Abstract:
A resist solution applying apparatus and a method of using the resist solution applying apparatus. The apparatus comprises a hold and rotate member that holds and rotates a member to be processed, a resist solution discharge nozzle that discharges a resist solution almost at a center of rotation of the member to be processed, a resist solution supply mechanism that supplies the resist solution to the resist solution discharge nozzle, and a discharge controller connected to the rest solution supply mechanism that controls a predetermined amount of the resist solution discharged from the resist solution discharge nozzle to be reduced gradually or in stages after discharge is started, and increased again before the discharge is stopped.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to an apparatus and method of applying a resist solution onto a glass substrate used in, for example, a liquid crystal display (LCD). 
     The priority of the present application has been claimed on the basis of Japanese Patent Application No. 10/346638 (Nov. 20, 1998). The contents of the Japanese application are incorporated in the present application. 
     In a producing process of an LCD, the same photolithography as that employed for production of a semiconductor device is employed to form a thin film of ITO (Indium Tin Oxide) and an electrode pattern on a glass substrate for the LCD. According to the photolithography, photoresist is applied onto a substrate, exposed and developed. 
     In a major resist applying step, spin coating is employed. By the spin coating, a resist solution is dropped onto a glass substrate while rotating the glass substrate, and the resist solution is diffused by the rotationally centrifugal force, to form a uniform resist film on a glass substrate. According to this method, however, most of the resist solution may be dropped from the substrate and wasted. An example teaches that only about 10% of the total amount of the resist contribute to formation of the film. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is accomplished to solve the above problem, and its object is to provide an apparatus and method capable of reducing an amount of use of a solution. 
     To solve the problem, the present invention according to its first major concept is a resist solution applying apparatus, comprising a holding and rotating member for rotating while holding a member to be processed; a resist solution discharging nozzle for discharging a resist solution almost at a center of rotation of the member to be processed; a resist solution supplying mechanism for supplying the resist solution to the resist solution discharging nozzle; and a discharge control section connected to the resist solution supplying mechanism, for controlling an amount of the resist solution discharged from the resist solution discharging nozzle to be reduced gradually or in stages, after discharging has been started. 
     According to this structure, a resist solution extends all over the member to be processed by the centrifugal force after discharging has been started, and a resist solution is further discharged on the extending resist solution. The resist solution discharged after that is easily extended to have a uniform thickness even if an amount of the discharging is reduced. Therefore, even if the amount of discharge is reduced after discharging has been started, the resist solution can be applied all over the member to be processed to have a uniform thickness, and the use of the resist solution can be reduced as compared with that in prior art. 
     It is preferable that the embodiment comprises a casing for sealing airtight an atmosphere around the member to be processed, while the resist solution is discharged or the member to be processed is rotated. According to the structure, the solvent included in the resist solution is hardly vaporized. Therefore, the advantage of controlling the discharge can be achieved certainly. Further, the supply of the resist solution can be reduced. In this case, it is preferable that the member to be processed and its casing are rotated synchronously with one another. According to this structure, the solvent included in the resist solution ca be made to be vaporized further hardly. 
     According to the embodiment of the first concept, the discharge control portion controls an amount of the resist solution discharged from the resist solution discharging nozzle to be a predetermined amount in a period from the time when discharging is started to the time when the resist solution has extended all over the member to be processed, and then controls the amount to be gradually reduced. 
     According to the embodiment of the first concept, the discharge control portion controls an amount of the resist solution discharged to the resist solution discharging nozzle to be a predetermined amount in a period from the time when discharging is started to the time when the resist solution has extended all over the member to be processed, and then controls the amount to be gradually reduced, and further controls the amount to be increased again. 
     The present invention of the second major concept, in addition to the first concept, provides a resist solution applying apparatus further comprising a rotation speed control portion for controlling a rotation speed of the member to be processed determined by the holding and rotating member, synchronously with the control of the amount of discharge by the discharge control portion. 
     According to this structure, even when the discharge of the resist solution is limited, the solution can be applied uniformly onto the entire member to be processed. 
     According to the embodiment of the second concept, the rotation speed control portion controls the rotation speed of the member to be processed determined by the holding and rotating member, to be constant, at least when the amount of the resist solution discharged to the resist solution discharging nozzle is controlled to be reduced gradually. 
     According to the embodiment of the second concept, the discharge control portion controls an amount of the resist solution discharged from the resist solution discharging nozzle to be a predetermined amount in a period from the time when discharging is started to the time when the resist solution has extended all over the member to be processed, and then controls the amount to be gradually reduced; and the rotation speed control portion controls the rotation speed of the member to be processed determined by the holding and rotating member, to be accelerated when the amount of the resist solution discharged to the resist solution discharging nozzle is a predetermined amount, and controls the rotation speed to be constant when the amount of the resist solution is controlled to be reduced gradually. 
     According to the embodiment of the second concept, the discharge control portion controls an amount of the resist solution discharged to the resist solution discharging nozzle to be a predetermined amount in a period from the time when discharging is started to the time when the resist solution has extended all over the member to be processed and then controls the amount to be gradually reduced, and further controls the amount to be increased again; and the rotation speed control portion controls the rotation speed of the member to be processed determined by the holding and rotating member, to be accelerated when the amount of the resist solution discharged to the resist solution discharging nozzle is a predetermined amount, controls the rotation speed to be constant when the amount of the resist solution is controlled to be reduced gradually, and controls the rotation speed to be decelerated when the amount of the resist solution is controlled to be increased again. 
     The present invention according to the third concept provides a method of applying a resist solution, comprising the steps of supplying the resist solution to a member to be processed; extending the resist solution on the member to be processed by rotating the member to be processed in a sealed casing; and controlling an amount of the resist solution discharged onto the member to be processed, to be reduced gradually or in stages after discharging has started. 
     The present invention according to the fourth concept, in addition to the third concept, provides the method further comprising a step of controlling a rotation speed of the member to be processed, synchronously with the control of the amount of the discharged resist solution. 
     The present invention according to the fifth concept provides a resist solution applying apparatus, comprising: a holding and rotating member for rotating while holding a member to be processed; a casing for sealing airtight an atmosphere around the member to be processed, while the member to be processed is rotated; a resist solution discharging nozzle for discharging a resist solution almost at a center of rotation of the member to be processed; a resist solution supplying mechanism for supplying the resist solution to the resist solution discharging nozzle; and a discharge control section connected to the resist solution supplying mechanism, for varying an amount of the resist solution discharged from the resist solution discharging nozzle, after discharging has been started. 
     The other characteristics and advantages of the present invention can be further understood by a person skilled in the art, from the following drawings and preferred embodiment. 
     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 view of a resist applying/developing system according to an embodiment of the present invention; 
     FIG. 2 is a front view of the resist applying apparatus shown in FIG. 1; 
     FIG. 3 is a plan view of the resist applying apparatus shown in FIG. 1; 
     FIG. 4 is a side view showing essential parts of the resist applying apparatus shown in FIG. 1; 
     FIG. 5A-5D are graphs to explain the control of the discharge of the resist solution by a discharge control portion; and 
     FIG. 6 is a graph to explain the control of the rotational amount of a spin chuck by a rotational amount control mechanism. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will be described below with reference to the drawings. 
     FIG. 1 is a perspective view of a resist applying/developing system according to the embodiment of the present invention. 
     As shown in FIG. 1, a loader/unloader portion  2  for loading/unloading a glass substrate G in/from the resist applying/developing system  1  is provided in front of (at the left side, in the figure, of) the resist applying/developing system  1 . A cassette table  3  on which cassettes C each containing, for example, twenty five glass plates G are aligned and placed at predetermined positions, and a loader-unloader  4  for unloading a glass substrate G to be processed from each cassette C and loading again the glass substrate G which has been processed in the resist applying/developing system  1  into each cassette C, are provided at the loader/unloader portion  2 . 
     The loader-unloader  4  is moved in the aligning direction of the cassettes C by the run of a main body  5 , and a glass substrate G is unloaded from each cassette C by a plate-like pin set  6  mounted on the main body  5  and loaded again into each cassette C. A substrate positioning member  7  for holding and positioning four corners of a glass substrate G is provided at both sides of the pin set  6 . 
     Corridor-like transfer paths  10  and  11  arranged in the longitudinal direction are provided in a straight line via a first acceptance portion  12 , at the central part of the resist applying/developing system  1 . Various processing devices  16  to  23  for executing the processings about the glass substrates G are arranged at both sides of the transfer paths  10  and  11 . At one side of the transfer path  10 , for example, two cleaning devices  16  for brushing a glass substrate G and cleaning it by high-pressure jet water are provided. At the opposite side of the transfer path  10 , two developing devices  17  are provided, and two heating devices  18  are piled up beside the developing devices  17 . 
     At one side of the transfer path  11 , an adhesion device  20  for subjecting the glass substrate G in the hydrophobic process before applying the resist solution onto the glass substrate G is provided, and a cooling device  21  is arranged under the adhesion device  20 . In addition, heating devices  22  are stacked in two rows, two in each row, beside the adhesion device  20  and the cooling device  21 . At the opposite side of the transfer path  11 , resist applying devices  23  for applying the resist solution onto the surface of the glass substrate G to form a resist film thereon are arranged. An exposing device and the like for exposing a predetermined fine pattern on the resist film formed on the glass substrate G via a second acceptance portion  128  are provided at the side portion of the resist applying device  23 , though not shown in the figure. The second acceptance portion  128  comprises an outgoing/incoming pin set  129  for allowing the glass substrate G to outgo/income, and an acceptance table  130 . 
     The above processing devices  16 - 18  and  20 - 23  are arranged at both sides of the transfer paths  10  and  11 , so that their inlet/outlet openings of the glass substrate G face inwardly. A first transfer device  25  moves in the transfer path  10  between the loder/unloader device  2 , the processing devices  16 - 18  and the first acceptance device  12  to transfer the glass substrate G. A second transfer device  26  moves in the transfer path  11  between the first acceptance device  12 , the second acceptance device  28 , and the processing devices  20 - 23  to transfer the glass substrate G. 
     Each of the transfer devices  25  and  26  has a pair of upper and lower arms  27 ,  27 . When it accesses the processing devices  16 - 18  and  20 - 23 , the processed glass substrate G is carried out of the chamber of each processing device by one of the arms  27  and the pre-processed glass substrate G is carried into the chamber by another arm  27 . 
     FIG. 2 is a front view and FIG. 3 is a plan view, showing the resist applying device  23  shown in FIG.  1 . FIG. 4 is a side view showing essential portions thereof. 
     As shown in the figures, a cup  29  is arranged almost at the center of the resist applying device  23 , and a spin chuck  28  serving as a holding and rotating member for holding the glass substrate G is arranged inside the cup  29 . 
     A vacuum adsorption device  37  for holding the glass substitute G in the vacuum adsorption is connected to the spin chuck  28 . An opening portion  38  through which the glass substrate G is taken in/out is provided at the upper portion of the cup  29 . A lid  30  covers the openinng portion  38 . The lid  30  is supported to be moved up and down by an opening/closing mechanism (not shown). An insertion aperture  30   a  through which a nozzel  74  to be described later is inserted into the cup  29  is formed at the lid  30 . 
     A first motor  31  is a driving source for rotating the spin chuck  28 , and a second motor  32  is a driving source for rotating the cup  29 . An elevating cylinder  33  is a driving source for moving up and down the spin chuck  28  in the direction of axis Z. 
     A sealing member  41  is attached to a bottom surface of an outer periphery side of a table portion  40  of the spin chuck  28 . When the sealing member  41  abuts on the bottom portion of the cup  29  by lowering the spin chuck  28 , an air-tight processing space  42  is formed. 
     The first motor  31  and the second motor  32  are controlled to rotate by a CPU  36 . The elevating cylinder  33  is controlled to move up and down by the CPU  36 . 
     A rotation shaft  43  of the elevating cylinder  33  is slidably connected to a spline bearing  47 , which is fitted on a circumferential surface of a rotation cylinder  46  mounted rotatably on an inner peripheral surface of a fixed collar  44  via a bearing  45 . A follower pulley  48  is mounted on the spline bearing  47 , and a timing belt  51  bridges between the follower pulley  48  and a driving pulley  50  mounted on a driving shaft  49  of the first motor  31 . 
     Therefore, the rotation shaft  43  is rotated by the drive of the first motor  31  via the timing belt  51  and thereby the spin chuck  28  is rotated. 
     The lower side of the rotation shaft  43  is provided in a cylindrical body (not shown). In the cylindrical body, the rotation shaft  43  can be moved in a direction of axis Z by the drive of the elevating cylinder  33  via a vacuum sealing portion  52 . 
     The cup  29  is provided via a connection cylinder  55  fixed at an upper end portion of a rotary outer cylinder  54  mounted on an outer peripheral surface of the fixed collar  44  via a bearing  53 . The drive from the second motor  32  is transmitted to the cup  29  by a timing belt  59  bridging between a follower pulley  56  mounted on the rotary outer cylinder  54  and a driving pulley  58  mounted on a driving shaft  57  of the second motor  32 , and thus the cup  29  is rotated horizontally. 
     In addition, a drain cup  60  shaped in a hollow ring is arranged at the outer peripheral side of the cup  29 , so as to collect mist flying from the cup  29 . 
     Further, an encoder  61  is attached to the first motor  31 , and an encoder  62  is attached to the second motor  32 . Detection signals detected by the encoders  61  and  62  are transmitted to the CPU  36 . In accordance with output signals compared in the CPU  36 , the rotation of the first motor  31  and the second motor  32  is controlled. 
