JP6444843B2 - Substrate processing method, substrate processing apparatus, and storage medium - Google Patents

Description

  The present invention relates to a substrate processing method, a substrate processing apparatus, and a storage medium for removing liquid adhering to the surface of a substrate using a fluid in a supercritical state.

  In the manufacturing process of a semiconductor device in which a laminated structure of integrated circuits is formed on the surface of a semiconductor wafer (hereinafter referred to as a wafer) as a substrate, a minute dust or a natural oxide film on the wafer surface is removed by a cleaning liquid such as a chemical solution. A liquid processing step for processing the wafer surface using a liquid is provided.

  However, with the high integration of semiconductor devices, a phenomenon called so-called pattern collapse has become a problem when removing liquid adhering to the wafer surface in such a liquid processing step.

  As a technique for removing the liquid adhering to the wafer surface while suppressing the occurrence of such pattern collapse, a method using a fluid in a supercritical state is known.

  For example, in Patent Document 1, fluorine is added to both the liquid for preventing drying and the fluid in the supercritical state from the viewpoint of high replacement of the liquid and the fluid in the supercritical state and suppression of moisture introduction during the liquid treatment. Contains organic solvent. In addition, the fluorine-containing organic solvent is suitable as a liquid for preventing drying in view of flame retardancy.

  By the way, a wafer filled with a liquid for preventing drying (for example, FC43) is transferred into a container for a supercritical processing unit, and the supercritical fluid having a boiling point lower than that of the liquid for preventing drying in the container for a supercritical processing unit. After supplying the processing liquid (for example, FC72) and then mixing the anti-drying liquid and the supercritical processing liquid, the inside of the supercritical processing unit container is heated to make the mixed liquid into a supercritical fluid. Supercritical processing technology has been developed.

  When a supercritical processing fluid such as liquid or vapor is supplied into the supercritical processing unit container, the supercritical processing unit container is heated and the supercritical processing fluid is in a supercritical state, Pattern collapse may occur.

Japanese Patent Laid-Open No. 2014-22566

  The present invention has been made in consideration of such points, and in order to remove the liquid adhering to the surface of the wafer, the liquid adhering to the wafer surface can be removed by supercritical processing, and in the wafer. It is an object of the present invention to provide a substrate processing method, a substrate processing apparatus, and a storage medium that can prevent pattern collapse.

  The present invention includes a step of transporting an object to be processed, which is filled with a liquid for preventing drying, into a container for a supercritical processing unit, and a boiling point lower than that of the liquid for preventing drying into the container for a supercritical processing unit. Supplying a supercritical processing fluid having a liquid to form a mixed liquid of the anti-drying liquid and the supercritical processing fluid, and heating the mixed liquid in the supercritical processing unit container to form a supercritical state The drying prevention liquid and the supercritical processing fluid contain different contents, have surface tensions close to each other, and dissolve with affinity to each other. This is a substrate processing method.

  The present invention provides a transport means for transporting an object to be processed, which is filled with a liquid for preventing drying, into a container for a supercritical processing unit, and is lower than the liquid for preventing drying into the container for a supercritical processing unit. A supercritical processing fluid supply section for supplying a supercritical processing fluid having a boiling point to form a mixed liquid of a drying prevention liquid and a supercritical processing fluid; and the mixed liquid in the supercritical processing unit container A heating unit that forms a supercritical high pressure fluid by heating the liquid, and the anti-drying liquid and the supercritical processing fluid contain different contents, have surface tensions close to each other, and A substrate processing apparatus that melts with affinity.

  The present invention relates to a storage medium for causing a computer to execute a substrate processing method. The substrate processing method includes a step of transporting an object to be processed, which is filled with a liquid for preventing drying, into a container for a supercritical processing unit; Supplying a supercritical processing fluid having a low boiling point with the anti-drying liquid into the supercritical processing unit container to form a mixture of the anti-drying liquid and the supercritical processing fluid; Heating the mixed liquid in the supercritical processing unit container to form a high-pressure fluid in a supercritical state, and the anti-drying liquid and the supercritical processing fluid contain different contents from each other. The storage medium is characterized by having surface tensions close to each other and dissolving with affinity to each other.

  According to this embodiment, the liquid adhering to the surface of the wafer can be removed by supercritical processing without causing pattern collapse.

