measurement errors and miniaturization

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|" P#E¢|S Measurement errors and each other as in most metrological D.J. Whitehouse, Micro- investigations, engineering Centre, Department of miniaturization 'The position of the centre and Engineering, University of Warwick, radius of the best-fit circle affect the Coventry, Warwickshire CV4 7AL, UK In a paper published in the assessment of eccentricity, concen- November 1983 issue of J. Phys. E: tricity, squareness, taper, cylin- Scientific Instruments 16 (11), 1076- dricity, sphericity and a multiplicity 1080, Professor David Whitehouse of parameters associated with circu- discusses the problem of errors lar features. It is as well to note that introduced into the measurement of 70% of all engineering parts contain form due to miniaturization. Increas- an axis of circular symmetry some- ingly, he points out, very high where.' dimensional and form tolerances Whitehouse breaks his problem are necessary to achieve the desired into three parts and in turn discus- performance in engineering applica- ses the theory of radius assessment, tions: the effect on eccentricity, and con- 'This used to be possible by centricity. A summary of his reason- specifying such things as positional ing is inappropriate and reading the t r..i error quite independently of the complete paper is recommended, error in form such as the out-of- but a final quote from the 'Conclu- ~1 roundness. However, as the compo- sions' is offered: ii nents get smaller it is becoming 'It seems highly likely that in the W impossible to divorce dimensional future the whole concept of splitting ~ error from form error and, more up a component into size, form and critically, form error from surface texture will have to be revised to ~+"~ texture.' deal with all the component as one The particular problem addres- geometrical entity evaluated from sed in the paper is that of measuring many data points. In some simple the centre of circular parts and cases this is now possible. Until it is roundness, and its associated general, in the transition period The MIG300 500]~ liquid metal ion parameters, which depends critically where conventional parameters are gun on the assessment of the position of being measred under more and the centre and radius of the best-fit more difficult conditions mainly circle from which to measure. This is brought about by miniaturization, it Etching with sub-micron not an insignificant problem, he is as well to know the nature and ion beams points out, because errors build on extent of the errors involved.' Microfocussed liquid metal ion guns produce intense and highly stable beams which can be used for micro- machining or surface analysis. The MIG300 gun from VG Scientific pro- duces an ion beam spot size variable down to less than 500 A. Ion ener- gies are in the range 1-30 keV with current densities up to 2 A.cm -2. The position of the beam is con- trolled using a digital electrostatic scan unit with manual or external computer control. The gun is available as a seper- ate item or as part of a complete ion beam system including sample manipulation, analysis, computer control and associated data proces- sing. Applications of the new gun include high resolution SIMS analysis, ion-beam machining and microfabrication, ion beam repair of optical or X-ray lithographic masks, ion implantation and ion beam resist exposure. A brochure describing the sources and their applications is Sub-micron ion beam etching: A game recorded on a micro-scale played available. with the MIG 300 using 30 kV Ga ÷ ions under computer control. Linewidths VG Scientific Limited, Imber- are approximately 4000 ]~. The ion-induced secondary electron image was horne Lane, East Grinstead, West obtained using the same beam Sussex RH19 1UB, UK PRECISION ENGINEERING 161

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Page 1: Measurement errors and miniaturization

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P#E¢|S Measurement errors and each other as in most metrological D.J. Whitehouse, Micro-

investigations, engineering Centre, Department of miniaturization 'The position of the centre and Engineering, University of Warwick,

radius of the best-fit circle affect the Coventry, Warwickshire CV4 7AL, UK In a paper published in the assessment of eccentricity, concen- November 1983 issue of J. Phys. E: tricity, squareness, taper, cylin- Scientific Instruments 16 (11), 1076- dricity, sphericity and a multiplicity 1080, Professor David Whitehouse of parameters associated with circu- discusses the problem of errors lar features. It is as well to note that introduced into the measurement of 70% of all engineering parts contain form due to miniaturization. Increas- an axis of circular symmetry some- ingly, he points out, very high where.' dimensional and form tolerances Whitehouse breaks his problem are necessary to achieve the desired into three parts and in turn discus- performance in engineering applica- ses the theory of radius assessment, tions: the effect on eccentricity, and con-

'This used to be possible by centricity. A summary of his reason- specifying such things as positional ing is inappropriate and reading the t

r.. i error quite independently of the complete paper is recommended, error in form such as the out-of- but a final quote from the 'Conclu- ~1 roundness. However, as the compo- sions' is offered: i i nents get smaller it is becoming 'It seems highly likely that in the W impossible to divorce dimensional future the whole concept of splitting ~ error from form error and, more up a component into size, form and critically, form error from surface texture will have to be revised to ~+"~ texture.' deal with all the component as one

The particular problem addres- geometrical entity evaluated from sed in the paper is that of measuring many data points. In some simple the centre of circular parts and cases this is now possible. Until it is roundness, and its associated general, in the transition period The MIG300 500]~ l iquid metal ion parameters, which depends critically where conventional parameters are gun on the assessment of the position of being measred under more and the centre and radius of the best-fit more difficult conditions mainly circle from which to measure. This is brought about by miniaturization, it Etching with sub-micron not an insignificant problem, he is as well to know the nature and ion beams points out, because errors build on extent of the errors involved.'

Microfocussed liquid metal ion guns produce intense and highly stable beams which can be used for micro- machining or surface analysis. The MIG300 gun from VG Scientific pro- duces an ion beam spot size variable down to less than 500 A. Ion ener- gies are in the range 1-30 keV with current densities up to 2 A.cm -2. The position of the beam is con- trolled using a digital electrostatic scan unit with manual or external computer control.

The gun is available as a seper- ate item or as part of a complete ion beam system including sample manipulation, analysis, computer control and associated data proces- sing. Applications of the new gun include high resolution SIMS analysis, ion-beam machining and microfabrication, ion beam repair of optical or X-ray lithographic masks, ion implantation and ion beam resist exposure. A brochure describing the sources and their applications is

Sub-micron ion beam etching: A game recorded on a micro-scale played available. with the MIG 300 using 30 kV Ga ÷ ions under computer control. Linewidths VG Scientific Limited, Imber- are approximately 4000 ]~. The ion-induced secondary electron image was horne Lane, East Grinstead, West obtained using the same beam Sussex RH19 1UB, UK

PRECISION ENGINEERING 161