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

Abstract

This bismuth chloride contains BiCl3 and has a purity of 99.999 mass% or more and a Pb content of less than 1 mass ppm.

Description

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

[0001] This specification describes bismuth chloride containing BiCl₃, a method for producing bismuth chloride, and a method for producing a film.

[0002] In the semiconductor industry, among lithography technologies that have become increasingly important with device scaling, resists having a crosslinked structure of metal and oxygen are attracting attention as next-generation resists for next-generation EUV (extreme ultraviolet) exposure. As such a resist, metal oxide resist (Metal Oxide Resist, MOR) is considered promising, and is formed by coating an organometallic complex. Additionally, dry resists formed by vapor-depositing an organometallic complex through vapor phase growth such as Chemical Vapor Deposition (CVD) are also considered promising. Metal chloride is often used as a starting material for the synthesis of these organometallic complexes for MOR and dry resist applications.

[0003] In recent years, CVD and Atomic Layer Deposition (ALD) have been used as film formation methods for fine regions such as transistors in cutting-edge logic devices, and metal chlorides are attracting attention as precursors and raw materials for precursors of organometallic complexes.

[0004] As a technology related to this, for example, one described in Patent Document 1 is known.

[0005] International Publication No. WO 2021 / 171742

[0006] Among metal chlorides used in the above-mentioned EUV materials for semiconductors, film-forming materials and the like, there are several candidate metal chlorides containing different metal elements, but any of these metal chlorides may be required to have extremely high purity. In particular, metal impurities tend to be easily mixed into metal chlorides derived from raw materials for producing the metal chloride, and when contained in the metal chloride, they diffuse or react into the metal wiring / insulator / semiconductor Si portion of the device to be manufactured, which may cause deterioration of semiconductor performance.

[0007] This specification provides bismuth chloride having relatively high purity and reduced metal impurity content, a method for producing bismuth chloride, and a method for producing a film.

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

[0009] The method for producing bismuth chloride described in this specification is a method for producing bismuth chloride containing BiCl3, and 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 while supplying chlorine gas in a reaction tube.

[0010] The method for manufacturing a membrane described in this specification involves forming a membrane using the bismuth chloride described above.

[0011] The bismuth chloride described above has relatively high purity and a reduced content of specific metal impurities.

[0012] This is an equilibrium phase diagram for the chlorination reaction of metallic bismuth with metallic silver and metallic copper. This is an equilibrium phase diagram for the chlorination reaction of metallic bismuth with metallic lead. This is a schematic diagram showing the chlorination equipment used in the example. This is the PXRD profile of the bismuth chloride obtained in the example.

[0013] The embodiments of the bismuth chloride described above will be explained in detail below. One embodiment of the bismuth chloride contains BiCl3 (bismuth(III) chloride), has a purity of 99.999% by mass or higher, and a Pb content of less than 1 ppm by mass. This bismuth chloride is highly pure and has a sufficiently low Pb content, which can lead to a decrease in semiconductor performance, making it particularly suitable for the aforementioned EUV materials and film-forming materials for semiconductors.

[0014] The presence of BiCl3 in bismuth chloride can be confirmed by powder X-ray diffraction (PXRD). Specifically, this can be proven by sealing bismuth chloride in a sealed cell under an inert gas atmosphere such as nitrogen gas, performing a PXRD measurement, and confirming that the observed diffraction peak belongs to BiCl3. Here, a multi-purpose X-ray diffractometer (SmartLab) manufactured by Rigaku Corporation or an equivalent device can be used as the apparatus. For the measurement, Cu Kα rays are used as the X-ray source, the tube voltage is 40 kV, and the tube current is 30 mA. The measurement is performed in 2θ scan mode, with a step size of 0.01 degrees and a scan angle of 20 degrees per minute, in the range of 2θ from 10 to 120 degrees.

[0015] It is preferable that bismuth chloride contains as little BiOCL as possible. During the synthesis of bismuth chloride, BiOCL may be formed as a side reaction by combining with water or dissolved oxygen. If the starting material contains BiOCL, there is a concern that by-products or intermediates different from the target organometallic complex will be formed, leading to a decrease in the yield after synthesis. Furthermore, it may affect the physical properties of the organometallic complex, such as its melting point and volatility, so it is desirable to omit BiOCL.

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

[0017] The diffraction peak intensity of BiOCl in 101 diffraction is preferably 1 / 10 or less, more preferably 1 / 25 or less, and especially preferably 1 / 100 or less, of the diffraction peak intensity of BiCl3 in 101 diffraction. Furthermore, it is preferable that the diffraction peak intensity of BiCl3 in 121 diffraction is 1 / 10 or less, more preferably 1 / 25 or less, and especially preferably 1 / 100 or less.

