JP3297939B2 - 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 semiconductor device manufacturing and the like, and more particularly to any one of resist selectivity, silicon base selectivity, high speed, low damage, and low contamination. And a method for dry etching a silicon compound layer.

[0002]

2. Description of the Related Art As high integration and high performance of semiconductor devices have progressed as seen in recent VLSI, ULSI, etc., dry etching of a silicon compound layer typified by silicon oxide (SiO ₂ ) is also required. Technical requirements are becoming more stringent.

First, the area of device chips has been increased due to high integration, and the diameter of the wafer has been increased. The pattern to be formed has been highly miniaturized, and uniform processing within the wafer surface has been required. Due to the demand for high-mix low-volume production as represented by the ASIC, 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 the conventional one, the etching rate per wafer must be greatly improved.

Further, under the circumstances where the junction depth of the impurity diffusion region is reduced 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 better than before. An etching technique with less damage is required. For example, an impurity diffusion region formed in a semiconductor substrate or a PM used as a resistance load element of an SRAM.
For example, when a contact is to be formed in a source / drain region of an OS transistor or the like, etching of a SiO ₂ interlayer insulating film using a silicon substrate or a polycrystalline silicon layer as a base is an example.

[0005] Further, improvement of the selectivity to resist 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.

Conventionally, etching of a SiO ₂ -based material layer has been performed in a mode in which ionicity is increased in order to cut a strong Si—O bond. Typical etching gases are CHF ₃ , CF _4, etc., and utilize the incident energy of CF _x ⁺ generated from them. However, in order to perform high-speed etching, it is necessary to increase the incident ion energy, and since the etching reaction is close to a physical sputter reaction, there is a demand for high-speed and high selectivity and low damage. The request was always in conflict.

Therefore, usually, the apparent C / F ratio (ratio between the number of carbon atoms and the number of fluorine atoms) of the etching reaction system is adjusted by adding H ₂ or a depositing hydrocarbon gas to the etching gas. High selectivity is achieved by increasing and accelerating the deposition of carbon-based polymers that compete with the etching reaction.

[0008]

By the way, in the conventional method, it was necessary to deposit a carbon-based polymer to a certain thickness in order to obtain a sufficiently high selectivity. But,
Increasing the deposition amount of the carbon-based polymer causes new problems such as a decrease in etching rate and an increase in particle contamination. In recent years, single-wafer processing has become the mainstream in dry etching, so that the time required for etching per wafer increases or the frequency of maintenance for cleaning the etching chamber increases. And cause serious hindrance to economics.

Accordingly, an object of the present invention is to provide a dry etching method for a silicon compound layer which is excellent not only in high selectivity and low damage, but also in high speed and low contamination.

[0010]

SUMMARY OF THE INVENTION A dry etching method according to the present invention is proposed to achieve the above object, and includes at least one kind of inorganic oxide selected from carbon oxide, nitrogen oxide, and sulfur oxide. And a just etching step of etching the silicon compound layer to a depth substantially not exceeding the thickness of the silicon compound layer using an etching gas containing the fluorine-based compound, and a content ratio of the inorganic oxide in the etching gas. And an over-etching step of etching the remaining part of the silicon compound layer as larger than that in the just etching step.

[0011]

[0012]

The present invention further provides S ₂ F ₂ , SF ₂ , SF ₄ , S ₄ after performing just etching using an etching gas containing the above-mentioned inorganic oxide and fluorine compound.
And performs over-etched using an etching gas containing at least one kind of sulfur fluoride and the inorganic oxide selected from ₂ F _10.

In the present invention, the above-mentioned inorganic oxide is
It is used as a component of the etching gas.
Therefore, in consideration of handling properties, it is gaseous at normal temperature and normal pressure.
Or select compounds that can be easily vaporized
There is. From this point of view, as highly practical carbon oxide
Is CO (carbon monoxide), CO _Two(Carbon dioxide), C_Three
O_Two(Tricarbon dioxide, boiling point 7 ° C)
You. Carbon oxides also have an additional number of carbon atoms in the molecule.
There are more compounds called carbon suboxides than the number of elementary atoms.
It is known that when performing silent discharge in carbon monoxide,
Generates substances of variable composition, pentacarbon dioxide, acetic acid
12 carbon (melittic anhydride) and the like.

