Patent Application
20050173253
1. Field of the Invention
Embodiments of the invention are generally related to a method for minimizing defects resulting from thermal shock encountered by a substrate during transfer from a fluid processing cell into an annealing chamber.
2. Description of the Related Art
Metallization of sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. More particularly, in devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio, i.e., greater than about 4:1, interconnect features with a conductive material. The most common conductive material used in large scale integration devices is copper. Copper is generally deposited into the high aspect ratio features of these devices using plating processes, such as electrochemical plating (ECP) and/or electroless plating.
In an ECP process, for example, high aspect ratio features formed into the surface of a substrate, which generally have a conductive seed layer deposited thereon, are filled with a conductive material. ECP processes are generally performed in a two stages. First, the seed layer is formed over the surface features, generally through PVD, CVD, or other deposition process. Second, the surface features of the substrate having the seed layer thereon are exposed to an electrolyte solution, while an electrical bias is applied between the seed layer and an anode positioned in the solution. The solution contains the conductive material to be plated onto the surface of the substrate, and the application of the electrical bias between the seed layer and the anode is configured to cause the conductive material in the solution to be plated onto the seed layer and into the interconnect features, thus filling the features.
Once the plating process is completed, the substrate is generally transferred to at least one of a substrate rinsing cell or a bevel edge clean cell. Bevel edge clean cells, often called IBC cells, are generally configured to dispense an etchant onto the perimeter of the substrate to remove unwanted metal plated thereon. The substrate rinse cells, often called spin rinse dry cells, or “SRD” cells, generally operate to rinse the entire surface of the substrate, front and/or back, with a rinsing and/or cleaning solution to remove any excess processing fluids or contaminants therefrom. The SRD cells are also generally configured to spin the substrate at a high rate of speed in order to spin off any fluid droplets adhering to the substrate surface. Once the remaining fluid droplets are spun off, the substrate is generally clean and dry.
Once the substrate is clean and dry, the substrate is generally exposed to an increased temperature to stabilize film properties, such as the crystalline structure and the resistivity of the film. For this portion of the process, the substrate may be transferred to an annealing station. A typical annealing station may include an enclosure having a heated substrate support member positioned therein. Alternatively, a substrate support member may be used to support the substrate, while a heating source, such as heating lamps, is used to heat the substrate. Regardless of the heating source used, the annealing station is generally configured to increase the temperature of the substrate from room temperature to between about 200° C. and about 400° C. in less than about 1 minute.
However, one challenge with conventional plating systems is that the rapid increase in the temperature of the substrate in the annealing chamber has been shown to cause voids and cracking in the plated layer and between the plated layer and the adjoining dielectric layer. Voids and cracks in the plated layer may be reduced by slowing the anneal temperature ramp, however, slowing the temperature ramp inherently slows the throughput of the ECP process, which is critical to semiconductor processing.
Therefore, there is a need for an ECP system and method for processing substrates, wherein the system and method includes an annealing step that both maximizes throughput and minimizes voids and cracking that result from rapid temperature ramp processes.
Embodiments of the invention generally provide a semiconductor processing apparatus and method configured to minimize voids and cracks in films resulting from rapid anneal temperature ramping. The apparatus of the invention includes a fluid processing cell configured to preheat the substrate prior to the substrate being transferred to the annealing chamber. The fluid processing cell that is used to preheat the substrate is generally an SRD cell. The method of the invention generally includes supplying a heated fluid to an SRD cell on a semiconductor processing platform. The heated fluid is used to increase the temperature of the substrate to a temperature between room temperature and the annealing temperature prior to the substrate being transferred to the annealing chamber. Further, the heated fluid is applied as part of a previously required processing step, i.e., a rinsing step, and as such, the application of the heated fluid does not have a negative impact on the throughput of the system. Preheating prior to anneal may also be used to shorten the required anneal time, and as such, increase throughput of the processing system.
Embodiments of the invention may further provide a method for processing a substrate. The method includes plating a conductive layer onto a substrate, transferring the substrate from a plating cell to a cleaning cell, cleaning the substrate in the cleaning cell via application of a heated cleaning fluid to the substrate, drying the substrate in the cleaning cell, transferring the substrate from the cleaning cell to an annealing chamber, and annealing the substrate in the annealing chamber at a temperature of between about 150° C. and about 450° C.
Embodiments of the invention may further provide a method for processing a substrate, wherein the method includes plating a conductive layer onto a substrate, rinsing the substrate of unwanted residue chemicals, preheating the substrate during the rinsing process to a temperature of between about 25° C. and about 100° C., and annealing the substrate in an annealing chamber at a temperature of up to about 450° C. subsequent to the preheating process.
Embodiments of the invention may further provide an apparatus for processing a substrate, wherein the apparatus includes a plating cell positioned on a processing platform, the plating cell being configured to plate a conductive layer onto the substrate, a rinsing cell positioned on the processing platform, and an annealing station positioned on the processing platform. The rinsing cell generally includes a substrate support member configured to support the substrate for processing, a fluid dispensing nozzle positioned to dispense a rinsing solution onto the substrate, and a fluid heating assembly positioned in fluid communication with the fluid dispensing nozzle, the fluid heating assembly being configured to supply a heated rinsing solution at a temperature of between about 50° C. and about 100° C.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Embodiments of the invention generally provide an electrochemical plating system configured to plate conductive materials onto semiconductor substrates. The plating system generally includes a substrate loading area in communication with a substrate processing platform. The loading area is generally configured to receive substrate containing cassettes and transfer substrates received from the cassettes into the plating system for processing. The loading area generally includes a robot configured to transfer substrates to and from the cassettes and to the processing platform or a substrate annealing chamber positioned in communication with the loading area. The processing platform generally includes at least one substrate transfer robot and a plurality of substrate processing cells, i.e., ECP cells, bevel clean cells, spin rinse dry cells, substrate cleaning cells, and/or electroless plating cells.
The position of the robot 132 allows the robot 132 to access substrate cassettes 134 positioned on the loading stations, and to then deliver the substrates to one of the processing cell stations shown at 114 and 116 on the mainframe 113. Similarly, the robot 132 may be used to retrieve substrates from the processing cells 114, 116, or transfer substrates to or from an annealing chamber 135. After a substrate processing sequence is complete, robot 132 generally operates to return substrates to one of the cassettes 134 for removal from the ECP system 100. Additional configurations and implementations of an electrochemical processing system are illustrated in commonly assigned U.S. patent application Ser. No. 10/435,121 filed on Dec. 19, 2002 entitled “Multi-Chemistry Electrochemical Processing System”, which is incorporated herein by reference in its entirety.
The anneal chamber 135 generally includes a two position annealing station, wherein a cooling plate 136 and a heating plate 137 are positioned adjacently with a substrate transfer robot 140 positioned proximate thereto, e.g., between the two plates. The robot 140 is generally configured to move substrates between the respective heating 137 and cooling plates 136. Further, although the anneal station 135 is illustrated as being positioned such that it is accessed from the link tunnel 115, embodiments of the invention are not limited to any particular configuration or placement. As such, the anneal station 135 may be positioned in communication with the mainframe 113. Additional information relative to the anneal station 135 of the invention may be found in a commonly assigned U.S. Patent Application Ser. No. 60/463,860, entitled “Two Position Anneal Chamber,” which is hereby incorporated by reference in its entirety.
ECP system 100 also includes a processing mainframe 113. A substrate transfer robot 120 is positioned on the mainframe 113, and includes one or more blades 122, 124 configured to support and transfer substrates. Additionally, robot 120 and the accompanying blades 122, 124 are generally configured to extend, rotate about a central point, and vertically move, so that the robot 120 may insert and remove substrates from a plurality of processing cells 102, 104, 106, 108, 110, 112, 114, 116 positioned on the mainframe 113. Generally, processing cells 102, 104, 106, 108, 110, 112, 114, 116 may be any number of processing cells utilized in an electrochemical plating process, e.g., electrochemical plating cells, rinsing cells, bevel clean cells, spin rinse dry cells, substrate surface cleaning cells, electroless plating cells, metrology inspection stations, and/or other processing cells that may be beneficially used in conjunction with a plating process. Each of the respective processing stations and robots are generally in communication with a process controller 111, which may be a microprocessor-based control system configured to receive inputs from a user and/or various sensors positioned on the system 100 and appropriately control the operation of the system 100 in accordance with the inputs and/or a predetermined control sequence.
In the exemplary plating system illustrated in
A membrane 208 is stretched across the support 206. The membrane operates to fluidly separate catholyte chamber and anolyte chamber portions of the plating cell 200. The membrane support assembly may include an o-ring type seal positioned near a perimeter of the membrane 208, wherein the seal is configured to prevent fluids from traveling from one side of the membrane secured on the membrane support 206 to the other side of the membrane 208. A diffusion plate 210, which is generally a porous ceramic disk member, is configured to generate a substantially laminar flow or even flow of fluid in the direction of the substrate being plated. The diffusion plate 210 is positioned in the cell 200 between membrane 208 and the substrate being plated. The exemplary plating cell is further illustrated in commonly assigned U.S. patent application Ser. No. 10/268,284, which was filed on Oct. 9, 2002 under the title “Electrochemical Processing Cell”, claiming priority to U.S. Provisional Application Ser. No. 60/398,345, which was filed on Jul. 24, 2002, both of which are incorporated herein by reference in their entireties.
A plurality of upstanding substrate engaging fingers 303 are positioned radially around the perimeter of flywheel 302. Generally, fingers 303 are airfoil shaped when viewed from the top, so that the fingers 303 will generate minimal turbulence when flywheel 302 is rotated. In the illustrated embodiment of the invention, four fingers 303 may be utilized, however, the invention is not limited to any particular number of fingers. Fingers 303 are configured to rotatably support a substrate 304 at the bevel edge thereof for processing in SRD 300. Together, the flywheel 302 and the substrate engaging fingers 303 serve as a rotatable substrate support member. However, other embodiments may be provided where the engaging fingers 303 are connected to the side wall or other components of the cell than a flywheel.
