Etching method

Abstract

To provide an etching method capable of deeply etching a device containing silicon oxide (SiO2) and silicon nitride (SiN) without using a deposition gas.SOLUTION: The etching method is for etching a device containing at least silicon oxide (SiO2) and silicon nitride (SiN) using a gas plasma of an etching gas containing a compound represented by the general formula (1): C2HyFz (1) [where y is an integer from 1 to 4, and z is an integer from 2 to 5], the method including selecting the type and concentration of the compound represented by the general formula (1) according to the exposed etching target material in the device.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an etching method. [Background technology]

[0002] Semiconductor devices, particularly 3D-NAND flash memory, are used in smartphones, solid-state drives (SSDs), data center servers, etc., and production volumes are expected to continue to increase. Known etching gases used in the manufacture of such semiconductor devices include, for example, an etching gas containing a predetermined amount of 1,1,2-trifluoroethane and an inert gas, which has similar etching rates for polycrystalline silicon films and silicon oxide films (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-136584 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to provide an etching method that can deeply etch silicon oxide (SiO2) and silicon nitride (SiN)-containing devices without using deposition gases. [Means for solving the problem]

[0005] The present disclosure encompasses the following configurations. Item 1. A device containing at least silicon oxide (SiO2) and silicon nitride (SiN) is formed by using a material represented by the general formula (1): C2H y F z (1) [In the formula, y represents an integer of 1 to 4, and z represents an integer of 2 to 5.] A method for etching with gas plasma of an etching gas containing a compound represented by the formula: An etching method in which the type and concentration of the compound represented by the general formula (1) are selected according to the exposed member to be etched in the device. Item 2. The etching method according to Item 1, wherein the device further contains polycrystalline silicon (poly-Si). Item 3. The etching method according to Item 1 or 2, wherein the compound represented by the general formula (1) is one or more selected from 1,1-difluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2,2-pentafluoroethane. Item 4. The etching method according to any one of Items 1 to 3, wherein the etching gas further contains a rare gas. Item 5. (1) When the member to be etched is silicon oxide (SiO2), the content of 1,1,1,2,2-pentafluoroethane in the etching gas is set to 20 to 80% in terms of flow rate ratio; and (2) When the member to be etched is silicon nitride (SiN), the content of 1,1-difluoroethane and / or 1,1,1-trifluoroethane in the etching gas is set to 20 to 80% in terms of flow rate ratio. 5. The etching method according to any one of items 1 to 4, wherein an etching gas to be used is selected so as to satisfy the following. Item 6. The etching method according to Item 5, wherein when the member to be etched is polycrystalline silicon (poly-Si), the content of the compound represented by the general formula (1) in the etching gas is 20 to 80% in terms of flow rate ratio. Item 7. An etching gas containing at least two selected from the group consisting of 1,1-difluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2,2-pentafluoroethane. Item 8. The etching gas according to Item 7, containing 1,1-difluoroethane and / or 1,1,1-trifluoroethane and 1,1,1,2,2-pentafluoroethane. [Effects of the Invention]

[0006] According to the present disclosure, an etching method can be provided that can deeply etch devices containing silicon oxide (SiO 2 ) and silicon nitride (SiN) without using a deposition gas. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the structure of a 3D-NAND flash memory. [Figure 2] The ion species and etching rate generated from the etching gas produced in Production Example 1 are shown. [Figure 3] 1 shows the ion species generated from the etching gas produced in Production Example 2 and the etching rate. [Figure 4] 1 shows the ion species and etching rate generated from the etching gas produced in Production Example 3. [Figure 5] The etching rates for the etching gases produced in Production Examples 1 to 3 are shown. DETAILED DESCRIPTION OF THE INVENTION

[0008] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of."

[0009] In this specification, when a numerical range is expressed as "A to B," it means "not less than A and not more than B."

[0010] 1. Etching method The etching method of the present disclosure involves etching a device containing at least silicon oxide (SiO2) and silicon nitride (SiN) with a compound represented by the general formula (1): C2H y F z (1) [In the formula, y represents an integer of 1 to 4, and z represents an integer of 2 to 5.] A method for etching with gas plasma of an etching gas containing a compound represented by the formula: The type and concentration of the compound represented by the general formula (1) are selected according to the exposed member to be etched in the device.

[0011] (1-1) Device In the etching method of the present disclosure, the device to be etched is a device, particularly a semiconductor device, containing at least silicon oxide (SiO2) and silicon nitride (SiN). This device may also contain polycrystalline silicon (poly-Si).

[0012] As described above, such devices are not particularly limited as long as they contain silicon oxide (SiO2) and silicon nitride (SiN). Examples include 3D-NAND flash memories having a structure in which silicon oxide (SiO2) films and silicon nitride (SiN) films are alternately stacked, as well as 3D-NAND flash memories having a structure in which silicon oxide (SiO2) films and silicon nitride (SiN) films are alternately stacked with polycrystalline silicon (poly-Si) films interposed between them, as shown in Figure 1.

[0013] (1-2) Etching gas and etching method When using devices containing silicon dioxide (SiO2) and silicon nitride (SiN), such as the 3D-NAND flash memory described above, simultaneous etching of silicon dioxide (SiO2), silicon nitride (SiN), etc. is required. However, when attempting to simultaneously etch these materials, the etching gas used cannot selectively etch only one material; instead, a gas that etches both materials equally must be used. In this case, to maintain the etched shape, a deposition gas must be used during the etching process to adjust the etched shape while proceeding, which complicates the process. Furthermore, when using an etching gas with a carbon number of three or more, the highly depositive nature of the material leads to deposition at the etched opening, which can easily cause the opening to become clogged.

[0014] For this reason, the etching gas is selected from the group consisting of compounds of the general formula (1): C2H y F z (1) [In the formula, y represents an integer of 1 to 4, and z represents an integer of 2 to 5.] The compound may contain a compound represented by the following formula:

[0015] Specific examples of such etching gases include 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2), etc. These gases can be used alone or in combination of two or more.

[0016] The etching gas may further contain a rare gas such as argon, krypton, or xenon.

[0017] Furthermore, when etching silicon oxide (SiO2), silicon nitride (SiN), and other materials, the chemical species that dissociate and ionize in plasma are important. In particular, C-C bonds (bond energy 348 kJ / mol) are more easily broken than C-H bonds (bond energy 413 kJ / mol) and C-F bonds (bond energy 482 kJ / mol). Therefore, the ions generated by plasma can be adjusted by the structure of the etching gas used. As a result, the desired material can be etched by selecting the type of gas used.

[0018] Specifically, when etching silicon oxide (SiO2), CF3 + , CHF2 + , CHF + Gases containing the above-mentioned rare gases as product species can be used, such as 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2). In this case, the content of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) is preferably 20 to 80% in terms of flow rate ratio, and more preferably 50 to 60%. In this case, the content of the rare gas is preferably 20 to 80% in terms of flow rate ratio, and more preferably 50 to 60%.

[0019] Also, when etching silicon nitride (SiN), C2H2F3 + , C2H3F2 + , CH3 + Gases containing rare gases such as 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc. can be used. In this case, the content of 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc. is preferably 20 to 50% in terms of flow rate ratio, and more preferably 30 to 40%. In this case, the content of rare gas is preferably 50 to 80% in terms of flow rate ratio, and more preferably 60 to 70%.

[0020] In this manner, devices containing silicon oxide (SiO2) and silicon nitride (SiN) can be etched.

[0021] In a 3D-NAND flash memory with the structure shown in Figure 1, etching a silicon dioxide (SiO2) film with 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) stops when it reaches the adjacent polycrystalline silicon (poly-Si) film. However, reducing the inflow of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) dilutes the HFC-125 content in the etching gas, allowing the polycrystalline silicon (poly-Si) film to be etched. Subsequently, by switching the inflow gas to 1,1-difluoroethane (HFC-152a; CHF2CH3) or 1,1,1-trifluoroethane (HFC-143a; CF3CH3), the adjacent silicon nitride (SiN) film can be etched. When etching a polycrystalline silicon (poly-Si) film with a low content of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2), the content of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) in the etching gas is preferably 10 to 60% in terms of flow rate ratio, and more preferably 20 to 40%. In this case, the content of the rare gas is preferably 40 to 90% in terms of flow rate ratio, and more preferably 60 to 80%.

