Edges in CNC polishing: from mirror-segments towards semiconductors, paper 1: edges on processing the global surface

Walker, David D.; Yu, Guoyu; Li, Hongyu; Messelink, Wilhelmus A. C. M.; Evans, RA; Beaucamp, Anthony

doi:10.1364/oe.20.019787

Cited by 65 publications

(26 citation statements)

References 15 publications

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“…A series of papers on edge control in precessed bonnet polishing was recently published [8][9][10] These papers introduced a strategy of edge distortion minimization on segmented telescope mirrors by reducing the geometrical spot size in the vicinity of edges.…”

Section: Edge Control Characterizationmentioning

confidence: 99%

Corrective finishing of extreme ultraviolet photomask blanks by precessed bonnet polisher

2014

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The progressive transition from Excimer to extreme ultraviolet (EUV) lithography is driving a need for flatter and smoother photomask blanks. It is, however, proving difficult to meet the next-generation specification with the conventional chemical mechanical polishing technology commonly used for finishing photomask blanks. This paper reports on the application of subaperture computer numerical control precessed bonnet polishing technology to the corrective finishing of photomask substrates for EUV lithography. Full-factorial analysis was used to identify process parameters capable of delivering microroughness below 0.5 nm rms while retaining relatively high removal rates. Experimental results show that masks prepolished to 300-600 nm peak-to-valley (P-V) flatness by chemical/mechanical polishing can then be improved down to 50-100 nm P-V flatness using the automated technology described in this paper. A series of edge polishing experiments also hints at the possibility of increasing the quality area beyond the 142 mm square defined in the official EUV photomask specification.

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Section: Edge Control Characterizationmentioning

confidence: 99%

Corrective finishing of extreme ultraviolet photomask blanks by precessed bonnet polisher

2014

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“…We have described in a previous paper [10] an end-to-end process-chain for mirror segments, targeted at the E-ELT, as well as other applications such as semiconductor polishing. This work has provided evidence that a fast, cost-effective process for polishing of the bulk surface and edges, directly on precision-ground aspheric hexagons, is achievable.…”

Section: Introductionmentioning

confidence: 99%

Research on edge-control methods in CNC polishing

Walker

et al. 2017

J. Eur. Opt. Soc.-Rapid Publ.

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Background: We have developed edge-control for the Precessions TM process suitable for fast fabrication of large mirror segments, and other applications sensitive to edge mis-figure. This has been applied to processing of European extremely large telescope (E-ELT) prototype mirror-segments, meeting the specification on maximum edge mis-figure. However we have observed residuals that have proved impossible to correct with this approach, being in part the legacy of asymmetries in the input edge-profiles. Methods: We have therefore compared different proposed methods experimentally and theoretically and report here on a new edge-rectification step, which operates locally on edges, does not disturb the completed bulk area. Results: A new toolpath has been developed and experiments have been carried out to demonstrate that local edge rectification can be carried out. Conclusions: With this method, the residue error on edges can be removed separately and has potential to reduce total process time.

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“…Traditional opticians need to balance working parameters for various kinds of tools and workpieces to ensure a good clear aperture. Based on previous research results [6][7][8][9][10][11], the edge effect includes two parts:…”

Section: Introductionmentioning

confidence: 99%

Edge control in a computer controlled optical surfacing process using a heterocercal tool influence function

Hu¹,

Zhang²,

Ford³

et al. 2016

Opt. Express

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Edge effect is regarded as one of the most difficult technical issues in a computer controlled optical surfacing (CCOS) process. Traditional opticians have to even up the consequences of the two following cases. Operating CCOS in a large overhang condition affects the accuracy of material removal, while in a small overhang condition, it achieves a more accurate performance, but leaves a narrow rolled-up edge, which takes time and effort to remove. In order to control the edge residuals in the latter case, we present a new concept of the 'heterocercal' tool influence function (TIF). Generated from compound motion equipment, this type of TIF can 'transfer' the material removal from the inner place to the edge, meanwhile maintaining the high accuracy and efficiency of CCOS. We call it the 'heterocercal' TIF, because of the inspiration from the heterocercal tails of sharks, whose upper lobe provides most of the explosive power. The heterocercal TIF was theoretically analyzed, and physically realized in CCOS facilities. Experimental and simulation results showed good agreement. It enables significant control of the edge effect and convergence of entire surface errors in large tool-to-mirror size-ratio conditions. This improvement will largely help manufacturing efficiency in some extremely large optical system projects, like the tertiary mirror of the Thirty Meter Telescope. References and links1. V. Rupp, "The development of optical surfaces during the grinding process,"

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Edges in CNC polishing: from mirror-segments towards semiconductors, paper 1: edges on processing the global surface

Cited by 65 publications

References 15 publications

Corrective finishing of extreme ultraviolet photomask blanks by precessed bonnet polisher

Corrective finishing of extreme ultraviolet photomask blanks by precessed bonnet polisher

Research on edge-control methods in CNC polishing

Edge control in a computer controlled optical surfacing process using a heterocercal tool influence function

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