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Phase Shift Transfer layer Repair Process

IP.com Disclosure Number: IPCOM000014676D
Original Publication Date: 2000-Nov-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Abstract

Title of disclosure (in English) Phase Shift Transfer layer Repair Process Idea of disclosure Phase shift masks (PSM) require a transfer layer pattern typically in chrome. This chrome layer is transcribed into the underlying film by an isotropic wet etch or an anisotropic dry etch process. Presently any defects seen in the chrome film are left for repair at a latter time due to selectivity issues with the etch process. Currently if chrome defects are ablated the underlying PSM material is also removed. Subsequently if the remaining PSM is etched, the exposed quartz is also etched, and a phase pit in the quartz is created. The solution to this problem lies in the reduction of power in the ablation process and the layered removal of the patterning material. This layering removal effect is created by the use of a short pulsed, femtosecond duration, laser. The pulse length is in the range of 100 femtoseconds and delivers approximately 10 micro joules of energy per pulse to the chrome surface. This pulse can be repeated to allow only the removal of the chrome. By removing only the chrome portion of the defect the underlying PSM material remains and prevents exposure of quartz. This process also maintains the underlying transmission of light of the PSM material and has been shown via the Aerial Image Measurement System (AIMS, MS-100) to remove all chrome at the defect. This AIMS system emulates a wafer stepper system by considering the actual exposure wavelength and the lens parameters used and gives the measurement of the impact of the repair to the chips final performance. AIMS traces of the repaired chrome transfer layer indicate a good match to the transmission (T%) at approx. 6-7% at 248nm wavelength of the underlying PSM material

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Phase Shift Transfer layer Repair Process

Title of disclosure (in English)

Phase Shift Transfer layer Repair Process

Idea of disclosure

Phase shift masks (PSM) require a transfer layer pattern typically in chrome. This chrome layer is transcribed into the underlying film by an isotropic wet etch or an anisotropic dry etch process. Presently any defects seen in the chrome film are left for repair at a latter time due to selectivity issues with the etch process. Currently if chrome defects are ablated the underlying PSM material is also removed. Subsequently if the remaining PSM is etched, the exposed quartz is also etched, and a phase pit in the quartz is created. The solution to this problem lies in the reduction of power in the ablation process and the layered removal of the patterning material. This layering removal effect is created by the use of a short pulsed, femtosecond duration, laser. The pulse length is in the range of 100 femtoseconds and delivers approximately 10 micro joules of energy per pulse to the chrome surface. This pulse can be repeated to allow only the removal of the chrome. By removing only the chrome portion of the defect the underlying PSM material remains and prevents exposure of quartz. This process also maintains the underlying transmission of light of the PSM material and has been shown via the Aerial Image Measurement System (AIMS, MS-100) to remove all chrome at the defect. This AIMS system emulates a wafer stepper system by conside...