Coupling mechanism with spherical bearing, method of determining bearing radius of spherical bearing, and substrate polishing apparatus

A substrate polishing apparatus, comprising:

• a polishing table for supporting a polishing pad;
• a rotatable drive shaft,
• a polishing head coupled to the drive shaft by a coupling mechanism, the polishing head configured to be rotated by the drive shaft about an axis of rotation and to press a substrate against the polishing pad,
• the coupling mechanism comprising:
• an upper spherical bearing having a concave contact surface,
• a lower spherical bearing having a bearing radius measured from a rotational center, which aligns with the axis of rotation, and
• a contact member having an upper convex surface and a lower concave surface, the contact member being fixed to the drive shaft and disposed between the upper spherical bearing and the lower spherical bearing, wherein the upper convex surface slidable engages with the concave contact surface of the upper spherical bearing and the lower convex surface engages with the convex contact surface of the lower spherical bearing,
• wherein the lower bearing radius is greater than 20 mm and less than 24.5 mm so that a lower restoring torque, based on a sum of a frictional force between the polishing head and the polishing pad when the polishing head is rotated against the polishing pad offset by a frictional force between the contact member, is equal to zero or causes the polishing head to tilt toward a moving direction of the polishing pad and the lower bearing for a gimbal-axis height where the rotational center is below a bottom surface of the polishing head.

A substrate polishing apparatus comprising:

• a polishing table for supporting a polishing pad;
• a polishing head configured to press a substrate against the polishing pad;
• a rotatable drive shaft, and
• a dresser which is pressed against the polishing pad,
• wherein the dresser is coupled to the drive shaft by a coupling mechanism, the dresser configured to be rotated by the drive shaft about an axis of rotation,
• the coupling mechanism comprising an upper spherical bearing having a concave contact surface,
• a lower spherical bearing having a bearing radius measured from a rotational center, which aligns with the axis of rotation, and
• a contact member having an upper convex surface and a lower concave surface, the contact member being fixed to the drive shaft and disposed between the upper spherical bearing and the lower spherical bearing, wherein the upper convex surface slidable engages with the concave contact surface of the upper spherical bearing and the lower convex surface engages with the convex contact surface of the lower spherical bearing,
• wherein the lower bearing radius is greater than 20 mm and less than 24.5 mm, wherein a lower-restoring torque, based on a frictional force between the dresser and the polishing pad when the dresser is rotated against the polishing pad offset by a frictional force between the contact member and the lower bearing, is equal to zero or causes the dresser to tilt toward a moving direction of the polishing pad.