Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1995-06-07
2001-10-09
Niebling, John F. (Department: 2812)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C216S059000, C216S060000, C118S715000
Reexamination Certificate
active
06299722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an etching method for an object to be processed such as a semiconductor wafer, and more specifically to an etching method including a post-etching step for eliminating impurities created in an etching step, method of post-etching process and etching equipment.
2. Description of the Related Art
The degree of integration of the integrated circuit, which is the nucleus of the microelectronics, is presently increasing, and in accordance with an increase in the degree of integration, the width of the pattern is reduced, and the depth thereof is increased. In order to comply with this, there has been developed a dry etching method under a high vacuum condition as a thin film processing technique. In the dry etching, plasma is generated by using a reaction gas in a vacuum, and various materials on a semiconductor substrate is etched by ions, neutral radicals, atoms, and molecules in the plasma. In the dry etching, various types of gas can be used, and a type of gas is seized in accordance with a material to be etched. Thus, selection of an etching gas is a very important factor of the dry etching.
In the case where the material of an object to be processed is, for example, silicon (Si), or silicon oxide (SiO
2
), a fluorine-based (F) or fluorine-hydrogen-based (F—H) etching gas is used. In general, carbon tetrafluoride (CH
4
) is most commonly used. This is because it is essential in etching of a silicon oxide film that carbon (C) should be present and a great amount of fluorine ion should be generated.
In the etching of a SiO
2
film, the most important factor is to raise the selection ratio of etching with respect to its underlying silicon. In order to increase such selection ratio, there has been proposed an addition of hydrogen to an etching gas, and more specifically, trifluoromethane (CHF
3
) is used as such an etching gas. By use of CHF
3
, a deposition layer is formed as a cover on the surface of the silicon layer such that the surface of the silicon layer cannot be directly attacked by ions. Consequently, the silicon substrate (wafer) is hardly etched. Also, when attacked by accelerated fluorine ions, the silicon oxide film generates oxygen, by which the polymer formed of C—H on the film can be removed, thereby achieving a sufficient etching process.
During the etching process, a damage layer containing impurities is formed on the bottom of an etching hole. Such a damage layer is removed after the etching process.
The use of CHF
3
as the etching gas makes it likely that polymers adhere to the surface of the etched object. Due to the presence of the polymers, it requires a great amount of time in following steps such as ashing and light etching, after completion of the etching process, and the reproducibility of the etching is degraded.
Further, the polymers and resist include the following drawback. That is, in the case where fluorine radicals are used for removing the damage layer after the etching process, some of the fluorine radicals chemically react with the resist, and the damage layer cannot be fully removed as a result.
In order to solve such a problem, there has been proposed a technique for removing a damage layer, wherein polymers and a resist are removed, first, after the etching process, the object is once placed back to atmosphere, and once again, under a vacuum condition, the damage layer is removed. However, such a technique involves not only a large amount of time, but also a great number of facilities.
Presently, the size of the semiconductor wafer, the object to be processed, is changing from 6 inches to 8 inches, and under such circumstances, the drawbacks described above are delaying the processing time.
SUMMARY OF THE INVENTION
The present invention has been achieved in consideration of such circumstances, and an object thereof is to provide an etching method which can effectively removes polymers and damage layers adhered to a material during the etching step by post-processing step, thereby achieving a high etching producibility, a high through put, and reduction in size of facilities.
Another object is to provide a method of post-etching process which can effectively remove polymers and damage layers adhered to a material during the etching step, thereby achieving a high etching producibility, a high throughput, and reduction in size of facilities.
Still another object is to provide etching equipment which can effectively remove polymers and damage layers adhered to a material during the etching step, thereby achieving a high etching producibility, a high throughput, and reduction in size thereof.
According to the first aspect of the present invention, there is provided an etching method comprising: a main etching step for etching an object to be processed having a resist film serving as an etching mask; a post-processing step for processing the object after the main etching so as to eliminate part of the resist film remaining on the object, a polymer adhered to a surface of the object, and an impurity layer created by the primary etching, said post-processing step including a first step for eliminating the remaining part of the resist layer, and the polymer adhered to the surface of the object by plasma produced from a gas including O
2
gas, and a second step for eliminating the impurity layer by plasma made from a gas including halogen-containing gas and O
2
gas, after substantially completing the first step.
According to the second aspect of the present invention, there is provided a method of post-etching process carried out on an etched object with a resist film serving as an etching mask, comprising a first step for eliminating remaining part of a resist layer, and a polymer adhered to the surface of an object by plasma produced from a gas including O
2
gas, and a second step for eliminating an impurity layer by plasma produced from a gas including halogen-containing gas and O
2
gas, after substantially completing the first step.
According to the third aspect of the present invention, there is provided etching equipment comprising: an etching apparatus for main etching an object to be processed having a resist film serving as an etching mask by means of plasma of an etching gas; a post-processing apparatus for performing a plasma process on the object after the main etching with plasma produced from a gas including O
2
gas so as to eliminate part of the resist film remaining on the object and a polymer adhered to a surface of the object, and performing a plasma process with plasma made from a gas including a halogen-containing gas and O
2
gas so as to eliminate an impurity layer created by the main etching; conveying means for conveying the object from the etching apparatus to the post-processing apparatus; and switching means for switching a processing gas to the gas including the halogen-containing gas and O
2
gas after substantially completing the plasma processing by the plasma produced from the gas including O
2
gas, in the post-processing apparatus.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4345968 (1982-08-01), Coe
patent: 4479848 (1984-10-01), Otsubo et al.
patent: 5014217 (1991-05-01), Savage
patent: 5164034 (1992-11-01), Arai et al.
patent: 5186120 (1993-02-01), Ohnishi
patent: 5344542 (1994-09-01), Maher et al.
patent: 5376212 (1994-12-01), Saiki
patent: 5385624 (1995-01-01), Amemiya et al.
Nguyen Ha Tran
Niebling John F.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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