{"id":29263,"date":"2004-08-01T00:10:24","date_gmt":"2004-08-01T00:10:24","guid":{"rendered":"https:\/\/silvaco.com\/uncategorized\/electrostatic-effect-of-localized-charge-in-dual-bit-memory-cells-with-discretetraps\/"},"modified":"2021-07-08T18:29:37","modified_gmt":"2021-07-09T01:29:37","slug":"electrostatic-effect-of-localized-charge-in-dual-bit-memory-cells-with-discretetraps","status":"publish","type":"post","link":"https:\/\/silvaco.com\/ja\/simulation-standard\/electrostatic-effect-of-localized-charge-in-dual-bit-memory-cells-with-discretetraps\/","title":{"rendered":"Electrostatic Effect of Localized Charge in Dual Bit Memory Cells with DiscreteTraps"},"content":{"rendered":"
\n

Electrostatic Effect of Localized Charge in Dual Bit Memory Cells with DiscreteTraps<\/h1>\n

L. Perniola(1, 2,*), S. Bernardini(3), G. Iannaccone(1,6), B. De Salvo (4), G. Ghibaudo (2), P. Masson(3), C. Gerardi(5)<\/em><\/p>\n

(1)Dipartimento di Ingegneria dell\u2019Informazione, Universit\u00e0 degli Studi di Pisa, Via Caruso, 56122 Pisa, Italy, *perniola@enserg.fr
\n(2)IMEP-CNRS\/INPG, Avenue de Martyrs 32, 38016 Grenoble, France
\n(3) L2MP-Polytech \u2013 IMT Technop\u00f4le de Ch\u00e2teau Gombert, 13451 Marseille Cedex 20 France
\n(4)CEA-LETI, Avenue de Martyrs 16, 38054 Grenoble, France
\n(5)STMicroelectronics, Catania, Italy
\n(6)IEIIT-CNR, Via Caruso, 56122 Pisa, Italy.<\/em><\/span><\/p>\n

The following article, presented at ESSDERC 2004 conference, illustrates the capability of ATLAS in the validation and the comprehension of complex effects of new and promising devices like non-volatile discrete trap memory devices.<\/p>\n

Abstract<\/strong><\/p>\n

In this paper the electrostatic impact of Channel Hot Electron (CHE) injection in discrete-trap memories is quantitatively addressed. The dual bit behavior of the transfer characteristic during forward and reverse read of a written cell is thoroughly analysed with the help of an analytical model. Such model allows, for the first time, to estimate the effective charged portion of the discrete storage layer,\u00a0L2<\/sub><\/em>, and the quantity of electrons,\u00a0Q<\/em>, injected in the trapping sites from the experimental parameters of the\u00a0Id<\/sub>-Vg<\/sub><\/em>\u00a0characteristics, the reverse-forward threshold voltage shift\u00a0VRF<\/sub><\/em>, and the total threshold voltage shift\u00a0Vtot<\/em>. The viability of this model is confirmed with tests performed on nanocrystal memories, under different bias conditions. These results are confirmed with the help of a 2D drift-diffusion commercial code (ATLAS<\/em><\/strong>-SILVACO).<\/p>\n

1. Introduction<\/strong><\/p>\n

Channel Hot Electron injection is widely used as a standard writing method for non-volatile discrete-trap memory products [1]-[2]. It provides the opportunity to localise the charges injected in a small region of the trapping medium, and two-bit operation is achieved through multilevel storage [3]. The basic principle on which two-bit operation resides, is common to NROM memories and nanocrystal memories [4]-[5]. It is possible to trap charges near one junction (drain or source) with a programming stress, and read them in the reverse mode, compared to the programming, enhancing the electrostatic effect of these charges on the conductivity of the active channel (see Figure 1).<\/p>\n

It has been shown in the literature [1]-[3]-[6] that the threshold voltage during the forward read, Vth-F<\/sub><\/em>, is lower than the threshold voltage during the reverse read,\u00a0Vth-R<\/sub><\/em>, when the cell is polarised in the saturation regime.<\/p>\n

This is due to the strong two dimensional effects near the charged junction. If the injected charge, near the drain, is completely screened by the high\u00a0Vds<\/sub><\/em>\u00a0applied in forward read (which induces a long pinchoff region), the\u00a0Id<\/sub>-Vg<\/sub><\/em>\u00a0characteristic results very close to the characteristic of the fresh cell. In this case we have a low\u00a0Vth-F<\/sub><\/em>. On the other hand, during the reverse read the high\u00a0Vds<\/sub><\/em>\u00a0applied is not able to screen the effect of electrons and the conductivity of the active channel is lowered by the \u201cbottleneck\u201d near the low-voltage contact. In such a case we have a high\u00a0Vth-R<\/sub><\/em>\u00a0[2]-[6].<\/p>\n<\/div><\/section><\/div>

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