GAP FILL ENHANCEMENT WITH THERMAL ETCH

A method of forming an interconnect structure over a substrate includes forming a nucleation layer over a surface of the substrate. The surface of the substrate comprises a plurality of openings, and the process of forming the nucleation layer includes (a) exposing the substrate to a tungsten-containing precursor gas to form a tungsten-containing layer over a surface of each of the plurality of openings, (b) exposing the formed tungsten-containing layer to an etchant gas, wherein exposing the tungsten-containing layer to the etchant gas etches at least a portion of the tungsten-containing layer disposed at a top region of each of the plurality of openings, and repeating (a) and (b) one or more times. The method further includes forming a bulk layer over the formed nucleation layer.

BACKGROUND

Field

Embodiments herein are directed to methods used in electronic device manufacturing, and more particularly, to methods used for forming conductive structures containing tungsten in a semiconductor device.

Description of the Related Art

Tungsten (W) is widely used in integrated circuit (IC) device manufacturing to form conductive features where relatively low electrical resistance and relativity high resistance to electromigration are desired. For example, tungsten may be used as a metal fill material to form source contacts, drain contacts, metal gate fill, gate contacts, interconnects (e.g., horizontal features formed in a surface of a dielectric material layer), and vias (e.g., vertical features formed through a dielectric material layer to connect other interconnect features disposed there above and there below). Due to its relativity low resistivity and high melting point, tungsten is also commonly used to form bit lines and word lines used to address individual memory cells in a memory cell array of a dynamic random-access memory (DRAM) device.

As circuit densities increase and device features continue to shrink to meet the demands of the next generation of semiconductor devices, reliably producing tungsten features has become increasingly challenging. The advances in integrated circuit technology have necessitated improved methods depositing of refractory metals, particularly tungsten, to enhance the gap filling properties and reduce the stress of the same. Traditionally, the gap filling property and the stress are two characteristics of refractory metal layers that have been in conflict due to the competing desires to have a high deposition process throughput but also have a low level of stress and good gap fill characteristics.

Accordingly, there is a need for processes to form structures having a good gap fill characteristics.

SUMMARY

Embodiments of the disclosure include flowing a molybdenum-based etchant (molybdenum halides, molybdenum oxy-halides) during tungsten CVD deposition (or any other metals that forms volatile products), the growth at field and top regions of the gap structures can be suppressed or etch away with minimum damage of the substrate.

Embodiments of the present disclosure provide a method of forming an interconnect structure over a substrate. The method includes forming a nucleation layer over a surface of the substrate. The surface of the substrate comprises a plurality of openings, and the process of forming the nucleation layer includes (a) exposing the substrate to a tungsten-containing precursor gas to form a tungsten-containing layer over a surface of each of the plurality of openings, (b) exposing the formed tungsten-containing layer to an etchant gas, wherein exposing the tungsten-containing layer to the etchant gas etches at least a portion of the tungsten-containing layer disposed at a top region of each of the plurality of openings, and repeating (a) and (b) one or more times. The method further includes forming a bulk layer over the formed nucleation layer.

Embodiments of the present disclosure provide a method of depositing a tungsten-containing layer. The method includes performing a nucleation process in a processing chamber. The nucleation process includes forming a tungsten-containing layer on a substrate by exposing a substrate to a first tungsten-containing precursor gas, and etching the formed tungsten-containing layer by delivering a molybdenum-based etchant gas to the substrate. The method further includes performing a deposition process in the processing chamber. The deposition process comprises forming a bulk layer by flowing a second tungsten-containing precursor gas.

Embodiments of the present disclosure provide a processing system. The processing system includes a processing chamber, and a system controller configured to cause the processing system to perform a nucleation process in the processing chamber. The nucleation process includes forming a tungsten-containing layer on a substrate by exposing a substrate to a first tungsten-containing precursor gas, and etching the formed tungsten-containing layer by delivering a molybdenum-based etchant gas to the substrate. The system controller further causes the processing system to perform a deposition process in the processing chamber. The deposition process comprises forming a bulk layer by flowing a second tungsten-containing precursor gas.

