JP3154128B2 - 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 applied in the field of manufacturing semiconductor devices and the like, and more particularly, to a method excellent in selectivity with respect to resist and selectivity with respect to silicon underlayer.
In addition, the present invention relates to a dry etching method for a silicon compound layer which does not damage a silicon underlayer at a high speed.

[0002]

In recent years the VLSI, with the progress of high integration and performance of semiconductor devices, as seen in ULSI or the like, the dry etching method of the silicon compound layer represented by silicon oxide (SiO ₂₎ Even technical requirements are becoming more stringent. First, the high integration increases the area of the device chip and increases the diameter of the wafer. The pattern to be formed is highly miniaturized, and uniform processing within the wafer surface is required.
Due to the demand for high-mix low-volume production, as typified by ICs, etc., the mainstream of dry etching equipment is shifting from a conventional batch type to a single-wafer type. At this time, in order to maintain the same productivity as that of the related art, it is necessary to greatly improve the etching rate. In addition, under the circumstances where the junction depth of the impurity diffusion region becomes shallower and the thickness of various material layers is reduced in order to increase the speed and miniaturization of the device, the selectivity to the underlayer is superior to that of the prior art and less damage is caused. Etching technology is required. For example, when a contact is to be formed in an impurity diffusion region formed in a semiconductor substrate or a source / drain region of a PMOS transistor used as a resistance load element of an SRAM, a silicon substrate or a polycrystalline silicon layer is used as an underlayer. SiO performed as
An example is the etching of a _two- layer insulating film. Further, improvement of the resist selectivity is also an important issue. This is because, in submicron devices, the occurrence of slight dimensional change due to resist receding is no longer allowed. However, the characteristics such as high speed, high selectivity, and low damage are mutually selected, and it is extremely difficult to establish an etching process that satisfies all of them.

Conventionally, to dry-etch a silicon compound layer typified by a SiO ₂ layer while maintaining a high selectivity with respect to a silicon-based material layer, CHF ₃ , CF ₄ / H
_Two- mixed systems, CF ₄ / O ₂ mixed systems, C ₂ F ₆ / CHF ₃ mixed systems, and the like have been typically used as etching gases. Each of these is mainly composed of a fluorocarbon gas having a C / F ratio (ratio of the number of carbon atoms to the number of fluorine atoms in a molecule) of 0.25 or more. These gas systems are used because (a) C contained in the fluorocarbon-based gas forms a bond of CO on the surface of the SiO ₂ layer and cuts or weakens the Si-O bond. Yes, (b) SiO
Oxygen in SiO ₂ is reduced to CO ₂ because it can produce _two layers of main etching species, CF _n ⁺ (particularly n = 3), and (c) creates a relatively carbon-rich state in the plasma.
Alternatively, while being removed in the form of CO ₂ , the carbon-based polymer is deposited on the surface of the silicon-based material layer due to the contribution of C, H, F and the like contained in the gas system, and the etching rate is reduced.
This is based on the reason that a high selectivity with respect to the silicon-based material layer can be obtained. Note that the above-mentioned additive gases such as H ₂ and O ₂ are used for the purpose of controlling the selectivity, and can reduce or increase the amount of F ^* generated, respectively. That is, the apparent C of the etching reaction system
It has the effect of controlling the / F ratio.

On the other hand, the applicant of the present application has previously filed Japanese Patent Application No. Hei.
No. 75828 proposes a dry etching method for a silicon compound layer using a saturated or unsaturated chain-like higher-order fluorocarbon-based gas having 2 or more carbon atoms. These are C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₁₀ , C ₄ F ₈
By using a higher-order fluorocarbon-based gas such as that described above, CF _n ⁺ is efficiently generated and the etching speed is increased. However, the use of a single high-order fluorocarbon-based gas alone increases the amount of F ^* generated, and it is not possible to sufficiently increase the selectivity with respect to resist and the selectivity with respect to silicon underlayer. For example, when an SiO ₂ layer on a silicon substrate is etched using C ₃ F ₈ as an etching gas, high speed is achieved, but the selectivity to resist is as low as about 1.3, and etching resistance is insufficient. -A dimension conversion difference occurs due to the retreat of the edge. Further, since the selectivity with respect to silicon is about 4.1, there remains a problem in over-etching resistance. Therefore,
In order to solve these problems, in the above-mentioned prior art, the etching using the chain-like higher-order fluorocarbon gas alone is stopped immediately before the underlayer is exposed, and the carbon-based polymer is deposited when the remaining silicon compound layer is etched. Two-stage etching is performed in which a hydrocarbon-based gas such as ethylene (C ₂ H ₄ ) is further added to this gas in order to promote the etching. This is due to replenishment of C atoms in the etching reaction system and excess F ^* generated by H ^* generated in the plasma ^.
The purpose of this is to increase the apparent C / F ratio by changing to HF by consuming.

