Systems and methods for controlling substrate approach toward a target horizontal plane

A system for controlling substrate approach toward a target horizontal plane, comprising:

• a notch alignment feature location module configured to determine a real-time azimuthal position of a notch alignment feature located at a periphery of a lower surface of a substrate holder as the substrate holder rotates about a rotational axis oriented normal to the lower surface of the substrate holder, wherein the real-time azimuthal position of the notch alignment feature is determined relative to a fixed reference ray extending perpendicularly away from the rotational axis;
• and
• an approach initiation control module configured and programmed to determine an approach initiation azimuthal position of the notch alignment feature relative to the fixed reference ray at which initiation of vertical movement of the substrate holder in synchronization with rotation of the substrate holder positions the notch alignment feature at a prescribed azimuthal position relative to the fixed reference ray at a prescribed vertical position of the substrate holder, the approach initiation control module further configured and programmed to determine a time delay required to have the notch alignment feature located at the approach initiation azimuthal position based on the determined real-time azimuthal position of the notch alignment feature and on a real-time rotational status of the substrate holder, the approach initiation control module further configured and programmed to initiate vertical movement of the substrate holder in accordance with the determined time delay.

A method for controlling an approach of a substrate toward a target horizontal plane, comprising:

• having a substrate holder that has a lower surface configured to contact a backside of a substrate, the substrate holder configured to securely hold the substrate with a frontside of the substrate facing downward, the substrate holder having a notch alignment feature located at a periphery of the lower surface of the substrate holder, the substrate holder configured to rotate about a rotational axis extending through a centerpoint of the lower surface of the substrate holder, the rotational axis oriented normal to the lower surface of the substrate holder, the substrate holder configured to tilt relative to the target horizontal plane, the substrate holder configured to move vertically relative to the target horizontal plane located below the substrate holder;
• having a tilt mechanism connected to the substrate holder to provide angular position control of the lower surface of the substrate holder relative to the target horizontal plane;
• having a lift mechanism connected to the substrate holder to provide vertical position control of the substrate holder;
• having a rotation mechanism connected to the substrate holder to provide rotational control of the substrate holder about the rotational axis;
• having a controller configured and programmed to provide synchronized control of the lift mechanism and the rotation mechanism to achieve a prescribed azimuthal position of the notch alignment feature about the rotational axis relative to a fixed reference ray extending perpendicularly away from the rotational axis when the substrate holder reaches a prescribed vertical position at which the substrate held on the substrate holder first reaches the target horizontal plane;
• having a substrate on the substrate holder;
• operating the tilt mechanism to tilt the substrate holder to a prescribed angular position of the lower surface of the substrate holder relative to the target horizontal plane;
• operating the controller to direct the rotation mechanism to rotate the substrate holder about the rotational axis at a prescribed rotational speed;
• determining a real-time azimuthal position of the notch alignment feature as the substrate holder rotates about the rotational axis, wherein the real-time azimuthal position of the notch alignment feature is determined relative to the fixed reference ray;
• determining an approach initiation azimuthal position of the notch alignment feature relative to the fixed reference ray at which initiation of vertical movement of the substrate holder in synchronization with rotation of the substrate holder positions the notch alignment feature at a prescribed azimuthal position relative to the fixed reference ray at a prescribed vertical position of the substrate holder relative to the target horizontal plane;
• determining a time delay required to have the notch alignment feature located at the approach initiation azimuthal position based on the determined real-time azimuthal position of the notch alignment feature and on the prescribed rotational speed;
• and
• operating the controller to direct the lift mechanism to initiate vertical movement of the substrate holder toward the target horizontal plane in accordance with the determined time delay.