JPS6154631A - Etching process - Google Patents

Abstract

PURPOSE:To perform simply a dry etching by a method wherein a reactive substance is made to adhere on a material to be etched, an energy beam is irradiated on the material to make to promote a reaction and the substance of an unreacted component is removed from the material. CONSTITUTION:When the interior of a chamber 11 is exhausted to a vacuum, liquid nitrogen is injected in the tank 16 of a holder 15 and reaction gas is introduced 13 in the chamber 11, the gas is attracted on the surface of a material 17 on the holder 15 and a thin layer 21 is formed. After a constant amount of the reactive gas layer is formed, a feed of the gas is stopped. When an electron beam (e) is radiated from an electron gun 18 and the prescribed parts of the material 17 are irradiated, the gas being attracted at the irradiation regions is activated by the engergy of the beam and the irradiation regions react with the material 17. Generated gas is exhausted from a tube 12. After an etching is performed on the material in the prescribed depth, infrared rays are projected on the material 17 from a lamp 22 to remove the gas layer 21 attracted and the etching is completed. Incidentally, charged particles rays, such as an ion beam, or radioactive rays, such as a laser beam and X-rays, can be used instead of the electron beam and the reactive substance, which is made to adhere on the material 17, can be a thin film including reaction species.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel method for etching desired patterns onto processing materials such as semiconductor wafers.

[Prior Art] Etching is an indispensable technique for manufacturing integrated circuits such as LSIs, and various methods have been proposed and put into practice. Conventional etching can be broadly classified into wet etching using water and gas etching or dry etching, and today the latter, or dry etching, is the mainstream. Specific examples include plasma etching and reactive etching, but in these etchings, a reactive gas is selected according to the material to be etched, and this gas is ionized by electric discharge to generate reactive ions. Etching is performed through a chemical reaction between ions and the material.

FIG. 2 is a diagram schematically showing a conventional apparatus for performing reactive ion etching, in which a chamber 1 forms an anode. A material holder 2 serving as a cathode is fixed in this chamber via an insulator 3, and a material 4 such as a semiconductor wafer is held on top of the material holder 2. Above holder 2
is actually water-cooled to prevent the material 4 from being heated. This holder is supplied with high-frequency power from a high-frequency oscillator 6 via a matting box 5, and a high-frequency discharge is generated between the holder and the material 4 and the chamber 1, resulting in an area indicated by a dotted line in the figure. This becomes a plasma region, and ions are generated in this region. A shield electrode 7 prevents plasma from being generated in unnecessary parts such as the lower part of the holder. A gas introduction pipe 8 is connected to a gas cylinder (not shown) filled with a desired reactive gas, and its flow rate can be controlled by a valve 9. Reference numeral 10 denotes an exhaust pipe, which is connected to a suitable vacuum pump to exhaust internal gas.

In such an apparatus, a material 4 to be etched is placed in a chamber 1, and the chamber is evacuated by a vacuum pump with a reactive gas valve closed. Next, the valve 9 is opened and a reactive gas is introduced into the chamber 1. When the gas pressure reaches a predetermined value (for example, 1 to 10 Torr), a high frequency from a high frequency oscillator is supplied to the material holder 2, and a reactive gas is introduced into the chamber. Plasma is generated, the reactive gas is ionized, and the gas collides with the material 4 to cause a chemical reaction with the material, thereby progressing etching.

[Problems to be solved by the invention] Although this type of etching has the advantage of being simple because it does not use water, it is necessary to cover the areas that are not to be etched with a resist, as shown in Figure 3. As shown, there are many steps involved.

FIG. 3(a) shows a process of coating a photoresist 4h on a semiconductor wafer 4a, and after coating this resist, pattern exposure is performed, that is, light is irradiated to the area to be etched (or vice versa) ((b) )figure). This pattern-exposed material is developed to obtain a material partially covered with resist as shown in Figure (C), and this is inserted into the chamber of the reactive ion etching apparatus described in Figure 2. Then, a predetermined etching process is performed by applying an ion shower (Figure (d)). When etching is completed, the material is taken out from the chamber and the resist formed thereon is stripped off (step (e)).

SUMMARY OF THE INVENTION The present invention aims to eliminate the drawbacks of the conventional methods described above, and provides a method that allows dry etching to be performed with fewer manufacturing steps.

[Means for Solving the Problems] In order to achieve the above object, the present invention involves depositing a reactive substance on a material to be etched and activating the reactive substance in a desired area on the surface of the reactive substance. This etching method is characterized by irradiating an energy beam that promotes a chemical reaction with a material, and removing the reactive substance from the material when etching of the material due to a predetermined reaction is completed.

