JP3494939B2 - Supercritical drying method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical drying method and apparatus used for forming a fine pattern in semiconductor device formation, and more particularly to a supercritical drying method and apparatus used for forming a fine pattern by a lithography technique. .

[0002]

2. Description of the Related Art In recent years, with the increase in scale of MOS LSI,
With the increase in size of chips, miniaturization of patterns in LSI manufacturing is being promoted, and patterns having line widths less than 100 nm are now formed. And the fact that the line width becomes narrower results in an aspect ratio (height /
A pattern having a large width will be formed. In addition, forming a fine pattern inevitably requires a resist pattern as a processing mask used for etching processing to have a high aspect ratio. The resist pattern can be formed by processing a resist film which is an organic material by a lithographic technique. When the resist film is exposed, the molecular weight and molecular structure of the exposed area change, and there is a difference in solubility in the developing solution between the exposed area and the unexposed area. A pattern can be formed on the resist film.

In the above developing process, if the developing process is continued, the unexposed areas will start to dissolve in the developing solution and the pattern will disappear. Therefore, the rinsing process with the rinsing solution is performed to stop the developing process. . Then, finally, by drying to remove the rinse liquid, a resist pattern as a processing mask can be formed on the resist film. As a big problem at the time of drying in such fine pattern formation,
There is a collapse of the pattern 1101 as shown in the cross-sectional view of FIG.

A fine resist pattern having a large aspect ratio is formed by developing, rinsing and drying. A fine pattern having a large aspect ratio is also formed other than the resist. For example, after the substrate is etched using the resist pattern as a mask, cleaning, rinsing cleaning (water cleaning), and drying are performed, whereby a substrate pattern having a high aspect ratio is formed. Then, the pattern 1101 collapses during drying after the rinse treatment, and the phenomenon of collapse becomes more remarkable as the pattern 1101 has a higher aspect ratio.

As shown in FIG. 12, the phenomenon that the above pattern collapses is caused by the pattern 120 when the resist and the substrate are dried.
Rinse liquid 1202 remaining between 1 and the external air 120
This is due to the bending force (capillary force) 1210 that acts due to the pressure difference between the pressure and the pressure. It is reported that the capillary force 1210 depends on the surface tension generated at the gas-liquid interface between the rinse liquid 1202 and the pattern 1201 (Reference:
Applied Physics Letters, Volume 66, 2655
-2657, 1995).

This capillary force not only collapses the resist pattern made of an organic material, but also distorts a more durable pattern such as silicon which is an inorganic material. The problem is important. The problem due to the capillary force can be solved by performing the treatment using a rinse liquid having a small surface tension. For example, when water is used as the rinse liquid, the surface tension of water is about 72 dyn / cm, but the surface tension of methanol is about 23 dyn / cm. Therefore, rather than directly drying the water, the water is replaced with ethanol and then ethanol is used. The degree of pattern collapse is suppressed more by drying.

Further, if perfluorocarbon having a surface tension of 20 dyn / cm is used and the rinse liquid is replaced with the perfluorocarbon liquid and then the perfluorocarbon is dried, it is more effective for suppressing the pattern collapse.
However, although the use of a rinse liquid having a low surface tension can reduce the occurrence of pattern collapse, the pattern collapse cannot be eliminated as long as the liquid has a surface tension to some extent. In order to solve the pattern collapse problem, it is necessary to use a rinse liquid having a surface tension of zero, or to replace the rinse liquid with a liquid having a surface tension of zero, and then to dry the replaced liquid.

A supercritical fluid is a liquid having a surface tension of zero. A supercritical fluid is a substance at a temperature and pressure that exceeds the critical temperature and the critical pressure and has a dissolving power similar to a liquid, but tension and viscosity exhibit properties close to those of a gas, and the state of the gas is maintained. It can be called a liquid. Since the supercritical fluid does not form a gas-liquid interface, the surface tension becomes zero. Therefore, if drying in a supercritical state, the concept of surface tension disappears, and the pattern collapse does not occur. Generally, carbon dioxide is used as the supercritical fluid. Carbon dioxide has a low critical point (7.3 MPa,
Since it is 31 ° C) and is chemically stable, it has already been used as a critical fluid for observing biological samples.

Conventionally, supercritical drying using the supercritical state of carbon dioxide has been carried out as follows. First, liquefied carbon dioxide is introduced into a predetermined processing container in advance, and drainage is repeated to replace the rinse liquid. After the rinse liquid is replaced with carbon dioxide, the treatment container is heated to a temperature and pressure above the critical point, so that the liquefied carbon dioxide in the container becomes supercritical carbon dioxide. Here, the operation of inflowing and outflowing carbon dioxide in a supercritical state is not performed. Finally, with only the supercritical carbon dioxide adhered to the fine pattern, the pressure inside the container is reduced to vaporize the supercritical carbon dioxide and dry it.

[0010]

By the way, in the process of pattern formation by the photolithography technique, in general, the substrate is often washed last with water and then dried, but water cannot be directly replaced by carbon dioxide. After replacing water with ethanol, which is easily miscible with carbon dioxide, supercritical drying was performed. Further, some electron beam resists perform a rinse after development with n-propanol, and in this case, after the rinse, the rinse liquid is directly replaced with liquefied carbon dioxide. However, even though it is easy to mix, the solubility of alcohol such as ethanol and carbon dioxide is not sufficient, so that there is a problem that replacement takes time. Further, when trying to shorten the processing time, there are cases where a part that cannot be partially replaced occurs, and pattern collapse may occur.

The present invention has been made to solve the above problems, and an object thereof is to reduce the pattern collapse in supercritical drying as compared with the conventional case.

[0012]

The supercritical drying method of the present invention comprises a first step of exposing a patterned layer having a predetermined pattern formed on a substrate to alcohol, and a pattern after the first step. A second step of exposing the pattern layer to a liquid of a substance that is a gas in the atmosphere while the liquid of alcohol is attached to the layer, and after the second step, the substance keeps the liquid state. After cooling the liquid of this substance under the conditions, the alcohol liquid adhering to the pattern layer is dissolved in the liquid of the above substance to obtain a state in which the liquid of the above substance adheres to the pattern layer. 3 step, and after this 3rd step, the 4th step of bringing the above substances adhering to the pattern layer into a supercritical state, and after this 4th step, adhering to the pattern layer And the fifth step of vaporizing the supercritical substance It includes those were. According to the present invention, in the third step, since the liquid of the substance which is a gas in the air atmosphere is cooled, the density of this substance is increased and the solubility of alcohol is improved.

In the above invention, in the third step, the liquid temperature of the substance is lowered, and then the pressure applied to the liquid is changed under the condition that the substance keeps the liquid state. The liquid of is mixed. Also,
In the second step of the invention, if the liquid of the substance is cooled by cooling the substrate, the liquid of the substance around the pattern layer to which alcohol is actually attached is cooled. Further, in the above invention, the above substance is carbon dioxide, and in the second step, the liquid of the above substance may be cooled to 10 ° C. or lower. Also, all steps are
You may make it perform in the same container.

The supercritical drying apparatus of the present invention has a reaction chamber in which a substrate to be processed is placed and can be sealed, a means for supplying a substance that is a gas in the atmosphere into the reaction chamber, and a pressure in the reaction chamber. Pressure control means for pressurizing and controlling to a pressure at which the above substance becomes a supercritical state, temperature control means for controlling the temperature in the reaction chamber to a predetermined temperature, and substrate temperature control means for controlling the target substrate to a predetermined temperature. And at least. According to the present invention, the temperature around the substrate and the temperature in other regions in the reaction chamber are individually controlled. Further, in the above invention, the supercritical state includes a subcritical state.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) In the supercritical drying method of Embodiment 1, first, as shown in FIG. 1A, a substrate 101 on which a pattern 101a is formed is immersed in water 102 and washed, and then,
As shown in FIG. 1B, the substrate 101 is immersed in ethanol 103, the water adhering to the periphery of the pattern 101 a is dissolved in ethanol, and the pattern 101 is formed with ethanol 103.
Be attached.

Next, as shown in FIG. 1C, the substrate 101
Is immersed in liquefied carbon dioxide 104 contained in a reaction chamber (not shown) which is a predetermined sealable container, and the ethanol attached to the periphery of the pattern 101a is dissolved in liquefied carbon dioxide to form a pattern 101a. Liquefied carbon dioxide 1
It is assumed that 04 is attached. That is, ethanol is replaced with liquefied carbon dioxide. At this time, after the substrate is immersed in liquefied carbon dioxide, the temperature of the liquefied carbon dioxide 104 is cooled to, for example, −5 ° C. while the pressure inside the container is maintained at about 7.5 MPa to increase the density. in this way,
By increasing the density of liquefied carbon dioxide, the compatibility with ethanol is improved, the replacement time can be shortened, and substitution failure such as ethanol remaining can be suppressed.

After that, the substrate 101 and the pattern 101
a With the ambient pressure maintained at 7.5 MPa, the temperature of the liquefied carbon dioxide is set to 31 ° C. to bring it into a supercritical state, and FIG.
The substrate 101 is immersed in the supercritical carbon dioxide 105 as shown in FIG. Then, by vaporizing the supercritical carbon dioxide, as shown in FIG. 1E, the substrate 101 on which the pattern 101a is formed can be dried without pattern collapse. Note that the above-mentioned supercritical state includes a subcritical state, and the same applies hereafter.

Here, the compatibility between liquefied carbon dioxide and alcohol will be described. As described above, for example, in supercritical drying using a supercritical state of carbon dioxide, after washing with water in the pattern formation, the water adhering to the pattern is replaced with alcohol to make the state where the alcohol adheres to the pattern. , Alcohol is replaced with carbon dioxide in liquid or supercritical state. In this replacement of alcohol with carbon dioxide, compatibility between alcohol and carbon dioxide becomes a problem, but compatibility can be improved by increasing the density of carbon dioxide to improve solubility.

