JPS6127898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a plated metal electrode of a semiconductor device.

Electrodes are extremely important in semiconductor devices, and in order to prevent electromigration and improve high frequency characteristics and large current characteristics, electrodes must be formed thick and uniformly. Furthermore, in order to improve the reliability of a semiconductor device, it is often necessary to make at least the surface layer of the electrode with gold. As is well known, gold is an extremely chemically stable metal, so a relatively thick film of about 1 micron, obtained by vapor deposition or sputtering, can be fabricated into a semiconductor using processing techniques such as photolithography. It is extremely difficult to precisely process electrodes to the ultra-fine electrode width of several microns required for the device. For this reason, gold electrodes of semiconductor devices are usually formed by plating gold on a pre-formed base electrode. During this plating, a conductive material must be previously formed on the surface of the semiconductor device in order to conduct current from the plating device to the portion to be plated. The conductive material for this purpose is
Titanium or chromium is selected so that it can be easily removed after gold plating, and its formation is by vapor deposition. However, the insulating film covering the surface of the semiconductor device is removed in advance at the electrode formation area and at the peripheral edge of the semiconductor device (i.e., the scribe area), which corresponds to the dividing area when dividing the semiconductor wafer into individual semiconductor devices. Since there is a sharp step difference, if a conductive material for plating is deposited on top of the step, there is a drawback that the conductive state of the conductive material is likely to be unable to be maintained due to the step difference in the insulating film.

An object of the present invention is to prevent electrical disconnection of the metal layer, which serves as a current path to the plated portion, at the stepped portion of the insulator when at least a portion of the electrode of a semiconductor device is formed by plating. It is an object of the present invention to provide a method for manufacturing a semiconductor device, which can provide a structure that prevents this problem and can form a thick and uniform plating electrode.

To achieve the above object, the present invention provides a first semiconductor substrate having a contact hole exposing a part of a semiconductor region selectively formed in the substrate and a peripheral edge defining a scribe region of the substrate. forming an insulating film on the first insulating film having a contact hole larger than the contact hole and having a peripheral end located inside the peripheral end of the first insulating film; a step of forming an existing second insulating film, a step of covering the surface of the substrate having the first and second insulating films with a conductive film, and plating for the semiconductor region using the conductive film as a current path. The method is characterized in that it includes a step of selectively forming a metal electrode, and a step of selectively removing the conductive film using the plated metal electrode as a mask.

As described above, according to the present invention, the step difference at the end of the insulating film at the contact hole and the scribe portion is alleviated. Therefore, it becomes easy to uniformly apply the conductive film to the entire surface in a mechanically and electrically stable state. After this conductive film is deposited, an electrode is formed on the conductive film on the electrode forming portion by plating, using the conductive film as a current path. Here, the structure of the above-mentioned insulator is a single layer made only of silicon dioxide, etc., and a case where silicon nitride is further added on the insulating film such as silicon dioxide to prevent contamination with sodium ions of the silicon dioxide. In some cases, it is a multilayer structure consisting of stacked insulating films such as aluminum oxide or aluminum oxide, and in both configurations, the insulator end is formed so that the thickness of the insulator end gradually decreases from the inside of the insulator to the end. This makes it possible to deposit mechanically and electrically stable electrically conductive films.

In this way, in order to gradually reduce the thickness of the insulating material covering the surface of the semiconductor device from the inside to the end at the removed part, that is, the part where the step is created, a conductive film is plated using a vapor deposition method to form an electrical path. Since the insulator level difference is reduced when the conductive film is formed, there is almost no occurrence of the inconvenience that the conductive film is cut at this part. Therefore, electrodes of a semiconductor device can be formed extremely easily by plating.

Next, preferred embodiments of the present invention will be explained using the drawings.

FIG. 1 shows a preferred embodiment of the invention.

The surface of the semiconductor substrate 11 is covered with a silicon dioxide film 13 in which all necessary semiconductor regions 12 such as a base, emitter, source, drain, anode, and cathode are formed. As shown in FIG. 1A, this silicon dioxide film 13 is removed by photolithography at the electrode forming portion of the semiconductor region and further at the periphery of the device in a width of 20 to 30 microns from the end of the device. . Next, the silicon dioxide film 13 is covered with a silicon nitride film and a silicon dioxide film. At each step, the removal width from the end of the device is 2 to 3 microns shorter than that reaching the end of the silicon dioxide film 13 by photolithography. Next, using the uppermost silicon dioxide film 15 as a mask, the electrode forming portion and the device peripheral portion of the silicon nitride film are removed using phosphoric acid or the like. Through the above steps, the surface of the silicon dioxide film 13 is wrapped in the silicon nitride film 14 as shown in FIG. It is formed so that it gradually decreases from the inside to the end. Next, as shown in FIG. 1C, titanium is deposited to a thickness of 500 .ANG. over the entire surface of the semiconductor device having the selectively removed insulator.
Furthermore, as shown in FIG. 1D, a platinum layer 17 is formed by vapor deposition on the electrode forming portion of the titanium film 16. Next, only the upper surface of the platinum layer 17 is exposed, and the other surface is covered with a photoresist film 19, and then the semiconductor device is immersed in a gold plating bath. An electrode is formed by forming a gold layer 18 on the platinum layer 17 by plating, using the conductive film 16 as a cathode and the titanium conductive film 16 as a current path. Next, as shown in FIG. 1E, after removing the photoresist film 19, the exposed portion of the titanium film 1 on the surface is treated with hot sulfuric acid or the like.
Remove 6.

If the bottom layer silicon dioxide film 13, the silicon nitride film 14, and the top layer silicon dioxide film 15 share exactly the same periphery at the scribe groove portion of the periphery and the insulator end of the electrode forming portion, then from the surface of the base 11. The level difference to the surface of the uppermost silicon dioxide film 15 is extremely large, and in order to maintain the electrical connection of the titanium layer 16, which serves as a path for the plating current, the thickness of the deposited film is required. must be as thick as this step.
Further, the portion of the titanium layer 16 that is to become a path for the plating current is eventually chemically dissolved and removed, but must remain under the metal electrode 18 formed by plating. However, during this dissolution and removal, the titanium under the gold electrode also becomes thinner by a width approximately equal to its film thickness, and if the titanium film thickness and the width of the gold electrode are close, the width of the titanium under the gold electrode becomes The gold electrode becomes extremely thin compared to the width of the gold electrode or does not remain, making it impossible to form an effective electrode for a semiconductor device. However, if the thickness of the insulator is gradually reduced from the inside of the insulator to the ends as in the present invention, the titanium layer 16 can function as a conductive layer while remaining sufficiently thin. Therefore, gold electrodes with extremely fine structures can be easily realized.

[Brief explanation of the drawing]

FIGS. 1A to 1E are cross-sectional views showing each step of an embodiment of the present invention. 11 is a semiconductor substrate, 12 is a semiconductor region, 13 and 15 are silicon dioxide films, 14 is a silicon nitride film, 1
6 is a titanium film, 17 is a platinum layer, 18 is a gold electrode, 1
9 is a photoresist film.

Claims (1)

[Claims] 1. Forming on a semiconductor substrate a first insulating film having a contact hole that exposes a part of a semiconductor region selectively formed on the substrate and a peripheral edge defining a scribe region of the substrate; forming a second insulating film having a contact hole larger than the contact hole and having a peripheral edge located inside the peripheral edge of the first insulating film and existing on the first insulating film; a step of covering the surface of the substrate having the first and second insulating films with a conductive film; and a step of selectively forming a plated metal electrode for the semiconductor region using the conductive film as a current path. and selectively removing the conductive film using the plated metal electrode as a mask.