JPH09192573A - Method for forming thin film and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a smooth thin film free from local irregularities of film thickness and largely enhance usage efficiency of coating liquid by directing comparative movement at a second movement in a direction opposite to that of flow of the coating liquid caused by rotational motion of a substrate to be coated. SOLUTION: This film-forming method includes a first movement for moving comparatively with respect to an ink jet head 12a substrate 11 to be coated to a first position wherein the head 12 starts jetting coating liquid, a second movement for moving comparatively with respect to the head 12 the substrate 11 in the first position to a second position wherein the head 12 finishes jetting the coating liquid and a third movement for moving the substrate 11 in the second position comparatively with respect to the head 12. Rotation of the substrate 11 is made to overlap in time with at least the second movement, and the coating liquid is jetted to form a thin film by making the rotation overlap in time with the second movement. In this film-forming method comparative movement at the second movement is directed in a direction opposite to that of flow of the coating liquid caused by the rotation of the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method and apparatus, and more particularly to a thin film (in a broad sense) by discharging a liquid substance from a plurality of minute nozzles and adhering it to a substrate and drying and curing the adhered liquid substance. The present invention relates to a method and an apparatus for forming a film having a thickness of 100 μm or less and generally 10 μm or less).

[0002]

2. Description of the Related Art In recent years, the field of application of thin film technology has been diversified, and the method of forming it does not require an expensive vacuum device other than the method of using a vacuum device such as sputtering or vapor deposition, spin coating, printing, die coating, etc. It is also manufactured by the method of.

In particular, spin coating is not only used for forming a resist film or an interlayer insulating film such as SOG in a semiconductor manufacturing process, but is also widely used as a protective film forming technique in an optical disk manufacturing process. Has been done.

A conventional spin coater (spin coater) will be described below. FIG. 7 shows a thin film forming process using a conventional spin coater.

In FIG. 7, 100 is a rotary shaft of the spin coater main body, and 200 is a material fixing substrate. Also, 300
Is a nozzle for ejecting the coating liquid 500,
Is a substrate for forming a thin film placed on the material fixing substrate 200.

In such a spin coater, first, as shown in FIG.
As shown in FIG.
The liquid 500 is ejected on.

Then, as shown in FIG. 7B, the spin coater is rotated at a low speed rotation ω1 (for example, 60 rpm) so that the liquid 500 is adapted to the substrate 400.

Then, as shown in FIG. 7C, by rotating the substrate 400 at a high speed rotation ω2 (for example, 4500 rpm), excess liquid is removed from the substrate 400 as a splatter liquid 700 to obtain a desired film thickness. A thin film 600 is formed.

[0009]

By the way, in the above spin coating, what actually remains as a thin film on the substrate 400 of the liquid 500 supplied from the nozzle 300 depends on the compatibility between the substrate and the liquid. Generally, it is 20% or less of the supplied liquid, and most of the supplied liquid becomes the scattered liquid 700 and is removed from the substrate.

This is because if the liquid 500 is not sufficiently supplied onto the substrate 400, sufficient compatibility between the liquid 500 and the substrate 400 cannot be obtained, and if the amount of the liquid 500 is reduced, the liquid 500 and the substrate 400 become compatible with each other. The reason for this is that unpainted portions and non-uniform distribution of the film pressure will be generated in the poorly coated area.

Further, in order to remove such non-uniformity of the film thickness and obtain a good coating surface even when the environmental variables around the spin coating device are changed, a liquid amount much larger than the necessary amount is supplied. It must be.

For example, when a protective film having a thickness of 3 μm is formed on an optical disk having an outer diameter of 120 mm (corresponding to the substrate 400), an ultraviolet (UV) curable resin solution (corresponding to the liquid 500)
Is supplied from the nozzle 300 to the disk by about 2 g,
The actual amount of liquid required to form a film thickness of 3 μm is 40 m.
about 1.96, which corresponds to 98% of the amount of the supplied liquid.
As much as g of the liquid will be discarded as the scattered liquid 700.

Depending on the type of the liquid, it is possible to adopt a method of re-collecting the scattered liquid 700 and using it again and again, but it requires a new capital investment for the re-collecting device and, during repeated collection, There is a possibility that properties such as liquid deterioration, wettability, and surface tension may change, and its practicality is limited.

As described above, when the thin film is formed by the conventional spin coater, the utilization efficiency of the liquid is very poor and there is a problem that the production cost is increased.

[0015]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art by using an ink jet head that can be used for ejecting ink of a printing apparatus as an ejection head for supplying a coating liquid to a substrate. The thin film forming method and the thin film forming apparatus have a structure in which the relative movement of the substrate with respect to the ink jet head in the liquid discharge area is in the direction opposite to the flowing direction of the coating liquid flowing due to the rotational movement of the substrate.

