JP2017107919A - Method for forming coating film, apparatus for forming coating film, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such technology that film thickness of a coating film can be adjusted upon forming the coating film on a substrate by a spin coating method.SOLUTION: After a step of forming a liquid film by supplying a resist solution to a center part of a wafer W as a substrate while holding and rotating the wafer W with a spin chuck 11, a reflow step is carried out in which the wafer W is rotated at a rotational speed within a ±50 rpm range with respect to the rotational speed at the time of ending the supply of the resist solution so as to make the resist liquid film uniform. While carrying out the reflow step, gas is supplied to the surface of the wafer W. Then the rotational speed of the wafer W is increased to adjust the film thickness to a target film thickness, and then the rotational speed is decreased and the resist film is dried. Since the film thickness can be adjusted not only by controlling the rotational speed but by supplying gas to change the fluidity of the liquid film, resist films (coating films) having a broader range of film thickness can be formed from one resist solution (coating liquid).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a technique for forming a coating film by spreading a coating solution supplied to a substrate by rotating the substrate.

  In forming a coating film such as a resist film on a substrate, a technique called spin coating is widely used. In this method, a resist, which is a coating solution, is supplied to the central portion of the surface of the substrate held and rotated by a spin chuck, and the resist solution is spread to the peripheral edge of the substrate by the centrifugal force, and then the substrate continues to rotate. The resist film is formed by drying the liquid film on the substrate surface. The finished film thickness (target film thickness) of the resist film is adjusted by the rotation speed of the substrate and the viscosity of the resist solution.

  There is a demand in factories to form resist films having various film thicknesses for each process using the same resist solution, that is, a resist solution having the same type and viscosity of the resist solution and the solvent. By the way, when the film is formed on the surface of the substrate by spin coating, if the number of rotations of the substrate is too high, the surface of the film may be disturbed by an air flow formed on the substrate. On the other hand, if the rotational speed is too low, there is a problem that the time required for drying becomes long.

  For this reason, the use range of the number of rotations of the substrate is limited, and the adjustment range of the film thickness of the resist film formed using the same resist solution is limited. For this reason, when forming a resist film having a film thickness exceeding the adjustment range, it is necessary to prepare resist solutions having different viscosities. In this case, it is necessary to prepare a coating solution line for each viscosity of the resist solution, or when using a common coating solution line, it is necessary to replace the tank of the resist solution, resulting in an increase in the size of the apparatus and a complicated operation. There are concerns.

  Japanese Patent Application Laid-Open No. H10-228667 describes a technique for uniformizing the film thickness by supplying a solvent gas to a thick region of a film formed on a substrate and supplying a dry gas to a thin region of the film. However, this Patent Document 1 does not describe a technique for adjusting the average film thickness of the formed coating film.

Japanese Patent No. 4805758

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique capable of adjusting the film thickness of a coating film when the coating film is formed on a substrate by a spin coating method.

The coating film forming method of the present invention comprises:
A step of horizontally holding the substrate on a substrate holding portion that is rotatable about a vertical axis;
Next, supplying the coating liquid to the center of the substrate while rotating the substrate;
Leveling the liquid film of the coating liquid by rotating the substrate at a rotation speed in a range of ± 50 rpm with respect to the rotation speed of the substrate at the end of the supply of the coating liquid;
A step of lowering the fluidity of the coating liquid by supplying a gas to the surface of the substrate when performing the step of leveling the liquid film of the coating liquid;
Thereafter, in order to set the film thickness of the coating film to the target film thickness, the number of rotations of the substrate is higher than both the number of rotations at the end of the supply of the coating liquid and the number of rotations during the step of leveling the liquid film of the coating liquid. Maintaining the rotational speed;
Thereafter, the method includes a step of reducing the number of rotations of the substrate and drying the coating film.

The coating film forming apparatus of the present invention is
A substrate holder for horizontally holding the substrate;
A rotation mechanism for rotating the substrate holder around a vertical axis;
A coating liquid nozzle for supplying a coating liquid for forming a coating film on the substrate;
A gas supply unit for supplying a gas for reducing the fluidity of the coating solution to the surface of the substrate;
Supplying the coating liquid to the center of the substrate while rotating the substrate, and rotating the substrate at a rotational speed in a range of ± 50 rpm with respect to the rotational speed of the substrate at the end of the supply of the coating liquid. Leveling the liquid film, reducing the fluidity of the coating liquid by supplying a gas to the surface of the substrate when performing the step of leveling the liquid film of the coating liquid, and then the film thickness of the coating film Maintaining the number of rotations of the substrate at a higher number of rotations than the number of rotations at the end of the supply of the coating liquid and the number of rotations at the step of leveling the liquid film of the coating liquid. Then, a controller for executing the step of drying the coating film by decelerating the number of rotations of the substrate is provided.

