Chemical pump and method of discharging chemical solution

A chemical pump includes a pressure chamber, a partition member for dividing the pressure chamber into a cleaning pressure chamber and a discharging pressure chamber, a filter part disposed on the primary side of the discharging pressure chamber, and a single drive mechanism. A pair of openings with respective check valves mounted therein are provided in each of the cleaning and discharging pressure chambers, and are positioned so as to cause a resist solution to flow only in the +Z direction. The drive mechanism moves the partition member in the −X direction to cause the resist solution to be sucked into the cleaning pressure chamber and to cause the resist solution to be discharged from the discharging pressure chamber. The drive mechanism moves the partition member in the +X direction to cause the resist solution to be sucked from the filter part into the discharging pressure chamber and to cause the resist solution to be supplied from the cleaning pressure chamber to the filter part so that the sucked resist solution is equal in amount to the supplied resist solution. This prevents vapor lock and micro-bubble phenomena during the discharge of the resist solution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for discharging a chemical solution onto an objective surface of a substrate.

2. Description of the Background Art

Semiconductor products, LCD products and the like are manufactured by performing on substrates a series of processes including cleaning, resist coating, exposure, development, etching, interlayer insulation film formation, heat treatment and the like. These processes are conventionally performed in a substrate processing apparatus having incorporated therein a plurality of processing units such as a coating processing unit and a heat treatment unit. A transport robot in the substrate processing apparatus transports the substrates between the plurality of processing units in a predetermined sequence, and the processing units perform respective processes on the substrates, whereby the substrate processing sequence proceeds.

Of the processing units, a known unit for supplying chemicals (or a chemical solution) to a substrate, e.g. a coating processing unit for discharging a resist onto the substrate, includes a spin coater for coating the substrate with the chemical solution while spinning or rotating the substrate held in place.FIG. 17shows the construction of a coating processing unit100which is such a typical spin coater. The coating processing unit100comprises a chemical bottle101for supplying a chemical solution such as a resist solution, an electric pump102for causing the resist solution to flow in a predetermined direction, a motor103for driving the electric pump102, a filter104for removing contaminants and the like from the resist solution, a discharge valve105for opening and closing a flow passage of the resist solution, a nozzle106for discharging the resist solution toward a substrate W, a chuck107for holding the substrate W in position, and a spin motor108for rotating or spinning the substrate W held by the chuck107.

The process of coating the surface of the substrate W with the resist solution in the coating processing unit100will be briefly described. The motor103previously drives the electric pump102to pump up a predetermined amount of resist solution by suction from the chemical bottle101. Next, the spin motor108rotates the substrate W held by the chuck107. The discharge valve105is opened and the motor103drives the electric pump102, to force outwardly the predetermined amount of resist solution previously pumped up, thereby discharging the resist solution through the nozzle106onto the surface of the substrate W. The discharged resist solution spreads over the surface of the substrate W by centrifugal force of the substrate W to form a coating film of the resist solution on the surface of the substrate W. In this process, air bubbles, contaminants and the like are removed from the resist solution to be discharged by passing the resist solution through the filter104.

The formation of the resist film in the substrate manufacturing process must be accurately controlled to provide a desired thickness of the resist film. To this end, precise control is effected on the discharge amount, discharge timing, discharge time and average discharge rate of the resist solution. If these values are controlled to be constant, a difference in process (mainly in discharge rate distribution during a time interval between the start of the discharge to the end thereof) results in different shapes of the formed coating films from each other, to present a problem such that the repeatability of the coating films is not insured.

The discharge rate distribution of the resist solution depends on the conditions of the filter104(the wettability and pressure loss of the filter104and the degree to which the filter104is clogged) disposed on the secondary side (on the nozzle106side) of the electric pump102. Thus, the coating processing unit100presents a problem in that the quality of the coating film thickness is dependent on the change of the filter104with time and the quality of the filter104.

To solve the problems, it is contemplated to provide the filter104on the primary side (on the chemical bottle101side) of the electric pump102.FIG. 18shows the construction of a coating unit110including the filter104disposed on the primary side. The components of the coating unit110are identical in function with those of the coating processing unit100, and will not be described.

In the coating unit110, when the resist solution is pumped out of the electric pump102, the rate at which the resist solution is discharged from the nozzle106is not affected by the conditions of the filter104because the filter104is not provided on the secondary side. Thus, if the conditions for providing a desired coating film are previously determined by experiment or the like, the coating unit110can insure the repeatability of the discharge rate distributions of the resist solution to form a generally identical coating film in each formation operation, thereby achieving accurate control of the thickness of the coating films.

In the coating unit110, however, the electric pump102sucks the resist solution under a reduced pressure. Accordingly reduced pressure within the filter104promotes the formation of bubbles in the resist solution within the filter104. The coating unit110in which no filter is provided on the secondary side is not capable of removing the bubbles thus formed from the resist solution, to present serious problems such as vapor lock and micro-bubble phenomena, resulting in deterioration of accuracy of the coating process.

To prevent the occurrence of the vapor lock and micro-bubble phenomena in the coating process, it is important to sufficiently purge air from piping and the filter104upon startup of the apparatus or upon replacement of the chemical bottle101. The electric pump102in each of the coating processing unit100and the coating unit110alternately performs the operation of pumping up the resist solution and the operation of pumping out the resist solution for the purpose of accurate discharge. Thus, the resist solution alternately moves and stands still repeatedly within piping.

FIGS. 19A through 19Cshow a bubble within a pipe during the air purge. The bubble remaining in a curved part of the pipe as shown inFIG. 19Ais forced out to the position shown inFIG. 19Bwhen the electric pump102drives the resist solution. However, since the resist solution stands still for some time in this state, the bubble moves up as shown inFIG. 19Cand returns to the position shown inFIG. 19A. As described above, when the electric pump102alternately performs the pump-up and pump-out operations, air is not sufficiently purged. This results in the vapor lock and micro-bubble phenomena, to deteriorate the accuracy of the coating process.

SUMMARY OF THE INVENTION

The present invention is intended for a technique for discharging a chemical solution onto a surface (to be processed) of a substrate.

In combination with an acting element for exerting a predetermined action on a chemical solution, a chemical pump for pumping the chemical solution through the acting element, comprises: a pressure chamber divided by a movable partition member into a first chamber and a second chamber; and a single driving element for driving the partition member to reciprocate, thereby changing a volume ratio between the first chamber and the second chamber while the sum of the volumes of the first and second chambers is held constant, wherein the chemical solution sucked and introduced into the first chamber by driving the partition member in a first direction is moved via the acting element provided outside the pressure chamber into the second chamber by driving the partition member in a second direction, and is then discharged out of the second chamber by driving the partition member in the first direction again.

Thus, the single driving element drives the partition member to reciprocate, thereby changing the volume ratio between the first chamber and the second chamber while the sum of the volumes of the first and second chambers is held constant. Therefore, the chemical pump can make the amount of change in the volume of the first chamber and the amount of change in the volume of the second chamber equal to each other precisely and simultaneously, thereby to suppress vapor lock and micro-bubble phenomena without the need to provide the acting element on the secondary side of the chemical pump.

The present invention is also intended for a method of sucking and discharging a chemical solution. The method comprises the steps of: driving in a first direction a movable partition member having opposite surfaces approximately equal in surface area within a pressure chamber divided by the partition member into a first chamber and a second chamber on opposite sides of the partition member, to increase the volume of the first chamber while decreasing the volume of the second chamber, thereby sucking and introducing the chemical solution into the first chamber; driving the partition member in a second direction within the pressure chamber to decrease the volume of the first chamber while increasing the volume of the second chamber, thereby moving the chemical solution from the first chamber to the second chamber via an acting element provided outside the pressure chamber for exerting a predetermined action on the chemical solution; and causing the partition member to increase the volume of the first chamber again while decreasing the volume of the second chamber again, thereby discharging the chemical solution out of the second chamber.

Therefore, this method can make the amount of change in the volume of the first chamber and the amount of change in the volume of the second chamber equal to each other precisely and simultaneously, thereby to suppress the vapor lock and micro-bubble phenomena without the need to provide the acting element on the secondary side of the chemical pump.

It is therefore an object of the present invention to prevent vapor lock and micro-bubble phenomena during the discharge of a chemical solution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a plan view showing the overall construction of a substrate processing apparatus1according to a preferred embodiment of the present invention. For the sake of definiteness of directions relative to each other, an XYZ rectangular coordinate system is illustrated, as required, inFIG. 1and its subsequent figures.

The substrate processing apparatus1performs a resist coating process and a development process on objective surfaces of respective substrates. The substrate processing apparatus1comprises: an indexer ID for transporting the substrates into and out of the substrate processing apparatus1; a first processing part group PG1and a second processing part group PG2each including a plurality of processing units for performing processes on the substrates; an interface IF for transferring the substrates to and from an exposure apparatus (or a stepper) not shown; and a transport robot TR.

The substrates to be processed by the substrate processing apparatus1are circular semiconductor substrates (or wafers) for fabrication of electronic components such as LSIs. However, the substrate processing apparatus1may be used in modified form as an apparatus for performing the above-mentioned processes on rectangular glass substrates for fabrication of display panels of LCD devices or on various substrates for flat panel displays.

The indexer ID places thereon a cassette or carrier (not shown) which can accommodate a plurality of substrates, and includes a transfer robot. The indexer ID transfers an unprocessed substrate from the cassette to the transport robot TR, and receives a processed substrate from the transport robot TR to store the processed substrate in the cassette. The cassette may be of the following types: an OC (open cassette) which exposes the stored substrates to atmosphere; and a FOUP (front opening unified pod) and an SMIF (standard mechanical interface) pod which store substrates in an enclosed or sealed space. In this preferred embodiment, the cassette stores25substrates therein.

The interface IF has the functions of receiving a substrate subjected to the resist coating process from the transport robot TR to pass the substrate to an exposure apparatus not shown, and of receiving an exposed substrate from the exposure apparatus to pass the exposed substrate to the transport robot TR. The interface IF further has a buffer function for temporarily stocking therein substrates before and after exposure so as to adjust the time at which the substrates are transferred to and from the exposure apparatus. The interface IF comprises a robot for transferring the substrates from and to the transport robot TR, and a buffer cassette for placing the substrates thereon, although not shown.

The substrate processing apparatus1comprises a plurality of processing units (processing parts) for processing substrates. Some of the plurality of processing units constitute the first processing part group PG1, and the remaining processing units constitute the second processing part group PG2.FIG. 2shows the construction of the first processing part group PG1and the second processing part group PG2. The first processing part group PG1includes coating processing units SC1and SC2(or resist coating processing parts) serving as solution processing units, and a plurality of heat treatment units disposed over the coating processing units SC1and SC2. Although shown as disposed in a horizontal plane inFIG. 2for purposes of illustration, the processing units are actually stacked in a vertical direction (in the Z direction).

Each of the coating processing units SC1and SC2is a so-called spin coater for supplying a photoresist (or a chemical solution) onto a main surface of a substrate while rotating the substrate to provide uniform resist coating. The coating processing units SC1and SC2have incorporated therein a chemical pump and a piping system according to the present invention which will be described in detail later.

The heat treatment units are arranged in three stacks of three each and provided over the coating processing units SC1and SC2. Specifically, a first stack includes a cooling unit CP1, an adhesion promotion unit AH (or an adhesion promotion processing part) and a heating unit HP1, in bottom-to-top order. A second stack includes a cooling unit CP2, a heating unit HP2and a heating unit HP3, and a third stack includes a cooling unit CP3, a heating unit HP4and a heating unit HP5, in bottom-to-top order.

Similarly, the second processing part group PG2includes development processing units SD1and SD2serving as solution processing units, and a plurality of heat treatment units disposed over the development processing units SD1and SD2. Each of the development processing units SD1and SD2is a so-called spin developer for supplying a developing solution onto the exposed substrate to perform a development process. The heat treatment units are arranged in three stacks of three each, and provided over the development processing units SD1and SD2. Specifically, a first stack includes a cooling unit CP4, a post-exposure baking unit PEB and a heating unit HP6, in bottom-to-top order. A second stack includes a cooling unit CP5, a heating unit HP7and a heating unit HP8, and a third stack includes a cooling unit CP6, a heating unit HP9and a heating unit HP10, in bottom-to-top order.

The heating units HP1to HP10are so-called hot plates for heating a substrate up to a predetermined temperature. The adhesion promotion unit AH and the post-exposure baking unit PEB are heating units for heating a substrate before the resist coating process and immediately after the exposure, respectively. The cooling units CP1to CP6are so-called cool plates for cooling a substrate down to a predetermined temperature, and for maintaining the substrate at the predetermined temperature.

The processing units (heating units and cooling units) for adjusting the temperature of a substrate are referred to herein as the heat treatment units. The processing units for supplying a chemical solution to a substrate to perform a predetermined process, such as the coating processing units SC1and SC2and the development processing units SD1and SD2, are referred to herein as the solution processing units. The solution processing units and the heat treatment units are generically referred to as processing units.

Filter fan units FFU for forming a downflow of clean air at controlled temperature and humidity toward the solution processing units are provided immediately under the heat treatment units. Although not shown, a filter fan unit for forming a downflow of clean air toward a transport space is also provided over the transport robot TR.

A controller CR is provided in the substrate processing apparatus1. The controller CR is constructed using a computer including a memory, a CPU and the like. The controller CR controls the transport operation of the transport robot TR in accordance with a predetermined processing program, and gives instructions to the processing units to establish processing conditions.

FIG. 3is an external perspective view of the transport robot TR. The transport robot TR includes a telescopic body40having a telescopically nested multi-section structure, and an arm stage35provided on top of the telescopic body40and having transport arms31aand31b.

The telescopic body40has four sections40a,40b,40cand40d, in top-to-bottom order. The section40ais receivable in the section40b, and the section40bis receivable in the section40cwhich in turn is receivable in the section40d. Sliding the sections40ato40done into another shortens the telescopic body40into a retracted position, whereas sliding the sections40ato40done out of another elongates the telescopic body40into an extended position. Specifically, when the telescopic body40is in the retracted position, the section40ais received in the section40b, and the section40bis received in the section40cwhich in turn is received in the section40d. When the telescopic body40is in the extended position, on the other hand, the section40ais substantially extended from the section40b, and the section40bis substantially extended from the section40cwhich in turn is substantially extended from the section40d.

The extendable/retractable operation of the telescopic body40is achieved by an elevating mechanism provided therein. An example of the elevating mechanism used herein may include a mechanism wherein a multiple belt and roller assembly is driven by a motor. The transport robot TR uses such an elevating mechanism to vertically move the transport arms31aand31b.

The transport robot TR is also capable of accomplishing the horizontal back-and-forth movement and the pivotal movement of the transport arms31aand31b. Specifically, the arm stage35on top of the section40aaccomplishes the horizontal back-and-forth movement and the pivotal movement of the transport arms31aand31b. More specifically, the arm stage35folds and unfolds the arm segments of the transport arms31aand31bto accomplish the horizontal back-and-forth movement of the transport arms31aand31b, and the arm stage35itself pivots with respect to the telescopic body40to accomplish the pivotal movement of the transport arms31aand31b.

Thus, the transport robot TR is capable of accomplishing the vertical movement, the pivotal movement and the horizontal back-and-forth movement of the transport arms31aand31b. In other words, the transport robot TR is capable of moving the transport arms31aand31bin three dimensions. The transport arms31aand31bholding a substrate W move in three dimensions to transfer the substrate to and from the plurality of processing units, thereby allowing the substrate W to be transported to the plurality of processing units and to be subjected to various processes.

Next, a substrate processing procedure in the aforementioned substrate processing apparatus1will be briefly described.FIG. 4shows an example of the substrate processing procedure in the substrate processing apparatus1. First, an unprocessed substrate W transferred from the indexer ID to the transport robot TR is transported into the adhesion promotion unit AH. The adhesion promotion unit AH is an adhesion promotion processing part for performing a heating process on the substrate W to promote the adhesion of the resist to the substrate W. To be precise, the adhesion promotion unit AH sprays vaporized HMDS (hexamethyl disilazane) onto the heated substrate W to promote the adhesion. Next, the transport robot TR transports the substrate W subjected to the adhesion promotion process from the adhesion promotion unit AH to the cooling unit CP1. The cooling unit CP1is a cool plate for performing a cooling process on the substrate W heated by the adhesion promotion unit AH.

Then, the transport robot TR transports the substrate W subjected to the cooling process from the cooling unit CP1to the coating processing unit SC1. The coating processing unit SC1is constructed as a so-called spin coater for applying a resist solution to a main surface of the substrate W while rotating the substrate W to coat the main surface of the substrate W with the resist solution. The applied resist solution spreads over the main surface of the substrate W by centrifugal force to form a resist film.

Next, the transport robot TR transports the substrate subjected to the resist coating process from the coating processing unit SC1to the heating unit HP1. The heating unit HP1is a hot plate for performing a heating process on the substrate W coated with the resist by the coating processing unit SC1. This heating process is heat treatment known as a prebake which evaporates excess solvent components in the resist applied to the substrate W to provide firm adhesion of the resist to the substrate W, thereby forming the resist film having stable sensitivity.

The transport robot TR transports the substrate W subjected to the prebake from the heating unit HP1to the cooling unit CP2. The cooling unit CP2performs a cooling process on the substrate W subjected to the prebake.

After the cooling process, the transport robot TR transports the substrate W from the cooling unit CP2to the interface IF. The interface IF passes to the exposure apparatus (or the stepper) the substrate W formed with the resist film and received from the transport robot TR. The exposure apparatus performs an exposure process on the substrate W. The substrate W after the exposure process is passed from the exposure apparatus back to the interface IF.

The transport robot TR transports the substrate W passed back to the interface IF to the post-exposure baking unit PEB. The post-exposure baking unit PEB performs heat treatment (post-exposure bake) for uniformly diffusing products resulting from a photochemical reaction within the resist film. This heat treatment eliminates the nonuniformity of the resist on boundaries between exposed and unexposed portions to provide a good pattern.

The transport robot TR transports the substrate W subjected to the post-exposure bake from the post-exposure baking unit PEB to the cooling unit CP3. The cooling unit CP3performs a cooling process on the substrate W subjected to the post-exposure bake. Thereafter, the transport robot TR transports the substrate W from the cooling unit CP3to the development processing unit SD1. The development processing unit SD1performs a development process on the exposed substrate W.

The transport robot TR then transports the developed substrate W from the development processing unit SD1to the heating unit HP2. The heating unit HP2heats the developed substrate W. Thereafter, the transport robot TR transports the substrate W from the heating unit HP2to the cooling unit CP4which in turn cools the substrate W.

The substrate W cooled by the cooling unit CP4is transferred by the transport robot TR back to the indexer ID and stored into a cassette.

As described above, the transport robot TR transports the substrate W in accordance with the procedure shown inFIG. 4, whereby the substrate W is subjected to a series of processes including the resist coating process, the development process and accompanying heat treatment. In the procedure ofFIG. 4, the coating processing unit SC2similar in function to the coating processing unit SC1may be used in place of the coating processing unit SC1. Parallel processing may be performed such that the substrate W is transported into an empty one of the coating processing units SC1and SC2. This holds true for the development processing unit SD1, the heating unit HP1, the cooling unit CP1and the like which have equivalent processing units similar in function thereto.

The overall construction of the substrate processing apparatus1and the outline of the processing procedure in the substrate processing apparatus1have been described above. Next, the coating processing unit SC1provided in the substrate processing apparatus1will be described in detail. Although only the coating processing unit SC1will be described below, the coating processing unit SC2is similar to the coating processing unit SC1.

FIG. 5shows the construction of principal parts of the coating processing unit SC1according to a first preferred embodiment of the present invention. The coating processing unit SC1is constructed as a so-called spin coater for applying a resist solution serving as a chemical solution to the surface of a substrate W while rotating the substrate W in the process of selectively etching electrode layers and the like formed on the surface of the substrate W.

The coating processing unit SC1comprises: a chemical bottle11for storing the resist solution; a chemical pump12for discharging the resist solution pumped up (or sucked) from the chemical bottle11while pressurizing the resist solution; a discharge valve13for opening and closing a flow passage (or a pipe) of the resist solution; a nozzle14for discharging the resist solution toward the substrate W; a chuck15for holding the substrate W in position; and a spin motor16for rotating or spinning the substrate W.

The chemical pump12includes a pressure chamber20for reducing and exerting pressure on the resist solution, and a filter part21serving as an acting element.FIG. 6shows the construction of the pressure chamber20of the chemical pump12. The pressure chamber20is provided with a partition member22, a drive mechanism23, and a plurality of check valves24.

The pressure chamber20is made of a rigid material and has a hollow interior structure. The interior space of the pressure chamber20(having a volume V) is shaped so that the cross-sectional area S thereof substantially parallel to the Y-Z plane is constant along the X axis, and is divided by the partition member22into a cleaning pressure chamber20a(having a volume Va) and a discharging pressure chamber20b(having a volume Vb).

The filter part21is provided outside the pressure chamber20. The filter part21includes a pipe211for providing communication between the cleaning pressure chamber20aand the discharging pressure chamber20b, and a filter210inserted in the pipe211for removing bubbles and contaminants from the resist solution passing through the pipe211to clean the resist solution. Since the pipe211establishes a connection between the cleaning pressure chamber20aand the discharging pressure chamber20bas shown inFIG. 5, the resist solution passes through the cleaning pressure chamber20aand the discharging pressure chamber20bin order, which will be described in detail later. The coating processing unit SC1in the first preferred embodiment includes the filter part21serving as the acting element for exerting a predetermined action on the chemical solution. However, the acting element is not limited to the filter part21but may be, for example, a device for adjusting the temperature of the chemical solution. Such an acting element may be construed as a conditioner for adjusting the conditions of the chemical solution or as a converter for converting the physical or chemical properties of the chemical solution.

The partition member22is made of a material impermeable to the resist solution, and has an outer peripheral portion in intimate contact with the inner walls of the pressure chamber20to prevent the resist solution from directly passing between the cleaning pressure chamber20aand the discharging pressure chamber20b. Specifically, both a surface area Sa of the partition member22on the cleaning pressure chamber20aside and a surface area Sb thereof on the discharging pressure chamber20bside are equal to the cross-sectional area S of the pressure chamber20. Thus, the partition member22has the function of blocking the passage of the resist solution. The partition member22is integrally constructed of a material which undergoes a negligible change in volume and shape, and the positions of the surfaces of the partition member22on the cleaning pressure chamber20aside and on the discharging pressure chamber20bside relative to each other are unchanged. The material which undergoes a negligible change in volume and shape is termed in this preferred embodiment with the intention of permitting some alteration such as expansion and shrinkage due to temperature change and a change in shape due to wear. This term means that metal and alloys having a predetermined hardness or higher, ceramic, and the like apply to the above-mentioned material, but an elastic material such as rubber and a plastic material such as clay are excluded.

The drive mechanism23includes a motor230for generating a driving force for moving the partition member22, and a guide member231for defining the direction of movement of the partition member22. The motor230is capable of precisely controlling the direction, amount and speed of rotation, based on a control signal from the controller CR.

This effects more precise control of the direction, distance and speed of movement of the partition member22as compared with, for example, a cylinder mechanism which moves the partition member22.

The guide member231is a shaft-like member whose cross-sectional area in the Y-Z plane is constant at any position along the X axis, and is disposed within the pressure chamber20so as to extend through the pressure chamber20in a direction substantially parallel to the X axis, as shown inFIG. 6. The guide member231has the functions of transferring the driving force of the motor230to the partition member22and limiting the direction of movement of the partition member22to the X direction.

The drive mechanism23having such a construction smoothly reciprocates the partition member22in the X direction to make the volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bvariable, whereby the ratio between the volumes Va and Vb may be varied at will.

This provides variable volumes of the cleaning pressure chamber20aand the discharging pressure chamber20b. When the volume of each of the chambers20aand20bis increased, the pressure in each of the chambers20aand20bis reduced to cause the resist solution to be sucked. When the volume is decreased, on the other hand, pressure is applied to the interior of each of the chambers20aand20bto cause the resist solution to be discharged. The drive mechanism23(principally, the guide member231) is made of a material which undergoes a negligible change in volume and shape, like the partition member22, and is disposed so that the volume and shape thereof within the pressure chamber20are not changed by the movement of the partition member22, as shown inFIG. 6. Specifically, the drive mechanism23has the function of driving the partition member22to thereby change the volume ratio between the cleaning pressure chamber20aand the discharging pressure chamber20bso that the sum of the volumes of the cleaning pressure chamber20aand the discharging pressure chamber20b(or the volume of the pressure chamber20) is constant as expressed by
Va+Vb=V=const.  (1)

A check valve24is provided in each opening25to28provided in the pressure chamber20, as shown inFIG. 6.FIG. 7shows the details of the check valve24. The check valve24includes an enclosure240in a short tubular form, and a sphere241disposed in the enclosure240movably in the Z direction. Openings of the enclosure240are connected to, for example, pipes for the resist solution so that the interior of the enclosure240serves as a flow path of the resist solution.

The interior space of the enclosure240becomes narrower in the −Z direction to prevent the sphere241from moving beyond a shut-off position (indicated by the solid line ofFIG. 7) in the −Z direction. A stopper member not shown prevents the sphere241from moving beyond the position indicated by the dash-double-dot line ofFIG. 7in the +Z direction. When in the shut-off position, the sphere241shuts off the interior of the enclosure240(or the flow path of the resist solution) to prevent the resist solution from flowing, as shown inFIG. 7. Thus, the check valve24permits the resist solution to flow only in the +Z direction (indicated by the arrow ofFIG. 7). The structure of the check valve24is not limited to that shown inFIG. 7, but may be such that the controller CR controls the opening and closing of the flow path of the resist solution as in a solenoid valve. Any known structure may be used which functions to cause the resist solution to flow only in a predetermined direction in predetermined timed relation.

Thus, the opening25serves as the inlet of the cleaning pressure chamber20afor the resist solution, and the opening26serves as the outlet thereof. The opening27serves as the inlet of the discharging pressure chamber20bfor the resist solution, and the opening28serves as the outlet thereof. For example, when pressure is applied to the cleaning pressure chamber20a, the resist solution in the cleaning pressure chamber20ais forced outwardly through the opening26serving as the outlet but is not forced outwardly through the opening25serving as the inlet because of the presence of the check valves24.

The construction of the coating processing unit SC1according to the first preferred embodiment has been described above. Next, the operation of the coating process in the coating processing unit SC1will be described.FIG. 8is a flowchart showing the details of the operation of the coating processing unit SC1according to the first preferred embodiment. Unless otherwise specified, the controller CR is assumed to effect the control of the operation of the following components.

In the coating processing unit SC1, a judgment is initially made as to whether or not a substrate W subjected to the cooling process is transported from the cooling unit CP1by the transport robot TR (in Step S11). If the substrate W is transported, the chuck15holds the substrate W, and the spin motor16starts rotating the substrate W (in Step S12).

Next, the motor230of the drive mechanism23starts rotating to move the partition member22in the −X direction, thereby driving the resist solution (in Step S13). While the resist solution is driven, the discharge valve13is opened to discharge the resist solution through the nozzle14(in Step S14).

FIGS. 9A and 9Bshow the operation of the chemical pump12. Prior to the coating process, the partition member22in the chemical pump12is moved by the motor230to the position indicated by the solid lines ofFIG. 9Aas an initial position. The volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bat this time are denoted by Va1and Vb1, respectively.

As the partition member22moves in the −X direction in Step S13, the ratio between the volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bis varied, whereby the resist solution in the chemical pump12and the pipe is driven. The amount by which the volume Va of the cleaning pressure chamber20ais increased and the amount by which the volume Vb of the discharging pressure chamber20bis decreased at this time are denoted by ΔVa1and ΔVb1, respectively. Then, the movement of the partition member22in the −X direction increases the volume of the cleaning pressure chamber20aby the amount ΔVa1. Thus, the volume ΔVa1of the resist solution is sucked from the chemical bottle11through the opening25into the cleaning pressure chamber20a. Since the volume of the discharging pressure chamber20bis decreased by ΔVb1, the volume ΔVb1of the resist solution is discharged through the opening28. The resist solution discharged out of the discharging pressure chamber20bis discharged through the nozzle14onto the main surface of the substrate W by opening the discharge valve13in Step S14, and spreads over the main surface of the substrate W by centrifugal force to form a resist film.

The operation of moving the partition member22in the −X direction is equivalent to the operation of sucking the resist solution into the chemical pump12and the operation of discharging the resist solution out of the chemical pump12. The provision of the check valve24in each of the openings26and27as described above prevents the backflow of the resist solution through the opening26into the cleaning pressure chamber20aand the discharge of the resist solution through the opening27out of the discharging pressure chamber20b.

Since no filter is provided on the secondary side (between the opening28and the nozzle14) of the chemical pump12in the coating processing unit SC1according to the first preferred embodiment as shown inFIG. 5, the discharge rate of the resist solution during the discharge of the resist solution onto the substrate W depends only on the speed of movement of the partition member22. Therefore, the controller CR which controls the speed of rotation of the motor230so that the speed of movement of the partition member22satisfies the same conditions in every coating process can insure the repeatability of the resist solution discharge rate distribution without being affected by the change of the filter210with time.

When the discharge of the resist solution through the nozzle14starts, the controller CR judges whether or not predetermined discharge time T has elapsed (in Step S15). After the lapse of the predetermined discharge time T, the controller CR closes the discharge valve13and stops the movement of the partition member22, to thereby stop the discharge of the resist solution (in Step S16). It is assumed that the partition member22moves to the position indicated by the dash-double-dot lines ofFIG. 9A(or the position indicated by the solid lines ofFIG. 9B) during the discharge time T.

The speed of movement of the partition member22and the discharge time T are values whose repeatability can be insured in every coating process. The distance ΔX the partition member22moves during the discharge of the resist solution (during the lapse of the discharge time T) is accordingly a repeatable value. Since the partition member22is made of the material which undergoes a negligible change in volume and shape as described above, the distance the surface of the partition member22on the discharging pressure chamber20bside moves when the partition member22moves the distance ΔX is also the same distance ΔX, and satisfies
ΔVb1=Sb×ΔX(2)

Because of the negligible change in shape of the partition member22, the surface area Sb is a constant value. Accordingly, the repeatability of the total discharge amount ΔVb1of the resist solution is also insured in the coating processing unit SC1. Additionally, the controller CR judges the discharge timing of the resist solution based on the speed of rotation of the substrate W while controlling the spin motor16. Therefore, the repeatability of the discharge timing of the resist solution is also insured.

As discussed above, the discharge amount, the discharge timing, the discharge time, the average discharge rate and the discharge rate distribution are managed with good repeatability in the coating processing unit SC1. Thus, the coating processing unit SC1can form the coating films of resist solution on respective substrates W with good repeatability. Further, these conditions are established without any difference between apparatuses. Thus, when substrates W are processed in the plurality of coating processing units SC1and SC2, for example, as in the substrate processing apparatus1according to the first preferred embodiment, the coating processing units SC1and SC2can form substantially identical coating films on the respective substrates W. The accuracy of the coating process is improved by previously determining the conditions for the formation of a desired coating film by experiment and performing the coating process based on the conditions with good repeatability.

Next, the substrate W subjected to the resist coating process is transported by the transport robot TR from the coating processing unit SC1to the heating unit HP1(in Step S17). In the coating processing unit SC, the motor230starts moving the partition member22in the +X direction (in Step S18) in parallel with the transport of the substrate W by the transport robot TR. Prior to the execution of Step S18, the partition member22is previously located in the position indicated by the solid lines ofFIG. 9Bin Step S113. The volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bat this time are denoted by Va2and Vb2, respectively.

When the partition member22is moved in the +X direction in Step S18, the ratio between the volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bis varied again, whereby the resist solution is driven. The amount by which the volume Va of the cleaning pressure chamber20ais decreased and the amount by which the volume Vb of the discharging pressure chamber20bis increased at this time are denoted by ΔVa2and ΔVb2, respectively. Then, the movement of the partition member22in the +X direction increases the volume Vb of the discharging pressure chamber20bby the amount ΔVb2. Since the partition member22does not allow the direct passage of the resist solution, the volume ΔVb2of the resist solution is sucked from the secondary side of the filter part21through the opening27. However, since the volume Va of the cleaning pressure chamber20ais decreased by ΔVa2at the same time, the volume ΔVa2of the resist solution is supplied through the opening26to the primary side of the filter part21.

The provision of the check valve24in each of the openings25and28as described above prevents the discharge of the resist solution through the opening25out of the cleaning pressure chamber20aand the backflow of the resist solution through the opening28into the discharging pressure chamber20b.

The operation of moving the partition member22in the +X direction is equivalent to the operation of the discharging pressure chamber20bpreviously sucking an amount of the resist solution by which the nozzle14will discharge in the next coating process. This operation is also equivalent to the operation of the filter210removing the bubbles and contaminants from the resist solution to clean the resist solution because the cleaning pressure chamber20asupplies the resist solution through the filter part21to the discharging pressure chamber20b.

When the partition member22is moved to the position indicated by the dash-double-dot lines ofFIG. 9B, then
Va1=Va2−ΔVa2(3)
Vb1=Vb2+ΔVb2(4)
hold.

Since the volume V of the pressure chamber20is constant in the coating processing unit SC1according to the first preferred embodiment,
V=Va1+Vb1=Va2+Vb2(5)
holds.

Thus, the ratio between the volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bis varied by the movement of the partition member22in the +X direction, but the amounts ΔVa2and ΔVb2of change may be made equal. Equation (6) may be also derived from
ΔVa2=Sa×ΔX(7)
ΔVb2=Sb×ΔX(8)
S=Sa=Sb(9)

In the chemical pump12according to the first preferred embodiment as discussed above, control is effected to make the volume V of the pressure chamber20constant while the ratio between the volume Va of the cleaning pressure chamber20aand the volume Vb of the discharging pressure chamber20bis changed at will. Therefore, the same amount of resist solution as that sucked from the secondary side of the filter part21is supplied to the primary side of the filter part21as indicated by Equation (6).

This suppresses the reduction in pressure on the resist solution in the filter210to prevent the formation of bubbles in the resist solution. Therefore, the chemical pump12according to the first preferred embodiment can prevent the vapor lock and micro-bubble phenomena to improve the accuracy of the coating process without the need to provide a mechanism for removing bubbles similar to the filter210on the secondary side of the chemical pump12.

Equations (3) through (9) hold accurately also during the movement of the partition member22since the partition member22is integrally constructed of the material which undergoes a negligible change in volume and shape and the single drive mechanism23is used to move the partition member22. In other words, the first preferred embodiment can more precisely effect control to make the amount of resist solution supplied to the filter part21and the amount of resist solution sucked from the filter part21equal to each other, as compared with the synchronous control of a plurality of drive mechanisms by the controller CR for individual control of these amounts.

When the partition member22moves the predetermined distance (ΔX) to the position indicated by the dash-double-dot lines ofFIG. 9B(or the solid lines ofFIG. 9A), the coating processing unit SC1stops moving the partition member22(in Steps S19and S20).

Then, a judgment is made as to whether or not there is another substrate W to be subjected to the coating process in the substrate processing apparatus1(in Step S21). If there is another substrate W to be processed, the processing returns to Step S11to repeat the above-mentioned process. If there is no substrate W to be processed, the processing is terminated.

The substrate processing apparatus1according to the first preferred embodiment performs the above-mentioned steps to supply to the primary side of the filter part21the same amount of resist solution as that sucked from the secondary side of the filter part21. If the filter part21is positioned on the primary side of the discharging pressure chamber20bwhen the discharging pressure chamber20bsucks the resist solution, the substrate processing apparatus1according to the first preferred embodiment prevents the reduction in pressure in the filter210to suppress the formation of bubbles in the resist solution. This suppresses the vapor lock and micro-bubble phenomena without the need to locate the filter part21on the secondary side of the chemical pump12. Since the discharge rate distribution during the discharge of the resist solution is not affected by the change of the filter with time or other conditions, the substrate processing apparatus1according to the first preferred embodiment is capable of insuring the repeatability of the coating film thickness to improve the accuracy of the coating process.

Additionally, the coating processing unit SC1of the substrate processing apparatus1uses the single drive mechanism23to perform the operations of supplying the resist solution to the primary side of the filter part21and of sucking the resist solution from the secondary side of the filter part21, thereby effecting more precise control as compared with the use of a plurality of drive mechanisms.

Although the pressure chamber20according to the first preferred embodiment which is made of a rigid material is not changed in shape or the like by driving the partition member22, the pressure chamber20may be constructed to change its shape as the partition member22moves, so long as the volume V of the pressure chamber20is constant.

FIGS. 10A and 10Bare schematic views of the chemical pump12according to a second preferred embodiment of the present invention which is constructed based on the above principle. Like reference numerals and characters are used in the second and subsequent preferred embodiments to designate components similar in function to those of the first preferred embodiment.

With reference toFIGS. 10A and 10B, the pressure chamber20of the chemical pump12according to the second preferred embodiment is constructed of a bellows-like member capable of expanding and contracting in the X direction. As in the first preferred embodiment, the pressure chamber20is divided by the partition member22into the cleaning pressure chamber20aand the discharging pressure chamber20b, and the components of the cleaning pressure chamber20aand the components of the discharging pressure chamber20bare mirror images of each other.

The outer end (or the left-hand end as viewed inFIGS. 10A and 10B) of the cleaning pressure chamber20aon the positive side of the X direction and the outer end (or the right-hand end as viewed inFIGS. 10A and 10B) of the discharging pressure chamber20bon the negative side of the X direction (i.e., the outer ends to which check valves24are attached) are fixed in predetermined positions within the coating processing unit SC1. The inner end (or the right-hand end as viewed inFIGS. 10A and 10B) of the cleaning pressure chamber20aon the negative side of the X direction and the inner end (or the left-hand end as viewed inFIGS. 10A and 10B) of the discharging pressure chamber20bon the positive side of the X direction are attached to the partition member22.

The chemical pump12according to the second preferred embodiment is constructed in this manner. Thus, when the partition member22is moved in the X direction, the volume ratio between the cleaning pressure chamber20aand the discharging pressure chamber20bis varied depending on the X-axis position of the partition member22, and the resist solution is driven by the operation of moving the partition member22. However, the length of the pressure chamber20in the X direction is unchanged, and the amount of change in the volume Va of the cleaning pressure chamber20ais equal to the amount of change in the volume Vb of the discharging pressure chamber20b. The volume V of the pressure chamber20is constant.

The partition member22is made of a material which is not changed in shape and the like as in the first preferred embodiment. The partition member22is mounted to the guide member231of the drive mechanism23provided outside the pressure chamber20so as to be movable in the X direction. The rotation of the motor230moves the partition member22in the X direction along the guide member231.

The check valves24have the function of passing the resist solution only in one direction as in the first preferred embodiment, but differ in orientation from those of the chemical pump12of the first preferred embodiment, as shown inFIGS. 10A and 10B. The check valves24mounted in the openings25and28are oriented to pass the resist solution in the −X direction, whereas the check valves24mounted in the openings26and27are oriented to pass the resist solution in the +X direction.

With such an arrangement, when the drive mechanism23drives the partition member22in the −X direction as shown inFIG. 10A, the cleaning pressure chamber20aexpands to increase in volume Va. Then, the pressure in the cleaning pressure chamber20ais reduced to cause the resist solution to be supplied from the chemical bottle11through the opening25into the cleaning pressure chamber20a. At this time, the discharging pressure chamber20bcontacts to decrease in volume Vb. Then, pressure is applied to the interior of the discharging pressure chamber20bto cause the resist solution to be discharged from the discharging pressure chamber20bthrough the opening28toward the nozzle14.

On the other hand, when the drive mechanism23drives the partition member22in the +X direction as shown inFIG. 10B, the discharging pressure chamber20bexpands to increase in volume Vb. Then, the pressure in the discharging pressure chamber20bis reduced to cause the resist solution to be sucked from the secondary side of the filter part21through the opening27into the discharging pressure chamber20b. At this time, the cleaning pressure chamber20acontacts to decrease in volume Va. Then, pressure is applied to the interior of the cleaning pressure chamber20ato cause the resist solution to be supplied from the cleaning pressure chamber20athrough the opening26to the primary side of the filter part21. Since the amount by which the volume Va of the cleaning pressure chamber20ais decreased is equal to the amount by which the volume Vb of the discharging pressure chamber20bis increased, the amount of resist solution sucked from the secondary side of the filter part21is equal to the amount of resist solution supplied to the primary side of the filter part21.

As described above, the chemical pump12according to the second preferred embodiment has the structure in which the shape of the pressure chamber20is changed as the partition member22moves, but the volume V of the pressure chamber20is constant. Such a structure can supply to the primary side of the filter part21the same amount of resist solution as that sucked from the secondary side of the filter part21. Therefore, the second preferred embodiment produces effects similar to those of the substrate processing apparatus1according to the first preferred embodiment. The provision of the drive mechanism23outside the pressure chamber20prevents particles or the like from entering the resist solution.

Although the partition member22according to the first and second preferred embodiments is made of the material which undergoes a negligible change in volume and shape, the partition member22is not limited to this, but may be constructed to change in shape and the like.

FIGS. 11A and 11Bare schematic views of the chemical pump12according to a third preferred embodiment of the present invention which is constructed based on the above principle.

The pressure chamber20of the chemical pump12according to the third preferred embodiment is constructed of a tubular rigid member, and is divided by the partition member22having a pair of filmy members220and221into the cleaning pressure chamber20aand the discharging pressure chamber20b. The pair of filmy members220and221are fixed at their peripheral portions to the inner walls of the pressure chamber20, and are coupled to each other at their central portions by a support member222. The support member222is mounted to the guide member231of the drive mechanism23provided outside the pressure chamber20so as to be movable in the X direction. The rotation of the motor230moves the partition member22in the X direction along the guide member231.

The use of the partition member22having such a structure effects the following operation. When the drive mechanism23drives the support member222of the partition member22in the −X direction as shown inFIG. 11A, the filmy member220on the cleaning pressure chamber20aside is deformed to convex in the −X direction, thereby increasing the volume Va of cleaning pressure chamber20a. Then, the pressure in the cleaning pressure chamber20ais reduced to cause the resist solution to be supplied from the chemical bottle11through the opening25into the cleaning pressure chamber20a. At this time, the filmy member221on the discharging pressure chamber20bside is deformed similarly (while being maintained in geometrically similar form) to decrease the volume Vb of the discharging pressure chamber20b. Then, pressure is applied to the interior of the discharging pressure chamber20bto cause the resist solution to be discharged from the discharging pressure chamber20bthrough the opening28toward the nozzle14.

On the other hand, when the drive mechanism23drives the support member222of the partition member22in the +X direction as shown inFIG. 11B, the filmy member220on the cleaning pressure chamber20aside is deformed to convex in the +X direction, thereby decreasing the volume Va of cleaning pressure chamber20a. Then, pressure is applied to the interior of the cleaning pressure chamber20ato cause the resist solution to be supplied from the cleaning pressure chamber20athrough the opening26to the primary side of the filter part21. At this time, the filmy member221on the discharging pressure chamber20bside is deformed similarly to increase the volume Vb of the discharging pressure chamber20b. Then, the pressure in the discharging pressure chamber20bis reduced to cause the resist solution to be sucked from the secondary side of the filter part21through the opening27into the discharging pressure chamber20b.

As described above, the chemical pump12according to the third preferred embodiment sucks and discharges the resist solution by changing the shape of the partition member22, but is structured so that the volume V of the pressure chamber20is constant. Such a structure can supply to the primary side of the filter part21the same amount of resist solution as that sucked from the secondary side of the filter part21. Therefore, the third preferred embodiment produces effects similar to those of the substrate processing apparatus1according to the first preferred embodiment.

For suppression of the vapor lock and micro-bubble phenomena, it is also effective to sufficiently remove air trapped in a pipe and a filter when starting to drive the apparatus.

FIGS. 12 through 14show the chemical pump12and a piping system50in the coating processing unit SC1according to a fourth preferred embodiment of the present invention which is constructed based on the above principle.

Although the chemical pump12of the fourth preferred embodiment is similar in construction to that of the first preferred embodiment, the chemical pump12of the second or third preferred embodiment may be used instead.

The piping system50includes pipes51to53, switching valves54and55, and an on-off valve56. The switching valves54and55and the on-off valve56are controlled by the controller CR.

The pipe51provides a connection between the chemical bottle11and the opening27of the discharging pressure chamber20b, and the pipe52provides a connection between the opening26of the cleaning pressure chamber20aand the opening28of the discharging pressure chamber20b. The pipe53is connected to a blower not shown for purging air from the filter210.

The switching valve54includes on-off valves540and541, and allows selection as to whether to suck the resist solution to be directed to the opening27of the discharging pressure chamber20bfrom the chemical bottle11or from the secondary side of the filter210. Specifically, for the suction from the chemical bottle11, the on-off valve540is opened and the on-off valve541is closed (in a maintenance state), as shown inFIGS. 12 and 13. For the suction from the secondary side of the filter210, on the other hand, the on-off valve540is closed and the on-off valve541is opened (in a normal state), as shown inFIG. 14.

The switching valve55includes on-off valves550and551, and allows selection as to whether to supply the resist solution discharged through the opening28of the discharging pressure chamber20bto the primary side of the filter210or to the nozzle14. Specifically, for the supply to the primary side of the filter210, the on-off valve550is opened and the on-off valve551is closed (in the maintenance state), as shown inFIGS. 12 and 13. For the supply to the nozzle14, on the other hand, the on-off valve550is closed and the on-off valve551is opened (in the normal state), as shown inFIG. 14.

The on-off valve56is open (in the maintenance state) when purging air by the above-mentioned blower; otherwise, the on-off valve56is closed (in the normal state). The switching valves54and55and the on-off valve56are connected to the controller CR, and are switched between the maintenance state and the normal state, based on a control signal from the controller CR. In other words, the controller CR is principally equivalent to a switching element according to the present invention, and the switching valves54and55and the on-off valve56are principally equivalent to an opening and closing element according to the present invention.

