Method for joining semiconductor chips, and joining structure of semiconductor chips

Abstract

Even smaller semiconductor chips are diffuse-bonded to the circuit board. [Solution] A method for joining a semiconductor chip, comprising the steps of: surface-treating a bump electrode, which is composed of a resin core and a metal coating covering the surface of the resin core and provided on the main surface of a circuit board, and a chip electrode, which is provided on a semiconductor chip and whose surface is at least made of metal, with plasma; bringing the surface-treated bump electrode and the chip electrode into contact with each other and pressing the semiconductor chip against the bump electrode; and diffusing the metal coating of the bump electrode and the metal constituting the surface of the chip electrode with each other to join the bump electrode and the chip electrode without an interface.

Description

Technical Field

[0001] The present invention relates to a method for bonding semiconductor chips and a bonding structure of semiconductor chips.

Background Art

[0002] Conventionally, there is known a diffusion bonding technique in which metals are bonded to each other by applying pressure and heat in a state where the metals are in contact with each other and diffusing the atoms of each metal into the metal in contact.

[0003] For example, Patent Document 1 below discloses a method for manufacturing a thermocouple in which an electrode with a metal thin film electrode formed thereon is pressurized and heated at a low temperature to diffusively bond the electrode to the substrate in a short time at a low temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the low-temperature diffusion bonding disclosed in Patent Document 1, it was difficult to bond metals (for example, electrodes) provided in a fine region to each other.

[0006] Therefore, the present invention proposes a novel and improved method for bonding semiconductor chips and a bonding structure of semiconductor chips that can diffusively bond finer semiconductor chips to a circuit board.

Means for Solving the Problems

[0007] To solve the above problems, according to one aspect of the present invention, a method for joining a semiconductor chip is provided, which includes the steps of: surface-treating a bump electrode, which is composed of a resin core and a metal coating covering the surface of the resin core and is provided on the main surface of a circuit board, and a chip electrode, which is provided on a semiconductor chip and whose surface is made of metal at least; bringing the surface-treated bump electrode and the chip electrode into contact with each other and pressing the semiconductor chip against the bump electrode; and diffusing the metal coating of the bump electrode and the metal constituting the surface of the chip electrode with each other to join the bump electrode and the chip electrode without an interface.

[0008] Furthermore, in order to solve the above problems, according to another aspect of the present invention, a semiconductor chip bonding structure is provided, comprising a resin core and a metal coating covering the surface of the resin core, a bump electrode provided on the main surface of a circuit board, and a chip electrode having at least a surface made of metal, wherein the chip electrode is bonded to the bump electrode, and the metal coating of the bump electrode and the metal constituting the surface of the chip electrode are bonded without an interface. [Effects of the Invention]

[0009] As described above, according to the present invention, it is possible to diffuse bond even finer semiconductor chips to a circuit board. [Brief explanation of the drawing]

[0010] [Figure 1] This is a longitudinal cross-sectional view illustrating the configuration of the junction structure of a semiconductor chip according to one embodiment of the present invention. [Figure 2A] This is a longitudinal cross-sectional view showing plasma treatment of a circuit board. [Figure 2B] This is a longitudinal cross-sectional view showing plasma processing on a semiconductor chip. [Figure 3] This is a longitudinal cross-sectional view showing the pressing of a semiconductor chip onto a circuit board by a collet. [Figure 4]This is a longitudinal cross-sectional view illustrating the configuration of a semiconductor chip bonding structure according to a modified example of this embodiment. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0012] <1.Joint structure> First, with reference to Figure 1, the semiconductor chip junction structure 1 according to one embodiment of the present invention will be described. Figure 1 is a longitudinal cross-sectional view illustrating the configuration of the semiconductor chip junction structure 1 according to one embodiment of the present invention.

