Method and apparatus for forming a coating film

Abstract

The present invention provides a coating film forming apparatus that can easily improve the uniformity of the in-plane film thickness of the formed coating film compared to conventional methods. [Solution] The coating forming apparatus 10 includes a lid moving mechanism 11f that fixes the lid 11c to the cap 11b after the substrate 20 has been adsorbed onto the stage 11a and the coating agent has been supplied to the substrate; a rotation mechanism 11e that rotates the stage, cup and lid under a first rotation condition after the lid has been fixed to the cap; a lid moving mechanism 11f that separates the lid from the cup after the rotation has stopped under the first rotation condition; a rotation mechanism 11e that rotates at least the stage under a second rotation condition after the lid has been separated from the cup; and a control unit 19 that controls the coating agent supply mechanism 11d, the rotation mechanism 11e and the lid moving mechanism 11f.

Description

Technical Field

[0001] The present invention relates to a coating film forming method for forming a coating film on a substrate having a rectangular planar shape, and a coating film forming apparatus suitable for its implementation.

Background Art

[0002] When forming a thin film (coating film) of a coating agent on the main surface of a substrate having a rectangular planar shape, it is difficult to ensure the uniformity of the film thickness because the coating agent tends to accumulate at the four corners of the substrate. As a device for avoiding this, there is a coating film forming apparatus called a so-called rotary cup type. Examples thereof are disclosed in, for example, Patent Document 1 and Patent Document 2. Any of the devices includes a stage on which a substrate can be adsorbed and placed, a cup surrounding the side and bottom of the stage, a lid that contacts the cup above the stage and cooperates with the cup to seal the coating space, and a rotation mechanism that rotates the stage, the cup, and the lid coaxially. Since the space for rotating the substrate is a sealed space in any of the devices, the air in the space moves together when the stage or the like rotates, so that the centrifugal development of the coating agent can be performed with reduced air friction. In particular, in the case of the device of Patent Document 1, by providing a plurality of chamber structures (structures having holes) in the lid, the inside of the rotating cup is decompressed by centrifugal force, and the occurrence of air streaks in the coating film is reduced (Summary of Patent Document 1, FIG. 2, paragraph 7, etc.). In the case of the device of Patent Document 2, it includes a lid having two lids, and the state of the rotating cup can be selected from a state without a lid, a state covered with one lid, and a state covered with two lids, thereby controlling the air flow (paragraph 7, paragraph 8, etc. of Patent Document 2).

[0003] In any of the devices, during one spin coating process, the inflow of gas into the sealed space is controlled to obtain a uniform coating film for a wide range of chemical solutions (coating agents) (summaries of each patent document, etc.).

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-317353 [Patent Document 1] Japanese Patent Publication No. 2001-205166 [Overview of the project] [Problems that the invention aims to solve]

[0005] On the other hand, according to the inventor's research relating to this application, the following problems arise with conventional rotary cup type devices. Specifically, when a coating film of a coating agent with a relatively low viscosity (e.g., 1000 mPa / S or less) is applied to a substrate with a rectangular planar shape using a conventional rotary cup type device different from the devices described in Patent Documents 1 and 2, the surface tension of the coating agent causes the coating agent to accumulate at the four corners of the substrate, and it was found that the uniformity of the coating film thickness within the substrate cannot be achieved as desired. The inventor relating to this application has not investigated whether this problem can be solved with the devices of Patent Documents 1 and 2, but even if it is possible, the devices are complicated, such as the device in Patent Document 1 requiring multiple chamber structures (structures with holes) in the lid, and the device in Patent Document 2 requiring a lid with two lids. On the other hand, further research by the inventors of this application has shown that, when forming a coating film with a relatively low viscosity coating agent, the uniformity of the in-plane film thickness of the coating can be improved by simply making minor modifications to the conventional rotary cup type coating method. This application has been made in view of the above points, and therefore, the object of this application is to provide a coating film forming method and a coating film forming apparatus that can easily improve the uniformity of the in-plane film thickness of the formed coating film compared to conventional methods. [Means for solving the problem]

