A method and system for purifying semiconductor-grade ultra-high-purity titanium tetrachloride

Abstract

The present invention provides a method and system for purifying semiconductor-grade ultra-high-purity titanium tetrachloride. The purification system comprises at least a distillation tower, wherein the distillation column of the distillation tower comprises, from bottom to top, a stainless steel theta-ring packing section, a quartz packing section, an aluminum wire braided theta-ring packing section, and a quartz packing section. The aluminum section reacts with crude titanium tetrachloride to produce titanium trichloride, which reacts with difficult-to-remove impurities, raising the boiling point of the impurity compounds and significantly improving the purity of the product. The purification method comprises subjecting the crude titanium tetrachloride raw material to distillation in the purification system to obtain semiconductor-grade ultra-high-purity titanium tetrachloride. In the present invention, semiconductor-grade ultra-high-purity titanium tetrachloride is obtained through a single distillation through the synergistic action of each section. This process is simple, has low waste, and is easily scalable. The product purity reaches 99.99999999%, meeting the requirements for integrated circuit manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical purification, and in particular relates to a purification method and a purification system for semiconductor-grade ultra-high-purity titanium tetrachloride. Background Art

[0002] As a semiconductor electronic material, high-purity titanium tetrachloride plays a vital role in the production and manufacturing of integrated circuits, primarily as a precursor for ALD / CVD processes. With the advancement of integrated circuit manufacturing technology, titanium tetrachloride has found new applications, but purity requirements are becoming increasingly stringent. For the 14nm process, a purity exceeding 99.9999999% is required.

[0003] Numerous patents exist for the purification of titanium tetrachloride. For example, Chinese invention patent CN103011268A discloses a titanium tetrachloride purification system and method. This method involves passing crude titanium tetrachloride, after vanadium has been removed, through a light-removal column and then a heavy-removal column to purify the titanium tetrachloride. However, the titanium tetrachloride obtained by this method is not highly pure, and some titanium tetrachloride is lost during the process. Chinese invention patent CN105984894A discloses a method and system for preparing titanium tetrachloride. This method involves mixing crude titanium tetrachloride with an organic solvent and then evaporating it to obtain refined titanium tetrachloride. However, this method does not yield high purity and contains impurities such as vanadium that have not been completely removed.

[0004] TWi226875B "Method for Purifying Group IVb Metal Halides" uses TiH2 to reduce the impurity elements Zr / V / Hf in titanium tetrachloride to below 1 ppb, but does not specify the removal of other impurities and the final purity of titanium tetrachloride. Secondly, the solid-liquid reaction time during the purification process is long and the reaction is not sufficient. When the amount of titanium tetrachloride is large, there is a problem of incomplete impurity removal.

[0005] Chinese invention patent CN108178185A discloses a method for producing ultra-high-purity titanium tetrachloride, capable of producing titanium tetrachloride with a purity of 99.99999%. However, this purity still does not meet the current production requirements of advanced integrated circuits. Secondly, the multi-stage sub-boiling distillation process is slow, low in production efficiency, and the additional steps increase the risk of contamination. Summary of the Invention

[0006] The present invention provides a method and system for purifying semiconductor-grade ultra-high-purity titanium tetrachloride, aiming to solve the problem that the titanium tetrachloride prepared in the prior art has low purity and does not meet the production requirements of advanced integrated circuits.

[0007] In order to achieve the above technical effects, the technical solutions adopted by the present invention are as follows:

[0008] First, the present invention provides a method for purifying semiconductor-grade ultra-high-purity titanium tetrachloride, comprising using crude titanium tetrachloride as a raw material and rectifying the raw material to obtain ultra-high-purity titanium tetrachloride;

[0009] The distillation comprises distilling the raw material in a distillation tower;

[0010] The ultra-high-purity titanium tetrachloride is semiconductor-grade titanium tetrachloride with a purity of ≥99.9999999%.