     As shown in FIG. 3, a supply mechanism  70  for supplying thinner and the resist solution onto the glass substrate G is arranged outside the cup  29 . The supply mechanism  70  comprises a pivoting member  73  pivoted by a driving mechanism (not shown), and a supply head  74  having nozzles for supplying thinner and the resist solution almost at the center of the rotation of the glass substrate G is attached to the top portion of the pivoting member  73 . 
     Next, a solution supplying mechanism  80  for controlling the supply of the resist solution to the above-mentioned supply head  74  will be explained. The solution supplying mechanism  80  comprises a storage portion  81  of the resist solution and a pipe  82  for connecting the storage portion  81  to the supply head  74 , and a discharge control portion  83  is provided at the solution supplying mechanism  80 . Specifically, the discharge control portion  83  can be constituted to comprise, for example, a bellows pump  83   a  intervening in the pipe  82 , a stepping motor  83   b  for controlling the drive of the bellows pump  83   a , and a ball screw mechanism  83   c  provided between the bellows pump  83   a  and the stepping motor  83   b  to convert the rotary motion of the stepping motor  83   b  into a straight motion and operate the bellows pump  83   a , as shown in the figure. According to this structure, the operation of the bellows pump  83   a  can be controlled and the amount of the resist solution supplied to the supply head  74  can be also controlled, by varying the number of the pulse signals which are to be input to the stepping motor  83   b  by the CPU  36 . However, this is only an example and, the amount of discharge from the supply head  74  can be also controlled by providing a flow control valve (not shown) in the pipe  82 . 
     Moreover, a thinner supply mechanism  91  for supplying a thinner onto the glass substrate G prior to the supply of the resist solution, to improve the wetness, allow the resist solution to be applied more thinly and thus reduce the use of the resist solution, is provided for the resist applying apparatus  23  according to the present embodiment. The thinner supply mechanism  91 , which is constituted to supply the thinner from a thinner supply source (not shown) to a storage portion  92 , feeds the thinner onto the glass substrate G, from the supply head  74  provided on the glass substrate G via a pump  93  and a pipe  94 . 
     Next, the operations of the above-constituted resist applying apparatus  23  will be explained. Where the spin chuck  28  is moving up above the opening portion  38  of the cup  29 , the glass substrate G is moved onto the spin chuck  28  from the transfer device  26  and the vacuum adsorption is kept. 
     Then, the spin chuck  28  is lowered and the glass substrate G is transferred into the cup  29  through the opening portion  38 , by the drive of the elevating cylinder  33 . After that, the lid  30  is lowered to cover the cup  29 . 
     Then, the pivoting member  73  is pivoted, the supply head  74  at the top end of the pivoting member  73  is set at the position corresponding substantially to the center of the glass substrate G, and the top end is positioned in the cup  29  through the insertion aperture  30   a  of the lid  30 . At this time, the space between the outer periphery of the supply head  74  and the inner wall of the insertion aperture  30   a  is sealed air-tightly. 
     The spin chuck  28  starts rotating by the first motor  31  and, simultaneously, supply of the resist solution from the supply head nozzle  74  is started. At this time, the thinner may be supplied in advance onto the glass substrate G, from the storage portion  92  storing the thinner fed from the thinner supply source, via the pipe  94 , prior to the application of the resist solution. With this operation, the wetness of the resist solution on the glass substrate G can be improved, the resist solution can be applied more thinly and, therefore, the amount of the used resist solution can be reduced. 
     The amount of the resist solution discharged from the supply head  74  is controlled as shown in FIG. 5, by the discharge control portion  83  provided at the above-described resist solution supply mechanism  80 . According to the control shown in FIG. 5A, the amount of discharge is maximum when the discharge from the resist solution discharge nozzle  74  is started, and the amount is reduced gradually after the start of the discharge. When the resist solution is discharged onto the glass substrate G, the resist solution extends outwardly by the centrifugal force generated with the rotation of the spin chuck  28 , but the resist solution discharged after this is discharged on the extending resist solution and thus can be extended easily. Therefore, according to this manner, waste of the resist solution can be prevented and the resist solution can be applied in a uniform thickness, as compared with a conventional case of supplying the resist solution at a constant amount. At this time, since the atmosphere around the glass substrate G in the cup  29  is sealed airtight by the lid  30 , the solvent included in the resist solution is hardly vaporized and, for this reason, the viscosity of the resist solution is not changed so much. Therefore, the amount of the discharged resist solution can be reduced more effectively. 
