Patent Application
20240014015
The invention relates to a confinement ring used in a semiconductor process module.
In semiconductor processing, a substrate undergoes various operations to form features that define integrated circuits. For example, for a deposition operation, the substrate is received into a processing chamber and, depending on type of feature to be formed, specific types of reactive gases are supplied to the chamber and a radio frequency power is applied to generate plasma. The substrate is received on a substrate support defined on a lower electrode, such as an electro static chuck. An upper electrode, such as a showerhead, is used to provide the specific types of reactive gases into the process chamber. A radio frequency power is applied to the reactive gases through a corresponding match network to generate the plasma used to selectively deposit ions over a surface of the substrate to form microscopic features. The reactive gases generate by-products, such as particulates and gases, etc., which need to be promptly removed from the plasma chamber in order to maintain the integrity of the microscopic features formed on the surface of the substrate.
To confine the generated plasma within a process region, a set of confinement rings are defined to surround the process region. Further, to improve the yield and to ensure the bulk of the plasma is over the substrate received for processing, the confinement rings surrounding the plasma region may be designed to extend the process region so as to cover not only the region above the substrate but also the region over an edge ring disposed to surround the substrate, when received for processing, and an outer confinement ring disposed adjacent to the edge ring. The set of confinement rings not only act to confine the plasma within the process region but also act to protect the inside structure of the processing chamber, including chamber walls.
The integrity of the features formed on the surface of the substrate relies on uniform plasma density in the process region. Plasma uniformity can be modulated by adjusting the shape of a confinement ring (e.g., C-shroud) to increase the volume of the process region. However, any changes to the shape or design of the confinement ring to increase the size of the volume in the confinement ring, for example, may require significant changes to the hardware used within the processing chamber, such as processing chamber spacer plate, mating hardware, etc.). Alternately, changes to the design of the confinement ring may result in compromising the mechanical strength, or reducing the lifetime of the confinement ring.
It is in this context that embodiments of the invention arise.
Various implementations of the invention define a design of a confinement ring used in a plasma processing chamber for confining plasma within a plasma region. The confinement ring is defined to include a upper horizontal section that extends between a outer radius and an upper inner radius, a lower horizontal section that extends between the outer radius and a lower inner radius, and a vertical section extending between a bottom surface of the upper horizontal section and a top surface of the lower horizontal section defined at the outer radius. The top surface of the lower horizontal section of the confinement ring is defined by a slope that is defined by an angle provided along the top surface down toward the lower inner radius. The slope results in a difference in the thickness of the lower horizontal section, wherein the thickness of the lower horizontal section near an inside radius of the confinement ring is greater than the thickness of the lower horizontal section at the lower inner radius. In some implementations, a bottom surface of the lower horizontal section is defined to be flat. Alternately, in addition to defining the slope at the top surface, a second slope is defined along a bottom surface of the lower horizontal section. The second slope is formed by a second angle provided along the bottom surface down toward the lower inner radius. The second slope at the bottom surface may be defined by adding additional material used for the confinement ring. The formation of the second slope along the bottom surface of the lower horizontal section, in some implementations, results in a thickness of the lower horizontal section near the inside radius to be equal to the thickness of the lower horizontal section at the lower inner radius. In alternate implementations, the formation of the second slope along the bottom surface of the lower horizontal section may result in the thickness of the lower horizontal section near the inside radius to be different from the thickness of the lower horizontal section near the lower inner radius. Modifying the shape of the confinement ring by including sloped geometry for the lower horizontal section assists in modulating the plasma uniformity within the plasma region without requiring re-designing of other hardware components of the plasma processing chamber. Further, the modifications done to the lower horizontal section, (e.g., defining sloped surface along both the top and bottom surface of the lower horizontal section) avoids adversely affecting the mechanical strength or the lifetime of the consumable confinement ring.
The lower horizontal section includes a plurality of slots defined along the length of the lower horizontal section. Each slot is defined to extend radially from an inner diameter to an outer diameter along the lower horizontal section and vertically between the top surface and the bottom surface of the lower horizontal section. The plurality of slots is used to remove the by-products and neutral gas species generated within the plasma region while ensuring optimal confinement of the plasma in the plasma region. In some implementations, each of the slots may be defined to include parallel slot geometry, in that an inner slot radius defined at the inner diameter is equal to an outer slot radius defined at the outer diameter. In alternate implementations, in addition to including sloped geometry for the lower horizontal section, the plurality of slots is defined using tapered slot geometry. The tapered slot geometry is beneficial as the slots experience differential wear along the length of the slot due to constant exposure to the plasma. The tapered slot geometry assists in optimally managing the limited space between the slots while improving the lifetime of use of the confinement ring.
