Oxyhalide precursors

Abstract

The invention provides an oxyhalide precursor. The present invention provides a method of preparing molybdenum and tungsten oxyhalide compounds suitable for depositing thin films containing molybdenum and tungsten on various surfaces of microelectronic devices. In the inventive process, molybdenum trioxide or tungsten trioxide is heated in a solid medium or in a molten phase reaction comprising a eutectic blend comprising an alkali metal salt and / or an alkaline earth metal salt. The molybdenum or tungsten oxyhalide thus formed can be separated and crystallized in vapor form to provide a high purity precursor compound, such as MoO2Cl2.

Description

[0001] This application is a divisional application of the invention patent application with application date of July 8, 2020, application number 202080054603.3 and invention name “Oxyhalide Precursor”. Technical Field

[0002] The present invention relates to certain precursors for the vapor deposition of certain Group VI containing materials, methods for their preparation and novel crystal structures thereof. Background Art

[0003] Due to their characteristics of extremely high melting points, low coefficients of thermal expansion, low resistivity, and high thermal conductivity, Group VI metals such as molybdenum and tungsten are increasingly used in the manufacture of semiconductor devices, including in diffusion barriers, electrodes, photomasks, power electronic substrates, low resistivity gates, and interconnects.

[0004] The utility facilitates the deposition of molybdenum and tungsten thin films for such applications characterized by high conformality of the deposited films and high deposition rates that accommodate efficient high-volume processing operations. This in turn facilitates the development of improved molybdenum and tungsten source reagents suitable for vapor deposition operations, as well as improved process parameters utilizing such reagents.

[0005] Molybdenum pentachloride is most commonly used as a molybdenum source for chemical vapor deposition of molybdenum-containing materials. Another source reagent or precursor is MoO2Cl2, but there is still a need to prepare this reagent and other oxyhalides such as WOCl4, WO2Cl2, MoOCl4, etc. in high yield and high purity. Summary of the invention

[0006] The present invention provides a method for preparing certain Group VI metal oxyhalide compounds suitable for depositing Group VI containing thin films on various surfaces of microelectronic devices. In the method of the present invention, molybdenum trioxide or tungsten trioxide is heated in a solid medium or in a melt phase reaction containing a eutectic blend containing one or more alkali metal salts and / or alkaline earth metal salts. The molybdenum or tungsten oxyhalide thus formed can be separated in vapor form and crystallized to provide highly purified crystalline oxyhalides, such as MoO2Cl2 and WO2Cl2, to provide another aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is the crystal structure of the MoO2Cl2 unit cell.

[0008] Figure 2 Described is the thermogravimetric analysis of a mixture of MoO3 and LiCl / KCl which exhibits a significant mass loss upon combination of MoO3 and LiCl / KCl. The residual mass (%) is plotted against temperature (°C).

[0009] Figure 3 Thermogravimetric analysis of commercial MoO2Cl2 compared to MoO2Cl2 synthesized using the method of the present invention is described. The residual mass (%) is plotted against temperature (°C).

[0010] Figure 4 FTIR comparison of purchased MoO2Cl2 and MoO2Cl2 prepared using the method of the present invention.

[0011] Figure 5 Graph showing the experimental X-ray powder diffraction of MoO2Cl2 crystals compared with the spectrum calculated using the obtained MoO2Cl2 unit cell parameters (black line).

[0012] Figure 6 Figure 3 is the X-ray powder diffraction of hydrated MoO2Cl2, where the simulated MoO2Cl2 is shown as the vertical solid line below.

[0013] Figure 7 Simultaneous Thermogravimetric Analysis coupled with Differential Scanning Calorimetry (STA-DSC) is a method described. This data shows that the melting point occurs at a slightly different temperature than the LiCl / KCl eutectic alone. DETAILED DESCRIPTION

[0014] In a first aspect, the present invention provides a method for preparing a y X z wherein M is selected from molybdenum and tungsten, and X is selected from chlorine, fluorine, bromine and iodine, y is 1 or 2, and z is 2 or 4, the method comprising making a compound of the formula

[0015]

[0016] contacting with at least one compound of formula AX at a temperature of about 200°C to about 900°C, wherein A is selected from elements of Group 1, elements of Group 2, transition metals and main group elements of the periodic table.

[0017] As described herein, A can be any element capable of forming a halide.

[0018] In one embodiment, A is selected from alkali metals and alkaline earth metals.

[0019] In one embodiment, A is selected from lithium, sodium and potassium. In another embodiment, A is selected from magnesium, calcium, strontium, barium, beryllium, scandium, titanium, vanadium and chromium. In another embodiment, A is lithium or potassium.

[0020] In one embodiment, X is chlorine.

[0021] In another embodiment, the at least one compound of formula AX is a mixture of two or more compounds, and in certain embodiments, the compounds are selected so as to form a eutectic mixture.

[0022] In the process of the present invention, although the compound of formula AX and the compound of formula MO3 can interact when the compound of formula AX is in the solid state at a temperature range of about 200° C. to about 900° C., the compound of formula AX can also be advantageously selected from those alkali metal halides and alkaline earth metal halides that form eutectic blends. In this way, the eutectic blend of two or more compounds of formula AX allows the process of the present invention to be carried out in the melt phase at a processing temperature below the melting point of each individual alkali metal halide or alkaline earth metal halide, while providing a favorable reaction between the formed compound of formula MO3 and the eutectic mixture. y X z The compound sublimates in the melt phase reaction environment, which can then remove the formula MO y X z Compound and allowed to cool to provide pure crystalline form. Various blends of compounds of formula AX may be selected and selected in different proportions to provide a suitable reaction medium and halide source while providing a molten phase at a temperature high enough to facilitate sublimation of the desired product when it is formed. In certain embodiments, the ratio of individual alkali metal halides to alkaline earth metal halides may be about 1:1, but may also vary between 10:1 or 1:10, depending on any concentration of any component of the blend necessary to provide a molten phase reaction medium within the desired temperature range. In other embodiments, the mixture defined by formula AX may include three or more substances that form a eutectic blend that is used to form and sublime formula MO. y X z A molten phase is formed within the desired temperature range of the product.

[0023] Many compounds of formula AX are known to form eutectic blends, such as LiCl / KCl, as described in the experimental section below; and those described in GJ Janz et al., "Molten Salts: Volume 4, Part 2 Chlorides and Mixtures—electrical conductance, density, viscosity, and surface tension data," Journal of Physical and Chemical Reference Data 4, 871 (1975).

[0024] In one embodiment, the compound of formula AX is a mixture of lithium chloride and potassium chloride, which forms a eutectic mixture having a melting point of about 357° C. and a ratio of about 44 weight percent lithium chloride to about 56 weight percent potassium chloride.

[0025] In certain embodiments, the method is carried out at atmospheric pressure or under reduced pressure using an inert carrier gas (eg, nitrogen, argon, etc.), the parameters being selected to promote the reaction of formula MO y X z In one embodiment, when Y is 1 and Z is 4, a stoichiometric amount of the starting material of formula MO3 is selected to produce a higher yield of formula MO y X z In another embodiment, when Y is 2 and Z is 2, a stoichiometric amount of the starting material of formula MO3 is selected to produce a higher yield of formula MO y X z In yet another embodiment, the method is carried out in a state of partial sublimation while varying the pressure and temperature to produce a given species at different pressure / temperature combinations. In this way, species of the desired product where Y and Z are 2 can be separated from species of the desired product where Y is 1 and Z is 4, each forming a pure crystalline form upon cooling.

[0026] In a second aspect, the present invention provides a compound having the formula MO y X z The compound is in crystalline form, wherein M is selected from molybdenum and tungsten, X is selected from chlorine, fluorine, bromine and iodine, y is 1 or 2, and z is 2 or 4.

[0027] In one embodiment, Formula MO y X z In another embodiment, the crystalline form of the compound of formula MoO2Cl2 has the following Figure 1 The crystal structure depicted; this crystalline form of MoO2Cl2 is anhydrous. In another embodiment, the crystalline form of the compound of formula MoO2Cl2 has an orthorhombic crystal system and a unit cell size of about

[0028]

[0029] The approximate bond lengths for the crystalline form of the compound of formula MoO2Cl2 have been determined as follows:

[0030]

[0031] As used herein, the term "unit cell" refers to the smallest and simplest volume element of a crystal that completely represents the pattern unit of the crystal. The dimensions of a unit cell are defined by six numbers: dimensions a, b, and c, and angles α, β, and γ. A crystal is an effectively packed array of many unit cells.

[0032] As used herein, the term "orthorhombic unit cell" refers to a unit cell where a≠b≠c; α=β=γ=90°.

[0033] As used herein, "crystalline lattice" refers to the array of points defined by the vertices of stacked unit cells, as determined by single crystal x-ray diffraction analysis.

[0034] As used herein, "space group" refers to the symmetry of a unit cell. In the space group designation (e.g., C2), capital letters indicate the lattice type, and the other symbols represent symmetry operations that can be performed on the unit cell without changing the appearance of the unit cell.

[0035] In another embodiment, the crystalline form of MoO2Cl2 exhibits a powder XRD pattern having one or more peaks at 12.94, 23.64, 26.10, 39.50 and / or 40.28 ± 0.04 ° 2θ. In another embodiment, the crystalline form of MoO2Cl2 has a Figure 5 Powder XRD pattern depicted. In another embodiment, the crystalline MoO2Cl2 has a powder XRD pattern containing one or more peaks as determined from the single crystal unit cell parameters listed in Table 4.

[0036] In another embodiment, having the formula MO y X z And the compound in crystalline form is WO2Cl2.

[0037] The present invention may be further illustrated by the following examples of certain embodiments thereof, but it should be understood that these examples are included for illustrative purposes only and are not intended to limit the scope of the present invention unless specifically indicated otherwise.

[0038] Examples

[0039] Example 1. Synthesis of MoO2Cl2

[0040] A mixture of lithium chloride and potassium chloride (44 / 56 by weight) was combined with MO3 in a stainless steel ampoule and evacuated under reduced pressure (20 mTorr). The ampoule was heated to 475°C in a tubular furnace. The resulting MoO2Cl2 vapor was collected by a short-range tube equipped with a round-bottom flask. FTIR and STA analysis confirmed the synthesis of MoO2Cl2.

[0041] Table 1.4 (ICP-MS data for MoO2Cl2 synthesized using the described method. Data are reported in parts per million (ppm)).

[0042] Element List DL Sample A* Sample B Sample C aluminum 0.041 0.523 0.354 0.571 antimony 0.027 0.786 0.690 0.606 barium 0.018 0.019 <0.018 <0.018 calcium 1.851 1.851 1.272 0.919 chromium 0.027 <0.027 <0.027 <0.027 cobalt 0.026 <0.026 <0.026 <0.026 copper 0.028 <0.028 <0.028 <0.028 iron 0.028 0.482 0.404 0.704 lead 0.023 <0.023 <0.023 <0.023 lithium 0.036 0.238 0.067 0.133 magnesium 0.032 0.081 0.065 0.092 manganese 0.021 <0.021 <0.021 <0.021 nickel 0.022 0.033 0.056 0.045 Potassium 0.019 1.019 2.259 2.731 silver 0.027 <0.027 <0.027 <0.027 sodium 0.066 0.083 0.165 0.329 tin 0.043 0.115 0.119 0.409 titanium 0.067 <0.067 <0.067 0.068 vanadium 0.027 <0.027 <0.027 <0.027

[0043] * Each of samples A, B and C was taken from the same batch.

[0044] Table 2 Crystal data and structure refinement of MoO2Cl2

[0045]

[0046]

[0047] Table 3. Bond lengths for MoO2Cl2 and angle [°].

[0048]

[0049]

[0050] Symmetry transformations to produce equivalent atoms:

[0051] #1-x+1,y,z#2-x+1,-y+1,z+1 / 2#3-x+1,-y,z+1 / 2#4-x+1,-y+1,z-1 / 2#5-x+1,-y,z-1 / 2

[0052] Table 4.

[0053]

[0054]

[0055]

[0056] Table 4 is a simulated powder X-ray diffraction (PXRD) spectrum of a unit cell (MoO2Cl2 crystal structure) using commercially available software to model and simulate the PXRD data.

[0057] Table 5

[0058]

[0059]

[0060] Table 5 depicts the experimental X-ray powder diffraction of hydrated MoO2Cl2 obtained after MoO2Cl2 was exposed to ambient atmosphere for several hours.

[0061] In the drawings and specification, certain embodiments of the invention have been disclosed, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

1. A compound having the formula MoO2Cl2 and in anhydrous crystalline form, having an orthorhombic crystal system and the following unit cell dimensions: α=90° β=90° γ=90°.

2. The compound of claim 1, which exhibits a powder XRD pattern having one or more peaks at 12.94, 23.64, 26.10, 39.50 and / or 40.28 ± 0.04° 2θ.

3. A method for preparing MO y X z A method for preparing a compound wherein M is selected from molybdenum and tungsten, and X is selected from chlorine, fluorine, bromine and iodine, y is 1 or 2, and z is 2 or 4, the method comprising making a compound of the formula: contacting with at least one compound of formula AX at a temperature of 200° C. to 900° C., wherein A is selected from the group consisting of Group 1 elements, Group 2 elements, transition metals and main group elements, wherein the compound of formula AX comprises a eutectic blend of an alkali halide and an alkaline earth halide, and wherein the ratio of each of the alkali halide and the alkaline earth halide varies between 10:1 and 1:

10.

4. The method according to claim 3, wherein A is selected from lithium, sodium and potassium.

5. The process according to claim 3, wherein X is chlorine.

6. The method of claim 3, wherein A is selected from the group consisting of magnesium, calcium, strontium, barium, beryllium, scandium, titanium, vanadium and chromium.

7. The method of claim 3, wherein the compound of formula AX comprises a mixture of lithium chloride and potassium chloride.

8. The method according to claim 3, further comprising collecting the formula MO in vapor form y X z Compound and cooling the vapor to form the formula MO in crystalline form y X z Compound.

9. The method according to claim 3, wherein the formula MO y X z The compound is MoO2Cl2.

10. The method according to claim 3, wherein the formula MO y X z The compound is MoOCl4.

11. The method according to claim 3, wherein the formula MO y X z The compound is WO2Cl2.

12. The method according to claim 3, wherein the formula MO y X z The compound is WOCl4.

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