Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
2000-02-23
2004-10-26
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C118S7230IR, C216S066000
Reexamination Certificate
active
06808759
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to plasma processing methods such as dry etching, sputtering, and plasma CVD, as well as apparatuses therefor, to be used for manufacture of semiconductor or other electron devices and micromachines. More particularly, the present invention relates to a plasma processing method and apparatus for the use of plasma excited with high-frequency power of VHF or UHF band.
The present invention further relates to a matching box for a plasma processing apparatus to be used for impedance matching in supplying high-frequency power of VHF band, in particular, to a counter electrode for plasma excitation or to an antenna, and relates to a plasma processing method and apparatus using plasma excited with the high-frequency power of VHF band.
Japanese Laid-Open Patent Publication No. 8-83696 describes that the use of high-density plasma is important in order to meet the trend toward microstructures of semiconductors and other electron devices. Furthermore, low electron temperature plasma has recently been receiving attention by virtue of its high electron density and low electron temperature.
In the case where a gas having a high negativity, i.e., a gas that tends to generate negative ions, such as Cl
2
, SF
6
, is formed into plasma, when the electron temperature becomes about 3 eV or lower, larger amounts of negative ions are generated than with higher electron temperatures. Taking advantage of this phenomenon makes it possible to prevent etching configuration abnormalities, so-called notch, which may occur when positive charges are accumulated at the bottom of micro-patterns due to excessive incidence of positive ions. This allows etching of extremely micro patterns to be achieved with high precision.
Also, in the case where a gas containing carbon and fluorine, such as C
x
F
y
or C
x
H
y
F
z
(where x, y, z are natural numbers), which is generally used for etching of insulating films such as silicon oxide, is formed into plasma, when the electron temperature becomes about 3 eV or lower, gas dissociation is suppressed more than with higher electron temperatures, where, in particular, generation of F atoms, F radicals and the like is suppressed. Because F atoms, F radicals and the like are higher in the rate of silicon etching, insulating film etching can be carried out at larger selection ratios than silicon etching with lower electron temperatures.
Also, when the electron temperature becomes 3 eV or lower, ion temperature and plasma potential also becomes lower, so that ion damage to the substrate in plasma CVD can be reduced.
As a technique capable of generating plasma having low electron temperature, plasma sources using high-frequency power of VHF band or UHF band are now receiving attention.
FIG. 15
is a sectional view of a dual-frequency excitation parallel-flat plate type plasma processing apparatus. Referring to
FIG. 15
, while the interior of a vacuum chamber
201
is maintained at a specified pressure by introducing a specified gas from a gas supply unit
202
into the vacuum chamber
201
and simultaneously performing evacuation by a pump
203
as an evacuating device, a high-frequency power of 100 MHz is supplied to a counter electrode
205
by a counter-electrode-use-high-frequency power supply
204
. Then, plasma is generated in the vacuum chamber
201
, where plasma processing such as etching, deposition, and surface reforming can be carried out on a substrate
207
placed on a substrate electrode
206
. In this case, as shown in
FIG. 15
, by supplying high-frequency power also to the substrate electrode
206
by a substrate-electrode-use-high-frequency power supply
208
, ion energy that reaches the substrate
207
can be controlled. In addition, the counter electrode
205
is insulated from the vacuum chamber
201
by an insulating ring
211
.
FIG. 16
is a sectional view of a plasma processing apparatus which we have already proposed and which has an antenna type plasma source mounted thereon. Referring to
FIG. 16
, while the interior of a vacuum chamber
301
is maintained at a specified pressure by introducing a specified gas from a gas supply unit
302
into the vacuum chamber
301
and simultaneously performing evacuation by a pump
303
as an evacuating device, a high-frequency power of 100 MHz is supplied to a spiral antenna
313
on a dielectric window
314
by an antenna-use-high-frequency power supply
312
. Then, plasma is generated in the vacuum chamber
301
by electromagnetic waves radiated into the vacuum chamber
301
, where plasma processing such as etching, deposition, and surface reforming can be carried out on a substrate
307
placed on a substrate electrode
306
. In this case, as shown in
FIG. 16
, by supplying high-frequency power also to the substrate electrode
306
by a substrate-electrode-use-high-frequency power supply
308
, ion energy that reaches the substrate
307
can be controlled.
However, there has been an issue that the conventional methods shown in
FIGS. 15 and 16
have difficulty in obtaining uniform plasma generation.
FIG. 17
shows results of measuring ion saturation current density at a position just 20 mm above the substrate
207
in the plasma processing apparatus of FIG.
15
. Conditions for plasma generation are gas type of Cl
2
and gas flow rate of 100 sccm, a pressure of 1 Pa, and a high-frequency power of 2 kW. It can be understood from
FIG. 17
that plasma density is higher in peripheral regions.
FIG. 18
shows results of measuring ion saturation current density at a position just 20 mm above the substrate
307
in the plasma processing apparatus of FIG.
16
. Conditions for plasma generation are gas type of Cl
2
and gas flow rate of 100 sccm, a pressure of 1 Pa, and a high-frequency power of 2 kW. It can be understood from
FIG. 18
that plasma density is higher in peripheral regions.
Such nonuniformity of plasma is a phenomenon that could not be seen with the frequency of the high-frequency power of 50 MHz or less. Whereas the 50 MHz or higher high-frequency power needs to be used in order to lower the electron temperature of plasma, there are produced, in this frequency band, not only an advantage that plasma is generated by the counter electrode or antenna being capacitively or inductively coupled to the plasma, but also an advantage that plasma is generated by electromagnetic waves, which are radiated from the counter electrode or antenna, propagating on the surface of the plasma. In peripheral regions of the vacuum chamber, which serve as reflecting surfaces for the electromagnetic waves that have propagated on the surface of the plasma, stronger electric fields are developed so that thick plasma is generated.
Also, as described above, in the case where a gas having a high negativity, i.e., a gas that tends to generate negative ions, such as Cl
2
, SF
6
, is formed into plasma, when the electron temperature becomes about 3 eV or lower, larger amounts of negative ions are generated than with higher electron temperatures. Taking advantage of this phenomenon makes it possible to prevent a phenomenon that perpendicularity of the incident angle of ions onto the substrate worsens when positive charges are accumulated at the bottom of micro-patterns due to excessive incidence of positive ions. This allows etching of extremely micro patterns to be achieved with high precision. Besides, that is an expectation for process improvement making use of the high reactivity of negative ions.
Also, in the case where a gas containing carbon and fluorine, such as C
x
F
y
or C
X
H
Y
F
Z
(where x, y, z are natural numbers), which is generally used for etching of insulating films such as silicon oxide, is formed into plasma, when the electron temperature becomes about 3 eV or lower, gas dissociation is suppressed more than with higher electron temperatures, where, in particular, generation of F atoms, F radicals and the like is suppressed. Because F atoms, F radicals and the like are higher in the rate of silicon etching, insulating film etching can be carried out at l
Haraguchi Hideo
Matsuda Izuru
Matsui Takuya
Mitsuhashi Akio
Okumura Tomohiro
Padgett Marianne
Wenderoth , Lind & Ponack, L.L.P.
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