CN116716659A - Growth method of calcium fluoride crystal and calcium fluoride crystal - Google Patents
Growth method of calcium fluoride crystal and calcium fluoride crystal Download PDFInfo
- Publication number
- CN116716659A CN116716659A CN202310982967.3A CN202310982967A CN116716659A CN 116716659 A CN116716659 A CN 116716659A CN 202310982967 A CN202310982967 A CN 202310982967A CN 116716659 A CN116716659 A CN 116716659A
- Authority
- CN
- China
- Prior art keywords
- crystal
- calcium fluoride
- argon
- growth
- furnace
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000013078 crystal Substances 0.000 title claims abstract description 256
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 title claims abstract description 105
- 229910001634 calcium fluoride Inorganic materials 0.000 title claims abstract description 105
- 238000000034 method Methods 0.000 title claims abstract description 65
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 106
- 229910052786 argon Inorganic materials 0.000 claims abstract description 53
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical compound FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 claims abstract description 45
- 238000002834 transmittance Methods 0.000 claims abstract description 35
- 239000001307 helium Substances 0.000 claims abstract description 33
- 229910052734 helium Inorganic materials 0.000 claims abstract description 33
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims abstract description 33
- 230000008569 process Effects 0.000 claims abstract description 19
- 230000003287 optical effect Effects 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 8
- 238000005086 pumping Methods 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 17
- 238000002425 crystallisation Methods 0.000 abstract description 4
- 230000008025 crystallization Effects 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 20
- 239000000155 melt Substances 0.000 description 14
- 239000002994 raw material Substances 0.000 description 11
- 238000001816 cooling Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 230000007547 defect Effects 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 230000001681 protective effect Effects 0.000 description 5
- 238000005273 aeration Methods 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 238000010899 nucleation Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000007847 structural defect Effects 0.000 description 2
- 238000000233 ultraviolet lithography Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002109 crystal growth method Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000005429 filling process Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/12—Halides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The application relates to the technical field of crystal growth, and particularly discloses a growth method of calcium fluoride crystals and the calcium fluoride crystals. The growth method of the calcium fluoride crystal provided by the application comprises the following steps: the growth of calcium fluoride crystals is carried out in a closed crystal furnace, and the vacuum degree of the crystal furnace is kept within the range of 20-80kpa in the growth process; the atmosphere of the crystal furnace is as follows: the volume ratio is 100: (0.016-0.1): (0.02-0.2) argon, carbon tetrafluoride and helium. The growth method of the calcium fluoride crystal can well maintain the shape of the solid-liquid surface interface in the crystal growth process, improve the heat conduction performance of the calcium fluoride crystal, avoid crucible crystallization and generation of shoulder bubbles, and obtain the large-size calcium fluoride crystal with low dislocation density and high transmittance.
Description
Technical Field
The application relates to the technical field of crystal growth, in particular to a growth method of calcium fluoride crystals and calcium fluoride crystals.
Background
Calcium fluoride is one of natural crystals existing in nature, and is widely used for producing optical components because of its advantages of wide light transmission range, high transmittance, low refractive index, small absorption coefficient, and the like. At present, the growth method of calcium fluoride crystal mainly comprises a pulling method, a crucible descending method, a temperature gradient method and a horizontal growth method. The crystal growth method is characterized in that the crystal cannot contact with the crucible wall in the growth process, so that the crystal growth speed is high, the stress birefringence of the grown crystal is small, and the integrity is high.
The technological process of crystal growth by the pulling method mainly comprises the following steps: vacuumizing, inflating, heating, seeding, shouldering, equalizing diameter, cooling and the like. The gas filling process is to fill specific gas into the crystal growth furnace before the crystal growth, so as to provide a specific gas environment for the crystal growth. At present, in the calcium fluoride crystal growth process, the reaction atmosphere adopted by the aeration is mainly carbon tetrafluoride and argon. However, when the inflation process is adopted to grow large-size crystals (crystals with the diameter of 200-350 mm), the concave-convex shape of the solid-liquid interface of the crystals is often difficult to control, and the front edge of the melt relative to the interface of the crystals protrudes or is sunken, so that the defects of dislocation, polycrystal and the like of the calcium fluoride crystals are caused; in addition, as the diameter of the crystal is too large, heat in the crucible is not easy to be conducted out, and the crystal is easy to wrap gas to form bubbles, so that the crystal is deformed or cracked. Therefore, when the calcium fluoride crystal is directly used in an excimer laser and an ultraviolet lithography apparatus, the calcium fluoride crystal is gradually aged after long-term use due to structural defects such as dislocation, polycrystal, deformity or crack, and the ultraviolet transmittance of the calcium fluoride crystal is drastically reduced, so that the equipment cannot be used.
