Abstract:
In accordance with this disclosure, there are provided several inventions, including a substrate processing apparatus with multi-layer surfaces configured to face the plasma and resist against corrosion. These multi-layer surfaces may in one example include a base layer of aluminum, anodized aluminum, or quartz, a second layer of stabilized zirconia, and a second layer of a yttrium-aluminum composite such as yttrium aluminum garnet (YAG).

Description:
BACKGROUND 
       [0001]    The present invention relates to the formation of coated surfaces which may be used in semiconductor processing. 
         [0002]    In semiconductor material processing facilities, plasma processing chambers are often used, for example, for etching and deposition. The walls of these chambers, as well as liners, process kits, and dielectric windows, are often exposed to corrosive and erosive process gases, as well as plasma. Therefore, plasma chambers, typically composed of aluminum, are sometimes coated with protective layers to increase the life of the chamber. 
         [0003]    U.S. Pat. No. 8,619,406 B2 describes a coating of is yttrium oxide (yttria, Y 2 O 3 ), which has been applied directly to aluminum or with an intermediary layer of aluminum oxide. An improvement over yttria is yttria-stabilized zirconia (YSZ, ZrO 2 :Y 2 O 3 ). It is also possible to layer either of these components with other components. For example, U.S. Pat. No. 6,942,929 describes a coating of yttrium aluminum garnet (YAG, Y 3 Al 5 O 12 ) over aluminum. U.S. Patent Pub. No. 2008/0169588 A1 describes a coating in which there is an outer layer of yttria and an intermediate layer of YAG, above a third layer of alumina. Another example is U.S. Patent Pub. No. 2014/0295670 A1, which describes a coating of yttria over aluminum oxide, over aluminum or aluminum alloy. 
         [0004]    Given the expense and lost time in shutting down plasma processing chambers after they wear out, there is an interest in chamber coatings that have longer lifetimes, and which may have better protection against corrosive process chemicals. 
       SUMMARY 
       [0005]    Various inventive embodiments are described herein. One embodiment is a substrate processing apparatus comprising a chamber configured to contain a plasma, wherein the apparatus may comprise one or more multi-layer surfaces oriented to face the plasma, the one or more multi-layer surfaces may each comprise: a base material; a first layer over the base material comprising zirconia stabilized with a dopant oxide; and a second layer over the first layer, comprising a yttrium-aluminum composite. 
         [0006]    In another embodiment, at least one of the one or more multi-layer surfaces may be a transparent quartz window. The embodiment may further comprise: a spectrometric sensor positioned to take spectrometric measurements inside the chamber, through the quartz window; an analog to digital converter configured to convert signals corresponding to the spectrometric measurements into one or more digital signals; and a general purpose computer, which may comprise: one or more processors; a digital memory system; and an I/O bus in communication with the analog to digital converter and configured to receive the one or more digital signals; and one or more interconnection busses configured to transmit data between the one or more processors, the data receiver, the digital memory system, and the I/O bus. 
         [0007]    In another embodiment, a method of operating the above apparatus or related apparatuses disclosed herein may comprise: using the spectrometric sensor to repeatedly take spectrometric measurements of the level of zirconium within the chamber, through the quartz window, wherein the spectrometric measurements are converted into the one or more digital signals by the analog to digital converter and transmitted to the I/O bus of the general purpose computer; causing the general purpose computer to run computer executable program instructions comprising instructions to monitor the digital signals until the signals reflect a spike in the level of zirconium in the chamber, and then to transmit a signal indicating the failure of a coating on a surface within the apparatus. 
         [0008]    In another embodiment, a method of making any of the above apparatuses or related apparatuses disclosed herein may comprise, for each surface of the one or more surfaces: providing the base material; forming the first layer over the base material by exposing the surface to a plasma thermal spray; and after the first layer is formed, forming the second layer over the first layer by exposing the surface to a plasma thermal spray. 
         [0009]    These and other features of the present inventions will be described below in the detailed description and in conjunction with the following figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    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: 
           [0011]      FIG. 1  is a schematic cross-sectional view of a multi-layer coating. 
           [0012]      FIG. 2  is a schematic view of a processing chamber that may be used in practicing the disclosed inventions. 
           [0013]      FIG. 3  is a flowchart illustrating a process for creating a multi-layer coating. 
           [0014]      FIG. 4  is a schematic illustration of a computer system for implementing a sensor processing system used in embodiments of the disclosed inventions. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    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. 
