JPS6027752B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry etching method, and mainly relates to a dry etching technique for selectively removing metals such as aluminum when forming metal wirings in the manufacture of semiconductor devices.

By introducing an active gas such as CC〆4 into the reaction chamber (reaction chamber) and creating a plasma state, aluminum, aluminum and aluminum placed in the chamber are heated.
Etching the surface by reacting with a metal such as a silicon alloy or an aluminum/copper/silicon alloy is known as a so-called plasma etching technique.

The following problems arise when performing this type of plasma etching. When aluminum and aluminum alloys are left in the air, they tend to naturally form oxides such as A-203 on their surfaces, and the depth of the oxidation is uneven. When plasma etching aluminum or the like containing such oxides, the etching rate of the oxides is significantly different from the etching rate of pure metals or alloys to less than 1/10, so the oxides on the surface of the aluminum etc. The non-uniformity of etching is directly reflected in the non-uniformity of etching progress. For this reason, unevenness is produced particularly on the surface of the base forming film, which is the end point of the reaction, and this results in many adverse effects on the appearance and various characteristics of the device. The present invention has been made to overcome the above-mentioned drawbacks of the prior art, and its purpose is to provide a dry etching method that does not cause non-uniform etching based on the surface composition of the object to be processed.

According to one embodiment of the present invention, dry etching is performed in a high vacuum state of 10-3 or higher using an inert gas as a reactive gas in the first half process, and an active gas is used as a reactive gas in the second half process. It is characterized by eliminating non-uniformity in etching due to partial oxidation of the surface of the object to be processed, etc. by performing dry etching in a low vacuum of 1 or less.
The present invention will be specifically described below with reference to Examples.

FIG. 1 schematically shows the surface state of aluminum, where 1 is a base insulating film formed as an oxide (Si02) on the surface of a silicon substrate (not shown), and 2 is an aluminum film. The layer is formed to a thickness of about 1 m by aluminum electron beam evaporation or sputtering evaporation on the base insulating film, and 3 is an alumina layer formed when the surface of aluminum is exposed to air.
Q) The film has a non-uniform thickness with a width of several tens to 100 amps.

FIG. 2 shows a conventional method in which a photoresist mask 4 is formed on the aluminum layer shown in FIG. 1, CC film 4 is introduced, and plasma etching is performed while generating plasma discharge under a low vacuum.

In this case, as mentioned above, the selective etching property of the material is extremely high. For example, since the etching rate of the alumina film is less than one-tenth of that of aluminum, the etching rate of the alumina film is inversely proportional to the thickness of the alumina film. The aluminum is etched to a large extent, while the thicker portions are etched to a smaller extent, resulting in an extremely uneven etched shape. FIG. 3 shows that the aluminum layer shown in FIG. 1 was etched for a certain period of time by so-called sputtering, which involves introducing an inert gas such as argon and performing discharge under a relatively high vacuum while a photoresist mask was formed on the aluminum layer. Indicates the form of the case.

With this sputtering, the etching rate remains the same regardless of the type of material being processed, so the etched surface becomes flat. However, if this etching by argon discharge is continued further, the photoresist mask will be severely damaged due to the non-selectivity of the etching, and the surface and side surfaces of the aluminum under the mask will be deeply etched, as shown in Figure 4. Moreover, the underlying insulating film is also etched, which has a serious effect. At this time, the etching of the side surface of the aluminum reaches 0.1 rm or more on one side, which also reduces the etching accuracy. FIGS. 5 to 7 explain the form of the dry etching method according to the present invention divided into each step.

FIG. 5 schematically shows the surface condition of aluminum, and each component is indicated by the same symbol as in FIG. 1.

In FIG. 6, a photoresist mask 4 is formed on the surface of the aluminum, placed in a chamber, and inert argon is introduced for 10-3T.

When sputtering is performed in which etching is performed while discharging in a relatively high vacuum of rr or higher, a flat etched surface is obtained due to the non-selectivity of etching with respect to the object, as in the case of FIG. Figure 7 shows the state shown in Figure 6, but in the same chamber, the introduced gas is changed from argon to active CC, and the degree of vacuum is increased to 10-10.
This shows a form in which plasma etching is performed in which discharge is performed in a relatively low vacuum of 3 Torr or less.

In this case, since the etching selectivity is high, the damage to the photoresist 4 serving as an etching mask is minute, and the underlying insulating film 1 is not affected. Moreover, the aluminum layer can be uniformly etched while maintaining a flat etched surface. In the dry etching method according to the present invention described in the second embodiment, by skillfully combining non-selective sputtering and selective plasma etching, good uniformity can be achieved regardless of the state of acid residue on the surface. This allows etching.

The present invention is not limited to the embodiments described above, but has various modifications.

In other words, in addition to aluminum, dry etching products include aluminum-silicon alloys and aluminum-silicon alloys.
The method of the present invention can be similarly applied to metals such as copper-silicon alloys and substances whose surfaces are easily oxidized such as silicon. In addition to argon, rare gas elements such as krypton can also be used as the inert gas. In addition to CC Yu4, there are other active gases such as BC Yu4.

[Brief explanation of drawings]

FIGS. 1 to 4 are cross-sectional views showing the configuration in each step of a conventional single-method dry etching method. 5 to 7 are cross-sectional views showing a series of steps of the dry etching method according to the present invention. 1...
- Base insulating film, 2... Aluminum layer, 3.・
・・・． - Aluminum film, 4... Photoresist mask. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. In order to introduce a reaction gas into a reaction chamber and react with the object to be treated on the surface of a substrate placed in the chamber to dry-etch the surface, the type of the reaction gas introduced and; Alternatively, a dry etching method is characterized in that etching is performed by sequentially changing the degree of vacuum within a reaction chamber. 2. The first half of the dry etching process uses an inert gas as a reactive gas and is carried out under a relatively high vacuum, and the second half of the dry etching process uses an active gas as a reactive gas and is carried out under a relatively low vacuum. The dry etching method described in . 3. The dry etching method according to claim 1 or 2, wherein the object to be processed is aluminum or an alloy containing aluminum.