Cleaning and liquid contact with solids – Apparatus – Automatic controls
Reexamination Certificate
2000-07-12
2002-12-17
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
Automatic controls
C134S153000, C134S902000, C156S345420, C438S748000
Reexamination Certificate
active
06494219
ABSTRACT:
BACKGROUND OF THE INVENTION
Provisional Application Information
Field of the Invention
The invention relates to electrochemical deposition or electroplating methods, and systems for removal of unwanted deposits resulting from electrochemical deposition or electroplating processes.
Description of the Background Art
In semiconductor processes, multiple processes such a chemical vapor deposition (CVD), physical vapor deposition (PVD), and electroplating are performed in series on a substrate such as a semiconductor wafer. After electroplating is performed, edge bead removal (EBR) systems remove edge beads and other layers remaining on the substrates.
Modern metal electroplating can be can be accomplished by a variety of methods. Relatively high electrical conductivity, high electromagnetic resistance, good thermal conductivity, and availability in a highly pure form make copper and its alloys a choice electroplating metal. Typically, electroplating copper or other metals and alloys involves initially depositing a thin seed layer (having an approximate thickness of 2000 Angstroms) of a conductive material over the surface of the substrate including the features formed on the substrate. A layer is then plated onto the seed layer by applying an electric charge applied across the seed layer. The seed layer having an electric charge applied thereto attracts metal ions. The deposited layers and the dielectric layers can then be planarized to define a conductive interconnect feature, such as by chemical mechanical polishing (CMP).
During electroplating, metal ions contained in the electrolyte solution deposit on those substrate locations that electrolyte solution contacts that are covered by the seed layer. The seed layer is usually deposited on the front side of the substrate, however the seed layer may extend to the edge or the backside of the substrate. As such, metal may deposit on certain front side, edge, or backside locations that such metal depositions are not desired, as now described.
FIG. 2A
shows a cross sectional view of one embodiment of an edge of a substrate
22
including a bevel edge
33
, a seed layer
34
deposited on the substrate, and an electroplated conductive metal layer
38
deposited on the substrate. During processing of the substrate, the seed layer
34
is formed on a plating surface of the substrate (the plating surface faces downward in FIG.
2
A). The seed layer stops a short distance from the bevel edge
33
. A conductive metal layer is then deposited on the seed layer by an electroplating process. The conductive metal layer in
FIG. 2A
does not form on any portion of the substrate that does not have a seed layer. In the embodiment shown in
FIG. 2A
, an excess deposit buildup, known as an edge bead
36
, forms at the edge of the electroplated layer. The edge bead typically results from locally higher current densities at the edge of the seed layer
34
and usually forms within 2-5 mm from the edge of the substrate. Removal of the edge bead from the substrate is desired to ensure uniform thickness of the conductive metal layer on the substrate
22
.
FIG. 2B
shows a cross sectional view of another embodiment of an edge of a substrate
22
including the bevel edge
33
, the seed layer
34
deposited on the substrate, and the electroplated conductive metal layer
38
in FIG.
2
A. In this embodiment, the seed layer
34
covers the front side
35
of the substrate, both bevels
33
on the edge, and for a small distance on the backside
42
of the substrate. This type of seed layer is known as a full coverage seed layer. Metal deposits form on those seed layer surfaces that are exposed to electrolyte solution during electroplating. When a full-coverage seed layer is applied to a substrate, removing the edge bead
36
following the electroplating process is often desired. Removing the deposited layers on the seed layer that occur on the backside and/or edge of the substrate on the full coverage seed layers limit contamination from these layers deposited on the backside of the substrate.
FIG. 3
shows a cross sectional view of yet another embodiment of an edge of a substrate
22
including the bevel edge
33
, the seed layer
34
deposited on the substrate, and the electroplated conductive metal layer
38
deposited on the substrate. The electoplated conductive metal layer
38
includes a separated edge deposit
39
. Such a separated edge deposit
39
may form on a substrate following electroplating. The separated edge deposit
39
of the seed layer typically forms within 2-5 mm from the deposited edge material. The separated edge deposit often separates from the substrate
22
since the separated edge deposit is not secured to the seed layer that would attach the separated edge deposit to the substrate. A separated edge deposit
39
often tears off during subsequent processing such as chemical mechanical planarization (CMP). The CMP pads that contain material of the separated edge deposit
39
may abrade and damage the substrate during CMP. CMP pads that contain embedded particles may severely damage (by scratching) any wafer to which they contact.
Therefore, during electroplating copper contamination can form on the front, the backside, or the edge of the substrate. Such metal deposition at undesired locations occur from full coverage seed layer wrapping around to the backside, small deposits of electroplated copper on the backside of the substrate, or the copper from the wet electrolyte solution drying on the backside of the substrate. The existence of copper contamination on the backside of the substrate can degrade the performance of an electronic device that uses a portion of the wafer because of altered properties of the substrate. Providing a system by which the copper contamination can be removed from the backside or the edge of the substrate following the metal deposition is desirable.
Edge bead removal (EBR) systems remove the aforementioned edge bead, the separated deposited layer, or certain other undesired deposited layers on the substrate. Nozzles in the EBR systems can be adjusted to direct etchant (that removes the deposits) and/or rinse water at desired locations on the substrate. EBR systems therefore can apply a variety of chemicals at an electroplated substrate where the undesired deposits are located. The chemicals used in EBR systems comprise, for example, a mixture including a prescribed ratio of acid mixed with an oxidizer and deionized water.
Chemicals used in prior EBR systems are mixed in a batch to form an etchant. To limit the effort required to mix a large number of batches frequently, the individual batch sizes are large. The batch is maintained until the etchant is used or until the etchant becomes unusable. The usable lifetime of the etchant in EBR systems varies depending on such parameters as the specific chemicals and amounts of each chemical mixed to form the etchant, the temperature at which the etchant is stored, and the pressure applied to the etchant. However, once the etchant becomes unusable, the etchant must be disposed of and a new batch of etchant must be prepared. One embodiment of etchant used for copper electroplating processes becomes increasingly unstable at higher EBR system temperatures. Unfortunately, etch rates of the chemicals used in EBR systems typically increase with higher temperatures. When operators increase the temperature of the EBR system to increase throughput based on the higher etch rates, the time until each batch of etchant becomes altered or unstable diminishes.
It is desired to maximize throughput in EBR systems since the EBR system represents only one of a large number of expensive processes that are utilized in expensive semiconductor processing systems. The EBR system cannot be used for deposition removal purposes when a new batch of chemicals is being mixed therein to form etchant. Presently, batches of chemicals in EBR systems are mixed by diffusion, so some time is necessary after a large batch is mixed for the chemicals to properly mix into etchant. In an effort to limit down t
Dordi Yezdi
Hey Peter
Nayak Radha
Stevens Joseph
Applied Materials Inc.
Gulakowski Randy
Moser Patterson & Sheridan
Perrin Joseph
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