Dry etching agent composition and dry etching method

Abstract

Disclosed is the invention of a dry etching agent composition including: 1,3,3,3-tetrafluoropropene; and a hydrochlorofluorocarbon represented by CH.sub.xCl.sub.yF.sub.z (wherein x, y and z are integers of 1 or greater and x+y+z=4), wherein a concentration of the hydrochlorofluorocarbon relative to 1,3,3,3-tetrafluoropropene is 3 volume ppm or greater to less than 10000 volume ppm, and a use of this dry etching agent composition. An object of the present invention is to suppress corrosion of storage container, pipes and an etching chamber by suppressing generation of acidic substances by improving storage stability of HFO-1234ze without losing excellent etching characteristics of HFO-1234ze.

Claims

1. A dry etching agent composition, comprising: 1,3,3,3-tetrafluoropropene; and a hydrochlorofluorocarbon represented by CH.sub.xCl.sub.yF.sub.z (wherein x, y and z are integers of 1 or greater and x+y+z=4), wherein a concentration of the hydrochlorofluorocarbon relative to 1,3,3,3-tetrafluoropropene is 3 volume ppm or greater to less than 10000 volume ppm, and wherein the hydrochlorofluorocarbon is chlorodifluoromethane.

2. The dry etching agent composition according to claim 1, wherein a concentration of the hydrochlorofluorocarbon in the dry etching agent composition is 3 volume ppm or greater to less than 1000 volume ppm.

3. A storage container comprising a dry etching agent composition of claim 1.

4. The storage container according to claim 3, wherein, relative to 1,3,3,3-tetrafluoropropene, 10 volume ppm or greater to 10000 volume ppm or less of oxygen is contained, and 1 volume ppm or greater to 10000 volume ppm or less of water is contained in the storage container.

5. A dry etching method, comprising the steps of: converting a dry etching agent composition according to claim 1 to plasma; and etching silicon oxide or silicon nitride by using plasma gas converted into plasma.

6. The dry etching method according to claim 5, wherein the concentration of the hydrochlorofluorocarbon in the dry etching agent is 3 volume ppm or greater to less than 1000 volume ppm.

7. The dry etching method according to claim 5, wherein, relative to 1,3,3,3-tetrafluoropropene, 10 volume ppm or greater to 10000 volume ppm or less of oxygen is contained and 1 volume ppm or greater to 10000 volume ppm or less of water is contained in the dry etching agent.

8. The dry etching method according to claim 5, wherein the etching agent contains an additive gas, and wherein the additive gas is at least one gas selected from the group consisting of O.sub.2, O.sub.3, CO, CO.sub.2, COCl.sub.2, COF.sub.2, CF.sub.2(OF).sub.2, CF.sub.3OF, NO.sub.2, NO, F.sub.2, NF.sub.3, Cl.sub.2, Br.sub.2, I.sub.2 and XF.sub.n (wherein, in a formula, X represents Cl, Br, or I, n is an integer, and 1n7).

9. The dry etching method according to claim 5, wherein the dry etching agent further contains an inert gas, and wherein the inert gas is at least one gas selected from the group consisting of N.sub.2, He, Ar, Ne, Kr and Xe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a storage test container 10 used in Examples and Comparative Examples.

(2) FIG. 2 is a schematic diagram of a reactor 20 used in Examples and Comparative Examples.

DETAILED DESCRIPTION

(3) In the following, an embodiment of the present invention will be described below. In addition, the scope of the present invention is not limited to the description, and the present invention can be preferably modified without departing from the scope and spirit of the present invention other than the following examples, and then can be carried out.

(4) A dry etching method according to the present invention is a dry etching method including the steps of; converting the dry etching agent to plasma; and etching silicon oxide or silicon nitride by using plasma gas converted into plasma. A dry etching agent composition of the present invention is characterized by including: 1,3,3,3-tetrafluoropropene; and a hydrochlorofluorocarbon represented by CH.sub.xCl.sub.yF.sub.z (wherein x, y and z are integers of 1 or greater and x+y+z=4), wherein a concentration of the hydrochlorofluorocarbon relative to 1,3,3,3-tetrafluoropropene is 3 volume ppm or greater to less than 10000 volume ppm. In addition, hereinafter, values of volume ppm and volume % are values under one atmospheric pressure at 25 C.

