Abstract:
A developing apparatus comprises a table on which is disposed a substrate having a resist coating film formed thereon, a nozzle for supplying a developing solution to the substrate disposed on the table, a liquid supplying mechanism for supplying the developing solution to the nozzle, and a moving mechanism for relatively moving the nozzle and the substrate, wherein the nozzle includes a liquid inlet port communicating with the liquid supplying mechanism, a liquid reservoir for temporarily storing the developing solution supplied from the liquid supplying mechanism through the liquid inlet port, a narrow passageway communicating with the bottom portion of the liquid reservoir to cause pressure loss of the developing solution coming from the liquid reservoir, a linear liquid discharge section having a discharge port passageway communicating with the narrow passageway, and a buffering member arranged within the discharge port passageway and in the vicinity of the outlet port of the narrow passageway, the buffering member weakening the strength of the developing solution coming out of the narrow passageway so as to weaken the impact given by the developing solution discharged from the discharge port to the resist coating film.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-151362, filed May 31, 1999, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a developing apparatus and a developing nozzle used in the manufacture of a semiconductor device or a liquid crystal display (LCD) device, particularly, to a developing apparatus and a developing nozzle for development of a chemically amplified resist film in photolithography of a semiconductor device. 
     In a manufacturing process of a semiconductor device, a semiconductor wafer is coated with resist, and the coated resist film is baked, exposed to light and, then, developed. Used in such treatments are a coating-developing system disclosed in, for example, U.S. Pat. No. 5,664,254 and U.S. Pat. No. 5,700,127. The coating-developing system, which is used in combination with a light exposure apparatus in a photolithography for a semiconductor device, includes a resist coating unit and a developing unit. 
     In the developing unit, a wafer having a resist film formed thereon, said resist film bearing a light-exposed latent image, is held by a spin chuck, and a nozzle extending over the diameter of the wafer is positioned right above the wafer. Under this condition, the wafer is rotated to make at least half the complete rotation while supplying a developing solution from the discharge port of the nozzle onto the wafer. As a result, a film of the developing solution is formed in a uniform thickness over the entire upper surface of the wafer. The wafer having the film of the developing solution formed thereon is held stationary for a predetermined time to have the developing solution kept in contact with the resist film formed on the wafer so as to develop the light-exposed latent image formed in the resist film. The particular developing method is called a puddle development. 
     In the puddle development, it is desirable to make the total residence time (total contact time) of the developing solution uniform over the entire surface of the wafer in order to ensure uniformity of the line width of the circuit. Therefore, it is necessary to coat the entire surface of the wafer with the developing solution as promptly as possible and, thus, the developing solution is supplied from the supply source to the nozzle at a high pressure. 
     However, since the discharge port of the nozzle has a small diameter, a high supply pressure of the developing solution imparts an excessively large impact to the light-exposed latent image formed in the resist film, leading to nonuniformity in the line width. Particularly, since the line width of the pattern formed in a chemically amplified resist film is on the submicron order, a serious influence tends to be imparted to the light-exposed latent image formed in the resist film, if the developing solution discharged from the nozzle has a large colliding force. 
     It should also be noted that the developing nozzle is made of a resin having a high water repellency. Therefore, if the developing solution is discharged at a high speed, the discharge range of the developing solution tends to be narrowed when the developing solution is discharged from the discharge port, with the result that the developing solution tends to fail to be supplied to the entire region of the wafer so as to bring about undeveloped portions. The tendency is particularly prominent in the case of the scanning system in which the developing solution is discharged while the nozzle is moved along the wafer surface. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a developing apparatus that permits improving the uniformity of the line width and also permits preventing nonuniformity of resolution (nonuniform development). 
     Another object of the present invention is to provide a developing nozzle that permits suppressing the colliding force of the developing solution against the resist film and also permits uniformly supplying the developing solution over the entire region of the substrate. 
     According to a first aspect of the present invention, there is provided a developing apparatus, comprising a table on which is disposed a substrate having a resist coating film formed thereon, a nozzle for supplying a developing solution to the substrate disposed on the table, a liquid supplying mechanism for supplying the developing solution to the nozzle, and a moving mechanism for relatively moving the nozzle and the substrate, wherein the nozzle includes a liquid inlet port communicating with the liquid supplying mechanism, a liquid reservoir for temporarily storing the developing solution supplied from the liquid supplying mechanism through the liquid inlet port, a narrow passageway communicating with the bottom portion of the liquid reservoir to cause pressure loss of the developing solution coming from the liquid reservoir, a linear liquid discharge section having a discharge port passageway communicating with the narrow passageway, and a buffering member arranged within the discharge port passageway and in the vicinity of the outlet port of the narrow passageway, the buffering member weakening the strength of the developing solution coming out of the narrow passageway so as to weaken the impact given by the developing solution discharged from the discharge port to the resist coating film. 
     The buffering member is housed within the discharge port passageway so as to prevent the buffering member from coming out of the liquid discharge section. Also, it is desirable for the buffering member to be positioned above the lowermost portion of the liquid discharge section. 
     The buffering member, which consists of a single rod, extends from at least one end portion to the other end portion of the discharge port passageway. In this case, the both end portions of the rod-like buffering member are supported by the liquid discharge section. It is possible for the rod-like buffering member to have a circular cross section, an elliptical cross section or a gourd-shaped cross section. It is also possible for the rod-like buffering member to be externally threaded. 
     It is possible for the buffering member to consist of a plurality of granular bodies or lumps that are linearly arranged to extend from one end portion to the other end portion of the discharge port passageway. In this case, it is desirable for the plural granular bodies or lumps to be supported by the lower portion of the liquid discharge section. 
     It is possible for the narrow passageway to be open in the center at the bottom of the liquid reservoir and to consist of a large number of fine holes each having a diameter smaller than the clearance of the discharge port passageway. It is also possible for the narrow passageway to consist of a slit open in the center at the bottom of the liquid reservoir and having a width smaller than the width of the discharge port passageway. 
     The linear liquid discharge section is longer than at least the radius of the substrate. The nozzle of this type permits easily forming a layer of a developing solution on the substrate so as to facilitate formation of the puddle phenomenon. 
     According to a second aspect of the present invention, there is provided a developing nozzle used in a photolithography process, comprising a liquid inlet port for receiving a developing solution, a liquid reservoir for temporarily storing the developing solution received through the liquid inlet port, a narrow passageway communicating with the bottom portion of the liquid reservoir and serving to lower the pressure of the developing solution coming from the liquid reservoir, a linear liquid discharge section having a discharge port passageway communicating with the narrow passageway, and a buffering member arranged within the discharge port passageway and positioned in the vicinity of the outlet port of the narrow passageway, the buffering member serving to weaken the strength of the developing solution coming out of the narrow passageway so as to weaken the impact given by the developing solution discharged from the discharge port to the resist coating film. 
     The buffering member is arranged right under the opening of the narrow passageway and is positioned somewhat higher than the lowermost end of the liquid discharge section. Since the buffering member is held within the liquid discharge section, the developing solution is held within the liquid discharge section so as to prevent the developing solution from dropping from the discharge port of the nozzle during non-operation of the nozzle. Also, since the buffering member is not exposed to the outside through the discharge port, foreign matters are not attached to the buffering member. It follows that the buffering member is kept clean. 
     The buffering member is made of a hydrophilic material such as quartz so as to further improve the liquid holding function of the buffering member and the discharge port. Also, the hydrophilic buffering member facilitates the flow of the developing solution from the narrow passageway to the discharge port, with the result that the developing solution can be supplied smoothly to the discharge port. 
     Since the developing solution is alkaline, the buffering member is made of a material exhibiting a resistance to alkali and hydrophilic properties. The materials meeting these requirements include, for example, quartz, alumina, silicon nitride, silicon, a silicon-based ceramic material and a silicone resin. It is most desirable to use quarts for forming the buffering member. Since quarts exhibits excellent hydrophilic properties, the developing solution can be guided promptly from the header to the liquid discharge port via the buffering member made of quartz. Also, since the buffering member made of quarts firmly holds the developing solution, the developing solution is prevented without fail from being dropped from the discharge port during non-operation of the nozzle. Incidentally, the buffering member made of silicon or a silicone resin, even if dissolved in the developing solution, does not give a detrimental effect to the developing solution. In other words, the developing solution is not contaminated. 
     Additional objects and 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 objects and 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 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a perspective plan view showing a coating-developing system; 
     FIG. 2 is a plan view schematically showing a coating-developing system; 
     FIG. 3 is a back view schematically showing a coating-developing system; 
     FIG. 4 is a block diagram showing a developing apparatus according to one embodiment of the present invention; 
     FIG. 5 is a perspective plan view showing the developing apparatus according to one embodiment of the present invention; 
     FIG. 6 is an oblique view showing a developing nozzle according to another embodiment of the present invention; 
     FIG. 7A is a plan view showing a developing nozzle according to another embodiment of the present invention; 
     FIG. 7B is a cross sectional view showing a developing nozzle, as viewed sideways, according to another embodiment of the present invention; 
     FIG. 8 shows in a dismantled fashion a part of the developing nozzle according to another embodiment of the present invention; 
     FIG. 9 is a cross sectional view showing a developing nozzle according to another embodiment of the present invention; 
     FIG. 10 is a cross sectional view showing in a magnified fashion a gist portion of the developing nozzle according to another embodiment of the present invention; 
     FIG. 11 is an oblique view showing a gist portion of the developing nozzle according to another embodiment of the present invention; 
     FIG. 12 is an oblique view showing a gist portion of the developing nozzle according to another embodiment of the present invention; 
     FIG. 13 is an oblique view showing a gist portion of the developing nozzle according to another embodiment of the present invention; 
     FIG. 14 is an oblique view showing a gist portion of the developing nozzle according to another embodiment of the present invention; 
     FIG. 15 is a cross sectional view showing the developing nozzle according to another embodiment of the present invention; and 
     FIG. 16 is an oblique view showing the developing nozzle according to still another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Various preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
     As shown in FIGS. 1 to  3 , a coating-developing system  1  comprises a cassette section  10 , a process section  11  and an interface section  12 . The system  1  is connected to a light exposure apparatus (not shown) via the interface section  12 . 
     The cassette section  10  includes a table  20 , a first sub-arm mechanism  21  and a transfer path. A cassette CR is loaded on or unloaded from the cassette table  20  by a transfer robot (not shown) or by an operator (not shown). A plurality of semiconductor wafers W, e.g., 25 wafers W, are housed in the cassette CR loaded on the table  20 . Four projections  20   a  are mounted on the table  20  such that the position of the cassette CR relative to the system  1  is determined by each of the projections  20   a.    
     The transfer path extends in a direction of the X-axis along the table  20 , and the first sub-arm mechanism  21  is mounted within the X-axis transfer path. The first sub-arm mechanism  21  includes a wafer holder  211   a  for holding the wafer W and driving mechanisms (not shown) including a back-and-forth driving mechanism, an X-axis driving mechanism, a Z-axis driving mechanism, and a θ-swing driving mechanism. The back-and-forth driving mechanism moves the wafer holder  21   a  back and forth. The X-axis driving mechanism moves the wafer holder  21   a  in the X-axis direction. The Z-axis driving mechanism moves the wafer holder  21   a  in the Z-axis direction. Further, the θ-swing driving mechanism swings the wafer holder  21   a  about the Z-axis. On the other hand, the first sub-arm mechanism  21  takes the wafer W out of the cassette CR or puts the wafer W in the cassette CR. Also, the first sub-arm mechanism  21  gains access to an alignment unit (ALIM) and an extension unit (EXT) of the process section  11 . 
