High-k材料研究进展与存在的问题

随着集成电路的飞速发展,SiO2作为传统的栅介质将不能满足MOSFET器件高集成度的要求,需要一种新型High-k材料来代替传统的SiO2,这就要综合考虑以下几个方面问题:(1)介电常数和势垒高度;(2)热稳定性;(3)薄膜形态;(4)界面质量;(5)与Si基栅兼容;(6)工艺兼容性;(7)可靠性。本文综述了几类High-k栅介质材料的研究现状及存在的问题。目前任何一种有望替代SiO2的栅介质材料都不能完全满足上述几点要求。但是,科学工作者们已经发现了几种有希望的High-k候选材料。

Electrical Properties of Compositional Al2O3 Supplemented HfO2 Thin Films by Atomic Layer Deposition

With advanced research for dielectrics including capacitors in DRAMs, decoupling filters in microcircuits and insulating gates in transistors, a lot of demand for the new challenging of high-k materials in semiconductor industries has been emerged. This study explores and addresses the experimental approach for composite materials with one of the major concerns of high capacitance, and low leakage, as well as ease of integration technology. The characteristics of Al2O3 supported HfO2 (AHO) thin films for a series of different Hf ratios with Al2O3 dielectrics by atomic layer deposition demonstrated as a candidate material. A composite AHO films with the homogeneous compositions of Al and Hf atoms into the Al-Hf-O mixed oxide system could stabilize the polycrystalline structure with increasing of dielectric constant (k) and decreasing of leakage current density, as well as a higher breakdown voltage than HfO2 film on its own. 70 nm thick AHO thin films with different composition of Al and Hf contents were prepared by atomic layer deposition technique on titanium nitride (TiN) and silicon dioxide (SiO2) coated Si substrates. Photolithography and metal lift-off technique were used for the device fabrication of the metal-insulator-metal (MIM) capacitor structures. AHO films on TiN/SiO2/Si were measured by semiconductor analyzer and source/ measure system with probe station in the voltage range from -5 to 5 V with a frequency range from 10 kHz to 1 MHz were used to conduct capacitance-voltage (C-V) measurements with low/medium frequency range and current-voltage (I-V) measurements. It was found that Au/AHO/TiN/SiO2/Si MIM capacitors demonstrate a capacitance density of 1.5 - 4.5 fF/μm2 at 10 kHz, a loss tangent of 0.02 - 0.04 at 10 kHz, dielectric constant of 11.7 - 35.5 depending on the composition and a low leakage current of 1.7 × 10-9 A/cm2 at 0.5 MV/cm at room temperature. The acquired experimental results could show the possibility of compositional alloy thin films that could potentially replace or open new market for high-k challenges in semiconductor technology.

高k绝缘层研究动态

介绍了ITRS2003对高k绝缘层材料的要求、高k绝缘层材料必须满足的要求、高k绝缘材料(尤其是HfSiON材料)研究成果以及研究中存在的问题。

漂移区覆盖高k薄膜的高压LDMOS器件优化设计

为了获得高耐压、低导通电阻的横向双扩散MOSFET(LDMOS)器件,综合利用高介电常数(高k)薄膜技术和场板技术,设计出一种漂移区表面采用"高k薄膜+氧化层+场板"结构的功率器件,有效降低了PN结弯角高电场和场板边缘峰值电场。使用器件仿真工具MEDICI进行验证,并分析高k薄膜厚度、氧化层厚度、高k薄膜相对介电常数以及栅场板长度对器件性能的影响,最终实现了耐压达到820V、比导通电阻降至13.24Ω.mm2且性能稳定的LDMOS器件。

高K栅介质HfSi_xO_y薄膜的制备工艺与结构分析

采用射频磁控溅射法制备HfSixOy薄膜,系统研究工艺参数对HfSixOy薄膜沉积速率的影响规律。对沉积态和退火HfO2和HfSixOy薄膜的结构进行了对比分析。结果表明:HfSixOy薄膜的沉积速率随射频功率、Ar气体流量和粘贴Si面积的增大而增大,随溅射气压的增大而减小。衬底未加热时,制备的HfSixOy和HfO2薄膜均呈非晶态,随着衬底加热温度的上升,HfO2薄膜呈多晶态,而HfSixOy薄膜呈非晶态。HfSixOy薄膜在800℃退火后仍呈非晶态,而HfO2薄膜在400℃退火后已明显晶化,这表明HfSixOy薄膜具有较高的热稳定性。

