SUBSTRATE PROCESSING METHOD AND SUBSTRATE PROCESSING APPARATUS

Abstract

To provide a substrate processing method and a substrate processing apparatus for satisfactorily controlling an etching amount of a metal layer at accuracy of a nanometer or less at each position of a principal surface of a substrate.SOLUTION: A substrate processing method includes: a metal oxide layer forming step in which oxidizing fluid is supplied toward a principal surface of a substrate, thereby forming a metal oxide layer comprising one atomic layer or several atomic layers on a surface layer of a metal layer; and a metal oxide layer removing step in which etching fluid containing at least any one of water in a gaseous state and water in a mist state as well as a reactive gas that reacts with the metal oxide layer together with the water is supplied toward the principal surface of the substrate, thereby etching the metal oxide layer and selectively removing the metal oxide layer from the principal surface of the substrate. Cycle processing in which the metal oxide layer forming step and the metal oxide layer removing step are given as one cycle is executed at least in one cycle, thereby controlling an etching amount of the metal layer for each cycle at accuracy of a nanometer or less.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus for processing a substrate, which may include, for example, a semiconductor wafer, a substrate for a FPD (Flat Panel Display) such as a liquid crystal display device or an organic EL (Electroluminescence) display device, a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, a substrate for a photomask, a ceramic substrate, a substrate for a solar cell, etc. [Background technology]

[0002] In the substrate processing disclosed in Patent Document 1 below, in order to achieve etching of a metal layer with accuracy of less than a nanometer, a metal oxide layer forming process in which a metal layer on the main surface of a substrate is oxidized with an oxidizing agent such as hydrogen peroxide solution to form a metal oxide layer consisting of one or several atomic layers, and a metal oxide layer removing process in which the metal oxide layer is selectively removed with an etching solution such as dilute hydrofluoric acid are repeated. Between the metal oxide layer forming process and the metal oxide layer removing process, a rinsing process is performed with a rinsing solution that washes away the oxidizing agent and the etching solution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-61978 A Summary of the Invention [Problem to be solved by the invention]

[0004] A method of etching a metal layer with a liquid in units of one atomic layer or several atomic layers, such as the substrate processing disclosed in Patent Document 1, is called Atomic Layer Wet Etching (ALWE). In ALWE, if the concentration of oxygen (dissolved oxygen concentration) in the etching solution or rinsing solution is high, the metal layer may be oxidized by the oxygen in the etching solution, resulting in the formation of an unintended metal oxide layer. Therefore, in ALWE, it is necessary to sufficiently reduce the dissolved oxygen in the etching solution or rinsing solution to prevent a decrease in the removal selectivity of the metal oxide layer. Furthermore, if the rinsing solution or etching solution does not spread over the entire main surface of the substrate, there is a risk of unevenness in the amount of etching occurring at each position on the main surface of the substrate.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a substrate processing method and substrate processing apparatus that effectively control the amount of etching of a metal layer at each position on a main surface of a substrate with accuracy of less than a nanometer. [Means for solving the problem]

[0006] One embodiment of the present invention is a substrate processing method for processing a substrate having a metal layer on a main surface thereof. The substrate processing method includes a metal oxide layer forming step of forming a metal oxide layer consisting of one or several atomic layers on a surface layer of the metal layer by supplying an oxidizing fluid toward the main surface of the substrate, and a metal oxide layer removing step of etching the metal oxide layer by supplying an etching fluid containing at least one of water in a gaseous state and water in a mist state, and a reactive gas that reacts with the metal oxide layer together with the water, toward the main surface of the substrate, thereby selectively removing the metal oxide layer from the substrate. The amount of etching of the metal layer is controlled with accuracy of less than a nanometer by performing at least one cycle of cyclic processing in which the metal oxide layer forming step and the metal oxide layer removing step form one cycle.

[0007] In this substrate processing method, the metal oxide layer forming step forms a metal oxide layer consisting of one atomic layer or several atomic layers. The thickness of one atomic layer of metal and metal oxide is 1 nm or less (e.g., 0.3 nm or more and 0.4 nm or less). A several atomic layer means a layer of two to ten atomic layers. Therefore, the thickness of the metal oxide layer is several nm or less (e.g., 5 nm). Therefore, by selectively removing the metal oxide layer in the metal oxide layer removal step, it is possible to etch a portion of the metal layer that is 5 nm or less thick from the surface of the metal layer. Then, by performing at least one cycle of cyclic processing in which the metal oxide layer formation step and the metal oxide layer removal step form one cycle, it is possible to control the amount of etching of the metal layer with accuracy of less than a nanometer for each cycle. Accuracy of less than a nanometer means accuracy of a few nm (for example, 5 nm) or less.

[0008] The thickness of the metal layer etched by one cycle of the cycle treatment is almost constant, so a desired etching amount can be achieved by adjusting the number of times the metal oxide layer forming step and the metal oxide layer removing step are repeatedly performed. For example, if the metal layer is etched by 0.3 nm by performing one cycle of the cycle process, by adjusting the number of cycle processes to be performed, it is possible to perform a substrate process in which the metal layer is etched by 1.5 nm, or a substrate process in which the metal layer is etched by 1.8 nm. In other words, it is possible to control the amount of etching of the metal layer with an accuracy of approximately 0.3 nm.

[0009] Moreover, in this substrate processing method, an etching fluid containing at least one of water in a gaseous state (water vapor) and water in a mist state, and a reactive gas is used to selectively remove the metal oxide layer. Unlike this substrate processing method, when liquid water and a reactive liquid obtained by liquefying a reactive gas are supplied to the main surface of the substrate in a continuous flow, unevenness occurs at the interface between these liquids and the main surface of the substrate, which results in unevenness at the molecular level in the frequency of collisions between the main surface of the substrate and the molecules (hereinafter referred to as "reactive molecules") constituting the reactive liquid and reactive gas, or between the main surface of the substrate and water molecules at each position on the main surface of the substrate.

[0010] Water in a gaseous state or water in a mist state is more likely to diffuse near the main surface of the substrate than water in a continuous liquid state. Similarly, reactive gas is more likely to diffuse near the main surface of the substrate than reactive liquid. Therefore, water molecules and reactive molecules are more likely to collide evenly at each position on the main surface of the substrate. Therefore, if an etching fluid containing at least one of water in a gaseous state and water in a mist state and reactive gas is used, it is easier to suppress unevenness in the amount of etching on the main surface of the substrate with an accuracy of less than a nanometer compared to a configuration using an etching fluid containing water in a liquid state and reactive liquid.

[0011] As a result, the amount of etching of the metal layer can be well controlled with sub-nanometer accuracy at each position on the main surface of the substrate. In one embodiment of the present invention, the substrate processing method further includes a reactive gas elimination process, after the metal oxide layer removal process, in which the supply of at least one of gaseous water and mist-state water to the main surface of the substrate is continued to eliminate the reactive gas from a space adjacent to the main surface of the substrate.

[0012] According to this substrate processing method, instead of replacing the entire etching fluid with another gas, reactive gas is removed from the space adjacent to the main surface of the substrate by continuously supplying at least one of gaseous water and mist water that constitute the etching fluid, thereby allowing the reactive gas components adhering to the main surface of the substrate to be adsorbed by the water and quickly removed.

[0013] In one embodiment of the present invention, the substrate processing method further includes, after the reactive gas elimination step, a water elimination step of excluding water from a space in contact with the main surface of the substrate by replacing water present in the space in contact with the main surface of the substrate with an inert gas. According to this substrate processing method, water is replaced by the inert gas and removed from the space adjacent to the main surface of the substrate, thereby making it possible to suppress unintended etching of the metal layer caused by minute amounts of oxygen molecules adsorbed on the water molecules.

[0014] In one embodiment of the present invention, the substrate processing method further includes an oxidizing fluid removal step, after the metal oxide layer formation step and before the metal oxide layer removal step, of supplying an inert gas toward the main surface of the substrate to replace the oxidizing fluid present in the space in contact with the main surface of the substrate with an inert gas, thereby removing the oxidizing fluid from the space in contact with the main surface of the substrate.

[0015] According to this substrate processing method, the oxidizing fluid is removed from the space in contact with the main surface of the substrate before the metal oxide layer removal step, which makes it possible to suppress unintended oxidation of the metal layer in the metal oxide layer removal step. In one embodiment of the present invention, the metal oxide removal process includes an etching fluid supply process of supplying an etching fluid from an etching fluid supply unit toward the main surface of the substrate, and a temperature adjustment process of adjusting the temperature of the substrate to a temperature lower than that of the etching fluid supplied from the etching fluid supply unit.

[0016] Therefore, the temperature of the etching fluid decreases near the main surface of the substrate, and the kinetic energy of the reactive molecules and water molecules decreases near the main surface of the substrate. Therefore, the reactive molecules and water molecules adsorbed on the main surface of the substrate are prevented from leaving the main surface of the substrate. In other words, the adsorption of the reactive molecules and water molecules to the main surface of the substrate is promoted. This allows the etching rate of the metal layer to be increased. As a result, the etching rate of the metal layer can be increased while maintaining the etching amount per cycle of the cycle treatment at one atomic layer or several atomic layers.

[0017] In one embodiment of the present invention, the metal oxide layer forming step includes a heating and oxidation step of forming a metal oxide layer by supplying the oxidizing fluid toward the main surface of the substrate while heating the substrate, and the metal oxide layer removing step includes a low-temperature etching step of etching the metal oxide layer by supplying the etching fluid toward the main surface of the substrate while the temperature of the substrate is lower than the temperature of the substrate in the metal oxide layer forming step.

[0018] According to this substrate processing method, the metal layer on the main surface of the substrate is oxidized when the substrate temperature is relatively high (e.g., 100°C or higher and 400°C or lower). This makes it possible to increase the oxidation rate of the metal layer. On the other hand, etching is performed when the substrate temperature is relatively low (e.g., 25°C or higher and lower than 100°C). When the substrate temperature is relatively high, oxygen molecules present in small quantities in the etching fluid have oxidizing power. Therefore, by performing etching at a relatively low temperature, unintended oxidation of the metal layer in the metal oxide layer removal process can be suppressed.

[0019] In one embodiment of the present invention, in the thermal oxidation step, the substrate is heated by placing the substrate on a heating surface of a heating member disposed in a chamber while supplying the oxidizing fluid toward the main surface of the substrate, and in the low-temperature etching step, the temperature of the substrate is reduced by lowering the temperature of the heating member while maintaining the substrate placed on the heating surface.

[0020] According to this substrate processing method, both heating and cooling of the substrate are performed while the substrate is placed on the heating surface of a single heating member, which simplifies the substrate processing compared to a configuration in which the substrate is moved to a member other than the heating member to change the substrate temperature. In one embodiment of the present invention, in the thermal oxidation step, the substrate is heated by placing the substrate on a temperature adjustment surface of a first temperature adjustment member arranged in a first chamber while supplying the oxidizing fluid toward the main surface of the substrate, and in the low-temperature etching step, the temperature of the substrate is reduced by moving the substrate from the temperature adjustment surface and placing the substrate on a second temperature adjustment surface of a second temperature adjustment member arranged in a second chamber and having a lower temperature than the first temperature adjustment member.

[0021] According to this substrate processing method, the temperature of the substrate is adjusted on the first temperature adjustment surface of the first temperature adjustment member, and then on the second temperature adjustment surface of the second temperature adjustment member. In other words, two temperature adjustments are performed by different members. Therefore, the time required for adjusting the temperature of the substrate can be shortened compared to a configuration in which the temperature of the substrate is adjusted by changing the temperature of the temperature adjustment surface of a single temperature adjustment member. In one embodiment of the present invention, the metal layer comprises a metal nitride layer containing a group III metal. Group III metal means a metal in group 13 of the periodic table. Specifically, group III metals are aluminum (Al), gallium (Ga), indium (In) and thallium (Tl). Metal nitrides containing group III metals form oxides that react with water and reactive gases by oxidation.