For example, carbon dioxide has a large coefficient of thermal expansion,
As shown in FIG. 2, the density changes greatly with changes in temperature. As shown in FIG. 1C, when the alcohol is replaced with liquefied carbon dioxide, the density of the liquefied carbon dioxide changes within the range of 468 to 1200 g / L depending on the temperature condition. Even if the temperature is 31 ° C., if the pressure is 6 MPa or more, the carbon dioxide is liquefied, but the density of the liquefied carbon dioxide at this time is about 470 g / L. On the other hand, if the temperature is set to 15 ° C. even with the same pressure, the density of liquefied carbon dioxide doubles.

As shown in FIG. 1C, when the alcohol is replaced with liquefied carbon dioxide, the pressure is 7.5 MPa.
If the temperature of liquefied carbon dioxide is set to 20 ° C, the replacement will be 30
It takes time, but when the temperature is 15 ° C. at the same pressure, the replacement can be done in 25 minutes. As described above, by increasing the density of liquefied carbon dioxide, the replacement time of alcohol can be shortened, that is, the compatibility between alcohol and liquefied carbon dioxide is improved. The density of liquefied carbon dioxide is
Although the pressure can be increased by increasing the pressure, as is clear from FIG. 2, it is more efficient to increase the density by decreasing the temperature of the liquefied carbon dioxide.

In order to replace the alcohol with liquefied carbon dioxide within, for example, 20 minutes, the density of liquefied carbon dioxide should be at least 900 g / L, preferably 1
000 g / L is required. To obtain this density,
When the pressure in the reaction chamber is 7.5 MPa, the temperature of liquefied carbon dioxide needs to be 10 ° C or lower, preferably -10 ° C or lower. The temperature of liquefied carbon dioxide can be lowered below -10 ° C, but at the freezing point (at a pressure of 7.5 MPa-
If the temperature is lower than 56.6 ° C), the solid state cannot be used.

By the way, when the temperature of the liquefied carbon dioxide is lowered, the water present in the reaction chamber containing the liquefied carbon dioxide agglomerates on the inner wall of the reaction chamber, causing the resist pattern to swell as shown below. . When a resist pattern made of an organic material is dried by the above-described supercritical drying method, if water is adsorbed on the inner wall of the reaction chamber where supercritical drying is performed, this water absorbs the supercritical fluid and is absorbed in the resist film. This is because the supercritical fluid diffuses and is trapped in the resist film. When supercritical drying is performed in the presence of the supercritical fluid in the resist film, the supercritical fluid in the film is rapidly vaporized at the time of depressurization, causing pattern swelling.

Therefore, for example, the temperature in the reaction chamber is set to 30 ° C. in the initial stage so that dew condensation does not occur in the reaction chamber, the alcohol-treated substrate is placed in the reaction chamber, and then liquefied carbon dioxide is placed in the reaction chamber. Is introduced, and the temperature of the liquefied carbon dioxide may be lowered after the reaction chamber is filled with the liquefied carbon dioxide. By doing this,
Water can be prevented from entering the reaction chamber, and pattern swelling can be suppressed. Further, the substrate to be treated is placed in a reaction chamber in a temperature state where dew condensation does not occur in the reaction chamber, and after the reaction chamber is sealed, the solubility of water is lowered by heating, etc. May be introduced into the reaction chamber by pumping to suppress mixing of water into the reaction chamber. Also, after sealing the reaction chamber, a gas with a low water content such as nitrogen or argon is introduced, and residual air containing water is discharged from the reaction chamber, and then liquefied carbon dioxide is introduced into the reaction chamber. It may be introduced.

Hereinafter, the supercritical drying of the present invention will be described in more detail with reference to examples.

[Embodiment 1] First, a first embodiment will be described. First, a supercritical drying device that performs supercritical drying will be described. In the supercritical drying apparatus, as shown in FIG. 3, a substrate 301 to be processed is fixed and processed in a reaction chamber 302 which is a sealable container in which supercritical drying is performed. In the reaction chamber 302, a liquefied carbon dioxide cylinder 3 connected to the reaction chamber 302 via a pump unit 304.
And 03. Further, the reaction chamber 302 has a discharge pipe 30.
5, and a valve 306 is provided between the pump unit 304 and the reaction chamber 302. The reaction chamber 302 is
For example, the reaction chamber 302 is made of stainless steel, has a wall thickness of about 20 mm, and has a spherical shape with an inner diameter of about 100 mm.

A pressure control valve 307 for automatically controlling the pressure inside the reaction chamber 302 is provided in the discharge pipe 305. Further, the reaction chamber 302 has a temperature control device 308.
The internal temperature is controlled by. And reaction chamber 3
On the liquid inflow side of 02, a chemical liquid supply part 321 is provided, and a rinse liquid such as alcohol can be supplied into the reaction chamber 302. Regarding formation of a supercritical state in this supercritical drying apparatus, carbon dioxide will be described as an example. First, liquefied carbon dioxide supplied from a cylinder 303 is pumped into the reaction chamber 302 by a pump unit 304.
The amount of liquefied carbon dioxide discharged from the reaction chamber 302 is controlled by controlling the discharge state by the pressure control valve 307, and the pressure inside the reaction chamber 302 is adjusted to, for example, 7.5MP.
Control to about a. As a result, the reaction chamber 302 is filled with the liquefied carbon dioxide that has been pumped in a liquid state.

At this time, liquefied carbon dioxide is pumped into the reaction chamber 302 by the pump unit 304, and liquefied carbon dioxide in the reaction chamber 302 is discharged via the pressure control valve 307. If the temperature inside the reaction chamber 302 is controlled to 31 ° C. or higher by the temperature control device 308 while the inside pressure of the reaction chamber 302 is filled with liquefied carbon dioxide and the internal pressure is kept at 7.5 MPa, liquefaction inside the reaction chamber 302 Carbon dioxide becomes supercritical. When supercritical carbon dioxide is formed, if pumping of liquefied carbon dioxide by the pump unit 304 is stopped and the valve 304 is closed, the supply of carbon dioxide to the reaction chamber 302 is stopped and the inside of the reaction chamber 302 is stopped. Since the pressure of the above is reduced, the supercritical carbon dioxide in the reaction chamber 302 can be vaporized. At this time, the temperature in the reaction chamber 302 is kept at 31 ° C. or higher.

Next, using the above-mentioned supercritical dryer,
The supercritical drying of Example 1 will be described. First, FIG.
As shown in A, the surface of the silicon substrate 301 whose surface is the (110) plane is thermally oxidized to form the oxide film 4 with a thickness of about 30 nm.
01, and then as shown in FIG.
A thin resist pattern 402 is formed on the surface 1. The resist pattern 402 is formed by using a known lithographic technique.
A pattern having a width of about 0 nm was formed at 30 nm intervals.
Next, the oxide film 4 is formed using the resist pattern 402 as a mask.
After dry etching 01, the resist pattern 402 is removed, and a mask pattern 401a made of silicon oxide is formed on the silicon substrate 301 as shown in FIG. 4C.

Next, as shown in FIG. 5D, the silicon substrate 301 is immersed in an aqueous potassium hydroxide solution 403, and the silicon substrate 301 is masked with the mask pattern 401a.
Etch the surface. Since the surface of the silicon substrate 301 is the (110) plane, the etching with the potassium hydroxide aqueous solution 403 only advances the etching in the direction perpendicular to the surface of the silicon substrate 301. Therefore, FIG.
As shown in, a rectangular pattern 404 having a vertically long cross section can be formed on the silicon substrate 301.

When the height of the pattern 404 became about 150 nm, as shown in FIG. 5E, the substrate 301 was immersed in water 405 to stop the etching and washed with water. Next, the substrate 301 washed with water is introduced into the reaction chamber 302 shown in FIG. 3 and sealed before the surface is dried, and ethanol is supplied from the chemical solution supply unit 321 to generate ethanol in the reaction chamber 302. Fill with. As a result, FIG. 5F
As shown in FIG.
Be immersed in. Then, the water remaining on the surface of the pattern 404 is replaced with ethanol 406.

Next, after replacing the air in the reaction chamber 302 with nitrogen from the inside of the reaction chamber 302 to discharge ethanol, the ethanol on the surface of the substrate 301 is not dried and the reaction is performed while the ethanol is sufficiently wet. Liquefied carbon dioxide is introduced into the chamber 302 to fill the reaction chamber 302 with liquefied carbon dioxide,
The pressure in the reaction chamber 302 is maintained at about 7.5 MPa.
Then, the temperature inside the reaction chamber 302 is cooled to −5 ° C. by the temperature control device 308. As a result, the alcohol around the pattern 404 on the substrate 301 is dissolved in the cooled liquefied carbon dioxide, and the alcohol is replaced by the cooled liquefied carbon dioxide. By continuing this replacement for about 10 minutes, the periphery of the pattern 404 is exposed to liquefied carbon dioxide as shown in FIG. 5G.

After that, the pressure in the reaction chamber 302 is adjusted to 7.5M.
While maintaining the pressure at about Pa, the temperature inside the reaction chamber 301 was set to 35 ° C. by the temperature control device 308, and as shown in FIG. 5H, the surroundings of the pattern 404 were supercritical carbon dioxide 408. After making the carbon dioxide in the reaction chamber 301 into a supercritical state, the supply of carbon dioxide into the reaction chamber 302 is stopped, and the temperature in the reaction chamber is kept at 35 ° C. Was discharged. Due to this discharge, the pressure in the reaction chamber 302 is reduced and the supercritical carbon dioxide is vaporized, and as shown in FIG.
Approximately 30 nm wide and 150 nm high on the silicon substrate 301
A fine silicon pattern 404 was formed.

The supercritical carbon dioxide is discharged at a rate of about 1 liter / min, and the pressure inside the reaction chamber is 0.
It was in a state of descending at a speed of 25 MPa / min. The discharge time can be shortened by setting the discharge amount of supercritical carbon dioxide from the reaction chamber in two stages. When supercritical carbon dioxide is discharged from the reaction chamber, if a large amount of carbon dioxide is discharged at one time to cause a large pressure change, pattern collapse will occur. For this reason, it is usually about 1 liter / m 2.
It is discharged at a speed of in to prevent a sudden pressure change. However, for example, when the pressure in the reaction chamber is in the range of 7.5 to 5 MPa, 0.25 MPa / min
If the pressure drops at a speed of 5 MPa and the pressure drops at a high speed of 0.5 MPa / min in the range of 5 MPa to atmospheric pressure, the influence on the pattern can be reduced and the discharge time can be shortened. .

(Embodiment 2) Hereinafter, supercritical drying of Embodiment 2 using the supercritical drying apparatus of FIG. 3 will be described.
First, the supercritical drying device used in the second embodiment will be described. This supercritical drying apparatus, as shown in FIG.
Substrate temperature controller 3 is newly added to the supercritical dryer shown in
09, and a substrate table 310 for varying the temperature of the upper portion of the substrate 301 by the substrate temperature adjusting device 309. Other configurations are the same as those in FIG. In this supercritical drying apparatus, for example, when cooling the liquefied carbon dioxide filling the reaction chamber 302, the temperature of the liquefied carbon dioxide near the substrate 301 is quickly set to a predetermined temperature, for example, −5 ° C. It is a thing. In this supercritical drying apparatus, since the internal pressure is set to a very high state such as 7.5 Pa, the reaction chamber 302 has a thick structure so as to withstand high pressure. Therefore, in order to change the temperature of the entire reaction chamber 302, it takes a lot of time to reach the desired temperature.

By the way, as described above, the reason why the temperature of the liquefied carbon dioxide is as low as −5 ° C. is that the alcohol attached to the pattern formed on the substrate is
It is to make it more easily dissolved in liquefied carbon dioxide. Therefore, it is not necessary that the entire liquefied carbon dioxide in the reaction chamber be at a low temperature, as long as the liquefied carbon dioxide around the substrate 301 is at a predetermined low temperature state. Board 3
01 To lower the temperature of liquefied carbon dioxide around,
Compared to the case where the temperature of the entire reaction chamber 302 is lowered,
Doesn't need much time.

The supercritical drying apparatus shown in FIG. 6 is provided with a substrate table 310 whose temperature can be varied by the substrate temperature controller 309, and the temperature of the fluid around the substrate 301 together with the substrate 301 placed on the substrate table 310. Is, for example, −5 ° C.
I was able to control. As a result, in the supercritical drying apparatus of FIG. 6, the temperature of the fluid around the substrate 301 can be quickly controlled to a desired temperature. As a result, in the supercritical drying apparatus of FIG. 6, alcohol can be replaced with liquefied carbon dioxide more quickly than the supercritical drying apparatus of FIG.

Next, using the supercritical drying apparatus shown in FIG.
The supercritical drying of the second embodiment will be described. First, FIG.
As shown in A, the electron beam resist thin film 701 made of ZEP-520 (manufactured by Zeon Corporation) coated and formed on the silicon substrate 301 is exposed to an electron beam to form a latent image of a desired pattern. Next, the silicon substrate 301 is placed in the reaction chamber 3
02 (FIG. 6) and sealed, and by introducing xylene into this reaction chamber, as shown in FIG. 7B, the silicon substrate 301 is immersed in a developing solution 702 made of xylene for development to develop a silicon substrate. Resist pattern 70 on 301
1a is formed. The resist pattern 701a has a width of 30
The height was 150 nm and the distance between the adjacent patterns was 30 nm.

Next, the xylene in the reaction chamber 302 is discharged, and a new 2-
Propanol was introduced, and as shown in FIG. 7C, the silicon substrate 301 was immersed in a rinse 703 made of 2-propanol to stop the development. Then, with the reaction chamber 302 kept closed, liquefied carbon dioxide is introduced to discharge the rinse from the inside of the reaction chamber 302 and replace it with liquefied carbon dioxide, and the pressure in the reaction chamber 302 is set to 7.5 MPa to carry out the reaction. The inside of the chamber 302 is filled with liquefied carbon dioxide. Therefore, the silicon substrate 301 changes from a state of being exposed to 2-propanol in a wet state to a state of being exposed to liquefied carbon dioxide. And the temperature control device 3
08, the temperature in the reaction chamber 302 is set to 10 ° C., the temperature of the substrate table 310 is set to −5 ° C. by the substrate temperature adjusting device 309, and these states are held for 10 minutes.

