CN214458434U - Crystal growth device - Google Patents

Abstract

A crystal growth device relates to the field of crystal preparation, in particular to a device for preparing low-stress and low-defect crystals by using a Czochralski method. The device comprises a furnace body, a crucible and a heating and heat-preserving system which are arranged at the bottom of the furnace body, a crystal lifting mechanism and a quartz observation window, and also comprises a liftable heating cover mechanism which comprises a heating cover body, a heating cover supporting part, heating wires arranged around the heating cover body and a heating cover lifting mechanism. By adopting the device, the stress in the crystal can be reduced in the crystal growth process and in the cooling process after the crystal is lifted, the defects are reduced, the crystal cracking is avoided, meanwhile, the temperature gradient in the melt is kept, the stability of the crystal growth process is ensured, and the yield of the crystal is ensured.

Description

Crystal growth device

Technical Field

The utility model relates to a crystal preparation field especially relates to use and draws device of method preparation low stress, low defect crystal.

Background

The Czochralski method is a method for growing crystals from a melt, is a common growing method for semiconductor crystals, optical crystals and the like, and has the characteristics of high yield, high growth speed, easy observation and the like.

The Czochralski method is usually carried out by a single heater. In the pulling method, the temperature of the crystal pulled out first is lowered to a lower temperature because the temperature of the surrounding atmosphere is lower, in particular when the crystal is pulled out to a higher position. And the temperature at the solid-liquid interface of the crystal growth is always maintained near the melting point of the crystal, so that the gradient in the crystal is approximately equal to (T boundary-T table)/L, L being the distance from the solid-liquid interface of the crystal growth to the crystal surface, T boundary being the crystal surface temperature, and T boundary being the temperature at the solid-liquid interface of the crystal growth (about the melting point temperature of the crystal), assuming that the longitudinal temperature distribution in the crystal is linear. During steady state growth, Tterm is about equal to the melting point temperature of the crystal, which is about a fixed value. And the main way to reduce the temperature gradient of the crystal is to increase the surface temperature Ttable of the crystal. It is a common method to heat and preserve the temperature of the pulled crystal, thereby increasing the temperature gradient of the crystal surface.

At present, the mainstream mode is a mode of adding a heat-insulating cover and a rear heater above a crucible and a crystal, for example, chinese patent application 201810509188.0 discloses a czochralski CeAlO3 crystal growth device and a control method thereof. However, although this method has a certain effect of keeping the temperature of the crystal, it has a major drawback in practical application. Firstly, the heater and the upper cover the whole crucible body, and the temperature gradient of the melt is reduced, so that the growth process of the crystal is easy to be unstable, and the crystal is twinned and even polycrystallized. Particularly in the early stage of crystal growth (seeding and shouldering stages), the crystal is in the central area of the melt with low temperature gradient, the growth is not stable, and the crystal is easy to be polycrystallized. When the method is used for growing compound crystals containing volatile elements (such as indium phosphide, gallium arsenide, gallium phosphide, indium arsenide, indium antimonide, gallium antimonide, zinc germanium phosphide and the like), the crystal is heated by the post-heater, so that the crystal is dissociated, namely the volatile elements are volatilized into the atmosphere. If the degree of crystal dissociation is severe, the crystals may be rendered unusable. Therefore, when a crystal of a volatile compound is grown using such a thermal field, the power of the afterheater is limited.

Chinese patent application 200910112711.7 discloses a method and a device for growing large-size sodium yttrium tungstate crystals by a two-stage heating and pulling method, wherein two groups of fixed heating mechanisms are also arranged for respectively heating a crucible and the pulled crystals. However, in the device, the right upper part of the crystal is in an open state, so that heat dissipation is serious, the heat preservation effect on the crystal is not strong, and the stress reduction effect is not obvious. In particular, for crystals containing volatile elements, the dissociation of the heated crystals in a relatively open environment is very severe. For some materials with higher growth environment pressure, the high-pressure airflow can play a strong role in heat dissipation of the unsealed crystal, so that the heating effect of the post-heater is reduced.

Chinese patent application 201910631648.1 discloses a coil movable temperature field structure and a single crystal growth method suitable for the czochralski method, which adopts the technical scheme that a rear heating cylinder is arranged above a crucible, and the crucible and the rear heating cylinder are respectively heated by moving a heating coil. The device uses an external moving coil, can heat the crucible and the rear heating cylinder simultaneously, has power interference between the crucible and the rear heating cylinder, and is low in control precision. The crystal grows, and the stability to temperature in the crucible requires very much, and the coil that heats the crucible removes, will produce great influence to the thermal field, and moreover will respond to the cartridge heater simultaneously again, shunts coil power, causes the fuse-element temperature gradient to fluctuate on a large scale very easily, leads to crystal growth failure. The relative position of a heat preservation section of thick bamboo and crystal is far away, and back heating bucket plays the heating effect to whole environment to can reduce whole environment, including the temperature gradient in the melt, also can cause crystal growth to have lower stability. And the coil device respectively heats the melt and the crystal in the cooling process after the crystal growth is finished, the heat preservation and heating effects on the crystal in the crystal growth are not obvious, and the defects such as stress, dislocation and the like caused by the temperature difference between the upper end and the lower end of the crystal in the crystal growth process are not obviously improved.

