Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1994-03-18
2001-12-11
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C438S719000, C438S738000
Reexamination Certificate
active
06328845
ABSTRACT:
BACKGROUND OF TEE INVENTION
1. Field of the Invention
The present invention relates to a plasma-processing method and an apparatus for carrying out the same and, more particularly, to a plasma-processing method suitable for plasma-etching a workpiece, such as a film coating a semiconductor substrate, and an apparatus for carrying out the same.
2. Description of the Related Art
Etching techniques that vary the frequency of a RF bias voltage (radio-frequency bias voltage) to be applied to a substrate, such as a semiconductor wafer, when etching a film formed over the surface of a substrate are disclosed, for instance, in Japanese Patent Laid-open (Kokai) Nos. 4-27119 and 4-14853. The technique disclosed in Japanese Patent Laid-open (Kokai) No. 4-27119 employs frequency control in combination with RF bias power control because it is difficult to control ion energy only by RF bias power control. The specification of this known invention describes that there is the tendency that ion energy decreases with the increase of the bias frequency, and vice versa. Although effective in controlling anisotropy and reducing damages in the substrate, this known technique takes nothing into consideration about etch selectivity, i.e., the ratio of an etching rate with a material to be etched to the etching rate with an under layer under a layer of the material to be etched, and does not show any method of setting a frequency to provide a high etch selectivity.
The technique disclosed in Japanese Patent Laid-open (Kokai) No. 4-14853 utilizing a phenomenon that an etching reaction is caused principally by radicals when the frequency of the RF bias is high or principally by ions when the frequency of the RF bias is low uses an RF bias having a high frequency for etching a metallic suicide layer having a high melting point and uses a RF bias having a low frequency for etching a polycrystalline silicon layer. It is described on p. 7, left col. of the specification of Japanese Patent Laid-open (Kokai) No. 4-14853, in connection with process conditions for etching a polycrystalline silicon layer, that a high etch selectivity was obtained in an embodiment when the frequency of the RF bias was 800 KHz. However, there is no discussion about a method of setting a frequency that provides a maximum etch selectivity under various process conditions and no reference is made to an etching method that realizes a high etch selectivity at a high etching rate.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an etching method capable of etching an object film at a high etch selectivity relative to an under layer such as a ground film, a resist film and a substrate, and an apparatus for carrying out the etching method.
Another object of the present invention is to provide an etching method capable of etching one of two kinds of materials at an etching rate higher than that at which the other material is etched, and an apparatus for carrying out the etching method.
With the foregoing objects in view, the present invention employs, taking into consideration a fact that different materials differ from each other in the dependence of etching rate on ion energy, an ion generator that generates first ions that etch one of two materials of a sample placed in a processing chamber and do not etch the other material of the sample and second ions that etch both the materials of the sample in an energy distribution in which both the first and second ions are abundant.
The ion generator may have, for instance, an adjuster of a variable RF bias frequency type that adjusts the RF bias frequency so that the foregoing energy distribution is established.
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Fukuyama Ryooji
Nawata Makoto
Ohmoto Yutaka
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Mills Gregory
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