Taylor Hobson Limited

Rank Taylor Hobson

Daniel Ian Mansfield

Ivor McDonnell

Andrew Douglas Bankhead

Ian K Buehring

Paul James Scott

Jennifer Harding

Ian Bell

A method of determining a correction parameter for use in effecting alignment of a component of a metrological apparatus in at least one direction is described which includes: positioning an artefact on a support surface of a turntable of the metrological apparatus so that a measurement surface of the artefact is asymmetric with respect to a rotation axis of the turntable in the at least one direction; using a measurement probe of the measurement instrument to make a first measurement of the measurement surface; rotating the turntable; using the measurement probe of the measurement instrument to make a second measurement of the measurement surface after rotation of the turntable; and determining a correction parameter from the first and second measurements.

Surface measurement instrument and method

Light reflected by a sample surface region and a reference surface interfere. A detector senses light intensity at intervals during relative movement along a scan path between the sample surface and the reference surface to provide a series of intensity values representing interference fringes. A data processor receives first intensity data including a first series of intensity values resulting from a measurement operation on a surface area of a substrate and second intensity data including a second series of intensity values resulting from a measurement operation on a surface area of a thin film structure. A gain is determined for each thin film of the thin film structure. Substrate and apparent thin film structure surface characteristics are determined on the basis of the first and second intensity data, respectively. The apparent thin film structure surface characteristic is modified using the substrate surface characteristic and the determined gain or gains.

Apparatus for and a method of determining surface characteristics

A surface measurement instrument for obtaining surface characteristic data of a sample surface is described. Relative movement between a reference surface and a sample support is caused to occur while a sensor senses light intensity at intervals along a scan path to provide a series of intensity values representing interference fringes produced by a region of a sample surface during said relative movement and from which series of intensity values surface characteristic data can be derived. The sample support is both translatable and tiltable in at least one direction perpendicular to a scan direction so that the sample support can be both tilted to cause the scan path to be normal to the sample surface region and translated to compensate for translation movement due to the tilting.

Surface measurement instrument

A coherence scanning interferometer carries out: a coherence scanning measurement operation on a surface area using a low numeric aperture objective so that the pitch of the surface structure elements is less that the spread of the point spread function at the surface to obtain structure surface intensity data; and a coherence scanning measurement operation on a non-structure surface area to obtain non-structure surface intensity data. A frequency transform ratio determiner determines a frequency transform ratio related to the ratio between the structure surface intensity data and the non-structure surface intensity data. A structure provider sets that frequency transform ratio equal to an expression representing the electric field at the image plane of the interferometer in terms of surface structure element size (height or depth) and width-to-pitch ratio and derives the surface structure element size and width-to-pitch ratio using the frequency transform ratio.

Light reflected by a sample surface region and a reference surface interfere. A detector senses light intensity at intervals during relative movement along a scan path between the sample surface and the reference surface to provide a series of intensity values representing interference fringes. A data processor receives first intensity data comprising a first series of intensity values resulting from a measurement operation on a surface area of a substrate and second intensity data including a second series of intensity values resulting from a measurement operation on a surface area of a thin film structure. A gain is determined for each thin film of the thin film structure. Substrate and apparent thin film structure surface characteristics are determined on the basis of the first and second intensity data, respectively. The apparent thin film structure surface characteristic is modified using the substrate surface characteristic and the determined gain or gains.

A coherence scanning interferometer () carries out: a coherence scanning measurement operation on a surface area () carrying a structure using a low numeric aperture objective so that the pitch of the surface structure elements () is much less that the spread of the point spread function at the surface () to obtain structure surface intensity data; and a coherence scanning measurement operation on a non-structure surface area (), which may be part of the same sample or a different sample, to obtain non-structure surface intensity data. A frequency transform ratio determiner () determines a frequency transform ratio (the HCF function) related to the ratio between the structure surface intensity data and the non-structure surface intensity data. A structure provider () sets that frequency transform ratio equal to an expression which represents the electric field at the image plane of the coherence scanning interferometer in terms of surface structure element size (height or depth) and width-to-pitch ratio and derives the surface structure element size and width-to-pitch ratio using the frequency transform ratio. The structure provider () may also extract the surface structure element width, if the pitch is independently known.

A surface measurement instrument () for obtaining surface characteristic data of a sample surface () is described. Relative movement between a reference surface () and a sample support () is caused to occur while a sensor () senses light intensity at intervals along a scan path (SP) to provide a series of intensity values representing interference fringes produced by a region of a sample surface () during said relative movement and from which series of intensity values surface characteristic data can be derived. The sample support () is both translatable and tiltable in at least one direction perpendicular to a scan direction so that the sample support () can be both tilted to cause the scan path (SP) to be normal to the sample surface region and translated to compensate for translation movement due to the tilting.

In respective measurement operations on a first sample surface area having a layer structure () and a characterized second sample surface area (), light reflected by the region of the sample surface and the reference surface interfere and a sensing device () senses light intensity representing interference fringes at intervals during the relative movement along a measurement scan path to provide first intensity data in the form of a first series of intensity values resulting from a measurement operation on the first sample surface area and second intensity data in the form of a second series of intensity values resulting from a measurement operation on the second sample surface area. A layer structure determiner () determines a frequency transform ratio corresponding to a ratio between the first and second intensity data and fits a layer structure model having variable model parameters related to the layer thicknesses and refractive indices of the layers of a layer structure to the determined ratio by adjusting the model parameters, thereby obtaining for the model parameters values representing the layer thicknesses and refractive indices of the layers of the sample layer structure.

Apparatus for and a method of determining a characteristic of a layer or layers

An interferometer system () directs light along a sample path (SP) towards a sample surface () and along a reference path (RP) towards a reference surface (). Light reflected by a sample surface region and by the reference surface interfere. Sensing elements (SE) sense interference fringes at intervals along a scan path to provide a set of intensity data. A coherence peak position determiner () determines from the intensity data set a position on the scan path that corresponds to the height of the surface region. An amplitude determiner () determines amplitude data representing the amplitude of the intensity data at the determined height position. A modified surface height calculator () calculates modified height data by modifying the height data by a correction factor determined using the corresponding amplitude data and a correction parameter provided by a correction parameter provider ().

Interferometer system for and a method of determining a surface characteristic by modifying surface height data using corresponding amplitude data

Probe measurement apparatus using a curved grating displacement

Apparatus for measuring surface roughness utilizes diffraction patterns derived from the surface under test. The energies in the different orders are detected and processed utilizing various different algorithms dependent upon a number of factors such as the number of orders in the diffraction pattern and asymmetry in the diffraction pattern. Various filter functions both for the diffraction pattern itself and for values of surface roughness after measurement are disclosed. One algorithm for measuring surface roughness involves comparison of values representing the energy orders with reference values, preferably reference values obtained by an interpolation operation between one set of reference values representative of a diffraction pattern from a symmetrical surface and another set representative of a diffraction pattern from an asymmetrical surface.

Apparatus and method using optical diffraction to measure surface

A thermal imager having an array of sprite detectors is provided with a novel means for reducing or eliminating lininess in the reproduced image. This means comprises a low pass optical filter which cuts out wavelengths above 11.5 microns and adjustable gain buffer amplifiers in the respective channels. It is found that with the use of the optical filter the gains of the buffer amplifiers may be preset, when setting up the apparatus, to eliminate lininess and it is not necessary to include complex and noisy circuitry for continuously monitoring the signals output by the detectors and then applying appropriate corrections to the individual channels during operation of the apparatus, as in the prior art.

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Leicester, United Kingdom

Daniel Ian Mansfield