(5) 1,3,3,3-tetrafluoropropene to be used in the present invention is also referred to as HFO-1234ze, and either of cis and trans isomers or Z and E isomers can be used, and it can be manufactured by a conventionally well-known method. For example, by the present inventors, in Japanese Patent No. 3465865, a method for obtaining HFO-1234ze by acting HF on 1-chloro-3,3,3-trifluoropropene, which can be obtained on an industrial scale, in the presence of a gas phase fluorination catalyst has been disclosed. In addition, in Japanese Patent No. 3821514, a method for obtaining HFO-1234ze by acting HF on 1,1,3,3,3-pentachloropropane has been disclosed.

(6) A hydrochlorofluorocarbon represented by CH.sub.xCL.sub.yF.sub.z (wherein x, y and z are integers of 1 or more, and x+y+z=4) which is used in the present invention is one of chlorodifluoromethane, dichlorofluoromethane and chlorofluoromethane. Among them, it is preferable to use chlorodifluoromethane. Chlorodifluoromethane is also referred to as R22 or HCFC-22, and its chemical formula is CHClF.sub.2. When the content of the hydrochlorofluorocarbon was 3 volume ppm or greater relative to HFO-1234ze, a sufficient effect of suppressing generation of acid caused by decomposition of HFO-1234ze was recognized. In particular, the content of the hydrochlorofluorocarbon relative to HFO-1234ze may be 50 volume ppm or greater, or may be 100 volume ppm or greater. In addition, in a test using a molecule having a structure similar to that of R22, such as CF.sub.4 and CH.sub.4, the same effect was not recognized.

(7) Here, unlike metal salt, the hydrochlorofluorocarbon does not cause contamination of metal to a wafer.

(8) On the other hand, when paying attention to an influence on etching characteristics, in the patent document 1, it has been described that a side wall protection is affected by a double bond included in HFO-1234ze. On the other hand, the hydrochlorofluorocarbon does not include a double bond inside its molecule, and it can be considered that an influence on the side wall protection is poor. Therefore, the content of the hydrochlorofluorocarbon relative to HFO-1234ze is preferably less than 10000 volume ppm, in consideration of the influence on the etching characteristics. In addition, the content of R22 relative to HFO-1234ze is preferably less than 1000 volume ppm, in consideration of the influence on the etching characteristics.

(9) As a storage container for HFO-1234ze, if it is an airtight container which is capable of sealing gas-liquid mixture thereinside, one can be used which does not need a special structure and constituent material, and which has wide ranges of modes and functions. For example, general manganese steel and stainless steel cylinders that are storage containers for high-pressure gas can be used. In a manufacturing process, a purification process and a fulling process, there is case where, relative to HFO-1234ze, 10 volume ppm or greater to 10000 volume ppm or less of oxygen and 1 volume ppm or greater to 10000 volume ppm or less of water are mixed in the storage container. In particular, when 100 volume ppm or greater of oxygen is contained and 5 volume ppm or greater of water is contained, the present invention can be preferably applied thereto, and when 500 volume ppm or greater of oxygen is contained and the 10 volume ppm or greater of water is contained, the present invention can be further preferably applied thereto.

(10) In the present invention, it is preferable that HFO-1234ze and the hydrochlorofluorocarbon to be used are each highly purified to be a purity of at least 99.9 volume % or greater.

(11) Next, an etching method using a dry etching agent in the present invention will be described.

(12) The etching method of the present invention can be carried out under various dry etching conditions. A mixed gas of HFO-1234ze and the hydrochlorofluorocarbon only can be used for the etching agent. However, in general, from the point of view of cost effectiveness and the stability of plasma, various additive gasses and inert gasses can be added so as to be a desired etching rate, etching selection ratio and etching shape.

