Physical Vapor Deposition Tool Research Articles

Preparation of micro-textures on cemented carbide substrate surface by plasma-assisted laser machining to enhance the PVD tool coatings adhesion

The micro-texture fabricated on the substrate surface of coatings is an established method for enhancing the Physical Vapor Deposition (PVD) coatings adhesion. Currently, laser micromachining is widely used to prepare the micro-texture. Nevertheless, it suffers from the problem of low fabrication quality, such as irregular texture edges and irregular protrusions inside the textures. Meanwhile, to achieve sufficient coating adhesion, the improvement of physical-chemical bonding between coatings and substrate is crucial. Here, we propose a plasma-assisted laser machining approach to fabricate micro-texture, and the effect of plasma/laser textures on the interfacial properties of PVD tool coatings, especially the physical-chemical bonding interfaces is revealed for the first time. The micro-topography, chemical structure and wettability of the plasma/laser textured substrate surface were investigated. The scratch tests on the coatings with different pretreated substrates and dry cutting experiments of stainless steel were carried out. Results show that the plasma/ laser textured substrate was conducive to coatings in terms of wettability, phase composition, roughness and hardness, and specific surface area, which could enhance the interfacial properties of PVD coatings. Thus, the critical load of plasma/laser textured coatings (FN, C2 = 103 N) exhibited higher values compared to that of the untextured one (FN, C2 = 70 N), and an obviously reduction in cutting force of FX up to 34.82 %, FY up to 36.15 %, FZ up to 27.71 % by plasma/laser textured coated tool was achieved. Furthermore, the mechanisms for the effects of plasma/laser textures on the coating adhesion were discussed.

High aspect ratio through-silicon-via formation by using low-cost electroless-Ni as barrier and seed layers for 3D-LSI integration and packaging applications

A feasibility study has been carried out to find an alternative method to the laborious cum expensive physical vapor deposition (PVD)/atomic layer deposition for the deposition of barrier and seed metal layers inside the deep Si trenches with aspect ratio (AR) greater than 10, by using low-cost, highly-scalable, CMOS-compatible electroless (EL) plating method to plate Ni as (barrier cum) seed layer for the fabrication of sub-μm as well as 10 μm width copper through-silicon-vias (Cu-TSVs). Micro-structural data revealed that both sub-μm and 10 μm width TSVs with AR ranging from 12 to 17 were completely filled with Cu by using EL-Ni as a seed layer. Further, both scanning electron microscope and energy dispersive X-ray analyzes data confirms the conformal formation of EL-Ni all through TSV sidewall and TSV bottom, which is otherwise difficult to realize by the even sophisticated PVD tool. Therefore, the EL plating method appears to be a highly promising method for the conformal formation of barrier/seed layers inside the high AR TSVs for future three-dimensional integration and packaging applications.

Detecting Arcing Events in Semiconductor Manufacturing Equipment

Bi-polar arcs require a high voltage difference between two closely spaced points. As an example, if there is excessive deposition or contamination on the deposition and or cover ring in a physical vapor deposition tool (PVD) tool, a DC bipolar arc can occur leading to ablation of underlying materials, wafer breakage, or chamber damage caused by the discharge. In some cases these incidents are not identified until numerous wafers have been processed. Therefore, it is essential to identify arcing at the time of the event. In this paper, we address arc detection in a PVD chamber. The electrostatic chuck (ESC) critical parameter(s) are captured with 1000 Hz sampling frequency and signal processing techniques such as FFT and wavelet transforms are used to improve the signal-to-noise ratio enhancing the ability to isolate arcs from raw data. This methodology can be implemented on other plasma chamber types.

In situ plasma diagnostics study of a commercial high-power hollow cathode magnetron deposition tool

Using a newly designed and built plasma diagnostic system, the plasma parameters were investigated on a commercial 200mm high-power hollow cathode magnetron (HCM) physical vapor deposition tool using Ta target under argon plasma. A three dimensional (3D) scanning radio frequency (rf)-compensated Langmuir probe was constructed to measure the spatial distribution of the electron temperature (Te) and electron density (ne) in the substrate region of the HCM tool at various input powers (2–15kW) and pressures (10–70mTorr). The Te was in the range of 1–3eV, scaling with decreasing power and decreasing pressure. Meanwhile, ne was in the range of 4×1010–1×1012cm−3 scaling with increasing power and decreasing pressure. As metal deposits on the probe during the probe measurements, a self-cleaning plasma cup was designed and installed in the chamber to clean the tungsten probe tip. However, its effectiveness in recovering the measured plasma parameters was hindered by the metal layer deposited on the insulating probe tube which was accounted for the variation in the plasma measurements. Using a quartz crystal microbalance combined with electrostatic filters, the ionization fraction of the metal flux was measured at various input power of 2–16kW and pressure of 5–40mTorr. The metal ionization fraction reduced significantly with the increasing input power and decreasing gas pressure which were attributed to the corresponding variation in the ionization cross section and the residence time of the sputtered atoms in the plasma, respectively. Both the metal neutral and ion flux increased at higher power and lower pressure. The 3D measurements further showed that the ionization fraction decreased when moving up from the substrate to the cathode.