Disclosure of Invention

The utility model aims at solving the problem existing in the prior art.

Therefore, the utility model discloses a following technical means realize: the utility model provides a crystal growing device, includes the furnace body, arranges the crucible and the heating heat preservation system of furnace body bottom in, just to the crystal pulling mechanism at crucible center, arranges the quartzy observation window of furnace body side in, the heating heat preservation system includes crucible, heater, crucible pole, insulation cover, crystal pulling mechanism includes seed pole, seed chuck, and the key lies in, the device still includes liftable formula heating mantle mechanism, liftable formula heating mantle mechanism includes the heating mantle body, heating mantle supporting part, sets up heater strip, heating mantle elevating system around the heating mantle body, and the heating mantle internal portion sets up the thermocouple in the heating mantle body.

Furthermore, the top of the heating cover body is conical, the lower part of the heating cover body is cylindrical, the heating cover body is made of transparent materials, and the cylindrical outer diameter of the heating cover body is smaller than the inner diameter of the crucible.

Further, the seed rod penetrates through the heating cover body, and the heating cover lifting mechanism drives the liftable heating cover mechanism to move up and down along the seed rod.

Further, an air source box is further arranged inside the liftable heating cover mechanism.

By adopting the device, in the crystal growth stage, the heating cover descends to cover the growing crystal and form a consistent temperature field around the crystal, and compared with the traditional two-stage temperature field, the device has the following characteristics:

the coverage area is different.

In principle, the larger the temperature gradient of the melt, the higher the stability of crystal growth, and therefore it is desirable to strengthen the temperature gradient of the melt to ensure smooth crystallization of the crystal. The larger the temperature gradient in the crystal, the larger the thermal stress in the crystal, and therefore, the smaller the temperature gradient in the crystal is desired. The traditional two-stage temperature field is usually the whole covering of the crucible body, thus reducing the temperature gradient of the crystal and the temperature gradient of the melt. Although the stress reduction effect can be achieved to some extent, the crystal growth process is easy to destabilize, and twin crystals and even polycrystallization occur in the crystals. According to the invention, the heating cover body matched with the diameter of the crystal is utilized to preserve the heat of the crystal without covering the melt, so that the temperature gradient in the melt is not obviously reduced, and the stable growth of the crystal can be ensured.

The time period of coverage is different.

In the stage of seeding and shouldering, the crystal is positioned at the center of the melt, and the radial temperature gradient of the melt surface in the central area of the crucible is small, so that the crystal with smaller volume is easy to destabilize in the process of seeding and shouldering, and polycrystallization is caused. The traditional unmovable two-section thermal field covers the crucible in the whole process, so that the temperature gradient of a melt is small, thereby leading to seeding and being easy to polycrystallize in the shouldering process.

Adopt this device, can reduce the crystal growth in-process and the crystal and mention the inside temperature gradient of in-process crystal of back cooling down to reduce the stress in the crystal, reduce the defect, avoid the crystal fracture, keep the temperature gradient in the melt simultaneously, guarantee that the crystal growth process is stable, thereby guarantee crystal yield.

Drawings

Figure 1 is a schematic structural view of the present invention,

figure 2 is a diagram of an operating state,

figure 3 is a diagram of another operating state,

figure 4 is an illustration of a depth scale on a heating mantle,

FIG. 5 is an illustration of a depth scale on another heating mantle.

The device comprises a seed crystal 1, a seed crystal chuck 2, a seed crystal rod 3, a crystal 4, a covering agent 5, a melt 6, a heater 7, a heating cover body 8, a heating cover supporting part 9, a heating cover lifting mechanism 10, a quartz observation window 11, a crucible rod 12, a heat-insulating sleeve 13, a heating wire 14, a gas source box fixing pin 15, a gas source material 16, a gas source box 17, a crucible 18, a furnace body 19, a heating wire wrapping 20 and a thermocouple 21.

Detailed Description

The present invention will be further explained with reference to the accompanying drawings.

A crystal growth device, as shown in figure 1, comprises a furnace body 19, a crucible 18 and a heating and heat-preserving system which are arranged at the bottom of the furnace body 19, a crystal pulling mechanism which is opposite to the center of the crucible, and a quartz observation window 11 which is arranged at the side surface of the furnace body 19.

