Manufacturing process of gold micro-bumps with high aspect ratio and low bonding pressure on glass adapter plate

Abstract

The present invention provides a process for manufacturing gold micro-bumps with a high aspect ratio and low bonding pressure on a glass adapter plate. The method adopts a double-layer photoresist (cross-linked carbonized thin resist + thick resist) to form an electroplating pattern mask, thereby improving the adhesion of the photoresist without reducing the accuracy of the photoresist pattern, and reducing the problems of floating and debonding of the electroplated gold surface. Flattening and grayscale photolithography etching methods are adopted to prepare a bonding-enhancing microstructure on the surface of the micro-bumps, optimize the micro-bump height consistency and surface contact area, and reduce the bonding pressure requirement and bonding difficulty. Commonly used micro-nano processing technologies are adopted to effectively realize the preparation of micro-bumps required for three-dimensional integrated vertical interconnection of glass-based adapter plates in microwave components.

Description

Technical Field

[0001] The present invention relates to the technical field of glass transfer plates, and in particular to a method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate. Background Art

[0002] In response to the demand for miniaturization of electronic devices and the continuous advancement of integration technology, three-dimensional integration based on adapter plates has gradually become one of the main development directions for the integration of microwave components in electronic devices. To meet the demand for high-density integration of broadband millimeter-wave circuits and reduce RF losses, glass adapter plates are an important means of implementing three-dimensional integration of RF circuits. Stacked integration of glass adapter plates requires metal micro-bump bonding. Commonly used metal bumps include copper-tin bumps, gold-tin bumps, and gold bumps. To achieve good bonding and increase integration density, the metal bumps generally require a high aspect ratio to reduce bump area occupation and provide bonding height tolerance.

[0003] For glass adapter boards, due to reliability requirements, many adapter board surfaces use a gold strip line process, which is not compatible with copper bumps and requires the use of gold bumps. Current bump preparation methods include stripping and electroplating. Gold-tin bumps are usually made using the stripping method due to the high requirements for component control in electroplating, making it difficult to achieve bumps of larger thicknesses. Gold bumps can be made using either method, and high aspect ratio gold micro-bumps are usually achieved by electroplating. However, due to the inertness and low binding energy of the gold surface, photoresist has poor adhesion to its surface and is not resistant to electroplating. After a certain period of electroplating, phenomena such as floating and debonding are prone to occur, making it difficult to stably obtain high aspect ratio micro-bumps through electroplating. In addition, due to the low roughness of the electroplated surface, gold bumps require high bonding pressure to achieve high-reliability interconnections, which is also an unfavorable factor affecting stacked integration applications. The methods mentioned in the currently published patents involving micro-bump preparation are all aimed at solder bumps or copper pillar bumps, such as CN103337463A, CN108878296A and CN105023854A, which cannot meet the technical problems encountered in the processing of gold bumps on gold-based glass adapter boards, such as weak photoresist adhesion and high bonding pressure requirements for gold bumps. Summary of the Invention

[0004] The present invention aims to provide a process for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass adapter plate, so as to solve the problems of easy adhesive floating, adhesive debonding and high bonding pressure requirement in the electroplating process in the prior art.

[0005] The present invention provides a method for manufacturing gold micro-bumps with a high aspect ratio and low bonding pressure on a glass adapter plate, comprising the following steps:

[0006] S1, the surface of the glass adapter is prepared with strip lines and under-bump metallization, and the seed layer metal is deposited;

[0007] S2, a thin layer of photoresist is coated on the surface of the glass transfer plate, and then patterned by photolithography to reveal the bump growth locations;

[0008] S3, curing the thin photoresist on the surface of the glass adapter plate by thermal cross-linking and carbonization;

[0009] S4, coating thick photoresist on the surface of the thin photoresist with electroplating, and patterning by photolithography, so that the pattern is consistent with the thin photoresist;

[0010] S5, patterned electroplated gold bumps, slightly protruding from the thick photoresist surface;

[0011] S6, planarizing and polishing the thick photoresist and electroplated bumps;

[0012] S7, coating and etching photoresist on the surface, and performing grayscale lithography by laser direct writing exposure to obtain a photoresist pattern with a surface undulation morphology;

[0013] S8, based on the photoresist pattern after grayscale lithography, the bump surface is etched by ion beam etching to obtain a microstructure with high and low relief;

[0014] S9, wet removal of etched photoresist and thick photoresist;

[0015] S10, plasma ashing to remove the thermally cross-linked carbonized bottom thin photoresist;

[0016] S11, etching to remove the seed layer metal, completing the micro-bump preparation.

[0017] Preferably, in step S1 , the seed layer metal is deposited by sputtering.

[0018] Preferably, the seed layer metal is TiW / Au.

[0019] Preferably, in the seed layer metal, the thickness of the TiW layer is 50-100 nm, and the thickness of the Au layer is 150-200 nm.

[0020] Preferably, the thickness of the thin photoresist is 1-1.5 μm.

[0021] Preferably, the thickness of the thick photoresist is greater than 50 μm.

[0022] Preferably, the thickness of the etched photoresist is 4-5 μm.

[0023] Preferably, the height difference of the microstructure morphology is 3 to 5 μm.