Recipe-Independent Indicator for Tool Health Diagnosis and Predictive Maintenance

Advanced sensor and information technologies have made real-time tool data readily accessible to tool and process engineers. A significant number of tool parameters (status variable identifications) are collected during wafer processing, and a large amount of tool data is acquired and available for fault detection and classification (FDC). Many IC makers have substantially improved the process capabilities by implementing FDC. With the real-time tool data, one can also evaluate the overall tool condition so that tool maintenance can be more effectively scheduled and the post-maintenance tool condition can be more easily qualified. However, due to the frequent change of recipes and the diversity of operations, the overall tool health is very difficult to evaluate. In this paper, we propose a recipe-independent health indicator based on the generalized moving variance. It is shown that the indicator faithfully reveals the tool condition regardless of recipe/operation changes. With the tool health indicator, possible tool faults can be identified and proper maintenance measures can be scheduled accordingly. The proposed indicator will be demonstrated and validated through the case studies of a plasma-enhanced chemical vapor deposition and a physical vapor deposition tool from a local fab.

Alumina PVD Tool Coatings for the Use in Semi Solid Metal Forming of Steel

The process of semi solid metal forming with permanent moulds combines the advantages of the process technologies casting and forging. Semi solid metal forming of steel is a challenge with respect to very high thermal, mechanical and tribological stresses of tools. Alumina based ceramics show a very high potential for tool protection. Alumina occurs in different known meta stable phases. First experiments show that the high temperature γ-phase exhibits high strength and toughness. Various methods and technologies have examined γ-phase stabilisation by using different thin film process technologies. By using Physical Vapor Deposition (PVD) it was possible to deposit γ-Alumina in a temperature range, where hot working steel can be utilized. The properties of the by pulsed reactive magnetron sputtering deposited films were analyzed by common thin film techniques revealing hardness, Young´s modulus and coating adhesion. By using the reactive pulsed PVD-process it was possible to stabilize γ-Al2O3 on steel substrates for semi-solid melt protection. The γ-Al2O3 coatings showed an extra ordinary stability for thixoforging of X210CrW12 and 100Cr6 in field tests. The durability of the permanent moulds was increased by using PVD thin film coatings as a tool protection.

Vacuum requirements for next wafer size physical vapor deposition system

The major sources of impurities in sputtered Al alloy films for interconnects prepared by physical vapor deposition (PVD) include those originating from the target material, residual gases present in the vacuum system, and those introduced through the gas delivery system. In this study, we report the effect of impurities incorporated from residual gases present in vacuum systems on the properties of Al–Cu interconnects, in particular, electromigration performance of 0.6-μm-wide Al–1% Cu lines. Controlled leaks of isotope gases H2O18, N215, O218, and C13H4, in the 10−6–10−9 Torr range, were introduced into a PVD tool during the sputtering process. Using these isotope gases, the impurities originating from residual gases were distinguished from those originating from other sources of impurities. The sputtering target was found to be the major source of H and O impurities in the film, whereas N atoms are introduced in the film mainly through the gas phase. The microstructural properties of blanket Al–Cu films deposited with intentionally introduced residual gas phase contaminants were also investigated using transmission electron microscopy, x-ray diffraction, and secondary ion mass spectroscopy. Controlled leaks of N2 during the sputtering process were found to affect the distribution of Cu in the blanket Al–Cu films as well as the electromigration behavior of the patterned structures to a larger extent than O2, CH4, and H2O. On the other hand, upon controlled exposures of the above mentioned residual gases to blanket Al–Cu films, N2 was found to have the lowest sticking coefficient to a clean Al–Cu surface.

Physical vapor deposition tool coatings

Physical vapor deposition (PVD) of hard coatings such as titanium nitride have been an industrial reality since the beginning of the 1980s. Two PVD processes, low voltage electron beam and cathodic arc deposition, were responsible for the early commercial success of hard coatings on high speed steel tooling. Since that time, two other PVD processes have also been prosperous in the industrial world—high voltage triode electron beam and unbalanced magnetron sputtering. There are many similarities and differences between these four PVD hard coating processes, but not all of the commonly used PVD hard coatings can be deposited well in the four systems. Titanium nitride and titanium carbonitride are the two most widely used PVD tool coatings, and they can be deposited in all four PVD systems. Titanium aluminum nitride can be deposited easily with the unbalanced magnetron process and also with the cathodic arc processes as long as cast targets are used. Uniform composition cannot be maintained with the electron beam processes because of the different vapor pressures of titanium and aluminum. New PVD hard coatings are being developed and applied. Diamond-like carbon is now being tried for some non-ferrous cutting applications, and metal-carbon films are showing promise. Polycrystalline nitride superlattice coatings made of thin alternating layers of two hard coatings such as titanium nitride and niobium nitride are showing potential for abrasive cutting situations because of the very high hardness (up to 5200 HV) of these coatings. The search continues for potentially even better tool coatings. An intense effort is underway to produce the superhard crystalline carbon nitride, which is predicted to have a hardness as hard or even harder than diamond. Similarly, cubic boron nitride (CBN) coatings are still very much in the development stage. Thin CBN coatings can now be deposited up to approximately 2000 Å in thickness, but stress in the films prevents thicker films from being made. Aluminum oxide, which has been very difficult to make by PVD techniques, except in the very slow r.f. sputtering mode, can now be deposited in the d.c. magnetron mode when pulsed power is used.