Dielectric window for substrate processing chamber - Patents.com

Abstract

A lid assembly for a processing chamber in a substrate processing system includes a dielectric window. The dielectric window includes an upper portion having a flat upper surface and a lower surface. The lower surface is a surface of the dielectric window facing a plasma. The lower portion of the dielectric window is cylindrical and extends downward from the lower surface, and an outer diameter of the lower portion satisfies at least one of: being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and overlapping one of the inner coil and the outer coil.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 993,433, filed March 23, 2020. The disclosures of the above-referenced applications are hereby incorporated by reference in their entireties.

[0002] The present disclosure relates to a dielectric window for a substrate processing system. [Background technology]

[0003] The "Background" section provided herein is intended to provide a general background to the present disclosure. To the extent described in the "Background" section of the present disclosure, the work of the inventors named herein, as well as aspects of the present disclosure that may not be considered prior art at the time of filing, are not admitted, expressly or impliedly, as prior art to the present disclosure.

[0004] During the manufacture of semiconductor devices, etching and deposition processes may be performed in a processing chamber. An ionized gas, or plasma, may be introduced into the plasma chamber to etch (or remove) material from, and sputter or deposit material onto, a substrate, such as a semiconductor wafer. Forming a plasma for use in a manufacturing or fabrication process typically begins with introducing a process gas into the processing chamber. The substrate is positioned in the processing chamber on a substrate support, such as an electrostatic chuck or pedestal.

[0005] The process chamber may include a transformer coupled plasma (TCP) reactor coil. A radio frequency (RF) signal generated by a power supply is provided to the TCP reactor coil. The TCP reactor coil is driven by a transformer coupled capacitively tuned (TCCT) matching network. The TCCT matching network receives the RF signal provided by the power supply and allows for adjustment of the power provided to the TCP reactor coil. A dielectric window constructed from a material such as ceramic is incorporated into the top surface of the process chamber. The dielectric window allows the RF signal to be transmitted from the TCP reactor coil to the interior of the process chamber. The RF signal excites gas molecules in the process chamber to generate plasma. Summary of the Invention

[0006] A lid assembly for a processing chamber in a substrate processing system includes a dielectric window. The dielectric window includes an upper portion having a flat upper surface and a lower surface. The lower surface is a plasma-facing surface of the dielectric window. The lower portion of the dielectric window is cylindrical and extends downwardly from the lower surface, with an outer diameter of the lower portion satisfying at least one of: being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and overlapping one of the inner coil and the outer coil.

[0007] In other features, the outer diameter of the lower portion is aligned to the midpoint of the gap. The dielectric window is comprised of a single integrated piece comprising an upper portion and a lower portion. The upper portion and lower portion are separate pieces attached together. The lower portion is fixedly attached to the upper portion. The lower portion is removably attached to the upper portion.

[0008] In other features, the lower portion is constructed of quartz. The lower portion is constructed of alumina. The lower portion includes a plurality of gas channels configured to enable gas flow between an interior volume defined inside the lower portion and an exterior volume defined outside the lower portion. The lid assembly further includes an inner coil and an outer coil. The dielectric window has a pi-shaped cross section.

[0009] The processing chamber in the substrate processing system includes an inner coil and an outer coil configured to generate a first plasma field and a second plasma field in the processing chamber, and a dielectric window. The dielectric window includes an upper portion having a flat upper surface and a lower surface. The lower surface is a plasma-facing surface of the dielectric window. A lower portion of the dielectric window is configured to separate the first plasma field and the second plasma field. The lower portion is cylindrical and extends downwardly from the lower surface. An outer diameter of the lower portion satisfies at least one of: being aligned with a gap between the inner coil and the outer coil; and overlapping one of the inner coil and the outer coil.

[0010] In other features, an outer diameter of the lower portion is aligned to the midpoint of the gap. The dielectric window is comprised of a single integrated piece comprising an upper portion and a lower portion. The upper portion and lower portion are separate pieces attached together. The lower portion is removably attached to the upper portion. The lower portion is comprised of quartz. The lower portion is comprised of alumina. The lower portion includes a plurality of gas channels. The dielectric window has a pi-shaped cross section.

[0011] A dielectric window for a processing chamber in a substrate processing system includes an upper portion having a flat upper surface and a lower surface. The lower surface is a plasma-facing surface of the dielectric window. The lower portion of the dielectric window is comprised of one of quartz and alumina. The lower portion is cylindrical and extends downwardly from the lower surface. An outer diameter of the lower portion satisfies at least one of: (i) being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and (ii) overlapping one of the inner coil and the outer coil.

[0012] In other features, the dielectric window has a π-shaped cross section.

[0013] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of the disclosure. [Brief description of the drawings]

[0014] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, in which:

[0015] [Figure 1] FIG. 1 is a functional block diagram of an example plasma processing system including a dielectric window in accordance with the present disclosure.

[0016] [Figure 2A] FIG. 2A is a cross-sectional side view of an exemplary dielectric window according to the present disclosure.

[0017] [Figure 2B] FIG. 2B is a perspective view of the underside of an exemplary dielectric window according to the present disclosure.

[0018] [Figure 2C] FIG. 2C is a bottom view of an exemplary dielectric window according to the present disclosure.

[0019] [Figure 3A] FIG. 3A illustrates another exemplary dielectric window according to the present disclosure. [Figure 3B] FIG. 3B illustrates another exemplary dielectric window according to the present disclosure. [Figure 3C] FIG. 3C illustrates another exemplary dielectric window according to the present disclosure.

[0020] In the drawings, reference numbers may be reused to identify similar and / or identical elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A dielectric window (e.g., including a material such as ceramic) is incorporated into the top surface of a processing chamber in a substrate processing system. A radio frequency (RF) signal is transmitted into the interior volume of the processing chamber (e.g., from a transformer-coupled plasma (TCP) reactor coil including an inner coil and an outer coil) to generate a plasma. The inner coil and the outer coil generate two separate plasma fields (e.g., B-fields) in the processing chamber. Typically, the dielectric window has flat top and bottom surfaces. The flat bottom (plasma-facing) surface inhibits the control and adjustability of the distribution of RF power in the plasma. Thus, the adjustability of the plasma uniformity from center to edge is limited, and in some applications (e.g., high aspect ratio etching), a global etch tilt may occur.

[0022] Systems and methods according to the principles of the present disclosure implement a dielectric window having a pie (i.e., π)-shaped cross-section. For example, the dielectric window has a flat upper portion and a cylindrical lower portion extending downward from a lower surface of the upper portion. The cylindrical portion physically separates the plasma below the dielectric window into two isolated plasma zones corresponding to the inner and outer coils. The dimensions of the cylindrical portion (e.g., including but not limited to diameter, height, and thickness) may be selected according to desired plasma characteristics such as uniformity and adjustability.

[0023] 1 shows a plasma processing system 100 including a process chamber 104 and a TCP reactor coil 108. A dielectric (or TCP) window 112 is disposed between the TCP reactor coil 108 and the process chamber 104. The dielectric window 112 is disposed above a pinnacle 116 (PINNACLE is a registered trademark) for transmitting an RF source signal to the process chamber 104 to enable the generation of plasma. The pinnacle 116 may correspond to an upper liner of the process chamber 104. The pinnacle 116 may be configured to support a lid assembly 120 of the process chamber 104, including but not limited to the TCP reactor coil 108 and the dielectric window 112. The dielectric window 112 according to the present disclosure has a pie (i.e., π) shaped cross section as described in more detail below.

[0024] A first power supply 122 supplies a first RF power signal to a TCCT matching network 124. The TCCT (or first) matching network 124 is included between the first power supply 122 and the TCP reactor coil 108. The TCCT matching network 124 allows for adjustment of the power supplied to the TCP reactor coil 108.

[0025] A substrate support 128, such as an electrostatic chuck, pedestal, or other suitable substrate support, is disposed within the processing chamber 104. The substrate support 128 supports a substrate 130. The plasma processing system further includes a bias RF power supply 132 connected to a bias (or second) matching network 136. The second matching network 136 is connected between the bias RF power supply 132 and the substrate support 128. The second matching network 136 matches the impedance (e.g., 50Ω) of the bias RF power supply 132 as seen by the second matching network 136 to the impedance of the substrate support 128 and plasma 138 in the plasma processing chamber 104.

[0026] The plasma processing system 100 further includes a voltage control interface (VCI) 140. The VCI 140 may include a pickup device 142, a voltage sensor 144, a controller 146, and circuitry disposed between the voltage sensor 144 and the controller 146. The pickup device 142 extends into the substrate support 128. The pickup device 142 is connected to the voltage sensor 144 via a conductor 148 and generates an RF voltage signal.

