A method for purifying an electronic grade tungsten or molybdenum precursor

Abstract

The application discloses a purification method of electronic-grade tungsten or molybdenum precursor and belongs to the technical field of group VI transition metal precursors. The method comprises the following steps: in an inert gas atmosphere, heating and pressurizing a solid tungsten or molybdenum precursor crude product to convert it into a liquid phase and distilling the liquid-phase precursor; and further comprising the step of cooling the distillate to convert it into an electronic-grade tungsten / molybdenum precursor; the distillate is in a liquid phase or a gas phase. The purification method has the advantages of high impurity separation degree, short process time, high product bulk density, reduced requirements of process on the capacity design of a reaction kettle and improved purification process efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of Group VI transition metal precursors, and particularly relates to a purification method of an electronic-grade tungsten or molybdenum precursor. BACKGROUND

[0002] Group VI transition metals (such as molybdenum and tungsten) play a crucial role in semiconductor manufacturing processes, especially in the formation of key structures of advanced logic chips, 3D-NAND memory, and DRAM devices, which can be used as core components such as metal films, barrier layers, adhesion layers, and gate electrodes.

[0003] Taking molybdenum as an example, molybdenum has become a key research direction in the semiconductor field due to its low resistivity, refractory, high mechanical strength, excellent thermal stability, and high thermal conductivity. In the front-end-of-line (FEOL) process, molybdenum can provide reliable electrical connection physical support for transistors and active devices due to its mechanical strength and thermal stability. In the back-end-of-line (BEOL) process, good electrical conductivity and low resistivity enable it to be used as interconnection material, and its high thermal conductivity can effectively solve the heat dissipation problem of interconnection layers, improving the performance and reliability of semiconductor devices. In addition, compared with tungsten with a three-dimensional structure, a single layer of molybdenum has a two-dimensional structure, which can provide a larger surface area at the same thickness, further optimizing device performance, especially in the field of 3D-NAND memory, there is a trend of replacing part of the tungsten back-end material with molybdenum. For example, Samsung has introduced molybdenum as a replacement for tungsten in the metallization process of the 9th generation V-NAND flash memory technology.

[0004] Molybdenum-based or tungsten-based thin films can usually be prepared by chemical vapor deposition (CVD) process, which vaporizes and transports molybdenum or tungsten-containing precursors to the substrate surface, and forms a thin film through decomposition and surface reaction. With the continuous increase in device integration density and the continuous increase in the aspect ratio of contact holes, how to uniformly deposit a metal layer in a high aspect ratio structure has become one of the key challenges of thin film deposition process. The commonly used process is to first uniformly form a thin metal seed layer on the inner wall of the structure by atomic layer deposition (ALD) method, and then fill the contact plug or interconnection line by CVD or electroplating method. In CVD and ALD processes, the use of ultra-pure precursors is the guarantee for obtaining molybdenum-based or tungsten-based thin films with excellent performance.

[0005] The current market generally uses a pressure reduction sublimation process to purify solid molybdenum or tungsten precursors. This processing method generally has three major bottlenecks: first, it requires extremely high vacuum degree of the equipment and low single sublimation yield; second, it is difficult to control impurity elements, and multiple sublimations are often required to achieve ≥6N purity; third, the bulk density of molybdenum precursor products is usually only about 0.3 g / cm³, which is far lower than the standard of 1 g / cm³ or more required for wafer manufacturing, and cannot directly meet the requirements of high-end semiconductor processes. SUMMARY

[0006] The present application aims to provide a purification method of electronic-grade tungsten or molybdenum precursor to solve the problems of extremely strict equipment conditions, multiple purification times, waste of manpower and resources, and low bulk density of part of the products in the prior art process of purifying tungsten or molybdenum precursor.

[0007] To solve the above problems, first, the present application provides a purification method of electronic-grade tungsten or molybdenum precursor, which comprises the step of: converting a solid-phase tungsten or molybdenum precursor crude product into a liquid phase under an inert gas atmosphere and distilling the liquid-phase precursor.

[0008] Further, the tungsten or molybdenum precursor has the following structural formula (I):

[0009] Structural formula (I): MO a X b ;

[0010] wherein M is W or Mo, X is halogen selected from F or Cl, a is 0, 1, or 2, and b is 2, 4, or 5.

[0011] Further, the molybdenum precursor is any one of MoO2F2, MoOF4, MoO2Cl2, MoOCl4, or MoCl5; and the tungsten precursor is any one of WO2F2, WOF4, WCl5, or WOCl4.

