This paper presents an experimental study on a new concept of a surface defect detection method, in which surface defects will be detected by monitoring a change in heat flow between a micro thermal sensor and a smoothly-finished measuring surface such as magnetic disks, sapphire substrates and so on. In the proposed method, the micro thermal sensor is designed to detect surface defects without any contacts in between them. Since the change in heat flow across the gap is utilized, the method is expected to find out both the convex and concave defects. Searching for the possibility of the non-contact surface defect detection by the micro thermal sensor, in this paper, a simple heat transfer model is established to estimate the change in heat flow due to the change in gap between the measuring surface and the sensor surface. Some basic experiments are also carried out by using prototype micro thermal sensors, each of which is composed of a pair of electrodes and a thin metal film resistor, fabricated on both the silicon and glass substrates.

1. [1] E. Brinksmeier et al., “Ultra-precision grinding,” CIRP Ann. Manuf. Techn., Vol.59, No.2, pp. 652-671, 2010.
2. [2] B. Marchon and T. Olson, “Magnetic spacing trends: From LMR to PMR and beyond,” IEEE Trans. Magn., Vol.45, pp. 3608-3611, 2009.
3. [3] 2015 Int. Technology Roadmap for Semiconductors, http://www.semiconductors.org/ [accessed December 24, 2016]
4. [4] A. N. Murthy et al., “Thermal fly-height controlled glide for disk defect detection and defect size estimation for hard disk drives,” Microsyst. Technol., Vol.20, pp. 1523-1527, 2014.
5. [5] P. M. Lonardo, “Surface Characterization and Defect Detection by Analysis of Images Obtained with Coherent Light,” CIRP Ann. Manuf. Techn., Vol.40, No.1, pp. 541-544, 1991.
6. [6] K. Takami, “Defect inspection of wafers by laser scattering,” Mat. Sci. Eng. B-Solid, Vol.44, pp. 181-187, 1997.
7. [7] A. T. Young, “Rayleigh scattering,” Appl. Opt., Vol.20, No.4, pp. 533-535, 1981.
8. [8] D. Meshulach et al., “Advanced lithography: wafer defect scattering analysis at DUV,” Proc. of SPIE, Vol.7638, 76380K(10pp), 2010.
9. [9] R. Attota and R. Silver, “Nanometrology using a through-focus scanning optical microscopy method,” Meas. Sci. Technol., Vol.22, 024002(10pp), 2011.
10. [10] S. Takahashi et al., “Super resolution optical measurements of nanodefects on Si wafer surface using infrared standing evanescent wave,” CIRP Ann. Manuf. Techn., Vol.60, pp. 523-526, 2011.
11. [11] Y. Shimizu et al., “Feasibility study on the concept of thermal contact sensor for nanometre-level defect inspections on smooth surfaces,” Meas. Sci. Technol., Vol.25, 064006(11pp), 2014.
12. [12] Y. Shimizu, Y. Ohba, and W. Gao, “Investigation on Sensitivity of a Contact-Type Thermal Sensor for Surface Defect Inspections,” Int. J. Automation Technol., Vol.9, No.3, pp. 291-296, 2015.
13. [13] Y. Shimizu et al., “Nano-Scale Defect Mapping on a Magnetic Disk Surface Using a Contact Sensor,” IEEE Trans. Magn. 47, pp. 3426-3432, 2011.
14. [14] J. Martinek et al., “Thermal conductivity analysis of delaminated thin films by scanning thermal microscopy,” Measurement Science and Technology, Vol.25, 044022(7pp), 2014.
15. [15] S. Gomes et al., “Characterization of the thermal conductivity of insulating thin films by scanning thermal microscopy,” Microelectr. J., Vol.44, pp. 1029-1034, 2013.
16. [16] M. A. Lantz et al., “A micromechanical thermal displacement sensor with nanometre resolution,” Nanotechnology, Vol.16, pp. 1089-94, 2005.
17. [17] B. Krijnen et al., “A single-mask thermal displacement sensor in MEMS,” J. Micromech. Microeng., Vol.21, 074007(12pp), 2011.
18. [18] S. Zhang and D. B. Bogy, “A heat model for thermal fluctuations in a thin slider/disk air bearing,” Int. J. Heat Mass Transfer, Vol.42, pp. 1791-1800, 1999.
19. [19] F. Kreith, R. M. Manglik, and M. S. Bohn, “Principle of Heat Transfer,” 7th ed., SI ed., Cengage learning, 2011.
20. [20] W. Gao, “Precision Nanometrology: Sensors and Measuring Systems for Nanomanufacturing,” Springer, 2010.