JP2004141704A - Washing apparatus and washing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing apparatus capable of washing an object to be treated without destructing a fine structure only by treatment using a supercritical fluid, and a washing method using the same. <P>SOLUTION: The washing apparatus for supplying the supercritical fluid to the object to be treated to wash the object to be treated has oxidizing agent supply means 8, 9 and 10 for supplying an oxidizing agent to be added to the supercritical fluid. In washing the fine structure such as a semiconductor, a micromachine or the like, peroxide is added to carbon dioxide set to a supercritical state and the peroxide itself is dissociated in carbon dioxide set at the supercritical state to remove a pollutant such as resist or etching residue at the time of formation of a pattern without destructing the fine structure. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cleaning apparatus and a cleaning method for cleaning a semiconductor substrate, a glass substrate of a liquid crystal display, a substrate for a photomask, a substrate for an optical disk, and the like (hereinafter, simply referred to as a substrate). In particular, the present invention relates to a cleaning apparatus and a cleaning method for removing a resist and an etching residue for forming a fine structure pattern formed on a substrate.
[0002]
[Prior art]
Generally, in order to form a fine structure, a resist formed on a substrate is exposed and developed to form a pattern, and a thin film formed below is etched using this pattern. It is necessary to wash and remove the resist and the etching residue generated by the etching process.
[0003]
In addition, in general, when particles (fine particles) adhere to a semiconductor substrate in a manufacturing process of a semiconductor device, the semiconductor device malfunctions or deteriorates in performance, which causes a defect. Further, in a manufacturing process of a semiconductor device, a resist or the like on a semiconductor wafer is exposed using an exposure apparatus using a mask (reticle) to form a pattern. At this time, if foreign matter such as particles is present on the mask, the pattern exposed on the resist has an adverse effect such as generation of fixed defects, which also causes malfunction or failure of the semiconductor device. There is a need to.
[0004]
The former, resist and etching residue that are no longer required after pattern formation are conventionally removed by the following treatment. (1) A method of exposing to plasma generated from oxygen or the like and removing it by incineration. (2) Immersion in a solution having a strong oxidizing or reducing action, for example, a mixed solution of sulfuric acid and hydrogen peroxide (sulfuric acid peroxide), pure water in which ozone is dissolved (ozone water), or an organic alkali solution such as an amine And decompose and remove. (3) A method in which the resist is immersed in a dissolvable organic solvent, and the resist is stripped off.
[0005]
In the method (1), it is difficult to completely remove the resist and the etching residue, and the method (2) or (3) is used in combination. The method (2) or (3) may be used alone, but is generally used in combination with the method (1).
[0006]
However, in recent years, the pattern on the substrate has been miniaturized, and a structure that easily breaks, such as an air bridge, has been adopted in MEMS (Micro Electro Mechanical System). In the above method of immersing the substrate in a liquid, There is a concern that the structure may be destroyed by the action of surface tension.
[0007]
Therefore, conventionally, a method using a supercritical fluid has been proposed, and since such a supercritical fluid has a surface tension extremely close to zero, it is possible to perform a surface treatment without destroying a microstructure (for example, See Patent Documents 1 to 4.)
[0008]
In addition, many substances that have been confirmed to be supercritical fluids such as carbon dioxide, ammonia, water, alcohols, low-molecular-weight aliphatic saturated hydrocarbons, benzene, diethyl ether, etc. Can be used. Among them, carbon dioxide is a substance preferably used as a supercritical fluid because its critical temperature is relatively close to room temperature of 31.3 ° C. and its critical pressure is relatively low at 7.38 MPa among supercritical fluids.
[0009]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 1-220828 [Patent Document 2]
JP-A-1-286314 [Patent Document 3]
Japanese Patent Application Laid-Open No. 9-43857 [Patent Document 4]
JP-A-8-181050 [Patent Document 5]
JP 2001-165568 A
[Problems to be solved by the invention]
However, carbon dioxide, which is generally used as a supercritical fluid, exhibits properties similar to nonpolar organic solvents in the state of a supercritical fluid, so that substances that can be dissolved in carbon dioxide alone in the supercritical state are limited. Would.