[0012] Further, the purity of the tungsten or molybdenum precursor crude product is ≥4N, and the water content is ≤1000 ppm. If the purity of the crude product is too low, it will exceed the load of the above purification method, and more purification treatments, such as two, three, four, or the like, are required to obtain a product with a purity of 6N or above. In addition, the process of liquefying the product by heating is the process of decomposing the product hydrate into HCl, which is also a purification treatment of the crude product. If the water content of the product is too high, it will affect the water content of the product and the morphology of the sublimated product.

[0013] Further, the temperature and pressure for heating and pressurizing are temperature and pressure that can convert the tungsten or molybdenum precursor crude product from a solid phase to a liquid phase without directly converting it to a gas phase.

[0014] Further, the tungsten or molybdenum precursor crude product can be distilled in a solid-liquid mixed state (see FIG. 1), or after being completely converted into a liquid phase (see FIG. 2). Figure 2 Figure 1 Here, “completely converted into a liquid phase” does not mean “100% of the tungsten or molybdenum precursor crude product is converted into a liquid phase” in the literal sense, but should be understood as “the effective tungsten or molybdenum precursor can be regarded as completely converted into a liquid phase”. Since the tungsten or molybdenum precursor crude product contains non-melting solids such as MoO3, or impurities generated by heating and decomposition, it is impossible to achieve a 100% conversion in the literal sense. ​

[0015] Further, the distillation is performed at the elevated temperature and the pressurized pressure.

[0016] In one embodiment, the molybdenum precursor is MoO2Cl2, the elevated temperature is 200-350℃, and the pressurized pressure is 0.1-2MPa; in one embodiment, the molybdenum precursor is MoO2Cl2, the elevated temperature is 210-300℃, and the pressurized pressure is 0.2-1.5MPa. In one embodiment, the molybdenum precursor is MoO2Cl2, the elevated temperature is 220-280℃, and the pressurized pressure is 0.3-1.0MPa. In one embodiment, the molybdenum precursor is MoO2Cl2, the elevated temperature is 230-250℃, and the pressurized pressure is 0.4-0.7MPa.

[0017] In one embodiment, the molybdenum precursor is MoOCl4, the elevated temperature is 150-220℃, and the pressurized pressure is 0.2-3MPa; in one embodiment, the molybdenum precursor is MoOCl4, the elevated temperature is 160-200℃, and the pressurized pressure is 0.3-2MPa. In one embodiment, the molybdenum precursor is MoOCl4, the elevated temperature is 165-180℃, and the pressurized pressure is 0.5-1MPa.

[0018] In one embodiment, the molybdenum precursor is MoCl5, the elevated temperature is 200-270℃, and the pressurized pressure is 0.5-4MPa; in one embodiment, the molybdenum precursor is MoCl5, the elevated temperature is 220-250℃, and the pressurized pressure is 1-3MPa.

[0019] In one embodiment, the tungsten precursor is WCl5, the elevated temperature is 280-360℃, and the pressurized pressure is 0.5-5MPa; in one embodiment, the tungsten precursor is WCl5, the elevated temperature is 300-340℃, and the pressurized pressure is 0.8-2MPa.

[0020] In one embodiment, the tungsten precursor is WOCl4, the elevated temperature is 250-280℃, and the pressurized pressure is 0.2-1MPa.

[0021] Further, the method further comprises the step of cooling the distillate to convert it into an electronic-grade tungsten / molybdenum precursor; the distillate is in liquid phase or gas phase.

[0022] In one embodiment, an external cooling source is used to cool the distillate, which includes but is not limited to condensed water, cold air, other condensed medium (ethylene glycol, dry ice, liquid nitrogen), etc.

[0023] In one embodiment, the distillate is cooled by natural cooling.

[0024] In a preferred embodiment, the method comprises the following steps: a) cooling the distilled gaseous substance to obtain a liquid phase distillate; b) cooling the liquid phase distillate to room temperature to obtain an electronic grade tungsten / molybdenum precursor.

[0025] Further, the cooling temperature in step a) is below 270°C, preferably 50-270°C. In an embodiment, when the molybdenum precursor is MoO2Cl2, the cooling temperature in step a) is below 250°C, preferably 180-230°C. In an embodiment, when the molybdenum precursor is MoOCl4, the cooling temperature in step a) is below 95°C, preferably 60-95°C. In an embodiment, when the molybdenum precursor is MoCl5, the cooling temperature in step a) is below 190°C, preferably 150-190°C. In an embodiment, when the tungsten precursor is WOCl4, the cooling temperature in step a) is below 200°C, preferably 90-200°C. In an embodiment, when the tungsten precursor is WCl5, the cooling temperature in step a) is below 340°C, preferably 280-340°C.

