Shaping of Advanced Si wafer X-ray Optics

	X-ray Optics...Optics for XEUS
Novel Technologies for Future Large X-ray Telescopes Shaping of Advanced Si wafer X-ray Optics
R. Hudec, , L. Pína, A. Inneman, V. Semencová, M. Skulinová, L. véda, V. Broek, J. ik, M. Míka, R. Kačerovský, T. Kubina,

X-ray Multi Foil Optics (MFO)

X-ray optics based on multiple thin X-ray reflecting foils

The foils may be of various materials (e.g. glass, Si, metals)

Various arrangements and geometries possible, e.g. LOBSTER, K-B, Wolter, double conical approximation to Wolter, etc.

Various examples of X-ray MFO: foil thicknesses from 30 microns to 1 mm, foils 3 x 3 mm to 300 x 300 mm, planar & ellipsoidal

Our approach to X-ray MFO based on Si wafers

the Si wafers parameters are optimised already at the production stage

the Si wafers are shaped to precise optical surfaces/shapes

the internal stress is minimised

the shaped/bent Si wafers are stacked to form the MFO

MEASURING THE QUALITY OF SI WAFERS

the production of Si wafers is a complex process

at moment, the production of Si wafers is NOT optimised for X-ray optics applications

precise measurements and optimization already at production stage are important for X-ray optics based on Si wafers

Example of specification of standard Si wafers,
individual parameters may be improved according to customer requirements.

Optical profilometer STIL

Thickness homogenity of Si wafer produced by ON Semiconductor Czech Republic
Flatness and thickness uniformity of a Si wafer (diameter 150 mm)

Flat Si wafer, diameter 150 mm ON Semiconductor Czech Republic, profilometer measurement, 2 perpendicular axes

100 mm diameter, 0.8 mm thick Si wafer before (left) and after (right) bending (test cylinder R = 1.3 m)

Si WAFERS SHAPING . test cylindrical samples.gold-coated, d=100 mm, thickness 0.8 mm, R=1.3 m

DEVIATION / bent Si wafers

before processing (deviation from plane)

after processing (deviation from cylinder)

Parabolized Si wafer, D=100 mm Interferometer ZYGO
	profile plot
3D plot

Parabolized Si wafer, sample 2, D=150 mm,
ON Semiconductor profile measurement in 2 perpedicular axes

before processing (deviation from plane)

after processing (deviation from cylinder)

Summary - Si wafers

Interdisciplinary co-operation (team with 10 members) created within the Czech Republic with experienced teams including researchers at the large company producing Si wafers

Si wafers succesfully bent to desired geometry by 2 different techniques, the 3rd technique will be tested within 1 month

The bending before stacking is advantageous eg. to avoid increase of internal stress and to allow very long-term stability of the mirror array

The production of Si wafers very complex, need to modify and optimize the parameters at the production stage

Need to minimize the internal stress (25 years lifetime...)

The production of Si wafers and related techniques carefully analysed

MLs succesfully deposited and tested

Next steps:

3rd bending technology

bending of larger and high quality Si wafers

measurements of internal stress

tests of stacking

better measurements, metrology

tests at production stage to modify the parameters, decrease stress, allow more easy bending etc

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