FIG. 1 is a cross-sectional plan view of a liquid processing apparatus. FIG. 2 is a longitudinal side view of a liquid processing unit provided in the liquid processing apparatus. FIG. 3 is a configuration diagram of a supercritical processing unit provided in the liquid processing apparatus. FIG. 4 is an external perspective view of the processing container of the supercritical processing unit. FIG. 5 is a diagram showing a collapse result of the present embodiment. FIG. 6 is a plan view of the wafer showing the collapse result of the present embodiment.

<Substrate processing equipment>
First, a substrate processing apparatus according to the present invention will be described. As an example of a substrate processing apparatus, a liquid processing unit 2 for supplying various processing liquids to a wafer W (object to be processed), which is a substrate, and performing liquid processing, and a drying prevention adhering to the wafer W after liquid processing. A liquid processing apparatus 1 including a supercritical processing unit 3 (high pressure fluid processing unit) that transports liquid and performs supercritical processing on the wafer W will be described.

  FIG. 1 is a cross-sectional plan view showing the overall configuration of the liquid processing apparatus 1, and the left side is the front side in the figure. In the liquid processing apparatus 1, the FOUP 100 is mounted on the mounting unit 11, and a plurality of wafers W having a diameter of 300 mm, for example, stored in the FOUP 100 are transferred to the subsequent liquid processing unit via the loading / unloading unit 12 and the transfer unit 13. 14 is transferred to and from the supercritical processing unit 15 and is sequentially carried into the liquid processing unit 2 and the supercritical processing unit 3 to perform processing for removing the liquid for liquid processing and drying prevention. In the figure, reference numeral 121 denotes a first transfer mechanism for transferring the wafer W between the FOUP 100 and the transfer unit 13, and 131 denotes a wafer transferred between the carry-in / out unit 12, the liquid processing unit 14, and the supercritical processing unit 15. W is a delivery shelf that serves as a buffer on which W is temporarily placed.

  The liquid processing unit 14 and the supercritical processing unit 15 are provided with a transfer space 162 for the wafer W extending in the front-rear direction from the opening between the transfer unit 13 and the transfer unit 13. For example, four liquid processing units 2 are arranged along the transfer space 162 in the liquid processing unit 14 provided on the left hand side of the transfer space 162 when viewed from the front side. On the other hand, in the supercritical processing unit 15 provided on the right hand side of the transfer space 162, for example, two supercritical processing units 3 are arranged along the transfer space 162.

  The wafer W is transferred between the liquid processing unit 2, the supercritical processing unit 3, and the delivery unit 13 by the second transfer mechanism 161 disposed in the transfer space 162. The second transport mechanism 161 corresponds to a substrate transport unit. Here, the number of liquid processing units 2 and supercritical processing units 3 arranged in the liquid processing unit 14 and the supercritical processing unit 15 is the number of wafers W processed per unit time, the liquid processing unit 2 and the supercritical processing unit. 3 is selected as appropriate depending on the difference in processing time at 3 and the optimum layout is selected according to the number of the liquid processing units 2 and supercritical processing units 3 arranged.

  The liquid processing unit 2 is configured as a single-wafer type liquid processing unit 2 that cleans wafers W one by one, for example, by spin cleaning, and a liquid processing unit chamber that forms a processing space as shown in a vertical side view of FIG. An outer chamber 21, a wafer holding mechanism 23 that is disposed in the outer chamber, rotates the wafer W about the vertical axis while holding the wafer W substantially horizontally, and surrounds the wafer holding mechanism 23 from the side circumferential side. And an inner cup 22 that receives liquid scattered from the wafer W, and is configured to be movable between an upper position of the wafer W and a position retracted therefrom, and a nozzle arm provided with a nozzle 241 at the tip thereof 24.

  The nozzle 241 is supplied with a treatment liquid supply unit 201 that supplies various chemical solutions, a rinse liquid supply unit 202 that supplies a rinse liquid, and a first fluorine-containing organic solvent that is a liquid for preventing drying on the surface of the wafer W. A first fluorine-containing organic solvent supply unit 203a (first fluorine-containing organic solvent supply unit) and a second fluorine-containing organic solvent supply unit 203b (second fluorine) that supply the second fluorine-containing organic solvent. Containing organic solvent supply section). The first fluorine-containing organic solvent and the second fluorine-containing organic solvent are different from the fluorine-containing organic solvent for supercritical processing used in the supercritical processing described later, and the first fluorine-containing organic solvent is used. A solvent, a second fluorine-containing organic solvent, and a fluorine-containing organic solvent for supercritical processing, which have a predetermined relationship at the boiling point or critical temperature, are employed. Will be described later.

Further, the outer chamber 21 is provided with an FFU (Fan Filter Unit) 205, and air purified from the FFU 205 is supplied into the outer chamber 21. More outer chamber 21, a low humidity _{N 2} gas supply unit 206 is provided, a low humidity _{N 2} gas is supplied into the outer chamber 21 from the low humidity _{N 2} gas supply unit 206.

  Further, the chemical liquid supply path 231 may be formed inside the wafer holding mechanism 23, and the back surface of the wafer W may be cleaned with the chemical liquid and the rinsing liquid supplied therefrom. At the bottom of the outer chamber 21 and the inner cup 22, there are provided an exhaust port 212 for exhausting the internal atmosphere and drain ports 221 and 211 for discharging the liquid shaken off from the wafer W.

  A first fluorine-containing organic solvent and a second fluorine-containing organic solvent for preventing drying are supplied to the wafer W that has been subjected to the liquid processing in the liquid processing unit 2, and the surface of the wafer W has a second surface. In the state covered with the fluorine-containing organic solvent, it is transported to the supercritical processing unit 3 by the second transport mechanism 161. In the supercritical processing unit 3, supercritical processing is performed in which the wafer W is brought into contact with a supercritical processing fluid of a fluorine-containing organic solvent for supercritical processing to remove the second fluorine-containing organic solvent, and the wafer W is dried. Is called. Hereinafter, the configuration of the supercritical processing unit 3 will be described with reference to FIGS.

  The supercritical processing unit 3 includes a processing container 3A as a container for a supercritical processing unit in which processing for removing a liquid for preventing drying (second fluorine-containing organic solvent) attached to the surface of the wafer W is performed, and the processing container 3A is provided with a supercritical processing fluid supply unit 414 for supplying a fluorine-containing organic solvent for supercritical processing to 3A.

  As shown in FIG. 4, the processing container 3 </ b> A includes a housing-like container body 311 in which an opening 312 for carrying in / out the wafer W is formed, and a wafer tray 331 that can hold the wafer W to be processed horizontally. And a lid member 332 that supports the wafer tray 331 and seals the opening 312 when the wafer W is loaded into the container main body 311.

  The container main body 311 is a container in which a processing space of about 200 to 10000 cm 3 that can accommodate, for example, a wafer W having a diameter of 300 mm is formed, and a supercritical processing fluid is supplied to the upper surface of the processing body 311 in the processing container 3A. The supercritical processing fluid supply line 351 is connected to a discharge line 341 (discharge unit) provided with an on-off valve 342 for discharging the fluid in the processing container 3A. Further, the processing container 3A has a pressing mechanism (not shown) for pressing the lid member 332 toward the container body 311 against the internal pressure received from the supercritical processing fluid in the processing space and sealing the processing space. Is provided.

  The container main body 311 is provided with a heater 322 which is a heating unit made of, for example, a resistance heating element, and a temperature detection unit 323 including a thermocouple for detecting the temperature in the processing container 3A. By heating the main body 311, the temperature in the processing container 3 </ b> A can be heated to a preset temperature, thereby heating the internal wafer W. The heater 322 can change the amount of generated heat by changing the power supplied from the power supply unit 321, and sets the temperature in the processing container 3 </ b> A in advance based on the temperature detection result acquired from the temperature detection unit 323. Adjust to the adjusted temperature.

  The supercritical processing fluid supply unit 414 is connected to the upstream side of the supercritical processing fluid supply line 351 having an on-off valve 352 interposed therebetween. The supercritical processing fluid supply unit 414 is for supplying a liquid of a fluorine-containing organic solvent for supercritical processing.

  The supercritical processing fluid supply unit 414 includes a tank that stores a fluorine-containing organic solvent for supercritical processing in a liquid state, a liquid feed pump, a flow rate adjusting mechanism, and the like.

  The liquid processing apparatus 1 including the liquid processing unit 2 and the supercritical processing unit 3 having the above-described configuration is connected to the control unit 5 as shown in FIGS. The control unit 5 includes a computer having a CPU and a storage unit 5a (not shown). The operation of the liquid processing apparatus 1, that is, the wafer W is taken out from the FOUP 100 and processed in the liquid processing unit 2 in the storage unit 5a. Next, a program in which a group of steps (commands) related to the control from the process of drying the wafer W in the supercritical processing unit 3 to the loading of the wafer W into the FOUP 100 is recorded. This program is stored in a storage medium such as a hard disk, a compact disk, a magnetic optical disk, or a memory card, and installed in the computer therefrom.

  Next, the first fluorine-containing organic solvent, the second fluorine-containing organic solvent, and the second fluorine-containing organic solvent that are supplied to the surface of the wafer W by the liquid processing unit 2 are removed from the surface of the wafer W. Next, the fluorine-containing organic solvent for supercritical processing supplied to the processing vessel 3A will be described. The first fluorine-containing organic solvent, the second fluorine-containing organic solvent, and the fluorine-containing organic solvent for supercritical treatment are all fluorine-containing organic solvents containing fluorine atoms in hydrocarbon molecules.

  Of these fluorine-containing organic solvents, when one fluorine-containing organic solvent is selected as the fluorine-containing organic solvent for supercritical processing, the second fluorine-containing organic solvent includes the fluorine-containing organic solvent for supercritical processing. Those having a higher boiling point (low vapor pressure) are selected. As a result, compared with the case where a fluorine-containing organic solvent for supercritical processing is adopted as the liquid for preventing drying, the surface of the wafer W is transferred while being transferred from the liquid processing unit 2 to the supercritical processing unit 3. The amount of the fluorine-containing organic solvent that volatilizes can be reduced.

  More preferably, the boiling point of the first fluorine-containing organic solvent is around 100 ° C., and the boiling point of the second fluorine-containing organic solvent is preferably 100 ° C. or higher, which is higher than the boiling point of the first fluorine-containing organic solvent. . Since the second fluorine-containing organic solvent having a boiling point of 100 ° C. or more has a smaller volatilization amount during the transfer of the wafer W, for example, in the case of a wafer W having a diameter of 300 mm, about 0.01 to 5 cc, and in the case of a wafer W having a diameter of 450 mm Can maintain the wet state of the surface of the wafer W for about several tens of seconds to 10 minutes only by supplying a small amount of fluorine-containing organic solvent of about 0.02 to 10 cc. For reference, in order to keep the surface of the wafer W wet for the same time by IPA, a supply amount of about 10 to 50 cc is required.

  Further, when a fluorine-containing organic solvent for supercritical processing and a second fluorine-containing organic solvent are selected, the level of the boiling point corresponds to the level of the supercritical temperature. Therefore, a supercritical fluid can be formed at a low temperature by selecting a fluorine-containing organic solvent for supercritical processing used as a supercritical processing fluid that has a lower boiling point than the second fluorine-containing organic solvent. A possible fluorine-containing organic solvent can be used, and release of fluorine atoms due to decomposition of the fluorine-containing organic solvent can be suppressed.

<Operation of the present embodiment>
Next, the operation of the present embodiment having such a configuration will be described.

  In the present embodiment, for example, HFE7300 (Sumitomo 3M Co., Ltd. Novec (registered trademark) 7300, boiling point 98 ° C.) is used as the first fluorine-containing organic solvent, and FC43 (Sumitomo 3M Co., Ltd.) is used as the second fluorine-containing organic solvent. Fluorinate (registered trademark) FC-43, boiling point 174 ° C.) and, for example, FC72 (Sumitomo 3M Fluorinert (registered trademark) FC-72 boiling point 56 ° C.), a liquid containing fluorine for supercritical processing. The operation in the case of using a liquid supercritical processing fluid containing FC43 and FC72 as a solvent will be described.

  As a result of intensive investigations by the present inventors, a wafer W on which a second fluorine-containing organic solvent (for example, FC43) is dried is transferred into the processing container 3A, and this second container is transferred into the processing container 3A. Supply a liquid supercritical processing fluid (FC72) having a boiling point lower than that of the liquid for preventing drying of the fluorine-containing organic solvent (FC43), and then mix the liquid for preventing drying and the liquid supercritical processing fluid. In this case, the liquid supercritical processing liquid immediately becomes a gas in the processing vessel 3A, and the gaseous supercritical processing liquid is adsorbed and dissolved in the anti-drying liquid accumulated on the wafer surface. The anti-drying liquid evaporates and the anti-drying liquid does not evaporate locally.

  Alternatively, the Marangoni phenomenon occurs at the interface between the liquid for preventing drying (FC43) and the liquid supercritical processing fluid (FC72) due to the difference in surface tension between the liquid for preventing drying and the liquid supercritical processing. It was found that the pattern collapse occurred when the working fluid rapidly melted and the drying preventing liquid evaporated instantly.

  Therefore, the present inventor has conducted intensive research, and the second fluorine-containing organic solvent drying prevention liquid and liquid supercritical processing fluid both include FC43 and FC72, and the drying prevention liquid and liquid supercriticality. It has been found that the processing fluids have surface tensions close to each other and can be prevented from collapsing by being dissolved with affinity for each other. The present invention is based on this finding. Here, the second fluorine-containing organic solvent drying prevention liquid and the liquid supercritical processing fluid both contain FC43 and FC72, but the mixing ratios are different as described later. In this case, both liquids contain different contents. Also, when the second fluorine-containing organic solvent drying prevention liquid and the liquid supercritical processing fluid have different components, the two liquids contain different contents.

  Here, the mixing ratio of FC43 and FC72 in the drying prevention liquid as the second fluorine-containing organic solvent and the mixing ratio of FC43 and FC72 in the supercritical processing fluid will be described later. Both the supercritical fluids include FC43 and FC72. For this reason, the anti-drying liquid and the supercritical processing fluid have surface tensions close to each other and can be dissolved with affinity to each other.

  For example, the surface tension of FC43 is 16 mN / m2, and the surface tension of FC72 is 12 mN / m2. The difference in surface tension between the drying prevention liquid containing FC43 and FC72 and the supercritical processing fluid containing FC43 and FC72 is the surface of the drying prevention liquid when the surface tension of the drying prevention liquid is large. It is 10% or less with respect to the tension.

  In this way, the difference in surface tension between the anti-drying liquid and the supercritical fluid is kept small so that it is 10% or less of the surface tension of the anti-drying liquid. When a supercritical fluid is supplied to form a mixture of anti-drying liquid and supercritical fluid, the difference in surface tension between the anti-drying fluid and supercritical fluid Because it is small, the Marangoni phenomenon does not occur. For this reason, the anti-drying liquid and the supercritical processing fluid do not melt rapidly before they reach the supercritical state, and the anti-drying liquid does not evaporate instantaneously. This causes the pattern collapse of the wafer. This can be prevented in advance.

  Next, the specific operation of the present embodiment will be described below. First, the wafer W taken out from the FOUP 100 is loaded into the outer chamber 21 of the liquid processing unit 14 via the loading / unloading unit 12 and the transfer unit 13 and transferred to the wafer holding mechanism 23 of the liquid processing unit 2. Next, various processing liquids are supplied to the surface of the rotating wafer W to perform liquid processing.

  Such liquid processing is performed after the removal of particles and organic pollutants by chemical liquid supplied from the processing liquid supply section 201, for example, DHF (dilute hydrofluoric acid) which is an acidic chemical liquid, and then processing liquid supply section Deionized water cleaning with deionized water (DeIonize DI Water: DIW) supplied from 201 is performed.

  When the liquid treatment with the chemical solution and the rinse cleaning are completed, IPA is supplied from the rinse liquid supply unit 202 (IPA supply unit) to the surface of the rotating wafer W and replaced with DIW remaining on the front and back surfaces of the wafer W. When the liquid on the surface of the wafer W is sufficiently replaced with IPA, the first fluorine-containing organic solvent (HFE7300) is supplied from the first fluorine-containing organic solvent supply unit 203a to the surface of the rotating wafer W. Subsequently, after rotating the wafer W and supplying the second fluorine-containing organic solvent (FC43 + FC72) as a liquid for preventing drying to the surface of the rotating wafer W from the second fluorine-containing organic solvent supply unit 203b, The rotation of the wafer W is stopped. The surface of the wafer W after the rotation is stopped is covered with the second fluorine-containing organic solvent. In this case, since IPA has a high affinity with DIW and HFE7300, and HFE7300 has a high affinity with FC43 and FC72 in the liquid for IPA and anti-drying, DIW can be replaced by IPA, and then IPA Can be replaced by HFE7300. Next, the HFE 7300 can be easily replaced with FC43 and FC72, liquids for preventing drying.

During this period, that is, during the supply of DHF, the supply of DIW, the supply of IPA, the supply of the first fluorine-containing organic solvent, and the supply of the second fluorine-containing organic solvent, the humidity in the outer chamber 21 is continuously reduced. Low humidity (dew point −70 ° C. or lower) N ₂ gas is supplied from the N ₂ gas supply unit 206, and the inside of the outer chamber 21 is maintained in a low humidity N ₂ gas atmosphere. At this time, the humidity in the outer chamber 21 is preferably 3% or less.

Thus, by maintaining the inside of the outer chamber 21 in a low humidity N ₂ gas atmosphere, moisture absorption into the IPA can be suppressed, and pattern collapse of the wafer W can be prevented during supercritical processing as will be described later. be able to.

  The wafer W that has been subjected to the liquid processing in this way is unloaded from the liquid processing unit 2 by the second transfer mechanism 161 and transferred to the supercritical processing unit 3. At this time, the liquid for preventing drying remains on the wafer W. Since the liquid for preventing drying contains a fluorine-containing organic solvent having a high boiling point (low vapor pressure), for example, FC43, the amount of the fluorine-containing organic solvent that volatilizes from the surface of the wafer W during the transfer period may be reduced. It is possible to prevent the upper surface of the wafer W from being dried.

  Next, as shown in FIGS. 3 and 4, when the wafer W is loaded into the processing container 3A, the lid member 332 is closed and the processing container 3A is hermetically sealed. Thereafter, before the second fluorine-containing organic solvent on the surface of the wafer W is dried, the on-off valve 352 of the supercritical processing fluid supply line 351 is opened, and a liquid supercritical processing fluid is supplied from the supercritical processing fluid supply unit 414. (FC43 + FC72) is supplied.

  After the supercritical processing fluid is supplied from the supercritical processing fluid supply unit 414, the on-off valve 352 of the supercritical processing fluid supply line 351 is closed. Next, the heater 322 is activated to heat the inside of the processing container 3A.

  In this case, in the processing container 3A, the liquid for preventing drying (FC43 + FC72) remains on the wafer W in a state of being accumulated on the wafer W, and the supercritical processing fluid (FC43 + FC72) is left on the liquid for preventing drying. As a result, a mixed liquid of the anti-drying liquid and the supercritical processing fluid is formed on the wafer W.

  The mixing ratio (mass ratio) A1: B1 of FC43 and FC72 in the liquid for preventing drying is, for example, 20:30, and the mixing ratio (mass ratio) A2 of FC43 and FC72 in the fluid for supercritical processing is used. : B2 is, for example, 10:40.

  At this time, A1 / B1 = 0.67, A2 / B2 = 0.25, and A1 / B1> A2 / B2. For this reason, the liquid for drying sufficiently exhibits the function of preventing drying by FC43, and the fluid for supercritical processing can sufficiently exhibit the function of forming a supercritical state by FC72.

  Then, as described above, in the processing container 3A, the supercritical processing fluid is supplied onto the drying preventing liquid remaining on the wafer W, and the drying preventing liquid, the supercritical processing fluid, Then, the inside of the processing container 3A is heated. As a result, the liquid mixture on the wafer W can be heated and pressurized to bring the liquid mixture into a supercritical state.

  In this case, the drying prevention liquid and the supercritical processing fluid both include FC43 and FC72, and the difference in surface tension between them is 10% or less with respect to the surface tension of the drying liquid. Therefore, the Marangoni phenomenon does not occur at the interface between the liquid for preventing drying in the liquid mixture and the fluid for supercritical processing, and the liquid for preventing drying does not evaporate locally. For this reason, the wafer W can be covered with the liquid for preventing drying before the supercritical state is formed, and pattern collapse can be prevented in advance.

  Next, the behavior when the liquid mixture for preventing drying and the supercritical processing fluid in the processing container 3A is in a supercritical state will be described in detail. The inside of the processing vessel 3A is filled with a supercritical liquid mixture and sealed. At this time, paying attention to the surface of the wafer W in the processing container 3A, the liquid supercritical processing fluid comes into contact with the liquid for preventing drying.

  As described above, when the anti-drying liquid and the liquid supercritical processing fluid are kept in contact with each other, the anti-drying liquid and the supercritical processing fluid that are easily mixed with each other are mixed, and The dry prevention liquid is replaced with a mixed liquid of the dry prevention liquid and the supercritical processing fluid. Eventually, the anti-drying liquid is removed from the surface of the wafer W, and a mixed liquid of the anti-drying liquid and the supercritical processing fluid becomes a supercritical high-pressure fluid around the pattern. By forming a mixed liquid of anti-drying liquid and supercritical fluid in this way, the anti-drying liquid in the pattern can be removed, so the pattern can be reliably damaged without damaging the pattern. Can be dried.

  Thus, when the time necessary for removing the drying-preventing liquid from the surface of the wafer W has elapsed, the open / close valve 342 of the discharge line 341 is opened to discharge the mixed liquid from the processing container 3A. At this time, the inside of the processing container 3A is maintained at a temperature equal to or higher than the critical temperature of the mixed solution by the heater 322, for example. As a result, the liquid mixture can be discharged in a supercritical state or a gas state without liquefying the liquid for preventing drying, and the occurrence of pattern collapse at the time of fluid discharge can be avoided.

