• Korean Journal of Materials Research
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• v.16 no.2
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• pp.85-91
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• 2006

The fraction of $\varepsilon\;and\;\gamma$'-iron nitride in compound layer is predicted by x-ray diffraction using direct comparison method. The validity of formulation models was checked by comparing calculated results with metallographic analysis of iron nitride compound layer grown on steel S45C by gas nitriding. The fraction of $\varepsilon$ calculated by the three phase model, porous-$Fe_3N$/ dense-$Fe_3N$/ mixed layer with $Fe_3N\;and\;Fe_4N$, is 80 percent of that analyzed by etching technique. The $\varepsilon$ fraction predicted by mixed layer model is 122 percent of that measured by microscope.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.10
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• pp.17-22
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• 1999

In this paper, the results of the studies about a new proposal where the ONON(oxide-nitride-oxide-nitride) layer instead of the conventional ONO(oxide-nitride-oxide) layer is used as the IPD(inter-poly-dielectrics) layer to improve the data retention problem in the Flash EEPROM cell, have been discussed. For these studies, the stacked-gate Flash EEPROM cell with an about 10nm thick gate oxide and on ONO or ONON IPD layer have been fabricated. The measurement results have shown that the data retention characteristics of the devices with the ONO IPD layer are significantly degraded with an activation energy of 0.78 eV. which is much lower than the minimum value (1.0 eV) required for the Flash EEPROM cell. This is believed to be due to the partial or whole etching of the top oxide of the IPD layer during the cleaning process performed just prior to the dry oxidation process to grow the gate oxide of the peripheral MOSFET devices. Whereas the data retention characteristics of the devices with the ONON IPD layer have been found to be much (more than 50%) improved with an activation energy of 1.10 eV. This must be because the thin nitride layer on the top oxide layer in the ONON IPD layer protected the top oxide layer from being etched during the cleaning process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.58-62
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• 1995

Thermally stimulated currents have been measured to investigate the trap characteristics of the MONOS structures with the tunneling oxide layer of 27${\AA}$ thick nitride layer of 73${\AA}$ thick and blocking oxide layer of 40${\AA}$ thick. By changing the write-in voltage and the write-in temperature, peaks of the I-T characteristic curve due to the nitride bulk traps and the blocking oxide-nitride interface traps ware separated from each other experimentally. The results indicate that the nitride bulk traps are distributed spatially at a single energy level and the blocking oxide-nitride interface traps are distributed energetically at interface.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.312-316
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• 1999

The interfacial structure of duplex treated AISI 4140 consisting of iron nitride and TiN layer was characterized by optical microscope, SEM and XRD. A black layer was formed from the decomposition of iron nitride during Ti ion bombardment. The black layer was characterized as an a-Fe phase transformed from the iron nitride by XRD. In order to identify the formation mechanism of the black layer, a thermal analysis of iron nitride undertaken by DSC method. As an iron nitride was mostly consisted of ${\gamma}$'-Fe$_4$N and $\varepsilon$-$Fe_3$N phase after plasma nitriding, in this study, a ${\gamma}$'$-Fe_4$N and $\varepsilon$-$Fe_3$N powders were separately prepared by the different processing conditions of gas nitriding of iron powder in the fluidized bed. From the DSC thermal analysis, the phase transformation of ${\gamma}$'$-Fe_4$N, $\varepsilon$-$Fe_3$N was followed the path of transformation; $ \Upsilon{'}-Fe_4$Nlongrightarrow${\gamma}$-Felongrightarrowa-Fe and of $\varepsilon$-$Fe_3$Nlongrightarrow$\varepsilon$-$Fe_{2.5}$ /N+${\gamma}$'$-Fe_4$Nlongrightarrow${\gamma}$'-Fe$_4$Nlongrightarrow${\gamma}$longrightarrowFelongrightarrowalongrightarrowFe, respectively. It explains the reason why the $\varepsilon$ $-Fe_3$N phase disappeared in the first time and then ${\gamma}$'-Fe$_4$N in the formation of the black layer in the duplex coating.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.1
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• pp.8-16
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• 2001

The effects of gas composition, pressure, temperature and time on the case thickness, hardness and nitride formation in the surface of tool steels(STD11 and STD61) have been studied by micro-pulse plasma nitriding. External compound layer and internal diffusion layer and the diffusion layer were observed in the nitrided case of tool steels. The relative amounts and kind of phases formed in the nitrided case changed with the change of nitriding conditions. Generally, only nitride phases such as ${\gamma}(Fe_4N)$, ${\varepsilon}(Fe_{2-3}N)$, or $Cr_{1.75}V_{0.25}N_2$ phases were detected in the compound layer, while nitride and carbide phases such as ${\varepsilon}-nitride(Fe_{2-3}N)$, $(Cr,Fe)_{\gamma}C_3$ or $Fe_3C$ were detected in the diffusion layer by XRD analysis. The thickness of compound layer increased with the increase of nitrogen content in the gas composition. Maximum case depth was obtained at gas pressure of 200Pa.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.1
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• pp.73-79
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• 2013