With such a structure, a smooth thin film is uniformly formed on the entire surface of the substrate while the amount of the liquid supplied to the substrate is reduced, and the utilization efficiency of the coating liquid is improved and the production cost is suppressed. .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is
A first substrate which moves the substrate to be coated relative to the ejection head to a first position where the coating liquid starts to be ejected from the ejection head;
And a second moving step of moving the substrate to be coated at the first position relative to the ejection head to a second position at which the coating liquid is completely ejected from the ejection head; A third moving step of further moving the substrate to be coated at a position relative to the ejection head, a rotating step of rotating the substrate to be coated overlapping at least with the second moving step, and A thin film forming method comprising: a second moving step and a rotating step, which overlaps in time with the thin film forming step of discharging a coating liquid from the discharge head onto the substrate to be coated to form a thin film. The relative movement in the second movement step is a thin film forming method in which the coating liquid flows in the opposite direction to the flowing direction of the coating liquid due to the rotational movement of the substrate to be coated.

Here, as described in claim 2, the relative movement in the second movement step is opposite to the flow direction in which the coating liquid flows due to the rotational movement of the substrate to be coated, and the relative movement. It is preferred that the magnitude of the velocity is substantially equal to the flowing velocity.

Alternatively, as described in claim 14, a tank for storing the coating liquid, a discharging means for discharging the coating liquid from the tank onto the substrate to be coated, and the substrate to be coated with respect to the discharging means. A moving unit that relatively moves so as to pass through a first position where the discharge of the coating liquid starts and a second position where the discharge of the coating liquid ends, and a rotating unit that rotates the substrate to be coated. A flow direction in which the relative movement between the substrate to be coated and the discharging means is at least partly from the first position to the second position, and the coating liquid flows due to the rotational movement of the substrate to be coated. And a control means for controlling the moving means so as to be in the opposite direction.

With such a structure, the film surface of the coating liquid coated on the substrate to be coated is uniformly smoothed.

Further, as described in claims 3 and 4,
At the first position and / or the second position, the amount of the coating liquid discharged per unit area on the substrate to be coated is the unit area on the substrate to be coated from the first position to the second position. A configuration in which the amount of the coating liquid discharged per hit is larger than that is preferable.

More specifically, as described in claim 5,
The relative movement of the substrate to be coated is stopped for a predetermined period after the start of the discharge of the coating liquid and / or for a predetermined period after the end of the discharge of the coating liquid, and further, the discharge of the coating liquid according to claim 6. It is preferable that the substrate to be coated is rotated from a predetermined period before the start and / or a predetermined period after the discharge of the coating liquid is completed.

In other words, as described in claim 7, the second
The moving step is started after the first moving step is finished and a predetermined period has elapsed, the third moving step is started after the second moving step is finished and a predetermined period has passed, and the rotating step is the second step. It is preferable that the configuration is started before the start of the moving process of 1 and ended after the end of the second moving process.

Further, preferably, as described in claim 8,
There is a second rotating step of rotating the substrate to be coated after the discharge of the coating liquid, and the magnitude of the rotating speed in the second rotating step is larger than that of the rotating motion before the second rotating step. Also, the second rotating step and the third moving step may be temporally overlapped with each other.

More specifically, as described in claim 10,
The substrate to be coated is a disk-shaped substrate, the relative movement in the second movement step is a constant-velocity linear motion passing through the center of the disk-shaped substrate, and the rotational movement in the rotation step is a constant-velocity rotational movement. Is.

With the above structure, the substrate to be coated has a layer of the second material partially on the substrate of the first material, and the substrate and the second substrate are formed as described above. The boundary with the layer of the material is also coated with the coating liquid, and more preferably, the substrate to be coated has a structure in which the side surface of the substrate to be coated is also coated with the coating liquid.

With such a structure, burrs are formed at the boundary between the substrate of the substrate (polycarbonate substrate in the case of an optical disc) and the layer of another material (metal evaporated film in the case of the optical disc) on the substrate. The coating property of the substrate edge that is easy to improve is improved, and the second rotation process after that becomes the leveling process.
Form a uniform thin film on a substrate.

Here, the discharge head discharges the coating liquid from a plurality of fine nozzles as set forth in claim 13, and further,
It is preferable to have a control step of controlling the discharge amount of the coating liquid.

On the other hand, the relative movement between the substrate to be coated and the discharging means according to claim 14 is caused by the rotational movement of the substrate to be coated at least at a part from the first position to the second position. The control means for controlling the moving means so as to be in the opposite direction to the flowing direction of the liquid can also control the discharge amount of the coating liquid from the discharge means.

The control of the discharge amount of the coating liquid is performed according to claim 16.
As described above, the temperature around the discharge means and / or the temperature around the substrate to be coated is controlled, the height of the liquid level of the coating liquid in the tank is controlled, and a plurality of fine particles are formed by using the air flow. This is performed by controlling the air flow of the inkjet head that discharges the coating liquid from the nozzle.

With such control means, the application of the coating liquid is further performed without being influenced by the surrounding environment.

Further, for the purpose of eliminating or compensating for environmental fluctuations in the surroundings, a tank for storing the coating solution and an air flow of the coating solution from the tank are provided as described in claim 19. Ejecting means for ejecting onto the substrate to be coated from a plurality of fine nozzles using the first position, first position where the ejection of the coating liquid onto the substrate to be coated is started, and ejection of the coating liquid And a rotation means for rotating the substrate to be coated, a temperature around the discharge means, and / or
Alternatively, by controlling the temperature around the substrate to be coated, and / or by controlling the height of the liquid level of the coating liquid in the tank, and / or by controlling the air flow, A configuration having a control unit that controls the discharge amount of the coating liquid can also be adopted.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

(Embodiment) FIG. 1 is a schematic configuration diagram of a coating apparatus in the present embodiment.

