CN115910431A - Ceramic-based electrical interconnection feed-through substrate and preparation method thereof - Google Patents
Ceramic-based electrical interconnection feed-through substrate and preparation method thereof Download PDFInfo
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Abstract
The invention provides a ceramic-based electrically interconnected feedthrough substrate and method of making the same, the substrate comprising: the electric interconnection micro-column array formed by the conductive micro-columns is arranged in the ceramic substrate; an upper insulating layer located above the ceramic substrate; a lower insulating layer located below the ceramic substrate; the inner parts of the upper insulating layer and the lower insulating layer are respectively provided with a through hole array formed by a plurality of insulating layer through holes, the positions of the insulating layer through holes correspond to the positions of the conductive micro-columns, and the diameters of the insulating layer through holes are smaller than the diameters of the conductive micro-columns; the upper bonding pad is positioned above the upper insulating layer and is filled with an insulating layer through hole on the upper insulating layer and a gap between the upper insulating layer and the conductive microcolumn; and the lower bonding pad is positioned below the lower insulating layer and is filled in the insulating layer through hole on the lower insulating layer and the gap between the lower insulating layer and the conductive micro-column. The invention realizes the biocompatible airtight electrical interconnection feed-through capable of integrating the flexible implanted electrode.
Description
Technical Field
The invention relates to the technical field of flexible electrodes, in particular to a ceramic-based electric interconnection feed-through substrate and a preparation method thereof.
Background
Various activities within the living body are accompanied by the generation of physiological electrical signals. The collection of the physiological electric signals is beneficial to helping people to know the operation rule of biological tissues and cells, promoting the exploration process of mysterious organisms, and can also realize the intervention and treatment of diseases by monitoring the generation of abnormal electric signals. A bioelectronic device provides a method of acquiring physiological electrical signals.
Electronic devices implanted in animals and humans typically require a sealed enclosure. The outer shell prevents body fluids from corroding and degrading the internal silicon-based or metal electronic components, and it also prevents non-biocompatible materials from penetrating into body tissues. In order to transmit or receive voltage, current or other signals outside the housing, the components must typically be connected to wires whose conductive paths pass through the housing. The area where the conductive path passes through the housing is commonly referred to as a "hermetic feedthrough" or "hermetic substrate".
Sealed feedthroughs are typically made from a flat plate that is machined by a Computer Numerical Control (CNC) machine drill, water drill, or laser drilling, and subsequently filled with a conductive material. These drilling methods introduce stresses into the material that may lead to microcracks. For example, machine drilling can tear off metal chips, while laser drilling can cause some materials to evaporate due to intense heating of the materials. Moreover, the more holes that are to be formed, the longer the time required to drill the holes and the more chance of material leakage. Furthermore, flexible arrays connected to conventional feedthroughs sometimes use solder balls, which are quite large in diameter, making high density sealed feedthroughs using biocompatible materials with pitches less than 400 μm difficult to achieve.
Through Silicon Via (TSV) technology is considered by the industry as the fourth generation packaging technology following flip chip, which has the advantages of high density, short interconnection line length, etc. However, the TSV adopts a Bosch process to manufacture a through hole array, the process flow is long, the process cost is high, the inside of an etched hole is in a scallop spiral pattern shape, and the long-term performance of the feed-through is seriously influenced.
Therefore, there is a need for an electrical interconnect feedthrough having a high density of feedthroughs, high hermeticity, low process complexity, and uniform via profile.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to provide a ceramic-based electrical interconnect feedthrough substrate and method of making the same.
According to one aspect of the present invention, there is provided a ceramic-based electrical interconnect feedthrough substrate comprising:
the electric-interconnection micro-column array is formed by conductive micro-columns;
the upper insulating layer is positioned above the ceramic substrate;
a lower insulating layer located below the ceramic substrate;
through hole arrays formed by a plurality of insulating layer through holes are arranged in the upper insulating layer and the lower insulating layer, the positions of the insulating layer through holes correspond to the positions of the conductive micro-columns, and the diameters of the insulating layer through holes are smaller than those of the conductive micro-columns;
the upper bonding pad is positioned above the upper insulating layer and fills the insulating layer through hole on the upper insulating layer and the gap between the upper insulating layer and the conductive micro-column;
and the lower bonding pad is positioned below the lower insulating layer and fills the insulating layer through hole on the lower insulating layer and a gap between the lower insulating layer and the conductive micro-column.