For instance, the wear of the slot is greater at the inner diameter than at the outer diameter. This uneven wear may be attributed to the variance in the volume of plasma near the inner diameter of the slot as opposed to the outer diameter. When the wear reaches critical dimension, the confinement ring needs to be replaced to ensure plasma unconfinement does not occur. The tapered geometry of the slots assists in addressing the uneven wear while extending the lifetime of the confinement ring. The tapered slot geometry makes efficient use of the area around the slot by defining a narrow end at the inner diameter and a broader end at the outer diameter. The tapered geometry allows the narrow end of the slot to approach the critical dimension at about the same time as the broader end of the slot, resulting in the entire slot length reaching the critical confinement dimension at end of life. The tapered slot geometry makes efficient use of the area around the slot—especially at the outer diameter, thereby extending the usage life of the confinement ring while maintaining optimal plasma confinement within the plasma region. Consequently, the cost associated with the consumable confinement ring is lowered as the number of process cycles the confinement ring can be used in the plasma processing chamber is extended. Thus, with the modifications to the confinement ring structure (i.e., including the tapered slot profile and the sloped lower horizontal section) an original lifetime expectancy of the confinement ring is maintained (i.e., lifetime of the confinement ring is not compromised) without requiring re-design of other hardware components of the plasma processing chamber.
In one implementation, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring includes an upper horizontal section, a lower horizontal section and a vertical section. The upper horizontal section extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal section extends between a lower inner radius and the outer radius of the confinement ring. A top surface of the lower horizontal section provides for an angle down toward the lower inner radius, wherein the angle defines a slope along the top surface. The lower horizontal section includes an extension section that extends downward along the lower inner radius. The vertical section is disposed between the outer radius and an inside radius of the confinement ring. The vertical section connects the upper horizontal section to the lower horizontal section of the confinement ring.
In one implementation, a bottom surface of the lower horizontal section is flat, such that a first thickness of the lower horizontal section near the inside radius is greater than a second thickness of the lower horizontal section at the lower inner radius.
In one implementation, the first thickness is greater by about 10% to about 40% of the second thickness.
In one implementation, the angle defines a slope along the top surface of the lower horizontal section. The slope is defined to be between about 0.20° and about 1° measured from a horizontal x-axis.
In one implementation, a bottom surface of the lower horizontal section provides for a second angle down toward the lower inner radius. The second angle defines a second slope. The second angle of the second slope defined on the bottom surface is equal to the angle of the slope defined on the top surface of the lower horizontal section, such that a first thickness of the lower horizontal section near the inside radius is equal to a second thickness of the lower horizontal section defined at the lower inner radius.
In one implementation, a first height defined between a bottom surface of the upper horizontal section and the top surface of the lower horizontal section near the inside radius is less than a second height defined between the bottom surface of the upper horizontal section and the top surface of the lower horizontal section at the lower inner radius of the confinement ring.
In one implementation, the lower horizontal section, the upper horizontal section and the vertical section are integrally connected to define a C-shaped structure configured to confine plasma generated in the plasma processing chamber.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot of the plurality of slots extends radially from an inner diameter to an outer diameter along the lower horizontal section. An inner slot radius of each slot at the inner diameter is equal to an outer slot radius at the outer diameter.
In one implementation, the inner diameter of the slot is greater than an inner ring diameter defined by the lower inner radius, and the outer diameter of the slot is less than an outer ring diameter defined by the outer radius of the confinement ring.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot of the plurality of slots extends radially from an inner diameter to an outer diameter along the lower horizontal section. An inner slot radius of each slot at the inner diameter is less than an outer slot radius at the outer diameter.
In one implementation, a difference in the inner slot radius and the outer slot radius of each slot defines a slot taper, such that each slot tapers down from the outer diameter to the inner diameter. The inner slot radius and the outer slot radius influencing the slot taper are sized to be an inverse of a wear rate at the corresponding inner diameter and the outer diameter of the slot. A ratio of the inner slot radius to the outer slot radius is between about 1:1.1 and about 1:1.5.