As a result of the above, the liquefied carbon dioxide around the substrate is rapidly cooled to -0.5 ° C. and becomes denser,
The solubility of 2-propanol is improved, and 2-propanol remaining around the pattern formed on the substrate is
It is replaced more quickly by liquefied carbon dioxide. As a result, as shown in FIG. 7D, the silicon substrate 301 and the periphery of the pattern 701a are filled with cooled liquefied carbon dioxide 704. Thereafter, the delivery pressure of the liquefied carbon dioxide by the pump unit 304 and the pressure control valve 307
Amount of carbon dioxide discharged from the reaction chamber 302, the temperature control device 308, and the substrate temperature control device 309.
The temperature in 02 was adjusted respectively, the pressure in the reaction chamber 302 was 8 MPa, and the temperature in the reaction chamber 302 was 35 ° C.

As a result, carbon dioxide in the reaction chamber 302 is in a supercritical state, and as shown in FIG. 7E, the silicon substrate 301 and the periphery of the pattern 701a are filled with supercritical carbon dioxide 705. And the reaction chamber 30
After making carbon dioxide in 2 into a supercritical state, the reaction chamber 302
The supercritical carbon dioxide in the reactor was discharged at a rate of 0.5 liter / min, the pressure in the reaction chamber 302 was lowered to vaporize the supercritical carbon dioxide, and it was dried. As a result, as shown in FIG. 7F, the silicon substrate 301 on which the fine resist pattern 701a was formed was dried without pattern collapse. In addition, the discharge of supercritical carbon dioxide was performed by setting the discharge rate of supercritical carbon dioxide to 0.5 liter / min to moderate the pressure change in the reaction chamber and suppress the pattern collapse due to the rapid pressure change. .

(Second Embodiment) In the first embodiment,
When substituting the liquid with the liquid used as the supercritical fluid for the alcohol, the density of the liquid was increased to improve the compatibility with the alcohol, and the substitution was performed faster and more reliably. , The pressure may be changed so that the above replacement is performed more quickly. For example, in the step from FIG. 7C to FIG. 7D, the pressure inside the reaction chamber is set to 8 MPa.
By suddenly changing the pressure between 4.5 MPa and 4.5 MPa, the liquefied carbon dioxide in the reaction chamber can be stirred.
Substitution with alcohol can be done more quickly. Further, the degree of stirring of the liquefied carbon dioxide is more effective if the range of pressure change is increased. As is clear from the state diagram of FIG. 2, the lower the temperature is, the wider the pressure range of the liquid is. Therefore, the lower the temperature is, the better the pressure change is.

(Embodiment 3) In more detail, also in Embodiment 3, the supercritical drying apparatus shown in FIG. 6 is used to perform supercritical drying according to the steps shown in FIG. First, as shown in FIG. 7A, ZEP-52 formed by coating on a silicon substrate 301.
0 (manufactured by Zeon Corporation) electron beam resist thin film 701
Then, an electron beam is exposed to form a latent image of a desired pattern. Then, the silicon substrate 301 is placed and sealed in the reaction chamber 302 (FIG. 3), and xylene is introduced into the reaction chamber 302, so that the silicon substrate 3 is removed as shown in FIG. 7B.
01 is immersed in a developing solution 702 made of xylene for development, and a resist pattern 701a is formed on the silicon substrate 301.
To form. The resist pattern 701a has a width of 30 nm
Was formed to a height of 150 nm, and a space between the adjacent pattern was formed to be 30 nm.

Next, the xylene in the reaction chamber 302 is discharged, and a new 2-
By introducing propanol, as shown in FIG. 7C,
Development was stopped by immersing the silicon substrate 301 in a rinse 703 made of 2-propanol. The above is the same as in the second embodiment. Next, in Example 3, with the reaction chamber 302 kept closed, liquefied carbon dioxide was introduced into the reaction chamber 302 to discharge the rinse from the reaction chamber 302 and replace it with liquefied carbon dioxide. 302
The internal pressure is set to 8 MPa, and the inside of the reaction chamber 302 is filled with liquefied carbon dioxide. Therefore, the silicon substrate 301 changes from a state of being exposed to 2-propanol in a wet state to a state of being exposed to liquefied carbon dioxide. Then, the temperature inside the reaction chamber 302 was set to 10 ° C. by the temperature control device 308. In the third embodiment, it is not necessary to set the temperature of the substrate table 310 to −5 ° C. by the substrate temperature adjusting device 309.

In the third embodiment, while the supply (pressure feeding) of carbon dioxide into the reaction chamber 302 is continued, the discharge amount of liquefied carbon dioxide in the reaction chamber 302 is instantaneously controlled by controlling the pressure control valve 307. The pressure inside the reaction chamber 302 is decreased to 5 MPa. By increasing the discharge amount of the liquefied carbon dioxide instantaneously, for example, for about 1 second, and immediately after that, the original control state is restored, so that the pressure in the reaction chamber 302 is increased to 8 MPa. By repeating the above pressure drop and pressure rise three times, the liquefied carbon dioxide in the reaction chamber can be brought into a stirred state. Then, by setting this agitated state, the pattern surrounding the pattern formed on the substrate
-Propanol can be more efficiently replaced by liquefied carbon dioxide.

