Abstract:
A cleaning apparatus of this invention includes a cleaning water supply portion which supplies alkaline cleaning water, a high-pressure supply portion which supplies high-pressure air, and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the high-pressure air and sprays to a work piece.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2005-100330, filed Mar. 31, 2005; No. 2005-105071, filed Mar. 31, 2005; and No. 2005-105072, filed Mar. 31, 2005, the entire contents of all of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a cleaning method and cleaning apparatus for cleaning a work piece such as a semiconductor wafer and display, more particularly to an electronic device cleaning method and electronic device cleaning apparatus capable of removing particles without damaging a device pattern.  
         [0004]     2. Description of the Related Art  
         [0005]     A semiconductor device manufacturing process includes a step of forming fine patterns by repeating formation of film or etching on the surface of a semiconductor wafer. Since both surfaces of the semiconductor wafer, particularly its thin film formation surface needs to be kept clean to form the fine pattern, a process of cleaning the semiconductor wafer is carried out using a substrate cleaning apparatus. The substrate cleaning apparatus which cleans the semiconductor wafer removes adhering particles by atomizing pure water with high-pressure air or high-pressure nitrogen and strike it against the substrate using a two-fluid nozzle (see, for example, Jpn. Pat. Applin. KOKAI Publication No. 2002-270564).  
         [0006]     Like the semiconductor wafer, electronic devices such as a liquid crystal display and PDP substrate are cleaned using the same kind of the cleaning apparatus.  
         [0007]     The above-described method of cleaning the semiconductor wafer has a following problem. That is, according to the method of atomizing pure water with high-pressure air or high-pressure nitrogen so as to remove particles, particles leaving the surface of the semiconductor wafer adhere to the surface of the wafer again in a process of being carried for discharge within liquid film on the semiconductor wafer, so that the particles cannot be removed sufficiently.  
         [0008]     Raising the pressure of pure water pressure, high-pressure air or high-pressure nitrogen to improve particle removing rate has such a problem that it is not suitable for actual use because the raised pressure damages a device pattern formed on the surface of the semiconductor wafer.  
         [0009]     Although the material of the two-fluid nozzle is SUS in a process which does not need to consider metal impurity, resin such as Teflon, PEEK is used in a process which needs to control the metal impurity. As a result, electric charge is applied when liquid is atomized and carried in the air. This electric charge moves to the top of the substrate or component of the apparatus such as a spin cup and the charged substrate attracts particles in the air so that it may be polluted by the particles.  
         [0010]     Further, since water is collected on the substrate after cleaning, water is dried by spinning or blowing with nitrogen or the like. At this time, there is a fear that in case of a fine pattern, adjoining patterns may attract each other by the surface tension of water so that they may be damaged.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     An object of the present invention is to remove fine particles sufficiently without damaging the surface of a work piece.  
         [0012]     A cleaning method and a cleaning apparatus of the present invention are configured as follows.  
         [0013]     A cleaning method comprising: supplying alkaline cleaning water; supplying high-pressure air; and atomizing the supplied cleaning water by mixing with the air and spraying to a work piece.  
         [0014]     A cleaning apparatus comprising: cleaning water supply means for supplying alkaline cleaning water; high-pressure air supply means for supplying high-pressure air; and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece.  
         [0015]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water; high-pressure air supply means for supplying high-pressure air; and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece, wherein the two-fluid nozzle is formed of conductive material obtained by mixing nonconductive resin with carbon filler.  
         [0016]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water; high-pressure air supply means for supplying high-pressure air; and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece, wherein the two-fluid nozzle is formed of any of titanium, tantalum, zirconium and an alloy thereof.  
         [0017]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water; high-pressure air supply means for supplying high-pressure air; and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece, wherein the two-fluid nozzle is formed of silicone, silicone carbide or a mixture thereof doped with impurity.  
         [0018]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water; high-pressure air supply means for supplying high-pressure air; and a nonconductive two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece, wherein the two-fluid nozzle is provided with a grounding portion which grounds the cleaning water or the air passing through the two-fluid nozzle.  
