Reliability Study of Oxidized Deposited Polysilicon (ODP) Gate Oxide for Silicon Carbide Power Transistors

碳化硅功率晶体管氧化沉积多晶硅 (ODP) 栅极氧化物的可靠性研究

• 批准号: 9906543
• 负责人: John Ayers
• 金额: $ 3.89万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9906543&HistoricalAwards=false
• 关键词: Reliability; Study; Oxidized; Deposited; Polysilicon

9906543AyersSilicon carbide (SiC) is a wide-bandgap semiconductor of great interest for high-power and high-temperature applications. In particular, SiC metal oxide semiconductor field effect transistors (MOSFET's) are promising for high-power, high-temperature applications because of the inherent temperature stability of MOSFET's and because of the high quality of the oxide, which is SiO2. Of the various MOSFET designs, the U-groove MOSFET (U-MOSFET) is particularly well suited for high-power applications due to its high current capability. U-MOSFET's may be fabricated in SiC using epitaxy and ion implantation, followed by anisotropic etching to form the U-groove, and then thermal oxidation to form the gate oxide. This approach, although standard in Si technology, is problematic in SiC because of the strong anisotropy of the thermal oxidation. It has been shown recently that this problem can be solved by the deposition of polycrystalline silicon, followed by thermal oxidation. This two-step process results in gate-quality oxide with uniform thickness over U-groove structures. In addition, the use of oxidized deposited polysilicon (ODP) gate oxide provides great flexibility in nitridation of the gate oxide. Initial studies indicate that nitridation of the gate oxide in SiC MOSFET's can reduce hot carrier injection and improve reliability. To date however, there have been few studies of the reliability of gate oxides in SiC MOSFET's under high-temperature, high-field conditions, and there have been no such studies in the case of ODP gate oxide. The PI's propose to study the reliability of ODP gate oxide on SiC under high-stress conditions.For this study, polysilicon will be deposited in a chemical vapor deposition system on {0001} 4H SiC wafers. Polysilicon deposition will be carried out using silane diluted in UHP hydrogen, at 700oC. The polysilicon, approximately 100 nm thick, will be oxidized in dry O2 at 1100oC for a time sufficient to consume all of the polysilicon. Metal gates will then be deposited by the evaporation of aluminum or the deposition of doped polysilicon. The PI's will study the reliability of the resulting MOS capacitors under high-stress conditions. The MOS capacitors will be held at high field (106-107 V/cm) and high temperature (100-300oC). The PI's will periodicallycheck the flat band voltage throughout the course of the stressing to assess the degradation. The PI's will also use photo-CV measurements to determine the oxide interface state density before and after stressing.***

9906543 Ayers碳化硅（SiC）是一种宽带隙半导体，在高功率和高温应用中具有重要意义。 特别地，SiC金属氧化物半导体场效应晶体管（MOSFET）对于高功率、高温应用是有希望的，因为MOSFET的固有温度稳定性并且因为氧化物（其为SiO2）的高质量。在各种MOSFET设计中，U型槽MOSFET（U-MOSFET）由于其高电流能力而特别适合于高功率应用。 可以使用外延和离子注入在SiC中制造U-MOSFET，然后进行各向异性蚀刻以形成U形凹槽，然后进行热氧化以形成栅极氧化物。 这种方法虽然在Si技术中是标准的，但由于热氧化的强各向异性，在SiC中是有问题的。 最近已经表明，这个问题可以通过沉积多晶硅，然后进行热氧化来解决。 这种两步工艺在U形槽结构上产生具有均匀厚度的栅极质量氧化物。 此外，氧化沉积多晶硅（ODP）栅极氧化物的使用在栅极氧化物的氮化中提供了很大的灵活性。 初步研究表明，SiC MOSFET栅氧化层的氮化可以减少热载流子注入，提高可靠性。 然而，迄今为止，在高温、高场条件下，对SiC MOSFET的栅极氧化物的可靠性的研究很少，并且在ODP栅极氧化物的情况下也没有这样的研究。 PI的建议，以研究在高应力条件下的碳化硅上的ODP栅氧化层的可靠性。在这项研究中，多晶硅将在化学气相沉积系统中沉积在{0001} 4 H SiC晶片上。 多晶硅沉积将使用稀释在UHP氢气中的硅烷在700 oC下进行。 大约100 nm厚的多晶硅将在1100 oC的干燥O2中氧化足够长的时间以消耗所有多晶硅。 然后通过铝的蒸发或掺杂多晶硅的沉积来沉积金属栅极。 PI将研究高应力条件下所得MOS电容器的可靠性。 MOS电容器将保持在高场（106-107 V/cm）和高温（100- 300 oC）下。 PI将在整个强制降解过程中反复检查平带电压，以评估降解情况。 PI还将使用光CV测量来确定应力前后的氧化物界面态密度。*