JPH10312993A - Plasma-etching method of organic antireflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma-etching method with which the organic antireflection film can be patterned in a highly precise manner on a base material layer having a stepping. SOLUTION: An organic antireflection film 6 is plasma-etched by a halogen compound, having a thionyl group or a sulfuryl group and a halogen atom in a molecule, such as SOCl-containing an etching gas, for example. As a result, a solid sidewall protective film 8, which is mainly composed of a carbon polymer having superior etching resistance, is formed on the side face of a resist pattern 7 and the organic antireflection film 6 which is being patterned, and an undercut and the differences in dimensional conversion can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method for an organic anti-reflection film used in a manufacturing process of a semiconductor device or the like, and more particularly, to a highly accurate patterning of an organic anti-reflection film by reducing a dimensional conversion difference. The present invention relates to a plasma etching method for an organic anti-reflection film which enables the above.

[0002]

2. Description of the Related Art As the integration and performance of semiconductor devices such as LSIs increase, the design rules become finer, and the wavelength of exposure light during lithography, which determines the minimum line width, increases. The wavelength has been shortened. For example, a stepper used in lithography of a semiconductor device having a design rule of a sub-half micron region uses a KrF excimer laser (λ = 248 nm) as an exposure light source, and uses a KrF excimer laser as an exposure light source.
A lens having an NA of about 37 to 0.50 is used.

[0003] In this case, the exposure light source has a single wavelength, and it is known that when exposure is performed at a single wavelength, a phenomenon called a standing wave effect occurs. The cause of the standing wave effect is that multiple interference of exposure light occurs in the transparent resist film. That is, the incident light interferes with the reflected light from the interface between the resist film and the underlying material layer, and a periodic light intensity distribution occurs in the thickness direction of the resist film. As a result, the amount of absorbed light, which is the energy for photoreacting the resist, changes depending on the resist film thickness. The amount of absorbed light represents the amount of light absorbed by the resist film itself, excluding reflection on the resist film surface, absorption on the surface of the underlying material layer, re-emission from the resist film surface, and the like.

[0004] The degree of change in the amount of absorbed light varies slightly depending on the type and step of the underlying material layer.
It becomes difficult to control the size of the resist pattern obtained after development. This tendency is common to all resist types, and becomes more apparent as the pattern width becomes smaller.

In an actual semiconductor device, for example, a gate electrode made of tungsten polycide and a wiring extending therefrom (hereinafter referred to as a gate electrode / wiring) may be patterned. At this time, the problem that the WSi ₂ of the tungsten polycide upper layer has a high reflectance and a step exists in the bird's beak portion of the element isolation region (LOCOS), and the fluctuation of the standing wave effect significantly occurs is avoided. Can not do.

Therefore, as an effective method for suppressing the standing wave effect, it is indispensable to employ an antireflection film. As the antireflection film, those made of organic and inorganic materials are known. The organic material is a polymer containing a dye that absorbs at the exposure wavelength, and can almost completely block reflection from the underlying material layer. One inorganic material is Ti
N and SiO _x N _y : H are known, and among them, SiO _x N _y : H which can obtain a desired optical constant (n, k) by controlling CVD conditions is considered to be promising.

[0007]

Although such an antireflection film is effective for reducing the dimensional conversion difference, its etching process has several problems. First, when SiO _x N _y : H is used, the composition is S
Since it is located in the middle of i, SiO _2, or Si ₃ N ₄ , when Si etching conditions are employed for etching the antireflection film, shape abnormalities and decrease in selectivity due to release of oxygen and the like are likely to occur. Further, when the SiO ₂ etching condition is adopted, a tapered shape is easily formed, and a dimensional conversion difference increases.

