JP2002307007A - Rotating coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotating coating method for efficiently applying a coating liquid onto a wide area of a substrate at a uniform thickness. SOLUTION: The coating liquid is delivered to an approximate center of the surface of the substrate under a first delivery pressure, and after the coating liquid is delivered under the first delivery pressure for a predetermined time, the coating liquid is delivered under a second delivery pressure higher than the first delivery pressure within one minute or less and the delivery is completed within two minutes or less after the delivery is started under the second delivery pressure. Thereafter, the substrate is rotated at a high speed to apply the coating liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate, such as a semiconductor wafer, a glass substrate for a liquid crystal display panel, or a mask substrate for manufacturing a semiconductor (hereinafter simply referred to as a "substrate"), which is rotated while being horizontally supported. The present invention relates to a spin coating method for coating a coating liquid such as a photoresist liquid on a surface of a substrate.

[0002]

2. Description of the Related Art In a conventional spin coating method, a substrate is fixed on a spin chuck, and after a coating solution such as a resist solution is supplied to the surface of the spin plate, or while the spin plate is mounted while the spin solution is being supplied, the spin chuck is rotated. Is rotated to spread the coating liquid on the substrate surface and apply the coating liquid. This conventional spin coating method,
This will be described with reference to the drawings.

FIG. 4 is a view schematically showing the application of a coating solution to a substrate by a conventional spin coating method. In FIG. 4, reference numeral 1 denotes a substrate, 2 denotes a coating liquid, 3 denotes a nozzle, 4 denotes a rotary chuck, 5 denotes a coating film after completion of discharge, and 6 denotes a coating film after high-speed rotation coating.

First, a coating liquid 2 is discharged from a nozzle 3 onto the surface of a substrate 1 fixed on a rotary chuck 4 and stopped or rotating at a low speed (a). During the discharge, a discharge pressure is applied to the coating liquid 2, and the discharged coating liquid 2 spreads in a substantially circular shape on the surface of the substrate 1 (b). When the ejection is completed, the supply of the coating liquid 2 is stopped, so that when the viscosity of the coating liquid 2 is balanced, the spreading of the coating liquid 2 is stopped and the coating film 5 is formed (c). Next, the rotating chuck 4 is rotated at a high speed, and the excess coating liquid 2 is dispersed to form a coating film 6 having a predetermined thickness (d).

[0005]

However, in the conventional spin coating method, the discharge pressure applied to the coating liquid 2 disappears at the end of the discharge, so that the coating liquid 2 supplied at the end of the discharge stays in the center of the substrate 1. However, the coating film 5 after the end of the discharge becomes thick at the center. Even when the excess coating liquid 2 on the surface of the substrate 1 is separated by the high-speed rotation of the rotary chuck 4,
Since the peripheral speed is high, the coating liquid 2 is sufficiently dispersed by the action of a large centrifugal force, and the coating film becomes thin. But,
The central portion of the substrate 1 has a low peripheral speed and a small centrifugal force, so that the coating liquid 2 is less dispersed, and the coating film remains thick even after high-speed spin coating. In other words, the conventional spin coating method has a problem that the coating film is thick at the center of the substrate and thin at the periphery of the substrate, so that a coating film having a uniform thickness cannot be formed over the entire surface of the substrate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide a spin coating method for efficiently applying a coating liquid to a large area of a substrate to a uniform thickness. And

[0007]

According to a first spin coating method according to the present invention, a coating liquid is applied under pressure to a substantially center of the surface of a substrate and discharged, and the coating liquid is coated by rotating the substrate. In the spin coating method, after the coating liquid is discharged at a first discharge pressure, the coating liquid is discharged within one second at a second discharge pressure higher than the first discharge pressure, and the discharge is performed at a second discharge pressure. That is, the ejection is completed within 2 seconds after the start.

[0008] A second spin coating method according to the present invention is that in the first spin coating method of the present invention, the second discharge pressure is 1.3 to 3 times the first discharge pressure.

A third spin coating method according to the present invention is the spin coating method of rotating a substrate, applying and discharging a coating liquid toward a substantially center of the surface of the substrate, and applying the coating liquid. Discharging of the coating liquid is interrupted, and then the coating liquid is re-discharged within 2 seconds, and the discharge is terminated.

In a fourth spin coating method according to the present invention, in the third spin coating method of the present invention, the application liquid is interrupted and re-ejected a plurality of times.

[0011] A fifth spin coating method according to the present invention is that in the third or fourth spin coating method of the present invention, the time during which the discharge of the coating liquid is interrupted is set within 2 seconds.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a schematic diagram of a spin coating apparatus used in the spin coating method according to the first embodiment. In FIG. 1, 1 is a substrate, 3 is a nozzle, 4 is a rotary chuck, 7 is a liquid dripping prevention valve, 8 is a syringe, 9 is a connector tube, and 10 is a discharge control device. As shown in FIG. 1, the nozzle 3 is connected to a syringe 8 filled with the coating liquid 2 via a liquid dripping prevention valve 7, and the syringe 8 is connected to a discharge control device 10 via a connector tube 9.
It is connected to the. The discharge control device 10 includes a syringe 8
The pressure applied to the coating liquid 2 and the time during which the coating liquid 2 is discharged can be controlled, and the discharge amount of the coating liquid 2 can be controlled.

FIG. 2 is a diagram schematically showing the application of the coating liquid to the substrate in the spin coating method according to the first embodiment.
First, the ejection control device 10 controls the application liquid 2 in the syringe 8.
, A first discharge pressure equal to or higher than the spring pressure of the liquid dripping prevention valve 7 is applied. At this time, since the syringe 8 is connected to the nozzle 3 via the liquid dripping prevention valve 7, the coating liquid 2 is placed and fixed on the rotary chuck 4 from the nozzle 3 disposed substantially above the center of the substrate 1. It is discharged onto the surface of the substrate 1 (a). next,
When the pressure is applied to the liquid dripping prevention valve 7 and the valve is opened once, the valve remains open while the pressure is applied, so that the first discharge pressure is applied by the discharge control device 10 to the coating liquid in the syringe 8. 2 continuously, the coating liquid 2 is discharged from the nozzle 3 onto the surface of the substrate 1 at a constant speed. The discharged coating liquid 2 spreads substantially circularly on the substrate 1 by the action of its own weight and the discharge pressure. At this time, the rotary chuck 4 may be stopped or rotating at a low speed of, for example, 100 to 300 rpm (b).

Next, the coating liquid 2 is discharged within one second by setting the discharge pressure to a second discharge pressure 1.3 to 3 times the first discharge pressure (c). Within 2 seconds after the start of the discharge at the preset second discharge pressure, the coating liquid 2 in the syringe 8
Is stopped, and the ejection is terminated (d). That is,
After the ejection by the second ejection pressure for one second or less, the ejection may be terminated immediately or the pressure may be returned to the first ejection pressure.
The discharge time at the first discharge pressure, the discharge time at the second discharge pressure, the first discharge pressure, and the second discharge pressure are set in advance by the discharge control device 10. Next, the rotating chuck 4 is rotated at a high speed of, for example, 1500 to 6000 rpm, and the excess coating liquid 2 on the surface of the substrate 1 is dispersed to form a coating film 6 having a predetermined thickness (e).

Next, a mechanism for forming a uniform coating film on the substrate 1 in the spin coating method of the present embodiment will be described.
Before the end of the discharge, the discharge pressure is raised to the second discharge pressure, and the coating liquid 2 is discharged to the central portion of the substrate 1 at a large discharge pressure. Therefore, as shown in FIG. The coating liquid 2 in the central part is temporarily pushed to the periphery, and the coating liquid 2 is prevented from accumulating in the central part. That is, as shown in FIG. 2D, the center of the coating film 5 is thinner than the peripheral portion. By stopping the discharge within 2 seconds after the start of the discharge at the second discharge pressure, the substrate 1 is rotated at a high speed by the rotary chuck 4 before the coating liquid pushed to the periphery returns to the center of the substrate by the action of gravity. Rotated. Therefore, the rotating chuck 4
Is rotated at a high speed, and the excess coating liquid 2 on the surface of the substrate 1 is dispersed. Since the central portion of the film is thinner than the outside, the film thickness of the coating film 6 after the high-speed spin coating becomes uniform as shown in FIG.

