Novel Program Method of String Select Transistors for Layer Selection in Channel-Stacked NAND Flash Memory
In this paper, we propose new string select transistors (SSTs)/dummy SSTs (DSSTs) threshold voltage (Vth) setting methods in simplified channel-stacked array with layer selection by multilevel operation (SLSM). In these methods, SSTs/DSSTs on each layer are set to their targeted Vth values by incremental step pulse program/one erase with various erase voltages, respectively. In the fabricated pseudo-SLSM, the validity of the new methods is verified. As a result, it is confirmed that the Vth values of SSTs/DSSTs are set to the targeted Vth values by the new methods and SSTs with extremely narrow Vth distribution can be obtained in the consequence. Moreover, memory operations such as erase, program, and read are performed in the fabricated structure after setting the Vth values of all the SSTs/DSSTs by the new methods. Despite unique LSM operations, stable memory operations are obtained successfully without the interference between stacked layers.
Analysis on New Read Disturbance Induced by Hot Carrier Injections in 3-D Channel-Stacked NAND Flash Memory
Read disturbance is analyzed in vertically channel-stacked NAND flash memory, which has string select transistors (SSTs) to access each channel layer independently. Additional read disturbance is observed at the cells adjacent to the selected cell in the unselected channel layers as well as typical read disturbance caused by repetitive Fowler–Nordheim tunneling (F-N) stress. Technology computer-aided design simulations and measurements are performed to investigate the disturbance mechanisms. It is found that bitline-side [common-source line-side] adjacent cell is disturbed by the hot carrier injection (HCI), which results from positively [negatively] boosted channel potential by the rising [falling] of the voltage (<inline-formula> <tex-math notation="LaTeX">${V}_{\text {unsel}}$ </tex-math></inline-formula>) applied to unselected cells, respectively. A novel read operation, in which the selected cells are maintained in turned on state during the <inline-formula> <tex-math notation="LaTeX">${V}_{\text {unsel}}$ </tex-math></inline-formula> rising/falling and then are restored to their own states, is proposed to suppress the occurrence of the HCIs. As a result, it is revealed that the HCI-induced read disturbances are successfully suppressed by the proposed method.
Accurate measurements of output characteristics and detonations of motorbike high-speed racing engine and their optimization at actual atmospheric conditions and combusted mixture composition
Abstract At a motorbike high speed racing engine there is very important an output engine characteristics which depends significantly on a detonation combustion rate, atmospheric conditions and a combusted mixture composition. The combustion process has got a relevant influence on a wear degree of main engine parts or on their damage eventually. The detonation combustion rate is very important because this kind of burning can be not only destructive but a useful phenomenon, as well. If the process of detonation burning is kept on a certain level, it can help significantly to the next increasing of an engine power output. In this article there is described the measurements of output characteristics of a high-speed racing engine which were performed by means of a data-recording system and the detonation combustion was evaluated using a quantitative method. The actual values of atmospheric conditions and the mixture composition were added to the measured values. Then the obtained values are compared visually with a damage degree of an engine piston caused by the detonation burning. The result is a limit value expressed in a number of detonation units related to a run distance interval of the vehicle driven by the high-speed racing engine. In framework of this run distance interval there is the process of detonation burning profitable. As well as it increases an engine power output and together it is not destructive with regard to engine design parts.