         [0019]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water; high-pressure air supply means for supplying high-pressure air; a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece; and an ionizer which neutralizes the electronic device.  
         [0020]     A cleaning method comprising: supplying cleaning water; supplying high-pressure air; atomizing the supplied cleaning water by mixing with the air and spraying to a work piece; and neutralizing the electronic device with an ionizer.  
         [0021]     A cleaning method comprising: supplying cleaning water containing organic solvent; supplying high-pressure air; and atomizing the supplied cleaning water by mixing with the air and spraying to a work piece.  
         [0022]     A cleaning apparatus comprising: cleaning water supply means for supplying cleaning water containing organic solvent; high-pressure air supply means for supplying high-pressure air; and a two-fluid nozzle which atomizes the supplied cleaning water by mixing with the air and sprays to a work piece.  
         [0023]     Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0024]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiment of the invention, and together with the general description given above and the detailed description of the preferred embodiment given below, serve to explain the principles of the invention.  
         [0025]      FIG. 1  is an explanatory diagram showing the structure of a substrate cleaning apparatus according to a first embodiment of the present invention;  
         [0026]      FIG. 2  is a explanatory diagram showing the reason why alkali aqueous solution is used in the same substrate cleaning apparatus;  
         [0027]      FIG. 3  is a explanatory diagram showing the reason why alkali aqueous solution is used in the same substrate cleaning apparatus;  
         [0028]      FIG. 4  is a explanatory diagram showing the reason why alkali aqueous solution is used in the same substrate cleaning apparatus;  
         [0029]      FIG. 5  is a explanatory diagram showing the reason why alkali aqueous solution is used in the same substrate cleaning apparatus;  
         [0030]      FIG. 6  is an explanatory diagram showing the structure of a substrate cleaning apparatus according to a second embodiment of the present invention;  
         [0031]      FIG. 7  is a longitudinal sectional view showing a two-fluid nozzle incorporated in the same substrate cleaning apparatus;  
         [0032]      FIG. 8  is a longitudinal sectional view showing a modification of the same two-fluid nozzle;  
         [0033]      FIG. 9  is an explanatory diagram showing the structure of a substrate cleaning apparatus according to a third embodiment of the present invention;  
         [0034]      FIG. 10  is a diagram showing the relation between a flow rate of nitrogen and the quantity of damages of a device pattern in the same substrate cleaning apparatus; and  
         [0035]      FIG. 11  is a diagram showing the relation between the flow rate of nitrogen and the quantity of damages of the device pattern in the same substrate cleaning apparatus. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]      FIG. 1  is an explanatory diagram showing the structure of a substrate cleaning apparatus  10  according to a first embodiment of the present invention and FIGS.  2  to  5  are explanatory diagrams showing the reason why alkali aqueous solution is used in the substrate cleaning apparatus  10 .  
         [0037]     The substrate cleaning apparatus  10  comprises a cleaning portion  20 , a high-pressure air supply portion  40 , a cleaning water supply portion  50  and a control portion  60  for controlling these portions in harmony with each other.  
         [0038]     The cleaning portion  20  comprises an electric motor  21  which is controlled by the control portion  60 , a spin chuck  23  which is mounted on a rotation shaft  22  of this electric motor  21  for holding a semiconductor wafer W, and a two-fluid nozzle  30  disposed to oppose the spin chuck  23 . The two-fluid nozzle  30  includes a gas passage  31  through which high-pressure air flows which is disposed in the center and a cleaning water passage  32  which is disposed around this gas passage  31  and through which cleaning water flows. The gas passage  31  is connected to an air pipe  42  described later and the cleaning water passage  32  is connected to a cleaning water pipe  52  described later so that they introduce high-pressure air and high-pressure cleaning water respectively. The two-fluid nozzle  30  is supported by a lift/moving mechanism (not shown) so that it can change a cleaning water supply position within a plane of the semiconductor wafer W.  
