Patent Application
20240234104
The invention relates to a confinement ring design used in a semiconductor processing module.
In semiconductor processing, a substrate undergoes various operations to form features that define integrated circuits. For example, in 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. The 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, 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 set of confinement rings are generally C-shaped structure (i.e., C-shroud).
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 the set of confinement rings (e.g., C-shroud) to increase the volume of the process region. Any changes to the shape or design of the confinement rings have to ensure that the changes do not compromise the mechanical strength or reduce the lifetime of the confinement rings. Further, it would be advantageous if the changes to the shape or design of the confinement rings do not require changes to the hardware used within the processing chamber, such as processing chamber spacer plate, mating hardware, etc.
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 coupled to an upper electrode structure disposed in a top portion of the plasma processing chamber and is designed to have an S-shaped structure. The S-shaped confinement ring, according to some implementations, is defined to include an upper horizontal section, an upper vertical section, a mid-section, a lower vertical section, a lower horizontal section and a vertical extension. The upper horizontal section is defined to extend between a first outer radius and an inner upper radius. The mid-section is defined to extend between the inner upper radius and a second outer radius. The lower horizontal section is defined to extend between the second outer radius and an inner lower radius. The upper vertical section is defined to extend between the upper horizontal section and the mid-section at the inner upper radius and the lower vertical section is defined to extend between the mid-section and the lower horizontal section at the second outer radius. A vertical extension is defined to extend down from the lower horizontal section at the inner lower radius.
The S-shaped structure of the confinement ring assists in improving radial plasma density uniformity while keeping the gas conductance the same as the traditional confinement rings (i.e., C-shaped confinement rings). Further, the S-shape assists in reducing volume of the plasma in the plasma region while improving the substrate radial etch uniformity. Additional design configurations, such as including a slope in the bottom surface of the mid-section, and/or a slope in the top surface of the lower horizontal section, and/or sloped lower horizontal section, etc., may also be considered to improve radial plasma density uniformity, reduce volume and improve etch uniformity. The S-shaped structure helps in modulating the plasma density uniformity within the plasma region without requiring re-design of other hardware components of the plasma processing chamber. Further, the S-shaped design of the confinement ring ensures that the mechanical strength is preserved and the lifetime of the consumable confinement ring is maintained or improved.
The lower horizontal section includes a plurality of slots (also referred to as “conductance slots”) defined along the length of the lower horizontal section for removing the by-products and neutral gas species generated within the plasma region. The plurality of slots is designed to ensure optimal confinement of the plasma in the plasma region. 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. In some implementations, each slot of the plurality of slots is defined to include parallel slot geometry, wherein an inner slot radius defined at the inner diameter is equal to an outer slot radius defined at the outer diameter. In alternate implementations, each slot of the plurality of slots is defined using tapered slot geometry, wherein the inner slot radius defined at the inner diameter is smaller than the outer slot radius defined at the outer diameter.
The tapered slot geometry is designed to address the differential wear experienced along the length of the slots due to constant exposure to the plasma. Typically, 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 promptly replaced to ensure that a plasma unconfinement event does not occur. The tapered slot geometry makes efficient use of the area around the slot by defining a narrow end at the inner diameter thereby providing more area for wear and a broader end at the outer diameter providing less area for wear. This tapered geometry allows the narrow end to experience greater wear so that the wear at the narrow end of the slot approaches 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 efficiently manages the limited space between the slots resulting in extended 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. The S-shaped structure of the confinement ring provides the additional advantage of improving plasma density uniformity with less volume and does not require 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, an upper vertical section, a mid-section, a lower vertical section, a lower horizontal section and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The mid-section extends between the inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and the second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and the mid-section proximate to the inner upper radius. The lower vertical section extends between the mid-section and the lower horizontal section proximate to the second outer radius. The vertical extension extends downward proximate to the inner lower radius.
In one implementation, a plasma volume is disposed between an upper electrode structure, a lower electrode and the confinement ring.
In one implementation, an external volume is defined between the upper horizontal section, the upper vertical section and the mid section. The external volume is outside of the plasma volume.
In one implementation, an internal volume is defined between the mid-section, the lower vertical section and the lower horizontal section. The internal volume is inside the plasma volume.
In one implementation, an external volume is defined between the upper electrode structure, the upper vertical section and the mid-section, and an internal volume is defined between the mid-section, the lower vertical section and the lower horizontal section. The internal volume is inside a plasma volume of the plasma processing chamber and the external volume is outside of the plasma volume. The external volume reduces the plasma volume.
