News Column

Patent Issued for Octopole Device and Method for Spot Size Improvement

September 12, 2014



By a News Reporter-Staff News Editor at Health & Medicine Week -- ICT Integrated Circuit Testing Gesellschaft fur Halbleiterpruftechnik mbH (Heimstetten, DE) has been issued patent number 8816270, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also ICT Integrated Circuit Testing Gesellschaft fur Halbleiterpruftechnik mbH).

The patent's inventors are Kramer, Aleksandra (Munich, DE); Lanio, Stefan (Erding, DE).

This patent was filed on October 30, 2012 and was published online on August 26, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Charged particle beam apparatuses have many functions in a plurality of industrial fields, including, but not limited to, inspection of semiconductor devices during manufacturing, exposure systems for lithography, detecting devices and testing systems. Thus, there is a high demand for structuring and inspecting specimens within the micrometer and nanometer scale.

"Micrometer and nanometer scale process control, inspection or structuring, is often done with charged particle beams, e.g., electron beams, which are generated and focused in charged particle beam devices, such as electron microscopes or electron beam pattern generators. Charged particle beams offer superior spatial resolution compared to, e.g. photon beams due to their short wavelengths.

"Particle beam optical systems suffer from various types of imperfections, e.g. mechanical manufacturing imperfections, misalignment of optical components, material inhomogenities, imperfections of the electric and magnetic fields used for focusing, aligning and adjusting, electron optical aberrations, contaminations and charging of beam steering components. A good electron optical design aims at minimizing these imperfections by imposing strict tolerances on mechanical manufacturing, material properties and cleanliness and by optimizing the electron optical performance through proper design.

"However, with these measures alone the theoretical optical performance will not be obtainable. Therefore, a lot of devices and methods have been devised over the years which allow counteracting the influence of the above mentioned imperfections. Such devices can be, amongst others, dipole deflectors (to correct misalignment between components), quadrupole stigmators (to correct axial astigmatism in the image), heated sample holders and apertures (to avoid contamination and/or subsequent charging), in-situ plasma cleaning (to remove contaminations in the beam line), and the like.

"The above mentioned imperfections become more noticeable if resolution improves so that the spot deterioration becomes clearly visible, the beam leaves the paraxial region around the optical axis and experiences higher order aberrations, the beam current is increased, and/or the beam bundle diameter is increased, in order to reduce electron-electron interaction. This makes the beam more sensitive to higher order aberrations that deteriorate the diameter of the focused spot. Further, the above mentioned imperfections become more noticeable if the beam current in the system increases since this also increases the rate of contamination build-up that causes beam instabilities and spot size deterioration.

"These critical conditions are all fulfilled in modern electron beam inspection (EBI) columns. Accordingly, it is desirable to provide a device that compensates such influences that limit the performance of the high beam current system. This will improve resolution and make the system less sensitive to mechanical imperfections, contamination and contamination build-up over time since it provides a remedial measure. This would further assist in improving system performance and/or throughput, extending service intervals and lowering of cost of ownership."

Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "In light of the above, a method of compensating mechanical, magnetic and/or electrostatic inaccuracies in a scanning charged particle beam device and a scanning charged particle beam device as claimed are provided. Further aspects, advantages, and features of the present invention are apparent from the dependent claims, the description, and the accompanying drawings.

"According to one embodiment, a method of compensating mechanical, magnetic and/or electrostatic inaccuracies in a scanning charged particle beam device is provided. The method includes an alignment procedure, wherein the following steps are conducted: compensating 4-fold astigmatism with an element having at least 8-pole compensation capability, wherein the aligning and compensating steps of the alignment procedure act on the charged particle beam with beam dimensions in two orthogonal directions each of at least 50 .mu.m and coaxially aligned with at least the element having at least the 8-pole compensation capability.

"According to another embodiment, a scanning charged particle beam device is provided. The device includes an emitter with at least one emitter tip, one lens assembly configured for focusing the emitter tip on a specimen, the focusing assembly consists of a condenser lens assembly and an objective lens, wherein the condenser lens assembly and the objective lens are rotationally symmetric. The device further includes a compensation assembly for compensating mechanical, magnetic or electrostatic inaccuracies, wherein the compensation assembly comprises at least one element selected from the group consisting of: a first octopole element and a second octopole element acting in respective different directions, a rotatable octopole element; and an element being at least a 12-pole element.

"According to a further embodiment, a method of compensating mechanical, magnetic and/or electrostatic inaccuracies in a scanning charged particle beam device is provided. The method includes an alignment procedure, wherein the following steps are conducted in the below order: aligning a charged particle beam to be scanned over a specimen to an optical axis, compensating axial astigmatism with an element having at least 4-pole compensation capability, compensating 3-fold astigmatism with an element having at least 6-pole compensation capability, and compensating 4-fold astigmatism with an element having at least 8-pole compensation capability, wherein the aligning and compensating steps of the alignment procedure act on an the charged particle beam with beam dimensions in two orthogonal directions each of at least 50 .mu.m and coaxially aligned with at least the element having at least the 8-pole compensation capability.

"According to a yet further embodiment, a scanning charged particle beam device is provided. The device includes an emitter with at least one emitter tip, one lens assembly configured for focusing the emitter tip on a specimen, the focusing assembly consists of a condenser lens and an objective lens, a compensation assembly for compensating mechanical, magnetic or electrostatic inaccuracies, wherein the compensation assembly comprises at least one element selected from the group consisting of: a first octopole element and a second octopole element acting in respective different directions, a rotatable octopole element; and an element being at least a 12-pole element.

"Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method step. These method steps may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the invention are also directed at methods by which the described apparatus operates. It includes method steps for carrying out every function of the apparatus."

For the URL and additional information on this patent, see: Kramer, Aleksandra; Lanio, Stefan. Octopole Device and Method for Spot Size Improvement. U.S. Patent Number 8816270, filed October 30, 2012, and published online on August 26, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8816270.PN.&OS=PN/8816270RS=PN/8816270

Keywords for this news article include: Astigmatism, Eye Diseases, ICT Integrated Circuit Testing Gesellschaft fur Halbleiterpruftechnik mbH, Refractive Errors.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Health & Medicine Week


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