         [0039]     The high-pressure air supply portion  40  comprises a high-pressure air generating portion  41 , the air pipe  42  for feeding high-pressure air from the high-pressure air generating portion  41  to the two-fluid nozzle  30 , a pressure adjusting portion  43  provided halfway of this air pipe  42 , a pressure sensor  44  for measuring an air pressure in this pressure adjusting portion  43  and a flow rate sensor  45  provided halfway of the air pipe  42 . The pressure adjusting portion  43  adjusts the pressure according to an instruction from the control portion  60 . Outputs of the pressure sensor  44  and flow rate sensor  45  are inputted to the control portion  60 .  
         [0040]     The cleaning water supply portion  50  comprises a pure water supply tank  51 , a cleaning water pipe  52  for feeding cleaning water from this pure water supply tank  51  to the two-fluid nozzle  30 , a pressure adjusting portion  53  provided halfway of this cleaning water pipe  52 , a pressure sensor  54  for measuring a cleaning water pressure in the pressure adjusting portion  53 , a flow rate sensor  55  provided halfway of the cleaning water pipe  52  and an alkali aqueous solution supply portion  56  which is provided halfway of the cleaning water pipe  52  for obtaining cleaning water by adding alkali aqueous solution to the pure water. The pressure adjusting portion  53  adjusts the pressure according to an instruction from the control portion  60 . Outputs of the pressure sensor  54  and the flow rate sensor  55  are inputted to the control portion  60 .  
         [0041]     As the aforementioned alkali aqueous solution, ammonia, organic alkali such as tetramethylammonium hydroxide, choline, hydroxylamine is used. Further, it is permissible to omit the alkali aqueous solution supply portion  56  by using an alkali aqueous solution supply tank which accommodates alkali aqueous solution preliminarily instead of the pure water supply tank  51 .  
         [0042]     The substrate cleaning apparatus  10  having such a structure cleans the semiconductor wafer W as follows. That is, the semiconductor wafer W is rotated by rotating the electric motor  21 . The rotation speed at this time is, for example, about 500 rpm. Alkali aqueous solution is added to pure water supplied form the pure water supply tank  51  from the alkali aqueous solution supply portion  56 .  
         [0043]     Next, when the pressure adjusting portions  43 ,  53  are opened corresponding to a signal form the control portion  60  and air and cleaning water are supplied to the two-fluid nozzle  30 , the cleaning water is atomized with high-pressure air and sprayed to the surface of the semiconductor wafer W. As a result, particles are washed out. At this time, a control signal is sent from the control portion  60  to each of the pressure adjusting portions  43 ,  53  so as to adjust the pressures of air and cleaning water so that cleaning water is sprayed at a predetermined pressure. At the same time, results detected from the respective pressure sensors  44 ,  54  and flow rate sensors  45 ,  55  are fed back to the control portion  60  successively.  
         [0044]     An action of a case where alkali water is used as the cleaning water will be described here. That is, ζ potential is generated in a glide plane (S in  FIG. 2 ) in the cleaning water. This ζ potential differs depending on the material and changes depending on pH of the cleaning water as shown in  FIG. 3 . The material of the semiconductor wafer W is such that SiN is formed on SiO 2 , and a particle P is alumina.  
         [0045]     On the other hand, potential energy between two materials is a sum of intermolecular force and electrostatic potential and has a relation as shown in  FIG. 4 . That is, if the ζ potentials have an equal sign, a repulsive force is generated and if the ζ potentials have different signs, attractive force is generated. Therefore, if the cleaning water is alkaline (pH value is 8 or more), the ζ potential between the respective materials becomes minus so that as shown in  FIG. 5 , electric repulsion is generated.  
         [0046]     As a result, both the surface potential of the semiconductor wafer W and the surface potential of the particle P turn to minus in alkaline cleaning water, thereby suppressing re-adherence of the particle P to the semiconductor wafer W. Selection of the material of the surface of the semiconductor wafer W and the alkaline cleaning water for use enables addition of the removal effect of the particle P by slight etching of the surface of the semiconductor wafer W.  
