1. A fiber optical connector microlens with a focal plane aligning fiber trap, the microlens comprising:
a convex first lens surface;
a second lens surface;
a fiber trap integrally formed with the second lens surface for aligning a face of an unclad optical fiber core, without a ferrule, in a microlens focal plane;
a core stop integrally formed with the second lens surface to limit the insertion of the unclad fiber core into the fiber trap; and,
wherein, the microlens forms a focal point at the core stop when receiving light in a collimated beam via the first lens surface.
2. The microlens of claim 1 wherein the second lens surface is selected from a group consisting of convex and planar surfaces.
3. The microlens of claim 1 further comprising:
a lens body interposed between the first and second lens surfaces, having a cross-section with a lens center axis; and,
wherein the fiber trap includes a barrel having a first end attached to the second lens surface and a clamping mechanism to prevent an inserted fiber core, with a diameter about equal to a barrel interior surface diameter, from being withdrawn from the barrel.
4. The microlens of claim 3 wherein the fiber trap clamping mechanism includes an irregular barrel interior surface to frictionally engage a fiber core exterior surface.
5. The microlens of claim 3 wherein the fiber trap clamping mechanism is a constricted region of the barrel interior surface, having a diameter smaller than an uncompressed fiber core diameter.
6. The microlens of claim 3 wherein the fiber trap clamping mechanism is a corkscrew region of the barrel interior surface, with grooves having a diameter larger than the fiber core diameter and ridges having a passage smaller than the fiber core diameter.
7. The microlens of claim 1 further comprising:
a fiber alignment cavity integrally formed with the second lens surface, to accept an optical fiber core, the fiber alignment cavity having a center avis aligned with the lens center axis.
8. The microlens of claim 7
wherein the core stop limits the insertion of the unclad fiber core into the barrel; and,
wherein the microlens forms a focal point at the core stop, along the fiber alignment cavity center axis, when transceiving light collimated beam via the first lens surface.
9. The microlens of claim 1 further comprising:
a channel to accept a fiber core;
wherein the core stop limits the insertion of the unclad fiber core into the channel; and,
wherein the fiber trap includes a pivoting jaw to prevent the inserted unclad fiber core from being withdrawn from the channel.
10. A fiber optic connector plug with a focal plane aligning fiber trap, the plug comprising:
a mechanical body shaped to selectively engage and disengage a jack housing, and a microlens, the microlens having a convex first lens surface to transceive light in a collimated beam with a jack optical interface, a second lens surface, and a fiber trap integrally formed with the second lens surface for aligning a face of an unclad optical fiber core without a ferrule in a microlens focal plane, the microlens further comprising a core stop to limit the insertion of the unclad fiber core into the fiber trap; and,
wherein the microlens forms a focal point at the core stop when transceiving light in a collimated beam via the first lens surface.
11. The plug of claim 10 wherein the second lens surface is selected from a group consisting of convex and planar surfaces.
12. The plug of claim 10 wherein the microlens includes a lens body interposed between the first and second lens surfaces, having a cross-section with a lens center axis; and,
wherein the fiber trap includes a barrel having a first end attached to the second lens surface and a clamping mechanism to prevent an inserted fiber core, with a diameter about equal to a barrel interior surface diameter, from being withdrawn from the barrel.
13. The plug of claim 12 wherein the fiber trap clamping mechanism includes an irregular barrel interior surface to frictionally engage a fiber core exterior surface.
14. The plug of claim 12 wherein the fiber p clamping mechanism is a constricted region of the barrel interior surface, having a diameter smaller than an uncompressed fiber core diameter.
15. The plug of claim 12 wherein the fiber trap clamping mechanism is a corkscrew region of the barrel interior surface, with grooves having a diameter larger than the fiber core diameter and ridges having a passage smaller than the fiber core diameter.
16. The plug of claim 10 wherein the microlens includes a fiber alignment cavity integrally formed with the second lens surface, to accept the unclad optical fiber core, the fiber alignment cavity having a center axis aligned with the lens center axis.
17. The plug of claim 12 wherein the microlens core stop limits the insertion of the unclad fiber core into the barrel, forming a focal point at the core stop, along the fiber alignment cavity center axis, when transceiving light in a collimated beam via the first lens surface.
18. The plug of claim 10 further comprising:
a channel to accept a fiber core;
wherein the microlens core stop limits the insertion of the unclad fiber core into the channel; and,
wherein the fiber trap includes a pivoting jar to prevent the inserted unclad fiber core from being withdrawn from the channel.
19. The microlens of claim 1 further comprising:
a fiber core interface in the fiber trap adjacent the second lens surface to accept an index matching fluid.
20. The plug of claim 10 wherein the microlens further comprises a fiber core interface in the fiber trap adjacent the second lens surface to accept an index matching fluid.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of characterizing photolithography lens quality, comprising:
selecting first and second different overlay patterns, each of the first and second overlay patterns having a first feature with a first pitch and a second feature with a second pitch different than the first pitch;
performing a photolithography simulation to determine a first sensitivity coefficient for the first overlay pattern and a second sensitivity coefficient for the second overlay pattern, the first and second sensitivity coefficients being respectively associated with a first lens aberration pattern represented by a first Zernike coefficient and a second lens aberration pattern represented by a second Zernike coefficient different than the first Zernike coefficient;
providing first and second photomasks, the first photomask having the first overlay pattern thereon and the second photomask having the second overlay pattern thereon;
exposing, with a photolithography tool, first and second wafers with the first and second photomasks to form the first overlay pattern on the first wafer and the second overlay pattern on the second wafer;
measuring a first relative pattern placement error of the first overlay pattern formed on the first wafer and measuring a second relative pattern placement error of the second overlay pattern formed on the second wafer; and
solving a system of Zernike polynomial equations using the first and second relative patterns placement errors and the first and second sensitivity coefficients to determine values for the first and second Zernike coefficients.
2. The method of claim 1,
wherein the first feature and the second feature on each overlay pattern have the same center point; and
wherein measuring the first and second relative pattern placement errors of the first and second overlay patterns formed on the first and second wafers includes measuring a displacement between a center point of the first feature and a center point of the second feature on each of the first and second wafers.
3. The method of claim 2, wherein the first and second relative pattern placement errors are vectors having horizontal component values and a vertical component values.
4. The method of claim 1,
wherein the first sensitivity coefficient represents a ratio of an amount of pattern placement error that is produced by an amount of lens aberration associated with the first lens aberration pattern; and
wherein the second sensitivity coefficient represents a ratio of an amount of pattern placement error that is produced by an amount of lens aberration associated with the second lens aberration pattern.
5. The method of claim 1,
wherein the first photomask includes multiple instances of the first overlay pattern arranged in a row across a width of the first photomask;
wherein the second photomask includes multiple instances of the second overlay pattern arranged in a row across a width of the second photomask;
wherein the exposing includes directing radiation out of an exposure slit in the photolithography tool and through the first photomask to form a row of first overlay patterns on the first wafer, the overlay patterns in the row of second overlay patterns formed on the first wafer being respectively associated with a plurality of locations along a length of the exposure slit;
wherein the exposing includes directing radiation out of the exposure slit in the photolithography tool and through the second photomask to form a row of second overlay patterns on the second wafer, the overlay patterns in the row of second overlay patterns formed on the second wafer being respectively associated with the plurality of locations along the length of the exposure slit;
wherein the measuring includes measuring a first relative pattern placement error for each overlay pattern in the row of first overlay patterns on the first wafer; and
wherein the measuring includes measuring a second relative pattern placement error for each overlay pattern in the row of second overlay patterns on the second wafer.
6. The method of claim 5, wherein the solving includes solving a system of Zernike polynomial equations for each location in the plurality of locations along the length of the exposure slit using the first and second relative pattern placement errors respectively associated with the plurality of locations to determine values for the first and second Zernike coefficients associated with each location in the plurality of locations along the length of the exposure slit.
7. A method of characterizing photolithography lens quality, comprising:
selecting first and second different overlay pattern;
performing a photolithography simulation to determine a first sensitivity coefficient for the first overlay pattern and a second sensitivity coefficient for the second overlay pattern;
providing first and second photomasks, the first photomask having the first overlay pattern thereon and the second photomask having the second overlay pattern thereon;
exposing, with a photolithography tool, first and second wafers with the first and second photomasks to form the first overlay pattern on the first wafer and the second overlay pattern on the second wafer;
measuring a first relative pattern placement error of the first overlay pattern formed on the first wafer and measuring a second relative pattern placement error of the second overlay pattern formed on the second wafer; and
calculating a quality indicator for a lens in the photolithography tool using the first and second relative pattern placement errors and the first and second sensitivity coefficients.
8. The method of claim 7,
wherein each of the first and second overlay patterns has a first feature with a first pitch and a second feature with a second pitch different than the first pitch;
wherein the first feature and the second feature on each overlay pattern have the same center point; and
wherein measuring the first and second relative pattern placement errors of the first and second overlay patterns formed on the first and second wafers includes measuring a displacement between a center point of the first feature and a center point of the second feature on each of the first and second wafers.
9. The method of claim 8, where each of the first and second overlay patterns is one of a box-in-box pattern and an alternating bar pattern.
10. The method of claim 8, wherein each of the first and second relative pattern placement errors is a vector having a horizontal component value and a vertical component value.
11. The method of claim 7,
wherein the first sensitivity coefficient represents a ratio of an amount of pattern placement error that is produced by an amount of lens aberration associated with the first lens aberration pattern; and
wherein the second sensitivity coefficient represents a ratio of an amount of pattern placement error that is produced by an amount of lens aberration associated with the second lens aberration pattern.
12. The method of claim 7,
wherein the exposing includes exposing the first wafer a plurality of times to form the first overlay pattern in a plurality of fields on the first wafer;
wherein the measuring includes measuring the first relative pattern placement error of each first overlay pattern in the plurality of fields on the first wafer; and
wherein the calculating the quality indicator includes:
averaging the first relative pattern placement errors of the first overlay patterns to find an average first relative pattern placement error for the first wafer; and
calculating the quality indicator of the lens in the photolithography tool using the average first relative pattern placement error and the first sensitivity coefficient.
13. The method of claim 7,
wherein the first photomask includes multiple instances of the first overlay pattern that are arranged in a row across a width of the first photomask;
wherein the exposing includes directing radiation out of an exposure slit in the photolithography tool and through the first photomask to form a row of first overlay patterns on the first wafer, each first overlay pattern in the row of first overlay patterns formed on the first wafer being associated with a location along a length of the exposure slit; and
wherein the measuring includes measuring a first relative pattern placement error for each first overlay pattern in the row of first overlay patterns on the first wafer.
14. The method of claim 13, wherein the calculating a quality indicator includes calculating a quality indicator of the lens in the photolithography tool at a plurality of locations on the lens that correspond to locations along the length of the exposure slit using the first relative pattern placement errors of the first overlay patterns in the row of first overlay patterns formed on the first wafer.
15. The method of claim 7, wherein the calculating a quality indicator includes decomposing the first relative pattern placement error into horizontal and vertical components and calculating a horizontal quality indicator using the horizontal component and calculating a vertical quality indicator using the vertical component.
16. The method of claim 7, wherein calculating a quality indicator includes solving a system of Zernike polynomial equations using the first and second relative pattern placement errors and the first and second sensitivity coefficients to determine values for the first and second Zernike coefficients.
17. The method of claim 7, further including comparing the quality indicator against a historical quality indicator of the lens to monitor lens quality drift.
18. A system, comprising:
photolithography simulation tool configured to determine a first sensitivity coefficient for a first overlay pattern and a second sensitivity coefficient for a second overlay pattern;
a photolithography tool having a lens and an exposure slit, the photolithography tool configured to direct radiation from the exposure slit through a first photomask having the first overlay pattern thereon and onto a first wafer to form the first overlay pattern on the first wafer, the photolithography tool also configured to direct radiation from the exposure slit through a second photomask having the second overlay pattern thereon and onto a second wafer to form the second overlay pattern on the second wafer;
an overlay metrology tool configured to measure a first relative pattern placement error of the first overlay pattern formed on the first wafer and configured to measure a second relative pattern placement error of the second overlay pattern formed on the second wafer; and
a data processing tool configured to calculate a quality indicator for the lens in the photolithography tool using the first and second relative pattern placement errors and the first and second sensitivity coefficients.
19. The system of claim 18,
wherein each of the first and second overlay patterns has a first feature with a first pitch and a second feature with a second pitch different than the first pitch;
wherein the first feature and the second feature on each overlay pattern have the same center point; and
wherein the overlay metrology tool is further configured to measure a displacement between a center point of the first feature and a center point of the second feature on each of the first and second wafers.
20. The system of claim 18, wherein the data processing tool is configured to apply the first and second relative pattern placement errors and the first and second sensitivity coefficients to a system of Zernike polynomial equations to solve for first and second Zernike coefficients, the Zernike coefficients being the quality indicator.