Experimental verification of PSM polarimetry: monitoring polarization at 193nm high-NA with phase shift masks

Abstract

The initial experimental verification of a polarization monitoring technique is presented. A series of phase shifting mask patterns produce polarization dependent signals in photoresist and are capable of monitoring the Stokes parameters of any arbitrary illumination scheme. Experiments on two test reticles have been conducted. The first reticle consisted of a series of radial phase gratings (RPG) and employed special apertures to select particular illumination angles. Measurement sensitivities of about 0.3 percent of the clear field per percent change in polarization state were observed. The second test reticle employed the more sensitive proximity effect polarization analyzers (PEPA), a more robust experimental setup, and a backside pinhole layer for illumination angle selection and to enable characterization of the full illuminator. Despite an initial complication with the backside pinhole alignment, the results correlate with theory. Theory suggests that, once the pinhole alignment is corrected in the near future, the second reticle should achieve a measurement sensitivity of about 1 percent of the clear field per percent change in polarization state. This corresponds to a measurement of the Stokes parameters after test mask calibration, to within about 0.02 to 0.03. Various potential improvements to the design, fabrication of the mask, and experimental setup are discussed. Additionally, to decrease measurement time, a design modification and double exposure technique is proposed to enable electrical detection of the measurement signal.

Resist-based polarization monitoring with phase-shift masks at 1.35 numerical aperture

“…PSM Polarimetry, the concept behind the POLARIS TM Polarization Monitoring Test Reticle, has been previously introduced [1,2], theoretically investicated [3], and experimentally verified up to 0.93 numerical aperture (NA) [4,5]. The purpose of this paper is to describe an improved test reticle for NAs up to 1.35, to verify its imaging performance at hyper-NA, and to provide evidences that it may serve as the basis for a highly sensitive polarization monitoring technique for all hyper-NA applications where polarization quality is important.…”