         [0047]     As described above, the substrate cleaning method with the substrate cleaning apparatus  10  of this embodiment can prevent the particles which leave the surface of the semiconductor wafer W from re-adhering. Thus, the particles can be removed effectively. Therefore, the cleaning water does not need to be sprayed with a strong pressure, thereby preventing the device pattern from being damaged.  
         [0048]     Examples of experiments will be described here. A semiconductor wafer W in which 55 nm line/space pattern was formed was measured by a pattern inspecting device to count the quantity of defects. This semiconductor wafer was cleaned with the substrate cleaning apparatus  10  according to the “condition 1” to “condition 3” described below.  
         [0049]     Condition 1 is that pure water is 0.2 MPa (100 ml/min), high-pressure air is 0.2 MPa (60 L/min) and the rotation number of wafer is 500 rpm. Condition 2 is that pure water is 0.3 MPa (200 ml/min), high-pressure air is 0.3 MPa (80 L/min) and the rotation number of wafer is 500 rpm. Condition 3 is that 0.2 mmol/l ammonia water is 0.2 MPa (100 ml/min), high-pressure air is 0.2 MPa (60 L/min) and the rotation number of wafer is 500 rpm.  
         [0050]     After the above-described treatment, the semiconductor wafer W was measured with the pattern inspecting device so as to count the quantity of defects. Increased defects were observed with review SEM so as to verify whether or not a damage existed in the pattern. As a result, the rate of removal of particles which were counted as defects was 60% under the condition 1, 80% under the condition 2 and 85% under the condition 3. Although no damage of the pattern was found out under the conditions 1, 3, the pattern damage was found at 10 positions under the condition 2. Therefore, the pressures of the cleaning water and high-pressure air are preferred to be 0.3 MPa or less. Considering the effect of cleaning, the pressures of the cleaning water and high-pressure air are preferred to be 0.1 MPa or more.  
         [0051]      FIG. 6  is an explanatory diagram showing the structure of a substrate cleaning apparatus  110  according to a second embodiment of the present invention and  FIGS. 7, 8  are diagrams showing the relation between the flow rate of nitrogen in the substrate cleaning apparatus  110  and the quantity of damages of the device pattern.  
         [0052]     The substrate cleaning apparatus  110  comprises a cleaning portion  120 , a high-pressure nitrogen supply portion  140 , a cleaning water supply portion  150  and a control portion  160  for controlling these components in harmony with each other.  
         [0053]     The cleaning portion  120  includes an electric motor  121  which is controlled by the control portion  160 , a spin chuck  123  which is mounted on a rotation shaft  122  of this electric motor  121  for holding a semiconductor wafer W, and a two-fluid nozzle  130  which is disposed to oppose the spin chuck  123 .  
         [0054]     The two-fluid nozzle  130  comprises, as shown in  FIG. 7 , a nozzle main body  131  which is grounded, a gas passage  132  which is provided in the center of this nozzle main body  131  and through which high-pressure nitrogen passes, and a cleaning water passage  133  which is disposed around this gas passage  132  and through which cleaning water passes. Reference numeral  134  in  FIG. 6  denotes a nozzle orifice. The gas passage  132  is connected to a nitrogen pipe  142  described later, and the cleaning water passage  133  is connected to a cleaning water pipe  152  so as to introduce high-pressure nitrogen and cleaning water, respectively. The two-fluid nozzle  130  is supported by a lift/moving mechanism (not shown) so as to be able to change the supply position of the cleaning water within a plane of the semiconductor wafer W.  
         [0055]     The nozzle main body  131  for use is formed of for example, non-conductive resin (polyimide, polyether ether ketone, fluorine resin and mixture thereof) mixed with carbon filler. In the meantime, it is permissible to use titanium, tantalum, zirconium and alloy of these components. Further, it is permissible to use silicone, silicone carbide or any mixture of these components doped with impurity. These conductive materials produce no problem even when used in the cleaning process of the electronic device which needs to control metal impurity while it is unlikely to produce metal ion or produces no metal ion. In the meantime, any other conductive material may be used as long as it produces a small amount of metal ion or produces no metal ion.  