[0011] Furthermore, in the distillation tower, the distillation column is connected to four sections A, B, C, and D from bottom to top; wherein A is a 316L stainless steel θ ring packing section, B is a quartz packing section, C is an aluminum wire braided θ ring packing section, and D is a quartz packing section;

[0012] Furthermore, A, B, C, and D respectively occupy 15-25%, 25-35%, 2-5%, and 35-48% of the height of the distillation column.

[0013] Furthermore, the raw material purity is greater than or equal to 99.9%.

[0014] Furthermore, the aluminum wire braided θ-ring filler section can react with raw materials to generate titanium trichloride on the surface of the aluminum wire braided θ-ring filler section.

[0015] And / or, before using the distillation tower, the 316L stainless steel θ-ring packing section is surface treated with alkali and acid in sequence.

[0016] Furthermore, the surface treatment of the 316L stainless steel θ ring packing section includes first ultrasonic cleaning with 8%-12% sodium hydroxide solution for 20-40 minutes, rinsing with pure water until neutral, and then ultrasonic cleaning with 8-10% nitric acid for 5-10 minutes for surface treatment.

[0017] Furthermore, the quartz filler is in the shape of a hollow column with holes on the side wall.

[0018] Furthermore, the packing sizes of the A, B, C, and D sections are the same, which is 1 / 10 of the inner diameter of the distillation tower.

[0019] Furthermore, the holes on the side wall of the quartz filler are spaced apart in each row along the axial direction of the quartz filler by d, where d is the diameter of the hole.

[0020] Furthermore, the radius of the hole is 1 / 12-1 / 8 of the radius of the quartz filler.

[0021] Furthermore, nitrogen is introduced into the distillation tower during assembly to remove moisture;

[0022] Furthermore, during the distillation process, atmospheric pressure is maintained, the temperature at the top of the distillation tower is 130-136° C., and total reflux is performed for 2-4 hours.

[0023] Furthermore, during the distillation process, 10-20% is taken as a front fraction, and the reflux ratio of the front fraction is 10:1-15:1;

[0024] 40-50% of the middle fraction is taken, and the reflux ratio of the middle fraction is controlled at 3:1-5:1.

[0025] Semiconductor-grade ultra-high-purity titanium tetrachloride is obtained by the purification method provided by the invention.

[0026] Furthermore, the semiconductor-grade ultra-high-purity titanium tetrachloride has a purity of ≥99.99999999%.

[0027] The application of the above-mentioned semiconductor-grade ultra-high purity titanium tetrachloride in integrated circuits.

[0028] The present invention also provides a semiconductor ultra-high-purity titanium tetrachloride purification system, which includes a condenser, a distillation column, a reboiler, and a finished product tank; the distillation column includes, from bottom to top, an A-stainless steel θ ring packing section, a B-quartz packing section, a C-aluminum wire braided θ ring packing section, and a D-quartz packing section, wherein the A, B, C, and D sections are connected in sequence from bottom to top and occupy 15-25%, 25-35%, 2-5%, and 35-48% of the height of the distillation column, respectively.

[0029] Furthermore, the surface treatment of the 316L stainless steel θ ring packing section includes first ultrasonic cleaning with 8%-12% sodium hydroxide solution for 20-40 minutes, rinsing with pure water until neutral, and then ultrasonic cleaning with 8-10% nitric acid for 5-10 minutes for surface treatment.

[0030] Furthermore, the quartz filler is in a hollow cylindrical shape with holes on the side wall, and the holes are spaced d apart in each row along the axial direction of the quartz filler, where d is the diameter of the hole;

[0031] Furthermore, the radius of the hole is 1 / 12-1 / 8 of the radius of the quartz filler.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention can prepare semiconductor-grade ultra-high-purity titanium tetrachloride with a purity greater than or equal to 99.9999999%, meeting the purity requirements of titanium tetrachloride in technologies related to integrated circuits of 14nm and above.

[0034] 2. The purification method provided by the present invention can obtain high-purity titanium tetrachloride through a single distillation, which is simple to operate, has low loss, and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a schematic diagram of the distillation column in Example 1 of the present application.

