JP2008130685A - Microstructure processing method and apparatus, and the microstructure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstructure processing method and apparatus, and a microstructure, wherein the pattern of the microstructure formed on a wafer can be dried without causing it to collapse. <P>SOLUTION: In the microstructure processing method, a microstructure is processed by the processing method, having a process wherein the microstructure portion of the surface of the microstructure processed by a wet processing apparatus 2 is covered with a protective film made of a solid substance of a substituted medium, whose melting point is not lower than 31°C, in an environment having a pressure not lower than the critical pressure of super-critical carbon dioxide, and having a process for solving and removing the solid substance of the protective film of the surface of the microstructure by the supercritical carbon dioxide and then drying the microstructure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for processing a fine structure using a supercritical fluid, and a fine structure used in a process before drying. In particular, the present invention relates to a drying process of a microstructure using supercritical carbon dioxide.

  Lithography technology, which is the basis of ultra-fine processing in semiconductor device manufacturing, is to apply a thin film of photosensitive polymer called resist on a silicon wafer, and then expose the pattern shape through a mask to selectively cause photochemical reaction. This is a technique for forming a pattern based on a difference in dissolution rate between an exposed area and an unexposed area by immersing the resist that has occurred in a developer.

Along with the miniaturization of semiconductor devices, the pattern width of the resist has become less than 100 nm with the latest technology. However, since the resist thickness needs to be several hundred nm or more in order to ensure dry / wet etching resistance during microfabrication, a pattern having an aspect ratio (height / width) greatly exceeding 1 is formed. It has come to be. The resist after development is treated with a rinsing solution, and then the rinsing solution is dried. At the time of drying, the bending force due to the pressure caused by the meniscus of the rinsing solution remaining between adjacent patterns (the curved surface created by the surface of the rinsing solution) (Capillary force) is generated. As the resist aspect ratio increases, this capillary force causes the adjacent pattern to stick, resulting in the problem of pattern collapse.
When the surface tension of the liquid is γ and the radius of curvature of the liquid meniscus is r, the capillary force P is expressed by Equation 1.

  From Equation 1, it can be seen that the capillary force P increases as the radius of curvature r decreases. Therefore, the surface tension of the rinsing liquid may be reduced in order to avoid the pattern collapse due to the capillary force. For example, the capillary force is reduced to some extent by substituting with perfluorocarbon (surface tension <20 [mN / m]) having a smaller surface tension than water (surface tension = about 72 [mN / m]) and then drying. . However, if the pattern width is 150 nm or less and the aspect ratio is 3 or more, the pattern collapse cannot be completely avoided even if it is replaced with a liquid having a surface tension value of 20 [mN / m] or less and dried.

  In order to prevent pattern collapse due to such capillary force, a method of drying a fine pattern using a supercritical fluid having no surface tension has been proposed. Since the surface tension of the supercritical fluid is zero, no matter how small the radius of curvature of the liquid meniscus between patterns is, the capillary force P is also zero from Equation 1, so there is no sticking of adjacent patterns or pattern collapse. It will not occur. As a medium for a drying process using a supercritical fluid, carbon dioxide is a low critical point (7.3 MPa, 31 ° C.), chemically stable, non-toxic, inexpensive, and easy to reuse. Most commonly used.

  The water most commonly used in the rinsing liquid after resist development hardly dissolves in supercritical carbon dioxide, so water (rinsing liquid) is replaced with a solvent highly soluble in supercritical carbon dioxide, Thereafter, a process of replacing the solvent with supercritical carbon dioxide and finally drying the supercritical carbon dioxide by reducing the pressure has been proposed. For example, in Patent Document 1, after replacing water (rinse liquid) on a pattern formed on a substrate with alcohol or hydrocarbon, the alcohol or hydrocarbon is replaced with liquid carbon dioxide, and the liquid carbon dioxide is heated. Then, after making it supercritical carbon dioxide, a drying process has been proposed in which pattern collapse is avoided by completely removing the supercritical carbon dioxide by reducing the pressure.

  In the proposal in Patent Document 1, both wet processing and supercritical drying are performed in a single chamber, but the supercritical device is a high-pressure device and is used at normal pressure. Compared with wet processing equipment, there are many restrictions such as the inability to use strong acids. So, in patent document 2, it has a wet processing apparatus and a supercritical drying apparatus, and it conveys to the supercritical drying apparatus in the state where the fine structure part got wet without naturally drying the wafer processed with the said wet processing apparatus, A method of performing supercritical drying before natural drying has been proposed. According to this proposal, it is possible to dry a pattern without destroying a fine pattern even after a strong acidic or alkaline wet treatment that cannot be used because it corrodes the supercritical drying apparatus. .

However, as described in Patent Document 2, when a wafer processed by a wet processing apparatus is transferred to a supercritical drying apparatus in a state where the fine structure is wet, the wafer is tilted or slightly shaken due to the transfer. The liquid on the wafer spills out due to acceleration and deceleration, and a gas-liquid interface is formed in the vicinity of the resist pattern where the liquid film on the surface is lost. As a result, capillary force is generated, resulting in pattern collapse. End up. Accordingly, when introducing a wafer into the supercritical drying apparatus, careful handling is required without tilting the wafer at the same time and without causing vibration at the same time. As a result, the transfer time becomes longer and the throughput is reduced.
In order to solve this problem and stably transport a wafer from a wet processing apparatus to a supercritical drying apparatus, it is proposed in Patent Document 3 to cover the microstructure of the wafer with a liquid having a high viscosity. Yes.
JP 2001-165568 A JP 2002-329650 A JP 2004-140321 A

  By the way, as shown in Patent Document 3, if the replacement medium covering the fine structure of the wafer is made of a liquid having a high viscosity, the liquid can be prevented from spilling when the wafer is transferred. In the process of replacing the above high viscosity liquid with liquid carbon dioxide or supercritical carbon dioxide, the liquid carbon dioxide or supercritical carbon dioxide has a normal pressure of 30 atm or more, which is accompanied by the introduction of high pressure carbon dioxide. The resist pattern (fine structure) on the wafer is destroyed by the shearing force of the intense air current. Further, the highly viscous liquid on the wafer spills and the fine structure on the wafer surface is dried, and the resist pattern collapses due to the capillary force.

