Patent Application
20250087472
The field of the present disclosure relates generally to substrate processing and more specifically to plasma processing of substrates, inductively coupled plasma (ICP) and/or plasma processing of substrates for hard disk drives (HDD).
Substrate processing using various techniques and processing equipment for deposition or etching is a vital part of semiconductor processing and hard disk processing. Various chemical species of plasma, and various techniques and related apparatuses for generating, maintaining and applying plasmas, and for etching and deposition are in widespread use in various industries. Examples include impact spatter etching, plasmas formed through radiofrequency (RF) excitement, plasmas formed using remote radiofrequency coupling such as inductively coupled plasma (ICP), and plasmas with ion acceleration. Various transport arrangements position substrates to be processed within a chamber and hold the substrate during processing, such as described in U.S. Pat. No. 9,914,994 titled SYSTEM ARCHITECTURE FOR COMBINED STATIC AND PASS-BY PROCESSING, and U.S. Pat. No. 6,919,001 titled DISK COATING SYSTEM, both of which are assigned to Intevac, Inc. (the assignee of the present disclosure) and are herein incorporated by reference in their entirety into the present specification. Yet, there are problems with known equipment and techniques, and an ongoing need for improvements leading to higher processing throughput and/or higher quality end product. It is in this environment that present embodiments arise.
The following summary of the invention is included in order to provide a basic understanding of some aspects and features of the invention. This summary is not an extensive overview of the invention, and as such it is not intended to particularly identify key or critical elements of the invention, or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented below.
Embodiments and aspects of an inductively coupled plasma (ICP) station, and related method, are described.
In an embodiment, an ICP station includes a plasma reactor that has a vacuum chamber. The vacuum chamber has a first plasma cavity supporting a first plasma and a second plasma cavity supporting a second plasma. A transport arrangement transports and positions a substrate to be processed within the chamber, with the first plasma cavity aligned to a first axis that is normal to a first facet of the substrate and the second plasma cavity aligned to a second axis that is normal to a second facet of the substrate. Simultaneous processing is applied to the first facet and the second facet of the substrate using the first plasma and the second plasma. In one embodiment, a magnetic field generator is positioned around the chamber to generate magnetic flux in an annular region of the chamber, for each plasma cavity. The magnetic flux acts as bucking magnetic fields that inhibit electron travel to grounded surface(s) of the processing chamber.
In an embodiment, a substrate is held in a chamber of a plasma reactor, using a transport arrangement to position the substrate. In an embodiment the transport arrangement includes carriers that transport the substrates into the chamber, support the substrates within the chamber during processing, and then transport the substrates out of the chamber, serially one after another. A first plasma cavity of the plasma reactor is aligned to a first axis that is normal to a first facet of the substrate. A second plasma cavity of the plasma reactor is aligned to a second axis that is normal to a second facet of the substrate. The substrate is biased. Plasma is generated in each plasma cavity, to apply simultaneous plasma processing to first and second facets of the substrate. In one embodiment, a magnetic field generator is used to provide magnetic flux in an annular region of the chamber. The magnetic flux acts as bucking magnetic fields that inhibit electron travel to a grounded surface of the chamber, for each plasma cavity.
Other aspects and advantages of the embodiments will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.
The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments.
The accompanying drawings, which are incorporated in and constitute a part of this specification, exemplify the embodiments of the present invention and, together with the description, serve to explain and illustrate principles of the invention. The drawings are intended to illustrate major features of the exemplary embodiments in a diagrammatic manner. The drawings are not intended to depict every feature of actual embodiments nor relative dimensions of the depicted elements and are not drawn to scale.
Embodiments of the inventive etch system will now be described with reference to the drawings. Different embodiments may be used for processing different substrates or to achieve different benefits, such as throughput, etch uniformity, RF power utilization, etc. Depending on the outcome sought to be achieved, different features disclosed herein may be utilized partially or to their fullest, alone or in combination with other features, balancing advantages with requirements and constraints. Therefore, certain features and benefits will be highlighted with reference to different embodiments, but are not limited to the disclosed embodiments, and the features may be incorporated in other embodiments or with other combinations.