On the other hand, when an organic antireflection film is used, patterning is performed using an etching gas system mainly composed of oxygen. However, since the composition of the antireflection film is close to the composition of the resist, the etching selectivity is low. However, when the antireflection film is etched, the thickness of the resist film is greatly reduced, and a problem arises in that a dimensional conversion difference has already occurred in the resist mask itself when the original underlying material layer is etched. In the case where the underlying material layer is a substrate to be etched having a step due to LOCOS or a step due to DRAM cell, a film thickness difference occurs when an organic antireflection film is applied thereon. For this reason, excessive etching is applied to the thin portion of the organic antireflection film while the film thickness of the organic antireflection film is in progress, and a remarkable pattern narrowing (negative dimensional conversion difference) or undercut occurs in this portion. .

The present invention is proposed in view of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide a plasma etching method for an organic antireflection film capable of reducing a dimensional conversion difference regardless of the level difference of a base material layer.

[0010]

The present invention proposes to solve the above-mentioned problems. That is, the method for plasma-etching an organic anti-reflection film of the present invention comprises the steps of: forming an organic anti-reflection film formed on a base material layer into a halogen having one of a thionyl group and a sulfuryl group and a halogen atom in a molecule; In addition to using an etching gas containing a system compound, etching is performed while depositing a carbon-based polymer on a substrate to be etched.

According to another plasma etching method for an organic anti-reflection film of the present invention, an organic anti-reflection film formed on a base material layer is provided with one of a thionyl group and a sulfuryl group and a halogen atom in a molecule. While using an etching gas containing a halogen-based compound having atoms and a sulfur-based compound capable of releasing sulfur into plasma under discharge ionization conditions, a carbon-based polymer on a substrate to be etched,
It is characterized by etching while depositing a sulfur-based deposit.

Compounds having a thionyl group and a halogen atom in the molecule include SOF, SOCl, SOBr, SOC
l ₂ etc., the general formula SOX _n (X is F, Cl, Br and I
And n represents a natural number of 2 or less). Compounds having a sulfuryl group and a halogen atom in the molecule are
SO ₂ F ₂ , SO ₂ Cl ₂ , SO ₂ ClF, SO ₂ Br
Compounds represented by the general formula SO ₂ X ₂ such as F (X represents a halogen atom such as F, Cl, Br and I) are exemplified. These compounds may be used alone or as a mixture. Further, it may be used by mixing with another gas such as an oxygen-based gas.

During the etching of the organic antireflection film, it is desirable to control the temperature of the substrate to be etched to room temperature or lower. Here, the room temperature refers to a temperature in a clean room used in a normal semiconductor device manufacturing process. Although the lower limit of the temperature is not particularly limited, it is a design item determined by the temperature of the cooling medium usually used for cooling the substrate stage of the etching apparatus, the selection of the etching rate, and the like. Further, it is desirable to heat the substrate to be etched to at least 90 ° C. after the completion of the etching of the organic antireflection film. Although the upper limit of the heating temperature is not particularly limited, the upper limit temperature of the resist mask used for etching, for example, 18
A guideline is about 0 ° C.

Next, the operation will be described. In order to improve the etching selectivity between the organic antireflection film and the resist mask and to reduce the pattern conversion difference, the present inventor has strengthened the film quality of the carbon-based polymer which is a constituent material of the sidewall protective film. It has been found that increasing the etching resistance is extremely effective. That is, by increasing the etching resistance of the side wall protective film, the incident ion energy required for anisotropic processing can be reduced, the etching selectivity can be improved, and the resist mask can be prevented from receding. Further, the effect of protecting the pattern side wall from radical attack is enhanced, so that side etching can be prevented, and the pattern conversion difference can be reduced from this aspect as well.

The halogen-based compound having a thionyl group or a sulfuryl group and a halogen atom in the molecule employed in the present invention dissociates in plasma to generate free SO-based or SO ₂ -based chemical species and halogen. Among them, SO-based or SO ₂ -based chemical species are efficiently redissolved in plasma, particularly in high-density plasma, to generate oxygen-based chemical species, which serve as an etchant for the organic antireflection film. The other sulfur-based species generated by re-dissociation recombines with carbon or hydrocarbon fragments decomposed from the resist mask to form a strong carbon-based polymer having CS bonds. The carbon or hydrocarbon fragments decomposed from this resist mask are
Recombination and polymerization also occur with the halogen in the plasma, resulting in-(C
X ₂ ) A carbon-based polymer having _x − as the basic main chain structure is deposited on the substrate to be etched. Each of these carbon-based polymers has higher etching resistance than a polymer formed from only a decomposition product of a resist mask.