However, under the current situation where the design rule of a semiconductor device is highly miniaturized, a dimensional conversion difference from an etching mask has become almost unacceptable. However, it is necessary to further improve the selectivity in the first-stage etching. Also, with the further miniaturization in the future, the effect of particle contamination by the carbon-based polymer may become serious, so the amount of deposition gas such as hydrocarbon-based gas used in the second stage etching is also reduced. I want to reduce it as much as possible.

From this point of view, the present inventor has previously described Japanese Patent Application No. Hei.
In the specification of JP-295225, a silicon compound layer is etched using a chain unsaturated fluorocarbon-based gas having at least one unsaturated bond in a molecule while controlling the temperature of a substrate to be processed to 50 ° C. or less. Propose technology. The chain unsaturated fluorocarbon-based gas theoretically has two or more CFs from one molecule due to discharge dissociation.
_{Since n} ⁺ is generated, SiO ₂ can be etched at a high speed. Further, since the compound has an unsaturated bond in the molecule, a highly active radical is easily generated by dissociation, and the polymerization of the carbon-based polymer is promoted. Moreover, since the temperature of the substrate to be processed is controlled to 50 ° C. or less, the deposition of the carbon-based polymer is promoted. Therefore, selectivity with respect to resist and selectivity with respect to silicon underlayer can be improved. Octafluorobutene (C ₄ F ₈ ), hexafluoropropene (C ₃ F ₆ ), or the like is used as the chain unsaturated fluorocarbon-based gas. Also,
In the same specification, the etching by the chain unsaturated fluorocarbon-based gas alone is stopped halfway in the silicon compound layer, and the remaining etching and over-etching are performed by adding the above-mentioned chain unsaturated fluorocarbon-based gas to C ₂ H ₄ or the like. A technique using a gas to which a hydrocarbon-based gas is added has also been proposed at the same time. This is because a deposition gas is used in the middle of etching in order to further improve the selectivity to the underlying silicon.

As still another approach, the present inventor has previously disclosed in Japanese Patent Application No. 3-40966 that at least a part of a molecular structure is formed while controlling the temperature of a substrate to be processed to 50 ° C. or less. A technique for etching a silicon compound layer using a saturated or unsaturated fluorocarbon-based compound having This is because, for example, when compared between saturated compounds having the same number of carbon atoms, the C / F ratio of the etching reaction system is increased by utilizing the fact that the number of F atoms in the cyclic compound can be reduced by two compared to the chain compound. It is intended to be. In the above specification, C ₃ F ₆ , C
₄ F _8, C ₅ F ₁₀ or the like, also _{C 3 F 4, C 4 F} 6, C 5 F 8 or the like is exemplified as cyclic unsaturated fluorocarbon compounds.

[0008]

However, in the technology using a chain unsaturated fluorocarbon-based gas or a cyclic unsaturated fluorocarbon-based gas conventionally proposed, as is apparent from the above description, In order to obtain a high selectivity, it was practically necessary to use it in combination with H ₂ or a hydrocarbon gas. However, with the miniaturization of design rules, the influence of hydrogen contained in these additional gases cannot be ignored. For example, Applied
Physics Letters 1988 53
Vol. 18, pages 1735 to 1737, reports on the induction of defects in single crystal silicon by hydrogen plasma.
That is, H ⁺ generated in the hydrogen plasma has an extremely small ionic radius and mass, so that when implanted into the silicon substrate, H ⁺ penetrates with a large range and acts as a nucleus that induces crystal defects in the subsequent process. In addition, there is a concern that the crystal strain caused by the implantation of H ⁺ leads to an increase in the contact resistance, even if it does not reach the crystal defect. Therefore, in a normal process, light etching is performed from the surface layer of the silicon substrate to a depth of several tens nm to remove the damaged layer.

