Substrate processing method and substrate processing system

Abstract

This substrate processing method comprises: a step for preparing a substrate in which a metal layer is formed on a base layer; a first step for forming, on the metal layer, a mixing inhibition layer for inhibiting mixing between the base layer and the metal layer; and a second step for annealing, at a temperature of at least 950°C, the substrate in which the mixing inhibition layer is formed on the metal layer.

Description

Substrate processing method and substrate processing system

[0001] The present disclosure relates to a substrate processing method and a substrate processing system.

[0002] Patent Document 1 discloses a film formation method including a step of forming a barrier film made of any one of AlN, TiAlN, and TiCN on a substrate, and a step of forming a metal film on the barrier film. Patent Document 1 also discloses that the substrate on which the barrier film and the metal film have been formed is subjected to an annealing treatment.

[0003] Japanese Patent Application Laid-Open No. 2022-143537

[0004] The present disclosure provides a substrate processing method and a substrate processing system that can suppress mixing between an underlayer and a metal layer.

[0005] A substrate processing method according to one aspect of the present disclosure includes a step of preparing a substrate having a metal layer formed on an underlayer, a first step of forming a mixing suppression layer on the metal layer to suppress mixing between the underlayer and the metal layer, and a second step of annealing the substrate having the mixing suppression layer formed on the metal layer at a temperature of 950°C or higher.

[0006] According to the present disclosure, mixing between the underlayer and the metal layer can be suppressed.

[0007] FIG. 1 is a schematic cross-sectional view illustrating an example of a film formation apparatus according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view illustrating an example of an annealing apparatus according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a state of a substrate after formation of a graphene film according to the present embodiment. FIG. 4 is a flowchart illustrating an example of a substrate processing method according to the present embodiment. FIG. 5 is a diagram illustrating an example of a resistivity reduction effect achieved by a graphene cap. FIG. 6 is a diagram illustrating an example of mixing in the absence of a graphene cap. FIG. 7 is a diagram illustrating an example of a mixing suppression effect achieved by a graphene cap. FIG. 8 is a diagram illustrating an example of an analysis result obtained by X-ray photoelectron spectroscopy in the absence of a graphene cap. FIG. 9 is a diagram illustrating an example of an analysis result obtained by X-ray photoelectron spectroscopy in the presence of a graphene cap. FIG. 10 is a diagram illustrating an example of an oxidation suppression effect achieved by a graphene cap. FIG. 11 is a diagram illustrating an example of a comparison of resistivity with and without annealing treatment. FIG. 12 is a diagram illustrating an example of a relationship between the film thickness of a metal layer and a resistance reduction rate in the presence of a graphene cap. FIG. 13 is a diagram illustrating an example of a process employing graphene film formation and annealing treatment.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a substrate processing method and a substrate processing system will be described in detail below with reference to the accompanying drawings. However, the disclosed technology is not limited to the following embodiments.

[0009] In the wiring structure of a semiconductor device, it is known to form a metal film (metal layer) such as ruthenium on a silicon oxide film (e.g., a gate oxide film) as a metal wiring. It is also known to form a barrier film (underlayer) such as titanium nitride (TiN) under the metal film to improve the adhesion of the metal film. When a ruthenium film is used as the metal film, it is known to perform an annealing process to increase the crystal grain size of the ruthenium film and thereby reduce its resistance. However, when an annealing process is performed after forming a metal film on a barrier film, a phenomenon in which the barrier film (underlayer) and the metal film (metal layer) mix together (hereinafter referred to as "mixing") may occur. The occurrence of mixing may lead to deterioration of the characteristics of the metal wiring itself, such as an increase in the resistivity. Therefore, it is expected to suppress the mixing between the underlayer and the metal layer.

[0010] [Configuration of Film Forming Apparatus 1] Fig. 1 is a schematic cross-sectional view showing an example of a film forming apparatus according to an embodiment of the present disclosure. The film forming apparatus 1 illustrated in Fig. 1 is configured as, for example, an RLSA (registered trademark) microwave plasma type plasma processing apparatus. The film forming apparatus 1 is an example of a substrate processing apparatus. The film forming apparatus 1, together with an annealing apparatus 2 described below, constitutes a substrate processing system.

[0011] The film forming apparatus 1 includes an apparatus main body 10 and a control unit 11 that controls the apparatus main body 10. The apparatus main body 10 includes a chamber 101, a stage 102, a microwave introduction mechanism 103, a gas supply mechanism 104, and an exhaust mechanism 105.

[0012] The chamber 101 is formed in a substantially cylindrical shape, and an opening 110 is formed in the approximate center of a bottom wall 101a of the chamber 101. An exhaust chamber 111 that communicates with the opening 110 and protrudes downward is provided in the bottom wall 101a. An opening 117 through which a substrate (hereinafter also referred to as a wafer) W passes is formed in a side wall 101s of the chamber 101, and the opening 117 is opened and closed by a gate valve 118. The chamber 101 is an example of a processing vessel.

[0013] A substrate W to be processed is placed on the stage 102. The stage 102 is generally disk-shaped and made of ceramics such as AlN. The stage 102 is supported by a cylindrical support member 112 made of ceramics such as AlN and extending upward from approximately the center of the bottom of the exhaust chamber 111. An edge ring 113 is provided on the outer edge of the stage 102 so as to surround the substrate W placed on the stage 102. Furthermore, inside the stage 102, lift pins (not shown) for lifting and lowering the substrate W are provided so as to be protruding and retracting from the upper surface of the stage 102.

[0014] Furthermore, a resistance heating heater 114 is embedded inside the stage 102, and the heater 114 heats the substrate W placed on the stage 102 in accordance with power supplied from a heater power supply 115. A thermocouple (not shown) is also inserted into the stage 102, and the temperature of the substrate W can be controlled to, for example, 300 to 850°C based on a signal from the thermocouple. Furthermore, an electrode 116 having a size approximately the same as the substrate W is embedded above the heater 114 in the stage 102, and a bias power supply 119 is electrically connected to the electrode 116. The bias power supply 119 supplies bias power of a predetermined frequency and magnitude to the electrode 116. The bias power supplied to the electrode 116 attracts ions to the substrate W placed on the stage 102. Note that the bias power supply 119 may not be provided depending on the characteristics of the plasma processing.