In one implementation, the upper horizontal section, the upper vertical section, the mid-section, the lower vertical section and the lower horizontal section together define an S-shaped structure.
In one implementation, a length of the mid-section and a length of the lower horizontal section are of a uniform thickness.
In one implementation, a top surface of the mid-section includes a flat profile and a bottom surface of the mid-section is angled down from the inner upper radius toward the second outer radius, so that a first thickness of the mid-section proximate to the inner upper radius is less than a second thickness of the mid-section proximate to the second outer radius.
In one implementation, a first height defined between a top surface of the lower horizontal section and a bottom surface of the mid-section proximate to the second outer radius is less than a second height defined between a top surface of the mid-section and a bottom surface of the upper horizontal section proximate to the inner upper radius.
In one implementation, a first height defined between a top surface of the lower horizontal section and a bottom surface of the mid-section proximate to the second outer radius is equal to a second height defined between a top surface of the mid-section and a bottom surface of the upper horizontal section proximate to the inner upper radius and to a third height defined between the top surface of the lower horizontal section and the bottom surface of the mid-section proximate to the inner upper radius.
In one implementation, the second outer radius extends beyond the first outer radius, the second outer radius defines an outer radius of the confinement ring, and the inner upper radius is greater than the inner lower 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. The inner diameter of the slot is greater than an inner ring diameter of the confinement ring defined by the inner lower radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by the second outer radius. Each slot extends from a top surface to a bottom surface of the lower horizontal section.
In one implementation, 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. A difference in the inner slot radius and the outer slot radius of each slot defines a slot taper. 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 defined to be an inverse of a wear rate at the corresponding inner diameter and the outer diameter of the slot.
In one implementation, 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, 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.
In one implementation, a first height of the first vertical section is equal to a second height of the second vertical section.
In one implementation, a first height of the first vertical section is different from a second height of the second vertical section.
In one implementation, wherein the upper horizontal section, the upper vertical section, the mid-section, the lower vertical section and the lower horizontal section form a unitary S-shaped structure, and the vertical extension integrally continues the S-shaped structure downward proximate to the inner lower radius. The unitary S-shaped structure is configured to confine plasma within a plasma region defined in the plasma processing chamber.
In one implementation, the upper horizontal section, the upper vertical section, the mid-section, and the lower vertical section define a first unitary piece and the lower horizontal section defines a second piece. The first unitary piece is configured to be received over a radio frequency gasket defined on a top surface proximate to the second outer radius of the second piece.
In one implementation, the lower horizontal section includes a slope that extends down from the lower vertical section toward the inner lower radius. A thickness along a length of the lower horizontal section is uniform.
In one implementation, the lower vertical section includes one or more optical emission spectroscopy holes with probes disposed therein to monitor plasma within the plasma processing chamber for end-point detection.
In one implementation, a top surface of the upper horizontal section includes a plurality of holes configured to receive cam keys for coupling the confinement ring to corresponding cam locks disposed on a bottom surface of a backing plate disposed in the plasma processing chamber. Each one of the plurality of cam keys is disposed to align with a corresponding one of the plurality of cam locks.
In one implementation, the vertical extension is defined by an angled top section and a vertical bottom section. The angled top section is defined at an outer side adjacent to the top surface of the lower horizontal section at the inner lower radius and the vertical bottom section is defined to extend downward from a bottom portion of the angled top section at the inner lower radius.
In an alternate implementation, a confinement ring for use in a plasma processing chamber is disclosed. The confinement ring includes an upper horizontal section, an upper vertical section, a mid-section, a lower vertical section, a lower horizontal section and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The mid-section extends between the inner upper radius and a second outer radius and includes a top surface with a flat profile and a bottom surface that includes a slope that extends down from the inner upper radius toward the second outer radius. The lower horizontal section extends between an inner lower radius and the second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and the mid-section proximate to the inner upper radius. The lower vertical section extends between the mid-section and the lower horizontal section proximate to the second outer radius. A vertical extension extends downward from the lower horizontal section proximate to the inner lower radius.
In one implementation, a top surface of the lower horizontal section is defined by a first slope that extends down from the lower vertical section toward the inner lower radius.
