Cleaning method, processing apparatus, and storage medium

Deposits such as particles deposited on a surface of a target object can be easily removed while suppressing damage to the target object such as destruction of pattern formed on the surface of the target object or film roughness on the surface of the target object. In a pre-treatment, vapor of a hydrogen fluoride is supplied to a wafer W to dissolve a natural oxide film 11, so that a deposit 10 attached to a surface of the natural oxide film 11 is slightly separated from a surface of the wafer W. A carbon dioxide gas that does not react with an underlying film 12 is supplied to a processing gas atmosphere where the wafer W is placed, so that a gas cluster of the carbon dioxide gas is generated. Then, the gas cluster in a non-ionized state is irradiated toward the wafer W to remove the deposit 10.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a U.S. national phase application under 35 U.S.C. §371 of PCT Application No. PCT/JP2012/004521 filed on Jul. 12, 2012, which claims the benefit of Japanese Patent Application No. 2011-157955 filed on Jul. 19, 2011, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to a cleaning method and a processing apparatus for removing deposits such as particles deposited on a surface of a target object, and a storage medium that stores the method therein.

BACKGROUND

As a technology of removing deposits, for example, particles or contaminants, deposited on a surface of a substrate (hereinafter, referred to as “wafer”) as a target object, for example, a semiconductor wafer, there are known methods described in, for example, Patent Documents 1 and 2. In Patent Documents 1 and 2, it is described that a gas cluster ion beam is irradiated onto a surface of the wafer. In this technology, in order to overcome adhesive strength of the deposits to the wafer, for example, a physical shearing force of the gas cluster ion beam is adjusted by an acceleration voltage or an ionized amount.

However, along with miniaturization of a device structure formed on a wafer, the device structure can be easily damaged by a gas cluster ion beam. That is, by way of example, when a gas cluster ion beam is irradiated to a pattern having grooves and lines on a wafer, if a width of the line is, for example, several tens nm order, there is a risk that the line may be damaged by the irradiation of the gas cluster ion beam. Further, even if the pattern is not formed, after the gas cluster ion beam is irradiated, a surface shape of the wafer may be deteriorated.

Patent Document 3 describes a technology of removing a natural oxide film on a substrate with a chemical liquid and jetting air applied with ultrasonic vibration, and Patent Document 4 describes a technology of irradiating a pulsed laser onto a surface of a substrate. However, in Patent Documents 3 and 4, there is no description about removal of particles from a miniaturized device structure or damage to a wafer.

REFERENCES

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In view of the foregoing problems, example embodiments provide a cleaning method and a processing apparatus capable of easily removing deposits such as particles deposited on a surface of a target object while suppressing damage to the target object, and a storage medium that stores the method therein.

Means for Solving the Problems

In one example embodiment, a cleaning method of removing a deposit from a surface of a target object to which the deposit is attached includes: performing a pre-treatment including an etching process on at least one of the surface of the target object and the deposit; generating a gas cluster as an atomic or molecular cluster of a cleaning gas by discharging the cleaning gas, which does not react with a film exposed at the surface of the target object, at a processing gas atmosphere where the target object is placed from a region having a higher pressure than the processing gas atmosphere and adiabatically expanding the cleaning gas; and removing the deposit by irradiating the gas cluster of the cleaning gas to the surface of the target object on which the pre-treatment is performed.

The pre-treatment may include a modification process of modifying at least one of the surface of the target object and the deposit, and an etching process of etching a modification layer modified by the modification process. Further, the performing of the pre-treatment and the removing of the deposit may be performed at the same time. Furthermore, the pre-treatment may include an irradiation process of irradiating the gas cluster to perform the etching process.

The irradiation process of irradiating the gas cluster to perform the etching process may be performed by using a generating device identical to or different from a generating device that irradiates the gas cluster in the removing of the deposit by irradiating the gas cluster of the cleaning gas. Further, in the removing of the deposit by irradiating the gas cluster of the cleaning gas and the irradiation process of irradiating the gas cluster to perform the etching process, multiple generating devices each irradiating the gas cluster may be provided, and the gas cluster may be irradiated from the generating devices. Moreover, in the removing of the deposit by irradiating the gas cluster of the cleaning gas and the irradiation process of irradiating the gas cluster to perform the etching process, an angle of a generating device that irradiates the gas cluster with respect to the target object may be variable.

In another example embodiment, a processing apparatus that removes a deposit from a surface of a target object to which the deposit is attached includes: a pre-treatment chamber in which the target object is mounted; a pre-treatment module including a pre-treatment device configured to perform a pre-treatment having an etching process on at least one of the surface of the target object mounted in the pre-treatment chamber and the deposit; a cleaning chamber in which the target object is mounted; a gas cluster nozzle that is provided within the cleaning chamber, and configured to discharge a cleaning gas, which does not react with a film exposed at the surface of the target object, at a processing gas atmosphere within the cleaning chamber from a region having a higher pressure than the processing gas atmosphere to adiabatically expand the cleaning gas and generate the gas cluster as an atomic or molecular cluster of the cleaning gas, and configured to supply the gas cluster to the target object, on which the pre-treatment is performed, in order to remove the deposit; and a transfer device configured to transfer the target object into the pre-treatment chamber and the cleaning chamber.

