Supply method of composition, composition, and dry etching method

Abstract

A method for stably supplying trimethylamine containing monomethylamine or dimethylamine as trace impurities in a fixed composition is provided. The present invention is a method for supplying a composition, which is characterized in that a storage container filled with the composition is kept warm at a fixed temperature of 10 °C or higher, and then the gas of the above composition is supplied to a specified device. The gas phase of the above composition contains: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine.

Description

Technical Field

[0001] The present invention relates to a method for supplying a composition containing trimethylamine and dimethylethylamine, a composition containing trimethylamine and dimethylethylamine, and a dry etching method. Background Art

[0002] In the semiconductor field, in order to fix the microfabrication process, it is necessary to supply a source gas with a fixed composition. Therefore, generally, source gases for semiconductor applications need to be ultra-high purity products from which impurity components are removed as much as possible.

[0003] Amines such as trimethylamine have been studied as gases for high-speed / high-selectivity etching of silicon oxide films. However, in order to ultra-highly purify amines, large-scale equipment is required and a large amount of time is needed, so it often does not have a cost advantage. In particular, it is known that trimethylamine forms a complex azeotropic composition with dimethylamine or monomethylamine and is difficult to separate, making it difficult to obtain only trimethylamine in the form of a pure product (for example, Patent Document 1).

[0004] When using trimethylamine, the concentrations of dimethylamine and monomethylamine as impurities change depending on the pressure or usage amount (purge amount) during supply, so it is difficult to continuously supply trimethylamine with a fixed composition.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-63159

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 3-241832 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] As a supply method using azeotropic composition, a method of mixing hydrogen fluoride and ethanol for supply has been reported (for example, Patent Document 2). However, in the supply method of amines, a method using azeotropic composition is not yet known.

[0011] In view of the above technical problems, an object of the present invention is to provide a method for stably supplying trimethylamine with a fixed composition, where the trimethylamine contains monomethylamine or dimethylamine as trace impurities.

[0012] Solutions for Solving the Problems

[0013] The inventors of the present invention have conducted in-depth research and found that by adding a small amount of dimethylethylamine to trimethylamine, a stable azeotropic composition is formed with other methylamines such as monomethylamine and dimethylamine contained in trace amounts in trimethylamine, and it can be supplied with a stable gas composition regardless of the usage amount, thus completing the present invention.

[0014] Specifically, the method for supplying the composition of the present invention is characterized in that a storage container containing the composition is kept warm at a fixed temperature of 10°C or higher, and then the gas of the above composition is supplied to a specified device, and the gas phase of the above composition contains: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine.

[0015] According to the method for supplying the composition of the present invention, a composition containing: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine can be supplied with a stable gas composition regardless of the usage amount.

[0016] The composition of the present invention is a composition for the method for supplying the above composition, and is characterized in that it contains in the gas phase: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine.

[0017] The composition of the present invention contains dimethylethylamine, so even when trimethylamine contains dimethylamine and / or monomethylamine as impurities, trimethylamine can be supplied with a stable gas composition. In addition, the structure of dimethylethylamine is similar to that of trimethylamine, so when used as an etching gas, the advantage is that the influence caused by the inclusion of dimethylethylamine is small.

[0018] The dry etching method of the present invention is characterized in that, in the absence of a plasma state, a gas composition supplied by the above method for supplying the composition and gaseous hydrogen fluoride are reacted with silicon oxide.

[0019] In the dry etching method of the present invention, by using the above method for supplying the composition, the gas of the composition having a stable composition containing trimethylamine is reacted with silicon oxide, so that the etching treatment can be stably performed.

[0020] Effects of the Invention

[0021] According to the method for supplying the composition of the present invention, by adding a small amount of dimethylethylamine to trimethylamine, when supplying trimethylamine at a fixed temperature under fixed conditions, regardless of the usage amount of trimethylamine, the content of dimethylamine or monomethylamine contained as an impurity hardly changes, so trimethylamine can be supplied with a stable gas composition. Detailed Description

[0022] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below is an example of an embodiment of the present invention and is not limited to these specific contents. Various modifications can be made within the scope of the gist thereof for implementation.

[0023] The method for supplying the composition of the present invention is characterized in that a storage container containing the composition is kept warm at a fixed temperature of 10°C or higher, and then the gas of the above composition is supplied to a specified device. The gas phase of the above composition contains: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine.

