maining along the depth of the film is then etched with also intersecting at angles sufficient to show the effect
a gas mainly composed of a hydrogen-containing car- of the magnetic field.
bon fluoride gas, so that the etching can be performed It is preferred that in the main discharge region estabwithout damaging an underlying layer or layers. lished between the anode and cathode electrodes of the More particularly, the etching of the film to a given 5 etching apparatus, a third electrode having a fluorinedepth can be effected at a high rate. At a stage where containing resin is provided.
the film thickness is small or an underlying layer may be In this arrangement, a fluorine-based etchant is proinfluenced by the etching, a gas giving a less damage on duced from the fluorine-containing resin of the third the underlying layer is used for further etching. By the electrode, by which etching in the main discharge retwo-stage etching procedure, high rate and low damage 10 gion is facilitated with an increasing etching rate. In etching becomes possible according to the invention. general, fluorine-based ions are supplied by sputtering
In the practice of the invention, the gases used in the and function as an etchant.
respective etching procedures may comprise, aside The electrode used to introduce the etchant is formed
from the main gases, other gases such as inert gases. The as a third electrode and can be controlled separately
term "main gas" used herein is intended to mean that 15 from the cathode with respect to its supply power. This
the gas is contained in an etching gas system in such an makes it possible to independently control an energy for
amount that a desired level of etching can be achieved. the formation of the etchant and an energy for ions
The hydrogen-free carbon fluoride gas used in the implanted into materials to be etched, e.g. semiconduc
present invention includes fluorine-containing gases tive wafers. This is effective in achieving low damage
called Flon or Freon gases, of which no hydrogen atom 20 and high rate etching.
is contained in the molecule. Examples of the carbon The third electrode may be provided with the fluo
fluoride include those gases of the formulas, CnF2n+2 rine-containing resin in a manner sufficient to supply the
and CnF2n wherein n is an integer of not less than 1. etchant. Thus, it is not necessarily required to cover the
Preferred examples include C3F8, C2F6, C4F8 and the electrode with the resin although such covering is pre
like. 25 ferred.
On the other hand, the hydrogen-containing carbon The fluorine-containing resin is preferably so-called fluoride gases are fluorine-containing gases in which Teflon or polyethylene tetrafluoride. As a matter of hydrogen atom or atoms are contained. Examples of course, other fluorine-containing resins capable of resuch gases include those of the formula, leasing a fluorine-containing etchant may be likewise ... wherein n and m are, respectively, an 30 used.
integer of not less than 1. Specific and preferred exam- The present invention is more particularly described
pies include CHF3, CH2F2 and the like. by way of examples wherein reference is made to the
The silicon compound film to be etched in the accompanying drawings, method of the invention is a film made of various silicon
compounds such as oxides, nitrides and the like of sili- 35 fc.XAMl'Lfc.
con and is not critical provided that it can be etched. In this example, the method of the invention is partic
Si02, silicon nitrides such as ... and the like will be ularly described, which is especially suitable for fabrica
effectively etched especially when the underlying layer tion of highly integrated semiconductor devices.
is a silicon substrate which may be greatly damaged by In this example, etching of a SiC>2 film is described.
etching. 40 The etching of Si02 is considered to proceed based on
The apparatus for carrying out the method of the a so-called ion-assisted reaction where ions are chiefly
invention has been defined hereinbefore, which is char- contributed to etching. However, when a material to be
acterized in that one group of magnets are provided etched, such as a silicon wafer, is exposed to a high
behind an anode electrode so that they are movable density plasma using a highly dissociating gas capable
along a direction intersecting with an electric field and 45 of producing ions such as CF3+ ions having the capabil
have a magnetic field component intersecting with the ity of etching Si02, the damage of a substrate with the
electric field and that another group of magnets having incident ions is not negligible. If an acceleration voltage
a magnetic field component intersecting with the elec- of the incident ions is suppressed to an extent by dis
tric field are provided around a cathode electrode at charge from a magnetron, application of high RF
equal intervals. 50 power for high speed etching apparently results in an
In the apparatus of the invention, when one group of increase of damages accompanied by an increasing ion magnets having the magnetic field component intersect- current density. The suppression of such damages is ing with the electric field are moved along a direction possible only with a sacrifice of the etching rate. This is intersecting at right angles with an electric field behind completely overcome by the method of the invention or at a back side of the anode electrode, a magnetic field 55 wherein a Si02 film can be etched at a high rate while in a main discharge region formed between the anode suppressing damages of a substrate, and cathode electrodes is established. In addition, the In the method of the invention, a Si02 film formed on magnets provided equally around the cathode electrode an underlying layer or a substrate is subjected first to ensures a uniform magnetic field in the main discharge high speed anisotropic etching with a gas mainly cornregion, resulting in uniform etching. 60 posed of a H-free flon gas, e.g. C3F8 or C2F6, just before
The "behind or at the back side or' the anode elec- the underlying layer is exposed. Subsequently, an etch
trode is intended to mean a side opposite to the main ing gas mainly composed of a fluorine-containing gas
discharge region where the etching reaction proceeds containing at least one hydrogen atom in the molecule,
predominantly. The term "provided equally" used e.g. CHF3, is used instead, so that incident ion damages
herein means not only "provided at equal intervals", but 65 on the underlying layer can be suppressed,
also "provided to give a uniform magnetic field", result- The etching method using a cathode-coupling, paral
ing in uniform etching. Moreover, the term "intersect- lei plate-type magnetron RIE apparatus is particularly
ing" means not only "intersecting at right angles", but described.