JPS62183520A - Exposure apparatus - Google Patents

Abstract

PURPOSE:To eliminate the factor of degradation of alignment accuracy between a mask and a substrate created in an off-axis method by a method wherein an original is aligned with the predetermined position of an apparatus main part by every step and the original and an object to be exposed are aligned with each other by using the alignment mark of the original and the alignment mark of the object to be exposed. CONSTITUTION:When 1st mask 1a is exposed, at first the mask 1a is aligned with mask reference marks 17 on an apparatus side by a microscope 19. After that, the alignment marks of the mask 1a and the alignment marks of a substrate 3 formed in a previous process are measured by the microscope 19 to align the mask 1a and the substrate 3 and the 1st exposure is performed. Then, when 2nd mask 1b is exposed, the mask 1b is also aligned with the mask reference marks 17 on the apparatus side by the microscope 19 like the 1st mask and then the alignment marks of the mask 1b and the alignment marks of the substrate 3 are measured by a microscope 19 to align the mask 1b and the substrate 3 by driving the substrate 3 and the 2nd exposure is performed. The same exposure operation is repeated for the other masks thereafter and a large picture such as a liquid crystal display can be formed.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to an exposure apparatus that prints a pattern image on an original plate, such as a liquid crystal pattern, onto an exposed object with good positional alignment, and particularly relates to an exposure apparatus that prints a pattern image on an original plate, such as a liquid crystal pattern, onto an exposed object with good positional alignment, and particularly relates to an exposure apparatus that prints a pattern image on an original plate, such as a liquid crystal pattern, on an exposed object with good positional alignment. Regarding equipment.

[Prior Art] Conventionally, display devices used for displaying the output of computers, etc., have generally been based on the CRT system. However, in the CRT system, (1) the device is large in size and heavy;

■High power consumption.

■Flickering on the screen makes your eyes tired.

There were drawbacks such as. Therefore, in recent years, display devices other than the CRT type have been considered, and among them, liquid crystal displays have attracted particular attention.

The process of manufacturing this liquid crystal display is very similar to the semiconductor manufacturing process, and a semiconductor exposure device is used as the exposure device during manufacturing.

Common exposure methods for manufacturing liquid crystal displays include a method in which a mask and a substrate are exposed by contacting each other, and a proximity exposure method in which a gap of several tens of micrometers is maintained between the mask and the substrate for exposure. be. However, with these methods, productivity is low because many pattern defects occur due to mask damage or dust. Therefore, recently, a lens projection system or a mirror projection system is used, and multiple masks of different types are used to separate several exposed areas of the substrate, and the pattern of the mask corresponding to each exposed area is printed. An exposure method for forming a large liquid crystal screen is being considered. This involves changing the mask and aligning the mask substrate for each substrate step, performing static exposure in a lens projection system, and scanning exposure in a mirror projection system, and sequentially performing such partial exposure operations. By repeating this process, a large liquid crystal screen is formed.

An important point to consider when forming a large LCD screen using such divided exposure is that the patterns of multiple masks can be combined into one.
This is the placement accuracy of each mask pattern when transferred onto a single substrate. If this placement accuracy is poor, patterns may overlap or be separated from each other in the boundary area between each mask pattern, making it impossible to obtain sufficient performance of the liquid crystal screen. Therefore, it is necessary to transfer each mask pattern onto the substrate with high placement accuracy.

Normally, four to five overlapping exposure steps are required to form a liquid crystal screen. First, in the first step, each mask is positioned at a predetermined position, the substrate side is measured with a high-precision length measuring device such as a laser interferometer, and the image of a different type of mask is transferred at each step. do. After the second step,
With respect to the pattern printed in the first step, the substrate is again moved in steps in the same manner as in the first step to transfer the mask image in the second and subsequent steps.

The present invention relates to an exposure apparatus that suitably aligns a mask and a substrate in a second step and subsequent steps in which overlay printing is performed on the pattern printed in the first step.

Conventionally, an off-axis method has been used as a mask and substrate alignment method for this type of device.

The off-axis method aligns the alignment marks on the substrate formed in the previous process with a fixed microscope at two locations, and then measures the position of the substrate using a laser interferometer whose position is determined relative to the fixed microscope. In this method, the substrate is sequentially exposed to light while being moved step by step to a predetermined position.

In this method, there is no need to align the mask and substrate for each shot, so the takt time is short and productivity is high. However, since the substrate is moved in steps based on the measured values of the laser interferometer, it is not possible to measure positional deviations due to substrate factors such as expansion and contraction due to temperature of the substrate, positional deviations due to local deformation of the substrate, and positional deviations due to the magnification of the projection optical system. . Therefore, there was a problem that the alignment accuracy between the mask and the substrate deteriorated.

[Object of the Invention] In view of the above-mentioned problems of the conventional type, an object of the present invention is to improve the alignment accuracy between a mask and a substrate in an exposure apparatus using a divided exposure method.

