HK1197961A - Method of forming a conductive image on a non-conductive surface - Google Patents

Description

Method of forming conductive image on non-conductive surface

Cross reference to related applications

This application is related to (1) U.S. provisional patent application 61/525662 filed on 8/19/2011 in the name of William Wismann, (2) U.S. provisional patent application 61/568736 filed on 12/9/2011 in the name of William Wismann and claiming priority from these applications, and (3) a continuation of the application 13/403797 filed on 2/23/2012 in the name of William Wismann, all of which are incorporated herein by reference as if set forth in their entirety herein.

Technical Field

The present invention relates to the field of electronic device manufacturing.

Background

Conductive images on non-conductive or dielectric surfaces are ubiquitous in today's technology driven world. The most widely known example of such a situation might be an integrated circuit present in virtually all electronic devices. Integrated circuits are formed from a series of photographic and chemical processing steps by which circuits are progressively formed on dielectric substrates such as silicon wafers.

A typical wafer is made of very pure silicon grown into a single crystalline cylindrical mass, called a boule, up to 300 mm in diameter. The boule is then sliced into wafers approximately 0.75 mm thick and polished to obtain an extremely smooth planar surface.

The formation of circuits on a wafer requires a number of steps to be performed, which can be categorized into two major groups: front end of line (FEOL) processing and back end of line (BEOL) processing.

FEOL processing refers to the formation of circuits directly in silicon. The bare wafer is first subjected to epitaxial growth, growth of a silicon ultrapure crystal on a wafer, wherein the crystal mimics the orientation of the substrate.

After epitaxial growth, front end surface engineering typically consists of the steps of growth of a gate dielectric, traditionally silicate glass (SiO2), patterning of the gate, patterning of the source and drain regions, and subsequent implantation or diffusion of dopants to obtain the desired complementary electrical properties. In Dynamic Random Access Memory (DRAM) devices, a storage capacitor is also fabricated at this time, typically stacked above the access transistor.

Once the various semiconductor devices have been formed, they must be interconnected to form the desired circuitry, which includes the BEOL portion of the process. BEOL involves the formation of metal interconnect wires separated by dielectric layers. The insulating material is traditionally silicate glass SiO₂But other low dielectric constant materials can be used.

The metal interconnect wires often comprise aluminum. In a wiring scheme known as subtractive aluminum, a blanket film of aluminum is deposited, patterned and etched to form conductive lines. Subsequently, a dielectric material is deposited over the exposed conductive lines. The various metal layers are interconnected by etching holes, called vias, in the insulating material and depositing tungsten in the holes. This scheme is still used in the manufacture of memory chips such as DRAMs, due to the small number of interconnect levels.

More recently, as the number of interconnect levels has increased due to the large number of transistors that now need to be interconnected in modern microprocessors, timing delays in the wiring have become important, facilitating the change of wiring materials from aluminum to copper and from silicon dioxide to newer low-K materials. The result is not only enhanced performance but also reduced cost because the damascene process replaces subtractive aluminum techniques, thereby eliminating several steps. In a damascene process, a dielectric material is deposited as a blanket film, which is subsequently patterned and etched, leaving holes or trenches. In a single damascene process, copper is then deposited in the holes or trenches surrounded by the thin barrier film, creating filled vias or conductive lines. In dual damascene techniques, both the trench and via are fabricated prior to the deposition of copper, while forming the via and conductive line, thereby further reducing the number of processing steps. A thin barrier film called the Copper Barrier Species (CBS) is necessary to prevent copper diffusion into the dielectric. The barrier film is desirably as thin as possible. The formation of the thinnest continuous barrier represents one of the greatest continuing challenges in copper processing today, as the excessive barrier films present compete with the available copper wire cross-section.

As the number of interconnect levels increases, planarization of previous layers is required to ensure a flat surface prior to subsequent lithography. Without this, the levels would become increasingly curved and extend to the depth of focus of the available lithography, interfering with the ability to pattern. CMP (chemical mechanical planarization) is one process to achieve such planarization, but if the number of interconnect levels is low, dry etch back is sometimes still employed.