(13) As an additive gas, at least one gas selected from the group consisting of O.sub.2, O.sub.3, CO, CO.sub.2, COCl.sub.2, COF.sub.2, CF.sub.2(OF).sub.2, CF.sub.3OF, NO.sub.2, NO, F.sub.2, NF.sub.3, Cl.sub.2, Br.sub.2, I.sub.2 and XF.sub.n (In the formula, X represents Cl, Br, or I, n is an integer, and 1n7) can be used. In addition, to obtain a desired etching shape and etching rate, etching can be performed by adding one or more kinds of reducing gasses, fluorocarbons, hydrofluorocarbons and halogen-containing compounds (for example, at least one gas selected from the group consisting of H.sub.2, HF, HI, HBr, HCl, NH.sub.3, CF.sub.4, CF.sub.3H, CF.sub.2H.sub.2, CFH.sub.3, C.sub.2F.sub.6, C.sub.2F.sub.4H.sub.2, C.sub.2F.sub.5H, C.sub.3F.sub.8, C.sub.3F.sub.7H, C.sub.3F.sub.6H.sub.2, C.sub.3F.sub.5H.sub.3, C.sub.3F.sub.4H.sub.4, C.sub.3F.sub.3H.sub.5, C.sub.3F.sub.5H, C.sub.3F.sub.3H, C.sub.3ClF.sub.3H, C.sub.4F.sub.8, C.sub.4F.sub.8, C.sub.5F.sub.8 and C.sub.5F.sub.10). As an inert gas, at least one gas selected from the group consisting of N.sub.2, He, Ar, Ne, Kr and Xe can be used.

(14) A preferable composition ratio of an etching agent containing the mixed gas of HFO-1234ze and the hydrochlorofluorocarbon or the mixed gas of HFO-1234ze and R22 and further containing the additive gas and/or the inert gas is shown below. In addition, the total of the volume % of each gas is 100 volume %.

(15) The concentration of the mixed gas of HFO-1234ze and the hydrochlorofluorocarbon relative to the total of the mixed gas, the additive gas and the inert gas is preferably 1-50 volume %, more preferably 5-40 volume %, further preferably 10-30 volume %.

(16) In addition, the concentration of the additive gas relative to the total of the mixed gas, the additive gas and the inert gas is preferably 0-50 volume %, more preferably 0-10 volume %.

(17) Moreover, the concentration of the inert gas relative to the total of the mixed gas, the additive gas and the inert gas is preferably 0-98 volume %, more preferably 5-95 volume %, further preferably 60-90 volume %.

(18) The etching method to be used in the present invention can be carried out without being limited to various etching methods, such as capacitive coupling type plasma (CCP) etching, reactive ion etching (RIE), induction coupling type plasma (ICP) etching, electronic cyclotron resonance (ECR) plasma etching and microwave etching.

(19) As components contained in the etching gas, they can be independently introduced into a chamber, or can be introduced into the chamber, after being prepared as a mixed gas in advance behind the storage container. The total flow rate of the dry etching agent to be introduced into the reaction chamber can be properly selected, in consideration of the above-mentioned concentration condition and pressure condition, depending on the volume of the reaction chamber and the exhaust capacity of an exhaust portion.

(20) To obtain stable plasma and to suppress side etching by improving linearity of ions, the pressure at the time when the etching is performed is preferably 5 Pa or less, especially preferably 1 Pa or less. On the other hand, if the pressure inside the chamber is too low, ionized ions decrease, and sufficient plasma density cannot be obtained. Therefore it is preferably 0.05 Pa or greater.

(21) In addition, a substrate temperature at the time of the performing of the etching is preferably 100 C. or less, and in particular, to perform anisotropic etching, it is preferably 50 C. or less, especially preferably 20 C. or less. If the temperature exceeds a high temperature of 100 C., the formation of a protection film onto mask material, such as PR and a-C, is not sufficiently performed, and selectivity deteriorates. In addition, at a high temperature, the formation of a side wall protection film is not sufficiently performed, and there is possibility that shape abnormality called a so-called bowing in which the etching shape becomes a rounded shape occurs.

