JP2008016548A - High-pressure processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-pressure processing method capable of well cleaning a substrate with improved in-plane uniformity and uniformity among lots in cleaning the substrate. <P>SOLUTION: Start (step S3) of cleaning with a processing fluid supplying an etchant mixed into SCCO2 to a processing chamber makes methanol to be included in the etchant, and puts the inside of the processing chamber in high relative permittivity environments. In addition, after sending the etchant is stopped (step S4), sending of isopropyl alcohol (IPA) as an environment regulator is started (step S5), so that the inside of the processing chamber is put in low relative permittivity environments. Therefore, although a time lag is present between time points of starting and ending the cleaning, as an inlet and an outlet are located at different positions; time periods when respective parts of the substrate are processed at different etching speeds can be inhibited in fluctuation or can be shortened. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-pressure processing method in which a processing fluid in which hydrogen fluoride is essentially mixed with a high-pressure fluid is brought into contact with a substrate to perform a cleaning process on the substrate. Here, examples of the substrate include various substrates (hereinafter simply referred to as “substrate”) such as a semiconductor wafer, a glass substrate for photomask, a glass substrate for liquid crystal display, a glass substrate for plasma display, and a substrate for optical disk.

  In a processing step of performing a series of processes on a substrate such as a semiconductor wafer as an object to be processed, a natural oxide film and a chemical oxide film that are formed on the substrate itself or on various film surfaces formed thereon Alternatively, a cleaning process for removing unnecessary materials such as a resist that has become unnecessary after being applied on the substrate is an essential process. Therefore, as one of the processing methods for removing these unnecessary substances from the substrate, a processing fluid in which hydrogen fluoride is essentially mixed with a high-pressure fluid such as a supercritical fluid is brought into contact with the surface of the substrate to be removed from the substrate. A high-pressure treatment method for removing unnecessary substances has been proposed (see Patent Document 1).

JP 2004-158534 A (FIG. 1)

  In this high-pressure processing method, after a substrate to be cleaned is accommodated in a processing chamber formed inside a pressure vessel, a processing fluid is supplied from an inlet of the pressure vessel to clean the substrate surface. That is, when a processing fluid prepared by mixing hydrogen fluoride with a high-pressure fluid is supplied from the inlet of the pressure vessel, the concentration of hydrogen fluoride in the processing chamber gradually increases from zero, and after a certain time Reach a predetermined concentration. When the cleaning process is finished, the mixing of hydrogen fluoride into the high-pressure fluid is stopped, and the processing fluid not containing hydrogen fluoride is supplied from the inlet of the pressure vessel and cleaned from the outlet of the pressure vessel. The later processing fluid is discharged. As a result, the concentration of hydrogen fluoride in the processing chamber decreases and finally becomes zero, completing the cleaning process.

  The problem here is the distribution of the hydrogen fluoride concentration in the processing chamber. That is, in the pressure vessel, since the inlet and the outlet are usually provided at different positions, the temporal change in the hydrogen fluoride concentration in the processing chamber differs between the vicinity of the inlet and the outlet. For example, immediately after the start of the supply of the processing fluid containing hydrogen fluoride, the concentration of hydrogen fluoride in the vicinity of the inlet increases rapidly, but the concentration in the vicinity of the outlet remains low. And when predetermined time passes, the density | concentration in the vicinity of a discharge port will rise. Conversely, immediately after the start of the supply of the processing fluid not containing hydrogen fluoride, the concentration of hydrogen fluoride in the vicinity of the inlet decreases rapidly, but the concentration in the vicinity of the outlet is maintained high. When a predetermined time elapses, the concentration in the vicinity of the discharge port decreases, and the hydrogen fluoride concentration becomes zero in the entire processing chamber. Thus, a time lag occurs in the concentration change between the inlet and the outlet in the pressure vessel. As a result, there has been a problem that the in-plane uniformity of the cleaning process on the entire surface of the substrate is deteriorated.

  The present invention has been made in view of the above problems, and provides a high-pressure processing method capable of improving the in-plane uniformity of the cleaning process for the substrate to satisfactorily clean the substrate and increasing the uniformity between processing lots. The purpose is to do.

  In the present invention, a processing fluid containing a high-pressure fluid is supplied into the pressure vessel from the inlet of the pressure vessel to clean the substrate accommodated in the pressure vessel, while the processed processing fluid is supplied from the outlet of the pressure vessel. A high-pressure processing method for discharging and performing a cleaning process on a substrate. In order to achieve the above object, the cleaning process uses a high-pressure etchant containing a first solvent having a first relative dielectric constant and hydrogen fluoride. The high relative permittivity cleaning process for supplying the first fluid prepared by mixing with the fluid as the processing fluid from the inlet and adjusting the inside of the pressure vessel to a high relative permittivity environment and the high relative permittivity cleaning process are continued for a predetermined time. Then, the mixing of the etchant into the high-pressure fluid is stopped, and an environmental conditioner that essentially contains a second solvent having a second dielectric constant lower than the first dielectric constant is mixed with the high-pressure fluid. Note that treated second fluid is used as treatment fluid It is characterized in that a low dielectric constant cleaning process to arrange the pressure vessel and supplied from the mouth to the low dielectric constant environment.

  In the invention configured as described above, the processing fluid containing the high-pressure fluid is supplied into the pressure vessel from the inlet of the pressure vessel, and the cleaning process is performed on the substrate accommodated in the pressure vessel. Further, the processing fluid after cleaning is discharged from the discharge port of the pressure vessel. As described above, supply of the processing fluid to the pressure vessel is performed via the inlet, while discharging of the processing fluid from the pressure vessel is performed via the outlet. For this reason, a change in the concentration of hydrogen fluoride contained in the processing fluid causes a time lag between the inlet and the outlet in the pressure vessel. That is, a time zone in which the hydrogen fluoride concentration is different between the vicinity of the inlet and the outlet of the substrate surface occurs, and this is one of the main factors for reducing in-plane uniformity. Therefore, in the present invention, as described in detail below, immediately after the start of the cleaning process, the fact that the substrate cleaning ability (etching rate) by hydrogen fluoride changes according to the relative permittivity environment in the pressure vessel is used. The substrate cleaning ability is controlled immediately before the end. More specifically, immediately after the start of the cleaning process, the environment is adjusted to a high dielectric constant environment, and the cleaning process is performed with a desired substrate cleaning capability on the entire surface of the substrate within a relatively short time. On the other hand, the substrate cleaning ability becomes zero within a relatively short time after being adjusted to a low relative dielectric constant environment immediately before the end. This improves the in-plane uniformity of the cleaning process for the substrate.

  In the high-pressure treatment method according to the present invention, the high-pressure fluid used is preferably carbon dioxide from the viewpoints of safety, cost, and easy to make a supercritical state. The high pressure fluid is used because it has a high diffusion coefficient and can disperse dissolved pollutants in the medium. When the high pressure fluid is a supercritical fluid, it has an intermediate property between gas and liquid. The diffusion coefficient approaches the gas and can penetrate well into fine pattern portions. Also, the density of the supercritical fluid is close to that of a liquid and can contain a much larger amount of the stripping composition than gas.

  Here, the high-pressure fluid in the present invention is a fluid having a pressure of 1 MPa or more. The high-pressure fluid that can be preferably used is a fluid in which high-density, high-solubility, low-viscosity, and high-diffusibility properties are observed, and more preferable is a fluid in a supercritical state or subcritical state. In order to use carbon dioxide as a supercritical fluid, the temperature may be 31 ° C. and 7.4 MPa or more. In particular, a subcritical or supercritical fluid (high pressure fluid) of 5 to 30 MPa is preferably used for the cleaning process. It is more preferable to perform these treatments at 4 to 30 MPa.

  As described above, according to the present invention, the cleaning process performed on the substrate in the pressure vessel includes the above-described high relative dielectric constant cleaning step and the low relative dielectric constant cleaning step. For this reason, it is possible to execute the cleaning process on the entire surface of the substrate with a desired substrate cleaning capability in a relatively short time immediately after the start of the cleaning process, and in a relatively short time since the mixing of the etchant to the high-pressure fluid is stopped. The cleaning ability for the entire surface can be made zero. As a result, the in-plane uniformity of the cleaning process for the substrate can be improved and the substrate can be cleaned satisfactorily.

<Relationship between substrate cleaning ability and cleaning environment>
As described in Patent Document 1, a processing fluid prepared by essentially mixing hydrogen fluoride with a high-pressure fluid such as supercritical carbon dioxide is brought into contact with the substrate surface to be attached to the substrate surface. The substrate can be cleaned by etching away the oxide film and the like. Therefore, the present inventor made various studies on the substrate cleaning ability by the processing fluid, and obtained the knowledge that the substrate cleaning ability is strongly influenced by the cleaning environment, particularly the relative permittivity in the pressure vessel. That is, even if the hydrogen fluoride concentration in the processing fluid is the same, the cleaning ability increases as the relative dielectric constant increases. This will be described based on the etching rate when the oxide film formed on the silicon substrate is removed by etching under the following conditions.

  Here, the etching selection when the thermal oxide film and the boron phosphorous glass film (BPSG) are respectively etched by a processing fluid in which hydrogen fluoride and a solvent are mixed with supercritical carbon dioxide (hereinafter referred to as “SCCO 2”). That is, the etching rate selectivity (= BPSG / thermal oxide film) was examined. Further, in order to change the relative permittivity environment in the pressure vessel, the etching selectivity of the solvents having different relative permittivities was examined. As a result, a correlation as shown in FIG. 1 was obtained. . That is, the etching selectivity changes as the relative permittivity environment in the pressure vessel changes. More specifically, as the relative dielectric constant of the solvent increases, the etching selectivity decreases, and the rate of cleaning and removing the oxide film, that is, the etching rate increases. Therefore, the inventor of the present application can control the etching rate in the pressure vessel by selecting the type of solvent mixed with the high-pressure fluid and controlling the relative dielectric constant in the pressure vessel. I got the knowledge. That is, it has been found that the etching rate can be increased or decreased by selecting a solvent.

  More specifically, methanol, acetonitrile, formamide, methylformamide, dimethylformamide, methylacetamide, dimethylacetamide, ethylene carbonate, or the like is used as the first solvent for adjusting the pressure vessel to a high dielectric constant environment. Can do. In addition, it is desirable to employ a first dielectric constant of the first solvent that is 30 or more at 25 ° C. In order to form a high dielectric constant environment, it is desirable to set the content of the etchant in the high-pressure fluid to 1 to 20% by weight. In order to perform the cleaning process reliably and appropriately, the content of hydrogen fluoride in the etchant is preferably set to 0.0001 to 5% by weight. The etchant may further contain water, and the concentration of water in the etchant may be adjusted to 0.001 to 10% by weight. Further, the etchant may further include at least one selected from the group consisting of monohydric alcohols, polyhydric alcohols, dimethyl sulfoxide, N-methyl-2-pyrrolidone and propylene carbonate (propylene carbonate). Here, ethanol, propanol or butanol can be used as the “monohydric alcohol”. As the “polyhydric alcohol”, any of ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, dipropylene glycol, octylene glycol, butanediol, and pentamethylene glycol can be used.

  On the other hand, propanol, butanol, acetic acid, tetrahydrofuran (THF), acetone, or the like can be used as the second solvent for adjusting the inside of the pressure vessel to a low dielectric constant environment. In addition, it is desirable to employ a second dielectric constant of the second solvent that is 20.7 or less at 25 ° C. Moreover, in order to form a low dielectric constant environment, it is desirable to set the content of the environmental modifier in the high-pressure fluid to 1 to 20% by weight. Moreover, you may adjust the density | concentration of the water in an environmental control agent to 0.001 to 10 weight%. Furthermore, the environmental conditioner may further contain at least one selected from the group consisting of monohydric alcohols, polyhydric alcohols, dimethyl sulfoxide, N-methyl-2-pyrrolidone and propylene carbonate. Here, methanol or ethanol can be used as the “monohydric alcohol”. As the “polyhydric alcohol”, any of ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, dipropylene glycol, octylene glycol, butanediol, and pentamethylene glycol can be used.

  The inventor of the present application has created a technique for improving the in-plane uniformity of the cleaning process for the substrate based on the relationship between the substrate cleaning ability and the cleaning environment. Hereinafter, the present invention will be described in detail through embodiments.

<Embodiment>
FIG. 2 is a diagram showing a high-pressure processing apparatus capable of carrying out an embodiment of the high-pressure processing method according to the present invention. FIG. 3 is a block diagram showing an electrical configuration for controlling the high-pressure processing apparatus of FIG. This high-pressure processing apparatus introduces a processing fluid containing SCCO 2 into a processing chamber 11 formed inside the pressure vessel 1, and an oxide film that adheres to the surface of a substrate W such as a semiconductor wafer held in the processing chamber 11. It is a device that removes etching. Thus, the cleaning process for the substrate W is executed. Hereinafter, the configuration and operation will be described in detail.

  The high-pressure processing apparatus 100 is roughly divided into three units, (1) a processing fluid supply unit A that prepares a processing fluid and supplies it to the processing chamber 11, and (2) a pressure vessel 1. A substrate processing unit B that etches an oxide film with a processing fluid in the processing chamber 11 and (3) a storage unit C that collects and stores carbon dioxide and the like used for substrate processing are provided.

  Among these units, the processing fluid supply unit A includes a high-pressure carbon dioxide supply unit 2 that pumps SCCO 2 toward the pressure vessel 1, a hydrogen fluoride supply unit 3 that supplies hydrogen fluoride, and methanol. A methanol supply unit 4 for supplying and an IPA supply unit 5 for supplying isopropyl alcohol (IPA) are provided.

  The high-pressure carbon dioxide supply unit 2 includes a carbon dioxide storage tank 21 and a high-pressure pump 22. When SCCO2 is used as the high-pressure carbon dioxide as described above, liquefied carbon dioxide is usually stored in the carbon dioxide storage tank 21. Further, the fluid may be cooled in advance with a supercooler (not shown) to prevent gasification in the high-pressure pump 22. And if this fluid is pressurized with the high-pressure pump 22, high-pressure liquefied carbon dioxide can be obtained. The outlet side of the high-pressure pump 22 is connected to the inlet IP of the pressure vessel 1 by a high-pressure pipe 26 having a first heater 23, a high-pressure valve 24 and a second heater 25 interposed therebetween. Then, by opening the high-pressure valve 24 in accordance with an opening / closing command from the controller 10 that controls the entire apparatus, the high-pressure liquefied carbon dioxide pressurized by the high-pressure pump 22 is heated by the first heater 23 as high-pressure carbon dioxide. While obtaining SCCO2, this SCCO2 is directly pumped to the pressure vessel 1. Thereby, the processing fluid containing SCCO2 is supplied to the inside of the pressure vessel 1, that is, the processing chamber 11 through the inlet IP. Note that the high-pressure pipe 26 branches three branch pipes 31, 41, 51 between the high-pressure valve 24 and the second heater 25. The branch pipe 31 is connected to the hydrogen fluoride storage tank 32 of the hydrogen fluoride supply unit 3, the branch pipe 41 is connected to the methanol storage tank 42 of the methanol supply unit 4, and the branch pipe 51 is connected to the IPA supply unit 5. An IPA storage tank 52 is connected. The unit 3 among the three units 3 to 5 may be omitted, and a liquid in which hydrogen fluoride (HF) and methanol are premixed at a predetermined concentration may be stored in the tank 42 of the unit 4.

  The hydrogen fluoride supply unit 3 includes a hydrogen fluoride storage tank 32 that stores hydrogen fluoride. The hydrogen fluoride storage tank 32 is connected to the high-pressure pipe 26 by a branch pipe 31. In addition, a feed pump 33 and a high-pressure valve 34 are inserted in the branch pipe 31. For this reason, by controlling the opening / closing operation of the high-pressure valve 34 in accordance with the opening / closing command from the controller 10, the hydrogen fluoride in the hydrogen fluoride storage tank 32 is sent to the high-pressure pipe 26 and hydrogen fluoride is supplied to the SCCO2. Mixing is possible.

  Further, the methanol supply unit 4 includes a methanol storage tank 42 that stores methanol (relative permittivity at 25 ° C. = 32.6) functioning as the “first solvent” of the present invention in this embodiment. The methanol storage tank 42 is connected to the high-pressure pipe 26 by a branch pipe 41. In addition, a feed pump 43 and a high-pressure valve 44 are inserted in the branch pipe 41. For this reason, by controlling the opening / closing operation of the high-pressure valve 44 in accordance with the opening / closing command from the controller 10, the methanol in the methanol storage tank 42 is fed into the high-pressure pipe 26 and methanol can be mixed with the SCCO2. .

