JP3246145B2 - Dry etching method - Google Patents

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, and more particularly to, for example, etching of a refractory metal polycide layer to reduce incident ion energy required when forming a refractory metal polycide gate electrode / wiring. The present invention relates to a method for improving a selectivity between a base and a resist mask and preventing particle contamination.

[0002]

2. Description of the Related Art Polycrystalline silicon has been widely used as a gate electrode and wiring material for semiconductor devices such as LSIs. In recent years, the design rule has been miniaturized from half micron to quarter micron, and as the demand for high-speed devices such as highly integrated memory devices has increased, the resistance value is about one digit lower than that of polycrystalline silicon. Refractory metal silicides are being used.
When forming a gate electrode using refractory metal silicide, consider the interface characteristics with the gate insulating film, which easily affects device characteristics and reliability. Containing polycrystalline silicon (DOP)
An OS) layer is formed, and a refractory metal silicide layer is stacked thereon. Such a laminated structure is collectively called polycide. Tungsten silicide as a refractory metal silicide (WSi _x) is common, this W
In particular the polycide having a Si _x referred to as tungsten polycide (W polycide).

[0003] Incidentally, the polycide layer has brought new difficulties to the dry etching process since anisotropic etching must be continuously performed on two different types of material layers. That is, the lower polycrystalline silicon layer has a higher etching rate due to the difference in vapor pressure of the halide as an etching reaction product, and a new reaction layer is formed at the interface between the polycrystalline silicon layer and the polycide layer. For example, undercuts, side etches, and the like are likely to occur in the formed pattern due to the formation of a pattern. These shape abnormalities cause a shift in the width of the channel region, an offset region into which impurities are not implanted during ion implantation for forming the source / drain regions, and a decrease in dimensional accuracy when forming the sidewalls for realizing the LDD structure. Let it. There is also a problem of an increase in wiring resistance due to a reduction in wiring cross-sectional area, and none of these methods is acceptable for deep submicron devices.

Conventionally, a gas widely used as an etching gas for polycide is disclosed in, for example, Monthly Semiconductor World Magazine (Press Journal), Oct. 1989.
As reported in Monthly Pages 126 to 130, it is a chlorofluorocarbon (CFC) gas represented by Freon 113 (C ₂ Cl ₃ F ₃ ). This is because the reaction in the radical mode and the reaction in the ion assist mode both proceed because the F atom and the Cl atom coexist in the molecule, and the carbon-based plasma polymer is deposited to form the side wall protective film. Anisotropic etching is possible.

However, it has been pointed out that the CFC gas contributes to destruction of the ozone layer on the earth, as is well known, and in the field of dry etching, from the viewpoint of environmental protection, an etching gas and There is an urgent need to establish a technology for use, that is, a defluorocarbon process.

[0006] Such a demand for finer design rules,
In recent years, there has been an attempt to use a Br-based compound as a main etching species from the viewpoint of chlorofluorocarbon removal. For example, J.Vac.
Sci.Technol. , A8 (3) , May / Jun 1990, p1696, Digest
of Papers 1989 2nd MicroProcess Conference, p19
0, or HBr in Japanese Patent Application Laid-Open No. 02-89310.
N ⁺ type polycrystalline silicon gate electrode etching using Al and Br ₂ has been reported. Br has a large ionic radius,
It does not easily penetrate into the crystal lattice or crystal grain boundaries of the silicon-based material layer. Therefore, there is little concern that a silicon-based material layer is isotropically etched without control like a fluorine radical (hereinafter, referred to as F ^*, and other radical species will be similarly described). Anisotropic etching can proceed. Further, as is clear from the fact that the interatomic bond energy of the Si—O bond is much larger than that of the Si—Br bond, a high selectivity with respect to the gate insulating film made of SiO ₂ can be achieved. Further, since the surface of the resist mask can be coated with a CBr _x -based polymer having a low vapor pressure, a feature of the Br-based etching gas is that the selectivity with respect to the resist can be improved.

