Si Recess of Polycrystalline Silicon Gate Etching: Damage Enhanced by Ion Assisted Oxygen Diffusion
The cause of Si recess (i.e., formation of shallow hollows on a Si surface after removal of an oxide layer from the Si surface in a polycrystalline silicon gate etching process by a HBr plasma) has been identified as ion assisted oxygen diffusion, i.e., oxygen diffusion enhanced by hydrogen ion bomb...
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| Published in | Japanese Journal of Applied Physics Vol. 50; no. 8; pp. 08KD02 - 08KD02-5 |
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| Main Authors | , , , , |
| Format | Journal Article |
| Language | English |
| Published |
The Japan Society of Applied Physics
01.08.2011
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| Online Access | Get full text |
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| Summary: | The cause of Si recess (i.e., formation of shallow hollows on a Si surface after removal of an oxide layer from the Si surface in a polycrystalline silicon gate etching process by a HBr plasma) has been identified as ion assisted oxygen diffusion, i.e., oxygen diffusion enhanced by hydrogen ion bombardment from the plasma. Both plasma and multi-beam experiments were employed for the analysis of this oxidation mechanism. It has been also found in the analysis that oxidation of a Si surface exposed to oxygen radicals is significantly enhanced only if the surface is subject to both oxygen radical supply and energetic hydrogen ion bombardment simultaneously. |
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| Bibliography: | Schematic diagrams (top-views) of (a) the Multi-Beam Injection System used in this study and (b) the inside of the reaction chamber. Summary of HRBS measurement results of SiO 2 /Si substrates exposed to various plasmas. The plasma conditions are given in ref. . The horizontal axis is the depth measured from the substrate top surface. The "initial" indicates the structures of the substrate before the substrate was exposed to a plasma. It is seen that the substrate is initially covered by a native SiO 2 layer. Details of other data are found in the main text. The data were obtained from HRBS measurements. The atomic composition of the Si substrate after it was exposed to a 500 eV H + beam with a dose of $2.5\times 10^{17}$ cm -2 . The data were obtained from HRBS measurements. Since no hydrogen is counted by HRBS, only the ratio of the number of Si atoms that are not located at Si lattice position to the number of all Si atoms in percentage is plotted here. For the sake of simplicity, the composition of oxygen atoms is not plotted here. Thicknesses of dislocated Si layers caused by H + beams at various injection energies with an injection dose of $(1{\mbox{--}}2)\times 10^{17}$ cm -2 . The data were obtained from ellipsometry. Atomic compositions of the substrates obtained from HRBS for (a) oxygen radical exposure, (b) simultaneous exposure to thermal oxygen radicals and a 500 eV Ar + ion beam, and (c) simultaneous exposure to thermal oxygen radicals and a 500 eV H + ion beam. Replot of the atomic compositions of oxygen given in Fig. for easier comparison. It is clearly seen that oxygen diffuses into Si to a significantly larger depth when oxygen radicals are delivered to the surface simultaneously with H + ion injections. |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.50.08KD02 |