JP5142092B2 - TFT array inspection equipment - Google Patents

Description

  The present invention relates to a TFT array inspection apparatus, and more particularly to an inspection apparatus for inspecting defective pixels and performance inspection of a thin film transistor array (TFT array) used for a liquid crystal display, an organic EL display, or the like by a charged particle beam. This relates to the focus on the substrate.

  In electrical inspection of a TFT array substrate, an inspection method using a potential contrast is known as a technique for measuring the potential of a sample without contact. According to this potential contrast, the potential of the sample can be measured by measuring the energy of secondary electrons emitted from the sample surface by irradiating the sample with an electron beam.

  In this TFT array inspection apparatus, a predetermined pattern inspection signal is applied to a TFT array substrate used for a liquid crystal display, an organic EL display, etc., and a predetermined potential state is applied. This substrate is irradiated with an electron beam and generated from the TFT substrate. Secondary electrons are detected, whether or not a predetermined voltage is applied to the panel of the substrate is measured by a signal obtained from the secondary electrons, and a panel defect such as a short circuit is determined based on the measurement result.

  The shape of the pixel (pixel electrode) of the TFT array is usually rectangular or polygonal, and the size is from several tens of microns to several hundreds of microns. The size of the pixel electrode is determined by the size and resolution of the finished display. Therefore, when a plurality of types of TFT arrays having different sizes and resolutions are inspected by one TFT array inspection apparatus, it is necessary to inspect pixel electrodes having different sizes.

On the other hand, a conventional TFT array inspection apparatus using a charged particle beam irradiates and scans a TFT substrate with a charged particle beam having a constant aperture, and detects secondary electrons at a predetermined timing. Is getting.

  For example, when detecting from four detection points on one pixel, the charged particle beam is scanned in the X direction (lateral direction) with respect to the TFT array, and two points are detected while crossing one pixel. Secondary electrons are detected. The charged particle beam is then moved to an adjacent pixel and detected at two points while crossing the pixel.

  The charged particle beam scans the second row after the scanning of the first row of the TFT substrate, and similarly detects secondary electrons at the detection point on the pixel. By repeating this scanning and detection of secondary electron signals at a predetermined timing, four points are detected on the pixel.

  The position and number of detection points can be changed by changing the timing of detecting the secondary electron signal with respect to the scanning signal of the charged particle beam.

  In the conventional TFT array inspection using a charged particle beam, since the aperture of the charged particle beam is constant, there is a problem that the accuracy of defect detection varies depending on the relationship between the irradiation region of the charged particle beam and the pixel, Further, when the shape of the pixel is changed, the shape of the charged particle beam is constant, so that there is a problem that the accuracy of defect detection varies due to the difference in shape between the irradiation region of the charged particle beam and the pixel electrode.

  In the TFT array inspection apparatus, the applicant of the present invention has proposed Patent Document 1 as a configuration for solving the above-described problem and changing the beam diameter.

  In this TFT array inspection apparatus, the beam diameter and beam shape are set in advance corresponding to the pixel specification and the number of pixel signal acquisition points and stored in a data table, and the charged particle beam diameter and beam are read from the data table. The shape is read and controlled.

Japanese Patent No. 4158199

  In the TFT array inspection apparatus in which the beam diameter and beam shape are set and stored in the data table described above, it is necessary to newly register data such as the beam diameter and beam shape for the array configuration not registered in the table. There is a problem of becoming.

  In addition to the problem that this data registration requires work time and labor, if there is an error in the registration work, the correct detection position cannot be detected. is there.

  There is also a problem that it is not easy to confirm whether the cause is in the data registration or in the registered data when such an erroneous inspection or inspection failure occurs.

  Therefore, the present invention solves the above-mentioned problems, and when changing inspection conditions such as pixel specifications and pixel detection points in a TFT array inspection apparatus, it is not necessary to create a data table, and the time required for table creation is reduced. The purpose is to save work time.

  It is another object of the present invention to eliminate erroneous inspection due to a registration error by omitting data registration processing in the data table.

