Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-02-02
2002-07-09
Mills, Gregory (Department: 1763)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S711000, C427S569000, C427S585000, C156S345340, C156S345480, C156S345470, C156S345430, C118S7230ER, C118S7230IR
Reexamination Certificate
active
06417111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus to be used for forming a thin film on a surface of a workpiece or for etching a surface of a workpiece, and more particularly to a plasma processing apparatus for processing a surface of a workpiece having a deep groove or hole which is very small in dimension and high in an aspect ratio.
2. Description of the Related Art
Conventionally, a plasma processing apparatus utilizing a plasma has often been used as a processing apparatus for forming a thin film onto a fine pattern formed over a surface of an object to be processed such as a workpiece, for example, a substrate or a semiconductor wafer (hereinafter referred to as a “wafer”) or for performing fine processing of a surface of a workpiece. One or more processing gases are introduced into a processing chamber of the plasma processing apparatus, thereby generating a plasma. Consequently, some ions (reactive ions) and neutral particles (neutral radicals) contributing to the reaction are generated in the plasma. The ions are accelerated by the sheath on the surface of the workpiece and reach the surface of the workpiece, thereby contributing to the processing of the surface of the workpiece. The neutral radicals are transported to the surface of the workpiece by diffusion and deposit on the surface of the workpiece which contributes to the surface processing of the workpiece by performing a surface reaction or a reaction by the aid of the energy of ions incident on the surface.
For a method for forming a thin film on a surface of a deep groove or hole which is very small in dimension and high in an aspect ratio, molecular structures of a raw material for CVD (chemical vapor deposition) gas have been conventionally devised. Consequently, step coverage on a pattern surface has been improved and the formation of a thin film on a pattern having a high aspect ratio has been implemented.
On the other hand, as a method for performing fine processing of, for example, a deep groove or hole which is very small in dimension and high in an aspect ratio, there is a method for increasing the energy of ions incident on the surface of a workpiece. By this method, workability in the direction perpendicular to the surface of the workpiece has been improved and a pattern having a high aspect ratio has been formed.
However, as an aspect ratio of a pattern more increases, it becomes more difficult to process the surface thereof according to the conventional method.
In order to solve the above mentioned problem, several methods were proposed, which prevent the reaction by ions incident on a side wall of a pattern in plasma etching. For example, a method for forming an inhibitor layer on the side wall of the pattern, which layer protects the surface from the reactive species, is described in “Extended Abstracts of Solid State Devices and Materials, p 229 (1986)”; a method for reducing the temperature of a workpiece is described in “Appl. Phys. Lett., 52, 616 (1988)”; and a method for decreasing a gas pressure is described in “Jpn. J. Appl. Phys., 29, 792 (1990)”.
However, even if these methods are used, an incident flux of the neutral radicals into a pattern having a high aspect ratio decreases during etching of the pattern having a high aspect ratio. In some cases, therefore, the inhibitor layer formed on the side wall of the pattern became thin, so that etching by ions incident on the side wall of the pattern could not be prevented.
Moreover, Japanese Patent Kokai Publication No. 163465/1994 has proposed a method for supplying a sufficient amount of neutral radicals to a pattern bottom by separating a processing chamber from a plasma chamber, and keeping the gas pressure within the plasma chamber higher than that of the processing chamber to provide the neutral radicals and gas molecules with a kinetic energy in the direction to the substrate and to enhance the incident directivity of the neutral radicals being supplied.
According to the above mentioned method, a unit construction is proposed to produce the pressure difference between the plasma generating chamber and the processing chamber, wherein a porous plate having holes of small diameters (which are not more than 3 mm) is provided and a plurality of turbo molecule pumps are provided so that gas within the processing chamber is exhausted at a total exhausting rate of 4000 litters/sec. However, in addition to an increase in the size of the apparatus, it is difficult for ions to transport to the processing chamber due to the small diameters of the holes, and ions are confined within the plasma generating chamber. Therefore, a plasma density within the processing chamber or an incident ion flux onto the workpiece becomes insufficient for processing the workpiece. In the case where an oxide film etching of a pattern having a high aspect ratio is carried out, there was a problem that an etch rate rapidly decreases due to the insufficient incident ion flux, so that through-put is reduced. In other words, although the neutral radicals are easily incident on the bottom portion of the pattern having a high aspect ratio by the porous plate provided to enhance the incidence directivity of the neutral radicals, the ion flux transported to the processing chamber decreases. As a result of the decrease of the ion flux, ions contributing to the etching reaction become poor so that the etch rate is depressed. The above mentioned method may be considered to be effective in etching reaction of silicon or organic materials in which neutral radicals mainly contribute to the reaction, however it is not suitable for etching of oxide film in which ions mainly contribute to the reaction. Further, the neutral radicals pass through the porous plate more easily than the ions since the formers are not affected by the sheath, however, they have a limited lifetime since they easily recombine with other molecules to be changed into other kinds of molecules or readily deposit on the wall of an apparatus. According to the above mentioned method, even if the neutral particles easily reach the bottom portion of the pattern having a high aspect ratio, most of the neutral radicals deposit on the surface of the plasma generating chamber or the number thereof decreases within the plasma generating chamber, so that the flux of the neutral radical incident on the workpiece is not so large. Therefore, it was difficult to enhance an etch rate even in which the neutral radicals mainly contribute to the reaction.
SUMMARY OF THE INVENTION
In order to solve the above mentioned problems of the prior art, it is an object of the present invention to provide a plasma processing apparatus capable of forming a thin film over a groove or hole which is very small in dimension and high in an aspect ratio at a high rate or forming a pattern with high precision at a high etch rate.
A first aspect of the present invention is directed to a plasma processing apparatus which comprises a processing chamber, processing gas supply means for supplying one or more processing gases into the processing chamber, plasma generating means for changing the processing gases supplied into the processing chamber to a plasma, a mounting stage for mounting an object to be processed which is provided in the processing chamber, bias applying means for applying an electrical bias voltage to the mounting stage, a gas storage chamber which is placed at a position opposite to a face of the mounting stage (on which the object being processed is mounting) and which is provided with a supply system for supplying neutral particles or one or more gases to generate the neutral particles, a partition plate which separates the gas storage chamber from the processing chamber and having jet holes for jetting the neutral particles into the processing chamber, and an exhaust system.
A second aspect of the present invention is directed to the plasma processing apparatus according to the first aspect of the present invention, wherein the partition plate is a count
Nishikawa Kazuyasu
Oomori Tatsuo
Ootera Hiroki
Hassanzadeh P.
Mills Gregory
Mitsubishi Denki & Kabushiki Kaisha
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