Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K13/00—Etching, surface-brightening or pickling compositions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K13/00—Etching, surface-brightening or pickling compositions
  • C09K13/02—Etching, surface-brightening or pickling compositions containing an alkali metal hydroxide
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/01—Manufacture or treatment
  • H10D30/014—Manufacture or treatment of FETs having zero-dimensional [0D] or one-dimensional [1D] channels, e.g. quantum wire FETs, single-electron transistors [SET] or Coulomb blockade transistors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/01—Manufacture or treatment
  • H10D30/019—Manufacture or treatment of FETs having stacked nanowire, nanosheet or nanoribbon channels
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/01—Manufacture or treatment
  • H10D30/019—Manufacture or treatment of FETs having stacked nanowire, nanosheet or nanoribbon channels
  • H10D30/0191—Manufacture or treatment of FETs having stacked nanowire, nanosheet or nanoribbon channels forming stacked channels, e.g. changing their shapes or sizes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/40—FETs having zero-dimensional [0D], one-dimensional [1D] or two-dimensional [2D] charge carrier gas channels
  • H10D30/43—FETs having zero-dimensional [0D], one-dimensional [1D] or two-dimensional [2D] charge carrier gas channels having one-dimensional [1D] charge carrier gas channels, e.g. quantum wire FETs or transistors having 1D quantum-confined channels
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/60—Wet etching
  • H10P50/64—Wet etching of semiconductor materials
  • H10P50/642—Chemical etching
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/69—Etching of wafers, substrates or parts of devices using masks for semiconductor materials
  • H10P50/691—Etching of wafers, substrates or parts of devices using masks for semiconductor materials for Group V materials or Group III-V materials

Definitions

• the present invention relates to an etching composition, a method for producing an etching composition, an etching method, a method for producing a semiconductor device, and a gate-all-around transistor.
• fins perpendicular to the silicon substrate by forming fins perpendicular to the silicon substrate to create a multi-gate element, not only can the number of transistors per unit area be increased, but off-state leakage current can also be suppressed. This improves the effectiveness of the on-state current, achieving low power consumption and low heat generation.
• a nanosheet or nanowire-like channel is covered with a gate electrode, increasing the contact area between the channel and gate electrode, thereby improving the transistor performance per unit area.
• an etching solution is required to selectively etch silicon or silicon germanium from a structure in which silicon and silicon germanium are alternately stacked.
• Patent Document 1 discloses an etching solution containing a quaternary ammonium salt.
• Patent Document 1 does not consider the oxygen concentration in the etching composition. When the oxygen concentration in the etching composition of Patent Document 1 is high, the selective solubility of silicon in silicon germanium is not sufficient.
• An object of the present invention is to provide an etching composition that suppresses dissolution of silicon germanium, promotes dissolution of silicon, has excellent selective solubility of silicon relative to silicon germanium, and provides an excellent surface condition of a substrate after etching, and a method for producing the etching composition.
• Another object of the present invention is to provide an etching method using the etching composition, a method for manufacturing a semiconductor device, and a method for manufacturing a gate-all-around transistor.
• the inventors have discovered that the etching composition described below and the etching composition obtained by the method for producing the etching composition described below suppress the dissolution of silicon germanium, promote the dissolution of silicon, have excellent selective solubility of silicon relative to silicon germanium, and provide an excellent surface condition for the substrate after etching.
• the gist of the present invention is as follows.
• An etching composition comprising a semiclathrate hydrate-forming compound (A), the compound (A) being a compound having a melting point of 5°C or higher when made into an aqueous solution having a concentration of 1 mol/L, an oxygen concentration of 2 ppm by mass or less, and a mass ratio of oxygen to the compound (A) of 1 x 10-8 to 1 x 10-4 .
• etching composition according to any one of [1] to [5], wherein the concentration of the semiclathrate hydrate-forming compound (A) in the etching composition is 0.01 mol/L to 3 mol/L.
• concentration of the semiclathrate hydrate-forming compound (A) in the etching composition is 0.01 mol/L to 3 mol/L.
• An etching composition comprising a phosphonium salt compound and having an oxygen concentration of 2 ppm by mass or less.
• etching composition according to [9] wherein the concentration of the basic compound (B) in the etching composition is 0.01 mol/L to 3 mol/L.
• concentration of the basic compound (B) in the etching composition is 0.01 mol/L to 3 mol/L.
• the etching composition according to any one of [1] to [12] which selectively dissolves silicon relative to silicon germanium.
• a method for producing an etching composition comprising a step of bubbling a gas having an oxygen concentration of 8 vol. % or less into an etching composition containing a semiclathrate hydrate-forming compound (A).
• the etching composition of the present invention inhibits dissolution of silicon germanium, promotes dissolution of silicon, has excellent selective solubility of silicon relative to silicon germanium, and provides an excellent surface condition of a substrate after etching.
• the etching composition obtained by the method for producing an etching composition of the present invention suppresses dissolution of silicon germanium, promotes dissolution of silicon, has excellent selective solubility of silicon relative to silicon germanium, and provides an excellent surface condition of a substrate after etching.
• the etching method of the present invention, the manufacturing method of the semiconductor device of the present invention, and the manufacturing method of the gate-all-around transistor of the present invention which use such an etching composition of the present invention, suppress the dissolution of silicon germanium and promote the dissolution of silicon in the etching process, and due to the excellent selective solubility of silicon relative to silicon germanium, perform highly accurate etching and can manufacture desired products with excellent surface conditions with good yields.
• the etching composition according to the first embodiment of the present invention contains a semiclathrate hydrate-forming compound (A), which has a melting point of 5° C. or higher when made into an aqueous solution having a concentration of 1 mol/L, an oxygen concentration of 2 ppm by mass or less, and a mass ratio of oxygen to the compound (A) of 1 ⁇ 10 ⁇ 8 to 1 ⁇ 10 ⁇ 4 .
• the etching composition according to the second embodiment of the present invention contains a quaternary ammonium halide and has an oxygen concentration of 2 ppm by mass or less.
• An etching composition according to a third embodiment of the present invention contains a phosphonium salt compound and has an oxygen concentration of 2 ppm by mass or less.
• the etching composition according to the first embodiment of the present invention may be referred to as "etching composition (1) of the present invention”
• the etching composition according to the second embodiment of the present invention may be referred to as “etching composition (2) of the present invention”
• the etching composition according to the third embodiment of the present invention may be referred to as “etching composition (3) of the present invention”.
• the etching compositions (1) to (3) of the present invention may be collectively referred to as the "etching composition of the present invention.”
• Semiclathrate hydrates are known as special crystals formed by hydrogen bonding and incorporating molecules called guest molecules inside a cage-like structure formed by water molecules (Amid, M., et al., J Incl Phenom Macrocycl Chem 100, 109-129 (2021)).
• semiclathrate hydrates are defined as water molecules that form a cage-like crystal structure with molecules other than water molecules called guest molecules as part of the structure.
• semiclathrate hydrate-forming compounds are defined as molecules other than water that can form semiclathrate hydrates called guest molecules.
• the phase change temperature can be controlled by selecting guest molecules, which allows the melting point of the semiclathrate hydrate crystals to be changed.
• the semiclathrate hydrate melts, it is no longer in a crystalline state, but the hydration state in the solution is closely related to the hydration structure in the crystal. In other words, it is thought to form a special hydration state that is involved in the formation of special crystals called semiclathrate hydrates.
• the reaction of water molecules that form this special hydrated structure suppresses the dissolution of silicon germanium and promotes the dissolution of silicon. As a result, the selective solubility of silicon in silicon germanium is excellent, and the surface condition of the substrate after etching can be excellent.
• the etching rate of silicon germanium increases in the presence of oxygen, and the selective solubility of silicon in silicon germanium decreases.
• the hydration structure after melting of the semiclathrate hydrate significantly limits the diffusion of oxygen, and by keeping the oxygen concentration at 2 mass ppm or less, the selective solubility of silicon in silicon germanium is dramatically improved. This makes it possible to improve the surface condition of the substrate after etching.
• the etching composition (1) of the present invention contains a semiclathrate hydrate-forming compound (A) (hereinafter, sometimes referred to as “component (A)").
• the semiclathrate hydrate-forming compound is a molecule other than water that can form a semiclathrate hydrate.
• the compound is a guest molecule that stabilizes the clathrate hydrate by participating in a hydrogen bond network. Since the component (A) has excellent control over the reactivity of water molecules due to hydration in a temperature range where the etching rate is high, a compound having a melting point of 5°C or higher when made into an aqueous solution with a concentration of 1 mol/L is used.
• a compound having a melting point of 10°C to 40°C when made into an aqueous solution with a concentration of 1 mol/L is preferably used because it has excellent control over the reactivity of water molecules.
• the melting point can be measured by a differential scanning calorimeter (DSC).
• the melting point of 5° C. or higher can be confirmed by, for example, observing at least one endothermic peak with a peak top at 5° C. or higher when the compound is heated at a rate of 10° C./min or lower by DSC in an aqueous solution having a concentration of 1 mol/L.
• the etching composition (1) of the present invention contains component (A), which inhibits the dissolution of silicon germanium and promotes the dissolution of silicon, exhibits excellent selective solubility of silicon relative to silicon germanium, and provides an excellent surface condition of the substrate after etching.
• Examples of the component (A) include onium compounds such as ammonium salts and phosphonium salts.
• An onium compound is a substance generated by protonating a hydride, and a representative example is ammonium hydroxide.
• These components (A) may be used alone or in combination of two or more.
• derivatives in which a hydrogen atom is substituted with a single-bonded atomic group are preferred, derivatives in which a hydrogen atom is substituted with a single-bonded alkyl group are more preferred, ammonium salt compounds and phosphonium salt compounds are further preferred, and alkylammonium salt compounds and alkylphosphonium salt compounds are particularly preferred.
• Component (A) is preferably a compound having 10 or more carbon atoms, more preferably a compound having 14 to 32 carbon atoms, and even more preferably a compound having 16 to 24 carbon atoms, because this provides excellent stability to the semi-clathrate hydrate.
• the substituents of the onium compound of component (A) may be the same or different. In order to provide excellent stability to the semiclathrate hydrate, it is preferable that at least some of the substituents of the onium compound of component (A) are the same, and it is more preferable that all four substituents are the same.
• Examples of the component (A) that satisfies the above-mentioned preferable conditions include quaternary ammonium halides such as tetrabutylammonium hydroxide (melting point when made into an aqueous solution of 1 mol/L: 26° C.) and tetrabutylammonium bromide (melting point when made into an aqueous solution of 1 mol/L: 15° C.), and phosphonium salt compounds such as tetrabutylphosphonium hydroxide (melting point when made into an aqueous solution of 1 mol/L: 17° C.).
• quaternary ammonium halides such as tetrabutylammonium hydroxide (melting point when made into an aqueous solution of 1 mol/L: 26° C.) and tetrabutylammonium bromide (melting point when made into an aqueous solution of 1 mol/L: 15° C.)
• tetrabutylammonium hydroxide tetrabutylphosphonium hydroxide, and tetrabutylammonium bromide are preferred, tetrabutylammonium hydroxide and tetrabutylammonium bromide are more preferred, and tetrabutylammonium hydroxide is even more preferred, because they provide excellent stability to the semiclathrate hydrate.
• the etching composition (2) of the present invention contains a quaternary ammonium halide among the components (A) of the etching composition (1) of the present invention.
• a quaternary ammonium halide tetrabutylammonium hydroxide and tetrabutylammonium bromide are preferable, and tetrabutylammonium hydroxide is more preferable, because they have excellent stability of a semiclathrate hydrate.
• These quaternary ammonium halides may be used alone or in combination of two or more kinds.
• the etching composition (3) of the present invention contains a phosphonium salt compound among the components (A) of the etching composition (1) of the present invention.
• a phosphonium salt compound tetrabutylphosphonium hydroxide is preferred because it has excellent stability as a semiclathrate hydrate.
• These phosphonium salt compounds may be used alone or in combination of two or more.
• the concentration of component (A) in the etching composition (1) of the present invention is preferably 0.01 mol/L to 3 mol/L, more preferably 0.02 mol/L to 2 mol/L, and even more preferably 0.03 mol/L to 1.5 mol/L.
• concentration of component (A) is 0.01 mol/L or more, the selective solubility of silicon relative to silicon germanium is excellent.
• concentration of component (A) is 3 mol/L or less, the etching rate of silicon is excellent.
• the concentration of the quaternary ammonium halide in the etching composition (2) of the present invention is preferably 0.01 mol/L to 3 mol/L, more preferably 0.02 mol/L to 2 mol/L, and even more preferably 0.03 mol/L to 0.2 mol/L.
• concentration of the quaternary ammonium halide is 0.01 mol/L or more, the selective solubility of silicon relative to silicon germanium is excellent.
• the concentration of the quaternary ammonium halide is 3 mol/L or less, the etching rate of silicon is excellent.
• the concentration of the phosphonium salt compound in the etching composition (3) of the present invention is preferably 0.01 mol/L to 3 mol/L, more preferably 0.02 mol/L to 2 mol/L, and even more preferably 0.03 mol/L to 1.5 mol/L.
• concentration of the phosphonium salt compound is 0.01 mol/L or more, the selective solubility of silicon relative to silicon germanium is excellent.
• concentration of the phosphonium salt compound is 3 mol/L or less, the etching rate of silicon is excellent.
• the etching composition of the present invention has an excellent etching rate for silicon, it is preferable that the etching composition further contains a basic compound (B) (hereinafter, sometimes referred to as “component (B)”) in addition to the component (A) (including a quaternary ammonium halide or a phosphonium salt compound; the same applies below).
• component (B) a basic compound
• the etching composition contains the component (B).
• the term "basic compound” refers to a compound which, when dissolved in water, gives an aqueous solution having a higher pH than that before dissolution.
• Component (B) does not include any compound that falls under component (A).
• component (B) examples include tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, butyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, benzyltrimethylammonium hydroxide, sodium hydroxide, potassium hydroxide, and choline. These components (B) may be used alone or in combination of two or more.
• quaternary ammonium hydroxides in which the alkyl group has 3 or less carbon atoms such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, are preferred because of their excellent silicon etching rate, with tetramethylammonium hydroxide and tetraethylammonium hydroxide being more preferred, and tetramethylammonium hydroxide being even more preferred.
• the concentration of component (B) in the etching composition of the present invention is preferably 0.01 mol/L to 3 mol/L, more preferably 0.05 mol/L to 2.5 mol/L, and even more preferably 0.1 mol/L to 2 mol/L.
• concentration of component (B) is 0.01 mol/L or more, the etching rate of silicon is excellent.
• concentration of component (B) is 3 mol/L or less, the selective solubility of silicon relative to silicon germanium is excellent.
• the etching composition of the present invention has an excellent silicon etching rate, it is preferable that the etching composition further contains water in addition to the component (A) and the component (B).
• the water content in the etching composition of the present invention is preferably 5% by mass to 99% by mass, more preferably 10% by mass to 95% by mass, and even more preferably 50% by mass to 90% by mass.
• the water content is 5% by mass or more, the dissolution of silicon is promoted, and the selective solubility of silicon in silicon germanium is excellent.
• the water content is 99% by mass or less, the dissolution of silicon germanium is suppressed, and the selective solubility of silicon in silicon germanium is excellent.
• the etching composition of the present invention may further contain a water-miscible solvent in addition to the component (A), the component (B) and water.
• a water-miscible solvent may be any solvent that has excellent solubility in water, and is preferably a solvent with a solubility parameter (SP value) of 7.0 or more, more preferably 9.0 or more.
• SP value solubility parameter
• water-miscible solvents examples include polar protic solvents such as isopropanol, ethylene glycol, propylene glycol, methanol, ethanol, propanol, butanol, glycerol, and 2-(2-aminoethoxyethanol); and polar aprotic solvents such as acetone, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and acetonitrile. These water-miscible solvents may be used alone or in combination of two or more kinds.
• polar protic solvents such as isopropanol, ethylene glycol, propylene glycol, methanol, ethanol, propanol, butanol, glycerol, and 2-(2-aminoethoxyethanol)
• polar aprotic solvents such as acetone, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and aceton
• the content of the water-miscible solvent in the etching composition of the present invention is preferably 20 mass% or less, more preferably 10 mass% or less, and even more preferably 0 mass% in 100 mass% of the etching composition, because the water-miscible solvent promotes the dissolution of silicon and has excellent selective solubility of silicon relative to silicon germanium.
• the etching composition of the present invention may contain other components in addition to those described above, provided that the effects of the present invention are not impaired.
• examples of other components include a chelating agent and a surfactant.
• the molar ratio of component (B) to component (A) in the etching composition is preferably 0.01 to 1000, more preferably 0.1 to 100, and even more preferably 0.5 to 20.
• the molar ratio of component (B) to component (A) in the etching composition of the present invention is 0.01 or more, the etching rate is excellent.
• the molar ratio of component (B) to component (A) in the etching composition of the present invention is 1000 or less, the selective solubility of silicon in silicon germanium is excellent.
• the pH of the etching composition of the present invention is preferably 8 to 14, more preferably 9 to 14, and even more preferably 10 to 14, because this provides an excellent etching rate for silicon.
• the oxygen concentration is 2 ppm by mass or less, preferably 1 ppm by mass or less, and more preferably 0.5 ppm by mass or less.
• the lower limit of the oxygen concentration in the etching composition of the present invention is not particularly limited, but from the viewpoint of use in the atmosphere, it is usually 0.01 ppm by mass or more.
• the mass ratio of oxygen to component (A) in the etching composition is set to 1 ⁇ 10 ⁇ 8 to 1 ⁇ 10 ⁇ 4 . If this mass ratio is less than 1 ⁇ 10 ⁇ 8 , it is difficult to maintain the dissolved oxygen concentration in this range in the atmosphere, and maintaining it will incur additional costs, while if it exceeds 1 ⁇ 10 ⁇ 4 , it is difficult to obtain selective solubility of silicon in silicon germanium.
• the mass ratio of oxygen to component (A) in the etching composition is preferably from 1 ⁇ 10 ⁇ 8 to 5 ⁇ 10 ⁇ 5 , more preferably from 2 ⁇ 10 ⁇ 8 to 5 ⁇ 10 ⁇ 6 , and particularly preferably from 5 ⁇ 10 ⁇ 8 to 1 ⁇ 10 ⁇ 6 .
• the etching rate ER Si of silicon of the etching composition of the present invention in a structure in which silicon germanium having a thickness of 10 nm and silicon having a thickness of 10 nm are laminated is preferably 7 nm/min or more, and more preferably 10 nm/min or more, since the etching composition has excellent selective solubility of silicon in silicon germanium.
• the etching rate ER SiGe of silicon germanium of the etching composition of the present invention in a structure in which silicon germanium having a thickness of 10 nm and silicon having a thickness of 10 nm are laminated is preferably 6.5 nm/min or less, and more preferably 5 nm/min or less, since the etching composition has excellent selective solubility of silicon in silicon germanium.
• the etching composition of the present invention has a dissolution selectivity ratio (ER Si /ER SiGe ) of silicon germanium to silicon of preferably 1.50 or more, and more preferably 1.60 or more, since the etching composition has excellent selective solubility of silicon relative to silicon germanium.
• the etch rate ER Si , the etch rate ER SiGe and the dissolution selectivity are measured and calculated by the method described in the examples below.
• the etching composition of the present invention suppresses dissolution of silicon germanium, promotes dissolution of silicon, has excellent selective solubility of silicon to silicon germanium, and can make the surface condition of the substrate after etching excellent. Therefore, the etching composition of the present invention is suitable for etching a structure containing silicon and silicon germanium, such as a semiconductor device, and is particularly suitable for a structure in which silicon and silicon germanium are alternately stacked, which is necessary for forming a GAA type FET.
• the silicon to be etched is preferably single-crystal silicon, since single-crystal silicon germanium has excellent characteristics for gate-all-around transistors, and single-crystal silicon germanium is less likely to have defects when grown epitaxially on single-crystal silicon germanium.
• the silicon content in the silicon germanium to be etched is suitable for etching with the etching composition of the present invention, and is therefore preferably 10% by mass to 95% by mass, and more preferably 20% by mass to 85% by mass, out of 100% by mass of silicon germanium.
• the germanium content in the silicon germanium to be etched is preferably 5% by mass to 90% by mass, and more preferably 15% by mass to 80% by mass, out of 100% by mass of silicon germanium, in order to be suitable for etching with the etching composition of the present invention.
• the silicon germanium alloy film may be produced by deposition using known methods, but it is preferable to produce it by deposition using a crystal growth method, as this provides excellent mobility of electrons and holes after transistor formation.
• silicon oxide, silicon nitride, silicon carbonitride, etc. may be exposed.
• the method for producing the etching composition of the present invention is not particularly limited, and the composition can be produced by mixing component (A), and, if necessary, component (B), a solvent and other components.
• the order of mixing is not particularly limited, and all of the components may be mixed at once, or some of the components may be mixed in advance and then the remaining components may be mixed.
• the method for producing an etching composition of the present invention preferably includes a step of bubbling a gas having an oxygen concentration of 8% by volume or less (the remainder being preferably nitrogen gas) into a mixed liquid obtained by mixing component (A), and optionally component (B), a solvent, and other components, in order to obtain an etching composition having an oxygen concentration of 2 ppm by mass or less, more preferably includes a step of bubbling a gas having an oxygen concentration of 3% by volume or less (the remainder being preferably nitrogen gas), even more preferably includes a step of bubbling a gas having an oxygen concentration of 1% by volume or less (the remainder being preferably nitrogen gas), and most preferably includes a step of bubbling a gas of 100% by volume of nitrogen gas.
• the bubbling time in the step of bubbling such a gas with a low oxygen concentration is not particularly limited as long as an etching composition with an oxygen concentration of 2 ppm by mass or less can be obtained, but is usually about 1 to 15 minutes.
• there is no particular restriction on the processing temperature during bubbling and slight heating may be performed to enhance the efficiency of oxygen removal.
• the bubbling step is preferably carried out after mixing all the components of the etching composition and immediately before etching. It is preferable to continue bubbling during etching in order to maintain the oxygen concentration.
• the etching method of the present invention is a method for etching a structure containing silicon and silicon germanium using the etching composition of the present invention.
• the silicon to be etched is preferably single crystal silicon, since single crystal silicon germanium has excellent characteristics for gate-all-around transistors, and single crystal silicon germanium is less likely to have defects when epitaxially grown on single crystal silicon germanium.
• a known etching method can be used, such as a batch method or a single wafer method.
• the temperature during etching is preferably 15° C. or higher, and more preferably 20° C. or higher, since this allows the etching rate to be improved.
• the temperature during etching is preferably 100° C. or less, and more preferably 80° C. or less, from the viewpoints of reducing damage to the substrate and ensuring etching stability.
• the temperature during etching corresponds to the temperature of the etching composition during etching.
• the etching composition of the present invention suppresses the dissolution of silicon germanium, promotes the dissolution of silicon, has excellent selective solubility of silicon relative to silicon germanium, and can provide an excellent surface condition for a substrate after etching. Therefore, the etching composition of the present invention is suitable for an etching solution, is more suitable for an etching solution that dissolves silicon, and is particularly suitable for an etching solution that suppresses the dissolution of silicon germanium and dissolves silicon.
• the etching composition and the etching method of the present invention can be suitably used in the manufacture of semiconductor devices including a step of etching a structure containing silicon and silicon germanium, and can suppress dissolution of silicon germanium, promote dissolution of silicon, exhibit excellent selective solubility of silicon relative to silicon germanium, and provide an excellent surface condition of a substrate after etching. Therefore, the etching composition and the etching method of the present invention are particularly suitable for use in the manufacture of GAA type FETs, which includes a step of etching a structure containing silicon and silicon germanium, and are particularly suitable for structures in which silicon and silicon germanium are alternately stacked, which are necessary for the formation of GAA type FETs.
• Table 1 shows whether each of the above components had a melting point of 5°C or higher when made into an aqueous solution with a concentration of 1 mol/L, and the melting points. Melting points were measured using a Hitachi High-Tech Science DSC7020 differential scanning calorimeter. The aqueous solution was placed in a SUS sample pan for thermal analysis, sealed, and the temperature was changed in the following order: room temperature ⁇ 60°C (heating rate 20°C/min), 60°C ⁇ -70°C (heating rate 10°C/min), and -70°C ⁇ 60°C (heating rate 10°C/min).
• the endothermic peak that appeared near 0°C between -70°C ⁇ 60°C was determined to be the melting point derived from water, and the peak top temperature of any other endothermic peaks that appeared was determined to be the melting point derived from the compound.
• a substrate including a structure in which silicon germanium having a thickness of 10 nm and silicon having a thickness of 10 nm were laminated was immersed in a 0.5 mass% hydrofluoric acid aqueous solution for 60 seconds, rinsed with ultrapure water, dried, and stored under a nitrogen atmosphere.
• the substrate was then immersed in the etching compositions obtained in the Examples and Comparative Examples at the temperatures shown in Table 3 for the times shown in Table 3, rinsed with ultrapure water, and dried.
• the cross section of the substrate after immersion was observed with an electron microscope to measure the width [nm] of the silicon layer, and the silicon etch rate ER Si [nm/min] was calculated using the following formula (1).
• ER Si [nm/min] (width of silicon layer before immersion ⁇ width of silicon layer after immersion) ⁇ immersion time [min] (1)
• a substrate including a structure in which silicon germanium having a thickness of 10 nm and silicon having a thickness of 10 nm were laminated was immersed in a 0.5 mass% hydrofluoric acid aqueous solution for 60 seconds, rinsed with ultrapure water, dried, and stored under a nitrogen atmosphere.
• the substrate was then immersed in the etching compositions obtained in the Examples and Comparative Examples at the temperatures shown in Table 3 for the times shown in Table 3, rinsed with ultrapure water, and dried.
• the cross section of the substrate after immersion was observed with an electron microscope to measure the width [nm] of the silicon germanium layer, and the etch rate ER SiGe [nm/min] of the silicon germanium layer was calculated using the following formula (2).
• ER SiGe [nm/min] (width of silicon germanium layer before immersion ⁇ width of silicon germanium layer after immersion) ⁇ immersion time [min] (2)
• a substrate including a structure in which silicon germanium having a thickness of 10 nm and silicon having a thickness of 10 nm were laminated was immersed in a 0.5 mass% hydrofluoric acid aqueous solution for 60 seconds, rinsed with ultrapure water, dried, and stored under a nitrogen atmosphere.
• the substrate was then immersed in the etching compositions obtained in the Examples and Comparative Examples at the temperatures shown in Table 3 for the times shown in Table 3, rinsed with ultrapure water, and dried.
• the cross section of the substrate after immersion was observed with an electron microscope, and the substrate surface was evaluated according to the following criteria.
• Example 1 Component (A-1) was dissolved in water as a solvent so that the concentration of component (A-1) was 1 mol/L, and the resulting solution was bubbled with nitrogen gas having an oxygen concentration of 0% by volume for 10 minutes to obtain an etching composition having the oxygen concentration shown in Table 2A.
• the pH of this etching composition was measured using a HORIBA pH electrode 9632-10D for strong alkaline samples (HORIBA portable pH meter D-74 was used), and was found to be 14.
• the etching conditions and evaluation results of the obtained etching compositions are shown in Table 3A.
• Examples 2 to 18 The same operation as in Example 1 was performed except that the type and concentration of component (A), the type and concentration of component (B), and the oxygen concentration in the bubbled nitrogen gas were changed as shown in Table 2A, to obtain etching compositions having the oxygen concentrations and pHs shown in Table 2A.
• the etching conditions and evaluation results of the obtained etching compositions are shown in Table 3A.
• Example 19 The same procedure as in Example 16 was carried out except that the solvent was a mixed solvent of 90 mass % water and 10 mass % isopropyl alcohol, to obtain etching compositions having the oxygen concentrations and pHs shown in Table 2A.
• the etching conditions and evaluation results of the obtained etching compositions are shown in Table 3A.
• Example 1 The same procedure as in Example 1 was carried out except that the type and concentration of component (A), the type and concentration of component (B), and the oxygen concentration in the bubbled nitrogen gas were changed as shown in Table 2B, to obtain an etching composition having the oxygen concentration and pH shown in Table 2B.
• the etching conditions and evaluation results of the obtained etching compositions are shown in Table 3B.
• the mass ratio of oxygen to the compound (A) of the etching composition is represented as "O 2 /component (A)".
• the etching compositions obtained in the examples suppress the dissolution of silicon germanium, promote the dissolution of silicon, and are excellent in the selective solubility of silicon in silicon germanium, while providing excellent surface conditions for the substrate after etching.
• the etching compositions obtained in the comparative examples were inferior in at least one of the selective solubility of silicon in silicon germanium and the substrate surface condition, and were unable to achieve both.
• the etching composition of the present invention and the etching method of the present invention using this etching composition suppress the dissolution of silicon germanium, promote the dissolution of silicon, have excellent selective solubility of silicon relative to silicon germanium, and can provide an excellent surface condition of the substrate after etching. Therefore, the etching composition of the present invention and the etching method of the present invention using this etching composition are suitable for etching structures containing silicon and silicon germanium.
• the etching composition and etching method of the present invention can be suitably used in the manufacture of semiconductor devices, and in particular can be suitably used in the manufacture of GAA type FETs, which includes a step of etching a structure containing silicon and silicon germanium.

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