Micro-bump laser printing method for packaging three-dimensional integrated circuit

Abstract

Provided in the present invention is a micro-bump laser printing method for packaging a three-dimensional integrated circuit. The method comprises: placing, on a chuck below a donor film, a chiplet on which micro-pads have been prepared; and using pulsed laser to irradiate the donor film by means of aligning the pulsed laser with the donor film, such that the donor film is partially molten and generates metal droplets for spraying, and the metal droplets are deposited on surfaces of the micro-pads, and are then cooled and solidified to form a metal micro-bump array. In the present invention, the micro-bumps are prepared by means of laser direct-writing printing without requiring a mask, thereby realizing a simple process flow and a short period; micro-bump arrays having different sizes and position distributions are prepared by means of changing the sizes of laser spots and the position at which the donor film is irradiated, thereby realizing high process flexibility; and micro-bumps having different components are prepared by means of replacing the material of the donor film, thereby realizing a wide material application range.

Description

Laser printing method for micro-bumps in three-dimensional integrated circuit packaging Technical Field

[0001] The present invention relates to the technical field of three-dimensional integrated circuit packaging, and in particular to a three-dimensional integrated circuit packaging micro-bump laser printing method. Background Art

[0002] Three-dimensional integrated circuits (3DICs) are high-density integrated circuits formed by stacking multiple 2D ICs. They offer advantages such as low latency, high bandwidth, and compact size. Currently, the density of 3D IC components continues to increase. Microbumps, crucial components for electrical connections between chip layers, are also evolving towards high density, fine pitch, and compact size. This requires high-resolution microbump fabrication methods. Furthermore, the heterogeneous 3D integration of diverse chip types requires highly flexible fabrication methods for microbumps of varying materials and sizes.

[0003] Currently, common three-dimensional integrated circuit micro-bump packaging methods include mask electroplating, laser ball planting, and droplet injection.

[0004] Patent application number CN202111370657.3 discloses a method for producing microbumps using masked photolithography followed by electroplating. The method first involves transferring multiple chips to be bumped onto a temporary bonding film and then reconstructing them into wafers through injection molding. After debonding from the temporary bonding film, a passivation layer is formed on the pads of the reconstructed chip using photolithography, and a seed layer is sputtered to form a conductive layer. A photoresist is then used to pattern the plating space, and microbumps of varying sizes are deposited in a single electroplating process. Finally, the photoresist and seed layer are wet-removed and reflowed to obtain microbumps of varying sizes, which are then bonded to the chip. However, this method is cumbersome and costly. Furthermore, because the microbumps only occupy a small portion of the entire chip area, the material utilization rate of the sputtered conductive layer is low. Furthermore, this method has a long processing flow and a slow response, making it difficult to achieve flexible and variable microbump patterning.

[0005] Patent application number CN201010222496.9 discloses a method for producing microbumps using laser ball placement. A micro-solder ball is sucked up using a nozzle and placed in the center of a pad. A laser is then used to remelt the micro-solder ball to complete the ball placement and bonding of the pad. This process is maskless and produces consistent microbumps. However, removing the micro-solder ball takes additional time, resulting in low processing efficiency. Furthermore, the diameter of the micro-solder balls in this patent ranges from 40μm to 300μm, making it difficult to further improve processing resolution.

[0006] Patent application number CN202211297440.9 discloses a nozzle printing device and method for tin alloy bump arrays. Tin alloy is sprayed onto a substrate through a nozzle to form bumps. The bump height error is reduced by locally heating and melting the tops of the bumps and adjusting the initial oscillation height of the bumps, enabling the direct printing of high-coplanarity tin alloy bump arrays on a room-temperature substrate. Compared to electroplating processes, this method utilizes additive manufacturing, resulting in a simpler process and no waste liquid or other pollutants. However, nozzle printing suffers from low resolution and nozzle clogging.

[0007] Existing processing methods cannot take into account the processing requirements of micro-bump arrays of high resolution, high processing efficiency, high material utilization and high process flexibility. There is an urgent need for a three-dimensional integrated circuit packaging micro-bump preparation method that takes into account the above requirements.

[0008] Summary of the Invention

[0009] In view of the defects in the prior art, the purpose of the present invention is to provide a three-dimensional integrated circuit packaging micro-bump laser printing method.

[0010] According to the present invention, a method for laser printing micro-bumps for three-dimensional integrated circuit packaging is provided, comprising: placing a core particle with a prepared micro-pad on a chuck below a donor film, irradiating the donor film with a pulsed laser to locally melt the donor film and form metal droplets, which are deposited on the surface of the micro-pad and cooled and solidified to form a metal micro-bump array.

[0011] Preferably, the positions of the metal micro-bumps are determined by the positions of the laser irradiated thin films, and the preparation of patterned micro-bump arrays with different arrangements is achieved by adjusting the positions of the laser beam irradiating the donor film.

[0012] Preferably, the micro-bump array is prepared by using a spatial light modulator to generate a patterned light beam array with the same arrangement as the micro-bumps to be prepared; or, by controlling the laser beam deflection by a galvanometer to irradiate the donor film point by point.

[0013] Preferably, the size of the micro-bumps is adjusted by changing the laser spot size or the thickness of the donor film irradiated to meet the preparation requirements of micro-bumps for core particle packaging with different pad densities.

[0014] Preferably, the composition of the micro-bump material is consistent with that of the donor film material, and micro-bumps with different compositions can be prepared by replacing the donor film material.

[0015] Preferably, the chuck includes a preheating component, which preheats the micro pads on the surface of the core particle to a set temperature, so that the deposited metal droplets fully retract on the surface of the micro pads to form spherical micro bumps.

[0016] Preferably, the micro-bump preparation process is carried out in a normal environment, a vacuum environment or an environment filled with an inert gas.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Compared with micro-bump preparation processes such as electroplating and ball planting, the present invention manufactures micro-bumps through an additive manufacturing process of laser direct writing printing. The processing process is maskless and one laser pulse can complete a micro-bump manufacturing. It has the advantages of simple process flow, good material adaptability and high processing resolution.

[0019] 2. The present invention can realize micro-bump processing of different sizes by adjusting the shape of the patterned laser beam and the thickness of the donor film. The composition of the micro-bump can be controlled by adjusting the composition of the donor film. It is a highly flexible process.

[0020] 3. The present invention adjusts the position of the donor film irradiated by the patterned laser beam, and can densely arrange the irradiated areas on the donor film by rationally planning the path when the pads on the core particles are scattered, thereby improving the utilization rate of the donor film. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0022] FIG1 is a flow chart of a method for laser printing micro-bumps for three-dimensional integrated circuit packaging according to the present invention;

[0023] FIG2 is a schematic diagram of aligning the laser irradiation donor film position with the micro pad position in the present invention;

[0024] FIG3 is a schematic diagram of laser printing to prepare micro-bump arrays of different sizes, materials and spacings in the present invention;

[0025] FIG4 is a schematic diagram of the three-dimensional integrated circuit packaging effect after laser printing and preparation of micro-bumps in the present invention;

[0026] FIG5 shows the morphology of the micro-bumps prepared by laser printing under a scanning electron microscope in the present invention.

[0027] Description of reference numerals:

[0028] Micro pad 1

[0029] First batch of micro pads 1-1 transparent donor substrate 6

[0030] Second batch of micro pads 1-2 donor film 7

[0031] The third batch of micro pads 1-3 The first batch of micro bumps 8-1

[0032] Core 2 Second batch of micro bumps 8-2

[0033] The first chip 2-1 The third batch of micro bumps 8-3

[0034] Second chip 2-2 chuck 9

[0035] The third chip 2-3 adapter board 10

[0036] Patterned pulsed laser beam 5 DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0038] The present invention discloses a laser printing method for micro-bumps for three-dimensional integrated circuit packaging. As shown in FIG1 , a core particle 2, having micro-pads 1 formed thereon, is placed on a chuck 9 below a donor film 7. A focused pulsed laser 5 is then directed to irradiate the donor film 7 above the micro-pads 1, inducing local melting of the donor film 7 and forming a spray of metal droplets. The sprayed metal droplets are then deposited onto the surface of the micro-pads 1 directly below, where they cool and solidify to form metal micro-bumps. Based on the micro-bump material and size required for the core particle 2 packaging and the micro-pad 1 positional arrangement, the donor film 7 material, laser spot size, and irradiation position are selected to rapidly produce the metal micro-bumps. The micro-bumps interconnect different core particles 2, achieving three-dimensional integrated circuit packaging.