However, as described above, single-wafer processing is becoming the mainstream in the field of manufacturing semiconductor devices, and the type of dry etching equipment is high-density plasma such as magnetron type or ECR (Electron Cyclotron Resonance) type. The type of apparatus that performs high-speed etching will become mainstream in the future. When a wafer is placed in such high-density plasma, it is sufficiently predicted that H ⁺ generated by discharge dissociation from a hydrocarbon-based gas will cause a large damage to a silicon substrate. Even if the damaged layer is removed by light etching, the amount of silicon substrate removed by such post-processing cannot be neglected in the current situation where the junction depth of the impurity diffusion region is becoming increasingly shallow. It has become to. Therefore, it is desired to perform etching using a gas system that does not generate H ⁺ in plasma.

[0010] In this sense, the aforementioned Japanese Patent Application No. Hei.
The cyclic fluorocarbon-based compound proposed in the specification is also promising as an additive gas. This is because the cyclic fluorocarbon-based compound has a higher C
/ F ratio, and this addition can have the effect of increasing the apparent C / F ratio of the etching reaction system. In fact, in the specification, were etched the SiO ₂ interlayer insulation film by the addition of C ₄ F ₈ and C ₄ F ₆ in chain saturated fluorocarbon compounds such as C ₃ F ₈ good results Is described.

However, under the current situation where the surface step of the wafer is increasing with the three-dimensional device structure, over-etching of 100% or more is required even in the etching of the interlayer insulating film. Therefore, higher selectivity is required than before. In the field of dry etching in recent years, so-called low-temperature etching, in which a wafer is cooled to 0 ° C. or lower to perform etching, has attracted attention. This is because while maintaining the etching rate in the depth direction of the material layer to be etched at a practical level by ion-assisted reaction, the low-temperature cooling suppresses or freezes the radical reaction to reduce the lateral etching rate, It enables anisotropic processing even with ion incident energy. The wafer temperature during the etching is 200 ° C due to plasma radiation heat or reaction heat unless cooling is performed.
Since the temperature rises to the vicinity, even when the wafer temperature is around room temperature, it may be included in the low-temperature etching in a broad sense. When performing low-temperature etching, how to approach the wafer cooling temperature to the room temperature range is a very important factor that determines the practicality and throughput of the process. However, most of the conventional techniques require cooling at 0 ° C. or lower, and further improvement is required in this respect as well. Accordingly, an object of the present invention is to provide a method of etching a silicon compound layer having excellent selectivity in a temperature range close to room temperature without causing damage to a silicon substrate.

[0012]

A dry etching method according to the present invention is proposed to achieve the above-mentioned object, and controls the temperature of a substrate to be etched to 50 ° C. or lower and obtains a general formula C _x F _y (where x and y are natural numbers indicating the number of atoms and satisfy the condition of x ≧ 2, y ≦ 2x), and a general formula C _p F _q (where, , P and q are natural numbers indicating the number of atoms and satisfy the condition of p ≧ 3, q ≦ 2p-2), and are represented by the following formula: And etching the silicon compound layer using an etching gas containing the following.

In the present invention, a chain unsaturated fluorocarbon compound C _x F which constitutes one of the main components of the etching gas.
_y is a so-called higher-order fluorocarbon having 2 or more C atoms. The upper limit of the number x of C atoms is not particularly limited as long as the chain compound can be introduced into the etching reaction system in a vaporized state. The number of F atoms y is y ≦
Since the 2x condition is satisfied, the above-mentioned chain unsaturated fluorocarbon compound has at least one unsaturated bond in the molecule. The chain unsaturated fluorocarbon compound is higher in C / C than the chain saturated fluorocarbon compound.
Since the F ratio (the ratio of the number of C atoms to the number of F atoms) is high and a monomer that is advantageous for accelerating the polymerization of the carbon-based polymer by cleavage of the unsaturated bond is produced, the carbon-based polymer is relatively deposited. This facilitates etching with reduced influence of F ^* . Type and number of the unsaturated bond is not particularly limited, discharge dissociated by the plasma 2 or more CF _n ⁺ can be generated from one molecule, and reduce the etch rate due to excessive deposition of carbonaceous polymer It is desirable to select within a range that is not allowed. The structure of the carbon skeleton is not particularly limited, and may be linear or branched.

In the present invention, the cyclic unsaturated fluorocarbon compound, which is the other main component of the etching gas, is required to form a cyclic portion in at least a part of its molecular structure.
The number of atoms p is 3 or more. The number of F atoms q is q ≦ 2p−
Since the second condition is satisfied, the compound has at least one unsaturated bond in the molecular structure. The upper limit of the number p of C atoms is
The compound is not particularly limited as long as it is a compound that can be introduced into the etching reaction system in a state where the chain compound is vaporized and that can be technically manufactured and can stably exist. The type and number of unsaturated bonds are not particularly limited, either.
It is not preferable that the C / F ratio is extremely increased due to the presence of too many unsaturated bonds in the molecule. For example, Tokuho 1
Japanese Patent No. 60938 discloses that hexafluorobenzene (C ₆ F ₆ ; C / F ratio = 1) having three double bonds in a carbon 6-membered ring alone cannot constitute an SiO ₂ etching gas. Is mentioned. This is because C ₆ F ₆ generates a remarkably large amount of CF _n ⁺ in the plasma, so that the polymerization of the carbon-based polymer is excessively promoted and the etching reaction does not proceed. In the above publication, in order to suppress the generation of CF _n ⁺ , CF ₄ having the lowest C / F ratio among all fluorocarbon-based gases is mixed to enable etching of SiO ₂ . The above unsaturated fluorocarbon compounds are those having a saturated chain such as CF ₃ — bonded to an unsaturated ring, and those having an unsaturated chain such as CF ₂ ＝ CF— bonded to an unsaturated ring. , CF ₂ ＣC in a saturated ring
It may be one having an unsaturated chain such as F- bonded thereto.

Further, in the present invention, the temperature of the substrate to be etched during the etching is controlled to 50 ° C. or less. This temperature control may be performed in a room temperature range or in a temperature range of 0 ° C. or lower, which is generally called low-temperature etching, but in any case, etching can be performed in a much higher temperature range than the conventional technology. This is an advantage of the present invention. Usually, the temperature of the substrate to be etched rises to about 200 ° C. unless cooling is particularly performed in the process of dry etching. However, if the temperature is controlled to 50 ° C. or lower, the carbon-based polymer can be efficiently deposited by lowering the vapor pressure.

[0016]

From 1 molecule of chain unsaturated fluorocarbon compounds used in the present invention, theoretically two or more CF _n
⁺ Generates. Therefore, under the same gas pressure, CF
Compared to the case where a conventionally known gas such as ₃ H or CF ₂ H ₂ is used, the absolute amount of CF _n ⁺ in the plasma is increased, and high-speed etching can be performed. In addition, monoradicals are generated by discharge dissociation, or highly active biradicals such as carbene are generated depending on conditions.
By attacking the electronic system, the polymerization of the carbon-based polymer is promoted.

However, if the above-described so-called higher-order fluorocarbon is used, the amount of F ^* generated in the plasma naturally increases. Conventionally, H ₂ or a hydrocarbon-based gas has been added to increase the C / F ratio of the etching reaction system. However, in the present invention, a cyclic unsaturated fluorocarbon-based compound having a cyclic portion in at least a part of the molecular structure is used. Is added. That is, instead of increasing the C / F ratio by capturing F ^* with H ^* , a similar effect is obtained by using a compound having a different carbon skeleton. This is possible because the number of fluorine atoms of the cyclic unsaturated fluorocarbon-based compound is two or more less than that of the chain unsaturated fluorocarbon-based compound having the same type and number of carbon atoms and unsaturated bonds. Because. Further, this cyclic unsaturated fluorocarbon-based compound has an action of accelerating the polymerization of a carbon-based polymer similarly to the above-mentioned chain unsaturated fluorocarbon-based compound.

The above-mentioned carbon-based polymer is deposited on the substrate to be etched whose temperature is controlled to 50 ° C. or less. However, the surface of a silicon-based material layer such as monocrystalline silicon or polycrystalline silicon or the surface of a resist pattern is subjected to ion bombardment. Also, it is not easily removed. However, on the surface of a silicon compound layer such as SiO ₂ , oxygen contained in the layer is sputtered out and contributes to the decomposition of the carbon-based polymer, so that it is easily removed. Therefore, as the deposition of the carbon-based polymer increases, the selectivity to resist and the selectivity to silicon underlayer improve. However, in the present invention, since the absolute amount of CF _n ⁺ , which is an etching species of the silicon compound layer, is increased, the etching rate does not decrease at all even if the deposition of the carbon-based polymer is promoted. In addition, in the present invention, since a compound that generates H ⁺ is not added to the etching gas, there is no possibility that a defect of the silicon substrate is caused by the injection of H ⁺ . Conventionally, light etching is performed to remove a damaged layer formed on a surface layer portion of a silicon substrate. However, according to the present invention, this is not necessary. As described above, according to the present invention, it is possible to perform etching of a silicon compound layer while satisfying all requirements for dry etching, such as high base selectivity, high resist selectivity, high anisotropy, and high speed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. In the following description, when a cyclic unsaturated fluorocarbon-based compound having a cyclic portion is indicated, it is assumed that the composition formula has a cyclic head in order to avoid confusion with a chain unsaturated fluorocarbon-based compound. Represents c-
Notation is added.

Embodiment 1 In this embodiment, the present invention is applied to contact hole processing, and a mixed gas of hexafluoropropene (C ₃ F ₆ ) and hexafluorocyclobutene (c-C ₄ F ₆ ) is used. This is an example in which the SiO ₂ interlayer insulating film is etched by the following method. In the substrate to be etched (wafer) used as an etching sample in this embodiment, an SiO ₂ interlayer insulating film is formed on a single crystal silicon substrate on which impurity diffusion regions have been formed in advance, and the SiO ₂ interlayer insulating film is etched. A resist pattern is formed as a mask. The wafer was set on a wafer mounting electrode of a magnetron RIE (reactive ion etching) apparatus. Here, the wafer mounting electrode has a built-in cooling pipe, and by supplying a coolant to the cooling pipe from a cooling facility such as a chiller connected to the outside of the apparatus and circulating the same, the wafer temperature during etching is reduced by 50%. It is possible to control the temperature to below ° C. Here, ethanol is used as a coolant, and the wafer temperature during etching is 20 ° C.
To be maintained. In this state, for example, C ₃
F ₆ flow rate 45 SCCM, c-C ₄ F ₆ flow rate 5 SCCM,
Etching was performed under the conditions of a gas pressure of 2 Pa, an RF power density of 2.0 W / cm ² , and a magnetic field strength of 150 Gauss.

In the above-described etching process, etching of the SiO ₂ interlayer insulating film causes an ion-assisted reaction due to CF _n ⁺ generated in a large amount in the plasma by discharge dissociation of C ₃ F ₆ and c—C ₄ F _6. It proceeded at high speed by the main mechanism. At this time, on the surface of the resist pattern, the carbon-based polymer was efficiently deposited from C ₃ F ₆ and c-C ₄ F ₆ , but on the surface of the SiO ₂ interlayer insulating film, it was removed by etching itself. The carbon-based polymer was also removed. As a result, even though no operation such as addition of a deposition gas or switching of etching conditions has been performed, a contact having a good anisotropic shape has been obtained.
A hole was formed. The selectivity to resist in this process was 3.5 and the selectivity to silicon was about 15.
By obtaining the above selectivity with respect to resist, the dimensional conversion difference was significantly reduced as compared with the conventional case. In addition, since a high selectivity to silicon was obtained as described above,
%, The damage to the single crystal silicon substrate and the impurity diffusion region was minimized. Each value of the above selectivity was equivalent to the selectivity when using an etching gas to which a deposition gas containing H was added, such as a mixed gas of C ₃ F ₈ / C ₂ H ₄ . However, in this embodiment, since H ⁺ was not generated in the plasma, the substrate damage evaluated by the thermal wave method was suppressed to about の of the conventional one. Also, when the cross section of the etched wafer was observed with a transmission electron microscope, the crystal distortion characteristically observed in the surface layer of the impurity diffusion region when etching was conventionally performed with an etching gas containing H was performed. However, in this example, it was not observed at all.

For comparison, C ₃ F ₈ which is a chain saturated fluorocarbon compound is used in place of C ₃ F ₆ described above.
, And etching was performed under the same discharge conditions, but the wafer had to be cooled to 0 ° C. in order to obtain the same selectivity. This is because the C ₃ F ₈ does not produce carbon-based polymer, only c-C ₄ F ₆ is involved in the formation,
This is because it was necessary to further lower the temperature of the wafer by 20 ° C. in order to efficiently deposit the carbon-based polymer.

Embodiment 2 This embodiment is also an example of etching an SiO ₂ interlayer insulating film using a mixed gas of C ₃ F ₆ and c—C ₄ F ₆ , similarly to the first embodiment. However, in order to further improve the selectivity to the single crystal silicon substrate as the base, C ₃ F ₆ is required between the just etching step and the over etching step.
And changing the flow rate of c-C ₄ F _6. The wafer used in this example is the same as that used in Example 1.
The wafer is set in a magnetron RIE apparatus, and as an example, a C ₃ F ₆ flow rate of 46 SCCM, a c-C ₄ F ₆ flow rate of ₄ SCCM, a gas pressure of 2 Pa, and an RF power density of 2.0 W /
cm ² , magnetic field strength 150 Gauss, wafer temperature 30 ° C.
Under the conditions described above, the SiO ₂ interlayer insulating film was first etched to near the just etching. The term “just etching” as used herein refers to a state in which the underlying single crystal silicon substrate is first exposed in the wafer plane.

Next, as an example, a C ₃ F ₆ flow rate of 30 SCC
M, c-C ₄ F ₆ flow rate 20 SCCM, gas pressure 2 Pa, R
F power density 1.5 W / cm ² , magnetic field strength 150 Gau
Overetching was performed under the conditions of ss and a wafer temperature of 30 ° C. The progress of the etching reaction and the deposition mechanism of the carbon-based polymer in each of the above-described steps are basically the same as those in Example 1.
Is as described above. However, in the over-etching process, c-
The flow rate of C ₄ F ₆ has been greatly increased, and relatively F ^*
Conditions are set to reduce carbon dioxide and promote the deposition of carbon-based polymers. In addition, the RF power density is lowered to reduce the incident ion energy. As a result, despite the higher wafer temperature than in Example 1,
Sufficient high selectivity has been achieved.

Although the present invention has been described based on two embodiments, the present invention is not limited to these embodiments. For example, for the purpose of controlling the etching rate, O ₂ is added to the etching gas. A rare gas such as He or Ar may be added as appropriate in order to expect a sputtering effect, a dilution effect, a cooling effect and the like. Further, the material layer to be etched is not limited to the above-mentioned SiO ₂ , but may be PSG, BSG, BPSG, AsSG, ASG.
It may be sPSG, AsBSG, SiN or the like.

[0026]

As is clear from the above description, in the present invention, the etching of the silicon compound layer is performed by using an etching gas obtained by adding a cyclic unsaturated fluorocarbon compound to a chain unsaturated fluorocarbon compound. Do. Such an etching gas not only enables high-speed etching by generating a large amount of CF _n ⁺ , but also increases the C / F ratio to promote the deposition of a carbon-based polymer even at around room temperature, and has a selectivity with respect to an underlayer and a resist. Improve. Moreover, unlike the conventional means for improving selectivity, since a compound capable of generating H ⁺ is not added to the plasma, there is no danger of generating defects in the silicon substrate, and a method for removing the damaged layer is not required. No need for light etching. Therefore, the present invention is extremely suitable for manufacturing a semiconductor device which is designed based on a fine design rule and has a high degree of integration and high performance.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 H01L 21/302

Claims (1)

(57) [Claims] 1. The temperature of a substrate to be etched is controlled to 50 ° C. or lower, and a general formula C _x F _y (where x and y are natural numbers indicating the number of atoms and satisfy the conditions of x ≧ 2 and y ≦ 2x) .)
And a chain unsaturated fluorocarbon compound represented by the formula: and a general formula C _p F _q (where p and q are natural numbers indicating the number of atoms and satisfy the conditions of p ≧ 3, q ≦ 2p−2) And a cyclic unsaturated fluorocarbon-based compound having a cyclic portion in at least a part of its molecular structure.
A dry etching method comprising etching a silicon compound layer using a gas.