The above processes, while described with particular reference to silicon chip fabrication, are quite common for most types of printed circuits, printed circuit boards, antennas, solar cells, solar films, semiconductors, and the like. As can be seen, this process is subtractive; that is, a metal, typically copper, is uniformly deposited on the substrate surface, and the unwanted metal, i.e., the metal that does not comprise some portion of the final circuit, is subsequently removed. Multiple additive processes are known which solve some of the problems associated with the subtractive process but create their own problems, one of which is important relating to the adhesion of the formed conductive layer to the substrate.

What is needed is an additive process for integrated circuit fabrication that has all the advantages of other additive processes but exhibits improved adhesion properties to the substrate. The present invention provides one such addition process.

Disclosure of Invention

Accordingly, in one aspect, the present invention relates to a method of forming a conductive layer on a surface, comprising:

activating at least a portion of the non-conductive substrate surface;

applying a magnetic field to the surface;

depositing a metal coordination complex on at least a portion of the activated portion of the surface;

eliminating the magnetic field;

exposing the metal coordination complex to electromagnetic radiation;

reducing the metal coordination complex to elemental metal;

removing the unreduced metal coordination complex from the surface;

drying the surface; and

a conductive material is deposited onto the surface.

In one aspect of the invention, activating the surface of the substrate includes etching the surface.

In one aspect of the invention, etching the surface comprises chemical etching.

In one aspect of the invention, the chemical etching comprises acid etching, substrate etching or oxide etching.

In one aspect of the invention, etching the surface comprises mechanical etching.

In one aspect of the invention, etching the surface comprises plasma etching.

In one aspect of the invention, etching the surface comprises laser etching.

In one aspect of the invention, plasma or laser etching includes etching in a predetermined pattern.

In one aspect of the invention, the magnetic field has a magnetic flux density of at least 1000 gauss.

In one aspect of the invention, the magnetic field is orthogonal to the surface.

In one aspect of the invention, depositing the metal coordination complex on at least a portion of the surface includes using a mask.

In one aspect of the invention, the mask includes electronic circuitry.

In one aspect of the invention, the electronic circuit is selected from the group consisting of an analog circuit, a digital circuit, a mixed signal circuit, and an RF circuit.

One aspect of the invention is an analog circuit fabricated using the methods disclosed herein.

One aspect of the invention is a digital circuit fabricated using the method disclosed herein.

One aspect of the invention is a mixed signal circuit fabricated using the methods disclosed herein.

One aspect of the invention is an RF circuit fabricated using the methods disclosed herein.

In one aspect of the invention, exposing the metal coordination complex to electromagnetic radiation comprises microwave radiation, infrared radiation, visible light radiation, ultraviolet radiation, X-ray radiation, or gamma radiation.

In one aspect of the invention, reducing the metal coordination complex to a zero oxidation state metal comprises using a combination of metals and/or catalysts.

In one aspect of the invention, removing the unreduced metal coordination complex from the surface comprises rinsing the surface with a solvent.

In one aspect of the invention, drying the surface comprises drying at ambient temperature or drying at an elevated temperature.

In one aspect of the invention, drying the surface at ambient or elevated temperature includes using a vacuum chamber.

In one aspect of the invention, the conductive material is deposited onto the surface by electrolytic deposition of a metal onto the portion of the surface comprising the reduced metal coordination complex.

In one aspect of the invention, the electrolytic deposition of a metal onto a portion of a surface comprising a reduced metal coordination complex comprises:

contacting a negative terminal of a direct current power source with at least a portion of a surface including a reduced metal coordination complex;

providing an aqueous solution comprising a metal salt to be deposited, an electrode formed from a metal immersed in the aqueous solution, or a combination thereof;

contacting the positive terminal of the dc power supply with the aqueous solution;

contacting at least a portion of the surface comprising the reduced metal coordination complex with an aqueous solution; and

the power is turned on.

