Novel approaches for low cost fabrication of SOI

Two trials for low cost manufacture of silicon-on-insulator (SOI) wafers were implemented. Low dose separation by implantation of oxygen (SIMOX) procedure has been conducted on a beam-line ion implanter with mass analyzer. The energy dependence of the formed SOI structure was studied at varied implant dosages. The integrity of the buried oxide (BOX) layer was examined by transmission electron microscopy (TEM) and the threading dislocation in the top silicon layer was evaluated by Secco technique. The results indicated that not only the implanted oxygen dose but also the oxygen ion energy plays an important role in the formation of SOI structure with good crystallinity of top silicon, sharp Si/SiO₂ interfaces and highly integrated BOX layer free of silicon inclusion. For separation by plasma implantation of oxygen (SPIMOX) approach, water plasma, rather than oxygen plasma, was employed to avoid oxygen spread in the implant depth profile. The SPIMOX process using water plasma was carried out on a beam-line ion implanter without mass selector to simulate the plasma implantation procedure. Cross-sectional TEM study revealed that uniform BOX layer was formed under single crystal silicon superficial layer with the present approach. The interfaces between silicon superficial layer, BOX layer and bulk silicon were smooth and sharp. An implant dose window has been identified for fabricating the desirable SOI structure.     

Effect of implantation energy and dose on low-dose SIMOX structures

In order to form silicon (Si)-on-insulator (SOI) layers with various thicknesses, oxygen implantation with doses between 1.0×10¹⁷/cm² and 6.0×10¹⁷/cm² and at energies between 40 and 240 keV has been carried out into 300 mm diameter (100)Si wafers at a temperature of 560 °C. After implantation, Si wafers are annealed in dry Ar mixed with 1% O₂ at a temperature of 1350 °C for 4 h. The quality of buried oxide (BOX) layers and the microstructure in implanted layers before and after annealing is characterized by transmission electron microscopy. The results reveal that the appreciable number of threading dislocations (TDs) is generated in SOI layers implanted at energies above 200 keV under the optimum dose-energy conditions for the continuous BOX layer formation. Whereas, in the case of discontinuous BOX layers, the TD generation is observed in samples implanted at energies above 120 keV. The generation of TDs is discussed with the emphasis on the effect of implantation energy. PACS 61.72Ff; 61.72Lk     

Improvement on the breakdown voltage for silicon-on-insulator devices based on epitaxy-separation by implantation oxygen by a partial buried n+-layer

A novel silicon-on-insulator (SOI) high-voltage device based on epitaxy-separation by implantation oxygen (SIMOX) with a partial buried n⁺-layer silicon-on-insulator (PBN SOI) is proposed in this paper. Based on the proposed expressions of the vertical interface electric field, the high concentration interface charges which are accumulated on the interface between top silicon layer and buried oxide layer (BOX) effectively enhance the electric field of the BOX (E_I), resulting in a high breakdown voltage (BV) for the device. For the same thicknesses of top silicon layer (10 μm) and BOX (0.375 upmum), the E_I and BV of PBN SOI are improved by 186.5% and 45.4% in comparison with those of the conventional SOI, respectively.     

Total dose radiation response of modified commercial silicon-on-insulator materials with nitrogen implanted buried oxide

Nitrogen ions of various doses are implanted into the buried oxide(BOX) of commercial silicon-on-insulator(SOI) materials,and subsequent annealings are carried out at various temperatures.The total dose radiation responses of the nitrogen-implanted SOI wafers are characterized by the high frequency capacitance-voltage(C-V) technique after irradiation using a Co-60 source.It is found that there exist relatively complex relationships between the radiation hardness of the nitrogen implanted BOX and the nitrogen implantation dose at different irradiation doses.The experimental results also suggest that a lower dose nitrogen implantation and a higher post-implantation annealing temperature are suitable for improving the radiation hardness of SOI wafer.Based on the measured C-V data,secondary ion mass spectrometry(SIMS),and Fourier transform infrared(FTIR) spectroscopy,the total dose responses of the nitrogen-implanted SOI wafers are discussed.     

Radiation response of pseudo-MOS transistors fabricated in hardened fully-depleted SIMOX SOI wafers

The total dose radiation response of pseudo-MOS transistors fabricated in hardened and unhardened FD (fully-depleted) SIMOX (Separation by Implanted Oxygen) SOI (Silicon-on-insulator) wafers is presented.At 1 Mrad(Si) radiation dose, the threshold voltage shift of the pseudo-MOS transistor is reduced from -115.5 to -1.9 V by the hardening procedure.The centroid location of the net positive charge trapped in BOX, the hole-trap density and the hole capture fraction of BOX are also shown.The results suggest that hardened FD SIMOX SOI wafers can perform well in a radiation environment.     

Influence of nitrogen implantation into the buried oxide on the radiation hardness of silicon-on-insulator wafers

In order to improve the total-dose radiation hardness of the buried oxide of separation by implanted oxygen silicon-on-insulator wafers, nitrogen ions were implanted into the buried oxide with a dose of 1016 cm-2 , and subsequent annealing was performed at 1100°C. The effect of annealing time on the radiation hardness of the nitrogen implanted wafers has been studied by the high frequency capacitance-voltage technique. The results suggest that the improvement of the radiation hardness of the wafers can be achieved through a shorter time annealing after nitrogen implantation. The nitrogen-implanted sample with the shortest annealing time 0.5 h shows the highest tolerance to total-dose radiation. In particular, for the 1.0 and 1.5 h annealing samples, both total dose responses were unusual. After 300-krad(Si) irradiation, both the shifts of capacitance-voltage curve reached a maximum, respectively, and then decreased with increasing total dose. In addition, the wafers were analysed by the Fourier transform infrared spectroscopy technique, and some useful results have been obtained.     

Relaxed SiGe-on-insulator with high Ge fraction obtained by oxidation of SiGe/Si-on-insulator with hydrogen ions implantation

The SiGe-on-insulator (SGOI) materials were obtained by thermal oxidation of SiGe layers on SOI wafers. As a comparison, H ions were implanted into SiGe layer of some samples before oxidation. The high degree relaxed SGOI materials with high Ge fraction were fabricated by two kinds of samples, including the samples without and with H ions implantation, and relaxation degree of SiGe layers is above 93%. The different result is that implantation of H ions decreased the oxidation rate of SiGe layer and decreased the loss of Ge in SiGe layer during oxidation. The effect of implantation of H ions is discussed in the paper.     

SIMOX SOI埋氧注氮工艺对埋氧中固定正电荷密度的影响

在SIMOX SOI材料的埋氧中注氮是为了增强该类材料的抗辐射能力.通过C-V研究表明，对于埋氧层为150 nm的SIMOX SOI材料来说，当在其埋氧中注入4×10¹⁵cm^-2剂量的氮后，与未注氮埋氧相比，注氮埋氧中的固定正电荷密度显著增加了；而对于埋氧层为375nm的SIMOX SOI材料来说，当注氮剂量分别为2×10¹⁵cm^-2和3×10¹⁵cm^{-2关键词： SIMOX 埋氧 注氮 固定正电荷密度}     

Research on total-dose hardening for H-gate PD NMOSFET/SIMOX by ion implanting into buried oxide

In this work,we investigate the back-gate I-V characteristics for two kinds of NMOSFET/SIMOX transistors with H gate structure fabricated on two different SOI wafers.A transistors are made on the wafer implanted with Si+ and then annealed in N2,and B transistors are made on the wafer without implantation and annealing.It is demonstrated experimentally that A transistors have much less back-gate threshold voltage shift AVth than B transistors under X-ray total dose irradiation.Subthreshold charge separation technique is employed to estimate the build-up of oxide charge and interface traps during irradiation,showing that the reduced △Vth for A transistors is mainly due to its less build-up of oxide charge than B transistors.Photoluminescence (PL) research indicates that Si implantation results in the formation of silicon nanocrystalline (nanocluster) whose size increases with the implant dose.This structure can trap electrons to compensate the positive charge build-up in the buried oxide during irradiation,and thus reduce the threshold voltage negative shift.     

Role of masking oxide on the silicon surface on defect formation in SIMOX structures

The properties of Si/SiO₂ structures produced by oxygen implantation into silicon (SIMOX technology) are investigated by the high-frequency C-V method and by the electroluminescence (EL) method. The existence of electrically active and luminescence centers in the oxide layer near the interface is established. The effect of a SiO₂ masking layer on the silicon surface on defect formation in the SIMOX structure is elucidated. The dependence of the concentration of the electrically active and luminescence centers on the thickness of the masking layer is found.     

埋氧层注氮工艺对部分耗尽SOI nMOSFET特性的影响

研究了埋氧层中注氮后对制作出的部分耗尽SOInMOSFET的特性产生的影响.实验发现，与不注氮的SIMOX基片相比，由注氮SIMON基片制作的nMOSFET的电子迁移率降低了.且由最低注入剂量的SIMON基片制作的器件具有最低的迁移率.随注入剂量的增加，迁移率略有上升，并趋于饱和.分析认为，电子迁移率的降低是由于Si/SiO2界面的不平整造成的.实验还发现，随氮注入剂量的提高，nMOSFET的阈值电压往负向漂移.但是，对应最低注入剂量的器件阈值电压却大于用SIMOX基片制作出的器件.固定氧化物正电荷及界面陷阱密度的大小和分布的变化可能是导致阈值电压变化的主要因素.另外发现，用注氮基片制作出的部分耗尽SOInMOSFET的kink效应明显弱于用不注氮的SIMOX基片制作的器件. 关键词： SOI nMOSFET 氮注入 电子迁移率 阈值电压     

离子注入形成SOI结构的界面及埋层的俄歇能谱研究

本文中研究了O⁺(200keV,1.8×10¹⁸/cm²)和N⁺(190keV,1.8×10¹⁸/cm²)注入Si形成SOI(Silicon on Insulator)结构的界面及埋层的化学组成。俄歇能谱的测量和研究结果表明:注O⁺的SOI结构在经1300℃,5h退火后,其表层Si和氧化硅埋层的界面存在一个不饱和氧化硅状态,氧化硅埋层是由SiO₂相和这不饱和氧化硅态组成,而且氧化硅埋层和体硅界面不同于表层Si和氧化硅埋层界面;注N⁺的SOI结构在经1200℃,2h退火后,其氮化硅埋层中存在一个富N的疏松夹层,表层Si和氮化硅埋层界面与氮化硅埋层和体硅界面性质亦不同。这些结果与红外吸收和透射电子显微镜及离子背散射谱的分析结果相一致。还对两种SOI结构界面与埋层的不同特征的原因进行了分析讨论。 关键词：     

Effect of High Temperature—Pressure on Buried Silicon Dioxide in Simox and Soi Structures

The effect of annealing at 1520–1570 K under high pressure (HP, up to 1.2GPa) on the structure of SiO₂ in oxygen implanted silicon (Si:O) and in silicon with buried SiO₂ layer (SOI) was investigated by TEM, X-Ray and FTIR methods. Depending on the implantation and treatment parameters, SiO₂ precipitates or continuous SiO₂ layers, sometimes with defects at the SiO₂/Si boundary, are created. A stress dependent shift of asymmetric stretching vibration mode associated with Si-O bonds towards lower frequencies is detected for SiO₂ in the HT—HP treated Si:O and SOI samples.     

离子束合成钇硅化物的结构及红外谱特征

将稀土金属钇离子注入到n型单晶Si(111)中制备出钇硅化物埋层.利用x射线衍射、卢瑟福背散射和傅里叶红外吸收谱测量分析了样品的结构、原子的埋层分布和振动模式.结果表明，Y离子在注入过程中已与基底中的Si原子形成了YSi2结构相.真空下的红外光辐照处理促使YSi2择优取向生长，埋层中Si与Y的平均原子浓度比由24下降为20，与六方YSi2的化学计量比一致.还给出了钇硅化物的特征红外吸收谱.     

Defects in separation by implanted oxygen wafer probed by monoenergetic positron beams

Defects in the separation by implanted oxygen (SIMOX) wafers were studied by monoenergetic positron beams. For the as-implanted specimen, vacancies introduced by ion implantation were found to form vacancy-oxygen complexes. After high temperature annealing, a drastic increase in the formation probability of positronium was observed. This suggests an introduction of open-spaces by the formation of an amorphous SiO₂. The present investigation shows that positrons provide a nondestructive probe for the detection of defects in SIMOX wafers and microstructures of SiO₂.     