[0013] As shown in Figure 1, the bonding structure 1 includes, for example, a circuit board 100, bump electrodes 140, a semiconductor chip 110, and a stopper 120. The bonding structure 1 is a laminate in which the semiconductor chip 110 is bonded to the main surface of the circuit board 100. In the bonding structure 1, the chip electrode 111 and the bump electrode 140 are integrated without an interface, so the semiconductor chip 110 is physically fixed to the main surface of the circuit board 100 via the chip electrode 111 and the bump electrode 140. Although Figure 1 and others illustrate a structure in which only one semiconductor chip 110 is provided on the main surface of the circuit board 100, a large number of semiconductor chips 110 (not shown) are bonded in a two-dimensional arrangement on the main surface of the circuit board 100.

[0014] The circuit board 100 is a substrate on which circuit wiring 105, which is electrically connected to each of the semiconductor chips 110, is provided on its main surface. The circuit wiring 105 is made of a metal such as gold, silver, copper, or aluminum. The circuit wiring 105 can supply power to each of the semiconductor chips 110 bonded to the main surface of the circuit board 100 and input / output control signals via bump electrodes 140 and chip electrodes 111, which will be described later.

[0015] The circuit board 100 may be, for example, a glass substrate, a glass epoxy substrate, an epoxy substrate, a polyimide substrate, or a (meth)acrylic substrate, or it may be a flexible substrate made of polyester or polyethersulfone. The circuit board 100 is, for example, a pixel array substrate for a microLED display having a rectangular shape with sides of several tens of centimeters to 1 m.

[0016] The bump electrodes 140 are electrodes provided in multiple convex shapes on the main surface of the circuit board 100, electrically connected to the circuit wiring 105. The bump electrodes 140 electrically connect the circuit wiring 105 on the main surface of the circuit board 100 to the semiconductor chip 110. Specifically, the bump electrodes 140 are electrically connected to the chip electrodes 111 of the semiconductor chip 110, which is bonded to the circuit board 100, by bonding them without an interface. The shape of the bump electrodes 140 may be a convex shape such as a cylinder, a cylinder with a rounded tip, a cone, a cone shape, a hemispherical shape, or a flattened sphere. In order to increase the bonding area between the bump electrodes 140 and the chip electrodes 111, it is preferable that the shape of the bump electrodes 140 is a shape with a flat top surface, such as a cylinder or a cone shape.

[0017] More specifically, the bump electrode 140 may be configured as a resin core electrode including a resin core 141 made of organic resin and a metal coating 143 covering the surface of the resin core. With such a structure, the bump electrode 140 can more reliably connect to the chip electrode 111 of the semiconductor chip 110 by deforming the resin core 141 when compressed between the circuit board 100 and the semiconductor chip 110.

[0018] The resin core 141 may be composed of one or more organic resins, such as polyolefin resin, acrylic resin, epoxy resin, silicone resin, polyimide resin, polyalkylene terephthalate resin, polysulfone resin, polycarbonate resin, polyamide resin, phenolic resin, melamine resin, urethane resin, and urea resin.

[0019] The metal film 143 may be composed of one or more metals such as, for example, gold, nickel, copper, silver, tin, and palladium. The metal film 143 is formed as a thin film on the surface of the resin core 141 (the upper surface and the side surface when the resin core 141 has a cylindrical shape), for example, using plating or sputtering.

[0020] The metal film 143 is joined to the chip electrode 111 by diffusion bonding. Diffusion bonding is a method of physically and electrically strongly joining metals by diffusing atoms of the contacted metals into each other's metals. By diffusion bonding, the metal film 143 is physically and electrically strongly joined to the chip electrode 111.

[0021] The metal constituting the metal film 143 may be the same type of metal as the metal constituting the chip electrode 111. According to this, since the metal film 143 can be integrated with the chip electrode 111 without an interface by diffusion bonding, it can be joined more strongly. For example, the metal constituting the metal film 143 and the metal constituting the chip electrode 111 are preferably gold (Au). When the metal film 143 and the chip electrode 111 are made of gold (Au), the surfaces of the metal film 143 and the chip electrode 111 can be activated by plasma to increase the reactivity of gold atoms, so that the diffusibility of gold atoms can be increased. Therefore, the metal film 143 and the chip electrode 111 can be diffusion bonded to each other under milder conditions (for example, normal temperature and a pressing force of several kg to several tens of kg).

