CN209873178U - Single crystal furnace capable of reducing crystal defects - Google Patents
Single crystal furnace capable of reducing crystal defects Download PDFInfo
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- CN209873178U CN209873178U CN201920248345.7U CN201920248345U CN209873178U CN 209873178 U CN209873178 U CN 209873178U CN 201920248345 U CN201920248345 U CN 201920248345U CN 209873178 U CN209873178 U CN 209873178U
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Abstract
The utility model discloses a single crystal furnace for reducing crystal defects, which belongs to the technical field of single crystal furnace equipment and comprises a crucible and a heater surrounding the crucible, wherein the heater comprises a heating cylinder body and at least four electrode pins arranged at the bottom of the heating cylinder body; the heating cylinder body is made of U-shaped graphite strips which are roundabout up and down; the height of the heater is not higher than that of the molten liquid in the crucible, and the height of the heating cylinder is 1/3-2/3 of the total height of the heater; a driving mechanism which moves relatively is arranged between the crucible and the heater. The cylindrical structure forms a current loop through the positive and negative electrodes. In order to reduce energy loss, the heating of the heater is reduced by widening and thickening the electrode pin. More than four electrode pins are arranged to ensure the central symmetry of the heater. The driving mechanism arranged between the crucible and the heater can be used for adjusting the relative position of the heater and the height of the solution in the crucible, and the height of the heater is not higher than the height of the solution in the crucible, so that the quality of the single crystal is improved.
Description
Technical Field
The utility model relates to a single crystal growing furnace equipment technical field, specifically speaking relates to a reduce crystal defect's single crystal growing furnace.
Background
The Czochralski single crystal manufacturing method comprises putting raw material polycrystalline silicon ingot into a quartz crucible, heating and melting in a single crystal furnace, and putting seed crystal into the solution. At a proper temperature, silicon atoms in the solution form regular crystals on a solid-liquid interface along the silicon atom arrangement structure of the seed crystal to form a single crystal. The seed crystal is slightly rotated and lifted upwards, and silicon atoms in the solution continue to crystallize on the previously formed single crystal and continue to have a regular atomic arrangement structure. If the whole crystallization environment is stable, crystals can be formed repeatedly, and finally a cylindrical silicon single crystal with orderly arranged atoms, namely a silicon single crystal rod, is formed.
The crystal growth device is characterized in that a Czochralski crystal growing furnace is a device for growing dislocation-free single crystals by adopting a Czochralski method, a heater is a core component of a thermal field of the crystal growing furnace and provides heat energy for melting and growing crystals by polycrystals, and the design of the structure of the crystal growth device not only directly influences whether the crystals can be grown successfully and the quality of the single crystals, but also directly influences the manufacturing cost of the single crystals as one of main consumables.
The heating body of the conventional czochralski crystal growing furnace is usually only provided with a positive electrode and a negative electrode, which has no obvious quality problem in the single crystal material of a small-diameter semiconductor discrete device, the size of the line width of the single crystal silicon material for a large-scale integrated circuit reaches several nanometers, and the quality and the yield of the device are seriously influenced by micro defects with similar sizes, so that the defect control in the crystal is particularly critical.
Defects which can be seen by the single crystal silicon wafer under a spotlight through preferential etching are called as macroscopic defects, and the macroscopic defects such as vortexes, thermal oxidation fault rings and the like are not allowed, so that the whole device is scrapped once the macroscopic defects exist.
The central asymmetry of the thermal field seriously influences the formation of crystal defects among a plurality of influencing factors, the size of the used thermal field is correspondingly increased along with the continuous increase of the diameter of the growing single crystal, the heating element with the large diameter of more than 28 inches is difficult to ensure the central symmetry of the whole heating element only by the fixation of two traditional electrode pins due to the self weight and the heating deformation in the using process, the temperature fluctuation of a single crystal growing interface is caused by the distance difference between the outer side surface of the single crystal and the heating element in the single crystal growing process, so that the single crystal is transferred to the side with low temperature for fast growing, the growth is slowed down when the single crystal is transferred to the side with high temperature, even the melting back phenomenon of the grown crystal is generated, serious vortex can occur in the primary crystal, and the vortex phenomenon is more serious after thermal oxidation.
