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WO1998049368A1 - Procede et dispositif pour le nettoyage et l'activation de structures ou de surfaces de platines electroconductrices - Google Patents

Procede et dispositif pour le nettoyage et l'activation de structures ou de surfaces de platines electroconductrices Download PDF

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Publication number
WO1998049368A1
WO1998049368A1 PCT/DE1998/001141 DE9801141W WO9849368A1 WO 1998049368 A1 WO1998049368 A1 WO 1998049368A1 DE 9801141 W DE9801141 W DE 9801141W WO 9849368 A1 WO9849368 A1 WO 9849368A1
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WO
WIPO (PCT)
Prior art keywords
layer
dielectric
electrode
cleaning
discharge
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.)
Ceased
Application number
PCT/DE1998/001141
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German (de)
English (en)
Inventor
Jürgen E. LANG
Manfred Neiger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
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Publication of WO1998049368A1 publication Critical patent/WO1998049368A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
    • B08B7/0035—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32348—Dielectric barrier discharge
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3489—Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces

Definitions

  • the invention relates to a method and a corresponding device for cleaning or activating the surface of an electrically conductive, structured layer arranged on a carrier or the carrier surface in the vicinity of an electrically conductive, structured layer.
  • an electrically conductive, structured layer in the sense of the invention, both two-dimensional, i.e. superficial, as well as three-dimensional, i.e. spatially trained structures understood with an electrical function.
  • These include, for example, electrical conductor tracks (also with lateral dimensions in the range of a few ⁇ m), electrical contact areas, bond pads, contact pads, printed circuits, printed circuit boards, lithographic layers and structures of microelectronics, lithographically generated components and microelectronic components, for which the usual structure sizes range from a few ⁇ m to mm.
  • Industrially manufactured, electrically conductive, structured layers such as conductor tracks or contact surfaces of electronic circuits that are known as electrically conductive or semiconducting layer are arranged on a carrier, are manufactured and processed in several process steps.
  • the coatings can be both organic and inorganic layers and can consist, for example, of condensates from printed circuit board manufacture, adhesive and polymerisation residues, of carbon-containing compounds formed by oxidation, of metal oxides or metal hydrides.
  • Activation is understood to mean any desired chemical or physical reaction in preparation for a subsequent processing step, for example the activation of a copper surface by reducing the CuO to Cu.
  • chemical cleaning is carried out using a chemical cleaning and / or activating agent, which can be, for example, a fluorinated chlorinated hydrocarbon, chlorinated hydrocarbon, a hydrocarbon compound, a flux or an aqueous solution.
  • a chemical cleaning and / or activating agent can be, for example, a fluorinated chlorinated hydrocarbon, chlorinated hydrocarbon, a hydrocarbon compound, a flux or an aqueous solution.
  • a method for treating surface substrates made of different materials is known from document EP 0510503 A2.
  • the UV light is generated with a dielectric barrier discharge and emerges from the discharge space through a transparent grid electrode onto the workpiece arranged outside. For this reason, the environment must be UV-permeable, which requires the use of a protective gas atmosphere.
  • the program also contains zeßgas the lamp such as chlorine. The use of this aggressive gas excludes the previously known method for the field of application according to the invention.
  • the invention is based on the object of creating a method and a corresponding device for cleaning or activating the surface of an electrically conductive, structured layer arranged on a carrier or the carrier surface in the vicinity of an electrically conductive, structured layer, which avoids or reduces the disadvantages of the methods known from the prior art.
  • this method should be able to be integrated into a continuous process, in particular a manufacturing process, so that the risk of re-contamination by dust or dirt in the air or by handling the layer in the process is reduced.
  • the method should act as homogeneously as possible on the layer or the carrier surface and should cause little or no heating. It should be carried out in an environmentally friendly and cost-effective manner and should ensure a high mechanical and electrical load capacity and an improved corrosion behavior of the layer.
  • the method should, if possible, be feasible in such a way that the cleaning or activation effect can be limited locally and is concentrated, for example, on the conductive layer and thus the carrier is not attacked or is attacked only to a small extent.
  • the method should make it possible to dispense with flux or wet chemical activation baths during the subsequent soldering of the layer.
  • the layer or carrier surface to be cleaned or activated in a discharge space filled with filler gas between two electrodes, a dielectric being arranged between the layer and at least one electrode, and between the two electrodes by applying a voltage to ignite a discharge which is dielectrically impeded by the dielectric and whose micro-discharges act directly on the layer or carrier surface for cleaning or activation.
  • the invention makes use of the cleaning effect of a dielectric barrier discharge in order to achieve the above-mentioned advantages in the cleaning and activation of electrical conductor tracks or contact surfaces or the surrounding carrier surface.
