Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session RR1: Material Processing in Low Pressure Plasmas |
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Chair: Jean-Paul Booth, Ecole Polytechnic Room: Holiday Inn Salon CD |
Thursday, October 12, 2006 1:30PM - 2:00PM |
RR1.00001: The Role of Plasma Science in Materials Processing Invited Speaker: Plasma science has repeatedly enabled fundamental advances in materials processing since the late 1960's when it found its first applications in the manufacture of semiconductor integrated circuits. There have been numerous industrial uses of glow discharge plasmas outside of the semiconductor industry (e.g., the manufacture of hard disk drives, textiles, and MEMS); however, this paper will only give attention to its relevance in the semiconductor industry. It will begin with a historical perspective on the relevance of glow discharge plasmas to etching and vapor (i.e., chemical and physical) deposition of thin films. This will include its first uses in the bipolar integrated circuit industry as well as it's origins in more mainstream applications. Surprisingly, by 1985 there were already over twelve reactors being used for plasma etching. Next, this presentation will discuss the 1990's inception and misconceptions surrounding high density plasmas. Although many multi-frequency and multi-electrode (e.g., capacitive, inductive) plasma systems are commonly used today, only gap fill of dielectric thin films into small features currently utilizes a relatively high density plasma as typically defined by plasma science. The paper will conclude with a discussion of several current problems of great interest to the semiconductor equipment industry and discuss where limitations in plasma technology may impede Moore's law. [Preview Abstract] |
Thursday, October 12, 2006 2:00PM - 2:15PM |
RR1.00002: Spatial and temporal structure of a sheath formed in a 300 mm, dual-frequency capacitive argon discharge Ed Barnat, Paul Miller, Greg Hebner, Alex Paterson, John Holland The spatial and temporal distributions of the electric fields of a sheath formed by a dual-frequency driven capacitive argon discharge are measured as functions of relative mixing between a low frequency current (13.56 MHz) and high frequency current (67.8 MHz). This is the first time a Stark effect based technique has been employed to measure sheaths of this nature. We find that for a given total input power, as the high frequency power increases, both the total voltage across the sheath and the thickness of the sheath decreases. We also find that the temporal evolution of the potential across the sheath as well as the sheath thickness contain both rf components and that the high frequency oscillations become more prominent with increased high frequency power. For insight, comparisons of the measured spatial and temporal profiles are made to computational models commonly employed in the literature. These models include the collisional rf sheath model of Lieberman and extended to dual frequencies by Robiche et. al. Where possible, we compare on our measured trends to those predicted by the models, which in general, show good agreement. [Preview Abstract] |
Thursday, October 12, 2006 2:15PM - 2:30PM |
RR1.00003: Study of Nano-Contact Etching Characteristics Using C6F6 Gas. Jong-Woo Sun, Sung-Chan Park, Chul Ho Shin, Chang Jin Kang, Han Ku Cho, Joo Tae Moon As device feature size shrinks to sub-0.1µm, oxide contact etching has become difficult to satisfy the process requirements. Especially, the aspect ratio of device has become higher and the mask thickness thinner. In this paper, we chose C6F6 as one of the promising candidates of next generation HARC etching gas, and have studied plasma and etching characteristics. Compared to other common etching gas (such as C4F6, C4F8), C6F6 could make more polymer and it could resolve the selectivity and profile problem. To identify the difference between C6F6 and other gases, plasma and etching characteristics were compared by QMS, OES, XPS, and etching tests. C6F6 showed 1.7 times higher polymer deposition rate than C4F8, and lower C/F ratio in polymer than other gases. This C/F ratio in polymer affected selectivity and profile during etching. C6F6 cracked into relatively larger molecules than other gases and this fragment patterns also affect polymer condition and etching characteristics. From the experiments, we used C6F6 to etch sub-0.1µm HARC etching and compared other gases. [Preview Abstract] |
Thursday, October 12, 2006 2:30PM - 2:45PM |
RR1.00004: Etching of high-$k$ HfO$_{2}$ films in high-density chlorine-containing plasmas without rf biasing Kouichi Ono, Keisuke Nakamura, Daisuke Hamada, Kazushi Osari, Koji Eriguchi Plasma etching of high dielectric constant ($k)$ films is indispensable for the fabrication of high-$k$ gate stacks. This paper presents the etching of high-$k$ materials of HfO$_{2}$ in high-density chlorine-containing plasmas excited by electron cyclotron resonance. Experiments were performed with BCl$_{3}$/Cl$_{2}$ mixtures at a pressure of 5 mTorr in the absence of rf biasing; under these conditions, the difference between the plasma and floating potentials was of the order of 10 V. In pure BCl$_{3}$ plasma, some deposition was found to occur on HfO$_{2}$ surfaces to inhibit etching. By adding Cl$_{2}$ to BCl$_{3}$, the deposition was suppressed to result in the etching of HfO$_{2}$. The HfO$_{2}$ etch rate increased with increasing Cl$_{2}$ concentration, giving the maximum HfO$_{2}$ etch rate of about 100 nm/min at 60{\%} Cl$_{2}$. At lower Cl$_{2}$ concentrations of 25-50{\%}, the HfO$_{2}$ etch rate was $>$ 20 nm/min, while the Si etch rate remained almost zero, thus giving a high selectivity of $>>$ 50 over Si. Moreover, by adding a small amount of O$_{2}$ to BCl$_{3}$/60{\%}-Cl$_{2}$ plasma, the HfO$_{2}$ etch rate was found to increase to about 150 nm/min at 5{\%} O$_{2}$, while the Si etch rate was also increased to deteriorate the selectivity over Si down to 4. The addition of Cl$_{2}$ and/or O$_{2}$ to BCl$_{3}$ would increase the concentration of Cl and decrease that of inhibitors BCl$_{x}$ in the plasma. These results were compared with plasma and surface diagnostics, to understand plasma-surface interactions responsible for. [Preview Abstract] |
Thursday, October 12, 2006 2:45PM - 3:00PM |
RR1.00005: Study on the characteristics of etching organic hard mask for patterning high aspect ratio contact holes Hyun-Sil Hong, Sung-Il Cho, Mi-Na Choi, Chang-Jin Kang, Han-Ku Cho, Joo-Tae Moon A hard mask etch scheme for high aspect ratio contact holes has been developed to improve the low selectivity. The removable organic materials were investigated as possible candidates of mask. However, the organic materials showed the profile problem of crock shape due to isotropic etch effect in O2 chemistry. In this paper, we introduce HBr or Cl2 to improve the profile. Infra red spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) analyses were used to understand the etching mechanism. HBr and Cl2 control the mask CD (critical dimension) and the profile. Cl2 is more effective for profile changes than HBr. After etching the mask using Cl2 or HBr, the IR analyses showed the formation of C-Cl or C-Br bonds, while C=C, C$\equiv $C, and aromatic groups are disappearing. It was shown the Cl and Br component are appearing through the XPS analyses. Based on results, halogen gases react at the surface of organic materials and this layer prevents from reacting with O2. Passivation effect is prominent in the sidewall because the ion sputtering is low. Therefore, this halogenized layer prevents from isotropic etching and results in the tapered profile. [Preview Abstract] |
Thursday, October 12, 2006 3:00PM - 3:15PM |
RR1.00006: Low-pressure Plasma Fluorination of Polypropylene Yang Yang, Mark Strobel, Seth Kirk, Hyacinth Cabibil, Mark J. Kushner The surface energy and adhesion properties of commodity polymers such as polypropylene (PP) can be controlled by functionalization of the surface layers in plasmas. Affixing oxygen to the surface of PP, typically by atmospheric pressure coronas, raises surface energy and decreases hydrophobicity. Affixing fluorine lowers surface energy and increases hydrophobicity. In this paper, low-pressure plasma fluorination of PP will be discussed with results from computational and experimental investigations. PP was treated in low pressure ($<$ a few Torr) capacitively coupled plasmas sustained in gas mixtures containing F$_{2}$. Process parameters (e.g., power, pressure, flow rate, position of PP in discharge) were varied. The fractional coverage of surface resident groups (CH, CF, CF$_{2}$, CF$_{3})$ was measured using ESCA. Plasma and surface processes were simulated using a 2-dimensional plasma hydrodynamics and surface chemistry model. The surface reaction mechanism consists of a hierarchy of reactions beginning with H abstraction by F atoms and followed by passivation by F and F$_{2}$. Ion (sputtering, scission) and photon (H dissociation, scission) activated processes are included. Comparisons will be made between the model and experiments for surface coverages of CH and CF$_{n}$. [Preview Abstract] |
Thursday, October 12, 2006 3:15PM - 3:30PM |
RR1.00007: A modeling of inductively coupled plasma in SF$_{6}$/O$_{2}$ for deep reactive ion etching of silicon Toshikazu Sato, Toshiaki Makabe There is still a strong requirement for a deep reactive ion etching (RIE) of silicon in micrometer scale for the fabrications of through wafer interconnects of LSI chips and micro electro mechanical systems (MEMS). Especially high etch rate more than 10 $\mu $m/min is desirable for mass production of those devices. Here, attention should be given to the fact that the plasma is locally influenced by the wafer geometry comparable to the sheath thickness, causing distorted ion trajectories through the sheath. The design of fast silicon etching process can't be accomplished without understanding of the internal plasma properties and the plasma-surface interactions. In this work, we numerically investigate the 2D plasma structure in inductively coupled plasma in SF$_{6}$/O$_{2}$ and we also calculate the plasma structure near a sub-mm hole on a wafer. Calculation shows the thinner sheath as compared with that of electropositive gases. As a result, the sheath will be affected by smaller wafer geometry. The ion flux distributions at the position in a hole and the estimated etch rate will be discussed. [Preview Abstract] |
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