The accurate and reliable characterization of the sheet resistance of ultra-shallow (USJ) profiles is a key issue in the development of future CMOS technologies. Typically, conventional means, such as in-line four point probe measurements, have a limited accuracy due to the substrate contribution resulting from too much probe penetration, especially in the presence of highly doped underlying layers (such as well/halo-profiles). In this work, a series of advanced Boron doped layers (132 nm down to 2 nm) have been grown with Chemical Vapor Deposition (CVD) on medium and lowly doped substrates and have been characterized with a large variety of state-of-the art non-penetrating/non-contact sheet resistance tools.
The charge-based corona-Kelvin non-contact metrology, originally developed for Si IC fabrication, has recently been extended to wide energy gap semiconductors. We discuss principles of this extension and key applications, namely: high precision dopant measurement on SiC and GaN; two-dimensional electron gas characterization in AlGaN/GaN HEMT structures; interface and dielectric characterization on epi-layers with SiO 2 and SiN; comprehensive interfacial instability characterization of oxidized SiC; and whole wafer mapping of defects with a charge-assisted surface voltage technique, QUAD. This powerful set of measurements is performed without fabrication of any test structures or electrical contact. Corresponding commercial tools are currently being introduced. Based on the historical example of silicon IC, we believe that this approach shall offer enhanced testing for research and for manufacturing process control with reduced cost and fast data feedback benefiting wide-bandgap device technology. . This paper is part of the JSS Focus Issue on GaN-Based Electronics for Power, RF, and Rad-Hard Applications.Development of semiconductor devices and control of the manufacturing process requires cost effective metrology with rapid feedback to pilot or manufacturing lines. In this respect, silicon IC's have been benefiting from inventions (by IBM, Fishkill, NY 1 and by SDI, Tampa, FL 2 ) that created a foundation for the unique charge-based non-contact electrical metrology. 3In this technique, an electrical biasing is produced by corona charging of a surface and the response is monitored by measuring the surface voltage with a vibrating probe, such as a Kelvin-probe. The technique is commonly referred to as the corona-Kelvin method. 4 Corresponding commercial tools designed for Si wafers reduced the need for fabrication of electrical test devices and electric contacts; lowering the manufacturing cost and shortening the data feedback time from weeks to less than one hour. 5 The metrology has been continuously improved in sensitivity, precision, repeatability, and spatial resolution; meeting the demands of new technology nodes. It has been used by all major silicon IC manufacturing companies and has also been adopted by smaller silicon device fablines looking for cost effective metrology solutions.Very recent developments in corona-Kelvin, discussed in this work, are intended for rapidly advancing wide-bandgap semiconductor technology that includes SiC, GaN, and AlGaN/GaN heterostructures.
GaSb undoped layers grown by molecular-beam epitaxy on GaSb or on semi-insulating GaAs substrates at temperatures between 600 and 630 °C are shown to have carrier concentrations in the low 1013 cm−3 range, corresponding to almost intrinsic conditions. The materials have been characterized using current-voltage, capacitance-voltage, Hall effect, photoluminescence, thermally stimulated current, and secondary-ion mass spectrometry. Bulk GaSb (n type) is also found to have converted to high-resistance p type after a heat treatment at 630 °C. Speculations are offered for the responsible mechanism, but a definitive explanation does not exist at this time.
It is shown by spreading resistance and capacitance–voltage measurements that atomic hydrogen passivates shallow acceptors and donors in GaSb. Deep level passivation by hydrogen also occurs, as revealed by deep level transient spectroscopy measurements on Schottky diode structures. Effective diffusion coefficients for hydrogen were determined for both n+ and p+ GaSb; in the former case the diffusion is thermally activated with the relationship DH=3.4×10−5e−0.55 eV/kT, whereas in p+ material DH=1.5×10−6e−0.45 eV/kT over the temperature range 100–250 °C. Reactivation of passivated shallow and deep levels occurs for temperatures of 250–300 °C.
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