KR20180114676A - appratus for detecting defect density of thin film and method of using the same - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting defect density of a thin film that is capable of directly measuring a phenomenon where trouble gas like water vapor passing through defect activates fluorescent functions of a fluorescence material film under the thin film, thereby more accurately measuring a degree of defect of the thin film than a method for obtaining and directly analyzing an image of the thin film itself. According to the present invention, the apparatus for detecting defect density of a thin film includes: a table on which a sample for detecting a thin film like a barrier film; an optical system through which light emitted from the sample is passed to form image light; an image pickup element for sensing the image light passing through the optical system to generate an image signal; and a computer for activating a program, processing the image signal produced from the image pickup element, and measuring a degree of defect of the sample, wherein the sample is moved by the table to obtain the image light on respective areas of the sample, thereby providing the image signals over the area to be detected of the sample.

Description

[0001] The present invention relates to a defect density detecting apparatus and method for detecting a defect density of a thin film,

The present invention relates to an apparatus and method for inspecting a defect density of a thin film such as a barrier film used in an OLED or the like. More particularly, the present invention relates to a defect density inspection apparatus and a defect inspection method capable of easily and effectively measuring a defect density The present invention relates to an apparatus and method for inspecting a defect density of a thin film having a structure.

Recently, OLEDs, which have become important in the display field, are being used as display devices for various products ranging from small-sized mobile phones to large-screen TVs. One of the key technologies in OLED displays is gas barrier technology (moisture and oxygen barrier or encapsulation technology) that is related to the lifetime and durability of the OLED.

OLEDs are very sensitive to moisture and have a water vapor transmission rate (WVTR) tolerance of less than 10 ^-6 g / m2day (the amount of moisture permeated per square meter of substrate per day). Generally, glass substrates are used for OLED manufacturing, so there is no problem in the water permeability of the substrate itself. However, if the moisture permeability of the packaging material and the sealing material is high, water permeation problems may occur through these materials.

In addition, in the case of a flexible display, which has recently become a topic in the field of display, moisture permeation may occur because a plastic (polymer) substrate is used instead of glass in order to easily bend or fold the substrate.

For example, since the plastic substrate is composed of a structure having a low density between molecules, a large amount of moisture enters the device through the substrate itself, and the moisture permeability is 10 ^-1 g / m 2day or more . This value is 10 ⁵ times the WVTR tolerance required for OLED displays.

Accordingly, techniques for preventing WVTR by forming various types of barrier films together with a plastic substrate or a sealing film have been developed, and multilayered films of polymer / ceramics are typically used.

In the case of using a ceramic thin film such as aluminum oxide or silicon oxide as the barrier film, if there is a defect such as crack in the film, moisture penetration can be performed through the defect, so that it can not serve as a sufficient barrier film. Therefore, it is necessary to ensure that a dense, defect-free barrier film is formed in the process, and it is necessary to inspect how many serious defects occur in the sample barrier film formed under specific process conditions.

Generally, defects are known to be directly related to the barrier film moisture permeability, and as the defect density, which means the relative ratio of the defect area in the total area, increases, the amount of water permeating the film increases and the water permeability increases.

Theoretically, the water permeability value is determined according to the number of defects and the diameter of the defect, and it is known that the linear proportional relationship is established as the following equation.

Q = q _H / t = (AD? / L)

A =? (R?) ²

In this case, A is the cumulative defect area, q _H is the water vapor permeability, D is the diffusion coefficient, and φ is the water vapor density. Finally, the WVTR calculates the amount of water passing through the unit time and unit area .

According to the above, it is necessary to examine the density of crystal defects of the barrier film by sample inspection or the like in order to confirm the possibility of normal use of the barrier film used together with the polymer substrate or the sealing film in the production of the OLED. However, it is an easy task to detect an image of a barrier film using an optical microscope and to check the defect density therefrom. For example, even if there is a defect in the barrier film, there is a case where water vapor permeation is not actually made. In some cases, such a problem may lead to errors in measuring the defect density and determining whether the barrier film forming process is suitable.

This problem can occur when the optical image is automatically processed through image processing and the defect is confirmed. In other words, the automatic measurement itself may become difficult for the part where the defect image is ambiguous.

Therefore, an inspection apparatus and an inspection method capable of accurately checking or measuring the WVTR on the barrier film are required. Existing WVTR measurement techniques include IR measurement, mass spectrometry, and calcium test.

