Bottom heater for improving material melting efficiency of single crystal furnace

Abstract

The utility model relates to a bottom heater for improving the material melting efficiency of a single crystal furnace, which belongs to the technical field of a thermal field for producing single crystal silicon by a czochralski method and comprises a heating body and two foot plates which are symmetrically arranged left and right, are respectively positioned on two opposite sides of the heating body and are connected with the heating body; the heating body comprises a first heating body and a second heating body which are symmetrically arranged in the vertical direction; the middle of the foot plate extends and protrudes towards the center of the bottom heater to form an arc-shaped plate, and electrode holes are formed in the arc-shaped plate. The first heating body comprises a first heating unit, a second heating unit and a third heating unit, the first heating unit and the third heating unit are symmetrically arranged on the left side and the right side of the second heating unit, and the outer side of the first heating unit and the outer side of the third heating unit are each of a step-shaped structure. The bottom heater is simple in structure, high in heating power and uniform in heating, the occurrence rate of arcing and sparking of the bottom heater and the heat preservation cylinder caused by external factors is effectively reduced, the service life of the bottom heater is prolonged, the service life of a thermal field is prolonged, and the stability of the thermal field is improved.

Description

Technical Field

[0001] The utility model relates to a bottom heater, in particular to a bottom heater for improving the efficiency of single crystal furnace material processing, and belongs to the technical field of thermal field for producing single crystal silicon by Czochralski method. Background Art

[0002] The Czochralski process for producing single crystal silicon has a brief process of first loading solid silicon material into a quartz crucible, hoisting the quartz crucible with silicon material into the single crystal furnace through the single crystal furnace arm, and then sealing the furnace body and introducing argon gas to make the entire single crystal furnace in a vacuum state, extracting the gas and volatiles in the single crystal furnace to the outside of the single crystal furnace through a dry pump, heating the solid silicon material block to about 1420°C through the main and bottom heaters to melt into silicon liquid, and undergoing a cycle of temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter, and finishing process steps, so that the single crystal silicon atoms are arranged in an orderly manner according to a certain rule to complete the growth process of the single crystal, and after ensuring the amount of silicon material left in the furnace, the temperature is raised again for secondary feeding, and the solid silicon material block is heated and melted into silicon liquid through the main and bottom heaters, and undergoing a cycle of temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter, and finishing process steps. At present, the barrels used for feeding materials in the single crystal factory are high temperature resistant quartz barrels. After the specified time, the feeding is completed and no dopant is added. After the single crystal process operation time is reached, the heater is turned off to stop the furnace for cooling. The thermal system of the single crystal furnace is powered by the main bottom power cabinet on the first floor, and then connected to the copper electrode at the bottom of the single crystal furnace through an aluminum bar. There are four copper electrode columns in the single crystal furnace. The main bottom graphite electrodes are placed diagonally in pairs, and finally the two foot plates of the main and bottom additions are fixed on the graphite electrodes. The single crystal furnace supporting rotating mechanism finally fixes the crucible side, and a quartz crucible is placed inside the crucible side. During the melting process, the main feed radiates heat to the crucible side, and the crucible side transfers the heat to the quartz crucible, and the quartz crucible transfers the heat to the silicon material in the quartz crucible. The bottom feed radiates heat to the crucible side and the lower part of the quartz crucible, and the lower part of the crucible transfers the heat to the bottom of the quartz crucible, and then acts on the material block through the bottom of the quartz crucible to realize bottom-opening feeding, thereby preventing the main feed from melting the material on the side of the quartz crucible while the temperature at the bottom of the quartz crucible is low and crystallization cracks the quartz crucible.

[0003] The quartz crucible consists of an outer bubble layer and an inner transparent layer. Due to the different properties of the two types of quartz sand, it is easy to delaminate under long-term high-temperature baking, causing the quartz crucible to bulge.

[0004] In the current photovoltaic industry, the single crystal preparation technology and the Czochralski method for silicon single crystal melt generally have low bottom adding power and high main adding power, which has the following negative effects: because the main heater is close to the quartz crucible and has a larger area for heat radiation and heat conduction to the quartz crucible, while the bottom heater is far from the bottom of the quartz crucible and has a small heating area at the bottom of the quartz crucible, so it is baked less. The straight wall of the quartz crucible is baked at high temperature for a long time due to high power, causing the quartz crucible to bulge severely, and the bottom is affected by the rated power of the power cabinet, so the improvement of the bottom adding is imminent.