[0022] For example, if the metal nitride layer is a gallium nitride layer (GaN) and the oxidizing fluid is ozone gas, the gallium nitride is oxidized by the ozone molecules (O3) to produce gallium oxide (Ga2O3), as shown in the following chemical reaction formula 1. In more detail, the ozone molecules generate oxygen radicals when heated, and the gallium nitride is oxidized by these oxygen radicals.

[0023] [ka]

[0024] When the reactive gas contained in the etching fluid is ammonia gas (NH3), the reactions shown in the following chemical reaction formulas 2 and 3 occur. As shown in chemical reaction formula 2, gallium oxide reacts with hydroxide ions, and gallium oxide is dissolved in the etching fluid and becomes ionized. Also, as shown in chemical reaction formula 3, gallium oxide reacts with water and ammonia, and gallium oxide is dissolved in the etching fluid and becomes ionized.

[0025] [ka]

[0026] [ka]

[0027] When the reactive gas contained in the etching fluid is hydrogen chloride gas (HCl), the reactions shown in the following chemical reaction formulas 4 and 5 occur. As shown in chemical reaction formula 4, gallium oxide reacts with water and hydrogen chloride, and gallium oxide is dissolved in the etching fluid and becomes ionized. Also, as shown in chemical reaction formula 5, gallium oxide reacts with hydrogen chloride, and gallium oxide is dissolved in the etching fluid and becomes ionized.

[0028] [ka]

[0029] [ka]

[0030] In one embodiment of the present invention, the water contained in the etching fluid is gaseous water. When gaseous water is used in the metal oxide layer removal process, water in a bulk state (in the form of minute droplets) is less likely to adhere to the main surface of the substrate than when mist water is used. Therefore, when gaseous water is used as the water contained in the etching fluid, water molecules can be more evenly collided with each position on the main surface of the substrate.

[0031] Another embodiment of the present invention provides a substrate processing apparatus for processing a substrate having a metal layer on a main surface thereof, the substrate processing apparatus including: a temperature control member having a temperature control surface on which the substrate is placed and controlling a temperature of the substrate placed on the temperature control surface to a predetermined first temperature and a second temperature lower than the first temperature; a chamber accommodating the temperature control member; an oxidizing fluid supply unit supplying an oxidizing fluid into the chamber to form a metal oxide layer consisting of one atomic layer or several atomic layers on a surface of the metal layer; and an etching fluid supply unit supplying an etching fluid containing at least one of water in a gaseous state and water in a mist state and a reactive gas that reacts with the metal oxide layer together with the water into the chamber to selectively etch the metal oxide layer.

[0032] According to this substrate processing apparatus, a metal oxide layer consisting of one atomic layer or several atomic layers is formed by the oxidizing fluid supplied from the oxidizing fluid supply unit. Therefore, by selectively removing the metal oxide layer with the etching fluid supplied from the etching fluid supply unit, a portion of the metal layer having a thickness of 5 nm or less can be etched from the surface of the metal layer. By repeating the formation of the metal oxide layer by the oxidizing fluid supply unit and the selective removal of the metal oxide layer by the etching fluid supply unit, the amount of etching of the metal layer can be controlled with accuracy of less than a nanometer.

[0033] The thickness of the metal layer etched by performing the formation of the metal oxide layer by the oxidizing fluid supply unit once and the selective removal of the metal oxide layer by the etching fluid supply unit once is almost constant, so that the desired etching amount can be achieved by adjusting the number of times the formation of the metal oxide layer and the removal of the metal oxide layer are repeatedly performed. In addition, in this substrate processing apparatus, an etching fluid containing at least one of gaseous water (water vapor) and mist water, and a reactive gas is used to selectively remove the metal oxide layer. Therefore, as described above, it is easy to make the water molecules and reactive molecules collide evenly at each position on the main surface of the substrate. Therefore, if an etching fluid containing at least one of gaseous water and mist water and a reactive gas is used, unevenness in the amount of etching on the main surface of the substrate can be suppressed with an accuracy of less than a nanometer, compared to a configuration using an etching fluid containing liquid water and a reactive liquid.

[0034] As a result, the amount of etching of the metal layer can be well controlled with sub-nanometer accuracy at each position on the main surface of the substrate. In another embodiment of the present invention, the substrate processing apparatus further comprises a controller for controlling the oxidizing fluid supply unit and the etching fluid supply unit. Further The controller controls the oxidizing fluid to be supplied from the oxidizing fluid supply unit toward the main surface of the substrate. By providing The program is programmed to execute a metal oxide layer forming step of forming the metal oxide layer consisting of one atomic layer or several atomic layers on the surface of the metal layer, and a metal oxide layer removing step of etching the metal oxide layer and selectively removing it from the main surface of the substrate by supplying an etching fluid from the etching fluid supply unit toward the main surface of the substrate. At least one cycle of cyclic processing, which includes the metal oxide layer forming step and the metal oxide layer removing step, is executed, thereby controlling the amount of etching of the metal layer with an accuracy of less than a nanometer for each cycle.

[0035] According to this substrate processing apparatus, a cycle process in which a metal oxide layer forming step and a metal oxide layer removing step are one cycle can be automatically performed a desired number of times. The thickness of the metal layer etched by one cycle of the cycle process is almost constant. Therefore, a desired etching amount can be achieved by adjusting the number of times the metal oxide layer forming step and the metal oxide layer removing step are performed.

[0036] In another embodiment of the invention, the etching fluid supply unit is configured to supply the etching fluid into the chamber through a fluid introduction port opening in the chamber, and the second temperature is lower than a temperature of the etching fluid introduced into the chamber through the fluid introduction port. Therefore, the temperature of the etching fluid decreases near the main surface of the substrate, and the kinetic energy of the reactive molecules and water molecules decreases near the main surface of the substrate. Therefore, the reactive molecules and water molecules adsorbed on the main surface of the substrate are prevented from leaving the main surface of the substrate. In other words, the adsorption of the reactive molecules and water molecules to the main surface of the substrate is promoted. This allows the etching rate of the metal layer to be increased. As a result, the etching rate of the metal layer can be increased while maintaining the etching amount per cycle of the cycle treatment at one atomic layer or several atomic layers.

[0037] In another embodiment of the present invention, the temperature adjustment member has a single temperature adjustment surface, and the substrate is placed on the single temperature adjustment surface. Placement The temperature of the substrate is adjusted to the first temperature and the second temperature while the substrate is being heated. According to this substrate processing apparatus, both heating and cooling of the substrate are performed while the substrate is placed on a single temperature control surface, which simplifies the substrate processing compared to a configuration in which the substrate is moved to a member separate from the heating member to change the substrate temperature.

[0038] In another embodiment of the present invention, the temperature adjustment member has a first temperature adjustment surface as the temperature adjustment surface and adjusts the substrate placed on the first temperature adjustment surface to the first temperature, and a second temperature adjustment member has a second temperature adjustment surface as the temperature adjustment surface and adjusts the substrate placed on the second temperature adjustment surface to the second temperature. The chamber has a first chamber that houses the first temperature adjustment member and a second chamber that houses the second temperature adjustment member. The oxidizing fluid supply unit is configured to supply an oxidizing fluid into the first chamber, and the etching fluid supply unit is configured to supply an etching fluid into the second chamber.

[0039] According to this substrate processing apparatus, the temperature of the substrate is adjusted on the first temperature adjustment surface of the first temperature adjustment member, and then on the second temperature adjustment surface of the second temperature adjustment member. That is, two temperature adjustments are performed by different members. Therefore, the time required for adjusting the temperature of the substrate can be shortened compared to a configuration in which the temperature of the substrate is adjusted by changing the temperature of the temperature adjustment surface of a single temperature adjustment member. In another embodiment of the present invention, the first temperature is 100° C. or more and 400° C. or less, and the second temperature is 25° C. or more and less than 100° C. That is, when the temperature of the substrate is relatively high (e.g., 100° C. or more and 400° C. or less), the metal layer on the main surface of the substrate is oxidized. Therefore, the oxidation rate of the metal layer can be increased. On the other hand, etching is performed when the temperature of the substrate is relatively low (e.g., 25° C. or more and less than 100° C.). When the temperature of the substrate is relatively high, oxygen molecules present in small amounts in the etching fluid have oxidizing power. Therefore, by performing etching at a relatively low temperature, unintended oxidation of the metal layer can be suppressed. [Brief description of the drawings]

[0040] [Figure 1A] FIG. 1A is a plan view for explaining the configuration of a substrate processing apparatus according to a first embodiment of the present invention. [Figure 1B]FIG. 1B is a schematic elevational view for explaining the configuration of the substrate processing apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining a configuration example of a processing unit provided in the substrate processing apparatus. [Diagram 3] FIG. 3 is a schematic diagram for explaining how a substrate is carried in and out of a thermal processing unit provided in the substrate processing apparatus. [Figure 4] FIG. 4 is a block diagram for explaining a configuration example relating to control of the substrate processing apparatus. [Diagram 5] FIG. 5 is a flow chart for explaining a specific flow of substrate processing by the substrate processing apparatus. [Figure 6] FIG. 6 is a time chart of steps performed in the heat treatment chamber in the substrate processing. [Figure 7] FIG. 7 is a schematic diagram for explaining a change in the surface state of the substrate caused by repeating the metal oxide layer forming step and the metal oxide layer removing step in the substrate processing. [Figure 8] FIG. 8 is a schematic cross-sectional view of a modified example of the heat treatment unit. [Figure 9] FIG. 9 is a schematic cross-sectional view of a modified example of a processing unit provided in the substrate processing apparatus. [Figure 10] FIG. 10 is a schematic cross-sectional view for explaining an example of the configuration of a first thermal processing unit provided in a substrate processing apparatus according to a second embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view for explaining an example of the configuration of the second thermal processing unit provided in the substrate processing apparatus according to the second embodiment. [Figure 12] FIG. 12 is a flowchart for explaining a specific flow of substrate processing by the substrate processing apparatus according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. First Embodiment Fig. 1A is a plan view for explaining the configuration of a substrate processing apparatus 1 according to a first embodiment of the present invention, and Fig. 1B is a schematic elevational view for explaining the configuration of the substrate processing apparatus 1. The substrate processing apparatus 1 is a single-wafer processing apparatus that processes substrates W, such as silicon wafers, one by one. In this embodiment, the substrate W is a disk-shaped substrate. The substrate W has, for example, a first main surface W1 (see FIG. 1B) on which a metal layer is exposed, and a second main surface W2 opposite to the first main surface W1.

[0042] The metal layer exposed from the first main surface W1 is, for example, a metal nitride layer (metal nitride layer) containing a group III metal. Group III metal means a metal in group 13 of the periodic table. Specifically, group III metal means aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). The substrate processing apparatus 1 includes a plurality of processing units 2 that process substrates W with a processing fluid, a load port LP on which a carrier C that accommodates a plurality of substrates W to be processed in the processing units 2 is placed, transport robots IR and CR that transport the substrates W between the load port LP and the processing units 2, and a controller 3 that controls the substrate processing apparatus 1.

[0043] The transport robot IR transports the substrate W between the carrier C and the transport robot CR. The transport robot CR transports the substrate W between the transport robot IR and the processing units 2. The transport robots IR and CR are disposed on a transport path TR that extends from a plurality of load ports LP to a plurality of processing units 2. The multiple processing units 2 form four processing towers arranged at four horizontally spaced positions. Each processing tower includes multiple processing units 2 stacked vertically. The four processing towers are arranged two on each side of the transport path TR. In this embodiment, the processing units 2 are dry processing units that process the substrate W with a processing gas such as an oxidizing gas or an etching gas without supplying a liquid to the substrate W.

[0044] The processing unit 2 includes a dry chamber 4 provided with an loading / unloading opening 4a through which the substrate W passes, and a heat treatment unit 5 that supplies a processing gas to the substrate W while heating the substrate W in the dry chamber 4. An openable and closable shutter 6 is provided at the loading / unloading opening 4a. A hand H of the transport robot CR loads and unloads the substrate W into and from the dry chamber 4 through the loading / unloading opening 4a.

