JPH0350736A - Manufacture of bump of semiconductor chip - Google Patents

Abstract

PURPOSE:To manufacture a bump excellent in bondability at a low cost, by a method wherein, after a metal ball is formed at the tip of a metal thin wire in the same manner as the wire bonding method, and said metal ball is bonded to a specified position of a semiconductor chip, the surface of the metal ball is covered with solder by a method like solder dipping. CONSTITUTION:A metal thin wire 34 of Au, Ag, Cu, etc., is inserted into a tool 31, and electrically discharged by a discharging rod 33 or heated by hydrogen flame and the like, thereby forming a metal ball 23 at the tip of the metal thin wire 34. After the discharging rod 33 is made to retreat, the tool 31 is made to descend, and the metal ball 23 is pinched by the tool and an Al electrode 22. The metal ball 23 is bonded on the Al electrode 22 of a semiconductor chip 21. After that, while the metal thin wire 34 is clamped by a clamper 32, it is made to ascend, thereby cutting the metal thin wire 34 at the bonding part between the ball and the wire, and forming a desired ball bump. By dipping the metal ball 23 in melted solder in the state of a wafer as it is, the ball bump surface is covered with solder 24. Thereby a bump excellent in bondability can be easily formed at a low cost.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an electrode of a semiconductor chip or a Ti-Pt-Au, Tf-Cr-Cu or TL formed on the electrode.
- It relates to a method of manufacturing bumps for semiconductor chips in which bumps are formed on a barrier metal layer such as Cu-Au.

[Prior Art] FIGS. 4 and 5 show a method of manufacturing a semiconductor device using a conventional film carrier method. The film carrier tape 2 is composed of an insulating film as a support and a metal foil adhered onto the insulating film. This insulating film is made of polyimide or the like, and is provided with a sprocket hole 3 for conveyance and positioning, and a device hole 4 which is an opening into which the semiconductor chip 1 is inserted. and,
After bonding a metal foil such as copper onto the insulating film, the metal foil is formed into a desired shape by etching or the like to form leads 5 and pads 6 for electrical selection.

On the other hand, bumps 7, which are metal protrusions, are provided on the semiconductor chip 1 on its electrode terminals.

Such a film carrier tape 2 and a semiconductor chip 1
The leads 5 of the film carrier tape 2 and the bumps 7 of the semiconductor chip 1 are bonded to each other by a thermocompression method or a eutectic method, and the semiconductor chip 1 is prepared.
is mounted on the film carrier tape 2, a contactor is brought into contact with the electrical selection pad 6 to carry out an electrical selection or bias test. Upon completion of this test, the film carrier semiconductor device is completed.

In this case, in order to prevent deformation of the leads 5, suspenders 8 are provided in advance on the film carrier tape 2 by forming an insulating film into a frame shape, as shown in FIG. This suspender 8 supports the tip of the lead 5.

Further, in order to improve reliability and mechanical protection, as shown in FIG. 6, resin 9 may be potted onto the semiconductor chip 1 for resin sealing.

When mounting the film carrier semiconductor device manufactured as described above, first, the leads 5 are cut to a predetermined length, and then, as shown in FIG.
A semiconductor chip 1 is fixed to the substrate 1 with an adhesive 12. Next, the leads 5 are outer lead bonded to the bonding pads 10 on the printed circuit board 11. Thereby, the semiconductor chip 1 can be mounted on the printed circuit board 11.

These film carrier semiconductor devices have advantages such as high processing speed because the bonding process can be performed at once regardless of the number of leads, and easy automation of the work because they use film carrier tape. I'm having a baby.

The method of providing bumps on the electrodes of a semiconductor chip is as follows:
There is also a flip-chip method shown in FIG.

This is a bump 7 made of solder on the electrode of the semiconductor chip 1.
are formed in a lattice shape, and as shown in FIG. 9, bumps 7 are bonded directly onto bonding pads 10 provided on a printed circuit board 11 by soldering.

