HfO_x镶嵌结构的CMP及其机理研究
发布时间：2018-09-17 08:02
【摘要】：过渡金属氧化物材料氧化铪(Hf Ox)以其优异的性能而被广泛应用于微电子器件和光电子器件等领域,同时,相关的高性能器件对叠层材料的表面和界面也提出了极高的要求。在IC领域中,既能保证叠层材料的全局平坦化,又能实现器件的互连镶嵌结构的唯一技术就是化学机械平坦化(CMP)。作为下一代非挥发性存储器(NVM)最有力的竞争者之一的阻变存储器(RRAM)必须完成高密度高集成才可彰显其优势,因此,存储功能材料及相关电极材料的平坦化技术成为RRAM产业化推进的关键所在(ITRS-2005已经预测了NVM中的平坦化技术是不可或缺的关键工艺)。Hf Ox基RRAM被业界预测为最有可能或最早实现产业化的阻变器件之一,本论文针对Hf Ox基NVM器件制作过程中的关键工艺——CMP,开展了研究。主要研究了抛光液组分和抛光工艺参数对裸片和带通孔结构的Hf Ox-CMP的影响;结合AFM和FTIR等测试表征,对Hf Ox-CMP机理进行了初步探索;并基于Hf Ox-CMP工艺的优化制作了镶嵌(通孔)结构的阻变器件。本文首先通过p H值、添加剂Na BF4浓度和磨料粒径对抛光液进行了优化,从抛光速率、表面均方根(RMS)粗糙度以及抛光液稳定性方面进行了综合评判,发现当p H=6时,利用39.9nm的Si O2磨料在含0.2wt%-Na BF4的抛光液中对Hf Ox薄膜进行抛光,抛光速率可达70.1nm/min,抛光后表面粗糙度可达0.3nm,同时对Si O2的抛光选择比大于10;其次,利用最佳抛光液工艺参数,研究了抛光下压力和抛光盘转速对材料去除速率和表面粗糙度的影响,随着下压力和抛光盘转速的增大,Hf Ox的抛光速率成线性增加,符合Preston方程,但对表面粗糙度影响不大;同时,还对不同尺寸通孔经Hf Ox-CMP后形成的dishing情况进行了研究,发现当通孔尺寸由3μm增大至9μm时,dishing由19.80nm增加至60.85nm,但不同通孔dishing分布的离散性无较大变化。接着,在Hf Ox-CMP工艺研究的基础上,对其抛光机理进行了探索,一方面,根据对抛光下压力与抛光盘转速乘积的拟合,对Preston方程进行了修订:cRR?k PV?R,根据拟合结果得出截距Rc(5.58nm/min)与实验中Hf Ox腐蚀速率(~5.2nm/min)基本一致,因此将其定义为Hf Ox的静态腐蚀速率;另一方面,利用AFM和FTIR对抛光前后和经Na BF4溶液腐蚀前后的Hf Ox薄膜表面进行了表征,发现在抛光过程中有表面层的生成,软化了Hf Ox表面,促进了抛光的进行。结合以上两方面的分析,初步探索出Hf Ox的抛光机理为:Hf Ox薄膜首先与添加剂Na BF4反应生成硬度相对较小的表面层,接着在磨料机械磨削作用下,表面层被去除,两步过程交替进行完成对Hf Ox薄膜的抛光。最后,基于对Hf Ox-CMP工艺的优化和机理的分析,制作了通孔结构的Hf Ox基阻变器件,进行了电学性能的测试,并与无结构阻变器件进行了对比。结果表明:通孔结构阻变器件具有较小的Set电压、较小的Set电压和高低阻态分布的离散性,并且,通孔结构阻变器件cell间Set电压的一致性更好,分布更为集中。由此可判断,本论文针对Hf Ox-CMP工艺的优化和研究在器件制作过程中是有效的,也是可行的,为进一步提高阻变器件的一致性提供了方案和实验基础。
[Abstract]:Transition metal oxide material hafnium oxide (Hf Ox) is widely used in microelectronic devices and optoelectronic devices because of its excellent properties. At the same time, the related high-performance devices also put forward very high requirements for the surface and interface of the laminated materials. In IC field, it can not only ensure the overall flatness of the laminated materials, but also realize the device. Chemical mechanical flattening (CMP) is the only technology for interconnect mosaic structures. Resistive memory (RRAM), one of the most powerful competitors for the next generation of non-volatile memory (NVM), must have high density and high integration to demonstrate its advantages. Therefore, the flattening technology of storage functional materials and related electrode materials has become the industrialization of RRAM. Hf Ox-based RRAM has been predicted to be one of the most likely or earliest resistance devices to be industrialized. In this paper, CMP, the key technology in the fabrication of Hf Ox-based NVM devices, is studied. The influence of processing parameters on Hf Ox-CMP of bare wafer and through-hole structure was studied. The mechanism of Hf Ox-CMP was explored by combining the characterization of AFM and FTIR. Resistance devices with mosaic (through-hole) structure were fabricated based on the optimization of Hf Ox-CMP process. Firstly, the effect of P H value, concentration of additive Na BF4 and abrasive particle size on the polishing fluid was studied. The polishing rate, surface RMS roughness and the stability of polishing solution were optimized. It was found that the polishing rate of Hf Ox film in 0.2wt%-Na BF4 polishing solution with 39.9nm Si O2 abrasive was 70.1nm/min, and the surface roughness was 0.3nm after polishing. Secondly, the influence of polishing pressure and disc rotational speed on material removal rate and surface roughness was studied by using the optimum polishing fluid parameters. With the increase of downward pressure and disc rotational speed, the polishing rate of Hf Ox increased linearly, which accorded with Preston equation, but had little effect on surface roughness. The dishing of through holes with different sizes after Hf Ox-CMP was studied. It was found that the dishing increased from 19.80 nm to 60.85 nm when the size of through holes increased from 3 to 9 microns, but the dispersion of dishing distribution in different through holes did not change much. Then, the polishing mechanism was explored on the basis of Hf Ox-CMP process research. According to the fitting of the product of polishing pressure and rotational speed of polishing disc, the Preston equation was revised: cRR? K PV? R. According to the fitting results, the intercept Rc (5.58 nm/min) was basically consistent with the experimental Hf Ox corrosion rate (~5.2 nm/min), so it was defined as the static corrosion rate of Hf Ox; on the other hand, the static corrosion rate of Hf Ox before and after polishing and Na after polishing was determined by AFM and FTIR. The surface of Hf Ox film was characterized before and after corrosion by BF4 solution. It was found that there was a surface layer formed during the polishing process, which softened the surface of Hf Ox and promoted the polishing process. Then, the surface layer is removed by abrasive mechanical grinding, and the Hf Ox film is polished by two steps alternately. Finally, based on the optimization of Hf Ox-CMP process and the analysis of mechanism, the Hf Ox resistive devices with through-hole structure are fabricated, and the electrical properties are tested and compared with the unstructured resistive devices. Ming: The through-hole resistive devices have smaller Set voltage, smaller Set voltage and discrete distribution of high and low resistance states. Moreover, the through-hole resistive devices have better consistency and more concentrated distribution of Set voltage between cells. It provides a feasible and experimental basis for further improving the consistency of resistive devices.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN305.2