The heating and heat-insulating system comprises a heater 7 arranged around a crucible 18, a crucible rod 12 supporting the crucible 18 at the lower part, and a heat-insulating sleeve 13 outside the heater 7.

The crystal lifting mechanism comprises a seed rod 3 and a seed chuck 2.

The device also comprises a liftable heating cover mechanism which comprises a heating cover body 8, a heating cover supporting part 9, heating wires 14 arranged around the heating cover body 8 and a heating cover lifting mechanism 10. The heating mantle lifting mechanism 10 completes the lifting of the heating mantle body 8 through the heating mantle support member 9. The heating cover body 8 is internally provided with a thermocouple 21 for acquiring the internal temperature thereof.

The top of the heating cover body 8 is conical, the lower part of the heating cover body is cylindrical, transparent materials such as quartz, glass or sapphire are adopted, and the heat of the heating wire 14 can be radiated into the heating cover body to heat crystals. The periphery of the heating wire 14 is covered with a heating wire wrap 20, so that the crystal growth condition can be observed through the cover body after the heating cover body 8 descends.

The inner diameter of the heating cover body 8 is 5-10mm larger than the diameter of the crystal to be drawn, and the cylindrical outer diameter of the heating cover body is smaller than the inner diameter of the crucible 18, so that the crucible 18 cannot be covered integrally.

The top of the heating cover body 8 is of a multilayer hollow structure, a plurality of cavities are formed, and a certain heat preservation effect is achieved.

The heating cover mechanism is attached to the seed rod 3, the seed rod 3 penetrates through the heating cover body 8, and the heating cover lifting mechanism 10 drives the lifting type heating cover mechanism to move up and down along the seed rod 3.

The seed rod 3 is tightly embraced at the top of the heating cover 8, a gap is reserved between the heating cover 8 and the seed rod 3, the gap is not more than 2mm, the inside of the heating cover 8 and the inside of the furnace body 19 are communicated, and the pressure is kept basically the same.

The inside gas source box 17 that still sets up of liftable formula heating mantle mechanism, gas source box 17 use gas source box fixing pin 15 to fix a position in the inside upper end of the heating mantle body 8. The number of the air source box fixing pins 15 is not less than 4 along the radial distribution of the heating cover body 8, so that the position stability of the air source box is ensured.

In order to avoid the heating wire 14 from being immersed into the covering agent 5 and the melt 6, the heating wire 14 is not provided at the bottom of the heating mantle 8, and the starting position for providing the heating wire 14 is 1/6 which is greater than the length of the heating mantle 8 from the bottom of the heating mantle 8 upward.

For the convenience of observation, a depth marking is arranged on the periphery of the heating cover body 8 from the bottom, the depth marking adopts an inverted triangle figure, as shown in fig. 4, the depth of the heating cover body 8 immersed in the covering agent 5 is visually represented, and the depth can also be represented by a spacing line, as shown in fig. 5.

The observation window 11 is made of transparent material such as quartz, glass, or sapphire, and is used for observing the growth of the crystal. After the liftable heating cover mechanism descends, the quartz observation window 11 is aligned with the arranged marking.

The heating cover lifting mechanism 10 can finely adjust the heating cover body 8 up and down to ensure that the lower part of the heating cover body 8 is continuously contacted with the covering agent 5 when the liquid level of the covering agent 5 is lowered.

The working process is as follows:

gas source material 16 is a volatile elemental material from a compound crystal. Growing indium phosphide, gallium phosphide crystals, and the like using phosphorus as the gas source material 16; a gallium arsenide crystal is grown with arsenic as the source material 16. The source material 16 is placed in a source cartridge 17 and placed within the internal heating enclosure 8. Boron oxide was used as the covering agent 5.

Step one, placing raw materials and a covering agent in a crucible 18, starting a heater 7, continuing for a period of time, and covering the covering agent 5 above a raw material melt 6 when the raw materials and the covering agent 5 in the crucible 18 are melted and the density of the covering agent 5 is lower than that of the raw materials.

And step two, arranging the seed crystal 1 on the seed crystal chuck 2, descending the crystal pulling mechanism until the seed crystal 1 is contacted with the surface of the melt 6, and if the melt is at a proper temperature for crystal growth, gradually growing the contact position of the seed crystal 1 and the melt 6 to form a crystal 4.

And step three, observing the growth condition of the crystal 4 at the contact position of the seed crystal 1 and the melt 6 through a quartz observation window 11, and adjusting the power of the heater 7 through the expansion/contraction condition of the crystal 4 to enable the crystal 4 to grow gradually. And gradually changing the pulling speed of the pulling mechanism in the process of gradually growing the crystal.

And step four, when the crystal 4 grows to the required diameter, starting a power supply of the heating wire 14, and lowering the heating cover mechanism to enable the lower part of the heating cover body 8 to be in contact with the covering agent 5. The peripheral part of the heating wire 14 is covered with the heating wire wrap 20, and the part close to the observation window 11 is not covered, so that the observation window is left, as shown in fig. 2.