[0024] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0025] The present invention adopts a double-layer photoresist (cross-linked carbonized thin photoresist + thick photoresist) to form an electroplating pattern mask, which improves the adhesion of the photoresist without reducing the accuracy of the photoresist pattern and reduces the problems of floating and debonding of the electroplated gold surface; adopts flattening and grayscale photolithography etching methods to prepare a bonding-enhanced microstructure on the surface of the micro-bump, optimizes the height consistency and surface contact area of the micro-bump, and reduces the bonding pressure requirement and bonding difficulty; adopts common micro-nano processing technology to effectively realize the micro-bump preparation required for the three-dimensional integrated vertical interconnection of the glass-based adapter board in the microwave component. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Flowchart of the process for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to an embodiment of the present invention.

[0028] Figure 2 Schematic diagram of the high aspect ratio and low bonding pressure gold micro-bumps on the glass adapter plate implemented in an embodiment of the present invention.

[0029] Figure 3 Schematic diagram of a double-layer photoresist enhancing electroplating adhesion in an embodiment of the present invention.

[0030] Figure 4 Schematic diagram of the preparation of the gold micro-bump surface microstructure in an embodiment of the present invention.

[0031] Icons: 1-glass adapter, 2-gold micro-bump, 3-seed layer metal, 4-thermally cross-linked carbonized thin photoresist, 5-thick photoresist, 6-electroplated gold pillar, 7-photoresist pattern after grayscale lithography. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0034] Example

[0035] like Figure 1-4 As shown, this embodiment provides a method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate, comprising the following steps:

[0036] S1, after the surface of the glass transfer plate is prepared with strip lines and under-bump metallization, a seed layer of metal is deposited; preferably, the seed layer of metal is deposited by sputtering. The seed layer of metal is TiW / Au, wherein:

[0037] The thickness of the TiW layer is 50 to 100 nm;

[0038] The thickness of the Au layer is 150 to 200 nm.

[0039] S2, coating a thin photoresist on the surface of the glass transfer plate, and patterning the surface by photolithography to expose the bump growth position; preferably, the thickness of the thin photoresist is 1 to 1.5 μm.

[0040] S3, heating the glass transfer plate by a hot plate, thermally cross-linking and carbonizing the thin photoresist so that it solidifies on the surface of the glass transfer plate;

[0041] S4, coating a thick photoresist on the surface of the thin photoresist with electroplating, preferably, the thickness of the thick photoresist is greater than 50 μm, and patterning by photolithography, the pattern of which is consistent with the thin photoresist;

[0042] S5, patterned electroplated gold bumps, slightly protruding from the thick photoresist surface;

[0043] S6, planarizing and polishing the thick photoresist and electroplated bumps by chemical mechanical polishing equipment;

[0044] S7, coating the surface with an etched photoresist, preferably, the etched photoresist has a thickness of 4 to 5 μm, and performing grayscale lithography by laser direct writing exposure to obtain a photoresist pattern with a surface undulation;

[0045] S8, etching the surface of the bump by ion beam etching based on the photoresist pattern after grayscale photolithography to obtain a microstructure with high and low undulations, preferably, the height difference of the microstructure morphology is 3 to 5 μm;

[0046] S9, wet removal of etched photoresist and thick photoresist;

[0047] S10, removing the thermally cross-linked carbonized bottom thin photoresist by plasma ashing;

[0048] S11, removing the seed layer metal by ion beam etching to complete the micro-bump preparation.

[0049] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A process for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass adapter plate, characterized in that: The steps include: S1, the surface of the glass adapter is prepared with strip lines and under-bump metallization, and the seed layer metal is deposited; S2, a thin layer of photoresist is coated on the surface of the glass transfer plate, and then patterned by photolithography to reveal the bump growth locations; S3, curing the thin photoresist on the surface of the glass adapter plate by thermal cross-linking and carbonization; S4, coating thick photoresist on the surface of the thin photoresist with electroplating, and patterning by photolithography, so that the pattern is consistent with the thin photoresist; S5, patterned electroplated gold bumps, slightly protruding from the thick photoresist surface; S6, planarizing and polishing the thick photoresist and electroplated bumps; S7, coating and etching photoresist on the surface, and performing grayscale lithography by laser direct writing exposure to obtain a photoresist pattern with a surface undulation morphology; S8, based on the photoresist pattern after grayscale lithography, the bump surface is etched by ion beam etching to obtain a microstructure with high and low relief; S9, wet removal of etched photoresist and thick photoresist; S10, plasma ashing to remove the thermally cross-linked carbonized bottom thin photoresist; S11, etching to remove the seed layer metal, completing the micro-bump preparation.

2. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: In step S1 , a seed layer of metal is deposited by sputtering.

3. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: The seed layer metal is TiW / Au.

4. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 3, characterized in that: In the seed layer metal, the thickness of the TiW layer is 50-100 nm, and the thickness of the Au layer is 150-200 nm.

5. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: The thickness of the thin photoresist is 1 to 1.5 μm.

6. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: Thick photoresist thickness>50μm.

7. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: The thickness of the etched photoresist is 4 to 5 μm.

8. The method for manufacturing gold micro-bumps with high aspect ratio and low bonding pressure on a glass transfer plate according to claim 1, characterized in that: The height difference of the microstructure morphology is 3 to 5 μm.

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