[0022] Two bump electrodes 140 may be provided corresponding to one semiconductor chip 110 (corresponding to the positive and negative electrodes of the semiconductor chip 110, respectively). For example, two bump electrodes 140 may be two-dimensionally arranged on the main surface of the circuit board 100 corresponding to each of the semiconductor chips 110 two-dimensionally arranged on the main surface of the circuit board 100.

[0023] The semiconductor chip 110 is an electronic component made of semiconductor material. The semiconductor chip 110 is bonded to the main surface of the circuit board 100 via bump electrodes 140. For example, the semiconductor chip 110 may be an LED (Light-Emitting Diode) chip made of a compound semiconductor such as gallium nitride, gallium arsenide, or silicon carbide. The semiconductor chip 110, which is an LED chip, is provided in a two-dimensional arrangement on the main surface of the circuit board 100 as a pixel of a micro-LED display. Alternatively, the semiconductor chip 110 may be an IC (Integrated Circuit) chip made of silicon. The semiconductor chip 110, which is an IC chip, is provided in a two-dimensional arrangement on the main surface of the circuit board 100 for each group of LED chips, for example, as a pixel control IC that controls the LED chips of a micro-LED display.

[0024] On the surface of the semiconductor chip 110 facing the main surface of the circuit board 100, chip electrodes 111 are provided that connect to bump electrodes 140. The chip electrodes 111 are electrically connected to the circuit wiring 105 provided on the circuit board 100 via the bump electrodes 140. Two chip electrodes 111 (positive and negative electrodes) may be provided for each semiconductor chip 110.

[0025] The tip electrode 111 may be made of a metal such as gold, nickel, copper, silver, tin, or palladium. As described above, the tip electrode 111 is bonded to the metal film 143 by diffusion bonding. This firmly bonds the tip electrode 111 to the metal film 143 both physically and electrically.

[0026] As described above, the metal constituting the tip electrode 111 may be the same type of metal as the metal coating 143. In this case, the metal coating 143 can be integrated with the tip electrode 111 by diffusion bonding without a clear interface, thus achieving a stronger bond. Alternatively, the metal constituting the metal coating 143 and the metal constituting the tip electrode 111 may be gold (Au). In this case, the metal coating 143 and the tip electrode 111 can be diffusion-bonded to each other under milder conditions (for example, at room temperature and with a pressure of several kg to tens of kg).

[0027] The stopper 120 is provided projecting from the main surface of the circuit board 100 so as to surround the entire circumference of the area where the semiconductor chip 110 is bonded. In other words, the stopper 120 is provided projecting from the main surface of the circuit board 100 so as to separate the areas where the semiconductor chip 110 is bonded from each other. The stopper 120 may be made of a patterned organic resin. For example, the stopper 120 may be made of one or more of the organic resins listed as organic resins constituting the resin core 141.

[0028] The stopper 120 functions as a guide to hold the semiconductor chip 110 in place so that it does not shift laterally when the circuit board 100 and the semiconductor chip 110 are joined together. In addition, the stopper 120 functions to control the amount of pressure the semiconductor chip 110 is applied to the circuit board 100 by contacting the collet 200 (described later), which presses the semiconductor chip 110 from the back surface, when the circuit board 100 and the semiconductor chip 110 are joined together.

[0029] In the bonding structure 1 according to this embodiment, the metal coating 143 of the bump electrode 140 and the tip electrode 111 are bonded together without an interface by diffusion bonding. As a result, the bonding structure 1 can integrate the metal coating 143 and the tip electrode 111, thereby enabling a stronger physical and electrical bond between the metal coating 143 and the tip electrode 111. Therefore, the bonding structure 1 can improve the reliability of the bond between the circuit board 100 and the semiconductor chip 110. Furthermore, the bonding structure 1 can physically connect the circuit board 100 and the semiconductor chip 110 without using adhesives or the like.

[0030] <2.Joining method> Next, the method for joining the semiconductor chip 110 according to this embodiment will be described with reference to Figures 2A to 3. Figure 2A is a longitudinal cross-sectional view showing plasma treatment on the circuit board 100. Figure 2B is a longitudinal cross-sectional view showing plasma treatment on the semiconductor chip 110. Figure 3 is a longitudinal cross-sectional view showing the pressing of the semiconductor chip 110 onto the circuit board 100 by the collet 200.