[0011]
For example, low-molecular-weight organic substances such as a photoresist before exposure can be removed, but it is difficult to remove inorganic compounds such as a resist polymerized by exposure, ion implantation, dry etching, and etching residues, and the like. Become.
Therefore, before the treatment with carbon dioxide in a supercritical state, it is necessary to perform wet cleaning with a chemical solution that has been used in the past.
[0012]
In such a case, there is a concern that the structure may be destroyed by the surface tension of the liquid as the object to be cleaned passes through the gas-liquid interface. For this reason, there is a technology to transfer the chemical solution to the rinsing solution after the wet cleaning and replace the rinsing solution with supercritical carbon dioxide without passing through the gas-liquid interface, but the process becomes complicated. (For example, see Patent Document 5).
[0013]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cleaning apparatus and a cleaning apparatus capable of performing a cleaning process on an object to be processed without destroying a microstructure only by a process using a supercritical fluid. It is to provide a method.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a cleaning apparatus according to the present invention is a cleaning apparatus that performs a cleaning process by supplying a supercritical fluid to an object to be processed, and supplies an oxidizing agent to be added to the supercritical fluid. It has supply means.
[0015]
An energy beam irradiating means for irradiating the supercritical fluid to which the oxidizing agent is added with an energy beam to dissociate the oxidizing agent is further provided.
[0016]
The oxidant supply unit supplies a peroxide as the oxidant. The supercritical fluid is carbon dioxide.
[0017]
In the above-described cleaning apparatus of the present invention, the oxidant supplied by the oxidant supply unit is added to the supercritical fluid, so that the added oxidant is dissociated in the supercritical fluid.
Some of the contaminants of the object are dissolved in the supercritical fluid. Here, among the pollutants that cannot be dissolved by the supercritical fluid alone, the organic pollutants are oxidatively decomposed and dissolved in the supercritical fluid or the oxidant by the oxidizing action of the oxidant dissociated in the supercritical fluid. Become. Further, the inorganic contaminants are ionized by the oxidizing action of the oxidizing agent dissociated in the supercritical fluid and dissolved in the supercritical fluid or the oxidizing agent.
At this time, the dissociation of the oxidizing agent is promoted by irradiating the energy beam to the supercritical fluid to which the oxidizing agent has been added by the energy beam irradiating means.
[0018]
Further, in order to achieve the above object, a cleaning method of the present invention is a cleaning method of performing a cleaning process by supplying a supercritical fluid to a target object, wherein an oxidizing agent is added to the supercritical fluid. Features.
[0019]
The supercritical fluid to which the oxidizing agent is added is irradiated with an energy beam to dissociate the oxidizing agent.
[0020]
A peroxide is added to the supercritical fluid as the oxidizing agent. The supercritical fluid is carbon dioxide.
[0021]
In the above-described cleaning method of the present invention, the oxidizing agent is added to the supercritical fluid, so that the added oxidizing agent is dissociated in the supercritical fluid.
Some of the contaminants of the object are dissolved in the supercritical fluid. Here, among the pollutants that cannot be dissolved by the supercritical fluid alone, the organic pollutants are oxidatively decomposed and dissolved in the supercritical fluid or the oxidant by the oxidizing action of the oxidant dissociated in the supercritical fluid. Become. Further, the inorganic contaminants are ionized by the oxidizing action of the oxidizing agent dissociated in the supercritical fluid and dissolved in the supercritical fluid or the oxidizing agent.
At this time, dissociation of the oxidant is promoted by irradiating the energy beam to the supercritical fluid to which the oxidant has been added.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a cleaning apparatus and a cleaning method of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a configuration diagram illustrating an example of the cleaning device according to the present embodiment.
As shown in FIG. 1, a processing chamber 1 for housing a substrate (object to be processed) 2 is provided, and a fluid supply port 3 is provided in the processing chamber 1, and a supercritical fluid supplied from the fluid supply port 3 is provided. The substrate 2 is cleaned with the substance. Although not shown, a stage for holding the substrate 2 is provided in the processing chamber 1, and the stage holds the substrate 2 by vacuum suction or a mechanical chuck.