Further, Patent Document 3 exemplifies a fluorine-based solvent typified by hydrofluoroether as one of the replacement media for the resist rinsing liquid. Such a fluorine-based solvent causes the resist to swell and resists the resist. Will increase the line width.
Further, Patent Document 3 exemplifies a water-containing material such as polyvinyl alcohol as one of the replacement media for the resist rinsing liquid. To replace such a water-containing material with supercritical carbon dioxide, a supercritical carbon dioxide is used. It is necessary to contain water in the critical carbon dioxide, and the adhesiveness of the resist is lowered by the action of the contained water, and the pattern is collapsed.

  In view of the above-described points, the present invention provides a fine structure processing method and processing apparatus, and a fine structure, which can perform a drying process without collapsing the fine structure pattern formed on the wafer. To do.

  In order to solve the above-mentioned problems and achieve the object of the present invention, the microstructure processing method of the present invention is characterized in that the microstructure of the surface of the microstructure processed by the wet processing apparatus is converted to the criticality of supercritical carbon dioxide. The step of coating with a protective film made of a solid material that is a substitution medium having a melting point of 31 ° C. or higher under an environment of pressure or higher, and the solid material that is a protective film on the surface of the microstructure is dissolved and removed with supercritical carbon dioxide. And a step of drying the fine structure.

  The fine structure processing apparatus of the present invention includes a first processing means for performing wet processing on a fine structure having a fine structure portion on the surface, and an environment that is equal to or higher than a critical pressure of supercritical carbon dioxide dissolved after the wet processing. A wet processing apparatus having a second processing means for supplying a melt of a solid substance, which is a substitution medium having a melting point of 31 ° C. or more, to coat the fine structure with a protective film of the solid substance, and protecting the fine structure It is characterized by comprising a drying treatment apparatus for dissolving and removing the membrane with supercritical carbon dioxide and drying the fine structure.

  In addition, the microstructure of the present invention has a protective film made of a solid material that is a substitution medium in which the microstructure on the wafer surface has a melting point of 31 ° C. or higher in an environment at or above the critical pressure of supercritical carbon dioxide. It is characterized by that.

  In the present invention, since the fine structure is covered with the protective film made of the solid material, the fine structure can be handled without collapsing the fine structure portion on the surface of the fine structure. In addition, since the melting point of the solid substance is equal to or higher than the critical temperature of supercritical carbon dioxide, the solid substance can be dissolved and removed by contacting with the supercritical carbon dioxide.

  According to the present invention, a fine structure having a fine structure after wet processing is covered with a protective film made of a solid material, so that pattern collapse or the like can be prevented in the next drying step. Handling becomes easy. Furthermore, since this protective film is removed by being dissolved in supercritical carbon dioxide, it is possible to prevent the pattern collapse of the fine structure due to the capillary force of water.

A method for processing a fine structure including a drying method using a supercritical fluid according to the present invention, and an apparatus used therefor are provided in a pre-process of a drying process of a fine structure using a supercritical fluid. The top surface is covered with a solid material and configured to protect the microstructure. In other words, in the present invention, when a wafer processed by a wet processing apparatus is transported to a supercritical drying apparatus in a manufacturing process of a device having a microstructure such as a semiconductor device, the microstructure surface (resist pattern) on the wafer is transferred. In order to protect, a solid substance (solid medium) is used on the surface of the microstructure as a replacement medium with the rinsing liquid used in the wet processing apparatus. Carbon dioxide is used as the supercritical fluid.
At this time, a material having a melting point of the above-mentioned solid substance (solid medium) of 31 ° C. or higher which is the critical temperature of supercritical carbon dioxide at the supercritical pressure of supercritical carbon dioxide is used. Further, a solid material having a melting point equal to or lower than the boiling point of the resist rinsing solution at atmospheric pressure is used. This is to replace the rinsing liquid on the wafer surface in a state where the substitution medium, which is a solid substance, is melted. When the melting point of the solid substance is equal to or higher than the boiling point of the rinsing liquid of the resist, This is because they cannot coexist and cannot be replaced with a rinse solution. In particular, when the rinsing liquid is pure water, the solid material must have a melting point of 100 ° C. or lower, which is the boiling point of pure water at atmospheric pressure. In the drying process, a material having high solubility in supercritical carbon dioxide is used in order to be dissolved in supercritical carbon dioxide.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of a fine structure processing apparatus according to an embodiment of the present invention. The processing apparatus 1 which concerns on this Embodiment is a case where it applies to the processing apparatus which processes a semiconductor wafer.

