JPH0233929A - Semiconductor device - Google Patents

Abstract

PURPOSE:To alleviate load at the time of connecting an outer lead and ease the influence on a substrate by surrounding a second metal bump layer composed of hard metallic material by the use of a first and a third bump layers composed of a soft metallic material whose surface is difficultly oxidized. CONSTITUTION:An insulating film 12 on a semiconductor substrate 11 is opened on an Al electrode 13 to constitute a pad electrode and a first and a second metal films 14, 15 such as Ti/Cu or Ti/Pt are formed so as to cover the opening. Further a first comparatively soft metal bump layer 16 such as gold is formed on these metal films 14, 15 and a second comparatively hard metal bump layer 17 such as copper in the narrow range thereon. Further a third soft metal bump layer 18 such as gold is formed so as to cover the second metal bump layer 17 thereon and the device is constituted so that the second metal bump layer 17 can be surrounded by the first and the third metal bump layers 16, 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device having metal bumps.

[Conventional technology]

Conventionally, metal bumps formed on semiconductor devices as external connection electrodes are metal bumps 3 made of copper or the like, as shown in FIG.
It has a structure in which a metal layer 37 such as gold is formed on the surface of the wire 6 to improve adhesion with external lead wires. That is, in the metal bump having the structure shown in FIG. 3, an insulating film 32 formed on a semiconductor substrate 31 is opened on an aluminum electrode 33 to form a pad electrode, and a first pad electrode is formed on the aluminum electrode 33. Second metal films 34 and 35 are formed. Then, a photoresist or the like is adhered thereon, and an opening larger than the aluminum electrode 33 is opened, and a metal such as copper is selectively formed therein by a plating method to form a metal bump 36. Further, a metal layer 37 of gold or the like is formed on the metal bump 36. Then, the photoresist is removed, and the first. This is completed by etching the second metal films 34 and 35.

[Problem to be solved by the invention]

Since most of the conventional metal bumps described above are made of a relatively hard metal material such as copper, the pressure load associated with the connection of the external leads is directly transmitted to the semiconductor substrate 31.

This causes cracks to occur in the semiconductor substrate 31 or deterioration of characteristics of elements formed in the underlying layer. In this case, if the metal bumps are simply made of a soft metal, there is a risk that the metal bumps will collapse and spread laterally when external leads are connected, resulting in a short circuit with adjacent leads, etc., which will impede high density electrodes.

Further, the conventional metal bump 36 has a metal layer 3 such as gold on the top surface.
7, but the material is exposed on the side surfaces, and this side surface is easily oxidized and surface deterioration occurs. For this reason, there is a problem that the connection resistance with the external lead increases or a connection failure occurs, resulting in a decrease in the reliability of the semiconductor device.

An object of the present invention is to provide a semiconductor device which is improved in reliability by preventing surface deterioration due to oxidation, etc., and reducing pressure load during connection with external leads to prevent damage to the semiconductor device. It is an object.

[Means for Solving the Problems] The semiconductor device of the present invention provides a first pad electrode formed on a pad electrode provided on a semiconductor substrate using a metal material that is soft and whose surface is not easily oxidized.
a second metal bump layer made of a hard metal material on the first metal bump layer; and a third metal bump layer made of a soft metal material whose surface is not easily oxidized so as to cover the second metal bump layer. It has a metal bump composed of a metal bump layer.

[Effect]

In the double-connected configuration, the first and third metal bump layers are soft and difficult to oxidize, so the load when connecting external leads is alleviated by these metal bump layers to reduce the impact on the semiconductor substrate. On the other hand, it also prevents connection failures due to surface oxidation. In addition, the hard second metal bump layer minimizes crushing of the metal bumps and achieves high density electrodes.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of a metal bump applied to a semiconductor device of the present invention. As shown, a semiconductor substrate 1
A pad electrode is formed by opening the insulating film 12 on the aluminum electrode 13, and T i /
1. such as Cu or Ti/Pt. A second metal film 14.15 is formed.

Furthermore, a relatively soft first metal bump layer 16 made of gold or the like is formed on these metal films 14.15, and a relatively hard second metal bump layer 117 made of copper or the like is formed in a narrow area on top of this layer 16.
form. Further, a soft third metal bump layer 18 made of gold or the like is again formed thereon so as to cover the second metal bump layer 17, and then the first metal bump layer 18 is formed again. Third metal bump layer 16.1
8 surrounds the second metal bump layer 17.

FIGS. 2(a) to 2(g) are cross-sectional views showing the method for manufacturing the structure shown in FIG. 1 in order of steps.

