Ultra-high purity molybdenum powder for large-scale integrated circuits and preparation method thereof

Abstract

A method for preparing ultra-high purity molybdenum powder for large-scale integrated circuits comprises the following steps: using ammonium paramolybdate prepared by a crystallization method as a raw material, the chemical formula of which is (NH 4 )6Mo 7 O 24 ·4H 2 O; the raw material ammonium paramolybdate is placed in a tubular furnace and heated, MoO 3 Ammonia water is added for leaching to form an ammonium molybdate solution; the obtained ammonium molybdate solution is subjected to two-stage filtration to remove impurities; evaporation crystallization; crystallization drying; secondary purification and the like. The preparation method of ultra-high purity molybdenum powder for large-scale integrated circuits provided by the present invention has a simple process, high efficiency, and is easy to realize industrial production. In the production process, not only can the impurity elements in the raw materials be fully discharged, but also the secondary pollution in the process can be avoided. The prepared molybdenum powder has high purity and fully meets the requirements of large-scale integrated circuits. The obtained ultra-high purity molybdenum powder has a purity greater than 99.999% and a low content of key impurity elements, and is an ideal raw material for preparing molybdenum sputtering targets for large-scale integrated circuits.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-high purity metal material manufacturing, and specifically relates to ultra-high purity molybdenum powder for large-scale integrated circuits and a preparation method thereof. Background Art

[0002] Molybdenum is a refractory metal with a melting point of 2625℃. Because molybdenum has strong tensile strength and creep strength at high temperature, good thermal conductivity, electrical conductivity, and good corrosion resistance, etc. Therefore, molybdenum is widely used in chemical, metallurgical, and aerospace industries. With the rapid development of high-tech, molybdenum materials have been applied in many new ways. For example, ultra-high purity molybdenum is used in the microelectronics industry. At present, high-purity molybdenum is widely used as wiring material in the field of flat panel displays. In the field of large-scale integrated circuits, there is also a trend to use ultra-high purity molybdenum as wiring material because the film formed by molybdenum has low stress, good high-temperature stability, and good electrical conductivity.

[0003] Large-scale integrated circuits have very high requirements for the purity of materials, especially for alkaline metal elements such as Na, K, etc.; heavy metal elements such as Fe, Ni, Cr, etc.; radioactive elements such as U and Th, and gas elements such as oxygen. The lower the better. These elements are harmful elements in integrated circuits and must be removed as much as possible. For example, elements such as Fe and Ni affect the film formation of integrated circuits; oxygen affects the resistivity of the film; Na and K are prone to drift in the film.

[0004] Generally speaking, in the field of large-scale integrated circuits, molybdenum thin films are prepared by physical vapor deposition. After ultra-high purity molybdenum is prepared into a sputtering target, the molybdenum atoms are deposited on the silicon wafer by sputtering (i.e. physical vapor deposition) to form a thin film. To prepare ultra-high purity molybdenum sputtering targets, it is necessary to first prepare ultra-high purity molybdenum powder.

[0005] Therefore, the preparation of ultra-high purity molybdenum powder is the primary link. At present, the preparation of ordinary industrial molybdenum powder is relatively mature. The production methods of molybdenum powder mainly include reduction method, hydroxyl thermal decomposition method and molybdenum chloride steam method. Among them, the commonly used method for industrial production is reduction method. The industrial production of high-purity molybdenum powder generally adopts the method of purifying ammonium paramolybdate, calcining ammonium paramolybdate to obtain molybdenum oxide, and finally reducing the molybdenum oxide.

[0006] With the development of large-scale integrated circuits, the integration level continues to increase, and the electrode wiring continues to develop towards miniaturization, and has now reached the level of 3 nanometers. Molybdenum, as a material with low stress and high temperature resistance, has always been a potential metal electrode wiring material. However, under the limitation of a line width of only a few nanometers, the purity requirements of the material are very stringent, especially for alkaline metal elements such as Na, K, etc.; heavy metal elements such as Fe, Ni, Cr, etc.; radioactive elements such as U and Th, and gas elements such as oxygen. The lower the better. Therefore, there is an urgent need for a high-purity molybdenum powder raw material and preparation method that can meet the requirements of large-scale integrated circuits of 3 nanometers and below, so that it can meet the following requirements at the same time:

[0007] The material purity reaches 5N level, that is, the sum of metal impurities is less than 10ppm;

[0008] Fe content is less than 5ppm;

[0009] Ni content is less than 2ppm;

[0010] Cr element content is less than 3ppm;

[0011] The content of Na and K elements is less than 0.5ppm;

[0012] The contents of U and Th are both less than 0.001ppm.

[0013] Patent application No. 202210232753.X published by the State Intellectual Property Office of China discloses a high-purity molybdenum powder for sputtering target and its preparation method; however, the high-purity molybdenum powder produced by it does not reach the 5N grade, and its key elements do not meet the requirements for use in large-scale integrated circuits, and can only be used in fields such as flat-panel displays;

[0014] Patent application No. 201410051664.0 discloses a high-purity molybdenum powder and a preparation method thereof; the characteristics are that the oxygen content of the high-purity molybdenum powder is 1-1000ppm, the purity is 99.99-99.999%, and the Fisher particle size is 0.5-10 microns. Therefore, the molybdenum powder prepared by the method does not reach the purity of 5N, nor does it meet the use requirements of large-scale integrated circuits. Summary of the invention

[0015] To achieve the above object, the technical solution of the present invention is as follows:

[0016] A method for preparing ultra-high purity molybdenum powder for large-scale integrated circuits comprises the following steps:

[0017] The raw material is ammonium paramolybdate prepared by crystallization method, and its chemical formula is (NH4)6Mo7O 24 4H2O; the purity of the ammonium paramolybdate is above 99.95%;

[0018] Step 1: Place ammonium paramolybdate in a quartz tube and heat it in a tubular furnace:

[0019] The heating furnace is divided into three temperature zones, and ammonium paramolybdate passes through the three temperature zones in sequence:

[0020] The first temperature zone is set at a temperature range of 220-226°C, preferably 223°C; in this temperature zone, ammonium paramolybdate loses its crystal water;

[0021] The second temperature zone has a set temperature range of 235-245°C, preferably 240°C; ammonia and water are produced in this temperature zone;

[0022] The third temperature zone is set at a temperature range of 315-325°C, preferably 320°C. In this temperature zone, the ammonium ions are completely decomposed to form molybdenum trioxide.

[0023] After step 1, ammonium paramolybdate is completely decomposed into molybdenum oxide MoO3;

[0024] The heating rate of ammonium paramolybdate is 8-12°C / min, preferably 10°C / min;

[0025] Step 2: adding ammonia water to the MoO3 obtained in step 1 for leaching to form an ammonium molybdate solution;

[0026] The reaction tank is made of fiberglass;

[0027] Excess ammonia is discharged to the ammonia waste gas treatment system;

[0028] Step 3: The obtained ammonium molybdate solution is subjected to two-stage filtration to remove impurities, and the filter tank is made of polypropylene;

[0029] The filter material used in the first stage of filtration is polypropylene fiber; the precision is 10 microns;

[0030] The filter material used in the second stage of filtration is polypropylene fiber with a precision of 1 micron;

[0031] The pressure difference used for filtration is 2-4 bar, preferably 3 bar; the liquid flow rate is controlled at 10-40 L / min, preferably 20 L / min;

[0032] Step 4: Evaporating and crystallizing the solution obtained in step 3, controlling the concentration ratio to 40% to 80%, the container used for evaporation and crystallization is made of glass fiber reinforced plastics, and preferably, the inner layer of the reaction tank is made of HALAR material to prevent pollution;

[0033] The evaporation temperature is controlled at 80-110℃;

[0034] Step 5: Place the particles obtained by crystallization in step 4 into a drying furnace for slow drying;

[0035] The characteristics of the drying furnace are:

[0036] 1) Control the heating temperature to 60-150°C; preferably 110°C;

[0037] 2) The air in the furnace must be filtered through a HEPA filter; it enters from one side of the furnace and is discharged from the other side;

