JP3718537B2 - Plasma etching method for silicon oxide material layer - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a plasma etching method for a silicon oxide-based material layer applied in the field of manufacturing semiconductor devices and the like, and more particularly, useful for patterning a silicon oxide-based material layer on a substrate to be etched with high accuracy. The present invention relates to a plasma etching method for a silicon oxide-based material layer.
[0002]
[Prior art]
As the degree of integration and performance of semiconductor devices such as LSIs advances, the design rule is being reduced from half microns to sub-quarter microns. Accordingly, technical requirements for a plasma etching method for finely processing various material layers such as a silicon oxide-based material layer and patterning the material layers are becoming increasingly sophisticated.
[0003]
For example, with an increase in the diameter of the substrate to be etched, uniform processing is required over the entire surface of the substrate to be etched having a diameter of 8 inches or more. In addition, as represented by ASIC (Application Specific IC), there are some high demands for high-mix low-volume production. From these backgrounds, a single-wafer type plasma etching apparatus is mainly used. For this reason, in order to maintain the processing capability not inferior to the conventional batch type plasma etching apparatus, it is necessary to greatly improve the etching rate per one substrate to be etched.
[0004]
In addition, in order to increase the speed of signal processing of a semiconductor device and miniaturize the semiconductor element itself, for example, in a MOS transistor, the junction depth of an impurity diffusion layer is shallow, and the thicknesses of other various material layers are also thin. In the manufacturing process of such a semiconductor device, a plasma etching method is required which has a higher selectivity with respect to the base material layer than the conventional one and causes less damage to the base material layer.
[0005]
Furthermore, an improvement in the selection ratio of the resist mask is also an important problem. This is because, in order to stably manufacture a semiconductor device with a fine design rule, the occurrence of a dimensional conversion difference due to the receding of the resist mask that occurs during plasma etching is becoming difficult to tolerate even at a very small level.
[0006]
Since plasma etching of a silicon oxide-based material layer needs to cut a strong Si—O bond, an etching mode with strong ionicity has been conventionally employed. Common etching gas is CF_FourIs mainly composed of CF-based gas, and is dissociated and generated from CF-based gas._x ⁺The sputtering action by the incident ion energy and the decomposition action of the Si—O bond by the reducing property of the constituent element carbon are utilized. However, as a characteristic of ion mode plasma etching, the etching rate is generally small. Therefore, when the incident ion energy is increased by directing high-speed etching, the etching reaction becomes close to a physical sputtering reaction, and the selectivity is lowered. That is, it is difficult to achieve both high speed and selectivity in the plasma etching of the silicon oxide material layer using the CF gas.
[0007]
In order to improve the selectivity in the plasma etching of the silicon oxide material layer, H is added to the CF gas.₂CHF containing H in the molecule_ThreeThere are conventional techniques that employ an equivalent CHF-based gas. This is because H radicals (H^*) Due to excess F in the plasma.^*Is taken out of the etching chamber in the form of HF and is based on the idea of increasing the substantial C / F ratio (ratio of C atoms to F atoms) of the etching reaction system. The increase in the C / F ratio has the effect of reducing the content of F atoms in the fluorocarbon polymer deposited in competition with etching and strengthening the film quality such as ion incidence resistance. This has the effect of improving the selectivity. The fluorocarbon polymer is not deposited on the silicon oxide material layer because it is oxidized and removed by reacting with O atoms sputtered out from the surface thereof, and the etching rate is not substantially lowered. However, the fluorocarbon polymer is deposited exclusively on the surface of Si, which has no oxidizing action, and functions as a substantial etching stopper to protect the surface from the incidence of ions, which improves the selectivity. is there. Regarding the concept of the C / F ratio and the mechanism for achieving high selectivity, see, for example, J.A. Vac. Science. Tech,16(2), 391 (1979).
[0008]
Recently, there is a trend to review the film quality of fluorocarbon polymers from a standpoint different from the physical viewpoint of ion incidence resistance. That is, when an F-atom-rich fluorocarbon polymer is deposited on the exposed surface of Si or the like as the underlying material layer, the F atoms in the fluorocarbon polymer and the underlying Si atoms are simply adsorbed or adhered. In addition, the process proceeds with a chemical reaction and a desorption process of the reaction product with the assistance of ion incidence. This series of processes is correct etching, resulting in a failure to obtain the selectivity of the underlying material layer. From such a viewpoint, CO is added to the fluorocarbon-based gas, and excess F in the plasma is added.^*COF_xAn attempt to increase the C / F ratio by capturing in the form of etc. has been reported in the 39th Applied Physics-related Lecture Meeting (1993 Spring Annual Meeting), p614, Lecture No. 31a-ZE-10 . From the same point of view, NF_ThreeExcess F by adding CO to inorganic fluorine etching gas such as^*A proposal to improve the selectivity and the selectivity is disclosed, for example, in US Pat. No. 4,807,016.
