Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1998-12-22
2002-11-19
Dang, Thi (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S718000, C438S719000, C438S737000, C438S742000
Reexamination Certificate
active
06482747
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma treatment for performing etching or the like on a substrate to be treated; and, more particularly, invention relates to a plasma treatment method and plasma treatment apparatus in which the treatment characteristics in the central part of the substrate and those in the peripheral part of the substrate to be treated are uniformized.
2. Related Background Art
Various methods have been devised for conventional plasma treatment apparatuses in order to uniformize the plasma density (ion current value) and ion energy (RF bias voltage) in the plane of a substrate (wafer) and to uniformize the substrate temperature. For example, the publication of Japanese unexamined patent No. 7-18438 discloses a technique for uniformizing the temperature distribution in the substrate by forming roughness on the surface of an insulating material on a substrate supporting face of a flat electrode, changing the density or depth of the rough surface of the insulating material, and distributing the electrostatic adsorption.
As the substrate size increases and the etching size becomes finer, however, the influence of the distribution of etching reaction products in the central part and those in the peripheral part of a substrate becomes tangible.
FIG. 15
is a diagram for explaining the behavior of etching reaction products. As shown in the diagram, etching reaction products such as Al, Cl, C, and the like react with a plasma etching gas (ions and radicals) on a substrate (wafer)
2
to be treated, evaporate in a vapor phase, and become Al
2
Cl
6
or the like. The reaction products show complicated behavior such that they are directed again at the substrate
2
to be treated or they are dissociated again in the plasma and the dissociated species are directed at the substrate
2
. That is, etched Al on the bottom of the substrate is released as reaction products into a vapor phase and a part of them is dissociated again in the plasma and is again directed at the substrate
2
. A photo resist
25
is likewise etched so that the substrate is again irradiated with the reaction products of the resist. Electrically neutral species among the species dissociated from the reaction products in the plasma are directed also at the side walls of an area to be etched and are deposited. Such species, species which are obtained by etching the bottom face and directly deposited on the side walls, species directed at the side walls sputtered by the incident ions including physical or chemical elements, and the like are deposited, thereby forming a side wall protection layer
26
.
Among them, with respect to the re-irradiation of the reaction products, non-uniformity of an irradiation amount in the plane of the substrate tends to occur by the following reason. The reaction products obtained by etching and released into a vapor phase are exhausted as a gas from the etching chamber. The outer the position of the substrate is, the more the reaction products are exhausted efficiently. As shown in
FIG. 16
, therefore, in the density distribution of the reaction products in the vapor phase, that is, the re-irradiation amount distribution of the reaction products, inevitably, the density or the re-irradiation amount is high in the central part of the substrate and is low in a peripheral part.
As mentioned above, in a peripheral part of the substrate, the amount of the reaction products is smaller than that in the central part of the substrate since they are exhausted together with an etching gas. In case of metal etching, if the side wall protection layer is thick, the etch rate on the side walls by the ion assisted reaction becomes low. Because of this, when describing a process for a trench as an example, the shape of a part to be etched becomes a so-called tapered shape in which the width is reduced as the etch depth increases. On the contrary, when the side wall protection layer is too thin, the side walls are etched and the part to be etched becomes wider than a target width. Consequently, in order to obtain a vertical shape as an etched part, the amount of deposition of the side wall protection layer has to be optimized so as to obtain a proper thickness and prevent the side walls from becoming fat or thin.
On the other hand, with reduction in the etching size, the need for the processing accuracy of dimensions increases. For example, when about {fraction (1/10)} of a design dimension is a permissible level, the permissible level is ±0.05 &mgr;m for the design dimension of 0.5 &mgr;m. With reduction in the dimension to 0.25 &mgr;m and 0.13 &mgr;m, the permissible levels become ±0.025 &mgr;m and ±0.013 &mgr;m, respectively. In order to achieve such a required specification, factors exerting an influence on the processing dimension have to be made clear and controlled.
With the reduction in the etching size, also in dense and sparse patterns in which fine patterns and sparse patterns which are not so dense mixedly exist, the need for the processing accuracy of dimensions has been increasing.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide plasma treatment method and apparatus in which an influence on treatment characteristics of reaction products in a plasma treatment such as etching is offset and uniform treatment characteristics can be obtained in the plane of a substrate.
It is another object of the present invention to provide plasma treatment method and apparatus which improves the uniformity in the substrate plane of a shape to be processed in consideration of influences of reaction products at the time of plasma treatment such as etching.
It is further another object of the present invention to provide a plasma treatment method and a plasma treatment apparatus which can obtain an etching treatment characteristic such that there is no variation in processing dimension in dense and sparse patterns.
According to a feature of the invention, in a plasma treatment method of performing etch treatment to a substrate to be processed by using a gas plasma via a mask in a treatment chamber, plasma treatment is performed while maintaining the in-plane uniformity of a side wall protection layer formed on the side walls of a part to be etched in the substrate.
According to another feature of the invention, in a plasma treatment method of treating a substrate to be processed by using a gas plasma via a mask in a treatment chamber, plasma treatment is performed while equalizing an amount of deposition of a side wall protection layer formed on the substrate to be processed in the center of the substrate and that in an end part of the substrate, and maintaining the in-plane uniformity of the side wall protection layer.
According to further another feature of the invention, in a plasma treatment method of treating a substrate to be processed with a gas plasma by using a resist as a mask in a treatment chamber, plasma treatment is performed to the substrate while maintaining the uniformity of a deposition amount of reaction products which are generated by a reaction between the substrate to be processed and the plasma and are directed at and deposited on the substrate in the plane of the substrate to be processed, thereby forming a side wall protection layer having a uniform plane on the substrate.
According to another feature of the invention, in a plasma treatment method of performing plasma treatment to a substrate to be processed with a gas plasma by using a resist as a mask in a treatment chamber, the plasma treatment is performed while maintaining the in-plane uniformity of a side wall protection layer formed on the substrate by controlling the temperature of the substrate.
It is another feature of the invention that the plasma treatment is performed to the substrate to be processed while adjusting the pressure, flow rate, and mixing ratio of a process gas in the treatment chamber.
It is another feature of the invention that the plasma treatment is performed to the substrate to be processed
Ishizu Takazumi
Kanai Saburo
Satou Yoshiaki
Takahashi Kazue
Antonelli Terry Stout & Kraus LLP
Dang Thi
Hitachi , Ltd.
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