A vertically interconnected packaging substrate, preparation method and electroplating copper filling method

Abstract

The present invention provides a vertically interconnected packaging substrate, a preparation method and an electroplating copper filling method. The preparation method includes forming a through hole on a substrate, and forming a metal oxide film layer on the inner wall of the through hole by atomic layer deposition; depositing a titanium / copper seed layer on the surface of the metal oxide film layer in the through hole and the substrate surface by magnetron sputtering; depositing a reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering, and the reducing property of the reducing metal film layer is stronger than that of metallic copper (Cu); depositing an oxidizing film layer on the seed layer on the surface of the substrate by magnetron sputtering, and the reduction potential of the metal ions of the oxidizing film layer is higher than that of copper ions (Cu<supgt;2+< / supgt>), so as to achieve uniform copper filling in deep holes without holes. This method effectively improves the density and adhesion of the plating layer in the hole, is suitable for high-precision patterning packaging manufacturing of the substrate, and can be widely applied to fields such as high-frequency radio frequency devices, power modules and three-dimensional integrated packaging.

Description

Technical Field

[0001] The present application belongs to the field of electronic packaging technology, and specifically relates to a vertically interconnected packaging substrate, a preparation method and an electroplating copper filling method. Background Art

[0002] As electronic devices develop rapidly towards high performance, high integration and miniaturization, the requirements for thermal conductivity, insulation and mechanical stability of packaging substrates are becoming increasingly higher. Common packaging substrates such as ceramics, glass, and organic plastic substrates have been widely used in power modules, radio frequency devices, three-dimensional packaging and other fields. In order to achieve multi-layer circuit interconnection, heat dissipation enhancement and high-frequency signal transmission, deep hole structures are often required in packaging substrates and filled with metal (such as copper) to form vertical vias. At the same time, metal graphics need to be precisely processed on the surface of the packaging substrate to construct high-precision circuits. However, the existing technology still has significant technical bottlenecks in deep hole copper filling, plating bonding strength and graphic alignment accuracy, which are specifically manifested in the plating hole defects of deep hole copper filling.

[0003] In the traditional electroplating hole filling process, due to the high aspect ratio of the deep hole structure (usually greater than 5:1), the diffusion capacity of the plating solution in the hole is limited and the current distribution is uneven. The current density at the hole mouth is significantly higher than the inner wall of the hole, causing copper ions to preferentially deposit at the hole mouth, while the deposition inside the hole is slow, and micro-holes or gaps are easily formed in the hole. Such defects will significantly reduce the conductivity, mechanical strength and thermal conductivity of the via. Existing technologies attempt to improve the hole filling effect through pulse plating, additive optimization (such as brighteners, leveling agents) or gradient current adjustment, but there is still a lack of effective solutions for hole-free filling of high aspect ratio through holes on substrates (such as depth > 500μm and aperture < 100μm). Summary of the invention

[0004] In order to solve the problem of holes and gaps that are prone to occur when copper is electroplated and filled in high aspect ratio through holes on the package substrate due to uneven current distribution, the following technical solution is adopted.

[0005] A vertically interconnected packaging substrate, comprising:

[0006] a substrate having at least one through hole formed therein;

[0007] A metal oxide film layer is deposited on the inner wall of the through hole, a titanium / copper seed layer is deposited on the surface of the metal oxide film layer deposited on the inner wall of the through hole and on the surface of the substrate, and a reducing metal film layer is deposited on the surface of the titanium / copper seed layer on the inner wall of the through hole, and the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu);

[0008] An oxidative film layer is deposited on the titanium / copper seed layer on the surface of the substrate, and the metal ion reduction potential of the oxidative film layer is higher than that of copper ions (Cu 2+ ).

[0009] In a preferred embodiment, the reducing metal film layer is made of a material selected from: zinc-copper alloy, iron-zinc alloy, nickel-tin alloy, and aluminum-magnesium alloy.

[0010] In a preferred embodiment, the oxidizing film layer is selected from one of ferric oxide and molybdenum trioxide.

[0011] In a preferred embodiment, the substrate material is selected from ceramics, organic plastics and glass.

[0012] In a preferred embodiment, the metal oxide film layer is a titanium dioxide film layer with a thickness of 5 to 20 nm, the titanium layer in the titanium / copper seed layer has a thickness of 100 to 120 nm, and the copper layer has a thickness of 1 to 3 μm; the reducing metal film layer is a zinc-copper alloy film layer with a thickness of 100 to 300 nm, and the oxidizing film layer is a ferric oxide film layer with a thickness of 100 to 300 nm.

[0013] The present application embodiment provides a method for preparing the above-mentioned vertically interconnected packaging substrate, comprising the following steps:

[0014] forming a through hole on a substrate, and forming a metal oxide film layer on an inner wall of the through hole by atomic layer deposition;

[0015] Depositing a titanium / copper seed layer on the surface of the metal oxide film layer in the through hole and the surface of the substrate by magnetron sputtering;

[0016] Depositing a reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering, wherein the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu);

[0017] An oxidative film layer is deposited on the seed layer on the surface of the substrate by magnetron sputtering, wherein the metal ion reduction potential of the oxidative film layer is higher than that of copper ions (Cu 2+ ).

[0018] In a preferred embodiment, the vertically interconnected package substrate uses pulse electroplating to fill the through hole. When electroplating copper, the reducing metal film layer on the inner wall of the through hole has the following mechanism: the reducing metal film layer takes zinc-copper alloy as an example. Zn has stronger reducing property than Cu. In the whole electroplating process, it can first react with Cu 2+ Reaction: Zn + Cu 2+ → Zn 2+ + Cu; accelerates copper deposition on the pore wall through substitution reaction and increases the current density in the pore.

[0019] The presence of the reducing metal film layer reduces the difference in deposition rate inside and outside the hole, preventing the copper layer at the hole mouth from growing too fast and causing internal holes.

[0020] The mechanism of action of the oxidative film on the outer surface of the substrate is as follows: Taking ferric oxide as an example, the metal ion reduction potential of ferric oxide is higher than that of Cu 2+ , reduction reaction occurs preferentially in the cathode stage of electroplating: Fe 2 O 3 + 6H + +2e - →2Fe 2+ + 3H 2 O consumes electrons, inhibits the deposition of copper on the substrate surface, and makes the growth rate of copper in the hole significantly higher than that on the surface.

[0021] During the pulse plating hole filling process:

[0022] (1) When the pulse power supply is in the forward current time interval, the substrate is connected to the negative pole of the power supply, that is, the substrate is the cathode. At this time, the metal ion reduction potential of the oxidative film layer on the surface of the substrate is higher than that of copper ions (Cu 2+ ), so Fe 2 O 3 The reduction reaction Fe 2 O 3 + 6H + +2e - → 2Fe 2+ + 3H 2 O, thereby suppressing the growth rate of Cu on the substrate surface; at the same time, due to the Cu 2+ The oxidizing property of Cu is stronger than that of Zn, so a reduction reaction will occur. 2+ +2e - → Cu and substitution reaction Zn + Cu 2+ → Zn 2+ + Cu, thereby promoting the growth rate of Cu at the inner wall of the through hole.

[0023] (2) When the pulse power supply is in the reverse current time interval, the substrate is connected to the positive pole of the power supply, that is, when the substrate is the anode, the substrate loses electrons and an oxidation reaction occurs. At this time, the reducing property of Cu on the substrate surface is stronger than that of Fe. 2+ , so Cu preferentially undergoes oxidation reaction Cu - 2e - → Cu 2+ , which can consume the Cu on the substrate surface; at the same time, since the reducibility of Zn on the inner wall of the through hole is stronger than that of Cu, Zn preferentially undergoes oxidation reaction Zn - 2e - → Zn 2+ And the replacement reaction Zn + Cu occurs simultaneously 2+ → Zn 2+ + Cu, thereby limiting the consumption of Cu at the inner wall of the through hole, making the consumption rate of Cu at the inner wall of the through hole much lower than the consumption rate of Cu on the surface of the substrate.

[0024] The present invention achieves the technical effect of inhibiting growth on the substrate surface and preferentially depositing in the hole by the synergistic effect of the film layers. The reducing metal film layer catalyzes the reduction of Cu²⁺, accelerates the growth of copper on the inner wall of the hole, promotes the "bridging effect" in the hole, and reduces the number of holes. The oxidizing film layer preferentially consumes electrons, reduces the surface copper deposition rate, makes the copper growth rate in the hole greater than that on the surface, and avoids premature closure of the hole mouth, thereby achieving the technical effect of inhibiting growth on the substrate surface and preferentially depositing in the hole. The synergistic effect of the film layers can effectively avoid the occurrence of holes in the through-hole, and achieves complete filling of the through-hole of the substrate with metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a vertically interconnected packaging substrate structure according to an embodiment of the present application;

[0026] Figure 2a Schematic diagram of the X-shaped dislocation hole structure on the substrate;

[0027] Figure 2b Schematic diagram of the beam waist hole structure on the substrate;

[0028] Figure 2c Schematic diagram of the straight hole structure on the substrate;

[0029] Figure 2d Schematic diagram of the tapered hole structure on the substrate;

[0030] Figure 3 This is an optical microscope test image after electroplating via filling according to an embodiment of the present application;

[0031] Figure 4 This is an X-ray test image after electroplating via filling of an embodiment of the present application;

[0032] Figure 5 This is a schematic diagram of the structure of the positioning hole and the cross target on the substrate according to the embodiment of the present application;