In one aspect of the invention, depositing a conductive material onto a surface comprises electroless deposition of a metal onto a portion of the surface comprising a reduced metal coordination complex.

In one aspect of the invention, electrolessly depositing a metal onto the portion of the surface comprising the reduced metal coordination complex comprises contacting at least the portion of the surface comprising the metal coordination complex with a solution comprising a metal salt, a complexing agent, and a reducing agent.

In one aspect of the invention, depositing a conductive material onto a surface comprises deposition of a non-metallic conductive species onto a portion of the surface comprising a reduced metal coordination complex.

In one aspect of the invention, the non-metallic conductive material is deposited by electrostatic dispersion onto the portion of the surface comprising the reduced metal coordination complex.

In one aspect of the invention, the entire non-conductive substrate surface is activated and the metal coordination complex is deposited onto the entire surface.

In one aspect of the invention, the entire non-conductive substrate surface is activated and a metal coordination complex is deposited onto a portion of the activated surface.

Drawings

The figures herein are provided solely to aid in the understanding of the present invention and are not intended to, or should not be construed to, limit the scope of the invention in any way.

Drawing (A) 1A substrate to be processed using the method of the invention is shown, wherein the substrate is positioned in a magnetic field such that the magnetic field is orthogonal to the plane of the surface of the substrate.

Detailed Description

Discussion of the related Art

It is to be understood that, with respect to the present description and appended claims, reference to any aspect of the invention in the singular includes the plural and vice versa, except where such use is explicitly or clearly indicated from the context.

As used herein, any term of approximation such as, but not limited to, near, about, roughly, approximately, substantially, and the like, means that the word or phrase modified by the approximating term need not be exactly what is written, but may differ to some extent from the written description. The extent to which the description may vary will depend on how much modification can be effected and will enable those skilled in the art to recognize the modified version as still having the approximate properties, characteristics and capabilities of the term unmodified word or words. Generally, but in view of the foregoing discussion, numerical values herein modified by approximating language may differ by ± 10% from the stated value, unless expressly stated otherwise.

As used herein, the use of "preferred," "preferably," or "more preferred" and the like refers to preferences that exist at the time of filing this patent application.

As used herein, "conductive layer" refers to an electrically conductive surface, such as, but not limited to, a printed circuit.

As used herein, "non-conductive substance" refers to a substrate formed of a non-conductive material (sometimes referred to as an insulator or dielectric). Such materials include, but are not limited to, minerals such as silica, alumina, magnesium, zirconia, and the like, glass, and most plastics. Specific non-limiting examples include FR4, which is a general class designation for glass fiber reinforced epoxy resins, such as, but not limited to DuPont Kapton PV9103 polyimide and ULTRALAM liquid crystal polymer (Rogers, Chandler AZ).

As used herein, "activating a non-conductive substrate surface" or portions thereof refers to making the surface more amenable to some manner of interaction with another material disposed on the substrate surface and subsequent physical or chemical bonding to that material. In an embodiment of the invention, the another material can include a metal coordination complex. Additionally, changing the surface properties also means making the surface more dispersive to incident electromagnetic radiation. Altering the surface properties can be accomplished by altering the topography or permeability of the surface or a combination of both. The topography of the surface can be altered by mechanical or chemical means or a combination of both.

Mechanical means of altering the surface properties of the substrate include, but are not limited to, simple abrasion of the surface, such as using sandpaper or another abrasive material, rasping the surface using a rasp, scoring the surface using a sharp object such as, but not limited to, a tool tip, and laser etching. Combinations of these and any other methods of creating a wear surface are within the scope of the present invention.

In some embodiments, a surface may be prepared initially using a mold that includes a wear surface profile by disposing a molten polymer into the mold to form a substrate with altered surface properties. After removal of the mold, the cast object will have a modified surface compared to an object cast using a smooth surface mold. These methods of altering the surface properties are well known to those skilled in the art and need not be described further.

Chemical means of altering the surface properties of the substrate include, but are not limited to, acid etching, base etching, oxide etching, and plasma etching.

