A ceramic-based electrical interconnection feedthrough substrate and method of making the same

Abstract

The application provides a ceramic-based electric interconnection feedthrough substrate and a preparation method thereof. The substrate comprises a ceramic substrate, an upper insulating layer, a lower insulating layer, an upper pad and a lower pad. The ceramic substrate is internally provided with an electric interconnection microcolumn array formed by electrically conductive microcolumns. The upper insulating layer is located above the ceramic substrate. The lower insulating layer is located below the ceramic substrate. The upper insulating layer and the lower insulating layer are internally provided with a via array formed by a plurality of insulating layer vias. The positions of the insulating layer vias correspond to the positions of the electrically conductive microcolumns. The diameter of the insulating layer vias is smaller than the diameter of the electrically conductive microcolumns. The upper pad is located above the upper insulating layer and fills the insulating layer vias on the upper insulating layer and the gap between the upper insulating layer and the electrically conductive microcolumns. The lower pad is located below the lower insulating layer and fills the insulating layer vias on the lower insulating layer and the gap between the lower insulating layer and the electrically conductive microcolumns. The application realizes a biocompatible air-tight electric interconnection feedthrough which can be integrated with a flexible implantable electrode.

Description

Technical Field

[0001] This invention relates to the field of flexible electrode technology, and more specifically, to a ceramic-based electrical interconnect feedthrough substrate and its fabrication method. Background Technology

[0002] All activities within a living organism are accompanied by the generation of physiological electrical signals. Collecting these signals not only helps us understand the mechanisms of biological tissues and cells, advancing our exploration of the mysteries of life, but also allows for disease intervention and treatment by monitoring the generation of abnormal electrical signals. Bioelectronic devices provide methods for collecting these physiological electrical signals.

[0003] Electronic devices implanted in animals and humans typically require a sealed enclosure. The enclosure protects the internal silicon-based or metal electronic components from corrosion and degradation by bodily fluids, and also prevents non-biocompatible materials from seeping into body tissues. To transmit or receive voltage, current, or other signals outside the enclosure, components must usually be connected to wires whose conductive paths pass through the enclosure. The area where the conductive path passes through the enclosure is often referred to as a “sealed feedthrough” or “sealed substrate.”

[0004] Sealed feedthroughs are typically fabricated by drilling a flat plate using a computer numerical control (CNC) machine tool, water drill, or laser, and then filling it with a conductive material. These drilling methods introduce stress into the material, potentially leading to microcracks. For example, machine drilling can tear off metal fragments, while laser drilling can cause some material to evaporate due to intense heating. Furthermore, the more holes to create, the longer the drilling time and the greater the chance of material leakage. Additionally, flexible arrays connected to conventional feedthroughs sometimes use solder balls, which have a relatively large diameter, making it difficult to achieve high-density sealed feedthroughs with a spacing of less than 400 μm using biocompatible materials.

[0005] Through-Silicon Via (TSV) technology is recognized by the industry as the fourth-generation packaging technology after flip chips, offering advantages such as high density and short interconnect lengths. However, TSV uses Bosch's process to manufacture via arrays, which involves a long process flow, high process costs, and the etched vias exhibit a scalloped spiral morphology, severely impacting the long-term performance of feedthrough.

[0006] Therefore, there is an urgent need for an electrical interconnect feeder that combines high density feedthrough number, high sealing performance, low process complexity, and uniform through-hole morphology. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the purpose of this invention is to provide a ceramic-based electrical interconnect feedthrough substrate and its fabrication method.

[0008] According to one aspect of the present invention, a ceramic-based electrical interconnect feedthrough substrate is provided, the electrical interconnect feedthrough substrate comprising:

[0009] A ceramic substrate, wherein the interior of the ceramic substrate is provided with an array of electrically interconnected micropillars formed by conductive micropillars;

[0010] An upper insulating layer is located above the ceramic substrate;

[0011] A lower insulating layer is located below the ceramic substrate;

[0012] The upper insulating layer and the lower insulating layer each have an array of through holes formed by multiple insulating layer through holes inside. The positions of the insulating layer through holes correspond to the positions of the conductive micropillars, and the diameter of the insulating layer through holes is smaller than the diameter of the conductive micropillars.