[0015] The microwave introduction mechanism 103 is provided at the top of the chamber 101 and includes an antenna 121, a microwave output unit 122, and a microwave transmission mechanism 123. The antenna 121 has a large number of slots 121a that are through-holes. The microwave output unit 122 outputs microwaves. The microwave transmission mechanism 123 guides the microwaves output from the microwave output unit 122 to the antenna 121.

[0016] A dielectric window 124 made of a dielectric material is provided below the antenna 121. The dielectric window 124 is supported by a support member 132 that is ring-shaped and provided at the top of the chamber 101. A slow-wave plate 126 is provided above the antenna 121. A shield member 125 is provided above the antenna 121. A flow path (not shown) is provided inside the shield member 125, and the shield member 125 cools the antenna 121, the dielectric window 124, and the slow-wave plate 126 by a fluid such as water that flows through the flow path.

[0017] The antenna 121 is formed of, for example, a copper plate or aluminum plate with a silver or gold-plated surface, and has multiple slots 121a arranged in a predetermined pattern for radiating microwaves. The arrangement pattern of the slots 121a is appropriately set so that the microwaves are radiated uniformly. An example of a suitable pattern is a radial line slot, in which multiple pairs of slots 121a are arranged concentrically, with two slots 121a arranged in a T-shape. The length and spacing of the slots 121a are appropriately determined depending on the effective wavelength (λg) of the microwaves. The slots 121a may also have other shapes, such as a circular shape or an arc shape. Furthermore, the arrangement of the slots 121a is not particularly limited, and may be arranged in a spiral or radial pattern in addition to a concentric pattern. The pattern of the slots 121a is appropriately set so that microwave radiation characteristics that obtain a desired plasma density distribution are achieved.

[0018] The slow wave plate 126 is made of quartz, ceramics (Al ２ O ３ The antenna 121 is made of a dielectric material having a dielectric constant greater than that of a vacuum, such as polytetrafluoroethylene, polyimide, etc. The slow-wave plate 126 has the function of shortening the wavelength of the microwaves compared to that in a vacuum, thereby making the antenna 121 smaller. The dielectric window 124 is also made of a similar dielectric material.

[0019] The thicknesses of the dielectric window 124 and the slow-wave plate 126 are adjusted so that the equivalent circuit formed by the slow-wave plate 126, the antenna 121, the dielectric window 124, and the plasma satisfies the resonance condition. By adjusting the thickness of the slow-wave plate 126, the phase of the microwave can be adjusted. By adjusting the thickness of the slow-wave plate 126 so that the junction of the antenna 121 becomes the "antinode" of the standing wave, microwave reflection can be minimized and the microwave radiation energy can be maximized. Furthermore, by using the same material for the slow-wave plate 126 and the dielectric window 124, interface reflection of the microwave can be prevented.

[0020] The microwave output unit 122 has a microwave oscillator. The microwave oscillator may be a magnetron type or a solid-state type. The frequency of the microwave generated by the microwave oscillator is, for example, 300 MHz to 10 GHz. As an example, the microwave output unit 122 outputs a microwave of 2.45 GHz using a magnetron type microwave oscillator. Microwaves are an example of electromagnetic waves.

[0021] The microwave transmission mechanism 123 includes a waveguide 127 and a coaxial waveguide 128. It may further include a mode conversion mechanism. The waveguide 127 guides the microwaves output from the microwave output unit 122. The coaxial waveguide 128 includes an inner conductor connected to the center of the antenna 121 and an outer conductor outside the inner conductor. The mode conversion mechanism is provided between the waveguide 127 and the coaxial waveguide 128. The microwaves output from the microwave output unit 122 propagate through the waveguide 127 in TE mode and are converted from TE mode to TEM mode by the mode conversion mechanism. The microwaves converted to TEM mode propagate through the coaxial waveguide 128 to the slow-wave plate 126 and are radiated from the slow-wave plate 126 into the chamber 101 via the slot 121a of the antenna 121 and the dielectric window 124. A tuner (not shown) is provided midway along the waveguide 127 to match the impedance of the load (plasma) in the chamber 101 to the output impedance of the microwave output part 122 .

[0022] The gas supply mechanism 104 includes a shower ring 142 that is ring-shaped and arranged along the inner wall of the chamber 101. The shower ring 142 includes a ring-shaped flow channel 166 arranged therein and a number of outlet ports 167 that are connected to the flow channel 166 and open to the inside of the flow channel 166. A gas supply unit 163 is connected to the flow channel 166 via a pipe 161. The gas supply unit 163 includes a plurality of gas sources and a plurality of flow rate controllers. In one embodiment, the gas supply unit 163 is configured to supply at least one process gas from a corresponding gas source to the shower ring 142 via a corresponding flow rate controller. The gas supplied to the shower ring 142 is then supplied into the chamber 101 through the plurality of outlet ports 167.

[0023] When a graphene film is formed on the substrate W, the gas supply unit 163 supplies a carbon-containing gas, a hydrogen-containing gas, and a rare gas (noble gas) controlled at predetermined flow rates into the chamber 101 through the shower ring 142. In this embodiment, the carbon-containing gas is, for example, acetylene (C ２ H ２ ) gas. Acetylene (C ２ H ２ ) gas, as well as ethylene (C ２ H ４ ) gas, methane (CH ４ ) gas, ethane (C ２ H ６ ) gas, propane (C ３ H ８ ) gas, propylene (C ３ H ６ ) gas, methanol (CH ３ OH) gas, ethanol (C ２ H ５ In this embodiment, the hydrogen-containing gas is, for example, hydrogen gas. Note that, instead of or in addition to hydrogen gas, F ２ (Fluorine) gas, Cl ２ (chlorine) gas, or Br ２A halogen-based gas such as (bromine) gas may be used. In this embodiment, the rare gas is, for example, Ar gas. Instead of Ar gas, other rare gases such as He gas may be used.

[0024] The exhaust mechanism 105 includes an exhaust chamber 111, an exhaust pipe 181 provided on the side wall of the exhaust chamber 111, and an exhaust device 182 connected to the exhaust pipe 181. The exhaust device 182 includes a vacuum pump, a pressure control valve, and the like.

[0025] The control unit 11 has a memory, a processor, and an input / output interface. The memory stores programs to be executed by the processor and recipes including conditions for each process. The processor executes the programs read from the memory and controls each part of the apparatus main body 10 via the input / output interface based on the recipes stored in the memory.

[0026] For example, the control unit 11 controls each part of the film forming apparatus 1 to perform a substrate processing method described below. To give a detailed example, the control unit 11 executes a step of preparing a substrate W by loading the substrate W, which has a metal layer formed on an underlayer, into the chamber 101. The control unit 11 executes a first step of forming a mixing suppression layer on the metal layer, which suppresses mixing between the underlayer and the metal layer. For example, the first step includes supplying a carbon-containing gas to generate plasma, and using the generated plasma to form a graphene layer as a mixing suppression layer on the metal layer. Here, the carbon-containing gas is acetylene (C ), which is supplied from the gas supply unit 163. ２ H ２ ) gas can be used. The carbon-containing gas is not limited to acetylene. For example, ethylene (C ２ H ４ ) gas, methane (CH ４ ) gas, ethane (C ２ H ６ ) gas, propane (C ３ H ８ ) gas, propylene (C ３ H ６ ) gas, methanol (CH ３ OH) gas, ethanol (C ２ H ５OH) gas may be used.

[0027] [Configuration of Annealing Apparatus 2] Fig. 2 is a schematic cross-sectional view showing an example of an annealing apparatus according to an embodiment of the present disclosure. The annealing apparatus 2 shown in Fig. 2 is configured as, for example, a lamp heater type annealing apparatus.

[0028] The annealing apparatus 2 includes an apparatus main body 20 and a control unit 21 that controls the apparatus main body 20. The apparatus main body 20 includes a chamber 201, a stage 202, a lamp heater 203, a gas supply mechanism 204, and an exhaust mechanism 207.

[0029] The chamber 201 is formed in a substantially cylindrical shape, and a stage 202 is disposed approximately in the center of the bottom surface of the chamber 201. An opening 217 through which the substrate W passes is formed in the sidewall of the chamber 201, and the opening 217 is opened and closed by a gate valve 218. The chamber 201 is an example of a processing vessel.

[0030] A substrate W to be processed is placed on the stage 202. The stage 202 is generally disk-shaped and made of ceramics such as AlN. Inside the stage 202, lifting pins (not shown) for lifting and lowering the substrate W are provided so as to be protruding and retracting from the upper surface of the stage 202.

[0031] The lamp heater 203 is provided in the upper part of the chamber 201. The lamp heater 203 heats the substrate W with electromagnetic waves in the infrared region radiated from, for example, a halogen lamp. The lamp heater 203 can control the temperature of the substrate W to, for example, room temperature (RT) to 1100° C. by controlling the voltage.

[0032] The gas supply mechanism 204 is connected to, for example, the upper portion of the chamber 201 via a pipe 205. The pipe 205 is provided with a control valve 206. The gas supply mechanism 204 is provided with a plurality of gas sources and a plurality of flow rate controllers. In one embodiment, the gas supply mechanism 204 is configured to supply at least one process gas from a corresponding gas source into the chamber 201 via a corresponding flow rate controller. The process gas may be, for example, a hydrogen-containing gas. The control valve 206 controls the supply of the process gas to the chamber 201.

[0033] The exhaust mechanism 207 is connected to, for example, the bottom of the chamber 201 via a pipe 208. The pipe 208 is provided with a pressure control valve 209. The exhaust mechanism 207 is provided with a vacuum pump. In one embodiment, the exhaust mechanism 207 is configured to adjust the pressure inside the chamber 201 by controlling the vacuum pump and the pressure control valve 209.

[0034] The control unit 21 has a memory, a processor, and an input / output interface. The memory stores programs to be executed by the processor and recipes including conditions for each process. The processor executes the programs read from the memory and controls each part of the apparatus main body 20 via the input / output interface based on the recipes stored in the memory.

[0035] For example, the control unit 21 controls each unit of the annealing apparatus 2 to perform a substrate processing method described below. In one detailed example, the control unit 21 performs a step of loading the substrate W, which has been subjected to a first step in the film formation apparatus 1, into the chamber 201. The control unit 21 performs a second step of annealing the substrate W, which has a mixing suppression layer formed on a metal layer, at a temperature of 950° C. or higher.

[0036] [Mixing Suppression Layer] Next, the state of a substrate after the formation of a graphene film, which is an example of a mixing suppression layer, will be described with reference to FIG. 3 . FIG. 3 is a diagram showing an example of the state of a substrate after the formation of a graphene film in this embodiment. As shown in FIG. 3 , the substrate W has a silicon oxide layer 31 formed on a silicon substrate 30. The silicon substrate 30 may be, for example, silicon or silicon oxide. That is, the silicon oxide layer 31 may be included in the silicon substrate 30. An underlayer 32 is formed on the silicon oxide layer 31. Examples of the underlayer 32 include nitride films such as titanium nitride (TiN) and tantalum nitride (TaN). The underlayer 32 has a thickness of, for example, about several nanometers. A metal layer 33 is formed on the underlayer 32. Examples of the metal layer 33 include metal layers such as copper (Cu), tungsten (W), ruthenium (Ru), nickel (Ni), cobalt (Co), and molybdenum (Mo) used for metal microwiring, or metal-containing layers containing these metals. The metal layer 33 has a thickness of, for example, 50 nm or less. The metal layer 33 preferably has a thickness of, for example, 5 nm to 20 nm. The underlayer 32 and the metal layer 33 are formed by any one of a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, and a PVD (Physical Vapor Deposition) method.

[0037] A mixing suppression layer 34 is formed on the metal layer 33. The mixing suppression layer 34 may be, for example, a graphene layer (graphene film). The mixing suppression layer 34 may be a continuous film, for example, with a thickness in the range of 2 nm to 20 nm. The mixing suppression layer 34 preferably has a thickness in the range of 2 nm to 5 nm, and more preferably has a thickness in the range of 2 nm to 3 nm. A continuous film means that the metal layer 33 is not exposed. In the following description, a mixing suppression layer 34 using a graphene layer may be referred to as a graphene cap. The mixing suppression layer 34 is not limited to graphene, and may be another layer (film) such as silicon nitride (SiN) as long as it can suppress oxidation of the metal layer 33.

