SPM system for semiconductor device applications.

Abstract

Recently, scanning probe microscopy (SPM) is widely used for development of semiconductor devices. One of the important functions of SPM is high resolution topography, such as shape of the nanoscale devices and surface roughness of the films. Additionally, SPM can measure the electronic structure of the nanoscale-devices. SPM system for thin films was developed to characterize the thin films for device applications.First, SPM system which can be apply short pulses to the sample holder is constructed to evaluate the electronic response of the thin film without using complex patterning on the Si wafer as shown in Fig.1. Current design rule of the semiconductor devices is around 20 nm. The dimension of the devices are close to the probe radius of conductive SPM probes. The instrument was designed to characterize not only the static properties of nanoscale devices, but also the dynamic electronic properties. Shortest pulses which can be applied to the sample without destroying waveform were less than 50 nS. Time response of the current amplifier is ranging from 50 nS to 200 nS depending on the trans-impedance gains. The conditions (time and dimension) are similar to the active devices on the chip in the circuit. Thus, dynamic electronic properties of the thin films can be tested on a film without fabricating to the nanoscale devices. It is very helpful to optimizing the depositing conditions, such as sputtering parameters, of the thin film for semiconductor devices. For example, the system is used to optimize the film qualities for resistive memories [1].jmicro;63/suppl_1/i13-a/DFU091F1F1DFU091F1Fig. 1.Conductive probe microscopy, which is compatible to the pulse signals ranging to 50nS. The second function of the SPM system is the reproducible roughness measurement. Roughness of the film is also important for optimizing the depositing conditions of the thin film. Virtual reference probe method was developed for removing the variations of the SPM probes [2]. One of the biggest problems of SPM roughness measurement is the huge variations of the SPM probe apexes. The method is to normalizing the probe to the largest probe used in the measurements, after characterizing the probe shape with suitable reference artefact [3,4]. Image reconstruction, such as erosion and dilation process is used for the analysis.In this presentation, we will introduce the SPM system developed for semiconductor device applications. The SPM system also includes function to characterize the nanoscale contaminants on the Si wafer. AcknowledgmentI would like to thanks Ms. Ito and Dr. C.M. Wang in AIST for discussions. This study was partially supported from MEXT.