Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2001-04-11
2003-02-25
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298060, C204S298160, C204S298370
Reexamination Certificate
active
06524448
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a system and to a method for executing a plasma-based sputtering method, such as for example a PVD (Physical Vapor Deposition) method.
Layer deposition methods and structuring methods are used to manufacture microelectronic and microcircuitry components. For example, for depositing metals PVD (Physical Vapor Deposition) processes, also called sputtering processes, can be used. For the layer deposition of silicon or of dielectrics, for example CVD (Chemical Vapor Deposition) or PECVD (Plasma Enhanced CVD) processes are used. For structuring, for example dry etching processes with ionized atoms or molecules are used. These methods have in common that they are executed in a process chamber using a plasma.
The structures arranged on a substrate, such as for example trenches, have an aspect ratio (ratio of trench depth to trench diameter) that increases as the miniaturization of microelectronic components progresses.
Therefore, to an ever-greater degree, methods having a controllable directional characteristic are required. A known method having a directional characteristic is for example the directional deposition of metals in contact holes and printed conductors with the aid of an ionized metal plasma. The direction of the deposition results from an accelerating voltage that accelerates the ionized metal particles towards the substrate.
The directional deposition of dielectrics by means of ionized particles from high-density plasmas, and anisotropic dry etching using ionized atoms or molecules, are likewise possible.
Many of the directional etching and deposition methods are plasma-based, and exploit the effect that the electrical fields that are present have on the motion of the particles ionized in a plasma. The plasmas in question are for example what are known as high-density plasmas (HDP), at gas pressures in the range from 1 to 100 mTorr. The plasma thereby performs two functions. First, it produces the ionized particles in the plasma, and, second, on the basis of the always-present electrical field—possibly modified from the outside—it accelerates these particles in the direction towards the substrate to be processed. Between the substrate and a plasma, in the vicinity of the substrate a thin boundary layer standardly forms, where the electrical fields are always oriented perpendicular to the substrate. The voltage drop in the boundary layer can be estimated using the formula:
Δ
V
≈
log
(
m
i
m
e
)
T
e
e
≈
10
…
30
V
.
Here m
i
and m
e
are the masses of the ions and electrons, T
e
is the electron temperature in the plasma, and e is the elementary charge. The voltage in the boundary layer can be increased to several 100 V using an applied external voltage. In addition, located between the boundary layer and the plasma is what is known as a pre-layer, which has an extension of several mean free path lengths &lgr; (mean path that covers the distance between two impacts), so that it is several centimeters wide and is therefore considerably more extended than is the boundary layer. The overall voltage drop here is in the range of the thermal voltage for electrons and is approximately
Δ
V
≈
T
e
e
≈
3
V
and cannot be modified directly from the outside. Due to the extension of the pre-layer, the field is oriented perpendicular to the substrate only to a first approximation, so that geometric effects of the process chamber can cause a certain deviation from the perpendicular.
The angular distribution and energy distribution of the ionized particles impacting on the substrate is determined by the transport through the boundary layer and the pre-layer, in which the particles receive an impulse that has a component oriented perpendicular to the substrate surface and a component oriented tangential to the substrate surface. When the particles leave the plasma, they have for the most part only a very small perpendicular and tangential impulse. From the electrical field of the pre-layer and of the boundary layer, the particles can receive only a perpendicular impulse, because the electrical field is oriented perpendicular to the substrate surface. The particles can receive an impulse oriented tangentially to the substrate surface only through deflecting impacts with the process gas in the process chamber. In the thin boundary layer, these impacts are very improbable, while in the broader pre-layer these impacts are more probable, but the ion energy here is considerably less. Through this mechanism, the tangential impulse is limited to approximately {square root over (m
i
T
e
)}, so that the angular distribution of the ions, which deviates from the perpendicular to the substrate, is very small.
The perpendicular impulse is {square root over (20m
i
T
e
)}; the ion energy in the pre-layer is approximately T
e
.
Fields additionally coupled in, such as a direct voltage field (DC) or an alternating voltage field (RF), enlarge or modulate the voltage drop in the boundary layer, and thereby modify the component of the particle impulse that is oriented perpendicular to the substrate surface. These fields have no significant influence on the tangential component of the impulse.
For this reason, in conventional plasma processes the possibilities for controlling the energy distribution and angular distribution of the impacting particles are very limited. As stated above, the impulse of the ionized particles can be influenced only in its magnitude, but not in its direction.
The non-ionized particles impacting on the substrate, which in some circumstances can also be relevant for the process, are not influenced by the electrical fields existing in the pre-layer and in the boundary layer, because they do not interact with them. Therefore, neither the angular distribution nor the impact energy can be influenced by the non-ionized particles. However, there is a possibility of indirect control via the degree of ionization of the particles, whereby the ratio of the ionized particles that impact directionally on the substrate to the non-ionized particles that impact non-directionally (isotropically) on the substrate is influenced, and in this way the portion of particles impacting directionally and the portion of particles impacting non-directionally on the substrate surface can be adjusted.
In the cited directional processes, it is problematic that, due to the field arrangement of the acceleration voltage, the ions are accelerated exclusively perpendicularly towards the substrate surface. In many cases, this limited possibility of controlling the angular distribution is not sufficient. A typical example is the deposition of a metal in a contact hole with a large aspect ratio. Using an IPVD (Ionized Physical Vapor Deposition) method, it is predominantly achieved that the contact hole is not closed prematurely in the upper region, as is the case in non-ionized processes. For this reason, first as large a portion as possible of the metal atoms in the plasma are ionized, so that the flow of neutral metal atoms into the contact hole is minimal. The angular distribution of the neutral metal atoms is nearly isotropic, and would result in a premature closing of the upper region of the contact hole, before the contact hole is filled at the floor. The angular distribution of the ionized particles, in contrast, is predominantly oriented in perpendicular fashion, so that even given the absence of an additional bias (DC, RF), most of the particles impact on the substrate surface within an angle of 10 degrees from the perpendicular. The ionized particles reach the floor of the contact hole, but only seldom reach the side wall. In many cases, however, a thick deposition on the side wall is desired, which cannot be achieved by the low angular distribution of less than 10 degrees. An angular distribution beyond the mentioned 10 degrees would therefore be desirable
Brinkmann Ralf-Peter
Kersch Alfred
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
VerSteeg Steven H.
LandOfFree
Configuration for the execution of a plasma based sputter... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Configuration for the execution of a plasma based sputter..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Configuration for the execution of a plasma based sputter... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3121954