Furthermore, the storage medium of the present invention provides
A storage medium for storing a computer program used in a coating film forming apparatus that forms a coating film by supplying a coating liquid to a surface of a substrate held horizontally by a substrate holding unit that is rotatable around a vertical axis,
The computer program has a set of steps so as to execute the coating film forming method of the present invention.

  According to the present invention, after supplying the coating liquid to the substrate, by rotating the substrate in a range of ± 50 rpm with respect to the rotation speed at the end of the supply of the coating liquid, the liquid film on the substrate surface is leveled, Gas is supplied to the surface of the substrate to lower the fluidity of the coating solution. Next, after increasing the number of rotations once to adjust the film thickness, the coating film is formed by decelerating and drying the coating film. Therefore, in addition to adjusting the film thickness by controlling the number of rotations of the substrate, it is possible to adjust the film thickness by changing the fluidity of the liquid film by supplying gas to the surface of the substrate. Thus, a coating film having a wider range of film thickness can be formed.

It is a vertical side view which shows one Embodiment of the coating film forming apparatus of this invention. It is a top view of a coating film forming apparatus. It is the side view and bottom view which show the gas nozzle used for a coating film forming apparatus. It is explanatory drawing which shows the rotation speed of a wafer, the time chart of ON / OFF of supply of a resist liquid and gas. It is explanatory drawing which shows the process of the formation process of a resist film. It is a vertical side view which shows the other example of the ring plate used for a coating film forming apparatus. It is a top view which shows the other example of a ring plate. It is explanatory drawing which shows the other example of the time chart of the rotation speed of a wafer.

  One embodiment of a coating film forming apparatus of the present invention will be described using an example of forming a resist film as a coating film on a semiconductor wafer (hereinafter referred to as “wafer”) W as a substrate. As shown in FIGS. 1 and 2, the coating film forming apparatus 1 includes a spin chuck 11 that forms a substrate holding unit that holds and rotates a wafer W having a diameter of, for example, 300 mm. The spin chuck 11 adsorbs the center of the back surface of the wafer W to hold the wafer W horizontally, and is configured to be rotatable clockwise in plan view along the vertical axis by a rotation mechanism 13 connected by a shaft 12. ing.

  A cup 2 is provided around the wafer W held by the spin chuck 11. The cup 2 is evacuated through the exhaust pipe 21 and the liquid spilled from the wafer W into the cup 2 is removed by the drain pipe 22. In the figure, reference numeral 23 denotes an elevating pin, which is configured to be transferred by the elevating mechanism 24 so that the wafer W is transferred between the wafer W transfer mechanism (not shown) and the spin chuck 11.

  The coating film forming apparatus 1 includes a nozzle unit 3 for supplying a coating solution and a solvent. The tip of the nozzle unit 3 is provided with a coating liquid nozzle 30 for discharging the coating liquid and a solvent nozzle 31 for discharging the solvent. As the coating solution, for example, a resist solution having a viscosity of 1 kg / m · s (1000 cp) or more is used, and as the solvent, a prewetting solvent such as a resist solution is used. The coating liquid nozzle 30 and the solvent nozzle 31 are connected to a coating liquid supply mechanism 33 and a solvent supply mechanism 35 via supply paths 32 and 34, respectively. The coating liquid supply mechanism 33 and the solvent supply mechanism 35 include devices such as a pump, a valve, and a filter, for example, and are configured to discharge a predetermined amount of resist liquid and solvent from the tips of the coating liquid nozzle 30 and the solvent nozzle 31, respectively. Has been.

  As shown in FIG. 2, the coating solution nozzle 30 and the solvent nozzle 31 are supported by a common arm 37 configured to be movable up and down and horizontally in a horizontal direction by a moving mechanism 36, and on the center portion of the wafer W and the cup. 2 is configured to be movable between a retracted position outside the two. In the drawing, reference numeral 38 denotes a guide for moving the moving mechanism 36 in the horizontal direction as described above. For example, a standby bus 39 is provided at the retreat position.

