- Email : stil.sa@wanadoo.fr QUASI CONFOCAL EXTENDED FIELD SURFACE SENSING Joseph COHEN-SABBAN, Pierre-Jean CREPIN, Jérôme GAILLARD-GROLEAS STIL SA Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

The « SINGLE POINT » viewing system CONFOCAL IMAGING The « SINGLE POINT » viewing system S point source Confocal imaging consists in : 1) Imaging a point source S into a sharply focused point S’ 2) Reversely, imaging this sharply focused point S’ onto a tiny spatial filter S’’ Such an optical setup is absolutely blind for all the space except for the sharply focused point S’. S’’ spatial filter L S’ Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

defocused specular object defocused backscattering object CONFOCAL IMAGING The Property of « Optical Sectioning » L S A’ S’’ A B’ B sharp focus position S’ defocused specular object defocused backscattering object Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

- Email : stil.sa@wanadoo.fr « Z-axis » FIELD EXTENSION IN CONFOCAL IMAGING The SINGLE LINE viewing system S Polychromatic Point Source The field extension can be obtained by stretching the chromatic aberration of the focusing lens L. The new optical system is then the assembling of an infinity of purely confocal systems, one for each wavelength. S’’ Spatial filter Such a compound system is absolutely blind for all the space except for the sharply focused color coded segment [S’(l1), S’(ln)]. L l 1 Continuum of monochromatic images S’ (li) l i l n Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

- Email : stil.sa@wanadoo.fr EXTENDED FIELD CONFOCAL IMAGING The property of PERFECT FOCUS The SINGLE LINE viewing system presents the unique property of « PERFECT FOCUS » over all the chromatic EXTENDED FIELD since at any given point of the axial field of view there is only one wavelength perfectly focused on the object, all the other wavelengths being absolutely inactive. L Extended field Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EF - CSOM EXTENDED FIELD CONFOCAL SCANNING OPTICAL MICROSCOPY AVOIDS THE Z-AXIS STEPPING PROCESS USED TO GENERATE CONFOCAL SLICES THAT ARE COLLECTED TO CREATE A PERFECTLY FOCUSED IMAGE AVOIDS THE TIME CONSUMING COMPUTER RECONSTRUCTION OF THE OBJECT IMAGE CAN PROVIDE HIGHLY ACCURATE 3D SURFACE METROLOGY WHEN AN ADEQUATE SPECTRAL DECODING IS IMPLEMENTED Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING 3D SURFACE METROLOGY (1) 3D SURFACE METROLOGY CAN BE ACHIEVED WHEN SUCCESSIVELY PERFORMING THE FOLLOWING STEPS. SPACE CODING By stretching the axial chromatic aberration of the illuminating beam SPACE DECODING By analysing the spectral content of the backscattered / backreflected beam Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING 3D SURFACE METROLOGY (2) The confocal spatial filter limits the wavelengths bandwidth Dl to a narrow band centered on the wavelength li coming in perfect focus onto the object surface. S Polychromatic Point Source Spatial Filter Spectrometer S’’(li) monochromatic image The spectral decoding is performed by the spectrometer (position of the return quasi monochromatic beam on the CCD linear array). I L Dl l 1 Continuum of monochromatic images S’ (li) l l l i I l Object Surface n S’ Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING 3D SURFACE METROLOGY (3) The system is volontarily rendered Quasi-Confocal by enlarging the Point Source and the Spatial Filter pinholes. I Consequently, the filtered bandwidth Dl is enlarged in order to enable a highly resolved post processing and to get 30000 resolved points along the color coded segment [S’(l1), S’(ln)]. l l i Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING CHR 150 BLOCK DIAGRAM OPTOELECTRONIC CABINET Polychromatic light source Spectrometer Digital Signal Processing Fiberoptic coupler Analogic and digital outputs l1 ln Fiberoptic link Optical pen Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING CHR 150 OPTICAL PENS * With an optical fiber of 10 microns core diameter ** On specular surfaces. For scattering surfaces the maximum angular slope can reach 80 degrees Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING acquired simultaneously CHR 150 SIGNAL OUTPUTS (1) MEASURING MODE : * Single Surface mode : - Intensity, Height : Both data are acquired simultaneously * Double Surface mode : - Intensity and height of the first surface - Intensity and height of the second surface - Thickness : calculated in real time acquired simultaneously Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING CHR 150 SIGNAL OUTPUTS (2) Analog Signals : - 2 configurable outputs 0 - 10 V Digital Signals: - RS 232 serial link at 115200 bauds. - Birectionnal link used to : . transmit the measuring data to a PC . configure and drive the sensor from a PC Synchronization input and output : - 5V TTL signals. Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

EXTENDED FIELD CONFOCAL IMAGING Optoelectronic Cabinet CHR 150 Optical Sensor Optoelectronic Cabinet Optical pens Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen Diamond machined Diffractive Germanium lens 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

20 µm depth of field optical pen CHR 150 Optical Sensor 20 µm depth of field optical pen Diamond machined Diffractive Germanium lens 3D surface mapping - Height measurement Profile extracted along the black line Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen Holographic Transmission diffraction grating (ZnSe) 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

CHR 150 Optical Sensor 20 µm depth of field optical pen Groove top of a Holographic Transmission diffraction grating (ZnSe) Groove top area Roughness component filtered with a 0.04 mm cut-off Waviness component filtered with a 0.04 mm cut-off Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen CCD matrix area 3D surface metrology of a CCD matrix area Surface waviness of the same CCD matrix area Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen CCD matrix area 3D surface metrology of a CCD matrix area Surface waviness of the same CCD matrix area Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

CHR 150 Optical Sensor 80 µm depth of field optical pen Photogravure processed in LIGA technology 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 Sciences et Techniques Industrielles de la Lumière

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen Optical Waveguide 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

350 µm depth of field optical pen CHR 150 Optical Sensor 350 µm depth of field optical pen Ball Grid Array (BGA) Zoom on one bumps line 3D surface mapping Height measurement Profile extracted along the white line Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

20 µm depth of field optical pen CHR 150 Optical Sensor 20 µm depth of field optical pen Field Emission Display flat screen 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

20 µm depth of field optical pen CHR 150 Optical Sensor 20 µm depth of field optical pen Micro Opto Electro Mechanical System (MOEMS) 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

20 µm depth of field optical pen CHR 150 Optical Sensor 20 µm depth of field optical pen Microlens array 3D surface mapping - Height measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

300 µm depth of field optical pen CHR 150 Optical Sensor 300 µm depth of field optical pen Molded microlens 3D surface mapping Height measurement Photographic representation Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

300 µm depth of field optical pen CHR 150 Optical Sensor 300 µm depth of field optical pen Scratch on a Germanium lens 1 Extracted profile n°1 Extracted profile n°2 2 3 3D surface mapping Height measurement Extracted profile n°3 Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen Gold deposition on Alumina substrate 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

80 µm depth of field optical pen CHR 150 Optical Sensor 80 µm depth of field optical pen Laser marking on a component packaging 3D surface mapping Height measurement Profile extracted from the black line Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

20 µm depth of field optical pen CHR 150 Optical Sensor 20 µm depth of field optical pen Paper 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

350 µm depth of field optical pen CHR 150 Optical Sensor 350 µm depth of field optical pen Microwave Generator Gold Alumina 3D surface mapping Height measurement Photorealistic rendering Intensity measurement Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001

DUAL SURFACE ROUGHNESS MAPPING THICKNESS MAPPING DUAL SURFACE ROUGHNESS MAPPING Polychromatic point source Advantages * single side information pick-up * purely optical measurement * very fast * very accurate Spectrometer White light l1 l2 l1 l2 S1 S2 Dedicated software Roughness of S1 Roughness of S2 Thickness mapping : e = e ( x , y ) Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

ABSOLUTE 3D SURFACE MAPPING Advantages * thickness measurement mode * single side information pick-up * purely optical measurement * very fast * very accurate Polychromatic point source Spectrometer White light l1 l2 l1 l2 Reference Surface : S1 Dedicated software Object surface : S2 Thickness mapping e = e ( x , y ) S2 = S ( x , y ) Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

- Email : stil.sa@wanadoo.fr OPTICS MANUFACTURING QUALITY CONTROL Single Shot, FRONT and BACK SURFACES PICK-UP Polychromatic point source Advantages * no need to reverse the lens * purely optical measurement * very fast * very accurate Spectrometer White light l1 l2 l1 l2 R1 Radiuses : R1 R2 Tilt, Centering diameter f Central thickness Dedicated software R2 diameter f Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

- Email : stil.sa@wanadoo.fr SINGLE SHOT SPHEROMETRY Advantages * purely optical measurement * no moving parts * very fast * very accurate Polychromatic point source Spectrometer White light l1 l2 l1 l2 z2 (l2) - z1 (l1) = R Spherical object Radius R C Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr

CONFOCAL SCANNING OPTICAL MICROSCOPY CONCLUSION Implementation of controlled axial chromatic aberration to CONFOCAL SCANNING OPTICAL MICROSCOPY opens new ways to the application fields of : The proposed optical setup is capable of giving both information simultaneously. * Perfect Focus Free Shape Surface Microscopy * Free Shape 3D Surface Metrology Optical Metrology for the Semicon, Optical and Data Storage Industries SPIE’s 46th Annual Meeting - San Diego, CA 2-3 August, 2001 - Email : stil.sa@wanadoo.fr