[0045] FIG. 2 is a schematic cross-sectional view for explaining an example of the configuration of the heat-treating unit 5. As shown in FIG. The heat treatment unit 5 includes a hot plate 20 as a heating member, a heat treatment chamber 30 (chamber) that houses the hot plate 20, a plurality of lift pins 40 that move up and down through the hot plate 20, and a pin lifting drive mechanism 41 that moves the plurality of lift pins 40 in the vertical direction.

[0046] The hot plate 20 has a heating surface 20a on which the substrate W is placed. The hot plate 20 has a built-in heater 21. The heater 21 can heat the substrate W to a temperature substantially equal to that of the heater 21. The heater 21 is configured to heat the substrate W placed on the heating surface 20a in a temperature range from room temperature (e.g., 25°C) to 400°C. Specifically, a current supply unit (not shown) is connected to the heater 21, and the temperature of the heater 21 changes to a temperature within the temperature range by adjusting the current supplied from the current supply unit. The hot plate 20 is an example of a temperature adjustment member, and the heating surface 20a is an example of a temperature adjustment surface.

[0047] The heat treatment chamber 30 includes a chamber body 31 and a lid 32 that moves up and down above the chamber body 31. The heat treatment unit 5 includes a lid lifting mechanism 33 that lifts and lowers the lid 32 (moves it up and down). The chamber body 31 has an opening that opens upward. More specifically, the chamber body 31 includes a support portion 34 that supports the hot plate 20, and a tubular portion 35 that extends upward from the periphery of the support portion 34. The support portion 34 has a substantially circular shape in a plan view, and accordingly, the tubular portion 35 has a cylindrical shape. The opening of the chamber body 31 is formed by the tubular portion 35.

[0048] The lid 32 includes a plate portion 37 extending parallel to the heating surface 20a, and a tube portion 38 extending downward from the periphery of the plate portion 37. The plate portion 37 is substantially circular in plan view, and the tube portion 38 is cylindrical accordingly. The lower end of the tube portion 38 faces the upper end of the tube portion 35 of the chamber body 31. This allows the opening of the chamber body 31 to be opened and closed by the up and down movement of the lid 32. The gap between the tube portion 35 of the chamber body 31 and the tube portion 38 of the lid 32 is sealed by an elastic member 39 such as an O-ring. The lower surface of the plate portion 37 is parallel to the heating surface 20a of the hot plate 20. More specifically, when the substrate W is placed on the heating surface 20a, a space is formed between the substrate W and the plate portion 37.

[0049] The lid 32 is moved up and down by a lid lifting drive mechanism 33 between a lower position (position shown in FIG. 2) where it closes the opening of the chamber body 31 to form a sealed processing space SP inside, and an upper position (position shown in FIG. 3, described later) where it is retracted upward to open the opening. When the lid 32 is in the lower position, the chamber body 31 and the lid 32 come into contact. The sealed processing space SP is a space that contacts the upper surface of the substrate W. When the lid 32 is in the upper position, the hand H of the transport robot CR can access the inside of the heat treatment chamber 30.

[0050] The lid lifting / lowering drive mechanism 33 may be an electric motor or an air cylinder, or may be an actuator other than these. The multiple lift pins 40 are connected by a connecting plate 43. The multiple lift pins 40 are moved up and down between an upper position (position in FIG. 3 described later) where the substrate W is supported above the heating surface 20a, and a lower position (position shown in FIG. 2) where the tip portion (upper end portion) is recessed below the heating surface 20a, by a pin lifting drive mechanism 41 raising and lowering the connecting plate 43. The pin lifting drive mechanism 41 may be an electric motor or an air cylinder, or may be an actuator other than these.

[0051] The multiple lift pins 40 are inserted into multiple through holes 22 that penetrate the hot plate 20 and the chamber body 31. The intrusion of fluid from outside the heat treatment chamber 30 into the through holes 22 is prevented by a bellows 42 that surrounds the lift pins 40. The bellows 42 expands and contracts in response to the up and down movement of a connecting plate 43, and keeps the space within the heat treatment chamber 30 airtight.

[0052] The lift pins 40 include hemispherical upper ends that come into contact with the lower surface of the substrate W. The tips of the multiple lift pins 40 are disposed at the same height. The heat-treatment unit 5 has a plurality of fluid introduction ports 10 for introducing gas into the sealed treatment space SP in the heat-treatment chamber 30. Each fluid introduction port 10 is a through-hole penetrating the plate portion 37 of the lid 32. The multiple fluid introduction ports 10 are arranged at intervals in the circumferential and radial directions of the plate portion 37.

[0053] The multiple fluid introduction ports 10 include multiple first fluid introduction ports 10A to which a first fluid line 50 that introduces an inert gas and an oxidizing gas is connected, and multiple second fluid introduction ports 10B to which a second fluid line 51 that introduces an inert gas and an etching gas is connected. The first fluid line 50 and the second fluid line 51 are mainly composed of piping. The inert gas is, for example, nitrogen (N2) gas. The inert gas is a gas that does not react with the metal nitride layer exposed from the first main surface W1 of the substrate W (is inert with respect to the metal nitride layer).

[0054] The inert gas is not limited to nitrogen gas, but may be, for example, a rare gas such as argon (Ar) gas, or a mixed gas of nitrogen gas and a rare gas. That is, the inert gas may be a gas containing at least one of nitrogen gas and a rare gas. The oxidizing gas is, for example, ozone (O3) gas. The oxidizing gas is a gas that oxidizes the metal nitride layer exposed from the first main surface W1 of the substrate W to form a metal oxide layer (metal oxide layer). The oxidizing gas is not limited to ozone gas, and may be, for example, oxidizing water vapor, O2, N2O, NO2, N2O, or halogen gas such as F2 or Cl2. When the metal nitride layer is a gallium nitride layer, the metal nitride layer is oxidized by the oxidizing gas and changes into a gallium oxide layer. The oxidizing gas is also called a gaseous oxidizing agent.

[0055] The etching gas is a gas that etches the metal oxide layer to remove it from the first main surface W1 of the substrate W. The etching gas is a mixed gas of water vapor and a reactive gas. The reactive gas is a gas that has reactivity with the metal oxide layer in the presence of water, such as ammonia (NH3) gas. As the water vapor, it is preferable to use superheated water vapor that is sufficiently heated, i.e., heated to 100°C or higher. The etching gas is an example of an etching fluid.

[0056] The metal oxide constituting the metal oxide layer reacts with the reactive gas and water vapor to generate metal hydroxide that is adsorbed by the water vapor. The metal hydroxide is adsorbed by the water vapor in the etching gas, and is removed from the upper surface of the substrate W. The reactive gas is not limited to ammonia gas, but may be an alkaline gas containing an alkaline component that exhibits alkalinity in water or an acidic gas containing an acidic component that exhibits acidity in water. For example, ammonia gas is selected as the alkaline gas.

[0057] The acid gas is typically hydrogen chloride (HCl) gas. The acid gas may be composed of at least one gas selected from hydrogen chloride gas, carbon dioxide gas, hydrogen sulfide (H2S) gas, and sulfur dioxide (SO2) gas. Group III metals, like silicon (Si), are used as materials for power devices. Unlike silicon carbide (SiC) crystals, the group III metal oxides formed on the surfaces of group III metal nitride crystals can react with alkaline or acidic components in the presence of water to form water-soluble hydroxides.

[0058] When the metal nitride layer is a gallium nitride layer, as shown in the above-mentioned chemical reaction formula 1, the gallium nitride constituting the gallium nitride layer reacts with ozone gas as an oxidizing gas to generate gallium oxide (Ga2O3) constituting a gallium oxide layer as a metal oxide layer. When the reactive gas is ammonia gas, the gallium oxide constituting the gallium oxide layer reacts with ammonia gas, and as shown in the above-mentioned chemical reaction formulas 2 and 3, the gallium oxide reacts with ammonia or ammonia and water to form an ionized state (GaO 3- When the reactive gas contained in the etching fluid is hydrogen chloride gas, gallium oxide reacts with hydrogen chloride or hydrogen chloride and water to form an ionized state (GaO 3- )

[0059] To the first fluid line 50, a first inert gas line 52 for supplying an inert gas to the first fluid line 50, and an oxidizing fluid line 53 for supplying an oxidizing gas to the first fluid line 50 are connected. The first inert gas line 52 is provided with a first inert gas valve 62A for opening and closing the flow path, and a first inert gas flow rate adjustment valve 62B for adjusting the flow rate of the inert gas supplied to the first fluid line 50.

[0060] An oxidizing fluid valve 63A for opening and closing the flow path of the oxidizing fluid line 53, and an oxidizing fluid flow rate adjustment valve 63B for adjusting the flow rate of the oxidizing gas supplied to the first fluid line 50 are provided in the oxidizing fluid line 53. When the first inert gas valve 62A is opened, an inert gas is introduced into the sealed processing space SP through the multiple first fluid introduction ports 10A, and the inert gas is supplied toward the upper surface of the substrate W. When the oxidizing fluid valve 63A is opened, an oxidizing gas is introduced into the sealed processing space SP through the multiple first fluid introduction ports 10A, and the oxidizing gas is supplied toward the upper surface of the substrate W.

[0061] When both the first inert gas valve 62A and the oxidizing fluid valve 63A are opened, a mixed gas of an inert gas and an oxidizing gas is introduced into the sealed processing space SP from the first fluid introduction ports 10A. By adjusting the opening of the first inert gas flow control valve 62B and the oxidizing fluid flow control valve 63B, the concentration (partial pressure) of the oxidizing gas component in the mixed gas introduced into the sealed processing space SP from the first fluid introduction ports 10A can be adjusted.

[0062] The first fluid line 50, the first inert gas line 52, and the first inert gas valve 62A are an example of an inert gas supply unit. The first fluid line 50, the oxidizing fluid line 53, and the oxidizing fluid valve 63A are an example of an oxidizing fluid supply unit that supplies an oxidizing fluid into the heat treatment chamber 30. Connected to the second fluid line 51 are a second inert gas line 54 which supplies an inert gas to the second fluid line 51, a water line 55 which supplies water vapor to the second fluid line 51, and a reactive gas line 56 which supplies a reactive gas to the second fluid line 51.

[0063] The second inert gas line 54 is provided with a second inert gas valve 64A for opening and closing the flow path, and a second inert gas flow rate adjustment valve 64B for adjusting the flow rate of the inert gas supplied to the second fluid line 51. The water line 55 is provided with a water valve 65A for opening and closing the flow path thereof, and a water flow rate adjustment valve 65B for adjusting the flow rate of water vapor supplied to the second fluid line 51.

[0064] The reactive gas line 56 is provided with a reactive gas valve 66A for opening and closing the flow path thereof, and a reactive gas flow rate adjustment valve 66B for adjusting the flow rate of the reactive gas supplied to the second fluid line 51. When the second inert gas valve 64A is opened, an inert gas is introduced into the sealed processing space SP through the multiple second fluid introduction ports 10B, and the inert gas is supplied toward the upper surface of the substrate W. When the water valve 65A is opened, water vapor is introduced into the sealed processing space SP through the multiple second fluid introduction ports 10B, and the inert gas is supplied toward the upper surface of the substrate W. When the reactive gas valve 66A is opened, a reactive gas is introduced into the sealed processing space SP through the multiple second fluid introduction ports 10B, and the inert gas is supplied toward the upper surface of the substrate W.

[0065] When at least two of the second inert gas valve 64A, the water valve 65A, and the reactive gas valve 66A are opened, a mixed gas of the inert gas, the water vapor, and the reactive gas corresponding to the opened valve is introduced (supplied) into the sealed processing space SP from the second fluid introduction ports 10B. When both the water valve 65A and the reactive gas valve 66A are opened, the water vapor and the reactive gas are mixed in the second fluid line 51 to form an etching gas, and the etching gas is introduced into the sealed processing space SP from the second fluid introduction ports 10B.

[0066] By adjusting the opening of the second inert gas flow control valve 64B, the water flow control valve 65B, and the reactive gas flow control valve 66B, the concentration (partial pressure) of the reactive gas components and water vapor in the gas introduced into the sealed processing space SP from the multiple second fluid introduction ports 10B can be adjusted. The second fluid line 51, the second inert gas line 54, and the second inert gas valve 64A are an example of an inert gas supply unit. The second fluid line 51, the water line 55, and the water valve 65A are an example of a water supply unit (water vapor supply unit). The second fluid line 51, the reactive gas line 56, and the reactive gas valve 66A are an example of a reactive gas supply unit. The water supply unit and the reactive gas supply unit function as an etching gas supply unit (etching fluid supply unit) that supplies an etching gas into the heat treatment chamber 30.

[0067] The heat treatment unit 5 is provided with a plurality of fluid discharge ports 15 formed in the chamber body 31 and configured to exhaust the internal atmosphere of the heat treatment chamber 30. Each fluid discharge port 15 is a through-hole penetrating the support portion 34 of the chamber body 31 on the side of the hot plate 20. The plurality of fluid discharge ports 15 are preferably arranged at intervals in the circumferential direction of the support portion 34. The multiple fluid discharge ports 15 include multiple first fluid discharge ports 15A to which a first fluid discharge line 57 that mainly exhausts an oxidizing gas is connected, and multiple second fluid discharge ports 15B to which a second fluid discharge line 58 that mainly exhausts an etching gas is connected. The first fluid discharge line 57 and the second fluid discharge line 58 are mainly composed of piping.

[0068] A first fluid discharge valve 67 for opening and closing the flow path is provided in the first fluid discharge line 57, and a second fluid discharge valve 68 for opening and closing the flow path is provided in the second fluid discharge line 58. The first fluid discharge line 57 and the second fluid discharge line 58 may be configured to discharge fluid toward a common exhaust device (not shown), or may have different exhaust destinations.

[0069] FIG. 3 is a schematic diagram for explaining how the substrate W is carried in and out of the thermal processing unit 5. As shown in FIG. The substrate W is carried into the heat treatment unit 5 as follows. As shown in Fig. 3, with the lid 32 in the upper position and the multiple lift pins 40 in the upper position, the hand H of the transport robot CR enters the heat treatment chamber 30 and transfers the substrate W to the multiple lift pins 40. After the hand H is retracted from the heat treatment chamber 30, the pin lifting drive mechanism 41 lowers the multiple lift pins 40 supporting the substrate W from below to place the substrate W on the heating surface 20a of the hot plate 20 (see Fig. 2). With the substrate W placed on the heating surface 20a, the lid 32 is moved to the lower position to form a sealed treatment space SP, completing the carrying-in of the substrate W.

[0070] On the other hand, the substrate W is unloaded from the heat treatment unit 5 as follows. As shown in Fig. 3, the lid lift drive mechanism 33 moves the lid 32 to the upper position, and the pin lift drive mechanism 41 moves the multiple lift pins 40 to the upper position. With the lid 32 in the upper position and the multiple lift pins 40 in the upper position, the hand H of the transport robot CR enters the heat treatment chamber 30 and receives the substrate W from the multiple lift pins 40. Thereafter, the hand H of the transport robot CR retreats from the heat treatment chamber 30, completing the unloading of the substrate W.

[0071] 4 is a block diagram showing an electrical configuration of a main part of the substrate processing apparatus 1. The controller 3 includes a microcomputer, and controls objects to be controlled provided in the substrate processing apparatus 1 according to a predetermined control program. Specifically, the controller 3 may be a computer including a processor (CPU) 3a and a memory 3b storing a control program. The controller 3 is configured to execute various controls for substrate processing by the processor 3a executing the control program.

[0072] Specific objects to be controlled by the controller 3 are the transport robots IR, CR, the pin lifting drive mechanism 41, the lid lifting drive mechanism 33, the pin lifting drive mechanism 41, the heater 21, the first inert gas valve 62A, the first inert gas flow control valve 62B, the oxidizing fluid valve 63A, the oxidizing fluid flow control valve 63B, the second inert gas valve 64A, the second inert gas flow control valve 64B, the water valve 65A, the water flow control valve 65B, the reactive gas valve 66A, the reactive gas flow control valve 66B, the first fluid exhaust valve 67, the second fluid exhaust valve 68, etc.

[0073] An example of substrate processing in which the metal layer exposed from the first main surface W1 of the substrate W is a gallium nitride layer, the oxidizing fluid is ozone gas, and the reactive gas is ammonia gas will be described below. Fig. 5 is a flow chart for explaining an example of substrate processing performed by the substrate processing apparatus 1. Fig. 5 mainly shows processing realized by the controller 3 executing a program.

[0074] In the substrate processing by the substrate processing apparatus 1, for example, as shown in Fig. 5, a substrate loading step (step S1) and a preliminary replacement step (step S2) are first performed in this order. Then, an oxidizing gas supply step (step S3), an oxidizing gas removal step (step S4), an etching gas supply step (step S5), a water supply continuation step (step S6), and a water removal step (step S7) are each performed at least once in this order. Then, after the final water removal step, a substrate unloading step (step S8) is performed.

[0075] 6 is a time chart of steps in substrate processing carried out in the heat treatment chamber 30. In the following, reference will be made mainly to FIGS. First, an unprocessed substrate W is carried from a carrier C to a processing unit 2 by a transport robot IR, CR (see FIG. 1) (substrate carrying step: step S1). The substrate W is placed on the heating surface 20a of the hot plate 20 with the first main surface W1, on which the gallium nitride layer is exposed, facing upward (substrate placing step).

[0076] Thereafter, the lid 32 is lowered, so that the substrate W is placed on the hot plate 20 in the sealed processing space SP formed by the chamber body 31 and the lid 32. The substrate W placed on the heating surface 20a is heated to a predetermined oxidation temperature (first temperature) by the hot plate 20 (substrate heating step). The predetermined oxidation temperature is, for example, a temperature not lower than 100° C. and not higher than 400° C.

[0077] With the sealed processing space SP formed, the first fluid exhaust valve 67 and the first inert gas valve 62A are opened. As a result, an inert gas is introduced into the sealed processing space SP from the first fluid introduction port 10A, while the atmosphere in the sealed processing space SP is exhausted to the outside of the heat treatment chamber 30 via the first fluid exhaust port 15A. That is, before the oxidizing gas is supplied to the sealed processing space SP, the atmosphere in the sealed processing space SP is replaced with the inert gas (preliminary replacement step: step S2).

[0078] By continuing the supply of the inert gas for a predetermined replacement time, the atmosphere in the sealed processing space SP is sufficiently replaced with the inert gas, and the sealed processing space SP is filled with the inert gas. The predetermined replacement time is, for example, 10 seconds or more and 120 seconds or less. The flow rate of the inert gas in the preliminary replacement step (preliminary replacement flow rate) is a first flow rate. The first flow rate is, for example, 5 L / min or more and 50 L / min or less. The preliminary replacement flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from the multiple first fluid introduction ports 10A.

[0079] With the sealed processing space SP filled with inert gas, the oxidizing fluid valve 63A is opened. As a result, ozone gas is introduced into the sealed processing space SP from the multiple first fluid introduction ports 10A, and the ozone gas is supplied toward the first main surface W1 of the substrate W (oxidizing gas supplying step: step S3). The oxidizing gas supplying step is an example of an oxidizing fluid supplying step. The first main surface W1 of the substrate W is treated with ozone gas discharged from the multiple first fluid introduction ports 10A (oxidation treatment step). More specifically, a gallium oxide layer consisting of one or several atomic layers is formed on the surface of the gallium nitride layer exposed from the first main surface W1 of the substrate W (metal oxide layer forming step, gallium oxide layer forming step). The substrate W is heated to an oxidation temperature on the hot plate 20. Therefore, in the metal oxide layer forming step, a heating and oxidation step is performed in which ozone gas is supplied toward the first main surface W1 of the substrate W while the substrate W is heated to the oxidation temperature.

[0080] The introduction of the ozone gas into the sealed processing space SP continues for a predetermined oxidation processing time, which is, for example, not less than 10 seconds and not more than 300 seconds. The flow rate of the oxidizing gas in the oxidizing gas supplying step is a predetermined oxidizing flow rate. The oxidizing flow rate is, for example, 5 L / min or more and 50 L / min or less. The oxidizing flow rate means the total flow rate of the oxidizing gas introduced into the sealed processing space SP from all the first fluid introduction ports 10A.

[0081] During the introduction of the oxidizing gas into the sealed processing space SP, the flow rate of the inert gas is adjusted to a first partial pressure adjustment flow rate. The first partial pressure adjustment flow rate is, for example, a second flow rate lower than the first flow rate. The second flow rate is, for example, 0 L / min or more and 50 L / min or less. The first partial pressure adjustment flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from the multiple first fluid introduction ports 10A.

[0082] By adjusting the flow rate of the inert gas, the partial pressure of the ozone gas in the sealed processing space SP can be adjusted to a partial pressure suitable for oxidizing one or several atomic layers of the surface layer of the gallium nitride layer (ozone gas partial pressure adjustment process, oxidizing gas partial pressure adjustment process). Since the first fluid exhaust valve 67 continues to be open even during the supply of the ozone gas, the ozone gas in the sealed processing space SP is exhausted through the first fluid exhaust line 57.

[0083] After the first main surface W1 of the substrate W is treated with the ozone gas, the oxidizing fluid valve 63A is closed, whereby the discharge of the ozone gas is stopped while the discharge of the inert gas from the multiple first fluid introduction ports 10A continues. By supplying the inert gas toward the main surface of the substrate W, the atmosphere in the sealed processing space SP is replaced with the inert gas, and the ozone gas is removed from the sealed processing space SP (oxidizing gas removal process: step S4). The oxidizing gas removal process is an example of an oxidizing fluid removal process.

[0084] At the same time as or after the oxidizing fluid valve 63A is closed, the first inert gas flow rate control valve 62B is controlled to change the flow rate of the inert gas to a predetermined oxidizing fluid removal flow rate. The oxidizing fluid removal flow rate is, for example, a first flow rate. The oxidizing fluid removal flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from all the first fluid introduction ports 10A.

[0085] After the first main surface W1 of the substrate W is treated with ozone gas, the temperature of the hot plate 20 is lowered while the substrate W is kept placed on the heating surface 20a. As the temperature of the hot plate 20 is lowered, the temperature of the substrate W is lowered. Specifically, by changing the heater temperature to the etching temperature, the temperatures of the hot plate 20 and the substrate W are gradually lowered and reach the etching temperature (second temperature). In this way, the heating of the substrate W is weakened, and the temperature of the substrate W is adjusted to a predetermined etching temperature lower than the oxidation temperature (temperature adjustment step, heating weakening step, low-temperature heating step). The etching temperature is, for example, a temperature of 25°C or higher and lower than 100°C.

[0086] The hot plate 20 functions as a temperature adjusting member that adjusts the temperature of the substrate W placed on the heating surface 20a, which serves as a temperature adjusting surface, to a first temperature or a second temperature. In the process of lowering the temperature of the substrate W, the first fluid exhaust valve 67 is closed and the second fluid exhaust valve 68 is opened. This changes the exhaust destination of the atmosphere from the sealed processing space SP from the first fluid exhaust line 57 to the second fluid exhaust line 58 (fluid exhaust line changing step).

[0087] While the temperature of the substrate W is decreasing, the first inert gas valve 62A is closed and the second inert gas valve 64A is opened. This stops the discharge of the inert gas from the first fluid introduction ports 10A and starts the discharge of the inert gas from the second fluid introduction ports 10B. The second inert gas flow rate adjustment valve 64B is controlled to adjust the flow rate of the inert gas introduced into the sealed processing space SP from the second fluid introduction ports 10B to the first flow rate.

[0088] After the temperature of the substrate W reaches the etching temperature, the water valve 65A and the reactive gas valve 66A are opened. This allows an etching gas (a mixed gas of water vapor and ammonia gas) to be introduced into the sealed processing space SP from the multiple second fluid introduction ports 10B, and the etching gas is supplied toward the first main surface W1 of the substrate W (etching gas supplying step: step S5). The etching gas supplying step is an example of an etching fluid supplying step.

[0089] The first main surface W1 of the substrate W is processed by the etching gas discharged from the multiple second fluid introduction ports 10B (etching process). More specifically, the gallium oxide layer formed on the first main surface W1 of the substrate W is etched to selectively remove the gallium oxide layer (metal oxide layer removal process, gallium oxide layer removal process). In the metal oxide layer removal process, the gallium oxide layer is etched while the temperature of the substrate W is at the etching temperature (low-temperature etching process).

[0090] The introduction of the etching gas into the sealed processing space SP continues for a predetermined etching processing time, which is, for example, not less than 5 seconds and not more than 120 seconds. The flow rate of the water vapor in the etching gas supply process is a predetermined first etching flow rate. The first etching flow rate is, for example, 5 L / min or more and 50 L / min or less. The flow rate of the water vapor in the etching gas supply process means the total flow rate of the water vapor introduced into the sealed processing space SP from all the second fluid introduction ports 10B.

[0091] The flow rate of the ammonia gas in the etching gas supply process is a predetermined second etching flow rate. The second etching flow rate is, for example, 1 L / min or more and 50 L / min or less. The flow rate of the ammonia gas in the etching gas supply process means the total flow rate of the ammonia gas introduced into the sealed processing space SP from all the second fluid introduction ports 10B.

[0092] While the etching gas is being introduced into the sealed processing space SP from the multiple second fluid introduction ports 10B, the flow rate of the inert gas is adjusted to a second partial pressure adjustment flow rate by adjusting the aperture of the second inert gas flow rate control valve 64B. The second partial pressure adjustment flow rate is lower than the preliminary replacement flow rate, for example, the second flow rate. The second partial pressure adjustment flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from the multiple second fluid introduction ports 10B.

[0093] By adjusting the flow rate of the inert gas, the partial pressure of the water vapor and the partial pressure of the ammonia gas in the sealed processing space SP can be adjusted to partial pressures suitable for selectively etching the gallium oxide layer (etching gas partial pressure adjusting step). The temperature of the water vapor discharged from the multiple second fluid introduction ports 10B is higher than the temperature (etching temperature) of the substrate W in the etching gas supply step. Therefore, in the vicinity of the first main surface W1 of the substrate W, the temperature of the water vapor decreases, and fine liquid water particles are formed.

[0094] The concentration of ammonia gas dissolved in this fine mist of water is 1×10 -6If the concentration of ammonia gas dissolved in the fine mist of water is 1 mol / L or more and 15 mol / L or less, selective etching of a gallium oxide layer having a thickness of one or several atomic layers can be achieved. It is particularly preferable that the concentration of ammonia gas dissolved in the fine mist of water is 1 mol / L. After the gallium oxide layer is removed from the first main surface W1 of the substrate W, the water valve 65A is kept open while the reactive gas valve 66A is closed. This stops the introduction of ammonia gas from the second fluid introduction ports 10B into the sealed processing space SP, and continues the introduction of water vapor from the second fluid introduction ports 10B into the sealed processing space SP (water vapor supply continuation process: step S6). After the metal oxide layer removal process, the reactive gas is removed from the sealed processing space SP by continuing the introduction of water vapor into the sealed processing space SP (reactive gas removal process, ammonia gas removal process).

[0095] After the supply of the reactive gas is stopped, the introduction of water vapor into the sealed processing space SP is continued for a predetermined water supply duration, which is, for example, not less than 10 seconds and not more than 120 seconds. While the supply of water vapor to the sealed processing space SP is continued, the flow rate of the inert gas is adjusted to a predetermined ammonia gas removal flow rate by adjusting the aperture of the second inert gas flow rate control valve 64B. The ammonia gas removal flow rate is, for example, equal to the second partial pressure adjustment flow rate, i.e., a second flow rate. The flow rate of the inert gas in the water vapor supply continuation step means the total flow rate of the inert gas introduced from the multiple second fluid introduction ports 10B into the sealed processing space SP.

[0096] After the supply of water vapor continues for a predetermined water supply duration, the water valve 65A is closed. This stops the supply of water vapor to the sealed processing space SP. Meanwhile, the supply of inert gas to the sealed processing space SP continues, so that water vapor is removed from the sealed processing space SP (water removal process, water vapor removal process: step S7). At the same time as or after the water valve 65A is closed, the heating of the substrate W is intensified to adjust the temperature of the substrate W to the oxidation temperature (heating intensification step). Specifically, by changing the heater temperature to a predetermined etching temperature, the temperatures of the hot plate 20 and the substrate W gradually increase and reach the predetermined oxidation temperature.

[0097] In the process of increasing the temperature of the substrate W, the second fluid exhaust valve 68 is closed and the first fluid exhaust valve 67 is opened. This changes the exhaust destination of the atmosphere from the sealed processing space SP from the second fluid exhaust line 58 to the first fluid exhaust line 57 (fluid exhaust line changing step). At the same time as or after the water valve 65A is closed, the flow rate of the inert gas is changed to a predetermined water removal flow rate. The water removal flow rate is, for example, a first flow rate. The flow rate of the inert gas in the water removal process means the total flow rate of the inert gas introduced into the sealed processing space SP from all the second fluid introduction ports 10B.

[0098] Thereafter, the oxidizing gas supply step (step S3) to the water removal step (step S7) may be performed one or more times each. In FIG. 5, "N" means an integer equal to or greater than 0 (N=0, 1, 2,...). The cycle process is performed one or more times in total, and then the substrate removal step (step S8) is performed without performing a thermal strengthening step in the final water removal step (step S7). The substrate W removed from the thermal processing unit 5 is handed over from the transport robot CR to the transport robot IR, and stored in the carrier C by the transport robot IR.

[0099] FIG. 7 is a schematic diagram for explaining a change in the surface state of the substrate W caused by repeating a metal oxide layer forming step and a metal oxide layer removing step in substrate processing. The change in the appearance of the surface layer of the gallium nitride layer 100 due to the metal oxide layer forming step (step S3) and the metal oxide layer removing step (step S5) will be described with reference to Fig. 7. As shown in Fig. 7(a) and Fig. 7(b), a gallium oxide layer 101 consisting of one or several atomic layers is formed on the surface layer of the gallium nitride layer 100 by supplying ozone gas to the first main surface W1 of the substrate W (metal oxide layer forming step). The thickness D1 of the gallium oxide layer 101 is 0.3 nm or more and 5 nm or less.

[0100] In the metal oxide layer forming step, a gallium oxide layer 101 consisting of one atomic layer or several atomic layers is formed. The thickness of one atomic layer of the gallium nitride layer 100 is approximately the same as the thickness of one atomic layer of the gallium oxide layer 101. The thickness of one atomic layer of the gallium oxide layer 101 is 1 nm or less (for example, 0.3 nm to 0.4 nm). As described above, several atomic layers refers to two atomic layers to ten atomic layers.

[0101] 7(c) and 7(d), an etching gas is supplied toward the gallium oxide layer 101, thereby selectively removing the gallium oxide layer 101 from the substrate W (metal oxide layer removing step). That is, the entire gallium oxide layer 101 of one or several atomic layers formed on the surface of the gallium nitride layer 100 is removed. In this manner, by performing one cycle of cyclic processing in which the metal oxide layer forming step and the metal oxide layer removing step are one cycle, the gallium nitride layer 100 is etched by a thickness D1 of one or several atomic layers.

[0102] Thereafter, by performing another cycle of the cycle treatment as shown in Figures 7(e) and 7(f), the gallium nitride layer 100 is etched by a thickness D1 of one or several atomic layers. The thickness D1 of the gallium nitride layer 100 etched by performing one cycle of the cycle treatment is approximately constant. When the cycle treatment is performed multiple times, as shown in Fig. 7(g), a portion of the surface layer of the gallium nitride layer 100 having a thickness D2 equivalent to the product of the thickness D1 and the number of cycles (three cycles in Fig. 7(g)) is removed from the substrate W (D2 = D1 x number of cycles). The amount of the gallium nitride layer 100 etched by performing the cycle treatment multiple times corresponds to the thickness D2.

[0103] Therefore, by adjusting the number of times that the metal oxide layer forming step and the metal oxide layer removing step are repeatedly performed, a desired etching amount (the same amount as thickness D2) can be achieved. For example, if one cycle of the cycle treatment etches the gallium nitride layer 100 by 0.3 nm, by adjusting the number of times the cycle treatment is performed, it is possible to perform a substrate treatment in which the gallium nitride layer 100 is etched by 1.5 nm, or to perform a substrate treatment in which the gallium nitride layer 100 is etched by 1.8 nm. In other words, it is possible to control the amount of etching of the gallium nitride layer 100 for each cycle with accuracy of less than a nanometer.

[0104] In addition, in this substrate processing method, an etching gas containing water vapor and a reactive gas is used to selectively remove the gallium oxide layer 101. Unlike this substrate processing method, if liquid water and reactive liquid are supplied in a continuous flow to the first main surface W1 of the substrate W, unevenness occurs at the interface between the liquid water and the first main surface W1 of the substrate W. Therefore, at the molecular level, unevenness occurs in the frequency of collisions between the first main surface W1 of the substrate W and water molecules and reactive molecules at each position on the first main surface W1 of the substrate W.

[0105] Furthermore, in the heat treatment unit 5, the substrate W is not rotated during heat treatment, so when liquid water and reactive liquid are supplied in a continuous flow to the first main surface W1 of the substrate W, the first main surface W1 of the substrate W cannot be sufficiently dried, and watermarks may occur. Compared with liquid water, water vapor is more likely to diffuse near the first main surface W1 of the substrate W. Therefore, water molecules are more likely to collide evenly at each position on the first main surface W1 of the substrate W. Therefore, compared with the case where a liquid is used to remove the gallium oxide layer 101, it is possible to suppress unevenness in the amount of etching on the first main surface W1 of the substrate W with an accuracy of less than a nanometer. In particular, when the cycle process is performed multiple times, the effect of suppressing unevenness in the amount of etching on the first main surface W1 of the substrate W becomes significant.

[0106] Even if the material constituting the metal nitride layer is a nitride of a Group III metal other than gallium nitride, as described above, etching with water vapor and reactive gases with accuracy on the order of nanometers is possible. As described above, by performing the cyclic treatment at least once, the etching amount of the Group III metal nitride layer at each position on the first main surface W1 of the substrate W can be well controlled with accuracy of less than a nanometer.

[0107] When hydrogen chloride gas is used as the reactive gas, it is necessary to provide a silicon carbide film on the inner wall of the heat treatment chamber 30 to protect the heat treatment chamber from corrosion caused by hydrogen chloride. On the other hand, when ammonia gas is used as the reactive gas, it is not necessary to provide a protective film such as a silicon carbide film on the inner wall of the heat treatment chamber 30. Therefore, the cost of the substrate processing apparatus 1 can be reduced. According to the first embodiment, the etching gas is not entirely replaced with another gas, but the reactive gas is removed from the sealed processing space SP by continuing to supply water vapor constituting the etching gas (reactive gas removal process). This allows the reactive gas components adhering to the first main surface W1 of the substrate W to be adsorbed by water and quickly removed.

[0108] According to the first embodiment, after the reactive gas removal process, the water vapor present in the sealed processing space SP is replaced with an inert gas to remove the water vapor from the sealed processing space SP (water removal process). This makes it possible to suppress unintended etching of the metal nitride layer by water molecules or oxygen molecules slightly dissolved in water. According to the first embodiment, after the metal oxide layer forming step and before the metal oxide layer removing step, an inert gas is supplied to the first main surface W1 of the substrate W, thereby replacing the oxidizing gas present in the sealed processing space SP with the inert gas. This allows the oxidizing gas to be removed from the sealed processing space SP before the metal oxide layer removing step (oxidizing gas removing step). Therefore, unintended oxidation of the metal nitride layer in the metal oxide layer removing step can be suppressed.

[0109] According to the first embodiment, in the metal oxide layer removal step, the temperature of the substrate W is adjusted to a temperature lower than that of the etching gas supplied from the etching fluid supply unit toward the first main surface W1 of the substrate W (temperature adjustment step). Therefore, the temperature of the etching gas is lowered near the first main surface W1 of the substrate W, and the kinetic energy of the reactive molecules and water molecules near the first main surface W1 of the substrate W is reduced. Therefore, the reactive molecules and water molecules adsorbed on the first main surface W1 of the substrate W are suppressed from leaving the first main surface W1 of the substrate W. In other words, the adsorption of the reactive molecules and water molecules to the first main surface W1 of the substrate W is promoted. This makes it possible to increase the etching rate of the metal nitride layer. As a result, it is possible to increase the etching rate of the metal nitride layer while maintaining the etching amount per cycle of the cycle treatment at one atomic layer or several atomic layers.

[0110] According to the first embodiment, in the metal oxide layer forming step, an oxidizing gas is supplied toward the first main surface W1 of the substrate W while the substrate W is heated to an oxidation temperature (first temperature), thereby forming a metal oxide layer (thermal oxidation step). Then, in the metal oxide layer removing step, an etching fluid is supplied toward the first main surface W1 of the substrate W while the temperature of the substrate W is at an etching temperature (second temperature), thereby etching the metal oxide layer (low-temperature etching step).

[0111] Specifically, the metal nitride layer on the first main surface W1 of the substrate W is oxidized when the temperature of the substrate W is a relatively high oxidation temperature (e.g., 100°C or higher and 400°C or lower), and etching is performed when the temperature of the substrate W is a relatively low etching temperature (e.g., 25°C or higher and lower than 100°C). Therefore, in the metal oxide layer forming step, the oxidation rate of the metal nitride layer can be increased. On the other hand, in the metal oxide removing step, if the temperature of the substrate W is relatively high, the oxygen contained in the etching fluid in small amounts has oxidizing power, but the etching is performed at a relatively low temperature. Therefore, unintended oxidation of the metal nitride layer can be suppressed in the metal oxide layer removing step.

[0112] According to the first embodiment, both heating and temperature reduction of the substrate W are performed in a state where the substrate W is placed on the heating surface 20a of a single hot plate 20. Therefore, the substrate processing can be simplified compared to a configuration in which the substrate W is moved to a member separate from the hot plate 20 to change the temperature of the substrate W. Furthermore, according to the first embodiment, a cycle process in which the metal oxide layer forming step and the metal oxide layer removing step form one cycle is automatically performed a desired number of times by the controller 3. Therefore, a desired etching amount can be achieved by adjusting the number of times the metal oxide layer forming step and the metal oxide layer removing step are performed.

[0113] 8 is a schematic cross-sectional view of a modified example of the heat-treating unit 5 of the first embodiment. The heat-treating unit 5 according to the modified example may include a cool plate 70 that comes into contact with the hot plate 20 and reduces the temperature of the hot plate 20. The cool plate 70 is interposed between the support portion 34 of the chamber body 31 and the hot plate 20. A coolant path (not shown) is formed inside the cool plate 70, through which a coolant (typically, cooling water) circulates.

[0114] When substrate processing is performed using the thermal processing unit 5 according to this modification, the temperature of the hot plate 20 can be quickly lowered by starting the circulation of cooling water without changing the heater output of the hot plate 20. That is, the temperature of the substrate W can be quickly lowered. Fig. 9 is a schematic cross-sectional view of a modified example of the processing unit 2 of the first embodiment. As shown in Fig. 9, the processing unit 2 may further include a cooling unit 80 that cools the substrate W heated by the thermal processing unit 5 in the dry chamber 4, and an indoor transport mechanism 90 that transports the substrate W in the dry chamber 4. The cooling unit 80 is disposed in the dry chamber 4 near the load / unload port 4a.

[0115] The cooling unit 80 includes a cool plate 81, a plurality of lift pins 82 which penetrate the cool plate 81 and move up and down, and a pin lifting drive mechanism 83 which moves the lift pins 82 up and down. The cool plate 81 has a cooling surface 81a on which the substrate W is placed. The plurality of lift pins 82 are connected by a connecting plate 84. A coolant path (not shown) through which a coolant (typically, cooling water) circulates is formed inside the cool plate 81. The multiple lift pins 82 are vertically moved between an upper position where they support the substrate W above the cooling surface 81a and a lower position where their tips are recessed below the cooling surface 81a.

[0116] The indoor transport mechanism 90 transports the substrate W inside the dry chamber 4. More specifically, the indoor transport mechanism 90 includes an indoor transport hand 90H that transports the substrate W between the cooling unit 80 and the heat treatment unit 5. The indoor transport hand 90H is configured to be able to transfer the substrate W between the multiple lift pins 82 of the cooling unit 80 and to be able to transfer the substrate W between the lift pins 40 of the heat treatment unit 5. Thereby, the indoor transport hand 90H can operate to receive the substrate W from the lift pins 40 of the cooling unit 80 and transfer the substrate W to the lift pins 40 of the heat treatment unit 5. Furthermore, the indoor transport hand 90H can operate to receive the substrate W from the lift pins 40 of the heat treatment unit 5 and transfer the substrate W to the lift pins 40 of the cooling unit 80.

[0117] When the transport robot CR (see FIG. 1) loads the substrate W into the dry chamber 4, the shutter 6 is controlled to an open position that opens the load / unload port 4a. In this state, the hand H of the transport robot CR enters the dry chamber 4 and places the substrate W above the cool plate 81. Then, the multiple lift pins 82 rise to their upper positions and receive the substrate W from the hand H of the transport robot CR. Thereafter, the hand H of the transport robot CR retreats to the outside of the dry chamber 4.

[0118] Next, the indoor transport hand 90H of the indoor transport mechanism 90 receives the substrate W from the multiple lift pins 82 and transports the substrate W to the heat treatment unit 5. At this time, the lid 32 is in the open position (upper position), and the multiple lift pins 40 support the received substrate W at the upper position. After the indoor transport hand 90H retreats from the heat treatment chamber 30, the lift pins 40 descend to the lower position and place the substrate W on the heating surface 20a (see FIG. 2). Meanwhile, the lid 32 descends to the closed position (lower position) to form a sealed processing space SP containing the hot plate 20. In this state, the substrate W is subjected to heat treatment (for example, steps S2 to S8 in FIG. 4).

[0119] After the heat treatment is completed, the lid 32 rises to the open position (upper position) to open the heat treatment chamber 30. Furthermore, the multiple lift pins 40 rise to the upper position to push the substrate W above the heating surface 20a. In this state, the indoor transport hand 90H of the indoor transport mechanism 90 receives the substrate W from the multiple lift pins 40 and transports the substrate W to the multiple lift pins 82 of the cooling unit 80. The cooling unit 80 supports the received substrate W at the upper position. After the indoor transport hand 90H is retracted, the multiple lift pins 82 descend to the lower position, whereby the substrate W is placed on the cooling surface 81a of the cool plate 81. The substrate W is thereby cooled.

[0120] When cooling of the substrate W is completed, the lift pins 82 rise to the upper position, thereby pushing the substrate W above the cooling surface 81a. In this state, the shutter 6 is opened, and the hand H of the transport robot CR enters the dry chamber 4 and is positioned below the substrate W supported by the lift pins 40 at the upper position. In this state, the lift pins 40 are lowered, and the substrate W is handed over to the hand H of the transport robot CR. The hand H holding the substrate W retreats to the outside of the dry chamber 4, and then the shutter 6 closes the load / unload opening 4a.

[0121] <Second embodiment> The configuration of a substrate processing apparatus 1P according to a second embodiment of the present invention will be described below. The substrate processing apparatus 1P according to the second embodiment is mainly different from the substrate processing apparatus 1 according to the first embodiment in that the heat-treating unit 5 of the substrate processing apparatus 1P includes a first heat-treating unit 5A (see FIG. 10) and a second heat-treating unit 5B (see FIG. 11). FIG. 10 is a schematic cross-sectional view for explaining a configuration example of the first heat-treating unit 5A. FIG. 11 is a schematic cross-sectional view for explaining a configuration example of the second heat-treating unit 5B. In FIGS. 10 and 11 and FIG. 12 described later, components equivalent to those shown in the above-mentioned FIGS. 1 to 9 are denoted by the same reference numerals as in FIG. 1 and the like, and their description will be omitted.

[0122] 10, the first heat-treating unit 5A is mainly different from the heat-treating unit 5 according to the first embodiment in that the first heat-treating unit 5A does not have a second fluid line 51 (see FIG. 2), and all the fluid introduction ports 10 of the first heat-treating unit 5A are connected to the first fluid line 50. That is, all the fluid introduction ports 10 provided in the first heat-treating unit 5A are first fluid introduction ports 10A. Also, all the fluid discharge ports 15 provided in the first heat-treating unit 5A are first fluid discharge ports 15A that mainly exhaust oxidizing gas.

[0123] Hereinafter, the heat treatment chamber 30, the sealed processing space SP, the hot plate 20, and the lift pins 40 provided in the first heat treatment unit 5A will also be referred to as the first heat treatment chamber 30A (first chamber), the first sealed processing space SP1, the first hot plate 20A, and the first lift pins 40A, respectively. 11, the second heat-treating unit 5B is mainly different from the heat-treating unit 5 according to the first embodiment in that the second heat-treating unit 5B does not have a first fluid line 50, and all the fluid introduction ports 10 of the second heat-treating unit 5B are connected to second fluid lines 51. That is, all the fluid introduction ports 10 provided in the second heat-treating unit 5B are second fluid introduction ports 10B. Also, all the fluid discharge ports 15 provided in the second heat-treating unit 5B are second fluid discharge ports 15B that mainly exhaust etching gas.

[0124] Hereinafter, the heat treatment chamber 30, the sealed processing space SP, the hot plate 20, and the lift pins 40 provided in the second heat treatment unit 5B will also be referred to as the second heat treatment chamber 30B (second chamber), the second sealed processing space SP2, the second hot plate 20B, and the second lift pins 40B, respectively. The substrate processing by the substrate processing apparatus 1P according to the second embodiment is different from that of the substrate processing apparatus 1 according to the first embodiment. Specifically, the metal oxide layer forming step and the metal oxide layer removing step are performed in separate heat treatment units 5. Fig. 12 is a flow chart for explaining an example of the substrate processing performed by the substrate processing apparatus 1P.

[0125] In substrate processing by substrate processing apparatus 1P, for example, as shown in FIG. 12, first, a first substrate loading process (step S11), a first preliminary replacement process (step S12), an oxidizing gas supply process (step S13), an oxidizing gas removal process (step S14), a first substrate unloading process (step S15), a second substrate loading process (step S16), a second preliminary replacement process (step S17), an etching gas supply process (step S18), a water supply continuation process (step S19), a water removal process (step S20), and a second substrate unloading process (step S21) are performed at least once each in this order.

[0126] In the following, reference will be mainly made to FIGS. First, an unprocessed substrate W is carried into the first heat treatment unit 5A from the carrier C by the transport robots IR and CR (see FIG. 1) (first substrate carrying-in step: step S11). The substrate W is placed on the heating surface 20a of the first hot plate 20A with the first main surface W1, on which the gallium nitride is exposed, facing upward (first substrate placing step).

[0127] Thereafter, the lid 32 of the first heat treatment chamber 30A is lowered, so that the substrate W is placed on the first hot plate 20A in the first sealed processing space SP1 formed by the chamber body 31 and the lid 32. The substrate W placed on the heating surface 20a is heated to a predetermined oxidation temperature by the first hot plate 20A (substrate heating step). The predetermined oxidation temperature is, for example, a temperature of 100° C. or higher and 400° C. or lower. The first hot plate 20A is an example of a first temperature adjustment member, and the heating surface 20a of the first hot plate 20A is an example of a first temperature adjustment surface.

[0128] With the first sealed processing space SP1 formed, the first fluid exhaust valve 67 and the first inert gas valve 62A are opened. As a result, an inert gas is introduced into the first sealed processing space SP1 from the first fluid introduction ports 10A, while the atmosphere in the first sealed processing space SP1 is exhausted to the outside of the heat treatment chamber 30 via the first fluid exhaust ports 15A. That is, before the oxidizing gas is supplied to the first sealed processing space SP1, the atmosphere in the first sealed processing space SP1 is replaced with the inert gas (first preliminary replacement step: step S12).

[0129] By continuing the supply of the inert gas for a predetermined first replacement time, the atmosphere in the first sealed processing space SP1 is sufficiently replaced with the inert gas, and the first sealed processing space SP1 is filled with the inert gas. The predetermined first replacement time is, for example, 10 seconds or more and 120 seconds or less. The flow rate of the inert gas in the first preliminary replacement step (first preliminary replacement flow rate) is a predetermined first flow rate. The first flow rate is, for example, 5 L / min or more and 50 L / min or less. The flow rate of the inert gas in the first preliminary replacement step means the total flow rate of the inert gas introduced into the first sealed processing space SP1 from the multiple first fluid introduction ports 10A.

[0130] With the first sealed processing space SP1 filled with inert gas, the oxidizing fluid valve 63A is opened, whereby ozone gas is introduced into the first sealed processing space SP1 through the multiple first fluid introduction ports 10A, and the ozone gas is supplied toward the first main surface W1 of the substrate W (oxidizing gas supplying step, ozone gas supplying step: step S13). The first main surface W1 of the substrate W is treated with ozone gas discharged from the multiple first fluid introduction ports 10A (oxidation treatment process). More specifically, a gallium oxide layer consisting of one or several atomic layers is formed on the surface of the gallium nitride layer exposed from the first main surface W1 of the substrate W (metal oxide layer forming process, gallium oxide layer forming process). The introduction of ozone gas into the first sealed processing space SP1 continues for a predetermined oxidation treatment time. The predetermined oxidation treatment time is, for example, not less than 10 seconds and not more than 120 seconds.

[0131] The flow rate of the oxidizing gas in the oxidizing gas supplying step is a predetermined oxidation flow rate. The oxidation flow rate is, for example, 5 L / min or more and 50 L / min or less. The flow rate of the oxidizing gas in the oxidizing gas supplying step means the total flow rate of the oxidizing gas introduced from all the first fluid introduction ports 10A into the first sealed processing space SP1. During the introduction of the oxidizing gas into the first sealed processing space SP1, the first inert gas flow rate control valve 64B is controlled to adjust the flow rate of the inert gas to a first partial pressure adjustment flow rate. The first partial pressure adjustment flow rate is, for example, a second flow rate lower than the first flow rate. The second flow rate is, for example, 5 L / min or more and 50 L / min or less. The first partial pressure adjustment flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from the multiple first fluid introduction ports 10A.

[0132] By adjusting the flow rate of the inert gas, the partial pressure of the ozone gas in the first sealed processing space SP1 can be adjusted to a partial pressure suitable for oxidizing one or several atomic layers of the surface layer of the gallium nitride layer (ozone gas partial pressure adjustment process, oxidizing gas partial pressure adjustment process). Since the first fluid exhaust valve 67 continues to be open even during the supply of the ozone gas, the ozone gas in the first sealed processing space SP1 is exhausted through the first fluid exhaust line 57.

[0133] After the first main surface W1 of the substrate W is treated with the ozone gas, the oxidizing fluid valve 63A is closed, whereby the discharge of the ozone gas is stopped while the discharge of the inert gas from the multiple first fluid introduction ports 10A continues. By supplying the inert gas toward the main surface of the substrate W, the atmosphere in the first sealed processing space SP1 is replaced with the inert gas, and ozone gas is removed from the first sealed processing space SP1 (oxidizing gas removal process: step S14).

[0134] At the same time as or after the oxidizing fluid valve 63A is closed, the first inert gas flow rate control valve 62B is controlled to change the flow rate of the inert gas to a predetermined oxidizing fluid removal flow rate. The oxidizing fluid removal flow rate is, for example, a first flow rate. The oxidizing fluid removal flow rate means the total flow rate of the inert gas introduced into the first sealed processing space SP1 from the multiple first fluid introduction ports 10A.

[0135] Thereafter, the substrate W that has been subjected to the oxidation treatment is carried out to the outside of the first thermal treatment unit 5A (step S15: first substrate carrying-out step). The substrate W unloaded from the first thermal processing unit 5A is loaded into the second thermal processing unit 5B by the transport robot CR (step S16: second substrate loading step). The substrate W is placed on the heating surface 20a of the second hot plate 20B with the first main surface W1 facing upward (second substrate loading step).

[0136] Thereafter, the lid 32 of the second heat treatment chamber 30B is lowered, so that the substrate W is placed on the second hot plate 20B in the second sealed processing space SP2 formed by the chamber body 31 and the lid 32. The temperature of the substrate W placed on the heating surface 20a is adjusted to a predetermined etching temperature by the second hot plate 20B (temperature adjustment step). The predetermined etching temperature is, for example, a temperature of 25°C or higher and lower than 100°C (low-temperature heating step). The second hot plate 20B is an example of a second temperature adjustment member that is lower than the first temperature adjustment member, and the heating surface 20a of the second hot plate 20B is an example of a second temperature adjustment surface.

[0137] When the substrate W is loaded into the second heat treatment chamber 30B and has already been cooled to a temperature lower than the etching temperature, the substrate W is heated to the etching temperature by being placed on the heating surface 20a of the second hot plate 20B. Conversely, when the substrate W is loaded into the second heat treatment chamber 30B and has a temperature higher than the etching temperature, the substrate W is cooled to the etching temperature by being placed on the heating surface 20a of the second hot plate 20B.

[0138] With the second sealed processing space SP2 formed, the second fluid discharge valve 68 and the second inert gas valve 64A are opened. As a result, an inert gas is introduced into the second sealed processing space SP2 from the second fluid introduction ports 10B, while the atmosphere in the second sealed processing space SP2 is discharged to the outside of the second heat treatment chamber 30B through the second fluid discharge ports 15B. That is, before the oxidizing gas is supplied to the second sealed processing space SP2, the atmosphere in the second sealed processing space SP2 is replaced with the inert gas (second preliminary replacement step: step S17).

[0139] By continuing the supply of the inert gas for a predetermined second replacement time, the atmosphere in the second sealed processing space SP2 is sufficiently replaced with the inert gas, and the second sealed processing space SP2 is filled with the inert gas. The predetermined second replacement time is, for example, 30 seconds. The flow rate of the inert gas in the second preliminary replacement step (second preliminary replacement flow rate) is, for example, 5 L / min or more and 50 L / min or less. The second preliminary replacement flow rate may be the first flow rate that is the same as the first preliminary replacement flow rate. The flow rate of the inert gas in the second preliminary replacement step means the total flow rate of the inert gas introduced into the second sealed processing space SP2 from all the second fluid introduction ports 10B.

[0140] After the temperature of the substrate W reaches the etching temperature, the water valve 65A and the reactive gas valve 66A are opened, so that an etching gas (a mixed gas of water vapor and ammonia gas) is supplied from the second fluid introduction ports 10B to the second sealed processing space SP2 (etching gas supply step: step S18). The first main surface W1 of the substrate W is processed by the etching gas discharged from the multiple second fluid introduction ports 10B (etching process). More specifically, the gallium oxide layer formed on the first main surface W1 of the substrate W is etched to selectively remove the gallium oxide layer (metal oxide layer removal process, gallium oxide layer removal process). In the metal oxide layer removal process, the gallium oxide layer is etched while the temperature of the substrate W is at the etching temperature (low-temperature etching process).

[0141] The introduction of the etching gas into the second sealed processing space SP2 continues for a predetermined etching processing time, which is, for example, not less than 10 seconds and not more than 120 seconds. The flow rate of water vapor in the etching gas supply process is a predetermined flow rate of water vapor. For example, the flow rate of water vapor is 5 L / min or more and 50 L / min or less. The flow rate of water vapor in the etching gas supply process means the total flow rate of water vapor introduced into the second sealed processing space SP2 from all the second fluid introduction ports 10B.

[0142] The flow rate of the ammonia gas in the etching gas supply process is a predetermined ammonia flow rate. For example, the ammonia flow rate is 5 L / min or more and 50 L / min or less. The flow rate of the ammonia gas in the etching gas supply process means the total flow rate of the ammonia gas introduced into the second sealed processing space SP2 from all the second fluid introduction ports 10B.

[0143] While the etching gas is being introduced into the second sealed processing space SP2 from the second fluid introduction ports 10B, the second inert gas flow rate control valve 64B is controlled to adjust the flow rate of the inert gas to a second partial pressure adjustment flow rate. The second partial pressure adjustment flow rate is lower than the preliminary replacement flow rate, for example, the second flow rate. The second partial pressure adjustment flow rate means the total flow rate of the inert gas introduced into the sealed processing space SP from the second fluid introduction ports 10B.

[0144] By reducing the flow rate of the inert gas, the partial pressure of water vapor and the partial pressure of ammonia gas in the second sealed processing space SP2 can be adjusted to partial pressures suitable for selectively etching the gallium oxide layer (etching gas partial pressure adjusting step). The temperature of the water vapor discharged from the second fluid introduction ports 10B is higher than the temperature (etching temperature) of the substrate W in the etching gas supply process. Therefore, the temperature of the water vapor decreases near the first main surface W1 of the substrate W, and a fine mist of water is formed. The concentration of ammonia gas dissolved in this fine mist of water is 1×10 -6If the concentration of ammonia gas dissolved in the fine mist of water is 1 mol / L or more and 15 mol / L or less, selective etching of a gallium oxide layer having a thickness of one or several atomic layers can be achieved. It is particularly preferable that the concentration of ammonia gas dissolved in the fine mist of water is 1 mol / L.

[0145] After the gallium oxide layer is removed from the first main surface W1 of the substrate W, the water valve 65A is kept open while the reactive gas valve 66A is closed. This stops the introduction of ammonia gas from the second fluid introduction ports 10B into the second sealed processing space SP2, and continues the introduction of water vapor from the second fluid introduction ports 10B into the second sealed processing space SP2 (water vapor supply continuation step: step S19). By continuing the introduction of water vapor into the second sealed processing space SP2, the reactive gas is removed from the second sealed processing space SP2 (reactive gas removal step, ammonia gas removal step).

[0146] After the supply of the reactive gas is stopped, the introduction of water vapor into the second sealed processing space SP2 is continued for a predetermined water supply duration, which is, for example, not less than 10 seconds and not more than 120 seconds. While the supply of water vapor to the second sealed processing space SP2 is continued, the flow rate of the inert gas is adjusted to a predetermined ammonia gas removal flow rate. The ammonia gas removal flow rate is, for example, equal to the second partial pressure adjustment flow rate and is a second flow rate. The flow rate of the inert gas in the water vapor supply continuation step means the total flow rate of the inert gas introduced from the multiple second fluid introduction ports 10B into the second sealed processing space SP2.

[0147] After the supply of water vapor continues for a predetermined water supply duration, the water valve 65A is closed. This stops the supply of water vapor to the second sealed processing space SP2. Meanwhile, the supply of inert gas to the second sealed processing space SP2 continues, so that water vapor is removed from the second sealed processing space SP2 (water removal process, water vapor removal process: step S20). At the same time as or after the water valve 65A is closed, the flow rate of the inert gas is changed to a predetermined water removal flow rate. The water removal flow rate is, for example, a first flow rate. The flow rate of the inert gas in the water removal process means the total flow rate of the inert gas introduced into the second sealed processing space SP2 from all the second fluid introduction ports 10B.

[0148] Thereafter, the first substrate carry-in process (step S11) to the second substrate unloading process (step S21) may be performed one or more times each. In FIG. 12, "N" means an integer equal to or greater than 0 (N=0, 1, 2, ...). The cycle process is performed one or more times in total, and the substrate W that has been subjected to the etch process is unloaded from the second thermal processing unit 5B (step S21: second substrate unloading process). Then, in the final second substrate unloading process, the substrate W is handed over from the transport robot CR to the transport robot IR, and is stored in the carrier C by the transport robot IR.

