Abstract:
Disclosed is a substrate treatment method intended for a substrate having, on its surface, a composite product of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. The method comprises: an ultraviolet ray treatment step for irradiating the surface of the substrate with ultraviolet ray to remove a part of the organic material; a hydrogen fluoride processing step which is conducted after the ultraviolet ray processing step and which is for supplying a steam of hydrogen fluoride onto the surface of the substrate to remove at least a part of the inorganic material; and a heating processing step which is conducted after the ultraviolet ray processing step and which is for heating the substrate to cause the shrinkage of a part of the organic material that remains unremoved.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a technology for effectively removing a mixture or laminate of an inorganic material containing silicon oxide and a fluorine-based organic material formed on a substrate when, e.g., plasma processing is performed on the substrate. 
     BACKGROUND OF THE INVENTION 
     Semiconductor device manufacturing processes include an etching process for etching a substrate by using a plasma. In this etching process, etching gas reacts with a layer to be etched or a base layer to produce a composite product on the substrate, and the composite product can remain thereon. 
     For example, a contact hole for connecting an electrode to a source or drain region of a MOS transistor is formed in a silicon oxide layer on a silicon substrate by etching in which a CF-based etching gas and oxygen gas is used. 
       FIG. 16  schematically shows a composite product  208   a  produced on the bottom of a contact hole  208 . In  FIG. 16 , the components of the composite product  208   a  are also shown in a combined form. When a silicon oxide film  202  formed on a silicon layer  201  of a substrate  200  is etched by using a CF-based etching gas and an oxygen gas, an amorphous silicon layer  203  and the composite product  208   a  formed of a CF polymer  205  (containing carbon and fluorine) and a silicon oxide layer  204  are formed sequentially on the bottom of the contact hole  208 . This is considered to be formed by the following process. 
     When the silicon oxide film  202  is etched to expose the surface of the silicon layer  201 , as shown in  FIG. 17B , the surface layer of the silicon layer  201  is changed by a plasma energy into an amorphous silicon layer  203 . Further, the top portion of the amorphous silicon layer  203  is oxidized by a plasma of an oxygen gas to form the silicon oxide layer  204  ( FIG. 17C ). Thereafter, the CF polymer  205  containing carbon and fluorine is accumulated on the silicon oxide layer  204  to form the composite product ( 208   a ) ( FIG. 17D ). The composite product  208   a  increases contact resistance, thus reducing the yield of semiconductor devices. For this reason, the composite product  208   a  needs to be removed. 
     Conventionally, there is known a technique in which ashing is carried out by using an oxygen plasma to remove CF residues after completing etching process. However, the oxygen plasma cannot be used, because the use of the oxygen plasma increases an oxidation of the silicon layer  201  on the substrate  200 . 
     Further, from results of various experiments, it has been found that the composite product  208   a  is not a simple laminate schematically shown in  FIG. 17D . That is, the silicon oxide layer  204  may be a mixture of a silicon oxide  207  and a CF compound  206  as shown in  FIG. 18A  or a compound in which silicon, oxygen, carbon and fluorine are chemically bonded to each other as shown in  FIG. 18B , which is in a very stable state. For this reason, the composite product  208   a  has not been able to be sufficiently removed by a process of cleaning the substrate with an organic solvent or an acidic solution, which is generally carried out after etching. Particularly, as the design rule of semiconductor devices continues to be further miniatured or the aspect ratio increases, the cleaning solution cannot be (sufficiently diffused into holes or trenches, and thus sufficient cleaning cannot be achieved. 
     The composite product  208   a  is a composite of organic and inorganic materials. Thus, if a process for removing the inorganic material is carried out, the organic material cannot be removed, or if a process for removing the organic material is carried out, the inorganic material cannot be removed. That is, the composite product  208   a  is considered a very troublesome residue. For this reason, developing a method of removing such residue from the semiconductor device has become a very pressing task. 
     Further, it has been suggested that, in a process for manufacturing a specific kind of device, as shown in  FIG. 19A , etching is performed on a substrate in which a silicon oxide film  210  and a polysilicon film  211  are alternately laminated (for example, in two layers), through a resist film  215 , thereby forming a recess  220 . 
     In this case, a plasma of a halogen gas and a plasma of a gas containing carbon and fluorine are used to etch the polysilicon film  211  and the silicon oxide film  210 , respectively. In the etching of the polysilicon film  211 , a halogenated silicon oxide  213  containing halogen, silicon and oxygen is deposited on the sidewall of the recess  220 . Meanwhile, in the etching of the silicon oxide film  210 , a polymer  212  containing carbon and fluorine is deposited on the sidewall of the recess  220 . As a result, as shown in  FIG. 19B , a laminated product  214  laminated with the halogenated silicon oxide  213  and the polymer  212  is deposited on the sidewall of the recess  220 . 
     The laminated product  214  also reduces the yield of semiconductor devices, and thus needs to be removed. However, the laminated product is difficult to remove reliably, because it is a stable material. 
     Japanese Patent Laid-open Application No. H4-83340 (particularly, page 2, light column, lines 23-44, and page 7, left column, pages 10-15) discloses a method of removing particles produced during etching of a substrate by using HF steam after cleaning the substrate with alcohol steam. However, the above-described inorganic/organic composite product is not mentioned therein. 
     SUMMARY OF THE INVENTION 
     In view of the above, the present invention provides a substrate processing method and apparatus which can reliably remove a composite product of inorganic and organic materials, formed on a substrate by plasma processing. Further, the present invention can be applied to a method for cleaning either a processing chamber in which the above-described composite product has been generated or components in the processing chamber. 
     In accordance with a first aspect of the present invention, there is provided a substrate processing method performed on a substrate having a composite product formed on the surface thereof, the composite product being formed of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. 
     The method includes: ultraviolet ray processing of irradiating ultraviolet rays on the surface of the substrate to remove a part of the organic material; hydrogen fluoride processing which is performed after the ultraviolet ray processing to supply hydrogen fluoride steam onto the surface of the substrate to remove at least a part of the inorganic material; and heat processing which is performed after the ultraviolet ray processing and in which the substrate is heated to shrink a part of the organic material that still remains. 
     In accordance with the present invention, the composite product formed of inorganic and organic materials formed on the surface of the substrate can be very effectively removed by a combination of the ultraviolet ray processing, the hydrogen fluoride processing and the heat processing. 
     The hydrogen fluoride processing may be performed at least once before and at least once after the heat processing. 
     The substrate in the heat processing is preferably heated to 100° C. or higher. 
     In accordance with a second aspect there is provided a substrate processing method performed on a substrate having a composite product formed on the surface thereof, the composite product being formed of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. 