Further, the diameter of the insulating layer through hole is 1-20um smaller than that of the conductive micro-column.
Further, the upper insulating layer and the lower insulating layer are formed of a biocompatible insulating material, including: any one of silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides and polymers.
Further, the upper pad and the lower pad are formed by deposition of a biocompatible metal, and the material includes any one of a conductive polymer, titanium, platinum, chromium, gold, and an alloy formed between titanium, platinum, chromium, and gold.
According to another aspect of the present invention, there is provided a method of making the above-described ceramic-based electrical interconnect feedthrough substrate, the method comprising:
pouring ceramic powder into a mould, and sintering and forming, wherein a micro-column array formed by a plurality of micro-columns is arranged inside the mould;
demolding to obtain a ceramic substrate with a micropore hole array;
filling a conductive material into the micro-hole array to form an electrically interconnected micro-column array in the ceramic substrate;
flattening the front surface and the back surface of the ceramic substrate until the electrically interconnected micro-column array is exposed;
forming an upper insulating layer on top of the ceramic substrate;
depositing metal on the upper insulating layer to form an upper bonding pad, and filling the upper bonding pad into an insulating layer through hole of the upper insulating layer and a gap between the electrically interconnected micro-column array and the upper insulating layer;
the ceramic substrate is turned over, a lower insulating layer is deposited in accordance with a method of forming an upper insulating layer, and a lower pad is formed on the lower insulating layer in accordance with a method of forming a pad on the upper insulating layer.
Further, before pouring ceramic powder into the mould and sintering and forming, the method comprises the following steps: and the side wall of the microcolumn is uniform and smooth by adopting a laser ablation and polishing mode and is close to an ideal cylinder.
Further, ceramic powder is poured into the mold and sintered to form, wherein: the ceramic sintering method includes any one of hot-press sintering, hot isostatic pressing sintering, microwave sintering, and plasma activated sintering.
And further, filling a conductive material into the micropore array, and forming an electric interconnection micro-column array in the ceramic substrate, wherein the electric interconnection micro-column is formed in an electroplating mode or a metal powder sintering mode.
Further, the mold employs a doped silicon mold and a refractory metal mold to omit a demolding process.
Compared with the prior art, the invention has the following beneficial effects:
1. the ceramic-based electrical interconnection feed-through substrate realizes the biocompatible airtight electrical interconnection feed-through capable of integrating the flexible implanted electrode, and can be applied to the electrical interconnection airtight packaging of a solid-state device and a thin film circuit for biological application.
2. The preparation method of the invention provides a design scheme of airtight electric interconnection feed-through of the ceramic substrate, the feed-through substrate wraps the ceramic substrate with the micro-column array by adopting a ceramic powder sintering forming mode to form the micro-pore array, and compared with the common base for forming the pores by adopting a drill, the pores of the ceramic substrate have smaller internal stress and better airtightness in the formation process. All feed-through holes on the sealing substrate can be formed in one-step sintering demoulding, so that the low-efficiency hole forming mode that the common drilling can only process a single hole at a time is avoided, and the processing cost and the process complexity can be greatly reduced.
3. According to the preparation method, the MEMS processing technology is used according to the method, so that the processing which is highly controllable, highly repeatable and capable of being manufactured in batches can be realized.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic structural diagram of a ceramic-based electrical interconnect feedthrough substrate of one embodiment of the present invention;
FIG. 2 is a cross-sectional schematic view of a ceramic-based electrical interconnect feedthrough substrate of an embodiment of the present invention;
FIG. 3 is a schematic flow chart of a method of making a ceramic-based electrical interconnect feedthrough substrate in accordance with one embodiment of the present disclosure;
fig. 4 is a schematic structural diagram illustrating steps of a method of making a ceramic-based electrical interconnect feedthrough substrate according to one embodiment of the present disclosure.
