1. Motivation 2. Nanopositioning and Nanomeasuring Machine 3. Multi-Sensor Approach 4. Conclusion and Outlook

Transcription

1 Prospects of multi-sensor technology for large-area applications in micro- and nanometrology 08/21/ /25/2011, National Harbor E. Manske 1, G. Jäger 1, T. Hausotte 2 1 Ilmenau University of Technology, 2 University Erlangen-Nuremberg 1 Outline 1. Motivation 2. Nanopositioning and Nanomeasuring Machine 3. Multi-Sensor Approach 4. Conclusion and Outlook 2

2 Motivation Micro- and nanotechnology, micro-systems technology, precision optical manufacturing, micro-processing technology Metrology methods must routinely measure near and at atomic scale dimensions ITRS 2009 Structures reach atomic dimensions (ITRS) Structures are becoming more complex Increasingly larger surface regions Higher aspect ratios Increasing requirements for real 3D-measuring tasks Existing measurement approaches not sufficient Combination of Nanopositioning and Nanomeasuring Machines with Multi-Sensor Technology 3 Nanopositioning and Nanomeasuring Maschine Abbe error free measurement in all measuring axes permanent compensation of all guiding errors nanoprobes act as zero indicators nanoprobe Signal processing, control, operator system measuring frame specimen measuring table (mirror corner) length and angular measuring systems 4

3 3-D-Abbe-Comparator-Principle The measuring standard and the object to be measured have to be in line. 0 l off Ernst Abbe ( ) Extended approach: l i with l off i i x, y, z sin 0 i l offi 0 i and 0 The measuring apparatus is to be arranged in such a way that the distance to be measured is a straight-line extension of the graduation used as a scale. 5 NPM-Machine Approach with Laser Focus Sensor (Zero point indicator) sample Metrology frame x,y,z-stage of the NPNM-Machine NPM-Machine 6

4 Autocollimator for active angular control automatic control of pitch and yaw angle measurement of roll angle Measuring mirror Achromat Beam splitter Optical fiber Bending mirror Position sensitive diode Measuring range: 50 arcsec x 50 arcsec Resolution: arcsec Angular deviation of the NPM-machine: < 0.05 arcsec 7 Nanopositioning and Nanomeasuring Maschine Large measuring range (referred to atomic force microscopy): 25 mm x 25 mm x 5 mm Subnanometre resolution: 0.08 nm Nanometre reproducibility and uncertainty Universal applicability of several optical, tactile and AFM probes NPM-Machine 8

5 Basic components of the Nanomeasuring Machine Angular sensor Y-interferometer Angular sensor X-interferometer Abbe point Corner mirror 3D-Stage Metrology frame (Zerodur) measuring range: 25 x 25 x 5 mm 3, resolution: 0.1 nm 9 Positioning steps of 1 nm in all axes z-axis y-axis x-axis resolution: 0.1 nm

6 Measurement Stability of the NPM-Machine Stability of positioning (clodsed-loop control) Stability of interferometers (deactivated drives) Position/ nm z =0,23 nm y =0,27 nm Länge [nm] x =0,29 nm Position/ nm Länge [nm] 1 0 z =0,06 nm y =0,09 nm x =0,08 nm z-axis y-axis x-axis 0,5 0, ,5 1,5 22 2,5 3 3,5 time/ s 0,5 1 1,5 2 2,5 3 3,5 time/ s Laser focus probe with CCD camera microscope Hologram laser unit 12

7 Laser focus probe with CCD camera microscope Focus probe Single point sensor Vertical resolution: < 1nm High speed scanning: 6 mm/s Measurement height: up to 5 mm with standard deviation: ~ 1 nm 0.6 µm Lateral resolution: 0.6 µm 0.6 µm Microlens-array: Lens 25 mm x 251 mm (scanning x 1 mm time: 25 min) Laser spot Overview screen (800 µm x 600 µm) Stylus probe Disadvantage of optical probes: Diffraction effects at sharp edges Optical phase shift errors 14

8 Stylus probe in the NPM-Machine 0.6 µm R=2 µm Pick-up MarSurf MFW 1250 Measuring Force: 0.9 mn Diamond tipped stylus: 2 µm/ 90 Step height measurement (70 nm) AFM-probe Disadvantage of stylus probes: Large tip diameter 16

9 Atomic force microscope probe Focus probe Piezo translator Lens µm 0.5µm Cantilever adapter 10nm Vertical resolution: < 1 nm Lateral resolution: < 10 nm Scanning speed: > 10 µm/s 17 AFM-Sensor Pitch-Measurements PTB-calibration in nm Pitch NMM-results in nm exp. uncertainty Mode Pitch exp. uncertainty difference in nm AC-Mode 3000,350 0, , ,37 0,042 1 DC-Mode 3000,361 0, ,009 ( 1 k=2, 2 30 repetitions, k=2) 18

10 4. White light interference microscope Area sensor! Mirau interferometer 19 White light interferometer microscope In combination of stitching with nanometre accuracy (up to 25 mm x 25 mm) 69 nm Vertical resolution: < 1 nm Lateral resolution: 0.8 µm Z-scan: 2 mill. data points in 20 s Example: Measuring area: 4 x 4 mm 2 Number of fields: 64 Measuring time: 23 min. Data points: 21 mill. 20

11 71 Comparison of different probes in the NPMM Step height measurement Step height in nm Calibration value * Focus sensor Tactile stylus sensor AFM based on Focus sensor White-light interference sensor Deviation from calibration value: h < ± 0.8 nm Standard deviation of probes: u < 0.9 nm * Regarding the whole measuring field 21 Form measurement at steep flanks 10 mm PTB Micro Contour Standard Steep flanks can not be measured neither with laser focus probe nor with stylus probe 500 M. Neugebauer/ PTB µm Focus sensor Tactile stylus probe PTB-Measurement µm 22

12 5. CCD camera microscope combined with depth from focus method Disadvantage of laser focus probe: Single point data collection Limitation of slope angle CCD camera objective collimator beam splitter collimator light source hologram-laser-unit 23 Depth From Focus (DFF) Method combined with high precision stitching Single area: 360 µm x 360 µm Z-scan: 20 images/s Stitching of single z-scans with nanometre precision Measurement of steep slopes (80 ) on rough surfaces Standard deviation: up to 50 nm Micro contur standard 25 mm x 360 µm (Dr. Neugebauer/ PTB) 90 stitched areas, pictures, duration: 2.5 h, storage: 100 GByte 24

13 Multi-sensor approach on the base of laser focus probe CCD camera 5 sensors on one stage objective collimator beam splitter collimator light source hologram laser unit LWD objective Mirau objective focus lens lever piezo translator pivot piezo shaker stylus cantilever focus probe/ CCD microscope white light interference probe stylus probe AFM probe 25 Multi-sensor-arrangement with microscope revolver Mechanical revolver 100x Objective Focus sensor CCD-camera microscope White light interference microscope Stylus probe Mirau objective In preparation: AFM probe 3-D-Microprobe Stylus probe Fiducial marks necessary 26

14 AFM camera image 0.48 mm Large area AFM scan 25 x 25 mm² /10 nm line spacing: 200 years 0.65 mm Cantilever ~2000 single camera shots (30 min, 3 Gpixel) automatic stitching and segmentation directed AFM scans in small fields of interest Stitching (38x52 images) Segmentation AFM-Scans 25 mm 180 nm NT&D Nanotechnol & Devices 27 3-D-Orientation (fast WLI) Z-scan (limited by camera: 45 Hz): 3 µm /second Evaluation time: < 1 second (1032x768 Pixel) Example: Stitching of 9 x 9 regions: 4 x 3 mm² Measurement points: > 50 Mio., < 25 seconds/ region: 0.5 h Wafer - overview 28

15 3-D-Orientation Wafer 4 x 3 mm² 29 3-D-microprobes integrated in NPM-Machine NPL-probe (IBS Eindhoven) 3 copper beryllium flexures 3 capacitive sensors Stiffness: 10 N/m (isotropic) Reproducibility: 4.3 nm Ball diameter: 300 µm Measuring force: 0.1 mn Freeform area scan (constant force): 30 30

16 Multi-orientation Measurement of 3-D microstructures by rotation of the object 3-D fiducial elements (ruby balls) 31 Implementation of a rotary stage in the NPM-Machine Fiducial elements (ruby balls) Rotary stage Measuring table of NPM-machine 32

17 Conclusion Five different probing systems (with nanometre resolution) integrated in the NPM-machine Multi-sensor application on the base of a microscope revolver Several measurement strategies for large area scans, steep flanks and undercuts proposed and tested Further developement: Outlook Automatic probe charger (motorized revolver) Improvement of fiducial mark technology Improvement of large field measurements 33 Acknowledgement DFG: special research centre SFB 622: Nanopositioning and Nanomeasuring Machines EU-FP6-project: NanoCMM, especially SIOS Messtechnik GmbH all co-workers at Ilmenau University of Technology SFB