[0024] In the composition containing trimethylamine and the like, most of its weight is in the liquid phase in the storage container, and a part becomes the gas phase. In the method for supplying the composition of the present invention, the gas phase in the storage container, that is, the gas of the composition, is supplied to a specified device.

[0025] In the present invention, the composition enclosed in the storage container may be any composition that contains trimethylamine, dimethylethylamine, and at least one of dimethylamine and monomethylamine in the gas phase. The method for preparing the composition is not particularly limited. A method of adding dimethylethylamine to trimethylamine is preferred. Trimethylamine and dimethylethylamine may be obtained by separate synthesis or by purchase, and the obtaining method is not particularly limited. The trimethylamine used in the present invention may be trimethylamine containing at least one of dimethylamine and monomethylamine as an impurity.

[0026] When the total amount of the composition is set to 100% by weight, the amount of dimethylethylamine added is preferably 1 to 500 ppm by weight. More preferably, it is 1 to 100 ppm by weight. As a method of adding dimethylethylamine to trimethylamine, for example, methods known to those skilled in the art such as the pressure ratio mixing method, the weight method, the semi-weight method, and the flow-through mixing method can be used.

[0027] It is preferred to further mix after adding trimethylamine and dimethylethylamine into the storage container. The above mixing can be carried out, for example, by shaking mixing, inverting mixing, etc.

[0028] In the present invention, the gas phase of the above composition contains trimethylamine and dimethylethylamine, and also contains at least one of dimethylamine and monomethylamine. That is, the gas phase of the above composition contains trimethylamine, dimethylethylamine and dimethylamine, or contains trimethylamine, dimethylethylamine and monomethylamine, or contains trimethylamine, dimethylethylamine, dimethylamine and monomethylamine.

[0029] In the gas phase of the above composition, trimethylamine preferably contains 95% by volume or more, more preferably 98% by volume or more, and further preferably 99% by volume or more.

[0030] Dimethylethylamine preferably contains 1 to 100 volume ppm, more preferably 1 to 50 volume ppm, in the gas phase of the above composition.

[0031] Dimethylamine preferably contains 0 to 1000 volume ppm, more preferably 0 to 400 volume ppm, in the gas phase of the above composition.

[0032] Monomethylamine preferably contains 0 to 100 volume ppm, more preferably 0 to 50 volume ppm, in the gas phase of the above composition.

[0033] As a preferred embodiment of the present invention, trimethylamine in an amount of 95 volume % or more, dimethylethylamine in an amount of 1 to 100 volume ppm, dimethylamine in an amount of 0 to 1000 volume ppm, and monomethylamine in an amount of 0 to 100 volume ppm are contained in the gas phase of the above composition.

[0034] As a more preferred embodiment of the present invention, trimethylamine in an amount of 95 volume % or more, dimethylethylamine in an amount of 1 to 50 volume ppm, dimethylamine in an amount of 0 to 400 volume ppm, and monomethylamine in an amount of 0 to 50 volume ppm are contained in the gas phase of the above composition.

[0035] In the gas phase of the above composition, other impurities other than monomethylamine and dimethylamine may be contained. Examples of other impurities include moisture, inert gas, ammonia, carbon monoxide, carbon dioxide, methane, and methanol. The gas phase of the above composition may contain 1 to 1000 volume ppm of moisture. The content of the inert gas in the gas phase of the above composition is preferably 5 volume % or less, more preferably 1 volume % or less.

[0036] In the method for supplying the composition of the present invention, the storage container filled with the above composition is kept warm at a fixed temperature of 10°C or higher. When the temperature is less than 10°C, the gas composition in the gas phase in the storage container is unstable, and the concentrations of monomethylamine, dimethylamine, and dimethylethylamine will change significantly before supplying the gas of the composition and after supplying a fixed amount of gas. The storage temperature of the storage container is preferably 10 to 50°C, more preferably 15 to 40°C.

[0037] The storage container filled with the above composition is not particularly limited as long as it can store liquid trimethylamine and the like. As such a storage container, for example, containers made of stainless steel (SUS), manganese steel, nickel steel, chromium molybdenum steel, etc. can be used.

[0038] The method for keeping the storage container warm is not particularly limited, and methods known to those skilled in the art can be used.

