Method for selective barrier metal etching and method for forming metal containing feature

Abstract

A method for selectively etching a barrier metal includes: performing a hydrogen implantation process in an inductively coupled plasma (ICP) etching chamber to chemically reduce an oxidized portion of a barrier metal layer, the oxidized portion of the barrier metal layer being formed within a feature in a metal layer on the barrier metal layer; and performing an etching process in the ICP etching chamber to remove the hydrogen implanted portion of the barrier metal layer.

Description

[Technical Field]

[0001] The examples disclosed herein generally relate to methods for forming metallic features in semiconductor structures. In particular, embodiments of the disclosed invention provide a method for etching a metal layer having a barrier metal layer formed beneath the metal layer. [Previous Technology]

[0002] In semiconductor manufacturing, tungsten, cobalt, and copper have been used as contacts and interconnects in back-to-line (BEOL) and middle-to-line (MOL) structures for memory devices, such as dynamic random access memory (DRAM) devices. Tungsten, in particular, is the most reliable metal due to its mature, low-cost chemical vapor deposition (CVD) growth method. However, as semiconductor devices become smaller at sub-7nm nodes and the line critical size (CD) reaches several nanometers, the contact resistance of tungsten, with its small line CD, increases significantly. While cobalt may exhibit some reduction in line resistance compared to tungsten, this reduction may not be sufficient. Therefore, ruthenium has become a strong candidate to replace existing materials used for contacts and interconnects. Ruthenium also exhibits low resistivity even for the smaller pitch and smaller critical size at sub-7nm nodes.

[0003] However, complex problems exist in the lithography and etching processes for ruthenium-based structures. The ruthenium layer is typically formed on a barrier metal layer, such as titanium (Ti), titanium nitride (TiN), tantalum (Ta), and / or tantalum nitride (TaN), to prevent ruthenium from diffusing into the underlying silicon-based substrate and forming ruthenium silicate. When the ruthenium layer is etched using an oxygen-containing etching gas, the barrier metal layer is partially oxidized and sputtered onto the ruthenium layer, acting as a non-volatile etch stop layer. Therefore, the ruthenium layer cannot be etched to the surface of the barrier metal layer to produce the originally patterned etch profile.

[0004] Therefore, there is a need for a method for etching a metal layer formed of ruthenium on a barrier layer to provide a desired etching profile. [Summary of the Invention]

[0005] Embodiments of the present invention provide a method for selectively etching a barrier metal. The method includes performing a hydrogen implantation process in an inductively coupled plasma (ICP) etching chamber to chemically reduce an oxide portion of a barrier metal layer, the oxide portion of which is formed within a feature of a metal layer on the barrier metal layer; and performing an etching process in the ICP etching chamber to remove the hydrogen implantation portion of the barrier metal layer.

[0006] The embodiments disclosed in this case also provide a method for forming a metallic feature. The method includes performing a first etching process in an inductively coupled plasma (ICP) etching chamber using an oxygen-containing etching gas to form a feature in a metal layer on a metal barrier layer; performing a hydrogen implantation process in the ICP etching chamber to chemically reduce the oxide portion of the barrier metal layer formed within the feature in the metal layer; and performing a second etching process in the ICP etching chamber to remove the hydrogen implantation portion of the barrier metal layer by using a chlorine-containing etching gas.

[0007] This embodiment of the invention also provides a metal-containing structure. The metal-containing structure includes: a barrier metal layer formed on a substrate; a metal feature formed on the barrier metal layer; and a dielectric feature formed on the metal feature, wherein the metal feature and the dielectric feature have linewidths between 3 nm and 90 nm.

Implementation Method

[0013] The embodiments described herein provide methods for forming metallic features in a semiconductor structure. More specifically, the embodiments disclosed herein provide methods for etching a metal layer having a barrier metal layer formed beneath the metal layer. In sub-7 nm node semiconductor processes, ruthenium (Ru) is a candidate metal for replacing conventionally used metals such as tungsten to form contacts and interconnects. However, the barrier layer disposed between the ruthenium-based structure and the substrate is not etched by an oxygen-containing etching gas that etches the ruthenium-based structure. Instead, a portion of the barrier layer is oxidized and sputtered onto the ruthenium-based structure as an etch stop layer for the ruthenium-based structure. The method provided herein removes the oxidized portion of the barrier metal layer using atomic layer etching (ALE) technology, enabling the formation of a ruthenium-based structure with a desired line density (CD).

[0014] Figure 1 is a cross-sectional view of an example of an inductively coupled plasma (ICP) etching chamber 100 suitable for performing an etching process. Suitable ICP etching chambers suitable for use with the methods disclosed herein include inductively coupled plasma reactive ion etching (ICP-RIE) chambers, such as the CENTRIS® SYM3™ etching chamber available from Applied Materials, Santa Clara, California, USA. Although the ICP etching chamber 100 shown includes a plurality of features capable of achieving excellent etching performance, other ICP etching chambers may be suitable for benefiting from one or more of the inventive features disclosed herein.

[0015] The ICP etching chamber 100 includes a chamber body 102 and a cover 104 that enclose an internal space 106. The chamber body 102 is generally made of aluminum, stainless steel, or other suitable material. The chamber body 102 generally includes sidewalls 108 and a bottom 110. A substrate support base inlet / outlet (not shown) is generally defined in the sidewalls 108 and is selectively sealed by a slit valve to facilitate the entry and exit of the substrate W from the ICP etching process. An exhaust port 112 is defined in the chamber body 102 and couples the internal space 106 to a vacuum pump system 114. The vacuum pump system 114 generally includes one or more pumps and throttle valves for evacuating and regulating the pressure of the internal space 106 of the ICP etching chamber 100.

[0016] The cover 104 is sealed and supported on the side wall 108 of the chamber body 102. The cover 104 can be opened to allow access to the interior space 106 of the ICP etching chamber 100. The cover 104 includes a window 116 to facilitate optical process monitoring. In one embodiment, the window 116 comprises quartz or other suitable material that is transmissive to signals used by an optical monitoring system 118 mounted outside the ICP etching chamber 100.

[0017] The optical monitoring system 118 is positioned to view through window 116 at least one of the following: the internal space 106 of the chamber body 102 and / or the substrate W positioned on the substrate support base assembly 120. In one embodiment, the optical monitoring system 118 is coupled to cover 104 and facilitates an integrated deposition process that uses optical metrology to provide information enabling process adjustments to compensate for inconsistencies in incoming substrate pattern features (e.g., thickness), and to provide process status monitoring (e.g., plasma monitoring, temperature monitoring, etc.) as needed. One type of optical monitoring system suitable for benefiting from the disclosure herein is the EyeD® full-spectrum interferometry module available from Applied Materials, Inc., Santa Clara, California, USA.

[0018] A gas panel 122 is coupled to the ICP etching chamber 100 to provide process gas and / or cleaning gas to the interior space 106. In the example depicted in FIG1, inlet ports 124, 126 are provided in the cover 104 to allow gas to be delivered from the gas panel 122 to the interior space 106 of the ICP etching chamber 100. In one embodiment, the gas panel 122 is adapted to provide fluorinated process gas through the inlet ports 124, 126 and into the interior space 106 of the ICP etching chamber 100.

[0019] The nozzle assembly 128 is coupled to the inner surface 130 of the cover 104. The nozzle assembly 128 includes a plurality of apertures that allow gas to follow through the nozzle assembly 128 from the inlet ports 124, 126 into the interior space 106 of the ICP etching chamber 100 and to be distributed in a predetermined manner across the surface of the substrate W being processed in the ICP etching chamber 100.

[0020] The remote plasma source 132 may optionally be coupled to the gas control board 122 to facilitate the dissociation of the gas mixture from the remote plasma before it enters the internal space 106 for processing. The RF power supply 134 is coupled to the nozzle assembly 128 via a mating network 136. The RF power supply 134 is generally capable of generating up to about 3000W of power at an adjustable frequency in the range of about 50kHz to about 200MHz.

