JPH09260350A - Plasma etching method of oxide silicon-based insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent selection ratio to substratum material layers and a resist mask, and reduce microloading effect and particle contamination, by using mixture gas which contains gas containg N and H as constituent elements and gas containing C and F as constituent elements. SOLUTION: A silicon oxide-based insulating film 3 on substratum material layers 1, 2 is patterned by using mixture gas which contains gas containing N and H as constituent elements and gas containing C and F as constituent elements. For example, the silicon oxide-based insulating film 3 composed of SiO2 is formed on a semiconductor substrate 1 of Si or the like on which an impurity diffusion layer 2 or the like is previously formed. A resist mask 4 having an aperture diameter of 0.25μm is patterned on a connection hole aperture position. Then an exposed part of the silicon oxide-based insulating film 3 is plasma etched with mixture gas of C3 F8 and NH3 by using a magnetron RIE equipment which jointly uses an magnetic field, and a contact hole 5 is formed.

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 a silicon oxide-based insulating film applied in the field of manufacturing highly integrated semiconductor devices and the like, and more particularly to silicon oxide on a base material layer made of a conductive material or the like. The present invention relates to a plasma etching method for a silicon oxide insulating film, which is useful when a connection hole is opened in the insulating film.

[0002]

2. Description of the Related Art With the progress of higher integration and higher performance of semiconductor devices such as LSI, the design rule thereof is being reduced from half micron to subquarter micron. Along with this, the technical requirements for a plasma etching method for forming a connection hole or the like by subjecting a silicon oxide type insulating film to fine processing have become more and more strict.

For example, in order to speed up signal processing of a semiconductor device and miniaturize the semiconductor element itself, for example, MO
In the S transistor, the junction depth of the impurity diffusion layer is shallow. There is also a device structure in which a connection hole facing the source / drain region of a PMOS-TFT used as a load resistance element of SRAM is opened. In plasma etching of a silicon oxide insulating film having such a thin conductive material layer as a base, a plasma etching method which is more excellent in selectivity with respect to the base material layer than the conventional one and causes less damage to the base material layer is required.

Further, improving the selection ratio of resist masks is also an important issue. This is because, in order to stably manufacture a semiconductor device having a fine design rule, it is becoming difficult to allow the dimensional conversion difference due to the receding of the resist mask during plasma etching, even if the difference is extremely small.

In plasma etching of a silicon oxide-based material film, a strong Si--O bond (705 kJ / mol) needs to be cut, so that an etching mode having a strong ionic property with a sputtering effect is adopted. Common etching gases are CF ₄ and C ₃ F ₈ etc. Is mainly used, and the sputtering action by the incident ion energy of CF _x ⁺ that is dissociated and produced from the CF-based gas and S by the reducing property of carbon as a constituent element.
It utilizes the breaking action of the i—O bond and the generation and removal of SiF _x , which is a reaction product having a large vapor pressure. However, as a feature of ion mode plasma etching,
The etching rate is generally not high. Therefore, when the incident ion energy is increased by directing high-speed etching, the etching reaction mainly consists of physical sputtering, and the selectivity is lowered. That is, the plasma etching of the silicon oxide based material layer with the CF based gas is difficult to achieve both high speed and selectivity.

Further, in order to obtain a high selection ratio by the conventional technique, it is necessary to thickly deposit a fluorocarbon-based polymer mainly containing a reaction product of a CF-based gas, and such a gas chemistry is used in the same etching chamber. If the plasma etching is repeated at 1, the etching rate is lowered and the particle level is deteriorated. The lower the etching rate is, the more pronounced the finer the pattern becomes, and the defective contact hole is caused by the so-called microloading effect.

In order to improve the selection ratio in the plasma etching of the silicon oxide type insulating film, there is a conventional technique in which H ₂ is added to CF type gas or CHF type gas such as CHF ₃ containing H in the molecule is adopted. This is because H radicals (H ^* ) generated in the plasma trap excess F radicals (F ^* ) in the plasma and remove them in the form of HF to the outside of the etching chamber. It is based on the idea of increasing the F ratio (the ratio of C atoms to F atoms). Increasing the C / F ratio reduces the F atom content in the fluorocarbon-based polymer that is deposited in competition with etching, and has the effect of enhancing the film quality such as improving the ion injection resistance.
It has the effect of improving the selectivity of the i or the like with the base. The fluorocarbon-based polymer does not substantially deposit on the silicon oxide-based insulating film, which is the film to be etched, because it reacts with O atoms sputtered out from the surface and is oxidized and removed, thus lowering the etching rate. There is no such thing. However, the fluorocarbon polymer is exclusively deposited on the lower surface of Si, which does not have an oxidizing action, and functions as a substantial etching stopper to protect the base from the ion incidence, which improves the selection ratio. is there. For the concept of these C / F ratios and the mechanism by which high selectivity is achieved, see J. Vac. Scie
nce. Tech, 16 (2), 391 (1979).

Recently, there is a trend to reconsider the film quality of fluorocarbon polymers from a standpoint different from the physical viewpoint of ion incidence resistance. That is, when a fluorocarbon-based polymer rich in F atoms is deposited on an exposed surface such as Si which is the base material layer, the F atoms in the fluorocarbon-based polymer and the base Si atoms are simply adsorbed or attached. Not only the above, but also the process of desorption of chemical reaction and reaction products is assisted by the incidence of ions. This series of processes is an etching reaction, and causes a reduction in the selection ratio of the base material layer. From such a viewpoint, CO is added to a fluorocarbon gas to remove excess F ^* in the plasma from C
The fourth attempt is to capture it in the form of OF _x and increase the C / F ratio.
0th Joint Lecture on Applied Physics (Spring Annual Meeting 1993)
Reported in Lecture Proceedings p614, Lecture No. 31a-ZE-10. From the same point of view, there is a proposal of adding CO to an inorganic fluorine-based etching gas such as NF ₃ to capture surplus F ^* and improving the selection ratio, for example, US Pat.
No. 807,016.

However, in the method of adding H ₂ or CO to the fluorocarbon gas to improve the selectivity with respect to the underlying material layer, sufficient consideration must be given to the flammability and safety of these added gases. . Especially, there is a lot of room for consideration in handling in a closed space such as a clean room. In addition, for practical use, it is necessary to newly install exhaust gas treatment equipment.

On the other hand, in order to prevent the delay of signal propagation in the semiconductor device, an attempt to reduce the dielectric constant of the insulating film between the wirings to reduce the capacitance between the wirings is mainly applied to a semiconductor device such as a logic LSI which requires high speed. Is being studied as Si, which is a general interlayer insulating film material, as a low dielectric constant material
SiOF in which F is added to O ₂ is typical, and it is noted that it is continuous with the conventional technique in the film forming process. As an example, a plasma CVD method using a TEOS / O ₂ / CF ₄ type raw material gas is 1993 DryProc.
Reported in ess Symposium Proceedings p163, Lecture No. V-2. According to this method, SiO ₂
6 at. The relative permittivity is reduced from 4.1 to 3.2 by including about F of F.

However, in plasma etching of a low dielectric constant silicon oxide insulating film such as SiOF or SiONF, F ^* is successively released from these films to be etched during etching, and the F ^* concentration in plasma is increased. F ^* emitted from the film to be etched also serves as an etchant for the underlying material layer such as silicon and the resist mask, so that the etching selection ratio can be ensured by SiO ₂ , PSG, or BS.
It becomes more difficult as compared with general silicon oxide type insulating films such as G and BPSG.

[0012]

SUMMARY OF THE INVENTION The present invention provides the above-described S
It is an object to solve various problems regarding plasma etching of a silicon oxide insulating film including an iOF insulating film. That is, an object of the present invention is to pattern a silicon oxide-based insulating film formed on a base material layer, which has an excellent selection ratio between the base material layer and a resist mask, and which has a small microloading effect and little particle contamination. An etching method is provided.

Another object of the present invention is to eliminate from the etching gas system gases such as H ₂ and CO, which should be considered for their flammability and safety in use, and to newly invest in equipment such as an exhaust gas treatment facility. It is an object of the present invention to provide a plasma etching method for a silicon oxide-based insulating film that does not require.

Still another object of the present invention is to provide a plasma etching method for a low dielectric constant silicon oxide insulating film capable of stably manufacturing a highly integrated semiconductor device having a reduced wiring capacitance and an improved signal propagation speed. That is.

[0015]

A plasma etching method for a silicon oxide insulating film according to the present invention is proposed to achieve the above-mentioned object, and the first invention (Claim 1) thereof is N And a gas containing H as constituent elements,
A mixed gas containing C and F as constituent elements and a mixed gas containing C and F are used to pattern the silicon oxide insulating film on the base material layer.

The second invention (claim 2) uses a mixed gas containing a gas containing N and H as constituent elements and a gas containing C and F as constituent elements, and oxidizes the base material layer. The step of patterning the silicon-based insulating film until just before the base material layer is exposed, and N in the mixed gas
And a step of increasing the mixing ratio of the gas containing H as a constituent element and patterning the remaining portion of the silicon oxide insulating film on the base material layer in the film thickness direction, in this order. In the step (just etching step) of patterning until just before the underlying material layer is exposed, the underlying material layer may be inevitably slightly exposed on a part of the substrate to be etched due to slight non-uniformity of the etching rate. Although possible, such cases are also included.

Further, a third invention (claim 3) is a mixture containing a gas containing N and H as constituent elements and a sulfur-based compound gas capable of releasing free sulfur into plasma under discharge dissociation conditions. The method is characterized in that the silicon oxide insulating film on the underlying material layer is patterned while using a gas and controlling the substrate to be etched at room temperature or lower.

In the present invention, the gas containing N and H as constituent elements is NH ₃ (mp = −77.7 ° C., b
p = 33.35 ° C.), N ₂ H ₄ (mp = 2.0 ° C., bp
= 113.5 ° C.) and NH ₄ HS. Of these, NH ₄ HS (Ammonium
Hydrosulfide) is (NH ₄ ) ₂ S (Ammonium Sulfid
e, a compound produced by thermal decomposition of crystallization at -18 ° C or lower). Further, the gas containing C and F as constituent elements employed in the present invention is represented by the general formula C _n F _m or C _n H _l F in which some of the F atoms in these compounds are replaced with H.
_The compound is represented by _ml (n, m and l are natural numbers), and may be a saturated compound or an unsaturated compound, or a molecular structure such as a chain or a ring. Further, the sulfur-based compound gas capable of releasing free sulfur into plasma under the discharge dissociation conditions used in the present invention is specifically S ₂ F.
₂ , SF ₂ , SF ₄ , S ₂ F ₁₀ , S ₂ Cl ₂ , S ₃ Cl
Halogenated sulfur-based gases such as ₂ , SCl ₂ , S ₂ Br ₂ , S ₃ Br ₂ , and S ₂ Br, and H ₂ S are exemplified, and these can be used alone or in combination. A compound that is liquid at room temperature may be heated and vaporized by a known method before use. SF _{6, which} is a general halogenated sulfur gas, is excluded because it is difficult to release free sulfur into plasma under discharge dissociation conditions. The room temperature is the room temperature of a clean room used for a normal semiconductor device manufacturing process, and is usually 20 to 25 ° C.

The silicon oxide type insulating film to be etched in the present invention includes SiO ₂ , SiO _x F _z and SiO 2.
_x N _y F _z (abbreviated as SiOF and SiONF). Further, these silicon oxide insulating films may contain impurities such as P, B and As. The film forming method is a low pressure CVD method or a plasma CVD method.
Method, atmospheric pressure CVD method, sputtering method, coating and firing method, or the like.

Next, the operation will be described. As an action common to any of the inventions, H generated when a gas containing N and H as constituent elements is released into plasma under discharge dissociation conditions.
Not only the atom or its active species but also the N atom or its active species jointly capture the fluorine radical (F ^* ) which is an etchant of the silicon material or the resist mask, so that the reduction of the selection ratio due to excess F ^* is prevented. . In addition, since the fluorine content in the fluorocarbon-based polymer deposited in competition with etching is reduced, the composition becomes carbon-rich, the film quality is enhanced, and the resistance to attack of incident ions and radicals is increased. And the selection ratio with respect to the resist mask are improved. In particular, in the case of a low dielectric constant silicon oxide type insulating film such as SiOF having F as a constituent element, the etchant is apt to become excessive because F ^* is successively released during the progress of etching. Since the F ^* released from the membrane is also trapped, the reduction in selectivity is effectively avoided.

In the second invention, the mixing ratio of the mixed gas is changed at the time of patterning until just before the underlying material layer corresponding to the just etching step is exposed, and N and H are constituent elements in the subsequent overetching step. Increase the mixing ratio of the gas contained as. By this two-step etching, a practical high-speed etching rate can be secured in the just etching process. Further, in the over-etching process, F ^* in the plasma is further reduced, and a fluorocarbon-based polymer having a small F content is more effectively generated, so that high selective ratio etching can be performed even under the condition of reducing the incident ion energy. It will be possible. Naturally, this also reduces the ion irradiation damage of the base material layer.

Further, in the third aspect of the invention, the radical reaction is suppressed by controlling the temperature of the substrate to be etched to a low temperature, and the dissociation of the sulfur compound gas produces a fluorocarbon-based substance on the substrate to be etched. Due to the synergistic effect of depositing sulfur-based materials in addition to polymers, S
Further, the selection ratio to the underlying material such as i and the selection ratio to the resist mask are further improved. On the other hand, on the surface of the silicon oxide-based material layer, the sulfur-based material becomes SO or SO ₂ and is quickly removed by O released by sputtering, like CF-based polymers, so that the etching rate does not actually decrease. Therefore, high selectivity etching can be performed while maintaining the etching rate. After the patterning of the silicon oxide based material layer, the substrate to be etched is about 150
If heated to a temperature of not less than 0 ° C., the deposited sulfur-based material is quickly sublimated and removed, and there is no risk of contamination of the substrate to be etched or particle contamination. The sulfur-based material can be removed by oxidation at the same time as the resist during resist ashing. The sulfur-based material to be deposited includes elemental sulfur and polythiazyl produced by nitriding and polymerizing sulfur. Polythiazyl has a higher ion incidence resistance than sulfur, and has a high selection ratio improvement and damage prevention effect. Sulfur can be removed by sublimation under reduced pressure at about 90 ° C or higher and polythiazil at about 150 ° C or higher. As is clear from the sublimation temperatures of sulfur and polythiazyl, sulfur or polythiazyl can be deposited if the substrate temperature to be etched is lower than these sublimation temperatures.
However, from the viewpoint of the stability of the deposited film, it is desirable to control the temperature of the substrate to be etched to room temperature or lower, for example, 20 to 25 ° C. which is a general clean room temperature.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments in which the present invention is applied to the processing of contact holes and via holes will be described below with reference to the accompanying drawings.

Example 1 This example applies the first invention, and a mixed gas of C ₃ F ₈ which is a fluorocarbon-based gas and NH ₃ is used to form a silicon oxide system composed of SiO ₂ on a silicon substrate. This is an example in which a contact hole is formed by plasma etching an insulating film, which will be described with reference to FIGS.

First, as shown in FIG. 1A, S is formed on a semiconductor substrate 1 of Si or the like on which an impurity diffusion layer 2 and the like are formed in advance.
forming a silicon oxide insulating film 3 made of iO _2. This silicon oxide insulating film is, for example, TEOS / H ₂
The film is formed by plasma CVD using an O / O ₂ -based source gas. The thickness of the silicon oxide insulating film 3 is, for example, 500 nm. Next, by chemically amplified resist and KrF excimer laser lithography, 0.2
A resist mask 4 having an opening diameter of 5 μm is patterned at the contact hole opening position. Figure 1 (a) formed up to this point
The sample shown in 1 is used as the substrate to be etched.

Next, this substrate to be etched is placed on the substrate stage of a magnetron RIE apparatus that also uses a magnetic field, and the exposed portion of the silicon oxide based material layer 3 is plasma etched under the following conditions. The substrate stage can control the temperature to 0 ° C. or lower by incorporating a cooling pipe through which an alcohol-based refrigerant circulates, a resistance heater, a temperature sensor, and the like. C ₃ F ₈ 50 sccm NH ₃ 20 sccm Gas pressure 2.0 Pa RF power source power density 2.0 W / cm ² (13.56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Etching substrate temperature 5 ° C. Etching The substrate temperature was maintained at 5 ° C during the etching process. In this plasma etching process, the anisotropic reaction of the silicon oxide insulating film 3 proceeded with the radical reaction by F ^* being assisted mainly by the CF _x ⁺ ion incidence. Etching rate is 850 nm /
min.

In the plasma, not only H atoms generated by the dissociation of NH ₃ , but also N atoms or active species of these atoms dissociate C ₃ F ₈ or generate excess F ^* released from the layer to be etched. To capture. As a result, the fluorocarbon-based polymer (not shown) deposited on the substrate to be etched is F
It had a small content of components and had a high resistance to ion incidence. The fluorocarbon polymer is a semiconductor substrate such as silicon which is a base material layer exposed by plasma etching, to be precise, on the impurity diffusion layer 2 and the resist mask 4.
A high selectivity is obtained as a result of the deposition on top. That is, when the semiconductor substrate 1, which is the base material layer, is exposed, the fluorocarbon-based polymer is deposited on the surface of the semiconductor substrate 1, so that the etching rate is significantly reduced, and as a result, a high selection ratio is achieved. The selection ratio is about 40 for the base material layer,
The resist mask was about 7. FIG. 1B shows a state after the plasma etching is completed in which the contact hole 5 is opened in the substrate to be etched.

According to the present embodiment, the contact hole opening process satisfying both high selection ratio and uniformity is achieved by plasma etching the silicon oxide type insulating film using the mixed gas containing C ₃ F ₈ and NH _3. I was able to achieve it.

Example 2 In this example, the first invention is also applied, and C ₄ F ₈ and
This is an example in which a low dielectric constant silicon oxide based insulating film on the lower layer wiring is plasma-etched by a mixed gas containing NH ₃ to open a via hole. This will be described with reference to FIGS. 2A and 2B. .

The substrate to be etched shown in FIG. 2 (a) employed in this embodiment has a lower wiring 7 made of polycrystalline silicon containing impurities and a low dielectric constant silicon oxide made of SiOF on the lower interlayer insulating film 6. The insulating film 30 is formed, and the resist mask 4 having an opening of, for example, 0.25 μm, which faces the lower layer wiring 7, is formed. The low dielectric constant silicon oxide insulating film 30 is, for example, TEOS.
/ C ₂ F ₆ / H ₂ O / O ₂ -based material gas is formed by plasma CVD, and its thickness is, for example, 5
00 nm. This plasma CVD method was filed by the applicant of the present application as the specification of Japanese Patent Application No. 6-97631, and it has little residual hydroxyl groups and organic substances and is excellent in step coverage.

The substrate to be etched is placed on the substrate stage of the same magnetron RIE apparatus as in the previous embodiment, and the exposed portion of the low dielectric constant silicon oxide type insulating film 30 is plasma-etched under the following conditions. C ₄ F ₈ 50 sccm NH ₃ 10 sccm Gas pressure 2.0 Pa RF power source power density 2.0 W / cm ² (13.56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Etching substrate temperature 5 ° C. Etching The substrate temperature was maintained at 5 ° C during the etching process. In this plasma etching process, the low-dielectric-constant silicon oxide insulating film 30 is formed in such a manner that the radical reaction by F ^* is mainly assisted by the CF _x ⁺ ion incidence.
Anisotropic etching proceeded. Etching rate is 8
It was 50 nm / min.

