Etching treatment method and etching treatment apparatus

Abstract

The present invention provides an etching treatment method and an etching treatment apparatus. The etching treatment method includes: a step of preparing a compound; and a step of etching an etching object on which a mask film is formed in the presence of the compound, the step of etching the etching object includes a process of etching the etching object in the presence of hydrogen H and fluorine F when the etching object contains silicon nitride SiN, the step of etching the etching object includes a process of etching the etching object in the presence of nitrogen N, hydrogen H and fluorine F when the etching object contains silicon Si, and the compound contains carbon C and at least one halogen selected from chlorine Cl, bromine Br and iodine I. The present invention can improve the shape of an etching hole and increase a mask selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to an etching processing method and an etching processing apparatus. BACKGROUND

[0002] A method of etching a hole having a high aspect in a semiconductor wafer in which a silicon oxide film and a silicon nitride film are laminated in a low temperature environment is known (see Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-207840 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present application provides a technology capable of improving the shape of an etched hole and increasing a mask selectivity.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] The etching processing method of one aspect of the present application includes a step of preparing a compound; and a step of etching an etching object on which a mask film is formed in the presence of the compound, when the etching object contains silicon nitride SiN, the step of etching the etching object includes a process of etching the etching object in the presence of hydrogen H and fluorine F; and when the etching object contains silicon Si, the step of etching the etching object includes a process of etching the etching object in the presence of nitrogen N, hydrogen H and fluorine F, the compound contains carbon C and at least one halogen selected from chlorine Cl, bromine Br and iodine I.

[0010] EFFECTS OF THE INVENTION

[0011] According to the present application, an effect of being capable of improving the shape of an etched hole and increasing a mask selectivity is exerted. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a longitudinal sectional view showing an example of an etching processing apparatus.

[0013] Figure 2 is a view showing an example of a control apparatus.

[0014] Figure 3 is a graph showing the analysis result of a gas having a mass number m / z of 15 with respect to a by-product attached to the surface of a wafer etched using the etching processing method of Comparative Example 1 by TDS.

[0015] Figure 4 is a graph showing the analysis result of the gas having the mass number m / z of 16 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0016] Figure 5 is a graph showing the analysis result of the gas having the mass number m / z of 17 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0017] Figure 6 is a graph showing the analysis result of the gas having the mass number m / z of 19 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0018] Figure 7 is a graph showing the analysis result of the gas having the mass number m / z of 20 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0019] Figure 8 is a graph showing the analysis result of the gas having the mass number m / z of 47 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0020] Figure 9 is a graph showing the analysis result of the gas having the mass number m / z of 85 with respect to the by-products attached on the wafer surface etched using the etching treatment method of Comparative Example 1 by TDS.

[0021] Figure 10 is a graph showing the comparative result of the wafers etched using the etching treatment methods of Comparative Example 2, Comparative Example 3, and Example 1.

[0022] Figure 11 is a graph showing the comparative result of the wafers etched using the etching treatment methods of Example 1 and Example 2.

[0023] Figure 12 is a graph showing an example of the relationship between the size of the etching hole and the etching rate.

[0024] BRIEF DESCRIPTION OF DRAWINGS

[0025] 1: chamber

[0026] 5: processing space

[0027] 8: stage

[0028] 10: etching treatment device

[0029] 11: support stage

[0030] 12 electrostatic chuck

[0031] 21 cooler

[0032] 27 wafer

[0033] 31 gas shower head

[0034] 37 processing gas supply source

[0035] 41 power supply device

[0036] 42 first high frequency power source

[0037] 44 second high frequency power source DETAILED DESCRIPTION

[0038] Hereinafter, an embodiment of an etching processing method and an etching processing apparatus according to the present application will be described in detail based on the drawings.

[0039] A reaction product generated when etching an etching object containing silicon nitride SiN can become a factor that hinders etching, and deteriorate the shape of an etching hole. In this regard, a case where the reaction product is decomposed by performing etching in an environment where chlorine gas Cl2 is present was studied. However, in an environment where chlorine gas is present, there is a problem that the etching rate of a mask film formed on the etching object increases and the mask selectivity decreases. Therefore, it is desirable to improve the shape of the etching hole and increase the mask selectivity.

[0040] [Overall structure of etching processing apparatus 10]

[0041] Figure 1 is a longitudinal sectional view showing an example of the etching processing apparatus 10. The etching processing apparatus 10 is a capacitively coupled plasma processing apparatus, and includes a chamber 1, an exhaust device 2, and a gate valve 3. The chamber 1 is made of aluminum, is formed in a cylindrical shape, and has a surface subjected to an alumite process. The chamber 1 is electrically grounded. A processing space 5 is formed in the inside of the chamber 1. The chamber 1 isolates the processing space 5 from an outside atmosphere. An exhaust port 6 and an opening portion 7 are also formed in the chamber 1. The exhaust port 6 is formed in the bottom surface of the chamber 1. The opening portion 7 is formed in the side wall of the chamber 1. The exhaust device 2 is connected to the processing space 5 of the chamber 1 via the exhaust port 6. The exhaust device 2 exhausts gas from the processing space 5 via the exhaust port 6. The gate valve 3 opens or closes the opening portion 7.