In one implementation, the upper inner radius is greater than the lower inner radius of the confinement ring.
In one implementation, the extension section defined in the lower horizontal section extends vertically downward at the lower inner radius.
In one implementation, the extension section defined in the lower horizontal section is defined by an angled top section and a vertical bottom section. The angled top section provides a third angle down at a downward incline point defined on the top surface of the lower horizontal section at the lower inner radius and the vertical bottom section is defined to extend downward from a bottom portion of the angled top section.
In one implementation, a top surface of the upper horizontal section includes a plurality of holes. Each hole of the plurality of holes is configured to receive a portion of a fastener means defined on a bottom surface of the upper electrode for coupling the confinement ring to the upper electrode of the plasma processing chamber.
In one implementation, the extension section of the lower horizontal section is configured to rest on a radio frequency gasket defined on a top surface of a lower electrode of a plasma processing chamber.
In another alternate implementation, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring includes an upper horizontal section, a lower horizontal section and a vertical section. The upper horizontal section extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal section extends between a lower inner radius and the outer radius of the confinement ring. A top surface of the lower horizontal section provides for a first angle down toward the lower inner radius to define a first slope along the top surface. A bottom surface of the lower horizontal section provides for a second angle down toward the lower inner radius to define a second slope along the bottom surface. The lower horizontal section includes an extension section that extends down along the lower inner radius. The vertical section is disposed between the outer radius and an inside radius of the confinement ring. The vertical section connects the upper horizontal section to the lower horizontal section of the confinement ring.
In one implementation, the first angle of the first slope is equal a second angle of the second slope.
In one implementation, a first thickness of the lower horizontal section near the insdie radius is equal to a second thickness of the lower horizontal section at the lower inner radius. A first height defined between a bottom surface of the upper horizontal section and the top surface of the lower horizontal section near the inside radius is less than a second height defined between the bottom surface of the upper horizontal section and the top surface of the lower horizontal section at the lower inner radius.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot of the plurality of slots extends radially from an inner diameter to an outer diameter along the lower horizontal section. An inner slot radius of each slot at the inner diameter is equal to an outer slot radius of each slot at the outer diameter. The inner diameter of each slot is greater than an inner ring diameter of the confinement ring defined by the lower inner radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by the outer radius.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot of the plurality of slots extends radially from an inner diameter to an outer diameter along the lower horizontal section. An inner slot radius of each slot at the inner diameter is less than an outer slot radius at the outer diameter.
In yet another alternate implementation, a plasma processing chamber for confining plasma within is disclosed. The plasma processing chamber includes a lower electrode for supporting a substrate and an upper electrode disposed over the lower electrode. The plasma processing chamber includes a confinement ring disposed between the lower electrode and the upper electrode. The confinement ring includes an upper horizontal section, a lower horizontal section, and a vertical section. The upper horizontal section extends between an upper inner radius and an outer radius of the confinement ring. The lower horizontal section extends between a lower inner radius and the outer radius of the confinement ring. A top surface of the lower horizontal section provides an angle down toward the lower inner radius. The angle defines a slope along the top surface. The lower horizontal section has an extension section that extends down along the lower inner radius. The vertical section is disposed between the outer radius and an inside radius of the confinement ring. The vertical section connects the upper horizontal section and the lower horizontal section of the confinement ring.
In one implementation, a bottom surface of the lower horizontal section provides a second angle down toward the lower inner radius. The second angle defines a second slope along the bottom surface. The second angle of the second slope defined along the bottom surface is equal to an angle of the slope defined on the top surface of the lower horizontal section.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot of the plurality of slots is designed to extend radially from an inner diameter to an outer diameter along the lower horizontal section. An inner slot radius of each slot at the inner diameter is less than an outer slot radius of each slot at the outer diameter.
In one implementation, the inner diameter of each slot is greater than an inner ring diameter defined by the lower inner radius of the confinement ring, and the outer diameter of the slot is less than an outer ring diameter defined by the outer radius of the confinement ring.
In one implementation, the upper inner radius is greater than the lower inner radius of the confinement ring.
In one implementation, the lower horizontal section, the vertical section and the upper horizontal section of the confinement ring defines a contiguous C-shaped structure for confining plasma to a plasma region defined in the plasma processing chamber. The confinement ring is made from one of silicon, or polysilicon, or silicon carbide, or boron carbide, or ceramic, or aluminum.
