JPH08222551A - Plasma etching of silicon oxide based material layer - Google Patents

Abstract

PURPOSE: To provide plasma etching using a gas of high safety, which realizes high selectivity of a silicon oxide based material layer, practical etching rate and low particle level. CONSTITUTION: Using a mixed gas containing carbon fluoride based gas and steam, a contact hole 5 is opened in a silicon oxide based material layer 3 on a semiconductor substrate 1. Two-stage etching may be performed, changing the flow ratio of the mixed gas. In addition, deposition of sulfur may be used along with the etching. Thus, the quality of carbon fluoride based polymer deposited on a target substrate is raised, thus improving selectivity with respect to a resist mask 4 and the semiconductor substrate 1. Since the amount of deposited polymer can be reduced, the particle level is lowered. Devices, such as, a gas exhaust unit, need not be newly added.

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 material layer applied in the field of manufacturing semiconductor devices and the like. The present invention relates to a plasma etching method for a silicon oxide based material layer that is useful when patterning.

[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, technical requirements for a plasma etching method for performing fine processing on various material layers including a silicon oxide-based material layer and patterning the same have become more and more sophisticated.

For example, with the 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, ASIC (App
There is a high demand for high-mix low-volume production in some cases, as typified by the license specific IC.
From these backgrounds, the single-wafer type plasma etching apparatus is predominant. Therefore, in order to maintain the processing capability comparable to that of the conventional batch type plasma etching apparatus, it is necessary to greatly improve the etching rate per substrate to be etched.

In order to speed up the signal processing of a semiconductor device and miniaturize the semiconductor element itself, for example, a MOS is used.
In the transistor, the junction depth of the impurity diffusion layer is shallow, and the thickness of other various material layers is also thin. In the manufacturing process of such a semiconductor device, a plasma etching method which is more excellent in selectivity with respect to the underlying material layer than the conventional one and has less damage to the underlying material layer is required.

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

Plasma etching of the silicon oxide-based material layer requires breaking a strong Si--O bond.
Conventionally, an etching mode having a strong ionic property has been adopted. A typical etching gas is C represented by CF _4.
It is mainly composed of F-based gas, and has a sputtering action due to incident ion energy of CF _x ⁺ generated by dissociation from CF-based gas and Si due to the reducing property of carbon as a constituent element.
It utilizes the decomposition action of the -O bond. 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, the plasma etching of the silicon oxide based material layer with the CF based gas is difficult to achieve both high speed and selectivity.

In order to improve the selectivity in the plasma etching of the silicon oxide material layer, there is a conventional technique in which H ₂ is added to CF gas or CHF gas such as CHF ₃ containing H in the molecule is adopted. This is due to excess H ^* in the plasma due to H radicals (H ^* ) generated in the plasma ^.
Captured and removed in the form of HF outside the etching chamber,
It is based on the idea of increasing the substantial C / F ratio (ratio of C atoms and F atoms) of the etching reaction system. Increasing the C / F ratio has the effect of reducing the content of F atoms in the fluorocarbon-based polymer that is deposited in competition with etching, and strengthening the film quality such as the resistance to ion incidence, and therefore, it can be used as a base such as Si. Has the effect of improving the selectivity of. Fluorocarbon-based polymers are
On the silicon oxide-based material layer, it reacts with O atoms sputtered out from the surface and is oxidized and removed, so that it is not deposited and the etching rate is not substantially lowered. 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. V
ac. Science. 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 a correct etching, and the result is that the selectivity ratio to the underlying material layer cannot be obtained. From this point of view, C is added to the fluorocarbon gas.
An attempt to increase the C / F ratio by capturing excess F ^* in the plasma in the form of COF _x, etc. by adding O was preprinted at the 39th Joint Lecture on Applied Physics (Spring Annual Meeting 1993) Collection p
614, presentation number 31a-ZE-10. From the same viewpoint, there is a proposal of adding CO to an inorganic fluorine-based etching gas such as NF ₃ to trap excess F ^* and improving the selection ratio, for example, US Pat. No. 4,807,0.
No. 16 specification.

[0009]

As described above, in the method of adding H ₂ or CO to the fluorocarbon gas to improve the selectivity with respect to the underlying material layer, the flammability and safety of these added gases are improved. It is necessary to give sufficient consideration to sex. 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.

An object of the present invention is to solve various problems relating to the plasma etching of the silicon oxide material layer described above. That is, an object of the present invention is to provide a plasma etching method which is excellent in the selection ratio of the material layer to the underlying material layer and the resist mask when patterning the silicon oxide based material layer formed on the underlying material layer.

