JP2005005566A - Supercritical development method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercritical development method capable of controlling the size of a pattern with high accuracy without causing a fall of the pattern in the development using a supercritical fluid. <P>SOLUTION: Liquefied CHF<SB>3</SB>is introduced into a pressure vessel so as to bring a resist film 102 with a latent image formed thereon into contact with the liquefied CHF<SB>3</SB>104, the internal pressure and the internal temperature of the pressure vessel are brought into the critical point of the CHF<SB>3</SB>or over, the resist film 102 with the latent image formed thereon is developed by the CHF<SB>3</SB>(supercritical development agent) brought into the supercritical state, and thereafter supercritical helium is introduced to exclude the supercritical development agent, thereby bringing the surface of a substrate 101 and the pattern 106 into contact with the helium (supercritical rinse agent) 107 in the supercritical state and having no development property. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a development method using a supercritical fluid, and more particularly to a supercritical dry development method suitable for development that forms a fine pattern on the order of nm.
[0002]
[Prior art]
As is well known, an extremely fine pattern is used to manufacture a large-scale and high-performance device such as an LSI. This ultrafine pattern is, for example, a resist pattern made of an organic material that is sensitive to light, X-rays, or electron beams, which is formed through exposure, development, and rinsing. At present, patterns with dimensions smaller than 100 nm are used, and patterns with dimensions of 10 nm or less are also formed at the stage of research and development.
[0003]
An example of forming a resist pattern will be described. First, a resist film is formed on a substrate to a thickness of about 200 to 500 nm. Next, a desired pattern image is exposed to the film by a light source such as KrF or ArF laser. Next, it develops using the developing solution which consists of tetramethylammonium hydroxide (TMAH), and after this, a developing solution is removed by rinse processes, such as water washing, and development is stopped. Finally, a liquid such as water by the rinsing process is dried to finish the formation of the resist pattern.
[0004]
As described above, since the conventional development process is a liquid process, first, a waste liquid is generated, and this process is necessary. Generally, the developing waste liquid cannot be easily reused, and the waste liquid is disposed of, which causes problems from various viewpoints.
Further, in the resist for forming a fine pattern as described above, since the developer is easily impregnated in the pattern, there is a problem that the pattern is deformed when the formed pattern is dried. .
[0005]
Further, at the time of drying, a bending force (capillary force) works due to a pressure difference between the liquid remaining between the patterns and the external air, causing a problem that the formed pattern falls down. This falling phenomenon becomes more prominent as the pattern has a higher aspect ratio. It has been reported that the capillary force depends on the surface tension generated at the interface between a liquid and a gas between a rinse liquid such as water and a pattern (see Non-Patent Document 1).
[0006]
The surface tension of water is as large as about 72 × 10 ⁻³ N / m, and the above-mentioned capillary force not only defeats resist patterns made of organic materials, but also distorts stronger patterns such as silicon, which is an inorganic material. have. For this reason, the problem of the surface tension by the liquid mentioned above is important.
[0007]
As a technique for solving these problems, for example, a developing method using supercritical carbon dioxide has been proposed (see Patent Documents 1 and 2). In this developing method, an electron beam resist is applied to a silicon substrate, and this is exposed to an electron beam, and the exposed silicon substrate is immersed in a supercritical fluid for development. In this method, finally, the formed pattern is dried by vaporizing the supercritical fluid by lowering the temperature below the critical point or the like.
[0008]
According to this developing method, first, since a developing solution is not used, waste liquid processing becomes easy. Further, when the supercritical fluid is vaporized, the above-described pattern collapse does not occur because there is no liquid-gas interface.
[0009]
[Patent Document 1]
Japanese Patent No. 2663483 [Patent Document 2]
JP 2000-138156 A [Non-Patent Document 1]
Applied Physics Letters, 66, 2655-2657, 1995 [0010]
[Problems to be solved by the invention]
However, the conventional development method using a supercritical fluid does not perform development stop processing after development, so the development stop cannot be accurately controlled, and the dimension of the formed resist pattern cannot be accurately controlled. There was a problem. Here, after developing with the supercritical fluid, if the development is stopped with water or the like as in the prior art, the liquid is dried after that, and the pattern collapses.
[0011]
The present invention has been made to solve the above-described problems. In development using a supercritical fluid, the dimensions can be accurately controlled without causing pattern collapse. The purpose is to do.
[0012]
[Means for Solving the Problems]
In the supercritical development method according to the present invention, after exposing a predetermined pattern image to a photosensitive resist film formed on a substrate, first, the substrate is placed in a container, and the container is heated to a predetermined temperature and A first supercritical fluid, which is in a supercritical state with a first substance that is a gas in an air atmosphere, is introduced into the container under a critical condition of a predetermined pressure, and the resist film is developed with the first supercritical fluid to be formed on the substrate. Next, a resist pattern is formed, and then a second supercritical fluid in which a second substance, which is an inert gas, is supercritical is introduced into a critical container, and the first supercritical fluid is introduced from the container. The container is discharged and the inside of the container is filled with the second supercritical fluid, the development is stopped, and then the pressure in the container is lowered to vaporize the second supercritical fluid.
According to this development method, development and development are stopped without performing liquid treatment, and a dry pattern is formed. In the supercritical development method described above, developability can be improved by using a polar material as the first substance.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the supercritical development method in the present embodiment, development is performed with a fluid (first supercritical fluid) such as CHF ₃ or COF ₂ in a supercritical state, and subsequently, the first used for development. The supercritical fluid is replaced with a supercritical fluid of an inert gas such as helium (second supercritical fluid), whereby development is stopped, and then the inert gas supercritical fluid is vaporized and dried. In order to obtain a development pattern.
[0014]
First, as shown in FIG. 1A, a resist film 102 having photosensitivity is formed on a substrate 101. Next, as shown in FIG. A latent image 102 a is formed on the resist film 102. Hereinafter, the resist film 102 is a positive type resist, and the region of the latent image 102a formed by exposure is, for example, reduced in molecular weight decomposed by an acid generated by exposure and easily dissolved.
[0015]
Next, the substrate 101 is introduced into a predetermined pressure vessel, the pressure vessel is sealed, the inside of the pressure vessel is set to a predetermined pressure and a predetermined temperature, and liquefied CHF ₃ is introduced into this, and FIG. As shown in FIG. 4, the resist film 102 on which the latent image is formed is in contact with the liquefied CHF ₃ 104. Subsequently, development is performed with CHF ₃ (supercritical developer) in which the internal pressure and the internal temperature of the pressure vessel are set to be higher than the critical point of CHF ₃ and the resist film 102 on which the latent image is formed is in a supercritical state. As shown in (d), the resist pattern 106 is formed on the substrate 101. Here, the liquefied CHF ₃ is preferably set to a critical pressure or higher. If the liquefied CHF ₃ having a critical pressure or higher is introduced, the liquefied CHF ₃ can be brought into a supercritical state if the temperature is higher than the critical point. Note that instead of liquefied CHF ₃ , supercritical CHF ₃ may be introduced so that the inside of the pressure vessel is filled with the supercritical developer.
[0016]
Incidentally, the supercritical developer 105 is soluble in the resist pattern 106 which is an unexposed portion. For this reason, the resist pattern 106 continues to dissolve while in contact with the supercritical developer 105, and the size of the resist pattern 106 decreases. In order to avoid this state, that is, to stop development, it is necessary to eliminate the state where the resist pattern 106 is in contact with the supercritical developer 105 as shown in FIG.
Here, in this embodiment, after introducing the supercritical developer, an inert gas such as helium or nitrogen is put into a supercritical state, and this is introduced into the pressure vessel, and the supercritical developer is introduced from the pressure vessel. The development was stopped.
[0017]
For example, the inside of the pressure vessel is maintained in a state where the critical conditions of CHF ₃ are maintained, and helium having the pressure and temperature of the above critical conditions is introduced from a predetermined inlet, while the pressure vessel is introduced from a predetermined outlet. Drain the internal fluid. As a result, the supercritical developer (CHF ₃ ) inside the pressure vessel is discharged, the inside of the pressure vessel is filled with the introduced helium, and as shown in FIG. The surface and the resist pattern 106 are in a state of being in contact with the supercritical helium (supercritical rinsing agent) 107 having no developability.
[0018]
Thereafter, the fluid filled from the pressure vessel is discharged, the pressure in the pressure vessel is lowered, and the supercritical rinse agent 107 is vaporized, thereby causing pattern collapse or the like as shown in FIG. In this state, a resist pattern 106 is formed on the substrate 101. Since the development is stopped by introducing a supercritical fluid of an inert gas such as helium, the dimension control of the pattern formed by the development can be performed more accurately.
[0019]
In addition, according to the above-described development processing, the discharged fluid is a gas, so that the treatment of the waste liquid becomes extremely easy. For example, when the supercritical developer is discharged to the outside of the reaction vessel and vaporized, the resist material dissolved in the supercritical developer is solidified by development, so that it is very easy to separate the resist agent from the developer. It is easy to reuse the developer. Similarly, it is easy to reuse the rinse agent.
[0020]
In the above description, CHF ₃ is used as the first substance that acts as a developer in the supercritical state. However, the present invention is not limited to this. In addition to CHF ₃ , hydrofluorocarbons such as CH ₃ F, CHF ₂ CF ₃ , CH ₂ F ₂ , CF ₃ CH ₃ , and CHF ₂ CHF ₂ may be used. In addition, carbonyl fluoride compounds such as COF ₂ and CF ₃ COF, hypofluorite compounds such as CF ₃ OF and CHF ₂ OCHF _2, and halogenated nitrides such as FNO and F ₃ NO can be used. . Carbon dioxide or SF ₆ can also be used.
[0021]
Generally, a resist material having photosensitivity is a polymer material. In the negative type, for example, upon irradiation with high energy rays, for example, an epoxy group is opened to form a bridge between molecules, and the polymer is insoluble in a developer. become. In the positive type, the polymer cross-links are decomposed by irradiation with high energy rays and are dissolved in the developer. There are also polymers in which a reactive material that reacts with light or high energy rays, such as a novolac resin type or a chemical amplification type, is added to the polymer. These include a state in which a reactive material decomposes, for example, with light to generate an acid, decomposes a cross-link of a polymer resin based on the generated acid, and is easily dissolved in a developer. To do.
[0022]
The polymers constituting these resist materials have a softening temperature of about 100 ° C. When the temperature at which the above-described supercritical developer is in a supercritical state is a high temperature exceeding 100 ° C., the environment in which development is performed is the temperature at which the resist pattern is softened. This deforms the resist pattern. Therefore, it is necessary to use a material having a critical temperature lower than the softening temperature of the resist to be developed as the developer. Since the resist material is an organic material as described above, higher developability can be expected when a material having polarity is used as the first substance that acts as a developer in a supercritical state.
[0023]
In the above description, helium is used as the rinse agent. However, the present invention is not limited to this. Any inert material that does not dissolve the organic material may be used. For example, a rare gas such as Ne, Ar, or Xe or an inert gas such as nitrogen may be used as the supercritical state.
[0024]
Next, a supercritical developing apparatus that performs the above-described supercritical developing method will be described. FIG. 2 is a schematic cross-sectional view illustrating a configuration example of a supercritical developing apparatus that performs the supercritical developing method described above.
This apparatus is composed of a high-pressure vessel 201 that can be sealed and a reaction chamber 202 provided inside the high-pressure vessel 201.
[0025]
A stage 212 on which the substrate 101 to be processed is placed is disposed on the bottom surface of the reaction chamber 202. The high-pressure vessel 201 is made of stainless steel, for example, and has a wall thickness of about 20 mm.
The high-pressure vessel 201 includes a vessel upper portion 201a and a vessel lower portion 201b having a stage 212 fixed to the bottom. For example, by removing the vessel upper portion 201a, the inside of the reaction chamber 202 can be opened. Is possible.