     The method includes: ultraviolet ray processing of irradiating ultraviolet rays on the surface of the substrate to remove a part of the organic material; hydrogen fluoride processing which is performed after the ultraviolet ray processing to supply hydrogen fluoride steam onto the surface of the substrate to remove at least a part of the inorganic material, wherein a processing group formed of the ultraviolet ray processing and the hydrogen fluoride processing is repeated two or more times. 
     In accordance with the present invention, the composite product of inorganic and organic materials formed on the substrate can be very effectively removed by repeating the group formed of the ultraviolet ray processing and the hydrogen fluoride processing two or more times. 
     The above-described method further includes a heat processing of heating the substrate to shrink a portion of the organic material that still remains. In this case, the substrate in the heat processing is preferably heated to 100° C. or higher. 
     In accordance with a third aspect of the present invention, there is provided a substrate processing method including: composite product forming processing of subjecting a substrate to processing in which a composite product formed of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine is formed on a surface of the substrate; ultraviolet ray processing which is performed after the composite product forming processing to irradiate ultraviolet rays (onto the surface of the substrate to remove a part of the organic material; and hydrogen fluoride processing which is performed after the ultraviolet ray processing to supply hydrogen fluoride steam onto the surface of the substrate to remove at least a part of the inorganic material. 
     The composite product forming processing, the ultraviolet ray processing and the hydrogen fluoride processing are performed in a vacuum atmosphere. 
     In accordance with the present invention, the composite product of inorganic and organic materials can be very effectively removed by the ultraviolet ray processing and hydrogen fluoride processing, which are performed in a vacuum atmosphere. 
     Preferably, the composite product forming processing, the ultraviolet ray processing and the hydrogen fluoride processing are continuously performed in the same vacuum atmosphere. 
     In the composite product forming processing, a silicon oxide film formed on a silicon layer on the substrate may be etched in a predetermined pattern up to a surface portion of the silicon layer by a plasma generated from a processing gas including a gas containing carbon and fluorine and an oxygen gas, thereby forming a recess. 
     In the composite product forming processing, a laminate formed of a silicon oxide film and a polysilicon film, which are laminated on the substrate in that order, may be etched in a predetermined pattern, thereby forming a recess. 
     The processing includes: etching the polysilicon film by a plasma generated from a processing gas containing halogen; and etching the silicon oxide film by a plasma generated from a processing gas containing carbon and fluorine. 
     In accordance with a fourth aspect of the present invention, there is provided a cleaning method of cleaning an internal surface of a processing chamber and/or surfaces of the internal components of the processing chamber, after subjecting a substrate to processing in which a composite product formed of an inorganic material containing silicon and an organic material containing carbon and fluorine is formed on a surface of the substrate in the processing chamber. 
     The method includes: ultraviolet ray processing of irradiating ultraviolet rays onto the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber to remove a part of an organic material formed in the processing chamber and/or on the internal components of the processing chamber; hydrogen fluoride processing which is performed after the ultraviolet ray processing to supply hydrogen fluoride steam onto the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber to remove at least a part of an inorganic material formed in the processing chamber and/or on the internal components of the processing chamber; and heat processing which is performed after the ultraviolet ray processing to heat the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber to remove a part of the organic material that still remains. 
     In accordance with the present invention, the composite product formed of inorganic and organic materials formed on the internal surface of the processing chamber and/or on the surfaces of the internal components of the processing chamber can be very effectively cleaned and removed by a combination of the ultraviolet ray processing, the hydrogen fluoride processing and the heat processing. 
     The hydrogen fluoride processing may be performed at least once before and at least once after the heat processing. 
     The substrate in the heat processing may be heated to 100° C. or higher. 
     In accordance with a fifth aspect of the present invention, there is provided a method of cleaning an internal surface of a processing chamber and/or surfaces of the internal components of the processing chamber, after subjecting a substrate to processing in which a composite product formed of an inorganic material containing silicon and an organic material containing carbon and fluorine is formed on a surface of the substrate in the processing chamber. 
     The method includes: ultraviolet ray processing of irradiating ultraviolet rays onto the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber to remove a part of an organic material formed in the processing chamber and/or on the internal components of the processing chamber; and hydrogen fluoride processing which is performed after the ultraviolet ray processing to supply hydrogen fluoride steam onto the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber to remove at least a part of an inorganic material formed in the processing chamber and/or on the internal components of the processing chamber. 
     A group formed of the ultraviolet ray processing and the hydrogen fluoride processing is repeated two or more times. 
     In accordance with the present invention, the composite product formed of inorganic and organic materials formed on the internal surface of the processing chamber and/or on the surfaces of the internal components of the processing chamber can be very effectively cleaned and removed by repeating the group formed of the ultraviolet ray processing and the hydrogen fluoride processing two or more times. 
     The above-described method further includes a heat processing of heating the internal surface of the processing chamber and/or the surface of the internal components of the processing chamber to shrink a part of the organic material that still remains. In this case, the internal surface of the processing chamber and/or the surfaces of the internal components of the processing chamber are/is heated to 100° C. or above. 
     In accordance with a sixth aspect of the present invention, there is provided a substrate processing apparatus adopted to perform processing on a substrate having on the surface thereof a composite product formed of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. 
     The apparatus includes: an ultraviolet ray processing module in which ultraviolet rays are irradiated onto the surface of the substrate to remove a part of the organic material; a hydrogen fluoride processing module in which hydrogen fluoride steam is supplied onto the surface of the substrate to remove at least a part of the inorganic material; a heat treatment module in which the substrate is heated to shrink a part of the organic material that still remains; and a control unit which is connected to the ultraviolet ray processing module, the hydrogen fluoride processing module and the heat processing module to control these modules. 
     The control unit controls each of the modules so that, after processing by the ultraviolet ray processing module is performed, processing by the hydrogen fluoride processing module and processing by the heat processing module are performed in a proper order. 
     In accordance with the present invention, the composite product of inorganic and organic materials formed on the surface of the substrate can be very effectively removed by a combination of the ultraviolet ray processing module, the hydrogen fluoride processing module and the heat processing module. 
     The control unit may control each of the modules, so that processing by the hydrogen fluoride processing module is performed at least once before and also at least once after processing by the heat processing module. 