         [0056]     The high-pressure nitrogen supply portion  140  includes a high-pressure nitrogen generating portion  141 , a nitrogen pipe  142  for feeding high-pressure nitrogen from this high-pressure nitrogen generating portion  141  to the two-fluid nozzle  130 , a pressure adjusting portion  143  provided halfway of this nitrogen pipe  142 , a pressure sensor  144  for measuring nitrogen pressure in this pressure adjusting portion  143 , and a flow rate sensor  145  provided halfway of the nitrogen pipe  142 . The pressure adjusting portion  143  adjusts the pressure according to an instruction from the control portion  160 . Outputs of the pressure sensor  144  and the flow rate sensor  145  are inputted to the control portion  160 .  
         [0057]     The cleaning water supply portion  150  includes a cleaning water supply tank  151 , a cleaning water pipe  152  for feeding cleaning water from the cleaning water supply tank  151  to the two-fluid nozzle  130 , a pressure adjusting portion  153  provided halfway of this cleaning water pipe  152 , a pressure sensor  154  for measuring the pressure of the cleaning water in this pressure adjusting portion  153 , and a flow rate sensor  155  provided halfway of the cleaning water pipe  152 . The pressure adjusting portion  153  adjusts the pressure according to an instruction from the control portion  160 . Outputs of the pressure sensor  154  and the flow rate sensor  155  are inputted to the control portion  160 .  
         [0058]     The substrate cleaning apparatus  110  having such a structure cleans the semiconductor wafer W as follows. That is, the semiconductor wafer W is rotated by rotating the electric motor  121 . The rotation speed at this time is, for example, about 500 rpm.  
         [0059]     Next, the pressure adjusting portions  143 ,  153  are opened based on a signal from the control portion  160 . When the two-fluid nozzle  130  is supplied with nitrogen and cleaning water, the cleaning water is atomized by the high-pressure nitrogen and sprayed to the surface of the semiconductor wafer W. As a consequence, the particles are washed out. At this time, a control signal is sent from the control portions  160  to the respective pressure adjusting portions  143 ,  153  so as to adjust the pressures of nitrogen and cleaning water so that the cleaning water is sprayed at a predetermined pressure. At the same time, results detected by the respective pressure sensors  144 ,  154  and the flow rate sensors  145 ,  155  are fed back to the control portion  160  successively.  
         [0060]     Since the two-fluid nozzle  130  generates little metal ion even if it is exposed to high-pressure nitrogen and cleaning water as described above, no metal impurity adheres to the semiconductor wafer W. Further, since the two-fluid nozzle is entirely conductive and grounded, it is neutralized even if it is charged. Therefore, the semiconductor wafer W and the cleaning portion  120  are never charged, thereby preventing the semiconductor wafer W from being polluted by the particles by attraction of those in the air.  
         [0061]     As described above, the substrate cleaning apparatus  110  of this embodiment can suppress the charging when the cleaning water is atomized to a minimum extent by forming the two-fluid nozzle  130  of conductive material. Thus, the two-fluid nozzle  130 , the semiconductor wafer W and the like can be prevented from being charged so as to prevent the semiconductor wafer W from being polluted by particles by attraction of the particles in the air. Therefore, the cleanliness of the substrate after cleaning can be improved.  
         [0062]     Here, an example of experiment will be described. A semiconductor wafer W in which 55 nm line/space patterns were formed was measured with a pattern inspecting device and the quantity of defects was counted. This semiconductor wafer was cleaned with the substrate cleaning apparatus  110  under the following condition. That is, pure water is 0.2 MPa (100 ml/min), high-pressure air is 0.2 MPa (60 L/min) and the number of rotations of the semiconductor wafer is 500 rpm.  
