Method of removing titanium oxide film and substrate processing apparatus

Abstract

To remove a titanium oxide film provided on the surface of a substrate.SOLUTION: A method of removing a titanium oxide film on a surface of a substrate includes supplying a mixed gas containing a hydrogen fluoride gas and an ammonia gas to a surface of the titanium oxide film to cause a chemical reaction between the titanium oxide film and the mixed gas, thereby generating a gaseous reaction product from the titanium oxide film and removing the gaseous reaction product from the surface of the substrate, and heating the substrate to remove a deposit adhering to the substrate when the reaction product is generated.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a method for removing titanium oxide films and a substrate processing apparatus. [Background technology]

[0002] The manufacturing process of a semiconductor device includes a step of forming a metal film as a wiring layer on the upper side of a layer containing a metal such as TiN (titanium nitride) or W (tungsten) on a semiconductor wafer (hereinafter referred to as "wafer"), which is a substrate. When forming such a metal film, an oxide film may be formed in the lower metal-containing layer at a portion that forms a contact with the wiring layer. Because such an oxide film increases contact resistance, a process of removing the oxide film may be required.

[0003] For example, Patent Document 1 describes a method in which HF (hydrogen fluoride) gas and NH3 (ammonia) gas are supplied to an SiO2 film to generate ammonium silicofluoride ((NH4)2SiF6, AFS) as a reaction product, and the AFS is sublimated by heating to etch the SiO2 film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-180281 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique capable of removing a titanium oxide film formed on the surface of a substrate. [Means for solving the problem]

[0006] The method for removing a titanium oxide film on a surface of a substrate according to the present disclosure includes the steps of: supplying a mixed gas containing hydrogen fluoride gas and ammonia gas to the surface of the titanium oxide film, causing a chemical reaction between the titanium oxide film and the mixed gas, and generating a gaseous reaction product from the titanium oxide film and removing the gaseous reaction product from the surface of the substrate; and heating the substrate to remove any deposits that may have adhered to the substrate during the generation of the reaction product. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to remove a titanium oxide film formed on the surface of a substrate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view illustrating a substrate processing apparatus according to a first embodiment. [Figure 2] FIG. 2 is a vertical sectional side view showing a COR processing module of the substrate processing apparatus. [Figure 3] FIG. 2 is a vertical sectional side view showing a PHT processing module of the substrate processing apparatus. [Figure 4A] FIG. 2 is a diagram showing a surface layer of a substrate that changes due to processing in the first embodiment. [Figure 4B] FIG. 2 is a diagram showing a surface layer of a substrate that changes due to processing in the first embodiment. [Figure 4C] FIG. 2 is a diagram showing a surface layer of a substrate that changes due to processing in the first embodiment. [Figure 4D] FIG. 2 is a diagram showing a surface layer of a substrate that changes due to processing in the first embodiment. [Figure 5] FIG. 1 is a diagram illustrating a chemical reaction caused by a mixed gas. [Figure 6] 1 is a graph showing the vapor pressure of TiF4 and NH4F. [Figure 7A] 10A and 10B are diagrams showing the surface layer of the substrate that changes due to oxide film removal in the second embodiment. [Figure 7B] 10A and 10B are diagrams showing the surface layer of the substrate that changes due to oxide film removal in the second embodiment. [Figure 7C] 10A and 10B are diagrams showing the surface layer of the substrate that changes due to oxide film removal in the second embodiment. [Figure 8] 1 is a graph showing the atomic composition percentages of various elements in the wafer of Example 1. [Figure 9] 1 is a first graph for comparing the results of Experiment 1. [Figure 10] 2 is a second graph for comparing the results of Experiment 1. [Figure 11] 10 is a graph for comparing the results of Experiment 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment)

[0010] 1 illustrates a substrate processing apparatus according to a first embodiment. The substrate processing apparatus 1 is a multi-chamber system including a plurality of processing modules 101, 102, and 103 configured to perform a film formation process for forming a Ru (ruthenium) film as a metal film that will become a wiring layer on a substrate W. The processing module 103 is a Ru film formation processing module for forming the Ru film, and the processing modules 101 and 102 are processing modules for removing a Ti (titanium) oxide film formed on the surface of the substrate W as a pre-processing for the Ru film formation. The structure of the surface layer of the substrate W to be processed will be described later with reference to FIGS. 4A to 4D.

[0011] The processing module 101 is configured to perform a COR (Chemical Oxide Removal) process to remove a Ti (titanium) oxide film from the surface of the substrate W. Specifically, a mixed gas containing HF (hydrogen fluoride) gas and NH3 (ammonia) gas is supplied to the substrate W. The Ti oxide film chemically reacts with the mixed gas to become a gaseous reaction product, which is then removed from the substrate W. The processing module 102 performs a PHT (Post Heat Treatment) process to heat the substrate W to remove deposits that adhere to the substrate W when the reaction product is generated. Hereinafter, the processing modules 101, 102, and 103 may also be referred to as the COR processing module 101, the PHT processing module 102, and the Ru film formation processing module 103.

[0012] 1, in addition to the processing modules 101 to 103, the substrate processing apparatus 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 apparatus 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.

[0013] 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 left and right side of 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.

[0014] 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 inside the housing. The stage has a plurality of substrate support pins that can protrude from its surface, and is configured to be able to transfer the substrate W to and from the transfer mechanism 61a and the vacuum transfer mechanism 69 (described later), which each access the load lock module 62.

[0015] The first and second vacuum transfer modules 63, 64 are similarly configured and each include a housing 63a, 64a and a vacuum transfer mechanism 69 provided in the housing 63a, 64a. One end of an exhaust pipe is connected to the housing 63a, 64a, and the inside of the housing 63a, 64a is evacuated by a vacuum exhaust mechanism connected via the exhaust pipe, thereby maintaining a vacuum atmosphere. The vacuum exhaust mechanism uses, for example, a turbo molecular pump to create a high vacuum (for example, 1.33×10) inside the housing 63a, 64a. ―5 Pa(1×10 ―7 By keeping the pressure lower than (less than) Torr, oxidation of the base before the Ru film is formed may be suppressed.

[0016] In this example, two connection modules 65 are provided side by side. Each connection module 65 has a housing, and the housing is connected to the housings 63a, 64a 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 made into a vacuum atmosphere with the same pressure as the inside of the housings 63a, 64a. 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.

[0017] When viewed from the front side of the housing 63a of the first vacuum transfer module 63, a COR processing module 101 and a PHT processing module 102 are provided on both the left and right sides, respectively, arranged side by side. Each of the COR and PHT processing modules 101 and 102 is connected to the housing 63a via a gate valve G1. The transfer of substrates W between these COR and PHT processing modules 101 and 102 and the load lock module 62 is performed by a vacuum transfer mechanism 69 constituted by, for example, an articulated arm that can move back and forth and left and right. The vacuum transfer mechanism 69 similarly transfers substrates W between the COR and PHT processing modules 101 and 102, and also transfers substrates W from the connection module 65 to the load lock module 62.

[0018] Two Ru film formation modules 103 are arranged side by side on the left and right sides of the housing 64a of the second vacuum transfer module 64 when viewed from the front side. Each Ru film formation module 103 is connected to the housing 64a via a gate valve G1. The substrate W is transferred between these Ru film formation modules 103 and the connection module 65 by, for example, a vacuum transfer mechanism 69 of the second vacuum transfer module 64.

[0019] The substrate processing apparatus 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 above-described processes of removing an oxide film from the substrate W, heating, forming a film, and transporting the substrate W. 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.

[0020] The control unit 200 outputs control signals to each part of the substrate processing apparatus 1 according to the program, and controls the operation of each part. Specifically, the control unit 200 controls 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. The control of the operation of the processing modules 101 to 103 includes, for example, temperature control of the substrate W by supplying power to a heater or the like (to be described later), control of the power supplied by a high-frequency power supply (to be described later), and control of the supply and cut-off of each gas into the processing vessel 51.

[0021] Here, we will explain the transport path of the substrate W in the substrate processing apparatus 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 → COR processing module 101. Then, the substrate W that has undergone COR processing in the COR processing module 101 is transported in the order of the COR processing module 101 → first vacuum transfer module 63 → PHT processing module 102.

[0022] Then, the substrate W that has undergone the PHT treatment in the PHT treatment module 102 is transported in the order of the PHT treatment module 102 → first vacuum transfer module 63 → connection module 65 → second vacuum transfer module 64 → Ru film formation treatment module 103. The substrate W that has undergone Ru film formation in the Ru film formation treatment module 103 is transported in the order of the Ru film formation treatment module 103 → second vacuum transfer module 64 → connection module 65 → first vacuum transfer module 63 → load lock module 62 → loader module 61, and is returned to the transfer container C.

[0023] The configurations of the processing modules 101 to 103 will be described with reference to Fig. 2 and Fig. 3, which show longitudinal side views of representative COR processing module 101 and PHT processing module 102. Regarding the configuration of the common parts, the processing modules 101 to 103 each include a processing vessel 51 that is evacuated to create a vacuum atmosphere inside, a shower head 52 provided at the top of the processing vessel 51, and a substrate mounting table 53 provided within the processing vessel 51.

[0024] The shower head 52 is disposed in the processing chamber 51 so as to face the substrate mounting table 53, and its interior forms a gas diffusion space (not shown). The lower part of the shower head 52 constitutes a shower plate, and the shower plate has a plurality of through holes formed therein so as to uniformly release various gases supplied to the gas diffusion space toward the surface of the substrate W mounted on the substrate mounting table 53. An outlet hole to which a gas supply mechanism (described later) is connected is formed in the center of the upper part of the shower head 52.

