Mechanism of amorphous Ge_2Sb_2Te_5 removal during chemical mechanical planarization in acidic H_2O_2 slurry

In this paper, chemical mechanical planarization （CMP） of amorphous Ge2Sb2Te5 （a-GST） in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2. Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described.

Scratch formation and its mechanism in chemical mechanical planarization (CMP)

Chemical mechanical planarization(CMP)has become one of the most critical processes in semiconductor device fabrication to achieve global planarization.To achieve an efficient global planarization for device node dimensions of less than 32 nm,a comprehensive understanding of the physical,chemical,and tribo-mechanical/chemical action at the interface between the pad and wafer in the presence of a slurry medium is essential.During the CMP process,some issues such as film delamination,scratching,dishing,erosion,and corrosion can generate defects which can adversely affect the yield and reliability.In this article,an overview of material removal mechanism of CMP process,investigation of the scratch formation behavior based on polishing process conditions and consumables,scratch formation mechanism and the scratch inspection tools were extensively reviewed.The advantages of adopting the filtration unit and the jet spraying of water to reduce the scratch formation have been reviewed.The current research trends in the scratch formation,based on modeling perspective were also discussed.

Chemical mechanical planarization of amorphous Ge_2Sb_2Te_5 with a soft pad

Chemical mechanical planarization（CMP） of amorphous Ge_2Sb_2Te_5（a-GST） is investigated using two typical soft pads（politex REG and AT） in acidic slurry.After CMP,it is found that the removal rate（RR） of a-GST increases with an increase of runs number for both pads.However,it achieves the higher RR and better surface quality of a-GST for an AT pad.The in-situ sheet resistance（R_s） measure shows the higher R_s of a-GST polishing can be gained after CMP using both pads and the high R_s is beneficial to lower the reset current for the PCM cells. In order to find the root cause of the different RR of a-GST polishing with different pads,the surface morphology and characteristics of both new and used pads are analyzed,it shows that the AT pad has smaller porosity size and more pore counts than that of the REG pad,and thus the AT pad can transport more fresh slurry to the reaction interface between the pad and a-GST,which results in the high RR of a-GST due to enhanced chemical reaction.

Effect of polishing parameters on abrasive free chemical mechanical planarization of semi-polar(1122) aluminum nitride surface

An abrasive free chemical mechanical planarization（AFCMP） of semi-polar（1122） Al N surface has been demonstrated. The effect of slurry p H, polishing pressure, and platen velocity on the material removal rate（MRR） and surface quality（RMS roughness） have been studied. The effect of polishing pressure on the AFCMP of the（1122） Al N surface has been compared with that of the（1122） Al Ga N surface. The maximum MRR has been found to be 562 nm/h for the semi-polar（1122） Al N surface, under the experimental conditions of 38 k Pa pressure,90 rpm platen velocity, 30 rpm carrier velocity, slurry p H 3 and 0.4 M oxidizer concentration. The best root mean square（RMS） surface roughness of 1.2 nm and 0.7 nm, over a large scanning area of 0.70×0.96 mm^2, has been achieved on AFCMP processed semi-polar（1122） AlN and（AlGaN） surfaces using optimized slurry chemistry and processing parameters.

Defectivity control of aluminum chemical mechanical planarization in replacement metal gate process of MOSFET

The replacement metal gate（RMG） defectivity performance control is very challenging in high-k metal gate（HKMG） chemical mechanical polishing（CMP）. In this study, three major defect types, including fall-on particles, micro-scratch and corrosion have been investigated. The research studied the effects of polishing pad,pressure, rotating speed, flow rate and post-CMP cleaning on the three kinds of defect, which finally eliminated the defects and achieved good surface morphology. This study will provide an important reference value for the future research of aluminum metal gate CMP.

Planarization mechanism of alkaline copper CMP slurry based on chemical mechanical kinetics

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.

Effect of copper slurry on polishing characteristics

The composition of the polishing solution is optimized by investigating the impact of the WIWNU （the so-called within-wafer-non-uniformity WIWNU） and the removal rate （RR） on the polishing characteristics of copper, The oxidizer concentration is 1 Vol%; the abrasive concentration is 0.8 Vol%; the chelating agent of the solution is 2 Vol%. The working pressure is 1 kPa. The defect on the surface is degraded and the surface is clean after polishing. The removal rate is 289 nm/min and the WIWNU is 0,065. The surface roughness measured by AFM after CMP （chemical mechanical planarization） is 0.22 nm.

The optimization of FA/O barrier slurry with respect to removal rate selectivity on patterned Cu wafers

Because the polishing of different materials is required in barrier chemical mechanical planariza- tion （CMP） processes, the development of a kind of barrier slurry with improved removal rate selectivity for Cu/barrier/TEOS would reduce erosion and dishing defects on patterned Cu wafers. In this study, we developed a new benzotriazole-free barrier slurry named FA/O barrier slurry, containing 20 mL/L of the chelating agent FA/O, 5 mL/L surfactant, and a 1：5 concentration of abrasive particles. By controlling the polishing slurry ingredients, the removal rate of different materials could be controlled. For process integration considerations, the effect of the FA/O barrier slurry on the dielectric layer of the patterned Cu wafer was investigated. After CMP processing by the FA/O barrier slurry, the characteristics of the dielectric material were tested. The results showed that the dielectric characteristics met demands for industrial production. The current leakage was of pA scale. The resistance and capacitance were 2.4 k and 2.3 pF, respectively. The dishing and erosion defects were both below 30 nm in size. CMP-processed wafers using this barrier slurry could meet industrial production demands.