Disclosure of Invention
In order to reduce structural defects existing in the production of large-size calcium fluoride by a Czochralski method and further improve the quality of large-size calcium fluoride crystals, the application provides a growth method of calcium fluoride crystals and the calcium fluoride crystals.
The method for growing calcium fluoride crystals provided by the application adopts the following technical scheme:
a method for growing calcium fluoride crystals, comprising the steps of: the growth of calcium fluoride crystals is carried out in a closed crystal furnace, and the vacuum degree of the crystal furnace is kept within the range of 20-80kpa in the growth process;
the atmosphere of the crystal furnace is as follows: the volume ratio is 100: (0.016-0.1): (0.02-0.2) argon, carbon tetrafluoride and helium.
The application provides a growth method of calcium fluoride crystal, the inflation process of the growth method adopts argon, carbon tetrafluoride and helium to inflate a crystal furnace, and the formed atmosphere environment can improve the solid-liquid interface shape of the crystal growth process on one hand by controlling the volume ratio of the three gases in the range, avoid the problems of dislocation, polycrystal and the like of the crystal, and further improve the quality uniformity of the crystal; on the other hand, the heat conduction of the crystal can be increased, so that the heat dissipation of the crystal is increased, the crystallization at the bottom of the crucible is restrained, meanwhile, bubbles generated at the shoulder of the crystal are reduced, and the crystal is prevented from being deformed or cracked. Therefore, the growth method of the calcium fluoride crystal can maintain the shape of the solid-liquid surface interface of the crystal, increase the heat conduction of the crystal, and further obtain the calcium fluoride crystal with low dislocation density and good transmittance.
In the application, the main function of the carbon tetrafluoride is to change the concave-convex shape of the solid-liquid interface of the crystal, and when the addition amount of the carbon tetrafluoride is too high, the solid-liquid interface of the crystal is more concave to the crystal; the smaller the amount of carbon tetrafluoride charged, the more the solid-liquid interface of the crystal is recessed to the melt, and the defects such as dislocation and polycrystal of the calcium fluoride crystal are easily caused by the concave-convex shape of the solid-liquid interface, so that the transmittance of the calcium fluoride crystal is influenced. Therefore, the amount of carbon tetrafluoride is strictly controlled within the above range, the size of the solid-liquid interface roughness during the crystal growth process can be reduced, and the dislocation density of the calcium fluoride crystal can be reduced, thereby improving the transmittance of the calcium fluoride crystal and further improving the crystal quality.
In a specific embodiment, the argon, carbon tetrafluoride, and helium may be present in a volume ratio of 100:0.016:0.1, 100:0.025:0.1, 100:0.05:0.1, 100:0.075:0.1, 100:0.1:0.1, 100:0.05:0.02, 100:0.05:0.05, 100:0.05:0.15 or 100:0.05:0.2.
preferably, the volume ratio of the argon, the carbon tetrafluoride and the helium is 100: (0.025-0.075): (0.05-0.15).
In the application, experiments prove that the volume ratio of argon, carbon tetrafluoride and helium is further controlled within the range, the size of the convex solid-liquid interface to the melt or the convex melt to the crystal is less than or equal to 15mm in the growth process of the crystal,the obtained calcium fluoride crystal has more excellent crystal structure and higher transmittance, and the average dislocation density is less than or equal to 25/cm 2 The transmittance is more than 99 percent.
Preferably, the purity of the argon is 5N-6N.
Preferably, the growth method of calcium fluoride crystal further comprises vacuumizing, specifically: vacuum-pumping the crystal furnace to make vacuum degree be 1x10 -4 Pa below, and controlling the temperature of the crystal furnace to be 250-270 ℃.
