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For the introduction of EUV lithography, development of high performance EUV resists is of key importance. This development involves studies into resist sensitivity, resolving power and pattern uniformity. We have used a subnanometer-sized 30 keV helium ion beam to expose chemically amplified (CAR) EUV resists. There are similarities in the response of resists to He + ions and EUV photons: both excite Secondary Electrons with similar energy distributions. The weak backscattering of the He + ions results in ultra-low proximity effects. This fact enables the exposure of dense and detailed patterns by focused He + ion beams without the need for proximity correction. This paper presents contact holes and lines at 40-nm pitch in an EUV CAR resist. We have used resist sensitivity, contrast, resolution (CD) and pattern fidelity (LCDU, LWR and dose-to-print) as metrics for a comparison of SHIBL with EUVL. We show that Scanning Helium Ion Beam Lithography (SHIBL) can be a useful and economically attractive technology to (pre-)screen novel EUV resists prior to their final performance evaluation in an EUV scanner.

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Although Helium Ion Microscopy (HIM) was introduced only a few years ago, many new application fields are budding. The connecting factor between these novel applications is the unique interaction of the primary helium ion beam with the sample material at and just below its surface. In particular, the HIM secondary electron (SE) signal stems from an area that is very well localized around the point of incidence of the primary beam. This makes the HIM well-suited for both high-resolution imaging as well as high resolution nanofabrication. Another advantage in nanofabrication is the low ion backscattering fraction, leading to a weak proximity effect. The lack of a quantitative materials analysis mode (like EDX in Scanning Electron Microscopy, SEM) and a relatively low beam current as compared to the SEM and the Gallium Focused Ion Beam are the present drawbacks of the HIM.

Evaluations of CD-metrology tools usually focus on resolution, repeatability and accuracy. These are traditional metrics which relate to the capability to measure a local line width. These metrics do not cover the capability to map the CD fingerprint (uniformity map) of the wafer and scanner field, which are essential for sub-100nm lithography process control. In this study, CD-uniformity wafers of state-of-the-art step-and-scan systems were measured with different metrology tools. Analysis of the results revealed a random contribution that could not be attributed to the exposure tool or to the repeatability of the metrology tool. A test and analysis method was developed to separate out this random contribution from the test results. The level of this random CD variation, called the Total Test Repeatability (TTR), is proposed here as a new metric to compare CD-metrology tools in their capability to generate CD uniformity maps. The method was applied to study CD-SEM, Electrical Line width Measurements and CD-scatterometry. In general, the TTR appears to be much larger than the metrology tool repeatability. As such it is an important figure of merit for CD metrology tools used to reveal fingerprints of reticles, exposure tools or processing tools. The TTR is dependent on the metrology tool, measurement algorithm, but also on materials and processing flow and conditions. Some root causes have been identified, such as the wafer resistivity properties for ELM or line width roughness that appears as CD variation in CD-SEM tools. Modifications can be made in the metrology strategy to suppress the TTR and reveal more reliable CDuniformity fingerprints.