本文编号：2245241
[Abstract]:Transition metal oxide material hafnium oxide (Hf Ox) is widely used in microelectronic devices and optoelectronic devices because of its excellent properties. At the same time, the related high-performance devices also put forward very high requirements for the surface and interface of the laminated materials. In IC field, it can not only ensure the overall flatness of the laminated materials, but also realize the device. Chemical mechanical flattening (CMP) is the only technology for interconnect mosaic structures. Resistive memory (RRAM), one of the most powerful competitors for the next generation of non-volatile memory (NVM), must have high density and high integration to demonstrate its advantages. Therefore, the flattening technology of storage functional materials and related electrode materials has become the industrialization of RRAM. Hf Ox-based RRAM has been predicted to be one of the most likely or earliest resistance devices to be industrialized. In this paper, CMP, the key technology in the fabrication of Hf Ox-based NVM devices, is studied. The influence of processing parameters on Hf Ox-CMP of bare wafer and through-hole structure was studied. The mechanism of Hf Ox-CMP was explored by combining the characterization of AFM and FTIR. Resistance devices with mosaic (through-hole) structure were fabricated based on the optimization of Hf Ox-CMP process. Firstly, the effect of P H value, concentration of additive Na BF4 and abrasive particle size on the polishing fluid was studied. The polishing rate, surface RMS roughness and the stability of polishing solution were optimized. It was found that the polishing rate of Hf Ox film in 0.2wt%-Na BF4 polishing solution with 39.9nm Si O2 abrasive was 70.1nm/min, and the surface roughness was 0.3nm after polishing. Secondly, the influence of polishing pressure and disc rotational speed on material removal rate and surface roughness was studied by using the optimum polishing fluid parameters. With the increase of downward pressure and disc rotational speed, the polishing rate of Hf Ox increased linearly, which accorded with Preston equation, but had little effect on surface roughness. The dishing of through holes with different sizes after Hf Ox-CMP was studied. It was found that the dishing increased from 19.80 nm to 60.85 nm when the size of through holes increased from 3 to 9 microns, but the dispersion of dishing distribution in different through holes did not change much. Then, the polishing mechanism was explored on the basis of Hf Ox-CMP process research. According to the fitting of the product of polishing pressure and rotational speed of polishing disc, the Preston equation was revised: cRR? K PV? R. According to the fitting results, the intercept Rc (5.58 nm/min) was basically consistent with the experimental Hf Ox corrosion rate (~5.2 nm/min), so it was defined as the static corrosion rate of Hf Ox; on the other hand, the static corrosion rate of Hf Ox before and after polishing and Na after polishing was determined by AFM and FTIR. The surface of Hf Ox film was characterized before and after corrosion by BF4 solution. It was found that there was a surface layer formed during the polishing process, which softened the surface of Hf Ox and promoted the polishing process. Then, the surface layer is removed by abrasive mechanical grinding, and the Hf Ox film is polished by two steps alternately. Finally, based on the optimization of Hf Ox-CMP process and the analysis of mechanism, the Hf Ox resistive devices with through-hole structure are fabricated, and the electrical properties are tested and compared with the unstructured resistive devices. Ming: The through-hole resistive devices have smaller Set voltage, smaller Set voltage and discrete distribution of high and low resistance states. Moreover, the through-hole resistive devices have better consistency and more concentrated distribution of Set voltage between cells. It provides a feasible and experimental basis for further improving the consistency of resistive devices.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN305.2
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