The processing apparatus 1 according to the present embodiment is a processing apparatus including a resist film developing process in a lithography process and a subsequent drying process in a semiconductor device manufacturing process. The developing apparatus 2 and the supercritical drying apparatus 3 Consists of. The developing device 2 is a wet processing device, and includes a developing treatment tank 4, a nozzle 26 for supplying a developing solution to the developing treatment tank 4, a nozzle 5 for supplying a rinsing liquid (for example, pure water), and a nozzle for supplying a replacement fluid. 6. Inside the development processing layer 4, a support portion 9 for supporting a wafer 8 to be processed is disposed.
The supercritical drying apparatus 3 includes a drying treatment tank 7, a carbon dioxide supply unit 27, and a gas-liquid separation unit 28. The carbon dioxide supply means 27 includes a liquid carbon dioxide tank 13 that stores liquid carbon dioxide, an in-line warmer 14, and a high-pressure pump 15. These components are connected by a supply pipe 11, and the supply pipe 11 is connected to the drying treatment tank 7. Valves 22 and 24 are provided on the liquid carbon dioxide tank 13 side and the drying treatment tank 7 side of the supply pipe 11, respectively.
The gas-liquid separator 28 includes the gas-liquid separator 16, the waste liquid tank 17, the filter 18, the in-line cooler 19, and the liquefaction pump 20. These components are connected by a discharge pipe 12 extending from the drying treatment tank 7 and a waste liquid pipe 21, and the discharge pipe 12 is connected to a liquid carbon dioxide tank 13. In addition, a discharge pressure valve 25 that can adjust the pressure in the drying treatment tank 7 is installed on the discharge treatment tank 7 side of the discharge pipe 12, and a valve 23 is installed on the liquid carbon dioxide tank 13 side of the discharge pipe 12. The The treated supercritical carbon dioxide used in the treatment tank 7 is discharged through the discharge pipe 12, but is separated into a solid substance component and a carbon dioxide component by the gas-liquid separator 16, as will be described later.
Further, a support portion 10 that supports the wafer 8 is disposed inside the drying treatment tank 7.

  Next, an embodiment of a processing method of a fine structure according to the present invention, in which the fine structure portion on the surface of the wafer to be processed and the subsequent treatment on the fine structure portion are performed using the processing apparatus 1 having the above configuration. Will be explained. The processing method of the present embodiment is a process in which a resist film on the surface of a wafer to be processed, such as a semiconductor wafer, is developed to form a resist pattern as a microstructure, a rinse treatment of the microstructure, and a subsequent drying process This method is particularly characterized in a method for drying a semiconductor wafer (so-called fine structure) having a fine structure portion by a resist pattern. This will be described with reference to FIGS.

  First, a resist film 30 is formed on the surface of a processing target wafer, for example, a semiconductor wafer (hereinafter referred to as a wafer) 8, and the resist film 30 is exposed in a required pattern. The wafer 8 (see FIG. 2A) having the resist film 30 exposed to the required pattern on its surface is conveyed to the developing device 2 and supported on the support portion 9 in the development processing tank 4.

  Next, a developing solution 32 is supplied from the nozzle 26 to the surface of the wafer 8 and the exposed resist film 30 is developed to form a required resist pattern having a fine structure, that is, a so-called resist fine structure 33 (FIG. 2 (b)).

  Next, a rinsing liquid 34 made of pure water is supplied from the nozzle 5 to rinse the fine structure portion 33 (see FIG. 2C). The rinsing process is performed while rotating the wafer 8 via the support portion 9.

  After this rinsing step, a solid substance (hereinafter referred to as a replacement medium) 35 dissolved from the nozzle 6 is supplied onto the fine structure portion 33 on the surface of the wafer 8, and the rinsing liquid 34 is replaced with the replacement medium 35 (FIG. 2D). reference).

  Thereafter, the wafer 8 is rotated, the rinsing liquid 34 and the excess substitution medium 35 are removed by centrifugal force, and the substitution medium 35 is solidified by cooling to form a solid film 36 serving as a protective film (FIG. 2 ( e)). The solid coating 36 is in a state of thinly covering the entire fine structure 33 on the surface of the wafer 8. Through the above steps, the fine structure portion 33 according to the present embodiment is covered with the solid film 36 serving as a protective film.

  2A to 2E are performed by the development processing apparatus 2.

  As a method of replacing the rinsing liquid 34 with the replacement medium 35, the rinsing liquid 34 is placed on the rinsed wafer 8, the inside of the development processing tank 4 is heated to a temperature equal to or higher than the melting point of the replacement medium 35, and the liquid replacement medium There is a method in which the rinsing liquid 34 and the replacement medium 35 are replaced by introducing 35 into the surface of the wafer 31. Examples of the material of the substitution medium to which this method can be applied include those having a specific gravity greater than that of water. In addition, as described above, the melting point of the material used for the substitution medium to be used is the critical temperature of supercritical carbon dioxide of 31 ° C. or higher and the boiling point of water of 100 ° C. or lower at the supercritical pressure of supercritical carbon dioxide. is there.

  Subsequently, the wafer 8 obtained by the above-described process in which the fine structure portion 33 on the surface is covered with the solid film 36 is transferred to the supercritical drying apparatus 3 to perform a drying process.

  First, the wafer 8 covered with the solid film 36 shown in FIG. 2 (e) is transported from the development processing apparatus 2 to the supercritical drying apparatus 3 by any means, and is placed on the support portion 10 in the drying processing tank 7. Installed. At this time, the inside of the drying treatment tank 7 is at atmospheric pressure. Next, the valve 22 provided in the supply pipe 11 on the liquid carbon dioxide tank 13 side is opened. Then, the liquid carbon dioxide flowing through the pipe 11 is heated to a critical temperature of 31 ° C. or higher by the in-line heater 14. Then, the pressure is increased to the supercritical pressure or higher by the pressurizing pump 15, and the valve 24 is opened to supply the supercritical carbon dioxide into the drying treatment tank 7. Thereafter, the pressure in the drying treatment tank 7 is adjusted to be equal to or higher than the critical pressure by the discharge valve 25 provided in the discharge pipe 12, and the flow rate of carbon dioxide in the drying treatment tank 7 is adjusted in the state of supercritical carbon dioxide. Supply is made.

  At this time, the temperature of the supercritical carbon dioxide in the drying treatment tank 7 is set to be equal to or higher than the melting point temperature of the solid film 36 covering the surface of the wafer 8. For this reason, as shown in FIG. 2 (f), the wafer 31 in the drying treatment tank 7 is immersed in the supercritical carbon dioxide 37, so that the solid film 36 on the surface of the wafer 31 becomes the supercritical carbon dioxide 37. Start to dissolve. At this time, the solid film 36 is not suddenly dissolved, but is gradually and gradually dissolved from the contact surface with the supercritical carbon dioxide 37. In this way, the solid film 36 is gradually dissolved and finally removed completely from the surface of the wafer 8 (see FIG. 2G).

  2F and FIG. 2G are performed in the drying tank 7 of the supercritical drying apparatus 3.

  The dissolved solid film 36 is discharged out of the drying treatment tank 7 through the discharge pipe 12 at the same time as the supercritical carbon dioxide 37 is discharged. At this time, the gas-liquid separator 16 separates the carbon dioxide and the dissolved solid substance, and the dissolved solid substance is sent from the gas-liquid separator 16 to the waste liquid tank 17 through the waste liquid pipe 21. Further, the separated carbon dioxide is cooled through the filter 18 and the in-line cooler 19 for reuse, and then sent again to the liquid carbon dioxide tank 13 in a state of being liquefied by the liquefaction pump 20. .

As described above, the entire fine structure portion 33 formed of the resist on the wafer surface is covered with the thin solid film 36, so that the fine structure portion 33 on the wafer 8 is made of a solid substance in the subsequent process, that is, the supercritical drying process. Since it is protected by the film 36, the fine structure portion 33 can be prevented from collapsing due to the shearing force.
In addition, the fixed substance (substitution medium) is accompanied by the introduction of high-pressure carbon dioxide by using a material having a melting point of 31 ° C. or higher, which is the critical temperature of supercritical carbon dioxide, at the supercritical pressure of supercritical carbon dioxide. Even if the shearing force of the violent airflow, the solid film 36 on the wafer 8 does not suddenly peel off. The solid coating 36 is uniformly removed from the contact surface with the supercritical carbon dioxide in the supercritical drying process. Therefore, unlike the case where the replacement medium 35 is a liquid, the fine structure portion 33 that is a resist pattern is not exposed at a time when high-pressure carbon dioxide is introduced, and pattern collapse can be prevented by capillary force.

When moisture coexists on the wafer at the time of supercritical drying, the resist pattern may collapse. Therefore, the solubility of water in the solid material as the substitution medium is 1% by weight or less, particularly preferably 0.1% by weight or less. Preferably there is. As a result, the amount of water mixed in the film when replacing with the solid film becomes extremely small, and thus it is completely absorbed by supercritical carbon dioxide in the supercritical drying process. Therefore, it is possible to avoid resist adhesion deterioration and pattern destruction caused by the contained water.
Further, the material of the solid substance preferably does not dissolve the resist on the wafer and further does not contain a component that dissolves the resist.

Further, in the process of replacing the rinsing liquid and the replacement medium as described above, there is a possibility that the replacement medium applied in a liquid state shrinks in volume when solidified, and the resist pattern is destroyed by the stress. In order to avoid this, by reducing the elastic modulus (Young's modulus) of the replacement medium, the stress due to shrinkage when the replacement medium solidifies may be alleviated.
In order to reduce the Young's modulus, it is preferable to reduce the crystallinity by using a multi-component composition of the solid substance as a substitution medium.

  Furthermore, in order for the rinsing liquid on the wafer to be replaced with the replacement medium that is spontaneously melted, a material having a small contact angle with respect to the wafer of the melted solid substance (substitution medium), that is, a material that is easily wetted is preferable. For example, as the material of the solid substance, the contact angle is smaller than water (contact angle at room temperature with silicon hydrogen termination surface = 81 °, contact angle at room temperature with silicon dioxide surface = 10 °) with respect to the wafer. That is, a material that easily wets is mentioned. Specifically, a solid substance made of a material having a contact angle with a silicon hydrogen termination surface of 30 ° or less or a contact angle with a silicon oxide film of 5 ° or less has an overwhelming affinity for a silicon substrate compared to water. Because of the high performance, the substrate can be completely covered by replacing the rinse water in a very short time.

  Thus, the melting point is 31 ° C. or higher, the solubility in supercritical carbon dioxide is high, the solubility of moisture is small, the resist material is not damaged such as swelling, the Young's modulus is small, and the contact angle with the wafer surface As the solid substance (substitution medium) having a small value, for example, a chain-like or cyclic saturated hydrocarbon having 20 or more carbon atoms and a mixture thereof, aromatic hydrocarbons such as naphthalene and anthracene are preferable. In particular, when pure water is used as the rinsing liquid, it is preferable that the carbon number of the substance is 60 or less so that the melting point is 100 ° C. or less.

In addition, substances in which some or all of the hydrogen atoms of chain hydrocarbons and aromatic hydrocarbons are substituted with halogen atoms such as fluorine, chlorine, bromine and iodine have a higher specific gravity than water, so they are immersed in water. It is also advantageous that water replacement is promoted by gravity by dropping on the wafer. Although some of the halogen compounds are toxic substances, all the solid components used in the drying method are recovered and reused, so that slight toxicity of the halogen compounds does not become a problem. In particular, perfluorohydrocarbons in which chain hydrocarbons or aromatic hydrocarbon hydrogens are all replaced with fluorine are preferred materials because of their high affinity for supercritical carbon dioxide and their ease of dissolution in supercritical carbon dioxide. .
These substances can be used alone, but are preferably mixed to lower the crystallinity and lower the stress at the time of curing shrinkage to prevent pattern destruction.