[0037] Figure 2 This is a schematic diagram of the purification system in Example 1 of the present application.

[0038] Figure 3 This is a schematic diagram of the quartz packing in Example 1 of the present application.

[0039] Figure 4 This is a comparison chart of impurity elements and their contents in ultra-high-purity titanium tetrachloride prepared in Example 1 of the present application.

[0040] Figure 5 This is a comparison chart of impurity elements and their contents in ultra-high-purity titanium tetrachloride prepared in Example 2 of the present application.

[0041] Figure 6 This is a comparison chart of impurity elements and their contents in ultra-high-purity titanium tetrachloride prepared in Example 3 of the present application.

[0042] Figure 7 This is a comparison chart of impurity elements and their contents in ultra-high-purity titanium tetrachloride prepared in Example 4 of the present application.

[0043] Figure 8 This is a comparison chart of impurity elements and their contents in the purified titanium tetrachloride in Comparative Example 1 of the present application.

[0044] Figure 9 This is a comparison chart of impurity elements and their contents in the purified titanium tetrachloride in Comparative Example 2 of the present application.

[0045] Figure 10 This is a comparison chart of impurity elements and their contents in the purified titanium tetrachloride in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0046] Detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the present invention, which can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.

[0047] Example 1

[0048] This embodiment provides ultra-high-purity titanium tetrachloride, and the purification method includes: using crude titanium tetrachloride as a raw material, and distilling the crude titanium tetrachloride in a purification system to obtain ultra-high-purity titanium tetrachloride;

[0049] The purification system in this embodiment refers to Figure 2 The purification system mainly includes a condenser, a distillation column, a reboiler, and a finished product tank. The condenser and reboiler respectively condense and boil the distillation column, and the purified product is then stored in the finished product tank. The condenser, distillation column, reboiler, and finished product tank are all made of high-purity quartz.

[0050] See Figure 1 , a schematic diagram of the distillation column in the distillation tower of this embodiment, shows the distillation column, from bottom to top, comprising, in order: A - 316L stainless steel θ-ring packing section, B - quartz packing section, C - aluminum wire braided θ-ring packing section, and D - quartz packing section. Sections A, B, C, and D are connected in sequence from bottom to top, occupying 25%, 25%, 5%, and 45% of the distillation column height, respectively. After the distillation unit is assembled, heated high-purity nitrogen (120°C) is introduced to purge the interior of the unit. The dew point of the nitrogen at the exhaust end is measured. When the dew point reaches -80°C, the nitrogen heating is stopped, and the distillation unit is purged with cold nitrogen to room temperature to remove moisture.

[0051] Before starting the distillation, the A-316L stainless steel θ ring packing was first ultrasonically cleaned for 20 minutes using a 10% NaOH solution; then rinsed with pure water until neutral, and then ultrasonically cleaned for 5 minutes using 10% nitric acid for surface treatment.

[0052] Quartz packing used in distillation Figure 3 As shown in the figure, this packing, based on Raschig rings, features holes in the sidewalls of the hollow cylindrical packing, increasing the packing's porosity and gas-liquid contact surface, thereby improving separation efficiency. The holes are arranged in rows of four or three along the packing's axis, with a spacing of d between rows. D represents the hole diameter, and the hole radius is 1 / 8 the radius of the quartz packing, or 0.38 mm.

[0053] In a glove box, 1200 g of crude titanium tetrachloride raw material with a purity of 99.96% was placed in a 1 L quartz flask (reboiler) for rectification.

[0054] During the distillation and purification process, the aluminum-wire braided theta-ring packing in section C reacts with the crude titanium tetrachloride raw material to produce TiCl3, which coats the packing surface. TiCl3 is insoluble in titanium tetrachloride. Once the entire aluminum-wire braided theta-ring packing is covered, the titanium tetrachloride loses contact with the aluminum inside, and the reaction ceases.

