JP2019009190A - Substrate processing method and substrate processing apparatus - Google Patents

Abstract

The present invention provides a substrate processing method and a substrate processing apparatus capable of suppressing variation in etching rate. A substrate processing method according to an embodiment includes an etching step and an atmosphere adjustment step. In the etching step, the substrate is etched by supplying a chemical solution to the substrate. The atmosphere adjustment step controls the concentration of the etching species or the oxidizing agent contained in the chemical solution by adjusting the atmosphere to which the chemical solution supplied to the substrate is exposed in the etching step. [Selection] Figure 5

Description

  Embodiments disclosed herein relate to a substrate processing method and a substrate processing apparatus.

  Conventionally, in a semiconductor manufacturing process, an etching process for etching a substrate by supplying a chemical solution to the substrate such as a silicon wafer or a compound semiconductor wafer is performed (see Patent Document 1).

Japanese Patent Laid-Open No. 09-022891

  However, in the etching process, there are cases where the etching rate fluctuates due to changes in the etching species and the concentration of the oxidizing agent in the chemical solution.

  For example, when processing a single wafer, the etching species and the concentration of the oxidizing agent in the chemical solution may change between the center and the outer periphery of the substrate, and the etching rate varies between the center and the outer periphery of the substrate. May occur. Also, when collecting used chemicals and reusing them, the etching species and oxidizing agent concentration in the chemicals may vary depending on the number of times of use, etc., and multiple times with wafers processed using fresh chemicals. There is a possibility that the etching rate varies with the wafer processed using the used chemical solution.

  As described above, the above-described conventional technology has room for further improvement in terms of suppressing fluctuations in the etching rate.

  An object of one embodiment is to provide a substrate processing method and a substrate processing apparatus that can suppress variation in etching rate.

  A substrate processing method according to one aspect of an embodiment includes an etching step and an atmosphere adjustment step. In the etching step, the substrate is etched by supplying a chemical solution to the substrate. The atmosphere adjustment step controls the concentration of the etching species or the oxidizing agent contained in the chemical solution by adjusting the atmosphere to which the chemical solution supplied to the substrate is exposed in the etching step.

  According to one aspect of the embodiment, variation in the etching rate can be suppressed.

FIG. 1 is a diagram showing a schematic configuration of a substrate processing system according to the present embodiment. FIG. 2 is a diagram showing a schematic configuration of the processing unit. FIG. 3 is a diagram illustrating an example of a configuration of a chemical solution supply system included in the substrate processing system. FIG. 4 is a flowchart showing a series of substrate processing procedures executed by the processing unit according to the first embodiment. FIG. 5 is a diagram illustrating an example of the configuration of the atmosphere supply system. FIG. 6 is a diagram illustrating a schematic configuration of a processing unit according to the second embodiment. FIG. 7 is a diagram illustrating an example of a combination of chemicals to be used and components added to the air atmosphere. FIG. 8 is a diagram showing the relationship between the dissolved O 2 concentration in the TMAH aqueous solution and the etching rate of the polysilicon film. FIG. 9 is a diagram showing the relationship between the dissolved O 2 concentration in the TMAH aqueous solution and the in-wafer distribution of the etching rate of the polysilicon film. FIG. 10 is a diagram showing the relationship between the O2 concentration in the processing atmosphere and the in-wafer distribution of the etching rate of the polysilicon film. FIG. 11 is a diagram illustrating a configuration of an atmosphere supply system according to a modification.

  Hereinafter, embodiments of a substrate processing method and a substrate processing apparatus disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

(First embodiment)
First, a substrate processing apparatus according to the first embodiment will be described with reference to FIGS.

  FIG. 1 is a diagram showing a schematic configuration of a substrate processing system according to the present embodiment. In the following, in order to clarify the positional relationship, the X axis, the Y axis, and the Z axis that are orthogonal to each other are defined, and the positive direction of the Z axis is the vertically upward direction.

  As shown in FIG. 1, the substrate processing system 1 includes a carry-in / out station 2 and a processing station 3. The carry-in / out station 2 and the processing station 3 are provided adjacent to each other.

  The carry-in / out station 2 includes a carrier placement unit 11 and a transport unit 12. A plurality of carriers C that accommodate a plurality of substrates, in this embodiment a semiconductor wafer (hereinafter referred to as a wafer W) in a horizontal state, are placed on the carrier placement unit 11.

  The transport unit 12 is provided adjacent to the carrier placement unit 11 and includes a substrate transport device 13 and a delivery unit 14 inside. The substrate transfer device 13 includes a wafer holding mechanism that holds the wafer W. Further, the substrate transfer device 13 can move in the horizontal direction and the vertical direction and can turn around the vertical axis, and transfers the wafer W between the carrier C and the delivery unit 14 using the wafer holding mechanism. Do.

  The processing station 3 is provided adjacent to the transfer unit 12. The processing station 3 includes a transport unit 15 and a plurality of processing units 16. The plurality of processing units 16 are provided side by side on the transport unit 15.

  The transport unit 15 includes a substrate transport device 17 inside. The substrate transfer device 17 includes a wafer holding mechanism that holds the wafer W. Further, the substrate transfer device 17 can move in the horizontal direction and the vertical direction and can turn around the vertical axis, and transfers the wafer W between the delivery unit 14 and the processing unit 16 using a wafer holding mechanism. I do.

  The processing unit 16 performs predetermined substrate processing on the wafer W transferred by the substrate transfer device 17.

  Further, the substrate processing system 1 includes a control device 4. The control device 4 is a computer, for example, and includes a control unit 18 and a storage unit 19. The storage unit 19 stores a program for controlling various processes executed in the substrate processing system 1. The control unit 18 controls the operation of the substrate processing system 1 by reading and executing the program stored in the storage unit 19.

