JPH08196983A - Thin film forming method - Google Patents

Abstract

PURPOSE: To reduce running costs and to process at a high speed in a thin film forming method in which a liquid substance is discharged from fine nozzles to be stuck on a substrate, and the substance is dried and cured. CONSTITUTION: An ink jet head 11 having more than one fine liquid discharging nozzle 12 and a substrate 10 are rotated at the first relative velocity so that the surface of the substrate 10 is coated uniformly with a liquid to form the first coating state. Next, the head 11 and the substrate 10 are rotated at the second relative velocity which is larger than the first relative velocity to form a thin film in the second coating state which is more uniform than the first one by scattering off excessive liquid applied on the substrate in the first coating state.

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,
In particular, the present invention relates to a method of ejecting a liquid substance from a fine nozzle to adhere it to a substrate, drying and curing the adhered liquid substance to form a thin film (in a broad sense, a film thickness of 100 μm or less, generally 10 μm or less). It is a thing.

[0002]

2. Description of the Related Art In recent years, thin film technology has been applied in various fields, and spin coating, printing, die coating, etc. are being studied in addition to the method requiring a vacuum device such as sputtering or vapor deposition. Has been done.

In particular, spin coating is often used for resist coating and protective film formation in semiconductor processes.

A conventional spin coater (spin coater) will be described below. FIG. 6 shows a process of forming a thin film using a conventional general spin coater,
You.

In FIG. 6, 101 is a rotating shaft of the spin coater main body, 102 is a sample fixing substrate, 103 is a nozzle for ejecting a coating liquid, 104 is a thin film forming substrate, 10
5 and 106 are liquids, 107 is a thin film, and 108 is a scattered droplet.

In such a structure, first, FIG.
As shown in FIG. 3, the liquid 105 is placed on the substrate 104 by the nozzle 103.

Then, as shown in FIG. 6 (b), the spin coater is rotated at a low speed ω ₁ to bring the liquid 106 into the substrate 1.
Get used to 04.

Then, as shown in FIG. 6C, the thin film 107 is formed on the substrate 104 by rotating at a high speed rotation ω ₂ .

[0009]

However, in the above-mentioned conventional structure, as shown in FIG. 6 (c), scattered droplets 108 that are scattered and useless are generated, and the liquid droplets 80 to 90 are discharged. The result is that% is discarded.

This is because if the liquid 105 is not ejected in a sufficient amount, an unpainted portion will be formed in a portion that is not well compatible with the substrate 104, so that the liquid 105 must be ejected in a large amount.

As described above, the conventional spin coater has a problem that the use efficiency of the liquid is poor and most of the coating liquid is wasted.

The present invention solves the above-mentioned problems of the prior art, and an object of the present invention is to introduce a new liquid ejection head to provide a thin film forming method with high utilization efficiency of a coating liquid.

[0013]

In order to achieve this object, the present invention provides an inkjet head having a plurality of fine liquid ejecting nozzles for ejecting a liquid, and a substrate to which the liquid is attached. Is rotated at a first relative speed sufficient to be adhered onto the surface of the substrate, and the liquid is applied almost uniformly onto the substantially entire surface of the substrate to realize a first applied state, and After the coating step, the first relative speed is rotated at a second relative speed, which is higher than the first relative speed.
Forming a thin film on the substrate, which has a second coating state in which the coating state is made more uniform than the first coating state and the coating liquid excessively applied from the first coating state is scattered. This is a thin film forming method.

Further, the ink jet head may be an electrostatic suction type ink jet head for sucking and discharging the liquid to the outside of the liquid discharge nozzle by electrostatic force. In this case, a liquid having a viscosity of 50 cP or less is used. be able to.

Alternatively, the ink jet head may be an ink jet head which ejects a liquid by applying a differential pressure outward from the liquid supply source side to the meniscus formed in the liquid ejection nozzle. In this case, the liquid ejection is performed. An air discharge nozzle is provided opposite to the liquid discharge nozzle, an air flow is discharged outward through a gap between the liquid discharge nozzle and the air discharge nozzle, and the liquid is discharged to a meniscus formed in the liquid discharge nozzle. The liquid may be discharged to the outside by riding on the air flow by setting the air pressure in the vicinity of the air discharge nozzle side of the liquid discharge nozzle smaller than the air pressure applied from the supply source side.

