Bismuth chloride, method for producing bismuth chloride, and method for producing a film

Abstract

Provided are bismuth chloride having a relatively high purity and a reduced content of specific metal impurities, a method for producing bismuth chloride, and a method for producing a film. The bismuth chloride contains BiCl3, has a purity of 99.999% by mass or more, and has a Pb content of less than 1 ppm by mass.

Description

[Technical Field]

[0001] This specification describes bismuth chlorides containing BiCl3, a method for producing the bismuth chlorides, and a method for producing films. [Background technology]

[0002] In the semiconductor industry, lithography technologies are becoming increasingly important as device scaling progresses. Resists with cross-linked metal-oxygen structures are attracting attention as the next-generation resist for next-generation EUV (extreme ultraviolet) exposure. Metal oxide resists (MORs) are considered promising, formed by coating organometallic complexes. Dry resists, formed by depositing organometallic complexes using vapor deposition techniques such as chemical vapor deposition (CVD), are also promising. Metal chlorides are often used as starting materials for the synthesis of organometallic complexes for MOR and dry resist applications.

[0003] In recent years, CVD and atomic layer deposition (ALD) have been used as film deposition techniques for microscopic areas such as transistors in cutting-edge logic devices, and metal chlorides have been attracting attention as precursors and raw materials for organometallic complex precursors.

[0004] A related technique is described in Patent Document 1, for example. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 171742 Summary of the Invention [Problem to be solved by the invention]

[0006] There are several candidate metal chlorides with different metal elements that are used in the EUV materials and film-forming materials for semiconductors mentioned above, but extremely high purity is required for any metal chloride. In particular, metal impurities tend to be easily mixed into metal chlorides due to the raw materials used in the production of metal chlorides. If they are contained in metal chlorides, they may diffuse into or react with the metal wiring, insulators, or semiconductor Si parts of the device to be fabricated, resulting in a decrease in semiconductor performance.

[0007] This specification provides bismuth chloride having a relatively high purity and a reduced content of metal impurities, a method for producing bismuth chloride, and a method for producing a film. [Means for solving the problem]

[0008] The bismuth chloride described in this specification contains BiCl3, has a purity of 99.999% by mass or more, and has a Pb content of less than 1 ppm by mass. For semiconductors It is something.

[0009] The method for producing bismuth chloride described in this specification contains BiCl3 For semiconductors This method for producing bismuth chloride includes a chlorination step in which a bismuth raw material having a purity of 99.999% by mass or more and a Pb content of 1 ppm by mass or less is reacted with chlorine at 150 to 600°C in a reaction tube while chlorine gas is being supplied.

[0010] The method for producing the film described in this specification involves forming the film using the above-mentioned bismuth chloride. [Effects of the Invention]

[0011] The bismuth chloride has a relatively high purity and a reduced content of certain metal impurities. [Brief explanation of the drawings]

[0012] [Figure 1] This is an equilibrium diagram of the chloride reaction between metallic bismuth and metallic silver and copper. [Figure 2] This is an equilibrium diagram for the chloride reaction of metallic bismuth and metallic lead. [Figure 3] FIG. 1 is a schematic diagram showing chlorination equipment used in the examples. [Figure 4] 1 is a PXRD profile of the bismuth chloride obtained in the example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes in detail the embodiments of the above-mentioned bismuth chloride. In one embodiment, the bismuth chloride contains BiCl (bismuth (III) chloride), has a purity of 99.999% by mass or more, and a Pb content of less than 1 ppm by mass. This bismuth chloride is highly pure and has a sufficiently low content of Pb, which can cause a decrease in semiconductor performance, making it particularly suitable for use as an EUV material or a film-forming material for semiconductors.

[0014] The presence of BiCl3 in bismuth chloride can be confirmed by powder X-ray diffraction (PXRD). Specifically, bismuth chloride is sealed in a sealed cell under an inert gas atmosphere such as nitrogen gas, and PXRD measurement is performed to confirm that the observed diffraction peaks belong to BiCl3. A multipurpose X-ray diffractometer (SmartLab) manufactured by Rigaku Corporation or an equivalent device can be used. Measurements are performed using Cu Kα radiation as the X-ray source, with a tube voltage of 40 kV and a tube current of 30 mA. Measurements are performed in 2θ scan mode, with a step width of 0.01° over the 2θ range from 10° to 120°, and a scan angle of 20° per minute.

