Improvement of etch uniformity in radical etching using a confinement ring

Abstract

A confinement ring for use in a processing chamber includes a tubular extension configured to surround a processing region within the processing chamber. An upper end of the tubular extension is configured to connect to a showerhead of the processing chamber and a lower end is configured to extend into the processing region proximate an edge ring that surrounds a wafer received within the processing region. A foot extension has an inner end that joins the lower end of the tubular extension and extends outwardly from the processing region to an outer end. The foot extension provides an annular surface configured to form a gap with an upper surface of the edge ring.

Description

[Technical field]

[0001] The present embodiments relate to components that can be utilized in semiconductor processing chambers to control radicals, and more particularly, to confinement rings for improving etch rate uniformity over the surface of a wafer. [Background technology]

[0002] 2. Description of Related Art Semiconductor wafers undergo various processing processes to produce electronic devices. Processes used in the production of electronic devices include deposition processes, etching processes, and patterning processes, among others. Etching processes are carried out in a processing chamber (also called an "etcher"). In radical etching, relatively low energy ions or radicals are generated in a plasma and directed towards the surface of a substrate received on a grounded electrode. Excess radicals and processing gases are then removed from the etcher through an exhaust port.

[0003] In a particular radical etching chamber, tests were performed to measure a particular non-uniformity in etching. Data collected from tests and experiments show that the etching rate tends to gradually decrease from the center of the wafer to the wafer edge, and then the etching rate increases significantly near the wafer edge. Since the manufacturing cost of semiconductor devices is significant, chip designers generally desire to increase the semiconductor device density all the way to the wafer edge. Etching non-uniformity near the wafer edge can cause yield loss near the wafer edge because semiconductor devices manufactured near the wafer edge exhibit device performance degradation due to etching.

[0004] It is in this context that embodiments of the present invention arise. Summary of the Invention

[0005] Various embodiments of the present disclosure include devices and systems used to confine plasma radicals within a processing region of a processing chamber. During an etching process (e.g., dry etching), a plasma is generated in the processing chamber by ionizing a processing gas with a high frequency electromagnetic field. In the processing chamber, the generated plasma is directed onto the surface of the wafer. The plasma is generated locally within a processing region defined in the processing chamber or remotely outside the processing region. The generated plasma includes ions, electrons, and radicals. When the plasma is generated remotely, radicals from the plasma are delivered to the processing region through a showerhead or through a nozzle or other delivery mechanism.

[0006] In one embodiment, a confinement ring is used in a processing chamber to confine plasma radicals substantially above a surface of a wafer. The confinement ring includes a foot extension disposed along a peripheral portion of the wafer (e.g., approximately above an edge ring that surrounds the edge of the wafer). The separation between the foot extension and the edge ring can be configured to control the exhaust flow of radicals and process gases out of the processing region. As described in more detail below, this flow control is utilized to affect the velocity of radicals near the edge of the wafer to improve the uniformity of the etch rate near the wafer edge.

[0007] In one embodiment, the confinement ring is bonded to a bottom surface of the showerhead. The confinement ring comprises a tubular extension extending downward from the showerhead and surrounding the processing region. The foot extension may be integrally formed at a bottom end of the tubular extension. In one configuration, the tubular extension forms a wall surrounding the processing region. In some embodiments, the tubular extension may be aligned with an edge of a wafer received in the processing chamber. In some embodiments, the tubular extension may extend perpendicular to the bottom surface of the showerhead. In some embodiments, the tubular extension may be tilted inwardly or outwardly from an axis perpendicular to the bottom surface of the showerhead. In some embodiments, the foot extension is generally horizontal and parallel to a surface of a wafer received in the processing chamber. In some embodiments, the foot extension may be tilted so that it is not parallel to a surface of a wafer received in the processing chamber. The foot extension may have a width comparable to a width of an edge ring surrounding the wafer support surface.

[0008] The etch rate non-uniformity observed at the wafer edge may be caused by back-diffusion of reaction by-products from the edge ring to the edge of the wafer. Back-diffusion leads to an increase in the concentration of undesirable plasma radicals at the wafer edge. The confinement rings disclosed herein are designed to reduce back-diffusion and, with it, the concentration of undesirable plasma radicals at the wafer edge. Additionally, the increase in the concentration of plasma radicals at the wafer edge may be due to the material of the edge ring. Typically, the edge ring is made of a material (e.g., aluminum oxide, etc.) that does not consume as much fluorine in the plasma radicals as the surface of the wafer adjacent to the edge ring. The lack of fluorine consumption by the edge ring due to material differences may contribute to the accumulation (i.e., increase in concentration) of fluorine-containing plasma radicals at the wafer edge.

[0009] In one embodiment, a confinement ring for use in a processing chamber is disclosed. The confinement ring includes a tubular extension and a foot extension. The tubular extension is configured to surround a processing region defined within the processing chamber and extends between an upper end and a lower end. The upper end connects to a showerhead of the processing chamber. The tubular extension extends downwardly from the upper end such that the lower end is proximate to an edge ring that surrounds a wafer receiving surface. The foot extension extends between an inner end and an outer end, the outer end defining an outer diameter of the confinement ring. The inner end joins the lower end of the tubular extension and the outer end extends outwardly from the processing region. The foot extension provides a confinement annular surface that forms a gap with an upper surface of the edge ring.

[0010] Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 2 is a cross-sectional side view of a processing chamber in an active state (i.e., ready for processing) utilizing confinement rings and used to perform an etching operation using a radical etch, in one embodiment.

[0012] [Figure 1B] 1B is a side cross-sectional view of the processing chamber of FIG. 1A in an inactive state.

[0013] [Figure 1C] FIG. 1B is a cross-sectional side view of the processing chamber of FIG. 1A in an active state utilized to perform a waferless automatic cleaning (WAC) operation, in one embodiment.

