JPS6224627A - Dry etching method - Google Patents

Abstract

PURPOSE:To reduce undercut with a simplified method by providing a material part which controls amount of fluorine radical within the etching reaction chamber. CONSTITUTION:A cathode material 2 which forms a cathode 1 is formed by a hydrogen carbide system resin and a base material Si wafer which forms a material 3 to be etched is coated with a resist. For example, an etching stop layer 32 is formed of SiO2 and SiN layer on a base material Si 31, the resist is patterned on the etching stop layer 32 and a sample to be etched is formed by eliminating the etching stop layer 32 by etching with the resist used as the mask. When this material 3 to be etched is etched by REI using the F base gas, an extra F radical may be seized by the cathode material 2 and resist material 33. Thereby over etching can be prevented and etching with high controllability for shape can be realized. Accordingly, the shape of etching of material to be etched can be controlled with a simplified means and generation of undercut may also be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry etching method. In particular, the present invention relates to a dry etching method in which etching is performed using an etching gas containing at least fluorine as a constituent element. The present invention can be used, for example, for manufacturing semiconductors.

[Summary of the invention]

The present invention makes it possible to control the shape of the material to be etched by adjusting the amount of fluorine radicals by providing a material portion for controlling the amount of fluorine radicals in the etching reaction chamber.

[Conventional technology]

As semiconductor devices, especially integrated circuits, become smaller,
Dry etching, particularly reactive ion etching, which allows anisotropic processing, has come to be widely used. Recently, reactive ion etching has been used to process the substrate Sj (silicon) for element isolation and formation of capacitors (groove type).

Such reactive ion etching, for example for etching Si, usually uses F (fluorine)-based gases or CI (chlorine)-based gases.

(There are also examples where gases containing F and 01 are used.)
However, when comparing the reactivity of St, F, St and C1, according to calculations by 3eel et al., they are leV and 15eV, respectively.
There is a difference.

For example, FIGS. 5(a) and 5(b) schematically show the etching rates E and I when using an F-based gas such as Xepz and a C1-based gas such as Xeclt, respectively. For example, as shown in Figure (a), etching progresses even when Ar ions are off, and the rate increases even more when Ar ions are on, but in the case of C1 gas, when Ar ions are on, as shown in Figure (b), etching progresses. This appears as a phenomenon in which a certain degree of etching speed is obtained. Therefore, if F-based gas is used, Si can be etched without requiring a large ion assist effect. On the other hand, however, F-based gas tends to cause undercuts as a result of its high reactivity. On the other hand, if a C1-based gas is used, anisotropic processing is easy because it requires a large ion assist effect, but since a Cl-based gas is corrosive, it poses various problems in equipment maintenance and other aspects. There is. Therefore, at a production site where etching is actually performed, F-based gas is more convenient to use if shape control is possible.

[Problem that the invention seeks to solve]

As mentioned above, when F-based etching gas is used in the conventional dry etching method, although it is easy to use, there are problems in that it is difficult to control the shape, such as undercuts.

The present invention attempts to solve two problems, and its purpose is to reduce undercuts by a simple method even when dry etching is performed using an etching gas containing gas containing at least fluorine as a constituent element. Gain,
Therefore, the object is to provide a method that allows shape control.

[Failure to solve the problem]

The above problem can be solved by a dry etching method in which etching is performed using an etching gas containing a gas containing at least fluorine as a constituent element. , resolved.

As the material for controlling the amount of fluorine radicals, materials that capture fluorine radicals can be used, such as C, H
Organic materials containing 2O as a main constituent element can be used, and examples of such materials include phenolic resins such as novolac resins, hydrocarbon resins, and others. Further, a resist such as a positive resist can also be used as the material for controlling the amount of fluorine radicals. As for the location where such a material portion is provided, the cathode material may be made of this material, or a dummy wafer may be provided and the above-mentioned material portion such as a resist may be provided on this wafer. By changing the amount of this material, for example, the coating area, the controllability of the amount of fluorine radicals can be controlled, and thereby the shape of the material to be etched can be controlled.

The gas containing fluorine as a constituent element is appropriately selected depending on the material to be etched, and examples thereof include nitrogen fluoride such as NFI, CF, various fluorinated hydrocarbon gases, and XeF.
etc., and CO□ and Ar may be added to these as appropriate.

