Vacuum treatment method

Abstract

A vacuum processing method is provided that can prevent foreign matter from adhering to a wafer due to titanium (Ti)-based reaction products. The vacuum processing method can be applied to a plasma processing apparatus comprising: a sample stage disposed within a processing chamber within a vacuum container and holding a wafer having a titanium (Ti) film; a coil supplied with high-frequency power for forming plasma within the processing chamber; and a heating device that radiates electromagnetic waves to heat the wafer placed on the upper surface of the sample stage. The vacuum processing method includes the steps of etching the titanium (Ti) film and cleaning the processing chamber using a mixture of nitrogen trifluoride (NF3) gas, argon gas, and chlorine gas.

Description

Technical Field

[0001] The present invention relates to a vacuum processing method. Background Art

[0002] In the manufacturing process of semiconductor devices, there is a need to cope with the miniaturization and integration of components included in semiconductor devices. For example, in integrated circuits and nano-electromechanical systems, the nanoscale of structures is being further advanced.

[0003] Photolithography is commonly used to form fine patterns in semiconductor device manufacturing. This technique creates a pattern for the device structure on a resist layer, then selectively etches away the substrate exposed by the resist pattern. By depositing other materials within the etched areas in subsequent processing steps, integrated circuits are formed.

[0004] As a conventional technique, Patent Document 1 discloses a processing apparatus that performs an atomic layer etching process using an adsorption / desorption method in order to perform isotropic etching with high precision in a dry process.

[0005] This conventional processing apparatus performs a radical-based reaction layer generation step and an infrared-heated reaction layer removal step on a wafer placed on a worktable within a processing chamber located within a vacuum vessel. The reaction layer generation step first involves supplying a process gas to a radical generation space in the upper portion of the processing chamber, activating the gas and generating free radicals. The generated free radical particles are then supplied to the upper surface of the wafer placed in the processing chamber via a gas inlet pipe connecting the space to the lower processing chamber, where a reaction layer is formed.

[0006] Furthermore, the reaction layer removal step is performed after the reaction layer generation step. Infrared light is irradiated from a lamp positioned above the wafer to vaporize the product on the wafer surface and remove the reaction layer. These steps are repeated alternately to remove the target film on the wafer surface.

[0007] The etching process described above presents the problem of reaction products being generated during various steps and deposited within the processing chamber. In particular, reaction products are often deposited on the chamber sidewalls, the worktable surface, and the susceptor ring located near the wafer.

[0008] The adhesion and deposition of reaction products can cause various problems with the etching performance of processing equipment. For example, as a barrier to wafers, reaction products can remain in the processing chamber during the etching process. These products, which adhere to or deposit in the processing chamber during the etching process, can then be scattered onto devices, becoming foreign matter and causing pattern defects. This can also lead to variations in device dimensions over time, potentially preventing the expected performance. Furthermore, as a barrier to processing equipment, reaction products can deposit on the worktable surface, causing performance degradation such as poor electrostatic adsorption.

[0009] To prevent these problems, it is necessary to remove the reaction products through regular cleaning. As a representative cleaning method, as described in Patent Document 2, the following method is widely known: a mixture of sulfur hexafluoride (SF6) and argon (Ar) gas is used to generate highly reactive halogen radicals, which react with the deposits, thereby vaporizing the reaction products and exhausting them outside the vacuum chamber for removal.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Publication No. 2017-143186

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-273082 Summary of the Invention

[0014] Problems to be solved by the invention

[0015] However, the above-mentioned conventional cleaning methods have the following problems.

[0016] When etching wafers containing titanium (Ti) films, titanium (Ti)-based reaction products are generated. As described above, these products tend to adhere to and deposit within the processing chamber within the vacuum vessel. However, conventional cleaning methods utilizing a mixture of sulfur hexafluoride (SF6) and argon (Ar) gases have high reactivity with silicon (Si)-based reaction products but low reactivity with titanium (Ti)-based reaction products. Consequently, while silicon (Si)-based reaction products are effectively removed, titanium (Ti)-based reaction products are not removed from the processing chamber and continue to adhere and deposit.

