Ceramic substrate stack structure and manufacturing method thereof

Abstract

The invention belongs to the technical field of ceramic substrate stacking, and particularly relates to a ceramic substrate stacking manufacturing method which comprises the following steps: S1, selecting a ceramic substrate made of aluminum oxide, aluminum nitride or silicon nitride; s2, selecting a material with a lattice constant similar to that of Cu as a buffer film; s3, heating the ceramic substrate to a specified temperature, so that atoms in the buffer film can be arranged and grow on the ceramic substrate in a relatively tidy manner; and S4, performing plasma bombardment by using an Al target material in a reaction type sputtering manner to enable the Al target material to react with N2 so as to form the buffer film on the ceramic substrate. According to the invention, the AlN or ZnO buffer film is formed on the ceramic substrate, rough plating height and pores of the ceramic substrate are blocked, the buffer film forms the substrate to slow down fluctuating fall, so that the copper seed layer can reduce offset and is relatively flat, and when the copper seed layer is flat, the copper seed layer is prevented from falling off. And in the photoresist layer in the subsequent process, the photoresist lamination is more perfect, so that the diffusion plating problem during copper electroplating is reduced, and the overall quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic substrate stacking, and in particular relates to a ceramic substrate stacking structure and a manufacturing method thereof. Background Art

[0002] DPC (Direct Plating Copper) is a ceramic circuit processing technology developed on the basis of ceramic thin film processing. Ceramic is used as the circuit substrate, a metal layer is composited on the substrate surface by sputtering, and the circuit is formed by electroplating and photolithography.

[0003] The surface roughness of traditional ceramic materials is too high, and there are many pits of different sizes on the surface. This phenomenon will cause the surface flatness of the ceramic substrate made of ceramic materials to be poor. Especially when the surface of the ceramic substrate is processed by semiconductor process or yellow light circuit is formed on it, the high average surface roughness of the ceramic substrate often leads to a significant reduction in the process yield. In addition, the higher the surface roughness, the more difficult it is for dry film photoresist or liquid photoresist to adhere evenly to the substrate surface, which often results in poor adhesion and photoresist floating film, or circuit infiltration during electroplating;

[0004] In addition (such as Figure 3-4 As shown in the figure, if the lattice constant of the ceramic substrate differs too much from the copper lattice mismatch, it will cause too much stress in the film. For example, the lattice constant of Cu FCC is 3.61A. The hexagonal stacking of Al2O3 has a=4.758c=12.99. The lattice constants of the two differ by 31%. If the lattice constant of the substrate differs too much from the copper lattice mismatch, it will cause too much stress in the film and poor adhesion of the copper layer. When the accumulated stress is too large, it will cause the substrate to bend. Summary of the invention

[0005] The object of the present invention is to provide a ceramic substrate stack and a manufacturing method thereof, aiming to solve the problem that the surface roughness of the conventional ceramic material is too high and there are many pits of different sizes on the surface. This phenomenon will cause the surface flatness of the ceramic substrate made of the ceramic material to be poor. In particular, when the surface of the ceramic substrate is processed by a semiconductor process or a yellow light circuit is formed thereon, the high average surface roughness of the ceramic substrate often leads to a significant reduction in the process yield. Moreover, the higher the surface roughness, the more difficult it is for the dry film photoresist or liquid photoresist to be uniformly attached to the substrate surface, which often results in poor adhesion and causes the photoresist to float, or circuit infiltration during the electroplating process; in addition (such as Figure 4As shown in the figure, if the lattice constant of the ceramic substrate differs too much from the copper lattice mismatch, it will cause too much stress in the film. For example, the lattice constant of Cu FCC is 3.61A. The hexagonal stacking of Al2O3 has a=4.758c=12.99. The lattice constants of the two differ by 31%. If the lattice constant of the substrate differs too much from the copper lattice mismatch, it will cause too much stress in the film and poor adhesion of the copper layer. When the accumulated stress is too large, it will cause the substrate to bend.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for manufacturing a ceramic substrate stack structure, comprising the following steps:

[0007] S1. Select a ceramic substrate made of aluminum oxide, aluminum nitride or silicon nitride;

[0008] S2, select a material with a lattice constant close to that of Cu as the buffer film;

[0009] S3, heating the ceramic substrate to a specified temperature so that the atoms in the buffer film can be arranged and grown more neatly on the ceramic substrate;

[0010] S4, sputtering the ceramic substrate by a reactive sputtering method, using an Al target material to pass through N2 gas, bombarded by plasma and reacting with N2 to form a buffer film on the ceramic substrate;

[0011] S5. Apply vacuum back pressure to the ceramic substrate and the buffer film as required to reduce copper oxidation caused by oxygen during high-temperature sputtering;

[0012] S6, adjusting the temperature to sputter copper on the buffer film to form a copper seed layer. Due to the buffering of the buffer film, the sputtered copper seeds can be relatively flat;

[0013] S7, using dry film photoresist or liquid photoresist to form photoresist on the copper seed layer. Since the surface of the copper seed layer is flat, the photoresist can be flatly attached by pressing or coating;

[0014] S8. Patterning the photoresist, and then electroplating the formed thick copper to be located between the photoresist patterns to form a circuit.

[0015] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, the materials in S2 having a lattice constant close to that of Cu are: AlN and ZnO.

[0016] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, the thickness of the buffer film in S2 is between 50 nm and 800 nm.

[0017] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, the heating temperature of the ceramic substrate in S3 is between 200 and 1000 degrees Celsius.

[0018] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, the vacuum back pressure in S5 is required to be 10^-6torr.

[0019] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, the thickness of the copper seed layer in S6 can be 50nm to 800nm, and the temperature of the sputtering copper is between 200 and 600 degrees Celsius.

[0020] As a preferred method for manufacturing a ceramic substrate stack structure of the present invention, in S7, the dry film photoresist is pressed onto the copper seed layer by a hot pressing roller; the liquid photoresist is attached to the copper seed layer by slid coating or spin coating.

[0021] A ceramic substrate stack structure comprises a ceramic substrate, a buffer film and a copper seed layer. The buffer film is arranged on the top of the ceramic substrate, and the copper seed layer is arranged on the top of the buffer film.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. By forming an AlN or ZnO buffer film on the ceramic substrate, the rough plating height and pores of the ceramic substrate are blocked, and the buffer film forms a substrate to reduce the height difference, so that the copper seed layer can reduce the step difference and be relatively flat. When the copper seed layer is flat, the photoresist can be more perfectly bonded in the photoresist layer in the subsequent process, thereby reducing the problem of copper electroplating and improving the overall quality.

[0024] 2. By using AlN or ZnO buffer films, the microstructure growth of copper metal during sputtering can be better, and the docking arrangement of heterogeneous atoms can be more matched, so that the internal stress of subsequent copper film growth can be reduced. In addition, the use of AlN and ZnO buffer films can allow copper atoms to grow into a film structure with orientation and epitaxy, which can improve adhesion and reduce copper film stress, thereby reducing the warping area of ​​the ceramic substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 It is a logical schematic diagram of the present invention;

[0027] Figure 2 It is a schematic diagram of the main structure of the present invention;

[0028] Figure 3 It is an enlarged schematic diagram of the surface of a conventional ceramic substrate of the present invention;

[0029] Figure 4 It is a schematic diagram of the lattice of a conventional ceramic substrate of the present invention.

[0030] In the figure: 1. Ceramic substrate; 2. Buffer film; 3. Copper seed layer. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1:

[0033] See also Figure 1-Figure 2 The present invention provides the following technical solution: a method for manufacturing a ceramic substrate stack structure, comprising the following steps:

[0034] S1, selecting a ceramic substrate 1 made of aluminum oxide, aluminum nitride or silicon nitride;

[0035] S2, select a material with a lattice constant close to that of Cu as the buffer film 2;

[0036] S3, heating the ceramic substrate 1 to a specified temperature so that the atoms in the buffer film 2 can be arranged and grown more neatly on the ceramic substrate;

[0037] S4, sputtering the ceramic substrate 1 by a reactive sputtering method, using an Al target material to pass through N2 gas, and forming a buffer film 2 on the ceramic substrate 1 through plasma bombardment and reaction with N2;

[0038] S5, applying vacuum back pressure to the ceramic substrate 1 and the buffer film 2 as required to reduce copper oxidation caused by oxygen during the high-temperature sputtering process;

[0039] S6, adjusting the temperature to sputter copper on the buffer film 2 to form a copper seed layer 3, the sputtered copper seeds can be relatively flat due to the buffering of the buffer film 2;

[0040] S7, using dry film photoresist or liquid photoresist to form photoresist on the copper seed layer 3. Since the surface of the copper seed layer 3 is flat, the photoresist can be flatly attached by pressing or coating;

[0041] S8, patterning the photoresist, and then electroplating the formed thick copper to be located between the photoresist patterns to form a circuit;

