JPH1092829A - Bump forming method and semiconductor device manufacturing method - Google Patents

Abstract

(57) Abstract: The present invention provides a method for easily forming a solder bump having a height and composition controlled with high precision in a semiconductor device having a solder bump formed on a diced semiconductor chip. With the goal. A concave portion is formed on a surface of a substrate made of a material that does not wet with solder, and the substrate and the substrate having a flat surface are both immersed in a molten solder bath. Next, these substrates are brought into close contact with each other, and molten solder is sealed in the recess. Next, the substrate is taken out of the molten solder bath, and the solder existing in the concave portion is transferred to the electrode of the semiconductor chip and supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a bump and a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art A flip mounting technique is known in which an active element forming surface of a semiconductor chip and a circuit board are arranged to face each other and connected to each other by bump electrodes. This flip mounting technique mounts a semiconductor chip at a high density and does not increase the mounting outer shape of a semiconductor chip having many input / output electrodes. Therefore, this flip mounting technology is expected to reduce the size of mobile terminals and computers.

[0003] In the flip chip mounting, it is necessary to form solder bumps on the electrodes of the semiconductor chip. A conventional method of forming solder bumps is generally a method in which solder is collectively formed on a semiconductor wafer by vacuum evaporation or electrolytic plating in a wafer state before a semiconductor is cut into chips. However, commercially available semiconductor chips are divided into chips in advance by dicing for quality assurance, and only good chips are sold. Therefore, since it is practically impossible to obtain the wafer in a wafer state, a method for forming a bump on a semiconductor chip is required.

Therefore, as a method of forming bumps directly on electrodes of individual semiconductor chips, there is a method of forming gold bumps by wire bonding. However, this method has a problem in that a high pressure (0.3 N / bump or more) is applied at the time of bonding, so that the semiconductor element is likely to be broken or to have characteristic fluctuations.

[0005] The solder injection method ("Printed Circuits Society of Japan 8th Annual Scientific Congress" pp149-15
0 "), a method of forming solder bumps has been proposed. In this method, it is difficult to control the amount of solder, so that there is a problem that the height of the solder bumps varies widely.

[0006]

As described above, the conventional method of forming solder bumps on a semiconductor chip involves problems such as breakage of the semiconductor chip, change in characteristics, and variation in the amount of supplied solder.

The present invention has been made in view of the above problems, and has as its object to provide a bump having a uniform shape and height without destruction of a semiconductor chip or a change in characteristics. It is another object of the present invention to provide a method of manufacturing a semiconductor device in which the bumps are formed at high density on electrodes of a semiconductor chip.

[0008]

In order to achieve the above object, the present invention (claim 1) provides a first substrate having a concave portion formed on at least a part of the surface and a second substrate having a flat surface. Separately dipping in a molten solder tank, and bringing the surface of the first substrate and the surface of the second substrate into close contact with each other in the molten solder tank, and sealing the molten solder in the concave portion. Lifting the first and second substrates from the molten solder bath while keeping the surface of the first substrate and the surface of the second substrate in close contact with each other;
Cooling in a state where the surface of the substrate and the surface of the second substrate are in close contact with each other, and solidifying the solder in the concave portion; and removing the second substrate from the first substrate. And a method for forming a bump.

According to the present invention (claim 2), a step of preparing a substrate having a bump formed of solder in at least a part of the surface and forming a connection electrode having a width smaller than that of the recess is provided. Transferring the solder in the concave portion to the connection electrode, with the semiconductor element formed facing the substrate, and a method of manufacturing the semiconductor device.

The present invention (Claim 3) further comprises a step of separately immersing a first substrate having a concave portion at least at a position on the surface and a second substrate having a flat surface in a molten solder bath; Bringing the surface of the first substrate and the surface of the second substrate into close contact with each other in the molten solder bath, and sealing the molten solder in the concave portion; A step of lifting the first and second substrates from the molten solder tank in a state where the surface of the second substrate is in close contact with the surface of the second substrate; a step of peeling the second substrate from the first substrate; Opposing the semiconductor element on which the connection electrode having a smaller width is formed to the substrate, and transferring the molten solder in the concave portion to the connection electrode.

Further, the present invention (claims 4 and 5) provides
4. The method for forming a bump according to claim 1, wherein the depth D of the concave portion is not more than 2/3 (D / W) of the width W and not less than 0. I will provide a.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The first substrate (substrate for solder transfer) used in the present invention is preferably formed of a material whose inside surface of the recess is not wetted by solder. Also, the solder transfer substrate itself may be formed of a material that does not wet the solder.
By doing so, when supplying solder to the electrodes of the semiconductor chip, a uniform amount of solder can be supplied without the solder remaining in the recess. Further, it becomes possible to smoothly supply the solder from the inside of the concave portion to the electrode.

Further, since the surfaces of the solder transfer substrate and the second substrate (pressing substrate) are flat, the upper surface of the solder and the upper surface of the solder transfer substrate form the same plane. Is equal to Therefore, since a uniform amount of solder can be supplied, it is possible to provide bumps having a uniform height.

Further, since the composition of the molten solder can be arbitrarily controlled, a solder bump having high composition accuracy can be provided. First, a method for forming a bump according to the present invention will be described with reference to FIG.

A recess 5 is formed on the flat surface of the solder transfer substrate 1 made of quartz glass. The external dimensions of the solder transfer substrate are 5 mm × 5.2 mm × 1.2 mm, and cylindrical recesses having a diameter of 160 μm and a depth of 100 μm are formed around the substrate at 220 μm intervals. The material of the solder transfer substrate 1 does not need to be limited to quartz glass, but may be a material that does not wet with solder, such as silicon, titanium alloy, stainless steel, or alumina ceramic, or may be coated with a material that does not wet with solder. What was done may be.

As shown in FIG. 1A, a solder transfer substrate 1 and a pressing substrate 2 made of quartz glass and having a flat surface are immersed in a molten solder bath 3. In the molten solder tank 3, a molten solder 4 made of tin / lead (5% / 95% weight ratio) is used.
Is satisfied, and the temperature in the tank 3 is maintained at 350 ° C. The composition of the molten solder 4 in the molten solder tank 3 can be easily controlled by controlling the composition of the material put in the tank 3. For example, 1 part by weight of a tin ingot and 19 parts by weight of a lead ingot are put into a solder tank and melted, whereby tin and lead are diffused to obtain a molten solder having a tin / lead 5% / 95% weight ratio. .

By immersing the solder transfer substrate 1 in the molten solder tank 3 as described above, the molten solder 4 is filled in the recess 5 by the pressure generated by the weight of the molten solder. The molten solder 4 does not wet the solder transfer substrate 1. Since the surface tension of the solder, which is a factor for preventing the solder transfer substrate 1 and the solder from wetting, is one hundredth or less of the pressure caused by the weight of the molten solder 4, the molten solder 4 is sufficiently placed in the recess 5. Fill. The molten solder used in this embodiment need not be limited to tin / lead (95% / 5% by weight), but may be tin / lead (63% / 37% by weight) or an alloy composed of tin, lead and bismuth. , An alloy of tin and silver, an alloy of indium and lead, and a solder of an alloy of indium and tin.

Next, as shown in FIG. 1 (b), the surface of the solder transfer substrate 1 on which the concave portion 5 is formed and the surface of the pressing substrate 2 are opposed to each other and adhered to each other. Thus, the molten solder filled in the recess 5 is sealed.

Next, as shown in FIG. 1 (c), the solder transfer substrate 1 and the pressing substrate 2 which are in close contact with each other are pulled up from the molten solder tank 3, and are blown with high-pressure air or nitrogen by a nozzle 11 for forced air cooling. . Thus, the molten solder 4 in the recess 5 is solidified. Since the recess 5 is sealed,
The molten solder 4 is not oxidized.

Next, as shown in FIG. 1D, the pressing substrate 2 is removed from the solder transfer substrate 1. Since the solder surface 10 filled in the recess 5 and the surface 9 of the solder transfer substrate 1 form the same plane, and the solder volume is equal to the volume of the recess, the solder volume is increased by increasing the dimensional accuracy of the recess. It is possible to control with high accuracy.

Next, a method of manufacturing a semiconductor of the present invention in which a solder bump is formed on a semiconductor chip using a solder transfer substrate 1 having solder in a concave portion will be described with reference to FIG.
As shown in FIG. 2A, the solder transfer substrate 1 and the connection electrodes 7 on the semiconductor chip 6 are positioned so as to face each other. The connection electrode 7 is formed by sequentially laminating titanium (800 mm), nickel (5000 mm) and gold (600 mm), and has a diameter of 10 mm.
It is a 0 μm circular electrode. Since the transfer substrate 1 is transparent, alignment can be easily performed.

Next, as shown in FIG. 2B, the solder 12 in the recess 5 is melted by heating the solder transfer substrate 1 to 360 ° C., and the connection electrode 7 on the semiconductor chip 6 is heated.
To form solder bumps 8. Heating is performed in a belt furnace replaced with nitrogen containing 20% by volume of hydrogen. At this time, it is not necessary to use a soldering flux. Since the molten solder becomes spherical due to its own surface tension and does not wet the solder transfer substrate, all the solder is reliably transferred onto the connection electrodes.

The method of heating the solder transfer substrate 1 of the present embodiment is not limited to a belt furnace, and may use heat radiation or hot air blowing by an infrared heater, or a movable heating head. May be used. Further, a rosin-based or polymer-based soldering flux may be applied to the semiconductor chip 6 prior to heating to improve the wettability between the solder and the connection electrode.

Next, as shown in FIG. 2C, the solder transfer substrate 1 is removed from the semiconductor chip 6. At this time, since the depth of the concave portion 5 is not more than ２ of the width of the concave portion and the width of the concave portion is larger than the width of the connection electrode, the diameter of the solder bump is smaller than the diameter of the concave portion. It can be easily removed.

As described above, since the bump volume of the solder bump formed according to the present embodiment is equal to the volume of the concave portion of the transfer substrate, it is possible to control the solder volume with high precision by increasing the dimensional accuracy of the concave portion. It is possible. Also,
By controlling the solder composition of the molten solder tank, the composition of the solder bump can be easily controlled. Therefore, it is possible to easily form a solder bump having high height accuracy and high composition accuracy on a semiconductor chip diced by the present invention.

In this embodiment, the solder transfer substrate and the pressed substrate are taken out of the solder bath and then cooled once to solidify the solder. However, the solder in a molten state is supplied to the semiconductor chip without solidifying the solder. Is also good.

[0027]

As described above, according to the present invention, it is possible to easily form solder bumps having a uniform height and a uniform composition on individual diced semiconductor chips, thereby realizing a low-cost, high-performance semiconductor device. realizable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a bump forming method of the present invention.

FIG. 2 is a cross-sectional view illustrating a method for manufacturing a semiconductor device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate for solder transfer 2 Substrate for pressing 3 Melt solder bath 4 Melt solder 5 Concave 6 Semiconductor chip 7 Connection electrode 8 Solder bump 9 Solder transfer substrate surface 10 Solder surface 11 Nozzle 12 Solder

Claims (5)

[Claims] A step of separately immersing a first substrate having a concave portion formed in at least a part of a surface thereof and a second substrate having a flat surface in a molten solder bath; Contacting the surface of the second substrate with the surface of the second substrate in the molten solder bath, and sealing the molten solder in the concave portion; A step of pulling up the first and second substrates from the molten solder bath in a state where they are in close contact with each other; and cooling the surface of the first substrate and the surface of the second substrate in close contact with each other. And a step of solidifying the solder in the recess, and a step of peeling the second substrate from the first substrate. 2. A recess is formed in at least a part of the surface,
A step of preparing a substrate having a bump made of solder in the recess; a step of transferring a semiconductor element having a connection electrode smaller in width than the recess to the substrate and transferring the solder in the recess to the connection electrode; A method for manufacturing a semiconductor device, comprising: 3. A step of separately immersing a first substrate having a concave portion at least at a position on a surface thereof and a second substrate having a flat surface in a molten solder bath, and said surface of said first substrate. Contacting the surface of the second substrate with the surface of the second substrate in the molten solder bath, and sealing the molten solder in the concave portion; and the step of sealing the surface of the first substrate and the surface of the second substrate. A step of lifting the first and second substrates from the molten solder bath in a state of being in close contact, a step of peeling the second substrate from the first substrate, and forming a connection electrode having a width smaller than that of the concave portion. A step of transferring the melted solder in the concave portion to the connection electrode, with the semiconductor element thus formed facing the substrate. 4. The depth D of the recess is 2/3 (D / D) of the width W.
2. The method for forming a bump according to claim 1, wherein W is 0 or more. 5. The method according to claim 1, wherein the depth D of the concave portion is 2/3 (D / D) of the width W.
4. The method for manufacturing a semiconductor device according to claim 2, wherein W is 0 or more.