[0016]

With the above structure, the coating liquid is deposited on substantially the entire surface of the substrate which has been relatively rotated at a relatively low speed using a plurality of discharge nozzles in advance, and then the substrate is relatively rotated at a higher speed to remove unnecessary liquid. Make the coating liquid more uniform while scattering.

Therefore, the coating liquid that is scattered and wasted is minimized, and the time required for film formation is greatly shortened.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(First Embodiment) The first embodiment of the present invention will be described below.

FIG. 1 is a schematic configuration diagram of a spin coater used in a thin film forming method according to an embodiment of the present invention.

In FIG. 1, 10 is a substrate to be coated,
Reference numeral 11 is an inkjet head, and 12 is a nozzle.

Here, the ink jet head 11 discharges liquid from a minute nozzle (usually 0.1 mm or less),
It refers to a device that controls the ejection state of the liquid by an electric signal to attach the liquid to the recording medium.

There are a plurality of nozzles 12, which are arranged at regular intervals in the radial direction of the rotating substrate 10 to be coated.

The process of forming a thin film in such a structure will be described below. First, the nozzle 12 of the inkjet head 11 is rotated while the substrate 10 to be coated is rotated at a low speed.
The coating liquid is further discharged toward the substrate 10 to be coated, and the coating liquid starts to adhere to the substrate 10 to be coated.

Then, the coating liquid is ejected from the nozzle 12 of the ink jet head 11 toward the coating substrate 10 while rotating the coating substrate 10 at a low speed until the coating liquid is adhered to almost the entire surface of the coating substrate 10. . That is,
This low-speed rotation may be one that realizes a rotation speed sufficient for the coating liquid to adhere to the surface of the substrate 10 to be coated.

At this time, when the pitch between the plurality of nozzles 12 is wide and the lines of the coating liquid formed by the adjacent nozzles are separated without overlapping, the ink jet head 11 is moved in the radial direction of the substrate 10 to be coated. While moving the substrate 10 to, the substrate 10 to be coated is rotated a plurality of times at low speed,
The coating liquid is adhered to the entire surface of the substrate 10 to be coated without any gap.

Next, after confirming that the coating liquid has adhered to almost the entire surface of the substrate 10 to be coated, the substrate 10 to be coated is rotated at a high speed that is higher than the previous low speed rotation, and the excessively applied coating liquid is applied. And the uniformity of the coating film is further improved, and a thin film is formed on the substrate 10 to be coated.

Conventionally, the discharge nozzle used in the spin coater has an inner diameter of 0.5 to 1 mm, and it is difficult to control the minute discharge amount. However, as in this embodiment, the ink jet head 11 is used. By using it, a fine pattern can be drawn and a uniform and very thin film can be formed.

Further, according to the present embodiment, since the coating liquid is previously coated on the entire surface of the substrate 10 to be coated by the ink jet head 11, the amount of the coating liquid to be scattered at the time of high speed rotation can be small and the running cost can be reduced. it can. At the same time, the processing time is greatly reduced.

(Second Embodiment) A second embodiment of the present invention will be described below.

FIG. 2 is a sectional view of a main part of a spin coater showing an example of a detailed structure of an ink jet head used in the thin film forming method in one embodiment of the present invention.

In general, there are various types of ink jet recording systems, such as a bubble jet system in which bubbles are generated by thermal energy and liquid is ejected at the pressure, or a liquid chamber is compressed by a piezo element and pressure waves are generated by the pressure wave. There is a piezoelectric type on-demand method for ejecting a liquid, but these methods have many restrictions on the liquid that can be ejected, and for example, only those with a very small value of 1 to 5 cP can be used.

On the other hand, in comparison with these methods, the use of the ink jet head having a structure called the electrostatic suction method shown in FIG. 2 makes it possible to eject a liquid having a relatively high viscosity (about 50 cP or less).

In FIG. 2, reference numeral 20 is a substrate to be coated, 21 is an inkjet head of an electrostatic suction system, 22 is a discharge nozzle, and 23 is a substrate fixing base made of a conductive material such as metal, which serves as an electrode. I also have

Further, 24 is a high voltage generating circuit, and 25 is a liquid chamber. The operation of the spin coater configured as described above will be described below.
The principle is the same as that of the first embodiment.

First, the substrate 20 to be coated is rotated at a low speed, and the substrate fixing base 23 and the liquid chamber 25 are driven by the high voltage generating circuit 24.
During this period, a high voltage pulse is applied for a certain period.