In order to avoid the above phenomenon, the heating element of the existing single crystal furnace is provided with more electrode pins to ensure the central symmetry of the heating element, for example, the heaters of the single crystal furnace disclosed in the Chinese patent documents with the publication numbers of CN206015144U and CN105586634A are provided with at least 4 electrode pins to fix and adjust the central symmetry of the whole heating element.
Needless to say, increasing the number of electrode pins of the heating element not only greatly improves the quality of the single crystal, but also greatly prolongs the service life of the heating element, but also increases the number of electrode pins of the heating element, and accordingly increases the energy taken away by heat conduction through the electrode pins, resulting in an increase in the equal-diameter power and an increase in the unit energy consumption of crystal pulling.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a reduce crystal defect's single crystal growing furnace can guarantee the central symmetry of heat-generating body under the certain circumstances of energy consumption, improves the yield of single crystal.
In order to achieve the above object, the single crystal furnace for reducing crystal defects provided by the present invention comprises a crucible and a heater surrounding the crucible, wherein the heater comprises a heating cylinder and at least four electrode pins arranged at the bottom of the heating cylinder; the heating cylinder body is made of U-shaped graphite strips which are roundabout up and down; the height of the heater is not higher than that of the molten liquid in the crucible, and the height of the heating cylinder is 1/3-2/3 of the total height of the heater; a driving mechanism which moves relatively is arranged between the crucible and the heater.
In the technical scheme, the heating cylinder body of the cylindrical structure is of a U-shaped structure which is formed by graphite heating strips through slotting and is vertically circuitous, and a current loop is formed by positive and negative electrodes. In order to reduce energy loss, the heating of the heater is reduced by widening and thickening the electrode pin. More than four electrode pins are arranged to ensure the central symmetry of the heater. The driving mechanism arranged between the crucible and the heater can be used for adjusting the relative position of the heater and the height of the solution in the crucible, and the height of the heater is not higher than the height of the solution in the crucible, so that the quality of the single crystal is improved.
Preferably, the electrode foot comprises a heating leg and a heating foot which are perpendicular to each other, a threaded hole is formed in the bottom of the heating foot, and a bolt used for adjusting the stability of the heater is installed in the threaded hole. The heating legs and the heating feet form an L shape, and the heating legs are straight-line-shaped graphite strips. The heating foot is connected with the heating leg and is directly connected with the positive and negative electrodes of the furnace bottom. The whole heater ensures the central symmetry of a single crystal growth interface by adjusting the bolts of the heating pins, reduces the local meltback of the single crystal growth process, greatly reduces the vortex, adjusts the longitudinal temperature gradient of the heater by adjusting the height of the main heating body and the height and the number of the heating legs to control the oxygen-carbon content in the crystal and greatly reduce the density of thermal oxidation stacking fault (OISF) and body defect (BMD).
In order to realize the relative movement between the crucible and the heater, the driving mechanism preferably comprises a U-shaped frame arranged at the bottom of the heater, and the bottom of the U-shaped frame is provided with a lifting rod.
Preferably, the lifting rod comprises an outer rod and an inner rod which are sleeved with each other, the outer rod is fixed at the bottom of the U-shaped frame, the inner rod is fixed on the workbench, and a fastening screw is arranged between the outer rod and the inner rod. The outer rod and the inner rod are mutually sleeved to realize supporting and drive the heater to move up and down, and after the heater moves to a preset position, the fastening screw is screwed down. A driving cylinder can be arranged at the bottom of the U-shaped frame to drive the heater to move up and down.
In order to make the structure of the heater more stable, preferably, the U-shaped frame includes two crossed frames, and two ends of the top of the U-shaped frame are respectively fixed on the two symmetrical electrode pins. The heater is ensured to be stable when moving. Meanwhile, the U-shaped frame is made of insulating materials.
As another preferable scheme, the driving mechanism comprises a driving motor or a driving cylinder arranged at the bottom of the crucible. The driving motor drives the crucible to move up and down so as to realize that the height of the solution in the crucible is higher than that of the heater.
In order to make the movement of the crucible more stable, as the optimization, the bottom end of the crucible rod is sleeved with a guide sleeve matched with the crucible rod.
Preferably, threads matched with each other are arranged between the crucible rod and the guide sleeve. When the driving cylinder drives the crucible to rotate, the crucible is driven to move up and down through the threads.
