JPS5935178B2 - Method of forming solder bumps on electrodes on semiconductor substrates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming solder bumps on an electrode portion on a semiconductor substrate.

A wire bonding method using ultrafine Al wires, Au wires, or the like is used to connect the semiconductor substrate and external leads.

On the other hand, various wireless bonding methods that do not use wires have been proposed and some have been put into practical use for the purpose of improving the reliability of connection parts, increasing density, reducing costs, etc. The present invention
The present invention relates to a connection method using solder in this wireless bonding method. As is well known, the connection method using solder is the CCB method of IBM Corporation.

As shown in FIG. 1, this method uses a metal mask to sequentially deposit Cr-Cu-Au on the Al electrode portion 2 exposed from the insulating film 3 on the semiconductor substrate 1, and then Deposit solder using a metal mask. In this method of vacuum evaporating solder using a metal mask, controlling the amount of evaporated solder is very important from the viewpoint of reliability of the connection, and it is also true that the larger the amount of solder, the easier the connection. It's obvious. On the other hand, when a vacuum evaporation method is used as a solder supply method, the maximum evaporation thickness is limited to about 100 μm.

For this reason, in order to obtain the necessary amount of solder, IBM uses a metal mask with a hole diameter larger than the diameter of the Cr-Cu-Au deposited film on the electrode part to deposit the solder, as shown in Figure 2.
After that, it is melted and the required amount of solder is obtained by utilizing the property that solder is drawn onto the Cr--Cu--Au vapor deposited film due to surface tension. However, the hole shape of the metal mask used at that time is circular, and the hole shape is the electrode part (Cr-Cu-
The distance between adjacent electrodes had to be at least larger than the metal mask hole diameter.

If the metal mask hole diameter is larger than the distance between adjacent electrodes, as shown in Figure 3, the solder will be deposited between the adjacent electrodes, and the solder will be separated on the adjacent electrodes after melting. It is clear that variations in quantity occur. On the other hand, semiconductors have become denser with process C and LS processes, and in order to improve yields, the spacing between electrode parts tends to become smaller, and the required amount of solder cannot be achieved with conventional metal masks with circular hole shapes. I've become unable to do it. Therefore, the present invention aims at making the hole shape of the metal mask not circular but elongated in a direction that does not interfere with the adjacent electrodes, such as an oval or an ellipse.

When such a method is used, at least the Cr of the electrode part can be removed.
-If the distance between adjacent electrodes is equal to or larger than the diameter of the deposited Cu-Au film, the required amount of solder can be obtained. Next, a specific example will be explained using FIG. 4. When the electrodes 5 are arranged on the semiconductor substrate 1 as shown in FIG. 4a, the distance between adjacent electrodes is so small that the required amount of solder cannot be obtained with a conventional metal mask having a circular hole shape. It becomes necessary to rearrange the electrodes and widen the electrode spacing as shown in FIG. 4b. Also,
Even with this method, if sufficient electrode spacing cannot be obtained, it becomes necessary to increase the size of the semiconductor substrate itself. This results in a decrease in the yield of semiconductor substrates and an increase in cost. FIG. 4c shows a case where the metal mask according to the present invention is used, and has an oval hole shape extending in a direction that does not approach adjacent electrodes. This method has the great advantage that conventional semiconductor substrates can be used as they are. As explained above, the use of the metal mask of the present invention has the advantage of allowing the use of conventional wire-bonded semiconductor substrates as is, thereby preventing special mask changes and yield reductions, resulting in an increase in the cost of semiconductor substrates. In addition to minimizing the amount of noise, the connection method can be easily changed from traditional wire bonding to wireless bonding.

Note that the hole shape of the present invention is not limited to the ellipse of the above specific example, and it goes without saying that similar effects can be obtained even if other shapes are used.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the solder deposition process, Figure 2 is a cross-sectional view showing the solder melting state, Figure 3 is a plan view and cross-sectional view showing the difference due to electrode spacing, and Figures 4 a-c are conventional products. FIG. 3 is a plan view for comparison between the product manufactured by the method according to the present invention and the product manufactured by the method according to the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Al electrode part, 3... Insulating film, 4... Cr-Cu-
Metal mask for Au deposition, 5...Cr-Cu-
Au evaporation film, 6...metal mask for solder evaporation,
7...Solder vapor deposition film.

Claims (1)

[Claims] 1. In a method of forming a solder bump on an electrode part on a semiconductor substrate by using a metal mask and melting solder after vacuum evaporation, the hole shape of the metal mask does not approach the electrode part closest to the electrode part. A method of forming a solder bump on an electrode portion on a semiconductor substrate, the method comprising forming a solder bump into a shape extending in a direction.