[0033] Figure 6 Schematic diagram of redox reaction when the substrate acts as a cathode during the pulse electroplating hole filling process of an embodiment of the present application;

[0034] Figure 7 Schematic diagram of the redox reaction when the substrate acts as an anode during the pulse electroplating hole filling process of an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. Embodiment 1

[0036] A vertically interconnected package substrate, such as Figure 1As shown, it comprises: a substrate 1, on which at least one through hole 2 is formed; a metal oxide film layer is deposited on the inner wall of the through hole 2 of the substrate, a titanium / copper seed layer is deposited on the surface of the metal oxide film layer deposited on the inner wall of the through hole 2 and the surface of the substrate, a reducing metal film layer 3 is deposited on the surface of the titanium / copper inner wall seed layer in the through hole 2, and the reducing property of the reducing metal film layer 3 is stronger than that of metal copper (Cu); an oxidizing film layer 4 is deposited on the titanium / copper seed layer on the surface of the substrate, and the metal ion reduction potential of the oxidizing film layer is higher than that of copper ions (Cu 2+ ). Figure 1 It is only used to show the positional relationship between the substrate 1, the through hole 2, the reducing metal film layer 3, and the oxidizing film layer 4. Figure 1 The metal oxide film layer and the titanium / copper seed layer deposited on the inner wall of the through hole are not shown.

[0037] In another embodiment, Figure 2a As shown, the through hole is a staggered hole 21. The X-shaped staggered hole can be staggered and ablated on both sides of the substrate 1 by using an excimer laser (cold laser) to form a Figure 2a The X-shaped staggered hole shown has a bent portion 22 in the middle of the through hole. During the subsequent electroplating copper filling process, the current density at the bent portion 22 (also called the turning point) in the middle of the through hole is large, and the Cu growth rate in the middle of the through hole is fast, which is conducive to filling the hole.

[0038] As Figure 2a Variations of the embodiments, such as Figure 2b The through hole shown is a schematic diagram of the beam waist hole 23. Figure 2a Variations of the embodiments, such as Figure 2c The through hole shown is a schematic representation of a straight hole 24. Figure 2a Variations of the embodiments, such as Figure 2d The through hole shown is a schematic representation of the tapered hole 25 . Embodiment 2

[0039] A vertically interconnected packaging substrate comprises a substrate, the material of the substrate is selected from ceramics, and at least one through hole is formed on the substrate; a reducing metal film layer is also deposited on the inner wall surface of the through hole, and the reducing metal film layer is a zinc-copper alloy film layer with a thickness of 100 to 300 nm; an oxidizing film layer is deposited on the outer surface of the substrate, and the oxidizing film layer is a ferric oxide film layer with a thickness of 100 to 300 nm.

[0040] The package substrate using this method is electroplated with copper and then looks like this under an optical microscope. Figure 3 As shown, X-ray irradiation shows Figure 4 shown.

[0041] Figure 3Through optical microscope testing of the cross-section of the substrate, after the electroplated Cu hole filling is completed, it can be seen that the hole is filled with Cu without holes; Figure 4 Through X-ray testing of the substrate, after the electroplating Cu hole filling is completed, it can be seen that the Cu in the hole is filled without holes and the Cu layer is uniform and dense. Embodiment 3

[0042] A vertically interconnected packaging substrate includes a substrate, the material of which is selected from glass, a metal oxide film layer is deposited on the inner wall of the through hole of the substrate, a titanium / copper seed layer is deposited on the surface of the metal oxide film layer deposited on the inner wall of the through hole and the surface of the substrate, a reducing metal film layer is deposited on the surface of the seed layer on the titanium / copper inner wall of the through hole; and an oxidizing film layer is deposited on the titanium / copper seed layer on the surface of the substrate. Preferably, the metal oxide film layer is a titanium dioxide film layer with a thickness of 5 to 20 nm, the titanium layer in the titanium / copper seed layer has a thickness of 100 to 120 nm, and the copper layer has a thickness of 1 to 3 μm; the oxidizing film layer is selected from molybdenum trioxide with a thickness of 100 to 300 nm; and the reducing metal film layer is selected from aluminum-magnesium alloy with a thickness of 100 to 300 nm.

[0043] The reducing metal film layer of aluminum-magnesium alloy increases the current density in the hole and accelerates the deposition of copper ions on the inner wall of the through hole through replacement reaction and catalysis.