In the present embodiment, when the rotating chuck 4 is rotated at a low speed (for example, 100 to 300 rpm) at the time of discharge, the spread of the coating liquid 2 on the surface of the substrate 1 is increased, and the coating process can be shortened. . The spin coating method of the present embodiment is more effective than the conventional spin coating method in that the coating liquid 2 that easily accumulates at the center of the substrate uniformly applies the high-viscosity coating liquid 2 having a viscosity of 500 mPa · s or more. It is.

In the spin coating method of the present embodiment,
Since the discharge time at the second discharge pressure is within 1 second, the time when the discharge amount of the coating liquid 2 is large is short, the coating liquid 2 is not discharged more than necessary, and the coating film is used because a large amount of the coating liquid is used. An increase in formation cost can be prevented.

In the spin coating method of the present embodiment, the second discharge pressure is set to 1.3 to 3 times the first discharge pressure.
When the second discharge pressure is less than 1.3 times the first discharge pressure, when the viscosity of the coating liquid 2 is high, the discharge of the coating liquid 2 pushes the coating liquid 2 at the center of the substrate 1 to the periphery. Less,
In some cases, the accumulation of the coating liquid 2 at the center is not prevented. If the second discharge pressure is at least three times the first discharge pressure, the coating liquid 2 is scattered at the tip of the nozzle 3 during discharge, and the coating liquid 2 cannot be discharged properly without uneven coating.

In the spin coating method of the present embodiment, no special mechanism or the installation of a plurality of nozzles is required, and the coating liquid can be applied to the substrate with a uniform thickness by a conventional spin coating apparatus.
Equipment cost can be reduced.

Embodiment 2 The spin coating method according to the second embodiment of the present invention uses the spin coating apparatus shown in FIG.
A pressure equal to or higher than the spring pressure of the liquid dripping prevention valve 7 is applied to the coating liquid 2 to start discharging the coating liquid 2 onto the surface of the substrate 1. After a predetermined discharge time set in advance, the pressure applied to the application liquid 2 is eliminated, and the discharge is interrupted. After a certain period of time, the same pressure as at the start of the discharge is applied to restart the discharge, and the re-discharge of the coating liquid 2 is completed within 2 seconds after the restart of the discharge. Immediately after the re-discharge of the coating liquid 2 is completed, the rotating chuck 4 is rotated at a high speed (for example, 1500 to 60).
(00 rpm), and the excess coating solution 2 is dispersed to form a coating film 6 having a predetermined thickness.

Next, a mechanism for forming a uniform coating film on the substrate 1 in the spin coating method of the present embodiment will be described.
FIG. 3 is a diagram illustrating a change over time of the discharge speed of the coating liquid 2 in the spin coating method according to the second embodiment. First, at the start of discharge, a pressure equal to or higher than the spring pressure of the liquid dripping prevention valve 7 is applied to the coating liquid 2.
(A). At this time, the coating liquid 2 trapped in the syringe 8 is released from the pressure and flows out of the nozzle 3, so that the discharge speed temporarily increases. Thereafter, the discharge of the coating liquid 2 is continued at a constant discharge speed (b) determined by the discharge pressure, the viscosity of the coating liquid 2, and the shape of the nozzle 3. When the discharge of the coating liquid 2 is interrupted (C) after a predetermined time, the discharge speed of the coating liquid 2 becomes zero. At the start of re-discharge,
Since the discharge speed of the coating liquid 2 is temporarily increased as in the start of the discharge (d), the discharged coating liquid 2
A large force temporarily acts on the center of the. Thereafter, the coating liquid 2 is discharged at a constant discharge speed (e) before the discharge is interrupted,
Finally, the pressure applied to the coating liquid 2 becomes 0, and the discharge ends (f).