Preferably, the height of the heater cylinder is 1/2 the total height of the heater. The arrangement ensures that the central symmetry of the heater does not exceed plus or minus 3 mm.
In order to further secure the central symmetry of the heater, it is preferable that the electrode pins include six or eight uniformly arranged.
In order not to increase the constant diameter power, it is preferable that the width or thickness of the electrode legs is changed to 1 to n times the original resistance between the two electrodes every time the number of the electrode legs is increased by n times.
Compared with the prior art, the beneficial effects of the utility model are that:
the utility model discloses a single crystal growing furnace can guarantee the central symmetry of heat-generating body under the certain circumstances of energy consumption, when taking into account the quality of growing the brilliant, has reduced the energy consumption. So that the production cost is greatly reduced.
Drawings
FIG. 1 is a schematic structural view of a single crystal furnace according to embodiment 1 of the present invention;
fig. 2 is a plan view of a heater according to embodiment 1 of the present invention;
FIG. 3 is a comparison of the high temperature field and the low temperature field of example 1 of the present invention;
fig. 4 is a schematic structural view of a single crystal furnace according to embodiment 2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be further described below with reference to the following embodiments and accompanying drawings.
Example 1
Referring to fig. 1 and 2, the single crystal furnace of the present embodiment for reducing crystal defects includes a crucible 100 and a heater 200 surrounding the crucible 100.
The heater 200 comprises a heating cylinder 201 and six electrode pins 202 arranged at the bottom of the heating cylinder 201; the heating cylinder 201 is made of a U-shaped graphite strip which is circuitous up and down. The height of the heater 200 is not higher than the height of the solution in the crucible 100, and the height of the heating cylinder 201 is 1/2 of the total height of the heater 200.
The electrode pin 202 comprises a heating leg 2021 and a heating pin 2022 which are perpendicular to each other, a threaded hole 2023 is formed at the bottom of the heating pin 2022, and a bolt for adjusting the stability of the heater is installed in the threaded hole 2023. The heating leg 2021 and the heating foot 2022 form an L-shape, and the heating leg 2021 is a straight-line-shaped graphite strip. The heating foot 2022 is connected with the heating leg 2021 and is directly connected with the positive and negative electrodes of the furnace bottom. The whole heater 200 ensures the central symmetry of a single crystal growth interface by adjusting the bolts of the heating pins 2022, reduces the local meltback of the single crystal growth process, greatly reduces the vortex, and adjusts the longitudinal temperature gradient of the heater by adjusting the height of the main heating body and the height and the number of the heating legs 2021 to control the oxygen-carbon content in the crystal and greatly reduce the density of thermal oxidation stacking faults (OISF) and body defects (BMD).
A driving mechanism for relative movement is arranged between the crucible 100 and the heater 200 to ensure that the height of the heater 200 is not higher than the height of the solution in the crucible 100. The driving mechanism of this embodiment includes a U-shaped frame 203 disposed at the bottom of the heater 200, and a lifting rod 204 is disposed at the bottom of the U-shaped frame 203.
The lifting rod 204 comprises an outer rod 2041 and an inner rod 2042 which are mutually sleeved, the outer rod 2041 is fixed at the bottom of the U-shaped frame 203, the inner rod 2042 is fixed on the workbench, and a fastening screw 2043 is arranged between the outer rod 2041 and the inner rod 2042. The outer rod 2041 and the inner rod 2042 are sleeved with each other to support and drive the heater 200 to move up and down, and after the heater 200 moves to a preset position, the fastening screw 2043 is screwed down. A driving cylinder may be provided at the bottom of the U-shaped frame 203 to drive the up and down movement of the heater 200.
In order to stabilize the structure of the heater, the U-shaped frame of the present embodiment includes two crossing frames, and two ends of the top of the U-shaped frame are respectively fixed on the two symmetrical electrode pins 202. The heater 200 is moved smoothly.
In order to reduce the heat loss, the method of thickening and widening the electrode pin can be adopted, and the power consumed by the heater in the series loop can be reducedIs I2R, thickening the widened electrode foot, resistance reduces by a wide margin, and the temperature also reduces by a wide margin, and the heat of taking away through the bottom electrode also reduces correspondingly. Further realized by adjusting the heating voltage and current value of the heater.
Taking two electrode pins and four electrode pins as examples, taking that each shunt resistor is equal, and the shunt resistors of the two electrode pins and the four electrode pins are R respectively1And R2The heat loss of the electrode foot is now approximated in two extreme ways.
The total current and voltage are unchanged, the current of the two branches is I/2, and the power of the branches is (I/2)2R1Total power is I2R1A/2, four branches of current, each branch of current is I/4, and power per branch is (I/4)2R2The total power of the four branches is I2R2The current of four branches is only half of the current of two branches, and R is inevitable under the condition of keeping the branch voltages equal2＝2R1From this I2R2/4＝I2R1The total power of the two branches and the four branches is also equal,/2. In this case, the energy losses of the two branches and the four branches at the electrode feet are compared, and assuming that the electrode feet are identical and the resistance is r, the total power loss of the two branch electrode feet is I2r/2, total power loss of four shunt electrode pins is I2R/4, the power loss of four electrode pins is smaller, but this has a premise that R is2＝2R1The round graphite barrel is divided into four parts from two parts, the resistance is doubled, the graphite strip is likely to be cut into narrower parts, and the processing difficulty of the heater and the service life of the heater are likely to be influenced.
Secondly, the shape of the heating element is unchanged, the graphite strip is divided into two branches assuming that the total resistance of one circle of graphite strip is R, each branch is divided into four branches, each branch is R/2 in resistance, each branch is R/4 in resistance, and the total current of the two branches and the total current of the four branches are I respectively1And I2Total power of two branches is I1 2R/4, total power of four branches is I2 2R/16, to keep the total power equal, must I2＝2I1So that the current in each of the two branches and the four branches is, respectively, two branches I1/2, four branches I2/4＝2I1/4＝I1/2. Thus, the current of each branch of the two branches and the current of each branch of the four branches are the same, and under the condition that the resistance of the electrode pins is the same, the power loss of the four electrode pins is twice that of the two electrode pins.
Obviously, in the two ways, the first way loses lower heat, and the constant diameter power is obviously reduced. The heat generated by the actual electrode pin is not always completely lost, the heat generated by other parts of the heater can also be conducted through the electrode pin to generate heat loss, in order to reduce the energy loss caused by increasing the electrode pin, the graphite strip of the heating body is made narrower, the total current and the total voltage are kept to be changed little as much as possible, and the energy loss through the electrode pin can be obviously reduced.
Other defects in the crystal are related to the thermal field distribution of the melt, and research shows that OISF rings are related to the ratio of V/G (T), V is the crystal growth speed, G (T) is the temperature gradient across the solid-liquid interface, generally, the V/G ratio has a critical value which is larger than the critical value, the crystal grows into vacancy defects, the crystal grows into interstitial defects, the boundary of the vacancy type crystal and the interstitial type crystal is easy to form the OISF rings on the same growth meeting plane, in order to avoid the formation of the OISF rings, the method of increasing the pulling speed and reducing G (T) is generally adopted, the most effective method of reducing G (T) is to adopt a low temperature field, as shown in figure 3, the temperature low field obviously has lower G (T), the V/G ratio from the center to the edge on the whole growth interface can be kept to be not smaller than the critical value, the whole silicon crystal is vacancy type defect, and OISF ring can not appear.
In addition, in the short temperature field, because the temperature gradient in the whole melt is smaller, even the temperature at the bottom of the crucible is lower, the thermal convection of the melt is smaller, the temperature fluctuation is smaller, the defect density of a crucible point is reduced, meanwhile, the melt which is close to the crucible bottom or the vicinity of the crucible wall and is rich in oxygen is more difficult to flow to a growth interface, the oxygen content is also greatly reduced, the micro defect density of the crystal finally formed by the interaction of the point defect and interstitial oxygen is also greatly reduced, and finally, the bulk defect density (BMD) of the whole crystal is reduced.
The design of the whole heating body gives consideration to the quality of crystals, the smoothness of crystal growth and the service life (cost) of the heating body, the short temperature field means that the height of the main heating body is as short as possible relative to the height of a melt in the whole crucible, but the short temperature field possibly influences the smooth crystal growth, therefore, the height of the main heating body is controlled to be not lower than 1/3 of the highest height of the melt and not larger than 2/3 of the highest height of the melt, and the height of the whole heating body is close to the highest height of the melt, so the design has.