First, as shown in FIG. 2(a), an aluminum layer of about 1 μm is formed on the entire surface of the semiconductor substrate 11 on which semiconductor elements (not shown) are formed by a smoke deposition method or a sputtering method, and then a photolithography technique using a photoresist is applied. The aluminum electrode 13 is formed by selective etching. C on top of this
The aluminum electrode 1 is formed by forming an insulating film 12 such as a VD oxide film or a CVD nitride film, and selectively etching this insulating film 12 using photolithography technology.
A region constituting an electrode on 3 is opened to constitute a pad electrode.

Next, as shown in FIG. 2(b), the first and second metals, such as Ti/Cu or Ti/P, are deposited on the entire surface by sputtering. 14 and 15 are each formed to a thickness of about 10008. On top of this, a negative type first photoresist 2 is applied.
0 is deposited and an aperture window somewhat larger than the aperture of the insulating film 12 is formed.

Next, as shown in FIG. 2(c), by a plating method using the first photoresist 20 as a mask, the thickness of the photoresist 20 is equal to or slightly thinner, for example, 4 to 5.
A first metal bump layer 16 made of a relatively soft metal material such as gold is formed to a thickness of μm.

Next, as shown in FIG. 2(d), the first photoresist 20 is left as it is, a positive type second photoresist 21 is formed thereon, and the first metal bump layer 16 is formed thereon.
Open a window with a smaller opening.

Subsequently, as shown in FIG. 2(e), a second metal made of a relatively hard metal material such as copper is deposited on the first metal bump layer 16 by a plating method using the second photoresist 21 as a mask. A bump N17 is formed. After that, Fig. 2 (f
), the second photoresist 21 is exposed, developed and removed.

Thereafter, a relatively soft metal material such as gold is deposited on the first metal bump layer 16 and the second metal bump layer 17 to a thickness of 4 to 5 μm using the first photoresist 20 as a mask again. A third metal bump layer 18 is formed. Thereafter, the first photoresist 20 is removed, and the first and second metal films 14 and 15 are etched away using the third metal bump JilB as a mask, thereby completing the structure shown in FIG. . Note that these metal films 1
For etching in 4.15, Ti/Cu can be easily etched with a special etching solution, while Ti/Pt can be etched using a highly directional etching method such as ion milling. Use.

Therefore, in the metal bump having this configuration, since the relatively hard second metal bump layer 17 is surrounded by the relatively soft first and third metal bump layers 16 and 18, when connecting to the external lead, 1st and 3rd by pressure load
The metal bump layers 16 and 18 are crushed and absorb this pressure load, thereby alleviating the load applied to the semiconductor substrate 11 and preventing the occurrence of cracks and device defects. On the other hand, the hard second metal bump layer 17 present in the center can minimize crushing of the metal bumps and maintain high density of the electrodes.

Furthermore, in the metal bump having this configuration, the first and third metal bump layers 16 and 18 made of gold, which is difficult to oxidize, surround the second metal bump layer 17 made of copper, which is easily oxidized on the surface. This prevents surface deterioration, prevents poor contact with external leads, and improves connection reliability.

Note that in the embodiment described above, the first metal bump layer 16 and the third metal bump layer 18 are each made of gold, but they may be made of different materials. However, it is important that these metal materials are soft and resistant to surface oxidation.

〔Effect of the invention〕

As explained above, the present invention has a structure in which the second metal bump layer made of a hard metal material is surrounded by the first and third metal bump layers made of a metal material that is soft and whose surface is not easily oxidized. The third metal bump layer can reduce the load when connecting the external leads and reduce the influence on the semiconductor substrate, while also preventing connection failures due to surface oxidation. Moreover, the hard second metal bump layer can minimize crushing of the metal bumps and achieve high density electrodes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a metal bump of a semiconductor device of the present invention, FIGS. 2(a) to 2(g) are cross-sectional views showing the method of manufacturing the structure of FIG. 1 in order of steps, and FIG. FIG. 2 is a cross-sectional view of a metal bump of a conventional semiconductor device. 11... Semiconductor substrate, 12... Insulating film, 13...
Aluminum electrode, 14... first metal film, 15...
Second metal film, 16... First metal bump layer, 17...
Second metal bump layer, 18...Third metal bump layer, 20
... first photoresist, 21 ... second photoresist, 31 ... semiconductor substrate, 32 ... insulating film, 33
... Aluminum electrode, 34 ... First metal film, 35
...Second metal film, 36...Metal bump, 37...
metal layer. Figure 3 Figure 2 Figure 3

Claims (1)

[Claims] 1. A first metal bump layer made of a soft metal material whose surface is not easily oxidized and formed on a pad electrode provided on a semiconductor substrate, and a second metal bump layer made of a hard metal material formed on this first metal bump layer. It has a metal bump composed of a metal bump layer and a third metal bump layer formed on the first metal bump layer so as to cover the second metal bump layer and made of a metal material that is soft and whose surface is not easily oxidized. A semiconductor device characterized by: