Schott Ag

Schott Glas

Hellma Materials Gmbh & Co. Kg

Gunther Wehrhan

Lutz Parthier

Joerg Staeblein

Burkhard Speit

Lothar Ackermann

Daniel Rytz

Christian Kusch

Klaus Dupre

Hans-Joerg Axmann

Frank-Thomas Lentes

Jochen Alkemper

Martin Letz

Ewald Moersen

Clemens Kunisch

Regina Martin

Klaus Petermann

Joerg Kandler

Konrad Knapp

Peter Elzner

Andreas Weisleder

Richard Schatter

Thorsten Reichardt

Thomas Kaufhold

The method produces low-stress, large-volume crystals with low birefringence and uniform index of refraction. The method includes growing the crystal with larger than desired dimensions including diameter and height from a melt; cooling and tempering the crystal with the larger than desired dimensions and after the cooling and tempering removing edge regions of the crystal with the larger than desired dimensions so that a diameter reduction and a height reduction of at least five percent occurs respectively and so that the crystal has the desired dimensions of diameter and height. No further tempering takes place after removing of the edge regions.

Method for making low-stress large-volume crystals with reduced stress birefringence and more uniform refractive index and crystals made thereby

The method of making uniform low-stress crystals includes immersing a seed crystal held at a temperature under its melting point in a melt in a crucible and drawing it from the melt. The crystal and/or melt are rotated relative to each other and a planar phase boundary surface is maintained between them by detecting a surface temperature of the melt and/or crystal and controlling temperature fluctuations by increasing or decreasing the rotation speed. The single crystals obtained by this method have a diameter &#x2267;50 mm and no visible growth strips in a fishtail pattern when a 2-mm thick sample is observed between crossed polarizers. These crystals have an index of refraction uniformity &#x394;n of &#x3c;1 ppm and a stress birefringence of &#x3c;1 nm/cm at 193 nm, so that optical elements suitable for DUV lithography can be made from them.

Method and apparatus for making a highly uniform low-stress single crystal by drawing from a melt and uses of said crystal

The optical elements for ultraviolet radiation, especially for microlithography, are made from cubic granet, cubic spinel, cubic perovskite and/or cubic M(II)- as well as M(IV)-oxides. The optical elements are made from suitable crystals of YAlO, LuAlO, CaAlSiO, KNaAlF, KNaScF, KLiAlFand/or NaAlLiF, (Mg, Zn)AlO, CaAlO, CaBOand/or LiAlO, BaZrOand/or CaCeO. A front lens used in immersion optics for microlithography at wavelengths under 200 nm is an example of a preferred optical element of the present invention.

Method for making optical elements for microlithography, the lens systems obtained by the method and their uses

The method provides a uniform low-stress single crystal in a predetermined crystal orientation. The method of making it includes immersing a single crystal held at a temperature under its melting point in a melt of crystal raw material and drawing it from the melt to grow the crystal. The crystal and/or melt are rotated relative to each other during the crystal growth. A planar phase boundary surface is maintained by detecting at least one characteristic surface temperature in an interior of a crucible containing the melt and controlling temperature fluctuations by increasing or decreasing the rotation speed when they occur. The single crystals obtained by this method have a diameter of at least 50 mm and no visible growth strips in a fishtail pattern when a 2-mm thick sample is observed between crossed polarizers. Optical elements suitable for DUV lithography can be made from these crystals.

The method for producing single crystals includes drying crystal raw material by removing water, reaction of impurities with a scavenger, preferably a metal halide, and homogenizing the melt. The method is performed with the raw material in a melt vessel with a variable-sized through-going opening, in which drying occurs at 100&#xb0; C. to 600&#xb0; C. for at least 20 hours with a geometric conductance value for the through-going opening of 2.00 to 30.00 mm; the reacting occurs at 600&#xb0; C. to 1200&#xb0; C. for at least nine hours with a geometric conductance value of 0.0020 to 0.300 mmand the homogenizing occurs at above 1400&#xb0; C. for at least six hours with a geometric conductance value of 0.25 to 1.1 mm. Alternatively the geometric conductance value is the same during drying, reacting and homogenizing and takes a value between 0.25 and 1 mm.

Method and apparatus for purification of crystal material and for making crystals therefrom and use of crystals obtained thereby

A method is described for making an especially not-(111)-oriented low-stress large-volume crystal having a glide plane with reduced stress birefringence and more uniform refractive index. The method includes growing and tempering the crystal while heating and/or cooling to form a temperature gradient in order to relax stresses arising along the glide plane. During the tempering the heating and/or cooling occurs by heat transfer in a heat transfer direction and the heat transfer direction or temperature gradient is oriented at an angle of from 5&#xb0; to 90&#xb0; to the glide plane. Crystals with a uniform refractive index with variations of less than 0.025&#xd7;10(RMS value) are produced by the method.

Method for making low-stress large-volume not-(111)-oriented crystals with reduced stress birefringence and more uniform refractive index and crystals made thereby

In the method for growing large-volume monocrystals crystal raw material is heated in a melting vessel with heating elements to a temperature above its melting point until a melt is formed. A monocrystal is then formed on the bottom of the melting vessel by lowering the temperature at least to the crystallization point. A solid/liquid phase boundary is formed between the monocrystal and the melt. The monocrystal grows towards the melt surface in a direction that is perpendicular to the phase boundary. A vertical axial temperature gradient is produced and maintained between the bottom of the melting vessel and its upper opening and heat inflow and/or heat outflow through side walls of the melting vessel is prevented, so that the solid/liquid phase boundary has a curvature radius of at least one meter. A crystal-growing device for performing this process is also described.

Method and device for growing large-volume oriented monocrystals

In the method and apparatus for measuring the position of the phase interface during growth of a crystal from a melt in a crystal growth container according to the VGF method an incident optical signal is propagated to the phase interface between the melt and the crystal through a window () in the container () and a received optical signal reflected from the phase interface () is measured to determine the position of the phase interface. The position of the phase interface is established from the reflected signal by triangulation with a confocal optic system, by interferometric balancing or by transit time of the optical signal. The window () is preferably mounted in a preferably tilted orientation at the end of a tube (), which is immersed in the melt ().

Method and apparatus for measuring the position of a phase interface during crystal growth

The method for making a uniform, large-size single crystal of calcium fluoride includes placing a single precursor crystal of calcium fluoride in a tempering vessel provided with a cover; introducing calcium fluoride powder into the tempering vessel and subsequently heating the single precursor crystal, preferably in intimate contact with the calcium fluoride powder, in the tempering vessel together with the calcium fluoride powder for two or more hours at temperatures above 1150&deg; C. to temper the precursor crystal and thus form the uniform, large-scale single crystal of calcium fluoride. The uniform large-sized single crystals of calcium fluoride can be used to make improved lens, prism, light-conducting rod, optical window or other optical component for DUV photolithography, steppers, excimer lasers, wafers, computer chips and electronic devices containing the wafers and chips.

Growing community of inventors

Jena, Germany

Gunther Wehrhan