Electric heating – Metal heating – By arc
Reexamination Certificate
2000-05-09
2002-05-21
Paschall, Mark (Department: 3742)
Electric heating
Metal heating
By arc
C219S121590, C219S121420, C156S345420, C216S055000, C118S7230IR
Reexamination Certificate
active
06392187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to systems for providing a flow of particles in a plasma processing chamber, and particularly to systems for providing a flow of reactive and/or energetic particles for processing a substrate. The method and system are preferably used during poly or metal etch.
2. Discussion of the Background Art
In many electrical device and solid state manufacturing processes, energetic-charged or energetic-neutral gas particles are used to process a substrate, such as a semiconductor wafer. In one implementation, the particles can be supplied by a plasma which is generated in a gas within a particle source powered by an inductive or a capacitive plasma coupling element.
FIG. 1
illustrates an exemplary plasma processing system including an inductive plasma coupling element, i.e., helical RF coil
104
. One known inductive plasma generating system is disclosed in U.S. Pat. No. 5,234,529, issued to Wayne L. Johnson, the inventor of the present application. The contents of that patent are incorporated herein by reference.
As illustrated in
FIG. 1
, gas is supplied to a process chamber
102
through gas inlets
112
. An RF power source
110
having an output impedance R
S
supplies RF power to a plasma coupling element (e.g., RF coil
104
) which, in turn, ionizes the gas, exciting it into a plasma state within a particular region (plasma generation region
108
) of the process chamber
102
. The RF power can, optionally, be coupled into the plasma coupling element through an impedance matching network (MN). The resulting plasma produces charged particles (i.e., ions and electrons) and neutral particles (neutral atoms or molecules). In some configurations, particles are accelerated by applying a voltage to a chuck on which a substrate (e.g., wafer
106
) is mounted. The accelerated particles are emitted at the output
120
of the particle source
114
. The particles are used to process, or facilitate the processing of, the substrate
106
. For example, the particles can be used for ion-assisted deposition (IAD) or reactive ion-etching (RIE).
FIG. 2
schematically represents an example of a deposition system in which a film
304
is deposited on a substrate such as a wafer
106
by providing “add atoms”
206
(i.e., atoms deposited, or “added,” to form the film) from a film deposition source
202
(e.g., an evaporation source or a sputtering source). A flow of energetic particles
208
from a particle source
114
is directed toward the substrate
106
during deposition, and the particles
208
collide with the add atoms
206
, thereby supplying energy to the add atoms. The energetic ions
208
increase the energy of the add atoms
206
, thus add atoms
206
have higher mobility on the surface of the substrate
106
. Accordingly, the add atoms
206
are more likely to settle and adhere to a region of low energy (e.g., a location in the film
304
where there is a void in a solid material). Increasing the energy of the add atoms
206
has the benefit of producing films of higher quality. For example, the films have higher density, larger grains, and fewer defects. Higher density films can be advantageous because they provide: (a) higher conductivity (in the case of conductive materials), and (b) conductivity which is more stable with respect to time. Dielectric films produced by this method have dielectric constants closer to solid density dielectric constants and have increased dielectric strength.
Although the energy of the add atoms can be increased by raising the substrate temperature, IAD reduces the need for raising the substrate temperature. In fact, ion bombardment, which adds an average of one electron volt (eV) of energy per add atom, has an effect comparable to increasing the substrate temperature by approximately 200° C. The effectiveness of IAD can be increased further by supplying additional energy to the add atoms.
However, the addition of too much energy may have serious drawbacks on the processed substrates. If very high-energy atoms are used, the film can be damaged. For example, conventional ion sources for IAD provide ions having thousands of electron volts. Utilizing such high-energy ions has the disadvantage that it can cause implantation of the ions within the film. Implantation causes absorption of processing gases (e.g., argon used to provide the ions), which can deteriorate the films. Deterioration is caused (1) by reducing the density of the film, (2) by reducing the average grain size of the material in the film, or (3) by introducing additional defects into the film. Further, the addition of deeply implanted particles does not contribute to the desired mobility.
Reactive ion-etching can be used as part of a lithographic process for fabricating electronic circuits. An RIE process is described in
Microchip Fabrication—A Practical Guide to Semiconductor Processing,
by Peter Van Zant, and published by McGraw-Hill, Inc. The contents of the second and third editions of Van Zant are incorporated herein by reference. As designs become more compact across the horizontal plane of the substrate (i.e., in the x and y directions), and as designs increase in complexity, additional metalization layers are added (i.e., in the z direction). This change creates a need to process contact gaps and vias of varying heights and with higher aspect ratios. A description of the problems involved is discussed in the article entitled “The Interconnect Challenge: Filling Small, High Aspect Ratio Contact Holes,” published in the August 1994 edition of
Semiconductor International
magazine. The contents of this article are incorporated herein by reference.
In known reactive ion etching systems, a film of material to be etched is first grown (e.g., by oxidation) or deposited (e.g., by sputtering or evaporation) on a substrate. A layer of resist is deposited on the film and developed into a desired pattern to form an etching mask, resulting in the structure shown in FIG.
3
A. The substrate (e.g., a wafer) is then processed with ions
1602
A generated by a plasma within a particle source in order to etch the film. Etching uncovers the substrate in the regions where etching is occurring, thereby leaving a patterned film on the substrate. The resist
308
is then removed (e.g., by using an oxide plasma), leaving a bare, patterned film.
FIG. 3A
depicts the processing of a substrate which includes a film
304
on a substrate body
302
. The film
304
is etched by accelerated ions
1602
A from a conventional particle source in order to form a narrow orifice or slot
1606
. As the etching proceeds, electrons
1604
are attracted to, and adhere to, the resist layer
308
, thereby defocusing the beam of ions
1602
A and undesirably widening the orifice
1606
by side etching. In addition, the above-described side etching can cause narrowing of solid features such as conductive traces.
Since conventional sources of reactive particles produce ions with thousands of eV of energy, the etching selectivity of an etching process can be diminished (i.e., the process can undesirably etch the resist during etching of the grown or deposited film). In severe cases, high-energy particles can erode the resist enough to expose and undesirably etch portions of the film not intended for etching. Often, the resist is eroded near the edges of a feature, causing the feature to be reduced with respect to its intended size. Consequently, this can reduce the manufacturability of high-resolution patterns containing small features. Furthermore, high-energy particles can become implanted in the substrate body, or in a lower film beneath the film being etched, thereby degrading the electrical properties of the substrate body or the lower film.
Although the present invention is preferably applied to poly and metal etch processes, analogous problems exist when etching high aspect ratio holes in dielectric materials such as silicon dioxide. The process of etching high aspect ratio holes is further discussed in U.S. Pat. No. 5,468,339 to Gupta et al., ent
Oblon, Spivak, McClelland, Maier & Neustadt PC
Paschall Mark
Tokyo Electron Limited
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