[0015] It is preferable that the bismuth chloride contains as little BiOCl as possible. During the synthesis of bismuth chloride, BiOCl may be produced as a side reaction by combining with water or dissolved oxygen. If the starting material contains BiOCl, by-products or intermediates different from the target organometallic complex may be produced, resulting in a lower yield after synthesis. Furthermore, it is desirable to avoid BiOCl because it may affect the physical properties of the organometallic complex, such as its melting point and volatility.

[0016] More specifically, when the above-mentioned PXRD measurement is performed on bismuth chloride, in the resulting PXRD profile, the diffraction peak intensity of 001 diffraction of BiOCl is preferably 1 / 10 or less, more preferably 1 / 25 or less, and particularly preferably 1 / 100 or less of the diffraction peak intensity of 101 diffraction of BiCl3, and also preferably 1 / 10 or less, more preferably 1 / 25 or less, and particularly preferably 1 / 100 or less of the diffraction peak intensity of 121 diffraction of BiCl3.

[0017] The diffraction peak intensity of 101 diffraction of BiOCl is preferably 1 / 10 or less, more preferably 1 / 25 or less, and particularly preferably 1 / 100 or less of the diffraction peak intensity of 101 diffraction of BiCl3, and is also preferably 1 / 10 or less, more preferably 1 / 25 or less, and particularly preferably 1 / 100 or less of the diffraction peak intensity of 121 diffraction of BiCl3.

[0018] If BiOCl is included in the bismuth chloride, when measured at room temperature (20 to 30°C) using Cu Kα radiation as an X-ray source and an apparatus properly calibrated for 2θ, the PXRD profile shows that the 001 diffraction peak of BiOCl tends to appear at 2θ = 12.03° ± 0.2°, and the 101 diffraction peak of BiOCl tends to appear at 2θ = 25.92° ± 0.2°. Also, the 101 diffraction peak of BiCl3 tends to appear at 2θ = 18.25° ± 0.2°, and the 121 diffraction peak of BiCl3 tends to appear at 2θ = 26.71° ± 0.2°.

[0019] It is preferable that peaks derived from BiOCl, such as the diffraction peak of 001 diffraction of BiOCl and the diffraction peak of 101 diffraction of BiOCl, are not substantially observed.

[0020] If the purity of the bismuth chloride is less than 99.999% by mass, the impurities contained therein may adversely affect the performance of the semiconductor, and the bismuth chloride may not meet the requirements for use as an EUV material or a film forming material. From this perspective, the purity of the bismuth chloride is preferably 99.999% by mass or more, and more preferably 99.9999% by mass or more.

[0021] The purity of bismuth chloride is determined by subtracting the total content of impurities from 100% by mass, with the following elements considered to be impurities: Li, Be, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Ba, Pb, and Ag. While impurities may be present in bismuth chloride in the form of simple substances or compounds, the content of impurities in bismuth chloride is measured here regardless of their form. The content of impurities is measured using inductively coupled plasma mass spectrometry (ICP-MS). Specifically, an Agilent Technologies triple quadrupole ICP-MS8900 or a substantially equivalent instrument is used.

[0022] The bismuth chloride of this embodiment is expected to be used, for example, in EUV (extreme ultraviolet) exposure, for pattern exposure of wiring portions close to transistors in logic devices (especially for 7 nm nodes and below). In such cases, if the resist material contains impurity elements such as Cu (copper), Ag (silver), or Pb (lead), these impurity elements may diffuse into or react with the metal wiring, insulator, or semiconductor Si of the device to be fabricated, resulting in a decrease in semiconductor performance. Fe (iron) is also undesirable. For this reason, bismuth chlorides with a particularly low Pb content are required as starting materials for preparing MOR and dry resist materials. Among the above impurity elements, Pb, in particular, may be contained in the bismuth raw material used to manufacture bismuth chloride, and is difficult to remove during the chlorination reaction during the manufacturing process.