[0013] The upper pad is located above the upper insulating layer and fills the insulating layer vias on the upper insulating layer and the gap between the upper insulating layer and the conductive micropillars;

[0014] The lower pad is located below the lower insulating layer and fills the insulating layer vias on the lower insulating layer and the gap between the lower insulating layer and the conductive micropillar.

[0015] Furthermore, the diameter of the through-hole in the insulating layer is 1-20 μm smaller than the diameter of the conductive micropillar.

[0016] Furthermore, the upper insulating layer and the lower insulating layer are formed of biocompatible insulating materials, including any one of silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides, and polymers.

[0017] Furthermore, the upper pad and the lower pad are formed by biocompatible metal deposition, and the material includes any one of conductive polymers, titanium, platinum, chromium, gold, and alloys formed between titanium, platinum, chromium, and gold.

[0018] According to another aspect of the present invention, a method for fabricating the above-described ceramic-based electrical interconnect feedthrough substrate is provided, the method comprising:

[0019] Ceramic powder is poured into a mold and sintered to form a shape. The mold contains a micro-pillar array formed by multiple micro-pillars.

[0020] Demolding yields a ceramic substrate with a micropore array;

[0021] The micropore array is filled with conductive material to form an array of electrically interconnected micropillars within the ceramic substrate;

[0022] Planarize the front and back surfaces of the ceramic substrate until the array of electrically interconnected micropillars is exposed;

[0023] An insulating layer is formed on top of the ceramic substrate;

[0024] Metal is deposited on the upper insulating layer to form an upper pad, which fills the insulating layer vias of the upper insulating layer and the gap between the electrically interconnected micropillar array and the upper insulating layer.

[0025] Flip the ceramic substrate, deposit the lower insulating layer using the same method as forming the upper insulating layer, and form the lower pads on the lower insulating layer using the same method as forming the pads on the upper insulating layer.

[0026] Furthermore, before pouring ceramic powder into the mold and sintering it, the process includes: using laser ablation and polishing to make the sidewalls of the micropillars uniformly smooth and close to an ideal cylinder.

[0027] Further, ceramic powder is poured into the mold and sintered to form the shape, wherein the ceramic sintering method includes any one of hot pressing sintering, hot isostatic pressing sintering, microwave sintering and plasma activation sintering.

[0028] Furthermore, conductive material is filled into the micropore array to form an array of electrically interconnected micropillars within the ceramic substrate, wherein the electrically interconnected micropillars are formed by electroplating or sintering metal powder.

[0029] Furthermore, the mold is made of silicon-doped mold and high-melting-point metal mold to eliminate the demolding process.

[0030] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0031] 1. The ceramic-based electrical interconnect feedthrough substrate of the present invention realizes a biocompatible hermetically sealed electrical interconnect feedthrough that can integrate flexible implantable electrodes, and can be applied to the hermetically sealed electrical interconnect of thin film circuits in solid-state devices and biological applications.

[0032] 2. The above-mentioned preparation method of this invention proposes a design scheme for a hermetically sealed electrical interconnect feedthrough on a ceramic substrate. The feedthrough substrate is formed by sintering ceramic powder to encapsulate a mold with a micropillar array, thus forming a ceramic substrate with a micropore array. Compared with the conventional method of forming holes with drill bits, the hole formation process of the ceramic substrate has lower internal stress and better hermetically sealed properties. All feedthrough holes on this sealed substrate can be formed in a single sintering and demolding process, avoiding the inefficient hole-forming method of conventional drilling, which can only process a single hole at a time, and can greatly reduce processing costs and process complexity.

[0033] 3. In the above preparation method of the present invention, according to actual needs, the processing technology of MEMS can be used to achieve highly controllable, highly repeatable and mass-producible processing. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the structure of a ceramic-based electrical interconnect feedthrough substrate according to an embodiment of the present invention;

[0036] Figure 2 This is a cross-sectional schematic diagram of a ceramic-based electrical interconnect feedthrough substrate according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic flowchart of a method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of the structure corresponding to each step of the fabrication method of a ceramic-based electrical interconnect feedthrough substrate according to an embodiment of the present invention.

