Patent Application
20250116028
The present technology relates to methods, components, and apparatuses for semiconductor manufacturing. More specifically, the present technology relates to electroplating components and other semiconductor processing equipment.
Microelectronic devices, such as semiconductor devices, are fabricated on and/or in wafers or workpieces. A typical wafer plating process involves depositing a metal seed layer onto the surface of the wafer via vapor deposition. A photoresist may be deposited and patterned to expose the seed layer. The wafer is then moved into the vessel of an electroplating processor where electric current is conducted through an electrolyte to the wafer, to deposit a blanket layer or patterned layer of a metal or other conductive material onto the seed layer. Examples of conductive materials include permalloy, gold, silver, copper, cobalt, tin, nickel, and alloys of these metals. Subsequent processing steps form components, contacts and/or conductive lines on the wafer. Many aspects of an electroplating process may impact process uniformity, such as irregularities in the electric field due to pattern variations, mass-transfer rates, deposition rates, as well as other process and component parameters. Even minor discrepancies across a substrate may impact downline finishing processes.
Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.
Exemplary electroplating systems may include a vessel. The systems may include a head that is configured to hold a substrate. The head may be positionable within an interior of the vessel. The systems may include a spray jet array disposed within the interior of the vessel. The spray jet array may include a plate defining a plurality of apertures through a thickness of the plate. The systems may include at least one fluid pump that is fluidly coupled with an inlet end of each of the plurality of apertures.
In some embodiments, the head may be rotatable within the vessel. A center of rotation of the head may be offset from a center of the spray jet array. The head may be rotatable within the vessel. One or both of the head and the spray jet array may be laterally translatable within the vessel. The plate may include a plurality of tubes that extend upward from a top surface of the plate toward a bottom surface of the head. Each of the plurality of tubes may be aligned with and may partially define one of the plurality of apertures. The plate may be a first plate. The plurality of apertures may include a first plurality of apertures and a second plurality of apertures. The spray jet array may include a second plate coupled with the first plate on a bottom side of the first plate. An outlet end of each of the first plurality of apertures and each of the second plurality of apertures may extend through a top surface of the first plate. An inlet end of each of the first plurality of apertures may extend through a bottom surface of the first plate. An inlet end of each of the second plurality of apertures may extend through a bottom surface of the second plate. The first plurality of apertures and the second plurality of apertures may be arranged about the first plate in an alternating fashion. A plurality of tubes may extend between the first plate and the second plate. Each of the plurality of tubes may be aligned with and may partially define one of the second plurality of apertures. A plenum may be defined between the first plate and the second plate. The plenum may extend about an exterior of each of the plurality of tubes. The at least one fluid pump may be fluidly coupled with the first plurality of apertures via the plenum and may be fluidly coupled with the second plurality of apertures via the bottom surface of the second plate. A diameter of each of the plurality of apertures is no greater than 1 mm. The plate may define a plurality of drain tubes. A pitch to diameter ratio of a substantial percentage of the plurality of apertures is at least 8. A ratio of a gap between the plate and the substrate and a pitch of the plurality of apertures is at least 1.
Some embodiments of the present technology may encompass electroplating systems that may include a vessel. The systems may include a head that is configured to hold a substrate. The head may be positionable within an interior of the vessel. The systems may include a spray jet array disposed within the interior of the vessel. The spray jet array may include a plate defining a plurality of apertures through a thickness of the plate. The systems may include at least one fluid pump that is fluidly coupled with an inlet end of each of the plurality of apertures. The systems may include a power source that is configured to supply a current to the interior of the vessel.
In some embodiments, the plurality of apertures may include a first plurality of apertures forming a first fluid channel and a second plurality of apertures forming a second fluid channel. The at least one fluid pump may be operable to control a flow of fluid to the first plurality of apertures and the second plurality of apertures independently. The power source may be operable to deliver current to both the first plurality of apertures and the second plurality of apertures. The power source may be operable to independently control an amount of current delivered to the first plurality of apertures and the second plurality of apertures. An average pitch of the plurality of apertures may be no greater than 12 mm. When the head is in the plating position, outlet ends of each of the plurality of apertures may be within 25 mm of a bottom end of the head.
Some embodiments of the present technology may encompass methods of plating a substrate. The methods may include submerging a substrate within a liquid electrolyte disposed within a vessel. The methods may include spraying the substrate with a plurality of jets of the liquid electrolyte. A flow rate defining each jet of the plurality of jets may be at least 0.02 gallons per minute. The methods may include conducting ionic current through the liquid electrolyte.
In some embodiments, the plurality of jets may be generated by flowing a volume of the liquid electrolyte through a plurality of apertures defined by a plate of a spray jet array. The plate may include a plurality of tubes that extend upward from a top surface of the plate toward the substrate. Each of the plurality of tubes may be aligned with and may partially define one of the plurality of apertures. The plurality of apertures may include a first plurality of apertures forming a first fluid channel and a second plurality of apertures forming a second fluid channel. Spraying the substrate may include spraying the substrate with jets formed through only the first plurality of apertures. Spraying the substrate may include ceasing to spray the substrate with jets formed through the first plurality of apertures. Spraying the substrate may include spraying the substrate with jets formed through only the second plurality of apertures.