  When the processing with the supercritical fluid is completed, the dried wafer W from which the liquid has been removed is taken out by the second transfer mechanism 161 and stored in the FOUP 100 via the transfer unit 13 and the loading / unloading unit 12. Finish the process. In the liquid processing apparatus 1, the above processing is continuously performed on each wafer W in the FOUP 100.

  As described above, according to the present embodiment, the difference in surface tension between the anti-drying liquid and the supercritical processing fluid can be kept small relative to the surface tension of the anti-drying liquid. The Marangoni phenomenon does not occur at the interface between the liquid and the supercritical processing fluid. Therefore, the liquid for preventing drying and the fluid for supercritical processing dissolve rapidly before they reach a supercritical state, and the liquid for preventing drying evaporates instantaneously so that the pattern collapse of the wafer does not occur.

Next, a specific embodiment of the present invention will be described with reference to FIGS.
First, the mixing ratio of FC43: FC72 of the liquid for preventing drying was set to 20:30, and the mixing ratio of FC43: FC72 of the fluid for supercritical processing was set to 10:40.

  Further, 30 ml of the liquid for preventing drying was supplied onto the wafer W, and 500 ml of the fluid for supercritical processing was supplied into the processing container 3A. Thereafter, the mixed liquid of the anti-drying liquid and the supercritical processing fluid was heated to a supercritical state to dry the inside of the wafer W pattern. In this case, the surface tension of the drying prevention liquid and the supercritical processing fluid is 10% or less with respect to the surface tension of the drying prevention liquid. In this case, no pattern collapse was observed on the wafer W (FIG. 5). And FIG. 6 (a)).

  Here, FIG. 5 shows an example of the mixing ratio of the drying prevention liquid without pattern collapse and the supercritical processing fluids FC43 and FC72 in the area A, and the area B shows the drying prevention liquid in which the pattern collapse occurs. The example of the mixing ratio of FC43 and FC72 of the fluid for supercritical processing is shown.

  Next, the mixing ratio of FC43: FC72 of the liquid for preventing drying was set to 50: 0, and the mixing ratio of FC43: FC72 of the fluid for supercritical processing was set to 30:50.

  In this case, the surface tension of the anti-drying liquid and the supercritical fluid was 10% or more with respect to the surface tension of the anti-drying liquid. For this reason, pattern collapse was observed on the wafer W (see FIGS. 5 and 6B).

  Thereafter, the mixing ratio of FC43 and FC72, which are liquids for preventing drying, was variously changed, and the mixing ratio of FC43 and FC72, which is a fluid for supercritical processing, was variously changed. The result of the presence or absence of pattern collapse of the wafer W at this time is shown in FIG.

  In FIG. 5, a region A shows a case where there is no pattern collapse of the wafer W, and a region B shows a case where there is a pattern collapse of the wafer W.

  As shown in FIG. 5, when FC43: FC72 of the supercritical processing fluid in the region B is 50: 0 to 30:20, the mixed solution does not become a supercritical state in the processing container 3A, and the pattern collapses. It was seen.

  Further, in the region B, when the FC43: FC72 of the supercritical processing fluid is 20:30 to 0:50, the mixed solution is in a supercritical state in the processing container 3A. However, when FC43: FC72 of the liquid for preventing drying is in the range of 50: 0 to 30:50, the FC72 volatilizes quickly in the processing container 3A, and pattern collapse may occur. Further, in the region B, when the FC43: FC72 of the anti-drying liquid is in the range of 10:40 to 0:50, the anti-drying liquid dries out when being transported into the processing container 3A, and the pattern collapses. May occur.

<Modification of the present invention>
In the above-described embodiment, the example in which both the liquid for preventing drying and the fluid for supercritical processing include FC43 and FC72 is shown. However, the present invention is not limited thereto, and the liquid for preventing drying is FC43 having a single component. And the supercritical processing fluid may be composed of a single-component Bartrel Sinera (registered trademark) having substantially the same surface tension (16 mN / m 2) as FC43.

  In this case, since the drying prevention liquid and the supercritical processing fluid both have substantially the same surface tension, it is possible to prevent the Marangoni phenomenon from occurring at the interface between the drying prevention liquid and the supercritical processing fluid.

  Furthermore, although an example in which a liquid fluid is used as the supercritical processing fluid has been shown, the present invention is not limited thereto, and a gaseous supercritical processing fluid may be supplied into the processing container 3A.