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

[0012]

A plasma etching method for a silicon oxide material layer of the present invention is proposed to achieve the above-mentioned object, and uses a mixed gas containing a fluorocarbon gas and water vapor. The silicon oxide based material layer on the base material layer is patterned. The fluorocarbon-based gas used in the present invention has the general formula C _n
F _m or a compound represented by C _n H ₁ F _ml (n, m and l are each natural numbers) in which some of the F atoms in these compounds are replaced with H, and it may be a saturated compound or an unsaturated compound. It doesn't matter. It is desirable to use a high-order fluorocarbon-based gas in which n is 2 or more in view of the generation efficiency of CF _x ⁺ which is the main etchant generated by discharge dissociation.

In the plasma etching method for a silicon oxide based material layer according to the present invention, a carbon dioxide based gas and a first mixed gas containing water vapor are used, and the silicon oxide based material layer on the base material layer is Using the first etching step of patterning to a depth that does not substantially exceed the thickness and the second mixed gas in which the mixing ratio of water vapor in the first mixed gas is increased, the thickness direction of the silicon oxide based material layer is increased. The second etching step of patterning the remaining portion of the above to expose the underlying material layer is performed in this order. The patterning of the silicon oxide-based material layer on the base material layer described above to a depth that does not substantially exceed the layer thickness means that the patterning is performed until just before the base material layer is exposed. However, due to slight non-uniformity of the etching rate, a case where the underlying material layer is inevitably exposed slightly on a part of the substrate to be etched is also included.

Further, in the plasma etching method for a silicon oxide material layer of the present invention, the temperature of the substrate to be etched is controlled to be room temperature or below, and under the discharge dissociation condition in a mixed gas containing a fluorocarbon gas and water vapor. It is characterized by further adding a halogenated sulfur compound capable of releasing free sulfur into the plasma. The halogenated sulfur-based gas capable of releasing free sulfur into plasma under the conditions of discharge dissociation used in the present invention includes S ₂ F ₂ and SF.
₂ , SF ₄ , S ₂ F ₁₀ , S ₂ Cl ₂ , S ₃ Cl ₂ , SC
L ₂ , S ₂ Br ₂ , S ₃ Br ₂ , and S ₂ Br ₁₀ 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. Common S as halogenated sulfur gas
F ₆ is excluded because it is difficult to release free sulfur into the plasma under discharge dissociation conditions.

In the present invention, in any of the plasma etching methods, it is desirable to perform patterning while controlling the plasma density to 1 × 10 ¹⁰ / cm ³ or more and less than 1 × 10 ¹¹ / cm ³ .

[0016]

The skeleton of the present invention utilizes H ^* and H ⁺ which are generated when water vapor, that is, H ₂ O is dissociated in the plasma, and thereby traps excess F ^* and F ⁺ in the plasma to HF or H ^+. A part is removed in the form of HOF to the outside of the etching chamber to control the C / F ratio of the etching reaction system. As a result, the fluorocarbon-based polymer deposited on the substrate to be etched becomes a carbon-rich film having a high ion incidence resistance, and is mainly deposited on the exposed underlying material layer such as Si to improve the etching selectivity. Since this carbon-rich fluorocarbon polymer has a small amount of fluorine component, 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 the ion injection. The material layer selection ratio is improved.

Generation of H ^* and H ⁺ by dissociation of water vapor, and trapping of F ^* and F ⁺ to HF or partial H
In the reaction process of removing it in the form of OF to the outside of the etching chamber, the plasma density is 1 × 10 ¹⁰ / cm ³ or more and 1 × 10 ¹¹
/ Progresses effectively when controlled to less than ³ cm ³ . If the plasma density is less than 1 × 10 ¹⁰ / cm ³ , the dissociation efficiency of the fluorocarbon gas is insufficient, and C, which is the main etchant, is used.
F _x ⁺ is insufficient and it is difficult to obtain a practical etching rate. Moreover, dissociation of H ₂ O is also insufficient. On the other hand, when the plasma density exceeds 1 × 10 ¹¹ / cm ³ , the HF or HOF that should originally be exhausted to the outside of the etching chamber is re-dissociated and the trapping of F ^* and F ⁺ is insufficient, resulting in the deposition of the fluorocarbon-based material. It becomes difficult to reduce the F content in the polymer. That is, it becomes difficult to improve the etching selection ratio.

