Apparatus and method for isolating and measuring movement in a metrology apparatus

In an assembly for a metrology apparatus having a probe assembly, the assembly including an elongate actuator with a longitudinal axis and having a first end configured to be coupled to a frame of the microscope and a free end configured to be coupled to a sample holder, wherein the elongate actuator is configured to provide controllable translation in three orthogonal directions upon application of proper electrical stimuli, a method of reducing positioning errors at the free end of the elongate actuator comprising the steps of:

• fixing the probe assembly to the frame;
• supporting the sample holder with a reference structure of the metrology apparatus, the reference structure being substantially insensitive to longitudinal expansion or contraction of a first portion of the elongate actuator;
• isolating the reference structure from a longitudinal deflection of the first portion of the elongate actuator;
• driving the first portion of the elongate actuator;
• simultaneously generating both longitudinal deflections as well as lateral deflections in the first portion as a result of said driving step;
• and
• preventing the lateral deflections generated in the first portion of the elongate actuator from laterally deflecting the sample holder while simultaneously transmitting the longitudinal deflections to the sample holder.

A scanning probe microscope assembly, comprising:

• a microscope frame;
• a piezoelectric actuator having a first end fixed to said frame and a second free end coupled to a sample holder via multiple bar linkage that facilitates moving said sample holder substantially only in an intended direction of motion of said actuator;
• a first reflector assembly fixed proximate to said free end of said piezoelectric actuator;
• a first electromagnetic radiation source fixed with respect to said frame and disposed to direct radiation onto said first reflector assembly;
• and
• a first electromagnetic radiation detector disposed to receive light from said first source after it has been received and reflected by said first reflector assembly and to generate a signal indicative of a degree of longitudinal deflection of said piezoelectric actuator.

An apparatus for measuring movement of an actuator in a metrology apparatus, the measuring apparatus comprising:

• a sample holder coupled to the actuator;
• an optical measuring device including a light source that generates a light beam, said measuring device being configured to change the direction of said beam in response to movement of the actuator;
• sensor to detect said beam and generate a signal indicative of the movement of the actuator;
• and
• wherein said measuring device includes a movable bar assembly coupled to the actuator and to a reference structure, wherein said bar assembly has a reflecting surface that is adapted to deflect said beam, and wherein said bar assembly is responsive to movement of the actuator so as to change the direction of said deflected beam.

A method for measuring movement of an activator in a metrology apparatus, the method comprising:

• providing a movable bar assembly coupled to the actuator and to a reference structure;
• supporting a sample holder with the movable bar assembly;
• and
• measuring, in response to movement of the actuator, movement of said movable bar assembly, wherein the movement of said movable bar assembly is indicative of movement of the actuator.

In a metrology apparatus having an actuator for moving a sample in a particular direction, a reference assembly that generally decouples movement of the apparatus in a direction other than the particular direction from the sample, the reference assembly comprising:

• a reference structure;
• a sample holder coupled to said reference structure and to the actuator, the sample being attached to said sample holder;
• and
• a flexible bar having opposed ends, one of which is coupled to the actuator and the other of which is coupled to said sample holder via a movement isolating device, wherein said flexible bar and said reference structure, are adapted to collectively decouple movement of the actuator in the direction other than the particular direction from the sample.

A metrology apparatus for analyzing a sample the assembly comprising:

• an actuator including a first actuator stage configured to controllably move in first and second orthogonal directions, and a second actuator stage adjacent to the first actuator stage and configured to controllably move in a third direction orthogonal to the first and second orthogonal directions;
• a reference structure having first and second ends wherein the first end is fixed relative to movement of the second actuator stage;
• a coupling coupled to the second actuator stage and to a multi-bar linkage assembly fixed to the second end of the reference structure, wherein the second actuator stage and the coupling are configured to move the linkage in the third orthogonal direction in a manner that substantially isolates the linkage from any second actuator stage motion in the first and second directions;
• an objective fixed to the reference structure, wherein the objective is between a light source and a position sensor, and the position sensor measures first actuator stage motion in the first and second directions;
• and
• wherein the multi-bar linkage supports the sample.

An assembly comprising:

• an actuator with a longitudinal axis having a fixed end and a free end configured to translate a sample coupled thereto in three orthogonal directions with respect to the fixed end;
• a multiple bar linkage having first and second links mutually constrained to translate with respect to each other, and wherein the first link is fixed to a reference structure and the second link is constrained to translate in a direction generally parallel to the longitudinal axis of the actuator;
• a coupling having first and second ends, the first end being fixed to the actuator proximate to its free end, and the second end being fixed to the second link, the coupling adapted to transmit displacement in a direction substantially parallel to the longitudinal axis of the actuator;
• and
• an objective fixed to the reference structure, wherein the objective is between a light source and a position sensor, and the position sensor measures displacement of the objective in a direction generally perpendicular to the longitudinal axis of the actuator.

An optical apparatus for measuring movement of an actuator in a metrology apparatus, the optical measuring apparatus comprising:

• an objective fixed to a reference structure coupled to the actuator;
• a light source that generates a light beam, wherein the optical measuring apparatus changes the direction of the beam in response to movement of the objective;
• a position sensor that detects the beam and generates a displacement signal indicative of movement of the actuator in a direction generally perpendicular to a longitudinal axis of the actuator;
• and
• wherein a sample is coupled to the actuator;
• and
• and wherein said reference structure moves in the direction generally perpendicular to the longitudinal axis of the actuator.

A method for measuring movement of an actuator in a metrology apparatus, the method comprising:

• providing an objective mounted on a reference structure coupled to the actuator;
• measuring movement of the objective, wherein movement of the objective is indicative of movement of the actuator in a direction generally perpendicular to the longitudinal axis of the actuator;
• and
• wherein a sample is coupled to the actuator via a multiple bar linkage so that movement of the actuator in the direction when the actuator is excited to move in a direction coincident with the longitudinal axis of the actuator is substantially decoupled from the sample.