[0024]
A supercritical substance supply source 5 is connected to the fluid supply port 3 via a mixing unit 11, a supercritical substance supply valve 7, and a supercritical substance pressure / temperature control unit 6. The supercritical material supply source 5, the supercritical material pressure / temperature control means 6, and the supercritical material supply valve 7 constitute a supercritical material supply means.
[0025]
The supercritical substance supply source 5 stores and supplies a supercritical substance to be a supercritical fluid. The supercritical fluid is defined as follows. That is, a substance has a specific critical temperature and critical pressure at which a gas and a liquid cannot coexist, and a point at which the substance reaches a critical temperature and critical pressure state is called a critical point. A supercritical fluid is defined as a state in which a substance is in a temperature or pressure region beyond a critical point.
[0026]
A supercritical fluid defined in this way has a dissolving power close to that of a liquid, but exhibits a property similar to that of a gas in terms of tension and viscosity. Since the supercritical fluid does not form a gas-liquid interface, the surface tension becomes zero. Such a supercritical fluid can penetrate into fine parts, has a high diffusion coefficient, and can rapidly dissolve dissolved contaminants. Further, it has the characteristic that it becomes gaseous by returning to normal temperature and normal pressure and can be immediately evaporated and dried.
[0027]
Conditions for selecting a supercritical fluid include high safety, having a critical point that is easy to handle, and being inexpensive and economical. As a supercritical substance that satisfies these conditions (in this specification, a substance that becomes a supercritical fluid is called a supercritical substance), substances such as carbon dioxide, sulfur dioxide, nitrous oxide, ethane, propane, and chlorofluorocarbon are used. No. Among them, carbon dioxide (carbon dioxide) is most suitable. This is because carbon dioxide is almost harmless to living organisms, and its critical point is relatively easy to handle at a temperature of 31.3 ° C. and a pressure of 7.38 MPa, and it is cheap and easily available. For this reason, in the present embodiment, carbon dioxide is employed as the supercritical substance. However, substances other than the above-mentioned carbon dioxide may be used as the supercritical substance.
[0028]
The supercritical substance pressure / temperature control means 6 controls the temperature and pressure of the supercritical substance supplied from the supercritical substance supply source 5. The supercritical substance supply valve 7 controls the supply amount of the gaseous supercritical substance supplied from the supercritical substance pressure / temperature control means 6 to the mixing unit 11.
[0029]
An oxidizing agent supply source 8 is connected to the mixing unit 11 via an oxidizing agent supply valve 10 and an oxidizing agent pressure / temperature control unit 9. The oxidant supply source 8, the oxidant pressure / temperature control means 9 and the oxidant supply valve 10 constitute an oxidant supply means.
[0030]
The oxidant supply 8 stores and supplies the oxidant. In this embodiment, for example, a peroxide is used as the oxidizing agent. Specific examples of the peroxide include ozone gas-dissolved water, aqueous hydrogen peroxide, perchloric acid, persulfuric acid, acids containing an -O-O-bond among inorganic oxoacids such as perphosphoric acid, and formic acid. Examples include organic peroxides represented by RCO ₃ H such as peracetic acid, radical polymerization initiators such as benzoyl peroxide, and crosslinking agents such as divinyl adipate. By adding such a peroxide to the supercritical fluid, it is dissociated in the supercritical fluid without using a solvent. At this time, it is not necessary to add a compatibilizer.
[0031]
When carbon dioxide is used as a supercritical substance, it exhibits properties similar to a nonpolar organic solvent in a supercritical fluid state. Some of the contaminants dissolve in the supercritical fluid. Here, for example, organic contaminants that are not dissolved in a nonpolar solvent, such as a resist polymerized by etching or the like, are oxidatively decomposed by the oxidizing action of peroxide (radical species) dissociated in a supercritical fluid. It becomes soluble in a supercritical fluid or an oxidizing agent.
In addition, inorganic contaminants that are not dissolved in the nonpolar solvent, such as resist residues, are ionized and dissolved in the supercritical fluid or the oxidizing agent due to the oxidizing action of the oxidizing agent dissociated in the supercritical fluid. .
