Substrate processing method and substrate processing apparatus

Abstract

To provide a substrate processing method and a substrate processing apparatus that selectively etch silicon oxide films without using hydrogen fluoride.SOLUTION: A substrate processing method includes a reaction step of heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas, and an etching step of bringing the etching gas into contact with a substrate having a silicon oxide film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus. [Background technology]

[0002] Wet etching, plasma etching, and dry etching are known methods for etching silicon oxide films on substrates (wafers). However, when etching silicon oxide films using wet etching, the etching chemicals may adversely affect (damage) films on the substrate that are not the target of etching. When etching silicon oxide films using plasma etching, the plasma may adversely affect films on the substrate that are not the target of etching. Therefore, a method for etching silicon oxide films without adversely affecting films on the substrate that are not the target of etching is desired. In particular, to improve etching throughput, a method for selectively etching silicon oxide films is desired when silicon oxide films and silicon nitride films are present on the substrate surface.

[0003] Patent Document 1 discloses an etching method and a recording medium. This etching method relates to a method for etching a silicon oxide film, and is so-called dry etching. In this etching method, a modification step is performed in which a mixed gas containing hydrogen fluoride gas and ammonia gas is supplied to the surface of the silicon oxide film, causing a chemical reaction between the silicon oxide film and the mixed gas, thereby modifying the silicon oxide film and generating a reaction product, and then a heating step is performed in which the reaction product is heated and removed. In the modification step, the temperature of the silicon oxide film and the partial pressure of hydrogen fluoride gas (HF) in the mixed gas are adjusted depending on the type of silicon oxide film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-180418 Summary of the Invention [Problem to be solved by the invention]

[0005] The prior art disclosed in Patent Document 1 has the problem of using hydrogen fluoride, which is highly corrosive to metals and harmful to the human body. Therefore, it is desired to provide a substrate processing method and substrate processing apparatus that can selectively etch silicon oxide films without using hydrogen fluoride.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a substrate processing method and a substrate processing apparatus that selectively etch a silicon oxide film without using hydrogen fluoride. [Means for solving the problem]

[0007] In order to achieve the above object, a substrate processing method according to the present disclosure includes: a reaction step of heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas; and an etching step of bringing the etching gas into contact with a substrate having a silicon oxide film.

[0008] In order to achieve the above object, a substrate processing apparatus according to the present disclosure includes: a reaction section for heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas; and an etching processing section for bringing the etching gas into contact with a substrate having a silicon oxide film. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a substrate processing method and a substrate processing apparatus that selectively etch a silicon oxide film without using hydrogen fluoride. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an explanatory diagram of a configuration of the substrate processing apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0011] A substrate processing method and a substrate processing apparatus according to an embodiment of the present disclosure will be described below.

[0012] The substrate processing method according to this embodiment includes a reaction step of heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas, and an etching step of bringing the etching gas into contact with a substrate having a silicon oxide film.

[0013] According to the substrate processing method of this embodiment, it is possible to selectively etch a silicon oxide film without using hydrogen fluoride.

[0014] The substrate processing method according to this embodiment is realized, for example, by a substrate processing apparatus 100 as shown in FIG.

[0015] This substrate processing apparatus 100 includes a reaction section 1 that heats a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas, and an etching processing section 2 that brings the etching gas into contact with a substrate having a silicon oxide film.

[0016] The substrate processing method and the substrate processing apparatus according to this embodiment will be described in detail below. First, the substrate processing method according to this embodiment will be described in detail. As described above, the substrate processing method according to this embodiment includes a reaction step and an etching step.

[0017] The etching process is a process of etching a silicon oxide film on a substrate having a silicon oxide film thereon using the above-mentioned etching gas, i.e., an etching gas obtained by heating a mixed gas of a reducing gas and nitrogen trifluoride. As will be described later, this etching gas can selectively etch a silicon oxide film despite not containing hydrogen fluoride. The mixed gas and the etching gas may contain a carrier gas. An example of the carrier gas is nitrogen.

[0018] In the etching process, the pressure of the etching gas is preferably set to 133 Pa (abs) or more and 101323 Pa (abs) or less. Performing etching under such a reduced pressure of less than 1 atmosphere (101325 Pa) simplifies etching control. For example, within the above pressure range, etching conditions can be easily changed. Furthermore, within the above pressure range, etching rate control becomes easy. Furthermore, such a reduced pressure makes it easier to prevent leakage of the etching gas outside the system.

