JP2000305276A - Exposing method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a fine pattern having line width equal to or under the critical resolution of an optical projection system by dividing exposure in one stage to a plurality of times, performing exposure so that the integration of each exposure becomes optimum exposure, and performing the exposure by shifting a projected image on a substrate within the critical resolution of the optical projection system in every exposure. SOLUTION: A photomask having a line width (for example, 4 μm) near the critical resolution (for example, 3.5 μm) of the optical projection system of this aligner is fixed on a mask stage and the substrate coated with photosensitive agent is sucked and fixed on a substrate sucking stage. The pattern on the photomask is transferred by exposure to give the exposure being 1/2 of the appropriate exposure (go-path). Then, the substrate sucking stage having a higher resolution than the optical projection system is driven by 2 μm in an X or Y direction and the exposure for a return-path in a reverse direction to the scanning exposure direction for the go-path is performed so as to give the exposure being 1/2 of the appropriate exposure. By shifting the mask and the substrate between exposures for the go-path and for the return-path and exposing them, the pattern having the line width 2 μm being equal to or under the critical resolution of the optical projection system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and apparatus for exposing and transferring a pattern on a photomask onto a substrate on a suction stage, and particularly to exposing and transferring a fine pattern with a low pattern density. The present invention relates to an exposure method and apparatus suitable for exposure of a necessary liquid crystal display element or the like.

[0002]

2. Description of the Related Art As a conventional exposure method, a substrate coated with a photoresist (photosensitive agent) is mechanically positioned on a substrate suction stage, vacuum-adsorbed, and held in advance on a mask adsorption stage, regardless of the projection optical system. The alignment mark on the mask is aligned with the alignment mark on the substrate, and an appropriate exposure is given by one exposure. Alternatively, in the first step in which there is no alignment mark on the substrate, a proper exposure amount is given by one exposure without performing alignment using the alignment mark.

[0003]

However, in the above conventional example, the resolution that can be transferred onto the substrate largely depends on the performance of the optical system that projects the pattern on the photomask onto the substrate. Therefore, in order to transfer a finer pattern, at least a higher resolution projection optical system must be provided. In addition, the size of liquid crystal display elements is increasing year by year. Accordingly, the exposure area must be expanded. It is extremely difficult to achieve both a large projection optical system and high resolution.

The present invention has been made in view of the above-mentioned problems in the conventional example, and resolves a fine pattern which is higher than the resolution of the projection optical system, that is, lower than the limit resolution (resolution limit) of the projection optical system. It is an object of the present invention to provide a method of obtaining an exposure.

[0005]

In order to achieve the above object, the present invention uses a substrate suction stage having a resolution higher than that of a projection optical system, and divides exposure in one process into a plurality of exposures. The exposure is performed so that the integration of the exposure amount for each exposure becomes the optimal exposure amount, and the exposure image is shifted with the projection image onto the substrate within the limit resolution of the projection optical system for each exposure. .

[0006]

The line width pattern near the resolution of the projection optical system is usually the limit for exposing and transferring a finer pattern.
The present invention provides an exposure method for exposing and transferring a pattern having a line width smaller than the limit resolution of the projection optical system.

Conventionally, a pattern of a photomask is transferred and exposed on a substrate by one exposure. Therefore, it was impossible to transfer and expose a pattern having a line width narrower than the resolution of the projection optical system (that is, a line width smaller than the limit resolution of the projection optical system). An exposure apparatus that aligns the alignment mark on the photomask with the alignment mark on the substrate on the substrate suction stage, projects the pattern on the photomask onto the substrate, and performs transfer exposure has a high driving resolution for the substrate suction stage. In order to achieve alignment accuracy, it has a performance higher than the resolution of the projection optical system. In the exposure method of the present invention, the conventional one-time exposure transfer is divided into two or more times,
In each exposure, the mask and the substrate are slightly deliberately shifted, and exposure is performed so that the integrated exposure amount of the overlapped portion in each exposure is appropriate. At this time, the amount intentionally shifted is within the limit resolution of the projection optical system, so that only the line width equal to or smaller than the limit line width of the projection optical system gives an appropriate exposure amount. By developing the substrate, a photosensitive agent is selectively left only in a portion given an appropriate exposure amount (in the case of a positive resist, the photosensitive agent is selectively removed in the case of a negative resist). It is possible to obtain a line width equal to or less than the limit resolution.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first preferred embodiment of the present invention, a scanning liquid crystal is provided which has a substrate suction stage having a resolution higher than that of a projection optical system and performs projection exposure while scanning an exposure area. In the exposure apparatus, the exposure within one process is performed by two exposures so that the integration of the exposure amount for each exposure becomes an optimum exposure amount, and a photomask is formed by the first exposure in the forward pass and the second exposure in the return pass. Exposure is performed with the substrate coated with the photosensitive agent shifted by a dimension equal to or less than the limit resolution of the projection optical system.

By developing the substrate exposed by the above-described exposure method, a pattern having a resolution lower than the limit resolution of the projection optical system can be formed without greatly impairing the throughput.

In a second preferred embodiment of the present invention, exposure in one step is performed in two steps, and a photomask used in the second exposure is a reference position of the first photomask. Is provided with a displacement less than or equal to the limit resolution of the projection optical system. The overlapped portion has an optimum exposure amount by two exposures, and by developing, a pattern having a resolution lower than the limit resolution of the projection optical system can be formed.

Fortunately, liquid crystal display elements require fine processing, but the processing density is extremely low compared to semiconductor elements. Therefore, the exposure method of the present invention is most suitable for drawing a pattern such as a liquid crystal display element, and is used for transferring and exposing a pattern having a resolution higher than that of an existing projection optical system without changing to a higher resolution projection optical system. Can be provided.

An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) A case where a line width equal to or less than the limit resolution of the projection optical system is obtained by two exposures according to the above-described means will be described. A photomask having a line width (for example, 4 μm) near the limit resolution (for example, 3.5 μm) of a projection optical system of an exposure apparatus (for example, one-to-one scanning projection optics) is fixed by suction to a mask stage. The substrate coated with the photosensitive agent (positive resist) is fixed by suction to a substrate suction stage, and if it is the second step or later, the alignment marks on the photomask and the alignment marks on the substrate are aligned with high accuracy. Next, the pattern on the photomask is exposed and transferred to the substrate so as to give an exposure amount of １ ／ of the appropriate exposure amount (exposure transfer in the forward path). In an exposure apparatus using a scanning projection optical system, the scanning speed at this time is twice that at the time of proper exposure. FIG. 1 shows the exposure amount distribution of the pattern and the cross section when the first exposure on the outward path is completed by this exposure. Before performing the second exposure on the return path, which is the reverse direction to the scanning exposure direction on the forward path, the substrate suction stage having a resolution higher than the resolution of the projection optical system is intentionally driven by 2 μm in the X or Y direction, respectively. 1/1 of proper exposure
The pattern on the photomask is exposed and transferred to the substrate so as to give an exposure amount of 2. The return scanning speed is 2
Double. FIG. 2 shows the pattern transferred by the first exposure on the outward path and the second exposure on the return path, and the exposure amount distribution on the AA ′ section thereof. An appropriate exposure amount was obtained in a portion (2 μm) having a desired pattern line width equal to or less than the limit resolution (for example, 3.5 μm) of the projection optical system. Here, the substrate that has been selectively and appropriately exposed is carried out of the exposure apparatus, and then the photosensitive agent is developed.

In the developed substrate, only the portion (2 μm) to which the proper exposure amount is given selectively remains the photosensitive agent, and the photosensitive agent is peeled off in the portion below the appropriate exposure amount. FIG. 3 shows the pattern of the photosensitive agent after development.

In this manner, a scanning exposure apparatus having a substrate suction stage having a resolution higher than the resolution of the projection optical system is used, and an appropriate exposure amount can be obtained by performing two exposures, a forward pass and a return pass. Further, by exposing the mask and the substrate while shifting them in the forward path and the return path, a line width pattern smaller than the limit resolution of the projection optical system can be obtained. The time required for exposure in one step is the same as the time required for two scanning exposures, and the time required for driving the substrate suction stage in the X or Y direction by 2 μm immediately before the backward exposure is an extra time. . Therefore, it is possible to prevent a significant decrease in throughput.

(Second Embodiment) In the first embodiment, before the second exposure, the substrate attraction stage is driven to shift the pattern on the photomask to expose and transfer to the substrate.
It is also possible to prepare a photomask patterned for the second time. As described in the first embodiment, 4
A case where a line width of 2 μm is formed on a substrate with a pattern on a photomask of μm will be described. In contrast to the pattern of the first exposure photomask, the second exposure photomask pattern is basically formed as a 4 μm pattern in the same manner as the first exposure photomask pattern. However, the alignment marks are previously shifted by 2 μm in the X and Y directions. Further, it is preferable to form a pattern that corrects the overlapping partial shape in two exposures (see FIG. 4).

