Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With radio frequency antenna or inductive coil gas...
Reexamination Certificate
2002-02-04
2004-09-21
Alejandro-Mulero, Luz (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With radio frequency antenna or inductive coil gas...
C118S7230AN
Reexamination Certificate
active
06793768
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma-assisted processing apparatus; and, more particularly, the invention relates to a plasma-assisted processing apparatus capable of producing a highly dense, highly uniform plasma under different conditions defined by various parameters, including the types of gases, the pressure of gases and high-frequency power, which are variable in wide ranges, and of satisfactorily processing a workpiece by use of a plasma-assisted process.
Miniaturization of the components of ultralarge-scale integrated circuits (ULSI circuits) has made rapid progress in recent years, and ULSI circuits of minute structure having a minimum feature length on the order of 0.13 &mgr;m have been developed. Semiconductor wafers having a large diameter on the order of 300 mm have been used for forming such ULSI circuits thereon. There has been a need for processing apparatuses that are capable of accurately etching workpieces to form DRAMs and flash memories as well as system LSIs, and of processing large-diameter semiconductor wafers.
To meet such a requirement, a plasma-assisted process that is not only capable of highly uniformly processing a large area, but also of having an advanced control characteristic, is necessary. A plasma-assisted processing apparatus must be provided with a plasma-assisted processing unit that is capable of fine processing, and standards for dimensions have become strict. For example, a plasma-assisted etching process must prevent the occurrence of a shape anomaly called a “notch” resulting from the accumulation of positive charges in the bottom of a minute pattern. Negative gases used for etching, such as Cl
2
, BCl
3
, SF
6
and such, produce negative ions during an etching process. Those negative ions have a function to neutralize positive charges accumulated in the bottom of a minute pattern. Since negative ions are produced more easily at lower electron temperatures, it is desired to realize a plasma having a low electron temperature. Such a plasma of low electron temperature can be produced by a plasma-assisted processing apparatus using high-frequency power at a frequency in the VHF or the UHF band.
In a plasma-assisted processing apparatus, a plasma is produced through the capacitive coupling of an antenna or a counter electrode, when the frequency of high-frequency power applied to the plasma-assisted processing apparatus is 10 MHz or below. The wavelength of the high-frequency power is far smaller than the diameter of the antenna, and any potential distribution is not formed on the antenna. Therefore, a uniform plasma is produced in front of the antenna.
When the frequency of the high-frequency power applied to the plasma-assisted processing apparatus is not lower than the VHF band, the wavelength of the high-frequency power is short, but is long as compared with the diameter of the antenna. Consequently, the uniformity of the plasma produced in front of the antenna is unsatisfactory.
FIG. 12
is a schematic sectional view of a known plasma-assisted processing apparatus using high-frequency power at a frequency in the VHF or the UHF band.
In
FIG. 12
the apparatus includes a case
50
, a vacuum vessel
51
, a processing chamber
52
, a workpiece support (electrode)
53
for supporting a workpiece (wafer)
54
, a gas supply passage
55
, an exhaust passage
56
, a first high-frequency power source
57
, a high-frequency waveguide
58
, a matching device
59
, a shield
60
, a disk antenna
61
, a dielectric material
62
, magnetic field creating parts
63
, a window
64
, a gas-diffusing plate
65
and a second high-frequency power source
66
.
The vacuum vessel
51
is disposed in the case
50
. The vacuum vessel
51
defines the processing chamber
52
. The exhaust passage
56
is connected for evacuation to a lower part of the vacuum vessel
51
. The workpiece support
53
supporting the workpiece
54
is located in the processing chamber
52
. A large open end of the vacuum vessel
51
is closed hermetically by the window
64
and the gas-diffusing plate
65
. The gas supply passage
55
is connected to the gas-diffusing plate
65
to supply gases through the gas-diffusing plate
65
into the processing chamber
52
. The disk antenna
61
is placed on the window
64
. The disk antenna
61
and the dielectric material
62
are covered with the shield
60
. The high-frequency waveguide
58
, which penetrates the shield
60
, extends through a through hole formed in the case
50
to connect the disk antenna
61
to the external first high-frequency power source
57
. The high-frequency waveguide
58
has one end joined to the disk antenna
61
and the other end connected through the matching device
59
to the first high-frequency power source
57
. The high-frequency waveguide
58
guides high-frequency power at a frequency in the UHF band (or the VHF band) generated by the first high-frequency power source
57
to the disk antenna
61
. The magnetic field creating parts
63
are disposed in the case
50
to create a magnetic field in the processing chamber
52
. The second high-frequency power source
66
is connected to the workpiece support
53
to supply high-frequency power at a frequency in the UHF band (or the VHF band) to the workpiece support
53
.
When processing the workpiece
54
in the plasma-assisted processing apparatus, gases are supplied through the gas supply passage
55
into the processing chamber
52
, the first high-frequency power source
57
applies high-frequency power to the disk antenna
61
, the second high-frequency power source
66
applies high-frequency power to the workpiece support
53
, and the magnetic field creating parts
63
create a magnetic field in the processing chamber
52
. Thus, a plasma is produced in the processing chamber
52
. The plasma acts on the surface of the workpiece
54
for plasma-assisted processing.
Since the frequency of the high-frequency power is in the UHF band (or the VHF band), the high-frequency wave carrying the high-frequency power assumes the aspect of an electromagnetic wave. This high-frequency wave propagates only on the boundary region of the plasma and is absorbed. The high-frequency wave is not radiated simply from the disk antenna
61
, but also forms a standing wave in a sheath region on the boundary of the plasma and in the high-frequency waveguide
58
. The strength distribution of an electric field is dependent on the size and shape of the boundary region of the plasma. To create a high-frequency electric field of a desired strength distribution, such as a flat distribution extending in the direction of the length (diameter) of the workpiece
54
, notice must be taken not only of the electric field created in a region under the disk antenna
61
, but also of an electric field created around the workpiece
54
. This is because, as the high-frequency electric field created around the workpiece
54
tends to enlarge, the high-frequency power is concentrated on the region in which the plasma is produced after the plasma has been produced in the region around the workpiece
54
; and, consequently, the density of the plasma around the workpiece
54
increases progressively.
FIGS. 13A
to
13
D are views and graphs, respectively, which assist in explaining the creation of such a high-frequency electric field.
FIG. 13A
is a fragmentary sectional view of the plasma-assisted processing apparatus;
FIG. 13B
is a diagrammatic view showing the strength distribution of an electric field;
FIG. 13C
is a graph showing the strength distribution of an electric field with respect to a direction along the diameter of the disk antenna
61
; and
FIG. 13D
is a graph showing the variation of power absorption with position with respect to the diameter of the disk antenna
61
. In this example, the frequency f of the high-frequency power is 450 MHz, and the window
64
is formed of quartz (specific dielectric constant: 3.5).
In
FIG. 13A
, there is a sheath region
67
, and the other parts like or corresponding to those shown in
FIG. 12
ar
Edamura Manabu
Ikenaga Kazuyuki
Kazumi Hideyuki
Ootake Atsushi
Alejandro-Mulero Luz
Hitachi , Ltd.
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