The pre-treatment chamber may be a normal pressure processing chamber in which a pressure is maintained at a normal pressure atmosphere, and the pre-treatment chamber may be connected to a normal pressure transfer chamber configured to transfer the target object under the normal pressure atmosphere. The cleaning chamber may be a vacuum processing chamber in which a pressure is maintained at a vacuum pressure atmosphere, and the cleaning chamber is airtightly connected to a vacuum transfer chamber configured to transfer the target object under the vacuum pressure atmosphere. A load-lock chamber may be provided between the normal pressure transfer chamber and the vacuum transfer chamber and may be configured to switch an internal atmosphere thereof. A normal pressure transfer device and a vacuum transfer device as the transfer device may be provided in the normal pressure transfer chamber and the vacuum transfer chamber, respectively. Further, the pre-treatment chamber and the cleaning chamber may be vacuum processing chambers in which pressures are maintained at a vacuum pressure atmosphere, and a vacuum transfer chamber including the transfer device may be airtightly interposed between the pre-treatment chamber and the cleaning chamber. Furthermore, the pre-treatment chamber and the cleaning chamber may be provided as a common single chamber. Moreover, the vacuum transfer chamber may be airtightly connected to the vacuum processing chamber configured to perform a vacuum process before the pre-treatment or perform a vacuum process after the deposit is removed.

In still another example embodiment, a computer-readable storage medium has stored thereon computer-executable instructions that, in response to execution, cause a processing apparatus to perform the cleaning method as described above.

Effect of the Invention

In accordance with the example embodiments, a pre-treatment including an etching process is performed on at least one of a surface of a target object and a deposit, so that the deposit is easily separated from the surface of the target object. Then, a gas cluster is generated by using a cleaning gas which does not react with a film exposed on the surface of the target object. Therefore, even if the gas cluster of the cleaning gas is irradiated while being not ionized, the deposit can be easily separated and removed from the target object. Thus, it is possible to easily remove the deposit while suppressing damage to the target object.

MODE FOR CARRYING OUT THE INVENTION

First Example Embodiment: Silicon Substrate

A first example embodiment of a cleaning method will be explained with reference toFIG. 1toFIG. 5. Above all, a configuration of a wafer W to which the cleaning method is applied, and the cleaning method will be explained briefly. The wafer W is made of silicon (Si) as depicted inFIG. 1, and a pattern7having, for example, grooves5as recessed portions and lines6as protruded portions is formed on a surface of the wafer W. Further, according to the cleaning method, a deposit10on the surface of the wafer W as depicted inFIG. 2can be easily removed while suppressing occurrence of damage to the wafer W such as destruction of the lines6or film roughness on the surface of the wafer W as described below.

Hereinafter, the deposit10will be explained in detail. The deposit10is, for example, a residual material generated by a plasma etching process in which the pattern7is formed on the wafer W or a plasma ashing process which is preformed after the plasma etching process. To be specific, the deposit10may be formed of an inorganic material including silicon that is removed from the inside of the groove5or an organic material including carbon (C) as a residue of a photoresist mask that is stacked on an upper layer of the wafer W and made of an organic material. Herein, for example, since the wafer W in storage is exposed to atmosphere, the deposit10is not simply placed on the surface of the wafer W but is surrounded by a natural oxide film formed on the surface of the wafer W to be strongly attached thereon as depicted inFIG. 2in a microscopic view. That is, for example, a natural oxide film is formed on the surface of the wafer W to surround the deposit10, and the deposit10is buried in the natural oxide film accordingly. That is, the deposit10is held on the wafer W by being cross-linked on the surface of the wafer W.

In this case, the surface of the wafer W is oxidized, e.g., when the wafer W is transferred in the atmosphere, so that a natural oxide film11made of a silicon oxide SiO2is formed thereon. A thickness of the natural oxide film11is, for example, about 1 nm. A portion made of silicon and positioned under the natural oxide film11will be referred to as an underlying film12. Although the surface of the wafer W and the deposit10may be chemically bonded and connected to each other, there will be explained a case where the deposit10is held on the wafer W by being cross-linked therebetween as described above, for the sake of simplicity of explanation. Further, surface shapes and sizes of the wafer W and the deposit10are schematically depicted inFIG. 1and will be the same in the subsequent drawings.

Hereinafter, the cleaning method in the present example embodiment will be explained. As depicted inFIG. 3, in a pre-treatment, vapor of a hydrogen fluoride aqueous solution is supplied to the wafer W. The natural oxide film11is dissolved by the vapor of the hydrogen fluoride to become silicon tetrafluoride, and then exhausted in the form of a gas. In this case, the cross-linking between the wafer W and the deposit10is also etched. As depicted inFIG. 4, the surface of the wafer W is retreated in a downward direction as viewed from the deposit10, and a surface of the deposit10becomes exposed.

Therefore, the adhesive strength of the wafer W to the deposit10, which is buried in the natural oxide film on the surface of the wafer W and strongly attached to the wafer W, is reduced through the pre-treatment. That is, since the surface of the wafer W is etched, the deposit10becomes exposed to be in slight contact with the surface of the wafer W. In this case, as described below, if the deposit10contains a silicon oxide, the deposit10is also etched by the vapor of the hydrogen fluoride. Herein, however, only the surface of the wafer W is focused and explained. Although an upper surface of the wafer W (underlying film12) and a lower surface of the deposit10are illustrated as being separated from each other, the underlying film12and the deposit10are actually in slight contact with each other. A device that supplies the vapor of the hydrogen fluoride to the wafer W is formed by combining a well-known vaporizer with a processing chamber, and thus, will be explained later together with a processing apparatus that performs the cleaning method.