         [0063]     As the material of the two-fluid nozzle  130 , six kinds of (1) PTFE, (2) carbon filler contained PTFE, (3) PEEK, (4) carbon filler contained PEEK, (5) titanium and (6) SiC (conductive) were used. The PTFE and PEEK are non-conductive resin and turn to conductive by mixing carbon filler.  
         [0064]     After the above-described treatment, the semiconductor wafer W was measured with the pattern inspecting device and the quantity of defects was counted. As a consequence, the rate of removal of defects was 51% for (1), 65% for (2), 55% for (3), 69% for (4), 80% for (5) and 74% for (6). This result indicates that when the conductive material is used as the material of the two-fluid nozzle  30 , the particles can be prevented from adhering again by charging thereby improving the rate of removal of the defects.  
         [0065]      FIG. 8  is a diagram showing a modification of the two-fluid nozzle  130  according to this embodiment. If the nozzle main body  131  of the two-fluid nozzle  130  is formed of non-conductive material, it is permissible to mount an attachment (grounding portion)  135  formed of metal such as titanium around the periphery of the nozzle orifice  134  and neutralize the cleaning water by grounding this attachment  135 . Further, it is permissible to neutralize the charged semiconductor wafer W and cleaning portion  120  positively by using an ionizer shown at  124  in  FIG. 6  as well as neutralize the two-fluid nozzle  130  as described above to prevent occurrence of charging. Additionally, the cleanliness may be raised by combining the above-described plural methods.  
         [0066]      FIG. 9  is an explanatory diagram showing the structure of a substrate cleaning apparatus  210  according to a third embodiment of the present invention.  FIGS. 10 and 11  are diagrams showing the relation between the flow rate of nitrogen in the substrate cleaning apparatus  210  and the quantity of damages in the device pattern.  
         [0067]     The substrate cleaning apparatus  210  comprises a cleaning portion  220 , a high-pressure nitrogen supply portion  240 , a cleaning water supply portion  250  and a control portion  260  for controlling these components in harmony with each other.  
         [0068]     The cleaning portion  220  comprises an electric motor  221  which is controlled by the control portion  260 , a spin chuck  223  which is mounted on a rotation shaft  222  of this electric motor  221  to hold the semiconductor wafer W, and a two-fluid nozzle  230  disposed to oppose the spin chuck  223 . The two-fluid nozzle  230  includes a gas passage  231  through which high-pressure nitrogen passes in the center, and a cleaning water passage  232  which is disposed around this gas passage  231  and through which cleaning water passes. Reference numeral  233  in  FIG. 9  denotes a nozzle orifice. The gas passage  231  is connected to a nitrogen pipe  242  described later and the cleaning water passage  232  is connected to a cleaning water pipe  252  described later so as to introduce high-pressure nitrogen and cleaning water, respectively. The two-fluid nozzle  230  is supported by a lift/moving mechanism (not shown) so as to be able to change a supply position of the cleaning water within the plane of the semiconductor wafer W.  
         [0069]     The high-pressure nitrogen supply portion  240  comprises a high-pressure nitrogen generating portion  241 , a nitrogen pipe  242  for feeding high-pressure nitrogen from this high-pressure nitrogen generating portion  241  to the two-fluid nozzle  230 , a pressure adjusting portion  243  provided halfway of this nitrogen pipe  242 , a pressure sensor  244  for measuring the nitrogen pressure in this pressure adjusting portion  243 , and a flow rate sensor  245  provided halfway of the nitrogen pipe  242 . The pressure adjusting portion  243  adjusts the pressure according to an instruction from the control portion  260 . Outputs of the pressure sensor  244  and the flow rate sensor  245  are inputted to the control portion  260 .  
         [0070]     The cleaning water supply portion  250  includes a cleaning water supply tank  251 , a cleaning water pipe  252  for feeding the cleaning water from this cleaning water supply tank  251  to the two-fluid nozzle  230 , a pressure adjusting portion  253  provided halfway of this cleaning water pipe  252 , a pressure sensor  254  for measuring the pressure of the cleaning water in this pressure adjusting portion  253 , and a flow rate sensor  255  provided halfway of the cleaning water pipe  252 . The pressure adjusting portion  253  adjusts the pressure according to an instruction from the control portion  260 . Outputs of the pressure sensor  254  and the flow rate sensor  255  are inputted to the control portion  260 .  
