. The brushes are mounted on spindles 407, 408, 409 and 410 so that
 they are barely touching and rotate in the direction indicated. Deionized
 water and, if used, any cleaning chemistries are sprayed from nozzles 411
 and 412 and pumped 413 through the brushes from the spindles. The
 combination of the water and brush contact acts to remove residual
 cleaning composition from a semiconductor product wafer 414 which is
 passed through the brushes in the cleaning stations.
 In order to remove the slurry or other residue, deionized water is pumped
 through holes in the spindle to saturate the tubular brushes.
 Additionally, deionized water sprayed from nozzles above and below
 impinges the wafers. As the brushes rotate over the surface of the wafer,
 they tend to pick up and trap in the brush surface particles of the slurry
 and other residue of the cleaning composition. The slurries which
 eventually contaminate the cleaning brushes and render them ineffective
 for further cleaning comprise the slurries and other cleaning compositions
 described in the background section of this application.
 The cleaning brushes used in post CMP cleaning operations is employed in
 connection with resilient foam brushes such as those used on the Synergy
 wafer cleaning system manufactured by OnTrak Systems, Inc. of Milpitas,
 Calif. This system employs multiple sequential cleaning stations wherein
 each station comprises a pair of tubular brushes made of polyvinyl alcohol
 (PVA) in the form of a foam. Each brush has a length of approximately 10
 in. (25.4 cm), an outside diameter of approximately 23/8 in. (6.0 cm) and
 an inside diameter of approximately 11/4 in. (3.2 cm), and has an outer
 cylindrical surface covered with foam projections approximately 3/16 in.
 (0.5 cm) in height and A in. (0.7 cm) in diameter. Each brush is rotatably
 mounted on a spindle through which may be pumped water to saturate the
 brush and the brushes at each station are spaced so that the surfaces
 approximately contact each other. Given the resilience of the foam, this
 permits thin semiconductor wafers containing the cleaning composition
 residue to pass between the pairs of brushes as they rotate. Typically, as
 the cleaning system will have two (2) stations, with each station having a
 pair of the brushes as described above. The wafers pass directly from one
 station through the other.
 The semiconductor product wafers which may be cleaned by the system
 referenced herein include silicon, silicon nitride, silicon oxide,
 polysilicon or various metals and alloys. As used herein the term "product
 wafer" refers to the wafer which is to be intended to be produced in a
 final semiconductor device by further treatment. The CMP compositions
 which are used to planarize or otherwise treat and polish the surface of
 the semiconductor product wafers must be removed to a sufficient degree so
 that subsequent manufacture and deposition steps may be made to a clean
 surface.
 The above process and apparatus are merely illustrations of the present
 invention. It will be recognized that other modifications, variations, and
 alternatives can exist.
 Experimental
 To prove the operation and principle of the present invention, experiments
 have been performed. In these experiments, a system according to the
 present invention was made and used to show superior cleaning of sponge or
 porous polymeric products. The system used was a washer/extraction unit
 made by Dubix. A plurality of dirty sponge products were introduced into
 the system. As merely an example, the information in Table 1A and 1B show
 conventional impurity concentrations in a polymeric sponge product made by
 Kanebo Limited, but is not limited to this vendor. The sponge products
 were received in lengths of about 350 mm. They were cut to form a
 plurality of sponge products, each having a length of about 250 mm and
 less. These sponge products were loaded into the washer/extraction unit
 made by Dubix. A recipe was programmed into the washer/extraction unit by
 way of a computer software interface. The interface was provided by a
 company called Nova Systems, but is not limited to this vendor. As merely
 an example, the washer/extraction unit was programmed using the recipe in
 Table 2. As shown, the Table lists a sequential order of steps (e.g., 1,
 2, 3); operation (e.g. rinse, wash); process times (in minutes and
 seconds); general information (e.g., gentle wash cycle, normal wash
 cycle); water temperature (e.g., cold, hot); liquid level (in
 percentages); solution type (e.g., water, alcohol); and solenoid times.