Technology for improving adhesion and defects in tungsten carbide films

Abstract

Embodiments of the present disclosure generally relate to hard mask films and methods for depositing hard mask films. More specifically, embodiments of the present disclosure generally relate to tungsten carbide hard mask films and processes for depositing tungsten carbide hard mask films. In one embodiment, a method for forming a tungsten carbide film is provided. The method includes forming an initial layer of tungsten carbide on a silicon-containing surface of a substrate at a first deposition rate. The method further includes forming a tungsten carbide film on the initial layer of tungsten carbide at a second deposition rate, wherein the second deposition rate is greater than the first deposition rate.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to hard mask films and methods for depositing hard mask films. More specifically, embodiments of the present disclosure generally relate to tungsten carbide hard mask films and processes for depositing tungsten carbide hard mask films. Background Art

[0002] Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors, and resistors on a single chip. The evolution of chip design continues to involve faster circuits and higher circuit density. The demand for faster circuits with higher circuit density has increased the corresponding demand for materials used to manufacture such integrated circuits. Specifically, as the dimensions of integrated circuit components shrink to the sub-micron scale, low-resistance conductive materials and low-dielectric-constant insulating materials are used to obtain adequate electrical performance from such components.

[0003] The demand for higher integrated circuit density has also created a demand for process sequences used in the manufacture of integrated circuit components. For example, in a process sequence using conventional photolithography techniques, an energy-sensitive resist layer can be formed over a stack of material layers disposed on a substrate. The energy-sensitive resist layer is exposed to an image of a pattern to form a photoresist mask. Thereafter, an etching process is used to transfer the mask pattern to one or more of the stacked material layers. The chemical etchant used in the etching process is selected so as to have an etch selectivity to the stacked material layers that is greater than the etch selectivity to the mask of the energy-sensitive resist. That is, the chemical etchant etches one or more layers of the material stack at a much faster rate than it etches the energy-sensitive resist. The etch selectivity of the one or more material layers of the stack relative to the resist prevents the energy-sensitive resist from being consumed before the pattern transfer is complete. Thus, a highly selective etchant promotes accurate pattern transfer.

[0004] As the pattern size decreases, the thickness of the energy-sensitive resist is also reduced accordingly to control the pattern resolution. Due to the erosion of chemical etchants, such a thin resist layer may not be enough to cover the underlying material layer during the pattern transfer process. Because it has greater resistance to chemical etchants, an intermediate layer called a hard mask (such as silicon oxynitride, silicon carbide or carbon film) is usually used between the energy-sensitive resist layer and the underlying material layer to facilitate pattern transfer. The goal is a hard mask material with high etch selectivity and high deposition rate. As the critical dimension (CD) decreases, existing hard mask materials lack the target etch selectivity relative to the underlying material and are generally difficult to deposit.

[0005] Therefore, there is a need in the art for improved hard mask layers and methods for depositing improved hard mask layers. Summary of the Invention

[0006] Embodiments of the present disclosure generally relate to hard mask films and methods for depositing hard mask films. More specifically, embodiments of the present disclosure generally relate to tungsten carbide hard mask films and processes for depositing tungsten carbide hard mask films. In one embodiment, a method for forming a tungsten carbide film is provided. The method includes forming an initial layer of tungsten carbide on a silicon-containing surface of a substrate at a first deposition rate. The method further includes forming a tungsten carbide film on the initial layer of tungsten carbide at a second deposition rate, wherein the second deposition rate is greater than the first deposition rate.

[0007] In another embodiment, a method for forming a tungsten carbide film is provided. The method includes forming a tungsten carbide initial layer on a silicon-containing surface of a substrate at a first deposition rate, including exposing the silicon-containing surface to a first reactive gas comprising WF6, C3H6, and optionally H2 in a first PECVD process, the first PECVD process comprising a first RF plasma power of about 100 watts or less at a first pressure in a range of about 2 Torr to about 10 Torr. The method further includes forming a tungsten carbide film on the tungsten carbide initial layer at a second deposition rate, including exposing the tungsten carbide initial layer to a second reactive gas comprising WF6, C3H6, and H2 in a second PECVD process, the second PECVD process comprising a second RF plasma power of about 500 watts or greater at a second pressure in a range of about 2 Torr to about 10 Torr. The second deposition rate is greater than the first deposition rate.