[0038] 3) The tray used is molybdenum with a purity of more than 99.95%;

[0039] After drying, once purified ammonium paramolybdate is obtained;

[0040] Step 6: Repeat the above steps 1 to 5 to obtain secondary purified ammonium paramolybdate;

[0041] Step 7: Repeat step 1 to decompose the secondary purified ammonium paramolybdate into molybdenum oxide;

[0042] Step 8: Place the molybdenum oxide obtained in step 7 into a molybdenum boat with a purity greater than 99.95%, and reduce it with 5N grade hydrogen; the hydrogen must pass through a molecular sieve dryer to ensure that its dew point reaches below -50°C;

[0043] A two-stage reduction method is used, with the first stage reaction temperature being 400-600°C; the second stage reaction temperature being 800-1400°C; ultra-high purity molybdenum powder can be obtained after the reaction is completed.

[0044] The method for preparing ultra-high purity molybdenum powder for large-scale integrated circuits according to claim 1 is characterized in that: in step 1, the heating furnace body is made of stainless steel 304 or 316; the heating furnace heating wire is made of molybdenum strip or nickel-chromium (80 / 20wt%) alloy.

[0045] The method for preparing ultra-high purity molybdenum powder for large-scale integrated circuits according to claim 2 is characterized in that: in step 2, the inner layer of the reaction tank is a HALAR material, and the HALAR material is an alternating copolymer prepared by copolymerizing ethylene and chlorotrifluoroethylene in an equimolar ratio.

[0046] A high-purity molybdenum powder for large-scale integrated circuits, characterized by:

[0047] The material purity reaches 5N level, that is, the sum of metal impurities is less than 10ppm;

[0048] Fe content is less than 5ppm;

[0049] Ni content is less than 2ppm;

[0050] Cr element content is less than 3ppm;

[0051] The content of Na and K elements is less than 0.5ppm;

[0052] The contents of U and Th are both less than 0.001ppm.

[0053] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects: the preparation method of ultra-high purity molybdenum powder for large-scale integrated circuits provided by the present invention has simple process, high efficiency and is easy to realize industrial production. In the production process, not only can the impurity elements in the raw materials be fully discharged, but also the secondary pollution in the process can be avoided. The prepared molybdenum powder has high purity and fully meets the requirements of large-scale integrated circuits. The ultra-high purity molybdenum powder prepared by the above preparation method has a purity greater than 99.999% and a low content of key impurity elements. It is an ideal raw material for preparing molybdenum sputtering targets for large-scale integrated circuits.

[0054] Instruction Manual

[0055] Figure 1 The present invention is a flow chart of ultra-high purity molybdenum powder for large-scale integrated circuits and a preparation method thereof. DETAILED DESCRIPTION

[0056] The present invention will be further explained below in conjunction with specific implementation modes. It should be understood that the following specific implementation modes are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0057] Embodiment 1:

[0058] Ammonium paramolybdate prepared by a crystallization method is selected as a raw material, and the purity of the ammonium paramolybdate is above 99.95%. After analysis, the main components of the ammonium paramolybdate are shown in Table 1;

[0059] Step 1: Place ammonium paramolybdate in a quartz tube and heat it in a tubular furnace: the furnace body of the heating furnace is made of stainless steel 304; the heating wire of the heating furnace is made of molybdenum strip;

[0060] The heating furnace is divided into three temperature zones, and ammonium paramolybdate passes through the three temperature zones in sequence:

[0061] The first temperature zone is set at 223°C; the second temperature zone is set at 240°C; the third temperature zone is set at 320°C; after heating in these three temperature zones, ammonium paramolybdate is decomposed into molybdenum trioxide.

[0062] The temperature increase rate of ammonium paramolybdate was set to 10° C. / min.

[0063] Step 2: adding ammonia water to the MoO3 obtained in step 1 for leaching to form an ammonium molybdate solution;

[0064] The reaction tank is made of fiberglass and the inner layer of the reaction tank is made of HALAR material;

[0065] Step 3: The obtained ammonium molybdate solution is subjected to two-stage filtration to remove impurities, and the filter tank is made of polypropylene;

[0066] The filter material used in the first stage of filtration is polypropylene fiber; the precision is 10 microns;

[0067] The filter material used in the second stage of filtration is polypropylene fiber with a precision of 1 micron;

[0068] The pressure difference used for filtration is 3 bar; the liquid flow rate is controlled at 20 L / min;

[0069] Step 4: Evaporate and crystallize the solution obtained in step 3, and control the concentration ratio to 60%. The container used for evaporation and crystallization is made of fiberglass and the inner layer of the reaction tank is made of HALAR material to prevent pollution.

[0070] The evaporation temperature is controlled at 100°C;

[0071] Step 5: Place the particles obtained by crystallization in step 4 into a drying furnace for slow drying;

[0072] The characteristics of the drying furnace are:

[0073] 1) Control the heating temperature to 110°C;

[0074] 2) The air in the furnace must be filtered through a HEPA filter; it enters from one side of the furnace and is discharged from the other side;

[0075] 3) The tray used is molybdenum with a purity of more than 99.95%;

[0076] After drying, once purified ammonium paramolybdate is obtained;

[0077] Step 6: Repeat the above steps 1-5 to obtain secondary purified ammonium paramolybdate;

[0078] Step 7: Repeat step 1 to decompose the secondary purified ammonium paramolybdate into molybdenum oxide;

[0079] Step 8: Place the molybdenum oxide obtained in step 7 into a molybdenum boat with a purity greater than 99.95%, and reduce it with 5N grade hydrogen; the hydrogen must pass through a molecular sieve dryer to ensure that its dew point reaches below -50°C.

[0080] The two-stage reduction method is adopted, the reaction temperature of the first stage is 600℃; the reaction temperature of the second stage is 1200℃; after the reaction is completed, ultra-high purity molybdenum powder can be obtained. The composition of the high purity molybdenum powder is analyzed, and the results are shown in Table 1.

[0081] Embodiment 2: All steps are the same as those in Embodiment 1, but some steps use different parameters, as follows:

[0082] Step 1: The heating furnace is divided into three temperature zones, and ammonium paramolybdate passes through the three temperature zones in sequence:

[0083] The first temperature zone is set at 225°C; the second temperature zone is set at 245°C; the third temperature zone is set at 325°C;

[0084] Step 4: Evaporating and crystallizing the solution obtained in step 3, and controlling the concentration ratio to 45%;

[0085] The evaporation temperature is controlled at 90°C;

[0086] Other steps and parameters are consistent with those in Example 1.

[0087] Finally, the obtained high-purity molybdenum powder was analyzed and the results are shown in Table 1.

[0088] Embodiment 3: All steps are the same as those in Embodiment 1, but some steps use different parameters, as follows:

[0089] Step 3: The obtained ammonium molybdate solution is subjected to two-stage filtration to remove impurities. The filter tank is made of polypropylene. The filter material used in the first stage of filtration is polypropylene fiber with a precision of 10 microns.

[0090] The filter material used in the second stage of filtration is polypropylene fiber with a precision of 1 micron;

[0091] The pressure difference used for filtration is 2 bar, and the liquid flow rate is controlled at 30 L / min;

[0092] Step 4: Evaporate and crystallize the solution obtained in step 3, and control the concentration ratio to 45%. The container used for evaporation and crystallization is made of fiberglass. Preferably, the inner layer of the reaction tank is made of HALAR material to prevent pollution.

[0093] The evaporation temperature is controlled at 85°C;

[0094] Step 5: Place the particles obtained by crystallization in step 4 into a drying furnace for slow drying;

[0095] The characteristics of the drying furnace are:

[0096] 1) Control the heating temperature to 90°C;

[0097] 2) The air in the furnace must be filtered through a HEPA filter; it enters from one side of the furnace and is discharged from the other side;

[0098] 3) The tray used is molybdenum with a purity of more than 99.95%;

[0099] Other steps and parameters are consistent with those in Example 1.

