Patent Application
20240266202
An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in their entireties and for all purposes.
The subject matter disclosed herein relates to an electrostatic chuck (ESC) designed to increase a pedestal voltage isolation in a processing tool.
In a typical plasma-based processing system, current pedestals used in an ESC rely only on physical separation to isolate RF and AC signals from a ground plane. Any addition of extra electrodes, which carry high voltages, or gas lines (e.g., a nitrogen (N2) gas-purge line) reduce the physical separation distances to below specifications for given radio-frequency (RF), alternating current (AC), and/or direct current (DC) voltages. The reduced physical separation distances can cause arcing and other detrimental effects in the ESC.
The information described in this section is given to provide the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art.
The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter.
An electrostatic chuck (ESC) that supports and secures various types of substrates (e.g., silicon wafers) used in semiconductor processing operations. A pedestal supporting the ESC, and the ESC in general, are shown and discussed in greater detail with reference to
For example, RF power may be transmitted from, for example, at least the ESC in a plasma-based processing system. The plasma-based processing system may include a first heating element disposed at a first portion of the ESC and a second heating element disposed at a second portion of the ESC, The plasma-processing system may further include a power supply, such as an alternating current (AC) power supply, for powering the heating elements. AC circuitry supplies power to the heaters of the ESC through the pedestal. As is understood by the skilled artisan, the ESC heaters provide an important control to maintain a temperature profile of the process which ultimately leads to better uniformity and etch-rates on a substrate.
In a particular example, the ESC pedestal transmits RF, AC, and DC signals to grids that are embedded in a ceramic top plate of the ESC via nickel rods in a stem of the pedestal. These signals pass through a tube adapter portion that serves as an interface between the pedestal and a movable bracket used to raise or lower the substrate while mounted on the ESC. The tube adapter also serves as a ground plane. As disclosed herein, various embodiments of the disclosed subject matter used in the pedestal design use insulative tubes, tube adapters with dielectric-coated interior surfaces, and gaps in various geometries to separate the RF, AC, and DC signals from the ground plane, thereby preventing arcing. The inventive subject matter disclosed herein is described with reference to a plasma-based processing chamber.
With reference now to
In operation, the substrate 105 is loaded through a loading port 109 onto the substrate-support assembly 107A. A gas line 113 supplies one or more process gases to the showerhead electrode 103. In turn, the showerhead electrode 103 delivers the one or more process gases into the plasma-based processing chamber 101A. A gas source 111 to supply the one or more process gases is coupled to the gas line 113. An RF power source 115 is coupled to the showerhead electrode 103.
In operation, the plasma-based processing chamber 101A is evacuated by a vacuum pump 117. RF power is capacitively coupled between the showerhead electrode 103 and a lower electrode (not shown explicitly) contained within or on the substrate-support assembly 107A, The substrate-support assembly 107A is typically supplied with two or more RF frequencies. For example, in various embodiments, the RF frequencies may be selected from at least one frequency at about 1 MHz, 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, and other frequencies as desired. However, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will recognize that a coil required to block or partially block a particular RF frequency can be designed as needed. Therefore, particular frequencies discussed herein are provided merely for ease in understanding. The RF power is used to energize the one or more process gases into a plasma in the space between the substrate 105 and the showerhead electrode 103. As is known in the relevant art, the plasma can assist in depositing various layers (not shown) on the substrate 105. In other applications, the plasma can be used to etch device features into the various layers on the substrate 105. As noted above, the substrate-support assembly 107A may have heaters (not shown) incorporated therein. The person of ordinary skill in the art will recognize that, while the detailed design of the plasma-based processing chamber 101A may vary, RF power is coupled through at least the substrate-support assembly 107A.
Referring now to
In various embodiments, the ESC may be a tunable ESC (TESC) capable of a tunable temperature control in two-zones on the uppermost portion 107B of the substrate-support assembly 107A. The temperature-tuning capability of the ESC may be achieved by implementing two electric heating elements (shown as dashed lines in the substrate-support assembly 107A of
The electric heating elements may be powered by alternating current (AC) supplied by an AC power supply (not shown in the figures) through the AC connector 203 through the RF filter enclosure 201 and the power able 205. The RF filter enclosure 201 also contains an RF filter (not shown but known in the art) to prevent or reduce RF power from being delivered to the electric heating elements. The temperature of each of the electric heating elements may be controlled by techniques well-known in the art.
With concurrent reference to
Referring now to
The tube portion may be formed from a number of materials known to the skilled artisan, such as various types of metals (e.g., aluminum (Al) and stainless steel (e.g., a 316L alloy) or non-metals capable of withstanding the relatively high temperatures encountered within a plasma-based processing system (e.g., the temperature may be approximately 250° C.) In a specific exemplary embodiment, the tube portion is formed from aluminum with an insulating coating on an inner portion (as shown and described with regard to
Within the tube adapter 307, three insulative tubes, 309A, 309B, 309C, are shown through which, for example, RF signal electrodes travel to the top plate 301. The person of ordinary skill in the art will recognize that, based on a particular implementation of an ESC assembly, a larger or smaller number of insulative tubes may be used.
The insulative tubes 309A, 309B, 309C may be comprised of a number of insulating materials known in the relevant art, such as various types of polymers, provided that the material is chosen to maintain structural integrity in the relatively high temperatures encountered within a plasma-based processing system (e.g., the temperature may be approximately 250° C.). Further, the dielectric material should be chosen to have a dielectric strength that remains substantially consistent over time in the presence of the elevated temperatures and the voltages (described with regard to Table I, below), In a specific exemplary embodiment, the insulative tubes 309A, 309B, 309C are comprised of polyimide (such as Kapton®, a polymer of imide monomers). Kapton® is available from E. I. du Pont de Nemours and Company, 1007 Market Street, Wilmington, Del., USA.
The insulative tubes 309A, 309B, 309C are separated and held in place by lower separator sleeves 313B. These sleeves may be formed from a number of dielectric materials, such as various types of non-conducting ceramics. For example, in a specific exemplary embodiment, the lower separator sleeves 313B are formed from Macor®, Macor® is a machinable glass-ceramic available from Corning Incorporated, One Riverfront Plaza, Corning N.Y., USA.
In a specific exemplary embodiment, the lower separator sleeves 313B are sized such that they are loose enough such that the insulative tubes 309A, 309B, 309C may be readily removed or inserted during routine maintenance or repair operations of the ESC assembly 300.
The tube adapter 307 also is shown to include AC heater wires 311A, 311B and thermal chokes 325A, 325B, 325C, The ESC assembly is also shown to include a number of conductive rods 323A, 323B, 323C configured to carry, for example, high voltage signals.
In a specific exemplary embodiment, the thermal chokes 325A, 325B, 325C may comprise, for example, gold-plated Inconel (an austenitic, nickel-chromium-based alloy). Components comprising Inconel retain their shape and strength over a wide range of temperatures, whereas other metallic-based components, such as aluminum and steel, may creep or otherwise deform at increased temperatures.
Also, in various embodiments, the number of conductive rods 323A, 323B, 323C may comprise, for example, nickel. The number of conductive rods 323A, 323B, 323C are supported by rod supports 313A, which form a portion of the pedestal 303 that is internal to the stem. In various embodiments, the rod supports 313A may comprise, for example, alumina (Al2O3).
The tube adapter 307 also includes at least one gas-purge line (not shown as it is obscured by a center one of the insulative tubes 309B). The tube adapter 307 may also contain other power supply lines. The gas-purge lines may be, for example, brass or stainless steel. However, these materials can be the same as what is currently used on a contemporaneous ESC device and therefore do not need to be modified or changed in light of the disclosed subject matter. Brass is a non-ferrous material so nearby RF signals will have no effect on the purge-gas line. The at least one gas-purge line may carry a variety of gases such as nitrogen (N2) or argon (Ar) as noted above.
Overall, an example of various voltages that may be encountered within the ESC assembly are noted below in Table I.
By combining the various voltages shown in Table I, one can arrive at a total working voltage on the ESC as:
Therefore, to prevent arcing within the ESC assembly, a clearance specification may be determined by a skilled artisan based on, for example, air at a given relative humidity. In an example based on the example voltages supplied by Table I, a clearance specification to prevent arcing is about 394 V/mm (e.g., approximately 10 Volts/mil, where one mil=0.001 inches), mixed frequency. Therefore, by knowing the clearance specification, a skilled artisan may also calculate an air gap (shown and described with regard to
Further, by knowing the dielectric strength of various materials, the skilled artisan can determine a minimum thickness required for a material. For example, polyimide has a dielectric strength of about 118 V/mm (approximately 3000 V/mil). In comparison, a hard-anodized coating on aluminum is about 25 V/run (approximately 640 V/mil. By knowing each of the working voltage and the dielectric strength for a given material or coating, the skilled artisan can determine a minimum thickness for a particular application.
The skilled artisan will recognize that actual voltages encountered within an ESC assembly may vary depending on a given design requirements. Therefore, Table I should be considered to provide examples of voltages encountered simply to provide a better understanding of the disclosed subject matter in light of the various embodiments described herein.
As is also known to the skilled artisan, all thin coated or anodized layers should have broken (e.g., rounded) radii at sharp corners and edges to prevent a very thin or non-covered portion of the underlying material (e.g., various edges and corners of the tube adapter 307) from occurring. Also, the thin coated and anodized layers should be formed so as to prevent or reduce cracks through which arcing could occur.
Referring now to
In various embodiments, an enlarged gap portion 319 may be formed proximate to outboard ones of the conductive rods 323A, 323B, 323C to eliminate arcing by forming, for example, an enlarged air gap. The determination of a clearance specification for a size of the enlarged gap portion 319 is discussed above with reference to
Since the O-ring 315 is being forced outward, due to a higher pressure within the tube adapter 307 an outside the tube adapter 307 (at some level of vacuum during a processing operation), the O-ring 315 is pushed against peripheral (outer) walls of the tube adapter 307 and away from the enlarged gap portion 319, Therefore, an increase in the size of the enlarged gap portion 319 does not lessen the integrity of the seal provided by the O-ring 315.
With reference now to
As noted herein, the air gap 331 and the insulative tubes 309A, 309B, 309C insulates the high voltage lines within and proximate to the insulative tubes 309A, 309B, 309C from grounded portions (e.g., grounded portions of the tube adapter 307). Therefore, the insulative tubes 309A, 309B, 309C generally extend down to a point at which arcing between the HV lines and the grounded surfaces (e.g., distal to a lower portion of the tube adapter 307) can no longer occur. This point can be determined based on the calculations provided above with reference to
Overall, as shown and described herein, the disclosed subject matter incorporated into the ESC assembly 300 of
In specific exemplary embodiments as show described herein, one HV isolation technique uses polyimide tubes (e.g., the insulative tubes 309A, 309B, 309C) to enclose RF signal electrodes allowing isolation of these signals before the connection to their respective insulation wires. The use of polyimide is appropriate for this application as it is a very good insulator and can resist the high temperatures in this location. Another
Another exemplary embodiment uses a HV isolation technique employing a hard-anodized surface or polyimide coating treatment on the inner surface of the tube adapter 307. The surface treatment (e.g., the dielectric coating 317 of
Another exemplary embodiment uses a HV isolation technique employing one or more cut outs in the upper tube adapter geometry (e.g., the enlarged gap portions 319 of
Moreover, since all changes are made on an interior volume of the ESC assembly 300 (see FIC. 3A), specially within the tube adapter 307, the various embodiments disclosed herein may be readily retrofitted into an existing plasma-based processing or other substrate-processing system since all external dimensions and connections from the ESC assembly 300 are maintained. Therefore, no modifications to an existing processing system need to occur.
Therefore, the description above includes illustrative examples, devices, systems, and methods that embody the disclosed subject matter. In the description, for purposes of explanation, numerous specific details were set forth in order to provide an understanding of various embodiments of the disclosed subject matter. It will be evident, however, to those of ordinary skill in the art that various embodiments of the subject matter may be practiced without these specific details. Further, well-known structures, materials, and techniques have not been shown in detail, so as not to obscure the various illustrated embodiments.
As used herein, the term “or” may be construed in an inclusive or exclusive sense. Further, other embodiments will be understood by a person of ordinary skill in the art upon reading and understanding the disclosure provided. Further, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will readily understand that various combinations of the techniques and examples provided herein may all be applied in various combinations.
Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be inter-related and each may be used separately or in combination with other ESC embodiments discussed herein.
Consequently, many modifications and variations can be made, as will be apparent to the person of ordinary skill in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to the skilled artisan from the foregoing descriptions. Portions and features of sore embodiments may be included in, or substituted for, those of others. Such modifications and variations are intended to fall within a scope of the appended claims, Therefore, the present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the claims, in addition, in the foregoing Detailed Description, it may, be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.
| Number | Date | Country | |
|---|---|---|---|
| 62624619 | Jan 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16966833 | Jul 2020 | US |
| Child | 18637111 | US |