[0018] If bismuth chloride contains BiOCL, and measurements are taken at room temperature between 20°C and 30°C using Cu Kα rays as the X-ray source and with an instrument appropriately calibrated for the measured 2θ, the PXRD profile tends to show the 001 diffraction peak of BiOCL at 2θ = 12.03° ± 0.2°, and the 101 diffraction peak of BiOCL at 2θ = 25.92° ± 0.2°. Furthermore, 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 originating from BiOCL, such as the diffraction peak of BiOCL's 001 diffraction and the diffraction peak of BiOCL's 101 diffraction, are substantially not observed.

[0020] If the purity of bismuth chloride is less than 99.999% by mass, the impurities it contains may adversely affect the performance of semiconductors, and it may not meet the requirements for EUV materials or film-forming materials. From this perspective, the purity of bismuth chloride is preferably 99.999% by mass or higher, and more preferably 99.9999% by mass or higher.

[0021] The purity of bismuth chloride is determined by subtracting the total content of impurity elements (Li, Be, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Mo, Ba, Pb, Ag) from 100% by mass. While impurity elements can be present in bismuth chloride in elemental or compound forms, here we measure the content of impurity elements present in bismuth chloride regardless of their form. Inductively coupled plasma mass spectrometry (ICP-MS) is used to measure the content of impurity elements. More specifically, an Agilent Technologies triple quadrupole ICP-MS 8900 or a substantially equivalent instrument is used.

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

[0023] In contrast, the bismuth chloride of this embodiment, for example, is produced by the method described later, and 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.

[0024] Furthermore, it is preferable that the bismuth chloride has a Cu content, Ag content, and Fe content of at least one of these less than 1 ppm by mass. In particular, it is preferable that the Cu content be less than 0.5 ppm by mass, the Ag content be less than 0.5 ppm by mass, and the Fe content be less than 0.5 ppm by mass.

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

[0026] Furthermore, when using bismuth chloride as a starting material in the synthesis of organometallic complexes, it is desirable to minimize not only the aforementioned metal impurities, but also the adsorbed water of bismuth chloride and by-products (hydrates, hydroxides, oxychlorides, etc.) generated by water absorption reactions, in order to increase the yield.

[0027] In such cases, the bismuth chloride is preferably of a H2O content of less than 2000 ppm by mass, more 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. This is thought to contribute to improving the productivity of MOR resists.

[0028] The Karl Fischer method used to measure the H2O content of bismuth chloride specifically employs a Metrohm Japan Coulometer Model 899 or a substantially equivalent device. The measurement was performed using the moisture vaporization 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 taken as the measured value.

[0029] Furthermore, it is preferable that the residue of bismuth chloride after a vaporization test is less than 10%, more preferably less than 5%, and even more preferably less than 1%. This indicates that the bismuth chloride contains a low amount of other metal elements as impurities. The vaporization test was actually performed by the following method: A quartz boat loaded with 30.4 g of bismuth chloride was placed inside a quartz tube, the quartz tube was filled with an inert gas such as Ar, and the quartz tube was heated at 460°C for 20 minutes with a heater while maintaining the pressure inside the quartz tube at 1 atmosphere. The amount of residue after this was checked, and it was confirmed that there was 0.0 g of residue on the quartz boat.

[0030] The bismuth chloride described above can be produced, for example, by performing a chlorination process on a bismuth raw material containing metallic bismuth.

[0031] It is preferable to use bismuth raw material of high purity, specifically bismuth with a purity of 5N (99.999% by mass) or higher, and more preferably bismuth with a purity of 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, the bismuth raw material is preferably one with a Pb content of less than 1 ppm by mass, more preferably less than 0.1 ppm by mass, and 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, they are difficult to remove in the chlorination process.

[0033] The elemental content of bismuth raw materials is measured by glow discharge mass spectrometry (GD-MS). More specifically, a Nu Instruments Astrum glow discharge mass spectrometer for elemental analysis, or an equivalent instrument, can be used for GD-MS.

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

[0035] Purification of crude bismuth may include, 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 electrolysis using the bismuth nitrate solution, in this order. For electrolysis, the electrolytic cell is PVC, the cathode is titanium, the anode is bismuth, and the current density is 0.1–1.0 A / dm². 2 Conditions such as a catholite pH (starting): 0.0 to 1.5, anolite pH (starting): 0.0 to 1.5, anion exchange membrane: Celemion AMT, and a Bi concentration of bismuth nitrate solution of 5 to 120 g / L and a pH of 0.5 to 1.3 may be used. As a result of electrolytic purification, a Pb content of 1 ppm or less in the bismuth nitrate solution can be achieved (see: paragraph 0037 of Japanese Patent Application No. 2014-544474). Next, polonium ions are removed from the bismuth nitrate solution by contact with a metal element nobler than Bi or with an ion exchange resin. By reducing polonium ions, the decay from 210Po to 206Pb is prevented, and the Pb content can be further reduced (see: paragraph 0035 of Japanese Patent Application No. 2014-544474). In subsequent electrolytic extraction, known methods can be used.

[0036] In the chlorination process, for example, in a reaction tube made of quartz, the above-mentioned bismuth raw material is subjected to a supply of chlorine gas at a set temperature of 150 to 600°C, preferably 150 to 500°C, more preferably 250 to 450°C, where the metallic bismuth of the bismuth raw material reacts with chlorine to produce BiCl3. This is then cooled and solidified, yielding bismuth chloride containing solid BiCl3. The supply gas during heating and reaction is preferably Cl2 gas with a purity of 95% by volume or higher, preferably 99% by volume or higher, and even more preferably 99.9% by volume or higher. This is because using low-purity Cl2 gas may lead to 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 may reduce the mass productivity.

[0037] Regarding the temperature range during the reaction, if the temperature is too low, the reaction rate will decrease, making it difficult for the chlorination reaction to proceed, and there is a risk of a reduced yield due to an incomplete reaction. On the other hand, if the temperature is too high, reactions other than the intended reaction may proceed, and there is a possibility of contamination with impurities from by-reaction products. Therefore, by carrying out the chlorination reaction within an appropriate temperature range, it is possible to synthesize BiCl3 with a low impurity content.

[0038] Furthermore, to suppress contact between 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. In addition, the components used in the chlorination reaction, including the reaction tube, should be quartz or borosilicate glass, and it is preferable to perform a cleaning step beforehand, 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 dried, before the chlorination step. This suppresses contact with metal impurities other than Bi and moisture. In the hydrochloric acid and hydrogen peroxide mixture, Fe and Cu dissolve, and Pb and Ag precipitate as metal chlorides, so it is possible to remove metals that may 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 purged 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 present in the bismuth raw material are removed, thereby significantly reducing the content of these impurity elements in the bismuth chloride. Figure 1 shows the results of an equilibrium state calculation for the chlorination reaction of metallic bismuth with metallic silver and metallic copper, using the thermodynamic equilibrium calculation software FactSage, and the behavior of impurities can be understood from Figure 1. At the synthesis temperature of 150 to 600°C, gaseous BiCl3 is produced. Even if the raw material contains the same amount of Cu or Ag as Bi as impurities, the amount of gaseous (CuCl)3 produced is less than 1 / 100th below 450°C, and less than 1 / 10th even between 450 and 600°C. Furthermore, the amount of AgCl produced is less than 1 / 10,000th, meaning it is hardly produced at all and therefore separable. In reality, the content of Cu or Ag in the raw material is far less than that of Bi, so separation is even easier.

[0040] On the other hand, Pb, which is readily present in bismuth raw materials, is an adjacent element to Bi and is difficult to remove in the chlorination process. This can be understood from the equilibrium phase diagram of the equilibrium calculation results calculated using FactSage in the chlorination reaction of metallic bismuth and metallic lead shown in Figure 2. At temperatures below 250°C, PbCl4 is synthesized more easily than BiCl3, so BiCl3 and PbCl4 are transported simultaneously as gases, making their separation difficult. Furthermore, even in the range of 250 to 600°C, the difference in the ease of synthesis of BiCl3 and PbCl4 is not large, so a considerable amount of PbCl4 is synthesized along with BiCl3, making their separation difficult. Regarding vaporized BiCl3 and PbCl4, since their phase transition temperatures to solids are different, it is theoretically possible to separate the two chlorides by installing an impurity trap using a temperature gradient in the chlorination apparatus. However, this would complicate the apparatus configuration, reduce productivity, and the reproducibility and reduction effect would not be clear. As it is difficult to separate Pb in the chlorination process, it is essential to use bismuth raw materials such as purified bismuth with a sufficiently reduced Pb content in the chlorination process, as described above.

[0041] The low-Pb-containing bismuth chloride obtained as described above can be used not only as a starting material for EUV materials for semiconductors and as a precursor starting material for film deposition materials, but also as a vapor-deposited film material. A substrate is placed in a reactor, especially a conventional CVD or ALD reactor, and the bismuth chloride is sublimated at a temperature at which it becomes vapor and introduced into the reactor. In some cases, various gaseous components such as hydrogen, oxygen, nitrogen, sulfur, selenium-containing atmospheres or fluids, or any combination thereof, may be introduced. During the film deposition process, the pressure can be maintained between 1 Pa and 100,000 Pa. By depositing the bismuth chloride onto the substrate under the above conditions, a film can be formed on the substrate. Films can be manufactured using bismuth chloride in this way. Such films can be used in semiconductor memory, ferroelectric devices, and thermal expansion control materials.

