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Chemical mechanical polishing (CMP) is rapidly becoming the process of choice for planarizing dielectrics in very large scale integrated circuits. In addition, it is being used at an increasing rate in the removal of metals in order to define conducting levels. In the case of dielectric CMP, planarization ability is dictated by the mechanical aspects of polishing such as pad rigidity, polishing pressure and speed of the polishing platen, while inherent removal rate of the dielectric material is generally a function of the polishing chemistry. Polishing rate of both, dielectric and metallic films can be significantly increased by changing the nature of the dispersed abrasive in the slurry and that of the dispersing agent. However, such changes have profound implications to the surface quality, planarity, and cleaning of the polished surface. In addition, the polishing pad plays an important role in manufacturability of metal CMP processes. This work reviews the chemistry of polishing slurries containing silica, ceria and alumina abrasives for dielectric and metal CMP. Also, the contribution of the polishing pad to CMP processes is explained. The need for balancing the chemical and mechanical aspects of polishing in order to achieve overall planarization and pattern definition is demonstrated.

The rate of particle generation in a SiH4/NH3 rf discharge has been studied as a function of the discharge operating parameter space, electrode geometry, and power supply coupling mode. Measurements of the bulk quantity of particles produced in the discharge reveal that the mode of coupling (capacitive or dc) as well as the electrode temperature significantly affects particle generation rates. Laser light scattering measurements made as a function of the plasma power density indicate that particle generation abruptly ceases at a threshold value sufficient to induce spark breakdown at the cathode. Based on these observations, it is shown that particle growth in plasmas can be modeled entirely as a heterogeneous process. The initiation of particle growth is shown to be consistent with an electron surface desorption model involving vibrational excitation of surface clusters. Propagation of growth in the gas phase is shown to be consistent with an eliminative ion-molecular condensation reaction, and the pressure dependence of this mechanism is exploited to estimate a value for the rate constants for SiH4 and NH3 condensation in SiN:H particle growth.

Chemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to “cold flow” and/or “caking” of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness - which itself is dependant upon intrinsic polymer stiffness and cell density.

Selective and conformal chemical vapor deposition (CVD) of copper from (hfac)Cu(VTMS), where hfac=1,1,1,5,5,5-hexafluoroacetylacetonate, VTMS=vinyltrimethylsilane, has been studied. The compounds (hfac)CuL, L=VTMS, 1,5-COD, and 2-butyne, deposited copper on both SiO2 and W, nonselectively, under the conditions employed. Selective CVD onto W in the presence of SiO2 was obtained by passivating SiO2 surface hydroxyl groups via reaction with Me3SiCl in the liquid phase. However, selective deposition was maintained only for short periods (1 min), and loss of selectivity was attributed to the desorption of hydrogen-bonded Me3SiCl groups which exposed the reactive SiO2 surface sites (hydroxyl groups). To avoid this problem, gaseous (CH3)2SiCl2 was introduced during Cu CVD and resulted in selective deposition for longer periods at respectable rates (≳2500 Å/min at 170 °C). Highly conformal deposition was demonstrated on test structures with keyhole geometries and trenches with widths of 2.8–0.45 μm and aspect ratios of 0.35–1.40. Deposition rates were 1000–2500 Å/min at temperatures of 160–170 °C with (hfac)Cu(VTMS) partial pressures of 10–17 mTorr.

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Chemical Mechanical Polishing (CMP) is becoming a mainstream technology for the planarization of dielectrics at various process levels. Widely different types of glass films are now routinely processed using CMP techniques. In this work, the polish rates using an aqueous silica based slurry for thermally grown Si02, plasma deposited SiC2, and boro-phospho-silicate glasses have been compared. A polishing mechanism based on the concentration of water in the glass is proposed. It is also shown that the presence of phosphorous changes the polishing mechanism compared to undoped glasses and the rate increase due to phosphorous is much greater than that due to boron.

Methods for determining planarization ability of CMP were explored. Options included film thickness measurements of the dielectric over metal and field, TIR measurements using profilometry, and a combination of the two. The attempt to observe the in situ change in the topography was addressed in two distinct experimental approaches. The first approach involved processing wafers for predetermined intervals. The other approach processed different wafers for different amounts of time. The effects of down force and platen rpm on planarization ability were studied using the first approach. Results indicate that planarization is more efficient at higher down forces and higher platen rpm. Slurry property effects were examined using the second method. The planarization ability appears to suffer at elevated pH values. This is attributed to both the enhanced solubility of the silica particles and the dielectric itself.