[0017] In particular, since the table surface and the susceptor ring are located near the wafer, titanium (Ti)-based reaction products generated during the processing steps are easily attached and deposited, and these products are scattered onto the wafer, causing a problem of frequent foreign matter.

[0018] An object of the present invention is to provide a vacuum processing method capable of preventing foreign matter caused by titanium (Ti)-based reaction products from adhering to a wafer.

[0019] Means for solving problems

[0020] In order to solve the above-mentioned problems, one of the representative vacuum processing methods involved in the present invention is achieved as follows: a vacuum processing method for etching a film containing titanium in a processing chamber, the vacuum processing method having the following steps: etching the film; using a mixed gas of nitrogen trifluoride, i.e., NF3 gas, argon, i.e., Ar gas, and chlorine, i.e., Cl2 gas to clean the processing chamber.

[0021] Effects of the Invention

[0022] According to the present invention, a vacuum processing method capable of preventing foreign matter caused by titanium (Ti)-based reaction products from adhering to a wafer can be provided.

[0023] Other problems, structures, and effects than those described above will become clear from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a longitudinal sectional view schematically showing the structure of a plasma processing apparatus according to an embodiment of the present invention.

[0025] Figure 2 is a comparative example. Figure 1 FIG. 1 is a flowchart showing the flow of a cleaning process sequence in the plasma processing apparatus shown.

[0026] Figure 3 Graph showing etching rate results obtained by combining various gases used in the cleaning process during grinding in this embodiment.

[0027] Figure 4 This is a graph showing etching rate results expressing the dependence of the added nitrogen (N2) gas on the flow ratio.

[0028] Figure 5 It means in Figure 1 Flowchart showing the flow of a cleaning process sequence according to the present embodiment performed in the plasma processing apparatus shown. DETAILED DESCRIPTION

[0029] Embodiments of the present invention will be described with reference to the accompanying drawings.

[0030] Figure 1 It is a longitudinal sectional view schematically showing a plasma processing apparatus 100 according to an embodiment of the present invention.

[0031] First reference Figure 1The structure of plasma processing apparatus 100 will be described below. The plasma processing apparatus 100 shown in this figure includes a vacuum chamber 101. An exhaust opening is provided at the bottom of the chamber to reduce the pressure in the vacuum chamber 101. A vacuum pump 1015 is connected from the opening through an exhaust pipe. A pressure regulating valve 1016 is provided in the path between the opening and the vacuum pump 1015. The exhaust flow rate or speed is adjusted by increasing or decreasing the flow cross-sectional area of the path or opening.

[0032] The vacuum vessel 101 generally consists of a discharge section 102 at its upper portion and a processing chamber 104 at its lower portion. The discharge section 102 and processing chamber 104 are cylindrical spaces, with their central axes coaxial or nearly coaxial. They are separated by a circular dispersion plate 106, also positioned so that their central axes coincide or nearly coincide. The discharge section 102 and processing chamber 104 are connected via a plurality of through-holes concentrically arranged in the dispersion plate 106.

[0033] A cylindrical quartz chamber 107 is provided in the discharge section 102, and an ICP coil 108 is provided outside the quartz chamber 107. The ICP coil 108 is connected to a high-frequency power supply 110 via a matching unit 109. The plasma processing apparatus 100 can generate plasma 1011 using an inductively coupled plasma (ICP) discharge method. The high-frequency power of the high-frequency power supply 110 has a frequency range of several tens of MHz, such as 13.56 MHz.

[0034] A top plate 1012 is installed above the discharge section 102. A gas distribution plate is installed below the top plate 1012, through which the processing gas is introduced into the vacuum chamber 101. A sealing member, such as an O-ring, is sandwiched between the top plate 1012 and the upper surface of the upper end of the discharge section sidewall. This ensures an airtight seal between the interior of the discharge section 102 and the exterior of the vacuum chamber 101.