[0026] Further, the cooling in step b) is by natural cooling.

[0027] Further, the bulk density of the electronic grade tungsten or molybdenum precursor is ≥1.1 g / cm 3 , preferably ≥1.5 g / cm 3 , more preferably ≥2.0 g / cm 3 .

[0028] In an embodiment, the bulk density of the electronic grade tungsten or molybdenum precursor is ≥2.4 g / cm 3 .

[0029] Further, the purity of the electronic grade tungsten or molybdenum precursor is ≥6N.

[0030] Further, the inert gas atmosphere includes but is not limited to N2, He, Ar, etc.

[0031] Advantages of the present application:

[0032] (1) According to the three-phase state theory of matter, the solid phase electronic grade tungsten or molybdenum precursor will not melt under normal pressure heating, but only sublimate. Adjusting the environmental pressure to heat the solid phase electronic grade tungsten or molybdenum precursor to a liquid phase and using distillation to purify the product can solve the defects of poor impurity separation degree, long process time, and small product bulk density of conventional purification methods (such as reduced pressure sublimation). The present application completes a series of treatments on the solid phase precursor crude product to complete the phase transition, and the bulk density of the obtained molybdenum product can reach 2.7 g / cm 3 , which reduces the design requirements of the process on the capacity of the reaction kettle, and is beneficial to improving the efficiency of the purification process.

[0033] (2) The application uses distillation method to purify solid-phase electronic-grade tungsten or molybdenum precursor, which has high separation degree for impurities and can effectively reduce the number of purification; in the process, the precursor is transferred in liquid phase or gas phase which is easier to control, and more crude product can be processed in the same time (1 kg of precursor with purity ≥ 6N can be obtained in 6-10h on average). BRIEF DESCRIPTION OF DRAWINGS

[0034] By way of example only, some embodiments of the application are described herein with reference to the accompanying drawings. It should be emphasized that the embodiments are illustrated by way of example and for purposes of illustrative discussion of embodiments of the application, so as to allow those persons skilled in the art to better understand how the embodiments of the application can be put into practice.

[0035] Figure 1 Method flowchart of some embodiments of the application.

[0036] Figure 2 Method flowchart of some other embodiments of the application.

[0037] Figure 3 H NMR chart of crude MoO2Cl2 product of Example 1. 1 H NMR chart.

[0038] Figure 4 H NMR chart of electronic-grade MoO2Cl2 product of Example 2. 1 H NMR chart. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0040] Example 1

[0041] This embodiment provides a purification method of electronic-grade molybdenum precursor MoO2Cl2 (refer to the attached Figure 2 ), which comprises:

[0042] S1, place 4N-grade MoO2Cl2 crude product (water content ≤ 1000 ppm, Fe element ≤ 30 ppm, W element ≤ 15 ppm) in a reaction kettle, and protect the reaction kettle by passing nitrogen gas; heat the reaction kettle to 250℃±3℃, and control the pressure in the kettle to 0.5 MPa, so that the crude product of MoO2Cl2 is converted into liquid phase while distillation is carried out at this temperature and pressure.

[0043] S2, cooling the distilled gaseous substance to 230℃±3℃ to obtain liquid phase distillate.

[0044] S3, naturally cooling the liquid phase distillate to change it into solid phase, collecting the solid phase substance to obtain electronic grade MoO2Cl2 precursor.

[0045] In the above method, the electronic grade MoO2Cl2 has a metal purity of 6N and a bulk density of 2.4g / cm 3 .

[0046] Example 2

[0047] The present example provides a method for purifying electronic grade molybdenum precursor MoO2Cl2, which comprises:

[0048] S1, placing 4N grade MoO2Cl2 crude product (water content ≤1000ppm, Fe element ≤30ppm, W element ≤15ppm) in a reaction kettle, and passing nitrogen gas into the reaction kettle for protection; heating the reaction kettle to 220℃±3℃, and controlling the pressure in the kettle to 1.0MPa, so that the crude product of MoO2Cl2 changes into liquid phase while distillation is carried out at this temperature and pressure.

[0049] S2, cooling the distilled gaseous substance to 200℃±3℃ to obtain liquid phase distillate.

[0050] S3, naturally cooling the liquid phase distillate to change it into solid phase, collecting the solid phase substance to obtain electronic grade MoO2Cl2 precursor.

[0051] In the above method, the electronic grade MoO2Cl2 has a metal purity of 6N and a bulk density of 2.7g / cm 3 .

