TOPICS / Development of Highly-Functional Scanning Nonlinear Dielectric Microscopy (SNDM) and its Application to Electronic Devices

1. Introduction

Adopted as one of the national projects (S Class Grants-in-Aid for Scientific Research by MEXT and JSPS) in 2011, we have been conducting research on "Development of Highly-Functional Scanning Nonlinear Dielectric Microscopy (SNDM) and its Application to Electronic Devices". Our team consists of Assistant Professor Kohei Yamasue, Assistant Professor Yoshiomi Hiranaga, and myself. In this article, our main achievements and future plans are introduced.

2. Main Achievements

1) Development of new high performance SNDM

At the beginning of the research, we aimed to measure nonlinear dielectric signals at a fourth power polynomial of the electromagnetic field, but we have succeeded at measuring at a seventh power polynomial for semiconductor devices by using high sensitive probe. This measuring method enables us to analyze detailed characteristics of electronic devices, extends an epoch-making measurement system, and promotes the following research.

Figure 1 Surface Potential Visualization of Graphene on 4H-SiC(0001) using SNDP

Figure 1 Surface Potential Visualization of Graphene on 4H-SiC(0001) using SNDP

2) Enhancement of NC-SNDM

Based on the SNDM method, we have been developing an Ultra-High Vacuum Non-Contact SNDM (UHV-NC-SNDM). Adoption of a double vibration removal mechanism improved the stability of the equipment and atom-tracking technology enabled measurement of specific, single, surface atoms and molecules. For example, a Hydrogen adsorbed Si(111)-(7x7) surface was captured with this microscope. We also proposed a new measurement method for surface electrical potentials based on NC-SNDP (SNDP: Scanning Nonlinear Dielectric Potentiometry) and verified the performance of SNDP with the Si(111)-(7x7) surface. Moreover, we started investigations of the surface potential of Graphene using SNDP and made many discoveries.

3) Study of an Ultra-high density ferroelectric recording system

We have recently conducted high-density dot recording experiments on a hard disk drive (HDD) type ferroelectric recording system. Single crystal LiTaO3 was used in this case as the recording medium. The results indicate that a memory density of 3.44 Tbit/inch2 may be realized when two-dimensional recording is achieved.

Figure 2 (a)Cross Section Dopant Profile of SiC-DMOSFET( b)Visualization of guard ring of SiC-DMOSFET

Figure 2
(a)Cross Section Dopant Profile of SiC-DMOSFET
(b)Visualization of guard ring of SiC-DMOSFET

4) Application of SNDM measurement to semiconductor devices

By using SNDM, we have confirmed outstanding improvement of dopant profile analysis in semiconductor devices. We also succeeded in visualization of the dopant profile of cross-sectioned SiC-DMOSFET and its guard ring. This promotes the development of next generation power devices.

3. Future Plan

We are planning to expand our measuring method to the evaluation of many kinds of electronic devices following the success of the SiC power device dopant profile analysis. Estimation of Graphene and Graphene devices will be also in our scope using UHV-NC-SNDM. SNDP is not only applicable to areas as KPFM but also to dipole electrical potential measurements. In addition to the current achievements, we are confident we will overcome most of these challenges by the end of the project in March 2016.

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