By the way, the plasma density which can be generated by the parallel plate type RIE apparatus generally used conventionally is 1 × 1.
⁰⁹ / cm ³ unit, 1 × 10 ¹⁰ / cm ³ unit in a parallel plate type magnetron RIE device that also uses magnetic field, ECR (Electron Electron called High Density Plasma Etching Device)
Cyclotron Resonance plasma etching equipment, ICP (Inductively Co)
upled Plasma, the inductively coupled plasma) etching apparatus and a helicon wave plasma etching apparatus or the like which is approximately less than 1 × 10 ¹¹ / cm ³ Ultra 1 × 10 ¹³ / cm ^3. That is, the plasma etching method of the present invention,
Preferable results can be obtained when using a parallel plate magnetron RIE apparatus.

Although the present invention is based on the above technical idea, in order to further improve the etching rate and achieve a high selection ratio, a method of performing plasma etching in two stages is proposed. That is, the mixing ratio of the mixed gas is changed when the first plasma etching process corresponding to the just etching process is completed, and the mixing ratio of water vapor is increased in the second plasma etching process, that is, the overetching process. With this two-step etching, a practical high-speed etching rate can be achieved in the first plasma etching step, and a higher selection ratio to the underlying material layer can be achieved in the second plasma etching step.

The present invention further proposes a method of adding a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions while controlling the temperature of the substrate to be etched below room temperature. By the addition of these halogenated sulfur-based gases, sulfur is deposited on the substrate to be etched in addition to the fluorocarbon-based polymer, and the selection ratio to the underlying material such as Si 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 oxygen released by sputtering becomes SO or SO ₂ and is quickly removed, 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 material layer is completed, if the substrate to be etched is heated to 90 ° C. to 100 ° C., the deposited sulfur is sublimated and removed, and there is no risk of leaving contamination on the substrate to be etched. Sulfur can also be oxidized and removed simultaneously with the resist during resist ashing. If N-based gas such as N ₂ or N ₂ H ₄ is added together with these halogenated sulfur-based gas, polythiazyl which is a sulfur nitride polymer is deposited on the substrate to be etched. Polythiazyl has a higher ion incidence resistance than sulfur, and has a high selection ratio improvement and damage prevention effect. Polythiazil can also be removed by sublimation after plasma etching, and the sublimation temperature is about 15 under reduced pressure.
0 ° 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. or lower.

[0022]

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

Example 1 In this example, C ₄ F ₈ which is a fluorocarbon gas and H _{2 are used.}
FIG. 1 shows an example in which a contact hole is formed by plasma etching a silicon oxide material layer made of SiO ₂ on a silicon substrate with a mixed gas containing O.
This will be described with reference to (a) and (b).

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.
a silicon oxide-based material layer 3 composed of iO _2. Next, a chemically amplified resist and KrF excimer laser lithography are used to pattern a resist mask 4 having an opening diameter of 0.35 μm at the contact hole opening position. The thickness of the silicon oxide based material layer 3 is 600 nm, for example, and is formed by low pressure CVD or the like. The sample shown in FIG. 1A formed so far is used as a substrate to be etched.

Next, this substrate to be etched is placed on the substrate stage of a magnetron RIE apparatus which also uses a magnetic field, and the exposed portion of the silicon oxide 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 in which an alcohol-based refrigerant circulates. C ₄ F ₈ 70 sccm H ₂ O 30 sccm Gas pressure 4.0 Pa RF power supply power 700 W (13.56 MH
z) Magnetic field strength 1.5 × 10 ⁻² T Substrate temperature to be etched −20 ° C. In this plasma etching process, the radical reaction by F ^* is mainly assisted by the ion injection of CF _x ⁺ to form the silicon oxide based material. Plasma etching of the layer proceeded. Etching rate is 600 nm / min
Met.

In the plasma, H ^* and OH ^* produced by dissociation of H ₂ O or these ions are C ₄ F 2.
Generates well for dissociation of ₈ and traps excess F ^* and its ions. As a result, the fluorocarbon-based polymer deposited on the substrate to be etched had a low content of the F component and had a high resistance to ion incidence. The fluorocarbon polymer is mainly deposited on 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, and as a result, a high selection ratio is obtained. 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. In this example, since the substrate to be etched was controlled at −20 ° C., the radical reaction due to F ^* was suppressed. As a result, the etching rate of Si, which is the resist material and the underlying material layer, in which the etching mainly proceeds in the radical mode is lowered, and this is also considered to be one of the reasons for improving the selection ratio.
However, the majority of the contribution of the improvement of the selection ratio is due to the fluorocarbon polymer having a high ion injection resistance.
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.

According to this embodiment, by using the mixed gas containing the fluorocarbon-based gas and the steam, it is possible to achieve both a high selection ratio and a practical etching rate.

Example 2 In this example, C ₃ F ₈ and H ₂ were used as fluorocarbon gas.
This is an example in which the silicon oxide-based material layer is etched in two steps by a mixed gas containing O, and this is shown in FIGS.
Will be described with reference to.

The substrate to be etched shown in FIG. 2 (a) used in this embodiment is the same as the substrate to be etched shown in FIG. 1 (a) described in the first embodiment, and therefore the duplicated description will be omitted. This substrate to be etched is placed on the substrate stage of a magnetron RIE device that also uses a magnetic field.
The exposed portion of the silicon oxide based material layer 3 is plasma-etched under the above etching conditions. C ₃ F ₈ 80 sccm H ₂ O 20 sccm Gas pressure 4.0 Pa RF power supply power 700 W (13.56 MH
z) Magnetic field strength 1.5 × 10 ⁻² T substrate temperature to be etched −30 ° C. This first etching step is performed on the semiconductor substrate 1 which is a base material layer, more accurately on the impurity diffusion layer formed on the semiconductor substrate 1. It continued until just before 2 was exposed. The etching mechanism in this plasma etching process was 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-based gas. The state of the substrate to be etched after the completion of the first etching step is shown in FIG.

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 ₃ F ₈ 60 sccm H ₂ O 40 sccm Gas pressure 4.0 Pa RF power supply power 700 W (13.56 MH
z) Magnetic field strength 1.5 × 10 ⁻² T Substrate temperature to be etched −30 ° C. In the second etching process, the mixing ratio of H ₂ O is higher than that in the first etching condition. The film quality of the carbon-based polymer becomes stronger, and the exposed surface of the impurity diffusion layer 2 as the underlying material layer is surely protected. Although the etching rate of the second etching step is smaller than that of the first etching step, the remaining thickness of the silicon oxide based material layer 3 in the thickness direction is extremely thin, so that the throughput of the entire patterning step is high. Does not reach the point of decreasing. As a result, a contact hole having a good anisotropic shape was formed without damaging the underlying material layer. This state is shown in Figure 2.
It is shown in (c).

According to the present embodiment, the mixed gas containing C ₃ F ₈ and H ₂ O is used, and the two-step etching in which the mixing ratio is changed is adopted, so that the etching rate higher than that in the first embodiment is obtained. It is possible to achieve both a high selection ratio and low damage to the underlying material layer.

Example 3 In this example, C ₄ F ₈ which is a fluorocarbon gas and H _{2 are used.}
To the mixed gas containing O, S ₂ F ₂ was added as a halogenated sulfur compound capable of releasing free sulfur into plasma under discharge dissociation conditions, and the silicon oxide-based material was controlled while controlling the substrate to be etched below room temperature. This is an example of patterning a layer, which will be described again with reference to FIGS.

The above-described substrate to be etched shown in FIG. 1A was set on the substrate stage of a parallel plate type magnetron RIE apparatus, and the silicon oxide based material layer 3 was patterned under the following etching conditions as an example. The substrate stage can control the temperature to 0 ° C. or lower by incorporating a cooling pipe in which an alcohol-based refrigerant circulates, and can heat the substrate stage to 100 ° C. or higher by a built-in heater or the like. C ₄ F ₈ 50 sccm H ₂ O 20 sccm S ₂ F ₂ 30 sccm Gas pressure 4.0 Pa RF power supply power 700 W (13.56 MH)
z) magnetic field strength 1.5 × 10 ^-2 T substrate temperature to be etched -20 ° C. In this plasma etching process, C ₄ F ₈ and S
Plasma etching of the silicon oxide based material layer proceeded in such a manner that the radical reaction by F ^* generated by dissociation of ₂ F ₂ was assisted mainly by the ion injection of CF _x ⁺ and SF ⁺ .

Further, the fluorocarbon polymer deposited on the substrate to be etched has a small content of F component,
It has a high resistance to ion injection. At the same time, since sulfur is also deposited and contributes to the improvement of ion injection resistance, the purpose of the fluorocarbon-based polymer is achieved with a relatively small amount. The state of the substrate to be etched after completion of plasma etching is shown in FIG.

