JPH07201713A - Exposure apparatus and exposure method - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an exposure apparatus and an exposure method capable of ensuring the depth of focus at all positions on the exposure surface. [Arrangement] An illumination optical system 11 for irradiating the exposure light 2, a reticle stage 12, a reduction lens 13, and a sample stage 14 which are sequentially arranged in the optical path of the exposure light 2, and a reticle stage 12
The first detecting means 15 for detecting the inclination of the projection surface 5a of the reticle 5 arranged on the sample table, the second detecting means 16 for detecting the inclination of the exposure surface 4a of the sample 4 placed on the sample table 14, and the first detecting means 15.
The sample table 14 is driven so as to correct the inclination of the exposure surface 4a with respect to the inclination of the projection surface 5a based on the inclinations of the exposure surface 4a and the projection surface 5a input from the detection means 15 and the second detection means 16. An exposure apparatus including a correction unit 17,
The tilt of the exposure surface of the sample is corrected in accordance with the tilt of the image forming surface that varies depending on the arrangement state of the reticle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method.

[0002]

2. Description of the Related Art When a resist coated on a substrate is patterned by lithography in a semiconductor device manufacturing process, exposure is performed using, for example, a step-and-repeat type reduction projection exposure apparatus. The exposure apparatus is provided with an illumination optical system 31 for irradiating the exposure light 2 as shown in FIG. 3, for example. A reticle stage 32, a reduction lens 33, and a sample stage 34 are sequentially arranged on the optical path of the exposure light 2. A detecting means 35 is arranged between the reduction lens 33 and the sample table 34, and a correcting means 36 is connected to the sample table 34.

The illumination optical system 31, the reticle stage 32 and the reduction lens 33 are arranged so that the exposure light 2 emitted from the illumination optical system 31 and reduced by the reduction lens 33 forms an image on a horizontal plane. The detecting means 35 is arranged on the exposure surface 4a side of the sample 4 placed on the sample table 34,
The tilt of the exposure surface 4a of the sample 4 placed on the sample table 34 is detected. Then, the correction unit 36 is the detection unit 3
Based on the inclination of the exposure surface 4a detected in 5, the sample stage 34 is moved so that the exposure surface 4a becomes horizontal at the height position where the exposure light 2 forms an image, and the exposure position of the sample 4 is moved. Is.

In the method of exposing the sample surface using the exposure apparatus 3 described above, for example, as shown in FIG. 4, the reticle is loaded on the reticle stage, and the wafer to be the sample is loaded on the sample table to expose the wafer. Align the exposure position. Then, the inclination of the exposure surface is detected by the detection means, and the inclination of the sample stage is adjusted by the correction means based on this inclination to horizontally correct the exposure surface of the wafer. After that, the wafer is exposed by irradiating the exposure light from the illumination optical system.

In the above-mentioned exposure method, the inclination of the exposure surface 4a of the sample is corrected each time the exposure position is moved, so that the exposure surface of the sample and the image plane of the exposure light are aligned at each exposure position for exposure. I am trying.

[0006]

In the above exposure apparatus, the reticle stage, the illumination optical system, and the reduction lens are arranged so that the exposure light emitted from the illumination optical system forms an image on the horizontal plane. However, since the reticle arranged on the reticle stage is exchanged when performing exposure with a different exposure pattern, for example, a foreign substance was caught between the reticle stage and the reticle when exchanging the reticle. In this case, the reticle is placed in the exposure apparatus in a tilted state. Then, the exposure light emitted from the illumination optical system forms an image on a surface inclined in accordance with the inclination of the reticle. On the other hand, since the exposure surface of the sample is kept horizontal, the exposure is performed with the image forming surface of the exposure light and the exposure surface of the sample deviated from each other. Therefore, it becomes difficult to secure the depth of focus on the exposed surface of the sample. Further, in the above-described exposure method, since the step of detecting the inclination of the reticle arranged in the exposure apparatus is not performed, it becomes difficult to secure the depth of focus on the exposed surface of the sample as in the above.

In recent years, with the higher integration and higher functionality of semiconductor devices, miniaturization and multi-layering of device structures have been progressing.
Therefore, in the manufacturing process of a semiconductor device, it is required to form a resist pattern with high dimensional accuracy on a wafer having an enlarged surface step. Therefore, the decrease in the depth of focus as described above becomes a factor that hinders the miniaturization of the device structure.

Therefore, an object of the present invention is to provide an exposure apparatus and an exposure method capable of ensuring the depth of focus at all positions on the exposure surface, and particularly to miniaturize the device structure in a semiconductor device. To aim.

[0009]

An exposure apparatus of the present invention for achieving the above object comprises a reticle stage for holding a reticle, an illumination optical system for irradiating a reticle held on the reticle stage with exposure light, and the reticle. A sample table on which a sample to be exposed by the passing exposure light is placed, a first detecting means for detecting an inclination of a projection surface of a reticle arranged on a reticle stage, and an inclination of an exposure surface of a sample placed on the sample table. From the tilt of the exposure surface and the tilt of the projection surface input from the first detection means and the second detection means, the tilt of the exposure surface with respect to the tilt of the projection surface. Correction means for driving the sample table so as to correct

The exposure method of the present invention is an exposure method using an exposure apparatus and is performed according to the following procedure. First, the reticle is placed on the reticle stage of the projection exposure apparatus, and the inclination of the projection surface of the reticle is detected. Further, the sample is placed on the sample stage of the projection exposure apparatus to perform alignment. Next, after detecting the inclination of the exposure surface of the sample, the inclination of the exposure surface with respect to the inclination of the projection surface is corrected from the inclination of the exposure surface and the inclination of the projection surface. afterwards,
The exposure light is applied to the reticle, and the pattern formed on the reticle is projected onto the exposure surface of the sample by the exposure light that has passed through the projection surface of the reticle.

[0011]

The driving of the sample table by the correction means of the exposure apparatus is performed so as to correct the inclination of the exposure surface of the sample with respect to the inclination of the projection surface of the reticle. Therefore, if the reticle is placed on the reticle stage while tilted,
The exposed surface of the sample is corrected according to the tilt of the reticle.
In the exposure method described above, the exposure is performed after correcting the inclination of the exposure surface of the sample with respect to the inclination of the reticle. Therefore, the exposure is performed by correcting the inclination of the exposure surface of the sample in accordance with the inclination of the imaging surface that changes depending on the arrangement state of the reticle.

[0012]

EXAMPLES Examples of the present invention will be described below. First, an example of the configuration of the exposure apparatus 1 will be described based on the configuration diagram of FIG. The exposure apparatus 1 is provided with an illumination optical system 11 that irradiates the exposure light 2. A reticle stage 12, a reduction lens 13 and a sample stage 14 are sequentially arranged on the optical path of the exposure light 2 emitted from the illumination optical system 11. The illumination optical system 11, the reticle stage 12, and the reduction lens 13 are configured so that the exposure light 2 emitted from the illumination optical system 11 and passed through the reduction lens 13 forms an image on a horizontal plane.

A first detecting means 15 is arranged between the illumination optical system 11 and the reticle stage 12, and a second detecting means 16 is arranged between the reduction lens 13 and the sample table 14. There is. Then, the correction means 17 is provided on the sample table 14.
Are connected.

The reticle stage 12 includes a reticle 5
The projection surface 5a of the reticle 5 on which the mask pattern is formed is kept horizontal. The reduction lens 13 reduces the exposure light 2 emitted from the illumination optical system 11 and passing through the projection surface 5a of the reticle 5. The sample table 14 is used for the sample 4 to be exposed.
Is to be placed.

The first detecting means 15 is provided with, for example, a detecting section 151, a reflecting mirror 152, and a calculating section 153, and the reticle 5 mounted on the reticle stage 12 is used.
The inclination of the projection surface 5a of is detected. The detection unit 151 detects the exposure light 2 reflected by the reflecting mirror 152. The reflecting mirror 152 is the reflecting mirror 152.
The exposure light 2 incident from one surface is transmitted and the exposure light 2 incident from the opposite surface is reflected. The reflecting mirror 152 is arranged in the optical path of the exposure light 2 emitted from the illumination optical system 11 between the illumination optical system 11 and the reticle 5 arranged on the reticle stage 12. Then, the exposure light 2 emitted from the illumination optical system 11 is incident on the incident surface that transmits the exposure light 2, and the exposure light 2 reflected by the exposure surface 4a of the sample 4 is incident on the incident surface that reflects the exposure light 2. It is arranged to be incident. The first detector 151 and the reflecting mirror 15
2 is configured so as to be arranged at three or more positions with respect to the projection surface 5a, and in a state where they are not located on a straight line. Further, the calculation unit 153 is connected to each detection unit 151, and the intensity data of the exposure light 2 detected by the detection unit 151 and the sample 4 detected by the second detection unit 16 described below.
The inclination of the projection surface 5a with respect to the horizontal plane is calculated from the height position of the exposure surface 4a.

Then, the second detecting means 16 includes the light emitting section 1
61 and the light receiving section 162, and the sample table 15
The inclination of the exposure surface 4a of the sample 4 placed on the substrate is detected. The light emitting unit 161 emits the measurement light 6 from a predetermined angle and height position toward the exposure surface 4a. The light receiving section 162 receives the measurement light 6 reflected by the exposure surface 4a of the sample 4 at a predetermined angle and height position. The second detecting means 16 includes the exposure surface 4a.
In contrast, it is configured to be arranged in three or more places and not in a linear position. Then, it is arranged at a position that does not obstruct the optical path of the exposure light 2.

Further, the correction means 17 comprises a drive unit 171 and a control unit 172. The drive unit 171 is the sample table 1
4 and the control unit 172, and the tilt and the horizontal position of the sample table 14 are moved under the control of the control unit 172. The control unit 172 is connected to the calculation unit 153 of the first detecting unit 15 and the light receiving unit 162 of the second detecting unit 16. Then, the control unit 172 obtains the inclination of the exposure surface 4a with respect to the horizontal plane from the height position of each point of the exposure surface 4a detected by the second detection means 16, and the inclination obtained here and the calculation unit 153. Reticle 5 entered from
The inclination of the projection surface 5a of the sample table 14 so that the exposure surface 4a is parallel to the projection surface 5a within the focus range of the exposure light 2.
Control the tilt of.

In the exposure apparatus 1 having the above structure, the reticle 5 is arranged on the reticle stage 12, and the exposure surface 4 is placed on the sample table 14.
The sample 4 is placed with a facing upward. Then, by irradiating the exposure light 2 from the illumination optical system 11, the mask pattern (not shown) formed on the projection surface 5a of the reticle 5 is projected on the exposure surface 4a of the sample 4 in a reduced size. .

In the exposure apparatus 1, the projection surface 5a of the reticle 5 placed on the reticle stage 12 is also shown.
When detecting the inclination of, the following is done. First,
A reticle 5 having mask patterns for inspection formed at three or more places is prepared. In order to improve the detection accuracy of the inclination of the projection surface, the inspection patterns are arranged with the respective intervals as wide as possible. Then, the reticle 5 formed as described above is placed on the reticle stage 12.
Next, a reflecting mirror is mounted as the sample 4 on the sample table 14, and the exposure light 2 is emitted from the illumination optical system 11. And sample 4
The intensity of the exposure light 2 reflected by the portion of the exposure surface 4a of the reticle 5 onto which the inspection mask pattern is projected is monitored by each detection unit 151. At that time, the sample table 1
This is done while changing the height position of 4. Then, the height position of the exposure surface where the reflection intensity of the exposure light 2 is the strongest at each inspection location monitored above is set as the focal height at each inspection location. Then, the image plane is obtained from the respective focal heights and inspection points. Then, the inclination of the projection surface 5a of the reticle 5 is calculated from the shift of the image plane with respect to the plane. When the first detecting means 15 is configured to measure the focal height at four or more inspection points, the best image plane is obtained by using an approximation method such as the least square approximation method. Then, the inclination of the projection surface 5a of the reticle 5 is determined correspondingly.

The above-mentioned exposure apparatus 1 is constructed so that the image plane becomes horizontal with the reticle 5 arranged horizontally. Then, the correction means 17 causes the projection surface 5a of the reticle 5 to be projected.
And the exposure surface 4a of the sample 4 are parallel to each other. Therefore, when the reticle 5 is placed on the reticle stage 12 in a tilted state, the exposure surface 4 of the sample 4 is
In the state in which a is corrected, the exposure surface 4a is in a state of being coincident with the image plane.

Next, an exposure method using the exposure apparatus 3 will be described with reference to the flow charts shown in FIGS. 1 and 2. A wafer is used as the sample 4 to be exposed. First, step 1 in the first step (S201)
Then, the reticle 5 is arranged on the reticle stage 12 as a reticle load. The reticle 5 used here has a mask pattern for exposure and a mask pattern for inspection formed at four corners. And step 2
In (S202), the inclination of the projection surface 5a of the reticle 5 placed on the reticle stage 12 with respect to the horizontal plane is detected by the first detection means 15 as described above.

Further, step 3 in the second process (S20
In 3), the wafer to be exposed as the wafer load is placed on the sample table 14 as the sample 4. And step 4
In (S204), alignment of the exposure position of the wafer is performed. Here, for example, several positions on the exposure surface of the wafer are sampled and alignment is performed at the plurality of exposure positions.

Next, as a third step, step 5 (S
In 205), the first detection means 15 detects the tilt of the exposure surface 4a of the wafer at the exposure position.

Then, as a fourth step, step 6 (S
In 206), the exposure surface 4a is adjusted to the projection surface 5 of the reticle 5 by adjusting the inclination of the sample table 14 by the correction means 17.
The exposure surface 4a is corrected so as to be parallel to a. Exposure surface 4
The correction of a is performed within the range of the focus height of exposure.

After that, as a fifth step, step 7 (S
207), the exposure light 2 is emitted from the illumination optical system 11 to the reticle 5.
The exposure surface of the wafer is exposed by the exposure light 2 that has passed through the reticle 5.

In the above-mentioned exposure method, the projection surface 5a of the reticle 5 is exposed in the exposure using the exposure apparatus 1 in which the image plane becomes horizontal while the reticle is horizontally arranged.
After the exposure surface is corrected so that the exposure surface 4a of the sample 4 and the exposure surface 4a of the sample 4 are parallel to each other, the exposure is performed. Therefore, the exposure is performed in a state in which the tilt of the exposure surface 4a of the wafer, which is the sample 4, is corrected so as to match the tilt of the imaging surface due to the reticle 5 being tilted and arranged on the reticle stage 12.

When performing the exposure so as to form a plurality of exposure shots on the exposure surface of one wafer, in the next step 8 (S208), the exposure position is moved to perform the same exposure. Determine whether or not. Then, if it is determined to be performed, the exposure position is moved in a step not shown here based on the information of the alignment performed in advance, and then the process returns to step 5 (S205) to return the exposure surface of the wafer at that position. Is detected, and the subsequent steps are repeated.
It However, when the wafer is aligned every time the exposure position is moved, the exposure position is moved in a step not shown here, and then the process returns to step 4 (S204) to perform the alignment, and the subsequent steps are repeated.

Further, in the exposure apparatus shown in the above embodiment,
The detection means is used which detects the image plane by obtaining the focal heights at a plurality of inspection points and thereby calculates the inclination of the projection plane of the reticle. However, the present invention is not limited to this, and for example, a method of directly calculating the inclination of the projection surface of the reticle by reflecting the measurement light on the projection surface of the reticle, as in the case of the detection unit that detects the inclination of the exposure surface 4a, is used. The detection means used may be used. Further, the calculation unit of the first detection means is
It can be incorporated in the control unit of the correction means.

[0029]

As described above, according to the exposure apparatus of the present invention, the tilt of the exposure surface of the sample can be corrected in consideration of the tilt of the projection surface of the reticle, so that the tilt of the projection surface of the reticle is corrected. This makes it possible to arrange the sample so that the exposure surface of the sample is aligned with the tilted imaging surface. Therefore, at the time of exposure, it becomes possible to secure the depth of focus on the exposure surface. Further, according to the above-mentioned exposure method, the exposure is performed after the inclination of the exposure surface of the sample is corrected with respect to the inclination of the reticle, so that the exposure in which the deviation between the image plane and the exposure surface is prevented can be performed. Therefore, the depth of focus can be secured on the exposure surface during exposure, and a resist pattern with high dimensional accuracy can be formed on the upper surface of the step shape in the manufacturing process of the semiconductor device. Therefore, the device structure can be miniaturized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exposure apparatus according to an embodiment.

FIG. 2 is a flowchart showing an exposure method of the embodiment.

FIG. 3 is a configuration diagram of a conventional exposure apparatus.

FIG. 4 is a flowchart showing a conventional exposure method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 exposure apparatus 2 exposure light 4 sample 4a exposure surface 5 reticle 5a projection surface 11 illumination optical system 12 reticle stage 14 sample stage 15 first detection means 16 second detection means

Claims (2)

[Claims] 1. A reticle stage holding a reticle, an illumination optical system for irradiating the reticle held on the reticle stage with exposure light, and a sample table for mounting a sample to be exposed by the exposure light passing through the reticle. A first detecting means for detecting an inclination of a projection surface of a reticle arranged on the reticle stage; a second detecting means for detecting an inclination of an exposure surface of a sample placed on the sample table; The inclination of the exposure surface with respect to the inclination of the projection surface is calculated from the inclination of the exposure surface and the inclination of the projection surface which are input from the first detection means and the second detection means. An exposure apparatus comprising: a correction unit that drives the sample stage to perform correction. 2. An exposure method using an exposure apparatus, wherein a reticle is arranged on a reticle stage of a projection exposure apparatus,
A first step of detecting the inclination of the projection surface of the reticle, a second step of arranging the sample on the sample stage of the projection exposure apparatus for alignment, and a third step of detecting the inclination of the exposure surface of the sample. And a fourth step of correcting the inclination of the exposure surface with respect to the inclination of the projection surface from the inclination of the exposure surface and the inclination of the projection surface, and irradiating the reticle with exposure light to expose the reticle. And a step of projecting a pattern formed on the reticle onto the exposure surface of the sample by the exposure light that has passed through the projection surface.