阅读说明：本技术 低浓度位错铸锭单晶缓冲式籽晶熔化控制方法 (Low-concentration dislocation ingot single crystal buffer type seed crystal melting control method ) 是由 韩科选 薛赓 于 2021-06-07 设计创作，主要内容包括：本发明公开了低浓度位错铸锭单晶缓冲式籽晶熔化控制方法,包括以下步骤：(1)在石英坩埚底部铺设籽晶；(2)使用第一热电偶和第二热电偶获取石英坩埚底部边角部位的温度信号,温度信号为坩埚底部边角部位的温度和温度变化率的数值；(3)根据获取到的所述温度信号,判断所述籽晶熔化的高度；当所述温度信号出现突然上升的突变点时,表示籽晶熔化至设定高度,此时控制热场和工艺,进入长晶阶段；本发明将热电偶安装在坩埚底部边角部位,避开了侧部加热器对温度信号的影响,监测结果更准确。(The invention discloses a buffer type seed crystal melting control method for low-concentration dislocation ingot single crystals, which comprises the following steps: (1) seed crystals are laid at the bottom of the quartz crucible; (2) acquiring a temperature signal of a corner part at the bottom of the quartz crucible by using a first thermocouple and a second thermocouple, wherein the temperature signal is the temperature of the corner part at the bottom of the crucible and the value of the temperature change rate; (3) judging the melting height of the seed crystal according to the acquired temperature signal; when the temperature signal has a sudden rising catastrophe point, the seed crystal is melted to a set height, and at the moment, a thermal field and a process are controlled to enter a crystal growth stage; the thermocouple is arranged at the corner part at the bottom of the crucible, so that the influence of the side heater on the temperature signal is avoided, and the monitoring result is more accurate.)

1. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method is characterized by comprising the following steps of:

(1) and (3) laying seed crystals at the bottom of the quartz crucible:

step a, spraying silicon nitride powder on the inner surface of a quartz crucible and cooling the silicon nitride powder to be used as a protective layer;

b, paving a layer of rapeseed material with the thickness of 2cm on the bottom of the crucible by quartz

C, laying a seed crystal plate or a seed crystal block on the rapeseed material to serve as a seed crystal layer of the oriented casting semi-melting process;

d, filling gaps among the seed crystal plates or seed crystal blocks paved in the step by using small-particle primary monocrystalline silicon materials;

e, paving 50mm-mm rapeseed material on the seed crystal layer to serve as a buffer layer;

f, paving a plurality of crystal bricks consisting of head and tail materials on the buffer layer to serve as a barrier layer, wherein the crystal bricks of the barrier layer are gradually reduced from the crucible wall to the crucible center to form a sunken structure;

step g, stacking the following silicon materials on the barrier layer by layer: alternately laying head and tail single crystal waste, single crystal fragments, primary silicon materials and single crystal granules until the required silicon material requirement is met;

(2) acquiring a temperature signal of a corner part at the bottom of the quartz crucible by using a first thermocouple and a second thermocouple, wherein the temperature signal is the temperature of the corner part at the bottom of the crucible and the value of the temperature change rate;

(3) judging the melting height of the seed crystal according to the acquired temperature signal; when the temperature signal has a sudden rising catastrophe point, the temperature signal indicates that the seed crystal is melted to a set height, and at the moment, the thermal field and the process are controlled to enter a crystal growth stage.

2. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: in the step (3), the temperature signal is at least one of a temperature of the corner portion of the bottom of the crucible, a slope of a temperature change, and a cumulative slope of a temperature change, and the cumulative slope of a temperature change refers to an accumulated value of slopes of a plurality of temperature changes.

3. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: in the step (3), before the step of controlling the thermal field to enter the crystal growth stage from the melting stage when the seed crystal is melted to the set height, an early warning height can be set, and an alarm is given when the seed crystal is melted to the warning height.

4. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: and (3) setting an alarm setting value by using software, transmitting the temperature signal approaching or exceeding the alarm setting value to an alarm by using a PLC (programmable logic controller) when the temperature signal approaches or exceeds the alarm setting value, automatically alarming when the alarm receives the temperature signal, reminding the seed crystal of being fast melted or being melted to a set height, and then controlling a thermal field and a process to enter a crystal growth stage.

5. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: the preparation process of the seed crystal block in the step c is as follows: removing the flaw-piece from the monocrystalline silicon ingot to form a monocrystalline silicon rod, cutting the silicon rod into seed crystal blocks, wherein the size of each seed crystal block is as follows: 156mm 15 mm.

6. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: the preparation process of the seed crystal plate in the step c is as follows: the 8-inch crystal bar prepared by the Czochralski method is subjected to plate-shaped cutting along the Czochralski direction, and the size of the obtained seed crystal plate is 156mm by 980 mm.

7. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: the filling height of the buffer layer in the step e is 100-150 mm.

8. The low-concentration dislocation ingot single crystal buffer type seed crystal melting control method according to claim 1, characterized in that: and f, the length, the width and the height of the monocrystalline silicon crystal brick in the step f are respectively 156mm, 156mm and 30-40 mm.

Technical Field

The invention relates to the technical field of monocrystalline silicon melting, in particular to a low-concentration dislocation ingot monocrystalline buffer type seed crystal melting control method.

Background

Currently, in the rapidly developing solar photovoltaic power generation industry, the most widely used is a crystalline silicon solar cell, which is mainly made of a czochralski silicon wafer (CZ). The Czochralski silicon has high photoelectric conversion efficiency, low productivity and high production cost; compared with the Czochralski monocrystalline silicon, the ingot casting monocrystalline silicon piece has high productivity and low cost, but has lower photoelectric conversion efficiency.

In order to improve the efficiency of ingot casting of the monocrystalline silicon wafer, the technicians in the field combine the respective advantages of the two technologies and provide an ingot casting growth technology with seed crystals; for example, the ingot casting type single crystal technology of spreading monocrystalline silicon at the bottom of a crucible as seed crystals and the high-efficiency single crystal technology of spreading crushed silicon materials or crushed silicon wafers at the bottom of the crucible as seed crystals, namely, a layer of seed crystals are required to be spread at the bottom of the crucible for producing the type single crystal and the high-efficiency single crystal, then the silicon raw material is controlled to slowly melt from top to bottom, the seed crystals are required to be ensured not to be completely melted in the later stage of melting, and then high-quality crystals are directly grown on the seed crystals. At present, thermocouples are separately arranged on the side wall of a crucible, the temperature is detected to suddenly change along with the continuous descending of a molten silicon interface, and once the thermocouples detect the temperature sudden change, the melting interface reaches the height of the thermocouples. However, the thermocouple is installed on the side wall of the crucible and is easily affected by the heat radiation of the side heater, so that the thermocouple is difficult to detect the temperature rise of the melting interface, and the detection result is inaccurate. In view of the above drawbacks, it is actually necessary to design a low-concentration dislocation ingot single crystal buffer type seed crystal melting control method.

Disclosure of Invention

The invention aims to provide a buffer type seed crystal melting control method for a low-concentration dislocation ingot single crystal, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: the low-concentration dislocation ingot single crystal buffer type seed crystal melting control method comprises the following steps:

(1) and (3) laying seed crystals at the bottom of the quartz crucible:

step a, spraying silicon nitride powder on the inner surface of a quartz crucible and cooling the silicon nitride powder to be used as a protective layer;

b, paving a layer of rapeseed material with the thickness of 2cm on the bottom of the crucible by quartz

C, laying a seed crystal plate or a seed crystal block on the rapeseed material to serve as a seed crystal layer of the oriented casting semi-melting process;

d, filling gaps among the seed crystal plates or seed crystal blocks paved in the step by using small-particle primary monocrystalline silicon materials;

e, paving 50mm-mm rapeseed material on the seed crystal layer to serve as a buffer layer;

f, paving a plurality of crystal bricks consisting of head and tail materials on the buffer layer to serve as a barrier layer, wherein the crystal bricks of the barrier layer are gradually reduced from the crucible wall to the crucible center to form a sunken structure;

step g, stacking the following silicon materials on the barrier layer by layer: alternately laying head and tail single crystal waste, single crystal fragments, primary silicon materials and single crystal granules until the required silicon material requirement is met;

(2) acquiring a temperature signal of a corner part at the bottom of the quartz crucible by using a first thermocouple and a second thermocouple, wherein the temperature signal is the temperature of the corner part at the bottom of the crucible and the value of the temperature change rate;

(3) judging the melting height of the seed crystal according to the acquired temperature signal; when the temperature signal has a sudden rising catastrophe point, the temperature signal indicates that the seed crystal is melted to a set height, and at the moment, the thermal field and the process are controlled to enter a crystal growth stage.