Influence of Cr<Superscript>+</Superscript> ion implantation and pulsed ion-beam annealing on the formation and optical properties of Si/CrSi<Subscript>2</Subscript>/Si(111) heterostructures

The effect of pulsed ion-beam annealing on the surface morphology, structure, and composition of single-crystal Si(111) wafers implanted by chromium ions with a dose varying from 6 × 10¹⁵ to 6 × 10¹⁶ cm⁻² and on subsequent growth of silicon is investigated for the first time. It is found that pulsed ion-beam annealing causes chromium atom redistribution in the surface layer of the silicon and precipitation of the polycrystalline chromium disilicide (CrSi₂) phase. It is shown that the ultrahigh-vacuum cleaning of the silicon wafers at 850°C upon implantation and pulsed ion-beam annealing provides an atomically clean surface with a developed relief. The growth of silicon by molecular beam epitaxy generates oriented 3D silicon islands, which coalesce at a layer thickness of 100 nm and an implantation dose of 10¹⁶ cm⁻². At higher implantation doses, the silicon layer grows polycrystalline. As follows from Raman scattering data and optical reflectance spectroscopy data, semiconducting CrSi₂ precipitates arise inside the silicon substrate, which diffuse toward its surface during growth.     

硅键合SOI平面光波导探索

本文分析了ＳＩＭＯＸ／ＳＯＩ和ＤＷＢ／ＳＯＩ结构的性能特点。尝试用ＤＷＢ／ＳＯＩ材料制备不同波导层厚度的平面光波导样品，并测试了１．１５μｍ和１．５２３μｍ激光的ＴＥ和ＴＭ模的传输损耗。１．５２３μｍ光的ＴＥ模的最小传输损耗已达０．２７ｄＢ／ｃｍ。说明ＤＷＢ／ＳＯＩ材料是一种有潜力的光波导材料。     

氮氟复合注入对注氧隔离SOI材料埋氧层内固定正电荷密度的影响

为了抑制埋层注氮导致的埋层内正电荷密度的上升, 本文采用氮氟复合注入方式, 向先行注氮的埋层进行了注氮之后的氟离子注入, 并经适当的退火, 对埋层进行改性. 利用高频电容-电压 (C-V) 表征技术, 对复合注入后的埋层进行了正电荷密度的表征. 结果表明, 在大多数情况下, 氮氟复合注入能够有效地降低注氮埋层内的正电荷密度, 且其降低的程度与注氮后的退火时间密切相关. 分析认为, 注氟导致注氮埋层内的正电荷密度降低的原因是在埋层中引入了与氟相关的电子陷阱. 另外, 实验还观察到, 在个别情况下, 氮氟复合注入引起了埋层内正电荷密度的进一步上升. 结合测量结果, 讨论分析了该现象产生的原因. 关键词： 绝缘体上硅(SOI) 材料 注氮 注氟 埋氧层正电荷密度     

A new nanoporous material based on amorphous silicon dioxide

Processes for making nanoporous SiO₂ layers on Si via the irradiation of thermally oxidized silicon wafers with fast ions followed by chemical treatment in a solution or vapor of hydrofluoric acid are presented. It is shown that the density, shape, diameter, and length-to-diameter ratio of channels etched in silicon dioxide can be controlled by varying the regimes of fast ion irradiation or chemical treatment of SiO₂/Si structures. Track parameters calculated using the thermal spike model are compared with the chemical etching data.     

A novel P-channel SOI LDMOS structure with non-depletion potential-clamped layer

A novel structure is proposed for doubling the vertical breakdown voltage of silicon-on-insulator(SOI) devices. In this new structure, the conventional buried oxide(BOX) in an SOI device is split into two sections: the source-section BOX and the drain-section BOX. A highly-doped Si layer, referred to as a non-depletion potential-clamped layer(NPCL), is positioned under and close to the two BOX sections. In the split BOXes and the Si region above the BOXes, the blocking voltage(BV) is divided into two parts by the NPCL. The voltage in the NPCL is clamped to be nearly half of the drain voltage. When the drain voltage approaches a breakdown value, the voltage sustained by the source-section BOX and the Si region under the source are nearly the same as the voltage sustained by the drain-section BOX and the Si region under the drain. The vertical BV is therefore almost doubled. The effectiveness of this new structure was verified for a P-channel SOI lateral double-diffused metal-oxide semiconductor(LDMOS) and can be applied to other high-voltage SOI devices. The simulation results show that the BV in an NPCL P-channel SOI LDMOS is improved by 55% and the specific on-resistance(Ron,sp) is reduced by 69% in comparison to the conventional structure.