JPS6080227A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent generation of projections produced on a wiring metal by forming a sandwich construction of a semiconductor substrate-metallic oxide by coating the first metallic film with the second metallic oxide film. CONSTITUTION:A patterned Al film 22 is formed on a substrate 21. Then a metal which is oxidized wholly at a lower temperature than that for oxidizing Al which composes the film 22, e.g. Ta 23 is spreaded over the whole surface of the substrate 21 by spattering. When it is oxidized, Ta changes into Ta2O5 24. This film 24 functions so as to prevent generation of projections. In addition, window opening of the film 24 can be done by the same etching as of a PSG film as a cover at a time and there is no trouble in later processes. Also for Ta, a DC magnetron spattering device offering a large coating rate can be used similarly in the case for Al and it is suitable for mass-production processes.

Description

DETAILED DESCRIPTION OF THE INVENTION (11) Technical Field of the Invention This invention relates to a method of manufacturing a semiconductor device using a metal film as a wiring layer.

(2) Background of the Technology Aluminum (AI) is widely used as a wiring material for semiconductor devices because it has many advantages, so AI will be explained here as an example. After the AI is deposited on the substrate, wiring patterning is performed, and a bathobasic pattern is deposited thereon at about 400° C. by vapor phase growth. At this time, recrystallization of the amorphous Δl occurs, and the crystal grains push out the weak portions of the surface due to thermal stress, forming protrusions. The height of the large one is 11. t
It reaches up to m. These protrusions cause defects in the passivation film on the AI film, and also cause poor interlayer insulation and lff1 corrosion of the wiring in a multilayer wiring structure. In Fig. 1, numeral 1 indicates a semiconductor substrate (hereinafter abbreviated as a mounting board), and when an insulating film 4 is deposited on the 11th h-th AI film 2 having protrusions, the insulating film also protrudes following the protrusions. 1. When the resist 5 is applied on top of this, the resist is thinly applied only to this part, so when etching other parts, for example, when etching the insulating film on the first layer Δ1 film 3 for window opening, it is necessary to use an etching solution or The etching gas damages the insulating film at the convex portion, and the 21st Fi-th AI film (not shown) is short-circuited with the first-layer AI film at this portion. Therefore, a method for preventing the formation of protrusions is required.

(3) Prior Art and Problems In accordance with the concept of suppressing the protrusions by covering Δ1 with a film as a method for preventing the formation of protrusions in AI, appropriate materials for the coating have been studied. For example, a silicon oxide (S i O,) film is formed on the upper part of the AI by sputtering.
It covers the 15-day Δl film and is used for insulation between it and the second layer AI film. 5i0 by sputtering
Although 211J has the effect of preventing protrusions, it requires a special sputtering device different from that for Al, and therefore the process becomes complicated. It is desired to study a coating that is effective in preventing protrusions using the same equipment as AI.

In addition, a method of anodic oxidizing the A1 surface has been proposed, but this method requires special equipment and the process is also complicated. Moreover, since this method can be performed only before patterning AI, the side surfaces of A1 are not covered with anything after patterning, and there is a drawback that protrusions occur there.

(4) Object of the Invention It is an object of the present invention to provide a manufacturing method that eliminates the above-mentioned conventional drawbacks and prevents the occurrence of protrusions on a metal film for wiring.

After depositing and patterning the i-th metal film, a second metal film, the entire metal of which is oxidized at a lower temperature than the metal constituting the first metal film, is deposited to cover at least the first metal film. This method is characterized by including a step of oxidizing the second metal film.

The present invention relates to prevention of protrusions occurring in the first metal film. Types of protrusions include (b) those that occur during Al deposition, (b) those that occur due to heat treatment after deposition,
(C) The electric field applied to the wiring film causes non-uniformity in the flow of metal ions within the metal, resulting in the concentration of metal ions, etc., but the biggest problem in semiconductor device manufacturing is lb) It is a type of The cause in this case is thought to be as follows.

Since metal has a larger coefficient of thermal expansion than a semiconductor substrate, the metal film experiences compressive stress when heated (L), and it is thought that protrusions are formed to relieve that stress. Cooling reduces the height of the protrusions somewhat, but the protrusions remain.

As a measure to prevent the occurrence of protrusions, if the difference between the substrate temperature at the time of metal film deposition and the heat treatment temperature in the subsequent step is reduced, the thermal stress during the heat treatment will also be reduced, thereby suppressing the occurrence of protrusions. For this reason, a method of depositing metal while heating the substrate is used, but for example, when depositing AI on a silicon (Sl) substrate, protrusions may occur even if the deposition is performed while heating the substrate temperature to 200 to 400 degrees Celsius. The density of the metal is 105 to IQ3cm"l, and the effect cannot be said to be sufficient. In order to further improve the effect, the present invention coats a second metal oxide film on the first metal film. ,
This paper proposes a method for forming a semiconductor substrate-metal-metal oxide Santo-Nochi structure and depositing a metal oxide film for this purpose in order to alleviate thermal stress caused by heating.

(6) Embodiments of the Invention An embodiment of the present invention will be described using AI as the °C wiring material. FIG. 2 (81 shows the state in which the AI film 22 is patterned on the substrate 21, and the thickness is about 1 μIn.

Next, as shown in Fig. 2 (BL), Kuntal (Ta) was deposited on the entire surface of the ζ substrate by sputtering to a degree of OOO.
When heated in oxygen for 30 minutes at 450°C, a becomes tantalum oxide (Taz'05>24
Changes to This T a z Oc film serves to prevent the formation of protrusions.

Moreover, the opening of the 'I' a□09 film can be performed at the same time as the PSG film of the cover by the same etching, so that it does not interfere with subsequent processes. Furthermore, since 1'a is not an insulator, a DC magnetron sputtering device with a high deposition rate can be used like AI, making it suitable for mass production processes.

In the example, C used AI as the first metal film, but this was
It is also possible to use another material such as magnesium (Mg) that tends to cause protrusions, and although Ta is used as the second metal film, it may be replaced with another metal.

For example, high melting point transition metals Ti and W that oxidize at relatively low temperatures
etc. are also extremely effective.

That's all i5i! '! As described above, the method according to the present invention prevents the occurrence of protrusions on the metal film of the wiring qy/, and is suitable for the premature birth process.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a semiconductor substrate to explain the damage caused by protrusions;
1 shows the manufacturing method according to the present invention in the order of steps in cross-sectional views. ■, 21... Semiconductor pasting temporary, 2, 3. 22...AI film, 4...PSG film, 5...Resist 23...'ra film, 24...Go a20g1%. Figure 1 No.? figure

Claims (1)

[Claims] After depositing a first metal film for wiring material on a semiconductor substrate and patterning the first metal film, a second metal film is formed in which the entire metal is oxidized at a lower temperature than the metal constituting the first metal film. 1. A method of manufacturing a semiconductor device, comprising the steps of depositing a metal film covering at least the first metal film and oxidizing the second metal film.