[0009]
[Problems to be solved by the invention]
As described above, H is added to the fluorocarbon-based gas.₂In the method of improving the selection ratio with the base material layer by adding CO or CO, sufficient consideration must be given to the flammability and safety of these additive gases. In particular, there is much room for consideration in handling in closed spaces such as clean rooms. For practical use, it is necessary to newly provide an exhaust gas treatment facility.
[0010]
This invention makes it the subject to solve the various problems regarding the plasma etching of the silicon oxide type material layer mentioned above. That is, an object of the present invention is to provide a plasma etching method that is excellent in the selection ratio between a base material layer and a resist mask when patterning a silicon oxide-based material layer formed on the base material layer.
[0011]
Another problem of the present invention is that the etching gassing system eliminates H₂By eliminating the gas that can be examined for flammability and safety, such as CO and CO, and newly providing a plasma etching method for silicon oxide-based material layers that does not require capital investment such as exhaust gas treatment facilities is there.
[0012]
[Means for Solving the Problems]
The plasma etching method for a silicon oxide-based material layer according to the present invention is proposed in order to solve the above problems, and includes a high-order fluorocarbon-based gas having 2 or more carbon atoms and water vapor.FirstBy using the mixed gas and capturing the active fluorine generated by the dissociation of the higher order fluorocarbon-based gas with the active hydrogen generated by the plasma dissociation of the water vapor, it is relatively While depositing a carbon-rich fluorocarbon polymer on the substrate to be etched, a silicon oxide material layer on the underlying material layer is formed.The thickness of the silicon oxide-based material layer using the first etching step of patterning to a depth that does not substantially exceed the layer thickness and the second mixed gas in which the mixing ratio of water vapor in the first mixed gas is increased. A second etching step for patterning the remaining portion in the vertical direction to expose the underlying material layer is performed in this order. The meaning of patterning the silicon oxide-based material layer on the base material layer described here to a depth that does not substantially exceed the thickness of the silicon oxide-based material layer is to perform patterning until just before the base material layer is exposed. However, it includes the case where the underlying material layer is inevitably slightly exposed in part of the substrate to be etched due to slight non-uniformity of the etching rate.
[0013]
The high-order fluorocarbon gas having 2 or more carbon atoms employed in the present invention is represented by the general formula C _n F _m Alternatively, C in which some F atoms in these compounds are substituted with H _n H _l F _ml (N, m, and l are each a natural number, and n is 2 or more), regardless of whether it is a saturated compound or an unsaturated compound.
[0014]
  Furthermore, in the plasma etching method of the silicon oxide-based material layer of the present invention, while controlling the temperature of the substrate to be etched to room temperature or lower,Higher order with 2 or more carbon atomsA halogenated sulfur-based compound capable of releasing free sulfur into plasma under a discharge dissociation condition is further added to a mixed gas containing a fluorocarbon-based gas and water vapor. The sulfur halide gas capable of releasing free sulfur into the plasma under the discharge dissociation conditions used in the present invention is specifically S.₂F₂, SF₂, SF_Four, S₂F_Ten, S₂Cl₂, S_ThreeCl₂, SCl₂, S₂Br₂, S_ThreeBr₂, And S₂Br_TenAnd can be used alone or in combination. A compound which is liquid at room temperature may be used after being heated and vaporized by a known method. General SF as sulfur halide gas₆Exclude this because it is difficult to release free sulfur into the plasma under discharge dissociation conditions.
[0015]
In the present invention, in any plasma etching method, the plasma density is 1 × 10.^Ten/ Cm^Three1 × 10 or more¹¹/ Cm^ThreeIt is desirable to perform patterning while controlling to less than.