[0019] The reaction process involves heating the mixed gas to react nitrogen trifluoride with a reducing gas such as hydrogen (H2), ammonia (NH3), or hydrazine (N2H4), to produce a compound of the formula NH x F y (where x and y are integers)). x F y A gas of a salt of hydrogen fluoride and ammonia, such as ammonium fluoride represented by the formula (I), is simply referred to as ammonium fluoride or the like.

[0020] By using ammonium fluoride or the like as an etching gas in the etching process, etching of a silicon oxide film can be achieved without using hydrogen fluoride. In this case, for example, when a silicon oxide film and a silicon nitride film are formed on a substrate, selective etching of the silicon oxide film can be achieved. Details of etching using ammonium fluoride or the like will be described later.

[0021] In the reaction step, the mixed gas is preferably heated to 400° C. or higher and 600° C. or lower, which facilitates the formation of ammonium fluoride and the like.

[0022] In addition to hydrogen, ammonia, and hydrazine, the reducing gas may also be methylammonia (NH2CH3), diazene (N2H2), methylhydrazine (N2H3CH3), ethylhydrazine (N2H3C2H6), dimethylhydrazine (propylhydrazine) (N2H3C3H7), butylhydrazine (N2H3C4H9), hydrogen azide (N3H), cyclotriazane (N3H3), triazene (N3H3), and triazane (N3H8). The type of reducing gas is not limited.

[0023] The reducing gas may contain a plurality of the components listed above.

[0024] Ammonia and hydrazine are preferred as reducing gases, and when these are used as reducing gases, ammonium fluoride and the like can be efficiently purified.

[0025] A particularly preferred reducing gas is hydrazine. When hydrazine is used as the reducing gas, it reacts with nitrogen trifluoride to produce ammonium fluoride or the like and a compound having the composition formula N2H x F y An etching gas containing a salt of hydrogen fluoride and hydrazine, such as hydrazinium fluoride (N2H6F2) represented by the formula N2H x F y A gaseous salt of hydrogen fluoride and ammonia, such as hydrazinium fluoride represented by the formula (I), is simply referred to as hydrazinium fluoride or the like.

[0026] By using hydrazinium fluoride or the like as an etching gas in the etching process, it is possible to achieve efficient etching of a silicon oxide film without using hydrogen fluoride. Furthermore, in this case, for example, when a silicon oxide film and a silicon nitride film are formed on a substrate, it is possible to achieve more selective etching of the silicon oxide film. Details of etching using hydrazinium fluoride or the like will be described later.

[0027] Etching using ammonium fluoride or the like and hydrazinium fluoride or the like will be described.

[0028] Ammonium fluoride etc. reacts with the silicon oxide film (the ammonium fluoride etc. etches the silicon oxide film) to form ammonium silicofluoride (SiF6(NH4)2).

[0029] Hydrazinium fluoride or the like reacts with the silicon oxide film (the hydrazinium fluoride or the like etches the silicon oxide film), forming hydrazinium silicofluoride (SiF6(N2H5)2).

[0030] Ammonium silicofluoride thermally decomposes at temperatures below 200°C according to the following formula (1), turning into silicon tetrafluoride (SiF4), ammonia (NH3), and hydrogen fluoride (HF).

[0031] SiF6(NH4)2→SiF4+2NH3+2HF...(1)

[0032] Hydrazinium silicofluoride also undergoes thermal decomposition at temperatures of 200°C or less according to the following formula (2), yielding silicon tetrafluoride (SiF4), ammonia (NH3), nitrogen (N2), and hydrogen fluoride (HF).

[0033] SiF6(N2H5)2→SiF4+8 / 3NH3+2 / 3N2+2HF...(2)

[0034] The components produced by thermal decomposition of these ammonium fluorosilicium and hydrazinium fluorosilicium have high vapor pressures and can therefore be easily discharged outside the system after the etching step.

[0035] In the reactions shown in the above formulas (1) and (2), the formation enthalpy (ΔHf) The following values ​​were obtained by quantum chemical calculations. That is, the formation enthalpy of the reaction of formula (1) was 321 kJ / mol. The formation enthalpy of the reaction of formula (2) was 58 kJ / mol. In calculating these formation enthalpies, quantum chemical calculations were performed using the Gaussian 16 density functional (DFT: Density Functional Theory) method, the functional B3LYP, and the basis set cc-pVDZ.

[0036] The above calculation results of the formation enthalpy show that the formation enthalpy of formula (2) is smaller than that of formula (1), and therefore the thermal decomposition of hydrazinium fluorosilicate proceeds more easily than that of ammonium fluorosilicate. Therefore, the etching rate of silicon oxide films is faster when the mixed gas contains hydrazine as a reducing gas than when it contains only ammonia.

