Hermetic enclosures containing glass through-vias and medical implants containing said hermetic enclosures

Abstract

A hermetic enclosure (10) is proposed, comprising at least one glass substrate (12), wherein at least one glass substrate (12) has at least one electrical feedthrough configured as a glass through via (30), the via (30) comprising a conductive rod (32) that electrically connects the inside of the hermetic enclosure (10) to the outside through the glass substrate (12), the portion of the conductive rod (32) facing outward from the hermetic enclosure (10) is completely covered by a conductive coating (40), the conductive coating (40) being a multilayer structure including at least an adhesive layer (42) in direct contact with the conductive rod (32) and a corrosion-resistant layer.

Description

[Technical Field]

[0001] The present invention relates to a hermetic enclosure comprising at least one glass substrate, wherein at least one glass substrate has at least one electrical feedthrough configured as a glass through via, and the glass through via comprises a conductive rod that electrically connects the inside of the hermetic enclosure to the outside through the glass substrate.

[0002] Electronic devices can be used inside the human body for sensing (e.g., temperature, liquid composition, pressure, conductivity, chemical properties, systems) or for active therapy (e.g., cardiovascular stimulation, nerve stimulation, brain stimulation, drug delivery, drug activation). However, electronic devices should not be placed directly inside the human body. The human body environment has an average pH of 7.35–7.45 and a temperature of 36.5–37.5°C, making it susceptible to corrosion. Ordinary metal and plastic components may decompose in this environment, releasing harmful substances. Electronic devices used as implants are typically sealed within a casing. Titanium or titanium alloy casings are widely used for cardiac stimulation. However, when these casings are airtight, they become large, heavy, and bulky. Glass as an enclosure material can be a lightweight and robust alternative. For example, European Patent No. 3012059 describes a method for manufacturing a transparent component to protect an optical component. A novel laser welding method is used here.

[0003] Some electronic devices require a casing with an electrical feedthrough to provide an electrical connection to the outside. European Patent Application Publication No. 3812352 discloses a hermetic glass enclosure having vias for establishing an electrical contact connection from the inside to the outside of the enclosure, for example, for contact connection to an external contact pad of the enclosure.

[0004] Such glass through vias (TGVs) are formed from a metal, primarily tungsten, that connects the inner and outer surfaces of a glass substrate. However, the material of glass through vias can corrode when exposed to corrosive environments, and may even be released from the glass.

[0005] Therefore, an object of the present invention is to provide an improved electrical feedthrough through a glass substrate of a hermetic casing, suitable for use in corrosive environments, particularly for use as a medical implant.

[0006] Disclosure of the invention A hermetic enclosure is proposed comprising at least one glass substrate having at least one electrical feedthrough configured as a glass through via. The via comprises a conductive rod that electrically connects the inside of the enclosure to the outside through the glass substrate. The portion of the conductive rod facing outwards from the enclosure is completely covered by a conductive coating, which is a multilayer structure including at least an adhesive layer in direct contact with the conductive rod and a corrosion-resistant layer.

[0007] Such a hermetic enclosure is formed from two or more substrates hermetically bonded to each other to hermetically seal a functional area or cavity. For example, a hermetic enclosure may include three substrates. The base, formed of glass substrates, includes at least one electrical feedthrough, a spacer substrate, and a cover substrate. In this example, the base glass substrate defines the bottom wall of the sealed cavity, the spacer substrate defines the side wall of the sealed cavity, and the cover substrate defines the top wall of the sealed cavity. In another example, the hermetic enclosure may include two substrates, namely a base glass substrate including at least one electrical feedthrough and a cavity substrate. The cavity substrate has a cavity formed, for example, by etching, laser-assisted etching, CNC machining, or laser ablation, and defines the side and top walls of the sealed cavity, while the base glass substrate defines the bottom wall of the sealed cavity.

[0008] Hermetic enclosures can be obtained directly by stacking individual substrates and then bonding these substrates together. An efficient method for obtaining multiple hermetic enclosures involves stacking and bonding entire wafers, and then separating the formed enclosures, for example, by saw dicing. In one example, a spacer wafer has multiple openings, which together with adjacent base and cover wafers define a cavity. In another example, individual cavities formed within a cavity wafer define a cavity together with adjacent base wafers.

[0009] Bonding of substrates or wafers can be performed, for example, by laser bonding and / or laser welding, anodic bonding, fusion bonding, contact bonding, or glass frit bonding. Bonding methods that allow direct bonding of two adjacent substrates or wafers without the use of any intermediate or adhesive materials, such as laser bonding, are particularly preferred.

[0010] Bonding is preferably performed so that a hermetic enclosure is formed, and the cavity or functional area is sealed inside such an enclosure. As used herein, hermetic sealing means, in particular, 1.10 -8 Helium leakage rate less than mbar·l / sec, preferably 1·10 -10 mbar·l / sec~1·10 -9 This refers to an enclosure with a helium leakage rate in the range of mbar·l / sec.

[0011] In a preferred laser bonding process, a short-pulse laser beam from a laser source is focused to a predetermined spot within a formed substrate stack, with at least one of the substrates being transparent. By selecting the repetition rate and scanning rate of the laser, individual laser pulses can be closely aligned such that the nonlinear absorption regions of one laser pulse touch or even overlap with adjacent nonlinear absorption regions of another laser pulse, thereby causing heat accumulation. The accumulated heat locally melts the material of the substrate stack, resulting in a continuous weld "line." To form such a continuous weld line, the focal plane of the laser beam is positioned near, but not at, the interface between the two substrates. The laser beam is positioned at a predetermined distance below the interface between the two substrates, and the accumulated heat locally melts and mixes the materials of the first and second substrates, forming an airtight bond. The region where the heat accumulated by the incident laser melts and mixes the materials of the two substrates is referred to as the laser processing zone. In the region surrounding the laser-treated zone described above, the heat introduced by the laser is insufficient to melt the material, but it can cause modification of the material and / or conductive coating placed on the glass substrate. This region will be referred to as the heat-affected zone below.

[0012] Preferably, a glass substrate having at least one electrical feedthrough is bonded to another substrate, such as a spacer substrate or cavity substrate, by laser bonding, forming at least one bonding line where the materials of the glass substrate and the other substrate are melted and mixed, where the distance from the laser bonding line to the glass through via is preferably at least 50 μm. Additionally or alternatively, the distance from the laser bonding line to the glass through via is selected such that the glass through via is outside the heat-affected zone.

[0013] The sealed cavity formed by the proposed hermetic enclosure is particularly suitable for housing electronic devices. The devices are preferably electrically connected to an electrical feedthrough, and thus can send and receive electrical signals and / or currents from outside the hermetic enclosure.

[0014] The electrical feedthrough is configured as a glass through via and includes a conductive rod embedded in the glass substrate so that its front and rear surfaces are accessible. Preferably, the conductive rod is formed from or contains a metal such as tungsten, titanium, iron / nickel alloy, gold, silver, copper, or (doped) silicon, or a combination of these materials.

[0015] The length of the conductive rod is selected so that an electrical contact connection can be established through the glass substrate. The thickness of the glass substrate is preferably in the range of 200 μm to 4000 μm, more preferably in the range of 500 μm to 1000 μm. The length of the conductive rod is preferably in the range of 200 μm to 4000 μm, more preferably in the range of 500 μm to 1000 μm. The length of the conductive rod can be selected to be the same as the thickness of the glass substrate.

[0016] The material for the glass substrate is preferably selected from borosilicate glass, such as BOROFLOAT® 33 or D263® T eco or MEMpax® available from SCHOTT AG, quartz glass, fused silica, aluminoborosilicate glass, such as AF32® available from SCHOTT AG, alkali-free glass, SCHOTT B270®, or alkali silicate glass, such as AS87.

[0017] The material for other substrates, such as spacer substrates, cover substrates, and / or cavity substrates, is preferably selected from glass, glass ceramic, ceramic, silicon, sapphire, diamond, or other inorganic crystals. Suitable glass materials include those described for glass substrates. In the case of glass materials, glass suitable for glass substrates is also suitable as a material for other substrates.

[0018] For example, to protect electrical feedthroughs from damage due to corrosion, a multilayer conductive coating is provided so as to completely cover the material of the conductive rod of the feedthrough exposed on the side facing outwards from the enclosure, and consequently, the material on the side facing outwards from the glass substrate. Thus, the side of the conductive rod facing outwards, including the front surface facing the environment, which is not surrounded by the glass substrate and is therefore exposed from the glass substrate, is covered. However, the inventors have found that applying a corrosion-resistant coating layer only to the aforementioned front surface of the conductive rod is insufficient. For example, placing a gold coating only on the aforementioned front surface of a tungsten conductive rod does not reduce corrosion. Rather, such a gold coating has been found to surprisingly accelerate corrosion. To achieve the desired corrosion resistance, it is necessary to completely cover not only the front surface of the conductive rod, but the entire exposed surface. For example, when the enclosure is exposed to an aqueous NaCl solution, the acceleration of corrosion is thought to be caused by an electrochemical process between the coating material and the conductive rod material.

[0019] Therefore, it is preferable to form a conductive coating without creating a gap so that the entire material of the conductive rod exposed outside the enclosure is covered and thus shielded from the environment. To achieve a complete gap-free cover of the exposed surface of the metal rod, it is preferable to extend the conductive coating to the region of the glass substrate surface adjacent to each conductive rod. The adjacent region extends beyond the edge of the conductive rod, preferably over a distance of at least 1 μm, more preferably at least 2 μm, more preferably at least 5 μm, more preferably at least 10 μm, and most preferably at least 40 μm. Due to the accuracy of the patterning device, the extent to which the coating process can be well aligned and centered with respect to the conductive rod is limited, so the contact pad diameter d p is preferably selected to be larger than the via diameter d v , and thus, d p = d v + Δd, where Δd is more than 5 μm, more preferably 10 μm, and most preferably 20 μm or more. Without loss of generality, cylindrical conductive rods and conductive contact pads are assumed. If the cross-sections of the rod and the contact pad are not circular, d v = 2r max , where r max is the maximum radius measured from the center of the via cross-section, and d p = 2r min , where r min is the minimum distance measured from the center of the contact pad cross-section.

