A metallized via thin film circuit and its manufacturing method

Abstract

The present invention relates to the field of semiconductor technology, and particularly to a metallized via thin film circuit and a preparation method thereof. The preparation method of the metallized via thin film circuit provided by the present invention prolongs the process by performing separate metallization, without restricting the production capacity burden of a single process, so that the production capacity is consistent with the production capacity of non-metallized via production. This aspect can be formally applied to industrialization, with a large process margin and relatively easy to carry out mass production processes. Moreover, by separately metallizing the holes, the influence of other etching processes on the simultaneous metallization of the holes is reduced, and the temperature resistance of the metal holes in the thin film circuit is improved. Since the fixture used in the present invention is a general fixture, compared with selective electroplating using a lithography fixture (a fixture needs to be made for each metallized via pattern), the present invention can meet the requirements of the existing design rules for the preparation of metallized vias without using a fixture.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a metallized hole thin film circuit and a preparation method thereof. Background Art

[0002] The thin film circuit hole metallization process technology is widely used in hybrid integrated circuits. It has great value in reducing microwave circuit crosstalk and insertion loss, increasing circuit heat dissipation and reliability. At the same time, due to the high frequency of microwave circuits, the surface wiring accuracy is high, and semiconductor photolithography must be used for wiring. The photoresist in the photolithography process must be photoresist, and photoresist is a colloid. It is difficult to completely fill or completely remove the photoresist in the metal hole during the thin film circuit metallization hole photolithography process. Therefore, the yield rate is low according to the traditional photolithography preparation process, which is mainly manifested in the incomplete metal layer of the metallized hole wall, defects, ridges, peeling and cracks, poor firmness, poor high temperature resistance of the metallized hole, blistering, cracks and peeling of the metal layer after high temperature baking at 400℃ for 10min, high resistance between holes, low qualified rate and other problems. The grounding hole is prone to open circuit during the subsequent assembly process and use of the circuit, affecting the assembly yield rate and long-term reliability of the product.

[0003] At present, the preparation of thin film circuits must adopt selective electroplating (also called graphic electroplating or adhesive electroplating) process. Since the circuit thickness in the preparation of thin film circuits must be at least 4μm, and the line width and seam of the surface wiring circuit must be 10μm, and the line accuracy must be within ±3μm, under such conditions, selective electroplating must be adopted to prepare circuit graphics with such accuracy. In contrast, it is difficult to achieve high accuracy of thicker circuit wiring by full-plate electroplating followed by photolithography etching. In addition, selective electroplating can produce complex circuit graphics, with advantages such as small side growth of the strip line, steep line edges, and high graphic resolution. However, when selective electroplating process is currently adopted to produce thin film circuits with metallized through holes, the use of uniform glue or spray glue process, or multiple masking and mask exposure with changing direction will affect mass production and finished graphics. Even so, the photoresist on the inner wall of the metallized hole cannot be completely removed. Therefore, insufficient exposure of the photoresist on the hole wall results in photoresist residue after development. During electroplating, metal cannot be plated where there is photoresist residue, which ultimately leads to poor grounding of the metallized hole or even a short circuit.

[0004] At present, the thin-film circuit metallization hole preparation technology adopts two schemes for the preparation of metallization holes. The first scheme is: after the metal layer of the thin-film metallization substrate is electroplated to thicken the entire board, the hole is evenly sprayed using a spray glue process. In addition, the metallization holes and surface pads need to be completely covered with photoresist. The second scheme is: selective electroplating, which requires the complete removal of the photoresist on the inner wall of the metallization hole. Currently, two schemes are used for exposure and development. First, two masks are used for exposure. The first mask is used to expose the line pattern first, and the second mask is only used to expose the hole. Second, the mask exposure fixture is designed, and the photoresist on the inner wall of the hole is completely removed by one exposure. Our current plan is to prepare thin-film circuits with metallization holes based on selective electroplating. First, the ceramic substrate is metallized by laser drilling, and then thin-film metallization sputtering is performed on both sides and the inner wall of the hole. After sputtering, the pattern is prepared by uniform glue or spraying, and it is ensured that the photoresist on the inner wall of the hole is not developed cleanly. Finally, after the pattern preparation is completed, a certain film system is sputtered on the front and the inner wall of the hole by physical gas phase, and then the inner wall of the hole and the back side are protected by the metal anti-etching layer. Finally, after the metallization corrosion is completed, the anti-etching layer is removed and the thin-film circuit metallization hole is completed.

[0005] However, the current method of preparing thin-film circuit metallization has many production limitations. First, the full-board electroplating method is used to produce metallized hole thin-film circuits. This method has large growth on the side of the line, easy distortion of the line edge, and low graphic resolution, which is not suitable for the production of high-frequency microwave thin-film circuits. Second, the use of a fixture to expose the metallized hole has great limitations on the graphics. The number and size of the holes are affected by this, and there are design limitations on the number and size of the holes; and it affects production efficiency. Generally, the exposure machine exposes one piece at a time. If the inner wall of the hole needs to be exposed, the efficiency will be reduced by at least 2 times, which makes it difficult to meet the mass production of such products. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a metallized hole thin film circuit and a preparation method thereof.