[0149] According to the second embodiment, the same effect as that of the first embodiment is achieved. However, according to the second embodiment, the temperature adjustment of the substrate W is performed on the heating surface 20a of the first hot plate 20A, and then on the heating surface 20a of the second hot plate 20B. In other words, two temperature adjustments (e.g., heating and cooling of the substrate W) are performed by separate members (the first hot plate 20A and the second hot plate 20B). Therefore, the time required for temperature adjustment of the substrate W can be shortened compared to the configuration in which the temperature of the substrate W is adjusted by changing the temperature of the heating surface 20a of a single hot plate 20 as in the first embodiment.

[0150] The modified example of the first embodiment (see FIGS. 8 and 9) can also be applied to the second embodiment. In that case, in the first substrate unloading step (step S15) and the second substrate unloading step (step S21), the substrate W is cooled to room temperature by the cool plates 70, 81 before being unloaded from the processing unit 2 by the transport robot CR. <Other embodiments> The present invention is not limited to the above-described embodiment, and can be embodied in other forms.

[0151] For example, in the above-described embodiment, water vapor is used in the metal oxide layer removal step, but in the metal oxide layer removal step, a mixed fluid of water vapor, mist-state water, and reactive gas, or a mixed fluid of mist-state water and reactive gas may be used as the etching fluid. However, when the water vapor is contained in the etching gas discharged from the second fluid introduction port 10B as in each of the above-mentioned embodiments, compared to when water in a mist state is used, water in a bulk state (in the form of minute droplets) is less likely to adhere to the first main surface W1 of the substrate W. Therefore, when water vapor is used as the water contained in the etching gas, water molecules can be more evenly collided with each position on the first main surface W1 of the substrate W.

[0152] In the metal oxide forming process, it is not necessary to use an oxidizing gas such as ozone gas, and an oxidizing liquid such as hydrogen peroxide solution can also be used. When the oxidizing liquid is hydrogen peroxide solution, the concentration of hydrogen peroxide in the hydrogen peroxide solution is preferably 1 ppm or more and 100 ppm or less. The oxidizing gas and the oxidizing liquid are collectively referred to as the oxidizing fluid. In the metal oxide formation step, the metal layer may be formed using O radicals generated by exciting oxygen in the air with UV irradiation. In the metal oxide formation step, the O radicals formed by UV irradiation may be combined with an oxidizing fluid.

[0153] In the above-described embodiment, the substrate processing apparatus 1, 1P includes the transport robots IR, CR, the processing unit 2, and the controller 3. However, a single processing unit 2 may constitute the substrate processing apparatus of the present invention. In other words, the processing unit 2 may be an example of the substrate processing apparatus. In each of the above-mentioned embodiments, the inert gas and the oxidizing gas are introduced into the heat treatment chamber 30 (first heat treatment chamber 30A) from the first fluid introduction port 10A through the common first fluid line 50, and the inert gas, water vapor and the reactive gas are introduced into the heat treatment chamber 30 (second heat treatment chamber 30B) from the second fluid introduction port 10B through the common second fluid line 51. However, each fluid may be sent to the fluid introduction port 10 from an inert gas line, an oxidizing gas line, a water line, a reactive gas line, or the like directly connected to the fluid introduction port 10 without passing through a common line such as the first fluid line 50 or the second fluid line 51. In addition, the first fluid line 50 and the second fluid line 51 may be provided with a mixing valve for mixing the fluids.

[0154] Moreover, each fluid may be configured to be discharged from a nozzle provided in the heat treatment chamber 30 (first heat treatment chamber 30A, second heat treatment chamber 30B). Furthermore, the etching gas (etching fluid) does not need to be mixed in the second fluid line 51, and a premixed etching gas (etching fluid) may be supplied from a supply source to the second fluid line 51 or the like.

[0155] When the temperature (etching temperature) of the substrate W in the metal oxide layer removal step is room temperature (for example, 25° C.), in the substrate processing of the first embodiment, the temperature of the substrate W may be reduced by stopping heating by the hot plate 20. When the temperature (etching temperature) of the substrate W in the metal oxide layer removal step is room temperature (for example, 25° C.), there is no need to perform heating by the second hot plate 20B in the substrate processing of the second embodiment.

[0156] In addition, various modifications can be made within the scope of the claims. [Explanation of symbols]

[0157] 1: Substrate processing equipment 1P: Substrate processing equipment 2: Processing unit (substrate processing device) 3: Controller 10: Fluid introduction port 10A: First fluid introduction port 10B: Second fluid introduction port 20: Hot plate (temperature control component) 20A: First hot plate (first temperature control member) 20B: Second hot plate (second temperature control member) 20a: Heating surface (temperature control surface, first temperature control surface, second temperature control surface) 30: Heat treatment chamber (chamber) 30A: First heat treatment chamber (first chamber) 30B: Second heat treatment chamber (second chamber) 50: First fluid line (oxidizing fluid supply unit) 51: Second fluid line (etching fluid supply unit) 53: Oxidizing fluid line (oxidizing fluid supply unit) 55: Water line (etching fluid supply unit) 56: Reactive gas line (etching fluid supply unit) 63A: Oxidizing fluid valve (Oxidizing fluid supply unit) 65A: Water valve (etching fluid supply unit) 66A: Reactive gas valve (etching fluid supply unit) 100: Gallium nitride layer (metal layer) 101: Gallium oxide layer (metal oxide layer) SP: sealed processing space (space adjacent to the main surface of the substrate) SP1: First sealed processing space SP2: Second sealed processing space W: Substrate W1: First main surface

Claims

1. A substrate processing method for processing a substrate having a metal nitride layer containing a group III metal on a main surface thereof, comprising: a metal oxide layer forming step of forming a metal oxide layer consisting of one atomic layer or several atomic layers on a surface of the metal nitride layer by supplying an oxidizing fluid toward a main surface of the substrate; a metal oxide layer removing step of supplying an etching fluid containing at least one of water in a gaseous state and water in a mist state, and a reactive gas that reacts with the metal oxide layer together with the water, toward a main surface of the substrate, thereby etching the metal oxide layer and selectively removing it from the substrate; a metal nitride layer etching amount controlled with an accuracy of 5 nm or less for each cycle by performing at least one cycle of cyclic processing, the cycle consisting of the metal oxide layer forming step and the metal oxide layer removing step.

2. 2. The substrate processing method according to claim 1, further comprising a reactive gas removal step of, after the metal oxide layer removal step, continuing to supply at least one of water in a gaseous state and water in a mist state to the main surface of the substrate to remove the reactive gas from a space in contact with the main surface of the substrate.

3. 3. The substrate processing method according to claim 2, further comprising, after the reactive gas removal step, a water removal step of removing water from a space in contact with the main surface of the substrate by replacing water present in the space in contact with the main surface of the substrate with an inert gas.

4. The substrate processing method according to any one of claims 1 to 3, further comprising an oxidizing fluid removal step of supplying an inert gas toward the main surface of the substrate after the metal oxide layer formation step and before the metal oxide layer removal step, thereby replacing the oxidizing fluid present in the space in contact with the main surface of the substrate with an inert gas, thereby removing the oxidizing fluid from the space in contact with the main surface of the substrate.

5. 5. The substrate processing method according to claim 1, wherein the metal oxide layer removing step includes an etching fluid supplying step of supplying an etching fluid from an etching fluid supplying unit toward the main surface of the substrate, and a temperature adjusting step of adjusting a temperature of the substrate to a temperature lower than that of the etching fluid supplied from the etching fluid supplying unit.

6. the metal oxide layer forming step includes a heating and oxidation step of supplying the oxidizing fluid toward a main surface of the substrate while heating the substrate, thereby forming the metal oxide layer; The substrate processing method according to any one of claims 1 to 5, wherein the metal oxide layer removal process includes a low-temperature etching process of etching the metal oxide layer by supplying the etching fluid toward the main surface of the substrate while the temperature of the substrate is lower than the temperature of the substrate in the metal oxide layer formation process.

7. 7. The substrate processing method according to claim 6, wherein the temperature of the substrate in the thermal oxidation step is 100° C. or more and 400° C. or less, and the temperature of the substrate in the low-temperature etching step is 25° C. or more and less than 100° C.

8. In the heating and oxidizing step, the substrate is heated by placing the substrate on a heating surface of a heating member disposed in a chamber while supplying the oxidizing fluid toward a main surface of the substrate; 8. The substrate processing method according to claim 6, wherein in the low-temperature etching step, the temperature of the substrate is reduced by reducing the temperature of the heating member while maintaining the substrate placed on the heating surface.

9. In the heating and oxidizing step, the substrate is heated by placing the substrate on a first temperature adjustment surface of a first temperature adjustment member disposed in a first chamber while supplying the oxidizing fluid toward a main surface of the substrate; 8. The substrate processing method according to claim 6, wherein in the low-temperature etching step, the temperature of the substrate is reduced by moving the substrate from the first temperature adjustment surface and placing the substrate on a second temperature adjustment surface of a second temperature adjustment member disposed in a second chamber and having a lower temperature than the first temperature adjustment member.

10. 10. The substrate processing method according to claim 1, wherein the metal oxide layer formed in the metal oxide layer forming step has a thickness of 5 nm or less.

11. The substrate processing method according to any one of claims 1 to 10, wherein the metal nitride layer is a gallium nitride layer.

12. The substrate processing method according to any one of claims 1 to 11, wherein the water contained in the etching fluid is in a gaseous state.

13. The substrate processing method according to any one of claims 1 to 12, wherein the reactive gas is an ammonia gas.

14. A substrate processing apparatus for processing a substrate having a metal nitride layer containing a group III metal on a main surface thereof, comprising: a temperature adjustment member having a temperature adjustment surface on which the substrate is placed, the temperature adjustment member adjusting the temperature of the substrate placed on the temperature adjustment surface to a predetermined first temperature and a second temperature lower than the first temperature; A chamber that accommodates the temperature adjustment member; an oxidizing fluid supply unit that supplies an oxidizing fluid into the chamber and forms a metal oxide layer consisting of one atomic layer or several atomic layers on a surface of the metal nitride layer; an etching fluid supply unit that supplies into the chamber an etching fluid containing at least one of water in a gaseous state and water in a mist state, and a reactive gas that reacts with the metal oxide layer together with the water, and selectively etches the metal oxide layer; a controller for controlling the oxidizing fluid supply unit and the etching fluid supply unit; the controller is programmed to execute a metal oxide layer forming process of forming the metal oxide layer consisting of one atomic layer or several atomic layers on a surface of the metal nitride layer by supplying the oxidizing fluid from the oxidizing fluid supply unit toward the main surface of the substrate, and a metal oxide layer removing process of etching the metal oxide layer to selectively remove it from the main surface of the substrate by supplying an etching fluid from the etching fluid supply unit toward the main surface of the substrate, The substrate processing apparatus controls the amount of etching of the metal nitride layer with an accuracy of 5 nm or less for each cycle by performing at least one cycle of cyclic processing, one cycle being the metal oxide layer forming step and the metal oxide layer removing step.

15. the etching fluid supply unit is configured to supply an etching fluid into the chamber through a fluid introduction port that opens into the chamber; The substrate processing apparatus of claim 14 , wherein the second temperature is less than a temperature of an etching fluid introduced into the chamber through the fluid introduction port.

16. 16. The substrate processing apparatus of claim 14, wherein the temperature adjustment member has a single temperature adjustment surface and is configured to adjust the temperature of the substrate to the first temperature and the second temperature while the substrate is placed on the single temperature adjustment surface.

17. the temperature adjustment member has a first temperature adjustment surface as the temperature adjustment surface, and a first temperature adjustment member that adjusts the substrate placed on the first temperature adjustment surface to the first temperature, and a second temperature adjustment member has a second temperature adjustment surface as the temperature adjustment surface, and adjusts the substrate placed on the second temperature adjustment surface to the second temperature, The chamber includes a first chamber that houses the first temperature adjustment member and a second chamber that houses the second temperature adjustment member, the oxidizing fluid supply unit is configured to supply an oxidizing fluid into the first chamber; The substrate processing apparatus of claim 14 or 15, wherein the etching fluid supply unit is configured to supply an etching fluid into the second chamber.

18. 18. The substrate processing apparatus according to claim 14, wherein the first temperature is 100°C or more and 400°C or less, and the second temperature is 25°C or more and less than 100°C.

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