[0005] At present, patent CN218561686U discloses a thermal field structure for increasing the charge amount of a single crystal furnace. Its symmetrical structure makes the bottom pressure plate heated evenly, and bulging and deformation are not likely to occur, thereby reducing the sparking phenomenon caused by the bottom heater being too close. In addition, since the quartz crucible is closer to the bottom heater, the probability of silicon liquid crystallization at the bottom of the crucible is reduced, and the silicon leakage phenomenon caused by this can also be effectively avoided. However, it discloses that the bottom heater is an axisymmetric structure, and symmetrical left and right heating plates are provided on both sides. The heating plates are designed to be outside the bottom electrode, and the distance from the heating plate to the insulation tube is far. The arcing and sparking phenomenon between the bottom heater and the insulation tube caused by external factors is still easy to occur, and the service life of the bottom heater and the service life and stability of the thermal field are also easily affected.

[0006] Therefore, developing a bottom heater that can overcome the above defects and improve the efficiency of single crystal furnace charging has become a technical problem that needs to be solved urgently by those skilled in the art. Utility Model Content

[0007] The technical problem to be solved by the utility model is to overcome the shortcomings of the prior art and provide a bottom heater for improving the efficiency of single crystal furnace calcination. The bottom heater has a simple structure, high heating power and uniform heating, which effectively reduces the incidence of arcing and ignition between the bottom heater and the insulation tube caused by external factors, and increases the service life of the bottom heater and the life and stability of the thermal field.

[0008] In order to solve the above technical problems, the utility model provides a bottom heater for improving the efficiency of single crystal furnace oxidization, comprising a heating element and a foot plate, wherein two foot plates are symmetrically arranged on the left and right sides, respectively located on opposite sides of the heating element and connected to the heating element, and the heating element comprises a first heating element and a second heating element symmetrically arranged along the up and down direction, and the first heating element and the second heating element have the same structure;

[0009] The middle part of the foot plate extends and bulges toward the center direction of the bottom heater to form an arc-shaped plate, and the arc-shaped plate is provided with an electrode hole;

[0010] The first heating body includes a first heating unit, a second heating unit and a third heating unit which are connected in sequence. The first heating unit, the second heating unit and the third heating unit are respectively formed by mutually parallel heating strips which are connected end to end in sequence. The first heating unit and the third heating unit are symmetrically arranged on the left and right sides of the second heating unit. The outer sides of the first heating unit and the third heating unit are both stepped structures. The length of the heating strip of the second heating unit is shorter than that of the heating strip of the first heating unit.

[0011] The technical solution further defined in the utility model is:

[0012] Furthermore, the aforementioned bottom heater for improving the material oxidizing efficiency of the single crystal furnace also includes a bottom heater power cabinet, which is connected to the foot plate through the aluminum bar and the copper electrode in the single crystal furnace to provide power for the heating element, and at least three unit box modules are arranged in the bottom heater power cabinet.

[0013] Technical effect. From the perspective of the development of single crystal technology, the capacity increase of the bottom heater power cabinet is imminent. After the capacity increase of the bottom heater power cabinet, the power of the bottom heater can be increased higher, which can reduce the damage during the smelting process caused by the low temperature at the bottom of the quartz crucible under long-term operation. The current main power can be maintained. When necessary, the main power can be reduced, and the smelting efficiency of the single crystal furnace can still be increased. The bottom heater power cabinet of the utility model is provided with at least three unit box modules. Compared with the bottom heater power cabinet currently provided with one or two unit box modules, the purpose is to increase the rated output voltage and rated output current of the power cabinet by adding the power cabinet unit box modules, which can also increase the power of the bottom addition. Together with the newly improved bottom addition structure, the capacity of the bottom addition is increased, the power of the bottom addition is increased, the bottom addition can operate normally without sparking, thereby ensuring the service life of the bottom addition and the normal operation of the furnace.

[0014] In the aforementioned bottom heater for improving the efficiency of single crystal furnace fusion, the rated current in the bottom heater power cabinet is 3000mA, the power is 120kw, and the voltage is 54V.

[0015] In the above-mentioned bottom heater for improving the efficiency of single crystal furnace fusion, the heating element and the foot plate are an integrally formed structure.

[0016] Technical effect: the one-piece structure can be made of the same material to ensure uniform heating.

[0017] In the aforementioned bottom heater for improving the efficiency of single crystal furnace fusion, the heating strip is a straight strip structure.

[0018] Technical effect: The utility model adopts a straight heating strip structure, which is not only easy to process, but also easy to clean. It generates heat evenly during operation and is not prone to abnormal local excessive current. On the one hand, it can reduce ignition accidents and thus extend the service life.

[0019] In the above-mentioned bottom heater for improving the efficiency of single crystal furnace fusion, the distance between the two second heating units located in the middle of the first heating element and the second heating element is greater than the distance between the two first heating units and the two third heating units located on both sides, and the distance between the first heating element, the second heating element and the two foot plates forms a diamond structure.