[0023] In contrast, the bismuth chloride of this embodiment has a Pb content of less than 1 ppm by mass, preferably less than 0.1 ppm by mass, and more preferably 0.05 ppm by mass or less, due to being produced by, for example, a method described below.

[0024] In addition, the bismuth chloride preferably has at least one of a Cu content, an Ag content, and an Fe content of less than 1 ppm by mass. In particular, the Cu content is preferably less than 0.5 ppm by mass, the Ag content is preferably less than 0.5 ppm by mass, and the Fe content is preferably less than 0.5 ppm by mass.

[0025] The Pb content, Cu content, Ag content and Fe content can each be measured by the above-mentioned ICP-MS.

[0026] Furthermore, when bismuth chloride is used as a starting material for synthesizing an organometallic complex, it is desirable to minimize not only the above-mentioned metal impurities but also the amount of water adsorbed by the bismuth chloride and by-products (hydrates, hydroxides, oxychlorides, etc.) generated by the water absorption reaction, from the viewpoint of increasing the yield.

[0027] In such cases, the bismuth chloride should have an HO content of less than 2000 ppm by mass, preferably less than 500 ppm by mass, more preferably less than 200 ppm by mass, and even more preferably less than 100 ppm by mass, as measured by the Karl Fischer method, which is believed to contribute to improving the productivity of MOR resists.

[0028] The Karl Fischer method used to measure the HO content of bismuth chloride uses a Metrohm Japan Coulometer Model 899 or a device substantially equivalent thereto. Measurements were performed using the moisture evaporation method. Bismuth chloride was filled into a container in a glove box under an inert atmosphere. The heating temperature during measurement was 100°C or 150°C, and the average value of 4 to 6 measurements was used as the measured value.

[0029] Furthermore, when a vaporization test is performed on bismuth chloride, the residue should preferably be less than 10%, more preferably less than 5%, and even more preferably less than 1%. This indicates that the content of other metal elements contained as impurities in the bismuth chloride is low. The vaporization test was actually performed as follows: A quartz boat loaded with 30.4 g of bismuth chloride was placed in a quartz tube, which was filled with an inert gas such as Ar. While maintaining the pressure inside the quartz tube at 1 atmosphere, the boat was heated at 460°C for 20 minutes. The amount of residue remaining on the quartz boat was confirmed to be 0.0 g.

[0030] The above-mentioned bismuth chloride can be produced, for example, by subjecting a bismuth raw material containing metallic bismuth to a chlorination process.

[0031] It is preferable to use a high-purity bismuth raw material, specifically one with a purity of 5N (99.999% by mass) or higher, more preferably 6N (99.9999% by mass) or higher. This purity is the value obtained by subtracting the content of impurity elements from 100% by mass.

[0032] Furthermore, it is particularly preferable that the bismuth raw material has a Pb content of less than 1 ppm by mass, more preferably less than 0.1 ppm by mass, and even more preferably 0.05 ppm by mass or less. This is because Bi and Pb are adjacent elements among transition metals, and as will be described later, it is difficult to remove them in the chlorination step.

[0033] The elemental content of the bismuth raw material is measured by glow discharge mass spectrometry (GD-MS), which can be performed using a Nu Instruments Astrum elemental glow discharge mass spectrometer or equivalent.

[0034] Crude bismuth containing metallic bismuth obtained as a by-product of lead smelting may have a high Pb content and low purity. By purifying such crude bismuth to produce refined bismuth, the refined bismuth can be effectively used as a high-purity bismuth raw material with an extremely low Pb content as described above.

[0035] The purification of crude bismuth may involve, for example, dissolving crude bismuth in nitric acid by electrolysis to obtain a bismuth nitrate solution, removing polonium ions from the bismuth nitrate solution, and obtaining purified bismuth by electrowinning using the bismuth nitrate solution, in this order. Electrolysis is carried out using an electrolytic cell: PVC, a cathode: titanium, an anode: bismuth, and a current density: 0.1 to 1.0 A / dm 2The conditions include catholyte pH (initial): 0.0-1.5, anolyte pH (initial): 0.0-1.5, anion exchange membrane: Selemion AMT, etc., the Bi concentration of the bismuth nitrate solution is 5-120 g / L, and the pH is 0.5-1.3. As a result of electrorefining, the Pb content of the bismuth nitrate solution can be reduced to 1 ppm or less (see Japanese Patent Application No. 2014-544474, paragraph 0037). Next, the polonium ions are removed by contacting the bismuth nitrate solution with a metal element more noble than Bi or with an ion exchange resin. Reducing the polonium ions prevents the decay of 210Po to 206Pb, further reducing the Pb content (see Japanese Patent Application No. 2014-544474, paragraph 0035). Known methods can be used for subsequent electrowinning.