According to this embodiment, S ₂ F ₂ is further added to the mixed gas of C ₄ F ₈ and H ₂ O, and the silicon oxide material layer is patterned while controlling the substrate to be etched to room temperature or below. This makes it possible to achieve both a high selection ratio and low damage to the underlying material layer. Particularly in this embodiment, after the plasma etching is completed, the substrate stage is heated to 90 ° C. to 100 ° C., so that the sulfur deposited on the substrate to be etched or in the vicinity of the substrate stage can be easily sublimated and removed. Therefore, even when the number of substrates to be etched is increased and the continuous treatment is performed, the atmosphere in the chamber in which the fluorocarbon polymer is excessive is not formed, and the etching rate is not lowered and the microloading effect is not generated. . Further, the particle level in the chamber does not increase.

Although the present invention has been described above with reference to three embodiments, the present invention is not limited to these embodiments.

For example, as a fluorocarbon-based gas, C ₄ F ₈
And C ₃ F ₈ are illustrated, but other C, saturated or unsaturated,
The F-based gas can be used alone or in combination. A CHF-based gas in which some of the F 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.

Although SiO ₂ has been exemplified as the silicon oxide-based material layer, silicate glass containing impurities such as PSG and BPSG, or those containing elements such as SiON and SiOF such as N and F, or a laminated structure film thereof. It may be. Also, not limited to contact hole processing, via hole processing, LDD sidewall spacer processing, etc.
It can be applied to various plasma etchings that require a high selectivity with respect to the underlying material layer.

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]

As is apparent from the above description, according to the present invention, a silicon oxide based material layer is patterned by using a mixed gas containing a fluorocarbon based gas and water vapor, so that the fluorine deposited on the substrate to be etched is deposited. The film quality of the carbonized polymer can be enhanced. This makes it possible to improve the selection ratio to the underlying material layer and the selection ratio to the resist mask while maintaining a practical etching rate. In addition, the margin in which the quality of the deposited film is enhanced can be used for reducing the amount of the deposited film, and as a result, particle contamination can be reduced. The effects described here can be realized without adding new equipment such as waste gas treatment means and gas leak alarm means, because it is not necessary to use gases such as H ₂ and CO that leave room for safety consideration. .

Further, according to the invention of claim 2 of the present application, the etching process is made into two stages, and the mixing ratio of the etching gas is changed in the just etching process and the over etching process, so that a higher selection ratio can be obtained. Higher etching rate can be achieved.

According to the invention of claim 3 of the present application, a halogenated sulfur-based gas capable of releasing free sulfur into plasma under discharge dissociation conditions is added to a mixed gas containing a fluorocarbon-based gas and water vapor. By doing so, in addition to the effect of a high selection ratio, there is an effect of reducing particle contamination, preventing a decrease in etching rate, and preventing a microloading effect particularly when etching processes are repeated.

[Brief description of drawings]

1A and 1B are schematic cross-sectional views for explaining Examples 1 and 3 to which the plasma etching method of the present invention is applied, in the order of steps, in which (a) shows a resist mask for opening a contact hole on a silicon oxide material layer. In the formed state, (b) is a state where the contact hole is completed by patterning the silicon oxide based material layer.

2A to 2C are schematic cross-sectional views for explaining a second embodiment to which the plasma etching method of the present invention is applied, in the order of steps thereof,
(A) shows a state where a resist mask for opening a contact hole is formed on the silicon oxide based material layer, (b) shows a state where the silicon oxide based material layer is patterned to a depth that does not substantially exceed the layer thickness, ( In c), the contact hole is completed by patterning the remaining portion of the silicon oxide material layer in the layer thickness direction.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Impurity Diffusion Layer 3 Silicon Oxide Material Layer 4 Resist Mask 5 Contact Hole

Claims (4)

[Claims] 1. A plasma etching method for a silicon oxide based material layer, which comprises patterning a silicon oxide based material layer on a base material layer using a mixed gas containing a fluorocarbon based gas and water vapor. 2. A first containing carbon fluoride gas and water vapor
A first etching step of patterning the silicon oxide-based material layer on the underlying material layer to a depth that does not substantially exceed the layer thickness thereof, using the mixed gas of 1., and mixing the water vapor in the first mixed gas. A second etching step of exposing the underlying material layer by patterning the remaining portion of the silicon oxide based material layer in the thickness direction using a second mixed gas having a higher ratio, and performing the second etching step in this order. Method for plasma etching silicon oxide based material layer. 3. A halogenated sulfur compound capable of releasing free sulfur into plasma under discharge dissociation conditions is further added to the mixed gas while controlling the temperature of the substrate to be etched below room temperature. The plasma etching method according to claim 1, wherein 4. The plasma etching according to claim 1, wherein patterning is performed while controlling the plasma density to 1 × 10 ¹⁰ / cm ³ or more and less than 1 × 10 ¹¹ / cm ^3. Method.