As another measure against CFC removal, CFC1
The etching of the W polycide layer by using a Cl ₂ / CH ₂ F ₂ mixed gas system in place of 13 is performed, for example, in p.50 of the 52nd Annual Meeting of the Japan Society of Applied Physics (Autumn Meeting 1991).
8. There is a report in lecture number 9a-ZF-6. By optimizing the mixing ratio of the gas, anisotropic etching can be performed using a carbon-based polymer derived from CH ₂ F ₂ for the side wall protective film.

Further, instead of achieving high anisotropy in the sidewall protective film by depositing a polymer product, an attempt has been made to achieve this by cooling the substrate to be etched at a low temperature. This process, called so-called low-temperature etching, is a method of controlling a substrate to be etched at 0 ° C. or lower to freeze or suppress a radical reaction at a lower portion of a resist pattern to prevent a shape abnormality such as an undercut. For example, in the 35th Federation of Applied Physics-related Lectures (Spring Annual Meeting, 1988), p495, Lecture No. 28a-G-2, the wafer was cooled to −130 ° C. and silicon was formed using SF ₆ gas. Examples have been reported in which trench etching of a substrate and etching of an n ⁺ -type polycrystalline silicon layer were performed.

[0009]

As described above, although processes have been proposed in consideration of CFC removal in the past, each of the above-described dry etching methods still has problems to be solved. First, applying the process using HBr gas for etching the W polycide layer, it is sputtered a large amount of WBr _x during the etching of the upper layer of WSi _x, which is attached to the etch chamber wall since a small vapor pressure, the particle level make worse. In addition, there is a problem in that the etching rate is basically lowered because a Br-based chemical species having low reactivity is used as an etchant.

[0010] On the other hand, when etching is performed on a Cl ₂ / CH ₂ F ₂ mixed gas system, there is a problem that the deposition of a carbon-based polymer tends to be excessive. That is, CH ₂ F ₂ is C ₄ F ₈ ,
_{C 2 Cl 2 F 4 (CFC114} ) or CCl ₄ and the like of the reaction product in comparison to many gases, it etching rate with this the incident ions is low, for example 1988 Dry Process Symposium Abstracts p74, II-8 Reports. Therefore, the use of CH ₂ F ₂ gas has a great risk of leaving problems of particle contamination and etching rate.

In contrast to the above two methods, low-temperature etching is considered to be one of the most effective means of the CFC removal process. However, if the achievement of high anisotropy depends only on freezing or suppression of the radical reaction, temperature control at an extremely low temperature level which requires cooling with liquid nitrogen is required. For this reason, problems on the device such as maintenance of the cooling device and reliability of the vacuum seal portion occur separately. In addition, a decrease in throughput cannot be overlooked, for example, a long time is required for the cooling of the substrate to be etched and the subsequent temperature raising step.

It is therefore an object of the present invention to enhance various difficult-to-parallel characteristics such as a selectivity to a resist mask, a selectivity to a base material layer, high anisotropy and low contamination while securing a practical etching rate. It is an object of the present invention to provide a method of removing and dry-etching a refractory metal polycide layer which can be performed in a practical temperature range.

[0013]

The dry etching method of the present invention has been proposed in order to solve the above-mentioned problems, and comprises forming a polycide layer formed on a substrate by using at least one of alcohol, ether and ketone. The etching is performed using an etching gas containing one type of compound.

Further, the present invention provides a method for forming a refractory metal polycide layer formed on a substrate by using an etching gas containing a fluorine-based gas such as SF ₆ and at least one compound of alcohol, ether and ketone. A first etching step of etching the upper refractory metal silicide layer to a thickness not exceeding the thickness of the upper refractory metal silicide layer; And a second etching step of etching the lower portion and the underlying polycrystalline silicon layer.

Further, according to the present invention, a refractory metal polycide layer formed on a substrate is coated with a fluorine-based gas such as SF ₆ and at least one of alcohol, ether and ketone.
A first etching step of etching an upper refractory metal silicide layer to a thickness substantially not exceeding its thickness using an etching gas containing a compound of the type described above, a chlorine-based gas, alcohol, ether and A second etching step of etching the remaining portion of the refractory metal silicide layer in the thickness direction and the underlying polycrystalline silicon layer using an etching gas containing at least one compound of ketones; Is what you do.

Further, according to the present invention, there is provided a dry etching method for a refractory metal polycide layer formed on a substrate, wherein free sulfur (S) is contained in plasma under discharge ionization conditions.
Is etched while depositing sulfur on a substrate to be etched using a sulfur-based compound capable of releasing sulfur and an etching gas containing at least one compound of alcohol, ether and ketone.

Examples of the alcohol, ether and ketone used in the present invention include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol and t-butanol.
Butanol, methyl ethyl ether, diethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like can be used alone or in combination.

As the sulfur-based compound used in the present invention, which can release free sulfur into plasma under discharge ionization conditions, an SX-based gas having an X / S ratio of less than 6 (X is a halogen element or hydrogen) Represents, for example, S ₂ Cl ₂ , S ₃
Sulfur chloride gas such as Cl ₂ and SCl ₂ , S ₂ Br ₂ , S
₃ Sulfur bromide gas such as Br ₂ , SBr ₂ , S ₂ F ₂ , S
_{F 2, SF 4, S 2} F 10 fluoride other than SF _6, such as Iougasu, and can be exemplified H ₂ S, may be used singly or in combination. SF ₆ gas, which is well known as a sulfur fluoride compound, has an F / S ratio of 6, does not release free sulfur into plasma under discharge ionization conditions, and is not compatible with the spirit of the present invention. .

[0019]

The point of the present invention is to enhance the film quality of the carbon-based plasma polymer, which is an etching reaction product that contributes as a side wall protective film, to increase the ion impact resistance, and to obtain a sufficient anisotropy even if the deposition amount is reduced. The purpose of the present invention is to achieve processing and achieve a selectivity ratio to a resist pattern and a selectivity ratio to a base.

Alcohols, ethers and ketones (each represented by a general molecular formula C _x H _y O _z ) used as an etching gas in the present invention are composed of C—H bonds and C—H bonds generated by dissociation in discharge plasma. Atomic groups having a polarization structure such as O-bonds increase the degree of polymerization of the carbon-based plasma polymer which is a plasma polymerization product, and increase resistance to ion incidence and radical attack.

In addition, H atoms and CO released and generated in the discharge plasma capture the halogen radicals simultaneously introduced as etching species, thereby reducing the halogen element concentration in the carbon-based plasma polymer. An atomic group having the above-mentioned polarization structure is introduced into the plasma polymer molecular chain. Recent studies have revealed that the carbon-based plasma polymer having such a structure has higher chemical and physical stability than the conventional carbon-based plasma polymer having a repeating unit structure of-(CX) _n-. Yes (where X
Represents a halogen element, and n represents a natural number.) Compared with the bond energy between two atoms, this indicates that the C—O bond (1077 kJ / mol) is a C—C bond (607 kJ / mol).
mol).

As described above, since the film quality of the carbon-based plasma polymer itself is strengthened, the incident ion energy required for anisotropic etching can be reduced, and the selectivity to the resist mask and the underlying material layer is improved. In addition, reattachment to the side wall due to underlayer sputtering and plasma damage to the underlayer material layer are reduced. Further, even if the deposition amount of the carbon-based plasma polymer is reduced, sufficient anisotropic processing can be achieved, so that particle contamination can be reduced.

The present invention is based on the above principle, but also proposes a method aiming at further anisotropic processing, low particle contamination and high selectivity. One is to switch the etching gas composition between the etching of the refractory metal silicide layer and the etching of the polycrystalline silicon layer.
Step etching is performed.

[0024] The two-step process, especially assuming that the refractory metal silicide layer of the upper layer to form a large fluorine-based reaction product of the vapor pressure, such as WF _x, a in the first etching step F ^* It is intended to increase the etch rate of this layer by providing and increase the overall process throughput. Also, along with this,
In the etching step, F ^* is excluded from the reaction system,
The undercut of the lower polycrystalline silicon layer and the improvement of the selectivity to the gate insulating film are aimed at.