Preferably, in the step (3), the temperature signal is at least one of a temperature of the corner portion of the bottom of the crucible, a slope of a temperature change, and a cumulative slope of a temperature change, which means a cumulative value of slopes of a plurality of temperature changes.

Preferably, in the step (3), before the step of controlling the thermal field to enter the crystal growth stage from the melting stage when the seed crystal is melted to the set height, an early warning height may be set, and an alarm may be given when the seed crystal is melted to the warning height.

Preferably, an alarm setting value is set by software in the step (3), when the temperature signal is close to or exceeds the alarm setting value, the PLC is used for transmitting the temperature signal close to or exceeding the alarm setting value to an alarm, the alarm automatically alarms when receiving the temperature signal to remind that the seed crystal is fast melted or is melted to a set height, and then the thermal field and the process are controlled to enter a crystal growth stage.

Preferably, the seed crystal block in step c is prepared by the following steps: removing the flaw-piece from the monocrystalline silicon ingot to form a monocrystalline silicon rod, cutting the silicon rod into seed crystal blocks, wherein the size of each seed crystal block is as follows: 156mm 15 mm.

Preferably, the seed crystal plate in step c is prepared as follows: the 8-inch crystal bar prepared by the Czochralski method is subjected to plate-shaped cutting along the Czochralski direction, and the size of the obtained seed crystal plate is 156mm by 980 mm.

Preferably, the filling height of the buffer layer in the step e is 100-150 mm.

Preferably, the length, width and height of the monocrystalline silicon crystal brick in the step f are respectively 156mm, 156mm and 30-40 mm.

Compared with the prior art, the low-concentration dislocation ingot single crystal buffer type seed crystal melting control method comprises the steps of laying a 50-100 mm rapeseed material on a seed crystal plate to serve as a buffer layer, and then laying a plurality of crystal bricks consisting of head and tail materials on the seed crystal plate to form a barrier layer; the invention utilizes the thermocouple to obtain the temperature signal of the corner part at the bottom of the crucible, utilizes the characteristics of the melting convex interface, and controls the melting of the seed crystal by detecting the melting temperature rise of the silicon liquid at the corner part, thereby generating an alarm at the moment when the seed crystal at the corner part is just melted, and also generating multiple alarms in the time period from the approach of the seed crystal to the complete melting state of the seed crystal, so that most of the seed crystals can be stored. Meanwhile, the thermocouple is arranged at the corner part at the bottom of the crucible, so that the influence of the side heater on the temperature signal is avoided, and the monitoring result is more accurate.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a technical scheme that: the low-concentration dislocation ingot single crystal buffer type seed crystal melting control method comprises the following steps:

(1) and (3) laying seed crystals at the bottom of the quartz crucible:

step a, spraying silicon nitride powder on the inner surface of a quartz crucible and cooling the silicon nitride powder to be used as a protective layer;

b, paving a layer of rapeseed material with the thickness of 2cm on the bottom of the crucible by quartz

C, laying a seed crystal plate or a seed crystal block on the rapeseed material to serve as a seed crystal layer of the oriented casting semi-melting process;

d, filling gaps among the seed crystal plates or seed crystal blocks paved in the step by using small-particle primary monocrystalline silicon materials;

e, paving 50mm-mm rapeseed material on the seed crystal layer to serve as a buffer layer;

f, paving a plurality of crystal bricks consisting of head and tail materials on the buffer layer to serve as a barrier layer, wherein the crystal bricks of the barrier layer are gradually reduced from the crucible wall to the crucible center to form a sunken structure;

step g, stacking the following silicon materials on the barrier layer by layer: alternately laying head and tail single crystal waste, single crystal fragments, primary silicon materials and single crystal granules until the required silicon material requirement is met;

(2) acquiring a temperature signal of a corner part at the bottom of the quartz crucible by using a first thermocouple and a second thermocouple, wherein the temperature signal is the temperature of the corner part at the bottom of the crucible and the value of the temperature change rate;

the temperature signal is at least one of the temperature of the corner part of the bottom of the crucible, the slope of the temperature change and the cumulative slope of the temperature change, wherein the cumulative slope of the temperature change refers to the cumulative value of the slopes of the temperature changes. And signals of the first thermocouple and the second thermocouple are respectively fed back to an alarm of the monocrystalline silicon ingot furnace, when the alarm receives a sudden change signal of the monocrystalline silicon ingot furnace, level 1 and level 2 alarms are respectively carried out, an operator judges the residual height of the crystal seeds according to the alarm condition, and timely jumps to enter a crystal growth stage through a monitoring result. In the application, the alarm receives the signal fed back by the first thermocouple and gives an alarm, and after receiving the signal fed back by the second thermocouple, the alarm gives an alarm and jumps to enter the crystal growth stage.

(3) Judging the melting height of the seed crystal according to the acquired temperature signal; when the temperature signal has a sudden rising catastrophe point, the temperature signal indicates that the seed crystal is melted to a set height, and at the moment, the thermal field and the process are controlled to enter a crystal growth stage.

In the step, before the step of controlling the thermal field to enter the crystal growth stage from the melting stage when the seed crystal is melted to the set height, an early warning height can be set, and the warning is given when the seed crystal is melted to the warning height. At least one preset alarm height is arranged.

In the step, an alarm setting value is set by software, when the temperature signal is close to or exceeds the set alarm setting value, the temperature signal close to or exceeding the set alarm setting value is transmitted to an alarm by a PLC (programmable logic controller), the alarm automatically alarms when receiving the temperature signal to remind the seed crystal to be quickly melted or melted to a set height, and then the thermal field and the process are controlled to enter a crystal growth stage.

In the step, one or more alarm set values can be set by using software, and when the temperature signal is close to or exceeds the set alarm set value, an alarm is given to remind the seed crystal of being melted quickly or being melted to a set height so as to remind an operator of paying attention.

The principle of judging the melting height of the seed crystal is as follows: the heating device in the polysilicon ingot furnace in the prior art is usually arranged at the side part of the crucible, so that the temperature of the corner part at the bottom of the crucible is 10-15 ℃ higher than that of the center, the seed crystal at the corner part is faster than that of the center, and the melting interface of the seed crystal is a convex interface, therefore, when the seed crystal at the corner part is just melted, most of the seed crystal at the bottom of the crucible is not melted. The invention leads the seed crystal laid in the crucible and the polycrystalline silicon raw material above the seed crystal to be gradually melted from top to bottom by controlling the thermal field; when the seed crystals at the corner part of the bottom of the crucible are not melted, the temperature signal change at the corner part of the crucible is not large; along with the slow melting of the seed crystal at the corner part at the bottom of the crucible, the temperature signal at the bottom of the crucible is slowly increased till the seed crystal at the corner part is completely melted, the silicon liquid is completely contacted with the corner part at the bottom of the crucible, and the temperature signal at the corner part at the bottom of the crucible suddenly rises and has a sudden change point. When the temperature signal has a sudden rising catastrophe point, the temperature signal indicates that the seed crystals at the corner parts are completely melted, but most of the seed crystals in the middle of the crucible are still in a solid form, and at the moment, the thermal field and the process can be controlled to enter a crystal growth stage. The invention can also utilize the PLC controller to transmit the temperature signal which is close to or exceeds the set alarm set value to the alarm before entering the crystal growth stage, so as to automatically alarm, remind the seed crystal to be melted quickly or to be melted to the set height, and manually control the operator to skip to enter the crystal growth stage. So that the silicon liquid can be grown on the residual solid seed crystal.

The invention utilizes the thermocouple to obtain the temperature signal of the corner part at the bottom of the crucible, utilizes the characteristics of the melting convex interface, and controls the melting of the seed crystal by detecting the melting temperature rise of the silicon liquid at the corner part, thereby generating an alarm when the seed crystal at the corner part is just melted, and also generating multiple alarms in the time period from the approach of the seed crystal to the complete melting state, so that most of the seed crystals can be stored. The method has the advantages of no need of manpower, simple and convenient operation, accurate detection result, convenience for setting the melting height of the seed crystal, low cost and realization of automatic production by combining with an automatic system. Meanwhile, the thermocouple is arranged at the corner part at the bottom of the crucible, so that the influence of the side heater on the temperature signal is avoided, and the monitoring result is more accurate.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.