Then, the deposit10is removed from the surface of the wafer W by using a gas cluster. A gas is supplied to a processing gas atmosphere where the wafer W is placed from a region having a higher pressure than the processing gas atmosphere. Then the gas is adiabatically expanded to be cooled to the condensation temperature of the gas. As a result, the gas cluster is generated as an atomic or molecular cluster of the gas.FIG. 5illustrates an example of a nozzle23configured to generate the gas cluster. The nozzle23includes a pressure room32having a substantially cylindrical shape, and a gas diffusing portion33connected to the lower end portion of the pressure room32. The pressure room32is vertically extended, and a lower end portion of the pressure room32is opened. The gas diffusing portion33includes an orifice portion32aformed by being horizontally extended from the periphery of the lower end portion of the pressure room32toward a central portion of the pressure room32. Further, the gas diffusing portion33has a shape in which the diameter thereof is increased downwardly from the orifice portion32a. An opening diameter of the orifice portion32aand a distance between the orifice portion32aand the wafer W on a mounting table22are, for example, about 0.1 mm and about 6.5 mm, respectively. An upper end portion of the nozzle23is connected to a gas supply line34through which, for example, a carbon dioxide (CO2) gas is supplied into the pressure room32.

A process pressure in the processing gas atmosphere is set to be a vacuum atmosphere in a range of, for example, from about 1 Pa to about 100 Pa, and the carbon dioxide gas is supplied to the nozzle23at a pressure in a range of, for example, from about 0.3 MPa to about 2.0 MPa. When the carbon dioxide gas is supplied to the processing gas atmosphere, it is cooled to have a temperature equal to or lower than the condensation temperature thereof by the rapid adiabatic expansion, and, thus, molecules are bonded to each other by a van der Waals force to become a gas cluster. In this case, at the gas supply line34or a gas cluster flow path under the nozzle23, an ionization device configured to ionize the gas cluster is not provided. Therefore, the gas cluster in a non-ionized state is vertically irradiated toward the wafer W as depicted inFIG. 5.

As described above, the deposit10on the surface of the wafer W has a very weakened adhesive strength with respect to the wafer W through the pre-treatment and becomes in slight contact with the surface of the underlying film12. Therefore, if the deposit10on the wafer W collides with the gas cluster, the deposit10is blown away and removed from the surface of the wafer W by an injection pressure of the gas cluster as depicted inFIG. 5. In this case, the gas cluster is composed of a carbon dioxide gas that does not react with the underlying film12. Further, the gas cluster is not ionized, and the gas cluster in a non-ionized state is irradiated to the wafer W. Therefore, the underlying film12as the surface of the wafer W exposed through the pre-treatment can be suppressed from being removed by the irradiation of the gas cluster. Further, there is no risk that electric wirings formed within the underlying film12are electrically charged up. Therefore, it is possible to suppress damage to the electric wirings from being generated, or to allow the damage, if any, to be a very low level. For this reason, after the gas cluster is irradiated, the surface of the wafer W is patterned after the surface of the natural oxide film11.

If the wafer W is moved in a relatively horizontal direction with respect to the nozzle23in order for the gas cluster to be irradiated throughout an entire surface of the wafer W, the deposit10is removed throughout the entire surface of the wafer W and a cleaning process is carried out. Further, if there is generated water as a by-product from the natural oxide film11dissolved by the vapor of the hydrogen fluoride, the wafer W is heated by a temperature controller to be described later. Thus, it is possible to suppress water from remaining.

Hereinafter, a processing apparatus including the device that supplies the vapor of the hydrogen fluoride aqueous solution to the wafer W or a device that irradiates the gas cluster to the wafer W will be explained. The device that supplies the vapor of the hydrogen fluoride to the wafer W will be explained first with reference toFIG. 6. In this device, a pre-treatment module includes a processing chamber42accommodating therein a mounting table41configured to mount the wafer W thereon and a vaporizer43as a pre-treatment unit configured to supply the vapor of the hydrogen fluoride into the processing chamber42. InFIG. 6, a reference numeral44denotes a transfer opening of the wafer W, a reference numeral45denotes a heater configured to suppress condensation of the vapor of the hydrogen fluoride at the surface of the wafer W on the mounting table41.

On a ceiling surface of the processing chamber42, an end of a gas supply line46extended from the vaporizer43is connected to face the wafer W on the mounting table41. The vapor of the hydrogen fluoride is supplied together with a carrier gas such as a nitrogen (N2) gas through the gas supply line46to the wafer W. InFIG. 6, V and M denote a valve and a flow rate control unit, respectively.

On a bottom surface of the processing chamber42, an exhaust opening51for exhausting an atmosphere within the processing chamber42is formed at, for example, multiple positions. An exhaust path52extended from the exhaust opening51is connected to a vacuum pump54via a pressure control unit53such as a butterfly valve.

Further, in the processing chamber42, when the vapor of the hydrogen fluoride aqueous solution evaporated from the vaporizer43is supplied by the carrier gas to the wafer W on the mounting table41, the natural oxide film11is dissolved as described above.

Hereinafter, the device that irradiates the gas cluster to the wafer W will be explained with reference toFIG. 7. As depicted inFIG. 7, this device includes a cleaning chamber21configured to accommodate the wafer W therein and remove the deposit10. Further, within the cleaning chamber21, there is provided a mounting table22configured to mount the wafer W thereon. At a central portion on a ceiling surface of the cleaning chamber21, there is formed a protrusion portion21athat is upwardly protruded in a cylindrical shape. At the protrusion portion21a, the above-described nozzle23is provided as a gas cluster generating device. The nozzle23faces downwardly in a vertical direction in the present example embodiment. InFIG. 7, a reference numeral40denotes a transfer opening and G denotes a gate valve configured to open and close the transfer opening40.

