Dielectric constant adjustable ceramic window

Abstract

A dielectric window for a process chamber is provided. The dielectric window includes a disk-shaped body made of a first dielectric material having a first dielectric constant. An annular portion made of a second dielectric material having a second dielectric constant greater than the first dielectric constant is disposed within the disk-shaped body. The dielectric window has a substantially constant thickness across a process region of the process chamber. The process region is an interior region of the process chamber where plasma is generated during processing of a substrate in the process chamber. The placement of the annular portion on the disk-shaped body is configured to maintain a substantially constant thickness of the dielectric window.

Description

Technical Field

[0001] Implementations of the present disclosure relate to inductively coupled plasma chambers, and more particularly to a dielectric window having a plurality of materials configured to vary the dielectric constant and thus the RF coupling efficiency across the entire dielectric window.

Background Art

[0002] In the field of plasma processing, there is a pursuit of higher plasma uniformity in order to improve the uniformity of the process (e.g., etching uniformity, deposition uniformity in a plasma-assisted deposition process, etc.) and the resulting device yield. As the feature size decreases and the substrate / wafer size increases, the need to improve plasma uniformity is becoming increasingly important. For example, the tolerance for radial non-uniformity in a plasma etching process continues to decrease as manufacturers pursue improved yield.

[0003] Conventional solutions for improving plasma uniformity in an inductively coupled plasma (ICP) process chamber rely on varying the shape of the dielectric window along the plasma-facing side of the dielectric window. In this approach, essentially, the efficiency of power coupling into the process region is varied by changing the thickness of the dielectric window. However, with such a solution, a particular portion of the dielectric window protrudes into the process region below the dielectric window. This can lead to problems such as material buildup (e.g., polymer accumulation) around the protrusion. Further, such protrusions can impede the gas flow within the chamber and make it difficult to mount other components (e.g., Faraday shields).

[0004] The implementations of the present disclosure arise from such a background.

Summary of the Invention

[0005] The implementation of the present disclosure provides a dielectric window having multiple materials, such materials may have different dielectric constants, thereby causing different RF coupling efficiencies through the dielectric window.

[0006] In some implementations, a dielectric window for a process chamber is provided, comprising a disc-shaped body made of a first dielectric material having a first dielectric constant, and an annular portion made of a second dielectric material having a second dielectric constant greater than the first dielectric constant, and installed within the disc-shaped body, wherein the dielectric window has a substantially constant thickness over an internal region of the process chamber, which is a process region where plasma is generated during processing of a substrate within the process chamber, and the installation of the annular portion on the disc-shaped body is configured to maintain a substantially constant thickness of the dielectric window.

[0007] In some implementations, the upper surface of the disc-shaped body includes an annular recess that accommodates the annular portion.

[0008] In some implementations, the disc-shaped body and the annular portion are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window.

[0009] In some implementations, different radial regions include a first region where power is inductively coupled only through the first dielectric material, and a second region where power is inductively coupled through both the first and second dielectric materials.

[0010] In some implementation configurations, the disc-shaped body defines the bottom surface of the dielectric window such that the bottom surface of the dielectric window is defined solely from the first dielectric material.

[0011] In some implementation configurations, the upper surface of the dielectric window includes a surface region defined by a first dielectric material and a surface region defined by a second dielectric material.

[0012] In some implementations, the disc-shaped body spans the width of the process area, while the annular portion does not.

[0013] In some implementations, the annular portion is positioned substantially below the coil that inductively couples the power within the process region.

[0014] In some implementations, the disc-shaped body and annular portion reduce radial non-uniformity of the plasma generated in the process area.

[0015] In some implementations, the annular portion defines an insert having a bottom contour molded to match the upper contour of the disc-shaped body, so as to maintain a substantially constant thickness of the dielectric window.

[0016] In some implementations, the annular portion has a substantially rectangular cross-section.

[0017] In some implementations, the ring portion is embedded within the disc-shaped body.

[0018] In some implementations, a dielectric window for a process chamber is provided, comprising a disc-shaped body made of a first dielectric material having a first dielectric constant, and an annular cavity defined within the disc-shaped body and configured to contain a second dielectric material having a second dielectric constant greater than the first dielectric constant, wherein the second dielectric material is a fluid.

[0019] In some implementations, the disc-shaped body and the annular cavity are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window.

[0020] In some implementations, different radial regions include a first region where power is inductively coupled only through the first dielectric material, and a second region where power is inductively coupled through both the first and second dielectric materials.

[0021] In some implementations, the disk-shaped body spans the width of the process region, and the annular cavity does not span the width of the process region.

[0022] In some implementations, the annular cavity is positioned such that it is substantially disposed below a coil that inductively couples power within the process chamber.

[0023] In some implementations, the disk-shaped body and the annular cavity reduce the radial non-uniformity of the plasma generated within the process chamber.

[0024] [[ID=1十一年]] In some implementations, the annular cavity has a substantially rectangular cross-section.

[0025] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0030] [Figure 3A] Figure 3A shows a conceptual cross-sectional view of a dielectric window 100 for a plasma process chamber having a central insert, according to the implementation embodiment of this disclosure.

[0031] [Figure 3B] Figure 3B shows a conceptual cross-sectional view of a dielectric window 100 for a plasma process chamber having a central insert, according to the implementation embodiment of this disclosure.

[0032] [Figure 3C] Figure 3C shows a conceptual cross-sectional view of a dielectric window 100 for a plasma process chamber having a central insert, according to the implementation embodiment of this disclosure.

[0033] [Figure 4A] Figure 4A conceptually shows a cross-sectional view of a dielectric window 100 having an embedded channel for embedding materials having different dielectric constants, according to the implementation of the present disclosure.

[0034] [Figure 4B] Figure 4B conceptually shows a cross-section of a dielectric window 100 with multiple channels embedded inside, according to the implementation configuration of this disclosure.

[0035] [Figure 4C] Figure 4C conceptually shows a cross-sectional view of a dielectric window 100 having an embedded annular channel according to the implementation of this disclosure.

[0036] [Figure 5A] Figure 5A conceptually shows a cross-sectional view of a dielectric window 100 having an embedded cavity according to the implementation configuration of this disclosure.

[0037] [Figure 5B] Figure 5B conceptually shows a cross-sectional view of a dielectric window 100 having an embedded cavity according to the implementation configuration of this disclosure.

[0038] [Figure 5C] Figure 5C conceptually shows a cross-sectional view of a dielectric window 100 having an embedded cavity according to the implementation of this disclosure.

[0039] [Figure 6A] Figure 6A conceptually shows a cross-sectional view of a dielectric window 100 having an embedded channel through which a fluid circulates, according to the implementation of the present disclosure.

[0040] [Figure 6B] Figure 6B conceptually shows a cross-sectional view of a dielectric window 100 having a plurality of annular channels through which a fluid can circulate, according to the implementation of the present disclosure.

[0041] [Figure 7] Figure 7 conceptually illustrates an inductively coupled plasma system according to the implementation of this disclosure.

[0042] [Figure 8] Figure 8 shows a control module 800 for controlling each of the systems described herein, according to the implementation of this disclosure. [Modes for carrying out the invention]

[0043] In plasma processing of wafers / substrates, plasma uniformity can affect wafer uniformity. Conventional attempts to control the uniformity of transformer-coupled plasma (TCP) have relied on changes to RF coil design or dielectric window / lid shape. However, changing the dielectric window shape can complicate window manufacturing and further impact component lifespan. While changes to the RF coil may help improve plasma uniformity, such changes may introduce further unforeseen effects on plasma coupling.

[0044] In contrast to previous attempts to improve plasma uniformity, the implementation of this disclosure achieves modification of plasma uniformity by changing / adjusting the local dielectric constant of a window or material without changing the shape of the dielectric window or modifying the RF coil. The implementation of this disclosure achieves local modification of the dielectric constant using solid-phase, liquid-phase, or gas-phase materials to create a hybrid material window.

[0045] Therefore, unlike current solutions that attempt to improve wafer process uniformity by changing RF coils or lid shapes, the implementations according to this disclosure provide the concept of hybrid materials for modifying plasma coupling efficiency (determined / defined based on, for example, the power consumed in the matched network and RF coils). More specifically, in some implementations, materials with large dielectric constant differences are introduced into the window to adjust the local dielectric constant at specific locations within the window, thereby influencing RF coupling efficiency in a desired manner and improving plasma uniformity, and consequently, overall process uniformity. In various implementations, the introduced material can be solid-phase, liquid-phase, gas-phase, or a combination thereof. In some implementations, the dielectric constant can be adjusted by introducing different materials to suit various processes. Thus, the implementations of this disclosure can improve uniformity on the wafer without changing the hardware design of components other than the window itself.

[0046] While not bound by the specific operating theory for the currently disclosed implementations, the following explanation is provided for the purpose of providing a broader understanding and possible operating mechanisms. In inductively coupled plasma (ICP) or transformer-coupled plasma (TCP), plasma is generated by inducing current through electromagnetic induction. In the case of a planar inductive source, the electrodes typically take the form of a spiral coil placed above a dielectric window, and power is coupled to the process region of the process chamber through the dielectric window. A transformer is created by the coil outside the window and the induced current inside the chamber, but capacitive coupling through the dielectric window also exists. Previous studies have shown that increasing the thickness of the dielectric window reduces RF coupling efficiency. This can be understood from the capacitance equation, which states that capacitance is proportional to the dielectric constant and the area of ​​the overlapping plates, but inversely proportional to the distance between the plates. Therefore, as the window thickness increases, the mutual inductance decreases, and RF coupling efficiency decreases. While the effects of changing the window thickness have been explored, adjusting the dielectric constant as a technique that affects RF coupling efficiency has not been explored. Furthermore, although not bound by any particular theory of operation, the implementation of this disclosure is intended to locally adjust the dielectric constant by using various materials with different dielectric constants, thereby influencing the RF coupling efficiency. This is advantageous over conventional techniques in that it allows for local modification of the RF coupling efficiency without changing the chamber geometry or the thickness of the dielectric window, thus eliminating the need to redesign other components of the plasma processing system.

[0047] Figure 1A shows a conceptual cross-sectional view of a dielectric window 100 for a plasma process chamber according to the implementation of the present disclosure.

[0048] In the illustrated implementation, the TCP coil of the process chamber is defined to include an inner coil 106 and an outer coil 108 positioned above the dielectric window 100. The inner and outer coils 106 / 108 can be powered independently and are adjustable to have different power settings to optimize power supply to the chamber for a given plasma process. In some implementations, there are two or more coils. In some implementations, there is one TCP coil.

[0049] In the illustrated implementation, the dielectric window 100 consists of two parts, including a disc-shaped body 102 and an annular portion 104. The disc-shaped body 102 is formed from a first dielectric material (e.g., quartz, ceramic, or a material having a similar dielectric constant and similar coefficient of thermal expansion), and the annular portion 104 is formed from a second dielectric material having a dielectric constant different from that of the first dielectric material. In some implementations, the dielectric constant of the second material (of the annular portion 104) is greater than that of the first material (of the disc-shaped body 102).

[0050] As shown in the figure, the disc-shaped body 102 constitutes the body or main part of the dielectric window 100 and extends at least substantially over the entire lower plasma process region where plasma is generated in the process chamber. The disc-shaped body 102 can be described as having a diameter that spans the region where RF power is coupled from the coils mentioned above. Furthermore, the annular portion 104 is formed as an insert and placed within the disc-shaped body 102 so that the dielectric window 100 has a substantially constant thickness T across the process region of the process chamber. The process region will be understood as the internal region of the process chamber where plasma is generated during the processing of a substrate within the process chamber. The upper surface of the disc-shaped body 102 includes an annular recess 103 that accommodates the annular portion 104. By placing the annular portion 104 within the disc-shaped body 102, a substantially constant thickness of the dielectric window 100 can be maintained and it is not affected by changes in the shape of the dielectric window 100.

[0051] By using different dielectric materials for the disc-shaped body 102 and the annular portion 104, the dielectric constant through the dielectric window 100 differs for each different radial region of the dielectric window 100. Therefore, it can be understood that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region. In other words, by introducing a second dielectric material into the dielectric window 100, different radial regions are created, including a radial region where power is inductively coupled only through the first dielectric material, and a region where power is inductively coupled through both the first and second dielectric materials.

[0052] For example, in the illustrated implementation, the annular portion 104 is positioned substantially below the inner coil 106 such that the inner coil 106 is positioned directly above the annular portion 104. Therefore, for the radial region extending from the inner diameter ID of the annular portion 104 to the outer diameter OD of the annular portion 104, power is coupled through both the second dielectric material of the annular portion and the first dielectric material of the disc-shaped body 102. On the other hand, for the radial portion extending from the center to the inner diameter ID of the annular portion 104, and the radial portion extending from the outer diameter OD of the annular portion 104 to the periphery of the dielectric window 100, power is coupled only through the first dielectric material of the disc-shaped body 102.

[0053] It will be understood that the disc-shaped body defines the bottom (plasma-facing) surface of the dielectric window 100, thereby defining the bottom surface of the dielectric window 100 solely from the first dielectric material of the disc-shaped body. In this way, the plasma-facing side of the dielectric window 100 does not exhibit discontinuity in terms of surface structure, exhibits a consistent plasma-facing surface indistinguishable from conventional designs, and the dielectric window 100 can be used without changing the chamber design. Furthermore, the plasma-facing surface of the dielectric window 100 can be formed without protrusions or other contours that may present problems such as material deposition or interference with other internal components.

[0054] As shown in the figure, the annular portion 104 is placed within the disc-shaped body 102 to such a depth that the upper surface of the annular portion 104 aligns with the uppermost surface of the disc-shaped body 102. In this way, the thickness T of the dielectric window 100 is substantially constant from the center to the periphery of the dielectric window 100 above the process area of ​​the process chamber. In the illustrated configuration, it will be understood that the upper surface of the dielectric window 100 thus includes a surface region defined by the first dielectric material of the disc-shaped body 102 and a surface region defined by the second dielectric material of the annular portion 104. Thus, while the bottom surface of the dielectric window 100 is defined by a single material, the top surface of the dielectric window 100 is defined by multiple materials.

[0055] The configuration of the disc-shaped body 102 and the annular portion 104 is adjusted to reduce radial non-uniformity of the plasma generated within the process region. It will be understood that the dimensions of the annular portion 104 and the disc-shaped body 102 may differ in various implementation configurations. In some implementation configurations, the thickness T of the dielectric window 100 is in the range of approximately 1 to 2 inches (approximately 2 to 5 cm), in some implementation configurations, the thickness of the dielectric window 100 is approximately 1.3 to 1.7 inches (approximately 3 to 4 cm), and in some implementation configurations, it is approximately 1.5 inches (approximately 3.8 cm). In some implementation configurations, the thickness D of the annular portion 104 is in the range of approximately 0.5 to 1 inch (approximately 1 to 3 cm), and in some implementation configurations, it is approximately 0.7 to 0.8 inches (approximately 2 cm). In some implementation configurations, the thickness D of the annular portion 104 is approximately one-quarter to three-quarters of the total thickness T of the dielectric window 100. In some implementation configurations, the thickness D of the annular portion 104 is approximately half the total thickness T of the dielectric window 100.

[0056] In some implementations, the annular portion 104 is formed as an insert having a bottom contour that is molded to match the contour of the annular recess 103 of the disc-shaped body 102, so as to maintain a substantially constant thickness of the dielectric window 102. It will be understood that the upper surface of the annular portion 104 is horizontal so as to be at the same height as the uppermost surface of the disc-shaped body 102. Thus, in some implementations, the disc-shaped body 102 can be machined to form the annular recess 103, and the annular portion 104 can be formed to match the shape of the recess. In some implementations, the annular portion 104 is interchangeable, and various materials can be substituted to provide various dielectric constants and various RF coupling efficiencies.

[0057] In some implementations, the space between the RF coils (e.g., inner coil 106 and outer coil 108) and the dielectric window 100 is very small, for example, less than about 0.1 inches (less than about 0.3 mm) (for example, about 0.09 inches in some implementations). It will be understood that, according to the implementations of this disclosure, such a small space can be maintained while varying the dielectric constant and RF coupling efficiency across the entire dielectric window 100.

[0058] In the illustrated implementation, the annular portion 104 is shown having a substantially rectangular cross-sectional shape. However, in other implementations, the annular portion 104 may have other types of cross-sectional shapes. In some implementations, the annular portion can be embedded within the disc-shaped body.

[0059] Figure 1B shows a conceptual cross-sectional view of a dielectric window 101 for a plasma process chamber according to the implementation of the present disclosure.

[0060] In the implementation shown in Figure 1B, the dielectric window 101 consists of a disc-shaped body 110 and an annular portion 112. The annular portion 112 has a substantially semicircular or substantially semi-elliptical cross-section and is set in the disc-shaped body 110 within an annular recess 111 formed on the upper side of the disc-shaped body 110. The annular portion 112 is set in the disc-shaped body 110 so as to have a constant thickness T over the entire dielectric window 101, which is substantially above the process area of ​​the process chamber, as shown in the figure.

[0061] From the upper surface height of the dielectric window 101, the annular portion 112 may extend downward to a thickness / depth D. The annular portion 112 extends radially from the inner diameter ID to the outer diameter OD, having a radial width W. In some configurations, the annular portion 112 is positioned substantially below the inner coil 106. In other configurations, the annular portion 112 can be configured to be partially below the inner coil 106, or not below the inner coil 106.

[0062] As described above, the shape of the annular portion can be configured to allow the dielectric constant across the entire dielectric window 101 to be varied, thereby allowing the RF coupling efficiency through the window to be varied.

[0063] In the implementation configurations currently described, the dielectric constant of the annular portion differs from that of the disc-shaped body. In some implementation configurations, the dielectric constant of the annular portion is greater than that of the disc-shaped body. In some implementation configurations, the dielectric constant of the annular portion is two, three, four, five, or more times greater than that of the disc-shaped body.

[0064] Figure 2A shows a conceptual cross-sectional view of a dielectric window 200 for a plasma process chamber having a plurality of concentric inserts, according to the implementation embodiment of this disclosure.

[0065] In the illustrated implementation, the dielectric window 200 is shown having two annular portions installed inside (including an inner annular portion 202 installed in an annular recess 203 and an outer annular portion 204 installed in an annular recess 205). The inner annular portion 202 and the outer annular portion 204 are configured to be installed within the disc-shaped body 201 so that the thickness T of the dielectric window 200 is maintained at a substantially constant amount over its entire diameter.

[0066] The inner annular portion 202 has a radial width W1 extending from the inner diameter ID1 to the outer diameter OD1, as shown in the figure. The outer annular portion 204 has a radial width W2 extending from the inner diameter ID2 to the outer diameter OD2, as shown in the figure. In the illustrated configuration, the inner annular portion 202 is positioned below the inner coil 106, while the outer annular portion 204 is positioned below the outer coil 108. The inner coil 106 can be considered to extend radially from its innermost range to its outermost range, and it will be understood that the radial region from the innermost range to the outermost range is referred to for the purpose of defining what is positioned below or not below the inner coil 106. Therefore, when it is stated that the inner annular portion 202 is positioned below the inner coil 106, this means that the inner annular portion 202 is at least partially below the radial region defined by the inner coil 106. (It will be understood that a similar concept applies to the outer coil 108.)

[0067] In some configurations, as shown in the illustrated configuration, the thickness of the inner annular portion 202 is greater than the thickness of the outer annular portion 204. In other configurations, the thicknesses of the inner and outer annular portions 202 and 204 are substantially the same. In yet another configuration, the thickness of the outer annular portion 204 is greater than the thickness of the inner annular portion 202. In some configurations, the inner and outer annular portions 202 and 204 are made of the same material, while in other configurations, the inner and outer annular portions 202 and 204 are made of different materials.

[0068] The inner and outer annular portions 202 and 204 are each made of a material having a dielectric constant different from that of the disc-shaped body 201. Furthermore, in some implementations, the inner and outer portions 202 and 204 can be formed from different materials. In some implementations, the dielectric constant of the inner or outer annular portions 202 and 204 is greater than that of the disc-shaped body 201. As described in this implementation, by providing the annular portion with a material having a different dielectric constant, the dielectric window 200 may have different dielectric constants across its radius, resulting in different RF coupling efficiencies being provided through the dielectric window 200.

[0069] In the illustrated implementation configuration, two annular portions are shown, defined as inserts formed from materials having different dielectric constants than the disc-shaped body 201. However, in other implementation configurations, two or more annular portions may be present, and they may also have variably defined thickness, annular width, material composition, and concentric arrangement.

[0070] Figure 2B shows a conceptual cross-sectional view of a dielectric window 100 for a plasma process chamber having a plurality of concentric inserts, according to the implementation of the present disclosure.

[0071] In the illustrated configuration, the dielectric window 209 is defined to include a disc-shaped body 210 that forms the main body of the dielectric window 209, and a disc-shaped insert 212 that is centrally positioned within the disc-shaped body 210 in a recess 213 defined along the upper part of the disc-shaped body 210. As shown in the illustration, the disc-shaped insert 212 is positioned in the center of the dielectric window 209 and is further defined not to be substantially located below the inner coil 106. In the illustrated configuration, the disc-shaped insert 212 is rather located below the central gap of the inner coil 106.

[0072] Furthermore, in the illustrated configuration, the annular insert 214 is installed within the annular recess 215. As shown in the illustration, the annular insert 214 is positioned so as not to be substantially located below either the inner coil 106 or the outer coil 108. In the illustrated configuration, the annular insert 214 is located below the gap between the inner coil 106 and the outer coil 108.

[0073] In some implementations, the thickness of the disc-shaped insert 212 is greater than the thickness of the annular insert 214. In some implementations, the thicknesses of the disc-shaped insert 212 and the annular insert 214 are substantially similar.

[0074] As with other implementations described herein, the disc-shaped insert 212 and the annular insert 214 are defined from a material having a different dielectric constant than the disc-shaped body 210.

[0075] Figure 3A shows a conceptual cross-sectional view of a dielectric window 300 for a plasma process chamber having a central insert, according to a specific implementation of the present disclosure.

[0076] In the illustrated configuration, the dielectric window 300 includes a centrally positioned disc insert 302, which is located in a recess 304 positioned centrally along the top of the disc-shaped body 301. As shown in the illustration, the disc insert 302 extends outward from the center of the dielectric window 100, which is not located below the inner coil 106, to a diameter that is substantially located below the inner coil 106. Furthermore, the diameter of the disc insert 302 is configured to partially overlap the radial region of the inner coil 106, so that below the inner coil 106, the dielectric window 300 is configured such that the radial region of the inner coil 106 is partially above the disc insert 302 and partially above the disc-shaped body 301. Thus, RF coupling below the inner coil 106 occurs partly through the materials of both the disc insert 302 and the disc-shaped body 301, and partly through the material of the disc-shaped body 301 only.

[0077] It will be understood that the disc insert 302 is formed from a material having a different dielectric constant than the disc-shaped body 301, as described earlier, in order to provide different RF coupling efficiencies through the dielectric window 300.

[0078] Figure 3B shows a conceptual cross-sectional view of a dielectric window 309 for a plasma process chamber having a central insert, according to the implementation of the present disclosure.

[0079] In the illustrated configuration, the disc insert 312 is positioned within the recess 314 of the disc-shaped body 310, and the disc insert 312 is positioned in the center of the entire dielectric window 309. The disc insert 312 is configured to have varying thicknesses along its radius. More specifically, in the illustrated configuration, the disc insert 312 has a thickness that decreases from the center toward the outer diameter of the disc insert 312. Furthermore, in the illustrated configuration, the cross-sectional shape of the disc insert 312 passing through the center is substantially bowl-shaped, and it exhibits a convex curvature along its lower side. In this way, the RF coupling efficiency through the dielectric window 309 differs intermittently from the center to the edge in the region including the disc insert 312.

[0080] In the illustrated configuration, the diameter of the disc insert 312 is configured such that it extends from the center to a position below the inner coil 106. However, in other configurations, it would be understood that the diameter of the disc insert 312 can extend to longer or shorter lengths, including diameters that extend to or beyond the outer diameter of the inner coil 106, or diameters that extend shorter than the inner diameter of the inner coil 106.

[0081] Figure 3C shows a conceptual cross-sectional view of a dielectric window 319 for a plasma process chamber having a central insert, according to the implementation embodiment of this disclosure.

[0082] In the illustrated implementation, the disc insert 322 is shown positioned within a recess 324 along the upper surface of the disc-shaped body 320. As shown in the illustration, the contour along the lower side of the disc insert 322 is configured to have a convex curve with an additional bulge in the center.

[0083] As illustrated and explained, it will be understood that the number, arrangement, size, contour, and material composition of inserts can vary in various implementation configurations. Various non-limiting examples are provided as illustrations without limitation, and it will be understood that other configurations are also possible. Various parameters of the inserts can be specifically tuned for different processes and configured to mitigate non-uniformity by varying the RF power coupling efficiency across the radial span of the dielectric window. If the dielectric constant of the insert is greater than that of the body, the dielectric constant over the entire region of the dielectric window containing the insert will be greater than that over the region without the insert. Therefore, the RF coupling efficiency will be reduced / attenuated over the entire region of the dielectric window containing the insert compared to the region of the dielectric window without the insert. Furthermore, the RF coupling efficiency can be varied to a different degree by varying the thickness of the insert in specific regions; increasing the insert thickness increases resistance, thus reducing the RF coupling efficiency in those specific regions.

[0084] In some implementations, the RF coupling efficiency across the entire dielectric window is converted or correlated, at least approximately, to the plasma density generated in the chamber below the dielectric window. That is, in some implementations, the plasma density increases as the RF coupling efficiency increases, so reducing the RF coupling efficiency by placing an insert as described here results in a decrease in plasma density in the region approximately below the region of the insert, and the degree to which this decrease in plasma density differs is approximately correlated with the thickness of the insert in a given region of the dielectric window.

[0085] Figure 4A conceptually shows a cross-sectional view of a dielectric window 403 having an embedded channel for embedding materials having different dielectric constants, according to the implementation of the present disclosure.

[0086] In the illustrated implementation, the dielectric window 403 includes a disc-shaped body 400 in which an annular channel 401 is embedded. The annular channel 401 is filled with a material 402 having a dielectric constant different from that of the disc-shaped body 400. In some implementations, if the material 402 is solid, the material 402 essentially forms an insert similar to the insert described above, but is embedded within the disc-shaped body, as opposed to being positioned along the top surface of the dielectric window 100.

[0087] However, in other implementations, since the material 402 is embedded within the disc-shaped body 400, the material 402 can be a gel, liquid, or gas having a dielectric constant different from that of the disc-shaped body 400. In some implementations, the annular channel 401 can be filled with a combination of multiple materials, such as a combination of gel, liquid, or gas (e.g., gel and gas, liquid and gas). It will be understood that by adjusting the relative amounts of such materials used in combination, a desired variation in the dielectric constant across the entire dielectric window can be achieved (e.g., approximately 1:1, 1:2, 1:3, etc., in volume, for any two materials used to fill the annular channel).

[0088] Generally, the dielectric constant difference between a solid and a liquid / gas material can be more easily increased than between two solid materials (for example, the dielectric constant of quartz is about 9, while that of water is about 80). In other words, in some implementations, the dielectric constant of the gel, liquid, or gas can broaden the range of materials that have a greater dielectric constant difference from the solid material of the disc-shaped body (e.g., quartz, ceramic, etc.).

[0089] The effect of material 402 is the same as that described above for the aforementioned insert, changing the effective dielectric constant across the entire dielectric window 403 in the radial region containing material 402 compared to the radial region not containing material 402, thereby appropriately changing the RF coupling efficiency across the entire dielectric window 403.

[0090] It will be understood that the placement, thickness, and radial width of the annular channel 401 can be configured or adjusted to make a desired change to the RF coupling efficiency of a particular radial region of the dielectric window 403. In the illustrated configuration, the annular channel 401 is substantially located below the inner coil 106. However, in other configurations, the annular channel 401 may be located elsewhere and may (or may not) partially or completely overlap the inner coil 106 and / or the outer coil 108.

[0091] Figure 4B conceptually shows a cross-section of a dielectric window 409 with multiple channels embedded inside, according to the implementation configuration of this disclosure.

[0092] In the illustrated configuration, the dielectric window 409 is defined by having an inner annular channel / cavity 411 filled with material 412 and an outer annular channel 413 filled with material 414. In the illustrated configuration, the thickness of the inner annular channel 411 is greater than the thickness of the outer annular channel 413. In other configurations, however, the thickness of the inner annular channel 411 is approximately the same as or thinner than the thickness of the outer annular channel 413. As shown, the inner and outer annular channels 411 and 413 are substantially located below the inner and outer coils 106 and 108, respectively. However, in other configurations, the arrangement of the annular channels may differ from that shown, such as being partially located below the inner or outer coils. Furthermore, in some configurations, the radial widths of the inner and outer annular channels 411 and 413 may differ.

[0093] In various implementation configurations, various parameters of the annular channel can be adjusted to achieve desired effects on RF coupling efficiency, such as local reduction / decrease / attenuation. Such parameters may include, but are not limited to, the number of channels, radial arrangement, vertical arrangement (within the overall thickness of the dielectric window 409), radial width, thickness, cross-sectional shape, etc. These parameters can be adjusted or tuned to achieve a desired RF coupling efficiency profile and / or a desired plasma density profile in the plasma generated within the process chamber.

[0094] Further shapes and configurations of embedded channels or cavities are described below, but these are provided as examples without limitation to illustrate a particular implementation form.

[0095] Figure 4C conceptually shows a cross-sectional view of a dielectric window 100 having an embedded annular channel according to the implementation of this disclosure.

[0096] In the illustrated configuration, the dielectric window 419 is defined by having an annular channel 421 formed within a disc-shaped body 420, and the annular channel 422 is filled with a material 422 having a dielectric constant different from that of the disc-shaped body 420. As shown in the illustration, the annular channel 421 has a substantially elliptical shape. In some configurations, as also shown in the illustrated configuration, the annular channel 421 is substantially located below the inner coil 106.

[0097] Figure 5A conceptually shows a cross-sectional view of a dielectric window 503 having an embedded cavity according to the implementation configuration of this disclosure.

[0098] In the illustrated configuration, the dielectric window 503 is defined by a disc-shaped body 500 having a cavity 501 filled with material 502. As shown in the illustration, the cavity 501 is also substantially disc-shaped and has a substantially rectangular cross-sectional shape. Furthermore, in the illustrated configuration, the diameter of the cavity 501 is configured to extend at least to the outer diameter of the inner coil 106.

[0099] Figure 5B conceptually shows a cross-sectional view of a dielectric window 509 having an embedded cavity according to the implementation configuration of this disclosure.

[0100] In the illustrated configuration, the dielectric window 509 is defined by a disc-shaped body 510 having a cavity 511 filled with material 512. As shown in the illustration, the disc-shaped cavity 511 has a substantially elliptical cross-sectional shape.

[0101] Figure 5C conceptually shows a cross-sectional view of a dielectric window 519 having an embedded cavity according to the implementation of this disclosure.

[0102] In the illustrated implementation, the dielectric window 519 is defined by a disc-shaped body 520 having a cavity 521 filled with material 522. The disc-shaped cavity 521 has a substantially elliptical cross-sectional shape with a bulge in the center.

[0103] Figure 6A conceptually shows a cross-sectional view of a dielectric window 601 having an embedded channel through which a fluid circulates, according to the implementation of the present disclosure.

[0104] In the illustrated implementation, the dielectric window 601 is defined by a disc-shaped body 600 having an annular channel 602 filled with a fluid material 604 (same as in the implementation in Figure 4A). Furthermore, the annular channel 602 is configured so that its fluid material is circulated by a pump 606. That is, the fluid material is pumped in and out of the annular channel 602 by the pump 606. In some implementations, the pump 606 delivers the fluid material from the reservoir 608 through a hose 609 connected to an inlet channel 610 defined within the disc-shaped body 600, which is connected to the annular channel 602. Thus, the fluid material 604 is pumped into the annular channel 602 through the inlet channel 610.

[0105] The outlet channel 612 connects from the annular channel 602 to a hose 613, which in turn connects to a reservoir 608. Thus, the fluid material flows out of the annular channel 602 through the outlet channel 612 and hose 613, and returns to the reservoir 608. In this way, the fluid material is circulatory in and out of the annular channel 602. In the illustrated implementation, a single inlet channel and a single outlet channel are shown, but it will be understood that multiple inlet channels and / or multiple outlet channels (and accordingly, multiple corresponding hoses) may be present. Furthermore, in some implementations, multiple pumps and / or reservoirs may be present. In addition, in the illustrated implementation, the inlet channel 610 and outlet channel 612 are shown as radially oriented horizontal channels connecting from the annular channel 602 to the outer circumference of the dielectric window 601, but in other implementations, the inlet / outlet channels may have other configurations, such as being vertically oriented channels positioned above the annular channel 602.

[0106] In some implementations, the reservoir 608 or pump 606 includes a cooling mechanism for cooling the fluid material. In some implementations, the cooling mechanism may include passive or active cooling mechanisms such as radiators, heat sinks, heat exchangers, coolants, or refrigerants. This may be useful for maintaining the temperature of the fluid material within a desired temperature range and for preventing the fluid material from boiling due to heating that occurs within the dielectric window 601 during operation.

[0107] In some implementations, the fluid material can be changed from a first fluid material to a second fluid material. In some implementations, a second reservoir (not shown) is provided, and optionally a second pump (not shown) is provided, from which the second fluid material flows into the annular channel 604 and optionally circulates. In this way, different fluid materials with different dielectric constants can be supplied to the annular channel 602 depending on a specific process, thereby optimizing the selection of fluid material for a given process. In this way, by changing the fluid material supplied to the annular channel 602, the local dielectric constant can be dynamically adjusted, and as a result, the RF coupling efficiency can be adjusted by introducing different fluids into the annular channel 602.

[0108] In some implementations, multiple fluids are introduced into an annular channel in predetermined ratios to provide a mixture / solution with a predetermined dielectric constant, thereby providing a desired local RF coupling efficiency. In some implementations, the ratios of the multiple fluids can be varied (for example, by pumping the fluids into the annular channel at different rates) to vary the dielectric constants of the solutions / mixtures, thereby appropriately varying the RF coupling efficiency. This allows for further levels of RF coupling efficiency to be tuned and dynamically adjusted across the entire region having the annular channel 602.

[0109] Figure 6B conceptually shows a cross-sectional view of a dielectric window 619 having a plurality of annular channels through which a fluid can circulate, according to the implementation of the present disclosure.

[0110] The implementation shown in Figure 6B includes an inner annular channel 622 in which the fluid material 624 is placed and an outer annular channel 626 in which the fluid material 628 is placed. The inner annular channel 622 and the outer annular channel 628 may have similar or different thicknesses, but as shown in the implementation shown, the thickness of the inner annular channel 622 is greater than that of the outer annular channel 626. The pump 630 circulates the fluid material 624 in the inner annular channel 622, pumping the fluid material 624 from the reservoir 632 through the inlet hose 646 into the inlet channel 648 to the inner annular channel 622, and from the inner annular channel 622 through the outlet channel 650 to the outlet hose 652 connected to the reservoir 632. In some implementations, the reservoir and / or pump may include a cooling mechanism for cooling the fluid material 624.

[0111] Similarly, the pump 634 circulates the fluid material 628 in the outer annular channel 626, pumping the fluid material 628 from the reservoir 636 through the inlet hose 638 into the inlet channel 640 to the outer annular channel 626, and from the outer annular channel 626 through the outlet channel 642 to the outlet hose 644 connected to the reservoir 636. In some implementations, the reservoir and / or pump may include a cooling mechanism for cooling the fluid material 628.

[0112] In some implementations, fluid material 624 and fluid material 628 are the same material. On the other hand, in other implementations, fluid material 624 and fluid material 628 are different materials. As previously mentioned with reference to the implementation in Figure 6A, fluid material 624 and / or fluid material 628 can be changed from one fluid to another to adjust or dynamically adjust the RF coupling efficiency, and a mixture / solution may be employed to provide the aforementioned variability.

[0113] While specific implementation configurations have been described as including a mechanism for circulating and cooling fluid within a channel / cavity defined within the dielectric window 100, it will be understood that this is applicable to any other embedded channel / cavity configuration described herein.

[0114] Furthermore, while inserts and channels / cavities have various radial contours and configurations, in other implementations, inserts and channels / cavities may have profiles with different azimuthal angles. That is, the parameters of a given insert or channel (e.g., thickness, radial width, contour, shape, material composition, etc.) can be made to differ along the azimuthal angle or azimuthal direction (e.g., clockwise or counterclockwise).

[0115] Furthermore, in some implementations, the insert or channel / cavity may be discontinuous along the azimuthal angle or direction. In such implementations, a given radial portion of the dielectric window 619 may include one or more segments of the insert or channel.

[0116] As described above, the inserts and channels are composed of, or filled with, a material having a dielectric constant different from that of the main disc-shaped body of the dielectric window 619, which is typically composed of quartz or ceramic. In this regard, it will be understood that any variety of solid, liquid, or gaseous materials may be considered. Furthermore, while the differences in dielectric constants have been broadly explained, in some implementations where the material can be changed from one material to another, it is possible to introduce a material having a dielectric constant similar to that of the main disc-shaped body, for example, to adjust the RF coupling efficiency profile to suit a particular process. Table 1 below provides a non-exhaustive list of possible materials that may be used to construct the inserts and fill the channels / cavities. [Table 1]

[0117] Various techniques are available to form dielectric windows according to the implementations of this disclosure. These include various ceramic formation techniques such as powder deposition / molding. In some implementations, dielectric windows can be 3D printed by 3D printing two types of ceramics or by 3D printing channels within the dielectric window.

[0118] Figure 7 conceptually illustrates an inductively coupled plasma system according to the implementation of this disclosure.

[0119] Various implementations described herein may be carried out in an inductively coupled plasma (ICP) system. Referring to Figure 7, an exemplary ICP deposition system or apparatus may include a chamber 701 having a gas injector / showerhead / nozzle 703 for distributing a gas (705, 707, 709) (e.g., precursor, oxidizer, and purge gas) or other chemical into the chamber 701, a chamber wall 711, and a chuck 713 for holding a substrate or wafer 715 to be processed, which may include electrostatic electrodes for chucking and dechucking the wafer. The chuck 713 is heated for thermal control so that the substrate 715 can be heated to a desired temperature. In some implementations, the chuck 713 may be electrically charged using an RF power supply 717 to provide a bias voltage according to the implementations of this disclosure.

[0120] The RF power supply 719 is configured to power an RF antenna / coil 721, positioned above the dielectric window 723, to generate plasma 725 in the process space above the substrate 715. In some implementations, the chamber walls are heated to support thermal management and efficiency. A vacuum source 727 provides a vacuum to expel gas from the chamber 701. The system or apparatus may include a system controller 729 for controlling some or all of the operation of the chamber or apparatus, such as adjusting chamber pressure, inert gas flow, plasma power, plasma frequency, reactive gas flow (e.g., precursor, oxidizer, etc.), bias power, temperature, vacuum setting, and other process conditions.

[0121] In some implementations, the system / device may include multiple chambers for processing the substrate.

[0122] For throughput purposes, ALD systems typically employ small-volume chambers that can be quickly filled and purged. However, ICP reactors tend to have considerably larger volumes. Therefore, there is a problem of how to enable high-speed gas switching for ALD in relatively large-volume systems. One technique is to continuously purge the non-process volume space, so that only the process volume space directly above the wafer / substrate needs to be effectively purged during the purging operation of the ALD cycle. The process volume portion can be separated from the non-process volume space by an air curtain. Furthermore, high-speed gas exchange can be employed, and the gas flow and pressure can be adjusted to accelerate the transport and removal of gas from the process volume portion.

[0123] Figure 8 shows a control module 800 for controlling each of the systems described herein, according to the implementation of this disclosure.

[0124] For example, the control module 800 may include a processor, memory, and one or more interfaces. The control module 800 may be employed to control devices in the system based in part on sensed values. For example, the control module 800 may control one or more of the valve 802, filter heater 804, pump 806, and other devices 808 based on sensed values ​​and other control parameters. The control module 800 may, for example, receive sensed values ​​from a pressure manometer 810, a flow meter 812, a temperature sensor 814, and / or other sensors 816. The control module 800 may also be employed to control process conditions during reactant transport and plasma processing. The control module 800 will typically include one or more memory devices and one or more processors.

[0125] The control module 800 may control the activity of the reactant transport system and the plasma processing apparatus. The control module 800 runs a computer program that includes a set of instructions for controlling process timing, transport system temperature, pressure difference between filters, valve position, gas mixture, chamber pressure, chamber temperature, wafer temperature, RF power level, wafer ESC or pedestal position, and other parameters of a particular process. The control module 800 may also monitor the pressure difference and automatically switch vapor reactant transport from one or more paths to one or more other paths. Other computer programs stored in a memory device associated with the control module 800 may be employed in several implementations.

[0126] Typically, a user interface will be associated with the control module 800. The user interface may include a display 818 (e.g., a display screen and / or graphic software display of the device and / or process conditions) and user input devices 820 such as a pointing device, keyboard, touchscreen, or microphone.

[0127] Computer programs for controlling reactant transport, plasma treatment, and other processes in a process sequence can be written in any conventional computer-readable programming language, such as assembly language, C, C++, Pascal, Fortran, etc. The compiled object code or script is executed by the processor to perform the tasks specified within the program.

[0128] The control module parameters relate to, for example, plasma conditions such as filter pressure difference, process gas composition and flow rate, temperature, pressure, RF power level and RF frequency, cooling gas pressure, and process conditions such as chamber wall temperature.

[0129] The system software may be designed or configured in a variety of ways. For example, various chamber component subroutines or control objects may be described to control the operation of the chamber components necessary to perform the deposition process of the present invention. Examples of programs or parts of programs for this purpose include substrate positioning code, process gas control code, pressure control code, heater control code, and plasma control code.

[0130] While the aforementioned implementations are described in some detail for clarity, it will be clear that certain changes and modifications may be made within the scope of the disclosed implementations. It should be noted that many alternative ways exist to realize the processes, systems, and devices of these implementations. Therefore, these implementations are considered illustrative and not restrictive, and are not limited to the details shown herein. This disclosure includes the following examples of applications. [Application Example 1] An dielectric window for a process chamber, A disc-shaped body made of a first dielectric material having a first dielectric constant, It consists of a second dielectric material having a second dielectric constant greater than the first dielectric constant, and an annular portion installed within the disc-shaped body. Includes, The dielectric window has a substantially constant thickness within the internal region of the process chamber, and extends over the process region where plasma is generated during processing of the substrate within the process chamber. The installation of the annular portion onto the disc-shaped body is configured to maintain the substantially constant thickness of the dielectric window, wherein the dielectric window is a dielectric window. [Application Example 2] A dielectric window as described in Application Example 1, The upper surface of the disc-shaped body includes a dielectric window with an annular recess for accommodating the annular portion. [Application Example 3] A dielectric window as described in Application Example 1, A dielectric window wherein the disc-shaped body and the annular portion are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window. [Application Example 4] A dielectric window as described in Application Example 3, A dielectric window in which the different radial regions include a first region through which power is inductively coupled only through the first dielectric material, and a second region through which power is inductively coupled through both the first dielectric material and the second dielectric material. [Application Example 5] A dielectric window as described in Application Example 1, The disc-shaped body defines the bottom surface of the dielectric window such that the bottom surface of the dielectric window is defined solely from the first dielectric material. [Application Example 6] A dielectric window as described in Application Example 1, The dielectric window comprises a surface region defined by the first dielectric material and a surface region defined by the second dielectric material. [Application Example 7] A dielectric window as described in Application Example 1, A dielectric window wherein the disc-shaped body spans the width of the process region, and the annular portion does not span the width of the process region. [Application Example 8] A dielectric window as described in Application Example 1, The annular portion is positioned to be substantially located below a coil that inductively couples power within the process region, and is a dielectric window. [Application Example 9] A dielectric window as described in Application Example 1, The disc-shaped body and the annular portion are dielectric windows that reduce radial non-uniformity of the plasma generated in the process region. [Application Example 10] A dielectric window as described in Application Example 1, A dielectric window, wherein the annular portion defines an insert having a bottom contour molded to match the upper contour of the disc-shaped body, so as to maintain the substantially constant thickness of the dielectric window. [Application Example 11] A dielectric window as described in Application Example 1, The annular portion is a dielectric window having a substantially rectangular cross-section. [Application Example 12] A dielectric window as described in Application Example 1, The annular portion is a dielectric window embedded within the disc-shaped body. [Application Example 13] An dielectric window for a process chamber, A disc-shaped body made of a first dielectric material having a first dielectric constant, An annular cavity defined within the disc-shaped body and configured to contain a second dielectric material having a second dielectric constant greater than the first dielectric constant, Includes, A dielectric window in which the second dielectric material is a fluid. [Application Example 14] A dielectric window as described in Application Example 13, A dielectric window wherein the disc-shaped body and the annular cavity are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window. [Application Example 15] A dielectric window as described in Application Example 13, A dielectric window in which the different radial regions include a first region through which power is inductively coupled only through the first dielectric material, and a second region through which power is inductively coupled through both the first dielectric material and the second dielectric material. [Application Example 16] A dielectric window as described in Application Example 13, A dielectric window wherein the disc-shaped body spans the width of the process region, and the annular cavity does not span the width of the process region. [Application Example 17] A dielectric window as described in Application Example 13, The annular cavity is positioned substantially below a coil that inductively couples power within the process chamber, and is a dielectric window. [Application Example 18] A dielectric window as described in Application Example 13, The disc-shaped body and the annular cavity are dielectric windows that reduce radial non-uniformity of the plasma generated in the process chamber. [Application Example 19] A dielectric window as described in Application Example 13, The annular cavity is a dielectric window having a substantially rectangular cross-section.

Claims

1. An dielectric window for a process chamber, A disc-shaped body made of a first dielectric material having a first dielectric constant, It consists of a second dielectric material having a second dielectric constant greater than the first dielectric constant, and an annular portion installed within the disc-shaped body. Includes, The dielectric window has a substantially constant thickness within the internal region of the process chamber, and extends over the process region where plasma is generated during processing of the substrate within the process chamber. The installation of the annular portion onto the disc-shaped body is configured to maintain the substantially constant thickness of the dielectric window. The annular portion is located directly below at least the inner coil of a coil positioned above the dielectric window, and the coil includes the inner coil and the outer coil, and the coil inductively couples power within the process region. Dielectric window.

2. A dielectric window according to claim 1, The upper surface of the disc-shaped body includes a dielectric window with an annular recess for accommodating the annular portion.

3. A dielectric window according to claim 1, A dielectric window wherein the disc-shaped body and the annular portion are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window.

4. A dielectric window according to claim 3, A dielectric window in which the different radial regions include a first region through which power is inductively coupled only through the first dielectric material, and a second region through which power is inductively coupled through both the first dielectric material and the second dielectric material.

5. A dielectric window according to claim 1, The disc-shaped body defines the bottom surface of the dielectric window such that the bottom surface of the dielectric window is defined solely from the first dielectric material.

6. A dielectric window according to claim 1, The dielectric window comprises a surface region defined by the first dielectric material and a surface region defined by the second dielectric material.

7. A dielectric window according to claim 1, A dielectric window wherein the disc-shaped body spans the width of the process region, and the annular portion does not span the width of the process region.

8. A dielectric window according to claim 1, The disc-shaped body and the annular portion are dielectric windows that reduce radial non-uniformity of the plasma generated in the process region.

9. A dielectric window according to claim 1, A dielectric window, wherein the annular portion defines an insert having a bottom contour molded to match the upper contour of the disc-shaped body, so as to maintain the substantially constant thickness of the dielectric window.

10. A dielectric window according to claim 1, The annular portion is a dielectric window having a substantially rectangular cross-section.

11. A dielectric window according to claim 1, The annular portion is a dielectric window embedded within the disc-shaped body.

12. An dielectric window for a process chamber, A disc-shaped body made of a first dielectric material having a first dielectric constant, An annular cavity defined within the disc-shaped body and configured to contain a second dielectric material having a second dielectric constant greater than the first dielectric constant, Includes, The second dielectric material is a fluid, The annular cavity is located directly below at least the inner coil of a coil positioned above the dielectric window, and the coil includes the inner coil and the outer coil, and the coil inductively couples power within the process region. Dielectric window.

13. A dielectric window according to claim 12, A dielectric window wherein the disc-shaped body and the annular cavity are configured such that the efficiency of inductive coupling of power through the dielectric window differs for each different radial region of the dielectric window.

14. A dielectric window according to claim 13, A dielectric window in which the different radial regions include a first region through which power is inductively coupled only through the first dielectric material, and a second region through which power is inductively coupled through both the first dielectric material and the second dielectric material.

15. A dielectric window according to claim 12, A dielectric window wherein the disc-shaped body spans the width of the process region, and the annular cavity does not span the width of the process region.

16. A dielectric window according to claim 12, The disc-shaped body and the annular cavity are dielectric windows that reduce radial non-uniformity of the plasma generated in the process chamber.

17. A dielectric window according to claim 12, The annular cavity is a dielectric window having a substantially rectangular cross-section.

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