  In order to replace the rinsing liquid on the wafer with the solid substance, in addition to pouring the molten solid substance (substitution medium) onto the wafer as described above, a liquid in which the solid substance is dispersed in water having a melting point or higher is rinsed. There is a way to replace water. The fine particles of the solid substance dispersed and melted spontaneously adsorb on the wafer surface to form a thin film. However, if a surfactant is used to promote the dispersion of the solid substance, it is easy to incorporate moisture into the solid substance, and the moisture is likely to precipitate during supercritical drying and cause pattern collapse.

  As another method, a two-fluid nozzle is used to atomize a melted solid substance with pressurized air or inert gas and spray it onto the wafer surface, thereby adsorbing on the wafer surface to form a thin film. There is also a method. A schematic configuration diagram of a processing apparatus using a two-fluid nozzle is shown in FIG. A nozzle 40 for supplying a dissolved solid substance is provided with a nozzle 41 for supplying pressurized air or inert gas, thereby forming a two-fluid nozzle 42. When supplying the dissolved solid substance, the solid substance component is atomized by pressurized air or inert gas, and is replaced with the rinse liquid on the surface of the wafer 8. This method is useful when the specific gravity of the solid substance component is lighter than water. In FIG. 3, the same parts as those in FIG.

  Even if the solid material melted by any method described above is laminated on the wafer surface, by rotating the wafer and removing the rinse water and excess melted solid material by the centrifugal force, The thickness of the solid film serving as a protective film made of a solid substance can be adjusted in the range of 100 nm to 100 μm, and the in-plane uniformity can also be accurately controlled. When the thickness of the protective film is 100 nm or less, an uncovered portion is formed and pattern collapse occurs at that portion, and when the thickness of the protective film is 100 μm or more, it takes a lot of time to remove the protective film with supercritical carbon dioxide. .

  By making the protective film on the microstructure surface, which is the replacement medium, a solid substance, when the wafer processed by the wet processing equipment is transported to the supercritical drying equipment by a robot arm etc., the wafer is tilted or vibrated. Also, it is possible to prevent spillage of the replacement medium. In addition, by using a solid material having high solubility in supercritical carbon dioxide, drying can be performed in a shorter time without imposing a load on the microstructure on the wafer.

  Furthermore, as shown in FIG. 4, supercritical drying can be performed by an efficient batch supercritical drying processing apparatus 44. A solid film made of a solid substance is stable even at room temperature and atmospheric pressure, has a low volatilization rate, and can protect a pattern over a long period of time. Therefore, the wafers 8 after wet processing are put together in the supercritical drying processing tank 48. The drying process can be completed at once.

  In the present embodiment, carbon dioxide is heated and pressurized on the supply pipe, but is supplied into the drying treatment tank in a liquid state, where it is heated and pressurized, It is also possible to bring it into a supercritical carbon dioxide state. Since the fine structure in this embodiment is covered with a solid substance, the resist pattern does not fall down with the momentum supplied with the liquid, and thus can withstand various specifications.

  In addition, in the process of removing the protective film made of a solid material by supercritical carbon dioxide, a material having high compatibility with the solid material is added to the supercritical carbon dioxide, so that the solid material can be efficiently removed. The protective film can be removed. In this case, the additive having high compatibility with the solid substance can be removed by finally rinsing with pure supercritical carbon dioxide.

  In the microstructure having the protective film of the present invention laminated, examples of the fine structure before the protective film is laminated include a fine concavo-convex structure such as a resist pattern after development. A concavo-convex structure or a hollow structure having a high aspect ratio such as (micro electromechanical element) may be used, and the surface can be dried without collapsing the concavo-convex of the surface.

  As described above, since the solid replacement method, the drying treatment tank, and the like can be freely combined as appropriate, they are preferably selected from the conditions at that time.

  Specific examples will be described below with reference to FIGS.

[Example 1]
Embodiment 1 will be described using the processing apparatus 1 shown in FIG. 1 and the flow shown in FIG.
First, a JSR photoresist “KRF-M78Y” was spin-coated on a silicon wafer 8 having a diameter of 300 mm to form a resist film 30 having a thickness of 720 nm shown in FIG.
After pre-baking, the wafer 8 is transferred to the development processing tank 4 after exposure with a KRF stepper. After post-exposure baking, a 2.38% TMAH (tetramethylammonium hydroxide) aqueous solution (developer 32) is passed through the nozzle 26. By supplying and developing for 1 minute, a 1: 1 line having a width of 120 nm and a pitch of 240 nm as shown in FIG. 2B and a space structure was formed. The aspect ratio of the resist pattern (fine structure portion) 33 is 6.
Thereafter, a rinsing liquid 34 made of ultrapure water heated to 60 ° C. is supplied from the upper part of the wafer through the nozzle 5 to wash away the developing liquid 32 and form a liquid film of the rinsing liquid 34 (FIG. 2C). At the same time, the wafer 8 was heated.

  Subsequently, while rotating the wafer 8 while the surface of the wafer 8 is not dried, a dichlorobenzene mixture (paradichlorobenzene 92%, orthodichlorobenzene 4%, metadichlorobenzene 4%, melting point at atmospheric pressure = 36) is used as the replacement medium 35. C., melting point at 8.5 MPa = 39 ° C.) was heated to 50 ° C. to be liquefied, and discharged from the nozzle 6 onto the surface of the wafer 8. The contact angle of the dichlorobenzene mixture with the oxide film surface at room temperature is 3 °, and the affinity for the wafer 8 is higher than that of water (the contact angle at room temperature with the oxide film surface = 10 °) as the rinse liquid 34. . Furthermore, since the density of the chlorobenzene mixture is 1.2 [g / ml] and heavier than water, it easily sinks under the rinsing liquid 34, and the water on the surface of the wafer 8 is liquefied as shown in FIG. Fully substituted with chlorobenzene.