In the figure: 1 is a ceramic substrate, 2 is a conductive microcolumn, 3 is an insulating layer via, 4 is an upper insulating layer, 5 is an upper pad, 6 is a lower insulating layer, and 7 is a lower pad.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Embodiments of the present invention provide a ceramic-based electrical interconnect feedthrough substrate that includes, with reference to fig. 1-2: the electric-interconnection micro-column array comprises a ceramic substrate 1, an upper insulating layer 4, a lower insulating layer 6, an upper bonding pad 5 and a lower bonding pad 7, wherein an electric-interconnection micro-column array formed by conductive micro-columns 2 is arranged in the ceramic substrate 1; the upper insulating layer 4 is positioned above the ceramic substrate 1; the lower insulating layer 6 is positioned below the ceramic substrate 1; the inner parts of the upper insulating layer 4 and the lower insulating layer 6 are respectively provided with a through hole array formed by a plurality of insulating layer through holes 3, the positions of the insulating layer through holes 3 correspond to the positions of the conductive micro-columns 2, and the diameters of the insulating layer through holes 3 are smaller than the diameters of the conductive micro-columns 2; the upper bonding pad 5 is positioned above the upper insulating layer 4 and is filled in the insulating layer through hole 3 on the upper insulating layer 4 and the gap between the upper insulating layer 4 and the conductive microcolumn 2; the lower pad 7 is located below the lower insulating layer 6, and fills the insulating layer via-hole 3 on the lower insulating layer 6 and the gap between the lower insulating layer 6 and the conductive microcolumn 2.
In some embodiments, the ceramic substrate 1 is formed by pouring ceramic powder into a previously processed mold and sintering. The mould can adopt high-melting-point metal, graphite, silicon or ceramic materials, a concave basin-shaped structure with a micro-column array is formed by independent or combined modes of laser processing, etching and a precision machine tool, and the side wall of the micro-column can be further polished to be close to the appearance of an ideal cylinder, so that the flatness of the side wall of the micro-column is improved as much as possible. The ceramic sintering method comprises sintering modes such as hot-pressing sintering, hot isostatic pressing sintering, microwave sintering, plasma activated sintering and the like, and a micro-hole array formed by a plurality of micro-holes is formed in the ceramic substrate 1 in a sintering and demolding mode. The sintering demoulding mode has the advantages of batch production capacity, low process cost, good pore-forming appearance and uniform stress distribution in the formed micro-pores.
In some embodiments, the conductive micropillar array is formed by filling the array of micro-cavities with a conductive material. The conductive microcolumn 2 can be formed at the position of the micro-hole by an electroplating method, and the material can be any one of copper, copper-carbon nano tube, copper-tungsten, silver, graphene and the like; the material may be formed by sintering and hot pressing, and may include any one of molybdenum, tungsten, tantalum, copper, gold, and the like. Preferably, the conductive microcolumn 2 is formed using an inert material having good biocompatibility.
The insulating layer is deposited on the ceramic substrate 1, so that the problem of device failure caused by a gap possibly existing between the ceramic substrate 1 and the conductive microcolumn 2 can be solved. The upper insulating layer 4 and the lower insulating layer 6 are formed using a biocompatible insulating material, including: silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides such as alumina, zirconia, and polymers such as polyimide, pure epoxy, and the like. In some embodiments, the diameter of the insulating layer via-hole 3 is 1-20um smaller than the diameter of the conductive microcolumn 2. The insulating layer is provided with small holes at the conductive microcolumns 2, so that the insulating layer can cover gaps between the ceramic substrate 1 and the conductive microcolumns 2 and can keep the conductive microcolumns 2 electrically connected with the flexible electrodes or the redistribution layer, thereby being beneficial to realizing airtight packaging.
The welding pads are deposited at the through holes 3 of the insulating layer, so that subsequent packaging can be conveniently welded, and the like, and the upper welding pads 5 and the lower welding pads 7 need to be filled in the through holes 3 of the insulating layer and gaps between the insulating layer and the conductive micro-columns 2 and well contact with the conductive micro-columns 2. In some embodiments, the upper and lower pads 5, 7 are formed from a biocompatible metal deposition, the material including any of a conductive polymer, titanium, platinum, chromium, gold, and an alloy formed between titanium, platinum, chromium, gold.