[0039] In the figure: 1 is the ceramic substrate, 2 is the conductive micropillar, 3 is the insulating layer via, 4 is the upper insulating layer, 5 is the upper pad, 6 is the lower insulating layer, and 7 is the lower pad. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0041] This invention provides a ceramic-based electrical interconnect feedthrough substrate, with reference to... Figure 1-2 The electrical interconnect feedthrough substrate includes: a ceramic substrate 1, an upper insulating layer 4, a lower insulating layer 6, an upper pad 5, and a lower pad 7. The interior of the ceramic substrate 1 is provided with an array of electrical interconnect micropillars formed by conductive micropillars 2. The upper insulating layer 4 is located above the ceramic substrate 1. The lower insulating layer 6 is located below the ceramic substrate 1. Both the upper insulating layer 4 and the lower insulating layer 6 are provided with an array of through holes formed by multiple insulating layer through holes 3. The positions of the insulating layer through holes 3 correspond to the positions of the conductive micropillars 2, and the diameter of the insulating layer through holes 3 is smaller than the diameter of the conductive micropillars 2. The upper pad 5 is located above the upper insulating layer 4 and fills the insulating layer through holes 3 on the upper insulating layer 4 and the gap between the upper insulating layer 4 and the conductive micropillars 2. The lower pad 7 is located below the lower insulating layer 6 and fills the insulating layer through holes 3 on the lower insulating layer 6 and the gap between the lower insulating layer 6 and the conductive micropillars 2.

[0042] In some embodiments, the ceramic substrate 1 is formed by sintering ceramic powder into a pre-processed mold. The mold can be made of high-melting-point metal, graphite, silicon, or ceramic material, and is shaped into a concave basin-like structure with a micropillar array by laser processing, etching, or precision machine tools, either individually or in combination. The sidewalls of the micropillars can be further polished to a near-ideal cylindrical morphology to maximize the flatness of the micropillar sidewalls. Ceramic sintering methods include hot pressing, hot isostatic pressing, microwave sintering, and plasma-activated sintering. A micropore array consisting of multiple micropores is formed inside the ceramic substrate 1 by demolding after sintering. The demolding method of sintering allows for mass production, has low process costs, produces good pore morphology, and results in uniform stress distribution inside the formed micropores.

[0043] In some embodiments, a conductive micropillar array is formed by filling the micropore array with a conductive material. The conductive micropillars 2 can be formed at the micropore locations by electroplating, and the material can be any one of copper, copper-carbon nanotubes, copper-tungsten, silver, graphene, etc.; or they can be formed by sintering and hot pressing, and the material includes any one of molybdenum, tungsten, tantalum, copper, gold, etc. Preferably, the conductive micropillars 2 are formed from an inert material with good biocompatibility.

[0044] Depositing an insulating layer on the ceramic substrate 1 can solve the device failure problem caused by potential gaps between the ceramic substrate 1 and the conductive micropillars 2. The upper insulating layer 4 and the lower insulating layer 6 are formed using biocompatible insulating materials, including any one of: silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides such as alumina, zirconium oxide, and polymers such as polyimide, pure epoxy resin, etc. In some embodiments, the diameter of the through-holes 3 in the insulating layer is 1-20 μm smaller than the diameter of the conductive micropillars 2. The small holes in the insulating layer at the conductive micropillars 2 allow the insulating layer to both cover the gaps between the ceramic substrate 1 and the conductive micropillars 2 and maintain the electrical connection between the conductive micropillars 2 and the flexible electrode or redistribution layer, facilitating hermetic packaging.

[0045] Depositing pads at the insulating layer vias 3 facilitates subsequent encapsulation processes such as soldering. The upper pad 5 and lower pad 7 must fill the insulating layer vias 3 and the gap between the insulating layer and the conductive micropillars 2, ensuring good contact with the conductive micropillars 2. In some embodiments, the upper pad 5 and lower pad 7 are formed by biocompatible metal deposition, with materials including any one of conductive polymers, titanium, platinum, chromium, gold, and alloys formed from titanium, platinum, chromium, and gold.

[0046] In the above embodiments, the ceramic substrate 1 is formed from an inert material with good biocompatibility. Metal pads (including upper pad 5 and lower pad 7) deposited from biocompatible titanium, chromium, and gold materials cover the conductive micropillars 2. The biocompatible insulating layer on the surface of the ceramic substrate 1 further isolates its biotoxicity, thereby ensuring the biological tissue safety and long-term functional stability of the implantable feedthrough device. The ceramic substrate itself has high sealing performance; the through-holes in the insulating layer cover the gap between the conductive micropillars and the ceramic substrate, strengthening the protection against cracks that may exist at the contact surfaces of different materials. The above-mentioned electrical interconnect feedthrough substrate combines the advantages of high-density feedthrough count, high sealing performance, low process complexity, and uniform through-hole morphology, enabling hermetically sealed packaging of electrical interconnects between solid-state devices and thin-film circuits for biological applications.