  • dielectrically disabled discharges (DBE for short, also called silent discharge or barrier discharge, English "barrier discharge") is known in the prior art for generating incoherent, selective radiation by the formation of exe er molecules and the release of UV radiation in the process Dissociation and known for cleaning fats and oils on the surface of metal foils.
  • the dielectric barrier discharge would concentrate on the points with the shortest distance from the counterelectrode and the other points would remain untreated; targeted cleaning or activation of certain, selected areas of a structured surface is not possible.
  • the known method is limited to the removal of hydrocarbons, ie a cleaning effect, without a reducing effect being able to be achieved. Ozone and secondary products are created, eg N0 ⁇ , which leads to problems with regard to job security.
  • the DBE is a gas discharge in thermal non-equilibrium which, in contrast to other non-equilibrium discharges, can also be operated at high pressures of 0.1 to 10 bar.
  • the arrangement of a DBE consists of two metallic electrodes, between which there are one or more gas discharge spaces (gaps), each of which is sealed off on at least one side with a dielectric as a barrier.
  • the main task of the dielectrics is to prevent the formation of sparks or arcs that would occur between metal electrodes without a dielectric barrier, and to distribute the so-called filaments evenly over the dielectric surface.
  • the dielectrics limit the charge turnover and thus the amount of energy that can be coupled into a single filament.
  • the plasma in the discharge space usually consists of a large number of spatially and temporally distributed individual discharges, so-called micro-discharges or (discharge) filaments.
  • the discharge can be controlled by selecting the appropriate parameters so that multifilament operation or single-filament operation, that is to say the entire discharge consists only of a micro-discharge, can be carried out. Multi-filament operation is generally preferred for technical applications.
  • a dielectric barrier is placed in front of each metal electrode, so that the contact of the plasma with the metallic electrodes is prevented and thus chemical processes of the filling gas with the electrodes are prevented.
  • a harmonic or anharmonic voltage e.g. AC voltage
  • partial discharges or filaments are formed in the discharge space, depending on the frequency, the rate of voltage rise and the voltage level, if the ignition voltage or the ignition field strength in the discharge space is exceeded.
  • a homogeneous plasma is formed, or small thin discharge channels, the so-called filaments (micro-discharges) are created.
  • the carrier on which the layer to be cleaned or activated is located itself acts as a dielectric, that is to say is arranged between the layer and an electrode, in order to form a spark gap directly between the layer and to prevent the electrode. It is preferred if a further dielectric is arranged between the layer and the other electrode, that is to say the DBE is dielectrically impeded on both sides is.
  • the electrode is somewhat smaller than the dielectric, that is, the dielectric protrudes somewhat laterally (transversely to the direction of discharge) over the electrode.
  • the cleaning or activation of the electrically conductive layer or the carrier surface takes place through the direct action of the micro-discharges on the layer or carrier surface.
  • the cleaning or activation is supported by UV radiation which arises during the dielectric barrier discharge.
  • the cleaning or activation by chemical or physical effects of the filling gas on the layer during the dielectric barrier discharge which, for example, in UV radiation, in particular so-called internal UV radiation, i.e. UV radiation in the micro discharge in the immediate vicinity of the surface to be cleaned, in plasma chemical processes or in excitation or radical formation can be supported.
  • the formation of the discharge is of particular importance in the gentle treatment of layers, in particular electronic components.
  • the possible forms of discharge are homogeneous, full cone, narrow cone, short cone filament, channel-divided filament and thin filament. They depend on the gas mixture, the voltage shape and frequency as well as the gap distance. The smaller the gap, the easier it is to achieve homogeneous discharge. The more homogeneous the discharge, the greater the plasma efficiency, ie the more radicals are generated in the volume. ⁇ ",. ⁇ - to PCT / DE98 / 01141 98/49368
  • a homogeneous discharge not only has advantages with regard to the plasma efficiency, but also with regard to the gentle treatment of the layer.
  • discharge channels with a diameter of the order of 100 ⁇ m are formed with a surface sliding discharge with a diameter between 0.5 and 5 cm. This means that a high specific power of more than 1 W / cm 2 is injected into the plasma at the given voltages. This energy density is desirable when cleaning metal foils, but leads to damage to the semiconductor components when cleaning printed circuit boards equipped with semiconductor components.
  • the surface of the surface sliding discharge represents a qualitative measure of the local electric field strength.
  • the load on the components is significantly lower.
  • suitable dielectric barrier materials and emission peaks can be used. This is used to produce individual filaments with a smaller diameter and a larger areal density.
