Method for embedding ruthenium and device for embedding ruthenium

Abstract

The present invention reduces the difference in embedment height of ruthenium when embedding ruthenium in a recess formed in a substrate by repeating film formation and etching of ruthenium. This method for embedding ruthenium in a substrate that has a recess includes: (a) a step for forming a ruthenium layer in the recess by supplying a starting material gas that contains a ruthenium compound into a processing chamber in which the substrate is housed; (b) a step for performing a pretreatment of the ruthenium layer by supplying a pretreatment gas, which contains an oxygen gas or an ozone gas and has an ozone concentration of not less than 0 g / m3 but less than 150 g / m3, into the processing chamber; and (c) a step for etching a part of the ruthenium layer by supplying an etching gas, which contains an ozone gas and has an ozone concentration of 150 g / m3 to 400 g / m3 inclusive, into the processing chamber. In the method, a cycle in which the steps (a) to (c) are executed in this order is repeated.

Description

Method and apparatus for implanting ruthenium

[0001] The present disclosure relates to a method for implanting ruthenium and an apparatus for implanting ruthenium.

[0002] In the manufacturing process of semiconductor devices, a process of forming a ruthenium film is performed to form recesses such as holes and trenches in an insulating film formed on a substrate for manufacturing a semiconductor device, and to fill the recesses with ruthenium (Ru), which is an interconnect material.

[0003] Patent Document 1 describes a method of forming a first ruthenium film in a recess formed in an insulating film on a substrate, stopping the first ruthenium film formation process and supplying ozone gas to the substrate to etch the first ruthenium film until the sidewall of the recess is exposed while leaving the first ruthenium on the bottom side of the recess, and then forming a second ruthenium film so as to fill the recess with ruthenium, thereby preventing the opening of the recess from being blocked and voids from being formed in the ruthenium filled in the recess.

[0004] JP 2023-117899 A

[0005] The present disclosure provides a technique for reducing the difference in the filling height of ruthenium when ruthenium is filled into recesses formed in a substrate by repeatedly depositing and etching a ruthenium film.

[0006] The method of embedding ruthenium in a substrate having a recessed portion according to the present disclosure includes the steps of: (a) supplying a source gas containing a ruthenium compound into a processing vessel containing the substrate to form a ruthenium layer in the recessed portion; and (b) supplying oxygen gas or ozone gas into the processing vessel, the ozone concentration of which is 0 g / m or less. ３ Above, 150g / m ３ (c) supplying a pretreatment gas containing ozone gas into the treatment vessel, the pretreatment gas having an ozone concentration of 150 g / m or less (based on 0°C and 101.3 kPa; the same applies hereinafter to ozone concentration), to perform pretreatment of the ruthenium layer; ３ Above, 400g / m ３and etching a portion of the ruthenium layer by supplying the following etching gas, and repeating a cycle in which the steps (a), (b), and (c) are performed in this order.

[0007] According to the present disclosure, when ruthenium is filled into recesses formed in a substrate by repeatedly depositing and etching a ruthenium film, the difference in the filling height of the ruthenium can be reduced.

[0008] FIG. 1 is a plan view illustrating a substrate processing system according to an embodiment. FIG. 2 is a longitudinal sectional side view showing a film forming processing module of the substrate processing system. FIG. 3 is a longitudinal sectional side view showing a surface layer of a substrate before processing. FIG. 4 is a first view showing a surface layer of a substrate in a filling process of a comparative embodiment. FIG. 5 is a second view showing a surface layer of a substrate in a filling process of a comparative embodiment. FIG. 6 is a third view showing a surface layer of a substrate in a filling process of a comparative embodiment. FIG. 7 is a graph showing a change in etching amount with respect to etching gas supply time. FIG. 8 is a flowchart showing a ruthenium filling process according to an embodiment. FIG. 9 is a first view showing a surface layer of a substrate in a filling process of an embodiment. FIG. 10 is a second view showing a surface layer of a substrate in a filling process of an embodiment. FIG. 11 is a third view showing a surface layer of a substrate in a filling process of an embodiment. FIG. 12 is a fourth view showing a graph showing experimental results.

[0009] 1 is a schematic plan view illustrating a substrate processing system including a film forming apparatus according to an embodiment. The substrate processing system 1 is a multi-chamber system equipped with a plurality of processing modules 101, 102, and 103, including a processing module configured to embed ruthenium in a recess 13 (FIG. 3A) formed in a substrate W. The structure of the surface layer of the substrate W to be processed will be described later with reference to FIG. 3A.

[0010] In the substrate processing system 1, two processing modules 101 perform cleaning processing, four processing modules 102 perform film formation processing for embedding ruthenium in the recesses 13, and two processing modules 103 perform annealing processing. Hereinafter, processing module 101 may be referred to as cleaning processing module 101, processing module 102 as film formation processing module (device for embedding ruthenium) 102, and processing module 103 as annealing processing module 103.

[0011] The cleaning process module 101 performs a pre-cleaning process to remove a metal oxide film ( FIG. 3A ) that forms the bottom wall of the recess 13 before the ruthenium filling process. If the recess 13 of the substrate W has a tungsten layer underneath, the cleaning process module 101 removes a tungsten oxide film formed by oxidizing tungsten. Furthermore, if the recess 13 of the substrate W has a ruthenium layer underneath, the cleaning process module 101 removes a ruthenium oxide film formed by oxidizing ruthenium. The cleaning process module 101 reduces and removes metal oxide using hydrogen plasma, which is made by converting hydrogen gas into plasma.

[0012] The film forming module 102 is configured to form a Ru film by, for example, a thermal CVD method. The film forming module 102 uses a ruthenium compound, for example, Ru, as a ruthenium source. ３ (CO) １２ (hereinafter also referred to as DCR) is used to fill the recess 13 of the substrate W with ruthenium. The annealing device 28 anneals the formed ruthenium layer 14. The annealing device 28 is a device capable of heating the substrate W by a heating means such as a heater.

[0013] The number and arrangement of the processing modules 101 to 103 are not limited to the example shown in Fig. 1, and the number and arrangement of each device can be set to improve the overall throughput. For example, if the ruthenium implantation process or annealing process takes time, the number of each processing module 101 to 103 installed can be changed or the modules can be arranged in appropriate positions so that the ratio of the cleaning processing module 101 and the annealing processing module 103 increases from the above-mentioned number of modules installed.

[0014] 1, in addition to the processing modules 101 to 103, the substrate processing system 1 also includes a loader module 61, a load lock module 62, first and second vacuum transfer modules 63 and 64, and a connection module 65. The loader module 61, the load lock module 62, the first vacuum transfer module 63, the connection module 65, and the second vacuum transfer module 64 are arranged linearly in the front-to-rear direction in this order in a plan view. In the following description of the substrate processing system 1, the side where the loader module 61 is located will be referred to as the front side, and the side where the second vacuum transfer module 64 is located will be referred to as the rear side.

[0015] The loader module 61 includes a housing whose interior is at atmospheric pressure, a transport mechanism 61a for substrates W provided within the housing, and load ports 68. In this example, four load ports 68 are provided side by side on the front side of the housing. A transport container C called a FOUP (Front Opening Unified Pod) for storing substrates W is placed on each load port 68. The transport mechanism 61a is formed of, for example, an articulated arm that can move left and right, and is capable of transporting substrates W between the transport container C on each load port 68 and each load lock module 62.

[0016] In this example, three load lock modules 62 are provided side by side as viewed from the front. Each load lock module 62 has a housing, and the housing is connected to the loader module 61 and the first vacuum transfer module 63 via gate valves (not shown) provided on the front and rear sides of the housing. Each load lock module 62 can freely change the pressure inside the housing between atmospheric pressure and vacuum pressure when the gate valves on the front and rear sides of the housing are closed. A stage on which a substrate W is placed is also provided within the housing. The stage has a plurality of substrate support pins that can protrude from its surface, allowing the substrate W to be transferred to and from the transfer mechanism 61a and the vacuum transfer mechanism 69 (described later), which each access the load lock module 62.

[0017] The first and second vacuum transfer modules 63 and 64 are similarly configured and each include a housing 63 a and a vacuum transfer mechanism 69 provided within the housing 63 a and 64 a. One end of an exhaust pipe (not shown) is connected to the housing 63 a and 64 a, and the inside of the housing 63 a and 64 a is evacuated by a vacuum exhaust mechanism connected via the exhaust pipe, thereby maintaining a vacuum atmosphere. The vacuum exhaust mechanism may use, for example, a turbomolecular pump, to maintain the inside of the housing 63 a and 64 a at a desired high vacuum pressure, thereby suppressing oxidation of the surface portion of the Ru film.

[0018] In this example, two connection modules 65 are provided side by side. Each connection module 65 has a housing, which is connected to the housings 63 a, 64 a of the vacuum transfer modules 63, 64. By exhausting air using the vacuum exhaust mechanism, the inside of the housing of the connection module 65 is also created into a vacuum atmosphere with the same pressure as the inside of the housings 63 a, 64 a. Each connection module 65 is provided with a stage configured similarly to the stage of the load lock module 62 described above, and is configured to be able to transfer the placed substrate W between the vacuum transfer mechanisms 69 of the first and second vacuum transfer modules 63, 64.

[0019] A cleaning process module 101 and a film formation process module 102 are provided on both the left and right sides of the housing 63a of the first vacuum transfer module 63 when viewed from the front side. The process modules 101 and 102 are connected to the housing 63a via a gate valve G1. Substrates W are transferred between these process modules 101 and 102 and the load lock module 62 by a vacuum transfer mechanism 69 formed, for example, by an articulated arm that can move back and forth and left and right. The vacuum transfer mechanism 69 also transfers substrates W between the process modules 101 and 102 and between the connection module 65 and the load lock module 62 in the same way.

[0020] When viewed from the front side of the housing 64a of the second vacuum transfer module 64, a film forming process module 102 and an annealing process module 103 are provided on both the left and right sides, respectively, of the housing 64a. The process modules 102 and 103 are connected to the housing 64a via a gate valve G1. The transfer of substrates W between these process modules 102 and 103 and the connection module 65 is performed by, for example, a vacuum transfer mechanism 69 of the second vacuum transfer module 64. The vacuum transfer mechanism 69 also transfers substrates W between the process modules 102 and 103 in a similar manner.

[0021] The substrate processing system 1 includes a control unit 200, which is a computer, and the control unit 200 includes a program. The program incorporates instructions (steps) for carrying out each of the processes in the cleaning process, film formation process, annealing process, and transportation of the substrate W described above. The program is stored in a storage medium, such as a compact disc, a hard disk, a DVD, or a nonvolatile memory, and is read from the storage medium and installed in the control unit 200.

[0022] The control unit 200 outputs control signals to each part of the substrate processing system 1 according to the program, causing each part to perform its operation. Specifically, the control unit 200 controls operations such as the operation of the processing modules 101 to 103, opening and closing of the gate valve G1 and the like, the operation of the transfer mechanism 61a and the vacuum transfer mechanism 69, the operation of the exhaust mechanism, and switching of the pressure in the load lock module 62. Examples of control of the operations of the processing modules 101 to 103 include temperature control of the substrate W by supplying power to heaters and the like, which will be described later, and control of the amount of each gas supplied to the processing vessel 2 in each of the processing modules 101 to 103, which will be described later.

[0023] Here, a description will be given of the transport path of the substrate W in the substrate processing system 1. The substrate W is first transported in the order of the transport container C → loader module 61 → load lock module 62 → first vacuum transfer module 63 → cleaning module 101. Then, the substrate W that has been cleaned in the cleaning module 101 is transported in the order of the cleaning module 101 → first vacuum transfer module 63 → film formation module 102. When the substrate W is transported to the film formation module 102 on the second vacuum transfer module 64 side, the substrate W is transported in the order of the first vacuum transfer module 63 → connection module 65 → second vacuum transfer module 64 → film formation module 102.

[0024] Then, the substrate W that has been subjected to the ruthenium embedding process in the film forming process module 102 is transferred from the film forming process module 102 to the second vacuum transfer module 64, and then transferred to the annealing process module 103. The substrate W that has been subjected to the annealing process in the annealing process module 103 is transferred in the order of the annealing process module 103 → the second vacuum transfer module 64 → the connection module 65 → the first vacuum transfer module 63 → the load lock module 62 → the loader module 61, and is returned to the transfer container C.

[0025] The configurations of the process modules 101 to 103 will be described with reference to Figure 2, which shows a longitudinal side view of the film formation process module 102 as a representative example. The film formation process module 102 includes a process vessel 2 in which a substrate W is housed and a vacuum atmosphere is formed, and a mounting table 3 provided within the process vessel 2 for mounting the substrate W. The film formation process module 102 further includes a shower head 4 provided above the process vessel 2 opposite the mounting table 3 and for supplying a process gas to the surface of the substrate W.

[0026] The mounting table 3 is formed in a flat, circular plate shape and made of, for example, aluminum nitride or quartz. A heater 31 is embedded inside the mounting table 3 to heat the substrate W to a preset temperature. The heater 31 is formed, for example, of a sheet-like resistance heating element, and is provided such that the entire surface of the heater 3 is covered by the mounting table 3. The heater 31 receives power from a power supply (not shown) to heat the substrate W placed on the mounting table 3 to a temperature in the range of 100°C to 250°C, which is the Ru film formation temperature.

[0027] The mounting table 3 is preferably covered with a cover 32. The cover 32 is a removable quartz cover member that is arranged to cover the top and side surfaces of the mounting table 3 and prevents reaction products and by-products such as ruthenium from accumulating on the surface of the mounting table 3. A circular recess having a diameter slightly larger than that of the substrate W is formed in the central region of the top surface of the cover 32, forming the mounting surface of the mounting table 3. In this manner, the mounting surface positions the substrate W to be mounted. Furthermore, the top surface of the cover 32 is provided with through holes for accommodating the heads of lifting pins 35, which will be described later.

[0028] The mounting table 3 is supported, for example, at the center of the underside of the mounting table 3 by a columnar support member 34, and the support member 34 is configured to be raised and lowered by a lifting mechanism 34 a. By raising and lowering the support member 34, the mounting table 3 is raised and lowered between a transfer position where the substrate W is transferred to and from an external wafer transfer mechanism and a processing position where the substrate W is processed.

[0029] As shown in FIG. 2, the support member 34 penetrates the bottom of the processing vessel 2, more specifically, the bottom of the lower vessel 22 described below, and is connected to the lifting plate 23 which is raised and lowered by the previously described lifting mechanism 34 a, and the lifting plate 23 and the lower vessel 22 are airtightly joined by a bellows 24.

[0030] The mounting table 3 also supports the rear surface of the substrate W and is provided with, for example, three lifting pins 35 for placing the substrate W on the mounting surface of the mounting table 3 or for raising the substrate W above the mounting surface. These lifting pins 35 vertically penetrate the mounting table 3, with their lower ends protruding downward from the mounting table 3. A ring-shaped lifting member 36 is provided below each lifting pin 35. With the mounting table 3 lowered to the substrate W transfer position, the lifting member 36 is raised and lowered to raise and lower each lifting pin 35, thereby allowing the substrate W supported by the lifting pins 35 to be placed on or raised relative to the mounting surface of the mounting table 3.

[0031] Next, the configuration of the processing vessel 2 will be described. The lower vessel 22 of the processing vessel 2 contains a lower space and is open at the top. A circular exhaust duct 21 is stacked on the opening to form the processing vessel 2. The lower vessel 22 is made of, for example, aluminum, and has a through-hole at its bottom, through which the support member 34 of the mounting table 3 passes, as described above. The lower vessel 22 also has multiple purge gas supply holes 22b around the through-hole, to which a purge gas supply mechanism 79 is connected. Therefore, a purge gas, such as nitrogen gas, supplied from the purge gas supply mechanism 79 can be supplied to the lower space of the lower vessel 22 below the mounting table 3, which is in the processing position. A loading / unloading port is provided in the sidewall of the lower vessel 22, through which the substrate W is loaded and unloaded by the vacuum transfer mechanism 69, and the loading / unloading port is provided with the gate valve G1 described above.

[0032] The exhaust duct 21 is, for example, an annular body made of aluminum, and a plurality of openings 21a are formed on the inner peripheral wall of the exhaust duct 21, opening toward the area above the mounting table 3. An exhaust pipe 29 is connected to the outer peripheral wall of the exhaust duct 21, and the processing chamber 2 is evacuated to a vacuum by a vacuum pump 29a corresponding to an exhaust unit connected to the exhaust pipe 29. A pressure control valve, for example, an APC valve (not shown), is provided on the exhaust pipe 29 upstream of the vacuum pump 29a.

[0033] The processing vessel 2 further includes an inner ring 26, which is a surrounding member that surrounds the periphery of the mounting table 3 in the processing position. The inner ring 26, together with the mounting table 3 in the installed position, divides the interior of the processing vessel 2 into an upper processing space 40 and the previously described lower space. The processing space 40 corresponds to the space "inside the processing vessel containing the substrate" in the claims. The inner ring 26 is an annular member made of, for example, aluminum, and is mounted between the inner surface of the side wall of the lower vessel 22 and the side of the cover 32. The outer periphery of the upper surface of the inner ring 26 expands to form a flange, and the inner ring 26 is positioned within the processing vessel 2 by being engaged with the bottom wall of the exhaust duct 21.

[0034] Next, the configuration of the showerhead 4 will be described. The showerhead 4 has a disk shape, with an upper portion having a larger diameter than a lower portion. The upper portion is attached to the upper portion of the inner periphery of the exhaust duct 21. An O-ring is provided between the showerhead 4 and the exhaust duct 21 to seal the processing chamber 2. The showerhead 4 is disposed opposite the mounting table 3 in the processing chamber 2, and various processing gases can be supplied to a processing space 40 between the showerhead 4 and the mounting table 3 to perform various processing operations on the substrate W. A gas diffusion space (not shown) is provided inside the showerhead 4, and the lower portion of the showerhead 4 serves as a shower plate with multiple through-holes. The showerhead 4 can uniformly release the processing gases supplied to the gas diffusion space toward the surface of the substrate W placed on the mounting table 3. An outlet hole is formed in the upper center of the showerhead 4, to which a gas supply mechanism 7 (described later) is connected.

[0035] The gas supply mechanism 7 is configured to supply various process gases to the process chamber 2. Specifically, the gas supply mechanism 7 includes a source gas supply mechanism 71 for forming a ruthenium film, an ozone gas supply mechanism 72 for supplying an etching gas and a pre-processing gas described later, a reducing gas supply mechanism 73, and a gas supply pipe 74 branched to connect each of the supply mechanisms 71 to 73 to an outlet hole at the top of the shower head 4. The source gas supply mechanism 71 includes a source gas supply source 71a for Ru (ruthenium), a flow meter 71b, and a valve V1, which are arranged in this order downstream on the branched gas supply pipe 74. The flow meter 71b detects the flow rate of the source gas supplied from the source gas supply source 71a, and the valve V1 stops the flow of the source gas. The source gas supply source 71a supplies Ru (ruthenium) with, for example, CO (carbon monoxide) gas as a carrier gas. ３ (CO) １２ (dodecacarbonyltriruthenium) gas.

[0036] The ozone gas supply mechanism 72 ２ The apparatus includes an oxygen gas supply source 72a, a flow rate regulator 72b, two valves V2a and V2b, and an ozonizer 72d. ２ The gas supply source 72a, the valve V2a, the flow rate adjusting unit 72b, the ozonizer 72d, and the valve V2b are arranged in this order in the branched gas supply pipe 74 toward the downstream.

[0037] O ２ The oxygen gas supplied from the gas supply source 72a is supplied to the ozonizer 72d after the flow rate is controlled by the flow rate adjusting unit 72b. The ozonizer 72d is configured as, for example, a silent discharge type discharge tube, and generates a discharge by applying electric energy from an external power source (not shown), thereby activating at least a part of the supplied oxygen gas to produce ozone (O ３ The ozonizer 72d can supply ozone gas at a concentration of, for example, 0 g / m by adjusting the voltage applied from an external power source. ３ to 400 g / m ３ (Based on 0°C and 101.3 kPa. The same applies to the ozone concentration below.) Therefore, the ozonizer 72d can adjust the ozone concentration to 0 g / m ３) or ozone-containing oxygen gas (ozone gas concentration 0 g / m ３ Higher than 400g / m ３ (See below) will be supplied and distributed.

[0038] In the present disclosure, the ozonizer 72d has an ozone concentration of 0 g / m ３ Above, 150g / m ３ For example, an ozone concentration in the range of 0 g / m ３ The ozonizer 72d supplies oxygen gas with an ozone concentration of 150 g / m ３ Above, 400g / m ３ For example, ozone concentration within the following range: 150 g / m ３ Ozone-containing oxygen gas is supplied as an etching gas. ２ The flow rate of the oxygen gas supplied from the gas supply source 72a to the ozonizer 72d is, for example, 400 sccm to 2000 sccm for both the pretreatment gas and the etching gas. As described above, the common ozonizer constituting the ozone gas supply mechanism 72 corresponds to the pretreatment gas supply mechanism and the etching gas supply mechanism.

[0039] Similar to the source gas supply mechanism 71, the reducing gas supply mechanism 73 includes a supply source 73a of CO gas (reducing gas), a flow rate regulator 73b, and a valve V3. Similarly to the process gas supply mechanisms 71 to 73, the gas supply mechanism 7 preferably includes an inert gas supply mechanism connected to an outlet port at the top of the shower head 4. In this case, the supplied inert gas purges the process gases to prevent the process gases from reacting with each other and depositing products. The reducing gas supply mechanism 73 also supplies CO gas together with the Ru source gas in the ruthenium film formation process, in addition to the reducing gas supply process described below. The CO gas supplied together with the source gas suppresses decomposition of the Ru source gas in the gas supply pipe 74, the shower head 4, and the process space 40, thereby suppressing the deposition of ruthenium on areas other than the substrate W.

[0040] The film forming process module 102 according to the present disclosure preferably includes a clamp ring 5 for preventing the Ru source gas from flowing around to the underside of the substrate W placed on the mounting table 3. The clamp ring 5 includes a main body 51 made of an annular plate material, and is disposed in the process chamber 2 with the underside of the main body 51 placed on the inner ring 26. The inner edge of the main body 51 extends further inward than the inner periphery of the inner ring 26, and its inner end is located above the periphery of the substrate W placed on the mounting table 3. When placed on the inner ring 26, the inner end of the main body 51 extends downward beyond the upper surface of the inner ring 26, and the lower surface of the inner end forms a flat abutment surface.

[0041] The clamp ring 5 is displaced upward with its contact surface contacting substantially the entire periphery of the substrate W on the mounting table 3 as it moves to the processing position, and is lifted from the inner ring 26. When the mounting table 3 descends to the transport position, the clamp ring 5 is supported by the inner ring 26 and moves away from the periphery of the substrate W on the mounting table 3. The clamp ring 5 has a weight, for example, a weight of several hundred grams to several kilograms, sufficient to prevent the intrusion of reaction gas by pressing the contact surface against the substrate W on the mounting table 3.

[0042] A cylindrical wall portion 54 formed in a cylindrical shape along the circumferential direction of the clamp ring 5 is provided on the underside of the main body portion 51. The cylindrical wall portion 54 is disposed between the mounting table 3 located at the processing position and the inner ring 26. A plurality of positioning protrusions 53 are provided on the underside of the main body portion 51. The clamp ring 5 is placed at the mounting position on the inner ring 26 by arranging the protrusions 53 in recesses provided on the upper surface of the inner ring 26. The clamp ring 5 is made of a metal such as aluminum or a ceramic such as alumina.

[0043] In the film forming module 102, the mounting table is heated to, for example, 155° C. or 180° C., and the inside of the processing space 40 is set to, for example, 2.21 Pa (16.6 mTorr).

[0044] The following briefly describes the structures of the cleaning module 101 and the annealing module 103, focusing on the differences from the film forming module 102. As shown in FIG. 2, the gas supply mechanism of the cleaning module 101 is ２ Equipped with a gas supply mechanism and a purge gas supply mechanism. ２ The gas supply mechanism is the same as the reducing gas supply mechanism 73, and supplies H ２ It is composed of a gas supply source, a flow rate regulator, and a valve, and the purge gas supply mechanism is similarly composed. ２ The processing vessel and the stage of the cleaning processing module 101 that supplies the gas plasma are both grounded. The shower head is attached to the processing vessel via a ring-shaped insulating member and is connected to a high-frequency power supply via a matcher to function as an upper electrode. The matcher matches the internal impedance of the high-frequency power supply with the load impedance. The high-frequency power supply is connected to the H gas supplied by the gas supply mechanism described above. ２ Electric power having a preset frequency is applied to the shower head so as to convert the gas into plasma. The mounting table 3 is provided at the bottom of the processing chamber via an insulating member and functions as a lower electrode.

[0045] The cleaning module 101 described above is configured to remove H ２ The gas is converted into plasma and supplied to the substrate W. The processing modules 101 and 103 do not need to be provided with an inner ring, exhaust duct, or purge gas supply hole that separates the space below the mounting table from the processing space. In this case, the processing modules 101 and 103 are configured such that an exhaust hole is provided at the bottom of the processing vessel, an exhaust mechanism is connected to the exhaust hole, and the entire interior of the processing vessel is evacuated.

[0046] The gas supply mechanism of the annealing module 103 is, for example, N ２ The apparatus is provided with an inert gas supply mechanism for supplying an inert gas such as gas.