(22) As to a bias voltage between electrodes, which is generated at the time of the performing of the etching, it is simply selected in consideration of a desired etching shape. For example, when anisotropic etching is performed, it is desirable that a voltage between the electrodes of approximately 500V-10000V is generated to make ions high energy states. If the bias voltage is too high, the energy of the ions increases, and it may cause the deterioration of the selectivity.

(23) In consideration of the efficiency of an element manufacturing process, an etching time is preferably 30 minutes or less. Here, the etching time is a period of time during reacting the dry etching agent with a sample by generating plasma inside the chamber.

EXAMPLES

(24) In the following, although Examples of the present invention are cited with Comparative Examples, the present invention is not limited to the following Examples.

Example 1

(25) (Storage Stability Test)

(26) To evaluate corrosion of a container caused by generation of acid, a stability test using a test piece was carried out. FIG. 1 is a schematic diagram of a storage test container 10 used in Examples and Comparative Examples. A pressure-resistant container 14 made of SUS316 of which internal volume was 100 cc and in which a test peace 11 (2.0 mm10 mm30 mm) made of iron was sealed was made. The pressure-resistant container 14 is sealed by a lid 13, and the lid 13 includes a valve 12 which is capable of introducing gas to the pressure-resistant container 14. Forty grams of a mixed gas prepared by adding R22 to HFO-1234ze (E) which had been purified to be a high purity of 99.9 volume % or greater in advance, such that the content of R22 is 3 volume ppm, was sealed into the pressure-resistant container 14. Then, oxygen in an amount of 4000 volume ppm in gas phase components was added thereto, in consideration of mixture of air. In addition, the content of moisture contained inside the container was 10 volume ppm. This container was kept at 100 C. for 60 days.

(27) Thirty days later, the test piece was taken out, and its mass change was measured and the state of its surface was visually observed. As a result of this, the mass change of the test piece was less than 0.01%, and a change in appearance of the test piece was also not observed.

(28) (Etching Test)

(29) To investigate an influence on etching characteristics by R22, an etching test was carried out, using the mixture of HFO-1234ze (E) and R22 before the addition of oxygen. FIG. 2 is a schematic diagram of a reactor 20 used in Examples and Comparative Examples. A lower electrode 24 that functions to support a wafer and also functions as a stage, an upper electrode 25 and a pressure gauge 22 are disposed inside a chamber 21. In addition, a gas introduction port 26 is connected to the upper part of the chamber 21. The pressure inside the chamber 21 is adjustable, and it is possible to excite the dry etching agent by a high frequency power source (13.56 MHz) 23. With this, the etching of a sample 28 can be carried out by bringing the excited dry etching agent into contact with the sample 28 placed on the lower electrode 24. The reactor 20 is configured such that, in a state in which the dry etching agent is introduced, when a high frequency power is supplied from the high frequency power source 23, a DC voltage called as bias voltage is generated between the upper electrode 25 and the lower electrode 24 by the moving speed difference between ions and electrons in the plasma. The gas inside the chamber 21 is discharged via a gas discharge line 27.

(30) As the sample 28, a silicon wafer A having a SiO.sub.2 film and a silicon wafer B having a PR film were placed on the stage which was cooled to 15 C. The SiO.sub.2 film was formed by a CVD method. In addition, the PR film was formed by applying.

(31) Then, the etching was performed in a manner in which the flow rate of the mixture of 1,3,3,3-tetrafluoropropene (HFO-1234ze (E)) and R22, the flow rate of the O.sub.2 and the flow rage of Ar were respectively set to 25 sccm, 25 sccm, and 500 sccm, and the gas of the sufficiently mixed these gases was circulated in the chamber, and the high frequency power was supplied at 400 W to convert the etching agent into plasma.

(32) After the etching, an etching rate was obtained by changes in the thickness of the SiO.sub.2 film of the silicon wafer A and the thickness of the PR film of the silicon wafer B, before and after the etching. Moreover, as each etching selection ratio, a value calculated by dividing the etching rate of SiO.sub.2 by the etching rate of PR was obtained.

(33) As a result of this, in Example 1, the etching rate of SiO.sub.2 was 77.7 nm/min., and the etching rate of PR was 15.1 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 5.15.