     Further, the heat processing module may heat the substrate to 100° C. 
     The heat processing module may be provided together with the UV ray processing module by installing heating means in the UV ray processing module. 
     IN accordance with a seventh aspect of the present invention, there is provided a substrate processing apparatus adopted to perform processing on a substrate having on the surface thereof a composite product formed of an inorganic material containing silicon oxide and an organic material containing carbon and fluorine. 
     The apparatus includes: an ultraviolet ray processing module in which ultraviolet rays are irradiated onto the surface of the substrate to remove a part of the organic material; a hydrogen fluoride processing module in which hydrogen fluoride steam is supplied onto the surface of the substrate to remove at least a part of the inorganic material; and a control unit which is connected to the ultraviolet ray processing module and the hydrogen fluoride processing module to control these modules. 
     The control unit controls each of the modules so that a group formed of processing by the ultraviolet ray processing module and processing by the hydrogen fluoride processing module is repeatedly performed two or more times. 
     In accordance with the present invention, the composite product formed of inorganic and organic materials formed on the surface of the substrate can be very effectively removed by repeating the group formed of processing by the ultraviolet ray processing module and processing by the hydrogen fluoride processing module two or more times. 
     The apparatus further preferably includes a heat processing module in which the substrate is heated to shrink a part of the organic material that still remains, wherein the control unit is also connected to the heat processing module to control it. The heat processing module may heat the substrate to 100° C. or higher. 
     The heat processing module is preferably provided together with the ultraviolet ray processing module by installing heating means in the UV ray processing module. 
     The apparatus may further include: a processing module which subjects the substrate to processing in which the composite product formed of the inorganic material containing silicon oxide and the organic material containing carbon and fluorine is formed. 
     The apparatus preferably further includes a substrate transfer module having a chamber into which the substrate is loaded and substrate transfer means provided therein. An atmosphere inside of the chamber of the substrate transfer module may be a vacuum atmosphere. In this case, preferably, the substrate transfer module, the ultraviolet ray processing module and the hydrogen fluoride processing module are airtightly connected to communicate with each other. 
     In accordance with an eighth aspect of the present invention, there is provided a storage medium adopted to store a computer-readable program which is used in a substrate processing apparatus and operated on a computer, wherein the program is configured to execute the substrate processing method described above. 
     In accordance with a ninth aspect of the present invention, there is provided a storage medium adopted to store a computer-readable program which is used in a substrate processing apparatus and operated on a computer, wherein the program is configured to execute the cleaning method described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a process flowchart of a first embodiment of the present invention. 
         FIG. 2A  is a cross-sectional view of a substrate before etching in the first embodiment. 
         FIG. 2B  is a cross-sectional view of a substrate after etching in the first embodiment. 
         FIGS. 3A to 3E  schematically show cross-sectional views of the bottom of a contact hole in a substrate when respective steps of the first embodiment are performed. 
         FIG. 4A to 4C  schematically show cross-sectional views of a substrate when respective steps of the first embodiment are performed. 
         FIG. 5  is a process flowchart of a second embodiment of the present invention. 
         FIGS. 6A to 6E  schematically show cross-sectional views of the bottom of a contact hole in a substrate when respective steps of the second embodiment are performed. 
         FIG. 7  is a process flowchart of a third embodiment of the present invention. 
         FIGS. 8A to 8F  schematically show cross-sectional views of the bottom of a contact hole in a substrate when respective steps of the third embodiment are performed. 
         FIG. 9  is a horizontal cross-sectional view showing a first embodiment of a substrate processing apparatus in accordance with the present invention. 
         FIG. 10  is a longitudinal cross-sectional view of a plasma processing apparatus which is used in the plasma processing of the present invention. 
         FIG. 11  is a longitudinal cross-sectional view showing an example of a UV irradiation device which is used in a UV irradiation step of the present invention. 
         FIG. 12  is a longitudinal cross-sectional view showing an example of an HF steam cleaning unit which is used in an HF steam cleaning step of the present invention. 
         FIG. 13  is a horizontal cross-sectional view showing another embodiment of a substrate processing apparatus in accordance with the present invention. 
         FIG. 14  is a horizontal cross-sectional view showing still another embodiment of a substrate processing apparatus in accordance with the present invention. 
         FIGS. 15A to 15C  are schematic views showing TEM photographs of a cross-section of a substrate in an embodiment of the present invention. 
         FIG. 16  is a view showing a composite product formed by etching. 
         FIGS. 17A to 17D  are views showing a process in which the composite product of  FIG. 16  is formed. 
         FIGS. 18A and 18B  are conceptual views showing examples of the composition of the composite product shown in  FIG. 16 . 
         FIGS. 19A and 19B  are views showing a laminate product formed by etching. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     As an embodiment of a substrate processing method in accordance with the present invention, a first embodiment which is a process of removing a composite product after forming a contact hole by etching will now be described. 
       FIG. 1  is a flowchart showing a procedure starting from a formation of a composite product to a removal thereof in the first embodiment. In Step S 11 , etching is performed on a wafer W having a structure shown in  FIG. 2A  on the surface thereof. In  FIGS. 2A and 2B , reference numeral  100  is a silicon substrate,  101  is, for example, a silicon oxide film which is an insulating film, and  102  is a resist mask. Further, reference numeral  103  is a gate electrode,  104  is a gate oxide film,  105  is an impurity diffusion layer, and  106  is an isolation layer. 
     (Step S 11 : Step of Etching Silicon Oxide Film  101 ) 
     For example, in a plasma processing apparatus  51  which will be described later, a processing gas including, for example, CF 4  gas and O 2  gas, is converted into a plasma, and the silicon oxide film  101  is etched by the plasma. Thus, as shown in  FIG. 2B , contact holes  107  that are recesses are formed. By such etching, a composite product  111  is formed on the bottom of the contact hole  107  (the surface portion of the silicon substrate  100 ) as described above. At this time, the surface layer of the silicon substrate  100  which is exposed to the bottom surface of the contact hole  107  is changed into an amorphous silicon layer  108  by an energy of the plasma as described above. Further, the surface layer of the amorphous silicon layer  108  is oxidized by the plasma of oxygen gas to form a silicon oxide layer  109 . 
     In order to intuitively perceive the correspondence between respective processing steps and the states of the composite product  111 , the shapes of the bottom of one of the contact holes  107  are schematically shown in  FIGS. 3A to 3E . As shown therein, on the surface of the silicon oxide layer  109 , a polymer  110  containing carbon and fluorine is formed. Actually, the polymer  110  penetrates into the silicon oxide layer  109  in a form of particles or molecules and mixed with the silicon oxide  112  in a complicated form as shown in  FIG. 18A . The polymer  110  and the silicon oxide layer  109  form the composite product  111 . 
