Low-temperature Mo film deposition using a boron nucleation layer

Abstract

The present disclosure relates to a method for making a molybdenum film using a boron nucleation layer and a molybdenum nucleation layer. The resulting molybdenum film has a low resistivity, is substantially free of boron, and can be made at a reduced temperature compared to conventional chemical vapor deposition processes that do not use a boron nucleation layer or a molybdenum nucleation layer. The molybdenum nucleation layer formed by this process can protect the substrate from the etching action of MoCl5 or MoOCl4, facilitate the nucleation of subsequent CVD Mo growth on top of the molybdenum nucleation layer, and enable Mo CVD to be performed at a lower temperature. The nucleation layer can also be used to control the grain size of the subsequent CVD Mo growth, and thus control the resistivity of the Mo film.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a continuation-in-part of U.S. Patent Application No. 15 / 820,640, filed on November 22, 2017, which claims the benefit of U.S. Provisional Application No. 62 / 425,704, filed on November 23, 2016, the disclosure of which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] The present disclosure relates to vapor deposited molybdenum films or layers that can be produced at lower process temperatures, but at deposition rates similar to those achieved using conventional high temperature vapor deposition conditions for molybdenum. The resulting molybdenum films or layers formed by low temperature deposition also have low resistivity and can be used in a variety of articles, such as semiconductor devices and display devices. Background Art

[0004] Molybdenum is a low resistivity refractory metal that may have the potential to replace tungsten as a material for memory, logic chips, and other devices using polysilicon-metal gate electrode structures. Molybdenum-containing films can also be used in some organic light-emitting diodes, liquid crystal displays, and also in thin-film solar cells and photovoltaic devices. Thin molybdenum films can be used as barrier films.

[0005] Various precursors and vapor deposition techniques have been used to deposit thin molybdenum films. Precursors include inorganic agents and organometallic agents, and vapor deposition techniques can include chemical vapor deposition (CVD) and atomic layer deposition (ALD) and various improvements, such as ultraviolet laser photolysis CVD, plasma-assisted CVD, and plasma-assisted ALD. CVD and ALD processes are increasingly being used because they can give excellent conformal step coverage on highly non-planar microelectronic device geometries, but the cost and complexity of plasma-assisted deposition systems and high-temperature deposition systems may increase production costs and tool costs. High-temperature processes may also damage previously deposited or underlying structures.

[0006] In a typical CVD process, a precursor is passed over an optionally heated substrate (e.g., a wafer) in a low pressure or ambient pressure reaction chamber. The precursor reacts and / or decomposes on the substrate surface, thereby producing a thin film of a deposited material such as molybdenum. Volatile byproducts are removed by a gas flow through the reaction chamber. Some metal films are formed in a CVD process by providing two or more gases to a reaction chamber, where the reaction of the gases results in the deposition of the metal on the substrate. The deposited film thickness and uniformity depends on the coordination of multiple parameters such as temperature, pressure, gas flow rate and mixing uniformity, chemical depletion effects, and time.

[0007] Deposition of refractory metal films on substrates in a CVD process has involved heating a substrate such as silicon dioxide to a temperature of about 500°C to 800°C in a closed chamber; treating the heated surface with a vaporized substance such as molybdenum hexafluoride for a short period of time to increase the surface's adhesion to a subsequently deposited molybdenum layer; purging any unreacted molybdenum hexafluoride from the chamber; and then depositing a molybdenum film by mixing hydrogen with some of the newly vaporized molybdenum hexafluoride, thereby reducing the molybdenum hexafluoride, generating HF(g), and depositing some of the molybdenum on the heated surface. The high temperatures of this deposition complicate the processing equipment and consume the thermal budget of temperature-sensitive devices. In addition, the toxicity of HF(g) and the associated abatement and safety equipment for handling HF(g) make this process expensive and complex.

[0008] At high temperatures of about 700°C, smooth, low-resistivity molybdenum films with good step coverage can be deposited on substrates by chemical vapor deposition (CVD) using MoOCl4 or MoCl5 as molybdenum precursors and H2 as a reducing gas. These high-temperature molybdenum films are useful, but lower deposition temperatures will be even more advantageous because it consumes less of the thermal budget for making materials such as DRAM or photovoltaic devices, and because less expensive and complex equipment can be used to make the films. When the temperature of the substrate is reduced to below 700°C in the above-mentioned deposition process, it is observed that the reaction temperature cutoff values ​​of MoOCl4 and MoCl5 are both about 550°C. Near this temperature, the film roughness increases, the film resistivity increases, and the film deposition rate decreases and eventually stops below the cutoff temperature. This cutoff temperature also limits the step coverage performance of the molybdenum film. Smooth, low-resistivity molybdenum films with good step coverage are highly beneficial qualities for thin films used in semiconductor device fabrication.

