Focusing and leveling device, photolithography system and method for measuring defocus amount

Abstract

The present invention provides a focusing and leveling device, a photolithography system, and a method for measuring defocus, wherein the detection light spot provided by the illumination unit is projected onto a surface to be measured by the projection unit, and is reflected by the surface to be measured to form a reflection light spot and projected to the detection unit. The detection slit includes a light-transmitting area and a reflection area. The reflection light spot forms a first light spot through the light-transmitting area, and the first detector obtains the power of the first light spot; the reflection light spot forms a second light spot through the reflection area, and the second detector obtains the power of the second light spot. The data processing unit calculates the defocus of the surface to be measured according to the power of the first light spot and the power of the second light spot. Therefore, the present invention sets a light-transmitting area and a reflection area to respectively obtain the power of the first light spot and the second light spot, and then calculates the defocus, avoids swinging the scanning reflector, reduces noise interference, and improves the signal-to-noise ratio of the detection signal and the measurement accuracy of the defocus.

Claims

1. A focusing and leveling device, characterized in that: The focusing and leveling device comprises: an illumination unit, a projection unit, a detection unit and a data processing unit; wherein, The illumination unit is used to provide a detection light spot; The projection unit is used to project the detection light spot onto a surface to be tested, and the detection light spot is reflected by the surface to be tested to form a reflection light spot and projected to the detection unit; The detection unit includes a detection slit, a first detector and a second detector; the detection slit includes a light-transmitting area and a reflection area; the reflected light spot forms a first light spot through the light-transmitting area, and the first light spot is transmitted to the first detector; and the reflected light spot forms a second light spot through the reflection area, and the second light spot is transmitted to the second detector; the first detector obtains the power of the first light spot, and the second detector obtains the power of the second light spot; The data processing unit obtains the defocus amount of the surface to be measured according to the power of the first light spot and the power of the second light spot.

2. The focusing and leveling device according to claim 1, characterized in that: The area of ​​the light-transmitting region is equal to the area of ​​the reflective region.

3. The focusing and leveling device according to claim 1, characterized in that: The detection slit includes a plurality of sub-detection slits arranged in an array; wherein the relationship between the size of the sub-detection slits and the size of the reflected light spot is as follows: a2<a1 / 2, and b2≤b1; a1 is the length of the sub-detection slit in the first direction; b1 is the length of the sub-detection slit in the second direction; a2 is the length of the reflected light spot in the first direction; b2 is the length of the reflected light spot in the second direction; and the first direction is perpendicular to the second direction.

4. The focusing and leveling device according to claim 1, characterized in that: The illumination unit includes a light emitter, a coupling lens group, a filter, a collimating lens group, a first aperture, a first reflector and a projection slit; wherein, The light emitter is used to provide illumination, and the illumination sequentially passes through the coupling lens group, the filter, the collimating lens group, the first aperture, the first reflector and the projection slit, and forms the detection light spot through the effect of the projection slit; The coupling mirror group and the filter are used to modulate and select the wavelength band of the illumination; The collimating lens group is used to adjust the collimation of the illumination; The first aperture is used to filter the light outside the projection slit field of view; The first reflector is used to reflect the light passing through the first aperture to the projection slit; The projection slit is used to transform the light into the detection light spot.

5. The focusing and leveling device according to claim 4, characterized in that: The projection slit is located at the object plane position of the projection unit.

6. The focusing and leveling device according to claim 4, characterized in that: The position of the projection slit satisfies the following condition: tanω=mtanδ; wherein, ω is the incident angle of the detection light spot onto the surface to be measured; m is the magnification of the projection unit; δ is the emission angle of the detection light spot from the projection slit.

7. The focusing and leveling device according to claim 1, characterized in that: The position of the detection slit satisfies the following condition: tanξ=m1tanω1; wherein, ξ is the incident angle of the reflected light spot incident on the detection slit; m1 is the magnification of the detection unit; ω1 is the incident angle of the detection light spot onto the surface to be measured.

8. The focusing and leveling device according to claim 1, characterized in that: The projection unit includes a first lens, a second reflector and a second lens; the detection light spot is converged by the first lens and transmitted to the second reflector, after the propagation direction is changed by the second reflector, it is propagated to the second lens, converged by the second lens and projected onto the surface to be measured.

9. The focusing and leveling device according to claim 1, characterized in that: The detection unit also includes a third lens, a second aperture and a fourth lens; the third lens receives the reflected light spot and converges the reflected light spot to the second aperture, the second aperture limits the light beam size of the reflected light spot, and the reflected light spot propagates to the fourth lens after passing through the second aperture, and is imaged on the detection slit through the fourth lens.

10. The focusing and leveling device according to claim 1, characterized in that: The projection unit includes a third reflector, a first concave mirror, a second concave mirror, a first convex mirror and a fourth reflector; the detection light spot is sequentially projected onto the surface to be measured via the third reflector, the first concave mirror, the first convex mirror, the second concave mirror and the fourth reflector; wherein the third reflector and the fourth reflector are used to change the propagation direction of the detection light spot, the first concave mirror and the second concave mirror are used to reflect and converge the detection light spot, and the first convex mirror is used to convert the detection light spot converged by the first concave mirror into the divergent detection light spot and transmit it to the second concave mirror.

11. The focusing and leveling device according to claim 10, characterized in that: The detection unit also includes a fifth reflector, a third concave mirror, a fourth concave mirror, a second convex mirror and a sixth reflector; the reflected light spot is imaged onto the detection slit via the fifth reflector, the third concave mirror, the second convex mirror, the fourth concave mirror and the sixth reflector in sequence; wherein the fifth reflector and the sixth reflector are used to change the propagation direction of the reflected light spot, the third concave mirror and the fourth concave mirror are used to reflect and converge the reflected light spot, and the second convex mirror is used to convert the reflected light spot converged by the third concave mirror into a divergent reflected light spot and transmit it to the fourth concave mirror.

12. The focusing and leveling device according to claim 1, characterized in that: The defocus amount is calculated using the following formula: in, △Z is the defocus amount; D is the length of the detection slit in the first direction; M is the detection unit magnification; ω is the incident angle of the detection light spot onto the surface to be measured; A is the power of the first light spot; B is the power of the second light spot.

13. A photolithography system, characterized in that: The lithography system includes an objective lens and a focusing and leveling device as described in any one of claims 1 to 11; the focusing and leveling device is used to measure the defocus amount between the silicon wafer and the objective lens.

14. A method for measuring defocus, characterized in that: Using the lithography system as claimed in claim 13, the method for measuring the defocus amount comprises: The illumination unit provides a detection light spot; The detection light spot is incident on the silicon wafer through the projection unit, and is reflected by the silicon wafer. The detection light spot is reflected on the detection slit, and passes through the light-transmitting area and the reflection area on the detection slit to form the first light spot and the second light spot respectively; The first detector acquires the power of the first light spot, and the second detector acquires the power of the second light spot; The data processing unit calculates the defocus amount of the silicon wafer relative to the objective lens according to the power of the first light spot and the power of the second light spot.

15. The method for measuring defocus amount according to claim 14, wherein: The defocus amount is calculated using the following formula: in, △Z is the defocus amount; D is the length of the detection slit in the first direction; M is the detection unit magnification; ω is the incident angle of the detection light spot incident on the silicon wafer; A is the power of the first light spot; B is the power of the second light spot.

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