Example 2
Referring to fig. 4, the structure of the single crystal furnace for reducing crystal defects of the present embodiment is the same as that of embodiment 1 except for the driving mechanism between the crucible 100 and the heater 200, and thus the description thereof is omitted.
The driving mechanism of the present embodiment includes a driving cylinder 101 disposed at the bottom of the crucible 100. The crucible rod 102 at the bottom of the crucible 100 is pushed by the driving cylinder 101, so that the crucible 100 is driven to move up and down, and the solution in the crucible 100 is higher than the heater 200. In order to make the movement of the crucible 100 more stable, the lower end of the crucible rod 100 is fitted with a guide sleeve 103 fitted to the crucible rod.
Also can trade drive actuating cylinder for driving motor, set up intermeshing's screw between uide bushing and crucible pole, reciprocate through screw thread drive crucible when driving actuating cylinder and driving the crucible rotation.
Claims (8)
1. A single crystal furnace for reducing crystal defects, comprising a crucible and a heater surrounding the crucible, characterized in that:
the heater comprises a heating cylinder body and at least four electrode pins arranged at the bottom of the heating cylinder body; the heating cylinder body is made of U-shaped graphite strips which are roundabout up and down;
the height of the heater is not higher than that of the molten liquid in the crucible, and the height of the heating cylinder is 1/3-2/3 of the total height of the heater; and a driving mechanism which moves relatively is arranged between the crucible and the heater.
2. The single crystal furnace of claim 1, wherein: the electrode foot include mutually perpendicular's heating leg and heating foot, heating sole portion is equipped with the screw hole, the downthehole bolt that is used for adjusting the heater steady of installing of screw.
3. The single crystal furnace of claim 1, wherein: the driving mechanism comprises a driving motor arranged at the bottom of the crucible.
4. The single crystal furnace of claim 3, wherein: the bottom end of the crucible is sleeved with a guide sleeve matched with the crucible rod.
5. The single crystal furnace of claim 4, wherein: and threads matched with each other are arranged between the crucible rod and the guide sleeve.
6. The single crystal furnace of claim 1, wherein: the height of the heating cylinder body is 1/2 of the total height of the heater.
7. The single crystal furnace of claim 1, wherein: the electrode feet comprise six or eight evenly arranged electrode feet.
8. The single crystal furnace of claim 1, wherein: after the number of the electrode feet is increased by n times, the width or the thickness of the electrode feet is changed to ensure that the resistance between the two electrodes is 1 to n times of the original resistance.
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| CN201920248345.7U CN209873178U (en) | 2019-02-27 | 2019-02-27 | Single crystal furnace capable of reducing crystal defects |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109680330A (en) * | 2019-02-27 | 2019-04-26 | 刘冬雯 | A kind of single crystal growing furnace reducing crystal defect |
| CN111394798A (en) * | 2020-05-19 | 2020-07-10 | 邢台晶龙电子材料有限公司 | Single crystal furnace heater |
| CN111424315A (en) * | 2020-05-18 | 2020-07-17 | 西安奕斯伟硅片技术有限公司 | Single crystal furnace thermal field heater assembly and single crystal furnace |
| CN111733447A (en) * | 2020-05-27 | 2020-10-02 | 西安奕斯伟硅片技术有限公司 | Single crystal furnace heating device, single crystal furnace and heating method of single crystal furnace |
-
2019
- 2019-02-27 CN CN201920248345.7U patent/CN209873178U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109680330A (en) * | 2019-02-27 | 2019-04-26 | 刘冬雯 | A kind of single crystal growing furnace reducing crystal defect |
| CN111424315A (en) * | 2020-05-18 | 2020-07-17 | 西安奕斯伟硅片技术有限公司 | Single crystal furnace thermal field heater assembly and single crystal furnace |
| CN111394798A (en) * | 2020-05-19 | 2020-07-10 | 邢台晶龙电子材料有限公司 | Single crystal furnace heater |
| CN111733447A (en) * | 2020-05-27 | 2020-10-02 | 西安奕斯伟硅片技术有限公司 | Single crystal furnace heating device, single crystal furnace and heating method of single crystal furnace |
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