[0008] In another embodiment, a method of forming a tungsten carbide film is provided. The method includes forming an initial layer of tungsten carbide on a silicon-containing surface of a substrate at a first deposition rate, including exposing the silicon-containing surface to a first reactive gas including WF6, C3H6, and optionally H2 in a first PECVD process, the first PECVD process including a first RF plasma power of about 100 watts or less at a first pressure in a range of about 2 Torr to about 10 Torr. The method further includes forming a tungsten carbide film on the initial layer of tungsten carbide at a second deposition rate, including exposing the initial layer of tungsten carbide to a second reactive gas including WF6, C3H6, and H2 in a second PECVD process, the second PECVD process including a second RF plasma power of about 500 watts or greater at a second pressure in a range of about 2 Torr to about 10 Torr. The second deposition rate is greater than the first deposition rate. The initial layer of tungsten carbide has a deposition rate of about 100 watts or less at a second pressure in a range of about 2 Torr to about 10 Torr. to about The tungsten carbide film has a thickness greater than about or greater thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above-described features of the present disclosure, briefly summarized above, may be understood in detail by reference to the embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0010] Figure 1 depicts a schematic cross-sectional view of a PECVD system that may be used to practice embodiments described herein;

[0011] Figure 2 A flow chart depicting a method for forming a tungsten carbide hard mask layer on a film stack disposed on a substrate according to one embodiment of the present disclosure; and

[0012] Figures 3A to 3C Description based on Figure 2 One embodiment of a sequence for forming a tungsten hard mask layer on a film stack formed on a substrate is shown in FIG.

[0013] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION

[0014] The following disclosure describes techniques for depositing a tungsten carbide (WC) hard mask film on a substrate. Figures 1 to 3C Specific details are set forth in order to provide a thorough understanding of the various embodiments of the present disclosure. Other details of well-known structures and systems often associated with plasma processing and hard mask deposition are not set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments.

[0015] Many of the details, dimensions, angles, and other features shown in the accompanying drawings are merely illustrations of specific embodiments. Accordingly, other embodiments may have other details, components, dimensions, angles, and features without departing from the spirit or scope of the present disclosure. Furthermore, further embodiments of the present disclosure may be practiced without several of the details described below.

[0016] The embodiments described herein will be described below with reference to a PECVD process, which can be performed using any suitable thin film deposition system. Examples of suitable systems include System (which can be used Processing chamber), PRECISION system, system, GT TM system, XP PRECISION TM System and SE TM The present invention also provides a system that is commercially available from Applied Materials, Inc. in Santa Clara, California, USA. Other tools capable of performing PECVD processes may also be adapted to benefit from the embodiments described herein. In addition, any system that implements the PECVD process described herein may be advantageously used. The apparatus described herein is illustrative only and should not be inferred or interpreted as limiting the scope of the embodiments described herein.

[0017] Embodiments of the present disclosure generally relate to hard mask films and methods for depositing hard mask films. More specifically, embodiments of the present disclosure generally relate to tungsten carbide hard mask films and processes for depositing tungsten carbide hard mask films. Tungsten carbide films have been experimentally shown to have high etch selectivity as hard masks. However, the use of tungsten carbide films faces several challenges. For example, tungsten carbide films have poor adhesion to underlying substrates (e.g., oxides, nitrides, or silicon). In addition, these tungsten carbide films are difficult to adhere to the surfaces of chamber components, which can cause deposits to flake off during processing. One existing solution involves using a boron interface layer between the underlying substrate and the tungsten carbide film. However, using a different material layer such as a boron interface layer complicates the subsequent etching chemistry. Another existing solution involves treating the underlying surface with hydrogen and nitrogen plasma before depositing the tungsten carbide film. However, hydrogen has been shown to be corrosive to certain chamber components, which leads to excessive defects in the deposited film. Embodiments described herein enable deposition of a tungsten carbide hard mask film on an oxide, nitride, or bare silicon surface by depositing a tungsten carbide initial layer on the underlying surface. The tungsten carbide initial layer is deposited at a lower deposition rate than a subsequently deposited tungsten carbide film. The inventors have surprisingly discovered that depositing the tungsten carbide initial layer prior to depositing the bulk tungsten carbide film significantly improves the adhesion of the bulk tungsten carbide film to the underlying substrate. Furthermore, because the tungsten carbide initial layer comprises the same material as the bulk tungsten carbide film, the same etching chemistry can be used to etch both the tungsten carbide initial layer and the bulk tungsten carbide film. Thus, the tungsten carbide initial layer described herein enables deposition of tungsten carbide films with good adhesion on a variety of substrates or layers, such as oxides (e.g., SiO2), nitrides (e.g., SiN), a-Si, oxide-nitride stacks, silicon, and polysilicon.