[0006] To achieve this objective, according to the first invention of this application, a method for forming a coating film on a substrate using a stage capable of adsorbing and placing a substrate to be coated, a cup surrounding the sides and bottom of the stage, a coating agent supply mechanism for supplying a coating agent to the substrate, a lid that contacts the cup above the stage and cooperates with the cup to seal the coating space, and a rotation mechanism for coaxially rotating the stage, cup and lid, The method is characterized by comprising the steps of: adsorbing the substrate onto the stage; supplying a coating agent onto the adsorbed substrate; joining the lid to the cup after the supply is completed; rotating the stage, the cup and the lid according to a first rotation condition after the joining is completed; separating the lid from the cup and / or opening the cup after the rotation according to the first rotation condition has stopped; and rotating at least the stage according to a second rotation condition after the separation and / or opening is completed. In carrying out this first invention, the separation and / or opening step may be any of the following: a. separating the lid from the cup, b. opening the cup, for example by dividing the cup and separating the cup from the stage, or c. carrying out both a and b above. However, preferably, only the step of separating the lid from the cup is used. This is because even by separating the lid from the cup, the coating space that is the objective of this invention can be opened, and separating the lid from the cup is often easier to operate than opening the cup, for example by dividing the cup and separating the cup from the stage. The same applies to the coating apparatus of the second invention described below.

[0007] Furthermore, according to the second invention of this application, a coating film forming apparatus comprising: a stage capable of adsorbing and placing a substrate to be coated; a cup surrounding the sides and bottom of the stage; a coating agent supply mechanism for supplying a coating agent to the substrate; a lid that contacts the cup above the stage and cooperates with the cup to seal the coating space; and a rotation mechanism for coaxially rotating the stage, cup and lid, After the substrate is adsorbed onto the stage and the coating agent is supplied to the substrate, a lid fixing means is provided to fix the lid to the cap, After fixing the lid to the cap, a first rotating means rotates the stage, the cup and the lid under a first rotation condition, After the rotation stops due to the first rotation condition, a means for separating the lid from the cup and / or opening the cup, A second rotating means for rotating at least the stage under a second rotation condition in the separated and / or open state, It is characterized by being equipped with [the following features]. In carrying out this second invention, the separating and / or opening means may be any of a, b, or c as described in the preferred example of the first invention above, but it is preferable that it be a means equivalent to a, that is, a means for separating the lid from the cup. [Effects of the Invention]

[0008] According to the coating film forming method and coating film forming apparatus of this application, when the coating agent supplied to the cup-type substrate is rotated under the first rotation condition, it is spread by centrifugal force in a sealed state, thereby reducing the influence of air in the coating space, and a coating film can be formed on the substrate that is derived from the conventional effects of the rotating cup-type coating film forming method. However, in this application, once the processing under the first rotation condition is completed, the lid is then separated from the cup and / or the cup is opened, and processing under the second rotation condition is performed in the open space around the stage. This second rotation condition in an open state yields the following unique effects and benefits. When applying a coating agent to a rectangular substrate in plan view, and the coating agent used has low viscosity (1000 mPa / S or less according to the inventor's research), when the rotation under the first rotation condition stops, the coating agent that had accumulated at the four corners of the substrate returns to the center of the substrate, thus worsening the uniformity of the coating film thickness. In other words, when the coating agent has low viscosity, the advantages of the rotary cup coating method are not necessarily obtained. In contrast, in each invention of this application, after the first rotation condition treatment using the rotary cup method, treatment under the second rotation condition in an open state (treatment by spin coating method) is performed. Therefore, the coating agent that has accumulated at the four corners of the substrate after the first rotation condition in a sealed state is centrifuged and scattered from the four corners of the substrate to the outside of the substrate due to the influence of air from the open space and the action of the second rotation condition. Consequently, in each invention of this application, it is possible to reduce the thickness of the coating film at the four corners of the substrate, thereby improving the uniformity of the coating film thickness compared to conventional methods. Moreover, the uniformity of the coating film thickness can be improved by simply performing two rotational processes, which involve either joining / separating the lids or opening the cups. Therefore, it is possible to provide a coating film forming method and a coating film forming apparatus that can easily improve the uniformity of the in-plane film thickness of the formed coating film compared to conventional methods. [Brief explanation of the drawing]