[0014] [Figure 2A] 2 illustrates a side cross-sectional view of a portion of a showerhead having a confinement ring coupled thereto, in one embodiment.

[0015] [Figure 2B] 2B illustrates a profile of the confinement rings shown in FIG. 2A in an alternative embodiment.

[0016] [Figure 2C] FIG. 2B illustrates a profile of the confinement rings shown in FIG. 2A in another alternative embodiment.

[0017] [Figure 2D] FIG. 2B illustrates a profile of the confinement rings shown in FIG. 2A in another alternative embodiment.

[0018] [Figure 2E] FIG. 2B illustrates a profile of the confinement rings shown in FIG. 2A in another alternative embodiment.

[0019] [Figure 2F] 2B illustrates a profile of the confinement rings shown in FIG. 2A in yet another alternative embodiment.

[0020] [Figure 2G] 2B illustrates a profile of the confinement rings shown in FIG. 2A in yet another alternative embodiment.

[0021] [Diagram 3] 4 is a graph illustrating etch rate from wafer center to wafer edge as a function of different gap distances when a confinement ring with foot extensions is used to confine plasma within a processing volume of a processing chamber, in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without some or all of these specific details. Additionally, detailed descriptions of well-known process operations are omitted in order to avoid unnecessarily obscuring the present invention.

[0023] The embodiments of the present disclosure provide various details of confinement rings and systems that use the confinement rings to process semiconductor substrates (i.e., wafers). It should be appreciated that the embodiments can be embodied in numerous forms, such as a process, an apparatus, a system, a device, or a method. Some embodiments are described below.

[0024] Disclosed herein is a confinement ring used in a processing chamber to confine radicals within a processing region. The confinement ring is designed to control the flow and exhaust of radicals and other gases from the processing region during an etching operation. In one embodiment, the confinement ring used in the processing chamber is used to reduce radical concentration at the edge region of the wafer. In one example, the confinement ring is coupled to a bottom surface of a showerhead located in an upper portion of the processing chamber. In one configuration, the showerhead discussed herein is used to cause collisions of ions with the showerhead hardware, thereby neutralizing the ions but allowing radicals to flow to the processing region.

[0025] In some embodiments, the confinement ring comprises a tubular extension and a foot extension. The tubular extension has a length and depends from the showerhead to surround a portion of the processing region in the processing chamber. The foot extension may be integrally connected to a lower end of the tubular extension and extends outwardly away from the processing region. The foot extension forms an annular surface that allows for control of the separation between the foot extension and the edge ring. In operation, the separation between the foot extension and the edge ring allows for control of the rate at which radicals and other gases flow out of the processing region. This allows for reduced back-diffusion of by-products resulting from etching on the surface of the edge ring, thereby reducing the concentration gradient of radicals at the wafer edge and correspondingly increasing the uniformity of the etch rate at the wafer edge (e.g., the outer 20 mm of a 300 mm wafer).

[0026] According to some embodiments, the foot extension of the confinement ring is designed to form a narrow gap between the edge ring and the foot extension. The gap provides a path for radicals to flow out of the processing region toward an exhaust port provided in a lower portion of the processing chamber. In some embodiments, the gap is narrow enough to increase the velocity at which radicals exiting the processing region flow toward the exhaust port. The rate of radical removal from the processing region affects the concentration gradient on the wafer edge. By increasing the radical exit rate, the concentration of undesirable radicals near the wafer edge is reduced, thereby achieving better etch rate uniformity at the wafer edge. Thus, by varying the dimensions and / or shape of the foot extension of the confinement ring, the profile of the gap between the edge ring and the foot extension can be tailored to control the radical exit rate and therefore the etch rate to enhance the etch rate uniformity across the wafer.

[0027] Various features of the confinement rings will now be discussed with reference to the drawings.

[0028] FIG. 1A is a simplified diagram illustrating a processing chamber 100 used to process a wafer "W" in accordance with some embodiments of the present invention. In some embodiments, the processing chamber 100 is a single station chamber in that a single wafer is processed at any one time. The processing chamber 100 comprises an upper portion 102 housing an inner chamber 103 and a lower portion 104 housing a pedestal 105. The inner chamber 103 includes a plasma dome 103a. An opening 103b is defined at the top of the plasma dome 103a. The opening 103b is used to supply processing gases from one or more gas sources 110 to generate a plasma. The upper portion 102 of the processing chamber 100 comprises a showerhead 106. The showerhead 106 is used to flow processing gases and radicals into a processing region 122 and to neutralize ions by collision in the showerhead 106 before the ions enter the processing region 122. Ion bombardment typically occurs at the top showerhead 106a and the bottom showerhead 106b when they are positioned in a non-line-of-sight (i.e., non-linear) orientation with respect to one another. The flow of process gas supplied to the inner chamber 103 may be adjusted using a flow valve 112 coupled to a gas source 110.

[0029] In one embodiment, a first end of the coil 108 is coupled to a power source, such as a radio frequency (RF) power source (e.g., a first RF power source) 114, and a second end of the coil 108 is grounded. The coil 108 provides RF power to a process gas received in the plasma dome 103a of the inner chamber 103 to generate a plasma. As shown, a matching network 116 is provided to efficiently couple RF power from the RF power source 114 to the coil 108. The RF power source 114 is coupled to a controller 118 that is used to control the RF power provided to the coil 108.

