Design and Evaluation of System Configurations for an EUV Mask Inspection Microscope

Abstract

This document is the third sub-report of the EUV AIM design study being conducted at LLNL on behalf of International Sematech (ISMT). The purpose of this study as identified in section 1.2 of the statement of work is to research the basic user requirements of an actinic defect characterization tool, potential design configurations and top-level specifications. The objectives of this design study specifically identified in section 1.3 of the statement of work were to: (1) Determine the user requirements of an actinic defect characterization tool; (2) Determine if an EUV AIM tool is an appropriate platform for actinic defect characterization; (3) Determine possible design configurations and top-level performance specifications; (4) Identify potential technical issues and risks of different technical approaches; (5) Provide estimates of cost relating to different technical approaches; and (6) Provide simulated performance for key subsystems and the entire system. The sub-sections of the study to be addressed were accordingly defined in the statement of work as being: (1) Formulation of top-level specifications; (2) Identification of system configurations suitable for meeting the top-level specifications; (3) Preliminary design of imaging systems; (4) Preliminary design of illumination systems; (5) Prediction and comparison of performance through aerial image calculation; (6) Identification of sub-system requirements; (7) Identification of potential vendors; (8) Estimation of system cost; (9) Identification of technical issues; and (10) Definition of technology transfer or development required. Points 1 and 2 have already been addressed in previous reports to ISMT. This document addresses points 3 to 7, and 9 to 10 of the above list--formulation of a preliminary design of the imaging and illumination systems and the evaluation and comparison of potential designs through aerial image analysis. As such this report should be read in conjunction with and in the context of the previous two reports which separately addressed points 1 and 2 above. Item 8, estimation of system cost, will be addressed in a separate confidential report to ISMT. A number of potential configurations for an EUV AIM tool have been studied and technical aspects of the design approaches investigated. The requirements for AIM mode of emulating stepper quality imaging have been spelt out and strategies developed for assessing the suitability of different approaches to satisfying the technical requirements for AIM mode. A synopsis of the approaches considered, and conclusions reached, is presented in Table 17 below. Preliminary designs of several system configurations have been performed, and for each approach potential technical risks have been identified; illumination and source requirements have been analyzed for each implementation and may factor into selection of technical approach. It is important to note that identification of risk or required development does not disqualify a particular approach, rather it serves to raise an issue which must be addressed in any proposal to build a tool.