JP2003151888A - Alignment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alignment method that is effectively used in a projection aligner having a space optical modulator. SOLUTION: An exposure pattern is formed by a space optical modulator comprising a plurality of mirrors that can independently control the inclination of a reflecting surface. The exposure pattern is projected and exposed to an object for forming an irregular pattern in the object, and further other exposure patterns are projected and exposed to the object. At this time, light is projected to the irregular pattern of the object via a space optical modulator, and the alignment of the object is performed based on the detection result of the light image of the irregular pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment method performed, for example, when performing projection exposure.

[0002]

2. Description of the Related Art As a projection exposure apparatus for lithography, a DMD (digital mirror device: one of spatial light modulators) including a plurality of mirrors capable of independently controlling the tilt of a reflecting surface is provided, and a control computer is provided. A projection exposure apparatus is conceived in which the micromirrors are each controlled to rotate by the electrostatic solution action by, and a predetermined exposure pattern is carried on the DMD by this rotation control, and the predetermined pattern is projected onto the exposure target.

For example, when forming an integrated circuit pattern on a semiconductor substrate using this projection exposure apparatus, it is necessary to transfer different exposure patterns to the same object many times, and in that case, it is an object. Alignment of the semiconductor substrate is required each time.

[0004]

However, conventionally, there has been no effective alignment method for projection exposure having a spatial light modulator. Further, conventionally, there has been no effective autofocus method for projection exposure having a spatial light modulator.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide an alignment method effective for use in projection exposure having a spatial light modulator.

[0006]

According to one alignment apparatus of the present invention, an exposure pattern carried by a spatial light modulator including a plurality of mirrors capable of independently controlling the tilt of a reflecting surface is used as an object. Upon forming a concave-convex pattern on the target object by projection exposure and projecting and exposing another exposure pattern on the target object, light is projected on the concave-convex pattern of the target object through the spatial light modulator, The object may be aligned based on the detection result of the optical image of the concavo-convex pattern.

Further, another alignment apparatus of the present invention is
After forming an uneven pattern on the object by projecting and exposing one exposure pattern carried by a spatial light modulator including a plurality of mirrors that can independently control the inclination of the reflecting surface, another In projecting and exposing the exposure pattern of the object, the one exposure pattern carried by the spatial modulator is projected on the concave-convex pattern of the object,
The object may be aligned based on the detection result of the optical image of the concavo-convex pattern.

In these alignment methods, it is preferable to use the degree of deviation of the optical image from the reference position as the "optical image detection result". Furthermore, focusing may be performed in consideration of the "blur of the optical image". Also,
As the “spatial light modulator used for alignment”, the spatial light modulator used for the previous projection exposure and used for the next projection exposure is preferably used as it is. Further, when the light is projected onto the object through the spatial light modulator at the time of alignment or focusing by the one alignment method, it is not always necessary to use the entire spatial light modulator, and a part of the spatial light modulator is used. May be used. Further, the formation of the exposure pattern of the spatial light modulator is preferably performed by the control computer.

According to these alignment methods, when projection exposure is performed, light is projected onto an object through a spatial light modulator, the previous optical image of the concavo-convex pattern is detected, the deviation of the object is determined, and the deviation is obtained. Alignment will be performed according to the condition.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a projection exposure apparatus used in the alignment method of the embodiment. This projection exposure apparatus 100 is configured as follows.

In the figure, reference numeral 1 indicates a light source.
The light source 1 is not particularly limited, but a metal halide lamp, a halogen lamp, a xenon lamp, or the like is used. A reflector 2 is installed near the light source 1.
The reflector 2 has a function of reflecting the light from the light source 1 to convert it into focused light and directing it to a DMD (digital mirror device: spatial light modulator) 3 in the next stage. The focused light may be parallel light.

The parallel light from the reflector 2 is obliquely incident on the DMD 3. The DMD has a square or rectangular shape as a whole, and has a structure in which micromirrors are arranged in a matrix. The rotation of each micromirror is controlled by an electrostatic field effect by a control computer (not shown), and this rotation control allows the DMD 3 to carry a predetermined mirror pattern (exposure pattern).

In the figure, reference numeral 4 indicates an equal-magnification imaging telecentric optical system. This equal-magnification imaging telecentric optical system 4 has an optical axis parallel to the normal direction of the DMD 3. This equal-magnification imaging telecentric optical system 4 is a DMD.
The light reflected by 3 (reflected light) is collimated and applied to the surface to be inspected of the object 5.

The light source 1, the reflector 2, the DMD 3 and the equal-magnification image forming telecentric optical system 4 constitute a PC projector.

The object 5 is installed on the XYθ stage 10 (FIG. 2). The stage 10 is arranged in a plane orthogonal to the optical axis of the equal-magnification telecentric optical system 4.
The object 10 can be moved or rotated in two orthogonal directions, or the object 10 can be moved in the optical axis direction of the equal-magnification imaging telecentric optical system 4.

A half mirror 6 is provided between the DMD 3 and the equal-magnification imaging telecentric optical system 4. The half mirror 6 transmits the light from the DMD 3 toward the equal-magnification imaging telecentric optical system 4 and reflects the light from the equal-magnification imaging telecentric optical system 4 toward the detection unit 7. .

The detecting section 7 is composed of a photodiode. By this photodiode, the reflected light on the surface to be inspected is received via the equal-magnification imaging telecentric optical system 4 and the half mirror 6. In addition,
The detection unit 7 may be composed of CMOS instead of the photodiode.

Next, a control system of the projection exposure apparatus 100 of the embodiment will be described. FIG. 2 shows the configuration of the control system.

The control system is a control computer 21.
It is configured to include. The control computer 21 includes a light source 1, a DMD 3, a detection unit 7, a stage 10 and a display unit 2.
2 are connected via a driver or the like (not shown) so that data from them can be processed and their control can be performed based on the processing result of a predetermined program or data.

Here, the processing of the data from the detection unit 7 will be described. The optical image received by the detection unit 7 is converted into electrical data and sent to the control computer 21. In this case, the detection unit 7 receives the optical image by operating the stage 10 by the control computer 21 so that the object 5 is orthogonal to the surface in the plane orthogonal to the optical axis of the equal-magnification telecentric optical system 4. To move in two directions,
It is rotated, and several times in the meantime. Alignment is performed by processing the electrical data thus obtained.

The principle of alignment of this embodiment will be described. Now, when the concavo-convex pattern shown in FIG. 3 (the bright portion is a concave portion) is formed on the surface to be inspected of the object 5, when the object 5 moves in the XY direction, the bright portion also moves in the XY direction. Moving. This means that if the reference position in the XY directions is set and the amount of deviation of the bright part from the reference position is determined, the object 5
It means that it is possible to obtain the positional shift amount in the XY directions. The reference position in the XY directions in this case is uniquely determined from the previous exposure pattern (mirror pattern).
That is, it is possible to know which portion will be the concave portion or the convex portion when the previous exposure pattern is projected, and therefore, that portion can be set as the reference position. By the same method, the amount of positional deviation in the XY directions can be easily obtained.

The principle of focusing according to the present embodiment will be described. When the position of the object 5 is moved in the optical axis (Z) direction of the equal-magnification telecentric optical system 4, the optical image becomes fine and clear. It becomes thick or blurry. In this case, the target object 5 is aligned with the part where the light image is thin and clear (the part where there is focus). Whether or not the image is in focus is determined by calculating the width of the light image and comparing the widths.

This alignment method will be described by taking the case of forming a semiconductor integrated circuit pattern as an example.

When an insulating film is formed on a semiconductor substrate on which an impurity layer is formed and then a wiring contacting the impurity layer is formed on the insulating film, a photoresist (a positive resist is not particularly limited) is formed on the insulating film. And pre-bake and post-bake the photoresist. After that, the photoresist is projected and exposed (first projection exposure) with ultraviolet rays (light) having a hole pattern (exposure pattern) and developed. As a result, a hole is formed in a predetermined portion of the insulating film.
Then, the photoresist is stripped off and a wiring material is deposited on the entire surface. As a result, the wiring material contacts the impurity layer. Next, the wiring material is patterned. In this patterning, a photoresist (not specifically limited, a positive resist) is applied again, and the photoresist is pre-baked and post-baked. Thereafter, projection exposure (second projection exposure) is performed on the photoresist with ultraviolet rays (light) having a wiring pattern (exposure pattern), and development is performed.
Then, using the photoresist as a mask, the wiring material is etched and patterned.

In this case, it is necessary to align the semiconductor substrate during the second projection exposure. When performing the alignment, for example, the exposure pattern used during the first projection exposure is used. That is, after the semiconductor substrate is aligned to some extent, the DMD 3 projects the first exposure pattern onto the semiconductor substrate. Then, the reflected light (optical image) is detected by the detection unit 7. In this case, since the photoresist portion corresponding to the hole portion of the insulating film formed by the first exposure pattern is a concave portion following the insulating film, when the concave portion is exposed to light, the edge portion of the concave portion The light intensity of the light becomes weak due to scattering and becomes a dark portion, while the light intensity at the bottom of the recess becomes strong and becomes a bright portion. Therefore, it is possible to determine how much the boundary between the dark part and the bright part is displaced from the reference position.

It is also possible to detect the positional deviation by forming a special concave-convex pattern serving as an index and detecting it without using the circuit pattern.

It is preferable that the focus adjustment is performed before the position adjustment. This is because alignment is easier when the subject is in focus.

Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to such embodiments and various modifications can be made without departing from the scope of the invention.

For example, in the above embodiment, the half mirror 6 is provided between the DMD 3 and the equal-magnification imaging telecentric optical system 4, but it is provided between the equal-magnification imaging telecentric optical system 4 and the object 5. Good.

Although the previous exposure pattern is projected on the concave-convex pattern of the object, light having no pattern may be projected on the concave-convex pattern. Since the previous exposure pattern and the concavo-convex pattern have a one-to-one correspondence, if the previous exposure pattern is known, the concavo-convex pattern when the object is in the normal position, and thus the bright-dark pattern can be predicted. Therefore, it is possible to obtain the amount of deviation from the actual light-dark pattern based on the predicted light-dark pattern and perform alignment based on this amount of deviation.

[0031]

The effects of the typical ones of the present invention will be described. An exposure pattern carried by a spatial light modulator including a plurality of mirrors capable of independently controlling the inclination of a reflecting surface is used as an object. Upon projection-exposing another exposure pattern on the object after forming a concave-convex pattern on the object by projection exposure, projecting light through the spatial light modulator on the concave-convex pattern of the object, Since the alignment of the target object is performed based on the detection result of the optical image of the concavo-convex pattern, the alignment can be easily performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of a projection exposure apparatus used in an alignment method according to a first embodiment.

FIG. 2 is a diagram for explaining a control system of a projection exposure apparatus used in the alignment method of the first embodiment.

FIG. 3 is a diagram for explaining the alignment method of the first embodiment.

[Explanation of symbols]

1 light source 2 reflector 3 DMD 4x magnification telecentric optical system 5 objects 6 half mirror 7 Detector

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazumi Haga             37-share, 33-53, 3-chome, Kakusen, Komae-shi, Tokyo             Ceremony company New Creation F term (reference) 2F065 AA03 AA50 FF04 GG03 HH03                       HH07 JJ18 LL00 LL12 LL59                       MM03 MM04 PP12 SS02                 2H097 AA12 GB00 KA03                 5F046 CB02 DB05 FA10 FB10 FC03                       FC04

Claims (4)

[Claims] 1. An unevenness pattern is formed on an object by projecting and exposing an exposure pattern carried by a spatial light modulator including a plurality of mirrors capable of independently controlling the inclination of a reflecting surface. After projection exposure of the other exposure pattern to the target object, after projecting light through the spatial light modulator to the concave-convex pattern of the target object, based on the detection result of the optical image of the concave-convex pattern, An alignment method, wherein the object is aligned. 2. An exposure pattern carried by a spatial light modulator including a plurality of mirrors capable of independently controlling the tilt of a reflecting surface is projected onto a target object to expose a concave-convex pattern on the target object. Upon projecting and exposing another exposure pattern onto the object after formation, the one exposure pattern carried by the spatial modulator is projected onto the uneven pattern of the object, and an optical image of the uneven pattern is formed. An alignment method characterized in that the object is aligned based on a detection result. 3. The alignment method according to claim 1, wherein the alignment is performed by detecting the positional deviation of the concavo-convex pattern. 4. The alignment method according to claim 3, wherein the degree of blurring of the optical image of the concavo-convex pattern is detected and the object is moved in a direction in which the blurring is eliminated. .