[Function] In the present invention, the material placed in the chamber is cooled to a low temperature by a refrigerant such as liquid nitrogen, and reactive gas is adsorbed on its surface. Then, when an energy beam such as an electron beam is irradiated onto the area to be etched, the energy of the beam activates the adsorbed reactive gas, causing the material to undergo a chemical reaction with the reactive gas, and that area is etched. .

[Example] FIG. 1 shows an example of an apparatus for carrying out the method of the present invention, in which 11 is a chamber, the inside of which can be evacuated to a vacuum via an exhaust pipe 12. A reactive gas introduction pipe 13 is connected to a desired gas tank, and a predetermined gas can be introduced through a valve 14 at a predetermined flow rate. A material holder 15 has a refrigerant storage tank 16 formed therein, into which a refrigerant such as liquid nitrogen is injected from the outside. Thereby, the etching material 17 held on the holder is cooled to an extremely low temperature. An electron gun 18 is installed above the chamber to face the material holder 15, and the electron beam emitted from the electron gun is focused to a predetermined diameter by one focusing lens, and then irradiated onto the material 17. Ru. The irradiation position of the electron beam on this material is changed by an electron beam deflector 20.

Using such a device, first the material 17 is held in the holder 15 inside the chamber 11, and then the material 17 is held in the holder 15 inside the chamber 11.
Evacuate the inside to vacuum. In this state, liquid nitrogen is injected from the outside into the refrigerant storage tank 16 of the boulder 15, and at the same time, a predetermined reactive gas is introduced from the tank via the pipe 13.

Since the materials 131 and 17 are cooled to an extremely low temperature, this gas is adsorbed onto the surfaces of the materials and forms a thin layer 21 as shown in FIG. 4(a). After a certain amount of reactive gas layer is formed, the supply of the gas is stopped, and an electron beam is emitted from the electron gun 18 to irradiate a predetermined material portion with the electron beam (FIG. 4(b)). . In the region irradiated with the electron beam, the adsorbed reactive gas is activated by the energy thereof, and a chemical reaction occurs with the underlying material 17. The gas generated by this reaction is exhausted to the outside through the exhaust pipe 12. When etching to a predetermined depth is achieved in this way, infrared rays are irradiated onto the material 17 from, for example, an infrared lamp 22 installed in the chamber to remove the reactive gas layer 21 adsorbed on the material. Figure 4 (C)〉, etching is completed.

[Effects] As described above, in the present invention, a reactive gas is adsorbed onto the surface of a material to be etched, such as a semiconductor wafer, and an electron beam is irradiated from above to perform local etching. As is clear from the comparison between FIG. 3 and FIG. 4, the number of steps can be reduced compared to the conventional method, and this method is extremely useful in practice.

Note that the above is an example of the present invention, and various changes can be made in implementation. For example, the energy beam irradiated onto the adsorbed gas is not limited to an electron beam, but may be an appropriate ion beam or radiation such as a laser beam or X-ray. Moreover, although the reactive gas is adsorbed onto the material using cooling in the above example, the reactive species may be thinly deposited using a vapor deposition apparatus, sputtering, or the like. Furthermore, although a lamp was used above to remove the reactive gas layer, it is also possible to heat the material by wrapping a heater around the material holder or burying it and energizing the heater at the end of the etching process. It may be configured to warm the body.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention, FIG. 2 is a diagram showing an example of a conventional reactive ion etching apparatus, and FIG. 3 is a diagram of a conventional etching carried out using the apparatus shown in FIG. FIG. 4 is a diagram showing the steps of the method of the present invention. 11: Chamber 12 = Exhaust pipe 13: Gas introduction pipe 14: Valve 15: Material holder 16 = Refrigerant storage tank Q-

Claims (1)

[Claims] 1) depositing a reactive substance on the material to be etched;
An energy beam that activates the reactive substance and promotes a chemical reaction with the material is irradiated onto a desired area on the surface of the reactive substance, and after the etching of the material by a predetermined reaction is completed, the reactive substance is removed from the material. An etching method characterized by: 2) The etching method according to claim 1, wherein the reactive substance is formed by cooling a material and adsorbing a reactive gas thereon. 3) The etching method according to claim 1, wherein the reactive substance is formed as a thin film containing a reactive species. 4) The etching method according to claims 1 to 3, wherein the energy beam is a charged particle beam such as electrons or ions. 5) The etching method according to any one of claims 1 to 3, wherein the energy beam is a radiation such as a laser beam or an X-ray.