Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
2000-04-11
2003-07-08
Talbot, Brian K. (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C427S294000, C417S048000, C417S053000, C438S471000
Reexamination Certificate
active
06589599
ABSTRACT:
CLAIM OF FOREIGN PRIORITY PURSUANT TO 35 U.S.C. §119
This application claims foreign priority under 35 U.S.C. §119 from Italian Patent Application Serial Number MI99 A 000744 filed Apr. 12, 1999, which is incorporated herein by reference for all purposes.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention provides a getter device advantageously shaped like a substrate for use in a thin film deposition system and a method for its use.
2. Background
Processes for depositing thin films onto substrates are widely used in the manufacture of a wide array of commercial products. Examples of these processes include the fabrication of integrated electronic circuits (ICs) in which circuits are formed on a semiconductor substrate; the manufacture of data storage media, such as compact disks (CDs), where a thin layer of aluminum is deposited onto a substrate of a transparent plastic; the production of computer hard disks where a magnetic material is deposited onto a substrate such as aluminum; and the production of flat panel displays in which active elements are commonly created on glass substrates. Processes for depositing thin layers are also being adapted to the developing field of micromechanical devices, where micron-scale mechanical structures are fabricated with similar techniques to those utilized in the production of ICs. The main industrial techniques for the deposition of thin layers include chemical deposition from the vapor phase and physical deposition from the vapor phase, widely known in the art as “chemical vapor deposition” and “physical vapor deposition” respectively or by their acronyms “CVD” and “PVD”.
In CVD processing, two or more gaseous species are caused to react in an evacuated chamber containing a substrate. The reaction product forms a solid deposit on the substrate in the form of a thin film or layer. The degree to which the chamber must be evacuated will vary according to the particular CVD process employed. Some systems, those known as low-pressure or alternately ultra-high vacuum, can require initial evacuations of the deposition chamber to a pressure value in the range of 10
−8
-10
−9
mbar. Hereinafter, reference to CVD processing will refer to the low-pressure variants unless stated otherwise.
Physical vapor deposition (PVD) actually encompasses a number of different techniques that all share the following common features:
a target formed of a material to be deposited, generally having the shape of a squat cylinder or a disk, is positioned in a deposition chamber in front of a substrate and parallel thereto; and
the chamber is initially evacuated to a base pressure and thereafter back-filled with an inert gas, generally argon or another noble gas, to a pressure of about 10
−2
-10
−5
mbar; a potential difference of some thousands volts applied between the supports of the substrate and the target (providing the latter with a cathodic potential) generates a plasma of electrons and positive ions in the space between the substrate and the target; the positive ions are accelerated by the electric field into the target causing atoms or “clusters” of atoms to erode or “sputter” off of the surface of the target and into the atmosphere of the chamber; material thus eroded condenses onto the substrate to form a thin film or layer.
As is well known in the art, commercially useful processes frequently include the deposition of a plurality of successive thin layers which may be performed in a succession of deposition chambers or in a single chamber configured to perform multiple depositions. Hybrid processes, comprising aspects of both CVD and PVD processes are also well known in the art.
It is further understood in the art that the properties of thin layer devices, particularly ICs, are strongly dependent on the presence of defects within the deposited layers. These defects are most commonly due to the inclusion of impurity atoms or molecules within the deposited layers. Consequently, it is important to minimize the possible sources of contamination in all processing steps. For example, contamination can be reduced by using components of the highest possible purity (reactive gases in the case of CVD, targets in case of PVD, and inert gases generally) and ensuring the highest cleanliness of all surfaces within the production system and especially within the gas distribution system and each deposition chamber.
Presently, to create high quality films and to do so with the greatest efficiency, thin film deposition processes are commonly performed in systems comprising a plurality of chambers, each configured for a specific operation. For example, deposition steps are performed in deposition chambers, while conditioning chambers can be configured for cleaning or thermal processing steps like pre-heating substrates. Systems comprising multiple chambers can be arranged linearly such that one is directly connected to the next. Alternatively, multiple chambers can be disposed around a central transfer chamber.
Chambers are connected to one another by means of valves that are normally opened only to allow the transfer of substrates from one chamber to another. Substrates are passed between chambers by automated substrate handling equipment, in general mechanical arms that are configured to grasp or support a substrate typically along an edge by the use of tangs, clamps, and guides. The valves and the automated handling equipment are typically configured to the dimensions of the substrates, and are thus designed to accommodate objects that are both thin and broad. Semiconductor substrates, for example, are generally circular, often with a machined flat segment or notch to indicate crystallographic orientation, with thicknesses between about 0.5 mm and about 1 mm and lateral dimensions between about 150 mm to about 300 mm. Substrates used in the production of flat panel displays, on the other hand, are commonly rectangular with thicknesses between about 1 mm and 5 mm and lateral dimensions between about 10 cm and 1 meter.
In order to guarantee the highest cleanliness possible, all chambers are generally kept under vacuum with the highest vacuum levels being maintained in the deposition chambers. As is well known in the art, higher vacuum levels are typically achieved through the use of a series of pumps, each intended to operate in a different pressure range. Evacuation is typically initiated with a low-vacuum mechanical pump (e.g. a rotary pump) that is effective down to a pressure range of about 1-10
−2
mbar. Lower pressures can be achieved with medium and high-vacuum pumps such as turbomolecular or cryogenic pumps.
A simple example of a process system comprising multiple chambers arranged around a transfer chamber will serve to illustrate the pathway traveled by a substrate. Substrates are initially arranged in a suitably shaped carrier (e.g. a cassette or a pod) that is loaded into a first chamber. The inner walls of the carrier are provided with tangs or guides for the purpose of keeping the substrates separate from each other, and to simplify to automated handling operations. A vacuum of about 10
−5
-10
−6
mbar is achieved in the first chamber after the substrates are first introduced, and then a valve is opened between the first chamber and the transfer chamber. A mechanical arm removes a substrate from the carrier and transfers it to the transfer chamber where the pressure is maintained at a level lower than those in the first chamber, generally about 10
−7
mbar.
Next, a mechanical arm is employed, for example, to transfer the substrate from the transfer chamber to a deposition chamber through a second valve. The mechanical arm places the substrate on a sample holder near the center of the chamber. Typically, the sample-holder is supported on a pedestal that is moveable in some systems. The ability to heat the deposition zone, the region within the chamber surrounding the sample holder, is generally provided in deposition chambers both to help degas the pedestal during the initial stages
Conte Andrea
Mazza Francesco
Moraja Marco
Dort David Bogart
Hickman Paul L.
Perkins Coie LLP
Saes Getters S.p.A.
Talbot Brian K.
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