Mingwei Xu

Scanning spreading resistance microscopy and spectroscopy for routine and quantitative two-dimensional carrier profiling

As emphasized in the International Technological Roadmap for Semiconductors (ITRS), two-dimensional carrier profiling is one of the key elements in support of technology development. Scanning spreading resistance microscopy (SSRM) has been demonstrated to have attractive concentration sensitivity, an easy quantification, and is applicable to complementary metal–oxide–semiconductor Si and InP structures. Its commercial implementation and availability together with an ample supply of appropriate (diamond based) tips has enabled its more widespread use during recent years. In this article we propose a number of measurement procedures and software tools for its more reliable and fast routine application. First we present a program for the automatic generation of calibration curves and the fast quantification of one-dimensional and two-dimensional resistivity (and carrier) profiles. In view of the large tip consumption, a fast evaluation and calibration of newly mounted conductive tips is a major issue. Furthe...

Carrier spilling revisited: On-bevel junction behavior of different electrical depth profiling techniques

It is well known that the electrical junction depth position measured along a beveled surface, as is routinely done in the spreading resistance probe (SRP) technique, is shallower than the corresponding metallurgical junction as seen by secondary ion mass spectrometry. The amount of on bevel junction shift (i.e., the difference in electrical on bevel versus metallurgical junction depth) in SRP has previously been attributed to a combination of material removal during the beveling (i.e., one-dimensional zero-field Poisson model) and pressure enhanced carrier spilling (enhanced permittivity). Recently the interest in the application of two-dimensional electrical characterization techniques such as scanning capacitance microscopy, with virtually zero pressure, and scanning spreading resistance microscopy, with a much smaller contact, on beveled surfaces has emerged in order to meet the needed resolutions. The data from these techniques, however, indicate that our present understanding of the carrier-spilling...

Peel-off probe: a cost-effective probe for electrical atomic force microscopy

Full metal probes have proven their suitability for electrical atomic force microscopy (AFM) in the last few years. Such probes could be fabricated cheaper if one reduces the number of steps and processing time. Therefore we have developed a procedure which allows to manufacture full metal probes with only two lithography steps. The etching of thin membranes is dropped which reduces the processing time by 25% compared to our previous procedure. It requires only topside processing. The probes can be peeled off from the wafer due to a special metallization procedure. This paper discusses the process scheme and presents measurements on semiconductor devices.

Ultra shallow junction profiling

Highly precise (few %) and spatially (depth and laterally) resolved (nm) measurements of dopant and carrier distributions are required to establish the actual relation between the final dopant/carrier distribution and processing steps. This paper provides a review of recent progress in the field of dopant and carrier profile characterization. Factors limiting the final accuracy and depth resolution of SIMS and spreading resistance probe are discussed in combination with recent developments such as the Nanoprofiler and Carrier Illumination which may go to the sub-nm limit. Quantitative 2D-carrier profiling is dominated by scanning probe techniques but is still limited in spatial resolution (/spl sim/10 nm).

Fabrication of a full metal AFM probe and its applications for Si and InP device analysis

Pyramidal metal tips which are fixed to a silicon cantilever have proven to be very powerful probe tips in electrical Atomic Force Microscopy (AFM). Although silicon is currently the cantilever material of choice for most applications, solid metal cantilevers are an interesting alternative due to their higher electrical conductivity and a more simplified fabrication procedure. Therefore, we have developed a process scheme for such full metal probes and evaluated them in AFM. This paper discusses the fabrication scheme in detail and presents first results concerning the application of the fabricated probes for semiconductor device analysis. Our experiments clearly show that operational full metal probes can be made on a large scale in a 150 mm silicon wafer technology. Using the optimized process, full metal probes can be fabricated which can compete in contact-mode AFM with pyramidal metal tips fixed to a silicon cantilever. Our work is currently focussing on further improvement of batch reproducibility.

High resolution electrical characterization of laterally overgrown epitaxial InP

Dopant incorporation in epitaxial lateral over-growth of InP is investigated by scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM). Dramatic variations in doping contrast in the laterally overgrown regions are observed both in SCM and SSRM measurements implying highly inhomogeneous dopant incorporation. The observed doping variations are explained by surface bonding configurations in the different emerging planes during growth. The results show that methods such as SCM and SSRM not only provide detailed electrical information on a nanometer scale, but also give insights into the growth mechanisms.