  Further, the IPA supply unit 5 supplies isopropyl alcohol (relative permittivity at 25 ° C. = 19.9) functioning as the “second solvent” of the present invention in this embodiment, and stores isopropyl alcohol. An IPA storage tank 52 is provided. This IPA storage tank 52 is connected to the high-pressure pipe 26 by a branch pipe 51. In addition, a feed pump 53 and a high-pressure valve 54 are inserted in the branch pipe 51. For this reason, by controlling the opening / closing operation of the high-pressure valve 54 in accordance with the opening / closing command from the controller 10, the isopropyl alcohol in the IPA storage tank 52 is fed into the high-pressure pipe 26 and can be mixed with SCCO2. ing.

  In the substrate processing unit B, the discharge port OP of the pressure vessel 1 is communicated with the storage unit 6 of the storage unit C through the high-pressure pipe 12. In addition, a pressure regulating valve 13 is inserted in the high pressure pipe 12. For this reason, when the pressure regulating valve 13 is opened in response to the opening / closing command from the controller 10, the processing fluid or the like in the pressure vessel 1, that is, the processing chamber 11 is discharged from the discharge port OP to the storage unit 6, while the pressure adjusting valve When 13 is closed, the processing fluid can be confined in the pressure vessel 1. It is also possible to adjust the pressure in the processing chamber 11 by controlling the opening and closing of the pressure adjustment valve 13.

  As the storage unit 6 of the storage unit C, for example, a gas-liquid separation container or the like may be provided. SCCO2 is separated into a gas part and a liquid part using the gas-liquid separation container, and discarded through separate paths. Alternatively, each component may be recovered (and purified if necessary) and reused. In addition, you may discharge | emit the gas component and liquid component which were isolate | separated by the gas-liquid separation container out of the system through a separate path | route.

  Next, a cleaning process performed by the high-pressure processing apparatus 100 configured as described above will be described with reference to FIGS. 4 and 5. FIG. 4 is a flowchart showing an embodiment of the high-pressure processing method according to the present invention. FIG. 5 is a graph showing the processing status at the inlet and outlet of the pressure vessel. In the initial state of this device, all the valves 13, 24, 34, 44, 54 are closed and the pumps 22, 33, 43, 53 are also stopped.

  When one substrate W is loaded into the processing chamber 11 by a handling device such as an industrial robot or a transfer device, the processing chamber 11 is closed to complete processing preparation (step S1). Subsequently, the high pressure valve 24 is opened so that SCCO2 can be pumped from the high pressure carbon dioxide supply unit 2 to the processing chamber 11, and then the high pressure pump 22 is operated to start pumping SCCO2 to the processing chamber 11 ( Step S2). As a result, SCCO2 is pumped to the processing chamber 11, and the pressure in the processing chamber 11 gradually increases. At this time, the pressure in the processing chamber 11 is kept constant, for example, about 20 MPa, by controlling the pressure adjusting valve 13 according to an opening / closing command from the controller 10. The pressure adjustment by the opening / closing control is continued until the decompression process described later is completed. Further, when the temperature of the processing chamber 11 needs to be adjusted, the temperature is set to a temperature suitable for the surface treatment by the second heater 25 heater provided in the vicinity of the pressure vessel 1. Thus, in the present embodiment, process conditions relating to the pressure and temperature of SCCO 2 can be controlled.

  Next, in accordance with a control command from the controller 10, an etchant composed of hydrogen fluoride (HF) and methanol is sent to the high-pressure pipe 26, whereby the etchant composed of hydrogen fluoride and methanol is mixed with SCCO2 to prepare a processing fluid. Is done. This processing fluid corresponds to the “first fluid” of the present invention. Then, the processing fluid is supplied to the processing chamber 11 through the inlet IP (step S3). More specifically, in order to send in hydrogen fluoride, the feed pump 33 is operated and the high-pressure valve 34 is opened. As a result, hydrogen fluoride, which is a main component for substrate cleaning, is sent from the hydrogen fluoride storage tank 32 to the high-pressure pipe 26 via the branch pipe 31. Further, in order to send methanol as the “first solvent” of the present invention, the feed pump 43 is operated and the high-pressure valve 44 is opened. As a result, methanol is sent from the methanol storage tank 42 to the high-pressure pipe 26 via the branch pipe 41. As described above, in this embodiment, the first fluid obtained by mixing the etchant containing hydrogen fluoride (HF) and methanol with SCCO 2 is supplied to the processing chamber 11 from the inlet IP as the processing fluid. In a high relative dielectric constant environment, and a cleaning process is started on the substrate W with a processing fluid (SCCO 2 + HF + methanol) (high relative dielectric constant cleaning step).

