Wafer Edge Tilt and Etch Rate Uniformity

Abstract

[Solution] An edge ring for use in a plasma chamber includes a first pair of edge ring segments, each of the first pair of edge ring segments having a first thickness, and a second pair of edge ring segments, each of the second pair of edge ring segments having a second thickness, each of the first pair of edge ring segments disposed adjacent to each of the second pair of edge ring segments, and each of the second pair of edge ring segments disposed adjacent to each of the first pair of edge ring segments.

Description

[Technical field]

[0001] The present embodiments relate to components used to provide a uniform etch rate in a semiconductor process chamber, and more particularly to an edge ring with a modified shape to provide a uniform etch rate across the wafer surface. [Background technology]

[0002] Semiconductor wafers are subjected to various manufacturing processes to produce electronic devices. The processes used to produce electronic devices include deposition processes, etching processes, and patterning processes, among others. Etching processes are performed in a plasma chamber. Whether the plasma is generated remotely to the plasma chamber or in the plasma chamber, ions of the plasma are directed at the entire surface of the wafer to etch features that define the pattern. The pattern or patterns define the electronic devices. Due to high manufacturing costs, designers attempt to maximize wafer utilization, or yield, by increasing the density of electronic devices patterned on the wafer. One way to increase the density of electronic devices and improve yield is to define high aspect ratio features on the wafer. Another way to improve wafer yield is to maximize the use of the wafer's surface by etching high aspect ratio features.

[0003] To etch high aspect ratio features on the surface of the wafer, especially at the edge of the wafer, ion flux and ion tilt must be optimized. The pattern etched on the wafer surface is asymmetric. To optimize the ion flux and ion tilt and improve the control of the edge sheath at the wafer edge, an edge ring is provided adjacent to and surrounds the wafer. Various experiments have been performed and it has been found that the etch rate performance at the wafer edge varies depending on the orientation of the feature with respect to the radius of the wafer (i.e., whether the feature is perpendicular or parallel to the radius of the wafer). Currently available edge rings are axisymmetric, meaning that they have a symmetric shape along a given axis. Summary of the Invention

[0004] Various embodiments of the present disclosure include apparatus and systems used to approximate a nominal etch rate across the surface of a wafer. During the etching process, a plasma is generated in a plasma chamber using a process gas. The generated plasma is directed at the entire surface of a wafer received in the plasma chamber to define features. The features are part of a pattern used to define electronic devices. The features patterned on the wafer are asymmetric and may include slits, vias, or trenches.

[0005] The edge ring is disposed adjacent to and surrounds a wafer receiving area used to receive the wafer in the plasma chamber. The edge ring improves ion flux and ion tilt at the wafer edge by extending the process area from the edge of the wafer to the outer edge of the edge ring. As mentioned above, conventional edge rings are axially symmetric. That is, the shape (e.g., height, angle) of the edge ring is uniform along a given axis. It has been observed from various experiments performed that the etch rate at the wafer edge varies with the orientation of the features defined on the wafer relative to the wafer radius. For example, it has been observed that in regions where the features defined on the wafer are parallel to the wafer radius, the etch rate at the wafer edge is faster. It has also been observed that in regions where the features on the wafer are perpendicular to the wafer radius, the etch rate at the wafer edge is slower (which is the norm). This etch rate variation can be attributed to the shape of the plasma sheath at the wafer edge.

[0006] To address these etch rate variations and to better control the plasma sheath profile at the wafer edge, edge rings used in plasma chambers are designed with various shapes. Specifically, the edge ring is divided into segments and different segments of the edge ring are defined to extend to different heights. As a result, the shape of the edge ring has an asymmetrical feature that compensates for the asymmetry of the wafer pattern. The heights of the different zones are optimized to ensure that the edge ring with the new shape "compensates" for the faster etch rate in the corresponding areas of the wafer, resulting in a uniform etch rate over the surface of the wafer.

[0007] In one embodiment, an edge ring for surrounding a wafer in a plasma chamber is disclosed. The edge ring includes a first pair of edge ring segments, each edge ring segment of the first pair having a first thickness. The edge ring also includes a second pair of edge ring segments, each edge ring segment of the second pair having a second thickness. The first pair of edge ring segments face each other, and the second pair of edge ring segments face each other. Each of the first pair of edge ring segments is disposed adjacent to a second pair of edge ring segments. Each of the second pair of edge ring segments is disposed adjacent to a first pair of edge ring segments.

[0008] In another embodiment, an edge ring for surrounding a wafer in a plasma chamber is disclosed. The edge ring includes a first zone, a second zone, a third zone, and a fourth zone. The first zone is defined to have a first thickness. The second zone is defined to have a second thickness. The third zone is defined opposite the first zone and has a first thickness. The fourth zone is defined opposite the second zone and has a second thickness. Each of the second and fourth zones is adjacent to the first and third zones and is defined between the first and third zones. A transition region is defined between each adjacent pair of the first, second, third, and fourth zones.

[0009] Other aspects and advantages will become apparent from the following detailed description, taken in conjunction with the accompanying illustrative drawings. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1A illustrates, in one embodiment, the plasma sheath profile received at the edge of a wafer for processing when no edge ring is positioned adjacent to the wafer.

[0011] [Figure 1B]FIG. 1B illustrates a plasma sheath profile received at the edge of a wafer for processing when an edge ring of a first height is positioned adjacent the entire circumference of the wafer in one embodiment.

[0012] [Figure 1C] FIG. 1C illustrates a plasma sheath profile received at the edge of a wafer for processing when an edge ring of a second height is positioned adjacent the entire circumference of the wafer in one embodiment.

[0013] [Diagram 2] FIG. 2 is an overhead view of an edge ring surrounding a wafer having features defined thereon that extend radially across the wafer, according to one embodiment.

[0014] [Figure 3A] FIG. 3A is a side perspective view of a linear elongation of a multi-shaped edge ring that may be used to surround a wafer receiving area defined within a plasma chamber, according to some embodiments.

[0015] [Figure 3B] FIG. 3B illustrates different zones of an edge ring with different features when elongated in a straight line, according to some embodiments.

[0016] [Figure 3C] FIG. 3C shows different zones of the edge ring with different features stretched out in a straight line according to an alternative embodiment.

[0017] [Figure 4A] FIG. 4A is an overhead view of the edge ring shown in FIG. 3A with different zones, according to some embodiments.

[0018] [Figure 4B]FIG. 4B is an overhead view of the edge ring shown in FIG. 4A with transition regions defined between different zones, according to some embodiments.

[0019] [Figure 4C] FIG. 4C is an overhead view of the edge ring shown in FIG. 4A, illustrating the transition angles as well as the transition areas between the different zones according to some embodiments.

[0020] [Diagram 5] FIG. 5 illustrates, in tabular form, an etch rate graph that plots the etch rate at the edge of the wafer versus the height of specific zones of different edge ring heights in some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In the following description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments. However, it will be apparent to one of ordinary skill in the art that the described techniques may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail in order to not unnecessarily obscure the embodiments described.

[0022] Embodiments of the present disclosure provide various details of an edge ring and a system used to process a semiconductor substrate (i.e., a wafer) using an edge ring. It should be appreciated that the embodiments can be implemented in numerous ways, such as a process, an apparatus, a system, a device, or a method. Some exemplary implementations are described below.

[0023] The edge ring is disposed within the plasma chamber adjacent to and surrounds a wafer received in the plasma chamber for processing. The plasma chamber (not shown) includes a top and a bottom. The top may include an upper electrode. The upper electrode may be a showerhead, in one example. The upper electrode is coupled to one or more gas sources that provide one or more process gases to a process region defined in the plasma chamber. In some implementations, the upper electrode is coupled to a radio frequency (RF) power source through a matching network to receive RF power for generating a plasma in the process region with one or more process gases. The bottom of the plasma chamber includes a wafer receiving component, such as a pedestal, oriented opposite the upper electrode and defining a process region therebetween. The pedestal may be an electrostatic chuck (ESC) and includes a wafer receiving area defined thereon. The wafer is received on the wafer receiving area in a defined orientation for processing.

