JP2004363404A - Method for supercritical drying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for supercritical drying by which pressure reductions can be performed more quickly without causing the deformation of patterns, and so on, after a supercritical state is set. <P>SOLUTION: A pressure vessel is filled up with supercritical carbon dioxide 104 after the internal pressure and internal temperature of the pressure vessel are made higher than the critical points (7.3 MPa and 31°C) of carbon dioxide or higher. Then helium pressurized to 7.5 MPa is introduced into the pressure vessel, and the carbon dioxide 104 contained in the vessel is discharged. Thereafter, supercritical helium 105 is vaporized by lowering the pressure in the pressure vessel by discharging a fluid filled in the vessel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drying method using a supercritical fluid, and more particularly to a supercritical drying method suitable for drying a substrate on which a pattern is formed.
[0002]
[Prior art]
As is well known, in order to manufacture a large-scale and high-performance device such as an LSI, an extremely fine pattern is required. The ultrafine pattern is, for example, a resist pattern formed through exposure, development, and rinsing, and having sensitivity to light, X-rays, or electron beams. An etching pattern made of an inorganic material such as an oxide formed through etching, washing, and rinsing by selective etching using the resist pattern as a mask.
[0003]
The above-described resist pattern can be formed by processing a film of a photosensitive resist which is an organic material by a lithography technique. When the photosensitive resist film is exposed, the molecular weight and molecular structure of the exposed area change, and a difference in solubility in a developing solution occurs between the exposed area and the unexposed area. By the treatment, a finer pattern than the photosensitive resist film can be formed.
[0004]
In the above-described development processing, if the development is continued, the unexposed area eventually begins to dissolve in the developer and the pattern disappears. Therefore, the rinsing processing using the rinsing liquid is performed to stop the development. Finally, by drying and removing the rinsing liquid, a resist pattern as a processing mask can be formed on the resist film.
A major problem during drying in forming such a fine pattern is the collapse of the pattern as shown in the process diagrams of FIGS. 3 (a) to 3 (c).
[0005]
A fine resist pattern having a large aspect ratio is formed through development, rinsing and drying. A fine pattern having a large aspect ratio is formed other than the resist. For example, when a substrate is etched using a resist pattern as a mask to form a substrate pattern having a high aspect ratio, the substrate is cleaned after etching and the pattern 302 together with the substrate 301 is immersed in water 303 as shown in FIG. And rinse. Thereafter, drying is performed.
[0006]
However, as shown in FIG. 3B, during drying, a bending force (capillary force) 305 acts due to a pressure difference between the water 303 remaining between the patterns 302 and the external air 304. As a result, as shown in FIG. 3C, the pattern 302 of the pattern 302 collapses on the substrate 301. This falling phenomenon becomes more remarkable as the pattern becomes higher in aspect ratio. It has been reported that the capillary force depends on surface tension generated at an interface between a liquid and a gas between a rinsing liquid such as water and a pattern (see Non-Patent Document 1).
[0007]
The surface tension of water is as large as about 72 × 10 ⁻³ N / m, and the above-mentioned capillary force not only defeats a resist pattern made of an organic material but also distorts a stronger pattern such as an inorganic material such as silicon. have. For this reason, the problem of the surface tension caused by the rinsing liquid, the cleaning liquid, and the like described above is important. Surface tension occurs in a state where an interface between a liquid and a gas is formed. Therefore, the above-described problem can be solved by preventing the state in which the interface between the liquid and the gas is formed at the stage of drying, that is, the step of removing the liquid.
[0008]
Here, from the state of touching the liquid to the state of touching the supercritical fluid, if the drying is performed by vaporizing the supercritical fluid, the liquid is removed without forming an interface between the liquid and the gas. That is, it becomes possible to dry. In this case, an interface between the supercritical fluid and the gas is formed, but no surface tension acts on the supercritical fluid. Utilizing such features, a technique has been proposed for solving problems such as pattern collapse by drying with a fluid in a supercritical state (supercritical fluid) (see Patent Documents 1, 2, and 3).
[0009]
Supercritical fluid is a substance at a temperature and pressure exceeding the critical temperature and critical pressure, and has a dissolving power similar to a liquid, but has a tension and viscosity similar to those of a gas, and has maintained a gaseous state It can be called a liquid. Since a supercritical fluid having such characteristics does not form an interface between a liquid and a gas, the surface tension becomes zero. Therefore, if drying is performed in a supercritical state, the concept of surface tension is lost, and pattern collapse does not occur.
[0010]
A supercritical fluid has both gas diffusivity and liquid solubility (high density), and can change state from liquid to gas without passing through an equilibrium line. For this reason, when this supercritical fluid is gradually released from the state filled with the supercritical fluid, the interface between the liquid and the gas is not formed, so that the superfine pattern to be dried is dried without applying surface tension. be able to.
[0011]
As the supercritical fluid, carbon dioxide, which has a low critical point and is easy to handle, is often used. Supercritical drying using a supercritical fluid is started by performing a cleaning treatment with a cleaning liquid and then replacing the cleaning liquid adhering to the substrate surface with liquefied carbon dioxide in a closed container. If the carbon dioxide is pressurized to about 6 MPa, it liquefies at room temperature, so the above replacement is performed with the pressure in the vessel raised to about 6 MPa. After the cleaning liquid adhering to the substrate is replaced with liquefied carbon dioxide, the inside of the container is heated to a temperature and pressure higher than the critical point of carbon dioxide (critical point of carbon dioxide; 31 ° C., 7.3 MPa) to convert liquefied carbon dioxide. Convert to supercritical carbon dioxide.
[0012]
Finally, while maintaining the above temperature, part of the container is opened to release supercritical carbon dioxide to the outside, the pressure in the container is reduced to atmospheric pressure, and the supercritical carbon dioxide in the container is vaporized. Finish the drying. At the time of the pressure reduction, the carbon dioxide is vaporized without being liquefied, so that the interface between the liquid and the gas on which surface tension acts is not formed on the substrate. For this reason, it is possible to dry the ultrafine patterns formed on the substrate without causing them to collapse.
[0013]
Recently, a technique using a fluorine-based surfactant solution for promoting emulsification (dispersion) with carbon dioxide has been proposed. In this technique, first, a cleaning solution adhering to a pattern on a substrate is dissolved in a surfactant solution, and a state is established in which the surfactant solution is adhering to the pattern. From this state, supercritical carbon dioxide (supercritical carbon dioxide) is introduced into the container containing the substrate, and the surfactant solution adhering to the pattern in the supercritical state is converted into carbon dioxide. After dissolving and replacing, the pattern is brought into a state in which supercritical carbon dioxide is in contact.
[0014]
Thereafter, the pressure in the vessel is reduced to evaporate the supercritical carbon dioxide, thereby completing the supercritical drying. According to this technology, the pattern can be brought into a state in which the pattern is in contact with the supercritical carbon dioxide more quickly than in a technology in which liquefied carbon dioxide is introduced into the container and then brought into a supercritical state. .
[0015]
[Patent Document 1]
Japanese Patent Publication No. 22020828 [Patent Document 2]
Japanese Patent Application Laid-Open No. 8-197022 [Patent Document 3]
Japanese Patent Publication No. 1-170026 [Non-Patent Document 1]
Applied Physics Letters, 66, 2655-2657, 1995
[Problems to be solved by the invention]
By the way, in the supercritical drying, after filling the inside of the container in which the substrate is arranged with the supercritical fluid, and then reducing the pressure to vaporize the supercritical fluid, if the pressure decreasing speed is increased, FIG. As shown in FIG. 4C, a pattern deformation occurs. In the supercritical drying, as shown in FIG. 4A, the resist pattern 402 is immersed in a cleaning liquid 403 such as water together with the substrate 401 to perform a liquid treatment. Then, as shown in FIG. The cleaning liquid 403 is replaced with supercritical carbon dioxide 404.
[0017]
Thereafter, the pressure in the container is reduced to vaporize the supercritical carbon dioxide 404. When the pressure is reduced at a high rate and the pressure is rapidly reduced, the pattern 405 is deformed as shown in FIG.
The pattern deformation can be suppressed by slowing down the pressure reduction rate, but this requires a lot of time for the drying process. As described above, even if a supercritical state can be quickly replaced by using a surfactant or the like, supercritical drying cannot be rapidly performed because time is required in the decompression stage.
[0018]
The present invention has been made in order to solve the above problems, and has an object to make it possible to reduce pressure more quickly without causing deformation of a pattern after a supercritical state. .
[0019]
[Means for Solving the Problems]
In the supercritical drying method according to the present invention, after performing a liquid treatment such as exposing a substrate on which a predetermined pattern is formed to a predetermined liquid together with the pattern, the substrate is placed in a container while the liquid is attached to the pattern. The first substance, which is a gas in the air atmosphere, is introduced into the container, and the liquid adhering to the pattern is mixed with the first substance so that the pattern is exposed to the first substance. After that, the inside of the container is exposed to the first material in the supercritical state with the first substance in a supercritical state as a critical condition of a predetermined temperature and a predetermined pressure, and then the container is subjected to the critical condition. A second substance, which is an inert gas and has a smaller molecular weight than carbon dioxide, is introduced as a supercritical state, the first substance is discharged from the container, and the container is filled with a second substance in a supercritical state, and the pattern is supercritical. Exposed to the second substance in the state , Finally, it decreases the pressure in the vessel that is to vaporize a second substance in a supercritical state.
In this drying method, when the second substance in the supercritical state is vaporized and the substrate or the pattern is dried, the second substance that has entered the inside of the pattern is released to the outside of the pattern faster than carbon dioxide. You.
[0020]
In the supercritical drying method, the second substance may be helium or nitrogen. Further, carbon dioxide can be used as the first substance.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an example of the supercritical drying method according to the embodiment of the present invention will be described. In the supercritical drying method of the present embodiment, a liquid such as water or alcohol adhering to the pattern and wetting the pattern is replaced with, for example, carbon dioxide in a supercritical state (supercritical carbon dioxide), Carbon dioxide is replaced with helium in a supercritical state (supercritical helium), and thereafter, the supercritical helium is vaporized and dried.
[0022]
First, as shown in FIG. 1A, the resist pattern 102 formed on the substrate 101 is subjected to a liquid treatment with alcohol 103, so that the resist pattern 102 is wet with the alcohol 103. Next, while the resist pattern 102 is wet with the alcohol 103, these are introduced into a predetermined pressure vessel, and the pressure vessel is sealed. Next, liquefied carbon dioxide is introduced and filled into a pressure vessel having a predetermined pressure.
[0023]
Thus, the substrate 101 and the resist pattern 102 are immersed in liquefied carbon dioxide. As a result, the alcohol 103 adhering to the resist pattern 102 is dissolved in the liquefied carbon dioxide, and the alcohol 103 adhering to the resist pattern 102 and the surface of the substrate 101 is removed.
[0024]
Thereafter, the internal pressure and the internal temperature of the pressure vessel are set to be equal to or higher than the critical point of carbon dioxide (7.3 MPa, 31 ° C.), and the inside of the pressure vessel is filled with supercritical carbon dioxide 104 as shown in FIG. State. For example, the internal pressure of the pressure vessel is set to 7.5 MPa. As a result, the substrate 101 and the resist pattern 102 are immersed in the supercritical carbon dioxide 104, and the resist pattern 102 and the surface of the substrate 101 are in contact with the supercritical carbon dioxide 104.
[0025]
Next, helium pressurized to 7.5 MPa is introduced into the pressure vessel in the above-described state, and carbon dioxide inside the pressure vessel is exhausted, as shown in FIG. Is filled with supercritical helium 105. Since the critical point of helium is 0.224 MPa and -268 ° C., helium is in a supercritical state under the above-described conditions.
[0026]
Thus, the substrate 101 and the resist pattern 102 are immersed in the supercritical helium 105, and the resist pattern 102 and the surface of the substrate 101 are in contact with the supercritical helium 105. At this time, supercritical helium enters the inside of the resist pattern 102, and supercritical carbon dioxide inside the resist pattern 102 is released outside the resist pattern 102. If the state where the supercritical helium 105 is filled in the pressure vessel for a few minutes, for example, is maintained, the supercritical fluid entering the resist pattern 102 is only supercritical helium.
[0027]
Thereafter, the fluid filled in the pressure vessel is discharged to lower the pressure in the pressure vessel, and the supercritical helium 105 is vaporized, so that there is no deformation of the pattern as shown in FIG. In this state, a state where the resist pattern 102 on the substrate 101 is dried is obtained. Since helium does not liquefy when the pressure is reduced, no interface between the liquid and the gas is formed in the resist pattern 102, and no pattern collapse occurs.
[0028]
When the pressure in the pressure vessel is reduced, the supercritical helium that has entered the inside of the resist pattern 102 is easily released to the outside of the resist pattern 102, so that the resist pattern 102 may be deformed as described above. Be suppressed. For example, even if the pressure inside the pressure vessel at 7.5 MPa is reduced to about atmospheric pressure in about 5 minutes, the resist pattern 102 is not deformed.
[0029]
Here, the supercritical fluid impregnating (penetrating) into the resist pattern will be considered.
In a layer or a pattern (resist pattern) of an organic resin such as a photosensitive resist used in a manufacturing process of a semiconductor device, a hole called a free volume of about 2 nm exists. The fluid in a supercritical state (supercritical fluid) easily penetrates into the pores.
Therefore, even in the supercritical drying method, the supercritical fluid easily penetrates into the pores of the resist pattern exposed to the supercritical fluid. When the pressure inside the container is reduced to vaporize the supercritical fluid, the supercritical fluid that has entered the holes is also released from the holes to the outside of the resist pattern and vaporized.
[0030]
However, in the case of carbon dioxide or the like, the release speed of supercritical carbon dioxide that has penetrated into the pores is not so fast, and tends to remain inside the resist pattern. Further, when the resist pattern contains a solvent or the like, supercritical carbon dioxide dissolves in the solvent, and the supercritical fluid easily enters the resist pattern.
As described above, when the pressure inside the container is reduced while the supercritical fluid is impregnated inside the resist pattern, there is no problem if the impregnated supercritical fluid is easily released to the outside of the resist pattern. .
[0031]
However, since the conductance of carbon dioxide is small in the pores, the release rate of supercritical carbon dioxide impregnated inside the resist pattern is not high. Therefore, in the process of reducing the pressure, even when the pressure around the resist pattern is much lower than the critical point, supercritical carbon dioxide may remain inside the resist pattern. In such a state, the supercritical fluid vaporizes inside the resist pattern, causing the resist pattern to expand and deform. That is, when the inside of the container is reduced to atmospheric pressure by releasing carbon dioxide, the pressure inside the resist pattern becomes larger than the pressure inside the container outside the pattern, and the resist pattern is deformed.
[0032]
On the other hand, helium (supercritical helium) is easily released from the inside of the resist pattern. Therefore, when the pressure around the resist pattern is reduced to vaporize the supercritical helium, it hardly remains in the resist pattern. That is, a pressure difference between the inside of the resist pattern and the outside of the pattern (inside of the container) hardly occurs during the pressure reduction. As a result, according to the supercritical drying method of the present embodiment, after filling the inside of the pressure vessel with supercritical helium, the supercritical helium is vaporized, so that deformation of the resist pattern can be suppressed. .
[0033]
Since helium has a smaller molecular size (molecular weight) and larger conductance in pores than carbon dioxide, helium impregnated inside the resist pattern is easily released to the outside. Since helium is an inert gas, it does not react with the resist pattern to change the resist pattern.
In other words, any inert gas having a smaller molecular weight than carbon dioxide can be used instead of helium. For example, N ₂ , Ne, Ar, or the like can be used. Among them, helium is particularly suitable because of its low solubility in the liquid used for the liquid treatment. Nitrogen is readily available.
[0034]
Although carbon dioxide is used in the above description, the present invention is not limited to this. Instead of carbon dioxide, SF ₆ , CHF ₃ , N ₂ O or the like may be used. These are also substances that are gaseous in the atmosphere and are in a supercritical state. Further, these are easily miscible with alcohol and the like. In the above description, the alcohol is used for the liquid treatment, but the present invention is not limited to this. In the rinsing process or the like, alcohol may be used, or water may be used. After the liquid treatment with water, for example, a surfactant may be used to mix water with a carbon dioxide liquid or supercritical carbon dioxide.
[0035]
Next, a supercritical drying apparatus that performs the above-described supercritical drying method will be described. FIG. 2 is a schematic cross-sectional view illustrating a configuration example of a supercritical drying apparatus that performs the above-described supercritical drying method.
This apparatus includes a sealable high-pressure vessel 201 and a reaction chamber 202 provided inside the high-pressure vessel 201.
[0036]
On the bottom surface of the reaction chamber 202, a stage 212 on which the substrate 101 to be processed is placed is arranged. The high-pressure vessel 201 is made of, for example, stainless steel and has a wall thickness of about 20 mm.
The high-pressure vessel 201 includes a vessel upper part 201a and a vessel lower part 201b having a stage 212 fixed to a bottom part. For example, by removing the vessel upper part 201a, the inside of the reaction chamber 202 can be opened. It is possible.
[0037]
In addition, the high-pressure vessel 201 includes a heater 213 between the outer wall and the inner wall, and can heat the inside of the reaction chamber 202 under the control of the heater control unit 221. The heater 213 may be any heating means using, for example, resistance heating or high-frequency induction heating. Alternatively, electromagnetic wave heating using microwaves may be used. In this case, for example, the stage 212 may be made of a dielectric. According to the electromagnetic wave heating, it is possible to heat to a desired temperature in a shorter time.
[0038]
The apparatus also includes a cylinder 203 in which carbon dioxide is pressurized and stored, and a cylinder 203a in which helium is pressurized and stored. The carbon dioxide contained in the cylinder 203 passes through the pipe 204a and is introduced into the pipe 204 via the switching valve 223. The helium contained in the cylinder 203a passes through the pipe 204b and is introduced into the pipe 204 via the switching valve 223. Therefore, by switching the switching valve 223, the fluid introduced into the pipe 204 can be switched to carbon dioxide or helium.
[0039]
The carbon dioxide or helium introduced into the pipe 204 is introduced into the reaction chamber 202 through the introduction port 205. A pressure pump 206 and an introduction valve 207 are provided in the middle of the pipe 204, and a pressure gauge 208 for measuring the pressure at the discharge side of the pressure pump 206 is provided. The fluid introduced into the pipe 204 can be pressure-fed into the reaction chamber 202 by the pressure pump 206. Further, the opening degree of the introduction valve 207 can be controlled based on the pressure measurement result of the pressure gauge 208.
[0040]
Further, the present apparatus includes a pressure gauge 209 for measuring the internal pressure of the reaction chamber 202, an outlet 210 for discharging the fluid inside the reaction chamber 202, and a pressure control valve 211 provided in the middle of the outlet 210. ing. The pressure control valve 211 controls the opening degree based on the pressure measurement result of the pressure gauge 209, and controls the amount of fluid discharged from the discharge port 210. The cylinder 203 may contain SF ₆ , CHF ₃ , and N ₂ O instead of carbon dioxide. Further, the cylinder 203a may contain N ₂ , Ne, and Ar instead of helium.
[0041]
In this supercritical drying apparatus, carbon dioxide supplied from a cylinder 203 is pressure-fed to a pressure pump 206, passed through a pipe, and transported from an inlet 205 to the reaction chamber 202. For example, when the inside of the reaction chamber 202 is filled with the transported carbon dioxide while the carbon dioxide is being pumped at a high pressure, and the pressure control valve 211 is closed, the inside of the reaction chamber 202 is It is possible to set a pressure state in which carbon dioxide becomes a supercritical state. In addition, the heater 213 can be operated under the control of the heater control unit 221 to set the internal temperature of the reaction chamber 202 to a temperature at or above the critical point of carbon dioxide.
[0042]
In addition, the opening of the pressure control valve 211 is adjusted within a range where the pressure value measured by the pressure gauge 209 holds the pressure at the critical point of carbon dioxide, and the pressure value measured by the pressure gauge 208 becomes the critical point of carbon dioxide. It is also possible to adjust the pressure of the pressure feeding by the pressure feeding pump 206 within a range where the pressure is maintained. By doing so, a state where carbon dioxide is always supplied into the reaction chamber 202 is obtained. The same applies to the case where helium is supplied from the cylinder 203a by switching the switching valve 223. Alternatively, if helium controlled to a predetermined pressure is used, helium can be introduced into the reaction chamber 202 without passing through the pressure pump 206.
[0043]
First, carbon dioxide is supplied from the cylinder 203, and after the inside of the reaction chamber 202 is filled with supercritical carbon dioxide, the switching valve 223 is switched so that helium is supplied from the cylinder 203 a. Is filled with supercritical helium.
In this way, after the substrate 101 (resist pattern 102) is exposed to the supercritical helium in the reaction chamber 202, the supply valve 207 is closed to stop the supply of helium, and the fluid in the inside is removed. If the internal pressure of the reaction chamber 202 is reduced by discharging from the discharge port 210, the fluid in the supercritical state is vaporized, and the drying is completed.
[0044]
Next, examples of the supercritical drying method of the present invention will be described in more detail.
First, a resist pattern is formed on a substrate 101 made of silicon by a known lithography technique. For example, an electron beam resist (ZEP-7000) is applied on the substrate 101 to form a resist film having a thickness of about 250 nm, and a latent image having a predetermined pattern is formed on the resist film by electron beam exposure. The pattern to be exposed has, for example, a pattern width of 20 to 100 nm.
[0045]
Next, a development process using normal hexyl acetate and a rinsing process using 2-propanol (alcohol) are performed to form a desired resist pattern 102 using an electron beam resist on the substrate 101. Next, the substrate 101 wet with alcohol by the rinsing process is fixed to the stage 212, and the inside of the reaction chamber 202 is sealed. At this time, the heater 213 is operated under the control of the heater control unit 211, and the internal temperature of the reaction chamber 202 is set to about 23 ° C.
[0046]
Thereafter, before the alcohol on the surface of the substrate 101 fixed on the stage 212 is dried, carbon dioxide contained in the cylinder 203 is pumped by the pump 206 to fill the inside of the reaction chamber 202 with carbon dioxide. State. Here, the internal pressure of the reaction chamber 202 is set to about 7.5 MPa. At this time, since the inside of the reaction chamber 202 is controlled at 23 ° C., the inside of the reaction chamber 202 is in a state filled with liquefied carbon dioxide.
[0047]
As a result, the alcohol on the surface of the substrate 101 is mixed with the liquefied carbon dioxide, and the alcohol is removed from the surface of the substrate 101 (resist pattern 102). Here, the opening of the pressure control valve 211 is adjusted in a range where the pressure value measured by the pressure gauge 209 holds 7.5 MPa, and in a range where the pressure value measured by the pressure gauge 208 holds 7.5 MPa. The carbon dioxide is pumped by the pump 206.
[0048]
As a result, the liquefied carbon dioxide mixed with the alcohol is discharged from the outlet 210, and the inside of the reaction chamber 202 is filled with the liquefied carbon dioxide not mixed with the alcohol introduced from the inlet 205. .
After maintaining the above state for 5 minutes, the heater 213 is operated under the control of the heater control unit 211 to increase the internal temperature of the reaction chamber 202 to 35 ° C. As a result, the liquefied carbon dioxide filled in the reaction chamber 202 becomes supercritical carbon dioxide.