[0047] Another embodiment of the present invention provides a method for fabricating the above-described ceramic-based electrical interconnect feedthrough substrate, referring to... Figure 3 The method includes:

[0048] Step 1: Pour ceramic powder into the mold and sinter it into shape. The mold has a micro-pillar array formed by multiple micro-pillars inside.

[0049] Step 2: Demolding to obtain a ceramic substrate with a micropore array; the ceramic substrate is made of non-conductive ceramic, so that the ceramic substrate itself has insulation properties;

[0050] Step 3: Fill the micropore array with conductive material to form an array of electrically interconnected micropillars within the ceramic substrate;

[0051] Step 4: Planarize the front and back surfaces of the ceramic substrate until the electrical interconnect micropillar array is exposed;

[0052] Step 5: An upper insulating layer is formed on the top of the ceramic substrate, and the upper insulating layer has through holes corresponding to the electrical interconnect micropillar array;

[0053] Step 6: Deposit metal on the upper insulating layer to form an upper pad, so that the upper pad fills the insulating layer vias of the upper insulating layer and the gap between the electrically interconnected micropillar array and the upper insulating layer. While filling the gaps, the electrical connection between the upper pad and the conductive micropillar is completed.

[0054] Step 7: Flip the ceramic substrate, deposit the lower insulating layer using the same method as forming the upper insulating layer, and form the lower pads on the lower insulating layer using the same method as forming the pads on the upper insulating layer. After fabricating the ceramic-based electrical interconnect feedthrough substrate, proceed as follows... Figure 2 As shown in the diagram, the lower pad is located below the lower insulating layer.

[0055] In the above preparation method, the mold is shaped like a concave basin, and the mold material includes any one of high-melting-point metals, graphite, silicon, and ceramic materials. The mold can be formed by etching, laser processing, precision machine tool cutting, or other micro-nano processing methods. To facilitate demolding, a layer of lubricating release agent can be sprayed into the mold beforehand. The lubricating release agent includes, but is not limited to, ultra-heat resistant silicone oil, boron nitride release spray, etc.

[0056] In some implementations, before pouring ceramic powder into the mold and sintering, the process includes: using laser ablation and polishing to make the sidewalls of the micropillars uniformly smooth and closely approximate an ideal cylinder. Compared to the scalloped thread-like through-holes formed by the Bosch process in TSV technology, the ideal cylindrical micropillar array in the mold has fewer internal stress concentration points, resulting in a more stable feedthrough connection over a longer period.

[0057] In some embodiments, ceramic powder is poured into a mold and sintered to form the desired shape. The ceramic sintering method includes any one of hot pressing, hot isostatic pressing, microwave sintering, and plasma-activated sintering. For example, Al2O3 powder, CuO-TiO2-Nb2O5 composite additive powder, and deionized water are ground and stirred to form a ceramic slurry, which is then dried in an oven. After drying, the slurry is ground into powder. The powder is then pressed into a mold, and the mold is subsequently sintered in a high-temperature furnace. After natural cooling, the powder is removed. Specifically, the process of preparing an electrical interconnect feedthrough substrate using this method includes: sintering ceramic powder in a recessed basin-shaped mold with a micropillar array; separating the ceramic from the mold to expose the micropore array in the ceramic; filling the micropillar pores in the ceramic with electroplated metal or other methods to form electrical interconnect micropillars; subsequently grinding or polishing the ceramic surface to create a flat surface forming a through-current channel; and finally depositing an insulating layer and metal pads to bring out the conductive micropillar array for interconnect packaging.

[0058] In the above embodiments, the feedthrough substrate is formed by sintering ceramic powder to encapsulate a mold with a micropillar array, thus forming a ceramic substrate with a micropore array. Compared to substrates that use drill bits to form holes, the hole formation process of the ceramic substrate has lower internal stress and better airtightness. All feedthrough holes on this sealed substrate can be formed in a single sintering and demolding process, avoiding the inefficient hole-forming method of ordinary drilling, which can only process a single hole at a time, and greatly reducing processing costs and process complexity.