[0038] [Substrate Processing Method] Next, a substrate processing method according to this embodiment will be described with reference to a flowchart of FIG.

[0039] In the substrate processing method according to this embodiment, first, a film formation process is performed in the film formation apparatus 1. The control unit 11 of the film formation apparatus 1 performs a degassing process to remove residual oxygen while the interior of the chamber 101 is cleaned (step S1). The control unit 11 controls the gate valve 118 to open the opening 117. While the opening 117 is open, a substrate to be cleaned is carried into the processing space of the chamber 101 through the opening 117 and placed on the stage 102. The control unit 11 controls the gate valve 118 to close the opening 117.

[0040] The control unit 11 controls the gas supply unit 163 to supply a hydrogen-containing gas to the chamber 101 from the plurality of outlets 167. The control unit 11 also controls the exhaust mechanism 105 to control the pressure inside the chamber 101 to a predetermined pressure (for example, 50 mTorr to 1 Torr (6.67 Pa to 133 Pa)). The hydrogen-containing gas or nitrogen-containing gas used in the degassing step may be, for example, H ２ Gas and N ２ The control unit 11 controls the microwave introduction mechanism 103 to ignite the plasma. The control unit 11 executes a degassing process using the plasma of the hydrogen-containing gas or the nitrogen-containing gas for a predetermined time (for example, 120 to 600 seconds). In the degassing process, the O remaining in the chamber 101 is removed. ２ , H ２ Oxidizing components such as O are discharged as O-containing radicals. Note that the degassing step does not necessarily require the use of a cleaning substrate. The degassing step may also be omitted.

[0041] When the degassing step is completed, the control unit 11 controls the gate valve 118 to open the opening 117. The substrate W having the metal layer 33 formed on the underlayer 32 is loaded into the processing space of the chamber 101 through the opening 117 while the opening 117 is open, and placed on the stage 102. That is, the control unit 11 controls the apparatus main body 10 to load the substrate W having the metal layer 33 formed on the underlayer 32 into the chamber 101 (step S2). The control unit 11 closes the opening 117 by controlling the gate valve 118. Note that step S2 is an example of a step of preparing the substrate W having the metal layer 33 formed on the underlayer 32.

[0042] The control unit 11 controls the exhaust mechanism 105 to reduce the pressure inside the chamber 101 to a predetermined pressure (for example, 50 mTorr to 1 Torr). The control unit 11 controls the gas supply unit 163 to supply a hydrogen-containing gas and a carbon-containing gas, which are plasma generating gases, to the chamber 101 from the outlet 167. The hydrogen-containing gas is hydrogen (H ２ The carbon-containing gas is a gas containing C ｘ H ｙ (x, y are natural numbers) ２ H ２ The control unit 11 controls the microwave introduction mechanism 103 to ignite plasma using microwaves of a predetermined power (e.g., 100 W to 1500 W). The control unit 11 then performs a pretreatment step (step S3) for a predetermined time (e.g., 5 seconds to 15 minutes) using the plasma of the hydrogen-containing gas and the carbon-containing gas to improve various surface properties of the metal layer 33. For example, the pretreatment step improves the adhesion between the metal layer 33 and the mixing suppression layer 34.

[0043] The plasma generating gas is H ２ Gas, C ｘ H ｙ In the pretreatment step, one or more of C gas and Ar gas may be used. ｘ H ｙEven if a gas is supplied, graphene film formation is not performed. Furthermore, in the pretreatment step, an annealing treatment may be performed in addition to or instead of the plasma treatment. When the annealing treatment is performed, the pressure in the chamber 101 is reduced to a predetermined pressure (e.g., 50 mTorr to 1 Torr), and, for example, a hydrogen-containing gas is supplied to the chamber 101. Furthermore, the pretreatment step may be omitted.

[0044] When the pre-processing step is completed, the control unit 11 stops the microwaves to stop the generation of plasma. The control unit 11 controls the exhaust mechanism 105 to reduce the pressure inside the chamber 101 to a predetermined pressure (for example, 1 mTorr to 1 Torr (0.133 Pa to 133 Pa)). The control unit 11 controls the heater power supply 115 to heat the substrate W to a predetermined temperature (for example, 300°C to 500°C). The control unit 11 controls the gas supply unit 163 to supply a hydrogen-containing gas and a carbon-containing gas, which are plasma generating gases, to the chamber 101 from the outlet 167. The hydrogen-containing gas is hydrogen (H ２ The plasma generating gas may be an inert gas instead of the hydrogen-containing gas. The carbon-containing gas may be, for example, a C ２ H ２ Gas or C ２ H ４ The base layer 32 is a gas. The control unit 11 also controls the microwave introduction mechanism 103 to ignite plasma at a predetermined power (e.g., 300 W to 1500 W). The control unit 11 then executes a film formation process (first process) for a predetermined time (e.g., 5 seconds to 15 minutes) using plasma of the hydrogen-containing gas and the carbon-containing gas to form a mixing suppression layer 34 on the metal layer 33 (step S4). That is, step S4 is an example of a first process for forming a mixing suppression layer 34 on the metal layer 33 that suppresses mixing between the base layer 32 and the metal layer 33. In step S4, which is an example of the first process, a carbon-containing gas is supplied to generate plasma, and the generated plasma is used to form a graphene layer as the mixing suppression layer 34 on the metal layer 33.

[0045] When the film formation process is completed, the control unit 11 stops the microwaves to stop the generation of plasma. The control unit 11 also controls the gate valve 118 to open the opening 117. The control unit 11 controls the apparatus body 10 to lift the substrate W by causing substrate support pins (not shown) to protrude from the upper surface of the stage 102. When the opening 117 is open, the substrate W is unloaded from the chamber 101 by an arm of a transfer chamber (not shown) through the opening 117. That is, the control unit 11 controls the apparatus body 10 to unload the substrate W from the chamber 101 (step S5). The substrate W is then loaded into the annealing apparatus 2 by an arm of a transfer chamber (not shown).

[0046] When the film formation process in the film formation apparatus 1 is completed, the annealing process is performed in the annealing apparatus 2. The control unit 21 of the annealing apparatus 2 controls the gate valve 218 to open the opening 217. When the opening 217 is open, the substrate W is loaded into the processing space of the chamber 201 through the opening 217 and placed on the stage 202. That is, the control unit 21 controls the apparatus body 20 to load the substrate W into the chamber 201 (step S6). The control unit 21 controls the gate valve 218 to close the opening 217.

[0047] The control unit 21 controls the exhaust mechanism 207 to reduce the pressure inside the chamber 201 to a predetermined pressure (for example, 50 mTorr to 1000 Torr (0.133 Pa to 133 kPa)). The pressure inside the chamber 201 is preferably, for example, 700 Torr (93.3 kPa). The control unit 21 controls the gas supply mechanism 204 to supply a nitrogen-containing gas to the chamber 201. The nitrogen-containing gas is, for example, nitrogen (N ２ ) gas plus hydrogen (H ２The nitrogen-containing gas may contain Ar gas. The nitrogen-to-hydrogen ratio of the nitrogen-to-hydrogen gas is preferably in the range of 100:0 to 96:4. The nitrogen-containing gas may contain Ar gas. The control unit 21 may also control the gas supply mechanism 204 to supply a hydrogen-containing gas to the chamber 201 instead of the nitrogen-containing gas. The hydrogen-containing gas may be, for example, a mixed gas of hydrogen gas and Ar gas. The control unit 21 controls the lamp heater 203 to heat the substrate W to a predetermined temperature (e.g., 950°C to 1100°C). The control unit 21 performs an annealing step (second step) for increasing the grain size of the crystals in the metal layer 33 by heating the substrate W for a predetermined time (e.g., 5 seconds to 10 minutes) while suppressing mixing between the underlayer 32 and the metal layer 33 with the mixing suppression layer 34 (step S7). That is, step S7 is an example of a second step in which the substrate W having the mixing suppression layer 34 formed on the metal layer 33 is annealed at a temperature of 950° C. or higher. Step S7, which is an example of the second step, may be performed in an atmosphere containing at least one of nitrogen and hydrogen, or may be performed in an atmosphere containing nitrogen and hydrogen.

[0048] When the annealing process is completed, the control unit 21 stops the lamp heater 203. The control unit 21 controls the gas supply mechanism 204 and the exhaust mechanism 207 to supply, for example, an inert gas (e.g., N ２ The gas (ammonia gas) is supplied to the chamber 201 as a purge gas while being exhausted. That is, the control unit 21 controls the gas supply mechanism 204 and the exhaust mechanism 207 to cool the substrate W to room temperature, for example. That is, the control unit 21 executes a cooling step of cooling the substrate W to room temperature (step S8).

[0049] When the cooling process is completed, the control unit 21 stops the supply and evacuation of the inert gas. The control unit 21 also controls the gate valve 218 to open the opening 217. The control unit 21 controls the apparatus main body 20 to lift the substrate W by causing substrate support pins (not shown) to protrude from the upper surface of the stage 202. When the opening 217 is open, the substrate W is unloaded from the chamber 201 by an arm of the transfer chamber (not shown) through the opening 217. That is, the control unit 21 controls the apparatus main body 20 to unload the substrate W from the chamber 201 (step S9). In this way, by performing an annealing process in which the substrate is heated to a temperature of 950°C or higher after the film formation process, the crystal grain size of the metal layer 33 can be increased and the resistance can be reduced. Furthermore, since the mixing suppression layer 34 is formed on the metal layer 33, mixing between the underlayer 32 and the metal layer 33 can be suppressed.

[0050] [Experimental Results] Next, experimental results for this embodiment and a reference example will be described with reference to FIGS. 5 to 12. FIG. 5 illustrates an example of the resistivity reduction effect of a graphene cap. FIG. 5 shows a graph 40 of a substrate Wt of a reference example in which a graphene cap is not formed as the mixing suppression layer 34, and a graph 41 of a substrate W of this embodiment in which a graphene cap is formed as the mixing suppression layer 34. As will be described later, the substrate Wt of the reference example includes a silicon oxide layer 51, an underlayer 52, and a metal layer 53 corresponding to the silicon oxide layer 31, the underlayer 32, and the metal layer 33. FIG. 5 also illustrates the resistivity after annealing when tungsten is used as the metal layers 33 and 53, respectively, and when the thicknesses of the metal layers 33 and 53 are 5 nm and slightly less than 20 nm (approximately 19 nm). The annealing was performed at 950° C. for 1 minute at 700 Torr in a nitrogen gas atmosphere with a nitrogen / hydrogen ratio of 100:0. As shown in graph 40, when the thickness of the metal layer 53 on the substrate Wt is 5 nm, the resistivity becomes very high and is omitted because it is far beyond the range of the graph in Fig. 5. Also, as shown in graph 40, when the thickness of the metal layer 53 on the substrate Wt is just under 20 nm, the resistivity is about 38 [μΩ cm], and conductivity is maintained.

[0051] On the other hand, as shown in graph 41, when the thickness of the metal layer 33 of the substrate W is 5 nm, the resistivity is about 42 μΩ·cm, maintaining conductivity. Also, as shown in graph 41, when the thickness of the metal layer 33 of the substrate W is just under 20 nm (about 19 nm), the resistivity is about 32 μΩ·cm, maintaining conductivity. This indicates that when a graphene cap is formed as the mixing suppression layer 34, the resistivity of the metal layer 33 is reduced compared to when no graphene cap is formed, regardless of whether the thickness of the metal layer 33 is 5 nm or just under 20 nm. The reduction in resistivity of the metal layer 33 is thought to be due to the mixing suppression layer 34 suppressing film roughening of the metal layer 33 and the mixing suppression layer 34 suppressing inelastic scattering of electrons at the interface.