[0031] When a semiconductor chip 110 is bonded to a circuit board 100, first, plasma treatment is performed on both the circuit board 100 and the semiconductor chip 110.

[0032] For example, as shown in Figure 2A, when the circuit board 100 is irradiated with plasma P, the surface of the metal coating 143 of the bump electrode 140 is activated. Specifically, the irradiation with plasma P removes residual organic matter from the surface of the metal coating 143, and also introduces hydrophilic functional groups such as hydroxyl groups to the surface of the metal coating 143. This further improves the wettability and reactivity of the surface of the metal coating 143.

[0033] Similarly, as shown in Figure 2B, the surface of the chip electrode 111 is activated when the semiconductor chip 110 is irradiated with plasma P. Specifically, the irradiation with plasma P removes residual organic matter from the surface of the chip electrode 111 and introduces hydrophilic functional groups such as hydroxyl groups to the surface of the chip electrode 111. This further improves the wettability and reactivity of the surface of the chip electrode 111.

[0034] The plasma P irradiated onto the circuit board 100 and semiconductor chip 110 may be vacuum plasma generated under vacuum, or atmospheric pressure plasma generated under atmospheric pressure. However, when plasma treatment is performed on the entire surface of the circuit board 100 and semiconductor chip 110 at once, it is desirable to use vacuum plasma capable of simultaneously treating a large area. In such cases, areas of the circuit board 100 and semiconductor chip 110 that are not irradiated with plasma P may be covered with a mask or the like to prevent irradiation with plasma P. The gas used to generate plasma P may be any readily available gas, such as oxygen, argon, water vapor, or air. The discharge method used to generate plasma P is also not particularly limited.

[0035] After the circuit board 100 and semiconductor chip 110 have been plasma-treated, the semiconductor chip 110 is pressed against the circuit board 100 with a pressing force of several kg to tens of kg at room temperature via a collet 200, as shown in Figure 3. The collet 200 is a jig that uniformly presses the semiconductor chip 110 against the circuit board 100 from the side opposite to the side on which the chip electrodes 111 are provided. The collet 200 may be a flat plate jig made of a rigid material such as glass or silicon, having a main surface area larger than that of the semiconductor chip 110. The collet 200 may also be a flat plate jig with a large main surface area capable of pressing multiple semiconductor chips 110.

[0036] The amount of pressure the semiconductor chip 110 exerts on the circuit board 100 is controlled by the contact between the peripheral edge of the collet 200 protruding from the semiconductor chip 110 and the stopper 120. As the semiconductor chip 110 is pressed against the circuit board 100, the bump electrode 140 is compressed and deformed by the chip electrode 111 of the semiconductor chip 110.

[0037] Furthermore, when the chip electrode 111 of the semiconductor chip 110 is pressed against the bump electrode 140 of the circuit board 100, diffusion bonding occurs between the metal film 143 and the chip electrode 111, which are in contact with each other. As a result, the metal film 143 and the chip electrode 111 become one without an interface, and the semiconductor chip 110 is physically fixed to the circuit board 100. Through these steps, the semiconductor chip 110 is mounted on the circuit board 100, and the bond structure 1 shown in Figure 1 is formed.

[0038] In the semiconductor chip 110 bonding method according to this embodiment, the metal coating 143 of the bump electrode 140 and the surface of the chip electrode 111 are activated with plasma, allowing the metal coating 143 and the chip electrode 111 to be diffusely bonded under milder conditions (room temperature and pressing force of several kg to tens of kg). Therefore, the bonding method according to this embodiment can reduce the pressing force and shorten the pressing time when diffusion bonding the metal coating 143 and the chip electrode 111. As a result, the bonding method according to this embodiment can further reduce the manufacturing cost of microLED displays.

[0039] Furthermore, the bonding method for the semiconductor chip 110 according to this embodiment can further enhance the reliability of the physical connection between the circuit board 100 and the semiconductor chip 110 by firmly bonding the metal film 143 and the chip electrode 111 without an interface. As a result, the bonding method according to this embodiment can eliminate the need to apply adhesive or the like to physically connect the circuit board 100 and the semiconductor chip 110, thereby further reducing the manufacturing cost of the microLED display.

