Leica Microsystems Jena Gmbh

Hakon Mikkelsen

Joachim Wienecke

Horst Engel

Lambert Danner

Matthias Slodowski

Kuno Backhaus

Christof Stey

The invention concerns a method for the determination of layer thickness ranges of layers of a specimen, in which the reflection spectrum of the specimen is measured in a specified wavelength range and then smoothed, the number of extremes in the smoothed reflection spectrum is determined, and the determination of the layer thickness ranges is accomplished by comparison with the number of extremes in the modeled reflection spectra, such that for each layer the thickness in that layer is varied in steps having a predetermined increment, and a reflection spectrum is modeled. In a method of this kind, the wavelength range and the increments are specified in self-consistent fashion using a sensitivity criterion.

Method for determining layer thickness ranges

A method and apparatus for determination of layer thicknesses and optical parameters of a number of layers of a specimen, in which the reflectance spectrum of the specimen is measured and then smoothed, and a modeled reflectance spectrum is adapted to the measured one by means of an optimization criterion so as thereby to determine the layer thickness. The optimization criterion is determined by the totality of the absolute values of the wavelength differences of all pairs of wavelengths, a pair of wavelengths being constituted by those wavelengths that respectively correspond to a selected extreme in the measured reflectance spectrum characterized by an index counting the extremes in ascending or descending order, and a selected extreme in the modeled reflectance spectrum having the same index.

Method and apparatus for the determination of layer thicknesses

The invention refers to an optical measurement arrangement, in particular for layer thickness measurement and for ascertaining optical material properties such as refractive index, extinction factor, etc. of a specimen (P), having an illumination device ( ) for emitting a measurement light beam ( ), a beam splitter ( ) for dividing the measurement light beam ( ) into a specimen light beam ( ) and a reference light beam ( ), a measurement objective for directing the specimen light beam ( ) onto a measurement location (M) on the surface of the specimen (P) and for acquiring the light reflected from the measurement location (M), and an analysis device ( ) into which the reference light beam ( ) and the specimen light beam ( ) reflected from the specimen (P) are coupled in order to obtain information about the specimen (P), in particular about layer thicknesses present thereon. Light-guiding devices ( ) having a plurality of light-guiding fibers are provided for coupling the specimen light beam ( ) and the reference light beam ( ) into the analysis device ( ). The result is to create a compact optical measurement arrangement that can be flexibly set up and is insensitive to disturbance, which is suitable in particular for automatic monitoring of continuous production processes, in particular in semiconductor chip manufacture.

Optical measurement arrangement, in particular for layer thickness measurement

The invention concerns an optical measurement arrangement having an ellipsometer, in which an incident beam ( ) of polarized light is directed at an angle of incidence &agr;&ne;0&deg; onto a measurement location (M) on the surface of a specimen (P). Information concerning properties of the specimen (P), preferably concerning layer thicknesses and optical material properties such as refractive index n, extinction coefficient k, and the like, is obtained from an analysis of a return beam ( ) reflected from the specimen (P). The incident beam ( ) is directed by a mirror objective ( ) onto the surface of the specimen (P). The return beam ( ) is also captured by the mirror objective ( ). The result is to create an optical measurement arrangement, operating on the ellipsometric principle, which has a simple, compact configuration and permits a high measurement accuracy down to the sub-nanometer range.

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Göttingen, Germany

Hakon Mikkelsen