The processing cell 300 also includes a fluid dispensing arm 350 that may be pivotally mounted to the side wall, or a structure positioned outside of the cell 300, such that a distal end of the arm having a fluid dispensing nozzle positioned thereon may be pivoted to a position over a substrate 304 being processed in the cell 300. The pivotal motion of the arm 350 is generally in a plane that is parallel and above the substrate 304 being processed. The pivotal movement of the arm 350 allows the nozzle positioned on the end of the arm 350 to be positioned over specific radial positions on the substrate, i.e., over the center of the substrate or over a point that is a specific radius from the center of the substrate 304, for example.
Processing cell 300 also includes an upper cell wall 309 attached to the catch cup 314 and curved surface 316, all of which may be raised and lowered to facilitate loading and unloading of substrates. For example, when a substrate is loaded, upper wall 309 may be raised from cell bowl 301 to allow for access to the substrate engaging fingers 303. When processing begins, then wall 309 may be lowered to position the catch cup 314 and curved wall 316 next to the substrate so the that the fluid spun off of the substrate may be captured and airflow over the perimeter of the substrate controlled. Exemplary processing cells that may be used to advantage to practice the invention include commonly assigned U.S. patent application Ser. No. 10/680,616, filed Oct. 6, 2003 and U.S. Pat. No. 6,290,865, both of which are hereby incorporated by reference in their entireties.
Processing cell 300 also includes a heating source configured to increase the temperature of the substrate during a fluid processing step. The heating source may include a heated fluid source 375 in fluid communication with the fluid dispensing arm 350 and/or the backside nozzles 308. The source of heated fluid 375 may include a fluid tank having a resistive heating element 382 positioned therein. Heating element 380 is in electrical communication with a source of power 382. The source of power 382 may be in communication with controller 111, and as such, be controlled by controller 111 illustrated in
In another embodiment of the invention, the source of heated fluid 375 may be replaced or supplemented with heating lamps 402 positioned to heat the substrate during the fluid processing step, as illustrated on processing cell 400 in
In operation, embodiments of the invention are generally configured to preheat a substrate prior to an anneal process in order to minimize voids, cracks, and peeling associated with the thermal shock of placing a room temperature substrate into a high temperature annealing chamber. The preheating process is generally conducted in a fluid processing cell, and more particularly, in an SRD cell positioned on the processing platform, wherein the SRD cell is configured to dispense a heated fluid onto the substrate to increase the temperature of the substrate prior to transferring the substrate to the anneal chamber.
As noted above, a conventional ECP process includes plating a conductive layer onto a substrate, transferring to a bevel edge cleaning cell for bevel cleaning, transferring to a spin rinse dry cell for rinsing and/or cleaning and drying the substrate, and then transferring to an anneal chamber where the substrate is heated to stabilize the conductive layer. The present invention adds a substrate heating step into the spin rinse dry process. More particularly, a conventional substrate spin rinse dry process includes rotating the substrate at a rate of between about 10 rpm and about 500 rpm while a rinsing and/or cleaning solution is dispensed onto the top and/or bottom surfaces of the substrate. The rinsing fluid of the present invention is provided to the spin rinse dry cell at a temperature of between about 25° C. and about 100° C., or alternatively, between about 50° C. and about 100° C. or between about 75° C. and 100° C. The heated rinsing fluid may be applied to the front and/or backside of the substrate while the substrate is rotated. The fluid contacts the substrate surface and transfers heat from the fluid to the substrate, thus heating the substrate to a temperature near the temperature of the rinsing fluid. The heated rinsing fluid may be dispensed onto the substrate until the substrate surfaces are sufficiently clean and the substrate is heated to the desired temperature. In one embodiment of the invention, deionized water at a temperature of between about 50° C. and about 100° C. is dispensed onto the substrate surface while the substrate is rotated. The heated deionized water is dispensed for between about 5 seconds and about 20 seconds before the flow of the heated water is terminated and a drying process is initiated.
Once the rinsing process is completed, the flow of the rinsing fluid is terminated, and the substrate may be rotated at a higher rotation rate to dry the substrate. For example, the substrate may be rotated at between about 500 rpm and about 3000 rpm for between about 10 seconds and about 60 seconds to dry the substrate, or alternatively, between about 5 seconds and about 25 seconds. The higher rotation speed of the substrate generates a centrifugal force sufficient to urge fluid outward and off of the surfaces of the substrate, thus drying the substrate. In the present invention, it is desirable to spin the substrate at between about 2000 rpm and about 3000 rpm during the drying process so that the drying time is minimized, as an extended drying time has been shown to decrease the substrate temperature. Therefore, once the substrate is heated with the heated rinsing fluid, embodiments of the invention are configured to minimize delay and transfer the substrate to the annealing chamber as soon as practicable.
Once the drying process is completed, the substrate is transferred to the annealing chamber. In the system illustrated in
