JP2008177205A - Cleaning apparatus and cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve cleaning efficiency of a cleaning target while using a supercritical fluid and reduce the burden on a back pressure valve. <P>SOLUTION: The cleaning apparatus suddenly causes the pressure of the supercritical fluid to vary, and supplies the fluid to a substrate 14 as a cleaning target to clean the target. The cleaning apparatus is provided with a processing chamber 13 for arranging the substrate 14, an auxiliary chamber 18 communicating with the processing chamber 13, and a control means for executing opening/closing control of an opening/closing valve 17 for draining the supercritical fluid from the processing chamber 13 to the auxiliary chamber 18 in changing the pressure of the supercritical fluid to apply cleaning processing to the substrate 14 arranged in the processing chamber 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cleaning apparatus and a cleaning method for a semiconductor substrate, a glass substrate of a liquid crystal display, a substrate for a photomask, a substrate for an optical disk (hereinafter simply referred to as a cleaning object), and in particular, on the cleaning object. The present invention relates to a cleaning apparatus and a cleaning method that are suitable for use in a cleaning apparatus and a cleaning method for removing residues when forming a fine structure pattern to be formed.

  In general, in order to form a fine structure, a resist is formed on a substrate by forming a pattern by exposing and developing, and using this pattern, a thin film formed in a lower layer is formed by etching. It is necessary to wash away the resist after the pattern formation process and the residue generated by the etching process.

  Further, in the manufacturing process of a semiconductor device, if particles (microparticles) adhere to the semiconductor substrate, it causes malfunction of the semiconductor device and performance deterioration, which causes a defect.

  Also, in the manufacturing process of semiconductor devices, the resist on the semiconductor wafer is exposed using an exposure device that uses a mask (reticle) to form a pattern. At this time, foreign substances such as particles are present on the mask. Then, the pattern exposed on the resist has an adverse effect such as generation of a fixed defect, which also causes a malfunction or failure of the semiconductor device. Therefore, it is necessary to remove it from the substrate.

  Conventionally, the resist that has become unnecessary after the pattern formation and the residue generated by the etching process are conventionally removed by the following process.

1. A method of removing by ashing by exposing to plasma generated from oxygen.
2. Decompose by immersing in a solution that has a strong oxidizing or reducing action, such as a mixture of sulfuric acid and hydrogen peroxide (sulfuric acid / hydrogen peroxide), pure water in which ozone is dissolved (ozone water), or an organic alkali solution such as amine. How to remove.
3. A method in which the resist is immersed in a soluble organic solvent and dissolved and peeled off.

  In the above method 1, it is difficult to completely remove the resist and etching residue, and the methods 2 and 3 are used in combination. The method 2 or 3 may be used alone, but is generally used in combination with the method 1.

  However, in recent years, the pattern on the substrate has been miniaturized, or a structure that easily breaks such as an air bridge has been adopted, and in the above method of immersing the substrate in liquid, due to the action of the surface tension of the liquid, There is concern that the structure will be destroyed.

  Therefore, as disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4, a method using a supercritical fluid has been proposed. Such a supercritical fluid has a surface tension that is very close to zero, and therefore can treat the surface without destroying the microstructure.

  In addition, supercritical materials include carbon dioxide, ammonia, water, alcohols, low molecular weight aliphatic saturated hydrocarbons, benzene, diethyl ether, and many other substances that have been confirmed to be supercritical fluids. Among them, carbon dioxide is a material that is preferably used as a supercritical fluid because its critical temperature is 31.3 ° C, which is relatively close to room temperature, and its critical pressure is 7.38 MPa, which is relatively low among supercritical fluids. It is.

  In this cleaning method using a supercritical fluid, the pressure changes sharply to cause a phase change from a supercritical state to a subcritical state, resulting in an explosive volume change, and the fluid speed increases. The cleaning effect such as removal of foreign matters and residues is enhanced.

Japanese Patent Laid-Open No. 1-200828 JP-A-1-286314 Japanese Patent Laid-Open No. 9-43857 JP-A-8-181050

  However, pressure control of a conventional apparatus using a supercritical fluid is performed by controlling the opening degree and opening / closing time of a valve (back pressure valve 35) on the exhaust side of the processing chamber 33 as shown in FIG. If the pressure is changed rapidly, the back pressure valve 35 is frozen due to a temperature drop accompanying the expansion of the volume, and it is difficult not only to control the valve opening but also to open and close the back pressure valve 35. Furthermore, a sudden temperature change leads to destruction of the seal portion of the back pressure valve 35 and a life reduction.

  Accordingly, the present invention eliminates the need for foreign matter adhering to the semiconductor surface or after pattern formation in a processing apparatus using a supercritical fluid, which generates rapid pressure fluctuations without destroying apparatus components such as valves. It is an object of the present invention to provide a method for removing residues generated by resist and etching processes.

  The present invention has been made to achieve the above object, and is a processing chamber in which a cleaning object is arranged in a cleaning apparatus that rapidly changes the pressure of a supercritical fluid and supplies the cleaning object to the cleaning object. And a preliminary chamber that communicates with the processing chamber, and when the cleaning process is performed by changing the pressure of the supercritical fluid on the cleaning target disposed in the processing chamber, the supercritical fluid is discharged from the processing chamber to the preliminary chamber side. And a control unit that performs control.

  Further, the present invention provides a cleaning method in which the pressure of the supercritical fluid is rapidly changed and supplied to the object to be cleaned to perform the cleaning process. This is a cleaning method in which the supercritical fluid is discharged to the side of the preliminary chamber communicating with the processing chamber when the cleaning process is performed while varying the pressure.

  For example, an open / close valve is provided between the processing chamber and the spare chamber, and pressure fluctuation control by discharging the supercritical fluid from the process chamber to the spare chamber is performed by controlling the pressure of the spare chamber and opening / closing the open / close valve. Or by providing a movable partition wall between the processing chamber and the preliminary chamber and controlling the volume of the processing chamber by moving the movable partition wall, the supercritical fluid is transferred from the processing chamber to the preliminary chamber side. Controls pressure fluctuation due to discharge.

  Therefore, according to the present invention, the pressure due to the discharge of the supercritical fluid from the processing chamber to the preliminary chamber is provided by providing the preliminary chamber in communication with the processing chamber and controlling the volume of the processing chamber by controlling the open / close valve and the movable partition wall. Fluctuation control can reduce the burden on the back pressure valve installed in the subsequent stage of the processing chamber, and the pressure in the processing chamber can be rapidly changed without causing malfunction of the back pressure valve or shortening the service life. It becomes. As a result, it is possible to improve the cleaning performance using the supercritical fluid for the object to be cleaned.

  Hereinafter, embodiments of the present invention will be described in detail. In the present embodiment, a semiconductor substrate is described as an example of the object to be cleaned, but the same applies to other objects to be cleaned.

  The cleaning apparatus according to this embodiment is an apparatus that cleans a semiconductor substrate in a supercritical state. In the first embodiment, a processing chamber serving as a cleaning tank and a spare chamber coupled through an opening / closing valve are provided, and pressure fluctuations in the processing chamber are controlled by pressure control of the spare chamber and opening / closing control of the opening / closing valve. Is.

  In the second embodiment, a movable partition is provided in the processing chamber, and volume control of the processing chamber is performed by moving the movable partition, thereby controlling pressure fluctuations in the processing chamber.

  In any of the embodiments, the pressure of the processing chamber is reduced without causing a malfunction or a reduction in the lifetime of the back pressure valve connected to the processing chamber due to a rapid pressure fluctuation of the supercritical fluid fed into the processing chamber. It becomes possible to make it fluctuate rapidly, and it becomes possible to improve the cleaning performance of the semiconductor substrate using the supercritical fluid.

(First embodiment)
FIG. 1 is a block diagram illustrating a cleaning device according to the first embodiment. That is, the cleaning apparatus according to the first embodiment communicates with a processing chamber 13 that houses a semiconductor substrate (hereinafter simply referred to as “substrate”) that is an object to be cleaned, and the processing chamber 13 and the open / close valve 17. And a control unit (not shown) for controlling the opening and closing of the pressurizing pump and various valves.

  A processing chamber pressurizing valve 12 is provided on the upper side of the supercritical fluid flow path of the processing chamber 13, and a pressurizing pump 11 is provided on the upper side. Further, a processing chamber back pressure valve 15 is provided on the lower side of the supercritical fluid flow path of the processing chamber 13.

  Further, the piping is branched between the pressurizing pump 11 and the processing chamber pressurizing valve 12 and connected to the spare chamber 18 via the spare chamber pressurizing valve 16. Further, a spare chamber back pressure valve 19 is provided on the downstream side of the supercritical fluid flow path of the spare chamber 18.

  That is, in this cleaning apparatus, the processing chamber 13 containing the substrate 14 is connected to the pressurizing pump 11 through the processing chamber pressurizing valve 12, and is connected to the exhaust through the processing chamber back pressure valve 15. At this time, the pressure in the processing chamber 13 is controlled by controlling the processing chamber back pressure valve 15.

  Further, the processing chamber 13 is connected to the auxiliary chamber 18 through the opening / closing valve 17. The preliminary chamber 18 is connected to the pressurizing pump 11 through the preliminary chamber pressurizing valve 16. Further, it is connected to the exhaust through the spare chamber back pressure valve 19, and the pressure of the spare chamber 18 is controlled by controlling the spare chamber back pressure valve 19.

  Next, a substrate cleaning method using this cleaning apparatus will be described. First, the substrate 14 is accommodated in the processing chamber 13, the processing chamber pressurization valve 13 is opened, and the pressure is controlled by adjusting the processing chamber back pressure valve 15. Is introduced into the processing chamber 13.

  At this time, if the supercritical material is continuously introduced while the temperature is controlled to be higher than the critical temperature so that the supplied supercritical material does not become liquid, the pressure in the processing chamber 13 becomes higher than the critical pressure. The processing chamber 13 becomes a supercritical fluid directly from the gas, and the processing chamber 13 can be filled with the supercritical fluid without exposing the substrate 14 on which the microstructure is formed to the gas-liquid interface.

  For example, when the supercritical material is carbon dioxide, if the temperature is controlled to 31.3 ° C. or higher, the gas becomes a supercritical fluid directly from the gas when the pressure in the processing chamber 13 is 7.38 MPa or higher.

  In this way, the processing chamber pressurization valve 12 is closed after the processing chamber 13 is filled with the supercritical fluid.

  Next, the preliminary chamber pressurization valve 16 is opened, and the supercritical material is supplied to the preliminary chamber 18. After the pressure in the spare chamber 18 is controlled to a predetermined pressure by the spare chamber back pressure valve 19, the spare chamber pressurizing valve 16 is closed and the open / close valve 17 is opened to rapidly change the pressure in the processing chamber 13. . Thereby, the contaminant of the board | substrate 14 is removed effectively.

  After the cleaning process according to the above flow is completed, the supercritical material in the processing chamber 13 is discharged by adjusting the processing chamber back pressure valve 15 or the preliminary chamber back pressure valve 19 while controlling the temperature of the processing chamber 13. Then, the supercritical substance in the processing chamber 13 is brought into a gaseous state. Thereby, the substrate 14 is dried.

  By such processing, even if there is a sudden pressure fluctuation of the supercritical fluid fed into the processing chamber 13, the supercritical fluid is exhausted from the preliminary chamber 18 through the preliminary chamber back pressure valve 19. No burden is applied to the back pressure valve connected to the, and it does not cause malfunction such as freezing or a decrease in life.

  Further, the pressure in the processing chamber 13 can be rapidly changed with respect to the substrate 14 in the processing chamber 13, and the cleaning performance of the substrate 14 using the supercritical fluid can be improved.

  According to the cleaning apparatus and the cleaning method of the present embodiment, when the pressure in the processing chamber 13 is reduced from 20 MPa to 5 to 7 MPa, conventionally, from the viewpoint of protecting the processing chamber back pressure valve 15, from several tens to several tens. The depressurization time, which took a minute, can be performed in a few seconds, and effective cleaning by rapid depressurization that cannot be obtained in the past can be performed.

(Second Embodiment)
FIG. 2 is a block diagram illustrating a cleaning apparatus according to the second embodiment. That is, the cleaning apparatus according to the second embodiment includes a processing chamber 23 that accommodates a substrate 24 that is an object to be cleaned, a preliminary chamber 28 that communicates with the processing chamber 23 via a movable partition wall 26, a pressure pump, and various types. And a control unit (not shown) that performs valve opening / closing control and movable control of the movable partition wall 26. In the present embodiment, the processing chamber 23 and the spare chamber are integrally provided and are partitioned by the movable partition wall 26.

  A processing chamber pressurization valve 22 is provided on the upper side of the supercritical fluid flow path of the processing chamber 23, and a pressurization pump 21 is provided on the upper side. Further, a processing chamber back pressure valve 25 is provided on the lower side of the supercritical fluid flow path of the processing chamber 23.

  That is, in this cleaning apparatus, the processing chamber 23 containing the substrate 24 is connected to the pressurizing pump 21 through the processing chamber pressurizing valve 22 and connected to the exhaust gas through the processing chamber back pressure valve 25. At this time, the pressure in the processing chamber 23 is controlled by controlling the processing chamber back pressure valve 25.

  Further, a partition wall 26 is installed in the processing chamber 23, and the pressure of the processing chamber 23 is controlled by changing the volume of the processing chamber 23.

  Next, a substrate cleaning method using this cleaning apparatus will be described. First, the substrate 24 is accommodated in the processing chamber 23, the processing chamber pressurization valve 23 is opened, and the pressure is controlled by adjusting the processing chamber back pressure valve 25. Is introduced into the processing chamber 23.

  At this time, if the supercritical material is continuously introduced while the temperature is controlled to be higher than the critical temperature so that the supplied supercritical material does not become liquid, the pressure in the processing chamber 23 becomes higher than the critical pressure. The processing chamber 23 becomes a supercritical fluid directly from the gas, and the inside of the processing chamber 23 can be filled with the supercritical fluid without exposing the substrate 24 on which the microstructure is formed to the gas-liquid interface.

  For example, when the supercritical material is carbon dioxide, if the temperature is controlled to 31.3 ° C. or higher, the gas becomes a supercritical fluid directly from the gas when the pressure in the processing chamber 23 is 7.38 MPa or higher.

  In this way, after the processing chamber 23 is filled with the supercritical fluid, the processing chamber pressurization valve 22 is closed.

  Next, the movable partition wall 26 installed in the processing chamber 23 is operated to rapidly change the pressure in the processing chamber 23. Thereby, the contaminant of the board | substrate 24 is removed effectively.

  After the cleaning process by the above process is completed, the process chamber back pressure valve 25 is adjusted while controlling the temperature of the process chamber 23, thereby discharging the supercritical substance in the process chamber 23, and The critical substance is in a gaseous state. Thereby, the substrate 24 is dried.

  By such processing, even if there is a sudden pressure fluctuation of the supercritical fluid fed into the processing chamber 23, the back pressure valve connected to the processing chamber 25 is not burdened by the change in volume of the processing chamber 23, and freezing is performed. It will not cause malfunctions such as the above and a decrease in service life.

  Further, the pressure in the processing chamber 23 can be rapidly changed with respect to the substrate 24 in the processing chamber 23, and the cleaning performance of the substrate 24 using the supercritical fluid can be improved.

  FIG. 3 is a cross-sectional view of the back pressure valve used in the first embodiment and the second embodiment. In each of the above embodiments, it is possible to reduce the burden on the back pressure valve due to a rapid pressure fluctuation of the supercritical fluid supplied into the processing chamber.

  As shown in FIG. 3, this back pressure valve can adjust the pressure depending on the position of the main valve 101 provided between INLET (inlet) and OUTLET (outlet). The main valve 101 is used for pressure adjustment. The spring 102 is pressed by the urging force.

  The pressure can be adjusted by turning the adjustment knob 103 to change the urging force of the pressure adjustment spring 102 against the main valve 101. In such a back pressure valve, various seals 104 are used between movable parts. The valve body is made of metal, and the seal 104 is made of resin.

  When such a back pressure valve is applied to a flow path of a supercritical fluid, the valve freezes or the like due to a temperature drop accompanying rapid volume expansion of the supercritical fluid. This valve freezing not only controls the valve opening but also makes the opening and closing operation itself difficult. In addition, due to such a rapid temperature change, the seal 104 is particularly damaged, leading to breakage and a reduction in life.

  In this embodiment, the load on the back pressure valve can be remarkably reduced while improving the cleaning ability by utilizing the rapid volume expansion of the supercritical fluid, preventing damage to parts, extending the service life, and maintaining the equipment maintenance cycle. Can be extended.

It is a schematic diagram explaining 1st Embodiment. It is a schematic diagram explaining 2nd Embodiment. It is a schematic diagram explaining a prior art example. It is sectional drawing explaining the structure of a back pressure valve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Pressure pump, 12 ... Processing chamber pressurization valve, 13 ... Processing chamber, 14 ... Substrate, 15 ... Processing chamber back pressure valve, 16 ... Open / close valve, 17 ... Open / close valve, 18 ... Preliminary chamber, 19 ... Preliminary chamber Back pressure valve

Claims (6)

In a cleaning device that rapidly changes the pressure of the supercritical fluid, supplies it to the object to be cleaned, and performs a cleaning process,
A processing chamber in which the object to be cleaned is disposed;
A reserve chamber in communication with the processing chamber;
Control means for controlling the discharge of the supercritical fluid from the processing chamber to the spare chamber side when performing the cleaning process by changing the pressure of the supercritical fluid on the object to be cleaned disposed in the processing chamber And a cleaning device. An open / close valve is provided between the processing chamber and the auxiliary chamber;
The cleaning device according to claim 1, wherein the control unit controls to open the opening / closing valve when discharging the supercritical fluid. A movable partition is provided between the processing chamber and the auxiliary chamber;
The cleaning device according to claim 1, wherein the control unit controls the movable partition to move when the supercritical fluid is discharged. In the cleaning method of rapidly changing the pressure of the supercritical fluid and supplying it to the object to be cleaned for cleaning treatment,
The cleaning object is placed in the processing chamber, and when the cleaning process is performed by changing the pressure of the supercritical fluid, the supercritical fluid is discharged to the spare chamber side communicating with the processing chamber. A cleaning method characterized by. The cleaning method according to claim 4, wherein an opening / closing valve is provided between the processing chamber and the preliminary chamber, and the opening / closing valve is controlled to be opened when the supercritical fluid is discharged. The cleaning according to claim 4, wherein a movable partition is provided between the processing chamber and the preliminary chamber, and the movable partition is controlled to move when the supercritical fluid is discharged. Method.

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