[0007] The present invention provides a method for preparing a metallized hole thin film circuit, comprising the following steps:

[0008] A) Drilling holes on the ceramic substrate with a laser and cleaning it;

[0009] B) depositing a tantalum nitride film on the front and back sides of the ceramic substrate obtained in step A), and sequentially sputtering a first titanium tungsten film and a first gold film on the tantalum nitride film to obtain a composite ceramic substrate;

[0010] C) The thin-film circuit is fabricated using a selective electroplating process. After the spray coating or spin coating process, photoresist is coated on the front side of the composite ceramic substrate obtained in step B) and inside the metallized holes. The metallized holes and non-graphic areas are covered, and after exposure, the thin-film circuit is selectively developed, and the photoresist on the inner wall of the holes and in the non-graphic areas is not developed;

[0011] D) After the selective development is completed, it is placed in a gold electroplating solution for gold electroplating, so that the areas where the photoresist is removed are covered with a gold electroplating layer;

[0012] E) Remove the photoresist on the inner wall of the holes and in the non-graphic areas, and etch the metallized hole areas and non-graphic areas to remove the metal layers in the metallized hole areas and non-graphic areas;

[0013] F) Sputter a second titanium-tungsten thin film and a second gold thin film in sequence on the front side of the thin-film circuit substrate obtained in step E) and on the inner wall of the metallized holes;

[0014] G) Perform a full-panel gold electroplating process on both sides of the thin-film circuit substrate obtained in step F);

[0015] H) Use a dry film as a photoresist on the front side of the thin-film circuit substrate obtained in step G) for exposure and development, so that the hole areas are developed and other areas are covered by the dry film, and then electroplate nickel. After the nickel electroplating is completed, remove the surface dry film;

[0016] I) Etch off the gold electroplating layer on the front side of the thin-film circuit substrate obtained in step H) with a gold etching solution prepared from a mixed aqueous solution of iodine and potassium iodide, wet-etch off the unnecessary titanium-tungsten thin film outside the designed pattern with a titanium-tungsten etching solution, and remove the nickel electroplating layer on the back side of the thin-film circuit substrate and on the inner wall of the holes with a nickel etching solution to obtain a metallized hole thin-film circuit.

[0017] Preferably, in step B), the method for depositing the tantalum nitride thin film is magnetron sputtering deposition;

[0018] The reaction gases used for depositing the tantalum nitride thin film include nitrogen and argon, and the gas partial pressure ratio of nitrogen to argon is 1:2 - 5;

[0019] The sheet resistance of the tantalum nitride thin film is 10 - 200 Ω / square;

[0020] The reaction gas used for sputtering the first titanium-tungsten thin film is argon, and the gas flow rate of argon is 65 - 75 sccm;

[0021] The thickness of the first titanium-tungsten thin film is 0.01 - 0.2 μm;

[0022] The reaction gas used for sputtering the first gold thin film is argon, and the gas flow rate of argon is 65 - 75 sccm;

[0023] The thickness of the first gold film is 0.1-0.3 μm.

[0024] Preferably, in step C), in the glue spraying process, the glue spraying solution ratio is 1:10, the glue spraying temperature is 83-87°C, the glue spraying flow rate is 1.2 mL / min, the glue spraying times are 4 times, and then the temperature is kept at 113-117°C for 4-6 minutes;

[0025] In the coating process, a layer of photoresist is obtained by spin coating, the rotation speed of the coating is 6800-7200 rpm, the coating time is 28-32 seconds, and then the coating is dried at 85-95° C. for 10-20 minutes;

[0026] Use a mask to cover the metallized holes and non-graphic areas;

[0027] The size of the hole on the mask is smaller than the size of the metallized hole.

[0028] Preferably, in step C), the development is carried out in an aqueous solution of sodium hydroxide;

[0029] The mass concentration of the aqueous solution of sodium hydroxide is 0.3% to 0.5%;

[0030] The development is carried out at room temperature, and the development time is 15 to 25 seconds.

[0031] Preferably, in step D), the current density of the gold electroplating is 0.1 to 0.3 A / dm 2 ;

[0032] The thickness of the electroplated gold layer is greater than 3 μm.

[0033] Preferably, in step E), acetone is used to remove the photoresist on the inner wall of the hole and the photoresist in the non-pattern area;

[0034] Etching the metallized hole region and the non-pattern region to remove the metal layer in the metallized hole region and the non-pattern region comprises:

[0035] Firstly, gold is etched by dry etching, and then titanium tungsten and tantalum nitride are etched by wet etching, so as to remove the metal layer in the metallized hole area and the non-pattern area;

[0036] The gold etching adopts argon gas, and the gas flow rate of the argon gas is 45-55 sccm;

[0037] The titanium-tungsten corrosion adopts a corrosion liquid of a hydrogen peroxide solution with a mass concentration of 25% to 35%, and the titanium-tungsten corrosion time is 1 to 10 minutes;

[0038] The etching solution used in the tantalum nitride etching includes hydrofluoric acid, nitric acid and water; the volume ratio of the hydrofluoric acid, nitric acid and water is 1.5-2.5:6-8:8-12;

[0039] The tantalum nitride is corroded at a temperature of 40 to 60° C. and for a time of 1 to 5 seconds.

[0040] Preferably, in step F), the reaction gas used for sputtering the second titanium-tungsten film is argon gas, and the gas flow rate of the argon gas is 65-75 sccm;

[0041] The thickness of the second titanium-tungsten film is 0.03-0.07 μm;

[0042] The reaction gas used for sputtering the second gold film is argon gas, and the gas flow rate of the argon gas is 65-75 sccm;

[0043] The thickness of the second gold film is 0.03-0.07 μm.

[0044] Preferably, in step G), the current density of the gold electroplating is 0.1 to 0.3 A / dm 2 ;

[0045] The thickness of the electroplated gold layer is greater than 1 μm.

[0046] Preferably, in step H), the exposure power is 580-620W and the exposure time is 8-12s;

[0047] The current density of the nickel electroplating is 0.1 to 0.3 A / dm 2 , time is 2 to 4 minutes;

[0048] The surface dry film is removed by using alcohol with a mass concentration of 93% to 98%.

[0049] Preferably, in step I), the iodine content in the gold etching solution is 55-65 g / L, and the potassium iodide content is 150-250 g / L;

[0050] The titanium-tungsten etching solution is a hydrogen peroxide solution with a mass concentration of 25% to 35%;

[0051] The nickel corrosion solution comprises sodium persulfate, nitric acid and water; the dosage ratio of the sodium sulfate, nitric acid and water is 13-17 g: 35-45 mL: 95-105 mL.

[0052] The present invention also provides a metallized hole thin film circuit prepared by the preparation method described above.

