JPH0630334B2 - Exposure method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for printing a pattern image on an original plate, for example, a liquid crystal pattern onto an object to be exposed with good positional alignment, and particularly to exposure for dividing a large screen and exposing. Regarding the method.

[Prior Art] Conventionally, a CRT system has been generally used as a display device used for output display of a computer. However, in the CRT system, the shape of the device is large and the weight is heavy.

High power consumption.

Eyes get tired due to flickering on the screen.

There were drawbacks such as. Therefore, in recent years, a display device other than the CRT system has been considered, and among them, a liquid crystal display has particularly attracted attention.

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

As a general exposure method for manufacturing a liquid crystal display, there is a method of exposing by contacting a mask and a substrate, or a proximity exposure method of exposing while maintaining a gap of several tens of μm between the mask and the substrate. is there. However, in these methods, many defects of the pattern due to the damage of the mask or dust are generated, and the productivity is poor. Therefore, recently, using a lens projection system or a mirror projection system, the exposed area of the substrate is divided into several areas, and a plurality of masks of different types are used to print the mask pattern corresponding to each exposed area. An exposure method for forming a large LCD screen has been considered. This is because the mask is replaced and the mask substrate is aligned for each substrate step, static exposure is performed in the lens projection system, and scanning exposure is performed in the mirror projection system. This is repeated to form a large liquid crystal screen.

An important point to consider when forming a large liquid crystal screen by such divided exposure is that the pattern of a plurality of masks is
It is the placement accuracy of each mask pattern when transferred onto one substrate. If the placement accuracy is poor, the patterns overlap or separate at the boundary region between the mask patterns, and the performance of the liquid crystal screen cannot be obtained sufficiently. Therefore, it is necessary to transfer each mask pattern onto the substrate with high placement accuracy.

Usually, in order to form a liquid crystal screen, overexposure of 4 to 5 steps is required. First, in the first step, each mask is positioned at a predetermined position, the substrate side is measured by a high-precision length measuring device such as a laser interferometer, and step movement is performed, and an image of a mask of a different type is transferred at each step. To do. After the second step,
As with the first step, the substrate is again stepwise moved to the pattern printed by the first step to transfer the image of the mask after the second step.

The present invention relates to an exposure apparatus that suitably performs alignment of a mask and a substrate after a second step of performing overlay printing on the pattern printed by the first step.

Conventionally, a die-by-die method has been generally used as an alignment method for a mask and a substrate of this type of apparatus. The die-by-die method irradiates both the alignment mark provided on the mask positioned at a predetermined position and the alignment mark provided on the substrate in the previous step with light such as laser light and reflects it through the projection optical system and microscope. The position of both marks is detected from the change in the amount of incoming light, the amount of positional deviation between the mask and the substrate is calculated by the arithmetic circuit, and the positioning operation to drive the substrate based on the amount of positional deviation is performed for each shot. is there.

In the die-by-die system, the exposed surface area of the substrate is divided into several areas and alignment is performed for each shot area. Therefore, the expansion and contraction due to the temperature of the substrate, the positional displacement due to the substrate factors such as the local displacement of the substrate, and the projection optical The positional deviation due to the system magnification can be corrected, and the alignment accuracy is improved. However, since the alignment is performed for each shot, the time required for the alignment (normal shot alignment time of 2 seconds) is added, and the takt time of the apparatus becomes long, resulting in a problem of reduced productivity.

[Object of the Invention] In view of the above-mentioned problems of the conventional type, an object of the present invention is to eliminate alignment time when exposing the second and subsequent masks in the exposure method by the division exposure method, thereby reducing the takt time of the apparatus. It is about shortening and improving productivity.

[Outline of the Invention] In order to achieve the above object, in the present invention, the mask is always positioned at a predetermined position, and the positioning mark of the mask to be exposed first and the positioning mark of the substrate formed in the previous step are used. Measure the positional deviation between the mask and the substrate, and drive the substrate side to align the mask and the substrate.
Perform exposure. Next, when the second and subsequent masks are exposed, the mask is also positioned at a predetermined position, and the substrate is exposed by performing step movement to a predetermined position while measuring with a laser interferometer or the like. In this case, the time required for the second and subsequent alignments is not required, the takt time of the apparatus is shortened, and the productivity is improved.

Description of Embodiments Embodiments of the present invention will be described below with reference to 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 exposes a large screen by divided scanning using a mirror projection system.

In the figure, 1 is a photomask on which a printing pattern is formed, and 2 is a mask stage on which the mask 1 is mounted and which can be moved in X, Y, and θ directions. 3 is a glass substrate on the surface of which a large number of pixels and switching transistors for controlling the on / off of these pixels are formed in order to manufacture a liquid crystal display plate, and the length of the diagonal line. Is a 14 inch square. A substrate stage 4 holds the substrate 3 and is movable in X, Y, and θ directions. The step movement of the substrate stage 4 is controlled by a precision measuring system using a laser interferometer (not shown). A well-known mirror projection system 5 is a combination of a concave mirror and a convex mirror, and projects the pattern image of the mask 1 aligned at a predetermined position by the mask stage 2 onto the substrate 3 at the same size. An illumination optical system 6 illuminates the mask 1 at the exposure position with light of a specific wavelength from a light source (not shown), and exposes a photosensitive layer on the substrate 3 through a pattern on the mask to expose the photosensitive layer on the mask. This is for allowing the pattern to be transferred onto the substrate 3. The optical axis of the projection system 5 is made to coincide with the optical axis of the illumination system 6.

Reference numeral 7 is a LAB (linear air bearing) movable along two guide rails 8 provided in the Y direction (direction perpendicular to the paper surface), one of which is the X direction (left and right direction of the paper surface) and Z direction (of the paper surface). Vertical direction) restraint type, the other is Z direction restraint type. Reference numeral 9 denotes a holder (carriage) which holds the mask stage 2 and the substrate stage 4 in a fixed relationship.
By being supported by 7, the mask 1 on the mask stage 2 and the substrate 3 on the substrate stage 4 can be integrally transferred.

Reference numeral 11 is a mask transfer device for sequentially transferring each mask 1 to the mask stage 2, and reference numeral 12 is a gap sensor for detecting a distance between the focus surface of the projection system 5 and the surface of the substrate 3, such as an air microsensor or It is a photoelectric type sensor that detects the interval by the reflected light from the substrate 3. Reference numeral 13 is a base for mounting the projection system 5, the illumination system 6 and the guide rail 8 in a fixed relationship.

In the apparatus shown in the figure, the surface of the substrate 3 is divided into, for example, four exposure regions, and these exposure regions are sequentially sent to the exposure regions under the mask 1 and the projection optical system 5 by stepwise movement of the substrate stage 4. Then, the mask pattern is exposed four times, and a pattern for one layer of the liquid crystal display panel is printed on the entire surface of the substrate 3.

FIG. 2 is a schematic configuration diagram for explaining an exposure operation after the second step in the apparatus of FIG. The same or common parts as in FIG. 1 are designated by the same reference numerals. In FIG. 2, 1a is a photomask on which the first printing pattern is formed, and 1b, 1c, and 1d are the same as in the second, third, and third photomasks.
It is a photomask on which a fourth baking pattern is formed. Further, 14 is a laser interferometer, 15 is a square, 17 is a mask reference mark on the apparatus side, 19 is a positioning mark of the mask 1 and the mask reference mark 17, and also a positioning mark of the mask 1 and the substrate 3 is measured. Is a microscope. In order to show the path of light from the laser interferometer 14, LAB
7 and a part of the holder 9 are omitted.

In FIG. 2, 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 a microscope 19. Then mask 1
The positioning mark of a 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, first, the mask 1b is placed on the mask reference mark 17 on the apparatus side with respect to the microscope 19
Use to position. After that, while measuring the position of the substrate 3 using the laser interferometer 14 and the squeezer 15 provided on the stage, the substrate 3 is accurately stepwise moved so that the substrate 3 is set at a predetermined position, and exposure is performed. .

FIG. 3 shows a schematic structure 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 divided exposure using a lens projection system.

In the figure, 1 is a photomask on which a printing pattern is formed, and 2 is a mask stage on which the mask 1 is mounted and which can be moved in X, Y, and θ directions. 3 is a glass substrate on the surface of which a large number of pixels and switching transistors for controlling the on / off of these pixels are formed in order to manufacture a liquid crystal display plate, and the length of the diagonal line. Is a 14 inch square. A substrate stage 4 holds the substrate 3 and is movable in X, Y, and θ directions. The step movement of the substrate stage 4 is controlled by a precision measuring system using a laser interferometer (not shown). Reference numeral 31 denotes a lens projection system including 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. It should be noted that the projection magnification may be reduced, enlarged, or the same size.
Reference numeral 32 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). By exposing the photosensitive layer on the substrate 3 through the pattern on the mask 1,
The pattern on the mask 1 can be transferred onto the substrate 3. The optical axis of the projection system 31 is made to coincide with the optical axis of the illumination system 32.

Reference numeral 11 is a mask transfer device for sequentially transferring each mask 1 to the mask stage 2, and reference numeral 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 exposed regions, and these exposed regions are sequentially sent to the exposed regions below the mask 1 and the projection optical system 31 by stepwise movement of the substrate stage 4. Then, the mask pattern is exposed four times, and a pattern for one layer of the liquid crystal display panel is printed on the entire surface of the substrate 3.

FIG. 4 is a schematic configuration diagram for explaining the exposure operation after the second step in the apparatus of FIG. The same or common parts as in FIG. 3 are designated by the same reference numerals. In FIG. 4, 1a is a photomask on which the first printing pattern is formed, and 1b, 1c, and 1d are similarly the second, third, and third photomasks.
It is a photomask on which a fourth baking pattern is formed. Further, 14 is a laser interferometer, 15 is a square, 17 is a mask reference mark on the apparatus side, 19 is a positioning mark of the mask 1 and the mask reference mark 17, and also a positioning mark of the mask 1 and the substrate 3 is measured. Is a microscope.

In FIG. 4, when exposing the first mask 1a, first, the mask 1a is positioned using the microscope 19 with respect to the mask reference mark 17 on the apparatus side. Then mask 1
The positioning mark of a and the positioning mark of the substrate 3 formed in the previous step are measured with 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, first, the mask 1b is placed on the mask reference mark 17 on the apparatus side with respect to the microscope 19
Use to position. After that, while measuring the position of the substrate 3 using the laser interferometer 14 and the squeezer 15 provided on the stage, the substrate 3 is accurately stepwise moved so that the substrate 3 is set at a predetermined position, and exposure is performed. .

[Effects of the Invention] As described above, according to the present invention, in the exposure method based on the divided exposure method, for the first exposure, alignment is performed using the positioning mark of the original plate and the positioning mark of the exposed object, For the second and subsequent exposures, alignment by the positioning marks is not performed, and the exposed object is stepwise moved by another means such as a laser interferometer so as to be accurately at a predetermined position. Therefore, the second and subsequent masks are exposed. It is possible to improve productivity by eliminating the alignment time at the time and shortening the takt time of the device.

[Brief description of drawings]

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 an exposure operation after the second step in the apparatus of FIG. 1, FIG. FIG. 4 is a schematic configuration diagram of an exposure apparatus according to another embodiment of the present invention, and FIG. 4 is a schematic configuration diagram for explaining an exposure operation after the second step in the apparatus of FIG. 1: Photomask, 2: Mask stage, 3: Substrate, 4: Substrate stage, 5: Mirror projection system, 9: Holder (carriage), 13: Base, 14: Laser interferometer, 15: Square, 17: Mask Reference mark, 19: microscope, 31: lens projection system, 32: illumination system.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/68 G 8418-4M

Claims (1)

[Claims] 1. A method of exposing different areas on an object to be exposed with patterns of different kinds of original plates, wherein the positional relationship between the alignment mark of the first original plate and the alignment mark of the object to be exposed is detected, A first exposure step of aligning the first region of the exposed object with the first original plate based on the detection result, and then exposing the first region of the exposed object with the pattern of the first original plate; A second original plate is arranged at a position substantially the same as the position of the first original plate in the first exposure step, and the exposed object is moved by a predetermined amount, and the second region of the exposed object with respect to the second original plate. And a second exposure step of exposing the second region of the exposed object with the pattern of the second original plate.