JPH0529281A - Dry etching method - Google Patents

Abstract

(57) [Summary] [Purpose] In a dry etching method, a fine pattern can be easily tapered. [Structure] As a mask pattern of a material to be etched, a mask pattern whose cross-sectional shape is wide at least from the bottom to the upper side is used, and dry etching is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method useful for taper etching of a material to be etched.

[0002]

2. Description of the Related Art Conventionally, dry etching methods such as plasma etching, sputter etching, and reactive ion etching (RIE) have been used as a method for forming fine patterns of highly integrated semiconductors. In order to enable the multilayer wiring structure described above, not only the fine pattern is formed by the dry etching method, but also the fine pattern is tapered to improve the coverage of the film laminated on the pattern. The so-called taper etching is performed.

Various methods of taper etching have been reported. For example, as a well-known method of taper-etching a wiring material, a resist pattern serving as a mask of the wiring material is tapered and the etching selectivity between the wiring material and the mask is lowered during etching to reduce the resist receding. Method to form a taper in the pattern of the wiring material by the method (Spring 1985 Proceedings of the Japan Society of Applied Physics,
338) is known. Figure 4 is an explanatory view of such a tapered etching method, according to this method, first as shown in the figure (A), SiO ₂ film 2 on the substrate 1, an aluminum film is etched material 3 are sequentially laminated, and a tapered resist pattern 4 is further formed thereon. The tapered resist pattern 4 can be formed by forming a resist pattern by a conventional method and then performing heat treatment or the like. Then
Using the tapered resist pattern 4 as a mask, etching is performed by reactive ion etching under the condition that the selectivity ratio to the resist is about 1, and the taper of the resist pattern 4 is transferred to the aluminum film 3 by the resist receding, as shown in FIG. A wiring pattern is formed as in B).

Another method of taper etching is to add a deposition gas into the etching chamber,
A method of forming a taper by a competitive reaction between etching and deposition (Dry Process Symposium, 1986, p. 48) has been reported, and recently a method of forming a taper by controlling the temperature of a wafer (Spring 1987 Applied Physics) The conference proceedings, p. 462) are also reported.

[0005]

However, in the method of tapering the resist pattern to reduce the etching selectivity between the wiring material and the mask, the pattern of the wiring wiring material is tapered by the resist receding. Is large, the difference between the initial size of the resist pattern and the size of the wiring material after etching is large, and dimensional control becomes difficult. Further, since the pattern width of the wiring material is restricted by the taper width of the resist pattern formed in advance, it becomes difficult to form a fine pattern on the wiring material. Further, since the taper of the wiring material is formed by transferring the taper of the resist pattern, it is essentially necessary to reduce the selection ratio with respect to the resist. Therefore, it is necessary to form the resist film relatively thick. Therefore, this method cannot cope with pattern formation, which tends to become finer in the future.

In addition, in the method of adding a deposition gas and forming a taper by a competitive reaction between etching and deposition, the deposition gas has a deposition property.
There is a concern that a polymer that causes particle contamination may be generated in the entire etching chamber.

In the method of forming the taper by controlling the temperature of the wafer, it is necessary to strictly control the temperature of the wafer, but at present, there is a method of accurately evaluating the temperature of the wafer in-process. Therefore, there is concern that the reliability of the process may be reduced.

Therefore, the conventional taper etching methods are insufficient to form a fine pattern with high precision, and none of them has been put to practical use.

The present invention is intended to solve the problems of the prior art as described above, and an object of the present invention is to provide a dry etching method capable of easily tapering a fine pattern.

[0010]

In order to achieve the above object, the present invention provides a method of forming a mask pattern on a material to be etched and performing dry etching, in which the cross-sectional shape of the mask pattern is at least upward from the bottom. The present invention provides a dry etching method characterized in that the dry etching method is formed so as to be wide.

In the method of the present invention, the material to be etched can be easily used by using a mask pattern whose cross-sectional shape is wide at least from the bottom to the top as a mask pattern used when performing dry etching. This enables taper etching.

In this case, applicable dry etching methods include reactive ion etching,
Various dry etching methods suitable for forming a fine pattern can be mentioned.

As the mask pattern to be used, various mask patterns can be used, for example, a negative resist or a positive resist can be used. As such a photoresist, when forming a narrow taper required for tapering a fine pattern,
It is preferable to use one having a relatively small absorptance at the exposure wavelength.

In the present invention, the shape of the mask pattern is such that its cross section is formed so as to be wide at least from the bottom to the top. As such a cross-sectional shape, the mask pattern has an eaves-like shape in which the upper portion is wider than the bottom portion in contact with the material to be etched to form an eaves-like shape. Is not particularly limited as long as it forms a region that does not reach. For example, the cross section of the mask pattern may be wide from the bottom to the center and may be a barrel type in which the width is narrow from the center to the top, or it may be a so-called reverse taper type that is wide from the bottom to the top. it can.

The method of forming such a mask pattern is not particularly limited, and the forming method can be appropriately determined according to the type of resist or material to be etched to be used. For example, in the case of forming a mask pattern from a positive type resist, the best focus at the time of exposure may be shifted slightly above the surface of the material to be etched in the pattern forming method by the conventional photolithography. As a result, a resist pattern having a barrel-shaped cross section can be easily formed on the material to be etched by using a photolithography apparatus which has been conventionally used. Further, when a high-brightness material having a high reflectance such as aluminum is used as the material to be etched, the resist usually contains a dye to suppress the influence of light scattering during exposure. Although used, when the mask pattern having a cross-sectional shape suitable for the present invention is used, the addition amount of such a dye may be reduced.