[0032]
The oxidant pressure / temperature control means 9 controls the temperature and pressure of the oxidant supplied from the oxidant supply source 8. The oxidant supply valve 10 controls the supply amount of the gaseous oxidant supplied from the oxidant pressure / temperature control means 9 to the mixing section 11.
[0033]
The mixing unit 11 mixes the supercritical substance supplied from the supercritical substance supply unit and the oxidant supplied from the oxidant supply unit. The mixed supercritical substance and oxidant are supplied to the processing chamber 1 through the fluid supply port 3.
[0034]
The processing chamber 1 is provided with a fluid discharge port 4. The fluid discharge port 4 is connected to a pressure control valve 12, and the pressure control valve 12 is connected to discharge gas-liquid separation means 13. An exhaust line 14 and a drain line 15 are connected to the liquid separating means 13. The discharge means is constituted by the pressure regulating valve 12, the discharged gas-liquid separation means 13, the exhaust line 14, and the discharge line 15.
[0035]
The pressure in the processing chamber 1 is controlled to a predetermined pressure by the operation of the pressure adjusting valve 12. Of the supercritical substances, oxidants and pollutants discharged by the action of the discharged gas-liquid separation means 13, substances that become gas at normal temperature and pressure are exhausted by the exhaust line 14, and those that become liquid are discharged by the drain line 15. Is drained.
At this time, the fluid discharged from the exhaust line 14 and the drain line 15 can be recovered by a recovery device (not shown) and reused.
[0036]
The processing chamber 1 is connected to a processing chamber temperature control unit 16 including, for example, a heater. The processing chamber temperature control means 16 controls the temperature in the processing chamber 1 to a temperature equal to or higher than the critical point so that the supercritical substance supplied into the processing chamber 1 becomes a supercritical fluid.
[0037]
An optical window 17 made of quartz or the like is provided in the processing chamber 1, and further, an energy beam 19 for irradiating a supercritical fluid in the processing chamber 1 with an energy beam 19 through the optical window 17 installed in the processing chamber 1. Means 18 are provided. The energy beam irradiating means 18 includes, for example, a UV lamp, and irradiates the processing chamber 1 with ultraviolet light as an energy beam 19. The reason why the energy beam irradiation means 18 is provided is to promote the dissociation of the peroxide added to the supercritical fluid and improve the oxidizing power.
[0038]
FIG. 2 is a cross-sectional view illustrating an example of a substrate to be subjected to a cleaning process in the present embodiment.
On the substrate 2, a processed film 21 which has been subjected to pattern processing is formed. Usually, in order to process the processed film 21, a resist 22 having a predetermined pattern is formed on the processed film 21 by exposure and development, and etching is performed using the resist 22 as a mask. Therefore, the resist 22 remains on the processed film 21 after the etching. Further, an etching residue 23 remains in the pattern of the film 21 to be processed.
[0039]
The etching residue 23 is defined as a substance remaining on the substrate 1 when the processing target film 21 is etched using the resist 22 as a mask. As a cause of the generation of the etching residue 23, a reaction product of low volatility such as a plasma polymer, a sputter decomposition product, or a low volatility substance in the film to be processed 21 is generated as a nucleus. Generally, the etching residue is an inorganic compound.
[0040]
In the present embodiment, an example in which a resist 22 and an etching residue 23 (hereinafter, referred to as contaminants) after a pattern is formed on a film 21 to be processed on a substrate will be described as an example. However, besides this, it is also applicable to the removal of particles on the substrate. Further, the substrate 2 may be a glass substrate of a liquid crystal display, a substrate for a photomask, or a substrate for an optical disk, in addition to a semiconductor substrate such as silicon.
[0041]
Next, a substrate cleaning method using the above-described cleaning apparatus will be described with reference to a flowchart shown in FIG.
[0042]
First, the substrate 2 is housed in the processing chamber 1, the supercritical substance supply valve 7 is adjusted, and the temperature and pressure are controlled by the supercritical substance pressure / temperature control means 6, while the gas is supplied from the supercritical substance supply source 5. A supercritical substance is introduced into the processing chamber 1 (step ST1).
