Patent Application
20160379806
This disclosure relates to the coating of polymer components in etch chambers used in semiconductor processing.
Polymer components have many uses within plasma processing chambers, including rings, seals, and bushings. To maximize lifetime of polymer components, prior designs have used plasma-resistant polymers. One dilemma is that some polymers could be resistant against one type of radical (e.g., the F radical) but not others (e.g., O or H radicals). Another challenge is that achieving one order difference in erosion rate of polymers by engineering the chain structure may not be a simple task even for a highly skilled polymer chemist, because one must balance against other properties of the materials.
Another strategy is to add plasma resistant metallic oxide fillers into the polymer matrix to retard the attacks of radicals. However, polymer materials could be preferentially etched by radicals, leaving filler materials loose and potentially flaking off as a particle source.
New ways are therefore needed to extend the lifetime of polymer components in plasma chambers.
Disclosed herein are various embodiments, including an electrostatic chuck (ESC) for a plasma processing chamber. This ESC may in one embodiment comprise aluminum or aluminum alloy. It may further include a ceramic top plate for holding a wafer, bonded to the base. It may have a polymer material between the base and the ceramic top plate, with at least one exposed portion, and a plasma resistant atomic layer deposition coating on the at least one exposed portion.
In various further embodiments of the above electrostatic chucks, the ceramic top plate may be bonded to the base by an adhesive, and the polymer material may comprise a bead surrounding the adhesive. The plasma resistant atomic layer deposition coating may be a dielectric material. The plasma resistant atomic layer deposition coating may comprise alumina. The plasma resistant atomic layer deposition coating may comprise an oxide comprising yttrium. The polymer material may comprise strengthening additives for enhanced mechanical properties. The base may comprise gas distribution channels. The above ESC may also be part of a plasma processing chamber, and also may include an O-ring. This O-ring may comprise a plasma resistant atomic layer deposition coating.
This application also describes embodiments of a confinement ring for a plasma processing chamber. This confinement ring may include a support structure for supporting the confinement ring. This support structure may comprise a polymer material. This polymer material may be coated by a plasma resistant atomic layer deposition coating.
In various further embodiments of the above confinement rings, the polymer material may comprise polyimide. The plasma resistant atomic layer deposition coating may also be alumina.
This application also describes methods of making an electrostatic chuck for a plasma processing chamber. This method may include any or all of the following steps: providing a base comprising aluminum or aluminum alloy; providing a ceramic top plate for holding a wafer; bonding the ceramic top plate to the base; applying a polymer material between the base and the ceramic top plate, having at least one exposed portion; and depositing by atomic layer deposition a plasma resistant layer on the at least one exposed portion.
In various further embodiments of the above methods, the step of bonding may comprise joining the ceramic top plate to the base with an adhesive. The step of applying a polymer material may also comprise applying a polymer bead surrounding the adhesive. The plasma resistant atomic layer deposition coating may be a dielectric material. The plasma resistant atomic layer deposition coating may comprise alumina. The plasma resistant atomic layer deposition coating may comprise an oxide comprising yttrium. The polymer material may comprise strengthening additives for enhanced mechanical properties. The base may comprise gas distribution channels.
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.
Polymers have many uses within plasma processing chambers; for example, as the polymer bead or seal for an electrostatic chuck, as polyamide-imide bushings, or as polyimide laminate rings. Due to their organic nature, polymers are susceptible to radical attacks even in the absence of ion bombardment within plasma etchers, for example by attacking C—C or Si—O bonds. This either shortens the lifetime of consumable parts made from polymers, or even worse, jeopardizes the lifetime of a whole assembly.
In one embodiment, the lifetime of polymer components may be extended by using an atomic layer deposition (ALD) coating as a radical-resistant protective barrier to completely shield polymers from radical attacks. Example ALD coating materials may include ceramics, dielectric materials, alumina, zirconia, yttria, combinations of aluminum, zirconium, yttrium, and/or oxygen such as YAG or YSZ, and materials known in the art to have superior resistance to radicals. The material may in several embodiments also be metal oxide, nitride, fluoride, or carbide, or combinations thereof.
ALD coatings as used in the context of these embodiments may be super-conformal and uniform, and have numerous other advantages such as increasing the lifetime of a polymer part and reducing sources of contamination. The ALD coatings can be operated at low temperature (even at room temperature) which will not compromise structural and chemical properties of polymers (e.g., soften the polymer). The coatings can be pinhole or pore free, and provide a superior radical barrier.
Another advantage for use in coating polymer materials in plasma processing chambers is that ALD coatings are typically very pure, and can be made to show no detectable metal impurities, perhaps other than Aluminum from coating. Carbon impurity within film can also be made low.
ALD coatings of polymers can be super-conformal and uniform, and exhibit a coating thickness that is independent of aspect ratio. The coating need not alter the part dimension, which can be important for many components such as thermal interface materials, sacrificial protection shims, or O-rings. In addition, a very thin ALD coating need not interfere with the functionality of coated parts such as thermal interface materials by adding thermal impedance.
Furthermore, ALD coatings can be made flexible, which can make them suitable for flexible polymer parts. An ALD inorganic coating can be used, for example, as a moisture barrier for flexible displays. Without being bound by theory, a mechanism of its flexibility may be its low thickness or amorphous structure.
Methods of ALD coating are known in the art. See, e.g., U.S. Patent Pub. No. 2014/0113457 A1 (published Apr. 24, 2014), incorporated herein by reference in its entirety. They use surface-mediated deposition reactions to deposit films on a layer-by-layer basis. In one example ALD process, a substrate surface, including a population of surface active sites, is exposed to a gas phase distribution of a first film precursor (P1). Some molecules of P1 may form a condensed phase atop the substrate surface, including chemisorbed species and physisorbed molecules of P1. The reactor is then evacuated to remove gas phase and physisorbed P1 so that only chemisorbed species remain. A second film precursor (P2) is then introduced to the reactor so that some molecules of P2 adsorb to the substrate surface. The reactor may again be evacuated, this time to remove unbound P2. Subsequently, thermal energy provided to the substrate activates surface reactions between adsorbed molecules of P1 and P2, forming a film layer. Finally, the reactor is evacuated to remove reaction by-products and possibly unreacted P1 and P2, ending the ALD cycle. Additional ALD cycles may be included to build film thickness.
Polymer components for plasma chambers which may be suitable for coating with ALD layers may include any components that are susceptible to radical erosion in plasma etch, as well as deposition, or which are in downstream chambers. Non-limiting examples may include:
In one embodiment, polymer parts may be coated via ALD prior to assembly in the chamber. In another embodiment, parts may be coated after the chamber is assembled, or part of a chamber is assembled. For example, an electrostatic chuck may be assembled including polymer parts, and the entire electrostatic chuck may be coated via ALD.
ALD coatings over a polymer for use in a plasma chamber according to the embodiments disclosed herein may be very thin, or may have a wide range of thicknesses. For example, the thickness may in one embodiment be in the range of about 10 nm to about 1 μm. Preferably, the range may be from about 100 nm to about 500 nm.
In one embodiment, the ceramic plate 104 comprises a dielectric material. In another embodiment, it comprises alumina.
During operation, the plasma chamber area 101 may produce radicals such as F radical, which may flow (100) around the edge of the wafer into the region 106 around the adhesive 105 or the polymer bead 107. Adhesive 105 (or if present, bead 107) may be coated by ALD on at least the side facing area 106 with a plasma resistant coating, such that the ALD coating 115 will be resistant to radical attack.
In one embodiment, the plasma resistant coating 115 may be a dielectric material. In another embodiment, the coating may comprise alumina. In another embodiment, the adhesive material 105 may comprise strengthening additives, such as fibers or particles, for enhanced mechanical properties. In previous designs, the strengthening additives to polymers were detrimental because of the possibility of contamination. However, coating an strengthened polymer material by ALD makes it possible to seal such additives within the coating, thus allowing the use of strengthened polymer materials inside a plasma processing chamber.
Some plasma processing chambers use confinement rings in order to confine plasma to a particular location within the chamber. In some configurations, such as that described in U.S. Patent Application Pub. No. 2012/0073754 A1 (published Mar. 29, 2012, incorporated herein by reference in its entirety), such confinement rings may be positioned using hangers made of polymer materials such as PEEK (polyetheretherketone).
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.