[0059] The aforementioned ceramic substrate achieves electrical interconnection with a chip or sensor through a micro-pore array filled with conductive paste. In some embodiments, conductive material is filled into the micro-pore array to form an array of electrically interconnected micropillars within the ceramic substrate. The electrically interconnected micropillars are formed using electroplating, and the metal pillars used as the electrically interconnected micropillars include, but are not limited to, copper, copper-carbon nanotubes, copper-tungsten, silver, and graphene. The electroplating process includes the following steps:

[0060] (1) Prepare the electroplating solution and additives in sequence, and mix the electroplating solution and additives evenly; specifically, the additives include accelerators, inhibitors and leveling agents, which are used to control the rate of copper deposition in different parts of the through hole to achieve no internal hole filling.

[0061] (2) Pre-wetting and vacuuming of the ceramic substrate;

[0062] (3) Electroplating parameters are set in the copper electroplating system for electroplating; specifically, the pre-sputtered seed layer is the anode and the electroplating solution is the cathode. If electroplating is used to fill through holes, an electroplating solution should be prepared, for example, a copper-electroplating solution prepared with 80 g / L copper methanesulfonate, 20 g / L methanesulfonic acid, 50 ppm chloride ions, and additives. Copper ions undergo a reduction reaction at the seed layer and are adsorbed there, thus gradually filling the hole. After electroplating, metal pillars of copper, copper-carbon nanotubes, copper-tungsten, silver, and graphene are formed.

[0063] (4) After electroplating, rinse with deionized water.

[0064] In some alternative embodiments, conductive material is filled into the micropore array to form an array of electrically interconnected micropillars within the ceramic substrate. The electrically interconnected micropillars are formed by sintering metal powder, wherein the metal powder includes molybdenum, tungsten, tantalum, copper, gold, etc.

[0065] In some implementations, the mold material is made of a conductive material, such as a high-melting-point metal mold or a silicon-doped mold, to omit the demolding process and directly perform planarization treatment, grinding the bottom of the mold flat so that the mold micropillars are embedded in the ceramic substrate and isolated from each other.

[0066] In some implementations, planarization methods include, but are not limited to, chemical / mechanical polishing, grinding, fly cutting, laser ablation, etching, or spin coating of a planarization layer.

[0067] In one specific embodiment, the method for fabricating the ceramic-based electrical interconnect feedthrough substrate includes the following steps:

[0068] 1) Pour ceramic powder into a concave basin-shaped mold with a micropillar array, and pre-spray a layer of lubricating release agent into the mold;

[0069] 2) Sintering ceramic powder under certain temperature, atmosphere and pressure conditions to transform it into dense polycrystalline ceramic material, and the sintered ceramic substrate completely encapsulates the micropillar array in the mold.

[0070] 3) Separate the ceramic substrate from the mold to form a micropore array in the ceramic substrate;

[0071] 4) Fill the micropore array in the ceramic substrate with conductive material to form electrically interconnected micropillars;

[0072] 5) Planarize the top and back surfaces of the ceramic substrate until the array of electrically interconnected micropillars is exposed;

[0073] 6) Deposit a biocompatible insulating layer on the top and sidewalls of the ceramic substrate;

[0074] 7) Conductive pads are deposited on the insulating layer to fill the holes between the electrical interconnect feedthrough and the insulating layer;

[0075] 8) Flip the ceramic substrate and perform the processing steps in 6) and 7) on the back of the ceramic substrate.

[0076] The above-mentioned method for fabricating ceramic-based electrical interconnect feedthrough substrates can be made using MEMS processing technology to achieve highly controllable, highly repeatable, and mass-producible processing, depending on actual needs.

[0077] The above-described method for fabricating ceramic-based electrical interconnect feedthrough substrates, compared to CNC machine tool drilling, allows for micrometer-level linewidth processing via MEMS technology. Compared to TSV (Through-Screen Vias), the scalloped vias formed by deep silicon etching cannot undergo subsequent smoothing. However, the vias in the embodiments of this invention are formed using a molding process, which allows for high-precision processing methods such as femtosecond lasers to improve the smoothness and uniformity of the mold, thereby indirectly improving the morphological uniformity of the ceramic vias. The electrical interconnect feedthrough substrates fabricated using the above method possess advantages such as high feedthrough density, high sealing performance, low process complexity, and uniform via morphology.

