Metal etch

Abstract

A method for etching a metal-containing material is provided. The metal-containing material is exposed to a halogen-containing fluid or plasma to convert at least some of the metal-containing material into a metal halide material. The metal halide material is then exposed to a ligand-containing fluid or plasma, wherein at least some of the metal halide material forms a metal halide ligand complex. At least some of the metal halide ligand complexes are then vaporized.

Description

Technical Field

[0001] This invention relates to a method for forming a semiconductor device on a semiconductor wafer. More specifically, this invention relates to the selective etching of a semiconductor device. [Cross-reference to related applications]

[0002] This application claims priority to U.S. Application No. 63 / 138,263, filed January 15, 2021, which is incorporated herein by reference for all purposes. Prior Technology

[0003] The prior art description provided herein is intended to generally introduce the background of the present invention. Nothing described in this prior art section, nor any potential forms of written description, is intended or implied to be prior art to the present invention.

[0004] In the fabrication of semiconductor devices, pattern transfer processes can be used to form magnetic random access memory (MRAM). These pattern transfer processes employ etching. MRAM stacks contain non-volatile and ferromagnetic materials such as cobalt (Co), iron (Fe), manganese (Mn), nickel (Ni), platinum (Pt), palladium (Pd), and ruthenium (Ru). These materials are extremely difficult to pattern without complex methods such as ion beam etching (IBE), reactive ion etching (RIE), and wet chemistry. Despite years of development, current patterning techniques are plagued by several drawbacks, such as sidewall redeposition leading to tapered profiles and short circuits to the setter layer via magnetic tunneling junctions (MTJs), and corrosion damaging the MTJ layer. In some prior art techniques, chlorine-containing chemicals are used to etch the metal, but etching byproducts include non-volatile compounds. These non-volatile compounds may subsequently redeposit on the sidewalls of the features. However, as devices shrink and the fabrication of various types of structures becomes more complex, some etching byproducts may redeposit on other exposed areas of the substrate. Redeposition byproducts can lead to defects and ultimately, equipment failure.

[0005] For large critical size (CD) structures with wide pitch, single-step or multi-step IBE formulations may be sufficient. However, for smaller CD or closely spaced features below 100 nm, patterning using IBE is difficult. A fundamental limitation lies in the ion incidence blocked by the mask. This limitation prevents effective etching and trimming of the MRAM stack. Summary of the Invention

[0006] To achieve the foregoing and in accordance with the purposes of this disclosure, a method for etching a metal-containing material is provided. The metal-containing material is exposed to a halogen-containing fluid or plasma to convert at least some of the metal-containing material into a metal halide material. The metal halide material is then exposed to a ligand-containing fluid or plasma, wherein at least some of the metal halide material forms a metal halide ligand complex. At least some of the metal halide ligand complexes are then vaporized.

[0007] In another embodiment, a method for etching a metallic material is provided. The metallic material is exposed to an etching solution or plasma containing phosphorus and chlorine, causing the metal to form at least one complex of a phosphorus chloride ligand complex. At least some of the phosphorus chloride ligand complex is then vaporized.

[0008] The above and other features of the present invention will be described in detail in the following embodiments and in conjunction with the following figures. Simple Explanation of the Diagram

[0009] The invention is depicted by way of example (and not in a limiting sense) in the accompanying drawings, wherein similar reference numerals represent similar elements, and wherein:

[0010] Figure 1 is a high-level flowchart of an embodiment.

[0011] Figures 2A-D are schematic cross-sectional views of a stack processed according to one embodiment.

[0012] Figure 3 is a more detailed flowchart of the steps for converting the metal in the metal-containing layer into a metal halide.

[0013] Figure 4 is a more detailed flowchart of the steps for converting a metal halide into a metal halide ligand complex.

[0014] Figure 5 is a flowchart of atomic layer etching.

[0015] Figures 6A-D are schematic cross-sectional views of the stack processed in another embodiment.

[0016] Figure 7 is a high-order flowchart in which metal etching is used to etch metal residues in the plasma processing chamber.

[0017] Figure 8 is a schematic diagram of a plasma processing chamber that can be used in one embodiment.

[0018] Figure 9 is a schematic diagram of a computer system that can be used to implement one embodiment. Implementation

[0019] This disclosure will now be described in detail with reference to several preferred embodiments as illustrated in the accompanying drawings. To provide a thorough understanding of the invention, numerous specific details are set forth in the following description. However, it will be apparent to those skilled in the art that this disclosure can be practiced without some or all of these specific details. In other examples, conventional processing steps and / or structures have not been described in detail to avoid obscuring this disclosure.

[0020] During semiconductor wafer processing, features can be etched through metal layers. In the formation of magnetic random access memory (MRAM), multiple thin metal layers or films can be sequentially etched to form a magnetic tunneling interface stack.

[0021] Magnetic tunneling junctions (MTJs) consist of a thin dielectric barrier layer located between two magnetic materials. Electrons pass through the barrier via a quantum tunneling process. This can serve as the basis for magnetically based memories that utilize spin-transfer torque.

[0022] Spin-transfer torque is an effect that can modify the orientation of magnetic layers in a magnetostatic junction (MTJ) using a spin-polarized current. Charge carriers (such as electrons) possess a property called spin. Spin is a small amount of angular momentum inherent to the carrier. Current is generally non-polarized (50% spin-up and 50% spin-down electrons). By passing current through a thick magnetic layer (often called a "fixed layer"), a spin-polarized current with more electrons of either spin can be generated. If this spin-polarized current is directed into a second, thinner magnetic layer ("free layer"), angular momentum can be transferred to this layer, thus changing its orientation. This effect can be used to excite oscillations or even flip the orientation of a magnet.

[0023] Spin torque can be used to flip active components in magnetic random access memory. Spin torque magnetic random access memory (STT-RAM or STT-MRAM) has the advantages of lower power consumption and better scalability than conventional MRAM. MRAM uses a magnetic field to flip active components.

[0024] STT-RAM device patterning has been demonstrated using reactive ion etching followed by ion beam etching (IBE); or via a complete inert gas beveled IBE strategy. Reactive ion etching (RIE) processes generally result in tapered profiles and thick sidewall redeposition of etching byproducts. Furthermore, the chemical damage to the magnesium oxide (MgO) layer limits the use of RIE as the sole method for MRAM patterning.

[0025] IBE (In-line Beam Emission) technology was developed for MRAM pattern transfer while simultaneously minimizing MTJ (Metal-Tunneling Jet) damage caused by reactive species. A common approach involves first performing IBE with normal incidence to shape the MTJ and minimize footing, followed by grazing incidence IBE to provide sidewall cleaning and remove redeposition from the initial step. Since IBE relies on the sputtering of inert ions, sidewall redeposition occurs during pattern transfer. Typically, IBE and oxidation cycles are performed to remove short-circuit paths and stop at the MgO tunnel barrier, thus preserving a pristine and continuous free layer for spin transport.

[0026] The plasma dry etching method for MRAM stacks is described in U.S. Patent No. 9,806,252, "Dry Plasma Etch Method to Pattern MRAM Stack," published October 31, 2017, by Tan et al., which is incorporated herein by reference for all purposes. The method for providing ion beam etching is described in U.S. Patent No. 9,257,295, "Ion Beam Etching System," published February 9, 2016, by Singh et al., which is incorporated herein by reference for all purposes.

[0027] For large critical size (CD) structures with wide pitch, single-step or multi-step IBE formulations may be sufficient. However, for smaller CDs or closely spaced features below 100 nm, patterning using IBE is difficult. A fundamental limitation lies in the ion incidence blocked by the mask. This limitation prevents effective etching and trimming of the MRAM stack.

[0028] To aid understanding, Figure 1 is a high-order flowchart illustrating a procedure for etching a metal-containing layer in one embodiment. Various embodiments may have more or fewer steps. Furthermore, in various embodiments, these steps may be performed in different orders or simultaneously. The metal in the metal-containing layer is formed into a metal halide (step 104). The metal can be any possible metal in any possible stack. In one embodiment, the metal-containing layer is part of an MRAM stack. Figure 2A is a schematic cross-sectional view of an exemplary stack 200 that can be processed using the procedure shown in Figure 1. The stack 200 is located on a substrate having a silicon or silicon oxide (Si / SiO2) layer 204. A first tantalum (Ta) layer 208 is on top of the Si / SiO2 layer 204. A platinum (Pt) layer 212 is on top of the first Ta layer 208. A cobalt-platinum alloy (CoPt) layer 216 is on top of the Pt layer 212. A magnesium oxide (MgO) layer 220 is on top of the CoPt layer 216. A cobalt-iron-boron (CoFeB) layer 224 is formed on top of the MgO layer 220. A second Ta layer 228 is formed on top of the CoFeB layer 224. A ruthenium (Ru) layer 232 is formed on top of the second Ta layer 228. A patterned mask is formed on the stack 200. In this embodiment, the patterned mask includes a titanium nitride layer 236 located below the SiO2 layer 240 and below the Ru layer 244. In this embodiment, optional opening etching of the Ru layer 244 is provided prior to etching of the metal layer. The opening etching of the Ru layer 244 is provided using an oxygen-containing plasma. Furthermore, the Ru layer 232 of the MRAM stack 200 has been etched using a conventional oxygen etching process.

[0029] Figure 3 is a flowchart showing exemplary details of forming a metal halide in a metal-containing layer (step 104). In various embodiments, forming a metal halide in a metal-containing layer (step 104) can be performed in a manner different from the procedure shown in Figure 3, for example, by adding or omitting steps in Figure 3 or by performing steps in a different order or simultaneously. A halogen-containing gas is provided (step 304). In this embodiment, the halogen-containing gas is chlorine (Cl2). In one embodiment, the flow rate of the Cl2 gas may be in the range of 10 sccm to 500 sccm. In other embodiments, the halogen-containing gas may include at least one of nitrogen trifluoride (NF3), hydrogen bromide (HBr), boron trichloride (BCl3), bromine (Br2), sulfur hexafluoride (SF6), and phosphorus trichloride (PCl3). The halogen-containing gas is converted into a halogen-containing plasma (step 308). As some illustrative conditions, plasma power between approximately 100 W and 900 W can be used to generate plasma. The temperature during this operation can be between approximately 60°C and approximately 200°C. The chamber pressure during this operation can be between approximately 1 mTorr and approximately 500 mTorr.

[0030] The stack 200 is exposed to a halogen-containing plasma. In this embodiment, the chlorinated plasma is capable of etching the second Ta layer 228. When the second Ta layer 228 is etched away, a portion of the CoFeB layer 224 is exposed to the chlorinated plasma. The chlorinated plasma cannot etch the CoFeB layer 224, but it can form chlorides with cobalt and iron according to the following equation: , where M is a metal and x is an integer.

[0031] Table 1 provides examples of metal halides that can be formed in some embodiments. In this embodiment, the metal halides that can be formed are ferric chloride (II) (FeCl₂), ferric chloride (FeCl₃), and cobalt chloride (II) (CoCl₂). The melting points of the metal halides in Table 1 are in the range of 304°C to 1170°C. In this embodiment, these melting points are higher than the process temperature. It is not desirable to subject the stack 200 to many of these melting point temperatures. Figure 2B is a schematic cross-sectional view of an exemplary stack 200 after a portion of the second Ta layer 228 has been etched away by the chlorine-containing plasma and a portion of the CoFeB layer 224 has been formed into cobalt chloride and ferric chloride (thus providing cobalt chloride and ferric chloride regions 252, which are shaded). [Table 1] [Metal chlorides and bromides] [Melting Point] [(]°C [)] FeCl2 667 FeCl3 304 CoCl 2 470 CoBr 2 678 FeBr 2 691 NiBr 2 963 CrCl 2 814 InF 3 1170

[0032] After the metal halide is formed, the metal halide material is exposed to a plasma containing ligands, wherein at least some of the metal halides are formed as metal halide ligand complexes (step 108). Figure 4 is a flowchart showing exemplary details of the formation of metal halide as metal halide ligand complexes (step 108). The formation of metal halide as metal halide ligand complexes (step 108) can be performed in different ways, such as by adding or omitting the steps in Figure 4 or by performing the steps in a different order or simultaneously. A fluid containing ligands is provided (step 404). In this embodiment, the fluid containing ligands is water (H₂O) vapor. In one embodiment, the flow rate of water vapor may be in the range of 10 sccm to 500 sccm. In other embodiments, the fluid containing ligands may include at least one of carbon monoxide (CO), carbon dioxide (CO₂), hydroxide (OH), and ammonia (NH₃). The fluid containing ligands may be a gas or a liquid. The liquid may be a vapor. The fluid containing the ligand is converted into a plasma containing the ligand (step 408). As some exemplary conditions, the plasma can be generated using a plasma power between about 100 W and 900 W. The temperature during this operation can be between about 60°C and about 200°C. The chamber pressure during this operation can be between about 1 mTorr and about 500 mTorr.

[0033] The stack 200 is exposed to a ligand-containing plasma. The ligand-containing plasma causes the metal halide to form a metal halide-ligand complex according to the following equation: , where y is an integer. In other embodiments, metal halide ligand complexes are formed without converting the vapor containing the ligands into plasma.

[0034] In this embodiment, the metal halide ligand complexes that can be formed are ferric chloride (III) hexahydrate (FeCl3·6H2O) with a melting point of about 37°C and ferric tetracarbonyl hydride (FeH2(CO)4) with a melting point of about -70°C. In this embodiment, the melting point or vaporization temperature of the metal halide ligand complex is lower than the process temperature. Providing a process temperature higher than the melting point of the metal halide ligand complex and a pressure in the range of about 1 mTorr to about 500 mTorr causes the liquid metal halide ligand complex to be vaporized (step 112). In some embodiments, a pressure in the range of 1 mTorr to 50 mTorr is provided. Figure 2C is a schematic cross-sectional view of an exemplary stack 200 after the metal halide is converted into a metal halide ligand complex (which is vaporized), resulting in the etching of a portion of the CoFeB layer 224.

[0035] In one embodiment, the following steps are provided simultaneously in a continuous single-step etching process: forming a metal halide by exposing a metal-containing material to a halogen-containing plasma (step 104); forming a metal halide ligand complex by exposing the metal halide to a ligand-containing plasma (step 108); and vaporizing the metal halide ligand complex (step 112). In another embodiment, the following steps are performed sequentially and / or cyclically: forming a metal halide by exposing a metal-containing material to a halogen-containing plasma (step 104); and forming a metal halide ligand complex by exposing the metal halide to a ligand-containing plasma (step 108), thereby providing an atomic layer etching (ALE) process. Figure 5 is a flowchart of atomic layer etching 504. Various embodiments may have more or fewer steps. Furthermore, these steps may be performed in different orders or simultaneously. In this embodiment, each atomic layer etching cycle includes a metal halide formation step (step 508) and a metal halide ligand complex formation step (step 512). In this embodiment, the substrate is heated to a temperature above 120°C, causing the metal halide ligand complex to vaporize during the metal halide ligand complex formation step (step 512). In other embodiments, the substrate is heated to a temperature above about 100°C. Such atomic layer etching may be slower than a single-step process, but it provides a more controlled and conformal etching process.

[0036] If the etching process is performed as a single step (wherein a continuous single-step etching process is provided simultaneously by exposing the metal-containing material to a halogen-containing plasma to form a metal halide (step 104), by exposing the metal halide to a ligand-containing plasma to form a metal halide ligand complex (step 108), and by vaporizing the metal halide ligand complex (step 112), then the stack 200 is etched after a period of time. If the etching process sequentially provides multiple cycles of atomic layer etching (where each cycle includes a metal halide formation step (step 508) and a metal halide ligand complex formation step (step 512)), then these cycles are repeated until the stack 200 is etched. However, to etch the first Ta layer 208 or the second Ta layer 228, a single step of forming a metal halide without converting the metal halide into a metal halide ligand complex can be provided. This is because some tantalum halides have boiling points lower than the processing temperature. Therefore, tantalum halides can be vaporized without forming tantalum halide ligand complexes.

[0037] In this embodiment, an etching process is used to provide directional patterning etching of the stack 200 beneath the hard mask. The taper of the sidewalls of the stack 200 may be smaller compared to an etching process using ion beam etching. For ion beam etching, the ion beam is provided in a non-perpendicular direction. The non-perpendicular direction of ion beam etching results in tapered sidewalls of the resulting stack. In these embodiments, the stack 200 is an MRAM stack. However, the various processes described herein can also be used to etch other types of devices, particularly those with stacked structures containing magnetic materials. Examples may include, but are not limited to, the formation of cobalt or ruthenium interconnects.

[0038] In another embodiment, isotropic etching is provided. For ease of understanding, FIG. 6A is a schematic cross-sectional view of a stack 600 used in one embodiment. The stack 600 includes a substrate 604 located beneath a metal-containing layer 608, which is located beneath a hard mask 612. In this example, the substrate is silicon or silicon oxide (Si / SiO2). In this embodiment, the metal-containing layer 608 is cobalt (Co), and the hard mask 612 is ruthenium (Ru). In this embodiment, an ALE process is used. In this embodiment, some of the Co is converted to a metal halide (step 104). In this embodiment, the stack 600 is exposed to a plasma formed by Br2 gas. According to the equation: Plasma reacts with cobalt to form metal halides. Figure 6B is a schematic diagram of the stack 600 after the stack 600 is exposed to plasma to form a CoBr 2 metal halide layer 616.

[0039] After stopping the exposure of the stack 600 to the halogen plasma, the stack 600 is exposed to a plasma containing ligands to form a metal halide ligand complex (step 108). In this embodiment, according to the exemplary equation... The metal halide is formed into a metal halide hydride. The metal halide ligand complex is vaporized (step 112). Figure 6C is a schematic diagram of the stack 600 after it has been exposed to plasma to form a metal halide ligand complex layer (which is vaporized). The metal layer 608 is partially etched horizontally or laterally.

[0040] Atomic layer etching (ALE) can be repeated for one or more cycles until the metal-containing layer 608 is etched to a desired amount. Figure 6D is a schematic diagram of the stack 600 after multiple ALE cycles (thus providing a complete lateral etching of the metal-containing layer 608). Controlled lateral etching of the metal-containing layer 608 allows for controlled thinning of the metal-containing layer 608. Using ALE reduces aspect ratio dependence and variability of etch relative to depth. ALE also reduces chemical damage because the cyclic use of halogens and Ar sputtering minimizes halogen exposure. For MRAM stacks, minimizing MgO layer damage is critical to avoiding electrical degradation of the MRAM stack.

[0041] Another embodiment can be used to clean metal residues within the plasma processing chamber. For clarity, Figure 7 is a high-order flowchart illustrating the use of metal etching to etch metal residues within the plasma processing chamber. Various embodiments may have more or fewer steps. Furthermore, these steps may be performed in different orders or simultaneously. In this embodiment, a process wafer with a stack is placed in the plasma processing chamber (step 704). The wafer and stack may be the stack 200 shown in Figure 2A or another metal-containing stack. The stack is processed (step 708). For example, the stack may undergo one or more processes. The stack may be subjected to ion beam etching or other etching processes that result in the deposition of metal residues within the plasma processing chamber. Deposition processes may also form metal residues. The stack is removed from the plasma processing chamber (step 712).

[0042] A cover is placed in the plasma processing chamber and on the substrate support (step 716). The cover may be a wafer. In some embodiments, the cover is not placed on the substrate support. Metal residues are removed from the interior of the plasma processing chamber (step 720). In this embodiment, residue removal is performed simultaneously in a single continuous process by: exposing the metal-containing material containing the metal residues to a halogen-containing plasma to convert at least some of the metal-containing material containing the metal residues into metal halides (step 104); exposing the metal halide material to a ligand-containing plasma to convert at least some of the metal halides into metal halide ligand complexes (step 108); and vaporizing at least some of the metal halide ligand complexes (step 112). This process removes various types of metals. Additional chamber cleaning may be used before or after metal removal of the metal-containing residues. The cover is removed (step 724). Next, it is determined whether to process another stack (step 728). If another stack is to be processed, the procedure returns to the step of placing the stack in the plasma processing chamber (step 704).

[0043] This embodiment can remove many different metal residues exposed to plasma without the need for an ion beam. As a result, this embodiment can remove many different metal residues from all plasma-facing surfaces of the plasma treatment chamber. One embodiment can use a single cleaning step to remove residues of Fe, Ni, Cr, In, Pt, Pd, Ta, Ti, Mg, W, Mo, Hf, Al, and Co. Therefore, different residues can be removed rapidly. In some embodiments, a separate step of providing oxygen-containing plasma can be provided to remove Ru-containing residues. Furthermore, this embodiment can remove metal residues from all surfaces exposed to the cleaning plasma. With ion beam cleaning, only the surfaces bombarded by the ion beam are cleaned.

[0044] In various embodiments, metal etching can be used in other applications besides vertical pattern etching under a mask, horizontal or isotropic etching, and chamber cleaning. For example, when metal deposition fills a pattern and forms a capping layer, recessed etching is required to remove the capping layer, and back etching is used to etch back into the pattern.

[0045] In various embodiments, other metal-containing residues may be etched. An example of such reactions used in the various embodiments provides a first reaction in which a halogen combines with a metal or metal oxide to form a metal halide (step 104). An example indicative equation is: Other halogens (e.g., F, Br, and I) can be used to replace chlorine (Cl). The metal halide is then formed into a metal halide ligand complex (step 108). In some embodiments, the metal halide is formed into a metal halide ligand complex, wherein the metal halide ligand complex is a metal halide hydride byproduct, which is based on the following equation: In some embodiments, the metal halide is formed into a metal halide ligand complex, wherein the metal halide ligand complex is a volatile metal halide carbonyl byproduct, which is determined according to the following equation: In these embodiments, hydrogen is partially replaced by CO. The metal halide ligand complex is then vaporized (step 112). In some embodiments, ammonia is added to the ligand-containing fluid along with carbon dioxide or carbon monoxide to promote the formation of volatile byproducts of the metal halide carbonyl group. Ammonia contributes to the generation of more CO radicals.

[0046] In other embodiments, phosphorus (P)-containing ligands may be used. In one embodiment, fluorine is used to form a metal halide according to the following equation (step 104): The metal halide is formed into a metal halide ligand complex (step 108). In this embodiment, according to the equation: The ligand contains phosphorus. Next, the metal halide ligand complex is vaporized (step 112). In some embodiments, the metal M may be ruthenium.

[0047] Phosphorus pentachloride (PCl₅) forms relatively stable and volatile transition metal complexes. Similar to carbon monoxide (CO), but slightly less so than phosphorus trichloride (PF₃), PCl₅ exhibits strong pi-backbonding properties, stabilizing many low-valence transition metal compounds. PCl₅ is a volatile liquid at room temperature with a boiling point of 166°C. PCl₅ is also a volatile solid, sublimating at approximately 160°C. Both can be transported as pure vapors or entrained in an inert carrier gas stream. PCl₅ can react directly with metal surfaces (with or without plasma activation) to form volatile metal phosphorus chloride ligand complexes in the form of M(PCl₃)ₓCl₂ complexes, where M is a metal and x is an integer between 1 and 6 (inclusive). Therefore, metal layers can be exposed to PCl₅ fluids (liquid or gas) or to plasmas formed from PCl₅ to convert the metal into metal halides. In some embodiments, metal M can be ruthenium. Similarly, by plasma activation, the transition metal can react with PCl3 to form volatile byproducts, i.e., Ni + PCl3 → Ni(PCl3)4.

[0048] In another embodiment, the ALE process has a first step in which the metal is formed into a metal halide (which is a metal fluoride) (step 104). An example of a halogen-containing gas is nitrogen trifluoride (NF3). The equation for the first step of the ALE process is: Step 1: M (metal to be etched) + NF 3 (direct or remote plasma activation) → MF x For the second step of the ALE process in this embodiment, the ligand-containing fluid includes PCl3. Phosphorus has a high affinity for fluorine, and PCl3 reacts with many metal fluorides to generate PF3 gas and the corresponding metal chlorides. Since PF3 (or PF3-xClx, where x=1 or 2) promotes the formation of more stable and volatile metal complexes, this facilitates the atomic layer etching (ALE) sequence, as illustrated below: Step 2: MF x + PCl 3 → MCl x (PF 3) y (volatile etching byproduct).

[0049] In various embodiments, the stack 200 may be a stack for MRAM. In various embodiments, the stack 200 may be a magnetic tunneling junction (MTJ) consisting of a thin dielectric barrier layer between two magnetic materials. In various embodiments, the stack 200 includes at least one metal-containing layer. The metal-containing layer may include at least one of Cr, Mo, Ir, Ti, Ru, Mn, Ni, Pd, Ta, Co, Fe, Mg, and Pt. In one example, the stack includes at least one layer of MgO. Other stacks may have other transition metals (e.g., Group IV, Group V, and Group VI transition metals) in the first, second, and third columns, including metals such as Cu.

[0050] To provide an embodiment of the processing chamber that can be used in the embodiments, FIG8 schematically illustrates an example of a plasma processing chamber system 800 that can be used in a plasma processing process. The plasma processing chamber system 800 includes a plasma reactor 802 having a plasma processing confinement chamber 804 located therein. A plasma power supply 806, adjusted via a plasma matching network 808, supplies power to a transformer-coupled plasma (TCP) coil 810 located near a dielectric induction power window 812, thereby generating plasma 814 in the plasma processing confinement chamber 804 by providing inductively coupled power. A spire 872 extends from the chamber wall 876 of the plasma processing confinement chamber 804 to the dielectric induction power window 812, thereby forming a spire ring. The apex 872 is inclined relative to the chamber wall 876 and the dielectric induction power window 812, such that the interior angle between the apex 872 and the chamber wall 876 and the interior angle between the apex 872 and the dielectric induction power window 812 are each greater than 90° and less than 180°. The apex 872 provides an inclined ring near the top of the plasma processing confinement chamber 804, as shown in the figure.

[0051] A configurable TCP coil (upper power supply) 810 can be used to generate a uniform diffusion profile within the plasma processing confinement chamber 804. For example, the TCP coil 810 can be configured to generate a ring-shaped power distribution within the plasma 814. A dielectric induction power window 812 is provided to separate the TCP coil 810 from the plasma processing confinement chamber 804 while allowing energy to pass from the TCP coil 810 to the plasma processing confinement chamber 804. The TCP coil 810 serves as an electrode for providing radio frequency (RF) power to the plasma processing confinement chamber 804. A wafer bias power supply 816, adjusted via a bias matching network 818, provides power to the electrode 820 to set the bias voltage on the substrate 866. The substrate 866 is supported by the electrode 820, which acts as a substrate support. A controller 824 controls the plasma power supply 806 and the wafer bias power supply 816.

[0052] The plasma power supply 806 and the wafer bias power supply 816 can be configured to operate at specific radio frequencies such as 13.56 MHz, 27 MHz, 2 MHz, 60 MHz, 400 kHz, 2.54 GHz, or combinations thereof. The plasma power supply 806 and the wafer bias power supply 816 can be appropriately configured to supply a power range to achieve desired process performance. For example, in one embodiment, the plasma power supply 806 can supply power in the range of 50 to 5000 watts, while the wafer bias power supply 816 can supply bias in the range of 20 to 2000 V. Furthermore, the TCP coil 810 and / or electrode 820 can consist of two or more sub-coils or sub-electrodes. These sub-coils or sub-electrodes can be powered by a single power supply or by multiple power supplies.

[0053] As shown in Figure 8, the plasma processing chamber system 800 further includes a gas source / gas supply mechanism 830. The gas source 830 is fluidly connected to the plasma processing confinement chamber 804 via a gas inlet (e.g., a gas injector 840). The gas injector 840 can be located in any advantageous position within the plasma processing confinement chamber 804 and can take any form for injecting gas. However, preferably, the gas inlet can be configured to produce an "adjustable" gas injection distribution. An adjustable gas injection distribution allows for independent adjustment of the corresponding flow of gas to multiple zones within the plasma processing confinement chamber 804. More preferably, the gas injector is mounted on a dielectric induction power window 812. The gas injector can be mounted on, within, or as part of the power window. Processing gases and byproducts are removed from the plasma processing confinement chamber 804 via a pressure control valve 842 and a pump 844. Pressure control valve 842 and pump 844 are also used to maintain a specific pressure within the plasma processing confinement chamber 804. Pressure control valve 842 can maintain a pressure of less than 1 torr during processing. An edge ring 860 is positioned around the substrate 866. Gas source / gas supply mechanism 830 is controlled by controller 824. For example, an embodiment can be implemented using a Kiyo® tool manufactured by Lamb Research, Inc., Fremont, California.

[0054] Figure 9 is a high-level block diagram showing a computer system 900. The computer system 900 is suitable for implementing the controller 824 used in the embodiments. The computer system 900 can have many physical forms, ranging from integrated circuits, printed circuit boards, and small handheld devices to large supercomputers. The computer system 900 includes one or more processors 902, and may further include an electronic display device 904 (for displaying images, text, and other data), main memory 906 (e.g., random access memory (RAM)), storage device 908 (e.g., hard disk), removable storage device 910 (e.g., optical disk drive), user interface device 912 (e.g., keyboard, touch panel, keypad, mouse, or other pointing device), and communication interface 914 (e.g., wireless network interface). The communication interface 914 allows software and data to be transferred between the computer system 900 and external devices via a connection. The system may also include communication infrastructure 916 (e.g., communication bus, crossbar, or network), to which the aforementioned devices or modules are connected.

[0055] Information transmitted via communication interface 914 may be in the form of signals such as electronic, electromagnetic, optical, or other signals that can be received by communication interface 914 through a communication connection (which carries signals and can be implemented using wires or cables, optical fibers, telephone lines, mobile phone connections, radio frequency connections, and / or other communication channels). Through such communication interface 914, it is anticipated that one or more processors 902 can receive information from or output information to the network during the steps of the aforementioned method. Furthermore, the method embodiments may be executed independently on a processor or via a network (e.g., the Internet), sharing some processing work with a remote processor.

[0056] The term "non-transitory computer-readable media" is generally used to refer to media such as main memory, secondary memory, removable storage, and storage devices (e.g., hard drives, flash memory, disk drive memory, CD-ROMs, and other forms of persistent memory), and should not be construed as encompassing transient types (e.g., carrier waves or signals). Examples of computer-readable code include machine code (e.g., machine code generated by a compiler) and files containing high-level code that are executed by a computer using a decoder. Computer-readable media can also be computer code that transmits computer data signals.

[0057] In some embodiments, the computer-readable medium may include computer-readable code for transferring the stack to the plasma processing chamber system 800, computer-readable code for forming a metal halide (step 104), computer-readable code for forming a metal halide ligand complex (step 108), and computer-readable code for vaporizing the metal halide ligand complex (step 112).

[0058] Although this disclosure has described several preferred embodiments, variations, arrangements, modifications, and various equivalents thereof are all included within the scope of this disclosure. It should be noted that there are many alternative ways to perform the methods and apparatus of this disclosure. Therefore, the appended claims should be interpreted as including all variations, arrangements, and various equivalents within the spirit and scope of this disclosure.

[0059] 104: Steps 108: Steps 112: Steps 200: Stacked body 204: Silicon or silicon oxide (Si / SiO2) layer 208: First tantalum (Ta) layer 212: Platinum (Pt) layer 216: Cobalt-platinum alloy (CoPt) layer 220: Magnesium oxide (MgO) layer 224: Cobalt-iron-boron (CoFeB) layer 228: Second tantalum (Ta) layer 232: Ruthenium (Ru) layer 236: Titanium nitride layer 240:SiO 2-layer 244: Ru layer 252: Cobalt chloride and ferric chloride region 304: Steps 308: Steps 404: Steps 408: Steps 504: Atomic Layer Etching 508: Steps 512: Steps 600: Stacked body 604:Substrate 608: Contains a metal layer 612: Hard Mask 616: Metal halide layer 704: Steps 708: Steps 712: Steps 716: Steps 720: Steps 724: Steps 728: Steps 800: Plasma Processing Chamber System 802: Plasma Reactor 804: Plasma treatment confined chamber 806: Plasma Power Supply 808: Plasma Matching Network 810: Transformer-coupled plasma (TCP) coil 812: Dielectric Induction Power Window 814: Plasma 816: Wafer Bias Power Supply 818: Bias Matching Network 820: Electrode 824: Controller 830: Gas Source 840: Gas Injector 842: Pressure control valve 844: Pump 860: Edge ring 866:Substrate 872: Spire 876: Chamber wall 900: Computer System 902: Processor 904: Electronic display device 906: Main Memory 908: Storage device 910: Portable storage device 912: User Interface Device 914: Communication Interface 916: Communications Infrastructure

Claims

1. A method for etching a metal-containing material, comprising: exposing the metal-containing material to a halogen-containing fluid or plasma to convert at least some of the metal-containing material into a metal halide material; exposing the metal halide material to a ligand-containing fluid or plasma, wherein at least some of the metal halide material forms a metal halide ligand complex; and vaporizing at least some of the metal halide ligand complex.

2. The method for etching a metal-containing material as claimed in claim 1, wherein the step of exposing the metal halide material to the ligand-containing plasma comprises: providing a fluid containing the ligand; and forming a plasma from the fluid containing the ligand.

3. The method for etching metallic materials as claimed in claim 2, wherein the fluid containing ligands includes a gas or vapor containing ligands, comprising at least one of H2O, CO, CO2, CH3OH, OH, NH3, PF3, and PCl3.

4. The method for etching a metallic material as claimed in claim 1, wherein the step of exposing the metallic material to the halogenated fluid or plasma comprises: providing a halogenated gas; and forming a plasma from the halogenated gas.

5. The method for etching metallic materials as claimed in claim 4, wherein the halogen-containing gas includes at least one of NF3, Cl2, HBr, BCl3, Br2, and SF6.

6. The method for etching a metal-containing material as claimed in claim 1, wherein the steps of exposing the metal-containing material to the halogen-containing fluid or plasma and the steps of exposing the metal halide material to the ligand-containing fluid or plasma are performed simultaneously, wherein the halogen-containing fluid system is different from the ligand-containing fluid.

7. The method for etching a metal-containing material as claimed in claim 1, wherein the steps of exposing the metal-containing material to the halogen-containing fluid or plasma and the steps of exposing the metal halide material to the ligand-containing fluid or plasma are performed sequentially in multiple cycles.

8. The method for etching a metallic material as claimed in claim 1, wherein the metallic material includes at least one of Fe, Ni, Cr, In, Pt, Pd, Co, and other transition metals.

9. The method for etching a metallic material as claimed in claim 1 further comprises heating the metal halide ligand complex to a temperature above 120°C to vaporize the metal halide ligand complex.

10. The method for etching metallic materials as claimed in claim 1 further includes providing a pressure in the range of about 1 millitor (mTorr) to about 500 mTorr.

11. The method for etching a metallic material as claimed in claim 1, wherein the metallic material is a metallic residue on a portion of the processing chamber.

12. The method for etching a metal-containing material as claimed in claim 11, wherein the steps of exposing the metal-containing material to the halogen-containing fluid or plasma and the steps of exposing the metal halide material to the ligand-containing fluid or plasma are performed during a chamber cleaning process.

13. The method for etching a metal-containing material as claimed in claim 1, wherein the steps of exposing the metal-containing material to the halogen-containing fluid or plasma and the steps of exposing the metal halide material to the ligand-containing fluid or plasma provide isotropic etching of the metal-containing material.

14. The method for etching a metal-containing material as claimed in claim 1, wherein the steps of exposing the metal-containing material to the halogen-containing fluid or plasma and the steps of exposing the metal halide material to the ligand-containing fluid or plasma provide patterned etching.

15. A magnetic random access memory stack, etched according to the method for etching a metallic material as claimed in claim 1.

16. A method for etching a metal-containing material, comprising: exposing the metal-containing material to an etching solution or plasma containing phosphorus and chlorine to form at least one complex of a metal-phosphorus chloride ligand complex, wherein the step of exposing the metal-containing material to the etching solution or plasma comprises: providing an etching solution containing PCl5; forming the etching solution into a plasma; and vaporizing at least some of the metal-phosphorus chloride ligand complex.

17. The method for etching a metallic material as claimed in claim 16, wherein at least one of the metal phosphate chloride ligand complexes comprises M(PCl3)xCl2, wherein M is a metal and x is an integer between 1 and 6 and including 1 and 6.

Images