This study investigated the wettability effect of polysilicon on the polishing performance and organic defect contamination during polysilicon chemical mechanical polishing ͑CMP͒. Contact angle measurement was utilized to understand the nature of polysilicon surfaces. An oxidizer, H 2 O 2 , was added to the silica slurry to modify a hydrophobic polysilicon surface to a hydrophilic surface during polishing. The adhesion force was measured between a polymeric pad particle and a poly-Si wafer surface in KOH solution ͑pH 11͒ as a function of H 2 O 2 concentration. The adhesion force of the polymeric pad particle on the polysilicon decreased from 14 to 8 nN as the peroxide concentration increased to 10 vol %, at which the surface became hydrophilic. The hydrophilization of the polysilicon surface during polishing drastically reduced the organic contamination on the polysilicon wafers after polishing. The removal rate, frictional force, and pad temperature during CMP, with and without oxidizing the surface, were measured. They all decreased with the increasing concentrations of the oxidizer. The decrease was attributed to the formation of the lubrication layer of the oxide surface due to the oxidation of polysilicon.Dynamic random access memory ͑DRAM͒ process technology has become a leading semiconductor technology, with the highest production volume among very large scale integration ͑VLSI͒ semiconductor products. The density of DRAM quadrupled approximately every three years by virtue of advances in DRAM technology. 1 Because of the decrease in device feature size, the chemical mechanical polishing ͑CMP͒ process has become a necessary processing step for planarizing the surfaces during the DRAM process. 2 Poly-Si CMP is implemented to reduce the step height of a gate poly-Si in the construction of a recess channel array transistor and Fin Field Effect Transistor ͑FinFET͒ three-dimensional structures. 3 Although the CMP process is performed effectually, there are several problems that need to be overcome, such as local dishing/erosion, scratches, and abrasive and organic particle contamination. 4 After the CMP process, the wafer surface might be contaminated by the abrasive particles and polymeric residues from the pad, the retainer ring, and other consumables. The removal of organic residues from the wafer surfaces is a great challenge for the next processing step. The surface of poly-Si is hydrophobic in nature. Hence, it attracts hydrophobic organic residues, mostly pad debris, during the CMP process. These organic defects are difficult to be removed by general post-CMP cleaning methods. 5-7 Because there is much concern about organic contamination on polished polysilicon surfaces after polishing, understanding the interaction between the organic residues and the polysilicon surface is required.Therefore, this study investigated the organic contamination mechanism of polymeric residues on polished polysilicon surfaces. H 2 O 2 , as an oxidizer, was added to the silica slurry to modify the wettability of the polysil...

This paper attempts to establish planarization model in chemical mechanical polishing of silicon oxide using high selective ceria slurry. Though removal rate of the high area is increased due to a high pressure focused on the area with abrasive and pad, the removal rate of the same area is not increased but decreased even in the very beginning of polishing with ceria slurry. It also observed that only the elevated area is polished and dishing is not occurred during the polishing in high selective ceria CMP. In this work, it is proposed that ceria abrasives are filled in the low trench area and then support the pad as well as high area during the CMP, which results in planarization without dishing.

The effects of surfactants on oxide-to-polysilicon selectivity during chemical mechanical polishing have been investigated. Slurries with nonionic surfactants such as Brij surfactants, polyethylene oxide ͑PEO͒, and ethylene oxide-propylene oxide-ethylene oxide triblock copolymer enhanced oxide-to-polysilicon polishing selectivity. Although a current conventional oxide slurry has a low oxide-to-polysilicon selectivity of 0.5:1, slurries with nonionic surfactants show a higher selectivity due to a combined effect of adsorption and interfacial adhesion of added nonionic surfactant molecules on the polysilicon surface. The oxide-to-polysilicon selectivity of the Brij surfactant added slurry displayed a stronger dependency on the hydrophile-lipophile-balance ͑HLB͒ value than the type of alkyl group or the chain length of surfactants. Especially, Brij52 with low HLB value gave an oxide-to-polysilicon selectivity of 9.3, which is 17 times higher than the selectivity of a commercial oxide slurry. A high molecular weight polymeric surfactant such as PEO also gave a greater selectivity than a low molecular weight surfactant. In addition, slurries with nonionic surfactants reduce the final thickness variation effectively in damascene structure having a polysilicon stopping layer. The final thickness variation polished with the Brij52 added slurry was decreased to one fourth of that with the conventional oxide slurry only.As the design rule decreases in semiconductor manufacturing industry, multilayer integration using chemical mechanical polishing ͑CMP͒ is being widely adopted to obtain a flat surface during processing. Current CMP processes are focused on meeting a higher planarity and uniformity requirements. As a result, the process windows of CMP processes become tighter. 1-5 In general, high selective slurry to a stopping layer is required to obtain these performances simultaneously. When a high selective slurry is used, effective stop on a stopping layer becomes possible due to the high selectivity of materials. Typical examples of selective polishing with highly selective slurry are shallow trench isolation CMP process with silicon nitride stopper and copper CMP process with tantalum ͑Ta͒ or tantalum nitride ͑TaN͒ stopping layer. 1-7 The concept of selective CMP process is important especially in a damascene structured pattern. When a single material is polished to planarize an oxide layer like interlayer dielectric ͑ILD͒ or intermetal dielectric ͑IMD͒, the selectivity is not critical. 1-4 However, the selectivity to the stopper material is indispensable for uniformity and planarity when two or more materials are polished simultaneously.Polysilicon is one of the candidates as a stopping material for a damascene structure. CMP process with efficient stop on polysilicon requires a improved selective slurry to polysilicon. However, the current conventional oxide slurry composed of fumed silica abrasive does not stop effectively on polysilicon due to the low oxide-topolysilicon polishing selectivity of 0.5:1. To increase...

The purpose of this study is to investigate the effects of slurry pH on the adhesion and removal of silica and ceria abrasive particles on the poly Si, TEOS, SiN and SAC (self aligned memory cell contact) and STI (shallow trench isolation) patterned wafer surfaces. The adhesion force of silica and ceria particles were theoretically and experimentally investigated in STI and poly Si CMP process. A stronger adhesion force was observed for silica particles on the poly Si wafer in acidic rather than in alkaline solutions. The adhesion force of ceria particle was lower than that of silica in investigated pH ranges. STI patterned wafer showed lower adhesion force than SAC patterned wafer. Lower adhesion force between particles and surface resulted in a lower level of particle contamination.

Highly selective chemical mechanical polishing (CMP) of Si3N4 over SiO2 is achieved by using a modified silica abrasive. Controlling the removal rate of Si3N4/SiO2, chemical reaction is a dominant factor for ceria abrasive, but physical force such as repulsion/attraction is a primary one for silica abrasive. In order to maximize mechanical action in CMP process using silica slurry, we modified the surface charge of silica abrasive into having more negative charge, which resulting in −50 mV of zeta potential in a low pH (< 3.0) slurry. This strong negative zeta potential of the modified silica abrasive enables enhancing attractive forces to Si3N4 and repulsive forces to SiO2 in a low pH environment. In addition, a cocoon shape silica abrasive shows 3 times higher Si3N4 RR than a spherical shape one. Consequently, selectivity of Si3N4 over SiO2 reaches 95.0, which is significantly improved from 0.0167 in the conventional silica abrasive case. When this modified silicon abrasive and the optimum pH condition are applied, in-chip uniformity at various pattern densities of Si3N4 (0, 12, and 32%) turns out to be well controlled under 100 Å. This result is an acceptable level for our semiconductor device integration.