     In a macroscopic view, the polymer  110  is shown to be deposited on the silicon oxide layer  109 . However, the silicon oxide layer  109  is formed with a silicon oxide  112  and a polymer  110   a , and thus the reference numerals  110  and  110   a  will be used with distinction therebetween in the description of the schematic views. 
     (Step S 12 : UV Irradiation Step) 
     Then, a wafer W is irradiated with UV lights of a wavelength of, for example, 172 nm, for a predetermined time, while the wafer W is heated to be kept at 200° C. by heating means (not shown) such as a halogen lamp. 
     The UV irradiation breaks, for example, carbon-fluorine bonds or carbon-carbon bonds in the polymer  110 , so that the polymer  110  is gasified and removed as shown in  FIG. 4A . Due to the removal of the polymer  110 , the UV lights also irradiate the exposed surface of the silicon oxide layer  109 , whereby the polymer  110   a  on the surface of the silicon oxide layer  109  is removed. Further, by heating the wafer W, removal of the polymer  110  and the polymer  110   a  in this step is facilitated. 
     As a result, the silicon oxide  112  in the silicon oxide layer  109  is exposed, whereby, as shown in  FIG. 3B , the ratio of the silicon oxide  112  in the surface of the silicon oxide layer  109  increases. Further, as shown in  FIG. 3A , the polymer  110  formed on the silicon oxide layer  109  is thicker than the polymer  110   a  in the silicon oxide layer  109 . However, the polymer  110  is quickly removed during the heating of the wafer W together with UV light irradiation. 
     (Step S 13 : Step of Cleaning with HF Steam) 
     Then, hydrogen fluoride (HF) steam is supplied onto the wafer W for, for example, 600 seconds. When the wafer W is exposed to the HF steam, as shown in  FIG. 4B , the silicon oxide  112  on the surface of the wafer W is dissolved by the HF steam and removed together with the HF steam from the wafer W. As a result, the polymer  110   a  in the silicon oxide layer  109  is exposed, whereby, the ratio of the polymer  110   a  in the surface of the silicon oxide layer  109  increases as shown in  FIG. 3C . 
     Further, by the HF steam, the surface of the silicon oxide film  101  (the top surface and sidewall of the contact hole  107 ) is also etched, but the etched amount is very small. Thus, the description of this etching will be omitted herein. 
     (Step S 14 : Heating Step) 
     Then, the wafer W is heated to, for example, 300° C. 
     By such heating, as shown in  FIG. 4C , a portion having weak bonding strength of the polymer  110   a  either dispersed in the silicon oxide layer  109  or bonded with the silicon oxide  112  in the silicon oxide layer  109  is released from its bonding to be separated and gasified. The gas passes through a gap between, for example, the polymer  110   a  and the silicon oxide  112 , is diffused to the surface of the wafer W and removed from the wafer W. 
     As a result, only a portion having strong bonding strength in the polymer  110   a  remains mainly in the silicon oxide layer  109 , and thus, as shown in  FIG. 3D , the volume of the polymer  110   a  is shrunk. By the shrinkage of the polymer  110   a , the gap between the polymer  110   a  and the silicon oxide  112  widens, so that the above-described gas can easily escape out of the surface of the wafer W. For this reason, the shrinkage of the polymer  110   a  rapidly progresses and is also accelerated. 
     (Step S 15 : Step of Cleaning with HF Steam) 
     Then, HF steam is supplied again onto the wafer W for, for example, 600 seconds. Since the gap between the polymer  110   a  and the silicon oxide  112  widens as the result of the heating step of Step S 14 , the HF steam can diffuse to the inside of the silicon oxide layer  109  via the gap. Accordingly, the silicon oxide  112  in the silicon oxide layer  109  is almost removed. At this time, even though a small amount of the polymer  110   a  remains in the silicon oxide layer  109 , a force for physically maintaining the polymer  110   a  is weakened, because the silicon oxide  112  around the polymer  110   a  is almost removed. For this reason, the polymer  110   a  is detached or separated from the silicon oxide layer  109 . Thus, a small amount of the silicon oxide  112  attached to the polymer  110   a  is detached or separated. As a result, as shown in  FIG. 3E , the silicon oxide layer  109  is removed. After that, processes of cleaning the wafer and the like are performed, and an electrode is formed in the contact hole  107 . 
     In accordance with the first embodiment as described above, the composite product  111  formed of the polymer  110  and the silicon oxide layer  109  is first irradiated with UV light, and subsequently, cleaned with HF steam, thereby removing the polymer  110  and the silicon oxide layer  109  to some extent. Then, the wafer W is heated, whereby the remaining polymer  110   a  is gasified, thereby shrinking the volume of the polymer  110   a . In this state, since cleaning by HF steam is performed again, the HF steam easily reaches to the silicon oxide layer  109 , and for this reason, the silicon oxide  112  and the polymer  110   a  are also removed as described. As a result, the silicon oxide layer  109  is easily removed. Accordingly, when an electrode is subsequently formed in the contact hole  107 , an increase in contact resistance can be suppressed, and the yield of semiconductor devices can be improved. 
     By performing a series of the above-described steps, the composite product  111  is sufficiently removed. However, as apparent in embodiments which will be described later, after these steps, a heating step may also be performed and HF cleaning may subsequently be performed. 
     Moreover, the UV irradiation step (Step S 12 ) and the HF steam cleaning step (Step S 13 ) may be repeated two or more times. 
     Further, after the UV irradiation step, the heating step may be performed without performing the HF steam cleaning step of Step S 13 . In this case, there is an advantage in that the subsequent HF steam cleaning step (Step S 15 ) can be effectively performed, because the polymer  110   a  has been shrunk by the heating. 
     Moreover, if the UV irradiation step is performed two or more times, the heating of the wafer W need not be performed in the second and later UV irradiation steps, because the polymer  110  of the thick film has already been removed in the first UV irradiation step. 
     Second Embodiment 
     Hereinafter, a second embodiment of the substrate processing method in accordance with the present invention will be described. 
     In this embodiment, the following process is performed on a wafer W having the structure of  FIG. 2A  on the surface thereof.  FIG. 5  shows a process flowchart of this embodiment, and  FIGS. 6A to 6E  schematically show cross sectional views of a bottom of the contact hole  107  in the wafer W in respective steps. 
     (Step S 51 : Step of Etching Silicon Oxide Film  101 ) 
     Etching is performed in the same manner as in the above-described Step S 11 . By such etching, the composite product  111  is formed on the bottom of the contact hole  107 . 
     (Step S 52 : UV Irradiation Step) 
     In the same manner as in the above-described Step S 12 , the wafer W is irradiated with UV light, while the wafer W is heated. As a result, as shown in  FIG. 6B , the polymer  110  and the exposed polymer  110   a  in the surface of the silicon oxide layer  109  are removed, and thus the ratio of the silicon oxide  112  in the surface of the silicon oxide layer  109  increases. 
     (Step S 53 : Step of Cleaning with HF Steam) 
     In the same manner as in the above-described Step S 13 , by supplying HF steam onto the wafer W, the exposed silicon oxide  112  in the silicon oxide layer  109  is removed. As a result, as shown in  FIG. 6C , the ratio of the polymer  110   a  in the silicon oxide layer  109  increases. 
     (Step S 54 : Repeated Step) 
     The above-described Step S 52  and Step S 53  are repeated a predetermined number of times. In this embodiment, a heating step corresponding to the above-described Step S 14  is not performed; however, as shown in  FIGS. 6D and 6E , the silicon oxide  112  and the polymer  110   a  are sequentially removed. Thus, the composite product  111  can be easily removed, so that an increase in contact resistance can be suppressed. Further, in the embodiment, the heating of the wafer W need not be performed in the second and later UV irradiation steps. 
