Observation of Dopant Profile of Transistors Using Scanning Nonlinear Dielectric Microscopy
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1195-B09-01
Observation of Dopant Profile of Transistors Using Scanning Nonlinear Dielectric Microscopy Koichiro Honda1, and Yasuo Cho2 1 Device and Materials Laboratory, Fujitsu laboratories, Atsugi. 243-0197, Japan 2 Research Institute of Electrical Communications, Tohoku University, Sendai. 980-8577, Japan ABSTRACT We have demonstrated that scanning nonlinear dielectric microscopy (SNDM) exhibited high performance and high resolution in observing the dopant concentration profile of transistors. In this study, good quantitative agreement between the SNDM signals and dopant density values obtained by SIMS in standard Si samples, which dopant concentrations have been calibrated. We succeeded in visualizing high-resolution dopant profiles in n- and p-type MOSFET with 40 nm gate channels. It is considered that SNDM would be an effective method in measuring the quantitative two-dimensional dopant profiles of transistors. Finally, we have succeeded in detecting the dopant profiles of SRAM memory cell transistors. INTRODUCTION It is very important to design and analyze Large Scale Integrated Circuits (LSIs) to measure two dimensional density profile of the dopant injected into the source/drain and channel area of transistors with high accuracy. In this regard, several analytical methods, which include Scanning Probe Microscopic methods such as Scanning Capacitance Microscopy (SCM) 1) and Scanning Spreading Resistance Microscopy (SSRM) 2), and Electron Holography with a Transmission Electron Microscope 3), have been developed. In those methods, the Scanning Probe Microscopy (SPM) technology is thought to be the most advantageous mainly due to the ease of the sample preparation. The SPM method uses an Atomic Force Microscope (AFM) that especially equipped with an electrically conductive cantilever. SCM is a method to measure the distribution of the capacitance change to an external impressed voltage by using conductive AFM, and SSRM is a method to measure the resistivity distribution. From our previous studies we have shown the effectiveness of Scanning Nonlinear Dielectric Microscopy (SNDM) of the SPM category 4-7). This technique has been mainly applied to observe the distribution of the polarization on the surface of ferroelectric materials. For example, the polarization distribution of LiTaO3, the thickness observation of the polarization wall of PbxZ1-xT, and the application of the ferroelectric memory that uses nano-size domains, and so on. In the case of semiconductor applications, the 7×7 surface reconstruction of clean Si surface was detected by the high-resolution observation in a high vacuum 8). We have also succeeded in visualizing the charges in nonvolatile flash memory by using SNDM 9, 10). In order to apply SNDM to LSI analysis, here, we report on the measurement of the dopant concentration profile of the source-channel-drain area in transistors. SNDM
A schematic diagram of the SNDM system 4-7) is shown in Figure 1. SNDM is one of the microwave microscopy measurement techniques that use an AFM where a rin
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