[0039] In the present invention, the storage container filled with the above composition is kept warm at a fixed temperature of 10°C or higher, and then the gas of the composition is supplied to a specified device.

[0040] The velocity of the gas supplying the composition is not particularly limited, preferably 1 to 5000 ml / min, more preferably 5 to 1000 ml / min.

[0041] As a method for supplying the gas of the composition to a specified device, for example, the following method can be used: a supply part connecting a storage container filled with the above composition to the specified device is provided, and the gas of the composition is directly introduced from the storage container into the specified device.

[0042] The above specified device is not particularly limited, and examples thereof include an etching device for etching a silicon oxide film.

[0043] In the present invention, the increase or decrease of the content of each of trimethylamine, dimethylethylamine, dimethylamine, and monomethylamine in the gas phase after supplying 90% by weight of the gas of the above composition based on the total amount of the composition is preferably within 10% compared with that before the start of supply. That is, when using the supply method of the composition of the present invention, the difference between the content of each of trimethylamine, dimethylethylamine, dimethylamine, and monomethylamine in the gas phase before the start of supply and the content of each of trimethylamine, dimethylethylamine, dimethylamine, and monomethylamine in the gas phase after supplying 90% by weight based on the total amount of the composition can be set within 10%.

[0044] In addition, the present invention relates to a composition for the supply method of the above composition, and the composition contains in the gas phase: trimethylamine; dimethylethylamine; and at least one of dimethylamine and monomethylamine.

[0045] In addition, the present invention relates to a dry etching method, characterized in that, in the absence of a plasma state, a gas composition supplied by the supply method of the above composition and gaseous hydrogen fluoride are reacted with silicon oxide. The gas composition supplied by the supply method of the above composition refers to the gas of the above composition, mainly containing trimethylamine, and also containing dimethylethylamine and at least one of dimethylamine and monomethylamine.

[0046] In the etching method of the present invention, gaseous trimethylamine and gaseous hydrogen fluoride are reacted with silicon oxide in the absence of a plasma state, so dry etching of silicon oxide is performed without generating gas plasma.

[0047] The dry etching method of the present invention can be divided into a first embodiment and a second embodiment. In the first embodiment, a gas of hydrogen fluoride and a gas of a composition containing trimethylamine are supplied to an etching apparatus and brought into contact with silicon oxide, thereby dry etching the silicon oxide. In the second embodiment, the gas of the composition containing trimethylamine and the gas of hydrogen fluoride are separately supplied to the etching apparatus, thereby dry etching the silicon oxide. In either embodiment, the finally generated reaction compound is a trimethylamine salt of hexafluorosilicic acid, and the above compound sublimes into a gas while being generated or thermally decomposes into a gas.

[0048] In the first embodiment, part or all of the gas of hydrogen fluoride and the gas of the composition containing trimethylamine may become a hydrogen fluoride salt of the composition containing trimethylamine.

[0049] When the gas of hydrogen fluoride and the gas of the composition containing trimethylamine are brought into contact with silicon oxide, the temperature is preferably 200 °C or lower, more preferably 150 °C or lower, and particularly preferably 120 °C or lower. In addition, the contact temperature is preferably 20 °C or higher, more preferably 50 °C or higher, and particularly preferably 80 °C or higher.

[0050] The mixing ratio of hydrogen fluoride to the gas of the composition containing trimethylamine is the value obtained by dividing the total molar number of the composition containing trimethylamine by the molar number of hydrogen fluoride, and is preferably 0.001 or more and 100 or less, more preferably 0.01 or more and 10 or less, and particularly preferably 0.1 or more and 5 or less.

[0051] The dry etching method of the present invention can be applied to the etching of a semiconductor substrate having a silicon oxide film. For example, for a substrate to be processed in which both a silicon oxide film and a silicon nitride film are exposed, only the silicon oxide film can be selectively etched.

[0052] Examples

[0053] Hereinafter, examples for more specifically disclosing the embodiments of the present invention are shown. It should be noted that the present invention is not limited to these examples.

[0054] [Example 1]

[0055] 1 kg of trimethylamine (TMA) with a purity of 99.9 vol% or more was filled into a SUS container, and 15 mg of dimethylethylamine (DMEA) was added. While the container was kept at room temperature, after sufficient mixing, the gas was discharged from the container for gas-phase composition analysis. As a result, it contained DMEA at a concentration of 12 vol ppm, dimethylamine (DMA) at a concentration of 387 vol ppm, water at a concentration of 410 vol ppm, and the monomethylamine (MMA) concentration was less than 1 vol ppm. The gas-phase composition analysis was performed using a gas chromatograph analysis device (GC-2014, manufactured by Shimadzu Corporation, detector: FID). The container was cooled to 15 °C and purged at a flow rate of 1000 ml / min. After confirming that the residual amount of TMA in the container had become 0.1 kg (using 90 wt% TMA), the gas-phase composition analysis was performed again. The gas-phase composition analysis at this time was performed at room temperature on the gas purged from the container cooled to 15 °C. As a result, the TMA concentration was 99.9 vol% or more, the DMA concentration was 380 vol ppm, the MMA concentration was less than 1 vol ppm, and the DMEA concentration was 13 vol ppm. The results are shown in Table 1.

[0056] [Example 2]

[0057] 1 kg of trimethylamine (TMA) with a purity of 99.9 vol% or more, different from that in Example 1, was filled into a SUS container, 15 mg of dimethylethylamine (DMEA) was added, and after sufficient mixing, the gas was discharged from the container for gas-phase composition analysis. As a result, the composition of the gas phase was such that the DMA concentration was 12 vol ppm, the MMA concentration was less than 1 vol ppm, the DMEA concentration was 11 vol ppm, and the water concentration was 10 vol ppm. Then, purging was performed under the same conditions as in Example 1, and then composition analysis was performed. The results are shown in Table 1.

[0058] [Example 3]

[0059] 1 kg of trimethylamine (TMA) with a purity of 99.9 vol% or more, different from that in Example 1 and Example 2, was filled into a SUS container, 15 mg of dimethylethylamine (DMEA) was added, and after sufficient mixing, the gas was discharged from the container for gas-phase composition analysis. As a result, the composition of the gas phase was such that the DMA concentration was 13 vol ppm, the MMA concentration was 45 vol ppm, the DMEA concentration was 5 vol ppm, and the water concentration was 1 vol ppm. Then, purging was performed under the same conditions as in Example 1 except that the container temperature was set to 40 °C, and then composition analysis was performed. The results are shown in Table 1.

[0060] [Comparative Example 1]

[0061] Except for not adding DMEA, the same trimethylamine (TMA) as in Example 1 was used, purged under the same conditions as in Example 1, and then subjected to compositional analysis. The results are shown in Table 1.

[0062] [Comparative Example 2]

[0063] Except for not adding DMEA, the same trimethylamine (TMA) as in Example 3 was used, purged under the same conditions as in Example 1, and then subjected to compositional analysis. The results are shown in Table 1.

[0064] [Comparative Example 3]

[0065] The same trimethylamine (TMA) as in Example 1 was used, 15 mg of dimethylethylamine (DMEA) was added in the same manner as in Example 1, and its composition was analyzed. The results were the values shown in Table 1. Then, the container temperature was cooled to 5°C, purged under the same conditions as in Example 1, and then subjected to compositional analysis. The results are shown in Table 1.

[0066] [Table 1]

[0067]

[0068] Regarding Examples 1 and 2 where DMEA was added and the purge temperature was set to 15°C, and Example 3 where the purge temperature was set to 40°C, after purging 90% by weight of the gas composition, compared with the gas composition before purging, in terms of the relative change amount Δ[(gas composition after using 90% - gas composition before use) / gas composition before use], TMA, DMA, MMA, and DMEA all increased or decreased by 0 to several %. On the other hand, regarding Comparative Examples 1 and 2 where DMEA was not added, in Comparative Example 1, the concentration of DMA decreased by approximately 75% in terms of the relative change amount Δ, in Comparative Example 2, DMA decreased by approximately 82% in terms of the relative change amount Δ, and MMA decreased by approximately 79% in terms of the relative change amount Δ. In addition, in Comparative Example 3 where DMEA was added but the purge temperature was set to 5°C, the concentration of DMA decreased by approximately 65% in terms of the relative change amount Δ, and the concentration of DMEA increased by approximately 113% in terms of the relative change amount Δ.

