CN113448192B

CN113448192B - Alignment system and photoetching machine

Info

Publication number: CN113448192B
Application number: CN202010225236.0A
Authority: CN
Inventors: 高安
Original assignee: Shanghai Micro Electronics Equipment Co Ltd
Current assignee: Shanghai Micro Electronics Equipment Co Ltd
Priority date: 2020-03-26
Filing date: 2020-03-26
Publication date: 2022-08-30
Anticipated expiration: 2040-03-26
Also published as: CN113448192A

Abstract

The embodiment of the invention provides an alignment system and a photoetching machine, wherein the alignment system comprises: an alignment beam generating unit for generating an alignment beam; the polarization beam splitting unit is positioned on an emergent light path of the alignment light beam generating unit and is used for splitting the alignment light beam into a first light beam and a second light beam which have mutually vertical polarization directions and different transmission directions; an alignment mark imaging unit located on a propagation path of the first light beam, the alignment mark imaging unit including an alignment mark; the alignment mark imaging unit is used for converting the first light beam projected onto the alignment mark into a first diffracted light beam and projecting the first diffracted light beam to the polarization splitting unit; the reference mark imaging unit is positioned on the propagation path of the second light beam and comprises a spatial light modulator, and the spatial light modulator is formed with a periodic structure; an interference information detection unit. The embodiment of the invention provides an alignment system and a photoetching machine, which are compatible with different alignment marks and reduce the cost of the alignment system.

Description

Alignment system and photoetching machine

Technical Field

The present invention relates to lithography, and more particularly, to an alignment system and a lithography machine.

Background

Lithographic projection apparatus can be used, for example, in the manufacture of Integrated Circuits (ICs). A critical step in the lithographic process is to align the substrate with the lithographic apparatus so that the projected image of the mask pattern is in the correct position on the substrate. Semiconductor and other devices due to photolithography require multiple exposures to form multiple layers in the device, and it is important that the layers be properly aligned. As smaller features are imaged, the requirements for overlap and, consequently, the accuracy of the alignment operation become more stringent.

In an alignment system using a reference grating, a new corresponding reference grating is often required for changing the diffraction order, grating direction, and the like of an alignment mark, thereby increasing the cost of the alignment system.

Disclosure of Invention

The embodiment of the invention provides an alignment system and a photoetching machine, which are compatible with different alignment marks and reduce the cost of the alignment system.

In a first aspect, an embodiment of the present invention provides an alignment system, including:

an alignment beam generating unit for generating an alignment beam;

the polarization light splitting unit is positioned on an emergent light path of the alignment light beam generating unit and is used for splitting the alignment light beam into a first light beam and a second light beam which have mutually vertical polarization directions and different propagation directions;

an alignment mark imaging unit located on a propagation path of the first light beam, the alignment mark imaging unit including an alignment mark; the alignment mark imaging unit is used for converting the first light beam projected onto the alignment mark into a first diffracted light beam and projecting the first diffracted light beam to the polarization splitting unit;

a reference mark imaging unit located on a propagation path of the second light beam, the reference mark imaging unit including a spatial light modulator formed with a periodic structure; the reference mark imaging unit is used for converting the second light beam projected onto the spatial light modulator into a second diffracted light beam and projecting the second diffracted light beam to the polarization splitting unit;

and an interference information detection unit, located on the propagation paths of the first diffracted beam and the second diffracted beam, located downstream of the optical path of the polarization splitting unit, and configured to detect interference light intensities of positive-order diffracted light and negative-order diffracted light in the first diffracted beam and the second diffracted beam.

Optionally, the alignment light beam generating unit and the alignment mark imaging unit are located on two opposite sides of the polarization beam splitting unit, and the reference mark imaging unit and the interference information detecting unit are located on two opposite sides of the polarization beam splitting unit; or,

the alignment light beam generating unit and the reference mark imaging unit are positioned on two opposite sides of the polarization beam splitting unit, and the alignment mark imaging unit and the interference information detecting unit are positioned on two opposite sides of the polarization beam splitting unit.

Optionally, the polarization splitting unit includes a first polarization splitting prism.

Optionally, the alignment mark imaging unit includes a first quarter wave plate and a first lens group, and the first lens group is located on a propagation path of the first light beam between the first quarter wave plate and the alignment mark.