     Third Embodiment 
     Hereinafter, a third embodiment of the substrate processing method in accordance with the present invention will be described. 
       FIG. 7  shows a process flowchart in this embodiment.  FIG. 8A  shows a wafer W in which a silicon oxide film  121 , a polysilicon film  122 , a silicon oxide film  123  and a polysilicon film  124  are sequentially deposited on a silicon substrate  120 . The following process is performed on the wafer W. 
     In this embodiment, the following steps are all performed in a vacuum atmosphere. Further, between the steps (during the transfer of the wafer W), the wafer W is kept in a vacuum atmosphere, such that it is not exposed to an atmospheric atmosphere. 
     (Step S 71 : Step of Etching Polysilicon Film  124 ) 
     In approximately the same manner as in Step S 11 , a gas containing halogen gas, for example, hydrogen bromide (HBr) gas, is converted to plasma, and as shown in  8 B, the polysilicon film  124  is etched by the plasma to form recess  125 . By such etching, a halogenated silicon oxide  126  which is an inorganic product resulting from the diffusion of bromine into silicon oxide is formed on the sidewall of the recess  125 . 
     (Step S 72 : Step of Etching Silicon Oxide Film  123 ) 
     Then, in approximately the same manner as in the above-described Step S 71 , a gas containing carbon and fluorine, for example, CF 4  gas, is converted to plasma to etch the silicon oxide film  123  as shown in  FIG. 8C . By such etching, a polymer  127  which is an organic product containing carbon and fluorine is formed on the above-described halogenated silicon oxide  126  in the sidewall of the recess  125 . 
     (Step S 73 : Step of Etching Polysilicon Film  122 ) 
     In the same manner as in the above-described Step S 71 , the polysilicon film  122  is etched as shown in  FIG. 8D . By such etching, the halogenated silicon oxide  126  is formed again on the sidewall of the recess  125 . 
     (Step S 74 : Step of Etching Silicon Oxide Film  121 ) 
     In the same manner as in the above-described Step S 72 , as shown in  FIG. 8E , the silicon oxide film  121  is etched. By such etching, the polymer  127  is formed again on the sidewall of the recess  125 . 
     As a result, on the sidewall of the recess  125 , a laminate product  128  which is a laminate of the halogenated silicon oxide  126  and the polymer  127  is formed. 
     (Step S 75 : UV Irradiation Step) 
     Then, the same treatment as the UV irradiation step of Step S 52  of the second embodiment is performed on the wafer W, whereby the polymer  127  on the surface of the recess  125  is removed. In this step, the heating of the wafer W need not be performed. 
     (Step S 76 : Step of Cleaning with HF Steam) 
     Subsequently, in the same manner as in the Step S 53  of the second embodiment, HF steam is supplied onto the wafer W, so that the halogenated silicon oxide  126  on the recess  125  is removed. 
     (Step S 77 : Repeated Step) 
     In the same manner as in Step S 54  of the second embodiment, Step S 75  and Step S 76  are repeated a predetermined number of times. As a result, as shown in  FIG. 8F , the laminate product  128  formed on the sidewall of the recess  125  is removed. In this embodiment, Step S 75  and Step S 76  are repeated twice. Then, for example, a step of cleaning the wafer W is performed, and an electrode or a metal wiring is formed in the recess  125 . 
     In accordance with the third embodiment as described above, in the process for removing the laminate product  128  which is a composite product in which the halogenated silicon oxide  126  and the polymer  127  are alternately laminated, the transfer of the wafer W or each of the steps is performed in a vacuum atmosphere, so that the water W is not exposed to the atmospheric atmosphere. Therefore, the halogenated silicon oxide  126  can be removed, before the oxidation thereof progresses to form a stable material. 
     Further, a metal film formed in the recess  125  can be prevented from being oxidized by moisture absorption by halogen. Moreover, since the UV irradiation step and the HF steam cleaning step are repeated, the laminate product  128  can be removed in a simple and reliable manner. In this case, the repeat number of UV irradiation steps and HF steam cleaning steps may be determined depending on the number of portions to be etched, that is, the lamination number of silicon oxide films  121  and  123  and polysilicon films  122  and  124 . If the number of layers laminated is 1, each of the steps need not be repeated. 
     In accordance with the embodiments of the present invention, the effects described in each of the embodiments can be obtained. The common advantage to the embodiments is that, even when the openings of the contact holes  107  and  125  are small, UV lights and HF steam can enter the contact holes  107  and  125 , because UV lights and HF steam rather than a liquid such as an organic solvent or an acidic solution is used to remove the composite product  111  and the laminate product  128 . Therefore, the composite product  111  and the laminate product  128  can be quickly removed. In addition, since a plasma of oxygen gas is not used, the oxidation of the silicon substrates  100  and  120  can be suppressed, and even if a SiOCH film containing silicon, carbon, fluorine and hydrogen, which is recently receiving attention as a low-dielectric film is included, a the SiOCH film is prevented from being ashed by oxygen. 
     As a process of removing the laminate product  128 , the method of the first embodiment may be applied. 
     [Configuration of the Apparatus] 
     Hereinafter, an example of a substrate processing apparatus for performing the substrate processing method in accordance with the present invention will be briefly described with reference to  FIG. 9 . 
     A substrate processing apparatus  11  shown in  FIG. 9  is a multi-chamber system for performing the above-described substrate processing and includes carrier chambers  12   a  to  12   c , a first transfer chamber  13  that is a loader module, load-lock chambers  14  and  15 , and a second transfer chamber  16  that is a substrate transfer module. To the second transfer chamber  16 , plasma processing devices  51  to  54  that are processing modules, a UV irradiation device  55  that is a UV processing and heating module, and a HF cleaning device  56  that is a hydrogen fluoride module are airtightly connected to communicate with each other. Further, at one side of the first transfer chamber  13 , an alignment chamber  19  is provided. Each of the load-lock chambers  14  and  15  includes a vacuum pump and a leak valve (not shown), and the inside of the load-lock chambers can be changed-over between an atmospheric atmosphere and a vacuum atmosphere. That is, since the first transfer chamber  13  and the second transfer chamber  16  can be kept under the atmospheric atmosphere and the vacuum atmosphere, respectively, the load-lock chambers  14  and  15  can adjust the atmosphere to which the wafer W is exposed during the wafer transfer between the first and second transfer chambers  14  and  15 . 
     The first and second transfer chambers  13  and  16  include a first transfer unit  17  and a second transfer unit  18 , respectively. The first transfer unit  17  is a transfer arm for carrying out the transfer of the wafer W between the carrier chamber  12   a ,  12   b  or  12   c  and the load-lock chamber  14  or  15  and between the first transfer chamber  13  and the alignment chamber  19 . The second transfer unit  18  is a transfer arm for carrying out the transfer of the wafer W between the load-lock chamber  14  or  15 , the plasma processing device  51 ,  52 ,  53  or  54 , the UV irradiation device  55  and the HF cleaning device  56 . 
     For the plasma processing device  51 ,  52 ,  53  or  54 , for example, a plasma processing device of parallel plate type known in the art can be used. An example of the configuration thereof is shown in  FIG. 10 . The plasma processing device  51  includes a processing chamber  21 , the inside thereof being kept in a vacuum. In the processing chamber  21 , a mounting table  3  disposed in the central portion of the bottom of the processing chamber  21  and serving as a lower electrode, and an upper electrode  4  forming a gas showerhead provided in the ceiling portion of the processing chamber  21 , are provided to face each other. 
     Further, the processing chamber is configured such that a processing gas is introduced through a processing gas inlet line  41  via the upper electrode  4  into the processing chamber  21  to be converted into a plasma by applying a high frequency power from a high frequency power supply  31  between the mounting table  3  and the upper electrode  4 . Furthermore, the processing chamber is configured such that etching is performed on the wafer W electrostatically attracted to the mounting table  3  by introducing ions of the plasma to the wafer W by applying a high frequency power from a bias power supply  32 . In  FIG. 10 , reference numeral  24  denotes a gas exhaust line,  23  is a vacuum pump,  25  is a wafer transfer port, and G is a gate. 
     In the plasma processing device  51 , when the wafer W is loaded into the processing chamber  21  from the transfer port  25  by the second transfer unit  18  and mounted on the mounting table  3 , the inside of the processing chamber  21  is vacuum-evacuated via a gas exhaust line  24  by the vacuum pump  23 . Then, the plasma processing (etching) is performed by the plasma of the processing gas. The processing gas may also contain argon (Ar) or the like as a dilution gas. 
     The UV irradiation device  55  is described with reference to  FIG. 11 . The UV irradiation device  55  includes, in a processing chamber  62  which can be kept in a vacuum, a mounting table  61  made of a transparent material, for example, quartz, and capable of attracting the wafer W, halogen lamps  63  provided below the mounting table  61  and serving as a unit for heating the wafer W, and a UV lamp unit  64  provided above the mounting table  61 . Since the UV irradiation device  55  includes the heating unit, it also serves as a heating device for heating the wafer W (e.g., Step S 14  of  FIG. 1 ). 
     The mounting table  61  is supported on the bottom of the processing chamber  62  by a support  61   a  and can be rotated by, for example, a motor  60  connected to the support  61   a . The halogen lamps  63  formed of five annular lamps are connected to a power supply (not shown) and fixed in an approximately cylindrical reflector  63   a  which opens upward. Further, the processing chamber  62  includes a measurement device for measuring the temperature of the wafer W mounted on the mounting table  61 . Based on the measurement results obtained by the measurement device, the output of the halogen lamps can be controlled. 
     The UV lamp unit  64  is connected to a power supply (not shown) and includes, for example, a plurality of UV irradiation tubes. A gas supply port  66  is provided at one side of the processing chamber  62 , and, for example, nitrogen gas is supplied into the processing chamber  62  from a gas supply source  67  through the gas supply port. At the bottom of the processing chamber  62 , a gas exhaust port  68  is formed, and the internal atmosphere of the processing chamber  62  can be evacuated by a vacuum pump  69 . Further, at a side of the processing chamber  62 , a transfer opening  65  for the wafer is formed so that it can be opened or closed by a gate G. Furthermore, the UV lamp unit  64  may include, for example, a plurality of annular radiation tubes having different diameters. 
     In the UV irradiation device  55 , when the wafer W is loaded into the processing chamber  62  through the transport opening  65  and mounted on the mounting table  61 , the mounting table  61  is rotated by the motor  60 , and the inside of the processing chamber  62  is vacuum-evacuated by the vacuum pump  69 . At this time, for example, nitrogen gas is supplied from the gas supply source  67 , and in this state, the above-described UV irradiation step or heating step is performed on the wafer W. That is, in the UV irradiation step, the wafer W is irradiated with UV lights from the UV lamp unit  64 , and in the heating step, the wafer W is heated by the halogen lamps  63 . 
     The HF cleaning device  56  is described with reference to  FIG. 12 . The HF cleaning device  56  includes a processing chamber  72  and a mounting table  71  fixed to the bottom of the processing chamber  72  by a support  71   a . At the top surface of the processing chamber  72 , an HF steam supply port  76  is formed to face the mounting table  71 . The HF steam supply port  76  is connected to an HF supply source  77  for supplying HF steam via a valve  80   a . The HF supply source  77  includes a storage tank  73  for storing HF solution. The storage tank  73  includes a heater  74  for evaporating the HF solution. Further, a carrier gas supply port  80  for supplying a carrier gas is formed in the storage tank  73 , and the storage tank  73  is configured such that a carrier gas such as nitrogen gas can be supplied into the storage tank  73 , and the HF steam evaporated by the heater  74  can be supplied into the processing chamber  72 . At the bottom of the processing chamber  72 , a gas exhaust port  78  is formed, so that the atmosphere of the processing chamber  72  can be evacuated by the vacuum pump  79 . Further, at a side of the processing chamber  72 , a transfer opening  75  for the wafer W is formed so that it can be opened or closed by the gate G. 
     In the HF cleaning device  56 , when the wafer W is loaded into the processing chamber  72  through the transfer opening  75  and mounted on the mounting table  71 , the inside of the processing chamber  72  is evacuated by the vacuum pump  79 . Then, the HF solution in the storage tank  73  is heated by the heater  74  to form HF steam and is supplied for a predetermined time into the processing chamber  72  from the HF supply source  77  by using nitrogen gas as carrier gas. Therefore, the above-described HF steam cleaning step is carried out. 
     As shown in  FIG. 9 , the substrate processing apparatus  11  includes a controller  2 A which is, for example, a computer. The controller  2 A includes a data processing module made up of a program, memory, a CPU, and the like. The program includes instructions so that it transmits a control signal from the controller  2 A to each unit of the substrate processing apparatus  11  to perform a corresponding step. Further, the memory has a region in which processing parameter values, including a processing pressure, a processing temperature, a processing time, a gas flow rate a power value and the like are stored. Therefore, when the CPU executes each instruction, the processing parameters are read, and control signals corresponding to the parameter values thereof are transmitted to respective units of the substrate processing unit  11 . For example, the program (also including program relating to the input operation or display of the processing parameters) is stored in a storage unit  2 B which is a computer-readable storage medium, for example, flexible discs, compact discs, hard discs or magneto-optical discs (MO), and is installed in the controller  2 A. 
     (Flow of Wafer (W)) 
     Hereinafter, the flow (movement) of the wafer W when carrying out each of the above-described steps in the substrate processing apparatus  11  will be described. 
     First, a carrier which is a container for transferring a wafer W is loaded into one of the carrier chambers  12   a  to  12   c  from the outside through a gate door GT. Then, the wafer W is loaded into the first transfer chamber  13  from the carrier by the first transfer unit  17 . Then, the wafer W is transferred to the alignment chamber  19  in which the direction or eccentricity of the wafer W is controlled. Then, the wafer W is transferred into the load-lock chamber  14  (or  15 ). Once the internal pressure of the load-lock chamber  14  is adjusted, the wafer W is transferred into the plasma processing device  51  via the second transfer chamber  16  from the load-lock chamber  14  by the second transfer unit  18 . In the plasma processing device  51 , the above-described plasma processing is carried out. Then, the wafer W is unloaded from the plasma processing device  51  by the second transfer unit  18  and transferred into the UV irradiation device  55  or the HF cleaning device  56 , in which the above-described UV irradiation or HF cleaning is carried out. Then, the wafer W is returned to the carrier by following a reversed route to that when the wafer was loaded (wafer unloading). 
