JP5272376B2 - Method for forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a formation method of a coating film which enables the formation of a coating film with uniform film thickness and is free from linear unevenness etc., when forming the circular coating film on a base. <P>SOLUTION: This formation method of a coating film employs a coating device constituted of a rotatable table for horizontally retaining the base and a horizontally movable nozzle which is ascendable/descendable to the table and equipped with a discharge orifice at the apex. In addition, the method forms the circular coating film by rotating the table and at the same time, supplying a liquid coating solution to the surface of the base from the discharge orifice, while moving the nozzle in one direction between the rotational center of the table and a specified outer position in such a state that the nozzle is retained at a specified height to the table. Given the viscosity of the liquid coating solution as "&eta;", the film thickness after coating as "h" and the wavelength of the surface swell of the coating solution after coating as &lambda;, the coating film has to be formed on condition that the half-life t<SB>1/2</SB>represented by formula (1) be not more than 8. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for forming a circular coating film on a substrate.

  As a method for forming a circular coating film on a substrate, for example, as a method for coating a liquid coating solution on a circular wafer, there is a coating method using a spin coater. However, this method has a very poor yield because most of the coating solution (about 95%) is discarded without being used. Further, the screen printing method has a problem that it is difficult to control the thickness of the coating film.

  In order to solve these problems, in recent years, it is composed of a rotatable table that holds the substrate horizontally and a nozzle that can move up and down relative to the table and that has a discharge hole at the tip. A circular shape for supplying the liquid coating liquid from the ejection holes onto the substrate while rotating the table using the coating device and moving the nozzle in one direction with the nozzle held at a predetermined height with respect to the rotating table. A coating film forming method has been proposed (see Patent Document 1 and Patent Document 2). However, in this method, there is a problem that it is difficult to control the coating conditions, it is difficult to obtain a uniform film thickness, and in particular, unevenness of the coating solution is likely to occur during coating.

JP 2001-310155 A JP 2005-305440 A

  An object of the present invention is to provide a method of forming a coating film having a uniform film thickness and free from uneven stripes when a circular coating film is formed on a substrate.

The present invention is as follows.
(1) Using a coating apparatus that includes a rotatable table that holds a substrate horizontally, and a horizontally movable nozzle that is movable up and down relative to the table and that has a discharge hole at the tip. While the table is rotated and the nozzle is held at a predetermined height with respect to the rotating table, the liquid is applied from the discharge hole while moving in one direction between the rotation center of the table and a predetermined outward position. A method of forming a circular coating film for supplying a liquid onto the substrate, wherein the viscosity of the liquid coating liquid is η, the film thickness of the coating liquid after coating is h, and the wavelength of the undulation of the surface of the coating liquid after coating A coating film forming method characterized in that the coating film is formed under the condition that the half-life t _1/2 represented by the following formula (1) is 8 or less, where λ is λ.

(2) The method for forming a coating film according to (1), wherein the substrate is a semiconductor wafer.
(3) The method for forming a coating film according to (1) or (2), wherein the liquid coating solution is composed of a resin composition containing a solid epoxy resin and a solvent at room temperature.

  According to the coating film forming method of the present invention, a circular coating film can be formed on the substrate with a uniform film thickness.

Hereinafter, embodiments of the present invention will be described in detail.
The present invention uses a coating apparatus comprising a rotatable table that holds a substrate horizontally, and a horizontally movable nozzle that is movable up and down relative to the table and that has a discharge hole at the tip. The liquid coating liquid is discharged from the discharge hole while rotating the table and moving the nozzle in one direction between the rotation center of the table and a predetermined outward position with the nozzle held at a predetermined height with respect to the rotating table. This is a method for forming a circular coating film to be supplied onto a substrate.

In the coating film forming method of the present invention, a liquid coating solution is applied to a substrate using, for example, a coating apparatus as shown in FIG.
The coating apparatus 100 includes a table 1 and a head 2 including a nozzle 22 that can supply a liquid coating liquid to the table 1.
As shown in FIG. 1, the table 1 is disposed on the upper side of the base 11 so as to be rotatable with respect to the base 11, and is joined to a shaft portion (not shown) provided through the base 11. Yes. The shaft portion is provided with a gear (not shown), and driven by a motor (not shown) via this gear, the table 1 rotates in the direction A in FIG.

The support pillar 3 is installed in the edge part of the width direction of the base 11, and the back direction (back side direction in FIG. 1) of the base 11 is above the support pillar 3 (upper side in FIG. 1). The rail 31 is extended to. A box 32 is provided at the upper end of the support column 3, and the head 2 is provided at the tip of the box 32. The box 32 can be moved in the direction C in FIG. 1 by a pulley wire or a rack and pinion mechanism that is driven along the rail 31.
The head 2 includes a head portion 21 and a nozzle 22 that extends downward at a lower portion of the head portion 21. The head portion 21 and the nozzle 22 are provided with a tube (not shown) so that a liquid coating solution can be supplied.

The head unit 21 can move to the inside of the box 32 in the B direction. For example, a motor that drives a pinion gear of a rack and pinion mechanism is built in the box 32. This motor can be rotated in both forward and reverse directions, so that the head portion 21 can be moved in the B direction so as to freely advance and retract.
Further, since the box 32 is movable in the C direction as described above, the head 2 is also movable in the C direction.
Therefore, the nozzle 22 can be arranged at an arbitrary position in the surface direction of the base 11.

  By using such a coating apparatus 100, a substrate is mounted on the table 1, the liquid coating liquid is discharged from the nozzle while moving the substrate and the nozzle relatively, and the liquid coating liquid is discharged from the nozzle. It can be applied to one side of the substrate. For example, a method of moving the nozzle 22 in the direction of arrow B in FIG. 1 while rotating the substrate, a method of moving the nozzle 22 in the direction of arrow B while moving the nozzle 22 in the direction of arrow C in FIG. Thus, a liquid coating solution can be applied.

A method for applying the liquid coating solution will be described based on a preferred embodiment.
In the coating method of the liquid coating solution of the present invention, the substrate 12 is sucked from the table 1 surface side so that the rotation center of the table 1 and the rotation center of the substrate 12 coincide as shown in FIG. While fixing.
Next, the head portion 21 is extended from the box body 32, and the tip portion of the nozzle 22 is disposed at the center of the substrate 12. At this time, the rotation center of the substrate 12 and the axis of the nozzle 22 are made to coincide (this position is set as a reference position).

Then, while rotating the substrate 12, the head 2 is moved from the reference position in the B1 direction and the liquid coating solution 4 is discharged from the nozzle 22. As a result, the liquid coating solution 4 is spirally applied to the substrate 12. The liquid coating liquid 4 is spread and flattened by the viscosity. Here, the liquid coating solution 4 is not formed into a film only by centrifugal force unlike the spin coating method.
Then, when the nozzle 22 reaches the outer peripheral portion of the substrate 12, the discharge of the liquid coating liquid 4 is stopped. As described above, in the present invention, the liquid coating solution 4 is applied to one surface of the substrate 12 by ejecting the liquid coating solution 4 from the nozzle 22 while relatively moving the substrate 12 and the nozzle 22. Features. Thereby, the liquid coating liquid 4 having an optimum thickness can be applied to the substrate 12. In addition, this makes it possible to apply only a necessary amount of the liquid coating solution 4 and reduce unnecessary raw materials that cause problems in the spin coating method.

  Thus, since the head 2 (nozzle 22) is moved in the radial direction of the substrate 12 while the substrate 12 is rotated, the liquid coating solution 4 is applied circumferentially. Here, the coating amount of the liquid coating solution 4 may be constant in the radial direction from the center of the substrate 12, but the peripheral speed changes as the position of the nozzle 22 moves in the radial direction from the center of the substrate 12. Therefore, it is preferable to adjust the coating amount in accordance with the change in the peripheral speed. That is, it is preferable to apply the liquid coating solution 4 so that the coating amount of the liquid coating solution 4 near the center of the substrate 12 is smaller than that near the outer periphery of the substrate 12. As a result, the liquid coating solution 4 can be applied to the substrate 12 with a uniform thickness.

  Further, the rotation speed of the substrate 12 may be a constant speed, but the rotation speed may be changed so that the peripheral speed at the coating position is constant. However, when the rotation speed of the substrate 12 is increased, a large shearing force acts on the liquid coating liquid 4 discharged from the tip of the nozzle 22 and the liquid coating liquid 4 may be interrupted by the action of this force. That is, the rotation speed has an upper limit value.

  The moving speed of the nozzle 22 is good enough to move by the width of the liquid coating liquid discharged from the discharge hole of the nozzle while the substrate 12 rotates once. However, the distance may be larger than the width of the discharged liquid coating liquid depending on the properties of the liquid coating liquid.

  The distance (gap) between the tip of the nozzle 22 and the surface of the substrate 12 is made higher than the height of the film thickness of the liquid coating liquid (the thickness of the liquid film) and less than the distance at which the tip of the nozzle 22 and the liquid film are separated. There is a need. If the tip of the nozzle 22 is lower than the thickness of the liquid film, the nozzle 22 may scrape off the liquid film, and if it is larger than the thickness of the liquid film, the tip of the nozzle 22 and the liquid film may be separated. is there.

