KR19980058661A - Focal plane measuring apparatus and method of exposure process - Google Patents

Abstract

The present invention relates to a focal plane measuring device for fixing exposure and a method thereof, comprising: a reticle engraved with measuring marks in X and Y directions; A projection lens system for condensing light output through the reticle; A plate on which light collected through the projection lens system is irradiated, a measurement mark is engraved, and a photosensitive film is coated; A plate stage on which the plate is placed; Light sensing means mounted on the plate stage and configured to receive light incident through a measurement mark of the plate and output a corresponding electrical signal; Control to output the corresponding control signal to move the plate by a predetermined step in each of the X, Y, Z directions, and calculate the position corresponding to the best focal plane by the signal output from the light sensing means in accordance with the movement of the plate Means; It comprises a stage driving means for driving in accordance with the control signal output from the control means for moving the plate stage to the corresponding position, in order to check the correct focal plane of the plate in the exposure apparatus, according to the photoelectric method By using the reticle and the test plate to perform the overlapping exposure step by step in the Z direction on the plate according to the first confirmed exposure range, the best focal plane can be identified within a short time without any additional preparation step. Can provide.

Description

Focal plane measuring apparatus and method of exposure process

1 is a block diagram of a focal plane measuring apparatus of an exposure process according to an embodiment of the present invention,

FIG. 2 is a block diagram of an electronic control part of the focal plane measuring apparatus of the exposure process according to the embodiment of the present invention.

3 is a state diagram of measurement marks formed on a test reticle and a test plate according to an embodiment of the present invention,

4 is a cross-sectional view showing the mounting state of the optical sensor according to an embodiment of the present invention,

5 is a view showing an image scanning state of a focus mark according to an embodiment of the present invention.

6 is a detailed circuit diagram of an interface unit according to an embodiment of the present invention.

7 is an output signal waveform diagram of an interface unit according to an embodiment of the present invention.

8 is a graph showing the relationship of Z step to output signal according to an embodiment of the present invention,

9A and 9B are pattern diagrams of a reticle used in verifying a focal plane according to an embodiment of the present invention.

10 is a view showing an overlapping exposure state according to an embodiment of the present invention,

11 is a pattern diagram of a test reticle according to another embodiment of the present invention,

12 is a pattern diagram of a test plate according to another embodiment of the present invention,

13 is a pattern diagram of a test mask according to another embodiment of the present invention,

14 is a flowchart of a focal plane measuring method of an exposure process according to an embodiment of the present invention.

The present invention relates to a focal plane measuring device and a method for fixing the exposure, and in order to confirm the correct focal plane of the plate in the exposure apparatus, the focal plane was first checked using a test reticle and a test plate according to the photoelectric method. Next, the present invention relates to an apparatus for measuring a focal plane of an exposure process for performing stepwise overlapping exposure in a Z direction on a plate according to an identified exposure range, and a method thereof.

In the manufacture of liquid crystal display devices (hereinafter referred to as LCDs), the electrical circuits formed on the original plate (hereinafter referred to as the reticle) on the flat glass (plate) are engraved using a debt. The exposure process is the most important process.

In the exposure process, in order to engrave the electrical circuits engraved on the reticle on the flat glass using a debt, a photosensitive material (PR: Photo Resist) that is exposed to a specific wavelength band debt must be uniformly applied on the plate.

Therefore, the LCD exposure apparatus includes a reticle stage for mounting a reticle having an electric circuit pattern engraved thereon and a plate stage for fixing a plate having an electric circuit pattern engraved therebetween, and a lens system for condensing an exposure light source is located between the two stages. do.

A blinder is mounted on the reticle stage to limit the exposure light source to the circuit pattern on the reticle so as to illuminate only the portion of the electrical circuit pattern on the reticle on the plate.

Due to their mutual operation, the circuit image of the reticle is exposed on the plate surface. At this time, the reticle becomes a circuit for driving the LCD panel, and therefore, the reticle must be exposed at the correct focus.

In order to expose the pattern of the reticle to the correct focus position, all the exposure apparatuses have a driving part capable of driving the plate stage slightly in the Z direction, and the driving part can be used to position a plate for exposing to the correct focal plane. .

In such an exposure apparatus, the pattern engraved on the reticle is accurately imaged on the plate, so that the photosensitive film on the plate is accurately exposed, which is one of the basic requirements.

To this end, various measurement and evaluation processes such as distortion evaluation, resolution evaluation, overlapping exposure precision evaluation, and screen joint precision evaluation of the optical system of the exposure apparatus must be performed in advance and verified.

Since the evaluation items are assumed to be performed in the mode accurate focal plane, it is very important to check the correct focal plane first for many of the above evaluations.

The conventional exposure apparatus uses a test-only reticle and a test-only plate engraved with a special pattern in order to confirm the correct focal plane. The most widely used method among various methods is a method of developing and confirming an exposure result through a direct exposure method.

This method comprises the steps of first forming a photoresist film on a plate, exposing a pattern on the plate using a test reticle having a predetermined test pattern engraved thereon, and developing and verifying the exposed plate. Is made of.

In the most primitive method consisting of the above steps, the photosensitive film forming, exposing, developing, measuring and verifying step are performed for each step in the Z direction with respect to a specific area defined on the plate using one plate. As a method, the method has the most accurate advantage in that it can exclude the inherent property of each plate, that is, the difference in planar properties of the plate, but has a disadvantage in that a huge time loss occurs.

In order to reduce the time loss as described above, by performing exposure in a step in which the measurement pattern is moved to a minute position with respect to one plate at a predetermined interval, one plate rather than exposure in one stem to one plate There is a method of performing exposure in several steps in the Z direction with respect to.

However, the method has a reduced execution time to some extent, but there is a disadvantage that the precision is lowered due to the difference in planarity of each part on the same plate and the thickness difference of the coated photoresist.

However, while the above-described method prevents some time loss, the conventional methods move the stage in units of microsteps in the Z direction to confirm the correct focal plane of the plate stage, and then expose the plate to which the photosensitive film is coated. The enormous loss of time is inevitable because of the development, measurement and verification process.

That is, since every step of the Z-direction moving thread is about 2 to 5 μm, the total focal length in the Z direction is approximately 200 to 500 steps. Confirming that the exposure, development, measurement and verification process to be performed by this level, there is a disadvantage that a huge time loss occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages, and in order to check the correct focal plane of the plate in the exposure apparatus, the focal plane is first checked using a test reticle and a test plate according to an optoelectronic method. A focal plane measuring device and method thereof in an exposure process capable of reducing the time required for focal plane measurement and measuring the focal plane more precisely by performing overlapped exposure for each step in the Z direction according to the identified exposure range. It is about.

The configuration of the present invention for achieving the above object,

A reticle engraved with measuring marks in X and Y directions;

A projection lens system for condensing light output through the reticle;

A plate on which light collected through the projection lens system is irradiated and engraved with a measurement mark;

A plate stage on which the plate is placed;

Light sensing means mounted on the plate stage and configured to receive light incident through a measurement mark of the plate and output a corresponding electrical signal;

Control to output the control signal so that the plate is moved by each step in each of the X, Y, Z direction, and calculates the position corresponding to the best focal plane by the signal output from the light sensing means in accordance with the movement of the plate Means;

And stage driving means for driving in accordance with a control signal output from the control means to move the plate stage to a corresponding position.

Another configuration of the present invention for achieving the above object,

Forming a photoresist film on the plate;

Performing a first exposure to the plate while moving the plate by a predetermined step in the X, Y, and Z directions with respect to the reticle on which the measurement pattern is formed;

Calculating a best focal plane according to the optical signal measured according to the first exposure;

Repeatedly exposing a pattern of the verification reticle on the plate by moving the plate by a predetermined step in the X, Y, and Z directions based on the calculated best focal plane;

And developing the repeatedly exposed plate, and then inspecting a proximity pattern group among the repeatedly exposed patterns.

By the above configuration, the most preferred embodiment that can be easily carried out by those skilled in the art with reference to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a focal plane measuring apparatus of an exposure process according to an embodiment of the present invention,

FIG. 2 is a block diagram of an electronic control part of the focal plane measuring apparatus of the exposure process according to the embodiment of the present invention.

