Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-07-09
2001-07-10
Gorgos, Kathryn (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S269000
Reexamination Certificate
active
06258223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the fabrication of integrated circuits on substrates. More specifically, the invention relates to a system and method that deposits an electroless seed layer prior to electroplating on the substrate.
2. Background of the Invention
Sub-quarter micron multilevel metallization represents one of the key technologies for the next generation of ultra large scale integration (ULSI) for integrated circuits. Reliable formation of multilevel interconnect features, including contacts, vias, lines, and trenches is very important to the success of ULSI and to the continued effort to increase circuit density on individual substrates and die. As circuit densities increase, the widths of vias, contacts and other features decrease to 0.25 &mgr;m or less, whereas the thicknesses of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Many traditional deposition processes have difficulty filling strictures where the aspect ratio exceeds 6:1, and particularly where it approaches 10:1.
One traditional process is a physical vapor deposition (PVD) process. Generally, bias is created in a PVD chamber between a target having sputterable material and a substrate on which the material is to be sputtered. An inert gas is flown into the chamber and a plasma is created of inert gas ions between the target and substrate. The inert gas ions impact the target, dislodge the target material, and some of the material is directed to the substrate and deposited thereon.
FIG. 1
a
is a side view schematic of material deposited in a feature with PVD processing. In high aspect ratio features, the deposition from a PVD process is typically concentrated near the opening of the feature and leaves voids in the deposition in the lower portions of the features such as the bottom and corners of the feature. The opening can become sealed creating a void in the feature, leading to defects in the substrate.
One alternative to traditional PVD processing that has recently been developed is a high pressure PVD process, which ionizes the target material after it has been sputtered and directs the target material in an highly aligned path parallel to the depth of the high aspect features. Such a process, known as an ionized metal plasma (IMP) process, deposits more material on the bottom of the feature than traditional PVD processing. PVD processing and high pressure PVD processing is described in co-pending U.S. Ser. No. 08/989,759 filed Dec. 12, 1997 and is incorporated herein by reference.
FIG. 1
b
is a side view schematic of material deposited in a feature with IMP processing. However, the ionized material does not uniformly deposit on the sidewalls of the feature, particularly near the middle of the feature. As the deposit increases, the opening can be closed, also creating a void near the middle of the feature.
Because of the difficulties in filling high aspect ratio features, processes other than PVD are being developed to deposit metals such as copper or aluminum. Electroplating, used in other industries, has recently been explored as a viable alternative for filling sub-quarter micron features. Generally, the electroplating process is able to grow the deposited material on a conductive surface and fill even the high aspect ratio features substantially free of voids. Typically, electroplating uses a suspension of generally positively charged ions of deposition material in contact with a negatively charged substrate, as a source of electrons, to plate out the deposition material on the charged substrate. On a typical non-conductive substrate, a thin conductive material is first deposited on the substrate and in the features and provides an electrical path across the surfaces. An electrical current is supplied to the conductive material and the substrate is electroplated with an appropriate conductive material, such as aluminum or copper. However, the integrity of the initial conductive material layer determines the integrity of the subsequent electroplated layer. For instance, discontinuities in the initial conductive layer can affect the electrical current and cause defects in the electroplated layer.
Therefore, there remains a need to provide a system and method that extends the reliability of depositions in features by enhancing an initial conductive layer for a subsequent electroplating process.
SUMMARY OF THE INVENTION
The present invention generally provides a system and method that deposits an electroless seed layer on a substrate prior to subsequent processing. The system is designed with flexible architecture and can be configured in several ways. The electroless deposition process is preferably performed in-situ with an electroplating process to minimize oxidation and other contaminants prior to the electroplating process. The system allows the substrate to be transferred from an electroless deposition processing area to an electroplating processing area with a protective coating to also minimize oxidation. The system generally includes a mainframe having a mainframe substrate transfer robot, a loading station disposed in connection with the mainframe, one or more processing facilities disposed in connection with the mainframe, and an electroless supply fluidly connected to the one or more processing applicators. Preferably, the electro-chemical deposition system includes a spin-rinse-dry (SRD) station disposed between the loading station and the mainframe, a rapid thermal anneal chamber attached to the loading station, and a system controller for controlling the deposition processes and the components of the electro-chemical deposition system. The electroless deposition fills defects and discontinuities in the activation, or seed, layer and allows subsequent processing, such as electroplating, to fill the remainder of the features without substantial voids in the deposited material.
In one aspect, the invention provides a system for depositing a conductive layer on a substrate, comprising an electroplating processing mainframe having a transfer robot, a loading station coupled to the mainframe, an electroless deposition applicator coupled to the mainframe, and an electroless deposition fluid supply fluidly connected to the electroless deposition applicator. In another aspect, the invention provides a system for depositing a conductive layer on a substrate, comprising a chamber having a bottom and a sidewall, a pedestal disposed in the chamber, a first fluid inlet disposed proximate the pedestal and fluidicly connected to a supply of electroless deposition fluid, a second fluid inlet disposed proximate the pedestal and fluidicly connected to a supply of rinsing fluid, and an actuator coupled to the pedestal. In another aspect, the invention provides a method for depositing a conductive layer in a feature on a substrate, comprising depositing a first conductive layer in a feature on the substrate, depositing by an electroless deposition process a second conductive layer in the feature, and electroplating a third conductive layer in the feature to at least partially fill the feature.
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Lowenheim, Frederick A., “Modern Electroplating,” 3rdEdition, Chapter 31, pp. 710-747. Month not available.
Carl Daniel A.
Chen Liang-Yuh
Cheung Robin
Dordi Yezdi
Hey Peter
Applied Materials Inc.
Gorgos Kathryn
Smith-Hicks Erica
Thomason, Moser & Patterson L.L.P.
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