[0042] The etching processing apparatus 10 further includes a support table 8. The support table 8 is disposed in the processing space 5 and is provided at the bottom of the chamber 1. The support table 8 includes a support table 11 and an electrostatic chuck 12. The support table 11 is formed of a conductor such as aluminum Al, titanium Ti, silicon carbide SiC. The support table 11 is supported by the chamber 1. The inside of the support table 11 is formed with a refrigerant flow path 14. The electrostatic chuck 12 is disposed on the upper side of the support table 11 and is supported by the support table 11. The electrostatic chuck 12 includes an electrostatic chuck main body 15 and a chuck electrode 16. The electrostatic chuck main body 15 is formed of an insulator. The electrostatic chuck 12 is formed by embedding the chuck electrode 16 in the electrostatic chuck main body 15. The etching processing apparatus 10 further includes a direct current voltage source 17. The direct current voltage source 17 is electrically connected to the chuck electrode 16 and supplies a direct current to the chuck electrode 16.

[0043] The etching processing apparatus 10 further includes a cooler 21, a refrigerant inlet pipe 22, and a refrigerant outlet pipe 23. The cooler 21 is connected to the refrigerant flow path 14 via the refrigerant inlet pipe 22 and the refrigerant outlet pipe 23. The cooler 21 cools a cooling medium such as chilled water or brine, circulates the cooled cooling medium into the refrigerant flow path 14 via the refrigerant inlet pipe 22 and the refrigerant outlet pipe 23, and cools the electrostatic chuck 12 of the support table 8.

[0044] The etching processing apparatus 10 further includes a heat conductive gas supply source 25 and a heat conductive gas supply passage 26. The heat conductive gas supply passage 26 is formed so that one end thereof is formed on the upper surface of the electrostatic chuck 12. The heat conductive gas supply source 25 supplies a heat conductive gas such as helium He or argon Ar to the heat conductive gas supply passage 26 and supplies the heat conductive gas to the wafer 27 interposed between the support table 8 and the electrostatic chuck 12.

[0045] The etching processing apparatus 10 further includes a gas shower head 31 and a shield ring 32. The gas shower head 31 is formed in a circular plate shape by a conductor. The gas shower head 31 is disposed so as to face the support table 8 and is substantially parallel to the plane along the upper surface of the support table 8 along the plane of the lower surface of the gas shower head 31. The gas shower head 31 is also disposed so as to close the opening formed in the top of the chamber 1. The shield ring 32 is formed in a ring shape by an insulator. The shield ring 32 covers the peripheral edge portion of the gas shower head 31. The gas shower head 31 is supported to the chamber 1 with the gas shower head 31 insulated from the chamber 1 via the shield ring 32. The gas shower head 31 is electrically grounded. Further, the gas shower head 31 can also be connected to a variable direct current power source to apply a prescribed direct current voltage.

[0046] A central side diffusion chamber 33, an edge side diffusion chamber 34, a gas introduction port 35, and a plurality of gas supply holes 36 are formed in the gas shower head 31. The central side diffusion chamber 33 is formed in the center of the inside of the gas shower head 31. The edge side diffusion chamber 34 is formed in the edge side of the inside of the gas shower head 31, and is formed between the edge of the gas shower head 31 and the central side diffusion chamber 33. The gas introduction port 35 is formed in the upper side of the central side diffusion chamber 33 and the edge side diffusion chamber 34 in the gas shower head 31, and communicates with the central side diffusion chamber 33 and the edge side diffusion chamber 34, respectively. The plurality of gas supply holes 36 are formed in the lower side of the central side diffusion chamber 33 and the edge side diffusion chamber 34 in the gas shower head 31, and communicate with the central side diffusion chamber 33 and the edge side diffusion chamber 34, and communicate with the processing space 5.

[0047] The etching processing apparatus 10 further includes a processing gas supply source 37. The processing gas supply source 37 is connected to the gas introduction port 35. The processing gas supply source 37 supplies a prescribed processing gas to the gas introduction port 35. The processing gas contains a mixed gas in which carbon tetrafluoride CF4 and hydrogen H2 are mixed. A prescribed compound is further added to the processing gas. As the compound, chlorine Cl2, silicon tetrachloride SiCl4, hydrogen bromide HBr, and hydrogen iodide HI can be exemplified. Instead of carbon tetrafluoride CF4, sulfur hexafluoride SF6 and sulfur tetrafluoride SF4 can also be used.

[0048] The support table 11 of the stage 8 is used as a lower electrode, and the gas shower head 31 is used as an upper electrode. The etching processing apparatus 10 further includes a power supply apparatus 41. The power supply apparatus 41 includes a first high frequency power source 42, a first matcher 43, a second high frequency power source 44, and a second matcher 45. The first high frequency power source 42 is connected to the stage 8 via the first matcher 43. The first high frequency power source 42 supplies a first high frequency of a first frequency (for example, 40 MHz) to the support table 11 of the stage 8 at a prescribed power. The first matcher 43 matches a load impedance with an internal (or output) impedance of the first high frequency power source 42. The function of the first matcher 43 is to make the internal impedance of the first high frequency power source 42 and the load impedance appear to be consistent when plasma is generated in the processing space 5.

[0049] The second high frequency power source 44 is connected to the stage 8 via the second matcher 45. The second high frequency power source 44 supplies a second high frequency having a second frequency (for example, 0.3 MHz) lower than the first frequency to the stage 8 at a prescribed power. The second matcher 45 matches a load impedance with an internal (or output) impedance of the second high frequency power source 44. The function of the second matcher 45 is to make the internal impedance of the second high frequency power source 44 and the load impedance appear to be consistent when plasma is generated in the processing space 5. Further, in the present embodiment, the first high frequency and the second high frequency are applied to the stage 8, but can be applied to the gas shower head 31.

[0050] The etching processing apparatus 10 further includes a control device 51. Figure 2 Fig. is a diagram showing an example of the control device 51. The control device 51 is realized by a computer 90. The computer 90 includes a CPU (Central Processing Unit) 91, a RAM (Random Access Memory) 92, and a ROM (Read Only Memory) 93. The CPU 91 works based on a program installed in the computer 90, and controls each part of the computer 90 to control the etching processing apparatus 10. A boot program to be executed by the CPU 91 at the start of the computer 90 and a program dependent on the hardware of the computer 90 are stored in the ROM 93.

[0051] The computer 90 further includes an auxiliary storage device 94, a communication interface 95, an input-output interface 96, and a medium interface 97. The auxiliary storage device 94 stores a program to be executed by the CPU 91 and data used by the program. The auxiliary storage device 94 can exemplify an HDD (Hard Disk Drive) and an SSD (Solid State Drive). The CPU 91 reads the program from the auxiliary storage device 94 and loads it to the RAM 92, and executes the loaded program.

[0052] The communication interface 95 communicates with the etching processing apparatus 10 via a communication line exemplified by a LAN (Local Area Network). The communication interface 95 transmits information received from the etching processing apparatus 10 to the CPU 91 via the communication line, and transmits data generated by the CPU 91 to the etching processing apparatus 10 via the communication line.

[0053] The computer 90 further includes an input device exemplified by a keyboard and an output device exemplified by a display. The CPU 91 controls the input device and the output device by means of the input-output interface 96. The input-output interface 96 transmits a signal input through the input device to the CPU 91, and outputs data generated by the CPU 91 to the output device.

[0054] The medium interface 97 reads a program or data stored in a non-transitory tangible storage medium 98. As the storage medium 98, an optical storage medium, a magneto-optical storage medium, a magnetic tape medium, a magnetic storage medium, or a semiconductor memory can be exemplified. As the optical storage medium, a DVD (Digital versatile disc), a PD (Phase change rewritable Disk) can be exemplified. As the magneto-optical storage medium, an MO (Magneto-Optical disk) can be exemplified.

[0055] The CPU 91 executes a program read from the storage medium 98 via the medium interface 97, but as another example, the CPU 91 can also execute a program acquired from another device via the communication interface 95.

[0056] [Etching processing method]

[0057] The etching processing method is implemented using the etching processing apparatus 10. In the etching processing method, first, the control device 51 opens the opening portion 7 by controlling the gate valve 3. The wafer 27 as a processed object is fed into the processing space 5 of the chamber 1 via the opening portion 7 when the opening portion 7 is opened, and is placed on the placement table 8. After the wafer 27 is placed on the placement table 8, the control device 51 applies a direct current voltage to the chuck electrode 16 by controlling the direct current voltage source 17. When the direct current voltage is applied to the chuck electrode 16, the wafer 27 is held on the electrostatic chuck 12 due to a Coulomb force. The control device 51 also closes the opening portion 7 by controlling the gate valve 3. When the opening portion 7 is closed, the control device 51 evacuates the gas from the processing space 5 by controlling the exhaust device 2 so that the atmosphere of the processing space 5 becomes a prescribed vacuum degree.

[0058] In a state where the wafer 27 is held on the electrostatic chuck 12, the control device 51 supplies the thermally conductive gas to the thermally conductive gas supply passage 26 by controlling the thermally conductive gas supply source 25, and supplies the thermally conductive gas to between the electrostatic chuck 12 and the wafer 27. The control device 51 also cools the electrostatic chuck 12 by controlling the cooler 21 so that the refrigerant cooled to a prescribed temperature circulates in the refrigerant flow path 14. At this time, the wafer 27 is temperature-adjusted so that the temperature of the wafer 27 is included in a prescribed temperature range by thermally conducting from the electrostatic chuck 12 to the wafer 27 with the thermally conductive gas supplied to between the electrostatic chuck 12 and the wafer 27.

[0059] When the temperature of the wafer 27 is adjusted to a prescribed temperature, the control device 51 supplies the processing gas having a prescribed composition to the gas introduction port 46 by controlling the processing gas supply source 37. The processing gas is supplied to the central side diffusion chamber 33 and the edge side diffusion chamber 34 after being supplied to the gas introduction port 46, and is diffused in the central side diffusion chamber 33 and the edge side diffusion chamber 34. The processing gas is supplied to the processing space 5 of the chamber 1 in a shower shape via the plurality of gas supply holes 36 after being diffused in the central side diffusion chamber 33 and the edge side diffusion chamber 34, and is filled in the processing space 5.

[0060] The control device 51 controls the first high-frequency power supply 42 and the second high-frequency power supply 44 to supply the first high frequency for plasma excitation and the second high frequency for bias to the stage 8. By supplying the first high frequency to the stage 8, plasma is generated in the processing space 5, and radicals, ions, light, electrons, and the like are produced. By supplying the second high frequency to the stage 8, ions in the plasma are accelerated toward the wafer 27. The wafer 27 is etched by radicals and ions contained in the plasma generated in the processing space 5.

[0061] After the wafer 27 is etched, the control device 51 controls the first high-frequency power supply 42 and the second high-frequency power supply 44 to stop supplying high-frequency power to the processing space 5. The control device 51 also controls the direct-current voltage source 17 to apply a direct-current voltage opposite in polarity to that applied when the wafer 27 is attracted to the chuck electrode 16. By applying the reverse direct-current voltage to the chuck electrode 16, the wafer 27 is discharged and peeled from the electrostatic chuck 12. The control device 51 also controls the gate valve 3 to open the opening portion 7. When the opening portion 7 is opened, the wafer 27 is carried out from the processing space 5 of the chamber 1 via the opening portion 7 without being held by the electrostatic chuck 12.

[0062] It is known that by using a fluorocarbon gas for plasma etching of an etching target containing silicon nitride SiN, a modified layer can be formed on the surface of the etching target. It is known that by heating the etching target to about 200°C, the modified layer can be decomposed or sublimated.

[0063] In the etching processing method described above, the wafer 27 is etched in an atmosphere containing hydrogen H and fluorine F. In the etching processing method described above, it is presumed that when the wafer 27 contains silicon dioxide SiO2, a chemical reaction represented by the following chemical reaction formula is performed.

[0064] Si(OH)4+ HF → SiF(OH)3+ H2O - 0.40 eV

[0065] SiF(OH)3+ HF → SiF2(OH)2+ H2O - 0.78 eV

[0066] SiF2(OH)2+ HF → SiF3(OH) + H2O - 1.11 eV

[0067] SiF3(OH) + HF → SiF4+ H2O - 1.38 eV

[0068] By this chemical reaction, silicon tetrafluoride SiF4 is generated when the wafer 27 is etched in an atmosphere in which hydrogen H and fluorine F are present. Silicon tetrafluoride SiF4 has high volatility. Therefore, in a case where the wafer 27 is formed only of silicon dioxide SiO2, silicon tetrafluoride SiF4 is difficult to adhere to the surface of the wafer 27 when the wafer 27 is etched with hydrogen fluoride HF.

[0069] In the etching treatment method described above, in a case where it is presumed that the wafer 27 contains silicon nitride SiN, a chemical reaction represented by the following chemical reaction formula is performed.

[0070] Si(NH2)4 + HF → SiF(NH2)3 + NH3 - 1.08 eV

[0071] SiF(NH2)3 + HF → SiF2(NH2)2 + NH3 - 2.03 eV

[0072] SiF2(NH2)2 + HF → SiF3(NH2) + NH3 - 2.77 eV

[0073] SiF3(NH2) + HF → SiF4 + NH3 - 3.04 eV

[0074] SiF4 + HF + NH3 → (NH4)SiF5 - 3.90 eV

[0075] (NH4)SiF5 + HF + NH3 → (NH4)2SiF6 - 4.80 eV

[0076] As for this chemical reaction, as in a case where silicon dioxide SiO2 is etched in an atmosphere in which hydrogen H and fluorine F are present, silicon tetrafluoride SiF4 is generated. By this chemical reaction, ammonia NH3 is also generated when the wafer 27 is etched in an atmosphere in which hydrogen H and fluorine F are present. By this chemical reaction, it is presumed that ammonium silicon fluoride salt (NH4)2SiF6 (hereinafter referred to as "salt AFS") is also generated from silicon tetrafluoride SiF4 and ammonia NH3.

[0077] Figure 3 is a graph of analysis results of a gas with respect to mass number m / z of 15 of a by-product adhered to the surface of the wafer 27 etched using the etching treatment method of Comparative Example 1 by TDS (Thermal Desorption Spectroscopy). In the etching treatment method of Comparative Example 1, the wafer 27 contains silicon nitride SiN, and the wafer 27 is etched under the following treatment conditions. TDS analysis was performed three times in total for one untreated wafer and two treated wafers.

[0078] Pressure of the treatment space 5: 80 mTorr

[0079] The first high frequency: 100MHz

[0080] The power of the first high frequency: 2500W (effective)

[0081] The second highest frequency: 400kHz

[0082] The power of the second high frequency: 1000W

[0083] Composition of the treated gas: SF6 / H2

[0084] Wafer temperature: -60℃

[0085] Figure 3 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 15 is generated from the surface of the wafer 27. This gas with a mass number m / z of 15 is presumed to be NH₃. + .therefore, Figure 3 The graph shows that it can be inferred that the byproducts attached to the surface of wafer 27 by the etching process of Comparative Example 1 are NH4+-containing compounds. + Compounds.

[0086] Figure 4 This is a graph showing the results of TDS analysis of byproducts adhering to the surface of wafer 27 etched using the etching process of Comparative Example 1 with respect to a gas with a mass number m / z of 16. Figure 4 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 16 is generated from the surface of the wafer 27. This gas with a mass number m / z of 16 is presumed to be NH2. + .therefore, Figure 4 The graph shows that it can be inferred that the byproducts attached to the surface of wafer 27 by the etching process of Comparative Example 1 are NH2-containing. + Compounds.

[0087] Figure 5 This is a graph showing the results of TDS analysis of byproducts adhering to the surface of wafer 27 etched using the etching process of Comparative Example 1 with respect to a gas with a mass number m / z of 17. Figure 5 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 17 is generated from the surface of the wafer 27. This gas with a mass number m / z of 17 is presumed to be NH3. + .therefore, Figure 5The graph shows that it can be inferred that the byproducts attached to the surface of wafer 27 by the etching process of Comparative Example 1 are NH3-containing. + The compound. Furthermore, a peak near 400°C was also observed in the untreated wafer, suggesting that this peak was caused by the substrate.

[0088] Figure 6 This is a graph showing the results of TDS analysis of byproducts attached to the surface of wafer 27 etched using the etching process of Comparative Example 1 with respect to a gas with a mass number m / z of 19. Figure 6 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 19 is generated from the surface of the wafer 27. This gas with a mass number m / z of 19 is presumed to be F. + .therefore, Figure 6 The graph shows that it can be inferred that the byproducts attached to the surface of wafer 27 by the etching process of Comparative Example 1 are containing F. + Compounds.

[0089] Figure 7 This is a graph showing the results of TDS analysis of byproducts adhering to the surface of wafer 27 etched using the etching process of Comparative Example 1 with respect to a gas with a mass number m / z of 20. Figure 7 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 20 is generated from the surface of the wafer 27. This gas with a mass number m / z of 20 is presumed to be HF. + .therefore, Figure 7 The graph shows that it can be inferred that the byproducts adhering to the surface of wafer 27 by the etching process of Comparative Example 1 are HF-containing. + Compounds.

[0090] Figure 8 This is a graph showing the results of TDS analysis of byproducts attached to the surface of wafer 27 etched using the etching process of Comparative Example 1 with respect to a gas with a mass number m / z of 47. Figure 8 The graph shows that when the wafer 27 etched using the etching method of Comparative Example 1 is heated to 200°C, a gas with a mass number m / z of 47 is generated from the surface of the wafer 27. This gas with a mass number m / z of 47 is presumed to be SiF. + .therefore, Figure 8 The graph shows that it can be inferred that the byproducts attached to the surface of wafer 27 by the etching process of Comparative Example 1 are SiF-containing byproducts. + Compounds.

[0091] Figure 9 is a graph showing the results of analysis of a gas having a mass number m / z of 85, which is a by-product adhered to the surface of the wafer 27 etched by the etching treatment method of Comparative Example 1, by TDS. Figure 9 The graph of Comparative Example 1 indicates that when the wafer 27 etched by the etching treatment method of Comparative Example 1 is heated to the extent of 2000C, a gas having a mass number m / z of 85 is generated from the surface of the wafer 27. As the gas having a mass number m / z of 85, SiF3 + is presumed. Figure 9 The graph of Comparative Example 1 indicates that it can be presumed that the by-product adhered to the surface of the wafer 27 by the etching treatment method of Comparative Example 1 is a compound containing SiF3 + .

[0092] Figures 3 to 9 The graph of Comparative Example 1 indicates that it can be presumed that the by-product adhered to the surface of the wafer 27 by the etching treatment method of Comparative Example 1 is a compound containing NH + , NH2 + , NH3 + , F + , HF + , SiF + , SiF3 + . That is, Figures 3 to 9 The graph of Comparative Example 1 indicates that the by-product generated by the etching treatment method of Comparative Example 1 is a salt AFS.

[0093] Figure 10 is a graph showing the results of comparison of wafers 101 to 103 etched by the etching treatment methods of Comparative Example 2, Comparative Example 3, and Example 1. The wafer 101 etched by the etching treatment method of Comparative Example 2 includes a silicon substrate, a silicon nitride film, and a mask film. The silicon nitride film is formed of silicon nitride SiN. The silicon nitride film is formed on one surface of the silicon substrate. The mask film is, for example, an organic film formed with openings of a prescribed pattern. The mask film is formed on the silicon nitride film in such a manner that the silicon nitride film is interposed between the silicon substrate and the mask film. In the etching treatment method of Comparative Example 2, the wafer 101 was etched under the following treatment conditions.

[0094] Pressure of the treatment space 5: 25 mTorr

[0095] Frequency of the first high frequency: 40 MHz

[0096] Power of the first high frequency: 4.5 kW

[0097] Frequency of the second high frequency: 0.4 MHz

[0098] Power of the second high frequency: 7 kW

[0099] Composition of the treatment gas: CF4 / H2

[0100] Temperature of wafer: -60°C

[0101] The wafer 102 etched using the etching processing method of Comparative Example 3 was formed in the same manner as the wafer 101. In the etching processing method of Comparative Example 3, the wafer 102 was etched under the following processing conditions. That is, in the etching processing method of Comparative Example 3, chlorine Cl2 was added to the processing gas, and the other conditions were the same as those of the etching processing method of Comparative Example 2.

[0102] Pressure of processing space 5: 25 mTorr

[0103] Frequency of first high frequency: 40 MHz

[0104] Power of first high frequency: 4.5 kW

[0105] Frequency of second high frequency: 0.4 MHz

[0106] Power of second high frequency: 7 kW

[0107] Composition of processing gas: CF4 / H2 / Cl2 (+20 seem)

[0108] Temperature of wafer: -60°C

[0109] The wafer 103 etched using the etching processing method of Example 1 was formed in the same manner as the wafer 101. In the etching processing method of Example 1, the wafer 103 was etched under the following processing conditions. That is, in the etching processing method of Example 1, chloroform CHCl3 was added to the processing gas, and the other conditions were the same as those of the etching processing method of Comparative Example 2.

[0110] Pressure of processing space 5: 25 mTorr

[0111] Frequency of first high frequency: 40 MHz

[0112] Power of first high frequency: 4.5 kW

[0113] Frequency of second high frequency: 0.4 MHz

[0114] Power of second high frequency: 7 kW

[0115] Composition of processing gas: CF4 / H2 / CHCl3 (+20 seem)

[0116] Temperature of wafer: -60°C.

[0117] Figure 10 Cross sections of the wafer 101, the wafer 102, and the wafer 103 are shown from the left side. Figure 10Also, the etching rate (E / R), the mask selectivity, and the bottom CD of the etching hole are described for each of the wafers 101 to 103. Figure 10 The comparison result of the bottom CD of the etching hole 105 formed in the wafer 102 is larger than that of the etching hole 104 formed in the wafer 101. Also, the comparison result of the bottom CD of the etching hole 106 formed in the wafer 103 is larger than that of the etching hole 104 formed in the wafer 101. When the size of the opening portion of the etching hole is constant, the larger the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a rectangular shape, and the smaller the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a wedge shape with a thin tip. That is, Figure 10 The comparison result of the bottom CD of the etching hole 105 formed in the wafer 102 is larger than that of the etching hole 104 formed in the wafer 101. Also, the comparison result of the bottom CD of the etching hole 106 formed in the wafer 103 is larger than that of the etching hole 104 formed in the wafer 101. When the size of the opening portion of the etching hole is constant, the larger the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a rectangular shape, and the smaller the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a wedge shape with a thin tip. That is, Figure 10 The comparison result of the bottom CD of the etching hole 105 formed in the wafer 102 is larger than that of the etching hole 104 formed in the wafer 101. Also, the comparison result of the bottom CD of the etching hole 106 formed in the wafer 103 is larger than that of the etching hole 104 formed in the wafer 101. When the size of the opening portion of the etching hole is constant, the larger the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a rectangular shape, and the smaller the bottom CD of the etching hole is, the closer the cross-sectional shape of the etching hole is to a wedge shape with a thin tip. That is,

[0118] It is presumed that, in the case where the chlorine gas Cl2 is injected, the salt AFS performs a chemical reaction represented by the following chemical reaction formula, is decomposed, and is sublimed.

[0119] (NH4)2SiF6 [-2688 kJ / mol] + Cl2 [0 kJ / mol] + 760 kJ / mol (7.8 eV)

[0120] → NH4Cl [-314 kJ / mol] + SiF4↑ [-1614 kJ / mol]

[0121] → NH3↑ [-46 kJ / mol] + HCl↑ [-92 kJ / mol] + SiF4↑ [-1614 kJ / mol] + SiCl4↑ [-657 kJ / mol]

[0122] That is, it is presumed that the etching processing method of the above-described Comparative Example 3 can reduce the amount of the by-product attached to the wafer surface by decomposing the salt AFS generated by etching using the chlorine gas Cl2. Therefore, it is presumed that the etching processing method of the above-described Example 1 can reduce the amount of the by-product attached to the wafer surface by decomposing the salt AFS generated by etching using the chloroform CHCl3.

[0123] Figure 10 The comparison result of the mask selectivity of the wafer 102 is smaller than that of the wafer 101. That is, Figure 10The comparative results show that the etching treatment method of Comparative Example 3 has a larger consumption amount of the mask film than the etching treatment method of Comparative Example 2. In contrast, Figure 10 The comparative results also show that the mask selectivity ratio of wafer 103 is larger than the mask selectivity ratios of wafer 101 and wafer 102. That is, Figure 10 The comparative results show that the etching treatment method of Example 1 can further improve the mask selectivity ratio compared to the etching treatment methods of Comparative Example 2 and Comparative Example 3. It can be inferred from this that the etching treatment method of Example 1 can protect the mask film by depositing carbon C contained in chloroform CHCl3 as a deposit on the mask film, and as a result, can also suppress the consumption amount of the mask film.

[0124] Therefore, the etching treatment method of the present embodiment includes a step of preparing chloroform CHCl3, and a step of etching a wafer 27 on which a mask film is formed in an atmosphere in which the chloroform CHCl3 is present. Even in a case where the wafer 27 is etched at a temperature lower than a temperature at which salt AFS is decomposed or sublimated (for example, 200°C), this etching treatment method can decompose salt AFS adhering to the wafer 27, and reduce the amount of salt AFS adhering to the wafer 27. The etching treatment method can improve the shape of an etching hole by reducing the amount of salt AFS adhering to the wafer 27. In addition, the etching treatment method can improve the mask selectivity ratio by depositing carbon C contained in chloroform CHCl3 as a deposit on the mask film.

[0125] In addition, the composition produced by the decomposition of salt AFS needs to be removed by being volatilized, and cannot be left in place. That is, it is desirable that the temperature of the wafer be higher than the temperature at which a reaction product containing silicon included in the composition produced by the decomposition of salt AFS, which is represented by a halogenated silicon such as SiF4or SiCl4having a relatively low vapor pressure, is volatilized. It is particularly desirable that the temperature of the wafer surface on which a chemical reaction occurs in the decomposition of salt AFS be high. Higher than the temperature at which the reaction product is volatilized means higher than the temperature indicated by the vapor pressure curve of the reaction product. When the reaction product contains a plurality of substances, one having a higher temperature is selected.

[0126] The temperature of the wafer is adjusted by transferring heat from the electrostatic chuck 12, which is cooled by circulating a coolant cooled to a prescribed temperature, to the wafer via a heat-conducting gas. Here, the wafer is exposed to plasma generated by the first high-frequency power source 42 for plasma excitation, and ions accelerated by the second high-frequency power source 44 for bias are irradiated to the wafer from the plasma, so the temperature of the wafer, particularly the surface of the wafer facing the plasma, is sometimes higher than the adjusted temperature. Therefore, if the actual wafer temperature during the etching process can be measured, or if the temperature difference between the adjusted temperature of the wafer and the actual wafer surface temperature can be estimated from the processing conditions, the set temperature for adjusting the temperature of the wafer can also be lowered in a range in which the wafer surface temperature becomes higher than the temperature indicated by the vapor pressure curve of the reaction product.

[0127] In addition, in the etching process method of the embodiment, the wafer 27 is disposed between the support table 11 of the mounting table 8 and the gas shower head 31. At this time, the first high frequency for generating plasma in the processing space 5 and the second high frequency for accelerating the plasma for bias are applied to the support table 11 of the mounting table 8 and the gas shower head 31. This etching process method can form a high aspect ratio etching hole in the wafer by etching the wafer with such plasma, and can appropriately etch the wafer 27.

[0128] Further, in the etching process method of the embodiment, the surface temperature of the wafer 27 is higher than the temperature indicated by the vapor pressure curve of the silicon-containing reaction product, and is included in a range of 100°C or lower. Even if a device that is destructible at high temperature is formed on the wafer 27, this etching process method can remove the salt AFS adhering to the wafer 27 from the wafer 27, and can appropriately etch the wafer 27.

[0129] Further, in the etching process method of the above-described embodiment 1, the wafer 27 is etched when the temperature of the wafer 27 is 100°C or lower, but the wafer 27 can also be etched when the temperature of the wafer 27 is 100°C or higher. In this case, the etching process method can also remove the salt AFS adhering to the wafer 27 from the wafer 27, and can appropriately etch the wafer 27.

[0130] In the etching treatment method of the above-described embodiment 1, the wafer including the silicon nitride SiN is etched, but a wafer including a multilayer film in which a multilayer of a silicon oxide film and a silicon nitride film is stacked can also be etched as an etching target. A wafer including the silicon dioxide SiO2 or a wafer including the silicon nitride SiN and the silicon dioxide SiO2 can also be etched as an etching target. In the case of etching such an etching target, the etching treatment method of the embodiment can also reduce the amount of the salt AFS attached to the etching target, and can improve the shape of the etching hole. Furthermore, in the etching method of the embodiment, even in the case of etching such an etching target, the mask selectivity can be improved by depositing carbon C contained in the chloroform CHCl3 as a deposit on the mask film.

[0131] In the etching treatment method of the above-described embodiment 1, the chloroform CHCl3 is added to the processing gas, but other compounds containing carbon C and chlorine Cl, or other compounds containing other halogens different from carbon C and chlorine Cl can also be added. As the other halogens, bromine Br and iodine I can be exemplified. As the other compounds, halogenated hydrocarbons, carbonyl halides, and halogenated benzene can be exemplified. As the halogenated hydrocarbons, dichloromethane CH2Cl2, chloromethane CH3Cl, carbon tetrachloride CCl4, bromoform CHBr3, iodoform CHI3, monofluorotrichloromethane CFCI3, and chloroethylene C2H3Cl can be exemplified. As the carbonyl halides, phosgene COCl2 and acetyl chloride C2H3ClO can be exemplified. As the halogenated benzene, chlorobenzene C6H5Cl and dichlorobenzene C6H4Cl2 can be exemplified.

[0132] Figure 10 The comparison result of the etching rates of the wafers 103 and 102 also indicates that the etching rate of the wafer 103 is greater than the etching rate of the wafer 102. That is, the etching rate of the wafer 103 is greater than the etching rate of the wafer 102. Figure 10 The comparison result of the etching rates of the wafers 103 and 102 also indicates that the etching rate of the wafer 103 is greater than the etching rate of the wafer 102. That is, the etching rate of the wafer 103 is greater than the etching rate of the wafer 102.

[0133] In addition, in the etching treatment method of the above-described embodiment 1, the flow rate of the chloroform CHCl3 added to the processing gas is fixed to 20 seem, but the proportion of the flow rate of the chloroform CHCl3 to the total flow rate of the processing gas can also be changed.

[0134] Figure 11is a graph showing the results of a comparison of wafers 103, 104 etched using the etching processing method of Example 1 and the etching processing method of Example 2. The processing conditions of the etching processing method of Example 2 are such that the composition of the processing gas among the processing conditions of the etching processing method of Example 1 is replaced with CF4 / H2 / CHCl3 (+ 30 seem), and the other conditions are the same as the processing conditions of the etching processing method of Example 1.

[0135] Figure 11 Cross sections of the wafer 103 etched using the etching processing method of Example 1 and the wafer 104 etched using the etching processing method of Example 2 are shown from the left side. Furthermore, Figure 11 The etching rate (E / R), the mask selectivity, and the bottom surface size (Bottom CD) of the etching hole of each of the wafers 103, 104 are also described. Figure 11 The results of the comparison of show that the bottom surface size of the etching hole 107 formed in the wafer 104 is larger than the size of the etching hole 106 formed in the wafer 103. That is, Figure 11 The results of the comparison of show that the more the chloroform CHCl3 added to the processing gas in the etching processing method of the embodiment, the larger the etching hole whose bottom surface size can be formed, and the shape of the etching hole can be further improved.

[0136] Figure 11 The results of the comparison of show that the etching rate of the wafer 104 is smaller than the etching rate of the wafer 103. That is, Figure 11 The results of the comparison of show that the more the chloroform CHCl3 added to the processing gas, the lower the etching rate of the wafer. It is thus known that there is a tradeoff relationship between the size of the etching hole formed in the wafer and the etching rate of the wafer.

[0137] Figure 12 is a graph showing an example of the relationship between the size of the etching hole and the etching rate. Figure 12 The results obtained by etching a wafer while changing the flow rate of the gas added to the processing gas, and then measuring the size of the etching hole and the etching rate are shown. The gas added to the processing gas is either chlorine Cl2 or chloroform CHCl3. Figure 12 In, the flow rate of the chloroform CHCl3 added is expressed as a ratio to the total flow rate of the processing gas. Figure 12It is shown that the etching rate is less reduced with respect to the increase in the size of the etching hole than in the case where the processing gas to which chlorine Cl2 is added is used. However, when the flow rate of the added chloroform CHCl3 exceeds 15%, the etching rate is increased and reduced with respect to the increase in the size of the etching hole to the same extent as in the case where the processing gas to which chlorine Cl2 is added is used. Accordingly, the flow rate of the chloroform CHCl3 added to the processing gas with respect to the total flow rate of the processing gas is preferably in the range of 15% or less, and more preferably in the range of 7% or less.

[0138] In the etching processing method described above, the etching target containing silicon Si and nitrogen N such as a silicon nitride film is etched, but an etching target containing silicon Si and not containing nitrogen N can also be etched. As such an etching target, a silicon oxide film, silicon carbide, a silicon-containing low dielectric constant film, a single-crystal silicon film, a polycrystal silicon film, an amorphous silicon film, and the like can be exemplified. At this time, the processing gas is also mixed with a compound containing nitrogen N. As the compound, ammonia NH3 and nitrogen trifluoride NF3 can be exemplified. In this case, as a by-product of etching, salt AFS is also generated. Therefore, this etching processing method can be able to reduce the amount of the by-product attached to the surface of the etching target by decomposing the salt AFS, and can appropriately etch the etching target.

[0139] In addition, in the etching processing method described above, the wafer 27 is etched using a capacitively coupled plasma (CCP), but other plasma can also be used. As the plasma, an inductively coupled plasma (ICP), a plasma using a radial line slot antenna, and the like can be exemplified. As the plasma, an electron cyclotron resonance plasma (ECR), a helicon wave plasma (HWP), and the like can also be exemplified.

[0140] In addition, in the etching processing method of the above-described embodiment, plasma is used, but a liquid can also be used. In this case, the etching processing method can also reduce the amount of the salt AFS attached to the surface of the etching target, and can appropriately etch the etching target.

[0141] The embodiments disclosed this time can be applied to not only the embodiments described above but also various other embodiments and applications without departing from the spirit and scope of the claims. Therefore, the descriptions in the embodiments are not intended to limit the applications in any way.

Claims

1. An etching process, characterized in that, include: Steps for preparing compounds; and The step of etching an object to which a mask film is formed in an environment in which the compound is present. When the object to be etched contains silicon nitride (SiN), the etching process includes etching the object in an environment containing hydrogen (H) and fluorine (F). When the object to be etched contains silicon (Si), the step of etching the object includes etching the object in an environment containing nitrogen (N), hydrogen (H), and fluorine (F). The temperature of the object being etched is higher than the volatilization temperature of the silicon-containing reaction products generated by etching the object. The compound is chloroform (CHCl3). The flow rate of the chloroform (CHCl3) is less than 15% of the total flow rate of the process gas containing the compound.

2. The etching method as described in claim 1, characterized in that: The etched object is positioned between a pair of electrodes. A high-frequency generator for generating plasma in a processing space filled with a processing gas containing the compound is applied to the pair of electrodes; and a high-frequency bias generator for accelerating the plasma. The object to be etched is etched by the plasma.

3. The etching process method as described in claim 1, characterized in that: The temperature of the etched object is within the range of below 100°C.

4. The etching process method as described in claim 3, characterized in that: The reaction product is silicon halide.

5. The etching process method as described in claim 1, characterized in that: The etched objects comprise silicon nitride (SiN) and silicon dioxide (SiO2).

6. The etching process method as described in claim 5, characterized in that: The etched object is formed by stacking a multilayer silicon nitride layer containing silicon nitride (SiN) and a multilayer silicon oxide film layer containing silicon dioxide (SiO2).

7. The etching method as described in claim 1, characterized in that: The evaporation temperature of the reaction product is the temperature shown by the vapor pressure curve of the reaction product.

8. The etching process method as described in claim 1, characterized in that: The flow rate of the chloroform (CHCl3) is less than 7% of the total flow rate of the processed gas.

9. An etching processing apparatus, characterized in that, include: A chamber is formed to create a processing space capable of etching the object being etched; A gas supply source that supplies processing gases containing compounds to the processing space; and Control device, The control device is capable of controlling the etching process apparatus to perform the etching process method according to any one of claims 1 to 8.

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