Further, nitrogen oxides having high practicality include N
₂ O (dinitrogen oxide), NO (nitrogen monoxide), N ₂ O
₃ (dinitrogen trioxide), NO ₂ (nitrogen dioxide), NO
₃ (nitrogen trioxide). Other known nitric oxides include N ₂ O ₅ (dinitrogen pentoxide).
And N ₂ O ₆ (dinitrogen hexaoxide), the former having a sublimation point of 3
A solid at 2.4 ° C. (1 atm), the latter being an unstable solid.

Furthermore, as a highly practical sulfur oxide
Is SO (sulfur monoxide), SO_Two(Sulfur dioxide)
Can be mentioned. There are several other types of sulfur oxide
Although it is known, near room temperature, complicated phases and
Many exist as mixtures having a composition. for example
If S_TwoO_Three(Sulfur trioxide) becomes S, S by heating
O, SO_TwoIt is a solid that decomposes into SO_Three(Io trioxide
C) is a liquid near room temperature, or α-type with a different melting point,
It is a solid that takes either β-type or γ-type. S_TwoO₇
(Sulfur heptoxide) is a solid with a melting point of 0 ° C and a sublimation point of 10 ° C.
is there. Furthermore, SO _Four(Sulfur tetroxide) is a solid with a melting point of 3 ° C.
Although it is a body, it generates oxygen and decomposes it, producing sulfur dioxide
Generate.

[0017]

The point of the present invention is to enhance the film quality of the carbon-based polymer itself to achieve sufficiently high resist selectivity and underlayer selectivity even if the deposition amount is reduced. The aim is to achieve damage. In the present invention, at least one of carbon oxide, nitrogen oxide, and sulfur oxide is used as a component of the etching gas. These inorganic oxides have multiple bonds between different atoms in the molecule and exist as resonance hybrids of several polarization structures, but certain of these polarization structures have high polymerization promoting activity. Have. As a result, the degree of polymerization of the carbon-based polymer derived from the decomposition product of the etching gas or the decomposition product of the organic material pattern used as the etching mask is increased, and the etching resistance is improved.

Decomposition products of these inorganic oxides include carbonyl groups (> C ＝ O), nitrosyl groups (—N ＝ O), nitrile groups (—NO ₂ ), thionyl groups> S ＯO) and a polar group such as a sulfuryl group (—SO ₂ ) can be introduced. When such a polar group is introduced into a carbon-based polymer, chemical and physical stability may be increased as compared with a conventional carbon-based polymer having a repeating structure of -CX _2- (X represents a halogen atom). Recent studies have revealed this. There are roughly two reasons for the reason for this phenomenon:

One of them is a C—O bond (1077 kJ).
/ Mol), C—N bond (770 kJ / mol), N-
O bond (631 kJ / mol), CS bond (713 kJ / mol)
J / mol), the C—C
This is the fact that it is larger than the C bond (607 kJ / mol). The other is that the introduction of the functional group increases the polarity of the carbon-based polymer, and increases the electrostatic attraction force of the negatively charged wafer being etched.

As described above, since the film quality of the carbon-based polymer itself is enhanced and the carbon-based polymer exhibits high resistance to incident ions, the selectivity to the organic material pattern or the underlying material layer serving as an etching mask is improved. In addition, damage to the underlying material layer is reduced. In addition, the amount of carbon-based polymer deposited required to achieve high selectivity can be relatively reduced, so that particle contamination can be reduced as compared with the prior art.

The above-mentioned inorganic oxide also contributes to speeding up of etching. That is, the above can be generated from the functional groups _{^{CO *, SO *, SO 2}} *, radicals NO ^* such has a strong reducing action, it is possible to pull out the O atoms in the SiO _2. This is because the interatomic bond energy calculated from the heat of formation of a diatomic molecule is 1 for a CO bond.
076 kJ / mol, 523 kJ / mo for SO bond
It is understood from the fact that it is 632 kJ / mol for the 1, N—O bond, which is larger than 465 kJ / mol for the Si—O bond in the crystal. The Si atoms from which the O atoms have been extracted are quickly removed in the form of a halide by binding to F ^* (fluorine radical), which is the main etching species present in the etching reaction system.

