JP2006156565A - Rotation applying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation applying method applying uniformly an application solution over the entire region that forms an application film on a substrate irrespective of the surface state of the substrate. <P>SOLUTION: In an application solution diffusion process for diffusing to the surface of the substrate the application solution supplied to the surface by rotating the substrate, the substrate is rotated at a second rotational speed V2 lower than a first rotational speed V1 after being rotated at the first rotational speed V1, and then rotated at a third rotational speed V3 higher than the second rotational speed V2. Consequently, even when there are portions on the surface of the substrate such as uneven portions or portions not adapted to the application solution where the application solution is unlikely to be applied, the application solution is applied uniformly over the entire region where formation of the application film is scheduled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spin coating method in which a coating liquid supplied to a surface portion of a substrate is applied to the surface portion of the substrate by rotating the substrate to form a coating film.

  The spin coating method is used, for example, for forming a resist film or the like on a surface portion of a wafer made of a semiconductor material or the like in a photolithography process or the like in a semiconductor device manufacturing process. FIG. 7 is a flowchart showing the procedure of a conventional spin coating method. FIG. 8 is a diagram schematically showing the relationship between the resist dropping time and the wafer rotation speed when a resist film is formed by a conventional spin coating method. FIG. 8A shows the time lapse of the rotation speed of the wafer, and FIG. 8B shows the time lapse of the resist dropping. In FIG. 8, the horizontal axis represents time. In FIG. 8A, the vertical axis indicates the rotation speed of the wafer.

  When a resist film is formed by a conventional spin coating method, the resist is dropped outwardly in the rotational radial direction by the centrifugal force generated by the rotation of the wafer by dropping the resist onto the center of the substantially circular wafer and rotating the wafer. And spread a resist film on the wafer surface. Specifically, as shown in FIGS. 7 and 8, in step s52, the dropping of the resist is started at time T1 while the wafer is stationary, and the rotation of the wafer is started at time T2. Next, in step s53, the wafer is rotated at the first rotation speed P1 for a certain time while dropping the resist. Then, in step s54, the rotation speed of the wafer is increased at time T4, and the wafer is moved to the second rotation speed P2 ( After rotating for a certain time in P2> P1), the dropping of the resist is stopped at time T6. Next, in step s55, at time T7, the rotation speed of the wafer is further increased, and the wafer is rotated at a third rotation speed P3 (P3> P2) for a predetermined time to adjust the film thickness of the resist film.

  The surface of the wafer on which the resist film is formed has uneven portions due to the electrode pattern, scribe line, etc. formed in the previous step, and the resist may not be applied partially due to the uneven portions. Also, depending on the film quality formed on the wafer surface, the resist may be repelled and not applied. For example, nitride films, SIPOS films, and the like are poor in wettability with a resist, and when these films are formed on the wafer surface, a portion where the resist is not applied to the wafer surface is likely to occur. In particular, when the diameter of the wafer becomes as large as about 12.5 cm, for example, such uneven application of resist is likely to occur. Here, SIPOS is silicon oxide represented by SiOx (x = 0.8 to 1.2).

  When uneven application of resist occurs, the resist film cannot be formed into a desired shape by exposure. For this reason, if etching is performed using the formed resist mask, the wafer cannot be etched to a desired state, and the semiconductor device does not function, resulting in characteristic defects. In order to prevent such a characteristic defect, it is necessary to remove the resist film from the wafer on which the resist application unevenness has occurred, and to form the resist film again, resulting in a problem of reduced productivity.

  Techniques for preventing uneven application of resist include dropping the resist in multiple steps, increasing the amount of resist dripping more than the amount necessary to form a resist film with a desired film thickness, etc. Has been proposed. In addition, the resist is dropped while the wafer is stationary, and the rotation of the wafer is started after the resist is naturally spread on the wafer surface without rotating the wafer, and the wafer is rotated to rotate the resist onto the wafer surface. It has also been proposed to temporarily stop the rotation of the wafer after being spread to a certain extent and then restart the rotation of the wafer by gradually increasing the rotation speed (see, for example, Patent Document 1).

JP-A-2-156626 (page 2-3, FIG. 1)

  In the method of dropping the resist divided into a plurality of times as described above, the method of increasing the amount of resist dripping more than necessary, the speed at which the resist diffuses on the wafer surface does not change, so even if these methods are used, The occurrence of uneven coating cannot be sufficiently suppressed.

  In addition, in the method in which the rotation of the wafer is started after the resist is naturally spread on the wafer surface, uneven portions and portions having poor wettability with the resist are formed on the outer side in the rotation radius direction of the wafer than the range in which the resist naturally spreads. If present, the effect cannot be obtained, and a portion where the resist is not applied is generated. Similarly, in the technique disclosed in Patent Document 1, since the resist is diffused again from the position spread by the first rotation, the uneven portion, the resist In the case where there is a film that is difficult to conform, the resist is repelled and not uniformly diffused, and a portion where the resist is not applied is generated. In particular, when the resist is dropped on the center of the wafer, the resist is less likely to be applied to the outer portion of the wafer in the radial direction of rotation than the region having a diameter of 1/2 to 2/3 of the diameter of the wafer. Even if these methods are used, the occurrence of uneven coating cannot be prevented. In addition, these methods also have a problem that the time required for resist application becomes long and productivity is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spin coating method capable of coating a coating solution such as a resist evenly over the entire region where a coating film is formed on a substrate, regardless of the surface state of the substrate such as a wafer.

