Etching method for alkaline earth metal oxide

Abstract

A method of processing a substrate, the method comprising: loading a substrate into a plasma processing chamber, the substrate having a surface comprising an oxide, the oxide comprising an alkaline earth metal; flowing a process gas comprising CCl4 into the plasma processing chamber; forming a fluoride-free plasma from the process gas by applying source power to a source electrode of the plasma processing chamber in the plasma processing chamber; and exposing the substrate to a fluoride-free plasma to etch the oxide of the surface.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Non-Provisional Application No. 17 / 746,406, filed on May 17, 2022, which is incorporated herein by reference. Technical Field

[0003] The present invention generally relates to a method of processing a substrate and, in a particular embodiment, to etching alkaline earth metal oxides. Background Art

[0004] Typically, semiconductor devices for electronic devices such as mobile phones, digital cameras, and computers are manufactured by sequentially depositing and patterning dielectric material layers, conductive material layers, and semiconductor material layers on a semiconductor substrate, using photolithography and etching to form structures used as circuit components (e.g., transistors, resistors, and capacitors) and interconnection elements (e.g., wires, contacts, and vias). Driven by the demand for low-cost electronic devices, the semiconductor industry has repeatedly reduced the minimum feature size of semiconductor devices to a few nanometers through innovations in photolithography (e.g., immersion lithography and multiple patterning) to increase the packaging density of components, thereby reducing the cost of integrated circuits (ICs). Further increases in density and further reductions in cost are achieved using three-dimensional (3D) structures (e.g., fin field effect transistors (FinFETs)) and, in some cases, stacking electronic components such as memory storage elements (e.g., ferroelectric capacitors, magnetic tunnel junctions (MTJs), etc.) and precision passive components (e.g., thin film resistors (TFRs) and metal-insulator-metal (MIM) capacitors) in layers between successive interconnection levels.

[0005] Plasma processing techniques such as reactive ion etching (RIE), plasma enhanced chemical vapor deposition (PECVD), plasma enhanced atomic layer etching and deposition (PEALE and PEALD), sputter etching, physical vapor deposition (PVD) and cyclic etch deposition (e.g., Bosch etching process) have become indispensable in the manufacture of ICs. The variety of materials used in IC manufacturing, such as semiconductors, insulators (including SiO2, Si3N4, high-k gate dielectrics and low-k dielectrics), magnetic films and ferroelectric films, and metals for interconnects and electrodes, makes the development of plasma processes a challenge. Miniaturization to a few nanometers further exacerbates the challenges. Plasma processes are expected to provide precise dimensions (e.g., line width, etch depth, and film thickness) in the nanometer range and precisely controlled features such as conformality, anisotropy, selectivity, surface and line edge roughness, and edge profiles, which are typically uniform on wide (e.g., 300 mm) wafers at atomic scale. Furthermore, the introduction of unconventional materials (eg, high-k dielectrics such as barium titanate) may cause new problems in developing plasma etch and deposition processes that are compatible with conventional Si IC manufacturing. Summary of the invention

[0006] According to an embodiment of the present invention, a method for processing a substrate includes: loading the substrate into a plasma processing chamber, the substrate having a surface containing an oxide containing an alkaline earth metal; flowing a process gas containing CCl4 into the plasma processing chamber; in the plasma processing chamber, forming a fluorine-free plasma from the process gas by applying source power to a source electrode of the plasma processing chamber; and exposing the substrate to the fluorine-free plasma to etch the oxide on the surface.

[0007] According to an embodiment of the present invention, a method for processing a substrate includes: loading the substrate into a plasma processing chamber, the substrate having a surface containing barium; flowing a process gas into the plasma processing chamber, the process gas containing a mixture of Cl2 and BCl3; in the plasma processing chamber, forming a fluorine-free plasma from the process gas by applying source power to a source electrode of the plasma processing chamber; and exposing the substrate to the fluorine-free plasma to etch the barium on the surface.

[0008] According to an embodiment of the present invention, a method for processing a substrate includes: loading the substrate into a plasma processing chamber, the substrate having a surface containing a mixed oxide, the mixed oxide containing an alkaline earth metal and another metal; and performing a plurality of cyclic processes, each of the plurality of cyclic processes including: exposing the mixed oxide to a first fluorine-free substance provided by a first process gas so that the mixed oxide reacts with the first substance and forms a reaction product containing the alkaline earth metal; and exposing the reaction product to a second fluorine-free substance provided by a second process gas to remove the reaction product from the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the present invention and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1A-Figure 1D 1 shows cross-sectional views of an exemplary substrate at various stages during a manufacturing process including etching a high-k dielectric (HK) layer according to various embodiments, wherein Figure 1A A feed substrate including a HK layer is shown, Figure 1B shows the substrate after etching the HK layer, Figure 1C shows the substrate after spacer material deposition and spacer top hat etching, and Figure 1D shows the substrate after source / drain formation;

[0011] Figure 2A-2B A cross-sectional view of another exemplary substrate including a high-k dielectric (HK) layer during high-k / metal gate (HKMG) fabrication according to an alternative embodiment is shown, wherein Figure 2A shows the substrate after etching the HK layer, spacer material deposition, spacer top hat etching, source / drain formation, dielectric deposition, and dummy gate removal, and Figure 2B shows the substrate after metal gate formation;

[0012] Figure 3 The reaction path of barium titanate under etching conditions according to one embodiment is shown, and the reaction energy of the reaction path is calculated;

[0013] Figure 4 showing an alternative reaction pathway for barium titanate having a calculated reaction energy under etching conditions including boron or carbon according to an alternative embodiment, the reaction energy of the alternative reaction pathway being calculated; and

[0014] Figure 5A-5C An exemplary process flow diagram for etching an alkaline earth metal-containing layer is shown, wherein Figure 5A An embodiment is shown. Figure 5B Alternative embodiments are presented, and Figure 5CYet another embodiment is presented. DETAILED DESCRIPTION

[0015] The present invention relates to a method for processing a substrate, and more particularly to a method for etching alkaline earth metal oxides such as barium perovskite. For the design and manufacture of advanced logic and memory devices, new materials have been proposed to replace conventional materials. For example, barium titanate (BaTiO 3 ) and similar perovskite materials as promising candidates for novel high-k gate dielectric materials. However, there is currently no satisfactory etching method for these materials that is compatible with semiconductor manufacturing processes. In particular, due to the low volatility of possible etching products (e.g., fluorides and chlorides), it is challenging to etch barium titanate using a halogen-based plasma process. The embodiments of the present application disclose a method for fluorine-free etching of alkaline earth metal oxides using chlorine (e.g., boron chloride or carbon tetrachloride), which can advantageously provide a thermodynamically more favorable reaction path and volatile etching products. Through density functional theory (DFT) calculations, the inventors of the present application found that some chloride compounds such as boron chloride and / or carbon tetrachloride can promote the metal-oxygen bond breakage in the oxide and form volatile etching products containing boron-oxygen bonds or carbon-oxygen bonds. Although the following description in this disclosure is mainly barium titanate, the method herein can also be applied to other barium oxides, and more generally to alkaline earth metal oxides, including mixed oxides of alkaline earth metals and other metals. By providing new etch chemistries specifically tailored for these metal oxides, embodiment methods may alleviate their etching challenges, enabling their application as high-k dielectrics in advanced logic and memory devices.

[0016] In the following, according to various embodiments, reference is first made to Figure 1A-Figure 1D and Figure 2A-2B to describe exemplary steps in semiconductor fabrication including etching of high-k dielectrics such as barium titanate. Figure 3 and Figure 4 Possible reaction pathways for etching barium titanate with calculated reaction energies are presented in Figure 2 to compare two exemplary conditions: the Cl-only condition ( Figure 3 ) and the condition of adding B / C ( Figure 4 ).exist Figure 5A-5C An exemplary process flow diagram is shown in . All drawings in this disclosure are for illustration purposes only and are not drawn to scale, including the aspect ratios of features.

[0017] Figure 1A-Figure 1DA cross-sectional view of an exemplary substrate 100 at various stages during a manufacturing process including etching a high-k dielectric (HK) layer 110 according to various embodiments is shown. In the example shown, a portion of a manufacturing process for a metal oxide semiconductor field effect transistor (MOSFET) using a high-k material for a gate dielectric is described. However, the methods herein can be applied to any manufacturing process for etching alkaline earth metal oxides, including but not limited to applications in transistors, quantum computing, and photonics.

[0018] Figure 1A A feeder substrate 100 including a high-k dielectric (HK) layer 110 is shown.

[0019] In various embodiments, the substrate 100 may be part of a semiconductor device, or include a semiconductor device, and may undergo multiple processing steps, such as following conventional processes. Thus, the substrate 100 may include semiconductor layers useful in various microelectronics. For example, a semiconductor structure may include the substrate 100 in which various device regions are formed.

[0020] In one or more embodiments, the substrate 100 may be a silicon wafer or a silicon on insulator (SOI) wafer. In certain embodiments, the substrate 100 may include a silicon germanium wafer, a silicon carbide wafer, a gallium arsenide wafer, a gallium nitride wafer, and other compound semiconductors. In other embodiments, the substrate 100 includes a heterogeneous layer, such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, and a layer of silicon on silicon or SOI substrate. In various embodiments, the substrate 100 is patterned or embedded in other components of a semiconductor device.

[0021] On the substrate 100, a high-k dielectric (HK) layer 110 may be formed. In various embodiments, the HK layer 110 includes barium perovskite, including but not limited to barium titanate (BaTiO 3 ), barium strontium titanate (Ba x Ti y Sr z O m ), barium stannate (BaSnO 3 ), barium strontium stannate (Ba x Ti y Sr z O m) and any mixture thereof. Although their composition can be presented in chemical formulas, barium perovskite or any other oxide may not be strictly stoichiometric. In alternative embodiments, the HK layer 110 may include another oxide containing an alkaline earth metal. The HK layer 110 is a layer to be etched using the embodiment method described in the present disclosure to manufacture, for example, a gate dielectric for a MOSFET. The HK layer 110 may be deposited on the substrate 100 using appropriate deposition techniques such as vapor deposition (including atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD)) and other plasma processes such as plasma enhanced CVD (PECVD), sputtering and other processes. In some embodiments, an optional insulating layer, such as a silicon oxide layer, may be formed between the substrate 100 and the HK layer 110.

[0022] On the HK layer 110, a polysilicon layer 120 may be formed and patterned. The polysilicon used in the polysilicon layer 120 may include doped polysilicon to have desired material properties including electrical properties. The polysilicon layer 120 may be deposited on the HK layer 110 using appropriate deposition techniques such as vapor deposition (including chemical vapor deposition (CVD), physical vapor deposition (PVD)), and other plasma processes such as plasma enhanced CVD (PECVD), sputtering, and other processes. In one or more embodiments, the polysilicon layer 120 may have a thickness of about 50 nm to about 500 nm.

[0023] In various embodiments, the polysilicon layer 120 is patterned to form a gate structure or a dummy gate structure for a semiconductor device. Therefore, the polysilicon layer 120 can be patterned into a fin, a column, or any suitable shape. The patterning of the polysilicon layer 120 can be performed using a plasma dry etching process such as a reactive ion etching (RIE) process. During such an etching process of the polysilicon layer 120, the hard mask layer 130 can be used as an etching mask.

[0024] Still reference Figure 1AIn one embodiment, the hard mask layer 130 may include silicon oxide. In various embodiments, the hard mask layer 130 may include silicon nitride, silicon carbonitride (SiCN), or silicon oxycarbide (SiOC). In an alternative embodiment, the hard mask layer 130 may include titanium nitride. In one or more embodiments, the hard mask layer 130 may include other suitable organic materials, such as a spin-on carbon hard mask (SOH) material. In addition, the hard mask layer 130 may be a stacked hard mask, which includes, for example, two or more layers using two different materials. In some such embodiments, the first hard mask of the hard mask layer 130 may include a metal-based layer, such as titanium nitride, titanium, tantalum nitride, tantalum, tungsten-based compounds, ruthenium-based compounds, or aluminum-based compounds, and the second hard mask material of the hard mask layer 130 may include a dielectric layer, such as silicon oxide, silicon nitride, SiCN, SiOC, silicon oxynitride, or silicon carbide. The hard mask layer 130 may be deposited using a suitable deposition technique such as vapor deposition (including chemical vapor deposition (CVD), physical vapor deposition (PVD)), and other plasma processes such as plasma enhanced CVD (PECVD), sputtering, and other processes (including wet processes). In various embodiments, the hard mask layer 130 may have a thickness of about 5 nm to about 50 nm. In one or more embodiments, additional layers such as a silicon-containing anti-reflective coating film (SiARC) or other ARC films may be formed on the hard mask layer 130. In other embodiments, a photoresist that may have been used to pattern the hard mask layer 130 by photolithography may remain on the hard mask layer 130.

[0025] Figure 1B The substrate 100 is shown after etching the high-k dielectric (HK) layer 110 .

[0026] In various embodiments, the etching of the HK layer 110 may be performed in a plasma processing chamber using a chlorine-based plasma dry etching process. In some embodiments, the etching gas may contain boron chloride (BCl 3 ) or carbon tetrachloride (CCl 4 In one or more embodiments, the etching gas may include chlorine (Cl 2 In addition to chlorine, the etching gas may further contain a rare gas (eg, Ar, He, Xe, etc.). For example, in one embodiment, the etching gas may be Ar / Cl 2 / BCl 3 or Ar / Cl 2 / CCl 4 In other embodiments, the etching gas may contain other halogens besides fluorine. For example, the etching gas may contain BBr 3 , BBr 2 Cl、BBrCl 2, CBr 4 , CBr 3 Cl, CBr 2 Cl 2 or CBrCl 3 In an alternative embodiment, the etching gas may contain N 2 、SO 2 In addition, in one or more embodiments, the etching gas may contain any molecule that can react with oxygen from the surface, including but not limited to CO, CO 2 , NO and NO 2 . As shown below Figure 3-Figure 4 As further described, the use of boron chloride, boron tetrachloride, or both in the etching gas may have unique advantages over the use of chlorine gas alone because such chlorides can promote the breaking of metal-oxygen bonds of the dielectric material of the HK layer 110 and, in addition to other chloride etching products (e.g., BaCl 2 and TiCl 4 ) also forms volatile etch products (e.g., BOCl, CO, and COCl 2 In various embodiments, the etching gas and the plasma formed from the etching gas may be substantially free of fluorine to avoid the formation of metal fluorides such as barium fluoride, which may have lower volatility than metal chlorides. Although chlorine-based plasma processes are commonly used to etch various materials, etching of metal oxides of alkaline earth metals is difficult, primarily due to the low volatility of the etched products. The inventors of the present application have discovered that when used alone or in combination with other chlorine-containing gases (e.g., Cl 2 ) are used in combination with certain gases (e.g. BCl 3 and CCl 4 ) can improve the etching of such metal oxides because the boron or carbon in the etching gas can form bonds with the metal atoms of the metal oxide on the surface.

[0027] In some embodiments, the etching gas and the plasma formed from the etching gas may also be substantially free of hydrogen to avoid the formation of water or other hydrogen-containing products. In some embodiments, water molecules may be undesirable because they may easily react with some etching products such as TiCl 4 Therefore, in one or more embodiments, in order to eliminate fluorine and hydrogen from the plasma used for etching, it is possible to avoid adding fluorocarbons (e.g., CF 4 ) and hydrofluorocarbons (e.g., CHF 3 ) as a component of the etching gas. Similarly, in some embodiments, other hydrogen-containing halogen compounds, such as methyl chloride (CH 3 Cl), dichloromethane (CH 2 Cl2 ) and chloroform (CHCl 3 In the present disclosure, fluorine-free plasma and hydrogen-free plasma refer to a plasma that does not contain fluorine or hydrogen, respectively, or a plasma in which the concentration of fluorine or hydrogen is significantly lower than any amount that may cause chemical or physical effects in the process.

[0028] In some embodiments, the noble gas component of the etching gas may utilize ions (e.g., argon ions Ar + ) provides additional ion bombardment to cause some damage and enhance etching by removing etching products from the surface of HK layer 110. The ions in the plasma are accelerated toward the substrate by the vertical electric field in the sheath region. The strength of the vertical electric field can be adjusted by the bias voltage supplied to the substrate holder. For example, a relatively heavy (40 amu) Ar + The ions can impact the etch products (e.g., BaCl 2 ) and remove them from the surface, even though the energy is too low to cause significant sputtering of the HK layer 110.

[0029] In an alternative embodiment, the fluorine-free, chlorine-based plasma dry etching process for the HK layer 110 can be performed as a cyclic process of atomic layer etching (ALE) or in a quasi-ALE manner. The first step (reaction step) of the cyclic process is to treat the surface of the HK layer 110 (which may or may not be a monolayer) with one or more chlorine compounds (e.g., Cl 2 and BCl 3 ) reaction, as described in the previous embodiment. After the first step, although some etching products may be directly formed as gaseous products (e.g., BClO), some etching products (e.g., BaCl 2 、TiCl 4 ) may remain on the surface due to relatively low volatility. The second step (removal step) of the cyclic process is to treat the substrate with an optimized plasma to remove these residual etch products. In various embodiments, the desired plasma conditions for this second step (removal step) may include high bias power to achieve high ion bombardment energy (E i ), while the first step (reaction step) may include low bias power and low E i The second step may use a process gas that is the same as the etching gas or a process gas that is different from the etching gas. In one or more embodiments, the etching gas used in the first step may include / may be Ar / Cl 2 / BCl 3 or Ar / Cl 2 / CCl 4In one or more embodiments, the cyclic embodiment of the fluorine-free, chlorine-based plasma dry etching process may further include additional steps with or without plasma, such as a purge step using an inert gas. For example, in each cycle, a purge step may be inserted between the reaction step and the removal step.

[0030] The plasma for etching the HK layer 110 can be generated from an etching gas in a plasma processing chamber by applying source power to a source electrode of the plasma processing chamber. The embodiment method can be performed in a suitable plasma processing chamber equipped with one or more plasma sources such as inductively coupled plasma (ICP), capacitively coupled plasma (CCP), microwave plasma (MW), surface wave plasma (SWP) or others. The process conditions for plasma etching can be selected so that anisotropic selective etching can be achieved. As a result, Figure 1B As shown, the pattern of the polysilicon layer 120 can be transferred to the HK layer 110. For example, the chamber pressure can affect the etching rate by changing the adsorption equilibrium of the etching products. A relatively low chamber pressure can be conducive to the desorption of etching products from the surface. The chamber pressure can be 1000 mTorr or less in one embodiment, but 20 mTorr or less in another embodiment. In one embodiment, a source power of 20W or more and a bias voltage of 10V or more can be used. In one embodiment, the bias voltage can be 5000V or less. In various embodiments, the source power and the bias voltage can be high enough to enable sufficient ion bombardment on the surface, while the bias voltage also enables anisotropy of etching. In some embodiments, if sufficient ion bombardment energy (E i ), physical sputtering can assist in etching of the HK layer 110. In various embodiments, the substrate temperature can be maintained at any reasonable temperature.

[0031] Although not described herein, embodiments of the present invention may also be applied to remote plasma systems as well as batch systems. For example, a substrate holder may be capable of supporting multiple wafers that rotate about a central axis as they pass through different plasma zones. Various cyclic embodiments of etching methods may be advantageously implemented using a system with multiple plasma zones.

[0032] In some embodiments, the fluorine-free, chlorine-based plasma dry etching process for etching the HK layer 110 can be performed using two or more plasma conditions, one of which enables the HK layer 110 to react with the substance provided by the plasma, and another condition enables the etching products to be effectively removed from the surface. In one or more embodiments, source / bias power pulses, chamber pressure and temperature throttling and / or gas flow rate regulation can be used to achieve such conditions. As part of a cyclic process, the substrate 100 can be repeatedly treated under each of these conditions to improve the etching rate and selectivity. For example, in order to remove the etching products, higher temperatures and lower chamber pressures may be advantageous. Relatively high bias voltages can also enhance the effects of ion bombardment on the surface. In addition, as described in the previous embodiments, a variety of plasma conditions can be combined with changing the etching gas composition to perform an ALE or quasi-ALE process.

[0033] Figure 1C The substrate 100 is shown after spacer material deposition and spacer top hat etching.

[0034] After etching the high-k dielectric (HK) layer 110, subsequent process steps may be performed to continue manufacturing the MOSFET. A gate spacer material 140, such as silicon nitride, may be deposited on the substrate 100 using appropriate deposition techniques such as vapor deposition (including atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD)) and other plasma processes such as plasma enhanced CVD (PECVD), sputtering, and other processes. Subsequently, the top surface of the gate spacer material 140 may be removed by spacer top cap etching using a plasma dry etching process (e.g., a reactive ion etching (RIE) process).

[0035] Figure 1D The substrate 100 is shown after source / drain formation.

[0036] exist Figure 1D In the embodiment of the present invention, a source / drain region 150 can be formed near the gate structure by performing ion implantation in the substrate 100. Ion implantation can implant dopant atoms into the substrate 100 to change the electronic structure and characteristics of the implanted region. In the ion implantation process, ions are provided by an ion source and then electrostatically accelerated to impact the substrate 100. Various dopants can be used for source / drain formation, including p-type dopants (e.g., boron) and n-type dopants (e.g., phosphorus). Doping can also be achieved by other techniques such as gas cluster ion beam (GCIB) and atomic layer deposition (ALD).

[0037] After the source / drain is formed, other manufacturing process steps such as metallization and other middle-end (MOL) / back-end (BEOL) processes may be performed. In the example shown above, polysilicon is used as the gate material, but in other embodiments, other MOSFET device structures may be fabricated, such as MOSFET device structures using non-silicon gate materials.

[0038] Figure 2A-2B A cross-sectional view of another exemplary substrate 100 including a high-k dielectric (HK) layer 110 during high-k / metal gate (HKMG) fabrication according to an alternative embodiment is shown, wherein polysilicon is used as a dummy gate and replaced with a metal gate. In the illustrated example, the substrate 100 has Figure 1A The same initial structure as the previous embodiment shown is then followed by the same Figure 1B-Figure 1D The same steps are described, and therefore the same structures as the previous embodiments and the details of these steps will not be repeated.

[0039] Figure 2A The substrate is shown after etching of the HK layer 110, spacer material deposition, spacer top cap etch, source / drain formation, dielectric deposition, and dummy gate removal.

[0040] exist Figure 2A In the above-described steps (i.e., Figure 1B The HK layer 110 is etched. Figure 1C spacer material deposition and spacer top hat etching in Figure 1D source / drain formation in) to produce a Figure 1A After these steps, a low-k dielectric 160 may be deposited on the substrate 100, and the polysilicon layer 120 ( Figure 1A-Figure 1D ) (dummy gate removed), forming a recess 165 for filling a replacement metal gate (RMG) material 170 (eg Figure 2B ). The low-k dielectric 160 may include a silicon-based dielectric material having a low dielectric constant (i.e., a low-k value), such as organic silicate glass (SiCOH), dense SiCOH, porous SiCOH, and other porous dielectric materials. The low-k dielectric may be deposited using deposition techniques such as vapor deposition (including chemical vapor deposition (CVD), physical vapor deposition (PVD), and atomic layer deposition (ALD)), as well as other plasma processes such as plasma enhanced CVD (PECVD), sputtering, and other processes.

[0041] Still reference Figure 2A, a plasma dry etching process, such as a reactive ion etching (RIE) process for selectively removing polysilicon, may be used to remove the polysilicon layer 120. In various embodiments, the RIE process for the polysilicon layer 120 may use an etching gas containing, for example, a halogen gas. In some embodiments, the etching gas may contain hydrogen bromide (HBr) and chlorine (Cl 2 The etching gas may also contain additional gases, such as oxygen (O 2 ) and / or rare gases (eg, He, Ne, Ar, Kr, etc.). The etching gas and process conditions may be selected so that the first plasma that etches polysilicon has high selectivity and a high polysilicon etching rate.

[0042] Figure 2B The substrate 100 is shown after metal gate formation.

[0043] After removing the dummy gate, the recess 165 can be filled with a replacement metal gate (RMG) material 170. In various embodiments, the RMG material 170 may include a combination of several layers, including a work function metal and a metallic filler. The work function metal of the RMG material may include titanium nitride, tantalum nitride, or a metal alloy such as AlC, TiAl, and TiAlC. The work function metal for n-type FETs is typically different from the work function metal for p-type FETs in order to select different threshold voltages for different types of FETs. Metal deposition is continued until the recess 165 is filled with an excess of metal filling material. In some embodiments, the metal filling material may include a low resistivity metal, such as tungsten (W), copper (Cu), cobalt (Co), or aluminum (Al). In some embodiments, the RMG material 170 may be deposited on the substrate 100 using a highly conformal process such as an atomic layer deposition (ALD) process.

[0044] After the recess 165 is filled with the RMG material 170, any excess metal may be removed by a planarization process (e.g., a chemical mechanical planarization process). The resulting top surface includes the tops of the RMG material 170, the low-k dielectric 160, and the gate spacer material 140. Subsequently, a middle of line (MOL) process / back end of line (BEOL) process may be performed.

[0045] Reference below Figure 3 and Figure 4 , the effect of adding a boron-containing reagent or a carbon-containing reagent to the etching gas is described by comparing the calculated reaction energies.

[0046] Figure 3 The reaction pathway of barium titanate under etching conditions according to one embodiment is shown.

[0047] exist Figure 3In , it is assumed that the etching of barium titanate proceeds by reaction with chlorine species from plasma. Based on density functional theory (DFT) calculations, the reaction energies of the three reaction steps are obtained as follows.

[0048] (1)BaTiO 3 (s)+6Cl(g)=BaCl 2 (s)+TiCl 4 (s)+3O(g); ΔE=0.857eV

[0049] (2a)BaCl 2 (s)=BaCl 2 (g); ΔE = 2.883 eV

[0050] (2b)TiCl 4 (s)=TiCl 4 (g); ΔE = 0.0054 eV

[0051] Reaction (1), that is, barium titanate forms solid barium chloride (BaCl 2 ), solid titanium chloride (TiCl 2 ) and oxygen atoms, which is shown to be only slightly endothermic (almost thermodynamically neutral) with a reaction energy of 0.857 eV. In addition, DFT calculations show that the formation of gas-phase BaCl 2 (2a) requires a large amount of energy (2.883 eV), which means that BaCl 2 is only moderately volatile. On the other hand, TiCl 2 is highly volatile, with a very small energy difference (0.054 eV) between the solid and gas phases. This result demonstrates the removal of etching products from the surface, especially BaCl 2 In other words, the barium-oxygen bond of BaTiO3 is very stable and requires a lot of energy to break. Therefore, providing only chlorine (e.g., Cl alone) 2 ) may not be able to effectively etch BaTiO 3 However, it should be noted that a chlorine-based plasma etching process may still be advantageous compared to a fluorine-based plasma etching process because barium fluoride and titanium fluoride are even less volatile (i.e., more difficult to remove from the surface). Therefore, in various embodiments, the etching gas contains a halogen other than fluorine (e.g., chlorine and bromine).

[0052] Figure 4 Alternative reaction pathways for barium titanate under etching conditions including boron or carbon are demonstrated according to alternative embodiments.

[0053] exist Figure 4Three additional DFT calculations, including reactions with boron or carbon, show that etching of BaTiO can be mitigated by realizing new oxygen-containing etching products. 3 difficulty. Figure 4 The three additional reactions shown are of oxygen atoms with (A) boron chloride (BCl3), (B) carbon, and (C) dichloromethylene (CCl 2 ), which produce oxygen-containing etching products BClO, CO and COCl respectively. 2 All calculated reactions exhibit significant negative reaction energies in the range between approximately -35.1 eV and -23.5 eV, as shown below in (A)-(C), as well as (1) the initial reaction with chlorine.

[0054] (1)BaTiO3(s)+6Cl(g)=BaCl2(g)+TiCl4(g)+3O(g); ΔE=3.795eV

[0055] (A) 3O(g)+3BCl(g)=3BClO(g); ΔE=-26.964eV

[0056] (B)3O(g)+3C(g)=3CO(g); ΔE=-35.092eV

[0057] (C)3O(g)+3CCl 2 (g) = 3COCl 2 (g); ΔE = -23.538 eV

[0058] These values ​​are significantly larger than (1) by making BaTiO 3 Reacts with chlorine to form BaCl 2 、TiCl 4 The moderate positive reaction energy with oxygen atoms (i.e. 3.795 eV) is therefore 3 The etching of BaTiO3 combined with one or more additional reactions can make the overall reaction thermodynamically favorable (i.e., exothermic). In other words, the addition of boron or carbon to the etching gas can significantly improve the etching of BaTiO3 by breaking the barium-oxygen bonds and forming stable etching products with boron-oxygen bonds or carbon-oxygen bonds. In these etching products, the bond order of these bonds can be any reasonable value. In other words, in various embodiments, single bonds, double bonds and / or triple bonds can be formed with oxygen. In order to make these etching products possible, the etching gas can therefore also contain boron or carbon in addition to chlorine. In various embodiments, boron chloride (BCl 3 ) or carbon tetrafluoride (CCl 4 ) can be used alone as an etching gas, or as an etching gas containing another chlorine source such as chlorine (Cl 2) is an additive to the etching gas. In some embodiments, other molecules may also be included in the etching gas to promote the breaking of the barium-oxygen bond by providing new oxygen-containing etching products. Such molecules may include but are not limited to N 2 、SO 2 、COS、NO、NO 2 ,CO,CO 2 , BBr 3 , BBr 2 Cl、BBrCl 2 , CBr 4 , CBr 3 Cl, CBr 2 Cl 2 or CBrCl 3 .

[0059] Figure 5A-5C A process flow diagram is shown of a method of etching barium titanate or similar oxides according to various embodiments.

[0060] exist Figure 5A In the process flow 50, a substrate is loaded into a plasma processing chamber, wherein the substrate has a surface comprising an alkaline earth metal oxide (block 500, Figure 1A Next, the carbon tetrachloride (CCl 4 ) flows into the plasma processing chamber (block 510), and a fluorine-free plasma can be formed from the process gas by applying source power to a source electrode of the plasma processing chamber (block 520, Figure 1B ). The substrate may then be exposed to a plasma to etch the surface oxide (block 530, Figure 1B ).

[0061] exist Figure 5B In the process flow 52, ​​a substrate is loaded into a plasma processing chamber, wherein the substrate has a surface containing barium (e.g., barium titanate) (block 502, Figure 1A Next, chlorine gas (Cl 2 ) and boron chloride (BCl 3 ) flows into the plasma processing chamber (block 512), and a fluorine-free plasma can be formed from the process gas by applying source power to a source electrode of the plasma processing chamber (block 520, Figure 1B ). The substrate may then be exposed to a plasma to etch the surface barium (block 532, Figure 1B ).

[0062] exist Figure 5CIn the process flow 54, a substrate is loaded into a plasma processing chamber, wherein the substrate has a surface comprising a mixed oxide comprising an alkaline earth metal and another metal (block 504, Figure 1A Next, a cyclic process may be performed. The cyclic process may include first exposing the mixed oxide to a first fluorine-free substance provided by a first process gas to react the mixed oxide with the first substance and form a reaction product including an alkaline earth metal (block 534, Figure 1B ), and then exposing the reaction product to a second fluorine-free species provided by a second process gas to remove the reaction product from the surface (block 536, Figure 1B ).

[0063] Exemplary embodiments of the present invention are summarized here. Other embodiments may also be understood from the entirety of the specification and the claims submitted herein.

[0064] Example 1. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface containing an oxide, the oxide containing an alkaline earth metal; flowing a process gas containing CCl4 into the plasma processing chamber; in the plasma processing chamber, forming a fluorine-free plasma from the process gas by applying source power to a source electrode of the plasma processing chamber; and exposing the substrate to the fluorine-free plasma to etch the oxide on the surface.

[0065] Example 2. The method of Example 1, wherein the plasma does not contain hydrogen.

[0066] Example 3. The method of one of examples 1 or 2, further comprising flowing a noble gas into the plasma processing chamber.

[0067] Example 4. The method of one of Examples 1 to 3, wherein the process gas further comprises Cl2, BCl3, BCl2Br, BClBr2 or BBr3.

[0068] Example 5. The method of one of Examples 1 to 4, wherein the process gas further comprises N2, NO, NO2, CO, CO2, SO2 or COS.

[0069] Example 6. The method of one of examples 1 to 5, wherein etching the oxide includes forming volatile products comprising carbon-oxygen bonds.

[0070] Example 7. The method of one of examples 1 to 6, wherein the oxide is barium titanate.

[0071] Example 8. The method of one of examples 1 to 7, wherein the oxide is barium strontium titanate.

[0072] Example 9. The method of one of examples 1 to 8, wherein the oxide is barium stannate.

[0073] Example 10. The method of one of examples 1 to 9, wherein the alkaline earth metal is calcium (Ca) or magnesium (Mg), and the oxide is titanate perovskite.

[0074] Example 11. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface containing barium; flowing a process gas into the plasma processing chamber, the process gas containing a mixture of Cl2 and BCl3; in the plasma processing chamber, forming a fluorine-free plasma from the process gas by applying source power to a source electrode of the plasma processing chamber; and exposing the substrate to the fluorine-free plasma to etch the barium on the surface.

[0075] Example 12. The method of Example 11, wherein the fluorine-free plasma does not contain hydrogen.

[0076] Example 13. The method of one of Examples 11 or 12, further comprising flowing a noble gas into the plasma processing chamber.

[0077] Example 14. The method of one of examples 11 to 13, wherein the surface further comprises oxygen, and wherein etching barium comprises forming volatile products comprising boron-oxygen bonds.

[0078] Example 15. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface comprising a mixed oxide, the mixed oxide comprising an alkaline earth metal and another metal; and performing a plurality of cyclic processes, each of the plurality of cyclic processes comprising: exposing the mixed oxide to a first fluorine-free substance provided by a first process gas so that the mixed oxide reacts with the first substance and forms a reaction product comprising the alkaline earth metal; and exposing the reaction product to a second fluorine-free substance provided by a second process gas to remove the reaction product from the surface.

[0079] Example 16. The method of Example 15, further comprising forming a first plasma to generate the first fluorine-free species.

[0080] Example 17. The method of one of Examples 15 or 16, wherein the first process gas comprises a halogen other than fluorine.

[0081] Example 18. A method as described in one of Examples 15 to 17, wherein the first process gas contains BCl3, BCl2Br, BClBr2, BBr3, CCl4, CCl3Br, CCl2Br2, CClBr3 or CBr4, and wherein the first process gas further contains N2, NO, NO2, CO, CO2, SO2 or COS.

[0082] Example 19. The method of one of Examples 15 to 18, further comprising forming a second plasma to generate the second fluorine-free species, wherein the second process gas comprises a noble gas.

[0083] Example 20. The method of one of Examples 15 to 19, wherein each of the plurality of cyclic processes further comprises purging the plasma processing chamber to remove the first species before exposing the reaction product to the second species.

[0084] Although the present invention has been described with reference to illustrative embodiments, this description is not intended to be interpreted in a limiting sense. Various modifications and combinations of the illustrative embodiments and other embodiments of the present invention will be apparent to those skilled in the art by reference to the description. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface comprising an oxide, the oxide comprising an alkaline earth metal; Allowing a process gas containing CCl4 to flow into the plasma processing chamber; forming a fluorine-free plasma from the process gas in the plasma processing chamber by applying source power to a source electrode of the plasma processing chamber; and The substrate is exposed to the fluorine-free plasma to etch oxide on the surface.

2. The method of claim 1, wherein: The plasma does not contain hydrogen.

3. The method of claim 1, further comprising flowing a noble gas into the plasma processing chamber.

4. The method of claim 1, wherein: The process gas further comprises Cl2, BCl3, BCl2Br, BClBr2 or BBr3.

5. The method of claim 1, wherein: The process gas further comprises N2, NO, NO2, CO, CO2, SO2 or COS.

6. The method of claim 1, wherein: Etching the oxide includes forming volatile products including carbon-oxygen bonds.

7. The method of claim 1, wherein: The oxide is barium titanate.

8. The method of claim 1, wherein: The oxide is barium strontium titanate.

9. The method of claim 1, wherein: The oxide is barium stannate.

10. The method of claim 1, wherein: The alkaline earth metal is calcium (Ca) or magnesium (Mg), and the oxide is titanate perovskite.

11. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface comprising barium; flowing a process gas into the plasma processing chamber, the process gas comprising a mixture of Cl2 and BCl3; forming a fluorine-free plasma from the process gas in the plasma processing chamber by applying source power to a source electrode of the plasma processing chamber; and The substrate is exposed to the fluorine-free plasma to etch barium from the surface.

12. The method of claim 11, wherein: The fluorine-free plasma does not contain hydrogen.

13. The method of claim 11, further comprising flowing a noble gas into the plasma processing chamber.

14. The method of claim 11, wherein: The surface further comprises oxygen, and wherein etching the barium comprises forming volatile products comprising boron-oxygen bonds.

15. A method for processing a substrate, the method comprising: loading the substrate into a plasma processing chamber, the substrate having a surface comprising a mixed oxide comprising an alkaline earth metal and another metal; as well as A plurality of cyclic processes are performed, each of the plurality of cyclic processes comprising: exposing the mixed oxide to a first fluorine-free species provided by a first process gas to react the mixed oxide with the first species and form a reaction product comprising the alkaline earth metal; as well as The reaction product is exposed to a second fluorine-free species provided by a second process gas to remove the reaction product from the surface.

16. The method of claim 15, further comprising forming a first plasma to generate the first fluorine-free species.

17. The method of claim 15, wherein: The first process gas contains a halogen other than fluorine.

18. The method of claim 15, wherein: The first process gas contains BCl3, BCl2Br, BClBr2, BBr3, CCl4, CCl3Br, CCl2Br2, CClBr3 or CBr4, and wherein the first process gas further contains N2, NO, NO2, CO, CO2, SO2 or COS.

19. The method of claim 15, further comprising forming a second plasma to generate the second fluorine-free species, wherein the second process gas comprises a noble gas.

20. The method of claim 15, wherein: Each of the plurality of cyclic processes further comprises purging the plasma processing chamber to remove the first species prior to exposing the reaction product to the second species.

Images