In the above embodiment, the ceramic substrate 1 is formed by using an inert material with good biocompatibility. The conductive microcolumns 2 are covered by metal pads (comprising an upper pad 5 and a lower pad 7) formed by depositing biocompatible titanium, chromium and gold materials, and the biological toxicity of the conductive microcolumns is further isolated by a biocompatible insulating layer on the surface of the ceramic substrate 1, so that the biological tissue safety and the long-term functional stability of the implantable feed-through device are guaranteed. The substrate of ceramic material itself has high sealing performance; the insulating layer through hole covers the gap between the conductive microcolumn and the ceramic substrate, and strengthens the cracks possibly existing on the contact surfaces made of different materials. The electric interconnection feed-through substrate has the advantages of high density feed-through number, high tightness, low process complexity and uniform through hole appearance, and can realize the airtight packaging of the electric interconnection of the thin film circuit of the solid-state device and the biological application.
Another embodiment of the present invention provides a method for preparing the above-mentioned ceramic-based electrical interconnect feedthrough substrate, referring to fig. 3, the method comprising:
step 3, filling a conductive material into the micro-hole array to form an electrically interconnected micro-column array in the ceramic substrate;
step 5, forming an upper insulating layer on the top of the ceramic substrate, wherein the upper insulating layer is provided with insulating layer through holes corresponding to the electrically interconnected micropillar array;
and 7, overturning the ceramic substrate, depositing a lower insulating layer according to a method for forming an upper insulating layer, and forming a lower bonding pad on the lower insulating layer according to a method for forming a bonding pad on the upper insulating layer. After the ceramic-based electrical interconnect feedthrough substrate is prepared, it is placed as shown in fig. 2 with the lower pad under the lower insulating layer.
In the preparation method, the mould is in a concave basin shape, and the material of the mould comprises any one of high-melting-point metal, graphite, silicon and ceramic material. The mold can be formed by etching, laser processing, precision machine tool cutting or other micro-nano processing modes. To facilitate demolding, a layer of lubricating mold release agent, including but not limited to super heat resistant silicone oil, boron nitride release spray, etc., may be sprayed in advance in the mold.
In some embodiments, before pouring the ceramic powder into the mold and sintering to shape, the method comprises the following steps: the side wall of the microcolumn is uniform and smooth by adopting the laser ablation and polishing modes and is close to an ideal cylinder. Compared with the scallop-shaped through hole formed by adopting a Bosch process in the TSV technology, the ideal cylindrical micropillar array of the die has fewer internal stress concentration points, and more long-term stable feed-through connection can be obtained.
In some embodiments, a ceramic powder is poured into a mold and sintered into shape, wherein: the ceramic sintering method includes any one of hot-press sintering, hot isostatic pressing sintering, microwave sintering, and plasma activated sintering. For example, mixing Al 2 O 3 Powder, cuO-TiO 2 -Nb 2 O 5 Grinding and stirring the composite additive powder and deionized water to form ceramic slurry, drying in a drying oven, taking out the dried slurry, and grinding the dried slurry into powder. Pressing the powder into a die, then putting the die into a high-temperature furnace for sintering, and taking out after natural cooling. Specifically, the process of preparing the electrical interconnection feed-through substrate by adopting the method comprises the following steps: placing ceramic powder into a concave basin ground-shaped die with a micro-column array for sintering, separating the ceramic from the die to expose the micro-hole array in the ceramic, filling micro-column holes in the ceramic by adopting electroplated metal or other methods to form an electrically interconnected micro-column, then grinding or polishing the surface of the ceramic in other ways to create a flat surface to form a vertically through current channel, and finally depositing an insulating layer and a metal bonding pad to lead out the electrically-conductive micro-column array for interconnection and packaging.
In the above embodiment, the feed-through substrate is wrapped by the mold having the micropillar array to form the ceramic substrate having the micropillar array in a ceramic powder sintering forming manner, and compared with a substrate in which holes are formed by a drill, the holes of the ceramic substrate have smaller internal stress and better air tightness in the hole forming process. All feed-through holes on the sealing substrate can be formed in one-time sintering demoulding, so that the low-efficiency hole forming mode that the common drilling can only process a single hole at a time is avoided, and the processing cost and the process complexity can be greatly reduced.
The ceramic substrate is electrically interconnected with a chip or a sensor by filling conductive slurry into a micropore array in the substrate, in some embodiments, a conductive material is filled into the micropore array, and an electrically interconnected micropillar array is formed in the ceramic substrate, wherein an electroplating method is adopted to form an electrically interconnected micropillar, and metal posts serving as the electrically interconnected micropillar include but are not limited to copper, copper-carbon nanotubes, copper-tungsten, silver, graphene and the like; the electroplating process comprises the following steps:
(1) Sequentially preparing electroplating solution and additives, and uniformly mixing the electroplating solution and the additives; specifically, the additives comprise an accelerator, an inhibitor and a leveling agent, and are used for controlling the rate of copper electroplating deposition at different parts in the through hole and realizing filling without internal holes;
(2) Pre-soaking and vacuumizing a ceramic substrate;
(3) Setting electroplating parameters in an electroplating copper system for electroplating; specifically, the seed layer sputtered in advance during electroplating is an anode, and the electroplating solution is a cathode. If the through-hole is filled by electroplating, a copper-plating solution is prepared by adding additives such as 80g/L copper methanesulfonate, 20g/L methanesulfonic acid, and 50ppm chloride ion. The copper ions are subjected to reduction reaction at the seed layer and adsorbed at the seed layer, so that the filling is gradually completed. And forming metal columns of copper, copper-carbon nanotubes, copper-tungsten, silver and graphene after electroplating.
(4) And (5) washing with deionized water after the electroplating is finished.
In some alternative embodiments, the conductive material is filled into the micro-hole array to form an array of electrically interconnected micro-pillars within the ceramic substrate, wherein the electrically interconnected micro-pillars are formed by sintering metal powder, wherein: the metal powder includes molybdenum, tungsten, tantalum, copper, gold, and the like.
In some embodiments, the mold material is a material with conductive ability, such as a refractory metal mold or a doped silicon mold, so as to omit the demolding process, directly perform a planarization process, and polish the bottom of the mold flat, so that the mold micropillars are embedded in the ceramic substrate and isolated from each other.
In some embodiments, the planarization method includes, but is not limited to, chemical/mechanical polishing, grinding, fly-cutting, laser ablation, etching, or spin-coating a planarization layer.
In one embodiment, the method for preparing the ceramic-based electrical interconnect feedthrough substrate comprises the steps of:
1) Pouring ceramic powder into a concave basin-shaped mold with a micro-column array, and spraying a layer of lubricating release agent in the mold in advance;
2) Sintering ceramic powder under certain temperature, atmosphere and pressure conditions to convert the ceramic powder into a compact polycrystalline ceramic material, wherein the sintered ceramic substrate completely wraps the micro-column array in the mold;
3) Separating the ceramic substrate from the mold to form a micro-hole array in the ceramic substrate;
4) Filling a conductive material in the micro-hole array in the ceramic substrate to form an electrically interconnected micro-column;
5) Planarizing the top and back surfaces of the ceramic substrate until the array of electrically interconnected micropillars is exposed;
6) Depositing a biocompatible insulating layer on the top and sidewalls of the ceramic substrate;
7) Depositing a conductive pad on the insulating layer such that the conductive pad fills the hole between the electrical interconnect feedthrough and the insulating layer;
8) The ceramic substrate is turned over and the processing steps in 6) 7) are performed on the back of the ceramic substrate.
According to the preparation method of the ceramic-based electric interconnection feed-through substrate, the processing technology of the MEMS can realize the processing with high controllability, high repeatability and batch manufacturing according to actual needs.
Compared with the drilling mode of a numerical control machine tool, the preparation method of the ceramic-based electric interconnection feed-through substrate can realize the processing line width of micron order by the MEMS process. Compared with TSV, the scallop pattern through holes formed by deep silicon etching cannot be subjected to subsequent smoothing treatment, and the through holes formed by the reverse mold process in the embodiment of the invention can improve the smooth uniformity of the mold by adopting high-precision processing modes such as femtosecond laser and the like, so that the appearance uniformity of the ceramic through holes is indirectly improved. The electric interconnection feed-through substrate prepared by the method has the advantages of high density feed-through number, high sealing property, low process complexity and uniform through hole appearance.
The ceramic-based electrical interconnect feedthrough substrate of the present invention and the method of making it are further described by the following specific examples.
