JPH0129061B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming metal protrusions on a connecting metal when bonding an electrode on a semiconductor element and an external lead (connecting metal).

Conventional configurations and their problems In recent years, semiconductor elements such as ICs and LSIs have been introduced into the fields of various home appliances and industrial equipment. In order to save resources and power, or to expand the scope of use, these household electrical appliances and industrial equipment are being made smaller and thinner, so-called portable.

In order to make semiconductor devices portable, there has been a demand for smaller and thinner packaging. After the diffusion process and electrode wiring process have been completed, the silicon rice is cut into chips for each semiconductor element, and electrode leads are taken out from the aluminum electrode terminals provided around the chips to external terminals for ease of handling and for mechanical protection. packaged. Usually, DIL, chip carrier, tape carrier methods, etc. are used for packaging these semiconductor devices. Among these, the tape carrier method is one that has high reliability at connection points and can provide smaller, thinner packaging. In packaging a semiconductor device using the tape carrier method, a multilayer metal film called a barrier metal is provided on the electrode terminals on the semiconductor device, and metal protrusions are further provided on this multilayer metal film by electroplating. Then, metal lead terminals are provided on a long polyimide tape of a constant width, and the metal protrusions on the electrode terminals of the semiconductor element and the lead terminals are simultaneously connected at once regardless of the number of electrode terminals.

However, conventional tape carrier systems also include various problems. Therefore, the inventors of the present invention
In No. 56-37499 (Japanese Unexamined Patent Publication No. 57-152147), we proposed a new bonding method (hereinafter referred to as the transfer bump method) based on the tape carrier method.

The main feature of the present invention is that there is no need to form metal protrusions on the semiconductor element, and furthermore, the metal protrusions are formed on the metal lead side by a transfer method.

FIG. 1 shows a method according to an embodiment of the above invention previously proposed by the present inventors.

First, electrode leads 22 are formed on a long polyimide resin tape 21 . The electrode lead 22 is made of, for example, a 35 .mu.m thick Cu foil plated with Sn to a thickness of about 0.2 to 1.0 .mu.m, and has the same structure as that used in a normal film carrier system. Next, board 2
Metal protrusions 24 having the same dimensions as the spacing between the metal leads 22 are formed on the metal leads 3 by electrolytic plating (FIG. 1a).

If the metal protrusion 24 and the metal lead 22 are aligned and heated and pressurized as shown by the arrow 27 using the tool 26 (FIG. 1b), if the metal protrusion 24 is made of Au, the metal lead 22 will be is formed
A perfect bond can be obtained by forming eutectic formation with Sn. When the pressure 27 is removed, the metal protrusion 24 is peeled off from the substrate 23 side and becomes bonded to the metal lead 22 (FIG. 1c). In the state shown in FIG. 2c, the metal projections 24 of the substrate 23 are transferred to the metal leads 22 side.

Next, the aluminum electrode 2 on the semiconductor element 25 is
The metal protrusion 24 is aligned at 8 and heated and pressurized as shown at 27' with a tool 26' (FIG. 1d). By this operation, the Au of the metal protrusion 24 and the semiconductor element 2
It can be alloyed with the aluminum electrode 28 on top 5 to obtain a perfect bond. This state is shown in Figure 1 e.
It was shown to.

In the method shown in FIG.
The intervals of are the same value.

The method previously proposed by the inventors described above is based on the lead of the commonly used film carrier.
Joining metal protrusions formed on another substrate,
At this stage, the metal protrusions are transferred to the leads. The metal protrusions formed on the leads are easily joined to aluminum electrodes on the semiconductor element.

In such a transfer bump method, the substrate 23 for forming the metal protrusions 24 becomes unnecessary after the metal protrusions 24 are transferred and bonded to the metal leads 22. In other words, the substrate is only placed with metal protrusions formed once;
In the conventional transfer bump method, it was used only once. If the substrate 23 is used to form the metal protrusions 24 only once, different substrates will be used as the metal protrusions are transferred, and the dimensional accuracy of the positional spacing between the metal protrusions will vary. This results in insufficient alignment accuracy with aluminum electrodes on semiconductor elements formed with high precision, and increases the mounting cost of the entire system.

OBJECT OF THE INVENTION The present invention has been made to eliminate the above-mentioned conventional drawbacks, and provides a method for forming metal protrusions on a connecting metal, in which a substrate on which metal protrusions are formed can be used many times, and The purpose of this invention is to repeatedly form metal protrusions with high precision and uniformity, thereby improving the transfer yield.

Structure of the Invention The method for forming metal protrusions on a connection metal of the present invention includes forming a metal film for plating on a substrate, and forming a plurality of openings on the metal film, the bottoms of which are covered with the metal film. a process of forming a heat-resistant insulating film having a heat-resistant insulating film, a process of simultaneously forming one metal protrusion in each of the plurality of openings by a plating method, and positioning a connecting metal from above the plurality of metal protrusions. , heating and pressurizing the lower surface of the connecting metal and the upper surface of the plurality of metal protrusions with the metal protrusions facing upward to join them without melting the entire metal protrusions;
separating the metal protrusion from the substrate above the substrate; forming the metal protrusion again in the opening formed by the metal film and the insulating film on the substrate and bonding the metal protrusion to the connection metal; It is equipped with a process to perform. According to the present invention, metal protrusions can be formed with extremely high precision, and transfer can also be achieved with high yield.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described based on FIGS. 2a and 2b. Insulating substrate 31 made of glass, ceramic, etc.
Au serves as the cathode electrode when forming metal protrusions on top;
Thousands of metal layers 32 made of Pt, Pd, Cu, Ni, etc.
It is formed over the entire surface to a thickness of Å to several μm. Next, a heat-resistant resin film, such as a polyimide resin or silicone resin film 33, is deposited on the metal layer 32 to a thickness of several thousand Å to several μm,
As shown in the figure, a large number of openings 34 whose bottoms are covered with a metal layer 32 are formed in areas where metal protrusions are to be formed.
2, the structure shown in FIG. 2a is obtained.