[0052] Figure 1 Figure 3 is the H NMR chart of MoO2Cl2 crude product of the present example. 1 The proton peak of water in MoO2Cl2 crude product is shifted to about 5.5ppm; the water content of the crude product is 400ppm. Figure 4 Figure 2 1 is the H NMR chart of electronic grade MoO2Cl2 of the present example. Figure 3 Figure 2 Figure 4 It can be seen that the electronic grade MoO2Cl2 treated by the purification method of the present application basically does not contain water, 1 and the H peak of water does not appear in the H NMR chart.

[0053] Example 3

[0054] The present example provides a method for purifying electronic grade molybdenum precursor MoO2Cl2, which comprises:

[0055] S1, 4N MoO2Cl2 crude product (water content ≤1000 ppm, Fe element ≤30 ppm, W element ≤15 ppm) was placed in a reaction kettle, and nitrogen was passed into the reaction kettle for protection; the reaction kettle was heated to 250℃±3℃, and the pressure in the kettle was controlled at 0.1 MPa, so that the crude MoO2Cl2 was converted into liquid phase, and distillation was carried out at this temperature and pressure.

[0056] S2, the gaseous material distilled out was cooled to 220℃±3℃ to obtain liquid phase distillate.

[0057] S3, the liquid phase distillate was naturally cooled to convert it into solid phase, and the solid phase material was collected to obtain electronic grade MoO2Cl2 precursor.

[0058] In the above method, the metal purity of electronic grade MoO2Cl2 is 6N, and the bulk density is 1.8g / cm 3 .

[0059] Example 4

[0060] The embodiment provides a purification method of electronic grade molybdenum precursor MoO2Cl2, which comprises the following steps:

[0061] S1, 4N MoO2Cl2 crude product (water content ≤1000 ppm, Fe element ≤30 ppm, W element ≤15 ppm) was placed in a reaction kettle, and nitrogen was passed into the reaction kettle for protection; the reaction kettle was heated to 250℃±3℃, and the pressure in the kettle was controlled at 0.1 MPa, so that the crude MoO2Cl2 was converted into liquid phase, and distillation was carried out at this temperature and pressure.

[0062] S2, the gaseous material distilled out was cooled to 220℃±3℃ to obtain liquid phase distillate.

[0063] S3, the liquid phase distillate was naturally cooled to convert it into solid phase, and the solid phase material was collected to obtain electronic grade MoO2Cl2 precursor.

[0064] In the above method, the metal purity of electronic grade MoO2Cl2 is 6N, and the bulk density is 1.8g / cm 3 .

[0065] Example 5

[0066] The embodiment provides a purification method of electronic grade tungsten precursor WOCl4, which comprises the following steps:

[0067] S1, place 4N grade WOCl4 crude product (water content ≤1000ppm) in a reaction kettle, and protect the reaction kettle by passing nitrogen gas into it; heat the reaction kettle to 280℃±3℃, and control the pressure in the kettle to be 0.4MPa, so that the WOCl4 crude product is converted into liquid phase, and distillation is carried out at this temperature and pressure.

[0068] S2, cool the gaseous material distilled out to 190℃±3℃ to obtain liquid phase distillate.

[0069] S3, naturally cool the liquid phase distillate so that it is converted into solid phase, and collect the solid phase material to obtain electronic grade WOCl4 precursor.

[0070] The metal purity of the electronic grade WOCl4 in the above method is 6N.

[0071] Example 6

[0072] The present example provides a method for purifying electronic grade tungsten precursor WCl5, which comprises:

[0073] S1, place 4N grade WCl5 crude product (water content ≤1000ppm) in a reaction kettle, and protect the reaction kettle by passing nitrogen gas into it; heat the reaction kettle to 320℃±3℃, and control the pressure in the kettle to be 1.0MPa, so that the WCl5 crude product is converted into liquid phase, and distillation is carried out at this temperature and pressure.

[0074] S2, cool the gaseous material distilled out to 220℃±3℃ to obtain liquid phase distillate.

[0075] S3, naturally cool the liquid phase distillate so that it is converted into solid phase, and collect the solid phase material to obtain electronic grade WCl5 precursor.

[0076] The metal purity of the electronic grade WCl5 in the above method is 6N.

[0077] Example 7

[0078] The present example provides a method for purifying electronic grade tungsten precursor MoCl5, which comprises:

[0079] S1, place 4N grade MoCl5 crude product (water content ≤1000ppm) in a reaction kettle, and protect the reaction kettle by passing nitrogen gas into it; heat the reaction kettle to 230℃±3℃, and control the pressure in the kettle to be 1.5MPa, so that the MoCl5 crude product is converted into liquid phase, and distillation is carried out at this temperature and pressure.