The present invention is a spin coating method including a coating liquid diffusion step of diffusing a coating liquid supplied to a surface portion of a substrate on which a coating film is formed, on the surface portion by rotating the substrate,
The coating liquid diffusion process
A first rotation step of rotating the substrate at a first rotation speed V1,
A second rotation step of rotating the substrate at a second rotation speed V2 smaller than the first rotation speed V1,
And a third rotation step of rotating the substrate at a third rotation speed V3 larger than the second rotation speed V2.

Further, the present invention provides a coating solution diffusion step,
When the coating liquid is diffused to a region having a diameter of ½ to 2/3 of the diameter of the circular region on which the coating film is to be formed on the surface portion of the substrate, the second rotation is performed from the first rotation step. It is characterized by moving to a step.

In the present invention, at least one of the first rotation step, the second rotation step, and the third rotation step includes:
A coating liquid is supplied to the surface portion of the substrate in a rotating state.

  Further, the present invention is characterized in that a position where the coating liquid is supplied to the surface portion of the substrate in the first rotation step is different from a position where the coating liquid is supplied to the surface portion of the substrate in the second rotation step. To do.

In the present invention, the coating liquid diffusion step
A supply stop step for stopping the supply of the coating liquid is included between the first rotation step and the second rotation step.

In the present invention, the third rotation step further includes a pre-rotation step and a post-rotation step,
The substrate rotation speed V32 in the post-rotation step is larger than the substrate rotation speed V31 in the pre-rotation step.

  According to the present invention, when the coating liquid supplied to the surface portion of the substrate on which the coating film is formed is diffused to the surface portion, the substrate is rotated at the first rotation speed V1 and then the first rotation speed. The rotation is performed at the second rotation speed V2 smaller than V1, and then the rotation is performed at the third rotation speed V3 larger than the second rotation speed V2. By reducing the rotation speed of the substrate from the first rotation speed V1 to the second rotation speed V2, the centrifugal force due to the rotation of the substrate is reduced, and the speed at which the coating solution is diffused on the surface portion of the substrate is reduced. Since it can be made smaller than when rotating at the rotation speed V1, it is possible to increase the time during which the coating liquid stays in a part of the surface portion of the substrate, and to facilitate application. For example, the coating liquid can be applied to a portion that is difficult to be applied by reducing the rotational speed of the base when the coating liquid passes through a portion that is difficult to be applied on the surface of the substrate. Therefore, as described above, by reducing the rotational speed of the substrate once and then accelerating it, the coating liquid such as the uneven portion on the surface portion of the substrate, the wettability with the coating solution, and the portion that does not easily blend with the coating solution are removed. Even when there is a portion that is difficult to be applied, the coating liquid can be applied evenly over the entire region where the coating film is to be formed.

  Further, according to the present invention, the coating solution is at least 1/2 (1/2) or more than 2/3 (2/3) of the diameter of the circular region on which the coating film is to be formed on the surface portion of the substrate. ) When the region having the following diameter is diffused, the process proceeds from the first rotation step to the second rotation step. This makes it difficult for the coating liquid to be applied, and the diffusion rate of the coating liquid in the part exceeding the area part having a diameter of ½ to 2/3 with respect to the diameter of the circular area is determined with respect to the diameter of the circular area. It can be made smaller than the diffusion rate of the coating solution in the region having a diameter of 1/2 to 2/3. Therefore, it is possible to more reliably apply the coating liquid over the entire circular region where the coating film is to be formed on the surface portion of the base.

  According to the invention, in at least one of the first rotation step, the second rotation step, and the third rotation step, the coating liquid is supplied to the surface portion of the substrate that is rotating. As a result, since a necessary amount of coating solution can be gradually supplied to form a coating film on the surface portion of the substrate, the coating amount can be applied as compared with the case where a necessary amount of coating solution is supplied all at once. The liquid is easily applied to the surface portion of the substrate. Therefore, it is possible to prevent the occurrence of uneven coating more reliably.

  According to the invention, in the second rotation step, the coating liquid is supplied to the surface portion of the substrate at a position different from the position where the coating liquid is supplied to the surface portion of the substrate in the first rotation step. As a result, for example, in the second rotation step, the application liquid can be supplied by moving the supply position of the application liquid to a part where the application liquid is difficult to be applied. Can be prevented. Further, since the distance from the position where the coating solution is supplied to the portion of the surface portion of the substrate where the coating solution is not diffused can be shortened, the entire region where the coating film on the surface portion of the substrate is scheduled to be formed Thus, the time required for diffusing the coating solution can be reduced, and the productivity can be improved.

  Further, according to the present invention, the supply of the coating liquid is stopped before shifting from the first rotation step to the second rotation step. As a result, when the rotational speed of the substrate is reduced, the coating solution is prevented from staying in a part of the surface portion of the substrate, and more coating solution is applied to a portion of the surface portion of the substrate than the other portions. Can be prevented. Therefore, the uniformity of the coating film thickness can be improved.

  According to the invention, the third rotation step includes a pre-rotation step and a post-rotation step. In the pre-rotation step, the base is rotated at a third pre-rotation speed V31 that is greater than the second rotation speed V2, In the post-rotation step, the substrate is rotated at a third post-rotation speed V32 that is greater than the third pre-rotation speed V31. Thus, by gradually accelerating from the second rotation speed V2 to the third pre-rotation speed V31 and the third post-rotation speed V32, the speed at which the coating liquid is diffused on the surface portion of the substrate is gradually reduced. It can be accelerated. Therefore, since a rapid increase in the diffusion rate of the coating solution can be suppressed and the coating solution can be uniformly diffused to the surface portion of the substrate, the uniformity of the coating film thickness can be further improved.

