Process for dry etching of aluminum and its alloy

Details Process for dry etching of aluminum and its alloy Process for dry etching of aluminum and its alloy

1982-12-15

1985-04-16

Powell, William A.

Adhesive bonding and miscellaneous chemical manufacture

Delaminating processes adapted for specified product

Delaminating in preparation for post processing recycling step

156646, 156656, 156665, 204192E, 252 791, C23F 102, B44C 122, C03C 1500, C03C 2506

Patent

active

045114293

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
This invention relates to a processing of aluminum and its alloys, particularly to a processing of aluminum and aluminum alloy layers in the production of minute electronic parts such as semiconductor elements, magnetic material elements, dielectric elements and semiconductor integrated circuits, and more particularly to a process for dry etching of aluminum and aluminum alloy layers, especially a process for dry etching in the formation of a fine wiring of aluminum and aluminum alloy layers of the minute electronic parts.
2. Background Art
Previously aluminum wirings of integrated circuits have been prepared by a wet etching method using a phosphosphate solution, but recently a dry etching method using glow discharge plasma enabling high-accuracy fine processing has been introduced corresponding to the fineness and high integration of integrated circuits. This method is believed to have a characteristic in that it does not cause the formation of so-called side-etching phenomenon by which a lower side of a masked pattern is also etched in case of the wet etching, because chemically active chlorine ions formed in the plasma have a rectilinear propagation property to vertically attack an etching surface. Thus the resulting etching strictly follows the mask pattern. There are, however, practically a number of neutral radicals which are not in an ionized but in an excited state and have strong chemical activities in a gaseous plasma. These radicals are responsible for the side-etching as in the wet etching because of their electric neutrality which causes the isotropy of an angle of incidence into an etching surface. Accordingly the lowering of the concentration of neutral radicals is a very important factor in the fine processing without suffering from the side-etching in the dry etching. To achieve this purpose, several methods of increasing an ionization ratio by increasing an electron temperature are proposed, e.g., the lowering of plasma pressure and the increase of high frequency field strength generating a plasma. These proposals bring about various difficulties in the selection of apparatuses. For example, a strikingly large evacuation velocity is required of a vacuum pump to maintain a degree of vacuum of approximately 10.sup.-3 -10.sup.- 4 Torr while flowing a 10-100 ml/min gas into an etching chamber, or a high-power, high-frequency power source is required. Moreover, at a high electron temperature, the surface temperature of a workpiece rises frequently to above 100.degree. C. or the etching rate of materials besides the desired one increases, thus lowering the selectivity of etching.


DISCLOSURE OF INVENTION

An object of this invention is to provide a process for dry etching of aluminum and its alloy without suffering from the side-etching by neutral radicals in a plasma and free from difficulties mentioned above.
To achieve the above object, the process for dry etching of aluminum and its alloy comprises adding 0.5-10 vol.%, preferably 1-4 vol.% of at least one member selected from hydrogen and gaseous hydrogen compounds in a gaseous glow discharge plasma containing gaseous chlorides.
More than 10 vol.% content of hydrogen and/or gaseous hydrogen compounds considerably lowers the etching rate and selectivity of aluminum and its alloy, and particularly the etching rate becomes nearly equal to that of Si. On the contrary, less than 0.5 vol.% content exhibits a very small effect of suppressing the side-etching. The 1-4 vol.% content is particularly preferable because of a sufficient suppressing effect on the side-etching and a high etching rate.
At least one gas selected from hydrogen chloride, methane, ethylene, methyl chloride and ethyl chloride may be used, for example, as the above hydrogen compounds. All gaseous chlorides used hitherto for the etching of aluminum and its alloy may be used as the above gaseous chlorides. Generally, boron trichloride, carbon tetrachloride or a mixed gas thereof, and particularly boron trichloride may be used preferably. These chl

REFERENCES:
patent: 3994793 (1976-11-01), Harvilchuck et al.
patent: 4073669 (1978-02-01), Heinecke et al.
patent: 4267013 (1981-05-01), Iida et al.
patent: 4380488 (1983-04-01), Reichelderfer

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