  Such a program may be recorded on a computer-readable storage medium, and may be installed in the storage unit 19 of the control device 4 from the storage medium. Examples of the computer-readable storage medium include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnetic optical disk (MO), and a memory card.

  In the substrate processing system 1 configured as described above, first, the substrate transfer device 13 of the loading / unloading station 2 takes out the wafer W from the carrier C placed on the carrier placement unit 11 and receives the taken-out wafer W. Place on the transfer section 14. The wafer W placed on the delivery unit 14 is taken out from the delivery unit 14 by the substrate transfer device 17 of the processing station 3 and carried into the processing unit 16.

  The wafer W carried into the processing unit 16 is processed by the processing unit 16, then unloaded from the processing unit 16 by the substrate transfer device 17, and placed on the delivery unit 14. Then, the processed wafer W placed on the delivery unit 14 is returned to the carrier C of the carrier placement unit 11 by the substrate transfer device 13.

  Next, the configuration of the processing unit 16 will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of the processing unit 16.

  As shown in FIG. 2, the processing unit 16 includes a chamber 20, a substrate holding mechanism 30, a processing fluid supply unit 40, and a recovery cup 50.

  The chamber 20 accommodates the substrate holding mechanism 30, the processing fluid supply unit 40, and the recovery cup 50. An FFU (Fan Filter Unit) 21 is provided on the ceiling of the chamber 20. The FFU 21 forms a down flow in the chamber 20.

  The substrate holding mechanism 30 includes a holding unit 31, a support unit 32, and a driving unit 33. The holding unit 31 holds the wafer W horizontally. The support | pillar part 32 is a member extended in a perpendicular direction, a base end part is rotatably supported by the drive part 33, and supports the holding | maintenance part 31 horizontally in a front-end | tip part. The drive unit 33 rotates the column unit 32 around the vertical axis. The substrate holding mechanism 30 rotates the support unit 31 by rotating the support unit 32 using the drive unit 33, thereby rotating the wafer W held by the support unit 31. .

  The processing fluid supply unit 40 supplies a processing fluid to the wafer W. The processing fluid supply unit 40 is connected to a processing fluid supply source 70.

  The collection cup 50 is disposed so as to surround the holding unit 31, and collects the processing liquid scattered from the wafer W by the rotation of the holding unit 31. A drain port 51 is formed at the bottom of the recovery cup 50, and the processing liquid collected by the recovery cup 50 is discharged from the drain port 51 to the outside of the processing unit 16. Further, an exhaust port 52 for discharging the gas supplied from the FFU 21 to the outside of the processing unit 16 is formed at the bottom of the recovery cup 50.

  The processing unit 16 according to the first embodiment sequentially supplies a BHF aqueous solution (an example of a chemical solution) and DIW (an example of a rinsing solution) as processing fluids from the processing fluid supply unit 40 to the wafer W. BHF (buffered hydrofluoric acid) is a mixture of HF (hydrofluoric acid) and NH4F (ammonium fluoride). DIW is pure water at room temperature (about 25 degrees).

  Here, an example of the structure of the chemical solution supply system for supplying the BHF aqueous solution will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of a configuration of a chemical solution supply system included in the substrate processing system 1.

  As shown in FIG. 3, the chemical solution supply system included in the substrate processing system 1 includes a processing fluid supply source 70 that supplies the BHF aqueous solution to the plurality of processing units 16.

  The processing fluid supply source 70 includes a tank 102 that stores the BHF aqueous solution, and a circulation line 104 that exits the tank 102 and returns to the tank 102. The circulation line 104 is provided with a pump 106. The pump 106 creates a circulating flow that exits the tank 102, passes through the circulation line 104, and returns to the tank 102. A filter 108 for removing contaminants such as particles contained in the BHF aqueous solution is provided in the circulation line 104 on the downstream side of the pump 106. If necessary, auxiliary equipment (such as a heater) may be further provided in the circulation line 104.

  One or more branch lines 112 are connected to the connection area 110 set in the circulation line 104. Each branch line 112 supplies the BHF aqueous solution flowing through the circulation line 104 to the corresponding processing unit 16. Each branch line 112 can be provided with a flow rate adjusting mechanism such as a flow rate control valve, a filter, or the like, if necessary.

  Further, the processing fluid supply source 70 includes a recovery line 113. The recovery line 113 has one end connected to each processing unit 16 and the other end connected to the tank 102. The BHF aqueous solution used in each processing unit 16 is collected in the tank 102 through the collection line 113.

  The chemical liquid supply system includes a tank liquid replenishing unit 116 that replenishes the tank 102 with a new BHF aqueous solution. The tank 102 is provided with a drain unit 118 for discarding the processing liquid in the tank 102.

  Next, a series of substrate processing procedures executed by the processing unit 16 according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a series of substrate processing procedures executed by the processing unit 16 according to the first embodiment. The series of substrate processing shown in FIG. 4 is executed by the control unit 18 controlling the processing unit 16 and the like. The control unit 18 is, for example, a CPU (Central Processing Unit), and controls the processing unit 16 and the like according to a program (not shown) stored in the storage unit 19.

  As shown in FIG. 4, in the processing unit 16, a wafer W loading process is first performed (step S101). In such carry-in processing, the substrate transfer device 17 (see FIG. 1) places the wafer W on the support pins (not shown) of the holding unit 31 (see FIG. 2), and then the substrate holding mechanism 30 (see FIG. 2). A chuck (not shown) that is provided and holds the wafer W from the side surface holds the wafer W.

  Subsequently, the processing unit 16 performs an etching process (step S102). In the etching process, first, the driving unit 33 rotates the holding unit 31 to rotate the wafer W held by the holding unit 31 at a predetermined number of rotations. Subsequently, the nozzle of the processing fluid supply unit 40 is located above the center of the wafer W.

  Thereafter, an aqueous BHF solution supplied from the tank 102 via the circulation line 104 and the branch line 112 is supplied from the nozzle to the surface of the wafer W. The BHF aqueous solution supplied to the wafer W is spread over the entire surface of the wafer W by centrifugal force accompanying the rotation of the wafer W. Thereby, a film (for example, a thermal oxide film) formed on the surface of the wafer W is etched by the BHF aqueous solution.

  Subsequently, in the processing unit 16, the surface of the wafer W is rinsed with DIW (step S103). In the rinsing process, DIW supplied from a DIW supply source (not shown) is supplied from the nozzle of the processing fluid supply unit 40 to the surface of the wafer W, and the BHF aqueous solution remaining on the wafer W is washed away.

  Subsequently, in the processing unit 16, a drying process is performed (step S104). In such a drying process, the DIW on the wafer W is shaken off by increasing the rotation speed of the wafer W to dry the wafer W.

  Subsequently, in the processing unit 16, an unloading process is performed (step S105). In such unloading processing, after the rotation of the wafer W by the driving unit 33 is stopped, the wafer W is unloaded from the processing unit 16 by the substrate transfer device 17 (see FIG. 1). When such unloading processing is completed, a series of substrate processing for one wafer W is completed.

  The etching rate depends on the etching species in the chemical solution and the concentration of the oxidizing agent. However, the concentration of the etching species and the oxidizing agent in the chemical solution changes due to the deactivation and volatilization of the etching species and the oxidizing agent during the etching process. For this reason, in an etching process, there exists a possibility that an etching rate may change with the density | concentration change of an etching seed | species or an oxidizing agent.

  For example, when used chemicals are collected and reused as in the processing unit 16 according to the first embodiment, when the number of processed wafers W increases, the concentration of etching species in the chemicals increases due to evaporation or the like. It may change and the etching rate may fluctuate. Thereby, the uniformity of the etching rate between the processing units may be deteriorated.

  Further, when the wafer W is subjected to single wafer processing like the processing unit 16 according to the first embodiment, the etching rate of the etching rate is changed by changing the etching species or the concentration of the oxidizing agent in the chemical solution within the wafer W surface. In-plane uniformity may also deteriorate.

  In addition, when the etching species and the oxidizing agent in the chemical solution evaporate, there may be a difference in the concentration of the etching species and the oxidizing agent between a portion near the liquid surface and a portion far from the liquid surface in the chemical solution. For this reason, for example, when an uneven pattern (so-called trench structure) is formed on the wafer W, the uniformity of the etching rate at the upper and lower portions of the pattern may be deteriorated.

  Therefore, in the substrate processing system 1 according to the first embodiment, the concentration of the etching species or the oxidant contained in the chemical supplied to the wafer W is adjusted by adjusting the atmosphere to which the chemical supplied to the wafer W is exposed. By controlling, it was decided to suppress changes in the concentration of etching species and oxidants in the chemical solution.

  This point will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the configuration of the atmosphere supply system.

  As shown in FIG. 5, the substrate processing system 1 according to the first embodiment includes an air supply system that supplies air as an atmosphere supply system that supplies an atmosphere into a chamber 20 (an example of a processing space) of the processing unit 16. A water supply system for supplying water, an NH3-containing gas supply system for supplying NH3-containing gas, and an HF-containing gas supply system for supplying HF-containing gas.

  The air supply system includes an air supply path 211 having one end connected to the FFU 21 and an air supply source 212 connected to the other end of the air supply path 211.

  The air supply system supplies air supplied from the air supply source 212 from the FFU 21 to the inside of the chamber 20 via the air supply path 211. Note that the air supplied from the air supply source 212 is, for example, air in a clean room where the substrate processing system 1 is installed (clean air, humidity 30 to 50%). The air may be dry air having a lower humidity than the inside air.

  The moisture supply system includes, for example, a moisture supply path 301a whose one end is connected to the middle part of the air supply path 211, an H2O supply source 302a connected to the other end of the moisture supply path 301a, and a middle part of the moisture supply path 301a. Provided with a water vapor generation unit 303a. The steam generation unit 303a is, for example, a humidifier.

  Such a water supply system supplies water (for example, DIW) supplied from the H2O supply source 302a to the water vapor generation unit 303a, and supplies water vapor generated by the water vapor generation unit 303a to the air supply channel 211 via the water supply channel 301a. To do. Thereby, water vapor is added to the air flowing through the air supply path 211.

  The NH3-containing gas supply system includes, for example, an NH3-containing gas supply path 301b whose one end is connected to the middle part of the air supply path 211, and an NH3-containing gas supply source 302b connected to the other end of the NH3-containing gas supply path 301b. Prepare. The NH3 containing gas supply system adjusts the flow rate of the NH3 containing gas flowing through the NH3 containing gas supply path 301b and the valve 303b for opening and closing the NH3 containing gas supply path 301b in the middle of the NH3 containing gas supply path 301b. And a flow rate adjusting unit 304b.

  The NH3-containing gas supply system supplies the NH3 gas supplied from the NH3-containing gas supply source 302b to the air supply path 211 via the NH3-containing gas supply path 301b. Thereby, NH 3 gas is added to the air flowing through the air supply path 211.

  Note that the NH3-containing gas supplied by the NH3-containing gas supply system only needs to contain at least NH3, and is not necessarily NH3 gas. For example, the NH 3 -containing gas supply system may supply NH 4 OH gas into the chamber 20 instead of the NH 3 gas.

  The HF-containing gas supply system includes, for example, an HF-containing gas supply path 301c whose one end is connected to the middle part of the air supply path 211, and an HF-containing gas supply source 302c connected to the other end of the HF-containing gas supply path 301c. Prepare. The HF-containing gas supply system adjusts the flow rate of the HF-containing gas flowing through the HF-containing gas supply path 301c and the valve 303c that opens and closes the HF-containing gas supply path 301c in the middle of the HF-containing gas supply path 301c. And a flow rate adjusting unit 304c.

  The HF-containing gas supply system supplies the HF gas supplied from the HF-containing gas supply source 302c to the air supply path 211 via the HF-containing gas supply path 301c. Thereby, HF gas is added to the air flowing through the air supply path 211. Note that the HF-containing gas supplied by the HF-containing gas supply system only needs to contain at least HF, and is not necessarily required to be HF gas.

  Thus, in the substrate processing system 1 according to the first embodiment, the moisture supply system, the NH 3 -containing gas supply system, and the HF-containing gas supply system are connected to the air supply system. As a result, an atmosphere in which moisture, NH 3 gas, and HF gas are added to the air is supplied from the FFU 21 into the chamber 20.

  The control unit 18 adds moisture, NH 3 gas, and HF gas to the air supplied from the air supply system into the chamber 20 after the carry-in process in step S 101 shown in FIG. 4 and before the etching process in step S 102. For example, the control unit 18 causes the substrate transfer device 17 (see FIG. 1) to exit from the chamber 20 in step S101 and closes a shutter (not shown) of the chamber 20, and then starts generation of water vapor by the water vapor generation unit 303a. The valves 303b and 303c are opened, and the supply of NH3 gas and HF gas into the chamber 20 is started.

  As a result, in the etching process of step S102, the BHF aqueous solution supplied to the wafer W from the nozzle 41 of the processing fluid supply unit 40 is exposed to an atmosphere containing NH3 and HF contained as etching species in the BHF aqueous solution. Become.

  As described above, when the single wafer processing is performed, the in-plane uniformity of the etching rate may be deteriorated due to the change in the concentration of the etching species in the chemical solution within the wafer W surface. For example, when a BHF aqueous solution is used as a chemical, NH3 and HF that are etching species evaporate, but NH3 tends to evaporate in particular, and the concentration of HF becomes relatively high. The etching rate may be higher than the etching rate at the center of the wafer W.

  On the other hand, in the substrate processing system 1 according to the first embodiment, the NH 3 and HF in the atmosphere are brought into contact with the BHF aqueous solution supplied to the wafer W by bringing the NH 3 and HF atmosphere into contact with the BHF aqueous solution. It can be taken in. That is, NH3 and HF can be supplemented to the BHF aqueous solution. Thereby, the NH3 and HF concentration change in the wafer W surface of the BHF aqueous solution supplied to the wafer W can be suppressed. Therefore, according to the substrate processing system 1 according to the first embodiment, it is possible to suppress variations in the etching rate at the central portion of the wafer W and the etching rate at the outer peripheral portion. That is, fluctuations in the etching rate within the wafer W surface can be suppressed.

  Further, since the BHF aqueous solution supplemented with NH3 and HF is recovered, the change in the concentration of NH3 and HF due to circulation can be suppressed. Therefore, according to the substrate processing system 1 according to the first embodiment, the processing unit 1 Variation in the etching rate can also be suppressed.

  In the substrate processing system 1 according to the first embodiment, moisture is added to the air supplied from the air supply system as well as NH3 and HF as etching species. Therefore, changes in the concentration of NH 3 and HF accompanying the evaporation of moisture can also be suppressed. The atmosphere in the chamber 20 is adjusted to a humidity of 50% or more by the moisture supplied from the moisture supply system.

  As shown in FIG. 5, the substrate processing system 1 according to the first embodiment includes a hygrometer 401a that measures the humidity of the atmosphere in the chamber 20, and an NH3 concentration meter 401b that measures the NH3 concentration in the atmosphere in the chamber 20. And an HF concentration meter 401 c that measures the HF concentration in the atmosphere in the chamber 20.

  The hygrometer 401a, the NH3 concentration meter 401b, and the HF concentration meter 401c measure the humidity (moisture concentration), NH3 concentration, and HF concentration of the atmosphere in the chamber 20 during the etching process, respectively.

  The control unit 18 controls the water vapor generation unit 303a and the flow rate adjustment units 304b and 304c in accordance with the measurement results by the hygrometer 401a, the NH3 concentration meter 401b, and the HF concentration meter 401c, so that the air supply system enters the chamber 20. The flow rate of moisture, NH3 gas, and HF gas added to the supplied air is adjusted.

  For example, the control unit 18 makes the measurement results by the hygrometer 401a, the NH3 concentration meter 401b, and the HF concentration meter 401c constant, that is, the humidity of the atmosphere in the chamber 20, the concentration of NH3, and the concentration of HF are constant. Thus, the water vapor generating unit 303a and the flow rate adjusting units 304b and 304c are controlled. Thereby, the variation of the etching rate can be suppressed with higher accuracy.

  When the etching process in step S102 is completed, the control unit 18 stops the generation of water vapor by the water vapor generation unit 303a and closes the valves 303b and 303c to stop the supply of NH3 gas and HF gas into the chamber 20.

  Here, moisture, NH 3 gas, and HF gas are supplied into the chamber 20, but the substrate processing system 1 does not necessarily need to supply all of moisture, NH 3 gas, and HF gas into the chamber 20. For example, the substrate processing system 1 may supply any one or two of moisture, NH 3 gas, and HF gas into the chamber 20.

  As described above, the substrate processing system 1 (an example of the substrate processing apparatus) according to the first embodiment is an atmosphere supply including the holding unit 31, the processing fluid supply unit 40 (an example of a chemical solution supply unit), and the FFU 21. A system (an example of a gas supply unit) and a control unit 18 are provided. The holding unit 31 holds a wafer W (an example of a substrate). The processing fluid supply unit 40 supplies a BHF aqueous solution (an example of a chemical solution) to the wafer W held by the holding unit 31. The atmosphere supply system supplies air, moisture, NH 3 -containing gas, and HF-containing gas. The control unit 18 controls the processing fluid supply unit 40 and the atmosphere supply system to perform etching processing for etching the wafer W by supplying the BHF aqueous solution from the processing fluid supply unit 40 to the wafer W held by the holding unit 31. In the etching process, NH3 and HF (etching species or HF) contained in the BHF aqueous solution are adjusted by adjusting the atmosphere to which the BHF aqueous solution supplied to the wafer W is exposed by moisture, NH3 gas, and HF gas supplied from the atmosphere supply system. An atmosphere adjustment process for controlling the concentration of an example of the oxidizing agent is performed.

  Therefore, according to the substrate processing system 1 which concerns on 1st Embodiment, the fluctuation | variation of an etching rate can be suppressed.

  Here, the moisture supply system, the NH 3 -containing gas supply system, and the HF-containing gas supply system are connected to the air supply system to supply moisture, NH 3 gas, and HF gas from the FFU 21 into the chamber 20. The NH 3 gas and the HF gas are not necessarily supplied from the FFU 21. That is, a supply port for moisture, NH 3 gas, and HF gas may be provided at a place other than the FFU 21, and moisture, NH 3 gas, and HF gas may be supplied into the chamber 20 from the supply port.

(Second Embodiment)
In the above-described first embodiment, an example in the case of performing single wafer processing on the wafer W has been described. However, the substrate processing method disclosed in the present application is batch processing in which a plurality of wafers W are processed as a single processing unit. It is also applicable when performing the above. Therefore, an example of batch processing will be described below.

  FIG. 6 is a diagram illustrating a schematic configuration of a processing unit according to the second embodiment. In the following description, parts that are the same as those already described are given the same reference numerals as those already described, and redundant descriptions are omitted.

  As illustrated in FIG. 6, the processing unit 16A according to the second embodiment includes a chamber 20A, a processing tank 60 and an outer tank 80 provided in the chamber 20A, and the processing tank 60 includes A BHF aqueous solution as a chemical solution is stored. Then, the BHF aqueous solution is stored in the processing tank 60 by supplying the BHF aqueous solution into the processing tank 60 through a nozzle 62 provided in the processing tank 60 from a BHF aqueous solution supply source 61 described later. Then, an etching process is performed while immersing a plurality of wafers W held by a holding unit 31 </ b> A described later in the BHF aqueous solution stored in the processing bath 60 and overflowing the BHF aqueous solution from the processing bath 60. The BHF aqueous solution overflowed from the processing tank 60 is received by the outer tank 80 and then supplied from the nozzle 62 to the processing tank 60 again.

  An FFU 21 is provided in the chamber 20A. An air supply source 212 is connected to the FFU 21 via an air supply path 211, and air supplied from the air supply source 212 is supplied from the FFU 21 into the chamber 20 </ b> A via the air supply path 211.

  The holding unit 31A holds, for example, 50 wafers W vertically and spaced apart from each other. The holding portion 31 </ b> A can move a plurality of wafers W in and out of the processing bath 60 by moving up and down by a driving mechanism (not shown).

  The processing tank 60 is provided with a lid 63 that covers the opening at the top of the processing tank 60 so as to be freely opened and closed. The lid 63 is divided into two parts 63a and 63b. When the processing tank 60 is closed by the lid 63, a substantially sealed closed space is formed inside the processing tank 60.

  A nozzle 42 is disposed in a closed space formed by the processing tank 60 and the lid 63. The nozzle 42 is connected to the same water supply system, NH 3 -containing gas supply system, and HF-containing gas supply system as those described in the first embodiment.

  The processing unit 16A is provided with a hygrometer 401a, an NH3 concentration meter 401b, and an HF concentration meter 401c similar to those described in the first embodiment. The hygrometer 401a, the NH3 concentration meter 401b, and the HF concentration meter 401c measure the humidity, NH3 concentration, and HF concentration of the atmosphere in the closed space formed by the processing tank 60 and the lid 63, respectively.

  One end of a supply pipe 64 is connected to the nozzle 62, and a BHF aqueous solution supply source 61 is disposed on the other end side of the supply pipe 64. A pipe 65 extending from the BHF aqueous solution supply source 61 is connected to the supply pipe 64. A valve 66 is provided in the middle of the pipe 65.

  The supply pipe 64 forms a circulation path for returning the BHF aqueous solution overflowed to the outer tank 80 into the processing tank 60. The supply pipe 64 is provided with a pump 67, a filter 68, and a valve 69 in order from the upstream side.

  A discharge pipe 81 is connected to the bottom of the processing tank 60, and a valve 82 is provided in the discharge pipe 81. When replacing the BHF aqueous solution, the valve 82 is opened to discharge the BHF aqueous solution stored in the processing tank 60 from the discharge pipe 81, and then the valve 82 is closed to supply the next BHF aqueous solution into the processing tank 60. .

  The lid 63, the valves 66, 69, 82, the pump 67, and the like of the processing unit 16A are controlled by the control unit 18A.

  In the processing unit 16A configured as described above, the etching process is performed as follows. First, in the processing unit 16A, a plurality of wafers W are loaded into the chamber 20A of the processing unit 16A using a substrate transfer device (not shown) and delivered to the holding unit 31A.

  Subsequently, the lid 63 of the processing tank 60 is opened, the holding unit 31A is lowered by a driving mechanism (not shown), and the plurality of wafers W are immersed in the BHF aqueous solution stored in the processing tank 60. Thereafter, the lid 63 is closed to form a closed space between the processing tank 60 and the lid 63.

  Subsequently, the BHF aqueous solution is supplied from the nozzle 62 into the processing tank 60, and the plurality of wafers W are immersed in the BHF aqueous solution for a predetermined time while overflowing the BHF aqueous solution from the processing tank 60, thereby maintaining a plurality of times. The wafer W is etched.

  In the etching process, the control unit 18A, for example, closes the lid 63 of the processing tank 60, that is, after a closed space is formed by the processing tank 60 and the lid 63, the moisture, A mixed gas of NH 3 gas and HF gas is supplied from the nozzle 42.

  As a result, the BHF aqueous solution stored in the treatment tank 60 is exposed to an atmosphere containing NH3 and HF, and NH3 and HF in the atmosphere are taken into the BHF aqueous solution, and are lost from the BHF aqueous solution by evaporation or the like. Supplied NH3 and HF. Then, by recovering the BHF aqueous solution supplemented with NH 3 and HF, changes in the concentration of NH 3 and HF accompanying the circulation recovery can be suppressed. Thereby, the fluctuation | variation of the etching rate between process units can be suppressed.

  Further, by adding moisture as well as etching species NH3 and HF, changes in the concentration of NH3 and HF due to evaporation of moisture can be suppressed.

  Thus, the substrate processing method disclosed in the present application is applicable not only to single wafer processing but also to batch processing.

  In the processing unit 16A, there is a possibility that moisture, NH 3 and HF are constantly evaporated from the BHF aqueous solution stored in the processing tank 60. For this reason, moisture, NH 3 gas and HF gas may be constantly supplied without being limited to the etching process.

  Here, the moisture, NH3 gas, and HF gas are supplied to the closed space formed by the processing tank 60 and the lid 63. However, the moisture, NH3 gas, and HF gas are supplied from, for example, the FFU 21 to the chamber 20A. It is good also as supplying to.

(Third embodiment)
In the first and second embodiments described above, when the wafer W is etched using the BHF aqueous solution, the moisture, NH 3, and HF gas contained in the BHF aqueous solution are added to the air atmosphere, so that the It was decided to suppress changes in the concentration of NH3 and HF. However, the substrate processing method disclosed in the present application is also applicable to the case of using a chemical solution other than the BHF aqueous solution. Therefore, an example in the case of using a chemical solution other than the BHF aqueous solution will be described below.

  FIG. 7 is a diagram illustrating an example of a combination of chemicals to be used and components added to the air atmosphere. As shown in FIG. 7, as the chemical used for the etching process, there are, for example, an HF aqueous solution, a mixed acid aqueous solution, SC1, and a TMAH aqueous solution in addition to the above-described BHF aqueous solution.

  Among HF aqueous solutions, HF aqueous solutions having an HF concentration of less than 1 wt% (hereinafter referred to as “low HF aqueous solution”) are likely to evaporate moisture. Therefore, when a low HF aqueous solution is used as the chemical solution, it is preferable to add moisture to the air supplied from the air supply system. Thereby, it can suppress that the density | concentration of HF contained as an etching seed | species in low HF aqueous solution changes by evaporation of a water | moisture content.

  The configuration of the processing unit when using a low HF aqueous solution as the chemical solution is, for example, a configuration in which the NH 3 -containing gas supply system, the HF-containing gas supply system, the NH 3 concentration meter 401 b and the HF concentration meter 401 c are removed from the processing units 16 and 16 A. can do.

  On the other hand, among HF aqueous solutions, HF aqueous solutions having an HF concentration exceeding 10 wt% (hereinafter referred to as “high HF aqueous solution”) tend to evaporate HF in addition to moisture. Therefore, when a high HF aqueous solution is used as the chemical solution, it is preferable to add moisture and an HF-containing gas to the air supplied from the air supply system. Thereby, it can suppress that the density | concentration of HF contained as an etching seed | species in high HF aqueous solution changes with the evaporation of a water | moisture content and HF.

  The configuration of the processing unit in the case of using the high HF aqueous solution as the chemical solution can be configured such that, for example, the NH 3 -containing gas supply system and the NH 3 concentration meter 401 b are removed from the processing units 16 and 16A.

  The mixed acid aqueous solution easily evaporates acetic acid (CH3COOH) and nitric acid (HNO3) in addition to moisture. Therefore, when a mixed acid aqueous solution is used as the chemical solution, it is preferable to add moisture, acetic acid and nitric acid to the air supplied from the air supply system. Thereby, it can suppress that the density | concentration of the acetic acid and nitric acid contained as etching seed | species in mixed acid aqueous solution changes with evaporation of a water | moisture content, an acetic acid, and nitric acid.

  The configuration of the processing unit in the case of using the mixed acid aqueous solution, for example, excludes the NH 3 -containing gas supply system, the HF-containing gas supply system, the NH 3 concentration meter 401 b and the HF concentration meter 401 c from the processing units 16 and 16 A, and contains acetic acid. An acetic acid-containing gas supply system for supplying an acetic acid-containing gas (for example, acetic acid gas), a nitric acid-containing gas supply system for supplying a nitric acid-containing gas (for example, nitric acid gas) containing nitric acid, and an acetic acid concentration meter for measuring the acetic acid concentration in the processing atmosphere A nitric acid concentration meter for measuring the nitric acid concentration in the processing atmosphere can be added. The mixed acid aqueous solution is used, for example, when etching a metal film such as tungsten or titanium.

  The SC1 and TMAH aqueous solutions are, for example, chemicals used when etching a polysilicon film, and NH3 contained in SC1 and TMAH contained in the TMAH aqueous solution are etching species that dissolve silicon. However, the etching species alone greatly depends on the silicon crystal plane orientation of the etching rate, and there is a possibility that surface roughness of the polysilicon film and silicon residue may occur. Therefore, SC2 and TMAH contain H2O2 and O2 as oxidizing agents, respectively. By these oxidizing agents, the surface of the polysilicon film is oxidized and the variation in the etching amount of the silicon crystal plane orientation is alleviated, so that the surface roughness of the polysilicon film and the generation of silicon residues can be prevented.

  SC1 has an etching species of NH3 and an oxidizing agent of H2O2. Since NH 3 is easily volatilized and H 2 O 2 is easily decomposed, the etching rate changes in the plane of the wafer W due to the concentration change of these NH 3 and H 2 O 2. Therefore, when SC1 is used as the chemical solution, it is preferable to add moisture, NH3 gas, and H2O2 gas to the air supplied from the air supply system. As a result, changes in the concentration of NH3 and H2O2 in SC1 supplied to the wafer W can be suppressed, so that variations in the etching rate within the wafer W surface can be suppressed.

  The configuration of the processing unit when SC1 is used as the chemical solution, for example, excludes the HF-containing gas supply system and the HF concentration meter 401c from the processing units 16 and 16A and supplies an H2O2-containing gas (for example, H2O2 gas) containing H2O2. And a H2O2 concentration meter for measuring the H2O2 concentration in the processing atmosphere.

  In the TMAH aqueous solution, the etching species is TMAH, and the oxidizing agent is O2. The etching rate of the polysilicon film by the TMAH aqueous solution depends on the dissolved O2 concentration in the TMAH aqueous solution.

  This point will be described with reference to FIGS. FIG. 8 is a diagram showing the relationship between the dissolved O 2 concentration in the TMAH aqueous solution and the etching rate of the polysilicon film. FIG. 9 is a diagram showing the dissolved O2 concentration in the TMAH aqueous solution and the in-wafer distribution of the etching rate of the polysilicon film. FIG. 10 is a diagram showing the relationship between the O2 concentration in the processing atmosphere and the in-wafer distribution of the etching rate of the polysilicon film.

  8 and 9 show the results when the polysilicon film is etched by single wafer processing using a TMAH aqueous solution in an air atmosphere.

  As shown in FIGS. 8 and 9, the etching rate of the polysilicon film tends to decrease as the dissolved O 2 concentration in the TMAH aqueous solution increases. This is considered to be because when the dissolved O2 concentration in the TMAH aqueous solution is high, an oxide film is formed on the surface of the polysilicon film and the polysilicon film is protected, thereby suppressing the etching of the polysilicon film by TMAH. It is done.

  Further, when etching of the polysilicon film using the TMAH aqueous solution is performed in an air atmosphere and an N 2 atmosphere, the distribution of the etching rate of the polysilicon film in the wafer W in the air atmosphere and the N 2 atmosphere changes. I understood it.

  Specifically, as shown in FIG. 10, it was found that when etching is performed in an air atmosphere, the etching rate of the polysilicon film is lower in the outer peripheral portion than in the central portion of the wafer W. This is because when the O2 concentration in the processing atmosphere is relatively high as in the air atmosphere, the O2 in the processing atmosphere is taken into the TMAH aqueous solution as the TMAH aqueous solution flows from the center to the outer periphery of the wafer W. This is considered to be because the dissolved O2 concentration in the TMAH aqueous solution increases. As shown in FIG. 8, the etching rate decreases as the dissolved O 2 concentration in the TMAH aqueous solution increases.

  On the other hand, when etching was performed in an N 2 atmosphere, it was found that the etching rate of the polysilicon film was higher at the outer peripheral portion than at the central portion of the wafer W. This is because when the O2 concentration in the processing atmosphere is low as in the N2 atmosphere, the dissolved O2 in the TMAH aqueous solution volatilizes from the TMAH aqueous solution due to volatilization as the TMAH aqueous solution flows from the center to the outer periphery of the wafer W. It is considered that the concentration of dissolved O2 in the TMAH aqueous solution decreases due to escaping.

  As described above, the dissolved O 2 concentration of the TMAH aqueous solution supplied to the wafer W changes in the wafer W plane, and the mode of the change varies depending on the O 2 concentration in the processing atmosphere. Therefore, by adjusting the O2 concentration in the processing atmosphere, it is possible to suppress the concentration change in the wafer W surface of the dissolved O2 in the TMAH aqueous solution (see the solid line in FIG. 10).

  The O2 concentration in the processing atmosphere can be adjusted by adding an inert gas such as N2 gas to the air atmosphere, for example. Since the O2 concentration in the air is about 21%, it is possible to adjust the O2 concentration in the processing atmosphere within the range of more than 0% and less than 21% by adding an inert gas. The optimal dissolved O2 concentration in the TMAH aqueous solution is 1 to 10 ppm. By adjusting the O2 concentration in the processing atmosphere within the above range (0 to 21%), the dissolved O2 concentration in the TMAH aqueous solution is adjusted within the wafer W plane. Can be constant.

  As described above, by adjusting the O2 concentration in the processing atmosphere to suppress the concentration change of the dissolved O2 in the TMAH aqueous solution, it is possible to suppress the variation in the etching rate in the wafer W plane.

  The configuration of the processing unit when using the TMAH aqueous solution as the chemical solution is, for example, by removing the NH 3 -containing gas supply system, the HF-containing gas supply system, the NH 3 concentration meter 401 b and the HF concentration meter 401 c from the processing units 16 and 16 A, and N 2 gas. In addition, an inert gas supply system that supplies an inert gas such as argon gas and an O 2 concentration meter that measures the O 2 concentration in the processing atmosphere can be added. By providing an O2 gas supply system that supplies O2 gas, the O2 concentration in the processing atmosphere can be increased to 21% or more.

(Other embodiments)
When performing single wafer processing on the wafer W, a gas added to the air supplied from the air supply system may be directly supplied to the chemical solution supplied to the wafer W. This point will be described with reference to FIG. FIG. 11 is a diagram illustrating a configuration of an atmosphere supply system according to a modification.

  As shown in FIG. 11, in the processing unit 16 </ b> B according to the modification, the moisture supply system, the NH 3 -containing gas supply system, and the HF-containing gas supply system are connected to a nozzle 42 disposed in the chamber 20. The hygrometer 401a, the NH3 concentration meter 401b, and the HF concentration meter 401c measure the humidity, NH3 concentration, and HF concentration of the atmosphere in the recovery cup 50, respectively.