[0055] Impurities react with the titanium trichloride on the surface, exposing the aluminum inside. The aluminum then reacts with titanium tetrachloride to form titanium trichloride, and the cycle continues. Impurity levels are extremely low, and very little aluminum is consumed. The theta ring packing is woven from aluminum wire, only coated with TiCl3, which does not affect its separation function as a packing.

[0056] Among them, impurities mainly include Zr, V, etc. The boiling point of the impurity compounds is first increased, and then these impurities are separated through the quartz filler on the D layer. During the distillation process, the top temperature is controlled at 136°C, and the full reflux is 2 hours. The reflux ratio of the front fraction is 10:1, and 10% of the front fraction is taken; then the reflux ratio is adjusted to 5:1, and 50% of the middle fraction is taken.

[0057] The purity of the middle fraction was checked by ICPMS. Figure 4 , Figure 4 The impurities and their corresponding contents in the purified titanium tetrachloride are given in the report. Fourteen impurity elements were detected, with individual impurity levels below 300 ppt. The titanium tetrachloride achieved a purity of 9N, or ≥99.9999999%. Fe and Na were the two most abundant impurities, at 221.7 ppt and 289 ppt, respectively. Impurity elements such as V and Sn were not detected in the purified titanium tetrachloride after distillation. The overall yield was 50%.

[0058] Example 2

[0059] The purification system used in Example 2 is the same as that used in Example 1, except that the filling materials in the distillation tower of this embodiment are as follows:

[0060] The packing of layer A is 316L stainless steel θ ring packing, which accounts for 15% of the effective separation height of the distillation column;

[0061] The filler in layer B is quartz filler, which accounts for 35% of the effective separation height of the distillation column;

[0062] The packing of layer C is aluminum wire braided θ ring packing, which accounts for 2% of the effective separation height of the distillation column;

[0063] The D layer filler is quartz filler, which accounts for 48% of the effective separation height of the distillation column.

[0064] The A-316L stainless steel θ-ring packing was first ultrasonically cleaned for 20 minutes using a 10% NaOH solution before starting the distillation; then rinsed with pure water until neutral, and then ultrasonically cleaned for 5 minutes using 10% nitric acid.

[0065] In a glove box, 1200 g of titanium tetrachloride raw material with a purity of 99.96% was placed in a 1 L quartz flask (reboiler) for rectification and purification.

[0066] The distillation top temperature was controlled at 130°C and total reflux was applied for 4 hours. The reflux ratio of the top fraction was 15:1, and 20% of the top fraction was taken. The reflux ratio was then adjusted to 3:1, and 40% of the middle fraction was taken. The remaining conditions were the same as in Example 1.

[0067] The purity of the middle fraction was checked by ICPMS. Figure 5 , which is a comparison chart of impurity elements and their contents in the ultra-high-purity titanium tetrachloride purified in this example.

[0068] The results show that the total gold impurity content of the distilled titanium tetrachloride is less than 1 ppb, and each impurity is less than 200 ppt. The purity of the titanium tetrachloride can reach 9N level, with a purity of ≥99.9999999%, and the yield of the entire process is 40%.

[0069] Example 3

[0070] The purification system used in Example 3 is the same as that used in Example 1, except that the filling materials in the distillation tower of this embodiment are as follows:

[0071] The packing of layer A is 316L stainless steel θ ring packing, which accounts for 25% of the effective separation height of the distillation column;

[0072] The filler in layer B is quartz filler, which accounts for 35% of the effective separation height of the distillation column;

[0073] The packing of layer C is aluminum wire braided θ ring packing, which accounts for 5% of the effective separation height of the distillation column;

[0074] The D layer filler is quartz filler, which accounts for 35% of the effective separation height of the distillation column.

[0075] The remaining conditions are the same as those in Example 1.

[0076] The purity of the 50% fraction was determined by ICPMS. Figure 6 , which is a comparison chart of impurity elements and their contents in the ultra-high-purity titanium tetrachloride purified in this example.

[0077] Figure 6 Most impurities are controlled below 100ppt, with Cu and Na below 200ppt. The purity of titanium tetrachloride reaches 9N, with a purity of ≥99.9999999%, meeting the purity requirements for integrated circuits. The overall yield is 50%.

[0078] Example 4

[0079] The purification system used in Example 4 is the same as that used in Example 1, except that:

[0080] In Example 4, the radius of the quartz packing sidewall opening is 0.25 mm, which is 1 / 12 of the radius of the quartz packing. The other conditions remain the same as in Example 1.

[0081] The purity of the 50% fraction was determined by ICPMS. Figure 7 , which is a comparison chart of impurity elements and their contents in the ultra-high-purity titanium tetrachloride purified in this example.

[0082] from Figure 7 As can be seen from the data, the impurities Cu, Fe, and Na are controlled within 200ppt, and the remaining impurities are controlled within 100ppt. The purity of titanium tetrachloride reaches 9N level, with a purity of ≥99.9999999%, which generally meets the purity requirements for titanium tetrachloride used in integrated circuits. The yield of the entire process is 50%.

[0083] Comparative Example 1

[0084] The only difference between Comparative Example 1 and Example 1 is that the C-aluminum wire braided θ ring packing is not assembled in the distillation column of Comparative Example 1, and the other conditions remain the same as those of Example 1.

[0085] The purity of the middle fraction was checked by ICPMS. Figure 8 , is a comparison chart of impurity elements and their contents in the purified titanium tetrachloride in Comparative Example 1.

[0086] from Figure 8 It can be seen that the impurity Zr content exceeds 1 ppb and the V content exceeds 0.5 ppb, which can no longer meet the purity requirements of titanium tetrachloride in advanced integrated circuits.

[0087] Comparative Example 2

[0088] The only difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the fillers in layers A, B, C, and D account for 30%, 25%, 10%, and 35% of the distillation column, respectively. The distillation column top temperature is controlled at 135°C, and total reflux is applied for 2 hours. The reflux ratio of the top fraction is 10:1, and 10% of the top fraction is taken. The reflux ratio is then adjusted to 5:1, and 50% of the middle fraction is taken. All other conditions remain the same as in Example 1.

[0089] The purity of the middle fraction was checked by ICPMS. Figure 9 , which is a comparison chart of impurity elements and contents in Comparative Example 2. It can be seen from the figure that the total metal impurities exceed 2 ppb, and the single-phase impurities exceed 1 ppb, which cannot meet the purity requirements of titanium tetrachloride in advanced integrated circuits.

[0090] Comparative Example 3

[0091] The only difference between Comparative Example 3 and Example 1 is that the A-316L stainless steel θ ring packing is not surface treated in Comparative Example 3. The other conditions remain the same as in Example 1.

[0092] The purity of the 50% fraction was determined by ICPMS. Figure 10 , which is a comparison chart of the impurity content of the purified titanium tetrachloride in Comparative Example 3. The figure shows that the content of Fe / Cr related impurities is greatly increased, and cannot meet the purity requirement of titanium tetrachloride in integrated circuits.

[0093] In summary, the method for purifying semiconductor-grade ultra-high-purity titanium tetrachloride provided by the present invention is to obtain semiconductor-grade ultra-high-purity titanium tetrachloride by distilling and purifying the raw material crude titanium tetrachloride through a purification system; the purification system provided by the present invention includes a distillation tower, and the distillation column in the distillation tower includes, from bottom to top, an A-316L stainless steel θ ring packing section, a B-quartz packing section, a C-aluminum wire braided θ ring packing section, and a D-quartz packing section. The A layer packing needs to be surface treated before use, which greatly improves its separation efficiency and can separate most of the heavy component impurities; then, some heavy components and Fe / Cr-containing impurities are separated by the B layer packing; the C layer packing reacts with the crude titanium tetrachloride to generate TICl3, and TiCl3 reacts with some impurities (which have a boiling point close to that of TiCl4 and are difficult to separate), thereby increasing the boiling point of the impurity compounds, thereby once again greatly improving the purity of the product; the impurities that react in the C layer and a small amount of heavy component impurities are finally mostly or completely separated in the D layer. The process of obtaining semiconductor-grade ultra-high-purity titanium tetrachloride through single distillation is simple, has low loss, and is easy to promote. The purity of titanium tetrachloride obtained by the purification method provided by the present invention reaches 99.99999999%, which can meet the production requirements of integrated circuits.