[0027] The operation of voltage sensor 144 may be monitored, manually controlled, and / or controlled via controller 146. Controller 146 may display the output voltages of the channels of voltage sensor 144 on display 150. Display 150 is shown separate from controller 146, but may be included in controller 146. A system operator may provide input signals indicating (i) whether to switch between channels, (ii) which one or more of the channels to activate, and / or (ii) which one or more of the channels to deactivate.

[0028] In operation, an ionizable gas flows into the plasma processing chamber 104 through the gas inlet 156 and flows out of the plasma processing chamber 104 through the gas outlet 158. A first RF signal is generated by the RF power supply 122 and delivered to the TCP reactor coil 108. The first RF signal radiates from the TCP reactor coil 108, passes through the dielectric window 112, and enters the processing chamber 104. This causes the gas in the processing chamber 104 to ionize and form a plasma 138. The plasma 138 creates a sheath 160 along the walls of the processing chamber 104. The plasma 138 includes electrons and positively charged ions. The electrons, being much lighter than the positively charged ions, tend to move more easily, creating a DC bias voltage and a DC sheath potential at the inner surfaces of the plasma processing chamber 104. The average DC bias voltage and DC sheath potential at the substrate 130 affect the energy with which the positively charged ions impact the substrate 130. This energy affects process characteristics such as the rate at which etching or deposition occurs.

[0029] The controller 146 may adjust the bias RF signal generated by the RF power supply 132 to vary the magnitude of the DC bias and / or DC sheath potential at the substrate 130. The controller 146 may compare the output of the channels of the voltage sensor 144 and / or a representative value derived based on the output of the channels to one or more set point values. The set point values ​​may be predetermined and stored in the memory 162 of the controller 146. The bias RF signal may be adjusted based on the difference between (i) the output and / or the representative value of the voltage sensor 144 and (ii) the one or more set point values. The bias RF signal passes through the second matching network 136. The output provided by the second matching network 136 (referred to as the matched signal) is then sent to the substrate support 128. The bias RF signal is sent through the insulator 128 to the substrate 130.

[0030] A gas supply system 164 selectively supplies one or more gas mixtures (e.g., a process gas mixture, a purge gas, etc.) to the processing chamber 104 via gas injectors 168. For example, the gas supply system 164 may include one or more sets of gas sources, valves, flow controllers, gas manifolds, etc. (not shown) to supply the gas mixtures to the gas injectors 168. The controller 146 may be configured to control the gas supply system 164 and / or the gas injectors 168 to supply the gas mixtures to the processing chamber 104.

[0031] 2A, 2B, and 2C, an exemplary dielectric window 200 in accordance with the principles of the present disclosure has a pie (i.e., π) shaped cross-section. Figure 2A is a cross-sectional side view of the dielectric window 200. Figure 2B is a perspective view of the underside of the dielectric window 200. Figure 2C is a bottom view of the dielectric window 200. As shown, the dielectric window 200 has a flat upper (e.g., circular or disk shaped) portion 204 and a cylindrical lower portion (e.g., annular ring) 208 extending downwardly from a lower surface 212 of the upper portion 204.

[0032] The upper portion 204 and the lower portion 208 may comprise the same or different materials. For example, the lower portion 208 may be constructed of quartz or other suitable dielectric material (e.g., high purity alumina). In some embodiments, the upper portion 204 and the lower portion 208 may comprise a single integrated part. In other embodiments, the lower portion 208 may correspond to a separate part that is fixedly or removably attached to the upper portion 204. For example, the lower portion 208 may be attached to the upper portion 204 using a plasma resistant adhesive, such as an epoxy.

[0033] In embodiments in which the lower portion 208 is removably attached to the upper portion 204, the lower portion 208 may be removed to facilitate maintenance, cleaning, and / or repair of the lower portion 208. Additionally, the lower portion 208 may be removed and replaced without removing the upper portion 204.

[0034] The cylindrical portion 208 physically separates the plasma below the dielectric window 200 into two isolated volumes 220 and 224 corresponding to respective plasma zones generated by an inner coil 228 and an outer coil 232 (e.g., of the TCP reactor coil 108). For example, the lower portion 208 surrounds and defines the volume 220, while the volume 220 is defined outside the lower portion 208. The dimensions of the cylindrical portion 208 (e.g., including but not limited to diameter, height, and thickness) may be selected according to desired plasma characteristics, such as uniformity and adjustability.

[0035] As shown, the lower portion 208 is positioned according to the gap 236 between the inner coil 228 and the outer coil 232. For example, the diameter of the lower portion 208 is selected such that the outer edge (i.e., outer diameter) of the lower portion 208 is located within the gap 236 between the inner coil 228 and the outer coil 232. The diameter of the lower portion 208 may be selected according to the desired performance characteristics of the plasma. In one embodiment, the diameter of the lower portion 208 is selected such that the outer diameter of the lower portion 208 is located at or near the midpoint of the gap 236 (as shown in FIG. 2A ). In another embodiment, the diameter of the lower portion 208 is selected such that the outer diameter of the lower portion 208 is closer to one of the inner coil 228 and the outer coil 232. In another embodiment, the diameter of the lower portion 208 is selected such that the outer diameter of the lower portion 208 overlaps one of the inner coil 228 and the outer coil 232.

[0036] In embodiments in which the lower portion 208 is removable, the lower portion 208 may be replaced depending on the desired performance and adjustment characteristics. For example, the lower portion 208 may be replaced with a lower portion having the desired dimensions (e.g., material, height, diameter, thickness, etc.) to adjust performance characteristics. Thus, the diameter of the inner portion 208 may vary from 6 to 14 inches (e.g., 152 to 281 mm). The height of the inner portion 208 may vary from 1 to 5 inches (e.g., 25 to 127 mm). The thickness of the inner portion 208 may vary from 0.5 to 2 inches (e.g., 12 to 51 mm).

[0037] 3A, 3B, and 3C show another example of a dielectric window 300 including an upper portion 304 and a lower portion 308 according to the present disclosure. An inner coil 312 and an outer coil 316 are disposed in the upper portion 304. In FIG. 3A, the outer diameter of the lower portion 308 is located closer to the outer coil 316 than the inner coil 312. In FIG. 3B, the outer diameter of the lower portion 308 overlaps a portion of the outer coil 316.

[0038] In Figure 3C, the lower portion 308 includes a number of gas channels or holes 320. The holes 320 allow gas provided to an interior volume of the lower portion 308 (e.g., interior volume 220 of Figure 2A) to flow into an exterior volume outside the lower portion 308 (e.g., exterior volume 224 of Figure 2A). The holes 320 may have the same or different diameters. By way of example only, the holes 320 may have a diameter of 0.25 to 2 inches (e.g., 6 to 51 mm).

[0039] The foregoing description is merely exemplary in nature and is not intended to limit the disclosure, its application, or uses in any way. The broad teachings of the disclosure can be embodied in various forms. Thus, while the disclosure includes specific examples, other modifications will become apparent upon study of the drawings, the specification, and the following claims, and the true scope of the disclosure should not be so limited. It should be understood that one or more steps in a method may be performed in a different order (or simultaneously) without altering the principles of the disclosure. Furthermore, although each of the embodiments is described above as having certain features, any one or more of these features described with respect to any embodiment of the disclosure may be implemented in any of the other embodiments and / or combined with features of any of the other embodiments, even if the combinations are not explicitly described. In other words, the described embodiments are not mutually exclusive, and permuting one or more of the embodiments with one another remains within the scope of the disclosure.

[0040] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms including "connected," "engaged," "coupled," "adjacent," "next to," "on," "above," "below," and "disposed." Unless expressly described as "direct," when a relationship between a first element and a second element is described in the disclosure above, the relationship may be a direct relationship where there are no other intervening elements between the first element and the second element, but it may also be an indirect relationship where one or more intervening elements (either spatially or functionally) exist between the first element and the second element. As used herein, the phrase at least one of A, B, and C should be interpreted to mean a logical non-exclusive OR (A OR B OR C), and not to mean "at least one of A, at least one of B, and at least one of C."

[0041] In some implementations, the controller is part of a system that may be part of the examples described above. Such systems may include semiconductor processing equipment, including processing tool(s), chamber(s), processing platform(s), and / or specific processing components (wafer pedestal, gas flow system, etc.). These systems may be integrated with electronics for controlling pre-, during, and post-processing operations of semiconductor wafers or substrates. The electronics may be referred to as a "controller" that may control various components or subparts of the system(s). The controller may be programmed to control any process disclosed herein, including delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow settings, fluid delivery settings, position and operation settings, wafer transfer to and from tools and other transport tools and / or load locks connected or interfaced with the particular system, depending on the processing requirements and / or type of system.

[0042] Broadly speaking, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software to receive instructions, issue instructions, control operations, enable cleaning operations, and enable endpoint measurements. Integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files) that define operational parameters for performing a particular process on or for a semiconductor wafer or for a system. In some embodiments, the operational parameters may be part of a recipe defined by a process engineer to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0043] In some implementations, the controller may be part of or coupled to a computer that is embedded in, coupled to, or networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or all or part of a fab host computer system, which may enable remote access of wafer processing. The computer may enable remote access to the system to monitor the current progress of a fabrication operation, examine the history of past fabrication operations, examine trends or performance indicators from multiple fabrication operations, modify parameters of a current process, set up processing steps following a current process, or start a new process. In some embodiments, a remote computer (e.g., a server) may provide a process recipe to the system over a network, which may include a local network or the Internet. The remote computer may include a user interface that allows for entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some embodiments, the controller receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool with which the controller is configured to interface or control. Thus, as discussed above, the controller may be distributed, such as by comprising one or more individual controllers networked together and operating toward a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes may be one or more integrated circuits on the chamber in communication with one or more remotely located integrated circuits (e.g., at the platform level or as part of a remote computer) that combine to control the process in the chamber.

[0044] Without being limited thereto, exemplary systems may include a plasma etch chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0045] As described above, depending on the process steps being performed by the tool, the controller may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, a main computer, another controller, or tools used in material transport to and from wafer containers to and from tool locations and / or load ports within a semiconductor manufacturing factory. The present disclosure includes the following application examples: [Application example 1] 1. A lid assembly for a processing chamber in a substrate processing system, the lid assembly comprising: a dielectric window, the dielectric window comprising: an upper portion having flat upper and lower surfaces, the lower surface being a plasma-facing surface of the dielectric window; a lower portion, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and (ii) being overlapped with one of the inner coil and the outer coil; A lid assembly comprising: [Application example 2] A lid assembly as described in Application Example 1, wherein the outer diameter of the lower portion is aligned with the midpoint of the gap. [Application example 3] A lid assembly as described in Application Example 1, wherein the dielectric window is constructed of a single integrated part comprising the upper and lower portions. [Application example 4] A lid assembly as described in Application Example 1, wherein the upper and lower parts are separate pieces attached together. [Application example 5] A lid assembly as described in Application Example 4, wherein the lower portion is fixedly attached to the upper portion. [Application Example 6] A lid assembly as described in Application Example 4, wherein the lower portion is removably attached to the upper portion. [Application Example 7] A lid assembly according to Application Example 1, wherein the lower portion is made of quartz. [Application Example 8] A lid assembly according to Application Example 1, wherein the lower portion is made of alumina. [Application Example 9] A lid assembly as described in Application Example 1, wherein the lower portion includes a plurality of gas channels configured to enable gas flow between an internal volume defined inside the lower portion and an external volume defined outside the lower portion. [Example 10] A lid assembly as described in Application Example 1, further comprising the inner coil and the outer coil. [Application Example 11] A lid assembly according to Application Example 1, wherein the dielectric window has a π-shaped cross section. [Application Example 12] 1. A process chamber in a substrate processing system, comprising: an inner coil and an outer coil configured to generate a first plasma field and a second plasma field within the processing chamber; and a dielectric window, the dielectric window comprising: an upper portion having flat upper and lower surfaces, the lower surface being a plasma-facing surface of the dielectric window; a lower portion configured to separate the first plasma field and the second plasma field, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between the inner coil and the outer coil; and (ii) overlapping one of the inner coil and the outer coil; A processing chamber comprising: [Application Example 13] 13. The processing chamber of claim 12, wherein the outer diameter of the lower portion is aligned with a midpoint of the gap. [Example 14] 13. The processing chamber of claim 12, wherein the dielectric window is formed of a single integrated part comprising the upper and lower portions. [Example 15] 13. The processing chamber of claim 12, wherein the upper and lower portions are separate pieces attached together. [Example 16] A processing chamber according to application example 15, wherein the lower portion is removably attached to the upper portion. [Application Example 17] A processing chamber according to application example 12, wherein the lower portion is made of quartz. [Example 18] A processing chamber according to application example 12, wherein the lower portion is made of alumina. [Example 19] 13. The processing chamber of claim 12, wherein the lower portion includes a plurality of gas channels. [Example 20] 13. The processing chamber of claim 12, wherein the dielectric window has a π-shaped cross section. [Example 21] 1. A dielectric window for a processing chamber in a substrate processing system, the dielectric window comprising: an upper portion having flat upper and lower surfaces, the lower surface being a plasma-facing surface of the dielectric window; a lower portion constructed of one of quartz and alumina, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and (ii) overlapping one of the inner coil and the outer coil; A dielectric window comprising: [Example 22] A dielectric window as described in Application Example 21, having a π-shaped cross section.

Claims

1. 1. A lid assembly for a processing chamber in a substrate processing system, the lid assembly comprising: a dielectric window, the dielectric window comprising: a top portion having sidewalls, an upper surface, and a lower surface, the lower surface being a plasma-facing surface of the dielectric window, and the sidewalls being vertical and flat; a lower portion, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and (ii) being overlapped with one of the inner coil and the outer coil; A lid assembly comprising:

2. The lid assembly of claim 1 , wherein the outer diameter of the lower portion is aligned with a midpoint of the gap.

3. 2. The lid assembly of claim 1, wherein the dielectric window is constructed of a single integrated piece comprising the upper and lower portions.

4. The lid assembly of claim 1 , wherein the upper and lower portions are separate pieces attached together.

5. The lid assembly of claim 4 , wherein the lower portion is fixedly attached to the upper portion.

6. The lid assembly of claim 4 , wherein the lower portion is removably attached to the upper portion.

7. The lid assembly of claim 1 , wherein the lower portion is constructed of quartz.

8. 10. The lid assembly of claim 1, wherein the lower portion is constructed of alumina.

9. 2. The lid assembly of claim 1, wherein the lower portion includes a plurality of gas channels configured to permit gas flow between an interior volume defined inside the lower portion and an exterior volume defined outside the lower portion.

10. The lid assembly of claim 1 further comprising the inner coil and the outer coil.

11. The lid assembly of claim 1 , wherein the dielectric window has a π-shaped cross section.

12. 1. A process chamber in a substrate processing system, comprising: an inner coil and an outer coil configured to generate a first plasma field and a second plasma field within the processing chamber; A dielectric window, the dielectric window comprising: a top portion having sidewalls, an upper surface, and a lower surface, the lower surface being a plasma-facing surface of the dielectric window, and the sidewalls being vertical and flat; a dielectric window including a lower portion configured to separate the first plasma field and the second plasma field, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between the inner coil and the outer coil; and (ii) overlapping one of the inner coil and the outer coil; an annular support structure disposed in an upper portion of the processing chamber and supporting the dielectric window, the inner coil, and the outer coil; A processing chamber comprising:

13. 13. The processing chamber of claim 12, wherein the outer diameter of the lower portion is aligned with a midpoint of the gap.

14. 13. The processing chamber of claim 12, wherein the dielectric window is comprised of a single integrated piece comprising the upper and lower portions.

15. 13. The processing chamber of claim 12, wherein the upper and lower portions are separate pieces attached together.

16. 16. The processing chamber of claim 15, wherein the lower portion is removably attached to the upper portion.

17. 13. The processing chamber of claim 12, wherein the lower portion is constructed of quartz.

18. 13. The processing chamber of claim 12, wherein the lower portion is constructed of alumina.

19. 13. The processing chamber of claim 12, wherein the lower portion comprises a plurality of gas channels.

20. 13. The processing chamber of claim 12, wherein the dielectric window has a π-shaped cross section.

21. 1. A dielectric window for a processing chamber in a substrate processing system, the dielectric window comprising: a top portion having sidewalls, an upper surface, and a lower surface, the lower surface being a plasma-facing surface of the dielectric window, and the sidewalls being vertical and flat; a lower portion constructed of one of quartz and alumina, the lower portion being cylindrical and extending downwardly from the lower surface, an outer diameter of the lower portion satisfying at least one of: (i) being aligned with a gap between an inner coil and an outer coil disposed above the dielectric window; and (ii) being overlapped with one of the inner coil and the outer coil; A dielectric window comprising:

22. 22. The dielectric window of claim 21, having a π-shaped cross section.

23. The lid assembly of claim 9 , wherein the gas channels have the same diameter.

24. The lid assembly of claim 9 , wherein the plurality of gas channels have different diameters.

25. 20. The processing chamber of claim 19, wherein the gas channels have the same diameter.

26. 20. The processing chamber of claim 19, wherein the plurality of gas channels have different diameters.

Images