Abstract:
A method of fabrication and device made by preparing a photosensitive glass substrate comprising at least silica, lithium oxide, aluminum oxide, and cerium oxide, masking a design layout comprising one or more holes to form one or more electrical conduction paths on the photosensitive glass substrate, exposing at least one portion of the photosensitive glass substrate to an activating energy source, exposing the photosensitive glass substrate to a heating phase of at least ten minutes above its glass transition temperature, cooling the photosensitive glass substrate to transform at least part of the exposed glass to a crystalline material to form a glass-crystalline substrate and etching the glass-crystalline substrate with an etchant solution to form one or more angled channels that are then coated.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to creating an inductive current device in a photo definable glass structure, in particular, creating Inductors, Antenna, and Transformers devices and arrays in glass ceramic substrates for electronic, microwave and radiofrequency in general. 
       BACKGROUND ART 
       [0002]    Photosensitive glass structures have been suggested for a number of micromachining and microfabrication processes such as integrated electronic elements in conjunction with other elements systems or subsystems. Silicon microfabrication of traditional glass is expensive and low yield while injection modeling or embossing processes produce inconsistent shapes. Silicon microfabrication processes rely on expensive capital equipment; photolithography and reactive ion etching or ion beam milling tools that generally cost in excess of one million dollars each and require an ultra-clean, high-production silicon fabrication facility costing millions to billions more. Injection molding and embossing are less costly methods of producing a three dimensional shapes but generate defects with in the transfer or have differences due to the stochastic curing process. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention provides creates a cost effective glass ceramic inductive individual or array device. Where glass ceramic substrate has demonstrated capability to form such structures through the processing of both the vertical as well as horizontal planes either separately or at the same time to form, two or three-dimensional inductive devices. 
         [0004]    The present invention includes a method to fabricate a substrate with one or more, two or three dimensional inductive device by preparing a photosensitive glass substrate and further coating or filling with one or more metals. 
         [0005]    A method of fabrication and device made by preparing a photosensitive glass ceramic composite substrate comprising at least silica, lithium oxide, aluminum oxide, and cerium oxide, masking a design layout comprising one or more, two or three dimensional inductive device in the photosensitive glass substrate, exposing at least one portion of the photosensitive glass substrate to an activating energy source, exposing the photosensitive glass substrate to a heating phase of at least ten minutes above its glass transition temperature, cooling the photosensitive glass substrate to transform at least part of the exposed glass to a crystalline material to form a glass-crystalline substrate and etching the glass-crystalline substrate with an etchant solution to form one or more angled channels or through holes that are then used in the inductive device. 
         [0006]    The present invention provides a method to fabricate an inductive device created in or on photo-definable glass comprising the steps of: preparing a photosensitive glass substrate comprising at least silica, lithium oxide, aluminum oxide, and cerium oxide; masking a design layout comprising one or more structures to form one or more electrical conduction paths on the photosensitive glass substrate; exposing at least one portion of the photosensitive glass substrate to an activating energy source; exposing the photosensitive glass substrate to a heating phase of at least ten minutes above its glass transition temperature; cooling the photosensitive glass substrate to transform at least part of the exposed glass to a crystalline material to form a glass-crystalline substrate; etching the glass-crystalline substrate with an etchant solution to form the one or more angled channels in the device; wherein the glass-crystalline substrate adjacent to the trenches may also be converted to a ceramic phase; coating the one or more angled channels with one or more metals; coating all or part of the inductor structure with a dielectric media; removing all or part of the dielectric media to provide electrical contact or free standing inductive device; and wherein the metal is connected to a circuitry through a surface or buried contact. 
         [0007]    The inductive device stores current and functions as a current storage device. The one or more metals are designed to operate as an inductor at the appropriate frequencies. The inductive device has a magnetic permeability greater than or equal to copper for frequencies greater than 100 MHz. The inductive device has a magnetic permeability greater than copper for frequencies less than 100 MHz. The ceramic phase can be etched from one side or both sides to partially or fully remove the glass-ceramic material. The method can further include the step of converting at least a portion of the glass into ceramic and etching away the ceramic to at least partially expose the metal structure. The method can further include the step of converting at least a portion of the glass into ceramic and etching away the ceramic to fully expose the metal structure. 
