大尺寸藍寶石泡生單晶爐溫場模擬研究
發(fā)布時間：2019-04-03 16:47
【摘要】：由于藍寶石晶體良好的光學特性、穩(wěn)定的化學結構和較強的機械強度,使其廣泛應用于衛(wèi)星空間技術、紅外軍事裝置、高強度激光的窗口等軍事領域;因其晶格常數(shù)與GaN接近,生長工藝成熟,使藍寶石單晶廣泛應用于SOS微電子電路、LED燈珠等襯底行業(yè);因其硬度高、介電常數(shù)符合電容屏要求,使藍寶石單晶應用于可穿戴設備窗口領域;又因其原子能級躍遷的特殊性質,使摻鈦藍寶石單晶應用于高功率激光器增益介質。隨著這些行業(yè)的快速發(fā)展,藍寶石的需求量日益增加,生長大尺寸、高質量藍寶石單晶變得尤為迫切。因此,大尺寸藍寶石泡生單晶爐溫場的研究具有重大的應用價值。本論文利用CGSim模擬軟件,并結合實際長晶實驗的結果,探究了單晶爐溫場老化的原因。利用金相顯微鏡、掃描電子顯微鏡(SEM)和干涉儀測試老化單晶爐鉬屏的成分、微結構和反射率,結果表明單晶爐上、中、下層鉬屏老化的機理明顯不同:上部鉬屏老化的機理是由于鉬屏長期工作在低溫區(qū)而被Al、O、Mo、W等揮發(fā)物附著,形成凸凹不平、大小不一的黑色附著物,吸附在鉬屏表面的黑色揮發(fā)物改變了鉬屏的反射率,降低了其保溫效果;中部鉬屏因工作區(qū)域溫度沒有達到其最高工作溫度,表面形貌變化不大,反射率也沒有太多變化;下層鉬屏由于長期工作在高溫區(qū)而造成鉬元素揮發(fā),在其表面形成了許多方向混亂、大小不一的微鏡面,因微鏡面的散射而降低鉬屏的保溫效果。將測得老化溫場鉬屏各部分反射率的結果導入計算機,模擬計算發(fā)現(xiàn),由于鉬屏保溫效果改變,其溫場溫度梯度、固液面、熔體液流也發(fā)生了改變。通過實驗長晶,晶體品質檢測,發(fā)現(xiàn)與原溫場對比晶體品質出現(xiàn)嚴重下降。利用藍寶石單晶模擬軟件CGSim,研究了氧化鋯、氧化鋁和金屬組合溫場的性能。首次提出了下部由鉬屏與鋯石結合、側部由鉬屏與氧化鋁結合的保溫系統(tǒng)。模擬結果顯示:在保持側屏厚度不變的情況下,將等厚度的鉬屏更替為氧化鋁后,溫場的保溫效果反而變差;在保證內部鉬屏層數(shù)不變的情況下,不斷增加鋯石或氧化鋁厚度,溫場保溫效果明顯增強,功耗下降。但增加到一定厚度后,功耗下降趨緩。通過模擬相同溫場構造、不同坩堝尺寸的單晶爐溫場,探究120kg、200kg和300kg級的溫場性能,結果顯示:隨著坩堝尺寸的增大,溫場的保溫效果變差、功耗增加;生長角變大、應力變大并出現(xiàn)應力富集現(xiàn)象;溫度梯度減小;熔體液流保持不變。設計大尺寸單晶爐時,增強側保溫和下保溫效果,擴大引晶與晶體交界面,防止應力富集現(xiàn)象出現(xiàn)。
[Abstract]:Because of its good optical properties, stable chemical structure and strong mechanical strength, sapphire crystal is widely used in military fields such as satellite space technology, infrared military devices, high-intensity laser windows and so on. Because its lattice constant is close to that of GaN and its growth process is mature, sapphire single crystal is widely used in SOS microelectronics circuit, LED lamp bead and other substrate industries. Because of its high hardness and dielectric constant, sapphire single crystal is applied to the window field of wearable devices, and because of its special properties of atomic level transition, Ti-doped sapphire single crystal is used in gain medium of high power laser. With the rapid development of these industries, the demand for sapphire is increasing day by day. It is very urgent to grow sapphire single crystal with large size and high quality. Therefore, the study of large size sapphire bubble single crystal furnace temperature field has great application value. In this paper, the reason of temperature field aging of single crystal furnace is investigated by using CGSim simulation software and the results of practical long crystal experiment. The composition, microstructure and reflectivity of molybdenum screen in aging single crystal furnace were measured by metallographic microscope, scanning electron microscope (SEM) and interferometer. The results showed that, in the single crystal furnace, the composition, microstructure and reflectivity of molybdenum screen were measured. The mechanism of molybdenum screen aging in the lower layer is obviously different: the aging mechanism of the upper molybdenum screen is that the molybdenum screen is attached by volatiles such as Al,O,Mo,W because the molybdenum screen works in low temperature for a long time, resulting in uneven black attachments of varying sizes. The black volatiles adsorbed on the surface of the molybdenum screen changed the reflectivity of the molybdenum screen and reduced its thermal insulation effect. Because the temperature of the middle molybdenum screen did not reach its highest working temperature, the surface morphology did not change much, and the reflectivity did not change much. Molybdenum element volatilization is caused by long-term work in the high temperature region of the lower molybdenum screen. There are many disordered micromirrors with different sizes on the surface of the molybdenum screen, which reduces the thermal insulation effect of the molybdenum screen due to scattering of the micro-mirror surface. The results of measuring the reflectivity of the molybdenum screen in the aging temperature field are introduced into the computer. The simulation results show that the temperature gradient of the temperature field, the solid liquid level and the melt liquid flow also change due to the change of the thermal insulation effect of the molybdenum screen. It was found that the crystal quality decreased seriously compared with the original temperature field through the experiment of long crystal and crystal quality test. The temperature fields of zirconia, alumina and metal have been studied by using the sapphire single crystal simulation software CGSim,. For the first time, a thermal insulation system is put forward, in which the lower part is bonded with zircons and the lateral part is bonded by molybdenum screen and alumina. The simulation results show that when the thickness of the side screen is kept constant, the thermal insulation effect of the temperature field becomes worse when the molybdenum screen of equal thickness is replaced by alumina. Under the condition of keeping the number of layers of molybdenum screen constant, the thickness of zircon or alumina is continuously increased, the thermal insulation effect of temperature field is obviously enhanced, and the power consumption is decreased. However, after increasing to a certain thickness, the power consumption decreases slowly. By simulating the temperature field of single crystal furnace with the same temperature field structure and different crucible sizes, the temperature field performance of 120 kg, 200 kg and 300kg grades is investigated. The results show that with the increase of crucible size, the thermal insulation effect of the temperature field becomes worse and the power consumption increases. The growth angle becomes larger and the stress increases and stress enrichment occurs; the temperature gradient decreases and the melt flow remains unchanged. In the design of large size single crystal furnace, the effect of side and bottom heat preservation is enhanced, the interface between crystal and crystal is enlarged, and the phenomenon of stress enrichment is prevented.