         [0016]    In plasma process chambers with a particular prior art coating of yttrium oxide, the inventors have observed an average lifetime of 3700 RF hours. This failure can be much earlier, depending on the chemistry of the plasma process. Failure mechanisms for such coatings may include delamination during the cleaning process upon, for example, exposure to chlorine or fluorine. The inventors have observed, however, that a coating of YSZ over aluminum may last approximately 10 times longer than a Y 2 O 3  coating in the test involving HF solution to mimic fluorine plasma exposure in a reactor. However, in a similar test involving an HCl solution to mimic chlorine plasma exposure in a reactor, there is minimal improvement in the lifetime of the coating. A coating of YAG over aluminum may last approximately 6 times longer than the Y 2 O 3  coating in a test involving HCl solution to mimic chlorine plasma exposure in a reactor, but a similar test involving HF solution only approximately doubles the lifetime with respect to Y 2 O 3 . Thermal cycling does not appear to substantially affect these results. The inventors have determined that there are advantages to combining the benefits of YAG with the benefits of YSZ in a single coating which, among its other benefits, would be resistant to both HCl and HF. 
         [0017]      FIG. 1  shows one embodiment of such a coating  100  that combines the advantages of YSZ and YAG in the same coating. In this example, aluminum is the base/bulk material to be coated  101 , which is an interior surface of a plasma chamber. Above the aluminum is a layer of Al 2 O 3    102 . Above that is a layer of YSZ  103 . Finally, on the top is a layer of YAG  104 . The YAG layer  104  in this example is facing the plasma side of a chamber. 
         [0018]    In other embodiments, zirconia may be stabilized with other oxides than yttria in layer  103 , such as magnesia (MgO), calcium oxide (CaO), and cerium(III) oxide (Ce 2 O 3 ), iridium(IV) oxide (IrO 2 ), titanium(IV) oxide (TiO 2 ), or oxides of elements from atomic numbers 57 (La) to 71 (Lu). In another embodiment, the Al 2 O 3  layer  102  may be omitted. Also, other embodiments may include other yttrium-aluminum composites, such as yttrium aluminum monoclinic (YAM) and yttrium aluminum perovskite (YAP). In some cases, coatings of YAG may contain small amounts of other components such as YAP and/or YAM, while still considered to be YAG. 
         [0019]    In other embodiments, there may be intermediate layers of other materials, or multiple layers of any of the above materials, arranged in any order. Various plasma processing chamber base materials  101  may be used, including aluminum (Al), aluminum oxide (Al 2 O 3 ), an Al 2 O 3  film on Al (created, for example, by anodization), a non-aluminum containing metal, quartz, or other known plasma chamber materials. 
         [0020]    The layers of the coating  103  and  104  may, in one embodiment, be applied by plasma thermal spraying. In other embodiments, they may be applied by sputtering, plasma enhanced chemical vapor deposition or other chemical vapor deposition, electron beam physical vapor deposition or other physical vapor deposition, chemical solution deposition, atomic layer deposition, pulse laser deposition, cathodic arc deposition, electrohydrodynamic deposition, sol-gel precursor deposition, aerosol deposition, and the like. 
         [0021]    In one embodiment, the total thickness of layers  103  and  104  is about 0.2 mm (8 mils). The total thickness of the layers may be more or less; however, there is a trade-off relating to the thickness of the layers. The thicker the layers, the greater the corrosion resistance and lifetime of the coating is likely to be. However, as the layer gets thicker, the adhesion to the underlying layer(s) may decrease. Thus, a thinner layer may be better, assuming the surface can be coated uniformly. In one embodiment, layer  103  can be approximately 0.05-0.1 mm (2-4 mils) thick, and layer  104  can be approximately 0.05-0.15 mm (2-6 mils) thick. 
         [0022]    Surfaces, as described, may in one embodiment be configured to withstand a lifetime of approximately 6,000 to 10,000 RF hours before failure, or in another embodiment, higher than 10,000 RF hours. The surfaces may also be designed to fail within a given expected range, such as 6,000 to 8,000 RF hours, 7,000 to 9,000 RF hours, or 8,000 to 10,000 RF hours. 
         [0023]    The chamber may be configured in various ways known in the art. Suitable chambers may include 2300® Versys® Kiyo45™ chambers provided by Lam Research Corporation, or the like. The surfaces may be formed by any method known in the art. In addition, in one embodiment, both an intermediate zirconium-containing layer and an outer yttrium-aluminum composite layer may be deposited by plasma thermal spray. In one embodiment, the interior of plasma chamber composed of aluminum and/or one or more quartz windows may be coated by plasma thermal spray, to produce at least two coatings. 
         [0024]    In another embodiment, a plasma chamber may comprise one or more replaceable linings. These linings may be coated in a controlled environment, and then inserted into the plasma chamber.  FIG. 2  is a schematic, simplified view of an embodiment of a plasma processing chamber showing replaceable coated liners. Inside the chamber  200 , a chuck  201  may be used for holding substrates. An injector  202  may be used to inject process gasses into the chamber. Liners  204 ,  205 , and  206  may be used in any configuration to protect the chamber from corrosion. Such liners may be made of any suitable material. In one embodiment, the liners may be composed of aluminum, and coated in accordance with one of the coatings described herein. 
         [0025]    The embodiment of  FIG. 2  includes a quartz window  203 , which may also be coated as described herein, with the coating facing the plasma-side of the chamber. In one embodiment, a sensor  207  may be placed behind the quartz window, and connected via sensor circuitry to a processor  208  for processing signals from the sensor  207 . 
         [0026]    In one embodiment, the failure of a surface coated as described herein may be recognized by the use of sensors to monitor the presence of zirconium in the chamber. In a configuration where zirconium is only a component within an intermediate layer, zirconium may thus serve as a signal that layers above the zirconium layer have been breached. In one example, a zirconium spike may be recognized in the plasma, or on the surface of a substrate being processed. Such a spike may indicate, for example, that there has been a significant corrosion through an outer YAG layer and that an intermediate YSZ layer is being corroded. This could therefore result in a marked increase in the measured zirconium level. A spike may be recognized in several ways, including by setting a predetermined threshold for zirconium concentration in the chamber, such that when the threshold is met, this may be an indication that a surface coating within the chamber has failed. In an alternate embodiment, a threshold can be set for the rate of change in zirconium concentration as a function of time. 
         [0027]    When a coating in the interior of a chamber fails, the chamber may be replaced or re-coated, or a part of the chamber may be replaced or re-coated. In one embodiment, the chamber may contain replaceable coated liners, and when the coating on one of the liners fails, the liner may be replaced. In another embodiment, a quartz window insert may similarly be coated, and the window replaced when the coating fails. In another embodiment, a gas injector into the chamber may be coated as described above, and when the coating on the gas injector fails, the injector may be replaced. 
         [0028]      FIG. 3  shows an embodiment of an algorithm for determining when a surface inside a chamber, and in particular a replaceable liner surface, has failed. In step  301 , sensor  207  may be used to measure the zirconium level in the chamber. The process loops ( 302 ) so long as a spike in the zirconium level has not been detected. If a spike is detected, however, the process may indicate to an operator that a chamber coating has failed,  303 . An operator may in one embodiment respond by stopping the process, inspecting the liners, and replacing all the liners, or just the liner or liners that have failed. The algorithm may be performed by analog alarm circuitry as known in the art, or by digital circuitry such as a special- or general-purpose computer. An operator may be notified by various means, including a visual display, an audible alarm, or a text message. Such notifications can, in one embodiment, be sent over a wired or wireless network or otherwise via any appropriate telecommunications medium. 
         [0029]      FIG. 4  is a high level block diagram illustrating a computer system  400  for implementing a sensor processing system used in embodiments of the disclosed inventions. The computer system may have many physical forms ranging from an integrated circuit, a printed circuit board, and a small handheld device up to a huge super computer. The computer system  400  may include one or more processors  402 , and further can include an electronic display device  404  (for displaying graphics, text, and other data), a main memory  406  (e.g., random access memory (RAM)), storage device  408  (e.g., hard disk drive), removable storage device  410  (e.g., optical disk drive), user interface devices  412  (e.g., keyboards, touch screens, keypads, mice or other pointing devices, etc.), and/or a communication interface  414  (e.g., wireless network interface). The communication interface  414  may allow software and/or data to be transferred between the computer system  400  and external devices via a link. The system may also include a communications infrastructure  416  (e.g., a communications bus, cross-over bar, or network) to which the aforementioned devices/modules may be connected. 
         [0030]    Information transferred via communications interface  414  may be in the form of signals such as electronic, electromagnetic, optical, or other signals capable of being received by communications interface  414 , via a communication link that carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, a radio frequency link, and/or other communication channels. With such a communications interface, it is contemplated that the one or more processors  402  might receive information from a network, or might output information to the network in the course of performing the above-described method steps. Furthermore, method embodiments of the present invention may execute solely upon the processors or may execute over a network such as the Internet in conjunction with remote processors that shares a portion of the processing. 
         [0031]    The term “non-transient computer readable medium” is used generally to refer to media such as main memory, secondary memory, removable storage, and storage devices, such as hard disks, flash memory, disk drive memory, CD-ROM and other forms of persistent memory and shall not be construed to cover transitory subject matter, such as carrier waves or signals. Examples of computer code include machine code, such as produced by a compiler, and files containing higher level code that are executed by a computer using an interpreter. Computer readable media may also be computer code transmitted by a computer data signal embodied in a carrier wave and representing a sequence of instructions that are executable by a processor. 
         [0032]    The computer device  400  may serve as the processor  208  for processing signals from the sensor  207  in  FIG. 2 . For example, signals from sensor  207  may be processed through an analog-to-digital computer, such that a digital signal may be transmitted to the computing device  208 , for example via the communications interface  414 , which may include an I/O bus. 
         [0033]    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.