As a result, also in the third embodiment, as shown in FIG.
As shown in D, the silicon substrate 301 and the pattern 7
The area around 01a is filled with cooled liquefied carbon dioxide 704. Thereafter, the delivery pressure of liquefied carbon dioxide by the pump unit 304, the discharge amount of carbon dioxide from the reaction chamber 302 by the pressure control valve 307, the temperature control device 308, and the reaction chamber 30 by the substrate temperature control device 309.
The temperature inside 2 was adjusted, the pressure inside reaction chamber 302 was 8 MPa, and the temperature inside reaction chamber 302 was 35 ° C.

As a result, carbon dioxide in the reaction chamber 302 is in a supercritical state, and as shown in FIG. 7E, the silicon substrate 301 and the periphery of the pattern 701a are filled with supercritical carbon dioxide 705. And the reaction chamber 30
After putting carbon dioxide in 2 into a supercritical state, raise the temperature to 35 ° C.
The supercritical carbon dioxide in the reaction chamber 302 is discharged at a rate of 0.5 liter / min while being kept at
The internal pressure was reduced to vaporize the supercritical carbon dioxide and to dry it. As a result, as shown in FIG. 7F, the silicon substrate 301 on which the fine resist pattern 701a is formed.
However, it was possible to dry without pattern collapse.

The supercritical drying apparatus used for supercritical drying is not limited to the supercritical drying apparatus shown in FIGS. 3 and 6. For example, the supercritical drying device shown in FIG. 8 may be used. Briefly describing the configuration of the supercritical drying apparatus of FIG. 8, first, a substrate 802 is held in a reaction chamber 801, a liquefied carbon dioxide cylinder 803, a pump unit 804 and a heating means 805 connected in parallel and cooling. It is connected to the reaction chamber 801 via means 806. A discharge pipe 807 is also provided in the reaction chamber 801. A flow meter 808 and a pressure regulator 809 are connected to the discharge pipe 807. A valve 811 and a valve 812 are provided on the discharge side of the heating means 805 and the cooling means 806, and a cylinder 803 of the reaction chamber 801 is provided.
A valve 813 is provided on the side, and a valve 814 is provided on the discharge pipe 807 side of the reaction chamber 801. And
The reaction chamber 801 is provided with a temperature adjusting device 821 that controls the temperature inside the reaction chamber 801.

Further, in the supercritical drying of FIG. 8, as shown in FIG. 9, the supercritical carbon dioxide treated by the heating means 905 may be cooled by the cooling means 806 to be liquefied carbon dioxide. Note that, in FIG. 9, other parts indicated by the same reference numerals are the same as those in FIG. Further, as shown in FIG. 10, first, when introducing liquefied carbon dioxide into the reaction chamber 801, simply by pressurizing with the pump unit 804, the reaction chamber 8 remains liquefied carbon dioxide from the cylinder 803.
01. When supercritical carbon dioxide is introduced into the reaction chamber 801, the liquefied carbon dioxide is heated by the heating means 805, and the liquefied carbon dioxide is introduced into the reaction chamber 801 in a state where the liquefied carbon dioxide is likely to be in a supercritical state. And the pressure regulator 80
The liquefied carbon dioxide introduced may be brought into a state of supercritical carbon dioxide by adjusting the pressure in the reaction chamber 801 under the control of 8.

In the supercritical drying apparatus shown in FIG. 10, carbon dioxide which has been brought into a supercritical state by being heated by the heating means 805 is introduced and is introduced by adjusting the temperature in the reaction chamber 801 by the temperature adjusting device 821. Alternatively, supercritical carbon dioxide may be liquefied carbon dioxide. In this case, although the liquefaction takes time, the same effect as the above case can be obtained. Note that, also in FIG. 10, the other parts indicated by the same reference numerals are the same as those in FIG. The supercritical drying apparatus shown in FIGS. 8 to 10 may also be provided with a mechanism for controlling the temperature of the substrate to be processed to, for example, −5 ° C., such as the substrate temperature adjusting apparatus shown in FIG. 6. Further, as shown in FIG. 3, it goes without saying that a configuration for supplying another chemical solution into the reaction chamber may be added.

Further, in the above-mentioned first embodiment, the case where the silicon pattern is dried has been described as an example, but the present invention is not limited to this, and the same can be applied to a pattern of a compound semiconductor or the like. Further, the resist pattern is not limited to the resist pattern used in the second embodiment, and a pattern made of another polymer material can be applied. Moreover,
The supercritical fluid is not limited to carbon dioxide, and a nonpolar substance such as ethane or propane may be used.

