The stability of a novel weakly alkaline slurry of copper interconnection CMP for GLSI

Chemical mechanical polishing (CMP) is one of the important machining procedures of multilayered copper interconnection for GLSI,meanwhile polishing slurry is a critical factor for realizing the high polishing performance such as high planarization efficiency,low surface roughness.The effect of slurry components such as abrasive (colloidal silica),complexing agent (glycine),inhibitor (BTA) and oxidizing agent (H2O2) on the stability of the novel weakly alkaline slurry of copper interconnection CMP for GLSI was investigated in this paper.First,the synergistic and competitive relationship of them in a peroxide-based weakly alkaline slurry during the copper CMP process was studied and the stability mechanism was put forward.Then 1 wt％ colloidal silica,2.5 wt％ glycine,200 ppm BTA,20 mL/L H2O2 had been selected as the appropriate concentration to prepare copper slurry,and using such slurry the copper blanket wafer was polished.From the variations of copper removal rate,root-mean square roughness (Sq) value with the setting time,it indicates that the working-life of the novel weakly alkaline slurry can reach more than 7 days,which satisfies the requirement of microelectronics further development.     

A new weakly alkaline slurry for copper planarization at a reduced down pressure

This study reports a new weakly alkaline slurry for copper chemical mechanical planarization （CMP）, it can achieve a high planarization efficiency at a reduced down pressure of 1.0 psi. The slurry is studied through the polish rate, planarization, copper surface roughness and stability. The copper polishing experiment result shows that the polish rate can reach 10032 A/rain. From the multi-layers copper CMP test, a good result is obtained, that is a big step height （10870 A） that can be eliminated in just 35 s, and the copper root mean square surface roughness （sq） is very low （〈 1 rim）. Apart from this, compared with the alkaline slurry researched before, it has a good progress on stability of copper polishing rate, stable for 12 h at least. All the results presented here are relevant for further developments in the area of copper CMP.     

基于化学机械动力学的碱性铜抛光液平坦化机理研究

The planarization mechanism of alkaline copper slurry is studied in the chemical mechanical polishing (CMP) process from the perspective of chemical mechanical kinetics.Different from the international dominant acidic copper slurry,the copper slurry used in this research adopted the way of alkaline technology based on complexation. According to the passivation property of copper in alkaline conditions,the protection of copper film at the concave position on a copper pattern wafer surface can be achieved without the corrosion inhibitors such as benzotriazole(BTA),by which the problems caused by BTA can be avoided.Through the experiments and theories research,the chemical mechanical kinetics theory of copper removal in alkaline CMP conditions was proposed. Based on the chemical mechanical kinetics theory,the planarization mechanism of alkaline copper slurry was established. In alkaline CMP conditions,the complexation reaction between chelating agent and copper ions needs to break through the reaction barrier.The kinetic energy at the concave position should be lower than the complexation reaction barrier,which is the key to achieve planarization.     

盐酸胍在阻挡层化学机械抛光中对速率选择性及表面形貌的影响

We propose an alkaline barrier slurry containing guanidine hydrochloride（GH） and hydrogen peroxide.The slurry does not contain any corrosion inhibitors, such as benzotriazole（BTA）. 3-inch samples of tantalum copper and oxide were polished to observe the removal rate. The effect of GH on removal rate selectivity along withhydrogenperoxidewasinvestigatedbycomparingslurrycontainingGHandH2O2withslurrycontainingonly GH. Details about the tantalum polishing mechanism in an alkaline guanidine-based slurry and the electrochemical reactions are discussed. The results show that guanidine hydrochloride can increase the tantalum polishing rate and the selectivity of copper and barrier materials. The variation of the dishing and wire line resistance with the polishing time was measured. The dishing value after a 300 mm pattern wafer polishing suggests that the slurry has an effective performance in topography modification. The result obtained from the copper wire line resistance test reveals that the wire line in the trench has a low copper loss.     

Alkaline barrier slurry applied in TSV chemical mechanical planarization

We have proposed a TSV （through-silicon-via） alkaline barrier slurry without any inhibitors for barrier CMP （chemical mechanical planarization） and investigated its CMP performance. The characteristics of removal rate and selectivity of Ti/SiO2/Cu were investigated under the same process conditions. The results obtained from 6.2 mm copper, titanium and silica show that copper has a low removal rate during barrier CMP by using this slurry, and Ti and SiO2 have high removal rate selectivity to Cu. Thus it may be helpful to modify the dishing. The TSV wafer results reveal that the alkaline barrier slurry has an obvious effect on surface topography correction, and can be applied in TSV barrier CME     

碱性铜抛光液在300mm平坦化系统中CMP工艺优化的研究

CMP process optimization for bulk copper removal based on alkaline copper slurry was performed on a 300 mm Applied Materials Reflexion LK system. Under the DOE condition, we conclude that as the pressure increases, the removal rate increases and non-uniformity is improved. As the slurry flow rate increases, there is no significant improvement in the material removal rate, but it does slightly reduce the WIWNU and thus improve uniformity. The optimal variables are obtained at a reduced pressure of 1.5 psi and a slurry flow rate of 300 ml/min. Platen/carrier rotary speed is set at a constant value of 97/103 rpm. We obtain optimized CMP characteristics including a removal rate over 6452 A/min and non-uniformity below 4% on blanket wafer and the step height is reduced by nearly 8000 A/min in the center of the wafer on eight layers of copper patterned wafer, the surface roughness is reduced to 0.225 nm.     