That is, immediately after the discharge is resumed, a large force is temporarily applied to the central portion of the substrate 1 by the coating liquid 2 discharged at a high discharge speed, and the coating liquid 2 accumulated in the central portion of the substrate 1 is removed. As a result, the coating film in the center of the substrate 1 becomes thinner than the coating film in the peripheral portion. Then, in order to finish the discharge within 2 seconds after the discharge is resumed, the substrate 1 is rotated by the rotary chuck 4 at a high speed (for example, 1500 to 6000 rp) before the coating solution pushed to the periphery returns to the center of the substrate by the action of gravity.
m) can be rotated. Therefore, when the excess coating liquid is dispersed, the thickness of the applied coating film is uniform even if the dispersion of the coating liquid in the peripheral portion of the substrate having a high peripheral speed is larger than that in the central portion.

In the spin coating method of the present embodiment, since the time for interrupting the ejection is within 2 seconds, the solvent contained in the coating liquid 2 applied to the substrate 1 during the interruption time hardly volatilizes, and 2 can be suppressed, and even when a high-viscosity coating liquid is applied, the coating liquid is less likely to be separated during high-speed rotation, and the coating film can be prevented from becoming uneven.

Embodiment 3 FIG. The coating liquid is spin-coated on the surface of the substrate to form a coating film 6 having a predetermined thickness in the same manner as in the second embodiment, except that the interruption and the re-discharge of the coating liquid 2 are repeated a plurality of times.

[0025]

Next, the present invention will be described in more detail by way of examples.

Embodiment 1 FIG. The viscosity as the coating liquid 2 is 190
A 100 cc syringe 8 is filled with a silicone ladder polymer dissolved in 0 mPa · s anisole. The nozzle 3 having an inner diameter of 1.99 mm is connected to the syringe 8 via a liquid dripping prevention valve 7 having a spring pressure of 9.8 kPa. The discharge control device 10 applies a first discharge pressure (P1) of 30 kPa to the coating liquid 2 in the syringe, places the coating liquid 2 from the nozzle 3 on the rotary chuck 4, is fixed, and rotates at 200 rpm. Discharge is started on the surface of a 5-inch silicon wafer that is the substrate 1. Eight seconds after the start of discharge, the discharge pressure is 39 kP
After the application liquid 2 is discharged for 1 second while switching to the second discharge pressure (P2) in a, the discharge is terminated. The first discharge pressure (P
1), the second discharge pressure (P2), the discharge time at the first discharge pressure (T1), and the discharge time at the second discharge pressure (T
2) The time (T3) from the start of discharge at the second discharge pressure to the end of discharge is predetermined by the discharge control device.

After the end of the discharge, the rotating chuck 4 is moved
Rotating at 00 rpm, the excess coating solution is dispersed to form a coating film having an average thickness of about 6 μm. From the following equation (1), the in-plane distribution (D) of the film thickness of the coating film was determined and is shown in Table 1. D = (maximum thickness−minimum thickness) / (maximum thickness + minimum thickness) × 100 (%) (1)

Embodiment 2 FIG. ~ 4. Table 1 shows the time (T2) of discharge at the second discharge pressure, the time (T3) from the start of discharge at the second discharge pressure to the end of discharge, and the second discharge pressure (P2) shown in Table 1. A coating film was formed on the surface of a silicon wafer as a substrate by the same spin coating method as in Example 1 except for using, and the in-plane distribution (D) of the coating film formed from the formula (1) was obtained. It was shown to.

Comparative Example 1 A coating liquid was applied to a silicon wafer in the same manner as in Example 1 except that the coating liquid 2 was discharged at a first discharging pressure (P1) of 30 kPa without switching the discharging pressure from the first discharging pressure to the second discharging pressure. It was applied to the surface to form a coating film, and the in-plane distribution (D) of the coating film formed from the formula (1) was determined and is shown in Table 1.

Comparative Example 2 ~ 4. As shown in Table 1, the second
The time (T3) from the start of discharge at the discharge pressure to the end of discharge is 3 seconds, and the second discharge pressure (P2) is 36 kPa or 1.2 times the first discharge pressure (P1). In the same manner as in Example 1 except that the discharge pressure (P2) of No. 2 was set to 96 kPa, which was 3.2 times the first discharge pressure (P1),
Apply the coating liquid to the silicon wafer surface to form a coating film,
The in-plane distribution (D) of the coating film formed from equation (1) was determined and is shown in Table 1.

As is clear from Table 1, in the method of spin-coating the coating liquid, the second discharge pressure is 1.3 to 3 times the first discharge pressure.
A coating film with a uniform thickness is formed on a silicon wafer by discharging the coating liquid within 1 second at a discharge pressure of 1 second and ending the discharge within 2 seconds after starting discharge at a second discharge pressure. it can.

[0032]

[Table 1]

Embodiment 5 FIG. 30 k in the same manner as in the first embodiment.
The discharge of the coating liquid onto the silicon wafer surface is started at a discharge pressure of Pa (P3). 30kPa constant pressure (P
In 3), the discharge is continued, and after 8 seconds from the start of the discharge, the pressure applied to the coating liquid 2 is eliminated, and the discharge is interrupted. 30k after one second
Pa discharge pressure is applied, discharge is restarted, and discharge is performed for 2 seconds. Thereafter, a coating film was formed on the surface of the silicon wafer by the same process as in Example 1, and the in-plane distribution (D) of the coating film formed from the formula (1) was determined and shown in Table 2.

Embodiment 6 FIG. ~ 8. The discharge time (T4) until the discharge was interrupted, the time during which the discharge was interrupted (Ts), and the time during which the discharge was re-discharged (T5) were the same as in Example 5 except that the values shown in Table 2 were used. Then, a coating film was formed on the surface of the silicon wafer, and the in-plane distribution (D) of the coating film formed from the formula (1) was determined and is shown in Table 2.

Embodiment 9 FIG. Forming a coating film on the silicon wafer surface in the same manner as in Example 7 except that the discharge time (T4) until the discharge is interrupted is 7 seconds, the discharge of 1 second is interrupted and the re-discharge of 1 second is repeated three times. Then, the in-plane distribution (D) of the coating film formed from equation (1) was determined and is shown in Table 2.

Comparative Example 5 A coating film was formed on the silicon wafer surface in the same manner as in Example 7 except that the re-discharge time (T5) was set to 3 seconds, and the in-plane distribution (D) of the coating film formed from the formula (1) was determined. The results are shown in Table 2.

Embodiment 10 FIG. The viscosity of the coating liquid 2 is 25
A coating film was formed on the surface of a silicon wafer in the same manner as in Example 5 except that a silicon ladder polymer dissolved in anisole of 00 mPa · s was used, and the in-plane distribution of the coating film formed by equation (1) was obtained. It was shown to.

Comparative Example 6 Discharge time (T
A film was formed on the surface of the silicon wafer in the same manner as in Example 10 except that s) was set to 4 seconds, and the in-plane distribution (D) of the formed film was determined from the formula (1) and shown in Table 3. .

As is clear from Table 2, in the spin coating method according to the second embodiment, by setting the re-discharge time (Ts) of the coating liquid 2 within 2 seconds, a uniform film can be formed on the silicon wafer. A thick coating film can be formed. Further, as is apparent from Table 2, even when the interruption and re-ejection of the application liquid are repeated a plurality of times, a coating film having a uniform film thickness can be formed on the silicon wafer. Further, as is clear from Table 3, in the spin coating method of the second embodiment, even when the viscosity of the coating liquid 2 is high, if the time (Ts) during which the ejection is interrupted is within 2 seconds, the silicon A coating film having a uniform thickness can be formed on a wafer.

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

According to the first spin coating method according to the present invention,
Pressurizes and discharges the coating liquid toward the approximate center of the substrate surface,
In the spin coating method of coating the coating liquid by rotating the substrate, the coating liquid is discharged at a first discharge pressure, and then the coating liquid is discharged at a second discharge pressure higher than the first discharge pressure.
Discharge within 2 seconds and start discharging at the second discharge pressure.
Dispensing is completed within seconds, no special mechanism or extra nozzles are required in the spin coating device, and a uniform film can be formed on the substrate using the conventional spin coating device without increasing the cost of the device. A thick coating film can be formed. In addition, since the time for discharging by raising the discharge pressure is short, the time for the large amount of the coating liquid is short, the coating liquid is not discharged more than necessary, the use of a large amount of the coating liquid can be prevented, and the cost of forming the coating film can be reduced. A coating film having a uniform thickness can be formed on the substrate without increasing the thickness.

According to a second spin coating method of the present invention, in the first spin coating method of the present invention, the second discharge pressure is set to 1.3 to 3 times the first discharge pressure. An inexpensive conventional spin coating apparatus can form a coating film having a uniform thickness on a substrate without increasing the cost of forming a coating film.

A third spin coating method according to the present invention is the spin coating method of rotating a substrate, applying and discharging a coating liquid toward substantially the center of the surface of the substrate, and applying the coating liquid. Discharging of the coating liquid is interrupted, and then re-discharging of the coating liquid within 2 seconds is performed, thereby terminating the discharge.
An inexpensive conventional spin coating apparatus can form a coating film having a uniform thickness on a substrate without increasing the cost of forming a coating film.

A fourth spin coating method according to the present invention is the same as the third spin coating method according to the present invention, in which the discharge of the coating liquid is interrupted and re-discharged a plurality of times. By using the apparatus, a coating film having a uniform thickness can be formed on the substrate without increasing the cost of forming the coating film.

In a fifth spin coating method according to the present invention, in the third or fourth spin coating method of the present invention, the time during which the discharge of the coating liquid is interrupted is set to within 2 seconds. Little change in viscosity of coating solution due to evaporation of solvent,
Even when a coating solution having a high viscosity is used, a coating film having a uniform thickness can be formed on the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a spin coating apparatus used in a spin coating method according to a first embodiment.

FIG. 2 is a diagram schematically showing application of a coating liquid to a substrate in a spin coating method according to the first embodiment.

FIG. 3 is a diagram showing a change over time of a discharge speed of a coating liquid in a spin coating method according to a second embodiment.

FIG. 4 is a diagram schematically showing application of a coating liquid to a substrate by a conventional spin coating method.

[Explanation of symbols]

1 substrate, 2 coating liquids, 3 nozzles, 4 rotating chucks, 5 coating films after completion of discharge, 6 coating films after high-speed rotation coating, 7 liquid dripping prevention valves, 8 syringes, 9 connector tubes, 10 discharge control devices.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AB16 AB20 EA05 4D075 AC06 AC64 AC79 AC91 AC95 CA48 DA06 DB13 DB14 DC22 DC24 EA07 EA45 EB43 5F045 AA00 BB02 EB02 EB20 5F046 JA01

Claims (5)

[Claims] In a rotary coating method for applying a coating liquid by applying a pressure to a substantially center of the surface of a substrate and discharging the coating liquid by rotating the substrate, the coating liquid is discharged at a first discharge pressure. After that, the application liquid is discharged within one second at a second discharge pressure higher than the first discharge pressure, and the discharge is completed within two seconds after starting the discharge at the second discharge pressure. Spin coating method. 2. The method according to claim 1, wherein the second discharge pressure is set to be equal to the first discharge pressure.
2. The spin coating method according to claim 1, wherein said method is 3 to 3 times. 3. A method of rotating a substrate, wherein the substrate is rotated and the application liquid is pressed and discharged toward substantially the center of the surface of the substrate, and the discharge of the application liquid is interrupted. A spin coating method, wherein the coating liquid is re-discharged within 2 seconds and the discharge is terminated. 4. The spin coating method according to claim 3, wherein the suspension and re-discharge of the coating liquid are performed a plurality of times. 5. The spin coating method according to claim 3, wherein the time during which the discharge of the coating liquid is interrupted is set within 2 seconds.