Overlap design of one-turn coil

Details Overlap design of one-turn coil Overlap design of one-turn coil

1998-03-16

2003-01-14

McDonald, Rodney G. (Department: 1753)

Chemistry: electrical and wave energy

Processes and products

Coating, forming or etching by sputtering

C204S298060, C204S298120, C204S298160

Reexamination Certificate

active

06506287

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to plasma generators, and more particularly, to a method and apparatus for generating a plasma to sputter deposit a layer of material in the fabrication of semiconductor devices.
BACKGROUND OF THE INVENTION
Plasmas have become convenient sources of energetic ions and activated atoms which can be employed in a variety of semiconductor device fabrication processes including surface treatments, depositions, and etching processes. For example, to deposit materials onto a semiconductor wafer using a sputter deposition process, a plasma is produced in the vicinity of a sputter target material which is negatively biased. Ions created within the plasma impact the surface of the target to dislodge, i.e., “sputter” material from the target. The sputtered materials are then transported and deposited on the surface of the semiconductor wafer.
Sputtered material has a tendency to travel in straight line paths from the target to the substrate being deposited at angles which are oblique to the surface of the substrate. As a consequence, materials deposited in etched trenches and holes of semiconductor devices having trenches or holes with a high depth to width aspect ratio, can buildup an overhang which can bridge over causing undesirable cavities in the deposition layer. To prevent such overhang, the sputtered material can be redirected into substantially vertical paths between the target and the substrate by negatively charging the substrate and positioning appropriate vertically oriented electric fields adjacent the substrate if the sputtered material is sufficiently ionized by the plasma. However, material sputtered by a low density plasma often has an ionization degree of less than 1% which is usually insufficient to avoid the formation of overhangs. Accordingly, it is desirable to increase the density of the plasma to increase the ionization rate of the sputtered material in order to decrease unwanted overhang formation in the deposition layer. As used herein, the term “dense plasma” is intended to refer to one that has a high electron and ion density.
There are several known techniques for exciting a plasma with RF fields including capacitive coupling, inductive coupling and wave heating. In a standard inductively coupled plasma (ICP) generator, RF current passing through a coil induces electromagnetic fields and generates a high density plasma. These currents heat the conducting plasma by ohmic heating, so that it is sustained in steady state. As shown in U.S. Pat. No. 4,362,632, for example, current through a coil is supplied by an RF generator coupled to the coil through an impedance matching network, such that the coil acts as the first windings of a transformer. The plasma acts as a single turn second winding of a transformer.
In many high density plasma applications, it is preferable for the chamber to be operated at a relatively high pressure so that the frequency of collisions between the plasma ions or plasma precursor gas atoms and the deposition material atoms is increased to increase thereby the resident time of the sputtered material in the high density plasma zone. As a consequence, the likelihood that deposition material atoms may be ionized is increased thereby increasing the overall ionization rate. However, scattering of the deposition atoms is likewise increased. This scattering of the deposition atoms often causes the thickness of the deposition layer on the substrate to be thicker on that portion of the substrate aligned with the center of the target and thinner in the outlying regions.
In order to improve the uniformity of deposition, the coil which is used to couple RF energy into the plasma has been adapted to sputter material from the coil onto the workpiece to supplement the material being sputtered from a target onto the workpiece, as set forth in greater detail in copending application Ser. No. 08/680,335, filed Jul. 10, 1996 now abandoned, entitled “Coils for Generating a Plasma and for Sputtering” by Jaim Nulman et al., which is assigned to the assignee of the present application and is incorporated herein by reference in its entirety. As discussed therein, the coil is positioned adjacent to the substrate so that material sputtered from the coil is deposited primarily onto the periphery of the workpiece. One end of the coil is coupled to an RF generator and the other end of the coil is coupled to the system ground, typically through a blocking capacitor to develop a DC bias on the coil to facilitate sputtering of the coil. If the coil is a single turn coil, the ends of the coil are typically positioned close together but spaced by a gap (typically on the order of ¼ inch (4-8 mm)) to prevent a short between the RF generator and the blocking capacitor which would bypass the coil.
Although sputtering material from the coil onto the workpiece can improve the uniformity of deposition, it has been noted by the present applicant that nonuniformities in the deposition can nonetheless occur. Accordingly, further improvements in deposition uniformity is desired.
SUMMARY OF THE PREFERRED EMBODIMENTS
It is an object of the present invention to provide an improved method and apparatus for generating a plasma within a chamber and for sputter depositing a layer which obviate, for practical purposes, the above-mentioned limitations.
These and other objects and advantages are achieved by, in accordance with one aspect of the invention, a plasma generating apparatus which inductively couples electromagnetic energy and sputters material from a coil which has two spaced but overlapping ends. It has been recognized by the present applicant that the gap which normally spaces the two ends of a prior single turn coil may cause a discontinuity in the deposition rate of material sputtered from the coil onto the portion of the substrate closest to the coil gap as compared to other portions of the substrate. By overlapping the two ends of the coil in a close but spaced relationship, it is believed that the coil can provide a more uniform source of deposition material around the circumference of the coil, even adjacent to the ends. It is further believed that such a coil can improve the plasma uniformity adjacent to the coil ends.
In several illustrated embodiments, the coil ends overlap in a direction generally parallel to the axis of the substrate holder and the substrate supported on the holder. In alternative illustrated embodiments, the coil ends overlap radially. In each of the embodiments described herein below, it is believed that such overlapping of the coil ends can improve the quality of the layer deposited onto the substrate.


REFERENCES:
patent: 118252 (1871-08-01), Lewis
patent: 565698 (1896-08-01), Sparks
patent: 4154011 (1979-05-01), Rakestraw et al.
patent: 4336118 (1982-06-01), Patten et al.
patent: 4361472 (1982-11-01), Morrison, Jr.
patent: 4422896 (1983-12-01), Class et al.
patent: 4478437 (1984-10-01), Skinner
patent: 4626312 (1986-12-01), Tracy
patent: 4661228 (1987-04-01), Mintz
patent: 4871421 (1989-10-01), Ogle et al.
patent: 4941915 (1990-07-01), Matsuoka et al.
patent: 4999096 (1991-03-01), Nihei et al.
patent: 5001816 (1991-03-01), Oetiker
patent: 5102496 (1992-04-01), Savas
patent: 5135634 (1992-08-01), Clarke
patent: 5150503 (1992-09-01), Müller
patent: 5178739 (1993-01-01), Barnes et al.
patent: 5198725 (1993-03-01), Chen et al.
patent: 5231334 (1993-07-01), Paranjpe
patent: 5401350 (1995-03-01), Patrick et al.
patent: 5430355 (1995-07-01), Paranjpe
patent: 5433812 (1995-07-01), Cuomo et al.
patent: 5434353 (1995-07-01), Kraus
patent: 5503676 (1996-04-01), Shufflebotham et al.
patent: 5556501 (1996-09-01), Collins et al.
patent: 5573595 (1996-11-01), Dible
patent: 5637961 (1997-06-01), Ishii et al.
patent: 5669975 (1997-09-01), Ashtiani
patent: 5681393 (1997-10-01), Takagi
patent: 5683537 (1997-11-01), Ishii
patent: 5690781 (1997-11-01), Yoshida et al.
patent: 5707498 (1998-01-01), Ngan
patent: 5721021 (1998-02-01), Tobe et al.
patent: 5770098 (1998-06-01), Araki et al.
patent: 5783492

Affiliated with

Also associated with

Rating

Overlap design of one-turn coil does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Overlap design of one-turn coil, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Overlap design of one-turn coil will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3000740