Acid etching, as its name implies, refers to the use of strong acids such as sulfuric, hydrochloric, and nitric acids. Hydrochloric acid and nitric acid mix to produce aqua regia, a very strong acid that can be used to alter the surface properties of the substrate. Most commonly, however, the surface to be acid etched is glass and the acid used to etch the glass is hydrochloric acid. This and other acid etching techniques are well known in the art and as such need not be explained in detail.

Base etching is the reverse of acid etching and involves the use of a base substance to alter the topography of the surface of the substrate. Many organic polymers are susceptible to chemical dissolution with a base substance. For example, but not by way of limitation, potassium hydroxide will react with polyesters, polyimides, and polyepoxides to change their surface properties. Other materials susceptible to substrate etching will be well known to those skilled in the art. All such materials are within the scope of the present invention.

Oxidative etching refers to the modification of the surface properties of a substrate by exposing the surface to a strong oxidizing agent, such as but not limited to potassium permanganate.

Plasma etching refers to the process of striking the surface of a substrate by a high-speed glow discharge current of a suitable gas. The etching species may include charged ions or neutral atoms and radicals. During the etching process, elements of the material being etched may chemically react with reactive species generated by the plasma. Additionally, the atoms of the plasma-generating species may embed themselves in the surface of the substrate, or just below it, thereby further altering the properties of the surface. Plasma etching is well known in the art for other methods of altering the properties of a surface and need not be described further for the present invention.

Laser etching is well known in the art. Briefly, a laser beam is directed at a surface in the focal plane of the laser. The movement of the laser is computer controlled. As the laser focus moves across the surface, the material of the surface typically vaporizes, thereby leaving an image that is traced by the laser on the surface. With respect to the present invention, a laser may be used to impart an overall pattern on the surface of the substrate, or it may be used to track the actual image to ultimately cause conduction on the substrate.

Another way of changing the surface properties of the substrate involves exposing the surface of the substrate to a liquid known to soften the surface, usually with swelling of the surface. When the coating is applied to the intumescent surface, the material is able to physically interact at its boundary with the intumescent surface, which enables the material to adhere more strongly to the surface, particularly when the coated substrate is dry.

As used herein, "applying a magnetic field" to a surface of a substrate refers to placing the surface of the substrate on or near a source of the magnetic field. The magnetic field may be generated by a permanent magnet, an electromagnet, or a combination thereof. A single magnet or multiple magnets may be used. The surface of the substrate in contact with or in the vicinity of the magnet may be the surface opposite to the surface to which the metal coordination complex is to be precipitated, or it may be the surface to which the metal coordination complex is to be precipitated. That is, the magnetic field source can be above or below the substrate, where "above" refers to the activated surface of the substrate and "below" refers to the surface opposite the activated surface. If permanent magnets are used to generate the magnetic field, any type of magnet may be used as long as the field strength is at least 1000 gauss, more preferably at least 2000 gauss. The presently preferred permanent magnet is a neodymium magnet. It is also preferred that the permanent magnet has dimensions such that the proximity or all of the active surface of the substrate is contained within the dimensions of the magnet. Such an arrangement is shown in fig. 1. In fig. 1, a substrate 10 has an activated surface 15. The permanent magnet 20 is disposed below the substrate 10 and is positioned such that the magnetic field generated by the magnet is orthogonal to the activation surface 15, which is a presently preferred configuration.

As used herein, "paramagnetic or ferromagnetic metal coordination complexes" are understood to have the meaning of those classes to which the skilled person would ascribe a metal complex. The metal coordination complex must be ferromagnetic or paramagnetic and, therefore, when disposed on the surface of the substrate, it is affected by an orthogonal magnetic field. Without being held to any particular theory, it is believed that under the influence of the magnetic field, the complex will be drawn completely towards the magnetic field source and thereby injected deeper into the surface of the substrate, or the magnetic field may cause the ligands of the complex to align with the magnetic field, thereby drawing the ligands further into the substrate. A combination of the two processes may also be performed. The result in any case will be a more closely adhering complex than would be obtained under the influence of no magnetic field.

