JPH10199792A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner of an image processing type alignment optical system wherein off-axis system contrast and resolution are high. SOLUTION: An alignment optical system 30 of this aligner is provided with the following; a light source 32 capable of changing light intensity, a condenser lens 24, a splitter 34 capable of changing the angle of a splitter surface to the optical axis of the optical system, a filter 36 capable of changing transmittance, an objective 28, a CCD camera 18 picking up an image obtained by the optical system and converting the image into an electric signal, a pin hole type stop 38 which is installed on the path of an incident light to the CCD camera 18 and can change the stop, a data processing system 20 for processing the electric signal obtained by the CCD camera 18, and a first, a second and a third control equipments 40, 42 and 44 for controlling the camera 18, the stop 38, the system 20, etc. Thereby an alignment optical system having high contrast and high resolution can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction projection type exposure apparatus having an off-axis type image processing type alignment optical system for performing alignment for exposure. The present invention relates to an exposure apparatus having high resolution and capable of performing high-sensitivity, high-accuracy alignment control.

[0002]

2. Description of the Related Art In reduction projection exposure, when exposing a substrate, it is necessary to perform alignment (alignment) in order to accurately transfer a mask pattern to a predetermined exposure area on the substrate. Usually, alignment is performed using an alignment optical system provided in the exposure apparatus with reference to an alignment mark on the substrate. The alignment optical system is roughly classified into an off-axis type and a TTL (Through The Lens) type.
As shown in FIG. 3, it is provided separately from the exposure optical system.

Normally, a reduction projection type exposure apparatus 10 which performs alignment using an off-axis type alignment optical system is shown in FIG.
As shown in FIG. 1, an exposure optical system 1 having a reduction projection lens
2 and a light source 1 provided separately from the exposure optical system 12.
4. Positioning optical system 16, Positioning optical system 16
Camera 1 that captures the image obtained in step 1 and converts it into an electric signal
And an alignment optical system 22 having a data processing system 20 for processing electric signals obtained by the CCD camera 18. The positioning optical system 16 includes an optical system having a light source 14 for emitting parallel light for positioning, a condenser lens 24 for converging the parallel light, a splitter 26, and an objective lens 28 in that order. Light source 14
For example, a broadband He-Ne laser, a halogen lamp that emits long-wavelength broadband light, or the like is used. Light from the light source 14 is focused by the condenser lens 24, and is irradiated on the substrate W via the splitter 26 and the objective lens 28.

In the off-axis position alignment, first, the amount of displacement of the reticle with respect to a reference point on the stage is determined through the exposure optical system 12, and the amount of deviation of the entire alignment optical system is determined through the alignment optical system 22, respectively. . Next, the alignment mark M of the substrate W is aligned with the alignment optical system 22 at a position determined with respect to the exposure axis.
With this, the positional relationship between the reticle and the substrate is determined, and then the XY stage is moved by a predetermined distance to bring the substrate to the first exposure position. Thereafter, the stage is moved stepwise to expose the entire surface of the substrate one chip at a time.

[0005]

However, in the above-described exposure apparatus having the conventional off-axis type image processing type alignment optical system, the observation microscope unit including the light source 14, the alignment optical system 16 and the CCD camera 18 is used. In the above, only the reflected light from the focal plane cannot be made incident on the CCD camera 18, and the reflected light from the out-of-focus plane is also made incident on the CCD camera 18 at the same time. Therefore, there is a problem that the contrast of the image is poor and the resolution is low. In this case, it is difficult to cope with pattern miniaturization expected in the future.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus having an off-axis image processing type alignment optical system having high contrast and high resolution.

[0007]

The present inventor has conceived of improving the contrast and resolution by adopting a confocal optical system in an observation microscope for observing an alignment mark, and has completed the present invention. Was. In order to achieve the above object, an exposure apparatus according to the present invention includes an optical system having a light source, a condenser lens, a splitter, and an objective lens sequentially, a CCD camera that captures an image obtained by the optical system and converts the image into an electric signal. A reduction projection exposure apparatus that includes an off-axis image processing type alignment optical system including a data processing system for processing an electric signal obtained by a CCD camera and performs alignment for exposure; A filter provided between the objective lens and
A light stop means is provided on a light incident path to the CCD camera, and stops light entering the CCD camera and selectively enters the light. Preferably, the filter used in the present invention is a variable transmittance filter, for example, a filter in which two polarizers are overlapped and the transmittance is variable depending on the overlapping angle. Further, the optical stop means is preferably a pinhole type aperture stop.

In the present invention, by providing an optimum filter in front of the objective lens as required, the optimum amount of incident light to the objective lens and the optimum amount of reflected light to the splitter for each substrate sample in real time. Can be selected. In addition, by using a variable transmittance filter as a filter, depending on the alignment mark on the substrate, the formed photoresist film, and the state of the step of the photoresist film, etc., if the mark shape is good, the step If the mark shape is bad, use a bright-field observation method that uses only reflected light. Can be switched in accordance with

In a preferred embodiment of the present invention, a light source having a variable light intensity of radiated light is provided as a light source, and the light intensity of the light source and the transmittance of a variable transmittance filter are adjusted.
A first controller for optimizing the amount of light incident on the CD camera is provided, and the amount of light incident on the CCD camera can be optimized to improve resolution and contrast. In another preferred embodiment of the present invention, the angle of the splitter surface with respect to the optical axis of the alignment optical system is variable, the aperture is variable, and the aperture is variable. A second controller that adjusts the shape of light incident on the CCD camera to optimize the shape of light incident on the CCD camera to improve resolution and contrast.

Still another preferred embodiment of the present invention is a light source having a variable light intensity of emitted light, a splitter having a variable angle with respect to an optical axis of an optical system, and a variable stop optical stop means. A first controller for adjusting the light intensity of the light source and the transmittance of the variable transmittance filter to optimize the amount of light incident on the CCD camera, and adjusting the angle of the splitter and the aperture of the optical aperture means. A second control device for optimizing the shape of light incident on the CCD camera, and a filter for changing the optimum light intensity and transmittance of the light source based on a signal output state output from the CCD camera to the data processing system. The optimum transmittance is input to the first control device, the optimum angle of the splitter and the optimum stop of the light stop means are input to the second control device as setting values, and the optimum output signal from the CCD camera is input to the data processing system. I will send it to By providing a third control apparatus, it is possible to further improve the contrast and resolution.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an embodiment of an exposure apparatus having an off-axis type image processing type alignment optical system according to the present invention. FIG. 1 shows a configuration of an image processing type alignment optical system of the exposure apparatus of this embodiment. FIG. The alignment optical system of the alignment optical system 30 of the exposure apparatus of the present embodiment is replaced with the light source 14 and the splitter 26 of the alignment optical system 16 shown in FIG. And a splitter 34 in which the angle of the splitter surface with respect to the optical axis of the alignment optical system is variable. Further, the alignment optical system of the alignment optical system 30 has a variable transmittance filter 36 between the splitter 26 and the objective lens 28 and a CCD camera in addition to the configuration of the alignment optical system 16 shown in FIG. In order to narrow down and selectively enter the light, a variable aperture type pinhole type aperture stop 38 provided immediately before the CCD camera 18 on the light incident path to the CCD camera is provided.

The alignment optical system 30 includes a first control device 40, a second control device 42, and a third control device as control devices.
The control device 44 is provided. The first control device 40 includes:
The light intensity of the light source 32 and the transmittance of the transmittance variable filter 36 are adjusted to optimize the amount of light incident on the CCD camera 18. The second controller 42 adjusts the angle of the splitter 34 and the aperture of the pinhole aperture 38, and controls the CCD.
Optimize the shape of the light incident on the camera. The third control device determines the optimum light intensity of the light source 32 and the optimum transmittance of the transmittance variable filter 36 based on the signal output state output from the CCD camera 18 to the data processing system 20. In addition, the optimum angle of the splitter 34 and the optimum stop of the pinhole type aperture stop 38 are transmitted to the second control device 42.
Each is input as a set value, and an optimal output signal is sent from the CCD camera 18 to the data processing system 20.

As shown in FIG. 2 (a control device is omitted in FIG. 2 for the sake of clarity), in the alignment optical system 30 of this embodiment, light emitted from a light source 32 and converted into parallel light Is focused by the condenser lens 24 and irradiates the substrate via the splitter 34, the filter 36, and the objective lens 28. The reflected light from the focused substrate W enters the CCD camera 18 through a pinhole type aperture stop 38 as shown by a solid line. On the other hand, the reflected light from the out-of-focus substrate W 'is blocked by the pinhole type aperture stop 38 and does not enter the CCD camera 18 as shown by the broken line. With the above configuration, only the reflected light from the focal plane can be selectively captured into the CCD camera 18, so that good contrast and resolution can be obtained.
Pattern recognition is improved.

Further, the amount of light incident on the objective lens 28 and the splitter
By optimizing the amount of reflected light to the surface 4, according to the state of the alignment mark, the photoresist film, and the surface step on the substrate, if the mark shape is good, a dark-field observation method is used. In this case, it is possible to switch between the bright-field observation method and the surface condition of the photoresist film on the substrate as appropriate. Furthermore, hybrid observation that makes use of the advantages of both the dark-field observation method and the bright-field observation method is also possible. Further, the incidence of excessive reflected light on the CCD camera 18 can be suppressed.

The first controller 40 adjusts the light intensity of the light source 32 and the transmittance of the filter 36, and the second controller 42 adjusts the angle of the splitter 34 and the aperture of the pinhole type aperture stop 38. By complementarily controlling
The light quantity and shape of light entering the CCD camera 18 are optimized. Further, the CCD camera 1 is controlled by the third control device 44.
By optimizing the output of the video signal output from the control unit 8, high-sensitivity and high-precision image processing alignment is realized.

[0016]

According to the structure of the present invention, in a reduction projection type exposure apparatus having an off-axis type image processing type alignment optical system, a filter is provided between a splitter and an objective lens, and a filter for a CCD camera is provided. By providing a light stop means provided on the light incident path to selectively stop and enter the light entering the CCD camera, alignment marks on the substrate, the formed photoresist film, steps of the photoresist film, etc. Depending on the state, it is possible to obtain an image with high contrast and high resolution by switching to either the dark-field observation method or the bright-field observation method, or by using both. In addition, by providing a control device, the light intensity of the light source,
The transmittance of the filter, the angle of the splitter, and the aperture of the optical aperture means are adjusted to optimize the amount and shape of light to the CCD camera. Therefore, if the exposure apparatus according to the present invention is used, high-sensitivity and high-accuracy alignment control can be performed in accordance with future pattern miniaturization, and the product yield of semiconductor devices can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an alignment optical system in an embodiment of an exposure apparatus according to the present invention.

FIG. 2 is a diagram illustrating an operation of a positioning optical system according to the embodiment.

FIG. 3 is a configuration diagram of an exposure apparatus having an off-axis image processing type alignment optical system.

FIG. 4 is a configuration diagram of a conventional positioning optical system.

[Explanation of symbols]

Reference numeral 10 denotes a reduction projection type exposure apparatus for performing off-axis alignment, 12 denotes an exposure optical system, 14 denotes a light source, and 16 denotes a light source.
... Positioning optical system, 18 CCD camera, 20
...... Data processing system, 22 Alignment optical system, 24
…… Condenser lens, 26 …… Splitter, 28…
... Objective lens, 30... Alignment optical system of the exposure apparatus according to the present invention, 32... Light source with variable light intensity of light emitted from the light source, 34. Variable splitter, 36 ...
.., A variable transmittance filter, 38, a variable aperture pinhole aperture stop, 40, a first controller, 42, a second controller, 44, a third controller.

Claims (6)

[Claims] 1. An optical system having a light source, a condenser lens, a splitter, and an objective lens sequentially, a CCD camera for capturing an image obtained by the optical system and converting the image into an electric signal, and a CCD.
A reduction projection type exposure apparatus having an off-axis image processing type alignment optical system comprising an off-axis type image processing type alignment optical system comprising a data processing system for processing an electric signal obtained by a camera and performing alignment for exposure, comprising a splitter and an objective lens. And a light stop means provided on a light incident path of the light to the CCD camera to stop light entering the CCD camera and to selectively input the light. Exposure equipment. 2. The exposure apparatus according to claim 1, wherein the filter is a variable transmittance filter. 3. A light source whose light intensity is variable, and a light intensity of the light source and a transmittance of a variable transmittance filter are adjusted to optimize a light amount of light incident on the CCD camera. 3. The control device according to claim 2, wherein
3. The exposure apparatus according to claim 1. 4. A splitter in which the angle of the splitter surface with respect to the optical axis of the alignment optical system is variable, a variable aperture optical stop means, the angle of the splitter and the aperture of the optical stop means are adjusted,
The exposure apparatus according to any one of claims 1 to 3, further comprising a second control device that optimizes a shape of light incident on the CD camera. 5. A light source having a variable light intensity of emitted light; a splitter having a variable angle with respect to an optical axis of an optical system; a variable aperture stop means; a variable light intensity and transmittance of a light source; A first controller that adjusts the transmittance of the filter to optimize the amount of light incident on the CCD camera; and adjusts the angle of the splitter and the aperture of the optical aperture unit, and
A second control device for optimizing the shape of light incident on the CD camera, and an optimum light intensity of the light source and an optimum transmission of the transmittance variable filter based on a signal output state output from the CCD camera to the data processing system. The ratio is input to the first controller and the optimal angle of the splitter and the optimal aperture of the optical aperture are input to the second controller as set values, respectively, and the optimal output signal is sent from the CCD camera to the data processing system. The third
The exposure apparatus according to claim 2, further comprising: a control device. 6. The optical system according to claim 1, wherein the optical stop means is a pinhole type aperture stop.
Exposure apparatus according to Item.