  As a gaseous supercritical processing fluid, PFC gas such as C4F8 gas (boiling point −5.8 ° C., critical pressure 2.7 MPa, critical temperature 115 ° C.) may be supplied from a cylinder (not shown) into the processing vessel 3A. . Thereby, gas adsorption can be prevented at the interface between the drying prevention liquid and the supercritical processing fluid, and the Marangoni phenomenon can be prevented from occurring.

W wafer 1 liquid processing apparatus 2 liquid processing unit 3 supercritical processing unit 3A processing vessel 5 control unit 5a storage unit 21 outer chamber 121 first transfer mechanism 161 second transfer mechanism 201 process liquid supply unit 202 rinse liquid supply unit 203a First fluorine-containing organic solvent supply unit 203b Second fluorine-containing organic solvent supply unit 311 Container body 322 Heater 414 Supercritical processing fluid supply unit

Claims (5)

A step of transporting the object to be processed, which is filled with a liquid for preventing drying, into the container for the supercritical processing unit;
Supplying a supercritical processing fluid having a lower boiling point than the anti-drying liquid into the supercritical processing unit container to form a mixture of the anti-drying liquid and the supercritical processing fluid; Heating the mixed liquid in the supercritical processing unit container to form a fluid in a supercritical state,
The anti-drying liquid and the supercritical processing fluid contain different contents, have surface tensions close to each other , dissolve with affinity to each other ,
The difference in surface tension between the liquid for preventing drying and the fluid for supercritical processing is within 10% with respect to the surface tension of any one having high surface tension, and the liquid for preventing drying has a high boiling point. Including a fluorine-containing organic solvent and a low-boiling fluorine-containing organic solvent,
The substrate processing method , wherein the supercritical processing fluid contains the high-boiling fluorine-containing organic solvent and the low-boiling fluorine-containing organic solvent . The drying prevention liquid includes FC43 and FC72,
The supercritical processing fluid includes FC43 and FC72,
The mass ratio of FC43 and FC72 in the anti-drying liquid is A1: B1,
2. The substrate processing method according to claim 1 , wherein a mass ratio of FC43 and FC72 of the supercritical processing fluid is A2: B2, and A1 / B1> A2 / B2. 3. The substrate processing method according to claim 1, wherein the supercritical processing fluid is composed of a liquid or a gas that is not in a supercritical state. A transport means for transporting an object to be processed, which is filled with a liquid for preventing drying, into a container for a supercritical processing unit;
Supercritical processing in which a supercritical processing fluid having a boiling point lower than that of the liquid for preventing drying is supplied into the container for the supercritical processing unit to form a mixture of the liquid for preventing drying and the fluid for supercritical processing. Fluid supply section,
A heating unit that heats the mixed liquid in the supercritical processing unit container to form a supercritical high-pressure fluid, and
The anti-drying liquid and the supercritical processing fluid contain different contents, have surface tensions close to each other , melt with affinity to each other ,
The difference in surface tension between the liquid for preventing drying and the fluid for supercritical processing is within 10% with respect to the surface tension of any one having high surface tension, and the liquid for preventing drying has a high boiling point. Including a fluorine-containing organic solvent and a low-boiling fluorine-containing organic solvent,
The substrate processing apparatus , wherein the supercritical processing fluid includes the high-boiling fluorine-containing organic solvent and the low-boiling fluorine-containing organic solvent . In a storage medium for causing a computer to execute a substrate processing method,
The substrate processing method includes a step of conveying an object to be processed, which is filled with a liquid for preventing drying, into a container for a supercritical processing unit,
Supplying a supercritical processing fluid having a low boiling point with the anti-drying liquid into the supercritical processing unit container to form a mixture of the anti-drying liquid and the supercritical processing fluid;
Heating the mixed liquid in the supercritical processing unit container to form a high-pressure fluid in a supercritical state,
The anti-drying liquid and the supercritical processing fluid contain different contents, have surface tensions close to each other , dissolve with affinity to each other ,
The difference in surface tension between the liquid for preventing drying and the fluid for supercritical processing is within 10% with respect to the surface tension of any one having high surface tension, and the liquid for preventing drying has a high boiling point. Including a fluorine-containing organic solvent and a low-boiling fluorine-containing organic solvent,
The storage medium , wherein the supercritical processing fluid includes the high-boiling fluorine-containing organic solvent and the low-boiling fluorine-containing organic solvent .

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