JPH0529282A - Dry etching method - Google Patents

Abstract

PURPOSE:To enable a tapered fine pattern to be easily formed high in throughput by a method wherein an etching material is etched using a multilayered resist composed of a lower resist and an inorganic material layer formed on the lower resist as a mask, and the etching of the etching material is made to proceed even after the inorganic material layer is etched off. CONSTITUTION:An SiO2 film 2, an aluminum film 3, and a multilayer resist M are formed on a substrate 1, where the multilayered resist M is composed of a lower resist 4, an inorganic material layer 8, and an upper resist 6. The layer 8 is etched through the layer 6 as a mask. The layer 4 is etched using the layers 8 and 6 as a mask, and the layer 6 is concurrently etched off. The layer 3 is etched through the multilayered resist M as a mask to be provided with an undercut. When the film 3 is etched so far as prescribed, the layer 8 is etched off to enable the lower resist 4 to be exposed. Thereafter, the film 3 proceeds to be anisotropically etched. By this setup, the upper part of the film 3 is tapered.

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 for taper-etching a material to be etched by using a multilayer resist having an inorganic material layer formed on a lower resist as a mask.

[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 of forming a fine pattern 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 fine pattern. That is, so-called taper etching is performed.

Various methods of taper etching have been reported. For example, as a generally well-known method for taper etching of 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 (Spring 1985 Abstracts of Applied Physics Society,
338) is known. Figure 4 is an explanatory view of such a tapered etching method, as shown in (A) of first drawing According to this method, SiO ₂ film 2 on the substrate 1,
Aluminum films 3 to be etched are sequentially laminated,
Further, a tapered resist pattern 7 is formed thereon. In addition, such a tapered resist pattern 7
Can be formed by forming a resist pattern by a conventional method and then performing heat treatment or the like. Next, using the tapered resist pattern 7 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 resist pattern 7 is removed by resist receding.
The taper is transferred to the aluminum film 3 to form a wiring pattern as shown in FIG.

As another taper etching method, a multilayer resist is used as a mask, and each layer of the multilayer resist is removed so that the material to be etched is sequentially subjected to isotropic etching and anisotropic etching. Another method has been proposed (Japanese Patent Laid-Open No. 2-244631). FIG. 3 is an explanatory view of such a taper etching method. According to this method, for example, as shown in FIG. 3A, first, an insulating film 2 made of a thermal oxide film and wiring are formed on a Si substrate 1. 3 μm thickness, which is the material and the material to be etched
Aluminum film 3 is laminated and a thickness of 4μ
m lower layer resist 4 (for example, NPR-820, manufactured by Nagase & Co., Ltd.), 0.4 μm thick intermediate layer resin 5 (for example, OC
D-7, manufactured by Tokyo Ohka), upper layer resist 6 with a thickness of 1 μm
A multilayer resist made of (for example, PFPR-800, manufactured by Tokyo Ohka) is formed, and the upper resist 6 having a thickness of 1 μm is patterned by ordinary photolithography. Then, the intermediate layer resin 5 is patterned by performing etching by the RIE method using the pattern of the upper layer resist 6 as a mask, and further, as shown in FIG.
The lower layer resist 4 is patterned using the above pattern as a mask. After that, the aluminum film 3 is etched by 1 μm by the RIE method using Bl ₃ / Cl ₂ gas. In this case, the surface of the multi-layer resist is the intermediate layer resin 5 in which resist decomposition products are not generated even if ion sputtering is performed, and as a result, the sidewall protection film is not formed on the pattern of the aluminum film 3. Therefore, isotropic etching progresses in the aluminum film 3, and the pattern shape becomes undercut ((C) in the same figure). Then, the intermediate layer resin 5 is removed. Then, the remaining aluminum film 3 is etched again. In this case, the surface of the multilayer resist is not the intermediate layer resin 5 but the lower layer resist 4
Therefore, a decomposed product of resist is generated, a side wall protective film is formed, and anisotropic etching proceeds on the aluminum film 3. For this reason, such etching is continued until the pattern of the aluminum film 3 reaches a desired depth, and when the etching is finished, a pattern with a taper on the upper part is formed as shown in FIG. Will be obtained.

As another taper etching method, a deposition gas is added into the etching chamber to form a taper by a competitive reaction between etching and deposition (1986 Dry Process Symposium, 4
8), and recently, a method of forming a taper by controlling the temperature of the wafer (19
Proceedings of Applied Physics in Spring 1987, p. 462) are also reported.

[0006]

However, in the method of tapering the resist pattern shown in FIG.
Since the pattern of the wiring / wiring material is tapered by the resist receding, the conversion difference is large, the difference between the initial dimension of the resist pattern and the dimension 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 necessary to originally reduce the selection ratio to the resist. Therefore, it is necessary to form the resist film relatively thick. Also occurs. Therefore, this method cannot deal with the pattern formation which tends to become finer in the future.

On the other hand, according to the method shown in FIG. 3 in which a multilayer resist is used as a mask, it becomes possible to taper a fine pattern. However, this method requires a step of separately removing the intermediate layer resin 5 between the step of advancing the isotropic etching of the material to be etched and the step of advancing the anisotropic etching. That is, since a resin material that serves as an etching stopper is used as the intermediate layer resin 5, the intermediate layer resin 5 is removed by the RIE method similar to the etching of the material to be etched, and both etchings are performed continuously. Even if it is attempted in one step, it is difficult to find an etching gas that suitably etches both the material to be etched and the intermediate layer resin 5, and the step of removing the intermediate layer resin 5 is different from the etching of the material to be etched. Must be performed under completely different conditions. Therefore, there is a problem that the throughput of the etching process is reduced.

Further, in the method of forming a taper by adding a deposition gas and competing reaction between etching and deposition, since the deposition gas has a depositing 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.

As described above, with the conventional taper etching methods, it is not possible to form a tapered fine pattern with high accuracy and high throughput. Therefore, in reality, taper etching has not been put to practical use.

The present invention is intended to solve the above-mentioned problems of the prior art, and an object thereof is to provide a dry etching method capable of easily tapering a fine pattern with high throughput. There is.

[0012]

In order to achieve the above-mentioned object, the present invention provides a method for dry etching a material to be etched using a multilayer resist consisting of a lower resist and an inorganic material layer formed thereon as a mask, As the etching of the material to be etched progresses, the etching of the inorganic material layer also progresses, and the inorganic material layer is etched off before the etching of the material to be etched is completed, and the material to be etched is continuously etched even after the etching off of the inorganic material layer. A dry etching method is provided.

The method of the present invention comprises an inorganic material layer in which the material to be etched is isotropically etched when used as a mask, and a resist layer in which the material to be etched is anisotropically etched when used as a mask. It is a dry etching method in which a material to be etched is etched using a laminated multilayer resist. In that case, by appropriately determining the material and film thickness of the inorganic material layer, the inorganic material layer is etched together with the material to be etched, and the inorganic material layer is etched off before the etching of the material to be etched is completed. After that, the etching of the material to be etched is performed using the resist layer as a mask so that isotropic etching and anisotropic etching of the material to be etched are continuously performed. It is a thing.

Therefore, in the method of the present invention, the inorganic material layer of the multi-layer resist used as a mask is made of a material that can be etched together with the material to be etched, preferably one that can obtain an etching rate similar to that of the material to be etched. It is appropriately selected according to the type of material to be etched.
For example, when the material to be etched is made of an aluminum material, the inorganic material layer is titanium oxynitride (T
iON), titanium, silicon nitride, silicon oxide, silicon-based material, etc.,
When the material to be etched is made of a silicon-based material such as a polycide structure made of polysilicon and tungsten silicide (WSix _x = 1 to 3), the inorganic material layer is doped with polysilicon, tungsten silicide, phosphorus or boron. Can be formed from polysilicon, silicon oxide, silicon nitride, etc.
Particularly, it is preferably formed of polysilicon. Also,
Even when the material to be etched is made of a refractory metal such as tungsten or molybdenum, the inorganic material layer is made of polysilicon,
It can be preferably formed from titanium or titanium oxynitride.

The thickness of the inorganic material layer is appropriately determined according to the size of the taper applied to the pattern of the material to be etched, the material of the material to be etched and the material of the inorganic material layer, and the like.

As the material of the lower layer resist, any material may be used as long as it produces a decomposed product of the resist when it is used as a mask to form a side wall protective film of the pattern of the material to be etched, and is made of a usual organic material. Various resist materials can be used.

The multilayer resist used in the present invention is one in which an inorganic material layer is formed on the lower layer resist as described above, but other layers may be provided if necessary. For example, an upper layer resist that serves as a mask for forming the inorganic material layer in a predetermined pattern may be provided on the inorganic material layer.

The method of the present invention can be carried out in various dry etching methods such as reactive ion etching, plasma etching and sputter etching.
Particularly, reactive ion etching can be preferably carried out.

[0019]

In the method of the present invention, when the material to be etched is dry-etched by using the multilayer resist in which the inorganic material layer is formed on the lower resist as a mask, the material of the material to be etched such as the material and thickness of the inorganic material layer is used. The inorganic material layer is also etched along with the etching, and the inorganic material layer is etched off before the etching of the material to be etched is completed, and the material to be etched is continuously etched even after the etching off of the inorganic material layer. To do so. Therefore, when the inorganic material layer functions as a mask for the material to be etched during etching, isotropic etching progresses in the material to be etched and an undercut pattern is formed.

On the other hand, the inorganic material layer itself is also etched while the etching of the material to be etched is progressing, and the material is etched off when the etching of the material to be etched reaches a desired state of progress. Therefore, after that, the lower layer resist formed under the inorganic material layer functions as a mask, and the etching of the material to be etched is continued. In this etching that masks the lower layer resist, a resist decomposition product is generated in the lower layer resist layer, so that a sidewall protective film is formed on the pattern of the material to be etched, and anisotropic etching proceeds. Therefore, by performing such etching, a fine pattern in which an undercut is formed only on the upper end is formed. In this case, since the shape of this undercut has a suitable taper, a fine pattern having a taper on the upper end can be obtained. The lower layer resist remaining on the fine pattern thus formed can be easily removed by a conventional method.

As described above, according to the method of the present invention, a fine pattern having a tapered upper end can be obtained, and the fine pattern can be easily formed by a single etching process. Therefore, according to the present invention, it is possible to improve the throughput of taper etching.

When taper etching is performed in this manner, 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.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. In the drawings, the same reference numerals represent the same or equivalent constituent elements. Embodiment 1 FIG. 1 is an explanatory diagram of a process of an embodiment of the present invention. In this embodiment, first, a SiO ₂ film 2 by thermal oxidation is formed as an insulating film on the surface of a silicon substrate 1, and an aluminum film 3 to be microfabricated is further formed thereon to a thickness of 1 μm.
m formed. And as the multilayer resist M of the present invention,
Lower layer resist (OFPR-800, manufactured by Nagase & Co.) 4 having a thickness of 1 μm, inorganic material layer 8 made of titanium oxynitride (TiON) having a thickness of 4000 nm, thickness 0.5 μm
An upper layer resist (OFPR-800, manufactured by Nagase & Co., Ltd.) 6 was formed, and the upper layer resist 6 was patterned by a conventional photolithography ((A) of FIG. 1).

Next, the inorganic material layer 8 is etched by the RIE apparatus using the upper resist 6 as a mask (etching gas CF ₄ 100 sccm and O _{2 2} sccm, pressure 35 mTorr, 1000 W), and the inorganic material layer 8 and the upper resist 6 are used as masks. RIE the lower resist layer 4
Etching with an apparatus (etching gas = O ₂ 100
sccm, pressure = 5 mmTorr, 1000 W), and at the same time, the upper layer resist 6 was etched off ((B) of FIG. 1).

Next, the multilayer resist M formed in this way
Using the pattern as a mask, the aluminum film 3 was etched under the following conditions. That is, in the microwave plasma etching apparatus, etching gas = BCl
₃ 60sccm, Cl ₂ 90sccm, pressure = 16mT
orr, microwave = 800W, RF bias = 40W
And The etching rate of the aluminum film 3 under this condition is 1 μm / min, and the titanium oxynitride (T
The etching rate of the inorganic material layer 6 made of iON) is 130.
nm / min.

When etching is started, since the upper surface of the multilayer resist M is the inorganic material layer 8 made of titanium oxynitride (TiON) at the initial stage of etching, no resist decomposition product is generated and the side wall protective film is also formed. Not formed, but an undercut was formed in the aluminum film 3 as shown in FIG. The inorganic material layer 8 was etched off when the aluminum film 3 was etched to a thickness of 310 nm 18 seconds after the start of etching, and the surface of the lower layer resist 4 was exposed. Then, after that, a resist decomposition product was generated, and anisotropic etching proceeded to the aluminum film 3. Thus, as shown in FIG. 1D, the undercut can be formed only on the upper portion of the aluminum film 3, and an ideal tapered pattern can be obtained. Embodiment 2 FIG. 2 is an explanatory view of a process of another embodiment of the present invention. In this embodiment, after the SiO ₂ film 2 is formed on the surface of the silicon substrate 1, the polysilicon film 3 is used as the material to be etched.
a and tungsten silicide _(WSi x, x = _1~
3) A polycide structure film 3c was formed by sequentially stacking the films 3b.

Then, a lower layer resist 4 is formed in the same manner as in Example 1, an inorganic material layer 8 made of tungsten silicide is further formed to a film thickness similar to the tungsten silicide film 3b, and an upper layer is formed thereon in the same manner as in Example 1. A resist 6 was formed to obtain a multilayer resist M.

Next, the upper layer resist 6 was patterned (FIG. 2 (A)), and the lower layer resist 4 and the inorganic material layer 8 were patterned (FIG. 2 (B)).

Then, using the RIE device, mainly HBr
The polycide structure film 3c was etched using gas. Then, the resist decomposition product was not generated while the etching proceeded with the inorganic material layer 8 made of tungsten silicide as a mask, and the undercut was formed in the tungsten silicide film 3b.

When the etching further progressed and the polysilicon film 3a was exposed, the inorganic material layer 8 was etched off, and the lower layer resist 4 appeared ((C) in FIG. 2). After that,
Etching of the polysilicon film 3a using the lower resist 4 as a mask progressed. Therefore, a decomposed product of the lower layer resist 4 was generated, and anisotropic etching proceeded to the polysilicon film 3a. Thus, as shown in FIG. 2D, an undercut was formed only in the tungsten silicide film 3b, and a tapered pattern of the polycide structure film 3c could be obtained.

[0031]

According to the dry etching method of the present invention, it becomes possible to easily form a tapered fine pattern with high throughput.

[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 diagram of a conventional taper etching method using a multilayer resist.

FIG. 4 is an explanatory view of a conventional taper etching method using a tapered resist pattern.

[Explanation of symbols]

1 Substrate 2 SiO ₂ 3 Aluminum Film 4 Lower Layer Resist 5 Middle Layer Resin 6 Upper Layer Resist 7 Resist Pattern 8 Inorganic Material Layer M Multilayer Resist

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 21/3205

Claims (1)

Claim: What is claimed is: 1. A method of dry-etching a material to be etched with a multilayer resist comprising a lower layer resist and an inorganic material layer formed thereon as a mask, wherein the material to be etched is formed along with the etching of the material to be etched. A dry etching method, characterized in that the inorganic material layer is etched off before the etching of the material to be etched is completed, and the material to be etched is continuously etched even after the etching off of the inorganic material layer.