[0053] The present invention provides a method for preparing a thin-film circuit with a metallized hole. By performing separate metallization, the process is extended, and the capacity burden of a single process is not limited, so that the production capacity is consistent with the production capacity of non-metallized holes. This aspect can be formally applied to industrialization, has a large process margin, and is easier to carry out large-scale quantitative process production; furthermore, by performing metallization treatment on the holes separately, the influence of other etching processes of the metallized holes is reduced, thereby improving the temperature resistance of the metal holes in the thin-film circuit; since the fixture used in the present invention is a universal fixture, compared with the selective electroplating using a photolithography fixture (each metallized hole pattern requires a fixture), the present invention can prepare metallized holes that meet the requirements of existing design rules without using a fixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A three-dimensional diagram of a ceramic sheet used in preparing a mask provided in one embodiment of the present invention;

[0055] Figure 2 A top view of a ceramic sheet used for preparing a mask provided in one embodiment of the present invention;

[0056] Figure 3 A schematic structural diagram of a mask provided by an embodiment of the present invention;

[0057] Figure 4 A schematic diagram of the structure of a composite ceramic substrate obtained in step B) according to an embodiment of the present invention;

[0058] Figure 5 A schematic diagram of the structure of a thin film circuit after exposure provided by an embodiment of the present invention;

[0059] Figure 6 A schematic diagram of the structure of a thin film circuit after gold electroplating provided by an embodiment of the present invention;

[0060] Figure 7 A schematic diagram of the structure of a thin film circuit after etching provided by an embodiment of the present invention;

[0061] Figure 8 A schematic diagram of the structure of a thin film circuit obtained in step F) according to an embodiment of the present invention;

[0062] Fig. 9 A schematic diagram of the structure of a thin film circuit after a full-board gold plating process provided by an embodiment of the present invention;

[0063] Fig.10 A schematic diagram of the structure of a thin film circuit after nickel electroplating provided by an embodiment of the present invention;

[0064] Fig.11A schematic diagram of the structure of a metallized hole thin film circuit provided by an embodiment of the present invention;

[0065] Fig.12 This is a hole wall morphology image of a metallized hole after baking in Example 2 of the present invention. DETAILED DESCRIPTION

[0066] The technical solution of the present invention will be clearly and completely described below in conjunction with 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.

[0067] The present invention provides a method for preparing a metallized hole thin film circuit, comprising the following steps:

[0068] A) Drilling holes on the ceramic substrate with a laser and cleaning it;

[0069] B) depositing a tantalum nitride film on the front and back sides of the ceramic substrate obtained in step A), and sequentially sputtering a first titanium tungsten film and a first gold film on the tantalum nitride film to obtain a composite ceramic substrate;

[0070] C) using a selective electroplating process to make a thin film circuit, after a spraying or coating process, the front side of the composite ceramic substrate obtained in step B) and the metallized holes are covered with photoresist, the metallized holes and non-patterned areas are covered, and after exposure, the thin film circuit is selectively developed, and the photoresist on the inner wall of the hole and the photoresist in the non-patterned area are not developed;

[0071] D) after the selective development is completed, placing the solution in a gold electroplating solution for gold electroplating, so that the area where the photoresist is removed is covered with a gold electroplating layer;

[0072] E) removing the photoresist on the inner wall of the hole and the photoresist in the non-pattern area, and etching the metallized hole area and the non-pattern area to remove the metal layer in the metallized hole area and the non-pattern area;

[0073] F) sputtering a second titanium-tungsten thin film and a second gold thin film in sequence on the front surface of the thin film circuit substrate and the inner wall of the metallized hole obtained in step E);

[0074] G) performing a full-plate gold plating process on both sides of the thin film circuit substrate obtained in step F);

[0075] H) exposing and developing the front side of the thin film circuit substrate obtained in step G) using the dry film as a photoresist so that the hole area is developed and other areas are covered by the dry film, and then electroplating nickel is performed, and after the electroplating nickel is completed, the surface dry film is removed;

[0076] I) using a gold etching solution prepared from a mixed aqueous solution of iodine and potassium iodide to etch away the electroplated gold layer on the front side of the thin film circuit substrate obtained in step H), using a titanium tungsten etching solution to wet-etch away unnecessary titanium tungsten thin films outside the design pattern, and using a nickel etching solution to remove the electroplated nickel layer on the back side of the thin film circuit substrate and the inner wall of the hole, thereby obtaining a metallized hole thin film circuit.

[0077] In step A):

[0078] In some embodiments of the present invention, drilling holes on the ceramic substrate using a laser includes: drilling holes on the ceramic substrate using a laser using a layout of holes on a mask.

[0079] In some embodiments of the present invention, the mask is prepared according to the following method:

[0080] A ceramic sheet with a size of 4 mm × 6 mm was selected and arranged in a square area of ​​50.8 mm × 50.8 mm to prepare a mask.

[0081] In some embodiments of the present invention, the diameter of the metallized hole of the ceramic sheet is 0.3 mm, and the thickness of the ceramic sheet is 0.381 mm.

[0082] In some embodiments of the present invention, the non-pattern area on the mask is opaque, and the pattern area is translucent. During the mask preparation process, the hole pattern diameter of the ceramic sheet is reduced by 0.01 mm and is opaque.

[0083] Figure 1 A three-dimensional diagram of a ceramic sheet used in preparing a mask provided in one embodiment of the present invention; Figure 2 A top view of a ceramic sheet used for preparing a mask provided in one embodiment of the present invention; Figure 3 A schematic structural diagram of a mask provided in one embodiment of the present invention.

[0084] In some embodiments of the present invention, the size of the ceramic substrate is 50.8 mm×50.8 mm×0.381 mm.

[0085] In some embodiments of the present invention, the diameter of the hole drilled on the ceramic substrate by laser is 0.3 mm.

[0086] In some embodiments of the present invention, the laser device is a fiber laser device or an ultraviolet laser device.

[0087] In some embodiments of the present invention, the cleaning comprises: ultrasonic cleaning using acetone and alcohol in sequence.

[0088] In step B):

[0089] In certain embodiments of the present invention, the method for depositing tantalum nitride thin film is magnetron sputtering deposition, and a tantalum target with a purity of 99.99% is used.

[0090] In certain embodiments of the present invention, the reactive gases used for depositing tantalum nitride thin film include nitrogen and argon, and the gas partial pressure ratio of nitrogen to argon is 1:2 to 5. In certain embodiments, the gas partial pressure ratio of nitrogen to argon is 1:3.

[0091] In certain embodiments of the present invention, the sheet resistance of the tantalum nitride thin film is 10 to 200 Ω / square. In certain embodiments, the sheet resistance of the tantalum nitride thin film is 36 to 45 Ω / square. In certain embodiments, the sheet resistance of the tantalum nitride thin film is 40 ± 5% Ω / square.

[0092] In certain embodiments of the present invention, the reactive gas used for sputtering the first titanium tungsten thin film is argon, and the gas flow rate of argon is 65 to 75 sccm. In certain embodiments, the gas flow rate of argon is 70 sccm.

[0093] In certain embodiments of the present invention, the thickness of the first titanium tungsten thin film is 0.01 to 0.2 μm. In certain embodiments, the thickness of the first titanium tungsten thin film is 0.12 μm.

[0094] In certain embodiments of the present invention, a titanium tungsten target is used for sputtering the first titanium tungsten thin film.

[0095] In certain embodiments of the present invention, the reactive gas used for sputtering the first gold thin film is argon, and the gas flow rate of argon is 65 to 75 sccm. In certain embodiments, the gas flow rate of argon is 70 sccm.

[0096] In certain embodiments of the present invention, a gold target with a purity of 99.999% is used for sputtering the first gold thin film.

[0097] In certain embodiments of the present invention, the thickness of the first gold thin film is 0.1 to 0.3 μm. In certain embodiments, the thickness of the first gold thin film is 0.2 μm.

[0098] Figure 4 Schematic structural diagram of the composite ceramic substrate obtained in step B) provided for an embodiment of the present invention.

[0099] In step C):

[0100] In certain embodiments of the present invention, the photoresist is AZP4620 positive photoresist.

[0101] In some embodiments of the present invention, in the glue spraying process, the glue spraying solution ratio is 1:8-12, the glue spraying temperature is 83-87°C, the glue spraying flow rate is 0.8-1.5 mL / min, the glue spraying times are 1-6 times, and then the temperature is kept at 113-117°C for 4-6 minutes. In some embodiments, in the glue spraying process, the glue spraying solution ratio is 1:10, the glue spraying temperature is 85°C, the glue spraying flow rate is 1.2 mL / min, the glue spraying times are 4 times, and then the temperature is kept at 115°C for 5 minutes.

[0102] In some embodiments of the present invention, in the coating process, a layer of photoresist is obtained by spin coating, the coating speed is 6800-7200 rpm, the coating time is 28-32 s, and then the coating is dried at 85-95° C. for 10-20 min. In some embodiments, the coating speed is 7000 rpm, the coating time is 30 s, and then the coating is dried at 90° C. for 15 min.

[0103] In some embodiments of the present invention, the metallized holes and non-patterned areas are covered by the mask described above. The hole size on the mask is smaller than the size of the metallized holes. In some embodiments of the present invention, the hole size on the mask is 0.01 mm smaller than the size of the metallized holes.

[0104] In some embodiments of the invention, the exposing comprises:

[0105] The photolithography equipment is aligned and ultraviolet contact exposure is adopted.

[0106] In some embodiments of the present invention, the exposure light intensity is 15-25 mW / cm 2 In some embodiments, the exposure light intensity is 20 mW / cm 2 .

[0107] In some embodiments of the present invention, the exposure time of the glue spraying process is 18 to 22 seconds. In some embodiments, the exposure time of the glue spraying process is 20 seconds.

[0108] In some embodiments of the present invention, the exposure time of the coating process is 8 to 12 seconds. In some embodiments, the exposure time of the coating process is 10 seconds.

[0109] Figure 5 A schematic diagram of the structure of a thin film circuit after exposure provided by an embodiment of the present invention.

[0110] In some embodiments of the present invention, the development is performed in a sodium hydroxide solution; the mass concentration of the sodium hydroxide aqueous solution is 0.3% to 0.5%. In some embodiments, the mass concentration of the sodium hydroxide aqueous solution is 0.5%.

[0111] In some embodiments of the present invention, the development is performed at room temperature for 15 to 25 seconds. In some embodiments, the development time is 20 seconds.

[0112] In some embodiments of the present invention, after the development, the process further comprises: rinsing with deionized water, drying with nitrogen, and then drying. In some embodiments, the deionized water rinsing time is 30 seconds; the drying temperature is 115° C. and the drying time is 20 minutes.

[0113] In step D):

[0114] In some embodiments of the present invention, before placing in a gold electroplating solution for gold electroplating, the method further comprises:

[0115] At room temperature, the product is sequentially subjected to degreasing treatment with a degreasing agent for 30 to 60 seconds, washing with high-purity water for 60 seconds, acid activation with hydrochloric acid having a mass concentration of 8% to 12% for 30 to 60 seconds, and washing with high-purity water for 60 seconds.

[0116] The present invention has no special restrictions on the type and source of the electroplating gold solution, and the electroplating gold solution can be a common commercially available electroplating gold solution.

[0117] In some embodiments of the present invention, the current density of the electroplated gold is 0.1-0.3A / dm 2 In some embodiments, the current density of the electroplated gold is 0.2A / dm 2 .

[0118] In some embodiments of the present invention, the thickness of the electroplated gold layer is greater than 3 μm. In some embodiments, the thickness of the electroplated gold layer is 4 μm.

[0119] In some embodiments of the present invention, after the gold electroplating is completed, the process further comprises: washing with high-purity water for 50 to 70 seconds, then boiling in boiling water for 8 to 12 minutes, and drying. In some embodiments, after the gold electroplating is completed, the process further comprises: washing with high-purity water for 60 seconds, then boiling in boiling water for 10 minutes, and drying using a spin dryer.