After the metal coordination complex is applied to the surface of the substrate under the influence of the applied magnetic field, the magnetic field source is removed.

Subsequently, the metal coordination complex coated substrate is exposed to electromagnetic radiation to activate the metal coordination complex toward the reducing agent. As used herein, electromagnetic radiation includes virtually the entire spectrum of such radiation, i.e., microwave, infrared, visible, ultraviolet, X-ray, and gamma ray radiation. The composition of the metal coordination complex can be tailored to be sensitive to a particular range of the electromagnetic spectrum, or if desired, a sensitizer can be added to the complex to render the complex photosensitive when the complex is disposed on a substrate, or even more photosensitive if the complex itself is photosensitive. As used herein, "light sensitive" has its dictionary definition: sensitive or responsive to light or other radiant energy, which would include each of the types of radiation mentioned above.

Exposure to radiation renders a portion of the metal coordination complex susceptible to reduction. The reducing agent will reduce the metal coordination complex to elemental metal. The reducing agent can be any metal-containing salt in which the metal has a greater reduction potential, i.e., conventionally has a more negative reduction potential than the metal of the coordination complex. The following chart shows the reduction potentials of a number of common species. The higher species on the list can be those that reduce below it.

Reducing potential (V) of the reducing agent

Li -3.04

Na -2.71

Mg -2.38

Al -1.66

H_{2( g)} + 2OH^- -0.83

Cr -0.74

Fe -0.44

H₂ 0.00

Sn²⁺ +0.15

Cu⁺ +0.16

Ag +0.80

2Br^- +1.07

2CI^- +1.36

Mn²⁺ + 4H₂O +1.49

The elemental metal resulting from the reduction step is of course insoluble in most solvents. Thus, rinsing the surface of the substrate with an appropriate solvent determined by the composition of the initial metal coordination complex will remove the unexposed complex, leaving the metal behind. The metal may be uniformly dispersed over the surface of the substrate if the surface of the substrate is generally exposed, or the metal may form a discrete pattern if the surface of the substrate is exposed through a mask. The mask is simply the material that is placed between the electromagnetic radiation source and the surface of the substrate and that includes the image to be transferred to the surface of the substrate. The image may be a negative image, in which case the portions of the surface of the substrate that receive the radiation correspond to those portions of the mask that are transparent to the particular radiation, or a positive image, in which case the portions of the surface of the substrate that receive the radiation correspond to those portions outside the image area of the mask.

Once the unexposed metal coordination complex is removed, the substrate is dried to complete the formation of the metal image.

The metal image can be used as is, plated with another metal, or coated with a non-metallic conductive material.

Such electroplating can be done electrolytically or electroless if the metal image is to be plated with another metal. In this way, the conductive metal layer is formed only in the areas of the image that include the metal image, with the result that the conductive surface is embossed.

Electroless plating of metal image portions of a surface of a substrate can be accomplished by, but is not limited to, contacting the surface with a solution of a metal salt to be deposited in the presence of a complexing agent to maintain metal ions in the solution and to substantially stabilize the solution. The complexing metal salt is contacted with or at least in the vicinity of the surface simultaneously or continuously with an aqueous solution of a reducing agent. The metal complex is reduced to provide elemental metal that adheres to the metal image already on the surface of the substrate; i.e. to produce an electroless deposition of metal on the metal.

The metal complex solution and the reducing solution can be simultaneously sprayed onto the patterned substrate from separate spray units, the spray streams being directed so as to intersect at or near the substrate surface, or from a single spray unit having separate reservoirs and spray tip holes, the two streams mixing when emerging from the spray head and impinging on the substrate surface.

Electrodeposition contemplated herein is well known in the art and need not be described extensively. Briefly, the elemental metal image is connected to the negative terminal (cathode) of a direct current power supply, which may be simply a battery, but is more commonly a rectifier. The anode constituting the second metal to be deposited on the first metal image is connected to the positive terminal (anode) of the power supply. The anode and cathode are electrically connected by means of an electrolyte solution, wherein the imaged metal surface is submerged or immersed by spraying with the solution.