In one implementation, a first height defined between the bottom surface of the mid-section and the top surface of the lower horizontal section proximate to the second outer radius is less than a second height defined between the bottom surface of the mid-section and the top surface of the lower horizontal section proximate to the inner lower radius.
In one implementation, a bottom surface of the lower horizontal section is defined to include a flat profile, such that the fist slope of the lower horizontal section defines a variable thickness along a length of the lower horizontal section. The variable thickness is defined by a first thickness proximate to the second outer radius and a second thickness proximate to the inner lower radius, wherein the first thickness is greater than the second thickness.
In one implementation, a bottom surface of the lower horizontal section is defined by a second slope that extends down from the lower vertical section toward the inner lower radius. A first angle of inclination of the first slope is equal to a second angle of inclination of the second slope, so that a thickness along a length of the lower horizontal section is uniform.
In one implementation, the upper horizontal section, the upper vertical section, the mid-section, the lower vertical section, and the lower horizontal section together form a unitary S-shaped structure. The vertical extension continues the S-shaped structure downward proximate to the inner lower radius.
In one implementation, the upper horizontal section, the upper vertical section, the mid-section, and the lower vertical section define a first unitary piece and the lower horizontal section defines a second piece. The first unitary piece is configured to be received over a radio frequency gasket defined on a top surface disposed proximate to the second outer radius of the second piece.
In one implementation, the lower horizontal section includes a plurality of slots. Each slot extends radially from an inner diameter to an outer diameter along the lower horizontal section. The inner diameter of the slot is greater than an inner ring diameter of the confinement ring defined by the inner lower radius, and the outer diameter of the slot is less than an outer ring diameter of the confinement ring defined by the second outer radius. Each slot extends from a top surface to a bottom surface of the lower horizontal section.
In yet another alternate implementation, a plasma processing chamber for confining plasma within, is disclosed. The plasma processing chamber includes a lower electrode, an upper electrode structure and a confinement ring disposed between the lower electrode and the upper electrode structure. The lower electrode is disposed in a lower section (i.e., lower portion) of the plasma processing chamber and includes a support surface for supporting a substrate. The upper electrode structure is disposed in an upper section (i.e., upper portion) of the plasma processing chamber and is oriented opposite the lower electrode. The confinement ring is coupled to the upper electrode structure and is disposed between the lower electrode and the upper electrode structure. The confinement ring includes an upper horizontal section, an upper vertical section, a mid-section, a lower vertical section, a lower horizontal section and a vertical extension. The upper horizontal section extends between an inner upper radius and a first outer radius. The mid-section extends between the inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and the second outer radius of the confinement ring. The upper vertical section extends between the upper horizontal section and the mid-section proximate to the inner upper radius. The lower vertical section extends between the mid-section and the lower horizontal section proximate to the second outer radius. The vertical extension extends downward from the lower horizontal section proximate to the inner lower radius.
In one implementation, a plasma volume is disposed between the upper electrode, the lower electrode and the confinement ring.
In one implementation, the upper electrode structure includes an outer electrode disposed in the center of the upper electrode structure, an outer electrode that is disposed adjacent to the upper electrode, and a backing plate is disposed to surround the outer electrode. The backing plate includes an outer portion that is disposed adjacent to the outer electrode such that the outer electrode is disposed between the upper electrode and the outer portion of the backing plate, and an inner portion that is disposed over a portion of the outer electrode. A bottom surface of the outer portion of the backing plate includes a plurality of cam locks that align with corresponding keys disposed on a top surface of the upper horizontal section of the confinement ring. The cam keys and the cam locks are used to couple the outer electrode to the confinement ring.
In one implementation, the plurality of cam keys is coupled to a controller, wherein the controller is configured to generate a first signal to activate the plurality of cam keys to engage and lock with the plurality of cam locks during coupling to the backing plate and a second signal to activate the plurality of cam keys to enable unlocking of the plurality of cam locks during decoupling of the confinement ring from the backing plate. The plurality of cam locks and the plurality of cam keys are part of an electronic cam lock mechanism used for coupling the confinement ring to the upper electrode structure and is configured to be controlled by signals from the controller.
In one implementation, the backing plate and the upper electrode of the upper electrode structure are electrically grounded and the lower electrode is coupled to a radio frequency (RF) generator via a corresponding match network. The RF generator is configured to provide RF power to the lower electrode for generating plasma within the plasma processing chamber.
In the various implementations described herein, a confinement ring for use in a plasma processing chamber is designed to maintain plasma uniformity in the plasma region. The confinement ring is designed to have a S-shaped configuration. The S-shape reduces the volume within the plasma region in which the plasma is contained leading to less amount of RF power needed to generate the plasma to fill the plasma region. With less volume of plasma, radial plasma density uniformity in the plasma region is improved, thereby improving the substrate radial etch uniformity. Further, the S-shaped design of the confinement ring can be used within the plasma processing chamber with the current configuration of other hardware components and does not require re-designing of other hardware components. In some implementations, the hardware components may be re-designed, although not required, to further reduce the volume of plasma maintained in the plasma region.
A plurality of slots (i.e., conductance slots) is provided at a bottom portion of the S-shaped confinement ring to efficiently remove by-products from the plasma region while optimally confining the plasma within the plasma region, resulting in improved gas conductance. The slots may be shaped to have a parallel slot profile or a tapered slot profile. The tapered slot design may be used to address the differential wear experienced along the length of the slots and to make efficient use of the area around the slot. The tapered slot profile enhances usage life of the confinement ring by ensuring optimal usage of the limited space between the slots. Consequently, the cost associated with replacing the consumable confinement ring is lowered as the number of process cycles in which the confinement ring can be used in the plasma processing chamber is extended. The S-shaped design of the confinement ring thus maintains plasma uniformity with less volume while improving density and gas conductance.
The S-shaped confinement ring used in the plasma processing chamber includes an upper horizontal section, an upper vertical section, a mid-section, a lower vertical section and a lower horizontal section. The lower horizontal section further includes a vertical extension that is used to rest the confinement ring on top of a RF gasket defined in a portion of a lower electrode. The upper horizontal section extends between a first outer radius and an inner upper radius. The mid-section extends between the inner upper radius and a second outer radius. The lower horizontal section extends between an inner lower radius and the second outer radius. The upper vertical section extends between the upper horizontal section and the mid-section proximate to the inner upper radius and the lower vertical section extends between the mid-section and the lower horizontal section proximate to the second outer radius. The vertical extension extends downward proximate to the inner lower radius and integrally continues the lower horizontal section. The upper horizontal section, the upper vertical section, the mid-section, the lower vertical section and the lower horizontal section together form an S-shaped structure that is used to reduce the amount of plasma contained in the plasma region while effectively confining the plasma generated within the plasma processing chamber.
Variations in the profile of the mid-section and, in some implementations, the lower horizontal section can also be envisioned, wherein the variations influence the amount of plasma and the density of the plasma contained in the plasma region. Like the conventional C-shaped confinement ring, the S-shaped confinement ring structure improves plasma density uniformity in the plasma region defined in the plasma processing chamber. The variation in the profile of the mid-section may be in the form of a slope along a bottom surface of the mid-section, wherein the slope extends down from the inner upper radius toward the second outer radius. The slope in the mid-section may cause a variation in the thickness along a length of the mid-section, wherein the thickness proximate to the inner upper radius is less than the thickness proximate to the second outer radius. Similarly, variation in the profile of the lower horizontal section may be in the form of a slope defined on a top surface of the lower horizontal section, wherein the slope in the lower horizontal section extends down from the second outer radius toward the inner lower radius. Additional slope may be defined in the bottom surface of the lower horizontal section so as to make the thickness of the lower horizontal section uniform along the length of the lower horizontal section.
The slope in the mid-section results in a reduction in the plasma volume within the plasma region. The reduction in the plasma volume results in less amount of gas(es) needed to form plasma for filling the plasma region. Even with the reduced volume, the S-shaped confinement ring ensures improved plasma density uniformity as well as the substrate etch uniformity in the plasma region. Further, with the S-shaped structure the mechanical strength of the confinement ring is not compromised, thereby maintaining the lifetime usage of the confinement ring. These benefits are realized without requiring changes to any hardware component (e.g., chamber spacer plate, mating hardware, etc.) in the plasma processing chamber as the changes made to the confinement ring structure do not substantially deviate from the overall structure of conventional confinement ring.
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 (e.g., electrostatic chuck (ESC)) 104 defines a substrate support surface on which a substrate 110 (e.g., wafer) is received for processing. In some implementation, the substrate support surface is defined in a recess defined on the top surface of the lower electrode, wherein a height of the recess is equal to the thickness of the substrate 110. 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. It is noted that throughout this application the substrate may be interchangeably referred to as a wafer and refers to a thin slice of semiconductor material (mostly made of silicon) that acts as a base on which a plurality of fabrication operations are performed to fabricate electronic integrated circuits, wherein at least one of the fabrication operations uses the plasma generated within the plasma processing chamber in which the S-shaped confinement ring is used. In some implementations, the edge ring 112 is designed such that a top surface of the edge ring 112 is co-planar with a top surface of the substrate 110, when the substrate 110 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. A cover ring 114 is disposed adjacent to the edge ring 112, such that the edge ring 112 is disposed between the cover ring 114 and the substrate 110, when the substrate is received on the substrate support surface. In some implementations, the cover ring 114 is designed such that a top surface of the cover ring 114 is co-planar with the top surface of the edge ring 112 so as to further extend the processing region from the outer edge of the edge ring 112 to an outer edge of the cover ring 114. 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.
One or more insulation elements 120 are disposed below the cover ring 114 and adjacent to the lower electrode 104 so as to surround the lower electrode 104. In one implementation, the insulation elements 120 may be made of quartz material, and hence may also be referred to as quartz elements, although other insulation materials may also be employed. A ground ring 122 is disposed adjacent to the insulation element (e.g., quartz element) 120 and below the cover ring 114 such that the ground ring 122 surrounds the quartz element 120 and the lower electrode 104. A support structure in the form of a ground bucket 124 is disposed in the lower electrode 104 so as to surround a portion of the ground ring 122. In one implementation, a gap may exist between the ground ring 122 and the ground bucket 124 to provide capacitive coupling to the ground ring 122. The ground bucket 124 provides a ground return for the RF power supplied to the plasma processing chamber 100. The ground bucket 124 also provides sufficient support for a portion of the upper electrode structure 102 to rest on. For instance, a bottom portion of the S-shaped structure of the confinement ring 130 coupled to the portion of the upper electrode structure 102 rests on the ground bucket 124. In this instance, the ground bucket 124 provides an indirect support to the upper electrode structure 102 via the S-shaped confinement ring structure 130. The ground bucket 124, in one implementation, includes a fixed ring 124a at the bottom and a floating element 124b at the top. A flexible RF strap 125 is defined between the fixed ring 124a and the floating element 124b. A RF gasket 116 is disposed on a top surface of the floating element 124b of the ground bucket 124. The components of the ground bucket 124 (i.e., the fixed ring 124a, the floating element 124b and the flexible RF strap 125), in one implementation, are made of Aluminum. In other implementations, the components of the ground bucket 124 are made of any other conductive material that is suitable for conducting the RF power in the plasma processing chamber 100 to ground. In some implementation, the RF gasket 116 may be disposed within a channel defined on the top surface of the floating element 124b.
In one implementation, the upper electrode structure 102 may include an upper electrode 102a disposed in the center and an outer electrode 102b that is disposed adjacent to and surrounds the upper electrode 102a. The upper electrode 102a 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 (not shown) distributed in a bottom surface of the upper electrode 102a 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 102a and the lower electrode 104. The upper electrode 102a, in this implementation, is electrically grounded to provide the RF power supplied to the plasma processing chamber 100 a return path to ground. In one implementation illustrated in
In one implementation, the upper electrode structure 102 with the coupled confinement ring structure 130 is configured to move vertically up and down while the lower electrode 104 is fixed. When the plasma processing chamber 100 is to be prepared for processing, the upper electrode structure 102 with the confinement ring structure 130 is lowered to allow the confinement ring structure 130 to rest on the RF gasket 116 disposed on the top surface of the floating element 124b of the ground bucket 124. The confinement ring structure 130 pushes down on the RF gasket 116 causing the RF gasket 116 to compress to form a tight coupling between the upper electrode structure 102 and the lower electrode 104. The compression of the RF gasket 116 causes the floating element 124b to be pushed down leading to the flexible RF strap 125 to compress. When the upper electrode structure 102 is moved up, the confinement ring structure 130 moves up and away from the RF gasket 116, allowing the RF gasket 116 to relax. This causes the floating element 124b and the flexible RF strap 125 to move up from a compressed state to a relaxed state.
The confinement ring structure (or simply referred to henceforth as “confinement ring”) 130 coupled to the backing plate 105 acts as a coupling interface between the upper electrode structure 102 and the lower electrode 104. The confinement ring 130 defines a confined plasma volume between the upper electrode structure and the lower electrode (102, 104) in which the plasma generated in the chamber is sufficiently contained. The plasma volume defines the plasma region 108. The confinement ring 130 is an S-shaped structure with an opening at the lower portion of the S-shape facing an inside of the plasma region 108.
It is to be noted that the plasma processing chamber of
The confinement ring130, broadly speaking, is defined by a plurality of components, including an upper horizontal section, an upper vertical section, a mid-section, a lower vertical section, a lower horizontal section and a vertical extension. A plurality of cam locks are distributed on atop surface of the upper horizontal section and are used for coupling the confinement ring 130 to the outer portion 105a of the backing plate 105 of the upper electrode structure 102, wherein the upper electrode structure 102 includes the upper electrode 102a, the outer electrode 102b and the backing plate 105 The upper vertical section of the S-shaped confinement ring 130 acts to reduce the plasma volume within the plasma region 108 for receiving the plasma. The reduction in the plasma volume is done without adversely affecting the density of the plasma or the plasma distribution in the plasma region 108. Details of the various components of the confinement ring 130 will be described in greater detail with reference to
In one implementation, an S-shaped confinement ring 130 is coupled to the outer portion 105a of the backing plate 105 using a fastening mechanism (e.g., cam lock structure) (not shown). The cam lock structure, for example, includes one or more cam locks that can be operated using corresponding one or more cam keys. In this implementation, a plurality of cam locks (not shown) is distributed uniformly across a bottom surface of the outer portion 105a of the backing plate 105. The cam locks may be disposed such that each cam lock aligns with a corresponding cam key (not shown) provided on a top surface of the S-shaped confinement ring 130 that is disposed below the outer portion 105a of the backing plate 105. In one implementation, the cam lock structure is an electronic cam lock structure, wherein the cam keys disposed on the top surface of the confinement ring 130 are coupled to a controller and operated using signals from the controller (not shown). The controller may be coupled to the plasma processing chamber 100 and used to control process parameters of the plasma processing chamber 100. For example, the controller may be used to control the process recipe of process gas(es) used in the plasma processing chamber 100, the RF power provided to the plasma processing chamber, the exposure time of the substrate 110 to the plasma, the concentration of gas(es) used in the plasma processing chamber, etc. The controller may be coupled to a computer or may be part of a computer that is used to provide the process recipes for generating the plasma in the plasma processing chamber 100. In addition to controlling the various process parameters, the controller may also be used to provide appropriate signals to the cam keys for locking with the cam locks. For instance, in one implementation, the controller may be used to generate a first signal to activate the plurality of cam keys to engage and lock into the cam locks, when the confinement ring 130 needs to be coupled to the outer portion 105a of the backing plate 105. Similarly, the controller may be used to generate a second signal to the cam keys to unlock the cam keys from the cam locks, when the confinement ring 130 is to be de-coupled from the backing plate 105. In some implementations, the first signal for locking may be generated upon detecting a new confinement ring 130 being installed in the plasma processing chamber 100. In some implementations, the second signal for unlocking may be generated when an existing confinement ring 130 has to be removed, for example, after reaching the end of usage life of the confinement ring 130. The implementations are not restricted to the electronic cam lock structure. Instead, other types of cam locks or other types of locking mechanism (e.g., threaded screws, etc.) may be used to couple the confinement ring 130 to the backing plate 105.
In the implementation illustrated in
In one implementation, the quartz element 120 in the lower electrode 104 of
The S-shaped confinement ring 130 includes an upper horizontal section 131, an upper vertical section 132, a mid-section 133, a lower vertical section 134, and a lower horizontal section 135. A vertical extension 136 extends down from the lower horizontal section 135 proximate to the inner lower radius. The upper horizontal section 131 extends between an inner upper radius and a first outer radius of the confinement ring 130. In one implementation, a top surface of the upper horizontal section at the inner upper radius includes a step 148 on which a lip extension defined at the outer edge of the bottom surface of the outer electrode 102b is received. The height of the step 148 is defined to provide a reliable mating surface for receiving and supporting the outer electrode 102b. The upper horizontal section 131 is defined by a top surface 131a and a bottom surface 131b. The top surface 131a of the upper horizontal section 131 is defined to be flat and includes a plurality of cam keys (not shown) defined to align with corresponding cam locks (not shown) defined on a bottom surface in the outer portion 105a of the backing plate 105. The cam locks are used to keep the confinement ring 130 in place, when the confinement ring 130 is coupled to the backing plate 105. The bottom surface 131b of the upper horizontal section 131 is defined to be flat such that a thickness along a length of the upper horizontal section 131 is uniform.
The mid-section 133 extends between the inner upper radius and a second outer radius of the confinement ring 130. The mid-section is also defined by a top surface 133a and a bottom surface 133b. In one implementation illustrated in
The lower horizontal section 135 is defined to extend from an inner lower radius to the second outer radius. The lower horizontal section 135 is defined by a top surface 135a and a bottom surface 135b. In the implementation illustrated in
The lower vertical section 134 extends between the mid-section 133 and the lower horizontal section 135 proximate to the second outer radius. The lower vertical section extends for a height ‘h1’ proximate to the second outer radius and a height ‘h3’ proximate to the inner upper radius. In the implementation illustrated in
The plasma region 108 is defined between the upper electrode structure 102, the lower electrode 104 and the confinement ring 130. The plasma region 108 defines a plasma volume into which the plasma generated in the plasma processing chamber 100 is received. The plasma volume in the plasma region 108 includes an external volume 108a and an internal volume 108b. The external volume 108a is defined between the upper horizontal section 131, the upper vertical section 132 and the mid-section 133. The external volume 108a is defined in the area immediately below the upper electrode 102a and the outer electrode 102b and outside (i.e., on top of or above) the internal volume 108b in the plasma region 108. The external volume 108a reduces the overall volume of plasma in the plasma region 108. In one implementation, the amount of plasma volume in the plasma region 108 reduced by the external volume 108a is driven by the length of the mid-section 133, the height h2 of upper vertical section 132 and may, to some extent, the thickness of the mid-section 133. The internal volume 108b is defined between the mid-section 133, the lower vertical section 134 and the lower horizontal section 135. The internal volume 108b is defined to be inside the plasma volume and is between the external volume 108a in the top and the substrate support surface of the lower electrode 104. The amount of plasma that can be accommodated in the internal volume 108b depends on the length of the mid-section 133, the height h1 of the lower vertical section 134 and the length of the lower horizontal section 135.
The vertical extension 136 is defined to extend down from the lower horizontal section 135 proximate to the inner lower radius and integrally continue the lower horizontal section 135 downward for a height. In some implementations, the vertical extension 136 is used during coupling of the upper electrode structure 102 to the lower electrode 104. For example, when the plasma processing chamber 100 is being prepared for processing, the upper electrode structure 102 is brought down so that the vertical extension 136 of the S-shaped confinement ring 130 rests on the RF gasket 116 disposed on the top surface of the ground bucket 124 defined in the lower electrode 104. In one implementation, the upper horizontal section 131, the upper vertical section 132, the mid-section 133, the lower vertical section 134, and the lower horizontal section 135 together form a unitary S-shaped confinement ring 130. The vertical extension 136 defined proximate to the inner lower radius extends the lower horizontal section 135 downward. In alternate implementations, the S-shaped confinement ring 130 may be made of a plurality of pieces, as will be described with reference to
In one implementation, the first flat lower section 103c1 may include an angled or rounded inner edge defined adjacent to the upper electrode 102a. The slanted lower section 103c2 is disposed adjacent to the first flat lower section 103c1, and extends for a second length. The second flat lower section 103c3 is disposed adjacent to the slanted lower section 103c2 such that the slanted lower section 103c2 is defined between the first flat lower section 103c1 and the second flat lower section 103c3. The second flat lower section 103c3 extends to the outer edge of the outer electrode 102b′ and covers a third length. The slanted lower section 103c2 includes a slope that extends down from the first flat lower section 103c1 toward the second flat lower section 103c3. In one implementation, an angle of the slope of the slanted lower section 103c2 and an angle of the angled inner edge (if any) of the outer electrode 102b′ may be defined to allow the plasma to flow freely within the plasma region 108. The angle of the slanted lower section 103c2 causes a variance in the height at the inner side and the outer side of the outer electrode 102b′, wherein, a height of the inner side of the outer electrode 102b′ is less than a height of the outer side of the outer electrode 102b′. Consequently, the outer side of the outer electrode 102b′ that is adjacent to the inner side of the upper vertical portion 132 covers a portion of the upper vertical section 132 of the S-shaped confinement ring 130. The variance in the height of the inner side to the outer side of the outer electrode 102b′ depends on the angle of the slope of the slanted lower section 103c2. In one implementation, the length of each of the sections—first flat lower section 103c1, the slanted lower section 103c2, and the second flat lower section 103c3, are equal. In alternate implementations, the length of each of the sections is different. For example, the length of the first and the second flat lower sections 103c1, 103c3, may be equal while the length of the slanted lower section 103c2 may be lesser than or greater than the length of the first and the second flat lower sections 103c1, 103c3. The slanted lower section 103c2 reduces the volume within the plasma region 108 further. As a result, lesser volume of plasma is needed within the plasma region 108 for performing the fabrication operation. Even with lesser volume, the density of the plasma is improved due to more plasma contained within the smaller internal volume of the plasma region 108 and the plasma uniformity and the gas conductance are maintained at the optimal level in the plasma volume of the plasma region 108.
Due to the slopes defined in both the mid-section 133′ and the lower horizontal section 135′, the heights h1 and h3 may vary. Consequently, in the implementation illustrated in
In one implementation, an angle of the slope defined in the bottom surface of the mid-section 133 to a horizontal x-axis may be defined to be equal to an angle of the slope defined on the top surface of the lower horizontal section 135. In alternate implementation, the angle of the slop in the bottom surface of the mid-section 133 to the horizontal x-axis may be defined to be greater than the angle of the slope defined on the top surface of the lower horizontal section 135. The aforementioned range for the angle of the slope in the mid-section 133 and the lower horizontal section 135 are provided as mere examples and should not be considered restrictive. Consequently, in some implementations, the angle of the slope in the mid-section 133 and/or in the lower horizontal section 135 can be envisioned to be greater or lesser than the aforementioned 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, amount of internal volume 108a that is desired in the plasma region 108, type of process gases used to generate the plasma, type of by-products and neutral gas species that are generated and need to be removed, access openings of the plasma processing chamber, etc. In one implementation, the confinement ring 130 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 135 includes a vertical extension 136 defined proximate to the inner lower radius. In one implementation illustrated in
The amount of taper defined by the ISR 140c′ and the OSR 140d′ is defined to be an inverse of wear rate at the corresponding ID1140a and the OD1140b. The wear along the length of the slot 140′ is uneven due to amount of exposure the different portions along the length of the slot 140′ have to the plasma within the plasma region 108, with the area of the slot 140′ at the ID1140a getting more wear than the area of the slot 140′ at the OD1140b. As the slot wear varies along the slot length, sizing the slot taper as a function of the wear rate ensures that the high wear rate at the ID1140a is compensated for by the low wear rate at the OD1140b, thereby resulting in an approximate straight slot profile at end of life of the confinement ring. The tapered profile of the slot 140′ provides more area at the ID1140a for the slot wear than at the OD1140b so that the tapered slot 140′ as a whole can reach the critical dimension at about the same time when the confinement ring 130′ needs to be replaced. 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 140′ 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. Even with the taper slot profile of the slots 140′, the size of the ISR 140c′ and the OSR 140d′ are defined to enable removal of the by-products and the neutral gas species from the plasma region 108. The slots 140 of
For more information with regards to use of tapered slot profile for defining the slots 140′ along the lower horizontal section 135 of the confinement ring, reference can be made to co-owned and co-pending International Patent Application No. PCT/US20/053894, filed on Oct. 30, 2020, and entitled “Wear Compensating Confinement Ring”, which is incorporated herein by reference in its entirety. Variations in the design of the confinement ring 130, such as defining slope along the top surface 135a of the lower horizontal section 135 and slots 140 with the parallel slot profile, or defining slope along the top surface 135a of the lower horizontal section 135 and slots 140′ with tapered slot profile may also be envisioned to improve the plasma density across the length of the substrate surface.
The advantages of the S-shaped confinement ring described in the various implementations include improving plasma density 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. Further, the S-shape assists in reducing volume within the plasma region, which can result in less amount of gas(es) required for generating the plasma to fill the reduced volume of the plasma region, thereby conserving the process gas(es) used. Further adjustment to the volume and the plasma density uniformity can be modulated by providing modifications to the shape of the different surfaces of the confinement ring (i.e., providing slants on a bottom surface of the mid-section and/or the top surface of the lower horizontal section) without affecting the strength or the original lifetime usage of the confinement ring. This results in improved substrate etch uniformity and 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/US22/29494 | 5/16/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63192511 | May 2021 | US |
