JPS5914546B2 - Dry etching method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of etching an aluminum layer.

The conventional method of etching an aluminum layer is called a wet method, and is generally performed using a phosphoric acid-acetic acid-nitric acid based etching solution.

However, with these methods, it is difficult to avoid side etching (also, due to the shape of the step in the wiring section, wiring in the aluminum layer is likely to occur due to liquid getting around, etc.). Incidentally, when etching an aluminum line with a width of 4 μm, there is side etching of about 2 μm in total.
Furthermore, the relationship between the liquid temperature and the etching rate is delicate, and it is difficult to control this, making it the most problematic step in the LSI manufacturing process. A number of anodic oxidation methods (5V), which have a different concept from these, have been studied, but there are problems that have not been completely solved, such as leakage between aluminum layers.

On the other hand, with advances in dry process technology, Si) polycrystalline Si
Nowadays, plasma etching technology for SiN, etc. is rapidly spreading, and etching of finer patterns than 10-inches is required for VLSI, etc., and the need for dry etching of aluminum layers is extremely important. I'm getting used to it. Dry process for aluminum etching 1
As a method, an etching system called freon sputter etching15 has been developed, but with this method, although there are some differences in etching speed for photoresist, aluminum, SiO2, Si, etc., it is almost indiscriminate etching. The resist also has the disadvantage of being easily degraded. On the other hand, a method called ion etching is also considered, but it is also almost indiscriminate etching, and since the selective etching ability of aluminum is small, it is difficult to put it into practical use. The present invention has been made in view of these circumstances, and its purpose is to provide a dry etching method that has excellent etching selectivity for aluminum layers, reduces side etching, and can etch aluminum layers at high speed. This is what we provide. The details of the present invention will be explained below. Aluminum with chlorine gas (C4, CC4, 30CF2C12, C
When exposed to gas plasma generated by F3Cl, etc.),
The chlorine radicals generated in this reaction react with aluminum to produce aluminum chloride.

The aluminum chloride produced at this time does not sublimate at room temperature, but sublimes by 35% at about 180°C. The present invention takes advantage of this characteristic. In the present invention, a wafer coated with an aluminum layer with a mask formed on the surface is placed on one side of a pair of electrodes facing each other in a chamber, and a high frequency power is applied between the pair of electrodes. At the same time, a chlorine-based gas is introduced into the chamber to generate plasma to selectively etch the aluminum layer with respect to the mask.

According to the etching method of the present invention, anisotropic etching is achieved, unlike the conventional technique in which the wafer is processed inside plasma by providing the wafer on the electrode 7, and moreover, in the present invention, reactive chlorine is used. Since a system gas is used, the radicals generated can provide a dramatically higher etching speed than conventional sputter etching using argon or chlorofluorocarbon gas.

Furthermore, according to the present invention, since the etching speed of aluminum is fast, there is no need to bombard the wafer with ions at a high acceleration voltage as in sputter etching, and the aluminum layer mask is less likely to be damaged. It has excellent selective etching properties of 2 to 4 times or more. An embodiment of the present invention will be described below.

The drawing shows →1 of the apparatus for use in the method of the invention.

In the figure, a wafer 2 on which an aluminum layer 1 is deposited
The stand 3 on which the
It has been heated to ℃. Heating was performed using resistance heating built into the stand, but is not limited thereto. The entire chamber 4 is kept at a vacuum level of about 0.5 to 1.0 t0rrf), and CC4 gas 5 is passed through it.

The Cct4 gas is supplied into the chamber through the valve 6 by heating the liquid. 13.

A 56 MHz high frequency RF power source r is connected between the electrodes 3 and 8, and the Cct4 gas is discharged to generate chlorine gas plasma.

Although the table 3 is used also as an electrode, it may be a separate body. C
Ct radicals generated by the decomposition of ct4 react with the aluminum layer 1, and aluminum chloride is generated by the reaction of At+3CtTc4.

At this time, since the temperature of the table 3 on which the wafer 1 2 is placed is higher than the sublimation point of aluminum chloride, the aluminum chloride sublimates and the aluminum is removed. The removal rate is about 2000 angstroms per minute.
It was twice the amount of solution etching. At this time, a photoresist (not shown) is previously applied as a mask on the aluminum 1 in accordance with a predetermined pattern. Photoresist is quite stable against chlorine radicals, so it can be used satisfactorily as a mask. It is particularly desirable to use a negative type resist in order to keep the temperature at 100-odd degrees Celsius. P
Because the reaction proceeds in the manner described above, a large step surface of etch factors is obtained which is more similar to ion etching or sputter etching than to isomethod etching such as conventional wet etching or plasma etching methods. This tendency was particularly strong when heating was performed from the side opposite to the aluminum-adhered surface of the wafer. The advantages of the present invention are that dry etching of the aluminum layer and low mixed etching have become possible, that high-speed anisotropic fine pattern formation with extremely little side etching has become possible, and that the use of chlorine radicals has enabled SiO2 etching. , Si, polycrystalline-Si, etc. are hardly etched, so SiO2, which normally exists under the aluminum layer, acts as a stopper, making it easy to see the etching end point, and providing good etching selection with respect to the mask.

Moreover, if the above-mentioned example is further followed by rinsing using methanol, water, or the like as a rinsing material after etching, the effect will be further improved.

Needless to say, it is also suitable for automation.

[Brief explanation of drawings]

The figure is a configuration diagram for explaining an example of a device used in the present invention. In the figure, 1... aluminum layer, 3... stand, 5
...Cct4 gas, 7...RF power supply.

Claims (1)

[Claims] 1 A wafer coated with an aluminum layer with a mask formed on the surface is placed on one of a pair of electrodes facing each other in a chamber, and a high frequency power is applied between the pair of electrodes, and a chlorine-based gas is introduced into the chamber. A dry etching method, characterized in that the aluminum layer is selectively etched with respect to the mask by introducing plasma to generate plasma.