Abstract:
A substrate treating apparatus includes a spin chuck for supporting a substrate to be rotatable in a plane including a principal surface of the substrate, a motor for rotating the spin chuck, a circulating pump for circulating a removal liquid and transmitting the removal liquid to a first nozzle, and a heater for heating the removal liquid in circulation. When removing a reaction product, the spin chuck is rotated at a rotational frequency of at least 100 rpm and not exceeding 3,000 rpm, and the first nozzle supplies the removal liquid at a rate of at least 50 ml per minute to the surface of the substrate supported and rotated by the spin chuck.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a substrate treating apparatus and substrate treating method for removing organic substances from substrates. In particular, the invention relates to a substrate treating apparatus and substrate treating method for removing a reaction product, which is an organic substance, from substrates. More particularly, the invention relates to a substrate treating apparatus and substrate treating method for removing, by using a removal liquid, a reaction product generated on surfaces of substrates having a patterned film formed by dry etching using a resist film as a mask.  
           [0003]    2. Description of the Related Art  
           [0004]    In manufacture of semiconductor devices, an etching process is carried out to make a pattern, by using a resist film as a mask, from a film (e.g. a film of metal such as aluminum, copper or the like) formed on the surface of a substrate, e.g. a semiconductor wafer. For forming a microcircuit pattern in the etching process, dry etching such as RIE (Reactive Ion Etching) is employed.  
           [0005]    Reactive ions used in dry etching have such strong power as to resolve the resist film to some extent before the etching of the film is completed. Part of the resist film undergoes a change in property, turns into a reaction product such as a polymer, and deposits on side walls of the film. This reaction product cannot be removed in a resist removing process to follow. It is therefore necessary to remove the reaction product after the resist removing process.  
           [0006]    Conventionally, therefore, a reaction product removing process is carried out after the resist removing process, to remove the reaction product from the side walls of the film by supplying the substrate with a removal liquid capable of removing the reaction product.  
           [0007]    The above “reaction product resulting from a change in property of the resist” is an organic substance. A process may also be carried out to supply the substrate with an organic substance removal liquid for removing other organic substances from the substrate.  
           [0008]    Generally, the removal liquid used in the process of removing such reaction product and other organic substances is the type used at room temperature. Recently, however, a removal liquid has been developed that is used at a temperature higher than room temperature for an enhanced organic substance removing performance. In use, the removal liquid is heated to a proper temperature in the range of 50 to 80° C. to realize a maximum removal rate.  
           [0009]    However, even when the removal liquid is heated to the proper temperature, the removal liquid actually supplied to the substrate loses some of its heat to the substrate, thereby to cool below the proper temperature. Thus, even the use of the removal liquid heated to the proper temperature achieves only a low efficiency of removing reaction products, to impair the quality of substrate treatment.  
           [0010]    To deal with such a problem, it is conceivable to supply the substrate with the removal liquid heated a temperature above the proper temperature. However, the composition of the removal liquid is sensitive to temperature variations. When the removal liquid is heated above the proper temperature, a change in the composition reduces its ability to remove reaction product.  
         SUMMARY OF THE INVENTION  
         [0011]    The object of the present invention, therefore, is to provide a substrate treating apparatus and substrate treating method for removing organic substances with high efficiency.  
           [0012]    The above object is fulfilled, according to the present invention, by a substrate treating apparatus for removing, by using a removal liquid, a reaction product from a surface of a substrate having a film formed on the surface and patterned by dry etching with a resist film acting as a mask, the apparatus comprising a substrate supporting device for supporting the substrate to be rotatable in a plane including a principal surface of the substrate, a driving device for rotating the substrate supporting device at a rotational frequency of at least 100 rpm, a removal liquid supplying device for supplying the removal liquid at a rate of at least 50 ml per minute to the substrate supported and rotated by the substrate supporting device, and a removal liquid heating device for heating the removal liquid to be supplied to the substrate by the removal liquid supplying device.  
           [0013]    With this substrate treating apparatus, the phenomenon of the removal liquid cooling from the proper temperature may be restrained over the entire surface of the substrate. Thus, the reaction product may be removed with high removing efficiency.  
           [0014]    In a preferred embodiment of the invention, the apparatus further comprises a scatter preventive cup surrounding the substrate supported and rotated by the substrate supporting device, for preventing scattering of the removal liquid, wherein the driving device rotates the substrate at a rotational frequency of at most 3,000 rpm. This construction is effective to avoid lowering of the reaction product removing efficiency and contamination of the substrate due to the removal liquid rebounding from the scatter preventive cup back to the surface of the substrate.  