[0078] The ceramic-based electrical interconnect feedthrough substrate and its fabrication method of the present invention will be further described below through specific embodiments.

[0079] Example 1

[0080] This embodiment provides a method for fabricating a ceramic-based hermetically tight electrical interconnect feedthrough substrate using a ceramic mold, referring to... Figure 4 The preparation method includes the following steps:

[0081] like Figure 4 As shown in S1, fused mullite, capacitor white corundum, sintered α-Al2O3 micro powder, and SiO2 micro powder are ground and mixed, and a water-soluble resin binder is added. The mixture is then poured into a ceramic mold with a micro-pillar array.

[0082] like Figure 4 As shown in S2, after drying at 110°C for 24 hours under a pressure atmosphere of 120MPa, the mold and ceramic powder are placed in a high-temperature gas furnace and hot-pressed at 1750°C for 6 hours.

[0083] like Figure 4As shown in S3, the sintered ceramic is separated from the mold to obtain a ceramic substrate with a micropore array.

[0084] like Figure 4 As shown in S4, a 10nm chromium barrier layer and a 30nm copper seed layer are sputtered at the micropores, and the micropore array is filled using an electroplating copper process to form a conductive micropillar array. The specific electroplating copper method is as follows:

[0085] 1) Electroplating solution preparation: copper methanesulfonate 80g / L, methanesulfonic acid 20g / L, chloride ion 50ppm;

[0086] 2) Additive formulation: Accelerator DVF-B 5.5ml / L, Inhibitor DVF-C 20ml / L, Leveling agent DVF-D 5ml / L;

[0087] 3) Stir the above-prepared solution using a magnetic stirrer;

[0088] 4) Pre-wetting and vacuuming of silicon wafers;

[0089] 5) Set the electroplating parameters in the copper electroplating system: voltage 10V, current 10mA / cm. 2 ;

[0090] 6) After electroplating, rinse with deionized water.

[0091] like Figure 4 As shown, the ceramic sintering and electroplating processes on the top and back of the ceramic substrate result in unevenness across the entire substrate surface.

[0092] like Figure 4 As shown in S5, the surface of the ceramic substrate is planarized by chemical mechanical polishing to obtain a conductive feedthrough structure that is connected vertically.

[0093] like Figure 4 As shown in S6, a silicon carbide (SiC) layer of approximately 1 μm is deposited using plasma-enhanced chemical vapor deposition. Before depositing the silicon carbide, a mask needs to be pre-coated near the micropillar holes to prevent the SiC from clogging the silicon pillar holes. The diameter of the through-holes inside the SiC insulating layer is slightly smaller than the diameter of the conductive micropillars in the ceramic substrate.

[0094] like Figure 4 As shown in S7, metal pads with 30 nm chromium and 1.2 μm gold are sputtered and deposited at the opening of the SiC insulating layer, i.e., the micropillar hole.

[0095] Figure 4 S8 demonstrates the process of flipping a ceramic substrate and depositing a SiC insulating layer and depositing metal pads on the flipped surface, with the relevant parameters being consistent with those described above.

[0096] Example 2

[0097] The method for fabricating a ceramic-based hermetically tight electrical interconnect feedthrough substrate in this embodiment uses a doped silicon wafer with electrical conductivity as a sintering mold. Since silicon wafers are brittle, the ceramic sintering process must be carried out under normal pressure. The specific steps are as follows:

[0098] S1: Clean the 4-inch 500μm thick silicon wafer. The specific cleaning process is as follows: 1) Soak the wafer in acetone for 5 minutes; 2) Remove the wafer and soak it in anhydrous ethanol for 5 minutes; 3) Remove the wafer and soak it in deionized water for 5 minutes; repeat 1), 2), and 3) 3 times; 4) Dry the wafer with nitrogen gas; 5) Place the wafer on a hot plate at 180℃ for more than 15 minutes.

[0099] S2: Spin-coat a 20μm thick layer of positive photoresist AZ P4620 onto a silicon substrate (1000 rpm for 7s, 1500 rpm for 30s), followed by pre-baking at 100℃ for 500s, and exposure at 1500mJ / cm². 2 After developing for 5 minutes, an etch mask is obtained.