     After performing the plasma processing, the wafer W is transferred in a vacuum atmosphere, and then the UV irradiation step and steam cleaning step are respectively performed in the processing chamber  62  and in the processing chamber  72  each of which has been vacuum-evacuated. However, in the first and second embodiments, the wafer W may be exposed to an atmospheric atmosphere after the plasma processing. An example of an apparatus having such configuration is described with reference to  FIG. 13  below. 
       FIG. 13  shows a substrate processing apparatus  300  which is an example of the apparatus applicable in the first and second embodiments. In the substrate processing apparatus  300 , the HF cleaning device  56  is connected to the first transfer chamber  13 , and a new plasma processing device  57  is connected to the second transfer chamber  16  instead. Except for this, the substrate processing apparatus  300  has the same configuration as the substrate processing apparatus  11  shown in  FIG. 9 . In the substrate processing apparatus  300 , like parts are indicated by like reference numerals as used in the substrate processing apparatus  11 . 
     The HF cleaning device  56  is connected to the first transfer unit  13  via the gate G. Further, the HF cleaning device  56  includes a leak valve (not shown). By the leak valve and the above-described vacuum pump  79 , the inside of the processing chamber  72  can be switched between an atmospheric atmosphere and a vacuum atmosphere. 
     The operation of the substrate processing apparatus  300  will now be briefly described. Steps in this embodiment are the same as those in the first and second embodiments except for the HF steam cleaning step. In the HF steam cleaning step, the wafer W is processed in the following manner. 
     (HF Steam Cleaning Step) 
     In the substrate processing apparatus  300 , the wafer W is transferred from the second transfer chamber  16  to the first transfer chamber  13  of an atmospheric atmosphere via the route reversed to that when the wafer W was loaded into the above-described substrate processing apparatus  11 . Then, the wafer W is mounted on the mounting table  71  in the HF cleaning device  56  by the first transfer unit  17 . Thereafter, the output of the vacuum pump  79  and the flow rate of nitrogen gas are controlled so that the internal pressure of the processing unit  72  becomes an atmospheric atmosphere, while the same processing as the above-described HF steam cleaning step is performed. After HF steam has been supplied for a predetermined time, a valve  80   a  is closed to stop the supply of HF steam, and the gas in the processing chamber  72  is evacuated by the vacuum pump  79 . After the inside of the processing chamber  72  is changed to an atmospheric atmosphere by adjusting a leak valve (not shown), the wafer W is unloaded by the first transfer unit  17  and subjected to a next process. 
     In the substrate processing apparatus  300  as described above, although the HF steam cleaning step is performed in an atmospheric atmosphere, the UV irradiation step may also be performed in an atmospheric atmosphere by connecting the UV irradiation device  55  to the first transfer chamber  13 . Further, both steps may be performed in an atmospheric atmosphere. 
     In the above-described substrate processing apparatus  11  and substrate processing apparatus  300 , the halogen lamps  63  as heating unit are provided in the UV irradiation device  55  to perform the heating step in the UV irradiation device  55  where the UV irradiation step is performed. For this reason, the units for performing the UV irradiation step and the heating step need not be provided separately, and the installation area of the substrate processing apparatus  11  or  300  can be minimized. Each of the units may also be provided separately. 
     Further, although one UV irradiation device  55  and one HF cleaning device  56  have been installed, two or more UV irradiation devices  55  and two or more HF cleaning devices  56  may also be provided. Furthermore, although the UV irradiation device  55  and the HF cleaning device  56  have been provided separately, a configuration in which the UV irradiation step and the HF cleaning step are performed in one unit may be adopted. In this case, each internal component of the unit is preferably made of a material which is not deteriorated or corroded by either UV lights or HF steam. 
     Further, a silicon oxide  112  (or halogenated silicon oxide  126 ) and a polymer  110  (or a polymer  127 ) are deposited to the internal components of the processing chamber  21  in the plasma processing device  51  by etching similarly to the surface of the wafer W. In this case, these components may be cleaned in the same manner as the cleaning step of the above-described embodiments after separating the components and loading the separated components into the UV irradiation device  55  and the HF cleaning device  56 . In this case, when the HF steam cleaning is performed, the processing time or the number of times of processing is suitably controlled so that the materials attached to each component are removed without corroding them. 
     The substrate processing apparatus of the present invention is not limited to the configuration in which it is included in the above-described multi-chamber system. For example, the substrate processing apparatus may be configured as a stand-alone type apparatus which is separated from the plasma processing device  51  and performs processing in a vacuum atmosphere. As an example thereof, a substrate processing unit  400  is shown in  FIG. 14 . In  FIG. 14 , reference numeral  91  denotes a carrier stage, and  92  is a housing forming the body of the apparatus. The housing  92  includes a UV processing module  93  serving also as a heating module, an HF processing module  94  and a transfer arm  95 . In this embodiment, the wafer W in a FOUP (closed carrier)  96  loaded onto a carrier stage  91  is unloaded by a transfer arm  95  and is transferred sequentially to the modules  93  and  94 , so that the above-described steps are respectively performed in the modules based on the control signal from the controller  97 . After each step, the wafer is returned to the FOUP  96 . Further, the atmosphere in the substrate processing apparatus  400  may be an atmospheric atmosphere as described in the first and second embodiments. 
     Experimental Example 1 
     An experiment carried out in the present invention will now be described. In the experiment, a substrate processing apparatus for an experiment was used and an experimental wafer W having a silicon oxide film  101  formed on a silicon substrate  100  was used. A process of etching the silicon oxide film  101 , corresponding to Step S 11  of the first embodiment, was performed on the wafer W, thereby forming a contact hole  107 . Then, the processes shown in Table 1 below were performed on the wafer W. Herein, in the initial UV irradiation step, UV lights were irradiated for 360 seconds, while the wafer W was heated to 200° C. Meanwhile, in the subsequent UV irradiation step, UV lights were irradiated for 300 seconds. Further, in the HF steam cleaning step, HF steam was supplied for 1 hour, and in the heating step, heat treatment was carried out at 300° C. in air for 1 hour. 
     After each of the treatments has been performed, the contact angle of water on the surface of the silicon oxide layer  109  was measured by a contact angle meter. The silicon oxide  112  has a hydrophilic property, while the polymer  110   a  containing carbon and fluorine has a hydrophobic property, and thus it is considered that the ratio between the silicon oxide  112  and the polymer  110   a  can be evaluated by measuring the contact angle of water. Further, since the amorphous silicon layer  108  formed under the silicon oxide layer  109  has a hydrophobic property, it is considered that the contact angle of water shows the highest value when the silicon oxide layer  109  is removed. That is, it is considered that, in the silicon oxide layer  109  formed of a mixture of the hydrophobic material (polymer  110   a ) and the hydrophilic material (silicon oxide  112 ), the contact angle of water shows an intermediate value between the values of both materials. However, it is considered that, if the silicon oxide layer  109  is removed, a monolayer of a material having water repellency (amorphous silicon layer  108 ) remains, and therefore the contact angle of water becomes the largest. Table 1 shows the treatments conducted in the experiment and the measurement results of water contact angle in those treatments. 
     
