University of California

Andrew R Neureuther

Gregory R McIntyre

Frank E Gennari

Avideh Zakhor

Kostas Adam

Garth C Robins

MoSong Cheng

Yong Liu

The present invention presents three new classes of phase-shifting mask patterns. In optical image forming systems, a mask with phase shifted regions can act as a precision instrument for characterizing imaging. Three new classes of phase-shifting mask patterns have been invented to characterize projection printing tool illumination and phase-shifting mask (PSM) performance. The linear phase grating (LPG) and linear phase ring (LPR) both serve to characterize illumination angular distribution and uniformity. A third new class, the interferometric-probe monitor for phase-shifting masks (IPM-PSM), measures the effective phase, transmittance and edge effects of various phase-shifted mask features. All three patterns allow performance comparison across the field, tool-to-tool, over time, or to intended design.

Phase shifting test mask patterns for characterizing illumination and mask quality in image forming optical systems

A method to monitor the state of polarization incident on a photomask in projection printing is presented. The method includes a series of phase-shifting mask patterns that take advantage of high NA effects to create a signal dependent on only one incident polarization component. The patterns include in two embodiments a Radial Phase Grating (RPG) and Proximity Effect Polarization Analyzers (PEPA). A test reticle design includes multiple polarimeters with an array of pinholes on the backside of the photomask. This technique is able to monitor any arbitrary illumination scheme for a particular tool.

Phase-shifting test mask patterns for characterizing illumination polarization balance in image forming optical systems

Aberrations in a lens and lens system are identified by projecting an optical beam through a mask having an opening (probe) and a surrounding open geometry (pattern) and through the lens to an image plane. Lens aberrations are identified from the combined intensity of the beam in the image plane. In one embodiment the pattern is a plurality of rings concentric with the probe. Spillover between the probe and the geometry becomes intermixed in passing through the lens and alters the light intensity in the image plane. Vision of a patient can be tested by providing a plurality of probe openings and surrounding geometries that are illuminated. The patient then compares the images for brighter and darker probes as a measure of pupil aberrations. Areas in an integrated circuit mask layout impacted by aberrations in projection printing can be identified by sequentially comparing an aberration function to a mask layout, which can then be used to modify the mask layout.

Characterizing aberrations in an imaging lens and applications to visual testing and integrated circuit mask analysis

A method for enhancing resist sensitivity and resolution based on influencing the effects of photoacid drift and diffusion by an externally applied electric field that may optionally include a direct current offset bias is disclosed. An electric field applied to the resist film during post exposure bake (PEB) enhances photoacid drift in the direction of the applied electric field, reduces bake time, and results in less undesired diffusion. Electric-field enhanced PEB can reduce PEB time by about 30%, and at the same time, improve the sharpness of 2D corners and increase the verticality of resist sidewalls. Electric-field-enhanced PEB also significantly improves the tolerance of over-exposure and provides better critical dimension control. It is estimated that the lateral acid diffusion length is reduced by about 50%. An apparatus for carrying out the aforementioned method is also provided.

Method and apparatus for enhancing resist sensitivity and resolution by application of an alternating electric field during post-exposure bake

A method for making a mask for optical lithography or other projection printing, wherein the mask is represented by a mask pattern, is disclosed herein. The mask provides a substantially binary output image on the surface of a wafer as light is applied to the mask. Light passes through the mask and onto a wafer at varying intensities, such intensities represented by output intensity values, the threshold values of which produce output images within predetermined constraints. The method includes the steps of defining sampling points which are representative of the binary output image. These sampling points are used in defining local objective functions, which are combined to give a total objective function. The present invention further includes the steps of adjusting the mask pattern to provide for minimization by optimization of the objective function, transferring the mask pattern to a mask generating machine to generate a mask, and generating a mask. Moreover, the present invention includes the step of providing an output image which is focused on a plurality of optical planes. Furthermore, the present invention includes the step isolating three of the plurality of optical planes so that their output intensity is optimized at these planes, thereby producing a focusing plane shift at the center focal plane as well as producing an extended depth of focus.

Growing community of inventors

Berkeley, CA, United States of America

Andrew R Neureuther