Claims

1. A method for supplying a composition, characterized in that, Keep the storage container filled with the composition at a fixed temperature of 10°C or higher, and then supply the gas of the composition to a specified device. The gas phase of the composition contains: trimethylamine; dimethyl ethylamine; and at least one of dimethylamine and monomethylamine, The gas phase contains 95% by volume or more of trimethylamine.

2. The method for supplying the composition according to claim 1, characterized in that, The gas phase contains 1 to 100 volume ppm of dimethyl ethylamine, 0 to 1000 volume ppm of dimethylamine, and 0 to 100 volume ppm of monomethylamine.

3. The method for supplying the composition according to claim 1, characterized in that, The gas phase contains 1 to 50 volume ppm of dimethyl ethylamine, 0 to 400 volume ppm of dimethylamine, and 0 to 50 volume ppm of monomethylamine.

4. The method for supplying the composition according to claim 1, wherein, Keep the storage container at a fixed temperature of 10 to 50°C.

5. The method for supplying the composition according to claim 1, wherein Keep the storage container at a fixed temperature of 15 to 40°C.

6. The method for supplying the composition according to claim 1, wherein, After supplying 90% by weight of the gas of the composition based on the total amount of the composition, the increase or decrease in the content of each of trimethylamine, dimethyl ethylamine, dimethylamine, and monomethylamine in the gas phase is within 10% compared to before the start of the supply.

7. The method for supplying the composition according to claim 1, characterized in that, The gas phase further contains 1 to 1000 volume ppm of moisture.

8. The method for supplying the composition according to claim 1, characterized in that, The gas phase further contains an inert gas.

9. The supply method of the composition according to claim 1, wherein, In the gas phase of the composition, it contains 98% by volume or more of trimethylamine.

10. The method for supplying the composition according to claim 1, wherein, In the gas phase of the composition, it contains 99% by volume or more of trimethylamine.

11. The method for supplying the composition according to claim 1, wherein, When the total amount of the composition is set to 100% by weight, the amount of dimethyl ethylamine is 1 to 500 weight ppm.

12. The method for supplying the composition according to claim 1, wherein, When the total amount of the composition is set to 100% by weight, the amount of dimethyl ethylamine is 1 to 100 weight ppm.

13. The method for supplying the composition according to claim 1, wherein, The storage container is a container made of stainless steel, manganese steel, nickel steel, or chrome molybdenum steel.

14. The method for supplying the composition according to claim 1, wherein, The specified device is an etching device for etching a silicon oxide film.

15. The method for supplying the composition according to claim 1, wherein, Provide a supply section connecting the storage container filled with the composition to the specified device, and directly introduce the gas of the composition from the storage container into the specified device.

16. The method for supplying the composition according to claim 1, wherein, The gas phase further contains 1 to 10 volume ppm of moisture.

17. The method for supplying the composition according to claim 8, wherein, In the gas phase of the composition, the content of the inert gas is 5% by volume or less.

18. The supply method of the composition according to claim 8, wherein, In the gas phase of the composition, the content of the inert gas is 1% by volume or less.

19. The method for supplying the composition according to claim 1, wherein, The gas phase of the composition contains trimethylamine, dimethyl ethylamine, and dimethylamine.

20. The method for supplying the composition according to claim 1, wherein, The gas phase of the composition contains trimethylamine, dimethyl ethylamine, dimethylamine, and monomethylamine.

21. The supply method of the composition according to claim 1, wherein, Add trimethylamine and dimethyl ethylamine into the storage container and then mix further.

22. The method for supplying the composition according to claim 1, which is used in a dry etching method.

23. The method for supplying the composition according to claim 22, wherein, The dry etching method is used for etching a semiconductor substrate having a silicon oxide film.

24. The method for supplying the composition according to claim 22, wherein, For a substrate to be processed where both a silicon oxide film and a silicon nitride film are exposed, selectively etch only the silicon oxide film.

25. The method for supplying the composition according to claim 1, wherein, In the storage container, most of the composition containing trimethylamine is in the liquid phase by weight, and a part becomes the gas phase.

26. The method for supplying the composition according to claim 1, wherein, The supply rate of the gas of the composition is 1 to 5000 ml / minute.

27. The method for supplying the composition according to claim 1, wherein, The supply rate of the gas of the composition is 5 to 1000 ml / minute.

28. A composition for use in the method for supplying the composition according to any one of claims 1 to 27, The composition contains in the gas phase: Trimethylamine; Dimethylethylamine; and At least one of dimethylamine and monomethylamine, The gas phase contains more than 95% by volume of trimethylamine.

29. The composition according to claim 28, wherein, The gas phase contains 1 to 100 volume ppm of dimethylethylamine, 0 to 1000 volume ppm of dimethylamine, and 0 to 100 volume ppm of monomethylamine.

30. The composition according to claim 28, wherein, The gas phase contains 1 to 50 volume ppm of dimethylethylamine, 0 to 400 volume ppm of dimethylamine, and 0 to 50 volume ppm of monomethylamine.

31. The composition according to claim 28, wherein, The gas phase further contains 1 to 1000 volume ppm of moisture.

32. The composition according to claim 28, wherein, The gas phase further contains an inert gas.

33. The composition according to claim 28, wherein, In the gas phase of the composition, it contains more than 98% by volume of trimethylamine.

34. The composition according to claim 28, wherein, In the gas phase of the composition, it contains more than 99% by volume of trimethylamine.

35. The composition according to claim 28, wherein, When the total amount of the composition is set to 100% by weight, the amount of dimethylethylamine is 1 to 500 weight ppm.

36. The composition according to claim 28, wherein, When the total amount of the composition is set to 100% by weight, the amount of dimethylethylamine is 1 to 100 weight ppm.

37. The composition according to claim 28, wherein The gas phase further contains 1 to 10 volume ppm of moisture.

38. The composition according to claim 32, wherein, In the gas phase of the composition, the content of the inert gas is 5% by volume or less.

39. The composition according to claim 32, wherein, In the gas phase of the composition, the content of the inert gas is 1% by volume or less.

40. The composition according to claim 28, wherein, The gas phase of the composition contains trimethylamine, dimethylethylamine, and dimethylamine.

41. The composition according to claim 28, wherein, The gas phase of the composition contains trimethylamine, dimethylethylamine, dimethylamine, and monomethylamine.

42. A dry etching method, characterized in that, Without being accompanied by a plasma state, the gas composition supplied by the supply method of the composition according to any one of claims 1 to 27 and gaseous hydrogen fluoride are reacted with silicon oxide.

43. The dry etching method according to claim 42, wherein, Gaseous hydrogen fluoride and the gas of the composition containing trimethylamine are supplied to an etching apparatus and brought into contact with silicon oxide, thereby dry-etching the silicon oxide.

44. The dry etching method according to claim 42, wherein, The gas of the composition containing trimethylamine and gaseous hydrogen fluoride are separately supplied to an etching apparatus, thereby dry-etching the silicon oxide.

45. The dry etching method according to claim 43, wherein, Part or all of the gaseous hydrogen fluoride and the gas of the composition containing trimethylamine become a hydrogen fluoride salt of the composition containing trimethylamine.

46. The dry etching method according to claim 42, wherein, The temperature when gaseous hydrogen fluoride and the gas of the composition containing trimethylamine are brought into contact with silicon oxide is 20°C or higher and 200°C or lower.

47. The dry etching method according to claim 42, wherein, The temperature when gaseous hydrogen fluoride and the gas of the composition containing trimethylamine are brought into contact with silicon oxide is 50°C or higher and 150°C or lower.

48. The dry etching method according to claim 42, wherein, The temperature when gaseous hydrogen fluoride and the gas of the composition containing trimethylamine are brought into contact with silicon oxide is 80°C or higher and 120°C or lower.

49. The dry etching method according to claim 42, wherein, The mixing ratio of hydrogen fluoride to the gas of the composition containing trimethylamine is the value obtained by dividing the total molar amount of the composition containing trimethylamine by the molar amount of hydrogen fluoride, and the mixing ratio is 0.001 or higher and 100 or lower.

50. The dry etching method according to claim 49, wherein, The mixing ratio is 0.01 or higher and 10 or lower.

51. The dry etching method according to claim 49, wherein, The mixing ratio is 0.1 or higher and 5 or lower.

52. The dry-etching method according to claim 42, which is used for etching a semiconductor substrate having a silicon oxide film.

53. The dry etching method according to claim 42, wherein, For a substrate to be processed where both a silicon oxide film and a silicon nitride film are exposed, only the silicon oxide film is selectively etched.

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