3 is a state diagram of measurement marks formed on a test reticle and a test plate according to an embodiment of the present invention,

4 is a cross-sectional view showing the mounting state of the optical sensor according to an embodiment of the present invention,

5 is a view showing an image scanning state of a focus mark according to an embodiment of the present invention.

6 is a detailed circuit diagram of an interface unit according to an embodiment of the present invention.

7 is an output signal waveform diagram of an interface unit according to an embodiment of the present invention.

8 is a graph showing the relationship of Z step to output signal according to an embodiment of the present invention,

9A and 9B are pattern diagrams of a reticle used in verifying a focal plane according to an embodiment of the present invention.

10 is a view showing an overlapping exposure state according to an embodiment of the present invention,

11 is a pattern diagram of a test reticle according to another embodiment of the present invention,

12 is a pattern diagram of a test plate according to another embodiment of the present invention,

13 is a pattern diagram of a test mask according to another embodiment of the present invention;

14 is a flowchart of a focal plane measuring method of an exposure process according to an embodiment of the present invention.

As shown in FIG. 1 and FIG. 2, the configuration of the focal plane measuring apparatus during the exposure process according to the embodiment of the present invention is

A reticle 2 on which an X-direction measuring mark 21 and a Y-direction measuring mark 23 are formed,

The rake stage 1 in which the reticle 2 is located,

A projection lens system 3 for condensing and outputting light incident through the reticle 2;

A plate 4 on which the light collected by the projection lens system 3 is irradiated, and the measurement mark 41 is formed;

A plate stage 5 on which the plate 4 is located,

An optical sensor 6 mounted on a part of the plate stage 5 to receive light incident through the measurement mark 7 of the plate 4 and to output a corresponding signal;

An interface unit 7 for amplifying and outputting the signal output from the optical sensor 6;

A control device 8 for calculating a best focal plane according to the signal output from the interface unit 7 and outputting a corresponding stage driving signal according to a set focus measurement operation;

It is composed of a stage driver 9 for moving the plate stage 5 in the corresponding direction in accordance with a stage driving signal applied to the output terminal of the control device 8.

The optical sensor 6 is mounted in the plate stage 5, as shown in the attached FIG. 4, and has a structure recessed inward so that the plate 4 can be placed on the plate stage 5.

As shown in FIG. 7, the sensor interface unit 7 includes: a current / voltage unit 71 for varying and outputting an input current signal into a corresponding voltage signal;

A voltage amplifying unit 72 for amplifying and outputting a voltage signal output from the current / voltage unit 71;

A signal output unit 73 for outputting an amplified signal output from the voltage amplifier 72;

A signal inverting unit 74 inverts and outputs an amplified signal output from the voltage amplifying unit 72.

Referring to the operation of the focal plane measuring device during the exposure process according to the embodiment of the present invention by the above configuration as follows.

In the present invention, a photoelectric method and an overlapping exposure method are used to measure an accurate focal plane. The optoelectronic method uses a test reticle and a test plate having a measurement pattern engraved therein, and is mounted on a plate stage. The sensor measures the signal according to the pattern interference on the test reticle and the test plate, and then checks the focal plane according to the level of the measured interference signal.

First, a photosensitive film is formed on the test plate 4 (S100), and then the control device 8 operates the stage driver 9 to move the test plate 4 to a base position in the Z direction. After moving, the X direction measurement mark 21 on the test reticle 2 and the measurement mark 41 of the test plate 4 are aligned.

The measurement marks 21 and 23 formed on the test reticle 2 have separate shapes in the X and Y directions, respectively, as shown in FIG. 3 and have a focal plane for the X and Y directions. It is used to measure and is of the same size to measure together the influence of astigmatism by the projection lens system 3 mounted between the test reticle 2 and the plate stage 5.

And the measurement mark 41 formed on the test plate 4 is made in the form of a dot, as shown in Figure 3 attached, the size and the measurement marks (21, 23) formed on the test reticle (2) same.

In addition, the width of the dot formed in the measurement mark 41 is comprised similarly to the line width of the mark formed in the said test reticle 2, and can be used for both X and Y directions.

The light output from a light source not shown on the test reticle 2 is irradiated, and then irradiated onto the test plate 4 through the test reticle 2.

In this state, the control device 8 operates the stage driver 9 to move the test plate 4 in the X direction by a predetermined distance, whereby the test plate 4 is used as the measurement mark image of the test reticle 2. Perform the X-direction focal plane measurement by scanning the measurement mark.

That is, as the test plate 4 moves from the lowest position in the X direction by a predetermined distance, the position where the reticle measurement mark image output from the test reticle 2 is formed into the plate measurement mark 41 is varied. do.

Therefore, as shown in FIG. 4, the intensity and incidence of the light incident on the optical sensor 6 positioned under the plate measuring mark 41 are varied, and the optical sensor 6 is configured to correspond to the incident light. Outputs to the interface unit 7.

The signal output from the optical sensor 6 is converted into a corresponding voltage signal through the current / voltage unit 71 of the interface unit 7 as shown in FIG. 72 is amplified to a predetermined level and output.

The amplified signal output from the voltage amplifying unit 72 is output to the control device 2 through the signal output unit 73, and the amplified signal output from the voltage amplifying unit 72 is to remove noise on the transmission. The signal is inverted and amplified again through the signal inversion unit 74 and output to the control device 8.

The control device 8 stores the X-direction focal plane measurement data measured according to the scan operation in the X-direction in the corresponding region of the internal memory, and then moves the test plate 4 upward by each step set in the Z-direction. The above scan operation is repeatedly performed.

That is, when the scan operation according to the movement of the predetermined distance in the X direction is completed, the test plate 4 is moved for each step set from the basic position in the Z direction to the top position in the Z direction, Like the directional focal plane measurement, a Z-direction focal plane measurement operation is performed to scan the plate measurement mark with the reticle measurement mark image.

The control device 8 stores the focus measurement data in the Z direction measured in the same area as the scan operation in the X direction in the corresponding area of the memory.

When the Z direction focal plane measurement is completed, the control device 8 aligns the measurement mark 41 of the test plate 4 with the measurement mark 22 of the Y direction on the test reticle 2 and then the test plate. By moving (4) by a predetermined distance in the Y direction, the Y-direction focal plane measurement operation is performed as described above, and the measured Y-direction focal plane measurement data is stored in the corresponding region of the memory (S120).

The photoelectrically changed signal processed by the optical sensor 6 according to the above scan operation is as shown in FIG. In the scanning process, due to the correlation effect between the measurement marks 3 and 4 of the test reticle 2 and the measurement mark 41 of the test plate 4, the signal output from the interface unit 7 is: It is shown in the form of a sinusoidal signal in which peaks appear at the same period as the interval between the test reticle 2 and the two marks ((21, 7) (22, 7) on the test plate 4).

At this time, the amplitude of the signal output from the interface unit 7 varies for each step in the Z direction where the measurement mark 41 on the test plate 4 is positioned, and the image of the reticle measurement mark is most accurately measured. 4) the intensity of the light incident on the optical sensor 6 is the strongest at the position in the Z direction which is bound on the image.

Therefore, when the position of the test plate 4 with respect to the test reticle 2 is at the best focus, that is, when it is accurately focused, the amplitude of the signal output from the interface unit 7 becomes maximum. .

In addition, the number of peaks appearing in the output signal of the interface unit 7 is proportional to the scan distance of the plate stage 5.

For accurate measurement in the above process, the amplitude signal level obtained for each Z step is calculated as follows, and then the average value is used.

Vav = (V1 + V2 +… + Vn) / n

In the above, Vav represents an average of amplitudes in each Z step, and n represents the number of peaks of a signal output from the interface unit 7.

FIG. 8 is a graph showing Z steps versus output voltages obtained by photoelectric scanning from the lowest position in the Z direction to the highest position as described above. The Z step in which the voltage of the output signal reaches the maximum is the test reticle ( It becomes the best focus surface of the test plate 4 for 2) (S130).