[0042] It is worth noting that the lattice constant mismatch between AlN and Cu is about 20%, the lattice constant of ZnO is a=3.25nm, c=0.52, and the lattice constant mismatch between ZnO and Cu is about 9.9%. AlN or ZnO buffer film is used to evenly cover the ceramic substrate 1 to shield the many defects generated during the sintering of AlN / Al2O3 / SiN / SiC on the ceramic substrate 1. These defects include microcracks, pores, impurities, grain boundary precipitates... The use of AlN or ZnO buffer film can make the Cu metal grow better during the sputtering microstructure, and the heterogeneous atoms can be more matched in docking and arrangement, so that the internal stress of the subsequent Cu film growth is reduced. The use of AlN and ZnO buffer films can make Cu atoms grow into a film structure with orientation and epitaxy, which can improve adhesion and reduce Cu film stress. Reduce the substrate warping area.

[0043] Preferred materials in S2 that have a lattice constant close to that of Cu are: AlN and ZnO.

[0044] Preferably, the thickness of the buffer film 2 in S2 is between 50 nm and 800 nm.

[0045] Preferably, the heating temperature of the ceramic substrate 1 in S3 is between 200 and 1000 degrees Celsius.

[0046] Preferably: the vacuum back pressure in S5 is required to be 10^-6torr.

[0047] Preferably, the thickness of the copper seed layer 3 in S6 may be 50 nm to 800 nm and the temperature of sputtering copper may be between 200 and 600 degrees Celsius.

[0048] Preferably, in S7 , the dry film photoresist is pressed onto the copper seed layer 3 by a hot pressing roller; the liquid photoresist is attached onto the copper seed layer 3 by slid coating or spin coating.

[0049] A ceramic substrate 1 stack structure comprises a ceramic substrate 1, a buffer film 2 and a copper seed layer 3. The buffer film 2 is arranged on the top of the ceramic substrate 1, and the copper seed layer 3 is arranged on the top of the buffer film 2.

[0050] Embodiment 2:

[0051] During processing, the DPC ceramic substrate 1 may need to be punched on both sides of the ceramic substrate 1 by laser. After the laser-punched hole wall is melted, it will be ups and downs, making the hole wall uneven, and the hole wall is prone to leakage during copper plating, resulting in the subsequent electroplating copper being unable to be uniformly plated. When the above situation occurs, the following methods are used:

[0052] 1. First, a ceramic substrate 1 made of aluminum oxide, aluminum nitride, or silicon nitride is selected, and a through hole is formed on both sides of the ceramic substrate 1 using a laser, and an AlN and ZnO buffer film is formed on the surface of the ceramic substrate 1 and on the side wall of the through hole;

[0053] 2. The ceramic substrate 1 is first heated to a specified temperature and then sputtered. This is mainly to allow the atoms in the buffer film 2 to be arranged and grown in a relatively neat manner, forming a smooth and well-arranged buffer layer on the ceramic substrate 1, wherein the substrate heating temperature can be 200 to 1000 degrees Celsius;

[0054] 3. Reactive sputtering is adopted, and Al target is used to react with N2 through plasma bombardment to form a buffer film 2 on the ceramic substrate 1. At this time, there will be high-temperature residues on the surface of the through hole. The buffer film 2 fills the height difference of the through hole side wall to make the hole wall smooth, and the hole wall can be evenly plated with copper during sputtering of copper in the subsequent process, and the electrical conduction can be made during the subsequent electroplating of copper to allow the through hole to be evenly plated with copper;

[0055] 4. Then, copper is sputtered onto the buffer film 2. The thickness of the copper layer can be 50nm to 800nm. The thickness of the buffer film can be 50nm to 800nm. Due to the buffering of the buffer film 2, the copper seed layer 3 can be flat after coating. When sputtering copper, the temperature needs to be adjusted to between 200 and 600 degrees Celsius, and the vacuum back pressure before sputtering is required to be pumped to 10^-6torr, so as to reduce the copper oxidation caused by oxygen during the high-temperature sputtering process;

[0056] 5. Use dry film photoresist or liquid photoresist. Dry film photoresist is pressed onto the copper seed layer 3 using a hot pressing roller, while liquid photoresist is applied by slid coating or spin coating. Since the surface of the copper seed layer 3 is flat, the photoresist can be evenly attached by pressing or coating.

[0057] 6. Then pattern the photoresist, and then use electroplating to make the formed thick copper located between the photoresist patterns to form a circuit;

[0058] By forming an AlN or ZnO buffer film on the surface of the ceramic substrate 1 and on the side walls of the through-hole, the buffer film 2 will fill the height difference of the side walls of the through-hole, so that the hole wall can be flat, and during the subsequent sputtering of copper, the hole wall can be evenly plated with copper and can be electrically conductive during electroplating of copper, allowing the through-hole to be evenly plated with copper.

