Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the...
Reexamination Certificate
2001-01-10
2004-04-27
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
C315S111210, C118S7230IR
Reexamination Certificate
active
06727654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to modified magnetron high-frequency discharge plasma processing apparatuses, and in particular to apparatuses performing various kinds of processes using a plasma, plasma etching apparatuses for dry etching with a plasma, for example, films formed on the surface of a substrate to be processed, and plasma CVD (chemical vapor deposition) apparatuses for forming thin films on the surface of a substrate to be processed using gas phase reactions induced by a plasma.
2. Description of the Related Art
In recent years, plasma processing is increasingly used in the manufacturing process for a variety of semiconductor devices, liquid crystal displays, and solar batteries. The active species and ions generated in a plasma are used to etch a silicon oxide film formed on a silicon semiconductor as one method for dry etching, for example. With the increasing integration of semiconductor devices, wiring is laid out in multiple layers, so that insulating films between the wiring layers (interlayer insulating films) have to be provided. One known method for forming a film on the surface of a substrate is to introduce a reaction gas into the reaction chamber where the process is performed, and add heat to cause the gas to react. However, for this method, relatively high temperatures are necessary, so that there are many defects in the devices, and recently plasma CVD is often used, in which the energy that is necessary for the activation of the reaction is inferred by a plasma induced by glow discharge. Moreover, films for solar batteries are also formed by plasma CVD.
In dry etching, which is a typical plasma process, there is a need for uniform high-density plasmas suitable for substrates with larger surface areas with which the throughput of the apparatus can be increased, and for increased processing precision and selectivity, suitable for finer electronic device structures and a larger number of layers. There is also a need for plasmas with higher uniformity, so as to reduce charge-up damage. The development of a variety of plasma sources supposed to satisfy these needs is progressing.
However, although the density of plasmas generated with ECR (electron cyclotron resonance) plasma sources, ICP (inductively coupled plasma) plasma sources, and high-density plasma sources using surface microwaves plasma sources and helicon waves plasma sources is sufficient, it is currently impossible to ensure uniformity within Ø300 mm. In addition, in these high-density plasma sources, the electron temperature of the plasma has to be kept low, so as to suppress excessive ionization of the plasma gas. Especially with regard to etching silicon oxide films, high-density plasma sources addressing these requirements are still under development, and lower etching selectivity due to excessive ionization of the gas and charge accumulation at the substrate surface are still big problems.
In etching processes using current high-density plasma sources, the lower selectivity with respect to the underlying silicon when etching small silicon oxide film contact holes, undesired side etching due to charge build-up when etching gate polysilicon electrodes, and insulation breakdown of the gate oxide film are real problems. It seems that these phenomena are caused by large electron temperatures (that is, the presence of high-energy electrons) in the low-pressure high-density plasma. But low-pressure and high-density plasmas are necessary for plasma CVD processes.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plasma processing apparatus, in which the uniformity of the plasma density can be increased, and the electron temperature can be kept low.
A plasma processing apparatus in accordance with the present invention includes a vacuum vessel made of a dielectric material, such as quartz or alumina, defining a plasma processing region in its inside; a gas supply/exhaust system that supplies/exhausts gas to/from the vacuum vessel; a tubular first electrode disposed around the periphery of the vacuum vessel and inducing discharges in the gas supplied to the vacuum vessel; a magnet disposed around the periphery of the vacuum vessel; and a high-frequency power apply system that applies high-frequency power to the tubular first electrode; wherein applying high-frequency power to the tubular first electrode generates a plasma inside the vacuum vessel. Here, “tubular” includes the shapes of, for example, circular, elliptical and polygonal rings, tubes and sleeves. The magnet can be a permanent magnet or an electromagnet, for example.
In accordance with this invention, gas is supplied by the gas supply system to the inside of the vacuum vessel, and the atmosphere inside the vacuum vessel is exhausted by the gas exhaust system. Moreover, a predetermined magnetic field is formed by the magnet. Furthermore, high-frequency power is applied by the high-frequency power apply system to the first electrode. Thus, a predetermined high-frequency electric field is formed. As a result, the electrons emitted from the first electrode are trapped in magnetron motion. Thus, a plasma having a high density is generated near the first electrode. Due to diffusion, a portion of this plasma moves toward the central portion of the plasma processing region. Thus, a plasma that has a high and uniform density is generated across the entire plasma processing region. As a result, it becomes possible to generate a plasma having a uniform density across a region of 30 mm diameter.
Moreover, in accordance with this invention, it is also possible to keep the electron temperature of the plasma low. Thus, the decrease of the etching selectivity and the charge density at the substrate surface can be reduced.
Furthermore, in accordance with this invention, the tubular first electrode does not form part of the wall of the vacuum vessel wall, because the tubular first electrode is arranged outside the vacuum vessel. Therefore, different to apparatuses in which a tubular electrode is sandwiched by portions of the vacuum vessel through insulating rings, it is not necessary to provide sealing members between the wall of the vacuum vessel and the insulating rings, and between the insulating rings and the tubular electrode. As a result, the assembly of the apparatus is simplified. Moreover, the number of sealed locations can be reduced, so that the apparatus is suitable for high vacuums in the vacuum vessel.
Furthermore, in accordance with the present invention, the surface of the first electrode can be prevented from contacting the plasma by arranging the first electrode outside the vacuum vessel. Thus, metal contamination caused when plasma damages are inflicted on the first electrode can be prevented.
Moreover, in the present invention, when the vacuum vessel is made of a dielectric material, such as quartz or alumina (Al
2
O
3
), plasma damages at the wall of the vacuum vessel as when the vacuum vessel is made of metal do not occur, and metal contamination of the substrate to be processed in the vacuum vessel caused by plasma damages can be effectively prevented.
From the above, in accordance with the present invention, metal contamination can be effectively avoided for processes near the gate, such as spacer films or gate dielectric films.
Furthermore, in accordance with the present invention, the vacuum vessel in the present invention is made of a dielectric material, so that there is no need to arrange a conducting material, such as an aluminum chamber, near the tubular first electrode. Therefore, electric power losses can be reduced considerably, and the efficiency of the plasma process can be improved.
It is preferable that the vacuum vessel comprises an upper vessel and a lower vessel, and that the upper vessel is dome-shaped and formed in one seamless piece, except that it has an open bottom portion. If the upper vessel is dome-shaped and formed in one seamless piece, then the assembly of the vacuum vessel becomes even easier.
It is preferable that th
Ogawa Unryu
Sato Takayuki
Hitachi Kokusai Electric Inc.
Vu Jimmy T.
Wong Don
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