  • the type of electrical excitation can also contribute to this.
  • the individual filaments can have a diameter of less than 0.5 cm and protrude up to the micrometer range.
  • the number and density of the microfilaments increases accordingly, so that there is an optical impression corresponding to a low-pressure plasma discharge; the individual micro-discharges are then no longer recognizable and the result is a uniformly distributed, homogeneous glow in an extended area, without a significant amount of channel formation occurring in the individual filaments.
  • individual micro discharge channels for example as Lichtenberg cones, may or may not be visible. In this way it can be achieved that the local loading of the layer by a single filament is relatively low, even if a larger area is treated.
  • FIG. 5 shows a modification to FIG. 4,
  • FIG. 6 shows an arrangement for a dielectric barrier discharge for cleaning a substrate with microelectronic components
  • FIG. 6 is a plan view of FIG. 6,
  • the 1 shows four exemplary basic arrangements for carrying out a dielectric barrier discharge. They each comprise two electrodes 1, 2 to which a high voltage can be applied.
  • the carrier is introduced into the discharge space 3 and the DBE is ignited.
  • the layer or the carrier surface can be cleaned or activated by the micro-discharges that form in the process.
  • FIG. 2 schematically shows the formation of a micro-discharge 5 in a discharge arrangement with a dielectric barrier on one side.
  • FIG. 3 shows a micro-discharge 5 in a discharge arrangement which is dielectrically impeded on both sides, in which two dielectrics 4a, 4b are arranged between the electrodes 1, 2.
  • the micro-discharges 5 can be widened conically on the dielectric 4, where a surface sliding discharge is formed. The smaller the diameter of this cone, the lower the energy contained in the microfilament 5.
  • very fine, distributed micro-discharges 5 are formed or the tip of the cone is formed up to the opposite electrode 1, so that a cylindrical, uniform discharge volume results.
  • the first electrode 1 is a metallic plate, which can be at zero potential, for example.
  • the second electrode 2 is connected to a high-voltage unit, not shown.
  • the carrier 6 is a circuit board, for example based on an epoxy resin, on a ceramic basis or on a polymer basis (inter alia polypropylene or polyimides). It carries electrical conductor tracks 7 and electrical contact surfaces 8, which can consist, for example, of copper, another metallic conductor or a semiconductor.
  • the circuit board 6 is located between the conductor tracks 7 or contact surfaces 8 and the first electrode 1 and serves as a dielectric barrier. Another dielectric 4 is arranged between the conductor tracks 7 or contact surfaces 8 and the second electrode 2.
  • the electrode 1 is preferably somewhat smaller than the circuit board 6 in order to prevent sparks from jumping over to the side.
  • the electrons in the discharge filaments 5 can interact with the atoms and molecules of the filling gas in the discharge space 3 and with the substances, for example aliphatics, adhering to the surface of the conductor tracks 7 and contact surfaces 8, which leads to fragmentation, radical formation and to oxidation and reduction processes leads.
  • the conductor tracks 7 or contact surfaces 8 are raised relative to the carrier 6 or consist of metallic materials, there are selective discharges which no longer uniformly cover the surface of the carrier 6, but instead concentrate on the conductor tracks 7 and contact surfaces 8 (NF Operation), which is advantageous.
  • the lighting phenomenon associated with the DBE which occurs, for example, in air, is an indicator of the extent of the emission area and thus of the electrical power coupled in.
  • the filament formation depends on the pressure in the discharge space 3, the gas type of the filling gas, the rate of voltage rise, the voltage level, the distance in the discharge space 3 (gap distance), the type and thickness of the dielectrics and the frequency.
  • the dielectric barrier 4 on the side which faces the layer to be cleaned that is to say the conductor track 7 and the contact surface 8 has a raised formation which corresponds to the contour of the layer and is arranged opposite the layer 9 on.
  • This can be useful in special applications in order to concentrate the micro-discharges even more strongly on the layer to be cleaned.
  • this is not necessary in the case of two-dimensionally structured layers, since the micro-discharges, as explained above, are already largely self-focusing, the technical outlay for producing specially shaped formations 9 on the dielectric barrier 4 can be high, and then the universal applicability of the corresponding arrangement cannot more is guaranteed.
  • the contour of the formation 9 corresponds precisely to that of the layer, but it can are sufficient if the raised shape 9 represents a simplified image.
  • micro-discharges 5 located on the conductor track 7. It is noteworthy here that the micro-discharges 5 concentrate on the conductor tracks 7 of the circuit board 6 and not, or only to a small extent, on the other areas of the circuit board 6 which are not coated with conductor tracks 7 or the areas of the metallic areas which are not covered by the circuit board 6 Act on electrode 1.
  • the dielectric barrier 4 all materials known for the DBE can be considered as the dielectric barrier 4.
  • Diamond or ceramics e.g. Al 2 0 3 , glasses, porcelain or other high-voltage-resistant ceramic insulating materials (e.g. according to DIN 40685) as well as insulating plastics (e.g. according to VDE 0303) such as fluorocarbon, polyvinyl chloride or phenoplasts (with admixtures) with pronounced high-voltage capability as well as are particularly suitable Teflon and PVC.
  • the surface of the dielectric 4 facing the conductor tracks 7 is tempered, for example with a diamond layer. The criteria wear and heat resistance are generally not important when choosing the material, as there is no significant wear or thermal stress on the barrier.
  • FIG. 6 shows a section of an arrangement for a dielectrically disabled discharge for cleaning a carrier 6 with microelectronic components 22 which are connected to conductor tracks 7.
  • the components are, for example, a first chip 22a, a second chip 22b and a capacitor 22c.
  • the layer to be cleaned is thus structured three-dimensionally and should be in one local area around the first chip 22a, in which there are contact areas 8 for contacting the chip 22a by means of bonding, and on the chip 22a, which itself has contact areas 8 for bonding.
  • FIG. 6 shows the homogeneous discharge formed from micro-discharges 5, which is concentrated on the first chip 22a and the adjacent contact areas 8.
  • the dielectric 4 has a contour corresponding to the layer and the layer or the support surface Forming arranged opposite one another, in particular a raised form 9.
  • the shape can represent a simplified image, in particular an enlarged simplified image of the contour of the layer or of the carrier surface. Simplified means that the contour and surface of the formation do not have to correspond to the finely resolved details of the layer or carrier surface to be cleaned, but only to the extent required by practical requirements.
  • FIG. 7 shows a top view of the layer of FIG. 6 to be cleaned.
  • the contour of the formation 9 is also shown.
  • the cleaning is limited to the first chip 22a or its contact areas 8 and the contact areas 8 arranged next to the first chip 22a. After the cleaning, the contact areas 8 can be connected, for example, by bonding.
  • FIG. 8 shows an example of a workpiece to be cleaned, the height of which relates to a planar electrode locally varied by up to 20 mm and more. This is the case, for example, with modern sensors, for example microsensors.
  • Such workpieces can also be cleaned with the method according to the invention if the electrode 1 and / or the dielectric 4 are shaped and adapted accordingly by an approximately uniform gap distance between the layers to be cleaned and the opposite electrode 1 or the opposite dielectric 4 to achieve.
  • the contour of the formation does not have to follow the contour of the workpiece to be treated precisely into microscopic areas, but it is sufficient if the contour of the formation represents an enlarged and simplified image of the layer to be cleaned.
  • the electrode 1 and the dielectric 4 are modeled or reshaped from the workpiece in such a way that the contact surfaces 8a arranged on the top of the component 22 and the contact surfaces 8b arranged approximately 20 mm lower on the carrier 6 can be cleaned for subsequent bonding .
  • the electrode 1 can be an electrolyte electrode, for example.
  • FIG. 9 shows an arrangement for carrying out a DBE. It comprises an insulating housing, which is composed of a base plate 10, a cover 11 and side plates 12.
  • the lower electrode 1 is at ground potential and the upper electrode 2 is connected to a high-voltage unit 13 via a bushing 14.
  • the electrodes 1, 2 can be designed in a known manner, for example as a metallic plate, as a mesh or grid electrode or as an electrolyte electrode.
  • the discharge space 3 is filled with a filling gas.
  • the filling gas can be essentially air or an inert gas and / or a special gas.
  • target process gas ie chemically passive substances, are noble gases and nitrogen.
  • the composition can be variable. For reasons of cost, N 2 and Ar are preferred.
  • the inert gas will mainly participate in the cleaning or activation through physical shocks or UV production.
  • a process gas is preferably a gaseous reaction mediator, which thus supports the chemical reaction.
  • the reaction mediator can be oxidizing, for example 0 2 , N0 ⁇ , H 2 0, or reducing, for example H 2 , N 2 or hydrocarbon, in particular a short-chain.
  • reaction gas is advantageously 1 to 5 percent by volume or the proportion of air or the inert gas is typically 90 to 95%.
  • the respective composition and the proportions of the individual components can be adapted depending on the application and vary widely.