As described above, the control device 8 performs the X-direction focal plane, the Y-direction focal plane, and the Z-direction focal plane measurements, respectively, according to the photoelectric scanning method of the test plate 4, and then outputs the signal accordingly. Calculate the best focal plane of the test plate 4 with respect to the test tickle 2, and then operate the stage driver 9 again to move the test plate 4 in the Z direction corresponding to the calculated best focal plane. Move to step.

Next, instead of the test reticle 2A used for the focal plane measurement, the reticle 2A for the focal plane verification shown in FIG. 9 is placed in the corresponding position, and then placed in the reticle 2A. The formed pattern is exposed on a plate coated with a photosensitive film.

Located in the pattern group of the reticle 2A used for verification of the focal plane, each corner portion 2Al and the center line portion 2A3 of the rectangular outline, a comb-shaped mark is provided to check the effect of astigmatism. Engraved.

After first exposing the reticle 2A having the pattern group formed as described above onto a plate positioned on the best focal plane, the control device 8 again rolls the stage drive unit 9 as shown in FIG. The seesaw plate is moved in the vertical Z direction by the predetermined step from the position of the best focal plane, and moved by the predetermined steps 11 and 12 in the X and Y directions.

The pattern is repeatedly exposed on the plate so that the outline of the reticle 2A overlaps (S140).

Therefore, the patterns exposed at the focal level within a predetermined range in the Z direction based on the photoelectrically confirmed best focal plane are exposed over the entire plate.

In addition, since the same pattern P on the reticle 2A is separated by minute distances 11 and 12 in the X and Y directions while varying the focal level, the partial plan view of the plate, the difference in coating thickness of the photoresist film, and the like are caused by the pattern group ( In P), there is almost no.

After repeating the exposure by the same pattern as described above, the repeatedly exposed plate is developed, and the adjacent pattern group is inspected by the developed pattern group (S150).

In the above-described embodiment, only one X and Y direction measuring marks 21 and 23 are formed on the test reticle 2 for the best focal plane measurement, and as shown in FIG. By forming a plurality of over, the profile of the entire focal plane can be checked by measuring the focal plane at various points of the plate stage while moving the plate stage corresponding to a wider exposure area.

Also, as shown in FIG. 12 attached to the measurement mark 41 on the test plate 4 rather than one bidirectional mark, the focal plane measurement may be performed using two marks in each direction.

In addition, instead of using a test plate having a separate mark formed on the optical sensor 6 mounted in the plate stage 5, as shown in FIG. 13, the focal plane measurement is performed by using a glass filter-shaped mask. Can be done.

As described above, in order to check the correct focal plane of the plate in the exposure apparatus, the focal plane is first checked using the test reticle and the test plate according to the photoelectric method, and then the identified exposure By performing overlapping exposure step by step in the Z direction according to the range, the best focal plane can be confirmed within a short time without any additional preparation step.

In addition, the focal plane measuring apparatus and method of the exposure process having the effect of improving the accuracy by re-checking the exact best focal plane by exposing the same pattern of the reticle on the plate while moving a predetermined range around the calculated best focal plane Can be provided.

Claims (18)