[0100] S3: Etching is performed on the silicon substrate to form etching pillars. The silicon pillars are approximately 300 μm high, and the diameter of the circular holes in the silicon pillars is approximately 50 μm. The etching process uses Bosch technology, with C4F8 as the passivation layer and SF6 as the etching gas.

[0101] S4: A slurry composed of α-Si3N4, β-Si3N4, Si, AlN, and α-Al2O3 ceramic powders mixed with a binder is filled into the aforementioned silicon substrate. Under a nitrogen atmosphere of 0.1 MPa, the substrate is sintered at 1100°C for 2 hours, 1300°C for 1.5 hours, and 1500°C for 6 hours, respectively, and then cooled to room temperature for shaping.

[0102] S5: The substrate surface is planarized by chemical mechanical polishing to obtain a flat ceramic substrate with interconnected conductive silicon pillars.

[0103] S6: A silicon carbide (SiC) layer of approximately 1 μm is deposited on the upper surface and sidewalls of the ceramic using plasma-enhanced chemical vapor deposition. Before depositing the silicon carbide, a mask is pre-coated near the micropillar holes to prevent the SiC from clogging the silicon pillar holes. The diameter of the through-holes inside the SiC insulating layer is slightly smaller than the diameter of the conductive micropillars in the ceramic substrate.

[0104] S7: At the opening of the SiC insulating layer, i.e. the micropillar hole, a metal pad with 30nm chromium and 1.2μm gold is sputtered and deposited.

[0105] S8: The process of flipping the ceramic substrate and depositing a SiC insulating layer and depositing metal pads on the flipped surface, with the relevant parameters being the same as described above.

[0106] Example 3

[0107] The method for fabricating a ceramic-based hermetically tight electrical interconnect feedthrough substrate in this embodiment uses a copper-titanium alloy as the sintering mold. Since the copper-titanium alloy has high hardness and a variable melting point, the sintering temperature should not be significantly higher than the melting point of pure copper at atmospheric pressure (1083°C). The specific steps are as follows:

[0108] S1: Raw materials such as titanium and copper are placed in a vacuum melting furnace in a certain proportion and kept at 10 Pa and 1300℃ for 20 minutes. After melting, the mixture is cast into a concave basin-shaped ingot with a cylindrical array. Subsequently, the ingot undergoes a hot deformation-first solution treatment-cold deformation-second solution treatment-aging process to prepare a copper-titanium alloy with a cylindrical array and concave basin shape. It should be noted that this embodiment does not specifically limit the casting method of the alloy, but adopts a general copper-titanium alloy casting process.

[0109] S2: Polish and grind the surface of the copper-titanium alloy until there are no abnormal protrusions around the alloy and the height of the inner cylindrical array is 300μm.

[0110] S3: Using laser processing technology, a cylindrical array is etched in the copper-titanium alloy to form a micro-pillar array with smooth sidewalls and a circular diameter of less than 100μm. This creates a concave basin-shaped copper-titanium alloy mold with a near-ideal cylindrical micro-pillar array.

[0111] S4: Al2O3 powder, CuO-TiO2-Nb2O5 composite additive powder, and deionized water are ground and stirred to form a ceramic slurry, which is then placed in an 80℃ oven for 12 hours. After drying, the slurry is ground into powder and pressed into a copper-titanium alloy mold. The mold is then placed in a 1100℃ high-temperature furnace for sintering for 5 hours, and removed after natural cooling.

[0112] S5: The surface of the ceramic substrate is planarized by chemical mechanical polishing to obtain a flat ceramic substrate with conductive metal pillars connected from top to bottom.

[0113] S6: A layer of silicon carbide (SiC) approximately 1 μm thick is deposited on the upper surface and sidewalls of the ceramic using plasma-enhanced chemical vapor deposition. Before depositing the silicon carbide, a mask is pre-coated near the micropillar holes to prevent the SiC from clogging the metal pillar holes. The diameter of the through-holes inside the SiC insulating layer is slightly smaller than the diameter of the conductive micropillars in the ceramic substrate.

[0114] S7: At the opening of the SiC insulating layer, i.e. the micropillar hole, a metal pad with 30nm chromium and 1.2μm gold is sputtered and deposited.