The electrolyte solution contains dissolved metal salts of the metal to be plated and other ions that make the electrolyte conductive.

Upon application of a power source to the system, the metal anode is oxidized to produce cations of the metal to be deposited, and the positively charged cations migrate to the cathode, i.e., the metal image on the surface of the substrate, where they are reduced to a zero valence state of the metal and deposited on the surface.

In an embodiment of the invention, a solution of the cation of the metal to be deposited can be prepared and the solution can be sprayed onto the metallization structure.

The conductive material to be coated on the elemental metal image may also include a non-metallic conductive substance such as, but not limited to, carbon or a conductive polymer. Such materials can be deposited on the metal image by techniques such as, but not limited to, electrostatic powder coating and electrostatic dispersion coating, which can be done as a wet (from solvent) or dry process. The process may be performed by electrostatically charging the metal image and then contacting the image with nano-or micron-sized particles that have been electrostatically charged by the opposite charge applied to the metal image. In addition, to further ensure that only the metallic image is coated, the non-conductive substance may be grounded to eliminate any possibility of an attractive charge developing on the substrate, or the substrate may be charged with the same polarity charge as the substance to be deposited, so that the substrate rejects the substance.

Examples of the invention

Example 1

1. Chemical etching of flakelet DuPont Kapton PV9103 polyimide using a mixture of 0.1N KOH (5.6 grams potassium hydroxide per 1 liter deionized water (DI)) and a 60% solution by weight of isopropyl alcohol for 2 to 4 minutes

2. The etched polyimide sheets were rinsed with DI water and dried in a 100 ℃ oven for 30 minutes.

3. 10 g of ammonium iron oxalate (solution 1) were suspended in 25 l of DI water (in a dark room).

4. 10 g of ammonium iron oxalate and 1.0 g of potassium chlorate and 25 ml of DI water (also in the dark) were mixed (solution 2).

5. 2.3 g of ammonium chloroplatinate (ll) and 1.7 g of lithium chloride and 2 ml of DI water (solution 3) were mixed.

6. Solutions 1, 2 and 3 were mixed together in equal amounts.

7. The etched polyimide sheet was placed on a 2000 gauss magnet having a size larger than the size of the polymer sheet, and the surface of the sheet was thinly coated with the mixture of step 6 (in a dark room) using a sponge brush.

8. The coated polyimide sheet was air dried for 30 minutes (alternatively, the coated sheet could be placed in a 40 ℃ oven for about 5 minutes or until dry).

9. A mask including the desired tab image is placed on top of the coating.

10. Exposing the masked surface of the polyimide sheet to a full intensity ASC365 UV light source for no less than 3 minutes

11. The light source was removed, the mask and substrate surface were separated, and the surface was rinsed with DI water for 5 minutes, and then placed in an EDTA cell containing 15 grams of ethylenediaminetetraacetic acid (EDTA) per 1000 milliliters of DI water for 10 minutes.

12. The rinsed substrate was placed in a 40 ℃ oven for 5 minutes or until dry.

13. The substrates were placed at 5 minute 25 ℃ intervals in a cell containing Shipley electroless Cuposit 328 with 27.5% 328 (a-12.5%, L-12.5%, C-2.5%) and 72.5% DI to record plating.

14. The resulting copper-plated polyimide was rinsed with DI water for 10 minutes and air dried for 30 minutes (or can be placed in a 40 ℃ oven for 5 minutes or until dry).

Example 2

1. Rogers ULTRALAM 3000 Liquid Crystalline Polymer (LCP) sheets were chemically etched by about 5% by volume (40 grams of sodium hydroxide per liter) using Electro-Brits E-prep 102

2. The sheet was then statically rinsed by a two-stage water wash.

3. Subsequently, the rinsed etched wafer is treated with an E-neutralizer and rinsed again.

4. Subsequently, the sheet was immersed in a 10% sulfuric acid solution for 10 seconds, and then rinsed.

5. 10 g of silver nitrate (in a dark room) was dissolved in 25 ml of DI water.