In one implementation, the extension section is integral with the lower horizontal section, the vertical section and the upper horizontal section of the confinement ring. The extension section is configured to extend vertically below a bottom surface of the lower horizontal section.
In one implementation, the upper electrode is electrically grounded and the lower electrode is connected to a radio frequency power source through a corresponding match network.
In the various implementations described herein, a confinement ring for use in a plasma processing chamber is designed to improve the usage life of the confinement ring while ensuring optimal plasma confinement within a plasma region defined in the plasma processing chamber. The confinement ring used in the plasma processing chamber includes an upper horizontal section, a vertical section and a lower horizontal section. The upper horizontal section is defined to extend from an outer radius to an upper inner radius and a top surface and a bottom surface of the upper horizontal section is defined to be flat. The lower horizontal section is defined to extend from the outer radius to a lower inner radius. The vertical section is disposed between the outer radius and an inside radius of the confinement ring and connects the upper horizontal section to the lower horizontal section of the confinement ring. A top surface of the lower horizontal section includes a tapered geometry to define a slope that slopes down toward the lower inner radius. The slope defined at the top surface results in a variation in thickness of the lower horizontal section of the confinement ring near the inside radius and the lower inner radius. Additionally, the slope results in a variation in a height of the gap defined between a bottom surface of the upper horizontal section and the top surface of the lower horizontal section near the inside radius and at the lower inner radius. The variation in the height results in an increase in the volume of the plasma generated in the plasma region, particularly in the region covered by the confinement ring (e.g., over the edge exclusion region of the substrate, when present in the plasma processing chamber, and in the region over an edge ring surrounding the substrate).
Increasing the gap in the confinement ring positively affects the plasma uniformity. The plasma uniformity may be attributed to changes in the plasma diffusion due to the increased volume within the plasma region. Thus, plasma uniformity can be modulated by changing a shape of the confinement ring used to confine the plasma in the plasma region without requiring re-designing other hardware components of the plasma processing chamber. Existing methods for changing the conventional design of the confinement ring require significant changes to the hardware, or result in compromising mechanical strength and consequently the lifetime of the confinement ring.
Select changes are made to the confinement ring (e.g., including a slope along a lower horizontal section of the confinement ring) to increase the volume of the plasma. The changes made to the confinement ring do not require modification to any other hardware component (e.g., chamber spacer plate, mating hardware, etc.,) within the plasma processing chamber as the changes made to the confinement ring structure do not substantially deviate from the overall structure of confinement ring. Additional improvements may be made to a bottom surface of the lower horizontal section by including a slope, in some implementations, to improve the mechanical strength of the confinement ring and the overall lifetime of the confinement ring. The slope may be defined in the bottom surface by adding additional material of the confinement ring along the length of the bottom section so as to provide an angle down toward the lower inner radius. The additional material in the bottom surface is designed to increase the thickness of the lower horizontal section so as to provide overall thickness uniformity along the length of the lower horizontal section while continuing to maintain the slope at the lower horizontal section.
The lower horizontal section includes a plurality of slots for efficient removal of by-products from the plasma region while preserving plasma confinement within the plasma region. The slots are defined to extend lengthwise from an inner diameter to an outer diameter along the lower horizontal section and depth-wise between the top surface and the bottom surface of the lower horizontal section so as to provide the conduit for the by-products out of the plasma region. The slots, in some implementation, may be defined to include parallel slot geometry along the length, wherein the inner slot radius at the inner diameter is the same as the outer slot radius at the outer diameter. In alternate implementations, the slots may be defined to include tapered slot geometry, such that the slot is narrow at the inner diameter and is broad at the outer diameter. The broader side at the outer diameter has a broader outer slot radius and the narrow side at the inner diameter has a narrow inner slot radius. The inner slot radius at the inner diameter and the outer slot radius at the outer diameter of each slot are sized to be an inverse of the wear rate at the corresponding inner diameter and the outer diameter. By starting with a narrower slot at the inner diameter allows for more wear to occur at the inner diameter before critical dimension for plasma un-confinement is reached. At end of the usage life, the smaller inner slot radius at the inner diameter compensates for the high wear rate at the inner diameter while the broader outer slot radius compensates for the low wear rate at the outer diameter thereby resulting in a straight slot profile along the length of the slot. The difference in the inner slot radius and the outer slot radius results in each slot along the entire slot length to reach the confinement limit at the same time. The tapered slot may result in some open area along the narrow side. To compensate for the open area along the narrow side, the total number of slots may be increased. The increase in the total number of slots takes into consideration the amount of wear anticipated along the narrow side of the tapered slots.
The modified confinement ring structure with the sloped geometry along the length of the lower horizontal section and the tapered slot geometry of the plurality of slots defined along the length of the lower horizontal section results in, (a) overall improvement in the plasma uniformity, (b) efficient removal of the by-products, and (c) overall improvement in the lifetime of the confinement ring. The aforementioned benefits are realized without requiring re-design of other hardware components (e.g., chamber spacer plate, mating hardware, etc.,) within the plasma processing chamber. With the aforementioned overview of the invention, specific implementations will now be described with reference to the various figures.
In one implementation, a top surface of the lower electrode 104 defines a substrate support surface on which a substrate 110 is received for processing. An edge ring 112 is defined adjacent to the substrate support surface of the lower electrode 104 so as to surround the substrate 110, when the substrate 110 is received for processing. The top surface of the edge ring 112 is defined to be co-planar with a top surface of the substrate 110, when the substrate is supported on the substrate support surface of the lower electrode 104. The edge ring 112 is configured to extend the processing region for the plasma (represented by the plasma region 108) generated within the plasma processing chamber 100 to extend over an area that is beyond an edge of the substrate to an extended processing region covering an outer edge of the edge ring 112 and beyond. One or more dielectric rings 120 are disposed adjacent to the outer edge of the edge ring 112. RF power source 106 is connected to a bottom portion of the lower electrode via the match network 107 and provides RF power to the plasma processing chamber 100. A ground ring 122 is disposed adjacent to and below a portion of the one or more dielectric rings 120 and is configured to surround the lower electrode 104. A support structure 118 is disposed to surround a portion of the ground ring 122 of the lower electrode 104. A RF gasket 116 is disposed on a top surface of the support structure 118. In some implementation, the RF gasket 116 may be disposed within a channel defined on the top surface of the support structure 118. The support structure 118 may be made of a quartz element or any other insulation material that is suitable for use in the plasma processing chamber 100.
In one implementation, the upper electrode 102 may be a showerhead that includes one or more inlets (not shown) connected to one or more process gas sources (not shown) and a plurality of outlets distributed at a bottom surface of the upper electrode 102 facing the lower electrode 104. The plurality of outlets are configured to supply the process gases from the one or more process gas sources to a plasma processing region (or simply referred to as “plasma region”) 108 defined between the upper electrode 102 and the lower electrode 104. The upper electrode 102 may be made up of a plurality of electrodes.
The confinement ring structure (or simply referred to henceforth as “confinement ring”) 140 is disposed between the upper electrode 102 and the lower electrode 104. The confinement ring 140 defines a confined chamber volume in which the plasma generated in the chamber is sufficiently contained. The confinement chamber volume defines the plasma region 108. The confinement ring 140 is a C-shaped structure with an opening of the C-shape facing an inside of the plasma region 108 defined between the upper and the lower electrodes 102, 104, of the processing chamber 100. Based on the shape of the confinement ring 140 and the function to confine the plasma to an area, the confinement ring may also be referred to as a “C-shroud”. The confinement ring 140 is used to confine the plasma within an extended plasma region 108 in the plasma processing chamber 100. The confinement ring 140 is configured to be coupled at the top to the outer electrode 102b that is part of the upper electrode 102. The confinement ring 140 is part of the upper electrode 102 and a bottom section of the confinement ring 140 is configured to rest on a top surface of a support structure 118 of the lower electrode 104. An RF gasket 116 is provided on the top surface of the support structure 118 to provide a tight coupling between the upper electrode 102 and the lower electrode 104, when the plasma processing chamber 100 is to be engaged for processing. The RF gasket 116 ensures that the coupling between the upper and the lower electrodes 102, 104 is air-tight. In one implementation, the support structure 118 is configured to surround a region of the lower electrode 104 that includes at least the substrate support surface, the edge ring 112, the one or more dielectric rings 120, and the ground ring 122.
It is to be noted that the plasma processing chamber of
Broadly speaking, the confinement ring 140 includes an upper horizontal section 141, a vertical section 142, and a lower horizontal section 143. The upper horizontal section 141 extends a first length and is defined by a bottom surface 141a that faces the plasma region 108 and a top surface 141b that faces away from the plasma region 108. A plurality of holes are distributed across the top surface 141b to receive fastener means defined on the bottom surface of the outer electrode 102b when coupling the confinement ring 140 to the upper electrode 102. In one implementation, the bottom surface 141a and the top surface 141b of the upper horizontal section 141 are substantially flat (i.e., horizontal). In another implementation, a first step 148a is defined on the top surface 141b of the upper horizontal section 141 at the inside edge of the upper horizontal section 141. The first step may be used to receive the outer electrode 102b and may be used to offer reliable mating of the confinement ring 140 when coupling the confinement ring 140 to the outer electrode 102b. In this implementation, the bottom surface 141a of the upper horizontal section 141 is substantially flat. In yet another implementation, the first step 148a is defined on the top surface 141b of the upper horizontal section 141 and a second step 148b is defined on the bottom surface 141a of the upper horizontal section 141 at the inside edge of the upper horizontal section 141. In this implementation, the first step 148a and the second step 148b may both extend for a height. In another implementation, the first step 148a may extend for a first height and the second step 148b may extend for a second height. In another implementation, the bottom surface 141a of the upper horizontal section 141 provides for an angle up toward an upper inner radius 151 to define a slope along the upper horizontal section. The angle of the slope on the bottom surface of the upper horizontal section, in one example, may be defined to be greater than 0° and less than 1°, although other ranges for the slope may also be envisioned.
The vertical section 142 includes an inner surface 142a that is facing the plasma region 108 and an outer surface 142b that is facing away from the plasma region 108 and toward an inner side of a wall of the processing chamber 100. In one implementation, the inner surface 142a and the outer surface 142b of the vertical section 142 is vertical.
The lower horizontal section 143 extends a second length and is defined by a top surface 143a that is facing the plasma region 108 and a bottom surface 143b that is facing away from the plasma region 108. The top surface 143a of the lower horizontal section 143 is sloped down from the vertical section toward an inside edge of the lower horizontal section 143. The slope in the lower horizontal section 143 causes a variation in height of a gap defined between the upper horizontal section 141 and the lower horizontal section 143. In some implementation, a first height ‘h1’ defined between the upper and lower horizontal sections 141, 143 near the vertical section 142 is less than a second height ‘h2’ defined between the upper and lower horizontal sections 141, 143 near the inside edge of the lower horizontal section 143. Additionally, the lower horizontal section 143 includes an extension section 144 that is disposed at the inside edge of the lower horizontal section 143 and extends down from the bottom surface 143b of the lower horizontal section 143. In one implementation illustrated in
In one implementation, the upper horizontal section 141, the vertical section 142 and the lower horizontal section 143 may be integrally connected to define a C-shaped structure. In another implementation, the upper horizontal section 141, the vertical section 142 and the lower horizontal section 143 may be three separate pieces with a bottom surface of the upper horizontal section 141 designed to rest on top of the vertical section 142 and be coupled to a top surface of the vertical section 142. A bottom surface of the vertical section 142 is designed to rest on top of the lower horizontal section 143 and be coupled to the top surface 143a of the lower horizontal section 143. The upper horizontal section 141, the vertical section 142 and the lower horizontal section together form a C-shaped structure for confining the plasma generated within the plasma processing chamber 100 to the plasma region 108.
The vertical section 142 of the confinement ring is disposed between the outer radius 150 and an inside radius 153 of the confinement ring 140. The vertical section 142 includes an inner surface 142a facing the inside of the plasma region 108 and the outer surface 142b facing away from the plasma region 108. One or both of the inner surface 142a and outer surface 142b of the vertical section 142 may be vertical or bowed. The vertical section extends between the upper horizontal section 141 and the lower horizontal section 143 for a height to define a gap in which the plasma is confined. In some implementations, the vertical section 142 couples the upper horizontal section 141 to the lower horizontal section 143 to define the C-shaped structure.
The lower horizontal section 143 extends between the outer radius 150 and a lower inner radius 152 of the confinement ring 140. In one implementation, the lower inner radius 152 of the confinement ring 140 is smaller than the upper inner radius 151 of the confinement ring 140. The lower horizontal section includes a top surface 143a and a bottom surface 143b. The top surface 143a of the lower horizontal section 143 is defined to provide an angle down toward the lower inner radius 152, while the bottom surface 143b of the lower horizontal section 143 is defined to be flat. The angle defines a slope along the top surface 143a of the lower horizontal section 143. In one implementation, the slope begins near the inside radius 153 of the confinement ring and extends toward the lower inner radius 152. The top surface 143a with the slope and the bottom surface 143b with a flat profile results in a variation in the thickness along the length of the lower horizontal section 143. For instance, the slope along the top surface 143a results in the lower horizontal section 143 to have a first thickness ‘T1’ near the inside radius 153 of the confinement ring 140 and a second thickness ‘T2’ near the lower inner radius 152 of the confinement ring 140, wherein T1>T2. In one implementation, the first thickness T1 is defined to be about 10% to about 40% greater than the second thickness T2. Further, the variation in the thickness causes a variation in the height of a gap defined between the bottom surface 141a of the upper horizontal section 141 and the top surface 143a of the lower horizontal section 143, wherein the gap defines the plasma region 108. For instance, the slope results in a first height ‘h1’ defined near the inside radius of the confinement ring 140 and a second height ‘h2’ near the lower inner radius 152, wherein the first height h1 is less than the second height h2.
In one implementation, an angle of inclination 147 defined by the slope in the lower horizontal section 143 to a horizontal x-axis may be defined to be between about 0.20° and about 1°. The aforementioned range for the angle of the slope is provided as a mere example and should not be considered restrictive. Consequently, in some implementations, the angle of the slope can be envisioned to be greater or lesser than the range, and such increase or decrease in the angle may be based on the inner dimensions of the plasma processing chamber 100, type of process that is being performed, type of process gases used to generate the plasma, type of by-products and neutral gas species that are generated and are to be removed, access openings of the plasma processing chamber, etc. In one implementation, the confinement ring is made of silicon. In other implementations, the confinement ring may be made of polysilicon, or silicon carbide, or boron carbide, or ceramic, or aluminum, or any other material that can withstand the processing conditions of the plasma region 108.
The lower horizontal section 143 includes an extension section 144′ defined at the lower inner radius 152. In the implementation illustrated in
In another implementation, the second angle of the second slope defined along the bottom surface 143b may be different from the slope defined along the top surface 143a. For instance, the second angle of the second slope may be greater than the angle of the slope along the top surface 143a leading to a variation in the thickness along the length of the lower horizontal section 143. In this implementation, the thickness T1 near the inside radius 153 may be less than the thickness T2 near the lower inner radius 152. This implementation is a variation of the implementation illustrated in
The implementations illustrated in
In one implementation, the amount of slope along the lower horizontal section may be defined to increase the first height ‘h1’ and the second height ‘112’ (i.e., the gap defined between the upper horizontal section 141 and the lower horizontal section 143) by about +2 mm to about +8 mm. The impact of such increase on blanket etch rate, is shown by the graph line 302, especially in the region covered by box 303. As an example, a slope of between about 0.55° and about 0.60° defined along the top surface 143a of the lower horizontal section 143 would result in a difference in the second height ‘h2’ from about 0.60 mm to about 0.65 mm from the first height ‘h1’. In one implementation, the upper inner radius 151 is defined to be between about 203 mm (about 8 inches) and about 218.5 mm (about 8.6 inches). In one implementation, the lower inner radius 152 is defined to be between about 177 mm (about 7 inches) and about 198.5 mm (about 7.8 inches). In one implementation, the inside radius 153 is defined to be between about 248 mm (about 9.8 inches) and about 262 mm (about 10.3 inches). In one implementation, the outer radius is defined to be between about 254 mm (about 10 inches) and about 267 mm (about 10.5 inches). In one implementation, the length of the slot 145 is defined to be between about 48 mm (about 1.9 inches) and about 61 mm (about 2.4 inches). In one implementation, the depth of the lower horizontal section 143a (i.e., thickness T1) is defined to be between about 6 mm (about 0.25 inch) and about 8.4 mm (about 0.33 inch). In one implementation, the slope defined on the lower horizontal section 143a may result in the first height h1 to be between about 29 mm (about 1.18 inches) and about 31 mm (about 1.22 inches) and the second height to be between about 31 mm (about 1.22 inches) and about 32 mm (about 1.24 inches). In one implementation, thickness T2 due to the slope on the lower horizontal section 143a may be defined to be between about 5.8 mm (about 0.23 inch) and about 7.2 mm (about 0.28 inch). The aforementioned range for the various components of the confinement ring has been provided as mere examples and should not be considered restrictive. Other ranges or adjustment to aforementioned ranges for the various components may be envisioned based on the inner dimensions of the plasma processing chamber 100, type of process that is being performed, type of process gases used to generate the plasma, type of by-products and neutral gas species that are generated and are to be removed, access openings of the plasma processing chamber, geometry of hardware components of the plasma processing chamber, etc.
The ISR 145c′ and the OSR 145d′ of each slot 145′ are sized to be an inverse of a wear rate at the corresponding inner and outer diameters (ID 145a, OD 145b) of the slot 145′. The wear along the length of the slot 145′ is uneven due to amount of exposure the different portions along the length of the slot 145′ have to the plasma with the area of the slot 145′ at the inner diameter getting more wear than the area of the slot 145′ at the outer diameter. Making the slots narrower at the ID 145a will increase the lifetime of the confinement ring by offsetting the onset of reaching the critical width when plasma escapes through the slot. At the same time, making the OD 145b of the slot larger ensures that there is no loss in gas conductance due to the ID 145a being narrower. The tapered slot geometry allows the wear of the slot 145′ at the ID 145a to reach the critical dimension at about the same time as the wear of the slot 145′ at the OD 145b. Even with the taper slot geometry, the size of the ISR and the OSR are defined to enable removal of the by-products and the neutral gas species from the plasma region 108. The taper geometry used to define the slot extends the usage life of the confinement ring 140′.
The slots 145 and 145′ illustrated in
Thus, in order to prevent the premature replacement of the confinement ring 140 and to prolong the usage life of the confinement ring while ensuring the mechanical strength of the confinement ring is not compromised throughout its useful life, the confinement ring 140 may be designed to include the lower horizontal section 143 with the slope defined along both the top surface 143a and the bottom surface 143b of the lower horizontal section 143 and slots 145′ with tapered slot profile. Adding the slope to the bottom surface 143b of the lower horizontal section 143, keeps the bottom surface parallel to the angled top surface, especially when the slope defined on the bottom surface 143b is equal to the slope defined on the top surface 143a, improving the mechanical strength of the confinement ring. Variations in the design of the confinement ring 140, such as defining slope along the top surface 143a of the lower horizontal section 143 and slots 145 with the parallel slot profile, or defining slope along the top surface 143a of the lower horizontal section 143 and slots 145′ with tapered slot profile may also be envisioned to improve the plasma density across the length of the substrate surface.
In some implementation, the slot taper defined by the wider slot dimension at the outer diameter OD 145b and the narrow slot dimension at the inner diameter ID 145a, is sized to be an inverse of the wear rate. By sizing the slot taper as a function of the wear rate, the high wear rate at the inner diameter ID 145a is compensated for by the low wear rate at the outer diameter OD 145b, thereby resulting in an approximate straight slot profile at end of life. The slot width along the entire slot length reaches the confinement limit (i.e., critical dimension) at about the same time. The tapered geometry makes use of the area at the outer diameter more effectively. To compensate for the open areas in the lower horizontal section due to decrease in the dimension of the slot at the inner diameter, additional slots may be defined. The number of additional slots may be defined by taking into consideration the amount of wear space required at the narrow end and the broad end for each slot to reach the critical dimension. The tapered slot geometry extends the amount of wear the slot can tolerate before reaching the unconfinement limit, resulting in longer usage life and improved cost of consumables.
The advantages of the confinement ring described in the various implementations include improving plasma uniformity without adversely affecting other hardware components (e.g., chamber spacer plate, mating hardware, etc.) or adversely impacting the mechanical strength or lifetime usage of the confinement ring. The plasma uniformity is modulated by doing modifications to the shape of the confinement ring without affecting the strength or the original lifetime expectancy of the confinement ring. This results in improved cost of the consumable confinement ring as the confinement ring can withstand more process operations before reaching the critical dimension limits along the lower horizontal section and along the length of the slot. Other advantages will be envisioned by one skilled in the art upon reviewing the various implementations described herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US22/12618 | 1/14/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63149186 | Feb 2021 | US |
