JP2006066698A - Drying method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method that allows a super-critical process to be conducted after a liquid process for drying with pattern deformation suppressed. <P>SOLUTION: A transfer tray 103 is raised from a secondary treatment tank 102, the transfer tray 103 is filled with washing water 104, and then a board 111 is soaked into the above washing water 104. Next, isopropanol is poured into the above transfer tray 103 to replace washing water 104 in the transfer tray 103 with isopropanol, and then the transfer tray 103 is filled with isopropanol 105 so that the board 111 can be soaked in the isopropanol 105. Then, the transfer tray is accommodated in the reaction chamber of the super-critical process equipment 106. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drying method and apparatus for suppressing deformation such as collapse of a fine pattern due to surface tension of a liquid during drying after treatment with the liquid.

As is well known, in order to manufacture a large-scale and high-performance device such as an LSI, an extremely fine pattern is required. This ultrafine pattern is, for example, a resist pattern that is formed by exposure, development, and rinsing, and that has photosensitivity to light, X-rays, or electron beams.
For example, a resist pattern is formed by exposing light or an electron beam to a resist layer formed on a substrate through a mask original plate provided with a mask pattern arranged based on a designed circuit.

  In the next-generation exposure technology using X-rays or the like, a stencil-type silicon mask having a structure in which an exposure transmission portion penetrates is used as a mask original plate. In the manufacture of a stencil-type silicon mask, a silicon oxide substrate having a silicon layer on the surface is used, and a pattern penetrating the silicon layer is formed in the exposure region provided in the center of the substrate, and then the silicon oxide substrate in the exposure region is formed. Etching is removed with hydrofluoric acid.

  On the other hand, in recent years, MEMS (Micro Electro Mechanical System), which combines a fine movable structure (micro machine) and electrical elements, has been actively researched and developed. It's being used. For example, using a SOI (Silicon on Insulator) substrate, a resist pattern is formed on the SOI layer on the buried insulating layer, and the SOI layer is etched using the formed resist pattern as a mask to form a silicon pattern. By removing the predetermined region buried insulating layer under the formed silicon pattern, a silicon pattern serving as a movable microphone machine is formed.

In these pattern formations, after selective etching using a resist pattern as a mask, liquid treatment with water or chemicals is performed.
For example, the resist pattern is removed by, for example, dissolving the resist pattern with a chemical solution, and then a cleaning process such as water washing is performed to remove the chemical solution from the top of the substrate. Then, treatment with a chemical such as hydrofluoric acid is performed.

  A major problem during drying in the formation of such a fine pattern is the collapse of the pattern. At the time of drying after the treatment with the liquid, a bending force (capillary force) works due to a pressure difference between the liquid remaining between the formed patterns and the external air. As a result, pattern collapse occurs. 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 liquid and gas between patterns (see Non-Patent Document 1).

The surface tension of water is as large as about 72 × 10 ⁻³ N / m, and the above-described capillary force has a force to distort a stronger pattern such as silicon which is an inorganic material. For this reason, the problem of surface tension due to the liquid during the drying process is important.
As a technique for solving this problem, there has been proposed a technique for solving problems such as pattern collapse by using a fluid in a supercritical state and drying after the surface tension does not act (Patent Document 1, Patent Document 1). 2, 3, see Non-Patent Document 2).

  A fluid in a supercritical state (supercritical fluid) is a substance at a temperature and pressure exceeding the critical temperature and pressure, and has a dissolving power close to that of a liquid, but tension and viscosity exhibit properties close to a gas. It can be said that the liquid is kept in a gaseous state. Since the supercritical fluid having such characteristics does not form an interface between the liquid and the gas, the surface tension becomes zero. Therefore, if it is dried in a supercritical state, the concept of surface tension is eliminated, and pattern collapse is eliminated.

