Phase-shift mask

About: Phase-shift mask is a research topic. Over the lifetime, 2088 publications have been published within this topic receiving 18058 citations.

Dense only phase-shift template lithography

Abstract: The steady move towards feature sizes ever deeper in the subwavelength regime has necessitated the increased use of aggressive resolution enhancement techniques (RET) in optical lithography. The use of ever more complex RET methods including strong phase shift masks and complex OPC has led to an alarming increase in the cost of photomasks, which cannot be amortized by many types of semiconductor applications. This paper reviews an alternative RET approach, dense template phase shift lithography, that can substantially reduce the cost of optical RET. The use of simple dense grating templates can also eliminate serious problems encountered in subwavelength lithography including optical proximity and spatial frequency effects. We show that, despite additional design rule restrictions and the use of multiple exposures per critical level, this type of lithography approach can make economic sense depending on the number of wafers produced per critical photomask.

High-transmission attenuated PSM: benefits and limitations through a validation study of 33%, 20%, and 6% transmission masks

Abstract: Simulations indicate high transmission attenuated phase shift mask to improve resolution, reduce line end shortening, corner rounding and provide process window enhancements for some pitches. They also indicate that as the transmission is increased for line feature, the Normalized image log slope increases for all pitches. In this work the performance of 33 percent and 20 percent attenuated masks has been compared against 6 percent and binary masks. Imaging results were obtained for 160nm features at various pitches with a 0.6NA 248nm SVGL MSIII with conventional and annular illumination. Performance of high transmission in terms of Depth of Focus, overlapping process windows, exposure latitude and proximity effects with the various percent transmissions. Critical issues such as manufacturing of tri-tone masks, inspection, repair and material availability for high transmission masks will be addressed.

Method for pattern defect correction of a photomask

Abstract: A pattern defect correction method of a photomask includes the steps of directing a focused ion beam to scan a small region including a pattern defect after a planarization film is formed on a region including a pattern defect of a phase shift mask to etch the small region. By monitoring a change in the intensity of a secondary signal, the end of an etching process is detected, followed by removal of the planarization film. According to this method, a pattern defect of a phase shift mask which is used in manufacturing an LSI can be corrected in high precision.

Electrical CD characterisation of binary and alternating aperture phase shifting masks

Abstract: Many of the recent advances in optical lithography have been driven by the utilisation of complex photomasks using Optical Proximity Correction (OPC) or phase shifting technologies. These masks are difficult and expensive to manufacture so the ability to test and characterise the mask making process is very important. This paper examines the issues involved in the use of relatively low cost Electrical Critical Dimension (ECD) measurement of mask features. Modified cross-bridge test structures have been designed to allow the on-mask measurement of dense and isolated, binary and phase shifted layouts. The results of electrical and Critical Dimension Scanning Electron Microscope (CD-SEM) testing of these structures are presented and indicate the lower variability associated with ECD measurements. In particular the adverse effect of phase shifting elements on the accuracy of SEM measurements is highlighted.

Phase shift mask and its inspection method

Abstract: A periodic line and space pattern made of chromium film is formed on a glass substrate, and a phase shifter is arranged on every other transparent portion of the line and space pattern. Using a stepper and the phase shift mask, photoresist film coated on a wafer is exposed several times to light of i-line by varying the focus, then developed. Next, the width Ws of the photoresist pattern formed by the exposure to the light through the phase shifter, and the width Wo of the photoresist pattern formed by the exposure to the light without passing through the phase shifter are measured. Based on the relation between Ws and Wo for defocusing, the transmittance error and the phase shift angle error of the phase shifter are obtained.