Potentials for high pressure/environmental SEM microscopy for photomask dimensional metrology

Postek, Michael T.; Vladár, András; Rice, T; Knowles, R

doi:10.1117/12.488115

Cited by 12 publications

(2 citation statements)

References 10 publications

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“…These instruments are optimized for throughput and not resolution. In a recent paper, Postek et al (2003) showed that in laboratory instrumentation a similar detail at high accelerating voltage can be obtained; however, charging is still possible, even at the low accelerating voltages employed. Figure 5 shows a segment of a 250 nm nominal chromium line at about 140 Pa (1.1 torr) and 9 kV accelerating voltage.…”

Section: Photomask Imagingmentioning

confidence: 99%

New application of variable‐pressure/environmental microscopy to semiconductor inspection and metrology

Postek

Vladár

2004

Scanning

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Summary: Variable-pressure/environmental scanning electron microscopy has been used for successful investigation binary and phase-shifting chromium on quartz optical photomasks. This methodology was also applied to patterned 193 nm photoresist structures. The application of this methodology to semiconductor metrology is new because of the recent availability of variable-pressure scanning electron microscopy (SEM) instrumentation equipped with high-resolution, high-signal, thermally assisted field emission technology in conjunction with large chamber and sample transfer capabilities. The variable-pressure SEM methodology employs a gaseous environment around the sample to help diminish the charge build-up that occurs under irradiation with the electron beam. Although very desirable for the charge reduction in many biological, pharmaceutical, and food applications, this methodology has not been employed for semiconductor photomask or wafer metrology until now. This is a new application of this technology to this area, and it shows great promise in inspection, imaging, and metrology in a charge-free operational mode. For accurate metrology, variable-pressure SEM methodology also affords a path that minimizes, if not eliminates, the need for charge modeling. This paper presents some of the early results in the variable-pressure SEM metrology of photomask and photoresist structures.

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Section: Photomask Imagingmentioning

confidence: 99%

New application of variable‐pressure/environmental microscopy to semiconductor inspection and metrology

Postek

Vladár

2004

Scanning

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“…Photomasks can be very difficult to image in the SEM due to charge build-up in the quartz. Postek et al (2003) successfully used variable pressure SEM to dissipate the charge build-up for the imaging and metrology of chromium photomasks [28]. However, as shown in Figure 10, the HIM can also be successfully employed in the imaging and metrology of these samples.…”

Section: Charge Reductionmentioning

confidence: 99%

Understanding Imaging and Metrology with the Helium Ion Microscope

Postek¹,

Vladár²,

Ming³

2009

AIP Conference Proceedings

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Abstract. One barrier to innovation confronting all phases of nanotechnology is the lack of accurate metrology for the characterization of nanomaterials. Ultra-high resolution microscopy is a key technology needed to achieve this goal. But, current microscope technology is being pushed to its limits. The scanning and transmission electron microscopes have incrementally improved in performance and other scanned probe technologies such as atomic force microscopy, scanning tunneling microscopy and focused ion beam microscopes have all been applied to nanotechnology with various levels of success. A relatively new tool for nanotechnology is the scanning helium ion microscope (HIM). The HIM is a new complementary imaging and metrology technology for nanotechnology which may be able to push the current resolution barrier lower. But, successful imaging and metrology with this instrument entails new ion beam/specimen interaction physics which must be fully understood. As a new methodology, HIM is beginning to show promise and the abundance of potentially advantageous applications for nanotechnology have yet to be fully exploited. This presentation will discuss some of the progress made at NIST in understanding the science behind this new technique.

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Modeling of imaging processes in the low‐vacuum SEM

Thiel

2005

Surface & Interface Analysis

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The presence of a gas in the specimen chamber of low-vacuum scanning electron microscopes (SEMs) gives rise to a number of interactions that are not found in their high-vacuum counterparts. Many of these interactions are integral to the specimen charge neutralizing capabilities of these instruments. However, these interactions, and the electronic charge state of the specimen, give rise to a number of processes that influence, and sometimes even dominate, secondary electron contrast. As many of the processes are stochastic in nature, and depend on discrete interactions between electrons, gaseous ions, neutral molecules, and the specimen surface, modeling can offer important insights for contrast interpretation. This paper discusses these interactions and the mechanisms through which contrast is influenced. Copyright MODELING OF IMAGING PROCESSES IN THE LOW-VACUUM SEMLow-vacuum scanning electron microscopy is emerging as a powerful new technique for the study of poorly conducting materials and other difficult samples.1 -3 Because of these attributes, it is also being considered as a candidate for the next generation of sub-10 nm critical dimension metrology tools for the semiconductor manufacturing industry. 4,5 Widespread acceptance of the technique is hindered because the image formation process is considerably more complicated than in high-vacuum scanning electron microscopes (SEMs). Interactions between electrons and gas molecules, as well as the behavior of positive gaseous ions, all influence the appearance and information content of secondary electron (SE) images. Furthermore, SE images obtained from dielectric materials appear to contain more information than their high-vacuum counterparts, related to the local dielectric properties of the material. 3,6 Considerable work needs to be done before it will be possible to make routine interpretations of the SE contrast. Many of the processes that influence the information content of SE images have complicated nonlinear interdependencies, which make simple analytic descriptions unlikely. The situation is exacerbated by the commercial introduction of detectors with increasingly complicated physical and electromagnetic field geometries. However, since many of the processes are stochastic in nature, computer modeling can offer insights. The processes that contribute to image formation can be divided into three categories: cascade amplification/ion production, intrinsic SE emission from dielectrics, and modulation of SE emissions by the gaseous ions. Most commercial low-vacuum SEMs use some degree of gas cascade amplification to amplify the secondary electron emission current, regardless of the form of the signal that is actually measured. Another critical function of the cascade is to produce a flux of positive ions sufficient to stabilize electronic charging of insulating samples. In its simplest form, the gas cascade is manipulated by placing a positively biased anode (typically a few hundred volts positive) in the vicinity of the specimen. Secondary electrons ...

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Potentials for high pressure/environmental SEM microscopy for photomask dimensional metrology

Cited by 12 publications

References 10 publications

New application of variable‐pressure/environmental microscopy to semiconductor inspection and metrology

New application of variable‐pressure/environmental microscopy to semiconductor inspection and metrology

Understanding Imaging and Metrology with the Helium Ion Microscope

Modeling of imaging processes in the low‐vacuum SEM

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