[0009] [Figure 1] (A) is a block diagram illustrating the outline of the coating apparatus 10 of the embodiment, and (B) is a diagram illustrating the outline of the coating mechanism 11 provided in the coating apparatus 10 of the embodiment. [Figure 2] This is a process diagram showing the apparatus in order to explain the steps of the coating method of the embodiment. [Figure 3] This figure, following Figure 2, shows the apparatus in a state that illustrates the steps of the coating method of the embodiment. [Figure 4] This is a flowchart illustrating the steps of the coating method according to the embodiment. [Figure 5] This figure illustrates the effects of the present invention based on its transmittance characteristics. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of each invention of this application will be described with reference to the drawings. Note that each drawing used in the description only schematically shows the inventions to an extent that they can be understood. Also, in each drawing used in the description, similar components are denoted by the same numbers, and the description thereof may be omitted. Further, the mechanism examples, device shapes, materials, etc. described in the following embodiments are merely preferred examples within the scope of this invention. Therefore, this invention is not limited only to the following embodiments.

[0011] 1. Coating device suitable for implementing the coating method FIGS. 1(A) and (B) are diagrams for explaining a coating device 10 suitable for implementing the coating method of the present invention. In particular, FIG. 1(A) is a block diagram for explaining the overall outline of the coating device 10, and FIG. 1(B) is a block diagram for explaining a coating mechanism unit 11 and a control unit 19 provided in the coating device 10. The coating device 10 includes a coating mechanism unit 11, a substrate loading unit 13, a substrate unloading unit 15, a substrate transfer unit 17, and a control unit 19. The coating mechanism unit 11, details of which will be described later, applies a coating agent to the main surface of the substrate 20 to form a desired coating film. Note that the substrate 20 is a substrate to be coated with the coating agent, and can be various substrates, for example, a glass substrate for an optical filter or a substrate made of crystal. Also, the substrate 20 can have an arbitrary planar shape, but in the figure, a substrate having a square planar shape, which is the planar shape regarded as a problem in the present invention, is shown.

[0012] The substrate loading unit 13 is, for example, a cassette type for storing a plurality of substrates 20. Also, the substrate unloading unit 15 is for accommodating the substrate on which the coating film of the coating agent has been formed by the coating mechanism unit 11, and is, for example, a cassette type. The substrate transfer unit 17 transfers the substrate 20 to the substrate loading unit 13, the stage 11a of the coating mechanism unit 11, and the substrate unloading unit 15 each time a predetermined process is completed. The substrate transfer unit 17 can be configured by a well-known device such as a robot having a transfer arm 17a having an arbitrary mechanism such as an adsorption mechanism capable of adsorbing the substrate 20 or a gripping mechanism capable of sandwiching the side surface of the substrate 20. The control unit 19 controls the operations of the substrate loading unit 13, the coating mechanism unit 11, the substrate unloading unit 15, and the substrate transfer unit 17. The control unit 19 can be configured to include, for example, a microcomputer (CPU) 19a and a ROM (Read Only Memory) 19b that stores a program for realizing a predetermined operation referred to in the present invention. Further, the control unit 19 has a keyboard, a display, etc., and is configured such that an operator can change various operating conditions of the coating film coating apparatus 10, such as the rotation conditions of the stage 11a.

[0013] Next, mainly referring to FIG. 1(B), the coating mechanism unit 11 will be specifically described. The coating mechanism unit 11 supplies a coating agent to the main surface of the substrate 20, rotates the substrate, and forms a desired coating film of the coating agent on the substrate. The coating mechanism unit 11 in this case includes a stage 11a, a cup 11b, a lid 11c, a coating agent supply mechanism 11d, a rotation mechanism 11e, and a lid movement mechanism 11f. The stage 11a can adsorb and place the substrate 20. The stage 11a is disk-shaped in plan view and has a hole for substrate adsorption at its center, and is made of a material having chemical resistance. Further, a rotation shaft, which is a part of the rotation mechanism 11e, is connected below the stage 11a. The rotation shaft has a hollow center, and a vacuum pump can be connected to the hollow portion. Therefore, the substrate 20 can be adsorbed to the stage 11a. The cup 11b surrounds the side and below of the stage 11a. Specifically, it is a cup-shaped body formed by integrating a wall member that surrounds the periphery of the stage 11a at a position a predetermined distance away from the stage 11a and a lower plate that surrounds the lower part of the stage 11a without contacting the rotation shaft. The cup 11b is also made of a material having chemical resistance.

[0014] The lid 11c contacts the cup 11b above the stage 11a and works in cooperation with the cup 11b to seal the coating space S. In this case, the lid 11c is joined to the cup 11b at the top surface of the wall member of the cup 11b and is made of a chemical-resistant material. The lid 11c can be joined to and separated from the cup 11b by the lid moving mechanism 11f, which will be described later. Moreover, the lid 11c rotates together with the stage 11a and the cup 11b. Therefore, the lid 11c and the cup 11b have an arbitrary and suitable structure that can withstand rotation, be fixed to each other when joined, and separate smoothly when separated. The coating agent supply mechanism 11d supplies the target coating agent 30 (see Figure 2(A)) to the surface of the substrate 20 that is adsorbed onto the stage 11a and is intended for coating film formation. In this example, the coating agent supply mechanism 11d is a mechanism that allows the tip of the supply nozzle to move to near the center of the substrate 20 when supplying the coating agent to the substrate 20, and to move the nozzle to a position away from the cup or the like at other times. The coating agent 30 can be supplied to the substrate by means of nitrogen gas pressure, for example.

[0015] The rotating mechanism 11e is capable of coaxially and synchronously rotating the stage 11a, cup 11b, and lid 11c. Moreover, it can rotate at any rotational speed, at any rise speed to any rotational speed, and at any rotational speed for a predetermined holding time. The rotating mechanism 11e comprises a shared rotating shaft connected to the stage 11a, cup 11b, and lid 11c, and a motor connected to the rotating shaft. The lid moving mechanism 11f moves the lid 11c onto the cup 11b in a detachable manner. The lid moving mechanism 11f can be composed of any conventionally known moving mechanism such as a slider or a robot. The lid moving mechanism 11f is, of course, equipped with a sensor (not shown) for detecting the movement position. The coating agent supply mechanism 11d, the rotation mechanism 11e, and the lid moving mechanism 11f are connected to the control unit 19 and perform predetermined operations according to a predetermined program stored in the ROM 19b of the control unit 19. In the coating apparatus 10 of this embodiment, the separation and / or opening means as referred to in the present invention can be composed of a lid moving mechanism 11f and a control unit 19. Furthermore, the first rotating means and the second rotating means as referred to in the present invention can be composed of a rotating mechanism 11e and a control unit 19.

[0016] 2. Embodiment of the application method Next, embodiments of the coating method will be described, mainly with reference to Figures 2, 3, and 4. Here, Figures 2 and 3 are process diagrams showing the apparatus in order to explain the steps of the coating method of the embodiment. Figure 4 is a flowchart for explaining the steps of the coating method of the embodiment. The program that can implement the method described in Figures 2, 3, and 4 is stored in the ROM 19b of the control unit 19.

[0017] In the coating method of this embodiment, first, the substrate 20 is placed on the stage 11a by the substrate transfer unit 17, and then adsorbed onto the stage 11a (steps S1 and S2 in Figure 4). Next, the coating agent 30 is supplied onto the substrate 20 on which the stage 11a has been adsorbed by the coating agent supply mechanism 11d (Step S3 in Figures 2(A) and 4). In addition, an adhesion modifier such as a silane coupling agent may be applied to improve the adhesion of the completed coating film to the substrate 20. After the supply of the coating agent is complete, the lid moving mechanism 11f joins the lid 11c to the cup 11b (Steps S4 and S41 in Figure 2(B) and Figure 4). At this time, the lid 11c and the cup 11b are fixed to each other so as to withstand rotation. After the lid 11c is joined to the cup 11b, the lid moving mechanism 11f becomes non-contact with the lid 11c.

[0018] After the above joining is complete, the stage 11a, cup 11b, and lid 11c are rotated by the rotation mechanism 11e according to the first rotation condition (Steps S4 and S42 in Figure 2(B) and Figure 4). Here, the first rotation condition refers to the rotation condition that takes into account the type of coating agent and the desired thickness of the coating film. Specifically, the first rotation condition includes the rise speed from which the stage etc. moves from a stopped state to the desired rotation speed, the desired rotation speed, and the maintenance time for maintaining rotation at the desired rotation speed. This first rotation condition is realized by the program written to the ROM 19b of the control unit 19 and the rotation mechanism 11e.

[0019] After rotation stops due to the first rotation condition, the lid 11c is separated from the cup 11b by the lid moving mechanism 11f (step S43 in Figures 3(A) and 4). This separation operation can be performed by the control unit 19 and the lid moving mechanism 11f. Once the lid 11c has separated from the cup 11b, the space above the stage 11a and between the wall member of the cup 11b and the stage 11a becomes open. In this open state, the stage 11a is then rotated according to the second rotation condition (steps S5 and S51 in Figures 3(B) and 4). Here, rotating at least the stage 11a is necessary, but the cup 11b may not be rotated. However, realizing a mechanism that rotates the stage 11a but not the cup 11b would complicate the structure of the rotation mechanism, so it is simpler to rotate both the stage 11a and the cup 11b, and even if this is done, the objective of the present invention is achieved according to the inventor's experiments in this application.

[0020] Here, the second rotation condition, like the first rotation condition, is a rotation condition that takes into account the type of coating agent and the desired thickness of the coating film. Specifically, the second rotation condition is defined by the rise speed from which the stage etc. moves from a stopped state to the desired rotation speed, the desired rotation speed, and the duration for which the rotation is maintained at the desired rotation speed. The second rotation condition is usually a preferred condition different from the first rotation condition, but it may also be the same as the first rotation condition. Furthermore, the interruption time between completing the rotation process under the first rotation condition and starting the rotation under the second rotation condition should be short enough to prevent the coating film from drying out. After the rotation process under the second rotation condition is completed, the suction of the substrate 20 by the stage 11a is released (step S6 in Figure 4). Next, the substrate 20 is removed from the stage. This removal is performed by the substrate transfer unit 17. If heating and drying of the coated film is required, the removed substrate is placed in a suitable temperature bath for drying.

[0021] 3. Experimental Results Next, experimental results will be explained to help understand the effects of the present invention. This explanation will be given with reference to Figure 5. Here, Figure 5(A) shows an example in which infrared absorbing paint 30a is applied as a coating agent to one main surface of a glass substrate 20. However, in this experiment, three types of samples were prepared: an example sample coated using the method of the embodiment described above, a comparative example 1 sample in which the coating film was formed by a conventionally known simple spin-coating method, and a comparative example 2 sample in which the coating film was formed by a conventional cup-type method (a method in which the lid is not opened).

[0022] Then, as shown in Figure 5(A), the transmittance was measured for multiple measurement points P1 to Pn in the sample. Figure 5(B) shows the measurement results, with wavelength on the horizontal axis and transmittance on the vertical axis, showing the transmittance characteristics T1 to Tn for each measurement point. Note that the original transmittance characteristics are for a wide wavelength range as shown in the upper left of Figure 5(B), but the main part of Figure 5(B) is an enlarged view of the area enclosed by the circular dashed line in the characteristic diagram in the upper left of Figure 5(B). In this case, the evaluation is based on how much the transmittance at a specific wavelength λo is 50% at each measurement point P1 to Pn. That is, in the transmittance characteristics T1 to Tn, when the degree of spreading with respect to wavelength λo is Wa and Wb (Wa > Wb), the narrower the degree of spreading, i.e., the closer it is to the Wb state, the better the in-plane uniformity of the film thickness of the coating. From this perspective, it was found that the spread of the transmittance characteristics of the sample in the example was narrower to 1 / 6.6th that of the sample in Comparative Example 1, and narrower to 1 / 5.4th that of the sample in Comparative Example 2. Therefore, it can be seen that the coating film forming method and coating film forming apparatus of the present invention are effective in improving the uniformity of the film thickness when forming a coating film of a coating agent on a substrate. [Explanation of symbols]

[0023] 10: Coating film forming apparatus according to the embodiment 11: Coating mechanism 11a: Stage 11b: Cup 11c: Cover 11d: Coating agent supply mechanism 11e: Rotation mechanism 11f: Lid movement mechanism 13: PCB loading section 13 15: PCB unloading section 15 17: Substrate transfer unit 17 19: Control unit 20: Substrate 30: Coating agent 30a: Coating film

Claims

1. A coating film forming method for forming a coating film on a substrate, comprising: a stage capable of adsorbing and placing a substrate to be coated; a cup surrounding the sides and bottom of the stage; a coating agent supply mechanism for supplying a coating agent to the substrate; a lid that contacts the cup above the stage and cooperates with the cup to seal the coating space; and a rotation mechanism for coaxially rotating the stage, cup and lid, wherein A step of adsorbing the substrate onto the stage, A step of supplying a coating agent onto the adsorbed substrate, After the supply is completed, the lid is joined to the cup, After the joining is completed, the step of rotating the stage, the cup and the lid according to a first rotation condition, A separation and / or opening step, after rotation stops due to the first rotation condition, in which the lid is separated from the cup and / or the cup is opened, A method for forming a coating film, characterized by comprising the step of rotating the stage at least by a second rotation condition after completing the separation and / or opening.

2. The method for forming a coating film according to claim 1, characterized in that the separation and / or release step is a step of separating the lid from the cup.

3. A coating forming apparatus comprising: a stage capable of adsorbing and placing a substrate to be coated; a cup surrounding the sides and bottom of the stage; a coating agent supply mechanism for supplying a coating agent to the substrate; a lid that contacts the cup above the stage and cooperates with the cup to seal the coating space; and a rotation mechanism for coaxially rotating the stage, cup and lid, After the substrate is adsorbed onto the stage and the coating agent is supplied to the substrate, a lid fixing means is provided to fix the lid to the cap, After fixing the lid to the cap, a first rotating means rotates the stage, the cup and the lid under a first rotation condition, After the rotation stops due to the first rotation condition, a means for separating the lid from the cup and / or opening the cup, A second rotating means for rotating at least the stage under a second rotation condition in the separated and / or open state, A coating film forming apparatus characterized by comprising the following:

4. The coating film forming apparatus according to claim 3, characterized in that the separating and / or releasing means is a means for separating the lid from the cup.

5. The coating film forming apparatus according to claim 3 or 4, further comprising a control unit that includes a program for controlling the first rotation condition, the second rotation condition, and the interruption time from the completion of the rotation process under the first rotation condition until rotation is performed under the second rotation condition.

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