Optionally, the reference mark imaging unit further comprises a second half wave plate and a second lens group, the second lens group being located on a propagation path of the second light beam between the second half wave plate and the spatial light modulator.

Optionally, a period of the periodic structure is the same as a grating period of the alignment mark.

Optionally, the alignment beam generated by the alignment beam generating unit includes 45 ° linearly polarized light or circularly polarized light.

Optionally, the interference information detection unit includes a half-wave plate, a second polarization splitting prism, a first detector and a second detector; the half-wave plate is located on a propagation path of the first diffracted light beam and the second diffracted light beam between the polarization splitting unit and the second polarization splitting prism, and the first detector and the second detector are located on a downstream of a light path of the second polarization splitting prism.

Optionally, the alignment beam generating unit includes a plurality of lasers and a light combiner, where the wavelengths of the laser beams emitted by any two of the lasers are different, and the light combiner is located on the emitting light paths of the plurality of lasers and is configured to combine the laser beams emitted by the plurality of lasers into one beam;

the interference information detection unit further comprises a first optical splitter and a second optical splitter, the first optical splitter is located on the first diffracted light beam and the second diffracted light beam propagation path between the first detector and the second polarization splitting prism, and the second optical splitter is located on the first diffracted light beam and the second diffracted light beam propagation path between the second detector and the second polarization splitting prism.

In a second aspect, an embodiment of the present invention provides a lithographic apparatus including the alignment system of the first aspect.

In the alignment system provided by the embodiment of the invention, the alignment mark imaging unit comprises the alignment mark, the reference mark imaging unit comprises the spatial light modulator, after the diffraction order, the grating direction and the like of the alignment mark are changed, the periodic structure on the spatial light modulator is correspondingly changed, but the same spatial light modulator is still used, and the replacement of a new spatial light modulator is not needed, so that different alignment marks are compatible, and the cost of the alignment system is reduced.

Drawings

Fig. 1 is a schematic structural diagram of an alignment system according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of another alignment system provided in an embodiment of the present invention;

fig. 3 is a schematic structural diagram of another alignment system according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

Fig. 1 is a schematic structural diagram of an alignment system according to an embodiment of the present invention, and referring to fig. 1, the alignment system includes an alignment beam generating unit 1, a polarization splitting unit 2, an alignment mark imaging unit 3, a reference mark imaging unit 4, and an interference information detecting unit 5. The alignment beam generating unit 1 is for generating an alignment beam. The polarization splitting unit 2 is located on the outgoing light path of the alignment beam generating unit 1, and is configured to split the alignment beam into a first light beam 101 and a second light beam 102, which have polarization directions perpendicular to each other and different propagation directions. The alignment mark imaging unit 3 is located on a propagation path of the first light beam 101, the alignment mark imaging unit 3 includes an alignment mark 31, and the alignment mark imaging unit 3 is configured to convert the first light beam 101 projected onto the alignment mark 31 into a first diffracted light beam 301 and project the first diffracted light beam 301 to the polarization splitting unit 2. Wherein the alignment marks 31 comprise diffraction gratings. The first diffracted beam 301 includes positive order diffracted light and negative order diffracted light. The reference mark imaging unit 4 is located on a propagation path of the second light beam 102, the reference mark imaging unit 4 includes a spatial light modulator 41, the spatial light modulator 41 is formed with a periodic structure, and the reference mark imaging unit 4 is configured to convert the second light beam 102 projected onto the spatial light modulator 41 into a second diffracted light beam 401, and project the second diffracted light beam 401 to the polarization splitting unit 2. The spatial light modulator 41 may be, for example, a reflective spatial light modulator, and the periodic structure formed by the spatial light modulator 41 may be an image displayed by an array of light modulation units in the spatial light modulator. Second diffracted beam 401 includes positive order diffracted light and negative order diffracted light. The interference information detection unit 5 is located on the propagation paths of the first diffracted beam 301 and the second diffracted beam 401, located downstream of the polarization beam splitting unit 2, and is used for detecting the interference light intensity of the positive-order diffracted light and the negative-order diffracted light in the first diffracted beam 301 and the second diffracted beam 401.

In the alignment system provided by the embodiment of the invention, the alignment mark imaging unit comprises the alignment mark, the reference mark imaging unit comprises the spatial light modulator, after the diffraction order, the grating direction and the like of the alignment mark are changed, the periodic structure on the spatial light modulator is correspondingly changed, but the same spatial light modulator is still used without replacing a new spatial light modulator, so that different alignment marks are compatible, and the cost of the alignment system is reduced.

Alternatively, referring to fig. 1, the alignment beam generating unit 1 and the alignment mark imaging unit 3 are located on opposite sides of the polarization beam splitting unit 2, and the reference mark imaging unit 4 and the interference information detecting unit 5 are located on opposite sides of the polarization beam splitting unit 2. The part of the alignment beam generated by the alignment beam generating unit 1 that passes through the polarization splitting unit 2 is a first beam 101, and the first beam 101 is projected to the alignment mark imaging unit 3. The part of the alignment beam generated by the alignment beam generating unit 1 reflected by the polarization splitting unit 2 is a second beam 102, and the second beam 102 is projected to the reference mark imaging unit 4.

Fig. 2 is a schematic structural diagram of another alignment system according to an embodiment of the present invention, and referring to fig. 2, the alignment beam generating unit 1 and the reference mark imaging unit 4 are located on two opposite sides of the polarization beam splitting unit 2, and the alignment mark imaging unit 3 and the interference information detecting unit 5 are located on two opposite sides of the polarization beam splitting unit 2.

The part of the alignment beam generated by the alignment beam generating unit 1 that passes through the polarization splitting unit 2 is a second beam 102, and the second beam 102 is projected to the reference mark imaging unit 4. The portion of the alignment beam generated by the alignment beam generating unit 1 reflected by the polarization splitting unit 2 is a first beam 101, and the first beam 101 is projected to the alignment mark imaging unit 3.

Alternatively, referring to fig. 1, the polarization splitting unit 1 includes a first polarization splitting prism.

Exemplarily, referring to fig. 1, the first light beam 101 is a light beam transmitted through the first polarization splitting prism, and the first light beam 101 is linearly polarized light of P polarization. The P-polarized linearly polarized light refers to linearly polarized light having a polarization direction within the incident plane and a polarization direction perpendicular to the propagation direction of the light. The second light beam 102 is reflected by the first polarization splitting prism, the second light beam 102 is S-polarized linearly polarized light, and the S-polarized linearly polarized light refers to linearly polarized light with a polarization direction perpendicular to the incident plane.

Alternatively, referring to fig. 1, the alignment mark imaging unit 3 includes a first quarter wave plate 33 and a first lens group 32, and the first lens group 32 is located on a propagation path of the first light beam 101 between the first quarter wave plate 33 and the alignment mark 31.

Exemplarily, referring to fig. 1, the first lens group 32 is located between the first quarter-wave plate 33 and the alignment mark 31.

Alternatively, referring to fig. 1, the reference mark imaging unit 4 further includes a second half wave plate 43 and a second lens group 42, and the second lens group 42 is located on the propagation path of the second light beam 102 between the second half wave plate 43 and the spatial light modulator 41.

Exemplarily, referring to fig. 1, the second lens group 42 is located between the second half wave plate 43 and the spatial light modulator 41.

Alternatively, referring to fig. 1, the period of the periodic structure of the spatial light modulator 41 is the same as the grating period of the alignment mark 31. The periodic structure of the spatial light modulator 41 generates diffracted light of the same angle as the alignment mark 31.

Illustratively, referring to FIG. 1, the +1 st order diffracted light and the-1 st order diffracted light in the second diffracted beam 401 generated by the periodic structure of the spatial light modulator 41 have the same angle as the +1 st order diffracted light and the-1 st order diffracted light in the first diffracted beam 301 generated by the alignment mark 31.

Alternatively, referring to fig. 1, the alignment beam generated by the alignment beam generating unit 1 includes 45 ° linearly polarized light. The 45 ° linearly polarized light corresponds to light obtained by combining S-polarized linearly polarized light and P-polarized linearly polarized light.

Exemplarily, referring to fig. 1, the alignment beam generated by the alignment beam generating unit 1 includes 45 ° linearly polarized light, a P-polarized linearly polarized light component of the 45 ° linearly polarized light is transmitted through the first polarization splitting prism, and an S-polarized linearly polarized light component of the 45 ° linearly polarized light is reflected by the first polarization splitting prism.