A reticle engraved with measuring marks in X and Y directions; A projection lens system for condensing light output through the reticle; A plate on which light collected through the projection lens system is irradiated and engraved with a measurement mark; A plate stage on which the plate is placed; Light sensing means mounted on the plate stage and configured to receive light incident through a measurement mark of the plate and output a corresponding electrical signal; Control to output the corresponding control signal to move the plate by a predetermined step in each of the X, Y, Z directions, and calculate the position corresponding to the best focal plane by the signal output from the light sensing means in accordance with the movement of the plate Means; And stage driving means for driving in accordance with a control signal output from the control means to move the plate stage to a corresponding position. The method of claim 1, The measuring marks formed on the reticle have shapes separated in the X and Y directions, respectively, and have the same size to measure the influence of astigmatism by the projection lens system. The method of claim 2, The said X, Y direction measuring mark is formed in multiple numbers over the whole surface of a reticle, The focal plane measuring apparatus of an exposure process. The method of claim 3, And said X and Y directions measuring marks each have a slit shape having a different direction. The method of claim 1, The focal plane measuring apparatus of the exposure process is made in the form of a measurement mark dot formed on the plate, the size is the same as the measurement mark formed on the reticle. The method of claim 5, The width of the dot of the measurement mark formed on the plate is configured to be the same as the slit line width of the measurement mark formed on the reticle, and is used in both X and Y directions. The method of claim 5, The measuring surface formed in the said plate consists of two marks for measuring each X, Y direction, The focal plane measuring apparatus of the exposure process characterized by the above-mentioned. The method of claim 1, wherein the light sensing means, An apparatus for measuring a focal plane of an exposure process, the apparatus being mounted in the plate stage and having a structure recessed therein so that the plate can be placed on the plate stage. The method of claim 1, A current / voltage unit for outputting the signal output from the light sensing means by converting the signal into a corresponding voltage signal; A voltage amplifier for amplifying and outputting the voltage signal output from the current / voltage unit; A signal output unit configured to output an amplified signal output from the voltage amplifier to a control unit; And an interface means comprising a signal inversion portion for inverting and outputting the amplified signal output from the voltage amplifier to a control means. The method of claim 9, And the amplitude of the signal output from the interface means is different for each of the threads in the Z direction in which the measurement mark on the plate is located. The method of claim 1, wherein the control means, Performing the X-direction focal plane measurement operation of scanning the plate measurement mark with the reticle measurement mark image while moving the plate stage a predetermined distance from the base position in the X direction, and then setting the step from the base position in the Z direction to the highest position in the Z direction After performing the Z direction focal plane measurement operation while moving the plate stage, the Y focal plane measurement operation is performed again by moving the plate stage by a predetermined distance in the Y direction, and the light sensing means according to the focal plane measurement operation. A focal plane measuring device of the exposure process for calculating the best focal plane based on the signal output from the. The said control means of Claim 1 or 9, A focal plane measuring apparatus of the exposure process of setting the plate position at the corresponding Z step as the best focal plane when the voltage of the signal output from the interface means becomes maximum. Forming a photoresist film on the plate; Performing a first exposure to the plate while moving the plate by a predetermined step in the X, Y, and Z directions with respect to the reticle on which the measurement pattern is formed; Calculating a best focal plane according to the optical signal measured according to the first exposure; Repeatedly exposing a pattern of the verification reticle on the plate by moving the plate by a predetermined step in the X, Y, and Z directions based on the calculated best focal plane; Developing the repeatedly exposed plate, and then inspecting a proximity pattern group among the repeatedly exposed patterns. The method of claim 13, wherein in performing the primary exposure: Perform the X-direction focal plane measurement operation, which scans the plate measurement mark with the reticle measurement mark image while moving the plate stage a certain distance in the X direction from the base position, and then for each step set from the base position in the Z direction to the highest position in the Z direction. After performing the Z direction focal plane measurement operation while moving the plate stage, and then performing the Y direction focal plane measurement operation while moving the plate stage by a predetermined distance in the Y direction, the reticle measurement mark image is exposed to the plate. Focal plane measurement method. The method of claim 13, wherein the step of calculating the best focal plane: Photoelectric conversion of the reticle image incident on the plate according to the X, Y, and Z direction focal plane measurement operation, and then the plate position in the Z direction step where the voltage of the photoelectrically converted signal is maximized as the best focal plane The focal plane measuring method of the exposure process to set. The method of claim 13, wherein in the first exposure step: X and Y bidirectional, each having the same size as the measurement mark formed on the reticle, using a reticle separated in the X and Y directions and having measurement marks having the same size to measure the influence of astigmatism by the projection lens system. A focal plane measuring apparatus of the exposure fixing process, characterized in that the exposure to turn on a plate formed with one measurement mark having a. The method of claim 13, wherein in the step of performing repeated exposures, The focus of the exposure process in which the plate is moved up and down in the Z direction by the predetermined step at the position of the best focal plane, and the predetermined step is moved in the X and Y directions, and then the pattern is repeatedly exposed on the plate so that the outline of the verification reticle overlaps. Cotton measurement method. The method of claim 17, A focal plane measurement method of an exposure process, characterized in that the exposure is repeated using a verification reticle engraved with a pattern formed in the shape of a non-pattern located at each corner portion and the center line of the rectangular outline.