One method for realizing this process is to use any one of the above-mentioned alcohols, ethers and ketones as an etching gas for the refractory metal silicide layer and a fluorine-based gas such as SF _6. And a bromine-based gas is used as an etching gas for the polycrystalline silicon layer. The etching mechanism and merits of the Br-based etchant are as described above.

Another method of the two-step etching is that, in the above-mentioned second etching step, any one of the above-mentioned alcohols, ethers and ketones is used as an etching gas for the polycrystalline silicon layer, such as Cl ₂ . An etching gas containing a suitable chlorine-based gas is used. The Cl-based gas has an effect of increasing the etching rate of the polycrystalline silicon layer by the ion assist effect of Cl ⁺ . At this time, there is no fear that the anisotropy of the undercut, which is a concern due to the improvement of the reactivity, is reduced because the above-described strengthening of the strong sidewall protective film is continued.

The second of the methods aiming at further anisotropic processing, low particle contamination and high selectivity is to release any one of alcohols, ethers and ketones into the plasma under discharge ionization conditions. Is to add a sulfur-based compound capable of releasing sulfur (S) and etch while depositing sulfur on the substrate to be etched. In this case, in addition to the carbon-based plasma polymer which is an etching reaction product, the deposition of sulfur can be used as the sidewall protective film. Therefore, the incident ion energy can be further reduced, and a high selectivity and low plasma damage can be achieved. Further, the deposition amount of the carbon-based plasma polymer can be relatively reduced, and the particle contamination can be reduced accordingly. Sulfur can be deposited on the surface of the substrate by controlling the temperature of the substrate to be etched to room temperature or lower, for example, 25 ° C. or lower. In addition, the deposited sulfur can be easily removed by sublimation by heating the substrate to be etched to about 90 ° C. or more after etching, so that it does not remain on the substrate to be etched, and the sulfur itself does not become a source of particle contamination. .

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Embodiment 1 In this embodiment, the present invention is applied to gate electrode and wiring processing.
This is an example in which a W polycide layer is etched using a mixed gas of HBr / SF ₆ / CH ₃ OH (methanol, bp = 64.6 ° C.). This process will be described with reference to FIG.

First, as shown in FIG.
After a gate insulating film 2 made of SiO ₂ is formed to a thickness of 10 nm on a silicon substrate 1 having an inch diameter, a refractory metal polycide layer 5 is formed thereon, and a resist mask 6 patterned in a predetermined shape is formed thereon. The substrate to be etched is used. The refractory metal polycide layer 5 is a 100 nm-thick polycrystalline silicon layer 3 doped with an n-type impurity.
When is obtained by a refractory metal silicide layer 4 are sequentially deposited laminate consisting of a thickness of 100nm for example WSi _x. The resist mask 6 is, for example, a negative-type three-component chemically amplified photoresist (manufactured by Shipley, trade name: SA).
L-601) was applied thereto, and subjected to KrF excimer laser exposure to form a pattern with a pattern width of 0.35 μm. The active layers and the like in the silicon substrate 1 are not shown.

Next, the substrate to be etched is set in, for example, an ECR plasma etching apparatus of a high frequency bias application type, and the refractory metal polycide layer 5 is etched using the resist pattern 6 as a mask. The etching conditions at this time were as follows, for example. HBr flow rate 30 sccm SF ₆ flow rate 30 sccm CH ₃ OH flow rate 10 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 150 W (13.56 MH)
z) Substrate temperature Room temperature Since CH ₃ OH is liquid at room temperature, CH ₃ O
The H container is heated by a heater, vaporized, and introduced into the etching chamber. At this time, the introduction piping system was heated by a ribbon heater or the like to prevent condensation due to condensation of CH ₃ OH inside the piping.

In this etching process, a radical reaction using F ^* as a main etching species dissociated and generated from SF ₆ by ECR discharge proceeds with a mechanism assisted by ions such as Br ⁺ , SF _x ^+, etc. The melting metal polycide layer 5 becomes WF _x , SiF _x , and SiBr _{x and is} selectively removed. At the same time, CF _x and CBr _x derived from the decomposition product of the resist mask 6 are generated, and these have a polarized structure such as a CH bond or a CO bond, which is a dissociation product of CH ₃ OH. Reacts with atomic groups to produce a carbon-based plasma polymer. This carbon-based plasma polymer is CH ₃
Since the degree of polymerization is high and the content of halogen elements is small as compared with the conventional etching gas containing no OH, it is strong. However, since the surface of the resist mask 6 is also covered with CF _x and CBr _x , the generation amount of the carbon-based plasma polymer is not so large as in the past. This carbon-based plasma polymer is deposited on the pattern side wall to form a side wall protective film 7 as shown in FIG. 1 (b). Although the deposited amount is small, it exhibits high etching resistance and contributes to anisotropic processing.
The sidewall protective film 7 also includes WBr _x and WO _x generated during the etching of the refractory metal silicide layer 4.

As a result of this etching, as shown in FIG. 1B, a refractory metal polycide pattern 5a having a good anisotropic shape was formed immediately below the resist mask 6. Further, since the etching reaction system contains a Br-based chemical species, a high selectivity can be obtained even for the underlying gate insulating film 2. In the drawings, each material pattern after etching has a new reference number by adding a suffix a to the reference number of the corresponding original material layer.

After the etching, the substrate to be etched is transferred to a plasma ashing device attached to the above etching device, and the resist mask 6 and the side wall protective film 7 are removed by O ₂ plasma ashing. Finally, ashing spin cleaning with pure water is performed to remove ashing residues and dried. Megasonic cleaning and brush scrubbing are also effective for removing ashing residues. As a result, as shown in FIG. 1 (c), a gate electrode / wiring composed of a refractory metal polycide pattern 5a having a good shape with a width of 0.35 μm was obtained.

[0035] Example 2 This example etching of the same refractory metal polycide layer 2 staged, after first etching the upper side of WSi _x in SF ₆ / CH ₃ OH mixture gas, the HBr, the lower side This is for etching the polycrystalline silicon layer. This process will be described with reference to FIG. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals.

FIG. 2A shows a substrate to be etched in this embodiment.
Shown in Since this is the same as FIG. 1A, the description is omitted. This was set in a high-frequency bias application type ECR plasma etching apparatus, WSi _x in the following conditions as an example
The first etching is performed on the refractory metal silicide layer 4 made of to a depth that does not substantially exceed the layer thickness. SF ₆ flow rate 35 sccm CH ₃ OH flow rate 15 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 150 W (13.56 MH)
z) Substrate temperature to be etched Room temperature

In this etching process, as shown in FIG. 2B, high-speed etching is performed by a large amount of F ^* generated by dissociation from SF _{6. At} the same time, the carbon-based plasma polymer forming the sidewall protective film 7 is strengthened. Therefore, the high-melting-point metal silicide pattern 4a that also achieves high anisotropy and has a good shape is formed. The end point of the first etching is when the surface of the underlying polycrystalline silicon layer 3 is exposed in the etching region where the resist mask 6 is not formed, which is monitored by a change in the emission spectrum intensity of SiF or the like. It is possible. However, in the actual process, due to the microloading effect and the like, the remaining portion 4b of the refractory metal silicide layer
Some are seen.

Therefore, as an example, the etching conditions are switched as follows, and the remaining portion 4 of the refractory metal silicide layer is changed.
b and the polycrystalline silicon layer 3 are subjected to a second etching. HBr flow rate 50 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 150 W (13.56 MH)
z) Substrate temperature to be etched Room temperature

In this etching process, the reaction proceeds with Br ^* as the main etching species. Here, since F ^* does not exist, no undercut is formed in the high melting point metal polycide pattern 5a as shown in FIG.
Since there is no involvement of ^*, a high selectivity and a low damage property to the underlying gate insulating film 2 are secured.

After the completion of the etching, ashing and washing were performed in the same manner as in Example 1 to obtain a gate electrode and a wiring composed of a refractory metal polycide pattern 5a having a pattern width of 0.35 μm.

[0041] EXAMPLE 3 This example in a method of two-step etching the refractory metal polycide layer, a refractory metal silicide layer SF ₆ /
CH ₃ OCH ₃ (dimethyl ether, bp = −24 ° C.)
The mixed gas and the polycrystalline silicon layer are formed by Cl ₂ / HBr / CH ₃
This is an example in which etching is performed using an OCH ₃ mixed gas, which will also be described with reference to FIG.

The substrate to be etched shown in FIG.
The refractory metal silicide layer 4 was just etched under the following conditions as an example by setting it in an F bias application type ECR etching apparatus. SF ₆ flow rate 35 sccm (CH ₃ ) ₂ O flow rate 15 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 150 W (13.56 MH)
z) Substrate temperature to be etched Room temperature

The mechanism of the etching under the above conditions is almost the same as that of the preceding stage of the second embodiment. As a result, a refractory metal silicide pattern 4a having a favorable anisotropic shape is formed as shown in FIG.
The remaining portion 4b of the refractory metal silicide layer is also observed on the exposed polycrystalline silicon device 3.

Subsequently, as one example, the etching conditions are switched as follows, and the remaining portion 4 of the refractory metal silicide layer is changed.
b and the polycrystalline silicon layer 3 are etched. Cl ₂ flow rate 20 sccm HBr flow rate 20 sccm (CH ₃ ) ₂ O flow rate 10 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 120 W (13.56 MH)
z) Substrate temperature to be etched Room temperature

In this etching process, Cl ₂ is added to the etching reaction system, so that an ion assist effect by Cl ⁺ can be expected. For this reason, the etching rate can be improved as compared with the latter-stage etching of the second embodiment. In the present embodiment, the carbon-based plasma polymer, that is, the side wall protective film 7 is continuously strengthened by the introduction of ether also in the second etching step, so that the substrate bias required for anisotropic processing can be reduced. It is possible. As a result, as shown in FIG.
A refractory metal polycide pattern 5a having an anisotropic shape with a good width was obtained, and the underlying gate insulating film 2 was less damaged.

Embodiment 4 In this embodiment, the refractory metal polycide layer is formed of SF ₆ / S
₂ Br ₂ / CH ₃ COCH ₃ (acetone, bp = 56.
5 ° C.) This is an example of low-temperature etching using a mixed gas,
This will be described again with reference to FIG.

The substrate to be etched shown in FIG. 1A was set in a high frequency bias application type ECR plasma etching apparatus, and as an example, the high melting point metal polycide layer 5 was etched under the following conditions. SF ₆ flow rate 20 sccm S ₂ Br ₂ flow rate 20 sccm CH ₃ COCH ₃ flow rate 10 sccm Gas pressure 0.67 Pa Microwave power 850 W (2.45 GHz) RF bias power 100 W (13.56 MH)
z) Temperature of substrate to be etched −50 ° C. Since CH ₃ COCH ₃ is also liquid at room temperature, it is introduced into the etching chamber in the same manner as in CH ₃ OH in the first embodiment.

The temperature of the substrate was controlled by circulating and supplying an ethanol-based refrigerant from a chiller provided outside the etching chamber to a cooling pipe in the wafer stage. Of the above gas compositions, S ₂ Br ₂ supplies Br-based chemical species and contributes to improvement of the selectivity with the gate insulating film 2, but free S (S) under discharge dissociation conditions. It plays an important role in releasing. That is, in this embodiment, the composition ratio of the halogen element is small, and in addition to the strong carbon-based plasma polymer having a C—O bond and a C—H bond incorporated in its structure, this S is also a low-temperature cooled substrate to be etched. It is deposited on the upper surface and participates in the formation of the sidewall protective film 7. As described above, when the deposition of S can be used together, the deposition of the carbon-based plasma polymer required for securing the anisotropy can be relatively reduced. As a result, it is effective in reducing the particle level in the etching chamber. This is because the deposited S disappears by sublimation when the substrate to be etched is heated to about 90 ° C. or more after the etching.

Further, in this embodiment, since the radical reaction on the pattern side wall is suppressed by lowering the temperature, good anisotropic etching can be performed despite the fact that the RF bias power is considerably reduced as compared with the previous embodiment. Was completed. The lower bias has an advantage that the selectivity with respect to the underlying gate insulating film is improved, and the damage is reduced more thoroughly.

After completion of the etching, the side wall protective film 7 was removed by O ₂ plasma ashing and pure water cleaning.
As shown in (c), a refractory metal polycide pattern 5a having a good anisotropic shape with a width of 0.35 μm is obtained. As described above, S is sublimated when heated to a temperature of about 90 ° C. or higher by plasma radiation heat or reaction heat, but is also removed by an oxidation reaction by O ^{* in the} ashing process, causing any particle contamination. Will not be.

Although the present invention has been described with reference to the four embodiments, the present invention is not limited to these embodiments.

For example, as the fluorine-based gas,
SF shown₆In addition to NF_Three, ClF _Three, XeF_TwoEtc. F original
Compounds having a parent can be used.

Odor used for etching the polycrystalline silicon layer
As the base gas, in addition to HBr, Br _Two, BBr_ThreeUse
It is also possible. These compounds are liquid at room temperature.
Therefore, appropriate means such as heating evaporation, He gas bubbling, etc.
What is necessary is just to vaporize and introduce it into an etching chamber.

Similarly, as the chlorine-based gas used for etching the polycrystalline silicon, in addition to Cl ₂ , HCl and BCl ₃
Etc. can be used.

As examples of alcohols, ethers and ketones, and examples of sulfur-based compounds capable of releasing free sulfur under discharge dissociation conditions, the above-mentioned compounds can be appropriately used in addition to the compounds exemplified in the examples. .

Various combinations of the above compounds are possible.
However, based on the spirit of the present invention, at least
When etching the silicide layer
To F ^*A compound capable of releasing
At the time of etching of crystalline silicon, Br^*Let out
That the compound contains
It is preferable from the viewpoint of achieving both high selectivity and high selectivity.

In addition, when a rare gas such as He or Ar is used as an additive gas, each effect such as sputtering, cooling, dilution, and stability of discharge can be expected.

In particular, if N ₂ is introduced as an additive gas,
The reaction with S atoms released from the sulfur-based compound and the deposition of a sulfur nitride-based compound such as an inorganic polymer of polythiazyl (SN) _n can be used as a sidewall protective film. This etching method is also a method excellent in realizing a high selectivity, a high anisotropy and a low damage property. Polythiazyl, like S, is deposited when the substrate to be etched is cooled to room temperature or lower, and sublimates when heated to about 150 ° C. or higher, and does not become a particle contamination source.

The refractory metal silicide layer is made of the above-described WSi
Besides MoSi _x of _x, TaSi _x, it may be a TiSi _x and various silicide layer.

As a lower layer of the refractory metal polycide layer, it is usual to use polycrystalline silicon. However, as disclosed in Japanese Patent Application Laid-Open No. 63-163 filed earlier by the present applicant, amorphous silicon is used. May be used. The etching characteristics of amorphous silicon are almost the same as those of polycrystalline silicon. At the stage where this amorphous silicon finally functions as the gate electrode and wiring of the MOSFET, the amorphous silicon is changed to polycrystalline silicon by the heat treatment for activating the implanted impurities, and thus has a polycide structure.

Further, it goes without saying that the etching apparatus to be used, the etching conditions, the configuration of the substrate to be etched, and the like can be appropriately changed.

[0062]

As is apparent from the above description, the present invention provides a method of etching a refractory metal polycide layer by using an etching gas containing any one of alcohol, ether and ketone, thereby providing a carbon layer functioning as a sidewall protective film. Since the film quality of the system plasma polymer can be enhanced, the incident ion energy required for anisotropic etching can be reduced. Therefore, the selectivity with respect to the underlying gate insulating film is improved, the damage to the gate insulating film can be reduced, and the problem of reattachment due to underlying sputtering can be solved. Of course, the selectivity with respect to the resist mask is also improved, which is advantageous for reducing the dimensional conversion difference due to the receding of the resist pattern or the like.

Since the film quality of the sidewall protective film becomes strong, undercut does not occur even if the deposition amount is reduced, and a high etching rate can be obtained while securing a practical etching rate. Can be achieved.

Also, since the amount of deposition of the carbon-based plasma polymer forming the sidewall protective film can be reduced, the particle level in the substrate to be etched and the etching chamber can be reduced, and a clean process can be realized.

Since no CFC-based gas is used,
This makes it possible to remove the chlorofluorocarbon and contribute to environmental cleanup.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic cross-sectional views illustrating Examples 1 and 2 to which the present invention is applied in the order of steps, and FIG. 1A is a schematic cross-sectional view including a polycrystalline silicon layer and a refractory metal silicide layer on a base gate insulating film. (B) A state in which a high melting point metal polycide layer is etched to form a high melting point metal polycide pattern, and (c) is a state in which a resist mask is formed. The film is removed to complete the refractory metal polycide pattern.

FIGS. 2A and 2B are schematic cross-sectional views for explaining Examples 3 and 4 to which the present invention is applied in the order of steps, and FIG. (B) shows a state in which the polycrystalline silicon layer is exposed by etching the refractory metal silicide layer, and (c) shows a state in which the polycrystalline silicon layer is exposed. Etched to form a refractory metal polycide pattern,
(D) shows a state in which the resist mask and the side wall protective film are removed to complete the refractory metal polycide pattern.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 gate insulating film 3 polycrystalline silicon layer 4 refractory metal silicide layer 5 refractory metal polycide layer 6 resist mask 7 sidewall protective film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H01L 21/28

Claims (4)

(57) [Claims] 1. A dry etching method for a high melting point metal polycide layer formed by laminating a polycrystalline silicon layer and a high melting point metal silicide layer on a substrate in this order, wherein at least one selected from the group consisting of alcohol, ether and ketone. A dry etching method characterized by performing etching using an etching gas containing various kinds of compounds. 2. A dry etching method for a refractory metal polycide layer formed by laminating a polycrystalline silicon layer and a refractory metal silicide layer on a substrate in this order, comprising a group consisting of a fluorine-based gas, alcohol, ether and ketone. A first etching step of etching the refractory metal silicide layer to a thickness substantially not exceeding its thickness using an etching gas containing at least one compound selected from the group consisting of: A dry etching method comprising a second etching step of etching a remaining portion of the refractory metal silicide layer in a thickness direction and the polycrystalline silicon layer using an etching gas. 3. A dry etching method for a high melting point metal polycide layer formed by laminating a polycrystalline silicon layer and a high melting point metal silicide layer on a substrate in this order, the method comprising a group consisting of a fluorine-based gas, alcohol, ether and ketone. A first etching step of etching the refractory metal silicide layer to a thickness substantially not exceeding its thickness using an etching gas containing at least one compound selected from the group consisting of: a chlorine-based gas; A second step of etching the remaining portion of the refractory metal silicide layer in the thickness direction and the polycrystalline silicon layer using an etching gas containing at least one compound selected from the group consisting of alcohol, ether and ketone. A dry etching method, comprising: 4. A dry etching method for a refractory metal polycide layer formed by laminating a polycrystalline silicon layer and a refractory metal silicide layer on a substrate in this order, wherein free sulfur is released into plasma under discharge ionization conditions. Etching by depositing sulfur on a substrate to be etched using an etching gas containing a sulfur-based compound that can be used and at least one compound selected from the group consisting of alcohol, ether and ketone. Item 6. The dry etching method according to Item 1.