JP2006156539A - Gas for plasma reaction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide gas for plasma reaction that forms a fluorocarbon film for preventing corrosive gas from being hardly generated in heat treatment after film formation, and also forms an appropriate pattern shape with a high selection ratio and at a high etching speed to a semiconductor material, and also to provide: a film-formation method of the fluorocarbon film using the gas for plasma reaction; a dry etching method; and a method for manufacturing a semiconductor device having at least one process from a dry etching process, a CVD process, and an ashing process. <P>SOLUTION: The gas for plasma reaction is made of an unsaturated fluorinated carbon compound, where the amount of compound containing nitrogen atoms is 100 wt. ppm or smaller. The film formation method of the fluorocarbon film by the CVD method and the dry etching method use the gas for plasma reaction. The method for manufacturing the semiconductor device has at least one process from the dry etching process, the CVD process, and the ashing process using the gas for plasma reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a plasma reaction gas useful in the field of manufacturing semiconductor devices, a fluorocarbon film forming method using the plasma reaction gas, a dry etching method, and a semiconductor device manufacturing method.

  In recent years, as seen in VLSI (Large Scale Integrated Circuit), ULSI (Ultra Large Scale Integrated Circuit), etc., higher integration and higher performance of semiconductor devices have been developed. Along with this, technical requirements for dry etching methods used for manufacturing these semiconductor devices, interlayer insulating films for semiconductor devices, organic EL displays, protective films for biosensor devices, and the like have become increasingly severe.

  Under these circumstances, particularly in recent years, plasmas using fluorinated carbon compounds have excellent water repellency, oil repellency, and transparency, and can form a fluorocarbon film having a low dielectric constant and are environmentally friendly. Researches on CVD (Chemical Vapor Deposition) method and dry etching method are actively conducted.

  For example, in Patent Document 1, in order to reduce the inter-wiring capacity, a fluorinated carbon compound such as hexafluoro-1,3-butadiene, octafluorobutene or the like is used as a raw material gas, and a low-pressure film made of a fluorocarbon film is formed by plasma CVD. It has been studied to obtain a dielectric film having a dielectric constant. However, the fluorocarbon film obtained by the plasma CVD method using these gases has a problem that corrosive gas is generated in the heat treatment after the film formation.

  Patent Document 2 discusses the use of octafluorocyclobutane, hexafluorocyclobutene, or the like as a dry etching gas in order to form contact holes in the silicon oxide interlayer insulating film. However, the etching rate and resist selectivity are not sufficient.

JP 2002-220668 A JP-A-4-258117

The present invention has been made in view of such a state of the art, and can form a fluorocarbon film that hardly generates corrosive gas in the heat treatment after film formation. It is a first object to provide a plasma reaction gas capable of forming a good pattern shape with high selectivity and high etching rate.
The present invention also provides a method for forming a fluorocarbon film, a dry etching method, and a method for manufacturing a semiconductor device having at least one of a dry etching process, a CVD process, and an ashing process using the plasma reaction gas. This is a second problem.

  In order to solve the above-mentioned problems, the present inventors paid attention to the unsaturated fluorinated carbon compound described in the above-mentioned document as a plasma reaction gas, and using this unsaturated fluorinated carbon compound as a plasma reaction gas, the CVD method and A dry etching method was tried. As a result, (i) in the CVD method, active species derived from chlorine are generated and taken into the fluorocarbon film that is generated, which may cause corrosion problems and the like in the subsequent steps. In the dry etching method, it has been found that the active species derived from chlorine causes a decrease in etching rate and a significant decrease in selectivity to photoresist.

  The main cause of the generation of the active species derived from chlorine is that a chlorine atom-containing compound, which is a starting material for producing an unsaturated fluorinated carbon compound, remains in the reaction system in an unreacted state, which is an impurity. The inventors have found that this is because they are mixed in the plasma reaction gas, and have completed the present invention based on these findings.

Thus, according to the first aspect of the present invention, the following plasma reaction gases (1) to (5) are provided.
(1) A plasma reaction gas containing 90% by volume or more of an unsaturated fluorinated carbon compound and having a chlorine atom-containing compound content of 100 ppm by weight or less.
(2) The gas for plasma reaction according to (1), wherein the unsaturated fluorinated carbon compound is hexafluorocyclobutene.
(3) A plasma reaction gas containing 90% by volume or more of an unsaturated fluorinated carbon compound and having a chlorotrifluoroethylene content of 100 ppm by weight or less.
(4) The plasma reaction gas according to any one of (1) to (3), wherein the total amount of nitrogen gas and oxygen gas contained as the remaining trace gas is 200 ppm by volume or less with respect to the total amount of the plasma reaction gas.
(5) The plasma reaction gas according to any one of (1) to (4), wherein the water content is 30 ppm by weight or less.