[0009] There is a continuing need to fabricate molybdenum metal films and coatings on a variety of substrates at lower deposition temperatures and without the need for complex and expensive heating and vapor elimination equipment. Summary of the invention

[0010] To overcome the problems of high temperature molybdenum processing, including the formation of rough and high resistivity films between 550°C and 700°C, a boron decomposition layer or boron nucleation layer is deposited on the substrate, and then replaced with a high quality molybdenum nucleation layer on the substrate at a temperature below 550°C. It was found that the molybdenum nucleation layer prepared in this way protects the underlying substrate from the etching action of, for example, MoCl5, to facilitate the nucleation of the subsequent smooth CVD Mo growth on top and enable the CVD Mo deposition to be carried out at a lower temperature. The molybdenum nucleation layer can also be used to control the grain size of the subsequent CVD growth of bulk molybdenum, and thus control the resistivity of the final molybdenum film. In some cases, it can be seen by SEM that a high content of boron is found under the molybdenum layer, which increases the film resistivity. This is particularly problematic in the case where multiple alternating layers of boron and molybdenum are deposited. The solution to the problem of high temperature molybdenum film formation and the presence of a large amount of boron in the deposited molybdenum nucleation layer is to consume or replace substantially all of the deposited solid boron nucleation layer on the substrate by reacting with vapors of molecules containing molybdenum and chlorine, such as MoOCl4 or MoCl5. This reaction forms a molybdenum nucleation layer, which can occur in the presence or absence of a reducing gas such as hydrogen, and simultaneously replaces the boron nucleation layer. The resulting molybdenum nucleation layer reduces the cutoff temperature of the subsequent bulk Mo CVD film formation process, using, for example, a vapor composition containing MoOCl4 or MoCl5 in the presence of a reducing gas such as hydrogen, with a cutoff temperature of 400°C to 575°C for MoOCl4 and a cutoff temperature of 450°C to 550°C for MoCl5. The molybdenum CVD film formed in this manner has a low film resistivity, is smooth, and has better step coverage than a molybdenum film deposited on a substrate by chemical vapor deposition (CVD) of molybdenum using MoOCl4 or MoCl5 as a molybdenum precursor and H2 as a reducing gas at a high temperature of about 700°C.

[0011] The present disclosure relates to compositions and a method of making a molybdenum nucleation layer on a substrate. Optionally, the substrate itself can be the molybdenum nucleation layer. Alternatively, the substrate can be substantially free of molybdenum.

[0012] The method may include an action or step of reacting a pre-existing solid boron-containing nucleation layer on a substrate with a vapor composition comprising molecules containing molybdenum atoms and chlorine atoms. In some variations, the vapor composition is substantially free of reducing gases. The substrate is maintained at a temperature between 450°C and 550°C and the reaction with the vapor consumes at least a portion of the boron nucleation layer while forming a molybdenum nucleation layer atop the substrate. In some variations, the molybdenum nucleation layer may be formed on a substrate maintained at a temperature between 450°C and 480°C. In some variations, the deposited molybdenum nucleation layer may have a relative humidity of approximately 5 angstroms. To about 100 angstroms Suitably, the thickness of the deposited molybdenum nucleation layer can be in the range of about 5 angstroms to about 50 angstroms, optionally in the range of 5 angstroms to about 30 angstroms, for example in the range of about 5 angstroms to about 20 angstroms. A vapor composition comprising molecules of molybdenum and chlorine can be present in a reaction chamber with a heated substrate at a pressure of 10 torr to 60 torr (and in some variations, at a pressure of 20 torr to 40 torr).

[0013] One aspect of the present invention provides a method for manufacturing a molybdenum layer, the method comprising: reacting a boron nucleation layer on a substrate with a vapor composition comprising molecules containing molybdenum atoms and chlorine atoms, the temperature of the substrate being between 450°C and 550°C; the reaction consumes at least a portion of the boron nucleation layer and forms a molybdenum nucleation layer on top of the substrate.

[0014] The thickness of the substantially consumed boron-containing nucleation layer may be about To about Suitably, the thickness of the boron-containing nucleation layer may be in the range of about 5 angstroms to about 50 angstroms, optionally in the range of about 5 angstroms to about 30 angstroms, such as in the range of about 5 angstroms to about 20 angstroms.

[0015] Advantageously, the boron-containing nucleation layer is substantially consumed by the reaction such that the molybdenum layer comprises less than 5 wt% boron, optionally less than 1 wt% boron by elemental analysis.

[0016] The boron nucleation layer can be suitably formed by decomposition of B2H6 on a heated substrate. In some variations, the substrate is heated to 300°C to 450°C during the deposition of the boron nucleation layer. Other boron-containing precursors and conditions can be used to deposit the boron nucleation layer. For example, the same or substantially the same temperature (450°C to 550°C) used for molybdenum deposition can be used for the deposition of the boron nucleation layer.

[0017] Thus. In some variations, the method includes depositing a boron-containing nucleation layer atop a substrate, the temperature of the substrate being between 300°C and 550°C.

[0018] The method may optionally include: depositing another boron-containing nucleation layer on top of the molybdenum nucleation layer on top of the substrate, the temperature of the substrate being between 300°C and 550°C, optionally between 300°C and 450°C; and reacting the another boron-containing nucleation layer with a vapor composition comprising molecules containing molybdenum atoms and chlorine atoms, the temperature of the substrate being between 450°C and 550°C; the reaction consumes at least a portion of the another boron nucleation layer and forms another molybdenum nucleation layer.

[0019] The thickness of the other boron-containing nucleation layer may suitably be between to Suitably, the thickness of the further boron-containing nucleation layer may be in the range of about 5 angstroms to about 50 angstroms, optionally in the range of about 5 angstroms to about 30 angstroms, for example in the range of about 5 angstroms to about 20 angstroms. The deposited thickness of the further boron-containing nucleation layer may be less than the deposited thickness of the boron-containing nucleation layer on top of the substrate.

[0020] The method may include vapor depositing a boron-containing nucleation layer atop a substrate for a first time period and vapor depositing another boron-containing nucleation layer for a second time period, the second time period being shorter than the first time period.

