Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Utility Patent
1999-09-01
2001-01-02
Diamond, Alan (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298020, C204S298080, C204S298120, C204S298150, C336S015000, C336S170000, C336S177000, C336S180000, C336S182000, C336S188000, C336S211000, C336S220000, C336S223000, C336S225000, C336S229000, C323S355000
Utility Patent
active
06168696
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to ionized physical vapor deposition (PVD), and, more specifically, to an ionized PVD apparatus in which the ionization energy is provided by an RF induction coil located inside the processing chamber. In particular, the invention relates to an improved RF induction coil design that reduces processing time and cost.
2. State of the Art
Ionized physical vapor deposition, also known as ionized sputtering, is a process used to deposit thin material films onto a substrate, or workpiece, and is well known in the art. Ionized sputtering processes are commonly employed in the semiconductor industry to deposit thin material films, typically conductive materials, such as, for example, metals, onto the surface of a semiconductor wafer or other such substrates.
Inductively coupled ionized sputtering refers to a specific ionized PVD process in which the ionization energy is provided, as illustrated in
FIG. 4
, by an induction coil
204
located inside a deposition chamber
202
adjacent a target
206
(material to be deposited) and workpiece
208
(object to receive deposited material) which is supported on a pedestal
212
. The pedestal
212
is selectively connectable to an RF or DC power bias
214
and the target
206
is selectively connectable to an RF or DC power source
216
.
A sputtering gas (not shown), such as argon, is introduced into the deposition chamber
202
. A negative DC voltage, relative to the electrically grounded walls
218
of the deposition chamber
202
, is applied to the target
206
with the DC power source
216
to excite the sputtering gas near the target
206
into a plasma state to form a plasma field. The negative voltage then accelerates sputtering gas ions
228
within the plasma field toward the target
206
. Upon impacting the target
206
, the sputtering gas ions
228
dislodge atoms of the target
206
, resulting in an emission, or sputtering, of target atoms
226
away from the surface of the target
206
. The sputtered target atoms
226
travel away from the target at varying angles, resulting in a wide distribution of trajectories.
An RF power source
232
energizes the induction coil
204
, exciting a relatively high density plasma region
224
in a region between the target
206
and the workpiece
208
. Target atoms
226
traveling into the high density plasma region
224
are ionized to form ionized target atoms
236
. A negative DC voltage is also applied to the workpiece
208
relative to the electrically grounded walls
218
of the deposition chamber
202
. The negative voltage of the workpiece
208
, relative to the high density plasma region
224
, accelerates the ionized sputtered target atoms
236
toward the workpiece
208
. The path of each ionized target atom
236
from the high density plasma region
224
and toward the workpiece
208
is substantially perpendicular to an exposed surface
238
of the workpiece
208
. Thus, the wide trajectory distribution of target atoms
226
sputtered off the target
206
is essentially focused into a much narrower band of substantially perpendicular trajectories toward the exposed surface
238
. A distribution of ionized target atoms
236
incident on the workpiece
208
that is generally perpendicular to their trajectories facilitates the filling of cavities on the exposed surface
238
of the workpiece
208
that have a high depth to width ratio (aspect ratio). Such a distribution of perpendicularly-focused target atoms
226
is especially useful in the semiconductor industry for producing high aspect ratio features on the surface of a workpiece in the form of a semiconductor wafer or other substrate of semiconductor material.
Induction coils
204
for inductively coupled ionized sputtering processes are well known in the art and have been designed in a variety of configurations. U.S. Pat. No. 5,122,251, issued Jun. 16, 1992 to Campbell et al., discloses a single loop induction coil (see FIG.
5
); U.S. Pat. No. 4,999,096, issued Mar. 12, 1991 to Nihei et al., shows a multiple loop induction coil (see FIG.
6
); U.S. Pat. No. 5,280,154, issued Jan. 18, 1994 to Cuomo et al., discloses various multiple loop, shaped induction coils with generally flattened surfaces formed by parallel conductors; U.S. Pat. No. 5,401,350, issued Mar. 28, 1995 to Patrick et al., and U.S. Pat. No. 5,578,165, issued Nov. 26, 1996 to Patrick et al., disclose various multiple loop induction coil configurations including a spiral induction coil (see FIG.
7
), a variable pitch spiral induction coil (see FIG.
8
), and an S-shaped induction coil (see FIG.
9
); and U.S. Pat. No. 4,990,229, issued Feb. 5, 1991 to Campbell et al., discloses various multiple loop, shaped induction coil configurations.
One problem which occurs with the inductively coupled ionized sputtering process is the potential contamination of the workpiece and chamber with induction coil material. During the inductively coupled ionized sputtering process, the RF power applied to the induction coil usually produces negative instantaneous voltages along the induction coil. When any point on the induction coil is subjected to a negative instantaneous voltage, that portion of the induction coil will be bombarded by sputtering gas ions, causing induction coil material to be sputtered away from the induction coil surface. The sputtered induction coil atoms may deposit on the workpiece (such as a semiconductor wafer), resulting in contamination of the deposited material or film.
Various solutions have been proposed to solve this form of contamination. For example, U.S. Pat. No. 5,707,498, issued Jan. 13, 1998 to Ngan (“the Ngan patent”), hereby incorporated herein by reference, discloses a method in which the induction coil is pasted, or pre-coated, with target material prior to initiating the sputtering process on an actual workpiece. However, depending on the target material and film thickness, such material deposited onto the induction coil surface may subsequently flake off the induction coil. Flaking or peeling of such material results when the contraction of newly applied material (upon cooling) is restrained by the adhesion between the newly sputtered film and the surface upon which it is deposited. Flaking of material sputter deposited onto the induction coil or other hardware located within the vacuum chamber is a problem well known in the art and a discussion of the causes of flaking is found in U.S. Pat. No. 5,518,593, issued May 21, 1996 to Hosokawa et al., hereby incorporated herein by reference.
The Ngan patent suggests that the surface of the induction coil be roughened to enhance the adhesion of sputtered target material onto the induction coil surface. A rough induction coil surface reduces peeling by breaking up the newly sputtered film into small sections, which are less susceptible to flaking due to the stress relief occurring at section breaks, and by providing increased surface area on which the sputtered material can adhere. The roughened induction coil surface can be introduced in any number of ways including bead blasting (as suggested in the Ngan patent) or machine knurling.
Using a roughened surface to increase adhesion and prevent flaking is not limited to an induction coil. U.S. Pat. No. 5,762,748, issued Jun. 9, 1998 to Banholzer et al., discloses a lid and door for a vacuum chamber that are bead blasted to enhance their adhesion properties. Similarly, both U.S. Pat. No. 5,391,275, issued Feb. 21, 1995 to Mintz, and U.S. Pat. No. 5,202,008, issued Apr. 13, 1993 to Talieh et al., disclose a vacuum chamber shield that is pretreated with bead blasting in order to facilitate adhesion of sputtering material.
An alternative to pre-coating the induction coil with sputtering material is discussed in U.S. Pat. No. 5,178,739, issued Jan. 12, 1993 to Barnes et al. (“the Barnes patent”). To prevent contamination, the Barnes patent suggests fabricating the induction coil from material identical to that of the target. Atoms of induction coil material,
Burton Randle D.
Meikle Scott G.
Schindel James A.
Britt Trask
Diamond Alan
Micro)n Technology, Inc.
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