On the other hand, the plasma contains SO-based or SO-based gas.
_Although there are some undissociated _2- system species, these species have a polarized structure and therefore have high polymerization promoting activity. Therefore, the degree of polymerization of the carbon-based polymer deposited on the substrate to be etched as the sidewall protective film is increased. From this aspect as well, the film quality of the carbon-based polymer becomes strong and works in the direction of increasing the etching resistance of the sidewall protective film.

The present invention supplies both an etchant and a deposition product from a halogen-based compound having a thionyl group or a sulfuryl group and a halogen atom in the molecule as described above. The balance between the etchant and the deposition product to obtain an anisotropic shape can be achieved by controlling the source power of the plasma etching apparatus, the substrate bias, and the temperature of the substrate to be etched. The organic antireflection film can be patterned by a single gas of a halogen-based compound having a thionyl group or a sulfuryl group and a halogen atom.

As described above, the basic concept of the present invention is to enhance the etching resistance by strengthening the film quality of the carbon-based polymer. By using a mixed gas containing a sulfur-based compound capable of releasing sulfur into plasma under ionization conditions, a sulfur-based deposit is deposited on a substrate to be etched together with a carbon-based polymer, and is used as a sidewall protective film. This sulfur-based deposit is supplied in a small amount by the dissociation of a halogen-based compound having a thionyl group or a sulfuryl group and a halogen atom in the molecule, but the sulfur-based deposit can release sulfur into plasma under discharge ionization conditions. The addition of the compound makes this deposition more reliable.

The sulfur-based deposits include, in addition to elemental sulfur, sulfur nitride generated by reaction with nitrogen-based species in plasma, and (SN) _n , a polymerization product of sulfur nitride, that is, polythiazyl. . Among them, polythiazyl is an inorganic polymer stably existing at 208 ° C. under normal pressure and around 140 ° C. to 150 ° C. under ordinary reduced pressure conditions used for plasma etching, and has high ion impact resistance and radical attack resistance. The sulfur-based deposit can be easily removed by sublimation by heating the substrate to be etched after the completion of the etching, so that there is no possibility of causing contamination to the substrate to be etched. The sublimation temperature is about 90C for elemental sulfur and about 140-150C for polythiazyl. These sulfur-based deposits can be removed simultaneously with the ashing of the resist mask.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the plasma etching method of the organic antireflection film of the present invention can be performed using a conventional type etching apparatus such as a parallel plate type RIE etching apparatus. From the viewpoint of handling a substrate to be etched and high-precision and uniform etching processing, ECR (Electr
onCyclotron Resonance plasma etching equipment, MCR (Magnetically)
(Confined Reactor) etching equipment, helicon wave plasma etching equipment or ICP
(Inductively Coupled Plas
ma) It is desirable to use a low pressure / high density plasma etching apparatus such as an etching apparatus. In any of the plasma etching apparatuses, a high frequency power supply for applying a substrate bias to a substrate stage on which a substrate to be etched is mounted, and a refrigerant for cooling the substrate to be etched (for example,
It is desirable to provide a circulating means of Fluorinert (trade name), a heating means such as a resistance heater for heating, and a monopolar electrostatic chuck.

Embodiment 1 In this embodiment, a plasma etching method for an organic antireflection film of the present invention is used for processing a gate electrode made of tungsten polycide and a wiring extending from the gate electrode onto LOCOS, that is, processing of the gate electrode and wiring. This is an example of application, and this step will be described with reference to FIGS.