[0030] An inlet is provided in the top showerhead 106a to deliver radicals and ions from the plasma generated in the plasma dome 103a to the bottom showerhead 106b. In some embodiments, the top showerhead 106a is connected to the bottom showerhead 106b using, for example, fasteners, connectors, screws, O-rings, etc. In other embodiments, the top and bottom showerheads (106a, 106b) are fabricated from a single piece of metal. The lower portion 104 of the processing chamber 100 includes a pedestal 105. In some embodiments, the pedestal is an electrostatic chuck (ESC). The ESC pedestal (or simply referred to hereinafter as "ESC") 105 includes a wafer receiving surface (not shown). A wafer is received on the wafer receiving surface for processing. An edge ring 126 is disposed adjacent to and surrounds the wafer received on the wafer receiving surface. The ESC 105 is connected to a power source (such as a second RF power source 117) through a corresponding matching network (i.e., a second matching network) 115. The ESC 105 is coupled to a pedestal height adjuster 120 to allow the ESC 105 to move vertically up or down. The pedestal height adjuster 120 is in turn connected to a controller 118. The pedestal height adjuster 120 adjusts the height of the ESC 105 using a signal from the controller 118. A confinement ring 130 is disposed below the bottom showerhead 106b and is used to surround a processing region 122 defined in the processing chamber 100.

[0031] In one embodiment, the pedestal height adjuster 120 can change the height of the ESC 105 so that the ESC 105 is closer to or farther from the bottom surface of the foot extension 134 of the confinement ring 130. This height adjustment thus allows for adjustment of the gap (i.e., separation distance) between the bottom surface of the foot extension 134 and the top surface of the edge ring 126 disposed on the top surface of the ESC 105. For example, in FIG. 1A, the ESC 105 is at a height "h1", which makes the separation between the bottom surface of the foot extension 134 and the top surface of the edge ring 126 a height (or separation distance) "h2". This position can be referred to as the operating position where etching is performed. The foot extension 134 of the confinement ring 130 thus allows for modification of the rate at which radicals and other gases are removed from the processing region 122. As an example, if the separation (h2) is further reduced but still greater than zero, the rate at which radicals are removed from the processing region 122 is increased near the wafer edge. The rate at which radicals are removed from the processing region 122 is adjusted by changing the separation (h2) distance above zero. In general, a smaller separation h2 results in a faster exit rate and therefore a lower concentration of undesirable radicals near the wafer edge. In these embodiments, the confinement ring 130 may be rigidly attached to the upper portion of the processing chamber. In other embodiments, the confinement ring 130 may be attached to the upper portion of the processing chamber using fasteners, connectors, screws, O-rings, etc. In yet other embodiments, the confinement ring 130 may be attached to the upper portion of the processing chamber using an adjustable mount. For example, the confinement ring 130 is attached to the bottom showerhead 106b or to a structure next to the showerhead 106. In some embodiments, the structure next to the showerhead 106 may be a top plate (not shown).

[0032] In some embodiments, the separation (h2) between the bottom surface of the foot extension 134 and the top surface of the edge ring 126 can be controlled by raising and lowering the confinement ring 130. The confinement ring 130, mounted on or next to the showerhead 106, is coupled to a motor (not shown), which is connected to the controller 118. A signal from the controller 118 is used to adjust the position of the confinement ring 130, thereby driving the separation. In various embodiments, only the confinement ring 130 adjustably mounted on the upper portion of the processing chamber is moved to adjust the separation, only the showerhead 106 with the confinement ring 130 mounted thereon is moved to adjust the separation, both the confinement ring 130 adjustably mounted on the upper portion of the processing chamber and the ESC 105 are moved to adjust the separation, or both the showerhead 106 with the confinement ring 130 mounted thereon and the ESC 105 are moved to adjust the separation. The movement of the ESC 105 and the showerhead 106 with the attached confinement ring 130 can be controlled independently or together using signals from the controller 118.

[0033] It is believed that the concentration of radicals increases near the wafer edge due to the difference in materials the radicals encounter at the wafer-edge ring interface. Typically, the wafer is formed of silicon and may include polysilicon materials. In contrast, if the edge ring is formed of a material such as alumina (i.e., aluminum oxide) that does not consume fluorine during etching, more fluorine tends to back-diffuse toward the wafer edge and may cause secondary reactions around the edge of the wafer. As a result, a substantial increase in back-diffusion of radicals is observed to occur at the wafer edge, leading to etching non-uniformity. Advantageously, the confinement ring 130 of the present disclosure may be configured to prevent back-diffusion of radicals by increasing the exit velocity of radicals from the processing region 122 near the wafer edge. As shown in FIG. 1A, example streamlines show radicals exiting the processing region 122 with increased velocity through a gap 136 of height h2 defined between the foot extension 134 and the edge ring 126.

[0034] 1A, the confinement ring 130 is coupled to the bottom showerhead 106b as described above and includes a tubular extension 132 that forms a sidewall surrounding the processing region 122. The foot extension 134 defines an annular surface that flares outward from the bottom of the tubular extension 132 and away from the processing region 122. The confinement ring 130 is formed from a conductive metal (such as aluminum, for example). In some examples, the confinement ring 130 is formed from aluminum coated with a dielectric material. In some implementations where the ESC 105 is poled to the second RF power source 117 through the second matching network 115, the confinement ring 130 may be formed from a ceramic or other insulating material to avoid RF coupling to the confinement ring 130. As shown, the tubular extension 132 of the confinement ring 130 extends downward by a height "H1". As described above, the ESC 105 is movable to a position appropriate for the etching operation. Also, in this example, the bottom surface of the bottom showerhead 106b is at a height "H2" above the top surface of the wafer. In this example, the height H2 is equal to the height H1+h2 (i.e., the height of the tubular extension 132 of the confinement ring 130 plus the height of the gap 136 between the annular surface (i.e., bottom surface) of the foot extension 134 and the top surface of the edge ring 126). The gap 136 provides a passage (i.e., a pathway) for radicals and gases to be routed from the processing region 122 toward an exhaust port 128 defined in the lower portion 104 of the processing chamber 100.

[0035] As mentioned above, narrowing the passage increases the exit velocity of radicals exiting the processing region 122. The increased velocity may be due to the processing chamber 100 attempting to maintain equilibrium between the inflow and outflow of radicals and gases within the processing region 122. The increased exit velocity leads to reduced back-diffusion of radicals and reduced concentration gradients of radicals at the wafer edge.

[0036] FIG. 1B is a simplified diagram showing the processing chamber 100 with the ESC 105 in a lowered position. In the lowered position, a wafer may be transferred to or removed from the processing chamber 100. As described above, the pedestal height adjuster 120 can control the movement of the ESC 105 up or down, and in this case, the ESC 105 has been moved down to a height h3. This position increases the gap 136 between the foot extension 134 and the edge ring 126 to a height h4 (i.e., h4>h2). In some cases, the ESC 105 may be lowered to a position between the operating position (shown in FIG. 1A) and the lowered position (shown in FIG. 1B) to perform an etching operation or other operation.

[0037] 1C is a cross-sectional view of a process chamber 100 in which a waferless automatic cleaning (WAC) operation is performed. During a WAC operation, radicals and ions are used to clean the interior surfaces surrounding the processing region 122 of the process chamber 100, where polymers and other by-products released during the etching operation may accumulate. As a result, a WAC operation is performed periodically between wafer etching sessions. As shown, the ESC 105 is also connected to an RF power source 117 through a corresponding matching network 115.

[0038] In some embodiments, the confinement rings 130 are formed of a conductive material. In such embodiments, the confinement rings 130 are connected to ground to provide an RF return path to ground for RF current from the powered ESCs 105 to exit the processing region 122. In some embodiments, a ground disconnect 140 is provided. The ground disconnect 140 is configured to disconnect the structure of the confinement rings 130 from ground, causing the confinement rings to electrically float.

[0039] The ground disconnect 140 can be a switch or a mechanical element that can be moved to make or break the electrical connection. In some embodiments, the ground disconnect 140 is an RF switch. Even when the RF connection is broken, the confinement ring 130 can be mechanically connected to the showerhead 106 using some type of insulating connector. In one example, the controller 118 can set the ground disconnect 140 to be RF floating or RF connected. In one embodiment, the ground disconnect 140 can have a motor that allows mechanical movement of the switch or connector.

[0040] By RF floating the confinement rings 130, the RF power is directed to an alternate path to ground. The alternate path can be, for example, through the showerhead 106 or an interior wall of the processing chamber 100. RF floating the confinement rings 130 is not limited to WAC operations. Rather, the confinement rings 130 may be RF floating during other etching operations that require RF power from the ESC 105 to power a plasma in the processing region 122.

[0041] 2A is an enlarged cross-sectional view of a confinement ring 130 used in the processing chamber 100 according to some embodiments. The confinement ring 130 is configured to confine radicals and gases within the processing region 122 and control the removal of radicals from the processing region 122. The confinement ring 130 may be coupled to the bottom showerhead 106b using fasteners, connectors, screws, etc. Additionally, an optional O-ring 139 may provide a seal between the confinement ring 130 and the bottom showerhead 106b. For example, the top surface of the confinement ring 130 includes a groove 138 in which the O-ring 139 is received. The confinement ring 130 is coupled to the bottom showerhead 106b by compressing the O-ring to seal the gap. In other embodiments, the confinement ring 130 may be coupled to a structure that is or may extend outside the radius of the showerhead 106. Although not explicitly shown in the drawings, in some embodiments, two or more O-rings and / or different types of seals may be used, either independently or in conjunction with one or more O-rings, to seal any gaps between the confinement ring 130 and the bottom showerhead 106b.

[0042] As described above, the confinement ring 130 includes a tubular extension 132 and a foot extension 134. The tubular extension 132 extends downward between its upper and lower ends. The foot extension 134 extends between an inner end (facing the processing region) and an outer end (facing away from the processing region). The lower end of the tubular extension 132 is connected to or otherwise integrated with the inner end of the foot extension 134. In this example, the tubular extension 132 extends at a straight angle "SA" between its upper and lower ends and is perpendicular to the bottom surface 107 of the bottom showerhead 106b. The tubular extension 132 extends over a height H1 such that the lower end is adjacent to the edge ring 126 (received on the ESC 105). In some embodiments, the term "close" is defined such that the separation distance between the top surface of the edge ring 126 and the bottom surface of the foot extension 134 of the confinement ring 130 is between 1 mm and 50 mm. In some embodiments, the separation distance may vary by + / - 20% of the aforementioned range. In some embodiments, the separation distance between the top surface of the edge ring 126 and the bottom surface of the foot extension 134 of the confinement ring 130 is defined as about 37 mm. In an alternative embodiment, the separation distance between the top surface of the edge ring 126 and the bottom surface of the foot extension 134 of the confinement ring 130 is defined as about 50 mm. Examples of separation distances that have been tested are discussed with reference to FIG. 3. As mentioned above, this is an adjustable parameter that may be set depending on the process being performed, the gases utilized, and other operating parameters. Thus, the foot extension 134 between the inner and outer ends defines an annular surface. The term "about" is defined to include a + / - 15% variation of the specified value.

[0043] In some embodiments, the tubular extension 132 is configured to align over an outer edge of a wafer receiving surface defined on the ESC 105. The tubular extension 132 provides a sidewall surrounding the processing region 122 such that radicals and gases may be substantially confined over the wafer during operation. In some embodiments, the width of the annular surface of the foot extension 134 is defined to at least partially cover a width of a surface of the edge ring 126. In some embodiments, the width of the annular surface of the foot extension 134 substantially covers the entire width "W1" of the surface of the edge ring 126. In some embodiments, the width "W2" of the foot extension 134 is longer than the width W1 of the edge ring 126 such that when the tubular extension 132 is aligned with the outer edge of a wafer received on the ESC 105, the outer edge of the foot extension 134 extends beyond the width W1 of the edge ring 126 received adjacent the outer edge of the wafer W. In some embodiments, the width "W2" of the foot extension 134 is longer than W1 of the edge ring 126 such that when the outer edge of the foot extension 134 is aligned with the outer edge of the edge ring 126 received adjacent to the wafer W, the inner edge of the foot extension 134 can align or overlap with the area above the outer edge of the wafer.

[0044] The foot extension 134 is defined, in some embodiments, to be perpendicular to the tubular extension 132, and the annular surface of the foot extension 134 is substantially parallel (+ / - 5%) to the edge ring 126. Still referring to FIG. 2A, the gap 136 defined between the annular surface of the foot extension 134 and the edge ring 126 is substantially uniform throughout the length of the gap 136 (i.e., the height "h2" of the gap 136 is uniform along the width of the annulus of the foot extension 134). The passageway defined by the gap 136 may be configured to increase the outflow rate of radicals and gases flowing out of the processing region 122 from V1 to V2 (i.e., V2>V1). Also, the height h2 of the gap 136 is preferably configured so that the gap is not too narrow to create a bottleneck. For example, a gap 136 of less than about 1 mm may potentially lead to increased back-diffusion of radicals into the processing region 122.

[0045] 2B-2G show non-limiting examples of different profiles of the confinement ring 130 that may be utilized in the processing chamber 100 to confine radicals and shape the exhaust flow under the foot extension 134. FIGS. 2B, 2C, 2F, and 2G show different profiles of the tubular extension 132, and FIGS. 2D, 2E, and 2F show different profiles of the foot extension 134. With reference to FIG. 2B, the tubular extension 132 is angled at an angle "α" with respect to the straight angle "SA". o The tubular extension 132 extends downward and inward toward the treatment area 122. The angle (α o ) is different from the perpendicular angle to the bottom showerhead 106b shown in FIG. 2A.

[0046] Similar to the embodiment of FIG. 2A, the tubular extension 132 of the confinement ring 130 shown in FIG. 2B extends over a height H1 between an upper end and a lower end. The foot extension 134 joins the lower end of the tubular extension 132 so as to be substantially parallel (+ / - 5%) with the edge ring 126 and the bottom showerhead 106b. The lower end of the tubular extension 132 is aligned around the outer edge of the wafer. Additionally, the outer edge of the foot extension 134 is aligned with the outer edge of the edge ring 126 in this embodiment. The annular surface of the foot extension 134 defined between the inner and outer ends extends over a width "W2". The width W2 of the annular surface of the foot extension 134 is greater than the width "W1" of the edge ring 126. The gap 136 defined between the annular surface of the foot extension 134 and the edge ring 126 is substantially uniform (+ / - 5%) and extends over a height h2. The flux rate of radicals flowing out of the processing region 122 increases from V1 to V2 (i.e., V2>V1) as they flow through the passage of the gap 136. Again, the increase in rate V2 can be tailored by setting the gap 136 at the separation that is most effective in reducing etch rate non-uniformity at the wafer edge.

[0047] FIG. 2C illustrates an alternative confinement ring profile to those shown in FIGS. 2A and 2B, in one embodiment. In this embodiment, the tubular extension 132 is angled at an angle "β" with respect to the straight angle. o ". Additionally, the tubular extension 132 extends downward and outwardly away from the processing region 122. The tubular extension 132 of the confinement ring 130 extends across a height H1 between its upper and lower ends. The foot extension 134 extends from the lower end of the tubular extension 132 and is substantially parallel to the edge ring 126 and the bottom showerhead 106b.

[0048] Figure 2D illustrates an alternative confinement ring profile to those shown in Figures 2A-2C, in one embodiment. In Figure 2D, the tubular extension 132 extends vertically downward from its top to its bottom and is perpendicular to the bottom showerhead 106b. However, the foot extension 134 extends downward at an angle other than perpendicular to the tubular extension 132.

[0049] In FIG. 2D, the foot extension 134 is tapered at an angle θ oThe tubular extension 132 extends downwardly from the inner and outer ends of the containment ring 130 at a height H1. The tubular extension 132 is aligned with the inner edge of the edge ring 126, and the outer end of the foot extension 134 is aligned with the outer edge of the edge ring 126. The height of the tubular extension 132 of the containment ring 130 between the upper and lower ends is H1, and the width of the annular surface of the foot extension 134 is equal to the width "W1" of the edge ring 126. In some embodiments, the outer end of the foot extension 134 extends over a width that is greater or less than the outer end of the edge ring 126. Due to the downward slope of the foot extension 134 from the tubular extension 132, the height of the gap 136 between the annular surface of the foot extension 134 and the edge ring 126 is not uniform (i.e., may vary) across the width of the foot extension 134. Instead, the height of the gap 136 gradually decreases from a height h2 at the inner end of the foot extension 134 to a height "h5" at the outer end of the foot extension 134, where h2>h5. The further narrowing of the gap 136 at the outer end of the foot extension 134 causes the radicals and other gases flowing through the gap 136 to accelerate toward the exhaust port 128, increasing the exit velocity from V1 (i.e., the velocity measured before the radicals enter the gap 136) to V2' (i.e., the velocity measured as the radicals exit the gap 136) (i.e., V2'>V1). By way of example, the exit velocity V2' may be greater than the exit velocity V2 of FIGS. 2A-2C. Although not explicitly shown in the drawings, in some embodiments, the top surface or edge ring 126 may be sloped such that the thickness of the inner diameter is greater than the thickness of the outer diameter. In such embodiments, the difference between h2 and h5 would be smaller compared to that shown in FIG. 2D. In some such instances, h2 is substantially equal to h5.

[0050] Figure 2E illustrates yet another alternative confinement ring profile to those shown in Figures 2A-2D. Similar to Figure 2D, the tubular extension 132 in this example extends vertically downward from top to bottom and is substantially perpendicular (+ / - 5%) to the bottom showerhead 106b. The foot extension 134 has a taper angle γ oThe tubular extension 132 and the inner end of the foot extension 134 are aligned with the inner edge of the edge ring 126, and the outer end of the foot extension 134 is aligned with the outer edge of the edge ring 126. The height of the tubular extension 132 of the containment ring 130 between the upper and lower ends is H1, and the width of the annular surface of the foot extension 134 is equal to the width "W1" of the edge ring 126. Due to the upward and outward slope of the foot extension 134 toward the outer end, the height of the gap 136 between the annular surface of the foot extension 134 and the edge ring 126 is not uniform across the width of the foot extension 134. Instead, the height of the gap 136 gradually increases from a height h2 at the inner end of the foot extension 134 to a height "h6" at the outer end of the foot extension 134, where h6>h2.

[0051] The edge ring 126 is positioned such that the top surface of the edge ring 126 is flush with the top surface of the wafer W. The passageway defined by the gap 136, the height of which increases from the inner end to the outer end of the foot extension 134, is configured to increase the exit velocity of radicals and gases exiting the processing region 122 from V1 (i.e., the velocity of the radicals before they enter the gap 136) to V2" (i.e., the velocity measured as the radicals pass through the narrow inner end of the gap 136) (i.e., V2">V1). However, the exit velocity decreases from V2" at the inner end of the gap 136 to V2''' at the outer end. The decrease in exit velocity can be attributed to the increasing height of the gap 136 toward the outer end. Exit velocity V2''' is still faster than exit velocity V1 in the processing region 122, but slower than exit velocity V2 in FIGS. 2A-2C and V2' in FIG. 2D.

[0052] 2F shows an alternative confinement ring profile to those shown in FIGS. 2A-2E in an alternative embodiment. The tubular extension 132 is oriented at an angle (β ) other than the normal (+ / - 5%) to the bottom surface 107 of the bottom showerhead 106b in this embodiment. o) extending from the upper end to the lower end. The angle of outward slope of the tubular extension 132 is shown to be similar to that shown in FIG. 2C. In some embodiments, the angle of outward slope of the tubular extension 132 is β o In addition to the outward inclination of the tubular extension 132, the foot extension 134 has a taper angle θ o 2D. The angle of the downward slope of the foot extension 134 is shown to be similar to that shown in FIG. 2D.

[0053] In an alternative embodiment, the angle of the downward slope of the foot extension 134 is θ oThe tubular extension 132 is aligned at its upper end with the inner edge of the edge ring 126, and the outer end of the foot extension 134 is aligned with the outer edge of the edge ring 126. The height of the tubular extension 132 of the confinement ring 130 between its upper and lower ends is H1, and the width of the annular surface of the foot extension 134 is equal to the width "W1" of the edge ring 126. Due to the downward slope of the foot extension 134 outward from the tubular extension 132, the height of the gap 136 between the annular surface of the foot extension 134 and the edge ring 126 is not uniform across the width of the foot extension 134. Instead, the height of the gap gradually decreases from a height h2 at the inner end of the foot extension 134 to a height "h5" at the outer end of the foot extension 134, where h2>h5. The edge ring 126 is positioned such that the top surface of the edge ring 126 is flush with the top surface of the wafer W. By further narrowing the gap 136 from the inner end to the outer end of the foot extension 134, the radicals flowing through the gap 136 accelerate as they pass the initial narrow end of the gap 136 toward the exhaust port 128, increasing their exit velocity from V1 (i.e., the velocity measured before the radicals enter the gap 136) to V2' (i.e., the velocity measured as the radicals exit the gap 136), where V2'>V1. Although not explicitly shown in the drawings, in some embodiments, the top surface or edge ring 126 may be sloped such that the thickness of the inner diameter is greater than the thickness of the outer diameter. In such embodiments, the difference between h2 and h5 in FIG. 2F would be smaller. In some such examples, h2 is substantially equal to h5.

[0054] 2G illustrates another alternative confinement ring profile in one embodiment. The confinement ring 130 in this embodiment includes multiple segments. For example, the confinement ring 130 includes a tubular extension 132, a first segment 132a, a second segment 132b, a third segment 132c, and a foot extension 134. The tubular extension 132 of the confinement ring 130 extends vertically downward from its top end to its bottom end. The first segment 132a extends along a horizontal axis at the top end and is used to couple the confinement ring 130 to the bottom showerhead 106b. The first segment 132a extends outwardly away from the processing region 122. The second segment 132b extends vertically downward from the top end to a height "H3" with the first segment 132a. The third segment 132c extends downwardly from the bottom of the second segment 132b to the outer end of the foot extension 134 for a height "H4." In some embodiments, the third segment 132c is at an angle "δ o " extending downwardly and inwardly. Foot extension 134 extends across a width W1 between the inner and outer ends.

[0055] In some embodiments, the confinement ring 130 has a different design (not shown) than that shown in FIG. 2G. In such embodiments, the multiple segments of the confinement ring 130 include a first segment 132a, a second segment 132b, a third segment 132c, and a foot extension 134, where the first, second, and third segments (132a, 132b, 132c) together define a tubular extension 132. The positions and orientations of the first, second, and third segments (132a, 132b, 132c) and the position and orientation of the foot extension 134 are similar to those shown in FIG. 2G. The design of the confinement ring 130 in these embodiments differs from that shown in FIG. 2G in that the confinement ring 130 in FIG. 2G includes an additional tubular extension 132 that extends vertically downward from the bottom surface 107 of the bottom showerhead 106b.

[0056] The various containment ring profiles are provided by way of example only, and other profiles are contemplated, such as a tubular extension 132 including, in whole or in part, first, second, and third segments (132a, 132b, 132c), a tubular extension 132 extending downward and outward away from the processing region 122, or a tubular extension 132 extending downward and inward from the processing region 122, and a foot extension 134 extending upward or downward from an inner end to an outer end. Additionally, the upward / downward / outward / inward slope angles of the tubular extension 132 including the first, second, and third segments (132a, 132b, 132c) and the foot extension 134 are provided by way of example and are not intended to limit the embodiments of the present disclosure. It should be noted that the thickness of the tubular extension including the first, second, and third segments (132a, 132b, 132c) and / or the foot extension 134 may vary across the length or width of the respective components and need not be uniform. Furthermore, if a slope is present in any component of the containment ring 132 (i.e., the tubular extension 132 including the first, second, and third (132a, 132b, 132c) segments and / or the foot extension 134), the slope need not be constant but may vary along the direction of the respective component. It should also be understood that in some embodiments, the containment ring 130 may be formed from separate pieces (e.g., the tubular extension 132 is separate from the foot extension 134). Furthermore, the first, second, and third segments (132a, 132b, 132c) may be separate pieces. When the confinement ring 130 is formed of separate pieces, the pieces may be connected using mechanical fasteners, adhesives, screws, and / or the like. In various confinement ring profiles, a foot extension 134 extending substantially over the top surface of the edge ring may mean that the foot extension 134 extends completely over the top surface of the edge ring 126. Alternatively, a foot extension 134 extending substantially over the top surface of the edge ring may mean that the foot extension 134 extends partially over the top surface of the edge ring (e.g., extends over an inner portion or an outer portion of the edge ring).

[0057] In some embodiments, the height H1 of the tubular extension 132 of the confinement ring 130 is defined as between about 20 mm and 65 mm. In yet another embodiment, the height H1 of the tubular extension 132 is defined as about 50 mm. In some embodiments, the confinement ring 130 is comprised of aluminum. In some embodiments, the confinement ring 130 is formed of anodized aluminum oxide. In some embodiments, the confinement ring 130 is coated with a material such as ALD (atomic layer deposition) yttria (yttrium oxide). In some embodiments, the confinement ring is formed of a dielectric material, which does not require the use of a ground disconnect 140. In these embodiments, the dielectric material includes any of aluminum oxide (alumina), yttria, quartz, silicon nitride, silicon carbide, or combinations thereof. The above list of dielectric materials is provided by way of example only and should not be considered limiting.

[0058] In some embodiments, the confinement ring 130 is integrated with the bottom showerhead 106b to form a one-piece bottom showerhead with plasma confinement capabilities. It should be noted that the designs, dimensions, and materials used to define the confinement ring 130, as well as the designs, dimensions, and materials of the other components of the processing chamber 100, are all provided as examples and should not be considered as comprehensive or limiting.

[0059] FIG. 3 shows a graph of etch rate versus distance from wafer center plotted for an etching operation performed in a processing chamber 100 using a confinement ring 130 with foot extensions 134. Based on testing and experimentation, the various graph lines plotted in the etch rate graph represent different etch profiles for different separations of the gap 136 (i.e., the gap between the top surface of the edge ring 126 and the bottom surface of the foot extension 134 of the confinement ring 130, or the gap between the top surface of the edge ring 126 and the bottom surface of the bottom showerhead). This graph shows that various gaps can be useful in tuning the etch performance to eliminate or reduce etch non-uniformity. Although the etch rate near the edge of the wafer is not always exactly the same as the etch rate at the wafer center, these plots show a significant improvement and improved etch rate uniformity near the wafer edge compared to prior art systems that do not utilize the confinement ring 130 with foot extensions 134 disclosed in the present invention.

[0060] For example, graph line 1 shows a baseline etch rate profile from wafer center to wafer edge for a 300 mm wafer plotted when no confinement ring is present. Graph lines 2-5 show etch rate profiles for different gaps defined between the foot extension 134 of the confinement ring 130 and the edge ring 126 when the confinement ring 130 with foot extension is present. Graph line 1 shows the etch rate profile when the gap 136 between the top surface of the edge ring 126 and the bottom surface of the lower showerhead is about 37.5 mm. Graph line 2 shows the etch rate when the gap 136 between the top surface of the edge ring 126 and the foot extension 134 of the confinement ring 130 is about 17.7 mm. Graph line 3 shows the etch rate profile when the gap 136 between the top surface of the edge ring 126 and the foot extension 134 of the confinement ring 130 is about 12.7 mm.

[0061] Graph 4 shows an etch rate profile when the gap 136 between the top surface of the edge ring 126 and the foot extension 134 of the confinement ring 130 is about 8.5 mm. Graph 5 shows an etch rate profile similar to graph 5 when the gap 136 between the top surface of the edge ring 126 and the foot extension 134 of the confinement ring 130 is about 6.5 mm. Based on the etch rate profiles of the various graph lines shown in the etch rate graph of FIG. 3, in order to achieve a substantially uniform etch rate at the wafer edge, the gap 136 is defined between about 3.5 mm and about 37.5 mm in some embodiments. In some embodiments, in order to achieve a substantially uniform etch rate at the wafer edge, the gap 136 is defined between about 6 mm and about 20 mm. In yet another embodiment, the gap 136 is defined at about 13 mm. As shown, the confinement ring 130 with the foot extension 134 significantly helps reduce the radical concentration gradient at the wafer edge, leading to improved etch uniformity across the wafer including and up to the wafer edge.

[0062] The above description of various embodiments is for purposes of illustration and description. It is not intended to be exhaustive or limiting of the present invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment and, where applicable, may be interchanged and utilized in the selected embodiment unless otherwise shown or described. The same may be modified in many ways. Such modifications are not considered a departure from the present invention, and all such modifications are intended to be included within the scope of the present invention.

[0063] Although the present embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be made within the scope of the appended claims. The present embodiments are therefore to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein, but may be modified within the scope of the claims and their equivalents.

Claims

1. 1. A confinement ring for use in a processing chamber, comprising: a tubular extension configured to surround a processing region within the processing chamber, the tubular extension having an upper end configured to connect to a showerhead disposed within the processing chamber and a lower end configured to extend proximate an edge ring, the edge ring configured to surround the wafer when the wafer is received in the processing chamber for processing; a foot extension having an inner end joining the lower end of the tubular extension and extending outwardly from the processing region to an outer end, the foot extension defining an annular surface configured to form a gap with a top surface of the edge ring, the gap being used to channel radicals out of the processing region; A containment ring comprising:

2. 10. The confinement ring of claim 1, The tubular extension extends vertically downward from the showerhead at a straight angle.

3. 10. The confinement ring of claim 1, the tubular extension extends at an angle different from an angle of the showerhead, the angle being one of acute and obtuse relative to the angle.

4. 10. The confinement ring of claim 1, the annular surface of the foot extension is substantially parallel to the top surface of the edge ring.

5. 5. The confinement ring of claim 4, The gap is uniform in height along a width of the foot extension.

6. 10. The confinement ring of claim 1, The foot extension extends substantially perpendicular to the tubular extension.

7. 10. The confinement ring of claim 1, The confinement ring, wherein the foot extension extends at a taper angle relative to the tubular extension other than a right angle, the taper angle being one of an acute angle and an obtuse angle.

8. 8. The confinement ring of claim 7, the gap varies in height along a width of the foot extension; The height of the gap gradually increases or decreases outwardly.

9. 10. The confinement ring of claim 1, A confinement ring, the width of the annular surface being equal to the width of the edge ring.

10. 10. The confinement ring of claim 1, A confinement ring, wherein the width of the annular surface is greater than or less than the width of the edge ring.

11. 10. The confinement ring of claim 1, A confinement ring, the size of the gap being defined to increase the velocity of radicals flowing through the gap and prevent backflow of radicals.

12. 10. The confinement ring of claim 1, The showerhead comprises a top showerhead and a bottom showerhead, the tubular extension being connected to the bottom showerhead.

13. 10. The confinement ring of claim 1, The confinement ring is integral to the showerhead.

14. 10. The confinement ring of claim 1, a confinement ring, the confinement ring comprising: an electrostatic chuck (ESC) disposed in a lower portion of the processing chamber, the confinement ring having an inner diameter extending to an outer diameter of the wafer received on the upper surface of the ESC, the tubular extension being aligned with an outer edge of the wafer, and the annular surface of the foot extension extending substantially over the upper surface of the edge ring.

15. 10. The confinement ring of claim 1, A confinement ring, wherein a top surface of the confinement ring includes a groove for receiving an O-ring, the O-ring being used to form a seal when the confinement ring is connected to the showerhead.

16. 10. The confinement ring of claim 1, The confinement rings are formed of one of aluminum, anodized aluminum, atomic layer deposition (ALD) yttria, or aluminum coated with a dielectric material.

17. 1. A process chamber used to etch a wafer, comprising: an electrostatic chuck (ESC) disposed in a lower portion of the processing chamber, the ESC having a top surface configured to receive a wafer and an edge ring, the edge ring configured to be positioned adjacent to and surrounding the wafer; a plasma chamber disposed in an upper portion of the processing chamber, a plasma chamber coupled to one or more gas sources for receiving a process gas, the plasma chamber including one or more coils disposed surrounding the plasma chamber, the one or more coils connected to an RF power source through a matching network for receiving RF power, the RF power being used to heat the process gas to generate a plasma; a showerhead at a bottom of the plasma chamber, the showerhead having an inlet for directing radicals of the plasma toward a processing region of the processing chamber defined between the showerhead and the ESC; A confinement ring for use in the processing chamber, comprising: a tubular extension configured to surround the processing region within the processing chamber, the tubular extension having an upper end configured to connect to a bottom surface of the showerhead disposed within the processing chamber and a lower end configured to extend proximate the edge ring surrounding the wafer; a foot extension having an inner end joining the lower end of the tubular extension and extending outwardly from the processing region to an outer end, the foot extension defining an annular surface configured to form a gap with a top surface of the edge ring, the gap being used to flow plasma out of the processing region; A processing chamber comprising:

18. 20. The processing chamber of claim 17, comprising: The processing chamber, wherein the showerhead comprises a top showerhead and a bottom showerhead, and the tubular extension of the confinement ring is connected to the bottom showerhead.

19. 20. The processing chamber of claim 17, comprising: a processing chamber, wherein an inner diameter of the confinement ring extends to an outer diameter of the wafer received on the top surface of the ESC and the tubular extension is aligned with an outer edge of the wafer when the wafer is received on the ESC.

20. 20. The processing chamber of claim 17, comprising: the tubular extension extends vertically downward from the showerhead at a straight angle; The annular surface of the foot extension is substantially parallel to the top surface of the edge ring.

21. 1. A confinement ring for use in a processing chamber, comprising: a tubular extension configured to surround a processing region within the processing chamber, the tubular extension having an upper end configured to connect to a top plate of the processing chamber and a lower end configured to extend proximate an edge ring, the edge ring configured to surround the wafer when the wafer is received in the processing chamber for processing; a foot extension having an inner end joining the lower end of the tubular extension and extending outwardly from the processing region to an outer end, the foot extension defining an annular surface configured to form a gap with a top surface of the edge ring, the gap being used to flow plasma out of the processing region.

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