         [0008]    The present invention also includes an inductive device having a glass-ceramic material surrounding one or more inductive coils wherein the one or more inductive coils are at least partially surround by air. 
         [0009]    The one or more inductive coils include one or more angled channels in the glass-crystalline substrate with a metal coating over at least a portion of the one or more angled channels. The inductive element is further surrounded by a magnetically permeable material. The inductive element does not touch the magnetically permeable material. The inductive element comprises a cavity filled with a magnetically permeable material on one side, both sides or through the glass-ceramic material. The one or more inductors interact with each other. The one or more inductors share a magnetically permeable material. The metal coating may reside partially through, fully through, or on top of the glass-ceramic material, or a combination there of The inductive device of further includes 1 or more second metal layer on any surface. 
         [0010]    The present invention also includes an inductive device having a glass-crystalline substrate surrounding one or more inductive coils wherein the one or more inductive coils are at least partially surround by air. The inductive device includes one or more inductive coils are that are supported by one or more rails on the glass-crystalline substrate. The inductive device includes one or more inductive coils are that are positioned in one or more pits in the glass-crystalline substrate. The inductive device may include a metal coating, a multilayer metal coating, an alloy coating, a multilayer alloy coating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which: 
           [0012]      FIG. 1  shows a coreless transformer design. 
           [0013]      FIG. 2  shows interlocking square spirals etched into APEX® glass. 
           [0014]      FIG. 3A  top view of an inductive device in/on APEX® glass. 
           [0015]      FIG. 3B  side view of an inductive device in/on APEX® glass. 
           [0016]      FIG. 4A  is an image of a free-standing copper RF antenna bridge structure. 
           [0017]      FIG. 4B  is an image of a free-standing coil. 
           [0018]      FIG. 5  is an image of a partially etched inductor, where the surrounding ceramic has been partially etched away to allow mostly air to surround the inductive device. 
           [0019]      FIG. 6  is an isometric image of a fully etched inductor, where the surrounding ceramic has been fully etched away to allow only air to surround the inductive device. 
           [0020]      FIG. 7A and 7B  are side image of a fully etched inductor, where the surrounding ceramic has been fully etched away to allow only air to surround the inductive device. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0021]    While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not restrict the scope of the invention. 
         [0022]    To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims. 
         [0023]      FIG. 1  shows a coreless transformer design.  FIG. 2  shows interlocking square spirals etched into APEX® glass.  FIG. 3A  top view of an inductive device in/on APEX® glass.  FIG. 3B  side view of an inductive device in/on APEX® glass.  FIG. 4A  is an image of a free-standing copper RF antenna bridge structure.  FIG. 4B  is an image of a free-standing coil.  FIG. 5  is an image of a partially etched inductor, where the surrounding ceramic has been partially etched away to allow mostly air to surround the inductive device.  FIG. 6  is an isometric image of a fully etched inductor, where the surrounding ceramic has been fully etched away to allow only air to surround the inductive device.  FIG. 7A and 7B  are side image of a fully etched inductor, where the surrounding ceramic has been fully etched away to allow only air to surround the inductive device. 
