Inflatable compliant bladder assembly

Details Inflatable compliant bladder assembly Inflatable compliant bladder assembly

1998-11-30

2001-05-08

Gorgos, Kathryn (Department: 1744)

Chemistry: electrical and wave energy

Apparatus

Electrolytic

C204S297080

Reexamination Certificate

active

06228233

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to deposition of a metal layer onto a substrate. More particularly, the present invention relates to an apparatus and method used in electroplating a metal layer onto a substrate.
2. Description of the Related Art
Sub-quarter micron, multi-level metallization is one of the key technologies for the next generation of ultra large scale integration (ULSI). The multilevel interconnects that lie at the heart of this technology require planarization of interconnect features formed in high aspect ratio apertures, including contacts, vias, lines and other features. Reliable formation of these interconnect features is very important to the success of ULSI and to the continued effort to increase circuit density and quality on individual substrates and die.
As circuit densities increase, the widths of vias, contacts and other features decrease to less than 250 nanometers, whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, ie., their height divided by width, increases. Additionally, as the feature widths decrease, the device current remains constant or increases, which results in an increased current density in the feature. Many traditional deposition processes, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have difficulty filling structures where the aspect ratio exceed 4:1, and particularly where it exceeds 10:1.
As a result of process limitations, plating, which had previously been limited to the fabrication of lines on circuit boards, is emerging as a new process of choice to fill vias and contacts on semiconductor devices. Metal electroplating is generally known and can be achieved by a variety of techniques. Present designs of cells for electroplating a metal on a substrate are based on a fountain plater configuration.
FIG. 1
is a cross sectional view of a simplified typical fountain plater
10
incorporating contact pins. Generally, the fountain plater
10
includes an electrolyte container
12
having a top opening, a substrate holder
14
disposed above the electrolyte container
12
, an anode
16
disposed at a bottom portion of the electrolyte container
12
and a contact ring
20
contacting the substrate
22
. A plurality of grooves
24
are formed in the lower surface of the substrate holder
14
. A vacuum pump (not shown) is coupled to the substrate holder
14
and communicates with the grooves
24
to create a vacuum condition capable of securing the substrate
22
to the substrate holder
14
during processing. The contact ring
20
comprises a plurality of metallic or semi-metallic contact pins
26
distributed about the peripheral portion of the substrate
22
to define a central substrate plating surface. The plurality of contact pins
26
extend radially inwardly over a narrow perimeter portion of the substrate
22
and contact a, conductive seed layer of the substrate
22
at the tips of the contact pins
26
. A power supply (not shown) is attached to the pins
26
thereby providing an electrical bias to the substrate
22
. The substrate
22
is positioned above the cylindrical electrolyte container
12
and electrolyte flow impinges perpendicularly on the substrate plating surface during operation of the cell
10
.
While present day electroplating cells, such as the one shown in
FIG. 1
, achieve acceptable results on larger scale substrates, a number of obstacles impair consistent reliable electroplating onto substrates having micron-sized, high aspect ratio features. Generally, these obstacles include providing uniform power distribution and current density across the: substrate plating surface to form a metal layer having uniform thickness, preventing backside deposition and contamination, and selecting a vacuum or pressure condition at the substrate backside.
Repeatable uniform contact resistance between the contact pins and the seed layer on a particular substrate as well as from one substrate to the next is critical to achieving overall deposition uniformity. The deposition rate and quality are directly related to current flow. A. tenuous pin/seed layer contact restricts current flow resulting in lower deposition rates or unrepeatable results. Conversely, a firm pin/seed layer contact can improve repeatability and reduce contact resistance which will allow increased current flow and superior deposition. Therefore, the variations in contact resistance from pin to pin produces non-uniform plating across the substrate and, consequently, inferior or defective devices.
One attempt to improve power distribution is by increasing the surface area of the contact pins to cover a larger portion of the substrate. However, high points on the substrate abut portions of the plating cell, such as the substrate holder
14
and contact ring
20
shown in.
FIG. 1
, and skew the substrate leading to contact differentials from pin to pin on each substrate. Because contact pins are typically made of a rigid material, such as copper plated stainless steel, platinum, or copper, they do not accommodate the contact height differentials. Skewing may be further exacerbated by the irregularities and rigidity of the substrate holder
14
which supplies the contact force. Thus, adjustments to the geometry of the pins do not remedy the problems associated with topographical irregularities on the backside of the substrate or the substrate holder
14
.
Current flow is further affected by the oxidation of the contact pins
26
. The formation of an oxide layer on the contact pins
26
acts as a dielectric to restrict current flow. Over time the oxide layer reaches an unacceptable level requiring cleaning of the contact pins
215
. Attempts to minimize oxidation have been made by constructing the contact pins
26
of a material resistant to oxidation such as copper or gold. However, although slowing the process, oxidation layers still formed on the contact pins
26
resulting in poor and inconsistent plating.
Another problem created by the substrate's backside topographical irregularities is failure of the vacuum condition between the substrate holder and the substrate. A hermetic seal at the perimeter of the substrate's backside is critical to ensuring the vacuum condition. Current technology employs the use of vacuum plates such as the substrate holder
14
shown in FIG.
1
. However, the rigidity of the substrate holder
14
and the substrate
22
prevents a perfectly flush interface between the two components resulting in leaks. Leaks compromise the vacuum and require constant pumping to maintain the substrate
22
secured against the substrate holder
14
. These problems may also be exacerbated by the irregularities of the hardware such as the substrate holder
14
and the contact pins
26
.
The cell
10
in
FIG. 1
also suffers from the problem of backside plating. Because the contact pins
26
only shield a small portion of the substrate surface area, the electrolyte is able to communicate with the backside of the substrate
22
and deposit thereon. The problem is exacerbated by seal failure between the substrate holder
14
and the substrate
22
, is discussed above. Leaks in the seal allow the electrolytic solution onto the substrate's backside. Backside plating requires post-plating cleaning to avoid contamination problems upstream and increases the cost of processing.
Therefore, there remains a need for a method and apparatus maintaining a uniform and repeatable contact resistance delivering a uniform electrical power distribution to a substrate surface in an electroplating cell, maintaining a stable and constant vacuum or pressure condition between the substrate holder and the substrate, and preventing backside deposition.
SUMMARY OF THE INVENTION
The invention generally provides an apparatus for use in electrochemical deposition of a uniform metal layer onto a substrate. More specifically, the invention provides an inflatable bladder assembly which assists in

Affiliated with

Also associated with

Rating

Inflatable compliant bladder assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Inflatable compliant bladder assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inflatable compliant bladder assembly will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2540070