[0115] S8: The process of flipping the ceramic substrate and depositing a SiC insulating layer and depositing metal pads on the flipped surface, with the relevant parameters being the same as described above.

[0116] The present invention proposes a design scheme for a hermetically tight electrical interconnect feedthrough on a ceramic substrate in the above-described preparation method. The ceramic substrate is sintered using a mold with a micropillar array, then demolded, and filled with conductive material to form the feedthrough. Specifically, if the mold has good conductivity, the demolding process can be omitted. Compared to substrates that typically use drills to form holes, the hole-forming process of the ceramic substrate exhibits better consistency and better hermetically tightness. Compared to TSV technology, the internal pore morphology of the ceramic substrate can approach an ideal cylindrical morphology, resulting in a more uniform stress distribution.

[0117] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.

Claims

1. A ceramic-based electrical interconnect feedthrough substrate, characterized in that, include: A ceramic substrate, wherein the interior of the ceramic substrate is provided with an array of electrically interconnected micropillars formed by conductive micropillars; An upper insulating layer is located above the ceramic substrate; A lower insulating layer is located below the ceramic substrate; The upper insulating layer and the lower insulating layer each have an array of through holes formed by multiple insulating layer through holes inside. The positions of the insulating layer through holes correspond to the positions of the conductive micropillars, and the diameter of the insulating layer through holes is smaller than the diameter of the conductive micropillars. The upper insulating layer and the lower insulating layer cover the gap between the ceramic substrate and the conductive micropillars. The upper pad is located above the upper insulating layer and fills the insulating layer vias on the upper insulating layer and the gap between the upper insulating layer and the conductive micropillars; The lower pad is located below the lower insulating layer and fills the insulating layer vias on the lower insulating layer and the gap between the lower insulating layer and the conductive micropillar.

2. The ceramic-based electrical interconnect feedthrough substrate according to claim 1, characterized in that, The diameter of the through-hole in the insulating layer is 1-20 μm smaller than the diameter of the conductive micropillar.

3. The ceramic-based electrical interconnect feedthrough substrate according to claim 1, characterized in that, The upper and lower insulating layers are formed of biocompatible insulating materials, including any one of silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides, and polymers.

4. The ceramic-based electrical interconnect feedthrough substrate according to claim 1, characterized in that, The upper and lower pads are formed by biocompatible metal deposition, and the materials include any one of conductive polymers, titanium, platinum, chromium, gold, and alloys formed between titanium, platinum, chromium, and gold.

5. A method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to any one of claims 1-4, characterized in that, include: Ceramic powder is poured into a mold and sintered to form a shape. The mold contains a micro-pillar array formed by multiple micro-pillars. Demolding yields a ceramic substrate with a micropore array; The micropore array is filled with conductive material to form an array of electrically interconnected micropillars within the ceramic substrate; Planarize the front and back surfaces of the ceramic substrate until the array of electrically interconnected micropillars is exposed; An insulating layer is formed on top of the ceramic substrate; Metal is deposited on the upper insulating layer to form an upper pad, which fills the insulating layer vias of the upper insulating layer and the gap between the electrically interconnected micropillar array and the upper insulating layer. Flip the ceramic substrate, deposit the lower insulating layer using the same method as forming the upper insulating layer, and form the lower pads on the lower insulating layer using the same method as forming the pads on the upper insulating layer.

6. The method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to claim 5, characterized in that, Before pouring ceramic powder into the mold and sintering it, the process includes: using laser ablation and polishing to make the sidewalls of the micropillars uniformly smooth and close to an ideal cylinder.

7. The method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to claim 5, characterized in that, Pour ceramic powder into a mold and sinter it into shape, wherein the ceramic sintering method includes any one of hot pressing sintering, hot isostatic pressing sintering, microwave sintering and plasma activation sintering.

8. The method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to claim 5, characterized in that, A conductive material is filled into a micropore array to form an array of electrically interconnected micropillars within the ceramic substrate, wherein the electrically interconnected micropillars are formed by electroplating or sintering metal powder.

9. The method for fabricating a ceramic-based electrical interconnect feedthrough substrate according to claim 5, characterized in that, The mold uses a silicon-doped mold and a high-melting-point metal mold to eliminate the demolding process.

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