           [0015]    The substrate supported by the substrate supporting device may be the 8-inch type. Then, the removal liquid supplying device supplies the removal liquid at a rate of 150 ml to 500 ml per minute to the substrate supported by the substrate supporting device.  
           [0016]    In another preferred embodiment, the substrate supported by the substrate supporting device is the 12-inch type, and the removal liquid supplying device supplies the removal liquid at a rate of 200 ml to 1,000 ml per minute to the substrate supported by the substrate supporting device.  
           [0017]    In another aspect of this invention, a substrate treating apparatus is provided for removing an organic substance from a substrate by using a removal liquid capable of removing organic substances, the apparatus comprising a substrate supporting device for supporting the substrate to be rotatable in a plane including a principal surface of the substrate, a driving device for rotating the substrate supporting device at a rotational frequency of at least 100 rpm, a removal liquid supplying device for supplying the removal liquid at a rate of at least 50 ml per minute to the substrate supported and rotated by the substrate supporting device, and a removal liquid heating device for heating the removal liquid to be supplied to the substrate by the removal liquid supplying device.  
           [0018]    In a further aspect of the invention, a substrate treating method is provided for removing an organic substance from a substrate by using a removal liquid capable of removing organic substances, the method comprising the steps of rotating the substrate in a plane including a principal surface of the substrate at a rotational frequency of at least 100 rpm, and supplying the removal liquid at a rate of at least 50 ml per minute to the substrate in rotation.  
           [0019]    Other features and advantages of the present invention will be apparent from the following detailed description of the embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown.  
         [0021]    [0021]FIG. 1 is a schematic side view of a substrate treating apparatus according to the invention:  
         [0022]    [0022]FIG. 2 is another schematic side view of the substrate treating apparatus;  
         [0023]    [0023]FIG. 3 is yet another schematic side view of the substrate treating apparatus; and  
         [0024]    [0024]FIG. 4 is a flow chart showing a substrate treating operation of the substrate treating apparatus. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    The construction of a substrate treating apparatus according to the invention will be described hereinafter.  
         [0026]    This substrate treating apparatus is designed for removing a reaction product, which is an organic substance, from a substrate. In this embodiment, the apparatus removes a polymer as the reaction product from the surface of a substrate, e.g. a silicon semiconductor wafer, with a film formed thereon. The above polymer results from dry etching of the film under a resist film used as a mask.  
         [0027]    The resist herein is a photosensitive material, and more particularly a photosensitive material containing an organic substance.  
         [0028]    The film noted above is, for example, a film of metal such as copper, aluminum, titanium or tungsten, or a film of a mixture of metals such as copper, aluminum, titanium and tungsten, or an insulating film such as a silicon oxide film, a silicon nitride film, an organic insulating film, a low dielectric layer insulating film or a high dielectric layer insulating film.  
         [0029]    [0029]FIGS. 1 through 3 are schematic side views of the substrate treating apparatus, respectively.  
         [0030]    This substrate treating apparatus includes a spin chuck  58  driven by a motor  57  to rotate with a wafer W having a primary surface thereof in horizontal posture, a first nozzle  41  for supplying the removal liquid to the wafer W held by the spin chuck  58 , a second nozzle  42  for supplying deionized water to the wafer W held by the spin chuck  58 , and an annular, vertically movable cup  51  and an annular fixed cup  52  acting as a scatter preventive cup for capturing the removal liquid and deionized water scattering from the wafer W in time of wafer treatment.  
         [0031]    The first nozzle  41  is connected at a proximal end thereof to a support shaft  43  rotatably supported by a motor  45 . The motor  45  is connected to an air cylinder  48  through a bracket  47 . Thus, the first nozzle  41  is driven by the air cylinder  48  to move vertically between a removal liquid supplying position shown in solid lines in FIGS. 1 through 3, and a raised position shown in two-dot chain lines in FIGS. 1 through 3. Further, the first nozzle  41  is driven by the motor  45  to swing a distal end thereof between a position opposed to the center of wafer W held by the spin chuck  58 , a position opposed to the vicinity of an edge of wafer W held by the spin chuck  58 , and a position outside the movable cup  51  and fixed cup  52 .  
         [0032]    The first nozzle  41  is connected to a removal liquid reservoir  62  through a removal liquid circulating and heating mechanism for circulating and heating the removal liquid.  
         [0033]    The removal liquid circulating and heating mechanism includes a common supply line  63  extending between the removal liquid reservoir  62  and first nozzle  41 , a first circulating line  66  branching from a first branch point  1  on the common supply line and extending to the removal liquid reservoir  62 , and a second circulating line  65  branching from a second branch point  2  on the common supply line between the first branch point  1  and first nozzle  41  and extending to the removal liquid reservoir  62 . The common supply line  63  has, arranged between the removal liquid reservoir  62  and first branch point  1 , a circulating pump  64  in the form of a bellows pump, for example, and a removal liquid heating unit  69  with a heater for heating the removal liquid. The first circulating line  66  has a flow control valve  68  such as a flowmeter with a needle. The common supply line  63  has a filter  70  disposed between the first branch point  1  and second branch point  2  for filtering the removal liquid flowing between the two branch points  1  and  2 . The second circulating line  65  has a flow control valve  67  similar to the flow control valve  68 . An electromagnetic switch valve  71  is disposed between the second branch point  2  and first nozzle  41 .  
         [0034]    The electromagnetic switch valve  71  is normally closed. In this state, the removal liquid in the removal liquid reservoir  62 , by the action of circulating pump  64 , circulates through the common circulation line  63  and through both the first circulating line  66  and second circulating line  65 . That is, the removal liquid that circulates through the common circulation line  63  and first circulating line  66 , by the action of circulating pump  64 , passes through the removal liquid heating unit  69  to be heated, and flows through the flow control valve  68  to be collected in the removal liquid reservoir  62 . The removal liquid that circulates through the common circulation line  63  and second circulating line  65 , by the action of circulation pump  64 , passes through the removal liquid heating unit  69  to be heated, and after being filtered by the filter  70 , flows through the flow control valve  67  to be collected in the removal liquid reservoir  62 .  
         [0035]    The electromagnetic switch valve  71  is opened when supplying the removal liquid. In this state, the removal liquid that circulates through the second circulating line  65  is transmitted to the first nozzle  41  through the electromagnetic switch valve  71  to be supplied to the surface of wafer W held and rotated by the spin chuck  58 . The removal liquid feed rate per unit time is adjusted by the flow control valves  67  and  68 .  
         [0036]    That is, the quantity of the removal liquid circulating through the first circulating line  66  and the quantity of the removal liquid circulating through the second circulating line  65  are adjusted by the flow control valves  67  and  68 . At this time, the quantity of the removal liquid circulating through the first circulating line  66  is set to an appropriate flow rate for maintaining the removal liquid at a proper temperature. The quantity of the removal liquid circulating through the second circulating line  65  is set to such a flow rate that the removal liquid is supplied at a desired rate per unit time from the first nozzle  41  to the surface of wafer W.  
         [0037]    The removal liquid supplied from the first nozzle  41  to the wafer W may be an organic amine-based removal liquid containing an organic amine such as dimethyl sulfoxide or dimethylformamide, a removal liquid containing ammonium fluoride, or an inorganic removal liquid.  
         [0038]    Specifically, the organic amine-based removal liquid may be a mixed solution of monoethanolamine, water and aromatic triol, a mixed solution of 2-(2-aminoethoxy)ethanol, hydroxyamine and catechol, a mixed solution of alkanolamine, water, dialkylsulfoxide, hydroxyamine and an amine-based anticorrosive, a mixed solution of alkanolamine, glycol ether and water, a mixed solution of dimethylsulfoxide, hydroxyamine, triethylene-tetramine, pyrocatechol and water, a mixed solution of water, hydroxyamine and pyrogallol, a mixed solution of 2-amino-ethanol, ether and sugar alcohol, or a mixed solution of 2-(2-aminoethoxy)ethanol, N, N-dimethylacetamide, water and triethanolamine.  
         [0039]    The solution containing an ammonium fluoride substance (called an ammonium fluoride removal liquid) may be a mixed solution of an organic alkali, sugar alcohol and water, a mixed solution of a fluorine compound, an organic carboxylic acid and an acid/amide-based solvent, a mixed solution of alkylamide, water and ammonium fluoride, a mixed solution of dimethylsulfoxide, 2-aminoethanol, an aqueous solution of an organic alkali and aromatic hydrocarbon, a mixed solution of dimethylsulfoxide, ammonium fluoride and water, a mixed solution of ammonium fluoride, triethanolamine, pentamethyldiethylene triamine, iminodiacetate and water, a mixed solution of glycol, alkyl sulfate, organic salt, organic acid and inorganic salt, or a mixed solution of amide, organic salt, organic acid and inorganic salt.  
         [0040]    An inorganic solution (or inorganic removal liquid) may be a mixed solution of water and a phosphoric acid derivative.  
         [0041]    The second nozzle  42  is connected at a proximal end thereof to a support shaft  44  rotatably supported by a motor  46 . The motor  46  is connected to an air cylinder  49  through the bracket  47 . Thus, the second nozzle  42  is driven by the air cylinder  49  to move vertically between a deionized water supplying position shown in solid lines in FIGS. 1 through 3, and a raised shown in two-dot chain lines in FIGS. 1 through 3. Further, the second nozzle  42  is driven by the motor  46  to swing a distal end thereof between a position opposed to the center of wafer W held by the spin chuck  58 , a position opposed to the vicinity of an edge of wafer W held by the spin chuck  58 , and a position outside the movable cup  51  and fixed cup  52 .  
         [0042]    The second nozzle  42  is connected by piping to a deionized water source not shown. Deionized water fed from the deionized water source is supplied from the second nozzle  42  to the surface of wafer W held by the spin chuck  58 .  
         [0043]    The vertically movable cup  51  is connected to an air cylinder  54  through a support  53 . Thus, the movable cup  51  is driven by the air cylinder  54  to move vertically between a position shown in FIG. 1 for allowing loading and unloading of the wafer W, a deionized water collecting position shown in FIG. 2, and a removal liquid collecting position shown in FIG. 3.  
         [0044]    When the movable cup  51  is in the position shown in FIG. 1, a transport mechanism not shown may transport the wafer W into or out of the substrate treating apparatus. In the deionized water collecting position shown in FIG. 2, the movable cup  51  captures the deionized water scattering from the wafer W when the deionized water is supplied to the wafer W for treatment of the wafer W. In the removal liquid collecting position shown in FIG. 3, the movable cup  51  captures the removal liquid scattering from the wafer W when the removal liquid is supplied to the wafer W for treatment of the wafer W.  
         [0045]    The fixed cup  52  has a first recess  55  formed circumferentially, and a second recess  56  formed circumferentially and inwardly of the first recess  55 . The first recess  55  is used for collecting the removal liquid captured by the movable cup  51  in the removal liquid collecting position shown in FIG. 3. The second recess  56  is used for collecting the deionized water captured by the movable cup  51  in the deionized water collecting position shown in FIG. 2.  
         [0046]    The first recess  55  is connected to the removal liquid reservoir  62  through piping  61 . The removal liquid collected in the first recess  55  is once stored in the removal liquid reservoir  62 , and thereafter transmitted by the action of circulating pump  64  to the first nozzle  41  again to be supplied to the surface of wafer W held by the spin chuck  58 . The second recess  56  is connected to a deionized water collector  11 . The deionized water collected in the collector  11  is discarded.  
         [0047]    Next, an operation of this substrate treating apparatus for treating a wafer W will be described. FIG. 4 is a flow chart showing the treating operation of the substrate treating apparatus.  
         [0048]    First, a wafer W to be treated is loaded into the substrate treating apparatus (Step S 1 ). For loading the wafer W into the apparatus, the movable cup  51  is lowered to the position shown in FIG. 1 for allowing loading and unloading of the wafer W. The distal ends of the first nozzle  41  and second nozzle  42  are kept outside the movable cup  51  and fixed cup  52 .  
         [0049]    After the transport mechanism places the wafer W on the spin chuck  58 , the removal liquid is supplied to the wafer W in the following manner (Step S 2 ).  
         [0050]    In time of supplying the removal liquid, the movable cup  51  is raised to the removal liquid collecting position as shown in FIG. 3. Thereafter, the air cylinder  48  is operated to raise the first nozzle  41  once to the upper position shown in two-dot chain lines in FIG. 3, and then the motor  45  is operated to rotate the support shaft  43 , thereby moving the distal end of first nozzle  41  from the position outside the movable cup  51  and fixed cup  52  to the position opposed to the center of the wafer W held by the spin chuck  58 . Next, the air cylinder  48  is operated to lower the first nozzle  41  to the removal liquid supplying position shown in solid lines in FIG. 3.  
         [0051]    In this state, the motor  57  is operated to spin the spin chuck  58 , and the electromagnetic switch valve  71  is opened to supply the removal liquid to the surface of the spinning wafer W held by the spin chuck  58 . In this way, a process is carried out for removing the reaction product. In time of this removing process, the supply per unit time of the removal liquid from the first nozzle  41  to the surface of wafer W and the rotational frequency of spin chuck  58  are controlled to be predetermined values.  
         [0052]    That is, in this removing step, the reaction product may be removed with high efficiency by supplying the removal liquid at a rate of 50 ml or more per minute.  
         [0053]    As noted hereinbefore, even when the removal liquid is heated to a proper temperature to realize a maximum rate of removing the reaction product, the removal liquid actually supplied to the wafer W loses some of its heat to the wafer W. This results in a phenomenon of lowering the efficiency of removing the reaction product. When the removal liquid is continuously supplied to the wafer W at 50 ml or more, the wafer W is heated by the removal liquid to restrain the removal liquid cooling down from the proper temperature. This effectively avoids the phenomenon of lowering the efficiency of removing the reaction product and impairing the quality of treatment of the wafer W.  
         [0054]    Where the wafer W is the 8-inch type, it is desirable to supply the removal liquid at a rate of 150 ml to 500 ml per minute to the wafer W. Where the wafer W is the 12-inch type, it is desirable to supply the removal liquid at a rate of 200 ml to 1,000 ml per minute to the wafer W. By setting the removal liquid supplying rate per unit time of the removal liquid to such values, the reaction product may be removed from the wafer W with increased efficiency.  
         [0055]    The wafer W described in this specification is a substantially circular semiconductor wafer. The wafer W of the 8-inch type is a 200 mm wafer specified by SEMI INTERNATIONAL STANDARDS. The wafer W of the 12-inch type is a 300 mm wafer specified by SEMI INTERNATIONAL STANDARDS. According to the dimensions provided by SEMI INTERNATIONAL STANDARDS, the wafer W of the 8-inch type is 200 mm+0.2 mm, and the wafer W of the 12-inch type 300 mm+0.5 mm.  
         [0056]    In the removing step, the reaction product may be removed with high efficiency by setting the rotational frequency of spin chuck  58  to a first speed of at least 100 rpm.  
         [0057]    When the rotational frequency of spin chuck  58  is lower than the above value, the removal liquid supplied to the wafer W does not spread quickly over the entire surface of wafer W. Consequently, the wafer W spinning with the spin chuck  58  is lower in temperature adjacent the edge than adjacent the center of rotation. This causes a phenomenon of the temperature of the removal liquid lowering below the proper temperature adjacent the edge of the wafer W, to lower the efficiency of removing the reaction product decreases. This inconvenience may be avoided by setting the rotational frequency of spin chuck  58  to 100 rpm or higher.  
         [0058]    It is desirable that the rotational frequency of spin chuck  58  at this time does not exceed 3,000 rpm.  
         [0059]    When the rotational frequency of spin chuck  58  exceeds the above value, the removal liquid scattering from the edge of the spinning wafer W could rebound from the movable cup  51  back to the surface of wafer W. Since the removal liquid scattering from the edge of wafer W has a reduced temperature, this removal liquid could lower the temperature of the removal liquid supplied from the first nozzle  41  to the surface of wafer W, to lower the efficiency of removing the reaction product. Further, contaminants could mix into the removal liquid scattering from the edge of wafer W and rebounding from the movable cup  51 , to affect the results of treatment of the wafer W. Such an inconvenience may be avoided by setting the rotational frequency of spin chuck  58  to 3,000 rpm or less.  
         [0060]    The rotational frequency of spin chuck  58  noted above is controlled by controlling the rotational frequency of motor  58  acting as the driving device for spinning the spin chuck  58 .  
         [0061]    After completing the removal liquid supplying step under the above conditions, a removal liquid scattering step is executed next (Step S 3 ).  
         [0062]    In this scattering step, the spin chuck  58  is spun at a second speed faster than the above first speed to scatter the removal liquid from the wafer W. The removal liquid scattering from the edge of the wafer W is captured by the lower end of vertically movable cup  51  as indicated by arrows in FIG. 3, and collected in the removal liquid reservoir  62  through the first recess  55  in the fixed cup  52 . In this way, reuse may be made of the expensive removal liquid. Upon completion of the process of removing the reaction product by using the removal liquid, the distal end of first nozzle  41  is moved outside the movable cup  51  and fixed cup  52 .  
         [0063]    In the removal liquid scattering step also, the rotational frequency of spin chuck  58 , preferably, is 3,000 rpm or less.  
         [0064]    Next, a deionized water supplying step is executed (Step S 4 ).  
         [0065]    For executing the deionized water supplying step, the movable cup  51  is lowered to the deionized water collecting position shown in FIG. 2. The air cylinder  49  is operated to raise the second nozzle  42  once to the upper position shown in two-dot chain lines in FIG. 2, and then the motor  46  is operated to rotate the support shaft  44 , thereby moving the distal end of second nozzle  42  from the position outside the movable cup  51  and fixed cup  52  to the position opposed to the center of the wafer W held by the spin chuck  58 . Next, the air cylinder  49  is operated to lower the second nozzle  42  to the deionized water supplying position shown in solid lines in FIG. 2.  
         [0066]    In this state, the wafer W is spun with the spin chuck  58 , and the deionized water is supplied from the second nozzle  42  to the surface of wafer W to clean the wafer W.  
         [0067]    At this time, the deionized water scattering from the edge of the wafer W is captured by the side wall of movable cup  51  as indicated by arrows in FIG. 2, and collected in the deionized water collector  11  through the second recess  56  in the fixed cup  52 .  
         [0068]    After the cleaning process using the deionized water, a spin-drying step is executed (Step S 5 ). In the spin-drying step, the spin chuck  58  is spun at high speed to spin-dry the wafer W.  
         [0069]    Finally, a wafer unloading step is executed (Step S 6 ). For executing the wafer unloading step, the distal end of the second nozzle  42  is moved outside the movable cup  51  and fixed cup  52 . The movable cup  51  is lowered to the position for allowing loading and unloading of the wafer W. Then, the transport mechanism, not shown, unloads the wafer W from the spin chuck  58 .  
         [0070]    The above embodiment discloses a process for removing a polymer, which is a reaction product generated during dry etching, from the wafer having undergone the dry etching. However, the invention is not limited to the removal from the wafer of a reaction product generated during dry etching.  
         [0071]    For example, the invention is applicable also to removal from the wafer of a reaction product generated during plasma ashing.  
         [0072]    When an impurity diffusion process is carried out with a resist film acting as a mask, the whole or part of the resist film changes into a reaction product. The invention includes the case of removing such reaction product also.  
         [0073]    Thus, the invention is applicable also to removal from substrates of reaction products resulting from resists during various processes not limited to dry etching.  
         [0074]    Further, the invention is not limited to removal of the resist-originated reaction product from the substrate, but includes also a case of removing the resist itself from the substrate.  
         [0075]    For example, a resist may be applied to a substrate to form a resist film thereon, a pattern (e.g. a wiring pattern) is exposed on the resist film, and the exposed resist film is developed. The pattern defined by the developed resist film may be used as a mask to perform a lower film process on a film (which is called a lower film) present under the resist. The invention is applicable also to removal of the resist film no longer necessary after the lower film process.  
         [0076]    More particularly, for example, the lower film may be etched after development of the resist film. Whether the etching process is wet etching or dry etching such as RIE, the resist film becomes unnecessary and should be removed after the etching process. The invention includes also such resist removal following the etching process.  
         [0077]    Further, in a different case of removing a resist itself from a substrate, an impurity diffusion process may be conducted as a lower film process after the resist film is developed. The resist film becomes unnecessary and should be removed after the diffusion process. The invention includes also such resist removal.  
         [0078]    In these cases, any reaction product resulting from a change in property of the resist film may be removed together with the unwanted resist film. This is advantageous in improving throughput and reducing cost.  
         [0079]    When, for example, the lower film is dry-etched in the above etching process, a resist-originated reaction product is also generated. As a result, the resist film itself serving as a mask for the lower film during the dry etching and the reaction product resulting from a change in property of the resist film may be removed at the same time.  
         [0080]    A resist-originated reaction product is generated also when the impurity diffusion process (e.g. ion implantation) is conducted on the lower film. Consequently, the resist film itself serving as a mask for the lower film during the impurity diffusion process and the reaction product resulting from a change in property of the resist film may be removed at the same time.  
         [0081]    Furthermore, according to the invention, it is possible to remove not only the resist-originated reaction product and the resist itself, but also organic matter not originating from the resist, such as minute contaminants emanating from the human body.  
         [0082]    The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.