     The process section  11  includes a plurality of process unit groups G 1  to G 4 (G 5 ), a main arm mechanism  22  and a vertical transfer path  22   a . The main arm mechanism  22  is positioned substantially in the center of the process section  11 , and the process unit groups G 1  to G 4 (G 5 ) are arranged to surround the main arm mechanism  22 . 
     As shown in FIG. 3, the main arm mechanism  22  includes a transfer section  46 , a cylindrical support member  49  and driving mechanisms (not shown) such as a back-and-forth driving mechanism, a Z-axis driving mechanism and a θ-swing driving mechanism. The cylindrical support member  49  extends in the direction of Z-axis. The Z-axis driving mechanism moves the transfer section  46  in the Z-direction within the cylindrical support member  49 . Further, the θ-swing driving mechanism swings the transfer section  46  about the Z-axis within the cylindrical support member  49 . The transfer section  46  includes a plurality of wafer holders  48  and the back-and-forth driving mechanism serving to independently move each of the wafer holders  48  back and forth. 
     As shown in FIGS. 1 and 2, the first and second process unit groups G 1  and G 2  are arranged side by side on the front side of the system  1 . As shown in FIGS. 1 and 3, the third process unit group G 3  is arranged adjacent to the cassette section  10 , and the fourth process unit group G 4  is arranged adjacent to the interface section  12 . Incidentally, it is possible to arrange the fifth process unit group G 5  on the back side of the system  1 . 
     The first process unit group G 1  includes two spinner type process units (COT)/(DEV). These spinner type process units (COT)/(DEV) are stacked one upon the other and are provided with cups  32  for the liquid processing. In the embodiment shown in the drawing, the developing unit  30  is stacked on the resist coating unit  31 . The second process unit group G 2  is substantially equal in construction to the first process unit group G 1 . 
     As shown in FIG. 3, the third process unit group G 3  includes 8 oven-type process units consisting of a cleaning unit (COL), an adhesion unit (AD), an alignment unit (ALIM), and an extension unit (EXT), and four hot plate units (HP), which are stacked in the order mentioned such that the cleaning unit (COL) is arranged in the lowermost position. It is possible to use a cleaning unit (COL) in place of the alignment unit (ALIM) to allow the cleaning unit (COL) to perform the function of positioning the wafer as desired. 
     The fourth process unit group G 4  also includes 8 oven-type process units consisting of a cleaning unit (COL), an extension-cleaning unit (EXTCOL), an extension unit (EXT), a cleaning unit (COL), and four hot plate units (HP), which are stacked one upon the other in the order mentioned such that the cleaning unit (COL) referred to first is arranged in the lowermost position. 
     It is possible to arrange the fifth process unit group G 5  on the back side of the main arm mechanism  22 . The fifth process unit group G 5  is movable in the Y-axis direction along a guide rail  25 , making it possible to apply maintenance to the main arm mechanism  22  from behind the main arm mechanism  22 . The fifth process unit group G 5  is substantially equal in construction to the third and fourth process unit groups G 3 , G 4 . 
     The interface section  12  includes a pick-up cassette CR that can be transferred, a buffer cassette BR, which is held stationary, a peripheral light-exposure device  23 , and a second sub-arm mechanism  24 . The second sub-arm mechanism  24  is substantially equal in construction to the first sub-arm mechanism  21 . The second sub-arm mechanism  24  is capable of gaining access to the extension unit (EXT) of the process section  11  and to a wafer delivery table (not shown) of the light exposure device. 
     The developing unit  30  (DEV) will now be described with reference to FIGS. 4 and 5. 
     A wafer delivery port  70  is formed on one side wall of the developing unit  30 . The wafer delivery port  70  can be opened or closed by a shutter (not shown). If the shutter is opened, the wafer W held by the wafer holder  48  of the main arm mechanism  22  is put into or taken out of the developing unit  30  through the wafer delivery port  70 . 
     The cup  32  is arranged in substantially the center of the developing unit  30 , and a spin chuck  52  is arranged inside the cup  32 . The spin chuck  52  is provided with a rotary driving mechanism (not shown), a vertical driving mechanism (not shown) and a vacuum suction mechanism (not shown). A motor  54  of the rotary driving mechanism is controlled by a controller  110  so as to permit rotation of the spin chuck  52 . A cylinder  60  of the vertical driving mechanism is controlled by the controller  110  so as to permit the spin chuck  52  to be moved in a vertical direction. Further, a pump (not shown) of the vacuum suction mechanism is controlled by the controller  110  so as to permit the wafer W to be sucked and held by the spin chuck  52 . Incidentally, a reference numeral  64  denotes a cap flange made of aluminum, a reference numeral  62  denotes a guide for the vertical movement, and a reference numeral  64  denotes a cooling jacket made of a stainless steel. The cap flange  58  is mounted to cover the upper half portion of the cooling jacket  64 . Also, the guide  62  for the vertical movement is mounted to the cap flange  58  so as to be parallel to the axis of the cylinder  60 . 
     During the developing treatment, the lower end of the cap flange  58  is in contact with a unit bottom plate  50  in the vicinity of the outer periphery of the opening of the unit bottom plate  50 . As a result, the inner space of the developing unit is hermetically closed. When the wafer W is delivered between the spin chuck  52  and the main arm mechanism  22 , the vertical driving mechanism  60  moves upward the driving motor  54  or the spin chuck  52  so as to permit the lower end of the cap flange  58  to float from the unit bottom plate  50 . As described previously, the wafer delivery port  70  is formed in the side wall of the developing unit  30 . The wafer W held by the holder  48  is put into or taken out of the developing unit  30  through the wafer delivery port  70 . 
     A developing nozzle  86  communicates with a developing solution supply unit  89  via a supply pipe  88 . A gas pressure transfer system disclosed in, for example, U.S. Pat. No. 5,868,307 is used in the developing solution supply unit  89 . A developing solution  90  is transferred under a pressure of 1 to 2 kgf/cm 2  from the developing solution supply unit  89  to the nozzle  86 . The concentration and temperature of the developing solution are precisely controlled within the developing solution supply unit  89 . Incidentally, a 2.38% tetramethylammonium hydroxide solution (TMAH solution) is housed as the developing solution in the supply source of the developing solution supply unit  89 . Traces of a surfactant is also contained in the developing solution together with TMAH. 
     An arm  92  is detachably mounted to the tip portion of the developing nozzle  86 . A guide rail  94  is mounted on the unit bottom plate  50  and extends in the Y-axis direction. The arm  92  is movably supported by a post  96  via the Z-axis driving mechanism  112 . Further, the post  96  is movably supported by the guide rail  94  via the Y-axis driving mechanism  111 . Each of the Y-axis driving mechanism  111  and the Z-axis driving mechanism  112  is controlled by the controller  110 , and the developing nozzle  86  is moved in Y-axis direction and the Z-axis direction between the home position and the operating position. 
     A rinse nozzle  102  is detachably mounted to the tip portion of an arm  104 . The arm  104  is movably supported by a post  106  via the Z-axis driving mechanism (not shown). Further, the post  106  is movably supported by the guide rail  94  via the Y-axis driving mechanism (not shown). Each of the Y-axis driving mechanism and the Z-axis driving mechanism is controlled by the controller  110 , and the rinse nozzle  102  is moved in the Y-axis direction and the Z-axis direction between the home position and the operating position. 
     As shown in FIG. 5, a nozzle waiting section  115  is arranged in the home position of the developing nozzle  86 . The developing nozzle  86  during non-operation is positioned in the waiting section  115 . A washing mechanism  116  is arranged in the waiting section  115  such that a liquid discharge section  121  of the nozzle  86  is washed by the washing mechanism  116 . 
     The developing nozzle  86  will now be described with reference to FIGS. 6,  7 A,  7 B,  8 ,  9  and  10 . 
     A nozzle body  120  of the developing nozzle  86  is in the shape of a rectangular box. Formed within the nozzle body  120  are a liquid reservoir  122 , an outlet port  124  formed at the bottom of the liquid reservoir  122 , a large number of fine holes  125  positioned below and communicating with the outlet port  124 , and a discharge port passageway  123  positioned below and communicating with the fine holes  125 . 
     The upper opening of the liquid reservoir  122  is closed by a lid  129 . The developing solution supply pipe  88  is mounted to an appropriate position of the lid  129 . An opening  88   a  of the supply pipe  88  communicates with the liquid reservoir  122  such that the developing solution  90  is supplied from the developing solution supply unit  89  into the liquid reservoir  122  through the supply pipe  88 . Incidentally, it is desirable to mount two or three supply pipes  88  to the lid  129 , though it is possible to mount only one supply pipe  88  to the lid  129 . 
     The length L 1  of the nozzle body  120  is slightly larger than the diameter of the wafer W. A linear liquid discharge section  121  is formed in a lower portion of the nozzle body  120 . A slit-like discharge port passageway  123  is open at the lowermost end of the liquid discharge section  121  such that the developing solution is discharged from the discharge port passageway  123 . 
     The outlet port  124 , which is concave, is formed in the center at the bottom of the liquid reservoir  122 . Also, a large number of fine holes  125  are open at the bottom portion of the outlet port  124 . These fine holes  125  are linearly arranged equidistantly along the length of the nozzle body  120 . The liquid reservoir  122  communicates with the discharge port passageway  123  via the fine holes  125 . The fine hole  125  (narrow passageway) functions as a resistor of the fluid circuit so as to lower the pressure (to cause pressure loss) of the developing solution  90  coming from the liquid reservoir  122 , with the result that the developing solution of a low pressure is supplied to the discharge port passageway  123 . Incidentally, the diameter of the discharge port passageway  123  is made larger than the diameter of the fine hole  125 . 
     It is desirable to use a resin material having a high water repellency such as PCTFE for forming the nozzle body  120 . On the other hand, it is desirable to use a material excellent in resistance to chemicals such as quartz or ceramic material for forming a buffering rod  130 . Also, it is desirable for the buffering rod  130  to exhibit hydrophilic or water-absorbing properties like quartz. Further, in order to enable the buffering rod  130  to exhibit water-absorbing properties, it is possible for the buffering rod  130  itself to be made of a porous material such as a porous ceramic material. Incidentally, it is desirable for the diameter D 1  of the buffering rod  130  to fall within a range of between 2.5 and 5.0 mm. Also, it is desirable for the diameter D 2  of the slit-like discharge port passageway  123  to fall within a range of between 3 and 6 mm. 
     As shown in FIGS. 9 and 10, the buffering rod  130  is arranged within the discharge port passageway  123 . The buffering rod  130  is arranged right under the lower opening of the fine hole  125  and is positioned slightly above the lowermost end of the liquid discharge section  121 . In other words, the lower end of the buffering rod  130  is away from the lowermost end of the liquid discharge section  121  by a distance L 6 . Where the buffering rod  130  is retracted within the liquid discharge section  121  in this fashion, it is possible to increase the capability of holding the developing solution  90  within the liquid discharge section  121 , with the result that the developing solution  90  is prevented from dropping from the discharge port passageway  123  during non-operation of the nozzle. Also, since the buffering rod  130  is not exposed to the outside through the discharge port passageway  123 , foreign materials are unlikely to be attached to the buffering rod  130 . Further, since the buffering rod  130  is made of a hydrophilic material such as quartz, the buffering rod  130  and the discharge port passageway  123  are allowed to exhibit a further improved function of holding the developing solution  90 . What should also be noted is that the hydrophilic quartz rod  130  facilitates the transfer of the developing solution  90  from the fine hole  125  into the discharge port passageway  123 , with the result that the developing solution  90  can be supplied smoothly to the discharge port passageway  123 . 
     As shown in FIGS. 7B and 8, a hole  127  is formed on each side portion of the liquid discharge section  121 , and the buffering rod  130  is inserted from the hole  127  on one side portion into the hole  127  on the other side portion. The both end portions of the buffering rod  130  are supported by supporting sections  126 . The supporting section  126  is internally threaded and a cap stopper  132 , which is externally threaded, is engaged with the internally threaded supporting section  126 . Since the both end portions of the buffering rod  130  are fixed by the supporting section  126  and the cap stopper  132  engaged with the supporting rod  126 , the buffering rod  130  do not drop down from the discharge port passageway  123 . 
     The size of each section of the nozzle  86  for an 8-inch wafer is as follows: 
     Length L 1  of nozzle body: 250 mm 
     Length L 2  of discharge port: 214 mm 
     Length L 3  of buffering rod: 221 mm 
     Width L 4  of nozzle body: 38 mm 
     Height L 5  of nozzle body: 36 mm 
     Distance L 6  between buffering rod and lowermost end of discharge port: 0.5 to 2.0 mm 
     Distance L 7  between buffering rod and lower end of fine hole: 0.2 to 1.0 mm 
     Distance L 8  between lower end of discharge port and wafer: 0.5 to 10.0 mm 
     Diameter D 1  of buffering rod: 3.0 mm 
     Diameter D 2  of discharge port: 3.4 mm 
     Diameter D 3  of fine hole: 0.4 mm 
     The number of fine holes: 106 
     Distance between adjacent fine holes: 2.0 mm 
     A chemically amplified resist film subjected to a post-exposure baking is developed by the developing unit  30  as follows. 
     In the first step, the wafer W held by the holder  48  of the main arm mechanism  22  is transferred into the developing unit  30  through the wafer delivery port  70 . In this step, the spin chuck  52  is moved upward by the vertical driving mechanism  60  so as to transfer the wafer W from the holder  48  onto the spin chuck  52 . The wafer W is held by vacuum suction by the spin chuck  52 , and the main arm mechanism  22  is operated to permit the holder  48  to be moved out of the developing unit  30 . Incidentally, a downstream of a clean air is formed within the developing unit  30 . 
     In the next step, the developing nozzle  86  is moved from the home position to the operating position to permit the liquid discharge section  121  to be positioned close to the wafer W. Under this condition, a developing solution  90  is supplied with a predetermined supply pressure from the developing solution supply unit  89  to the nozzle  86 , with the result that the developing solution  90  is discharged to form a band from the nozzle  86 . While the developing solution  90  is being discharged from the nozzle  86 , the wafer W is rotated to make at least half the complete rotation, e.g., to make one complete rotation. Alternatively, the developing nozzle  86  is scanned along the guide rail  94 . During the operation, the developing solution  90  is moved to pass successively through the liquid reservoir  122 , the outlet port  124  and the fine hole  125  so as to collide against the buffering rod  130 . Finally, the developing solution  90  is discharged from the discharge port passageway  123 . 
     In this step, the developing solution  90  looses pressure when passing through the fine hole  125  and the strength of the developing solution  90  is weakened by collision against the buffering rod  130 . Under this condition, the developing solution  90  passes through the clearance between the buffering rod  130  and the liquid discharge section  121 , said clearance constituting a part of the discharge port passageway  123 , so as to be discharged from the discharge port passageway  123 . As a result, the developing solution  90  is allowed to land soft on the resist coating film so as to supply promptly the developing solution  90  onto the wafer W in an amount required for the puddle development without giving a serious influence to the light exposed latent image. 
     What should also be noted is that the liquid discharge section  121  is in the shape of a slit, with the result that the developing solution  90  is expanded and diffused uniformly over a wide range along the buffering rod  130 . Therefore, even in the case of the conventional scanning movement system, in which the developing solution tended to fail to be supplied uniformly, the portion where the developing solution is it not supplied can be eliminated so as to carry out uniformly the developing treatment. 
     After completion of the developing treatment for a predetermined time, the wafer W is rotated by the spin chuck  52  so as to centrifugally remove the developing solution from the wafer W. Then, the rinse nozzle  102  is moved onto a region above the wafer W so as to wash away the developing solution remaining on the wafer W with the rinsing solution discharged from the rinsing nozzle  102 . Further, the spin chuck  52  is rotated at a high speed so as to scatter the developing solution and the rinsing solution remaining on the wafer W so as to dry the wafer W, thereby finishing a series of the developing treatment. 
     After the developing treatment, the developing nozzle  86  is moved to the waiting position  115 , and the liquid discharge section  121  of the developing nozzle  86  is washed with a nozzle washing mechanism (nozzle bath)  116 . 
     Another embodiment of the present invention will now be described with reference to FIGS. 11 to  16 . 
     As shown in FIG. 11, a developing nozzle  86 A comprises a colliding rod  130 A having an elliptical cross section. The colliding rod  130 A is supported by the liquid discharge section  121  such that the longer axis of the elliptical cross section extends in a vertical direction. The colliding rod  130 A of the particular shape facilitates the flow of the developing solution  90  within the discharge port passageway  123  so as to allow the developing solution  90  to be discharged more smoothly from the discharge port passageway  123 . Incidentally, the cross sectional shape of the colliding rod is not limited to an elliptical shape. For example, it is possible for the colliding rod to have a inverse triangular cross section, a diamond-shaped cross section or a heart-shaped cross section. 
     FIG. 12 shows that a developing nozzle  86 B comprises an externally threaded colliding rod  130 B. The colliding rod  130 B of the particular shape is excellent in its liquid holding function and a liquid guiding function. The developing nozzle  86 B also comprises a slit  125 B constituting a narrow passageway. The slit  125 B communicates with each of the liquid reservoir  122  and the discharge port passageway  123  and functions as a resistor of the fluid circuit so as to decrease the pressure (to cause pressure loss) of the developing solution  90  coming from the liquid reservoir  122 . It is desirable for the width of the slit  125 B to fall within a range of between 0.3 and 0.5 mm. Since the strength of the developing solution  90 , whose pressure has been decreased by the slit  125 B, is weakened by the colliding rod  130 B, the developing solution discharged from the discharge port passageway  123  scarcely gives impact to the wafer W. 
     FIG. 13 shows that a developing nozzle  86 C comprises a colliding rod  130 C having a gourd-shaped cross section. The colliding rod  130 C is supported by the liquid discharge section  121  such that recesses  130   n  are positioned on both sides of the cross section. The colliding rod  130 C of the particular shape is also excellent in its liquid holding function and the liquid guiding function. 
     FIG. 14 shows a developing nozzle  86 D comprising a large number of buffering balls  130 D acting as buffering members. These buffering balls  130 D are aligned in the liquid discharge section  121  to form a single row within the discharge port passageway  123 . It is desirable for the buffering ball  130 D to have a diameter of 3 to 5 mm. 
     FIG. 15 shows a developing nozzle  86 E comprising a plurality of bent passageways  141 ,  142 . The lower end of the bent passageway  141  communicates with the discharge port passageway  123 , with the upper end communicating with the bent passageway  142 . The bent passageway  141  is formed within the side wall of the nozzle body  120 , and the other bent passageway  142  extends through the lid  129  so as to be open on the upper end. since these bent passageways  141 ,  142  serve to maintain the inner pressure of the discharge port passageway  123  at the atmospheric pressure, discharge of the developing solution  90  from the discharge port passageway  123  is promoted. Incidentally, these bent passageways  141 ,  142  may be either fine holes or slits. 
     Further, FIG. 16 shows a developing nozzle  86 F, in which a plurality of fine discharge ports  150  are formed at the tip portion of the liquid discharge section  121 . These fine discharge ports  150  communicate with the discharge port passageway  123 . The discharge pressure of the developing solution  90  is further lowered by the fine discharge ports  150 . 
     As described above, the discharge pressure (or discharge speed) of the developing solution is lowered by the buffering member in the present invention so as to markedly diminish the impact given by the developing solution to the substrate. It follows that it is possible to develop the resist film with a high resolution without impairing the patterned latent image. 
     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.