在铜CMP过程中降低抛光压力与磨料的机械作用

Chemical mechanical planarization(CMP) is a critical process in deep sub-micron integrated circuit manufacturing. This study aims to improve the planarization capability of slurry, while minimizing the mechanical action of the pressure and silica abrasive. Through conducting a series of single-factor experiments, the appropriate pressure and the optimum abrasive concentration for the alkaline slurry were confirmed. However, the reduced mechanical action may bring about a decline of the polishing rate, and further resulting in the decrease of throughput.Therefore, we take an approach to compensating for the loss of mechanical action by optimizing the composition of the slurry to enhance the chemical action in the CMP process. So 0.5 wt% abrasive concentration of alkaline slurry for copper polishing was developed, it can achieve planarization efficiently and obtain a wafer surface with no corrosion defect at a reduced pressure of 1.0 psi. The results presented here will contribute to the development of a “softer gentler polishing” technique in the future.     

Effect of 1,2,4-triazole on galvanic corrosion between cobalt and copper in CMP based alkaline slurry

Cobalt has become a new type of barrier material with its unique advantages since the copper-interconnects in the great-large scale integrated circuits (GLSI) into 10 nm and below technical nodes,but cobalt and copper have severe galvanic corrosion during chemical-mechanical flattening.The effect of 1,2,4-triazole on Co/Cu galvanic corrosion in alkaline slurry and the control of rate selectivity of copper and cobalt were investigated in this work.The results of electrochemical experiments and polishing experiments had indicated that a certain concentration of 1,2,4-triazole could form a layer of insoluble and dense passive film on the surface of cobalt and copper,which reduced the corrosion potential difference between cobalt and copper.Meantime,the removal rate of cobalt and copper could be effectively controlled according to demand during the CMP process.When the study optimized slurry was composed of 0.5 wt％ colloidal silica,0.1％vol.hydrogen peroxide,0.05 wt％ FA/O,345 ppm 1,2,4-triazole,cobalt had higher corrosion potential than copper and the galvanic corrosion could be reduced effectively when the corrosion potential difference between them decreased to 1 mV and the galvanic corrosion current density reached 0.02 nA/cm2.Meanwhile,the removal rate of Co was 62.396 nrn/min,the removal rate of Cu was 47.328 nm/min,so that the removal rate ratio of cobalt and copper was 1.32:1,which was a good amendment to the dishing pits.The contact potential corrosion of Co/Cu was very weak,which could be better for meeting the requirements of the barrier CMP.     

低磨料浓度的碱性铜抛光液平坦化性能的研究

A novel alkaline copper slurry that possesses a relatively high planarization performance is investigated under a low abrasive concentration.Based on the action mechanism of CMP,the feasibility of using one type of slurry in copper bulk elimination process and residual copper elimination process,with different process parameters,was analyzed.In addition,we investigated the regular change of abrasive concentration effect on copper and tantalum removal rate and within wafer non-uniformity(WIWNU) in CMP process.When the abrasive concentration is 3 wt%,in bulk elimination process,the copper removal rate achieves 6125 °/min,while WIWNU is 3.5%,simultaneously.In residual copper elimination process,the copper removal rate is approximately 2700°/min,while WIWNU is 2.8%.Nevertheless,the tantalum removal rate is 0 °/min,which indicates that barrier layer isn’t eliminated in residual copper elimination process.The planarization experimental results show that an excellent planarization performance is obtained with a relatively high copper removal rate in bulk elimination process.Meanwhile,after residual copper elimination process,the dishing value increased inconspicuously,in a controllable range,and the wafer surface roughness is only 0.326 nm(sq < 1 nm) after polishing.By comparison,the planarization performance and surface quality of alkaline slurry show almost no major differences with two kinds of commercial acid slurries after polishing.All experimental results are conducive to research and improvement of alkaline slurry in the future.     

Characterization and optimization of copper chemical mechanical planarization

The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors (ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements, the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node.     

