This paper reviews the concepts, status and challenges for the DRAM scaling down to 40nm. The technologies that are discussed are the DRAM cell capacitor structures and materials, as well as the cell transistor structures.

In etch plasmas used for semiconductor processing, concentrations of the precursor gas NF 3 and of the etch product SiF 4 are measured online and in situ using a new diagnostic arrangement, the Q-MACS Etch system, which is based on quantum cascade laser absorption spectroscopy (QCLAS). In addition, the etch rates of SiO 2 layers and of the silicon wafer are monitored including plasma-etching endpoint detection. For this purpose the Q-MACS Etch system is working as an interferometer arrangement. The experiments are performed in an industrial, dual-frequency, capacitively coupled, magnetically enhanced, reactive ion etcher (MERIE), which is a plasma reactor developed for dynamic random access memory (DRAM) technologies. In the spectral range 1028 ± 0.3 cm -1 , the absorption cross-sections of SiF 4 and NF 3 are determined to be r = (7.7 ± 0.7) × 10 -18 cm 2 molecule -1 and r = (8.7 ± 0.8) × 10 -20 cm 2 molecule -1 , respectively.

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In this paper, first measurements with a particularly designed quantum-cascade-laser (QCL) arrangement for application in semiconductor industrial environments for in situ wafer-to-wafer etch monitoring are reported. The combination of QCLs and infrared absorption spectroscopy (QCLAS) opens up new possibilities for plasma process monitoring and control. In silicon etch plasmas, concentrations of the etch product SiF 4 were measured real time in an industrial-production environment. The comparison of the results with inline data of the processed wafers shows a correlation between the amount of produced SiF 4 and the measures of the trench depth and the bottom void. Furthermore, it is shown that the characteristics of the refractive index of Si and SiO 2 in the mid-infrared can be used to determine etch rates of SiO 2 and Si wafers during the processing.

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