[0044] The titanium / copper seed layer ensures uniform copper deposition, and the titanium dioxide film layer enhances adhesion and prevents the coating from peeling off. The oxidizing film layer of molybdenum trioxide preferentially consumes electrons, interferes with the reduction rate of copper ions, and inhibits the deposition of copper at the pores on the surface of the substrate. This inhibitory effect avoids the excessive growth of the copper layer at the pores, preventing the pores from closing prematurely and forming holes. Embodiment 4

[0045] A vertically interconnected packaging substrate comprises a substrate, the substrate is made of organic plastic, and at least one through hole is formed on the substrate; a reducing metal film layer is deposited on the inner wall surface of the through hole, and the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu); an oxidizing film layer is deposited on the outer surface of the substrate, and an oxidizing film layer is deposited on the outer surface of the substrate, and the metal ion reduction potential of the oxidizing film layer is higher than that of copper ions (Cu 2+ ); the reducing metal film layer material is selected from: zinc-copper alloy, iron-zinc alloy, nickel-tin alloy, aluminum-magnesium alloy; the oxidizing film layer is selected from ferric oxide or molybdenum trioxide.

[0046] The reducing film layer on the inner wall of the through-hole increases the current density in the hole through replacement and catalysis, and accelerates the deposition of copper ions on the inner wall of the through-hole. Embodiment 5

[0047] As a preferred solution based on Example 1, Figure 5As shown, the vertically interconnected packaging substrate includes a substrate on which positioning holes 11 and a plurality of cross targets 12 are arranged.

[0048] For substrates with a thickness of 0.1 to 5 mm, a straight through hole is prepared using a laser with an aperture ratio of 20:1, and positioning holes and several cross targets of different sizes are prepared on both sides of the substrate for positioning in the subsequent circuit graphic process on the substrate surface.

[0049] Positioning method during exposure: Place the substrate coated with photoresist or with dry film and the corresponding mask into the corresponding position of the exposure machine, fix the mask, adjust the position of the substrate so that the cross target / positioning hole on the substrate and the cross target / positioning hole on the mask completely overlap, move the viewing angle to the position of the next cross target or positioning hole, and continue to adjust until all cross targets and positioning holes of different sizes on the substrate and the mask completely overlap. This method can control the alignment accuracy within ±1μm. Embodiment 6

[0050] A method for preparing a vertically interconnected packaging substrate comprises the following steps:

[0051] forming a through hole in the substrate,

[0052] Depositing a reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering, wherein the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu);

[0053] An oxidized film layer is deposited on the outer surface of the seed layer of the substrate by magnetron sputtering, and the metal ion reduction potential of the oxidized film layer is higher than that of copper ions (Cu² + ).

[0054] In other more detailed specific examples, the preparation method of the vertically interconnected packaging substrate includes forming a through hole on the substrate, roughening the inner wall of the through hole, and increasing the roughness by plasma etching and ultraviolet light cleaning; forming a titanium dioxide metal oxide film layer on the inner wall of the through hole by atomic layer deposition; depositing a titanium / copper seed layer on the surface of the metal oxide film layer and the surface of the substrate by magnetron sputtering; depositing a zinc-copper alloy reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering; and depositing an oxidizing film layer of iron trioxide on the outer surface of the seed layer of the substrate by magnetron sputtering.

[0055] The specific steps of roughening the inner wall of the through hole include:

[0056] (1) Spin coating photoresist: Place the substrate on the spin coater, pour an appropriate amount of photoresist, and then start at a low speed (usually 500-1000 rpm) for pre-spin coating. Then gradually increase the speed to 2000-4000 rpm and maintain for tens of seconds (such as 50 seconds) to ensure that the photoresist is evenly distributed on the substrate surface.

[0057] (2) Soft baking: After spin coating, the substrate is placed in an oven for soft baking, usually at a temperature of 80°C to 120°C for 1 to 10 minutes to remove the solvent in the photoresist.

[0058] (3) Exposure: Place the substrate coated with photoresist or with dry film and the corresponding mask into the corresponding position of the exposure machine, fix the mask, adjust the position of the substrate so that the cross target / positioning hole on the substrate completely overlaps with the cross target / positioning hole on the mask, move the viewing angle to the position of the next cross target / positioning hole, continue to adjust until all cross targets and positioning holes of different sizes on the substrate and the mask completely overlap, and then perform exposure for 1 to 30 seconds. This method can control the alignment accuracy within ±1μm.

[0059] (4) Development: The exposed substrate is developed using a developer. The photoresist on the inner wall of the through hole or on the surface of the substrate will be removed.

[0060] (5) After development, the photoresist on the inner wall of the through hole of the substrate is removed, while the photoresist on the surface still exists. The inner wall of the through hole is cleaned using ultraviolet light with a wavelength of 254nm, and the inner wall of the through hole is etched using plasma. The surface of the substrate is protected by the photoresist and will not be etched, thereby only increasing the roughness of the inner wall of the through hole, which is beneficial to improving the current density and coating bonding strength of the inner wall of the through hole during the subsequent electroplating copper filling process.