  The present invention has a configuration in which setting data such as a beam diameter and a beam shape is obtained by calculation instead of the configuration in which data is stored in a data table. According to this configuration, the setting data can be sequentially obtained when the setting data is required due to changes in the inspection conditions such as the pixel specifications and the number of detection points of the pixel, and the creation of a data table is not required. Can do. This shortens the work time and avoids registration errors.

  A TFT array inspection apparatus according to the present invention irradiates a TFT substrate with a charged particle beam, and inspects the TFT array by detecting secondary electrons generated from the pixel electrode of the TFT substrate by this charged particle beam irradiation. A focus parameter calculating means for calculating a focus parameter for determining the focus of the charged particle beam based on the sampling pitch of the charged particle beam, and a focus control means for controlling the focus of the charged particle beam based on the calculated focus parameter. Prepare.

  The focus parameter is the beam diameter and beam shape of the charged particle beam at the irradiation position. The beam diameter is the radial length of the beam in the X direction and the Y direction, and the beam shape can be a ratio of the radial length in the X direction to the radial length in the Y direction. Since the focus parameter of the beam diameter or beam shape depends on the distance from the focus lens that narrows the beam of the charged particle beam, it can be determined at a position at a predetermined distance from the focus lens. For example, at a substrate position that is set at a predetermined distance from the focus lens, it can be determined within a range in which the beam is irradiated when a charged particle beam is irradiated onto the substrate position.

  The focus parameter calculation unit calculates the focus parameter based on the sampling pitch of the charged particle beam. The sampling pitch of the charged particle beam is an interval between irradiation points that are adjacently irradiated when the pixel of the TFT substrate is irradiated with the charged particle beam. The sampling pitch is determined based on the pixel size, pixel arrangement, and resolution. Here, the resolution is the number of detection points detected from one pixel, and a high resolution can be obtained by setting a large number of detection points in one pixel. The resolution can be determined corresponding to the number of charged particle beams irradiated in one pixel.

  The focus parameter calculation means uses a sampling pitch as a variable to calculate a beam diameter length in the X direction and the Y direction, and a calculation program to determine the ratio of the beam diameter from the calculated beam diameter lengths in the X direction and the Y direction. Is provided. The focus parameter calculation means calculates the beam diameter and ratio by substituting the value of the sampling pitch into the calculation program and performing calculation processing.

  According to the focus parameter calculation means of the present invention, by obtaining the focus parameter by calculation, it is possible to obtain the focus parameter without obtaining the focus parameter in advance and storing it in the data table. Also, focus parameters that are not prepared in the data table can be acquired by simply performing arithmetic processing.

  The focus control unit controls the focus of the charged particle beam by deflecting the charged particle beam in the X direction and the Y direction based on the beam diameter and ratio calculated by the focus parameter calculating unit, and the charged particle beam at the irradiation position. The beam diameter and the beam shape are controlled so as to have a predetermined diameter and shape.

  The focus control means is a means for controlling the focus of the charged particle beam, and generates a control signal for driving the focus lens based on the beam diameter and ratio calculated by the focus parameter calculation means. The focus lens deflects the charged particle beam in the X direction and the Y direction based on the control signal generated by the focus control means, and controls the beam diameter and the beam shape to have a predetermined diameter and shape by the deflection of the beam. .

  The focus control unit corrects the deflection amount of the charged particle beam according to the deflection angle of the charged particle beam, and sets the beam diameter and the beam shape to a predetermined diameter and shape at any deflection angle.

  Here, the deflection angle of the charged particle beam is an angle at which the charged particle beam is shaken when the substrate is scanned with the charged particle beam. When the charged particle beam is scanned on the pixel by swinging the charged particle beam in the X direction or the Y direction in a state where the charged particle beam source and the substrate are in a predetermined positional relationship, the incident angle of the charged particle beam with respect to the pixel is Varies depending on the deflection angle of the charged particle beam. The beam diameter and beam shape of the charged particle beam on the pixel vary depending on the incident angle of the charged particle beam with respect to the pixel.

