JP2006190777A - Bump forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bump forming method capable of bonding by a different composite of metal and reducing damage or mounting distortion of a chip or a substrate, by reducing diffusion energy to be applied in mounting (bonding) in bump bonding or flip chip bonding. <P>SOLUTION: The above problem is solved by the bump forming method for forming a bump bonding portion 2 to be bonded with bumps on a substrate 1 and forming the bumps 3 on this bump bonding portion, wherein a bump material forming the bumps is prepared by mixing a material composing the bump bonding portion. Also, the bump bonding portion is preferably formed by an evaporation method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present technology relates to a bump forming method and the like. More specifically, the present technology relates to a bump forming method that can reduce energy required for bump bonding or Philip chip bonding, and causes little damage to a substrate.

  Conventionally, a mounting method using a wire bonding method has been used in semiconductor devices and the like. At present, bump bonding or flip chip bonding is spreading as a means of mounting in response to the recent trend toward thinner, lighter, and more sophisticated electronic devices.

  In this bump bonding or flip chip bonding method, bump electrodes called bumps are bonded onto the electrodes on the surface of the semiconductor chip or the electrodes on the surface of the wiring board, and the front and back sides of the semiconductor chip are reversed, so-called face down bonding is performed on the wiring board. The electrodes, bumps, and electrodes of the semiconductor chip are aligned, and mounting is performed by applying ultrasonic waves, pressure, or heat.

  Currently, flip-chip bonding methods using ultrasonic waves are being established for general LSI (large-scale integration) among semiconductor devices and the like, as disclosed in Patent Document 1. . On the other hand, among semiconductor devices and the like, LEDs (light-emitting diodes), LDs (laser diodes) and the like, and semiconductor devices using a substrate material such as a crystal or a composite crystal such as sapphire, etc. However, face down bonding is expected in the future, and establishment of a flip chip bonding method used for these semiconductor devices is desired.

  In general, it is considered that ultrasonic metal-to-metal bonding is generally performed by gold-gold bonding called GGI (Gold to Gold Interconection) and Au-bump formation on Al wiring (bad).

  However, in recent years, when an LED, LD or the like, a quartz substrate or the like as described above is used, a material other than Au or Al, a metal or metal alloy other than Au or Al, or a heterogeneous metal is laminated in multiple layers. Such composite metal layers are used, and the demand for bump mounting and Philip chip joining methods on such composite metal materials is increasing.

Au-bump mounting on composite metal materials requires a larger amount of energy for mounting than ordinary gold-gold bonding and gold-Al wiring, and it gives too much energy such as load, ultrasonic waves, heat, etc. In addition, the base material is likely to be damaged such as cracks and structural destruction. Further, when the thermal energy applied at the time of mounting becomes excessive, the change with time on the chip or the substrate side becomes remarkable. The same applies to the case of Philip chip bonding, and the risk of chip destruction increases due to the extreme energy applied during mounting.
JP2002-43354

  Therefore, the present application eliminates the disadvantages occurring in the background art described above, reduces the diffusion energy applied during mounting (bonding) in bump bonding or dip chip bonding, allows bonding with different composite metals, An object is to provide a bump forming method capable of reducing damage to a substrate, mounting distortion, and the like.

  In order to solve the above-described problem, the bump forming method according to claim 1 is a method of forming a bump bonding portion to be bonded to a bump on a substrate and forming the bump on the bump bonding portion. The bump material for forming the bump is a mixture of materials constituting the bump bonding portion.

  The bump forming method according to claim 2, wherein the bump bonding portion is made of a material containing at least one metal selected from the group consisting of Pd, Pt, Ag, Fe, Mg, Au alloy, The material is characterized in that it contains the metal and Au contained in the material constituting the bump bonding portion.

  The bump forming method according to claim 3 is characterized in that, in the bump material, a mixing ratio of the metal to Au is 100: 0.001-1.

  Furthermore, in the bump forming method according to claim 4, the bump joint is formed on the substrate by vapor deposition.

The bump forming method according to claim 5 is characterized in that the bump bonding portion has a film thickness of 500 to 20000 mm.
Furthermore, in order to solve said subject, the bump formation method of Claim 6 forms the bump junction part joined with a bump on a board | substrate, In the method of forming a bump on this bump junction part, The bump bonding portion is formed by vapor deposition.

  In the case where bump joints to be bonded to bumps such as electrodes, pads, and wirings formed on a substrate are formed from a composite metal material, the researchers intentionally set bumps such as electrodes on bump materials. Mounting by mixing the materials on the joint side and bonding between metals, and further promoting the diffusion during mounting by forming the bump joint part that was generally formed by sputtering method by vapor deposition method The present inventors have found that diffusion energy applied during (bonding) can be reduced, bonding with dissimilar composite metals can be performed, damage to a chip or a substrate, mounting distortion, and the like can be reduced.

  Below, with reference to drawings, the bump formation method concerning this art is explained concretely.

  In the first embodiment shown in FIG. 1, a bump bonding portion 2 to be bonded to a bump such as an electrode, a pad, or a wiring is formed on the surface of a base material 1 by a vapor deposition method.

  The substrate used in the present technology is not particularly limited, and for example, a silicon wafer, a crystal material such as quartz, sapphire, GaAs, or GaN, a composite crystal, or the like can be used. Alternatively, the bumps can be provided on the side of various semiconductor chips such as LSI, LED, and LD mounted on the semiconductor device. Therefore, in this specification, the term “substrate” is used to include such a semiconductor chip. The bump forming method according to the present technology is particularly advantageous when applied to a bonding method on a substrate made of a crystal material such as quartz, sapphire, or a composite crystal.

  Further, the material constituting the bump bonding portion 2 is not particularly limited because it depends on the type of the substrate to be used, the type of chip to be mounted, and the like. For example, the substrate is made of crystal, sapphire, or the like. In the case of a crystal material, a material containing at least one metal selected from the group consisting of Pd, Pt, and Ag is used. Note that such a bump bonding portion can be formed of an alloy made of a plurality of metals, or a composite metal layer in which a plurality of different metal layers are laminated. Although it does not specifically limit as a composite metal layer, Specifically, Ti + Pd, Cr + Au, Cr + Au + Ag, Ag + Pd, Al + Cu, Al + Si + Cu etc. are used, for example.

  The film thickness of the bump bonding part 2 is not particularly limited, but is preferably about 10,000 to 20000 mm. This is because if the film thickness is extremely thin, sufficient diffusion in the inter-metal bonding cannot be obtained in bump bonding or Philip chip bonding, and sufficient bonding strength may not be obtained.

  In addition, as shown in the embodiment shown in FIG. 1, the method for forming the bump bonding portion is not particularly limited to the vapor deposition method, and as shown in another embodiment shown in FIG. It can be formed as a film 2a, or can be formed by a conventionally known film formation method such as CVD, MOCVD, or plating. However, depending on the plating method, generally a thick film layer is formed. In addition, since the intermolecular bonds in the film are strong and the film is hard, there is a possibility that the diffusion in the intermetallic bonds as described above may not occur sufficiently. .

  The bump 3 is formed on the surface of the bump bonding portion 2 formed in this manner by using the wire bonder 4. However, in the present technology, the bump material constituting the bump 3 is the bump bonding portion. 2 are mixed.

  Specifically, for example, when a composite layer composed of two layers of a Ti underlayer and a Pd upper layer is sequentially formed on the surface of the substrate 1 as a bump bonding portion (electrode) 2, the bump material is Au. As a substrate, a mixture of Pd is used. For example, when the material constituting the bump bonding portion is a binary or ternary or higher alloy, the bump material according to the present technology includes at least one metal element constituting the alloy. I just need it.

  Further, in the bump material according to the present technology, the blending ratio of the material constituting the bump joint portion such as Pd mixed with the base metal such as Au is not particularly limited, and the blended metal For example, the mass ratio is preferably 100: 0.001 to 5, particularly 100: 0.001 to 1, although it depends on the seeds. If the blending ratio of the material constituting the bump joint is less than this range, the effect of promoting metal diffusion at the time of mounting cannot be sufficiently obtained, while if it is greater than this range, the bump This is because the physical and electrical characteristics of the base metal suitable as a material may be deteriorated.

  Next, a second bump forming method according to the present technology is characterized in that a metal layer constituting a bump bonding portion is formed on a substrate by a vapor deposition method. As described above, the metal layer formed by the vapor deposition method has better diffusibility than the metal layer formed by the plating / plating method which is generally performed conventionally, so that the bump bonding or This is because relatively good bonding strength can be obtained in Philip chip bonding.

  In the second bump forming method, the bump material is not limited to the above-described embodiment in which the material constituting the bump joint is mixed with the base metal such as Au. It is also possible to use metal species and alloys that are not included in the bump joint.

  In the bump forming method according to the present technology, as described above, the bump is formed by using a material in which the bump joint portion such as an electrode, a pad, and a wiring is mixed as a bump material for forming the bump. However, the subsequent bump bonding or Philip chip bonding can be performed in the same manner as a conventionally known operation.

  That is, for example, as illustrated in FIG. 3, the manufacture of the semiconductor device 10 using the present technology has been described above using the wire bonder 20 on the substrate 15 on which the first electrode thin film 14 as the bump bonding portion is formed. After a bump bonding step (a) for forming such a bump 12, a flip chip bonding step (b) for bonding the semiconductor chip 11 to the substrate 15 on which the first electrode thin film 14 is formed via the bump 12 is performed. Can be implemented. In the flip chip bonding step (b), the material of the bumps 12 diffuses into the first electrode thin film 14 by applying ultrasonic waves, weight (pressure), heat, or the like to the semiconductor chip 11. In addition, regarding the bump formed by the bump forming method according to the present technology, an ultrasonic wave is most appropriate as a force applied at the time of Philip chip bonding. As the semiconductor chip 11, various chips such as LSI, LED, and LD are used, for example. These semiconductor chips 11 are generally known to be mounted on a semiconductor substrate 15. A second electrode thin film 16 is formed at a site where the semiconductor chip 11 is bonded to the bump 12. Further, if necessary, a heat treatment step (c) can be performed after the flip chip bonding step (b). For example, in the heat treatment step (c), at least one of heating and cooling is performed by annealing, dry ringing, and measurement of temperature characteristics, filtering, frequency characteristics, or the like in the case of a semiconductor device for a mobile phone. 3A and 3B, the upper part of each figure schematically shows the actual operation, and the lower part of each figure diffuses the material for forming the bumps 12 into the first electrode thin film 14. The mode to do is shown.

  In the example shown in FIG. 3, the bump is formed on the wiring substrate 15 side and the semiconductor chip is mounted. However, as described above, the bump is formed on the semiconductor chip 11 side and the wiring substrate is mounted. Bonding to the 15 side can also be performed as is conventionally known.

  Hereinafter, the bump forming method according to the present technology will be described more specifically with reference to examples.

Example 1
First, a Ti layer having a thickness of 30 mm and a Pd layer having a thickness of 0.3 μm were sequentially formed on a quartz substrate by a plating method to form bump bonding portions. An Au-Pd bonding wire (GBC wire manufactured by Tanaka Kikinzoku Co., Ltd., Pd content of less than 1%) was bonded to the upper portion using a wire bonder (SBB-5 manufactured by Shinkawa Co., Ltd.).

  Next, the quartz substrate having the bumps thus formed was mounted on the Au electrode of the ceramic package using a Philip chip bonder.

  The sample thus obtained was subjected to a peeling test (test machine data, 2400) to break the bonding interface, and the peeling strength and peeling mode at that time were examined. The test was performed on 10 samples.

  In the peeling mode, when the semiconductor chip and the substrate are peeled off by a peeling test, as shown in FIG. 4A, the two are separated at the interface between the bump and the electrode thin film of the semiconductor chip. B mode when both are separated inside the mode and the bump, C mode when both are separated at the boundary between the bump and the bump joint made of the Ti layer and the Pd layer, and between the quartz substrate and the bump joint The case where the two were separated at the boundary of D was the D mode, and the case where both were separated inside the quartz substrate was the E mode.

  As a result, the peel strength was an average of 42.2 g (maximum 57.3 g, minimum 28.6 g, deviation 28.7 g), and the peeling mode was C mode. Further, at the peeling interface, as shown in the enlarged photograph shown in FIG.

(Example 2)
First, a Cr layer, an Ag layer, a Cr layer, an Ag layer, and an Au layer were sequentially laminated on a quartz substrate by a vapor deposition method to form a composite vapor deposition film having a total thickness of 2 μm to form a bump bonding portion. In the same manner as in Example 1, an Au—Pd bonding line (Tanaka Kikinzoku Co., Ltd. GBC wire, Pd content of less than 1%) was bonded to the upper portion using a wire bonder (SBB-5, manufactured by Shinkawa Co., Ltd.).

  Next, Philip chip bonding was performed in the same manner as in Example 1, and the sample was subjected to a peeling test.

  In the peeling mode, when the semiconductor chip and the substrate are peeled off by the peeling test, as shown in FIG. 4B, the two are separated at the interface between the bump and the electrode thin film of the semiconductor chip. B mode when both are separated inside the mode and the bump, C mode when both are separated at the boundary between the bump and the bump bonded portion made of the Cr + Ag + Cr + Ag + Au deposited film, and the boundary between the quartz substrate and the bump bonded portion The case in which the two are separated is referred to as the D mode, and the case in which the two are separated inside the quartz substrate is referred to as the E mode.

  As a result, the peel strength averaged 38.6 g (maximum 49.2 g, minimum 18.4 g, deviation 30.8 g), and the peeling mode was C mode. Further, at the peeling interface, as shown in the enlarged photograph shown in FIG.

(Comparative example)
First, a Cu layer and an Ag layer were sequentially laminated on a quartz substrate by a sputtering method to form a composite sputtering film having a total thickness of 1.4 μm, thereby forming a bump bonding portion. In the same manner as in Example 1, an Au—Pd bonding line (Tanaka Kikinzoku Co., Ltd. GBC wire, Pd content of less than 1%) was bonded to the upper portion using a wire bonder (SBB-5, manufactured by Shinkawa Co., Ltd.).

  Next, Philip chip bonding was performed in the same manner as in Example 1, and the sample was subjected to a peeling test.

  In the peeling mode, when the semiconductor chip and the substrate are peeled off by the peeling test, as shown in FIG. 4C, the two are separated at the interface between the bump and the electrode thin film of the semiconductor chip. B mode when both are separated in the mode and the inside of the bump, C mode when both are separated at the boundary between the bump and the bump joint made of the Cu + Ag sputtering film, and the boundary between the quartz substrate and the bump joint The case in which the two are separated is referred to as the D mode, and the case in which the two are separated inside the quartz substrate is referred to as the E mode.

  As a result, the peel strength averaged 34.4 g (maximum 40.1 g, minimum 28.9 g, deviation 11.2 g), and the peeling mode was C mode. Moreover, outer periphery diffusion was observed in the peeling interface as in the enlarged photograph shown in FIG.

It is the schematic which shows typically an example of the bump formation method which concerns on this technique. It is the schematic which shows typically another example of the bump formation method which concerns on this technique. (A)-(c) is the schematic which shows the manufacturing process of a semiconductor device. (A)-(c) is drawing explaining the peeling mode in an Example and a comparative example. (A)-(c) is an enlarged photograph which shows the state of the sample interface after the peeling test in an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,15 ... Board | substrate 2 ... Bump joint part 2a ... Bump joint part by a sputtered film 3, 12 ... Bump 4, 20 ... Wire bonder 10 ... Semiconductor device 10A, 10B, 10C ... Semiconductor device in the middle of manufacture 11 ... Semiconductor chip 14 ... First One electrode thin film 15 ... Substrate 16 ... Second electrode thin film 25 ... Philip chip bonder

Claims (6)

  In the method of forming a bump bonding portion to be bonded to a bump on a substrate and forming the bump on the bump bonding portion, the bump material for forming the bump is a mixture of the materials constituting the bump bonding portion. A bump forming method characterized by the above.   The bump bonding portion is made of a material containing at least one metal selected from the group consisting of Pd, Pt, Ag, Fe, Mg, and Au alloy, and the bump material includes the material constituting the bump bonding portion. The bump forming method according to claim 1, comprising metal and Au.   The bump forming method according to claim 2, wherein in the bump material, a mixing ratio of the metal to Au is 100: 0.001-1 in terms of mass ratio.   The bump forming method according to claim 1, wherein the bump bonding portion is formed on the substrate by vapor deposition.   The bump forming method according to claim 4, wherein the bump bonding portion has a thickness of 500 to 20000 mm.   A method of forming a bump bonding portion to be bonded to a bump on a substrate and forming the bump on the bump bonding portion, wherein the bump bonding portion is formed by vapor deposition. .

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