In the application, the crystal furnace is vacuumized before the inflation process, so that oxygen in the crystal furnace is pumped out, and the calcium fluoride crystal can be in an anaerobic environment, thereby effectively avoiding the generation of calcium oxide.
In a second aspect, the present application provides a calcium fluoride crystal.
A calcium fluoride crystal prepared by the growth method of the calcium fluoride crystal.
Preferably, the calcium fluoride crystals have a diameter of 200-350mm.
The growth method of the calcium fluoride crystal provided by the application can prepare the large-size calcium fluoride crystal with the diameter of 200-350mm, and the obtained crystal has low dislocation density and good transmittance, and can be used for preparing high-end optical components such as excimer laser cavity mirrors, optical instrument prisms, perspective mirrors, windows and the like.
In a specific embodiment, the calcium fluoride crystals may have a diameter of 200mm, 280mm or 200mm.
Preferably, the calcium fluoride crystals have an average dislocation density of < 25/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The transmittance is more than 99 percent.
In a third aspect, the application provides the use of calcium fluoride crystals in excimer laser cavity mirrors, optical instrument prisms, mirror mirrors and windows.
In summary, the application has the following beneficial effects:
1. the application provides a growth method of calcium fluoride crystal, which adopts the aeration process with the volume ratio of 100: (0.016-0.1): the argon, carbon tetrafluoride and helium in the atmosphere of (0.02-0.2) are inflated, so that on one hand, the shape of a solid-liquid interface in the crystal growth process can be improved, defects such as dislocation and polycrystal of calcium fluoride crystals are avoided, and the quality uniformity of the crystals is improved; on the other hand, the heat conduction of the crystal can be increased, and the crystallization at the bottom of the crucible is inhibited; meanwhile, the heat dissipation of the crystal can also reduce the generation of shoulder bubbles, and avoid the defects of deformity, crack or cavity and the like of the crystal.
2. The application further controls the volume ratio of argon, carbon tetrafluoride and helium to 100: (0.025-0.075): in the range of (0.05-0.15), the obtained calcium fluoride crystal has more excellent crystal structure and higher transmittance, and the average dislocation density is less than or equal to 25/cm 2 The transmittance is more than 99 percent.
3. The growth method of the calcium fluoride crystal provided by the application can prepare the large-size calcium fluoride crystal with the diameter of 200-350mm, and the obtained crystal has low dislocation density and good transmittance, and can be used for preparing high-end optical components such as excimer laser cavity mirrors, optical instrument prisms, perspective mirrors, windows and the like.
Detailed Description
The application provides a growth method of calcium fluoride crystals, which comprises the following steps:
(1) Pretreatment: charging a calcium fluoride raw material into a graphite crucible; then starting a vacuum system to vacuumize the crystal furnace to make the vacuum degree reach 1x10 -4 And (3) simultaneously starting a heater under Pa to control the temperature in the furnace to be 250-270 ℃.
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches 20-80kpa, the argon filling is stopped; then charging carbon tetrafluoride and helium into the crystal furnace; wherein the purity of the argon is 5N-6N; the volume ratio of argon, carbon tetrafluoride and helium is 100: (0.016-0.1): (0.02-0.2); further, the volume ratio of argon, carbon tetrafluoride and helium is 100: (0.025-0.075): (0.05-0.15). In addition, carbon tetrafluoride and helium can be charged sequentially in any order, or can be charged simultaneously.
(3) Heating: heating the polycrystal material, keeping the constant temperature for more than 5 hours after the temperature is raised to 1380-1400 ℃ until the raw materials are melted and the temperature of the melt in the crucible reaches balance, and welding seed crystals.
(4) Seeding: setting the downward movement speed of the seed crystal to be 4.5-5.5mm/min, descending until the bottom surface of the seed crystal contacts the liquid level of the raw material, continuing descending for 2-3mm after contact, enabling the seed crystal to fully contact the melt, starting an automatic rotation program, rotating the seed crystal at the speed of 8-12rpm, and keeping for 0.5-1h. When the weight of the seed crystal is constant and unchanged, the temperature of the heater at the side of the crystal furnace is raised to melt the diameter of the seed crystal by 2-3mm, then an automatic cooling program is started, the temperature of the side heater is lowered by 2-3 ℃/h, and the crystal at the seed crystal grows.
(5) Shoulder placing: when the crystal at the seed crystal grows to be the same as the diameter of the raw material, a pulling program is started, the temperature of a bottom heater is kept constant, a side heater is cooled at a speed of 3-6 ℃/h, the seed crystal is pulled upwards at a speed of 1.5-2mm/h and rotates at a speed of 9-10rpm, a crucible and the seed crystal rotate reversely at a speed of 1-2rpm, and the crystal diameter is gradually enlarged.
(6) Equal diameter: when the diameter of the crystal grows to the required size, starting a diameter automatic control program, setting the pulling speed to be 1.5-2mm/h, setting the rotation speed of the seed crystal to be 8-9rpm, reversely rotating the crucible and the seed crystal at the speed of 1-2rpm, and finishing the pulling process after the seed crystal is pulled upwards for 48 hours; then keeping the temperature of the side heater constant, and raising the temperature of the bottom heater by 20-25 ℃ to enable the bottom of the crystal and the melt to be naturally fused; finally, the crystal is lifted upwards to be more than or equal to 10 to 15mm at the speed of 5 to 6 mm/mm, so that the crystal and the melt are completely separated.
(7) And (3) cooling: cooling the crystal furnace, and starting a vacuum pump to vacuumize the crystal furnace after cooling to room temperature to ensure that the vacuum degree in the crystal furnace reaches 10 -2 And standing for 40-50min at Pa above, and charging dry air to 0Pa to obtain calcium fluoride crystal.
In the application, the grain diameter of the calcium fluoride raw material is 3-7mm, and the oxygen content is less than 0.00001%; the diameter of the seed crystal is 45m, and the length is 120mm; the remaining materials, reagents, etc. are commercially available.
The present application will be described in further detail with reference to examples and performance test.
Example 1
Example 1 provides a method for growing calcium fluoride crystals comprising the steps of:
(1) Pretreatment: charging a calcium fluoride raw material into a graphite crucible of a crystal furnace; then a vacuum system is started to vacuumize the crystal furnace to ensure that the vacuum degree is 5x10 -5 Pa, and simultaneously turning on the heater to make the temperature in the furnace 260 ℃.
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches 20kpa, the argon filling is stopped; then charging carbon tetrafluoride and helium into the crystal furnace simultaneously; wherein the purity of the argon is 5N; the volume ratio of argon, carbon tetrafluoride and helium is 100:0.016:0.1.
(3) Heating: heating the crystal furnace, keeping the constant temperature for more than 5 hours after the temperature is raised to 1380 ℃ until the raw materials are melted and the temperature of the melt in the crucible reaches balance, and welding seed crystals.
(4) Seeding: setting the downward movement speed of the seed crystal to be 5mm/min, descending until the bottom surface of the seed crystal contacts the liquid level of the raw material, continuing descending for 3mm after contacting, enabling the seed crystal to fully contact the melt, starting an automatic rotation program, rotating the seed crystal at the speed of 10pm, and keeping for 0.5h; when the weight of the seed crystal is constant and unchanged, the temperature of the heater at the side of the crystal furnace is raised to melt the diameter of the seed crystal by 2-3mm, then an automatic cooling program is started, the temperature of the side heater is lowered by 3 ℃/h, and the crystal at the seed crystal grows.
(5) Shoulder placing: when the crystal at the seed crystal grows to be the same as the diameter of the raw material, a pulling program is started, the temperature of a bottom heater is kept constant, a side heater is cooled at a speed of 5 ℃/h, the seed crystal is pulled upwards at a speed of 2mm/h and rotated at a speed of 10rpm, and a crucible and the seed crystal are rotated reversely at a speed of 2rpm until the crystal diameter grows to 200mm.
(6) Equal diameter: when the diameter of the crystal grows to 200mm, controlling the pulling speed to be 2mm/h, controlling the rotation speed of the seed crystal to be 8rpm, enabling the crucible to rotate reversely with the seed crystal at the speed of 2rpm, and finishing the pulling process after the seed crystal is pulled upwards for 48 h; then keeping the temperature of the side heater constant, and raising the temperature of the bottom heater by 20 ℃ to enable the bottom of the crystal and the melt to be naturally fused; finally, the crystal is lifted upwards by 10mm at a speed of 5mm/min, so that the crystal and the melt are completely separated.
(7) And (3) cooling: furnace the crystal toThe cooling rate of 8 ℃/h is reduced to 850 ℃, and then the temperature is reduced to room temperature at the cooling rate of 15 ℃/h; then a vacuum pump is started to vacuumize the crystal furnace, so that the vacuum degree in the crystal furnace reaches 10 -2 And standing for 45min at a pressure of more than Pa, and filling dry air to 0Pa to obtain calcium fluoride crystals. The obtained calcium fluoride crystals had a diameter of 200mm and a length of 100mm.
Examples 2 to 9
Examples 2-9 were performed as in example 1, except that: argon, carbon tetrafluoride and helium.
TABLE 1 volume ratio of argon, carbon tetrafluoride and helium in examples 1-9
Example 10
Example 10 was performed as in example 3, except that: the calcium fluoride crystals obtained in example 10 had a diameter of 280mm and a length of 40mm; the shoulder placing step of example 10 is:
(5) Shoulder placing: when the crystal at the seed crystal grows to be the same as the diameter of the raw material, a pulling program is started, the temperature of a bottom heater is kept constant, a side heater is cooled at a speed of 5 ℃/h, the seed crystal is pulled upwards at a speed of 2mm/h and rotated at a speed of 10rpm, and a crucible and the seed crystal are rotated reversely at a speed of 2rpm until the diameter of the crystal grows to 280mm.
Example 11
Example 11 was performed as in example 3, except that: the calcium fluoride crystals obtained in example 11 had a diameter of 350mm and a length of 30mm; the shoulder placing step of example 11 is:
(5) Shoulder placing: when the crystal at the seed crystal grows to be the same as the diameter of the raw material, a pulling program is started, the temperature of a bottom heater is kept constant, a side heater is cooled at a speed of 5 ℃/h, the seed crystal is pulled upwards at a speed of 2mm/h and rotated at a speed of 10rpm, and a crucible and the seed crystal are rotated reversely at a speed of 2rpm until the crystal diameter grows to 350mm.
Comparative example 1
Comparative example 1 was conducted in accordance with the method of example 3 except that: (2) an inflation step. The inflation procedure of comparative example 1 is:
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches-20 kpa, the argon filling is stopped; then simultaneously charging carbon tetrafluoride into the crystal furnace; wherein the purity of the argon is 5N; the volume ratio of argon to carbon tetrafluoride is 100:0.05.
comparative example 2
Comparative example 2 was conducted in accordance with the method of example 3 except that: (2) an inflation step. The inflation procedure for comparative example 2 is:
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches-20 kpa, the argon filling is stopped; then simultaneously charging carbon tetrafluoride into the crystal furnace; wherein the purity of the argon is 5N; the volume ratio of argon to carbon tetrafluoride is 100:5.
comparative example 3
Comparative example 3 was conducted in accordance with the method of example 3 except that: (2) In the aeration step, the volume ratio of argon, carbon tetrafluoride and helium is calculated. The inflation procedure for comparative example 3 is:
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches-20 kpa, the argon filling is stopped; then charging carbon tetrafluoride and helium into the crystal furnace simultaneously; wherein the purity of the argon is 5N; the volume ratio of argon, carbon tetrafluoride and helium is 100:0.2:0.1.
comparative example 4
Comparative example 4 was conducted in accordance with the method of example 3 except that: (2) In the aeration step, the volume ratio of argon, carbon tetrafluoride and helium is calculated. The inflation procedure for comparative example 4 is:
(2) And (3) inflation: argon is filled into the crystal furnace, and when the vacuum degree in the crystal furnace reaches-20 kpa, the argon filling is stopped; then charging carbon tetrafluoride and helium into the crystal furnace simultaneously; wherein the purity of the argon is 5N; the volume ratio of argon, carbon tetrafluoride and helium is 100:0.05:0.3.
performance test
The size of the irregularities of the solid-liquid interface during the growth of the calcium fluoride crystals of examples 1 to 11 and comparative examples 1 to 4 and the properties of the obtained calcium fluoride crystals were examined.
1. Concave-convex size of solid-liquid interface: in the constant diameter growth process of calcium fluoride crystals, a CCD imaging technology is adopted to observe the solid-liquid interface of the crystals, and the size of the crystals protruding to the melt or the size of the crystals protruding to the melt is measured.
2. Dislocation density: the dislocation distribution of calcium fluoride crystal is characterized by adopting an etching method. The method comprises the following steps: and longitudinally cutting the calcium fluoride crystal along the growth direction of the seed crystal, putting the calcium fluoride crystal into 0.25mol/L dilute hydrochloric acid solution, standing for 1h, taking out, and observing dislocation distribution of the cut surface of the crystal after corrosion by an optical microscope after cleaning. The observation object is a 3 inch diameter calcium fluoride wafer; the calcium fluoride wafer is provided with 37 test points (each test point has an area of 0.024 cm) 2 ) The number of pits at 37 test points was recorded, and the dislocation pit densities were calculated and averaged.
3. Transmittance: slicing the calcium fluoride crystal, processing the calcium fluoride crystal into a sample with the diameter of 30mm and the thickness of 10mm, and polishing two planes of the sample to obtain a test sample; the transmittance of the test sample at 200-400nm was then measured using a spectrophotometer, and then the transmittance of the crystal at 200nm was calculated as follows:
wherein Ti: inner transmittance; t (T) λ : spectral transmittance at wavelength λ; r is R λ : residual reflectivity at wavelength λ; d: sample thickness in cm.
TABLE 2 Performance test results of calcium fluoride crystals obtained in examples 1 to 11 and comparative examples 1 to 4
As can be seen from the results of the performance tests in Table 2, the calcium fluoride crystals obtained in examples 1 to 11 have an average dislocation density of 30 pieces/cm or less 2 Through the transmission ofThe rate is more than 98 percent. The method for growing the calcium fluoride crystal can prepare the large-size calcium fluoride crystal with excellent crystal structure, low dislocation density and high transmittance.
In comparative example 1, when only argon gas and carbon tetrafluoride are used as protective atmosphere, not only crystallization is easy to occur at the bottom of a crucible in the crystal growth stage, but also the transmittance of the obtained calcium fluoride crystal is poor, because heat in the crucible is not easy to be led out, so that gas is wrapped when the crystal grows, bubbles are formed in the crucible, and further the crystal is slightly deformed, cracked and other defects are caused, and the transmittance of the crystal is affected.
Comparative example 2 employed a volume ratio of 100:5, and the average dislocation density of the prepared calcium fluoride crystal is up to 44/cm when the argon and the carbon tetrafluoride are used as protective atmosphere 2 The transmittance was only 95.2%. The reason is that the addition amount of carbon tetrafluoride is too high, so that a solid-liquid interface presents a melt protruding to the crystal in the crystal growth process, and further, the defects of dislocation, polycrystal and the like of the calcium fluoride crystal appear, and the transmittance of the calcium fluoride crystal is affected.
The results of the tests of examples 1 to 5 and comparative example 3 show that the volume ratio of comparative example 3 is 100:0.2:0.1 argon, carbon tetrafluoride and helium as protective atmosphere, the average dislocation density of the calcium fluoride crystals produced was 34/cm 2 The transmittance is 97.3%; whereas examples 1-5 employed a volume ratio of 100: (0.016-0.1): 0.1 argon, carbon tetrafluoride and helium as protective atmosphere, the average dislocation density of the prepared calcium fluoride crystal is less than or equal to 30/cm 2 The transmittance is more than 98 percent. Further comparison shows that examples 2-4 provide argon, carbon tetrafluoride and helium in a volume ratio of 100: (0.025-0.075): at 0.1, the average dislocation density of the obtained calcium fluoride crystal is not more than 25 per cm 2 The transmittance is more than 99 percent. Thus, the application is illustrated to further control the volume ratio of argon, carbon tetrafluoride and helium to 100: (0.025-0.075): at 0.1, the obtained calcium fluoride crystal has more excellent crystal structure and higher transmittance.
The results of the tests in example 3, examples 6 to 9 and comparative example 4 show that the volume ratio of comparative example 4 is 100:0.05:0.3 argon, carbon tetrafluoride and helium as protectionsThe average dislocation density of the prepared calcium fluoride crystal is 26/cm under the protection of atmosphere 2 The transmittance is 96.4%; whereas examples 3 and examples 6 to 9 employed a volume ratio of 100:0.05: (0.02-0.2) when argon, carbon tetrafluoride and helium are used as protective atmosphere, the average dislocation density of the prepared calcium fluoride crystal is less than or equal to 30/cm 2 The transmittance is more than 98 percent. Further comparison shows that the volume ratio of argon, carbon tetrafluoride and helium in examples 3 and 7-8 is 100:0.05: (0.05-0.15) the calcium fluoride crystals obtained have an average dislocation density of 25/cm or less 2 The transmittance is more than 99 percent. Thus, the application is illustrated to further control the volume ratio of argon, carbon tetrafluoride and helium to 100:0.05: (0.05-0.15), the calcium fluoride crystal obtained is more excellent in crystal structure and higher in transmittance.
The calcium fluoride crystals obtained in example 10 had a diameter of 280mm and a length of 40mm and an average dislocation density of 20 pieces/cm 2 The transmittance is 99.6%; the calcium fluoride crystals obtained in example 11 had a diameter of 350mm and a length of 30mm and an average dislocation density of 18 pieces/cm 2 The transmittance was 99.7%. Therefore, the method for growing the calcium fluoride crystal can prepare the large-size calcium fluoride crystal with the diameter of 200-350mm, and the prepared calcium fluoride crystal has low dislocation density and high transmittance and can be used for manufacturing excimer laser cavity mirrors and optical devices in ultraviolet lithography instruments.
While the application has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the application and are intended to be within the scope of the application as claimed.
Claims (9)
1. A method for growing calcium fluoride crystals, comprising the steps of: the growth of calcium fluoride crystals is carried out in a closed crystal furnace, and the vacuum degree of the crystal furnace is kept within the range of 20-80kpa in the growth process;
the atmosphere of the crystal furnace is as follows: the volume ratio is 100: (0.016-0.1): (0.02-0.2) argon, carbon tetrafluoride and helium.
2. The method for growing calcium fluoride crystals according to claim 1, wherein the volume ratio of argon, carbon tetrafluoride and helium is 100: (0.025-0.075): (0.05-0.15).
3. The method for growing calcium fluoride crystals according to claim 1, wherein the volume ratio of argon, carbon tetrafluoride and helium is 100:0.05:0.1.
4. the method for growing calcium fluoride crystals according to claim 1, wherein the purity of the argon gas is 5N to 6N.
5. The method for growing calcium fluoride crystals according to any one of claims 1 to 4, further comprising evacuating, in particular: vacuum-pumping the crystal furnace to make vacuum degree be 1x10 -4 Pa below, and controlling the temperature of the crystal furnace to be 250-270 ℃.
6. Calcium fluoride crystals obtained by the method for growing calcium fluoride crystals according to any one of claims 1 to 5.
7. The calcium fluoride crystal according to claim 6, wherein the diameter of the calcium fluoride crystal is 200-350mm.
8. The calcium fluoride crystal according to claim 6, characterized in that the calcium fluoride crystal has an average dislocation density < 25/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the The transmittance is more than 99 percent.
9. Use of a calcium fluoride crystal according to any one of claims 6-8 in excimer laser cavity mirrors, optical instrument prisms, mirror and windows.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310982967.3A CN116716659B (en) | 2023-08-07 | 2023-08-07 | Growth method of calcium fluoride crystal and calcium fluoride crystal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310982967.3A CN116716659B (en) | 2023-08-07 | 2023-08-07 | Growth method of calcium fluoride crystal and calcium fluoride crystal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116716659A true CN116716659A (en) | 2023-09-08 |
| CN116716659B CN116716659B (en) | 2023-10-31 |
Family
ID=87875505
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310982967.3A Active CN116716659B (en) | 2023-08-07 | 2023-08-07 | Growth method of calcium fluoride crystal and calcium fluoride crystal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116716659B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003002789A (en) * | 2001-04-09 | 2003-01-08 | Kobe Steel Ltd | Method for manufacturing fluoride single crystal |
| US20120057222A1 (en) * | 2010-09-03 | 2012-03-08 | Yasuhiro Hashimoto | Single crystal of magnesium fluoride, optical member and optical element comprising the same |
| CN105133005A (en) * | 2014-06-03 | 2015-12-09 | 长春理工大学 | Crystal growth method for obtaining flat solid-liquid interface, and apparatus thereof |
| CN111270309A (en) * | 2020-03-05 | 2020-06-12 | 秦皇岛本征晶体科技有限公司 | Growth method of calcium fluoride single crystal and used device |
-
2023
- 2023-08-07 CN CN202310982967.3A patent/CN116716659B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003002789A (en) * | 2001-04-09 | 2003-01-08 | Kobe Steel Ltd | Method for manufacturing fluoride single crystal |
| US20120057222A1 (en) * | 2010-09-03 | 2012-03-08 | Yasuhiro Hashimoto | Single crystal of magnesium fluoride, optical member and optical element comprising the same |
| CN105133005A (en) * | 2014-06-03 | 2015-12-09 | 长春理工大学 | Crystal growth method for obtaining flat solid-liquid interface, and apparatus thereof |
| CN111270309A (en) * | 2020-03-05 | 2020-06-12 | 秦皇岛本征晶体科技有限公司 | Growth method of calcium fluoride single crystal and used device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116716659B (en) | 2023-10-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP2075355B1 (en) | Inner crystallization crucible and pulling method using the crucible | |
| JP4702898B2 (en) | Method for producing quartz glass crucible for pulling silicon single crystal | |
| JP4863710B2 (en) | Pulling apparatus for producing metal fluoride single crystal and method for producing metal fluoride single crystal using the apparatus | |
| US8163083B2 (en) | Silica glass crucible and method for pulling up silicon single crystal using the same | |
| JP4844428B2 (en) | Method for producing sapphire single crystal | |
| JP5433632B2 (en) | GaAs single crystal manufacturing method and GaAs single crystal wafer | |
| JP6759020B2 (en) | Silicon single crystal manufacturing method and quartz crucible for silicon single crystal manufacturing after modification treatment | |
| JP4174086B2 (en) | Seed and fluoride crystals for crystal growth | |
| CN116716659B (en) | Growth method of calcium fluoride crystal and calcium fluoride crystal | |
| TWI580827B (en) | Sapphire single crystal nucleus and its manufacturing method | |
| JP4844429B2 (en) | Method for producing sapphire single crystal | |
| JP4726138B2 (en) | Quartz glass crucible | |
| JP3659377B2 (en) | Method for producing fluoride crystals | |
| JP5489614B2 (en) | Manufacturing method of optical member | |
| JP4425181B2 (en) | Method for producing metal fluoride single crystal | |
| JP4425185B2 (en) | Annealing method of metal fluoride single crystal | |
| JPH1149597A (en) | Quartz crucible for pulling up silicon single crystal | |
| KR20040044365A (en) | As-Grown Single Crystal of Alkaline Earth Metal Fluoride | |
| JP4484208B2 (en) | Method for producing metal fluoride single crystal | |
| JP2009280411A (en) | Seed crystal for producing metal fluoride single crystal | |
| CN111621849B (en) | Magneto-optical crystal, magneto-optical device and preparation method | |
| CN116732612B (en) | Calcium fluoride crystal and preparation method and application thereof | |
| JP2013060335A (en) | METHOD FOR PRODUCING MgF2 SINGLE CRYSTAL | |
| JP4146835B2 (en) | Crystal growth method | |
| TW202302935A (en) | Ga2o3-based single crystal substrate and method for manufacturing ga2o3-based single crystal substrate |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |