Compositions and methods for selectively etching p-type doped polysilicon relative to silicon nitride - Patents.com

Abstract

To provide a method for selectively removing a p-doped polysilicon from a micro electronic device included in an upper face relative to silicon nitride.SOLUTION: The method comprises the step of bringing a substrate containing a p-doped polysilicon and silicon nitride into contact with a removal composition. In the method, the removal composition serves to selectively remove the p-doped polysilicon relative to silicon nitride, and contains at least one kind of nitrate of 0.1 wt.% to 1 wt.%, at least one kind of fluoride of 0.1 wt.% to 3 wt.%, at least one kind of strong acid of 50 wt.% to 85 wt.%, and at least one kind of solvent of 11 wt.% to 49.8 wt.%. The removal composition is 2 to -8 in pH, of which the proportion of at least one kind of nitrate and at least one kind of fluoride on the weight percentage basis falls in a range of 0.2:1 to 2:1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to compositions and methods for selectively removing p-type doped polysilicon relative to silicon nitride from substrates containing same, preferably those with a high-k / metal gate integration scheme. [Background technology]

[0002] A conventional semiconductor device may include a large number of metal-oxide-semiconductor field effect transistors ("MOSFETs"), each with at least one source, drain, and gate region. Complementary metal-oxide-semiconductor ("CMOS") uses complementary, symmetric pairs of p-type and n-type MOSFETs to enable dense logic functions on a chip.

[0003] The gate region of a MOS or CMOS transistor is typically composed of a gate material (e.g., polysilicon) disposed on or above an oxide insulator / dielectric (e.g., SiO2) that overlays or resides on top of a semiconductor material, a combination commonly referred to as a "gate stack." Despite the "metal" in metal gate and metal oxide semiconductor, polysilicon is the most common gate material in conventional gate fabrication. Polysilicon is the preferred material for fabricating gate electrodes due to its ease of deposition, tolerance to extremely high temperatures (>900-1000°C) in subsequent fabrication steps (e.g., annealing), and ability to form self-aligned gates. Metal gate fabrication suffers from many problems that are avoided with polysilicon.

[0004] The gate dielectric of choice in the prior art has long been silicon dioxide. As the size of transistors is reduced, the thickness of the silicon dioxide dielectric is also reduced to improve the gate capacitance, thereby increasing the current and device performance. Reducing the silicon dioxide gate thickness to less than approximately 2 nm results in a dramatic increase in leakage current due to tunneling, which leads to very high power consumption and reduced device reliability. The solution has been to replace the silicon dioxide gate dielectric with a high-k material that allows for an increase in gate capacitance without the attendant leakage effects. However, replacing the silicon dioxide gate dielectric with another material has been found to complicate the manufacturing process.

[0005] Due to compatibility concerns between standard polysilicon gates and high-k gate dielectrics, high-k gate dielectrics are more conveniently paired with metal gate electrodes (e.g., TiN for p-type gates; TiAlN for n-type gates). However, metal gates present some additional challenges in semiconductor fabrication, such as a tendency to disperse into silicon and / or migrate toward mid-gap work function during high-temperature thermal annealing. It is important that metals incorporated into semiconductor wafers are not exposed to high temperatures. One proposed solution is the use of a gate-last process strategy (also known as "replacement gate," "dummy poly gate," or "cold flow process"), which deposits metal electrodes after high-temperature activation anneal(s). In the gate-last process, a polysilicon dummy gate is patterned in a conventional self-aligned manner. After the remaining processing steps are completed, the dummy gate is removed to expose the recess and metal is deposited in place. The recesses can be filled with metal using PVD ("physical vapor deposition"), CVD ("chemical vapor deposition"), or ALD ("atomic layer deposition"). However, removal of the dummy gate by conventional methods presents difficulties unique to gate-last processes.

[0006] Conventional semiconductor etching methods (wet and dry) are not selective and will attack not only the sacrificial polysilicon dummy gate, but also other exposed films such as silicon nitride as well. Strong bases will attack silicon dioxide, oxidants will attack TiN, and many HF-containing (or generating) reagents will attack all layers.

[0007] Furthermore, among p-type and n-type polysilicon transistors, p-type doped polysilicon is very difficult to etch. Ammonium hydroxide etching is commonly used to remove n-type polysilicon. Removal of p-type polysilicon is conventionally performed by wet etching with tetramethylammonium hydroxide, but the etching rate tends to be slow due to p-type, e.g., boron, doping. Furthermore, it is known that undoped polysilicon can be etched by nitric acid / HF / water compositions, but only when the nitric acid concentration is high. Therefore, a solution containing nitric acid (high concentration) / HF / water is not favored due to the high nitrogen content. Furthermore, it is unclear how effective such nitric acid (high concentration) / HF / water compositions are in etching p-type doped polysilicon, e.g., boron doped polysilicon, for which the compatibility of the composition with silicon nitride is much lower.

[0008] As a result, the art continues to seek improved methods for fabricating semiconductor devices with dummy poly-gate techniques, particularly p-type doped polysilicon devices. Summary of the Invention

[0009] Embodiments of the present invention generally relate to compositions and methods for removing p-type doped polysilicon relative to silicon nitride from substrates containing same, preferably those with high-k / metal gate integration schemes.

[0010] In one aspect, a method is described for selectively removing p-type doped polysilicon relative to silicon nitride from a substrate comprising the same, the method comprising contacting the substrate comprising p-type doped polysilicon and silicon nitride with a removal composition that selectively removes the p-type doped polysilicon relative to silicon nitride. In one embodiment, the p-type doped polysilicon is boron doped polysilicon.

[0011] In another aspect, a method is described for selectively removing p-type doped polysilicon relative to silicon nitride from a substrate comprising the same, the method comprising contacting a substrate comprising p-type doped polysilicon and silicon nitride with a removal composition that selectively removes p-type doped polysilicon relative to silicon nitride, the removal composition comprising at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source or at least one reducing agent, and optionally at least one solvent. In one embodiment, the p-type doped polysilicon is boron doped polysilicon.

[0012] Other aspects, features and advantages of the present invention will become more fully apparent from the following disclosure and the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Embodiments of the present invention generally relate to compositions and methods for selectively removing p-type doped polysilicon relative to silicon nitride from a substrate containing same, and more particularly, embodiments of the present invention generally relate to compositions and wet-based methods for removing p-type doped polysilicon, e.g., boron doped polysilicon, relative to silicon nitride, from a substrate containing same, without substantially removing other gate stack materials present on the substrate.

[0014] For ease of reference, "microelectronic device" is equivalent to semiconductor substrates, flat panel displays, phase change memory devices, solar panels, and other products manufactured for use in microelectronics, integrated circuit, energy integration, or computer chip applications, such as solar cell devices, photovoltaics, and microelectromechanical systems (MEMS). It should be understood that the terms "microelectronic device," "microelectronic substrate," and "microelectronic device structure" are not intended to be limiting in any way and include any substrate or structure that will ultimately become a microelectronic device or microelectronic assembly. Microelectronic devices can be patterned devices, blanketed devices, control devices, and / or test devices.

[0015] As defined herein, a "metal gate material" corresponds to a material having a Fermi level corresponding to the mid-gap of a semiconductor substrate, such as Ti, Ta, W, Mo, Ru, Al, La, titanium nitride, tantalum nitride, tantalum carbide, titanium carbide, molybdenum nitride, tungsten nitride, ruthenium (IV) oxide, tantalum silicon nitride, titanium silicon nitride, tantalum carbon nitride, titanium carbon nitride, titanium aluminide, tantalum aluminide, titanium aluminum nitride, tantalum aluminum nitride, lanthanum oxide, or combinations thereof. It will be appreciated that the compounds disclosed as metal gate materials may have a variety of stoichiometries. Thus, titanium nitride is referred to herein as TiN. x and tantalum nitride is herein denoted as TaN x It is stated that:

[0016] As defined herein, "high dielectric constant" materials include: hafnium oxide (e.g., HfO2); zirconium oxide (e.g., ZrO2); hafnium oxysilicate; hafnium silicate; zirconium silicate; titanium silicate; aluminum oxide; its lanthanum doped analogues (e.g., LaAlO3); aluminum silicate; tantalates (e.g., Ta2O5); hafnium and silicon oxides and nitrides (e.g., HfSiON); its lanthanum doped analogues (e.g., HfSiON(La)); barium strontium titanate (BST); hafnium and aluminum oxides (e.g., Hf x Al y O z ); strontium titanate (SrTiO3); barium titanate (BaTiO3); and combinations thereof.

[0017] As defined herein, "gate stack materials" correspond to: tantalum, tantalum nitride, titanium nitride, titanium, nickel, cobalt, tungsten, tungsten nitride, and silicides of the aforementioned metals on microelectronic devices; low-k materials; polysilicon; poly-SiGe; silicon oxide; silicon nitride; BEOL layers; high-k replacement gates; hafnium oxide; hafnium oxysilicate; zirconium oxide; oxides of the lanthanide elements; titanates; their nitrogen-doped analogs; ruthenium; iridium; cadmium; lead; selenium; silver; MoTa; and combinations and salts thereof.

[0018] As defined herein, "amine" species include at least one of primary amines, secondary amines, tertiary amines, and amine-N-oxides, although ammonium-containing salts are not considered "amines" according to this definition. The formula for an amine is NR 1 R 2 R 3 where R 1 , R 2 and R 3 may be the same or different, and are each a hydrogen atom, a straight or branched C1-C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), a C6-C10 aryl (e.g., benzyl), linear or branched C1-C6 alkanol (e.g., methanol, ethanol, propanol, butanol, pentanol, hexanol), and combinations thereof. As defined herein, "ammonium-containing salts" include salts containing a cation [NR 1 R 2 R 3 R 4 ] + In the formula, R 1 , R 2 , R 3 and R 4 are the same or different and include hydrogen, C1-C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), C1-C6 alkanol (e.g., methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy) and C6-C 10 aryl (eg, benzyl).

[0019] As used herein, "about" is intended to mean ±5% of the stated value.

[0020] "Substantially free" is defined herein as less than 2 wt.%, preferably less than 1 wt.%, more preferably less than 0.5 wt.%, even more preferably less than 0.1 wt.%, and most preferably 0 wt.%.

[0021] As used herein, "selectively remove p-type doped polysilicon relative to silicon nitride" corresponds to an etch rate selectivity of about 2:1 to about 1000:1, preferably about 10:1 to about 300:1, and most preferably about 50:1 to about 200:1, where the ratio is based on thickness as a function of time. In other words, an etch rate of p-type doped polysilicon of 2 nm / min or less is approximately 2 nm / min. -1 (or 1000 nm / min -1 When the etching rate is 1 nm / min, the etching rate of silicon nitride is 1 nm / min. -1 It is.

[0022] As used herein, the term "removing" corresponds to the selective removal of p-type doped, e.g., boron doped, polysilicon from a substrate using a removal composition. It will be recognized that the p-type doped polysilicon, e.g., boron doped polysilicon, will dissolve or otherwise be solubilized, preferably dissolved, in the removal composition. Furthermore, one skilled in the art will recognize that the composition may contain a negligible amount of silicon nitride (from the substrate) that is dissolved or otherwise solubilized.

[0023] As used herein, a "fluoride" species includes, but is not limited to, the fluoride ion (F - ) and HF2 - or salts thereof. It should be appreciated that the fluoride species may be present as a fluoride species or may be generated in situ.

[0024] As used herein, "nitrate" species refers to species that include, but are not limited to, nitric acid and its salts, preferably ammonium nitrate, or esters thereof.

[0025] As used herein, "silicon nitride" and "Si3N4" refer to pure silicon nitride (Si3N4) as well as impure silicon nitrides that contain hydrogen, carbon and / or oxygen impurities within their crystal structure.

[0026] As used herein, "polysilicon" or polycrystalline Si or poly-Si is understood by those skilled in the art to be a polycrystalline form of silicon consisting of many small silicon crystals. It is typically deposited using low pressure chemical vapor deposition (LPCVD) and is often doped n-type or p-type polysilicon. The degree of doping can range from light doping (e.g., 10 13 / cm -3 -10 18 / cm -3 ) to severe doping (e.g., 10 18 / cm -3The doping density can vary from 0.1 to 1000 nm (up to 1000 nm, up ...

[0027] The compositions of the present invention may be embodied in a wide variety of specific formulations, as described more fully herein below.

[0028] In all such compositions, when specific components of the composition are discussed in terms of a weight percentage range including a lower limit of zero, it will be understood that such components may or may not be present in various specific embodiments of the composition, and that when present, such components may be present in concentrations as low as 0.00001 weight percent, based on the total weight of the composition in which such component is used.

[0029] In one aspect, a method is described for selectively removing p-type doped polysilicon relative to silicon nitride from a substrate comprising the same, comprising contacting a substrate comprising p-type doped polysilicon and silicon nitride with a removal composition that selectively removes the p-type doped polysilicon relative to silicon nitride. Preferably, the composition does not substantially remove other gate stack materials present on the substrate. In one embodiment, the p-type doped polysilicon comprises boron. The substrate is preferably one with a high-k / metal gate integration scheme.

[0030] The method selectively removes p-type doped polysilicon relative to silicon nitride at temperatures ranging from about 10° C. to about 75° C., preferably from about 20° C. to about 50° C. Those skilled in the art will recognize that removal times will vary depending on whether the removal is performed in a single wafer tool or a multi-wafer tool, where the times preferentially range from about 30 seconds to about 4 minutes in the former case and from about 1 minute to about 20 minutes in the latter case. Such contact times and temperatures are exemplary, and any other suitable time and temperature conditions effective to selectively remove p-type doped polysilicon relative to silicon nitride from a substrate may be used.

[0031] Preferably, the removal rate of p-type doped polysilicon is about 50 nm / min. -1 -About 500nm / min -1 , more preferably about 100 nm / min -1 -About 300nm / min -1 , most preferably about 120 nm / min -1 -About 300nm / min -1 The removal rate of silicon nitride, as described herein, is slower than that of p-type doped polysilicon, such as boron doped polysilicon. For example, the removal rate of silicon nitride is preferably about 3 nm / min. -1 More preferably less than about 2 nm / min -1 less than about 1 nm / min, most preferably -1 is less than.

[0032] As introduced hereinabove, it is known that nitric acid / HF / water composition can etch p-type polysilicon, but only when the nitric acid concentration is high, but high nitrogen content is disadvantageous.Surprisingly, the inventors have found that lowering the nitric acid concentration while adding sulfuric acid results in a removal composition that can selectively remove p-type doped polysilicon, such as boron doped polysilicon, compared to silicon nitride, but still has a high p-type doped polysilicon etching rate.

[0033] In a second aspect, a removal composition is described for selectively removing p-type doped polysilicon relative to silicon nitride, comprising at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source, optionally at least one reducing agent, and optionally at least one solvent. Preferably, the composition does not substantially remove other gate stack materials present on the substrate. In one embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, and at least one strong acid. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, and at least one strong sulfur-containing acid. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, and at least one solvent. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, and at least one strong acid, and is substantially free of added water. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, and at least one strong sulfur-containing acid, and is substantially free of added water. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, and at least one silicon source or at least one reducing agent. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, and at least one silicon source. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, and at least one reducing agent. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, at least one silicon source or at least one reducing agent, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one sulfur-containing acid, at least one silicon source, and at least one solvent. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one sulfur-containing acid, at least one reducing agent, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, and at least one silicon source or at least one reducing agent, and is substantially free of added water. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, at least one silicon source or at least one reducing agent, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, and at least one silicon source, and is substantially free of added water. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, at least one silicon source, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, and at least one reducing agent, and is substantially free of added water. In another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong sulfur-containing acid, at least one reducing agent, and at least one solvent. In yet another embodiment, the removal composition comprises, consists of, or consists essentially of at least one nitrate, at least one fluoride, at least one strong acid, at least one silicon source, at least one reducing agent, and at least one solvent.

[0034] In one preferred embodiment of the present invention, the removal composition comprises XeF2, an amine, a chloride (Cl -), metal halides, chelating agents (e.g., iminodiacetic acid, malonic acid, oxalic acid, succinic acid, boric acid, malic acid, 2,4-pentanedione, and / or glycol ether chelating agents), and combinations thereof. The pH (or Hammett's acidity function, H0) of the removal composition of the second embodiment is preferably less than 2, preferably in the range of 2 to about -8, more preferably in the range of -1 to about -5.

[0035] The at least one solvent may be water and / or methanol, ethanol, isopropanol, butanol, pentanol, hexanol, 2-ethyl-1-hexanol, heptanol, octanol, ethylene glycol, propylene glycol, butylene glycol, butylene carbonate, ethylene carbonate, propylene carbonate, dipropylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, The at least one water-miscible organic solvent may be selected from the group consisting of dipropylene glycol ether (DPGME), tripropylene glycol methyl ether (TPGME), dipropylene glycol dimethyl ether, dipropylene glycol ethyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether (DPGPE), tripropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, 2,3-dihydrodecafluoropentane, ethyl perfluorobutyl ether, methyl perfluorobutyl ether, alkyl carbonate, alkylene carbonate, 4-methyl-2-pentanol, dimethyl sulfoxide, sulfolane, methylsulfonylmethane, acetic acid, acetic anhydride, trifluoroacetic acid, dense fluids, and combinations thereof. Preferably, the at least one solvent comprises water, sulfolane, methylsulfonylmethane, and any combination thereof.

[0036] The at least one fluoride source may include, but is not limited to, hydrofluoric acid, ammonium fluoride, ammonium difluoride, hexafluorosilicic acid, tetrafluoroboric acid, tetrabutylammonium tetrafluoroborate (TBA-BF4), hexafluorotantalic acid, hexafluorotitanic acid, ammonium hexafluorotantalate, hexafluorotantalic acid represented by the formula [NR 1 R 2 R 3 R 4 ]F(wherein, R 1 , R 2 , R 3 and R 4 are the same or different, and include C1-C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl) and C6-C 10 aryl (e.g., selected from the group consisting of benzyl), tetraalkylammonium fluoride, such as tetramethylammonium fluoride, or combinations thereof. Preferably, the at least one fluoride comprises HF.

[0037] Nitrates contemplated herein include, but are not limited to, nitric acid, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, calcium nitrate, ammonium nitrate, and nitrates of the formula [NR 1 R 2 R 3 R 4 ]NO3(wherein, R 1 , R 2 , R 3 and R 4 are the same or different, and include C1-C6 alkyl (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl) and C6-C 10 aryl (e.g., selected from the group consisting of benzyl), tetraalkylammonium nitrate, such as tetramethylammonium nitrate, and combinations thereof. Preferably, the at least one nitrate comprises nitric acid.

[0038] The at least one strong acid includes, but is not limited to, sulfuric acid, alkanesulfonic acids (e.g., methanesulfonic acid (MSA), ethanesulfonic acid, 2-hydroxyethanesulfonic acid, n-propanesulfonic acid, isopropanesulfonic acid, isobutenesulfonic acid, n-butanesulfonic acid, n-octanesulfonic acid), trifluoromethanesulfonic acid, p-toluenesulfonic acid, tetrafluoroboric acid, perchloric acid, and combinations thereof. Preferably, the at least one strong acid comprises a sulfur-containing acid such as sulfuric acid.

[0039] Without wishing to be bound by theory, it is believed that the silicon source stabilizes the etch rate of the p-type doped polysilicon. The silicon source may be added to the removal composition as silicon powder or as silane or a combination of both. Silanes include, but are not limited to, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane, bis[3-(trimethoxysilyl)propyl]-ethylenediamine, bis[3-(triethoxysilyl)propyl]-ethylenediamine, methyltrimethoxysilane (MTMS), polydimethylsilane (PDMS), propyltrimethoxysilane (PTMS), methyltriethoxysilane (MTES), ethyltriethoxysilane, triethoxysilane, trimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, bis(3-trimethoxysilylpropyl)-N-methylamine, 3-(2-aminoethylamino)propyltriethoxysilane, N-propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, methylcyclohexyldimethoxysilane, dimethyldimethoxysilane, dicyclopentyl Dimethoxysilane, 3-[2(vinylbenzylamino)ethylamino]propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(aminopropyl)dimethylethoxysilane, 3-(aminopropyl)methyldiethoxysilane, 3-(aminopropyl)methyldimethoxysilane, 3-(aminopropyl)dimethylmethoxysilane, N-butyl-3-aminopropyltriethoxysilane, N-butyl-3-aminopropyltrimethoxysilane, N-(β-

[0036] Examples of suitable silanes include N-(2-aminoethyl)-γ-amino-propyltriethoxysilane, 4-amino-butyldimethylethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldiethoxysilane, 1,1,3,3-tetramethyldisiloxane, 1,1,3,3-tetramethyldisilazane, (N,N-dimethylamino)dimethylsilane, or combinations thereof.Alternatively or additionally, the silicon source may be a quaternary ammonium silicate, such as a tetraalkylammonium silicate. The silicon source(s) is preferably soluble in the removal composition. Preferably, the silicon source comprises silicon powder.

[0040] Without wishing to be bound by theory, another stabilization mechanism of the etch rate is believed to involve the presence of reduced nitrogen species, such as nitric oxide, nitrous acid, and nitrogen dioxide (possibly in cationic form). Such species may be formed in situ by the reduction of at least one nitrate, such as nitric acid, by a silicon source. The silicon source may be added to the removal composition as silicon powder or as a silane or a combination of both.Silanes include, but are not limited to, triethoxysilane, trimethoxysilane, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane, bis[3-(trimethoxysilyl)propyl]-ethylenediamine, bis[3-(triethoxysilyl)propyl]-ethylenediamine, methyltrimethoxysilane (MTMS), polydimethylsilane (PDMS), propyltrimethoxysilane (PTMS), methyltriethoxysilane (MT ... silane (MTES), ethyl triethoxysilane, triethoxysilane, trimethoxysilane, dimethyl diethoxysilane, diethyl diethoxysilane, diethyl dimethoxysilane, bis(3-trimethoxysilylpropyl)-N-methylamine, 3-(2-aminoethylamino)propyl triethoxysilane, N-propyl triethoxysilane, 3-(2-aminoethylamino)propyl trimethoxysilane, methylcyclohexyl dimethoxysilane, dimethyl dimethoxysilane, dicyclopentyl dimethoxysilane, 3-[2(vinylbenzylamino)ethylamino]propyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-(aminopropyl)dimethylethoxysilane, 3-(aminopropyl)methyl diethoxysilane, 3-(aminopropyl)methyl dimethoxysilane, 3-(aminopropyl)dimethyl methoxysilane, N-butyl-3-aminopropyl triethoxysilane, N-butyl-3-aminopropyl trimethoxysilane, Examples of suitable silicon sources include N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, 4-aminobutyldimethylethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldiethoxysilane, 1,1,3,3-tetramethyldisiloxane, 1,1,3,3-tetramethyldisilazane, (N,N-dimethylamino)dimethylsilane, or combinations thereof. Alternatively or additionally, the silicon source may be a quaternary ammonium silicate, such as a tetraalkylammonium silicate. The silicon source(s) is preferably soluble in the removal composition. Preferably, the silicon source comprises silicon powder.

[0041] Also, some of the at least one nitrate, for example nitric acid, may be reduced using at least one reducing agent. For example, reduction may be performed by adding sulfur dioxide solution, sulfite (e.g., ammonium hydrogen sulfite) or thiosulfate (e.g., ammonium thiosulfate) or elemental sulfur. Other reducing agents include, but are not limited to, dimethyl sulfoxide, formic acid and formaldehyde (oxidized to CO2), glyoxylic acid or glyoxal (oxidized to oxalic acid), hydrazine sulfate, hydroxylamine sulfate, boroxine (H3B3O3, oxidized to boric acid), borane-amine or borane-ammonia complex, tetramethylammonium borohydride, sulfurous acid, or potassium borohydride. Preferably, sulfurous acid is used as a reducing agent to generate reduced nitrogen species. Another option without additives is the electrochemical reduction of the at least one nitrate to reduced nitrogen species.

[0042] It will be appreciated that reduced nitrogen species may be part of the formulation as an additive, and in particular nitrous acid is most conveniently added in the form of a nitrite salt, such as potassium nitrite, dicyclohexylamine nitrite, or tetrabutylammonium nitrite. Other compounds that may directly add reduced nitrogen species to the stripping composition include nitrosylsulfonic acid, nitrosyl tetrafluoroborate, as well as nitric oxide (NO), nitrogen dioxide (NO2), or mixtures thereof. Preferably, the gas is bubbled through the stripping composition. The aforementioned reduced nitrogen species could be added in place of or in addition to at least one nitrate described herein.

[0043] Of note, hydrofluoric acid, sulfuric acid, and nitric acid are typically shipped with residual amounts of water, so that water may be present in the removal composition in addition to any water intentionally added to the chemical combination. Alternatively, anhydrous hydrogen fluoride gas and / or fuming nitric acid (100%) may be used, in which case additional water or other solvent(s) may be added. As will be appreciated by those skilled in the art, water present in nature (e.g., in concentrated sulfuric acid, concentrated nitric acid, concentrated HF, etc.) is not considered "added water."

[0044] In a preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000001.tif24170.

[0045] In another preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000002.tif24170.

[0046] In yet another preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000003.tif32170.

[0047] In yet another preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000004.tif32170.

[0048] In yet another preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000005.tif36170.

[0049] In yet another preferred embodiment, the removal composition of the second aspect comprises: Contains, consists of, or consists essentially of TIFF0007656647000006.tif37170.

[0050] Advantageously, the removal compositions described herein are capable of etching p-type doped polysilicon (e.g., boron doped polysilicon) at a high etch rate while being compatible with silicon nitride (i.e., having a low etch rate for silicon nitride). Furthermore, the process temperatures are moderate, the removal compositions are water soluble, the cost of preparing the compositions is low, and the low phosphorus and nitrogen content in the removal compositions results in low waste.

[0051] Without wishing to be bound by theory, it is believed that the selectivity of p-type doped polysilicon over silicon nitride is caused by the weight percent ratio of nitrate(s) to fluoride(s). Initial results suggest that a weight percent ratio of 70% nitric acid to 49% HF in the range of about 0.2:1 to about 2:1, preferably about 0.3:1 to about 1:1, results in the best selectivity (greater than 50:1) of p-type doped polysilicon over silicon nitride (e.g., boron doped polysilicon). Furthermore, initial results suggest that there may be an optimal weight percent of the sulfur-containing acid(s), e.g., sulfuric acid, present (e.g., concentrated sulfuric acid in the range of about 60 wt% to about 70 wt%) that results in the best selectivity (greater than 50:1) of p-type doped polysilicon over silicon nitride (e.g., boron doped polysilicon). It has also been found that the addition of at least one silicon source or at least one reducing agent catalyzes and provides a stable etch rate for p-type doped polysilicon.

[0052] In another aspect of the invention, the removal compositions described herein may further comprise dissolved p-type doped polysilicon, such as boron doped polysilicon. For example, the removal composition may comprise, consist essentially of, or consist of at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source or at least one reducing agent, and optionally at least one solvent.

[0053] It will be appreciated that it is common practice to dilute a concentrated form of the removal composition prior to use. For example, a removal composition comprising at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source, optionally at least one reducing agent, and optionally at least one solvent may be manufactured in a more concentrated form and then diluted with solvent and / or additional of the strong acid at the manufacturer prior to use and / or during use during manufacture. The dilution ratio may range from about 0.1 parts diluent:1 part removal composition concentrate to about 100 parts diluent:1 part removal composition concentrate.

[0054] Furthermore, it will be appreciated that a limitation of the system used to distribute or process the mixture during use is that modification of the rheological profile may be required to reduce the viscosity of the mixture. To this end, the viscosity or overall rheological profile may be reduced (i.e., from Newtonian to non-Newtonian) through the use of surfactants, polymers, etc., improving the processability of the mixture. There is a potential additional benefit of using removal compositions that feature high aspect ratios as well as improved rinsing properties after processing.

[0055] The removal compositions of the present invention are easily formulated by simply adding each component and mixing to a uniform state. Moreover, the removal compositions can be easily formulated as single package formulations or as multi-part formulations, preferably multi-part formulations, that are mixed at or before the point of use. The individual parts of the multi-part formulation can be mixed at the tool or in a mixing region / area, such as in an in-line mixer or a storage tank upstream of the tool. It is contemplated that the various parts of the multi-part formulation can contain any combination of ingredients / components that when mixed together form the desired removal composition. It will be recognized that the concentration of each component can vary widely in various specific removal compositions, i.e., they can be more dilute or more concentrated in the broad implementation of the present invention, and that the removal compositions of the present invention can alternatively comprise, consist of, or consist essentially of any combination of ingredients consistent with the disclosure herein.

[0056] Therefore, another aspect of the present invention relates to a kit comprising one or more components adapted to form the composition of the present invention in one or more containers. Preferably, the kit comprises at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source, optionally at least one reducing agent, and optionally at least one solvent in one or more containers for combining with a solvent and / or additional strong acid at the time of manufacture or at the time of use. The container of the kit should be suitable for storing and shipping the removal composition, for example, a NOWPak® container (Advanced Technology Materials, Inc., Danbury, Conn., USA). The one or more containers containing the components of the removal composition preferably include a means for fluidly communicating the components in the one or more containers for blending and dispensing. For example, referring to a NOWPak® container, gas pressure can be applied to the exterior of the liner of the one or more containers to cause at least a portion of the contents of the liner of the one or more containers to be evacuated, thus allowing fluid communication for blending and dispensing. Alternatively, gas pressure may be applied to the headspace of a conventional pressurized vessel, and a pump may be used to provide fluid communication, and the system preferably includes a dispensing port for dispensing the blended removal composition to a process tool.

[0057] Substantially chemically inert, impurity-free, flexible and resilient polymeric film materials, such as high density polyethylene, are preferably used to fabricate the liners of the one or more containers. Desirable liner materials are those that are processed without the need for coextrusion or barrier layers and are free of pigments, UV inhibitors, or processing chemicals that may adversely affect the purity requirements of the components disposed within the liner. The list of desirable liner materials includes films including virgin (additive-free) polyethylene, virgin polytetrafluoroethylene (PTFE), polypropylene, polyurethane, polyvinylidene chloride, polyvinyl chloride, polyacetal, polystyrene, polyacrylonitrile, polybutylene, and the like. The preferred thickness of such liner materials ranges from about 5 mils (0.005 inches) to about 30 mils (0.030 inches), e.g., 20 mils (0.020 inches) thick.

[0058] With respect to containers for the kits, the disclosures of the following patents and patent applications are each incorporated herein in their entirety by reference: U.S. Patent No. 7,188,644, entitled "Apparatus and Method for Minimizing Particle Generation in Ultrapure Liquids;" U.S. Patent No. 6,698,619, entitled "Returnable and Reusable Bag-In-Drum Liquid Storage and Dispensing Container System;" and U.S. Patent Application No. 12 / 599,291, entitled "System and Method for Material Blending and Distribution," filed November 24, 2009 in the name of John EQ Hughes.

[0059] When applied to microelectronics manufacturing operations, the removal compositions described herein are useful for selectively removing p-type doped polysilicon (e.g., boron doped polysilicon) relative to silicon nitride from a surface of a microelectronic device, and may be applied to the surface before or after the application of other compositions formulated to remove other materials from the surface of the device. Importantly, the removal compositions described herein selectively remove p-type doped polysilicon (e.g., boron doped polysilicon) relative to silicon nitride, while not substantially removing other metal stack materials present on the substrate.

[0060] In removal applications, the removal composition is applied to the device in any suitable manner, such as by spraying the removal composition onto the device surface, by immersing the device in a static or dynamic volume of the removal composition, by contacting the device with another material that has absorbed the removal composition, such as a pad or fibrous absorbent applicator element, or by any other suitable means, manner, or technique that removeively contacts the removal composition with the device, including p-type doped polysilicon and silicon nitride. Additionally, batch or single wafer processing is contemplated herein.

[0061] After the desired removal action is achieved, the removal composition may be easily removed from the device to which it was previously applied, for example, by rinsing, washing, or other removal step(s), which may be desirable and effective. For example, the device may be rinsed with a rinse solution, such as deionized water, and / or dried (e.g., spin-dry, N2, solvent (e.g., IPA) vapor drying, etc.). Optionally, a small amount of a basic reagent, such as ammonia, may be added to the rinse water to achieve a pH of about 10. This modification may be useful in inhibiting sulfate contamination of silicon-based surfaces that have been treated with high-concentration sulfuric acid solutions.

[0062] Another aspect of the invention relates to improved microelectronic devices made by the methods of the invention and to articles of manufacture that include such microelectronic devices.

[0063] Yet a further aspect of the invention relates to a method of manufacturing an article comprising a microelectronic device, the method comprising contacting the microelectronic device with a removal composition for a time sufficient to selectively remove p-type doped polysilicon (e.g., boron doped polysilicon) relative to silicon nitride from the microelectronic device comprising said material thereon, and incorporating said microelectronic device into said article. The removal composition may comprise, consist of, or consist essentially of at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source or at least one reducing agent, and optionally at least one solvent.

[0064] Another aspect of the invention relates to an article of manufacture comprising a microelectronic device substrate and a removal composition, the microelectronic device substrate comprising p-type doped polysilicon (e.g., boron doped polysilicon) and silicon nitride. For example, the removal composition can include at least one nitrate, at least one fluoride, at least one strong acid, optionally at least one silicon source or at least one reducing agent, and optionally at least one solvent.

[0065] In another aspect, the present disclosure relates to a method of fabricating a semiconductor device comprising performing a gate-last process including forming a dummy gate of p-type doped polysilicon and then removing the dummy gate for replacement with a metal gate, the dummy gate being removed by the removal composition described herein.

[0066] Those skilled in the art will recognize that the removal compositions described herein are not limited to selectively removing p-type doped polysilicon over silicon nitride, but may be used to remove silicon-containing materials in general, such as sacrificial polysilicon (doped or undoped) and crystalline silicon, as will be appreciated by those skilled in the art.

[0067] The features and advantages of the present invention are more fully illustrated by the illustrative examples discussed below. EXAMPLES

[0068] Example 1 Examples of sample formulations are shown in Table 1 below. Table 1: Formulation AD TIFF0007656647000007.tif45170

[0069] The performance of Formulation AD is shown below in Table 2. Etch rates were measured on wafers spinning at 400 RPM. Accelerated shelf life tests were performed at 55° C. for periods ranging up to 37.4 days. The periods shown in Table 2 are of expected aging behavior at 20° C. and include an estimated acceleration factor of 10x. Table 2: Experimental results for formulations AD TIFF0007656647000008.tif93170

[0070] While the present invention has been variously disclosed herein with respect to illustrative embodiments and features, it will be recognized that the embodiments and features described herein above are not intended to limit the present invention, and that other variations, modifications, and alternative embodiments will be suggested to those skilled in the art based on the disclosure herein. Accordingly, the present invention is to be broadly construed, with all such variations, modifications, and alternative embodiments being encompassed within the spirit and scope of the claims set forth hereinafter.

Claims

1. 1. A method for selectively removing p-type doped polysilicon relative to silicon nitride, comprising contacting a substrate comprising p-type doped polysilicon and silicon nitride with a removal composition, wherein the removal composition selectively removes the p-type doped polysilicon relative to silicon nitride; 0.1 wt % to 1 wt % of at least one nitrate; 0.1 wt % to 3 wt % of at least one fluoride; 60 wt % to 80 wt % of at least one strong acid, and 16 wt % to 39.8 wt % of at least one solvent Including, The at least one nitrate is selected from the group consisting of nitric acid, sodium nitrate, potassium nitrate, rubidium nitrate, magnesium nitrate, calcium nitrate, ammonium nitrate, and nitrates of the formula [NR １ R ２ R ３ R ４ ]NO ３ (In the formula, R １ , R ２ , R ３ and R ４ are the same or different from each other, and C １ -C ６ Alkyl and C ６ -C １０ aryl), and combinations thereof; At least one fluoride is selected from the group consisting of hydrofluoric acid, ammonium fluoride, ammonium difluoride, hexafluorosilicic acid, tetrafluoroboric acid, and tetrabutylammonium tetrafluoroborate (TBA-BF ４ ), hexafluorotantalic acid, hexafluorotitanic acid, ammonium hexafluorotantalate, １ R ２ R ３ R ４ ]F (wherein, R １ , R ２ , R ３ and R ４ are the same or different from each other, and C １ -C ６ Alkyl and C ６ -C １０ aryl), and combinations thereof; the at least one strong acid comprises a species selected from the group consisting of sulfuric acid, methanesulfonic acid (MSA), ethanesulfonic acid, 2-hydroxyethanesulfonic acid, n-propanesulfonic acid, isopropanesulfonic acid, isobutenesulfonic acid, n-butanesulfonic acid, n-octanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, tetrafluoroboric acid, perchloric acid, and combinations thereof; At least one solvent is selected from the group consisting of water, methanol, ethanol, isopropanol, butanol, pentanol, hexanol, 2-ethyl-1-hexanol, heptanol, octanol, ethylene glycol, propylene glycol, butylene glycol, butylene carbonate, ethylene carbonate, propylene carbonate, dipropylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, propylene glycol methyl ether, dipropylene glycol glycol methyl ether (DPGME), tripropylene glycol methyl ether (TPGME), dipropylene glycol dimethyl ether, dipropylene glycol ethyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether (DPGPE), tripropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, 2,3-dihydrodecafluoropentane, ethyl perfluorobutyl ether, methyl perfluorobutyl ether, alkyl carbonates, alkylene carbonates, 4-methyl-2-pentanol, acetic acid, acetic anhydride, trifluoroacetic acid, dimethyl sulfoxide, sulfolane, methylsulfonylmethane, densified fluids, and combinations thereof; The method wherein the removal composition has a pH of -1 to -5 and a weight percent ratio of the at least one nitrate to the at least one fluoride ranging from 0.2:1 to 2:

1.

2. The method further comprises at least one silicon source, at least one reducing agent, or both, wherein the at least one silicon source is selected from the group consisting of silicon powder, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane, bis[3-(trimethoxysilyl)propyl]-ethylenediamine, bis[3-(triethoxysilyl)propyl]-ethylenediamine, methyltrimethoxysilane (MTMS), polydimethylsilane (PDMS), propyltrimethoxysilane ( PTMS), methyltriethoxysilane (MTES), ethyltriethoxysilane, triethoxysilane, trimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, bis(3-trimethoxysilylpropyl)-N-methylamine, 3-(2-aminoethylamino)propyltriethoxysilane, N-propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, methylcyclohexyldimethoxysilane, dimethyldimethoxysilane , dicyclopentyldimethoxysilane, 3-[2(vinylbenzylamino)ethylamino]propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(aminopropyl)dimethylethoxysilane, 3-(aminopropyl)methyldiethoxysilane, 3-(aminopropyl)methyldimethoxysilane, 3-(aminopropyl)dimethylmethoxysilane, N-butyl-3-aminopropyltriethoxysilane, N-butyl-3-aminopropyltrimethoxysilane, N-(β-aminoethyl) - selected from the group consisting of γ-amino-propyltriethoxysilane, 4-amino-butyldimethylethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-aminopropylmethyldiethoxysilane, 1,1,3,3-tetramethyldisiloxane, 1,1,3,3-tetramethyldisilazane, (N,N-dimethylamino)dimethylsilane, tetraalkylammonium silicates, and combinations thereof; 10. The method of claim 1, wherein the at least one reducing agent comprises a species selected from the group consisting of sulfur dioxide solution, sulfites, thiosulfates, sulfurous acid, elemental sulfur, dimethylsulfoxide, formic acid, formaldehyde, glyoxylic acid, glyoxal, hydrazine sulfate, hydroxylamine sulfate, boroxines, borane-amine complexes, borane-ammonia complexes, tetramethylammonium borohydride, potassium borohydride, and combinations thereof.

3. 3. The method of claim 2, wherein the amount of the at least one nitrate is 0.1 wt % to 1 wt %, the amount of the at least one fluoride is 0.1 wt % to 3 wt %, the amount of the at least one strong acid is 60 wt % to 80 wt %, the amount of the at least one silicon source or the at least one reducing agent is 0.00001 wt % to 0.5 wt %, and the amount of the at least one solvent is 16 wt % to 39.8 wt %.

4. The removal composition is XeF ２ , amines, chlorides (Cl － ), metal halides, iminodiacetic acid, malonic acid, oxalic acid, succinic acid, boric acid, malic acid, 2,4-pentanedione, glycol ether chelating agents, or combinations thereof.

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