JPS5913592B2 - Etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a plasma etching method for aluminum or aluminum alloy, which is particularly used for wiring in large scale integrated circuits (LSI).

Traditionally, aluminum, aluminum-silicon, aluminum-silicon, aluminum-
Aluminum alloys such as silicon-copper, aluminum-copper, and aluminum-manganese have been widely used.

In response to the demand for miniaturization of LSIs, it is widely recognized that dry etching, especially plasma 15 etching, is superior to conventional wet etching methods, and various attempts have also been made for aluminum wiring.

As a result, it has been experimentally confirmed that plasma etching of aluminum is possible using a gas containing Cl element such as CCl4 or BrCl3.
However, in the conventional method, as shown in FIG. 1, it is known that the etching starts at a time indicated by To, which is later than the plasma etching start time.
The reason for this is said to be that there is a time required to remove alumina 4 formed on the surface of aluminum 3, as shown in FIG. 25, which is a partial cross-sectional view of the LSI before plasma etching. Note that 1 is a silicon substrate and 2 is an oxide film. The alumina 4 is formed when the surface of the aluminum 3 is exposed to the atmosphere or naturally reacts with oxygen during the washing step 30 with water, and has a thickness of about 20 to 50 pieces.
It is impossible to control it artificially, and this alumina 4
Due to variations in the film thickness, the etching start time T varies from sample to sample as shown in FIG. Or T. 'There are 35 pieces like this. Time TE (FIG. 1) and T required to etch aluminum 3. is the same value (3 to 8
(minutes) (that is, the etching rate of aluminum is much faster than that of alumina), and as a result, it is impossible to control the end of etching with time. The present invention has been made to improve the above-mentioned drawbacks, and will be explained below based on examples.

As shown in FIG. 3a, a sample having a desired shape of photoresist or electron beam resist 5 on aluminum 3 is placed in an etching reaction chamber, and then the reaction chamber is evacuated.

Then, after introducing an inert gas such as Ar into the reaction chamber, plasma is generated in the reaction chamber.

By appropriately arranging the sample and the position of the electrode for generating plasma, the sample surface can be sputtered with inert Ar ions 6 as shown in FIG. 3a. After the alumina 4 is removed by Ar ion sputter etching in this way, a gas such as CCl4 for etching the aluminum 3 is introduced into the reaction chamber, and then the aluminum 3 is plasma etched as shown in FIG. 3b. Do as shown. In this case, since the reactive group 7 etches only the aluminum 2, there is no delay in the start time of etching. By the way, alumina 4 is produced by sputter etching.
When removing alumina 4 and aluminum 3, the etching speed is almost the same, and since the etching speed is low, it takes at most 50λ of time to remove alumina 4 (about 10
(min), the thickness of aluminum 3 hardly changes.

Therefore, the step of removing alumina 4 and the step of etching aluminum 3 can be separated, and the time required for sputter etching and plasma etching can be separated, and plasma etching of aluminum 3 can be performed with good reproducibility. be able to.

In the example described above, aluminum was used as the material to be etched, but aluminum
Aluminum alloys such as silicon, aluminum-silicon copper, aluminum-copper, aluminum-manganese, etc. may also be used.

Also, as a gas for sputter etching, N2 other than Ar,
An inert gas such as KrNe may also be used. Also, when transitioning from sputter etching to plasma etching, A
CCl4 may be introduced while continuing to introduce r gas, or CCl4 may be introduced after stopping introduction of Ar gas. In addition to LSI, hybrid integrated circuits, individual semiconductor devices,
It is also applicable to any other device using wiring made of aluminum or aluminum alloy.

[Brief explanation of the drawing]

Fig. 1 is an etching characteristic diagram showing the relationship between etching time and etching depth when aluminum is plasma etched, Fig. 2 is a cross-sectional view illustrating that alumina is naturally formed on the aluminum surface, and Fig. FIG. 3 is an explanatory diagram of an embodiment of the present invention. In the figure, 1 is a silicon substrate, 2 is an oxidation layer, 3 is aluminum, 4 is alumina, 5 is a resist, 6 is an Ar ion, and 7 is a reactive group.

Claims (1)

[Claims] 1 Step of forming a resist having a desired shape on the main surface of a thin film of aluminum or aluminum alloy formed on a substrate, then inserting the substrate into a plasma etching reaction chamber, and etching aluminum or aluminum alloy with inert ions. An etching method comprising the steps of sputter etching the main surface of a thin film, and then introducing an etching gas of aluminum or aluminum alloy to plasma-etch the aluminum or aluminum alloy thin film into a desired shape.