[0021] The further boron-containing nucleation layer may be substantially consumed by the reaction such that the further molybdenum layer comprises less than 5 wt % boron, optionally less than 1 wt % boron by elemental analysis.

[0022] Advantageously, the steps of deposition and reaction may be repeated, thereby forming a plurality of further molybdenum nucleation layers.

[0023] Optionally, the molybdenum nucleation layer may be formed on a substrate maintained at a temperature between 450° C. and 480° C. Advantageously, the pressure of the vapor composition may be between 10 Torr and 60 Torr. The vapor composition may be substantially free of reducing gases.

[0024] It will be appreciated that the method may include fabricating a top molybdenum nucleation layer. The molybdenum nucleation layer or another molybdenum nucleation layer atop the substrate may constitute the top molybdenum nucleation layer.

[0025] In fact, another variation of the method for producing a top molybdenum nucleation layer comprises: depositing a boron-containing nucleation layer on top of a substrate or on top of a molybdenum nucleation layer on top of a substrate, wherein the temperature of the substrate or the molybdenum nucleation layer on top of the substrate is between 300°C and 550°C, optionally between 300°C and 450°C; and subsequently reacting the boron-containing nucleation layer with a vapor composition comprising molecules containing molybdenum atoms and chlorine atoms, wherein the temperature of the substrate is between 450°C and 550°C.

[0026] The reaction between the vapor composition and the boron layer consumes at least a portion of the boron nucleation layer and forms a top molybdenum nucleation layer. In a variation of the method, the thickness of the boron nucleation layer may be between 10 and 200 nm. to Suitably, the thickness of the boron-containing nucleation layer may be in the range of about 5 angstroms to about 50 angstroms, optionally in the range of about 5 angstroms to about 30 angstroms, such as in the range of about 5 angstroms to about 20 angstroms.

[0027] In some variations of the method of fabricating a top molybdenum layer on a substrate, consuming at least a portion of the boron nucleation layer substantially or completely consumes the boron nucleation layer. Consuming at least a portion of the boron nucleation layer may generate a volatile boron compound.

[0028] In various variations of the method of making a top molybdenum nucleation layer, the steps of depositing a boron-containing nucleation layer (also referred to as a boron decomposition layer) and reacting the boron-containing nucleation layer with a vapor composition comprising molecules containing molybdenum and chlorine can be repeated one or more times. The one or more molybdenum nucleation layers can be substantially free of boron, as determined by SEM analysis, elemental analysis, or resistivity measurement.

[0029] The method of making a molybdenum nucleation layer may include vapor depositing a bulk molybdenum layer atop the top molybdenum nucleation layer at a temperature of 450° C. to 550° C. A molybdenum complex may be used to vapor deposit the bulk molybdenum layer. In some variations, the molybdenum complex contains molybdenum and chlorine. In yet other variations, the molybdenum complex may include MoCl5 or it may include MoOCl4.

[0030] Suitably, the thickness of the film may be 200 angstroms or greater, and the resistivity of the molybdenum film may be ±20% of the resistivity of a molybdenum film of substantially similar thickness ±10% measured at room temperature (RT, 20°C-23°C), wherein the molybdenum film of substantially similar thickness ±10% is deposited from the molybdenum complex at 700°C on a substrate in the absence of a molybdenum nucleation layer.

[0031] In variations of the method of making a molybdenum film, the molybdenum film atop the substrate includes a topmost bulk molybdenum layer and one or more underlying molybdenum nucleation layers. The molybdenum film may have a resistivity of less than 25 μΩ·cm for a molybdenum film layer thickness of 200 angstroms or greater, and in some variations, the molybdenum film has a resistivity of less than 20 μΩ·cm for a molybdenum layer thickness of 200 angstroms or greater. Lower resistivity molybdenum films consume less power and generate less heat than devices having higher resistivity molybdenum films.

[0032] In other variations of the method of making a molybdenum film, the molybdenum film on top of the substrate includes a topmost bulk molybdenum layer and one or more underlying molybdenum nucleation layers. The molybdenum film on top of the substrate has a resistivity measured at room temperature (RT, 20°C-23°C) between 10 μΩ·cm and 25 μΩ·cm, in some variations, the resistivity can be between 12 μΩ·cm and 25 μΩ·cm, and in some other variations, for a molybdenum film with a thickness between 800 angstroms and 200 angstroms, the resistivity can be between 10 μΩ·cm and 20 μΩ·cm. In some variations, the thickness of the molybdenum film is to In some other variations of the method of manufacturing the molybdenum film, the resistivity of the molybdenum film can be within ±20% of the resistivity of a vapor-deposited molybdenum film of similar thickness ±10% measured at room temperature (RT, 20°C-23°C), wherein the vapor-deposited molybdenum film of similar thickness ±10% is deposited on a similar substrate at 700°C.

[0033] A variation of the method for manufacturing a molybdenum film on a substrate may include the following actions or steps: exposing the substrate to B2H6 gas at a temperature ranging from 250°C to 550°C and a pressure ranging from 10 Torr to 60 Torr; forming a solid boron nucleation layer on the surface of the substrate; at a temperature above 450°C, exposing the boron nucleation layer to a vapor containing molybdenum atoms and chlorine atoms and converting the boron layer into a molybdenum nucleation layer and producing a boron compound, such as BCl3(g) or BOCl(g); optionally repeating the first four steps one or more times to form additional molybdenum nucleation layers; and CVD depositing molybdenum on top of the top molybdenum nucleation layer at a temperature of 550°C or lower by reducing a molybdenum complex containing molybdenum atoms and chlorine atoms with H2.