Example 1
The present embodiment provides a method of making a ceramic-based hermetic electrical interconnect feedthrough substrate using a ceramic die process, comprising the steps of, with reference to fig. 4:
as shown in S1 in figure 4, the fused mullite, the capacitance white corundum and the sintered alpha-Al are mixed 2 O 3 Micropowder of SiO 2 Grinding and mixing the micro powder, adding a water-soluble resin binder, and pouring into a ceramic mold with a micro-column array.
As shown in S2 in fig. 4, after drying at 110 ℃ for 24 hours under 120MPa pressure, the mold and the ceramic powder were placed in a high temperature gas kiln at 1750 ℃ for hot press sintering for 6 hours.
The ceramic formed by sintering was separated from the mold as shown by S3 in fig. 4, and a ceramic substrate having an array of micro-cavities was obtained.
And as shown in S4 in figure 4, sputtering a 10nm chromium barrier layer and a 30nm copper seed layer at the micropores, and filling the micropore hole array by adopting an electroplating copper process to form the conductive micropillar array. The specific copper electroplating method comprises the following steps:
1) Preparing electroplating solution: 80g/L of copper methylsulfonate, 20g/L of methanesulfonic acid and 50ppm of chloride ions;
2) Preparing an additive: 5.5ml/L of accelerator DVF-B, 20ml/L of inhibitor DVF-C and 5ml/L of leveling agent DVF-D;
3) Stirring the prepared solution by a magnetic stirrer;
4) Pre-soaking and vacuumizing the silicon wafer;
5) Setting electroplating parameters in the copper electroplating system: voltage 10V, current 10mA/cm 2 ；
6) And (5) washing with deionized water after the electroplating is finished.
As shown in fig. 4, the ceramic sintering process and the plating process cause unevenness of the entire base surface on the top and back of the ceramic substrate.
As shown in S5 in fig. 4, the ceramic substrate surface is planarized by chemical mechanical polishing to obtain a conductive feed-through structure with top and bottom connected;
as shown in S6 of fig. 4, a layer of silicon carbide (SiC) of about 1 μm is deposited by plasma enhanced chemical vapor deposition, and a mask is previously applied around the micropillar holes before depositing the silicon carbide to prevent the SiC from blocking the silicon pillar holes. The diameter of the through hole in the SiC insulating layer is slightly smaller than that of the conductive microcolumn in the ceramic substrate.
As shown at S7 in fig. 4, metal pads of 30nm chromium and 1.2 μm gold are sputter deposited at the openings of the SiC insulating layer, i.e., the micropillar holes.
In fig. 4, S8 shows a process of turning the ceramic substrate upside down, and depositing the SiC insulating layer and depositing the metal pad on the turned surface, and relevant parameters are consistent with the foregoing.
Example 2
The method for manufacturing the ceramic-based hermetic electrical interconnection feed-through substrate of this embodiment uses a doped silicon wafer with conductive capability as a sintering mold, and since the silicon wafer is brittle, the ceramic sintering process needs to be performed under normal pressure. The method comprises the following specific steps:
s1: cleaning a 4-inch silicon wafer with the thickness of 500 mu m, wherein the specific cleaning process comprises the following steps: 1) Putting the slices into acetone, and performing ultrasonic treatment for 5min; 2) Taking out the slices, and ultrasonically treating in anhydrous ethanol for 5min; 3) Taking out the slices, and putting the slices into deionized water for 5min; 1) 2) 3) cycles; 4) Drying the slices with nitrogen; 5) Baking the slices on a hot plate at 180 ℃ for more than 15 min.
S2: spin coating a layer of 20 μm thick positive photoresist AZ P4620 (1000 r 7s,1500 r 30 s) on a silicon substrate, pre-baking at 100 deg.C for 500s, and exposing to light at 1500mJ/cm 2 And developing for 5min to obtain an etching mask.
S3: and etching the silicon substrate to form an etching column. The height of the silicon column is about 300 μm, and the diameter of the circular hole of the silicon column is about 50 μm. Etching by the Bosch process, C 4 F 8 As a passivation layer, SF 6 As an etching gas.
