1. Novel X-ray Optics with Si Wafers and Formed Glass
IBWS Vlasim 2006
R. Hudec, L. Pína, A. Inneman, V. Semencová, M. Skulinová, L. Švéda, V. Brožek, J. Šik, M. Míka, R. Kačerovský, J. Prokop
Astronomical Institute, Academy of Sciences of the Czech Republic, Ondřejov, Czech Republic
Czech Technical University, Prague, Czech Republic
Centre for Advanced X-ray Technologies, Reflex sro, Czech Republic
Institute of Chemical Technology, Prague, Czech Republic
ON Semiconductor, Rožnov pod Radhoštěm, Czech Republic

2. Long Term ISS Utilisation

3. ESA XEUS

5. XEUS will have a very large collecting area and fine angular resolution of 2..5" so very light-weight novel X-ray optics is to be developed

6. Czech participation
ESA PECS project accepted for funding from Dec 2006, PI L. Pina Reflex, CI ASU, VSCHT, FJFI CVUT. Duration 4 years.
Preliminary results described in this talk were obtaained WITHOUT any funding thanks to the enthuniasmus of participants.

7. Our approach to X-ray optics based on Si wafers
the Si wafers parameters are optimized already at the production stage
the Si wafers are shaped to precise optical surfaces/shapes
the internal stress is minimized. Important. The standard Si wafers are not stress-free.
the shaped/bent Si wafers are stacked to form the Multi Foil Optics (MFO)

8. Measuring the quality of flat Si wafers
the production of Si wafers is a complex process. The recent Si wafers are optimized for semiconductor industry but not for X-ray optics applications
we use Si wafers already at production optimized for X-ray optics application
precise measurements and optimization already at production stage are important for X-ray optics based on Si wafers

9. Comparison of properties of Si wafers produced by different manufacturers
CZ2 – ON Semiconductor Czech Republic
MEMC – MEMC Electronic Materials
SHE – Shin Etsu SEH
WW – Wafers Works
standard Si wafers

10. Thickness homogeneity of standard Si wafer
produced by ON Semiconductor Czech Republic
min. thickness mm
max.thickness mm
ave. thickness mm
cen. thickness mm
TTV Total Thickness Variation
1.68 mm
TIR Total Indicated Reading
1.81 mm
Flatness and thickness uniformity of a standard Si wafer (diameter 150 mm). Expected to further improve due to technological innovations planned.

11. 6“ Silicon Wafer Manufacturing Process Flow Chart
SINGLE CRYSTAL GROWING
INGOT SHAPING EVALUATION
FLATTING
SLICING EDGE GRINDING
LASER MARKING*
LAPING AND CLEANING
ACID ETCH
ANNEALING*
BACKSIDE TREATMENT*
BACKSEAL OXIDE, POLYSILICON*
New step: GRINDING
POLISHING
CHEMICAL CLEANING
MECHANICAL CLEANING
INSPECTION
* Optional

12. Diamond Grinding Technology for Ideal Flatness
Ground Si wafer
TTV 0.37 m

13. 6“ Silicon Polished Wafer: Flatness Evolution (TTV)
TTV < 2 m (2005)
process optimization
TTV < 1 m (2006)
grinding technology
TTV < 0.5 m (2007)
new polisher (ordered)
TTV = 1.68 m
TTV = 0.76 m
measured Total Thickness Variation

14. flat Si wafer (dopant As), D = 150 mm, t = 0.625 mm
Measuring of shape
Still optical profilometer – 3D chart
flat Si wafer (dopant As), D = 150 mm, t = mm
Special very flat Si wafers have been developed in the collaborating industry for use in X-ray optics

15. ON Semiconductor Czech Republic,
Flat Si wafer, D = 150 mm, t = mm
ON Semiconductor Czech Republic,
Taylor-Hobson profilometer, 2 perpendicular axes
Flatness better than 1 mm

16. Measuring of microroughness AFM microscope, Ra ~ 0.1 nm in 10 x 10 mm
Flat Si wafer
D=150 mm
t=0.625 mm)
ON SEMICONDUCTOR

17. Measuring of roughness
Interferometer Zygo, Ra ~ 0.2 nm in 1.4 x 1.1 mm
dopant B, D = 150 mm, t = mm
ON Semiconductor, Czech Republic

18. Measuring of roughness effect of various dopants on roughness
Interferometer Zygo
effect of various dopants on roughness
(boron-B and phosphorus-P)

19. SHAPING OF SI WAFERS
the goal is to precisely shape Si wafers to desired optical shape and to remove the internal stress
3 different technologies tested (I, II, III)
so far, Si wafers have been shaped to test cylindrical and parabolic surfaces both in 1 and in 2 dimensions

20. Si wafers shaping
test cylindrical samples gold-coated, D= mm, t= mm, R=1.5 m

21. Measuring of roughness after shaping Bent (cylinder) Si wafer
Interferometer Zygo
concave side
convex side
Bent (cylinder) Si wafer
R = 1650 mm, D=150 mm, t = 1.3 mm

22. Measuring of shape Still optical profilometer – 3D chart
flat Si wafer (dopant P)
D = 150 mm
t = mm
bent Si wafer (dopant P)
D = 150 mm
t = 1.3 mm
R = 1650 mm

23. Deviation bent Si wafers
before
processing
(deviation
from plane)
± 2 µm
after
processing
(deviation
from cylinder)
± 2.5 µm

24. Parabolically shaped Si wafer, D = 150 mm, t = 0.625 mm
profile measurement in 2 perpendicular axes

25. Measuring of shape
Taylor-Hobson profilometer – deviation from ideal shape
D = 150 mm, t = mm, parabolic shape
Except edge effects PV < 0.5 mm

26. Thermally formed Si wafers
thermally formed Si wafer to test cylinder
(R = 150 mm, 72 x 23 x mm)
thermally formed Si wafers to test cylinder
(R = 150 mm, 50 x 7 x mm)

27. Optimizing parameters of thermal forming of Si wafers
The effect of elastic tension on deviation from ideal surface (thermal forming of Si wafers)

28. SUMMARY Si wafers
Interdisciplinary co-operation (team with 11 members from 5 Institutions) created within the Czech Republic with experienced teams including researchers at the large company producing Si wafers.
Si wafers successfully bent to desired geometry by 3 different techniques with PV ~ 1 mm in the best case.
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.

29. X-RAY OPTICS BASED ON GLASS THERMAL FORMING (GTF)
alternative glass technologies represent glass forming avoiding heat

30. The parameters of the GTF may be improved by:
optimization of the glass material (limited)
optimization of the mandrel material/design
optimization of the GTF process
optimization of the GTF temperature and duration
Expectations (goals)
microroughness of float - glass not degraded
~ 0.5 nm RMS
deviation PV < 0.02 mm

31. Various approaches in Glass Thermal Forming
low-cost design needed (the goal is to produce very large number of shells at a low cost)
expensive production/material are to be avoided
the mandrel material/design is important
recent design: proprietary technology (composite)

32. Glass Thermal Forming – one of studied approaches
parabolic profile

33. Glass thermal forming (GTF)
cylinder profile 75 x 25 x 0.7 mm
parabolic profile 100 x 150 x 0.7 mm
the largest samples so far 300 x 300 mm

34. (flat glass substrates)
Measuring float glass
(flat glass substrates)
used for GTF

35. Measuring of roughness before slumping
Interferometer Zygo
flat thin glass , 100 x 70 x 0.75 mm

36. Measuring of roughness after sluming
Interferometer Zygo
bent glass , R = 150 mm, 75 x 25 x 0.75 mm

37. Measuring of the roughness after slumping
Interferometer Zygo, bent glass, 75 x 25 x 0.75 mm, optimization using > 100 samples formed at different conditions
minimal
value
Optimizing the parameters of GTF
Ra [nm]
RMS[nm]

38. Waviness of the surface as function of time and temperature of GTF
based on TH profilometer measurements of numerous samples
(75 x 25 x 0.75 mm, R = 150 mm) - optimization

39. thermally formed glass, parabolic profile
Measuring of shape
Still optical profilometer – 3D chart
thermally formed glass, parabolic profile
R = 150 mm, 100 x 150 x 0.75 mm, PV from ideal shape ~ 0.7 mm in the best case recently

40. SUMMARY GTF
surface microroughness not degraded down to measuring accuracy ~ few 0.1 nm
profile deviations 0.7 µm (peak-valley) in the best case recently, expectations < 0.02 µm
sensitive to T and other parameters of the TGF process = need for optimization
sensitive to mandrel design / material / process => need for optimization

41. Contact: rhudec@asu.cas.cz
SUMMARY
Samples of test X-ray mirrors have been produced using novel technologies.
Shaped thin glass mirrors and Si mirrors have been successfully produced.
Both approaches show promising results justifying further efforts in these directions.
We acknowledge collaboration with ON Semiconductor CR, Rožnov pod Radhoštěm, Optical Development Workshop of the AS CR Turnov, and TTS sro Prague
Contact:

42. The End 