Such a flip-chip type semiconductor device has advantages such as being advantageous in providing a large number of electrodes because electrodes can be provided in a grid pattern on the surface of the semiconductor chip.

Incidentally, the semiconductor chip 1 mounted on the conventional film carrier semiconductor device and the flip-chip type semiconductor device described above requires bumps 7 to be formed on the electrodes thereof. Conventionally, when forming the bumps 7 on the surface of the semiconductor chip 1, it is carried out by electrolytic plating on the electrodes of the semiconductor chip 1 in a wafer state. However, this conventional bump forming method has a high processing cost. It has the disadvantage of being expensive. The main reasons for this are that the bumps are formed by selective plating, and that not all of the semiconductor chips formed on the wafer are good, but some are defective, resulting in poor processing efficiency.

To solve this problem, various bump forming methods have been introduced. -For example, 5solid StateTe
chnology Japanese version November 1978 issue P33
There is a film carrier tape with bumps (hereinafter referred to as B-TAB) proposed in P35 and the like. Besides that,
National Technical Report
vol 3l-Na3 Jun, 1985 PllB
- The transfer bump method described in PI24 etc., as well as JP-A-54-2862 and JP-A-Sho [1O-1945]
There is a method of using metal balls as bumps in wire bonding (hereinafter referred to as ball bumps), as disclosed in No. 43 and the like.

[Problems to be Solved by the Invention] However, all of these conventional bump forming methods have the following drawbacks. First, the B-TAB method half-etches the other lead portions of the film carrier tape, leaving only the lead tips, and bumps the tips that remain in a convex shape without being half-etched.

However, since this method half-etches a portion of the lead, it is necessary to pattern and etch both sides of the metal foil, respectively, and - it is carried out using a partial film carrier tape with only the metal foil inside the shell. Therefore, each lead has the disadvantage that electrical selection is difficult. To solve this problem, it is possible to similarly form bumps on the leads formed on the insulating film as described above, but this has the disadvantage of complicating the process and increasing costs.

The transfer bump method is a method in which bumps are formed on a substrate such as glass by electrolytic plating, and the leads of a film carrier tape are bonded to transfer the bumps from the substrate to the leads. Although this method has many advantages in terms of cost compared to the conventional method of forming bumps on a wafer due to the necessity, it has the disadvantage that the process is complicated.

In the ball bump method, only the metal balls formed during thermocompression wire bonding are bonded onto the electrodes of the semiconductor chip to form bumps. Since thermal and mechanical stresses are applied to the electrodes of the semiconductor chip twice during bonding, there is a drawback that the electrode portions are easily destroyed and reliability is poor.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a bump manufacturing method for a semiconductor chip that can easily form solder-coated metal bumps and can manufacture bumps with excellent bonding properties at low cost.

[Means for Solving the Problems] A method for manufacturing a bump for a semiconductor chip according to the present invention includes a step of forming a metal ball at the tip of a thin metal wire, a step of bonding the metal ball to a predetermined position of a semiconductor chip, The method is characterized in that the steps of separating the thin metal wire from the metal ball and installing the metal ball at the predetermined position and coating the surface of the metal ball with solder are performed.

[Function] In the present invention, Ti-Pt-Au+'ri-Cr-C formed on the electrode of the semiconductor chip or on this electrode is used.
When forming a bump on a barrier metal layer such as U or Ti-Cu-Au, a metal ball is formed at the tip of a thin metal wire in the same manner as the wire bonding method, and this metal ball is bonded onto the electrode or barrier metal layer. . Then, the thin metal wire is separated from the metal ball, leaving the metal ball. Thereafter, the surface of the metal ball is coated with solder by a method such as solder dipping. In this way, in the present invention, a metal ball coated with solder can be easily formed, and since the solder is used to join the lead, bonding can be performed at low temperature and low pressure. Since there is a metal ball inside, there is no problem of the bump being crushed during bonding.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a bump of a semiconductor chip manufactured by the method of the first embodiment of the present invention.