Further, the coating film forming apparatus 1 includes a gas nozzle 4 for supplying gas. The gas is used to lower the fluidity of the resist solution, and for example, an inert gas such as nitrogen (N ₂ ) gas is used. FIG. 3A is a side view of the gas nozzle 4, and FIG. 3B is a bottom view of the gas nozzle 4. As shown in this figure, the gas nozzle 4 includes, for example, a flat cylindrical buffer chamber 41, and a large number of gas discharge holes 42 are dispersedly formed on the lower surface of the buffer chamber 41. For example, a cylindrical gas introduction portion 43 is provided at the center of the upper surface of the buffer chamber 41, and the gas introduction portion 43 is connected to a gas supply mechanism 45 via a supply path 44.

  The gas supply mechanism 45 includes devices such as a valve and a gas heating mechanism, and is configured to discharge gas heated to, for example, 60 ° C. from the gas nozzle 4 in a shower shape. The heating mechanism is configured, for example, by providing a heating unit including, for example, a heater around a gas flow path, and is heated when the gas passes through the flow path. Since the gas nozzle 4 in this example discharges the gas from the plurality of gas discharge holes 42 in a shower-like manner via the buffer chamber 41, a low flow rate gas is supplied over a wide range at a high flow rate. The gas nozzle 4, the supply pipe 44, and the gas supply mechanism 45 constitute a gas supply unit. As shown in FIG. 2, the gas nozzle 4 is supported by an arm 47 configured to be movable up and down and moved in the horizontal direction by a moving mechanism 46, and between the position on the wafer W and the retracted position outside the cup 2. It is configured to be movable. In the figure, 48 is a guide for the moving mechanism 46 to move in the horizontal direction as described above.

  As shown in FIGS. 1 and 2, the coating film forming apparatus 1 includes a ring plate 5 that is an annular member. The ring plate 5 is formed in an annular shape in which a circular opening 51 having a diameter of 100 mm to 200 mm, for example, is provided at the center of the disk. The ring plate 5 is formed along the peripheral edge so as to cover the upper side of the peripheral edge of the wafer W held by the spin chuck 11, and the center of the ring plate 5, that is, the center of the opening 51 is the center of the spin chuck 11. It is provided so that it may be located on a rotating shaft.

  The ring plate 5 is supported by the support member 52 in a horizontal posture, and is moved up and down between a raised position indicated by a chain line in FIG. 1 and a lowered position indicated by a solid line by a moving mechanism 53 that raises and lowers the support member 52. It is configured freely. In this example, the lowered position corresponds to the position where the ring plate 5 covers the upper peripheral edge of the wafer W, and the raised position corresponds to the standby position. The distance between the lower surface of the ring plate 5 and the surface of the wafer W at the lowered position is set to 0.5 mm to 50 mm, for example. Further, in the ring plate 5, in order to form a moving region in which the gas nozzle 4 moves in the horizontal direction on the radius of the wafer W, a notch 54 extending from the inner periphery to the outer periphery is formed in a part of the circumferential direction. ing.

  The moving area of the cup 2, the nozzle unit 3 and the gas nozzle 4 is formed in a casing (not shown), and a fan filter unit (FFU) 14 is provided on the ceiling of the casing as shown in FIG. ing. The FFU 14 is configured to supply clean gas as a down flow toward the cup 2.

  Furthermore, the coating film forming apparatus 1 includes a control unit 6. The control unit 6 is composed of a computer, for example, and has a program storage unit (not shown). The program storage unit stores a program in which instructions (step groups) are set so that a coating film forming process described later can be performed. The program includes a recipe that describes the processing procedure, and the control unit 6 outputs a control signal to each unit of the coating film forming apparatus 1 according to this program, thereby controlling the operation of each unit. Specifically, the rotation speed of the wafer W is changed by the rotation mechanism 13, the nozzle unit 3 and the gas nozzle 4 are moved, and the coating liquid (from the coating liquid supply mechanism 33 and the solvent supply mechanism 35 to the coating liquid nozzle 30 and the solvent nozzle 31 ( The operations such as the supply and disconnection of the resist solution and the solvent, the supply and disconnection of the gas from the gas supply mechanism 45 to the gas nozzle 4, and the raising and lowering of the ring plate 5 are controlled. The program is stored in the program storage unit while being stored in a storage medium such as a hard disk, a compact disk, a magnetic optical disk, or a memory card.

  Next, a coating film forming process performed in the coating film forming apparatus 1 will be described with reference to FIGS. 4 and 5. FIG. 4 shows a profile with respect to the elapsed time of the rotation speed of the wafer W. The value on the vertical axis of this graph is the number of revolutions of the wafer W rpm (number of revolutions / minute). This graph is a visual description of the pattern in order to facilitate understanding of the present invention. This is not a reproduction of the actual rotational speed pattern. The graphs after the second stage are a time chart showing the supply and stop of the resist solution from the upper stage side, and a time chart showing the supply and stop of the gas.

  First, the ring plate 5 is placed at the raised position, the wafer W is loaded into the coating film forming apparatus 1 by an external transfer mechanism (not shown), and is received by the spin chuck 11 by the cooperative operation of the transfer mechanism and the lift pins 23. hand over. The casing is in a state where an inert gas is supplied toward the cup 2 by the FFU 14. A series of operations including this operation is executed by a program in the control unit 6.

  Next, the nozzle unit 3 in the retracted position is moved to the upper side of the central portion of the wafer W, and the prewetting solvent is discharged from the solvent nozzle 31 to the central portion of the wafer W rotated by the spin chuck 11. Thus, the solvent is applied to the entire surface of the wafer W by centrifugal force, and the wettability of the surface of the wafer W to the coating liquid is improved. Next, the rotation speed of the spin chuck 11 is reduced, and for example, the rotation of the spin chuck 11 is stopped.

  Subsequently, a resist film that is a coating liquid is supplied to the wafer W, and a liquid film forming process for forming a liquid film of the resist liquid is performed. In this step, as shown in FIG. 5A, the ring plate 5 is placed at the raised position, and the resist solution is applied from the coating solution nozzle 30 to the center of the wafer W while the wafer W is rotated by the spin chuck 11. Supply. As shown in FIG. 4, in this step, the rotation speed of the spin chuck 11 is changed from 0 rpm, for example, until the rotation speed at the end of the supply of the resist solution (first rotation speed) reaches 500 rpm, for example, 1000 rpm / s. Then, the resist solution is supplied in a state of being gradually and continuously accelerated. The resist solution supplied to the central portion of the wafer W spreads outward in the wafer surface by the centrifugal force of the rotation of the wafer W, and a liquid film is formed on the entire surface of the wafer W. When the supply of the resist solution is finished, the nozzle unit 3 moves to the retracted position.

  Since a resist solution having a high viscosity of 1000 cp or more has low fluidity compared to a resist solution having a low viscosity, if the rotational speed at the start of supplying the resist solution is large, the resist solution spreads in an irregular shape on the wafer surface. On the other hand, if the resist solution is rotated at a constant low rotational speed from the start to the end of the resist solution supply, the fluidity of the resist solution decreases toward the peripheral edge of the wafer W, and it becomes difficult to spread. For this reason, in the liquid film forming step, the resist liquid is uniformly spread in the radial direction in the wafer surface by supplying the resist liquid while gradually accelerating the spin chuck 11 from the stopped state to the first rotational speed, for example. It is preferable. In addition, if the rotation speed at the end of the supply of the resist solution (first rotation speed) is too high, the surface of the film tends to be disturbed, and it is not suitable for forming a resist film having a large target film thickness. If the rotational speed is too low, it takes a long time to form a resist film on the entire wafer surface. For this reason, it is preferable to set the first rotational speed to, for example, 200 rpm to 700 rpm.

  In such a resist solution having a high viscosity, it takes time until the resist solution spreads over the entire surface of the wafer. Therefore, the resist solution may be continuously supplied from the coating solution nozzle 30 during the liquid film forming step. The supply of the resist solution may be stopped midway, and the wafer W may be continuously rotated to spread the resist solution. The supply timing of the resist solution is appropriately set depending on the viscosity and type of the resist solution. In the liquid film forming step, the wafer W is accelerated to the first rotation speed at the end of the supply of the resist solution, and then rotated at the first rotation speed ± 50 rpm until the resist solution reaches the entire surface of the wafer. May be.

  Subsequently, a reflow process for leveling the liquid film of the coating liquid is performed. In this reflow process, as shown in FIG. 5B, the wafer W is rotated at the second rotational speed while the ring plate 5 is disposed at the raised position, and the gas nozzle 4 is positioned above the wafer W. To supply heated gas. The gas nozzle 4 is set, for example, at a height such that the lower surface thereof is aligned with the lower surface of the ring plate 5, and discharges gas while horizontally moving in the notch 54 formed in the ring plate 5 along the radial direction of the wafer W. To do. FIG. 5B shows how the gas nozzle 4 moves through the notch 54 of the ring plate 5.

  For example, the region to which the gas is supplied in the wafer W having a size of 300 mm is between a position away from the center of the wafer W, for example, 50 mm outward, and an outer edge of the wafer W (position away from the center of the wafer W, 150 mm) It is an area. In this region, the gas is supplied for, for example, 7 seconds while the gas nozzle 4 is reciprocated repeatedly.

  In this reflow process, by supplying gas to the liquid film on the wafer surface, volatilization of the solvent contained in the resist solution is promoted, and the viscosity of the resist solution is increased. In this way, in the state where the fluidity of the resist liquid on the wafer surface is lowered, the liquid film of the resist liquid is leveled, and the in-plane distribution of the film thickness of the liquid film is adjusted. In this example, the supply of gas from the gas nozzle 4 is stopped at the end of the reflow process, and the gas nozzle 4 moves to the retracted position.

  If the number of rotations of the wafer W during the reflow process is too high, the film surface tends to be disturbed when the gas is blown. For this reason, the second rotational speed is within a range of ± 50 rpm with respect to the first rotational speed (the rotational speed at the end of the supply of the resist solution) from the viewpoint of leveling the resist film and suppressing disturbance of the film thickness. And, for example, it is preferably set to 500 rpm or less. In addition, the gas supply flow rate in the reflow process is appropriately set so as to volatilize the solvent in the resist solution and suppress the disturbance of the resist film thickness due to the gas flow.

  Furthermore, in the 300 mm wafer W, the gas supply area is set to a range of, for example, 50 mm to 150 mm from the center of the wafer W. When the gas is discharged to a position too close to the center of the wafer W, the gas is sprayed on the wafer surface. This is because there is a concern that the flow range of the wafer W is locally reduced and the fluidity of the wafer W is locally lowered and it becomes difficult to adjust the film thickness uniformity. By blowing gas over a wide area from the center of the wafer W to, for example, an area outside 50 mm, the fluidity of the liquid film over a wide range on the wafer surface is lowered, and the uniformity of the film thickness can be easily adjusted. Further, by supplying the gas while moving the gas nozzle 4, the fluidity of the resist film in a wider range on the wafer surface can be lowered, so that the adjustment of the film thickness uniformity is further facilitated.

  In the profile shown in FIG. 4, gas is supplied during the reflow process. However, in the reflow process, gas may be continuously supplied during the process, or gas may be supplied during the process. Supply may be stopped. Since the fluidity of the resist solution is reduced by supplying the gas, the gas is preferably supplied after the resist solution has spread over the entire surface of the wafer W. For example, the gas may be supplied at the end of the liquid film forming step. It may be.

  Furthermore, in the above example, the gas nozzle 4 is supplied while being moved. However, the gas supply position may be fixed without moving the gas nozzle 4. When the gas supply position is fixed, the position closest to the center of the wafer W in the range in which the gas is supplied is preferably, for example, 50 mm to 130 mm from the center of the wafer W. If the gas supply position is fixed at a position that is too close to the periphery of the wafer W and the gas is supplied, the region where the gas is sprayed on the surface of the wafer W is limited to a narrow range of the periphery.

  Next, a film thickness adjusting step for adjusting the film thickness of the coating film to the target film thickness is performed. In this film thickness adjustment step, for example, as shown in FIG. 5C, the ring plate 5 is disposed at the lowered position, and the wafer W is rotated at the first rotation number in the liquid film formation step and at the second rotation number in the reflow step. This is performed by rotating at a third rotation number higher than any of the above, for example, 1000 rpm for a predetermined time, for example, 1-2 seconds. In this film thickness adjustment step, the wafer W is instantaneously rotated at a high rotation speed to adjust the film thickness according to the rotation speed. Since the film thickness is adjusted to some extent in the reflow process, it takes no time to adjust the film thickness without increasing the rotation speed, and the film surface may be disturbed if the rotation speed is too high. The number of rotations of 3 is preferably set to, for example, 500 rpm to 1200 rpm. Moreover, since the film thickness is adjusted to some extent in the reflow process, it is preferable to set the execution time of the film thickness adjustment process to, for example, 2 seconds to 10 seconds.

  Thereafter, a drying process for drying the coating film is performed. In this drying process, the ring plate 5 is placed in the lowered position, and the wafer W is rotated at a fourth rotational speed lower than the third rotational speed in the film thickness adjusting process to dry the resist film. The fourth number of revolutions is preferably set to a number of revolutions, for example, 5 rpm to 200 rpm, such that the resist film is dried and the resist solution is not shaken off. In this example, the resist film is dried while rotating at a rotation speed lower than the first rotation speed in the liquid film forming step, for example, 10 rpm, while suppressing the flow of the resist liquid from the wafer surface.

  As described above, the ring plate 5 is arranged at the raised position in the step of supplying a solvent, the step of forming a liquid film supplying a resist solution, and the step of reflowing the resist film. For this reason, it is possible to prevent the solvent and the resist solution scattered from the wafer W from adhering to the ring plate 5 when the solvent or the resist solution is supplied or when the resist solution is shaken off.

  On the other hand, the ring plate 5 is disposed at the lowered position in the resist film thickness adjusting step and the drying step. As a result, the height of the flow path of the air flow from the central portion to the peripheral portion of the wafer W is limited by the lower surface of the ring plate 5, so that the air flow from the central portion of the wafer W to the peripheral portion does not become a turbulent flow. It flows as a laminar flow. The higher the rotation speed of the wafer W, the more easily the turbulent air flow on the wafer W. However, since the air flow above the peripheral edge of the wafer W is rectified by the ring plate 5, turbulence occurs on the surface of the resist film. The disturbance of the film due to the flow is suppressed, and the in-plane uniformity of the film thickness is improved. Thus, after performing the drying process for a predetermined time, the rotation of the wafer W is stopped, and a series of coating processes is completed.

  In the above-described embodiment, after supplying the resist solution to the wafer W in the spin coating method, the wafer W is rotated at a rotational speed in a range of ± 50 rpm with respect to the rotational speed of the wafer W at the end of the supply of the resist liquid. As a result, the fluid of the resist solution is lowered by supplying gas to the surface of the wafer W while leveling the resist liquid film. Thereafter, the number of rotations of the wafer W is increased to adjust the film thickness, and then the number of rotations is reduced to dry the resist film. By reducing the fluidity of the resist solution by supplying gas to the surface of the wafer W, the thickness of the resist film can be increased compared to the case where no gas is supplied. Therefore, in addition to adjusting the film thickness by controlling the number of rotations of the wafer W, the film thickness can be adjusted by supplying gas, and a wider range of film thickness can be obtained using the same resist solution having the same viscosity and type. The resist film can be formed. For example, it is suitable for forming a coating film using a high-viscosity resist solution (coating solution) having a viscosity of 1000 cp or more. By using a coating solution having such a viscosity, for example, a coating film having a thickness of 1 μm or more can be formed. Can be formed.

  Subsequently, as another example of the embodiment of the present invention, a configuration example in which gas is supplied via the ring plate 7 will be described. As shown in FIGS. 6 and 7, a large number of gas discharge holes 72 are dispersed in a part of the ring plate 7 that forms an annular member having an opening 71 at the center so as to penetrate the ring plate 7. Is provided. A buffer chamber 73 that covers the gas discharge holes 72 is formed on the surface side of the ring plate 7, and a gas introduction portion 74 is provided in the upper center of the buffer chamber 73. The gas introduction unit 74 is connected to the gas supply mechanism 45 through the supply path 44.

  FIG. 7A is a plan view seen from above the buffer chamber 73, and FIG. 7B is a plan view when the buffer chamber 73 is removed. In this example, a gas supply section is configured by the gas discharge hole 72 of the ring plate 7, the buffer chamber 73, the gas introduction section 74, the supply path 44, and the gas supply mechanism 45. Further, the ring plate 7 is supported in a horizontal posture by the support member 52 in the same manner as in the above-described embodiment, and can be moved up and down by a moving mechanism 53 connected to the support member 52.