By way of example, at a position close to the transfer opening40on a bottom surface of the cleaning chamber21, although illustration is omitted herein, a supporting pin is provided to pass through a through hole formed in the mounting table22. Further, the wafer W is elevated with respect to the mounting table22by a combination of a non-illustrated elevating device provided at the mounting table22and the supporting pin, and the wafer W is transferred to a non-illustrated wafer transfer arm outside the cleaning chamber21. On the bottom surface of the cleaning chamber21, one end of an exhaust path24for vacuum-exhausting an atmosphere within the cleaning chamber21is connected. The other end of the exhaust path24is connected to a vacuum pump26via a pressure control unit25such as a butterfly valve.

The mounting table22is configured to be movable in a horizontal direction within the cleaning process21in order for the nozzle23to relatively scan throughout the entire surface of the wafer W on the mounting table22. To be specific, under the mounting table22on the bottom surface of the cleaning chamber21, an X-axis rail27extended horizontally along an X-axis direction and an Y-axis rail29configured to be movable along the X-axis rail27are provided. Further, the mounting table22is supported on the Y-axis rail29. Furthermore, the mounting table22includes a non-illustrated temperature control device configured to control a temperature of the wafer W on the mounting table22.

An upper end of the pressure room32is connected to one end of the gas supply line34extended to pass through the ceiling surface of the cleaning chamber21. The other end of the gas supply line34is connected to a gas source37, in which carbon dioxide is stored, via a valve36and the flow rate control unit35. The pressure room32includes a non-illustrated pressure gauge, and a flow rate of a gas to be supplied into the pressure room32is controlled by a control unit67to be described later via the pressure gauge. Further, an angle or a distance of the nozzle23with respect to the mounting table22may be controlled by a non-illustrated driving unit. If an angle or a distance of the nozzle23is controlled, it is possible to suppress the deposit10removed from the wafer W from being attached again to the wafer W. Moreover, it is possible to reduce damage to the pattern7and also possible to easily remove the deposit10attached to a bottom surface of the groove5. As described below, when a gas cluster is irradiated during the pre-treatment, an angle or a distance of the nozzle23may also be controlled in the same manner.

Hereinafter, the overall configuration of the processing apparatus including the processing chamber42and the cleaning chamber21will be explained with reference toFIG. 8. In the processing apparatus, a loading/unloading port60for mounting a FOUP 1 as an airtight transfer container that accommodates, for example, 25 sheets of the wafer W is arranged in parallel transversely at, for example, three positions. An atmospheric transfer chamber61is provided along the arrangement of the loading/unloading ports60. Within the atmospheric transfer chamber61, a wafer transfer device61aincluding a multi-joint arm for transferring the wafer W is provided as a normal pressure transfer device. Further, at one side of the atmospheric transfer chamber61, an alignment chamber62for adjusting a direction and a position of the wafer W is provided. At the other side of the atmospheric transfer chamber61, the above-described processing chamber42is connected to face the alignment chamber62. At the atmospheric transfer chamber61's surface opposite to the loading/unloading ports60, a load-lock chamber63configured to switch an atmosphere between a normal pressure atmosphere and an atmospheric atmosphere is connected airtightly. In the present example embodiment, the load-lock chamber63is arranged in parallel transversely at two positions.

At an inner side than the load-lock chambers63as viewed from the atmospheric transfer chamber61, a vacuum transfer chamber64including a transfer arm64aas a vacuum transfer device for transferring the wafer W in a vacuum atmosphere is connected airtightly. The vacuum transfer chamber64is connected airtightly to the above-described cleaning chamber21. Further, the vacuum transfer chamber64is also connected airtightly to an etching chamber65in which a plasma etching process for forming the pattern7on the wafer W is performed and an ashing chamber66in which a plasma ashing process is performed onto the photoresist mask. Furthermore, the vacuum transfer chamber64may be connected airtightly a processing chamber in which, for example, a CVD (Chemical Vapor Deposition) process is performed after the deposit10is removed.

The processing apparatus further includes the control unit67including a computer configured to control overall operations of the devices. A memory of the control unit67stores a program configured to perform the above-described pre-treatment, cleaning process, etching process, and ashing process. The program includes a step group for performing an operation of the device corresponding to the process with respect to the wafer W. The program in a storage unit68as a storage medium such as a hard disk, a compact disk, a magneto-optical disk, a memory card, a flexible disk, and the like may be installed in the control unit67.

In the processing apparatus, when the FOUP 1 is mounted on the loading/unloading port60, the wafer W is unloaded from the FOUP 1 by the wafer transfer device61a. On the surface of the wafer W, for example, a photoresist mask corresponding to the above-described pattern7is formed. Then, after the wafer W is aligned in the alignment chamber62, the wafer W is loaded into the load-lock chamber63set to be in the atmospheric atmosphere. After an atmosphere within the load-lock chamber63is evacuated to a vacuum atmosphere, the wafer W is transferred to the etching chamber65and the ashing chamber66in sequence by the transfer arm64a. Then, the above-described pattern7is formed and the ashing process is carried out in sequence. Thereafter, the wafer W is transferred into the processing chamber42via the load-lock chamber63and the atmospheric transfer chamber61, and the above-described pre-treatment is carried out. Then, the wafer W is loaded into the cleaning chamber21, and a gas cluster is irradiated. Thereafter, the processed wafer W is returned back to the FOUP 1 through the load-lock chamber63and the atmospheric transfer chamber61.

