JPS594857B2 - Method for forming electrodes and wiring layers of semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming electrodes and wiring layers of a semiconductor device.

10 In manufacturing a semiconductor device, it is essential to form an electrode and a wiring layer connected to the electrode.

Conventionally, this type of electrode and wiring layer is formed by forming an insulating film on a semiconductor substrate, and drilling 15 holes in a predetermined portion of the insulating film to expose a part of the semiconductor active region. An aluminum layer is formed on the entire surface of the insulating film by a vapor deposition method or a sputtering method, and this aluminum layer is selectively removed by a photoetching technique to form a shape 20.

In the photo-etching method, first, a photosensitive resin film is coated on the aluminum layer, and then the photosensitive resin film is partially exposed through a predetermined photomask prepared separately.
After development, a pattern is formed using the photosensitive resin 25.

Next, using this patterned photosensitive resin film as a mask, the exposed portion of the aluminum layer is etched away using an etching solution mainly composed of phosphoric acid, nitric acid, acetic acid, etc., and then the patterned photosensitive resin film is etched away. By removing the resin film, electrodes and wiring patterns are obtained from the remaining aluminum layer. In recent years, as the density and performance of semiconductor devices have increased,
There is a strong demand for finer patterns, but in the conventional method described above, when a negative type photosensitive resin is used, the main polyurethane (8F) of the negative resist is 1 is more than an order of magnitude larger than that of a positive resist, making it impossible to obtain a clear negative image and making it impossible to form a fine pattern.On the other hand, in the case of a positive resist, the fine Although it is possible to form patterns, the adhesive strength with the underlying aluminum layer is low, and the patterned photosensitive resin film may peel off or undercuts may occur during etching, making it difficult to form fine electrodes or wiring patterns. It was extremely difficult to form.

This invention aims to improve these conventional disadvantages, and its purpose is to provide a method for easily forming finely patterned aluminum electrodes and wiring layers through simple steps. It is to be.

In order to achieve this object, in the present invention, an aluminum surface layer is formed on the semiconductor substrate via an insulating film and is connected to the semiconductor active region, and then tungsten, molybdenum, antimony, titanium, A thin film layer is formed of an element whose oxide has selectivity to gas plasma etching compared to aluminum, and whose chloride has a low boiling point, or an oxide thereof. A pattern is formed using a photosensitive resin on the surface of the substrate, and then the thin film layer and the aluminum surface layer covered with the patterned photosensitive resin are etched away using gas plasma to obtain electrodes and wiring layers. Hereinafter, one embodiment of the method of the present invention will be described in detail with reference to the accompanying drawings.

The attached drawings are cross-sectional views showing the method of forming electrodes and wiring layers according to this embodiment in the order of steps. First, as shown in FIG.
An insulating film 2 made of a silicon oxide film is formed on the surface of the insulating film 2, and a hole is formed in a part of the active region.
For example, the aluminum surface layer 3 is formed by a sputtering method.

Next, as shown in FIG. b, a thin film layer 5 made of tungsten is formed on the surface of the aluminum surface layer 3 by, for example, sputtering, to a thickness of 200λ in this example. Next, as shown in FIG. By partially exposing and developing, a pattern 6 made of photosensitive resin is formed.

Furthermore, this has a high frequency output of 160W (13.56MHz)
, gas pressure 0.3T0rr1 gas composition CCl4:N2:
The thin film layer 5 and the aluminum surface layer 3 in the portion covered with the photosensitive resin pattern 6 were removed by gas plasma etching under the conditions of 0.02=1:2:7, leaving the remaining portion as shown in Figure d. Electrodes and wiring layers made of the aluminum surface layer 3 could be obtained. The reason why the gas plasma etches only the portions of the thin film layer and aluminum surface layer covered by the photosensitive resin pattern 6, and the etching of the exposed portions that are not covered does not proceed. You can think about it as follows.

That is, on the surface of the thin film layer 5 made of tungsten,
Tungsten naturally forms WO3 with an extremely high melting point (melting point 1,473°C), making this surface extremely difficult to etch, but in areas covered with photosensitive resin, decomposition of this resin occurs. C that is a thing
Due to reducing substances such as O, the reduction reaction of WO3 on the same surface progresses, and W reacts with Cl to form WOCl4 (melting point 209
℃), WCl5 (melting point: 248°C), WCl6 (melting point: 275°C), and other volatile substances are generated, and because of this, etching progresses. And this kind of effect is
In addition to the tungsten, molybdenum, antimony,
Similar results can be obtained using elements constituting high melting point compounds as oxides such as titanium, or oxides thereof.

Therefore, in the method of this invention, the photosensitive resin film that is normally used as a mask material becomes a material that promotes etching.

Furthermore, when using the method of the present invention, it is sufficient that the adhesive strength between the photosensitive resin coating layer and the underlying thin film layer is strong enough to withstand exposure and development of the photosensitive resin. In general, positive-type resists with weak adhesive strength are sufficient to achieve this effect, and it is possible to form high-resolution patterns unique to positive-type resists, and a high-melting point thin film layer is formed on the aluminum surface layer. Because of this, there are fewer undercuts during etching, which makes it possible to form fine patterns on the aluminum surface layer.In addition, since the photosensitive resin film is decomposed during etching, it is necessary to make it photosensitive again after etching is completed. This method has the advantage that there is no need to remove the resin, and the process can be simplified compared to conventional photoetching methods.

[Brief explanation of the drawing]

The attached drawings a to d are cross-sectional views showing an embodiment of the method of the present invention in the order of steps. 1... Semiconductor substrate, 2... Insulating film, 3
... Aluminum surface layer, 4 ... Semiconductor active region, 5 ... Thin film layer consisting of an element constituting a high melting point compound as an oxide or its oxide,
6...Photosensitive resin pattern.

Claims (1)

[Claims] 1. A process of forming an aluminum surface layer connected to a semiconductor active region and on a semiconductor substrate via an insulating film, and oxides of tungsten, molybdenum, antimony, titanium, etc. A process of forming a thin film layer made of an element or an oxide thereof that is selective to plasma etching and whose chloride has a low boiling point, and a process of forming a pattern with a photosensitive resin on the surface of the thin film layer. and a step of gas plasma etching the thin film layer covered with the photosensitive resin and the aluminum surface layer, which oxidizes or removes the above elements in the areas of the thin film layer that are not covered with the photosensitive resin. In addition to maintaining the oxide and using it as a mask for plasma etching, the area covered with the photosensitive resin is treated with chlorine in the plasma gas under reducing conditions due to reductive decomposition products during etching of the photosensitive resin. A method for forming electrodes and wiring layers for a semiconductor device, characterized in that an element or its oxide is removed by volatilization as a low-boiling chloride, and an underlying aluminum surface layer is removed by etching.