First, as shown in FIG. 1A, a LOCOS 2 serving as an element isolation region is formed on a semiconductor substrate 1 of silicon or the like by a conventional method, and a gate insulating film 3 is formed by thermal oxidation to a thickness of 5 n.
m, 100 nm of polycrystalline silicon 4 by low pressure CVD,
It was sequentially formed to a thickness of likewise 100nm the WSi _x 5 by plasma CVD. In this embodiment, a tungsten polycide made of polycrystalline silicon 4 and WSi _x 5 corresponds to a base material layer, here is formed a step due to LOCOS2. Accordingly, the base material directly onto the layer a resist film is applied, highly accurate exposure for irregular light reflection at this WSi _x 5 having a high reflectance be added exposure, in particular stepped portion LOCOS2 It cannot be applied.

[0023] Therefore WSi _x 5 as shown in FIG. 1 (b)
An organic antireflection film 6 was formed thereon. In the present embodiment, DUV-18 (Bre
was applied by a spin coating method. The thickness of the organic antireflection film 6 after drying is 70 nm on the LOCOS2 region,
It was set to 150 nm on the region. As a result, the surface of the organic antireflection film 6 was formed almost flat.

Next, as shown in FIG. 1C, a resist pattern 7 is formed on the organic antireflection film 6. In this embodiment, a resist is applied on the organic anti-reflection film 6 and then exposed and developed by an excimer laser stepper to form a resist.
A plurality of resist patterns 7 having a width of 5 μm were formed on the LOCOS2 region and the gate insulating film 3 region. In this lithography process it has a step due LOCOS2, moreover albeit at exposure on large WSi _x 5 in reflectance, standing waves or step height accuracy without the influence of the anti-reflection effect of the organic antireflection film 6 The resist pattern 7 was formed.

Next, the substrate to be etched shown in FIG. 1C is set on a substrate stage of an ECR plasma etching apparatus of a substrate bias application type, and as an example, a resist pattern is formed under the following plasma etching conditions. The organic antireflection film 6 was patterned using 7 as an etching mask. SOCl flow rate 40 SCCM Gas pressure 1.0 Pa Microwave output 1200 W (2.45 GHz) RF bias 100 W (800 kHz) Substrate to be etched temperature -20 ° C Etching amount 200 nm The state after the end of etching is shown in FIG. Show. In this etching step, the decomposition products of the resist pattern 7 are recombined with sulfur-based chemical species dissociated and generated from SOCl by high-density plasma, and chlorine.
Highly polymerized carbon-based polymer with CS bonds and-(CCl ₂ ) _x -as the basic main chain structure is deposited on the substrate to be etched, and the side walls of the resist mask and the organic layer being patterned are less exposed to ion irradiation. The strong anti-reflection film 6 is selectively deposited on the side wall of the pattern to form a strong side wall protection film 8. As a result, in the organic anti-reflection film 6 on the LOCOS 2 region, despite the over-etching of almost 200%, no dimensional conversion difference or undercut occurs in the pattern of the organic anti-reflection film 6 in this portion. The patterning has been completed. The same applies to the organic antireflection film 6 pattern on the gate insulating film 3 region. Further, the phenomenon that the resist pattern 7 receded was not observed.

[0026] Then, using the same substrate bias application type ECR plasma etching apparatus, patterning the WSi _x 5 and the polycrystalline silicon 4 in one step by switching the etching conditions. An example of the etching conditions is shown below. Cl ₂ flow rate 80 SCCM O ₂ flow rate 8 SCCM Gas pressure 0.4 Pa Microwave output 900 W (2.45 GHz) RF bias 80 W (800 kHz) (Main etching) RF bias 30 W (800 kHz) (Over etching) Etching the substrate temperature 20 ° C. over-etching of 20% the etching process, the patterned resist pattern 7 and the organic anti-reflection film 6 pattern with high precision as an etching mask, WSi _x 5 and the polycrystalline silicon 4 is exactly 0.25μm width Anisotropically etched. FIG. 2E shows the state after the completion of the etching.

Thereafter, for example, an ashing process is performed to completely remove the resist pattern 7, the pattern of the organic antireflection film 6, and the side wall protective film 8. As a result,
As shown in FIG. 2F, a fine gate electrode and wiring having a polycide structure having no pattern conversion difference were formed on both the LOCOS 2 region and the gate insulating film 3. According to this embodiment, the organic anti-reflection film on the base material layer having the step is plasma-etched with the SOCl gas alone, so that the organic anti-reflection film pattern is undercut even when a large excessive over-etching is performed. And a dimensional conversion difference can be prevented.