According to the above-described example embodiment, when the deposit10attached to the surface of the wafer W is removed, the vapor of the hydrogen fluoride is supplied to the wafer W in the pre-treatment to dissolve the natural oxide film11on the surface of the wafer W. For this reason, the deposit10becomes in slight contact with the surface of the wafer W and has a very weakened adhesive strength with respect to the surface. Therefore, by irradiating the gas cluster composed of a carbon dioxide gas to the deposit10, the deposit10can be easily removed. Accordingly, when removing the deposit10, even if the fine pattern7is formed on the wafer W as described above, it is possible to suppress occurrence of damage such as destruction of the line6by controlling, for example, an irradiation speed of the gas cluster.

In this case, the carbon dioxide gas does not react with the underlying film12of the wafer W. Further, the gas cluster is irradiated to the wafer W while being not ionized. For this reason, when the gas cluster is irradiated to the wafer W, occurrence of damage, in which the surface of the wafer W is roughened or physically cut off, can be suppressed. Further, since the gas cluster is not ionized, for example, it is not required to provide a device that ionizes a gas or a gas cluster in the above-described cleaning chamber21. Therefore, it is possible to suppress a cost of the device.

Further, since the wafer W is exposed to an atmosphere of the vapor of the hydrogen fluoride within the processing chamber42, adhesive strength of the deposit10with respect to the entire surface of the wafer W is reduced at a time through the pre-treatment. For this reason, as compared with a conventional case where the deposit10is removed by using only a gas cluster of the reactive gas, it is possible to uniformly perform the process throughout the entire surface in a short time, and also possible to increase throughput. Furthermore, by combining the pre-treatment and the irradiation of the gas cluster, it is possible to suppress an amount of the gas or chemical liquid used as compared with a case where the deposit10is removed by using only a gas or a gas cluster, or by using only a chemical liquid. In this case, in all of the processes including the pre-treatment and the irradiation of the gas cluster, a chemical liquid is not supplied to the wafer W, it is possible to suppress a cost required to waste the liquid.

By performing the above-described pre-treatment, the surface of the wafer W is changed from the natural oxide film11that does not have conductivity to the underlying film12that has conductivity, so that the surface of the wafer W has conductivity. For this reason, even if the deposit10is attracted to the natural oxide film11by the above-described physical adhesive force together with, for example, an electrostatic force, the electrostatic force may be lost or weakened by the pre-treatment, and, thus, the deposit10can be easily removed from the wafer W. Further, even if the natural oxide film11and the deposit10are chemically bonded to each other, since the bonded natural oxide film11is etched, the deposit10can be easily removed as described above.

Modification Example of First Example Embodiment: Oxidation of Silicon Substrate

Hereinafter, a modification example of the first example embodiment will be explained with reference toFIG. 9. In the first example embodiment as described above, there has been explained a case where the natural oxide film11on the surface of the wafer W is removed. However, it is difficult to control a film thickness of the natural oxide film11, and, thus, if controllability or reproducibility is needed in a cleaning process, a pre-treatment is performed as follows.

If controllability or reproducibility is needed in a cleaning process, a surface layer of the underlying film12is oxidized first. To be specific, as depicted inFIG. 9, an oxidizing gas such as an ozone gas is supplied to the surface of the wafer W. By this ozone gas, the surface layer of the underlying film12in contact with the deposit10is slightly oxidized by, for example, about 1 nm to form an oxide film13as a modification layer. Then, a supply of the vapor of the hydrogen fluoride and irradiation of the gas cluster composed of a carbon dioxide gas are carried out in this sequence, and the deposit10is removed throughout the entire surface together with the oxide film13. In the modification example, the pre-treatment is carried out by supplying the vapor of the hydrogen fluoride and performing oxidation process of the underlying film12with the ozone gas. As a device that supplies the ozone gas to the wafer W, a device including an ozone gas supply source (not illustrated) instead of the vaporizer43shown inFIG. 6is used.

Herein, in order to oxidize the underlying film12of the wafer W, the ozone gas is supplied to the wafer W. However, instead of the ozone gas, ozone water (an aqueous solution containing an ozone gas) may be supplied. An example of a pre-treatment module that supplies ozone water to the wafer W will be explained briefly with reference toFIG. 10. Since an operation of oxidizing the underlying film12with ozone water, or a subsequent etching process for the oxide film13or irradiation of a gas cluster is the same as the above-described example embodiment, explanation thereof will be omitted.

This device includes a processing chamber81configured to supply ozone water to the wafer W and a spin chuck82serving as a mounting table configured to mount the wafer W thereon. The spin chuck82supports a central portion of a lower surface of the wafer W, and is configured to be rotatable around a vertical axis and vertically movable by a driving unit83. Above the spin chuck82, an ozone water nozzle84for discharging ozone water to the wafer W is provided as a pre-treatment device. At an upper portion of the spin chuck82, a cover body85configured to airtightly seal an atmosphere, in which a pre-treatment is performed on the wafer W, is provided to be vertically movable by a non-illustrated elevating device. The ozone water nozzle84is provided at a central portion of the cover body85. At a side of the spin chuck82, a ring-shaped exhaust path86is provided in the vicinity of a periphery of the wafer W in a circumference direction thereof. A lower surface of the exhaust path86is connected to a vacuum pump88via a pressure control device87such as a butterfly valve or the like. InFIG. 10, a reference numeral81adenotes a transfer opening of the wafer W and a reference numeral81bdenotes a shutter for opening and closing the transfer opening81a.

