Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With radio frequency antenna or inductive coil gas...
Reexamination Certificate
1999-03-05
2002-10-29
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With radio frequency antenna or inductive coil gas...
C216S067000, C216S068000, C118S7230ER, C118S7230IR, C118S7230IR
Reexamination Certificate
active
06471822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of plasma assisted deposition and etching of a workpiece using a high density plasma source.
2. Description of the Related Art
Plasma reactors, particularly radio frequency (RF) plasma reactors of the type employed in semiconductor wafer plasma processing in the manufacturing of microelectronic integrated circuits, confine a plasma over a semiconductor wafer in the processing chamber by walls defining a processing chamber. Such an approach for plasma confinement has several inherent problems where employed in plasma reactors for processing semiconductor wafers.
First, the walls confining the plasma are subject to attack from ions in the plasma, typically, for example, by ion bombardment. Such attack can consume the material in the walls or introduce incompatible material from the chamber walls into the plasma process carried out on the wafer, thereby contaminating the process. Such incompatible material may be either the material of the chamber wall itself or may be material (e.g., polymer) previously deposited on the chamber walls during plasma processing, which can flake off or be sputtered off. As one example, if the chamber walls are aluminum and the plasma process to be performed is plasma etching of silicon dioxide, then the material of the chamber wall itself, if sputtered into the plasma, is incompatible with the process and can destroy the integrity of the process.
Second, it is necessary to provide certain openings in the chamber walls and, unfortunately, plasma tends to leak or flow from the chamber through these openings. Such leakage can reduce plasma density near the openings, thereby upsetting the plasma process carried out on the wafer. Also, such leakage can permit the plasma to attack surfaces outside of the chamber interior. As one example of an opening through which plasma can leak from the chamber, a wafer slit valve is conventionally provided in the chamber side wall for inserting the wafer into the chamber and withdrawing the wafer from the chamber. The slit valve must be unobstructed to permit efficient wafer ingress and egress. As another example, a pumping annulus is typically provided, the pumping annulus being an annular volume below the wafer pedestal coupled to a vacuum pump for maintaining a desired chamber pressure. The chamber is coupled to the pumping annulus through a gap between the wafer pedestal periphery and the chamber side wall. The flow of plasma into the pumping annulus permits the plasma to attack the interior surfaces or walls of the pumping annulus. This flow must be unobstructed in order for the vacuum pump to efficiently control the chamber pressure, and therefore the pedestal-to-side wall gap must be free of obstructions.
The above problems are intensified in reactors capable of generating high density plasmas such as a Magnetically Enhanced Inductively Coupled Plasma reactor. With the Magnetically Enhanced Inductively Coupled Plasma reactor or MEICP reactor, the plasma is generated by generating a helicon wave in a plasma source chamber located above and in an axial relationship to a substrate processing chamber. The substrate processing chamber typically is surrounded by vertical permanent magnets extending part way down the outside of the processing chamber to form a magnetic bucket for confining the plasma as it enters from the source chamber.
With this type of MEICP reactor, the permanent magnets are oriented so that one pole of each magnet faces the interior of the processing chamber with successive magnets having an opposite polarity facing the chamber. This creates a magnetic field with vertical cusps, which extend part way into the interior of the processing chamber.
It is significant to note that the permanent magnets extend only part way down the sidewall of the processing chamber. A portion of the chamber is located below the magnetic bucket, including the workpiece insertion opening and the pump opening.
With this type reactor, the magnetic bucket is used to provide a uniform plasma in a central zone within the processing chamber. The workpiece is placed on a pedestal below the magnetic bucket and then raised into the magnetic bucket for processing.
This type of plasma reactor also utilizes bias power and cooling apparatus connected via lines to the pedestal. As the pedestal must be moved into the magnetic bucket, the bias power and cooling lines must follow which is not desirable. Also, the pedestal adjustment mechanism itself must be maintained to ensure proper functionality.
As discussed above, a problem inherent to plasma reactors, including MEICP reactores, is degradation of reactor components exposed to the plasma. The surface of the walls confining the plasma are subject to attack from ions in the plasma. Such attack can consume the material causing periodic maintenance and reactor down time. In addition, the chamber wall may introduce an incompatible material into the plasma. For example, if a silicon dioxide etch is being performed and the chamber walls are aluminum, the aluminum may sputter into the plasma and deposit on the workpiece, thereby contaminating the workpiece. Likewise, any by-products deposited on the chamber walls may also sputter or flake off and contaminate the workpiece.
In addition to the surface of the walls, any openings, such as the opening for workpiece placement on the pedestal or the vacuum pump opening are also subject to degradation. Such degradation may prevent those openings from functioning properly. For example, the workpiece opening which is normally sealed during processing may not seal properly due to degradation and as a result, allow air to leak in thereby reducing plasma density and upsetting workpiece processing. Or, by-products may deposit in or around the opening prohibiting insertion of the workpiece. Likewise, the pumping opening may become obstructed thereby affecting pumping efficiency.
Another problem with this type reactor is that the magnetic bucket protects the sidewalls but not the top wall. The top wall or ceiling, therefore, may be exposed to plasma and other process gases. Because the plasma near the ceiling has very high density as it exits the plasma source chamber, the exposed ceiling experiences a greater degree of degradation by the plasma.
Furthermore, because the ceiling is unprotected, build-up is more likely to occur. Build-up on the ceiling can change processing parameters and degrade processing. For example, to control ion energy at the workpiece, an RF bias may be applied to the workpiece, with the walls of the processing chamber serving as the anode and being grounded. In such a case, the coupling of bias power to the workpiece affects the ion energy. Any decrease in the bias power will reduce ion energy. Changes in bias power can occur, for example, when polymer is used during oxide etch to control etch selectivity. Polymer builds up on the anode and thereby changes its impedance. Polymer build-up on the anode, therefore, will cause ion energy to drift, thereby reducing ion energy at the workpiece.
Changes in ion energy will affect processing parameters. Changes in ion energy due to polymer build-up could be compensated for by increasing bias power during processing if the changes were predictable. Increasing bias power during processing, however, would further complicate processing and introduce uncertainties to processing.
Furthermore, the problem is exaggerated after several workpieces have been processed and more build-up is added to the anode. Cleaning of the chamber after processing each workpiece is possible but not desirable because it would lower throughput and increase costs.
In certain ion driven processes, such as oxide etch, ion energy is critical. Changes in ion energy during processing results in different and often unacceptable etch characteristics. For example, polymer build-up during an etch process could lead to etch stopping. Therefore, the build-up of polymer during ion etch is particularly problematic.
BRIEF SUMMARY OF THE I
Katz Dan
Kholodenko Arnold
Lee Chii
Loewenhardt Peter
Shan Hong Chin
Applied Materials Inc.
Bach Joseph
Dang Thi
Michaelson and Wallace
LandOfFree
Magnetically enhanced inductively coupled plasma reactor... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetically enhanced inductively coupled plasma reactor..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetically enhanced inductively coupled plasma reactor... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2977440