Methods and systems for lithography process control

A wafer measurement system for use within a wafer process tool, comprising:

• a wafer handler associated with the wafer process tool for feeding wafers between a cassette and any one or more of a plurality of stations of the wafer process tool;
• a wafer measurement station forming one of the stations of the wafer process tool, the measurement station having a wafer support in communication with the wafer handler, the measurement station also having therein an optical measurement system forming a scatterometry instrument that is moveable by a stage to specified locations over the wafer support, the optical measurement system optically coupled to a light source to direct a light beam as a spot onto patterned features of a wafer surface on the wafer support, wherein the light beam is characterized by a spot size that is larger at the wafer surface than a periodicity of the patterned features, the head also having a light collector associated with a detector whereby illuminated features on the wafer yield characteristic optical signatures with independent optical parameters in the signatures including one or more of wavelength, incidence angle, and altitude and azimuthal collection angles;
• and
• a data processor analyzing the characteristic signatures of a wafer using a scattering model for possible periodic structures on a wafer to obtain a measure of the patterned features on the wafer so that a process carried out by the wafer process tool can be analyzed.

A scatterometry instrument integrated within a wafer measurement station that forms one station of wafer process tool, the process tool having a wafer handler associated therewith feeding wafers between a cassette and one or more of a plurality of stations of the process tool, the wafer measurement station having, in addition to the spectrometry instrument, a wafer support with a capacity for locating a wafer at a measurement position, wherein the scatterometry instrument comprises:

• a movable stage;
• an optical measurement system mounted on said stage for movement by said stage to one or more specified locations over a wafer held by a stationary or movable wafer support in the measurement position, the measurement system being in optical communication with a light source for directing a light beam as a spot onto patterned features of a wafer on the wafer support, wherein the light beam is characterized by a spot size that is larger at the wafer surface than a periodicity of the patterned features, the measurement system having collection optics associated with a detector for collecting and detecting light scattered from the portion of the wafer illuminated by the light beam, whereby features on the wafer yield characteristic optical signatures with independent optical parameters of the signatures including one or more of wavelength, incidence angle, and altitude and azimuthal collection angles;
• and
• a data processor in communication with the detector, the data processor analyzing the characteristic optical signatures using a scattering model for possible periodic structures on a wafer to obtain a measure of the patterned features on the wafer such that a process carried out by the wafer process tool can be analyzed.

A wafer measurement method for cooperative use with a wafer process tool of the type having a wafer handler associated with a cassette of wafers, comprising:

• within the wafer process tool after completion of any of one or more process steps carried out in processing stations of the process tool, receiving in an integrated measuring station of the process tool a wafer from a wafer handler associated within the process tool without first transferring wafers out of the process tool to another cassette or cassette loading station, and depositing the wafer at an unspecified orientation in the measurement station relative to a moveable optical measurement system;
• moving an optical measurement system to a plurality of locations over the wafer;
• directing a beam of light normally onto the wafer surface as a light spot at each of said plurality of locations, the light spot characterized by a spot size that is larger at the wafer surface than a periodicity of pattern features on the wafer;
• detecting light reflected from the wafer surface to obtain data for an optical characteristic of surface pattern features of the wafer at said plurality of locations;
• and
• analyzing the optical characteristic data using a scattering model of possible periodic structures on a wafer to obtain a measure of critical dimensions of the surface pattern features on the wafer.

A method of measuring a wafer within a wafer process tool, comprising:

• transferring a wafer robotically from a process station of the process tool to a measurement station of the process tool;
• positioning a measurement spot of an optical head of a measurement instrument within the measurement station over a first location of the wafer;
• rotating the wafer and translating the optical head to position the measurement spot over a second location of the wafer;
• repeating the wafer rotation and optical head translation to successively position the measurement spot over different locations of the wafer;
• and
• measuring an optical characteristic of the wafer at each of the successive measurement locations.