  2, while the substrate 12 is rotated, the nozzle 22 for supplying the liquid coating solution 4 in the radial direction of the substrate 12 is linearly moved from the center of the substrate 12 toward the outer peripheral end, Although the method of applying the liquid coating solution 4 has been described, the coating method of the present invention is not limited to this. For example, a method of linearly moving the nozzle 22 from the outer peripheral end portion of the substrate 12 toward the central portion while rotating the substrate 12, or moving the nozzle 22 from the central portion of the substrate 12 to the outer peripheral end while rotating the substrate 12. For example, there may be mentioned a method of moving in two stages such as once moving still in the outer peripheral direction after being stopped.

  As a board | substrate used for this invention, the thing of various shapes and various materials are used according to a use. An organic substrate, a glass substrate, a ceramic substrate, a silicon substrate and the like can be mentioned, and a silicon wafer for semiconductor is particularly preferably used.

  Although it does not specifically limit as a liquid coating liquid used for this invention, The coating liquid utilized for semiconductor manufacture and magnetic disk manufactures, such as a photoresist liquid, a heat resistant insulating liquid, and a liquid coating liquid, is used suitably. In particular, the coating liquid is preferably composed of a resin composition containing an epoxy resin component and an organic solvent component that are solid at room temperature.

When the liquid coating solution is applied to the substrate by the method of the present invention, the surface state of the coating solution after coating is in a state having irregularities as shown in FIG. The unevenness in such a state is flattened with time by the leveling force of the coating liquid.
The coating liquid after the coating, the half-life t ₁ When assuming unevenness of course the wet coating film whose surface is flat is represented by sin curve, where the unevenness of peaks and valleys depth a is 1/2 _{/ 2} is expressed by the following equation.

  In equation (1), η is the viscosity (Pa · s) of the liquid coating solution, γ is the surface tension (mN / m) of the liquid coating solution, h is the film thickness (mm) of the coating solution after coating, and λ is after coating. Wavelength (mm) of the swell of the surface of the coating liquid.

  From the above equation, the wet film thickness h is thicker, and the smaller the wave length λ is, the more easily it becomes flat. In addition, the lower the viscosity η of the coating solution and the higher the surface tension γ, the easier it becomes to be flat.

In the present invention, it is necessary to form the coating film under the condition that the half-life t _1/2 represented by the formula (1) is 8 or less. Preferably it is 7 or less, More preferably, it is 5 or less, More preferably, it is 2 or less.
If the half-life t _1/2 exceeds the upper limit value, it becomes easy for the coating solution to become uneven during coating, and it may be difficult to obtain a uniform film thickness because it is difficult to flatten.

As a method for reducing the half-life t _1/2 , adjustments such as reducing the viscosity of the coating solution and increasing the surface tension can be mentioned. In addition, a method of adjusting by, for example, narrowing the wave length λ (coating pitch) of the waviness under the coating conditions may be mentioned.
The wave length λ is adjusted by the number of rotations of the table, the nozzle moving speed, and the like.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

"substrate"
A 6 inch silicon wafer was used. The diameter is 150 mm and the thickness is 625 ± 25 μm.

<Liquid coating liquid>
<Liquid resin composition A>
Orthocresol novolac type epoxy resin (softening point 70 ° C., epoxy equivalent 210) 16.5 g
13.7 g of phenol aralkyl resin (softening point 75 ° C., hydroxyl group equivalent 175)
Acrylic ester copolymer (SG80H manufactured by Nagase ChemteX Corporation) 10g
γ-butyrolactone (boiling point 204 ° C.) 63 g
The above raw materials were blended in a separable flask and stirred at 150 ° C. for 1 hour to obtain a pale yellow transparent liquid. After cooling this to room temperature, the following raw materials were added, and after stirring at room temperature for 30 minutes,
Liquid resin composition A was obtained by filtering with a 1 μm mesh.
3-glycidoxypropyltrimethoxysilane 0.14 g
Phosphorus catalyst 0.09g
The viscosity of the liquid resin composition A was 8 Pa · s, the surface tension was 39.6 mN / m, and the RC (resin content) was 39 wt%.
<Liquid resin composition B>
Further, γ-butyrolactone was added to the liquid resin composition A to adjust RC (resin content) to 24 wt%. The viscosity of the liquid resin composition B was 1.5 Pa · s, and the surface tension was 32.5 mN / m.

Example 1
Using the coating apparatus shown in FIG. 2, the liquid resin composition A is applied in an area of φ140 mm of a 6-inch silicon wafer, an average coating amount of 0.45 cc / min, a wafer rotation speed of 25 rpm, a nozzle moving speed of 0.5 mm / sec, The coating was performed under the condition that the distance (gap) between the tip of the nozzle 22 and the surface of the substrate 12 was 100 μm. The average film thickness h in the wet state after coating was 66 μm, the surface waviness wavelength λ was 1.2 mm, and the appearance was good. Subsequently, it heat-processed for 10 minutes on the 120 degreeC hotplate. The film thickness after drying was 24 to 28 μm (film thickness variation 4 μm).

Example 2
Using the coating apparatus shown in FIG. 1, the liquid resin composition B is in the range of φ140 mm of a 6-inch silicon wafer, the average coating amount is 0.683 cc / min, the wafer rotation speed is 25 rpm, the nozzle movement speed is 0.5 mm / sec, The coating was performed under the condition that the distance (gap) between the tip of the nozzle 22 and the surface of the substrate 12 was 150 μm. The average film thickness h in the wet state after coating was 100 μm, the surface waviness wavelength λ was 1.2 mm, and the appearance was good. Subsequently, it heat-processed for 10 minutes on the 120 degreeC hotplate. The film thickness after drying was 25 to 30 μm (film thickness variation 5 μm).

Example 3
Using the coating apparatus shown in FIG. 1, the liquid resin composition B is in the range of φ140 mm of a 6-inch silicon wafer, the average coating amount is 0.273 cc / min, the wafer rotation speed is 25 rpm, the nozzle movement speed is 0.5 mm / sec, The coating was performed under the condition of a distance (gap) of 60 μm between the tip of the nozzle 22 and the surface of the substrate 12. The average film thickness h in the wet state after coating was 40 μm, the surface waviness wavelength λ was 1.2 mm, and the appearance was good. Subsequently, it heat-processed for 10 minutes on the 120 degreeC hotplate. The film thickness after drying was 9 to 11 μm (film thickness variation 2 μm).

<< Comparative Example 1 >>
Using the coating apparatus shown in FIG. 1, the liquid resin composition A is in the range of φ140 mm of a 6-inch silicon wafer, the average coating amount is 0.273 cc / min, the wafer rotation speed is 25 rpm, the nozzle movement speed is 0.5 mm / sec, The coating was performed under the condition of a distance (gap) of 60 μm between the tip of the nozzle 22 and the surface of the substrate 12. Although the average film thickness h in the wet state after coating was 40 μm and the surface waviness wavelength λ was 1.2 mm, a large number of stripes were generated.

  Table 1 shows the coating conditions and coating results of Examples and Comparative Examples.

The evaluation method is as follows.
(1) Viscosity of liquid coating solution The viscosity was measured at 25 ° C. and 2.5 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., 3 ° cone).
(2) Surface tension of liquid coating liquid The surface tension was measured by a hanging drop method (pendant drop method) at 23 ° C. using a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd.). A needle having an inner diameter of 0.8 mm was used for producing the droplet.
(3) Wavelength of waviness after coating It was calculated from the following formula from the wafer rotation speed and the nozzle movement speed.
Wavelength of wave (mm) = Nozzle movement speed (mm / sec) / ( Wafer rotation speed ( rpm ) / 60)
(4) Film thickness in wet state Calculated from the film thickness after drying and the resin content (wt%).
(5) Film thickness after drying The coating film is scraped at an interval of 5 mm in the radial direction from the center of the coating surface, and the wafer surface and the coating surface are moved in the displacement mode of a double-scan high-precision laser measuring instrument (manufactured by Keyence Corporation). The step (film thickness) was measured, and the average step was calculated as the film thickness after drying.

Schematic of an example of a coating apparatus used in the present invention Schematic of an example of the coating method of the present invention Schematic showing the surface state of the coating liquid after coating

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Table 11 Base 12 Board | substrate 2 Head 21 Head part 22 Nozzle 3 Support pillar 31 Rail 32 Box 4 Liquid coating liquid 100 Coating apparatus

Claims (1)

Using a coating device comprising a rotatable table that holds the substrate horizontally and a nozzle that can move up and down relative to the table and that has a discharge hole at the tip, the table is While rotating, the liquid coating liquid is discharged from the discharge hole while moving the nozzle in one direction between the rotation center of the table and a predetermined outward position with the nozzle held at a predetermined height with respect to the rotating table. A method for forming a circular coating film to be supplied on a substrate,
The substrate is a semiconductor wafer;
The liquid coating liquid is composed of a resin composition containing a solid epoxy resin and a solvent at room temperature,
The viscosity of the liquid coating liquid is η (Pa · s), the film thickness of the coating liquid after coating is h (m), the wavelength of the surface of the coating liquid after coating is λ (m), and the surface tension of the liquid coating liquid The coating film is characterized in that the coating film is formed under the condition that the half-life t _1/2 (sec) represented by the following formula (1) is 8 or less, where γ is (N / m) Forming method.