In the processing chamber81, when ozone water is discharged from the ozone water nozzle84toward a central portion of the wafer W attracted and held by the spin chuck82and rotated around the vertical axis, the ozone water is diffused toward the periphery of the wafer W by a centrifugal force and forms a liquid film throughout the entire surface of the wafer W. Then, when the oxidation process is finished, the spin chuck82is rotated at a high speed to push the ozone water toward an outer periphery of the wafer W. Thereafter, the surface of the wafer W is cleaned with a rinse liquid discharged from a non-illustrated rinse nozzle.

In the first example embodiment and the modification example of the first example embodiment, there has been explained a case where the pattern7is formed on the wafer W. However, it is possible to easily remove the deposit10from even a silicon oxide film or a silicon film, on which the pattern7is not formed, by performing the pre-treatment and irradiating the gas cluster composed of a carbon dioxide gas in the same manner. That is, a source gas used for forming the film by, for example, a CVD method, contains an organic material. Accordingly, if this organic material is attached as the deposit10to the surface of the wafer W, it is removed in the same manner as explained above.

Further, although the pre-treatment is carried out in an atmospheric atmosphere in the above-described examples, the pre-treatment may be carried out in a vacuum atmosphere. In this case, the processing chamber42for performing the pre-treatment and the cleaning chamber21for performing a cleaning process may be separately connected to the vacuum transfer chamber64shown inFIG. 8, or the processing chamber42and the cleaning chamber21may be provided as a common single chamber. To be specific, as depicted inFIG. 11andFIG. 12, the vacuum transfer chamber64is airtightly connected to the cleaning chamber21also serving as the processing chamber42. In the cleaning chamber21, the nozzle23and a gas source47for storing a hydrogen fluoride gas are provided. In the modification example, at a ceiling surface of the cleaning chamber21at a side outer than an outer periphery of the protrusion portion21a, the gas supply line46extended from the gas source47is connected to multiple portions, and an opening end of each gas supply line46is provided to face the central portion of the wafer W on the mounting table22.

In the device depicted inFIG. 12, for example, a pressure within the cleaning chamber21is set to be a process pressure for performing a pre-treatment, and the pre-treatment is performed onto the wafer W. Then, after the pressure within the cleaning chamber21is set to be lower (high vacuum) than the process pressure, the above-described cleaning process is performed.

Second Example Embodiment: Germanium Film

Hereinafter, a second example embodiment will be explained with reference toFIG. 13toFIG. 16. In the second example embodiment, the underlying layer12formed of a germanium (Ge) film is formed on a silicon layer14of the wafer W as depicted inFIG. 13. Further, the deposit10is attached to a surface of the underlying film12. In this case, the deposit10contains a by-product generated when the underlying film12is formed by, for example, a CVD method or the like. In the second example embodiment, a pre-treatment is performed as follows.

To be specific, an ozone gas is supplied to the surface of the underlying film12. By this ozone gas, a surface layer of the underlying film12is slightly oxidized to form a germanium oxide film (Ge—O) film15as a modification layer as depicted inFIG. 14. Then, as depicted inFIG. 15, when a gas cluster composed of, for example, water vapor (H2O) is irradiated to the wafer W, the germanium oxide film15is dissolved and etched by the water vapor. For this reason, through the oxidation process of the underlying film12with the ozone gas and the pre-treatment by supplying a gas cluster of the water vapor, the deposit10becomes in slight contact with the surface of the wafer W as depicted inFIG. 16and an adhesive strength becomes very weakened. In this case, the gas cluster composed of the water vapor does not react with the germanium film as the underlying film12. For this reason, while suppressing the damage to the underlying film12by the gas cluster composed of the water vapor, the germanium oxide film15is selectively etched.

Then, a gas cluster composed of a carbon dioxide gas is irradiated to the wafer W. Since the gas cluster of the carbon dioxide gas does not react with the germanium film as the underlying film12, the deposit10only or together with the germanium oxide film15dissolved by the water vapor is removed while the underlying film12is not damaged.

In the second example embodiment, a device for oxidizing the underlying film12has the same configuration as the device depicted inFIG. 6except that instead of the vaporizer43, an ozone gas source is connected. Further, in a device for irradiating the gas cluster composed of the water vapor, a pre-treatment chamber having the same configuration as the above-described cleaning chamber21is airtightly connected to the vacuum transfer chamber64, and a vaporizer, as the gas source37, for vaporizing pure water is provided. In the second example embodiment, the gas supply line46for supplying an ozone gas to the wafer W and the nozzle for irradiating the gas cluster composed of the water vapor constitute a pre-treatment device. Further, when the underlying film12is oxidized, the above-described device depicted inFIG. 10may be used to supply ozone water, instead of an ozone gas, to the wafer W.

In this case, if the gas cluster composed of an ozone gas is used, the device may have the following configuration. That is, as depicted inFIG. 17, together with the gas supply line34for irradiating a gas cluster composed of a carbon dioxide gas or the gas source37, a vaporizer38for vaporizing pure water and a water vapor supply line39extended from the vaporizer38may be connected to the nozzle23. Therefore, in the second example embodiment, a device for generating a gas cluster in a pre-treatment is the same as a device for generating a gas cluster in a cleaning process. In this case, as explained above, after the underlying film12is oxidized, a supply of the gas cluster composed of the water vapor and a supply of the gas cluster composed of the carbon dioxide gas may be carried out in this sequence. Further, as can be seen from an experimental example to be described below, these gas clusters may be simultaneously supplied to the wafer W to perform an etching process onto the germanium oxide film15and remove the deposit10at the same time. When the germanium oxide film15is etched, water vapor in the gas phase or pure water in the liquid phase may be supplied to the wafer W instead of supplying the gas cluster composed of the water vapor. In this case, in the devices depicted inFIG. 6andFIG. 10, pure water is used instead of the hydrogen fluoride aqueous solution or the ozone water.

