摘要:

Recent studies have produced 0.1 × 0.1 μm ferroelectric cells in both bismuth titanate and strontium bismuth tantalate, thus taking thin-film ferroelectric memories into the regime of nanoscale (100 nm or less) devices. A review is presented of deposition, switching, and leakage current in these devices, which are small enough to permit 1 Gbit memories on a standard Si chip.

ISSN:1058-4587    

DOI:10.1080/10584589808202046

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The need for higher DRAM densities, for cost effective manufacturing and the price pressure puts the DRAM development on a highly innovative path. The fast pace with which DRAM cell sizes are reduced results in many technology issues. This talk discusses the deep trench cell architecture, its advantages and the main technology innovations that have made the aggressive scaling of the DRAM cell possible. The issues related to Gbit DRAMs, the new challenges and potential innovations will be presented.

ISSN:1058-4587    

DOI:10.1080/10584589808202047

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Detailed equivalent circuit models of ferroelectric and high-permittivity dielectric capacitors are required for the development of FeRAM and ultra-dense DRAM devices. This review comprises the frequency dependence of C-V and P-V characteristics, grain size effects, electrode interface effects, as well as reversible and irreversible contributions to the ferroelectric polarization and discusses their impact on the equivalent circuit modeling.

ISSN:1058-4587    

DOI:10.1080/10584589808202048

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ferroelectric memory is expected not only for a standard memory but also for embedded memories in logic LSIs such as smart cards and microcomputers, because it's electrical characteristics and process compatibility are adequate for embedded. For embedded devices, a high speed operation and a reduction in memory cell area are required. In order to apply the ferroelectric memory to the embedded devices widely, a multi level metallization (for high speed operation), a stacked capacitor cell (for reduction the cell area) and other techniques are necessary. In this paper, our approach for the ferroelectric embedded device will be presented.

ISSN:1058-4587    

DOI:10.1080/10584589808202049

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The dry etch behavior of MOCVD (Ba, Sr)TiO3(BST) films has been investigated with Cl2/SF6and Cl2/CF4gas mixtures. The etch response of blanket films was evaluated as a function of gas mix, self-bias voltage, and chamber pressure. Plasma deposition effects interfered with pristine etching by the Cl2/CF4gas mixes. Etch rates for the Cl2/SF6gas mixes exhibited a weak maxima at 10% SF6, which then dropped to a local minima at 20% SF6. The strongest etch response occurred with respect to self-bias voltage, where the etch rate exhibited a dependence that was approximately linear. Finally, at low rf powers the etch rate decreased monotonically with increasing pressure. However, at high power a weak maxima appeared at 20 mT. Overall, these power and pressure responses are consistent with physical sputtering. Therefore, it should be expected that the etch effluent of BST films will form sidewall redeposits on steeply sloped patterned structures in high dielectric constant capacitor DRAM memory applications.

ISSN:1058-4587    

DOI:10.1080/10584589808202050

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

(Pb1-xLax)(ZryTi1-y)1-x/4O3, PLZT, thin films, possessing pure perovskite phase and good ferroelectric properties (Pr=21-25μC/cm2) were successfully deposited on Pt-coated Si substrates, using SrRuO3perovskite as buffer layer. Precoating a metallic Ru-layer on Pt(Si) substrates prior to the deposition of SrRuO3buffer layer further improved thin films' electrical properties. The optimum ferroelectric properties achieved are Pr=25.6 μC/cm2, Ec=47.1 kV/cm and ϵr=1,204. Analyses of elemental depth profiles using secondary ions mass spectroscopy (SIMS) indicate that the significant outward diffusion of Ti-and Si-species has been markedly suppressed at the presence of metallic Ru-layer. The effective suppression on the interdiffusion between the SrRuO3buffer layer and the subsequently deposited PLZT is presumed to be the main factor resulting in better ferroelectric properties for PLZT thin films.

ISSN:1058-4587    

DOI:10.1080/10584589808202051

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Sr2Nb2O7(SNO) family are suitable as ferroelectric materials for ferroelectric memory FETs, because they have low dielectric constant, low coercive fieldEcand high heat-resistance. In this study, we succeeded to prepare the Sr2(Ta, Nb)2O7(STN) capacitors on the poly-Si. These capacitors were applied to FFRAM (Floating gate type Ferroelectric Random Access Memory) cells. The STN thin films were prepared by the sol-gel method. After several times spin coating and preannealing, these films were crystallized at about 950°C in oxygen for 30 sec by RTA (Rapid Thermal Annealing). When the Nb/(Ta+Nb) ratio was between 0.1 and 0.3, the ferroelectricities were confirmed. The maximum remanent polarizationPrshowed 0.4μC/cm2when the ratio was 0.3. The FFRAM cell using STN thin films showed good memory characteristics.

ISSN:1058-4587    

DOI:10.1080/10584589808202052

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Degradation of ferroelectricity in PZT (Pb(Zr0.52, Ti0.48)O3) thin-film capacitors caused by heat treatment in a reductive ambience is investigated. We have found that the degradation of ferroelectricity depends upon the metal used for the top electrode of the PZT capacitor. The increased degradation in the case of a PZT capacitor with Pt electrodes can be explained by a catalytic reaction on the Pt surface. With the use of an IrO2non-catalytic top electrode, we have made the ferroelectricity of an IrO2/PZT/Pt capacitor retained even after the H2annealing at 400°C, or above. This IrO2/PZT/Pt capacitor is a useful structure to avoid H2damage in actual LSI fabrication processes.

ISSN:1058-4587    

DOI:10.1080/10584589808202053

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

PZT is promising material for FeRAM. It has a serious problem on the CMOS wafer process that electrical properties are degraded with forming gas annealing. Recently, the degradation mechanism has been investigated actively, but it isn't understood enough. We studied electric properties and SIMS profiles after N2-H2annealing on Pt/PZT/Pt capacitors. For the first time, we found that hydrogen atoms increased in PZT layer and oxygen atoms decreased in upper Pt layer after N2-H2annealing. The nonvolatile polarization (Pnv) decreased in proportional to the hydrogen content in PZT. And the annealing induced the voltage shift of hysteresis when capacitors polarized before anneal. On the other hand, a clear corelation was not seen between Pnv and the oxygen content in Pt; however, the adhesion of Pt/PZT became poor in case of a small amount of oxygen in Pt. The oxygen in Pt has a contribution to the adhesion of Pt/PZT.

ISSN:1058-4587    

DOI:10.1080/10584589808202054

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Electrical properties of Ir/IrO2/PZT/Ir/IrO2and IrO2/Ir/PZT/Ir/IrO2capacitors were investigated. SIMS analysis showed that the Ir/IrO2bottom electrode acted as a good barrier layer of the interdiffusion. Ir/IrO2/PZT/Ir/IrO2capacitors did not show good electrical properties due to plasma damage during top electrode sputtering. On the other hand, IrO2/Ir/PZT/Ir/IrO2capacitors showed no fatigue up to 109cycles, when annealing after top electrode deposition was performed. Electrical properties of IrO2/Ir/PZT/Ir/IrO2capacitors were dependent on the thickness of Ir/IrO2bottom electrode. These experimental results suggested that electrical properties of PZT capacitors were influenced by the interdiffusion at the bottom interface and the plasma damage at the upper interface.

ISSN:1058-4587    

DOI:10.1080/10584589808202055

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor