JP2000070834A - Abnormality detection and substrate coating apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect the generation of coating irregularity by observing the liquid droplets of a coating soln. between the emitting orifice of a nozzle and the surface of a substrate. SOLUTION: In an abnormality detection method, the generation of coating irregularity is detected when a coating soln. R is supplied to a substrate W to form a coating film. In this case, after the emission of the coating soln. R is stopped, coating irregularity is detected on the basis of the presence of the liquid droplets (r) of the coating soln. R between the emitting orifice 5a of a nozzle 5 and the surface of the substrate W. The coating irregularity is detected on the basis of the generation of these liquid droplets (r) and, if the presence of the liquid droplets (r) is detected, the generation of the coating irregularity can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a photoresist liquid or the like to a semiconductor wafer, a glass substrate for a photomask, a glass substrate for a liquid crystal display, a substrate for an optical disk (hereinafter simply referred to as a substrate). The present invention relates to an abnormality detection method for detecting occurrence of coating unevenness when a coating liquid is supplied to form a coating film, and a substrate coating apparatus using the same.

[0002]

2. Description of the Related Art In order to form a photoresist film on a substrate, for example, a substrate is rotated at a low speed in a horizontal posture by a rotation support section of a substrate coating apparatus, and a photoresist liquid is supplied from a nozzle near the center of rotation. After the supplied photoresist solution covers the entire surface of the substrate, the system is switched to high-speed rotation to shake off the excess photoresist solution and volatilize the solvent to form a photoresist film of a constant thickness on the surface of the substrate. It is supposed to.

[0003] In recent semiconductor manufacturing techniques, thinning of a photoresist film has been accompanied by miniaturization of circuits, that is, the viscosity of a photoresist solution has been reduced. Has become. Typical examples of the coating unevenness include a circular unevenness (called a "lake") and a non-uniform linear unevenness (called a "striation") radially generated toward the periphery of a substrate. It is. If the coating unevenness occurs, the film thickness becomes non-uniform and adversely affects subsequent processes. Therefore, if the coating unevenness occurs, the photoresist film is once peeled off, and then the photoresist film is formed again. Has become. A visual inspection by an operator is generally used to determine whether or not coating unevenness has occurred.

[0004]

However, the prior art having such a structure has the following problems. That is, since the coating unevenness is determined by the visual inspection, there is a problem that the inspection cannot be performed for each coating process on one substrate, and the coating unevenness cannot be easily detected. For example, in the case where 25 substrates are continuously processed, the inspection is performed at once after the application processing to all the substrates is completed. In general, since a failure occurs in a mechanism relating to ejection and the like, and application unevenness occurs, when application unevenness occurs on one substrate, application unevenness occurs on all subsequent substrates. Very often. Therefore, when the coating unevenness is found by the visual inspection, usually, after adjusting the mechanism related to the ejection, the recoating process is performed on the substrate that has been subjected to the peeling process, so that the operation rate of the substrate coating apparatus is reduced.

The present invention has been made in view of such circumstances, and focuses on a droplet of a coating liquid generated between a discharge port of a nozzle and a substrate surface, thereby preventing the occurrence of coating unevenness. An object of the present invention is to provide an abnormality detection method that can be easily detected.

Another object of the present invention is to provide a substrate coating apparatus capable of easily detecting occurrence of coating unevenness, preventing coating unevenness from continuously occurring on a substrate, and improving the operation rate. To provide.

[0007]

The present invention has the following configuration in order to achieve the above object. That is, the method invention according to claim 1 is an abnormality detection method for detecting occurrence of coating unevenness when forming a coating film by supplying a coating liquid to a substrate. After that, the application unevenness is detected based on the existence of the droplet of the application liquid between the discharge port of the nozzle and the substrate surface.

According to a second aspect of the present invention, in the abnormality detecting method according to the first aspect, the application unevenness is detected based on the existence of the droplet of the application liquid for 30 msec or more. It is characterized by the following.

According to a third aspect of the present invention, there is provided a substrate coating apparatus for forming a coating film by supplying a coating liquid to a substrate from a discharge port of a nozzle. Photographing means for photographing the interval, detecting means for detecting the presence of the droplet based on the image photographed by the photographing means, and detecting the presence of the droplet after the ejection of the application liquid is stopped. Notification means for notifying the occurrence of coating unevenness based on the detection.

According to a fourth aspect of the present invention, in the substrate coating apparatus according to the third aspect, the notifying means includes:
It is characterized in that the occurrence of coating unevenness is notified based on the detection means detecting the presence of a droplet of the coating liquid for 30 msec or more.

[0011]

What is the mechanism by which the inventors generate "Rake" which is a circular unevenness and "Striation" which is an uneven linear unevenness radially generated toward the periphery of a substrate? An experiment was performed to find out. Specifically, a video camera for high-speed photography in which the shutter speed is set to 1/1000 sec, from the start of discharge of a photoresist solution as a coating solution to the discharge port of a nozzle from the stop of discharge to the formation of a film. An image was taken between the substrate and the substrate surface. Then, when coating unevenness such as striation or rake occurred, the behavior of the photoresist liquid as shown in FIG. 8 was observed between the discharge port of the nozzle and the substrate surface.

That is, from the state where the photoresist liquid R is being supplied from the discharge port 5a of the nozzle 5 to the surface of the substrate W (FIG. 8A), the on-off valve is closed to stop the supply. Then, the photoresist liquid R does not stop immediately, but the discharge width gradually narrows according to the closing speed of the on-off valve (FIG. 8B). Eventually, the photoresist liquid R is interrupted from the discharge port 5a, and a part of the photoresist liquid R is returned to the discharge port 5a, while most of the other liquid is removed from the substrate W.
8 and fall down toward the surface of the
(C)). At this time, the upper end portion of the photoresist liquid R which falls is separated into several droplets r (only one is shown in the drawing for the sake of illustration) and lags behind the upper end portion of the fine thread-shaped photoresist liquid R. And fall. In other words, it was found that after the photoresist liquid R was completely dropped on the surface of the substrate W, a few drops r were dropped with a delay.

Therefore, in the method invention according to claim 1,
After the discharge of the coating liquid is stopped, the occurrence of the coating unevenness can be known only by detecting whether or not the liquid droplet of the coating liquid exists between the discharge port of the nozzle and the substrate surface.

According to experiments by the inventors, FIG.
(C), it was found that the coating unevenness particularly occurred when the time required for the droplet r to fall on the surface of the substrate W as shown in FIG. 8D was about 30 msec or more. When the drop time of the droplet r is about 30 to 100 msec, "rake" tends to occur, and when the drop time exceeds about 100 msec and is as long as several hundred msec, "striation" tends to occur. Was also found.

Therefore, according to the second aspect of the present invention, after the discharge of the coating liquid is stopped, it is only necessary to detect whether or not there is a droplet of the coating liquid between the discharge port of the nozzle and the substrate surface. Instead, the occurrence of coating unevenness can be more surely known by considering the falling time.

The operation of the device invention according to claim 3 is as follows. The detecting means detects the presence of the liquid droplets of the coating liquid based on the image photographed by the photographing means, and when the liquid droplets are detected, the notifying means notifies the occurrence of the coating unevenness. Therefore, it is possible to easily detect the presence of the droplet and automatically report the occurrence of the coating unevenness.

According to the fourth aspect of the present invention, when the detecting means detects a droplet of the coating liquid for 30 msec or more, that is, when it detects that the falling time is a predetermined time or more, the notifying means is provided. By reporting the occurrence of the coating unevenness, the occurrence of the coating unevenness can be known more reliably.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a substrate coating apparatus using the abnormality detection method according to the present invention.

The substrate W is suction-supported in a horizontal posture by a suction-type spin chuck 1 and is driven to rotate about a rotation center P by an electric motor 3 via a rotation shaft 2. Around the substrate W, a scattering prevention cup 4a for preventing scattering of a photoresist liquid, which is an example of a coating liquid, is provided.
Further, an upper lid member 4b having a plurality of openings formed therein for taking in a downflow is fixed to the frame of the apparatus and fixed to the upper opening of the scattering prevention cup 4a. Have been. When a transport mechanism (not shown) places an unprocessed substrate W on the suction-type spin chuck 1 or receives a processed substrate W, a lifting mechanism (not shown) lowers only the scattering prevention cup 4a. Then, the scattering prevention cup 4a and the upper lid member 4b are separated from each other, and the suction type spin chuck 1 is moved to the scattering prevention cup 4a.
a is projected upward from the upper opening of the a.