[For production]

As described above, in the dry etching method of the present invention, a material portion for controlling the amount of fluorine radicals is provided in the etching reaction chamber, so that the amount of fluorine radicals is controlled by the material. When a fluorine-based gas is used in etching, the gas that exhibits isotropic action is considered to be F radicals, but the amount of F radicals generated under certain etching conditions is determined by the discharge conditions. If a material portion for controlling the amount of fluorine radicals is provided in the etching reaction chamber, the etching characteristics can be controlled by controlling the amount of radicals. Therefore, the etching shape can be easily controlled. As described above, according to the present invention, the amount of F radicals can be controlled to be small compared to the area to be etched, regardless of the type of device, and the isotropic effect can be significantly reduced. This makes it possible to control the etching shape. Unfavorable shapes such as undercuts can also be avoided.

Therefore, the present invention can be suitably used for etching various materials, and particularly for manufacturing integrated circuit devices, which will become increasingly finer in the future.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In this example, the present invention is applied to etching an St-based material. FIG. 1 shows the apparatus of this embodiment, which is an example of an etching apparatus embodying the etching method of the present invention.

In this example, the cathode material 2 constituting the cathode 1 is reversed. This hydrocarbon resin and resist constitute materials that control the amount of F radicals. Specifically, in this example, as shown in FIG.
An etching stop layer 32 is formed of (silicon nitride layer) or the like, a resist is patterned on the etching stop layer 32, and the etching stop Ji 32 is etched away using this as a mask to form a sample to be etched. 33 in FIG. 2 indicates a resist material. Further, in FIG. 1, 4 indicates an anode, and 5 indicates an etching reaction chamber.

When this material to be etched 3 (sample) is etched by RIE using F base gas, excess F radicals are captured by the cathode material 2 and resist material 33, resulting in etching with good shape controllability that prevents overetching. It will be done. Therefore, an etching shape 35 with good pattern controllability without such an overetched part as shown in FIG. 3(b) has been replaced with the conventional shape shown in FIG. can get. This is because the cathode material 2 and resist material 33 are etched by ion bombardment due to the voltage drop of the self-bias, and H etc. are released, which removes F radicals in the form of H+F''-HF. This is thought to reduce the isotropic effect and enable anisotropic processing of Si.When the resist is gone, the effect of F radical uptake is reduced, so the remaining amount of resist can be actively determined using optical interferometry, etc. It's for a reason.

The above embodiment is an example in which all areas other than the Si etching area are covered with an organic material, but in addition to the wafer which is the material to be etched 3 as shown in FIG. 4, the amount of F radicals in resist etc. is controlled. It is also possible to adopt a configuration in which a dummy wafer 6 containing a material to be etched is placed on the etching table.

For example, a dummy wafer with full-surface resist can be used. Further, the etching shape can be controlled by intentionally changing the area covered with the organic material on the cathode material 2 or the dummy wafer 6 as described above.

In addition, by changing the coverage ratio of the cathode material 2, it is possible to support a single-wafer type, and by changing that of the dummy wafer 6 in addition to the cathode material, it is also possible to support a multi-wafer type (batch type) 'AN. .

By using the above embodiment, surplus F radicals can be recombined and taken in by H sputtered out from the cathode material 2 and mask material (resist material) 33, and the ratio can be adjusted to Since the area covered by the organic material (resist material 33, etc.) can be controlled by changing it, the etched shape of the material 3 to be etched can be controlled to a desired shape. Note that the present invention is of course not limited to the above embodiments, and it is also possible to use only one of the cathode material and the resist material (or, for example, in addition to the Si substrate, PolySi
or other Si-based materials may be used as the material to be etched, or other appropriate materials may be used as the material to be etched, and materials for controlling the amount of F radicals may include other organic materials and other materials exhibiting the effect of the present invention. You can take whatever you can get.

[Effects of the Invention] As described above, the dry etching method of the present invention can control the etched shape of the material to be etched by a simple means, and can also suppress the formation of undercuts. Since a fluorine-based gas is used, maintenance of the equipment is easier than in the case of a Cl-based gas.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG. 2 is a sectional view of a material to be etched used in the same embodiment. FIG. 3 is a diagram showing a comparison of etching shapes between the same example and a conventional example. FIG. 4 is a schematic illustration of another embodiment of the invention. Fifth
The figure shows a comparison of etching characteristics depending on the gas used. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Fluorine radical control material (cathode material), 3... Etched material, 33...
Fluorine radical control material (resist material), 4... Anode, 5... Etching reaction chamber, 6... Dummy wafer. Fig. 2 (.) (b) ft2 shape' * I41Ffi's ratio Fig. 3

Claims (1)

[Claims] 1. A method for etching using an etching gas containing a gas having at least fluorine as a constituent element, characterized in that a material portion for controlling the amount of fluorine radicals is provided in an etching reaction chamber. Etching method.