Scanning spreading resistance microscopy of shallow doping proﬁles in silicon A. Suchodolskis a,b, * , A. Halle ´n a , J. Gran c , T.-E. Hansen d , U.O. Karlsson a a Royal Inst. of Technology, IMIT-MSP, P.O. Box Electrum 229 SE-164 40 Kista, Sweden b Semiconductor Physics Institute, LT 01108 Vilnius, Lithuania c Justervesendet, Fetveien 99, N-2007 Kjeller, Norway d AME, P.O. Box 83, N-3191 Horten, Norway Available online 13 November 2006 Abstract We demonstrate the application of scanning spreading resistance microscopy (SSRM) for characterization of shallow highly-conduc- tive layers formed by boron implantation of lowly doped n-type silicon substrate followed by a post-implantation annealing. The elec- trically active dopant concentration versus depth was obtained from a cross-section of freshly cleaved samples where the Si-surface could be clearly distinguished by depositing a SiO 2 -layer before cleavage. To quantify free carrier concentration we calibrated our data against samples with implanted/annealed boron proﬁles established by secondary ion mass spectrometry (SIMS). A good ﬁt of SSRM and SIMS data is possible for free carrier concentrations lower than 10 20 cm 3 , but for higher concentrations there is a discrepancy indicating an incomplete activation of the boron. Ó 2006 Elsevier B.V. All rights reserved. 1. Introduction The down-scaling of electronic components puts severe restriction on the applicability of routine characterization techniques, like spreading resistance proﬁling (SRP) [1], used up to now to monitor the reliability of doping pro- cesses [2]. New methods are necessary to monitor the dopant distributions in future devices for very shallow junctions. Scanning spreading resistance microscopy (SSRM) makes use of atomic force microscopy (AFM) and provides information about the local resistance between a point con- tact and a sample under investigation [2,3]. The method utilizes spreading resistance measurements and is based on the same principles as a conventional SRP [1]. During measurements a biased conductive probe is scanned in a contact mode across a surface. The output information is a two-dimensional (2D) map of resistivity distribution over the surface of the sample. The variation of resistance corre- lates with the concentration of local free carriers through the local spreading resistance which dominates the overall resistance. Several electrical [3] and physical [4,5] models of the contact have been proposed, but a general theoreti- cal model of the probe/sample contact does not exist which could be applied for quantitative characterization. Instead quantitative information is most commonly extracted by making use of the calibration procedure where experimen- tal data are compared to the data measured on the sample with known parameters [3]. The small area of the contact is deﬁned by the probe tip curvature, usually in the order of 20–30 nm, and allows direct measurements on the cross-section of cleaved sam- ples with a high spatial resolution (down to 10 nm). The dynamic range extends through many orders of magnitudes covering dopant concentrations from 10 14 up to 10 20 cm 3 [4]. The primary target of the present investigation was the application of SSRM for characterization of the implanted p + -top layer in a Si photodiode structure in order to extract 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.10.050 * Corresponding author. Address: Semiconductor Physics Institute, LT 01108 Vilnius, Lithuania. Tel.: +370 6 345 53 22; fax: +370 5 262 71 23. E-mail address: suchy@pﬁ.lt (A. Suchodolskis). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 253 (2006) 141–144 NIM B Beam Interactions with Materials & Atoms