Crystalline silicon solar cells with $SiN_x/SiN_x$ and $SiN_x/SiO_x$ double layer anti-reflection coatings(ARC) were studied in this paper. Optimizing passivation effect and optical properties of $SiN_x$ and $SiO_x$ layer deposited by PECVD was performed prior to double layer application. When the refractive index (n) of silicon nitride was varied in range of 1.9~2.3, silicon wafer deposited with silicon nitride layer of 80 nm thickness and n= 2.2 showed the effective lifetime of $1,370{\mu}m$. Silicon nitride with n= 1.9 had the smallest extinction coefficient among these conditions. Silicon oxide layer with 110 nm thickness and n= 1.46 showed the extinction coefficient spectrum near to zero in the 300~1,100 nm region, similar to silicon nitride with n= 1.9. Thus silicon nitride with n= 1.9 and silicon oxide with n= 1.46 would be proper as the upper ARC layer with low extinction coefficient, and silicon nitride with n=2.2 as the lower layer with good passivation effect. As a result, the double layer AR coated silicon wafer showed lower surface reflection and so more light absorption, compared with $SiN_x$ single layer. With the completed solar cell with $SiN_x/SiN_x$ of n= 2.2/1.9 and $SiN_x/SiO_x$ of n= 2.2/1.46, the electrical characteristics was improved as ${\Delta}V_{oc}$= 3.7 mV, ${\Delta}_{sc}=0.11mA/cm^2$ and ${\Delta}V_{oc}$=5.2 mV, ${\Delta}J_{sc}=0.23mA/cm^2$, respectively. It led to the efficiency improvement as 0.1% and 0.23%.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.211.1-211.1
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• 2014

Recently, the scaling of conventional planar NAND flash devices is facing its limits by decreasing numbers of electron stored in the floating gate and increasing difficulties in patterning. Three-dimensional vertical NAND devices have been proposed to overcome these issues. Atomic layer deposition (ALD) is the most promising method to deposit charge trap layer of vertical NAND devices, SiN, with excellent quality due to not only its self-limiting growth characteristics but also low process temperature. ALD of silicon nitride were studied using NH3 and silicon chloride precursors, such as SiCl4[1], SiH2Cl2[2], Si2Cl6[3], and Si3Cl8. However, the reaction mechanism of ALD silicon nitride process was rarely reported. In the present study, we used density functional theory (DFT) method to calculate the reaction of silicon chloride precursors with a silicon nitride surface. DFT is a quantum mechanical modeling method to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. The bond dissociation energy of each precursor was calculated and compared with each other. The different reactivities of silicon chlorides precursors were discussed using the calculated results.

• 연구논문집
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• s.28
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• pp.219-227
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• 1998

In order to investigate the interfacial structure between TiN and iron nitride, an AISI 4140 steel was nitrided to form a layer of thickness 15$\mum$ by DC ion nitriding, then the surface was bombarded with Ti ions and subsequently coated a TiN film of 5$\mum$ by arc ion plating method. The interfacial microstructure between TiN and iron nitride was characterized by optical microscope, SEM and XRD. So called black layer was observed in the duplex treatment. It was resulted from the decomposition of iron nitride during the bombardment. Its thickness was increased with increasing bombardment time at high bias voltage. But the thickness was greatly decreased when the iron nitride was bombarded with a nitrogen gas or at a reduced bias voltage. The adhesion strength of the top TiN coating was decreased with increasing thickness of the black layer. Furthermore, the reduced adhesion strength in this system was discussed in view of the interfacial structural relationship between TiN and iron nitride.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.2
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• pp.81-88
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• 2001

The effects of post-oxidation and sulfnitriding treatments on the phase transformation in the nitrided case of tool steels have been studied. Dense and compact $Fe_3O_4$ layer was formed at the outer surface of nitride compound layer by post-oxidation treatment and multi layer of iron sulfide(FeS) was formed in the compound layer by sulfnitriding treatment. The surface hardness decreased because of formation of the soft oxide or sulfide at the nitride surface. Diffusion layer of nitride case was not affected by post-oxidation treatment or sulfnitriding treatment of nitrided alloy tool steels.

• Journal of the Korean institute of surface engineering
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• v.44 no.3
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• pp.75-81
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• 2011

Growth behaviors of iron-nitride on S45C steels at low pressure gas nitriding were examined. Surfaces of the steels covered with fine and porous oxide during the pre-oxidation using $N_2O$ gas. Well faceted particles connected with them were observed after 1 min nitriding. They grew steadily and filled inter-pores during additional nitriding process. From the X-ray diffraction analysis, ${\gamma}'$-iron nitride was dominantly formed at the initial stage but the amount of ${\varepsilon}$-iron nitride was rapidly increased as nitriding treatment time. The porous layer was formed on the particles and thickened up to half of nitride layer after 60 min nitriding. The observed growth behaviors were discussed in internal stress related with volume expansion involved in transforming from iron to iron-nitrides.