2D-mapping of dopant distribution in deep sub micron CMOS devices by electron holography using adapted FIB-preparation

Abstract

Transmission electron microscopy (TEM) is a widely used tool for analysis of very large scale integrated (VLSI) semiconductor devices. As a special TEM-feature, off-axis electron holography obtains information about the electrical characteristics of a specimen, which are connected to the dopant concentration in the bulk material. Compared with conventional TEM, application of electron holography for dopant profiling demands a higher quality of specimen preparation, e.g. in terms of thickness homogeneity. Since preparation by means of focused ion beam (FIB) has become an industrial standard for TEM-investigations, its facilities are investigated for meeting the high holographic demands. It turned out that, besides many advantages like precision and speed, the use of FIB for preparation introduces new specific problems, e.g. it is hardly possible to visualize doped areas of semiconductors on a classical, thin FIB specimen. Additionally, some artifacts of FIB-preparation have no great importance for normal TEM analysis, but do significantly influence the results of holographic analysis. In order to satisfy the higher demands of preparation for holography, a special procedure for FIB-preparation has been newly developed.

Electric and Magnetic Phenomena Studied byIn SituTransmission Electron Microscopy

“…[22][23][24][25][26][27] These results have revealed, among other results, that there can be an electrostatic "dead layer" in these devices near their surfaces. [22][23][24][25][26][27] These results have revealed, among other results, that there can be an electrostatic "dead layer" in these devices near their surfaces.…”

Quantitative off‐axis electron holography of GaAs p‐n junctions prepared by focused ion beam milling

“…Table 1 shows the values of V bi and the electrically ‘inactive’ thickness calculated for the three different specimens. Although this method of measuring V bi is independent of the electrically ‘inactive’ thickness in all instances it is evident that the measurement of the value of V bi is around half the theoretically predicted value of 1.34 V. In this paper, we will show that a combination of effects such as the electrical damage of the specimen introduced during FIB milling (Brown et al , 1999) and the effects of electron irradiation are responsible for this discrepancy (Houben et al , 2005; Cooper et al , 2007).…”

Quantitative dopant profiling of p-n junction in InGaAs∕AlGaAs light-emitting diode using off-axis electron holography

“…19,20 The optimum thickness range results from a trade-off between the need for a strong phase signal against the increasing background noise caused by increases in inelastic scattering with greater sample thickness. 21 A thinner sample area is necessary for STEM imaging and analysis. Thus, Ar-ion milling was used for a few minutes at 3.5 keV, with a current of 13 A and a milling angle of 5°.…”