  • Particularly advantageous filling gases can be an inert gas, a short-chain hydrocarbon, nitrogen, Ar / H 2 0, N 2 / H 2 , Ar / 0 2 (approx. 5: 1), N 2 / NO ⁇ , H 2 / H 2 0 ( preferably 1: 1 to 3: 1) in Ar, Ar / H 2 (preferably 1: 4 to 4: 1), N 2/0 2, Ar / H 2 / H 2 0 (preferably about 3: 1: 1 ) or a combination thereof.
  • the composition of the filling gas is varied, controlled or regulated.
  • the moisture content of the filling gas is varied, controlled, regulated or maintained below its dew point or the saturation vapor pressure.
  • a safety distance from the dew point or saturation vapor pressure is advantageously maintained. This can be advantageous in order to prevent moisture precipitation due to the tion product water to avoid, as this would make the dielectric barrier discharge no longer feasible.
  • the pressure in the discharge space 3 is advantageously between 10 mbar and 10 bar.
  • a particularly advantageous embodiment for integrating the method according to the invention into a manufacturing process consists in the discharge space 3 being under normal or ambient conditions.
  • the filling gas is supplied to the discharge space 3 via the filling gas supply 15.
  • a plurality of inflow openings or inflow nozzles 16 can be provided, as a result of which the gas can be supplied in a gas-saving manner and a rapid gas exchange for removing the end products, for example C0 2 , S0 2 and H 2 0, is made possible from the discharge space 3.
  • the process may need to be controlled in the direction of oxidation or reduction.
  • the gas suction 17 can be followed by a gas scrubber 18, for example to wash out HC1 as a degradation product of chlorinated hydrocarbons or other pollutants.
  • the voltage supplied by the high-voltage unit 13 can be sinusoidal or rectangular or have another alternating profile.
  • the voltage is typically between 200 V and 15 kV and the electrical power coupled into the discharge space 3 is approximately 1 mW / cm 2 to 1 W / cm 2 at a typical distance between the electrodes 1, 2 of 0.2 mm to 20 mm based on the electrode surface.
  • the gap distance between the layer or the carrier surface and the adjacent electrode 2 or the adjacent dielectric 4 is less than 10 mm, preferably less than 5 mm .
  • the gap distance is also referred to as the gas space height.
  • the gap distance is more than 1 ⁇ m, preferably more than 100 ⁇ m.
  • a range between 0.5 and 2 mm is particularly preferred.
  • This information applies in particular when the pressure in the discharge space roughly corresponds to normal conditions.
  • the dielectric barrier 4 consisted of quartz glass, which was used for generating emission peaks 19 for 30 minutes. was etched with hydrofluoric acid. The thickness of the quartz glass was 1 to 4 mm with a typical value of 2 mm. The insulation and spacers consisted of 2 mm thick Teflon. The electrodes 1, 2 were made of steel and had a thickness of 1 cm. A sinusoidal voltage of 1 kHz with 12 to 16 kV was used as the voltage source. The gap distance was 2 mm. Air was used as the filling gas. The pressure was 1 bar and it was flushed at an exchange rate of 10 liters per minute. With this arrangement, a ceramic pia tine, which was provided with conductor tracks in thin and thick film technology, can be successfully cleaned.
  • the electron energy distribution can be optimally adjusted, inter alia, by the composition of the filling gas in connection with the distance (gap width, gap distance) of the electrodes 1, 2.
  • the composition of the filling gas in connection with the distance (gap width, gap distance) of the electrodes 1, 2.
  • average electron energies around 5 eV are optimal for electron collision dissociation from 0 2 , which is important for the production of oxygen radicals.
  • a further possibility for homogenizing the discharge at low voltage values which is realized in the arrangement shown in FIG. 9, is that the side of the dielectric 4 facing the layer to be cleaned or to be activated has emission peaks 19 facing the layer. Emission peaks can reduce filament formation and influence the local, temporal and electrical properties of the DBE.
  • Such emission peaks 19 can be easily and specifically produced, for example, by etching the dielectric base material (for example Al 2 O 3 bulk) with hydrofluoric acid (see W. Lang, Technische Rundschau Transfer No. 10 (1996) p. 32, DE 4304846 AI and DE 4315075 AI), which can then significantly reduce the field strength required for the electron emission of the partial discharge.
  • the field strength required for partial discharge is reduced depending on the design of the Peaks from approx. 10 7 V / cm up to 10 4 V / cm and thus the required ignition voltage.
  • etching process for generating tips is described in the publication W. Genthe, VDI Report No. 272, for the use of porous silicon or silicates or semiconductors.
  • the grain boundaries of the dielectric material are formed in an etching process, so that, for example in the case of Al 2 O 3 , whose grain size is typically 20 ⁇ m in diameter, radii of curvature of the grain tips of approximately 1 ⁇ m can be achieved.
  • such tips can also be produced by other application or removal processes, for example by UV structuring according to document DE 4113524 AI.
  • Emission peaks 19 are understood in the context of the invention to mean all types of elevations, edges and peaks which have such small radii of curvature that the emission preferably takes place at these points.
  • Emission peaks of this type can therefore be arranged, for example, in a needle-shaped distribution, that is to say they can be isolated individual peaks, and can also be generated by surface profiling of a corresponding material. For example, this can also be a scale-like structuring or a different type of fissuring of a surface. It is essential that the emission tips have a small radius of curvature, which is preferably essentially between 10 nm and 0.5 mm, so that the emission is concentrated on the tips and is thereby facilitated.
  • the emission peaks are preferably formed in the dielectric itself, it being possible for the electrode to be planar.
  • the surface density will advantageously be between 1 and 100 per cm 2 .
  • the height of the emission peaks can be up to 1 cm or more.
  • the size is variable and depends on the material used, for example glass or ceramic.
  • the density results from the grain size of the ceramic.
  • the distribution of the grains and their size vary statistically around a typical, material-dependent mean. The same applies to their shape.
  • Other conditions can exist if the surface is not processed by means of an ablation process, but rather by means of an abrading process, as can be the case, for example, with diamond or silicon.
  • ion peaks 19 through which corona effects are added to the DBE and a hybrid discharge takes place, is that the discharge is homogenized and the requirements with regard to the performance characteristics of the high-voltage unit 13 are reduced.
  • the locally distributed micro-discharges ignite at the same time; however, since the total energy of a discharge process is predetermined, the average energy per micro-discharge, ie per discharge filament, is lower and the treatment is therefore gentler.
  • emission tips 19 When using emission tips 19, the required voltage level and / or the voltage rise rate can be reduced.
  • high voltages or voltage rise rates of greater than 10 kV / ⁇ s for electrodes or dielectric barriers that are flat on the surface. This value can be considerably lower due to emission peaks 19, so that technologically less complex and thus more cost-effective high-voltage units 13 can be used.
  • emission peaks 19 can be used to increase the mean electron energy that can be achieved locally in the peak environment to ranges above 6 to 12 eV, which makes novel and energy-efficient chemical-physical reactions and reaction channels possible which were previously used in surface cleaning and at higher pressures or under normal conditions had no meaning.
  • the homogenization of the discharge has the advantage that the locally distributed micro-discharges (discharge filaments) 5 ignite simultaneously at low voltages, and an intensive cleaning or activation effect is thus achieved.
  • a particularly advantageous embodiment can consist in that the emission tips 19 are arranged only in a region opposite the layer or carrier surface to be cleaned or activated, that is to say they are arranged at least approximately in correspondence with their contour.
  • FIG. 10 schematically shows the formation of a micro-discharge 5 on a metal electrode 2, which has emission tips 19b.
  • the electrode 12 shows a schematic representation of an arrangement for cleaning a circuit board 6 with arranged electrical traces.
  • the electrode 2 has emission peaks 19 which are shown schematically in their depth distribution.
  • the electrode 1 under the board 6 is somewhat smaller than the board 6 and optionally enclosed by a side plate 12.
  • the position of the electrode 1 under the circuit board 6 is indicated by a dashed line in the circuit board 6.
  • the insulating fitting frame of the side plate 12 can also be omitted.
  • Another advantageous feature can be that the method according to the invention is carried out in two or more stages, for example the level of the voltage at the electrodes 1, 2, the time profile, the electrical power or the composition or the pressure of the filling gas is varied.
  • Controlling the composition of the filling gas in two or more phases, for example in an oxidation and reduction phase, can be useful since the article by Ch. Oehr mentioned at the beginning showed that the oxide layer is used in oxidative plasma cleaning, for example in silver, Copper or steel samples are growing. This can sometimes be desirable, for example when anodizing, but as a rule an oxide layer affects the quality of the component or its solderability.
  • one can work with less strongly oxidizing plasmas for example argon, argon / nitrogen plasma, argon / hydrogen plasma or nitrogen / hydrogen plasma, the long-chain hydrocarbons being fragmented into short-chain hydrocarbons and the fragments due to their higher vapor pressure change into the gas phase so that the surface becomes clean.
  • plasmas for example argon, argon / nitrogen plasma, argon / hydrogen plasma or nitrogen / hydrogen plasma
  • some oxides can be reduced to the metals, for example Cu, Ni or Fe.
  • Suboxides are obtained from others, for example titanium and vanadium.
  • the difference dG is, for example, particularly large in the case of the metals Al, Mg and Ca, so that their oxides are particularly difficult to reduce, but this is particularly desirable in the case of dielectric barrier materials such as A1 2 0 3 (requires approximately 10 eV), since these should not be attacked.