[0094] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

Claims

1. A method for purifying semiconductor-grade ultra-high-purity titanium tetrachloride, characterized in that: include: Using crude titanium tetrachloride as a raw material, the raw material is distilled to obtain ultra-high-purity titanium tetrachloride; The distillation comprises distilling the raw material in a distillation tower; in the distillation tower, the distillation column is connected to four sections A, B, C, and D from bottom to top; wherein A is a 316L stainless steel θ ring packing section, B is a quartz packing section, C is an aluminum wire braided θ ring packing section, and D is a quartz packing section; A, B, C, and D respectively occupy 15-25%, 25-35%, 2-5%, and 35-48% of the height of the distillation column; The aluminum wire braided θ ring packing section can react with the raw material to generate titanium trichloride on the surface of the aluminum wire braided θ ring packing section; The quartz packing of the quartz packing section is hollow cylindrical and has holes on its side wall. The holes are spaced d apart in each row along the axial direction of the quartz packing, where d is the diameter of the hole; the radius of the hole is 1 / 12-1 / 8 of the radius of the quartz packing; When assembling the distillation tower, nitrogen is introduced to discharge moisture; During the distillation process, atmospheric pressure is maintained, the temperature at the top of the distillation tower is 130-136° C., and total reflux is performed for 2-4 hours; During the distillation process, 10-20% is taken as the front fraction, and the reflux ratio of the front fraction is 10:1-15:1; 40-50% is taken as the middle fraction, and the reflux ratio of the middle fraction is 3:1-5:1; Before purification, the 316L stainless steel θ ring packing section is first ultrasonically cleaned with 8%-12% sodium hydroxide solution for 20-40 minutes, rinsed with pure water until neutral, and then ultrasonically cleaned with 8-10% nitric acid for 5-10 minutes for surface treatment; The ultra-high-purity titanium tetrachloride is semiconductor-grade titanium tetrachloride with a purity of ≥99.9999999%; The purity of the raw material is greater than or equal to 99.9%.

2. A semiconductor ultra-high purity titanium tetrachloride purification system, comprising a condenser, a rectification column, a reboiler, and a finished product tank, characterized in that: The distillation column includes, from bottom to top, A-316L stainless steel θ ring packing section, B-quartz packing section, C-aluminum wire braided θ ring packing section, and D-quartz packing section, wherein sections A, B, C, and D occupy 15-25%, 25-35%, 2-5%, and 35-48% of the height of the distillation column, respectively; The aluminum wire braided θ ring packing section can react with the raw material to generate titanium trichloride on the surface of the aluminum wire braided θ ring packing section; The quartz packing of the quartz packing section is hollow cylindrical and has holes on its side wall. The holes are spaced d apart in each row along the axial direction of the quartz packing, where d is the diameter of the hole; the radius of the hole is 1 / 12-1 / 8 of the radius of the quartz packing; When assembling the distillation tower, nitrogen is introduced to discharge moisture; During the distillation process, atmospheric pressure is maintained, the temperature at the top of the distillation tower is 130-136° C., and total reflux is performed for 2-4 hours; During the distillation process, 10-20% is taken as the front fraction, and the reflux ratio of the front fraction is 10:1-15:1; 40-50% is taken as the middle fraction, and the reflux ratio of the middle fraction is 3:1-5:1; Before purification, the 316L stainless steel θ ring packing section is first ultrasonically cleaned with 8%-12% sodium hydroxide solution for 20-40 minutes, rinsed with pure water until neutral, and then ultrasonically cleaned with 8-10% nitric acid for 5-10 minutes for surface treatment; The ultra-high-purity titanium tetrachloride is semiconductor-grade titanium tetrachloride with a purity of ≥99.9999999%; The purity of the raw material is greater than or equal to 99.9%.

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