         [0071]     The cleaning water containing organic solvent includes alcohol (for example, ethyl alcohol, isopropyl alcohol and the like) or hydrofluoroether (for example, C 4 F 9 OCH 3 , C 4 F 9 OC 2 H 5  and the like).  
         [0072]     The substrate cleaning apparatus  210  having such a structure cleans the semiconductor wafer W as follows. That is, the semiconductor wafer W is rotated by rotating the electric motor  221 . The rotation speed at this time is, for example, about 500 rpm.  
         [0073]     Next, the pressure adjusting portions  243 ,  253  are opened according to a signal from the control portion  260 . When nitrogen and cleaning water are supplied to the two-fluid nozzle  230 , the cleaning water is atomized by high-pressure nitrogen and sprayed to the surface of the semiconductor wafer W. As a consequence, particles are washed out. At this time, a control signal is sent from the control portion  260  to the respective pressure adjusting portions  243 ,  253  to adjust the pressures of nitrogen and cleaning water so that the cleaning water is sprayed at a predetermined pressure. At the same time, results detected by the respective pressure sensors  244 ,  254  and the flow rate sensors  245 ,  255  are fed back to the control portion  260  successively.  
         [0074]     Here, an action of a case of using cleaning water containing organic solvent will be described in detail. That is, organic solvent has a surface tension smaller than that of pure water. Therefore, even when drying water left between device patterns, the adjoining patterns are never attracted by each other, so that they are protected from a damage.  
         [0075]     As described above, the substrate cleaning method with the substrate cleaning apparatus  210  of this embodiment uses cleaning water containing organic solvent having a surface tension smaller than that of pure water. Therefore, when drying water left between the device patterns, the adjoining patterns are never attracted by each other, so that they are protected from a damage.  
         [0076]     Here, an example of experiment will be described. A semiconductor wafer W in which 55 nm isolated pattern was formed was measured by a pattern inspecting device and the quantity of defects was counted. This semiconductor wafer was cleaned with the substrate cleaning apparatus  210  under the following condition 1 to condition 3.  
         [0077]     The condition 1 is that C 4 F 9 OCH 3  is 0.2 MPa (100 ml/min), high-pressure nitrogen is 0.2 MPa (60 L/min) and the rotation number of the semiconductor wafer is 500 rpm. The condition 2 is that C 4 F 9 OC 2 H 5  is 0.2 MPa (100 ml/min), high-pressure nitrogen is 0.2 MPa (60 L/min) and the rotation number of the semiconductor wafer is 500 rpm. The condition 3 is that pure water is 0.2 MPa (100 ml/min), high-pressure nitrogen is 0.2 MPa (60 L/min) and the rotation number of the semiconductor wafer is 500 rpm.  
         [0078]     After the above-described treatment, the semiconductor wafer W was measured with the pattern inspecting device so as to count the quantity of defects. Further, the increased defects were observed with a review SEM so as to confirm whether or not the pattern was damaged. As a result, the rate of removal of defects was 60% for the condition 1, 70% for the condition 2 and 80% for the condition 3. Although no damage was found in the pattern under the condition 1 and condition 2, the pattern damages were found at seven positions under the condition 3. Therefore, the pressures of the cleaning water and high-pressure nitrogen are preferred to be 0.3 MPa or less.  
         [0079]      FIGS. 10 and 11  are graphs showing the relation between the flow rate of nitrogen in the substrate cleaning apparatus  210  and the quantity of damages of the device pattern. Based on this relation, it is evident that the flow rate of nitrogen is preferred to be 70 L/min or less, that is, 0.0055 m 2  or less per 1 mm 2  in the nozzle orifice  233  of the two-fluid nozzle  230 .  
         [0080]     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.