A system and related method for simultaneous etching of multi-faceted substrates is described herein, in various embodiments and in various aspects that can be combined in various embodiments applicable to substrate processing. An inductively coupled plasma (ICP) station and a method of operation of an ICP station are described as examples with variations. These present technological solution(s) to the following technological problem.
In the course of simultaneously processing multiple facets of substrates (e.g., front and back sides or opposite faces of a substrate), etch removal rates with known equipment and techniques are found too low to facilitate economic considerations. This is especially problematic when the best method of removal is impact sputter etching as is generally the case for metal surfaces. Moreover, as the removal rate scales with the density of capable species, plasmas formed at pressures greater than are sustainable for gridded sources are required. Such plasmas are typically formed using remote radio frequency (RF) coupling, such as inductively coupled plasma (ICP). While this technique is utile to generate the desired plasma density, the species (ions and radicals) form essentially adiabatically. Therefore, a cathode potential is required to generate the requisite acceleration of ion species to facilitate energetic etching. One method, e.g., an alternative to or augmentation of ICP, uses capacitive coupling of the plasma to enable a biasing function. However, this technique is not straightforward in application when attempting simultaneous etching of both sides or faces of a flat substrate because it requires an insulating housing to surround the area to be etched. This is particularly intractable for such applications wherein the substrate is an annular surface (e.g., a recording disc, or a hard disk for hard disk drives).
Technological solutions disclosed herein to the above problem(s) make use of multiple plasma cavities, each aligned to a specific facet (e.g., face, side or surface) of a substrate. For example, in a plasma reactor that has a processing chamber for processing a substrate, one plasma cavity is aligned to one face of a substrate and another plasma cavity is aligned to another face of the substrate. This enables simultaneous processing of multiple facets of the substrate, for example both faces of a wafer or hard disk. Further embodiments with other numbers of plasma cavity for processing substrates that have other numbers of facets to be processed are readily developed in keeping with the teachings herein. Some embodiments further solve technological problems by providing magnetic flux in the processing chamber to act as bucking magnetic fields that inhibit electron travel to a grounded surface of the processing chamber. Operating conditions and principles for specific examples are described below, followed by description of aspects of embodiments with reference to drawings.
A plasma reactor for round substrates has a cylindrical cavity, as a processing chamber, that is evacuated to a vacuum condition, e.g., below 1 millitorr, with a sample substrate situated in the middle of the cylindrical cavity and oriented to face opposed ends of the cylindrical cavity. Each end of the cylindrical cavity or processing chamber forms a plasma cavity oriented to one face of the sample substrate. Gas desired for etch processing is re-introduced into the cavity at pressures between 0.5 and 30 mTorr, following the evacuation. Typical gases include Ar, Kr, Xe and others for energetic etching, and O2, H2, HN2, SF6 and others for reactive processing.
Plasma forms by applying an RF power to a coil situated as shown in the drawings at high frequencies (e.g., 13.6 MHz) ex-situ to a dielectric quartz window at the back of the cylinder structure, for each plasma cavity, e.g., two coils for two plasma cavities for processing a two-sided or double-faced substrate. The inductive coupling and plasma excitation creates a high fraction of ionized species. Self-extinction issues at the reactor walls are limited by the imposition of designed bucking magnetic fields to inhibit electron travel to the grounded surface, e.g., interior wall(s) in the plasma cavities or processing chamber.
In this way, plasma ion species saturate the cavity region area are then used to facilitate uniform erosion of the sample substrate opposite the back chamber wall/window for plasma etching, or uniform deposition to the sample substrate for plasma deposition, i.e., as processing dependent. The ions are extracted from the dense plasma region by the attractive electrostatic forces provided by the bias charged substrate. This is accomplished favorably by removing the high plasma density region from direct contact with the sample holder to not create conductive shorts to ground. For example, suitable design dimensions for the plasma cavities and the processing chamber overall should be employed and/or dimensions of the processing chamber and spacing of substrate to end-walls of the plasma cavities can be adjusted through the use of spacers in some embodiments. Various embodiments allow the simultaneous processing of multiple facets (e.g., the front and back side of a disk, disc, planar annulus, wafer or other substrate). Each facet or side has a unique relationship with a plasma source (e.g., RF generator) and corresponding plasma cavity (as described). The etch rate is then governed by application of a DC-bias to the substrate holder.
One plasma cavity assembly 106, including a coil 112 in an end cap 116, an adaption cylinder plate 118 and a chamber cylinder section 120, is located to one side of a plasma chamber midsection 110, another plasma cavity assembly 108 (with similar design and parts) is located to another side, in this example the opposed side, of the plasma chamber midsection 110. For operation in a linear system, where substrate carriers traverse multiple chambers in a linear travel fashion, an aperture 122 in the plasma chamber midsection 110 provides access to the plasma chamber for a substrate holder entering the chamber, and a complementary aperture is provided on the opposite wall for the substrate carrier to exit the chamber. The apertures can be sealed with gate valves, not shown in
Previous methods and apparatuses have used a gas source, RF coil and plasma for only one sided processing of a substrate. Attempting to insert a two-sided (or multiple faceted) substrate into the middle of a plasma in such apparatuses has disrupted the plasma, preventing plasma processing of the side of the substrate facing away from the RF energized coil. Present embodiments improve upon such previous methods and apparatuses, and present a technological solution to this technological problem, through the use of multiple plasma distribution zones each oriented to a respective facet of a multi-faceted substrate.
Continuing with
Adaption cylinder plate 118 has cylindrical interior walls, as does chamber cylinder section 120, and these along with end cap 116 form the plasma cavity assembly 106, with plasma cavity assembly 108 being formed similarly as mirrored image. In one embodiment, magnets are arrayed in the chamber cylinder section 120 (see
In one embodiment, it has been found that the length of the processing chamber, which is cylindrical in this embodiment, is at least two thirds the diameter of the cylinder, for optimal processing. In one embodiment, it has been found that the length of the cylindrical processing chamber is equal to the diameter of the cylinder, for optimal processing.
In one embodiment, polarity from one magnet to its nearest neighbors is opposite, throughout the array. Here, the magnets alternate North, South, North, South, etc., around the annulus, which coincides with the normal to the rotational axis of the substrate (See,
In one embodiment, magnets are polarized through the thickness of the annulus and arranged with alternating or interleaved opposing magnetization vectors around the annulus. For example, magnetization vectors 432 of every other magnet 406, 410, 414, 418, 422, 426 pointing from the magnet towards the center 434 of the annulus are interleaved or alternating with magnetization vectors 430 of every other magnet 404, 408, 412, 416, 420, 424 pointing away from the center of the annulus to the magnet. Variations with other numbers of magnets and orientations are readily devised.
In one embodiment, sidewalls of the plasma reactor are constructed to provide an inner diameter that defines the gas expansion limit, and a slightly larger diameter but concentric wall that creates a pocket for storage of an annular magnetic array, for example as depicted in
In order to facilitate insertion of the substrate 206 to the holder 516, retention of the substrate 206 by the holder 516, and removal of the substrate 206 from the holder 516, one embodiment of the holder 516 has three prongs 504, 506, 508 that physically contact the substrate 206. One or more of the three prongs 504, 506, 508 also establishes and maintains electrical contact to the substrate 206, for electrical bias of the substrate 206, which is readily achieved with a suitable electrical bias source, connection and control to charge the substrate and sustain current flow. In this embodiment, two of the prongs 504, 506 are fixed in the holder 516, and one prong 508 is movable in a longitudinal direction 514 of the prong 508, i.e., away from and towards the substrate 206. Prong tips 516, 518, 520 could have various features to contact and retain the substrate 206, for example each could have a fork, a cup, a gripper, a channel, texturing, ribs, etc., in various embodiments. In
In an action 602, the apparatus holds a substrate in the plasma reactor processing chamber, with each plasma cavity aligned to a facet of the substrate. For example, a two-sided or two-faced substrate is held with a first plasma cavity aligned to a first side or face of the substrate, and a second plasma cavity aligned to a second side or face of the substrate.
In an action 604, the apparatus provides magnetic flux for each plasma cavity, to act as bucking magnetic fields. The bucking magnetic fields inhibit electron travel to a grounded surface of the processing chamber. For example, annular arrays of magnets, one in each plasma cavity, can provide magnetic flux that so acts.
In an action 606, the apparatus generates a plasma in each plasma cavity, to apply simultaneous processing to all facets of the substrate, for example both sides or faces of a two-sided or two-faced substrate.
In one embodiment, electrical bias is applied to the substrate.
It should be appreciated that, in a variation, it is possible to perform actions 602 and 606 without action 604 and the magnetic flux. This variation may be less optimal, and have less even application of plasma or greater amount of deposits on chamber surfaces, but it is nonetheless possible as an embodiment. Notably, without the application of the magnetic flux electrons from the plasma can travel to the chamber's walls and the plasma would become unstable or it may extinguish.
Detailed illustrative embodiments are disclosed herein. However, specific functional details disclosed herein are merely representative for purposes of describing embodiments. Embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. It should be appreciated that descriptions of direction and orientation are for convenience of interpretation, and the apparatus is not limited as to orientation with respect to gravity. In other words, the apparatus could be mounted upside down, right side up, diagonally, vertically, horizontally, etc., and the descriptions of direction and orientation are relative to portions of the apparatus itself, and not absolute.
It should be understood that although the terms first, second, etc. may be used herein to describe various steps or calculations, these steps or calculations should not be limited by these terms. These terms are only used to distinguish one step or calculation from another. For example, a first calculation could be termed a second calculation, and, similarly, a second step could be termed a first step, without departing from the scope of this disclosure. As used herein, the term “and/or” and the “/” symbol includes any and all combinations of one or more of the associated listed items.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Therefore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
Although the method operations were described in a specific order, it should be understood that other operations may be performed in between described operations, described operations may be adjusted so that they occur at slightly different times or the described operations may be distributed in a system which allows the occurrence of the processing operations at various intervals associated with the processing.
Various units, circuits, or other components may be described or claimed as “configured to”, or “to”, perform a task or tasks. In such contexts, the phrase “configured to” is used to connote structure by indicating that the units/circuits/components include structure (e.g., circuitry or mechanical features) that performs the task or tasks during operation. As such, the unit/circuit/component can be said to be configured to perform the task even when the specified unit/circuit/component is not currently operational (e.g., is not on). The units/circuits/components used with the “configured to” language include hardware—for example, circuits, memory storing program instructions executable to implement the operation, etc. Reciting that a unit/circuit/component is “configured to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. 112, sixth paragraph, for that unit/circuit/component. Additionally, “configured to” can include generic structure (e.g., generic circuitry) that is manipulated by software and/or firmware (e.g., an FPGA or a general-purpose processor executing software) to operate in manner that is capable of performing the task(s) at issue. “Configured to” may also include adapting a manufacturing process (e.g., a semiconductor fabrication facility) to fabricate devices (e.g., integrated circuits or manufactured articles) that are adapted to implement or perform one or more tasks, or designing an article or apparatus to have certain features or capabilities.
The foregoing description, for the purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the embodiments and its practical applications, to thereby enable others skilled in the art to best utilize the embodiments and various modifications as may be suited to the particular use contemplated. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.