[0018] Figure 1A schematic cross-sectional view of a PECVD substrate processing system 132 that can be used to practice embodiments described herein is depicted. The PECVD substrate processing system 132 includes a processing chamber 100 coupled to a gas panel 130 and a controller 110. The processing chamber 100 generally includes a top wall 124, sidewalls 101, and a bottom wall 122 that define a processing volume 126. A support pedestal 150 for supporting a substrate is provided within the processing volume 126 of the processing chamber 100. The support pedestal 150 is supported by rods 160 and can be generally made of aluminum, ceramic, or other suitable materials. A displacement mechanism (not shown) can be used to move the support pedestal 150 vertically within the processing chamber 100.

[0019] The support base 150 may include a heater element 170 adapted to control the temperature of a substrate 190 supported on a surface 192 of the support base 150. The heater element 170 may be embedded in the support base. The support base 150 may be resistively heated by applying a current from the power supply 106 to the heater element 170. The heater element 170 may be formed of a nickel-iron-chromium alloy (e.g., ) sheath. The current supplied from the power supply 106 is regulated by the controller 110 to control the heat generated by the heater element 170, thereby maintaining the substrate 190 and the support pedestal 150 at a substantially constant temperature during film deposition. The supplied current can be adjusted to selectively control the temperature of the support pedestal 150 between approximately 100 degrees Celsius and approximately 700 degrees Celsius.

[0020] In some embodiments, a temperature sensor 172, such as a thermocouple, may be embedded in the support pedestal 150 to monitor the temperature of the support pedestal 150. The measured temperature is used by the controller 110 to control the power supplied to the heater element 170 to maintain the substrate at a target temperature.

[0021] The vacuum pump 102 is coupled to a port formed in the bottom of the processing chamber 100. The vacuum pump 102 is used to maintain a target gas pressure in the processing chamber 100. The vacuum pump 102 may also exhaust post-processing gases and process byproducts from the processing chamber 100.

[0022] The PECVD substrate processing system 132 may further include additional equipment to control chamber pressure, such as valves (eg, throttle valves and isolation valves) positioned between the processing chamber 100 and the vacuum pump 102 to control chamber pressure.

[0023] A showerhead 120 having a plurality of holes 128 is disposed at the top of the processing chamber 100, above the support pedestal 150. The holes 128 of the showerhead 120 are used to introduce process gases into the processing chamber 100. The holes 128 can have different sizes, numbers, distributions, shapes, designs, and diameters to facilitate the flow of various process gases for different process requirements. The showerhead 120 is connected to a gas panel 130, which allows the various gases to be supplied to the processing volume 126 during processing. In one embodiment, a plasma is formed from the process gas mixture exiting the showerhead 120 to enhance thermal decomposition of the process gases, which causes material to be deposited on the surface 191 of the substrate 190.

[0024] The showerhead 120 and the support pedestal 150 may form a pair of spaced apart electrodes in the processing volume 126. One or more RF power supplies 140 provide a bias potential to the showerhead 120 through a matching network 138 to facilitate generating a plasma between the showerhead 120 and the support pedestal 150. Alternatively, the RF power supply 140 and the matching network 138 may be coupled to the showerhead 120, the support pedestal 150, or both the showerhead 120 and the support pedestal 150, or to an antenna (not shown) disposed external to the processing chamber 100. In one embodiment, the RF power supply 140 may provide between about 100 watts and about 3000 watts at a frequency of about 50 kHz to about 13.6 MHz. In another embodiment, the RF power supply 140 may provide between about 500 watts and about 1800 watts at a frequency of about 50 kHz to about 13.6 MHz.

[0025] The controller 110 includes a central processing unit (CPU) 112, memory 116, and support circuitry 114 for controlling the process sequence and regulating the gas flow from the gas panel 130. The CPU 112 may be in the form of any general-purpose computer processor used in an industrial environment. Software routines may be stored in the memory 116, such as random access memory, read-only memory, a floppy disk, a hard disk, or another form of digital storage. The support circuitry 114 is coupled to the CPU 112 and may include cache memory, clock circuitry, input / output systems, power supplies, etc. Bidirectional communication between the controller 110 and the various components of the PECVD substrate processing system 132 is handled by a number of signal cables, collectively referred to as a signal bus 118, some of which are shown in FIG. Figure 1 .

[0026] Figure 2 A flow chart depicts a method 200 for forming a tungsten carbide hard mask layer on a film stack disposed on a substrate according to one embodiment of the present disclosure. The tungsten carbide hard mask layer formed on the film stack can be used, for example, to form a stair-like structure in the film stack. Figures 3A to 3CA schematic cross-sectional view illustrates a sequence for forming a tungsten carbide hard mask layer on a film stack disposed on a substrate according to method 200. Although method 200 is described below with reference to a hard mask layer that may be formed on a film stack used to create a stair-step structure in the film stack for use in a three-dimensional semiconductor device, method 200 may also be advantageously used in other device manufacturing applications.

[0027] The method 200 comprises: Figure 3A The substrate 300 depicted in FIG. 3 is positioned in a processing chamber such as Figure 1 100 of the PECVD substrate processing system 132 depicted in FIG. 1 , the process begins at operation 210. In one embodiment, the substrate includes an exposed surface. In one embodiment, the substrate 300 is similar to Figure 1 . In some embodiments, the exposed surface is selected from an exposed oxide surface (e.g., SiO2), an exposed nitride surface (e.g., SiN), an exposed a-Si surface, an oxide-nitride stack, an exposed silicon surface, or an exposed polysilicon surface. In one embodiment, the exposed surface is an oxide surface. The oxide surface can be any suitable oxide, including but not limited to silicon oxide. In some embodiments, the substrate comprises silicon and the oxide surface comprises silicon oxide. The oxide surface can be a native oxide or a grown oxide. For example, the surface can form a native oxide due to exposure to air, or the surface can be oxidized to form an oxide film having a predetermined thickness. In one embodiment, the exposed surface is a nitride surface. The nitride surface can be any suitable nitride, including but not limited to silicon nitride.

[0028] In one embodiment, a substrate 300 can be positioned on a support base, for example, on the surface 192 of the support base 150. The substrate 300 can be a silicon-based material, or any suitable insulating or conductive material as desired, and can have a film stack 304 disposed thereon. The film stack 304 can be utilized to form a structure 302 in the film stack 304, such as a stepped structure.

[0029] As depicted in Figure 3AAs shown in the exemplary embodiment of FIG, substrate 300 may have a substantially flat surface, an uneven surface, or a substantially flat surface with structures formed thereon. Film stack 304 is formed on substrate 300. In one embodiment, film stack 304 may be used to form a gate structure, a contact structure, or an interconnect structure in a front-end process or a back-end process. Method 200 may be performed on film stack 304 to form a stair-like structure in film stack 304, which is used in a memory structure (such as a NAND structure). In one embodiment, the material of substrate 300 may be crystalline silicon (e.g., Si <100> or Si <111> ), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon substrates and patterned or unpatterned substrates silicon or silicon on insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire and the like. The substrate 300 may have various sizes, such as 200-mm, 300-mm and 450-mm, or other diameter substrates, and may also be a rectangular panel or a square panel. Unless otherwise specified, the embodiments and examples described herein are performed on a substrate having a 200-mm diameter, a 300-mm diameter or a 450-mm diameter substrate. In one embodiment using an SOI structure as the substrate 300, the substrate 300 may include a buried dielectric layer disposed on a silicon crystalline substrate. In the embodiments described herein, the substrate 300 may be a crystalline silicon substrate.

[0030] In one embodiment, the film stack 304 disposed on the substrate 300 may have a plurality of vertically stacked layers. The film stack 304 may include a pair including a first layer (shown as 308a1, 308a2, 308a3, ..., 308a n ) and the second layer (shown as 308b1, 308b2, 308b3, ..., 308b n The pair includes alternating first layers (shown as 308a1, 308a2, 308a3, ..., 308a n ) and the second layer (shown as 308b1, 308b2, 308b3, ..., 308b n ), the alternating first and second layers are repeatedly formed until a target number of pairs of the first and second layers is reached.

[0031] The film stack 304 may be part of a semiconductor chip, such as a three-dimensional memory chip. Figures 3A to 3C The first layer (shown as 308a1, 308a2, 308a3, ..., 308a n) and a second layer (shown as 308b1, 308b2, 308b3, ..., 308b n ), but note that any target number of repetition pairs of the first and second layers can be utilized as desired.

[0032] In one embodiment, the film stack 304 can be used to form multiple gate structures for a three-dimensional memory chip. The first layers 308a1, 308a2, 308a3, ..., 308a formed in the film stack 304 n It can be a first dielectric layer, and the second layers 308b1, 308b2, 308b3, ..., 308b n It can be a second dielectric layer. It can be used to form the first layer 308a1, 308a2, 308a3, ..., 308a n and the second layers 308b1, 308b2, 308b3, ..., 308b n Suitable dielectric layers include silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, titanium nitride, composites of oxides and nitrides, at least one or more oxide layers sandwiching nitride layers, and combinations thereof. In certain embodiments, the dielectric layer may be a high-k material having a dielectric constant greater than 4. Suitable examples of high-k materials include hafnium dioxide (HfO2), zirconium dioxide (ZrO2), hafnium silicon oxide (HfSiO2), hafnium aluminum oxide (HfAlO), zirconium silicon oxide (ZrSiO2), tantalum dioxide (TaO2), aluminum oxide, aluminum-doped hafnium dioxide, bismuth strontium titanium (BST), and platinum zirconium titanium (PZT).

[0033] In a specific example, the first layers 308a1, 308a2, 308a3, ..., 308a n is a silicon oxide layer, and the second layers 308b1, 308b2, 308b3, ..., 308b n The first layer 308a1, 308a2, 308a3, ..., 308a n In one embodiment, the first layers 308a1, 308a2, 308a3, ..., 308a n The thickness can be controlled to be between about With Between, such as And the second layers 308b1, 308b2, 308b3, ..., 308b n The thickness of each layer can be controlled to be between about With Between, such as The film stack 304 may have a thickness between about With In one embodiment, the total thickness of the film stack 304 is from about 3 microns to about 10 microns, and may vary as technology advances.

[0034] Note that the hard mask layer may be formed on any surface or any portion of the substrate 300 with or without the film stack 304 being present on the substrate 300 .

[0035] At operation 220, an initial layer of tungsten carbide (such as initial layer 310) is formed on a substrate (such as substrate 300). Initial layer 310 is formed at a first deposition rate that is less than a deposition rate of a subsequently deposited tungsten carbide film. In one embodiment, initial layer 310 is deposited at the following deposition rates: seconds or less, seconds or less, seconds or less, seconds or less, or seconds or less. In one embodiment, between about Seconds and About seconds (e.g., between approximately Seconds and About seconds; or between approximately Seconds and About The tungsten carbide initiation layer 310 was deposited at a deposition rate of between 10 and 200 s. The inventors surprisingly discovered that forming the tungsten carbide initiation layer 310 at a low deposition rate improved the adhesion of the subsequently deposited tungsten carbide film 311 to the underlying silicon-containing surface (e.g., silicon oxide). It was observed that without the tungsten carbide initiation layer 310, the tungsten carbide film 311 was not well formed on the underlying silicon-containing surface.

[0036] In certain embodiments, the tungsten carbide initial layer 310 comprises a tungsten carbide film on top of a silicon-containing surface, such as the oxide surface of the first layer 308a1. Those skilled in the art will appreciate that the bottom portion of the tungsten carbide initial layer 310 may diffuse to the top of the oxide surface.

[0037] In one or more embodiments, the lower silicon-containing layer is exposed to a reactive gas comprising a mixture of WF6, Ar and C3H6 and optionally H2 that flows together into the process region of the processing chamber in the presence of plasma. The reactive gas used to form the tungsten carbide initial layer 310 may be referred to as a first reactive gas to distinguish it from the gas composition and conditions of other reactive gas processes. The C3H6 flow may be ramped up from no flow to a predetermined value within the first few seconds of the process. The WF6 flow may be ramped up from no flow to a predetermined value within the first few seconds of the process. The atomic percentage of tungsten in the tungsten carbide hard mask may be adjusted by changing the ratio of C3H6:WF6 during the process. In certain embodiments, the C3H6 and WF6 in the first reactive gas are present in a ratio (C3H6:WF6) of 2:1 or greater. In certain embodiments, C3H6 and WF6 in the first reactive gas are present in a ratio (C3H6:WF6) in the range of about 2:1 to about 10:1, or in the range of about 10:1 to about 50:1, or in the range of about 15:1 to about 30:1, or about 20:1.

[0038] In certain embodiments, the flow of CH in the first reactive gas is ramped up to a final predetermined flow rate over a time in the range of about 2 seconds to about 10 seconds. In certain embodiments, the flow of CH is ramped to a predetermined value over about 8 seconds, 7 seconds, 6 seconds, 5 seconds, 4 seconds, or 3 seconds.

[0039] In certain embodiments, the flow of WF6 in the first reactive gas is ramped up to a final predetermined flow rate over a time in the range of about 1 second to about 60 seconds (e.g., from about 2 seconds to about 10 seconds). In certain embodiments, the flow of WF6 is ramped to a predetermined value in about 8 seconds, 7 seconds, 6 seconds, 5 seconds, 4 seconds, or 3 seconds.

[0040] The PECVD process used to deposit the initial layer 310 of tungsten carbide includes an RF plasma generated at a predetermined frequency, power, and pressure. The plasma frequency can be any suitable frequency, including but not limited to 2 MHz, 13.56 MHz, 40 MHz, 60 MHz, and 100 MHz. In certain embodiments, the plasma frequency is approximately 13.56 MHz.

[0041] In certain embodiments, the power of the RF plasma used to deposit the tungsten carbide initial layer 310 is less than about 1000 W. In certain embodiments, the RF power used at any stage of the PECVD process is in the range of about 100 W to about 900 W, or in the range of about 200 W to about 800 W, or in the range of about 300 W to about 700 W, or in the range of about 400 W to about 600 W. In certain embodiments, the RF power is about 500 W.

[0042] The pressure in the process area can be any suitable process pressure. For example, the pressure can be in the range of about 1 Torr to about 50 Torr. In certain embodiments, the pressure is in the range of about 2 Torr to about 10 Torr. In one or more embodiments, the pressure is greater than 1 Torr and less than 50 Torr, 40 Torr, 30 Torr, or 20 Torr.

[0043] The underlying silicon-containing surface may be exposed to the RF plasma for any suitable time, depending on, for example, the process conditions and the desired thickness of the tungsten carbide initial layer 310 being deposited. In certain embodiments, the underlying silicon-containing surface is exposed to the PECVD process for a time in a range from about 1 second to about 60 seconds (e.g., about 1 second to about 30 seconds). In certain embodiments, the underlying silicon-containing surface is exposed to the PECVD process for about 10 seconds to form the tungsten carbide initial layer 310.

[0044] The thickness of the tungsten carbide initial layer 310 may vary depending on, for example, the desired thickness of the tungsten carbide film 311 to be deposited. In certain embodiments, the tungsten carbide initial layer 310 has a thickness of about to about In one or more embodiments, the tungsten carbide initial layer 310 has a thickness in the range of about to about 100 In various embodiments, the tungsten carbide initial layer 310 has a thickness of less than about or In certain embodiments, the tungsten carbide initial layer 310 has a thickness greater than about or thickness.

[0045] At operation 230, a tungsten carbide film (such as tungsten carbide film 311) is formed on the tungsten carbide initial layer (such as tungsten carbide initial layer 310). Tungsten carbide film 311 is also referred to as a hard mask layer. Tungsten carbide film 311 is formed at a second deposition rate that is greater than the first deposition rate of the previously deposited tungsten carbide initial layer 310. In one embodiment, tungsten carbide film 311 is deposited at the following deposition rates: seconds or more, seconds or more, seconds or more, seconds or more, or seconds or greater. In one embodiment, between about Seconds and Approx. seconds (e.g., between approximately Seconds and About seconds; or between approximately Seconds and Approx. The tungsten carbide film 311 is deposited at a deposition rate of between 10 and 20 s. In one embodiment, the ratio of the second deposition rate to the first deposition rate is 2:1 or greater, 3:1 or greater, 4:1 or greater, or 5:1 or greater. In one embodiment, the ratio of the second deposition rate to the first deposition rate is in a range of about 3:1 to about 5:1, or in a range of about 3:1 to about 4:1, or about 3:1.

[0046] In certain embodiments, the tungsten carbide film 311 may be formed by a second reactive gas, which is made by co-flowing WF6, Ar, and C3H6, and optionally H2, in the presence of an RF plasma. The reactive gas used to form the tungsten carbide film 311 may be referred to as a second reactive gas to distinguish it from the gas composition and conditions of other reactive gas processes. By varying the ratio of C3H6:WF6 during the process, the atomic percentage of tungsten in the tungsten carbide film 311 may be adjusted. In certain embodiments, the C3H6 and WF6 in the second reactive gas are present in a ratio (C3H6:WF6) of 2:1 or greater. In certain embodiments, the C3H6 and WF6 in the second reactive gas may be present in a ratio (C3H6:WF6) of about 2:1 to about 10:1, or in a range of about 10:1 to about 50:1, or in a range of about 15:1 to about 30:1, or about 20:1.

[0047] The PECVD process used to deposit the tungsten carbide film 311 includes an RF plasma generated at a predetermined frequency, power, and pressure. The plasma frequency can be any suitable frequency, including but not limited to 2 MHz, 13.56 MHz, 40 MHz, 60 MHz, and 100 MHz. In some embodiments, the plasma frequency is approximately 13.56 MHz.

[0048] In some embodiments, the power of the RF plasma used to deposit the tungsten carbide film 311 is less than about 1000 W. In some embodiments, the RF power used in any of the PECVD process stages is in the range of about 100 W to about 900 W, or in the range of about 200 W to about 800 W, or in the range of about 300 W to about 700 W, or in the range of about 400 W to about 600 W. In some embodiments, the RF power is about 500 W.

[0049] The pressure of the RF plasma can be any suitable process pressure. For example, the pressure can be in the range of about 1 Torr to about 50 Torr. In certain embodiments, the pressure is in the range of about 2 Torr to about 10 Torr. In one or more embodiments, the pressure is greater than or equal to about 1 Torr and less than or equal to about 50 Torr, 40 Torr, 30 Torr, or 20 Torr.

[0050] The tungsten carbide initial layer 310 can be exposed to the RF plasma for any suitable time depending on, for example, process conditions and the desired thickness of the tungsten carbide film 311 to be deposited. In some embodiments, the tungsten carbide initial layer 310 is exposed to the PECVD process for a time in a range from about 1 second to about 60 seconds (e.g., from about 1 second to about 30 seconds). In some embodiments, the tungsten carbide initial layer 310 is exposed to the PECVD process for about 10 seconds to form the tungsten carbide film 311.

[0051] The thickness of the tungsten carbide film 311 may vary depending on, for example, the process conditions of the tungsten-containing film deposition. In some embodiments, the tungsten carbide film 311 has a thickness greater than or equal to about or In one embodiment, the tungsten carbide film 311 has a thickness greater than about In one embodiment, the thickness of the tungsten carbide film 311 is about to about within the range.

[0052] The temperature at which each process stage occurs can be the same as or different from any other process stage. The temperature can be varied depending on, for example, the thermal budget of the device to be formed. In certain embodiments, the formation of the tungsten carbide initial layer 310 and the tungsten carbide film 311 occurs at a temperature in the range of about 100 degrees Celsius to about 700 degrees Celsius, or in the range of about 200 degrees Celsius to about 600 degrees Celsius, or in the range of about 400 degrees Celsius to about 550 degrees Celsius, or at about 450 degrees Celsius.

[0053] After forming the tungsten carbide film 311 , the tungsten carbide film 311 may be used as a patterning mask in an etching process to form a three-dimensional structure, such as a stair-like structure.

[0054] Thus, a method for forming a tungsten carbide hard mask layer is provided, which can be used to form a stepped structure for manufacturing three-dimensional stacks of semiconductor devices. The tungsten carbide hard mask layer can include an initial tungsten carbide layer and a bulk tungsten carbide film, providing a bonded structure with low surface roughness and improved adhesion at the interface between the underlying substrate and the tungsten carbide hard mask layer. By utilizing a tungsten carbide hard mask layer with targeted robust film properties and etch selectivity, improved dimensional and profile control of the resulting structure formed in the film stack can be achieved, as well as improved electrical performance of chip devices in applications for three-dimensional stacking of semiconductor structures.

[0055] In summary, certain embodiments described herein can deposit a tungsten carbide hard mask film on an oxide, nitride, or bare silicon surface by depositing a tungsten carbide initial layer on the underlying surface. The tungsten carbide initial layer is deposited at a lower deposition rate than the subsequently deposited tungsten carbide film. Depositing the tungsten carbide initial layer before depositing the bulk tungsten carbide film significantly improves the adhesion of the bulk tungsten carbide film to the underlying substrate. In addition, because the tungsten carbide initial layer comprises the same material as the bulk tungsten carbide film, the same etching chemistry can be used to etch both the tungsten carbide initial layer and the bulk tungsten carbide film. Therefore, the tungsten carbide initial layer described herein can deposit the tungsten carbide film with good adhesion on various substrates or layers such as oxides (e.g., SiO2), nitrides (e.g., SiN), a-Si, oxide-nitride stacks, silicon, and polysilicon.

[0056] When introducing elements or exemplary aspects of the present disclosure or embodiment(s) thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements.

[0057] The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0058] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is to be determined by the claims that follow.

Claims

1. A method for forming a tungsten carbide film, comprising: forming an initial layer of tungsten carbide directly on the silicon-containing surface of the substrate by plasma enhanced chemical vapor deposition (PECVD) at a first deposition rate; as well as forming a tungsten carbide film on the tungsten carbide initial layer at a second deposition rate, wherein the second deposition rate is greater than the first deposition rate, The forming of the tungsten carbide initial layer includes: exposing the silicon-containing surface to a first reactive gas in a first PECVD process, wherein the first reactive gas includes WF6, C3H6 and H2. 2 . The method of claim 1 , wherein a ratio of the second deposition rate to the first deposition rate is 3:1 or greater.

3. The method of claim 2, wherein the second deposition rate is or greater, and the first deposition rate is or smaller.

4. The method of claim 3, wherein the second deposition rate is to and the first deposition rate is within the range of to within the range.

5. The method of claim 1, wherein the tungsten carbide initial layer has to The thickness is within the range of .

6. The method of claim 5, wherein the tungsten carbide film has or greater thickness.

7. The method of claim 6, wherein the first PECVD process comprises a first RF plasma power of 100 watts or less at a first pressure within a first range of 2 Torr to 10 Torr.

8. The method of claim 7, wherein C3H6 and WF6 in the first reactive gas are present in a ratio of 2:1 or greater.

9. The method of claim 7, wherein forming the tungsten carbide film comprises: In a second PECVD process, the tungsten carbide initial layer is exposed to a second reactive gas, the second reactive gas comprising WF6, C3H6 and H2, the second PECVD process comprising a second RF plasma power of 500 watts or greater at a second pressure, the second pressure being in a second range of 2 Torr to 10 Torr.

10. The method of claim 1, wherein the silicon-containing surface comprises silicon oxide, silicon nitride, or a combination thereof.

11. A method for forming a tungsten carbide film, comprising: forming an initial layer of tungsten carbide directly on a silicon-containing surface of a substrate at a first deposition rate, comprising: exposing the silicon-containing surface to a first reactive gas in a first PECVD process, the first reactive gas comprising WF6, C3H6, and H2, the first PECVD process comprising a first RF plasma power of 100 watts or less at a first pressure, the first pressure being in a range of 2 Torr to 10 Torr; and Forming a tungsten carbide film on the tungsten carbide initial layer at a second deposition rate includes exposing the tungsten carbide initial layer to a second reactive gas in a second PECVD process, the second reactive gas including WF6, C3H6 and H2, the second PECVD process including a second RF plasma power of 500 watts or greater at a second pressure, the second pressure being in a range of 2 Torr to 10 Torr, wherein the second deposition rate is greater than the first deposition rate. 12 . The method of claim 11 , wherein a ratio of the second deposition rate to the first deposition rate is 3:1 or greater.

13. The method of claim 12, wherein the second deposition rate is or greater, and the first deposition rate is or smaller.

14. The method of claim 13, wherein the second deposition rate is to In the range of to within the range.

15. The method of claim 11, wherein the initial layer of tungsten carbide has to The thickness is within the range of .

16. A method for forming a tungsten carbide film, comprising: forming an initial layer of tungsten carbide directly on a silicon-containing surface of a substrate at a first deposition rate, comprising: exposing the silicon-containing surface to a first reactive gas in a first PECVD process, the first reactive gas comprising WF6, C3H6, and H2, the first PECVD process comprising a first RF plasma power of 100 watts or less at a first pressure, the first pressure being in a range of 2 Torr to 10 Torr; and forming a tungsten carbide film on the tungsten carbide initial layer at a second deposition rate, comprising: exposing the tungsten carbide initial layer to a second reactive gas in a second PECVD process, the second reactive gas comprising WF6, C3H6, and H2, the second PECVD process comprising a second RF plasma power of 500 watts or greater at a second pressure, the second pressure being in a range of 2 Torr to 10 Torr, wherein the second deposition rate is greater than the first deposition rate, The tungsten carbide initial layer has to The thickness is within the range of wherein the tungsten carbide film has a thickness greater than or greater thickness.

17. The method of claim 16, wherein C3H6 and WF6 in the first reactive gas are present in a ratio of 2:1 or greater.

18. The method of claim 17, wherein a ratio of the second deposition rate to the first deposition rate is 3:1 or greater.

19. The method of claim 18, wherein the second deposition rate is or greater, and the first deposition rate is or smaller.

20. The method of claim 19, wherein the second deposition rate is to In the range of to within the range.

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