A kind of growth method of more than 80kg large-size sapphire single-crystal
(1) technical field
The present invention relates to a kind of growth technique of more than 80kg large-size sapphire single-crystal, be specifically related to a kind of large-size sapphire single-crystal growth technique in conjunction with crystal pulling method and kyropoulos advantage.
(2) background technology
Sapphire single-crystal has excellent optics, machinery, chemistry and electrical property, can work under the mal-condition close to 2000 DEG C of high temperature, be widely used as the window material of various optical element, infrared military installation, space vehicle and high intensity laser beam device, and become the preferred material of current LED semiconducter substrate.
Along with the exploitation to sapphire application market, the continuous expansion especially (as Mobile phone screen, showing mirror etc.) in commercial market, also increase the demand of sapphire single-crystal, many industry relevant enterprises are expanded production for this reason all one after another thereupon.In the face of further fierce market competition, crystal mass not only will improve in crystal growth enterprise, and meanwhile, what is more important increases the size of sapphire crystal ingot, to meet the demand of more large-size sapphire product.
But, more problem can be faced during growing large-size sapphire single-crystal: as large-size sapphire single-crystal more easily causes crystal cleavage because gluing the problems such as crucible, bottom polycrystalline, crystal stress are large.In addition, the requirement of large-size crystals growth to thermal field design and technique is stricter, the appropriate design of thermal field is the basis of growing high quality large-size sapphire single-crystal, but, due to the feature of kyropoulos itself, the formulation of technique is also particularly important, otherwise crystal easily produces the defect such as bubble, cloud and mist, reduces volume recovery.Therefore, growing large-size sapphire single-crystal must formulate a set of rational growth technique.
In numerous growth methods of sapphire single-crystal, kyropoulos (KY) is substantially identical with crystal pulling method (CZ) principle, and main difference part is, crystal head is only pulled out during tradition KY method growth, crystal block section controls crystal growth by temperature variation, and crystal is in melt encirclement all the time, and stress is less.And CZ method upwards lifts with certain speed in process of growth always, crystal is crystallization on liquid level, is in cold-zone, and crystalline growth velocity is very fast.In addition, CZ method rotates at the simultaneous of lift, it is advantageous that crystal is heated evenly, and profile is level and smooth, and not easily sticky crucible, pulls Automated condtrol.But because the crystal block section grown is in rotating state always, the natural liquid stream superposition of rotating under the forced convection and gravity field caused can form complicated liquid stream, easily introduces defect.
Cold core float die (SAPMAC) comes from CZ method, but along with micropulling in process of growth, both can ensure the growth interface dimpling of crystal, pull rate can be avoided again too fast and the melt disturbance that causes, is conducive to reducing lattice defect.But for produced problem in large-size sapphire single-crystal process of growth, the advantage of crystal pulling method can be used for reference further, learn from other's strong points to offset one's weaknesses, to grow high-quality sapphire single-crystal.
(3) summary of the invention
The present invention is directed to large-size sapphire single-crystal and grow the subject matter faced, on the basis of original SAPMAC method Sapphire Crystal Growth technique, in conjunction with crystal pulling method process advantage, redesign, form a kind of growth method that can solve more than the 80kg large-size sapphire single-crystal of the problems such as large-size sapphire single-crystal easily glues crucible, bottom easily produces polycrystalline, subsurface defect is many.
The object of the present invention is achieved like this: concrete control stage of crystal growth primarily of: seeding, shouldering, turn shoulder correction of the flank shape, isometrical, ending pulls and annealing stage composition of lowering the temperature, at the initial stage in shouldering stage, control cooling rate, ensure that monocrystalline slowly grows; Single crystal growing turns the shoulder correction of the flank shape stage to entering during 1.0 ~ 1.5kg, first raises voltage and monocrystalline is stopped growing, regulate rotation parameter simultaneously, seed crystal is rotated with certain speed; After keeping for some time, reduce the discharge of body of heater heat exchanger, accelerate lift simultaneously, ensure the protrusion rate of growth interface; The isodiametric growth stage, reduce pull rate, accelerate cooling rate simultaneously, single crystal growing pulls the stage to entering ending during clout 1 ~ 3kg, until monocrystalline is by the end of growth, accelerate cooling rate crystal to be mentioned fast simultaneously, make its completely and bottom remainder melt depart from, the ending realizing crystal pulls; Segmentation cooling method is taked to anneal after crystal pulls.
The present invention also has some features like this:
1, in the described shouldering stage, voltage, lift parameter are set to-4 ~-10mv/h and 0.1 ~ 0.3mm/h respectively, ensure that monocrystalline slowly grows with the speed of 0.05 ~ 0.1kg/h.
