JP2005286105A - Fine structure drying method and apparatus thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fine structure drying method for protecting drying during transportation, preventing pattern errors on a large substrate with fine patterns formed on the surface, and drying the substrate at short time; and to provide an apparatus for implementing the method. <P>SOLUTION: An object having a fine structure soaked in or damped with rinsing liquid is placed in a high-pressure treatment vessel, and the above rinsing liquid on the above dried object is exhausted from the above high-pressure treatment vessel through the use of liquid that turns gas under normal temperature and normal pressure and turns liquid under high pressure. The drying method has a process for introducing the above liquid to the above high-pressure treatment vessel, a process for exhausting the above introduced liquid from the above high-pressure treatment vessel, and a process for repeating the above two processes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel fine structure drying method and apparatus for drying fine structures such as semiconductor integrated circuit (LSI) resist patterns and MEMS (Micro Electromechanical System) elements with a liquefied gas.

  Conventionally, in order to manufacture a large-scale, high-density, high-performance device, a resist formed on a silicon wafer is exposed, developed, rinsed and dried to form a pattern, and then coated, etched, and rinsed. It is manufactured through a process such as drying. In particular, the resist is a polymer material that is sensitive to light, X-rays, electron beams, etc., and in each process, a chemical solution such as a developer or a rinse solution is used in the development and rinse cleaning process, so the rinse cleaning process After that, a rinsing liquid drying step is essential.

In this drying process, when the space width between the resist patterns formed on the substrate is about 100 nm or less, the surface tension of the chemical solution remaining between the patterns causes Laplace force (capillary force) to act between the patterns, resulting in pattern collapse. The problem that occurs occurs. On the other hand, for example, the manufacture of a MEMS part of a three-dimensional microstructure part having a movable part such as an acceleration sensor or an actuator includes a process of forming a microstructure including a movable part with an etchant such as hydrofluoric acid, and etching by pure water rinsing. It includes a liquid washing and removing step and a subsequent drying step. In this drying process as well as the resist pattern, the surface tension due to the chemical remaining between the microstructures acts,
There is a phenomenon in which the movable part sticks to the substrate. In order to prevent pattern collapse and sticking due to the action of the surface tension of the chemical solution remaining between the fine structures, a drying process for reducing the surface tension acting between the fine structures is performed according to a predetermined process shown in Patent Documents 1 to 3. There is a method using a supercritical fluid such as carbon dioxide using a pressure vessel.

A conventional drying method using a supercritical fluid such as carbon dioxide has the following basic steps.
(1) Residual liquid such as water in a sample that is not soluble in a liquid or a fluid in a supercritical state is replaced with a rinsing liquid such as an organic solvent or a mixed liquid thereof such as ethanol or 2-propanol that is soluble in a fluid in advance. The process to keep.
(2) A step of horizontally transporting and setting in a high-pressure container serving as a drying chamber in a state dipped or wetted in the rinse liquid, specifically, a condition in which the rinse liquid is placed on the substrate.
(3) A step of sealing the high-pressure vessel.
(4) A step of introducing a fluid in a liquid state or a supercritical state into a high-pressure vessel and increasing the pressure to a predetermined pressure.
(5) A step of replacing the liquid or supercritical fluid introduced into the high-pressure vessel with the rinse liquid.
(6) A step of increasing the pressure and raising the temperature of the high-pressure vessel to a critical point or more after replacing the liquid fluid and the rinsing liquid when a liquid fluid is introduced into the high-pressure vessel.
(7) A step of gradually discharging the supercritical fluid from the high-pressure vessel.
(8) A step of taking out the substrate from the high-pressure vessel.

JP 2003-109933 A JP-A-9-139374 JP-A-5-315241

  As described above, the resist pattern formation is performed through the steps of exposure, development, rinsing and drying. In pattern drying of a fine structure having a high aspect ratio, pattern collapse occurs due to the surface tension of the rinsing liquid. The supercritical drying method for improving this can prevent collapse of the fine structure by bringing the liquefied gas into a supercritical state and reducing the surface tension to zero. However, since the conveyance to the pressure vessel passes through the atmosphere after the rinsing process, the pattern collapses due to the drying of the surface. Moreover, the conventional drying method using a supercritical fluid requires a drying time of about several tens of minutes to 1 hour or more, especially for a fine structure uniformly formed on a large-diameter substrate having a diameter of 100 mm or more. There was no pattern collapse and uniform drying was not possible. Thus, as a method for improving the drying during the conveyance, there is a method of conveying the fine structure in a state of being immersed in the rinsing liquid, but the replacement time of the rinsing liquid and the liquefied gas becomes long. In addition, since the supercritical drying treatment apparatus uses supercritical carbon dioxide at a high pressure, it takes time to discharge, and throughput is a problem.

  The object of the present invention is to prevent drying during transportation by covering with a sufficient rinsing liquid, and to dry uniformly in a short time without pattern collapse on a large-diameter substrate having a fine pattern formed on the surface. It is an object of the present invention to provide a fine structure drying method and an apparatus thereof.

  The present invention covers the fine structure surface of the material to be dried, which is a fine structure, from the time of conveyance with the minimum required rinse liquid when transported to a high-pressure container after the rinse treatment, and further replaces the rinse liquid with liquefied carbon dioxide gas. Occasionally, vibration is generated using open / close valves before and after the high-pressure vessel to perform efficient replacement, and then the microstructure is dried at a critical temperature state.

  That is, the present invention includes a transporting process for transporting an object to be dried, the surface of which is covered with a rinsing liquid, into a high-pressure container, and a fluid that is a gas at normal temperature and normal pressure and a liquid that is liquid at high pressure in the high-pressure container. A step of introducing a liquid or a supercritical state up to a set pressure; a step of raising the temperature of the fluid above a critical temperature while maintaining the set pressure of the fluid; and a discharge of the fluid while maintaining the critical temperature state And a step of sequentially performing introduction and discharge of the fluid into the high-pressure vessel, and applying vibration to the fluid.

  The present invention prevents the to-be-dried material from being dried during transportation by having the above-mentioned transporting step for transporting the to-be-dried material, which is covered with the minimum required rinse liquid and installed on the ring-shaped installation table, into the pressure vessel. can do.

  After the installation base is installed in the high-pressure vessel, the fluid in a liquid state is introduced to replace the rinse liquid. Here, in order to efficiently replace the rinsing liquid remaining between the fine structures, first, the pressure and temperature of the fluid are adjusted, and the liquid level of the fluid is further set to be higher than that of the object to be dried installed in the sample holder. Slightly increase. From the above state, the fluid in the high-pressure vessel is vibrated by repeatedly introducing and discharging using the valves arranged before and after in the high-pressure vessel. By this vibration, the rinse liquid remaining between the fine structures can be efficiently replaced.

  After the rinsing liquid is replaced, the temperature controller raises the temperature of the fluid in the liquid state to make it a supercritical state. After making the supercritical fluid, the supercritical fluid is discharged to atmospheric pressure while maintaining the temperature above the critical temperature. Thereafter, the temperature in the high-pressure vessel is set to room temperature and drying is completed.

  In addition, the present invention provides an object to be dried having a fine structure immersed or wet in a rinsing liquid on an installation table in a high-pressure processing container, and the rinsing liquid on the object to be dried is a gas at normal temperature and normal pressure. In the fine structure drying apparatus for discharging from the high-pressure processing container using a fluid that becomes liquid under high pressure, the installation table has a structure in which the rinse liquid is held on the object to be dried, and the liquid The bottom of the fluid supply port and the discharge port has a position equivalent to the height of the installation table.

  According to the present invention, it is possible to prevent drying during conveyance by covering with a sufficient rinsing liquid, and to dry uniformly in a short time without pattern collapse on a large-diameter substrate having a fine pattern formed on the surface. It is possible to provide a fine structure drying method and apparatus capable of performing the same.

  FIG. 1 is a cross-sectional view showing an example of the fine structure drying apparatus of the present invention. The high-pressure vessel 4 that is a drying processing chamber is composed of an upper lid 12 and a lower vessel 6, and the lid 12 is opened to place a wafer 9 that is an object to be dried on a wafer holder 5 that is an installation table. A fine structure is formed on the surface of the wafer 9 through development and rinsing steps after exposure, and a rinse liquid 8 is placed on the surface of the wafer 9 and has a ring-shaped flat plate formed at the bottom of the cylinder. It is installed in the wafer holder 5. The wafer holder 5 on which the wafer 9 is mounted is transferred into the high-pressure vessel 4.

  A high-pressure pump 14 and a liquefied carbon dioxide container 15 are connected to the high-pressure vessel 4 via an opening / closing valve 1, and a pressure control valve 13 is connected to the high-pressure vessel 4 via an opening / closing valve 1. In the lower container 6 of the high-pressure vessel 4, a discharge port 16 provided at the bottom and a discharge port 17 provided at a position equivalent to the height of the wafer 9 are connected to the pressure control valve 2 via the open / close valves 16, 17. When the pressure in the high pressure vessel 4 exceeds the set pressure, the fluid or rinse liquid in the high pressure vessel 4 is discharged. In particular, the rinsing liquid 8 opens at the discharge port 16 when the rinsing liquid 8 is heavier than the liquefied carbon dioxide gas 11, and opens the valve 19 at the discharge port 17 when the rinsing liquid 8 is lighter than the liquefied carbon dioxide gas 11. And discharged from each outlet. The bottom height of the introduction port and the discharge port 17 for the liquid carbon dioxide gas 11 is provided at an equivalent position slightly higher than the height of the surface of the wafer 9 installed in the high-pressure vessel 4.

  In the present embodiment, the high-pressure vessel 4 has a structure in which a heating medium or a cooling medium can be circulated so as to be heated or cooled formed in the high-pressure vessel 4 itself, has a temperature adjustment function, and in the range of 0 to 60 ° C. The temperature of the fluid can be controlled. Filter 7 for removing solid matter in the liquefied carbon dioxide gas 11 between the on-off valve 1 and the high-pressure vessel 4, a high-pressure pump 14 for pumping it to the high-pressure vessel 4, and temperature adjustment capable of controlling the temperature of the wafer 9 locally or entirely. A container 10. The temperature regulator 10 is entirely disc-shaped so that the temperature of the wafer 9 can be locally or entirely controlled, and the heating body is formed so as to be independently controllable radially around the circle. Hereinafter, the drying process of a present Example is demonstrated.

(1) An EB resist (ZEP-7000: manufactured by Nippon Zeon Co., Ltd.) with a film thickness of 220 nm is formed on an LSI silicon substrate (wafer 9) having a diameter of 200 mm, dried, and after drawing a pattern with an electron beam, an acetate acetate The wafer 9 having a fine structure formed on the surface after being developed with ruhexyl for 90 seconds and rinsed with 2-propanol for 100 seconds is placed in the wafer holder 5 of the high-pressure vessel 4. As shown in FIG. 1, a rinse solution 8 of 2-propanol soluble in liquid carbon dioxide or supercritical carbon dioxide covers the entire surface of the wafer 9 while being held by the wafer holder 5 on the wafer 9.

(2) As shown in FIG. 1, the wafer 9 is covered with a rinsing liquid 8 supported by a ring-shaped wafer holder 5. The upper lid 12 of the high-pressure vessel 4 is opened, and the wafer 9 is transferred into the high-pressure vessel 4. Is done. The wafer holder 5 has a cylindrical shape, and the bottom portion has a ring shape with a flat plate. The height of the cylindrical portion is slightly higher than the surface of the wafer 9 so that the rinse liquid is sufficiently held on the wafer 9. It is configured as follows. The wafer 9 having a fine structure such as a resist pattern is in close contact with and in contact with the ring-shaped bottom portion of the wafer holder 5, so that the rinse liquid 8 is kept on the wafer 9. The bottom of the wafer holder 5 is a ring shape with a flat plate, but has a planar shape that does not leak the rinse liquid 8 in accordance with the planar shape of the wafer 9. The planar shape of the wafer 9 is a disk, and a straight portion orientation flat or V-notch is formed in a part of the circumferential portion thereof, so that the rinsing liquid 8 does not leak in accordance with these shapes. .

(3) After the wafer holder 5 is installed in the high-pressure vessel 4, the lid 12 of the high-pressure vessel 4 is closed and sealed. After the high-pressure vessel 4 is sealed, the valve 1 is opened and liquid carbon dioxide 11 is introduced from the liquid carbon dioxide vessel 15. The pressure and temperature in the high-pressure vessel are controlled, and the liquid carbon dioxide 11 is introduced so that the liquid carbon dioxide is slightly higher than the upper surface of the wafer 9 as shown in FIG. In this embodiment, since the rinsing liquid 8 is heavier than the liquid carbon dioxide 11, the valve 18 is opened, and the valve 1 and the valve 2 before and after the high-pressure vessel 4 are opened and closed repeatedly from this state, as shown in FIG. By repeating the introduction, its stop, and its discharge a plurality of times, the stirring effect of the rinse liquid 8 and the liquid carbon dioxide 11 is improved, and the rinse liquid 8 can be efficiently replaced by the liquid carbon dioxide 11 and discharged.

  As another embodiment, when the rinsing liquid 8 is lighter than the liquid carbon dioxide 11, the valve 18 is closed and the valve 19 is opened as described above. From this state, the high-pressure vessel 4 is opened as shown in FIG. By repeating the opening and closing of the front and rear valves 1 and 2 and repeatedly introducing and stopping the liquid carbon dioxide 11, the stirring effect of the rinsing liquid 8 and the liquid carbon dioxide 11 is improved. Can be well replaced and discharged.

(4) After the replacement of the rinse liquid 8 is completed, the pressure in the high-pressure vessel 4 is set to a critical pressure or higher, and then the temperature in the high-pressure vessel is set to a critical temperature or higher. With this temperature change, the state of the liquid carbon dioxide 11 in the high-pressure vessel 4 changes to a supercritical state. In this change of state, the surface tension of the liquid carbon dioxide 11 does not act on the fine structure.

(5) Next, the valve 1 is closed, and supercritical carbon dioxide is discharged from the pressure control valve 2 while keeping the temperature in the high-pressure vessel 4 at 35 ° C. When the pressure in the high-pressure vessel 4 becomes 7.38 MPa or less, the state of the liquid carbon dioxide that has filled the high-pressure vessel 4 changes to a gas. Further, the pressure control valve 2 continues to discharge, and the drying ends when the pressure in the high-pressure vessel 4 becomes atmospheric pressure.

  According to this embodiment, since the rinsing liquid 8 is transported while sufficiently covering the surface of the wafer 9, drying during the transportation is prevented and the replacement time of the rinsing liquid 8 is shortened. It can respond to the rapid discharge aimed at. Then, according to the present embodiment, the surface fine structure having a pattern width of 100 nm or less, further a pattern width of 70 nm or less, particularly a pattern width of 30 nm or less, such as resist after exposure, development, and rinsing for manufacturing LSI etc. on a large scale The large-diameter substrate having a diameter of 100 mm or more can be uniformly dried in a shorter time without pattern collapse. Therefore, it has a processing speed that can be applied to a device manufacturing line.

  According to the present embodiment, drying during transportation is prevented, and furthermore, there is no pattern collapse on a large-diameter substrate having a fine pattern formed on the surface, and drying is performed uniformly in a short time, and particles are reduced. be able to.

It is sectional drawing of the supercritical drying processing apparatus of this invention. It is sectional drawing which shows the condition in a high pressure container when repeating opening and closing of the valve | bulb in the supercritical drying processing apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 18, 19 ... Valve, 2 ... Pressure control valve, 3 ... Back pressure control valve, 4 ... High pressure container, 5 ... Wafer holder, 6 ... Lower container, 7 ... Filter, 8 ... Rinse solution, 9 ... Wafer, 10 ... Temperature regulator, 11 ... liquid carbon dioxide, 12 ... lid, 13 ... pressure control device, 14 ... high pressure pump, 15 ... liquid carbon dioxide storage container, 16, 17 ... outlet.

Claims (10)

  A to-be-dried object having a fine structure immersed or wet in a rinsing liquid is placed in a high-pressure treatment container, and the rinsing liquid on the to-be-dried object is a gas at normal temperature and normal pressure, and a fluid that becomes liquid at high pressure. In the fine structure drying processing method using and discharging from the high-pressure processing container, an introducing step of introducing the fluid into the high-pressure processing container in a liquid state, and discharging the introduced fluid from the high-pressure processing container A fine structure drying method, comprising: a discharging step, and a repeating step of repeating the introduction step and the discharging step.   2. The microstructure drying method according to claim 1, wherein the repeating step is performed in a state where the liquid level of the fluid is slightly higher than the surface of the substrate.   In Claim 1 or 2, the conveyance process which conveys the to-be-dried object which has the microstructure immersed or rinsed in the rinse liquid in a high-pressure processing container, the above-mentioned repetition process, and the fluid above the critical pressure and critical temperature A microstructure drying treatment method characterized by sequentially comprising the step of raising the temperature and raising the temperature and the step of discharging the fluid from the high-pressure treatment vessel while keeping the temperature of the fluid at a critical temperature or higher.   An object to be dried having a fine structure immersed or wet in a rinsing liquid is placed in a high-pressure processing vessel, and the rinsing liquid on the substrate is a gas that is a gas at normal temperature and normal pressure and a liquid that is liquid at high pressure. In the fine structure drying apparatus for discharging from the inside of the high pressure processing container, the fluid discharge port is provided at a position equivalent to the height of the object to be dried in the high pressure processing container.   5. The fine structure drying apparatus according to claim 4, wherein the fluid outlet has a bottom portion of the high-pressure processing vessel.   6. The fine structure drying apparatus according to claim 4, further comprising a filter between the open / close valve for introducing the fluid and the high-pressure vessel.   7. The fine structure drying apparatus according to claim 4, further comprising a high-pressure pump that pumps the fluid to the high-pressure vessel.   The microstructure drying according to any one of claims 4 to 7, further comprising a temperature controller capable of locally or entirely controlling the temperature of the substrate on an installation base for installing the object to be dried in the high-pressure processing vessel. Processing equipment.   9. The microstructure drying apparatus according to claim 4, further comprising means for vibrating or stirring the fluid.   10. The fluid storage container for storing a fluid that is gas at normal temperature and normal pressure and liquid at high pressure in a liquid or supercritical state, and a pump that pumps the fluid into the high-pressure processing container according to claim 4. A temperature controller provided on the lower side of the material to be dried and controlling the temperature of the material to be dried, a pressure control device for controlling the pressure of the fluid in the high pressure processing vessel, and into the high pressure processing vessel And a pressure increase speed control means for controlling the pressure increase speed when the fluid is introduced.

Images