[0061] In one embodiment, a metal oxide film layer is deposited on the inner wall of the through hole, and the specific steps include:

[0062] (1) Atomic deposition layer deposition of metal oxide film: Ti(OPr) 4 and H 2 O 2 High-purity nitrogen was introduced into the reactor as a carrier gas in the form of pulses at 60°C. 4 The vapor pressure is maintained at about 6.6 Pa, and the inert gas purge state is maintained between two pulses to achieve the purpose of cleaning by-products and non-chemically adsorbed molecules on the surface; a layer of metal oxide TiO is deposited on the inner wall of the through hole. 2 The film layer can improve the bonding force between the subsequent coating and the substrate through nanoscale mechanical pinning.

[0063] (2) Removal of photoresist: Perform 80kHz ultrasonic cleaning for 10 minutes at room temperature in a special degumming solution to remove the photoresist on the surface of the substrate.

[0064] Depositing a seed layer on the surface of the substrate and the inner wall of the through hole includes:

[0065] Under the conditions of vacuum degree of 0.2-0.5 Pa, bias voltage of -100--60 V, substrate temperature of 100-200° C., sputtering power of 5-8 kW, sputtering time of 30-40 min, the thickness of the deposited titanium layer of 100-120 nm;

[0066] Under the conditions of vacuum degree of 0.1 to 0.5 Pa, bias voltage of -50 to -200 V, substrate temperature of 25 to 300° C., and sputtering power of 1 to 15 kW, the sputtering time is 30 to 300 minutes, and the thickness of the deposited copper layer is 1 to 10 μm.

[0067] The steps of depositing a zinc-copper alloy reducing metal film layer on the inner wall of the through hole include:

[0068] (1) The photoresist is coated on the substrate surface by spin coating, soft baking, exposure and development, and the photoresist in the through hole is removed by development.

[0069] (2) Using a zinc-copper alloy target, under the conditions of vacuum degree of 0.1 to 0.5 Pa, bias voltage of -50 to -200 V, substrate temperature of 25 to 300 °C, and sputtering power of 1 to 5 kW, the sputtering time is 10 to 30 min, and a zinc-copper alloy layer with a thickness of 100 to 300 nm is deposited on the surface of the seed layer in the through hole.

[0070] (3) Removal of photoresist: Perform 80kHz ultrasonic cleaning for 10 minutes at room temperature in a special degumming solution to remove the photoresist on the surface of the substrate.

[0071] Fe is deposited on the outer surface of the substrate 2 O 3 The specific steps of the oxidative film layer include:

[0072] (1) The inner wall of the through hole is coated with photoresist by spin coating, soft baking, exposure, and development, and the photoresist on the surface of the substrate is removed by development.

[0073] (2) Using Fe 2 O 3 The target material is subjected to the conditions of vacuum degree of 0.1 to 0.5 Pa, bias voltage of -50 to -150 V, substrate temperature of 100 to 300° C., and radio frequency sputtering power of 2 to 7 kW, and the sputtering time is 20 to 40 min, and the thickness of the iron oxide layer deposited on the surface of the substrate is 100 to 300 nm;

[0074] (3) Removing photoresist: Perform 80kHz ultrasonic cleaning for 10 minutes at room temperature in a special degumming solution to remove the photoresist on the inner wall of the through hole. Embodiment 7

[0075] A method for electroplating copper filling using a vertically interconnected packaging substrate adopts a pulse electroplating method to fill through holes. In the method, the reducing metal film layer is a zinc-copper alloy film layer, and the oxidizing film layer is a ferric oxide film layer.

[0076] Plating solution: 200~250g / L CuSO 4 ·5H 2 O, 50~100g / LH 2 SO 4 With 20~100 mg / L Cl – The composition comprises: the electroplating copper additives are a leveler, a brightener, and an inhibitor; the brightener comprises PEG (polyethylene glycol) at a concentration of 1 to 5 g / L, which is used to promote copper deposition and refine grains; the inhibitor comprises SPS (sodium thiosulfate) at a concentration of 1 to 5 mg / L, which is used to increase cathode polarization and reduce surface tension; the leveler comprises Janus Green B at a concentration of 0.1 to 1 mg / L, which is used to inhibit copper deposition in high current density areas; Figure 6 Schematic diagram of the redox reaction occurring on the substrate surface and the inner wall of the through-hole when the substrate is used as a cathode during the pulse electroplating hole filling process; the brightener (accelerator) in the electroplating solution can accelerate the Cu 2+ The brightener is easy to accumulate in the location with large curvature. As the bridge is gradually formed in the middle of the hole, the curvature increases, and the brightener is easy to accumulate in the middle of the hole, accelerating the deposition of Cu in the middle of the hole. 2+ Deposition is beneficial to the filling of holes. Inhibitors and levelers tend to accumulate at the hole mouth, which will inhibit the Cu 2+ The deposition of Cu at the hole mouth is slow, so that the growth rate of Cu in the hole is lower than that of Cu in the hole, which is conducive to filling the hole. There is a layer of reducing metal film on the inner wall of the hole. During the process of electroplating Cu to fill the hole, the reducing metal can reduce the Cu in the solution. 2+ Reduced to Cu and attached to the surface, it can also increase the Cu near the inside of the hole 2+ The exchange rate of Cu in the middle of the hole is accelerated. 2+ There is a layer of oxidizing material film outside the hole / hole mouth. During the electroplating Cu hole filling process, the oxidizing material will take precedence over Cu 2+ discharge, thereby reducing the Cu outside the hole / hole mouth 2+ The deposition rate.

[0077] Figure 7 Schematic diagram of the redox reaction occurring on the substrate surface and the inner wall of the through-hole when the substrate is used as an anode during the pulse electroplating hole filling process. The surface Cu is preferentially Fe 2+ Oxidation reaction occurs; Zn in the pore undergoes oxidation reaction first.

[0078] During the electroplating process, the forward and reverse current ratio is controlled to be 2:1-4:1, the forward and reverse time ratio is 8:1-80:1, and the current density is 1-4ASD.

[0079] During the pulse plating hole filling process:

[0080] (1) When in the forward current time interval, the substrate is the cathode and receives electrons to undergo a reduction reaction. At this time, the oxidized film on the surface of the substrate is Fe 2 O 3 , which is more oxidizing than Cu 2+ , so Fe 2 O 3 The reduction reaction Fe 2 O 3 +6H + +2e - → 2Fe 2+ + 3H 2 O, thereby suppressing the growth rate of Cu on the substrate surface; at the same time, due to the Cu 2+ The oxidizing property of Cu is stronger than that of Zn, so a reduction reaction will occur. 2+ +2e - → Cu and substitution reaction Zn + Cu 2+ → Zn 2+ + Cu, thereby promoting the growth rate of Cu at the inner wall of the through hole.

[0081] (2) When in the reverse current time interval, the substrate is the anode, loses electrons and undergoes an oxidation reaction. At this time, the reducing property of Cu on the substrate surface is stronger than that of Fe. 2+ , so Cu preferentially undergoes oxidation reaction Cu - 2e - → Cu 2+ , which can consume the Cu on the surface of the substrate; at the same time, since the reducibility of Zn at the inner wall of the through hole is stronger than that of Cu, Zn preferentially undergoes oxidation reaction Zn -2e - → Zn 2+ , thereby limiting the consumption of Cu at the inner wall of the through hole, making the consumption rate of Cu at the inner wall of the through hole much lower than the consumption rate of Cu on the substrate surface.

[0082] The oxidative film layer on the substrate surface and the reduced metal film layer in the hole can effectively promote the growth rate of copper in the hole and reduce the growth rate of copper on the substrate surface. Embodiment 8

[0083] A method for preparing a pattern on the surface of a vertically interconnected packaging substrate comprises the following steps:

[0084] S1. Use laser to form through holes, positioning holes and cross targets on the substrate;

[0085] S2. Spin-coating photoresist on the substrate surface and inside the through-hole, and then placing it in an oven for soft baking;

[0086] The substrate and the corresponding mask are aligned using the positioning holes and the cross target, and then exposed and developed. At this time, the photoresist in the hole is dissolved or removed, while the photoresist on the surface of the substrate remains intact;

[0087] Then, the inner wall of the through hole is roughened by laser to increase the roughness of the inner wall; this step can improve the bonding strength of the subsequent coating and increase the current density of the inner wall during the subsequent electroplating hole filling process, so that the electroplated copper grows faster, which is conducive to filling the hole;

[0088] S3. Depositing a metal oxide film layer on the inner wall of the hole by atomic layer deposition, the material of the metal oxide film layer is selected from titanium dioxide, indium gallium zinc oxide or indium tin oxide;

[0089] Then, a special degumming solution is used to remove the photoresist on the surface of the substrate;

[0090] S4. Depositing a seed layer on the surface of the substrate and the surface of the hole, in which the seed layer is deposited on the surface of the substrate and the surface of the hole by magnetron sputtering;

[0091] S5. Spin-coating a photoresist on the substrate surface and inside the through-hole, and then placing it in an oven for soft baking;

[0092] The substrate and the corresponding mask are aligned using the positioning holes and the cross target, and then exposed and developed. At this time, the photoresist in the hole is dissolved or removed, while the photoresist on the surface of the substrate remains intact;

[0093] The substrate is placed in a plasma etcher, where the remaining photoresist in the holes is precisely removed by the physical or chemical reaction of the plasma without damaging the surface or the formed structure;

[0094] S6. depositing a reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering. In this step, a reducing metal film layer is deposited on the surface of the Cu seed layer in the hole by magnetron sputtering. In the subsequent electroplating copper filling process, the reducing metal film layer can directly replace copper ions, accelerate the growth of the Cu layer on the inner wall, and is conducive to the filling of the Cu layer in the hole. At the same time, it can also increase the ion concentration at the inner wall and improve the current density there, which is conducive to the growth and deposition of the Cu layer there during the electroplating process.

[0095] S7. Spin-coating photoresist on the substrate surface and inside the through hole, and then placing it in an oven for soft baking;

[0096] The substrate and the corresponding mask are aligned using the positioning holes and the cross target, and then exposed and developed. At this time, the photoresist on the surface of the substrate is dissolved or removed, while the photoresist on the inner wall of the through hole remains intact;

[0097] S8. Deposit an oxidized film layer on the surface of the substrate by magnetron sputtering, and the oxidized film layer is discharged before copper ions. The oxidized film layer is gradually consumed during the copper electroplating process. 2 O 3 film layer, which discharges preferentially over copper ions, Fe 2 O 3 Get electrons to generate Fe 2+ , thereby reducing the deposition rate of copper ions on the substrate surface; thereby avoiding the problem that the copper at the hole mouth / outside the hole grows faster than the inner wall of the hole;

[0098] Then, a special degumming liquid is used to remove the photoresist on the inner wall of the through hole;

[0099] S9. Preparing a pattern on the substrate surface by dry film, exposure, and development, the specific steps include:

[0100] (1) Dry film pretreatment: Use pure water spray drying; the forward speed of the line is 5m / min, and the spray pressure is 1-3kg / cm 2 , drying temperature 100℃.

[0101] (2) Pressing dry film: pressure 1~4kg / cm 2 , speed 1~1.5m / min, temperature 80~90℃.

[0102] (3) Exposure: Place the substrate with dry film and the corresponding mask into the corresponding position of the exposure machine, fix the mask, adjust the position of the substrate so that the cross target / positioning hole on the substrate completely overlaps with the cross target / positioning hole on the mask, move the viewing angle to the position of the next cross target / positioning hole, continue to adjust until all cross targets and positioning holes of different sizes on the substrate and the mask completely overlap, and then perform exposure. The exposure time is 20 to 40 seconds. This method can control the alignment accuracy within ±1μm.

[0103] (4) Development: Use a special developer for dry film at a temperature of 30-40°C, a speed of 2-5 m / min, and a spray pressure of 1-3 kg / cm 2 .

[0104] S10. Use pulse electroplating to fill copper holes. During electroplating, use a hanger to place the substrate in the electroplating tank. During the electroplating process, use the hanger to slowly move the substrate up and down to avoid excessive consumption of plating solution in a small area, which leads to uneven composition of the plating solution. At the same time, during the electroplating process, ultrasonic vibration is used to evenly distribute the composition of the plating solution; nozzles are installed around the electroplating tank to spray the plating solution so that the components of the plating solution are evenly mixed.

[0105] S11. A Ni / Pd / Au layer is prepared on the surface of the substrate by chemical plating, and the specific steps are as follows:

[0106] (1) Film removal: Use a special film removal liquid to remove the dry film at a temperature of 30-40°C, a speed of 2-5 m / min, and a spray pressure of 1-3 kg / cm 2 .

[0107] (2) Etching: Sodium persulfate and hydrofluoric acid are used to etch the copper and titanium seed layers respectively, at a temperature of 30-40°C, a speed of 2-5 m / min, and a spray pressure of 1-3 kg / cm 2 .

[0108] (3) Chemical Ni plating: temperature 80-95°C, nickel ion concentration 2.6-3.3 g / L, pH controlled at 5.2-6.1, time 10-50 min, Ni thickness 3-6 μm;

[0109] (4) Chemical plating of Pd: palladium salt concentration 0.5-2 g / L, temperature 50-70°C, pH controlled at 4.0-7.0, time 10-40 min, Pd thickness 0.07-0.3 μm;

[0110] (5) Chemical Au plating: potassium gold cyanide (KAu(CN) 2 ) concentration 1~3 g / L, temperature 80~95℃, PH controlled at 4.0~6.0, time 20~60min, Au thickness 0.3~0.6μm.

[0111] This application realizes a technical solution of hole-free copper filling by modifying the substrate surface, film layer synergy and pulse electroplating process. It is applicable to the field of electronic devices with strict requirements on electrical performance and thermal management, such as high-frequency radio frequency devices, power modules, and three-dimensional integrated packaging. First, a through hole is prepared on the substrate and the inner wall is etched to increase the roughness; a metal oxide film layer is formed on the inner wall of the hole by atomic layer deposition to enhance the binding force of the seed layer; then a titanium / copper seed layer is deposited by magnetron sputtering, and a metal film layer with stronger reducibility than copper is selectively sputtered in the hole, and an oxidizing film layer is sputtered on the surface of the substrate; combined with the pulse electroplating process, the metal ions in the oxidizing film layer are preferentially reduced to inhibit copper deposition on the surface of the substrate, and the reducing film layer promotes the rapid deposition of copper ions in the hole, so as to achieve uniform copper filling in the deep hole. By aligning the positioning hole with the cross target, the graphic accuracy reaches ±1μm. This method effectively improves the density and adhesion of the coating in the hole, avoids premature closure of the hole mouth, and forms holes, and is suitable for high-precision graphic packaging manufacturing of high aperture ratio substrates.

[0112] The above embodiments are only for illustrating the technical concept and features of the present application, and their purpose is to enable people familiar with the technology to understand the content of the present application and implement it accordingly, and they cannot be used to limit the protection scope of the present application. Any modifications made according to the spirit of the main technical solution of the present application shall be included in the protection scope of the present application.

Claims

1. A vertically interconnected packaging substrate, characterized in that: include: a substrate having at least one through hole formed therein; A metal oxide film layer is deposited on the inner wall of the through hole, a titanium / copper seed layer is deposited on the surface of the metal oxide film layer deposited on the inner wall of the through hole and on the surface of the substrate, and a reducing metal film layer is deposited on the surface of the titanium / copper seed layer on the inner wall of the through hole, and the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu); An oxidative film layer is deposited on the titanium / copper seed layer on the surface of the substrate, and the metal ion reduction potential of the oxidative film layer is higher than that of copper ions (Cu 2+ ).

2. The vertically interconnected packaging substrate according to claim 1, characterized in that: The reducing metal film layer is made of a material selected from zinc-copper alloy, iron-zinc alloy, nickel-tin alloy or aluminum-magnesium alloy; The oxidizing film layer is selected from ferric oxide or molybdenum oxide.

3. The vertically interconnected packaging substrate according to claim 1, characterized in that: The through hole comprises one of an offset hole, a waisted hole, a tapered hole or a straight hole.

4. The vertically interconnected packaging substrate according to claim 1, characterized in that: Positioning holes and a plurality of cross targets are arranged on the substrate.

5. The vertically interconnected packaging substrate according to claim 1, characterized in that: The metal oxide film layer is a titanium dioxide film layer, and its thickness is 5 to 20 nm. The titanium layer in the titanium / copper seed layer has a thickness of 100 to 120 nm, and the copper layer has a thickness of 1 to 3 μm; The reducing metal film layer is a zinc-copper alloy film layer with a thickness of 100 to 300 nm. The oxidizing film layer is a ferric oxide film layer with a thickness of 100 to 300 nm.

6. The vertically interconnected packaging substrate according to claim 1, characterized in that: The material of the substrate is selected from ceramics, organic plastics or glass.

7. A method for preparing the vertically interconnected packaging substrate according to claim 1, characterized in that: The following steps are involved: forming a through hole on a substrate, and forming a metal oxide film layer on an inner wall of the through hole by atomic layer deposition; Depositing a titanium / copper seed layer on the surface of the metal oxide film layer in the through hole and the surface of the substrate by magnetron sputtering; Depositing a reducing metal film layer on the surface of the seed layer in the through hole by magnetron sputtering, wherein the reducing property of the reducing metal film layer is stronger than that of metal copper (Cu); An oxidative film layer is deposited on the seed layer on the surface of the substrate by magnetron sputtering, wherein the metal ion reduction potential of the oxidative film layer is higher than that of copper ions (Cu 2+ ).

8. The method according to claim 7, characterized in that The step of forming a through hole on the substrate and forming a metal oxide film layer on the inner wall of the through hole by atomic layer deposition comprises: forming a through hole on the substrate, and providing positioning holes and cross targets on both sides of the substrate; Plasma etching and ultraviolet cleaning are performed on the inner wall of the through hole to increase the roughness; A titanium dioxide metal oxide film layer is formed on the inner wall of the through hole by atomic layer deposition.

9. The method according to claim 7, characterized in that: The step of depositing a titanium / copper seed layer on the surface of the metal oxide film layer in the through hole and the surface of the substrate by magnetron sputtering comprises: Depositing a titanium / copper seed layer on the surface of the metal oxide film layer in the through hole and the surface of the substrate by magnetron sputtering; Depositing a zinc-copper alloy reducing metal film layer on the surface of the titanium / copper seed layer in the through hole by magnetron sputtering; An oxidative film layer is deposited on the titanium / copper seed layer on the surface of the substrate by magnetron sputtering.

10. A method for electroplating copper filling using the vertically interconnected packaging substrate of claim 1, characterized in that: Pulse plating is used to fill the through holes.

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