[0080] S2, cool the gaseous material distilled out to 170℃±3℃ to obtain liquid phase distillate.

[0081] S3, the natural cooling liquid distillate is converted into solid phase, and the solid phase material is collected to obtain the electronic grade MoCl5 precursor.

[0082] In the above method, the purity of the product metal is 6N.

[0083] Comparative Example 1

[0084] The present comparative example provides a method for purifying an electronic grade molybdenum precursor MoO2Cl2, which comprises:

[0085] S1, under the protection of nitrogen, crude MoO2Cl2 (water content ≤1000 ppm, Fe element ≤30 ppm, W element ≤15 ppm) is introduced into a reaction kettle, and the temperature is slowly raised to 150°C to remove the solvent.

[0086] S2, after the solvent is evaporated, the reaction kettle is replaced with nitrogen twice, the temperature is maintained, and the reaction kettle is reduced to-0.1 MPa for sublimation, and the collection kettle is cooled to 0°C to collect the solid electronic grade MoO2Cl2 product.

[0087] In the above method, the metal purity of the electronic grade MoO2Cl2 is 5N, and the bulk density is 0.3 g / cm 3 .

[0088] It should be noted that in this paper, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0089] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for purifying an electronic grade tungsten or molybdenum precursor, characterized by, The method comprises the steps of: heating and pressurizing the solid tungsten or molybdenum precursor crude product in an inert gas atmosphere to convert it into a liquid phase and distilling the liquid phase precursor. The tungsten or molybdenum precursor has the following structural formula (I): Structural formula (I): MO a X b ; wherein M is W or Mo, X is halogen selected from F or Cl, a is 0, 1 or 2, and b is 2, 4 or 5.

2. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, characterized by, The heating temperature and the pressurizing pressure are the temperature and pressure that can convert the tungsten or molybdenum precursor crude product from a solid phase into a liquid phase without directly converting it into a gas phase.

3. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, characterized by, The molybdenum precursor is MoO2Cl2, the heating temperature is 200-350℃, and the pressurizing pressure is 0.1-2MPa; and / or, the molybdenum precursor is MoOCl4, the heating temperature is 150-220℃, and the pressurizing pressure is 0.2-3MPa; and / or, the molybdenum precursor is MoCl5, the heating temperature is 200-270℃, and the pressurizing pressure is 0.5-4MPa; and / or, the tungsten precursor is WCl5, the heating temperature is 280-360℃, and the pressurizing pressure is 0.5-5MPa.

4. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, characterized by, The molybdenum precursor is MoO2Cl2, the heating temperature is 210-300℃, and the pressurizing pressure is 0.2-1.5MPa; and / or, the molybdenum precursor is MoOCl4, the heating temperature is 160-200℃, and the pressurizing pressure is 0.3-2MPa; and / or, the molybdenum precursor is MoCl5, the heating temperature is 220-250℃, and the pressurizing pressure is 1-3MPa; and / or, the tungsten precursor is WCl5, the heating temperature is 300-340℃, and the pressurizing pressure is 0.8-2MPa; and / or, the tungsten precursor is WOCl4, the heating temperature is 250-280℃, and the pressurizing pressure is 0.2-1MPa.

5. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, characterized by, The molybdenum precursor is MoO2Cl2, the heating temperature is 220-280℃, and the pressurizing pressure is 0.3-1.0MPa; and / or, the molybdenum precursor is MoOCl4, the heating temperature is 165-180℃, and the pressurizing pressure is 0.5-1MPa.

6. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, characterized by, The molybdenum precursor is MoO2Cl2, the heating temperature is 230-250℃, and the pressurizing pressure is 0.4-0.7MPa.

7. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 1, wherein The method further comprises the step of cooling the distillate to convert it into a solid phase electronic grade tungsten / molybdenum precursor; the distillate is in a liquid phase or a gas phase.

8. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 7, characterized by, The method comprises the following steps: a) cooling the distilled gaseous substance to obtain a liquid phase distillate; b) cooling the liquid phase distillate to room temperature to obtain an electronic grade tungsten / molybdenum precursor.

9. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 8, characterized by, The cooling temperature in step a) is below 270℃.

10. The purification method of the electronic-grade tungsten or molybdenum precursor according to claim 7, wherein Bulk density of electronic grade tungsten or molybdenum precursor ≥ 1.1 g / cm3 3 .

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