While this high-voltage pulse is being applied, the meniscus of the liquid formed in the discharge nozzle 22 is sucked and discharged toward the substrate fixing base 23, and the substrate 2 to be coated 2 is coated.
0 is attached.

Generally, when the distance between the discharge nozzle 22 and the substrate fixing base 23 is 2 to 3 mm, the liquid can be discharged with a voltage of about 2 to 4 kV.

In such an electrostatic suction type ink jet, a solution of an organic solvent having a high insulating property of about 50 cP or less can be applied, and a polyimide solution, a resist solution or the like can be ejected.

Next, after confirming that the coating liquid has adhered to almost the entire surface of the substrate 20 to be coated, the substrate 20 to be coated is rotated at a high speed that is higher than the previous low speed rotation, and the excessively applied coating liquid is applied. And the uniformity of the coating film is further improved, and a thin film is formed on the substrate 20 to be coated.

Also in this embodiment, a finer pattern can be drawn as compared with the conventional spin coater, and a uniform and extremely thin film can be formed.

Further, since the coating liquid is applied to the entire surface of the substrate 20 to be coated by the ink jet head 21 using electrostatic force in advance, the amount of the coating liquid scattered at the time of high speed rotation can be small and the running cost can be reduced. ,at the same time,
The processing time is also greatly reduced.

(Embodiment 3) The third embodiment of the present invention will be described below.

FIG. 3 is a sectional view of a main part of a spin coater showing an example of a detailed structure of an ink jet head used in the thin film forming method in one embodiment of the present invention.

In FIG. 3, 30 is an ink jet head, 31 is an air supply source, 32 is a liquid reservoir, 33 is a pressure adjusting mechanism, 34 is a liquid inlet, 35 is an air inlet, 36 is an air outlet, and 37 is an outlet. It is the exit.

Inkjet head 3 in this embodiment
No. 0 uses an air flow, and the air flow from the air supply source 31 is sent to the liquid reservoir 32 on the one hand to apply a constant pressure to the liquid in the liquid reservoir 32, and on the other hand, the pressure adjusting mechanism 33.
To the air inlet port 35 of the inkjet head 30.

The air flowing into the head 30 through the air inlet 35 flows out through the air outlet 36 at a constant flow velocity.

On the other hand, the liquid in the liquid reservoir 32 flows into the head 30 through the liquid inflow port 34 and is guided to the ejection port 37.

Further, the pressure adjusting mechanism 33 includes the ejection head 30.
The air flow rate to be sent to the air conditioner is adjusted. For example, the configuration shown in FIG. 4 can be adopted.

FIG. 4 shows the air flow from the air supply source 31
The structure which switches a flow path by the solenoid valve 50 is shown.

In FIG. 4, in the normal state, the air flow is designed to flow along the path A, but when the signal of the discharge command is applied during the liquid discharge, the air flow is switched to the flow path B.

Since the flow path B is provided with a flow path resistor 51 such as a throttle valve having a large pressure loss in the flow path, the flow rate of the air flowing into the ink jet head 30 is reduced. .

Next, FIG. 5 shows an ink jet head 30.
3 is an enlarged sectional view of the vicinity of the air discharge port 36 and the discharge port 37 of FIG.

FIG. 5A shows a state in which the liquid is not ejected, and the air pressure Pa near the outlet of the ejection port 37 generated by the air flow sent to the head 30 is the air pressure applied to the liquid reservoir. The liquid pressure is almost equal to the liquid pressure Pi, and the meniscus of the liquid is stably held in the ejection port 37.

On the other hand, the solenoid valve 40 shown in FIG.
When the air flow changes from the route A to the route B, FIG.
As shown in (b), the air pressure near the discharge port drops to Pb,
The pressure of the liquid becomes higher, the meniscus collapses, and the liquid is ejected.

On the other hand, since the air flow still flows out from the air discharge port 36, the discharged liquid is wrapped in this air flow, passes through the air discharge port 36, and is discharged to the outside. become.

The thin film forming operation itself of the spin coater using the ink jet head 30 having the above structure is the same as that of the first embodiment in principle.

Therefore, although a detailed description is omitted, also in this embodiment, a finer pattern can be drawn as compared with the conventional spin coater, and a uniform and extremely thin film can be formed.

Furthermore, since the coating liquid is applied to the entire surface of the substrate to be coated by the ink jet head 30 using electrostatic force in advance, the amount of the coating liquid to be scattered at the time of high speed rotation can be small and the running cost can be reduced. At the same time, the processing time is greatly reduced.