  • oxidation / reduction processes can lead to structural disturbances and changes in the morphology compared to the original metal surface, which can impair the functionality of a component, for example, through crack formation. It should therefore be checked in individual cases whether strong oxidizing air plasma can be used to remove organic contaminants or whether another plasma, for example Ar / H 2, leads to a comparable cleaning success without oxidizing the metal.
  • An exemplary process can look as follows.
  • the circuit board is then cleaned under an oxidative atmosphere and, if appropriate, subsequently provided with a structuring protective coating.
  • the areas to be soldered are activated by a reducing fill gas.
  • a chemical bath for surface activation is not required.
  • UV and VUV radiation can be generated in the method according to the invention, which contributes to cleaning or activation.
  • the term internal radiation means that the radiation is generated in the immediate vicinity of the surface to be cleaned or activated. This has particular advantages, since UV radiation and, to an even greater extent, VUV radiation have a short free path length and therefore an adverse absorption in the filling gas takes place with external radiation.
  • UV and VUV radiation can make a particularly efficient and intensive contribution due to the formation in the immediate vicinity of the surface on which it acts.
  • An exemplary process is the interaction of a fast electron with an N 2 molecule. This results in a slow electron and 2 N (4S), from which, for example, an N (4S) and N ( 2 D) result.
  • the rest of the process can be done according to Lawrence Livermore National Laboratory's publication UCRL-JC-122532 of November 21, 1995.
  • the reaction chains for atoms and molecules, which are excited by electron impact in a first step, can be determined from this by examining the released energies and the possible reaction pathways, whereby further excited atoms and molecules can arise after reactions. For example, a primary oxidizing plasma is generated in air and at average electron energies of approx. 4 eV, with 0 3 P and 0 1D being formed in a ratio of 2: 1, as well as NO molecules and OH radicals.
  • An exemplary reaction cycle for the degradation of long-chain hydrocarbons is the oxidation of R-CH 3 via the steps alkane, alkyl, alkyl peroxide, alkyloxy, aldehyde to the alkane reduced by the CH 3 group, as shown in FIG. 13. This is preceded by generation of 0 3 P and 0 ld by electron collisions .
  • FIG. 13 An exemplary reaction cycle for the degradation of long-chain hydrocarbons is the oxidation of R-CH 3 via the steps alkane, alkyl, alkyl peroxide, alkyloxy, aldehyde to the alkane reduced by the CH 3 group, as shown in FIG. 13. This is preceded by generation of 0 3 P and 0 ld by electron collisions .
  • reference numerals 101 denote long-chain hydrocarbons on the surface to be cleaned, 102 degradation products which pass into the gas phase, 103 OH radicals as the product of O ⁇ D) + H 2 0 -> 2 OH, 104 0 2 from the process gas or from air, 105 0 2 as a reaction product, 106 H 2 0 from the process gas and 107 H 2 0 as a reaction product.
  • Chemical radicals 108 according to the equation H0 2 + NO -> N0 2 + OH are also remarkable.
  • Another exemplary reaction cycle for the degradation of chlorine-containing hydrocarbons is the oxidation of tetra to C0 2 , HCl and Cl 2 , as shown in Fig. 14 (Dis ⁇ ertation Z. Falken ⁇ tein, University of Düsseldorf 1996).
  • the long-lived intermediate or final substances 20 and the chain propagators 21 are particularly emphasized.
  • First electrode Second electrode Discharge chamber Dielectric Micro discharge Carrier (circuit board) Conductor contact surface Formation Base plate Cover Side plate High voltage unit Execution Filling gas supply Inlet nozzles Gas extraction Gas washing Gas emission tips Long-lasting substances Chain propagator component

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  • Optics & Photonics (AREA)
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Abstract

L'invention concerne un procédé pour le nettoyage ou l'activation de couches électroconductrices structurées. Selon l'invention, il est prévu d'utiliser à cet effet une décharge inhibée diélectriquement.
PCT/DE1998/001141 1997-04-26 1998-04-22 Procede et dispositif pour le nettoyage et l'activation de structures ou de surfaces de platines electroconductrices Ceased WO1998049368A1 (fr)

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DE1997117698 DE19717698A1 (de) 1997-04-26 1997-04-26 Verfahren und Vorrichtung zur Reinigung von Aktivierung von elektrischen Leiterbahnen und Platinenoberflächen
DE19717698.4 1997-04-26

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SG144714A1 (en) * 2003-04-28 2008-08-28 Air Prod & Chem Removal of surface oxides by electron attachment for wafer bumping applications
DE102011105713A1 (de) * 2011-06-23 2012-12-27 Cinogy Gmbh Elektrodenanordnung für eine dielektrisch behinderte Gasentladung
WO2012097904A3 (fr) * 2011-01-21 2013-07-18 Hochschule Für Angewandte Wissenschaft Und Kunst Hildesheim/Holzminden/Göttingen Source de décharge coplanaire diélectrique pour un traitement de surface sous pression atmosphérique
EP3754695A4 (fr) * 2018-02-13 2021-12-01 Korea Institute of Fusion Energy Module de gravure par point faisant appel à un appareil à plasma à décharge de surface annulaire et procédé de commande de profil de gravure de module de gravure par point

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US6355571B1 (en) 1998-11-17 2002-03-12 Applied Materials, Inc. Method and apparatus for reducing copper oxidation and contamination in a semiconductor device
US20010049181A1 (en) * 1998-11-17 2001-12-06 Sudha Rathi Plasma treatment for cooper oxide reduction
DE19920693C1 (de) * 1999-05-05 2001-04-26 Inst Oberflaechenmodifizierung Offener UV/VUV-Excimerstrahler und Verfahren zur Oberflächenmodifizierung von Polymeren
US6821571B2 (en) 1999-06-18 2004-11-23 Applied Materials Inc. Plasma treatment to enhance adhesion and to minimize oxidation of carbon-containing layers
EP1073091A3 (fr) * 1999-07-27 2004-10-06 Matsushita Electric Works, Ltd. Electrode pour la production de plasma, appareil de traitement par plasma utilisant une telle électrode, et traitement par plasma à l'aide de cet appareil
US6794311B2 (en) 2000-07-14 2004-09-21 Applied Materials Inc. Method and apparatus for treating low k dielectric layers to reduce diffusion
US20020148816A1 (en) * 2001-04-17 2002-10-17 Jung Chang Bo Method and apparatus for fabricating printed circuit board using atmospheric pressure capillary discharge plasma shower
DE10257344A1 (de) * 2002-12-06 2004-07-08 OTB Oberflächentechnik in Berlin GmbH & Co. Verfahren zur Konservierung von Metalloberflächen
US8361340B2 (en) 2003-04-28 2013-01-29 Air Products And Chemicals, Inc. Removal of surface oxides by electron attachment
DE10320472A1 (de) * 2003-05-08 2004-12-02 Kolektor D.O.O. Plasmabehandlung zur Reinigung von Kupfer oder Nickel
US7229911B2 (en) 2004-04-19 2007-06-12 Applied Materials, Inc. Adhesion improvement for low k dielectrics to conductive materials
DE102006011312B4 (de) * 2006-03-11 2010-04-15 Fachhochschule Hildesheim/Holzminden/Göttingen - Körperschaft des öffentlichen Rechts - Vorrichtung zur Plasmabehandlung unter Atmosphärendruck
DE102007033701A1 (de) 2007-07-14 2009-01-22 Xtreme Technologies Gmbh Verfahren und Anordnung zur Reinigung von optischen Oberflächen in plasmabasierten Strahlungsquellen
DE102009060627B4 (de) * 2009-12-24 2014-06-05 Cinogy Gmbh Elektrodenanordnung für eine dielektrisch behinderte Plasmabehandlung

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SG144714A1 (en) * 2003-04-28 2008-08-28 Air Prod & Chem Removal of surface oxides by electron attachment for wafer bumping applications
WO2012097904A3 (fr) * 2011-01-21 2013-07-18 Hochschule Für Angewandte Wissenschaft Und Kunst Hildesheim/Holzminden/Göttingen Source de décharge coplanaire diélectrique pour un traitement de surface sous pression atmosphérique
DE102011105713A1 (de) * 2011-06-23 2012-12-27 Cinogy Gmbh Elektrodenanordnung für eine dielektrisch behinderte Gasentladung
WO2012175066A1 (fr) * 2011-06-23 2012-12-27 Cinogy Gmbh Agencement d'électrode pour une décharge gazeuse à barrière diélectrique
DE102011105713B4 (de) * 2011-06-23 2014-06-05 Cinogy Gmbh Elektrodenanordnung für eine dielektrisch behinderte Gasentladung
US9330890B2 (en) 2011-06-23 2016-05-03 Cinogy Gmbh Electrode arrangement for a dielectrically limited gas discharge
EP3754695A4 (fr) * 2018-02-13 2021-12-01 Korea Institute of Fusion Energy Module de gravure par point faisant appel à un appareil à plasma à décharge de surface annulaire et procédé de commande de profil de gravure de module de gravure par point

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