Method and apparatus for determination of source polarization matrix
A method and apparatus for resolving both the angular (nx,ny) and spatial (x,y) dependence of the effective source coherence matrix for lithographic steppers and scanners is described. First an in-situ source metrology instrument is combined with in-situ polarization elements to create an in-situ source imaging polarizer or ISIP. The ISIP is loaded into a photolithographic exposure tool, aligned, and then exposed onto a suitable recording media or recording sensor. The recording sensor comprising either resist coated wafers or electronic sensors capture the image intensity at a multiplicity of different field points. The resulting measurements are entered into a computer program that reconstructs the source coherence matrix as a function of direction cosine at multiple field points. Alternative ISIP configurations are discussed in some detail. Applications of the ISIP include polarization source mapping for deep-UV and EUV lithography, process optimization, process monitoring, and chip manufacturing.
1. A method of determining a polarization state of a source in a projection imaging system, the method comprising:
exposing at least one in-situ polarizing element group onto a recording media with a source of unknown polarization, the in-situ polarizing element group being attached to a reticle and the in-situ polarizing element group comprising at least one polarizing element and at least one infinity imaged in-situ source metrology instrument;
measuring an intensity at subcomponents within the exposed polarizing element group, wherein light from the source passes through projection imaging optics with unknown transmission profile before the measuring; and
reconstructing a two dimensional angular (nx,ny) dependent polarization matrix of the source based upon the intensity measurements.
2. A method as defined in claim 1 , wherein the at least one in-situ polarization element group is included in an in-situ source imaging polarizer.
3. A method of claim 2 , wherein the in-situ source imaging polarizer further comprises the reticle.
4. A method as defined in claim 2 , wherein the in-situ source imaging polarizer further comprises the in-situ source metrology instrument.
5. A method as defined in claim 1 , wherein the recording media is located on a substrate.
6. A method as defined in claim 1 , wherein the recording media comprises an electronic sensor.
7. An apparatus for determining a previously unknown state of polarization of a projection imaging tool, the apparatus comprising:
an in-situ polarizing element group, the in-situ polarizing element group being attached to a reticle, the reticle comprising a first surface and a second surface, the second surface being disposed above the first surface, and the first surface comprising a chrome coating with at least one opening in the chrome coating; and
the in-situ polarizing element group comprising at least one infinity imaged in-situ source metrology instrument and at least one polarizing element.
8. An apparatus as defined in claim 7 , wherein the apparatus further comprises:
at least one lens adjacent to the second surface of the reticle;
an aperture plate mounted above the second surface of the reticle, wherein at least one opening in the aperture plate corresponds to at least one lens.
9. An apparatus as defined in claim 7 , wherein the apparatus further comprises:
at least one lens adjacent to the first surface of the reticle;
an aperture plate mounted above the second surface of the reticle, wherein at least one opening in the aperture plate corresponds to at least one lens and wherein an image of the aperture plate opening is focused at infinity.
10. An apparatus as defined in claim 7 , wherein the polarizing element group comprises at least two polarizing elements arranged linearly across the reticle at multiple field points.
11. An apparatus as defined in claim 7 , wherein the polarizing element group is reproduced and arranged in 2-dimensional arrays across a first surface of the in-situ source metrology instrument in such a way as to cover an entire lithographic field of interest.
12. An apparatus as defined in claim 7 , wherein a state of polarization of light leaving individual polarizing elements is increased or decreased by a fixed amount.
13. An apparatus as defined in claim 7 , wherein at least one element of the polarizing element group comprises first and second 45-degree polarizing beam splitter elements mounted to the second surface of the reticle, wherein the first polarizing beam splitter element divides the source into two orthogonal polarization components, such that one polarization component is passed perpendicular to a Z-direction to the second beam splitter, wherein each polarizing element is aligned to a corresponding opening in an aperture plate, and wherein polarized light passes through the aperture plate opening.
14. An apparatus as defined in claim 7 , wherein at least one element of the polarizing element group comprises a non-45-degree polarizing beam splitting element mounted to the second surface of the reticle, wherein the polarizing beam splitter divides the source into two orthogonal polarization components, one of which is passed through a corresponding hole in an aperture plate.
15. An apparatus as defined in claim 14 , further comprising at least one quarter wave plate included with the polarizing element group that comprises two polarizing beam splitters, wherein the quarter wave plate is mounted to the reticle adjacent to and on top of the first polarizing beam splitter, under the first beam splitter on the first surface of the reticle, adjacent to and perpendicular to a Z-direction to the first beam splitter, under the second beam splitter, or under the second beam splitter on the first surface of the reticle.
16. An apparatus as defined in claim 14 , further comprising at least one quarter wave plate included with the polarizing element group that comprises two polarizing beam splitters, wherein the quarter wave plate is mounted under the beam splitter on the first or second surface of the reticle.
17. An apparatus as defined in claim 7 , wherein the polarizing element group comprises a polarizer placed between an input and an output illuminator.
18. An apparatus as defined in claim 7 , wherein the polarizing element group comprises a light source with a known state of polarization.