  FIG. 1 is a side view showing a simplified configuration of a spin coating apparatus 1 used in the spin coating method according to the first embodiment of the present invention. The spin-coating apparatus 1 includes a holding member 12 that holds a wafer 11 as a substrate and holds it horizontally, and a motor 14 that is a rotational drive source that rotates the holding member 12 about a rotation axis 13 parallel to the vertical direction. The coating liquid supply means 15 for supplying the coating liquid to the wafer 11 held by the holding member 12 and a control means (not shown) are included.

  In the spin coating method of the present embodiment, for example, a resist is applied as a coating liquid to a surface portion on one side in the thickness direction of the wafer 11 (hereinafter simply referred to as one surface portion), and a resist film is applied as the coating film 16. Used for forming. Among them, the spin coating method according to the present embodiment is particularly preferably used when a coating solution having a viscosity of 20 to 100 Pa · s (20 Pa · s to 100 Pa · s) at 25 ° C. is applied like a resist. It is done.

  The wafer 11 is held by the holding member 12 such that the surface portion on the other side in the thickness direction (hereinafter simply referred to as the other surface portion) is in contact with the holding member 12. Wafer 11 used in the present embodiment is a circular substrate, and its diameter is, for example, 12.5 cm. The shape of the wafer 11 is not limited to this, and may be a polygonal shape such as a rectangular shape.

  The motor 14 has a rotating shaft 17, and the holding member 12 is fixed to the rotating shaft 17. The motor 14 is configured to have a variable rotation speed. A suction source 18 is connected to the holding member 12 via a conduit 19 or the like. The holding member 12 is configured such that the other surface portion of the wafer 11 placed on the surface portion of the holding member 12 opposite to the side to which the motor 14 is fixed is vacuum-sucked by the suction force of the suction source 18, thereby 11 is held.

  The coating liquid supply means 15 has an arm 20, and a coating liquid supply source 22 is connected to the arm 20 via a coating liquid supply pipe 21. A base end (not shown) of the arm 20 is provided outside the rotational movement region of the holding member 12 and the wafer 11 held by the holding member 12 so as to be angularly displaceable about a rotation axis parallel to the vertical direction. The free end portion 23 of the arm 20 is provided with a nozzle 24 that opens downward toward the holding member 12, that is, toward the paper surface of FIG. 1. An angular displacement driving means (not shown) is connected to the arm 20. The angular displacement driving means angularly drives the arm 20 over a rest position outside the rotational movement region of the wafer 11 and a supply position where the nozzle 24 exists in the vicinity of the rotation axis 13 of the holding member 12.

  Between the coating liquid supply source 22 and the arm 20, a coating liquid flow rate adjusting device (not shown) for adjusting the flow rate of the coating liquid is provided. The coating liquid flow rate adjusting device is realized by a flow rate control valve such as a variable throttle valve. As the coating liquid supplied from the coating liquid supply source 22, for example, when a resist film is formed as the coating film 16, a resist is used.

  The control means includes a timer and controls the operation of each part of the spin coater 1. Specifically, the control means performs speed control of the motor 14 that rotationally drives the holding member 12. The control unit controls the operation of the coating liquid flow rate adjusting device that adjusts the supply amount of the coating liquid to the arm 20 of the coating liquid supply unit 15. Further, the control means controls the operation of the angular displacement driving means for angularly driving the base end portion of the arm 20 of the coating liquid supply means 15. The control means is given an output of an input means (not shown) operated by an operator and an output of a speed sensor (not shown) for detecting the rotation speed of the holding member 12 by the motor 14. The control means is realized by a microcomputer or the like.

  FIG. 2 is a flowchart showing the procedure of the spin coating method of the first embodiment. The spin coating method according to the present embodiment includes a stationary coating liquid supply step (step s2) for supplying a coating liquid to the surface portion of the wafer 11 on which the coating film 16 is formed while the wafer 11 is stationary, and the wafer 11. A coating liquid diffusion step (steps s3 to s6) in which the coating liquid supplied to the surface portion on which the coating film 16 is formed is diffused to the surface portion by rotating the wafer 11.

  The coating liquid diffusion step further includes a first rotation step s3 for rotating the wafer 11 at the first rotation speed V1, and a rotation at a second rotation speed V2 (V2 <V1) smaller than the first rotation speed V1. A second rotation step s4, a third rotation step s5 for rotating the wafer 11 at a third rotation speed V3 (V3> V2) greater than the second rotation speed V2, and a wafer rotation of the wafer 11 greater than the third rotation speed V3. And a fourth rotation step s6 that rotates at a rotation speed V4 (V4> V3). In the present embodiment, in the first rotation step s3, the second rotation step s4, and the third rotation step s5, the coating liquid is supplied to the surface portion of the wafer 11 that is rotating.

  The first rotation speed V1 that is the rotation speed of the wafer 11 in the first rotation step s3 is selected to be, for example, 300 to 1000 rotations per minute (300 to 1000 rpm). The second rotation speed V2 that is the rotation speed of the wafer 11 in the second rotation step s4 is selected to be, for example, 50 to 300 rotations per minute (50 to 300 rpm). The third rotation speed V3 that is the rotation speed of the wafer 11 in the third rotation step s5 is selected, for example, to 300 to 3000 rotations per minute (300 to 3000 rpm). The fourth rotation speed V4 that is the rotation speed of the wafer 11 in the fourth rotation step s6 is selected, for example, to 2000 to 6000 rotations per minute (2000 to 6000 rpm). In particular, when the viscosity of the coating solution is 20 to 100 Pa · s at 25 ° C., it is preferable that the first to fourth rotation speeds are selected in the above ranges, respectively. However, the mutual relationship between the first to fourth rotational speeds V1 to V4 needs to satisfy the above-described magnitude relationship. In consideration of productivity, the third rotation speed V3 is preferably the same as the first rotation speed V1 or higher than the first rotation speed V1. An example of the preferred magnitude relationship of the rotational speeds is as shown in FIG.