[0100] Finally, the obtained high-purity molybdenum powder was analyzed and the results are shown in Table 1.

[0101] Comparative Example 1:

[0102] Steps 1-5 were performed to obtain purified ammonium paramolybdate; then steps 1-5 were not repeated, but steps 7 and 8 were directly performed, and the parameters were exactly the same as those in Example 1. Finally, the obtained molybdenum powder was analyzed, and the results are shown in Table 1.

[0103]

[0104] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing ultra-high purity molybdenum powder for large-scale integrated circuits, characterized in that: The following steps are involved: The raw material is ammonium paramolybdate prepared by crystallization method, and its chemical formula is (NH4)6Mo7O 24 4H2O; the purity of the ammonium paramolybdate is above 99.95%; Step 1: Place ammonium paramolybdate in a quartz tube and heat it in a tubular furnace: The heating furnace is divided into three temperature zones, and ammonium paramolybdate passes through the three temperature zones in sequence: The first temperature zone has a set temperature range of 220-226°C; in this temperature zone, ammonium paramolybdate loses its crystal water; The second temperature zone has a set temperature range of 235-245°C; ammonia and water are produced in this temperature zone; The third temperature zone has a set temperature range of 315-325°C. In this temperature zone, the ammonium ions are completely decomposed to form molybdenum trioxide. After step 1, ammonium paramolybdate is completely decomposed into molybdenum oxide MoO3; The heating rate of ammonium paramolybdate is 8-12 ºC / min; Step 2: adding ammonia water to the MoO3 obtained in step 1 for leaching to form an ammonium molybdate solution; The reaction tank is made of fiberglass; Excess ammonia is discharged to the ammonia waste gas treatment system; Step 3: The obtained ammonium molybdate solution is subjected to two-stage filtration to remove impurities, and the filter tank is made of polypropylene; The filter material used in the first stage of filtration is polypropylene fiber; the precision is 10 microns; The filter material used in the second stage of filtration is polypropylene fiber with a precision of 1 micron; The pressure difference used for filtration is 2-4 bar; the liquid flow rate is controlled at 10-40L / min; Step 4: Evaporate and crystallize the solution obtained in step 3, and control the concentration ratio to 40% to 80%. The container used for evaporation and crystallization is made of fiberglass, and the inner layer of the reaction tank is made of HALAR material to prevent pollution; The evaporation temperature is controlled at 80-110 ºC; Step 5: Place the particles obtained by crystallization in step 4 into a drying furnace for slow drying; The characteristics of the drying furnace are: 1) Control the heating temperature to 60-150ºC; 2) The air in the furnace must be filtered through a HEPA filter; it enters from one side of the furnace and is discharged from the other side; 3) The tray used is molybdenum with a purity of more than 99.95%; After drying, once purified ammonium paramolybdate is obtained; Step 6: Repeat the above steps 1 to 5 to obtain secondary purified ammonium paramolybdate; Step 7: Repeat step 1 to decompose the secondary purified ammonium paramolybdate into molybdenum oxide; Step 8: Place the molybdenum oxide obtained in step 7 into a molybdenum boat with a purity greater than 99.95%, and reduce it with 5N grade hydrogen; the hydrogen must pass through a molecular sieve dryer to ensure that its dew point is below -50°C; A two-stage reduction method is used, with the first stage reaction temperature being 400-600 ºC; the second stage reaction temperature being 800-1400 ºC; ultra-high purity molybdenum powder can be obtained after the reaction is completed.

2. A method for preparing ultra-high purity molybdenum powder for large-scale integrated circuit according to claim 1, characterized in that: In step 1, the furnace body of the heating furnace is made of stainless steel 304 or 316; the heating wire of the heating furnace is made of molybdenum strip or nickel-chromium (80 / 20wt%) alloy.

3. A method for preparing ultra-high purity molybdenum powder for large-scale integrated circuit according to claim 2, characterized in that: In step 2, the inner layer of the reaction tank is HALAR material, and the HALAR material is an alternating copolymer prepared by copolymerizing ethylene and chlorotrifluoroethylene in an equimolar ratio.

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