  After the supply of the melted dichlorobenzene was stopped, the wafer 8 was rotated at 3000 rpm, thereby adjusting the film thickness of the in-plane dichlorobenzene that was the dissolved substitution medium 35 to 1.6 μm. During the final rotation, the wafer 8 was naturally cooled to 40 ° C. or lower, and the dichlorobenzene on the wafer 8 was solidified to form a solid film 36 as shown in FIG. This dichlorobenzene mixture is subjected to sublimation purification, so that impurities such as metals are reduced to a ppb level or lower.

  Next, after the wafer 8 is charged and sealed in a drying treatment tank 7 maintained at 33 ° C. by a robot arm (not shown), liquid carbon dioxide previously heated to 33 ° C. is pressurized by an in-line heater 14. The pressure pump 15 is pressurized and introduced into the supercritical drying apparatus, and the pressure adjusting valve 7 is used to adjust the pressure of carbon dioxide in the treatment tank 7 to 8.5 MPa. As a supercritical state, 500 ml / min. It was supplied at a flow rate (FIG. 2 (f)). In this way, the wafer 8 in the processing bath 7 is immersed in the supercritical carbon dioxide 37. Although there is a great impact when liquid carbon dioxide is introduced, the resist pattern 33 is not collapsed because the resist is sufficiently protected by the solid film 36 of the dichlorobenzene mixture. Although the solid film of solidified dichlorobenzene on the wafer 8 was visually removed by flowing the supercritical carbon dioxide 37 for 3 minutes, the supercritical carbon dioxide 37 was passed for 2 minutes (5 minutes in total), The dichlorobenzene on the surface 8 was completely removed (FIG. 2 (g)).

  Thereafter, while maintaining the temperature at 35 ° C., the pressure in the supercritical drying tank 7 was reduced to atmospheric pressure, and the wafer 8 having the resist pattern 33 was dried. As a result of observing the resist pattern 33 with an electron microscope, no pattern collapse was observed.

[Example 2]
The second embodiment is performed by a combination of the apparatuses shown in FIGS. That is, the processing apparatus in the second embodiment is implemented by a combination of the developing apparatus 43 having the two-fluid nozzle 42 shown in FIG. 3 and the batch type supercritical drying processing apparatus 44 shown in FIG.
A photoresist “TMGR-EN007” manufactured by Tokyo Ohka Co., Ltd. was spin-coated on a silicon wafer 8 having a diameter of 300 mm to form a resist film 30 having a thickness of 400 nm. After pre-baking, patterning was performed by electron beam exposure. Next, the wafer 8 is transferred to the developing device 2, and after the post-exposure baking, development is performed with a 2.38% TMAH (tetramethylammonium hydroxide) aqueous solution (developing solution 32) for 1 minute. : A line and space structure was formed. The aspect ratio of the resist pattern 33 is 5. Thereafter, a rinsing liquid 34, which is ultrapure water heated to 60 ° C., is supplied from the upper part of the wafer 8 through the nozzle 5, thereby washing the developer 32 and heating the wafer 8 at the same time.

  Subsequently, while rotating the wafer 8 before the surface of the wafer 8 is dried, a mixture of chain saturated hydrocarbons having 30 to 45 carbon atoms (paraffin wax, melting point at atmospheric pressure = 45 ° C., 8.5 MPa) (The melting point of the liquid crystal = 50 ° C., the contact angle of the room temperature with the oxide film surface = 5 °) is liquefied by heating to 60 ° C. and introduced into the two-fluid nozzle 42 having a heating means and pressurized to 3 atm By atomizing with gas and spraying on the wafer 8 at an average speed of 80 m / s, the rinsing liquid 34 on the surface was completely replaced with paraffin wax which is a liquefied replacement medium 35. After the supply of paraffin wax was stopped, the wafer 8 was rotated at 3000 rpm to adjust the thickness of the in-plane paraffin wax to 1.8 μm. During the last rotation, the wafer 8 was cooled to 40 ° C. or lower, and the paraffin wax on the wafer 8 was solidified to form a film. By performing sublimation purification on this paraffin wax, impurities such as metals are reduced to the ppb level or lower.

  Next, the wafer 8 was loaded into a supercritical drying apparatus 44 maintained at 35 ° C. by a robot arm. At this time, the drying processing apparatus 3 is of a batch type shown in FIG. In the supercritical drying treatment tank 48, 50 wafers 8 can be mounted. After inserting and sealing 50 wafers 8, liquid carbon dioxide heated to 35 ° C. in advance by the in-line heater 14 is pressurized and pressurized by the pressure pump 15 and introduced into the supercritical drying tank 48. At the same time, the pressure of carbon dioxide in the processing tank 48 was adjusted to 8.5 MPa by the exhaust pressure valve 25, and the supercritical state was supplied at a flow rate of 500 ml / min (FIG. 2 (f)). Although the film of solid paraffin wax solidified on the wafer by the flow of supercritical carbon dioxide for 3 minutes was visually removed, the supercritical carbon dioxide was passed for 2 minutes (total 5 minutes) to remove the paraffin wax on the wafer surface. It was completely removed (FIG. 2 (g)).

  Thereafter, while maintaining the temperature at 35 ° C., the pressure in the supercritical drying tank 48 was reduced to atmospheric pressure, and the wafer 8 having a resist pattern was dried. As a result of observing the resist pattern with an electron microscope, no pattern collapse was observed.