The construction of, in particular, the chemical pump12and the piping system50according to the fourth preferred embodiment has been described. Next, the operation of the substrate processing apparatus1according to the fourth preferred embodiment will be described.FIGS. 15 and 16are flowcharts showing the operation of the coating processing unit SC1according to the fourth preferred embodiment.

In the coating processing unit SC1, the controller CR initially opens or closes each of the switching valves54and55and the on-off valve56to place the valves54,55and56in the maintenance state and to switch the piping system50to a maintenance mode (in Step S31). Thus, each of the valves54,55and56is in an open or closed position shown inFIGS. 12 and 13.

Next, the drive mechanism23moves the partition member22in the X direction, and the above-mentioned blower exerts suction on the pipe53, thereby to drive the resist solution and to purge air from the piping and the filter210(in Step S32).

Step S32will be described in detail. While the partition member22moves in the −X direction as shown inFIG. 12, the pressure in the cleaning pressure chamber20ais reduced, and pressure is applied to the interior of the discharging pressure chamber20b. At this time, since the check valve24is provided in the opening27and the on-off valve541of the switching valve54is closed, the resist solution is supplied from the chemical bottle11through the opening25into the cleaning pressure chamber20a. The resist solution discharged through the opening28of the discharging pressure chamber20b, on the other hand, is supplied through the pipe52to the secondary side of the filter210since the on-off valve551of the switching valve55is closed and the check valve24is provided in the opening26. Since the on-off valve56is open and the on-off valve541of the switching valve54is closed, the resist solution supplied to the secondary side of the filter210passes through the pipe53and is sucked by the blower not shown, whereby air is purged.

While the partition member22moves in the +X direction as shown inFIG. 13, pressure is applied to the interior of the cleaning pressure chamber20a, and the pressure in the discharging pressure chamber20bis reduced. At this time, since the on-off valve551of the switching valve55is closed and the check valve24is provided in the opening28, the resist solution discharged through the opening26of the cleaning pressure chamber20ais supplied to the secondary side of the filter210. Since the on-off valve56is open and the on-off valve541of the switching valve54is closed, the resist solution supplied to the secondary side of the filter210passes through the pipe53and is sucked by the blower not shown, whereby air is purged, as discussed above. On the other hand, the resist solution is supplied from the chemical bottle11through the pipe51and the opening27into the discharging pressure chamber20bsince the on-off valve541of the switching valve54is closed and the check valve24is provided in the opening25.

In this manner, while the partition member22of the chemical pump12moves in either direction, the resist solution flows through the piping between the chemical bottle11and the chemical pump12and through the filter210. Therefore, the substrate processing apparatus1can achieve the air purge in a shorter time than the conventional apparatuses which alternately sucks and discharges the resist solution. Additionally, since the resist solution does not stand still for a while during the air purge, the substrate processing apparatus1prevents the problem shown inFIGS. 19A to 19Csuch that an air bubble returns to the original position while the resist solution stands still, thereby to sufficiently purge air from the piping prior to the coating process. This prevents the vapor lock and micro-bubble phenomena in the coating process.

In the coating processing unit SC1, Step S32is repeated until a lapse of predetermined time (in Step S33). After the lapse of the predetermined time, the drive mechanism23moves the partition member22to its initial position (corresponding to the position indicated by the solid lines ofFIG. 9A), and the controller CR opens or closes each of the switching valves54and55and the on-off valve56, thereby to place the valves54,55and56in the normal state and to switch the piping system50to a normal mode (in Step S34). Thus, each of the valves54,55and56is in an open or closed position shown inFIG. 14. The switching to the normal mode places the chemical pump12and the piping system50in the coating processing unit SC1in the fourth preferred embodiment into similar piping conditions to the chemical pump12(SeeFIG. 5) in the first preferred embodiment.

After the piping system50is switched to the normal mode in Step S34, the coating processing unit SC1according to the fourth preferred embodiment performs processes similar to those (Steps S11through S21inFIG. 8) of the coating processing unit SC1according to the first preferred embodiment.

These processes will be briefly described. The coating processing unit SC1waits until a substrate W is transported thereto by the transport robot TR (in Step S41). After the substrate W is transported, the coating processing unit SC1holds the substrate W, and thereafter starts rotating the substrate W (in Step S42). When the rpm of the substrate W reaches a predetermined value, the partition member22is moved in the −X direction to drive the resist solution, and the discharge valve13is opened to discharge the resist solution through the nozzle14toward the substrate W until a lapse of predetermined time (Steps S43through S45).

After the lapse of the predetermined time, the discharge valve13is closed, and the substrate W is transported out of the coating processing unit SC1(in Steps S46and S47). Then, the partition member22is moved a predetermined distance in the +X direction to drive the resist solution, whereby the filter210cleans the resist solution (in Steps S48and S49). At this time, the chemical pump12supplies from the cleaning pressure chamber20ato the primary side of the filter210the same amount of resist solution as that sucked from the secondary side of the filter210into the discharging pressure chamber20b. Therefore, the fourth preferred embodiment can also suppress the formation of bubbles without the reduction in pressure on the resist solution in the filter210.

When the partition member22is moved to a predetermined position (or the position shown inFIG. 14), the partition member22is stopped (Step S50). Then, a judgment is made as to whether or not there is another substrate W to be subjected to the coating process in the substrate processing apparatus1(in Step S51). If there is another substrate W to be processed, the processing returns to Step S41to repeat the above-mentioned process. If there is no substrate W to be processed, the processing is terminated.

As above discussed, the substrate processing apparatus1according to the fourth preferred embodiment can also produce effects similar to those of the first to third preferred embodiments.

Changing the piping system50into the maintenance mode allows the resist solution to be driven in the piping between the chemical bottle11and the chemical pump12and in the filter210while the partition member22of the chemical pump12moves in either direction. Therefore, the substrate processing apparatus1can achieve the air purge in a shorter time than the conventional apparatuses which alternately sucks and discharges the resist solution.

Additionally, since the resist solution does not stand still for a while during the air purge, the substrate processing apparatus1prevents an air bubble from returning to the original position while the resist solution stands still, thereby to sufficiently purge air from the piping prior to the coating process. This prevents the vapor lock and micro-bubble phenomena in the coating process.

While the preferred embodiments of the present invention have been described above, the number and position of valves provided in the coating processing unit SC1are not limited to those of the first to fourth preferred embodiments. As an example, an on-off valve which opens and closes in synchronism with the on-off valve541may be provided in the immediate vicinity of the secondary side of the filter210in the fourth preferred embodiment. The discharge valve13and the on-off valve551may be combined into a dual-purpose valve which opens and closes in timed relation to the opening and closing of the discharge valve13.

In the fourth preferred embodiment, when to terminate the air purge in the maintenance mode is judged by time. However, an input part having, for example, a control button may be provided in the substrate processing apparatus1so that this judgment is made by operator's command input through the control button.