Optimized Wafer Thickness for TLS Measurements
- Practical Electron Microscopy and Database -
- An Online Book -

http://www.globalsino.com/EM/  



 
This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

=================================================================================

In many cases of TLS (thermal laser stimulation) measurements, wafer back grinding is needed because thinning of the wafers improves the signal strength. Figure 2809 shows the percent transmission as a function of wavelength and p-doping concentration for 625 pm of Si [1]. Heavier doping increases laser absorption and thus reduces transmission. The percent transmission of infrared wavelengths is given by [1],

          percent transmission of infrared wavelengths ----------------------------- [2809]

where,
          %T -- The percent transmission,
          r -- The reflection coefficient,
          α -- The absorption coefficient,
          d -- The thickness of Si wafer.

As indicated in Equation 2809, decreasing the thickness can dramatically increase the %T and therefore the TLS signal.

Optimized Wafer Thickness for TLS Measurements

Figure 2809. Percent transmission of laser intensity through p-doped Si in 625 pm thickness and having doping concentrations of (a) 1.5 x 1016, (b) 3.3 x 1017, (c) 1.2 x 1018, and (d) 7.3 x 1018 cm-3. The 1340 nm wavelength is marked by a vertical line. [2]

 

 

 

[1] S. E. Aw, H. S. Tan, and C. K. Qng, “Optical Absorption Measurements of Band-gap Shrinkage in Moderately and Heavily Doped Silicon”, J. Phys.: Condens. Mutter, 3, 1991, pp. 8213-8223.
[2] Cole, EI; Tangyunyong, P; Barton, DL, Backside localization of open and shorted IC interconnections, 36th Annual IEEE International Reliability Physics Symposium, (1998). DOI: 10.1109/RELPHY.1998.670462.

 

 

=================================================================================

The book author (Yougui Liao) welcomes your comments, suggestions, and corrections, please click here for submission. If you let book author know once you have cited this book, the brief information of your publication will appear on the “Times Cited” page.