The "required diameter" is about +5mm of the standard wafer size. If a crystal with the target diameter of 2 inches is manufactured, the required diameter is 55.8 mm; target diameter is 3 inches of crystal, desired diameter is 81.2 mm; target diameter is 4 inches of crystal, desired diameter is 105 mm; the target diameter was 6 inch crystals, and the desired diameter was 155 mm.

And step five, gradually increasing the heating power of the heating wire 14, so that the atmosphere temperature in the heating cover is obviously increased, and determining the temperature range according to the gas source elements. If the gas source element is phosphorus, the temperature is raised to 500-600 ℃, so that the gas source begins to volatilize gas, and the partial pressure of the gas source element atmosphere in the heating cover body 8 is ensured. The heating is continued, and the temperature in the heating cover body 8 is maintained. The temperature is determined according to the thermocouple 21.

A small gap is formed between the heating cover body 8 and the seed crystal rod 3, the pressure of gas inside and outside the heating cover body 8 is the same, but the partial pressure ratio of gas source elements in the heating cover body 8 is higher, and the function of inhibiting crystal dissociation can be achieved.

The furnace 19 is filled with an inert gas such as nitrogen, argon, etc., but the inert gas has a limited effect on the dissociation of the crystal and the partial pressure of the corresponding gas element has a function of suppressing the dissociation, so that the gas source material 16 is used to provide the partial pressure of the element gas around the crystal for restricting the element from escaping from the crystal surface.

And step six, along with the gradual growth and the pulling of the crystal 4, the liquid level of the melt 6 and the covering agent 5 gradually descends, so that the heating cover mechanism also needs to gradually descend along with the descending of the liquid level, the observation is carried out through the observation window 11, the position is adjusted according to the marked line, the heating cover body 8 is ensured to be in contact with the boron oxide of the covering agent 5, and meanwhile, the heating wire 14 is prevented from being immersed into the covering agent 5.

And seventhly, pulling the crystal 4 to a position meeting the weight, quickly pulling the crystal pulling mechanism and the liftable heating cover mechanism, and pulling the crystal 4 out of the melt 6 and the boron oxide 5, as shown in figure 3.

Step eight, setting a cooling program for the heater 7, and returning to the room temperature within 5-20 hours; the heating wire 14 is started to reduce the temperature, and the temperature is reduced to the room temperature within 5-20 hours.

Step nine, disassembling the furnace and disassembling the crystal.

Claims (10)

1. The utility model provides a crystal growth device, includes furnace body (19), arranges crucible (18) and the heating heat preservation system of furnace body (19) bottom in, just to the crystal pulling mechanism at crucible (18) center, arranges quartz observation window (11) of furnace body (19) side in, the heating heat preservation system includes heater (7), crucible pole (12), insulation cover (13), crystal pulling mechanism includes seed crystal pole (3), seed chuck (2), its characterized in that, the device still includes liftable formula heating mantle mechanism, liftable formula heating mantle mechanism includes the heating mantle body (8), heating mantle supporting component (9), sets up heater strip (14), heating mantle elevating system (10) all around the heating mantle body (8), and the heating mantle body (8) is inside to set up thermocouple (21).

2. Crystal growth apparatus according to claim 1, characterized in that the heating enclosure (8) is conical at the top and cylindrical at the bottom, made of transparent material, and has a cylindrical outer diameter smaller than the inner diameter of the crucible (18).

3. The crystal growth apparatus according to claim 1 or 2, characterized in that the top of the heating enclosure (8) is a multi-layer hollow structure.

4. The crystal growth apparatus according to claim 1 or 2, wherein the seed rod (3) passes through the heating enclosure (8), and the heating enclosure lifting mechanism (10) drives the liftable heating enclosure mechanism to move up and down along the seed rod (3).

5. The crystal growth apparatus of claim 4, wherein the gap between the seed rod (3) and the top of the heating enclosure (8) is no more than 2 mm.

6. The crystal growth apparatus of claim 1, wherein the liftable heating mantle mechanism further comprises a gas source box (17) disposed therein.

7. The crystal growth apparatus of claim 6, wherein the gas supply cartridge (17) is positioned at the inner upper end of the heated enclosure (8) using gas supply cartridge retaining pins (15).

8. Crystal growth apparatus according to claim 1, characterized in that the starting point for the heating wire (14) is located from the bottom of the heating enclosure (8) upwards, greater than 1/6 of the length of the heating enclosure (8).

9. The crystal growth apparatus of claim 1, wherein the periphery of the heating enclosure (8) is provided with a depth scale from the bottom.

10. The crystal growth apparatus of claim 9, wherein the quartz sight glass (11) is aligned with a set reticle after the liftable heating mantle mechanism is lowered.

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