  FIG. 3 is a diagram schematically showing the relationship between the coating liquid supply timing and the rotation speed of the wafer 11 when the coating film 16 is formed by the spin coating method of the first embodiment. 3A shows the passage of time of the rotation speed of the wafer 11, and FIG. 3B shows the passage of time of supply of the coating liquid by the coating liquid supply means 15. In FIG. 3, the horizontal axis indicates time. In FIG. 3A, the vertical axis indicates the rotation speed of the wafer 11. The time lapse of the rotation speed of the wafer 11 shown in FIG. 3A corresponds to the time lapse of the rotation speed of the holding member 12 by the motor 14. In FIG. 3A, the first rotation speed V1 is 700 rotations per minute (700 rpm), the second rotation speed V2 is 200 rotations per minute (200 rpm), the third rotation speed V3 is 1500 rotations per minute (1500 rpm), The case where the 4 rotation speed V4 is 4000 rotations per minute (4000 rpm) is shown. FIG. 3A schematically shows the relative magnitude relationship between the first to fourth rotational speeds V1 to V4 for easy understanding, although it is slightly different from the actual scale.

  With reference to FIGS. 2 and 3, the spin coating method of the present embodiment will be described more specifically. The spin coating operation according to the spin coating method of the present embodiment starts at step s1 and proceeds to step s2. In the stationary coating liquid supply step of step s2, first, the arm 20 of the coating liquid supply means 15 is angularly displaced from the rest position to the supply position by the angular displacement driving means, and the nozzle 24 is disposed on the rotation axis 13 of the holding member 12. To do. Next, as shown in FIG. 3B, at time t <b> 1, dripping of the coating liquid is started on one surface portion on which the coating film 16 of the wafer 11 held by the holding member 12 is formed. In this way, the coating solution is dropped on the central portion of the surface portion of the wafer 11 and diffused in the vicinity of the central portion. The flow rate of the coating solution is selected to be 60 mL per minute, for example.

  In the present embodiment, the dropping of the coating liquid is performed under the stationary coating liquid supply process in step s1 until a predetermined time W1 elapses from the time t1 when the dropping of the coating liquid is started until the time counted by the timer of the control unit. To s5 for the third rotation step. The time W1 is selected as 3 seconds, for example.

  Next, in the first rotation step of step s3, first, when the time measured by the timer from the time t1 at which the supply of the coating liquid is started elapses a predetermined time W2, the motor 14 rotates the holding member 12 at the time t2. Start driving. Thereby, the rotation of the wafer 11 held by the holding member 12 is started, and accordingly, the coating liquid starts to diffuse outward from the vicinity of the center of the surface of the wafer 11 in the rotational radius direction of the wafer 11. The time W2 is selected to be 0.5 seconds, for example.

  When the rotation speed of the holding member 12 increases and the rotation speed of the holding member 12 detected by a speed sensor (not shown) reaches a predetermined first rotation speed V1 at time t3, a predetermined time W3 after the time t3, The rotational speed of the holding member 12 by the motor 14 is maintained at the first rotational speed V1, and the rotational speed of the wafer 11 is maintained at the first rotational speed V1. The first rotation speed V1 is selected to be 700 rotations per minute (700 rpm), for example.

  The time W3 is selected as 1 second, for example. In the present embodiment, when the coating liquid is diffused to a region having a diameter of ½ to 2/3 of the diameter of the wafer 11, the process proceeds from the first rotation step s3 to the second rotation step s4. Thus, the time W3 is selected.

  When the time measured by the timer from time t3 has passed a predetermined time W3, in the second rotation step of the next step s4, the rotation speed of the holding member 12 by the motor 14 is decreased at time t4. As a result, the rotation speed of the wafer 11 decreases. When the rotation speed of the holding member 12 decreases and the rotation speed of the holding member 12 detected by the speed sensor reaches the predetermined second rotation speed V2 at time t5, the predetermined time W4 and the motor after the time t5. 14, the rotation speed of the holding member 12 is maintained at the second rotation speed V2, thereby maintaining the rotation speed of the wafer 11 at the second rotation speed V2. The second rotational speed V2 is selected to be 200 revolutions per minute (200 rpm), for example.

  When the time measured by the timer from time t5 has passed a predetermined time W4, in the third rotation step of the next step s5, the rotation speed of the holding member 12 by the motor 14 is increased at time t6, and the wafer 11 Increase rotation speed. When the rotation speed of the holding member 12 increases and the rotation speed of the holding member 12 detected by the speed sensor reaches a predetermined third rotation speed V3 at time t7, the time W5 and the motor determined in advance after that time t7. 14, the rotation speed of the holding member 12 is maintained at the third rotation speed V3. Thereby, the rotational speed of the wafer 11 is maintained at the third rotational speed V3. The third rotation speed V3 is selected, for example, as 1500 rotations per minute (1500 rpm).

  Further, when a predetermined time W6 elapses from the time t7 and when the predetermined time W1 elapses from the time t1 when the dropping of the coating liquid is started, the dropping of the coating liquid is stopped at the time t8. . In the present embodiment, the time W6 is shorter than the time W5 (W6 <W5), and is selected to be 0.5 seconds, for example.