[0039] In the above scheme, the location of the microbumps is determined by the position of the laser irradiated film. By adjusting the position of the laser beam irradiating the donor film 7, patterned microbumps with different arrangements can be produced. A patterned microbump array can be produced using a spatial light modulator to generate a patterned beam array identical to the microbump arrangement to be produced. Alternatively, a galvanometer can be used to control the deflection of the laser beam and irradiate the donor film 7 point by point. The size of the microbumps can be adjusted by varying the laser spot size or thickness of the donor film 7, meeting the requirements for microbump production for core particles 2 with different pad densities. The composition of the microbump material is consistent with that of the donor film 7, and microbumps with different compositions can be produced by changing the material of the donor film 7. The chuck 9 used to hold the core particles 2 has a preheating function, which is used to heat the micropads 1 on the surface of the core particles 2 to a certain temperature, allowing the deposited metal droplets to fully retract on the surface of the micropads 1 to form spherical microbumps. Anti-oxidation measures can be incorporated into the entire microbump production process, such as vacuum or an inert gas environment.

[0040] The present invention is further described in detail below with reference to a specific case.

[0041] The present invention can realize the laser printing manufacturing and packaging of three-dimensional integrated circuit micro-bumps, and has the advantages of high resolution, high process flexibility, high material utilization and high processing efficiency, which meets the three-dimensional packaging needs of chips in the semiconductor industry.

[0042] 2 to 5 , this embodiment is a method for laser printing micro-bumps for three-dimensional integrated circuit packaging, comprising the following steps:

[0043] Step S1: selecting a suitable donor film 7, a preheating temperature of the chuck 9, parameters of the patterned pulse laser beam 5, and anti-oxidation measures according to the material and size of the micro bumps 8-1 to be prepared on the first core particle 2-1;

[0044] Step S2: As shown in FIG2 , the irradiation position of the patterned pulsed laser beam 5 is aligned with the first batch of micro-pads 1-1 corresponding to the micro-bumps 8-1 to be produced. Then, as shown in FIG2 , the laser beam emits pulsed light, passes through the transparent donor substrate 6, and prints the irradiated donor film 7 material onto the first batch of micro-pads 1-1 below. The material cools to form the first batch of micro-bumps 8-1.

[0045] Step S3: As shown in Figure 3, repeat steps S1-S2 to prepare other micro-bump arrays 8-2 and 8-3 with different sizes, materials, or spacing. During this process, the relative positions of the patterned pulsed laser beam 5, the donor film 7, and the second batch of micro-pads 1-2 and the third batch of micro-pads 1-3 are adjusted so that the irradiated areas on the donor film 7 are closely arranged to improve material utilization.

[0046] Step S4: As shown in FIG4 , after completing the preparation of each batch of micro bumps 8-1, 8-2 and 8-3, the first chip 2-1, the second chip 2-2 and the third chip 2-3 are stacked and packaged on the adapter board 10 in sequence to realize three-dimensional integrated circuit packaging.

[0047] The morphology of the processed micro-bumps under a scanning electron microscope is shown in Figure 5, which shows good roundness.

[0048] The present invention realizes the manufacturing of micro-bumps for three-dimensional integrated circuit packaging through a laser direct writing printing processing method, aiming to realize batch manufacturing of micro-bumps for three-dimensional integrated circuits in a manner that takes into account high resolution, high process flexibility, high material utilization and high processing speed, which is conducive to the efficient packaging of three-dimensional integrated circuits.

[0049] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0050] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A three-dimensional integrated circuit packaging micro-bump laser printing method, characterized in that: include: The core particles of the prepared micro-pads are placed on the chuck below the donor film, and the donor film is irradiated with a pulsed laser to melt the donor film locally and form metal droplets, which are deposited on the surface of the micro-pads and cooled and solidified to form a metal micro-bump array.

2. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The positions of the metal micro-bumps are determined by the positions of the laser-irradiated thin films, and the preparation of patterned micro-bump arrays with different arrangements is achieved by adjusting the positions of the laser beam irradiating the donor film.

3. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The micro-bump array is prepared by using a spatial light modulator to generate a patterned light beam array with the same arrangement as the micro-bumps to be prepared; or, by controlling the laser beam deflection by a galvanometer to irradiate the donor film point by point.

4. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The size of the micro-bumps is adjusted by changing the laser spot size or the thickness of the donor film irradiating the donor film, so as to meet the preparation requirements of micro-bumps for core particle packaging with different pad densities.

5. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The composition of the micro-bump material is consistent with that of the donor film material, and the preparation of micro-bumps with different compositions can be achieved by replacing the donor film material.

6. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The chuck comprises a preheating component, and the preheating component preheats the micro pads on the surface of the core particle to a set temperature, so that the deposited metal droplets fully shrink on the surface of the micro pads to form spherical micro bumps.

7. The three-dimensional integrated circuit packaging micro-bump laser printing method according to claim 1, characterized in that: The micro-bump preparation process is carried out in a normal environment, a vacuum environment or an environment filled with an inert gas.

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