[0037] Next, the substrate processing apparatus 100 will be described in detail. As shown in Fig. 1, the substrate processing apparatus 100 includes a reaction section 1 and an etching processing section 2. In addition to the reaction section 1 and the etching processing section 2, the substrate processing apparatus 100 may further include a pressure control mechanism 5 that controls the pressure of the etching gas in the etching processing section 2, and a heat exchanger 6. Fig. 1 is an explanatory diagram illustrating the configuration and processing flow of the substrate processing apparatus 100.

[0038] The reaction section 1 may include a reaction chamber 10 to which the mixed gas of the above-mentioned reducing gas and nitrogen trifluoride is supplied, and a heating device 3 for heating the mixed gas in the reaction chamber 10.

[0039] In the reaction chamber 10, the supplied mixed gas is heated by the heater 3 to generate an etching gas. The etching gas is the above-mentioned ammonium fluoride or hydrazinium fluoride. A supply source 91 such as a gas cylinder filled with nitrogen trifluoride, a supply source 92 such as a gas cylinder filled with a reducing gas, and a supply source 90 such as a gas cylinder filled with a carrier gas may be connected to the reaction chamber 10 via gas piping or the like. An example of the carrier gas is nitrogen gas, as described above.

[0040] An example of the reaction chamber 10 is a gas-phase reaction tube having an inlet for the mixed gas and an exhaust port for exhausting the etching gas obtained by heating the mixed gas. An example of the gas-phase reaction tube is a cylindrical (tubular) container made of alumina or the like. The mixed gas is heated while flowing, for example, inside the gas-phase reaction tube. The inner diameter (pipe diameter) of the tube of the gas-phase reaction tube is, for example, 50 mm to 100 mm. Note that the tube diameter and the material of the above-mentioned gas-phase reaction tube are merely examples and are not particularly limited. When the reaction chamber 10 is tubular, the residence time of the mixed gas can be adjusted by increasing or decreasing the tube diameter.

[0041] An electric heater is an example of the heating device 3. The heating device 3 is preferably capable of heating the mixed gas in the reaction chamber 10 to 400°C or higher and 600°C or lower.

[0042] The etching processing unit 2 may include a processing chamber 20 to which the above-mentioned etching gas is supplied and which accommodates a substrate on which a silicon oxide film and a silicon nitride film are formed, and a heating mechanism 4 which heats the etching gas and the substrate in the processing chamber 20.

[0043] An example of the processing chamber 20 is a sealed container having an inlet for an etching gas, an exhaust port for exhausting the exhaust gas after the etching process, and an internal space for accommodating a substrate and for allowing the etching gas to flow through. A specific example of the processing chamber 20 is a cylindrical (tubular) container made of alumina or the like.

[0044] The heating mechanism 4 may include an electric heater, etc. The heating mechanism 4 may heat the etching gas (for example, to 80°C) in the processing chamber 20 or heat the substrate (for example, to 80°C) to create a temperature atmosphere in the processing chamber 20 suitable for the desired etching process.

[0045] The pressure control mechanism 5 is a mechanism for controlling the pressure of the atmosphere (etching gas) within the processing chamber 20. The pressure control mechanism 5 may include, for example, a vacuum pump 50 that suctions and reduces the pressure within the processing chamber 20 (exhaust gas from the processing chamber 20), pressure reduction valves 90a, 91a, and 92a of supply sources 90, 91, and 92, and a pressure gauge 59 that measures the pressure within the processing chamber 20. By reducing the pressure within the processing chamber 20 to between 133 Pa (abs) and 101,323 Pa (abs), which is lower than 1 atmosphere (101,225 Pa), the etching rate can be increased. Furthermore, by reducing the pressure in this manner, leakage of the etching gas to the outside of the system can be easily prevented.

[0046] The heat exchanger 6 may cool the etching gas supplied from the reaction chamber 10 by the exhaust gas from the processing chamber 20. The exhaust gas from the processing chamber 20 that has been heat exchanged in the heat exchanger 6 may then be sent to a recovery device or the like by a blower 7 or the like.

[0047] (Example) The substrate processing method according to this embodiment will be described below based on examples.

[0048] In this example, a silicon substrate having a silicon nitride film (SiN film, thickness 100 nm) and a silicon oxide film (SiO film, thickness 100 nm) was etched as follows (Examples 1 to 10). In this substrate, the silicon nitride film and the silicon oxide film have the same surface area. The main conditions for each example are shown in Table 1.

[0049] [Table 1]

[0050] Nitrogen gas was used as the carrier gas for the mixed gas. The reducing gas used in the mixed gas in each example is as shown in Table 1. The concentrations of nitrogen trifluoride and reducing gas in the mixed gas are also shown in Table 1. In Table 1, the concentration of nitrogen trifluoride is shown as "nitrogen trifluoride concentration (%)." The concentration of reducing gas is shown as "reducing gas concentration (%)." In the description of this example, when simply indicated as "%," it means volume %.