[0026]
In addition, the present apparatus includes a cylinder 203 in which CHF ₃ is pressurized and accommodated, and a cylinder 203a in which helium is pressurized and accommodated. CHF ₃ accommodated in the cylinder 203 is introduced into the pipe 204 through the switching valve 223 through the pipe 204a. Further, helium accommodated in the cylinder 203a is introduced into the pipe 204 through the switching valve 223 through the pipe 204b. Accordingly, by switching the switching valve 223, the fluid introduced into the pipe 204 can be switched to CHF ₃ or helium.
[0027]
The CHF ₃ or helium introduced into the pipe 204 is introduced into the reaction chamber 202 through the introduction port 205. In the middle of the pipe 204, a pressure feed pump 206 and an introduction valve 207 are provided, and on the discharge side of the pressure feed pump 206, a pressure gauge 208 for measuring the pressure is provided. The fluid introduced into the pipe 204 can be pumped into the reaction chamber 202 by the pressure pump 206. Further, the opening degree of the introduction valve 207 can be controlled by the pressure measurement result of the pressure gauge 208.
[0028]
The apparatus also includes a pressure gauge 209 that measures the internal pressure of the reaction chamber 202, a discharge port 210 that discharges the fluid inside the reaction chamber 202, and a pressure control valve 211 provided in the middle of the discharge port 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. Note that the cylinder 203 may contain a material that can be used as the developer described above instead of the CHF ₃ . The cylinder 203a may contain a material that can be used as the rinse agent described above instead of helium.
[0029]
In addition, the high-pressure vessel 201 includes a heater 213 between the outer wall and the inner wall, and the inside of the reaction chamber 202 can be heated by the control of the heater control unit 221. In addition, a heater 213 is also provided in the pipe 204 on the reaction chamber 202 side from the pressure pump 206. The heater 213 may be a heating means by resistance heating or high frequency induction heating, for example.
[0030]
In this supercritical developing device, CHF ₃ supplied from the cylinder 203 is pumped to the pumping pump 206, passes through the piping, and is transported to the reaction chamber 202 from the inlet 205. Further, the CHF ₃ to be pumped is heated to a predetermined temperature by a heater 213 provided in the pipe 204 and transported to the reaction chamber 202. According to this apparatus, for example, CHF ₃ in a supercritical state can be transported to the inside of the reaction chamber 202 by setting it to a critical pressure or higher with the pressure feed pump 206 and setting it to a critical temperature or higher with the heater 213. .
[0031]
In addition, the opening of the pressure control valve 211 is adjusted so that the pressure value measured by the pressure gauge 209 maintains the pressure at the critical point of CHF ₃ , and the pressure value measured by the pressure gauge 208 is equal to the critical point of CHF ₃ . It is also possible to adjust the pressure of the pumping by the pumping pump 206 within a range where the pressure is maintained. By doing so, a state in which CHF _{3 in} a supercritical state is always supplied into the reaction chamber 202 is obtained. Further, the switching valve 223 is switched to supply helium from the cylinder 203a as described above. Alternatively, if helium controlled to a predetermined pressure is used, helium can be introduced into the reaction chamber 202 without using the pumping pump 206.
[0032]
First, after CHF ₃ is supplied from the cylinder 203 and the inside of the reaction chamber 202 is filled with supercritical CHF ₃ , if the switching valve 223 is switched, helium is supplied from the cylinder 203a. The inside of is filled with supercritical helium.
In this way, if the substrate 101 (resist pattern 106) is exposed to supercritical helium in the reaction chamber 202, development can be stopped.
[0033]
In addition, the supercritical fluid filled in the reaction chamber 202 can be agitated by the following.
With the inside of the reaction chamber 202 already filled with supercritical CHF ₃ , first, the opening of the introduction valve 207 is controlled by the pressure measurement value of the pressure gauge 208, and the discharge side of the pressure feed pump 206 and the introduction valve 207 are controlled. The introduction valve 207 is closed until the pressure in the pipe 204 between the pressure and the pressure (pressure measurement value of the pressure gauge 208) reaches 20 MPa. If the introduction valve 207 is closed while the pressure pump 206 is operated, the pressure in the pipe 204 between the discharge side of the pressure pump 206 and the introduction valve 207 increases instantaneously. Further, the internal temperature of the pipe 204 is set to about 50 ° C. by the heater 213.
[0034]
Next, when the measured value of the pressure gauge 208 reaches 20 MPa, the introduction valve 207 is opened. As a result, supercritical CHF ₃ in the pipe 204 set to the critical temperature or higher and the critical pressure or higher is introduced into the reaction chamber 202, and the internal pressure of the reaction chamber 202 increases instantaneously. Here, if the opening degree of the pressure control valve 211 is controlled by the pressure measurement value of the pressure gauge 209 so that the internal pressure in the reaction chamber 202 becomes 15 MPa, the internal pressure in the reaction chamber 202 immediately becomes about 15 MPa. To drop.
[0035]
The fact that the pressure in the reaction chamber 202 has decreased to about 15 MPa is also detected by the pressure gauge 208 because the introduction valve 207 is opened. When the measured value of the pressure gauge 208 reaches 15 MPa, the introduction valve 207 is closed again. As a result, the pressure between the discharge side of the pressure pump 206 and the introduction valve 207 again instantaneously increases. On the other hand, the inside of the reaction chamber 202 is maintained at about 15 MPa by a pressure gauge 209 and a pressure control valve 211.
[0036]
By closing the introduction valve 207 again, the pressure between the discharge side of the pressure feed pump 206 and the introduction valve 207 is increased until the pressure measurement value of the pressure gauge 208 reaches 20 MPa, and then the introduction valve 207 is immediately opened. Let As a result, the internal pressure of the reaction chamber 202 rises instantaneously again.
[0037]
By repeating the above, the internal pressure of the reaction chamber 202 can be varied. For example, as shown in FIG. 3, as time elapses, the introduction valve 207 is closed at the time point A and the introduction valve 207 is opened at the time point B, and the fluctuation of the internal pressure in the reaction chamber 202 is repeated. By such pressure fluctuation, the supercritical CHF ₃ in the reaction chamber 202 can be brought into a stirred state.
[0038]
Further, as shown in FIG. 4, a rectifying mechanism 420 in which a plurality of fins are fixed may be provided inside the reaction chamber 202, and the above-described stirring due to pressure fluctuation may be performed more effectively. For example, as shown in the perspective view of FIG. 5, the rectifying mechanism 420 is configured such that a plurality of fins are fixed upright on a ring-shaped frame disposed on the same plane as the substrate 101. For example, the fluid introduced from the introduction port 205 flows onto the substrate 101 with the flow direction changed by the rectifying mechanism 420 as indicated by a dotted line in the plan view of FIG.
[0039]
In this manner, by using the rectifying mechanism 420 inside the reaction chamber 202 and rectifying a fluid such as liquefied carbon dioxide supplied onto the substrate 101, development on the substrate 101 can be performed more efficiently. Become. Further, the effect of the rectifying mechanism 420 is improved as the flow velocity of the supercritical fluid supplied from the inlet 205 is faster.
Note that the rectifying mechanism does not have to be provided so as to surround the entire circumference of the substrate 101, and may be partially disposed in the vicinity of the introduction port 205. Any rectifying mechanism may be provided as long as the fluid introduced from the inlet 205 rectifies so as to flow in a curved manner on the substrate 101.
[0040]
Next, examples of the supercritical development method of the present invention will be described in more detail.
First, a substrate made of silicon is prepared, and an ultraviolet resist (SEPR551: manufactured by Shin-Etsu Chemical) is applied thereon to form a resist film having a thickness of about 300 nm. Next, a predetermined light image using KrF as a light source is exposed to the formed resist film, and a heat treatment at a predetermined temperature is applied to form a latent image having a predetermined pattern. This pattern has a width of about 100 nm.
[0041]
When the latent image is formed as described above, the substrate is fixed on the stage 212 of the apparatus shown in FIG. 2, the reaction chamber 202 is sealed, and each heater 213 is heated under the control of the heater control unit 221. The internal temperature of the pipe 204 and the reaction chamber 202 is set to 50 ° C. In this state, CHF ₃ accommodated in the cylinder 203 is pumped into the reaction chamber 202 by the pump pump 206 at a pressure of 15 MPa.
[0042]
As described above, supercritical CHF ₃ is supplied into the reaction chamber 202 from the introduction port 205, and the inside of the reaction chamber 202 is filled with supercritical CHF ₃ . Thereafter, as described above, the pressure fluctuation is caused to bring the supercritical CHF ₃ inside the reaction chamber 202 into a stirred state. This state is maintained for about 5 minutes. By this 5 minutes, the resist film on the substrate on which the latent image is formed is developed with supercritical CHF ₃ which is a supercritical developer, and a pattern is formed.
[0043]
Thereafter, the switching valve 223 is switched so that the helium contained in the cylinder 203a is pumped. As a result, supercritical helium is supplied into the reaction chamber 202, passes through the pressure control valve 211 whose opening degree is controlled to keep the internal pressure of the reaction chamber 202 at 15 MPa, and is supercritical CHF from the discharge port 210. ₃ is discharged. As a result, the supercritical developer is replaced with the supercritical rinse agent on the substrate, and the development is stopped.
[0044]
After the development is stopped as described above, first, the pumping by the pumping pump 206 is stopped, and the introduction valve is closed. Further, the opening degree of the pressure control valve 211 is set to a predetermined state, the fluid inside the reaction chamber 202 is discharged, the internal pressure is lowered, and the supercritical rinse agent is vaporized. As a result, the resist pattern can be formed in a dry state on the substrate without causing problems such as collapse and deformation.
In the above description, the development of a positive resist has been described as an example, but the present invention is not limited to this. The same applies to the development of a negative resist.
[0045]
【The invention's effect】
As described above, in the present invention, the first supercritical fluid in which the first substance, which is a gas in the air atmosphere, is brought into a supercritical state is introduced into the container, and the resist film is developed with the first supercritical fluid. A second supercritical fluid in which the second substance, which is an inert gas, is supercritical is introduced into the container, and the first supercritical fluid is discharged from the container. The development was stopped by filling with fluid. Therefore, according to the present invention, since development can be stopped without using liquid processing, the dimensions can be accurately controlled without causing pattern collapse in development using a supercritical fluid. An excellent effect is obtained.
[Brief description of the drawings]
FIG. 1 is a process diagram for explaining an example of a supercritical development method in an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view schematically showing a configuration example of a supercritical developing device for carrying out the supercritical developing method of the embodiment.
FIG. 3 is a timing chart showing timings for causing pressure fluctuations.
FIG. 4 is a schematic cross-sectional view (a) schematically showing another configuration example of a supercritical developing apparatus for carrying out the supercritical developing method of the embodiment, and a plan view (b) showing a part thereof. .
FIG. 5 is a perspective view partially showing another configuration example of the supercritical developing device for carrying out the supercritical developing method of the embodiment.
[Explanation of symbols]
101 ... substrate, 102 ... resist film, 102a ... latent image, 103 ... photomask, 104 ... liquefied _CHF 3, 105 ... supercritical developer, 106 ... resist pattern, 107 ... supercritical helium (supercritical rinse) .

Claims (2)

A first step of exposing a predetermined pattern image to a photosensitive resist film formed on a substrate;
The substrate is placed in a container, the container is filled with a first supercritical fluid in a supercritical state in which the first substance, which is a gas in the atmosphere, is in a supercritical state under a critical condition of a predetermined temperature and a predetermined pressure. A second step of introducing and developing the resist film with the first supercritical fluid to form a resist pattern on the substrate;
A second supercritical fluid in which a second substance that is an inert gas is in a supercritical state is introduced into the container having the critical condition, and the first supercritical fluid is discharged from the container to discharge the first supercritical fluid. A third step of filling the interior with the second supercritical fluid and stopping the development;
A supercritical development method comprising at least a fourth step of evaporating the second supercritical fluid by reducing the pressure in the container. In the supercritical development method according to claim 1,
The supercritical development method, wherein the first substance has polarity.

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