[0034] Another variation of manufacturing a molybdenum film on a substrate may include the following actions or steps: first exposing the substrate to a B2H6 gas having a temperature range of 300°C to 550°C and a pressure range of 10 torr to 60 torr. A boron decomposition layer or a boron nucleation layer is formed on the substrate surface, and the thickness of the layer can be controlled by the B2H6 flow rate and the dose time. The boron layer is then exposed to MoCl5 at a temperature above 450°C. The reaction converts the boron layer into a molybdenum nucleation layer, wherein the volatile gas contains BCl3(g) or BOCl(g) as a byproduct. The thickness of the resulting molybdenum nucleation layer depends on the starting thickness of the boron decomposition layer. The process of manufacturing a boron nucleation layer and converting it into a molybdenum nucleation layer may be repeated multiple times until the desired top molybdenum nucleation layer is obtained. Subsequently, conventional CVD molybdenum deposition may be performed on the top molybdenum nucleation layer. The molybdenum nucleation layer may help reduce the deposition cutoff temperature of CVD molybdenum from 550°C to 450°C. The CVD molybdenum film deposited on the top nucleation layer has low roughness and good step coverage on deep through-hole structures.

[0035] Variations of the method for making a molybdenum film may be performed in a fabrication process for forming a semiconductor device on a substrate. The molybdenum film of the present disclosure may also be deposited during the fabrication of various electronic devices, display devices, or photovoltaic devices. Examples of electronic devices include dynamic random access devices (DRAM) for digital storage devices and 3-D NAND logic gates for flash memory devices. DETAILED DESCRIPTION

[0036] The present disclosure relates to a method for making a molybdenum film on a substrate using a boron nucleation layer and a molybdenum nucleation layer. Compared to conventional chemical vapor deposition processes that do not use a boron nucleation layer or a molybdenum nucleation layer, the resulting molybdenum film can have a low resistivity, can be substantially free of boron, and can be made at a reduced temperature. The molybdenum nucleation layer formed by this process can protect the substrate from etching by chlorine-containing precursors (such as MoCl5 or MoOCl4), can facilitate the nucleation of subsequent CVD Mo growth on top of the molybdenum nucleation layer, and the molybdenum CVD can be performed at a lower temperature. The molybdenum nucleation layer can also be used to control the grain size of the subsequent CVD molybdenum growth, and thus control the resistivity of the final molybdenum film.

[0037] The boron nucleation layer can be formed by first exposing the substrate (which may include a thin overlying film) to B2H6 gas at a temperature ranging from 300°C to 550°C and a pressure ranging from 10 torr to 60 torr. A solid nucleation or decomposition layer containing boron is formed on the substrate surface (or overlying film), and the thickness of the boron-containing nucleation layer or the boron-containing decomposition layer can be controlled by the B2H6 flow rate and the dose time. The thickness of the boron-containing nucleation layer can be controlled by the B2H6 flow rate and the dose time. to Suitably, the thickness of the boron-containing nucleation layer may be in the range of about 5 angstroms to about 50 angstroms, optionally in the range of 5 angstroms to about 30 angstroms, such as in the range of about 5 angstroms to about 20 angstroms.

[0038] The molybdenum nucleation layer can be formed by exposing the boron nucleation layer to and reacting with a vapor composition comprising molybdenum, chlorine, and optionally oxygen at high temperature. This reaction with the vapor composition consumes the boron nucleation layer and replaces the boron nucleation layer with the molybdenum nucleation layer. The vapor composition can include MoCl5, MoOCl4, or other materials. For example, a substrate with a boron nucleation layer can be maintained at a temperature of 450°C to 550°C on a stage in a reactor and can be exposed to a composition comprising MoCl5 or consisting only of MoCl5, or to a composition that can be a mixture of MoCl5 and an inert gas such as argon (Ar), or to a composition that can be a mixture of MoCl5 and a reducing gas such as hydrogen (H2). In another example, the substrate on the heated stage with the boron nucleation layer can be maintained at a temperature of 450° C. to 550° C. and exposed to a composition comprising or consisting of MoOCl4, or to a composition that can be a mixture of MoOCl4 and an inert gas such as argon (Ar), or to a composition that can be a mixture of MoOCl4 and a reducing gas such as hydrogen (H2). Exposing the boron nucleation layer to one or more of these compositions at a temperature of 450° C. to 550° C. can convert the boron nucleation layer into a molybdenum-containing nucleation layer.

[0039] BCl3 or other boron-containing volatiles may be produced as a byproduct of the conversion of the boron nucleation layer to the molybdenum nucleation layer. The cutoff temperature of this reaction is about 450°C.

[0040] In the presence of H2, reaction byproducts may include HCl, BCl3, and OCl2 (in the case where the vapor composition comprises MoOCl4). The reaction may occur with or without H2 co-reactant on the boron nucleation layer.

[0041] The thickness of the resulting platinum nucleation layer depends on the initial thickness of the boron nucleation layer. In some variations, a vapor composition comprising platinum, chlorine, and optionally oxygen but not including a reducing gas can be used to convert the boron nucleation layer into a platinum nucleation layer. The thickness of the resulting platinum nucleation layer is proportional to the thickness of the boron nucleation layer.

[0042] Advantageously, the steps of depositing a boron nucleation layer and reacting the boron nucleation layer to form a molybdenum nucleation layer may be repeated to form one or more further boron nucleation layers.

[0043] Where multiple boron nucleation layers are formed, these layers may be made in substantially the same manner. Alternatively, different layers may employ different conditions, for example, as described elsewhere herein.

[0044] The method may include fabricating a top molybdenum nucleation layer. The molybdenum nucleation layer or another molybdenum nucleation layer atop the substrate may constitute the top molybdenum nucleation layer.

[0045] Variations of the molybdenum film formation process may further include an action or step of vapor depositing a molybdenum complex on the top molybdenum nucleation layer on the substrate to form a bulk molybdenum layer. The bulk molybdenum layer and one or more underlying molybdenum nucleation layers constitute a molybdenum film, and the molybdenum film has to In some variations, the thickness of the molybdenum film can be in the range of to During the bulk vapor deposition action or step, the temperature of the substrate may be between 450°C and 550°C. In some variations, the molybdenum complex may be a vapor composition comprising molybdenum atoms and chlorine atoms, and in other cases, the molybdenum complex may be a vapor composition comprising molybdenum atoms, chlorine atoms, and oxygen atoms. Examples of molybdenum complexes that may be used in variations of the method include MoCl5 and MoOCl4.

[0046] A composition containing molecules containing molybdenum atoms and chlorine atoms or a molybdenum complex containing molybdenum atoms and chlorine atoms can be vaporized to produce a vapor composition containing molybdenum atoms and chlorine atoms for a molybdenum film forming method. The composition or complex can contain MoCl5 (in some variations, 99% or more molecular purity) or MoOCl4 (in some variations, 99% or more molecular purity), respectively. In some variations, the molybdenum complex can be an organic metal molybdenum compound containing a cyclopentadienyl group and other ligands. The molybdenum complex can be purified to a molecular purity greater than 99.99% by sublimation. For example, MoCl5 can be purified by sublimation to remove trace amounts of MoOCl4 with a higher vapor pressure. A variation of the present disclosure may include an ampoule suitable for a vapor deposition process, the ampoule containing MoCl5 with a molecular purity greater than 99.99%. Another variation of the present disclosure may include an ampoule suitable for a vapor deposition process, the ampoule containing MoOCl4 with a molecular purity greater than 99.99%. Sublimation can be used to purify MoCl5 or MoOCl4 and remove unwanted metal halides and metal oxyhalides.

[0047] In variations of the method of making a molybdenum film, reference to the boron nucleation layer being substantially consumed may refer to the absence of boron by SEM analysis of a cross section of a sample in which one or more boron nucleation layers are replaced by one or more molybdenum nucleation layers. Substantially consumed may additionally or alternatively refer to the presence of less than 5 wt %, and in some cases less than 1 wt %, of boron in the molybdenum film and any underlying molybdenum nucleation layer. The boron content may be determined by acid dissolution of the film from the substrate and measured by elemental analysis. Substantially consumed may also refer to a molybdenum film having a resistivity measured at room temperature (RT, 20°C-23°C) within the range of ±20% or less of a molybdenum layer of similar thickness (±10%) vapor deposited from MoCl5 at 700°C on a similar substrate.

[0048] Thermal budget refers to the cumulative thermal energy given to semiconductor microelectronic transistors, logic gates or photovoltaic devices by all thermal processing steps during fabrication. Controlling the thermal budget of the process helps prevent dopant redistribution in the joints and diffusion of metals through barrier layers. If high temperatures are required during fabrication, a moderate thermal budget can be achieved by limiting the duration of the process. Similarly, if the process takes a long time to complete, the temperature can be reduced to avoid excessive thermal budgets. In a variation of the method, the molybdenum nucleation layer and the bulk molybdenum layer can be deposited at a temperature below 500°C and have similar deposition times compared to a 700°C molybdenum process without a Mo nucleation layer. The lower deposition temperature of the new method disclosed herein can be used to reduce the need for thermal budgets in processes where molybdenum films are used in the fabrication of semiconductor devices. In addition, the lower process temperatures achieved by the current process can reduce costs by allowing the use of cheaper process equipment and designs.

[0049] In a variation of the method for manufacturing a molybdenum film, the decomposition layer or nucleation layer containing boron is substantially free of boride. Similarly, the molybdenum nucleation layer and the molybdenum film are substantially free of boride. Boride is a material formed between boron and a more electronegative element (such as silicon). Boride layers have been suggested as barrier layers in the manufacture of integrated circuits to inhibit the diffusion of metals and other impurities into the area below the barrier layer. Borides are typically formed using chemical vapor deposition (CVD) techniques. For example, CVD can be used to react metal tetrachloride with diborane to form metal diboride. However, when chlorine-based chemicals are used to form boride barrier layers, reliability issues may occur. Specifically, boride layers formed using CVD chlorine-based chemicals typically have a high chlorine content (e.g., a chlorine content greater than about 3%). High chlorine content is undesirable because chlorine may migrate from the boride barrier layer to an adjacent interconnect layer, which may increase the contact resistance of such an interconnect layer and potentially change the characteristics of the integrated circuit manufactured therefrom. It has been found that the molybdenum film prepared by the method disclosed in this article protects the substrate from the etching effect of MoCl5 and MoOCl4.

[0050] In various variations of forming a molybdenum film atop a substrate, bulk molybdenum, a molybdenum nucleation layer, and a boron nucleation layer may be deposited by vapor deposition. Vapor deposition includes any of chemical vapor deposition (CVD), atomic layer deposition (ALD), high pressure and low pressure variations of these depositions, and variations of assisted variations of these depositions including, for example, but not limited to, plasma enhanced CVD, laser assisted, and microwave assisted.

[0051] In some variations of the present disclosure, there is a layer of material overlying the substrate. The layer may be, for example, but not limited to, titanium nitride, molybdenum, or other material underlying a bulk molybdenum layer in a semiconductor device. For example, when a refractory elemental metal such as molybdenum is used in a polysilicon-metal gate electrode structure, a thin conductive diffusion barrier layer may be provided between the polysilicon and the elemental metal to prevent silicidation of the elemental metal during high temperature processing. The diffusion barrier layer is typically composed of a conductive metal nitride, such as tungsten nitride (WN), titanium nitride (TiN), tantalum nitride (TaN), and / or corresponding silicon-containing ternary compounds, such as WSiN, TiSiN, and TaSiN.

[0052] In some variations, the substrate comprises a molybdenum nucleation layer, such as a molybdenum nucleation layer preformed in accordance with the present invention.

[0053] Substrates that can be used in variations of the method include silicon, silicon oxide, gallium arsenide, aluminum oxide, and other ceramics and metals with suitable chemical and temperature properties.

[0054] The boron nucleation layer or the boron decomposition layer may have a thickness of about 5 angstroms. To about 100 angstroms The molybdenum nucleation layer may have a thickness in the range of about 5 angstroms. To about 100 angstroms The boron nucleation layer may be deposited on a substrate or on top of a substrate on a layer heated to a temperature between 250°C and 550°C. In some variations, the boron nucleation layer may be deposited on a substrate or on top of a substrate on a layer heated to a temperature between 300°C and 450°C. The boron nucleation layer fabricated at 300°C and 450°C provides a smooth bulk molybdenum layer with low resistivity. The one or more B2H6 nucleation layers may be deposited by exposing the substrate to a B2H6 gas having a temperature in the range of 300°C to 550°C and a pressure in the range of 10 Torr to 60 Torr.

[0055] Bulk molybdenum vapor deposition from the molybdenum complex onto the top nucleation layer can occur in the presence of a reducing gas such as hydrogen. For example, the molybdenum pentachloride MoCl5 complex can be delivered to the reaction chamber by sublimation from a container or ampoule with a N2 or Ar carrier gas flow. For example, an ampoule container containing molybdenum pentachloride as the complex can be heated to a temperature between 70°C and 100°C. The vaporization temperature will vary depending on the molybdenum complex used. A lower ampoule temperature is beneficial to the generation of all vapors because it can reduce the decomposition of the molybdenum complex and thereby provide a more consistent molybdenum deposition rate.

[0056] Example 1

[0057] This example shows that the substrate Molybdenum was deposited on top of the thick titanium nitride layer. The thickness of the titanium nitride layer after deposition of the Mo nucleation layer and bulk Mo was within ±20% of the initial measured TiN layer thickness, indicating that the Mo nucleation layer provided etch resistance to the underlying TiN produced by the chlorine-containing precursors and byproducts.

[0058] The molybdenum film on top of the substrate is deposited by a multi-step process at different temperatures and pressures, as detailed in Table 1 below. The first step includes the following sub-steps: depositing a solid boron nucleation layer on the titanium nitride layer on top of the SiO2 substrate; and exposing the solid boron nucleation layer (or boron decomposition layer) to a composition including MoCl5 and hydrogen, thereby causing the boron nucleation layer to be fully replaced by the molybdenum nucleation layer.

[0059] The next step is to deposit a new boron nucleation layer on top of the molybdenum nucleation layer in a shorter immersion time than the nucleation of the first boron layer, and then bulk molybdenum deposition, which is initiated by the following steps: substantially consuming the new boron nucleation to form molybdenum; and then seamlessly bulk depositing molybdenum by reaction of MoCl5 with H2 to form a molybdenum film on the substrate.

[0060] The resistivity of the films was measured at room temperature (RT, 20° C. to 23° C.).

[0061] Table 1

[0062]

[0063] As detailed in Table 1, the deposition of the molybdenum nucleation layer was carried out at a temperature of 480° C. to 450° C., and in particular at a temperature of 480° C., 460° C. or 450° C. The pressure of the nucleated molybdenum or bulk molybdenum deposition step varied between 10 Torr and 40 Torr. The MoCl5 ampoule temperature (Amp Temperature ° C.) was 90 degrees Celsius.

[0064] The results of this example show that at a process pressure of 10 Torr, little or no Mo deposition is obtained at 480°C. However, at a process pressure of 40 Torr, the Mo film deposition rate forms about or thicker films, and the deposition rate decreases with decreasing deposition temperature. At 480°C and 40 Torr pressure, the molybdenum deposition rate is about At 460°C and 40 Torr pressure, the Mo deposition rate is about And at 460°C and 40 Torr pressure, the molybdenum deposition rate is about

[0065] The results of this example also show that the manufactured molybdenum film includes a bulk molybdenum layer and one or more molybdenum nucleation layers, and for a molybdenum film with a thickness of 700 angstroms to 300 angstroms, the four-point resistivity of the bulk molybdenum layer and the one or more molybdenum nucleation layers measured at room temperature (RT, 20°C-23°C) is between 12μΩ·cm and 20μΩ·cm, respectively. When measured at room temperature (RT, 20°C-23°C), all films show a low resistivity of less than 20μΩ·cm.

[0066] Example 2

[0067] This comparative example shows the deposition of molybdenum on a substrate without a molybdenum nucleation layer. The deposition was tested at stage temperatures ranging from 550°C to 700°C, and the deposition time was varied from 30 seconds to 600 seconds. MoCl5 was deposited on the TiN layer to form Mo. The MoCl5 ampoule was heated to 70°C, the chamber pressure was 60 Torr, the H2 flow rate was 2000 sccm, and the Argon carrier gas flow rate was 50 sccm.

[0068] The results in Table 2 show that CVD of Mo films on TiN-coated substrates is achieved using MoCl5 / H2 at stage temperatures above 550°C. At lower temperatures (e.g., <550°C stage temperature), Mo deposition ceases due to the substrate etching effect of MoCl5 and insufficient nucleation.

[0069] Table 2

[0070]

[0071] The results of this example show that at the same deposition time of about 180 seconds, the thickness of the deposited molybdenum film increases from 700°C to (The deposition rate is ) is reduced to 600℃ (The deposition rate is ), and as low as 550°C (The deposition rate is ). For films of similar thickness prepared at different temperatures, the resistivity of Mo films measured at room temperature (RT, 20°C-23°C) increases with decreasing deposition temperature. For example, the resistivity of Mo films deposited at 550°C increases with decreasing deposition temperature. The resistivity of the thick Mo film is 60μΩ·cm; the Mo film deposited at 600℃ The resistivity of the thick Mo film is 30.3 μΩ·cm, while that deposited at 700°C The thick film resistivity is 21.8 μΩ·cm.

[0072] Example 3

[0073] This example illustrates the fabrication of a molybdenum film comprising one or more molybdenum nucleation layers and a bulk molybdenum layer deposited by vapor deposition from MoCl5.

[0074] The resulting molybdenum films were prepared and characterized as detailed in Table 3. The substrate used had a The formation of a solid boron nucleation layer on the TiN layer was performed at a stage temperature of 300°C, a chamber pressure of 40 Torr, a B2H6 flow rate of 35 sccm, and an Ar flow rate of 250 sccm; the time varied between 60 seconds and 30 seconds depending on whether the boron nucleation layer was formed on the TiN or on the initial molybdenum nucleation layer. The estimated thickness of the boron nucleation layer was 5 angstroms to 30 angstroms.

[0075] The MoCl5 ampoule temperature was 90°C, the chamber pressure was 20 Torr, the Ar carrier gas flow was 100 sccm, the H2 was 2000 sccm, and the stage temperature was varied from 480°C to 500°C. The reaction time varied from 30 seconds to 600 seconds depending on whether the Mo nucleation layer was formed by consuming the initial Boron nucleation layer or the second Mo nucleation layer was formed after bulk Mo CVD.

[0076] Table 3

[0077]

[0078] The resistivity of these molybdenum films measured at room temperature was between 12 μΩ·cm and 25 μΩ·cm for molybdenum layers having thicknesses of 800 angstroms to 200 angstroms, respectively.

[0079] The results of this example further show that low resistivity molybdenum films can be produced at substrate temperatures of 480°C to 500°C by consuming the boron nucleation layer by reaction of the boron-containing nucleation layer on the substrate with a vapor composition containing molecules containing molybdenum atoms and chlorine atoms. The bulk molybdenum film resistivity in this example is ±20% of the resistivity of a bulk molybdenum layer of substantially similar thickness (±10%) measured at room temperature, wherein the bulk molybdenum layer of substantially similar thickness (±10%) is deposited from the same molybdenum complex at 700°C on a similar substrate without a molybdenum nucleation layer. For example, in Example 2, molybdenum was deposited on a similar substrate using the molybdenum complex of sample 322-237-12, and for The thick film obtained had a resistivity of about 16.1 μΩ·cm.

[0080] Example 4

[0081] This example shows the detrimental effect of excess residual boron on the resistivity of molybdenum films deposited with a boron nucleation layer and the cutoff temperature of molybdenum deposited using a boron nucleation layer.

[0082] The Mo film thickness after deposition at substrate temperatures of 450°C, 500°C, and 550°C was measured after 1, 2, 3, 4, and 5 cycles. After 5 nucleation cycles, the Mo film thickness at a deposition temperature of 450°C was less than After 5 nucleation cycles, the Mo film thickness at a deposition temperature of 500°C is about After 5 nucleation cycles, the Mo film thickness at a deposition temperature of 550°C is about Based on these results, it was determined that the cutoff temperature for the reaction between MoCl5 and boron would be between 450°C and 500°C.

[0083] After deposition at substrate temperatures of 500°C and 550°C, the resistivity of the molybdenum film measured at room temperature was measured after 1, 2, 3, 4, and 5 cycles. The resistivity after 1 nucleation cycle at 500°C was too high to be measured, while the resistivity of the molybdenum film after 1 nucleation cycle at 550°C was about 310 μΩ·cm. The resistivity of the molybdenum film after 2 nucleation cycles at 500°C was about 250 μΩ·cm, while the resistivity of the molybdenum film after 2 nucleation cycles at 550°C was about 275 μΩ·cm. The resistivity of the molybdenum film after 5 nucleation cycles at 500°C was about 250 μΩ·cm, while the resistivity of the molybdenum film after 5 nucleation cycles at 550°C was about 340 μΩ·cm. In this example, the resistivity after 2 nucleation cycles is much higher than that of a similar film made after 2 nucleation cycles in Example 1, and without wishing to be bound by theory, this is believed to be due to the presence of boron in the film.

[0084] Example 5

[0085] This example shows the deposition of molybdenum on a substrate without a boron nucleation layer having a TiN layer. The substrate was heated to 700°C on a stage in a reactor and treated with a composition comprising MoCl5 vapor and different amounts of hydrogen. The process conditions included an inert argon flow of 50 sccm, a chamber pressure of 60 Torr, a low hydrogen flow rate of 2000 sccm, and a high hydrogen flow rate of 4000 sccm.

[0086] The results of this example show that the 4-point measured resistivity of the molybdenum film deposited on the substrate without the nucleation layer is Thick Mo films of 15 μΩ·cm to 23 μΩ·cm without depositing a boron nucleation layer The resistivity of all films prepared using higher hydrogen flow rates was lower than that of films prepared at lower hydrogen flow rates, and for films prepared at about For thick Mo films, the resistivity of the films made at higher hydrogen flow rates is about 5 μΩ·cm lower than that of the samples made at lower hydrogen flow rates. The resistivity of Mo films decreases with increasing film thickness.

[0087] Although various compositions and methods are described, it is to be understood that the invention is not limited to the specific molecules, compositions, designs, methods or schemes described, as these may vary. It is also to be understood that the terms used in the specification are only for the purpose of describing specific variations or embodiments and are not intended to limit the scope of the invention, which is limited only by the appended claims.

[0088] It must also be noted that, 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, a reference to a "nucleation layer" is a reference to one or more nucleation layers known to those skilled in the art and their equivalents, and so on. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art. Methods and materials similar or equivalent to those described herein may be used in the practice or testing of embodiments of the present invention. All publications mentioned herein are incorporated by reference in their entirety. Nothing herein should be construed as an admission that the present invention is not entitled to antedate such disclosures by virtue of prior invention. "Optional" or "optionally" means that the subsequently described event or situation may or may not occur, and the description includes situations in which the event occurs and situations in which the event does not occur. Whether or not explicitly stated, all numerical values ​​herein may be modified by the term "approximately". The term "approximately" generally refers to a numerical range that a person skilled in the art would consider equivalent to the stated value (i.e., having the same function or result). In some embodiments, the term "approximately" refers to the value ± 10%, in other embodiments, the term "approximately" refers to the value ± 2%. Although compositions and methods are described in terms of "comprising" various components or steps (interpreted to mean "including but not limited to"), compositions and methods can also "consist essentially of" or "consist of" the various components and steps, and such terms should be interpreted as defining essentially closed or closed groups of components.

[0089] Although the present invention has been shown and described for one or more embodiments, other technicians in the art will think of equivalent changes and modifications based on reading and understanding of this specification and the accompanying drawings. The present invention includes all such modifications and changes and is limited only by the scope of the following claims. In addition, although the specific features or aspects of the present invention may be disclosed only for one of several embodiments, such features or aspects may be combined with one or more other features or aspects of other embodiments if it may be desirable and advantageous for any given or specific application. In addition, to the extent that the terms "including", "having, has", "with" or their variations are used in any of the specific embodiments or claims, such terms are intended to be included in a manner similar to the term "comprising". In addition, the term "exemplary" only means an example, not the best. It should also be understood that for the purpose of simplicity and ease of understanding, the features, layers and / or elements depicted herein are shown in specific sizes and / or orientations relative to each other, and the actual sizes and / or orientations may be substantially different from the sizes and / or orientations shown herein.

Claims

1. A method for manufacturing a molybdenum layer, the method comprising: A boron-containing nucleation layer on a substrate is reacted with a vapor composition containing molecules containing molybdenum atoms and chlorine atoms, wherein the temperature of the substrate is between 450°C and 550°C; the reaction consumes at least a portion of the boron-containing nucleation layer and forms a molybdenum nucleation layer on top of the substrate, wherein the boron-containing nucleation layer is consumed by the reaction so that, by elemental analysis, the molybdenum nucleation layer contains less than 5wt% boron.

2. The method of claim 1, wherein the molybdenum nucleation layer comprises less than 1 wt% boron.

3. The method according to claim 1, wherein the thickness of the boron-containing nucleation layer is to between.

4. The method according to claim 1, further comprising: depositing another boron-containing nucleation layer on top of the molybdenum nucleation layer on top of the substrate, the temperature of the substrate being between 300° C. and 550° C.; and The other boron-containing nucleation layer is reacted with a vapor composition comprising molecules containing molybdenum atoms and chlorine atoms, and the temperature of the substrate is between 450°C and 550°C; the reaction consumes at least a portion of the other boron-containing nucleation layer and forms another molybdenum nucleation layer. The method of claim 4 , wherein the deposition thickness of the further boron-containing nucleation layer is less than the deposition thickness of the boron-containing nucleation layer atop the substrate.

6. The method of claim 4, comprising vapor depositing the boron-containing nucleation layer atop the substrate during a first time period, and vapor depositing the further boron-containing nucleation layer during a second time period, the second time period being shorter than the first time period.

7. The method of claim 4, wherein the another boron-containing nucleation layer is consumed by the reaction such that the another molybdenum nucleation layer comprises less than 5 wt% boron by elemental analysis.

8. The method of claim 7, wherein the further molybdenum nucleation layer comprises less than 1 wt% boron.

9. The method of claim 1, wherein the vapor composition is free of reducing gases.

10. The method of claim 1, wherein the molybdenum nucleation layer or another molybdenum nucleation layer atop the substrate constitutes a top molybdenum nucleation layer.

11. The method of claim 10, comprising vapor depositing a molybdenum complex at a temperature of 450°C to 550°C to form a bulk molybdenum layer atop the top molybdenum nucleation layer.

12. The method of claim 11, wherein the molybdenum complex comprises MoCl5 or MoOCl4.

Images