JPS61189644A - Dry etching method - Google Patents

Abstract

PURPOSE:To enable the etching of an ultrathin film of monomolecular, mono- atomic or several-molecular several-atomic layer from the substrate surface, by a method wherein the etching gas is introduced after exhaust of a reaction chamber provided with a substrate to be etched; the introduced etching gas is exhausted after adsorption to the substrate, and then the substrate surface to be etched is irradiated with photo energy. CONSTITUTION:After installation of a substrate 5 to be etched in a reaction chamber 4, the whole system is evacuated by means of an exhaust device 7. Next, the etching gas is guided from an etching gas source 1 into the reaction chamber 4 by opening a valve 2, thus depositing the etching gas to the surface of this substrate 5. Thereafter, the etching gas remaining in the reaction chamber 4 is exhausted, and the surface of the substrate 5 is irradiated with the light from a light source 8 through a lens 9 and a light introduction window 10; thus, etching reaction is induced by activating the adsorbed etching gas. When the etching gas adsorbed to the substrate 5 is consumed by reaction, etching reaction does not advance, even when the substrate 5 is irradiated with the light of the light source 8, because of no more presence of etching gas in the reaction chamber 4.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a dry etching method suitable for etching a monomolecular layer, a monoatomic layer, or several molecular layers or several atomic layers from the surface of a substrate to be etched. It is about the method.

[Background of the invention]

As LSI manufacturing processes continue to become smaller and smaller, methods that utilize photo-induced chemical reactions are attracting attention as a new etching technology. The main reason for the high expectations for the photo-induced process is that in addition to realizing a low-temperature process and reducing damage to the substrate to be etched, it is also possible to etch only the light-irradiated area (i.e., improve the spatial selectivity of the reaction). The content of this kind of photo-assisted etching can be found in, for example, Sem1cond.
u (torWorld, 1984, p. 11+103). However, at present, there are many unknowns about the reaction process that progresses on solid surfaces when irradiated with light, and various surface measurement techniques are being used to For example, in the article mentioned above, the surface reaction process that occurs when the surface of silicon adsorbed with sulfur hexafluoride (SF6) is irradiated with a carbon dioxide laser is explained using photoelectrons. We estimate this based on spectroscopic data and consider the relationship with the etching mechanism of the substrate surface.

In the above-mentioned known example, it has been revealed that the substrate surface is etched by photoactivation of adsorbed molecules and atoms.

Looking at this phenomenon from another perspective, it is predicted that the etching reaction will stop when the adsorbed etching gas is exhausted. This means that by controlling the amount of etching gas adsorbed onto the solid surface and irradiating the substrate surface with light while removing etching gases other than the adsorbed gas from the system, the depth of etching can be controlled at the molecular or atomic level. This suggests that it can be precisely controlled.

[Purpose of the invention]

The object of the present invention is to obtain a method of etching an ultra-thin film that is controlled at the molecular/atomic level by utilizing a photo-induced reaction, and also to obtain a low-temperature process technology in which the ultra-thin film is advanced by light irradiation.

[Summary of the invention]

In order to achieve the above object, the dry etching method according to the present invention includes the steps of evacuating a reaction chamber in which a substrate to be etched is provided, a step of introducing an etching gas into the reaction chamber, and a step of using the introduced etching gas to etch the substrate. The method includes a step of adsorbing the etched substrate and then evacuation, and a step of irradiating the surface of the substrate to be etched with light energy.

[Embodiments of the invention]

Next, embodiments of the present invention will be explained with reference to drawings. Fig. 1 is a block diagram showing a first embodiment of the dry etching method according to the present invention, Fig. 2 is a block diagram showing a second embodiment of the present invention, and Fig. 3 is a block diagram showing a first embodiment of the dry etching method according to the present invention. The figure is a partial diagram showing the configuration of a third embodiment of the invention, FIG. 4 is a partial diagram showing the configuration of a fourth embodiment of the invention, and FIG. 5 is a partial diagram showing the main part of a fifth embodiment of the invention. In the explanatory diagrams, (a) is a partial explanatory diagram of the configuration, and (b) is a diagram showing interference fringes. In FIG. 1, the etching gas source 1 is an inlet pipe 3 with a valve 2.
The reaction chamber 4 is connected to a reaction chamber 4 through which a substrate 5 to be etched is installed, and an exhaust device 7 is connected to the reaction chamber 4 through an exhaust pipe 6.
It is connected to the. Further, the light emitted from the light source 8 passes through a lens 9 and is irradiated onto the substrate 5 to be etched through a light introducing window 10 provided in the reaction chamber 4.

