Toshiroh Karaki Doy

Characteristics of Abrasive-Free Micelle Slurry for Copper CMP

The need for a next-generation chemical mechanical polishing (CMP) slurry for copper planarization, to meet the requirements posed by advanced copper damascene processes, has led to the conception and development of a new type of slurry. The new micelle slurry is based on a mixture of surfactant and heteropolyacid, which takes the form of surfactant micelles enveloping the copper-reactive heteropolyacid. When used in the CMP process in place of conventional slurries, it effects copper planarization by a chemical mechanism with little or no mechanical abrasion. The mechanism enables a high rate of copper removal under low polishing pressures with minimal copper dishing, largely free from the scratching or erosion that may be encountered in CMP with conventional slurries due to their abrasive particle contents. These characteristics are advantageous for planarization of advanced copper damascene interconnects and particularly those including the relatively fragile low-k dielectrics. The micelle slurry also reduces the need for frequent dressing of foamed pads and enables a remarkably high rate of copper planarization with nonfoamed hard pads under low polishing pressures. It may therefore lengthen the pad service life and reduce the complexity and cost of CMP, particularly for copper damascene interconnects incorporating low-k dielectrics.

Impact of novel pad groove designs on removal rate and uniformity of dielectric and copper CMP

The effect of pad surface texture on dielectric and copper removal rates was studied theoretically and experimentally by investigating the fluid behavior of the slurry layer using methodologies similar to those found in tribological investigations of fluid bearings. It is shown that new nonfoamed hard plastic pads with intricate groove patterns are critical in modulating removal rates. Removal rate results of dielectric chemical mechanical polishing were in close agreement with model predictions for several of the groove designs tested. Combined patterns, consisting of spiral and logarithmic grooves, were shown to impact several key attributes of the dielectric and copper processes in terms of slurry retention, hydrodynamic pressure, tribological mechanism, and material removal rates.

Novel retaining ring to reduce CMP edge exclusion

This study presents a new approach to edge profile control during air back carrier Chemical Mechanical Polishing (CMP). Control of wafer edge profile proves to be difficult as different factors are reported to influence polishing characteristics. To evaluate a CMP on the wafers edge it needs to look at polish characteristics of leading and trailing edges separately. To understand polish performance on both leading and trailing edges, and their impact on resulting wafers edge profile a non-rotating carrier experiment had been conducted. Based on the results of the nonrotating carrier experiment a novel retaining ring design has been proposed. In the course of this study CMP of the wafers edge evaluation for a novel retaining ring has been performed on blanket PETEOS 200 mm wafers for different retaining pressures. Edge profile evaluation provided a proof for the Pad Wave Hypothesis and helped to significantly enhance the CMP performance by increasing process stability and achieving wider process window for retaining ring pressure.

Integrated planarization technique with consistency in abrasive machining for advanced semiconductor chip fabrication

Abstract This paper proposes the establishment of a new integrated planarization technique using ultrafine abrasive machining for application to advanced semiconductor chip fabrication. The main features implemented are integrated planarization for the silicon substrate, blanket films of oxide and wafers with pattern topography. Planarization concepts were brought out for these wafers with different shape and material. The authors tried to apply not only loose-abrasive methods such as chemical mechanical polishing(CMP), but also bonded abrasive methods such as ductile mode grinding using ultrafine abrasives. New developments in the proposed ultrafine machining processes were presented. Finally the use of planarization machining techniques appropriate for each kind of wafer produced good planar surface respectively.

Development of a novel air-back wafer carrier with an integrated endpoint detector for copper CMP application

This study presents the development of a novel air-back polishing carrier with an integrated Linear Variable Differential Transformer Endpoint Detector (LVDT EPD). In the course of this study, uniformity evaluation was performed on blanket PETEOS oxide and blanket copper wafers and dishing/erosion multi-step polish on patterned wafers. Employment of an air-back polishing carrier resulted in non-uniformity <3% 1/spl sigma/. The LVDT EPD showed an excellent S/N ratio. The combination of LVDT EPD and air-back polishing carrier significantly enhanced the process performance in Cu CMP.

Control of edge polishing profile with air float carrier

An air float carrier is developed to achieve uniform polishing with continuous air supply during polishing of the wafer. The carrier has a thin support film inside the retainer ring. Retainer pressure enables the support film to push the wafer edge down to the pad locally to control edge-polishing profile. Using this air float carrier, we try to evaluate the relationship between pressure profile measured under static condition and actual edge-polishing profile at various retainer extensions and various retainer pressures. As a result of this comparison, it has become evident that the calculated pressure profile corresponds to the actual edge-polishing profile and retainer pressure has a great influence on the actual edge-polishing profile.

Step Height Differences between Simultaneously Mirror-Polished Work Surfaces Composed of Various Materials. Study on Super-Smooth Polishing Methods. (1st Report).

This paper deals with the basic research on super-smooth polishing methods and step height differences between work surfaces composed of various materials when mirror-polishing. A theoretical equation of step height was applied, and its calculated results showed good conformity to the actual values obtained by polishing of the specimens consisted of four different glasses, using cerium oxide powders and polyurethane polishers. When polisher was used over about 15 hours, its surface became stable and a constant step height was kept up on work surface. When, however, the polisher was dressed or washed, the polisher surface became unstable and relatively large difference in the step height was produced. The step height also showed a tendency to increase when rather soft polishers were used. Moreover, the elastic deformation amount affecting the step height was obtained for some polishers, by applying the experimental data and the equation.