单晶Tm_2O_3高k栅介质漏电流输运机制研究

利用分子束外延技术在p型Si(001)衬底上外延生长了单晶Tm2O3高k栅介质薄膜,分别在不同温度下测量了薄膜的电流-电压特性。基于变温电流-电压特性数据的漏电流输运机制分析表明,单晶Tm2O3栅介质薄膜在正偏压下的主要漏电流输运机制为肖特基发射,而在负偏压下的主要漏电流输运机制为Frenkel-Poole发射。

高耐压LDMOS用的高K薄膜湿法刻蚀研究

为了对横向双扩散MOSFET(LDMOS)器件所采用的锆钛酸铅(PZT)高介电常数(高K)薄膜进行微图形化,对湿法刻蚀过程中腐蚀液、光刻、刻蚀等工艺进行了优化研究,发现由BOE+HCl+HNO3+H2O+缓冲剂组成的腐蚀液刻蚀效果较好。刻蚀结果表明,所刻蚀薄膜的厚度约为600nm,最小线条宽度约为3μm,侧蚀比减小到1.07∶1,符合功率器件制备的尺度要求,由此所制备的LDMOS器件耐压提高了近2倍。

溶液法制备的高k Y_2O_3薄膜电学性质分析

近年来,原来占据主流地位的介电材料SiO2已经被高介电常数（高k）材料（HfO2,ZrO2,Y2O3,Al2O3,etc）代替。高k材料能在减小漏电流密度的同时增大电容密度使AOS TFTs具有较低的阈值电压,较小的亚阈值摆幅和较高载流子迁移率[1]。迄今为止,在应用于AOS TFTs器件的介电材料中,Y2O3是最好的选择,因其具有良好的热稳定性和化学稳定性,较低的漏电流,较高的反射系数（-2）,

择优取向生长的Gd_2O_3高K栅介质薄膜

使用射频磁控溅射法在n型Si(001)基片上生长了Gd2O3薄膜。X射线衍射扫描研究和高分辨透射电子显微镜观察表明,薄膜由立方相和单斜相混合构成,且表现出立方(111)晶面和单斜(401)晶面的择优取向生长。XPS分析表明薄膜的元素组成接近化学计量比。电性能测试发现,薄膜拥有合适的介电常数,较小的漏电流密度和较大的击穿场强,厚度为15 nm的薄膜介电常数为23,漏电流密度为3.6×10-5A.cm-2(偏压为+1 V时),击穿场强为3.5 MV.cm-1。

Experimental Characterization of ALD Grown Al<SUB>2</SUB>O<SUB>3</SUB>Film for Microelectronic Applications

The study of high dielectric materials has received great attention lately as a key passive component for the application of metal-insulator-metal (MIM) capacitors. In this paper, 50 nm thick Al2O3 thin films have been prepared by atomic layer deposition technique on indium tin oxide (ITO) pre-coated glass substrates and titanium nitride (TiN) coated Si substrates with typical MIM capacitor structure. Photolithography and metal lift-off technique were used for processing of the MIM capacitors. Semiconductor Analyzer with probe station was used to perform capacitance-voltage (C-V) characterization with low-medium frequency range. Current-voltage (I-V) characteristics of MIM capacitors were measured on precision source/measurement system. The performance of Al2O3 films of MIM capacitors on glass was examined in the voltage range from −5 to 5 V with a frequency range from 10 kHz to 5 MHz. Au/Al2O3/ITO/Glass MIM capacitors demonstrate a capacitance density of 1.6 fF/μm2at 100 kHz, a loss tangent ~0.005 at 100 kHz and a leakage current of 1.79 × 10−8 A/cm2 at 1 MV/cm (5 V) at room temperature. Au/Al2O3/TiN/Si MIM capacitors demonstrate a capacitance density of 1.5 fF/μm2 at 100 kHz, a loss tangent ~0.007 at 100 kHz and a lower leakage current of 2.93 × 10−10 A/cm2 at 1 MV/cm (5 V) at room temperature. The obtained electrical properties could indicate a promising application of MIM Capacitors.

Structural and electrical properties of reactive magnetron sputtered yttrium-doped HfO_2 films

Hafnium oxide thin films doped with different concentrations of yttrium are prepared on Si（100） substrates at room temperature using a reactive magnetron sputtering system.The effects of Y content on the bonding structure,crystallographic structure,and electrical properties of Y-doped HfO2 films are investigated.The x-ray photoelectron spectrum（XPS） indicates that the core level peak positions of Hf 4 f and O 1 s shift toward lower energy due to the structure change after Y doping.The depth profiling of XPS shows that the surface of the film is completely oxidized while the oxygen deficiency emerges after the stripping depths have increased.The x-ray diffraction and high resolution transmission electron microscopy（HRTEM） analyses reveal the evolution from monoclinic HfO2 phase towards stabilized cubic HfO2 phase and the preferred orientation of（111） appears with increasing Y content,while pure HfO2 shows the monoclinic phase only.The leakage current and permittivity are determined as a function of the Y content.The best combination of low leakage current of 10-7 A/cm^2 at 1 V and a highest permittivity value of 29 is achieved when the doping ratio of Y increases to 9 mol%.A correlation among Y content,phase evolution and electrical properties of Y-doped HfO2 ultra-thin film is investigated.

高介电常数的栅极电介质LaAlO_3薄膜的性能研究

在室温下,采用射频磁控溅射法在Si衬底上制备了具有高介电常数的LaAlO3薄膜,这是一种新的栅极电介质材料.在高纯O2中经过15min650℃的高温退火后LaAlO3薄膜仍然不晶化,这种热稳定性有利于减小薄膜的漏电流.本工作研究了LaAlO3薄膜的介电性能,其电容等效氧化物厚度为2.33nm,在外加偏压±1V处的漏电流很低,分别为3.73mA/cm2(+1V处)和5.32×10-4mA/cm2(-1V处),两者相差四个数量级.此结果表明,Pt/LaAlO3/Si结构具有良好的单向导电性能. C-V曲线的滞后电压VH=0.09V,界面态密度的值约为8.35×1011cm-2.研究结果表明,在今后的半导体器件的甚大规模集成(ULSI)中,具有高介电常数的LaAlO3薄膜将会是一种极有希望的栅极电介质材料.

原子层沉积系统设计的研究

本文介绍作者自行设计的原子层沉积(ALD)实验系统和所沉积薄膜的检测结果。为了研究ALD技术,作者设计了一套试验性的ALD沉积系统。该系统主要由反应腔、前驱体容器、真空泵、控制系统等部件构成。两个前驱体容器带有加热装置,支持气体或液体前驱体。前驱体、反应腔的温度,沉积过程中气体的交替,以及各种参数都可以设定,并由控制系统自动控制。在系统测试中,使用Al2(CH3)3和H2O作为前驱体,在含有Si-H键的Si基片上沉积Al2O3高k介质薄膜。使用电子探针分析仪分析薄膜成分后,证实了所沉积的薄膜是Al2O3。使用XPS分析薄膜表面时只检测到Al,O元素,没有检测到Si元素,说明Al2O3薄膜是连续的,完整地覆盖了Si表面。使用X射线光电子谱检测元素面分布的结果显示,Al,O在Si上的分布具有较好均一性,表明Al2O3薄膜的均匀性良好。使用电子束照射已沉积Al2O3的Si基片时,发现有大量电子累积在薄膜表面,说明所沉积的Al2O3具有良好的介电性。

高介陶瓷薄膜小型化器件制备关键工艺

为满足电子系统小型化和轻量化的集成需求,采用高介陶瓷制作射频无源器件以减小系统关键部位的体积。试验并优化了高介陶瓷薄膜电路制作流程中的关键工艺,确定了与高介陶瓷匹配的工艺方法及参数,成功制作出了基于高介陶瓷的小型化薄膜器件。与传统氧化铝基器件对比,在性能相当的情况下,器件体积缩小了55%,小型化效果显著,满足了应用需求。

快速退火对Ni-Al-O栅介质结构和介电性能的影响

采用反应脉冲激光沉积方法(PLD)分别在n-Si(100)和Pt/Ti/SiO2/Si(111)衬底上生长了Ni-Al-O栅介质薄膜,将样品在不同温度下进行快速退火处理.通过XRD和AFM对其结构和表面形貌进行了表征,利用LCR表和Keithley表对其介电性能和漏电流进行了研究.结果表明,样品经过750℃退火后仍然保持非晶状态,且样品的表面平整,均方根粗糙度小于0.5 nm.在1 MHz测试频率下,由Pt/Ni-Al-O/Pt电容器测得的介电常数为9.9.MOS电容器的电学测试显示,700℃以上退火的样品有较高的电容值,较低的漏电流密度.研究表明,Ni-Al-O薄膜是一种有潜力的新型高k栅介质材料.

原子层沉积技术的发展现状及应用前景

随着微电子行业的发展,集成度不断提高、器件尺寸持续减小,使得许多传统微电子材料和科技面临巨大挑战,然而原子层沉积(ALD)技术作为一种优异的镀膜技术,因其沉淀的薄膜纯度高、均匀性及保行性好,还能十分精确地控制薄膜的厚度与成分,仍然备受关注并被广泛应用于半导体、光学、光电子、太阳能等诸多领域。本文简要介绍了ALD技术的原理、沉积周期、特征、优势、化学吸附自限制ALD技术和顺次反应自限制ALD技术及ALD本身作为一种技术的发展状况(T-ALD,PEALD和EC-ALD等);重点叙述了ALD技术在半导体领域(高k材料、IC互连技术等)、光学薄膜方面、纳米材料方面、催化剂的应用和新成果。最后,对ALD未来的发展应用前景进行了展望。

浮栅型有机非易失性存储器的研究

有机柔性电子器件具有低制造成本、大面积、可柔性折叠等优点,是近年来国内外学术界和工业界的研究热点.有机非易失存储器是一种重要的有机柔性电子器件.介绍了浮栅型有机非易失性存储器件的工作原理;综述了国内外学术界对浮栅型有机非易失性存储器的研究进展、存在的问题及解决对策.

后退火处理对La_2Ti_2O_7薄膜结构和介电物理性质的影响（英文）

采用脉冲激光沉积镀膜技术在Si(100)衬底上生长了La_2Ti_2O_7栅介质薄膜.通过X射线衍射、原子力显微及同步辐射红外透射光谱技术探索了不同温度下的后退火处理对薄膜结构及介电性能产生的影响.结果表明,未经退火处理的La_2Ti_2O_7薄膜为非晶态,退火后薄膜结晶形成单斜结构.红外谱表明退火处理能够显著增加薄膜介电常数.沉积的非晶态薄膜具有较低的介电常数是因为损失了一些声子振动模式,尤其在低波数段损失的更加明显.实验结果说明后退火处理对La_2Ti_2O_7薄膜的介电性能有非常重要的影响.

正偏压作用下多弧离子镀ZrO_2薄膜的组织结构与力学性能研究

在氧气和氩气的混合气体中,以O2/Ar流量比固定为1/4的条件,通过改变正偏压大小,采用多弧离子镀方法制备了新型高k栅介质——ZrO2薄膜。通过X射线衍射(XRD)和原子力显微镜(AFM)研究了在不同正偏压作用下正偏压值与薄膜的相结构、表面形貌之间的关系,利用纳米压痕仪测量了不同正偏压作用下沉积得到的ZrO2薄膜的硬度及弹性模量,并观察了ZrO2薄膜经不同温度退火处理后的相结构及表面形貌的变化。结果表明,在各个正偏压条件下,薄膜结构呈微晶或非晶;ZrO2薄膜的均方根粗糙度随着正偏压的升高而降低;正偏压为100V时硬度和弹性模量均达到最大值,分别为16.1GPa和210GPa。

新型高K栅介质ZrO_2薄膜材料的制备及表征

采用超高真空电子束蒸发法制备了新型高K栅介质—非晶ZrO2薄膜。X射线光电子能谱(XPS)中Zr3d5/2和Zr3d3/2对应的结合能分别为182.1eV和184.3eV,Zr元素的主要存在形式为Zr4+,说明薄膜由完全氧化的ZrO2组成,并且纵向分布均一。扩展电阻法(SRP)显示ZrO2薄膜的电阻率在108Ω·cm以上,通过高分辨率透射电镜(HR-XTEM)可以观察ZrO2/Si界面陡直,没有界面反应产物,证明600℃快速退火后ZrO2薄膜是非晶结构。原子力显微镜(AFM)表征了薄膜的表面粗糙度,所有样品表面都很平整,其中600℃快速退火样品(RTA)的RMS为0.480nm。