注硅对SIMOX材料性能影响的研究

首先采用注硅的方法改进sIMOx（注氧隔离）SOI（绝缘体上硅）材料，对硅注入在SIMOX材料的绝缘埋层中形成的纳米硅团簇的条件和纳米团簇的结构进行了论述。并对埋层结构与抗辐射性能的机理进行了分析。最后，对利用注硅改进的SIMOX材料制备的MOSFET的辐射特性进行了报道。     

注氮剂量对SIMON材料性能影响的研究

采用氧氮共注的方法制备了氮氧共注隔离SOI(SIMON)圆片,对制备的样品进行了二次离子质谱和透射电镜分析,并对埋层结构与抗辐射性能的机理进行了分析。结果表明,注氮剂量较低时埋层质量较好。机理分析结果表明,圆片的抗辐照性能与埋层质量之间存在很密切的关系,埋层的绝缘性能是影响器件抗辐射效应的关键因素。     

低能低剂量注水形成SOI结构材料的研究

采用无质量分析器的离子注入机，以低能量低剂量注水的方式替代常规SIMOX注氧制备SOI材料，测试结果表明，此技术成功地制备了界面陡峭，平整，表层硅单晶质量好的SOI结构材料，在剂量一定的条件下，研究不同注入能量对SOI结构形成的影响，使用剖面透射电镜技术（XTEM）和二次离子质谱技术（SIMS）等测试方法对注入样品和退火后样品进行分析，结果表明，表层硅厚度随注入能量增大不断增大；埋层二氧化硅厚度相对独立，仅在超低能（50keV)低剂量情况下厚度出现明显降低；埋层质量（包括界面平整度，硅岛密度等）与注入能量变化相关。     

注硅工艺对UNIBOND SOI材料抗辐照性能的影响

SOI材料天然具有抗瞬时辐射的能力，而通过特定的改性处理后，SOI的抗总剂量能力也可以得到大幅度的提高。SOI材料主流的制备方法包括SIMOX（注氧隔离方法）和UNIBOND SOI（智能剥离方法制备）。在SIMOX SOI的抗辐射加固领域，采用氮离子注入、氮氧共注入以及硅离子注入的方法都曾取得过很有效的结果。采用硅离子注入的方法对UNIBOND SOI进行了抗总剂量加固。采用P-MOS的表征方法对加固前后的样品进行了比较和分析，在HP-4155B半导体测试仪上得到的I-V曲线和提取的参数表明，注入的离子有效地减少了埋层中积累的正电荷得，圆片抗总剂量能力得到了大幅度提高。初步的理论分析表明是注入的硅离子形成的纳米团簇起到了俘获正电荷的作用。     

低剂量 SIMOX圆片线缺陷和针孔的研究

用Secco法、Cu-plating法分别表征了低剂量SIMOX圆片顶层硅线缺陷、埋层的针孔密度。结果显示,低剂量SIMOX圆片的顶层硅缺陷密度低,但埋层质量稍差。通过注入工艺和退火过程的进一步优化,低剂量SIMOX将是一种有前途的SOI材料制备工艺。     

离子注入改性SOI材料总剂量辐射退火效应和机理研究

基于绝缘体上硅(SOI)的CMOS电路具有天然的抗单粒子优势,但绝缘埋层的存在使得其总剂量效应尤为突出和复杂。本文研究了利用离子注入改性SOI材料的总剂量辐射和退火效应、基于赝MOS技术的SOI材料辐射效应评估技术和离子注入改性提高SOI材料抗辐射性能的机理。实验结果表明,采用该技术制备的绝缘体上硅材料抗总剂量能力达到1Mrad(Si);离子注入改性SOI材料在经过室温和高温退火后,辐射导致的固定电荷和界面态可以完全恢复;离子注入和高温退火在二氧化硅薄膜中形成硅纳米团簇结构,从而引入深电子陷阱,补偿总剂量辐射引起的绝缘埋层中的空穴积累。     

Pseudo-MOS方法表征SIMOX SOI材料总剂量辐照效应

为了缩短SOI材料的改性研究周期,利用pseudo-MOS方法研究了SIMOX SOI材料的总剂量辐照效应.试验采用硅注入绝缘埋层后退火得到改性的SIMOX SOI材料,通过对比改性前后样品在辐照前后的pseudo-MOSFET ID-VG特性曲线,分析改性工艺的影响.研究结果表明,合适的改性工艺能有效提高材料抗总剂量辐照效应的能力,pseudo-MOS方法在大大缩短SOI材料改性周期的基础上,能准确、快捷地对材料的总剂量辐照效应进行表征.     

硅中氦氧共注入纳米孔氧化埋层的研究

将１×１０１７／ｃｍ２的氦离子以３５ｋｅＶ的能量注入到单晶硅中，在硅表层下面形成纳米空腔。将１×１０１７／ｃｍ２的氧离子注入到空腔层的下方。用ＲＢＳ／Ｃ、ＳＲＰ及ＸＴＥＭ等测试手段对样品进行研究。结果表明，纳米空腔对氧有强烈的吸附作用，１００００Ｃ退火后氧从原注入位置释放，并被空腔俘获，形成含纳米孔的氧化埋层。氧与空腔的互作用抑制了纳米空腔的迁移、聚合。利用这一现象有望制备出纳米氧化埋层ＳＩＭＯＸ材料。     

部分耗尽环栅CMOS/SOI总剂量辐射效应研究

采用硅离子注入工艺对注氧隔离(SIMOX)材料进行改性,在改性材料和标准SIMOX材料上制作了部分耗尽环型栅CMOS/SOI反相器,并对其进行60Co γ射线总剂量辐照试验.结果表明,受到同样总剂量辐射后,改性材料制作的反相器与标准SIMOX材料制作的反相器相比,转换电压漂移小的多,亚阈漏电也得到明显改善,具有较高的抗总剂量辐射水平.     

污染氧对氢离子辐照前后50%TiC-C薄膜的影响研究

采用离子束混合技术在不锈钢衬底上制备50%TiC-C薄膜,用剂量1×1018ions/cm2、能量5keV的氢离子对薄膜进行辐照.通过X射线光电子能谱对氢离子辐照前后的50%TiC-C薄膜进行组成元素化学结合能谱的分析,着重研究污染氧对薄膜氢离子辐照前后的影响.研究发现氢离子辐照会引入更多的污染氧进入膜内,但污染氧不影响薄膜的阻氢性能.     

Fabrication and Characterization of Silicon (100) Membranes for a Multi-beam Superconducting Heterodyne Receiver

We fabricated silicon (100) membranes of 3 mm in diameter on the surface of silicon-on-insulator (SOI) substrates and investigated the characteristics of the membranes. The handle layer of one SOI substrate was etched using deep reactive ion etching process with the buried oxide (BOX) layer that remained together with the device layer. The BOX layer of the other SOI substrate was removed using C₄F₈-based plasma etching after the handle layer etching. The surfaces of both silicon (100) membranes were observed using the scanning white light interferometer system at room temperature. Both silicon (100) membranes have dome-like deformations. The silicon (100) membranes are effectively flattened by etching the BOX layer under the device layer. Both silicon (100) membranes were cooled from room temperature to 4 K by a Gifford–McMahon refrigerator. Wrinkles appeared on the surfaces of both silicon (100) membranes when the temperature dropped to about 200 K. However, the wrinkles disappeared below about 180 K. This phenomenon indicates the wrinkles at low temperature would depend on the properties of the silicon (100) of the device layers and independent of the properties of the BOX layers under the silicon (100) membranes.     

Hydrogen annealing effects on epitaxy of SOI wafer

Thick silicon on insulator (SOI) wafers have been fabricated by chemical vapor deposition (CVD) after separation by implantation of oxygen (SIMOX) process. The hydrogen annealing effects on epitaxial Si layer were studied. The hydrogen annealing could remove the surface damages of substrate caused by SIMOX process and provide a smoother epitaxial substrate. The number of dislocations and stacking faults in the epitaxial layer decreased remarkably by hydrogen annealing SOI substrate. Meanwhile, compared with other reports, our hydrogen annealing did not degrade the buried oxide layer and top Si layer of SOI substrate.     

Low-dose SIMOX wafers for LSIs fabricated with internal-thermal-oxidation (ITOX) process: electrical characterization

Electrical performance of separation by implanted oxygen (SIMOX) wafers manufactured by internal-thermal-oxidation (ITOX) process was evaluated. Breakdown behaviour of the buried oxide (BOX) layer was confirmed quantitatively to be dominated by Si islands therein, which were found to be reduced in size or eliminated by the ITOX process. By optimizing the oxygen dose and ITOX amount, a BOX breakdown field of about 8 MV/cm, comparable to those of thermally-grown oxide, was attained. The gate oxide integrity on an ITOX-SIMOX wafer was found to be superior to that of bulk Si wafers, indicating the wafer surface was improved by the high temperature annealing.     

