WO1995007764A1 - Liquid spin coating method and apparatus therefor - Google Patents

Abstract

A liquid spin coating method comprising the steps of first discharging a liquid film (Fe) onto the surface of a plate-like article (D) to be coated which is horizontally rotated at a relatively low speed from an airless spray nozzle (3) for fan-like spraying under relatively low pressure, effecting a preliminary coating by spreading the liquid film over the entire surface of the article (D) to be coated, thereafter increasing the rotation speed of the article (D) to be coated so as to spin off excessive liquid inside the applied liquid film (Fe) outwardly of the article (D) to be coated by virtue of a greater centrifugal force, whereby a liquid film (Fcf) thinner and more uniform in thickness is applied as finishing to the article (D) to be coated, and a liquid spin coating apparatus in which the airless spray nozzle (3) for fan-like spraying is provided in such a manner that it can be moved radially from a rotation center portion of the plate-like article (D) to be coated.

Description

 Specification

 Liquid spin coating method and device Technical field r

 The present invention relates to a liquid spin coating method and a liquid spin coating apparatus.

Background art

Recently, products with thin coatings on various disk surfaces as computer parts have been rapidly increasing. For example, wafers that are substrates for integrated circuits, CDs, FDs, LDs, and glass panels for liquid crystals. The thickness of these coatings is on the order of microns, and their uniformity is strictly required. Spin coating is the most widely used coating method. The method will be described briefly. See FIG. First, the application liquid is discharged (E s) in the center of the horizontally rotating disk (D) from a nozzle (73) such as a drip dispenser (71) into a drip or string form. Then, wrap it in embankment or clog (E sa). Next, the disk (D) is rotated at a low speed (200 to 400 rpm) for 5 to 6 seconds, and as shown in FIG. ) Spread over the surface and shake off the excess outside the disk (Fd). Then, when the coating liquid has become a substantially flat liquid film (Fc9), the rotation speed is then increased, and the rotation is continued for about 40 seconds under a high speed rotation of 1,000 to 3000 rpm. Then, the liquid film becomes thinner and more uniform due to a larger centrifugal force. The uniform thickness of the liquid film is obtained by Debarah's formula, depending on other factors such as the angular velocity of the disk, the shear viscosity of the coating solution, the shear stress, the shear rate, and the density. That is known.

 In the above method, the yield of the coating solution was extremely poor. In other words, it takes about 6 seconds to expand the embankment-like or clog-like lump into a liquid film by rotating at low speed, and in order to shorten it as much as possible, a spiral as shown in Fig. 11 is used. Attempts to apply in the form of (Esp) force have had some effect, but have not led to an improvement in yield. This means that the amount of the coating liquid displaced by the centrifugal force in the first low-speed rotation is particularly large (this is abandoned). For example, in the case of a photo resist solution, when the supply liquid amount is about 4 g, the film thickness of the coating liquid is about 100 microns by the primary rotation, and the yield is about 15%. That is, 85% of the supplied liquid is lost. If it is finished by the next secondary high-speed rotation and its thickness is about 2 microns, the final yield will be about 0.3%. That is, since most of the loss occurs in the first rotation, it is an object of the present invention to reduce the loss.

Disclosure of the invention

 According to the present invention, first, a liquid is applied in a substantially flat film form from an airless spray nozzle for fan-shaped spraying onto the surface of a workpiece rotating at a low speed, and then the high-speed rotation is immediately started to finish a uniform thin film. It is an object of the present invention to provide a method and an apparatus for starting the process.

The method of the present invention will be described. See FIG. The disk (D) mounted on the chuck board (4) is first rotated at low speed (200 to 400 rpm). The liquid is discharged onto the disk (D) surface from above by a fan-shaped spray nozzle (3). At this time, discharge the liquid under relatively low pressure (1 to 4 kg / cm ² ). Then, from 5 to 5 O mm from the tip of the nozzle (3), the liquid does not atomize, but leaves as a leaf-like liquid film (F e) and flows down. The width of the liquid film is 5 to 5 mm. A 30 mm strip of liquid film (F e) is applied on the disk (D) surface. The width of the band-shaped liquid film (F e) is concentrically or spirally applied, and a substantially flat liquid film (F c) is applied over the entire disk surface. That is, preliminary coating is performed.

 In the conventional pre-coating, as described in the previous section, first, a stagnation or spiral liquid, that is, a string of fluid (E sa, E sp) is turned into a substantially flat liquid film by the centrifugal force of low-speed rotation. (Fc9) was obtained, but in this method, the process was omitted and the liquid film was directly applied to immediately obtain a substantially flat liquid film. In addition, considerable reductions can be made. What used to take 5 to 6 seconds in the past can be reduced to 2 to 3 seconds, or more than a half.

 At the same time, since the thickness of the preliminary coating film (F c) can be relatively thin, the amount of shaking off by the centrifugal force in the first low-speed rotation can be reduced by the amount of the conventional clog-type coating. It requires less. For example, assuming that the thickness of the pre-coated film is 100 microns, a disc with a diameter of 90 mm only needs to apply a little less than 1 g, which is 4 minutes compared to the conventional 4 g. Of one or more savings.

 In the present invention, the airless spray nozzle for fan-shaped spray (3) is mainly used, and the reason will be described. The nozzle (3) is small and light, easy to handle and adjust, easy to work and easy to maintain, and has a low cost for a liquid film slit nozzle.

Next, the device of the present invention will be described. See also Figure 1 No. The structure of the apparatus of the present invention may be interpreted as replacing the dispenser with a fan-shaped spray airless spray nozzle (3) in a conventional mobile dispenser spin coating apparatus. That is, a gun body to which the airless spray nozzle (3) is attached

(1) is mounted on the horizontal slider (10). A screw (12) is screwed into the slider (10) from the lateral direction, and a sprocket (13) is attached to the other end of the shaft of the screw (12). By 16), it is connected to the sprocket (15) on the output shaft of the motor (17).

 Below the airless spray nozzle (3), an air chuck board (4) is provided horizontally, and below the chuck board (4), a chuck rotating shaft (5) is connected with a vacuum pipe joint (21). And electromagnetic clutch

(22), and is supported through sprockets (23). The block (23) is connected to the drive motor (27) by a chain. The air chuck board (4) and the airless spray nozzle (3) are surrounded by a booth (9). The gun body (1) to which the nozzle (3) is attached has a liquid supply pipe (7). ) To the liquid tank (3 1) via the solenoid on-off valve (33), and the operating air supply pipe (8) to the pressurized tank (19) via the electromagnetic on-off valve (18). The vacuum connection (21) is connected to a vacuum device (29) via an electromagnetic switching valve (28). Each of the above-mentioned electromagnetic switching valves, each electric motor, and the electromagnetic clutch (22) are electrically connected to a control panel (35).

See also FIG. The disk (D) is supplied onto the air chuck disk (4) by a disk supply device (not shown in the drawing). H The electromagnetic clutch (22) is actuated by the transmission of the signal of the completion of the jack, the rotation from the electric motor (27) is transmitted to the chuck shaft (5), and the coaxial speed is low.

(200-400 rpm). At the same time, the liquid supply gun valve (33) is opened, and the liquid film (F e) is discharged from the airless spray nozzle (3) for the fan-shaped spray, and the coating starts on the disk (D) surface. Is done. Next, the rotation of the electric motor (17) causes the shaft of the screw (12) to rotate through the sprocket (15, 13) and the chain (16), and is screwed to the screw (12). Slider

(10) The gun (1) and nozzle (3) fixed above move simultaneously in the horizontal direction. The liquid film discharged from the nozzle (3)

(F e) is spirally or concentrically coated with a liquid film (F c) over the entire surface of the disk (D). At the same time, the excess liquid in the liquid film is After two or three seconds after being shaken, the remaining liquid film is made to have a required and substantially uniform thickness (50 to 200 microns). This is called pre-coating.

 After the completion of the pre-coating, the disk (D) was accelerated to a high speed (1000 to 2000 rpm), and the pre-coated liquid film (F c) became more dog-like. The excess liquid in the liquid film is shaken off again by centrifugal force, and after 15 to 20 seconds, the thickness of the remaining liquid film becomes 0.1 to 2 microns, and the coating film has a uniform thickness. Finished. This is referred to as coating finish.

The pre-coating time (T p) and coating finish time (T f) were shortened as described above, and FIG. 7 shows a typical example of the graph. Fig. 8 shows an example of the conventional pre-coating (spiral shape), and the pre-coating and coating finishing time was dog compared to the above case. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an explanatory diagram of the method and the apparatus of the present invention.

 FIG. 2 is an explanatory diagram of a first embodiment of the method of the present invention.

 FIG. 3 is an explanatory diagram of the second embodiment.

 4A and 4B are explanatory diagrams of the third embodiment.

 5A and 5B are explanatory diagrams of the fourth embodiment.

 FIG. 6 is an explanatory diagram of the fifth embodiment.

 FIG. 7 is a graph of the number of rotations and the time during pre-coating and coating finishing of an object to be coated by the method of the present invention.

 FIG. 8 is a graph in comparison with the above graph according to the conventional method. Fig. 9 shows a conventional spinning method for applying a coating solution in pre-coating.

 FIG. 10 is an explanatory view showing a state in which the spinning-type coated object is flattened by rotating the object to be coated.

 FIG. 11 is a perspective view of a case where a spiral type coating is used instead of the watering wheel type.

BEST MODE FOR CARRYING OUT THE INVENTION

 First embodiment

Les, see Figure 2. The width (w) of the leaf-shaped liquid film (F el) discharged from the airless spray nozzle for fan-shaped spraying is 5 to 40 mm. Therefore, a single coating is not sufficient for disks with a radius of 4 O mm or more. In this example, an annular ring having a width w is applied in multiple stages from the inside or outside of the disc on the disc surface. That is, first, a circle (Fc 1) having a radius w from the inside, that is, the center, is placed outside, and then a second ring is formed in contact with the outer periphery of the circle (F cl). Then, (Fc2) is applied while being in contact with the third ring (Fc3). In the stepwise coating method, the axis (CL) of the airless spray nozzle (3) is a pitch of approximately w

It is moved stepwise in the radial direction with (w1, w2). Alternatively, the gun nozzle (3) may move inward from the outside of the disc (D).

 Second embodiment

 See FIG. In this example, a single gun and a fan-shaped spray nozzle (3A) are moved outward from the center of the disk (D) in a spiral (SP) shape outwardly into a band-shaped liquid film (Fsp). ) Is pre-applied (Fc4) over the entire surface, with both side edges touching each other. Spiral coating may be applied from the outside toward the center. Third embodiment

 See Figure 4A. In this example, a plurality of fanless spray airless spray nozzles are installed side-by-side, i.e., multiple, at the upper part corresponding to the radius (R) of the disk (43A, 43B, 43C). It is a continuous type. If the total width of the liquid film (F e5, F e6, F e7) discharged from each nozzle is approximately equivalent to the length of the above radius (R), fix those nozzles. The entire surface can be applied all at once while keeping it as it is. In addition, the thickness of the liquid film (F e5, F e6, F e7) from each of the nozzles is gradually increased from the inside to the outside of the disk (D) as shown in Fig. 4B. It is desirable to set (t 1 <t 2 <T 3) so that

 Fourth embodiment

See Fig. 5 5. As compared with the multiple nozzle in the third embodiment. The liquid film equal to the total width of the remaining liquid film, that is, the liquid film with a width almost equal to the radius of the disk (D) is discharged at once from one film slit nozzle (53) and applied. How to Originally, in the fanless spray airless spray nozzle used in the present invention, the liquid squirts from the small hole under high pressure (60 to 80 kg / cm ² ) to form a fan (fan). If the pressure to be sprayed is set to a low pressure (2 to 5 kgZc m ² ), it is discharged as a leaf-like liquid film without spraying. In this state, the operation is almost the same as that of a film slit nozzle used for general extrusion type film formation. Therefore, this slit nozzle is also included in the same category as the fanless spray airless spray nozzle. This is adopted in the present embodiment. Also in this case, as shown in FIG. 5B, it is desirable that the thickness of the liquid film (F e 8) gradually increases outward from the center of the disk (t 4 <t 5). .

 Fifth embodiment

 In each of the above embodiments, the object to be coated was all in the form of a disk, that is, a disk. However, in this embodiment, a coating method for a square flat plate will be described. In this case, it is applied by the method in each of the above-mentioned embodiments so that it is inscribed or circumscribed (see FIG. 6). Inscribed coating is when the viscosity of the coating liquid is relatively low. The reason depends on how easy the liquid is to flow.

At present, the spin coating method is said to be the optimal method for applying a thin and uniform liquid film. However, there was one drawback. Because of the centrifugal force at the time of rotation, At about 70% or more, and at a high rotation of the finish of the coating film, about 20% or more loss was generated, and the yield was extremely uneconomical with only a few%. In particular, in the preliminary coating, the bulk liquid supplied on the object is shaken off at a low speed to form a rough film, but in the present invention, the supply of the bulk is stopped. However, since the film is directly supplied in the form of a film, it is possible to prevent the occurrence of the above-mentioned loss of about 85596 or more before the film is formed into a lump. In addition, the time required for forming the film, that is, the time for preliminary coating, is reduced from about 6 seconds to about 2 seconds, and the coating finishing time is also reduced from about 30 seconds to about 20 seconds. You can do it. Thus, according to the method and the apparatus of the present invention, material can be saved and time can be shortened, which can greatly contribute to cost reduction.

Claims

The scope of the claims  1. First, a liquid film (F e) is placed on the surface of a plate-shaped workpiece (D) that rotates horizontally at a relatively low speed under relatively low pressure from the airless spray nozzle for fan-like spray (3). And apply the liquid film over the surface of the object to be coated (D) (F c) to make the pre-coating. Then, the rotation of the object to be coated (D) is further accelerated. The excess liquid in the applied liquid film (Fc) is applied to the substrate by stronger centrifugal force. (D) by spinning it outward and finishing and applying a thinner and more uniform liquid film (F cf) on the surface of the object (D). .  2. The pre-coating applies the band-shaped liquid film (F e 1) discharged from one airless spray nozzle for fan-shaped spray (F e1) to the outside or inside on the surface of the object (D) rotating at low speed. Applying a plurality of annular liquid films (Fc1, Fc2, Fc3, ...) more gradually and concentrically to the inside or outside while contacting their inner and outer edges. 2. The method for spin coating a liquid according to claim 1, wherein the method comprises:  3. The pre-coating applies the band-shaped liquid film (F e 4) discharged from one airless spray nozzle for fan-shaped spray (3A) to the outside or inside on the surface of the object (D) rotating at low speed. Claim 1 wherein the liquid film (Fc4) is applied in a spiral shape (Sp) from the both sides and in contact with each other (Fsp) inwardly or outwardly. Liquid spin coating method. 4. The same number of liquid films (F e5, F e6, F) as those of the plurality of fanless spray airless spray nozzles (43A, 43B, 43C,…;) e 7,… :) are discharged and their Apply the entire surface of the application section so that the total (W) of the width (w) on the application surface covers the radius (R) of the application section on the surface of the workpiece (D) rotating at a low speed. 2. The spin coating method for a liquid according to claim 1, wherein the method is:  5. The airless spray nozzle for fan-shaped spray is a slit nozzle for film, and the pre-coating is performed by the slit nozzle. The film (F e 8) discharged from (53) has a width (W1) that covers the radius (R) of the coating section on the surface of the workpiece (D) that rotates at a low speed. 2. The method for spin coating a liquid according to claim 1, wherein the method comprises applying a liquid.  6. At the center of the booth (9), a horizontal air chuck board (4) and a high / low speed switching rotary drive (24) are provided on an extension shaft below the rotating shaft of the board, and the chuck board ( 4) Dispenser force that drops liquid toward the center of rotation of plate-shaped workpiece (D) chucked on top. Spindle that moves in the radial direction from the center of rotation of plate-shaped workpiece (D). A liquid spin-coating apparatus characterized by being provided with a gun (1) and a fanless spray airless spray nozzle (3) in place of the dispenser described above.  7. The liquid spin coating apparatus according to claim 6, wherein the fanless spray airless spray nozzle (3) is a film forming slit nozzle (53 or 63, 63A).