[0059] Working principle: When using the ceramic substrate stack and its manufacturing method, first, select a ceramic substrate 1 made of aluminum oxide, aluminum nitride or silicon nitride, and select a material with a lattice constant close to that of Cu as the buffer film 2, then heat the ceramic substrate 1 to a specified temperature so that the atoms in the buffer film 2 can be arranged and grown more neatly on the ceramic substrate, and then use reactive sputtering to sputter the ceramic substrate 1, using Al target material through N2 gas, plasma bombardment and reaction with N2 to form a buffer film on the ceramic substrate 1 2. Apply vacuum back pressure to the ceramic substrate 1 and the buffer film 2 as required to reduce copper oxidation caused by oxygen during high-temperature sputtering. Adjust the temperature to sputter copper on the buffer film 2 to form a copper seed layer 3. Due to the buffering of the buffer film 2, the sputtered copper seed can be relatively flat. Use dry film photoresist or liquid photoresist to form photoresist on the copper seed layer 3. Since the surface of the copper seed layer 3 is flat, the photoresist can be flatly attached by pressing or coating. Finally, pattern the photoresist, and then use electroplating to make the formed thick copper located between the photoresist patterns to form a circuit.

[0060] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a ceramic substrate stack structure, characterized in that: The following steps are involved: S1, selecting a ceramic substrate (1) made of aluminum oxide, aluminum nitride or silicon nitride; S2, selecting a material with a lattice constant close to that of Cu as a buffer film (2); S3, heating the ceramic substrate (1) to a specified temperature so that the atoms in the buffer film (2) can be arranged and grown more neatly on the ceramic substrate; S4, evacuating the ceramic substrate (1) and the buffer film (2) as required to reduce copper oxidation caused by oxygen during the high-temperature sputtering process; S5, performing sputtering on the ceramic substrate (1) to form a buffer film (2) on both the front and back surfaces of the ceramic substrate (1); S6, adjusting the temperature to sputter copper onto the buffer film to form a copper seed layer (3), and the sputtered copper seeds can be relatively flat due to the buffering of the buffer film (2); S7, using dry film photoresist or liquid photoresist to form photoresist on the copper seed layer (3). Since the surface of the copper seed layer (3) is flat, the photoresist can be evenly attached by pressing or coating; S8, patterning the photoresist, exposing and developing the photoresist to form a pattern; S9, then electroplating is performed so that the formed thick copper is located between the photoresist patterns; S10, removing the photoresist to expose the copper seed layer (3) below the photoresist; S11, etching the copper seed layer (3) to form a circuit.

2. A method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The step S5 is to use reactive sputtering to introduce nitrogen and argon to form plasma, bombard the aluminum target, and reactively sputter to form an aluminum nitride AlN buffer film (2).

3. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The step S5 is to use the composite target material for sputtering, introduce argon gas to form plasma, bombard the AlN or ZnO or AZO composite target, and sputter-plate to form AlN, ZnO, AZO buffer films (2) respectively.

4. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The step S5 is to use reactive sputtering to introduce oxygen and argon to form plasma, bombard the aluminum target and the zinc target, and reactively sputter to form a zinc oxide ZnO or AZO buffer film (2).

5. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The thickness of the buffer film (2) in S2 is between 50nm and 800nm.

6. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The heating temperature of the ceramic substrate (1) in S3 is between 200 and 1000 degrees Celsius.

7. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The vacuum back pressure in S4 is required to be 10^-5torr~10^-6torr.

8. The method for manufacturing a ceramic substrate stack according to claim 1, characterized in that: The thickness of the copper seed layer (3) in S6 may be 50 nm to 800 nm, and the temperature of the sputtering copper is between 200 and 600 degrees Celsius.

9. The method for manufacturing a ceramic substrate stack structure according to claim 1, characterized in that: In S7, the dry film photoresist is pressed onto the copper seed layer (3) by a hot pressing roller; the liquid photoresist is attached to the copper seed layer (3) by slid coating or spin coating.

10. A ceramic substrate stack structure, comprising any one of claims 1 to 9, characterized in that: It comprises a ceramic substrate (1), a buffer film (2) and a copper seed layer (3), wherein the buffer film (2) is arranged on the top of the ceramic substrate (1), and the copper seed layer (3) is arranged on the top of the buffer film (2).

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