  As described above, the cleaning process starts when the supply of the processing fluid to the processing chamber 11 is started. At this time, the processing fluid (SCCO 2 + hydrogen fluoride + methanol) is supplied to the processing chamber 11 and sealed in the processing chamber 11 for cleaning. Processing may be continued. Further, the SCCO2 and the etchant (hydrogen fluoride + methanol) are continuously fed and the opening and closing of the pressure regulating valve 13 is controlled to perform the cleaning process while maintaining the pressure state in the processing chamber 11 constant. Also good. However, considering that the HF concentration decreases with the cleaning process, it is desirable that the processing fluid is always circulated as in the latter case.

  The processing state in the processing chamber 11 in this high relative dielectric constant cleaning step will be described with reference to FIG. In the vicinity of the inlet IP in the processing chamber 11, the processing fluid (SCCO 2 + HF + methanol) is supplied almost simultaneously with the start of feeding of the etchant (timing T 1), and the increase in the HF concentration is started. On the other hand, in the vicinity of the discharge port OP, the HF concentration rises only after the time lag TLs corresponding to the volume of the processing chamber 11 has elapsed. The HF concentration is different between the vicinity of the injection port IP and the vicinity of the discharge port OP for a time ΔThs from when the etchant is started until the HF concentration reaches a constant value in the vicinity of the discharge port OP. Thus, there exists a time zone ΔThs in which the HF concentration is partially different in the processing chamber 11. However, in this embodiment, since the inside of the processing chamber 11 is adjusted to a high relative permittivity environment from the start of the cleaning process, the etching rate reaches a constant value very rapidly. Therefore, the time for which the etching rate is high is shortened. That is, during the time ΔThs, the time during which the etching rate is high at the inlet IP and the outlet OP can be made as small as possible. This is because if the etchant delivery varies in a high state, the variation in the etching process time also increases. In particular, if the valve opening / closing degree of the high-pressure processing apparatus 100 or the flow rate of the SCCO2 fluctuates irregularly, the etchant concentration varies among the lots of processing, and this influence also increases the variation in etching processing time and also increases the non-uniformity between lots. . Therefore, non-uniformity between lots can be suppressed by reducing the etching rate during the time ΔThs.

  After the cleaning process is started in this way, the supply of the processing fluid (SCCO 2 + HF + methanol) is continued for a predetermined time, and the cleaning process in the high relative permittivity environment is executed. Then, when a predetermined time has elapsed, the feeding of the etchant is stopped (step S4), and the feeding of isopropyl alcohol (IPA) as an environmental adjusting agent is started (step S5). That is, isopropyl alcohol is mixed with SCCO2 instead of the etchant to prepare a processing fluid. This processing fluid corresponds to the “second fluid” of the present invention. Then, the processing fluid is supplied to the processing chamber 11 through the inlet IP. Thus, in this embodiment, the second fluid obtained by mixing SCCO2 with isopropyl alcohol having a dielectric constant lower than that of the first solvent is supplied to the processing chamber 11 from the inlet IP as a processing fluid, and the processing chamber 11 While adjusting the inside to a low relative dielectric constant environment, the etching rate is reduced, and the cleaning process for the substrate W is finished (low relative dielectric constant cleaning step).

  The processing state in the processing chamber 11 in this low dielectric constant cleaning step will be described with reference to FIG. In the vicinity of the inlet IP in the processing chamber 11, the processing fluid (SCCO2 + IPA) is supplied almost simultaneously with the start of feeding of isopropyl alcohol (timing T2), and the decrease in the HF concentration is started. On the other hand, in the vicinity of the discharge port OP, the HF concentration begins to decrease only after the time lag TLe corresponding to the volume of the processing chamber 11 has elapsed. A processing chamber is formed between the vicinity of the injection port IP and the vicinity of the discharge port OP for a time ΔTh from the switch from the etchant to the environmental conditioner (timing T2) until the HF concentration becomes zero in the vicinity of the discharge port OP. 11 has different HF concentrations remaining. As described above, there exists a time zone ΔThe in which the HF concentration is partially different in the processing chamber 11. However, in the present embodiment, since the inside of the processing chamber 11 is adjusted to a low relative dielectric constant environment from the start of the feeding of the environmental adjusting agent, the etching rate decreases extremely rapidly, so that it is effectively almost zero in a short time. Has reached. Therefore, the time ΔTre from the timing T2 until the etching rate on the discharge port OP side reaches zero is shorter than the time ΔThe. That is, although the time lag TLe is present at the end of cleaning due to the injection port IP and the discharge port OP being disposed at different positions, the time during which each part of the substrate is processed at different etching rates can be reduced. . Here, the time during which the etching rate is high at the inlet IP and the outlet OP during the time ΔThe can be made as small as possible. As a result, the etching non-uniformity between lots can be suppressed similarly to the time ΔThs.

  Returning to FIG. 4, the description will be continued. When the cleaning process is completed as described above, the supply of isopropyl alcohol is stopped at timing T3 (step S6), but the SCCO2 pumping is continued as it is, and only SCCO2 is supplied to the processing chamber 11 (step S7). ). Thereby, the 2nd solvent component which exists in the substrate surface and the processing chamber 11 is discharged | emitted to the storage part 6 via the high pressure piping 12 and the pressure control valve 13 (rinsing process). When all of the second solvent component is exhausted from the substrate surface and the processing chamber 11 in this way, the high-pressure pump 22 is stopped to stop the pumping of SCCO2. Then, the inside of the processing chamber 11 is returned to normal pressure by controlling the opening and closing of the pressure regulating valve 13 (step S8). In this decompression process, the SCCO2 remaining in the processing chamber 11 becomes a gas and evaporates, so that the substrate W can be dried without causing defects such as spots on the substrate surface. Moreover, in recent years, a fine pattern is often formed on the surface of the substrate, and the problem that the fine pattern is destroyed during the drying process has been highlighted, but the above problem can be solved by using reduced pressure drying. Can do.

  When the processing chamber 11 returns to normal pressure, the processing chamber 11 is opened, and the substrate W that has been cleaned is unloaded by a handling device such as an industrial robot or a transfer device (step S9). In this way, a series of surface processes, that is, a cleaning process + a rinsing process + a drying process is completed. Then, when the next unprocessed substrate W is transported, the above operation is repeated.

  As described above, in this embodiment, the processing fluid in which the etchant is mixed with SCCO2 in step S3 is supplied to the processing chamber 11 to start the cleaning process. However, the cleaning process starts when methanol is contained in the etchant. Further, the inside of the processing chamber 11 is arranged in a high relative dielectric constant environment. Therefore, the cleaning process is performed on the entire surface of the substrate at a desired etching rate (cleaning capability) from the state where the etching rate is reduced within the time ΔThs. On the other hand, after stopping the feeding of the etchant (step S4), the feeding of isopropyl alcohol (IPA) as an environmental adjusting agent is started (step S5), and the inside of the processing chamber 11 is adjusted to a low relative dielectric constant environment. . For this reason, the etching rate is effectively substantially zero within a relatively short time ΔTre. Therefore, although there are time zones ΔThs and ΔTh where the HF concentrations are partially different immediately after the start of cleaning and immediately before the end of cleaning due to the placement of the inlet IP and the outlet OP at different positions, Variations in processing time at different etching rates can be suppressed or the time can be shortened. As a result, the in-plane uniformity of the cleaning process with respect to the substrate W can be improved, and the substrate W can be satisfactorily cleaned, and the uniformity between processing lots can be increased.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the present invention is applied to a single-wafer type high-pressure processing method that processes substrates one by one. However, the present invention is applied to a so-called batch-type high-pressure processing method that simultaneously processes a plurality of substrates. The present invention can also be applied to this.

  Furthermore, the mixed solution used in the high relative dielectric constant process is not necessarily constituted only by 30 or more high relative dielectric constant components. The mixed solution only needs to be 30 or more as a whole. For example, even if it contains a low dielectric constant component such as THF or IPA, a mixed solution having a high relative dielectric constant as a whole by adding water or methanol. If so, that's fine. The same applies to the low dielectric constant process. Even if water, ethylene carbonate, or methanol is contained, it is sufficient if the entire system has a low dielectric constant.

  The present invention can be applied to all high-pressure processing methods in which a processing fluid in which hydrogen fluoride is essentially mixed with a high-pressure fluid is brought into contact with the substrate to perform a cleaning process on the substrate.

It is a graph which shows the relationship between the dielectric constant environment in a pressure vessel, and etching selectivity. It is a figure which shows the high-pressure processing apparatus which can implement one Embodiment of the high-pressure processing method concerning this invention. FIG. 3 is a block diagram showing an electrical configuration for controlling the high-pressure processing apparatus of FIG. 2. It is a flowchart which shows one Embodiment of the high voltage | pressure processing method concerning this invention. It is a graph which shows the processing condition in the inlet and outlet of a pressure vessel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pressure vessel 2 ... High pressure carbon dioxide supply part 3 ... Hydrogen fluoride supply part 4 ... Methanol supply part 5 ... IPA supply part 11 ... Processing chamber IP ... (Pressure vessel) inlet OP ... (Pressure vessel) outlet W ... Board

Claims (12)

A processing fluid containing a high-pressure fluid is supplied into the pressure vessel from the inlet of the pressure vessel to clean the substrate accommodated in the pressure vessel, and the cleaned processing fluid is discharged from the outlet of the pressure vessel. A high-pressure processing method for performing a cleaning process on the substrate,
The washing process
A first fluid prepared by mixing an etchant essentially containing a first solvent having a first dielectric constant and hydrogen fluoride with the high-pressure fluid is supplied from the inlet as the processing fluid, and the inside of the pressure vessel High relative permittivity cleaning process to arrange the high relative permittivity environment,
After the high dielectric constant cleaning step is continued for a predetermined time, mixing of the etchant into the high pressure fluid is stopped, and a second solvent having a second dielectric constant lower than the first dielectric constant is added. A low relative permittivity cleaning step for adjusting the inside of the pressure vessel to a low relative permittivity environment by supplying a second fluid prepared by mixing an environmental conditioner, which is essentially contained, with the high pressure fluid as the processing fluid from the inlet. And a high-pressure treatment method.   The high-pressure processing method according to claim 1, wherein a content of the etchant in the high-pressure fluid in the high dielectric constant cleaning step is 1 to 20% by weight.   The high-pressure processing method according to claim 1 or 2, wherein the first relative dielectric constant is 30 or more at 25 ° C.   The high-pressure treatment method according to claim 1 or 2, wherein the first solvent contains at least one selected from the group consisting of methanol, acetonitrile, formamide, methylformamide, dimethylformamide, methylacetamide, dimethylacetamide, and ethylene carbonate. .   The high-pressure treatment method according to any one of claims 1 to 4, wherein a content of hydrogen fluoride in the etchant is 0.0001 to 5% by weight in the high dielectric constant cleaning step.   The high-pressure treatment method according to any one of claims 1 to 5, wherein a content of the environmental conditioner in the high-pressure fluid in the low relative permittivity cleaning step is 1 to 20% by weight.   The high pressure processing method according to any one of claims 1 to 6, wherein the second relative dielectric constant is 20.7 or less at 25 ° C.   The high-pressure treatment method according to claim 1, wherein the second solvent contains at least one selected from the group consisting of propanol, butanol, acetic acid, tetrahydrofuran (THF), and acetone.   9. The high-pressure treatment according to claim 1, wherein the etchant further includes water in the high dielectric constant cleaning step, and the concentration of water in the etchant is adjusted to 0.001 to 10 wt%. Method.   2. The etchant in the high dielectric constant cleaning step further includes at least one selected from the group consisting of monohydric alcohols, polyhydric alcohols, dimethyl sulfoxide, N-methyl-2-pyrrolidone and propylene carbonate. The high pressure processing method according to any one of Items 9 to 9.   The high-pressure treatment method according to any one of claims 1 to 10, wherein a concentration of water in the environmental modifier is adjusted to 0.001 to 10% by weight in the low dielectric constant cleaning step.   In the low dielectric constant cleaning step, the environmental modifier further includes at least one selected from the group consisting of monohydric alcohol, polyhydric alcohol, dimethyl sulfoxide, N-methyl-2-pyrrolidone and propylene carbonate. Item 12. The high pressure treatment method according to any one of Items 1 to 11.

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