[0020] Technical effect: The distance between the two second heating units located in the middle of the first heating element and the second heating element of the utility model is greater than the distance between the two first heating units and the two third heating units located on both sides. Through this structure, heat can be avoided from being concentrated in the middle, thereby affecting the heating effect on the silicon material, making the heating more uniform.

[0021] In the above-mentioned bottom heater for improving the efficiency of single crystal furnace fusion, the heating element and the base plate are both made of graphite material.

[0022] The beneficial effects of the utility model are:

[0023] The first heating unit and the second heating unit adopted in the utility model have a stepped structure on the outside and are evenly distributed in multiple directions, thereby ensuring the uniformity of heating.

[0024] The power supply of the main heater is turned off during the crystal pulling process from the beginning of melting until the furnace is stopped, and the bottom heater is turned on only during the melting process. The bottom heater is turned off during the crystal pulling process. The rated power of all bottom heater power cabinets is mostly lower than the rated power of the main heater power cabinet. The utility model increases the bottom heater power by increasing the capacity of the bottom heater power cabinet of the single crystal furnace, thereby increasing the melting efficiency of the single crystal furnace when the power of the main heater remains unchanged. After the capacity of the bottom heater power cabinet is increased, the temperature of the silicon liquid in the furnace can be increased, because there are material blocks in the quartz crucible, and the material blocks absorb the increased preheat in the quartz crucible, thereby improving the feeding efficiency and shortening the baking of the straight wall of the quartz crucible by the heating zone of the main heater, reducing the bulging rate of the quartz crucible, and reducing the risk of quartz crucible rupture and silicon leakage due to the increased temperature at the bottom of the quartz crucible.

[0025] Generally, the space for thermal field heaters is limited. In order to prevent the bottom temperature from being too low and to make the bottom of the crucible heated more evenly, the bottom heater will be designed to be as large as possible. However, the single crystal furnace has electrode columns that limit the positions of the bottom heater and the main heater, and the spatial distance must be limited. High power is prone to abnormal arcing due to bottom heater resistance, causing damage to the main heater and thermal field in the furnace, and higher requirements are placed on the setting shape and graphite material of the bottom heater. After the power of the bottom heater is increased, a bottom heater with a new structure is required. The foot plate of the bottom heater of the utility model is designed to be designed inside the bottom electrode, which increases the actual distance between the bottom heater and the foot plate of the main heater, and increases the distance to the insulation tube compared to the foot plate of the conventional bottom heater, thereby reducing the incidence of arcing and ignition between the bottom heater and the insulation tube caused by external factors, and increasing the service life of the bottom heater and the life and stability of the thermal field. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of a bottom heater for improving the efficiency of single crystal furnace material processing according to an embodiment of the utility model;

[0027] Figure 2 for Figure 1 Schematic diagram of the structure of the mid-foot plate;

[0028] Figure 3 for Figure 1 A schematic diagram of the structure of the first heating element;

[0029] In the figure: 1-foot plate, 2-first heating element, 21-first heating unit, 22-second heating unit, 23-third heating unit, 3-second heating element, 4-arc plate. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model. Example 1

[0031] This embodiment provides a bottom heater that improves the efficiency of single crystal furnace charging, and the structure is as follows: Figure 1-3 As shown, it includes an integrally formed heating element and a foot plate 1 made of graphite material, two foot plates 1 are symmetrically arranged on the left and right sides, respectively located on opposite sides of the heating element and connected to the heating element, and the heating element includes a first heating element 2 and a second heating element 3 symmetrically arranged along the up and down direction, and the first heating element 2 and the second heating element 3 have the same structure of a serpentine structure;

[0032] The middle part of the foot plate 1 extends and bulges toward the center of the bottom heater to form an arc plate 4, and the arc plate 4 is provided with an electrode hole;

[0033] The first heating element 2 includes a first heating unit 21, a second heating unit 22 and a third heating unit 23 which are connected in sequence. The first heating unit 21, the second heating unit 22 and the third heating unit 23 are respectively formed by mutually parallel straight heating strips which are connected end to end in sequence. The first heating unit 21 and the third heating unit 23 are symmetrically arranged on the left and right sides of the second heating unit 22. The outer sides of the first heating unit 21 and the third heating unit 23 are both stepped structures. The length of the heating strip of the second heating unit 22 is shorter than the length of the heating strip of the first heating unit 21. The distance between the two second heating units 22 located in the middle of the first heating element 2 and the second heating element 3 is greater than the distance between the two first heating units 21 and the two third heating units 23 located on the two sides. The distance between the first heating element 2, the second heating element 3 and the two foot plates 1 forms a rhombus structure.

[0034] It also includes a bottom heater power cabinet, which is connected to the foot plate 1 through the aluminum bar and the copper electrode in the single crystal furnace to provide power for the heating element. Three unit box modules are arranged in the bottom heater power cabinet. The rated current of the bottom heater power cabinet is 3000mA, the power is 120kw, and the voltage is 54V.

[0035] The direct current passes through the electrode and the foot plate, and then passes through the heating area formed by the first heating element and the second heating element to generate heat, thereby providing heat from the bottom of the crucible to ensure that the silicon material in the crucible is evenly heated and melted.

[0036] Take the 36-inch 630 hot field furnace for pulling 12-inch single crystal rods as an example:

[0037]

[0038] After the bottom adding power is increased, the temperature of the silicon liquid in the quartz crucible is prevented from being too high, and the material melting speed is too fast, causing the quartz crucible to collapse or bulge, and the feeding time interval is shortened during use; the purpose of preheating is to increase the temperature of the remaining silicon liquid in the furnace to prevent the material blocks from entering the low-temperature silicon liquid and crystallizing and cracking the quartz crucible after the material is added. After the bottom adding capacity is increased, the power is increased and the preheating time is also shortened.

[0039] Note: The maximum power of the bottom heater before capacity expansion is 100kw, and the theoretical value of the capacity expansion power of the bottom heater is 150kw. It is set at 120kw (the power safety value of the graphite bottom heater is 110-120kw). If the bottom increase exceeds the safety value, the bottom increase and main increase resistance will be abnormal, and the probability of abnormal damage will increase, so it is controlled at 120kw.

[0040] ①. The single crystal furnace is charged with 450kg of material for the second time, which reduces the charging time by 45 minutes per piece and increases the charging efficiency by 10.5kg / h;

[0041] ②. Yield contribution: 190kg / h (target yield) / 24h*0.75h=5.93kg / D.

[0042] The utility model can improve the single crystal furnace output by 5.93kg / D, and can effectively prevent quartz crucible bulging and silicon leakage of the quartz crucible.

[0043] From the perspective of the development of single crystal technology, the capacity increase of the bottom heater power cabinet is imminent. After the capacity increase of the bottom heater power cabinet, the power of the bottom heater can be increased to a higher level, which can reduce the damage during the material processing caused by the low temperature at the bottom of the quartz crucible under long-term operation, and can maintain the current main power. When necessary, the main power can be reduced, and the material processing efficiency of the single crystal furnace can still be increased. The foot plate of the utility model is designed to be designed toward the inside of the bottom electrode, which increases the actual distance between the bottom heater and the main heater foot plate, and increases the distance to the insulation tube compared with the conventional bottom heater foot plate, thereby reducing the incidence of arcing and ignition between the bottom heater and the insulation tube caused by external factors, and increasing the service life of the bottom heater and the life and stability of the thermal field.

[0044] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A bottom heater for improving the efficiency of single crystal furnace calcination, comprising a heating element and a foot plate (1), characterized in that: The foot plates (1) are symmetrically arranged at two ends, respectively located at two opposite sides of the heating element and connected to the heating element. The heating element comprises a first heating element (2) and a second heating element (3) symmetrically arranged in the up-down direction. The first heating element (2) and the second heating element (3) have the same structure. The middle part of the foot plate (1) extends and bulges toward the center direction of the bottom heater to form an arc-shaped plate (4), and the arc-shaped plate (4) is provided with an electrode hole; The first heating element (2) comprises a first heating unit (21), a second heating unit (22) and a third heating unit (23) which are connected in sequence. The first heating unit (21), the second heating unit (22) and the third heating unit (23) are respectively formed by mutually parallel heating strips which are connected end to end in sequence. The first heating unit (21) and the third heating unit (23) are symmetrically arranged on the left and right sides of the second heating unit (22). The outer sides of the first heating unit (21) and the third heating unit (23) are both in a stepped structure. The length of the heating strip of the second heating unit (22) is shorter than the length of the heating strip of the first heating unit (21).

2. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 1, characterized in that: It also includes a bottom heater power cabinet, which is connected to the foot plate (1) through an aluminum bar and a copper electrode in the single crystal furnace to provide power for the heating element, and the bottom heater power cabinet is provided with at least three unit box modules.

3. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 2, characterized in that: The rated current in the bottom heater power cabinet is 3000mA, the power is 120kw, and the voltage is 54V.

4. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 1, characterized in that: The heating element and the foot plate (1) are an integrally formed structure.

5. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 1, characterized in that: The heating strip is a straight strip structure.

6. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 1, characterized in that: The distance between the two second heating units (22) located in the middle of the first heating element (2) and the second heating element (3) is greater than the distance between the two first heating units (21) and the two third heating units (23) located on the two sides, and the distance between the first heating element (2), the second heating element (3) and the two foot plates (1) forms a diamond structure.

7. The bottom heater for improving the efficiency of single crystal furnace material processing according to claim 1, characterized in that: The heating element and the foot plate (1) are both made of graphite material.

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