Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-05-10
2002-03-12
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C118S7230AN, C438S729000
Reexamination Certificate
active
06355573
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method 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 plasma processing method and apparatus for use of plasma excited with high-frequency power of VHF or UHF band.
Whereas Japanese Laid-Open Patent Publication No. 8-83696 describes that use of high-density plasma is important in order to meet the trend toward microstructures of semiconductors and other electron devices, 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
and 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 extreme micro-patterns to be achieved with high precision.
Also, in a case where a gas containing carbon and fluorine, such as CxFy or CxHyFz (where x, y, z are natural numbers), which is generally used for the etching of insulating films such as a silicon oxide film, 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 to silicon etching the more with lower electron temperatures.
Also, when the electron temperature becomes 3 eV or lower, ion temperature and plasma potential are also lower, so that ion damage to the substrate in plasma CVD can be reduced.
It is plasma sources using high-frequency power of VHF or UHF band that are now receiving attention as a technique capable of generating plasma having low electron temperature.
FIG. 10
is a sectional view of a dual-frequency excitation parallel-plate type plasma processing apparatus. Referring to
FIG. 10
, while an interior of a vacuum chamber
1
is maintained to a specified pressure by introducing a specified gas from a gas supply device
2
into the vacuum chamber
1
and simultaneously performing evacuation by a pump
3
as an evacuating device, a high-frequency power of 100 MHz is supplied to a counter electrode
17
by a counter-electrode use high-frequency power supply
16
. Then, plasma is generated in the vacuum chamber
1
, where plasma processing such as etching, deposition, and surface reforming can be carried out on a substrate
7
placed on a substrate electrode
6
. In this case, as shown in
FIG. 10
, by supplying high-frequency power also to the substrate electrode
6
by a substrate-electrode use high-frequency power supply
8
, ion energy that reaches the substrate
7
can be controlled. In addition, the counter electrode
17
is insulated from the vacuum chamber
1
by an insulating ring
18
.
However, there has been an issue that the conventional method shown in
FIG. 10
has difficulty in obtaining a uniformity of plasma.
FIG. 11
shows results of measuring ion saturation current density at a position 20 mm just above the substrate
7
in the plasma processing apparatus of FIG.
10
. Conditions for plasma generation are gas type, a gas flow rate of Cl
2
=100 sccm, a pressure of 1.5 Pa, and a high-frequency power of 2 kW. It can be understood from
FIG. 11
that plasma is biased to one side.
Such nonuniformity of plasma is a phenomenon that could not be seen with a 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 and the plasma being capacitively or inductively coupled to itself, but also an advantage that the plasma is generated by electromagnetic waves, which are radiated from the counter electrode, propagating on the surface of the plasma. In this frequency band, because the size of the counter electrode and the wavelength of the electromagnetic wave are close to each other, a large number of modes are permitted to be present as an electromagnetic distribution generated in the counter electrode, so that a biased electromagnetic distribution occurs on the counter electrode. On this account, it could be considered, the capacitive or inductive coupling of the counter electrode and the plasma is biased, causing electromagnetic waves radiated from the counter electrode to be also biased, so that plasma is biased.
In view of these issues of the prior art, an object of the present invention is to provide a plasma processing method and apparatus capable of generating uniform plasma.
SUMMARY OF THE INVENTION
In accomplishing these and other aspects, according to a first aspect of the present invention, there is provided a plasma processing method.
The plasma processing method comprises controlling an interior of a vacuum chamber to a specified pressure by introducing gas into the vacuum chamber and evacuating the interior of the vacuum chamber, supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to a site of an antenna other than its center and periphery with the antenna provided opposite to a substrate in the vacuum chamber, in a state where a general center of the antenna and the vacuum chamber are short-circuited to each other, while the interior of the vacuum chamber is controlled to the specified pressure, and generating plasma within the vacuum chamber and processing the substrate placed on a substrate electrode within the vacuum chamber.
According to a second aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the high-frequency power having the frequency of 50 MHz to 3 GHz is supplied to the antenna via a through hole provided at a site of a dielectric other than its center and periphery with the antenna provided within the vacuum chamber and with a dielectric sandwiched between the antenna and the vacuum chamber, in a state where the antenna and the vacuum chamber are short-circuited to each other via a through hole provided at a general center of the dielectric.
According to a third aspect of the present invention, there is provided a plasma processing method according to the first aspect, wherein the high-frequency power having the same phase is supplied to a plurality of sites of the antenna which are generally equidistantly spaced around the center of the antenna so as to more uniformity of plasma.
According to a fourth aspect of the present invention, there is provided a plasma processing method.
The plasma processing method comprises controlling an interior of a vacuum chamber to a specified pressure by introducing gas into the vacuum chamber and evacuating the interior of the vacuum chamber, supplying a high-frequency power having a frequency of 50 MHz to 3 GHz to a general center of an antenna with the antenna provided opposite to a substrate in the vacuum chamber, in a state where a site of the antenna other than its center and periphery and the vacuum chamber are short-circuited to each other, while the interior of the vacuum chamber is controlled to the specified pressure, and generating plasma within the vacuum chamber and processing the substrate placed on a substrate electrode within the vacuum chamber.
According to a fifth aspect of the present invention, there is provided a plasma processing method accordi
Matsui Takuya
Okumura Tomohiro
Suzuki Masaki
Everhart Caridad
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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