Example 2

(34) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 235 volume ppm, which was obtained by adding R22 to HFO-1234ze was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 12 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was carried out, using the mixture of R22 and HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 79.2 nm/min., and the etching rate of PR was 15.8 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 5.01.

Example 3

(35) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 986 volume ppm, which was obtained by adding R22 to HFO-1234ze (E) was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 15 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was carried out, using the mixture of R22 and HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 78.5 nm/min., and the etching rate of PR was 15.6 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 5.03.

Example 4

(36) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 3098 volume ppm, which was obtained by adding R22 to HFO-1234ze (E) was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 11 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was carried out, using the mixture of R22 and HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 76.1 nm/min., and the etching rate of PR was 17.2 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 4.42.

Example 5

(37) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 8029 volume ppm, which was obtained by adding R22 to HFO-1234ze (E) was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 13 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was carried out, using the mixture of R22 and HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 76.8 nm/min., and the etching rate of PR was 17.4 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 4.41.

Example 6

(38) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 3 volume ppm, was used and oxygen in an amount of 500 volume ppm in gas phase components was added. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 14 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed.

Comparative Example 1

(39) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E) in which the content of R22 was less than 1 volume ppm was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 22 volume ppm. As a result of this, a mass change of the test piece before and after the test was 0.03%, and coloring that seems like rust was observed on the surface thereof. Moreover, in the same manner as in Example 1, an etching test was carried out, using HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 77.3 nm/min., and the etching rate of PR was 14.9 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 5.19.

Comparative Example 2

(40) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E), in which the content of R22 was 12521 volume ppm, which was obtained by adding R22 to HFO-1234ze (E) was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 19 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was carried out, using the mixture of R22 and HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 68.9 nm/min., and the etching rate of PR was 17.5 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 3.94, and the selection ratio of 4.0 or greater that is generally required was not obtained.

Comparative Example 3

(41) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E) containing 288 volume ppm of CF.sub.4, instead of R22, was used. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 17 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.02%, and coloring that seems like rust was observed on the surface thereof. Moreover, in the same manner as in Example 1, an etching test was also carried out, using HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 75.1 nm/min., and the etching rate of PR was 18.2 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 4.13.

Comparative Example 4

(42) A storage test sample was prepared under the same condition as that of Example 1, except that CH.sub.4 was used instead of R22, and the content of CH.sub.4 was set to be 9030 volume ppm. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 35 volume ppm. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed. In addition, in the same manner as in Example 1, an etching test was also carried out, using HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 60.1 nm/min. On the other hand, the etching of PR did not proceed, and a deposition was observed on a film, and the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was therefore infinite in theory. However, if a deposition occurs on the film, trenches and holes needed to be etched are covered with a deposition film and then are closed. Therefore, such a condition is not practically adopted.

Comparative Example 5

(43) A storage test sample was prepared under the same condition as that of Example 1, except that CH.sub.4 was used instead of R22, and the content of CH.sub.4 was set to be 14 volume ppm. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 16 volume ppm. As a result of this, a mass change of the test piece before and after the test was 0.03%, and coloring that seems like rust was slightly observed on the surface thereof. Moreover, in the same manner as in Example 1, an etching test was also carried out, using HFO-1234ze (E) before addition of oxygen. As a result of this, the etching rate of SiO.sub.2 was 74.7 nm/min., and the etching rate of PR was 15.1 nm/min. Therefore the selection ratio of PR to SiO.sub.2 (SiO.sub.2/PR) was 4.95.

Comparative Example 6

(44) A storage test sample was prepared under the same condition as that of Example 1, except that HFO-1234ze (E) in which the content of R22 was less than 1 volume ppm was used and oxygen in an amount of 500 volume ppm in gas phase components was added. In addition, the content of moisture contained in HFO-1234ze (E) filled in the pressure-resistant container was 19 volume ppm. As a result of this, it was observed that a mass change of the test piece before and after the test was 0.02%, and coloring that seems like rust was observed on the surface thereof.

Reference Example 1

(45) In Reference Example 1, HFO-1234ze (E) of which a moisture value was lowered to less than 1 ppm by performing sufficient dehydration was used. In addition, R22 was not mixed to HFO-1234ze (E), and it was confirmed that the content of R22 was less than 1 ppm. Except that, a storage test sample was prepared under the same condition as that of Example 1. Moreover, in the same manner as in Example 1, an etching test was also carried out, using HFO-1234ze (E) before addition of oxygen. As a result of this, a mass change of the test piece before and after the test was less than 0.01%, and a change in appearance of the test piece was also not observed.

Reference Example 2

(46) As the sample 28, by using one in which 5 m of a SiO.sub.2 film was formed on a single crystal silicon wafer and a resist in which opening portions each having 0.3 m in line width were provided was applied onto the film, etching was carried out under the same condition as that of Example 1. After the etching, the cross section of the silicon wafer was observed with SEM, and, as a result, shape abnormality such as bowing was hardly observed. In addition, it was confirmed that excellent etching characteristics having an aspect ratio of 10 or greater could be obtained.

Reference Example 3

(47) As the sample 28, by using one in which 5 m of a SiO.sub.2 film was formed on a single crystal silicon wafer and a resist in which opening portions each having 0.3 m in line width were provided was applied onto the film, etching was carried out under the same condition as that of Example 5. After the etching, the cross section of the silicon wafer was observed with SEM, and, as a result, shape abnormality such as bowing was hardly observed. In addition, it was confirmed that excellent etching characteristics having an aspect ratio of 10 or greater could be obtained.

Reference Example 4

(48) As the sample 28, by using one in which 5 m of a SiO.sub.2 film was formed on a single crystal silicon wafer and a resist in which opening portions each having 0.3 m in line width were provided was applied onto the film, etching was carried out under the same condition as that of Reference Example 2. After the etching, the cross section of the silicon wafer was observed with SEM, and, as a result, the etching proceeded halfway. However, a resist part on the surface was burnt by the etching, and the surface of the SiO.sub.2 film was etched.

(49) TABLE-US-00001 TABLE 1 Addition Corrosion resistant test Component amount of Period of Change Content oxygen Moisture time Temperature in mass Kind [ppm] [ppm] [ppm] [day] [ C.] [%] Example 1 R22 3 4000 10 60 100 None Example 2 R22 235 4000 12 60 100 None Example 3 R22 986 4000 15 60 100 None Example 4 R22 3098 4000 11 60 100 None Example 5 R22 8029 4000 13 60 100 None Example 6 R22 3 500 14 60 100 None Comparative R22 <1 4000 22 60 100 0.03 Example 1 Comparative R22 12521 4000 19 60 100 None Example 2 Comparative CF.sub.4 288 4000 17 60 100 0.02 Example 3 Comparative CH.sub.4 9030 4000 35 60 100 None Example 4 Comparative CH.sub.4 14 4000 16 60 100 0.03 Example 5 Comparative R22 <1 500 19 60 100 0.02 Example 6 Reference 4000 <1 60 100 None Example 1

(50) TABLE-US-00002 TABLE 2 Component Etching test Content SiO.sub.2 PR Kind [ppm] [nm/min.] SiO.sub.2/PR Example 1 R22 3 77.7 15.1 5.15 Example 2 R22 235 79.2 15.8 5.01 Example 3 R22 986 78.5 15.6 5.03 Example 4 R22 3098 76.1 17.2 4.42 Example 5 R22 8029 76.8 17.4 4.41 Comparative R22 <1 77.3 14.9 5.19 Example 1 Comparative R22 12521 68.9 17.5 3.94 Example 2 Comparative CF.sub.4 288 75.1 18.2 4.13 Example 3 Comparative CH.sub.4 9030 60.1 0 depo Example 4 Comparative CH.sub.4 14 74.7 15.1 4.95 Example 5

(51) The above results are shown in Tables. In each of Comparative Example 1 and Comparative Example 6, although the etching characteristics were excellent, corrosion occurred to the test piece. This can be considered that acid generated from HFO-1234ze (E) decomposed by a radical generated from oxygen reacted with moisture existing in the system, and then iron corroded.

