JP2006332151A - Method of packaging semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a process of activation by plasma irradiation, or the like for reducing cycle time in a method for packaging a semiconductor element onto a substrate by a flip-chip method. <P>SOLUTION: In the same manner as conventional cold junction, plasma is applied onto the surface of an electrode 8 on the substrate 3 as shown in Fig. 1 (c) for activating the surface. The plasma is not applied to the side of a stud bump 6 formed on the semiconductor element 2 as shown in Fig. 1 (a). Instead, the diameter of the crystal grain of the stud bump 6 is made large by applying laser beams as shown in Fig. 1 (b). After that, pressurizing is performed onto the surface of the electrode 8 for junction as shown in Fig. 1 (d), thus breaking a shell by an oxide film and deposit on the surface of the stud bump 6, and exposing the new surface of the stud bump 6 for integrating with the new surface of the electrode 8. Therefore, junction precision in the cold junction is enhanced and the process of activation by plasma is required only once, thus shortening the cycle time. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a mounting method for a semiconductor device, and more particularly to a mounting method that is suitably used for flip-chip mounting a chip on a substrate.

A typical conventional technique for flip-chip mounting a chip on a substrate as described above is disclosed in Patent Document 1. According to the prior art, as shown in FIGS. 3 (a) and 3 (b), each surface of the object to be bonded is irradiated with plasma and activated (cleaned), and then in FIG. 3 (c). As shown, the surfaces are opposed and pressed to perform bonding at room temperature to improve the bonding accuracy.
JP 2001-351892 A

  In the above-described prior art, plasma irradiation is performed on each object to be bonded, for example, a silicon chip and a substrate, and gold bumps formed on the silicon chip and gold-plated portions of electrodes formed on the substrate are activated. .

  Accordingly, there is a problem that two plasma irradiation steps are required, and the tact time becomes long. In addition, when the time from plasma irradiation to bonding becomes long, the activity decreases and the bonding property deteriorates. For this reason, it is necessary to make the plasma irradiation process of a to-be-joined object correspond, and there also exists a problem that management of a process is complicated.

  An object of the present invention is to provide a method of mounting a semiconductor device that can shorten the activation process and shorten the tact time.

  The method for mounting a semiconductor device according to the present invention includes a step of activating a surface of an electrode of the substrate and a step of forming a bump on the semiconductor element in a method for mounting a semiconductor device by flip-chip mounting a semiconductor element on a substrate. And a step of enlarging the crystal grains of the bump, and a step of pressing the enlarged bump to the electrode of the activated substrate and bonding the semiconductor element to the substrate. And

  According to the above configuration, in the method for flip-chip mounting the semiconductor element on the substrate, the activation process is performed by irradiating the surface of the electrode with plasma or the like as in the conventional room temperature bonding. In the invention, the plasma irradiation is not performed on the bump side formed on the semiconductor element, and instead, the crystal grains of the bump are enlarged by laser irradiation or the like. The step of activating the electrode surface of these substrates and the step of forming bumps on the semiconductor element and increasing the diameter of the crystal grains may be performed sequentially in any order, or in parallel. It may be done. Thereafter, the bump is pressed against the surface of the electrode and bonded, thereby breaking the shell of the bump surface due to the oxide film and the deposits, exposing the new surface of the bump, and integrating it with the new surface of the electrode.

  Therefore, the activation process by plasma irradiation or the like may be performed once, and the activation process can be shortened and the tact time can be shortened while improving the bonding accuracy by bonding at room temperature.

  In the semiconductor device mounting method of the present invention, the step of increasing the diameter of the crystal grains of the bump is performed by laser irradiation.

  According to the above configuration, since the laser can irradiate only the bumps with spots, the crystal grains can be enlarged without damaging the semiconductor element.

  Furthermore, in the method of mounting a semiconductor device according to the present invention, the bump is formed of a stud bump, and the bump forming step includes forming a bump by sparking a wire and using the ultrasonic wave in combination with the semiconductor element. The step of pressing the electrode and the capillary is slightly raised and displaced in the plane direction of the semiconductor element to expose the enlarged portion of the crystal grain formed by the spark on the bottom surface of the capillary, And a step of cutting the tip of the wire.

  According to said structure, the large diameter part of the crystal grain of a bump can be exposed to the surface, without adding an additional heating process.

  The semiconductor device mounting method of the present invention further includes a step of softening the electrode by heat-treating the substrate before the step of activating the electrode surface of the substrate.

  According to the above configuration, since the substrate side is also softened, deformation at the time of bonding is facilitated on the substrate side in addition to the bump side, a new surface is easily produced, and bondability can be further improved.

  Furthermore, in the semiconductor device mounting method of the present invention, the bump is made of gold, and the electrode surface is also made of gold.

  According to said structure, since gold | metal | money does not oxidize, the process of joining the said semiconductor element to a board | substrate can be performed in air | atmosphere.

  As described above, the method for mounting a semiconductor device of the present invention is a method for flip-chip mounting a semiconductor element on a substrate. While performing the step of activating the surface, in the present invention, the bumps formed on the semiconductor element are not irradiated with the plasma, but instead, the crystal grains of the bumps are enlarged by laser irradiation or the like, and then Then, the bump is pressed against the surface of the electrode to be bonded, thereby breaking the shell of the bump surface due to the oxide film or adhering matter, exposing the new surface of the bump, and integrating it with the new surface of the electrode.

  Therefore, the activation process by plasma irradiation or the like may be performed once, and the activation process can be shortened and the tact time can be shortened while improving the bonding accuracy by bonding at room temperature.

[Embodiment 1]
FIG. 1 is a cross-sectional view for explaining a mounting method of a semiconductor device 1 according to an embodiment of the present invention. As shown in FIG. 1D, the semiconductor device 1 of the present invention is formed by flip-chip mounting a semiconductor element 2 such as an integrated circuit chip or a micro electro mechanical systems (MEMS) chip on a substrate 3.

  In the semiconductor element 2 having a thickness of 0.1 to 0.7 mm formed of Si, as shown in FIG. 1A, φ30 formed by sparking an Au wire 5 of φ15 to 35 μm on the electrode 4. An Au stud bump 6 having a diameter of 40 to 100 μm and a height of 40 to 150 μm is formed by crushing an Au ball of ˜80 μm by applying a load while using an ultrasonic wave, and then pull-cutting.

  Next, as shown in FIG. 1B, the stud bump 6 is irradiated with a third harmonic YAG laser indicated by reference numeral 7 with a diameter of 50 μm. Thus, by locally applying heat to the stud bump 6 to melt the protruding portion 6a, the protruding portion 6a is melted and lowered, but the melted portion has larger crystal grains and softened hardness. In this way, a portion where the crystal grains are enlarged is formed on the outermost surface.

  On the other hand, a ceramic substrate, an organic substrate (FR-4) or the like is used as the substrate 3 to be bonded. A Cu wiring 8a is usually provided on the substrate 3. Here, in order to perform Au-Au bonding with the stud bump 6 made of Au, Ni: 3 to 5 [mu] m, Au: An electrode 8 is formed by laminating a plating layer 8b of 0.1 μm or more. Subsequently, as shown by reference numeral 9, the substrate 3 is irradiated with Ar plasma, and the surface of the electrode 8 is activated. As a result, the surface of the electrode 8 is purified and the new surface is exposed. For the activation, the substrate 3 is placed in a chamber, and after evacuating, for example, to 10 to 5 Torr or less, Ar is sealed until it reaches 1 to 10 Pa. For about 180 seconds, Ar plasma is generated and Au on the surface layer of the electrode 8 is etched by several nm.

  The step of activating the surface of the electrode 8 of the substrate 3 and the step of forming the stud bump 6 on the semiconductor element 2 and increasing the diameter of the crystal grains are sequentially performed in either order. Or may be performed in parallel.

  Thereafter, the activated substrate 3 is taken out of the chamber and set on the table of the flip chip bonder, and the semiconductor element 2 having the portion whose crystal grains are enlarged in the previous step on the outermost surface of the stud bump 6 is shown in FIG. As shown in d), inversion, alignment, and pressure bonding are performed at room temperature. At that time, by applying a load of 50 to 300 g per bump, a new surface of Au that appears to be crushed on the side of the stud bump 6 is bonded to Au on the surface layer of the electrode 8 of the activated substrate 3. Since Au does not oxidize, the activated state remains in about 10 minutes even if it is taken out from the chamber as described above after being activated and placed in the atmosphere, and the Au stud bump 6 and the substrate Au electrode 8 remain. Can be joined. However, it goes without saying that pressure bonding may be performed in the chamber without taking out from the chamber.

  By mounting in this manner, the activation process by the plasma irradiation or the like may be performed once, the activation process can be shortened, and the bonding property can be improved. As a result, the reliability of the semiconductor device 1 and the semiconductor device 1 such as a semiconductor module mounted thereon can be improved. In addition, since the step of increasing the diameter of the crystal grains of the stud bump 6 is performed by laser irradiation, the laser can irradiate only the stud bump 6 with a spot, thereby damaging the semiconductor element 2. In addition, the crystal grains can be enlarged.

[Embodiment 2]
FIG. 2 is a cross-sectional view for explaining a mounting method of a semiconductor device 11 according to another embodiment of the present invention. The semiconductor device 11 is similar to the semiconductor device 1 shown in FIG. 1 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  First, Au stud bumps 6 are formed on the semiconductor element 2 by Au balls formed by sparking the Au wires 5 being crushed by applying a load on the bottom surface of the capillary 10 together with ultrasonic waves. . Further, in the present embodiment, as shown in FIG. 2A, the capillary 10 is lifted by about 10 μm and displaced in the surface direction of the semiconductor element 2, so that a crystal formed by sparks on the bottom surface of the capillary 10. After exposing the enlarged portion of the grain, the tip of the wire 5 is excised.

On the other hand, the substrate 3 to be bonded is subjected to a heat treatment as shown in FIG. 2B before the Ar plasma irradiation similar to that in FIG. 1C is performed in FIG. Specifically, the substrate 3 is made of a ceramic substrate, an organic substrate, or the like, and an electrode 8 in which a plating layer 8b is laminated on the Cu wiring 8a is formed. The substrate 3 is put into a high temperature furnace 12 filled in an N ₂ atmosphere at 300 ° C. for about 1 hour to soften Au. Due to this softening, deformation at the time of bonding is facilitated on the substrate 3 side in addition to the stud bump 6 side, and the bonding property is improved. Thereafter, Ar plasma irradiation shown in FIG.

  Also in this embodiment, the step of exposing the new surface to the surface of the electrode 8 of the substrate 3 shown in FIGS. 2B and 2C, and the stud bump on the semiconductor element 2 shown in FIG. The step of forming 6 and increasing the diameter of the crystal grains may be performed sequentially in any order, or may be performed in parallel. Thereafter, as in FIG. 1D, the activated substrate 3 is taken out of the chamber and pressure bonded to the semiconductor element 2 as shown in FIG. 2D.

  Also by mounting in this manner, the activation process by the plasma irradiation or the like may be performed once, the activation process can be shortened, and the bonding property can be improved. As a result, the reliability of the semiconductor device 1 and the semiconductor device 1 such as a semiconductor module mounted thereon can be improved. Further, after forming the stud bump 6, the capillary 10 is slightly raised and displaced in the surface direction of the semiconductor element 2, so that the crystal grain diameter of the stud bump 6 can be increased without additional heating process. Can be exposed.

  Furthermore, before the substrate 3 is irradiated with plasma, the substrate 3 is heat-treated to be softened, so that deformation at the time of bonding is facilitated on the substrate 3 side in addition to the stud bump 6 side, and a new surface is likely to appear. Thus, the bondability can be further improved.

  Each condition shown in the first and second embodiments described above is a condition in one embodiment, such as the size and material of the electrodes 4 and 8 and the stud bump 6, and the bonding strength required between them. Is appropriately changed and set according to the above. Such setting of each condition is a matter that can be appropriately performed by those skilled in the art. Accordingly, changes made by a person skilled in the art should be construed as being encompassed within the scope of the claims, unless they depart from the scope of the claims set forth in the claims.

It is sectional drawing for demonstrating the mounting method of the semiconductor device which concerns on one Embodiment of this invention. It is sectional drawing for demonstrating the mounting method of the semiconductor device which concerns on the other embodiment of this invention. It is sectional drawing for demonstrating the mounting method of the semiconductor device by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Semiconductor device 2 Semiconductor element 3 Substrate 4, 8 Electrode 5 Wire 6 Stud bump 7 Laser irradiation 9 Ar plasma irradiation 12 High temperature furnace

Claims (6)

In a mounting method of a semiconductor device formed by flip-chip mounting a semiconductor element on a substrate,
Activating the surface of the electrode of the substrate;
Forming bumps on the semiconductor element;
A step of increasing the diameter of crystal grains of the bump;
A method of mounting a semiconductor device, comprising: pressing the bumps having an increased diameter against an electrode of the activated substrate, and bonding the semiconductor element to the substrate.   2. The method of mounting a semiconductor device according to claim 1, wherein the step of activating the surface of the electrode of the substrate is performed by plasma irradiation.   3. The semiconductor device mounting method according to claim 1, wherein the step of increasing the diameter of the crystal grains of the bump is performed by laser irradiation. The bump is made of a stud bump, and the bump forming step includes:
Forming a bump by sparking the wire;
A process of pressing the bump against the electrode of the semiconductor element while using ultrasonic waves,
A step of cutting the tip of the wire after exposing the enlarged portion of the crystal grain formed by the spark at the bottom of the capillary by slightly raising the capillary and displacing it in the plane of the semiconductor element The method for mounting a semiconductor device according to claim 1, further comprising:   The semiconductor device according to claim 1, further comprising a step of softening the electrode by heat-treating the substrate before the step of activating the electrode surface of the substrate. Implementation method.   The semiconductor device mounting method according to claim 1, wherein the bump is made of gold, and the electrode surface is also made of gold.

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