[0120] Figure 6 A schematic structural diagram of a thin film circuit after gold electroplating provided by an embodiment of the present invention.

[0121] In step E):

[0122] In some embodiments of the present invention, acetone is used to remove the photoresist on the inner wall of the hole and the photoresist in the non-pattern area.

[0123] In some embodiments of the present invention, etching the metallized hole region and the non-pattern region to remove the metal layer in the metallized hole region and the non-pattern region comprises:

[0124] Gold etching is first performed by dry etching, and titanium tungsten etching and tantalum nitride etching are then performed by wet etching, thereby removing the metal layer in the metallized hole area and the non-pattern area.

[0125] In some embodiments of the present invention, the gold etching is performed using argon gas, and the gas flow rate of the argon gas is 45-55 sccm. In some embodiments, the gas flow rate of the argon gas is 50 sccm.

[0126] In some embodiments of the present invention, RIE600 dry etching equipment is used to perform gold etching.

[0127] In some embodiments of the present invention, the etching liquid used in the titanium-tungsten corrosion is a hydrogen peroxide solution with a mass concentration of 25% to 35%, and the titanium-tungsten corrosion time is 1 to 10 minutes. In some embodiments, the etching liquid used in the titanium-tungsten corrosion is a hydrogen peroxide solution with a mass concentration of 30%, and the titanium-tungsten corrosion time is 5 minutes.

[0128] In some embodiments of the present invention, the etching solution used for the tantalum nitride etching includes hydrofluoric acid, nitric acid and water; the volume ratio of the hydrofluoric acid, nitric acid and water is 1.5-2.5:6-8:8-12. In some embodiments, the volume ratio of the hydrofluoric acid, nitric acid and water is 2:7:10.

[0129] In some embodiments of the present invention, the temperature of the tantalum nitride etching is 40-60° C., and the time is 1-5 seconds. In some embodiments, the temperature of the tantalum nitride etching is 50° C., and the time is 3 seconds.

[0130] Figure 7 A schematic diagram of the structure of a thin film circuit after etching provided by an embodiment of the present invention.

[0131] In step F):

[0132] In some embodiments of the present invention, before sputtering the second titanium-tungsten film and the second gold film, the process further includes: sequentially cleaning the front surface of the thin film circuit substrate and the inner wall of the metallized hole obtained in step E) with acetone and alcohol, and drying.

[0133] In some embodiments of the present invention, the reaction gas used for sputtering the second titanium-tungsten film is argon gas, and the gas flow rate of the argon gas is 65-75 sccm. In some embodiments, the gas flow rate of the argon gas is 70 sccm.

[0134] In some embodiments of the present invention, the thickness of the second titanium-tungsten film is 0.03-0.07 μm. In some embodiments, the thickness of the second titanium-tungsten film is 0.05 μm.

[0135] In some embodiments of the present invention, a titanium-tungsten target is used for sputtering the second titanium-tungsten film.

[0136] In some embodiments of the present invention, the reaction gas used for sputtering the second gold film is argon gas, and the gas flow rate of the argon gas is 65-75 sccm. In some embodiments, the gas flow rate of the argon gas is 70 sccm.

[0137] In some embodiments of the present invention, a gold target with a purity of 99.999% is used for sputtering the second gold film.

[0138] In some embodiments of the present invention, the thickness of the second gold film is 0.03-0.07 μm. In some embodiments, the thickness of the second gold film is 0.05 μm.

[0139] Figure 8 A schematic diagram of the structure of a thin film circuit obtained in step F) according to an embodiment of the present invention.

[0140] In step G):

[0141] In some embodiments of the present invention, before performing full-board gold electroplating, the method further includes:

[0142] At room temperature, the product is sequentially subjected to degreasing treatment with a degreasing agent for 30 to 60 seconds, washing with high-purity water for 60 seconds, acid activation with hydrochloric acid having a mass concentration of 8% to 12% for 30 to 60 seconds, and washing with high-purity water for 60 seconds.

[0143] The present invention has no special restrictions on the type and source of the electroplating gold solution, and the electroplating gold solution can be a common commercially available electroplating gold solution.

[0144] In some embodiments of the present invention, the current density of the electroplated gold is 0.1-0.3A / dm 2 In some embodiments, the current density of the electroplated gold is 0.2A / dm 2 .

[0145] In some embodiments of the present invention, the thickness of the electroplated gold layer is greater than 1 μm. In some embodiments, the thickness of the electroplated gold layer is 1.5 μm.

[0146] In some embodiments of the present invention, after the gold electroplating is completed, the process further comprises: washing with high-purity water for 50 to 70 seconds, then boiling in boiling water for 8 to 12 minutes, and drying. In some embodiments, after the gold electroplating is completed, the process further comprises: washing with high-purity water for 60 seconds, then boiling in boiling water for 10 minutes, and drying using a spin dryer.

[0147] Fig. 9 A schematic diagram of the structure of a thin film circuit after a full-board gold plating process is provided in one embodiment of the present invention.

[0148] In step H):

[0149] In some embodiments of the present invention, the dry film is DuPont FX940; the temperature of applying the dry film on the front of the thin film circuit substrate obtained in step G) is 90-100° C. In some embodiments, the temperature of applying the dry film on the front of the thin film circuit substrate obtained in step G) is 95° C.

[0150] In certain embodiments of the present invention, a photomask is used for exposure. During the exposure process, the metallized hole area of ​​the thin film circuit substrate needs to be light-transmissive. The light-transmitting hole size of the photomask is 0.03 mm smaller than the metallized hole size, and other areas are covered by dry film.

[0151] In some embodiments of the present invention, the exposure power is 580-620W, and the exposure time is 8-12s. In some embodiments, the exposure power is 600W, and the exposure time is 10s.

[0152] In some embodiments of the present invention, the current density of the nickel electroplating is 0.1-0.3A / dm 2 In some embodiments, the current density of the nickel electroplating is 0.2A / dm 2 , time is 3min.

[0153] In some embodiments of the present invention, the thickness of the electroplated nickel is 0.2-1.5 μm. In some embodiments, the thickness of the electroplated nickel is 0.5 μm.

[0154] The present invention has no special restrictions on the type and source of the nickel electroplating solution used in the nickel electroplating, and it can be a common commercially available nickel electroplating solution.

[0155] Fig.10 A schematic diagram of the structure of a thin film circuit after nickel electroplating provided by an embodiment of the present invention.

[0156] In certain embodiments of the present invention, the surface dry film is removed by using alcohol having a mass concentration of 93% to 98%.

[0157] In step I):

[0158] In some embodiments of the present invention, the iodine content of the gold etching solution is 55-65 g / L, and the potassium iodide content is 150-250 g / L. In some embodiments, the iodine content of the gold etching solution is 60 g / L, and the potassium iodide content is 200 g / L.

[0159] In some embodiments of the present invention, the titanium-tungsten etching solution is a hydrogen peroxide solution with a mass concentration of 25% to 35%. In some embodiments, the titanium-tungsten etching solution is a hydrogen peroxide solution with a mass concentration of 30%.

[0160] In some embodiments of the present invention, the nickel corrosion solution includes sodium persulfate, nitric acid and water; the usage ratio of sodium sulfate, nitric acid and water is 13-17 g: 35-45 mL: 95-105 mL. In some embodiments, the usage ratio of sodium sulfate, nitric acid and water is 15 g: 40 mL: 100 mL.

[0161] In some embodiments of the present invention, after removing the electroplated nickel layer, the process further comprises: rinsing with high-purity water and vacuum drying. In some embodiments, the high-purity water rinsing time is 60 seconds, and the vacuum drying temperature is 85-110°C.

[0162] Fig.11 A schematic diagram of the structure of a metallized hole film circuit provided by an embodiment of the present invention.

[0163] The present invention also provides a metallized hole thin film circuit as described above.

[0164] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0165] Beneficial effects:

[0166] The present invention performs metallization treatment on the holes separately without affecting the front circuit, so that the yield of the metallized holes can be improved by adding processes under selective electroplating, and the integrity rate of the metallized holes can be guaranteed to reach more than 99%, and the metallized holes of the thin film circuit can withstand a high temperature of 400°C.

[0167] The preparation method provided by the present invention is applied to industrialization, has a large process margin, and is relatively easy to carry out large-scale quantitative process production.

[0168] Compared with selective electroplating using a photolithography fixture (each metallized hole pattern requires a fixture), the present invention can prepare metallized holes that meet the requirements of existing design rules without using a fixture.

[0169] To further illustrate the present invention, a metallized via thin film circuit and its preparation method provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0170] The raw materials used in the following examples are all commercially available.

[0171] Example 1

[0172] 1. Select a ceramic chip with dimensions of 4 mm × 6 mm (as shown in Figure 1 and Figure 2 ). The metallized via aperture of the ceramic chip is 0.3 mm, and the thickness of the ceramic chip is 0.381 mm. It is typeset within a square area of 50.8 mm × 50.8 mm to prepare a mask plate (as shown in Figure 3 ). The non-graphic area on the mask plate is light-impermeable, and the graphic area is light-permeable. During the preparation of the mask plate, the hole pattern diameter of the ceramic chip is reduced by 0.01 mm and is light-impermeable.

[0173] 2. Use the hole layout method on the mask plate to punch holes in a ceramic substrate with dimensions of 50.8 mm × 50.8 mm × 0.381 mm using a laser. The aperture of the punched hole is 0.3 mm.

[0174] 3. Deposit tantalum nitride thin films on the front and back of the ceramic substrate by magnetron sputtering, and sequentially sputter a first titanium tungsten thin film and a first gold thin film on the tantalum nitride thin films to obtain a composite ceramic substrate.

[0175] When depositing the tantalum nitride thin film, a tantalum target with a purity of 99.99% is used, and the reaction gases include nitrogen and argon. The gas partial pressure ratio of nitrogen and argon is 1:3, and the sheet resistance of the tantalum nitride thin film is 40 ± 5% Ω / square.

[0176] When sputtering the first titanium tungsten thin film, a titanium tungsten target is used, and the reaction gas is argon. The gas flow rate of argon is 70 sccm, and the thickness of the first titanium tungsten thin film is 0.12 μm.

[0177] When sputtering the first gold thin film, a gold target with a purity of 99.999% is used, and the reaction gas is argon. The gas flow rate of argon is 70 sccm, and the thickness of the first gold thin film is 0.2 μm. As shown in Figure 4 ;

[0178] 4. Use a selective electroplating process to fabricate the thin film circuit. Use a spin coating process to cover the AZP4620 positive photoresist on the front of the composite ceramic substrate and inside the metallized vias, cover the metallized vias and non-graphic areas, align through a lithography machine, and use ultraviolet contact exposure (as shown in Figure 5As shown), the thin film circuit is selectively developed, and the photoresist on the inner wall of the hole and the photoresist in the non-pattern area are not developed;

[0179] In the glue-spinning process, the glue-spinning speed is 7000 rpm, the glue-spinning time is 30 s, and then it is dried in a constant temperature drying oven at 90°C for 15 min;

[0180] The exposure light intensity is 20 mW / cm 2 , time is 10s;

[0181] The development is carried out in a sodium hydroxide aqueous solution with a mass concentration of 0.5%;

[0182] The development is carried out at room temperature, and the development time is 20s;

[0183] After the development, the film was rinsed with deionized water for 30 seconds, dried with nitrogen, and then dried at 115° C. for 20 minutes;

[0184] 5. After the selective development is completed, the product is subjected to degreasing treatment with a degreasing agent for 40 seconds, washing with high-purity water for 60 seconds, activation with 10% hydrochloric acid for 40 seconds, and washing with high-purity water for 60 seconds at room temperature.

[0185] Then, the gold was electroplated in a gold plating solution with a current density of 0.2A / dm 2 , so that the area where the photoresist is removed covers the electroplated gold layer (such as Figure 6 As shown), the thickness of the electroplated gold layer is 4 μm. After the electroplating, it is washed with high-purity water for 60 seconds, then boiled in boiling water for 10 minutes, and dried using a spin dryer;

[0186] 6. Acetone was used to remove the photoresist on the inner wall of the hole and the photoresist in the non-patterned area, and RIE600 dry etching equipment was used to perform gold etching on the entire thin film circuit. Argon gas was used for gold etching, and the gas flow rate of argon gas was 50 sccm. After the gold was etched, the titanium tungsten in the non-patterned area and the inner wall of the metallized hole was corroded. The etching liquid was a 30% hydrogen peroxide solution, and the etching time was 5 min. After the titanium tungsten was corroded, the tantalum nitride in the non-patterned area and the inner wall of the metallized hole was corroded. The tantalum nitride etching solution was HF:HNO 3 :H 2 O = 2mL: 7mL: 10mL, the etching temperature is 50°C, and the etching time is 3s; thereby removing the metal layer in the metallized hole area and the non-pattern area (such as Figure 7 shown);

[0187] 7. Clean the front surface of the thin film circuit substrate and the inner wall of the metallized hole obtained in step E) with acetone and alcohol in sequence, and after drying, sputter a second titanium tungsten film and a second gold film (such as Figure 8 shown);

[0188] The second titanium-tungsten film is sputtered using a titanium-tungsten target, and the reaction gas is argon gas, and the gas flow rate of the argon gas is 70 sccm; the thickness of the second titanium-tungsten film is 0.05 μm;

[0189] The second gold film is sputtered using a gold target with a purity of 99.999%, and the reaction gas is argon gas with a gas flow rate of 70 sccm; the thickness of the second gold film is 0.05 μm;

[0190] 8. At room temperature, the thin film circuit substrate obtained in step 7 is subjected to a degreasing agent degreasing treatment for 30 to 60 seconds, a high-purity water cleaning for 60 seconds, an 8% to 12% hydrochloric acid pickling activation for 30 to 60 seconds, and a high-purity water cleaning for 60 seconds; then, the thin film circuit substrate is subjected to a full-board electroplating gold process (such as Fig. 9 The current density of the electroplated gold is 2A / dm 2 The thickness of the electroplated gold layer was 1.5 μm. After the electroplating, it was washed with high-purity water for 60 seconds, then boiled in boiling water for 10 minutes, and dried in a spin dryer.

[0191] 9. Use the dry film as a photoresist for exposure and development. The dry film is DuPont FX940. The dry film is attached to the front of the thin film circuit substrate obtained in step 8. The film attaching temperature is 95° C. The exposure uses a photomask. During the exposure process, the metallized hole area of ​​the thin film circuit substrate needs to be transparent, and other areas are covered by the dry film. The transparent hole size of the photomask is 0.03 mm smaller than the metallized hole size. The exposure power is 600 W and the time is 10 s. After the metallized hole area is developed, electroplating nickel (such as Fig.10 As shown), after the nickel plating is completed, the surface dry film is removed;

[0192] The current density of the nickel electroplating is 0.2A / dm 2 , time is 3min, and the electroplating nickel thickness is 0.5μm;

[0193] The surface dry film is removed by using alcohol with a mass concentration of 95%;

[0194] 10. Use a gold etching solution prepared from a mixed aqueous solution of iodine and potassium iodide to etch off the electroplated gold layer on the front side of the thin film circuit substrate obtained in step 9, use a titanium tungsten etching solution to wet-etch off the unnecessary titanium tungsten film outside the design pattern, and use a nickel etching solution to remove the electroplated nickel layer on the back side of the thin film circuit substrate and the inner wall of the hole, rinse with pure water, and then put it in an oven for drying. The obtained metallized hole thin film circuit (such as Fig.11 shown);

[0195] The gold etching solution has an iodine content of 60 g / L and a potassium iodide content of 200 g / L;

[0196] The titanium-tungsten etching solution is a hydrogen peroxide solution with a mass concentration of 30%;

[0197] The nickel corrosion solution comprises sodium persulfate, nitric acid and water; the volume ratio of the sodium sulfate, nitric acid and water is 15g:40mL:100mL.

[0198] The integrity rate of the metallized holes in the metallized hole thin film circuit obtained in Example 1 was examined, and the experimental results showed that the integrity rate of the metallized holes in the metallized hole thin film circuit was greater than 99%.

[0199] Example 2

[0200] The 50.8mm×50.8mm×0.381mm metallized hole thin film circuit prepared in Example 1 was placed in a 400℃ oven for 5min, 10min, 30min, and 8h baking. The side effects of each hole were observed. It was found that after baking for no more than 8h, the metal layers on both sides of the 140 metal holes on the 50.8mm×50.8mm×0.381mm ceramic substrate were intact and without defects, and the metal layer on the hole wall had almost no bulges, peeling, or cracks; the metallized holes had good high temperature resistance, and the metal layer on the hole wall had no blistering, cracks, or peeling; the resistance between the two metallized holes was less than 0.02Ω. The hole wall morphology is as follows Fig.12 shown. Fig.12 This is a hole wall morphology image of a metallized hole after baking in Example 2 of the present invention. Fig.12 It can be seen that there is no blistering, cracking, peeling or cracking in the metal layer of the hole wall.

[0201] Therefore, the preparation method of the present invention improves the production capacity of the metallized hole thin film circuit substrate and effectively solves the problem of low qualified rate of microwave thin film circuit substrate products.