(52) On the other hand, as shown in the result of each of Examples 1 to 6, when HFO-1234ze (E) containing R22 was used, the corrosion did not occur. Although there are many unclear points about the process of suppression of the corrosion, it can be considered that R22 suppressed the decomposition of HFO-1234ze (E) due to the oxygen radical, or activation of the acid due to the moisture. In particular, in each of Examples 1 to 5, although the content of oxygen is 3000 volume ppm or greater, and it is considered that polymerization reaction and the like proceed with this content thereof in the patent document 4, by containing 3 volume ppm or greater of R22, the corrosion of the test piece did not occur.

(53) However, the etching rate to PR was changed in accordance with the content of R22 in HFO-1234ze (E). In each of Examples, the selection ratio to SiO.sub.2 (SiO.sub.2/PR) was sufficient. In particular, in each of Examples 1 to 3 in which the content of R22 was 1000 volume ppm or less, the SiO.sub.2/PR-etching selection ratio exceeded five, and etching characteristics were excellent. As shown in each of Reference Examples 2 and 3, also in hole pattern etching, closing of pores did not occur. Therefore, it can be said that excellent etching characteristics were obtained, in case where HFO-1234ze (E) in which 3 volume ppm or greater to 10000 volume ppm or less of R22 was contained was used.

(54) On the other hand, as shown in each of Comparative Example 2 and Reference Example 4, when the content of R22 exceeded 10000 volume ppm, the SiO.sub.2/PR-etching selection ratio was lowered. In pattern etching, the resist part was burnt by etching gas, and the surface of the SiO.sub.2 film was etched, and it resulted in deterioration of a function as the etching gas.

(55) HFO-1234ze (E) is a compound with high polymerizability when decomposed in a plasma state, because it has an unsaturated bond in its molecule in its structure. Therefore it can be considered that a deposition film that becomes a protection film is formed on the PR that is an organic film, thereby contributing the increase of the selectivity. On the other hand, R22 does not have such an unsaturated bond, and polymerizability is poor. In addition, in a system in which a large amount of R22 is contained, it can be considered that in addition to the low of protection film formability of R22 itself, when activated by plasma, chlorine attacked the unsaturated bond, and the polymerizability deteriorated, and consequently, it led to the lowering of the selectivity.

(56) On the other hand, in each of Comparative Examples 3 to 5, an influence caused by an additive other than R22 was investigated. As a result of this, as shown in Comparative Example 3, an effect of reducing the corrosion of the test piece was not observed when CF.sub.4 was contained, as was seen an effect by R22. As shown in Comparative Example 4, when a large amount of CH.sub.4 was contained, the corrosion of the test piece was not observed, probably because the decomposition of HFO-12343ze was suppressed. However, the influence on the etching characteristics was large, and it was not preferable as an additive. On the other hand, as shown in Comparative Example 5, in case where a small amount of CH.sub.4 was contained, an effect of suppression of the corrosion of the test piece was not observed, differently from case where R22 was contained.

(57) In addition, in Reference Example 1, the relation of the corrosion between moisture, oxygen and HFO-1234ze (E) and the test piece was confirmed. By this result, it was confirmed that if a moisture value was low, HFO-1234ze (E) and 02 did not directly corrode the test piece.

(58) In each of Reference Example 2 and Reference Example 3, an excellent etching shape was obtained, and it was found that HFO-1234ze (E) containing 3 volume ppm or greater to less than 10000 volume ppm of R22 acted as an excellent etching agent practically. On the other hand, in Reference Example 4, HFO-1234ze (E) containing 10000 volume ppm or greater of R22 did not act as an excellent etching agent, because a resist part was burnt by etching.

INDUSTRIAL APPLICABILITY

(59) The present invention can be used for a selective etching process of SiO.sub.2, in a process for manufacturing a semiconductor.

EXPLANATION OF SIGNS

(60) 10: Storage test container 11: Test piece 12: Valve 13: Lid 14: Pressure-resistant container 20: Reactor 21: Chamber 22: Pressure gauge 23: High frequency power source 24: Lower electrode 25: Upper electrode 26: Gas introduction port 27: Gas discharge line 28: Sample