[Summary of the Invention] In order to achieve the above object, the present invention positions the mask at a predetermined position each time it is replaced, and at each step, aligns both the mask alignment mark and the alignment mark provided on the substrate in the previous process. position and perform exposure. This positioning of the mask and substrate is performed by irradiating the alignment marks on the mask and substrate with light such as a laser, detecting the positions of both marks from changes in the amount of light reflected through the projection optical system and microscope, and then using the arithmetic circuit to detect the positions of both marks. This is done by calculating the amount of misalignment between the mask and the substrate, and driving the substrate based on the amount of misalignment.

This eliminates the cause of deterioration in alignment accuracy between the mask and the substrate that occurs in the off-axis method, and enables highly accurate alignment.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows a schematic configuration of an exposure apparatus according to an embodiment of the present invention. The apparatus shown in the figure is a step-and-scan type exposure apparatus that uses a mirror projection system to expose a large screen by divided scanning.

In the figure, 1 is a photomask on which a printed pattern is formed, and 2 is an X with mask 1 mounted thereon.

This is a mask stage that can move in the Y and θ directions.

3 is a glass substrate on which a large number of pixels and switching transistors for controlling on/off of these pixels are formed by normal photolithography procedures in order to manufacture a liquid crystal display board, and the length of the diagonal line is is about 14 inches square. Reference numeral 4 denotes a substrate stage that can hold the substrate 3 and move in the X, Y, and θ directions. The step movement of the substrate stage 4 is controlled by a precision length measurement system using a laser interferometer (not shown). 5 is a well-known mirror projection system consisting of a combination of a concave mirror and a convex mirror, and the mask stage 2
The pattern image of the mask 1 aligned at a predetermined position is projected onto the substrate 3 at the same size.

Reference numeral 6 denotes an illumination optical system that illuminates the mask 1 at the exposure position with light of a specific wavelength from a light source (not shown), and by exposing the photosensitive layer on the substrate 3 through the pattern on the mask, This is to enable the pattern to be transferred onto the substrate 3. Note that the optical axis of the projection system 5 is made to coincide with the optical axis of the illumination system 6.

7 is a LAB (linear air bearing) that can be moved along two guide rails 8 provided in the Y direction (perpendicular to the page), one of which is movable in the X direction (horizontal direction of the page) and Z direction (direction perpendicular to the page). The other type is a Z-direction restraint type. 9 is a holder (carriage) that holds the mask stage 2 and substrate stage 4 in a fixed relationship;
7, the mask 1 on the mask stage 2 and the substrate 3 on the substrate stage 4 can be integrally transferred.

11 is a mask transport device for sequentially transporting each mask 1 to the mask stage 2; 12 is a gap sensor for detecting the distance between the focal plane of the projection system 5 and the surface of the substrate 3;
For example, an air microsensor or a photoelectric type sensor that detects the distance using reflected light from the substrate 3 is used. Reference numeral 13 denotes a base on which the projection system 5, illumination system 6, and guide rail 8 are mounted in a fixed relationship.

In the apparatus shown in the figure, the surface of the substrate 3 is divided into, for example, four exposed areas, and these exposed areas are sequentially sent to the exposure area under the mask 1 and the projection optical system 5 by step movement of the substrate stage 4. The mask pattern is exposed four times, and the pattern for the liquid crystal display board is printed on the entire surface of the substrate 3.

FIG. 2 is a schematic configuration diagram for explaining the exposure operation in the apparatus of FIG. 1. Note that the same or common parts as in FIG. 1 are indicated by the same reference numerals. In Fig. 2, 1a is a photomask on which a pattern is formed on the first printing, and lb, 1c, and 1d are photomasks on which a pattern is formed on the 2nd, 3rd, and 4th printings. . Also,
17 is a mask reference mark on the apparatus side; 19 is a microscope for measuring the positioning mark of the mask 1 and the mask reference mark 17; and also for measuring the positioning marks of the mask 1 and the substrate 3.

In FIG. 2, when exposing the first mask 1a, the mask 1a is first positioned with respect to the mask reference mark 17 on the apparatus side using the microscope 19.

Thereafter, the positioning mark of the mask 1a and the positioning mark of the substrate 3 formed in the previous step are measured using the microscope 19 to position the mask 1a and the substrate 3, and the first exposure is performed.

Next, when exposing the second mask 1b, similarly,
The mask 1b is positioned with respect to the mask reference mark 17 on the apparatus side using the microscope 19, and then the positioning mark of the mask 1b and the positioning mark of the substrate 3 formed in the previous process are measured using the microscope 19, and the positioning mark of the substrate 3 is measured using the microscope 19. 3 to align the mask 1b and the substrate 3, and then exposure is performed. Exposure operations are similarly performed for subsequent masks to form large screens such as liquid crystal.

FIG. 3 shows a schematic configuration of an exposure apparatus according to another embodiment of the present invention. The apparatus shown in the figure is a step-and-repeat type exposure apparatus that exposes a large screen by dividing exposure using a lens projection system.

In the figure, 1 is a photomask on which a printed pattern is formed, and 2 is an X with mask 1 mounted thereon.

This is a mask stage that can move in the Y and θ directions.

3 is a glass substrate on which a large number of pixels and switching transistors for controlling on/off of these pixels are formed by normal photolithography procedures in order to manufacture a liquid crystal display board, and the length of the diagonal line is is about 14 inches square. Reference numeral 4 denotes a substrate stage that can hold the substrate 3 and move in the X, Y, and θ directions. The step movement of the substrate stage 4 is controlled by a precision length measurement system using a laser interferometer (not shown). Reference numeral 31 denotes a lens projection system consisting of a plurality of lenses, which projects a pattern image of the mask 1 aligned at a predetermined position by the mask stage 2 onto the substrate 3.
Project upward. Note that the projection magnification may be reduced, enlarged, or same size. 32 is an illumination optical system that illuminates the mask 1 at the exposure position with light of a specific wavelength from a light source (not shown), which illuminates the substrate 3 through the pattern on the mask 1.
This is to enable the pattern on the mask 1 to be transferred to the substrate 3 by exposing the upper photosensitive layer. In addition,
The optical axis of the projection system 31 is made to coincide with the optical axis of the illumination system 32.

11 is a mask transport device for sequentially transporting each mask 1 to the mask stage 2, and 13 is a base for mounting the projection system 31, the illumination system 32, and the substrate stage 4 in a fixed relationship.

In the apparatus shown in the figure, the surface of the substrate 3 is divided into, for example, four regions to be exposed, and these regions are divided into the mask 1 and the projection optical system 31 by step movement of the substrate stage 4.
The mask pattern is exposed to light four times by sequentially sending it to the lower exposure area, and a pattern for the LCD panel is printed on the entire surface of the substrate 3.

FIG. 4 is a schematic configuration diagram for explaining the exposure operation in the apparatus of FIG. 3. Note that the same or common parts as in FIG. 3 are indicated by the same reference numerals. In Fig. 4, 1a is a photomask on which a pattern is formed on the first printing, and 1b, 1c, and 1d are photomasks on which a pattern is formed on the 2nd, 3rd, and 4th printings. . In addition, 17 is a mask reference mark on the device side, and 19 is a mask 1
This microscope is used to measure the positioning marks of the mask 1 and the mask reference mark 17, and also to measure the positioning marks of the mask 1 and the substrate 3.

In FIG. 4, when exposing the first mask 1a, first, the mask 1a is positioned with respect to the mask reference mark 17 on the apparatus side using the microscope 19.

Thereafter, the positioning mark of the mask 1a and the positioning mark of the substrate 3 formed in the previous step are measured using the microscope 19 to position the mask 1a and the substrate 3, and the first exposure is performed.

Next, when exposing the second mask 1b, similarly,
The mask 1b is positioned with respect to the mask reference mark 17 on the apparatus side using the microscope 19, and then the positioning mark of the mask 1b and the positioning mark of the substrate 3 formed in the previous process are measured using the microscope 19, and the positioning mark of the substrate 3 is measured using the microscope 19. 3 to align the mask 1b and the substrate 3, and then exposure is performed. Exposure operations are similarly performed for subsequent masks to form large screens such as liquid crystal.

[Effects of the Invention] As explained above, according to the present invention, in an exposure apparatus using a split exposure method, the original plate is positioned at a predetermined position on the main body of the apparatus for each step, and the original plate and the exposed object are connected to each other by the positioning marks on the original plate. Since the positioning is performed using the positioning marks of the exposed object and the positioning mark of the exposed object, the cause of deterioration of the alignment accuracy between the mask and the substrate that occurs in the off-axis method is eliminated, and highly accurate alignment is possible.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an exposure apparatus according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram for explaining the exposure operation in the apparatus of FIG. 1, and FIG. Schematic configuration diagram of an exposure apparatus according to another embodiment FIG. 4 is a schematic configuration diagram for explaining the exposure operation in the apparatus of FIG. 3. 1: Photomask, 2: Mask stage, 3: Substrate, 4: Substrate stage, 5: Mirror projection system, 9: Holder (
carriage), 13: base, 17: mask reference mark, 19: microscope, 31: lens projection system.

Claims (1)

[Scope of Claims] 1. An exposure apparatus that divides the surface of an exposed object into a plurality of exposed regions, moves the exposed object in steps, and projects images of different types of originals onto each exposed region. When exposing each original plate, the original plate is positioned at a predetermined position on the main body of the apparatus in each step, and the positioning mark attached to the original plate and the positioning mark on the exposed object formed in advance in the previous process are aligned. An exposure apparatus characterized in that an object to be exposed is positioned with respect to the original plate using the above-mentioned original plate and exposed to light. 2. Claim 1, wherein the exposure device projects an image of the original plate onto the exposed object by integrally scanning the original plate and the exposed object with respect to a projection optical system. exposure equipment. 3. The exposure apparatus according to claim 1, wherein the exposure apparatus projects an image of the original plate onto the object to be exposed using a lens. 4. The exposure apparatus according to claim 1, wherein the exposure apparatus exposes the original plate and the object to be exposed in close proximity or in close contact with each other.