On-axis focus sensor and method
AssigneeRudolph Technologies, Inc.
InventorsDennis L. Ohren, Christopher J. Voges, Andrew E. Rotering
Life of this patent
Estimating the term…
Abstract
A focus height sensor in an optical system for inspection of semiconductor devices includes a sensor beam source that emits a beam of electromagnetic radiation. A reflector receives the beam of electromagnetic radiation from the sensor beam source and directs the beam toward a surface of a semiconductor device positioned within a field of view of the optical system. The reflector is positioned to receive at least a portion of the beam back from the surface of the semiconductor device to direct the returned beam to a sensor. The sensor receives the returned beam and outputs a signal correlating to a position of the surface within the field of view along an optical axis of the optical system.
Claims13
In an optical system for inspection of semiconductor devices, a focus height sensor comprising:
- a sensor beam source that emits a beam of electromagnetic radiation;
- a reflector for receiving the beam of electromagnetic radiation from the sensor beam source and directing said beam toward a surface of a semiconductor device that is positioned within a field of view of the optical system, the reflector also being positioned to receive at least a portion of said beam back from the surface of the semiconductor device to direct the returned beam to a sensor;
- and,
- the sensor receiving the returned beam and outputting a signal correlating to a position of the surface within the field of view along an optical axis of the optical system.
A method of capturing images of a semiconductor substrate comprising:
- positioning selectively a reflector in an operative position to direct a sensor beam toward a semiconductor substrate, the reflector receiving from the semiconductor substrate at least a portion of the sensor beam and directing it to a sensor which outputs a signal to a controller correlated to a position of a surface of the semiconductor substrate;
- controlling a focusing mechanism of an optical system to position an object plane of the optical system at substantially the same position output by the sensor and reported to the controller;
- and,
- positioning selectively an objective of an optical system in an operative position to capture an image of the semiconductor substrate.
A method of capturing images of a semiconductor substrate comprising:
- actuating a turret of an optical system to place a reflector in an operative position to direct a measuring beam onto a surface of a semiconductor substrate and to return at least a portion of the measuring beam from the semiconductor surface to a sensor to determine a height of the semiconductor substrate;
- actuating a focusing mechanism of the optical system to focus the optical system at the height determined by the sensor;
- actuating the turret to place an objective in an operative position to capture an image of the semiconductor substrate at substantially the location at which the height of the semiconductor substrate was measured;
- and,
- capturing an image of the semiconductor substrate using the optical system.
A method of calibrating a position of an optical system comprising:
- driving an optical system focusing mechanism to a predetermined location;
- measuring the position of the optical system using a height sensor;
- measuring the position of the optical system using an autofocus height process conducted by the optical system;
- comparing the respective position information to determine if there is acceptable agreement between the data;
- and,
- where acceptable agreement exists, continuing or starting a imaging process and where acceptable agreement does not exist, modifying the height data obtained from one of the height sensor and the optical system to ensure acceptable agreement therebetween.
Dependencies are inferred from the claim text.