[0016]

In the dry etching method of the present invention,
The cross-sectional shape of the mask pattern provided on the material to be etched is
It is formed wide at least from the bottom to the upper side. Therefore, for example, as shown in FIG.
In the case where a SiO ₂ film 2 and an aluminum film 3 to be etched are sequentially laminated on a substrate 1 and a resist pattern 5 having a narrow bottom portion 5a and a wide central portion 5b is formed as a mask pattern thereon. In the region 3a of the aluminum film below the central portion 5b of the resist pattern, the central portion 5b of the resist pattern 5 serves as an eaves during etching and the vertically incident ions (a ⁺ ) cannot reach the diagonal incident ions (b ⁺ Only) will be reachable. On the other hand, in the region 3b of the aluminum film 3 which does not enter under the eaves of the wide central portion 5b of the resist pattern 5, obliquely incident ions (b
Not only ⁺ ) but also vertically incident ions (a ⁺ ) arrive. Therefore, the etching rate of the region 3a of the aluminum film 3 is lower than that of the region 3b, and when the etching is advanced to the desired state and terminated, as shown in FIG.
The taper 3c is formed in the region where the etch rate is lowered. The resist pattern 5 remaining on the pattern of the aluminum film 3 at the end of etching can be easily removed by a conventional method. In this way, it becomes possible to form a tapered pattern on the aluminum film 3 with a low conversion rate to the resist pattern.

Therefore, according to the method of the present invention, even if the pattern formed on the material to be etched is fine, it is possible to provide a fine taper corresponding thereto.

When the pattern is tapered as described above, it is not necessary to use a deposition gas having a deposition property as in the conventional example, so that particle contamination does not occur.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. In each drawing, the same reference numerals represent the same or equivalent constituent elements. Embodiment 1 FIG. 1 is an explanatory diagram of an embodiment of the present invention. In this embodiment, Si as an insulating film is formed on the surface of the silicon substrate 1.
An O ₂ film 2 was formed, and an aluminum film 3 to be finely processed was further formed on the O ₂ film 2. Thereafter, a resist pattern 5 having a barrel-shaped cross section was formed with a positive resist ((A) of FIG. 1).

Next, the aluminum film 3 was etched using the resist pattern 5 thus formed as a mask. A microwave plasma etching apparatus is used as an etching method, and boron trichloride (BCl 3) is used as a reaction gas.
₃ ) Gas and chlorine gas were used at a flow rate ratio of 60 sccm to 90 sccm. The pressure was 16 mTorr, the microwave power was 800 W, and the RF bias was 40 W. In such microwave plasma etching, etching proceeds due to radical species and ionic species generated by the discharge, but as described with reference to FIG. 3, the wide central portion 5b of the resist pattern 5 serves as an eaves portion, so that the aluminum film is formed. Vertically incident ions do not reach the region 3a of 3 and etching proceeds by obliquely incident ions. For this reason, after the etching is advanced to the initial state, the etching is terminated and the resist pattern 5 is removed, so that the upper corners are removed and the tapered aluminum film 3 is removed as shown in FIG. The pattern was obtained. Embodiment 2 FIG. 2 is an explanatory view of another embodiment of the present invention. In this embodiment, the silicon substrate 1, a SiO ₂ film 2 is formed as a gate oxide film, a polycide film 8 to be microfabricated thereon, polycrystalline silicon film 6 and a tungsten silicide (WSi _x, x = 1 to 3) Membrane 7
Were sequentially formed, and then a resist pattern 5 similar to that in Example 1 was formed ((A) of FIG. 2).

Next, the polycide film 8 consisting of the polycrystalline silicon film 6 and the tungsten silicide film 7 was etched. As the etching method, a reactive ion etching apparatus was used, and hydrogen bromide gas and sulfur hexafluoride gas were used as reaction gases at a flow rate ratio of 50 sccm to 5 sccm. The pressure was 30 mTorr and the microwave power was 300 W.

As a result, as shown in FIG. 2B, a pattern in which the upper end of the tungsten silicide film 7 has a sharp corner was obtained.

[0023]

According to the dry etching method of the present invention, even when a fine pattern is formed on a material to be etched, it is possible to easily taper the pattern or take a corner at the end of the pattern. Is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of another embodiment of the present invention.

FIG. 3 is an explanatory view of the operation of the dry etching method of the present invention.

FIG. 4 is an explanatory diagram of conventional taper etching.

[Explanation of symbols]

1 substrate 2 SiO ₂ film 3 aluminum film 4 conventional tapered resist pattern 5 barrel resist pattern of the present invention

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H01L 21/3205 H05H 1/46 9014-2G

Claims (2)

[Claims] 1. A method of forming a mask pattern on a material to be etched and performing dry etching, wherein the cross-sectional shape of the mask pattern is formed so as to widen at least from the bottom to the upper side. Method. 2. The dry etching method according to claim 1, wherein the mask pattern is made of a positive type resist.