The calcium test method is a typical method for measuring the transmittance at a trace amount of 10 ^-4 g / m ² day or less. This technique uses the UV-Visible light to measure the transmittance of opaque calcium by the reaction with moisture . Generally, a method of measuring the WVTR by measuring the degree of permeability of the reaction material (calcium hydroxide) by saturating water vapor with an inert gas or dry air and sending them to a certain amount of reactant (for example, calcium) .

However, in this method, since the test specimen can obtain moisture permeability for a small portion of a few cm or less and obtain relative relative value instead of absolute moisture permeability, the moisture permeability of the substrate and the barrier film of the large- There is a problem that is difficult to be used for measurement.

IR measurement method as rotation, vibration, of and the energy level of translation is available for the IR wavelength scientifically is widely used as utilizing the principle that absorbed if it is to be the light of the IR wavelength irradiation, but the detector sensitivity limit of the water molecules ^{10 It} is difficult to measure the water permeation amount of ⁴ g / m 2day or less.

Mass spectrometry can measure moisture permeability based on scientific principles, but it is industrially difficult to measure moisture permeability below 10 ^-4 g / ㎡day due to various problems such as IR measurement. In addition, moisture permeability is the most important factor affecting the film. Therefore, real-time monitoring of defects is very important for solving moisture permeability.

Accordingly, there is a great demand for a high-speed measurement method and apparatus capable of effectively measuring moisture permeation amount and defect density for a thin film formed under specific conditions and measuring within a short period of time.

Korean Patent Publication No. 10-2017-0031419: Barrier film Korean Patent Laid-Open Publication No. 10-2016-0080737: Moisture detection sensor, defect detection sensor and sensor array using the same

An object of the present invention is to provide an inspection apparatus and an inspection method which can more accurately confirm or measure the degree of defects of a barrier film than an inspection method in which an image of a thin film itself is obtained and analyzed directly.

It is an object of the present invention to provide an inspection apparatus capable of performing thin film defect density more quickly and automatically and an inspection method using the same.

In the present invention, the inspection apparatus is provided with a detection section such as a table on which a sample is placed, an optical system including an objective lens, and an image pickup element for detecting image light reflected by the sample passed through the optical system.

In the present invention, the image light arriving at the image pickup device is converted into a data signal having the image light information in the image pickup device and is transmitted to the computer device. The computer device analyzes the image light or data signal through the built- The defect density or the number and size of defects.

Since the image light in the present invention does not usually refer to the entire area of the sample but to the corresponding region which is a divided part of the sample area to be inspected, image light for the entire sample area to be inspected reaches the imaging element while moving the sample on the table plane The defect density, which is the defect sample area per unit area of the sample, can be calculated by measuring the total number and size of defects by analyzing these image lights, deducing the total defect area and dividing the total defect area by the sample area to be inspected.

The present invention is for inspecting a sample for measuring a defect density produced by laminating a fluorescent material film on a substrate, forming a thin film such as a barrier film for sealing, and sealing the periphery of the film. For this purpose, A separate illumination control unit may be provided for controlling or selecting the light around the sample or the table so as to easily find a fluorescence generation point indicating a defect in a black field or a dark field state by screening through a filter .

In the present invention, a table on which a sample is placed may be a movable table that receives a signal by a program in a computer device, and the illumination may be interrupted or controlled by a program signal.

An inspection method using an inspection apparatus according to the present invention comprises the steps of: forming a fluorescent material film on a substrate, a thin film to be inspected in order, and sealing the periphery of the sample with a cured resin that prevents gas permeation; preparing an optical microscope having a movable table Preparing a test apparatus of the present invention for inspecting a sample, activating a computer program of the testing apparatus, acquiring image light at each position while moving the table in order, storing corresponding image data in a computer, Acquiring image data, and analyzing image light according to an image analysis program in a computer to extract a defect density.

In the inspection method of the present invention, the image data (image) analysis can be performed together with the acquisition storage and analysis substantially without any time step. In the image analysis, the number of defects and the size of the defects are obtained, , And adding the defect areas of all the defects to obtain the total defect area.

In the present invention, the image pickup device and the computer device may be configured to obtain the defect density or the number and size of defects in the image light as well as the degree of the defect to determine the degree of defect. In this case, the computer device measures the amount of defects for each area by checking whether the light sensing signal sent from each pixel of the imaging device and the intensity of the light sensing signal are multiplied and accumulated for all the pixels, It is possible to take a method of calculating the contrast total content.

According to the present invention, it is possible to more precisely measure the degree of defects of the thin film than the inspection method in which the problem gas such as water vapor passing through the defect activates the fluorescence function of the fluorescent material film in the lower part of the thin film, have.

Since the present invention can directly identify defects directly caused by water vapor penetration, it is possible to eliminate defects that seem to be defects in appearance by using a general optical measuring method. Therefore, the defects of the thin films can be detected more easily It is possible to measure accurately.

According to the present invention, it is possible to judge the possibility of actual use of the thin film formed under the current thin film forming conditions, and to help secure the usable thin film forming conditions while changing the thin film forming conditions.

Particularly, by using a computer apparatus having an automatic inspection program, it is possible to more quickly and automatically check the density of thin film defects and to more easily detect thin film forming conditions applicable to substrate sealing.

Brief Description of the Drawings Fig. 1 is a conceptual diagram schematically showing an embodiment of the inspection apparatus of the present invention,
2 is a vertical sectional view showing an example of a test sample for thin film defect measurement,
3 is a conceptual diagram conceptually showing a configuration of a movable table on which a sample is placed in an embodiment of the present invention,
FIG. 4 is an explanatory diagram showing a corresponding area in a sample taken in accordance with the movement of the movable table in order through arrows in one embodiment of the present invention; FIG.
FIG. 5 is a flowchart showing an embodiment of an inspection method using an apparatus according to an embodiment, including a method of obtaining image light of a corresponding region of a sample in the same manner as FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual block diagram schematically showing an embodiment of the inspection apparatus of the present invention. FIG.

1, the inspection apparatus of the present embodiment includes an illumination light 10 for irradiating light onto a sample 40, a table 50 on which a sample is placed and which can move in the x- and y-axis planes, an illumination light 10 An optical system 30 such as an objective lens through which the image light emitted from the sample 40 passes by irradiating the sample 40 while passing through the optical system 30 and an image pickup element 70 for detecting the image light emitted from the sample passed through the optical system 30, And a computer 80 or a computer device for analyzing a signal having video light information sent from the image pickup device 70 through its own program to derive sample defect information.

A sample (40) to be inspected is mounted on the table (50). 2, first, the fluorescent material film 43 is coated on the substrate 41 such as glass having a very low permeability and the barrier film 45 is laminated. Then, the sample 40 to be examined is sufficiently It is possible to remove moisture or a solvent component and seal the periphery thereof with a hardened resin 49 such as epoxy excellent in airtightness.

At this time, the fluorescent material film 43 does not have the characteristic of a fluorescent substance at first, but is activated when it absorbs water vapor or other activating gas components in the surrounding, and becomes a fluorescent substance. For example, the fluorescent material film 43 contains 1 mM (millimolar) Calcein (3-, 3'-Bis [N, N-di (carboxymethyl) For ease of coating, a solution prepared by adding polyethylene oxide (PEO) in an amount of 1% by weight based on dimethylformamide (DMF) solvent may be coated on a substrate by spin coating and dried. It is preferable that the kind, thickness, and formation conditions of the epoxy are all adjusted to have the condition stability of the sample.

A driving device such as a motor for moving the sample in the inspection table 50 is driven by a signal from a computer device. Accordingly, when a video signal for the corresponding region of the sample is received from the imaging device (imaging device) without any abnormality in the computer device, the computer device gives a signal to the motor to move the table on which the sample is placed to the next corresponding area, This operation can be repeated until the entire area is completed.

Fig. 3 is a schematic conceptual diagram showing the construction of the inspection table 50, and Fig. 4 is a conceptual explanatory diagram for explaining the change or progress of the corresponding region of the sample to be imaged in accordance with the movement of the inspection table.

This table 50 driving is commonly used in semiconductor exposure equipment such as a stepper or an inspection equipment and usually includes a table specimen stage 51 and an x axis 52 which linearly moves in the x axis 52 while supporting the table specimen stage 51. [ A y-axis 54 for supporting the motor and conveying device 53, the x-axis motor and the conveying device 53 itself, a y-axis motor and a conveying device 55 for linearly moving them along the y-axis, And a main body 57 having a built-in unit for sending signals to the transfer devices.

The computer apparatus can change the position of the sample corresponding region 43 in turn by driving the x, y axis motor and the transfer device as indicated by the arrows of FIG. 4 as determined according to the sample transfer program. It is possible to acquire a plurality of images with respect to the entire inspection area 41 of the inspection area 40.

The specific components and the operation method of the inspection table 50 as described above are generally well known, and will be described later in more detail with reference to FIG. However, since the mechanical structure is conventional, a further detailed description thereof will be omitted.

The optical system 30 is an optical system constituting a kind of optical microscope together with peripheral elements, and may be composed of a plurality of lens systems which can be simply made of a single lens but can usually control the focus.

When the illumination light 10 is in the form of a pulse, both the movement of the inspection table 50 and the illumination light 10 may be operated by a signal from the computer 80. [ When the pulse illumination time is very short compared with the moving speed of the inspection table, the movement method of the inspection table can be performed in a continuous operation mode as well as a step and repeat method in which movement and stop are repeated along a predetermined path. For example, if the table is irradiated with a certain period of illumination and the table on which the sample is placed is moved at a constant speed, the first corresponding region is photographed in the first pulsed light, and when the next region comes to the correct position, Is sent to the image pickup device, image lights corresponding to the entire inspection area of the sample can be obtained and sent to the image pickup device, and the computer device can analyze the image.

The illumination light 10 may be an illumination light having a wavelength that is specific to the fluorescence activated film of the sample 40. Herein, the general illumination light is used, and the general illumination light is input to the optical system 30 by the specific frequency selection filter 20 So that only the light of a specific wavelength can pass through it. In addition, when the inspection apparatus is based on a fluorescence microscope, it can be assumed that the illumination light system is configured to block external light.

The sample shall be exposed to water vapor for a certain period of time. If the illumination light continuously illuminates the target area of the sample placed on the inspection table or the area where the barrier film is defective in the area, water vapor introduced from outside through the defect is activated as a fluorescent material by contacting with the fluorescent material film, It will diverge.

In this case, the sample serves as a water vapor detector activated by the water vapor. However, if necessary, the detection gas may be a gas other than water vapor. If the surrounding environment is a dry environment with low water vapor, And a reversible film in which moisture may inversely pass out through the barrier film to cause fluorescence inactivation.

The image light for the sample region passes through the optical system 30, is reflected by the beam splitter or the reflection mirror, and travels toward the imaging element 70. In this process, the image light can pass through the filter 60 specialized for the fluorescence wavelength, and scattered light, reflected light, and the like other than fluorescence can be removed from the filter 60.

Therefore, the image light reaching the image pickup element 70 represents a dark filed image in which only the region of fluorescence emission is bright and the remaining region is dark, and the image pickup element receives the image and transmits the image pickup signal to the computer 80).

Preferably, each pixel of the imaging device detects the position and intensity of the fluorescence, and the signal sent from the pixel determines whether the computer device has fluorescence in the pixel portion and how bright the fluorescence is (Detection of the number and size of fluorescence in the corresponding region).

If the image analysis program of the computer device finds the number of fluorescence in the corresponding region and the size or diameter of each fluorescence, the defect density can be obtained by the size and the number (or frequency) of the fluorescence. The water vapor permeation amount per unit area of the sample can be estimated by applying the related calculation formula shown in the technical section.

Since each image light captured by the image pickup element at one time is not a general area of the sample but represents a divided part of the sample area to be inspected, the image light for the entire image is captured in the sample area to be inspected while moving the sample on the table plane It is possible to calculate defect density which is a defect area per unit sample area by measuring the total number and size of defects by analyzing these image lights and dividing the total number of defects by the sample area to be inspected.

The image analysis program can also calculate the water vapor permeability per unit area in a different way. For example, if the amount of water vapor transmitted through the barrier film defect in the corresponding region of the sample is equal to or less than a predetermined value (for example, indicated by the numerical value 0 or 1) and the luminous intensity It is possible to estimate the amount of water vapor transmission in the corresponding region by accumulating all the luminous intensities of the respective pixels sensed by the pixel groups of the image pickup device corresponding to the corresponding region of the sample, By accumulating the estimated water vapor permeability of the region again, it is possible to estimate the total amount of water vapor passing through the area of the sample to be irradiated. By dividing the total amount of water vapor passing through the area of the sample to be inspected, the estimated permeation amount per unit area of the sample can be obtained. Of course, these estimates can also be obtained through the relevant experiments and by applying the related expressions in the description of the background of the invention.

The image analysis program can be produced by using it as needed, or it can be used by selecting an appropriate program. For example, by using existing freeware such as Image J, the entire image light acquired by the image pickup device is read, a defect boundary is set, the number and size of fluorescence are detected in each image light, The area may be detected.

FIG. 5 is a flowchart illustrating an exemplary process of acquiring image light and image signals or data for the entire sample while sequentially changing the corresponding region of the sample using the inspection apparatus of the present invention as shown in FIG.

First, a sample preparation operation is performed by a preliminary operation (S10). That is, after a fluorescent material film is laminated on a substrate, a barrier film to be a substantial inspection object is laminated, and a periphery of the layer structure is sealed so as to prevent water vapor from penetrating sideways without passing through the barrier film. It is also conceivable to form a layer structure by further laminating an additional protective breathable film on the barrier film in the sample work.

When such a sample is exposed to a gas (water vapor) environment constituting a fluorescent substance upon contact with the fluorescent substance film, the gas passing through the polymer membrane and passing through the defect portion in the barrier film activates the fluorescent substance film to have fluorescence characteristics do.

In addition, an inspection apparatus, for example, a fluorescence microscope is prepared (S20). The fluorescence microscope is arranged so as to block the light outside the predetermined dimmer, and the illumination light and the inspection table are installed so as to receive the inspection signal from the computer apparatus provided with the inspection program.

The image is picked up at each position of the corresponding area of each sample by the objective optical system (step S30), while the sample is placed at a predetermined position of the inspection table (step S30) And the image signal or data is transmitted to and stored in the computer device (S70).

S50, S80, and S80 may be obtained through the above-described method while changing the position of the corresponding region through logical steps of sequentially increasing and changing the index related to the corresponding region position, S90, S100, S110). When all of the image lights are obtained, a step of deriving the defect density is performed by analyzing them through image processing (S120).

In the case of FIG. 4, the total area of the sample to be inspected is the sum of corresponding areas arranged in a matrix of 5 rows and 5 columns. When the program is first run, the inspection table is in the initial position so that the corresponding region of x = 1, y = 1 of the sample is imaged (S50), so that the y coordinate is changed from 1 to 5 (S80, S90). Next, after moving the corresponding region of x = 2, y = 1 to be imaged (S100), the camera moves so that the y coordinate changes again. In this way, all target areas of the sample can be imaged while increasing the x value (S100, S110).

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. That is, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

10: illumination light 20, 60: filter
30: Optical system 40:
41: substrate 43: fluorescent material film
45: barrier film
49: hardened resin 50: table
70: Imaging element 80: Computer (computer device)

Claims (6)

A table on which a sample is placed, an optical system for allowing light emitted from the sample to pass therethrough to form an image light, an imaging device for generating an image signal by sensing image light passing through the optical system, a program for processing the image signal obtained by the imaging device And a computer for measuring a degree of defect of the sample,
The sample is a fluorescent substance film which is brought into contact with water on a substrate for fluorescence activation for thin film inspection, and a thin film are laminated in order, and the periphery thereof is sealed with a hermetic curing resin.
Wherein the table is configured to obtain a video signal over the entire inspection target region of the sample by moving the sample to acquire image light of each corresponding region of the sample. The method according to claim 1,
Wherein the illumination light has a light source of a wavelength band that generates fluorescence when the fluorescent material film is activated and a filter that selectively passes the light of the wavelength range,
Wherein a filter for passing only light in a fluorescent wavelength band is provided in front of the imaging element on the optical path so that only the fluorescent light in the corresponding area is detected in the dark field. The method according to claim 1,
The table includes two different axial direction transfer means for moving the specimen on the table plane. The specimen is moved in response to a signal according to the program of the computer, so that the image light of each corresponding region of the specimen can be acquired Wherein the thin film defect density inspection apparatus comprises: The inspection method using the thin film defect density inspection apparatus according to any one of claims 1 to 3,
Preparing the sample,
Preparing the inspection apparatus,
Installing the sample on the table of the inspection apparatus,
The program of the computer is executed to move the table to the initial position and the image light picked up at the first corresponding area position of the sample is formed in the pixel portion of the image pickup element through the optical system and the image signal is transmitted to and stored in the computer step,
Obtaining a video signal for the entire inspection target area of the sample while changing the position of the corresponding area by giving a signal to the table by the computer according to the program,
And analyzing the image signal to derive a degree of defect of the sample. 5. The method of claim 4,
Wherein the computer analyzes the image signal to measure the number and size of fluorescence in the image light, adds the size of each fluorescence to derive the total defect area, and divides the total defect area by the total area of the sample, . 5. The method of claim 4,
The computer analyzes the image signal to measure the luminous intensity of the fluorescent light sensed by each pixel of the image sensing element to accumulate the luminous intensities of the fluorescently sensed pixels to derive the total defective amount and divide the total defective amount by the total area of the sample, Wherein the inspection is carried out in a predetermined order.

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