[0024] The edge ring is defined to include a plurality of ring segments. The edge ring is used to extend the process region from the edge of the wafer to the outer edge of the edge ring. The edge ring is positioned such that the top surface of the edge ring is flush with the top surface of the wafer when the wafer is received into the plasma chamber. Just as the wafer is received into the plasma chamber with a defined orientation, the edge ring is also positioned in the plasma chamber with a defined orientation. The defined orientation allows each ring segment of the edge ring to be adjacent to and match a corresponding region of the wafer. For example, a first ring segment is positioned adjacent to and match a corresponding first region of the wafer, and a second ring segment is positioned adjacent to and match a second region. In various embodiments described herein, the edge ring is designed to have different thicknesses for different ring segments. The thickness of each ring segment of the edge ring is defined to correspond to the orientation of features defined on the corresponding region of the wafer. For example, ring segments adjacent to regions of the wafer where features are parallel or substantially parallel to the wafer radius are defined to have a first thickness. Similarly, ring segments adjacent to regions of the wafer where features are perpendicular or substantially perpendicular to the wafer radius are defined to have a second thickness. The difference in thickness of different ring segments of the edge ring affects the ion flux and ion tilt in the respective regions of the wafer edge. By controlling the ion flux and ion tilt, the plasma sheath profile at the wafer edge is controlled. This results in a substantially uniform etch rate over a given area along the length of the wafer surface, including the wafer edge.

[0025] Various features of the edge ring will now be described with reference to the drawings.

[0026] 1A-1C show various plasma sheath profiles obtained for different shaped edge rings. To determine the optimal shape of the edge ring, it is useful to understand the different plasma sheath profiles formed at the wafer edge in different scenarios and identify the scenario that provides the optimal plasma sheath profile at the wafer edge. FIG. 1A-1C show plasma sheath profiles (i.e., ion flow profiles) at the wafer edge obtained from various experiments performed with edge rings of various thicknesses in some embodiments. FIG. 1A shows the plasma sheath profile (i.e., ion flow-plasma sheath profile A) at the edge of the wafer W when the edge ring is not adjacent to the wafer W. Note that in this figure, the plasma sheath profile A is curved downwards, indicating that the ion flux is concentrated along the wafer edge. Further experiments were performed and it was found that the increase in ion flux at the wafer edge correlated with the orientation of the features patterned on the wafer surface with respect to the radial direction of the wafer. For example, it was found that the etch rate was faster in certain areas where the features are parallel to the radial direction of the wafer and was nominal in other areas where the features are perpendicular to the radial direction of the wafer. The increased etch rate can result from an increased ion flux in those regions along the wafer edge.

[0027] 1B illustrates, in one embodiment, a plasma sheath profile (plasma sheath profile B) at the edge of a wafer W when a conventional edge ring having a flat ring profile (i.e., an edge ring having a uniform, nominal thickness along its entire circumference) is used adjacent to the wafer W. Plasma sheath profile B is shown as a straight line, indicating that the ion flux at different regions of the wafer edge is similar to the ion flux at the wafer center.

[0028] 1C shows a plasma sheath profile (plasma sheath profile C) along the edge of a wafer W when an edge ring of increased thickness (e.g., twice the rated thickness) is used in one embodiment. Plasma sheath profile C is shown bowed upward at the wafer edge, indicating that the ion flux is directed up from the wafer edge, away from the wafer edge, toward the edge ring surface.

[0029] Various experiments have shown that the plasma sheath profile is significantly affected by the presence of an edge ring and the thickness of the edge ring. Therefore, to address the different etch rates in different regions of the wafer edge, a conventional edge ring is redesigned to have different thicknesses in different sections to affect the etch rate at different parts of the wafer edge. Thus, according to some embodiments, the shape of the edge ring is designed to include multiple zones, each zone representing a ring segment. Each of the ring segments (i.e., zones) of the edge ring corresponds to a different region of the wafer. The ring segments are defined to have different thicknesses. For example, the thickness of the edge ring is increased in the ring segments that correspond to regions of the wafer where the features are parallel to the radial direction of the wafer. The increased thickness of these ring segments causes the ion flux to move away from the wafer edge in the corresponding regions. This redesigned shape is shown to level out the etch rate across the wafer, as described with reference to FIGS. 2-5.

[0030] FIG. 2 illustrates an overhead view of an edge ring 100 that, in some embodiments, is positioned adjacent to and surrounds a wafer W received in a plasma chamber for processing. The edge ring surrounding the wafer W is shown divided into four zones (zones 1-4, also referred to herein as "ring segments"). Each zone is defined to match a particular area on the adjacent wafer W. The wafer W includes a plurality of features defined thereon, one or more of which define electronic devices. FIG. 2 illustrates the orientation of features F1-F5 defined on the wafer W, indicated by sample numbers F1 through F5. The plurality of features illustrated in FIG. 2 is provided for purposes of illustrating the orientation of some features relative to the radial direction of the wafer. The wafer W may include five or more features. It should be noted that in some embodiments, the wafer W may have as many as 500 features or the like defined thereon. Each feature is oriented relative to the x-axis and the y-axis. For example, as shown in FIG. 2, features F1 and F3 are shown to be located along the x-axis and parallel to the radial direction of the wafer defined along the x-axis. Features F2 and F4 are shown to be located along the y-axis and perpendicular to the radial direction of the wafer, and feature F0 is located at the center of the wafer, which is the intersection of the xy axes (i.e., perpendicular to the y-axis and parallel to the x-axis). Features patterned on the wafer may be asymmetric and include, for example, vias, trenches, slits, etc., between word line cuts. The zones on the edge ring shown in FIG. 2 (zones 1-4) are all shown to be of equal size, but are not necessarily identical.

[0031] 3A-3C show simplified cross-sectional side views of an edge ring in some embodiments, which are linearly expanded to show the variation in height of different portions of the edge ring. The edge ring is defined to have a different shape than a conventional edge ring. Specifically, the edge ring depicted in FIGS. 3A-3C is asymmetric in that the thickness of the edge ring varies and is non-uniform along the circumference. The asymmetry of the edge ring is defined to compensate for the asymmetry of the features patterned on the wafer W. In contrast, a conventional edge ring is defined to be axially symmetric, in that the thickness of the edge ring is uniform along the circumference.

[0032] The asymmetric design of the edge ring 100 is achieved by dividing the edge ring 100 into multiple ring segments. Each ring segment is defined to match a certain area of ​​the wafer on which features are to be formed. Each of the multiple ring segments is defined to have a specific thickness, and the thickness of any two consecutive ring segments is different. FIG. 3A shows the edge ring 100 divided into four ring segments (represented as zones 1-4) according to some embodiments. The angles depicted in FIG. 3A correspond to the edge ring angles identified in FIG. 2. The number and size of the ring segments are determined based on the variation in etch rate observed in different regions along the edge of the wafer received adjacent the edge ring. Thus, the number of ring segments (i.e., four ring segments or zones) shown in FIG. 3A is provided only as an example, and additional ring segments may be added if necessary. As discussed above, it is observed that the etch rate of different portions of the wafer edge varies based on the orientation of the features formed on the wafer relative to the radial direction of the wafer. For example, the etch rate is observed to be faster at portions of the wafer edge where the features are substantially parallel to the wafer radius, and similarly, the etch rate is observed to be at a nominal value (i.e., typical or nominal value) at portions of the wafer edge where the features are substantially perpendicular to the wafer radius.

[0033] As a result, various ring segments are defined on the edge ring 100 to match corresponding regions of the wafer where different etch rates are observed along the wafer edge. A first pair of ring segments (designated as zones 1 and 3) are defined on the edge ring 100 to match a corresponding first set of regions of the wafer edge where the patterned features are substantially parallel to the wafer radius. The first set of regions at the wafer edge are where faster etch rates are observed. A second pair of ring segments (designated as zones 2 and 4) are defined on the edge ring to match a corresponding second set of regions at the wafer edge where the patterned features are substantially perpendicular to the wafer radius. The second set of regions at the wafer edge are where the rated etch rate (i.e., nominal or typical, not faster) is observed. Zones 1 and 3, representing the first set of ring segments, are aligned along a horizontal axis, and zones 2 and 4, representing the second set of ring segments, are aligned along a vertical axis.

[0034] An edge ring is shown in FIG. 3A with zones 1-4 defined relative to the angle of the circular edge ring. Note that in this application, zone and ring segment are used interchangeably to refer to a section or portion of the edge ring. In the embodiment shown in FIG. 3A, zones 1-4 are shown as being of equal size. The zones are not always of equal size because the effect of the ion flux affects only a small portion of the wafer area while the remaining majority has the rated etch rate. Thus, the size of zones 1-4 may vary, as will be described with reference to FIG. 3C.

[0035] As mentioned above, edge etch rate variations in different regions of the wafer can be attributed to several factors, including gas flow direction, ion direction, and device orientation as defined by features patterned on the wafer. The shape of the edge ring 100 is purposefully altered in certain ring segments that coincide with regions of the wafer that have a faster edge etch rate to "compensate" for the faster etch rate and make the etch rate in those regions similar to the other regions of the wafer. The shape of the edge ring is altered by increasing the edge ring thickness in zones 1 and 3 (i.e., the first set of ring segments) and maintaining the nominal thickness in zones 2 and 4 (i.e., the second set of ring segments). A transition region is defined at the interface between the increased thickness and the nominal thickness. Thus, at each successive pair of interfaces of the zones, a transition region is defined. The transition region extends from a first transition point (TPa) to a second transition point (TPb) as a transition length (not shown). At the first transition point TPa, the thickness is increased, and at the second transition point TPb, the thickness is at the nominal value. Furthermore, the transition between the first transition point TPa and the second transition point TPb is smooth and gradual, not linear or abrupt. That is, the transition points TPa and TPb do not have straight edges, but are smoothly curved.

[0036] FIG. 3B provides additional details of the ring segments defined in the edge ring 100. As discussed above, in some embodiments, a transition region is defined between each pair of consecutive ring segments (represented as zones) defined in the edge ring 100. A transition region TR1 is defined at a first interface between zone 1 and zone 2, and a transition region TR2 is defined at a second interface between zone 2 and zone 3. Each transition region transitions between an increased thickness ring segment and a nominal thickness ring segment. In some embodiments, the increased thickness of a first pair of ring segments represented by zones 1 and 3 is defined to be a height "h1" and the nominal thickness of a second pair of ring segments represented by zones 2 and 4 is defined to be a height "h2", where height h1 is greater than thickness h2. As discussed above, the increased thickness in certain portions of the edge ring (i.e., zones 1 and 3) is intended to slow the edge etch rate in those regions of the wafer edge. Since edge etch rate is affected by the direction of ion flow, increasing the thickness of edge ring 100 in zones 1 and 3 directs the ion flow away from the wafer edge and upwards rather than towards the edge ring, resulting in an edge ring shape with a compensatory asymmetry to the asymmetry of the features patterned on the wafer, as previously described.

[0037] In the embodiment depicted in Figures 3A and 3B, each of zones 1-4 covers an equal portion of the edge ring. Thus, each zone is defined to cover approximately 90° of the circumference of edge ring 100. Thus, zones 1 and 3 of edge ring 100, which are disposed opposite each other, cover one-quarter of the circumference of edge ring 100. Similarly, zones 2 and 4 of edge ring 100, which are disposed opposite each other, each cover one-quarter of the circumference of edge ring 100.

[0038] FIG. 3C illustrates an alternative embodiment in which a first pair of edge ring segments represented by zones 1 and 3 have a different size than a second pair of edge ring segments represented by zones 2 and 4. Each zone of the first pair (i.e., zones 1 and 3) is defined by a first size, and each zone of the second pair (i.e., zones 2 and 4) is defined by a second size, the first size being smaller than the second size. In some embodiments, zones 1 and 3 are defined to cover one-half the size covered by zones 2 and 4. For example, if zones 2 and 4 each cover about 120° of the circumference of edge ring 100, then zones 1 and 3 each cover about 60° of the circumference of edge ring 100. In an alternative embodiment, zones 1 and 3 are defined to cover one-fifth the size covered by zones 2 and 4. Of course, the size of each zone of the first and second pairs is determined by the areas of the wafer that have similar etch rate characteristics (i.e., a faster etch rate relative to the nominal etch rate).

[0039] FIG. 4A is a top view of edge rings 100 having various shapes that are used in a plasma chamber in some embodiments. The edge ring is divided into different zones similar to those shown in FIG. 3C, each zone representing an edge ring segment. The zone division lines are represented by lines CC and DD. As described with reference to FIG. 3C, zones 1 and 3 are part of a first pair of ring segments, oriented opposite each other and aligned along a horizontal axis. Zones 2 and 4 are part of a second pair of ring segments, oriented opposite each other and aligned along a vertical axis. The edge ring is received in the plasma chamber in a defined orientation. In some embodiments, the defined orientation is determined relative to a wafer notch that is used to orient the wafer when it is received in the plasma chamber. As described in FIG. 4A, zones 1 and 3 are of equal size, and zones 2 and 4 are of equal size. However, zone 1 is smaller than zone 2. Although not shown in FIG. 4A, the thickness of the edge ring in zones 1 and 3 is greater than the thickness of the edge ring in zones 2 and 4.

[0040] 4B illustrates transition regions defined between each pair of consecutive zones in some embodiments. The transition regions are depicted between lines C1-C1, C2-C2, D1-D1, and D2-D2. For example, transition region 1 (TR1) is defined at the interface of zones 1 and 2, TR2 at the interface of zones 2 and 3, TR3 at the interface of zones 3 and 4, and TR4 at the interface of zones 4 and 1. Additionally, the orientation of the zones is shown relative to the radians of the edge ring 100. Zone 1 is shown symmetrically oriented around 0°, zone 2 symmetrically oriented around 90°, zone 3 symmetrically oriented around 180°, and zone 4 symmetrically oriented around 270°.

[0041] FIG. 4C illustrates the orientation of the zones relative to radians of a circular edge ring in some embodiments. As previously described, the zones are separated by transition regions defined at the interface between two consecutive zones. Thus, an edge ring with four zones defined thereon has four transition regions TR1-TR4. Each transition region spans a transition length from a first transition point (TPa) at the increased thickness to a second transition point (TPb) at the nominal thickness. In some embodiments, the transition length is defined to be between about 1 mm and about 3 mm. In some embodiments, the angle of the slope between TPa and TPb in the transition region is defined to be between about 30° and about 40°. In other embodiments, the angle of the slope between TPa and TPb depends on the increased thickness h1, the nominal thickness h2, and the length of the transition region. In some embodiments, zones 1 and 3 of the first pair of ring segments are defined at an angle of about α° from the horizontal axis (i.e., the x-axis). Zones 2 and 4 of the second pair of ring segments are defined to be about (180°-α°). In some implementations, α° is defined to be an acute angle. In some implementations, α° is defined to be about 15°. In alternative implementations, α° is defined to be about 30°. In still other implementations, α° is defined to be between about 15° and about 30°. In some implementations, the increased thickness h1 defined in zones 1 and 3 is defined to be between about 6.7 mm and about 7.7 mm. In some implementations, the nominal thickness h2 defined in zones 2 and 4 is defined to be between about 6.3 mm and about 7.0 mm. Of course, the various dimensions contained herein are provided by way of example and should not be considered limiting or restrictive. Furthermore, the use of the term "about" to define various dimensions may include a variation of ±15% of the defined range. In some implementations, the edge ring is made of silicon. In other implementations, the edge ring may include silicon and other polysilicon materials.

[0042] FIG. 5 provides a simplified tabular summary of the effect of edge rings and edge ring thickness on etch rate in some embodiments. As previously described, row 1 shows the etch rate on the wafer edge when a flat edge ring (i.e., an axisymmetric edge ring) is used adjacent to and surrounding the wafer in a plasma chamber. The etch rate varies along different regions of the wafer, with zones 1 and 3 exhibiting faster etch rates and zones 2 and 4 exhibiting nominal etch rates. Row 2 shows a multi-level edge ring shape that is used to address the various etch rates observed at the wafer edge. In this case, the etch rate can be uniform across the wafer. As previously described, the edge ring is defined into multiple zones, each zone corresponding to a certain area of ​​the wafer. The edge ring thickness increases to a height h1 in zones 1 and 3 and remains at a height h2 in zones 2 and 4. The edge ring is oriented in a plasma chamber so that the various zones correspond to corresponding areas of the wafer and affect the etch rate at the corresponding areas of the wafer edge. For example, zones 1 and 3 are positioned adjacent to and match areas of the wafer having a faster etch rate, while zones 2 and 4 are positioned adjacent to and match areas of the wafer edge having a nominal etch rate.

[0043] The third row shows the etch rates obtained at different regions of the wafer edge when a multi-level edge ring is used in the plasma chamber in some embodiments. With a multi-level edge ring, it is observed that all regions of the wafer edge corresponding to corresponding zones of the multi-level edge ring exhibit the nominal etch rate. For example, the regions on the wafer edge corresponding to zones 1 and 3 exhibit a decrease in etch rate from the faster etch rate shown in the first row to the nominal etch rate shown in the third row.

[0044] As previously mentioned, the newly designed shape makes the edge ring asymmetric to compensate for the asymmetry of the features patterned on the wafer, as opposed to the axially symmetric configuration of the conventional edge ring. The height of the raised portion of the edge ring is optimized to reduce the etch rate in areas of the wafer that have been shown to have a faster etch rate. The new edge ring design achieves a substantially uniform etch rate across the entire surface of the wafer, including various portions of the wafer edge, by reducing ion tilt and optimizing the ion flux at the wafer edge.

[0045] The foregoing description of various embodiments is provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the described technology. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, may be interchangeable and used in the selected embodiment even if not specifically shown or described. The same may also be subject to various modifications. Such modifications are not to be considered as departures from the embodiments described, and all such modifications are intended to be included within the scope of the embodiments described.

[0046] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. Thus, the present embodiments are to be considered as illustrative and not restrictive, and the present embodiments should not be limited to the details given herein, but may be modified within the scope of the claims and their equivalents.

Claims

1. An edge ring surrounding a wafer in a plasma chamber, comprising: a first pair of edge ring segments, each of the first pair of edge ring segments having a first thickness; a second pair of edge ring segments, each of the second pair of edge ring segments having a second thickness, the first pair of edge ring segments being oriented opposite one another, and the second pair of edge ring segments being oriented opposite one another; Equipped with An edge ring, wherein each of the first pair of edge ring segments is positioned adjacent to each of the second pair of edge ring segments, and each of the second pair of edge ring segments is positioned adjacent to each of the first pair of edge ring segments.

2. 2. The edge ring of claim 1, An edge ring, wherein a transition region is defined as a junction region of the first thickness and the second thickness.

3. 3. The edge ring of claim 2, an edge ring, the transition region as the junction region spanning a transition length from a first transition point to a second transition point, the first transition point being defined at the first thickness and the second transition point being defined at the second thickness.

4. 4. The edge ring of claim 3, The transition length ranges from about 1 mm to about 3 mm.

5. 4. The edge ring of claim 3, The transition region includes a slope of between about 30° and about 40° between the first transition point and the second transition point of the junction region.

6. 2. The edge ring of claim 1, The first thickness is greater than the second thickness.

7. 2. The edge ring of claim 1, an edge ring, wherein each of the first pair of edge ring segments has a first size and each of the second pair of edge ring segments has a second size, the first size being smaller than the second size.

8. 2. The edge ring of claim 1, the first pair of ring segments are aligned along a horizontal axis and the second pair of ring segments are aligned along a vertical axis; each of the first pair of ring segments is positioned to cover an area subtending an acute angle about the horizontal axis; Edge ring.

9. 2. The edge ring of claim 1, An edge ring, wherein the first pair of ring segments define a first zone and a third zone, and the second pair of ring segments define a second zone and a fourth zone.

10. 2. The edge ring of claim 1, The edge ring, wherein the first thickness is defined to be between about 6.7 mm and about 7.7 mm, and the second thickness is defined to be between about 6.3 mm and about 7.0 mm.

11. 1. A plasma chamber for processing a wafer, comprising: an upper electrode defined at a top thereof for supplying a process gas into said plasma chamber; a pedestal defined at a bottom thereof and oriented opposite the upper electrode, the pedestal having a wafer receiving area defined thereon; an edge ring adjacent to and surrounding the wafer receiving area; Equipped with The edge ring is a first pair of edge ring segments, each of the first pair of edge ring segments having a first thickness; a second pair of edge ring segments, each of the second pair of edge ring segments having a second thickness, the first pair of edge ring segments being oriented opposite one another, and the second pair of edge ring segments being oriented opposite one another; Including, each of the first pair of edge ring segments is disposed adjacent to each of the second pair of edge ring segments, and each of the second pair of edge ring segments is disposed adjacent to each of the first pair of edge ring segments; Plasma chamber.

12. 12. The plasma chamber of claim 11, The edge ring is positioned within the plasma chamber such that the first pair of edge ring segments and the second pair of edge ring segments are in a predetermined orientation.

13. 12. The plasma chamber of claim 11, the first thickness is greater than the second thickness; A plasma chamber, wherein each of the first pair of edge ring segments is defined by a first size and each of the second pair of edge ring segments is defined by a second size.

14. 14. The plasma chamber of claim 13, The first dimension is smaller than the second dimension.

15. 14. The plasma chamber of claim 13, The first dimension is equal to the second dimension of the plasma chamber.

16. 1. An edge ring for surrounding a wafer in a plasma chamber, comprising: a first zone having a first thickness; a second zone having a second thickness; a third zone defined opposite the first zone and having the first thickness; a fourth zone defined opposite the second zone and having the second thickness, the second zone and the fourth zone each being adjacent to the first zone and the third zone and defined between the first zone and the third zone; a transition region defined between successive pairs of each of the first zone, the second zone, the third zone, and the fourth zone; Including the edge ring.

17. 17. The edge ring of claim 16, The first thickness is greater than the second thickness.

18. 17. The edge ring of claim 16, The edge ring, wherein the first zone and the third zone are aligned along a horizontal axis and the second zone and the fourth zone are aligned along a vertical axis.

19. 17. The edge ring of claim 16, The transition region extends from a first transition point defined at the first thickness to a second transition point defined at the second thickness.

20. 17. The edge ring of claim 16, an edge ring, wherein the first zone and the third zone each have a first size, and the second zone and the fourth zone each have a second size, the first size being smaller than the second size.

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