[0020] In addition to applying the conductive coating to the side facing the outside, it is also possible to dispose the conductive coating on the side facing the inside of the conductive rod. Further, in order to form a conductive structure, it is possible to expand the conductive coating over a part of the surface of the substrate. When the conductive coating is applied to the side facing the inside of the substrate and / or the conductive rod, the coating preferably covers the entire side facing the inside of the conductive rod, but it is also possible to cover only a part of the front surface of the conductive rod.

[0021] The corrosion-resistant contact layer serves both to protect the conductive rod from the influence of the environment and to form a highly reliable electrical contact surface for establishing an electrical connection. Thanks to the corrosion-resistant contact layer, the hermetic enclosure can be used in corrosive environments, including the bodies of animals and humans.

[0022] The corrosion-resistant contact layer provides a contact surface that can be used to establish a permanent electrical connection, for example, by soldering a wire to the contact surface. The contact surface can also be used as part of a connector or receptacle for establishing a separable electrical connection.

[0023] When a solder connection is desired, the conductive coating can be configured such that solder pads are formed.

[0024] Preferably, the electrical feedthrough has recesses or protrusions on the side facing the outside of the glass substrate and / or on the side facing the inside of the glass substrate, the recesses / indentations or protrusions surround the conductive rod, and preferably form the same plane as the front surface of the conductive rod, and the depth of the recess or the height of the protrusion is preferably at least 250 nm and / or less than 3 μm, more preferably less than 500 nm. In the case of a recess, the depth of the recess can be selected to correspond to the total thickness of the conductive coating so that the conductive coating forms a substantially flat surface with the surface of the glass substrate surrounding the recess.

[0025] By selecting the depth / height of the recess / recess and the length of the conductive rod such that the front surface of the conductive rod forms a coplanar surface with the recess / recess, a flat and homogeneous surface is obtained that allows the corrosion-resistant conductive coating to extend seamlessly from the front surface of the conductive rod to the surface portion of the glass substrate. In this case, the contact pad or solder pad formed by the coating can be selected to have a surface area larger than the size of the front surface of the conductive rod, making it easier to establish an electrical connection.

[0026] Preferably, the depth / height and / or shape of the recess / indentation or ridge is configured such that the recess or ridge functions as a solder flow boundary. The recess / indentation or ridge forms a boundary that influences and restricts the flow of solder material. For example, if the entire area of ​​the ridge or recess is covered with a conductive coating, the solder will only come into contact with the formed solder pad and not with the glass substrate.

[0027] The structural portions of the glass substrate, formed by recesses / indentations or raised areas, can also function as anchors for the coating, thereby improving the adhesion of the coating.

[0028] Preferably, the conductive coating is also placed on at least a portion of the glass substrate, and the conductive coating is on the via diameter d of the conductive rod to which the contact pad is electrically connected. v Larger pad diameter d p A contact pad having the following characteristics is formed.

[0029] Additionally or alternatively, the conductive coating may be configured to form at least one conductive trace. Such a conductive trace can form an electrical connection between one or more electrical feedthroughs, between an electrical feedthrough and a contact pad, or between two contact pads located on the surface of a glass substrate. The conductive trace may also be configured to form an antenna and / or coil structure. Such a structure can be located on the inward and / or outward-facing sides of the substrate of the enclosure.

[0030] A conductive coating is a multilayer structure having at least two layers. Since the multilayer structure is conductive, each layer is selected from a conductive material.

[0031] The corrosion-resistant layer is preferably configured as a diffusion barrier layer and / or a corrosion-resistant contact layer. The conductive coating may include both a diffusion barrier layer and a corrosion-resistant contact layer.

[0032] The corrosion-resistant layer is preferably made of or selected from a material containing at least one element from the platinum group, such as platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), and osmium (Os). The corrosion-resistant layer may also consist of or contain a platinum oxide. In particular, the corrosion-resistant layer may contain or consist of iridium oxide (IrO2) or ruthenium oxide (RuO2).

[0033] Preferably, the multilayer structure of the conductive coating includes, in this order, an adhesive layer in direct contact with the conductive rod, at least one diffusion barrier layer, and a corrosion-resistant contact layer.

[0034] The adhesive layer is selected to have good adhesion to the material of the conductive rod and / or the material of the glass substrate. Suitable adhesive layers are formed from or contain, for example, Ti, Ta, Cr, Ni, NiCr, TiAl, and combinations thereof.

[0035] The thickness of the adhesive layer is preferably in the range of 2 nm to 200 nm, more preferably in the range of 10 nm to 150 nm, and most preferably in the range of 20 nm to 100 nm.

[0036] The diffusion barrier layer is selected to prevent diffusion or propagation of material from the corrosion-resistant contact layer or substances from outside the hermetic enclosure toward the conductive rod, and similarly to prevent diffusion or propagation in the reverse direction. In particular, the diffusion barrier layer is selected so that materials contained in the solder or adhesive material, as well as oxygen from the environment, do not damage the conductive rod of the electrical feedthrough. Furthermore, the material of the diffusion barrier layer is preferably selected to be biocompatible. Biocompatible materials are non-toxic and do not have harmful effects on the biological system.