An electrode 22 made of A) film or the like is selectively formed on the semiconductor chip 21, and an insulating layer 25 is formed on the entire surface of the electrode 22. Electrode 22 in insulating layer 25
A metal ball 23 is bonded to the upper portion by a method similar to wire bonding. The periphery of this metal ball 23 is coated with solder 24.

Next, regarding a method for forming a bump having the above structure,
This will be explained in detail with reference to FIG.

FIGS. 2(a) to 2(C) are schematic diagrams showing the method of forming this bump in the order of steps. That is, in this embodiment, only the metal balls formed by thermocompression wire bonding are connected to the A! Press it onto the electrode to form a ball bump.

First, as shown in FIG. 2(a), A u r A g
A metal ball 23 is formed at the tip of the metal wire 34 by passing a metal wire 34 made of +Cu or the like into the tool 31 and causing an electric discharge with a discharge rod 33 or heating with a hydrogen flame or the like.

Next, as shown in FIG. 2(b), after retracting the discharge rod 33, the tool 31 is lowered and the metal ball 23 is
The metal ball 23 is sandwiched between the f electrode 22 and the A! of the semiconductor chip 21 (wafer 30). It is bonded onto the electrode 22 by a bonding method such as thermocompression bonding or ultrasonic bonding.

Thereafter, as shown in FIG. 2(C), by raising the clamper 32 while holding the thin metal wire 34, the thin metal wire 34 is cut at the joint with the metal ball 23, and a desired ball is formed. Form a bump.

Note that in order to easily cut the thin metal wire 34 at the joint with the metal ball 23, the metal ball 23 is connected to the electrode 2.
2, it is preferable to vibrate the tool 31 from side to side.

Furthermore, before separating the semiconductor chips 1 from the wafer 30, ball bumps can be formed in the wafer 30 as in the above embodiment, and only good semiconductor chips can be selected to form the ball bumps. preferable.

Next, the metal balls 23 are immersed in the molten solder while the wafer 30 remains, and the surfaces of the ball bumps (metal balls 23) are coated with solder 24. As a result, a metal bump according to this embodiment as shown in FIG. 1 is formed.

The method for coating the metal balls 23 with the solder 24 is as follows:
In addition to the dipping method, there are other methods, such as a method in which the wafer surface is interposed in the jet of molten solder and the jet of molten solder is applied to the surface of the metal ball, and a method in which solder paste is applied to the surface of the metal ball and melted. However, since an insulating layer 25 such as an oxide film and a nitride film is formed on the wafer surface other than the ball bumps, a method such as the solder dipping method that causes solder to adhere to the entire surface of the wafer 30 is not used. However, metal ball 23
It is possible to selectively coat the surface of the solder 24 with the solder 24. Therefore, the surface of the metal ball 23 can be selectively coated with solder easily and at low cost by a simple means such as this dipping method.

Next, a method for mounting a semiconductor chip having such ball bumps formed thereon will be described. First, in the case of a film carrier semiconductor device, a film carrier tape with leads formed thereon is prepared, the leads are aligned with the bumps of the semiconductor chip, and then bonding is performed by applying heat and pressure with a heating tool.

Lead bonding of conventional film carrier semiconductor devices involves bumps made of Au or Au-plated Cu, etc.
This is done by Au-Au thermocompression bonding method or Au-8n eutectic alloy method, etc. in combination with leads plated with U or Sn. It was necessary to heat it to a temperature of 500° C. to 500° C. and pressurize it at a pressure of 50 to 100 g/C4 per lead.

However, with the recent increase in the functionality of semiconductor devices, the chip size and the number of leads have increased significantly. Moreover, the increase in the chip size makes it difficult to maintain temperature uniformity of the heating tool, and the increase in the number of leads increases the pressing force, complicating the structure of the device. In particular, increasing the number of leads is 70g/c per lead.
Even if a pressure of J is applied, a total pressure of 35 kg/cJ is required for a 500 lead semiconductor chip.
Significant changes are required to the pressure mechanism of the bonding device and the balance adjustment between it and the stage.