[0049]
Immediately after the temperature is increased, the switching valve 223 is switched to a state where helium is supplied from the pressure feed pump 206. Here, the opening of the pressure control valve 211 is adjusted in a range where the pressure value measured by the pressure gauge 209 holds 7.5 MPa, and in a range where the pressure value measured by the pressure gauge 208 holds 7.5 MPa. The pressure of the helium pumping by the pumping pump 206 is adjusted. With this, helium is supplied from the inlet 205 and carbon dioxide is discharged from the outlet 210 in a state where the inside of the reaction chamber 202 is in a range where carbon dioxide is in a supercritical state. The state is filled with supercritical helium.
[0050]
More simply, opening the helium introduction valve held at 7.5 MPa and opening the pressure control valve (or another release valve) releases carbon dioxide, and automatically sets the reaction chamber to 7.5 MPa. Helium is typically introduced into the reaction chamber. Helium can also be introduced by a method not using the pressure pump.
[0051]
Thereafter, for example, the supply amount of helium by the pressure pump 206 is stopped, the pressure control valve 211 is almost fully opened, the internal pressure of the reaction chamber 202 is rapidly reduced, and the supercritical helium Is vaporized to bring the inside of the reaction chamber 202 into an atmospheric pressure state. Thus, the drying process can be performed without the pattern expanding and without the pattern falling down.
In the above-described embodiment, the same applies even when nitrogen (N ₂ ) is used instead of helium.
[0052]
【The invention's effect】
As described above, in the present invention, the liquid adhering to the pattern is mixed with the first substance so that the pattern is exposed to the first substance, and the inside of the container is subjected to the critical conditions of a predetermined temperature and a predetermined pressure. After the first substance is brought into the supercritical state and the pattern is exposed to the first substance in the supercritical state, the second substance, which is an inert gas and has a smaller molecular weight than carbon dioxide, is placed in a container under the critical condition. It is introduced as a supercritical state, the first substance is discharged from the container, and the inside of the container is filled with the second substance in the supercritical state. Thereafter, the pressure in the container is reduced to remove the second substance in the supercritical state. I vaporized it.
[0053]
Therefore, according to the present invention, when the second substance in the supercritical state evaporates and the substrate or the pattern dries, the second substance that has entered the inside of the pattern is more quickly out of the pattern than carbon dioxide. Therefore, an excellent effect that the pressure can be reduced more quickly without changing the pattern after the supercritical state is obtained is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing steps for explaining a supercritical drying method according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view illustrating a configuration example of a supercritical drying apparatus according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing a pattern collapse.
FIG. 4 is an explanatory diagram for explaining pattern deformation by a conventional supercritical drying method.
[Explanation of symbols]
101: substrate, 102: pattern, 103: alcohol, 104: supercritical carbon dioxide, 105: supercritical helium.

Claims (4)

A first step of exposing the substrate on which the predetermined pattern is formed to a predetermined liquid together with the pattern,
In a state where the liquid is attached to the pattern, the substrate is placed in a container, a first substance that is a gas in an atmospheric atmosphere is introduced into the container, and the liquid attached to the pattern is removed by the first method. A second step of mixing with one substance so that the pattern is exposed to the first substance;
A third step in which the container is exposed to the first substance in a supercritical state by setting the first substance in a supercritical state as a critical condition of a predetermined temperature and a predetermined pressure in the container;
Introducing a second substance, which is an inert gas, into a supercritical state into the container having the critical condition, discharging the first substance from the container, and discharging the second substance in a supercritical state inside the container. A fourth step in which the pattern is exposed to the second substance in a supercritical state,
A fifth step of reducing the pressure in the container to vaporize the second substance in a supercritical state,
The supercritical drying method, wherein the second substance has a smaller molecular weight than carbon dioxide. The supercritical drying method according to claim 1,
The method of claim 2, wherein the second material is helium. The supercritical drying method according to claim 1,
The supercritical drying method, wherein the second substance is nitrogen. The supercritical drying method according to any one of claims 1 to 3,
The supercritical drying method, wherein the first substance is carbon dioxide.

Images