Patent Application
20170047202
This disclosure relates to the manufacturing of semiconductor devices. More specifically, the disclosure relates to the manufacturing of semiconductor devices in a plasma processing chamber.
Control of the plasma sheath and ion trajectory at the extreme edge is dictated by the mechanical design of the edge ring. The profile in this region, over which part of the wafer hangs, is sloped. It is variation in this slope that allows for control of uniformity at the extreme edge. However, the change in slope can only be used to control uniformity for a limited number of processes. Moreover, a significant drawback is that the edge ring has to be changed every time the process regime shifts, in order to provide for a different slope.
Disclosed herein are various embodiments, including an apparatus, for treating a substrate in a plasma processing chamber with an electromagnet power source with leads. An edge ring body surrounds the substrate. An electromagnet is embedded within or attached to a surface of the edge ring body, extending more than half way around the edge ring, wherein the electromagnet is configured to provide a magnetic flux greater than 0.1 mTesla along more than half of an outer edge of the substrate, wherein the electromagnet comprises at least one winding, wherein the leads of the electromagnet power source are electrically connected to the at least one winding.
In another manifestation, plasma processing chamber for processing a substrate with an area is provided. A processing chamber is provided. A substrate support supports the substrate within the processing chamber. A gas inlet provides gas into the processing chamber above a surface of the substrate. An edge ring surrounds the substrate support. An electromagnet power source is provided. An electromagnet is incorporated in the substrate support or edge ring configured to provide a magnetic flux greater than 0.1 mTesla along more than half of an outer edge of the substrate, wherein the electromagnet encloses an area of at least half of the area of the substrate and comprises at least one winding and a pair of leads electrically connected to the electromagnet power source.
In another manifestation, an apparatus for treating a substrate on a substrate support in a plasma processing chamber is provided. A toroidal electromagnet is provided within the plasma processing chamber and configured to provide a toroidal magnetic flux greater than 0.1 mTesla at an outer edge of the substrate.
These and other features of the present inventions will be described in more detail below in the detailed description and in conjunction with the following figures.
The disclosed inventions are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
Inventions will now be described in detail with reference to a few of the embodiments thereof as illustrated in the accompanying drawings. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced without some or all of these specific details, and the disclosure encompasses modifications which may be made in accordance with the knowledge generally available within this field of technology. Well-known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present disclosure.
Growth in the semiconductor industry is driven by advances in plasma processing and design of chamber hardware. Device manufacturers want to maximize the yield and efficiently utilize the real estate available on the substrate. This is most challenging at the extreme edge of the wafer which, in most commonly used designs in the industry, is not in contact with the ESC. This part of the wafer hangs over what is known as the edge ring. This edge ring is electrically isolated from both the ESC and the wafer. Maintaining uniformity in this region is dictated by a plurality of factors that are dependent on the regime used for processing the substrate. However, control of uniformity and plasma at this extreme edge is currently only possible by altering the mechanical design of the edge ring, i.e., a new edge ring is potentially required for different process regimes. This document describes a technology where-in magnetic fields are provided by means of wires, embedded in the edge ring, at the very edge of the wafer. By controlling the currents in the electromagnets one could potentially obtain arbitrary magnetic field configurations. This in turn allows control of the plasma sheath and ion trajectory at the very edge providing finer control at the extreme edge without need to change the edge ring for various processes.
To facilitate understanding,
The plasma power supply 106 and the wafer bias voltage power supply 116 may be configured to operate at specific radio frequencies such as, for example, 13.56 MHz, 27 MHz, 2 MHz, 60 MHz, 400 kHz, 2.54 GHz, or combinations thereof. Plasma power supply 106 and wafer bias voltage power supply 116 may be appropriately sized to supply a range of powers in order to achieve desired process performance. For example, in one embodiment of the present invention, the plasma power supply 106 may supply the power in a range of 50 to 5000 Watts, and the wafer bias voltage power supply 116 may supply a bias voltage in a range of 20 to 2000 V. In addition, the TCP coil 110 and/or the electrode 120 may be comprised of two or more sub-coils or sub-electrodes, which may be powered by a single power supply or powered by multiple power supplies.
As shown in
By supplying current to the wires, poloidal and toroidal magnetic fields are generated. The strength of these fields is directly a function of the supplied current, wire geometry and surrounding dielectric medium. Of course the amount of current supplied to both wires can be different. In doing so, one can, by the superposition principle in electromagnetic theory, generate arbitrary field configurations that extend into the space beyond the edge ring. Since a plasma follows the magnetic field lines, the ion path follows the field configuration. This allows for control of the shape of the sheath of the plasma at the very edge. One notes that various sheath profiles can be obtained by simply changing the currents in the wires without the need to replace the edge ring.
The edge ring may also containing circuitry for filtering the RF supplied to generate the plasma. This filter may be internal (embedded in the edge ring) or external. This is important so as to ensure that the field lines are not disrupted by extraneous currents which could change the intended plasma sheath profile. The filter may be simple containing only passive RLC (resistive, inductive, and capacitive) components, which would include cascaded versions, or may contain active components such as transistors and diodes.
Other embodiments may also use a permanent magnet for the edge ring material, but such permanent magnets would not provide adjustable or tunable magnetic fields.
Some advantages provided by some embodiments may include, but may not be limited to the following: Potential low cost: Compared to using different edge rings with different slopes for various processes, the above outlined technology provides a potentially cheaper alternative by allowing change in the extreme edge uniformity by simply changing the currents in the wires. Applicability to all processes: The technology is applicable to dielectric and conductor processes. Further it can be implemented on legacy systems. Finer control of extreme edge profile: Due to ability to control the magnetic field through currents, it is possible to obtain more granularity in control of uniformity and profile at the extreme edge of the wafer.
AC power can also be supplied to the electromagnets. The frequency of AC should be at least 0.01 Hz. AC clamping requires redesign of the edge ring, which are not backward compatible with existing edge ring technology. AC clamping requires providing high current and filtering circuitry to power the wires in the edge ring.
If a wafer is subjected to many different processes the current in the electromagnet may be varied for each different process. A purely mechanical edge ring would not be so adjustable. An embodiment may program the controller 124 to have different steps, so that each different process step may provide different process gases, different plasma powers and different electromagnet powers.
Preferably, an electromagnet extends at least half way around the circumference of the edge ring. Most preferably, an electromagnet extends at least completely around the circumference of the edge ring. Preferably, an electromagnet has an electrical resistivity of less than 10−4 ohm-m at 20° C. Preferably, the electromagnet produces a magnetic flux density of at least 0.1 mT at the outer edge of the substrate. In this embodiment, since the electromagnet is adjacent to the entire outer edge of the substrate, the electromagnet produces a magnetic flux density of at least 0.1 mT at the entire outer edge of the substrate. In other embodiments, the electromagnet produces a magnetic flux density of at least 0.1 mT for more than half of the outer edge of the substrate. More preferably the electromagnet produces a magnetic flux density of between 10−1 mT and 103 mT at the outer edge of the substrate. If the resistance of the electromagnet is too high, the current in the electromagnet would bet too low, which would cause a magnetic field of less than 0.1 mT, which would not provide a significant improvement in confinement.
In some embodiments, the power is inductively coupled to the plasma. In other embodiments, the power is capacitive coupled to the plasma. In some embodiments the edge ring may be hollow. In other embodiments the edge ring may be solid. In other embodiments the edge ring may be hollow and filled with a dielectric material to optimize magnetic field density. In various embodiments, the edge rings may be made of various dielectric materials, such as, silicon, silicon nitride, or silicon carbide. In various embodiments, the edge rings may be of an isolative ceramic material. In other embodiments, instead of being embedded in an edge ring, the electromagnets may be bound to a surface of an edge ring. However, if the electromagnets are on a surface of an edge ring, the electromagnets may need additional shielding for protection from RF power and from etching conditions. An advantage of having electromagnets within the edge ring helps control polymer accumulation near the edge of a wafer. Embodiments may also use the controller to provide a feedback loop to further tune the electromagnets.
In some embodiments the substrate has a larger diameter than the substrate support, so that the outer edges of the substrate extend over the edge ring. In order to provide a magnetic flux density of at least 0.1 mTesla at the edge of the substrate, in one embodiment the electromagnet is located between 10% inside the substrate diameter and 10% outside the substrate diameter. In such embodiments, the electromagnet may have a diameter equal to between 90% to 110% of the diameter of the substrate. For example, if the substrate has a 300 mm diameter, the electromagnet would have a diameter between 270 mm and 330 mm and the center of the electromagnet would align with the center of the substrate. As a result the electromagnet forms a ring with an inner area that is at least half of the area of the substrate. Since the substrate support has a diameter that is less than the diameter of the substrate, the diameter of the electromagnet would be between 90% and 110% of the diameter of the substrate support. In an embodiment, the electromagnet only tunes confinement at the edge of the substrate. Therefore, in such an embodiment the magnetic field from the electromagnet significantly drops towards the center of the substrate. For example, the magnetic flux may drop more than 80% between the edge of the substrate and half the distance to the center of the substrate.
Embodiments that provide a toroidal electromagnet may provide a toroidal magnetic field less half the outer edge of the substrate.
While inventions have been described in terms of several preferred embodiments, there are alterations, permutations, and various substitute equivalents, which fall within the scope of this invention. There are many alternative ways of implementing the methods and apparatuses disclosed herein. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and various substitute equivalents as fall within the true spirit and scope of the present invention.
