Conventional Chemical Mechanical Polishing Process Research Articles

Fabrication of silicon-on-insulator with high uniform top Si for silicon photonics applications

Silicon-on-insulator (SOI) is the most suitable platform for silicon photonics applications owing to its unique structure and excellent compatibility. To satisfy the requirement of uniformity, HCl etching process is developed to smooth the surface of top silicon layer in this paper. The top silicon mean thickness is thinned down to 220 nm; the corresponding root mean square roughness is as low as 0.165 nm after the etching process, which is comparable to chemical mechanical polishing (CMP) process. Furthermore, HCl etching process shows great repeatability of thickness range and removal amount. The within wafer thickness range can be controlled below 30 Å and the removal amount can be controlled within ±4.5 Å, which is far better than conventional CMP process.

Development of super-smooth flat silicon mirror substrates using bowl-feed chemical-mechanical polishing

Silicon is one of the important optical substrate materials used for making high reflectivity, high damage threshold mirrors for high power/energy IR lasers and grazing incidence synchrotron X-ray mirrors. These applications require ultra-low roughness or super-smooth substrates that ensure extremely low scattering losses. The present work is an attempt to fabricate super-smooth, flat silicon substrates using the conventional Chemical-Mechanical Polishing (CMP) method with bowl-feed technique. The roughness parameters of the ultra-smooth flat silicon surfaces fabricated using bowl-feed CMP have been measured in Atomic Force Microscope (AFM) and by hard X-Ray Reflectivity (XRR) and are found to be of the order of 5 Å. The surface morphologies of the polished silicon surfaces were also investigated using a Scanning Electron Microscope (SEM). We briefly discuss the bowl-feed CMP process of producing super-smooth, flat silicon substrates and presented the results of surface roughness measurements using various techniques.

Chemical mechanical polishing to improve the efficiency uniformity of beam sampling grating

In order to improve the efficiency uniformity of large-aperture beam sampling gratings (BSGs), a conventional chemical mechanical polishing (CMP) process of fused silica by CeO₂ slurry is proposed to modify their groove profiles. With the proposed CMP process, the efficiency uniformity of several BSGs with an aperture of 430 mm×430 mm has been successfully controlled within an rms of 5%. The proposed CMP process is an effective method to improve the efficiency uniformity of large-aperture BSGs. Using the proposed CMP process, the requirement of the uniformity of the holographic ion beam etching process can be released in the realization of large-aperture BSGs.

A method to form self-aligned carbon-nanotube-vias using a Ta-cap layer on a Co-catalyst

A method to form self-aligned carbon nanotube (CNT) vias using a Ta-cap layer on a Co catalyst by chemical vapor deposition at 400°C is described. The Ta-cap layer protects the Co catalyst from oxidation. This protection potentially eliminated the need for additional processing steps to control the size and activity of the Co catalyst, which are two critical parameters for CNT formation. The Ta-cap layer was observed to remain on the top of the multi-walled CNTs as a contact layer after the synthesis at 400°C. The Ta-cap layer self-formed a continuous interface between the electrode layer and the CNT layer. Besides, it can avoid the conventional chemical mechanical polishing process. The Ta-cap layer thickness was found to be the key parameter affecting CNT growth and was optimized. O2 plasma treatment was implemented to remove residual amorphous carbon accumulated on the top of Ta-cap layer after CNT formation. The electrical properties were also measured to verify the feasibility of this CNT-via structure.

1H-Benzotriazole Incorporated Pad for Chemical Mechanical Planarization of Copper

Chemical mechanical polishing (CMP) pads are generally designed to play a passive role in terms of chemical reactions that occur on the surface to be polished. For copper CMP, a pad that is capable of initiating and controlling various chemical reactions on the copper surface can bring another dimension of flexibility to the CMP process. This work investigates such a model pad for its potential applications in copper CMP. More specifically, the physical and chemical properties of a polyurethane pad containing -benzotriazole (BTA) are examined. When applied to Cu blanket wafers, the BTA-containing pad yielded a higher removal rate compared to the conventional CMP process with the reference pad. For patterned wafer polishing, the results indicate that the BTA-containing pad is effective in improving the step height reduction efficiency and in minimizing dishing and erosion. The potential applications of a pad with such a design for gaining a fundamental understanding of the copper CMP process are discussed based on these experimental results.

Calculation on Temperature Rise of CMP Process: Roughness Effects Considered

Chemical mechanical polishing (CMP) has been widely accepted in modern integrated circuit (IC) industries and hard disk manufacturing processes, to insure wafer surface with high level of global and local planarity required. In CMP process, temperature rise has two-edged influences: temperature-rise accelerates the chemical activity and the motion of nano-particles contained in the slurry through which material removal ratio (MRR) is enhanced; the other side of the same coin is, however, that it will soften the pad surface and subsequently reduce the MRR. Furthermore, it is found that temperature-rise would cause agglomeration of nano-particles, which would cause the wafer surface defect. The net effects of temperature thus should be under investigation with scrutiny. In an attempt to study the temperature variation and influencing rule, in this paper we firstly establish the flow equation considering pad roughness, coupling the energy equation on the basis of thermodynamics. Then, by taking numerical simulation which is carried out to give out the temperature distribution of conventional CMP process. The results show that temperature-rise in the CMP process is very minor. The research will surely shed some lights on the mechanism of CMP and lay a feasible foundation for possible future utilization.

Study on Hard-Pad-Based CMP of Dielectric Global Planarization

Chemical-mechanical polishing (CMP) has been widely accepted for the planarization of multi-layer structures in semiconductor manufacturing. High performance CMP for the planarization of premetal and inter layer dielectrics is strongly required. Conventional CMP process using the stack-type pads shows good within-wafer uniformity. However this process produces degradation in planarity, especially between center and edge areas of logic devices. In this work, we described an approach to the optimized dielectric planarization method using the hard-pad-based CMP process and achieve improved wafer-scaled uniformity and within-die planarity, simultaneously. By optimizing both polishing conditions and the consumables of the polishers, the hard pad-based process showed an at least 1.6-time improvement in step height reduction compared to the stack-type pad process and a comparable within-wafer uniformity.

A Preliminary Model Accounting for the Suction Pressure in CMP Process

Chemical mechanical polishing (CMP) is a widely used technique to achieve high level of global and local planarity required in modern integrate circuit (IC) industries and hard disk manufacturing process, etc., which pleas for concentrate researches. The main purpose of the present research is in an attempt to express the counterintuitive experimental aftermath: the ‘negative’ pressure, i.e., a suction force occurred in conventional commercial CMP process. A preliminary two tiers wafer-scale flow model for CMP is presented considering the roughness as well as the elasticity of the bulk pad substrate. Numerical simulations were conducted to elucidate the contact pressure and flow pressure distributions. The results show that a divergence region appears near the leading edge, which contributes to the suction pressure. A stress-richened area near the edges will give rise to over polishing. The research aftermaths agree well with the experiments, that validate the proposed analysis to some extend. This will shed lights on the mechanism of CMP process, which for a long time is considered as a black art where empirical or semi-empirical data are dependent upon to optimize the CMP parameters.

Study of Slurry Composition Transition in a Rotary Copper CMP Process

AbstractThe polishing pad is one of the prime components in a typical Chemical Mechanical Polishing (CMP) process. The structure and transport properties of a polishing pad are critical in determining the particle and chemical utilization in a conventional CMP process. Our earlier paper investigated the particle retention and transport on two different polishing pads, IC-1400 and Suba-500, during copper polishing. In this paper, the results of chemical retention and transport of IC-1400 and Suba-500 pads during copper polishing are presented. The polish rate results from slurry-step-flow experiments with H2O2-glycine based slurries, where the concentrations of chemicals in the slurry are altered in steps during polishing, are correlated to the chemical retention and transport characteristics of these pads. It is found that IC-1400 has a higher chemical transport capability than Suba-500 pad, which is shown to affect the polish rates of copper.