[0050]

As described above, according to the present invention, the first step of exposing the pattern layer having a predetermined pattern formed on the substrate to alcohol, and the alcohol of the pattern layer after the first step. Second step of exposing the pattern layer to a liquid of a substance that is a gas in the atmosphere in the state where the liquid is attached, and after the second step, under the condition that the above substance keeps the liquid state. Third step of cooling the liquid of the substance, and then dissolving the alcohol liquid adhering to the pattern layer in the liquid of the substance to bring the liquid of the substance to the pattern layer And a fourth step after the third step to bring the above-mentioned substance adhering to the pattern layer into a supercritical state, and a supercritical state adhering to the pattern layer after the fourth step. And a fifth step of vaporizing the substance Was Unishi. According to the present invention, in the third step, since the liquid of the substance that is a gas in the atmosphere is cooled, the density of this substance is increased and the solubility of alcohol is improved. The liquid can be more efficiently replaced with the liquid, and the pattern collapse in the supercritical drying can be reduced as compared with the conventional case.

Further, in the present invention, the reaction chamber in which the substrate to be treated is placed and can be sealed, the means for supplying a substance that is a gas in the atmosphere into the reaction chamber, and the pressure in the reaction chamber is set to the above substance. At least a pressure control means for controlling the pressure to a supercritical state, a temperature control means for controlling the temperature in the reaction chamber to a predetermined temperature, and a substrate temperature control means for controlling the substrate to be processed to a predetermined temperature are provided. I did it.
As a result, the liquid of the substance can be cooled by cooling the substrate, and the liquid of the substance around the pattern layer to which alcohol is actually attached can be cooled more quickly. Therefore, the density of the substance that becomes the supercritical fluid in the region where the alcohol is actually replaced can be increased rapidly, and the solubility of the alcohol can be improved. Can be done more efficiently.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a supercritical drying method according to a first embodiment of the present invention.

FIG. 2 is a state diagram of carbon dioxide.

FIG. 3 is a configuration diagram showing a configuration of a supercritical drying apparatus used in an example of the present invention.

FIG. 4 is a process diagram illustrating a supercritical drying method in Example 1 of the present invention.

FIG. 5 is a process diagram that illustrates the supercritical drying method in Example 1 of the present invention, following FIG.

FIG. 6 is a configuration diagram showing another configuration of the supercritical drying apparatus used in the example of the present invention.

FIG. 7 is a process diagram illustrating a supercritical drying method in Example 2 of the present invention.

FIG. 8 is a configuration diagram showing another configuration of the supercritical drying apparatus used in the example of the present invention.

FIG. 9 is a configuration diagram showing another configuration of the supercritical drying apparatus used in the example of the present invention.

FIG. 10 is a configuration diagram showing another configuration of the supercritical drying apparatus used in the example of the present invention.

FIG. 11 is a cross-sectional view showing a pattern collapse state of a fine pattern.

FIG. 12 is a cross-sectional view showing a state in which a rinse liquid is present between fine patterns.

[Explanation of symbols]

101 ... Substrate, 101a ... Pattern, 102 ... Water, 10
3 ... Ethanol, 104 ... Liquefied carbon dioxide, 105 ... Supercritical carbon dioxide.

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/304 651 B08B 3/08 B08B 3/10 F26B 9/06 F26B 21/14

Claims (9)

(57) [Claims] 1. A first step of exposing a pattern layer having a predetermined pattern formed on a substrate to alcohol, and a state in which the alcohol liquid adheres to the pattern layer after the first step. In the second step, the pattern layer is exposed to a liquid of a substance that is a gas in the atmosphere, and after the second step, the liquid of the substance is cooled under the condition that the substance remains in the liquid state. From the above, the third step of dissolving the alcohol liquid adhering to the pattern layer in the liquid of the substance to bring the liquid of the substance adhered to the pattern layer, Then, a fourth step of bringing the substance attached to the pattern layer into a supercritical state, and a fifth step of vaporizing the substance in the supercritical state attached to the pattern layer after the fourth step. Having at least a process Supercritical drying method characterized. 2. The supercritical drying method according to claim 1, wherein in the third step, the temperature of the liquid of the substance is lowered, and then the substance is added to the liquid under the condition of maintaining the liquid state. A supercritical drying method characterized by varying the pressure. 3. The supercritical drying method according to claim 1, wherein in the second step, the liquid of the substance is cooled by cooling the substrate. 4. The supercritical drying method according to claim 1, wherein the substance is carbon dioxide. 5. The supercritical drying method according to claim 4, wherein in the second step, the liquid of the substance is cooled to 10 ° C. or lower. 6. The supercritical drying method according to claim 1, wherein all of the steps are performed in the same container. 7. The supercritical drying method according to claim 1, wherein the supercritical state includes a subcritical state. 8. A reaction chamber in which a substrate to be processed is placed and can be hermetically sealed, a means for supplying a substance that is a gas in an atmospheric atmosphere into the reaction chamber, and a pressure in the reaction chamber where the substance is supercritical. At least a pressure control means for controlling the pressure to reach a state, a temperature control means for controlling the temperature in the reaction chamber to a predetermined temperature, and a substrate temperature control means for controlling the substrate to be processed to a predetermined temperature. A supercritical drying device characterized in that 9. The supercritical drying apparatus according to claim 8, wherein the supercritical state includes a subcritical state.