[0016]
[Action]
The gist of the present invention is water vapor or H₂H generated by dissociation of O in plasma^*And H⁺This makes excess F in the plasma^*And F⁺Is captured and removed out of the etching chamber in the form of HF or a part of HOF to control the C / F ratio of the etching reaction system. As a result, the fluorocarbon polymer deposited on the substrate to be etched becomes a carbon-rich and highly ion-resistant film, and is deposited mainly on the exposed underlying material layer such as Si to improve the etching selectivity. This carbon-rich fluorocarbon polymer has few fluorine components, so it does not proceed with the chemical reaction and the desorption process of the reaction product with the underlying material layer in a form assisted by ion incidence. The material layer selectivity is improved.
In addition, CF, which is a main etchant generated by discharge dissociation, by using an etching gas containing a higher order fluorocarbon gas having 2 or more carbon atoms. _X ⁺ The generation efficiency of is improved.
[0017]
H by dissociation of water vapor^*And H⁺Generation and F^*And F⁺The reaction process of trapping and removing it out of the etching chamber in the form of HF or partially HOF results in a plasma density of 1 × 10^Ten/ Cm^Three1 × 10 or more¹¹/ Cm^ThreeProceeds effectively when controlled below. Plasma density is 1 × 10^Ten/ Cm^ThreeIf it is less than 1, the dissociation efficiency of the fluorocarbon gas is insufficient, and the main etchant CF_x ⁺Therefore, it is difficult to obtain a practical etching rate. H₂O dissociation is also insufficient. On the other hand, the plasma density is 1 × 10¹¹/ Cm^ThreeExceeds HF or HOF, which should be evacuated outside the etching chamber, re-dissociates, and F^*And F⁺Is not sufficiently captured, and it becomes difficult to reduce the F content in the fluorocarbon polymer to be deposited. That is, it becomes difficult to improve the etching selectivity.
[0018]
By the way, the plasma density that can be generated by a conventional parallel plate RIE apparatus is 1 × 10.⁹/ Cm^Three1 × 10 with parallel plate type magnetron RIE system using both table and magnetic field^Ten/ Cm^Three1 × 10 for an ECR (Electron Cyclotron Resonance) plasma etching device, an ICP (Inductively Coupled Plasma) etching device, a helicon wave plasma etching device, etc., called a high-density plasma etching device¹¹/ Cm^ThreeSuper 1 × 10¹³/ Cm^ThreeLess than. That is, the plasma etching method of the present invention can obtain a preferable result when a parallel plate type magnetron RIE apparatus is used.
[0019]
The present invention is based on the technical idea as described above, but in order to achieve further improvement in the etching rate and high selectivity, a method of plasma etching in two stages is proposed. That is, when the first plasma etching step corresponding to the just etching step is completed, the mixture ratio of the mixed gas is changed, and the water vapor mixture ratio is increased in the second plasma etching step, that is, the overetching step. By this two-stage etching, a practical high-speed etching rate can be achieved in the first plasma etching process, and a higher selectivity to the underlying material layer can be achieved in the second plasma etching process.
[0020]
The present invention further proposes a method of adding a sulfur halide gas capable of releasing free sulfur into the plasma under discharge dissociation conditions while controlling the temperature of the substrate to be etched at room temperature or lower. By adding these sulfur halide gases, sulfur is deposited on the substrate to be etched in addition to the fluorocarbon polymer, and the selectivity of the substrate material such as Si or the resist mask is further improved. On the other hand, on the surface of the silicon oxide-based material layer, SO or SO is released by O released by sputtering.₂As a result, the etching rate is virtually eliminated. Therefore, high selectivity etching can be performed while maintaining the etching rate.
[0021]
After the patterning of the silicon oxide-based material layer is completed, if the substrate to be etched is heated to 90 ° C. to 100 ° C., the deposited sulfur is sublimated and there is no possibility of leaving contamination on the substrate to be etched. Sulfur can be oxidized and removed simultaneously with the resist during resist ashing. Along with these sulfur halide gases, N₂Or N₂H_FourIf an N-based gas such as is added, polythiazyl which is a sulfur nitride polymer is deposited on the substrate to be etched. Polythiazil has a higher resistance to ion incidence than sulfur, and has a higher selectivity and an effect of preventing damage. Polythiazyl can also be sublimated and removed after plasma etching, and the sublimation temperature is about 150 ° C. or higher under reduced pressure. As is apparent from the sublimation temperatures of sulfur and polythiazil, 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. or lower.
[0022]
【Example】
Hereinafter, specific embodiments in which the present invention is applied to contact hole processing will be described with reference to the accompanying drawings.