  A supercritical fluid has both gas diffusivity and liquid solubility (high density), and can change state from liquid to gas without an equilibrium line. For this reason, if this supercritical fluid is gradually released from the state filled with the supercritical fluid, the interface between the liquid and gas will not be formed, so the surface is dried without applying surface tension to the ultrafine pattern to be dried. be able to.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
Japanese Patent Publication No. 1-220828 Japanese Patent Publication No. 1-170026 JP 2001-176837 A Applied Physics Letters, 66, 2655-2657, 1995 Proceedings of the 44th Joint Conference on Applied Physics, p778, Spring 1997

However, even when the supercritical drying method is used, for example, any movable pattern having an aspect ratio of 10 or more due to silicon may be deformed such as sticking to the substrate side.
For example, as shown in FIG. 4, an SOI substrate including a silicon layer 403 having a thickness of 1 μm is prepared on a silicon substrate 401 via a silicon oxide layer 402 having a thickness of 1 μm. A resist pattern is formed using photolithography technology, the silicon layer 403 is processed by dry etching using chlorine gas plasma using the resist pattern as a mask, and the silicon oxide layer 402 is penetrated over the pattern region of the silicon substrate 401. A silicon pattern having an opening to be formed is formed.

  Next, as shown in FIG. 4A, the silicon substrate 401 is immersed in the buffered hydrofluoric acid solution 430 accommodated in the container 450, and the silicon oxide layer 402 in the pattern region is removed by etching with the buffered hydrofluoric acid solution. 4A, the movable pattern 413 is formed on the silicon substrate 401. As shown in FIG.

Next, water is added to the container 450 to wash the silicon substrate 401 in a state where the water 431 is accommodated. Thereafter, the silicon substrate 401 is pulled up from the water 431 and the pulled silicon substrate is subjected to predetermined supercritical processing. It is carried into the apparatus, washed with alcohol inside the apparatus, and carbon dioxide is introduced almost simultaneously to perform known supercritical drying.
Even when the supercritical drying is performed in this way, as shown in FIG. 4B ′, the movable pattern 413 having an aspect ratio of 10 or more is deformed such as sticking to the substrate 401 side.

  Since the surface of silicon on which hydrofluoric acid has acted is in a hydrophobic state, the aqueous solution is very easily repelled on the surface of the formed silicon pattern. In such a state, the aqueous solution tends to decrease in a short time after the liquid treatment, and as described above, pattern deformation due to surface tension such as pattern sticking is likely to occur before performing the supercritical treatment. It becomes a state. In this way, when the pattern portion to be suppressed in deformation is in a state where it is easily dried, in the conventional technique, the pattern deformation occurs before the supercritical drying process is performed.

  The present invention has been made to solve the above-described problems, and allows a drying process to be performed by performing a supercritical process subsequent to a liquid process in a state where pattern deformation is suppressed. For the purpose.

The drying method according to the present invention includes a first step in which a substrate on which a predetermined pattern is formed is immersed in a liquid stored in a processing tank, and a substrate in the liquid stored in the processing tank. A second step of bringing the transfer tray into a state accommodated in the transfer tray, and a third step of pulling up the transfer tray from the liquid accommodated in the processing tank while the liquid in which the substrate is immersed in the transfer tray is accommodated. The substrate and the pattern are supercritical by bringing the transfer tray containing the liquid in which the substrate is immersed into the reaction chamber of the supercritical processing apparatus and by filling the reaction chamber with the supercritical fluid. At least a fifth step for immersing the fluid in a fluid and a sixth step for vaporizing the supercritical fluid in the reaction chamber are provided.
Accordingly, the substrate is kept immersed in the liquid until it is accommodated in the reaction chamber of the supercritical processing apparatus from the processing tank.

In the drying method, in the fifth step, after the liquid of the substance constituting the supercritical fluid is filled in the reaction chamber, the liquid of the filled substance is used as the supercritical fluid, so that the reaction chamber is a supercritical fluid. You may make it be the state filled.
In the above drying method, after the third step, another liquid having compatibility with the substance constituting the supercritical fluid is introduced into the transfer tray to replace the liquid with the other liquid, and the substrate is immersed in the other liquid. The fifth step may be performed after the state has been achieved.
The substance constituting the supercritical fluid may be carbon dioxide.

  In addition, the drying apparatus according to the present invention stores a liquid in which a substrate on which a predetermined pattern is formed is immersed, and stores the substrate in the liquid stored in the processing tank, and also stores the substrate in the processing tank. The transfer tray that accommodates and pulls up the liquid in which the substrate is immersed and the transfer tray that stores the liquid in which the substrate is immersed are carried in from the liquid that is immersed, and the supercritical fluid is introduced, and the introduced supercritical fluid And a supercritical processing apparatus having a reaction chamber for vaporizing the water.

  As described above, according to the present invention, by transferring the substrate to be processed using the transfer tray, the substrate is immersed in the liquid until it is accommodated in the reaction chamber of the supercritical processing apparatus from the processing tank. Therefore, an excellent effect is obtained in that a drying process in which a supercritical process is performed subsequent to the liquid process can be performed in a state in which the deformation of the pattern is suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, liquid treatment using water and an aqueous solution is described as an example, but the present invention is not limited to this, and can be applied to drying after other liquid treatment.
FIG. 1 is a process diagram for explaining an example of a drying method according to an embodiment of the present invention. First, as shown in FIG. 1A, a substrate 111 having a silicon layer 113 with a thickness of about 1 μm on a buried insulating layer 112 with a thickness of about 1 μm is prepared.

  Next, a resist pattern (not shown) having a width of 0.5 to 1 μm is formed on the silicon layer 113 by a known photolithography technique, and the silicon layer 113 is processed by dry etching with chlorine gas using the resist pattern as a mask. A silicon pattern 114 is formed on the buried insulating layer 112.

  Next, after removing the resist pattern by ashing treatment using oxygen plasma, a part of the buried insulating layer 112 is etched away with a buffered hydrofluoric acid aqueous solution contained in a predetermined treatment tank. A part of the buried insulating layer 112 at the lower part is removed by etching, and a space is formed below the silicon pattern 114.

  Next, as shown in FIG. 1A, the substrate 111 is immersed in the cleaning water 104 accommodated in the processing tank 101 including the sub-processing tank 102. For example, the above-described buffered hydrofluoric acid aqueous solution is accommodated in the treatment tank 101, and the washing water 104 is introduced into the treatment tank 101 from the state in which the substrate 111 is immersed in the buffered hydrofluoric acid aqueous solution. By replacing with 104, the state shown in FIG. At this time, the silicon pattern 114 formed on the substrate 111 is also immersed in the cleaning water 104 as shown in FIG.

Next, as shown in FIG. 1B, the substrate 111 is transferred to the sub-treatment tank 102 in the cleaning water 104 through the portion where the treatment tank 101 and the sub-treatment tank 102 are communicated. As shown in (c), the substrate 111 is accommodated in the transfer tray 103 submerged in the cleaning water 104 of the sub-treatment tank 102. For example, the substrate 111 may be transferred in the cleaning water 104 by holding and transferring the substrate 111 by the transfer arm 201 as shown in FIG.
As described above, the substrate 111 is immersed in the cleaning water 104 accommodated in the transfer tray 103.

Next, the transfer tray 103 is pulled up from the sub-treatment tank 102, and the cleaning water 104 is accommodated in the transfer tray 103 and the substrate 111 is immersed in the cleaning water 104 as shown in FIG. . Here, a part of the cleaning water 104 accommodated over the processing tank 101 and the sub-processing tank 102 may be discharged to lower the liquid level, so that the transfer tray 103 can be easily pulled up in the sub-processing tank 102.
In these processes, the substrate 111 is always immersed in the liquid.

  Next, for example, isopropyl alcohol is introduced into the transfer tray 103, and the washing water 104 stored in the transfer tray 103 is replaced with isopropyl alcohol. As shown in FIG. The alcohol 105 is accommodated, and the substrate 111 is immersed in the isopropyl alcohol 105. As a result, the silicon pattern 114 formed on the substrate 111 is also immersed in the isopropyl alcohol 105 as shown in FIG.

  Next, as shown in FIG. 1 (f), the transfer tray 103 is accommodated in the reaction chamber of the supercritical processing apparatus 106 having a predetermined reaction chamber that is sealed and held at a constant volume. Then, the liquefied carbon dioxide 107 is pumped into the reaction chamber of the supercritical processing device 106 so that the reaction chamber of the supercritical processing device 106 is filled with the liquefied carbon dioxide 107. Accordingly, as shown in FIG. 1 (f ′), the vicinity of the surface of the substrate 111 on which the silicon pattern 114 is formed is immersed in isopropyl alcohol 105, and these are immersed in liquefied carbon dioxide 107. Become.

  When the above-described state is maintained for a predetermined time, the isopropyl alcohol inside the transfer tray 103 is replaced with liquefied carbon dioxide, the isopropyl alcohol on the surface of the substrate 111 is replaced with liquefied carbon dioxide, and the substrate 111 is placed in the liquefied carbon dioxide. It will be in the state immersed. Further, the silicon pattern 114 portion of the substrate 111 is also immersed in the liquefied carbon dioxide.

  Next, by setting the critical condition of carbon dioxide, the liquefied carbon dioxide charged in the reaction chamber of the supercritical processing device 106 is changed to a supercritical state, and as shown in FIG. The reaction chamber of the apparatus 106 is filled with supercritical carbon dioxide 108. As a result, the substrate 111 and the silicon pattern 114 on the surface of the substrate 111 including the inside of the transfer tray 103 are immersed in the supercritical carbon dioxide 108 as shown in FIG.

  Next, if the pressure inside the reaction chamber of the supercritical processing device 106 is reduced to vaporize and discharge the supercritical carbon dioxide 108, as shown in FIG. Is a gas (air) atmosphere. As a result, as shown in FIG. 1 (h ′), the supercritical drying of the substrate 111 is completed in a state where the silicon pattern 114 is not deformed. Instead of liquefied carbon dioxide, supercritical carbon dioxide may be introduced to replace isopropyl alcohol with supercritical carbon dioxide.

  According to the drying method described above, the substrate 111 is always immersed in the liquid from the state shown in FIG. 1A to the state shown in FIG. 1F. Finally, the substrate 111 is liquefied. This liquefied carbon dioxide is brought into a supercritical state from the state immersed in carbon dioxide. Accordingly, the surface of the substrate 111 does not become dry or close to the state until the supercritical drying is completed from the state shown in FIG.

  For example, the supercritical processing apparatus 106 may be configured as shown in FIG. The supercritical processing apparatus shown in FIG. 3 is an apparatus that pumps liquefied carbon dioxide sealed in a cylinder 303 into a reaction chamber 302 in a sealable container 301 by a pump pump 304. In this apparatus, by opening the valve 305 on the liquefied carbon dioxide introduction side, liquefied carbon dioxide is introduced into the container 301, liquefied carbon dioxide is discharged from the tip of the inlet 306 communicating with the valve 305, and the reaction chamber 302. Liquefied carbon dioxide is injected onto the substrate 311 placed on the inner stage 312.

  At this time, for example, the liquefied carbon dioxide in the cylinder 303 is pumped into the reaction chamber 302 by the pump pump 304, and the opening degree of the valve 307 on the discharge side is adjusted in this state, and the liquefied carbon dioxide discharged from the discharge port 309 The pressure in the reaction chamber 302 is controlled by limiting the amount of. If, for example, an automatic pressure valve is used for the valve 307 on the discharge side, the above pressure control is possible.

