Etching a substrate: processes – Gas phase etching of substrate – Application of energy to the gaseous etchant or to the...
Reexamination Certificate
1997-07-21
2001-06-19
Dang, Thi (Department: 1763)
Etching a substrate: processes
Gas phase etching of substrate
Application of energy to the gaseous etchant or to the...
C438S729000, C156S345420, C118S7230IR
Reexamination Certificate
active
06248250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
the invention is related to radio frequency (R.F) inductively or capacitively coupled plasma reactors used in processing semiconductor wafers, and in particular to improvements therein for increasing the plasma ion density uniformity across the wafer surface.
2. Background Art
Inductively coupled plasma reactors are currently used to perform various processes on semiconductor wafers including metal etching, dielectric etching and chemical vapor deposition, as some examples. In an etch process, one advantage of an inductively coupled plasma is that a high density plasma ion density is provided to permit a large etch rate with a minimal plasma D.C. bias, thereby permitting more control of the plasma D.C. bias to reduce device damage. For this purpose, the source power applied to the antenna and the DC bias power applied to the wafer pedestal are separately controlled RF supplies. Separating the bias and source power supplies facilitates independent control of ion density and ion energy, in accordance with well-known techniques. To produce an inductively coupled plasma, the antenna is a coil inductor adjacent the chamber, the coil inductor being connected to the RF source power supply. The coil inductor provides the RF power which ignites and sustains the plasma. The geometry of the coil inductor can in large part determine spatial distribution of the plasma ion density within the reactor chamber.
One problem with such a plasma reactor is that the spatial distribution of the plasma ion density across the wafer surface is often non-uniform. This is a problem in a metal etch process, for example, because the etch rate is affected by plasma ion density, and therefore the etch rate is non-uniform across the wafer. As a result, the etch process is difficult to control and over-etches devices on some portions of the wafer and under-etches devices on other portions of the wafer, leading to reduced production yield.
One of the causes of non-uniform plasma ion distribution is the coil geometry and location. Another cause is the shape of the plasma itself, which is largely determined by the shape of the reactor chamber, particularly the reactor chamber ceiling.
Generally, the coil inductor of an inductively coupled plasma reactor is wrapped around the reactor chamber, although it does not necessarily conform to the shape of the reactor chamber walls. Necessarily, different regions of the wafer surface are displaced from the nearest coil windings by different distances and therefore experience different plasma ion densities.
Depending upon the shape of the reactor chamber ceiling, more plasma volume is located over the wafer center and less over the wafer edges, particularly in the case of a conical or hemispherical ceiling, for example. Accordingly, there tends to be inherent spatial non-uniformities in the ion flux density.
A different approach is disclosed in U.S. Pat. No. 4,948,458 to James Ogle in which a plasma reactor has a flat ceiling and a flat coil antenna overlying the ceiling. However, this approach has generally been found to provide no improvement in plasma ion density uniformity and moreover suffers from relatively large capacitive coupling in the plasma, hindering control of the plasma ion energy. A modification of that approach is disclosed in U.S. Pat. No. 5,368,710 to Chen et al., in which an attempt is made to adjust the plasma characteristics such as density by increasing the thickness of the dielectric chamber cover toward the center of the chamber. However, no versatile flexible way of adjusting plasma characteristics is facilitated with such a technique.
U.S. Pat. No. 5,346,578 assigned to Novellus discloses a reactor having an arcuate ceiling. However, no versatile flexible way of adjusting plasma characteristics is facilitated with such a technique.
Thus, there is a need for a plasma reactor which permits flexible versatile adjustment of plasma characteristics to optimize uniformity of plasma ion density distribution.
SUMMARY OF THE INVENTION
The invention is embodied in an inductively coupled RF plasma reactor for processing a semiconductor wafer, the reactor including a reactor chamber having a side wall and a ceiling, a wafer pedestal for supporting the wafer in the chamber, an RF power source, apparatus for introducing a processing gas into the reactor chamber, and a coil inductor adjacent the reactor chamber connected to the RF power source, the coil inductor including (a) a side section facing a portion of the side wall and including a bottom winding and a top winding, the top winding being at a height corresponding at least approximately to a top height of the ceiling, and (b) a top section extending radially inwardly from the top winding of the side section so as to overlie at least a substantial portion of the ceiling. Preferably, the ceiling includes a dome-shaped ceiling which can be a multi-radius dome-shaped having a minimum radius of curvature near a periphery of the ceiling and maximum radius of curvature near an apex of the ceiling. Preferably, the top section is a flat disk-shaped coil while the side section is ether a cylindrically-shaped coil, truncated conically-shaped coil whose radius decreases from bottom to top or a curved-shaped winding whose radius decreases from bottom to top. In one embodiment, the side section and the top section are formed as a single continuous coiled conductor. In another embodiment, the top section and the side section are separate windings and wherein the RF power source includes a pair of independent RF power sources, each of the independent RF power sources being connected to a respective one of the top section and the side section so as to enable independent control of RF power in each one of the top section and the side section.
The invention is embodied in a method of processing a workpiece in a plasma reactor, which includes providing in the reactor a pedestal defining thereon a workstation of a diameter d and placing on the pedestal a workpiece of similar diameter, providing a chamber enclosure, the enclosure including a side wall having a top and a ceiling having a base over the top of the side wall and a ceiling apex above the base, providing an inductive coil adjacent the ceiling and capable of being coupled to an RF power supply, and setting the height of the pedestal such that the base is at a height h above the pedestal and the ceiling apex is at a height H above the base, wherein H+h is on the order of approximately 4″ and 7″ for the workstation diameter d with in a range between the order of about 6″ and about 12″.
REFERENCES:
patent: 4795529 (1989-01-01), Kawasaki et al.
patent: 4842683 (1989-06-01), Cheng et al.
patent: 4844775 (1989-07-01), Keeble
patent: 4872947 (1989-10-01), Wang et al.
patent: 4948458 (1990-08-01), Ogle
patent: 4990229 (1991-02-01), Campbell et al.
patent: 4992665 (1991-02-01), Mohl
patent: 5122251 (1992-06-01), Campbell et al.
patent: 5234529 (1993-08-01), Johnson
patent: 5277751 (1994-01-01), Ogle
patent: 5280154 (1994-01-01), Cuomo et al.
patent: 5346578 (1994-09-01), Benzing et al.
patent: 5368710 (1994-11-01), Chen et al.
patent: 5401350 (1995-03-01), Patrick et al.
patent: 5449432 (1995-09-01), Hanawa
patent: 5614055 (1997-03-01), Fairbairn et al.
patent: 5777289 (1998-07-01), Hanawa et al.
patent: 0 379 828 A2 (1990-08-01), None
patent: 0 379 828 A3 (1990-08-01), None
patent: 489 407 A2 (1992-06-01), None
patent: 0 520 519 A1 (1992-12-01), None
patent: 0 552 491 A1 (1993-07-01), None
patent: 0 596 551 A1 (1994-05-01), None
patent: 0 641 013 A2 (1995-03-01), None
patent: 0 685 873 A1 (1995-12-01), None
patent: 0694949 (1996-01-01), None
patent: 0742577 (1996-11-01), None
patent: 0641013 (1997-03-01), None
patent: 231197 (1925-08-01), None
patent: WO 92/20833 (1992-11-01), None
Hanawa Hiroji
Loewenhardt Peter K.
Ma Diana Xiaobing
Saizman Philip M.
Yin Gerald Zheyao
Applied Materials Inc.
Dang Thi
Michaelson & Wallace
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