On the other hand, since the bumps of the present invention are joined by solder, the heating temperature only needs to be 250 to 350°C, and since the solder melting method is used, the pressure can be significantly reduced, which is a problem with conventional ball bumps. Thermal and mechanical shocks that were a problem can be significantly alleviated. Also, in the past, solder bumps were sometimes used instead of Au bumps, etc.
These solder bumps tend to collapse when the leads are heated and pressurized with a heating tool, making it impossible to maintain the height of the leads at a predetermined value after crimping. On the other hand, the ball bump of this embodiment does not have such a drawback because a metal ball such as Au is present in the center.

In the case of a flip-chip type semiconductor device as well, positioning bonding may be performed by positioning and positioning a semiconductor chip with bumps formed on a printed circuit board face down, as in the conventional case.

FIG. 2 is a sectional view showing a bump manufactured by the second embodiment method of the present invention. In FIG. 3, the same parts as in FIG. 1 are denoted by the same reference numerals, and their explanation will be omitted.

An electrode 22 is selectively formed on the surface of the semiconductor chip 21, and a Ti-Pt-Au layer and a Ti-Pt-Au layer are formed on the electrode 22.
A barrier metal layer 26 made of -Cu-Au layer or Cr-Cu-Au layer is selectively formed. Then, metal balls 23 and solder 24 are placed on this barrier metal layer 26.
A ball bump consisting of

In the method of this embodiment, first, for example, using a photoresist method, A! T s + P on the electrode 22
By selectively depositing a metal selected from L Cre Cul Au and the like, the barrier metal layer 26 is formed as a stack of layers made of these metals. Next, a metal ball 23 is bonded onto this barrier metal layer 26 in the same manner as in the first embodiment, and then the surface of the metal ball 23 is coated with solder 24 to complete the bump of this embodiment.

In this embodiment, since the A7 electrode 22 is covered with the barrier metal layer 26, there is an advantage that reliability is improved in addition to producing the same effects as the first embodiment.

Effects of the Invention As explained above, the present invention involves forming a metal ball in a manner similar to, for example, wire bonding, bonding the metal ball to a predetermined position on a semiconductor chip, and then immersing the entire body in molten solder. By doing this, the surface of the metal ball is coated with solder to form a bump, so that a bump with excellent bonding properties can be easily formed at low cost.

When mounting a semiconductor chip with solder-coated bumps formed in this way, the leads can be bonded at a lower temperature and pressure than before, and the bumps will not be crushed during bonding. A highly reliable semiconductor device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a bump manufactured by the method of the first embodiment of the present invention, FIGS. 2(a) to (c) are schematic diagrams showing the bump forming method in the order of steps, and FIG. the second of
Cross-sectional view showing the bump manufactured by the example method, No. 4
7 to 7 show a conventional film carrier semiconductor device, FIGS. 4 to 6 show the process in the middle of its manufacture, FIG. 7 shows its mounting state, and FIGS. 9
The figures show a conventional flip-chip semiconductor device. FIG. 8 is a plan view of the flip-chip type semiconductor chip, and FIG. 9 is a diagram showing its mounting state. 1.21; semiconductor chip, 2; film carrier tape, 7; bump, 22; electrode, 23; metal ball, 24;
Solder, 26; Barrier metal layer, 30; Wafer, 31; Tool, 34; Fine metal wire 21; Semiconductor knob 22: Ball 23; Metal hole 24; Solder 26: Barrier methanol Figure 9: Resin 11 Nearest Basic i Figure Figure Figure Figure

Claims (1)

[Claims] (1) A step of forming a metal ball at the tip of the thin metal wire,
a step of bonding the metal ball to a predetermined position of a semiconductor chip; a step of separating the metal thin wire from the metal ball and installing the metal ball at the predetermined position;
A method for manufacturing a bump for a semiconductor chip, comprising the step of coating the surface of the metal ball with solder.