Developing a neural network-based run-to-run process controller for chemical-mechanical planarization

A new neural network-based run-to-run process control system (NNRtRC) is proposed in this article. The key characteristic of this NNRtRC is that the linear and stationary process estimator and controller in the exponentially weighted moving average (EWMA) run-to-run control scheme are replaced by two multilayer feed-forward neural networks. An efficient learning algorithm inspired by the sliding mode control law is suggested for the neural network-based run-to-run controller. Computer simulations illustrate that the proposed NNRtRC performs better than the EWMA approach in terms of draft suppression and adaptation to environmental change. Experimental results show that the NNRtRC can precisely trace the desired target of material removal rate (MRR) and keep the within wafer non-uniformity (WIWNU) in an acceptable range.     

100mm InGaP/GaAs HBT及相关电路关键工艺

对100mm In0.49Ga0.51P/GaAs HBT器件及相关电路制备中的In0.49Ga0.51P腐蚀问题、聚酰亚胺平面化、空气桥等几项关键工艺进行了研究，解决了器件及电路制备过程中出现的难题，尤其是用很简单的方法解决了In0.49Ga0.51P腐蚀过程中经常出现的腐蚀“岛”问题，并且成功地制作出所设计的器件及电路．     

The Importance of Particle Size to the Performance of Abrasive Particles in the CMP Process

Chemical-mechanical planarization is an area of technology which is growing at a very rapid pace. As Fig. 1¹ shows, it is projected to continue its phenomenal growth over the next five years. In spite of its growth, it is still a relatively new field of investigation.² The mechanism of the process is understood to include oxidation and abrasion, but the details are a bit vague. The notion of applying an abrasive slurry to the wafer was quite radical and was expected to create some problems. One of the problems uncovered was the formation of micro-scratches in the wafer.³ From other applications for abrasives, this was known to be caused by the presence of larger particles in the slurry.⁴ This problem suggested that particle size would be a critical area for study.⁵ This idea has been borne out by some recent experiments.     

Effect of process conditions on uniformity of velocity and wear distance of pad and wafer during chemical mechanical planarization

The kinematics of conventional, rotary chemical mechanical planarization (CMP) was analyzed, and its effect on polishing results was assessed. The authors define a novel parameter, ζ, as a “kinematic number,” which includes the effects of wafer size, distance between rotation centers, and rotation ratio between wafer and pad. The analysis result suggests that velocity distribution, direction of friction force, uniformity of velocity distribution, distribution of sliding distance, and uniformity of sliding-distance distribution could be consistently expressed in terms of the kinematic number ζ. These results become more important as the wafer size increases and the requirement of within-wafer nonuniformity is more stringent.     

Topographically Flat Substrates with Embedded Nanoplasmonic Devices for Biosensing

The ability to precisely control the topography, roughness, and chemical properties of metallic nanostructures is crucial for applications in plasmonics, nanofluidics, electronics, and biosensing. Here a simple method to produce embedded nanoplasmonic devices that can generate tunable plasmonic fields on ultraflat surfaces is demonstrated. Using a template‐stripping technique, isolated metallic nanodisks and wires are embedded in optical epoxy, which is capped with a thin silica overlayer using atomic layer deposition. The top silica surface is topographically flat and laterally homogeneous, providing a uniform, high‐quality biocompatible substrate, while the nanoplasmonic architecture hidden underneath creates a tunable plasmonic landscape for optical imaging and sensing. The localized surface plasmon resonance of gold nanodisks embedded underneath flat silica films is used for real‐time kinetic sensing of the formation of a supported lipid bilayer and subsequent receptor‐ligand binding. Gold nanodisks can also be embedded in elastomeric materials, which can be peeled off the substrate to create flexible plasmonic membranes that conform to non‐planar surfaces.     

碱性抛光液中纳米SiO_2磨料在Cu CMP中的作用

GLSI多层铜互连线的平坦化中,抛光液中的SiO2磨料对铜的平坦化效率具有重要的作用。研究了碱性纳米SiO2质量分数对300 mm铜去除速率和300 mm铜布线平坦化作用的影响。结果表明,随着磨料质量分数的增大,铜的去除速率增大,晶圆的均匀性变好,但磨料质量分数过高时,铜的去除速率略有降低,可能由于纳米SiO2表面硅羟基吸附在金属铜表面,导致质量传递作用变弱,引起速率降低。通过对图形片平坦化实验研究表明,随着磨料质量分数的增大,平坦化能力增强,这是因为磨料的质量分数增大使得高低速率差增大,能够有效消除高低差,实现平坦化。     

Continuous ferrimagnetic Y3Fe5O12 layers on the ceramic PbZr0·45Ti0·55O3 substrates

For the first time, continuous layers of yttrium iron garnet (YIG, Y₃Fe₅O₁₂) with a thickness of about 2 μm were synthesized on ferroelectric ceramic substrates based on lead titanate zirconate (PZT, PbZr_0·45Ti_0·55O₃). The Y₃Fe₅O₁₂ layer was deposited by ion-beam sputtering – deposition on PZT substrates of 400 μm thick by sputtering a polycrystalline target of the composition Y₃Fe₅O₁₂ with a mixture of argon and oxygen ions. Due to preliminary planarization of the PZT surface with a TiO₂ layer, a high-quality plane-parallel YIG/PZT interface was obtained, which is confirmed by scanning electron microscopy in combination with the focused ion beam technique. Atomic force microscopy showed that planarization makes it possible to achieve surface smoothness of 10 nm.The YIG/PZT heterostructures obtained in this work are potentially attractive for use in logic circuits based on low-scattering spin waves, memory elements, as well as electrically controlled microwave devices.     

Synergic effect of benzotriazole and chloride ion on Cu passivation in a phosphate electrochemical mechanical planarization electrolyte

In this study, the effect of chloride ion (Cl⁻) in phosphate electrolytes of pH 2 containing benzotriazole (BTAH) developed for use in electrochemical mechanical planarization (ECMP) was investigated at various anodic potentials. According to D.C. and A.C. electrochemical analyses, the inhibition effect of the BTAH passive film formed in phosphate electrolyte containing both BTAH and Cl⁻ was superior to that formed in phosphate electrolytes containing BTAH alone, even at high anodic potential. The effective window for BTAH passivation reached ∼1.3 V vs. Ag/AgCl nearly three times that of the ∼0.5 V vs. Ag/AgCl recorded for electrolyte containing BTAH alone. According to analyses conducted by atomic force microscopy (AFM) and secondary ion mass spectrometer (SIMS), the thickness of the passive film grown from the BTAH-only electrolyte at 0.3 V vs. Ag/AgCl was ∼52 ± 7 nm and ∼55 nm, respectively. As for the passive film grown from the BTAH and Cl⁻ electrolyte, the thickness increased to ∼104 ± 18 nm and ∼106 nm, respectively. The mechanism for the enhanced inhibition capability was that the passive film grown from the BTAH and Cl⁻ electrolyte was thicker compared to that formed from the BTAH-only electrolyte due to the incorporation of Cl⁻ into the BTAH passive film. The ECMP polishing results also demonstrated an obvious step height reduction of ∼1000 nm in a patterned structure for only 60 s polishing at a high potential of 1.0 V vs. Ag/AgCl under a low downward pressure (∼0.5 psi). Subsequently, this study proposes that the control of Cl⁻ in a phosphate ECMP electrolyte of pH 2 may be useful in enhancing the passivation capability of BTAH passive film, thus expanding the operating potential window.     

Investigation of pad staining and its effect on removal rate in copper chemical mechanical planarization

In copper chemical mechanical planarization process, stains are often generated on the pad surface due to the build-up of polishing by-products. Pad staining is a major concern because it might affect defect, non-uniformity across the wafer, and removal rate variation during polishing. In this study, the characteristics of stains formed on an IC1000 XY grooved pad obtained under various polishing conditions were investigated. In addition, wafers were polished on an IC1000 plain pad to determine the effect of hydrodynamic pressure on staining pattern. Experiments were performed on a table-top axisymmetric polishing system consisting of a 300-mm non-rotating platen and 100-mm rotating wafers. Stains were successfully generated on the pad surface and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the stains contained copper polishing by-products. As the stains deposited on the pad land areas were darker in the direction of wafer rotation as well as in the pad radial direction, it was believed that staining agents were produced during polishing and subsequently advected downstream by the slurry flow. Although staining increased with polishing pressure, wafer rotation rate, polishing time and slurry flow rate, it did not seem to affect removal rate. The white light interferometric analysis indicated that the stains did not physically change the pad surface topography. It was observed that the hydrodynamic pressure significantly impacted the staining pattern on an IC1000 plain pad.     

Studying the effect of temperature on the copper oxidation process using hydrogen peroxide for use in multi-step chemical mechanical planarization models

Given that the mechanism responsible for removal during copper chemical mechanical planarization (CMP) is generally accepted to be based on the cyclic oxidation of copper and the subsequent removal of copper oxide, this study characterizes the copper oxide growth process as a function of temperature in aqueous hydrogen peroxide solutions. A copper oxidation model was proposed based on cation migration to adequately represent measured copper oxide growth profiles as a function of temperature. The two parameters extracted to fit the oxidation profiles, W and V, in the proposed model are related to activation energy of cation migration and the potential developed across the oxide film, respectively. The potential was found to be 0.95 V and did not vary with temperature. The activation energy was found to be 0.84 ± 0.01 eV and increased slightly with temperature. This slight increase, on the order of 2 to 3 kcal, has been previously reported and attributed to an increase in activation energy of cation solution in the oxide. The oxidized copper formation rates calculated suggest that the typical oxide thicknesses involved during the cyclic oxide growth and removal mechanism in copper CMP are between 7 and 12 Å. Though the oxidation model parameters are extracted from copper oxidation experiments on the minute time scale, there are a number of experimental, physical, and theoretical arguments that suggest the model represents the actual physical system and is applicable to the sub-second timescales involved during the oxidation processes in copper CMP.