[0037] Preferably, the diffusion barrier layer is formed from or contains at least one element from the platinum group, such as platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), and osmium (Os). The corrosion-resistant contact layer, if conductive, may consist of or contain a platinum oxide such as iridium oxide (IrO2) or ruthenium oxide (RuO2). For stability and density reasons, hydrogen or hydrogen oxide incorporated into the IrO2 should not be present. Ideally, the IrO2 coating should be hydrogen and hydrogen oxide-free. The diffusion barrier may be formed from or contain titanium nitride (TiN). The diffusion barrier may contain at least one or both of the elements from the platinum group and titanium nitride. If the diffusion barrier layer is the outermost layer of a multilayer structure, the material for the diffusion barrier layer is preferably selected from biocompatible materials.

[0038] The thickness of the diffusion barrier layer is preferably in the range of 20 nm to 200 nm, more preferably 40 nm to 150 nm, and most preferably 50 nm to 100 nm.

[0039] The corrosion-resistant contact layer is preferably made of a material that not only has resistance to corrosive environments but also has good conductivity and wettability to solder material in order to enable high-quality electrical connections. Furthermore, since the corrosion-resistant contact layer preferably forms the outermost layer of the conductive coating, it is preferably selected from biocompatible materials.

[0040] Preferably, the corrosion-resistant contact layer is made of or contains gold (Au). If the corrosion-resistant contact layer is conductive, it may be made of or contain platinum or platinum oxides, such as iridium oxide (IrO2) or ruthenium oxide (RuO2). In the case of IrO2, it is desirable that no hydrogen or hydrogen oxide incorporated into the IrO2 is present.

[0041] The thickness of the corrosion-resistant contact layer is preferably in the range of 50 nm to 200 nm, more preferably 80 nm to 150 nm, and most preferably 75 nm to 100 nm.

[0042] The conductive coating can be applied to the surface of a conductive rod and, optionally, to a portion of the surface of a glass substrate by any suitable coating method. Preferably, at least one layer of the conductive coating is obtained by electroplating, electroless plating, physical vapor deposition (PVD, e.g., sputtering or deposition, particularly resistive evaporation or electron beam deposition), chemical vapor deposition (CVD), preferably metal-organic CVD (MOCVD) and / or atomic layer deposition (ALD).

[0043] Preferably, the corrosion-resistant contact layer is a gold layer obtained by electroless plating. The process here may utilize the use of a seed layer to initiate autocatalytic deposition of gold. Preferably, an adhesive layer or a diffusion barrier layer, if present, is selected so that the above layer functions as a seed layer, thereby eliminating the need for an additional seed layer.

[0044] Preferably, the glass substrate material and / or conductive coating are selected to be resistant to exposure to an aqueous NaCl solution of the above material, particularly a 700 g / l NaCl solution. The enclosure may be immersed in the solution for 7 days at a temperature of, for example, 37°C, and then visually inspected for signs of corrosion. Furthermore, corrosion resistance can be evaluated by determining the weight loss. In this case, the material can be considered corrosion resistant if the weight loss rate is less than 5%, preferably less than 3%, and most preferably less than 1%. The total weight of the conductive coating is small, and therefore it is difficult to measure the weight loss of the conductive coating material. However, if the coating is not resistant, gaps will form after exposure to a corrosive environment, and these gaps will lead to exposure of the conductive rod to the NaCl solution. Therefore, if the conductive rod remains protected, and consequently the overall weight loss of the conductive rod material after the container is exposed to an aqueous NaCl solution containing 700 g / l of NaCl at a temperature of 37°C for 7 days is preferably less than 5%, more preferably less than 3%, and most preferably less than 1%, then the conductive coating material is considered to have particularly good corrosion resistance. Furthermore, for the glass substrate material, it is preferable that the weight loss of the glass substrate material is less than 5%, preferably less than 3%, and more preferably less than 1%.

[0045] Since the weight loss of the conductive rod is minimal, it is preferable to use a statistical population of multiple enclosures for corrosion resistance testing. For example, if the enclosure weighs m r If there are V conductive rods, the total weight of the conductive rods should be greater than 0.1g, that is, M r =N·V·m r >0.1g A statistical set of N enclosures is used to achieve this result.

[0046] Next, the measurement can be performed by first drying the sample using, for example, IR drying in a drying cabinet at 100°C for 30 minutes. After drying, the initial weight M0 of the dried statistical population is determined using, for example, a chemical balance (e.g., Avantor VWR I611-3350 / LA314i). Then, the statistical population in the enclosure is immersed in NaCl solution (700 g / l) at 37°C for 7 days. After the test period, the sample is rinsed with deionized water and then dried, for example, in a drying cabinet (IR drying, 100°C for 30 minutes). After drying, the weight M1 of the dried statistical population is determined using, for example, a chemical balance (e.g., Avantor VWR I611-3350 / LA314i).

[0047] Therefore, ΔM = M0 - M1, where ΔM / M r The percentage is <5%, <3%, and most preferably less than 1%.

[0048] To distinguish whether the weight loss is due to the weight loss of the conductive rod or to the corrosion of the glass (which also needs to be avoided), the same method can be used to repeat the test for one set of conforming statistics, using a glass enclosure with the same spatial dimensions and the same glass, but without glass through-vias and thus without the conductive rod. The difference in weight loss ΔM determined between these two measurements represents the weight loss of the conductive rod material.

[0049] The structure of the conductive coating is summarized in Table 1.

[0050] [Table 1]

[0051] Table 2 shows examples of suitable coatings to be applied to glass substrates with glass through vias.

[0052] [Table 2-1]

[0053] [Table 2-2]

[0054] The enclosure may be made of glass and may include two or more substrates having at least one glass through via. For example, not only the base substrate but also the cover substrate can be configured as glass substrates having feedthroughs protected by a conductive coating with a corrosion-resistant layer.

[0055] A further aspect of the present invention can be seen in providing a method for manufacturing a hermetic enclosure as described herein. The method includes the steps of preparing a glass substrate having at least one electrical feedthrough configured as a glass through-via, and subsequently coating the surface of the glass substrate with a conductive coating. After coating, an optional step is made available for selectively removing the conductive coating in areas between two or more glass through-vias in order to form contact pads or to configure conductive traces.

[0056] To selectively remove such coatings, a photolithography lift-off process can be performed. This process may include steps of applying a photoresist to a substrate, baking the photoresist, exposing the photoresist through a mask, developing the photoresist, removing the photoresist in areas where conductivity is to be applied, coating the substrate with a conductive coating, and lifting off the photoresist, removing the photoresist and any coatings placed on the resist.

[0057] To avoid corrosion of the conductive rods during the lift-off process, in which the top surface of the substrate is processed first and then the bottom surface is repeatedly processed, the multilayer structure used as a conductive coating fabricated on the top surface of the substrate preferably includes a tungsten sacrificial layer as the outermost layer. This prevents corrosion during the lift-off process because the contact layer cannot form galvanic pairs with the conductive rod material. For example, a gold layer used as a contact layer should be covered by such a sacrificial layer to avoid the formation of galvanic pairs with the tungsten used as the conductive rod material.

[0058] The material of the sacrificial layer can be, for example, the same material as the conductive rod. Therefore, in the case of a tungsten rod used as a conductive rod, tungsten can be selected as the material for the sacrificial layer.

[0059] Alternatively, an etching process can be performed. This process includes steps of applying a conductive coating to a substrate, applying a photoresist to a substrate, baking the photoresist, exposing the photoresist through a mask, developing the photoresist, removing the photoresist in areas where the conductive coating should be selectively removed, etching the conductive coating in the exposed areas, and removing any remaining photoresist on the conductive coating.

[0060] When selectively removing a conductive coating using an etching process, the portion of the conductive coating covered by the photoresist can be partially etched from its exposed side. In particular, the adhesive layer is susceptible to the etching process and may be partially and unintentionally removed because the etching solution can come into direct contact with the side edges of the coating. To protect the adhesive layer in particular during such etching processes, it is preferable to arrange a recess surrounding the conductive rod and make the diameter of the contact pad surrounding the conductive rod the same as or larger than the diameter of the recess. In such a configuration, the side walls of the recess act as a protective layer for the side edges of the coating within the recess, especially the adhesive layer.

[0061] A glass substrate is hermetically bonded to another substrate, preferably by laser bonding, where at least one bonding line is formed by melting and mixing the material of the glass substrate and the material of the other substrate. For laser bonding, at least one laser welding line is formed, preferably using an ultrashort pulse laser. Typical pulse widths are in the range of 100 fs to 100 ps. Methods for performing such laser bonding using one or more laser welding lines are known, for example, from European Patent No. 3012059.

[0062] The coating process and the airtight bonding process can be performed in any order.

[0063] The hermetic enclosures described herein are particularly suitable for use as casings for medical implants. Accordingly, a medical implant comprising one of the hermetic enclosures described herein is provided.

[0064] It is understood that the features described above and below can be used not only in each of the illustrated combinations but also in other combinations or individually, without departing from the scope of the present invention.

[0065] Preferred embodiments of the present invention are shown in the figures and described in more detail below. The same reference numerals refer to the same or similar components or elements.

[0066] The diagram provides a general overview of the following: [Brief explanation of the drawing]

[0067] [Figure 1] This is a schematic cross-sectional view showing a hermetic enclosure with coated glass through-vias, viewed from the side. [Figure 2] This is a side cross-sectional view showing a magnified view of the glass through-via. [Figure 3] This figure shows an enclosure with a connector receptacle. [Figure 4] This figure shows an enclosure with a clamping mechanism. [Figure 5] This diagram shows an enclosure with a contact pad on the opposite side of the through-contact. [Figure 6] This is a magnified side cross-sectional view showing a second example of a coated glass through-via. [Figure 7a] This figure shows an example of a multilayer coating configured to form a contact pad. [Figure 7b] This figure shows a second example of a multilayer coating configured to form a contact pad.

[0068] Figure 1 shows a schematic side view of a hermetic enclosure 10 having glass through vias 30. The enclosure 10 is formed by a glass substrate 12 including the glass through vias 30 and another substrate 14.

[0069] In the example shown in Figure 1, the base glass substrate 12 forms the bottom of the enclosure 10. A spacer substrate 16, as a first substrate 14, forms the side walls of the enclosure 10, and a cover substrate 18, as a second substrate 14, forms the top wall of the enclosure 10. The enclosure 10 defines a cavity or functional area 20.

[0070] To ensure that the functional area 20 is hermetically sealed, a laser bonding process is used to hermetically bond the glass substrate 12 to the spacer substrate 16, and the spacer substrate 16 is hermetically bonded to the cover substrate 18. In the laser bonding process described above, the materials at the interface of each of the two substrates 12, 16, and 18 are melted and mixed to form a bonding line 26. The bonding line 26 preferably completely surrounds the functional area 20.

[0071] In the example shown in Figure 1, the electrical device 22 is located within the functional area 20 and is therefore surrounded by the enclosure 10. To establish an electrical connection to the outside of the enclosure 10, the electrical device 22 is positioned above the glass through via 30 and is electrically connected to the glass through via 30 using a solder joint formed by solder droplets 24. Of course, other means of connecting the electrical device 22 to the glass through via 30 are also possible. For example, the electrical device 22 can be positioned adjacent to the glass through via 30 on the glass substrate 12, and bonding wires can be used to connect the electrical device 22 to the glass through via 30.

[0072] For corrosion protection, a conductive coating 40, which constitutes a contact pad 34, is positioned on the outward-facing side of the glass through via 30. The detailed structure of the glass through via 30 and the coating 40 will be further explained with reference to Figure 2.

[0073] Figure 2 shows an enlarged side cross-sectional view of the glass through via 30 of the hermetic enclosure 10 shown in Figure 1. The glass through via 30 includes a metal rod as a conductive rod, with one front surface of the conductive rod 32 positioned to form a coplanar plane with the inward-facing surface of the glass substrate 12. Another front surface of the conductive rod 32 forms a coplanar plane with the outward-facing surface of the glass substrate 12. This allows the conductive rod 32 to form a conductive connection from the inside to the outside of the enclosure 10.

[0074] To protect the glass through-via 30 from corrosion, and especially to protect the conductive rod 32 from corrosion, the conductive coating 40 is placed on the outward-facing front surface of the conductive rod 32 and on a portion of the outward-facing side surface of the glass substrate 12.

[0075] In the illustrated embodiment, the conductive coating 40 is configured as a layer structure having an adhesive layer 42, a diffusion barrier layer 44, and a corrosion-resistant contact layer 46 in that order. The coating 40 is located at the diameter d of the conductive rod 32 of the glass through via 30. v Larger diameter d p It is configured to form a contact pad 34 having the following characteristics. In this example, the material of the corrosion-resistant contact layer 46 is a material that has good wettability to solder material such as gold (Au).

[0076] In the example layer structure shown in Figure 2, the outermost layer is a corrosion-resistant contact layer 46. The material of the corrosion-resistant contact layer 46 is selected to withstand a given corrosive environment, such as a NaCl solution.

[0077] In alternative embodiments where soldering is not required, the diffusion barrier layer can be selected from a corrosion-resistant conductive material and thus can function as the outermost layer.

[0078] The diffusion barrier layer is selected from a material such as platinum (Pt) to prevent the diffusion of substances from the external environment into and out of the material of the conductive rod 32. In particular, the diffusion barrier layer is selected to prevent the diffusion of oxygen into the material of the conductive rod 32.

[0079] In this embodiment, the conductive coating 40 is located on both the outward-facing and inward-facing sides of the glass substrate 12. The conductive coating 40 on the inward-facing side, referring to Figure 1, functions as a contact pad 34 for solder droplets 24 that electrically connect the electrical device 22 to the glass through via 30.

[0080] In another embodiment, a raised or recessed portion of the glass substrate 12 surrounding the conductive rod 32 can be formed by raising or lowering a portion of the surface of the glass substrate 12 that surrounds the conductive rod 32 compared to the rest of the glass substrate 12. These raised or lowered portions preferably form coplanar with the end face of the conductive rod 32. Preferably, the conductive coating 40 forming the contact pad 34 covers the entirety of the raised or lowered portion. The raised or recessed portion may also be used to control the flow of solder material therein, in which case the solder material is preferably confined to the raised or recessed portion.

[0081] Since the enclosure 10 protects the sealed functional area 20 from external corrosion, corrosion resistance of the conductive coating 40 is not required on the inward-facing surface. However, by having the same conductive coating 40 on both surfaces, it becomes possible to use the same coating process, and a symmetrical glass substrate 12 is obtained such that one of the two sides faces the spacer substrate 16.

[0082] Figure 3 shows a cross-sectional view of the enclosure 10 formed by a glass substrate 12, a spacer substrate 16, and a cover substrate 18. The three substrates 12, 16, and 18 are bonded to each other via bonding lines 26. The enclosure 10 hermetically encloses a functional area 20 that houses an electrical device 22. The three substrates 12, 16, and 18 further define a connector receptacle area 50 that allows for the insertion of a suitable connector.

[0083] The connector receptacle region 50 described above is electrically in contact with the electrical device 22 by glass through vias 30 and conductive traces 36. The traces 36 are defined by structuring conductive coatings 40 that are placed on the outward-facing surfaces of the glass substrate 12 and the cover substrate 18, respectively.

[0084] Since it is not intended to form solder connections to the conductive trace 36, the conductive coating 40, which is placed on the outward-facing surfaces of the glass substrate 12 and the cover substrate 16, can be configured as a two-layer structure including an adhesive layer (42) and a barrier layer (44) as corrosion-resistant layers.

[0085] Within the connector receptacle region 50, the upper contact 54 and the lower contact 56 are defined by the structured portion of the conductive coating 40, which is positioned on the inward-facing surfaces of the glass substrate 12 and the cover substrate 18. Furthermore, connector notches 52 are formed in the glass substrate 12 and the cover substrate 18 for mechanical fastening of the connector. The connector notches 52 are configured to receive the latch elements of the connector.

[0086] Figure 4 shows another enclosure 10, similar to the enclosure described in relation to Figure 3. In contrast to the embodiment in Figure 3, the substrates 12, 16, and 18 are configured to form a clamp 60 designed to receive and hold the nerve 62.

[0087] Within the clamp 60, the conductive coating 40 is configured to form contact pads 40 for electrically contacting the clamped nerve 62. This allows, for example, the nerve 62 to be electrically contacted with an electrical device 22, and the nerve 62 to be stimulated by electrical pulses from the electrical device 22.

[0088] Figure 5 shows another enclosure 10, in which electrical contacts 34 are provided on the upper surface of the glass substrate 12 on both sides of a sealed functional area 20. The two electrical contact pads 34 are obtained by structuring a conductive coating 40. Each electrical contact pad 34 is connected to the rear side of the glass substrate 12 by a glass through via 30, and the electrical device 22 is similarly connected to the glass through via 30. Conductive traces 36 formed on the outward-facing surface of the glass substrate 12 by the structuring portion of the conductive coating 40 establish an electrical connection between the two glass through vias 30. The conductive coating 40 is configured such that, referring to Figure 2, the exposed surface of the conductive rod 32 of the glass through via 30 is covered by the coating 40.

[0089] In the arrangement shown in Figure 5, the spacer substrate 16 and cover substrate 18 are maintained without electrical contacts and glass through vias 30, while access to the contact pad 34 from the top surface of the enclosure 10 can still be provided through the free space 70 located above the contact pad 34. This ensures that the optical properties of the spacer substrate 16 and cover substrate 18 are not impaired.

[0090] Figure 6 shows an enlarged side section view of the glass through via 30 of the hermetic enclosure 10, similar to the embodiment shown in Figure 2. In contrast to the embodiment in Figure 2, the recess 28 of the glass substrate 12 is positioned to surround the conductive rod 32 on both sides of the substrate 12. The conductive rod 32 is positioned such that its front surface forms coplanar with the bottom surface of the recess 28. As also shown in Figure 2, the front surface of the conductive rod 32 is coated with a conductive coating 40, which is configured to form a contact pad 34. In this example, the diameter of the recess 28 is such that the conductive coating 40 forms coplanar with the surface of the substrate 12 outside the recess 28, and the diameter d of the contact pad 34 is such that the conductive coating 40 forms coplanar with the surface of the substrate 12 outside the recess 28. p Accordingly, the depth r of the recess 28 is selected to correspond to the total thickness of the conductive coating 40.

[0091] Figures 7a and 7b schematically show multilayer structures of conductive coatings 40 configured to form contact pads 34 on both front surfaces of the conductive rods 32. Figure 7a shows an exemplary multilayer structure when the conductive coatings 40 are structured using a lift-off process, and Figure 7b shows an exemplary multilayer structure when an etching process is used.

[0092] The multilayer structure in the illustrated examples of Figures 7a and 7b includes a 50 nm Ti adhesive layer, a 50 nm Pt diffusion barrier layer, and a 200 nm gold contact layer.

[0093] Figure 7a shows a two-sided lift-off process in which the conductive coating 40 is first manufactured and structured on the upper surface of the substrate 12, and then the process is repeated on the lower surface. During the lift-off process, in order to avoid corrosion of the tungsten rod used as the conductive rod 32, the multilayer structure used as the conductive coating 40 formed on the upper surface of the substrate 12 includes a tungsten sacrificial layer. This prevents corrosion during the lift-off process because the gold layer is covered and cannot form a galvanic pair with the tungsten of the conductive rod 32.

[0094] Figure 7b shows a two-sided etching process in which a conductive coating 40 is coated on both sides of the substrate 12 and structured by etching away unwanted portions of the conductive coating 40. During the etching process, a photoresist covers the portions of the conductive coating 40 that should remain. However, as the etching process is performed, the etching solution may come into contact with the side edges of the conductive coating 40. In the example shown in Figure 7b, the titanium adhesive layer is partially etched, thereby weakening the adhesion of the conductive coating 40. By arranging recesses 28 surrounding the conductive rod 32, as shown in Figure 6, protection of the edge surface during the etching process is provided, and thus the adhesion of the conductive coating 40 is improved.

[0095] Although the present invention has been described with reference to preferred examples of embodiments, the present invention is not limited thereto and can be modified in various ways. [Explanation of symbols]

[0096] 10 Enclosures 12 Glass substrate 14 Another circuit board 16 Spacer board 18 Cover board 20 functional areas 22 Electrical Devices 24 solder drops 26 Bonding lines 28 recesses 30 Glass-Through Beer 32 Conductive Rods 34 Contact pads 36 traces 40 Conductive coating 42 Adhesive layer 44 Diffusion barrier layer 46 Contact Layer 50 Connector receptacle area 52 Connector Notches 54 Upper contact 56 Lower contact 60 clamps 62 nerves 70 free space d v Glass through via diameter d p Contact pad diameter

Claims

1. A hermetic enclosure (10) comprising at least one glass substrate (12), The at least one glass substrate (12) has at least one electrical feedthrough configured as a glass through via (30), The glass through via (30) includes a conductive rod (32) that electrically connects the inside of the hermetic enclosure (10) to the outside through the glass substrate (12). In the hermetic enclosure (10), The portion of the conductive rod (32) facing outwards from the hermetic enclosure (10) is completely covered by a conductive coating (40). The conductive coating (40) has a multilayer structure that includes at least an adhesive layer (42) that is in direct contact with the conductive rod (32) and the corrosion-resistant layer. A hermetic enclosure (10) characterized by the above.

