Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Patent
1988-05-25
1991-06-11
Nguyen, Nam X.
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
20419212, 250423R, 2504923, 31511141, 31511181, C23C 1434, H01G 2700
Patent
active
050229770
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an ionization apparatus capable of efficient ionization by utilizing a sputtering process carried out by high density plasma. The present invention also relates to a thin film forming apparatus capable of forming various thin films at a high rate and a high degree of efficiency with ions and neutral particles produced by the ionization apparatus, and to an ion source with a high degree of efficiency and a high degree of yield (high ion current) from which the ions produced by the ionization apparatus are extracted so as to form various thin films and so as to carry out an etching process.
So-called sputtering apparatuses for sputtering targets as such thin film formation elements in plasma, thereby forming thin films, have been widely used to form films of various materials in various fields. For instance, as shown in FIG. 1, a conventional sputtering apparatus in which a target 1 and a substrate 2 are disposed in opposing relationship with each other in a vacuum chamber 4, which is generally called a two-electrode sputtering apparatus (refer to F.M.D'HEURLE: Metall. Trans. Vol. 1, March, 1970, 725732), has been used and is well known to those skilled in the art. So is the three-electrode sputtering apparatus shown in FIG. 2, in which a third electrode 3 for emitting ions is additionally provided (W.W.Y. Lee and D.Oblas: J. Appl. Phys. Vol. 46, No. 4, 1975, 1728-1732). Furthermore the magnetron sputtering process (refer to R. K. Waits: J. Vac. Sci. Technol, Vol. 15, No. 2, 1978, pp. 179-187) in which, as shown in FIG. 3, a magnet 5 is used to apply a magnetic field of suitable strength to the target 1 so that high density and low temperature plasma is produced, whereby a thin film is formed at a high rate, has been used and is well known to those skilled in the art. These apparatus mainly comprise the vacuum chamber 4 with the target 1 as a thin film forming element and the substrate 2 upon which a thin film is formed, a gas introduction system, and a gas discharge system, and plasma is generated within the vacuum chamber 4.
In order to form a thin film at a high rate using one of the above-mentioned apparatuses, it is necessary to maintain the plasma at a high density. However, in the case of the two-electrode or diode sputtering apparatus, the higher the density of plasma, the more quickly a voltage applied to the target is increased. At the same time, the temperature of the substrate quickly rises because of the bombardment of the substrate with high-energy particles and high-energy electrons within the plasma, so the risk of damage to the formed film increases. Therefore, this apparatus can be only used for special heat-resisting substrates, thin film materials and film compositions. In the case of the three-electrode or triode sputtering apparatus, the plasma density is increased because the electrons are supplied from the third electrode into the plasma, but just like the two-electrode or diode sputtering apparatus, if a thin film is to be formed at a high rate, the temperature of the substrate quickly rises. As a result, only a limited small number of thin film materials and substrates may be used.
On the other hand, in the case of the high rate magnetron sputtering apparatus, the gamma (.tau.) electrons (secondary electrons) emitted from the target, which are needed to ionize the gas in the plasma, are confined over the surface of the target by both the magnetic field and the electric field, so that a dense plasma can be produced at a low gas pressure. In practice, the high rate sputtering processes are carried out at a low gas pressure of the order of 10.sup.-3 Torr, so that they are widely used for forming various thin films at a high rate. However, in the case of the sputtering apparatus just-described above, because of the bombardment by the ions in the plasma (mainly Ar.sup.+ ions), the high-energy neutral particles emitted from the target (mainly Ar reflected at the surface of the target), and the negative ions on the film being fo
REFERENCES:
patent: 4721553 (1988-01-01), Saito et al.
patent: 4739169 (1988-04-01), Kurosawa et al.
patent: 4911814 (1990-03-01), Matsuoka et al.
Matsuoka Morito
Ono Ken'ichi
Nguyen Nam X.
Nippon Telegraph and Telephone Corporation
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