[0051] The mixed gas of each example was heated to the gas phase reaction tube temperature (° C.) shown in Table 1 and reacted to obtain the etching gas of each example.

[0052] This etching gas was supplied for 300 seconds into the etching chamber containing the substrate, and etching was performed. The temperature inside the chamber and the substrate during the etching process was 80°C. The pressure inside the etching chamber was 133 Pa. After the etching process (after the supply of the etching gas was stopped), the temperature inside the chamber was raised to 150°C while a carrier gas (nitrogen) was flowing into the chamber, and a finishing step (hereinafter referred to as the finishing step) was performed to remove ammonium fluorosilicone and hydrazinium fluorosilicone from the chamber. The etched substrate was then cooled to approximately room temperature and removed from the chamber.

[0053] The etching depths of the silicon nitride film and silicon oxide film on the substrates etched as described above were evaluated. The results are shown in Table 1. In Table 1, the etching depth (nm) of the silicon nitride film is indicated as "SiN." The etching depth of the silicon oxide film is indicated as "SiO." Table 1 also shows the selectivity of the silicon oxide film during etching as a selectivity ratio. In this example, the selectivity of the silicon oxide film refers to the degree to which the silicon oxide film is selectively etched relative to the silicon nitride film in an environment in which both the silicon nitride film and the silicon oxide film may be etched. The selectivity ratio is an example of a measure for evaluating the selectivity of the silicon oxide film. In this example, it is the value obtained by dividing the etching depth (nm) of the silicon oxide film on the substrate being evaluated by the etching depth (nm) of the silicon nitride film. The higher the selectivity ratio, the more selectively the silicon oxide film is etched. Hereinafter, the more selectively the silicon oxide film is etched or such a property may be referred to as "good selectivity." In addition, the fact that silicon oxide films are not selectively etched or such a property may be referred to as "poor selectivity." For example, when the selectivity ratio is large, the etching of silicon oxide films is referred to as "good selectivity." When the selectivity ratio is small, the etching of silicon oxide films is referred to as "poor selectivity."

[0054] As shown in Table 1, in Examples 2 to 4 and Examples 7 to 9 in which the etching gas was obtained by heating the mixed gas at 400°C or higher and 600°C or lower, the selectivity exceeded 3, and the selectivity to the silicon oxide film was good.

[0055] When this mixed gas was heated to a temperature between 400°C and 600°C, it was found that the selectivity to silicon oxide films was better when hydrazine was used as the reducing gas than when ammonia was used.

[0056] In Examples 1 and 6, in which the mixed gas was heated at 300°C to obtain the etching gas, and in Examples 5 and 10, in which the mixed gas was heated at 700°C to obtain the etching gas, the selectivity fell below 3, resulting in poor selectivity to the silicon oxide film.

[0057] When the mixed gas was heated to 300°C, it was assumed that the mixed gas did not react sufficiently, and that ammonium fluoride or hydrazinium fluoride, which are capable of selectively etching silicon oxide films, were not sufficiently generated. This is thought to have resulted in a decrease in the amount of silicon nitride film and silicon oxide film etched. This is also thought to have resulted in a decrease in selectivity to silicon oxide films.

[0058] When the mixed gas was heated to 700°C, the nitrogen trifluoride in the mixed gas was thermally decomposed to produce a highly active fluoride with poor selectivity to silicon oxide films, which is thought to have increased the amount of etching of silicon nitride films and silicon oxide films and also worsened the selectivity to silicon oxide films.

[0059] In a verification experiment in which etching was performed under the same conditions as in Examples 4 and 9, but only the finishing process was omitted, ammonium fluorosilicic acid and hydrazinium fluorosilicic acid, which are products of etching a silicon oxide film with ammonium fluoride or hydrazinium fluoride, remained on the surface of the substrate. These residues were detected by FTIR analysis. From these analysis results, it is believed that when the mixed gas is heated to 400°C or higher and 600°C or lower, sufficient ammonium fluoride or hydrazinium fluoride, which can realize selective etching of a silicon oxide film, is generated, improving the etching selectivity of the silicon oxide film.

[0060] As shown in the above examples, the substrate processing method according to this embodiment can realize an efficient etching method with high selectivity for silicon oxide films without using highly corrosive and dangerous hydrogen fluoride. Since the substrate processing method according to this embodiment does not require the use of highly corrosive hydrogen fluoride, accidents such as gas leakage due to corrosion of metal piping and worker exposure accidents caused by gas leakage can be avoided. Furthermore, even if a gas leak occurs due to a natural disaster or other accident, highly dangerous hydrogen fluoride will not leak.

[0061] In the above example, the pressure in the etching chamber was confirmed to be only 133 Pa, but the same effects and trends as those illustrated in the above example can be obtained if the pressure in the etching chamber is reduced below atmospheric pressure (1 atmosphere).

[0062] As described above, the substrate processing method according to this embodiment can provide a substrate processing method for selectively etching a silicon oxide film without using hydrogen fluoride, and can be realized by the substrate processing apparatus exemplified in the above embodiment.

[0063] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0064] The present disclosure can be applied to a substrate processing method and a substrate processing apparatus. [Explanation of symbols]

[0065] 1: Reaction section 10: Reaction chamber 100: Substrate processing apparatus 2: Etching processing section 20: Processing room 3: Heating device 4:Heating mechanism 5: Pressure control mechanism 50: Pressure reducing pump 59: Pressure gauge 6: Heat exchanger 7: Blower 90: Source 91: Source 92: Source 90a: Pressure reducing valve 91a: Pressure reducing valve 92a: Pressure reducing valve

Claims

1. a reaction step of heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas; an etching step of bringing the etching gas into contact with a substrate having a silicon oxide film.

2. 2. The substrate processing method according to claim 1, wherein the mixed gas is heated to 400[deg.] C. or higher and 600[deg.] C. or lower in the reaction step.

3. 2. The substrate processing method according to claim 1, wherein the etching gas has a pressure of 133 Pa (abs) or more and 101,323 Pa (abs) or less in the etching step.

4. 3. The substrate processing method according to claim 2, wherein the etching gas has a pressure of 133 Pa (abs) or more and 101,323 Pa (abs) or less in the etching step.

5. The reducing gas is hydrogen (H ２ ), ammonia (NH ３ ), methylammonia (NH ２ CH ３ ), Diazene (N ２ H ２ ), hydrazine (N ２ H ４ ), methylhydrazine (N ２ H ３ CH ３ ), ethylhydrazine (N ２ H ３ C ２ H ６ ), dimethylhydrazine (N ２ H ３ C ３ H ７ ), butylhydrazine (N ２ H ３ C ４ H ９ ), hydrogen azide (N ３ H), cyclotriazane (N ３ H ３ ), triazene (N ３ H ３ ) and triazane (N ３ H ８ 5. The substrate processing method according to claim 1, further comprising at least one component selected from the group consisting of:

6. The reducing gas is ammonia (NH ３ ) and hydrazine (N ２ H ４ 5. The substrate processing method according to claim 1, further comprising at least one of the steps of:

7. a reaction section for heating a mixed gas of a reducing gas and nitrogen trifluoride to obtain an etching gas; an etching processing section for bringing the etching gas into contact with a substrate having a silicon oxide film.

8. the reaction section includes a reaction chamber to which the mixed gas is supplied and a heating device that heats the mixed gas in the reaction chamber; The substrate processing apparatus according to claim 7 , wherein the heating device heats the mixed gas in the reaction chamber to a temperature of 400° C. or higher and 600° C. or lower.

9. a pressure control mechanism for controlling the pressure of the etching gas in the etching processing unit; 8. The substrate processing apparatus according to claim 7, wherein the pressure control mechanism controls the pressure of the etching gas to 133 Pa (abs) or more and 101,323 Pa (abs) or less.

10. a pressure control mechanism for controlling the pressure of the etching gas in the etching processing unit; 9. The substrate processing apparatus according to claim 8, wherein the pressure control mechanism controls the pressure of the etching gas to 133 Pa (abs) or more and 101,323 Pa (abs) or less.

11. The reducing gas is hydrogen (H ２ ), ammonia (NH ３ ), methylammonia (NH ２ CH ３ ), Diazene (N ２ H ２ ), hydrazine (N ２ H ４ ), methylhydrazine (N ２ H ３ CH ３ ), ethylhydrazine (N ２ H ３ C ２ H ６ ), dimethylhydrazine (N ２ H ３ C ３ H ７ ), butylhydrazine (N ２ H ３ C ４ H ９ ), hydrogen azide (N ３ H), cyclotriazane (N ３ H ３ ), triazene (N ３ H ３ ) and triazane (N ３ H ８ 11. The substrate processing apparatus according to claim 7, further comprising at least one component selected from the group consisting of:

12. The reducing gas is ammonia (NH ３ ) and hydrazine (N ２ H ４ 11. The substrate processing apparatus according to claim 7, further comprising at least one of:

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