       
         
               
             
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Change in water contact angle 
               
             
          
           
               
                 units: degrees 
               
             
          
           
               
                 Treatment sequence 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
               
               
                   
               
             
          
           
               
                 Example 1-1 
                 UV 
                 HF 
                 Heating 
                 HF 
                   
               
               
                   
                 21 
                 53 
                 21 
                 70 
                   
               
             
          
           
               
                 Example 1-2 
                 UV 
                 HF 
                 UV 
                 HF 
                 Heating 
                 HF 
               
               
                   
                 21 
                 53 
                  6 
                 56 
                 35 
                 65 
               
               
                 Example 1-3 
                 UV 
                 HF 
                 UV 
                 HF 
                 UV 
                 HF 
               
               
                   
                 21 
                 53 
                  6 
                 56 
                 — 
                 62 
               
             
          
           
               
                 Example 1-4 
                 UV 
                 Heating 
                 HF 
                   
               
               
                   
                 21 
                  3 
                 52 
               
               
                 Comparative 
                 UV 
                 HF 
                 Heating 
               
               
                 Example 1-1 
                 21 
                 53 
                 21 
               
               
                 Comparative 
                 UV 
                 HF 
                 UV 
               
               
                 Example 1-2 
                 21 
                 53 
                  6 
               
               
                   
               
               
                 UV: UV irradiation, HF: HF steam cleaning 
               
             
          
         
       
     
     As shown in Table 1, the contact angle of water on the surface of the silicon oxide layer  109  was greatly changed by the UV irradiation step and the HF steam cleaning step. That is, when the polymer  110   a  on the surface of the wafer W is removed by UV irradiation, the ratio of the silicon oxide  112  increases, and thus hydrophilic property is shown (the contact angle of water becomes smaller), whereas, when the silicon oxide  112  is removed by HF steam cleaning, the ratio of the polymer  110   a  increases, and the hydrophobic property is shown (the contact angle of water become larger). Further, it can be seen that, whenever the HF steam cleaning step was carried out, the silicon oxide layer  109  was slowly removed, because the contact angle of water became larger. In the fourth HF steam cleaning step of Example 1-1, the contact angle of water was increased to 70 degrees. This is considered to be a state in which the silicon oxide layer  109  was almost removed. 
     As shown in Table 1, Example 1-2, Example 1-3 and Comparative Examples showed water contact angles smaller than those of Example 1-1. Thus, it is considered that the silicon oxide layer  109  can also be removed (the contact angle of water can be increased to 70 degrees) by performing the UV irradiation step and the HF steam cleaning step and then repeating these steps. Further, when the wafer W treated in Example 1-1 was left in the air, the contact angles of water were decreased to 50 degrees and 46 degrees after 2 days and 13 days, respectively. This is considered to be due to the influence of the water of the air. 
     Example 2 
     On the wafer W having the same configuration as in Experimental Example 1, the etching of the silicon oxide film was performed. A TEM of (×1,000,000) of the bottom of the contact hole  107  is schematically shown in  FIG. 15A . It was observed that the composite product formed of the polymer  110  and the silicon oxide layer  109  was formed, because the polymer  110  on the silicon oxide layer  109  was entered into the silicon oxide layer  109  in the form of the polymer  110   a.    
     Then, treatments shown in Table 2 were performed on the wafer W. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Treatment sequence 
                 1 
                 2 
                 3 
                 4 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Example 2 
                 Step 
                 UV 
                 HF 
                 Heating 
                 HF 
               
               
                   
                   
                 Conditions 
                 360 sec, 
                 2 h 
                 1 h, 
                 2 h 
               
               
                   
                   
                   
                 200° C. 
                   
                 300° C. 
               
               
                   
                 Comparative 
                 Step 
                 UV 
                 HF 
                 UV 
               
               
                   
                 Example 2 
                 Conditions 
                 360 sec, 
                 2 h 
                 300 sec 
               
               
                   
                   
                   
                 200° C. 
               
               
                   
                   
               
             
          
         
       
     
     TEM photographs of the bottoms of the wafers F of Example 2 and Comparative Example 2 after the above treatments were performed are schematically shown in  FIGS. 15B and 15C . By a series of treatments in Example 2, the composite product  111  was almost removed, and thus a small amount of the silicon oxide layer  109  was barely observed in the wafer W. Therefore, it is considered that, in Example 1-1 in which substantially same treatment as Example 2 was performed, the silicon oxide layer  109  was also almost removed. Meanwhile, in Comparative Example 2, it was observed that a half of the initial thickness of the silicon oxide layer  109  was remained.