Use of pulsed grounding source in a plasma reactor

Details Use of pulsed grounding source in a plasma reactor Use of pulsed grounding source in a plasma reactor

2000-08-28

2002-11-26

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

With treating means

C438S783000, C438S016000, C438S714000, C438S710000

Reexamination Certificate

active

06485572

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma reactor apparatus and processes. More specifically, the present invention relates to grounding a semiconductor substrate pedestal of a plasma reactor apparatus during a portion of a positive voltage power bias oscillation cycle to increase the energy of ion particles of the plasma to increase the feature charging effects regarding a substrate being etched using the plasma reactor.
2. State of the Art
Higher performance, lower cost, increased miniaturization of electronic components, and greater density of integrated circuits are ongoing goals of the computer industry. One commonly used technique to increase the density of integrated circuits involves stacking multiple layers of active and passive components one atop another to allow for multilevel electrical interconnection between devices formed on each of these layers. This multilevel electrical interconnection is generally achieved with a plurality of metal-filled vias (“contacts”) extending through dielectric layers which separate the component layers from one another. These vias are generally formed by etching through each dielectric layer using etching methods known in the industry, such as plasma etching. Plasma etching is also used in the forming of a variety of features for the electronic components of integrated circuits. In addition, vertical capacitors may be formed by etching the features of the wall of the capacitor in the capacitor dielectric and forming the remaining capacitor structure around the etched dielectric. Typically, the capacitance of the capacitor is proportional to the surface area of the wall of the capacitor etched in the dielectric material.
In plasma etching, a glow discharge is used to produce reactive species, such as atoms, radicals, and/or ions, from relatively inert gas molecules in a bulk gas, such as a fluorinated gas, such as CF
4
,CHF
3
, C
2
F
6
, CH
2
F
2
, SF
6
, or other freons, and mixtures thereof, in combination with a carrier gas, such as Ar, He, Ne, Kr, O
2
, or mixtures thereof. Essentially, a plasma etching process comprises: 1) reactive species are generated in a plasma from the bulk gas, 2) the reactive species diffuse to a surface of a material being etched, 3) the reactive species are absorbed on the surface of the material being etched, 4) a chemical reaction occurs which results in the formation of a volatile byproduct, 5) the byproduct is desorbed from the surface of the material being etched, and 6) the desorbed byproduct diffuses into the bulk gas.
As illustrated in drawing
FIG. 4
, an apparatus
200
used in the plasma etching process consists of an etching chamber
202
in electrical communication with a first AC (Alternating Current) power source
204
. The etching chamber
202
further includes a pedestal
206
to support a semiconductor substrate
208
and an electrode
212
opposing the pedestal
206
. The electrode
212
is in electrical communication with a second AC power source
214
. The pedestal
206
has an AC power source
216
. The electrode
212
and power source
214
may be an inductively coupled plasma source, a microwave plasma source, or any suitable type plasma source.
In the etching chamber
202
, a plasma
222
is initiated and maintained by inductively coupling AC energy from the first AC power source
204
into an atmosphere of gases in the etching chamber
202
and the plasma
222
which comprises mobile, positively and negatively charged particles and reactive species. An electric field develops in a sheath layer
224
around the plasma
222
, accelerating charged species (not shown) toward the semiconductor substrate
208
by electrostatic coupling.
To assist with the etching, the potential difference between the plasma
222
and the semiconductor substrate
208
can be modulated by applying an oscillating bias power from the pedestal power bias source
216
to the pedestal
206
, as illustrated in drawing
FIG. 5A
(showing the voltage profiles during such oscillation). During the positive voltage phase
232
, the substrate collects electron current from electrons that have enough energy to cross the plasma sheath
124
having a plasma potential
236
(see drawing FIG.
5
A). The difference between the instantaneous plasma potential and the surface potential defines the sheath potential voltage drop
238
(FIG.
5
B). Since the plasma potential is more positive than the surface potential, this drop has a polarity that retards electron flow. Hence, only electrons with energy larger than this retarding potential are collected by the substrate. During the negative voltage phase
234
, positive ions are collected by the substrate. These ions are accelerated by the sheath voltage drop
238
and strike the substrate.
However, it is known that the plasma etch results, including profile modification, can occur if the features are charged enough to modify the trajectories of the ions and electrons that are injected into these features.
Illustrated in drawing
FIG. 6
is the phenomena of electrical charging on a semiconductor device in the process of a plasma etch. A material layer
244
to be etched is shown layered over a semiconductor substrate
242
. A patterned photoresist layer
246
is provided on the material layer
244
for the etching of a via. During the plasma etching process, the patterned photoresist layer
246
and material layer
244
are bombarded with positively charged ions
248
and negatively charged electrons
252
. This bombardment results in a charge distribution being developed on the patterned photoresist layer
246
and/or the semiconductor substrate
242
. This charge distribution is commonly called “feature charging.”
In order for feature charging to occur, the positively charged ions
248
and the negatively charged electrons
252
must become separated from one another. The positively charged ions
248
and negatively charged electrons
252
become separated by virtue of the structures being etched and by the differences in directionality and energy between the positive ions and electrons as they approach the feature being etched. As the structure (in this example a via
254
) is formed by etching, the aspect ratio (height to width ratio) becomes greater and greater. During plasma etching, the positively charged ions
248
are accelerated toward the patterned photoresist layer
246
and the material layer
244
in a relatively perpendicular manner, as illustrated in drawing
FIG. 7
by the arrows adjacent positively charged ions
248
. The negatively charged electrons
252
, however, are less affected by the AC power bias source at the semiconductor substrate
242
and, thus, move in a more random isotropic manner, as depicted in drawing
FIG. 8
by the arrows adjacent negatively charged electrons
252
. This results in an accumulation of a positive charge at a bottom
256
of via
254
because, on average, positively charged ions
248
are more likely to travel vertically towards the substrate
242
than are negatively charged electrons
252
. Thus, any structure with a high enough aspect ratio tends to charge more negatively at photoresist layer
246
and an upper portion of the material layer
244
to a distance A (i.e., illustrated with “−” indica) and more positively at the via bottom
256
and the sidewalls of the via
254
proximate the via bottom
256
(i.e., illustrated with “+” indica).
As shown in drawing
FIG. 7
, the negatively charged sidewalls of the top of the opening deflects the positively charged ions
248
in trajectories towards the sidewalls. In addition, the positively charged via bottom
256
also decreases the vertical component of the ion velocity and therefore increases the relative effect of initial deflection. The deflection results in ion bombardment of the sidewalls
258
proximate the via bottom
256
. This can generate a portion of the etched feature with a re-entrant profile, as shown in drawing FIG.
7
. Such a profile can be useful in etching a number of films. For example,

Affiliated with

Also associated with

Rating

Use of pulsed grounding source in a plasma reactor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Use of pulsed grounding source in a plasma reactor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Use of pulsed grounding source in a plasma reactor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2988332