X-ray diffraction techniques for thin films

1 X-ray diffraction techniques for thin films Rigaku Corporation Application Laboratory Takayuki Konya 1. Today's contents (PM). Introduction X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 2. 1. Advantage of X-ray diffraction (XRD) method Probed depth control by incidence angle Nondestructive Measurement under atmosphere pressure 3. What can we see? (hkl). a,b,c Thickness, Density, Roughness d Phase Identification Interface, transition layer, etc ? , . Crystal structure Crystal quality, lattice parameter, etc Crystal orientation Single: orientation relation of substrate & film Poly: preferred orientation 4.

2 2. What XRD reveals Position and coordinate of reciprocal lattice points lattice constant crystal orientation lattice distortion K. Shape of a reciprocal lattice spread of distribution reciprocal lattice points crystal perfection degree of preferred defects orientation mosaicity 5. Structure parameters Structure Parameter Order Analysis Method 1~103nm Thickness Xray Reflectivity Layer Precision :~several %. Structure Density H2O~Heavy Metals Xray Reflectivity Roughness ~several nm Xray Reflectivity In-Plane XRD. Phase ID - Out-of-Plane XRD etc In-Plane XRD. Crystal System - Out-of-Plane XRD etc Lattice ~several nm In-Plane XRD.

3 Crystal Constant Precision : ~ Out-of-Plane XRD etc Structure Poly~Single, Perfect In-Plane XRD. Crystal quality Crystals Out-of-Plane XRD etc Preferred Random~Preferred Orientation Pole Figure ect Orientation ~Single Crystal Orientation Relation between Rocking Curve Relation film & Substrate Reciprocal Space Map etc 6. 3. Today's contents (PM). Introduction X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 7. Today's contents (PM). Introduction X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 8.

4 4. Difference between Scan Modes The orientation of observed crystal plane depends on scanning mode. Out-of-Plane scan film scan In-Plane scan Observed plane Observed plane tilting perpendicular parallel to the surface (changing during a scan) to the surface 9. What is In-Plane XRD? The detector moves parallel to the surface. Diffracted X-ray diffraction angle 2 B. Incident X-ray Reflected X-ray . Grazing incidence (fixed angle). Observing planes are perpendicular to the surface. 10. 5. Outward of In-Plane Attachment Scanning motion is completely perpendicular to /2 scan.

5 /2 scan In-Plane measurement (2 / scan). 11. In-plane effect 100. 1400. 022 111. Intensity (cps). 80. Intensity (cps). In Plane 1200 Out of Plane 1000. 60. 800. 40 600. 111. 400. 20 220 113 004 331 224. 311 400133 422 200. 0 0. 20 30 40 50 60 70 80 90 20 30 40 50 60 70 80 90. 2 / (degree) 2 / (degree). 111. In -Plane In-Plane 220 Out -of-plane Out-of-plane poly-Si Glass 12. 6. Probed depth control ? 1. extinction distance (nm) 1000. 100 10. incident angle (degree). Sample:Al CuK 1 . 13. Surface & Interface Structure 250 In-Plane In-Plane XRD. XRD. Incident angle 200 Al(111) deg.

6 Deg. Transition layer Intensity (cps). 150 Al+Cu Al Al+Cu ~300nm 100 Al+Cu Cu(111) Al(220). Cu 50. Cu(200) Al(311). Cu(220) SiO2 Ta Al(222) Si (substrate). 0. 30 40 50 60 70 80. 2 / (degree). 14. 7. Today's contents (PM). Introduction Advantage of reciprocal lattice vector X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 15. Single crystal and random orientation Single crystal Fiber orientation Random orientation 16. 8. Orientation conditions and pole figure (111) pole figure (220) pole figure =90 =0 =90 =0.

7 Random orientation =90 =270 =90 =270 . =180 =180 . =90 =0 =90 =0 . = = . =90 =270 =90 =270 . {111} fiber orientation =180 =180 . =90 =0 =90 =0 . (111) single crystal =90 =270 =90 =270 . =180 =180 . 17. Today's contents (PM). Introduction Advantage of reciprocal lattice vector X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 18. 9. Reciprocal space mapping diffraction intensity distribution is plotted on reciprocal space. 2 / . ghkl / . kg 2 . ko . 19. Epitaxial layer structures Relaxation Strain Misorientation substrate[001].

8 00l 00l cubic[112] 00l cubic[112] film [001]. tetragonal[112]. hh0 hh0 hh0. 20. 10. Reciprocal space mapping Mosaic spread GaAs115. Broadening in direction qy/ -1. of sample rotation AlGaAs115. Mismatch (strained). Broadening in direction qx/ -1 of radial scan 21. Today's contents (PM). Introduction Advantage of reciprocal lattice vector X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 22. 11. High- resolution rocking curve The differences of lattice spacing between the substrate and epitaxial films are observed.

9 Thickness and composition ratio of epitaxial films (when the degree of relaxation is known. ). 2 / . K g kg log(I ). hkl ko 2 / . 23. When the sample has multilayer structure . Complicated oscillation composed of oscillation from each layer is observed. -1 (004). 10. -2. 10. GeSi Si -3. 10 GeSi Reflectivity -4. 10. GexSi(1-x) 50nm -5. 10 GexSi(1-x) 300nm -6. 10 Six= substrate -7. 10. x= x= -2000 -1000 0 1000. Deviation Angle (arcseconds). 24. 12. When the sample has superlattice structure . Satellite peaks are observed. 10-1 (004). 10-2. 0 GaAs 10-3. -1 1. Reflectivity 10-4.

10 10-5. -3 -2 2 3. 10-6 4 10L. GaAs 5nm 10-7. InxGa(1-x)As 5nm 10-8. GaAs substrate -8000 -4000 0 4000 8000. Deviation Angle (arcseconds) x= 25. How to interpret the profile Si substrate (004). -1. 10 SiGe mismatch -2. 10. SiGe mismatch 10. -3 GexSi(1-x) 50nm x= Oscillation period GexSi(1-x) 300nm x= Intensity Reflectivity -4.. 10 SiGe thickness Si substrate -5. 10. -6. 10. Oscillation period 10. -7 . SiGe thickness -2000 -1000 0 1000. diffraction Deviation Aangle ( arcsec.). ng le (arcs eco nds ). 26. 13. Today's contents (PM). Introduction X-ray diffraction method Out-of-Plane In-Plane Pole figure Reciprocal space mapping High resolution rocking curve X-ray reflectivity 27.