  As described above, in the present invention, the coating film may be formed according to the profile with respect to the elapsed time of the rotation speed of the wafer W in FIG. 8 according to the viscosity and type of the coating liquid. The profile of FIG. 8A is different from the profile of FIG. 4 in that the rotational speed at the time of the liquid film forming process for supplying the coating liquid is set to a constant value and then increased to the second rotational speed. It is to carry out a reflow process. Also in this case, the second rotational speed is set to a rotational speed in the range of +50 rpm with respect to the first rotational speed at the end of supplying the coating liquid. Thus, even if the rotation speed of the liquid film forming step is set to a constant value, the coating liquid can be uniformly spread on the surface of the wafer W depending on the viscosity of the coating film and the processing time of the liquid film forming step. As shown in FIG. 8A, when there is an adjustment time for increasing from the first rotation speed to the second rotation speed between the liquid film forming process and the reflow process, the rotation speed is added to the reflow process. The gas may be supplied toward the wafer W while moving up.

  Further, the profile of FIG. 8B is different from the profile of FIG. 4 in that the second rotational speed in the reflow process is lower than the first rotational speed at the end of supplying the coating liquid in the liquid film forming process. That is. Also in this case, the second rotational speed is set to a rotational speed in a range of −50 rpm with respect to the first rotational speed. Further, when the rotational speed is accelerated in the liquid film forming step, the rotational speed of the wafer W may be accelerated gradually or in a stepwise manner. . 4 and 8B, in the liquid film forming process, the rotational speed is gradually increased from the state where the rotation of the spin chuck 11 is stopped (0 rpm). The number of rotations of the spin chuck 11 is not necessarily 0 rpm. Furthermore, since the film thickness is determined in the reflow process and the film thickness adjustment process, the fourth rotation speed of the coating film drying process only needs to be lower than the third rotation speed of the film thickness adjustment process. You may set higher than the 1st rotation speed at the time of completion | finish of supply, and the 2nd rotation speed at the time of a reflow process.

  Further, the inventors of the present invention indicate that the longer the gas supply time during the reflow process, the larger the resist film thickness obtained, and the higher the gas temperature during the reflow process, the same supply time. It is understood that the film thickness of the resulting resist film increases. For this reason, for example, the resist film thickness may be adjusted by controlling at least one of the gas supply time and the gas temperature.

  Specifically, for each type of resist liquid (coating liquid), a target film thickness of the resist film (coating film) and a gas supply time for obtaining the target film thickness are obtained in advance by experiments. . Similarly, for each type of resist solution, the target film thickness of the resist film and the gas temperature at the same supply time for obtaining this target film thickness are obtained in advance by experiments. The type of resist solution is, for example, a resist solution having the same type of resist solution and solvent and having different viscosities, and is a type of resist solution used in one coating film forming apparatus.

  The memory of the control unit 6 stores the target film thickness of the resist film and the gas supply time in association with each other, for example, for each type of resist solution, and the operator stores the type of resist solution and the target of the resist film. The program may be configured such that the gas supply time is set by selecting the film thickness. Further, for example, the resist film target film thickness and the gas temperature are stored in the memory of the control unit 6 in association with each resist liquid type, and the operator stores the resist liquid type and the resist film target film. The program may be configured to set the gas temperature by selecting the thickness.

  In the coating film forming apparatus of the present invention, the moving mechanism 53 of the ring plates 5 and 7 is configured so that the support member 52 can be moved up and down and moved in the horizontal direction. The plate 5 or 7 may be set to a position moved in the horizontal direction from a position above the peripheral edge of the wafer W, for example, a position outside the cup 2. In addition, the coating film forming apparatus of the present invention may have a configuration in which no ring plate is provided, or may have a configuration in which a heating mechanism is not provided in the gas supply mechanism and supply a gas that is not heated. Further, instead of providing a heating mechanism in the gas supply mechanism, a heating mechanism such as a heater is provided around the buffer chambers 41 and 73 of the gas nozzle 4 and the ring plate 7 and the gas introducing portions 43 and 74, and these buffer chambers 41 and 73 Alternatively, the gas may be heated by heating the gas introducing portions 43 and 74. Furthermore, in the film thickness adjusting step and the drying step, gas may be supplied to the wafer surface. However, in order to save the amount of gas, it is preferable to stop supplying gas only to the reflow step.

