SCHOTT LITHOTEC ZERODUR - Mark Optics

1 Zero thermal expansion glass ceramicZERODUR ZERODUR SCHOTT LITHOTEC10152 e ba/kn/wo Printed in GermanySchott LITHOTEC ZERODUR For many years ZERODUR zero thermalexpansion material has provided for reliabledesigns in precision optical homogeneity of the material propertiesof ZERODUR enables opto-mechanicalengineering solutions with long-termmechanical and thermal stability. The easy-to-achieve optical figure and improvedmicroroughness have contributed to thesuccess of this is widely used as a mirrorsubstrate material and for precision framesin current state-of-the-art structuring of the material allowssuperior stability of designs in ambitiousdynamic environments, such as stages inwafer steppers and its ability to match zero thermalexpansion very closely, ZERODUR isone of the prime material candidates forsubstrates in lithography applications atwavelengths around 13 nm (EUVL).

2 Applications support from SCHOTT Lithotecis available for material properties andspecific customers designs of PShapes and dThe trods chargEven ShapDisksRodsPlatePolisLight8 inch Wafer Stagemade of ZERODUR Reticle stagemade of ZERODUR CriteYounPoissKnooDensSCHOTT LIT10152 e ba/kn/wo Printed in GermanySchott LITHOTEC AGSales 3255130 MainzGermanyPhone:+ 49 (0) 61 31 / 8 01 26 - 12 Fax:+ 49 (0) 61 31 / 8 01 26 - 27E-mail: MIf even higher thermal expansion quality is required and cooling rates other (or the initial cooling rate) can not be avoided in the critical temperatureregion during processing or use of ZERODUR , we recommend considering theuse of ZERODUR M as a material variation of ZERODUR .Thermal propertiesThe most important and significant properties of the optical glass ceramicZERODUR are the extremely small coefficient of linear thermal expansion aswell as the homogeneity of this coefficient throughout the entire pieces of ZERODUR (discs, plates, rods) can be supplied with a meancoefficient of linear thermal expansion in the temperature range 0 C to 50 Cin three expansion classes as follows:Material up to Expansion class 2 will be supplied as a standard.

3 Closer toleranceswill be supplied upon graph below illustrates the typical coefficient of linear thermal expansion . ZERODUR exhibits a very slight linear expansion over the entire temperaturerange. It is especially low in the room temperature coefficient oflinear thermal expansion0,60,40,20,0-0,2-0,4-0,6-0,8010 02003004005006007008009000 C100 CTemperature [K] [10-6/K]Expansion class 0 0 10-6/KExpansion class 1 0 10-6/KExpansion class 2 0 10-6/KMechanical PropertiesShapes and dimensional tolerancesInternal qualiBulk stressStriaeInclusionsThe table shows the typical and improved tolerances for disks, rectangular blocks,rods and complex shapes. Improved tolerances can be provided for an tighter tolerances can be provided upon special toleranceImprovedtoleranceDisksDiameter < 500 mm mm mmDiameter < 1000 mm mm mmDiameter < 4200 mm mm mmThickness mm mmProfile tolerance< 2000 mm mm mmzone of radiusProfile tolerance> 2000 mm mm mmzone of radiusRodsDiameterL 500 mm and/ mm mmor 80 mmDiameterL > 500 mm and/ mm or > 80 mmLength 80 mm mm mmLength > 80 mm mm mmPlatesLength/thickness mm mmFlatness < 500 mm mm mmFlatness 500 mm mm mmPolishing/ Detailed specification requiredLightweightingtageDUR DUR CriterionYoung s modulus (at 20 C, GPa) mean value 90,3 Poisson s ratio 0,243 Knoop hardness HK 0,1/20 acc.

4 To ISO 9385620 Density (g/cm3)2,53 The i Inc Stri BulAll ZEpermBulk path Bulk[nmdiam< 5 Streby swith< 5 StriaeslightThe sgivenMaxof inin mdiamof thIn th< 5In th< 5As a rInclussurfacInclus SpeclerancesInternal qualityBulk stressStriaeInclusionss for disks, rectangular blocks,be provided for an additionalal toleranceImprovedtolerance mm mm mm mm mm mm mm mm mm mm mm mmd/ mm mmd/ mm mm mm mm mm mm mm mm mm mm mmrequired 90,30,2436202,53 The internal quality of ZERODUR is essentially determined through Inclusions Striae Bulk stressAll ZERODUR parts are subjected to precision optical annealing in order to achievepermanent bulk stress, which is low and symmetrically stress causes optical birefringence. The stress birefringence is measured as apath stress birefringence StandardSpecial[nm/cm] for parts withdiameters or diagonals< 500 mm 6 4 Stress birefringence causedStandard Special Class 3 Class 2 Class 1by striae [nm/stria]]

5 For partswith diameters or diagonals< 500 mm604530 5 Striae are locally very limited transparent regions with composition differing onlyslightly from the basic striae values listed below are maximum values for five quality levels up to agiven diameter or diagonal of ZERODUR Class 1 Class 3 Class 2 Class 0 Maximum diameterof individual inclusionsin mm for differentdiameters or diagonalsof the ZERODUR partIn the critical volume< 500 the uncritical volume< 500 a rule inclusions are mainly bubbles and to some extent individual have no effect on the function of ZERODUR as a substrate material forsurfaces of the highest quality in so far as they lie completely within the in ZERODUR are distinguished by the designations Standard and Special and also draw on the Inclusion Classes 3 to 0 which apply to optical Bonded ComponentsShapes and Dimensional InformationLTB can be applied to solid parts as well as light-weighted (ribbed) ZERODUR components have been fabricated up to 2 inches indiameter with high strength suitable to subsequent post-processing(core drilling, blocking, grinding and polishing).

6 Lightweighted structures have been fabricated from ZERODUR upto sizes of 265 mm diameter with rib structures as thin as 2 mm. Anexample of a light-weighted ZERODUR sample is shown at the Appearance andBond ThicknessBonds formed between ZERODUR material are optically transparent andcan be tailored to fill gaps of definedthickness. Bond thicknesses can bevaried by modifying processing con-ditions and part attributes. TypicalFIB/SEM results are shown at the rightfor thick bonds as well as thin Low Temperature Bonding (LTB)informationNarrative adapted from telecom write-up previously prepared for ZERODUR components are mechanically robust and can bemachined, chemically durable in traditional grinding and polishingenvironments, and are thermally stable in environments ranging fromroom temperature to at least 600 StabilityAll samples made with polishedZERODUR surfaces, regardless ofcuring temperature, show no strengthdegradation after a 1- week treatmentunder 85/85 made using fine ground sur-faces, regardless of curing temperature,show a significant strength degrada-tion after the same 85/85 CureFlexure Strength (MPa)104017 PolishedRT CurePolishedStd.

7 CurePolishedStd. CureGroundRT CureGroundRT CureGroundStd. CureGroundStd. CureUn-treatedAfter 85/85 for 1 weekVacuum CompatibilityVacuum levels attained:10 12 mbar/liter/sec, meaning 1 liter of He leaking per second at10 12 mbar pressure, equivalent to ~3 x 107 atoms/sec (ultra-highvacuum range) Leak rate below current detection limit; lower than that typicallyspecified by manufacturers of UHV valves Same results on both heat-treated and non-heat treated samples;no signs of degassing in either sample, though samples had beenbonded ~1 month prior to test 10 9 torr also demonstrated at Honeywell on non- /3 parts: bothcured and non-curedTransmissionBonds are transparent from 160 nmto 2 m (see figures) and have anominal refractive index (25 C) components contain minimal residual stress (3nm/cm).Mechanical StrengthBonded ZERODUR components aremechanically robust, showing MOR scomparable to that of monolithicZERODUR as determined from 4 ptbend flexure Thermal ExpansionBonded ZERODUR components exhibit CTE performance(RT-300 C) commensurate to monolithic ZERODUR for bondingperpendicular to bonding (5mm)Mono 1 (5mm)Mono 2 (5mm)[T %]Lambda/nm10090807060504030201000500100 0150020002500 Bonded ZERODUR Monolithic ZERODUR [T %]Wavelength (nm)0102030405060705250324024 PolishedRT CureFlexure Strength (MPa)203531 PolishedRT CurePolishedStd.

8 CurePolishedStd. CureGroundRT CureGroundRT CureGroundStd. CureGroundStd. CureNot Thermally ShockedN2 ThermallyAverage CTE from 0 50 CCure TemperatureCTE Rod #2 CTE Rod #1 60 50 40 30 20 10020406080100120140 Thermal Shock ResistanceBonded samples were submerged in liquid nitrogen for nearly3 minutes. In all cases, there was no significant change in measuredbond strength after thermal on core drilled, fine ground specimens0102030405060705232243543 Polished SurfacesRT CurePolished SurfacesStd. CureGround SurfacesRT CureGround SurfacesStd. CureMonolithicFlexure Strength (MPa)TransmissionBonds are transparent from 160 nmto 2 m (see figures) and have anominal refractive index (25 C) components contain minimal residual stress (3nm/cm).Mechanical StrengthBonded ZERODUR components aremechanically robust, showing MOR scomparable to that of monolithicZERODUR as determined from 4 ptbend flexure Thermal ExpansionBonded ZERODUR components exhibit CTE performance(RT-300 C) commensurate to monolithic ZERODUR for bondingperpendicular to bonding (5mm)Mono 1 (5mm)Mono 2 (5mm)[T %]Lambda/nm10090807060504030201000500100 0150020002500 Bonded ZERODUR Monolithic ZERODUR [T %]Wavelength (nm)0102030405060705250324024 PolishedRT CureFlexure Strength (MPa)203531 PolishedRT CurePolishedStd.

9 CurePolishedStd. CureGroundRT CureGroundRT CureGroundStd. CureGroundStd. CureNot Thermally ShockedN2 ThermallyAverage CTE from 0 50 CCure TemperatureCTE Rod #2 CTE Rod #1 60 50 40 30 20 10020406080100120140 Thermal Shock ResistanceBonded samples were submerged in liquid nitrogen for nearly3 minutes. In all cases, there was no significant change in measuredbond strength after thermal on core drilled, fine ground specimens0102030405060705232243543 Polished SurfacesRT CurePolished SurfacesStd. CureGround SurfacesRT CureGround SurfacesStd. CureMonolithicFlexure Strength (MPa) ZERODUR Bonded ComponentsShapes and Dimensional InformationLTB can be applied to solid parts as well as light-weighted (ribbed) ZERODUR components have been fabricated up to 2 inches indiameter with high strength suitable to subsequent post-processing(core drilling, blocking, grinding and polishing).Lightweighted structures have been fabricated from ZERODUR upto sizes of 265 mm diameter with rib structures as thin as 2 mm.

10 Anexample of a light-weighted ZERODUR sample is shown at the Appearance andBond ThicknessBonds formed between ZERODUR material are optically transparent andcan be tailored to fill gaps of definedthickness. Bond thicknesses can bevaried by modifying processing con-ditions and part attributes. TypicalFIB/SEM results are shown at the rightfor thick bonds as well as thin Low Temperature Bonding (LTB)informationNarrative adapted from telecom write-up previously prepared for ZERODUR components are mechanically robust and can bemachined, chemically durable in traditional grinding and polishingenvironments, and are thermally stable in environments ranging fromroom temperature to at least 600 StabilityAll samples made with polishedZERODUR surfaces, regardless ofcuring temperature, show no strengthdegradation after a 1- week treatmentunder 85/85 made using fine ground sur-faces, regardless of curing temperature,show a significant strength degrada-tion after the same 85/85 CureFlexure Strength (MPa)104017 PolishedRT CurePolishedStd.