Transformation of hydrogen trapped onto microbubbles into H platelet layer in SI

Features of a process of delamination of a crystalline silicon layer from a silicon wafer along a hydrogen platelet layer formed by r.f. plasma hydrogenation are described. The process involves first making a buried layer of nuclei for hydrogen platelets. Ion implantation of inert or low-soluble gases is used to form the layer. The nuclei are microbubbles that appear along the R_p plane of implanted ions. Results for argon are presented. Wafers implanted with a dose of 10¹⁵ cm^–2 are then hydrogenated with an r.f. plasma. During hydrogenation, atomic hydrogen diffuses into the silicon wafer and collects onto internal surfaces of the microbubbles. Then the hydrogen increases the internal surface of the microbubbles by growing platelet-type extensions to the microbubbles. The extensions grow preferentially along the buried-layer plane. A silicon layer above the layer of grown platelets was delaminated through a pre-bonding/cut/post-bonding sequence as in a standard layer-transfer process. The plasma hydrogenation of the trap layer may be used as a step in a process of fabricating of SOI wafers with a very thin top crystalline silicon layer. Also, implant doses needed to form the microbubble trap layer are much lower than doses of direct implantation of hydrogen in the layer-transfer process.     

Formation of buried insulating layers by high dose oxygen implantation under controlled temperature conditions

A specially designed sample holder was used to form SOI structures by high dose oxygen implantation under controlled temperature conditions. This system uses a layer of molten tin to provide a good thermal contact between the silicon wafer and a resistively heated support. The layers formed under these conditions were characterized by RBS and XTEM. After annealing at 1150°C for 2 h the only remaining defects in the top silicon layers are dislocations with a density of less than 10⁷ cm^?2 and SiO₂ precipitates. Annealing at 1185°C for 6 h does not change the density of dislocations but leads to the formation of a 200 nm thick silicon layer free of SiO₂ precipitates, suitable for VLSI processing without growing an epitaxial layer.     

Structural and Optical Studies on Ion-implanted 6H-SiC Thin Films

A series of hot (600 °C) and room temperature C⁺/Al⁺ co-implanted 6H-SiC epitaxial films, under different implantation dose levels and high temperature (1550 °C) post-annealing, were studied by a variety of structural and optical characterization techniques, including secondary ion mass spectroscopy, high resolution X-ray diffraction, Fourier transform infrared reflectance, micro-Raman and photoluminescence (PL) spectroscopy. The damage and amorphization of SiC layer by co-implantation, and the elimination/suppression of the implantation induced amorphous layer via high temperature annealing are observed. The recovery of the crystallinity and the activation of the implant acceptors are confirmed. The results from hot or RT co-implantation are compared.     

硅离子注入引入纳米晶对SIMOX材料进行总剂量辐射加固

本研究工作采用硅离子注入和高温退火工艺对SIMOX材料的BOX层进行总剂量辐射加固.辐射实验结果证明了该加固方法的有效性.PL谱和HRTEM图像显示了硅离子注入及退火工艺在材料的BOX层中引入了Si纳米晶,形成电子陷阱能级,有效俘获电子,从而提高了材料BOX层的抗总剂量辐射能力.     

Transfer of single crystalline silicon nanolayer onto alien substrate

Starting from the 60-nm node, future generations of mainstream semiconductor devices (i.e., CMOS) will be mostly manufactured from silicon-on-insulator (SOI) initial substrates with the top silicon layer having a thickness 50 nm or less. We describe a process that is capable for transfer of nanoscale thick layers. The layer is delaminated from a single crystalline silicon substrate and laminated onto another substrate, thus resulting in SOI. The process includes: 1) forming a trap layer for hydrogen in an initial substrate; 2) delivery of hydrogen to the traps by diffusion of monatomic hydrogen; 3) evolving the trapped hydrogen into a layer of hydrogen platelets; 4) stiffening of the surface of the initial substrate by laminating to another substrate; and 5) delaminating a layer from the initial substrate along the hydrogen platelet layer. Details of the new layer transfer process are described. A depth where the buried trap layer locates is critical for the process. An implantation of heavy ions is used to form the trap layer. A trap capacity for hydrogen is evaluated as a function of implantation conditions. Plasma hydrogenation is used to deliver atomic hydrogen to the traps. Electron cyclotron resonance, microwave, RF, and dc plasma are compared as the hydrogenation sources. Dependence of a thickness of a transferred layer as a function of the mass of implanted ions and implantation energy is described. Types of layer transfer faults are also described. Mechanisms of the layer transfer faults are suggested. We discuss limits of scaling down of the thickness of the layer that is transferred from one substrate to another. The scaling limit of our process is compared to the limits of other (SIMOX, Smart-Cut, and ELTRAN) processes.