【作者】 曾波；

【导师】 王均； 常鸿；

【作者基本信息】 四川大学 ， 材料工程（专业学位）， 2021， 硕士

【摘要】 在硅晶片的制造过程中,干法刻蚀是重要的环节之一。通常是利用等离子体来对晶圆进行轰击,同时活性原子或原子团与晶圆材料反应,生成挥发性的物质被真空系统带走,从而达到刻蚀的目的。但在生产过程中,氟等离子体同样会对刻蚀腔内器件造成侵蚀,导致设备零部件寿命降低,维护成本升高。同时,形成的刻蚀产物以悬浮微粒的形式从内壁脱落,弥散在腔体中,也会导致晶圆污染,成品率下降。因此应当提高刻蚀腔内零部件的耐等离子刻蚀性能,通常是在其表面等离子喷涂陶瓷涂层来实现。Y₂O₃是目前半导体行业中应用极为广泛的耐等离子体刻蚀涂层。但目前相关报道缺乏对涂层制备工艺的系统研究,缺乏建立涂层制备工艺——微观结构——使用性能的联系。本文通过正交实验设计法对大气等离子喷涂Y₂O₃耐刻蚀涂层的工艺参数进行了优选。研究了工艺参数对涂层性能的影响和涂层喷涂过程中的物相转变,分析了涂层在氟等离子体环境中的刻蚀行为和孔隙率对涂层刻蚀过程的影响。主要得到以下结论:在以Ar/H2为工作气体的大气等离子喷涂制备氧化钇涂层的过程中,存在立方相Y₂O₃向单斜相Y₂O₃的转变,喷涂参数会影响相变的程度,单斜相Y₂O₃的含量在5%-8%左右。150mm的喷涂距离能提供颗粒最大的冲击压力,因此单斜相含量最高。涂层表面形貌能在一定程度上反映颗粒的熔化——撞击——铺展情况。涂层截面形貌中可见涂层与基体结合紧密,其结合方式为机械咬合;涂层中存在不同程度的孔隙、裂纹等缺陷,将影响涂层的整体性能。APS参数对涂层孔隙率存在显著直接影响,进而影响结合强度、硬度、刻蚀速率以及介电强度。在实验参数设计范围内,涂层孔隙率受工艺参数影响为:随着主氩气的升高先降低后升高,随着氢气的增加先降低后几乎不变,随着喷涂间距的增大而先降低后升高,随着喷涂速度的增大而逐步降低。确定了如下优选参数:主氩气流量50NLPM,氢气流量6NLPM,喷涂间距150mm,喷涂速度900mm/s。以优选参数进行喷涂,发现样品孔隙率最低,比初始组内最低孔隙率降幅约27.9%;硬度有提高但不明显;结合强度提高14.3%;介电强度提高5.9%;刻蚀速率降低了10.3%。等离子刻蚀过程增大了样品表面粗糙度。在刻蚀表面,氟化物含量基本稳定在较低水平,氟元素约占10at%。Y₂O₃陶瓷涂层在等离子体刻蚀情况下的损耗机理可以概括为局部腐蚀和均匀腐蚀。对涂层中存在的孔隙、裂纹等缺陷,腐蚀选择性地从边缘处开始,随后形成反映孔隙形状的腐蚀痕迹,其腐蚀速度也相对较快。对涂层中的致密区域,则发生均匀腐蚀,腐蚀速率较慢,同样形成凹坑,并且沿晶界的腐蚀更加严重。更低的孔隙率样品表现出更为优异的耐刻蚀性。孔隙率与涂层的刻蚀速率有显著相关性,降低孔隙率是提高Y₂O₃涂层耐刻蚀性能的关键。更多还原

【Abstract】 Dry etching is one of the most important steps in silicon wafer manufacture.Plasma is usually used to process wafer,while active atoms or radicals react with the wafer material,generating volatile substances that are taken away by the vacuum system,so as to achieve the purpose of etching.However,in the production process,fluorine plasma will also erode the inner components of the etched cavity,leading to reduced service life of equipment parts and increased maintenance costs.At the same time,the etched products formed fall off from the inner wall in the form of suspended particles and disperse in the cavity,resulting in wafer contamination and reduced yield.Therefore,the plasma etching resistance of the components in the etching cavity should be improved.It is usually achieved by plasma spraying ceramic coating on its surface.Y₂O₃ is a plasma etching resistant coating widely used in semiconductor industry at present.However,there is a lack of systematic study on the preparation process of coatings and the connection between the preparation process,microstructure and properties of coatings.In this paper,the process parameters of Y₂O₃ etching resistant coating by APS were optimized by orthogonal experimental design.The effect of process parameters on coating properties and phase transition during coating spraying were studied.The etching behavior of the coating in fluorine plasma and the effect of porosity on the etching process were analyzed.The main conclusions are as follows:In the process of preparing Y₂O₃ coating by APS with Ar /H2 as working gas,there is a phase transition from cubic to monoclinic.Spray parameters will affect the extent of phase transformation,and the content of monoclinic Y₂O₃ is about 5%-8%.The 150 mm spray distance provides the maximum impact pressure for the particles,resulting in the highest monoclinic content.The surface morphology of the coating can reflect the melting-impact-spreading of particles to a certain extent.The cross-section morphology of the coating shows that the coating and the substrate bond closely,and the bonding mode is mechanical occlusal.Different extent of pores,cracks and other defects in the coating will affect the properties of the coating.APS parameters have significant influence on the porosity of the coating,and then affect the bonding strength,hardness,etching rate and dielectric strength.Within the design range of experimental parameters,the coating porosity is affected by the process parameters as follows: first decreases and then increases with the increase of main argon,first decreases and then almost unchanged with the increase of hydrogen,first decreases and then increases with the increase of spraying spacing,and gradually decreases with the increase of spraying speed.The following optimal parameters were determined: main argon gas flow 50 NLPM,hydrogen flow 6NLPM,spraying distance150 mm,spraying speed 900mm/s.After spraying with the optimal parameters,the porosity of the sample was found to be the lowest,which is reduced by about 27.9%.The hardness is increased but not obvious.The binding strength increased by 14.3%.The dielectric strength increased by 5.9%.The etching rate decreased by 10.3%.The plasma etching process increases the surface roughness of the sample.On the sample surface,fluoride content is basically stable at a low level,and fluoride element accounts for about 10at%.The loss mechanism of Y₂O₃ ceramic coating under plasma etching can be summarized as local etching and uniform etching.For the defects such as pores and cracks in the coating,the corrosion starts selectively from the edge,and then corrosion traces that reflect the pore shape are formed,and the corrosion speed is relatively fast.For the dense area in the coating,uniform corrosion occurs and the corrosion rate is slower.The same pits are formed,and the corrosion along the grain boundary is more serious.The samples with lower porosity possess better etching resistance due to the smaller exposed surface area in the plasma atmosphere.There is a significant correlation between the porosity and the etching rate of the coating.Reducing the porosity is the key to improve the etching resistance of the Y₂O₃ coating.更多还原