6. 5 g of potassium chromate are mixed with 5 ml of DI water (in a dark room)

7. Silver nitrate was added dropwise to the potassium chromate solution until a red precipitate formed. The mixture was allowed to sit for 24 hours, then filtered and diluted to 100 ml (in the dark room) with DI water

8. Subsequently, the flakes were placed on a 2000 gauss magnet and thinly coated with a silver chromate mixture (in a dark room) using a sponge brush.

9. The coated sheet was placed in a 40 ℃ oven for 10 minutes or until dry.

10. A tensile test design mask was placed on the coated surface of the LCP sheet.

11. The masked LPC wafers were then exposed to uv light from an ASC365 uv light source for 5 minutes.

12. The UV light source was removed, the LCP sheets and mask were separated, and the sheets were rinsed with DI water for 5 minutes and then placed in an EDTA bath (15 grams of EDTA per 1000 milliliters of DI water) for 10 minutes.

13. Subsequently, the TCP sheet was rinsed with DI water for 10 minutes and placed in a 40 ℃ oven for 5 minutes or until dry.

14. The LCP sheets were then placed in a cell containing Shipley electroless Cuposit 328 at 25 ℃ at 5 minute intervals to record plating with 27.5% 328 (1-12.5%, L-12.5%, C-2.5%) and 72.5% deionized water in the cell.

15. The copper-plated LCP sheet was removed from the cell, washed with water for 10 minutes and then placed in a 40 ℃ oven for 5 minutes until dry.

Example 3

1. A thin sheet (0.15 inch thick) of FR4 was chemically etched using a 10% sulfuric acid solution for 3 minutes, then etched using a 6% potassium hydroxide solution.

2. Subsequently, the sheet was rinsed with DI water.

3. 30 grams of ferric ammonium citrate (green form, 7.5% ammonia, 15% ions, and 77.5% citric acid hydrate) and 35 milliliters of DI warm water (50 ℃) were mixed (in the dark room), and then DI water was used to form up to the final 50 milliliter quantity (in the dark room) in an amber bottle.

4. 1.8 g ammonium chloride and 3 g palladium chloride (ll) in 20 ml DI hot water (70-80 ℃) were mixed by stirring until dissolved and subsequently up to 25 ml was formed by addition of DI water.

5. The mixture was filtered and bottled upon cooling.

6. 6 drops of ferric ammonium citrate were added to 1 drop of palladium chloride solution in a beaker until 20 ml of solution was obtained (in a dark room).

7. The FR4 flakes were placed on a 2000 gauss magnet having a size larger than that of the FR4 flakes and the surface of the flakes was thinly coated with the coordination complex solution (in a dark room) using a sponge brush.

8. The FR4 flakes were then placed in a 40 ℃ oven for 10 minutes or until dry.

9. Subsequently, a tensile test design mask was placed on the treated surface of the FR4 sheet.

10. The masked FR4 flakes were then exposed to UV light from an ASC365 UV emitter for 6 minutes.

11. The UV light source was removed, the mask and FR4 sheet were separated, the sheet was rinsed with DI water for 5 minutes and then placed in an EDTA cell (15 grams of EDTA per 1000 milliliters of DI water) for 10 minutes.

12. The FR4 sheet was removed from the EDTA cell, rinsed with DI water for 10 minutes, and then placed in a 40 ℃ oven for 5 minutes or until dry.

13. The FR4 sheets were placed at 5 minute intervals at 25 ℃ in a pool of Shipley electroless Cuposit 328 with 27.5% 328 (A-12.5%, L-12.5%, C-2.5%) and 72.5% deionized water to record plating.

14. Subsequently, the copper plated FR4 sheet was rinsed for 10 minutes and placed in a 40 ℃ oven for 5 minutes until dry.

Claims (30)

1. A method of forming a conductive layer on a surface, comprising:

activating at least a portion of the non-conductive substrate surface;

applying a magnetic field to the surface;

depositing a metal coordination complex on at least a portion of the activated portion of the surface;

-eliminating said magnetic field;

exposing the metal coordination complex to electromagnetic radiation;

reducing the metal coordination complex to an elemental metal;

removing unreduced metal coordination complex from the surface;

drying the surface; and

depositing a conductive material onto the surface.

2. The method of claim 1, wherein activating the substrate surface comprises etching the surface.

3. The method of claim 2, wherein etching the surface comprises chemical etching.

4. The method of claim 3, wherein chemically etching comprises acid etching, substrate etching, or oxide etching.

5. The method of claim 2, wherein etching the surface comprises mechanical etching.

6. The method of claim 2, wherein etching the surface comprises plasma etching.

7. The method of claim 2, wherein etching the surface comprises laser etching.

8. The method of claim 6, wherein plasma or laser etching comprises etching in a predetermined pattern.

9. The method of claim 1, wherein the magnetic field has a magnetic flux density of at least 1000 gauss.

10. The method of claim 9, wherein the magnetic field is orthogonal to the surface.

11. The method of claim 1, wherein depositing a metal coordination complex on at least a portion of the surface comprises using a mask.

12. The method of claim 10, wherein the mask comprises an electronic circuit.

13. The method of claim 12, wherein the electronic circuit is selected from the group consisting of an analog circuit, a digital circuit, a mixed signal circuit, and an RF circuit.

14. An analog circuit fabricated using the method of claim 1.

15. A digital circuit fabricated using the method of claim 1.

16. A mixed signal circuit fabricated using the method of claim 1.

17. An RF circuit fabricated using the method of claim 1.

18. The method of claim 1, wherein exposing the metal coordination complex to electromagnetic radiation comprises microwave radiation, infrared radiation, visible light radiation, ultraviolet radiation, X-ray radiation, or gamma radiation.

19. The method of claim 1, wherein reducing the metal coordination complex to a zero oxidation state metal comprises using a combination of metals and/or catalysts.

20. The method of claim 1, wherein removing unreduced metal coordination complex from the surface comprises rinsing the surface with a solvent.

21. The method of claim 1, wherein drying the surface comprises drying at ambient temperature or drying at an elevated temperature.

22. The method of claim 21, wherein drying the surface at ambient or elevated temperature comprises using a vacuum chamber.

23. The method of claim 1, wherein depositing a conductive material onto the surface comprises electrolytic deposition of a metal onto a portion of the surface comprising the reduced metal coordination complex.

24. The method of claim 23, wherein the electrowinning of metal onto the portion of the surface comprising the reduced metal coordination complex comprises:

contacting a negative terminal of a direct current power source with at least the portion of the surface comprising the reduced metal coordination complex;

providing an aqueous solution comprising a metal salt to be deposited, an electrode formed from a metal immersed in the aqueous solution, or a combination thereof;

contacting a positive terminal of the direct current power supply with the aqueous solution;

contacting at least a portion of the surface comprising the reduced metal coordination complex with the aqueous solution; and

and turning on the power supply.

25. The method of claim 1, wherein depositing a conductive material onto the surface comprises electroless deposition of a metal onto a portion of the surface comprising the reduced metal coordination complex.

26. The method of claim 25, wherein electrolessly depositing a metal onto the portion of the surface comprising the reduced metal coordination complex comprises contacting at least the portion of the surface comprising the metal coordination complex with a solution comprising the metal salt, a complexing agent, and a reducing agent.

27. The method of claim 1, wherein depositing a conductive material onto the surface comprises deposition of a non-metallic conductive species onto a portion of the surface comprising the reduced metal coordination complex.

28. The method of claim 27, wherein the non-metallic conductive substance is deposited by electrostatic dispersion onto the portion of the surface comprising the reduced metal coordination complex.

29. The method of claim 1, wherein the entire non-conductive substrate surface is activated and the metal coordination complex is deposited onto the entire surface.

30. The method of claim 1, wherein the entire non-conductive substrate surface is activated and the metal coordination complex is deposited onto a portion of the activated surface.