[0023]
Example 1
In this example, C, which is a fluorocarbon gas, is used._FourF₈And H₂SiO on the silicon substrate by a mixed gas containing O₂This is an example in which a contact hole is formed by plasma etching of a silicon oxide-based material layer made of, which will be described with reference to FIGS.
[0024]
First, as shown in FIG. 1A, a SiO 2 or the like semiconductor substrate 1 on which an impurity diffusion layer 2 or the like is previously formed is formed on a SiO 2 substrate.₂A silicon oxide-based material layer 3 made of is formed. Next, a resist mask 4 having an opening diameter of 0.35 μm is patterned at a connection hole opening position by a chemically amplified resist and KrF excimer laser lithography. The thickness of the silicon oxide-based material layer 3 is 600 nm as an example, and is formed by low pressure CVD or the like. The sample formed so far and shown in FIG. 1A is a substrate to be etched.
[0025]
Next, the substrate to be etched is placed on a substrate stage of a magnetron RIE apparatus using 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 be controlled to a temperature of 0 ° C. or less by incorporating a cooling pipe through which the alcohol-based refrigerant circulates.
C_FourF₈                70 sccm
H₂O 30 sccm
Gas pressure 4.0 Pa
RF power supply 700 W (13.56 MHz)
Magnetic field strength 1.5 × 10^-2  T
Substrate temperature to be etched -20 ℃
In this plasma etching process, F^*The radical reaction by_x ⁺Plasma etching of the silicon oxide-based material layer proceeded in a manner assisted by ion incidence. The etching rate was 600 nm / min.
[0026]
There is also H in the plasma.₂H produced by dissociation of O^*Or OH^*Or these ions are C_FourF₈Good for the dissociation of the product and excess F^*And trap its ions. As a result, the fluorocarbon polymer deposited on the substrate to be etched has a low content of F component and has high ion incidence resistance. As a result of the fluorocarbon polymer being deposited mainly on a semiconductor substrate such as silicon, which is an underlying material layer exposed by plasma etching, precisely on the impurity diffusion layer 2 and the resist mask 4, a high selectivity can be obtained. That is, when the semiconductor substrate 1 as the underlying material layer is exposed, the fluorocarbon polymer is deposited on the surface of the semiconductor substrate 1, so that the etching rate is greatly reduced, and as a result, a high selectivity is achieved. In this embodiment, since the substrate to be etched is controlled at -20 ° C., F^*The radical reaction by is suppressed. As a result, the etching rate of Si, which is a resist material and an underlying material layer, which mainly proceeds in radical mode is lowered, which is considered to be a factor in improving the selectivity. However, the contribution of the improvement of the selection ratio is mostly due to the fluorocarbon polymer having a high resistance to ion incidence. The selection ratio was about 35 for the base material layer and about 10 for the resist mask. 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.
[0027]
According to the present embodiment, by using a mixed gas containing a fluorocarbon-based gas and water vapor, both a high selectivity and a practical etching rate can be achieved.
[0028]
Example 2
In this embodiment, C is used as the fluorocarbon gas._ThreeF₈And H₂This is an example in which a silicon oxide-based material layer is etched in two steps with a mixed gas containing O, and this will be described with reference to FIGS.
[0029]
The substrate to be etched shown in FIG. 2A employed in this example is the same as the substrate to be etched shown in FIG. 1A described in Example 1, and thus a duplicate description is omitted. This substrate to be etched is placed on a substrate stage of a magnetron RIE apparatus using a magnetic field, and the exposed portion of the silicon oxide-based material layer 3 is plasma etched under the following first etching conditions.
C_ThreeF₈                80 sccm
H₂O 20 sccm
Gas pressure 4.0 Pa
RF power supply 700 W (13.56 MHz)
Magnetic field strength 1.5 × 10^-2  T
Substrate temperature to be etched -30 ℃
This first etching process was continued until just before the semiconductor substrate 1 as the underlying material layer, more precisely, the impurity diffusion layer 2 formed on the semiconductor substrate 1 was exposed. The etching mechanism in this plasma etching process is basically the same as in the previous example, but the etching rate was about 700 nm / min due to the large mixing ratio of the fluorocarbon gas. FIG. 1B shows the state of the substrate to be etched after completion of the first etching process.
[0030]
Next, the etching conditions are switched, and as an example, the second etching process is performed under the following conditions. This process is an over-etching process.