新型GLSI弱碱性铜抛光液稳定性研究

随着极大规模集成电路(GLSI)技术节点逐渐降低至28 nm,多层铜布线化学机械抛光过程中弱碱性抛光液的稳定性成为人们研究的热点.以四乙基氢氧化铵作为pH调节剂,配制不同pH值的新型弱碱性抛光液,研究各组抛光液的pH值、粒径、Zeta电位以及铜去除速率、表面粗糙度和去除速率一致性随存放时间(0,12,24,36和48 h)的变化,并与KOH作为pH调节剂的抛光液进行了对比.结果表明,pH值、粒径、Zeta电位在存放时间内基本不变.pH值大于10时平坦化效果较差,pH值为9.0时,平坦化效果较好,0和48 h铜去除速率为530 nm/min和493.1 nm/min,抛光后铜表面粗糙度为0.718和0.855 nm,铜去除速率一致性为4.31％和4.54％,该抛光液加入双氧水后可以稳定存放48 h以上,可满足工业生产的要求.     

一种含有盐酸胍的新型TSV抛光液

本文中,对一种新型的含有盐酸胍的TSV抛光液在CMP(化学机械平坦化)中的性能进行了研究,该TSV抛光液是一种碱性抛光液,并且不含任何抑制剂。在抛光过程中,盐酸胍作为一种有效的表面复合单元,相对于铜和介质的去除速率,钛的去除速率是可以通过调节选择性来控制的。在TSV生产过程中对于表面蝶形坑的修正及得到好的表面平整度是有利的。本文主要研究了抛光液成分的作用机理以及盐酸胍在TSV抛光液中的巧妙应用。     

ULSI中多层Cu布线CMP表面粗糙度的分析和研究

分析介绍了Cu层表面粗糙度对器件性能的影响以及超大规模集成电路中多层Cu布线CMP的作用机理,研究分析了碱性抛光液对Cu的表面粗糙度的影响因素,如磨料、氧化剂、pH值、表面活性剂等对表面粗糙度的影响。实验证明,在一定的抛光条件下,选用SiO2为磨料、双氧水为氧化剂的碱性抛光液可以有效降低Cu层的表面粗糙度,使之达到纳米级,得到良好的抛光效果,从而解决了超大规模集成电路多层Cu布线化学机械抛光中比较重要的技术问题。     

碱性多羟多胺螯合剂对Cu CMP后BTA去除作用及机理

苯并三唑(BTA)在微电子领域常被用于铜抛光液中的抗蚀剂,抛光后的BTA残留需要通过化学机械抛光(CMP)后清洗工序从晶圆表面去除,否则会影响器件的性能.通过实验研究了碱性多羟多胺类螯合剂对抛光后晶圆表面残留BTA的去除效果及机理.首先通过傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)研究了BTA在铜表面的吸附状态,发现铜表面的氧化程度会影响BTA在晶圆表面的吸附状态;然后采用体积分数为0.02％、pH值为10.3的碱性多羟多胺螯合剂去除铜表面BTA薄膜.FTIR和XPS测试结果显示,碱性多羟多胺螯合剂可以有效去除铜表面BTA薄膜;最后,通过实验数据研究了碱性多羟多胺螯合剂去除BTA的机理.     

Effects of electric potential on chemical-mechanical polishing of copper

The effect of electric potential on the dissolution and polishing behavior of copper in acidic and alkaline media was investigated. The electromechanical polishing mechanism of copper is discussed based on removal rate of copper, pH of slurries, and surface morphology of polished copper. The most interesting phenomenon occurred in chemical-mechanical polishing (CMP) of copper with applied direct current (DC) voltage is the variation of pH during polishing. The dissolution experiments indicated that an acidic agent might have more hydrogen reduced with higher DC potential. The results demonstrated that the application of DC voltage is beneficial to improve planarization of copper polishing in an alkaline slurry.     

ULSI制备中多层布线导体铜的抛光液与抛光技术的研究

提出了在碱性浆料中ULSI多层布线导体铜化学机械抛光的模型,对铜CMP所需达到的平面化、选择性、抛光速率控制、浆料的稳定及洁净度、抛光液成分的优化选择进行了实验研究。     

不含抑制剂的碱性抛光液对铜布线平坦化的研究

本文提出一种碱性铜布线抛光液,其不含通用的腐蚀抑制剂,并对其化学机械抛光和平坦化 (CMP)性能进行了研究。首先研究了此抛光液对铜的静态腐蚀速率和抛光速率,并与含抑制 剂的铜抛光液做了对比实验。在静态条件下,此不含抑制剂的碱性铜抛光液对铜基本无腐蚀速率,而在动态抛光过程中对铜有较高的速率。而含抑制剂的抛光液对静态腐蚀速率略有降低,但是却大幅度降低了铜的去除速率。另外,对铜布线的化学机械平坦化研究表明,此不含抑制剂的碱性铜抛光液能够有效的去除铜布线表面的高低差,有较高的平坦化能力。此抛光液能够应用于铜CMP的第一步抛光,能够去除大量多余铜时初步实现平坦化。