  The focus control means of the present invention corrects the deflection amount for deflecting the charged particle beam according to the deflection angle of the charged particle beam. By correcting the deflection amount, the beam diameter and the beam shape on the pixel are made constant regardless of the deflection angle of the charged particle beam.

  According to the present invention, in the TFT array inspection apparatus, when changing inspection conditions such as pixel specifications and the number of detection points of pixels, it is not necessary to create a data table, and the work time is reduced by omitting the time required for table creation. can do.

It is the schematic for demonstrating the structure of the TFT array test | inspection apparatus of this invention. It is a figure for demonstrating the relationship between pixel size and a sampling pitch. It is a figure for demonstrating control of the charged particle beam of the TFT array inspection apparatus of this invention. It is a figure for demonstrating control of the charged particle beam of the TFT array inspection apparatus of this invention. It is a figure for demonstrating the structure of the beam parameter calculation means of this invention. It is a figure for demonstrating the beam diameter and beam shape of a charged particle beam.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view for explaining the configuration of a TFT array inspection apparatus according to the present invention.
In FIG. 1, a TFT array inspection apparatus 1 irradiates a panel 21 of a substrate 20 with a charged particle beam such as an electron beam from a charged particle beam source 2 such as an electron beam source, and emits secondary electrons and the like emitted from the panel 21. An example of a configuration of an inspection apparatus that detects a defect of a TFT array by detecting an electron beam with a detector 6 is shown.

  A focus lens 3 and a scanning lens 4 are disposed on the beam path between the charged particle beam source 2 and the substrate. The focus lens 3 is a lens system that controls the focus of the charged particle beam irradiated from the charged particle beam source 2. For example, an electromagnetic coil or an electrode is opposed to each other across the path of the charged particle beam in the X direction and the Y direction. Can be configured.

  The focus lens 3 changes the focus state of the charged particle beam by deflecting the charged particle beam in the X direction and the Y direction, and changes the beam diameter and the beam shape. The beam diameter can be determined by, for example, the diameter length of the beam in the X direction and the diameter length in the Y direction. The beam shape can be determined by, for example, the radial length in the X direction and the radial length in the Y direction.

  The focus lens can be changed from a simple elliptical shape to various shapes by configuring a plurality of sets of electromagnetic coils or electrodes arranged in the X and Y directions.

  The scanning lens 4 is a system that scans the charged particle beam on the panel 21 of the substrate 20 by oscillating the charged particle beam in the X direction or the Y direction. It can be configured by arranging the electrodes to face each other across the path of the charged particle beam in the X direction and the Y direction.

  The focus lens 3 is controlled by a focus control unit 12a, and the scanning lens 4 is controlled by a beam scanning control unit 12b. The focus control unit 12a and the beam scanning control unit 12b constitute a lens control unit 12.

  The substrate 20 is placed on the XY stage 5 and is movable in the X direction and the Y direction. The driving of the XY stage 5 is controlled by the stage control unit 15.

  The scanning control unit 14 sends a control signal to the stage control unit 15 to control the movement of the XY stage 5 in the X / Y direction, and sends a control signal to the beam scanning control unit 12b to deflect the charged particle beam by the scanning lens 4. Is controlled to scan the charged particle beam on the panel 21 of the substrate 20 and irradiate the entire surface of the panel with the charged particle beam.

  In the scanning of the charged particle beam, the panel is divided into a plurality of passes formed along the Y direction, and the charged lens beam is shaken in the X direction by the scanning lens 4 in each pass, and the substrate 20 is moved by the XY stage 5. The entire surface of the panel can be scanned by repeating the operation of scanning in the path by moving in the Y direction and further scanning in the next path by moving the substrate 20 in the X direction by the XY stage 5.

  The focus control unit 12a controls the focus lens 3 to control focus parameters such as a beam diameter and a beam shape. Control by the focus control unit 12 a is performed by a focus control signal generated by the focus control signal generation unit 13.

  The focus control signal controls the voltage or current supplied to the focus lens 3, changes the amount of deflection of the charged particle beam in the X direction and Y direction, changes the focus state of the charged particle beam, and changes the beam length in the X direction. The beam shape is changed by changing the beam diameter of the length in the Y direction and changing the ratio of the length in the X direction to the length in the Y direction.

  Since the beam diameter and the beam shape change depending on the distance from the focus lens 3, they are determined at a predetermined distance from the focus lens. The position of the predetermined distance can be an irradiation position of the charged particle beam on the panel, and can be determined within a range in which the beam is irradiated when the irradiation position is irradiated.

  The focus parameter calculation unit 11 calculates a focus parameter by calculation using the sampling pitch as a variable, and sends the calculated focus parameter to the focus control signal generation unit 13. The focus control signal generation unit 13 generates a focus control signal based on the focus parameter calculated by the focus parameter calculation unit 11, and sends the focus control signal to the focus control unit 12a.

  In order to detect defects in the TFT array, an inspection signal is applied to the TFT array of the panel of the substrate 20 to form a potential state of a predetermined pattern on the panel, and this potential state is scanned with a charged particle beam such as an electron beam. Detect by. The inspection signal application circuit 18 applies an inspection signal to the TFT array. The inspection signal has a signal pattern corresponding to the defect type detected by the TFT array.

  The signal processing unit 16 inputs the detection signal detected by the detector 6 and forms image data such as a secondary electron image. The defect detection unit 17 performs signal processing for detecting defective pixels using image data. Note that control of the entire TFT array inspection apparatus 1 is performed by a control unit (not shown).

  Note that each of the above-described units is shown for explaining the functions of the TFT array inspection according to the present invention, and does not necessarily have individual components that realize these functions, and is configured by a CPU, a memory, or the like. The circuit may be configured by software that executes each function.

  The relationship between the sampling pitch and the pixel size will be described with reference to FIG.

  FIG. 2A and FIG. 2B show the magnitude relationship between the pixel sizes and the magnitude relationship between the sampling pitches.

  FIG. 2A shows a case where the pixel size is relatively small, and the pixel 23a has [Px1, Py1] as the X direction size and the Y direction size. Here, when four detection points are set from one pixel 23a, the charged particle beam is irradiated to four places in one pixel. In this case, the sampling pitch SPx1 in the X direction can be determined by, for example, Px1 / 2 using the pixel size Px1 in the X direction, and the sampling pitch SPy1 in the Y direction can be determined by using, for example, the pixel size Py1 in the Y direction. 2 can be determined.

  On the other hand, FIG. 2B shows a case where the pixel size is relatively large, and the pixel 23b has [Px2, Py2] as the X direction size and the Y direction size. Here, as in FIG. 2A, when the charged particle beam is irradiated to four places in one pixel, the sampling pitch SPx2 in the X direction is determined by Px2 / 2 using the pixel size Px2 in the X direction, for example. The sampling pitch SPy2 in the Y direction can be determined by Py2 / 2 using the pixel size Py2 in the Y direction, for example.

  Next, control of the charged particle beam of the TFT array inspection apparatus of the present invention will be described with reference to FIGS. Here, an example of operation in which a beam parameter is calculated from the pixel size and resolution and a control signal for controlling the lens system is generated based on the calculated beam parameter will be described.

  First, the sampling pitch [SPx, SPy] (102 in FIG. 3) is obtained. As shown in FIG. 2, the sampling pitch can be obtained from the pixel size [Px, Py] (100 in FIG. 3) and the resolution (101 in FIG. 3).

  FIG. 4A shows the relationship between the pixel size [Px, Py] and the sampling pitch [SPx, SPy], and shows an example of irradiating four irradiation points 31 within one pixel 23 with charged particle beams. Yes. FIG. 4B shows an example of the sampling pitch [SPx, SPy].

  Next, the beam parameter (103 in FIG. 3) is calculated by the beam parameter calculator using the sampling pitch [SPx, SPy]. Here, the beam diameter [dx, dy] and the beam shape dx / dy are defined as the beam parameters. The beam diameter dx is the length of the beam in the X direction at the irradiation point, and the beam diameter dy is the length of the beam in the Y direction at the irradiation point. The beam parameter calculation unit has a calculation program for calculating beam parameters from the sampling pitch [SPx, SPy], and calculates the beam diameter [dx, dy] and the beam shape dx / dy by calculation processing. The beam parameter, beam diameter, and beam shape can be set with different definitions, and in this case, the calculation program corresponding to the set definition is used.

  FIG. 4C shows the relationship between the beam diameter [dx, dy] and the sampling pitch [SPx, SPy].

Next, a focus control signal and a beam scanning control signal are generated.
The focus control signal generation (105 in FIG. 3) is performed by the focus control signal generation unit. The focus control signal is a control signal for driving the focus lens (107), and is generated using the beam parameters (beam diameter, beam shape) calculated by the beam parameter calculation means and the deflection angle ω (104). Note that the deflection angle is used when correcting a deviation in beam diameter or beam shape due to a difference in incident angle of the charged particle beam with respect to the substrate.

  The generated focus control signal is sent to the focus control unit (106), and the focus control unit 106 generates a drive signal for driving the focus lens (107) based on the focus control signal.

  The generation of the beam scanning control signal (110 in FIG. 3) is performed by the scanning control unit. The beam scanning control signal is a control signal for driving the scanning lens (112), and is generated using the deflection angle ω (104).

  The generated beam scanning control signal is sent to the scanning control unit (111), and the scanning control unit 111 generates a driving signal for driving the scanning lens (112) based on the beam scanning control signal.

  FIG. 4D is a diagram for explaining the deviation of the beam diameter due to the deflection angle ω. In FIG. 4D, when the charged particle beam is incident on the substrate panel, the deflection angle ω when the charged particle beam is incident on the substrate panel at a right angle is set to “0”. The diameter length of the irradiation range 30A formed by the beam is defined as dx0. When the charged particle beam is shaken and the charged particle beam is obliquely incident on the substrate panel, if the diameter length of the irradiation range 30B formed by the charged particle beam is dx1, the diameter length dx1 is the diameter length dx0. The beam diameter and beam shape change.

  Therefore, fluctuation of the charged particle beam causes variation in the beam diameter and beam shape of the charged particle beam applied to the pixel, which causes a positional error of the pixel.

  In the present invention, when the beam scanning control signal is generated, correction is performed so that the beam diameter and the beam shape are constant according to the deflection angle ω. This correction can be obtained by geometric conditions such as the deflection angle ω, the distance between the scanning lens and the substrate position, and can be configured by an arithmetic program.

  Next, a configuration example of the focus parameter calculation unit 11 according to the present invention will be described with reference to FIG. In FIG. 5, the focus parameter calculation unit 11 includes a calculation unit 11 a that can be configured by a CPU and a memory, and a calculation program storage that stores a calculation program that causes the CPU to execute calculation processing represented by calculation formulas and calculation coefficients. It can comprise from the means 11b.

  The calculation means 11a inputs variables such as the pixel size and resolution, and sequentially reads out calculation programs necessary for calculation processing from the calculation program storage means 11b, thereby calculating beam parameters of the beam diameter and beam shape.

  The calculation formula of the calculation program is an example of calculating the beam diameter by dividing the pixel size by a coefficient determined by the resolution as an example, or by dividing the pixel size in the X direction by the pixel size in the Y direction. Although described in the example of calculation, this arithmetic expression is an example and is not limited to this, and can be arbitrarily set.

  In the calculation of the beam parameters according to the present invention, when a plurality of beams are irradiated to one pixel, the size and shape of each beam can be the same or different.

  FIG. 6 is a diagram for explaining an example of a beam diameter and a beam shape calculated by the beam parameter calculation unit.

  FIGS. 6A and 6B show an example in which four beams having the same size and the same shape are irradiated inside the pixel 23. In the figure, four beams are indicated by beam irradiation ranges 30a to 30d on the pixels.

  6A shows an example in which the irradiation ranges 30a to 30d of each beam are set inside one pixel 23, and FIG. 6B is an enlarged view of the irradiation ranges 30a to 30d of each beam. An example in which the setting is made to protrude outside the two pixels 23 is shown. According to the example of FIG. 6B, a portion where the beam is not irradiated in the pixel 23 can be narrowed, and a beam irradiation region can be set wide within the pixel.

  FIGS. 6C and 6D show an example in which beams having different sizes and shapes are irradiated in the pixels 23. The examples shown in FIGS. 6C and 6D are examples in which beams having different sizes and shapes are irradiated in order to match the shape of the pixels 23.

  In FIG. 6C, the three beams in the beam irradiation ranges 30b to 30 have the same size and the same shape, and the beams in the irradiation range 30a are made different to match the shape of the pixel 23.

  Further, in FIG. 6D, the two beams in the beam irradiation ranges 30c to 30 have the same size and the same shape, and the beams in the irradiation range 30a and the irradiation range 30b are different from each other, thereby forming the shape of the pixel 23. It is matched. In FIGS. 6A and 6B, the beam indicated by the irradiation range 30a can be formed by reducing the size in the Y direction and deviating in the Y direction.

  The present invention can be applied to a liquid crystal array inspection device, an EB tester, a TFT and transistor inspection device, an organic EL array inspection device, a scanning electron microscope, a nondestructive inspection device, an array inspection device for a flat panel television, and the like. .

DESCRIPTION OF SYMBOLS 1 Array test | inspection apparatus 2 Charged particle beam source 3 Focus lens 4 Scan lens 5 Stage 6 Detector 11 Focus parameter calculation part 11a Calculation means 11b Calculation program memory | storage means 12 Lens control part 12a Focus control part 12b Beam scanning control part 13 Focus control signal Generation unit 14 Scan control unit 15 Stage control unit 16 Signal processing unit 17 Defect detection unit 18 Inspection signal application circuit 20 Substrate 21 Panel 23 Pixel 23a Pixel 23b Pixel 30A Irradiation range 30B Irradiation range 30a-30d Irradiation range 31 Irradiation point

Claims (4)

In a TFT array inspection apparatus that inspects a TFT array by irradiating a charged particle beam to a TFT substrate and detecting secondary electrons generated from the pixel electrode of the TFT substrate by the charged particle beam irradiation.
A focus parameter calculating means for calculating a focus parameter for determining a focus of the charged particle beam based on a sampling pitch of the charged particle beam;
A TFT array inspection apparatus comprising: focus control means for controlling the focus of the charged particle beam based on the calculated focus parameter. The focus parameter is the beam diameter and beam shape of the charged particle beam at the irradiation position,
The beam diameter is the length in the X direction and the Y direction at a predetermined position,
The beam shape is a ratio of the radial length in the X direction to the radial length in the Y direction,
The focus control means includes
Based on the diameter and ratio of the beam calculated by the focus parameter calculation means, the charged particle beam is deflected in the X direction and the Y direction to control the focus of the charged particle beam,
The TFT array inspection apparatus according to claim 1, wherein a beam diameter and a beam shape of the charged particle beam at the irradiation position are set to a predetermined diameter and shape.   The focus parameter calculation means uses a sampling pitch as a variable, a calculation program for determining the beam length in the X direction and the Y direction, and a calculation for determining the ratio of the beam diameter from the calculated beam length in the X and Y directions. The TFT array inspection apparatus according to claim 2, further comprising a program.   The focus control unit corrects the deflection amount of the charged particle beam according to the deflection angle of the charged particle beam, and sets the beam diameter and the beam shape to a predetermined diameter and shape at any deflection angle. The TFT array inspection apparatus according to claim 2 or 3.