Electrolysis: processes – compositions used therein – and methods – Electrolytic erosion of a workpiece for shape or surface... – Local application of electrolyte
Reexamination Certificate
2002-09-20
2004-08-10
Bell, Bruce F. (Department: 1746)
Electrolysis: processes, compositions used therein, and methods
Electrolytic erosion of a workpiece for shape or surface...
Local application of electrolyte
C205S640000, C205S653000, C205S668000, C205S672000
Reexamination Certificate
active
06773576
ABSTRACT:
BAGKROUND OF THE INVENTION
Multi-level integrated circuit manufacturing requires many steps of metal and insulator film depositions followed by photoresist patterning and etching or other means of material removal. After photolithography and etching, the resulting wafer or substrate surface is non-planar and contains many features such as vias, lines or channels. Often, these features need to be filled with a specific material, such as a metal, a dielectric, or both. For high performance applications, the wafer topographic surface needs to be planarized, making it ready again for the next level of processing, which commonly involves deposition of a material, and a photolithographic step. It is most preferred that the substrate surface be flat before the photolithographic step so that proper focusing and level-to-level registration or alignment can be achieved. Therefore, after each deposition step that yields a non-planar surface on the wafer, there is often a step of surface planarization.
Electrodeposition is a widely accepted technique used in IC manufacturing for the deposition of a highly conductive material such as copper into the features such as vias and channels opened in an insulating layer on the semiconductor wafer surface.
FIGS. 1
a
through
1
c
show an example of a procedure for filling surface features with electrodeposited copper and then polishing the wafer to obtain a structure with a planar surface and electrically isolated copper (Cu) plugs or wires.
Features
1
in
FIG. 1
a
are opened in the insulator layer
2
and are to be filled with Cu. To achieve this, a barrier layer
3
is first deposited over the whole wafer surface. A conductive Cu seed layer
4
is then deposited over the barrier layer
3
. Upon making electrical contact to the Cu seed layer
4
and/or the barrier layer
3
, and applying electrical power, Cu is electrodeposited over the wafer surface to obtain the structure depicted in
FIG. 1
b
. As can be seen in
FIG. 1
b
, in this conventional approach, the electrodeposited Cu layer
5
forms a metal overburden
6
on the barrier layer disposed on the top surface of the insulator layer
2
. This overburden and portions of the barrier layer
3
are then removed by polishing, yielding the structure shown in
FIG. 1
c
which has a planar surface and electrically isolated Cu-filled features. It should be noted that
FIG. 1
c
depicts an ideal situation. In practice, it is difficult to obtain a metal layer with an absolutely flat surface, especially over large features. “Dishing” is often observed in such features after a chemical mechanical polishing (CMP) step; dishing is indicted by dotted lines
5
a
in
FIG. 1
c.
Electrodeposition is commonly carried out cathodically in a specially formulated electrolyte containing copper ions as well as additives that control the texture, morphology and plating behavior of the copper layer. A proper electrical contact is made to the seed layer on the wafer surface, typically along the circumference of the round wafer. A consumable Cu or inert anode plate is placed in the electrolyte. Deposition of Cu on the wafer surface can then be initiated when a cathodic potential is applied to the wafer surface with respect to an anode, i.e., when a negative voltage is applied to the wafer surface with respect to an anode plate.
CMP is a widely used method of surface planarization. In CMP, the wafer is loaded on a carrier head, and a wafer surface, with non-planar features, is brought into contact with a polishing pad and an appropriately selected polishing slurry. The pad and the wafer are then pressed together and moved with respect to each other to initiate polishing by way of abrasive particles in the slurry, eventually yielding the desired planar surface.
SUMMARY OF THE INVENTION
The customary approach to achieve the structure following the metal deposition step as depicted in
FIG. 1
b
and the structure following the polishing step as depicted in
FIG. 1
c
is to use two different processes in two different machines; typically, one process in a first machine is used for deposition of a conductor such as copper, and a second process in a second machine is used for CMP to obtain planarization. Co-pending U.S. patent application Ser. No. 09/201,929, filed on Dec. 1, 1998, titled “Method And Apparatus For Electrochemical Mechanical Deposition”, relates to a method and an electrochemical mechanical deposition (ECMD) apparatus to achieve both deposition and planarization steps in the same apparatus at the same time or in a sequential manner. Commonly owned U.S. provisional application No. 60/182,100, title Modified Plating Solution For Plating And Planarization, filed Feb. 11, 2000, and commonly owned U.S. Patent application Ser. No. 09/544,558, titled Modified Plating Solution For Plating And Planarization And Process Utilizing Same, filed Apr. 6, 2000, relate to plating solution chemistries that can be used to plate and at the same time planarize conductive layers on a substrate. The disclosures of these applications are incorporated herein by reference in their entireties. The present invention relates to an innovative anode assembly design that can be used in a plating apparatus, a plating and planarizing machine, or even in a CMP machine. Our preferred use of this design, however, is in a machine that achieves both plating of a conductive layer and its planarization. Another important application of the present design is in electroetching or etching as will be discussed later in this application.
It is one object of this invention to provide an improved anode assembly which can be used in such a machine. According to the present invention, this object is achieved by using a particular anode assembly to supply a solution for any of a plating operation, a planarization operation, and a plating and planarization operation to be performed on a semiconductor wafer. The anode assembly includes a rotatable shaft disposed within a chamber in which the operation is performed, an anode housing connected to the shaft, and a porous pad support plate attached to the anode housing. The pad support plate has a top surface adapted to support a pad which is to face the wafer, and, together with the anode housing, defines an anode cavity. The anode assembly additionally includes solution delivery structure by which the solution can be delivered to the anode cavity. In one preferred configuration, the solution delivery structure is contained within the chamber in which the operation is performed.
The solution delivery structure includes a passage, having a substantially vertical feed hole and at least one substantially horizontal feed hole, defined in the shaft. In certain constructions, the solution delivery structure may further include a slip ring within which the shaft can rotate. The slip ring defines a slip ring cavity through which the solution can be delivered to the passage. A distribution plate can overlie the passage, and the solution can be routed into the anode cavity by way of the distribution plate. In addition, the solution delivery structure may include tubing extending within the chamber between a solution inlet port defined in a wall of the chamber and the slip ring.
A retaining device can be provided within the chamber to prevent the slip ring from rotating when the rotatable shaft is rotated. In addition a vent may be defined between the anode cavity and the chamber to eliminate accumulation of gas within the anode cavity. The porous pad support plate can be either smaller or larger than the wafer on which the particularly selected operation is performed.
The anode cavity can be adapted to receive a consumable anode providing plating material to the solution. The consumable anode, in this case, is single piece and porous, and the anode assembly further includes filter material by which debris generated during consumption of the anode is retained within the anode cavity. It is possible to make the anode of multiple pieces. In fact, it can consist of balls or pieces. In this configuration, a bypass system i
Talieh Homayoun
Uzoh Cyprian
Volodarsky Konstantin
Volodarsky Rimma
Young Douglas W.
Bell Bruce F.
NuTool Inc.
NuTool Legal Department
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