[0036] In the chlorination step, the bismuth raw material is heated in a reaction tube, such as a quartz tube, under the supply of chlorine gas at a set temperature of 150 to 600°C, preferably 150 to 500°C, and more preferably 250 to 450°C, where metallic bismuth in the bismuth raw material reacts with chlorine to produce BiCl. This solidifies upon cooling, yielding a bismuth chloride containing solid BiCl. The gas supplied during the temperature increase and reaction is preferably Cl gas with a purity of 95% by volume or more, preferably 99% by volume or more, and more preferably 99.9% by volume or more. This is because using low-purity Cl gas can lead to concerns about the formation of BiOCl due to the influence of moisture and the formation of an oxide film on the bismuth raw material due to the influence of oxygen, which can reduce mass productivity.

[0037] Regarding the temperature range during the reaction, if the temperature is low, the reaction rate will be slow and the chlorination reaction will not proceed easily, which may result in an incomplete reaction and a reduced yield. On the other hand, if the temperature is high, reactions other than the target reaction will proceed and there is a possibility of impurities being mixed in as side reaction products. Therefore, by carrying out the chlorination reaction within the appropriate temperature range, BiCl3 with low impurity content can be synthesized.

[0038] To prevent contact between the bismuth chloride and moisture in the air, it is desirable to purge the reaction system, including the reaction tube, with nitrogen gas before and after the reaction. Furthermore, the components used in the chlorination reaction, including the reaction tube, are made of quartz or borosilicate glass. It is preferable to perform a cleaning process in which at least the reaction tube, and preferably other components, are washed with an acid and an oxidizing agent, preferably hydrochloric acid and hydrogen peroxide, and then dried before the chlorination step. This prevents contact with metal impurities other than Bi and moisture. In a mixture of hydrochloric acid and hydrogen peroxide, Fe and Cu dissolve, and Pb and Ag precipitate as metal chlorides, making it possible to remove metals that could become impurities before the reaction. Furthermore, it is desirable to heat the reaction system, including the reaction tube, with a heater or heat gun while purging with nitrogen gas to remove moisture adsorbed on the surface.

[0039] In the chlorination process, impurity elements such as Ag and Cu that may be contained in the bismuth raw material are removed, thereby sufficiently reducing the content of these impurity elements in the bismuth chloride. Figure 1 shows the results of an equilibrium calculation for the chlorination reaction of metallic bismuth with metallic silver and copper, performed using FactSage, a thermodynamic equilibrium calculation software, and the behavior of the impurities can be understood from Figure 1. At synthesis temperatures of 150-600°C, gaseous BiCl3 is produced, but even if the raw materials contain the same amount of Cu or Ag as Bi as an impurity, the amount of gaseous (CuCl)3 produced is less than one-hundredth at temperatures below 450°C, and less than one-tenth at temperatures between 450-600°C. Furthermore, the amount of AgCl produced is so minimal, less than one-ten-thousandth, that it can be separated. In reality, the Cu or Ag content in the raw materials is much lower than the Bi content, making separation even easier.

[0040] On the other hand, Pb, which is often contained in bismuth raw materials, is a neighboring element of Bi and is difficult to remove during the chlorination process. This can be seen from the equilibrium phase diagram shown in Figure 2, which is a result of equilibrium calculations using FactSage for the chlorination reaction of metallic bismuth and metallic lead. Because PbCl4 is synthesized more easily than BiCl3 at temperatures below 250°C, BiCl3 and PbCl4 are transported simultaneously as gases, making their separation difficult. Furthermore, even in the 250–600°C range, the difference in the ease of synthesis between BiCl3 and PbCl4 is not significant, so a significant amount of PbCl4 is synthesized along with BiCl3, making their separation difficult. Because the phase transition temperatures of vaporized BiCl3 and PbCl4 to solids are different, it is theoretically possible to separate the two chlorides by installing an impurity trap utilizing a temperature gradient within the chlorination apparatus. However, this approach would require a complex system configuration, reducing productivity, and the reproducibility and reduction effects are unclear. As described above, since it is difficult to separate Pb in the chlorination step, it is important to carry out the chlorination step using a bismuth raw material such as purified bismuth whose Pb content has been sufficiently reduced, as described above.

[0041] The low-Pb bismuth chloride obtained by the above method can be used as a starting material for EUV materials for semiconductors, a precursor for film formation, and as a deposition film material. A substrate is placed in a reactor, particularly a conventional CVD or ALD reactor, and the bismuth chloride is sublimated at a temperature at which it becomes vapor. The bismuth chloride is then introduced into the reactor, optionally with the addition of various gaseous components, such as hydrogen, oxygen, nitrogen, sulfur, or selenium-containing atmospheres or fluids, or any combination thereof. Pressures can be maintained between 1 Pa and 100,000 Pa during the film deposition process. Films can be formed on substrates by evaporation under the above conditions. Bismuth chloride can be used to fabricate films in this manner. Such films can be used in semiconductor memory, ferroelectric devices, and thermal expansion control materials.

[0042] (Potential contribution to SDGs) According to the embodiment described above, it is possible to provide bismuth chloride having a relatively high purity and a reduced content of specific metal impurities. Therefore, when used as an EUV material or a film forming material for semiconductors, it is possible that deterioration in semiconductor performance can be suppressed and that this can contribute to improving yields. Improving yields leads to a stable supply of products and reduced loss of metal raw materials, which are limited resources. Therefore, one embodiment of the present invention may contribute to the achievement of Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 12 "Ensure sustainable consumption and production patterns" of the United Nations-led Sustainable Development Goals (SDGs). [Example]

[0043] Next, the method for synthesizing the above-mentioned bismuth chloride will be described in detail below, but the description here is for illustrative purposes only and is not intended to be limiting.

[0044] Bismuth chloride synthesis was performed using the chlorination equipment shown in Figure 3. 200 g of metallic bismuth (Bi raw material) was loaded onto a quartz sample boat and placed in an L-shaped quartz reaction tube (quartz tube) that had been washed with hydrochloric acid and hydrogen peroxide and then dried. High-purity Bi was used as the raw material. In particular, the Pb content of the Bi raw material was less than 0.05 mass ppm. The L-shaped reaction tube and separable cover were connected with a 45 / 50 common joint coated with MOLYKOTE grease (HP-300, DuPont-Toray Specialty Materials Co., Ltd.). The separable cover and collection container were connected with an O-ring coated with MOLYKOTE grease. N2 gas was supplied to the closed reaction system at 0.02 MPa (G), and the internal pressure of the reaction system was monitored and leaks were checked using a leak checker. After confirming that there was no leak, the reaction system was opened and N2 gas was circulated overnight at 1 L / min to replace the atmosphere in the reaction system with N2 gas.

[0045] After another leak check to confirm that there were no leaks, the reaction tube and L-shaped tube were heated and dried at 150°C for 15 minutes using a tubular furnace and ribbon heater. The collection container was heated and dried using a heat gun. The reaction tube was then heated from 150°C to the reaction temperature of 450°C at a rate of 40°C / min. After reaching the reaction temperature, the reaction was carried out for a predetermined time. The gas circulating during the temperature increase and reaction was Cl2 gas with a purity of 99.4% by volume or higher.

[0046] After the reaction, the output of the tubular furnace was turned off and the temperature was allowed to drop naturally. After confirming that the temperature inside the furnace had dropped below 400°C, the supply of Cl2 gas was stopped and N2 gas was circulated at 2 L / min for 2 hours to replace the reaction system with N2 gas. To prevent air from entering the recovery container, the N2 gas line was changed so that N2 gas was always flowing out of the recovery container, and the recovery container was removed from the reaction system.