[0025] Three substrate support pins (not shown) are provided on the substrate mounting table 53 in the processing chamber 51 so as to be movable up and down. The substrate support pins are inserted into through holes formed in the substrate mounting table 53 and protrude and retract relative to the upper surface of the substrate mounting table 53, thereby enabling the transfer of the substrate W between the vacuum transfer mechanism 69 shown in FIG. 1 and the substrate mounting table 53.

[0026] An exhaust pipe 54 having an exhaust hole at its upstream end is connected to the bottom of the processing vessel 51, and a pressure control valve, such as an APC valve (not shown), is provided in the exhaust pipe 54. An exhaust mechanism 55 is provided at the downstream end of the exhaust pipe 54. Each of the processing modules 101 to 103 includes a gas supply mechanism for supplying various gases into the processing vessel 51 via the shower head 52, and is configured to perform various processes on a substrate W placed on a substrate placement table 53.

[0027] As shown in FIG. 2, the COR processing module 101 includes a mixed gas supply mechanism 7A as a gas supply mechanism. The mixed gas supply mechanism 7A is configured to supply a mixed gas containing HF gas and NH gas to the shower head 52 and includes an HF gas supply mechanism 71 and an NH gas supply mechanism 72. The HF gas supply mechanism 71 includes an HF gas supply source 71a, a pipe 71b for supplying HF gas to the shower head 52, and a flow rate adjustment mechanism M1 attached to the pipe 71b for adjusting the supply flow rate of HF gas. Similar to the configuration of the HF gas supply mechanism 71, the NH gas supply mechanism 72 includes an NH gas supply source 72a, a pipe 72b, and a flow rate adjustment mechanism M2. The mixed gas supply mechanism 7A may be configured to include an inert gas supply mechanism (not shown) to supply a mixed gas containing an inert gas, as will be described in the following examples.

[0028] The supply flow rates of HF gas and NH3 are, for example, the same, 10 sccm (standard cubic centimeters / min) to 200 sccm each, specifically 20 sccm each. As the inert gas, for example, Ar (argon) and nitrogen (N2) are supplied, and their supply flow rates are higher than the supply flow rate of the mixed gas, for example, about 130 sccm each. The mixed gas and the inert gas are supplied simultaneously, for example, for 50 seconds or more, preferably 100 to 400 seconds, specifically 300 seconds. The pressure atmosphere in the processing chamber 51 is, for example, 13.3 Pa (0.1 Torr) to 133 Pa (1 Torr), specifically 66.6 Pa (0.5 Torr).

[0029] The substrate mounting table 53 of the COR processing module 101 has a mechanism for controlling the temperature of the substrate W. The sidewall of the processing vessel 51 of the COR processing module 101 and the shower head 52 are provided with heaters (not shown) for setting a preset temperature, such as 60°C.

[0030] 3, the gas supply mechanism 7B of the PHT processing module 102 includes an N2 gas supply mechanism 73. The N2 gas supply mechanism 73 is composed of an N2 gas supply source 73a, piping 73b, and a flow rate adjustment mechanism M3. In addition to the N2 gas supply mechanism 73, the gas supply mechanism 7B preferably includes a reducing gas supply mechanism, specifically an H2 (hydrogen) gas supply mechanism 74 and an NH3 gas supply mechanism 75.

[0031] The supply flow rate of N2 gas is, for example, 100 sccm to 5000 sccm, specifically 4000 sccm. The supply flow rate of H2 gas is, for example, 100 sccm to 5000 sccm, specifically 2000 sccm. The supply flow rate of NH3 gas is, for example, 100 sccm to 5000 sccm, specifically 4000 sccm. These gases are supplied simultaneously for, for example, 10 seconds to 100 seconds, specifically 20 seconds. The pressure inside the processing chamber 51 is, for example, 133 Pa (1 Torr) to 4000 Pa (30 Torr), specifically 1333 Pa (10 Torr).

[0032] The processing vessel 51 and substrate mounting table 53 of the PHT processing module 102 are both grounded. The shower head 52 is attached to the processing vessel 51 via a ring-shaped insulating member 57 and connected to a high-frequency power supply 79 via a matching box 78 to function as an upper electrode. The matching box 78 matches the internal impedance of the high-frequency power supply 79 with the load impedance, and the high-frequency power supply 79 applies power to the shower head 52 at a preset frequency so as to convert various gases supplied by the gas supply mechanism 7B into plasma. The substrate mounting table 53 is attached to the bottom of the processing vessel 51 via the insulating member 58 and functions as a lower electrode.

[0033] The PHT processing module 102 as described above converts various gases supplied between the shower head 52 and the substrate mounting table 53 into plasma and supplies the plasma to the substrate W. The substrate mounting table 53 of the PHT processing module 102 is provided with a heater 56 that uses, for example, resistance heat, and the heater 56 heats the temperature of the placed substrate W to a temperature higher than the temperature of the substrate W in the COR processing, for example, 400°C within a range of 100 to 500°C.

[0034] The Ru film forming module 103 is configured to form a Ru film by, for example, thermal CVD (individual components are not shown). The gas supply mechanism of the Ru film forming module 103 includes, for example, a CO (carbon monoxide) gas supply mechanism and a Ru source gas supply mechanism. The Ru source gas supply mechanism supplies Ru3(CO) using, for example, CO gas as a carrier gas as the Ru source gas. 12 The gas supply mechanism supplies Ru source gas and CO gas, for example, simultaneously. In the Ru film formation module 103, a heater provided on the substrate mounting table heats the substrate W to a temperature in the range of 150°C to 200°C, for example.

[0035] In the substrate processing apparatus 1 of the present disclosure having the above-described configuration, removal of a Ti oxide film formed on the surface of a substrate W and formation of a Ru film are performed. These processing operations will be described with reference to FIGS. 1 to 3. In advance, the first and second vacuum transfer modules 63 and 64 are evacuated to a vacuum atmosphere at a preset pressure, and in the processing modules 101 to 103, the exhaust mechanism 55 adjusts the pressure inside the processing container 51 to the preset vacuum atmosphere. In the PHT processing module 102 and the Ru film formation processing module 103, the substrate mounting table 53 is heated to the previously described temperature.

[0036] 4A to 4D are longitudinal side views showing the surface layer of a substrate W to be processed in the oxide film removal process and film formation process of the present disclosure. As shown in Fig. 4A, the surface layer of the substrate W before processing includes, for example, a TiN (titanium nitride) layer 11 and an SiOx layer 12 formed on the TiN layer 11, and the SiOx layer 12 has a plurality of vertically elongated recesses 13 formed by etching. Note that Figs. 4A to 4D show only one recess 13.

[0037] The recess 13 is provided for forming a wiring layer and opens to the surface of the substrate W. The lower end of the recess 13 reaches the TiN layer 11. The surface of the TiN layer 11 exposed in the recess 13 is naturally oxidized to form a Ti oxide film 11a by contact with the air atmosphere, for example, during the process of transporting the substrate W to the substrate processing apparatus 1. The TiN layer 11 can be referred to as a metal-containing layer in the claims and can be said to correspond to the base of the Ti oxide film 11a. The Ti oxide film 11a contains, for example, O (oxygen), N (nitrogen), and Ti (titanium).

[0038] The substrate W with the exposed Ti oxide film 11a is received by the vacuum transfer mechanism 69 in the first vacuum transfer module 63 from the load lock module 62 shown in Figure 1 and transferred to the COR processing module 101. The gate valve G1 of the COR processing module 101 is then opened, and the vacuum transfer mechanism 69 causes the substrate W to enter the processing vessel 51 through the loading port. The substrate W is then transferred to the substrate mounting table 53, and the vacuum transfer mechanism 69 is then moved out of the processing vessel 51, and the gate valve G1 is closed.

[0039] As described above, the substrate mounting table 53 of the COR processing module 101 has a temperature control mechanism, and the temperature of the substrate W mounted on the substrate mounting table 53 is, for example, within a range of 20 to 100°C, specifically, room temperature of 35°C. The pressure inside the processing chamber 51 is adjusted based on a recipe, and a mixed gas and an inert gas are supplied. This causes a chemical reaction between the Ti oxide film 11a and the mixed gas to generate a gaseous reaction product 11b from the Ti oxide film 11a, thereby removing the Ti oxide film 11a from the surface of the substrate W (step of generating a reaction product and removing it from the surface of the substrate, FIG. 4B).

[0040] The chemical reaction between the Ti oxide film 11a and the mixed gas will be described with reference to Fig. 5. As shown in Fig. 5(a), on the surface of the substrate W, a chemical reaction occurs between the HF gas in the mixed gas and the Ti oxide film 11a, producing TiF4 (titanium fluoride) as a reaction product 11b and water (HO) as a by-product 11c.

[0041] FIG. 6 is a graph showing the vapor pressures of TiF and NHF (ammonium fluoride), which will be described later. As shown in the figure, TiF has a relatively high vapor pressure and is in a gaseous state under the temperature and pressure conditions within the processing vessel 51. It is removed from the processing vessel 51 by exhaust using the exhaust mechanism 55. Once generated, the gaseous reaction product 11b is removed from the substrate W. Although not shown in FIG. 6, moisture, which has a relatively high vapor pressure, also becomes a gas under the temperature and pressure conditions within the processing vessel 51. Therefore, the by-product 11c is removed from the substrate W along with TiF. By reacting with the HF molecules in the mixed gas, the Ti oxide film 11a becomes gaseous TiF and moisture, and is generally removed from the substrate W (FIG. 5(a)), exposing the TiN layer 11 (FIG. 5(b)).

[0042] In parallel with the above-described chemical reaction of the Ti oxide film 11a, HF gas and NH3 gas also react with each other in the processing vessel 51 to produce NH4F (ammonium fluoride), as shown in FIG. 5(b). Because NH4F has a relatively low vapor pressure (FIG. 6), it does not vaporize under the temperature and pressure conditions of the processing vessel 51. Instead, it remains as deposits 11d on the surface of the substrate W, specifically, on the surface of the TiN layer 11 exposed by the removal of the Ti oxide film 11a (FIG. 4B). As shown in FIG. 5(c), the deposits 11d on the surface of the TiN layer 11 prevent the moisture (by-product 11c) generated during the supply of the mixed gas from coming into contact with the TiN layer 11, thereby preventing the oxidation of Ti, which is a metal in the TiN layer 11. The deposits 11d also contain gas molecules from the mixed gas, such as HF molecules. The HF molecules on the surface of the TiN layer 11 also effectively prevent moisture from oxidizing Ti.

[0043] After the Ti oxide film 11a is removed by supplying the mixed gas, the substrate W is transferred from the COR treatment module 101 by the vacuum transfer mechanism 69 of the first vacuum transfer module 63 and transferred to the waiting PHT treatment module 102. At this time, since the substrate W is transferred through the first vacuum transfer module 63, which is in a vacuum atmosphere, oxidation of the surface of the TiN layer 11 is suppressed in addition to the effect of the deposits 11d described above.

[0044] The PHT processing module 102 heats the substrate W placed on the substrate mounting table 53 to the aforementioned 400°C to sublimate and remove the deposits 11d (deposit removal step, FIG. 4C). The removal of the deposits 11d is performed in a plasma-generated supply gas atmosphere formed by supplying N2 gas, H2 gas, and NH3 gas based on a preset recipe and supplying high-frequency power to the shower head 52 using the high-frequency power supply 79. This effectively removes the deposits 11d while preventing oxidation of the TiN layer 11.

[0045] The substrate W, from which the deposits 11d have been removed and the TiN layer 11 is exposed as described above, is then transferred from the PHT processing module 102 by the vacuum transfer mechanism 69 of the first vacuum transfer module 63 and transferred to the second vacuum transfer module 64 via the connection module 65. Because the substrate W is transferred through the connection module 65 and the first and second vacuum transfer modules 63 and 64, which are in a vacuum atmosphere, the adhesion of molecules that could cause oxidation or impurities to the surface of the exposed TiN layer 11 is suppressed. The Ru film formation processing module 103, into which the substrate W is transferred by the second vacuum transfer module 64, supplies Ru source gas and CO gas based on a Ru film formation recipe to form a Ru film on the surface of the substrate W and form the wiring layer 14 in the recess 13 ( FIG. 4D ). Because the deposits 11d have been removed from the surface of the substrate W by the PHT processing module 102, it is possible to suppress effects on film formation, such as a decrease in the Ru film formation efficiency, and also to suppress degradation of the electrical performance of the wiring layer 14 due to impurities being mixed into the wiring layer 14.

[0046] As described above, according to the film formation method and film formation apparatus of the present disclosure, a mixed gas is supplied to the substrate W in the COR processing module 101, and a gaseous reaction product 11b and a by-product 11c are generated and removed by a chemical reaction between the Ti oxide film 11a and the mixed gas. As a result, the Ti oxide film 11a is removed. Then, a deposit 11d generated by the chemical reaction of the supplied mixed gas adheres to the surface of the TiN layer 11 exposed after the Ti oxide film 11a is removed, thereby suppressing oxidation of the TiN layer 11.

[0047] Next, in the PHT processing module 102, the substrate W with the deposits 11d attached thereto is heated to sublimate and remove the deposits 11d, thereby exposing the TiN layer 11. Furthermore, in the PHT processing module 102, the substrate W is exposed to the above-mentioned plasma gas atmosphere, thereby effectively removing the deposits 11d and preventing oxidation of the TiN layer 11. Next, in the Ru film formation processing module 103, a Ru film is formed on the exposed TiN layer 11 in this manner, thereby suppressing an increase in resistance due to the Ti oxide film 11a and the deposits 11d and suppressing their influence on the Ru film formation.

[0048] Furthermore, in a conventional technique different from the present disclosure, a method of removing the Ti oxide film 11a using a chlorine-based dry etching gas, such as Cl2 (chlorine) gas, is known. Regarding this point, the inventors have found that after removing the Ti oxide film 11a using a chlorine-containing dry etching gas, the formation of a Ru film may be hindered. The inventors speculate that this is because the chlorine remaining on the surface of the substrate W inhibits the adsorption of the Ru source gas. In this regard, according to the present disclosure, a chlorine-based dry etching gas is not supplied, so that Cl molecules that inhibit the formation of a Ru film do not remain, and a Ru film can be effectively formed.

[0049] (Variation) The metal-containing layer is not limited to the TiN layer 11. For example, it may be a layer containing Ti as a constituent element, or it may not contain Ti as a constituent element as shown in the second embodiment described later. The Ti oxide film 11a may contain Ti and O as constituent elements, and may contain other elements, for example, not N. The Ru film, which is a metal film, is not limited to this, and may be, for example, another metal film with a relatively low resistivity. In this case, the other metal film is expected to contain at least one metal, such as Al (aluminum), copper (Cu), W (tungsten), Ti (titanium), silver (Ag), or Mo (molybdenum), as a constituent element.

[0050] The PHT processing module 102 is configured to supply the aforementioned H2, NH3, and N2 gases using the gas supply mechanism 7B, but is not limited to this combination. Plasma of at least one gas selected from H2, NH3, and N2 may also be supplied. Furthermore, the PHT processing module 102 need not supply a reducing gas, as long as it can heat the substrate W and remove the deposits 11d. Even if a reducing gas is supplied, it is not essential that the reducing gas be turned into plasma.

[0051] In the COR processing module 101 of the present disclosure, HF gas and NH3 gas are simultaneously supplied as a mixed gas, but simultaneous supply of these gases is not essential. For example, HF gas and NH3 gas may be supplied sequentially, or these gases may be supplied alternately and repeatedly. The substrate stage 53 of the COR processing module 101 is provided with a heating mechanism, but this may not be provided, and the substrate W may not be heated.

[0052] In the substrate processing apparatus 1 of the present disclosure, it is not essential to provide the first and second vacuum transfer modules 63, 64 and the connection module 65. For example, the second vacuum transfer module 63 and the connection module 65 may not be provided, and the processing modules 101 to 103 may be arranged around the first vacuum transfer module 63.

[0053] (Second embodiment) The oxide film removal technique of the present disclosure is not limited to substrates W having the surface structure described above. Even for substrates W1 having different surface structures, other types of oxide films can be removed by utilizing the Ti oxide film removal technique using a mixed gas containing HF gas and NH3 gas. Figures 7A to 7C are longitudinal side views showing the surface of a substrate W1 that changes as a result of oxide film removal according to the second embodiment. In the substrate W1 shown in Figure 7A, a W (tungsten) layer 15 is provided as an underlying metal-containing layer, and a W oxide film 15a formed by natural oxidation of the surface of the W layer 15 is exposed within the recess 13.

[0054] The substrate processing apparatus 1 in this embodiment includes a processing module (not shown) for forming a Ti film as a pretreatment for the oxide film removal treatment by the COR and PHT processing modules 101 and 102. The processing module is, for example, a film-forming module for forming an anisotropic Ti film, and has a structure capable of converting a processing gas into plasma, similar to the PHT processing module 102. However, the gas supply mechanism is configured to supply TiCl gas, which is a source gas for the Ti film, and H gas, which is a reactive gas, as processing gases. Furthermore, a heater 56 heats the substrate W to, for example, 300°C to 600°C.

[0055] In this embodiment, first, a substrate W1 shown in FIG. 7A is heated in a processing module based on a preset Ti film formation recipe. Then, TiCl4 gas and H2 gas are supplied to a processing chamber, the pressure of which is adjusted to a vacuum atmosphere, and plasma is generated to form a Ti film 16 on the W oxide film 15a (FIG. 7B). The Ti film 16 immediately after deposition contains almost no oxygen and has a relatively high reducing power. However, since the substrate W is heated, the reducing power is further increased, making it susceptible to oxidation. Therefore, the Ti film 16 absorbs oxygen from the W oxide film 15a and becomes a Ti oxide film 16a, while the W oxide film 15a loses oxygen and is reduced, returning to a W layer 15 (FIG. 7C).

[0056] The Ti oxide film 16a provided to cover the surface of the W layer 15 effectively prevents re-oxidation of the W layer 15. The Ti oxide film 16a is removed in the COR and PHT processing modules 101 and 102 by the same method as that described in the first embodiment. If, for example, the Ti film 16 is not oxidized sufficiently and unoxidized Ti film 16 remains, the Ti oxide film 16a may be formed using O2 (oxygen) gas or O3 (ozone) gas, and then the Ti oxide film may be removed.

[0057] According to the oxide film removal method of this embodiment, the W oxide film 15a constituting the surface of the W layer 15 is reduced by the Ti film 16 formed on the W oxide film 15a to form the W layer 15. The Ti oxide film 16a, which is the result of oxidation of the Ti film 16, can be removed by the Ti oxide film removal using the COR and PHT processing modules 101 and 102 shown in the first embodiment.

[0058] As described above, according to the oxide film removal method of the present disclosure, an oxide film formed on the surface of a metal-containing layer can be removed by using the Ti oxide film removal method of the first embodiment. Even if the metal-containing layer does not contain, for example, Ti as a constituent element, as shown in this embodiment, a Ti film can be formed on the oxide film on the surface, the oxide film of the metal-containing layer can be reduced to return it to the metal-containing layer, and then the Ti oxide film underlying the metal-containing layer can be removed by the Ti oxide film removal method shown in the first embodiment.

[0059] Therefore, the metal-containing layer is not limited to one containing Ti or W as a constituent element, and may be one containing at least one of Al (aluminum), copper (Cu), silver (Ag), Mo (molybdenum), etc. Also, although it is preferable to form a Ti film 16 having a relatively high reducing power on the surface of the W oxide film 15a, a Ti-containing film other than the Ti film 16 and containing an element other than oxygen (for example, nitrogen N) as a constituent element may be formed as long as it has the reducing power. [Example]

[0060] (Experiment 1) To confirm the effect of the oxide film removal method of the present disclosure, a process different from the oxide film removal method of the present disclosure and a process equivalent to the oxide film removal method of the first embodiment were each performed on the surface of the TiN layer on which the native oxide film had been formed. Then, a TiN cap layer was formed, and the content of oxygen and other elements was analyzed. The analysis used EDX (Energy Dispersive X-ray Spectroscopy) to measure the content of each element, such as oxygen and fluorine.

[0061] A. Experimental conditions Three unpatterned, flat bare wafers were prepared. A TiN film was uniformly formed on the surface of each bare wafer, and the surface was allowed to naturally oxidize. Then, the surface of each wafer was subjected to Comparative Examples 1-1 and 1-2, which performed pretreatment different from the oxide film removal described in this disclosure, and Example 1, which performed treatment equivalent to the oxide film removal described in the first embodiment. The wafers were then transported to a TiN film deposition module using a vacuum transfer module, where a TiN film was formed. In this way, a TiN+TiN layer with a Ti oxide film that had been subjected to different treatments was formed on the surface side of each wafer.

[0062] In the pretreatment of Comparative Example 1-1, the wafers were not supplied with a mixed gas, but were instead exposed to a supply atmosphere of N2 gas, H2 gas, and NH3 gas plasmatized in the PHT treatment module 102 based on a predetermined recipe, without any heat treatment of the substrates. In the pretreatment of Comparative Example 1-2, the wafers were supplied with a mixed gas and an inert gas in the COR treatment module 101 based on the recipe described in the first embodiment, but the treatment with plasmatized gas as in Comparative Example 1-1 was not performed. In Example 1, the mixed gas was supplied to the wafers in the COR treatment module 101 as in Comparative Example 1-2, and then the wafers were treated with plasmatized gas in the PHT treatment module 102 as in Comparative Example 1-1. EDX was performed on each wafer with such a TiN+TiN layer.

[0063] B. Experimental Results Of the EDX graphs measured in Experiment 1, FIG. 8 shows the change in atomic percentage (At%) of various elements versus depth on the wafer surface side for Example 1 as a representative example. In this graph, it can be seen that the intermediate depth region, where the proportion of N atoms and the proportion of Ti atoms account for the majority, is the TiN+TiN layer. As shown in the figure, not only in Example 1 but also in Comparative Examples 1-1 and 1-2, the proportions of Cl atoms and F atoms in the TiN+TiN layer were almost zero with no significant difference.

[0064] FIG. 9 is a first graph comparing the results of Experiment 1. Specifically, it compares the atomic composition percentage of oxygen extracted from the atomic composition percentages of various elements relative to the depth on the surface side of each wafer in Experiment 1. The atomic percentage of oxygen in the depth region corresponding to the TiN+TiN layer of each wafer was lowest in Example 1, indicating a decrease in the oxygen content of the entire TiN stack. On the other hand, although the atomic percentage of oxygen in the stack of Comparative Example 1-1 was lower than that of Comparative Example 1-2, a peak of increased oxygen content was observed at a position corresponding to the interface of the stack. This is thought to be due to the absence of COR treatment, which generates and removes gaseous reaction products from the oxygen contained in the native oxide film of the underlying TiN film. In contrast, no peak was observed in the atomic percentage of oxygen in the TiN+TiN layer of Comparative Example 1-2 and Example 1, which were subjected to COR treatment. This suggests that gaseous reaction products were generated and removed from the oxygen contained in the native oxide film of the underlying TiN film.

[0065] Fig. 10 is a second graph for comparing the results of Experiment 1, which was obtained using SIMS (Secondary Ion Mass Spectrometry). Specifically, the atomic concentrations of O atoms and F atoms in the TiN+TiN layer in Experiment 1 [atoms / cm 3 ] is a bar graph comparing the O concentration of the TiN+TiN layers of Comparative Example 1-2 and Example 1, which were subjected to COR treatment, and the O concentration of the TiN+TiN layer of Comparative Example 1-1, which was not subjected to COR treatment, was lower, confirming that the oxide film could be removed by the COR treatment. The F concentration of the TiN+TiN layers of Comparative Example 1-1 and Example 1, which were subjected to treatment with the plasma gas, was lower than the F concentration of Comparative Example 1-2, which was not subjected to plasma gas treatment, confirming that the fluorine could be reduced by the plasma gas treatment. Note that the F concentration of Example 1 is higher than that of Comparative Example 1-1, but this is because Comparative Example 1-1 did not undergo COR treatment using HF gas, which provides F atoms.

[0066] Furthermore, evaluation tests other than those conducted in Experiment 1 have shown that factors that improve the effectiveness of PHT in removing oxygen and fluorine are the type and combination of gases supplied in the PHT process, and the plasma state of the gases supplied. Specifically, it has been confirmed that NH3 gas is preferable to H2 gas as the supply gas, and more preferably, NH3 gas and N2 gas are supplied simultaneously and then plasma-generated.

[0067] Regarding the COR process, it has been confirmed that the oxygen concentration is relatively high when NH3 gas is not included in the mixed gas. This is thought to be due to the absence of deposits 11d. It has also been confirmed that the oxygen concentration tends to increase when the wafer temperature during the COR process is increased to, for example, 80°C or when the pressure inside the process chamber is set to a relatively low pressure, for example, 13.3 Pa (0.1 Torr). Furthermore, as shown in Experiment 2 below, it has been found that the oxide film can be effectively removed by using a relatively long COR process time, but in this case, the fluorine concentration remains unchanged. As described above, in the Ti oxide film removal process of the present disclosure, the conditions can be appropriately adjusted as described above to suit the desired film quality, etc.

[0068] (Experiment 2) The effect of oxide film removal on the COR processing time in oxide film removal according to the present disclosure was confirmed.

[0069] A. Experimental conditions As in Experiment 1, three bare wafers with uniform TiN films were prepared, and the surfaces were subjected to the COR and PHT treatments similar to those in Example 1, after which a Ru film was formed. The treatment times for each COR treatment were 300 seconds, 120 seconds, and 60 seconds.

[0070] B. Experimental Results Figure 11 is a graph comparing the atomic composition percentage of oxygen among the atomic composition percentages of various elements versus depth on the surface side of each wafer in Experiment 2. This graph shows that the 60-second COR treatment resulted in a significant peak of oxygen elemental concentration at the boundary region between the Ru film and the TiN film, suggesting the presence of a relatively thick oxide film. The 120-second COR treatment also showed a lower oxygen elemental concentration peak at the boundary region than the 60-second COR treatment, but confirmed that the oxide film was more effectively reduced than the 60-second COR treatment. The 300-second COR treatment resulted in the oxygen percentage at the boundary region being nearly identical to that of the Ru film, suggesting that the oxide film was sufficiently removed. The results of Experiment 2 thus confirmed that the oxide film removal method disclosed herein can remove Ti oxide films in a stacked structure of TiN and Ru films, and that the oxide film removal effect can be improved by increasing the COR treatment time.

[0071] It should be noted that the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects, 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. [Explanation of symbols]

[0072] W substrate 11a Ti oxide film 11b Reaction products 11d. Adhesion 16a Ti oxide film

Claims

1. A method for removing a titanium oxide film on a surface of a substrate, comprising the steps of: supplying a mixed gas containing hydrogen fluoride gas and ammonia gas to the surface of the titanium oxide film, causing a chemical reaction between the titanium oxide film and the mixed gas, and generating a gaseous reaction product from the titanium oxide film and removing the gaseous reaction product from the surface of the substrate; and heating the substrate to remove any deposits that may have adhered to the substrate during the generation of the reaction product.

2. 2. The method according to claim 1, wherein the deposit adheres to the surface of the metal-containing layer underlying the titanium oxide film and inhibits the metal in the metal-containing layer from being oxidized by moisture, which is a by-product of the chemical reaction.

3. The method of claim 2 , wherein the metal-containing layer is a titanium nitride layer or a tungsten layer.

4. 10. The method of claim 1, wherein the reaction product is titanium fluoride and the deposit comprises ammonium fluoride and hydrogen fluoride.

5. 2. The method of claim 1, wherein the step of removing the reaction products from the surface of the substrate is carried out while the temperature of the substrate is in the range of 20°C to 100°C.

6. 2. The method of claim 1, wherein the step of removing the reaction product from the surface of the substrate is carried out under an atmosphere with a pressure in the range of 13.3 Pa to 133 Pa.

7. 2. The method according to claim 1, wherein the step of removing the deposits comprises heating the substrate to a temperature within a range of 100 to 500 degrees Celsius.

8. The method according to claim 1 , wherein the step of removing the deposits is carried out in an atmosphere supplied with a plasma-converted gas.

9. The method according to claim 8, wherein the gas that has been converted into plasma is at least one gas selected from the group consisting of hydrogen, ammonia, and nitrogen.

10. The method of claim 1 , further comprising the step of forming a metal film on the substrate after performing the step of removing the deposits.

11. The method of claim 10, wherein the metal film is a ruthenium film.

12. a first processing module for removing a titanium oxide film on a surface of the substrate, the first processing module including a gas supply mechanism configured to supply a mixed gas containing hydrogen fluoride gas and ammonia gas; a second processing module configured to heat the substrate; a control unit, the control unit is configured to output a control signal to execute, in the first processing module, a step of supplying the mixed gas to a surface of the titanium oxide film, causing a chemical reaction between the titanium oxide film and the mixed gas, generating a gaseous reaction product from the titanium oxide film, and removing the gaseous reaction product from the surface of the substrate; and a step of heating the substrate and removing deposits that have adhered to the substrate when the reaction product is generated, in the second processing module.

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