Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties
  • G01N21/211—Ellipsometry

Definitions

• the invention relates to a device and a method for measuring the amount, composition, and / or spatial distribution and dynamics of substances on substrates.
• Imaging techniques which detect an area of the surface spatially resolved are particularly interesting: Classically, the reflection, transmission, absorption, the scattered light or the phase shift are mapped. This can be done at one wavelength or spectrally resolved. An important parameter that can also be varied is the angle of incidence.
• an ellipsometer comprises at least means for exposing a sample to polarized light and means for measuring the light reflected or transmitted by the sample, in each case for s and p polarization. From this, the optical properties of the surface to be analyzed can be derived.
• TIR Total Internal Reflection
• a measuring device comprising a light source assembly, a total reflection assembly and a detection assembly is known from US 6594011 to Kempen.
• the surface with the substance to be measured is formed as a total reflection layer system.
• the surface on which the substance to be analyzed comes to lie is formed by an interface of two transparent layers, whose relative refractive indices are selected such that light which is coupled into a transparent layer above the so-called critical angle is applied to one the Grenz ⁇ surfaces, which forms the substance to be analyzed is totally reflected.
• the mechanisms of total reflection are well known to those skilled in the art.
• SPR surface plasmon
• the ellipsometer measures the ellipsometric parameters Psi and Delta.
• Psi is analogous to the measurement signal of the classical SPR method, while delta provides additional information and in particular can show a sharp resonance as a function of the angle of incidence.
• the disadvantage is that the substrate on the surface of which the plasmons are to be excited is metallic or at least have a metallic film.
• the use of metallic films is often disadvantageous in the application of bioanalyses because these films cause difficulties in production, especially as far as reproducibility is concerned. In particular, the lifetime of metallic films is often very limited.
• Light decoupling is chosen so that the range of multipath Total reflection corresponds to the resolution of the detector array.
• the layer thickness is chosen such that in the layer the light is repeatedly totally reflected before it emerges from the layer.
• the configuration of the total reflection system results in a multiple interaction between the evanescent field of the coupled-in light and the layer to be analyzed in a spatial area around each measuring point which corresponds to the resolution capability of the detection arrangement.
• Such an arrangement is familiar to the person skilled in the art as an asymmetrical waveguide.
• the coupling into such a waveguide is a typical optical resonance phenomenon.
• the described multiple total reflection is called waveguiding. Waveguide takes place only above a certain layer thickness and only for certain (resonance) angle.
• the associated propagation of light is referred to as waveguide modes.
• the asymmetric waveguide no longer undergoes any multiple total reflection, since no more mode is permitted.
• the path the light travels in the waveguide within a zigzag period corresponds to the inverse of the propagation constants.
• the cut-off thickness is 200nm. The light propagates just above the total reflection angle between the glass and the layer. In order to obtain twice total reflection at the outer interface, therefore, a propagation of more than 400 nm is needed. At 11 total reflections it is already 4 ⁇ m and limits the resolution to a very considerable extent.
• the device according to the invention comprises a resonance platform which is designed such that it enables the excitation of laterally localized resonances.
• This object is achieved by the fact that in the process a resonant platform is exposed to light with such parameters, which lead to the excitation of laterally localized resonances.
• the invention thus comprises a device for carrying out ellipsometry measurements, with an ellipsometer and a resonance platform, wherein means are provided on the resonance platform, by means of which laterally localized resonant modes can be excited when exposed to light from the ellipsometer.
• the means provided in the resonance platform may comprise a resonant grating whose grating period is of the order of the wavelength of the light which emits the light source of the ellipsometer.
• the resonance platform with the resonant grating may comprise a transparent substrate which is coated with at least one dielectric layer and the resonant grating is provided in this layer or at at least one of the boundary surface bounding this layer.
• the resonance platform in the device about an axis which is perpendicular to the surface of the resonance platform, relative to the plane of incidence of the light of the Eilipsometers is rotatably mounted and can be fixed in a rotated position.
• the device of the type described above may comprise an imaging ellipsometer.
• the following procedure can be used to measure the adsorption or desorption of substances on a surface:
• the position of the resonance curve on contact with the surface without the substance to be measured can be determined as a reference.
• the location of the reference curve can be determined locally. This opens up the possibility of processing the determined spatially resolved position data into an image.
• PSI indicates the ratio of the amplitude change of the s and p polarization after reflection
• DELTA the relative phase shift (delta) of the polarization components after reflection
• the method can be optimized by applying light to the excitation of latently localized modes.
• the device according to the invention and the method according to the invention will be discussed together below.
• SPRs surface plasmons
• any optical resonance is referred to which is not a plasmon resonance and which limits the resonant interaction with the surface essentially to a maximum of the order of magnitude of the classic total reflection associated with those skilled in the art - common Goos-Hänchen effect lies.
• the laterally localized resonance phenomena include, among others, the so-called evanescent resonance, which can be achieved, for example, by resonant gratings.
• the grating period is on the order of the light used to excite the resonance.
• the structures referred to in the English language literature as photonic band gap structures lead to extremely lossy and therefore localized modes in the propagation which have a high field at the surface, as described in detail in "Localization of One Photon States 1 " by C. Adlard , ER Pike Sarkar in Physical Review Letters, Vol. 79, No. 9, pages 1585-87 (1997).
• Some of the evanescent resonators exhibit abnormally high reflectance or transmittance at resonance.
• Such a structure with an abnormally high reflection is disclosed in patent application WO2001002839. It should be specifically noted that this structure is successfully used in the field of fluorescence analysis. Compared with the traditional waveguide structures, this lattice structure has the advantage that the light applied does not propagate near the high-index layer.
• other layer materials such as TiO 2, Nb 2 O 3 and others can be used with appropriately adapted parameters.
• nf 2.1
• other layer materials such as TiO 2, Nb 2 O 3 and others can be used with appropriately adapted parameters.
• nc 1.33
• the quotients necessary for calculating the quantities delta and psi can be well formed without disturbing any possible, for example, electronic background.
• the reflection for both TM and TE polarization in the angular range of 3.9 ° to 4.3 ° values is greater than 1%.
• the formation of the quotients TM / TE ensures that, for example, fluctuations in the light intensity are found out.
• special emphasis is placed on controlling the polarization.
• FIG. 3 again shows the same functions Psi and Delta for 4 different layer thicknesses (150 nm 150 nm and 150 nm and 151 nm).
• the thick lines correspond to the values for 150.lnm. As you can see a resolution of O.lnm and below is easily possible.
• a substrate according to the invention as described above can hereby be investigated in a spatially resolved and label-free manner with respect to adsorbed material. Since this is possible without contact, it is also possible to make dynamic measurements.
• Non-conical illumination denotes the exposure to light in which the plane of incidence is perpendicular to the bars, ie the grid vector lies in the plane of incidence. If the grating vector is turned out of the plane of incidence, it is called conical illumination.
• conical illumination can be used advantageously in the context of the invention.
• the resonance angle changes with the amount of the grating rotation angle, ie the angle amount by which the grating vector is rotated out of the plane of incidence.
• the Del ta gradient is limiting factor for the measurement accuracy.
• the table below gives the measured dependence of the delta slope on the lattice rotation angle. In the last column, this parameter translates into the sensitivity.
• the sensitivity achieved with the present invention is equal to that of a full SPR measurement.
• no complicated aids such as applying an electric field in the case of the tunable SPR sensor [Patent DE 100 19 359] are necessary.
• the use of a metal film is avoided.
• the disadvantage of metal films is that thiol must be used as an activator for the biological binding partners, and that the optical properties of gold films are not well reproducible. Handling is much simpler and faster without metal and without immersion oil.
• the parameters thickness, index, and extinction of the gold film on each sensor must be determined prior to kinetics, as these parameters generally vary across production batches. This problem does not exist with the resonant platform ; In comparison with the SPR, the resonance platform is therefore characterized by the fact that layer thicknesses on the Ta 2 O 5, for example in a reaction kinetics, are measured with less measurement effort and with higher accuracy.
• the recording of reaction kinetics in many channels simultaneously can be performed on the grating coupler as well as with imaging SPR on a SPR sensor.
• the change in delta during a change in layer thickness is recorded at a constant angle of incidence, and the layer thickness kinetics is determined therefrom.

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• General Physics & Mathematics (AREA)
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• Investigating Or Analysing Materials By Optical Means (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 2005
  • 2005-07-18 WO PCT/EP2005/007795 patent/WO2006008112A1/de not_active Application Discontinuation
  • 2005-07-18 CN CNA200580024803XA patent/CN101023337A/zh active Pending
  • 2005-07-18 EP EP05772604A patent/EP1769229A1/de not_active Withdrawn
  • 2005-07-18 US US11/572,284 patent/US20070216901A1/en not_active Abandoned
  • 2005-07-21 TW TW094124675A patent/TW200604489A/zh unknown

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