Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-01-08
2001-04-17
Bueker, Richard (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
Reexamination Certificate
active
06216632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Industrial Application
The present invention relates to a plasma processing system, and more particularly, to a plasma processing system having an improved plasma source capable of supplying ions, electrons, neutral radicals and ultra-violet and visible light useful for a process of chemical vapor deposition (CVD) or etching micron-scale elements on integrated circuits in the semiconductor industry.
2. Discussion of Related Art
With the advance of 300 mm Si wafers (substrates) in the semiconductor industry, high density plasmas with uniform plasma density over the front surface of a substrate to be processed are greatly required. Even though the scale-up of existing plasma systems designed to process 200 mm wafers is one approach to meet the requirement, it is impeded by hardware difficulties of the existing plasma systems. Two such conventional plasma sources are illustrated in
FIGS. 14 and 15
, which are mainly used for the conventional 200 mm wafer plasma processing systems.
One example of the conventional plasma sources shown in
FIG. 14
, has a reactor
50
made of a metal, which is formed by a top plate
51
, a bottom plate
52
and a cylindrical side wall
53
. In the reactor
50
, a substrate holder
54
on which a wafer or a substrate
61
is loaded is disposed at a lower position close to the bottom plate
52
, and is parallel to both the top plate
51
and the bottom plate
52
. The substrate holder
54
is electrically isolated from the reactor
50
by an insulator
57
and is supplied with a rf current generated by a rf electric power source
55
through a matching circuit
56
and a capacitor
60
. The reactor
50
is electrically grounded through a wire
58
. In accordance with the configuration of the reactor
50
, a plasma is generated in the space
59
between the top plate
51
and the substrate holder
54
on the basis of capacitive coupling of rf electrical power.
FIG. 15
shows the other example of a conventional plasma source. In this example, the configuration of reactor
70
is almost the same as the reactor
50
shown in
FIG. 14
, except for an extra rf electrode
71
. The reactor
70
also has the top plate
51
, the bottom plate
52
and the cylindrical side wall
53
, and it is made of a metal. Further, the reactor
70
is provided with the substrate holder
54
on which the substrate
61
is loaded, the rf electric power source
55
, the matching circuit
56
, the capacitor
60
, the insulator
57
and the ground wire
58
. The rf electrode
71
is placed slightly below the top plate
51
parallel to the substrate holder
54
. The top rf electrode
71
is electrically isolated from the reactor
70
and is given a rf current by a rf electric power source
72
through a matching circuit
73
. The rf current supplied to the rf electrode
71
usually has a frequency that is higher than that supplied to the substrate holder
54
. The plasma is generated between the rf electrode
71
and the substrate holder
54
by the capacitive coupling of rf electrical power.
One of the major problems of the conventional plasma sources shown in
FIGS. 14 and 15
is that the power transfer efficiencies from the rf electric sources (
55
,
72
) to the plasma is low. This is due to the consumption of a considerable fraction of the applied rf power by unwanted ion acceleration. This is an inherent property of the capacitively coupled plasmas, and results in a lower plasma density. Further, since the 300 mm wafer processing is combined with the 0.25 m technology, it is considered that chemical processes must be carried out at a lower pressure, for example, about 10 mTorr. However, the plasma density of capacitively coupled plasmas further drops with the lowering of pressure. Thus, a higher process rate that is required for an economically viable system can not be obtained.
If the diameter of the substrate to be processed is small, for example, it is 200 mm, a higher rf electric power can be applied to increase the plasma density. If the diameter of the substrate to be processed is 300 mm, however, the applied rf power must be increased at least by 2.25 times in order to maintain the same power density because the surface area of the 300 mm wafer is 2.25 times larger than that of the 200 mm wafer. Therefore, the requirement for the rf electric power to maintain the desirable power density may limit some of applications.
In addition, when a 200 mm wafer processing system is scaled up to a 300 mm wafer processing system, the pumping speed in a processing chamber also must be increased in order to maintain the same reaction rates.
Owing to these hardware difficulties, the conventional plasma sources for a 200 mm wafer shown in
FIGS. 14
an
15
can not be simply scaled up for 300 mm wafer plasma sources. In order to avoid these problems, it is important to design plasma sources that yield a higher plasma density over a 300 mm diameter region. Further, there must be a higher plasma uniformity over the surface of the 300 mm wafer because some semiconductor processing methods, such as a plasma assisted anisotrophic etching method, need a plasma uniformity more than 95% over the whole surface of the substrate to be processed.
OBJECTS AND SUMMARY
An object of the present invention is to provide a plasma processing system for producing a magnetically enhanced, capacitively coupled, planar plasma, which can yield a high density plasma over a large area with a uniform plasma density by the combination of a capacitive coupling mechanism and electron confinement by a magnetic field, for the chemical vapor deposition and etching of large area substrate used in semiconductor industry.
Further, another object of the present invention is to realize a plasma source with a lower aspect ratio.
A plasma processing system of the present invention, in order to attain the above-mentioned object, comprises a reactor including a plasma source and a substrate holder, which is configured by a top plate made of a nonmagnetic metal, a bottom plate made of a metal, and a side wall having at least in part a section made of a dielectric material, wherein the substrate holder is placed in the bottom plate. The system further includes a plurality of magnets separately arranged in the outside of the top plate, wherein the polarity of the magnets facing the inside of the reactor is alternately changed, and the magnets generate a magnetic field with closed magnetic fluxes near to the inner surface of the top plate.
In accordance with another aspect of the above-mentioned invention, the arrangement of magnets on the top plate makes a desirable magnetic field and magnetic field cusps below the top plate. In the magnetic field, the magnetic flux lines are generated in the space near to the inner surface of the top plate and all of the magnetic flux lines are closed to make loops. This magnetic field controls electrons and enhances capacitively coupled planar plasma to yield a high density plasma over a large area with a uniform plasma density.
In the above-mentioned configuration, the top plate may be of a planar circular shape, and the magnets may be directly fixed to the outer surface of the planar top plate. This top plate can be made as a simple form.
In the above-mentioned configuration, the top plate can be of a dome shape. This dome shaped top plate can change the arrangement of the magnets to desirable one.
In the above-mentioned configuration, the magnets can be arranged on the inner surface of a dome shaped cover that lies over said dome shaped top plate. In accordance with the magnet arrangement, the magnetic field formed within the reactor can be desirable.
In the above-mentioned configurations, the top plate can be electrically isolated from the rest of the reactor by placing the top plate on a section made of a dielectric material.
In the above-mentioned configurations, the top plate can be supplied with a rf electrical power.
In the above-mentioned configuration using the planar top plate, the magnets are preferably arranged on an edge region of the top
Anelva Corporation
Bueker Richard
Burns Doane , Swecker, Mathis LLP
Fieler Erin
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