[0040] <3. Variant> Next, a modified example of this embodiment will be described with reference to Figure 4. Figure 4 is a longitudinal cross-sectional view illustrating the configuration of the semiconductor chip bonding structure 1A according to a modified example of this embodiment.

[0041] The bonding structure 1A of the semiconductor chip 110 according to this modified example differs from the bonding structure 1 shown in Figure 1 in that an adhesive layer 130 is provided to bond the semiconductor chip 110 and the circuit board 100.

[0042] The adhesive layer 130 is provided in the area surrounded by the stopper 120 and adheres the semiconductor chip 110 and the circuit board 100. Specifically, the adhesive layer 130 is provided by filling the space between the semiconductor chip 110 and the circuit board 100, which are joined together, and the stopper 120 with a thermosetting adhesive. For example, the adhesive layer 130 may be composed of a phenolic thermosetting adhesive, an epoxy thermosetting adhesive, or an acrylic thermosetting adhesive. These thermosetting adhesives are applied to the circuit board 100 by screen printing or a dispenser after the semiconductor chip 110 has been joined to the circuit board 100. The adhesive layer 130 adheres the semiconductor chip 110 and the circuit board 100 by being thermoset after filling the space between the semiconductor chip 110 and the circuit board 100 and the stopper 120.

[0043] The bonding structure 1A of the semiconductor chip 110 according to this modified example allows for physical connection between the semiconductor chip 110 and the circuit board 100 by an adhesive layer 130, in addition to diffusion bonding between the metal film 143 and the chip electrode 111. Therefore, the bonding structure 1A according to this modified example can further enhance the reliability of the physical connection between the semiconductor chip 110 and the circuit board 100. As a result, the bonding structure 1A according to this modified example can be adapted to more severe environmental conditions and can be applied to applications such as PLP (panel-level packages).

[0044] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art to which the present invention belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Explanation of symbols]

[0045] 1,1A…Bonding structure, 100…Circuit board, 105…Circuit wiring, 110…Semiconductor chip, 111…Chip electrode, 120…Stopper, 130…Adhesive layer, 140…Bump electrode, 141…Resin core, 143…Metal coating, 200…Collet, P…Plasma

Claims

1. The process involves surface-treating a bump electrode, which is composed of a resin core and a metal coating covering the surface of the resin core and is provided on the main surface of a circuit board, and a chip electrode, which has at least a metal surface and is provided on a semiconductor chip, using plasma. The steps include bringing the surface-treated bump electrode and the chip electrode into contact with each other and pressing the semiconductor chip against the bump electrode, The steps include: diffusing the metal coating of the bump electrode and the metal constituting the surface of the tip electrode with each other to join the bump electrode and the tip electrode without an interface; A method for joining semiconductor chips, including [the specified element].

2. The method for joining semiconductor chips according to claim 1, wherein the plasma is generated using oxygen, argon, water vapor, air, or nitrogen.

3. The method for joining a semiconductor chip according to claim 1, wherein the metal coating and the surface of the chip electrode are made of the same type of metal.

4. The method for joining semiconductor chips according to claim 3, wherein the aforementioned metal of the same type is gold.

5. The method for bonding a semiconductor chip according to claim 1, wherein the pressing of the semiconductor chip onto the bump electrode is performed at room temperature.

6. A method for joining a semiconductor chip according to any one of claims 1 to 5, further comprising the step of applying an adhesive to the main surface of the circuit board to bond the circuit board and the semiconductor chip after joining the bump electrode and the chip electrode.

7. It consists of a resin core and a metal coating covering the surface of the resin core, and a bump electrode provided on the main surface of the circuit board, A semiconductor chip having a chip electrode whose surface is made of metal, and which is bonded to the main surface of the circuit board by bonding the chip electrode to the bump electrode, Equipped with, A bonding structure for a semiconductor chip in which the metal coating of the bump electrode and the metal constituting the surface of the chip electrode are bonded without an interface.

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