Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With radio frequency antenna or inductive coil gas...
Reexamination Certificate
2000-06-30
2003-03-11
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With radio frequency antenna or inductive coil gas...
C118S7230IR, C118S7230AN, C219S121520
Reexamination Certificate
active
06531029
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to plasma processors including radio frequency (r.f.) responsive coils for exciting gases in vacuum chambers to plasmas that process workpieces in the chamber and more particularly to such a processor including a substantially flat coil having substantially symmetric and asymmetric turns, and to such a coil. Another aspect of the invention relates to a method of plasma processing circular workpieces having different diameters and, more particularly, to a method wherein the same chamber or chambers having the same geometry are coupled to r.f. excitation coils having differing peripheral dimensions when workpieces having differing peripheral lengths are being processed.
BACKGROUND ART
One type of processor for treating workpieces with an r.f. plasma in a vacuum chamber includes a coil responsive to an r.f. source. The coil responds to the r.f. source to produce magnetic and electric fields that excite ionizable gas in the chamber to a plasma. Usually the coil is on or adjacent to a dielectric window that extends in a direction generally parallel to a planar horizontally extending surface of the processed workpiece. The excited plasma interacts with the workpiece in the chamber to etch the workpiece or to deposit material on it. The workpiece is typically a semiconductor wafer having a planar circular surface or a solid dielectric plate, e.g., a rectangular glass substrate used in flat panel displays, or a metal plate.
Ogle, U.S. Pat. No. 4,948,458, discloses a multi-turn spiral coil for achieving the above results. The spiral, which is generally of the Archimedes type, extends radially and circumferentially between its interior and exterior terminals connected to the r.f. source via an impedance matching network. Coils of this general type produce oscillating r.f. fields having magnetic and capacitive field components that propagate through the dielectric window to heat electrons in the gas in a portion of the plasma in the chamber close to the window. The oscillating r.f. fields induce in the plasma currents that heat electrons in the plasma. The spatial distribution of the magnetic field in the plasma portion close to the window is a function of the sum of individual magnetic field components produced by each turn of the coil. The magnetic field component produced by each of the turns is a function of the magnitude of r.f. current in each turn which differs for different turns because of transmission line effects of the coil at the frequency of the r.f. source.
For spiral designs as disclosed by and based on the Ogle '458 patent, the r.f. currents in the spiral coil are distributed to produce a torroidal shaped magnetic field region in the portion of the plasma close to the window, which is where power is absorbed by the gas to excite the gas to a plasma. At low pressures, in the 1.0 to 10 mTorr range, diffusion of the plasma from the ring shaped region produces plasma density peaks just above the workpiece in central and peripheral portions of the chamber, so the peak densities of the ions and electrons which process the workpiece are in proximity to the workpiece center line and workpiece periphery. At intermediate pressure ranges, in the 10 to 100 mTorr range, gas phase collisions of electrons, ions, and neutrons in the plasma prevent substantial diffusion of the plasma charged particles outside of the torroidal region. As a result, there is a relatively high plasma flux in a ring like region of the workpiece but low plasma fluxes in the center and peripheral workpiece portions.
These differing operating conditions result in substantially large plasma flux (i.e., plasma density) variations between the ring and the volumes inside and outside of the ring, resulting in a substantial standard deviation of the plasma flux incident on the workpiece. A measure of plasma flux incident on the workpiece is etch rate of the workpiece in Angstroms per minute; the standard deviation of etch rate uniformity of an Ogle type coil is typically more than 3.0%. The substantial standard deviation of the plasma flux incident on the workpiece has a tendency to cause non-uniform workpiece processing, i.e, different portions of the workpiece are etched to different extents and/or have different amounts of molecules deposited on them.
Many coils have been designed to improve the uniformity of the plasma. The commonly assigned U.S. Pat. No. 5,759,280, Holland et al., issued Jun. 2, 1998, discloses a coil which, in the commercial embodiment, has a diameter of 12″ and is operated in conjunction with a vacuum chamber having a 14.0 inch inner wall circular diameter. The coil applies magnetic and electric fields to the chamber interior via a quartz window having a 14.7 inch diameter and 0.8 inch uniform thickness. Circular semiconductor wafer workpieces having a 200 mm diameter are positioned on a workpiece holder about 4.7″ below a bottom face of the window so the center of each workpiece is coincident with a center line of the coil.
The coil of the '280 patent produces considerably smaller plasma flux variations across the workpiece than the coil of the '458 patent. The standard deviation of etch rate uniformity resulting from the plasma flux produced by the coil of the '280 patent on a 200 mm wafer in such a chamber operating at 5 milliTorr is about 2.0%, a considerable improvement over the standard deviation of approximately 3.0% for a coil of the '458 patent operating under the same conditions. The coil of the '280 patent causes the magnetic field to be such that the plasma density in the center of the workpiece is greater than in an intermediate part of the workpiece, which in turn exceeds the plasma density in the periphery of the workpiece. The plasma density variations in the different portions of the chamber for the coil of the '280 patent are much smaller than those of the coil of the '458 patent for the same operating conditions as produce the lower standard deviation.
With the advent of circular semiconductor wafers having 300 mm diameters, it has been proposed that the same vacuum chambers be used for plasma processing of circular semiconductor wafers having 200 mm and 300 mm diameters.
FIG. 1
is a drawing of a processor that can be used for processing wafers having both diameters. Processors of the type illustrated in
FIG. 1
are such that the same processor can be used at different times for both diameters or processors having chambers with the same geometries can be used for separately processing wafers having 200 mm and 300 mm diameters.
The vacuum plasma workpiece processor of
FIG. 1
includes vacuum chamber
10
, shaped as a cylinder including grounded metal wall
12
having an interior diameter of 20″, metal base plate
14
, and circular top plate structure
18
, consisting of a dielectric window structure
19
, having the same thickness from its center to its periphery and a diameter exceeding the inner diameter of chamber
10
so the window bears against the top edge of wall
12
. Sealing of vacuum chamber
10
is provided by conventional gaskets (not shown). The processor of
FIG. 1
is typically used for etching a circular semiconductor wafer (i.e., a substrate) or for depositing molecules on such a wafer.
A suitable ionizable gas that can be excited to a plasma state is supplied to the interior of chamber
10
from a gas source (not shown) via port
20
in window
19
. The interior of chamber
10
is maintained in a vacuum condition, at a pressure that can vary in the range of 1-100 milliTorr, by a vacuum pump (not shown), connected to port
22
in base plate
14
.
The gas in the chamber is excited by a suitable electric source to provide a plasma having a density that is considerably more uniform than the plasma excited by the coil disclosed in the Ogle '458 patent. The electric source includes a substantially planar metal coil
24
having a square cross-section and a hollow interior; coil
24
is typically made of square copper tubing. Coil
24
is mou
Choi Tom
Lin Frank Y.
Ni Tuqiang
Takeshita Kenji
Lam Research Corporation
Lowe Hauptman & Gilman & Berner LLP
Mills Gregory
Zervigon Rudy
LandOfFree
Vacuum plasma processor apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum plasma processor apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum plasma processor apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3085037