JPH09299850A - Preparation of thin film and apparatus for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preparing a thin film having a uniform film thickness at a low cost in preparing a thin film by employing a dip coating method and an apparatus for preparing the thin film by using the method. SOLUTION: A substrate (S) is immersed into a coating solution contained in a treating container 1 before the coating solution (L) in the treating container 1 is drained from a bottom of the container while the substrate (S) and the treating container are kept stationary so as to lower surface level of the solution at a constant speed. Thus, a thin film having a uniform thickness can be obtained without using complicated and expensive mechanisms for elevating the substrate and lowering the container.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thin film manufacturing method and apparatus based on a dip coating method.

[0002]

2. Description of the Related Art As a technique for forming a thin film on the surface of a substrate, PV is generally used in the semiconductor manufacturing process and the like.
D method, CVD method, sputtering method and the like can be mentioned.

Further, a thin film having a relatively large thickness (0.04 μm-
There is a dip coating method (sol-gel method) as a technique for obtaining about 1 μm), and this method is widely used in various fields such as the formation of a photocatalyst thin film (titanium oxide thin film, etc.), which has recently attracted attention.

The dip coating method is a method of obtaining a thin film on the surface of a substrate by dipping the substrate in a coating solution and pulling up the substrate or lowering a processing container containing the coating solution. This method is suitable for coating various shapes and for coating large area substrates.

In such a dip coating method, the contact angle (wettability) between the substrate surface and the solution surface
Is kept constant, that is, the pulling rate of the substrate (or the descending rate of the processing container) is constant in order to obtain a coating thin film having a uniform film thickness.

[0006]

However, in the prior art,
Since both the raising of the substrate and the lowering of the processing container are performed by mechanical devices, in order to obtain a coating thin film with a uniform thickness, the substrate lifting speed (or the processing container lowering speed) should be constant. However, it is not enough to control only the above, and it is also necessary to suppress the vibration during the movement of the substrate (or the processing container) and the shaking of the solution surface as much as possible.

Therefore, in the case of the method of pulling up the substrate,
Instead of simply suspending and supporting the substrate, a highly rigid guide is provided in the processing container and the substrate is moved up and down along this guide, but its moving mechanism has a complicated structure and a large size. However, since it is difficult to precisely control such a moving mechanism, there is a problem that the drive / control device and the like become expensive.

In the case of the method of lowering the processing container,
Since the heavy-load processing container containing the coating solution is moved up and down, it is necessary to make the lifting mechanism have a load-bearing structure, so that the above-mentioned problem becomes more remarkable.

In the dip coating method, a large number of substrates can be mass-produced by a batch process in which they are immersed in a coating solution to form a thin film on the surface of the substrates in a state where they are arranged at a predetermined interval. However, when performing such batch processing, the above-mentioned problems of vibration and shaking of the solution surface become remarkable due to the interaction between the substrates adjacent to each other, and more precise control is required than in the single-wafer type. Becomes

[0010] And, although the above-mentioned problems are suitable for coating a large-area substrate or for mass-producing thin films, the dip coating method is
It was a factor that hindered its realization.

The present invention has been made in view of such circumstances, and in producing a thin film by the dip coating method, a method capable of obtaining a thin film having a uniform film thickness at low cost and a thin film utilizing the method. The purpose is to provide a manufacturing apparatus.

[0012]

In order to achieve the above object, the thin film manufacturing method of the present invention is a method for forming a thin film on the surface of a substrate based on a dip coating method, which is a coating solution contained in a processing container. After the substrate is immersed in the substrate and the processing container is kept stationary, the coating solution in the processing container is extracted from the lower part of the container and the solution surface is lowered at a constant speed to form a thin film. To be

By adopting such a method, mechanical vibration is not applied to the substrate and the processing container during the thin film forming process, and the solution surface gently descends due to the outflow of the coating solution itself. It requires less shaking of the surface. Further, since the solution to be controlled is a solution, the control (flow rate adjustment) can be easily performed precisely.

Further, even if the processing container is enlarged, the liquid level control system (flow rate control system) of the coating solution does not become complicated and large, which allows the apparatus for coating a large area substrate and the batch processing. The device can also be easily realized.

The thin film manufacturing apparatus of the present invention is an apparatus utilizing the above-mentioned method of the present invention, and as shown in FIG. 1, a treatment in which the container for containing the coating solution L is provided with the liquid outlet 1a at the bottom thereof. The container 1 and the valve 2 connected to the liquid outlet 1a are provided, and the coating solution L in the processing container 1 is discharged to the outside of the container by adjusting the opening degree of the valve 2, and the solution surface is kept at a constant speed. It is characterized in that it is configured to form a thin film on the surface of the substrate S placed in the processing container 1 by lowering it.

According to the apparatus shown in FIG. 1, the processing container 1
It has a simple structure in which the liquid outlet 1a and the valve 2 are provided in the
In addition, since the coating solution L is discharged to the outside of the container by using gravity, a driving source is not required, so that a very thin film having a uniform film thickness can be obtained.

As another apparatus utilizing the method of the present invention, a plurality of processing vessels, a piping system for interconnecting the liquid inlets and outlets provided at the bottom of each processing vessel, and a piping system connected to this piping system are connected. A liquid transporting means (pump or the like) is provided, and by driving the liquid transporting means, the coating liquid contained in one of the plurality of processing vessels is sent into another processing vessel at a constant flow rate. There is also an apparatus configured to form a thin film on the surface of the substrate S placed in the processing container on the sending side by lowering the liquid level of the coating liquid in the processing container on the sending side at a constant speed.

Further, when a plurality of processing vessels are provided, as shown in FIG. 2, the number of processing vessels is two, and the liquid transportation means (pump unit 14) connected between the processing vessels 11 and 12 is used. ) Drive one processing container 11
After the coating solution L is sent from the other processing container 12 to the other processing container 12, the coating solution L stored in the other processing container 12 may be returned to the one processing container 11 again. In the case of the device shown in FIG.
Since the thin films can be alternately formed in the two processing vessels 11 and 12, the thin films can be efficiently manufactured.

The technical idea of circulating the coating solution between the processing vessels in this way is also applicable to the case where the number of processing vessels is three or more. Here, in the present invention, in addition to a catalytic functional thin film such as a titanium oxide photocatalyst, for example, a chemical / mechanical protective film (antioxidation film, silica glass film, etc.), an optical functional film (reflection film, antireflection film,
It can also be applied to the production of thin films used in various fields such as colored films) or electromagnetic functional films (transparent electrode films, antistatic films, etc.).

[0020]

FIG. 1 is a block diagram of an embodiment of the present invention. The thin film manufacturing apparatus of this example is an apparatus of a type in which gravity is used to lower the coating liquid level in the processing container 1.

The processing container 1 is an open type container whose upper part is opened, and a liquid outlet 1a is provided in the lower part of the side wall.
A flow rate adjustment valve 2 is connected to the liquid outlet 1a of the processing vessel 1, and the operation of the flow rate adjustment valve 2 causes the treatment vessel 1 to operate.
The coating solution L contained inside can be extracted to the outside. During use, the tank T for receiving the coating solution L flowing out from the flow rate adjusting valve 2 is arranged below the processing container 1.

Next, a method of using the apparatus shown in FIG. 1 will be described. First, titanium oxide is diluted with ethanol to prepare a coating solution L in advance, and the coating solution L is housed in the processing container 1. At this time, the flow rate adjusting valve 2 at the liquid outlet 1a is closed. Next, the glass substrate S for forming a thin film is mounted on the support member 3, and the substrate S is immersed in the coating solution L in the processing container 1.

After the above settings are completed, the flow rate adjusting valve 2 is opened [Fig. 1 (A)]. By this valve operation, the coating solution L in the processing container 1 flows out to the outside by the action of gravity, and the surface of the solution descends at a constant speed. Then, when the level of the liquid level of the coating solution L becomes lower than the lower end of the glass substrate S [FIG. 1 (C)], the flow rate adjusting valve 2 is closed. This completes one fabrication process.

Here, in the apparatus of FIG. 1, in order to perform more precise control of maintaining the liquid level lowering speed of the coating solution L, it is necessary to adjust the opening degree of the flow rate adjusting valve 2 in the process of forming the thin film. is there.

That is, as the thin film forming process progresses from the initial state [FIG. 1 (A)] to the final stage through the process [FIG. 1 (B)], the coating solution L is formed.
Of the solution L changes in proportion to the change of the head (energy) of the position of the liquid L. Therefore, the flow rate adjusting valve 2
If the opening degree of is constant, the outflow amount of the solution L decreases, and the descending speed of the solution surface becomes uneven. Therefore, in order to keep the descending speed of the solution surface constant, it is necessary to increase the flow path of the coating solution L, that is, the opening degree of the flow rate adjusting valve 2 in accordance with the degree of decrease of the liquid surface of the coating solution L.

As a method for adjusting the opening degree, for example, a calibration curve of the outflow amount is obtained in advance by calculation or experiment, and the flow rate adjusting valve 2 is controlled by a controller or the like based on the calibration curve. Is mentioned.

FIG. 2 is a block diagram of another embodiment of the present invention. The thin film manufacturing apparatus of this example includes two processing vessels 11 and 12 having the same shape and size, and the respective processing vessels 11 and 12.
It is mainly configured by a pipe system 13 that connects the liquid inlets and outlets 11 a and 12 a provided in the lower part of 12 with each other, and a pump unit 14 and a flow rate control device 15 connected to the pipe system 13.

The pump unit 14 comprises one pump P and four switching valves V1 connected to the suction side and the discharge side thereof.
a, V1b, V2a, V2b, and these four switching valves V1
By opening and closing a, V1b and V2a, V2b, the direction of transport of the solution L by the pump P is changed from one processing container 11 to the other processing container 12 or vice versa; processing container 12 → processing container 11 You can set the crab. Also,
The flow rate control device 15 is generally used,
It is provided to keep the flow rate of the coating solution L moved between the processing vessels 11 and 12 of the table constant.

Next, a method of using the apparatus shown in FIG. 2 will be described. First, the processing solution 11 prepared by diluting titanium oxide with ethanol is filled in the processing container 11 and the piping system 13, and a predetermined amount of the coating solution L is also stored in the processing container 12. Next, the two glass substrates S are mounted on the supporting member 3, and one of the glass substrates S is attached.
Is immersed in the coating solution L in the processing container 11, and the other glass substrate S is placed in the processing container 12.

After the above setting is completed, the switching valves V1a and V1b of the pump unit 14 are opened to switch the switching valve V2a.
And the pump P is driven with V2b closed. The coating solution L in the processing container 11 is driven by the pump,
It is sent out into the processing container 12 through the piping system 13, and the liquid level of the coating solution L in the processing container 11 on the sending side is lowered at a constant speed. Then, when the level of the liquid level of the coating solution L in the processing container 11 becomes lower than the lower end of the glass substrate S, the driving of the pump P is stopped and the switching valves V1a and V1b are closed. This completes the processing (thin film formation) of the glass substrate S placed in the processing container 11, and at this point, the coating solution L is placed in the processing container 12.
And the glass substrate S is immersed in the solution.

Next, after waiting for a predetermined time, the processed glass substrate S is dried (natural drying), and then the glass substrate S is taken out of the processing container 11 and then placed in the processing container 11. The glass substrate S of is set. When this operation is completed, the pump P is driven with only the switching valves V2a and V2b open. By driving the pump, the coating solution L in the processing container 12 is transferred to the processing container 11
Is delivered at a constant flow rate to the inside of the processing container 1 as before.
A thin film is formed on the glass substrate S disposed inside the processing container 2, and the processing solution 11 is filled with the coating solution L.

Then, the glass substrate S in the processing container 12 is dried and taken out, and the next glass substrate S is set to return to the initial state (state of FIG. 2).
The same operation as above is sequentially repeated to obtain two processing vessels 11
The processes (thin film formation) are alternately performed in and.

In the embodiment of FIG. 2, if a constant displacement pump is used as the pump P, the flow control device 15 of the piping system 13 can be omitted. Further, in the embodiment of FIG. 2, a configuration is adopted in which a thin film is formed by both of the two processing vessels 11 and 12, but the invention is not limited to this, and either one of the processing vessels 11 or 12 can be used. Alternatively, a configuration may be adopted in which the thin film is formed only by the other processing container as a container for storing a solution.

FIG. 3 is a configuration diagram (plan view) of still another embodiment of the present invention. The embodiment shown in FIG. 3 is an example in which the number of processing vessels is three, and the bottom of each of the processing vessels 21, 22, and 23 has the same liquid as the previous embodiment. The inlets / outlets 21a, 22a, 23a are provided, and the respective liquid inlets / outlets 21a, 22a, 23a are
They are connected to each other by a piping system 25 having a solution circulation unit 24.

The solution circulation unit 24 is provided with a pump, a switching valve, a flow rate control device, and the like, and when it is driven, the coating solution contained in the first processing container 21 is sent to the second processing container 22 at a constant flow rate. Then, the solution is circulated such that it is sent from the second processing container 22 to the third processing container 23 at a constant flow rate and then returned to the first processing container 21.

In the embodiment of FIG. 3, the second
While the solution is being sent from the processing container 22 to the third processing container 23, the first processing container 21 is in a standby state. During this time, the glass substrate after processing is dried and taken out, and the next glass is removed. The substrate can be set, and similarly, the glass substrate can be set while the second processing container 22 and the third processing container 23 are in the standby state, so that downtime is reduced. Complete. As a result, efficiency in mass production can be improved.

Here, the technical idea of the present invention, that is, the technical idea of changing the level of the solution surface in the processing container in a state where the processing container and the substrate are stationary, immerses the substrate in the solution at a constant speed. It can also be applied to progressive processing methods.In this case, while the substrate is placed in the processing container, the solution is supplied from the liquid inlet provided at the bottom of the container, and the solution surface in the container is kept at a constant speed. You can use the method of raising it with.

[0038]

As described above, according to the present invention,
After immersing the substrate in the coating solution housed in the processing container, with the substrate and the processing container still, the coating solution in the processing container was pulled out from the lower part of the container,
Since the solution surface is lowered at a constant speed to form a thin film, a complicated and expensive mechanism for raising the substrate and lowering the processing container is not required. As a result, a thin film having a uniform film thickness can be manufactured at low cost. Moreover,
By applying the present invention, it is possible to easily achieve an increase in the size of the processing container, and thus it is possible to realize a thin film manufacturing apparatus that can efficiently manufacture a large number of thin films having a uniform film thickness.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a configuration diagram of still another embodiment of the present invention.

[Explanation of symbols]

 1 Processing Container 1a Liquid Outlet 2 Solenoid Valve 3 Support Member L Coating Solution S Glass Substrate 11, 12 Processing Container 11a, 12a Liquid Inlet / Outlet 13 Piping System 14 Pump Unit P Pump V1a, V1b, V2a, V2b Switching Valve 15 Flow Control Device 21 , 22, 23 Processing vessels 21a, 22a, 23a Liquid inlet / outlet 24 Solution circulation unit 25 Piping system

Claims (4)

[Claims] 1. A method for forming a thin film on the surface of a substrate based on a dip coating method, which comprises immersing a substrate in a coating solution housed in a processing container and then leaving the substrate and the processing container stationary. A method for producing a thin film, characterized in that the coating solution in the processing container is drawn out from the lower part of the container and the surface of the solution is lowered at a constant speed to form a thin film. 2. A device for forming a thin film on the surface of a substrate based on a dip coating method, which is a container for containing a coating solution and provided with a liquid outlet at a lower portion, and a valve connected to the liquid outlet. The thin film manufacturing apparatus is characterized in that the coating solution in the processing container is discharged to the outside of the container by adjusting the opening of the valve, and the surface of the solution is lowered at a constant speed. 3. An apparatus for forming a thin film on a surface of a substrate based on a dip coating method, comprising a plurality of processing vessels, and a piping system interconnecting liquid inlets and outlets provided at the bottom of each processing vessel, A liquid transportation means connected to this piping system is provided, and the liquid transportation means is a plurality of processing vessels.
A thin film manufacturing apparatus, which is configured to send a coating liquid contained in one processing container to another processing container at a constant flow rate. 4. The apparatus according to claim 3, wherein the number of processing vessels is two, and the liquid transportation means connected between the processing vessels sends the coating solution from one processing vessel to the other processing vessel. After that, the coating solution contained in the other processing container is returned to the one processing container.