Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session BT1: Plasma Etching I |
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Chair: Makoto Sekine, Nagoya University Room: 162 |
Tuesday, October 5, 2010 8:30AM - 9:00AM |
BT1.00001: Synchronized pulsed plasmas: potential process improvements for patterning technologies Invited Speaker: Since more than 30 years, CW plasmas have been used in the microelectronics industry to pattern the complex stacks of materials involved in IC technologies. However, even if miniaturization challenges have been successfully addressed thanks to plasma patterning technologies, several fundamental limitations of the plasmas remain (ARDE phenomena, differential charging effects, plasma damage) and are limiting our ability to shrink further the device dimensions. In this work, we demonstrate that synchronized pulsed ICP plasmas can improve some of these limitations. In particular, we will demonstrate that profile dependence with aspect ratio can be improved during STI etching and that structural damage in materials can be reduced allowing the integration of ultra-thin layers in devices. These results are well correlated with gas phase analyses of pulsed plasmas and surface analyses of etched surfaces and allow a better understanding of the impact of pulsed conditions on plasma/surface interactions.\\[4pt] In collaboration with Maxime Darnon, Gilles Cunge, Erwine Pargon, Laurent Vallier, and Nader Sadeghi, CNRS; Thibault David, CEA-LETI-MINATEC; Moritz Haass, Fran\c{c}ois Boulard, Paul Bodart, Camille Petit-Etienne, CNRS; Samer Banna and Thorsten Lill, Applied Materials. [Preview Abstract] |
Tuesday, October 5, 2010 9:00AM - 9:15AM |
BT1.00002: Synchronous Plasma Pulsing for Etch Applications M. Haass, M. Darnon, E. Pargon, S. Banna, O. Joubert The use of plasma processes is the most viable technological solution to address the critical dimension control at the nanometer range required in microelectronics. However, conventional plasma etch processes are reaching their limits in terms of etch selectivity and profile control at the atomic scale. In this study, we investigate the potential of pulsed plasmas to further improve etching processes. The experiments are performed in a 300mm AdvantEdge tool from Applied Materials. The inductively coupled plasma is sustained by two RF generator (13.56 MHz) to create the plasma and to polarize the wafer, modified using Pulsync to allow synchronous pulsing at different frequencies and duty cycles. We demonstrate the interest of synchronously pulsed HBr/O2 plasmas to etch silicon trenches. In particular, experiments carried out at a frequency of 1 kHz and a duty cycle of 20{\%} show an enhanced quality of the patterned profiles, compared to continuous wave processes. A high selectivity, uniformity and a minimization of aspect ratio dependent phenomena are observed while the etch rate relative to the plasma ON time increases. These improvements are linked to the balance between plasma dissociation and recombination during the ON and OFF time of the pulsed plasma, influencing the composition of neutral and ion flux. Preliminary results show that this balance is controlled by the duty cycle rather than the pulsing frequency. [Preview Abstract] |
Tuesday, October 5, 2010 9:15AM - 9:30AM |
BT1.00003: The Etch Step in MEMS Deep Silicon Etch Iqbal Saraf, Matthew Goeckner, Lawrence Overzet The etch step of the Bosch process is examined by first forming standard trenches using a Plasma-Therm DSE-II and then etching those for an extended time. The resulting etch profiles are nearly isotropic at the trench mouth but become increasingly anisotropic as the aspect ratio (AR) increases. The sidewall etch near the trench top is largely due to F radicals having a large reaction coefficient; however, few F radicals reach the bottom of the trench. As a consequence, the etch at the bottom can be anisotropic and ion-enhanced without a wall film. Trenches having protected sidewalls (a thick CxFy film) to prevent etching by F radicals at the top also have a distinct AR dependence. While large AR trenches etch at the bottom, low AR trenches do not break through the protective film. In addition, the etch profile at the bottom of the high AR trenches has differing lateral and normal etch components. The normal etch component, driven by ions, is 3-4 times higher than the lateral etch component, which can have a facet dependency. These results indicate that it is more important to protect the top of the trench during the deposition step because anisotropic etching can occur without wall protection at the bottom of high AR trenches. [Preview Abstract] |
Tuesday, October 5, 2010 9:30AM - 9:45AM |
BT1.00004: Dual-RF-Mode Inductively Coupled Plasma (ICP) Source for Advanced Dry Etching Processes Samer Banna, Ankur Agarwal, Valentin Todorow, Shahid Rauf, Ken Collins Conventional industrial ICP sources for dry etching processes suffer inherently from the so-called M-shape etch rate (ER) pattern across the wafer. Such M-shape limits significantly the ER uniformity and the depth range of shallow trench isolation processes which are detrimental for processes in the 3x node technology and below. Among the commonly used ICP industrial sources are the cylindrical ones consisting of two vertical coils wound in a helical shape. In the latter the coils are wound at different diameters powered by 13.56MHz RF supply, enabling center-to-edge power deposition control. The two-coils' currents are in-phase, leading to a destructive interference in the magnetic field contributed by each coil in the region between the coils, which will be manifested as M-shape plasma density profile across the wafer. Recently, at Applied Materials Inc., we have developed a unique dual-RF-mode ICP source capable of controlling the current direction between the two coils to be either in-phase or out-of-phase. While being out-of-phase a constructive interference between the magnetic fields takes place providing a new regime of operation for which M-shape can be eliminated. Such ICP source enables flexible plasma density profile control and widens the operational window for advanced dry etching processes. [Preview Abstract] |
Tuesday, October 5, 2010 9:45AM - 10:00AM |
BT1.00005: Analysis of gallium nitride (GaN) surface interacted with chlorine etching plasma beams Shang Chen, Ryosuke Kometani, Kenji Ishikawa, Hiroki Kondo, Keigo Takeda, Hiroki Kano, Yutaka Tokuda, Makoto Sekine, Masaru Hori To improve electronic performance of the next generation GaN devices, plasma processes is an essential issue to stoichiometric composition and damage creation of the GaN surfaces. But the detail information according plasma internal parameter was insufficient. In this study, we analyze GaN surface stoichiometry by in situ x-ray photoelectron spectroscopy (XPS) after treated by chlorine (Cl2) inductively coupled plasma (ICP) etching system and radical ion flux ratio controllable novel plasma-ion-beam system. During exposure of chlorine plasma, surface was chlorinated under ordinary circumstance. With nitrogen radical irradiated the significant change of chlorinated surface residues was observed. As a results, under high etch-rate and radical-rich conditions, surfaces such after the ICP etching exhibited N-rich but for ion-rich conditions to Ga-rich. This indicated that surface state was strongly related to radical-ions ratio, nitrogen contained reaction products and an amount of chlorinated surface residues. [Preview Abstract] |
Tuesday, October 5, 2010 10:00AM - 10:15AM |
BT1.00006: Deep Gallium Nitride Etching Julien Ladroue, Mohamed Boufnichel, Thomas Tillocher, Philippe Lefaucheux, Pierre Ranson, R\'emi Dussart Due to the power density supplied to the next generation of power devices, deep structures as high as 10 $\mu $m should be build. Deep GaN etching implies etch rate issue as well as surface roughness defects. We showed that these etching defects are linked with dislocations inherent to the substrates and revealed during etching. For a better understanding of the etching mechanisms, optical emission spectroscopy, Langmuir probe and mass spectrometry are carried out as a function of process parameters. We observe that etching behaviour depends on coverplate material. An optimum etch rate as a function of source power is measured by using a silicon coverplate. Diagnostics suggest that silicon coverplate etching in chlorine plasmas consume Cl radicals which play a role on GaN etching. Different chemistries are studied as source of active species, sputtering ions or molecule scavenging impurities. We have shown that oxygen impurities are at the origin of columnar defects. We also showed that adding a small amount of nitrogen in the chemistry could increase the selectivity with SiO$_{2}$ mask. [Preview Abstract] |
Tuesday, October 5, 2010 10:15AM - 10:30AM |
BT1.00007: Anisotropic Cl$_{2}$-based ICP etching of III-Vs with the addition of Si-containing gases L. Gatilova, S. Bouchoule, G. Patriarche, S. Guilet Anisotropic etching of III-Vs (InP, GaAs) is a key building-block for photonic devices. We previously showed that it is achieved in Cl$_{2}$-H$_{2}$ or HBr ICP discharges via a SiOx sidewall passivation mechanism, with Si and O originating from the etching of the reactor surfaces and/or of the silicon wafer generally used as a sample tray to etch III-V samples of small size. We showed that passivation is promoted by H addition in the gas phase. For industrial large-surface applications, we have investigated the effect of small SiH$_{4}$ or SiCl$_{4}$ addition to develop passivating chemistries independent of the sample tray. We show that anisotropic etching is maintained by fine adjustment of SiH$_{4}$-H$_{2}$/Cl$_{2}$ or SiCl$_{4}$-Cl$_{2}$/H$_{2}$ ratios, and conclude that the Cl/H ratio should be kept roughly constant to promote the formation of the SiOx layer. We show that smooth and anisotropic etching can be obtained using a new simpler SiH$_{4}$/Cl$_{2}$ chemistry. Ex-situ spatially-resolved EDX-TEM analysis of the passivation layer deposited on the InP etched sidewalls showed that this layer is changed from Si-rich silicon oxide to nano-crystalline silicon. We will further discuss the effect of controlled oxygen addition on the passivation mechanism, and the use of HBr/SiH$_{4}$ plasma for anisotropic etching of InP/GaAs-based heterostructures. [Preview Abstract] |
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