JPH09237755A - Projection exposure equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection exposure apparatus having a function of detecting an intensity distribution of an aerial image of a mask pattern formed via a projection optical system at any time. A knife edge member having a transmitting portion that transmits illumination light and a light shielding portion that shields the illumination light, and a knife edge member having a knife edge formed from a boundary line between the transmission portion and the light shielding portion, and a projection optical system are provided. And a light receiving means for receiving light from the aerial image of the mask pattern formed on the knife edge member. Then, the intensity distribution of the aerial image of the mask pattern is detected based on the output of the light receiving means obtained by relatively moving the aerial image of the mask pattern and the knife edge member along a predetermined direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and more particularly, to a mask pattern formed through a projection optical system in a projection exposure apparatus used when manufacturing a semiconductor element, a liquid crystal display element or the like in a lithography process. Detecting the intensity distribution of an aerial image.

[0002]

2. Description of the Related Art FIG. 8 is a diagram for explaining the intensity distribution measurement of an aerial image of a mask pattern in a conventional projection exposure apparatus. In the conventional projection exposure apparatus of FIG. 8, the mask 51 is uniformly illuminated by an illumination optical system (not shown). Mask 51
The light transmitted through forms a mask pattern aerial image 53 through the projection optical system 52. The light from the aerial image 53
An enlarged image of the mask pattern is re-formed on the image pickup surface of the two-dimensional image pickup element 55 via the image forming optical system 54.

Thus, in the conventional projection exposure apparatus, the two-dimensional image sensor 55 detects the aerial image 53 of the mask pattern, and the intensity distribution of the aerial image 53 of the mask pattern is measured based on the output of the two-dimensional image sensor 55. To do. In the projection exposure apparatus, what is finally required for the projection optical system is not that the intensity distribution of the aerial image is good, but a resist (photosensitive member) applied to a photosensitive substrate such as a wafer. ) The image obtained by developing the resist after projecting the mask pattern image on it, that is, the resist image is good.

Therefore, the quality of the intensity distribution of the aerial image of the mask pattern formed through the projection optical system can be an index for adjusting the projection optical system, but in the end, the lens performance of the projection optical system is resist. The image is adjusted to be good. For the above reason, in the conventional projection exposure apparatus shown in FIG. 8, the function of the intensity distribution measuring device having the image forming optical system 54 and the two-dimensional image pickup element 55 is the function as the inspection device of the projection optical system 52 in the manufacturing stage. Is limited to. Therefore, this type of intensity distribution measuring device is not mounted in the projection exposure apparatus as a final product.

[0005]

As described above, in the conventional projection exposure apparatus, it is necessary to confirm the quality of the resist image in order to adjust the final lens performance of the projection optical system. Then, in order to judge the quality of the resist image, it is necessary to perform a very troublesome process of printing a pattern on a resist-coated wafer, performing a development process, and observing the resist image with an electron microscope. It was

By the way, with the recent progress of simulation technology, it has become possible to predict the quality of a resist image formed by actual exposure with a high degree of accuracy based on the intensity distribution of the aerial image of the mask pattern. There is. Moreover, the measurement of the intensity distribution of the aerial image is very simple. Therefore, there is an increasing demand for an intensity distribution measuring device that can be mounted on a projection exposure apparatus.

In response to such a demand, a method of mounting an image distribution type intensity distribution measuring device, which has been conventionally used as an inspection device of a projection optical system, on a projection exposure apparatus can be considered. In this case, in order to perform image detection of the aerial image of the mask pattern in the actual projection exposure apparatus, it is necessary to mount the image forming optical system on the wafer stage. In general, the space on the wafer stage is limited, and the size of the imaging optical system mounted on the wafer stage is also restricted. Therefore, the imaging optical system needs to be a small optical system.

On the other hand, as described above, the imaging optical system is an optical system that re-forms an image based on the light from the aerial image formed via the projection optical system. Therefore, the imaging optical system, by its nature, allows only a sufficiently small aberration as compared with the projection optical system. As a result, it is difficult to reduce the size of the imaging optical system sufficiently, and it is not realistic to mount a conventional image distribution type intensity distribution measuring device in a projection exposure apparatus. In addition, when the imaging optical system having almost no aberration is mounted on the wafer stage which repeats the movement at high speed, the influence of the generated vibration or heat on the imaging optical system cannot be ignored. Also in this respect, it is not realistic to mount the conventional image distribution type intensity distribution measuring device in the projection exposure apparatus.

The present invention has been made in view of the above problems, and provides a projection exposure apparatus having a function of detecting the intensity distribution of an aerial image of a mask pattern formed via a projection optical system at any time. The purpose is to

[0010]

In order to solve the above-mentioned problems, in the present invention, an illumination optical system for irradiating a mask having a predetermined pattern with illumination light, and a pattern image of the mask are exposed. In a projection exposure apparatus including a projection optical system for projecting onto a transparent substrate, the projection exposure apparatus includes a transmissive portion that transmits the illumination light and a light shielding portion that shields the illumination light, and the transmissive portion and the light shielding portion. A knife edge member having a knife edge formed from a boundary line between the knife edge member and a light receiving means for receiving light from an aerial image of the mask pattern formed on the knife edge member via the projection optical system. , The aerial image of the mask pattern based on the output of the light receiving means obtained by relatively moving the aerial image of the mask pattern and the knife edge member along a predetermined direction. To provide a projection exposure apparatus according to claim which comprises a detecting means for detecting the degree distribution.

According to a preferred aspect of the present invention, there is further provided a substrate stage for holding the substrate and positioning the substrate with respect to the projection optical system, and the knife edge member is provided on the substrate stage. The light receiving means is provided inside or outside the substrate stage. In addition, the detection means, based on the output of the light receiving means obtained by relatively moving the pattern space image and the knife edge member along a direction substantially orthogonal to the knife edge, the space of the mask pattern. It is preferable to detect the intensity distribution of the image.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a knife edge formed by a boundary line between a transmitting portion and a light shielding portion is provided on, for example, a substrate stage. Further, a light receiving sensor for receiving light from the mask pattern aerial image formed on the knife edge via the projection optical system is provided, for example, in the substrate stage. Therefore, for example, the intensity distribution of the aerial image of the mask pattern is detected based on the output of the light receiving sensor obtained by moving the substrate stage relative to the projection optical system and scanning the aerial image of the mask pattern with the knife edge. be able to.

As described above, according to the present invention, the intensity distribution of the aerial image of the mask pattern formed through the projection optical system is not subjected to steps such as pattern printing, development processing, and observation of a resist image with an electron microscope. Can be detected at any time. In this way, the optical performance of the projection optical system can be adjusted based on the detected intensity distribution of the aerial image without actually performing the exposure.

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of a projection exposure apparatus according to an embodiment of the present invention. 2 is a top view of the stage substrate 15 of FIG. In FIG. 1, the Z axis is parallel to the optical axis AX of the projection optical system 10, and the X axis is parallel to the plane of the paper of FIG. 1 in the plane perpendicular to the optical axis AX of the projection optical system 10. In the plane perpendicular to the axis AX, the Y axis is set perpendicularly to the paper surface of FIG.

The projection exposure apparatus of FIG. 1 is equipped with a light source 1 which is, for example, a mercury lamp. The light source 1 is positioned at a first focal position of an elliptical reflecting mirror 2 having a reflecting surface formed of a spheroidal surface. Therefore, the illumination light flux emitted from the light source 1 forms a light source image (primary light source) at the second focus position 3 of the elliptical reflecting mirror 2.

The light beam from the light source image is converted into a substantially parallel light beam by the input lens 4, and then enters a bandpass filter (not shown) which transmits only a light beam in a desired wavelength range. Exposure wavelength selected by bandpass filter (for example, i-line with wavelength 365nm or wavelength 4
The illumination light of the 36 nm g-line or the like is incident on the fly-eye integrator 5. The light flux incident on the fly-eye integrator 5 is divided by a plurality of lens elements forming the fly-eye integrator 5 to form a secondary light source composed of a plurality of light source images.

The light flux from the secondary light source is limited by the aperture stop 6, and then passes through the condenser lens 7 and the bending mirror 8 to form a mask 9 on which a predetermined pattern is formed.
Are illuminated in a superimposed manner. The mask 9 is supported on the mask stage 12 in the XY plane. The XY coordinates of the mask stage 12, and by extension, the XY coordinates of the mask 9 are constantly measured by a mask stage laser interferometer (not shown). The light flux that has passed through the pattern of the mask 9 reaches the wafer 11, which is a photosensitive substrate, via the projection optical system 10. Thus, the pattern image of the mask 9 is formed on the wafer 11.

The wafer 11 is supported on the wafer stage 14 in the XY plane via the wafer holder 13. The wafer stage 14 includes an XY stage that two-dimensionally positions the wafer 11 in the XY plane, a Z stage that positions the wafer 11 along the Z direction, and a leveling stage that corrects the tilt angle of the wafer 11. It is configured. The XY coordinates of the wafer stage 14, and hence the XY coordinates of the wafer 11, are constantly measured by a wafer stage laser interferometer (not shown). Therefore, the pattern of the mask 9 can be sequentially transferred to each exposure region of the wafer 11 by performing the exposure while controlling the two-dimensionally driving of the wafer 11.