That is, in the present invention, the breaking of the Si—O bond, which has conventionally relied solely on the physical sputtering action, can be performed by utilizing the chemical action. Moreover, the inorganic oxide used in the present invention has no significant effect on the resist material or the underlying Si-based material, and the etching rate of these materials is kept low.

[0023]

The present invention is based on the above concept, but also proposes a method aiming at further higher selection, lower contamination and lower damage. One of them is to separate the etching of the silicon compound layer into two steps, a just etching step immediately before the base material layer is exposed and an over-etching step thereafter, and the inorganic oxide in the etching gas in the latter half of the over-etching step. Is to be larger than that in the just etching step. According to this method, the etching of the SiO ₂ -based material layer in the vicinity of the interface with the underlayer progresses by a mechanism that reduces F ^* and promotes the O-atom abstraction reaction and the polymer strengthening. Is achieved.

Alternatively, an etch at the time of over-etching
The gas composition_TwoF_Two, SF _Two, SF_Four, S_TwoF
_TenAt least one kind of sulfur fluoride selected from
It may be a mixed system with an inorganic oxide. In other words, over
High speed is not particularly required at the time of etching.
Orocarbon-based compounds are not used
It eliminates any deposits.

The sulfur fluoride used herein is described in the specification of Japanese Patent Application No. 2-198,045 by the present applicant.
A compound proposed for etching an SiO ₂ -based material layer, and generates etching species such as SF _x ⁺ and F ^* . Further, the sulfur fluoride has a higher S / F ratio (ratio of the number of S atoms to the number of F atoms in one molecule) than SF ₆ which has been practically used as an etching gas. Free S (sulfur) can be released into the plasma. This S is deposited on the surface of the wafer if the temperature is controlled to be approximately equal to or lower than room temperature, depending on conditions. At this time, S is removed in the form of SO _{x on} the surface of the SiO ₂ -based material layer due to the supply of O atoms.
It is deposited as it is on the surface of the system material or on the pattern side wall, and contributes to achieving high selectivity and high anisotropy.

Moreover, the deposited S easily sublimates when the wafer is heated to about 90 ° C. or more after the etching, and the sulfur nitride-based compound is decomposed or sublimated at about 130 ° C. or more. Do not leave. Therefore, etching excellent in all of high speed, high selectivity, low contamination, and low damage can be performed.

When this sulfur fluoride is used in combination with nitrogen oxide, S generated from sulfur fluoride and N generated from this nitrogen oxide combine to form polythiazyl (SN).
_A sulfur nitride compound mainly composed of _x is generated. This sulfur nitride-based compound exerts a more effective surface protection effect than S alone.

[0029]

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

Embodiment 1 In this embodiment, the present invention is applied to contact hole processing, and an SiO ₂ interlayer insulating film is etched using a C ₃ O ₂ / SF ₆ mixed gas. This process is illustrated in FIG.
This will be described with reference to FIG. The wafer used as a sample in the present embodiment is, as shown in FIG.
An SiO ₂ interlayer insulating film 3 is formed on a single crystal silicon substrate 1 on which an impurity diffusion region 2 has been formed in advance, and
A resist mask 4 is formed as an etching mask for the O ₂ interlayer insulating film 3. The resist mask 4 has an opening 4a.

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 and circulating a coolant to the cooling pipe from a cooling facility such as a chiller connected to the outside of the apparatus,
It is possible to control the temperature of the wafer during etching to a temperature equal to or lower than room temperature. As an example, under the following conditions, SiO 2
The etching of the _two- layer insulating film 3 was performed.

C_ThreeO_TwoFlow 20 SCCM SF₆Flow rate 30 SCCM Gas pressure 2.0 Pa RF power density 2.2 W / cm^Two(1
3.56 MHz) Magnetic field strength 1.50 × 10^-2 T (= 150
G) Wafer temperature -30 ° C (alcohol type)
In this etching process, the Si exposed in the opening 4a is used.
O_TwoSF on the surface of the interlayer insulating film 3₆Raw in large quantities from
F to form^*Atom abstraction reaction by C and C_ThreeO
_TwoCO generated from^*The reaction of abstraction of O atoms by
F_x ⁺, CO_x ⁺SiO by etc._TwoSputter etch
Promotes etching and etches at an etching rate of about 250 nm / min.
The pitching proceeded.