Embodiment 2 This embodiment is an example in which the present invention is applied to the processing of a gate electrode and a wiring made of tungsten polycide according to the first embodiment, and this step is repeated in FIG. 1 and FIG. The description will be made with reference to FIG. However, description of the same parts as in the first embodiment will be omitted, and only the features of the present embodiment will be described.

The substrate to be etched employed in this embodiment is:
This is the same as that described in the first embodiment with reference to FIG.

Plasma Etching Step of Organic Antireflection Film The substrate to be etched shown in FIG. 1C is set on a substrate stage of an MCR type plasma etching apparatus in this embodiment. The organic antireflection film 6 was patterned using the resist pattern 7 as an etching mask. SOCl ₂ flow rate 30 SCCM Gas pressure 1.0 Pa Source output 1000 W (13.56 MHz) RF bias 50 W (450 kHz) Substrate to be etched 0 ° C. Etching amount 200 nm State after etching is completed FIG. 2 (d) Shown in This etching step proceeds by the same mechanism as in the first embodiment. However, the supply amount of chlorine for accelerating the formation of deposits is increased in the first embodiment.
Since the number is larger, the effect of protecting the side wall is further enhanced, and the process at the substrate temperature to be etched close to room temperature is possible.
As a result, in the organic anti-reflection film 6 on the LOCOS 2 region, despite the over-etching of almost 200%, no dimensional conversion difference or undercut occurs in the pattern of the organic anti-reflection film 6 in this portion. The patterning has been completed. The same applies to the organic antireflection film 6 pattern on the gate insulating film 3 region. Further, the phenomenon that the resist pattern 7 receded was not observed.

[0031] Then, using the same substrate bias application type MCR plasma etching apparatus, patterning the WSi _x 5 and the polycrystalline silicon 4 in one step by switching the etching conditions. An example of the etching conditions is shown below. Cl ₂ flow rate 80 SCCM O ₂ flow rate 2 SCCM Gas pressure 0.3 Pa Source output 900 W (13.56 MHz) RF bias 60 W (450 kHz) (Main etching) RF bias 20 W (450 kHz) (Over etching) Substrate to be etched the temperature 70 ° C. over-etching of 20% the etching process, the patterned resist pattern 7 and the organic anti-reflection film 6 pattern as an etching mask with high precision, exactly WSi _x 5 and the polycrystalline silicon 4 to 0.25μm width Anisotropically etched. FIG. 2E shows the state after the completion of the etching.

Thereafter, for example, an ashing process may be performed according to the first embodiment. As a result, as shown in FIG. 2F, a fine gate electrode and wiring having a polycide structure having no pattern conversion difference were formed on both the LOCOS 2 region and the gate insulating film 3. According to this embodiment, the organic antireflection film on the stepped base material layer is plasma-etched with SOCl ₂ gas alone, so that the substrate temperature to be etched closer to room temperature than in the previous embodiment 1 is adopted. Even if you apply excessive over-etching,
It is possible to prevent undercut and dimensional conversion difference of the organic antireflection film pattern.

Embodiment 3 This embodiment relates to a DRAM (Dynamic Random).
This is an example in which the plasma etching method for an organic anti-reflection film of the present invention is applied to a process of processing a storage node electrode of an access memory, and this process will be described with reference to FIGS.

The sample employed in this embodiment has the structure shown in FIG. 3A, and comprises a word line 9a and bit line 9b made of tungsten polycide and a polycrystalline silicon on a semiconductor substrate 1 such as silicon. A lower interlayer insulating film 10 having a wiring plug 12, a polycrystalline silicon 4 formed on the lower interlayer insulating film 10, and an upper interlayer insulating film 11 made of SiO ₂ are sequentially formed. this house,
The polycrystalline silicon 4 will be the bottom of the cylinder type storage node electrode in the future, and is formed to a thickness of 100 nm by low pressure CVD. The upper interlayer insulating film 11 is formed to a thickness of 600 nm by plasma CVD. A step is formed on the surface of the upper interlayer insulating film 11 due to the word lines 9a and the bit lines 9b. Even if a resist film is formed directly thereon and exposed to light, a highly accurate resist pattern cannot be obtained.

Therefore, an organic antireflection film 6 was formed on the upper interlayer insulating film 11 as shown in FIG. Also in this embodiment, DUV-18 is used as an organic antireflection film material.
(Brewer Science) was applied by spin coating. The thickness of the organic anti-reflection film 6 after drying is 70 n on the DRAM cell region at the stepped portion.
m, 250 nm on the peripheral circuit of the step recess. As a result, the surface of the organic antireflection film 6 was formed almost flat.
Next, a resist pattern 7 is formed on the organic antireflection film 6. In this embodiment, after a resist is applied on the organic antireflection film 6, a resist pattern 7 having a short side of 0.25 μm and a long side of 0.6 μm is formed on the substrate to be etched by exposing and developing with an excimer laser stepper. A dot was formed on the plug 12. In this lithography step, a highly accurate resist pattern 7 was formed without the influence of standing waves or steps due to the antireflection effect of the organic antireflection film 6.

Next, the substrate to be etched shown in FIG. 3B is set on a substrate stage of a helicon wave plasma etching apparatus, and as an example, the resist pattern 7 is etched under the following plasma etching conditions. The organic antireflection film 6 was patterned as a mask. SO ₂ Cl ₂ flow rate 40 SCCM Gas pressure 1.0 Pa Source output 1200 W (13.56 MHz) RF bias 50 W (400 kHz) Substrate to be etched temperature −30 ° C. Etching amount 300 nm The state after the end of etching is shown in FIG. ). In the present etching step, a decomposition product of the resist pattern 7 and a sulfur-based species and chlorine dissociated and generated from SO ₂ Cl ₂ by high-density plasma are recombined to have a CS bond. A highly polymerizable carbon-based polymer having-(CCl ₂ ) _x -as a basic main chain structure is deposited on the substrate to be etched, and as shown in FIG. A strong sidewall protective film 8 is formed by selectively depositing on the sidewall of the organic antireflection film 6 being patterned. As a result, in the organic anti-reflection film 6 on the storage node region, 250%
Despite the excessive over-etching, the patterning was completed without generating a dimensional conversion difference in the pattern of the organic antireflection film 6 in this portion. Further, the phenomenon that the resist pattern 7 receded was not observed.

Thereafter, using the same helicon wave plasma etching apparatus, the etching conditions were switched and the upper interlayer insulating film 11 and the polycrystalline silicon 4 were continuously patterned. An example of the etching conditions is shown below. Etching step of upper interlayer insulating film C ₄ F ₈ flow rate 100 SCCM O ₂ flow rate 10 SCCM gas pressure 0.4 Pa Source output 1200 W (13.56 MHz) RF bias 200 W (400 kHz) Substrate temperature to be etched −40 ° C. Overetching 20% polycrystalline silicon etching process Cl ₂ flow rate 50 SCCM O ₂ flow rate 5 SCCM gas pressure 0.4 Pa Source output 900 W (13.56 MHz) RF bias 70 W (400 kHz) (Main etching) RF bias 20 W (400 kHz) (Over-etching) Substrate to be etched -40 ° C Over-etching 20% By this etching process, the resist pattern 7 and the organic anti-reflection film 6 which are patterned with high precision are used as an etching mask. Layer interlayer insulating film 11 and the polycrystalline silicon 4 is correctly anisotropically etching the short side 0.25μm width. FIG. 4 shows the state after the etching is completed.
(D).

Thereafter, for example, an ashing process is performed to completely remove the resist pattern 7, the organic antireflection film 6 pattern, and the side wall protection film 8. As a result,
As shown in FIG. 4E, a polycrystalline silicon 4 pattern having no pattern conversion difference was formed on the wiring plug 12.

In the subsequent steps, a polycrystalline silicon film (not shown) is formed by, for example, low-pressure CVD, and this is etched back to form a side wall portion of the cylinder type storage node as shown in FIG. 13 is formed. Next, the cylinder-type storage node electrode is obtained by extracting the pattern of the upper interlayer insulating film 11 with dilute hydrofluoric acid or the like. Thereafter, a dielectric film and a capacitor electrode are formed by a conventional method, thereby completing a cylindrical capacitor cell. According to this embodiment, the organic anti-reflection film on the base material layer having a step is subjected to plasma etching with SO ₂ Cl ₂ gas alone, so that a large excess over etching is performed.
It is possible to prevent undercut and dimensional conversion difference of the organic antireflection film pattern. As a result, a large-capacity fine storage node can be processed with high precision on the step underlying material layer.

Embodiment 4 This embodiment is similar to the previous embodiment 3, except that a sulfur-based deposit is also used as a side wall protective film, and the plasma of the organic anti-reflection film of the present invention is used in the process of processing the storage node electrode of the DRAM. This is an example in which an etching method is applied, and this step will be described again with reference to FIGS. However, description of the same parts as in the third embodiment will be omitted, and only the features of the present embodiment will be described.

The substrate to be etched employed in this embodiment is:
According to the third embodiment described with reference to FIG. The substrate to be etched is applied to a substrate bias applying type ECR.
Set on the substrate stage of the plasma etching apparatus, as an example, under the following plasma etching conditions,
The organic antireflection film 6 was patterned. Plasma etching process of organic antireflection film SOBr flow rate 30 SCCM S ₂ Br ₂ flow rate 30 SCCM Gas pressure 1.0 Pa Microwave output 1200 W (2.45 GHz) RF bias 100 W (800 kHz) Etching substrate temperature 10 ° C. Etching FIG. 3C shows the state after the completion of the etching with the amount of 300 nm. In the present etching step, the decomposition product of the resist pattern 7, the sulfur-based chemical species dissociated and generated from SOBr by high-density plasma, and bromine are recombined,
A highly polymerizable carbon-based polymer having a CS bond and having-(CBr ₂ ) _x -as a basic main chain structure is deposited on the substrate to be etched, and as shown in FIG. A strong side wall protective film 8 is formed by selectively depositing on the side wall of the pattern 7 and the side wall of the organic anti-reflection film 6 being patterned. In particular, in the present embodiment, by adopting a carbon-based polymer having-(CBr ₂ ) _x -having a low vapor pressure as a basic main chain structure, the deposition amount of the carbon-based polymer increases as compared with the previous embodiment 3, In addition, due to the increased etching resistance, the organic layer on the storage node region is formed despite the fact that the substrate temperature to be etched is higher than that in the third embodiment and that overetching of more than 250% is applied. The patterning was completed without generating a dimensional conversion difference in the pattern of the system antireflection film 6. Further, the phenomenon that the resist pattern 7 receded was not observed.

Thereafter, using the same substrate bias applying type ECR plasma etching apparatus, the etching conditions were switched to continuously pattern the upper interlayer insulating film 11 and the polycrystalline silicon 4. An example of the etching conditions is shown below. Etching process of upper interlayer insulating film CHF ₃ flow rate 100 SCCM O ₂ flow rate 10 SCCM Gas pressure 0.4 Pa Microwave output 1200 W (13.56 MHz) RF bias 300 W (800 kHz) Substrate to be etched 0 ° C. Overetching 20% Etching process of polycrystalline silicon Cl ₂ flow rate 50 SCCM Gas pressure 0.4 Pa Microwave output 900 W (13.56 MHz) RF bias 80 W (800 kHz) (Main etching) RF bias 30 W (800 kHz) (Over etching) Etching substrate temperature 0 ° C. Overetching 20% In this etching step, the upper interlayer insulating film 11 and the And polycrystalline silicon 4 was accurately anisotropically etched to a width of 0.25 μm on the short side. FIG. 4 shows the state after the etching is completed.
(D).

The subsequent ashing step shown in FIGS. 4E to 4F, the step of forming the side wall portion 13 of the cylinder type storage node, and the like are the same as those in the third embodiment, so that the duplicated description will be omitted. . According to this embodiment, the organic antireflection film on the stepped base material layer is formed of SOBr and S ₂ Br _2.
By performing plasma etching using a mixed gas of the above, it is possible to prevent an undercut and a dimensional conversion difference of the organic antireflection film pattern even if a large excess overetching is performed. As a result, a large-capacity fine storage node can be patterned on the step underlying material layer with high accuracy.

As described above, the plasma etching method for the organic anti-reflection film of the present invention has been described with reference to four examples. However, the present invention is not limited to these examples, and various embodiments are possible. . For example, various modes can be adopted for the type of organic antireflection film material, the structure of the substrate to be etched, the additive gas in plasma etching, the plasma etching apparatus, and the like.

[0045]

As is clear from the above description, according to the plasma etching method for an organic anti-reflection film of the present invention, the organic anti-reflection film formed on the high reflectance base material layer having a step. Is adopted as a resist pattern as an etching mask, and patterning can be performed with high accuracy without generating undercuts or dimensional conversion differences.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the first half of the steps of Examples 1 and 2 of the present invention.

FIG. 2 is a schematic sectional view showing the latter half of the steps of Examples 1 and 2 of the present invention.

FIG. 3 is a schematic cross-sectional view showing the first half of the steps of Examples 3 and 4 of the present invention.

FIG. 4 is a schematic cross-sectional view showing the latter half of the steps of Examples 3 and 4 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... LOCOS, 3 ... Gate insulating film,
4 ... polycrystalline silicon, 5 ... WSi _x, 6 ... organic antireflection film, 7 ... resist pattern, 8 ... side wall protective film, 9a ...
Word line, 9b bit line, 10 lower interlayer insulating film, 1
DESCRIPTION OF SYMBOLS 1 ... Upper interlayer insulating film, 12 ... Wiring plug, 13 ... Side wall part of cylinder type storage node

Claims (7)

[Claims] An organic antireflection film formed on a base material layer is formed by using an etching gas containing a halogen compound having one of a thionyl group and a sulfuryl group and a halogen atom in a molecule, A plasma etching method for an organic antireflection film, comprising etching while depositing a carbon-based polymer on a substrate to be etched. 2. An organic antireflection film formed on a base material layer, comprising: a halogen compound having one of a thionyl group and a sulfuryl group and a halogen atom in a molecule; An organic anti-reflection coating characterized by using a sulfur-based compound capable of releasing sulfur therein and an etching gas containing, and etching while depositing a carbon-based polymer and a sulfur-based deposit on a substrate to be etched. Plasma etching method. 3. The compound having a thionyl group and a halogen atom in the molecule is a compound represented by a general formula SOX _n (X represents a halogen atom, and n represents a natural number of 2 or less). 3. The plasma etching method for an organic antireflection film according to claim 1, wherein: 4. The compound having a sulfuryl group and a halogen atom in the molecule is a compound represented by a general formula SO ₂ X ₂ (X represents a halogen atom). A plasma etching method for an organic antireflection film according to the above. 5. The sulfur-based compound capable of releasing sulfur into plasma under the conditions of discharge ionization is S ₂ F ₂ , SF ₂ ,
SF ₂ , S ₂ F ₁₀ , S ₃ Cl ₂ , S ₂ Cl ₂ , SC
l ₂ , S ₃ Br ₂ , S ₂ Br ₂ , SBr ₂ and H ₂ S
3. The method according to claim 2, wherein the compound is at least one compound selected from the group consisting of: 6. The method for plasma etching an organic antireflection film according to claim 1, wherein the substrate to be etched is controlled to a room temperature or lower during the etching. 7. The plasma etching method for an organic antireflection film according to claim 2, wherein the substrate to be etched is heated to at least 90 ° C. after completion of the etching.