【學位授予單位】：深圳大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O78
本文編號：2453369
[Abstract]:Because of its good optical properties, stable chemical structure and strong mechanical strength, sapphire crystal is widely used in military fields such as satellite space technology, infrared military devices, high-intensity laser windows and so on. Because its lattice constant is close to that of GaN and its growth process is mature, sapphire single crystal is widely used in SOS microelectronics circuit, LED lamp bead and other substrate industries. Because of its high hardness and dielectric constant, sapphire single crystal is applied to the window field of wearable devices, and because of its special properties of atomic level transition, Ti-doped sapphire single crystal is used in gain medium of high power laser. With the rapid development of these industries, the demand for sapphire is increasing day by day. It is very urgent to grow sapphire single crystal with large size and high quality. Therefore, the study of large size sapphire bubble single crystal furnace temperature field has great application value. In this paper, the reason of temperature field aging of single crystal furnace is investigated by using CGSim simulation software and the results of practical long crystal experiment. The composition, microstructure and reflectivity of molybdenum screen in aging single crystal furnace were measured by metallographic microscope, scanning electron microscope (SEM) and interferometer. The results showed that, in the single crystal furnace, the composition, microstructure and reflectivity of molybdenum screen were measured. The mechanism of molybdenum screen aging in the lower layer is obviously different: the aging mechanism of the upper molybdenum screen is that the molybdenum screen is attached by volatiles such as Al,O,Mo,W because the molybdenum screen works in low temperature for a long time, resulting in uneven black attachments of varying sizes. The black volatiles adsorbed on the surface of the molybdenum screen changed the reflectivity of the molybdenum screen and reduced its thermal insulation effect. Because the temperature of the middle molybdenum screen did not reach its highest working temperature, the surface morphology did not change much, and the reflectivity did not change much. Molybdenum element volatilization is caused by long-term work in the high temperature region of the lower molybdenum screen. There are many disordered micromirrors with different sizes on the surface of the molybdenum screen, which reduces the thermal insulation effect of the molybdenum screen due to scattering of the micro-mirror surface. The results of measuring the reflectivity of the molybdenum screen in the aging temperature field are introduced into the computer. The simulation results show that the temperature gradient of the temperature field, the solid liquid level and the melt liquid flow also change due to the change of the thermal insulation effect of the molybdenum screen. It was found that the crystal quality decreased seriously compared with the original temperature field through the experiment of long crystal and crystal quality test. The temperature fields of zirconia, alumina and metal have been studied by using the sapphire single crystal simulation software CGSim,. For the first time, a thermal insulation system is put forward, in which the lower part is bonded with zircons and the lateral part is bonded by molybdenum screen and alumina. The simulation results show that when the thickness of the side screen is kept constant, the thermal insulation effect of the temperature field becomes worse when the molybdenum screen of equal thickness is replaced by alumina. Under the condition of keeping the number of layers of molybdenum screen constant, the thickness of zircon or alumina is continuously increased, the thermal insulation effect of temperature field is obviously enhanced, and the power consumption is decreased. However, after increasing to a certain thickness, the power consumption decreases slowly. By simulating the temperature field of single crystal furnace with the same temperature field structure and different crucible sizes, the temperature field performance of 120 kg, 200 kg and 300kg grades is investigated. The results show that with the increase of crucible size, the thermal insulation effect of the temperature field becomes worse and the power consumption increases. The growth angle becomes larger and the stress increases and stress enrichment occurs; the temperature gradient decreases and the melt flow remains unchanged. In the design of large size single crystal furnace, the effect of side and bottom heat preservation is enhanced, the interface between crystal and crystal is enlarged, and the phenomenon of stress enrichment is prevented.
【學位授予單位】：深圳大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O78
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