On the other hand, carbon-based decomposition products supplied from the resist mask 4 by ion sputtering are as follows:
A strong carbon-based polymer was formed while incorporating a CO bond and a carbonyl group into the structure. This carbon-based polymer exhibited high etching resistance even in a small amount, and greatly reduced the etching rate on the resist mask 4 and the surface of the single-crystal silicon substrate 1. Further, since the wafer is cooled at a low temperature, a radical reaction due to F ^* is suppressed, and the etching rate of a resist material or a silicon-based material mainly etched in the radical mode is reduced to Si.
It was relatively lower than that of the O ₂ -based material.

For these reasons, the resist mask 4
And a very high selectivity with respect to the single crystal silicon substrate 1 was achieved. Particularly, since the shape of the resist mask 4 is favorably maintained, a contact hole 5 having a favorable anisotropic shape without generating a dimensional conversion difference is formed as shown in FIG. We were able to.

Embodiment 2 In this embodiment, a contact hole is also formed.
This is an example in which an SiO ₂ interlayer insulating film is etched using a NO / SF ₆ mixed gas. The wafer used as the etching sample in this embodiment is the same as that shown in FIG. The same applies to each embodiment described later.

An example of the etching conditions is shown below. NO flow rate 20 SCCM SF ₆ flow rate 30 SCCM gas pressure 2.0 Pa RF power density 2.2 W / cm ² (1
3.56 MHz) Magnetic field strength 1.50 × 10 ^-2 T (= 150
G) Wafer temperature −30 ° C. (using alcohol-based refrigerant) The etching mechanism that proceeds under the above conditions is almost the same as that in Example 1. Here, the carbon-based polymer is a C—N bond, a nitrosyl group, or the like. Was strengthened by the introduction of

Embodiment 3 In this embodiment, the same SiO ₂ interlayer insulating film 3 is formed using SO ₂ / S
Etching was performed using an F ₆ mixed gas. An example of the etching conditions is shown below. SO ₂ flow rate 20 SCCM SF ₆ flow rate 30 SCCM Gas pressure 2.0 Pa RF power density 2.2 W / cm ² (1
3.56 MHz) Magnetic field strength 1.50 × 10 ^-2 T (= 150
G) Wafer temperature −30 ° C. (using alcohol-based refrigerant) The etching mechanism that proceeds under the above conditions is almost the same as that in Example 1. Here, the carbon-based polymer is composed of a C—S bond, a sulfuryl group, Strengthened by the introduction of a thionyl group.

Embodiment 4 In this embodiment, the same interlayer insulating film 3 is formed of C ₃ O ₂ / CHF ₃
Etching was performed using a mixed gas. An example of the etching conditions is shown below. C ₃ O ₂ flow rate 20 SCCM CHF ₃ flow rate 30 SCCM Gas pressure 2.0 Pa RF power density 2.0 W / cm ² (1
3.56 MHz) Magnetic field strength 1.50 × 10 ^-2 T (= 150
G) Wafer temperature -30 ° C (using alcohol-based refrigerant)

In this embodiment, since an ion-assisted reaction by CF _x ⁺ can be expected, the etching rate is much higher than that of the first embodiment, and is about 450 nm / min.
In addition, by using CHF ₃ having a deposition property, a carbon-based polymer is also generated in the gas phase.
The supply amount of the decomposition product of the compound is small. In other words, the incident ion energy can be reduced as compared with the previous embodiments, and the sputtering of the resist mask 4 can be suppressed. In this embodiment, the resist mask 4
Almost no reduction in film thickness, retreat of pattern edges, breakage of shallow junctions due to overetching, etc. were observed. The selectivity to resist was about 5, and the selectivity to silicon was about 25.

Further, the relative content of CHF ₃ is reduced by the addition of C ₃ O ₂ to the etching gas, and the absolute amount of the carbon-based polymer produced is much smaller than in the conventional process. The frequency of maintenance required for cleaning the etching chamber can be reduced,
Throughput has been greatly improved.