[0035] The process gas supplied from the process gas source 1013 has its supply flow rate adjusted by a mass flow controller 1014, which is installed for each gas type. Combustible gas, combustion-supporting gas, a mixture thereof, or a mixture thereof diluted with an inert gas is used as the process gas. The process gas source 1013 and the mass flow controller 1014 constitute a gas supply device.

[0036] In the processing chamber 104 at the lower portion of the vacuum container 101 , a sample stage 103 for mounting a wafer 1017 is arranged at a position aligned with or approximately aligned with the central axis of the discharge portion 102 and the processing chamber 104 .

[0037] An IR lamp unit (heating device) 105 is provided between the sample stage 103 and the discharge section 102 to heat the wafer 1017. The IR lamp unit 105 mainly comprises an IR lamp 1018 that radiates IR light as electromagnetic waves, a reflector 1019 that reflects the IR light, and an IR light transmission window 1020.

[0038] The IR lamp 1018 is a ring-shaped (circular) lamp. The IR lamp 1018 emits light primarily in the visible to infrared range (herein referred to as IR light). The IR lamp 1018 is connected to a lamp power supply 1021, which supplies power. A high-frequency cutoff filter 1022 is placed between the two to prevent noise from the high-frequency power applied to the ICP coil from entering the lamp power supply.

[0039] Multiple (3 in the figure) IR lamps 1018 arranged on concentric circles are configured to independently adjust the amount of power supplied to their respective arc-shaped parts, thereby adjusting the radial distribution of the heating amount of the chip 1017.

[0040] A reflective plate 1019 is provided above the IR lamp 1018 to reflect the IR light outputted radially downward (in the direction in which the wafer is installed).

[0041] An IR light transmission window 1020 made of quartz for transmitting IR light is arranged extending from the bottom surface of the IR lamp unit 105 to the inner peripheral side wall surface.

[0042] The space inside the inner periphery of the IR lamp assembly 105 is a flow path through which the plasma 1011 formed in the discharge section 102 arranged above flows. A dielectric dispersion plate 106 is provided in the flow path to shield the ions and electrons generated in the plasma and to allow the neutral particles and free radicals of the gas to pass through.

[0043] In this embodiment, the dispersion plate 106 is also made of a transmissive member such as quartz, and IR light radiated from its outer periphery is not blocked by the dispersion plate 106 but passes therethrough, and most of the IR light reaches the interior of the processing chamber 104 .

[0044] Next, a comparative example of applying the cleaning method to a plasma processing device is used. Figure 2 The flow chart is shown.

[0045] The process begins at step 201, and in step 202, an etching process (film etching) is performed on a wafer containing a titanium (Ti) film. Subsequently, in step 203, sulfur hexafluoride (SF6) gas and argon (Ar) gas are supplied to the discharge section 102, and a discharge is performed. The free radicals generated by the dissociation are introduced into the processing chamber 104, where they react with silicon (Si)-based reaction products deposited within the processing chamber. Irradiation with IR light from an IR lamp 1018 heats and desorbs them, thereby performing a cleaning process. Subsequently, since the reaction products floating within the processing chamber are exhausted from the processing chamber 104, the exhaust pressure is adjusted up and down by a pressure regulating valve 1016 for purification.

[0046] However, in the cleaning method using a mixed gas obtained by diluting sulfur hexafluoride (SF 6 ) gas with argon (Ar) gas, the removal effect of titanium (Ti)-based reaction products is low.

[0047] In this regard, the inventors of the present invention thought that if the titanium (Ti)-based reaction products generated when processing titanium (Ti) film wafers are reacted with highly reactive free radicals to generate highly volatile reaction products in order to remove them, they should be able to be exhausted outside the vacuum container and removed.

[0048] Therefore, the inventors of the present invention conducted an experiment to confirm the etching rate using a titanium (Ti) film wafer, simulating the titanium (Ti)-based reaction products deposited in the processing chamber 104. In this experiment, a titanium (Ti)-based film wafer was tested as the titanium (Ti)-based film wafer. Since a high etching rate increases the reactivity with the titanium (Ti)-based reaction products, it is expected that the cleaning effect will be improved.

[0049] Next, show Figure 3 The experimental results for confirming the etching rate in each gas combination are shown.

[0050] For comparison, an etching rate confirmation experiment was performed by cleaning using a mixed gas obtained by diluting sulfur hexafluoride (SF 6 ) gas with argon (Ar) gas. As a result, an etching rate result 301 of 4.2 nm / min was obtained.

[0051] Next, an etching rate confirmation experiment of the gas used in the cleaning of this embodiment was conducted. Figure 1Experiments were conducted in a plasma processing apparatus under the following conditions: the chamber pressure was set to below 125 Pa using vacuum pump 1015 and pressure regulating valve 1016, and the RF power was set to 800 W. Furthermore, nitrogen trifluoride (NF3), which offers the highest rate among fluorine-based gases, was used instead of sulfur hexafluoride (SF6). Using NF3 facilitates reaction with titanium (Ti)-based reaction products with high coupling energy, generating highly volatile titanium tetrafluoride (TiF4), which can then be removed.

[0052] Furthermore, by adding chlorine (Cl2) gas, which is highly reactive with the metal film, titanium tetrachloride (TiCl4) is generated. Since titanium tetrachloride (TiCl4) has a higher vapor pressure than titanium tetrafluoride (TiF4), titanium (Ti)-based reaction products can be efficiently removed even in low-temperature areas.

[0053] As described above, cleaning experiments using a mixed gas of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, and argon (Ar) gas were conducted, and an etching rate of 11.4 nm / min was obtained as result 302. Compared with the experimental results using a mixed gas of sulfur hexafluoride (SF6) gas and argon (Ar) gas, it can be seen that the etching rate increased and the cleaning effect on titanium (Ti)-based reaction products was high.

[0054] Furthermore, the inventors conducted an etching rate verification experiment by adding nitrogen (N2) gas to the aforementioned mixture of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, and argon (Ar) gas. The addition of nitrogen (N2) gas can split the bonds of titanium nitride (TiN) into titanium (Ti) and nitrogen (N2), promoting the chlorination and fluorination of titanium (Ti).

[0055] In this manner, a confirmation experiment was conducted using a mixed gas of nitrogen trifluoride (NF3), chlorine (Cl2), argon (Ar), and nitrogen (N2) gas for cleaning, resulting in an etching rate of 72.6 nm / min, result 303. Adding nitrogen (N2) gas further increases the etching rate of titanium nitride (TiN).

[0056] Next, we conducted an experiment to confirm the etching rate dependence of nitrogen (N2) gas addition flow rate. Figure 4 As shown, even when the flow rate ratio of nitrogen (N2) gas to the mixed gas of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, and argon (Ar) gas is 0%, the etching rate is ensured.

[0057] Furthermore, as the flow rate ratio increases from 0%, the etching rate also increases, reaching its maximum at 14%. It was then found that the etching rate gradually decreases up to a flow rate of 30%. This demonstrates that while the addition of nitrogen (N2) gas improves the cleaning effect, excessive addition of nitrogen (N2) gas decreases the etching rate, potentially preventing efficient cleaning.

[0058] Therefore, it is preferred that the flow rate ratio of nitrogen (N2) gas to the mixed gas of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, argon (Ar) gas, and nitrogen (N2) gas be set to a range exceeding 0% and below 30%.

[0059] The cleaning of the titanium (Ti)-based reaction product obtained above is carried out as a vacuum treatment method. Figure 5 The flow chart shows, but omits Figure 2 Description of the common process of the processes shown. Among them, it is preferred to perform cyclic etching (including atomic layer etching (ALE)) in the etching process of the film. Alternatively, it can also be a conventional etching using plasma. According to this embodiment, after step 203 of the cleaning process, as step 501 of the cleaning process, a mixed gas of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, argon (Ar) gas and nitrogen (N2) gas, the effect of which has been confirmed by the above-mentioned experiment, is supplied to the discharge part 102, and discharge is performed, and the free radicals (or plasma) generated by the dissociation at this time are introduced into the processing chamber 104, react with the titanium (Ti)-based reaction products deposited in the processing chamber, and are detached by heating with an IR lamp 1018 to perform cleaning. Through this cleaning, the titanium (Ti)-based reaction products attached and deposited in the cavity can be removed efficiently.