In the plasma, not only H atoms generated by the dissociation of NH ₃ but also N atoms or active species of these atoms generate excessive F ^* released from C ₄ F ₈ dissociation or the layer to be etched. Since it was captured, the etching selection ratio was about 40 for the lower wiring 7 made of polycrystalline silicon as the base material layer, and about 6 for the resist mask 4. FIG. 2B shows a state after the plasma etching is completed in which the via hole 8 is opened. According to the present embodiment,
By plasma etching the low dielectric constant silicon oxide insulating film using a mixed gas containing C ₄ F ₈ and NH ₃ , a via hole opening process satisfying both a high selectivity and uniformity could be achieved.

Example 3 This example applies the second invention, and Si on a silicon substrate is used.
A silicon oxide insulating film made of O ₂ was mixed with a mixed gas containing C ₃ F ₈ which is a fluorocarbon gas and N ₂ H ₄ .
This is an example in which contact holes are formed by changing the mixing ratio and performing two-step plasma etching.
This will be described with reference to FIG.

The substrate to be etched shown in FIG. 3A is the same as the substrate to be etched shown in FIG. The substrate to be etched is placed on the substrate stage of a magnetron RIE apparatus, and the exposed portion of the silicon oxide based material layer 3 is plasma-etched until just before the underlying material layer is exposed under the following conditions. C ₃ F ₈ 50 sccm N ₂ H ₄ 10 sccm Gas pressure 2.0 Pa RF power source power density 2.2 W / cm ² (13.56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Etched substrate temperature 15 ° C. For the end point of etching, the etching rate of the silicon oxide insulating film 3 is obtained in advance under the same etching condition,
Determined by time control. The state after completion of the first-stage plasma etching is shown in FIG. On the bottom surface of the concave portion where the contact hole is to be opened, the remaining portion 3a of the silicon oxide insulating film is seen. In this etching step, the etching basically proceeds based on the same principle as in the first embodiment, but the etching rate is 1200 nm because the conditions of increasing the RF power source power density and the substrate temperature to be etched are adopted.
/ Min.

Next, the following plasma etching conditions in which the mixing ratio of N ₂ H ₄ is increased are switched to remove the remaining portion 3a of the silicon oxide type insulating film. C ₃ F ₈ 40 sccm N ₂ H ₄ 20 sccm Gas pressure 2.0 Pa RF power source power density 1.2 W / cm ² (13.56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Etched substrate temperature 15 ° C. In this overetching process, the contribution of F ^* being effectively captured by increasing the mixing ratio of N ₂ H ₄ and the reduction of the RF power source power density are
The etching selectivity was about 60 for the base material layer and about 9 for the resist mask. FIG. 3C shows a state after completion of the plasma etching in which the contact hole 5 is opened in the silicon oxide insulating film 3.

According to the present embodiment, by adopting the two-step etching condition in which the mixing ratio of N ₂ H ₄ is changed, plasma etching of the silicon oxide type insulating film satisfying both high selection ratio, uniformity and high throughput is possible. Becomes

Embodiment 4 This embodiment applies the third invention of the present application, and CF ₄ / NH ₃
This is an example in which a low dielectric constant silicon oxide based insulating film on a lower wiring is plasma-etched with a / S ₂ F ₂ mixed gas to open a via hole. This will be described again with reference to FIGS. 2 (a) and 2 (b). To do.