At the side of the scattering prevention cup 4a, a supply position (solid line in the figure) corresponding to above the rotation center P of the loaded substrate W, and a retracted position (see FIG. (Dotted line in the middle) is provided. The nozzle 5 is connected through a suckback valve 7 and an opening / closing valve 9 to a supply source 11 for supplying a photoresist solution. The suck-back valve 7 pulls the photoresist liquid exposed from the discharge port 5a of the nozzle 5 slightly after the on-off valve 9 is closed, and
It operates to prevent solidification and to suppress so-called "drips". The on-off valve 9 is connected to the control unit 12.
The opening / closing operation is controlled by this. When the supply start command in the processing program is executed, the opening operation is performed, and when the supply stop command is executed, the closing operation is performed.

A CCD camera 13 is provided on the left side of the upper inner peripheral surface of the upper cover member 4b, and a strobe 15 is provided on the right side thereof. The CCD camera 13 corresponding to the photographing means of the present invention includes a CCD which is a solid-state image sensor, an electronic shutter corresponding to a high speed, a lens, and the like, and its photographing visual field includes the discharge port 5a of the nozzle 5. Substrate W
It is set near the surface of. For example, as shown in FIG. 3, a wide field of view is set so that the surface of the substrate W can be photographed. In this photographing visual field, a slightly horizontally long rectangular area is set in advance as the processing area D1 so that the photoresist liquid can be captured just before being discharged from the discharge port 5a of the supply nozzle 5 and reaching the surface of the substrate W.

The strobe 15 is installed in a dark room so that the photoresist solution is not exposed to light.
It is intended to be used as lighting when shooting, for example,
It is configured by combining a xenon lamp and a bandpass filter that transmits a wavelength of 500 nm or more. The CCD camera 13 and the strobe 15 are connected to a droplet detector 20.

The droplet detecting section 20 will be described with reference to FIG. The strobe power supply 21 supplies required power to the strobe 15 to continuously light it. The camera control unit 22 controls the operation of the CCD camera 13, for example, controls the shooting timing and the operation speed of the electronic shutter. An instruction to start shooting to the camera control unit 22 is transmitted to the control unit 1.
2 is performed by outputting a trigger signal to the I / O control unit 23. As will be described in detail later, a trigger signal is given to the I / O control unit 23 together with a command to stop the discharge of the photoresist liquid onto the substrate, and at that time, the periodic imaging by the CCD camera 13 is started. The speed of the electronic shutter varies depending on the viscosity of the photoresist liquid, the number of rotations of the substrate at the time of supply, the distance between the discharge port 5a and the substrate surface, and the like. In order to accurately detect the falling time, the higher the speed is, the better for accurately measuring the falling time described later. For example, 1/100
It is about 0 sec.

An image signal in the field of view of the CCD camera 13 is transmitted to an image processing unit 24 via a camera control unit 22 and an I / O control unit 23, and a processing area D1 of the image signal (see FIG. 3). ) Are binarized and stored in the image memory 25 as still image data. The image processing unit 24 corresponding to the detecting means of the present invention determines whether or not there is a droplet separated from the photoresist liquid based on each pixel value of the still image data. further,
When the presence of a droplet is first detected, a timer (not shown) starts counting time and measures time until the droplet falls. Then, the control unit 12 compares the reference time stored in the reference time storage unit 30 in advance with the measured fall time, and when the fall time is longer than this time, “application unevenness” is generated. The occurrence is displayed on the monitor 29 via the I / O control unit 23.
Note that the control unit 12 and the monitor 29 correspond to a notification unit of the present invention.

Next, referring to the time chart of FIG.
The operation of the device configured as described above will be described. In this time chart, a method of supplying a photoresist liquid while rotating a substrate (a so-called dynamic method) is described as an example, but the present invention is limited to such a supply form of the photoresist liquid. Not something.

The controller 12 executes the rotation start command at time t = 0 and starts the rotation of the electric motor 3 at time t ₁ such that the rotation speed of the substrate W reaches R1 (for example, 1,500 rpm). I do. Thereafter, when the supply start command is executed at time t _S , first, the suck back valve 7 is deactivated and the opening / closing valve 9 is opened, and the photoresist liquid is supplied from the supply source 11 at a substantially constant flow rate. The supply of the photoresist liquid from the nozzle 5 to the rotation center of the substrate W rotating at a constant speed at the number R1 is started.

Then, when the control unit 12 executes the supply stop command at the time point t _E at which the predetermined time has elapsed, the supply of the photoresist liquid is stopped in an almost reverse order to the above-described procedure. The control unit 12 outputs a trigger signal to the droplet detection unit 20 along with the execution of the supply stop command.

Droplet detector 20 to which a trigger signal has been given
Executes the droplet detection process shown in the flowchart of FIG.

Step S1 (photographing / binarization processing) The I / O control unit 23 controls the CCD camera 13 via the camera control unit 22, and includes the discharge port 5a and the surface of the substrate W as shown in FIG. The field of view is photographed with a high-speed shutter. Then C
The image processing unit 24 processes the image signal of the visual field captured by the CD camera 13, and binarizes the processing area D1 (see FIG. 3) therein. Processing area D1 that has been binarized
Are stored in the image memory 25.

Step S2 (Drop Exists?) The image processing section 24 determines whether or not a drop is present based on each pixel value of the still image data. As used herein, the term “droplet” refers to the photoresist liquid R discharged from the discharge port 5a, the discharge width of which gradually narrows after the discharge is stopped, and returns to the discharge port 5a as shown in FIG. It is a fragment of the spherical photoresist solution R generated between the photoresist solution R falling on the W surface.

The still image data of the processing area D1 is divided into a plurality of pixels px as shown in the schematic diagram of FIG. 7, and a horizontal pixel group among the plurality of pixels px is defined as one group. ... While scanning the groups H1, H2,... In the horizontal direction, the pixel values of the pixels px in all the groups are checked. Then, it is determined whether or not the droplet r is present. For example, the following method can be used as the determination method. That is, attention is sequentially paid to each of the plurality of pixels px, and the value of the pixel of interest px is a black pixel (a portion indicated by hatching in FIG. 7), and pixels px around the pixel of interest px Are all white pixels, it is determined that the droplet r is present.

As a result, when the droplet r is present, the process shifts to step S3, and when the droplet r does not exist, the process returns to step S1. Even supposed to droplets repeatedly executes steps S1~ step S2 without causing, for example, the control unit 12 forcibly stops the process when the execution of the rotation increase command t ₂ time points, The inconvenience that the photographing is repeatedly performed uselessly does not occur.

Step S3 (start timing) The control unit 12 controls the image processing unit 2 via the I / O control unit 23.
When the first drop presence signal is received from 4,
Start the timer and start timing. The falling time of the droplet is measured by this timing.

Step S4 (Shooting / Binary Processing) The shooting near the discharge port 5a is again performed by the CCD camera 13, and the processing area D1 is binarized.

Step S5 (Drops Exist?) The presence of droplets is detected in the same manner as in step S2 described above. As shown in FIGS. 6 and 7, the droplet r also falls toward the surface of the substrate W, so that the droplet r drops to the photoresist liquid R on the surface of the substrate W and disappears after a lapse of time.
If it is no longer present, the process proceeds to step S6, and if it is still present, the process returns to step S4 and repeats until it no longer exists.

Step S6 (time stop) If it is determined in step S5 that no liquid droplet exists, it indicates that the liquid droplet generated near the discharge port 5a has finished dropping on the surface of the substrate W. Therefore, the time measurement is stopped in step S6, and the value is used as the drop time of the droplet.

Step S7 (Comparison of Fall Time) The controller 12 compares the reference time = 30 msec stored in the reference time storage section 30 with the measured fall time. If the measured falling time ≧ the reference time, the droplet r falls behind the photoresist liquid R falling in the form of a fine thread toward the surface of the substrate W. It has been found through experiments conducted by the inventors that "unevenness" is caused. Therefore, while the process proceeds to step S8, if this condition is not satisfied, the probability of occurrence of “application unevenness” is extremely low, so that the droplet detection process is terminated and the application process is continued as usual.

When a plurality of droplets are generated, it is preferable to measure the drop time individually and make a judgment based on the longest drop time.

Step S8 (alarm output) Since the application unevenness occurs due to the droplet, the monitor 29 displays "Application unevenness! ! And other warnings,
Sound the buzzer and notify the operator.

Step S9 (Process Stop) The control unit 12 closes the on-off valve 9, activates the suck-back valve 7, and stops the rotation of the electric motor 3;
The operation is stopped in a state where the substrate W on which the coating unevenness has occurred is carried out.

As described above, the occurrence of the coating unevenness can be easily detected by paying attention to the droplets, and the occurrence of the coating unevenness can be automatically notified, so that the coating unevenness continuously occurs over a plurality of substrates. Can be prevented. Therefore, the operation rate of the device can be improved. Further, by detecting that the drop time is equal to or longer than a predetermined time, it is possible to more reliably know the occurrence of coating unevenness, and it is possible to increase the accuracy of detecting an error in coating processing called coating unevenness.

[0042] In the case where it is determined in step S7 described above becomes No, as shown in the time chart of FIG. 4, to increase the number of revolutions R2 at t ₂ when a predetermined time the rotational speed After holding and shaking off the excess photoresist solution and drying the solvent, a rotation stop command is executed at time t ₄ to complete the coating process.

In the above embodiment, the reference time storage unit 30 stores 30 msec as the reference time.
It is preferable to set the time in consideration of an allowable degree of uneven coating. For example, it is set to an appropriate value of 0 to 100 msec.

In the apparatus of the embodiment described above, a CCD camera is adopted as the photographing means, but various image pickup devices can be used instead.

[0045]

As is apparent from the above description, according to the method of the present invention, the liquid droplets of the coating liquid which are the cause of the coating unevenness can be obtained without performing the visual inspection by the operator after the coating processing. Only need to be detected. Therefore,
The occurrence of coating unevenness can be easily known.

According to the second aspect of the present invention, not only is it possible to detect whether or not there is a droplet of the coating liquid, but also by taking into account the falling time of the coating liquid, the coating unevenness can be more reliably reduced. You can know the occurrence. Therefore, it is possible to enhance the accuracy of detecting an abnormality in the coating process, ie, coating unevenness.

According to the third aspect of the present invention, the detecting means detects the presence of the liquid droplets of the coating liquid based on the image photographed by the photographing means. , The occurrence of the coating unevenness is notified, so that the presence of the droplet can be easily detected and the occurrence of the coating unevenness can be automatically notified. Therefore, it is possible to prevent application unevenness from continuously occurring over a plurality of substrates, and as a result, it is possible to improve the operation rate of the apparatus.

According to the apparatus of the fourth aspect, by detecting that the falling time is equal to or longer than a predetermined time, it is possible to more reliably know the occurrence of coating unevenness. In this case, the accuracy of detecting an abnormality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a substrate coating apparatus according to an embodiment.

FIG. 2 is a block diagram illustrating a schematic configuration of a droplet detection unit.

FIG. 3 is a view showing a field of view of a CCD camera.

FIG. 4 is a time chart illustrating an example of a coating process.

FIG. 5 is a flowchart illustrating a droplet detection process.

FIG. 6 is a diagram showing a state in which droplets of a photoresist liquid are generated.

FIG. 7 is a schematic diagram for explaining detection of a droplet.

FIG. 8 is a diagram provided to explain a mechanism of occurrence of coating unevenness.

[Explanation of symbols]

 W ... Substrate 1 ... Suction spin chuck 3 ... Electric motor 4a ... Splash prevention cup 5 ... Nozzle 5a ... Discharge port 7 ... Suck back valve 9 ... Open / close valve 11 ... Supply source 12 ... Control unit (notification means) 13 ... CCD camera (Photographing means) 20: Droplet detection unit 21: Strobe power supply 22: Camera control unit 24: Image processing unit (detection unit)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AA00 AB15 AB16 AB17 AB20 EA00 EA05 4D075 AC11 AC92 AC99 DA06 DB13 DC21 4F042 AA07 DH02 DH09 EB18 EB29 5F046 JA01 JA02 JA04

Claims (4)

[Claims] In an abnormality detecting method for detecting occurrence of coating unevenness when a coating liquid is supplied to a substrate to form a coating film, the method comprises the steps of: An abnormality detection method, wherein coating unevenness is detected based on the presence of a coating liquid droplet between an outlet and a substrate surface. 2. The abnormality detection method according to claim 1, wherein the application unevenness is detected based on the presence of the droplet of the application liquid for 30 msec or more. 3. A substrate coating apparatus for supplying a coating liquid from a discharge port of a nozzle to a substrate to form a coating film, wherein: a photographing unit configured to photograph between the substrate surface and the discharge port of the nozzle; Detecting means for detecting the presence of liquid droplets based on an image taken by the photographing means; and occurrence of coating unevenness based on the detection of the presence of liquid droplets after the discharge of the coating liquid is stopped. And a notifying means for notifying the following. 4. The substrate coating apparatus according to claim 3, wherein the notification unit notifies the occurrence of coating unevenness based on the detection unit detecting the presence of the droplet of the coating liquid for 30 msec or more. A substrate coating apparatus, characterized in that: