JP2013169500A - Spin cup washing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain washing with a small amount of washing liquid in a short time even in the case of using a main solvent of particularly high viscosity as a coating liquid when washing the internal wall of a spin cup using the washing liquid.SOLUTION: A spin cup washing method for a rotary coating apparatus 1 including a rotating part rotated with a substrate S fixed, a nozzle N for supplying a coating liquid to the substrate, and a spin cup 5 surrounding the substrate fixed to the rotating part, includes processes for supplying a first washing liquid with the same solvent as a main solvent used for the coating liquid, to at least a part of an internal wall surface of the spin cup to form a film on the internal wall surface, and supplying a second washing liquid with a solvent different from the main solvent used for the coating liquid, to at least a part of the internal wall surface of the spin cup to wash the internal wall surface. The process for forming the film, and the process for washing the internal wall surface are switched according to the film forming process of the substrate.

Description

  In the present invention, for example, a photoresist or a developer is spin-coated on a substrate to be processed (hereinafter simply referred to as “substrate”) such as a semiconductor wafer, or a functional thin film is formed on the substrate by a chemical solution method. More particularly, the present invention relates to a spin coater for spin coating a coating solution, and more particularly, a cup cleaning method for cleaning a spin cup inner wall surface contaminated with a coating solution scattered from a substrate and a dried solidified product of the coating solution during a spin coating process. About.

For example, a coating solution such as a photoresist, a developing solution, or a precursor solution that becomes a functional thin film by a chemical solution method is dropped on the substrate to rotate the substrate at a high speed, and the centrifugal force causes the coating solution to spread to the outer periphery of the substrate. After that, a method of forming a uniform thin film by shaking off excess coating solution is well known as a spin coating method.
An apparatus for forming a thin film by a spin coating method is a spin coating apparatus generally called a spinner or a spin coater, and a substrate is horizontally placed on a spin table provided with a chuck mechanism at the upper end of a rotary shaft arranged in a vertical direction. The film is held and rotated to form a uniform thin film.
Furthermore, a spin coater is generally provided with a cylindrical spin cup so as to surround the periphery of the substrate, and the spin cup spatters excess coating liquid splashed from the periphery of the substrate by being shaken off during the spin coating process. By adhering to the inner wall, contamination around the device is prevented.

However, in the conventional spin coating method, after the excess coating solution is shaken off, the applied coating solution adheres to the inner wall of the cup and is dried and solidified. Then, when a crystal piece or a powder deposited from the coating solution is dried or solidified, it easily peels off from the inner wall due to the influence of vibration or the like, and in some cases, the crystal piece or the powder reattaches to the substrate, resulting in a product defect. For this reason, it is necessary to frequently clean the inner wall of the cup in order to prevent deposition of crystal pieces or powder that is dried and solidified in the coating solution. It is efficient to perform this cleaning operation before the coating solution is dried. However, in the case of a coating solution that dries quickly, cleaning before drying is difficult.
Therefore, in Patent Document 1, an annular inner peripheral surface cleaning pipe is provided at the upper part of the cup inner wall for the purpose of cleaning the cup inner wall, and a number of cleaning liquid discharge holes are opened toward the upper inner surface of the inner wall in the inner peripheral surface cleaning pipe. A configuration is disclosed in which a cleaning liquid is caused to flow from the opening along the inner wall. In addition, a configuration is also disclosed in which an annular inclined plate cleaning pipe is provided on the rectifying inclined plate located under the substrate, and a large number of cleaning liquid discharge holes are opened toward the upper side of the rectifying inclined surface in the inclined surface cleaning pipe. .
However, in the configuration in which the cleaning liquid is caused to flow from the discharge hole of the cleaning tube, there is a problem that the cleaning liquid easily passes through the path once passed and it is difficult to clean the entire inner wall.