2, when described single crystal growing weight reaches 1.0 ~ 1.5kg, enter and turn the shoulder correction of the flank shape stage.First carrying out turning shoulder, is 0 by lift parameter regulation, and voltage raises 10 ~ 40mv, and is 3 ~ 8r/min by seed rod speed setting, and rotational time continues 10 ~ 30min.
3, the described shoulder that turns terminates rear beginning correction of the flank shape.Voltage, lift parameter are set to-6 ~-12mv/h and 0.4 ~ 1.0mm/h respectively, and turn sidewall of the furnace body heat exchanger discharge down according to crystalline growth velocity, makes monocrystalline with the slow crystallization of the speed of 0.1 ~ 0.3kg/h, grow 20 ~ 35h under this condition.
4, in the described isodiametric growth stage, voltage and lift parameter are adjusted to-13 ~-20mv/h and 0.05 ~ 0.1mm/h by this stage respectively.
5, described single crystal growing pulls the stage to entering ending during clout 1 ~ 3kg, now, stop automatically lifting, voltage, lift parameter are set as-15 ~-25mv/h and 0mm/h respectively, then manually quick monocrystalline is mentioned 20 ~ 35mm, make it be separated completely with crucible bottom.
Beneficial effect of the present invention has:
1. in the present invention, slow down the speed of growth of crystal in the shouldering stage, the gas that interface is assembled has time enough effusion bath surface, reduces the probability of crystals trapped air bubbles.
2., in of the present invention turn of shoulder correction of the flank shape stage, carry out turning shoulder and growing crystal portion can be made to be heated evenly, reduce the probability that crystal glues crucible, reduce crystal internal stress.Meanwhile, stop single crystal growing when turning shoulder, effectively can avoid the lattice defect because swivel disturbance brings.
3. in of the present invention turn of shoulder correction of the flank shape stage, pull rate is increased during correction of the flank shape, reduce sidewall of the furnace body heat exchanger heat-sinking capability, shouldering angle is reduced, ensure crystal growth interface dimpling state, the probability of matter crystal internal defect can be reduced, crystal shoulder and isometrical intermediate location also can be avoided to produce larger stress.
4. in the isodiametric growth stage of the present invention, suitably accelerate cooling rate, reduce pull rate and be conducive to shortening technique duration, reduce costs, the problem causing crucible because pull rate is fast can be avoided simultaneously.
5. ending of the present invention pulls process implementation and pulls automatization, avoids easy generation polycrystalline and crystal bottom large-size sapphire single-crystal and easily falls the problem of crucible, reduce the probability of monocrystalline cracking.
(4) accompanying drawing explanation
Fig. 1 crystal growth phase schematic flow sheet.
(5) embodiment
Below in conjunction with accompanying drawing, the present invention is described in detail.
Fig. 1 is crystal growth phase schematic flow sheet, by technology controlling and process stage characteristic by crystal people for being divided into four parts, the respectively control stage of corresponding growth technique: seeding stage I, shouldering stage II(be subdivided into the shouldering initial stage with turn take on correction of the flank shape), isometrical stage III and ending pull stage IV, finally carry out cooling and anneal.
For 80kg Sapphire Crystal Growth: loaded in crucible by 80kg alumina raw material, carry out seeding by mode described in granted patent 20111007243.0.At the shouldering initial stage, voltage, lift parameter are set to-4mv/h and 0.1mm/h respectively, ensure that monocrystalline slowly grows with the speed of 0.05kg/h.When crystal growth is to starting during 1.2kg to turn shoulder, be 0 by lift parameter regulation, voltage raises 15mv, and is 3r/min by seed rod speed setting.Correction of the flank shape is started after growing 10min under this condition.Voltage, lift parameter are set to-6mv/h and 0.5mm/h respectively, and turn sidewall of the furnace body heat exchanger discharge down according to crystalline growth velocity, makes monocrystalline with the slow crystallization of the speed of 0.1kg/h, grow 22h under this condition.In the isodiametric growth stage, voltage and lift parameter are adjusted to-15mv/h and 0.05mm/h respectively, make crystal with comparatively faster growth rate.When crystal growth pulls the stage to entering ending during clout 1.5kg, now, stopping automatically lifting, voltage, lift parameter being set as-15mv/h and 0mm/h respectively, then manually quick monocrystalline being mentioned 20mm, make it be separated completely with crucible bottom.Take segmentation cooling method to anneal after crystal pulls, annealing stage initial stage and latter stage cool with the cooling rate of 30 ~ 80 DEG C/h, at 1800 ~ 1400 DEG C of temperature sections, cool with the cooling rate of 5 ~ 15 DEG C/h.