S4: alpha-Si is mixed 3 N 4 、β-Si 3 N 4 、Si、AlN、α-Al 2 O 3 The ceramic powder is mixed with a binder to form a slurry to be filled into the silicon substrate. Under the nitrogen atmosphere of 0.1MPa, sintering at 1100 deg.C, 2h,1300 deg.C, 1.5h,1500 deg.C and 6h respectively, and then cooling to recover room temperature for forming.
S5: flattening the surface of the substrate by adopting chemical mechanical polishing to obtain a conductive silicon column feed-through which is communicated up and down and a flat ceramic substrate;
s6: a layer of silicon carbide (SiC) with the thickness of about 1 mu m is deposited on the upper surface and the side wall of the ceramic by adopting a plasma enhanced chemical vapor deposition method, and a mask needs to be coated in advance near the micro-column holes before depositing the silicon carbide so as to prevent the SiC from blocking the silicon column holes. The diameter of the through hole in the SiC insulating layer is slightly smaller than that of the conductive microcolumn in the ceramic substrate.
S7: metal pads of 30nm chromium and 1.2 μm gold were sputter deposited at the openings, i.e., micropillars, of the SiC insulating layer.
S8: and (3) overturning the ceramic substrate, and depositing a SiC insulating layer and a metal bonding pad on the overturned surface, wherein relevant parameters are consistent with the parameters.
Example 3
In the method for manufacturing the ceramic-based hermetic electrical interconnection feed-through substrate of this embodiment, the copper-titanium alloy is used as the sintering mold, and since the hardness of the copper-titanium alloy is high and the melting point is not fixed, the temperature during the sintering process should not be significantly higher than the melting point of pure copper (1083 ℃) at normal pressure. The method comprises the following specific steps:
s1: putting raw materials of titanium, copper and other metal materials into a vacuum melting furnace according to a certain proportion, keeping the environment at 10Pa and 1300 ℃ for 20min, and pouring into a concave basin-shaped ingot blank with a cylindrical array after melting. And then the ingot blank is subjected to thermal deformation, primary solid solution, cold deformation, secondary solid solution and aging process to prepare the sunken basin-shaped copper-titanium alloy with the cylindrical array. It should be noted that, in this embodiment, the casting method of the alloy is not specifically limited, and a general copper-titanium alloy casting process is adopted.
S2: and polishing the surface of the prepared copper-titanium alloy until no abnormal bulge is formed around the alloy and the height of the cylindrical array in the alloy is 300 mu m.
S3: and etching the cylindrical array in the copper-titanium alloy by utilizing a laser processing technology to form a micro-cylindrical array with smooth side wall and the diameter of a circular surface smaller than 100 mu m. Thus, the concave basin-shaped copper-titanium alloy mold with the micro-column array with the nearly ideal cylindrical surface is formed.
S4: mixing Al 2 O 3 Powder, cuO-TiO 2 -Nb 2 O 5 And (3) compounding additive powder, grinding and stirring the additive powder and deionized water to form ceramic slurry, putting the ceramic slurry into an oven at 80 ℃ for 12 hours, taking out the ceramic slurry after drying, grinding the ceramic slurry into powder, and pressing the powder into a copper-titanium alloy die. And then placing the die into a high-temperature furnace at 1100 ℃ for sintering for 5 hours, and taking out after natural cooling.
S5: flattening the surface of the ceramic substrate by adopting chemical mechanical polishing to obtain a conductive metal column feed-through which is communicated up and down and a flat ceramic substrate;
s6: a layer of silicon carbide (SiC) with the thickness of about 1 mu m is deposited on the upper surface and the side wall of the ceramic by adopting a plasma enhanced chemical vapor deposition method, and a mask needs to be coated in advance near the micro-column holes before depositing the silicon carbide so as to prevent the SiC from blocking the metal column holes. The diameter of the through hole in the SiC insulating layer is slightly smaller than that of the conductive microcolumn in the ceramic substrate.
S7: metal pads of 30nm chromium and 1.2 μm gold are sputter deposited at the openings of the SiC insulating layer, i.e. the micropillars.
S8: and (3) overturning the ceramic substrate, and depositing a SiC insulating layer and a metal bonding pad on the overturned surface, wherein relevant parameters are consistent with the parameters.