[0052] FIG. 6 is a diagram illustrating an example of mixing when a graphene cap is not provided. FIG. 6 is a schematic cross-sectional view of a reference example substrate Wt before and after annealing when a graphene cap corresponding to the mixing suppression layer 34 is not provided. As shown before annealing in FIG. 6 , the substrate Wt has an underlayer 52 formed on a silicon oxide layer 51, and a metal layer 53 formed on the underlayer 52. The underlayer 52 is, for example, a titanium nitride film with a thickness of 3 nm. The metal layer 53 is, for example, a tungsten film with a thickness of 5 nm. When the substrate Wt is annealed, the underlayer 52 and the metal layer 53 mix (mix) with each other, forming a mixing layer 54, as shown after annealing in FIG. 6 .

[0053] FIG. 7 is a diagram illustrating an example of the mixing suppression effect of a graphene cap. FIG. 7 is a schematic cross-sectional view of a substrate W according to this embodiment before and after annealing when a graphene cap is used as the mixing suppression layer 34. As shown before annealing in FIG. 7 , the substrate W includes an underlayer 32 formed on a silicon oxide layer 31, and a metal layer 33 formed on the underlayer 32. Furthermore, a mixing suppression layer 34 is formed on the metal layer 33. The underlayer 32 is, for example, a titanium nitride film having a thickness of 3 nm. The metal layer 33 is, for example, a tungsten film having a thickness of 5 nm. The mixing suppression layer 34 is, for example, a graphene film having a thickness of 3 nm. When the substrate W is annealed, as shown after annealing in FIG. 7 , the mixing suppression layer 34 is reduced in thickness, and mixing between the underlayer 32 and the metal layer 33 is suppressed. From this, it is believed that the mixing-inhibiting layer 34 inhibits oxidation of the metal layer 33, and thus inhibits mixing that occurs as a result of oxidation.

[0054] FIG. 8 shows an example of the results of analysis by X-ray photoelectron spectroscopy (XPS) without a graphene cap. A graph 60 shown in FIG. 8 shows the atomic concentrations of carbon (C), nitrogen (N), oxygen (O), silicon (Si), titanium (Ti), and tungsten (W) in the depth direction of the substrate Wt of the reference example after annealing. As described above, the substrate Wt had a 3-nm-thick titanium nitride film formed as the underlayer 52 and a 5-nm-thick tungsten film formed as the metal layer 53 before annealing. Focusing on the graph 60 in the region between 0 nm and 10 nm in depth reveals that, after annealing, the tungsten film of the metal layer 53 of the substrate Wt is oxidized and the titanium nitride film of the underlayer 52 and the tungsten film of the metal layer 53 are mixed together.

[0055] 9 shows an example of the results of analysis by X-ray photoelectron spectroscopy when a graphene cap is provided. Graph 61 in FIG. 9 shows the atomic concentrations of carbon (C), nitrogen (N), oxygen (O), silicon (Si), titanium (Ti), and tungsten (W) in the depth direction of the substrate W of this embodiment after annealing. As described above, the substrate W includes a 3-nm-thick titanium nitride film in the underlayer 32, a 5-nm-thick tungsten film in the metal layer 33, and a 3-nm-thick graphene film in the mixing suppression layer 34 before annealing. Focusing on the depth range of 0 nm to 15 nm in graph 61, it can be seen that, after annealing, oxidation of the tungsten film in the metal layer 33 is suppressed and mixing between the titanium nitride film in the underlayer 32 and the tungsten film in the metal layer 33 is suppressed.

[0056] FIG. 10 is a diagram showing an example of the oxidation suppression effect of a graphene cap. Graph 62 shown in FIG. 10 is a graph that extracts oxygen from graph 60 in FIG. 8 and tungsten and oxygen from graph 61 in FIG. 9 . The components in each layer of the substrate W are shown below graph 62. Graph 63 corresponds to tungsten from graph 61, and graph 64 corresponds to oxygen from graph 61. Meanwhile, graph 65 corresponds to oxygen from graph 60. Comparing graphs 64 and 65, in graph 65 without the graphene cap, the oxygen concentration in the tungsten layer increases, indicating that tungsten is oxidized. In contrast, in graph 64 with the graphene cap (mixing suppression layer 34), the oxygen concentration in the tungsten layer does not increase, indicating that tungsten oxidation is suppressed.

[0057] FIG. 11 shows an example of a comparison of resistivity with and without annealing. In addition to graphs 40 and 41 of FIG. 5, FIG. 11 also shows graph 42, which represents the resistivity of the metal layer 33 of the substrate W before annealing. As shown in graph 42, when the thickness of the metal layer 33 of the substrate W is 6 nm, the resistivity is approximately 95 μΩ·cm, which indicates conductivity. Also, as shown in graph 42, when the thickness of the metal layer 33 of the substrate W is 17.5 nm, the resistivity is approximately 52 μΩ·cm, which indicates conductivity. For experimental purposes, multiple data showing thicknesses of the metal layer 33 near 5 nm and 20 nm were used. Comparing graphs 41 and 42, it can be seen that providing the mixing suppression layer 34 and performing annealing can reduce resistivity at thicknesses of the metal layer 33 near 5 nm and 20 nm. In other words, it can be seen that oxidation of the metal layer 33 is suppressed, thereby suppressing mixing between the underlayer 32 and the metal layer 33.

[0058] FIG. 12 is a diagram showing an example of the relationship between the film thickness of the metal layer and the resistance reduction rate when a graphene cap is provided. Graph 66 in FIG. 12 shows the relationship between the film thickness of the metal layer 33 and the resistance reduction rate when an annealing treatment is performed with the mixing suppression layer 34 provided. In other words, graph 66 shows the ratio between graph 40 and graph 41 in FIG. 11 . As shown in graph 66, when the film thickness of the metal layer 33 is 5 nm, the resistance reduction rate is nearly 100%, and when the film thickness of the metal layer 33 is just under 20 nm (approximately 19 nm), the resistance reduction rate is 20%. In other words, when the mixing suppression layer 34 (graphene cap) is not provided, the thinner the film, the higher the proportion of mixed or oxidized metal layer 33 (tungsten), the greater the effect of the mixing suppression layer 34.

[0059] [Application Example to Process] Next, as an application example to a process of this embodiment, a bit line formation process for a dynamic random access memory (DRAM) will be described. FIG. 13 is a diagram showing an example of a process to which graphene film deposition and annealing treatment are applied. The substrate W1 in state 70 shown in FIG. 13 is in a state before the mixing suppression layer 34 is deposited. In the substrate W1, a silicon oxide layer 31 is formed on a silicon substrate 30, and a bit line 75 is formed in the silicon oxide layer 31. The bit line 75 is formed, for example, by forming an underlayer 32 on the wall and bottom surfaces of a trench or the like and embedding a metal layer 33 on the underlayer 32. The surface of the substrate W1 on which the bit line 75 is formed is planarized, for example, by CMP (Chemical Mechanical Polishing).

[0060] As shown in state 71, the substrate W1 on which the bit line 75 is formed has the mixing suppression layer 34 (e.g., a graphene layer) formed on its surface by the above-described film formation process. The substrate W1 on which the mixing suppression layer 34 is formed is then annealed by the above-described annealing process. The annealing process can increase the grain size of tungsten crystals in the metal layer 33 of the substrate W1, for example.

[0061] As shown in a state 72, the annealed substrate W1 has a silicon nitride (Si ３ N ４ A silicon nitride layer 35 is then formed on the silicon nitride layer 35. Thereafter, a capacitor (not shown) is formed on the silicon nitride layer 35.

[0062] In the above-described embodiment, the film formation process performed in the film formation apparatus 1 involves preparing a substrate W having a metal layer 33 formed on an underlayer 32, and then forming the mixing suppression layer 34. However, this is not limiting. For example, the substrate W having a silicon oxide layer 31 formed on a silicon substrate 30 may be loaded into the film formation apparatus 1, and the steps of forming the underlayer 32 and forming the metal layer 33 on the underlayer 32 may be performed, followed by forming the mixing suppression layer 34 on the metal layer 33. The steps of forming the underlayer 32 and forming the metal layer 33 on the underlayer 32 may be performed by any one of CVD, ALD, and PVD. In this case, the steps of forming the underlayer 32, forming the metal layer 33 on the underlayer 32, and forming the mixing suppression layer 34 may each be performed in a different film formation apparatus.

[0063] As described above, according to this embodiment, the substrate processing system includes a film forming apparatus 1 and an annealing apparatus 2. The film forming apparatus 1 and the annealing apparatus 2 each include a processing vessel (chamber 101, 201) capable of accommodating a substrate W having a metal layer 33 on an underlayer 32, and a control unit 11, 21. The control unit 11 of the film forming apparatus 1 performs a step of loading the substrate W into the processing vessel of the film forming apparatus 1 and a first step of forming a mixing suppression layer 34 on the metal layer 33 to suppress mixing between the underlayer 32 and the metal layer 33. The control unit 21 of the annealing apparatus 2 performs a second step of annealing the substrate W having the mixing suppression layer 34 formed on the metal layer 33 at a temperature of 950° C. or higher. As a result, mixing between the underlayer 32 and the metal layer 33 can be suppressed.

[0064] According to the present embodiment, the mixing suppression layer 34 is a graphene layer, which can suppress mixing between the base layer 32 and the metal layer 33.

[0065] Furthermore, according to this embodiment, the metal layer 33 contains at least one of Ru, W, Mo, Ni, Co, and Cu, which allows the resistivity of the metal layer 33 to be reduced.

[0066] Furthermore, according to this embodiment, the underlayer 32 is made of either TiN or TaN, which reduces the influence of the metal layer 33 on the silicon oxide layer 31 during annealing.

[0067] Furthermore, according to this embodiment, the mixing suppression layer 34 is a continuous film, which makes it possible to suppress mixing between the underlayer 32 and the metal layer 33.

[0068] Furthermore, according to this embodiment, the thickness of the mixing suppression layer 34 is in the range of 2 nm to 5 nm, which makes it possible to suppress mixing between the underlayer 32 and the metal layer 33.

[0069] According to the present embodiment, the base layer 32 is formed by any one of the CVD method, the ALD method, and the PVD method, so that a film formation method suitable for forming the base layer 32 can be selected depending on the material of the base layer 32.

[0070] According to the present embodiment, the metal layer 33 is formed by any one of the CVD method, the ALD method, and the PVD method, so that a film formation method suitable for forming the metal layer 33 can be selected depending on the material of the metal layer 33.

[0071] Furthermore, according to the present embodiment, in the first step, a carbon-containing gas is supplied to generate plasma, and the generated plasma is used to form a graphene layer as the mixing-suppressing layer 34 on the metal layer 33. As a result, mixing between the base layer 32 and the metal layer 33 can be suppressed.

[0072] Furthermore, according to this embodiment, the plasma is microwave plasma, and as a result, the mixing suppression layer 34 can be formed.

[0073] Furthermore, according to this embodiment, in the first step, the substrate W is heated to a temperature in the range of 300° C. to 500° C., and the mixing suppression layer 34 is formed on the metal layer 33. As a result, a graphene layer can be formed on the metal layer 33 as the mixing suppression layer 34.

[0074] Furthermore, according to this embodiment, the second step is performed in an atmosphere containing at least one of nitrogen and hydrogen, which makes it possible to reduce the resistivity of the metal layer 33 while suppressing mixing between the underlayer 32 and the metal layer 33.

[0075] Furthermore, according to this embodiment, the second step is performed in an atmosphere containing nitrogen and hydrogen, which makes it possible to reduce the resistivity of the metal layer 33 while suppressing mixing between the underlayer 32 and the metal layer 33.

[0076] Furthermore, according to this embodiment, in the second step, the ratio of nitrogen to hydrogen is 100:0 to 96:4, which results in a reduction in the resistivity of the metal layer 33 while suppressing mixing between the underlayer 32 and the metal layer 33.

[0077] Furthermore, according to this embodiment, the thickness of the metal layer 33 is 5 nm to 20 nm, which results in a reduced resistivity of the metal layer 33.

[0078] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, and modifications may be made to the above-described embodiments without departing from the spirit and scope of the appended claims.

[0079] In the above embodiment, the lamp heater 203 is used as the heat source of the annealing device 2, but this is not limiting. For example, the heat source of the annealing device 2 may be various heat sources such as a laser or a stage heater.

[0080] In the above embodiment, the annealing process is performed on a single substrate, but this is not limiting. For example, the annealing process may be performed on a batch process of a plurality of substrates W after the film formation process.

[0081] In the above embodiment, the film forming apparatus 1 is described as an example in which microwave plasma is used as a plasma source to perform processes such as etching and film formation on the substrate W, but the disclosed technology is not limited to this. As long as the apparatus performs processes on the substrate W using plasma, the plasma source is not limited to microwave plasma, and any plasma source such as capacitively coupled plasma, inductively coupled plasma, or magnetron plasma can be used.

[0082] The present disclosure may also be configured as follows: (1) A substrate processing method comprising: a step of preparing a substrate having a metal layer formed on an underlayer; a first step of forming a mixing suppression layer on the metal layer to suppress mixing between the underlayer and the metal layer; and a second step of annealing the substrate having the mixing suppression layer formed on the metal layer at a temperature of 950°C or higher. (2) The substrate processing method according to (1), in which the mixing suppression layer is a graphene layer. (3) The substrate processing method according to (1) or (2), in which the metal layer contains at least one of Ru, W, Mo, Ni, Co, and Cu. (4) The substrate processing method according to any one of (1) to (3), in which the underlayer is one of TiN and TaN. (5) The substrate processing method according to any one of (1) to (4), wherein the mixing suppression layer is a continuous film. (6) The substrate processing method according to any one of (1) to (5), wherein the mixing suppression layer has a film thickness in the range of 2 nm to 5 nm. (7) The substrate processing method according to any one of (1) to (6), wherein the underlayer is formed by any one of a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, and a PVD (Physical Vapor Deposition) method. (8) The substrate processing method according to any one of (1) to (7), wherein the metal layer is formed by any one of a CVD method, an ALD method, and a PVD method. (9) The substrate processing method according to any one of (1) to (8), wherein the first step comprises supplying a carbon-containing gas to generate plasma and using the generated plasma to form a graphene layer as the mixing suppression layer on the metal layer. (10) The substrate processing method according to (9), wherein the plasma is microwave plasma. (11) The substrate processing method according to any one of (1) to (10), wherein the first step comprises heating the substrate to a temperature in the range of 300°C to 500°C and forming the mixing suppression layer on the metal layer.(12) The substrate processing method according to any one of (1) to (11), wherein the second step is performed in an atmosphere containing at least one of nitrogen and hydrogen. (13) The substrate processing method according to (12), wherein the second step is performed in an atmosphere containing nitrogen and hydrogen. (14) The substrate processing method according to (12), wherein a ratio of the nitrogen to the hydrogen is 100:0 to 96:4. (15) The substrate processing method according to any one of (1) to (14), wherein a film thickness of the metal layer is 5 nm to 20 nm. (16) A substrate processing system having a film formation apparatus and an annealing apparatus, wherein the film formation apparatus and the annealing apparatus each have a processing vessel capable of accommodating a substrate having a metal layer on a base layer, and a control unit, wherein the control unit of the film formation apparatus is configured to control the film formation apparatus to load the substrate into the processing vessel of the film formation apparatus, the control unit of the film formation apparatus is configured to control the film formation apparatus to form a mixing suppression layer on the metal layer that suppresses mixing between the base layer and the metal layer, and the control unit of the annealing apparatus is configured to control the annealing apparatus to anneal the substrate having the mixing suppression layer formed on the metal layer at a temperature of 950°C or higher.

[0083] REFERENCE SIGNS LIST 1 Film forming apparatus 2 Annealing apparatus 11, 21 Control unit 30 Silicon substrate 31 Silicon oxide layer 32 Underlayer 33 Metal layer 34 Mixing suppression layer 101, 201 Chamber W, W1 Substrate

Claims

1. A substrate processing method comprising: a step of preparing a substrate having a metal layer formed on an underlayer; a first step of forming a mixing suppression layer on the metal layer to suppress mixing between the underlayer and the metal layer; and a second step of annealing the substrate having the mixing suppression layer formed on the metal layer at a temperature of 950°C or higher.

2. The substrate processing method according to claim 1, wherein the mixing suppression layer is a graphene layer.

3. The substrate processing method according to claim 1, wherein the metal layer contains at least one of Ru, W, Mo, Ni, Co, and Cu.

4. The substrate processing method according to claim 1, wherein the underlayer is one of TiN and TaN.

5. The substrate processing method according to claim 1, wherein the mixing suppression layer is a continuous film.

6. The substrate processing method according to claim 1, wherein the thickness of the mixing suppression layer is in the range of 2 nm to 5 nm.

7. The substrate processing method according to claim 1, wherein the underlayer is formed by any one of a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, and a PVD (Physical Vapor Deposition) method.

8. The substrate processing method according to claim 1, wherein the metal layer is formed by any one of a CVD method, an ALD method, and a PVD method.

9. The substrate processing method according to claim 1, wherein the first step comprises supplying a carbon-containing gas to generate plasma, and using the generated plasma to form a graphene layer as the mixing suppression layer on the metal layer.

10. The substrate processing method according to claim 9, wherein the plasma is microwave plasma.

11. The substrate processing method according to claim 1, wherein the first step heats the substrate to a temperature in the range of 300°C to 500°C and forms the mixing suppression layer on the metal layer.

12. The substrate processing method according to claim 1, wherein the second step is performed in an atmosphere containing at least one of nitrogen and hydrogen.

13. The substrate processing method according to claim 12, wherein the second step is performed in an atmosphere containing nitrogen and hydrogen.

14. The substrate processing method according to claim 12, wherein the ratio of the nitrogen to the hydrogen is 100:0 to 96:

4.

15. The substrate processing method according to claim 1, wherein the metal layer has a film thickness of 5 nm to 20 nm.

16. A substrate processing system having a film formation apparatus and an annealing apparatus, wherein the film formation apparatus and the annealing apparatus each have a processing container capable of accommodating a substrate having a metal layer on an underlayer, and a control unit, wherein the control unit of the film formation apparatus is configured to control the film formation apparatus to load the substrate into the processing container of the film formation apparatus, the control unit of the film formation apparatus is configured to control the film formation apparatus to form a mixing suppression layer on the metal layer that suppresses mixing between the underlayer and the metal layer, and the control unit of the annealing apparatus is configured to control the annealing apparatus to anneal the substrate having the mixing suppression layer formed on the metal layer at a temperature of 950°C or higher.

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