[0047] In the substrate processing system 1 of the present disclosure having the above-described configuration, cleaning of the metal oxide film formed on the surface of the substrate W, embedding of ruthenium, and annealing are performed. This series of processes will be described with reference to FIGS. 1 and 2. The first and second vacuum transfer modules 63 and 64 are previously conditioned to a vacuum atmosphere at a preset pressure, and in the processing modules 101 to 103, the pressure inside the processing chamber 2 is adjusted to the preset vacuum atmosphere by the exhaust mechanism. Then, in each of the processing modules 101 to 103, the mounting table 3 is preheated to, for example, 200° C.

[0048] 3A is a longitudinal side view illustrating the central and peripheral sides of the surface of a substrate W before a series of processes, showing the recesses 13 on the central side and the recesses 13 on the peripheral side. As shown in the figure, the surface of the substrate W before a series of processes includes a metal layer 11, which is a tungsten layer, and an insulating layer 12, such as a silicon oxide film, formed on the metal layer 11. A plurality of recesses 13 are formed in the insulating layer 12 by etching. The recesses 13 are provided to embed a ruthenium layer 14, which is a wiring layer, and open to the surface of the substrate W. The recesses 13 are elongated, their width narrowing downward, and their bottoms are formed by the metal layer 11. Specifically, a tungsten oxide film (not shown) oxidized by the atmosphere or the like is exposed at the bottom of the recesses 13.

[0049] For this purpose, first, in the cleaning processing module 101, the oxide film of the metal layer 11 constituting the bottom surface of the recess 13 is removed by plasma H ２The oxide film on the metal layer 11 is removed by gas. The substrate W, from which the oxide film on the metal layer 11 has been removed, is then transported toward the film formation module 102. The gate valve G1 of the film formation module 102 shown in FIG. 2 is then opened, and the substrate W is loaded into the processing chamber 2 through the loading port by the vacuum transfer mechanism 69, and the substrate W is transferred to the mounting table 3 at the transfer position. The vacuum transfer mechanism 69 then leaves the processing chamber 2, and the gate valve G1 is closed. The mounting table 3 is then moved to the processing position, and the clamp ring 5 is positioned so that its contact surface contacts the entire peripheral edge of the substrate W. The clamp ring 5 prevents a Ru film from being formed on the peripheral edge or backside of the substrate W when thermal CVD is subsequently performed. After the clamp ring 5 is positioned in this manner, the substrate W is heated by the mounting table 3 to the aforementioned film formation temperature, and various process gases are supplied to the processing space 40 to perform processes such as film formation.

[0050] Before describing the details of the ruthenium filling method of the present disclosure, a ruthenium filling method according to a comparative embodiment will be described. Figures 3B to 3D are longitudinal sectional side views showing changes in the surface layer of a substrate W subjected to the ruthenium filling method of the comparative embodiment. Figures 3A and 3B show the process of changes in the surface layer of a substrate W that is common to the comparative embodiment described using Figures 3B to 3D and the ruthenium filling method of the present disclosure described using Figures 6A to 6D.

[0051] When the substrate W reaches a predetermined heating temperature, the Ru source gas, CO gas, and inert gas are supplied from the gas supply mechanism 7 into the processing space 40 while adjusting the pressure inside the processing vessel 2. Note that a purge gas is continuously supplied to the lower space of the processing vessel 2 from a purge gas supply mechanism 79.

[0052] As a result, the Ru source gas decomposes on the heated surface of the substrate W, and a ruthenium film is formed on the surface of the substrate W by thermal CVD. At this time, ruthenium is deposited on the bottom and side of the recess 13 ( FIG. 3B ). Specifically, on the bottom side of the recess 13, ruthenium is deposited from the bottom surface side of the recess 13 upward (bottom-up) to form a ruthenium layer (ruthenium layer) 14a. Furthermore, side-side ruthenium 14b is deposited in an island shape on the side surface of the recess 13. Note that FIG. 3B omits the illustration of the Ru film deposited on the surface region of the substrate W other than the recess 13.

[0053] Next, an etching gas is supplied to prevent the opening of the recess 13 from being blocked and creating a void due to an increase in thickness caused by further deposition of the side ruthenium 14b (FIG. 3C). Here, in the filling of ruthenium according to the comparative example, as described above, ozone generated by the ozonizer 72d, for example, at a concentration of 150 g / m ３ As a result, the surface portion of the bottom-side ruthenium layer 14a and the side-side ruthenium layer 14b react with the ozone gas to form volatile RuO ４ (ruthenium tetroxide), which is then removed by being exhausted by the vacuum pump 29a. In Fig. 3C, the surface of the bottom-side ruthenium layer 14a before the supply of the etching gas is indicated by a broken line.

[0054] After the etching gas is supplied, the surface portion of the remaining bottom-side ruthenium layer 14a reacts with the ozone gas and oxygen gas to form ruthenium oxide (RuO ２ : ruthenium dioxide) 14c. ２ The gas does not have the effect of etching ruthenium, but oxidizes ruthenium to form RuO ２ To do so.

[0055] The ruthenium filling process is completed by repeating the above-described cycle of film formation and etching a predetermined number of times ( FIG. 3D ). With regard to the ruthenium filling method according to the comparative embodiment described above, the inventors noticed that the filling height of the ruthenium layer 14 filled in the recess 13 was sometimes non-uniform. That is, the ruthenium layer 14 in the recess 13 became higher from the center toward the periphery of the substrate W, and was not uniform across the surface of the substrate W. After investigating the cause of this non-uniform filling state, the inventors focused on the difference in the etching rate of ruthenium by ozone gas.

[0056] The first factor causing the difference in etching rate is thought to be the influence of temperature differences within the surface of the substrate W. Generally, when etching metals with an etching gas, the etching rate tends to be higher under high-temperature conditions and lower under low-temperature conditions. In the film formation module 102 configured as shown in FIG. 2 , a cover 32 and a clamp ring 5 are attached to the periphery of the mounting table 3 in which the heater 31 is embedded. Therefore, the periphery of the mounting table 3 has a higher heat capacity than the central portion. Therefore, heat supplied from the heater 31 is also transferred to these components 32 and 5, and the temperature of the mounting table 3 tends to be lower on the periphery than on the central portion. As a result, the temperature of the substrate W also tends to be lower on the periphery than on the central portion. It is speculated that the influence of such a temperature distribution of the substrate W may have caused the etching rate of the surface of the bottom-side ruthenium layer 14 a to decrease from the central portion to the periphery of the substrate W in the comparative example ( FIG. 3C ).

[0057] A second possible factor is the difference in the concentration of ozone gas in the etching gas uniformly supplied within the surface. In thermal CVD, ruthenium also deposits on the clamp ring 5, which is arranged to cover the peripheral portion of the substrate W. Therefore, when etching gas is supplied, the Ru film deposited on the clamp ring 5 also consumes ozone gas in the etching gas. Therefore, it is presumed that the ozone gas concentration in the etching gas supplied within the surface of the substrate W is lower on the peripheral side of the substrate W adjacent to the clamp ring 5. From the above, it is considered that the etching rate of the surface of the bottom-side ruthenium layer 14a is lower on the peripheral side of the substrate W ( FIG. 3C ).

[0058] A third possible cause is the difference in etching rate between the unoxidized bottom-side ruthenium layer 14a and the ruthenium oxide layer 14c. Figure 4 is a graph showing the change in the amount of ruthenium etched versus the etching gas supply time. Figure 4 shows the change in the amount of ruthenium etched versus the etching gas supply time. When an ozone concentration of 300 g / m was applied to a bare wafer with a uniform Ru film formed on its surface, ３ , 150 g / m ３ The etching amount was measured at each time point when the etching gas was supplied. As shown in Figure 4, for each ozone concentration, the etching rate was relatively high immediately after the start of the etching gas supply, and as time passed from the start of the supply, the etching amount approached a constant value and then decreased. Furthermore, the higher the ozone concentration, the greater the etching amount during the period when the etching rate was high. As a result, during the period when the etching rate was high immediately after the start of the etching gas supply, the difference in etching amount between the center and the periphery of the substrate W became significant. The third factor is thought to be the large difference in etching amount between the center and the periphery immediately after the start of the etching gas supply due to the influence of the temperature difference and the etching gas concentration difference, which were considered as the first and second factors.

[0059] The etching rate immediately after the start of etching, which was explained as the third factor here, is thought to be significantly affected by the surface condition of Ru. Specifically, the surface of the Ru film before the start of etching is mostly unoxidized ruthenium. Therefore, the etching rate of unoxidized ruthenium is relatively high. On the other hand, after the start of etching, ruthenium oxide 14c (FIG. 3C) is formed on the surface of the Ru film by the etching gas. This ruthenium oxide 14c is converted into RuO by the ozone gas in the etching gas. ４ Therefore, in the ruthenium filling method of the present disclosure, a pretreatment is performed to convert the surface of the bottom-side ruthenium layer 14a into ruthenium oxide 14c over the entire surface of the substrate W, using low-concentration ozone gas, which has a low etching rate immediately after the start of gas supply, as shown by the arrows in Figure 4 before the supply of etching gas.

[0060] The ruthenium filling process of the present disclosure involves a multiple-cycle repetition of a film formation process (step (a)), a pretreatment process (step (b)), and an etching process (step (c)) in the film formation process module 102. This process will be described with reference to FIG. 5 , which shows a flowchart of the ruthenium filling process of the present disclosure. In the ruthenium filling process of the present disclosure, the substrate W is first placed on the mounting table 3 (step S1), and the mounting table 3 is placed in the processing position. After that, the first film formation cycle is performed. Specifically, as in the comparative example, as shown in FIG. 3B , various gases are supplied based on a film formation recipe to form a ruthenium layer 14 a in the recess 13 (step S2, ruthenium layer formation process). Next, the processing chamber 2 is purged by a purge gas supply mechanism (not shown) provided in the gas supply mechanism 7, and the processing space 40 is preferably set to, for example, 133.3 Pa (1 Torr) for pretreatment.

[0061] Next, as shown in FIG. 6A, a pretreatment gas is supplied by an ozone gas supply mechanism 72 to pretreat the bottom-side ruthenium layer 14a (step S4, a step of pretreating the ruthenium layer). As discussed with reference to FIG. 4, when the ozone concentration is 0 g / m ３ Above, 150g / m３ The pretreatment gas in the range of less than 150 g / m ３ Above, 400g / m ３ The etching rate immediately after the start of gas supply is relatively small (ozone concentration is 0 g / m) compared with the etching gases in the following ranges: ３ (The pretreatment gas in this range does not have the ability to etch ruthenium.) On the other hand, ozone-containing oxygen gas in this concentration range has the ability to oxidize ruthenium. Therefore, a pretreatment is performed using the pretreatment gas to oxidize the surface side of the bottom-side ruthenium layer 14a and the side-side ruthenium 14b to form ruthenium oxide 14c. Then, as shown in FIG. 6B , an etching gas is supplied by the ozone gas supply mechanism 72 to remove the side-side ruthenium 14b and the surface side of the bottom-side ruthenium layer 14a (step S5, etching a portion of the ruthenium layer). Because the side-side ruthenium 14b and the surface side of the bottom-side ruthenium layer 14a are already ruthenium oxide 14c before the supply of the etching gas, the etching rate is low from the start of the supply of the etching gas. Therefore, the difference in etching rate due to the first to third factors described above can be suppressed in the bottom-side ruthenium layer 14a located at the center and peripheral sides of the substrate W, and the etching amount can be made uniform across the surface of the substrate W.

[0062] Furthermore, even if all of the portions corresponding to ruthenium oxide 14c formed before etching have been removed, the etching gas removes the exposed bottom-side ruthenium layer 14a while sequentially oxidizing it. At this stage, the heating state of the substrate W has reached a steady state, the temperature difference within the surface has become small, and the amount of Ru deposited on the surface of the clamp ring 5 has also become small. Therefore, in this etching process, the difference in etching rate between the central side and the peripheral side of the substrate W, as described above, is reduced. Here, the pretreatment is performed for, for example, about 5 to 600 seconds, as long as it is possible to cover the surface side of all of the bottom-side ruthenium layer 14a with ruthenium oxide 14c.

[0063] After the etching gas supply is completed, the processing chamber 2 is purged by a purge gas supply mechanism (not shown) provided in the gas supply mechanism 7 (step S6), and a reducing gas is supplied by the reducing gas supply mechanism 73 (step S7, FIG. 6C ; a step of supplying a reducing gas; step (d)). As a result, the ruthenium oxide 14c on the surface side of the bottom-side ruthenium layer 14a is reduced to form an unoxidized bottom-side ruthenium layer 14a. Because the ruthenium oxide 14c increases the electrical resistance, it is preferable to perform a reduction process to improve the electrical characteristics of the ruthenium layer 14 after the filling is complete. After the reducing gas is supplied, the processing chamber 2 is purged (step S8), completing the first cycle of the ruthenium filling process. Next, the control unit 200 determines whether the number of cycles reaches a target number preset in the film formation recipe (step S9). The control unit 200 repeats the cycle until it determines that the target number of cycles has been reached, and the filling of the recess 13 with the ruthenium layer 14 is completed ( FIG. 6D ). Each of the ruthenium layers 14 after the filling is completed is connected to the metal layer 11 .

[0064] As described above, according to the ruthenium filling method of the present disclosure, after the formation of the bottom-side ruthenium layer 14a and before the supply of the etching gas, a pretreatment gas is supplied to uniformly convert the surface side of the bottom-side ruthenium layer 14a into ruthenium oxide 14c. This reduces the etching rate immediately after the supply of the etching gas and stabilizes the etching rate. This reduces the significant difference in etching amount between the center and peripheral sides of the bottom-side ruthenium layer 14a in the comparative example, and suppresses the difference in the filling height of the ruthenium layer 14 filled in the recess 13.

[0065] (Modifications) The surface shape of the substrate is not limited to that shown in the present disclosure. For example, the metal layer 11 connected to the ruthenium layer 14 is not limited to a tungsten layer, but may be a metal-containing layer containing other metals. The metal-containing layer may be a layer containing, for example, Si (silicon) or Ge (germanium). The insulating layer 12 may be an insulating layer other than silicon oxide, for example, silicon nitride (Si ３ N ４ ) layer may also be used.

[0066] The pretreatment gas disclosed in the present disclosure is an ozone gas having an ozone gas concentration of 0 g / m ３ However, the present invention is not limited to this, and may include, for example, oxygen gas or ozone gas, and the ozone gas concentration is 0 g / m ３ Above, 150g / m ３ As described above, the pretreatment gas may have an ozone gas concentration of 0 g / m ３ Even if the ozone concentration is 0 g / m, it is sufficient that oxygen gas is contained. ３ If it is higher, it may not contain oxygen, but may contain other gases, such as inert gases.

[0067] The etching gas of the present disclosure is an ozone gas having a concentration of 150 g / m ３ However, the present invention is not limited to this. The etching gas contains ozone gas, and the ozone gas concentration is, for example, 150 g / m ３ Above, 400g / m ３ Therefore, the etching gas does not have to be an ozone-containing oxygen gas, that is, it does not have to contain oxygen gas, as long as the ozone gas concentration is within this range. Such an etching gas that does not contain oxygen gas may contain other gases, such as an inert gas. If the inert gas is, for example, N ２ If NO reacted with ozone gas, ２ (Nitrogen dioxide) gas may be supplied as the etching gas.

[0068] The ozone gas supply mechanism 72 in the film forming module 102 includes, but is not limited to, a silent discharge ozonizer 72d that generates plasma as described above. For example, instead of the ozonizer 72d, an ozone generator using a chemical method, an electric field method, an ultraviolet method, or the like may be used as long as it can supply pretreatment gas and etching gas with the various ozone concentrations described above. Furthermore, while it is preferable that the film forming module 102 be provided with one ozonizer 72d as in the present disclosure, two or more ozonizers 72d may be provided. When two ozonizers 72d are provided, one ozonizer 72d may supply pretreatment gas and the other ozonizer 72d may supply etching gas.

[0069] Furthermore, it is preferable, but not essential, that the pretreatment gas be supplied by the ozone gas supply mechanism 72 together with the etching gas in terms of simplifying the equipment and improving processing efficiency. For example, the pretreatment gas may be a gas containing ozone gas or oxygen gas supplied by the ozonizer 72d, or another gas having an oxidizing power capable of sufficiently oxidizing the surface side of the bottom-side ruthenium layer 14a, such as H ２ The reducing gas supply source 73a of the reducing gas supply mechanism 73 is not limited to CO gas, and may be any gas that can sufficiently reduce the ruthenium oxide 14c on the surface of the bottom-side ruthenium layer 14a, such as H ２ Other reducing gases such as CO gas and H ２ The gases may be supplied simultaneously or alternately.

[0070] In the above-described example, a case where "film formation step (a) → pretreatment step (b) → etching step (c) → reduction step (d)" is performed in this order in each cycle (hereinafter also referred to as a "first cycle example"). It should be noted that a cycle in which each step is performed in the order of "reduction step (d) → film formation step (a) → pretreatment step (b) → etching step (c)" (also referred to as a "second cycle example") is also conceivable. However, the second cycle example is essentially the same as the first cycle example, except for the first and last cycles. Alternatively, for example, the reduction step (d) may be performed first before the pretreatment step (b) in each cycle, such as "film formation step (a) → reduction step (d) → pretreatment step (b) → etching step (c)." In this case, the surface of the ruthenium layer 14 after the film formation step (a) is reduced with a reducing gas, and then oxidized with a pretreatment gas, thereby enabling the surface to be oxidized more uniformly, which is effective in reducing the difference in etching amount. Furthermore, if there is no particular problem with the electrical characteristics of the ruthenium layer 14, it is not necessary to supply a reducing gas in this cycle.

[0071] The inner ring 26 or the clamp ring 5 may be fitted with a sheath heater for preheating the clamp ring 5. In this case, the aforementioned temperature drop on the peripheral side of the substrate W can be suppressed, and the difference in the amount of etching on the front surface of the bottom-side ruthenium layer 14a between the central side and the peripheral side can be further reduced. Alternatively, the clamp ring 5 may not be provided, and an electrostatic chuck may be provided on the upper surface of the mounting table 3. This allows the back surface of the substrate W to be tightly attached to the mounting table 3 by electrostatic attraction, preventing gas from seeping in.

[0072] The mounting table 3 of the film forming module 102 was set to 155°C or 180°C, which allows for good ruthenium embedding, but this is not limiting. In each cycle including ruthenium film formation, pretreatment, and etching, the temperature may be set in the range of 100°C to 250°C, and may be changed appropriately within this range. In each cycle, the pressure in the processing space 40 was set to 0.13 to 2666 Pa (1.0×10 －３ In particular, the pressure in the processing space 40 of the film forming module 102 is set to 133.3 Pa (1 Torr) in the pre-processing step, but may be changed appropriately within a range of, for example, 6.7 to 400 Pa (0.05 to 3 Torr) throughout the pre-processing step and the etching step.

[0073] In the substrate processing system 1 of the present disclosure, the pre-processing and etching processes are performed in the film forming process module 102, but they may also be performed in other process modules. Furthermore, a process module for performing the pre-processing and a process module for performing the etching process may be provided separately. In addition to the processes described above, the substrate processing system 1 may also perform, for example, a process for removing gaseous components contained in the substrate W (for example, H in the air adsorbed on the surface of the loaded substrate W) before the cleaning process. ２The substrate processing system 1 may be configured to perform a degassing process to release oxygen (O) from the substrate W. In this case, for example, a degassing process module configured to heat the substrate W in a vacuum atmosphere may be newly provided, or the degassing process may be performed in the annealing process module 103 or the load lock module 62. Furthermore, it is not essential that the first and second vacuum transfer modules 63, 64 and the connection module 65 are provided in the substrate processing system 1. For example, the second vacuum transfer module 63 and the connection module 65 may not be provided, and the process modules 101 to 103 may be arranged around the first vacuum transfer module 63.

[0074] (Experiment) In order to confirm the in-plane etching uniformity in the ruthenium filling method of the present disclosure, a comparative example in which the etching shown in the comparative example described above was performed and an example in which the pretreatment and etching shown in the embodiment were performed were performed, and the etching amount was confirmed.

[0075] A. Experimental Conditions Two flat bare wafers were prepared, each with an unpatterned, uniform ruthenium layer of the same thickness formed on its surface. The surface of the bare wafer to be treated in the example was subjected to four cycles of the pretreatment of the example, 60 seconds of etching gas supply, and reduction gas supply, in that order. The surface of the bare wafer to be treated in the comparative example was not subjected to pretreatment, and the etching gas supply and reduction gas supply were performed three times under the same conditions as in the example. For each bare wafer that had undergone the above treatment, the amount of ruthenium etched at the same radial position was measured.

[0076] B. Experimental Results Figure 7 is a graph showing the experimental results, specifically, the measurement results of the etching amount at each position on the same radius for each substrate on which the experiments of the comparative example and the example were performed. In the figure, the center-to-center distance of 0 nm indicates the center of the surface of the substrate, and the center-to-center distance of 150 nm indicates the peripheral edge of the surface of the substrate.

[0077] As shown in Figure 7, the etching amount of the comparative substrate was greatest at the center and decreased toward the periphery. From the data, the NU (within wafer non-uniformity) of the comparative substrate, which indicates the etching uniformity within the wafer, was calculated as the standard deviation / average value of the etching amount at each preset measurement point within the wafer, and was found to be 3.7%.

[0078] In the substrate of the example, the etching amount at each radial position was close to the etching amount at the central position, and did not decrease as it moved from the center to the periphery. The NU of the etching in the example was calculated in the same way as in the comparative example and was 1.4%, which indicated that etching was more uniform within the surface than in the comparative example. From the above experimental results, it was considered that the ruthenium filling method of the present disclosure can make the etching amount by the subsequent etching uniform within the surface by performing pretreatment, and can make the filling height of ruthenium uniform.

[0079] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made to the above-described embodiments without departing from the scope and spirit of the appended claims.

[0080] W substrate 13 recess 14a bottom side ruthenium layer 2 processing vessel

Claims

1. A method for embedding ruthenium in a substrate having a recess, comprising: (a) supplying a source gas containing a ruthenium compound into a processing vessel containing the substrate to form a ruthenium layer in the recess; and (b) supplying oxygen gas or ozone gas into the processing vessel, the source gas containing the ruthenium compound, and the ozone concentration being 0 g / m or less. ３ Above, 150g / m ３ (c) supplying a pretreatment gas containing ozone gas into the treatment vessel, the pretreatment gas having an ozone concentration of 150 g / m or less (based on 0°C and 101.3 kPa; the same applies hereinafter to ozone concentration), to perform pretreatment of the ruthenium layer; ３ Above, 400g / m ３ and etching a portion of the ruthenium layer by supplying the following etching gas, wherein the cycle of steps (a), (b), and (c) is repeated in this order.

2. The method according to claim 1, further comprising the step of (d) supplying into the processing vessel a reducing gas that reduces the ruthenium layer oxidized by supplying the pretreatment gas or the etching gas, and the step (d) is carried out before the step (b) or after the step (c) in the cycle.

3. The method of claim 2, wherein the reducing gas comprises at least one of hydrogen gas or carbon monoxide gas.

4. The method of claim 1, wherein in said cycle, said substrate is heated to a temperature in the range of 100 to 250°C.

5. The method according to claim 1, wherein the pressure inside the processing vessel is adjusted to a range of 0.13 to 2666 Pa in the cycle.

6. An apparatus for embedding ruthenium in a substrate having a recess, comprising: a processing vessel for accommodating the substrate; a source gas supply mechanism for supplying a source gas containing a ruthenium compound into the processing vessel; and a gas supply mechanism for supplying oxygen gas or ozone gas into the processing vessel, the gas supply mechanism containing oxygen gas or ozone gas, the ozone concentration of which is 0 g / m or less. ３ Above, 150g / m ３ a pretreatment gas supply mechanism for supplying a pretreatment gas containing ozone gas and having an ozone concentration of 150 g / m or less to the treatment vessel; ３ Above, 400g / m ３ an etching gas supply mechanism that supplies the following etching gases; and a control unit, wherein the control unit is configured to output a control signal to repeatedly execute a cycle of the following steps, which are executed in this order: (a) supplying the source gas into the processing vessel that accommodates the substrate to form a ruthenium layer in the recess; (b) supplying the pretreatment gas into the processing vessel to pretreatment the ruthenium layer; and (c) supplying the etching gas into the processing vessel to etch a portion of the ruthenium layer.

7. The apparatus according to claim 6, further comprising: a reducing gas supply mechanism that supplies a reducing gas to the processing vessel, and the cycle includes, before step (b) or after step (c), a step (d) of supplying the reducing gas into the processing vessel to reduce the ruthenium layer that has been oxidized by the supply of the pretreatment gas or the etching gas.

8. The apparatus of claim 7, wherein the reducing gas includes at least one of hydrogen gas or carbon monoxide gas.

9. The apparatus described in claim 6, wherein the mounting table is configured to be able to move up and down between a processing position and a transfer position below the processing position where substrates are transferred to and from the outside, and comprises: an enclosing member that is arranged to surround the mounting table at the processing position and divides the inside of the processing vessel into an upper processing space and a lower space; an exhaust unit that evacuates the processing space; and a clamp ring that is placed on the enclosing member when the mounting table is at the transfer position and is raised from the enclosing member when the mounting table is at the processing position, and whose inner edge abuts against the entire periphery of the substrate on the mounting table to prevent reaction gas from flowing around to the back side of the substrate.

10. The apparatus according to claim 6, wherein the pretreatment gas supply mechanism and the etching gas supply mechanism are configured as a common ozone gas supply mechanism, and the ozone gas supply mechanism includes an ozonizer configured to separately supply the pretreatment gas and the etching gas by adjusting the ozone concentration.

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