The above-described fabrication method of the present invention provides a design solution for a hermetic electrical interconnection feedthrough of a ceramic substrate, which is formed by sintering a mold having a micro-pillar array, followed by demolding and filling a conductive material on the ceramic substrate to form the feedthrough. In particular, if the mold has good conductivity, the demolding process may be omitted. Compared with the common base for forming the holes by adopting the drill, the hole forming process of the ceramic substrate has better consistency and better air tightness. Compared with the TSV technology, the shape of the inner hole of the ceramic substrate can be close to the shape of an ideal cylinder, and more uniform stress distribution is achieved.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The above-described preferred features may be used in any combination without conflict with each other.
Claims (9)
1. A ceramic-based electrical interconnect feedthrough substrate, comprising:
the electric interconnection micro-column array is formed by conductive micro-columns;
an upper insulating layer located above the ceramic substrate;
a lower insulating layer located below the ceramic substrate;
through hole arrays formed by a plurality of insulating layer through holes are arranged in the upper insulating layer and the lower insulating layer, the positions of the insulating layer through holes correspond to the positions of the conductive micro-columns, and the diameters of the insulating layer through holes are smaller than those of the conductive micro-columns;
the upper bonding pad is positioned above the upper insulating layer and is filled in the insulating layer through hole on the upper insulating layer and the gap between the upper insulating layer and the conductive microcolumn;
and the lower bonding pad is positioned below the lower insulating layer and fills the insulating layer through hole on the lower insulating layer and a gap between the lower insulating layer and the conductive micro-column.
2. The ceramic-based electrical interconnect feedthrough substrate of claim 1, wherein the insulating layer vias have a diameter 1-20um smaller than the diameter of the conductive micropillars.
3. The ceramic-based electrical interconnect feedthrough substrate of claim 1, wherein the upper and lower insulating layers are formed of a biocompatible insulating material comprising: any one of silicon dioxide, silicon tetroxide, silicon carbide, insulating metal oxides and polymers.
4. The ceramic-based electrical interconnect feedthrough substrate of claim 1, wherein the upper and lower pads are formed of a biocompatible metal deposit, the material comprising any of a conductive polymer, titanium, platinum, chromium, gold, and alloys formed between titanium, platinum, chromium, gold.
5. A method of making the ceramic-based electrical interconnect feedthrough substrate of any of claims 1-4, comprising:
pouring ceramic powder into a mould, and sintering and forming, wherein a micro-column array formed by a plurality of micro-columns is arranged inside the mould;
demolding to obtain a ceramic substrate with a micropore hole array;
filling a conductive material into the micro-hole array to form an electrically interconnected micro-column array in the ceramic substrate;
flattening the front surface and the back surface of the ceramic substrate until the electrically interconnected micro-column array is exposed;
forming an upper insulating layer on top of the ceramic substrate;
depositing metal on the upper insulating layer to form an upper bonding pad, and filling the upper bonding pad into an insulating layer through hole of the upper insulating layer and a gap between the electrically interconnected micro-column array and the upper insulating layer;
the ceramic substrate is turned over, a lower insulating layer is deposited in accordance with a method of forming an upper insulating layer, and a lower pad is formed on the lower insulating layer in accordance with a method of forming a pad on the upper insulating layer.
6. The method of claim 5, wherein prior to pouring ceramic powder into a mold and sintering to shape, comprising: and the side wall of the microcolumn is uniform and smooth by adopting a laser ablation and polishing mode and is close to an ideal cylinder.
7. The method of claim 5, wherein ceramic powder is poured into a mold and sintered to shape, wherein: the ceramic sintering method includes any one of hot press sintering, hot isostatic pressing sintering, microwave sintering, and plasma activated sintering.
8. The method of claim 5, wherein an array of electrically interconnected micropillars is formed within the ceramic substrate by filling an electrically conductive material into the array of micro-cavities, wherein the electrically interconnected micropillars are formed by electroplating or sintering a metal powder.
9. The method of claim 5, wherein the mold employs a doped silicon mold and a refractory metal mold to omit a demolding process.
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| CN202211393526.1A CN115910431A (en) | 2022-11-08 | 2022-11-08 | Ceramic-based electrical interconnection feed-through substrate and preparation method thereof |
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