Mask inspection

About: Mask inspection is a research topic. Over the lifetime, 1072 publications have been published within this topic receiving 8696 citations.

E-beam inspection of EUV mask defects: To etch or not to etch?

Abstract: EUV Lithography is aimed to be inserted into mainstream production for sub-20nm pattern fabrication Unlike conventional optical lithography, frequent defectivity monitors (adders, repeaters etc) are required in EUV lithography Due to sub-20nm pattern and defect dimensions e-beam inspection of critical pattern areas is essential for yield monitor In previous work we showed sub-10nm defect detection sensitivity 1 on patterned resist wafers In this work we report 8-10× improvement in scan rates of etched patterns compared to resist patterns without loss in defect detection sensitivity We observed good etch transfer of sub-10nm resist features A combination of smart scan strategies with improved etched pattern scan rates can further improve throughput of e-beam inspection An EUV programmed defect mask with Line/Space, Contact patterns was used to evaluate printability of defects and defect detection (Die-Die and Die-Database) capability of the e-beam inspection tool Defect inspection tool parameters such as averaging, threshold value were varied to assess its detection capability and were compared to previously obtained results on resist patterns

Evaluation of novel EUV mask inspection technologies

Abstract: EUV lithography is regarded as the leading technology solution for the post-ArF era. Significant progress was made in recent years in closing the gaps related to scanner technology. This progress rendered EUV mask defectivity and related infrastructure as the primary risk for EUV lithography. The smallness of mask features, the novel defectivity mechanisms associated with the multilayer reflecting coating, and the stringent constraints on both multilayer and pattern imposed by the EUV wavelength - present a major challenge to current inspection technology, which constitutes a predominant gap to EUVL production-worthiness. Here we present results from an evaluation of a DUV mask inspection system and e-beam mask inspection technology on EUV masks. On this 193nm DUV system, we studied sensitivity and contrast enhancements by resolution enhancement techniques. We studied both pattern and blank inspection. Next, we studied image formation and performance of e-beam mask inspection technology for patterned mask defects. We discuss the advantages and roadmap of DUV and EBI mask inspection solutions for blank and patterned masks.

Microscopic imaging system and procedure for the emulation of a high aperture imaging system, in particular for mask inspection

Abstract: A microscope imaging system for emulating high-aperture-type imaging systems has an imaging lens (2), a detector and an evaluating device. A beam splitter (3) with effective polarization fits optionally in an illuminating beam path for generating different polarization conditions for illuminating radiation and/or in an imaging beam path for different polarization parts of imaging radiation. An independent claim is also included for a method for emulating high-aperture-type imaging systems, especially for inspecting masks, with an imaging lens, a detector and an evaluating device.

Evaluation of novel projection electron microscopy (PEM) optics for EUV mask inspection

Abstract: In order to achieve inspection sensitivity and a attainability for 1× node, a projection electron microscopy (PEM) system is employed that enables us to do high-speed/ high-resolution inspection that is not possible with the conventional DUV and EB inspection systems. By selecting a higher electron energy in imaging using Electron Optics (EO) exposure, and by applying a newly designed model to the basic PEM optics model, we have minimized the aberration in imaging that occurs when working with EO; and we have improved the related transmittance of such a system. The experimental result by showing designs for the improved transmittance, is obtained by making electron throughput measurement.

Automatic classification of blank substrate defects

Abstract: Mask preparation stages are crucial in mask manufacturing, since this mask is to later act as a template for considerable number of dies on wafer. Defects on the initial blank substrate, and subsequent cleaned and coated substrates, can have a profound impact on the usability of the finished mask. This emphasizes the need for early and accurate identification of blank substrate defects and the risk they pose to the patterned reticle. While Automatic Defect Classification (ADC) is a well-developed technology for inspection and analysis of defects on patterned wafers and masks in the semiconductors industry, ADC for mask blanks is still in the early stages of adoption and development. Calibre ADC is a powerful analysis tool for fast, accurate, consistent and automatic classification of defects on mask blanks. Accurate, automated classification of mask blanks leads to better usability of blanks by enabling defect avoidance technologies during mask writing. Detailed information on blank defects can help to select appropriate job-decks to be written on the mask by defect avoidance tools [1][4][5]. Smart algorithms separate critical defects from the potentially large number of non-critical defects or false defects detected at various stages during mask blank preparation. Mechanisms used by Calibre ADC to identify and characterize defects include defect location and size, signal polarity (dark, bright) in both transmitted and reflected review images, distinguishing defect signals from background noise in defect images. The Calibre ADC engine then uses a decision tree to translate this information into a defect classification code. Using this automated process improves classification accuracy, repeatability and speed, while avoiding the subjectivity of human judgment compared to the alternative of manual defect classification by trained personnel [2]. This paper focuses on the results from the evaluation of Automatic Defect Classification (ADC) product at MP Mask Technology Center (MPMask). The Calibre ADC tool was qualified on production mask blanks against the manual classification. The classification accuracy of ADC is greater than 95% for critical defects with an overall accuracy of 90%. The sensitivity to weak defect signals and locating the defect in the images is a challenge we are resolving. The performance of the tool has been demonstrated on multiple mask types and is ready for deployment in full volume mask manufacturing production flow. Implementation of Calibre ADC is estimated to reduce the misclassification of critical defects by 60-80%.