基于芬顿反应的单晶SiC化学机械抛光加工研究

发布时间：2018-05-15 23:03

  本文选题：单晶碳化硅(SiC) + 芬顿反应　； 参考：《广东工业大学》2017年硕士论文

【摘要】：单晶SiC作为第三代半导体材料,因具备禁带宽度大、击穿电场高、热导率大、电子饱和漂移速率高、抗辐射能力强等优越性能,是固态光源和电力电子、微波射频器件的“核芯”,在半导体照明、新一代移动通信、能源互联网、高速轨道交通、新能源汽车、消费类电子等领域有广阔的应用前景。作为重要应用之一,用于外延工艺基片的单晶SiC表面要求超光滑、无缺陷、无表面/亚表面损伤,表面粗糙度达到Ra≤0.3nm,以满足外延膜生长的需要。但单晶SiC的硬度高(莫氏硬度9.2)、硬脆性大、化学稳定性好等原因,高效超精密平坦化加工SiC难度极大,严重制约了SiC半导体器件的应用和发展。本文通过芬顿羟基自由基(·OH)检测试验、SiC氧化反应试验,验证了芬顿反应能够氧化单晶SiC。芬顿反应过程能够生成氧化性极强的氧化剂—羟基自由基,羟基自由基能够与单晶SiC发生化学反应生成氧化层。对氧化层进行XPS物质属性分析发现,该氧化层为Si O2。氧化层的纳米压痕试验表明,Si O2氧化层的硬度和模量远小于原始SiC表面,采用磨粒加工可以很容易去除这层软质氧化层,证实了基于芬顿反应的化学机械抛光方法能够对单晶SiC进行超光滑平坦化加工。从化学影响因素角度,针对芬顿反应生成的羟基自由基浓度及其对SiC化学机械抛光的影响进行了系统的实验研究。比较了羟基自由基浓度对单晶SiC氧化效果的影响,研究了芬顿试剂组份(催化剂种类、Fe2+浓度、p H值、H2O2浓度等)对芬顿反应生成羟基自由基的规律及其对SiC化学机械抛光的影响。研究发现羟基自由基浓度越高,SiC表面生成的氧化层越厚,SiC化学机械抛光效果越好、抛光效率越高。芬顿试剂组份为0.02wt.%FeSO4、5wt.%H2O2、p H3时,芬顿反应生成的羟基自由基浓度较高,并能极大促进SiC化学机械抛光,获得了表面粗糙度Ra0.187nm的超光滑表面。从抛光工艺角度,对磨料种类、磨料浓度、磨粒粒径、抛光压力、抛光转速等工艺参数进行了单因素实验,研究对材料去除率和抛光效果的影响规律。结果发现选择硅溶胶磨料、磨料浓度为20%、磨粒粒径为50nm、抛光压力为0.02Mpa、抛光转速为60r/min时的加工效果最佳,能够获得表面粗糙度Ra≤0.3nm的超光滑表面。在研究基于芬顿反应SiC化学机械抛光的化学因素和工艺参数的基础上,分析了基于芬顿反应的化学机械抛光的材料去除过程,探究了抛光垫的特性、磨损、接触变形的作用机理及其对SiC抛光效果的影响,建立了基于芬顿反应的单晶SiC化学机械抛光材料去除模型,揭示了化学机械抛光机理。芬顿反应生成的羟基自由基能与单晶SiC发生化学反应生成一层软质易去除的Si O2氧化层,氧化层在磨粒的机械摩擦作用下被去除,化学和机械的交替作用最终实现SiC表面的材料去除。
[Abstract]:As the third generation semiconductor material, single crystal SiC is a solid state light source and power electronics because of its large band gap, high breakdown electric field, high thermal conductivity, high electron saturation drift rate, strong radiation resistance and so on. The "core" of microwave RF devices has a broad application prospect in semiconductor lighting, new generation mobile communications, energy Internet, high-speed rail transit, new energy vehicles, consumer electronics and other fields. As one of the important applications, the surface of single crystal SiC used in epitaxial substrate is super-smooth, non-defect, no surface / sub-surface damage, surface roughness is less than 0.3nmRa to meet the needs of epitaxial film growth. However, the single crystal SiC has high hardness (Mor hardness 9.2%, hard brittleness, good chemical stability, etc.). It is very difficult to process SiC by high-efficiency ultra-precision flatting, which seriously restricts the application and development of SiC semiconductor devices. The Fenton hydroxyl radical (OH) test and sic oxidation test have proved that Fenton reaction can oxidize single crystal sic. During the Fenton reaction, hydroxyl radical, which is an oxidizing oxidant, can be formed. Hydroxyl radical can react with single crystal SiC to form oxide layer. By analyzing the properties of the oxide layer by XPS, it is found that the oxide layer is Sio _ 2. The nano-indentation test of the oxide layer shows that the hardness and modulus of the oxide layer are much smaller than that of the original SiC surface, and the soft oxide layer can be easily removed by abrasive processing. It is proved that the chemical mechanical polishing method based on Fenton reaction can be used for ultra-smooth and flat processing of single crystal SiC. The concentration of hydroxyl radical produced by Fenton reaction and its effect on SiC chemical-mechanical polishing were studied systematically from the point of view of chemical influencing factors. The effect of hydroxyl radical concentration on the oxidation of single crystal SiC was compared. The effect of Fenton reagent composition (catalyst type Fe _ 2 concentration and H _ 2O _ 2) on the formation of hydroxyl radical in Fenton reaction and the effect on SiC chemical and mechanical polishing were studied. It is found that the higher the concentration of hydroxyl radical is, the thicker the oxide layer on sic surface is, the better the chemical and mechanical polishing effect is, and the higher the polishing efficiency is. When the Fenton reagent is composed of 0.02wt.SO4 5wt.H _ 2O _ 2H _ 3, the concentration of hydroxyl radical produced by Fenton reaction is higher, and it can greatly promote the SiC chemical-mechanical polishing, and the super-smooth surface of Ra0.187nm surface roughness is obtained. From the point of view of polishing technology, single factor experiments were carried out on the parameters of abrasive type, abrasive concentration, abrasive particle size, polishing pressure, polishing speed and so on, and the effects on material removal rate and polishing effect were studied. The results show that when the silica sol abrasive is chosen, the abrasive concentration is 20, the abrasive particle size is 50 nm, the polishing pressure is 0.02 MPA, and the polishing speed is 60r/min, the super-smooth surface with surface roughness Ra 鈮，

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