Feasibility of multiwavelength Raman spectroscopy was studied as a potential in-line monitoring technique for grain size distribution in channel poly-Si used in three dimensional stacked NAND (3D NAND) Flash memory devices. Various channel poly-Si materials in 3D-NAND Flash memory devices, converted from chemical vapor deposition (CVD) grown a-Si, were characterized using non-contact, multiwavelength Raman spectroscopy and high resolution cross-sectional transmission electron microscopy (HRXTEM). The Raman characterization results were compared with HRXTEM images. The correlation between the grain size distribution characterized by multiwavelength Raman spectroscopy and “on current” (ION) of 3D NAND Flash memory devices was investigated. Good correlation between these techniques was seen. Multiwavelength Raman spectroscopy is very promising as a non-destructive in-line monitoring technique for grain size distribution in channel poly-Si used in 3D NAND Flash memory devices.

We consider an M/G/1 retrial queue, where the service time distribution has a finite exponential moment. We show that the tail of the queue size distribution is asymptotically given by a geometric function multiplied by a power function. The result is obtained by investigating analytic properties of probability generating functions for the queue size and the server state.

We study a fork-join processing network in which jobs arrive according to a Poisson process and each job splits into m tasks, which are simultaneously assigned to m nodes that operate like M/M/s queueing systems. When all of its tasks are finished, the job is completed. The main result is a closed-form formula for approximating the distribution of the network's response time (the time to complete a job) in equilibrium. We also present an analogous approximation for the distribution of the equilibrium queue length (the number of jobs in the system), when each node has one server. Kolmogorov-Smirnov statistical tests show that these formulae are good fits for the distributions obtained from simulations.

Poly Si1−xGex films have been suggested as a promising alternative to the currently employed poly-Si gate electrode for CMOS technology due to lower resistivity, less boron penetration, and less gate depletion effect than those of poly Si gates. We investigated the formation of poly Si1−xGex films grown by UHV CVD using Si2H6 and GeH4 gases, and studied their microstructures as well as their electrical characteristics. The Ge content of the Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.3, and saturated above x=0.45. The deposition rate of the poly Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.1, above which it is slightly changed. The resistivity of the Si1−xGex films decreased as the Ge content increased, and was about one half of that of poly-Si films at the Ge content of 45%. The C-V measurements of the MOSCAP structures with poly Si1−xGex gates demonstrated that the flat band voltage of the poly Si1−xGex films was lower than that of poly-Si films by 0.2V.