[0202] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a metallized via thin film circuit, comprising the following steps: A) Punch holes in a ceramic substrate with a laser and clean it; B) Deposit tantalum nitride thin films on the front and back of the ceramic substrate obtained in step A), and sequentially sputter a first titanium tungsten thin film and a first gold thin film on the tantalum nitride thin films to obtain a composite ceramic substrate; C) Fabricate a thin film circuit using a selective electroplating process. After the spraying or spin coating process, a photoresist is covered on the front of the composite ceramic substrate obtained in step B) and inside the metallized vias. The metallized vias and non-graphic areas are covered, and after exposure, the thin film circuit is selectively developed, and the photoresist on the inner wall of the vias and the photoresist in the non-graphic areas are not developed; D) After the selective development is completed, place it in an electroplating gold solution for electroplating gold so that the areas where the photoresist is removed are covered with an electroplated gold layer; E) Remove the photoresist on the inner wall of the vias and the photoresist in the non-graphic areas, and etch the metallized via areas and non-graphic areas to remove the metal layers in the metallized via areas and non-graphic areas; F) Sequentially sputter a second titanium tungsten thin film and a second gold thin film on the front of the thin film circuit substrate obtained in step E) and on the inner wall of the metallized vias; G) Perform a full-plate electroplating gold process on both sides of the thin film circuit substrate obtained in step F); H) Use a dry film as a photoresist on the front of the thin film circuit substrate obtained in step G) for exposure and development, so that the via areas are developed and other areas are covered by the dry film, and then electroplate nickel. After the electroplating of nickel is completed, remove the surface dry film; I) Etch the electroplated gold layer on the front of the thin film circuit substrate obtained in step H) with a gold etching solution prepared from a mixed aqueous solution of iodine and potassium iodide, wet-etch the unnecessary titanium tungsten thin film outside the designed pattern with a titanium tungsten etching solution, and remove the electroplated nickel layer on the back of the thin film circuit substrate and the inner wall of the vias with a nickel etching solution to obtain a metallized via thin film circuit.

2. The preparation method according to claim 1, characterized in that, in step B), the method for depositing the tantalum nitride thin film is magnetron sputtering deposition; the reaction gases used for depositing the tantalum nitride thin film include nitrogen and argon, and the gas partial pressure ratio of the nitrogen and argon is 1:2 - 5; the sheet resistance of the tantalum nitride thin film is 10 - 200 Ω / square; the reaction gas used for sputtering the first titanium tungsten thin film is argon, and the gas flow rate of the argon is 65 - 75 sccm; the thickness of the first titanium tungsten thin film is 0.01 - 0.2 μm; the reaction gas used for sputtering the first gold thin film is argon, and the gas flow rate of the argon is 65 - 75 sccm; the thickness of the first gold thin film is 0.1 - 0.3 μm.

3. The preparation method according to claim 1, characterized in that, in step C), in the spraying process, the spraying solution ratio is 1:10, the spraying temperature is 83 - 87 °C, the spraying flow rate is 1.2 mL / min, the spraying times are 4 times, and then keep it warm at 113 - 117 °C for 4 - 6 min; in the spin coating process, a layer of photoresist is obtained by spin coating, the rotation speed of the spin coating is 6800 - 7200 rpm, the spin coating time is 28 - 32 s, and then dry it at 85 - 95 °C for 10 - 20 min; Cover the metallized holes and non-graphic areas with a mask; The hole size on the mask is smaller than the size of the metallized holes.

4. The preparation method according to claim 1, characterized in that, in step C), the development is carried out in an aqueous solution of sodium hydroxide; the mass concentration of the aqueous solution of sodium hydroxide is 0.3% - 0.5%; the development is carried out at room temperature, and the development time is 15 - 25 s.

5. The preparation method according to claim 1, characterized in that, In step D), the current density of the gold plating is 0.1 to 0.3 A / dm 2 ; the thickness of the electroplated gold layer is greater than 3 μm.

6. The preparation method according to claim 1, characterized in that, in step E), acetone is used to remove the photoresist on the inner wall of the holes and the photoresist in the non-graphic areas; etching the metallized hole area and the non-graphic area to remove the metal layer in the metallized hole area and the non-graphic area includes: first, gold etching is carried out by dry etching, and then titanium tungsten corrosion and tantalum nitride corrosion are carried out by wet etching, so as to remove the metal layer in the metallized hole area and the non-graphic area; argon gas is used for the gold etching, and the gas flow rate of the argon gas is 45 - 55 sccm; the etching solution used for the titanium tungsten corrosion is a hydrogen peroxide aqueous solution with a mass concentration of 25% - 35%, and the titanium tungsten corrosion time is 1 - 10 min; the etching solution used for the tantalum nitride corrosion includes hydrofluoric acid, nitric acid and water; the volume ratio of hydrofluoric acid, nitric acid and water is 1.5 - 2.5:6 - 8:8 - 12; the temperature of the tantalum nitride corrosion is 40 - 60 °C, and the time is 1 - 5 s.

7. The preparation method according to claim 1, characterized in that, in step F), the reaction gas used for sputtering the second titanium tungsten thin film is argon, and the gas flow rate of the argon gas is 65 - 75 sccm; the thickness of the second titanium tungsten thin film is 0.03 - 0.07 μm; the reaction gas used for sputtering the second gold thin film is argon, and the gas flow rate of the argon gas is 65 - 75 sccm; the thickness of the second gold thin film is 0.03 - 0.07 μm.

8. The preparation method according to claim 1, characterized in that, In step G), the current density of the gold plating is 0.1 to 0.3 A / dm 2 ; the thickness of the electroplated gold layer is greater than 1 μm.

9. The preparation method according to claim 1, characterized in that, in step H), the power of the exposure is 580 - 620 W, and the time is 8 - 12 s; The current density of the nickel electroplating is 0.1 to 0.3 A / dm 2 , and the time is 2 to 4 minutes; the surface dry film is removed using alcohol with a mass concentration of 93% - 98%.

10. The preparation method according to claim 1, characterized in that, in step I), in the gold etching solution, the iodine content is 55 - 65 g / L, and the potassium iodide content is 150 - 250 g / L; the titanium tungsten etching solution is a hydrogen peroxide aqueous solution with a mass concentration of 25% - 35%; the nickel etching solution includes sodium persulfate, nitric acid and water; the dosage ratio of sodium sulfate, nitric acid and water is 13 - 17 g:35 - 45 mL:95 - 105 mL.

11. A metallized hole thin film circuit prepared by the preparation method according to any one of claims 1 - 10.

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