Wafer holder 13 on wafer stage 14
A stage substrate 15 made of, for example, a glass substrate is provided in the vicinity of. The upper surface of the stage substrate 15 is set to have substantially the same height (the same position in the Z direction) as the exposed surface of the wafer 11. In addition, the stage substrate 15
As shown in FIG. 2, is formed of a transmissive portion 21 that transmits the exposure light and a light shielding portion 22 that shields the exposure light. Then, the boundary line between the transmissive portion 21 and the light shielding portion 22 constitutes a knife edge 23 extending along the Y direction. In addition,
The light shielding portion 22 is formed of, for example, a vapor deposition film of chromium or the like having a light shielding property.

Further, a light receiving sensor 16 is arranged below the stage substrate 15 in the figure. The light receiving sensor 16 has a light receiving surface that is sufficiently wide for a light beam to be received,
It is preferable that the sensitivity unevenness regarding the light receiving position and the sensitivity unevenness regarding the light receiving angle are sufficiently small. The output of the light receiving sensor 16 is supplied to the signal processing system 17. FIG. 3 is a diagram schematically showing the pattern formed on the mask 9 of FIG.
In the present embodiment, as shown in FIG. 3, in the pattern area PA of the mask 9, rectangular light transmitting portions 31 extending along the Y direction are arranged at a predetermined pitch along the X direction. That is, the mask pattern of FIG. 3 is a line-and-space blank pattern along the X direction.

Next, the operation of detecting the intensity distribution of the aerial image of the mask pattern formed via the projection optical system 10 in this embodiment will be described. When detecting the intensity distribution of the aerial image, first, the stage substrate 1 is placed below the projection optical system 10.
The wafer stage 14 is moved so that 5 is positioned. In this state, a spatial image of the pattern of the mask 9 is formed on the stage substrate 15 via the projection optical system 10. FIG. 4 is a diagram showing an actual intensity distribution of the aerial image of the mask pattern formed on the stage substrate 15.

Then, the wafer stage 14 is moved along the X direction to scan the aerial image of the mask pattern with the knife edge 23 of the stage substrate 15, while the light from the aerial image of the mask pattern is passed through the knife edge 23. The light receiving sensor 16 receives light. Thus, in the signal processing system 17,
As shown in FIG. 5, the light quantity distribution of the aerial image is obtained based on the output from the light receiving sensor 16. In FIG. 5, the horizontal axis represents time and the vertical axis represents the amount of light. The signal processing system 17 can detect the intensity distribution with respect to time of the aerial image (the vertical axis is intensity and the horizontal axis is time) by differentiating the light amount distribution shown in FIG. 5 with respect to time, as shown in FIG. it can.

Further, the signal processing system 17 converts the time information into position information based on the time-related intensity distribution of the aerial image of FIG. 6 and the position information from the laser interferometer for the wafer stage, as shown in FIG. Thus, the intensity distribution (the vertical axis is the intensity and the horizontal axis is the position) related to the position of the aerial image can be detected. Referring to FIGS. 4 and 7, the intensity distribution of the aerial image finally detected in the signal processing system 17 indicates the actual aerial image of the mask pattern formed on the stage substrate 15 via the projection optical system 10. It can be seen that the intensity distribution is almost the same.

As described above, in the present embodiment, the intensity of the aerial image of the mask pattern formed through the projection optical system is not passed through steps such as pattern printing, development processing, and observation of a resist image with an electron microscope. The distribution can be detected at any time. In this way, the simulation technique based on the intensity distribution of the detected aerial image allows the optical performance of the projection optical system to be adjusted at any time without actually performing the exposure.

Further, by detecting the intensity distribution of the aerial image, absolute position information of the aerial image of the mask pattern on the wafer can be obtained. On the other hand, the absolute position information of the mask pattern on the mask is known. Therefore, based on the absolute position information on the wafer of the aerial image of the mask pattern and the absolute position information on the mask of the mask pattern,
It is possible to measure the magnification of the projection optical system, measure the distortion of the projection optical system, and measure the mask position.

Further, in the projection exposure apparatus, the NA (numerical aperture) of the projection optical system, the NA of the illumination optical system, and the illumination method (normal illumination, which are important factors that affect the imaging performance of the projection optical system). Conditions such as annular illumination, modified illumination, etc.) may be changed. In this case, the intensity distribution of the aerial image of various mask patterns formed via the projection optical system is detected at any time, and the resist image that will actually be formed under the changed conditions is predicted by the simulation technique. It is possible to know the resolution state of various mask patterns by the projection optical system.

Further, while moving the wafer stage along the optical axis of the projection optical system, the intensity distribution of the aerial image of various mask patterns is detected, and the resist image that is actually formed in each defocus state is simulated. It is possible to predict the depth of focus (DOF) for various mask patterns of the projection optical system by using technology. In this way, by accumulating the aerial image intensity distributions of various mask patterns obtained by changing each condition, each condition can be optimized based on the accumulated data, and it is optimal for various mask patterns. A wide range of resolution and depth of focus can be achieved.

FIG. 9 shows a modification of the embodiment shown in FIG. In the embodiment of FIG. 1, the light receiving sensor 16 is arranged inside the wafer stage 14, but in the embodiment of FIG. 9, the light receiving sensor 16 is arranged outside the wafer stage 14. In FIG. 9, members having the same functions as those in FIG. 1 are designated by the same reference numerals as those in FIG. Specifically, as shown in FIG. 9, a condenser lens 18 for arranging and guiding the light from the knife edge pattern 23 on the stage substrate 15 to the incident end face of the optical fiber 20 as a light guide unit is arranged, Optical fiber 20
The light passing through is guided to the external light receiving sensor 16 arranged on the exit end face of the optical fiber 20. A mirror 19 for deflecting the optical path is arranged between the condenser lens 18 and the incident end face of the optical fiber 20.

Based on such a configuration, the light receiving sensor 1
By disposing 6 outside the wafer stage 14,
It is expected that the thermal expansion of the wafer stage 14 due to the heat generation of the light receiving sensor 16 and the fluctuation in the measurement optical path of the interferometer for measuring the position of the wafer stage 14 can be prevented. Therefore, by arranging the light receiving sensor 16 outside the wafer stage 14, the wafer stage 1
It is possible to maintain the stable measurement accuracy of 4.

In the above embodiment, the present invention is applied to the projection exposure apparatus that performs exposure while driving the wafer two-dimensionally with respect to the projection optical system. However,
It goes without saying that the present invention can also be applied to a scan type projection exposure apparatus that performs exposure while moving the wafer and the mask relative to the projection optical system.

[0031]

As described above, according to the present invention, since the intensity distribution of the aerial image of the mask pattern formed through the projection optical system can be detected at any time, the projection optical system can be used without performing actual exposure. The optical performance of the system can be adjusted at any time.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a top view of a stage substrate 15 shown in FIG.

FIG. 3 is a diagram schematically showing a pattern formed on the mask 9 of FIG.

4 is a diagram showing an actual intensity distribution of an aerial image of a mask pattern formed on a stage substrate 15. FIG.

FIG. 5 is a diagram showing a light amount distribution of an aerial image obtained based on an output from a light receiving sensor 16.

FIG. 6 is a diagram showing an intensity distribution with respect to time of an aerial image obtained based on the light amount distribution of FIG.

7 is a diagram showing the intensity distribution with respect to the position of the aerial image obtained based on the intensity distribution with respect to time of the aerial image of FIG. 6 and the position information from the laser interferometer for the wafer stage.

FIG. 8 is a diagram illustrating intensity distribution measurement of an aerial image of a mask pattern in a conventional projection exposure apparatus.

FIG. 9 is a diagram showing a modification of the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 elliptical reflecting mirror 3 second focal position 4 input lens 5 fly eye integrator 6 aperture stop 7 condenser lens 8 folding mirror 9 mask 10 projection optical system 11 wafer 12 mask stage 13 wafer holder 14 wafer stage 15 stage substrate 16 light receiving sensor 17 Signal processing system

Claims (3)

[Claims] 1. A projection including an illumination optical system for irradiating a mask having a predetermined pattern with illumination light, and a projection optical system for projecting a pattern image of the mask onto a photosensitive substrate. In the exposure apparatus, a knife edge member having a transmissive portion that transmits the illumination light and a light shielding portion that shields the illumination light, and a knife edge member having a knife edge formed from a boundary line between the transmissive portion and the light shielding portion, Light receiving means for receiving light from the aerial image of the mask pattern formed on the knife edge member via the projection optical system, and the aerial image of the mask pattern and the knife edge member in a predetermined direction. A detection means for detecting the intensity distribution of the aerial image of the mask pattern, based on the output of the light receiving means obtained by relative movement along the Projection exposure system. 2. A substrate stage for holding the substrate and positioning the substrate with respect to the projection optical system, wherein the knife edge member is provided on the substrate stage, and the light receiving means is the substrate. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is provided inside or outside the stage. 3. The mask based on the output of the light receiving means obtained by relatively moving the pattern space image and the knife edge member along a direction substantially orthogonal to the knife edge. The projection exposure apparatus according to claim 1, wherein the intensity distribution of the aerial image of the pattern is detected.