  In the processing unit 16B according to the modification, in the etching process, the nozzle 42 is disposed above the wafer W, and a mixed gas of moisture, NH 3 gas, and HF gas is directly applied to the BHF aqueous solution supplied from the nozzle 42 to the wafer W. Supply. Thereby, the concentration change of NH3 and HF in the BHF aqueous solution supplied to the wafer W can be suppressed as in the case of supplying from the FFU 21 as in the processing unit 16 according to the first embodiment.

  Further, in the processing unit 16B according to the modification, the concentration of moisture, NH3, and HF contained in the processing atmosphere is adjusted on the surface of the wafer W by adjusting the position of the nozzle 42 (gas discharge position) in the surface of the wafer W. Can be changed within. Thereby, for example, the etching rate can be locally increased or decreased in the wafer W plane.

  Here, the case where the chemical solution is a BHF aqueous solution has been described as an example, but the same applies to the case where a chemical solution other than the BHF aqueous solution is used. For example, when a TMAH aqueous solution is used as the chemical solution, an inert gas supply system may be connected to the nozzle 42 to supply the inert gas directly from the nozzle 42 to the TMAH aqueous solution supplied to the wafer W. .

  For example, when a BHF aqueous solution is used as a chemical solution, an inert gas is supplied from the nozzle 42 to the BHF aqueous solution supplied to the wafer W while supplying moisture, NH 3 gas and HF gas together with air from the FFU 21 into the chamber 20. May be supplied directly. In this case, for example, by supplying an inert gas from the nozzle 42 toward the center of the wafer W, the concentrations of moisture, NH 3 and HF are lowered at the center of the wafer W and increased at the outer periphery of the wafer W. Is possible.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

W Wafer 1 Substrate processing system 16 Processing unit 18 Control unit 20 Chamber 21 FFU
40 Processing fluid supply part 212 Air supply source 302a H2O supply source 302b NH3-containing gas supply source 302c HF-containing gas supply source 401a Hygrometer 401b NH3 concentration meter 401c HF concentration meter

Claims (10)

An etching step of etching the substrate by supplying a chemical to the substrate;
And adjusting the atmosphere to which the chemical solution supplied to the substrate is exposed to adjust the concentration of the etching species or the oxidant contained in the chemical solution. Method. The etching step includes an air supply step of supplying air to a processing space where etching is performed,
The atmosphere adjustment step includes
It is contained in the chemical supplied to the substrate by adding a gas containing a component contained as an etching species or an oxidant to the chemical to the air supplied to the processing space in the air supply step. The substrate processing method according to claim 1, wherein the concentration of the etching species or the oxidizing agent is controlled. The etching step includes
HF aqueous solution is supplied to the substrate as the chemical solution,
The atmosphere adjustment step includes
In the etching step, the concentration of HF contained in the chemical solution supplied to the substrate is controlled by adding a HF-containing gas containing HF to the air supplied to the processing space. The substrate processing method according to claim 2. The etching step includes
Supplying a BHF aqueous solution to the substrate as the chemical solution;
The atmosphere adjustment step includes
In the etching step, the concentration of NH3 contained in the chemical solution supplied to the substrate is controlled by adding an NH3-containing gas containing NH3 to the air supplied to the processing space. The substrate processing method according to claim 2. The etching step includes
SC1 is supplied to the substrate as the chemical solution,
The atmosphere adjustment step includes
In the etching step, the concentration of H2O2 contained in the chemical solution supplied to the substrate is controlled by adding a H2O2-containing gas containing H2O2 to the air supplied to the processing space. The substrate processing method according to claim 2. The etching step includes an air supply step of supplying air to a processing space where etching is performed,
The etching step includes
Supplying TMAH aqueous solution in which O2 is dissolved to the substrate as the chemical solution;
The atmosphere adjustment step includes
In the etching step, an inert gas is added to the air supplied to the processing space to adjust the O2 concentration in the air, thereby controlling the O2 concentration contained in the chemical solution supplied to the substrate. The substrate processing method according to claim 1, wherein: The etching step includes a concentration measuring step of measuring a concentration of the etching species or an oxidizing agent in the processing space,
The atmosphere adjustment step includes
The substrate processing method according to any one of claims 2 to 6, wherein a flow rate of a gas to be added to air supplied to the processing space is adjusted based on a measurement result in the concentration measuring step. . The etching step includes
The substrate is held using a holding unit that holds the substrate, and the substrate held by the holding unit is rotated using a rotating mechanism that rotates the holding unit, and then the center of the rotating substrate is rotated. Etching the substrate by supplying the chemical solution,
The atmosphere adjustment step includes
The substrate processing method according to claim 1, wherein an atmosphere in a chamber that accommodates the holding unit is adjusted. The etching step includes
A plurality of the substrates are held by using a holding unit that holds the plurality of substrates, and a plurality of the substrates held by the holding unit are immersed in a processing tank in which the chemical solution is stored. Etching the substrate,
The atmosphere adjustment step includes
The atmosphere in a chamber in which the processing tank is accommodated or an atmosphere in a space formed by the processing tank and a lid provided at an opening of the processing tank is adjusted. The substrate processing method as described in any one of these. A holding unit for holding the substrate;
A chemical supply unit for supplying a chemical to the substrate held by the holding unit;
A gas supply unit for supplying gas;
In the etching process, the chemical solution supply unit and the gas supply unit are controlled to etch the substrate by supplying the chemical solution from the chemical solution supply unit to the substrate held in the holding unit. A control unit that executes an atmosphere adjustment process for controlling the concentration of an etching species or an oxidant contained in the chemical solution by adjusting the atmosphere to which the chemical solution supplied to the substrate is exposed by the gas supplied from the gas supply unit. And a substrate processing apparatus.

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