Systems, devices, and methods for registering a superstrate of an imprint tool

An imprint system comprising:

• a sensor;
• a vacuum pump;
• a superstrate chuck including a ring portion, wherein the ring portion is configured to hold a periphery of a back surface of a plate;
• one or more memories;
• and
• one or more processors, wherein the one or more processors and the one or more memories cooperate to cause the imprint system to perform operations that comprise:
• controlling the vacuum pump to generate an atmospheric pressure at a central portion of the back surface of the plate that is lower than an atmospheric pressure at the central portion of a front surface of the plate such that the back surface of the plate forms a convex surface and the front surface of the plate forms a concave surface;
• controlling the sensor to measure, at each measuring point of a plurality of measuring points at or near the periphery of the front surface the plate, a height of the measuring point;
• and
• identifying a respective location of each transition point of one or more transition points of a tapered edge of the plate based on the respective height of each measuring point of the plurality of measuring points,
• wherein the front surface of the plate includes a contact surface that is surrounded by the tapered edge,
• wherein a thickness of the plate at an outer edge of the plate is less than a thickness of the plate throughout the contact surface of the plate,
• wherein the outer edge of the plate is an outer perimeter of the tapered edge,
• wherein an outer edge of the contact surface is an inner perimeter of the tapered edge,
• wherein each transition point of the one or more transition points is located on the inner perimeter of the tapered edge, and
• wherein the negative vacuum pressure bows the central portion of the plate towards the negative vacuum pressure such that the contact surface forms the concave surface and such that an outer edge of the concave surface is defined by the inner perimeter of the tapered edge.

A method comprising:

• holding a periphery of a back surface of a plate with a ring portion of a chuck, wherein the plate includes a front surface, wherein the front surface includes a contact surface that is surrounded by a sloping edge, and wherein, between the contact surface and an outer edge of the plate, the sloping edge slopes away from the contact surface toward the back surface;
• reducing an atmospheric pressure at a central portion of the back surface of the plate such that the back surface of the plate forms a convex surface and the front surface of the plate forms a concave surface;
• measuring, for each point of a plurality of points on the front surface of the plate that are at or near a periphery of the front surface of the plate, a respective height between the point and a plane of the chuck;
• and
• identifying at least one transition point between the sloping edge and the contact surface based on the respective heights,
• wherein a thickness of the plate at the outer edge of the plate is less than a thickness of the plate throughout the contact surface of the plate,
• wherein the outer edge of the plate is an outer perimeter of the sloping edge,
• wherein an outer edge of the contact surface is an inner perimeter of the sloping edge,
• wherein the at least one transition point is located on the inner perimeter of the sloping edge, and
• wherein the negative vacuum pressure bows the central portion of the plate towards the negative vacuum pressure such that the contact surface forms the concave surface and such that an outer edge of the concave surface is defined by the inner perimeter of the sloping edge.