[0043]
Then, the supercritical substance pressure and temperature control means 6 and the processing chamber temperature control means 16 control the temperature inside the processing chamber 1 to be equal to or higher than the critical temperature so that the supplied supercritical substance does not become a liquid. Continue to introduce.
As a result, the pressure in the processing chamber 1 becomes equal to or higher than the critical pressure, the supercritical substance in the processing chamber 1 directly changes from a gas to a supercritical fluid, and does not expose the substrate 2 on which the fine structure is formed to the gas-liquid interface. The processing chamber 1 can be filled with a supercritical fluid (step ST2). For example, when the supercritical substance is carbon dioxide, the temperature is controlled to 31.3 ° C. or more, and the pressure in the processing chamber 1 becomes 7.38 MPa or more, so that the gas is directly converted to a supercritical fluid.
[0044]
As described above, while the inside of the processing chamber 1 is filled with the supercritical fluid, the oxidizing agent supply valve 10 is adjusted, and while the temperature and pressure are controlled by the oxidizing agent pressure / temperature control means 9, the oxidizing agent supply source 8 The gaseous oxidant is sent to the mixing section 11. The supercritical substance and the oxidizing agent are mixed in the mixing section 11, and these are supplied to the processing chamber (step ST3).
[0045]
Then, the processing chamber 1 previously filled with the supercritical fluid is replaced with a supercritical fluid to which an oxidizing agent has been added, and the substrate 2 is subjected to a cleaning process (step ST4). That is, among contaminants that cannot be dissolved by the supercritical fluid alone, organic contaminants such as resist are oxidatively decomposed and dissolved in the supercritical fluid or the oxidant by the oxidizing action of the oxidant dissociated in the supercritical fluid. . Further, inorganic contaminants such as etching residues are ionized by the oxidizing action of the oxidizing agent dissociated in the supercritical fluid and dissolved in the supercritical fluid or the oxidizing agent.
The oxidizing agent added here is a peroxide such as ozone gas dissolved water or hydrogen peroxide as described above.
[0046]
At this time, the supercritical fluid is irradiated with, for example, ultraviolet light as an energy beam 19 from the energy beam irradiating means 18 through an optical window 17 provided in the processing chamber 1 so that the peroxide added to the supercritical fluid is irradiated. Dissociation is promoted. Thereby, the effect of removing contaminants on the substrate 2 can be improved.
[0047]
After the above cleaning process is completed, the oxidizing agent supply valve 10 is adjusted to stop the supply of the oxidizing agent, and the inside of the processing chamber 1 is replaced with a supercritical fluid without an oxidizing agent (step ST5). Thereby, the substrate 2 is rinsed by the supercritical fluid.
[0048]
While the inside of the processing chamber 1 is replaced with only the supercritical fluid, the mixture of the supercritical substance, the oxidant, and the contaminant discharged from the fluid outlet 4 is separated by the discharge gas-liquid separation means 13 into the oxidant and the contaminant. The mixture is separated into a gaseous supercritical substance and discharged or recovered from the drainage line 15 and the exhaust line 14, respectively.
[0049]
Thereafter, the supply of the supercritical substance to the processing chamber 1 is stopped by adjusting the supercritical substance supply valve 7 (step ST6), and the processing chamber temperature control means 16 and the pressure regulating valve 12 are adjusted to adjust the inside of the processing chamber 1. By lowering the temperature and pressure to below the critical temperature and critical pressure, respectively, to bring the supercritical substance in the processing chamber 1 into a gaseous state. Thus, the substrate 2 is subjected to a drying process (step ST7).
Thus, the substrate cleaning process is completed.
[0050]
According to the cleaning apparatus and the cleaning method according to the present embodiment, the oxidizing agent is added to the supercritical fluid, and the oxidizing agent itself is dissociated in the supercritical fluid, so that the fine structure of the substrate 2 is not destroyed. In addition, contaminants such as resist and etching residue at the time of pattern formation can be removed by washing with only a supercritical fluid.
As described above, since it is not necessary to perform wet cleaning using a chemical solution, it is possible to clean a substrate having a fine structure without complicating the process.
[0051]
In addition, by irradiating an energy beam for promoting the dissociation of the oxidant added to the supercritical fluid, the efficiency of removing contaminants by the oxidant can be further improved.
[0052]
Further, the cleaning as described above can be performed only by providing the oxidizing agent supplying means for supplying the oxidizing agent to be added to the supercritical fluid, so that the apparatus cost does not increase.
[0053]
As described above, since the process is simplified, the execution time required for the cleaning processing of the object to be processed is shortened, and the required cleaning processing can be achieved even with a small number of facilities.
[0054]
The present invention is not limited to the description of the above embodiment.
For example, as shown in FIG. 4, the supercritical substance supply port 3a and the oxidant supply port 3b are separately provided in the processing chamber 1 without providing the mixing unit 11, and only the oxidant is treated from the oxidant supply port 3b. The oxidizing agent may be added to the supercritical fluid in the processing chamber 1 by supplying the oxidizing agent to the processing chamber 1.
[0055]
Further, in the present embodiment, an example has been described in which contaminants such as a resist and an etching residue on the substrate 2 are removed, but the object to be cleaned is not limited to this. For example, even a contaminant composed of a metal substance is ionized by the oxidizing action of the oxidizing agent and dissolved in the supercritical fluid or in the oxidizing agent.
In addition, various changes can be made without departing from the spirit of the present invention.
[0056]
【The invention's effect】
According to the cleaning apparatus of the present invention, the object to be processed can be cleaned without destroying the fine structure only by the processing using the supercritical fluid, and thus the execution time required for the cleaning processing of the object to be processed is reduced. Thus, the required cleaning process can be achieved with a small number of equipment.
[0057]
According to the cleaning method of the present invention, the object to be processed can be cleaned without destroying the fine structure only by the processing using the supercritical fluid, and thus the execution time required for the cleaning processing of the object to be processed is reduced. can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an example of a cleaning device according to an embodiment.
FIG. 2 is a cross-sectional view illustrating an example of a substrate to be subjected to a cleaning process in the present embodiment.
FIG. 3 is a flowchart of a cleaning process according to the embodiment.
FIG. 4 is a configuration diagram illustrating a modified example of the cleaning device according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Processing chamber, 2 ... Substrate, 3 ... Fluid supply port, 3a ... Supercritical substance supply port, 3b ... Oxidant supply port, 4 ... Fluid discharge port, 5 ... Supercritical substance supply source, 6 ... Supercritical substance pressure Temperature control means, 7: supercritical substance supply valve, 8: oxidant supply source, 9: oxidant pressure / temperature control means, 10: oxidant supply valve, 11: mixing section, 12: pressure regulating valve, 13 ... Exhaust gas-liquid separating means, 14 ... Exhaust line, 15 ... Drainage line, 16 ... Processing chamber temperature control means, 17 ... Optical window, 18 ... Energy beam irradiation means, 19 ... Energy beam, 21 ... Film to be processed, 22 ... Resist 23: etching residue.

Claims (8)

A cleaning device that performs a cleaning process by supplying a supercritical fluid to a target object,
A cleaning device having an oxidant supply unit for supplying an oxidant to be added to the supercritical fluid; The cleaning apparatus according to claim 1, further comprising: an energy beam irradiation unit configured to irradiate the supercritical fluid to which the oxidant is added with an energy beam to dissociate the oxidant. The cleaning device according to claim 1, wherein the oxidant supply unit supplies a peroxide as the oxidant. The cleaning device according to claim 1, wherein the supercritical fluid is carbon dioxide. A cleaning method of performing a cleaning process by supplying a supercritical fluid to a target object,
A cleaning method in which an oxidizing agent is added to the supercritical fluid. The cleaning method according to claim 5, wherein the supercritical fluid to which the oxidizing agent is added is irradiated with an energy beam to dissociate the oxidizing agent. The cleaning method according to claim 5, wherein a peroxide is added as the oxidizing agent to the supercritical fluid. The cleaning method according to claim 5, wherein the supercritical fluid is carbon dioxide.

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