     On the other hand, according to the control shown in FIG. 5B, the resist solution is supplied at an amount more than a predetermined one from the resist solution discharge nozzle  74  during a predetermined period, or more specifically, during a period until the resist solution extends entirely over the glass substrate G and, after that, the amount of discharged resist solution is reduced gradually. According to this manner, since the resist solution is discharged at an amount more than a predetermined one until the resist solution extends certainly over the entire glass substrate G, the resist solution can extend easily to the outer peripheral portion of the glass substrate G. On the other hand, after the resist solution has extended entirely over the glass substrate G, the resist solution discharged after that works to make the thickness of the resist film uniform. Therefore, no problem is caused even when the amount of discharge is reduced, and the amount of use thereof can be reduced as compared with the conventional case. 
     The control shown in FIG. 5C is the same as that in FIG. 5B with respect to the feature of discharging much solution in the step of extending the resist solution over the glass substrate G, and reducing the discharge in the step of adjusting the film thickness uniformly, but is different in the feature of controlling to increase the discharge again before the discharge has been stopped. That is, in a case where the discharge is reduced gradually as the time to stop the discharging comes, as shown in FIGS. 5A and 5B, a lake of the resist solution may be generated at the outer peripheral portion of the glass substrate G because the discharge becomes reduced. If the amount of discharge is increased again before the discharging has been stopped, the solution flows and the lake disappears, and therefore, the thickness of the resist solution can be made uniform over the glass substrate G. The amount of discharge can be reduced in stages as shown in FIG.  5 D. 
     In addition, it is preferable that the CPU  36  constituting the rotation control mechanism of the spin chuck  28  serving as a holding and rotating member controls the discharge from the resist solution discharging nozzle  74  and also controls the rotary speed of the spin chuck  28 . With this operation, even when the amount of the discharged resist solution is controlled, the thickness of the resist solution can be certainly made uniform over the glass substrate G, which contributes to the reduction of use of the resist solution. For example, when the discharging is controlled as shown in FIGS. 5B and 5C, it is preferable that the discharging is accelerated to extend the resist solution over the glass substrate G while it is discharged at an amount more than a predetermined one, and the spin chuck  28  is rotated at a constant speed to easily make the thickness uniform while the amount of discharge is gradually reduced, i.e. the thickness of the solution is adjusted to be uniform, as shown in FIG.  6 . Once the thickness of the resist solution is uniform, the rotation of the first motor  31  is gradually decelerated. 
     After that, the rotation of the first motor  31  is stopped and thus the rotation of the glass substrate G is stopped. Subsequently, the supply head  74  is moved up and taken from within the cup  29 , and the pivoting member  73  is pivoted to the outside of the cup  29 . Therefore, the supply head  74  is moved to a standby position outside the cup  29 . At this time, the lid  30  keeps covering the opening portion  38  of the cup  29 . 
     The first motor  31  and the second motor  32  are rotated synchronously, and the spin chuck  28 , the cup  29 , the lid  30  and the glass substrate G are rotated integrally. As a result, the resist solution applied onto the glass substrate G is dried and the resist film is formed on the glass substrate G. 
     After that, the rotation of the first motor  31  and the second motor  32  is stopped, the integral rotation of the spin chuck  28 , the cup  29 , the lid  30  and the glass substrate G is stopped, and the lid  30  is moved up and the opening potion  38  is opened by an opening/closing mechanism (not shown). 
     Then, when the spin chuck  28  is moved up by the drive of the elevating cylinder  33 , the glass substrate G is transferred outside the cup  29  through the opening portion  38  and is moved from the spin chuck  28  to the transfer device  26 . 
     The present invention is not limited to the above-described embodiment, and can be variously modified within a range which does not change the gist of the invention. 
     For example, only the spin chuck is rotated when the resist solution is discharged (or when the thinner is supplied), bur the embodiment is not limited to this. The spin chuck  28 , the cup  29 , the lid  30  and the glass substrate G may be rotated integrally, by rotating the first motor  31  and the second motor  32  synchronously while supplying the resist solution from the supply head  74 . In this structure, when the glass substrate G is rotated, the atmosphere around the glass substrate G in the cup  29  can be prevented from rotating relatively to the glass substrate G. Therefore, the discharge of the resist solution can be controlled so that the solvent can be hardly vaporized from the resist solution. Thus, extension of the resist solution can be controlled more exactly. Therefore, the amount of the discharged resist solution can be reduced to a small one. 
     Further, for example, the present invention is applied to the resist solution applying apparatus in the above-described embodiment. Naturally, however, the present invention can be applied to an apparatus for applying other solutions, and also, applied not only to the glass substrate, but also to other processed members. 
     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.