Investigation of electron source and ion flux uniformity in high plasma density inductively coupled etching tools using two‐dimensional modeling
作者:
Peter L. G. Ventzek,
Michael Grapperhaus,
Mark J. Kushner,
期刊:
Journal of Vacuum Science&Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena
(AIP Available online 1994)
卷期:
Volume 12,
issue 6
页码: 3118-3137
ISSN:1071-1023
年代: 1994
DOI:10.1116/1.587488
出版商: American Vacuum Society
关键词: ETCHING;INDUCTIVELY COUPLED PLASMA;ELECTRON SOURCES;ION FLUX;PLASMA DENSITY;COMPUTERIZED SIMULATION;TWO−DIMENSIONAL CALCULATIONS;DESIGN;ELECTRIC COILS
数据来源: AIP
摘要:
Inductively coupled plasma (ICP) sources are being developed as reactors for high plasma density (1011–1012cm−3), low‐pressure (<10–20 mTorr) etching of semiconductors and metals for microelectronics fabrication. Transformer coupled plasmas (TCPs) are one variant of ICP etching tools which use a flat spiral coil having a rectangular cross section powered at radio frequencies (rf) to produce a dense plasma in a cylindrical plasma chamber. Capacitive rf biasing of the substrate may also be used to independently control ion energies incident on the wafer. The uniformity of generating the plasma and the uniformity of the flux of reactants to the substrate are functions of the geometry and placement of the coil; and of the materials used in the construction of the chamber. In this article, we use results from a two‐dimensional model to investigate design issues in TCPs for etching. We parametrize the number of turns and locations of the coil; and material properties of the reactor. We find that at low pressure, designs which produce ionization predominantly at larger radii near the edge of the wafer produce more uniform ion fluxes to the substrate. This results from a ‘‘converging’’ ion flux which compensates for losses to lateral surfaces. Careful attention must be paid to metal structures in the vicinity of the coils which restrict the azimuthal electrical field. This situation results in reduced power deposition at large radii, which can be compensated by over sizing the coil or by using auxiliary solenoidal coils. The plasma and neutral transport, dominated by diffusion, treats the advective flow from the gas inlets and pump port as local sources and sinks which are rapidly volume averaged.
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