  When a predetermined time W5 has elapsed from time t7, in the fourth rotation step of the next step s6, the rotation speed of the holding member 12 by the motor 14 is increased and the rotation speed of the wafer 11 is increased at time t9. When the rotational speed of the holding member 12 detected by the speed sensor reaches the predetermined fourth rotational speed V4 at time t10, the predetermined time W7 and the rotational speed of the holding member 12 by the motor 14 after the time t10 are changed to the first. The rotation speed of the wafer 11 is maintained at the fourth rotation speed V4. Thereby, the film thickness of the coating film 16 is adjusted. The fourth rotation speed V4 is selected, for example, as 4000 rotations per minute (4000 rpm).

  When a predetermined time W7 elapses from time t10, the rotation drive of the holding member 12 by the motor 14 is stopped at time t11. Accordingly, at time t12, the holding member 12 and the wafer 11 held by the holding member 12 are stopped. The time W7 is selected to be 25 seconds, for example.

  As described above, the coating liquid 16 is formed by diffusing the coating liquid on the surface portion of the wafer 11, and a series of operations is completed in step s7. When forming a film that needs to be cured after coating, such as a resist film, as the coating film 16, the wafer 11 is heated after the coating film 16 is formed, and the coating film 16 is cured.

  In the present embodiment, in the coating liquid diffusion process of steps s3 to s6, the rotation speed of the wafer 11 is changed from the first rotation speed V1 to the second rotation speed V2 (V2 <V1) smaller than the first rotation speed V1. After the decrease, the rotation speed is increased to a third rotation speed V3 (V3> V2) larger than the second rotation speed V2. By reducing the rotation speed of the wafer 11 from the first rotation speed V1 to the second rotation speed V2, the centrifugal force due to the rotation of the wafer 11 is reduced, and the speed at which the coating liquid is diffused on the surface portion of the wafer 11 is reduced. Therefore, it is possible to increase the time during which the coating liquid stays in a part of the surface portion of the wafer 11. As a result, even if the coating solution is a portion where the wafer 11 is difficult to be coated, such as a concavo-convex portion or a portion where a film having poor wettability with the coating solution is formed, the coating solution gets over the portion without being repelled. It can diffuse outward in the rotational radius direction. Therefore, in the present embodiment, even when the surface portion of the wafer 11 has a concavo-convex portion, poor wettability with the coating liquid, and there is a portion that is not easily compatible with the coating liquid, the coating liquid is applied over the entire surface portion of the wafer 11. Can be applied evenly.

  In particular, in the present embodiment, when the coating liquid is diffused to a region having a diameter of ½ to 2/3 of the diameter of the wafer 11, the first rotation step s3 to the second rotation step s4. Transition. As a result, when the coating solution is difficult to be applied and passes through a portion of the wafer 11 that is closer to the outer side in the radial direction of rotation than the region having a diameter of 1/2 to 2/3 of the diameter of the wafer 11 The diffusion rate of the liquid is reduced, and the coating liquid can be applied to this portion.

  In the first rotation step s 3, the second rotation step s 4 and the third rotation step s 5, the wafer 11 is rotated and the coating liquid is supplied to the surface portion of the wafer 11. As a result, an amount of coating solution necessary for forming the coating film 16 on the surface portion of the wafer 11 can be gradually supplied. For this reason, compared with the case where the coating liquid is diffused by rotating the wafer 11 after supplying the entire amount of the coating liquid necessary for the stationary coating liquid supply process in step s 1, the coating liquid is produced by the rotation of the wafer 11. It becomes susceptible to centrifugal force. Therefore, the effect of changing the rotation speed of the wafer 11 as described above is effectively exhibited, and the coating liquid is easily applied to the surface portion of the wafer 11, so that the occurrence of uneven coating can be more reliably prevented. Can do.

  Further, in order to more effectively exert the effect of changing the rotation speed of the wafer 11 as described above, the second rotation speed V2 is 30% to 50% (0 of the first rotation speed V1). .3V1 ≦ V2 ≦ 0.5V1). Moreover, when decelerating from the 1st rotation speed V1 to the 2nd rotation speed V2, it is preferable to decelerate at a stretch. Specifically, the falling time, which is the time required to reduce the rotation speed of the wafer 11 from the first rotation speed V1 to the second rotation speed V2, that is, the time from time t4 to t5 shown in FIG. It is preferable to reduce the time from 0.1 to 0.5 seconds and to switch from the first rotation speed V1 to the second rotation speed V2 in a short time. Similarly, when accelerating from the second rotational speed V2 to the third rotational speed V3, it is preferable to accelerate at once. Specifically, the rotational speed of the wafer 11 is changed from the second rotational speed V2 to the third rotational speed V3. The start-up time, which is the time required for acceleration, that is, the time from time t6 to t7 shown in FIG. 3, is reduced to, for example, 0.1 to 0.5 seconds, and the second rotation speed V2 to the third time are reduced in a short time. It is preferable to switch to the rotation speed V3.

  Moreover, it is preferable to change the 2nd rotational speed V2 according to the viscosity of a coating liquid. Specifically, it is preferable to rotate the wafer 11 faster by increasing the second rotation speed V2 as the viscosity of the coating liquid increases, and by decreasing the second rotation speed V2 as the viscosity of the coating liquid decreases. It is preferable to rotate 11 slowly.

  As described above, in the present embodiment, the coating film 16 is formed on one entire surface portion of the wafer 11, but it is also possible to partially form the coating film 16 on one surface portion of the wafer 11. . For example, the coating film 16 may be formed only on a portion excluding the vicinity of the outer edge portion of the wafer 11. In this case, when the coating liquid is diffused to a region having a diameter of 1/2 to 2/3 of the diameter of the circular region on which the coating film 16 is to be formed on the surface portion of the wafer 11, It is preferable to shift from the first rotation step to the second rotation step. As a result, the same effect as in the present embodiment can be obtained.

  In the case where there is a portion where the coating liquid is difficult to be applied, such as a concavo-convex portion or a portion having poor wettability with the coating solution, in a region having a diameter of 1/2 to 2/3 of the diameter of the wafer 11, Even in the vicinity thereof, it is preferable to provide steps similar to the second rotation step of step s4 and the third rotation step of step s5 so that the rotation speed of the wafer 11 is once decelerated and then accelerated.

  FIG. 4 is a flowchart showing the procedure of the spin coating method according to the second embodiment of the present invention. The spin coating method according to the present embodiment includes a stationary coating liquid supply process (step s12) and a coating liquid diffusion process (steps s13 to s17), similarly to the spin coating method according to the first embodiment described above. . In the spin coating method according to the present embodiment, it should be noted that the coating liquid diffusion step includes a supply stop step s14 that stops the supply of the coating liquid between the first rotation step s13 and the second rotation step s15. That is.

  FIG. 5 is a diagram schematically showing the relationship between the coating liquid supply timing and the rotation speed of the wafer 11 when the coating film 16 is formed by the spin coating method of the second embodiment. FIG. 5A shows the passage of time of the rotation speed of the wafer 11, and FIG. 5B shows the passage of time for supplying the coating liquid by the coating liquid supply means 15. In FIG. 5 (a), as in FIG. 3 (a), although the actual scale is slightly different, the relative magnitudes of the first to fourth rotational speeds V1 to V4 are easy to understand. The relationship is shown schematically. In the present embodiment, each part of the spin coater 1 is driven in the same manner as in the first embodiment except for the coating liquid supply means 15. For example, the holding member 12 is rotationally driven in the same manner as in the first embodiment, and the rotation speed of the wafer 11 changes in the same manner as in the first embodiment.

  The spin coating operation according to the spin coating method of the present embodiment is started in step s11 and proceeds to step s12. In the stationary coating liquid supply process in step s12, the dropping of the coating liquid is started at time t1, as in the first embodiment. In the present embodiment, the application liquid is dropped from the time t1 when the application liquid starts to be dropped to the time t4 when the predetermined time W11 elapses, and after the time t5 when the drop of the application liquid is resumed after the predetermined time W13. The process is performed intermittently with a predetermined time W12 until the time t8 passes. The time W11 is selected to be 1.5 seconds, for example. The time W13 is selected to be 1.5 seconds, for example. In the present embodiment, the time W11 and the time W13 are the sum of the time W11 for supplying the coating liquid and the time W13 (W11 + W13) being substantially the coating liquid supply time W1 in the first embodiment. Selected to be equal.

  In the first rotation step of step s13, the rotation drive of the holding member 12 by the motor 14 is started at time t2 after the time W2 has elapsed from time t1 when supply of the coating liquid was started, as in the first embodiment. Thereby, the rotation of the wafer 11 is started. The holding member 12 and the rotation speed of the wafer 11 held by the holding member 12 are maintained at the first rotation speed V1 from time t3 when the rotation speed of the holding member 12 reaches the predetermined first rotation speed V1 until time W3. .

  Next, in the supply stop step of step s14, at time t4 after time W3 has elapsed from time t3, the dropping of the coating liquid by the coating liquid supply means 15 is stopped, and the rotation speed of the holding member 12 by the motor 14 is decreased, The rotational speed of the wafer 11 is decreased. Next, the arm 20 of the coating liquid supply means 15 is angularly displaced from the supply position by the angular displacement driving means, and the nozzle 24 is rotated from the central portion at the surface portion of the wafer 11 from the rotation axis 13 of the holding member 12. It is moved to the outer side in the radial direction in the vicinity of a portion that is 1/2 to 2/3 away from the radius of the wafer 11.

  When the rotation speed of the holding member 12 reaches the predetermined second rotation speed V2 at the time t5 after the lapse of the time W12 from the time t4 when the supply of the coating liquid is stopped and the rotation speed of the holding member 12 is started to decrease. In the second rotation step of step s15, as in the first embodiment, after the time t5, a predetermined time W4 and the rotation speed of the holding member 12 by the motor 14 are maintained at the second rotation speed V2. Further, at the time t5, the dropping of the coating liquid by the coating liquid supply means 15 is resumed.

  When a predetermined time W4 has elapsed from time t5, the process proceeds to the third rotation step of the next step s16, and at time t6, the rotation speed of the holding member 12 by the motor 14 is increased, as in the first embodiment. After time t7 when the rotation speed of the holding member 12 reaches the predetermined third rotation speed V3, the rotation speed of the holding member 12 by the motor 14 is maintained at the third rotation speed V3 for a predetermined time W5.

  Further, when a predetermined time W14 elapses from the time t7 and when the above-described predetermined time W13 elapses from the time t5 when the dropping of the coating liquid is resumed, the dropping of the coating liquid is stopped at the time t18. . In the present embodiment, the time W14 is shorter than the time W5 (W14 <W5), and is selected to be 0.5 seconds, for example.

  Since the fourth rotation step of the next step s17 is the same as that of the first embodiment, the description thereof is omitted.

  As described above, in this embodiment, before the transition from the first rotation step of step s13 to the second rotation step of step s15, the supply of the coating liquid is stopped in the supply stop step of step s14. As a result, the rotation speed of the wafer 11 decreases, and the coating liquid stays in a part of the surface portion of the wafer 11 without being sufficiently diffused between time t4 and time t5 when the diffusion speed of the coating liquid decreases. Can be prevented. Accordingly, it is possible to prevent a part of the surface portion of the wafer 11 from being applied with a larger amount of coating liquid than the other parts, so that the coating film 16 having a uniform thickness can be formed.

  In particular, in the present embodiment, after the supply of the coating liquid is stopped, the supply position of the coating liquid is set in the vicinity of the outer edge of the region portion having a diameter of 1/2 to 2/3 with respect to the diameter of the wafer 11. Since the coating liquid is moved, the coating liquid is reliably applied to a portion of the wafer 11 that is closer to the outer side in the radial direction than a region having a diameter of ½ to 2/3 with respect to the diameter of the wafer 11. be able to. Therefore, the coating liquid can be more reliably applied over the entire surface portion of the wafer 11. Further, since the distance from the position where the coating solution is supplied to the portion where the coating solution is not diffused can be shortened in the surface portion of the wafer 11, in order to diffuse the coating solution over the entire surface portion of the wafer 11. It is possible to reduce the time required and improve productivity.

  The supply position of the coating liquid is preferably changed as appropriate according to the state of the surface portion of the wafer 11 on which the coating film 16 is formed. For example, if there is a portion where the coating liquid is difficult to be applied, such as an uneven portion or a portion having poor wettability with the coating solution, in a region having a diameter of 1/2 to 2/3 of the diameter of the wafer 11 It is preferable to supply the coating liquid by moving the position of the nozzle 24 so as to supply the coating liquid to the portion. As a result, the coating liquid can be directly supplied to the portion where the coating liquid is difficult to be applied, and thus the occurrence of uneven coating can be further suppressed.

  In the spin coating methods of the first embodiment and the second embodiment described above, the third rotation step is one rotation step. However, the third rotation step is not limited to this, and the third rotation step is the third higher than the second rotation speed V2. It may be divided into two rotation steps: a pre-rotation step for rotating at the pre-rotation speed V31 and a post-rotation step for rotating the wafer 11 at a third post-rotation speed V32 that is higher than the third pre-rotation speed V31.

  The third pre-rotation speed V31 that is the rotation speed of the wafer 11 in the third pre-rotation step is selected to be, for example, 300 to 1500 revolutions per minute (300 to 1500 rpm). The third post-rotation speed V32 that is the rotation speed of the wafer 11 in the third post-rotation step is selected to be, for example, 1500 to 3000 revolutions per minute (1500 to 3000 rpm). In particular, when the viscosity of the coating liquid is 20 to 100 Pa · s at 25 ° C., it is preferable that the third pre-rotation speed V31 and the third post-rotation speed V32 are selected in the above ranges, respectively. However, it is necessary to satisfy the relationship that the third pre-rotation speed V31 and the third post-rotation speed V32 are both larger than the second rotation speed V2 and smaller than the fourth rotation speed V4. An example of the preferred magnitude relationship of the rotational speeds is as shown in FIG.

  FIG. 6 shows the coating liquid supply timing and the rotation speed of the wafer 11 when the rotation speed of the wafer 11 according to the third embodiment of the present invention is increased from the second rotation speed V2 to the fourth rotation speed V4 in two stages. It is a figure which shows typically the relationship. 6A shows the passage of time of the rotation speed of the wafer 11, and FIG. 6B shows the passage of time for supplying the coating liquid by the coating liquid supply means 15. FIG. FIG. 6 shows a case where the coating liquid is continuously supplied from time t1 to time t8, as in the first embodiment. In FIG. 6A, the first rotation speed V1 is 700 rotations per minute (700 rpm), the second rotation speed V2 is 200 rotations per minute (200 rpm), and the third previous rotation speed V31 is 1000 rotations per minute (1000 rpm). ), The third post-rotation speed V32 is 2500 revolutions per minute (2500 rpm), and the fourth revolution speed V4 is 4000 revolutions per minute (4000 rpm). In FIG. 6 (a), as in FIG. 3 (a), although the actual scale is slightly different, the relative magnitudes of the first to fourth rotational speeds V1 to V4 are easy to understand. The relationship is shown schematically.

  When the third rotation step includes a pre-rotation step and a post-rotation step, the steps up to the second rotation step of step s4 are performed in the same manner as in the first embodiment. Next, in the pre-rotation step, at the time t6 when the first embodiment shifts to the third rotation step, that is, at the time t6 when the time W4 has elapsed from the time t5 when the rotation speed of the holding member 12 reaches the second rotation speed V2. Then, the rotation speed of the holding member 12 by the motor 14 is increased, and the rotation speed of the wafer 11 is increased. Also in the present embodiment, when accelerating from the second rotational speed V2 to the third previous rotational speed V31, as in the first embodiment, acceleration is performed at once, that is, from the second rotational speed V2 to the second rotational speed in a short time. 3 It is preferable to switch to the pre-rotation speed V31.

  When the rotation speed of the holding member 12 reaches a predetermined third pre-rotation speed V31 at time t7, after that time t7, the predetermined time W21, the rotation speed of the holding member 12 by the motor 14 is changed to the third pre-rotation speed V31. To maintain. Thereby, the rotation speed of the wafer 11 is maintained at the third previous rotation speed V31. The third pre-rotation speed V31 is selected, for example, as 1000 rotations per minute (1000 rpm).