According to a second aspect of the present invention, there is provided the following fluorocarbon film deposition method (6).
(6) A method for forming a fluorocarbon film by a CVD method using the plasma reaction gas of the present invention.
According to the third aspect of the present invention, the following dry etching method (7) is provided.
(7) A dry etching method using the plasma reaction gas of the present invention.
According to a fourth aspect of the present invention, there is provided the following semiconductor device manufacturing method (8).
(8) A method of manufacturing a semiconductor device having at least one of a dry etching process, a CVD process, and an ashing process using the plasma reaction gas of the present invention.

When CVD is carried out using the plasma reaction gas of the present invention, a fluorocarbon film that hardly generates corrosive gas can be obtained by heat treatment after film formation.
By performing dry etching using the plasma reaction gas of the present invention, it is possible to form a favorable pattern shape with high selectivity and high etching rate with respect to a semiconductor material.
According to the method for manufacturing a semiconductor device of the present invention, a high-performance semiconductor device with high integration, high density, and large diameter can be efficiently manufactured.

  Hereinafter, the present invention will be described in detail by dividing it into 1) a plasma reaction gas, 2) a method for forming a fluorocarbon film, 3) a dry etching method, and 4) a method for manufacturing a semiconductor device.

1) Gas for plasma reaction The gas for plasma reaction of the present invention is characterized in that it contains 90% by volume or more of an unsaturated fluorinated carbon compound and the content of chlorine atom-containing compound is 100 ppm by weight or less.

  The “plasma reaction gas” of the present invention is filled in an arbitrary container if necessary and used for a plasma reaction such as a manufacturing process of a semiconductor device. Further, the gas of the present invention is taken out from any of the above-mentioned arbitrary containers and the mixed gas to which another kind of plasma reaction gas or dilution gas that does not impede the object of the present invention is added, or from any of the above-mentioned containers, and does not obstruct the object of the present invention It also substantially includes a mixed gas filled in another container together with another kind of plasma reaction gas or dilution gas.

  The unsaturated fluorinated carbon compound used in the present invention is composed of only carbon atoms and fluorine atoms and has a double bond or triple bond. The number of carbon atoms is preferably 2 to 7, more preferably 2 to 5, still more preferably 4 to 5, and particularly preferably 4.

  Specific examples of the unsaturated fluorinated carbon compound include unsaturated fluorinated carbon compounds having 2 carbon atoms such as tetrafluoroethylene; hexafluoropropene, tetrafluoropropyne and tetrafluorocyclopropene having 3 carbon atoms. Unsaturated fluorinated carbon compounds of: hexafluoro-2-butyne, hexafluoro-1-butyne, hexafluorocyclobutene, hexafluoro-1,3-butadiene, hexafluoro- (1-methylcyclopropene), octafluoro- C4 unsaturated fluorinated carbon compounds such as 1-butene and octafluoro-2-butene; octafluoro-1-pentyne, octafluoro-2-pentyne, octafluoro-1,3-pentadiene, octafluoro- 1,4-pentadiene, octafluorocyclopente , Fluorinated carbon compounds having 5 carbon atoms such as octafluoroisoprene, hexafluorovinylacetylene, octafluoro- (1-methylcyclobutene) and octafluoro- (1,2-dimethylcyclopropene); 1-hexene, dodecafluoro-2-hexene, dodecafluoro-3-hexene, decafluoro-1,3-hexadiene, decafluoro-1,4-hexadiene, decafluoro-1,5-hexadiene, decafluoro-2, Carbon numbers such as 4-hexadiene, decafluorocyclohexene, hexafluorobenzene, octafluoro-2-hexyne, octafluoro-3-hexyne, octafluorocyclo-1,3-hexadiene and octafluorocyclo-1,4-hexadiene 6 unsaturated fluorine Carbon compound; undecafluoro-1-heptene, undecafluoro-2-heptene, the unsaturated fluorinated carbon compound having a carbon number such as undecafluoro-3-heptene and dodecafluoro triazabenzocycloheptene 7; and the like.

  Among these, since the effects of the present invention can be obtained more remarkably, hexafluorocyclobutene, hexafluoro-1,3-butadiene, hexafluoro- (1-methylcyclopropene), octafluoro-1-butene, octa Fluoro-2-butene, octafluoro-1-pentyne, octafluoro-2-pentyne, octafluoro-1,3-pentadiene, octafluoro-1,4-pentadiene and octafluorocyclopentene are preferred, hexafluorocyclobutene, octafluorocyclobutene Fluorocyclopentene and octafluoro-2-pentyne are more preferable, and hexafluorocyclobutene is particularly preferable because plasma active species can be easily generated.

  Hexafluorocyclobutene has a boiling point of 5 to 6 ° C. and is a gaseous compound at room temperature. However, since it has a 4-membered ring structure having one unsaturated bond, it is structurally distorted. It is assumed that plasma activated species can be easily generated when energy is applied.

  The plasma reaction gas of the present invention contains an unsaturated fluorinated carbon compound in an amount of usually 90% by volume or more, preferably 99% by volume or more, more preferably 99.95% by volume or more, and particularly preferably 99.98% by volume or more. . By being in the said range, the effect of this invention improves further. In addition, if the content of the unsaturated fluorinated carbon compound is too low, the gas purity (content of the unsaturated fluorinated carbon compound) may be biased in the container filled with the plasma reaction gas. Specifically, the gas purity may be greatly different between the initial use stage and the stage where the remaining amount is low. In such a case, when dry etching or film formation is performed, there is a large difference in performance when using each gas at the initial use stage and when the remaining amount is low, and in the factory production line There is a risk of reducing the yield. Therefore, by improving the purity of the gas for plasma reaction, there is no bias in the gas purity in the container, so there is no difference in performance when using the gas in the initial use stage and the stage where the remaining amount is low The gas can be used without waste.

  Further, the unsaturated fluorinated carbon compound can be used alone or in combination of two or more. However, it is preferable to use one kind alone because the effect of the present invention is more remarkably exhibited.

  The “content of unsaturated fluorinated carbon compound” is the capacity derived from the percentage (%) based on weight measured by gas chromatography analysis (hereinafter referred to as “GC analysis”) by the internal standard substance method. Standard purity.

  The plasma reaction gas of the present invention has a chlorine atom-containing compound content of 100 ppm by weight or less, preferably 50 ppm by weight or less, from the viewpoint of reducing the corrosiveness of the fluorocarbon film obtained by CVD and improving the dry etching rate and selectivity. More preferably, it is 10 ppm by weight or less, particularly preferably 1 ppm by weight or less. Here, the chlorine atom-containing compound amount represents the ratio of the total amount of organic compounds containing chlorine atoms to the plasma reaction gas.

  Specific examples of the chlorine atom-containing compound include chlorotrifluoroethylene, 1-chloro-2,3,3,4,4,5,5-heptafluorocyclopentene, 1,3-dichloro-2,3,4,4. , 5,5-hexafluorocyclopentene, 1,3,4-trichloro-2,3,4,5,5-pentafluorocyclopentene, 1-chloro-1,2,2,3,3,4,4,5 , 5-nonafluorocyclopentane, 1,4-dichloro-2,3,3,4,5,5-hexafluorocyclopentene, 1,4,4-trichloro-2,3,3,5,5-pentafluoro Examples include cyclocyclopentene and perfluoro-1,3-pentadiene.

  Among these, when hexafluorocyclobutene is used as the unsaturated fluorinated carbon compound, the chlorine atom-containing compound in which the effects of the present invention appear more remarkably is chlorotrifluoroethylene.

  In order to obtain hexafluorocyclobutene, a method in which chlorotrifluoroethylene is used as a starting material and dimerization is performed to obtain 1,2-dichlorohexafluorocyclobutane as an intermediate, and the intermediate is reduced from the viewpoint of productivity. Most preferably used. At this time, chlorotrifluoroethylene as a starting material is likely to remain in the plasma reaction gas, which causes the above-mentioned corrosion problem, lowering of the etching rate, and deterioration of selectivity to the photoresist.

  In the plasma reaction gas of the present invention, impurities such as moisture derived from air and nitrogen gas in production equipment, as well as solvents used during production, highly hygroscopic salts, alkalis, and the like are present as trace components. However, the content of nitrogen gas, oxygen gas, moisture, etc. is preferably as low as possible. The first reason is that impurities such as nitrogen, oxygen, and moisture are dissociated in the plasma reaction apparatus to generate various free radicals (etching species), so that the plasma reaction of unsaturated fluorinated carbon compound occurs. Secondly, when the nitrogen gas content exceeds a certain value, the plasma reaction itself of the unsaturated fluorinated carbon compound changes from decomposition into free radicals to polymerization, resulting in polymerization precipitates. Third, when the unsaturated fluorinated carbon compound is withdrawn from the container, the volatilization amount of nitrogen gas, oxygen gas, moisture, etc. greatly fluctuates over time, and the plasma reaction is kept under certain conditions. This is because it becomes difficult to perform stably.

  Therefore, the amount of nitrogen gas and oxygen gas contained as residual trace gas in the plasma reaction gas is preferably 200 ppm by volume or less with respect to the total amount of the plasma reaction gas, as the total amount of both. More preferably, it is 150 ppm by volume or less, and particularly preferably 100 ppm by volume or less. In addition, the water content is preferably 30 ppm by weight or less, more preferably 20 ppm by weight or less, and particularly preferably 10 ppm by weight or less.

  The above-mentioned “total amount of nitrogen gas and oxygen gas” is the total of the content (ppm) of nitrogen gas and oxygen gas based on volume measured by gas chromatography analysis by an absolute calibration curve method. Note that these volume standards can also be referred to as molar standards. The “water content” is usually a water content (ppm) based on weight measured by the Karl Fischer method.

  The plasma reaction gas of the present invention preferably contains no components other than the unsaturated fluorinated carbon compound, but can also contain another kind of plasma reaction gas or dilution gas as long as the object of the present invention is not impaired. .

  The plasma reaction gas of the present invention can be used as a dry etching gas, for example, by combining hydrofluorocarbon with the unsaturated fluorinated carbon compound. The combined use of hydrofluorocarbon may improve the pattern shape and improve the dry etching rate.

  The hydrofluorocarbon is usually filled in a separate container from the plasma reaction gas of the present invention and mixed in the etching chamber in many cases, but it is added to the unsaturated fluorinated carbon compound in advance and filled in the container. It is also possible to leave.

  The hydrofluorocarbon to be used is not particularly limited as long as it has volatility, but is usually selected from compounds obtained by substituting more than half of hydrogen atoms of linear, branched or cyclic saturated hydrocarbons with fluorine. Is done.

  Examples of the hydrofluorocarbon include trifluoromethane, difluoromethane, tetrafluoromethane, tetrafluoroethane, pentafluoroethane, heptafluoropropane, hexafluoropropane, pentafluoropropane, nonafluorobutane, octafluorobutane, heptafluorobutane, Hexafluorobutane, undecafluoropentane, tridecafluorohexane, dodecafluorohexane, undecafluorohexane, heptafluorocyclobutane, hexafluorocyclobutane, nonafluorocyclopentane, octafluorocyclopentane, heptafluorocyclopentane, etc. Of these, trifluoromethane, pentafluoroethane and tetrafluoroethane are preferred.These hydrofluorocarbon gases may be used alone or in combination of two or more.

  The amount of hydrofluorocarbon used varies depending on the degree of influence of the gas on the material to be etched, but is usually 50 mol% or less, preferably 30 mol% or less, particularly preferably 10 mol%, based on the unsaturated fluorinated carbon compound. It is as follows.

When the gas for plasma reaction of the present invention is, for example, hexafluorocyclobutene, for example, (a) 1,2-dichlorohexafluorocyclobutane is dropped into a mixed solution of a solvent, acetic acid and zinc powder, and about 70 ° C. The reaction step of collecting the gaseous product coming out from the top of the reflux condenser by heating to a crude hexafluorocyclobutene
(B) A distillation step of obtaining crude hexafluorocyclobutene by distilling crude hexafluorocyclobutene, (c) activated carbon pretreated at 350 ° C. for 5 hours or more in a helium atmosphere with high purity hexafluorocyclobutene And the activated carbon treatment step in which the product is allowed to stand for 2 days or more in a state cooled to 0 ° C. or less, (d) hexafluorocyclobutene after the activated carbon treatment step is filled into a cylinder having a connection valve with a vacuum line − It can be manufactured by cooling to 10 ° C. or less and performing a degassing step of reducing the nitrogen and oxygen in hexafluorocyclobutene by opening and closing the connection valve several times.

  The 1,2-dichlorohexafluorocyclobutane used in the step (a) is produced by, for example, the method described in Journal of Chemical Society, p3830 (1952) or the method described in JP-A-7-12944. Can do. That is, it can be produced by dimerizing chlorotrifluoroethylene, which is industrially used as a monomer of a fluororesin, as a raw material.

  Further, in the above method, 1,2-dichlorohexafluorocyclobutane is reduced (dechlorinated) with zinc, but dechlorination can be achieved by performing hydrogen reduction in the presence of a metal catalyst. Hexafluorocyclobutene can be produced.

The step (b) is obtained by distilling the crude hexafluorocyclobutene obtained in the step (a) to obtain high-purity hexafluorocyclobutene, but can be obtained even after purification by distillation. Hexafluorocyclobutene contains, as organic impurities, the composition formula C ₄ F ₈ , C ₂ F ₃ Cl (chlorotrifluoroethylene), chloropentafluorocyclobutene, C ₄ F ₆ and the like.

  The step (c) is a step for removing the chlorine atom-containing compound contained in the hexafluorocyclobutene obtained in the step (b). Specifically, the content of the chlorine atom-containing compound contained as impurities can be reduced to 100 ppm by weight or less by treating with activated carbon pretreated at 350 ° C. for 5 hours or more in a helium atmosphere.

  The step (d) is a step for reducing the contents of nitrogen, oxygen and moisture contained in the hexafluorocyclobutene after the activated carbon treatment step obtained in the step (c). Specifically, hexafluorocyclobutene after the activated carbon treatment step is filled in a cylinder having a connection valve with a vacuum line, cooled to −10 ° C. or lower, and the connection valve is opened and closed several times, thereby hexafluoro The total content of nitrogen and oxygen in cyclobutene can be reduced to 200 ppm by volume or less, and the water content to 30 ppm by weight or less.

  In the case of unsaturated fluorinated carbon compounds other than hexafluorocyclobutene, the steps (b), (c) and (d) are carried out after synthesizing the crude unsaturated fluorinated carbon compound by a conventionally known method. Thus, the plasma reaction gas of the present invention can be obtained.

  As for degassing (reduction of nitrogen, oxygen and water content), instead of (d) above, hexafluorocyclobutene after the activated carbon treatment process is placed in the distillation apparatus, and total reflux is performed while flowing high-purity helium. This can also be achieved by performing the operation for a predetermined time.

  The plasma reaction gas of the present invention is suitably used for plasma reactions such as CVD, dry etching or ashing, but is not limited thereto. However, the plasma reaction gas of the present invention is particularly suitably used for the CVD method because the effect of obtaining a fluorocarbon film with little generation of corrosive gas is particularly remarkable.

2) Film formation method of fluorocarbon film The film formation method of the fluorocarbon film of the present invention is based on the CVD method using the plasma reaction gas of the present invention. “CVD” using the plasma reaction gas of the present invention is a technique in which an unsaturated fluorinated carbon compound is activated and polymerized by plasma discharge to form thin fluorocarbon films on the surfaces of various objects to be processed.

The process of forming the fluorocarbon film is not necessarily clear, but it is considered that the unsaturated fluorinated carbon compound is decomposed and polymerized under a discharge dissociation condition to form a fluorocarbon film.
The thickness of the resulting fluorocarbon film is usually in the range of 0.01 to 10 μm.

As a CVD method using plasma, a conventionally known method, for example, a method described in Japanese Patent Laid-Open No. 9-237783 can be employed.
As plasma generation conditions, a radio frequency (RF) output of 10 W to 10 kW, an object temperature of 0 to 500 ° C., and a reaction chamber pressure of 0.005 to 13.3 kPa are usually employed.

  As an apparatus used for plasma CVD, a parallel plate CVD apparatus is generally used, but a microwave CVD apparatus, an ECR-CVD apparatus, and a high-density plasma CVD apparatus (helicon wave system, high frequency induction system) can be used.

  An inert gas selected from the group consisting of helium, neon, argon, xenon, and krypton may be added to control the concentration of active species generated in the plasma and promote dissociation of the source gas. Moreover, you may use an inert gas individually by 1 type or in mixture of 2 or more types. As for the addition amount of the inert gas, the total amount of the inert gas with respect to the unsaturated fluorinated carbon compound is preferably 2 to 200 by volume ratio, and particularly preferably 5 to 150.

  Furthermore, for the purpose of promoting dissociation of the plasma reaction gas and reducing damage to the object to be processed, ultraviolet irradiation by a low-pressure mercury lamp or the like can be performed, or ultrasonic waves can be irradiated to the object to be processed and the reaction space.

  The object to be treated is not particularly limited, but functions such as insulation, water repellency, corrosion resistance, acid resistance, lubricity, light anti-reflection, etc. in the semiconductor manufacturing field, electronic / electrical field, precision machine field, and other fields The surface of an article or member that requires properties, preferably the surface of an article or member that requires insulation in the semiconductor manufacturing field or the electronic / electric field, and a substrate used in this field is particularly preferred.

Specific examples of preferable substrates include silicon films such as a single crystal silicon film, a polycrystalline silicon film, and an amorphous silicon film; a silicide film made of tungsten, molybdenum, titanium, tantalum, or the like; SiN, SiON, SiO ₂ , BSG (boron- Silicate glass), PSG (phosphorus-silicate glass), BPSG (boron-phosphorus-silicate glass), AsSG (arsenic silicate glass), SbSG (antimony silicate glass), NSG (nitrogen-silicate glass), PbSG (lead-silicate glass) And silicon-containing insulating films such as SOG (spin-on-glass); conductive films such as TiN and TaN; gallium-arsenide substrates; diamond-like carbon films and aluminum plates; soda-lime glass; alumina films; zirconium oxide films; Armini And the like; ceramics consisting arm and aluminum oxide.

3) Dry Etching Method “Dry etching” using the plasma reaction gas according to the present invention refers to a technique for etching a very highly integrated fine pattern on a substrate to be etched used in a semiconductor device manufacturing process or the like. . The substrate to be etched is a substrate having a thin film layer of a material to be etched on a substrate such as a glass substrate, a silicon single crystal wafer, or gallium arsenide.

  Preferable specific examples of the material to be etched include a silicon oxide film; a TEOS film, a BPSG film, a PSG film, and an SOG film; an HSQ (Hydrogen silsesquioxane) film; an MSQ (Methyl silsesquioxane) film; a PCB film; an SiOF film Or a porous film of the above film, but a silicon oxide film is particularly preferred.

In the dry etching of the present invention, a plasma having a high density region of 10 ¹⁰ ions / cm ³ or more is usually generated as the plasma irradiated during the etching. In particular, by setting the plasma density to 10 ¹⁰ to 10 ¹³ ions / cm ³ , a high etching rate and high selectivity can be ensured, and a finer pattern can be formed.

  Examples of plasma generators include helicon wave system, high frequency induction system, parallel plate type, magnetron system and microwave system. However, since plasma generation in a high density region is easy, helicon wave system, high frequency induction. The apparatus of a system and a microwave system is used suitably.

  It is not necessary to select a special range for the pressure during dry etching. In general, the plasma reaction gas of the present invention is preferably contained in an etching chamber in an etching apparatus degassed to a vacuum. It introduce | transduces so that it may become 1300 Pa, Most preferably 0.13-1.3 Pa.

The ultimate temperature of the substrate to be etched during dry etching is preferably in the range of 0 to 300 ° C, more preferably 60 to 250 ° C, and particularly preferably 80 to 200 ° C.
The substrate temperature may or may not be controlled by cooling or the like. The time for the dry etching treatment is generally 10 seconds to 10 minutes. However, since the plasma reaction gas of the present invention can be etched at high speed, it is preferable to improve the productivity as 10 seconds to 3 minutes.

When an unsaturated fluorinated carbon compound is used as a dry etching gas, it is selected from the group consisting of helium, neon, argon, xenon, and krypton in order to control the concentration of etching species generated in the plasma and to control ion energy. An inert gas may be added. These inert gases can be used alone or in combination of two or more.
As for the addition amount of the inert gas, the total amount of the inert gas with respect to the unsaturated fluorinated carbon compound is preferably 2 to 200 by volume ratio, and particularly preferably 5 to 150.

Further, O ₂ or O ₃ may be added to alleviate the etching stop.
When adding O ₂ or O ₃ , the total amount of O ₂ and O ₃ with respect to the unsaturated fluorinated carbon compound is preferably 0.1 to 50, more preferably 0.5 to ₃₀ in terms of volume ratio.

Furthermore, one or more of CO and CO ₂ may be added to the dry etching gas in order to improve selectivity with respect to a mask such as a resist or polysilicon.
The total amount of CO and CO ₂ with respect to the unsaturated fluorinated carbon compound is preferably from 5 to 150, and particularly preferably from 10 to 100, by volume ratio.

4) Method for Manufacturing Semiconductor Device The method for manufacturing a semiconductor device of the present invention includes at least one of a dry etching process, a CVD process, and an ashing process using the plasma reaction gas of the present invention.

“Ashing” refers to ashing and removing contaminants in the chamber of dry etching equipment and CVD equipment by activating unsaturated fluorinated carbon compounds by plasma discharge using a gas containing plasma reaction gas. Say. Further, it means removing contaminants on the surface of an object to be processed by dry etching or CVD with active species, and further polishing and planarizing the surface of the object to be processed with active species. It is particularly preferably used for removing unnecessary polymer components deposited in the chamber, removing an oxide film from the semiconductor device substrate, and removing the resist from the semiconductor device.
In plasma ashing, generation of active species by plasma decomposition is necessary, and plasma reaction conditions for that purpose are appropriately selected.

  According to the method for manufacturing a semiconductor device of the present invention, a high-performance semiconductor device with high integration, high density, and large diameter can be efficiently manufactured.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these Examples. Unless otherwise specified, “parts”, “%”, and “ppm” represent “parts by weight”, “wt%”, and “weight ppm”, respectively.

Various analyzes were performed using the following analysis apparatus and analysis conditions.
(1) GC analysis A
Device name: HP-6890 manufactured by Hewlett-Packard Co., Ltd.
Column: Frontier Lab Ultra ALLOY ⁺ -1 (s) (50 m x ID 0.25 μm, 0.4 μmdf)
Column temperature: -20 ° C
Injection temperature: 200 ° C
Carrier gas: Nitrogen (flow rate 1mL / min)
Detector: FID
Internal standard: n-butane

(2) GC analysis B
Device name: GC-14B manufactured by Shimadzu Corporation
Column: Unibeads C 60/80 + MS-5A (length 2 m, inner diameter 3 mm, respectively)
Column temperature: 40 ° C
Carrier gas: He (flow rate 50 mL / min)
Detector: TCD

(3) GC-MS analysis [GC part]
Device name: HP-6890 manufactured by Hewlett-Packard Co., Ltd.
Column: Frontier Lab Ultra ALLOY ⁺ -1 (s) (60 m × ID 0.25 μm, 0.4 μmdf)
Column temperature: -20 ° C
[MS part]
Device name: Hewlett Packard 5973 NETWORK
Detector EI type (acceleration voltage: 70eV)

(4) Karl Fischer analysis Karl Fischer moisture meter: AQ-7 manufactured by Hiranuma Sangyo Co., Ltd.
Generating liquid: Hydranal (registered trademark) Aqualite RS
Counter electrode liquid: Aqualite CN

(Production Example 1) Production of hexafluorocyclobutene by the zinc reduction method of 1,2-dichlorohexafluorocyclobutane (1) Reaction process In a glass reactor equipped with a dropping funnel, a stirrer and a reflux condenser, zinc powder 56 Part, 80 parts triglyme and 8 parts acetic acid. Subsequently, 1,2-dichlorohexafluorocyclobutane (manufactured by Synquest Corp., 100 parts) was added dropwise with stirring while maintaining the temperature at 15 ° C. After completion of the dropping, the mixture was heated to increase the internal temperature to 70 ° C., and the gaseous product emerging from the upper part of the reflux condenser was collected in a glass trap cooled to −78 ° C. The contents in the glass trap were analyzed by gas chromatography (GC analysis A), and as a result, the product was hexafluorocyclobutene (53 parts, yield 76%) and chloropentafluorocyclobutene (3 8 parts, yield 5%).

(2) Distillation Step 262 parts of a mixture of hexafluorocyclobutene and chloropentafluorocyclobutene obtained by repeating the operation of (1) above was converted into a KS type rectification tower (Toshin Seiki Co., Ltd.) having 30 theoretical plates. ))). The temperature of the kettle was maintained at 5 ° C., and total reflux was performed for 1 hour, and then the reflux ratio was set in the range of 3/120 to 3/60, and the fraction was extracted and distilled. As a result, 125 parts of hexafluorocyclobutene having a purity of 99.93% was obtained. As a result of GC-MS analysis of the impurities contained in this hexafluorocyclobutene, the compounds represented by the composition formulas C ₄ F ₈ , C ₂ F ₃ Cl and C ₄ F ₆ were contained in 290 ppm, 280 ppm and 130 ppm, respectively. .

(Example 1) Production of hexafluorocyclobutene having a content of C ₂ F ₃ Cl of 0.5 ppm or less by treatment with activated carbon 10 parts of granular activated carbon (manufactured by Takeda Pharmaceutical Co., Ltd., GH2X UG) is 1 inch in diameter × 30 cm The SUS316 pipe was filled and heat-treated at 350 ° C. for 6 hours under a nitrogen stream. Thereafter, the activated carbon was taken out from the pipe and put into a cylinder having a capacity of 150 cc.
Next, 125 parts of hexafluorocyclobutene obtained in Production Example 1 was filled and stored in a freezer maintained at −15 ° C. After 3 days and 7 days, hexafluorocyclobutene in the cylinder was analyzed by gas chromatography (GC analysis A). After 7 days, C ₂ F ₃ Cl was below the detection limit (detection limit: 0.5 ppm). there were. The analysis results are shown in Table 1.

(Example 2) Manufacture of hexafluorocyclobutene with low nitrogen, oxygen and moisture content by valve opening and closing method A newly prepared 150 cc SUS316 cylinder (with valve) was dried under reduced pressure and obtained in Production Example 3. After filling the obtained hexafluorocyclobutene through a filter, the cylinder was immersed in a refrigerant kept at −30 ° C., and the valve outlet side line of the cylinder was connected to a vacuum line.
Next, the operation of opening the valve for 2 seconds to degas the cylinder was performed 5 times at 30 minute intervals. When the cylinder which performed this process was connected to the gas chromatography with a gas sampler and nitrogen and oxygen concentration were measured (GC analysis B), nitrogen was 8 volume ppm and oxygen was 5 volume ppm. In addition, a needle was attached to the outlet line of the valve, the tip of the needle was inserted into a Karl Fischer moisture analyzer, hexafluorocyclobutene was bubbled, and moisture was measured by Karl Fischer analysis. The amount was 5 ppm by weight.

(Example 3) Production of hexafluorocyclobutene having a low water content by a method of total reflux operation in high-purity helium A 30-stage theoretical distillation apparatus (filler: Helipac) with a three-way valve A boiling stone was placed in the kettle, the kettle was cooled to −30 ° C., and a −20 ° C. refrigerant was circulated through the reflux condenser. The hexafluorocyclobutene obtained in Example 2 was transferred from the cylinder to the kettle. High-purity helium having a purity of 99.9999% was introduced from one of the three-way valves at a flow rate of 20 mL / min, and the gas phase portion of the kettle, the column, and the condenser was replaced with helium for 3 minutes. Thereafter, the temperature of the kettle was gradually raised to 5 ° C. to reflux hexafluorocyclobutene. Meanwhile, helium was constantly supplied into the reflux apparatus to keep the system in a helium atmosphere. After 20 minutes, the refrigerant circulation for cooling the condenser was stopped, the hexafluorocyclobutene vapor was extracted from the three-way valve for 15 seconds, and then the refrigerant circulation was resumed to return to the reflux state. After 20 minutes, the valve was closed to seal the inside of the system, and the kettle was cooled to -30 ° C. The hexafluorocyclobutene in the kettle was transferred to a vacuumed cylinder. When nitrogen / oxygen in the cylinder was analyzed by gas chromatography (GC analysis B), it was decreased as shown in Table 2 compared to before the heating reflux operation.
Moreover, when the hexafluorocyclobutene water | moisture content after heating-refluxing operation was analyzed similarly to Example 2, water content was 8 weight ppm.

Example 4 Dry Etching Using Hexafluorocyclobutene (Plasma Reaction Gas) Produced in Example 2 A silicon oxide film having a thickness of about 2 μm is formed on a silicon substrate, and the photoresist is further made 4000 mm thick. By applying and exposing, a resist pattern of 0.13 μm was formed. This substrate was set in an ICP plasma etching apparatus, and the system was evacuated.
Next, hexafluorocyclobutene (plasma reaction gas) produced in Example 3, oxygen, and argon were introduced at a rate of 15 sccm, 15 sccm, and 500 sccm, respectively. Next, etching was performed at a plasma density of 10 ¹¹ ions / cm ³ while maintaining the pressure in the system at 0.1333 Pa, and the etching rate and selectivity to the resist were measured. The results are shown in Table 3.

(Comparative Example 1)
The experiment was performed in the same manner as in Example 4 except that the hexafluorocyclobutene obtained in Production Example 1 was used as the plasma reaction gas. The results are shown in Table 3.

(Example 5) Formation of fluorocarbon film by plasma CVD method using hexafluorocyclobutene produced in Example 3 as plasma reaction gas Hexafluorocyclobutene produced in Example 3 was used as plasma reaction gas, and plasma was formed. Film formation by the CVD method was performed.
Using a silicon oxide film wafer partially vapor-deposited as a substrate and using a microwave CVD apparatus as a plasma CVD apparatus, an experiment was performed under the following conditions to obtain a fluorocarbon film having a thickness of 0.3 μm on the substrate. This fluorocarbon film was dense and uniform without generation of voids, and had good adhesion to the substrate. The relative dielectric constant of the fluorocarbon film was 2.2.

Flow rate of hexafluorocyclobutene (gaseous): 80 sccm
Argon flow rate: 300 sccm
Reaction chamber pressure: 0.013 kPa
RF output (frequency 2.45 GHz): 1500 W
Shower head temperature: 280 ° C
Substrate temperature: 200 ° C
Chamber wall temperature: 300 ° C

  Next, the deposited silicon wafer was placed in a vacuum vessel and heated at 400 ° C. under reduced pressure. As a result, a mass spectrometer (5973 NETWORK, manufactured by Hewlett Packard) did not detect chlorine-derived ion species. It was.

(Comparative Example 2)
An experiment was conducted in the same manner as in Example 5 except that the hexafluorocyclobutene obtained in Production Example 1 was used as the plasma reaction gas. As a result, a fluorocarbon film having a thickness of 0.3 μm was obtained on the substrate. In this fluorocarbon film, voids were observed in some places, and the adhesion to the substrate was poor. The relative dielectric constant of the fluorocarbon film is 2.4. When the silicon wafer thus formed is placed in a vacuum container and heated at 400 ° C. under reduced pressure, the ion species derived from chlorine is detected by a mass spectrometer. was detected.

  In dry etching, Example 1 using hexafluorocyclobutene whose amount of chlorotrifluoroethylene was below the detection limit was higher in dry etching rate than Comparative Example 1 using hexafluorocyclobutene having a chlorotrifluoroethylene amount of 280 ppm. In addition, it was found that a good pattern can be formed with excellent selectivity to a resist.

  In addition, in CVD, the fluorocarbon film of Example 5 using hexafluorocyclobutene having a chlorotrifluoroethylene amount below the detection limit is the same as that of Comparative Example 2 using hexafluorocyclobutene having a chlorotrifluoroethylene amount of 280 ppm. The dielectric constant was lower than that of the fluorocarbon film, the adhesion to the substrate was excellent, and no void was generated. Further, it was excellent in that no ionic species (corrosive gas) derived from chlorine was generated in the heat treatment after film formation.

Claims (8)

  A plasma reaction gas containing 90% by volume or more of an unsaturated fluorinated carbon compound and a chlorine atom-containing compound content of 100 ppm by weight or less.   The gas for plasma reaction according to claim 1, wherein the unsaturated fluorinated carbon compound is hexafluorocyclobutene.   A plasma reaction gas containing 90% by volume or more of an unsaturated fluorinated carbon compound and having a content of chlorotrifluoroethylene of 100 ppm by weight or less.   The plasma reaction gas according to any one of claims 1 to 3, wherein the total amount of nitrogen gas and oxygen gas contained as the remaining trace gas is 200 ppm by volume or less with respect to the total amount of the plasma reaction gas.   The gas for plasma reaction according to any one of claims 1 to 4, wherein the water content is 30 ppm by weight or less.   A method for forming a fluorocarbon film by a CVD method using the plasma reaction gas according to claim 1.   A dry etching method using the plasma reaction gas according to claim 1.   A method for manufacturing a semiconductor device comprising at least one of a dry etching process, a CVD process, and an ashing process using the plasma reaction gas according to claim 1.