[0060] Furthermore, although an inductively coupled plasma etching apparatus is used in this embodiment, the present invention is applicable to any plasma generation method. For example, the present invention can be applied to a helicon wave plasma etching apparatus, an ECR plasma etching apparatus utilizing microwaves, a capacitively coupled plasma etching apparatus, and the like.

[0061] Furthermore, titanium (Ti)-based reaction products attached and deposited in the cavity can also be efficiently removed during cleaning using plasma generated by a mixture of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas and argon (Ar) gas, or a mixture of nitrogen trifluoride (NF3) gas, chlorine (Cl2) gas, argon (Ar) gas and nitrogen (N2) gas.

[0062] The above-described embodiments have been described in detail to facilitate understanding of the present invention, but are not necessarily limited to having all of the described structures. Furthermore, a portion of the structure of a particular embodiment may be replaced with a structure of another embodiment, and a structure of another embodiment may be incorporated into a structure of a particular embodiment. Furthermore, a portion of the structure of each embodiment may be added to, deleted from, or replaced with a portion of the structure of another embodiment.

[0063] Description of Reference Signs

[0064] 100 plasma processing apparatus, 101 vacuum container, 102 discharge unit, 104 processing chamber, 105 IR lamp assembly, 106 dispersion plate, 107 quartz chamber, 108 ICP coil, 109 matching element, 110 high-frequency power supply, 1011 plasma, 1012 top plate, 1015 vacuum pump, 1016 pressure regulating valve, 1017 wafer, 1018 IR lamp, 1019 reflective plate, 1020 IR light transmitting plate, 1021 lamp power supply, 1022 high-frequency cutoff filter.

Claims

1. A vacuum processing method for etching a titanium-containing film formed on a sample placed on a sample stage within a processing chamber, the vacuum processing method comprising: an etching step of performing cyclic etching on the film; and A cleaning process, after the etching process, allows free radicals generated by using a mixed gas of nitrogen trifluoride (NF3 gas), argon (Ar gas), chlorine (Cl2 gas) and nitrogen (N2 gas) to react with the reaction product deposited in the processing chamber and containing the titanium, and the reacted reaction product is heated by IR light to be separated and the reaction product is cleaned at the same time.

2. A vacuum processing method for etching a titanium-containing film formed on a sample placed on a sample stage within a processing chamber, the vacuum processing method comprising: an etching step of etching the film using plasma; and A cleaning process, after the etching process, allows free radicals generated by using a mixed gas of nitrogen trifluoride (NF3 gas), argon (Ar gas), chlorine (Cl2 gas) and nitrogen (N2 gas) to react with the reaction product deposited in the processing chamber and containing the titanium, and the reacted reaction product is heated by IR light to be separated and the reaction product is cleaned at the same time.

3. The vacuum treatment method according to claim 1 or 2, characterized in that: The flow rate ratio of the nitrogen, ie, N 2 gas, to the flow rate of the mixed gas is set to 30% or less.

4. The vacuum treatment method according to claim 1 or 2, characterized in that: The vacuum treatment method further comprises the following steps: using a mixed gas of sulfur hexafluoride (SF6) gas and argon (Ar) gas to clean the treatment chamber, The process is performed between the etching process and the cleaning process.

5. The vacuum processing method according to claim 4, characterized in that: In the process, free radicals generated by using a mixed gas of sulfur hexafluoride, i.e., SF6 gas, and argon, i.e., Ar gas, react with a reaction product containing silicon deposited in the processing chamber, and the reacted reaction product is heated by IR light to be desorbed, while the reaction product containing silicon is cleaned.

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