JPS5847854B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and in particular, the semiconductor device is directed to a high frequency transistor (or IC) in which a high melting point metal film is interposed between a substrate and aluminum.

In general, in high frequency transistors or ICs, the impurity diffusion layer is usually very shallow, and is formed to have a thickness of 0.3 μm or less.

If such a shallow diffusion layer is used and the electrode wiring is made of ordinary aluminum, the aluminum and silicon will diffuse into each other due to the temperature rise during the device manufacturing process, resulting in a shallow base-emitter junction. There is a problem with short circuit.

Therefore, it is necessary to prevent the above-mentioned mutual diffusion, and as a means for this purpose, a high melting point metal film such as molybdenum, titanium or chromium is interposed between the aluminum vapor deposited film and the silicon substrate.

The above-mentioned titanium and chromium react with aluminum at a low temperature, for example, 400 to 450° C., forming an intermetallic compound, thereby increasing the conductor resistance of the wiring.

For this reason, molybdenum is used, which does not react with aluminum at this temperature.

However, if you try to shape the wiring using the above-mentioned layered film of aluminum and molybdenum, use a part of the wiring as a bonding pad (external connection part), and connect the aluminum wire here by ultrasonic bonding, the surface insulation of the board The pad part is peeled off between the membrane and molybdenum,
Bonding failure occurred.

Such poor binding has become a big problem, especially in ICs, LSIs, etc., where the number of pounds per pellet is large.

As a result of investigating the cause of such peeling of the pad part, we found that
It has been revealed that because the adhesive strength between molybdenum and silicon oxide, which is the main component of the insulating film, is weak, it becomes easier to peel off due to the large shear force that is applied during ultrasonic bonding.

Therefore, the present invention improves adhesive strength by making the wiring pad different from the wiring.

Therefore, an object of the present invention is to improve the adhesive strength of a bonding pad using a wiring material to a substrate in a semiconductor device.

The present invention will be specifically described below with reference to Examples.

Embodiment FIG. 1 shows an example in which the present invention is applied to the manufacturing process of single-layer IC wiring.

(a) A base region 2 and an emitter region 3 of a transistor are formed on a Si (silicon) substrate 1 by a known method, and an SiO2 film 4 is formed by thermal oxidation or CVD (vapor phase chemical reaction) on the surface of the substrate, and the emitter region is The above S for the area
A contact hole 5 is made in the iO2 film.

(b) Platinum (Pt) is deposited on the Si substrate by a normal vacuum evaporation method.

After that, Pt-Si (platinum silicide) was heated at about 400℃ for several minutes to form a low resistance ohmic contact layer with Si.
Form layer 6.

Note that Pt on the surface of the SiO2 film 4 is removed by etching.

(c) Next, use a normal Subickling device to coat the entire surface with Mo.
A Mo film 7 with a thickness of about 1000 nm is deposited by sputtering.

The reason for this Mo film 7 is that if an Al film is formed directly on the Pt-Si layer 6, the Si in the Pt-Si layer 6 and its Al
This is to solve the problem of mutual diffusion.

(d) Al is deposited on the entire surface of the Si substrate 1 on which the SiO2 film 4 and the Mo film 7 are formed.
An Al film 9 is formed to a thickness of 7000 mm.

(e) Form a first layer wiring pattern by photoetching.

At this time, bonding pads are not formed, but wiring is formed up to the connection portion with the pads.

That is, the overlapping film of the Mo film 7 and the Al film 9 is simultaneously patterned to form a first wiring layer.

(0) An interlayer insulating film, for example a SiO2 film 10, is formed by CVD to a thickness of 6,000 to 7,000 layers.

(g) Contact holes (through holes) 11.10a are formed in the interlayer insulating film by photoetching.

This through hole is shaped to make sufficient contact with the lower layer of SiO2 for bonding pads to be formed later on.

(h) Vapor depositing Al on the entire surface, Al film 1 with a thickness of 1 to 1.5μ
form 2.

(i) A pattern 12a of the second layer wiring is formed by photoetching, and at the same time, a bonding pad 12b connected to the second layer wiring is also formed.

According to the present invention as explained in the embodiments above, the object can be achieved and the effects can be brought about for the following reasons.

(1) The bonding area between the bonding pad part and the SiO2 film has a structure in which the second layer Al and SiO2 are directly connected over most of the area, and since Al and SiO2 have the same adhesive strength, this When connecting the bonding wire to the bonding pad, the bonding portion will not peel off even if a strong force is applied by ultrasonic bonding.

In addition, if the insulating film under the bonding pad is SiO2 formed by thermal oxidation, the SiO2
Since SiO2 is harder than SiO2 formed by the CVD method, the amount of energy absorbed by SiO2 during ultrasonic bonding is considerable.

Therefore, the bonding line is reliably connected to the bonding pad.

(2) In the conventional A13-Mo stacked structure, the number of defects due to pad peeling was approximately 1% of the number of bondings, but this was reduced to less than 0.01% by the present invention.

(3) According to the present invention, even in an IC with a two-layer wiring structure using a first-layer wiring made of Mo-A6 and a second-layer wiring made only of Al,
It is possible to manufacture a general Al wiring IC with the same bonding yield.

In addition to the embodiments described above, the present invention can be implemented in the following embodiments.

(1) Mo film, that is, a high-melting point metal that does not have a high adhesive strength to SiO2, forms at least the electrode contact part of the semiconductor substrate, and also has the kl required for sufficient adhesive strength between at least the bonding pad part and SiO2. and SiO2 within a range that provides a bonding area.

The wiring from the electrode contact hole to the bonding pad should be made of Al or Mo and A to reduce resistance.
It is preferable to use two layers of Mo, but it is better to use Mo alone, which is not desirable because the resistance becomes significantly large.

The present invention can be applied to all electrode configurations of semiconductor devices such as transistors, ICs, and LSIs, and is particularly effective in application to high-frequency and high-speed switching semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view during the manufacturing process of a semiconductor device to which the present invention is applied. 1... Si substrate, 2... Base, 3...
...Emitta, 4...SiO2 film, 5.
...Contact hole, 6...Pt-
Si layer, 7... Mo film, 9... Wiring (
1st layer) Al film, 9a... wiring, 9b...
...Honda engine socket, 9c...Connection part, 10...Interlayer insulating layer (SiO2), 10a
...Contact hole, 11...Through hole, 12...Second layer Al film, 12b...
...Bonding pads.

Claims (1)

[Claims] 1. A first insulating film formed on the entire surface of the semiconductor body so as to selectively expose the entire surface of the semiconductor body, and a PN junction formed in the exposed semiconductor body. A first wiring layer made of two layers, a lower layer of high melting point metal and an upper layer of aluminum, electrically connected to the semiconductor region partitioned by and extending over a part of the first insulating film. and a second insulating film for an interlayer insulating film formed to expose a part of the surface of the first wiring layer and cover other surface parts including the ends thereof, and the first wiring layer. An aluminum bonding pad is formed to cover the other portion of the first insulating film where no layer is formed, and an electrical conductor is applied to the surface of the first wiring layer exposed from the second insulating film. a second wiring layer made of aluminum, which is electrically connected to the bonding pad, and which extends over a second insulating film that covers an end of the first wiring layer and is electrically connected to the bonding pad; A semiconductor device comprising: a bonding wire connected to the semiconductor device;