Etching a substrate: processes – Gas phase etching of substrate – Application of energy to the gaseous etchant or to the...
Reexamination Certificate
2002-07-19
2004-09-21
Goudreau, George A. (Department: 1763)
Etching a substrate: processes
Gas phase etching of substrate
Application of energy to the gaseous etchant or to the...
C216S071000, C427S535000, C438S174000, C438S734000
Reexamination Certificate
active
06793834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for and a method of processing an object to be processed, and, more particularly, to an apparatus for and a method of processing an object to be processed while restricting shading damages.
2. Description of the Related Art
Of reactive ion etching apparatuses, there is included a magnetron reactive ion etching apparatus, which efficiently performs etching processing with a magnetic field generated from a magnetron.
Etching processing using a magnetron reactive ion etching apparatus is performed as follows: First, high-frequency electric power is supplied to a pair of electrodes arranged inside a processing container of the magnetron reactive ion etching apparatus so as to form an electric field. Next, electrons are discharged from an etching gas, thereby to form a plasma at the periphery of the surface of an object to be processed, such as a semiconductor wafer or the like, arranged on the electrodes. Then, a magnetic field is formed in a horizontal direction with respect to the semiconductor wafer using magnetic field formation means, for example, a permanent magnet or the like. In doing this, the electrons are caused to be in cyclotron motion (spiral motion), whereby the frequency at which the electrons and neutral particles collide with each other is high. Under this structure where the electrons and the neutral particles collide with each other, a reactive gas is efficiently ionized at the periphery of the surface of the semiconductor wafer. The ions are injected into the processing surface of the semiconductor wafer, thus etching is efficiently performed as a result of both a sputtering effect and a chemical reaction of ions.
In thus structured magnetron reactive ion etching apparatus, it is important that a magnetic field is uniformly formed in a horizontal direction with respect to the semiconductor wafer. This is because if a magnetic field is not formed uniformly in the horizontal direction, the surface of the semiconductor wafer is etched at a variety of etching speeds.
FIG. 10
illustrates a dipole ring magnet as magnetic field formation means used in the magnetron reactive ion etching apparatus.
As illustrated in
FIG. 10
, a dipole ring magnet
101
comprises a dipole ring body
102
formed in a ring-like shape and a plurality of anisotropic segment cylindrical magnets
103
arranged in the dipole ring body
102
at equal intervals. The anisotropic segment cylindrical magnets
103
are arranged in such a way that their magnetization directions are slightly differently oriented from one another, so as to form a magnetic field totally in one direction.
The dipole ring magnet
101
is arranged outside a processing container
104
, and a magnetic field B is formed in a horizontal direction with respect to a semiconductor wafer
105
.
The dipole ring magnet
101
can rotate along its circumferential direction. In rotating this dipole ring magnet
101
, a rotational magnetic field is formed uniformly in a horizontal direction with respect to the semiconductor wafer
105
, and the density of a plasma on the semiconductor wafer
105
can uniformly be made.
The magnetic field strength is large in magnetron reactive ion etching, thus a problem is that shading damage is likely to occur in an over-etching process, for example. For the sake of easy description of shading damage,
FIG. 11
illustrates an exemplary diagram of a transistor in an over-etching process.
As illustrated in
FIG. 11
, a transistor
111
is a MOS type transistor wherein a gate oxide film
113
and a gate electrode
114
are formed on a semiconductor wafer
112
. The first interlayer insulating film
115
is formed on a corresponding part of the semiconductor wafer
112
on which the gate oxide film
113
and the gate electrode
114
are not formed. Metal wiring
116
is formed on the first interlayer insulating film
115
and the gate electrode
114
. The second interlayer insulating film
117
is formed on the metal wiring
116
, and a resist
118
is arranged on the second interlayer insulating film
117
. By performing a magnetron reactive ion etching process, some part of the second interlayer insulating film
117
which is not masked by the resist
118
is etched, resulting in forming a hole
119
.
During the magnetron reactive ion etching process, electrons are attracted (being in cyclotron motion) to a magnetic field. The speed (the speed of the electrons travelling in a top-down direction, as illustrated in
FIG. 11
) at which the electrons move toward the hole
119
is low, thus the electrons are hardly to enter the hole
119
. As compared to the electrons, positive charge ions are unlikely to be attracted to the magnetic field for some reasons that their mass is great and the like. Hence, the speed at which positive ions move toward the hole
119
is higher than the speed of electrons travelling to the hole
119
, and the positive ions are likely to enter the hole
119
. As shown in
FIG. 11
, electrons
121
are likely to be charged up on the resist
118
during the over-etching process, while positive ions
120
are likely to be charged up on the bottom of the hole
119
. As a result of this, a potential difference occurs in the upper and lower surfaces of the gate insulating film
113
. In addition, a current flows through the gate insulating film
113
in a direction shown with an arrow
122
in the drawing, resulting in shading damage in which the gate insulating film
113
is deteriorated.
As a method for preventing such an insulating film from being deteriorated, proposed in Unexamined Japanese Patent Application KOKAI Publication No. H5-308055 is a method for forming gate electrode wiring without deterioration of a gate oxide film. This formation of the gate electrode wiring is achieved by performing magnetic field high-density plasma etching when patterning metal wiring connected to a gate electrode, and performing non-magnetic field low-density plasma etching and patterning the metal wiring before the metal wiring is completely isolated therefrom.
According to this invention, it is possible that an insulating film is prevented from being deteriorated as a result of shading damage, etc., since changing from the magnetic field high-density plasma etching to the non-magnetic field low-density plasma etching can prevent electrons from being attracted to the magnetic field.
However, the etching speed dramatically decreases if the magnetic field high-density plasma etching is changed to the non-magnetic field low-density plasma etching. Therefore, if the magnetic field high-density plasma etching is not performed until just before the etching process is completed, the essential purpose of the magnetron reactive ion etching for efficiently performing an etching process is not realized.
On the contrary, if the magnetic field high-density plasma etching is performed until just before the etching process is completed, the gate oxide film is exposed from a part of a hole, which is made as a result of the etching. In the structure where the gate oxide film is thus exposed, the electrons are distributed not uniformly on the semiconductor wafer, bringing another problem that charge up damage occurs.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above problems. It is accordingly an object of the present invention to provide an apparatus for and a method of efficiently processing an object to be processed while restricting shading damages.
In order to accomplish the above object, according to the first aspect of the present invention, there is provided a processing apparatus, comprising:
a processing container;
an electrode unit which is arranged inside said processing container and includes a first electrode and a second electrode facing each other via an object to be processed;
a processing gas supply section which supplies a processing gas into said processing container;
a gas exhaust section which exhausts said processing container of a gas;
an electric fie
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Goudreau George A.
Tokyo Electron Limited
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