Third Example Embodiment: Photoresist Mask

Hereinafter, a third example embodiment will be explained with reference toFIG. 18andFIG. 19. In the third example embodiment, as depicted inFIG. 18, there will be explained a case where the deposit10attached to a photoresist mask16for forming the pattern7on the wafer W is removed. That is, after the photoresist mask16is patterned by performing an exposure process and a developing process, an organic material removed from the photoresist mask16by the patterning is attached, as the deposit10, to a surface of the photoresist mask16. For this reason, the deposit10is removed as follows.

To be specific, by using the device depicted inFIG. 6, instead of vapor of hydrogen fluoride, an ozone gas is supplied to the surface of the wafer W in a pre-treatment. Through the pre-treatment, as depicted inFIG. 19, a surface of the photoresist mask16is slightly oxidized and etched, and the deposit10has a very weakened adhesive strength with respect to the photoresist mask16. For this reason, when a gas cluster composed of a carbon dioxide gas is irradiated to the wafer W, since the gas cluster does not react with the photoresist mask16as the underlying film12under the surface thereof, a modification layer18together with the deposit10is removed.

In the third example embodiment, instead of the ozone gas, ozone water may be supplied to the wafer W. Further, in the pre-treatment, a gas cluster may be generated by using the ozone gas and the surface of the photoresist mask16may be oxidized by the gas cluster. In this case, the gas cluster composed of the ozone gas and the gas cluster composed of the carbon dioxide gas may be simultaneously supplied to the wafer W to perform the pre-treatment and remove the deposit10at the same time.

Further, if the deposit10on the photoresist mask16is removed, in a pre-treatment, ultraviolet (UV) rays may be irradiated as depicted inFIG. 20instead of supplying the ozone gas. That is, since the UV rays are irradiated, the surface of the photoresist mask16is hardened by degradation, so that it is easily removable. For this reason, when the gas cluster composed of the carbon dioxide gas is irradiated to the photoresist mask16, a hardened layer on the surface of the photoresist mask16is removed together with the deposit10in the same manner. Therefore, in the third example embodiment, the process of irradiating the gas cluster composed of the carbon dioxide gas serves as a part of the pre-treatment (etching the surface of the photoresist mask16). Alternatively, in the pre-treatment, a supply of the ozone gas and irradiation of the UV rays may be carried out at the same time. In this case, in the same manner as described above, an adhesive strength of the deposit10becomes very weakened through the etching of the surface thereof. As a result, when the gas cluster composed of the carbon dioxide gas is irradiated to the wafer W, the deposit10is easily removed.

A device that irradiates ultraviolet rays to the wafer W will be explained briefly with reference toFIG. 21. This device includes a processing chamber91and a mounting table92provided within the processing chamber91. At a portion of a ceiling surface of the processing chamber91facing the mounting table92, a transparent window93made of, for example, quartz or the like is airtightly provided. Above the transparent window93, a UV lamp94for irradiating ultraviolet rays to the wafer W on the mounting table92via the transparent window93is provided as a pre-treatment device. InFIG. 21, a reference numeral95denotes a gas supply line, a reference numeral96denotes a gas source that stores, for example, a nitrogen gas, a reference numeral97denotes a vacuum pump, and a reference numeral98denotes a transfer opening. The processing chamber91is airtightly connected to, for example, the above-described vacuum transfer chamber64. The processing chamber91where ultraviolet rays are irradiated to the wafer W and the processing chamber42where an ozone gas is supplied to the wafer W as depicted inFIG. 6may be provided as a common single chamber to supply an ozone gas and irradiate ultraviolet rays to the wafer W at the same time.

Fourth Example Embodiment: Metal Film

Hereinafter, a fourth example embodiment will be explained with reference toFIG. 22andFIG. 23. In the fourth example embodiment, there will be explained a case where the deposit10on a metal film17, which is formed on the silicon layer14of the wafer W or buried in the grooves5, is removed. In the fourth example embodiment, the metal film17is made of, for example, tungsten (W). That is, a source gas used for forming the metal film17by a CVD method contains an organic material as described above, and, thus, as depicted inFIG. 22, a residue formed of the organic material may be attached, as the deposit10, to a surface of the metal film17. Therefore, the deposit10is removed as follows.

To be specific, as depicted inFIG. 23, by using the device depicted inFIG. 6, a hydrogen chloride (HCl) gas is supplied to the wafer W in a pre-treatment. By this hydrogen chloride gas, a surface layer of the metal film17is slightly etched and removed. For this reason, an adhesive strength of the deposit10with respect to the metal film17becomes very weakened. Therefore, when a gas cluster composed of a carbon dioxide gas that does not react with respect to the metal film17serving as the underlying film12is irradiated to the wafer W, the deposit10is easily removed.

In this case, a gas used for the pre-treatment may be a chlorine trifluoride (ClF3) gas instead of the hydrogen chloride gas. Further, as the metal film17, a titanium film may be used instead of the tungsten film.

Fifth Example Embodiment: Etching of By-Product

Hereinafter, a fifth example embodiment will be explained. In each of the above-described example embodiments, there has been explained a case where a surface of the wafer W is etched in a pre-treatment. However, in the fifth example embodiment, instead of the surface of the wafer W, a surface of the deposit10is etched. That is, if a material of the deposit10is already known, or if a material contained in the deposit10is expected, when the material thereof is etched, for example, a lower end portion of the deposit10is retreated in an upward direction as viewed from the wafer W. Therefore, in this case, the deposit10becomes easily separated from the wafer W, and, thus, the deposit10is easily removed by a gas cluster composed of a carbon dioxide gas in the same manner.

InFIG. 24, the deposit10is made of silicon oxide, and the deposit10is attached to, for example, the metal film17as a surface of the wafer W. In this case, as depicted inFIG. 25, vapor of hydrogen fluoride is supplied to the wafer W and a surface of the deposit10is etched. Therefore, the deposit10is simply placed on the surface of the wafer W. For this reason, when a gas cluster composed of a carbon dioxide gas is irradiated thereafter, the deposit10is easily removed.

In the fifth example embodiment, there has been explained a case where the deposit10is made of silicon oxide. However, if the deposit10is made of an organic material, ozone or ultraviolet rays are supplied (irradiated) to the wafer W in the pre-treatment, and if the deposit10is formed of a metal particle, a chlorine-based gas is supplied in the pre-treatment. Further, if the deposit10is made of silicon, as explained in the modification example of the first example embodiment, a surface of the deposit10may be first oxidized before the surface of the deposit10is etched. Furthermore, even if an inner portion of the deposit10is not made of the same material in a uniform manner, if a portion of the deposit10contains a material to be etched, the portion is etched and an adhesive strength of the deposit10with respect to the surface of the wafer W can be reduced in the same manner.

Moreover, as depicted inFIG. 26, if the surface of the wafer W and the surface of the deposit10contain the same material, i.e., silicon oxide in the fifth example embodiment, the surface of the wafer W can be etched together with the surface of the deposit10. Therefore, an adhesive strength of the deposit10can be further reduced.

As a gas cluster to be irradiated to the wafer W in the cleaning chamber21, a carbon dioxide gas is used in each of the above-described example embodiments. However, as a gas used for a gas cluster, an inert gas, such as an argon (Ar) gas or a nitrogen (N2) gas, that does not react with the underlying film12of the wafer W may be used or a mixture of such gases may be used instead of the carbon dioxide gas. Here, the gas cluster composed of the carbon dioxide gas has a greater size, i.e., a greater kinetic energy, than the argon gas or the nitrogen gas. For this reason, a deposit10can be more easily removed. Therefore, it is desirable to generate a gas cluster by using a carbon dioxide gas.

Further, as shown in an experimental example to be described below, an etching gas for etching the surface of the wafer W or the surface of the deposit10may be used together with the inert gas. That is, a gas cluster may be generated by using the inert gas and the etching gas to perform a pre-treatment (etching process) and remove the deposit10at the same time.

In each of the above-described example embodiments, there is provided only one nozzle23for irradiating a gas cluster to the wafer W in a cleaning process or a pre-treatment, but the multiple nozzles23may be provided. In this case, for example, above the wafer W, multiple nozzles23are arranged in a ring shape to be concentric with an outer periphery of the wafer W. Further, multiple irradiating units each including the multiple nozzles23arranged in the ring shape are concentrically arranged from a central portion of the wafer W toward the outer periphery thereof. Furthermore, if the multiple nozzles23are provided, they may be arranged in a grid shape above the wafer W.

There has been explained the processing apparatus including a device that performs a pre-treatment and a device that irradiates a gas cluster composed of a carbon dioxide gas. However, these devices may be separately provided as stand-alone devices, and the wafer W may be transferred between these devices by an external wafer arm.

Further, even if a gas cluster irradiated when the deposit10is removed is ionized, for example, at a low dissociation degree, such a case is included in the scope of the present example embodiment.

Experimental Example

Hereinafter, a result obtained from an experiment regarding the example embodiments will be explained. In the experiment, particles each having a diameter of about 23 nm and made of silicon oxide (silica) are injected to a bare silicon wafer to artificially contaminate the wafer. Then, when a process is performed under the following experimental conditions, a change in attachment status of the particles is checked.

Comparative Example

Gas of gas cluster: Argon gas 100%

Experimental Example

Gas of gas cluster: Argon gas 95%+Hydrogen fluoride 5%

SEM (Scanning Electron Microscope) images are obtained before and after a gas cluster is irradiated in the comparative example, and are provided on the left and right sides, respectively, ofFIG. 27. It can be seen fromFIG. 27that when the gas cluster of the argon gas is irradiated, the particles are hardly removed.

Meanwhile, SEM images obtained before and after a gas cluster is irradiated in the experimental example are provided on the left and right sides, respectively, ofFIG. 28. It can be seen that after the gas cluster is irradiated, almost all the particles are removed. Therefore, it is found that with the gas cluster of the argon gas only, an adhesive strength between the particles and the wafer cannot be overcome, but by generating the gas cluster of the argon gas together with the hydrogen fluoride gas, the particles can be easily removed.

Accordingly, it can be found out that by the gas cluster of the hydrogen fluoride gas, the surface of the silica particle is etched as described above and an adhesive strength with respect to the wafer is reduced. For this reason, in the experimental example, even with the gas inlet pressure lower than that of the comparative example, the particles are easily removed. Although in the experimental example, the gas cluster is generated by using the argon gas together with the hydrogen fluoride gas, it can be seen that by mixing these gases, a pre-treatment and a cleaning process are performed at the same time, and more specifically, when the silica particles are etched, the silica particles are rapidly removed by the gas cluster of the argon gas. Therefore, it can be seen that even if a pre-treatment and a cleaning process are separately performed in this sequence, particles can be easily removed in the same manner as shown in the experimental example.

EXPLANATION OF REFERENCE NUMERALS