[0042] (Potential Contribution to SDGs) According to the embodiments described above, it is possible to provide bismuth chloride with relatively high purity and reduced content of predetermined metal impurities. Therefore, when used as an EUV material or film deposition material for semiconductors, it may be possible to suppress the degradation of semiconductor performance and contribute to improved yield. Improved yield leads to a stable supply of products and a reduction in the loss of metal raw materials, which are limited resources. For this reason, one embodiment of this invention may contribute to 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).

[0043] Next, the details of the bismuth chloride synthesis method described above will be explained below. However, this explanation is for illustrative purposes only and is not intended to be an exhaustive list.

[0044] The synthesis of bismuth chloride was performed in the chlorination facility shown in Figure 3. 200 g of metallic bismuth (Bi raw material) was loaded onto a quartz sample boat, and set in a quartz L-shaped reaction tube (quartz tube) that had been washed with hydrochloric acid and hydrogen peroxide water and dried. High-purity Bi was used as the raw material. In particular, the Pb content contained in the Bi raw material is 0.05 mass ppm or less. The L-shaped reaction tube and the separable cover were connected via a 45 / 50 common ground joint coated with MOLYKOTE grease (HP-300, manufactured by DuPont Toray Specialty Materials K.K.). The separable cover and the recovery container were connected with an O-ring coated with MOLYKOTE grease interposed therebetween. N₂ gas was supplied to the closed reaction system to 0.02 MPa (G), and a check for changes in internal pressure of the reaction system and a leak check of the reaction system were performed using a leak checker. After confirming that there was no leak, the reaction system was opened, N₂ gas was circulated at 1 L / min overnight, and the reaction system was purged with N₂ gas.

[0045] After confirming again that there was no leak by a leak check, the reaction tube and the L-shaped tube were heated and dried at 150°C for 15 minutes using a tube furnace and a ribbon heater. The recovery container was heated and dried using a heat gun. Thereafter, the temperature of the reaction tube was increased from 150°C to a reaction temperature of 450°C at a heating rate of 40°C / min. After reaching the reaction temperature, the reaction was allowed to proceed for a predetermined time. The circulating gas during temperature increase and reaction was Cl₂ gas with a purity of 99.4% by volume or more.

[0046] After the reaction, the output of the tube furnace was turned off and the system was allowed to cool naturally. After confirming that the furnace internal temperature had dropped to 400°C or lower, the supply of Cl₂ gas was stopped, N₂ gas was circulated at 2 L / min for 2 hours, and the reaction system was purged with N₂ gas. To prevent air from entering the recovery container, the recovery container was removed from the reaction system while adjusting the N₂ gas line such that N₂ gas always flowed out from the recovery container.

[0047] In a glove box under an inert atmosphere, the product was collected from the recovery container into an acid-washed, dried and dehydrated glass bottle, purged with an inert gas such as N₂ or Ar, and then evacuated. Inert gas purging and evacuation were repeated 5 times to remove Cl₂ gas trapped between the bismuth chloride particles.

[0048] When the bismuth chloride obtained in this manner was analyzed by PXRD in accordance with the method described above, it was confirmed that BiCl₃ was contained as shown in Fig. 4. On the other hand, no diffraction peaks derived from substances other than BiCl₃, such as BiOCl, were observed. From this fact, it can be said that the bismuth chloride obtained contains substantially no substances other than BiCl₃.

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

[0050]

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

[0052] For each of Sample A of the bismuth chloride obtained above and commercially available high-purity BiCl₃ Sample B, the H₂O content was measured by the Karl Fischer method in accordance with the method described above. The results are shown in Table 2. As can be seen from Table 2, the H₂O content of Sample A was sufficiently lower than 2000 mass ppm, whereas that of Sample B was 2000 mass ppm or more.

[0053]

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

Claims

1. Bismuth chloride containing BiCl3, with a purity of 99.999% by mass or higher, and a Pb content of less than 1 ppm by mass.

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

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

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

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

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

7. The bismuth chloride according to claim 1, wherein the purity is 99.9999% by mass or higher.

8. The bismuth chloride according to any one of claims 1 to 7, wherein the H2O content measured by the Karl Fischer method is less than 2000 ppm by mass.

9. The bismuth chloride according to any one of claims 1 to 7, wherein in the PXRD profile obtained by powder X-ray diffraction, the diffraction peak intensity of the 001 plane of BiOCl is 1 / 10 or less of the diffraction peak intensity of the 101 plane of BiCl3.

10. The bismuth chloride according to any one of claims 1 to 7, wherein the residue in the vaporization test is less than 10%.

11. A method for producing bismuth chloride containing BiCl3, comprising 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 while supplying chlorine gas in a reaction tube.

12. The method for producing bismuth chloride according to claim 11, comprising a cleaning step of cleaning 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 described in any one of claims 1 to 7.

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