In other embodiments, the alignment beam generated by the alignment beam generating unit 1 may also include circularly polarized light. The circularly polarized light corresponds to light obtained by combining S-polarized linearly polarized light and P-polarized linearly polarized light, and the S-polarized linearly polarized light and the P-polarized linearly polarized light have a certain phase difference.

Alternatively, referring to fig. 1, the interference information detecting unit 5 includes a half-wave plate 51, a second polarization splitting prism 52, a first detector 531, and a second detector 532. The half-wave plate 51 is located on the propagation paths of the first diffracted beam 301 and the second diffracted beam 401 between the polarization splitting unit 2 and the second polarization splitting prism 52, and the first detector 531 and the second detector 532 are located downstream of the optical path of the second polarization splitting prism 52.

Exemplarily, referring to fig. 1, the half-wave plate 51 is located between the first polarization splitting prism and the second polarization splitting prism 52, the first detector 531 and the second detector 532 are respectively located at two adjacent sides of the second polarization splitting prism, the first detector 531 is configured to receive interference light intensity generated by S-polarized linearly polarized light in the first diffracted light beam 301 and the second diffracted light beam 401, and the second detector 532 is configured to receive interference light intensity generated by P-polarized linearly polarized light in the first diffracted light beam 301 and the second diffracted light beam 401.

For ease of understanding, the working principle of the alignment system shown in fig. 1 is briefly described in the embodiment of the present invention, but the present invention is not limited thereto.

The alignment beam generation unit 1 generates 45 ° linearly polarized light, a P-polarized linearly polarized light component (i.e., the first light beam 101) of the 45 ° linearly polarized light transmits through the polarization splitting unit 2, passes through the first quarter-wave plate 33 and the first lens group 32, irradiates onto the alignment mark 31, and is diffracted at the alignment mark 31 to generate a first diffracted light beam 301 (including positive-order diffracted light and negative-order diffracted light), the first diffracted light beam 301 passes through the first lens group 32 and the first quarter-wave plate 33 again and becomes S-polarized linearly polarized light, and the S-polarized linearly polarized light is reflected by the polarization splitting unit 2 to the interference information detection unit 5. The S-polarized linearly polarized light component (i.e., the second light beam 102) in the 45 ° linearly polarized light is reflected by the polarization beam splitting unit 2, passes through the second quarter-wave plate 43 and the second lens group 42, is irradiated onto the periodic structure of the spatial light modulator 41, is diffracted at the spatial light modulator 41 to generate a second diffracted light beam 401 (including positive-order diffracted light and negative-order diffracted light), the second diffracted light beam 401 passes through the second lens group 42 and the second quarter-wave plate 43 again and is changed into P-polarized linearly polarized light, and the P-polarized linearly polarized light passes through the polarization beam splitting unit 2 to the interference information detection unit 5. Among the light beams projected to the interference information detection unit 5, the positive order diffracted light in the first diffracted light beam 301 and the negative order diffracted light in the second diffracted light beam 401 have the same propagation path, and the negative order diffracted light in the first diffracted light beam 301 and the positive order diffracted light in the second diffracted light beam 401 have the same propagation path. Illustratively, of the light beams projected to the interference information detection unit 5, the + n-th order diffracted light in the first diffracted light beam 301 has the same propagation path as the-n-th order diffracted light in the second diffracted light beam 401, the-n-th order diffracted light in the first diffracted light beam 301 has the same propagation path as the + n-th order diffracted light in the second diffracted light beam 401, and n is a positive integer. After the process, the positive and negative diffraction orders propagate along the same optical path, and finally the positive and negative diffraction orders with the same polarization interfere.

Fig. 3 is a schematic structural diagram of another alignment system according to an embodiment of the present invention, and referring to fig. 3, an alignment beam generating unit 1 includes a plurality of lasers 101 and a light combiner 15, where any two of the lasers 101 emit laser beams with different wavelengths, and the light combiner 15 is located on an outgoing light path of the plurality of lasers 101 and is configured to combine the laser beams emitted by the plurality of lasers 101 into one beam. The interference information detection unit 5 further includes a first optical splitter 541 and a second optical splitter 542, the first optical splitter 541 is located on propagation paths of the first diffracted light beam 301 and the second diffracted light beam 401 between the first detector 531 and the second polarization splitting prism 52, and the first optical splitter 541 is configured to split one incident light beam into multiple light beams according to wavelengths and emit the multiple light beams to the first detector 531. The second optical splitter 542 is located on the propagation path of the first diffracted light beam 301 and the second diffracted light beam 401 between the second detector 532 and the second polarization splitting prism 52. The second optical splitter 542 is configured to split a beam of incident light into multiple beams of light according to wavelength and emit the multiple beams of light to the second detector 532.

Exemplarily, referring to fig. 3, the alignment beam generating unit 1 includes a first laser 11, a second laser 12, a third laser 13, and a fourth laser 14. The laser beam emitted by the first laser 11 is a 45-degree linearly polarized light with a first wavelength, the laser beam emitted by the second laser 12 is a 45-degree linearly polarized light with a second wavelength, the laser beam emitted by the third laser 13 is a 45-degree linearly polarized light with a third wavelength, and the laser beam emitted by the fourth laser 14 is a 45-degree linearly polarized light with a fourth wavelength. The first detector 531 and the second detector 532 may be four-channel detectors that detect optical signals of four wavelengths, respectively.

The embodiment of the invention also provides a photoetching machine which comprises the alignment system in the embodiment. The lithography machine may further include an exposure system, a mask stage system, an illumination system, etc., which are not described in detail herein. Because the photoetching machine provided by the embodiment of the invention comprises the alignment system in the embodiment, the compatibility of photoetching to different alignment marks is increased, and the manufacturing cost of the photoetching machine is reduced.

It is to be noted that the foregoing description is only exemplary of the invention and that the principles of the technology may be employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An alignment system, comprising:

an alignment beam generating unit for generating an alignment beam;

2. The alignment system according to claim 1, wherein the alignment beam generating unit and the alignment mark imaging unit are located on opposite sides of the polarization beam splitting unit, and the reference mark imaging unit and the interference information detecting unit are located on opposite sides of the polarization beam splitting unit; or,

the alignment light beam generating unit and the reference mark imaging unit are located on two opposite sides of the polarization light splitting unit, and the alignment mark imaging unit and the interference information detection unit are located on two opposite sides of the polarization light splitting unit.

3. The alignment system of claim 1, wherein the polarization splitting unit comprises a first polarization splitting prism.

4. The alignment system of claim 1, wherein the alignment mark imaging unit comprises a first quarter wave plate and a first lens group, the first lens group being located on a propagation path of the first light beam between the first quarter wave plate and the alignment mark.

5. The alignment system of claim 1, wherein the reference mark imaging unit further comprises a second half-wave plate and a second lens group, the second lens group being located on a propagation path of the second light beam between the second half-wave plate and the spatial light modulator.

6. The alignment system of claim 1, wherein a period of the periodic structure is the same as a grating period of the alignment mark.

7. The alignment system of claim 1, wherein the alignment beam generated by the alignment beam generation unit comprises 45 ° linearly polarized light or circularly polarized light.

8. The alignment system of claim 1, wherein the interference information detection unit comprises a half-wave plate, a second polarization splitting prism, a first detector and a second detector; the half-wave plate is located on a propagation path of the first diffracted light beam and the second diffracted light beam between the polarization splitting unit and the second polarization splitting prism, and the first detector and the second detector are located on a downstream of a light path of the second polarization splitting prism.

9. The alignment system of claim 8, wherein the alignment beam generating unit comprises a plurality of lasers and a light combiner, the wavelengths of the laser beams emitted by any two of the lasers are different, and the light combiner is located on the emitting light paths of the plurality of lasers and is used for combining the laser beams emitted by the plurality of lasers into one beam;

the interference information detection unit further comprises a first optical splitter and a second optical splitter, wherein the first optical splitter is located on the first diffracted light beam and the second diffracted light beam propagation path between the first detector and the second polarization splitting prism, and the second optical splitter is located on the first diffracted light beam and the second diffracted light beam propagation path between the second detector and the second polarization splitting prism.

10. A lithography machine comprising an alignment system according to any one of claims 1 to 9.