The ink jet head 30 used in this embodiment is inferior in high-speed responsiveness because it is controlled by the solenoid valve 40. However, in order to form a uniform thin film as in the present invention, If there is no need to draw a different pattern, there is no practical problem.

Furthermore, since the method of this embodiment is a simple pressure control method, it is less susceptible to the physical properties of the liquid such as viscosity, surface tension, and specific resistance, and the flexibility of the applicable liquid is large. Have.

Further, in the above embodiments, the substrate to be coated is arranged in the horizontal direction, the vertical axis is the rotation axis, and the liquid is ejected from above. As a result, a thin film having desired properties can be formed. It goes without saying that the configuration is not limited to this, if possible.

[0063]

As described above, according to the present invention, the inkjet head having a plurality of fine nozzles and the substrate are relatively rotated at a relatively low speed, and the coating liquid is adhered to substantially the entire surface of the substrate, and then the substrate is further removed. By relatively rotating at a high speed, a uniform coating thin film can be obtained, and since the liquid that scatters and is discarded can be minimized, a thin film forming method with low running cost and high-speed processing can be provided. Can be provided.

Furthermore, by using an ink jet head, a fine pattern can be drawn and
A more uniform and very thin film can be formed.

In this case, if an electrostatic suction type ink jet is used, a solution of an organic solvent having a high insulating property of about 50 cP or less can be applied, and a polyimide solution, a resist solution or the like can be ejected.

Further, if an ink jet using an air flow is used, it is less affected by the physical properties of the liquid such as viscosity, surface tension, and specific resistance, and the flexibility of the applicable liquid is large.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a spin coater used in a thin film forming method according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an ink jet head of a thin film forming method according to the second embodiment.

FIG. 3 is a cross-sectional view showing an inkjet head of a thin film forming method according to the third embodiment.

FIG. 4 is a configuration diagram showing a pressure adjusting mechanism of an ink jet head of a thin film forming method in the third embodiment.

FIG. 5 is a cross-sectional view showing a nozzle portion of an inkjet head of a thin film forming method according to the third embodiment.

FIG. 6 is an explanatory view of a conventional thin film forming method.

[Explanation of symbols]

 10 substrate to be coated 11 inkjet head 12 nozzle 20 substrate to be coated 21 inkjet head 22 nozzle 23 substrate fixing base 24 voltage generating circuit 25 liquid chamber 30 inkjet head 31 inkjet head 32 liquid reservoir 33 pressure adjustment mechanism 34 liquid inlet 35 air inlet 36 Air Discharge Port 37 Discharge Port 40 Electromagnetic Valve 41 Flow Path Resistor 101 Rotation Shaft 102 Sample Fixed Substrate 103 Nozzle 104 Substrate 105 Liquid 106 Liquid 107 Thin Film 108 Splash Drop

Claims (5)

[Claims] 1. An inkjet head having a plurality of fine liquid ejecting nozzles for ejecting a liquid and a substrate to which the liquid is attached are provided with a first relative position sufficient to attach the liquid onto the surface of the substrate. A coating step of rotating the substrate at a speed to coat the liquid substantially uniformly over the entire surface of the substrate to achieve a first coating state; and a second coating speed larger than the first relative speed after the coating step. Rotating at a relative speed, the first
Forming a thin film on the substrate, which has a second coating state in which the coating state is made more uniform than the first coating state and the coating liquid excessively applied from the first coating state is scattered. Thin film forming method. 2. The thin film forming method according to claim 1, wherein the ink jet head is an electrostatic suction type ink jet head for sucking and discharging the liquid to the outside of the liquid discharge nozzle by electrostatic force. 3. The thin film forming method according to claim 2, wherein a liquid having a viscosity of 50 cP or less is used. 4. The thin film forming method according to claim 1, wherein the ink jet head is an ink jet head that applies a differential pressure outward from a liquid supply source side to a meniscus formed in a liquid ejection nozzle to eject the liquid. 5. An air discharge nozzle is provided so as to face the liquid discharge nozzle, and an air flow is discharged to the outside through a gap between the liquid discharge nozzle and the air discharge nozzle. By setting the air pressure in the vicinity of the air discharge nozzle side of the liquid discharge nozzle to be smaller than the air pressure applied from the liquid supply source side to the meniscus formed in the liquid, the liquid rides on the air flow and is discharged outward. Claim 4
The thin film forming method described.