JPH035657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device provided with an electrode wiring layer mainly composed of aluminum.

In semiconductor devices, especially integrated circuits, aluminum (Al) films are used as electrode wiring layers.
Poly-Si (or Al)-Al- from silicon wafer
There is a method in which Al such as Al is laminated in multiple layers and applied as a multilayer wiring. It is usually used in a resin molded state or in a package with air removed, but resin sealing materials contain a large amount of Na ⁺ and
Contains Cl ^- ions, which corrode Al films.

The present invention has been made in view of the above circumstances, and is designed to prevent this by covering only the uppermost layer of electrode wiring mainly composed of Al with an alloy of Ti or V. At this time, alloying only the top layer of the multilayer Al film is because if the entire multilayer Al film is covered with alloy, the alloying will eat away the Al, resulting in a significant increase in the resistance of the wiring, and furthermore, the lower layer Al wiring The line width is narrow (the top layer Al wiring takes into consideration the pattern accuracy due to the unevenness of the underlying layer, and the wiring is gathered in the upper layer, so it is wide), and when alloyed, the resistance increases significantly. This is because it is desirable to alloy only the top layer. In addition, it is sufficient to cover only the top layer with an alloy layer with a transition metal to prevent corrosion caused by Na ⁺ and Cl ^- ions.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of multilayer wiring of an integrated circuit. Reference numeral 1 denotes a silicon substrate wafer, on which elements such as bipolar transistors (in this case PMP) have already been formed through a diffusion process. Reference numeral 2 denotes an insulating film, which is made of silicon oxide or nitride, and has openings in the parts that are electrically connected to the element. Reference numeral 3 denotes an electrode wiring mainly made of aluminum and formed by patterning a deposited film. 4
is an insulating film, ie, a passivation film, such as phosphor glass, CVD-SiO ₂ film, or polyimide. Reference numeral 5 denotes a second layer of electrode wiring mainly made of aluminum, which is connected to the first layer of electrode wiring 3 through a hole provided in the insulating film 4. Although insulating films and electrode wiring may be alternately stacked on top of this, it is assumed here that the second layer of electrode wiring 5 is the top layer. In order to form a transition metal intermetallic compound layer on the surface of the uppermost layer of electrode wiring, a transition metal 6 is first vapor-deposited over the entire surface of the wafer as shown in FIG. Next, heat treatment is performed at an appropriate temperature to form an intermetallic compound layer 7 as shown in FIG. Finally, as shown in FIG. 4, only unreacted transition metals are removed using an etching solution. After this, the whole thing is molded in resin.

A specific example of preparation was performed as follows.
After completing the diffusion process, a silicon dioxide film with a thickness of 5000 Å is formed on the surface of the wafer by thermal oxidation, holes are made as necessary, and then aluminum is evaporated to a thickness of 1 μm.
A wiring pattern with a width of 4 μm was made using the usual etching method.
Next, phosphorus glass (PSG) was formed to a thickness of 1 μm using a CVD (Chemical Vapor Deposition) method. 1st
After making a hole in the phosphor glass at the contact point between the first layer wiring and the second layer wiring, the second layer aluminum wiring (1 μm thick) is formed by vapor deposition and etching.
A pattern width of 10 μm) was formed. Titanium or vanadium was used as the transition metal for forming the intermetallic compound, and the thickness of the deposited film was 1000 Å. The heat treatment to form the intermetallic compound was carried out at 450° C. for 30 minutes in a nitrogen atmosphere containing 10% hydrogen. The heat treatment conditions are generally the same as those for obtaining ohmic contact between the device and the wiring, and both can be performed at the same time. The thickness of the intermetallic compound layer formed after the heat treatment was approximately 3000 Å in the case of titanium. Vanadium may also be used. Unreacted transition metal (titanium or vanadium)
Removal of hydrofluoric acid (49%) and nitric acid (70%) at a volume ratio of 1
A solution consisting of 20 pairs was used. At this time, the etching rate of titanium and vanadium is more than 500 times that of aluminum, oxide film, and phosphorous glass.
Only unreacted titanium and vanadium can be removed. This solution generates a lot of bubbles when etching titanium or vanadium, and the bubbles disappear when etching is complete, so the point at which removal is complete can be clearly seen. In some cases, a passivation film of phosphor glass or polyimide may be further formed on the uppermost layer of electrode wiring.

The wiring resin-molded with the epoxy resin (silicon resin may also be used) thus obtained was compared with conventional aluminum wiring in a reliability life test. When we investigated the disconnection failure rate for up to 2,000 hours by subjecting the wiring to an electric field in a high-temperature, high-humidity tank at a temperature of 85°C and humidity of 85%, we found that wiring with titanium intermetallic compounds had a rate of 5%, while vanadium had a rate of 5%. The corrosion resistance of wiring with intermetallic compounds was 15%, and that of conventional aluminum wiring was 85%, indicating that wiring whose surfaces are coated with intermetallic compounds has excellent corrosion resistance. In addition, another reliability test revealed that it is also excellent against electromigration.

As stated above, what is important is to form a surface alloy for wiring that has a higher melting point, is denser, and has better corrosion resistance than aluminum.

[Brief explanation of the drawing]

FIGS. 1 to 4 are cross-sectional views of a silicon wafer showing the process of producing wiring coated with an intermetallic compound. 1... Silicon substrate, 2... Insulating film (oxide or nitride), 3... First layer electrode wiring mainly composed of aluminum, 4... Insulating film (phosphorous glass or polyimide), 5 ...Second layer (top layer) electrode wiring mainly composed of aluminum, 6
...transition metal, 7...intermetallic compound of aluminum and transition metal.

Claims (1)

[Claims] 1. In a semiconductor device in which two or more electrode wiring layers mainly composed of aluminum are laminated as multilayer wiring, only the electrode wiring layer mainly composed of aluminum, which is the uppermost layer of the semiconductor device, is mixed with this wiring layer and Ti or V. A semiconductor device characterized by being coated with an alloy layer of.