In FIG. 1, 10a is a θ stage and 10 is a stage.
Reference numeral b denotes an X stage, which can independently apply the rotational movement and the translational movement to the substrate 11 to be coated.

Here, the substrate 1 to be coated in the present embodiment
1 is an optical disk, and as described later, this surface is
It has a structure in which a metal vapor deposition film is applied only in the vicinity of the signal recording area of the polycarbonate substrate.

Next, 12 is an ink jet head represented by a pneumatic control system, 13 is a coating liquid tank for storing a coating liquid, and 14 is a pressure control system. This pressure control system 14
Is connected as shown in the drawing, and controls the air pressure and the air flow rate) so that a predetermined discharge amount can be obtained from the inkjet head 12.

Here, the coating liquid in this embodiment is U
This is a V-curable resin solution, which is used to form a protective film for preventing deterioration of a metal vapor deposition film of an optical disk as described later.

Further, since the pneumatic head 12 of the pneumatic control system continuously ejects a large amount of air downward while the pressurized air is supplied, the inkjet head is too close to the substrate. If so, the liquid surface after coating may be roughened by an air flow depending on the thickness of the coating film.

On the other hand, if the ink jet head is located too far from the substrate, the droplets from the nozzle will be diffused before reaching the substrate surface, and the boundary at the beginning of coating will be unclear. Since the coating liquid may be sprayed to an unnecessary region of the film, the distance between the two is determined in consideration of these points, but in the present embodiment, the distance is set to 3 mm to 5 mm.

Next, a centralized control system 15 controls the movement of the θ stage 10a and the X stage 10b, and controls the on / off timing of the discharge of the coating liquid. In cooperation with the environment control systems a to c and the pressure control system 14 described above, it also operates so as to cancel the influence on the coating device due to environmental changes around the coating device such as temperature, humidity and atmospheric pressure.

Specifically, the discharge amount of the coating liquid mainly depends on the following parameters. (1) viscosity and surface tension of the coating liquid; (2) air flow rate supplied to the inkjet head; and (3) liquid level height of the coating liquid tank based on the height of the nozzle surface of the inkjet head. is there.

Therefore, in order to prevent the parameters (1) to (3) from being affected by the fluctuations in the surrounding environment, the central control system 15 passes the environment control systems 16 and 18 to (1)
In order to control the viscosity and surface tension of the coating liquid of (1), temperature control is performed in the vicinity of the inkjet head 12 and the substrate 11 to be coated, and the air pressure control and the air flow rate control of (2) are performed via the pressure control system 14, Then, the height control of the liquid surface of (3) is performed through the environment control system 17.

Further, the physical properties of the coating liquid are preferably independent of lots, do not change with time, and are always constant, but in practice, there are some variations.

As a countermeasure for this, the physical properties of the coating liquid may be adjusted by monitoring it on a lot-by-lot basis or on a daily basis, or a coating liquid having a physical property value within a predetermined range may be selected and used in advance. Will lead to a rise.

However, if an environment control system is provided as in the present embodiment, such variations in the physical properties of the coating liquid are effectively absorbed, and unnecessary cost increase does not occur.

Further, when coating liquids of different liquid types, different physical properties are changed by operating the environmental control system, so that good coating can be achieved without drastically changing the process. It will also be possible to get a face.

This also suggests that the product can be easily transferred to other product lines, which means that it is possible to obtain great benefits such as reduction of equipment investment and improvement of equipment operating rate.

Next, the specific structure and operating principle of the ink jet head 12 shown in FIG. 1 will be described with reference to FIG.

Here, in the ink jet head of this embodiment, a large number of minute nozzles are distributed one-dimensionally or two-dimensionally, and FIG. 2 shows one of them as a representative. FIG. 3 is a cross-sectional view of the nozzle on a plane including the discharge direction of the coating liquid.

First, 19 is a coating liquid discharge port, and 20 is a gas discharge port. Reference numeral 21 denotes a coating liquid supplied from the coating liquid tank 13 of FIG. 1 to the inkjet head 12, and 22 denotes a flow (air flow) of a gas such as air supplied from the pressure control system 4 of FIG. .

In order to generate a stable air flow in the vicinity of the liquid discharge port 19, a bank-shaped convex portion is provided around the discharge side of the gas discharge port 20, and the distance between the liquid body discharge port 19 and the gas discharge port 20 is also increased. Adjusted appropriately.

The convex portion of the liquid discharge port 19 also has a role of improving the stability of the meniscus surface formed by the coating liquid at the outlet of the liquid discharge port 19.

The liquid discharge port 19 and the gas discharge port 20 are arranged coaxially with each other, and an air flow 22 having a constant flow velocity flows out from the gas discharge port 20. A stable pressure Pa is generated in the area.

On the other hand, since the coating liquid tank 13 of FIG. 1 is pressurized by the pressure control system 14, a pressure Pi is generated on the liquid surface of the coating liquid 21 at the liquid discharge port 19.

In FIG. 2A, Pa and Pi are almost equal to each other,
FIG. 2B shows a state in which the coating liquid is held at the discharge port 19.
1 is a state in which the pressure applied to the liquid discharge port 19 is adjusted to a pressure Pb smaller than Pi balanced with Pa by the pressure control of the pressure control system 14 in FIG. 1, and thus the coating liquid is discharged due to the pressure difference (Pi-Pb). Is shown.

Now, the pressure p is applied to the liquid surface of the coating liquid tank 13, the height difference between the liquid surface and the meniscus surface is h, the density of the coating liquid is ρ, and the meniscus surface when the meniscus surface is broken. When the maximum value of the applied pressure is Pmax and the liquid level height h and the pressure p are constant, the following pressure Pb (Equation 1)
If it is adjusted so that, the coating liquid is discharged correspondingly. It is assumed that there is no pressure loss in the coating liquid supply path.

[0058]

[Equation 1] In other words, the discharge amount of the coating liquid per unit time is the same as the apparatus configuration, but the physical properties such as the viscosity, the surface tension and the density of the coating liquid and the liquid level height h which is a geometrical parameter, and the liquid level Is determined by the pressure p applied to the gas and the gas pressure Pb.

Although the discharge amount can be controlled by using any of these parameters, in the present embodiment, the liquid level height h and the pressure that can be widely changed are mainly adjusted. The discharge amount was increased or decreased by Pb.

The remaining parameters are used by the environmental control system for environmental resistance variation.

Here, when adjusting the liquid level height h, it must actually be performed within a certain range.

The reason is that if the liquid surface is too low compared to the meniscus surface, the pressure control system 14 causes Pb to increase to Pi.
Even if the discharge of the coating liquid is stopped, the meniscus surface may not be stable at the coating liquid discharge port 19 and may be broken inward even if the discharge of the coating liquid is stopped, and air may flow back through the coating liquid supply path. There is.

On the other hand, if the liquid surface is too higher than the meniscus surface, even if Pb becomes Pa and the pressure at which the discharge of the coating liquid is supposed to be stopped is reached, the meniscus surface becomes the coating liquid discharge port 1.
The reason is that it does not exist stably at 9 and may be broken to the outside, and the ejection will be continued.

In order to introduce the coating apparatus of the present embodiment into an actual manufacturing line and operate it stably, it is necessary to turn on / off the discharge.
Since it is indispensable to perform the turning-off accurately and promptly, the above-mentioned tearing of the meniscus and spontaneous discharging when the discharging is turned off should not occur.

Therefore, the liquid level height h is set so that the meniscus surface always remains stable in the absence of ejection.
It is necessary to satisfy the following (Equation 2).

[0066]

[Equation 2] Next, the operation of the coating apparatus of this embodiment during the coating process will be described with reference to FIG.

FIG. 3A shows the X stage and the θ stage during the coating process of the UV curable resin solution as the coating liquid on the metal vapor deposition film surface of the optical disk which is the substrate 11 to be coated in the present embodiment. FIG. 3B is a diagram for explaining the operation and the timing of on / off of ejection, and FIG.
6A and 6B are diagrams for illustrating relative movement of the inkjet head 12;

In FIG. 3A, the horizontal axis corresponds to time, the vertical axis corresponds to the rotation speed of the θ stage and the moving speed of the X stage,
The solid line shows the time change of the moving speed of the X stage, the dotted line shows the time change of the rotation speed of the θ stage, and the thick solid line indicates that the ejection state continues.

Here, the coating step in this embodiment is
"Coating liquid supply process" in the first half and "Leveling process" in the second half
It is divided into two.

First, in the coating liquid supplying step, the main operation is to spray the coating liquid from the ink jet head onto the optical disc and to evenly deposit the coating liquid on the optical disc.

In the leveling process, the flow of the coating liquid generated by the inertial force (centrifugal force) in the radial direction of the optical disk is utilized to remove the nonuniformity of the film thickness remaining in the coating liquid supply process. Mainly the operation of driving the film thickness.

The operation in each step will be described below. First, as shown in FIG. 3B, the optical disk which is the substrate 11 to be coated is mounted on the θ stage 10a,
The X stage 10b is moved toward the position directly below the inkjet head 12 at a speed v1. Of course, the movement here may be performed by moving the inkjet head 12.

Next, before the time t2 when the nozzle of the ink jet head 12 reaches the coating start position r1 (t1 <
At t2), the rotational movement of the θ stage 10a is started from time t0 so that the rotation speed of the θ stage 10a reaches θ1.

This is because the θ stage 10a takes longer time to accelerate and decelerate than the X stage 10b unless special consideration is given. Therefore, acceleration of the θ stage 10a is started earlier in time and the coating process is performed. This is to reduce the overall time.

Then, the θ stage 10a reaches the rotation speed θ1, and the ink jet head 12 starts the coating at the position r.
When it is positioned at 1, the X stage 10b is stopped and the discharge of the coating liquid starts.

In this state, the X stage 10b moves at time t.
From 2 to time t3, it will be in a waiting state without moving,
The reason why this waiting time is necessary is shown in FIG.
This will be described with reference to FIG.

The waiting time is provided for the following purposes. That is: (a) Improving the coverage at the starting point of coating; (b) Smoothing the shape of the coating liquid at the beginning of coating;
And (c) creating a starting point for the radial flow of the coating liquid,
It is.

First, as shown in FIG. 4A, the surface of the optical disk, which is the substrate 11 to be coated, has a structure in which a metal vapor deposition film is applied only in the vicinity of the signal recording area of the polycarbonate substrate. In the optical disc, the area where the polycarbonate surface is exposed and the area of the metal vapor deposition film are adjacent to each other.

Since the UV-curable resin functions as a protective film for preventing deterioration of the metal vapor deposition film, the region of the metal vapor deposition film must be completely covered and hermetically sealed.

Therefore, the UV curable resin must be applied from the outside of the region of the metal vapor deposition film, that is, from the polycarbonate raw surface side. However, since the polycarbonate raw surface and the metal vapor deposition film surface have different wettability with respect to the UV curable resin. However, the coating liquid may be repelled at the boundary between the two regions, and the coating property of the coating liquid and the uniformity of the film may be deteriorated.

In order to prevent this, it is necessary to improve the coverage by supplying a larger amount of coating liquid per unit area at the beginning of coating, as compared with the subsequent coating region.

Next, in the leveling step, although it is the same as a generally used step, it is necessary to form the coating film by utilizing the radial flow of the coating solution generated by the centrifugal force. .

Here, if the boundary at the beginning of applying the coating liquid is
If it is not circular with the rotation axis of the θ stage 10a as the axis of symmetry, the centrifugal force applied to the coating liquid at the coating start position will be partially different, and a uniform flow of the coating liquid in the radial direction will occur. Since it disappears, a coating state with a spoke-like film thickness distribution as shown in FIG.

Therefore, in order to make the boundary shape at the beginning of coating circular, it is also necessary to supply a large amount of coating liquid per unit area at the beginning of coating, as compared with other areas to be coated thereafter.

Further, the signal recording area of the optical disc has a large number of minute pits called pits, and the distribution state varies depending on the type of data recorded on the optical disc.

This means that the wettability of the coating liquid has a non-uniform distribution, and in order to obtain a good coating film surface, the flow of the coating liquid which is not affected by the wettability of the surface due to the pits is required. Is.

For that purpose, it is necessary to facilitate the flow of the coating liquid in the radial direction so that the coating liquid reaches the outer periphery of the substrate.

Therefore, as shown in FIG. 4 (c), it is necessary to increase the film thickness at the beginning of coating compared to other regions thereafter, thereby forming the beginning of flow.

Now, returning to FIG. 3 again, after the waiting state from time t2 to t3 having such an effect, X
The stage 10b moves to the coating end position r2 at the speed v2 and stops (time t4). Needless to say, the inkjet head 12 may be moved here.

The speed v2 during coating is calculated by the following (Equation 3) from the discharge amount of the ink jet head and the liquid amount required for coating one substrate.

[0091]

(Equation 3) Here, t is the final protective film thickness, n is the ratio of the coating liquid supply amount of the optical disk to the liquid amount that finally remains as a film, ρ is the coating liquid density, π is the circular constant, and v is the inkjet. The mass of the coating liquid ejected from the head per unit time, k represents the volumetric shrinkage during curing, but in the present embodiment, t = 3 μm, n = 2, ρ = 1.07 g / cm, respectively.
³ , v = 0.8 g / min, k = 0.098, (t3−
t2) = 0.1 sec, (t5-t4) = 0.2 se
c, r1 = 17.5 mm and r2 = 59.5 mm.

As described above, in this embodiment, the supply amount of the coating liquid is suppressed to twice the required liquid amount (n = 2),
It can be seen that the supply amount is remarkably reduced as compared with 50 times that of the conventional spin coater.

It is possible to further reduce the supply amount of the coating liquid in this embodiment, but in consideration of the process reliability, n = 2.

When such parameters are adopted, the speed v2 during coating of the ink jet head is about 480 mm / min.

Now, one of the important parameters for determining the final smoothness of the surface of the protective film is θ in the coating liquid supplying step.
The rotation number θ1 of the stage 10a can be raised.

In the conventional spin coating method, the uneven distribution of the thickness of the coating liquid formed in the coating liquid supplying step cannot be compensated by the shake-off in the subsequent leveling step.
When the amount of the supplied liquid is reduced, the surface accuracy of the coating film tends to be extremely reduced.

That is, also in this embodiment, since the supply liquid amount is extremely reduced to n = 2, the surface accuracy of the coating film is
It does not depend on how uniformly the coating liquid is applied on the entire surface of the optical disc in the coating liquid supplying step.

Therefore, in the present embodiment, basically, an ink jet head having the ability to uniformly spray a small amount of liquid over a wide area is used.

