JPS60260131A - Anisotropic dry-etching - Google Patents

Abstract

PURPOSE:To effectively form ultra-miniaturized pattern having less plasma damages by utilizing the competitive reaction between the deposition by radical which has been excited by microwave and has expanded its service life and the etching by the radical excited with laser beam irradiating perpendicularly the area to be etched on the semiconductor. CONSTITUTION:Plasma and electrically neutralized radical are generated by supplying the Si(CH3)4 gas from an aperture of supply tube 6 and simultaneously utilizing the microwave (2.45GHz) to the external circumference of plasma generating chamber 7 from the microwave guide 8. The plasma excited by this microwave has comparatively long life and the radical assures long service life and is supplied, in parallel to the wafer 3, to the reaction chamber 1 made of quartz to which semiconductor wafer 3 is loaded through the transfer tube 5. Moreover, the Cl2 gas is supplied to the chamber 1 through another gas line. The etching surface of wafer 3 is irradiated perpendicularly with the laser beam (XeCl: wavelength of 308nm) from the outside of the chamber 1.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to an anisotropic dry etching method suitable for VLSI manufacturing processes, and in particular an anisotropic dry etching method that can efficiently etch ultra-fine patterns in the submicron region. Regarding.

(Background technology and its problems) Currently, to form fine patterns with a line width of 2μ or less required in the VLSI process, anisotropic etching is performed using reactive ions accelerated by an electric field in plasma. This etching is performed using RIE' (Reacti).
It is called on-l-on-eating). However, the surface of the silicon semiconductor substrate is severely damaged by the impact of reactive ions accelerated by this electric field. Furthermore, destruction of the gate oxide film, which is thought to be caused by charging of reactive ions, has been reported, and more recently, damage to the surface of a silicon substrate in plasma that is not accelerated by an electric field has also been reported.

For this reason, etching with radicals excited by ultraviolet rays has been proposed as one method for realizing etching that does not cause plasma damage. However, it is not possible to perform anisotropic etching by simply generating radicals through ultraviolet irradiation. To achieve anisotropic etching, an electric field perpendicular to the surface to be etched is applied to drive the reactive ions vertically. However, in this method, the wafer surface is damaged by the impact of the reactive ions.

As an anisotropic etching device using this optical excitation, the one shown in FIG. 2 has been proposed. In the figure, a wafer 3 as an object to be etched placed on a support stand 2 is loaded in a quartz container 1. As shown in FIG. This wafer 3 is made of polycrystalline silicon, for example.

On the surface of the wafer 3, Si024 is selectively formed as a mask for etching. Further, a mercury lamp 5 is provided outside the quartz container 1, and its irradiation light is set to be parallel to the wafer 3.

In such a device, CI2+Si (Cto1
3) 4/1-1 () Introduce the mixed gas and decompose the introduced mixed gas by irradiating the material surface of the polycrystalline silicon 3 with mercury lamp light (wavelength 253.7 nm) from the mercury lamp 4 in parallel. While a thin film is deposited to form a sidewall protective film, at the same time, by irradiating the sample surface of the polycrystalline silicon 3 with laser light (wavelength 308nll) perpendicularly, the polycrystalline silicon 3 undergoes radical etching. Etching progresses through a competitive reaction between this etching and thin film deposition, and this thin film acts as a protective film on the etched sidewalls to prevent undercuts.
Anisotropic etching is achieved.

However, such etching methods suffer from non-uniform competitive reactions due to warping of the wafer and steps produced in the latter half of the etching process. The reason for this is that the height of photodecomposition differs due to wafer warpage and step differences in deposition caused by lateral UV irradiation, which changes the deposition rate. It is also stated that the deposition rate becomes faster.

For this reason, it is difficult to uniformly etch the entire surface of a wafer, and many control elements are required to control the competing reactions in step operations such as those found in reduction projection exposure apparatus.

(Purpose) The present invention was developed in view of the problems of the etching methods that have already been proposed as described above. The present invention provides a fine anisotropic dry etching method that causes less plasma damage than is seen in ordinary plasma anisotropic etching through a competitive reaction with etching caused by laser light irradiated perpendicularly or parallel to the surface.

(Example) The present invention will be described in detail below. FIG. 1 shows a manufacturing apparatus according to a tweezing method of the present invention, and in the figure, a transport pipe 5 extends from one side of a quartz container 1, and its end is open. Further, a plasma generation chamber 6 is provided near the end of the transport pipe 5, and a microwave waveguide 6 is arranged around the plasma generation chamber 6.

With J3 in such a configuration, from the opening of the transport pipe 5 CI2→S
i (Cl-13) 4 /110 mixed gas is introduced, and microwaves (2,45 GHz >
to avoid generating plasma. The plasma excited by the microwaves has a long life and is introduced parallel to the wafer 3 through the transport pipe 5 into the quartz container 1, which is a reaction chamber loaded with the semiconductor wafer 3. In the structure in which the plasma generation part and the reaction part are separated, kinetic energy is lost during plasma transport through the transport pipe 5, and as a result, damage to the substrate 3 is extremely reduced, and chemical reactions are prevented. become. Also, from outside the container 1, the wafer 3 is exposed to a laser beam (Xecl: wavelength 308 cm) perpendicular to the etching process.
irradiate (nm). Ultra-fine anisotropic etching with little damage can be achieved through competitive reactions such as the deposition action by the long-lived radicals and the etching action by the laser beam.

The radicals introduced into the abrasive reaction chamber are distributed uniformly within the chamber, solving the problems of wafer warpage and step shape.
Uniform anisotropic dry etching becomes possible over the entire wafer surface. In the apparatus shown in FIG. 1, if the mask 4 is formed and covered with resist by a method similar to normal photoetching, the mask body (on which the pattern is formed) (
hard mask) does not need to be loaded into the quartz container 1.

In addition, when performing direct etching with a laser beam without using a resist, a hard mask such as a chrome mask placed outside the container 1 is used to selectively irradiate the laser beam onto the area to be etched. According to such a method, a stepping operation that can be seen without a reduction projection exposure system may be applied.

In addition, in FIG. 1, the generated plasma is introduced from the direction of the wafer 33, but in order to ensure uniformity, the radicals may be introduced from the top. In that case, the influence of the irradiation direction can be suppressed by irradiating the quartz 1 from around the quartz 1, avoiding the portions that are irradiated with the laser beam.

(Effects) As described above, according to the present invention, it is possible to efficiently form an ultra-fine pattern with less plasma damage on a semiconductor wafer to be etched.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of an etching apparatus according to the present invention, and FIG. 2 is a diagram showing a conventionally proposed etching apparatus. 1...6 Container 2...Support stand 3...Semiconductor wafer 4...Mask 5...Transport pipe 6... ...Plasma generation chamber 7...Microwave introduction tube Patent applicant Pioneer Co., Ltd. Figure 1 Figure 2 Sugishi - Delight procedure amendments September 12, 1981 Commissioner of the Patent Office Manabu Shiga 2. Title of the invention: Anisotropic dry cutting method 3. Relationship with the person making the amendment Patent applicant address: 1-4?11-4, Meguro 1-4, Meguro-ku, Tokyo, 153 Japan
, Text 3 of the specification subject to amendment, Contents of the amendment (correction of the entire text) Description 1, Name of the invention Anisotropic dry etching method 2, Claims In addition to applying radicals excited by microwaves to a semiconductor wafer. , by causing radicals excited by the laser beam to act, and performing anisotropic etching through a competitive reaction between the deposition effect of the radicals excited by the microwave and the etching effect of the radicals excited by the laser beam. An anisotropic dry etching method characterized by: 3. Detailed Description of the Invention (Technical Field) The present invention relates to an anisotropic dry etching method suitable for VLSI manufacturing processes, and in particular an anisotropic dry etching method that can efficiently etch ultra-fine patterns in the submicron region. Regarding. (Background technology and its problems) Currently, anisotropic etching is performed using reactive ions accelerated by an electric field in plasma to form fine patterns with a line width of 2 μm or less, which is required in the VLSI process. RIE (Reactive)
It is called e Ion E tching). However, the surface of the silicon semiconductor substrate is severely damaged by the impact of reactive ions accelerated by this electric field. Furthermore, destruction of the gate oxide film, which is thought to be caused by charging of reactive ions, has been reported, and more recently, damage to the surface of a silicon substrate in plasma that is not accelerated by an electric field has also been reported. For this reason, etching with radicals excited by ultraviolet rays has been proposed as one method for practical etching that does not cause plasma damage. However, it is not possible to perform anisotropic etching by simply generating radicals through ultraviolet irradiation. To achieve anisotropic etching, an electric field perpendicular to the surface to be etched is applied to drive the reactive ions vertically. However, in this method, the wafer surface is damaged by the impact of reactive ions. As an anisotropic etching device using this optical excitation, the one shown in FIG. 2 has been proposed. In the figure, a wafer 3 as an object to be etched placed on a support stand 2 is loaded in a quartz container 1. As shown in FIG. This wafer 3 has, for example, a silicon substrate on which polycrystalline silicon is deposited. A photoresist 4 is selectively formed on the surface of the wafer 3 as a mask for etching. Further, a mercury lamp 5 is provided outside the quartz container 1, and its irradiation light is set to be parallel to the wafer 3. In such an apparatus, CI2+ S i (C
) → 3) 4/HjJiff mixture gas is introduced, and the introduced mixture gas is decomposed by irradiating mercury lamp light (wavelength 253.γ nm) parallel to the material surface of polycrystalline silicon 3 from mercury lamp 4, While a thin film is deposited to form a sidewall protective film, the polycrystalline silicon 3 is simultaneously irradiated with a laser beam (wavelength 308 nm) perpendicularly to the sample surface of the polycrystalline silicon 3 by photoexcited radicals.
Etching progresses. Etching progresses due to a competitive reaction between this etching and the thin film deposition, and on the etched sidewalls, this thin film acts as a protective film to prevent undercutting and achieve anisotropic etching. However, such etching methods have disadvantages of non-uniformity of competitive reactions due to wafer warpage and C steps that occur in the latter half of the wafer process. The cause of this is that deposition due to lateral ultraviolet irradiation is caused by the fact that the height of photodecomposition differs due to wafer warping or steps, and the deposition rate changes; It is also stated that the deposition rate is faster on the surface. For this reason, it is difficult to uniformly etch the entire surface of a wafer, and many control elements are required to control the competing reactions in step operations such as those found in reduction projection exposure apparatus. (Purpose) - Therefore, the present invention was developed in view of the above-mentioned problems with the etching methods already proposed. This method provides a fine anisotropic dry etching method that causes less plasma damage than is seen in normal plasma anisotropic etching through a competitive reaction with etching caused by radicals excited by a laser beam irradiated perpendicular to the etching surface. . (Example) The present invention will be described in detail below using etching of polycrystalline silicon as an example. FIG. 1 shows a manufacturing apparatus according to the etching method of the present invention. In the figure, a transport pipe 6 extends from the left side of a quartz container 1, and its end is open. Further, a plasma generation chamber 7 is provided near the end of the transport pipe 6, and a microwave waveguide 8 is attached around the plasma generation chamber 7. In such a configuration, the opening of the transport pipe 6 5i(C)-
13) At the same time, microwaves (2,45
GHz) to generate plasma and electrically neutral radicals. While the plasma excited by the microwave has a relatively long life, radicals have a long life, and the wafer 3 is passed through the transport pipe 5 into the quartz container 1, which is a reaction chamber loaded with the semiconductor wafer 3. is introduced parallel to. Further, a gas line is provided in the container 1 separately from the transport pipe 5, and C12 gas is introduced through this line. Then, a laser beam (XeC1: wavelength 30
8nIll). Then, ultrafine anisotropic etching with little damage can be achieved through a competitive reaction between the deposition action of radicals whose lifetime has been extended by microwaves and the etching action of radicals excited by laser light. The long-lived radicals introduced into the reaction chamber at this time are uniformly distributed within the chamber, which solves the problems of wafer warpage and stepped shapes, making it possible to perform uniform anisotropic dry etching over the entire wafer surface. In addition, in the case of direct etching with a laser beam without using a resist in the apparatus shown in FIG. According to the Kakaru method, a stepping operation seen in a reduction projection exposure apparatus may be applied. In addition, in FIG. 1, the generated radicals are introduced from the side to the wafer 3, but in order to improve the uniformity, the radicals may be introduced from the top (in that case, Avoid the part that will be irradiated with the laser beam, and place the quartz 1
By irradiating from the surrounding area, the influence of the irradiation direction can be suppressed. (Effects) As described above, according to the present invention, it is possible to efficiently form an ultra-fine pattern with less plasma damage on a semiconductor wafer to be etched. 4. Brief Description of the Drawings FIG. 1 is a diagram showing an embodiment of an etching apparatus according to the present invention, and FIG. 2 is a diagram showing a conventionally proposed etching apparatus. 1... Quartz container 2... Support stand 3... Semiconductor wafer 4... Mask 5... Mercury lamp 6...・Transport pipe 7...Plasma generation chamber 8...Microwave introduction pipe 9...Gas line Patent applicant Pioneer Corporation

Claims (1)

[Claims] A semiconductor wafer is exposed to plasma excited by a single wave of a microphone and irradiated with laser light, so that anisotropic etching is performed through a competitive reaction between the deposition action of the plasma and the etching action of the laser light. An anisotropic dry etching method characterized by: