Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-08-01
2003-02-25
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230AN, C156S345480, C156S345490
Reexamination Certificate
active
06523493
ABSTRACT:
This invention relates to the generation of high-density plasma, particularly inductively coupled plasma (ICP), useful in processes such as semiconductor wafer processing.
BACKGROUND OF THE INVENTION
Gas plasma generation is widely used in a variety of integrated circuit (IC) fabrication processes, including plasma etching, plasma enhanced chemical vapor deposition (PECVD), and plasma sputter deposition applications. Generally, plasmas are produced within a process chamber by introducing a process gas at vacuum pressure into the chamber and then coupling electrical energy into the chamber to create and sustain a plasma in the process gas. The plasma may exist a t various ionization fractions from 10
−6
to a fully ionized plasma.
The plasma generally contains positively charged ions of working gas that are used for etching a surface of a substrate, sputtering material from a target for depositing a layer of the material onto such a substrate and ions of vaporized coating material to control the deposition of the material onto the substrate by ionized physical vapor deposition (iPVD). The plasma typically contains electrons equivalent in number to the positive charges in the plasma so that the plasma is macroscopically quasi-neutral.
Various ways of producing a plasma within a process chamber are used. Opposed electrodes can be oriented within the chamber to capacitively couple energy to the plasma. Microwave energy and electron cyclotron resonance (ECR) devices are also used. Inductive coupling of energy to the plasma is particularly desirable for producing a high-density plasma, particularly plasmas having a high ionization fraction with a relatively low electron energy or plasma potential. Inductively coupled plasmas (ICP) often use a coil or antenna-shaped and positioned with respect to the processing chamber to inductively couple energy into the processing chamber and thus create and sustain a plasma therein.
In some ICP systems, an inductive coil or antenna is positioned proximate the top portion of the chamber to create a plasma within the chamber. The antenna is positioned on one side of a dielectric plate or window at the top of the processing chamber, and electromagnetic energy from the antenna is coupled through the dielectric window and into the plasma. One such design is illustrated in U.S. Pat. No. 5,556,521. In other ICP systems, helical or solenoidal-shaped coils are wound around the outside of a cylindrical dielectric sidewall of the processing chamber to inductively couple energy to the plasma. One suitable dielectric material for a window or chamber sidewall is quartz.
The geometry of an ICP system is a factor in determining both plasma density and uniformity, which, in turn, can affect the processing uniformity over the area of the substrate. It is usually desirable to produce a uniform, high-density plasma over a significantly large area so that large substrate sizes can be accommodated. Ultra large-scale integrated (ULSI) circuits, for example, are presently formed on wafer substrates having diameters of 200 mm and 300 mm.
In an ICP system, plasma is excited by heating or exciting electrons in the plasma region of the processing chamber. The inductive currents which heat the plasma electrons are der iv ed from oscillating magnetic fields which are produced proximate the inside of the dielectric window or sidewall by RF currents within the inductive antenna or coil. The spatial distribution of those magnetic fields is a function of the sum of the individual magnetic fields produced by each portion or segment of the antenna or coil conductor. Therefore, the geometry of the inductive antenna or coil significantly determines the spatial distribution of the plasma, and particularly the spatial distribution and uniformity of the plasma ion density within the process chamber. Some coil configurations achieve a goal of delivering power linearly over a wide power range within a chamber of a given radius, but it is difficult to scale the process chamber to a larger size for handling larger substrates without significantly increasing the dimensions of the antenna or coil. Replacing an ICP antenna with one of a larger footprint calls for expensive modification to the processing system, and larger antennas and their associated plasmas exhibit greater sensitivity to process parameters within the chamber. For example, with a larger antenna, the plasma process becomes more sensitive to substrate-to-target distance, the target material, the pressure within the process chamber, and the height and width configuration of the chamber. Furthermore, large coils call for large dielectric windows, which must be very thick to withstand the pressure differential across the wall of a high vacuum chamber.
Current ICP systems utilizing planar spiral antennas exhibit asymmetry wherein the distribution of the plasma that is not aligned with the central axis of the chamber, which degrades the uniformity of the deposition or etch process over the area of the substrate. Further, planar antennas often exhibit a ring or doughnutshaped plasma for one process and corresponding set of parameters, while creating a centrally peaked plasma for another process and other parameters. Accordingly, the plasma shape and uniformity is not consistent within such ICP systems and will be process dependent. Therefore, the overall IC fabrication process will not be consistent from one plasma process to another plasma process.
Another drawback of planar antenna systems using an S-shaped coil is that the outer portions of the coil marginally affect the plasmas created by the central region of the coil and give an effect on the uniformity and density of the plasma that is different along one axis of the plane of the coil than along another axis in the plane of the coil.
SUMMARY OF THE INVENTION
An objective of the present invention is to overcome drawbacks in the prior art and provide a plasma processing system, particularly an ICP system, in which a dense, uniform plasma is created. Another objective of the present invention is to provide a uniform plasma that is less dependent upon the size and shape of the process chamber than current plasma processing systems. Still another objective of the invention is to provide a plasma that is symmetrical in the processing chamber.
A further objective of the present invention is to provide a uniform, dense plasma over a large area, such as an area sufficient to handle 200 mm and 300 mm wafers, while maintaining a compact and inexpensive design of the inductive coil or antenna. A still further objective of the present invention to provide consistent plasma generation and thereby provide consistent processes that are less dependent upon process parameters such as pressure and chamber geometry or size.
According to principles of the present invention, a high-density, inductively coupled plasma (ICP) producing source is provided for coupling RF energy into a vacuum processing chamber. The source includes a window of a dielectric material in the chamber wall and having a surface in contact with a processing gas within a vacuum processing chamber. An RF antenna in the form of a coil is isolated from the processing gas by the dielectric material and has first coil segments, preferably lying in a plane parallel to the window, extending circumferentially in a ring close to the surface of the window. A permanent magnet assembly is configured and positioned to generate a ring-shaped magnetic tunnel in the processing chamber near the surface of the dielectric material in a ring-shaped area opposite the window from the coil segments.
In preferred embodiments of the invention, the RF coil is a three-dimensional coil having further second coil segments extending farther from the surface of the window than those extending in the ring. The further segments preferably lie in planes that intersect the dielectric material. Preferably, the half turn segments close to the window include two pairs of segments. The turns of each pair extend around the ring so that current flows in opposit
Lund Jeffrie R.
Tokyo Electron Limited
Wood Herron & Evans L.L.P.
Zervigon Rudy
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