C_ThreeF₈                60 sccm
H₂O 40 sccm
Gas pressure 4.0 Pa
RF power supply 700 W (13.56 MHz)
Magnetic field strength 1.5 × 10^-2  T
Substrate temperature to be etched -30 ℃
In the second etching process, H₂Since the mixing ratio of O is higher than the first etching condition, the film quality of the fluorocarbon polymer to be deposited becomes stronger, and the surface of the impurity diffusion layer 2 that is the exposed base material layer is reliably protected. . Although the etching rate of the second etching step is smaller than the etching rate of the first etching step, the remaining thickness in the thickness direction of the silicon oxide-based material layer 3 is extremely thin, and thus the throughput of the entire patterning step It doesn't come until it falls. As a result, a contact hole having a good anisotropic shape was formed without damaging the underlying material layer. This state is shown in FIG.
[0031]
According to this embodiment, C_ThreeF₈And H₂By using a mixed gas containing O and using two-stage etching with different mixing ratios, both higher etching rate and higher selection ratio than in Example 1 and low damage to the underlying material layer are achieved. can do.
[0032]
Example 3
In this example, C, which is a fluorocarbon gas, is used._FourF₈And H₂As a halogenated sulfur compound capable of releasing free sulfur into the plasma under a discharge dissociation condition, S is added to the mixed gas containing O.₂F₂Is added, and the silicon oxide material layer is patterned while controlling the substrate to be etched at room temperature or lower. This will be described with reference to FIGS. 1A to 1B again.
[0033]
The substrate to be etched shown in FIG. 1A described above was set on the substrate stage of a parallel plate magnetron RIE apparatus, and the silicon oxide material layer 3 was patterned under the following etching conditions as an example. The substrate stage can be controlled to a temperature of 0 ° C. or less by incorporating a cooling pipe through which the alcohol-based refrigerant circulates, and can be heated to 100 ° C. or more by a built-in heater or the like.
C_FourF₈                50 sccm
H₂O 20 sccm
S₂F₂                30 sccm
Gas pressure 4.0 Pa
RF power supply 700 W (13.56 MHz)
Magnetic field strength 1.5 × 10^-2  T
Substrate temperature to be etched -20 ℃
In this plasma etching process, C_FourF₈And S₂F₂F generated by dissociation of^*The radical reaction by_x ⁺And SF⁺Plasma etching of the silicon oxide-based material layer proceeded in a manner assisted by ion incidence.
[0034]
The fluorocarbon polymer deposited on the substrate to be etched has a low content of F component and has high ion incidence resistance. At the same time, sulfur is deposited and contributes to improving the resistance to ion incidence. Therefore, the purpose of the deposition of the fluorocarbon polymer is achieved with a relatively small amount. The state of the substrate to be etched after the plasma etching is finished is shown in FIG.
[0035]
According to this embodiment, C_FourF₈And H₂In addition to the mixed gas of O, S₂F₂In addition, by patterning the silicon oxide-based material layer while controlling the substrate to be etched at room temperature or lower, it is possible to achieve both a high selectivity and a low damage property to the underlying material layer. Particularly in this embodiment, sulfur deposited on the substrate to be etched or in the vicinity of the substrate stage can be easily sublimated and removed by heating the substrate stage to 90 ° C. to 100 ° C. after the plasma etching is completed. For this reason, even if continuous processing is performed with the number of substrates to be etched being repeated, the atmosphere inside the chamber with excess fluorocarbon polymer is not formed, and the etching rate does not decrease and the microloading effect does not occur. . Further, the particle level in the chamber does not increase.
[0036]
As mentioned above, although this invention was demonstrated by three Example, this invention is not limited to these Examples at all.
[0037]
For example, C as the fluorocarbon gas_FourF₈And C_ThreeF₈However, other CF-based gases can be used alone or in combination regardless of saturation or unsaturation. A CHF-based gas in which a part of F atoms is replaced with H may be used. Similarly, a compound in which a part of the F atom is substituted with another halogen atom such as Cl or Br may be used.
[0038]
As a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions, S₂F₂Was taken up as a representative, but in addition to this SF₂, SF_Four, S₂F_Ten, S₂Cl₂, S_ThreeCl₂, SCl₂, S₂Br₂, S_ThreeBr₂, And S₂Br_TenAnd can be used alone or in combination.