DESCRIPTION OF SYMBOLS 1 Coating film formation apparatus 11 Spin chuck 13 Rotation mechanism 30 Coating liquid nozzle 4 Gas nozzle 5 Ring plate 6 Control part

Claims (12)

A step of horizontally holding the substrate on a substrate holding portion that is rotatable about a vertical axis;
Next, supplying the coating liquid to the center of the substrate while rotating the substrate;
Leveling the liquid film of the coating liquid by rotating the substrate at a rotation speed in a range of ± 50 rpm with respect to the rotation speed of the substrate at the end of the supply of the coating liquid;
A step of lowering the fluidity of the coating liquid by supplying a gas to the surface of the substrate when performing the step of leveling the liquid film of the coating liquid;
Thereafter, in order to set the film thickness of the coating film to the target film thickness, the number of rotations of the substrate is higher than both the number of rotations at the end of the supply of the coating liquid and the number of rotations during the step of leveling the liquid film of the coating liquid. Maintaining the rotational speed;
And then drying the coating film by reducing the number of rotations of the substrate.   The coating film forming method according to claim 1, wherein the viscosity of the coating solution is 1000 cp or more.   The method for forming a coating film according to claim 1, wherein the step of supplying the coating liquid to the central portion of the substrate is performed while accelerating the number of rotations of the substrate.   The coating film forming method according to claim 3, wherein the rotation speed of the substrate is accelerated continuously or stepwise.   5. The coating film forming method according to claim 1, wherein the number of rotations of the substrate at the end of the supply of the coating liquid is 200 rpm to 700 rpm.   6. The coating film forming method according to claim 1, wherein the number of rotations of the substrate in the step of drying the coating film is 5 rpm to 200 rpm.   In order to set the film thickness of the coating film to the target film thickness, the number of rotations of the substrate is higher than both the number of rotations at the end of supplying the coating liquid and the number of rotations during the process of leveling the coating liquid film The method of forming a coating film according to any one of claims 1 to 6, wherein the number of rotations of the substrate in the maintaining step is 500 rpm to 1200 rpm.   In the step of drying the coating film, an annular member formed in an annular shape along the circumferential direction of the substrate is set to a position that covers the upper peripheral portion of the substrate, and the air current above the peripheral portion of the substrate is rectified by the annular member. The method for forming a coating film according to any one of claims 1 to 7, further comprising a step.   9. The coating film forming method according to claim 1, wherein the gas is a heated gas. A substrate holder for horizontally holding the substrate;
A rotation mechanism for rotating the substrate holder around a vertical axis;
A coating liquid nozzle for supplying a coating liquid for forming a coating film on the substrate;
A gas supply unit for supplying a gas for reducing the fluidity of the coating solution to the surface of the substrate;
Supplying the coating liquid to the center of the substrate while rotating the substrate, and rotating the substrate at a rotational speed in a range of ± 50 rpm with respect to the rotational speed of the substrate at the end of the supply of the coating liquid. Leveling the liquid film, reducing the fluidity of the coating liquid by supplying a gas to the surface of the substrate when performing the step of leveling the liquid film of the coating liquid, and then the film thickness of the coating film Maintaining the number of rotations of the substrate at a higher number of rotations than the number of rotations at the end of the supply of the coating liquid and the number of rotations at the step of leveling the liquid film of the coating liquid. And a controller for executing a step of drying the coating film by decelerating the number of rotations of the substrate, and a coating film forming apparatus. In the step of drying the coating film, in order to rectify the airflow above the peripheral edge of the substrate, an annular member provided annularly so as to cover the peripheral edge of the substrate and follow the circumferential direction of the substrate;
The coating film forming apparatus according to claim 10, further comprising: a moving mechanism that moves the annular member between a position that covers the periphery of the substrate and a standby position. A storage medium for storing a computer program used in a coating film forming apparatus that forms a coating film by supplying a coating liquid to a surface of a substrate held horizontally by a substrate holding unit that is rotatable around a vertical axis,
A storage medium, wherein the computer program includes a set of steps so as to execute the coating film forming method according to any one of claims 1 to 9.

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