  In the apparatus shown in FIG. 3, the vessel 301 is heated to, for example, about 31 ° C. by the heater 313 while liquefied carbon dioxide is being injected onto the substrate through the introduction port 306, and the pressure in the reaction chamber 302 is reduced. When the pressure is 7.5 MPa or more, the liquefied carbon dioxide injected onto the substrate 311 in the reaction chamber 302 can be brought into a supercritical state.

  The pressure in the reaction chamber 302 can be increased by, for example, increasing the pumping amount by the pumping pump 304 and adjusting the valve 307 to reduce the amount of liquefied carbon dioxide discharged from the reaction chamber 302. . Thereafter, the valve 305 is closed and the valve 307 is opened, the pressure in the reaction chamber 302 is lowered, and the supercritical carbon dioxide injected into the reaction chamber 302 is vaporized to complete supercritical drying. It becomes a state.

  By the way, although the example which processes the one board | substrate 111 in the processing tank 101 was shown above, it is not restricted to this, You may make it process a several board | substrate in the processing tank 101. FIG. For example, when the embedded insulating layer 112 is etched from the buffered hydrofluoric acid aqueous solution in the processing bath 101, the etching with the buffered hydrofluoric acid aqueous solution requires one hour or more, so it is more efficient to process a plurality of substrates simultaneously. It is. The liquid processing in the processing tank 101 may be batch-processed in a state where a plurality of substrates are accommodated in a predetermined substrate carrier, and the single wafer processing is performed in a state where a single substrate is accommodated in a predetermined tray. You may make it do.

Further, in the above description, the cleaning water 104 is replaced with isopropyl alcohol 105, but the present invention is not limited to this, and may be replaced with other alcohols, and may be a hydrocarbon, a fluorinated compound, a silicon compound, or the like. A liquid having affinity (compatibility) with carbon dioxide may be used. By using a liquid having affinity for liquefied carbon dioxide, substitution with liquefied carbon dioxide can be performed more quickly.
In the above description, carbon dioxide is in a supercritical state. However, the present invention is not limited to this, and other critical substances may be used. At this time, supercritical drying may be performed with the liquid replacing the washing water 104 in a supercritical state in the reaction chamber.

  For example, in the stage shown in FIG. 1 (e), fluorinated ether is used instead of isopropyl alcohol 105, the washing water 104 stored in the transfer tray 103 is replaced with fluorinated ether, and the transfer tray 103 is fluorinated. Ether is accommodated and the substrate 111 is immersed in the fluorinated ether. As a result, the silicon pattern 114 formed on the substrate 111 is also immersed in the fluorinated ether.

  Next, the transfer tray 103 is accommodated in the reaction chamber of the supercritical processing device 106, and the fluorinated ether stored in the transfer tray 103 is heated in the sealed reaction chamber of the supercritical processing device 106. Then, the fluorinated ether is brought into a supercritical state, and the surface of the substrate 111 and the silicon pattern 114 are covered with the supercritical fluid of fluorinated ether in the sealed reaction chamber.

  The pressure inside the reaction chamber, which is sealed and has a constant volume, can be made the critical pressure of the fluorinated ether by increasing the gas of the fluorinated ether that is heated and vaporized. If heated to a critical temperature or higher in a critical pressure state, the fluorinated ether becomes a supercritical state. In this case, the subcritical state is included.

  Next, if the pressure inside the reaction chamber of the supercritical processing apparatus 106 is reduced to vaporize and discharge the supercritical fluorinated ether, the inside of the reaction chamber becomes a gas (air) atmosphere. As a result, the supercritical drying of the substrate 111 is completed in a state where the silicon pattern 114 is not deformed.

In the above description, the silicon pattern treated with hydrofluoric acid has been described as an example. However, the scope of the present invention is not limited to this, and it is needless to say that the present invention can be applied to other fine processing techniques.
For example, the present invention can also be applied when an ArF resist pattern is formed on a semiconductor substrate such as silicon.

Hereinafter, the formation of an ArF resist pattern will be described as an example. First, a 200 nm thick ArF resist film formed on a substrate is exposed using a known photolithography technique to form a latent image.
Next, tetramethylammonium hydride developer is accommodated in the processing tank 101 (sub-processing tank 102) shown in FIG. 1, and the ArF resist film on which the latent image is formed is developed for 1 minute to form a pattern. State.

Next, the cleaning water 104 is introduced into the processing tank 101, and the developer is replaced with the cleaning water 104, whereby the state shown in FIG.
Thereafter, in the same manner as described above, if the tray 103 is pulled up → substitute with isopropyl alcohol → supercritical drying with carbon dioxide, a resist pattern with a width of 90 nm can be formed without deformation such as sticking.

  By the way, when the pattern to be processed is made of silicon, the cleaning water 104 may contain ozone. When ozone is contained in the cleaning water 104, when the substrate or pattern to be processed is silicon, these surfaces are oxidized and the hydrophobic state is relaxed, so that the wettability of the surface is improved and the surface is dried. It becomes difficult. For example, ozone can be contained in the cleaning water by supplying the liquid as bubbles. Moreover, it can also be set as the state in which ozone was contained in washing water through the osmosis membrane. The ozone concentration in the wash water may be about 1 to several ppm. Further, the cleaning water containing ozone may be irradiated with ultraviolet rays to convert ozone into an active acid to improve the oxidation efficiency.

It is process drawing for demonstrating the example of the drying method in embodiment of this invention. It is typical sectional drawing which shows the structural example of a conveyance arm. It is typical sectional drawing which shows the structure of a supercritical drying apparatus. It is process drawing for demonstrating the conventional supercritical drying method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Processing tank, 102 ... Sub-processing tank, 103 ... Transfer tray, 104 ... Washing water, 105 ... Isopropyl alcohol, 106 ... Supercritical processing apparatus, 107 ... Liquefied carbon dioxide, 108 ... Supercritical carbon dioxide, 111 ... Substrate, 112 ... Embedded insulating layer, 113 ... Silicon layer, 114 ... Silicon pattern.

Claims (5)

A first step in which a substrate on which a predetermined pattern is formed is immersed in a liquid stored in a processing tank;
A second step in which the substrate is accommodated in a transfer tray in the liquid accommodated in the treatment tank;
A third step of pulling up the transfer tray from the liquid stored in the processing tank in a state where the liquid in which the substrate is immersed in the transfer tray is stored;
A fourth step of carrying the transfer tray containing the liquid in which the substrate is immersed into a reaction chamber of a supercritical processing apparatus;
A fifth step in which the reaction chamber is filled with a supercritical fluid so that the substrate and the pattern are immersed in the supercritical fluid;
And a sixth step of vaporizing the supercritical fluid in the reaction chamber. The drying method according to claim 1,
In the fifth step, after the substance liquid constituting the supercritical fluid is filled in the reaction chamber, the filled substance liquid is used as a supercritical fluid, so that the reaction chamber contains the supercritical fluid. A drying method characterized by being filled with. The drying method according to claim 1 or 2,
After the third step, another liquid having compatibility with the substance constituting the supercritical fluid is introduced into the transfer tray to replace the liquid with the other liquid, and the substrate is immersed in the other liquid. The drying method is characterized in that the fifth step is performed after the state is achieved. In the drying method of any one of Claims 1-3,
A drying method, wherein the substance constituting the supercritical fluid is carbon dioxide. A treatment tank containing a liquid in which a substrate on which a predetermined pattern is formed is immersed;
A transfer tray that accommodates and pulls up the liquid in which the substrate is immersed from the liquid that is accommodated in the treatment tank, while accommodating the substrate in the liquid that is accommodated in the treatment tank,
And a supercritical processing apparatus having a reaction chamber into which the transfer tray containing the liquid in which the substrate is immersed is loaded, a supercritical fluid is introduced, and the introduced supercritical fluid is vaporized. Drying equipment to do.

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