[0021] The nozzle assembly 128 additionally includes a region that is transmissive to optical metering signals. The optically transmissive region or channel 138 is adapted to allow the optical monitoring system 118 to view the interior space 106 and / or the substrate W positioned on the substrate support base assembly 120. The channel 138 may be a material formed or disposed in the nozzle assembly 128, a single aperture or a plurality of apertures, and is substantially transmissive to the wavelength of energy generated by (and reflected back to) the optical monitoring system 118.

[0022] In one embodiment, the nozzle assembly 128 is configured with a plurality of blocks that allow for individual control of the gas flowing into the interior space 106 of the ICP etching chamber 100. In the example illustrated in FIG1, the nozzle assembly 128 has an inner block 140 and an outer block 142, which are coupled to a gas control board 122 through separate inlet ports 124, 126.

[0023] A substrate support base assembly 120 is disposed within the internal space 106 of the ICP etching chamber 100 below the gas distribution (nozzle) assembly 128. The substrate support base assembly 120 holds the substrate W during processing. The substrate support base assembly 120 generally includes a plurality of lifting pins (not shown) arranged to pass through the substrate support base assembly 120 and configured to lift the substrate W from the substrate support base assembly 120 and facilitate the conventional exchange of the substrate W with a robot (not shown). An inner liner 144 may tightly surround the periphery of the substrate support base assembly 120.

[0024] In one embodiment, the substrate support base assembly 120 includes a mounting plate 146, a base 148, and an electrostatic chuck 150. The mounting plate 146 is coupled to the bottom 110 of the chamber body 102 and includes a plurality of channels for routing facilities (especially fluid, power lines, and sensor wires) to the base 148 and the electrostatic chuck 150. The electrostatic chuck 150 includes at least one clamping electrode 152 for holding the substrate W below the nozzle assembly 128. The electrostatic chuck 150 is driven by an adsorption power supply 154 to generate an electrostatic force that holds the substrate W on the adsorption surface, as is known in the art. Alternatively, the substrate W may be held in the substrate support base assembly 120 by clamping, vacuum, or gravity.

[0025] At least one of the base 148 or the electrostatic chuck 150 may include at least one optional embedded heater 156, at least one optional embedded isolator 158, and a plurality of conduits 160, 162 to control the lateral temperature profile of the substrate support base assembly 120. The conduits 160, 162 are fluidly coupled to a fluid source 164 through which temperature-regulating fluid is circulated. The heater 156 is regulated by a power supply 166. The conduits 160, 162 and the heater 156 are used to control the temperature of the base 148, thereby heating and / or cooling the electrostatic chuck 150, and ultimately controlling the temperature profile of the substrate W disposed on the base 148. A plurality of temperature sensors 168, 170 may be used to monitor the temperature of the electrostatic chuck 150 and the base 148. The electrostatic chuck 150 may further have a plurality of gas channels (not shown), such as grooves, formed in the substrate support base support surface of the electrostatic chuck 150 and fluidly coupled to a heat transfer (or back-side) gas source, such as helium (He). In operation, back-side gas is supplied to the gas channels at a controlled pressure to enhance heat transfer between the electrostatic chuck 150 and the substrate W.

[0026] In one embodiment, the substrate support base assembly 120 is configured as a cathode and includes an electrode 152 coupled to a plurality of RF bias power supplies 172, 174. The RF bias power supplies 172, 174 are coupled between the electrode 152 (disposed in the substrate support base assembly 120) and another electrode, such as a nozzle assembly 128 or a top plate (cover 104) of the chamber body 102. The RF bias power excites and sustains a plasma discharge formed by gas disposed in the processing area of ​​the chamber body 102.

[0027] In the example depicted in Figure 1, dual RF bias power supplies 172, 174 are coupled to electrodes 152 disposed in the substrate support assembly 120 via a matching circuit 176. Signals generated by the RF bias power supplies 172, 174 are transmitted via the matching circuit 176, through a single feed to the substrate support assembly 120, to ionize the gas mixture provided in the ICP etching chamber 100, thereby providing the ion energy required to perform deposition or other plasma-enhanced processes. The RF bias power supplies 172, 174 are generally capable of generating RF signals with frequencies from about 50 kHz to about 200 MHz and power between about 0 watts and about 5000 watts. An additional bias power supply 178 may be coupled to electrodes 152 to control plasma characteristics.

[0028] In one operating mode, the substrate W is disposed on the substrate support base assembly 120 in the ICP etching chamber 100. Process gas and / or gas mixture is introduced into the chamber body 102 from the gas control plate 122 through the nozzle assembly 128. The vacuum pump system 114 maintains the pressure within the chamber body 102 while removing deposition byproducts.

[0029] Controller 180 is coupled to ICP etching chamber 100 to control the operation of ICP etching chamber 100. Controller 180 includes a central processing unit (CPU) 182, memory 184, and support circuitry 186 for controlling the process sequence of ICP etching chamber 100 and regulating airflow from gas control board 122. CPU 182 can be any type of general-purpose computer processor that can be used in industrial facilities. Software is typically stored in memory 184, such as random access memory, read-only memory, floppy disk or hard disk drive, or other forms of digital storage devices. Support circuitry 256 is conventionally coupled to CPU 182 and may include cache memory, clock circuitry, input / output system, power supply, etc. Bidirectional communication between controller 180 and various components of ICP etching chamber 100 is handled through numerous signal cables.

[0030] FIG2 illustrates a flowchart of a method 200 for patterning a film stack 300 by photolithography and etching according to an embodiment. FIG3A to FIG3F illustrate cross-sectional views of a portion of the film stack 300 at various stages of method 200. Although FIG3A to FIG3F and method 200 are discussed in the context of patterning high aspect ratio (HAR) metal features, method 200 can be used to etch other metal features formed on other types of substrates, wherein the aforementioned high aspect ratio metal features are formed on the substrate and there is a barrier metal between the metal features and the substrate, which can be used for dynamic random access memory (DRAM), flash memory, and logic elements.

[0031] Referring to FIG. 3A, the film stack 300, having undergone photolithography and etching processes, includes a substrate 302, a barrier metal layer 304, a metal layer 306, and a masking layer 308. The film stack 300 may include an additional layer between the metal layer 306 and the masking layer 308. A capping layer 310 may be formed over the metal layer 306 to protect the metal layer 306 from photolithography. In DRAM applications, a dielectric layer 312, such as a silicon nitride (Si3N4) layer, may be formed between the capping layer 310 and the masking layer 308. In one example, the metal layer 306 and the dielectric layer 312 may be patterned to form metallic and dielectric features, and the patterned metal layer 306 and the dielectric layer 312 may serve as bit lines and storage trench capacitors in a DRAM element, respectively.

[0032] The substrate 302 may include materials such as: doped or undoped polycrystalline silicon, silicon oxide, doped or undoped silicon wafers and patterned or unpatterned wafers, crystalline silicon (e.g., Si<100> or Si<111>), strained silicon, silicon-germanium, silicon-on-insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, or sapphire. The substrate 302 may have various sizes, such as wafers with diameters of 200 mm, 300 mm, 450 mm, or other diameters, and rectangular or square panels.

[0033] The metal layer 306 includes a noble metal, such as ruthenium (Ru), iridium (Ir), platinum (Pt) or rhodium (Rd), which can be etched using an oxygen-containing etching gas.

[0034] A barrier metal layer 304 is disposed between the substrate 302 and the metal layer 306 to prevent metal species such as ruthenium (Ru) from diffusing from the metal layer 306 into the substrate 302, which could result in metal silicates, such as ruthenium silicate. The barrier metal layer 304 may include a titanium (Ti) layer 304A and a titanium nitride (TiN) layer 304B. In some embodiments, the barrier metal layer 304 includes a tantalum (Ta) layer 304A and a tantalum nitride (TaN) layer 304B.

[0035] The masking layer 308 may include a pad oxide layer, an amorphous carbon layer (ACL), or a silicon oxynitride (SiON) layer. The masking layer 308 may be formed by using any suitable deposition process, such as spin coating, chemical vapor deposition (CVD), etc.

[0036] Method 200 begins at block 210, in which a photolithography process is performed, as shown in FIG3B. In the photolithography process in block 210, the mask layer 308 and other layers between the mask layer 308 and the capping layer 310 (e.g., the dielectric layer 312 in the example shown in FIG3A) are patterned using a patterned photoresist layer (not shown) formed on the mask layer 308. Double patterning can be performed using a spacer layer (not shown) formed on the mask layer 308 to pattern multiple features having linewidths and line CDs smaller than those achievable with conventional photolithography in sub-7nm node semiconductor processes. The mask layer 308 can be removed after the photolithography process in block 210.

[0037] In block 220, a first etching process is performed to etch metal layer 306 to form features (e.g., trench 314) with line CD 316, as shown in FIG3C. The overburden etching process can be any suitable etching process, such as a dry plasma etching process in an ICP etching chamber, such as ICP etching chamber 100. The dry plasma etching process in block 220 is performed by simultaneously supplying an oxygen-containing etching gas and an inert gas, such as argon (Ar), nitrogen (N2), or helium (He), inert gas in the ICP etching chamber. Halogen-containing gases may also be supplied to increase the etching rate of metal layer 306. Suitable examples of oxygen-containing etching gases include O2, O3, H2O, H2O2, N2O, and NO2. Suitable examples of halogen-containing gases include Cl2, HCl, HF, F2, Br2, HCl, HBr, SF6, and NF3. In one particular paradigm, oxygen-containing etching gases include oxygen (O2), inert gases include argon (Ar) and nitrogen (N2), and halogen-containing gases include chlorine (Cl2).

[0038] During the dry plasma etching process in block 220, several process parameters can be adjusted. In one example, oxygen (O2) gas can be supplied at a flow rate between about 10 sccm and about 1000 sccm, for example, about 100 sccm. Argon (Ar) gas can be supplied at a flow rate between about 0 sccm and about 1000 sccm, for example, about 150 sccm. Nitrogen (N2) gas can be supplied at a flow rate between about 0 sccm and about 100 sccm, for example, about 10 sccm. Chlorine (Cl2) gas can be supplied at a flow rate between about 10 sccm and about 500 sccm, for example, about 30 sccm. The dry plasma etching process is performed for a duration between about 5 seconds and about 60 seconds, for example, about 10 seconds. In an exemplary embodiment, the process pressure in the ICP etching chamber is adjusted between about 3 mTorr and about 50 mTorr, for example, about 20 mTorr. The temperature of the substrate support (e.g., substrate support base assembly 120) located in the ICP etching chamber is maintained between about 0 degrees Celsius and about 100 degrees Celsius, for example, about 50 degrees Celsius.

[0039] The source RF power can be maintained between approximately 600 W and approximately 2000 W, for example, approximately 1500 W. A low RF bias power is applied to ions formed from a mixture of oxygen-containing and halogen-containing gases to bombard the film stack 300 with low energy. In one example, the bias RF power is maintained between approximately 50 W and approximately 400 W, for example, approximately 200 W.

[0040] In some embodiments, a cleanup operation can be performed after the first etching process in block 220. During the cleanup operation, non-surface-bonded oxygen and chlorine species are removed from the processing chamber. Species generated in oxygen and chlorine-based plasmas can be removed by stopping the plasma and allowing remaining species to decay, optionally in conjunction with chamber cleanup and / or evacuation. The cleanup operation can be performed using any inert gas (such as N2, Ar, Ne, He, or combinations thereof).

[0041] Because the barrier metal layer 304 has etching resistance to the oxygen-containing etching gas used in the first etching process for etching the metal layer 306 in block 220, the barrier metal layer 304 remains undamaged. However, a portion of the barrier metal layer 304 is oxidized and sputtered onto the unetched portion 318 of the metal layer 306, forming an oxidized portion 320 of the barrier metal layer 304, the aforementioned unetched portion 318 being close to the top surface of the barrier metal layer 304. This oxidized portion 320 is formed as titanium oxide (TiO2) in embodiments of the barrier metal layer 304 having a titanium (Ti) layer 304A and a titanium nitride (TiN) layer 304B, and as tantalum oxide (TaO2) in embodiments of the barrier metal layer 304 having a tantalum (Ta) layer 304A and a tantalum nitride (TaN) layer 304B. The oxide portion of the barrier metal layer 305 acts as an etch stop layer, preventing further etching of the metal layer 306 to the top surface of the barrier metal layer 304, leaving an unetched portion 318 (also referred to as a "foot structure") within the trench 314 near the bottom surface of the barrier metal layer 304. The thickness of the oxide portion 320 of the barrier metal layer 304 can be between 0.5 nm and 5 nm, for example, about 2 nm, corresponding to a metal oxide (i.e., titanium oxide or tantalum oxide) between about one monolayer and about ten monolayers. In one example, the linewidths of the etched metal layer 306 and the etched dielectric layer 312 are between about 5 nm and 12 nm, for example, about 8 nm, and the foot structure 318 can be between about 2 nm and 12 nm wide on each side of the trench 314, for example, about 4.5 nm, and thus the unetched portion 318 has a width between about 7 nm and 18 nm.

[0042] In block 230, a hydrogen (H2) implantation process is performed to chemically reduce (i.e., reverse oxidation) the oxide portion 320 of the barrier metal layer 304. The hydrogen implantation process in block 230 is performed by supplying a hydrogen-containing gas in an ICP etching chamber (e.g., ICP etching chamber 100). In some embodiments, the oxide portion 320 of the barrier metal layer 304 is bombarded with a plasma effluent 322 generated from the hydrogen-containing gas and directed toward the oxide portion of the barrier metal layer 304, thereby providing directional energy transfer and facilitating selective hydrogen implantation of the oxide portion 320 of the barrier metal layer 304 relative to the rest of the film stack 300. The oxide portion 320 of the barrier metal layer 304 reacts chemically with hydrogen (H2) to release water (H2O) and is reduced back to the original metal in the hydrogen-implanted portion 320' of the barrier metal layer 304, as shown in FIG3D. For example, the oxide portion 320 formed from titanium oxide (TiO2) is reduced to titanium (Ti). The oxide portion 320 formed from tantalum oxide (TaO2) is reduced to tantalum (Ta). This chemical reduction process is a self-limiting chemical modification process that only affects the outermost atomic layer of the oxide portion 320, and, in combination with the subsequent etching steps in block 240, allows the removal of individual atomic layers of the oxide portion 320 of the barrier metal layer 304 (referred to as atomic layer etching (ALE)).

[0043] During the hydrogen implantation process in block 230, several process parameters can be adjusted. In one example, hydrogen (H2) gas can be supplied at a flow rate between about 50 sccm and about 500 sccm, for example, about 200 sccm. The hydrogen implantation process is performed for a duration between about 5 seconds and about 40 seconds, for example, about 10 seconds. In an exemplary embodiment, the process pressure in the ICP etching chamber is adjusted between about 3 mTorr and about 50 mTorr, for example, about 10 mTorr. The temperature of the substrate support (e.g., substrate support base assembly 120) disposed in the ICP etching chamber is maintained between about 0 degrees Celsius and about 80 degrees Celsius, for example, about 40 degrees Celsius.

[0044] The source RF power can be maintained between about 300W and about 1000W, for example, about 500W. The bias RF power is maintained between about 0W and about 300W, for example, about 100W, to provide directionality of the ion flux toward the oxide portion 320 of the barrier metal layer 304.

[0045] In some embodiments, a purification operation can be performed after the hydrogen implantation process in block 230 to remove non-surface-bonded hydrogen species and water from the processing chamber. The purification operation can be performed using any inert gas (such as N2, Ar, Ne, He, or a combination thereof).

[0046] In block 240, a second etching process is performed to etch the chemically reduced hydrogen implantation portion 320', as shown in FIG3E. The second etching process following the hydrogen implantation process in block 230 completes the ALE process. This etching process can be any suitable etching process, such as a dry plasma etching process in an ICP etching chamber (such as ICP etching chamber 100). In an embodiment having a barrier metal layer 304 with a titanium (Ti) layer 304A and a titanium nitride (TiN) layer 304B, the hydrogen implantation portion 320' comprises titanium (Ti). In an embodiment having a barrier metal layer 304 with a tantalum (Ta) layer 304A and a tantalum nitride (TaN) layer 304B, the hydrogen implantation portion 320' comprises tantalum (Ta). The dry plasma etching process in block 240 is performed by simultaneously supplying a chlorine-containing gas and an inert gas (such as argon (Ar), nitrogen (N2), or helium (He)) within the ICP etching chamber. A carbon-containing gas can also be supplied as a catalyst to etch the barrier metal layer 304 of the titanium (Ti) layer 304A and the titanium nitride (TiN) layer 304B into TiCl4. Suitable examples of chlorine-containing gases include Cl2, HCl, CCl4, CHCl3, CH2Cl2, CH3Cl, etc. Suitable examples of carbon-containing gases include methane (CH4), ethane (C2H6), and ethylene (C2H4). In a particular example, the chlorine-containing gas includes Cl2, the inert gas includes argon (Ar), and the carbon-containing gas includes CH4.

[0047] During the dry plasma etching process in block 240, several process parameters can be adjusted. In one example, chlorine (Cl2) gas can be supplied at a flow rate between about 30 sccm and about 500 sccm, for example, about 420 sccm. Argon (Ar) gas can be supplied at a flow rate between about 0 sccm and about 400 sccm, for example, about 200 sccm. Methane (CH4) gas can be supplied at a flow rate between about 10 sccm and about 50 sccm, for example, about 15 sccm. The dry plasma etching process is performed for a duration between about 10 seconds and about 60 seconds, for example, about 30 seconds. In one exemplary embodiment, the process pressure in the ICP etching chamber is adjusted between about 5 mTorr and about 30 mTorr, for example, about 20 mTorr. The temperature of the substrate support (e.g., substrate support base assembly 120) disposed in the ICP etching chamber is maintained between about 0 degrees Celsius and about 80 degrees Celsius, for example, about 40 degrees Celsius.

[0048] The source RF power can be maintained between about 300W and about 1500W, for example, about 500W. A low RF bias power is applied to ions formed from a mixture of chlorine-containing and carbon-containing gases to bombard the film stack 300 with low energy. In one example, the bias RF power is maintained between about 0W and about 100W, for example, about 0W.

[0049] In some embodiments, purification can be performed after the second etching process in block 240 to remove non-surface-bonded chloride species and remove methane from the processing chamber. Purification can be performed using any inert gas (such as N2, Ar, Ne, He, or a combination of the above gases).

[0050] In block 250, after removing the hydrogen implantation portion 320' in block 240, a third etching process is performed to remove the foot structure 318 of the metal layer 306. The third process in block 250 is the same as the first etching process in block 220. In some embodiments, the third etching process in block 250 is different from the first etching process in block 220. For example, the duration of the third etching process in block 250 is shorter than that of the first etching process in block 220.

[0051] The process in blocks 230 to 250 is repeated until the foot structure 318 of the metal layer 306 is substantially removed, thereby creating a trench 314 with a desired opening (also referred to as a "foot CD") 324 at the bottom of the trench 314. The desired foot CD 324 can be no more than about 1 nm narrower than the line CD 316 of the trench 314. For example, by repeating the process in blocks 230 to 250 for about 5 cycles, the foot CD 324 can be increased by between about 3 nm and about 4 nm, and the width of the foot structure 318 of the metal layer 306 can be reduced to between about 0.5 nm and about 4.5 nm.

[0052] In the embodiments described herein, a method for forming a metallic feature in a semiconductor structure is provided. The method described herein can be used to form a metallic structure that can be etched by an oxygen-containing etching gas and formed on a barrier metal layer that is not etched by the oxygen-containing etching gas. A portion of the barrier metal layer oxidized by the oxygen-containing etching gas is first reduced by hydrogen implantation chemical reduction and then removed by a chlorine-containing etching gas. Therefore, the metallic structure can be etched to have a desired line CD without being interrupted by the oxidized portion of the barrier layer.

[0053] Although the foregoing content pertains to the embodiments disclosed in this case, other and further embodiments of the disclosed content can be designed without departing from the basic scope of this case, and the scope of this case is determined by the appended claims. [Simplified Explanation of the Diagram]

[0008] In order to understand in detail the above-described features of the embodiments disclosed herein, a more specific description of the briefly summarized disclosure can be obtained by referring to some of the embodiments illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only typical embodiments of the disclosure and should not be considered as limiting the scope of the disclosure, as other equivalent embodiments are permissible.

[0009] Figure 1 depicts an inductively coupled plasma (ICP) etching chamber according to one embodiment, which can be used to perform a patterning process.

[0010] Figure 2 illustrates a flowchart of a method for patterned film stacking according to one embodiment.

[0011] Figures 3A, 3B, 3C, 3D, 3E, and 3F are cross-sectional views of a portion of a membrane stack according to one embodiment.

[0012] For ease of understanding, the same element symbols are used to designate the same elements commonly used in the drawings whenever possible. Elements disclosed in one embodiment may be advantageously used in other embodiments without further description. [Biomaterial Storage]

[0055] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A method for selectively etching barrier metals, the method comprising: A hydrogen implantation process is performed to chemically reduce an oxide portion of a barrier metal layer located on a foot structure at the bottom of one of the features in a metal layer on the barrier metal layer; a first etching process is performed to remove the hydrogen implantation portion of the barrier metal layer; and a second etching process is performed to remove at least a portion of the foot structure, wherein the hydrogen implantation process, the first etching process, and the second etching process are repeated.

2. The method as described in claim 1, wherein the metal layer comprises ruthenium.

3. The method as described in claim 1, wherein the barrier metal layer comprises: A first layer comprising titanium; and a second layer comprising titanium nitride.

4. The method as described in claim 1, wherein the barrier metal layer comprises: A first layer comprising tantalum; and a second layer comprising tantalum nitride.

5. The method as described in claim 1, wherein the hydrogen implantation process includes: The plasma effluent generated by a hydrogen-containing gas is guided toward the oxidized portion of the barrier metal layer.

6. The method as described in claim 1, wherein the first etching process includes: A chlorine-containing gas, an inert gas, and a carbon-containing gas are supplied in an inductively coupled plasma (ICP) etching chamber.

7. The method as claimed in claim 1, wherein the hydrogen implantation process, the first etching process, and the second etching process are performed in an inductively coupled plasma (ICP) etching chamber, and the first etching process removes an outermost atomic layer of the hydrogen implantation portion of the barrier metal layer.

8. A method for forming a metal-containing feature, the method comprising: A first etching process is performed using an oxygen-containing etching gas to form a feature in a metal layer formed on a barrier metal layer, wherein after the first etching process, the feature has an unetched portion of the metal layer adjacent to a top surface of the barrier metal layer within the feature; a hydrogen implantation process is performed to chemically reduce an oxide portion of the barrier metal layer formed within the feature in the metal layer; a second etching process is performed to remove the hydrogen implanted portion of the barrier metal layer using a chlorine-containing etching gas; and a third etching process is performed to remove at least a portion of the unetched portion of the metal layer using the oxygen-containing etching gas, wherein the hydrogen implantation process, the second etching process, and the third etching process are repeated until the unetched portion of the metal layer is substantially removed.

9. The method as described in claim 8, wherein the metal layer comprises ruthenium.

10. The method as described in claim 8, wherein the barrier metal layer comprises: A first layer comprising titanium; and a second layer comprising titanium nitride.

11. The method as described in claim 8, wherein the barrier metal layer comprises: A first layer comprising tantalum; and a second layer comprising tantalum nitride.

12. The method as described in claim 8, wherein the hydrogen implantation process includes: The plasma effluent generated by a hydrogen-containing gas is guided toward the oxidized portion of the barrier metal layer.

13. The method as claimed in claim 8, wherein the first etching process, the hydrogen implantation process, and the second etching process are performed in an inductively coupled plasma (ICP) etching chamber, and the hydrogen implantation process and the second etching process remove an outermost atomic layer of the hydrogen implantation portion of the barrier metal layer.

14. The method as claimed in claim 8, wherein the oxide portion of the barrier metal layer formed within the feature in the metal layer has a thickness between 0.5 nm and 5 nm.

15. The method as described in claim 13, wherein the first etching process is different from the third etching process.

Images