Projection exposure system for microlithography with a measurement device

A projection exposure system for microlithography, comprising:

• a mask holding device holding a mask with mask structures disposed on the mask,
• a substrate holding device holding a substrate,
• projection optics arranged to image the mask structures onto the substrate during an exposure process,
• a reference element,
• a measurement structure which is disposed in a defined position with respect to the reference element, which defined position is mechanically uncoupled from the mask holding device,
• a detector arranged to record an image of the measurement structure imaged by the projection optics,
• wherein the mask holding device, the substrate holding device, the projection optics, the measurement structure, and the detector are arranged and configured such that the projection optics image the mask structures onto the substrate via a first optical path that terminates on the substrate and image the measurement structure to the detector at the same time via a second optical path that differs from the first optical path and terminates on the detector, and
• an evaluation device configured to establish a lateral position of the image of the measurement structure in an area of the detector during the exposure process,
• wherein the detector has a locally resolving two-dimensional sensor and a detector structure disposed in front of the two-dimensional sensor, and wherein the detector is configured to record the image produced on the detector by the projection optics by recording a pattern produced by superimposing the image of the measurement structure with the detector structure.

A projection exposure system for microlithography comprising:

• a mask holding device holding a reflection mask with mask structures disposed on the mask,
• projection optics arranged to image the mask structures onto a substrate,
• a radiation source configured to produce an illumination beam radiated obliquely onto the reflection mask such that a propagation direction of a reflected beam produced by reflection of the illumination beam on the reflection mask and directed towards the projection optics is tilted in relation to a direction that is opposite the propagation direction of the illumination beam, and
• a diverting device configured to divert a measurement beam from the illumination beam, the diverting device comprising:
• a coupling/uncoupling device and a measurement mirror having a measurement structure,
• wherein the coupling/uncoupling device and the measurement mirror are disposed in the optical path of the illumination beam such that, during operation of the projection exposure system, a partial beam of the illumination beam is directed by the coupling/uncoupling device onto the measurement structure of the measurement mirror, then is reflected back onto the coupling/uncoupling device, and is coupled as the measurement beam by the coupling/uncoupling device into the optical path of the beam reflected by the reflection mask.

A method for monitoring the lateral imaging stability of a projection exposure system for microlithography comprising:

• holding a mask with mask structures disposed on the mask with a mask holding device,
• disposing a measurement structure in a defined position with respect to a reference element of the projection exposure system, which defined position is mechanically uncoupled from a position of the mask holding device,
• imaging the mask structures onto a substrate in an exposure process and imaging the measurement structure into an area of a detector, the imaging of the mask structures and the imaging of the measurement structure respectively taking place at the same time with projection optics of the projection exposure system,
• recording the image of the measurement structure with the detector,
• establishing a lateral position of the image of the measurement structure in the area of the detector during the exposure process, and
• obtaining a respective defined position of at least one of the measurement structure and the detector by measuring a respective distance from the reference element to at least one of the measurement structure and the detector.