[0022] Furthermore, when using a 3D-NAND flash memory with the structure shown in Figure 1, if a silicon nitride (SiN) film is etched using 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc., the etching stops when it reaches the adjacent polycrystalline silicon (poly-Si) film. However, if the inflow of 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc. is reduced at this point, the content of 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc. in the etching gas becomes diluted, allowing the polycrystalline silicon (poly-Si) film to be etched. Thereafter, by switching the inflow gas to 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2), etc., it is possible to etch the adjacent silicon oxide (SiO2) film. When etching a polycrystalline silicon (poly-Si) film with a dilute content of 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc., in the etching gas, the content of 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), etc. in the etching gas is preferably 10 to 40% in terms of flow rate, more preferably 10 to 20%. In this case, the content of the rare gas is preferably 60 to 90% in terms of flow rate, more preferably 80 to 90%.

[0023] In the above explanation of the etching method, the etching method of the present disclosure has been mainly described in which the type and concentration of the compound represented by general formula (1) are selected according to the exposed member to be etched in the device. However, it is also possible to simultaneously etch a device containing silicon oxide (SiO) and silicon nitride (SiN) using an etching gas containing at least two of 1,1-difluoroethane (HFC-152a; CHFCH), 1,1,1-trifluoroethane (HFC-143a; CFCH), 1,1,1,2,2-pentafluoroethane (HFC-125; CFCHF), etc.

[0024] For example, 1,1,1,2,2-pentafluoroethane (HFC-125; CFCHF) can be mixed to etch silicon oxide (SiO) films, and 1,1-difluoroethane (HFC-152a; CHFCH) and 1,1,1-trifluoroethane (HFC-143a; CFCH) can be mixed to etch silicon nitride (SiN) films. In this case, the content of 1,1,1,2,2-pentafluoroethane (HFC-125; CFCHF) is preferably 20 to 80% in terms of flow rate, and more preferably 40 to 60%. Furthermore, the content of 1,1-difluoroethane (HFC-152a; CHFCH) and 1,1,1-trifluoroethane (HFC-143a; CFCH) is preferably 20 to 50% in terms of flow rate, and more preferably 30 to 40%. In this case, it is more preferable that the content of the rare gas is the balance.

[0025] While the embodiments of the present disclosure have been described above, various changes in form and details are possible without departing from the spirit and scope of the claims. [Example]

[0026] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples alone.

[0027] Production Examples 1 to 3: Production of etching gas Etching gases of various concentrations were produced by mixing argon with 1,1-difluoroethane (HFC-152a; CHF2CH3), 1,1,1-trifluoroethane (HFC-143a; CF3CH3), or 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2). Note that in the following compositions, the ratios are all flow rate ratios.

[0028] Production example 1-1: HFC-152a 10% + Ar 90% Production example 1-2: HFC-152a 20% + Ar 80% Production example 1-3: HFC-152a 40% + Ar 60% Production example 1-4: HFC-152a 60% + Ar 40% Production example 1-5: HFC-152a 100% Production example 2-1: HFC-143a 10% + Ar 90% Production example 2-2: HFC-143a 20% + Ar 80% Production example 2-3: HFC-143a 40% + Ar 60% Production example 2-4: HFC-143a 60% + Ar 40% Production example 2-5: HFC-143a 100% Production example 3-1: HFC-125 10% + Ar 90% Production example 3-2: HFC-125 20% + Ar 80% Production example 3-3: HFC-125 40% + Ar 60% Production example 3-4: HFC-125 60% + Ar 40% Production example 3-5: HFC-125 100%.

[0029] Example 1: Ion species generated by each etching gas The ion species generated from the etching gases obtained in Production Examples 1 to 3 were evaluated using a quadrupole mass spectrometer (QMS) under the condition of 20 eV, in two cases: when plasma was not generated and when plasma was generated (1000 W).

[0030] The results are shown in Figures 2 to 4.

[0031] Example 2: Etching rate of each etching gas ICP (Inductive Coupled Plasma), discharge power 1000W, bias power 300W, pressure 1Pa, electron density 8×10 10 ~2×10 11 cm -3 The etching rates of a 1 μm thick silicon oxide (SiO2) film formed on a silicon substrate, a 2 μm thick silicon nitride (SiN) film formed on a silicon substrate, and a 0.5 μm thick polycrystalline silicon (poly-Si) film formed on a silicon substrate were measured under etching conditions of an electron temperature of 2 to 3 eV. The silicon oxide (SiO2) film, silicon nitride (SiN) film, and polycrystalline silicon (poly-Si) film were formed according to standard methods. The results are shown in Figures 2 to 5.

[0032] From the above results, it can be seen that 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) has a higher etching rate for silicon oxide (SiO2) films compared to the other two gases, but its etching rate for polycrystalline silicon (poly-Si) is low. Therefore, in the 3D-NAND flash memory shown in Figure 1, when etching a silicon oxide (SiO2) film with 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2), the etching rate for the adjacent polycrystalline silicon (po Etching stops when it reaches the polycrystalline silicon (poly-Si) film, but since the etching rate of the polycrystalline silicon (poly-Si) film increases under dilute conditions (around 20%), it can be seen that if the inflow of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) is reduced, the content of 1,1,1,2,2-pentafluoroethane (HFC-125; CF3CHF2) in the etching gas becomes diluted, and it becomes possible to etch the polycrystalline silicon (poly-Si) film.

[0033] In addition, 1,1-difluoroethane (HFC-152a; CHF2CH3) and 1,1,1-trifluoroethane (HFC-143a; CF3CH3) have a higher etching rate for silicon nitride (SiN) films than for silicon oxide (SiO2) films, but their etching rate for polycrystalline silicon (poly-Si) is low. Therefore, in a 3D-NAND flash memory such as that shown in Figure 1, when etching a silicon nitride (SiN) film with 1,1-difluoroethane (HFC-152a; CHF2CH3) and 1,1,1-trifluoroethane (HFC-143a; CF3CH3), the etching rate of the adjacent polycrystalline silicon (poly-Si) is low. However, under dilute conditions (around 20%), the etching rate of the polycrystalline silicon (poly-Si) film increases. Therefore, it can be seen that if the inflow of 1,1-difluoroethane (HFC-152a; CHF2CH3) and 1,1,1-trifluoroethane (HFC-143a; CF3CH3) is reduced, the content of 1,1-difluoroethane (HFC-152a; CHF2CH3) and 1,1,1-trifluoroethane (HFC-143a; CF3CH3) in the etching gas becomes diluted, and the polycrystalline silicon (poly-Si) film can be etched.

[0034] By repeating the above operations, it is clear that even in the case of a 3D-NAND flash memory as shown in Figure 1, deep etching is possible without using a deposition gas, without depositing in the etching opening or blocking the opening.

[0035] The composition of ions and radicals dissociated in the plasma determines the etching and deposition surface reactions on silicon oxide (SiO2), silicon nitride (SiN), and polycrystalline silicon (poly-Si) films, so the same effects can be obtained when 1,1-difluoroethane and / or 1,1,1-trifluoroethane is contained and mixed with 1,1,1,2,2-pentafluoroethane. In particular, when switching gases, a mixed gas state occurs during the exhaust time determined by the exhaust speed, and this switching corresponds to the layered structure of the film, which is effective in etching multilayer films.

Claims

1. At least silicon oxide (SiO ２ ) and silicon nitride (SiN) containing a compound of the general formula (1): C ２ H ｙ F ｚ (1) [In the formula, y represents an integer of 1 to 4, and z represents an integer of 2 to 5.] A method for etching with gas plasma of an etching gas containing a compound represented by the formula: An etching method in which the type and concentration of the compound represented by the general formula (1) are selected according to the exposed member to be etched in the device.

2. 2. The etching method of claim 1, wherein the device further comprises polycrystalline silicon (poly-Si).

3. 2. The etching method according to claim 1, wherein the compound represented by the general formula (1) is one or more selected from 1,1-difluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2,2-pentafluoroethane.

4. The etching method according to claim 1 , wherein the etching gas further contains a rare gas.

5. (1) The member to be etched is silicon oxide (SiO ２ ) In this case, the content of 1,1,1,2,2-pentafluoroethane in the etching gas is set to 20 to 80% in terms of flow rate ratio; and (2) When the member to be etched is silicon nitride (SiN), the content of 1,1-difluoroethane and / or 1,1,1-trifluoroethane in the etching gas is set to 20 to 80% in terms of flow rate ratio.

5. The etching method according to claim 1, wherein an etching gas to be used is selected so as to satisfy the following:

6. 6. The etching method according to claim 5, wherein when the member to be etched is polycrystalline silicon (poly-Si), the content of the compound represented by the general formula (1) in the etching gas is 20 to 80% in terms of flow rate ratio.

7. An etching gas containing at least two members selected from the group consisting of 1,1-difluoroethane, 1,1,1-trifluoroethane, and 1,1,1,2,2-pentafluoroethane.

8. 8. The etching gas according to claim 7, which contains 1,1-difluoroethane and / or 1,1,1-trifluoroethane and 1,1,1,2,2-pentafluoroethane.

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