It should be noted that even when etching is performed under the same conditions except that N ₂ O or SO ₂ is used instead of C ₃ O ₂ , high-speed, high-selection, and low-contamination etching can be similarly performed. did it.

Embodiment 5 In this embodiment, a contact hole is also formed.
C ₃ O divided etching of SiO ₂ interlayer insulating film 3 into two stages of just etching step and over-etching process using a ₂ / CHF ₃ gas mixture, C ₃ O ₂ in the latter step
This is an example in which the selectivity is further improved by relatively increasing the content ratio of. This process will be described with reference to FIG. 2 and FIG. 1 described above.

First, the wafer shown in FIG.
As an example, under the following conditions, _TwoInterlayer insulating film 3
The process was performed until immediately before the impurity diffusion region 2 was substantially exposed. C_ThreeO_TwoFlow rate 15 SCCM (content ratio in etching gas 30%) CHF_ThreeFlow rate 35 SCCM Gas pressure 2.0 Pa RF power density 2.0 W / cm^Two(13.
56 MHz) Magnetic field strength 1.5 × 10^-2 T Wafer temperature 0 ℃

The etching mechanism in this just etching step is almost as described above in the fourth embodiment.
The end point was determined when the emission spectrum intensity of CO ^* at 483.5 nm or the emission spectrum intensity of SiF ^* at 777 nm started to change. This time corresponds to the time when the underlying impurity diffusion region 2 starts to be exposed on a part of the wafer. However, in another part of the wafer, as shown in FIG. 2, the contact hole 5 was formed only up to the middle part, and the remaining part 3a of the SiO ₂ interlayer insulating film 3 was left at the bottom.

Therefore, the etching conditions were switched to the following conditions as an example, and over-etching was performed to remove the remaining portion 3a. C ₃ O ₂ flow rate 30 SCCM (content ratio in etching gas 60%) CHF ₃ flow rate 20 SCCM gas pressure 2.0 Pa RF power density 1.2 W / cm ² (13.
56 MHz) Magnetic field intensity 1.5 × 10 ⁻² T Wafer temperature 0 ° C. In this over-etching step, the RF power density is reduced to reduce the incident ion energy, and a chemical O atom abstraction reaction by CO ^* is mainly performed. Was performed. Since the content ratio of CHF ₃ was reduced,
Although the production amount of the carbon-based polymer was reduced, the reinforcement was effectively performed.

As a result, excellent high-selection, low-damage, and low-contamination etching could be performed even though the wafer temperature was increased as compared with Example 4.

It should be noted that NO ₂ / C
Similarly, when using a mixed gas of HF ₃ or a mixed gas of SO ₂ / CHF ₃ and increasing the content ratio of NO ₂ or SO ₂ during over-etching, high-selection, low-damage, and low-contamination etching could be similarly performed. . In the case of using SO ₂ , the end point of the just etching step can be determined based on a change in the emission spectrum intensity of SO ^{* at} any of 306 nm, 317 nm, and 327 nm.

Embodiment 6 In this embodiment, CO ₂ / C is used in the just etching step.
HF ₃ / CF ₄ mixed gas, C in over-etching process
By using an O ₂ / S ₂ F ₂ mixed gas, thorough reduction of pollution was achieved. An example of the just etching condition is shown below.

CO ₂ flow rate 15 SCCM CHF ₃ flow rate 30 SCCM CF ₄ flow rate 5 SCCM gas pressure 2.0 Pa RF power density 2.0 W / cm ² (13.
56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Wafer temperature 0 ° C. Here, non-deposited CF ₄ was used as an F ^* source for increasing the etching rate.

Subsequently, as an example, over-etching was performed under the following conditions. CO ₂ flow rate 15 SCCM S ₂ F ₂ flow rate 35 SCCM Gas pressure 2.0 Pa RF power density 1.0 W / cm ² (13.
56 MHz) Magnetic field strength 1.5 × 10 ⁻² T Wafer temperature 0 ° C. In this over-etching step, the incident ion energy is reduced to promote the etching mainly based on the O-atom extraction reaction, and the S ₂ F ₂ S that generates dissociation
Was deposited on the surface of the resist mask 4 and the impurity diffusion region 2. As a result, high selectivity could be achieved with little carbon-based polymer deposited near the interface with the impurity diffusion region 2.

