FAQ

Q: Is the beam diameter determined in one coordinate?
A: The beam size is determined in two directions - x and y, parallel to the gratings on the silicon. If the beam is astigmatic in other directions, the software will give the projections of the beam size in the x and y axes.

Q: How many images are needed to extract the beam size?
A: Only one image is needed.

Q: Which beam size is displayed by the software - FWHM or sigma of a Gaussian beam?
A: The software displays FWHM - Full Width at Half Magnitude.

Q: What is the format of images suitable for BEAMETR?
A: bmp, jpg, and tiff formats are supported.

Q: Why is the commonly used knife edge method not accurate?
A: The widely used knife edge method is good for beam sizes of 100 nm and larger. As the beam size gets smaller, a spike at the edge due to secondary emissions becomes more pronounced. This brings uncertainty into determining the beam size and makes the method highly dependent on the operator. The noise in the edge signal adds volatility.

Knife edge method procedure
Ideal

Actual edge profile obtained using electron beam

Actual

In addition, there is one more fundamental factor: many people believe that the derivative of the edge signal is the shape of the beam, which is not true even for large beam sizes. The beam is normally round or elliptical. The signal of the edge is a convolution of the beam shape with a semi-plane, not with a variable aperture around the beam. This makes the signal derivative a more complex function than just the beam shape.

Q: What type of SEM image is needed for BEAMETR?
A: BEAMETR can work with any SEM image - backscattered, true secondary, and a mixture of both. The method depends on the image, not the method behind obtaining that image.

Q: What do you actually measure - beam size or image resolution?
A: The beam size is normally the biggest factor in image resolution. The software determines the image resolution, and at the same time the BEAMETR algorithm partially filters out image deterioration factors such as noise and jitter in order to extract the beam size more accurately.

Q: Is contamination of a sample a big issue?
A: We have not heard about customers experiencing contamination as a serious problem. In any case, additional patterns can be purchased separately as consumables, or the pattern can be cleaned.

Q: What material is the pattern made of?
A: The pattern in version 1.6 is a 30 nm thick gold grating on monocrystal silicon. These materials provide high contrast at all beam voltages.

Q: What range of beam sizes can be measured using BEAMETR?
A: Beams ranging from 4 nm to 130 nm in diameter can be measured.

Q: Do you have plans to extend the range of the beam size that can be measured?
A: The company is constantly working on improvements of the algorithms and extending the range of beam sizes that can be measured.

Q: We need a different type of pattern. Can it be done?
A: Custom patterns can be fabricated on request.

Q: Can this method be used to measure beams other than electron beams?
A: Absolutely. As long as an image of the pattern can be made using any other beam - laser, atomic, ion beam - the beam size can be determined.

Q: Where can I find more information about BEAMETR?
A: S. Babin, M. Gaevski, D. Joy, M. Machin, A. Martynov, "Technique to automatically measure electron-beam diameter and astigmatism: BEAMETR", J.Vac.Sci.Technol. B6, 2006, p. 2956-2959

Q: What is actually needed from an operator to measure the beam size using BEAMETR?
A: Install the BEAMETR nano-pattern into your e-beam system, take an image of it, and start the BEAMETR software. That is it. The software will automatically determine the beam size.

Automatic beam size detection