DETAILED DESCRIPTION

Embodiments herein are generally directed to electronic device manufacturing and, more particularly, to systems and methods for forming a structure having a material layer that includes tungsten (W) in a semiconductor device manufacturing scheme.

FIG.1Ais a schematic cross-sectional view of a substrate10illustrating a tungsten-containing interconnect structure. Here, the substrate10includes a patterned surface11including a dielectric layer12having a high aspect ratio opening formed therein (shown filled with a portion15A of a tungsten-containing layer15), a barrier material layer14deposited on the dielectric layer12to line the opening, and a portion15B of the tungsten-containing layer15deposited on the barrier material layer14.

The tungsten-containing layer15can be formed using a chemical vapor deposition (CVD), a plasma enhanced CVD, or atomic layer deposition (ALD) process where the tungsten-containing layer15is conformally deposited (grown) on the patterned surface11to fill the opening with the portion15A, to cover a planar surface with the portion15B, or a combination thereof. The structure includes a substantially uniform profile as the opening extends from the surface of the substrate10into the dielectric layer12.

The barrier material layer14can include a material suitable for utilization as barrier layer, such as, but not limited to, titanium and tantalum, alloys, combinations, mixtures, and nitrides thereof. In one example, the barrier material layer14can be a titanium nitride (TiN) layer, deposited on the dielectric layer12to conformally line the openings and facilitate the subsequent deposition of a nucleation layer13. In some embodiments, the barrier material layer14is deposited to a thickness of about 50 angstroms (Å) to about 150 Å.

In some embodiments, the tungsten-containing layer15includes the nucleation layer13and a bulk layer16, which can be deposited using one or more of the methods described below. The nucleation layer13includes tungsten that is deposited using a CVD, ALD or even PVD process. The bulk layer16includes a tungsten-containing layer. In one example, the bulk layer16essentially comprises tungsten. In some embodiments, the thickness of the tungsten-containing layer15is about 20 Å to about 1800 Å.

Accordingly, embodiments herein provide a processing system that is configured to perform a combination of the individual aspects of the methods without transferring a substrate between processing chambers, thus improving overall substrate processing throughput and capacity for the tungsten gap fill processing schemes described herein. In some embodiments, certain method disclosed herein are selected based on the topology of the substrate surface. Specifically, certain methods may be used for substrates having high aspect ratio feature, such as about 10:1 or higher, and other method are suitable for substrates having a substantially planar surface, or having features having low aspect ratios.

Conventional CVD deposition processes have poor control on nucleation layer step coverage and thickness when filling high aspect ratio (AR>20) trenches and via with small critical dimensions (CD<10 nm). Conventional deposition processes used to form the nucleation layer can result in the formation of a large seam (e.g., seam24shown inFIG.1A) in gap fill structures, especially when the top region of the openings is pinched off by the nucleation layer deposition.FIG.1Billustrates a configuration where a nucleation layer106deposited on a dielectric layer104is “pinching-off” the top region of the high aspect ratio feature105formed on a substrate102.

FIG.2schematically illustrate a processing system200that may be used to perform the processing methods described herein. Here, the processing system is configured to provide the processing conditions for each of a nucleation process, selective gap fill process, and surface deposition process within a single processing chamber202, i.e., without transferring a substrate between a plurality of processing chambers. However, in some embodiments, the substrate is transferred from the processing chamber202to other processing chambers that can be used to deposit additional layers over the substrate.

As shown inFIG.2, the processing system200includes a processing chamber202, a gas delivery system204fluidly coupled to the processing chamber202, and a system controller208. The processing chamber202includes a chamber lid assembly210, one or more sidewalls212, and a chamber base214, which collectively define a processing volume215. The processing volume215is fluidly coupled to an exhaust217, such as one or more vacuum pumps, used to maintain the processing volume215at sub-atmospheric conditions and to evacuate processing gases and processing by-products therefrom.

The chamber lid assembly210includes a lid plate216and a showerhead218coupled to the lid plate216to define a gas distribution volume219therewith. Here, the lid plate216is maintained at a desired temperature using one or more heaters229thermally coupled thereto. The showerhead218faces a substrate support assembly220disposed in the processing volume215. As discussed below, the substrate support assembly220is configured to move a substrate support222, and thus a substrate230disposed on the substrate support222, between a raised substrate processing position (as shown) and a lowered substrate transfer position (not shown). When the substrate support assembly220is in the raised substrate processing position, the showerhead218and the substrate support222define a processing region221.

The gas delivery system204is fluidly coupled to the processing chamber202through a gas inlet that is disposed through the lid plate216. Processing or cleaning gases delivered, by use of the gas delivery system204, flow through the gas inlet223into the gas distribution volume219and are distributed into the processing region221through the showerhead218. In some embodiments, the chamber lid assembly210further includes a perforated blocker plate225disposed between the gas inlet223and the showerhead218. In those embodiments, gases flowed into the gas distribution volume219are first diffused by the blocker plate225to, together with the showerhead218, provide a more uniform or desired distribution of gas flow into the processing region221.

The processing gases and processing by-products are evacuated radially outward from the processing region221through an annular channel226that surrounds the processing region221. The annular channel226may be formed in a first annular liner227disposed radially inward of the one or more sidewalls212(as shown) or may be formed in the one or more sidewalls212, which are used to protect the interior surfaces. In some embodiments, the processing chamber202includes one or more second liners228of the one or more sidewalls212or chamber base214from corrosive gases and/or undesired material deposition.

In some embodiments, a purge gas source237includes a first connection that is in fluid communication with the processing volume215so that it can be used to flow a chemically inert purge gas, such as argon (Ar), into a region disposed at a periphery of a substrate and/or beneath the substrate disposed on the substrate support222, e.g., through the opening in the chamber base214surrounding the movable support shaft262. The purge gas may be used to create a region of positive pressure below the substrate disposed on the substrate support222(when compared to the pressure in the processing region221) during substrate processing. In some configurations, the purge gas is introduced through the chamber base214so that it flows upwardly therefrom and around the edges of the substrate support222to be evacuated from the processing volume215through the annular channel226. In this configuration, the purge gas reduces undesirable material deposition on surfaces beneath the substrate support222by reducing and/or preventing the flow of material precursor gases thereinto.

The substrate support assembly220includes a movable support shaft262that sealingly extends through the chamber base214, such as being surrounded by a bellows265in the region below the chamber base214, and the substrate support222, which is disposed on the movable support shaft262. To facilitate substrate transfer to and from the substrate support222, the substrate support assembly220includes a lift pin assembly266comprising a plurality of lift pins267coupled to or disposed in engagement with a lift pin hoop268. The plurality of lift pins267are movably disposed in openings formed through the substrate support222.

The substrate230is transferred to and from the substrate support222through a door271, e.g., a slit valve disposed in one of the one or more sidewalls212. Here, one or more openings in a region surrounding the door271, e.g., openings in a door housing, are fluidly coupled to a purge gas source237, e.g., an argon (Ar) gas source. The purge gas is used to prevent processing and cleaning gases from contacting and/or degrading a seal surrounding the door, thus extending the useful lifetime thereof.

The substrate support222is configured for vacuum chucking where the substrate230is secured to the substrate support222by applying a vacuum to an interface between the substrate230and the substrate receiving surface, such as with a vacuum source272.

In some embodiments, the processing chamber202is configured for direct plasma processing. In those embodiments, the showerhead218may be electrically coupled to a first power supply231, such as an RF power supply, which supplies power to form and maintain a capacitively coupled plasma using processing gases flowed into the processing region221through the showerhead218. In some embodiments, the processing chamber202alternately comprises an inductively coupled plasma generator (not shown), and a plasma is formed through inductively coupling an RF power through an antenna disposed on the processing chamber202to the processing gas disposed in the processing volume215.

The processing system200is advantageously configured to perform each of the tungsten nucleation, and bulk tungsten deposition processes without removing the substrate230from the processing chamber202. The gases used to perform the individual processes, and to clean residues from the interior surfaces of the processing chamber, are delivered to the processing chamber202using the gas delivery system204fluidly coupled thereto.

Generally, the gas delivery system204includes one or more remote plasma sources, here radical generator206, a deposition gas source240, and the deposition gas source240to the chamber lid assembly210. The gas delivery system204further includes an isolation valve290, disposed between the radical generator206and the lid plate216, which may be used to fluidly isolate the radical generator206from the processing chamber202and from other radical generators, if applicable (not shown). Deposition gases, e.g., tungsten-containing precursors, molybdenum-containing precursors, and reducing agents, are delivered from the deposition gas source240to the processing chamber202using a conduit system294. The gas delivery system204further includes a purge gas source237to purge the conduit system294.

The radical generator206is coupled to a power supply293, such as a radio frequency (RF) power supply. The power supply293is used to ignite and maintain a plasma that is delivered to the plasma chamber volumes using gases provided from a corresponding gas source287fluidly coupled thereto.

Operation of the processing system200is facilitated by the system controller208. The system controller208includes a programmable central processing unit, here the CPU295, which is operable with a memory296(e.g., non-volatile memory) and support circuits297. The CPU295is one of any form of general-purpose computer processor used in an industrial setting, such as a programmable logic controller (PLC), for controlling various chamber components and sub-processors. The memory296, coupled to the CPU295, facilitates the operation of the processing chamber. The support circuits297are conventionally coupled to the CPU295and comprise cache, clock circuits, input/output subsystems, power supplies, and the like, and combinations thereof coupled to the various components of the processing system200to facilitate control of substrate processing operations therewith.

The instructions in the memory296are in the form of a program product, such as a program that implements the methods of the present disclosure. In one example, the disclosure may be implemented as a program product stored on computer-readable storage media for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein). Thus, the computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are embodiments of the present disclosure.

Deposition Process Example(s)

FIG.3depicts a process flow diagram of a method300used to deposit a tungsten-containing layer on a substrate according to some embodiments, which may be performed, at least in part, using the processing system200. In some implementations, the processing system200is capable of operating in one or more process modes to form at least a portion of an interconnect structure, such as a pulsed CVD mode, a plasma enhanced CVD mode, and an ALD mode.FIG.1Cillustrates schematic cross-sectional side views of a structure101during the various processes performed during method300.FIG.1Cdepicts a substrate102, which can include a silicon containing substrate (e.g., n-type Si substrate, p-type Si substrate) and one or more device layers formed thereon. A dielectric layer104is formed over the substrate102. The dielectric layer104includes a feature105formed therein. In some embodiments, the feature105is a high-aspect ratio feature, such as a trench or via, that has an aspect ratio of >20 and a critical dimension of <10 nm.

The method300includes activity301in which a nucleation layer106is formed over a surface105A of the feature105. In some embodiments, the surface105A can include a barrier layer and/or a liner layer formed over a surface of the dielectric layer104. In one example, the surface105A includes the barrier material layer14described above. In one embodiment, activity301includes a tungsten (W) layer deposition process302that is followed by a process (i.e., activity304) where the deposited tungsten layer formed during activity302is exposed to an etchant gas.

During activity302, in some embodiments, a tungsten layer is formed by use of an ALD process in which the substrate is exposed to a gas mixture including a tungsten-containing precursor gas (e.g., WF6), and a hydrogen-containing gas (e.g., H2). Alternately, the nucleation layer could be formed by use of a chemical vapor deposition (CVD), or a physical vapor deposition (PVD) process.

In activity304, an etchant gas is provided to the substrate disposed in the processing region of the process chamber to etch a portion of the tungsten layer formed during activity302. In one embodiment, the process performed during activity304includes a thermal based etching process that includes delivering a molybdenum-based etchant while the substrate is maintained at a temperature of between 20° C. and 550° C. It is believed that a thermally based etching process that utilizes a molybdenum-based etchant provides improved control over the etching and tungsten growth suppression process versus a plasma etching process. In this case, the exposure to an etchant gas containing molybdenum is used to etch and/or suppress the growth of subsequently deposited tungsten layers at the upper region of the feature105and thus reduce the amount of or eliminate the pinching-off of the upper portion of the feature105created by the formation of the nucleation layer106in the feature105during activity302. In some embodiments, the etchant gas comprises a molybdenum halide and/or a molybdenum oxy-halide containing gas. In one example, the etchant gas comprises molybdenum hexafluoride (MoF6). In another example, the etchant gas comprises molybdenum hexafluoride (MoF6) and a carrier gas (e.g., Ar). In another example, the etchant gas comprises molybdenum hexafluoride (MoF6), a carrier gas (e.g., Ar) and a hydrogen containing gas (e.g., H2). In yet another example, a tungsten-containing gas (e.g., WF6), a molybdenum based etchant gas (e.g., molybdenum hexafluoride (MoF6)), a carrier gas (e.g., Ar) and a hydrogen containing gas (e.g., H2) are co-flowed to achieve thinner nucleation layer with better step coverage.

In some embodiments, activity304is used as a method of tuning the tungsten layer's deposition profile formed on the substrate to improve gap fill in the subsequent activity306. In one example, profile tuning can include preferential removal of portions of tungsten layer deposited on the field region and top area of the features formed in the substrate, and thus promote growth within the features from the bottom-up and reduce or prevent a seam from forming in the features.

During activity301the activities302and304are cyclically completed until a nucleation layer having a desired thickness is formed. In one example, the nucleation layer has a thickness of between about 10 Å and 30 Å.

In activity306, a bulk layer108is deposited within the feature105using an ALD or CVD deposition process. In one embodiment, during activity306, a tungsten-containing precursor gas is flowed at a rate of about 100 sccm to about 1500 sccm. In some embodiments, a hydrogen-containing gas, such as H2, is co-flowed with the tungsten-containing precursor. The hydrogen-containing gas is flowed at a flow rate of about 3000 sccm to about 15000 sccm.

In one embodiment, during activity306, a bulk layer108is deposited within the feature105using an ALD process. In activity306, a pulsed amount of the tungsten-containing precursor gas is provided and then held within the processing region221for a duration of between about 1 second and about 10 seconds. Then a pulsed amount of a first purge gas is flowed between exposures of the tungsten precursors. The first purge gas includes an argon containing gas. In some embodiments, a pulsed amount of argon gas is then supplied at a purge time of about 1 second to about 5 seconds. The first purge gas may be delivered from the deposition gas source240or from the bypass gas source. A pulsed amount of a hydrogen-containing gas, such as H2, can then be flowed after each exposure of the purge gas. The hydrogen-containing gas is flowed at a purge time of about 1 second to 5 seconds. A pulsed amount of a second purge gas can then be flowed after the hydrogen-containing gas, such as argon gas. The second purge gas condition can be substantially the same as the first purge gas condition. In some embodiment, the second purge gas time is about 1 second to about 5 seconds. The ALD process steps are then cyclically performed until the bulk layer is deposited to a predetermined thickness.

Alternately, in activity306, a bulk layer108is deposited within the feature105using a plasma enhanced CVD deposition process. The tungsten-containing precursor gas is flowed at a rate of about 100 sccm to about 1500 sccm. The process may include exposing portions of the deposited tungsten-containing bulk layer108to a plasma formed by flowing one or more plasma processing gases, such as co-flowing a hydrogen-containing gas, such as H2, and an argon-containing gas. The hydrogen-containing gas is flowed at a flow rate of about 500 sccm to about 3000 sccm. The argon-containing gas is flowed at a flow rate of about 500 sccm to about 3000 sccm. During this process an amount of RF power is applied by a power source to the argon-containing gas and the hydrogen-containing gas, such as a gas disposed in a processing region of a remote plasma source or to an antenna or electrode disposed on or within the processing system. In some embodiments, a power of about 50 W to about 600 W is applied at an RF frequency (e.g., 13.56 MHz) to the processing region of the remote plasma source or processing region of the processing system. In some embodiments, the plasma is injected in the processing volume between exposures of the deposition gases describes with respect to the chemical vapor deposition process. The plasma exposure time can be between about 0.5 seconds and about 5 seconds. The plasma pressure condition is about 3 Torr to about 30 Torr within the processing region of the processing system. The exposure to a tungsten-containing precursor and then exposure to a plasma may be cyclically performed until the bulk layer is deposited to a predetermined thickness. The substrate is heated to about 400° C. to about 550° C.