  Next, when a predetermined time W21 elapses from the time t7 and when a predetermined time W1 elapses from the time t1 when the application liquid starts to be dropped, the process proceeds to a post-rotation step, and at the time t8, the motor 14 The rotation speed of the holding member 12 is further increased, and the dropping of the coating liquid is stopped. In the present embodiment, the time W21 is selected to be 0.5 seconds, for example, so as to shift to the post-rotation step at time t8 when the dropping of the coating liquid is stopped in the first embodiment.

  When the rotation speed of the holding member 12 reaches the predetermined third post-rotation speed V32 at time t20, the predetermined time W22 and the rotation speed of the holding member 12 by the motor 14 after the time t20 are set to the third post-rotation speed V32. To maintain. As a result, the rotation speed of the wafer 11 is maintained at the third post-rotation speed V32. The third post-rotation speed V32 is selected to be 2500 rotations per minute (2500 rpm), for example.

  When a predetermined time W22 elapses from time t20, the process proceeds to the next fourth rotation step, and the rotation speed of the holding member 12 by the motor 14 is further increased at time t9, as in the first embodiment. In the present embodiment, the time W22 is selected, for example, as 1 second so as to shift to the fourth rotation step at time t9, as in the first embodiment. That is, also in the present embodiment, the third rotation step including the pre-rotation step and the post-rotation step starts at time t6 and ends at time t9, similarly to the third rotation step of the first embodiment. . Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  As described above, in the present embodiment, the rotation speed of the wafer 11 is accelerated stepwise from the second rotation speed V2 to the third front rotation speed V31 and the third rear rotation speed V32 in this order. The acceleration of the rotation of the wafer 11 can be reduced as compared with the case where acceleration is performed in one step from V2 to the third rotation speed V3. For example, as in the present embodiment, the rotation of the wafer 11 is performed by performing the third rotation step in two steps of a pre-rotation step and a post-rotation step without changing the time required for the third rotation step. , That is, the slope of the straight line shown in FIG. Further, as described above, when switching from the second rotational speed V2 to the third previous rotational speed V31 is performed in a short time, it is possible to prevent the acceleration from becoming too large. Accordingly, the speed at which the coating liquid is diffused on the surface portion of the wafer 11 can be gradually accelerated, so that a rapid increase in the diffusion speed of the coating liquid is suppressed and the coating liquid is uniformly distributed on the surface portion of the wafer 11. Can diffuse. Therefore, the uniformity of the thickness of the coating film can be further improved.

  In the first to third embodiments described above, the coating film 16 is formed in the same time from time t1 to time t12. However, the start time of each step, the supply timing of the coating liquid, and the like are as follows. Depending on the surface condition of the wafer 11, etc., it can be selected as appropriate.

It is a side view which simplifies and shows the structure of the spin coater 1 used for the spin coat method which is the 1st Embodiment of this invention. It is a flowchart which shows the procedure of the spin coating method of 1st Embodiment. It is a figure which shows typically the relationship between the supply time of the coating liquid at the time of forming the coating film 16 with the spin coating method of 1st Embodiment, and the rotational speed of the wafer. It is a flowchart which shows the procedure of the spin coating method which is the 2nd Embodiment of this invention. It is a figure which shows typically the relationship between the supply time of the coating liquid at the time of forming the coating film 16 with the spin coating method of 2nd Embodiment, and the rotational speed of the wafer. It is a figure which shows typically the relationship between the supply time of the coating liquid at the time of forming the coating film 16 with the spin coating method of 3rd Embodiment, and the rotational speed of the wafer 11. FIG. It is a flowchart which shows the procedure of the conventional spin coating method. It is a figure which shows typically the relationship between the dripping timing of a resist at the time of forming a resist film with the conventional spin coating method, and the rotational speed of a wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation coating apparatus 11 Wafer 12 Holding member 13 Rotating axis 14 Motor 15 Coating film supply means 16 Coating film 17 Rotating shaft 18 Suction source

Claims (6)

A spin coating method comprising a coating liquid diffusion step of diffusing a coating liquid supplied to a surface portion of a substrate on which a coating film is formed on the surface portion by rotating the substrate,
The coating liquid diffusion process
A first rotation step of rotating the substrate at a first rotation speed V1,
A second rotation step of rotating the substrate at a second rotation speed V2 smaller than the first rotation speed V1,
And a third rotation step of rotating the substrate at a third rotation speed V3 larger than the second rotation speed V2. In the coating liquid diffusion process,
When the coating liquid is diffused to a region having a diameter of ½ to 2/3 of the diameter of the circular region on which the coating film is to be formed on the surface portion of the substrate, the second rotation is performed from the first rotation step. 2. The spin coating method according to claim 1, wherein the method is shifted to a step. In at least one of the first rotation step, the second rotation step, and the third rotation step,
3. The spin coating method according to claim 1, wherein a coating liquid is supplied to the surface portion of the substrate in a rotating state.   4. The position at which the coating liquid is supplied to the surface portion of the substrate in the first rotation step is different from the position at which the coating liquid is supplied to the surface portion of the substrate in the second rotation step. Spin coating method. The coating liquid diffusion process
5. The spin coating method according to claim 3, further comprising a supply stop step of stopping the supply of the coating liquid between the first rotation step and the second rotation step. The third rotation step further includes a pre-rotation step and a post-rotation step,
6. The spin coating method according to claim 1, wherein the rotation speed V32 of the substrate in the post-rotation step is larger than the rotation speed V31 of the substrate in the pre-rotation step.

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