Methods and patterning devices and apparatuses for measuring focus performance of a lithographic apparatus, device manufacturing method

A lithographic system comprising:

• a lithographic apparatus comprising:
• an illumination optical system arranged to illuminate a reflective patterning device;
• a projection optical system arranged to project an image of the patterning device onto a substrate;
• and
• a metrology apparatus configured to:
• use the lithographic apparatus to print at least one focus metrology pattern on the substrate, the printed focus metrology pattern with reflective and non-reflective portions of a patterning device, the non-reflective portions having first features and second features, both the first features and the second features being periodic in at least one direction, wherein each second feature is arranged between groups of the first features in an alternating manner, each of the second features having a dimension greater than a dimension of each of the first features and spaced apart from any adjacent group of the first features by a dimension larger than the dimension of each of the first features, and wherein the first features being positioned are based on a focus of the lithographic apparatus that performs the illuminating;
• measure a shift along the at least one direction of periodicity of at least one group of the first features associated with the printed focus metrology pattern;
• and
• derive a measurement of focus performance from the measurement of the shift,
• wherein the lithographic apparatus is arranged to use the measurement of focus performance derived by the metrology apparatus when applying the pattern to further substrates, and
• wherein printing is performed by illuminating the patterning device with patterning radiation incident at an oblique angle thereby obtaining the shift of the first features being dependent on a focus of the lithographic apparatus.

A non-transitory computer-readable media comprising processor readable instructions which, when run on suitable processor controlled apparatus, cause the processor controlled apparatus to perform operations comprising:

• illuminating reflective and non-reflective portions of a patterning device with EUV radiation incident to the patterning device at an oblique angle to define a printed focus metrology pattern, wherein the non-reflective portions of the patterning device comprise first features and second features, both the first features and the second features being periodic in at least one direction, wherein each second feature is arranged between groups of the first features in an alternating manner, each of the second features having a dimension greater than a dimension of each of the first features and spaced apart from any adjacent group of the first features by a dimension larger than the dimension of each of the first features, and wherein the first features being positioned based on a focus of a lithographic apparatus that performs the illuminating;
• measuring a shift along the at least one direction of periodicity of at least one group of the first features associated with the printed focus metrology pattern;
• and
• deriving a measurement of focus performance from the measurement of the shift.

A method of manufacturing devices wherein a device pattern is applied to a series of substrates using a lithographic process, the method measure focus performance of the lithographic process comprising:

• illuminating reflective and non-reflective portions of a patterning device with EUV radiation incident to the patterning device at an oblique angle to define a printed focus metrology pattern, wherein the non-reflective portions of the patterning device comprise first features and second features, both the first features and the second features being periodic in at least one direction, wherein each second feature is arranged between groups of the first features in an alternating manner, each of the second features having a dimension greater than a dimension of each of the first features and spaced apart from any adjacent group of the first features by a dimension larger than the dimension of each first feature, and wherein the first features being positioned based on a focus of a lithographic apparatus that performs the illuminating;
• measuring a shift along the at least one direction of periodicity of at least one group of the first features associated with the printed focus metrology pattern;
• deriving a measurement of focus performance from the measurement of the shift;
• and
• controlling the lithographic process for later substrates in accordance with the measured focus performance.