[Example 3]
The third embodiment is performed by a combination of the supercritical drying apparatus 3 in the processing apparatus 1 shown in FIG. 1 and the developing apparatus 43 shown in FIG.
In the same manner as in Example 2 until the rinsing step with ultrapure water in the development processing tank 4, the perfluoroalkane (mixture of 12 to 16 carbon atoms) was used as the replacement medium 35 before the rinsed wafer surface was dried. : (Melting point at atmospheric pressure = 48 ° C., melting point at 8.5 MPa = 51 ° C., contact angle at room temperature with the oxide film surface = 1 °) is heated to 60 ° C. to be liquefied to form a two-fluid nozzle 42 Atomized with nitrogen gas introduced and pressurized to 3 atm and sprayed onto the wafer 8 at an average speed of 80 m / s, thereby completely replacing the water, which is the rinsing liquid 34 on the surface, with the liquefied perfluoroalkane ( 2 (d)) After stopping the supply of perfluoroalkane, the film thickness of the in-plane perfluoroalkane was adjusted to 2.0 μm by rotating the wafer 8 at 3000 rpm. Was naturally cooled to 40 ° C. or lower, and the perfluoroalkane on the wafer was solidified to form a solid film 33.

  Next, the wafer is placed in the drying treatment tank 7 of the supercritical drying apparatus 3 maintained at 35 ° C. by a robot arm and sealed, and then liquid carbon dioxide heated to 35 ° C. is pressurized in advance to transfer the liquid. While being introduced into the supercritical drying treatment tank 7 by the pump 16, the pressure of the carbon dioxide in the treatment tank 7 was adjusted to 8.5 MPa by the pressure adjusting valve 17, and the supercritical state was supplied at a flow rate of 500 ml / min. . Although the solid film 36 of perfluoroalkane solidified on the wafer was visually removed by flowing supercritical carbon dioxide for 1 minute, supercritical carbon dioxide was further flown for 1 minute (2 minutes in total) to Perfluoroalkane was completely removed (FIG. 2f).

  Thereafter, while maintaining the temperature at 35 ° C., the pressure of the supercritical drying apparatus was reduced to atmospheric pressure, and the wafer having the resist pattern was dried. As a result of observing the resist pattern with an electron microscope, no pattern collapse was observed.

  Next, drying of a wafer having a fine structure using a conventional processing apparatus will be described as a comparative example.

[Comparative Example 1]
In Example 1 described above, after the rinsing step with ultrapure water, it was directly dried by a conventional spin drying method. When the resist pattern was observed with an electron microscope, adjacent patterns adhered to each other with respect to the 80% pattern.

[Comparative Example 2]
As Comparative Example 2, a drying process using the invention described in Patent Document 3 is performed.
In the same manner as in Example 1 until the rinsing step with ultrapure water, H (CF2CF2) nCH2OH (C4F9OC2H5; manufactured by Sumitomo 3M; ”; Boiling point of 76 ° C .; hereinafter abbreviated as“ HFE ”), the surface rinse water was completely removed by supplying the wafer to the wafer surface from the top while rotating the wafer. Before the wafer surface was dried, an HFE solution containing 10% of fluorinated oil (Mitsui DuPont, “Krytox”) was supplied to the surface of the wafer while rotating the wafer at an ambient temperature of 23 ° C. When the wafer was continuously rotated after the supply was stopped, HFE having a low vapor pressure was quickly evaporated, and a thin protective film only of fluorinated oil was formed.

  When this wafer was placed in a supercritical drying apparatus and liquid carbon dioxide previously heated to 50 ° C. was pressurized and introduced into the supercritical drying apparatus maintained at 50 ° C. by a liquid feed pump, about 4 MPa of liquid dioxide was obtained. Since carbon suddenly entered, a part of the thin protective film of fluorinated oil on the wafer surface was completely blown off, and the resist pattern was in contact with the gas phase, and a strong capillary force acted. In addition, the resist was directly impacted by the introduction of liquid carbon dioxide.

  Thereafter, the pressure of the carbon dioxide in the supercritical drying apparatus is adjusted to 8.0 MPa by a pressure adjusting valve, and in the supercritical state, first, the HFE is added to carbon dioxide at 1% in order to increase the extraction efficiency of the fluorinated oil. The added mixed fluid was supplied into the high-pressure vessel, and the fluorinated oil was discharged out of the vessel. After confirming that the fluorinated oil was completely discharged, the supply of HFE was stopped, only the carbon dioxide was continuously supplied, and the HFE was discharged. Through the flow of supercritical carbon dioxide, all the HFE was discharged, and the inside of the high-pressure vessel was replaced with only supercritical carbon dioxide. Thereafter, the pressure of the supercritical drying apparatus was reduced to atmospheric pressure while maintaining the temperature at 50 ° C., and the wafer having the resist film was dried.

  As a result of observing the resist pattern with an electron microscope, pattern collapse occurred in the portion where the fluorinated oil was blown off when carbon dioxide was introduced. Further, the resist pattern swelled due to the effect of HFE, and the line width increased by 10%.

[Comparative Example 3]
As Comparative Example 3, similarly to Comparative Example 2, a drying process using the invention described in Patent Document 3 is performed.
In the same manner as in Example 1 until the rinsing step with ultrapure water, a 1% aqueous solution of polyvinyl alcohol (PVA500 manufactured by Wako Pure Chemical Industries, Ltd.) is applied to the surface of the wafer while rotating the wafer surface before the rinsed wafer surface is dried. Supplied. When the wafer was continuously rotated even after the supply was stopped in an atmosphere at 23 ° C., water evaporated and a highly viscous water-containing PVA film was formed on the wafer surface.

A wafer with a protective layer made of this high-viscosity PVA film is loaded into a supercritical drying apparatus, introduced into a high-pressure vessel that has been preliminarily heated to 50 ° C. and maintained at 50 ° C. by a liquid feed pump, The pressure of the carbon dioxide in the processing vessel was adjusted to 8 MPa by a pressure adjusting valve to obtain a supercritical state. Initially, in order to increase the extraction efficiency of PVA, a mixed fluid obtained by adding 0.2% of water to carbon dioxide was supplied into the high-pressure vessel and discharged out of the PVA vessel. After confirming that the PVA was completely discharged, the water supply was stopped, and only carbon dioxide was continuously supplied to discharge the water. All the water was discharged by the supercritical carbon dioxide circulation, and only the supercritical carbon dioxide was replaced in the high-pressure vessel.
Thereafter, the pressure in the high-pressure vessel was reduced to atmospheric pressure while maintaining the temperature at 50 ° C., and the wafer having the resist film was dried.

  As a result of observing the resist pattern with an electron microscope, 1% of the pattern collapsed. As a result of examining the adsorbed species on the surface of the wafer in which the pattern collapsed by the temperature programmed desorption method (TDS), a large amount of water was observed. Since it is known that the moisture contained in supercritical carbon dioxide adsorbs to the pattern, the pattern collapse is accelerated (reference: Journal of Vacuum Science and Technology, B18 (6) 780, (2002)). It is obvious that a protective film that cannot be removed without using water-containing supercritical carbon dioxide is not suitable as a replacement medium.

As shown above, even when compared with Comparative Examples 1 to 3, Examples 1 to 3 according to the present invention can be excellently dried.
According to the present invention, in a wafer having a microstructure after rinsing with water, the rinsing liquid and a material having a melting point equal to or higher than the critical temperature of supercritical carbon dioxide are replaced and solidified to form a protective film. By forming a solid film, the protective film does not volatilize under normal pressure and atmospheric pressure, and the fine structure such as a resist pattern can be stably protected. The solid coating also has the effect of protecting the microstructure from the impact caused by the large pressure difference when introducing liquid carbon dioxide or supercritical carbon dioxide, and it dries the microstructure without any trouble such as pattern collapse. I can do it. Furthermore, according to the present invention, since no water is used, pattern collapse caused by moisture contained in supercritical carbon dioxide can be prevented.

It is a schematic block diagram of the processing apparatus which concerns on one embodiment of this invention. It is a figure which shows the process using the processing apparatus which concerns on one embodiment of this invention. It is a schematic block diagram of the development processing apparatus which concerns on the other form of this invention. It is a schematic block diagram of the supercritical drying processing apparatus which concerns on the other form of this invention.

Explanation of symbols

  1 .... Processing equipment, 2 .... Developing equipment, 3 .... Supercritical drying equipment, 4 .... Development processing tank, 5, 6, 26 .... Nozzle, 7 .... Dry processing tank, 8 .... Wafer, 9. 10 .... Supporting part, 11 .... Supply piping, 12 .... Drain piping, 13 .... Liquid carbon dioxide tank, 14 .... Inline warmer, 15 .... High pressure pump, 16 .... Gas-liquid separator, 17 .... -Waste liquid tank, 18-Filter, 19-In-line cooler, 20-Liquid pump, 21-Waste pipe, 22, 23, 24-Valve, 25-Pressure relief valve, 30-Resist film, 32 ..Developer, 33..Microstructure part, 34..Rinse solution, 35..Substitution medium, 36..Solid film, 37..Supercritical carbon dioxide, 40..Substitution medium nozzle, 41..Pressurization Gas nozzle, 42 ·· 2 fluid nozzle, 43 ·· 2 fluid nozzle Device, 44 ... batch supercritical drying apparatus

Claims (11)

The fine structure portion on the surface of the fine structure processed by the wet processing apparatus is covered with a protective film made of a solid material as a replacement medium having a melting point of 31 ° C. or higher in an environment at or above the critical pressure of supercritical carbon dioxide. Process,
And a step of dissolving and removing the solid material as the protective film on the surface of the fine structure with supercritical carbon dioxide and drying the fine structure. 2. The processing of a microstructure according to claim 1, wherein the protective film is formed by covering the microstructure in a liquid state in an environment having a melting point of the solid substance or higher and then solidifying. Method. The method for treating a microstructure according to claim 1, wherein the substitution medium has a saturated moisture content of 1% or less at normal pressure and 25 ° C. The method for treating a microstructure according to claim 1, wherein the substitution medium is composed of a chain-like or cyclic hydrocarbon having a carbon number of 20 or more, or a mixture thereof. The method for treating a microstructure according to claim 1, wherein the protective film is formed by spraying a liquid replacement medium onto the microstructure using a two-fluid nozzle. A first processing means for wet-processing a microstructure having a microstructure on the surface;
A supercritical carbon dioxide dissolved after wet processing has a melting point of 31 ° C. or higher in an environment of a critical pressure or higher, and supplies a solid substance dissolved as a substitution medium, and the microstructure is formed by a protective film made of the solid substance. A wet processing apparatus having a second processing means for coating;
A processing apparatus for a fine structure, comprising: a drying processing device for dissolving and removing the protective film of the fine structure with supercritical carbon dioxide and drying the fine structure. The fine structure processing apparatus according to claim 8, wherein the second processing unit includes a one-fluid nozzle or a two-fluid nozzle for supplying the dissolved substance of the solid substance. A microstructure used in a process prior to drying the microstructure using supercritical carbon dioxide,
The fine structure portion on the surface of the fine structure is covered with a protective film made of a solid material which is a substitution medium having a melting point of 31 ° C. or higher in an environment at or above the critical pressure of supercritical carbon dioxide. Structure. The microstructure according to claim 10, wherein the protective film is formed in a liquid state in an environment equal to or higher than the melting point of the replacement medium and then solidified. The microstructure according to claim 10, wherein the substitution medium has a saturated water content of 1% or less at normal pressure and 25 ° C. The microstructure according to claim 10, wherein the substitution medium is made of a single substance or a mixture of chain or cyclic hydrocarbons having 20 or more carbon atoms.

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