Then, by plating the metal film 32 as one electrode, the structure shown in FIG. 2b, that is, the metal projection 3 is formed.
5 can be formed on the aperture 34 of the heat-resistant resin film 35. At this time, one metal protrusion 34 is formed in each opening 34.

Further details of the steps shown in Fig. 2 a and b show that the thickness is 1
Ni then Au or Pt on Pyrex glass of mm
Ni is continuously deposited using a vacuum evaporation method at a substrate heating temperature of 250°C.
A film thickness of 1000 Å and an Au or Pt film thickness of 1000 Å were formed.
Next, a photosensitive polyimide resin (trade name: Photonice) film is formed to a thickness of 1 μm, and after forming the openings 34, metal protrusions 35 are formed by electroplating for 10 to 10 minutes.
Form to a thickness of 50 μm.

Align the metal lead from above the metal protrusion 35 formed in this way as shown in FIG. Heat, pressurize,
If the entire protrusion is transferred and bonded to the metal lead side without melting as shown in FIG. 1, the substrate 31 returns to the state shown in FIG. 2a. At the time of said joining
A temperature of about 200 to 350°C and a pressure of 0.1 to 2 kg/cm ² are applied, but under these conditions, the protrusion 35 does not melt entirely, and the photosensitive polyimide resin has heat resistance and flexibility. Therefore, another metal protrusion can be formed again without deforming or damaging the opening made of the photosensitive polyimide resin. In other words, the substrate and resin can withstand being reused more than 10 times to form metal protrusions, eliminating the conventional situation of single-use conditions. In addition, the metal protrusion formation position can be kept constant and high positional accuracy can be maintained.

Furthermore, since the method shown in FIG. 1 is a method of transferring and bonding the protrusion 35 to the metal lead side without melting the entire protrusion 35, the surface of the substrate 23 on which the protrusion is formed and the bonding tool 26 maintain extremely high parallelism. are doing. Therefore, if the heights of the formed protrusions are different, the metal lead will come into contact with the taller protrusions, resulting in bonding and
However, if there is even one low protrusion, the metal lead will not come into contact with this protrusion, so this low protrusion will not be transferred and will remain in the opening of the substrate, reducing the transfer rate. Experiments have shown that unless the variation in the height of each protrusion is made extremely small, the transfer rate will drop significantly. In order to suppress the variation in the height of the protrusion during plating formation, as shown in the configuration shown in Figure 2, the entire bottom of the hole is covered with a metal film to make the electrical resistance uniform throughout the hole. need to be set low. By doing so, the variation in height of the many metal protrusions formed can be made extremely small, and the metal film will not deteriorate.

After the uniformly formed metal protrusions 35 and the leads are bonded together, the protrusions are separated above the substrate as shown in FIG. The protrusions bonded and transferred to the leads can maintain the shape immediately after plating, and the protrusions can be formed on the leads with uniform precision.

Furthermore, as another embodiment of the method of the present invention,
Instead of the photosensitive resin 33, a film of metal oxide such as silicon oxide, aluminum oxide, titanium oxide, or silicon nitride can be used as a nitride. In this embodiment, since a relatively thin film and a more heat-resistant film can be obtained, a substrate having apertures for plating can be used more times.

Effects of the Invention The method for forming metal protrusions on a connecting metal according to the present invention uses a substrate on which a heat-resistant insulating film is formed in which openings for forming metal protrusions are formed, so that the substrate is plated multiple times. It is possible to obtain a substrate that can withstand the formation of metal protrusions and transfer bonding of the protrusions to a connecting metal, and can be used many times, and manufacturing costs can be significantly reduced. In addition, since the substrate on which the metal protrusions are formed can be reused, a different substrate is not supplied each time transfer bonding is performed, and the position and dimensions of the metal protrusions on the substrate can be kept reliably constant. The alignment accuracy between the connecting metal and the metal protrusion can always be kept high. As a result, the alignment accuracy between the metal protrusion and the electrode of the semiconductor element is improved, and highly reliable bonding can be obtained. Furthermore, according to the present invention, variations in the height of the metal protrusions are significantly reduced, and changes in the shape of the protrusions are also small, making it possible to improve the uniformity, reliability, and yield of bonding to the connecting metal and transfer. It is extremely effective in the transfer bump process.

[Brief explanation of drawings]

1A to 1E are process cross-sectional views of the transfer bump method previously proposed by the present inventors, and FIGS. 2A and 2B are process cross-sections showing a method of forming metal protrusions on metal leads in an embodiment of the present invention. It is a diagram. 31...Substrate, 32...Metal layer, 33...Heat-resistant insulating film, 34...Opening portion, 35...Metal protrusion.

Claims (1)

[Claims] 1. Forming a metal film for plating on a substrate, forming a heat-resistant insulating film having a plurality of openings whose bottoms are covered with the metal film on the metal film, and forming the plurality of openings. At the same time, one metal protrusion is formed on each of the metal protrusions using a plating method, and the connecting metal is aligned from above the plurality of metal protrusions, and with the metal protrusions facing upward, the connecting metal is The lower surface and the upper surface of the plurality of metal protrusions are heated and pressurized to join without melting the entire metal protrusions,
separating the metal protrusion from the substrate above the substrate; forming the metal protrusion again in the opening formed by the metal film and the insulating film on the substrate and bonding the metal protrusion to the connection metal; 1. A method for forming metal protrusions on a connecting metal, comprising the steps of: