JP2998164B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of etching a silicon-based material to be etched. SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a semiconductor device, which can form an etching pattern having a good shape on a silicon-based material when manufacturing the semiconductor device.

[Summary of the Invention]

The invention of claim 1 of the present application is to perform etching of a silicon-based material to be etched by using a gas containing hydrogen bromide, nitrogen, and a gas that can generate fluorine radicals.
It is intended to obtain a semiconductor device by performing etching of a good shape without using a fluorocarbon-based gas such as chlorofluorocarbon.

According to the invention of claim 2 of the present application, when etching a silicon-based material to be etched in which at least the uppermost layer is made of a high melting point metal silicide, the material to be etched itself or a reaction product generated by etching adheres to the resist side wall. With this configuration, it is possible to prevent the deterioration of the etching shape due to the receding of the resist, achieve the etching of a good shape, and obtain the semiconductor device.

[Background of the Invention]

Conventionally, etching of a silicon-based material has been used, for example, when forming an electronic material (such as a semiconductor device). In the etching technique, it is necessary to form a good pattern according to a desired pattern. However, depending on the material to be etched, good patterning may not always be achieved.

This problem is an important problem in the background described below.

First, there is a background that it has become difficult to use a fluorine-based gas, which has been conventionally used mainly, in etching a silicon-based material. For example, with the need for higher speed of various semiconductor devices such as LSIs, a polycide structure has been adopted as a gate material, and various methods of etching this structure have been developed and put into practical use. Currently, the mainstream is CFC-based gas (F1
13) etc.). However, it is considered that these fluorocarbon-based gases called Freon or Freon cannot be used in the future due to so-called "Freon regulation" due to the problem of environmental destruction. Therefore, there is an urgent need to develop technology for anisotropically processing a gate material such as a W (tungsten) polycide structure using a gas system other than chlorofluorocarbon. However,
It is not always easy to perform etching with a good pattern shape using a new gas system.

One technique of performing anisotropic processing with good processed shape, there is a method using a reaction product sidewall protection, the present inventors have also Si trench etching by HBr / N ₂ -based etching gas previously proposed I went (Japanese Patent Application No. 1-279905)
issue). However, this method of using a reaction product as a side wall protective material by using such a gas system has a problem that the shape of a wide portion is tapered by itself because the amount of the deposit depends on the area to be etched. May occur. For example, as shown in FIG. 3A, the refractory metal silicide layer on the substrate 1 and the SiO ₂ film 2 is formed by using two patterned resists 51 and 52 as a mask, as shown in FIG. 4 and the silicon layer 3 are to be etched, but the deposit adheres thinly to the side walls of the resists 51 and 52 as shown in FIG. In a wide place, as shown in FIG. 6b, the skirt may be flared as shown in FIG. This can lead to a deterioration of the etched shape. (As another technique using an attached film, there is Japanese Patent Application No. 63-241982 filed by the present applicant).

Therefore, there is a demand for the development of a technique capable of obtaining a good etching pattern without such a problem of the possibility of tapering.

The second problem is based on a demand for miniaturization of a pattern accompanying miniaturization of a device.

That is, in the case of semiconductor devices, for example, due to the fact that patterns have been increasingly miniaturized with the recent increase in the degree of integration of LSIs, the demands on the processing accuracy have become strict.

Conventionally, a method using a photoresist has been generally used for patterning. However, when dry etching is performed using the photoresist, the resist itself may be etched and become thin. For example, in the example shown in FIG. 4, as shown in FIG.
Is intended to etch the refractory metal silicide layer 4 and the silicon layer 3 on the substrate 1 and the SiO ₂ film 2 by etching. However, as shown in FIG. Cuts occur, the resist 5 becomes thinner, and each of the etching patterns 31 and 41 may become thinner than desired. For this reason, there is a problem that a conversion difference occurs between the resist pattern and the actually etched pattern.

Such a conversion difference is caused when the design rule is 0.35μ, for example.
The more severe the problem is, the more severe the problem is, as in the case of m, and the more the size is reduced to 0.2 μm.

Therefore, an etching method which does not cause such a conversion difference and can obtain a favorable etching pattern shape is desired.

[Object of the invention]

SUMMARY OF THE INVENTION The inventions of the present application have been made in the background described above, and an object of the invention is to provide a method of manufacturing a semiconductor device capable of forming a pattern capable of obtaining a good etching shape.

[Means for solving the problem]

The invention of claim 1 of the present application is a method for manufacturing a semiconductor device including a dry etching step of etching a silicon-based material to be etched, wherein the material to be etched has a wide area and a narrow area to be etched. And a method for manufacturing a semiconductor device, characterized in that etching is performed using a gas containing hydrogen bromide, nitrogen, and a gas that can generate fluorine radicals, and the above object has been achieved by this configuration. is there.

The invention according to claim 2 of the present application is a method for manufacturing a semiconductor device including a dry etching step of etching a silicon-based material to be etched, wherein the material to be etched comprises at least a refractory metal silicide in the uppermost layer. A method of manufacturing a semiconductor device, wherein a material to be etched is itself or a reaction product generated from the material to be etched by etching adheres to a resist side wall. Is achieved.

In the invention of claim 1, the silicon-based material to be etched is silicon (pure silicon such as polysilicon or single-crystal silicon, or a material obtained by doping impurities with these materials).
For example, doped polysilicon referred to as DOPOS), silicon alloy (silicon containing Al or Cu), silicon compound (oxide, nitride, metal silicon compound, etc.) are collectively referred to. In the first aspect of the present invention, the silicon-based material to be etched is preferably silicon such as polysilicon. In the invention of claim 1, the gas capable of generating fluorine radicals refers to a fluorine-containing gas capable of generating fluorine radicals during etching, for example, SF ₆ , NF ₃ , HF, F ₂ ,
ClF ₃ or the like can be used.

In the present invention, when using three kinds of mixed gas systems of HBr / N ₂ / gas capable of generating fluorine radicals (SF ₆ or the like) without any additional gas, the flow rate ratio is 27 to 33 / 1
It is preferable to be in the range of 8 to 22/18 to 22 (SCCM).

In the second aspect of the invention, the silicon-based material to be etched has the same meaning as in the first aspect of the invention, but the material to be etched in the second aspect of the invention has at least the uppermost layer made of a refractory metal silicide. It is. As the refractory metal silicide, silicide of W, TI, Mo, Ta or any other refractory metal can be used.

In the invention of claim 2, the material to be etched itself,
Or, a configuration in which a reaction product generated from the material to be etched by etching adheres to the resist side wall means that a sputter of the material to be etched itself or a reaction product generated at the time of etching from the material to be etched is applied to the resist side wall. A configuration is performed so as to adhere and exhibit a side wall protection action. It is not always clear whether the substance adhering to the resist side wall is the material to be etched itself or a reaction product generated during etching from the material to be etched, but in any case, it is included in the present invention. You. In order to allow the reaction product to adhere to the resist side wall, a means using a gas that reduces the vapor pressure of the reaction product with the material to be etched can be adopted as the etching gas. Preferred examples of such a gas include:
Examples thereof include HBr and bromine-containing gases such as Br ₂ , BBr ₃ , and SiBr ₄ . SF ₆ , NF ₃ , HF, F ₂ , ClF ₃
Such a gas that can generate a fluorine radical can be used alone, or preferably mixed with the above-mentioned bromine-containing gas.

In addition, a rare gas such as He, Ne, Ar, Xe, or Kr may be used as an etching gas so that the material to be etched itself adheres to the resist sidewall.

Furthermore, a mixed gas system in which a gas such as the above-mentioned bromine-containing gas, which lowers the vapor pressure of the reaction product, and a gas such as the above-mentioned rare gas can be used. A gas obtained by adding N ₂ or O ₂ gas or the like to a gas system can also be used.

(Operation)

According to the invention of claim 1 of the present application, the material to be etched can be patterned in a good shape, and particularly, good patterning can be achieved without using a carbon fluoride gas such as a so-called chlorofluorocarbon gas. Particularly, it is preferably applied to the etching of a heavy metal polycide structure which has conventionally mainly used a chlorofluorocarbon-based gas, and a good etching pattern can be formed.

According to the invention of claim 2 of the present application, the material to be etched can be patterned in a good shape, and in particular, the deterioration of the shape due to the conversion difference due to the so-called thinning or receding of the resist is prevented, and the desired pattern can be precisely formed. It is possible to form.

〔Example〕

Hereinafter, embodiments of each invention of the present application will be described. However, needless to say, each invention is not limited by each embodiment described below.

Embodiment 1 This embodiment embodies the invention of claim 1 of the present application and is particularly applied to a semiconductor device manufacturing technique.

More specifically, in the present embodiment, the above-described invention is applied to the case where a tungsten polycide structure is etched in manufacturing a semiconductor device. In particular, the present invention is used when a gate electrode structure is formed by a polycide structure.

The silicon-based material to be etched in this embodiment is the first material.
As shown in FIG. 1A, an SiO ₂ film as an insulating film 2 is formed on a silicon substrate as a substrate 1, and a DOPOS film as a silicon film 3 and a refractory metal silicide film 4 are further formed thereon. The material to be etched 10 is formed of a certain WSix (tungsten silicide) film, and has a so-called polycide structure.

In this embodiment, when dry-etching a silicon-based material to be etched, etching is performed using a gas containing hydrogen bromide, nitrogen, and at least a gas that can generate fluorine radicals. Specifically, the procedure was as follows.

That is, in this example, the etching conditions were as follows.

Etching gas: HBr / N ₂ / SF ₆ = 30/20/20 SCCM mixed gas system Gas pressure: 5 mTorr Microwave power: 250 mA RF bias power: 100 W As described above, in this embodiment, a gas that can generate fluorine radicals As SF ₆ which can easily generate fluorine radicals
This was added to the HBr / N ₂ gas system to obtain an etching gas.

When etched in a mixed gas system of only HBr / N ₂ containing no gas can result in fluorine radicals, the reaction product SiBr
The by-products of x and N ₂ are deposited on the side wall. The amount of the by-products depends on the area to be etched.
As shown in FIG. 6B by the reference numeral 6b, excessive deposition in a wide area to be etched causes a problem such as tapering of the shape. If SF ₆ is added, appropriate side wall protection can be performed. The deposit is presumed to be mainly composed of silicon nitride, which is presumably because the action of a gas (SF ₆ ) capable of generating fluorine radicals suppresses excessive generation of this deposit. Accordingly, a good anisotropic shape can be obtained.

That is, as shown in FIG. 1 (b), a protective film 6 having an appropriate thickness is formed on the side wall of the photoresist 5, and this is used as a mask to form a good refractory metal silicide (WSix) pattern 41 and silicon. (DOPOS) pattern 31 is obtained (see FIG. 1 (c)).

Accordingly, anisotropic processing of a silicon-based material (particularly, a tungsten polycide structure including WSix and polysilicon (particularly, DOPOS) in this embodiment) can be easily and favorably performed without using a problematic gas such as Freon. Can be performed.

As described above, in this embodiment, a gas (here, SF ₆₎ capable of easily generating at least F radicals is used as an etching gas in addition to an HBr / N ₂ -based mixed gas. Gas that can be used is added, thereby making it possible to proceed with etching while removing excessive deposits. Anisotropic etching of the shape can be realized.

Example 2 This example embodies the invention of claim 2 of the present application, and is applied to etching of a tungsten polycide structure in the manufacture of a semiconductor device, as in Example 1.

The material to be etched in this embodiment is shown in FIG.
As shown in FIG. 2, at least the uppermost layer is made of a refractory metal silicide 4. The etching in this embodiment is performed under the condition that the material to be etched itself or a reaction product generated by the etching adheres to the side wall of the resist 5.

More specifically, the silicon-based material to be etched in the present embodiment has the same structure as that in Embodiment 1,
As shown in FIG. 2A, an SiO ₂ film serving as an insulating film 2 is formed on a silicon substrate serving as a substrate 1, and a DOPOS film serving as a silicon film 3 and a refractory metal silicide film 4 serving as a silicon film are further formed thereon. And a WSix (tungsten silicide) film.

In this embodiment, an anisotropic etching is performed after a very thin protective film is formed on the side surface of the resist 5 by a sputter or a reaction product having a low vapor pressure at the beginning of the etching.

That is, in this embodiment, the sample to be etched is formed in advance as a tungsten polycide structure as shown in FIG.

Next, as a first step, etching (RIE) is performed under the following etching conditions.

Etching gas: HBr 10SCCM Gas pressure: 1.0 Pa RF power: 300 W Etching is performed under these conditions for 1 minute. By this etching, bromide of the WSix film, which is the refractory metal silicide 4, is sputtered. It is considered that this adheres to the side wall of the resist 5 thinly, thereby protecting the resist 5. This deposit is schematically shown in FIG. In any case, by etching under these conditions, the resist 5 does not recede even by a certain degree of ion bombardment (ion bombardment under normal conditions).

After performing the above processing, as the next second step,
Etching is performed under conditions that provide anisotropy. Thus, an etched pattern having a width corresponding to the patterned resist shape can be obtained. In FIG. 2 (c),
This is as shown in the figure as the refractory metal silicide pattern 41 and the silicon pattern 31. Therefore, in this embodiment, a pattern having a desired width corresponding to the resist width (a desired gate width in the case of forming a gate electrode structure) can be obtained in a good shape.

As described above, in this embodiment, in the initial stage of etching, a very thin protective film 6 is attached to the side wall of the photoresist pattern 5 by a sputter of the material to be etched itself or a reaction product having a low vapor pressure. Since the resist receding (resist thinning) in the formation etching is prevented, a good etched shape having a size corresponding to the original resist 5 obtained by patterning can be obtained.

In this embodiment, an HBr gas is used as an etching gas so that the vapor pressure of the reaction product with the material to be etched 10 is reduced, and the side wall of the resist 5 is mainly protected by the reaction product. Other appropriate conditions may be set. For example, as an etching gas, HBr / SF ₆ = 20/30 SCCM
Can be performed under the conditions of gas pressure 1.0 Pa and RF power 300 W,
Any condition can be used as long as anisotropic conditions can be realized.

Of course, the material to be etched 10 itself can be sputtered, and He, Ar, Xe, Kr
The present invention can also be implemented with a configuration using a rare gas such as.

Further, in addition to the above, a mixed gas of a gas that reduces the vapor pressure of a reaction product with the material to be etched 10 and the rare gas can be used, and N ₂ , O _2, etc. May be used as appropriate.

In each of Embodiments 1 and 2 described above, each invention was applied to the tungsten polycide structure. However, each invention is not limited to these embodiments, and is effective for other materials to be etched and the like within the scope of each invention. Needless to say, conditions can be appropriately selected according to the purpose.

〔The invention's effect〕

As described above, according to the first and second aspects of the present invention,
A silicon-based etching material can be patterned in a good shape. More particularly, according to the first aspect of the present invention, such a good etching shape can be obtained without using a fluorocarbon-based etching gas. In particular, according to the second aspect of the present invention, high-precision anisotropic processing can be achieved without changing the conversion due to the photoresist receding.

[Brief description of the drawings]

1 (a) to 1 (c) are cross-sectional views showing the steps of Example 1 in each step of a material to be etched. Second
(A)-(c) similarly show the process of Example-2. FIG. 3 and FIG. 4 are diagrams showing the prior art. 3 ... silicon (DOPOS), 4 ... refractory metal silicide (WSix), 5 ... photoresist, 6 ... adhered (deposited) matter, 10 ... material to be etched.

Claims (2)

(57) [Claims] 1. A method for manufacturing a semiconductor device comprising a dry etching step of etching a silicon-based material to be etched, wherein the material to be etched has a wide area and a narrow area to be etched, and A method for manufacturing a semiconductor device, wherein etching is performed using a gas containing hydrogen, nitrogen, and a gas that can generate fluorine radicals. 2. A method of manufacturing a semiconductor device comprising a dry etching step of etching a silicon-based material to be etched, wherein at least the uppermost layer of the material to be etched is made of a refractory metal silicide. A method of manufacturing a semiconductor device, wherein a material itself or a reaction product generated from a material to be etched by etching adheres to a resist side wall.