1. Field of the Invention
The present invention relates to a method and system for thin film deposition, and more particularly to a method and system for improved precursor vapor delivery in a thin film deposition system.
2. Description of Related Art
The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits can necessitate the use of diffusion barriers/liners to promote adhesion and growth of the Cu layers and to prevent diffusion of Cu into the dielectric materials. Barriers/liners that are deposited onto dielectric materials can include refractive materials, such as tungsten (W), molybdenum (Mo), and tantalum (Ta), that are non-reactive and immiscible in Cu, and can offer low electrical resistivity. Current integration schemes that integrate Cu metallization and dielectric materials can require barrier/liner deposition processes at substrate temperature between about 400° C. and about 500° C., or lower.
For example, Cu integration schemes for technology nodes less than or equal to 130 nm currently utilize a low dielectric constant (low-k) inter-level dielectric, followed by a physical vapor deposition (PVD) TaN layer and Ta barrier layer, followed by a PVD Cu seed layer, and an electrochemical deposition (ECD) Cu fill. Generally, Ta layers are chosen for their adhesion properties (i.e., their ability to adhere on low-k films), and Ta/TaN layers are generally chosen for their barrier properties (i.e., their ability to prevent Cu diffusion into the low-k film).
As described above, significant effort has been devoted to the study and implementation of thin transition metal layers as Cu diffusion barriers, these studies including such materials as chromium, tantalum, molybdenum and tungsten. Each of these materials exhibits low miscibility in Cu. More recently, other materials, such as ruthenium (Ru) and rhodium (Rh), have been identified as potential barrier layers since they are expected to behave similarly to conventional refractory metals. However, the use of Ru, or Rh can permit the use of only one barrier layer, as opposed to two layers, such as Ta/TaN. This observation is due to the adhesive and barrier properties of these materials. For example, one Ru layer can replace the Ta/taN barrier layer. Moreover, current research is finding that the one Ru layer can further replace the Cu seed layer, and bulk Cu fill can proceed directly following Ru deposition. This observation is due to good adhesion between the Cu and the Ru layers.
Conventionally, Ru layers can be formed by thermally decomposing a ruthenium-containing precursor, such as a ruthenium carbonyl precursor, in a thermal chemical vapor deposition (TCVD) process. Material properties of Ru layers that are deposited by thermal decomposition of metal-carbonyl precursors (e.g., Ru3(CO)12) can deteriorate when the substrate temperature is lowered to below about 400° C. As a result, an increase in the (electrical) resistivity of the Ru layers and poor surface morphology (e.g., the formation of nodules) at low deposition temperatures has been attributed to increased incorporation of CO reaction by-products into the thermally deposited Ru layers. Both effects can be explained by a reduced CO desorption rate from the thermal decomposition of the ruthenium-carbonyl precursor at substrate temperatures below about 400° C.
Additionally, the use of metal-carbonyls, such as ruthenium carbonyl, can lead to poor deposition rates due to their low vapor pressure and the transport issues associated therewith. For instance, transport issues can include excessive decomposition of the precursor vapor on internal surfaces of the deposition system, such as on the internal surfaces of the vapor delivery system used to transport the vapor from the evaporation system to the process chamber, thus further reducing the amount of precursor vapor that reaches the substrate surface. Overall, the inventor has observed that current deposition systems suffer from such a low rate, making the deposition of such metal films impractical.
A method and system is provided for improving the transport of precursor vapor in a thin film deposition system.
In one embodiment of the present invention, a method and system is provided for improving the transport of precursor vapor in a thin film deposition system by applying a coating to one or more internal surfaces of a vapor delivery system exposed to the precursor vapor.
In a further embodiment of the present invention, a method and system is provided for depositing a metal film from a metal-carbonyl precursor, and periodic cleaning of the coating applied to the internal surfaces is performed using an in-situ cleaning system.
According to another embodiment, a deposition system for forming a thin film on a substrate is provided comprising: a process chamber having a substrate holder configured to support and to heat the substrate, a vapor distribution system configured to introduce film precursor vapor above the substrate, and a pumping system configured to evacuate the process chamber; a film precursor evaporation system configured to evaporate a film precursor; a vapor delivery system having a first end coupled to an outlet of the film precursor evaporation system and a second end coupled to an inlet of the vapor distribution system of the process chamber; a carrier gas supply system coupled to at least one of the film precursor evaporation system or the vapor delivery system, or both, and configured to supply a carrier gas to transport the film precursor vapor in the carrier gas to the inlet of the vapor distribution system; and a coating applied to one or more internal surfaces vapor delivery system, wherein the coating is configured to reduce decomposition of the film precursor on the one or more internal surfaces.
According to yet another embodiment, a method for depositing a refractory metal film is provided comprising: applying a coating to at least one internal surface of a vapor delivery system for supplying metal precursor vapor to a process chamber of a deposition system configured to perform thermal chemical vapor deposition (TCVD) from a metal precursor; depositing the refractory metal film on one or more substrates using the deposition system; and cleaning the deposition system following the depositing of the refractory metal film on the one or more substrates using a cleaning composition formed in an in-situ cleaning system coupled to the deposition system.
In the accompanying drawings:
In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the deposition system and descriptions of various components. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,
The process chamber 10 is further coupled to a vacuum pumping system 38 through a duct 36, wherein the pumping system 38 is configured to evacuate the process chamber 10, vapor delivery system 40, and film precursor evaporation system 50 to a pressure suitable for forming the thin film on substrate 25, and suitable for evaporation of a film precursor 52 in the film precursor evaporation system 50.
Referring still to
In order to achieve the desired temperature for evaporating the film precursor 52 (or subliming the solid precursor), the film precursor evaporation system 50 is coupled to an evaporation temperature control system 54 configured to control the evaporation temperature. For instance, the temperature of the film precursor 52 is generally elevated to approximately 40° C. or greater in order to sublime, for instance, ruthenium carbonyl. At this temperature, the vapor pressure of the ruthenium carbonyl, for instance, ranges from approximately 1 to approximately 3 mTorr. As the film precursor is heated to cause evaporation (or sublimation), a carrier gas can be passed over the film precursor, by the film precursor, or through the film precursor, or any combination thereof. The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as CO, for use with metal-carbonyls, or a mixture thereof. For example, a carrier gas supply system 60 is coupled to the film precursor evaporation system 50, and it is configured to, for instance, supply the carrier gas beneath the film precursor 52 via feed line 61, or above the film precursor 52 via feed line 62. In another example, carrier gas supply system 60 is coupled to the vapor delivery system 40 and is configured to supply the carrier gas to the vapor of the film precursor 52 via feed line 63 as or after it enters the vapor delivery system 40. Although not shown, the carrier gas supply system 60 can comprise a gas source, one or more control valves, one or more filters, and a mass flow controller. For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm. For example, the flow rate of carrier gas can range from about 10 sccm to about 200 sccm. By way of further example, the flow rate of carrier gas can range from about 20 sccm to about 100 sccm.
Downstream from the film precursor evaporation system 50, the metal precursor vapor flows with the carrier gas through the vapor delivery system 40 until it enters a vapor distribution system 30 coupled to the process chamber 10. The vapor delivery system 40 can be coupled to a vapor line temperature control system 42 in order to control the vapor line temperature and prevent decomposition of the film precursor vapor as well as condensation of the film precursor vapor. For example, the vapor line temperature can be set to a value approximately equal to or greater than the evaporation temperature. Additionally, for example, the vapor delivery system 40 can be characterized by a high conductance in excess of about 50 liters/second.
Referring again to
Once film precursor vapor enters the processing zone 33, the film precursor vapor thermally decomposes upon adsorption at the substrate surface due to the elevated temperature of the substrate 25, and the thin film is formed on the substrate 25. The substrate holder 20 is configured to elevate the temperature of substrate 25 by virtue of the substrate holder 20 being coupled to a substrate temperature control system 22. For example, the substrate temperature control system 22 can be configured to elevate the temperature of substrate 25 up to approximately 500° C. In one embodiment, the substrate temperature can range from about 100° C. to about 500° C. In another embodiment, the substrate temperature can range from about 300° C. to about 400° C. Additionally, process chamber 10 can be coupled to a chamber temperature control system 12 configured to control the temperature of the chamber wails.
As described above, for example, conventional systems have contemplated operating the film precursor evaporation system 50, as well as the vapor delivery system 40, within a temperature range of approximately 40-45° C. for ruthenium carbonyl in order to limit metal vapor precursor decomposition and metal vapor precursor condensation. For example, ruthenium carbonyl precursor can decompose at elevated temperatures to form by-products, such as those illustrated below:
Ru3(CO)12*(ad)Ru3(CO)x*(ad)+(12−x)CO(g) (1)
or,
Ru3(CO)x*(ad)3Ru(s)+xCO(g) (2)
wherein these by-products can adsorb (ad), i.e., condense, on the interior surfaces of the deposition system 1. The accumulation of material on these surfaces can cause problems from one substrate to the next, such as process repeatability. Alternatively, for example, ruthenium carbonyl precursor can condense at depressed temperatures to cause recrystallization, viz.
Ru3 (CO)12 (g)Ru3(Co)12*(ad) (3).
The decomposition of metal precursor vapor, or condensation of metal vapor, can occur on one or more internal surfaces within the thin film deposition system 1 that are exposed to the vapor as it is transported from the film precursor evaporation system 50 to the substrate 25. These internal surfaces include, at a minimum, internal surfaces 41 of the vapor delivery system 40. In addition, decomposition or condensation may occur on internal surfaces 31 of the vapor distribution system 30, including surfaces within plenum 32 or on the vapor distribution plate 34 or one or more orifices therein, and on internal surfaces 11 of the process chamber 10 including wall surfaces or surfaces on the substrate holder 20, as well as surfaces of duct 36. Within such systems having a small process window, the deposition rate becomes extremely low, due in part to the low vapor pressure of ruthenium carbonyl, as well as excessive decomposition of the precursor vapor on internal surfaces 11, 31, 41. For instance, the deposition rate can be as low as approximately 1 Angstrom per minute.
The inventors have observed that applying a coating to one or more of these internal surfaces 11, 31, 41 causes a reduction of, for example, vapor precursor decomposition and, as a result, an improvement of the deposition rate. According to one embodiment, a coating is applied to one or more internal surfaces 41 in the vapor delivery system 40. In a further embodiment, a coating is also applied to one or more of the internal surfaces 11, 31 in thin film deposition system 1. For example, the coating can comprise a CxFy-containing polymer coating, also referred to as a fluorocarbon coating or fluoropolymer, which is chemically inert. By way of further example, the coating can comprise polytetrafluoroethylene, such as Teflon® PTFE from DuPont or Halon® from Allied Chemical Corp., or ethylene-chlorotrifluoroethylene, such as Halar® ECTFE from Solvay Solexis. By way of further example and not limitation, other fluorocarbon coatings include fluorinated ethylene propylene, polyvinylidene fluoride, perfluoroalkoxy, polychlorotrifluoroethylene, ethylene-tetrafluoroethylene, and polyvinylfluoride. As an example,
Thereafter, the deposition system 1 is optionally periodically cleaned using an optional in-situ cleaning system 70 coupled to, for example, the vapor delivery system 40, as shown in
During operation of a cleaning process, several parameters can be set and optimized for cleaning performance. For example, the operator can set, monitor, adjust, or control the flow rate of the cleaning composition, the vapor line temperature, the temperature of the vapor distribution plate, the temperature of the substrate holder (or “dummy” substrate), the temperature of the process chamber, the pressure in the process chamber, or any combination thereof. The inventors have observed that the application of a coating 43 to one or more internal surfaces 11, 31, 41 of thin film deposition system 1 permits in-situ cleaning of the thin film deposition system 1 with a reduced risk of damage to deposition system components during cleaning.
Still referring the
In yet another embodiment,
The process chamber 110 comprises an upper chamber section 111, a lower chamber section 112, and an exhaust chamber 113. An opening 114 is formed within lower chamber section 112, where bottom section 112 couples with exhaust chamber 113.
Referring still to
During processing, the heated substrate 125 can thermally decompose the vapor of film precursor 152, and enable deposition of a thin film on the substrate 125. According to one embodiment, the film precursor 152 includes a metal precursor. According to another embodiment, the film precursor 152 includes a solid precursor. According to another embodiment, the film precursor 152 includes a solid metal precursor. According to another embodiment, the film precursor 152 includes a metal-carbonyl precursor. According to yet another embodiment, the film precursor 152 can be a ruthenium-carbonyl precursor, for example Ru3(CO)12. According to yet another embodiment of the invention, the film precursor 152 can be a rhenium carbonyl precursor, for example Re2(CO)10. As will be appreciated by those skilled in the art of thermal chemical vapor deposition, other ruthenium carbonyl precursors and rhenium carbonyl precursors can be used without departing from the scope of the invention. In yet another embodiment, the film precursor 152 can be W(CO)6, Mo(CO)6, Co2(CO)8, Rh4(CO)12, Cr(CO)6, or Os3(CO)12, or the like. The substrate holder 120 is heated to a pre-determined temperature that is suitable for depositing the desired Ru, Re or other metal layer onto the substrate 125. Additionally, a heater (not shown), coupled to a chamber temperature control system 121, can be embedded in the walls of process chamber 110 to heat the chamber walls to a predetermined temperature. The heater can maintain the temperature of the walls of process chamber 110 from about 40° C. to about 150° C., for example from about 40° C. to about 80° C. A pressure gauge (not shown) is used to measure the process chamber pressure.
Also shown in
Furthermore, an opening 135 is provided in the upper chamber section 111 for introducing a vapor precursor from vapor delivery system 140 into vapor distribution plenum 132. Moreover, temperature control elements 136, such as concentric fluid channels configured to flow a cooled or heated fluid, are provided for controlling the temperature of the vapor distribution system 130, and thereby prevent the decomposition of the film precursor inside the vapor distribution system 130. For instance, a fluid, such as water, can be supplied to the fluid channels from a vapor distribution temperature control system 138. The vapor distribution temperature control system 138 can include a fluid source, a heat exchanger, one or more temperature sensors for measuring the fluid temperature or vapor distribution plate temperature or both, and a controller configured to control the temperature of the vapor distribution plate 131 from about 20° C. to about 100° C.
As illustrated in
As the film precursor 152 is heated to cause evaporation (or sublimation), a carrier gas can be passed over the film precursor, by the film precursor, or through the film precursor, or any combination thereof. The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as CO, for use with metal-carbonyls, or a mixture thereof. For example, a carrier gas supply system 160 is coupled to the film precursor evaporation system 150, and it is configured to, for instance, supply the carrier gas beneath the film precursor, or above the film precursor. Although not shown in
Additionally, a sensor 166 is provided for measuring the total gas flow from the film precursor evaporation system 150. The sensor 166 can, for example, comprise a mass flow controller, and the amount of film precursor vapor delivered to the process chamber 110 can be determined using sensor 166 and mass flow controller 165. Alternately, the sensor 166 can comprise a light absorption sensor to measure the concentration of the film precursor in the gas flow to the process chamber 110.
A bypass line 167 can be located downstream from sensor 166, and it can connect the vapor delivery system 140 to an exhaust line 116. Bypass line 167 is provided for evacuating the vapor delivery system 140, and for stabilizing the supply of the metal precursor to the process chamber 110. In addition, a bypass valve 168, located downstream from the branching of the vapor precursor delivery system 140, is provided on bypass line 167.
Referring still to
Moreover, dilution gases can be supplied from a dilution gas supply system 190. The dilution gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as CO, for use with metal-carbonyls, or a mixture thereof. For example, the dilution gas supply system 190 is coupled to the vapor delivery system 140, and it is configured to, for instance, supply the dilution gas to the film precursor vapor. The dilution gas supply system 190 can comprise a gas source 191, one or more control valves 192, one or more filters 194, and a mass flow controller 195. For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm.
Mass flow controllers 165 and 195, and valves 162, 192, 168, 141, and 142 are controlled by controller 196, which controls the supply, shutoff, and the flow of the carrier gas, the film precursor vapor, and the dilution gas. Sensor 166 is also connected to controller 196 and, based on output of the sensor 166, controller 196 can control the carrier gas flow through mass flow controller 165 to obtain the desired film precursor vapor flow to the process chamber 110.
Furthermore, as described above, and as shown in
As illustrated in
Referring back to the substrate holder 120 in the process chamber 110, as shown in
Referring again to
Controller 180 may be locally located relative to the deposition system 100, or it may be remotely located relative to the deposition system 100 via an internet or intranet. Thus, controller 180 can exchange data with the deposition system 100 using at least one of a direct connection, an intranet, or the internet. Controller 180 may be coupled to an intranet at a customer site (i.e., a device maker, etc.), or coupled to an intranet at a vendor site (i.e., an equipment manufacturer). Furthermore, another computer (i.e., controller, server, etc.) can access controller 180 to exchange data via at least one of a direct connection, an intranet, or the internet.
As described above, for example, conventional systems have contemplated operating the metal precursor evaporation system, as well as the vapor delivery system, within a temperature range of approximately 4045° C. for ruthenium carbonyl in order to limit metal vapor precursor decomposition and metal vapor precursor condensation. However, due to the low vapor pressure of metal-carbonyls, such as ruthenium carbonyl or rhenium carbonyl, at this temperature, the deposition rate of, for example, ruthenium or rhenium, is very low. In order to improve the deposition rate, the evaporation temperature is raised above about 40° C., for example above about 50° C. Following high temperature evaporation of the metal precursor for one or more substrates, the deposition system is periodically cleaned to remove residues formed on internal surfaces of the deposition system.
Referring now to
In 330, the metal precursor is heated to form a metal precursor vapor. The metal precursor vapor can then be transported to the process chamber through the vapor delivery system. In 340, the substrate is heated to a substrate temperature sufficient to decompose the metal precursor vapor, and, in 350, the substrate is exposed to the metal precursor vapor. Steps 310 to 350 may be repeated successively a desired number of times to deposit a metal film on a desired number of substrates.
Following the deposition of the refractory metal film on one or more substrates, the deposition system is optionally periodically cleaned in 360 by introducing a cleaning composition from an in-situ cleaning system coupled to the deposition system, and in particular, coupled to at least the vapor delivery system for providing the cleaning composition to the vapor delivery system, and optionally to the process chamber. The cleaning composition can, for example, include a halogen containing radical, fluorine radical, oxygen radical, ozone, or a combination thereof. The in-situ cleaning system can, for example, include a radical generator, or an ozone generator. When a cleaning process is performed, a “dummy” substrate can be utilized to protect the substrate holder. Furthermore, the film precursor evaporation system, the vapor delivery system, the process chamber, the vapor distribution system, or the substrate holder, or any combination thereof can be heated.
Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.