[0047] In an inert atmosphere glove box, the bismuth chloride particles were collected from the collection container into a glass bottle that had been acid-washed, dried, and dehydrated. The air was replaced with an inert gas such as N2 or Ar, and then a vacuum was drawn. The inert gas replacement and vacuum drawing were repeated five times to remove the Cl2 gas trapped between the bismuth chloride particles.

[0048] The bismuth chloride thus obtained was analyzed by PXRD according to the method described above, and it was confirmed that it contained BiCl3, as shown in Figure 4. On the other hand, no diffraction peaks attributable to substances other than BiCl3, such as BiOCl, were observed. From this, it can be said that the obtained bismuth chloride does not substantially contain any substances other than BiCl3.

[0049] The content of impurity elements in bismuth chloride (BiCl3) was measured by ICP-MS. The results are shown in Table 1, along with the content of impurity elements in the bismuth raw material. The content of impurity elements in the bismuth raw material in Table 1 was obtained by measurement using GD-MS. Furthermore, when 30.4 g of the obtained bismuth chloride was subjected to the vaporization test by the above-mentioned method, the amount of residue was 0.0 g, that is, 0%.

[0050] [Table 1]

[0051] As can be seen from Table 1, the purity of the bismuth chloride was 99.9999% by mass or more, the Pb content was less than 0.1 ppm by mass, and the Cu, Ag, and Fe contents were each less than 0.5 ppm by mass. Therefore, it can be said that it was possible to obtain bismuth chloride having a relatively high purity and a reduced content of certain metal impurities.

[0052] The HO content of Sample A, the bismuth chloride obtained above, and Sample B, a commercially available high-purity BiCl, was measured by the Karl Fischer method as described above. The results are shown in Table 2. As can be seen from Table 2, the HO content of Sample A was significantly less than 2000 ppm by mass, while that of Sample B was 2000 ppm by mass or more.

[0053] [Table 2]

[0054] From the above results, it was found that bismuth chloride having a relatively high purity and a reduced content of certain metal impurities could be obtained.

Claims

1. BiCl 3 1. A bismuth chloride for semiconductors, comprising:

2. 2. The bismuth chloride according to claim 1, wherein the Pb content is less than 0.1 ppm by mass.

3. 2. The bismuth chloride according to claim 1, wherein at least one of the Cu content, the Ag content, and the Fe content is less than 1 ppm by mass.

4. 2. The bismuth chloride according to claim 1, wherein the Cu content is less than 0.5 ppm by mass.

5. 2. The bismuth chloride according to claim 1, wherein the Ag content is less than 0.5 ppm by mass.

6. 2. The bismuth chloride according to claim 1, wherein the Fe content is less than 0.5 ppm by mass.

7. 2. The bismuth chloride according to claim 1, having a purity of 99.9999% by mass or more.

8. H measured by Karl Fischer method 2 The bismuth chloride according to any one of claims 1 to 7, having an O content of less than 2000 ppm by mass.

9. In the PXRD profile obtained by powder X-ray diffraction, the diffraction peak intensity of the 001 plane of BiOCl is 3 The bismuth chloride according to any one of claims 1 to 7, wherein the diffraction peak intensity of the 101 plane is 1 / 10 or less of that of the 102 plane of the bismuth chloride.

10. 8. The bismuth chloride according to any one of claims 1 to 7, which has a residue of less than 10% in a vaporization test.

11. BiCl 3 1. A method for producing a semiconductor grade bismuth chloride containing A method for producing bismuth chloride, comprising: a chlorination step of reacting a bismuth raw material having a purity of 99.999% by mass or more and a Pb content of 1 ppm by mass or less with chlorine at 150 to 600°C in a reaction tube while supplying chlorine gas.

12. 12. The method for producing bismuth chloride according to claim 11, further comprising a washing step of washing a reaction tube made of quartz or borosilicate glass with an acid and an oxidizing agent before the chlorination step.

13. The method for producing bismuth chloride according to claim 11 or 12, wherein the Pb content of the bismuth raw material is 0.1 ppm by mass or less.

14. A method for producing a film, comprising forming a film using the bismuth chloride according to any one of claims 1 to 7.

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