         [0024]    To address these needs, the present inventors developed a glass ceramic (APEX®) Glass ceramic) as a novel packaging and substrate material for semiconductors, RF electronics, microwave electronics, and optical imaging. APEX® Glass ceramic is processed using first generation semiconductor equipment in a simple three step process and the final material can be fashioned into either glass, ceramic, or contain regions of both glass and ceramic. The APEX® Glass ceramic possesses several benefits over current materials, including: easily fabricated high density vias, demonstrated microfluidic capability, micro-lens or micro-lens array, high Young&#39;s modulus for stiffer packages, halogen free manufacturing, and economical manufacturing. Photoetchable glasses have several advantages for the fabrication of a wide variety of microsystems components. Microstructures have been produced relatively inexpensively with these glasses using conventional semiconductor processing equipment. In general, glasses have high temperature stability, good mechanical and electrically properties, and have better chemical resistance than plastics and many metals. To our knowledge, the only commercially available photoetchable glass is FOTURAN®, made by Schott Corporation and imported into the U.S. only by Invenios Inc. FOTURAN® comprises a lithium-aluminum-silicate glass containing traces of silver ions plus other trace elements specifically silicon oxide (SiO 2 ) of 75-85% by weight, lithium oxide (Li 2 O) of 7-11% by weight, aluminum oxide (Al 2 O 3 ) of 3-6% by weight, sodium oxide (Na 2 O) of 1-2% by weight, 0.2-0.5% by weight antimonium trioxide (Sb2O3) or arsenic oxide (As 2 O 3 ), silver oxide (Ag 2 O) of 0.05-0.15% by weight, and cerium oxide (CeO 2 ) of 0.01-0.04% by weight. As used herein the terms “APEX® Glass ceramic”, “APEX® glass” or simply “APEX®” is used to denote one embodiment of the glass ceramic composition of the present invention. 
         [0025]    When exposed to UV-light within the absorption band of cerium oxide the cerium oxide acts as sensitizers, absorbing a photon and losing an electron that reduces neighboring silver oxide to form silver atoms, e.g., 
         [0000]      Ce 3+ +Ag + =Ce 4+ +Ag 0   
         [0000]    The silver atoms coalesce into silver nanoclusters during the baking process and induce nucleation sites for crystallization of the surrounding glass. If exposed to UV light through a mask, only the exposed regions of the glass will crystallize during subsequent heat treatment. 
         [0026]    This heat treatment must be performed at a temperature near the glass transformation temperature (e.g., greater than 465° C. in air for FOTURAN®). The crystalline phase is more soluble in etchants, such as hydrofluoric acid (HF), than the unexposed vitreous, amorphous regions. In particular, the crystalline regions of FOTURAN® are etched about 20 times faster than the amorphous regions in 10% HF, enabling microstructures with wall slopes ratios of about 20:1 when the exposed regions are removed. See T. R. Dietrich et al., “Fabrication technologies for microsystems utilizing photoetchable glass,” Microelectronic Engineering 30, 497 (1996), which is incorporated herein by reference. Preferably, the shaped glass structure contains at least one or more, two or three-dimensional inductive device. The inductive device is formed by making a series of connected loops to form a free-standing inductor. The loops can be either rectangular, circular, elliptical, fractal or other shapes that create and pattern that generates induction. The patterned regions of the APEX® glass can be filled with metal, alloys, composites, glass or other magnetic media, by a number of methods including plating or vapor phase deposition. The magnetic permittivity of the media combined with the dimensions and number of structures (loops, turns or other inductive element) in the device provide the inductance of devices. Depending on the frequency of operation the inductive device design will require different magnetic permittivity materials. At low frequencies, less than 100 MHz devices can use ferrites or other high different magnetic permittivity materials. At higher frequencies &gt;100 MHz high different magnetic permittivity materials can generate eddy currents creating large electrical losses. So at higher frequency operations material such as copper or other similar material is the media of choice for inductive devices. Once the inductive device has been generated the supporting APEX® glass can be left in place or removed to create a free-standing structure. The present invention provides a single material approach for the fabrication of optical microstructures with photo-definable/photopatternable APEX® glass for use in imaging applications by the shaped APEX® glass structures that are used for lenses and includes through-layer or in-layer designs. 
         [0027]    Generally, glass ceramics materials have had limited success in microstructure formation plagued by performance, uniformity, usability by others and availability issues. Past glass-ceramic materials have yield etch aspect-ratio of approximately 15:1 in contrast APEX®β glass has an average etch aspect ratio greater than 50:1. This allows users to create smaller and deeper features. Additionally, our manufacturing process enables product yields of greater than 90% (legacy glass yields are closer to 50%). Lastly, in legacy glass ceramics, approximately only 30% of the glass is converted into the ceramic state, whereas with APEX™ Glass ceramic this conversion is closer to 70%. 
         [0028]    APEX® composition provides three main mechanisms for its enhanced performance: (1) The higher amount of silver leads to the formation of smaller ceramic crystals which are etched faster at the grain boundaries, (2) the decrease in silica content (the main constituent etched by the HF acid) decreases the undesired etching of unexposed material, and (3) the higher total weight percent of the alkali metals and boron oxide produces a much more homogeneous glass during manufacturing. 
         [0029]    The present invention includes a method for fabricating a glass ceramic structure for use in forming inductive structures used in electromagnetic transmission, transformers and filtering applications. The present invention includes an inductive structures created in the multiple planes of a glass-ceramic substrate, such process employing the (a) exposure to excitation energy such that the exposure occurs at various angles by either altering the orientation of the substrate or of the energy source, (b) a bake step and (c) an etch step. Angle sizes can be either acute or obtuse. The curved and digital structures are difficult, if not infeasible to create in most glass, ceramic or silicon substrates. The present invention has created the capability to create such structures in both the vertical as well as horizontal plane for glass-ceramic substrates. The present invention includes a method for fabricating of an inductive structure on or in a glass ceramic. 
         [0030]    Ceramicization of the glass is accomplished by exposing the entire glass substrate to approximately 20 J/cm 2  of 310 nm light. When trying to create glass spaces within the ceramic, users expose all of the material, except where the glass is to remain glass. In one embodiment, the present invention provides a quartz/chrome mask containing a variety of concentric circles with different diameters. 
         [0031]    The present invention includes a method for fabricating an inductive device in or on glass ceramic structure electrical microwave and radio frequency applications. The glass ceramic substrate may be a photosensitive glass substrate having a wide number of compositional variations including but not limited to: 60-76 weight % silica; at least 3 weight % K 2 O with 6 weight %-16 weight % of a combination of K 2 O and Na 2 O; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag 2 O and Au 2 O; 0.003-2 weight % Cu 2 O; 0.75 weight %-7 weight % B 2 O 3 , and 6-7 weight % Al 2 O 3 ; with the combination of B 2 O 3 ; and Al 2 O 3  not exceeding 13 weight %; 8-15 weight % Li 2 O; and 0.001-0.1 weight % CeO 2 . This and other varied compositions are generally referred to as the APEX® glass. 
         [0032]    The exposed portion may be transformed into a crystalline material by heating the glass substrate to a temperature near the glass transformation temperature. When etching the glass substrate in an etchant such as hydrofluoric acid, the anisotropic-etch ratio of the exposed portion to the unexposed portion is at least 30:1 when the glass is exposed to a broad spectrum mid-ultraviolet (about 308-312 nm) flood lamp to provide a shaped glass structure that have an aspect ratio of at least 30:1, and to create an inductive structure. The mask for the exposure can be of a halftone mask that provides a continuous grey scale to the exposure to form a curved structure for the creation of an inductive structure/device. A digital mask can also be used with the flood exposure and can be used to produce the creation of a inductive structure/device. The exposed glass is then baked typically in a two-step process. Temperature range heated between of 420° C.-520° C. for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520° C.-620° C. for between 10 minutes and 2 hours allowing the lithium oxide to form around the silver nanoparticles. The glass plate is then etched. The glass substrate is etched in an etchant, of HF solution, typically 5% to 10% by volume, wherein the etch ratio of exposed portion to that of the unexposed portion is at least 30:1 when exposed with a broad spectrum mid-ultraviolet flood light, and greater than 30:1 when exposed with a laser, to provide a shaped glass structure with an anisotropic-etch ratio of at least 30:1. 
         [0033]    Where the material surrounding the inductive device is converted to ceramic before metal filling. Where the metallic material used to fill the etched structures is metal other than copper (i.e. nickel, iron alloys). Where the surface of the inductive device is coated with a dielectric material. Where the surface of the inductive device is patterned first with a dielectric material and then with a patterned metal. 
         [0034]    For embodiments that are surrounded by the ceramic phase: Where the ceramic is etched from one side or both sides to partially or fully remove the glass-ceramic material to partially expose the metal structures. An inductive device consisting of multiple unique inductive components. Said device where different inductive components are selectively plated with different metals into different etched features.