A process for etching the ultra-thin film layer of the substrate 5 to be etched using the dry etching apparatus having the above configuration will be described below. After the substrate 5 to be etched is placed in the reaction chamber 4, the entire system is evacuated by the exhaust device 7. Next, the valve 2 is opened, and the etching gas is introduced from the etching gas source 1 into the reaction chamber 4, and the etching gas is deposited on the surface of the substrate 5 to be etched. After that, the enching gas remaining in the reaction chamber 4 is exhausted, and the light from the light source 8 is passed through the lens 9.
Then, the surface of the substrate 5 to be etched is irradiated through the light introduction window IO to activate the adsorbed etching gas and induce an etching reaction. Reaction products evaporated from the surface of the substrate 5 to be etched during the etching process are exhausted to the outside of the system by an exhaust device 7. When the etching gas adsorbed on the substrate 5 to be etched is consumed in the reaction, the reaction chamber 4
Since there is no etching gas inside, the etching reaction does not proceed even if the substrate 5 to be etched is irradiated with light from the light source 8. As a result, through the above-described process, an ultra-thin film on the level of a single molecule/single atom or several molecules/several atoms can be removed by etching from the surface of the substrate 50 to be etched. In order to remove a desired film thickness by etching, a series of operations from the process of evacuation of the reaction chamber 4 to the process of irradiating the substrate 5 to be etched with light may be repeated. As the etching gas used in this example, a gas containing halogen is effective. For example, when etching a silicon substrate, the etching gas is sulfur hexafluoride fa (SF
If a) is used, a carbon dioxide laser that emits light of 942.4 cTL' may be used as the light source. In addition, when etching the silicon substrate with chlorine gas (Ct2),
A high-pressure mercury lamp or XeC1 excimer laser that emits light with a wavelength of around 30 nm, which matches the absorption band of chlorine gas, is effective.If the surface of the substrate to be etched 5 is scanned with a narrowly focused laser beam, The etching gas bubble adsorbed to the irradiated area is activated, and etching progresses in that area, making it possible to etch the desired pattern.The same effect can be obtained by fixing the laser beam and moving the substrate to be etched. This can also be achieved by using a mechanism that allows

A second embodiment of the present invention, shown in FIG. 2, has the same structure as the first embodiment, in which light from a light source 8 is irradiated through a mask 11 placed on the surface of a substrate 5 to be etched, and a desired amount of light is emitted. This is an effective method for drawing etched batons. In this embodiment as well, the same process as described in the -2 first embodiment may be followed. That is, the mask 11
After the substrate 5 to be etched facing the substrate 5 is placed in the reaction chamber 4, the entire system is evacuated by the exhaust device 7. Next, the etching gas is introduced into the reaction chamber 4 from the etching gas source 1,
It is attached to the surface of the substrate 5 to be etched through the gap between the mask 11 and the substrate 5 to be etched. Thereafter, the etching gas remaining in the reaction chamber 4 is exhausted, and the substrate 5 to be etched is irradiated with light from the light source 8 through the mask 11 to induce an etching reaction by the etching gas adsorbed on the substrate 5 to be etched. let As a result of etching, reaction products evaporated from the surface of the substrate 5 to be etched are exhausted from the reaction chamber 4 to the outside of the system by an exhaust device 7.

The reaction stops when the etching gas adsorbed on the surface of the substrate 5 to be etched is consumed, so through the above process, no monomolecules, monoatomic layers, or monolayers are removed from the surface of the substrate 5 to be etched.
Ultra-thin films of several molecules or atoms can be removed by etching. In the second embodiment, since the surface of the substrate 5 to be etched is irradiated with light through the mask 11, etching proceeds selectively at the portions irradiated with the light. Therefore, by preparing a mask on which a desired pattern is drawn, so-called resistless etching becomes possible.

In addition, in the case of performing etching to a desired depth in the second embodiment, the process from the step of exhausting the reaction chamber 4 to the step of irradiating the substrate 5 to be etched with light is repeated in the same manner as in the first embodiment. Bayoshi.

A third embodiment shown in FIG. 3 shows an apparatus configuration used to draw a desired etching pattern by a reduction projection exposure method. The light from the exposure light source 8 passes through the mask 12 and enters the reduction lens 13, and the light exiting the reduction lens 13 irradiates the substrate 5 in the reaction chamber 4, so that the pattern drawn on the mask I2 can be transformed into a desired pattern. The pattern reduced in size is projected onto the substrate 5 and exposed. When performing an etching operation using this embodiment, the process shown in the first embodiment may be followed. Although FIG. 3 shows, as an example, only the substrate 5 installed in the reaction chamber, the configuration of this embodiment is not limited to the above example. Note that an etching gas supply device and an exhaust device are provided for semi-heating, but are omitted from the drawing.

In the fourth embodiment shown in FIG. 4, a desired pattern is drawn on a substrate by scanning a laser beam using an optical fiber and a photocoupler. Note that FIG. 4 shows an example of the configuration, in which the substrate to be etched 5
Other components may also be installed within the reaction chamber 4.

Note that the etching gas supply device and exhaust device are omitted.

The laser beam transmitted by the optical fiber cable 14 irradiates the substrate 5 to be etched with a laser beam I6 from the tip of a photocoupler 15 incorporating a microlens or the like. The photocoupler 15 supported by the fixture 17 moves to draw a desired pattern under the action of the control unit 18 and irradiates the substrate 5 to be etched. A series of process steps including exhausting the reaction chamber, introducing etching gas and adsorbing it onto the surface of the substrate to be etched, exhausting the etching gas remaining in the reaction chamber, and irradiating the substrate with laser light. can be handled in the same way as in each of the above embodiments.

The fifth embodiment shown in FIG. 5 is used to draw fine striped etching patterns on the substrate to be etched by making two laser beams interfere and using the interference fringes to remove insects. It is. In FIG. 5), only the main parts are shown and the etching gas supply device, exhaust device, etc. are omitted.

The laser beam emitted from the laser light source 19 is divided by a nof mirror 21 into laser beams ρ and ρ. The laser beam n is reflected by each mirror 5.26 to become a laser beam n, and the laser beam n is reflected by a mirror 4 and a grave to become a laser beam 30. These two laser beams n and 30 interfere with each other to form interference fringes 31 on the substrate 5 to be etched as shown in FIG. 5(b). Bright part 3 of the interference fringes 31 above
In step 2, the etching gas adsorbed on the substrate 5 to be etched is activated, and the etching reaction of the substrate to be etched progresses in this area.

In the third embodiment shown in FIG. 3 above, the mask 12 is placed parallel to the substrate to be etched 5, but it can be placed at a desired position by providing a mechanism for reflecting it through a mirror or the like. can.

〔Effect of the invention〕

As described above, the dry etching method according to the present invention includes the steps of evacuating a reaction chamber in which a substrate to be etched is provided, introducing an etching gas into the reaction chamber, and evacuating the etching gas after adsorbing it to the substrate. By irradiating the surface of the substrate to be etched with light energy, the etching gas adsorbed on the surface of the substrate to be etched is activated, and a single molecule, monoatomic layer, or several monolayers are removed from the surface of the substrate. Ultra-thin film etching of molecular or several atomic layers is possible, and since the etching of the ultra-thin film is carried out using a photo-induced reaction, it is effective in lowering the process temperature.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the dry etching method according to the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIG. 3 is a block diagram showing the structure of a third embodiment of the present invention. FIG. 4 is a partial diagram showing the configuration of the fourth embodiment of the present invention, FIG. 5 is an explanatory diagram showing the main part of the fifth embodiment, ←) is a partial diagram showing the configuration, ) is a diagram showing interference fringes. DESCRIPTION OF SYMBOLS 1...Etching gas source, 4...Reaction chamber, 5...Substrate to be etched, 7...Exhaust device, 8...Light source, 10
...Light introduction window. Figure 1 8:'L 滉10: Light guide 29311 No. 2, Title of the invention Dry etching method 3, Relationship with the amended case Patent applicant name (510) Hitachi, Ltd. 4, Agent

Claims (8)

[Claims] (1) A step of evacuating a reaction chamber provided with a substrate to be etched, a step of introducing an etching gas into the reaction chamber, a step of adsorbing the introduced etching gas to the substrate and then evacuating it, and a step of evacuating the surface of the substrate to be etched. A dry etching method comprising the step of irradiating light energy to. (2) Etching to a desired depth is performed by repeating a process in which one cycle includes the step of evacuation of the reaction chamber to the step of irradiating light energy. Dry etching method described. (3) The dry etching method according to claim 1 or 2, wherein the etching gas is a gas containing a halogen element. (4) The dry etching method according to any one of claims 1 to 3, wherein the light energy is light energy that has passed through a desired pattern drawn on a mask. (5) The dry etching method according to any one of claims 1 to 3, wherein the light energy is light energy produced by a reduction projection exposure system. (6) The dry etching method according to any one of claims 1 to 4, wherein the light energy is light energy from a laser light source. (7) Claims 1 to 3, characterized in that the light energy is light energy irradiated by a photocoupler guided from a laser light source through an optical fiber.
The dry etching method described in either item or item 6. (8) The above-mentioned light energy is light energy obtained by dividing a laser beam emitted from a laser light source and by interference fringes formed by each of the divided laser beams. The dry etching method described in any one of Items 3 to 6.