[0039]
SiO as a silicon oxide-based material layer₂However, it may be a silicate glass containing impurities such as PSG or BPSG, or a film containing elements such as N or F, such as SiON or SiOF, or a laminated structure film thereof. Further, the present invention is not limited to contact hole processing, and can be applied to various plasma etchings that require a high selectivity with the base material layer, such as via hole processing and LDD sidewall spacer processing.
[0040]
In addition, the structure of the substrate to be etched, the plasma etching apparatus, the plasma etching conditions, and the like can be appropriately selected and applied within the scope of the technical idea of the present invention.
[0041]
【The invention's effect】
As is apparent from the above description, the present inventionHigher order with 2 or more carbon atomsUsing a mixed gas containing a fluorocarbon gas and water vapor,By capturing the active fluorine generated by the dissociation of the higher order fluorocarbon gas with the active hydrogen generated by the plasma dissociation of water vapor, the carbon-rich By depositing the carbon-based polymer on the substrate to be etched and patterning the silicon oxide-based material layer on the base material layer,The film quality of the fluorocarbon polymer deposited on the substrate to be etched can be enhanced. ThisCF as the main etchant _X ⁺ While improving the generation efficiency ofIt is possible to improve the selection ratio with respect to the underlying material layer and the selection ratio with respect to the resist mask while ensuring a practical etching rate. Further, a margin in which the quality of the deposited film is enhanced can be directed to reducing the amount of deposited film, and as a result, particle contamination can be reduced. The effect here is H₂Since it is not necessary to use a gas that leaves room for examination, such as CO and CO, this can be realized without adding new equipment such as waste gas processing means and gas leak alarm means.
[0042]
Also,By making the etching process into two stages and changing the mixing ratio of the etching gas in the just etching process and the overetching process, it is possible to achieve a higher selectivity and a higher etching rate.
[0043]
According to the invention of claim 3 of the present application, by adding a halogenated sulfur-based gas capable of releasing free sulfur into the plasma under a discharge dissociation condition to a mixed gas containing a fluorocarbon-based gas and water vapor. In addition to the effect of a high selection ratio, there are effects of reducing particle contamination, preventing an etching rate from being lowered, or preventing a microloading effect, particularly when etching steps are repeated.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating Embodiments 1 and 3 to which the plasma etching method of the present invention is applied, in the order of the steps. FIG. In the formed state, (b) shows a state where the contact hole is completed by patterning the silicon oxide material layer.
FIG. 2 is a schematic cross-sectional view for explaining Example 2 to which the plasma etching method of the present invention is applied in the order of the steps, in which FIG. State (b) is a state in which the silicon oxide-based material layer is patterned to a depth that does not substantially exceed the layer thickness. It is in a completed state.
[Explanation of symbols]
1 Semiconductor substrate
2 Impurity diffusion layer
3 Silicon oxide material layer
4 resist mask
5 Contact hole

Claims (4)

Using a high-order fluorocarbon gas having 2 or more carbon atoms and a first mixed gas containing water vapor, active fluorine generated by dissociation of the high-order fluorocarbon gas is generated by plasma dissociation of the water vapor. By capturing with active hydrogen, the silicon oxide-based material on the underlying material layer is deposited while depositing a relatively carbon-rich fluorocarbon-based polymer on the substrate to be etched as compared with the case where the water vapor is not mixed. A first etching step of patterning the layer to a depth that does not substantially exceed the layer thickness;
A second mixed gas having an increased mixing ratio of the water vapor in the first mixed gas is used to pattern the remainder in the thickness direction of the silicon oxide-based material layer to expose the base material layer. A plasma etching method for a silicon oxide-based material layer, wherein etching steps are performed in this order.   The plasma etching method according to claim 1, wherein the high-order fluorocarbon gas having 2 or more carbon atoms contains only carbon and fluorine as constituent elements. A plasma etching method for a silicon oxide-based material layer that patterns a silicon oxide-based material layer on a base material layer using a mixed gas containing a higher order fluorocarbon-based gas having 2 or more carbon atoms and water vapor,
Silicon oxide characterized by further adding a sulfur halide compound capable of releasing free sulfur into the plasma under discharge dissociation conditions while controlling the temperature of the substrate to be etched at room temperature or lower. Plasma etching method for a system material layer. 4. The plasma etching method according to claim 1, wherein the patterning is performed while controlling the plasma density to 1 × 10 ¹⁰ / cm ³ or more and less than 1 × 10 ¹¹ / cm ³ .

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