碳化硅RSD器件关键工艺探索

发布时间：2018-04-10 12:47

本文选题：碳化硅 + RSD　；参考：《华中科技大学》2015年硕士论文

【摘要】：碳化硅(Si C)是新型宽禁带半导体材料,具有宽带隙、高热导率、高电子饱和速度、高临界击穿场强等优点。用Si C材料制作功率半导体器件相对于传统Si基器件具有更高的耐压、更低的导通电阻和功率损耗、更强的散热能力等优势。在Si C材料的各种结构中,4H-Si C具有更高的载流子迁移率和更低的各向异性,应用更为广泛。反向开关晶体管RSD(Reversely Switched Dynistor)是专门应用于脉冲功率领域的半导体开关,相对其他脉冲功率领域的开关器件具有通流能力强、di/dt耐量高、开通速度快和易于串联等优点。采用Si C材料制作RSD器件可望进一步提高器件的阻断电压和电流密度,减小高耐压情况下的导通损耗,更有利于高压和重复频率应用。目前,在Si C功率器件的工艺制作领域仍然存在诸多难点,例如刻蚀技术、离子注入、P型欧姆接触制作的问题。本文主要研究4H-Si C RSD器件的制作工艺,并对Si C材料的工艺难点进行了探索。重点研究了4H-Si C材料的关键加工工艺之一——刻蚀工艺。采用感应耦合等离子体刻蚀(Inductively Coupled Plasma,ICP)方法,CF4/O2混合气体作为刻蚀气体,用正交实验的方法系统研究了ICP功率、RF功率、CF4流量、O2流量等工艺参数对4H-Si C材料刻蚀速率的影响,结果表明刻蚀速率随ICP功率和RF功率的增大而增大,随CF4流量先减小后增大,随O2流量先增大后减小。获得了最大的刻蚀速率213.47nm/min并测得其表面均方根粗糙度(RMS)为0.724nm,保证了较好的表面质量。设计并初步探索了4H-Si C RSD器件的全套工艺流程。实验前期进行了外延片结构设计、工艺流程设计和光刻版制定;然后在外延片基础上,进行了光刻、磁控溅射、金属剥离、ICP刻蚀、离子注入及退火、欧姆接触制作等一系列工艺步骤,对关键参数如曝光时间、显影时间、磁控溅射条件、剥离时间、离子注入能量及剂量、退火条件等进行了探索。最后提出了台面正斜角工艺以改善器件阻断特性,初步制得正向阻断电压约为600V的器件,为器件工艺的进一步完善和优化打下了基础。
[Abstract]:Silicon carbide (sic) is a new wide band gap semiconductor material with wide band gap, high thermal conductivity, high electron saturation rate and high critical breakdown field strength.Compared with the traditional Si based devices, the fabrication of power semiconductor devices with sic has the advantages of higher voltage, lower on-resistance and power loss, stronger heat dissipation and so on.4H-Si C has higher carrier mobility and lower anisotropy among the various structures of sic materials, so it is more widely used.The reverse switching transistor (RSD(Reversely Switched Dynistor) is a semiconductor switch which is specially used in the field of pulse power. Compared with other switching devices in the field of pulse power, it has the advantages of high current capacity, high throughput, high turn-on speed and easy to be connected in series.Using sic to fabricate RSD devices is expected to further increase the blocking voltage and current density, reduce the on-loss at high voltage, and be more favorable to the application of high voltage and repetition frequency.At present, there are still many difficulties in the fabrication of sic power devices, such as etching technology and the fabrication of ion implanted P-type ohmic contacts.In this paper, the fabrication process of 4H-Si C RSD devices is studied, and the process difficulties of sic materials are explored.The etching process, one of the key processing technology of 4H-Si C material, is studied emphatically.The inductively coupled Coupled plasma-ICP method is used to etch the mixed gas of CF4 / O2 as etching gas. The influence of ICP power, RF power and flow rate of CF4 on the etching rate of 4H-Si C is systematically studied by orthogonal experiment.The results show that the etching rate increases with the increase of ICP power and RF power, decreases firstly with the flow rate of CF4 and then increases with the flow rate of O2.The maximum etching rate (213.47nm/min) was obtained and the RMS of the surface RMS was 0.724 nm, which ensured the better surface quality.The complete process of 4H-Si C RSD device is designed and preliminarily explored.In the early stage of the experiment, the structure design, process design and lithography were carried out, and then the lithography, magnetron sputtering, metal stripping ICP etching, ion implantation and annealing were carried out on the basis of the epitaxial wafer.The key parameters such as exposure time, development time, magnetron sputtering condition, stripping time, ion implantation energy and dose, and annealing conditions were investigated.At last, a positive diagonal technique is proposed to improve the blocking characteristics of the device, and the device with a forward blocking voltage of about 600V is obtained, which lays a foundation for the further improvement and optimization of the device process.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.24

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