2. The corrosion-resistant layer is a material containing or composed of at least one element from the platinum group, such as platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), and osmium (Os), or a platinum oxide, particularly iridium oxide (IrO2). ２ ) or ruthenium oxide (RuO ２ The hermetic enclosure (10) according to claim 1, which is made of a material containing or derived from ).

3. The electrical feedthrough has a recess or protrusion on the surface of the glass substrate (12) facing outwards and / or on the surface of the glass substrate (12) facing inwards. The recess or the raised portion surrounds the conductive rod (32), The recess or the raised portion preferably forms the same plane as the front surface of the conductive rod (32). The depth of the recess or the height of the raised portion is preferably at least 250 nm and / or less than 3 μm. Hermetic enclosure (10) according to claim 1 or 2.

4. The hermetic enclosure (10) according to claim 3, wherein the depth / height and / or shape of the recess or the raised portion is preferably configured so that the solder does not come into contact with the glass substrate (12) so that the recess or the raised portion functions as a solder flow boundary.

5. The corrosion-resistant layer is configured as a diffusion barrier layer (44) and / or a corrosion-resistant contact layer (46). Preferably, the multilayer structure of the conductive coating (40) includes, in this order, the adhesive layer (42) in direct contact with the conductive rod (32), at least one diffusion barrier layer (44), and a corrosion-resistant contact layer (46). Hermetic enclosure (10) according to any one of claims 1 to 4.

6. The hermetic enclosure (10) according to claim 5, wherein the adhesive layer (42) is formed from or comprises Ti, Ta, Cr, Ni, NiCr, TiAl, and combinations thereof.

7. The hermetic enclosure (10) according to claim 5 or 6, wherein the diffusion barrier layer (44) is formed from or comprises platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), titanium nitride (TiN), and combinations thereof.

8. The corrosion-resistant contact layer (46) is made of gold (Au), iridium (Ir), iridium oxide (IrO2). ２ ), ruthenium (Ru), ruthenium oxide (RuO ２ A hermetic enclosure (10) according to any one of claims 1 to 7, which is formed from or includes the following:

9. The hermetic enclosure (10) according to any one of claims 1 to 8, wherein the conductive rod (32) is formed from or includes tungsten, titanium, iron / nickel alloy, gold, silver, copper, silicon, and combinations thereof.

10. The conductive coating (40) is also disposed on at least a portion of the surface of the glass substrate (12), and the conductive coating (40) is electrically connected to the contact pad (34) via diameter d of the conductive rod (32). ｖ Larger pad diameter d ｐ A contact pad (34) having and / or Preferably, the conductive coating (40) forms at least one conductive trace (36) that electrically connects two or more glass through vias (30). Hermetic enclosure (10) according to any one of claims 1 to 9.

11. The hermetic enclosure (10) according to any one of claims 1 to 10, wherein at least one of the layers of the conductive coating (40) is obtained by electroplating, electroless plating, physical vapor deposition (PVD), electron beam deposition, chemical vapor deposition (CVD) and / or atomic layer deposition (ALD).

12. The hermetic enclosure (10) according to any one of claims 1 to 11, wherein the corrosion-resistant contact layer (46) is a gold layer obtained by electroless plating.

13. The glass substrate (12) is bonded to another substrate (14) by laser bonding and / or laser welding. At least one bonding line (26) is formed by melting and mixing the materials of the glass substrate (12) and the other substrate (14), The distance from the laser bonding line (26) to the glass through via (30) is at least 50 μm. Hermetic enclosure (10) according to any one of claims 1 to 12.

14. The hermetic enclosure (10) according to any one of claims 1 to 13, wherein the material of the glass substrate (12) and the material of the corrosion-resistant layer of the conductive coating (40) are selected so as to be resistant to exposure to a 700 g / l NaCl aqueous solution at a temperature of 37°C for 7 days.

15. A method for manufacturing a hermetic enclosure (10) according to any one of claims 1 to 14, - A step of preparing a glass substrate (12) having at least one electrical feedthrough configured as a glass through via (30), - A step of coating the surface of the glass substrate (12) with a conductive coating (40), and then, as an optional means, selectively removing the conductive coating (40) in the region between two or more glass through vias (30) to form a contact pad (40) and / or a conductive trace (36), - A step of hermetically bonding the glass substrate (12) to another substrate (14) by laser bonding, wherein at least one bonding line (26) is formed by melting and mixing the materials of the glass substrate (12) and the other substrate (14). Includes, The coating step and the airtight bonding step can be performed in any order. method.

16. A medical implant comprising a hermetic enclosure (10) according to any one of claims 1 to 14, or obtained by the method according to claim 15.

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