A first exposure photomask is suction-fixed to a mask stage of an exposure apparatus. The substrate coated with the photosensitive agent is suction-fixed to the substrate suction stage, and the alignment marks on the photomask and the substrate are aligned with high accuracy. Next, the pattern on the photomask is exposed and transferred to the substrate so as to give an exposure amount of 適 正 of the appropriate exposure amount. Before performing the second exposure, the first photomask on the mask stage is removed (Unloaded), and the second photomask is mounted on the mask stage and fixed by suction. The alignment mark on the second photomask and the alignment mark on the substrate on the substrate suction stage are aligned with high accuracy. The pattern on the photomask is exposed and transferred to the substrate so as to give an exposure amount of の of the appropriate exposure amount. FIG. 5 shows the pattern transferred by the first exposure and the second exposure, and the exposure distribution of the cross section thereof. An appropriate exposure amount was obtained only in a portion where the two exposures overlap, and this portion is a portion (2 μm) having a desired pattern line width equal to or less than the limit resolution of the projection optical system. Here, the substrate that has been selectively and appropriately exposed is unloaded from the exposure apparatus, and then the photosensitive agent is developed. Thereafter, as in the case of the first embodiment, the photosensitive agent remains only in the portion provided with the appropriate exposure amount.
FIG. 6 shows the pattern of the remaining photosensitive agent after development.

By exposing two photomasks having a deviation smaller than the resolution of the projection optical system in such a manner as to obtain an appropriate exposure amount by two exposures, the resolution of the projection optical system is equal to or less than the limit resolution. A line width pattern can be obtained.

(Third Embodiment) FIG. 7 shows an example in which the shapes of the first and second patterns are different. Also in this case, only the overlapping portion is developed by the two exposures, and a line width pattern equal to or less than the limit resolution of the projection optical system as shown in FIG. 8 can be obtained.

[0019]

As described above, according to the present invention, it is possible to form a line width smaller than the limit resolution of the projection optical system of the existing exposure apparatus. In particular, a significant decrease in throughput does not occur by shifting between the forward path and the return path as in the first embodiment. Thus, a finer pattern can be formed without preparing an expensive exposure apparatus and without newly forming a projection optical system.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of a first (outward) exposure in a first embodiment.

FIG. 2 is a diagram illustrating a second (return) exposure state according to the first embodiment;

FIG. 3 is a diagram illustrating a state after development in the first embodiment.

FIG. 4 is a diagram illustrating a first photomask pattern and a second photomask pattern according to the second embodiment;

FIG. 5 is a diagram illustrating a state after first and second exposures according to a second embodiment;

FIG. 6 is a diagram illustrating a state after development in a second embodiment.

FIG. 7 is a diagram illustrating a state after first and second exposures according to a third embodiment;

FIG. 8 is a diagram illustrating a state after development in a third embodiment.

Claims (5)

[Claims] 1. An exposure method in an exposure apparatus comprising a projection optical system and a substrate suction stage having a resolution higher than the resolution of the projection optical system, wherein an exposure in one step is divided into a plurality of exposures. The relative position between the photomask and the substrate coated with the photosensitive agent is shifted within the range of the limit resolution of the projection optical system for each exposure, and the exposure is performed so that the integration of the exposure for each exposure becomes the optimum exposure. Exposure method characterized by the above-mentioned. 2. A scanning exposure apparatus comprising a projection optical system and a substrate suction stage having a resolution higher than the resolution of the projection optical system, and performing projection exposure while scanning an exposure area.
Exposure in the process is performed in two exposures so that the integration of the exposure amount for each exposure becomes the optimal exposure amount, and a photomask and a photosensitive agent are applied in the first exposure in the forward pass and the second exposure in the return pass. An exposure method, wherein a portion of the substrate which has been double-exposed by two reciprocal exposures is developed by displacing a substrate and a substrate having a size smaller than the limit resolution of the projection optical system. 3. An exposure method in an exposure apparatus comprising a projection optical system and a substrate suction stage having a resolution higher than the resolution of the projection optical system, wherein an exposure in one step is divided into a plurality of exposures. An exposure method, comprising: using a photomask in which the position of a pattern is shifted by a dimension less than or equal to the limit resolution of the projection optical system for each exposure, so that the integration of the exposure for each exposure becomes an optimal exposure. 4. A scanning exposure apparatus comprising a projection optical system and a substrate suction stage having a resolution higher than that of the projection optical system, and performing projection exposure while scanning an exposure area.
Exposure in the process is performed in two steps, and the photomask used in the second exposure is displaced from the reference position of the first photomask by a displacement equal to or less than the limit resolution of the projection optical system. An exposure method, comprising: 5. A scanning exposure apparatus comprising a substrate suction stage having a resolution higher than that of a projection optical system and performing projection exposure while scanning an exposure area, wherein exposure in one process is performed twice. Exposure amount control means for performing exposure so that the integration of the exposure amount for each exposure becomes the optimum exposure amount; two reciprocations in the same exposure area;
An exposure apparatus, comprising: stage control means for scanning a photomask and a substrate coated with a photosensitive agent by a predetermined dimension within a limit resolution of the projection optical system in the second exposure.