Further, Patent Document 2 discloses a configuration in which a spin nozzle is provided with a spray nozzle that cleans the inner wall surface of the spin cup and at the same time, the cleaning liquid is sprayed on the inner wall surface while rotating the spin cup.
However, in the configuration in which the spray cleaning is performed as described above, if the cleaning liquid is sprayed on the innermost peripheral portion of the spin cup, the sprayed cleaning liquid splashes on the spin table, causing a chuck failure of the substrate. Since the cleaning liquid adhering to the innermost inner wall surface drops on the substrate and causes a product defect, the cleaning operation cannot be performed by spraying the cleaning liquid to the innermost peripheral portion of the spin cup.
As a result, the coating liquid adheres to the innermost peripheral portion of the spin cup closest to the substrate, and the crystal pieces or powder that has been dried and solidified accumulates, and drops on the substrate to cause defects. In addition, this method has a problem that the amount of the cleaning liquid to be used or the cleaning waste liquid discharged at the same time becomes large.

  Further, in Patent Document 3, an attempt is made to prevent the occurrence of mist by a plurality of scattering prevention plates arranged on a plane parallel to the coating film forming surface of the substrate and a surface parallel thereto, but the mist adheres to these scattering prevention plates and is dried. -Since the countermeasure against the mist generated by the collision between the solidified / deposited crystal pieces or powder of the coating liquid and the coating droplets scattered by shaking is not taken, the occurrence of defects cannot be suppressed.

By the way, in the conventional examples as described above, it is usual to use the same solvent as the main solvent used in the coating solution as the cleaning solution for cleaning the inner wall of the spin cup. The reason is that in order to prevent the coating solution adhering to the inner wall of the spin cup from drying and solidifying, in other words, preventing the solute from precipitating due to an increase in the concentration of the coating solution, the solvent is added to the inner surface of the spin cup. This is because the method of diluting the concentration of the applied coating solution and flushing the diluted coating solution out of the spin cup as a cleaning waste solution together with the added solvent is the simplest and most reliable method.
However, when a high-viscosity solvent is used as the main solvent of the coating solution, the flow of the cleaning waste solution in which the attached coating solution and the added cleaning solution are compatible is poor. It became clear that the flow-off operation took a long time, the throughput of the coating work was deteriorated, and that a large amount of cleaning liquid was consumed when trying to process this in a short time. .

  The present invention has been made in view of the above problems, and when cleaning the inner wall of the spin cup using a cleaning liquid, even when a main solvent having a particularly high viscosity is used as a coating liquid, It is intended to enable cleaning in a short time and with a small amount of cleaning liquid.

  In order to solve the above problem, the invention according to claim 1 surrounds a rotating part that fixes and rotates a substrate, a nozzle that supplies a coating liquid to the substrate, and the substrate that is fixed to the rotating part. A spin cup cleaning method for a spin coater comprising: a first cleaning liquid of the same solvent as a main solvent used in the coating liquid supplied to at least a part of the inner wall surface of the spin cup. Forming a film on the inner wall surface, and supplying a second cleaning liquid of a solvent different from the main solvent used in the coating solution to at least a part of the inner wall surface of the spin cup, A step of cleaning, wherein the step of forming the film and the step of cleaning the inner wall surface are switched according to a film forming process of the substrate.

  According to the present invention, the cleaning operation is performed while switching a plurality of types of cleaning liquids of different solvents in accordance with the film forming process, so that the cleaning waste liquid to be discharged can be reduced in a shorter time.

It is sectional drawing of the spin coater which concerns on one Embodiment of this invention.

  The present invention will be described below based on the embodiment. The following embodiment shows an example of the present invention, and the same effect can be obtained even when the spin cup cleaning method according to the present invention is applied to a spin cup cleaning mechanism having a different basic configuration. It is done.

FIG. 1 is a cross-sectional view of a spin coater according to an embodiment of the present invention. The spin coater 1 includes a spin table 3 that adsorbs a substrate S that is a film formation target, a rotary shaft 2 that rotates the spin table 3, a nozzle N that supplies a coating liquid to the substrate S, and a spin table 3. The spin cup 5 that surrounds the periphery of the adsorbed substrate S (at least the outer peripheral portion of the substrate S), and the excess coating liquid or the like that is disposed below the substrate S adsorbed on the spin table 3 and flows down from the substrate S is received. The spin cup lower surface plate 6, and the opening 4 through which the excess coating liquid dropped on the inner wall surface of the spin cup 5 and the spin cup lower surface plate 6, the waste liquid of the cleaning liquid, and the like are discharged out of the spin coater 1. In addition, an inner wall surface refers to the wall surface located in the space side where the board | substrate S is arrange | positioned.
The spin table 3 and the rotating shaft 2 constitute a rotating unit of the spin coating device 1.
The spin cup 5 is a coating liquid dropped from the substrate S by centrifugal force among the coating liquid dropped from the nozzle N on the substrate S rotating at a high speed by the rotation of the rotating shaft 2 arranged in a substantially vertical direction. (Microdroplet: Mist) is received and flows down toward the opening 4. That is, the spin cup 5 prevents excess coating liquid from splashing outside the spin coating apparatus 1.

The spin cup lower surface plate 6 receives an excess coating liquid that has flowed down from the substrate S and a back rinse liquid that has cleaned the back surface of the substrate S, and flows down toward the opening 4.
Further, the exhaust generated when suctioning the extra small droplets (mist) of the coating solution that is scattered when the coating solution is dropped onto the substrate S rotated at high speed is also discharged from the opening 4.
Further, in the configuration according to the present invention, the spin cup 5 and the spin cup lower surface plate 6 are structured such that at least a part of the inner wall surface of each of the porous layers 5a and 6a and the spin cup 5 or the spin cup lower surface plate 6 is formed. It has a multilayer structure having shells 5b and 6b. Further, cleaning liquid channels 5c and 6c through which the cleaning liquid flows are formed between the porous layers 5a and 6a and the shells 5b and 6b.
The shells 5b and 6b are made of a material that does not allow the cleaning liquid to pass therethrough, and have strength to withstand the pressure when the cleaning liquid is injected.
In FIG. 1, the cleaning liquid is injected from below the spin cup 5 and the spin cup lower surface plate 6, but the injection position of the cleaning liquid is not particularly limited. For example, the cleaning liquid may be injected from above the spin cup 5 and the spin cup lower surface plate 6, or may be injected from holes provided at appropriate positions in the shells 5b and 6b.

The porous layers 5a and 6a are made of a porous ceramic having an average pore diameter of 1 to 3 μm, more preferably about 1 μm, and an average porosity of 40 to 60%, more preferably an average porosity of about 40%. It is formed using. The material of the ceramic is selected in consideration of the reactivity with the coating liquid to be used and the wettability, but an alumina-based ceramic is preferable.
Further, a cleaning liquid pipe 7 (7a, 7b) is connected to the cleaning liquid flow paths 5c, 6c via a port (not shown), and a cleaning liquid tank 9 storing different solvents (cleaning liquids) via the switching valve 8 at the end thereof. (9a, 9b) are connected. The cleaning liquid is a liquid (solvent) capable of diluting a coating liquid used for film formation or dissolving a dried coating liquid (or a solidified product of the coating liquid). In the cleaning liquid tank 9a, the same solvent (first cleaning liquid) as the main solvent used in the coating liquid is stored as the cleaning liquid, and the cleaning liquid tank 9b is a solvent different from the main solvent. A solvent (second cleaning liquid) having compatibility and lower viscosity than the main solvent is stored as a cleaning liquid.

The cleaning liquid is perforated from the cleaning liquid tanks 9a and 9b through the cleaning liquid pipes 7a and 7b and the cleaning liquid flow paths 5c and 6c, respectively, by a pump P that can change the supply amount (injection amount) and the supply pressure (injection pressure). It is supplied to the quality layers 5a and 6a. Instead of the pump P, a method may be used in which the cleaning liquid is accommodated in a pressurized tank and is fed by pressure from the pressurized tank.
The cleaning liquid pipe 7, the cleaning liquid tank 9, and the pump P constitute cleaning liquid supply means. The pump P constitutes an injection amount variable mechanism.

  The operation of the spin coater 1 is controlled by the control unit 10. The control unit 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores programs for executing processing, a RAM (Random Access Memory) that stores data, and the like. The control unit 10 is electrically connected to each part of the spin coating apparatus 1, and controls the drive of a motor (not shown) that rotates the rotary shaft 2, the dripping control of the coating liquid from the nozzle N, the porous layer 5a, Control of the supply amount of the cleaning liquid to 6a, etc. is performed according to the film forming process.

A film forming process using the spin coater 1 having the above-described configuration of the present invention and a spin cup cleaning method will be described below.
First, before starting the film forming process, the main solvent used for the coating liquid from the cleaning liquid tank 9a to the cleaning liquid flow paths 5c and 6c of the spin cup 5 and the spin cup lower surface plate 6 through the cleaning liquid pipe 7 and the switching valve 8 respectively. The same solvent is injected as a cleaning liquid, and the cleaning liquid is pressurized by a pump P at a predetermined pressure. Then, the cleaning liquid spreads over the entire porous layers 5a and 6a due to pressure and capillary action, oozes out from a large number of holes on the surfaces of the porous layers 5a and 6a, and the inner wall surfaces of the spin cup 5 and the spin cup lower surface plate 6 A film of the cleaning solution is formed on the surface (step of forming a film).

In this state, the coating solution is dropped onto the substrate S set on the spin table 3 to rotate the substrate S at a high speed, and the coating solution is spread to the outer periphery of the substrate S by the centrifugal force, and then the excess coating solution is shaken off. Thus, a uniform thin film is formed. At that time, a part of the coating liquid scattered around by high-speed rotation becomes minute droplets (mist), and is sucked together with air from the opening 4 by a blower (not shown) and exhausted outside the apparatus.
Further, another part of the coating solution scattered around the surface adheres to the inner wall surfaces of the spin cup 5 and the spin cup lower surface plate 6, that is, the surfaces of the porous layers 5a and 6a. Since these surfaces are coated with a cleaning solution that is the same solvent as the main solvent as described above, the applied coating solution immediately becomes familiar with the coating and becomes the same, and without drying and solidifying, the time is increased. At the same time, the flow gradually starts toward the opening 4.

Subsequently, when the switching valve 8 is switched at a timing immediately after the completion of the film forming process and a solvent different from the main solvent used for the coating liquid is injected from the cleaning liquid tank 9b as the cleaning liquid, the cleaning liquid is porous on the inner wall surface. The layers 5a and 6a are spread over the entire surface. Since this cleaning liquid employs a solvent having good compatibility with the main solvent, the same solvent as the main solvent of the coating liquid already coated, the coating liquid adhering to the film, and a solvent different from the main solvent Are integrated and flow toward the opening 4 and are finally collected in a waste liquid tank (not shown) outside the apparatus (step of cleaning the inner wall surface).
At this time, since the cleaning liquid supplied immediately after the completion of the film forming process employs a solvent having a lower viscosity than the main solvent, all the spin cup cleaning processes are performed using the same solvent cleaning liquid as the main solvent of the coating liquid. Compared to the case of using, the cleaning waste liquid can be discharged to the waste liquid tank outside the apparatus, and the entire film forming process time including the cleaning process can be shortened and the throughput can be increased. Regarding the pressure applied to the cleaning liquid by the pump P, the time required for the cleaning process may be further shortened by increasing the pressure applied in the step of cleaning the inner wall surface to the pressure applied in the step of forming the film.
As a result, the excess coating liquid shaken off from the substrate S is dried and solidified to deposit crystal pieces or powder in the apparatus, and the deposited crystal pieces or powder adhere to the substrate S during the coating process due to some trigger. , It is possible to avoid defects that cause product defects.

In this method, a coating film of a cleaning liquid of the same solvent as the main solvent of the coating liquid is formed on the inner wall surface of the spin cup 5 before the start of the film forming process, so that the coating liquid adhering to the inner wall surface is immediately adapted to the coating and diluted. However, immediately after completion of the film formation process, the film and the coating liquid adhering to the film are removed by a solvent cleaning liquid having a lower viscosity and higher fluidity than the main solvent. It is an operation of flowing down and discharging as a cleaning waste liquid to a waste liquid tank outside the apparatus, and all spin cup cleaning processes as described in the above-mentioned known technology use a cleaning liquid of the same solvent as the main solvent of the coating liquid In comparison, the total amount of cleaning liquid used can be reduced, in other words, the amount of waste liquid discharged can be reduced.
In addition, although it is a combination of a cleaning liquid of the same solvent as the main solvent and a cleaning liquid of a solvent different from the main solvent, it goes without saying that various combinations occur depending on the coating liquid used and the type of the main solvent. For example, for a resist solution in which the main solvent of the coating solution is ethyl lactate (viscosity: 2.6 cP), acetone (viscosity: 0.3 cP) is also used as a cleaning solution for a solvent different from the main solvent. A preferred combination.

Further, in the configuration of the spin coater 1 of the present invention shown in FIG. 1, the porous layer 5a is stretched to the innermost peripheral side of the inner wall surface of the spin cup 5, in other words, the portion closest to the substrate S. That is, in the cleaning method described in the above-mentioned known technique, the innermost peripheral portion where it is difficult to perform the cleaning operation, that is, the closest to the substrate S, the dried and solidified crystal pieces or powder of the attached cleaning liquid is likely to cause defects. A coating film of the cleaning liquid is formed even on the portion, and drying and solidification of the coating liquid adhering to the portion and occurrence of defects on the substrate due to the drying and solidification can be avoided.
The effect of the present invention is that the porous layer 5a is not stretched over the entire inner wall surface of the spin cup 5 as shown in FIG. 1, but the portion of the inner wall surface to which the coating liquid scattered by the swing-off operation during the coating process is most likely to adhere. More specifically, it is possible to obtain a great effect only by circulating the porous layer 5a only in the vicinity of the inner wall surface at a height position substantially equal to the thin film application surface of the substrate S and forming a cleaning liquid film on the same portion. However, it goes without saying that a more preferable effect can be obtained by stretching the entire inner wall surface of the spin cup 5 as shown in FIG.

After applying the coating liquid onto the silicon wafer substrate using the spin coater 1 according to the present invention, the silicon wafer substrate is baked to produce a wafer substrate on which a ferroelectric thin film (such as a PZT film) is formed. can do. Moreover, by processing the silicon wafer substrate on which the ferroelectric thin film is formed by a semiconductor process, an electronic element having an actuator function such as a MEMS or an inkjet head, or an electronic element having a sensor function such as a pyroelectric sensor (function) ) Can be formed. Furthermore, by using these elements, devices such as an inkjet printer, a projector manufactured using a MEMS mirror element, or an optical switch using a pyroelectric sensor can be manufactured.
As described above, since the occurrence of defects on the substrate can be avoided in the spin coating apparatus 1 according to the present invention, a wafer substrate in which defects occurring during the spin coating process are suppressed can be produced. When various functional devices are manufactured using the wafer substrate, and various devices are manufactured using the functional devices, it is possible to manufacture devices and devices with few defects at a high yield.

  DESCRIPTION OF SYMBOLS 1 ... Spin coating apparatus, 2 ... Rotating shaft, 3 ... Spin table, 4 ... Opening part, 5 ... Spin cup, 5a ... Porous layer, 5b ... Shell, 5c ... Cleaning-liquid flow path, 6 ... Spin cup lower surface plate, 6a ... Porous layer, 6b ... Shell, 6c ... Cleaning liquid flow path, 7 ... Cleaning liquid piping, 8 ... Switching valve, 9 ... Cleaning liquid tank, 10 ... Control part, N ... Nozzle, S ... Substrate, P ... Pump

Japanese Utility Model Publication No. 06-028223 JP 2002-143749 A JP 2004-330073 A

Claims (4)

A spin cup cleaning method for a spin coating apparatus, comprising: a rotating unit that fixes and rotates a substrate; a nozzle that supplies a coating liquid to the substrate; and a spin cup that surrounds the substrate fixed to the rotating unit. And
Supplying a first cleaning liquid of the same solvent as the main solvent used in the coating liquid to at least a part of the inner wall surface of the spin cup to form a film on the inner wall surface;
Supplying a second cleaning liquid of a solvent different from the main solvent used in the coating liquid to at least a part of the inner wall surface of the spin cup, and cleaning the inner wall surface,
A spin cup cleaning method, wherein the step of forming the film and the step of cleaning the inner wall surface are switched according to a film forming process of the substrate.   The spin cup cleaning method according to claim 1, wherein the second cleaning liquid is compatible with a main solvent of the coating liquid and has a viscosity lower than that of the main solvent of the coating liquid. The step of forming the film is a step performed before film formation on the substrate,
The spin cup cleaning method according to claim 1, wherein the step of cleaning the inner wall surface is a step performed immediately after completion of film formation on the substrate. At least a part of the inner wall surface of the spin cup is composed of a porous layer;
The step of forming the film and the step of cleaning the inner wall surface cause the first cleaning liquid or the second cleaning liquid to ooze out from the porous chamber layer to the inner wall surface of the spin cup, respectively. Item 4. The spin cup cleaning method according to any one of Items 1 to 3.

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