The deposited S could be easily removed by heating the wafer to about 90 ° C. after completion of the etching or sublimation or burning when ashing the resist mask 4. S deposited in the etching chamber could be removed as well. Therefore, in the present embodiment, the reduction of pollution was further thorough. As a result, the yield of the device was improved, and the throughput was also improved.

Also, based on the same concept, NO ₂ / C
Just etching using an HF ₃ / CF ₄ mixed gas and over-etching using a NO ₂ / S ₂ F ₂ mixed gas, or SO ₂ / CHF ₃ /
Similarly, when just etching was performed using a CF ₄ mixed gas and over-etching was performed using a SO ₂ / S ₂ F ₂ mixed gas, highly selective and low-contamination etching could also be performed.

Although the present invention has been described based on the six embodiments, the present invention is not limited to these embodiments. For example, as the fluorine-based compound, NF ₃ , ClF _3, or the like can be used in addition to SF ₆ described above. Although S ₂ F ₂ was used as the sulfur fluoride in the above embodiment, other sulfur fluorides limited by the present invention, that is, SF ₂ , SF ₄ , and S ₂ F ₁₀ can be used basically. Gives similar results.

The etching gas used in the present invention may be added with O ₂ or the like for the purpose of controlling the etching rate, or may be made of He, Ar or the like in the sense of expecting a sputtering effect, a dilution effect, a cooling effect and the like. A rare gas may be appropriately added. The material layer to be etched is not limited to the above-mentioned SiO ₂ interlayer insulating film, but may be PSG, BSG, BP.
Other Si such as SG, AsSG, AsPSG, AsBSG
O ₂ system may be a material layer, and further may be a Si _x N _y or the like.

In addition, it goes without saying that the configuration of the wafer, the etching apparatus to be used, the etching conditions, and the like can be appropriately changed.

[0056]

As is apparent from the above description, in the present invention, the etching of the silicon compound layer is performed by using an etching gas containing any one of carbon oxide, nitrogen oxide and sulfur oxide to thereby reduce the carbon-based polymer. High selectivity can be achieved even when the film quality is enhanced and the amount of deposition is reduced. As a result, the yield of devices can be improved, the maintenance frequency of the etching apparatus can be reduced, and the throughput can be improved. When used in combination with a sulfur-based compound that releases S under discharge dissociation conditions, higher selection, lower damage, and lower contamination can be achieved.

The present invention is designed on the basis of fine design rules, and is extremely suitable for manufacturing a semiconductor device that requires high integration, high performance, and high reliability.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a process example in which the present invention is applied to contact hole processing in the order of steps, (a) showing a state in which a resist mask is formed on an SiO ₂ interlayer insulating film, (b) ) Respectively indicate a state in which a contact hole is opened.

FIG. 2 shows another application of the present invention to contact hole processing.
In the process example of _TwoJust interlayer insulation film
It is a schematic sectional drawing which shows the state which was etched.

[Explanation of symbols]

1 ... monocrystalline silicon substrate 2 ... impurity diffusion regions 3 ... SiO ₂ interlayer insulating film 3a ... (the SiO ₂ interlayer insulating film) remainder 4 ... resist mask 4a ... opening Part 5: Contact hole

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

Claims (2)

(57) [Claims] An etching gas containing at least one kind of inorganic oxide selected from carbon oxide, nitrogen oxide and sulfur oxide and a fluorine compound does not substantially exceed the thickness of the silicon compound layer. A just etching step of etching to a depth, and an over etching step of etching the remaining part of the silicon compound layer by setting the content ratio of the inorganic oxide in the etching gas to be larger than that in the just etching step. A characteristic dry etching method. 2. A just etching step of etching a silicon compound layer to a depth substantially not exceeding its thickness according to the dry etching method of claim 1 .
Over etching the remaining portion of the silicon compound layer using an etching gas containing at least one kind of sulfur fluoride selected from S ₂ F ₂ , SF ₂ , SF ₄ and S ₂ F ₁₀ and the inorganic oxide. A dry etching method, comprising: an etching step.