The substrate to be etched shown in FIG. 2 (a) used in this embodiment is the same as that described in the second embodiment, and the duplicated description will be omitted. This substrate to be etched is used as a substrate bias application type ICP (Inductive).
The exposed portion of the low dielectric constant silicon oxide based insulating film 30 is plasma-etched under the following conditions by placing it on a substrate stage of a Ly Coupled Plasma etching apparatus. The substrate stage of this etching apparatus has a mechanism capable of cooling the substrate to be etched to −several tens of degrees Celsius by circulating an alcohol-based coolant cooled by a chiller. CF ₄ 20 sccm NH ₃ 20 sccm S ₂ F ₂ 20 sccm Gas pressure 0.8 Pa ICP power supply 1000 W (2.0 MHz) Substrate bias voltage 300 V Etching substrate temperature −30 ° C. Etching substrate temperature during etching process The temperature was maintained at -30 ° C. In this plasma etching process, C
F generated in plasma due to dissociation of F ₄ and S ₂ F ₂
The anisotropic reaction of the low dielectric constant silicon oxide insulating film 30 proceeded in such a manner that the radical reaction by ^* was mainly assisted by the CF _x ⁺ ion incidence. The etching rate was 950 nm / min.

Further, not only H atoms generated by the dissociation of NH ₃ but also N atoms or active species of these atoms trap excess F ^* in the plasma, and the activity of F ^* itself is suppressed by cooling at low temperature. Further, the etching selectivity is higher than that of the third embodiment due to the fact that the deposition of the sulfur-based material can be used in addition to the strong fluorocarbon-based polymer having a small F content. The value was obtained. In addition, it is possible to reduce the amount of fluorocarbon polymer deposited by the amount of sulfur deposited, and as a result, the microloading effect was effectively reduced. The state after completion of the plasma etching is shown in FIG. The sulfur-based material deposited according to this example was a mixture of elemental sulfur and polythiazyl.

According to the present embodiment, S ₂ F ₂ is further added to the mixed gas of CF ₄ and NH ₃ , and the low dielectric constant silicon oxide type insulating film is patterned while controlling the substrate to be etched at room temperature or below. This makes it possible to achieve both a high selection ratio and low damage to the underlying material layer. In particular, in this embodiment, by heating the substrate stage to 150 ° C. or higher after completion of plasma etching, the sulfur-based material deposited on the substrate to be etched or in the vicinity of the substrate stage can be easily sublimated and removed, resulting in particle contamination and contamination. Does not cause pollution. Further, it is possible to reduce the deposition of the fluorocarbon polymer, and even if the number of substrates to be etched is repeatedly processed continuously, the atmosphere in the chamber in which the fluorocarbon polymer is excessive is not formed, and the etching rate is reduced. No microloading effect occurs. Further, the particle level in the chamber does not increase.

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

For example, although NH ₃ and N ₂ H ₄ are exemplified as the gas containing N and H as constituent elements, NH ₄ HS can be used as described above. Although C ₄ F ₈ , C ₃ F ₈ and CF ₄ are exemplified as the gas containing C and F as constituent elements, other CF-based gases can be used alone or in combination regardless of whether they are saturated or unsaturated. F
A CHF-based gas in which some of the atoms are replaced with H may be used. Similarly, it may be a compound in which some of the F atoms are replaced with other halogen atoms such as Cl and Br.

As a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions, S ₂ F
₂ was taken as a representative, but in addition to this, SF ₂ , SF
₄ , S ₂ F ₁₀ , S ₂ Cl ₂ , S ₃ Cl ₂ , SCl ₂ , S
₂ Br ₂ , S ₃ Br ₂ , and S ₂ Br ₁₀ are exemplified,
These can be used alone or in combination. Since H ₂ S does not have an etching action by itself, it is necessary to use it in combination with a CF-based gas or another halogen-based gas.

Si as a low dielectric constant silicon oxide insulating film
Although OF has been exemplified, it may be SiONF containing nitrogen. These may further contain impurities such as P, B and As. Or SiO ₂ , PSG, BP
It may be a laminated structure film with a general dielectric material such as SG or Si ₃ N ₄ . Application to self-aligned contact without using a resist mask is also possible. Further, it is applicable not only to the processing of contact holes and via holes but also to various types of plasma etching, such as LDD sidewall spacer processing, which requires a high selection ratio with the underlying material layer.

In addition, the structure of the substrate to be etched, the plasma etching apparatus, the plasma etching conditions, etc. can be appropriately selected and applied within the scope of the technical idea of the present invention.

[0049]

As is apparent from the above description, according to the first invention of the present application, control of F ^* in plasma and F in fluorocarbon polymer deposited on the substrate to be etched are performed.
By controlling the content, it is possible to etch the silicon oxide insulating film with a high selectivity.

According to the second invention, by adopting the two-step etching in which the composition ratio of the mixed gas is changed, the above effect can be thoroughly achieved in addition to the high throughput processing.

According to the third aspect of the present invention, by using the deposition of sulfur or polythiazyl in combination, in addition to further improvement of the selection ratio and low damage, the effect of reducing the microloading effect and low contamination can be obtained.

According to the above effects, according to the present invention, it is possible to provide a plasma etching method for a silicon oxide type insulating film which can stably manufacture a highly integrated semiconductor device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating Example 1 to which a plasma etching method of the present invention is applied in the order of steps,
(A) shows a state where a resist mask for opening a contact hole is formed on the silicon oxide insulating film, and (b) shows a state where the contact hole is completed by patterning the silicon oxide insulating film.

2A and 2B are schematic cross-sectional views for explaining Examples 2 and 4 to which the plasma etching method of the present invention is applied, in the order of steps, in which (a) is a resist for opening via holes on a low dielectric constant silicon oxide insulating film. Mask formed, (b)
Is a state in which the via hole is completed by patterning the low dielectric constant silicon oxide insulating film.

FIG. 3 is a schematic cross-sectional view for explaining the third embodiment to which the plasma etching method of the present invention is applied, in the order of steps thereof,
(A) is a state where a resist mask for opening a contact hole is formed on the silicon oxide type insulating film, (b) is a state where the silicon oxide type insulating film is patterned until just before the underlying material layer is exposed, and (c) is an oxidized state. A contact hole is completed by patterning the remaining portion of the silicon-based insulating film in the film thickness direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Impurity diffusion layer, 3 ... Silicon oxide type insulating film, 3a ... Remaining part of silicon oxide type insulating film, 4 ...
Resist mask, 5 ... Contact hole, 6 ... Lower interlayer insulating film, 7 ... Lower wiring, 8 ... Via hole, 30 ... Low dielectric constant silicon oxide insulating film

Claims (5)

[Claims] 1. A silicon oxide insulating film on a base material layer is patterned using a mixed gas containing a gas containing N and H as constituent elements and a gas containing C and F as constituent elements. Method for plasma etching of silicon oxide insulating film. 2. A mixed gas containing a gas containing N and H as constituent elements and a gas containing C and F as constituent elements is used, and the silicon oxide insulating film on the base material layer is replaced by the base material layer. Patterning until just before the exposure, and increasing the mixing ratio of the gas containing N and H as constituent elements in the mixed gas to pattern the remaining portion of the silicon oxide insulating film on the underlying material layer in the film thickness direction. And a step of performing the above steps in this order. 3. A mixed gas containing a gas containing N and H as constituent elements and a sulfur-based compound gas capable of releasing free sulfur into plasma under discharge dissociation conditions is used, and the substrate to be etched is kept at room temperature. A plasma etching method for a silicon oxide based insulating film, which comprises patterning the silicon oxide based insulating film on a base material layer while controlling the following. 4. The gas containing N and H as constituent elements is at least one selected from NH ₃ , N ₂ H ₄ and NH ₄ HS.
The method for plasma etching a silicon oxide insulating film according to any one of claims 1 to 5. 5. The silicon oxide-based insulating film is any one of SiO ₂ , SiO _x F _z and SiO _x N _y F _z. Method for plasma etching of silicon oxide based insulating film of.