Such technology may provide numerous benefits over conventional systems and techniques. For example, embodiments of the present technology may improve co-planarity across a substrate. In particular, co-planarity may be improved on wafers that include deep trenches. Additionally, embodiments of the present invention may increase the mass transfer rate and therefore increase the allowable deposition rate of plating operations. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.
A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.
Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations and may include exaggerated material for illustrative purposes.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.
In many or most electroplating applications, it is important that the plated film or layer(s) of metal have a uniform thickness across the wafer or workpiece. Non-uniformities can be caused by irregularities in the electric field due to pattern variations, by mass-transfer rates, and/or other factors. For example, co-planarity issues may arise when a substrate has regions that have different trench depths and in particular with regions that have deep trenches. Co-planarity is worsened by regions that have different open areas. Co-planarity is worsened in patterns with deep features if mass-transfer rates to the substrate are too low or non-uniform. Conventional systems may attempt to improve such co-planarity issues by reducing a current applied to the electrolyte bath to gradually fill deep trenches before later increasing the current. However, such operations may introduce additional complexity, time, and/or cost into the electroplating operation and/or may cause other issues in the electroplating process. Additionally, conventional plating systems use paddle-based electrolyte agitation devices to increase the strain rate on the wafer surface, which is correlated to plating rate in deep features. However, such paddle agitation is limited to producing strain rates in the range of between 3,000 to 4,000 per second. Such strain rates limit the plating rate in deep features and limit the throughput of the plating system.
The present technology overcomes these challenges by replacing the agitation paddles with a submerged spray jet array that sprays a number of pressurized jets of electrolyte against the wafer. Such jet arrays may increase the strain rate by approximately an order of magnitude over conventional systems. For example, embodiments of the present technology may provide strain rates of between about 20,000 and 30,000 per second. The enhanced strain rate may improve the mass transfer rate to enable higher deposition rates. Additionally, the higher strain rate may be more effective at filling deep trenches and/or other features, which may enable the plating process to be performed at higher current levels throughout the entire plating operation. The use of higher current levels may further improve the efficiency and throughput of the plating system. Accordingly, the present technology may increase plating efficiency (i.e., deposition rate) and, in some cases, improve co-planarity of substrates during electroplating operations.
Although the remaining disclosure will routinely identify specific electroplating processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to other plating chambers and systems, as well as processes as may occur in the described systems. Accordingly, the technology should not be considered to be so limited as for use with these specific plating processes or systems alone. The disclosure will discuss one possible system that may include electroplating components according to embodiments of the present technology before additional variations and adjustments to this system according to embodiments of the present technology are described.
Head 110 may be positionable within an interior of vessel 105. For example, head 110 may be supported by a head lifter 120 that is coupled with vessel 105. Head lifter 120 may lift and/or invert head 110 into an open position to load and unload a substrate. Head lifter 120 may also lower the head 110 to a plating position in which head 110 may be inserted within the interior of vessel 105 and engaged with one or more components of vessel 105 for processing of the substrate. As illustrated, head lifter 120 pivots about an axis to move head 110 between the open and plating positions, however other movement mechanisms may be utilized in various embodiments. In the plating position, a bottom portion of head 110 may be submerged within the electrolyte. For example, the electrolyte level may extend beyond a top surface of the substrate, such as by being extending above the top surface of the substrate by up to 25 mm, up to 20 mm, up to 15 mm, up to 10 mm, up to 5 mm, up to 4 mm, up to 3 mm, up to 2 mm, up to 1 mm, or less. Other depths may be possible in various embodiments.
Head 110 may be movable to position the substrate holder into the plating position in vessel 105 in which the seed layer may be in contact with electrolyte in vessel 105. Electrical control and power cables (not shown) may be linked to the lift/rotate weir shield and to internal head components lead up from system 100 to facility connections, or to connections within multi-processor automated system. A rinse assembly may be included and may have tiered drain rings that may be provided above and/or about vessel 105 in some embodiments.
System 100 may include a submerged spray jet array 125 that is disposed within the interior of vessel 105. Spray jet array 125 may be mounted within vessel 105 at a position below head 110, when head 110 is in the plating position. Spray jet array 125 may include a plate 130 that defines a plurality of apertures 135 through a thickness of plate 130. A volume of the liquid electrolyte may be passed through apertures 135 to create a number of pressurized jets of liquid electrolyte that impinge on the substrate to increase the strain rate, and subsequently the mass transfer rate, of plating material on the substrate relative to traditional electrolyte agitation techniques (e.g., using agitation paddles). For example, system 100 may include one or more fluid pumps 140 that may be fluidly coupled with an inlet end of each of the apertures 135 and may deliver liquid electrolyte to apertures 135 to generate the pressurized jets. Fluid pumps 140 may be configured to deliver the liquid electrolyte at flow rates sufficient to generate the pressurized jets. For example, the fluid pump 140 may flow the liquid electrolyte at a rate of at least 10 gallons per minute, at least 15 gallons per minute, at least 20 gallons per minute, at least 25 gallons per minute, at least 30 gallons per minute, at least 35 gallons per minute, at least 40 gallons per minute, at least 45 gallons per minute, at least 50 gallons per minute, at least 55 gallons per minute, at least 60 gallons per minute, or more. Spray jet array 125 may be submerged within the electrolyte that is contained within vessel 105. Submerging spray jet array 125 within the electrolyte may ensure that the pressurized jets provide constant current delivery paths to the substrate and do not generate any air bubbles to reach the substrate that could cause defects to form on the substrate. In some embodiments, spray jet array 125 and head 110 may be positioned such that outlet ends of each aperture 135 are within 25 mm of a bottom surface of 110 head, within 20 mm of the bottom surface, within 15 mm of the bottom surface, within 10 mm of the bottom surface, within 8 mm of the bottom surface, within 7 mm or the bottom surface, within 6 mm of the bottom surface, within 5 mm of the bottom surface, or less.
In some embodiments, there may be mass transfer uniformity issues, particularly proximate the center of the substrate. More specifically, while rotation of head 110 and the substrate during plating may ensure that the pressurized jets impinge about different regions of the substrate, if a centermost jet is coaxial with the center of rotation of head 110, the central most jet will remain in a same position relative to the substrate, which may lead to increased mass transfer rates near the center of the substrate. Different techniques may be used to mitigate such effects by better averaging the mass transfer rate across the surface of the substrate. For example, in some embodiments a center of rotation (e.g., rotational axis) of head 110 may be offset from a center of spray jet array 125. More specifically, head 110 and spray jet array 125 may be arranged relative to one another such that no single aperture 135/pressurized jet is aligned with the center of rotation of head 110. Where apertures 135 are arranged in a grid-like pattern (e.g., in rows and/or columns) the offset between the center of rotation of head 110 and spray jet array 125 may be along an X-axis (e.g., a row of apertures 135), a Y-axis (e.g., a column of apertures 135), and/or both the X-axis and the Y-axis (e.g., at an angle between the X-axis and the Y-axis). An amount of the offset may be based on a pitch between adjacent apertures in some embodiments. For example, the distance of the offset may be less than about 1× of the pitch, less than or equal to 0.9× of the pitch, less than or equal to 0.8× of the pitch, less than or equal to 0.7× of the pitch, less than or equal to 0.6× of the pitch, less than or equal to 0.5× of the pitch, less than or equal to 0.4× of the pitch, less than or equal to 0.3× of the pitch, or less.
In some embodiments, head 110 and/or spray jet array 125 may be laterally translated relative to the other component, which may ensure that a central most aperture 135/pressurized jet does not remain in a same location relative to the center of the substrate during the entire plating operation. Head 110 and/or spray jet array 125 may be laterally translated along the X-axis, the Y-axis, and/or both the X-axis and the Y-axis (e.g., at an angle of 15°, 30°, 45°, 60°, 75°, etc.).
An amount of the offset may be based on a pitch between adjacent apertures in some embodiments. For example, the distance of the offset may be less than about 1× of the pitch, less than or equal to 0.9× of the pitch, less than or equal to 0.8× of the pitch, less than or equal to 0.7× of the pitch, less than or equal to 0.6× of the pitch, less than or equal to 0.5× of the pitch, less than or equal to 0.4× of the pitch, less than or equal to 0.3× of the pitch, or less.
In some embodiments, an arrangement of apertures 135 on plate 130 may be designed to improve the uniformity of mass transfer rate across a surface of a substrate. For example, in some embodiments apertures 135 may be distributed at regular sizes and/or intervals/pitches across a substantial portion (e.g., at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or more) of plate 130, with a size and/or pitch between apertures 135 within a central region (e.g., inner 25%, inner 20%, inner 15%, inner 10%, inner 5%, or less) may be adjusted to combat mass transfer uniformity issues near a center of the substrate. For example, a pitch may be reduced (e.g., aperture density decreased) and/or a cross-sectional area of one or more apertures 135 may be increased within the central region of plate 130 to help reduce mass transfer rates within the central region to improve mass transfer rate uniformity across the surface of the substrate. For example, the larger apertures 135 may reduce jet velocity and subsequently lower the strain rate/mass transfer rate, while a smaller pitch may help provide better averaging of the mass transfer rate. In areas proximate the center of the substrate, the crossflow effect is less pronounced, which may enable the use of smaller aperture pitches in this region. It will be appreciated that any of the techniques of improving mass transfer rate uniformity may be used alone or in combination with other techniques to improve the mass transfer rate uniformity across the surface of the substrate.
System 100 may include one or more power sources 145 that may be operable to deliver current to spray jet array 125, which may enable electrolyte formed through spray jet array 125, such as via apertures 135, to deliver current to the substrate. For example, system 100 may include an anode (not shown) below plate 130 and/or a membrane. Current supplied by power source 145 controls current flow from the anode to the cathode to plate the substrate. Due to the use of apertures 135 to conduct the current to the substrate, apertures 135 may be substantially evenly distributed about plate 130 to help ensure that the current density across the substrate is substantially constant (e.g., uniform to within 15%, within 10%, within 5%, within 3%, within 1%, or less). In some embodiments, a secondary cathode (e.g., a thief electrode) may be used to improve uniformity at the edge of the substrate.
In some embodiments, a flow conductance through each aperture may be substantially equal. In other embodiments, one or more apertures 208 may have different flow conductance values. All or substantially all apertures 208 (e.g., at least 90%, at least 95%, at least 99%, all but one aperture (e.g., a centermost aperture), or all apertures) may have an equal or substantially equal (e.g., within 10%, within 5%, within 3%, within 1%, or less) flow conductance across the surface of plate 202. In other embodiments, apertures 208 may be arranged to provide variable flow conductance across a surface of plate 202. For example, in some embodiments apertures 208 may be distributed at regular sizes and/or intervals/pitches across a substantial portion (e.g., at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or more) of plate 130, with a size and/or pitch between apertures 208 within a central region (e.g., inner 25%, inner 20%, inner 15%, inner 10%, inner 5%, or less) of plate 202 being adjusted to combat mass transfer uniformity issues near a center of the substrate. For example, a pitch may be increased (e.g., aperture density decreased) and/or a cross-sectional area of one or more apertures 208 may be decreased within the central region of plate 202 to help reduce mass transfer rates within the central region to improve mass transfer rate uniformity across the surface of the substrate. In some embodiments, a pitch may be reduced (e.g., aperture density decreased) and/or a cross-sectional area of one or more apertures 208 may be increased within the central region of plate 202 to help reduce mass transfer rates within the central region to improve mass transfer rate uniformity across the surface of the substrate. For example, the larger apertures 202 may reduce jet velocity and subsequently lower the strain rate/mass transfer rate, while a smaller pitch may help provide better averaging of the mass transfer rate. In areas proximate the center of the substrate, the crossflow effect is less pronounced, which may enable the use of smaller aperture pitches in this region.
Depending on the size of the plate 202 and the size of apertures 208, plate 202 may define any number of apertures 208 through plate 202, such as greater than or about 100 apertures, greater than or about 250 apertures, greater than or about 500 apertures, greater than or about 1,000 apertures, greater than or about 2,000 apertures, greater than or about 3,000 apertures, greater than or about 4,000 apertures, greater than or about 5,000 apertures, greater than or about 6,000 apertures, or more. As noted above, apertures 208 may be included in a set of rings extending outward from a central axis of plate 202 and may include any number of rings as described previously. The rings may be characterized by any number of shapes including circular or elliptical, as well as any other geometric pattern, such as rectangular, hexagonal, or any other geometric pattern that may include apertures distributed in a radially outward number of rings. The apertures may have a uniform or staggered spacing (i.e., pitch) and may be spaced apart at between or about 3 mm and 15 mm from center to center, between or about 4 mm and 12 mm, or between or about 5 mm and 10 mm, although other pitches are possible in various embodiments.
The rings may be characterized by any geometric shape as noted above, and in some embodiments, apertures may be characterized by a scaling function of apertures per ring. For example, in some embodiments a first aperture may extend through a center of plate 202, such as along the central axis as illustrated. A first ring of apertures may extend about the central aperture, and may include any number of apertures, such as between about 4 and about 10 apertures, which may be spaced equally about a geometric shape extending through a center of each aperture. Any number of additional rings of apertures may extend radially outward from the first ring and may include a number of apertures that may be a function of the number of apertures in the first ring. For example, the number of apertures in each successive ring may be characterized by a number of apertures within each corresponding ring according to the equation XR, where X is a base number of apertures, and R is the corresponding ring number. The base number of apertures may be the number of apertures within the first ring, and in some embodiments may be some other number, as will be described further below where the first ring has an augmented number of apertures. For example, for an exemplary plate having 5 apertures distributed about the first ring, and where 5 may be the base number of apertures, the second ring may be characterized by 10 apertures, (5)×(2), the third ring may be characterized by 15 apertures, (5)×(3), and the twentieth ring may be characterized by 100 apertures, (5)×(20). This may continue for any number of rings of apertures as noted previously, such as up to, greater than, or about 50 rings.
In some embodiments, one or more apertures 208 near a center of plate 202 may be different than the other apertures 208. For example, to avoid having one hole at a center of plate 202 (which may result in higher mass transfer rates at or near the center of the substrate, even with rotation of the substrate relative to spray jet array 200), the central most hole may be replaced by a number of smaller holes that are offset from a center of plate 202. To help maintain a consistent current density and strain rate across the substrate surface, the smaller holes may be sized to collectively deliver a same current rate and fluid flow rate as a single central aperture 208. In some embodiments, apertures 208 may each include a same diameter, while in other embodiments some or all of apertures 208 may have different diameters. For example, diameters proximate a center of plate 202 may be different sizes than apertures 208 further from the center of plate 202, which may enable the fluid conductance/flow rate to be varied across the substrate to help average the strain rate across the surface of the substrate.
Liquid electrolyte may be delivered to second surface 206 such that the liquid electrolyte is forced through apertures 208. Due to the small size of apertures 208, the liquid electrolyte passing through apertures 208 forms pressurized jets extending from first surface 204 that may be directed upon a surface of a substrate positioned within a head, such as head 110. The pressurized jets may increase the strain rate of electrolyte against the substrate and may therefore increase the mass transfer rate of the plating operation.
To ensure that the plating rate is substantially uniform across the surface of the substrate it may be desirable to maintain the current density upon the substrate at a substantially uniform level across the surface of the substrate. In some embodiments, to ensure that the current density is uniform across a surface of the substrate, the positioning of plate 202 relative to the head of the electroplating system and positioning of apertures 208 on plate 202 may be designed such that a ratio of the gap between first surface 204 of plate 202 and the substrate and/or bottom surface of the head and a pitch between adjacent apertures 208 on plate 202 meets a certain threshold. For example, the ratio between the gap and the pitch may be at least about at least about 1:1, at least about 1.1:1, at least about 1.25:1, at least about 1.5:1, or greater. Such relationships may be maintained across all or a substantial portion (e.g., at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, at least 99%, or more) of plate 202 and/or apertures 208.
In some embodiments, upon contacting the substrate, the pressurized jets of electrolyte may accumulate and scatter laterally outward from the surface of the substrate, creating a crossflow effect across at least a portion of the substrate surface, which may impact the mass transfer uniformity across the surface of the substrate as the crossflow may prevent the jets from impinging on the surface of the substrate in a uniform manner. To help reduce the effects of crossflow, a ratio between the pitch of apertures 208 on plate 202 to the diameter of apertures 208 on plate 202 may be at least 6:1, at least 6.5:1, at least 7:1, at least 7.5:1, at least 8:1, at least 8.5:1, at least 9:1, at least 9.5:1, at least 10:1, at least 11:1, at least 12:1, or greater. Such ratios may ensure that there is enough space between adjacent jets to prevent any crossflow from interfering with the impingement of a nearby jet. For example, the space between adjacent jets may provide clearance for laterally outward flowing fluid to pass to the edge of the substrate without interfering with the other jets. As will be discussed below in at least
While shown with first surface 204 and second surface 206 being planar, it will be appreciated that in some embodiments one or both of first surface 204 and second surface 206 may be nonplanar. For example, first surface 204 may include one or more higher and lower regions, which may place outlet ends of some of apertures 208 at different distances from the substrate. As just one example, a center portion of first surface 204 may be higher (or closer to the substrate) than an outer portion of first surface 204. Such adjustments may impact strain rates and mass transfer across the surface of the substrate by increasing the strain rate at some areas and/or decreasing the strain rate at other areas. Additionally, aperture pitch may be varied across plate 202 to control strain rate and/or electrical current uniformity across the surface of the substrate.
In some embodiments, each aperture 208 may be designed to produce turbulent jets of electrolyte. Turbulent flow may enhance mass transfer due to the flow dynamics, as well as due to enhanced turbulent diffusion. In some embodiments, the flow of electrolyte within each aperture 208 may be turbulent, along with the jets emanating from each aperture 208. In other embodiments, the jets may be turbulent even if flow within apertures 208 has not quite reached fully developed turbulent flow. Flow within apertures 208 may be considered turbulent the Reynolds number exceeds 2300. The Reynolds number depends upon the tube velocity and diameter as well as the fluid kinematic viscosity. For example, the Reynolds number may be equal to (Re=V*D/v). This Re criteria is for fully developed conditions in long apertures 208, however in some embodiments the jets emanating from apertures 208 that do not have Reynolds numbers exceeding 2300 may be turbulent. As noted above, aperture length may be a factor in generating fully developed turbulent flow within the aperture. As just one example, apertures 208 having diameters of 1 mm may have lengths of at least or about 16 mm to produce fully developed turbulent flow. A length of apertures 208 may be dictated by a thickness of plate 202 in the illustrated embodiment. In such embodiments, the transition to turbulence occurs over an entrance region of each aperture 208. It will be appreciated that other lengths may be possible depending on aperture diameter and electrolyte viscosity.
Plate 302 may include a number of tubes 310 that extend upward from first surface 304 (e.g., a top surface) of plate 302. Tubes 310 may extend toward a bottom surface of the substrate and the head of the electroplating system. Each tube 310 may be aligned with and may partially define one of the apertures 308. In some embodiments, a number of tubes 310 matches a number of apertures 308 such that each aperture 308 extends through one of the tubes 310. This may position an outlet end of each aperture 308 at a distance from first surface 304 that matches a length or height of tube 310, which may provide additional space (e.g., gullies formed between tubes 310) for any crossflow to pass through without having a large impact on mass transfer rate uniformity. Each tube 310 may have a same or different height (e.g., protrusion distance from first surface 304). For example, each tube 310 may have a height of between or about 5 mm and 20 mm, between or about 7.5 mm and 15 mm, or between or about 10 mm and 12 mm. The additional clearance space created between adjacent apertures 308 through the presence of tubes 310 may enable smaller aperture pitches to be used without significantly impacting the effects of crossflow (e.g., non-uniform mass transfer rates). For example, pitches for apertures 308 may be between 2 mm and 12 mm from center to center, between 3 mm and 10 mm, or between 5 mm and 8 mm, although other pitches are possible in various embodiments. Smaller pitches may enable smaller gaps between the outlet ends of apertures 208 and the substrate (e.g., based on the ratio of gap:pitch disclosed above. Smaller gaps may also enable better plating uniformity across the substrate.
To ensure that the plating rate is substantially uniform across the surface of the substrate it may be desirable to maintain the current density upon the substrate at substantially uniform levels across the surface of the substrate. In some embodiments, to ensure that the current density is uniform across a surface of the substrate, the positioning of plate 302 relative to the head of the electroplating system and positioning of apertures 308 on plate 302 may be designed such that a ratio of the gap between outlet ends of each aperture 308 (e.g., distal ends of tubes 310) and the substrate and/or bottom surface of the head and a pitch between adjacent apertures 308 on plate 302 meets a certain threshold. For example, the ratio between the gap and the pitch may be at least about 1:1, at least about 1.1:1, at least about 1.25:1, at least about 1.5:1, or greater. In some embodiments, spray jet array 300 may be positioned such that outlet ends of each aperture 308 are within 25 mm of a bottom surface of the substrate, within 20 mm of the substrate, within 15 mm of the substrate, within 10 mm of the substrate, within 8 mm of the substrate, within 7 mm or the substrate, within 6 mm of the substrate, within 5 mm of the substrate, or less. In some embodiments, a gap to diameter ratio may also be at least 6:1, at least 6.5:1, at least 7:1, at least 7.5:1, at least 8:1, at least 8.5:1, at least 9:1, at least 9.5:1, at least 10:1, at least 11:1, at least 12:1, or greater. To improve uniformity across the substrate, it may be desirable to use smaller gaps, which may lead the diameters of the apertures to be smaller (e.g., 1 mm or less). Smaller diameter apertures may generate higher jet velocities, which may lead to higher strain rates on the substrate surface. In some embodiments, high flow rates (such as at least 0.01 gpm, at least 0.02 gpm, at least 0.03 gpm, at least 0.04 gpm, at least 0.05 gpm, or more) per aperture may be used. Longer tubes may enable flow within the aperture/tube to become turbulent, which may enhance strain rates on the substrate. In some embodiments, plate 302 may be thinner than plate 202 while producing turbulent flow, as tubes 310 may add length to each aperture 308 that extends beyond a thickness of plate 302.
To help reduce the effects of crossflow, plate 402 may define a number of drain tubes 410 through a thickness of plate 402. In some embodiments, bottom ends of drain tubes 410 may extend beyond second surface 406, such as by a distance that extends beyond a fluid supply source that pumps the electrolyte to inlet ends of apertures 408. Such positioning may ensure that electrolyte is not pumped upward through drain tubes 410. Drain tubes 410 may be positioned about plate 402 to enable a portion of the liquid electrolyte to be drained from the gap between plate 402 and the substrate. For example, rather than being coupled with a fluid pump and delivering jets of fluid to the substrate like apertures 408, drain tubes 410 may collect and drain fluid that is circulating above plate 402. This drainage may help reduce the effects of crossflow on mass transfer uniformity. Drain tubes 410 may be positioned between some or all apertures 408. In some embodiments, drain tubes 410 may be distributed across an entire surface of plate 402, such as between each ring or row of apertures 408. In other embodiments, drain tubes 410 may be positioned at particular radial locations about plate 402. As just one example, drain holes 410 may be positioned at radial positions that are close to a center of plate 402 and/or within a medial region of plate 402. For example, drain holes 410 may be positioned within an inner 60%, inner 50%, inner 40%, inner 30%, inner 20%, inner 10%, inner 5%, or less of plate 402, although drain holes 410 may be positioned at any radial position in various embodiments. Drain holes 410 may be positioned at regular angular and/or radial intervals about plate 402. Drain holes 410 may have a same or different (e.g., smaller or larger) diameter than apertures 408. For example, in some embodiments each drain hole 410 may have a greater diameter than each aperture 408, which may enable fewer drain holes 410 to be used. In some embodiments, each drain hole 410 may have a diameter of between or about 1 mm and 10 mm, between or about 2 mm and 8 mm, or between or about 4 mm and 6 mm.
First plate 502 may define a number of second apertures 510 through first plate 502. First apertures 508 and second apertures 510 may form two different flow paths through first plate 502. Second apertures 510 may be positioned in between some or all of first apertures 508. For example, first apertures 508 and second apertures 510 may be arranged in an alternating fashion, with a second aperture 510 positioned within each gap between adjacent first apertures 508 in one or two rows/rings of first apertures 508. In some embodiments, first apertures 508 and second apertures 510 may be arranged in a same row/ring, with a second aperture 510 being positioned between each pair of adjacent first apertures 508. In some such embodiments, adjacent rows/rings apertures may be aligned such that along a given radial line, each row/ring includes only first apertures 508 or second apertures 510. In other such embodiments, adjacent rows/rings apertures may be aligned such that along a given radial line, each row/ring alternates between first apertures 508 and second apertures 510. In some embodiments, first apertures 508 and second apertures 510 may be arranged in different alternating rows/rings, with a row/ring of second apertures 510 being positioned between each pair of adjacent rows/rings first apertures 508. In some such embodiments, apertures in each row may be aligned along the same radial lines. In other such embodiments, adjacent rows/rings apertures may be aligned such that a second aperture 510 is disposed between four adjacent first apertures 508 (e.g., two first apertures 508 from one row/ring and two additional first apertures 508 from an adjacent row/ring). It will be appreciated that the arrangements described above are merely provided as examples and that other arrangements are possible. For example, first apertures 508 and second apertures 510 may be arranged in non-alternating fashions. Arrangements of first apertures 508 and/or second apertures 510 may be generally uniform and/or symmetric in some embodiments, while in other embodiments arrangements of first apertures 508 and/or second apertures 510 may be non-uniform and/or asymmetric.
In some embodiments, a number of first apertures 508 may match or substantially match (e.g., within 10%, within 5%, within 3%, within 1%, etc.) a number of second apertures 510. In other embodiments, a number of first apertures 508 may be substantially different (e.g., over 10%) than a number of second apertures 510. First apertures 508 and second apertures 510 may have the same or different diameters. Similarly, first apertures 508 may collectively have a same or substantially same (e.g., within 10%, within 5%, within 3%, within 1%, etc.) flow conductance and/or current conductance as second apertures 510, collectively.
Spray jet array 500 may include a second plate 512, which may be characterized by a first surface 514 (e.g., a top surface) and a second surface 516 (e.g., a bottom surface), which may be opposite first surface 514. In some embodiments, a peripheral wall may couple first plate 502 and second plate 512. Second plate 512 may be a bottom plate of spray jet array 500 and may define a portion of each second aperture 510 through second plate 512. Second plate 512 may be coupled with first plate 502, such as on a bottom side of first plate 502. A number of tubes 518 may extend between first plate 502 and second plate 512. Each lumen 518 may be aligned with and may partially define one of second apertures 510. A number of tubes 518 may match a number of second apertures 510 such that each second aperture 510 is defined by a respective lumen 518. In embodiments with two plates, an inlet end of each first aperture 508 may be formed through second surface 506 of first plate 502. An inlet end of each second aperture 510 may be formed through second surface 516 of second plate 512. An outlet end of each first aperture 508 and each second aperture 510 may be formed through first surface 504 of first plate 502.
A plenum 520 may be defined between first plate 502 and second plate 512, such as forming a portion of a volume between first plate 502 and second plate 512 that extends about an exterior of each lumen 518. Plenum 520 may form a portion of a flow path for pumping electrolyte through first apertures 508. For example, as shown in
The use of dual-channel spray jet array 500 may enable gaps between outlets of each aperture and the substrate to be smaller while also keeping a pitch between adjacent apertures small, which may result in improved strain rate uniformity and current density uniformity across a surface of the substrate. For example, flow of electrolyte through first apertures 508 and second apertures 510 may be cycled such that electrolyte flows through only a single set of apertures at a given time. In embodiments in which first apertures 508 and second apertures 510 are arranged about first plate 502 in an alternating fashion, such cycling may increase the effective pitch at a given instant as only half of the apertures on first plate 502 are delivering jets of electrolyte at that time. The increased pitch reduces the impact of crossflow on the strain rate uniformity. At a later point, the other half of the apertures on first plate 502 may deliver jets of electrolyte, which maintains a greater aperture pitch. The cycling ensures that at some point during the plating process, apertures proximate each radial location of the substrate are delivering jets of electrolyte. Current may be supplied to the substrate via the electrolyte, including the pressurized jets of electrolyte.
By cycling delivery of electrolyte to the different fluid channels (e.g., first apertures 508 and second apertures 510), spray jet array 500 may collectively provide an aperture pitch that may facilitate uniform strain rates across the substrate, while also being sufficiently large to prevent and/or mitigate crossflow effects. As just one example, first apertures 508 and second apertures 510 may be arranged in an alternating fashion about plate 502, such as with a pitch between adjacent first and second apertures being 5 mm (or some other small pitch). This pitch value enables the use of a gap on the order of 5 mm. However, a pitch between two adjacent first apertures 508 may be larger, such as 10 mm (or other first aperture pitch). Similarly, a pitch between two adjacent second apertures 510 may be larger, such as 10 mm (or other second aperture pitch). Thus, when only one set of apertures (e.g., first apertures 508) delivers electrolyte to the substrate, spray jet array 500 effectively operates with the larger 10 mm pitch. When the electrolyte is cycled to be delivered via the other set of apertures (e.g., second apertures 510), spray jet spray jet array 500 effectively operates with the larger 10 mm pitch. The larger flow pitch of 10 mm avoids cross flow effects that would be seen with the smaller 5 mm pitch. Collectively, however, the pitch is the smaller 5 mm pitch, as both sets of apertures have been used to deliver the electrolyte for some period of time (which may be the same or different). Any number of such cycles may be utilized in various plating operations. Additionally, due to the larger pitch at any given instant, a gap between first plate 502 and the substrate/carrier head may be reduced while still maintaining the ratios that promote uniform current density and strain rates across a surface of the wafer. For example, the gap between first plate 502 and the substrate/carrier head may be less than 10 mm, less than 9 mm, less than 8 mm, less 7 mm, less than 6 mm, less than 5 mm, or less.
It will be appreciated that spray jet arrays 200, 300, 400, and 500 are merely provided as examples and that numerous variations may exist. Additionally, various combinations of features from the example spray jet array (or other spray jet arrays) may be utilized in accordance with the present invention.
Method 600 may include submerging a substrate within a liquid electrolyte disposed within a vessel at operation 605. For example, the substrate may be secured against a carrier head that is moved downward relative to the vessel to at least partially submerge the substrate within the liquid electrolyte. At operation 610, the substrate may be sprayed with a plurality of jets of the liquid electrolyte. For example, one or more fluid pumps may deliver a volume of the liquid electrolyte to a spray jet array that is disposed within the vessel below the substrate and carrier head. In some embodiments, the flow rate of electrolyte delivered to the spray jet array may be constant, while in other embodiments, the flow rate may be varied. For example, the flow rate may be pulsed between two or more different rates at different points during the plating process to help even out and/or otherwise control the strain rate on the substrate. The amount of time each flow rate is maintained may be the same or different, and in some embodiments, the flow rate may be continuously varied across all or a portion of the plating process.
The spray jet array may be similar to those described herein, such as spray jet array 200, spray jet array 300, spray jet array 400, and spray jet array 500. In some embodiments, such as when the spray jet array is a dual-channel jet array similar to spray jet array 500, spraying the substrate may include spraying the substrate with jets formed through a first subset of apertures (e.g., first apertures 508), ceasing to spray the substrate with the jets formed through a first subset of apertures, and spraying the substrate with jets formed through a second subset of apertures (e.g., second apertures 510). As described above, such a process may enable an effective pitch of the apertures formed through the spray jet array to be sufficiently large to mitigate any effects of crossflow on strain rate uniformity, while still providing a sufficiently small aperture pitch to effectively plate an entire surface of the substrate.
At operation 615, ionic current may be conducted through the liquid electrolyte and/or spray jet array. For example, one or more power sources may apply ionic current to the electrolyte, such as via one or more anodes or other electrodes. The ionic current may initiate plating of a donor plating material onto one or more features formed on a surface of the substrate facing the spray jet array. The ionic current may be delivered to the substrate via the apertures formed in the plate(s). The ionic current may be delivered before, during, and/or after the jets are sprayed against the substrate.
In some embodiments, to help average out the strain rate and mass transfer rate across the surface of the substrate, the substrate and spray jet array may be rotated and/or laterally translated relative to one another. For example, the carrier head carrying the substrate may be rotated about a central axis and/or may be laterally translated back and forth relative to the substrate. In some embodiments, rather than, or in addition to, rotating and/or translating the carrier head, the spray jet assembly may be rotated and/or laterally translated. The rotation and/or lateral movement of the substrate relative to the spray jet assembly may ensure that individual spray jets do not impinge upon the substrate at one fixed location, which may result in better plating uniformity. In some embodiments, a gap between the spray jet array and the substrate may be constant, while in other embodiments the gap may be periodically varied during the plating process. For example, the carrier head and/or spray jet array may be configured to translate vertically within the plating vessel, which may enable the gap between the spray jet array and the substrate to be adjusted before and/or during plating operations. The time spent at each gap size may be the same or different, and in some embodiments, the gap may be continuously varied across all or a portion of the plating process.
In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly or conventionally understood. As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. “About” and/or “approximately” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, encompasses variations of 20% or +10%, +5%, or +0.1% from the specified value, as such variations are appropriate to in the context of the systems, devices, circuits, methods, and other implementations described herein. “Substantially” as used herein when referring to a measurable value such as an amount, a temporal duration, a physical attribute (such as frequency), and the like, also encompasses variations of 20% or +10%, +5%, or +0.1% from the specified value, as such variations are appropriate to in the context of the systems, devices, circuits, methods, and other implementations described herein.
Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a heater” includes a plurality of such heaters, and reference to “the protrusion” includes reference to one or more protrusions and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.