At the same time, when the position of the inkjet head is fixed when the coating liquid is ejected from the inkjet head, the optical disc is relatively moved to the side opposite to the direction in which the coating liquid flows on the optical disc ( That is, when the position of the optical disk is fixed, the inkjet head is moved relative to the direction in which the coating liquid flows), and the coating liquid is sequentially applied in the flowing direction.

However, the nozzles of the ink jet head in this embodiment are arranged one-dimensionally as shown in FIG. 3B, and the arrangement direction is perpendicular to the moving direction of the X stage. .

If the rotation speed θ1 is too small and the coating liquid ejected from the nozzle is hard to flow on the optical disc, the coating liquid draws a record-disc-shaped locus on the optical disc, and the leveling process is devised. However, the surface accuracy of the coated surface is not improved.

On the other hand, when the rotation speed θ1 is too large and the flow of the coating liquid is strong, a part of the coating liquid supplied from the coating liquid supplying step is shaken off, and as shown in FIG. 4B. Spoke-like uneven coating appears.

That is, it can be seen that the rotation speed θ1 has an appropriate usable area. In this embodiment, θ1 = 1500 rpm was specifically set, and a good coated surface comparable to the conventional spin coating method was obtained.

At this number of revolutions, a good coating surface with a small film thickness distribution can be obtained at the end of the coating liquid supply step, so that no abnormal flow occurs during the leveling step and the final surface shape is Although it will be better, as a result of a more detailed study, at this rotation speed, when the position of the inkjet head is fixed in the discharge area where the coating liquid is discharged from the inkjet head, the coating liquid on the optical disk is considered. In addition to the fact that the optical disc is relatively moved to the side opposite to the direction in which the fluid flows (that is, if the position of the optical disc is fixed, the inkjet head is relatively moved in the direction in which the coating liquid flows). It was confirmed that their speeds were almost equal.

That is, in the discharge area where the coating liquid is discharged onto the substrate to be coated, the flowing direction of the coating liquid on the substrate to be coated and the X stage on which the substrate to be coated is moved relative to the inkjet head. The opposite direction,
In addition, the flowing speed of the coating liquid and the relative moving speed of the X stage and the inkjet head are almost equal,
It was confirmed that the conditions were such that the best film surface was formed at the end of the coating liquid supply step.

Next, returning to FIG. 3 again, the description will be continued. In FIG. 3, the X stage 10b moves at time t4.
It moves to position r2 and stops.

Then, at the coating end position r2, the ejection is continued in the waiting state until time t5.

This stop waiting state is also shown in FIG.
Similar to the state of waiting for the start of coating to be stopped, it is provided to improve the coating property at the coating end position, but more specifically, it improves the coating property in the boundary area between the metal deposition film and the polycarbonate surface. In addition to
As shown in (a), it also includes coating on the side surface of the substrate.

Further, as shown in FIG. 5 (b), a bulged area with poor coverage may be formed near the edge of the substrate during the molding of the substrate. The stop waiting state from t4 to time t5 is necessary.

Then, at the end time t5 of the waiting state, the discharge of the coating liquid is also turned off, and the coating liquid supplying step is finished here.

After that, the X stage starts to convey the optical disc toward the apparatus in the next step shown in the drawing at a speed v3, while the θ stage drives the optical disk to a desired film thickness and leveling step for flattening the film surface. Start changing the rotation speed for.

Specifically, the rotation is accelerated from time t6 to time t7, and the rotation speed is increased from θ1 to θ2.

In this case, the carrying step and the leveling step do not have to be carried out at the same time, but if carried out at the same time, it is more efficient because the film thickness can be increased and flattened during the carrying.

Then, at time t8, rotation at a constant speed of θ2 is continued at a constant speed to finish driving into the desired film thickness and flattening of the film surface, and then decelerating by time t9 to stop the rotational motion. Then, the leveling process is completed.

The speed change of the θ stage is slower than that of the X stage.
In addition to the poor followability of the stage, the rapid acceleration / deceleration is slowed down in consideration of the possibility of causing an abnormal flow of the coating liquid in the azimuth direction.

In order to obtain the uniformity of the film thickness formed by using the leveling process as described above, a surplus amount of the coating liquid necessary for the original coating on the substrate is put on the substrate and the surplus is applied. It means that the liquid of the above is shaken off.

However, when this leveling process is used, the film thickness distribution after the leveling process is substantially dependent on the film thickness distribution at the start of the leveling process by giving a sufficient number of rotations and a time for shaking off. Therefore, it is premised that this leveling process is used rather than forming a very uniform film thickness distribution only in the previous coating process.At the previous stage, a uniform flow of the coating solution in the radial direction occurs. It is more efficient to set the film thickness distribution so that it can be easily performed.

For example, when a highly viscous UV curable resin solution having a predetermined uniform thickness adheres to a flat substrate to be coated such as an optical disk, the inertial force of the substrate when the substrate starts accelerating motion. The so-called shear motion of the liquid due to the above-mentioned is started, and the flow rate of the liquid due to the shear motion is proportional to the product of the cube of the thickness and the acceleration. Further, when the acceleration motion is a rotational motion, this inertial force is inversely proportional to the distance from the center, so that the flow rate of the coating liquid due to the shearing motion in the leveling step decreases in proportion to the distance from the center. That is, it means that the coating liquid is more likely to flow toward the central portion.

Therefore, although a large coating amount is required in the leveling step, the flow rate of the coating liquid can be appropriately adjusted, and as a result, a uniform film thickness distribution can be obtained efficiently. Become.

For more specific examination, a film thickness distribution that is constant regardless of the distance from the center, a film that decreases proportionally, and a film that decreases proportionally to the square are produced. The same leveling process was performed.

As a result, spoke-shaped nonuniformity was generated in the outer peripheral portion of the film with a constant film thickness, and spoke-shaped nonuniformity was observed in the central portion of the film with a decrease in proportion to the square. As a result, a film having good uniformity in the azimuth direction was formed.

This is because a film having a constant film thickness undergoes a rapid shearing motion on the outer periphery of the substrate, and a film having a proportion to the square has a shearing motion in the area at the beginning of coating, whereas a film having a proportional film thickness. It is considered that the film having the thickness distribution is because a uniform film was formed because the layered flow phenomenon occurred well in the entire coating region during the leveling process.

Here, in the present embodiment, in the coating liquid supplying step, the coating liquid is discharged in the direction in which the coating liquid flows on the substrate to be coated in the discharge region where the coating liquid is discharged from the ink jet head. By relatively moving the inkjet heads that are moving and making their speeds substantially equal, the film thickness distribution of the thin film formed at the end of this coating liquid supply step is substantially centered as shown in FIG. Since then, it has decreased proportionally.

Therefore, in the present embodiment, a layered flow phenomenon occurs well in the entire coating area during the leveling process, and as a result, an extremely uniform thin film is formed.

By the way, the UV curable resin film formed according to this embodiment generally has good uniformity in the azimuth direction, but if the leveling process is not sufficient, the film thickness increases in proportion to the distance from the center. There are cases.

This film thickness distribution can be relaxed by shaking off the excess coating liquid in the leveling process. However, when the viscosity of the coating liquid is low, the target film thickness and the uniformity of the film thickness can be reduced. Sometimes they are incompatible.

In such a case, it suffices to increase the viscosity of the coating liquid. Specifically, for example, the environment control system 16 and the environment control system 18 of FIG. It is enough to lower the temperature of the liquid.

Unlike the present embodiment, even if the θ stage 10a is fixed, the same effect can be realized by relatively sweeping the ink jet head 12 one-dimensionally with respect to the θ stage 10a. Is possible. However, considering the piping of air and coating liquid to the inkjet head 12 and the transfer of the substrate to the next step, realization of the sweep mechanism of the inkjet head 12 is complicated in terms of the apparatus configuration.

In the present embodiment, the ink jet head of the air flow control system is used, but of course, another ink jet head of another ejection system may be used as long as the coating liquid can be ejected.

The control of the discharge amount is possible in principle by using only one of the above-mentioned three parameters or a combination of the two, and all of the environment control systems 16-18 shown in FIG. It is not always necessary, and it is possible to suppress fluctuations in the discharge amount with respect to environmental fluctuations around the coating device by using any one or a combination of the two.

[0131]

As described above, according to the present invention, it is possible to form a smooth thin film without local nonuniformity of the film thickness.

At the same time, the use efficiency of the coating liquid can be greatly improved, and the cost for forming a thin film can be greatly reduced.

Furthermore, if an environment control system is provided, it is possible to effectively eliminate the influence of environmental changes around the thin film forming apparatus such as temperature, humidity and atmospheric pressure on the thin film formation, and to form a thin film of stable quality. did.

At the same time, the lot management can be simplified by effectively eliminating the change in the physical property value of the coating liquid for each lot, and the formation of a thin film having a high degree of freedom in application to different liquid types was realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a thin film forming apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a nozzle portion of an inkjet head of the thin film forming apparatus.

FIG. 3 is an explanatory view explaining the operations of the X stage and the θ stage during the same thin film forming process.

FIG. 4 is an explanatory view explaining the necessity of waiting time at the beginning of coating during the thin film forming process.

FIG. 5 is an explanatory diagram for explaining the necessity of waiting time at the end of coating during the thin film forming process.

FIG. 6 is an explanatory diagram showing a film thickness distribution of the coating liquid in the radial direction of the optical disk which has finished the coating liquid supply step in the thin film forming step.

FIG. 7 is an operation explanatory view of a conventional thin film forming method.

[Explanation of symbols]

 10a θ stage 10b X stage 11 substrate to be coated (optical disk) 12 inkjet head 13 coating liquid tank 14 pressure control system 15 centralized control system 16 environment control system a 17 environment control system b 18 environment control system c 19 coating liquid discharge port 20 gas Discharge port 21 Coating liquid 22 Gas flow

Front page continued (72) Inventor Toshiyuki Iwasawa 3-10-1, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Matsushita Giken Co., Ltd. (72) Hiroyuki Naka, 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Within

Claims (19)

[Claims] 1. A first moving step of relatively moving a substrate to be coated from a discharge head to a first position at which a coating liquid starts to be discharged; and a substrate to be coated at the first position, A second moving step of relatively moving the ejection head to a second position where the coating liquid is completely ejected from the ejection head; and a substrate to be coated at the second position is further moved relative to the ejection head. A third moving step, at least a time step overlapping with the second moving step, a rotating step for rotating the substrate to be coated, a time step overlapping with the second moving step and the rotating step. A thin film forming method of forming a thin film by discharging a coating liquid from the discharge head onto the substrate to be coated, wherein the relative movement in the second moving step is the substrate to be coated. Applied by the rotating motion of A method for forming a thin film, which is in a direction opposite to a flowing direction of a cloth liquid. 2. The relative movement in the second movement step is opposite to the flow direction in which the coating liquid flows due to the rotational movement of the substrate to be coated, and the relative movement speed is the flow. The thin film forming method according to claim 1, wherein the speed is substantially equal to the speed. 3. The amount of the coating liquid discharged per unit area on the substrate to be coated at the first position is equal to the unit area on the substrate to be coated from the first position to the second position. The thin film forming method according to claim 1, wherein the amount is larger than the amount of the applied coating liquid. 4. The amount of the coating liquid discharged per unit area on the substrate to be coated at the second position is equal to the unit area on the substrate to be coated from the first position to the second position. The thin film forming method according to any one of claims 1 to 3, wherein the amount is larger than the amount of the ejected coating liquid. 5. The relative movement of the substrate to be coated is stopped for a predetermined period after the start of discharging the coating liquid and / or for a predetermined period after the discharging of the coating liquid. Thin film forming method. 6. A predetermined period before the start of discharging the coating liquid and / or
Alternatively, the thin film forming method according to claim 1, wherein the substrate to be coated is rotationally moved for a predetermined period after the discharge of the coating liquid is completed. 7. The second moving step is started after a lapse of a predetermined period from the first moving step, and the third moving step is started after a lapse of a predetermined period from ending the second moving step, The thin film forming method according to claim 1, wherein the rotating step is started before starting the second moving step and ended after ending the second moving step. 8. The method further comprises a second rotating step of rotating the substrate to be coated after the discharge of the coating liquid, wherein the number of rotations in the second rotating step is the rotation before the second rotating step. The thin film forming method according to claim 1, wherein the thin film forming method is larger than the number of rotations of the movement. 9. The thin film forming method according to claim 8, wherein the second rotating step and the third moving step temporally overlap with each other. 10. The substrate to be coated is a disc-shaped substrate, and the second substrate
10. The thin film formation according to claim 1, wherein the relative movement in the moving step is a uniform linear motion passing through the center of the disk-shaped substrate, and the rotary motion in the rotating step is a constant rotary motion. Method. 11. The substrate to be coated partially has a layer of a second material on a substrate of a first material, and a boundary portion between the substrate and the layer of the second material is also coated with the coating liquid. The method for forming a thin film according to claim 3, wherein the thin film forming method is performed. 12. The thin film forming method according to claim 11, wherein the substrate to be coated is also coated with the coating liquid on the side surface of the substrate to be coated. 13. The thin film forming method according to claim 1, wherein the ejection head has a control step of ejecting the coating liquid from a plurality of fine nozzles and further controlling the ejection amount of the coating liquid. . 14. A tank for storing the coating liquid, and a discharging means for discharging the coating liquid from the tank onto the substrate to be coated,
A moving unit that relatively moves the substrate to be coated with respect to the discharging unit so as to pass through a first position where the discharging of the coating liquid starts and a second position where the discharging of the coating liquid ends. A rotating means for rotating the substrate to be coated and a relative movement of the substrate to be coated with respect to the discharging means at least at a part from the first position to the second position. A thin film forming apparatus comprising: a control unit that controls the moving unit so as to be in a direction opposite to a flow direction in which the coating liquid flows due to a rotational movement. 15. The thin film forming apparatus according to claim 14, wherein the control means also controls the discharge amount of the coating liquid from the discharge means. 16. The thin film forming apparatus according to claim 15, wherein the control unit controls the temperature around the discharge unit and / or the temperature around the substrate to be coated to control the discharge amount of the coating liquid from the discharge unit. 17. The thin film forming apparatus according to claim 15, wherein the control unit controls the height of the liquid surface of the coating liquid in the tank to control the discharge amount of the coating liquid from the discharging unit. 18. The discharge means discharges the coating liquid from a plurality of fine nozzles by utilizing the air flow, and the control means controls the air flow to control the discharge amount of the coating liquid from the discharge means. The thin film forming apparatus according to claim 15, which is controlled. 19. A tank for storing a coating liquid, a discharging means for discharging the coating liquid from the tank onto a substrate to be coated from a plurality of fine nozzles by using an air flow, and the substrate to be coated. Rotating the substrate to be coated and a moving unit that moves relative to the device so as to pass through a first position where the discharge of the coating liquid starts and a second position where the discharge of the coating liquid ends. And / or controlling the temperature around the discharge means and / or the temperature around the substrate to be coated, and / or controlling the height of the liquid level of the coating liquid in the tank, and / or Alternatively, a thin film forming apparatus having a control unit that controls the air flow to control the discharge amount of the coating liquid from the discharge unit.