阅读说明：本技术 一种高效单晶硅电池的氧化退火工艺 (Oxidation annealing process of high-efficiency monocrystalline silicon battery ) 是由 刘斌 黄辉巍 江建楷 于 2019-08-30 设计创作，主要内容包括：本发明涉及一种高效单晶硅电池的氧化退火工艺,包括以下步骤,1)进舟；2)升温；3)炉管抽真空并检漏；4)氧化；5)恒温退火,在压力100-150mbar,温度680-710℃下维持15-20min的退火并通入氮气5000-10000sccm；6)降温退火,在压力100-150mbar,温度620-650℃下维持15-20min的退火并通入氮气10000-20000sccm；7)充气回压；8)出舟,结束工艺。本发明将常压氧化退火改为低压氧化退火,并在退火过程中采用恒温退火以及降温退火,使得工艺过程中的气体氛围能够被精确控制,退火环境洁净也得到提高,使得电池片效率得到提升。(The invention relates to an oxidation annealing process of a high-efficiency monocrystalline silicon battery, which comprises the following steps of 1) feeding a boat; 2) heating; 3) vacuumizing a furnace tube and detecting leakage; 4) oxidizing; 5) constant temperature annealing, wherein annealing is maintained for 15-20min at the pressure of 100-; 6) cooling and annealing, maintaining the annealing at the pressure of 100-; 7) inflating and back-pressing; 8) and (5) discharging the boat and finishing the process. According to the invention, the normal-pressure oxidation annealing is changed into the low-pressure oxidation annealing, and the constant-temperature annealing and the cooling annealing are adopted in the annealing process, so that the gas atmosphere in the technological process can be accurately controlled, the annealing environment is clean and improved, and the efficiency of the battery piece is improved.)

1. An oxidation annealing process of a high-efficiency monocrystalline silicon battery is characterized in that: comprises the following steps of (a) carrying out,

1) entering the boat, setting the temperature of the furnace tube after entering the boat to be 530-580 ℃, introducing nitrogen gas of 10000-;

2) heating, setting the temperature at 680 ℃ and 710 ℃, introducing nitrogen at 10000 ℃ and 20000sccm, keeping the pressure at 800-1100 mbar for 10-15 min;

3) vacuumizing a furnace tube and detecting leakage, wherein the temperature is 680-710 ℃, the pressure is 100-;

4) oxidizing at 100-;

5) primary annealing, wherein annealing is maintained for 15-20min at the pressure of 100-;

6) secondary annealing, wherein annealing is maintained for 15-20min at the pressure of 100-;

7) inflating and returning pressure, and inflating nitrogen to the normal pressure of 800-1100 mbar;

8) and (5) discharging the boat and finishing the process.

2. The process of claim 1, wherein the annealing step comprises: in the step 5), the primary annealing is constant-temperature annealing at 700 ℃ and 100mbar, and nitrogen is introduced into the furnace at 8000sccm for 15 min.

3. The process of claim 1, wherein the annealing step comprises: in the step 6), the secondary annealing is cooling annealing, the temperature is 650 ℃, the pressure is 100mbar, 10000sccm of nitrogen is introduced, and the time is 15 min.

Technical Field

The invention relates to the technical field of solar cells, in particular to an oxidation annealing process of a high-efficiency monocrystalline silicon cell.

Background

In the solar cell industry, an oxidation process is often added after an etching process to improve the potential-induced degradation resistance of a cell, and then as the industry develops many companies, the oxidation process is improved, an annealing furnace is added, and oxidation and annealing are combined to improve the efficiency of the cell.

The oxidation and annealing effects of the battery piece are affected by the environment atmosphere, and at present, various companies basically encounter bottlenecks and are difficult to break through when trying to continue to improve the efficiency in the process through early adjustment and optimization. The method is mainly characterized in that the gas atmosphere in the tube is greatly influenced by power exhaust under the normal pressure process condition, and the gas atmosphere in the tube cannot be accurately controlled, so that the improvement of the efficiency of the battery plate in the process is restricted.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the oxidation annealing process of the high-efficiency monocrystalline silicon battery is provided, and the efficiency of the battery piece is improved by adjusting relevant process parameters.

The technical scheme adopted by the invention for solving the technical problems is as follows: an oxidation annealing process of a high-efficiency monocrystalline silicon battery comprises the following steps,

1) entering the boat, setting the temperature of the furnace tube after entering the boat to be 530-580 ℃, introducing nitrogen gas of 10000-;

2) heating, setting the temperature at 680 ℃ and 710 ℃, introducing nitrogen at 10000 ℃ and 20000sccm, keeping the pressure at 800-1100 mbar for 10-15 min;

3) vacuumizing a furnace tube and detecting leakage, wherein the temperature is 680-710 ℃, the pressure is 100-;

4) oxidizing at 100-;

5) primary annealing, wherein annealing is maintained for 15-20min at the pressure of 100-;

6) secondary annealing, wherein annealing is maintained for 15-20min at the pressure of 100-;

7) inflating and returning pressure, and inflating nitrogen to the normal pressure of 800-1100 mbar;

8) and (5) discharging the boat and finishing the process.

Further, in the step 5), the primary annealing is constant temperature annealing at 700 ℃, under 100mbar, and with 8000sccm of nitrogen gas being introduced for 15 min.

Furthermore, in the step 6), the secondary annealing is cooling annealing, wherein the temperature is 650 ℃, the pressure is 100mbar, 10000sccm of nitrogen is introduced, and the time is 15 min.

After the oxidation step, 680-710 ℃ constant temperature annealing is carried out, so that the surface concentration and junction depth of phosphorus diffusion of the cell can be adjusted, and the efficiency of the cell can be improved by long-time annealing.

The temperature reduction rate can be reduced when the temperature reduction annealing process is kept under the low-pressure condition, and the efficiency of slow temperature reduction annealing can be improved.

When the boat is moved, 10000 plus 20000sccm of nitrogen is introduced to increase the purging of the surface of the silicon wafer, and the high-quality rate is reduced if impurities exist on the surface of the silicon wafer in the high-temperature oxidation process, which easily causes white spots of subsequent coating.

The nitrogen in the oxidation step is mainly used for pushing oxygen, and simultaneously, the nitrogen in the constant temperature annealing step is used for adjusting the uniformity of the atmosphere in the furnace.

In the cooling annealing step, because the annealing is carried out under the low-pressure condition, the cooling rate is very slow, and the nitrogen flow is increased so as to properly improve the cooling rate. Although the cooling rate is low, the annealing effect is better, the temperature of the silicon wafer is not too high when the process is finished and the silicon wafer is taken out of the boat due to the limitation of the process time, otherwise, the temperature difference during the process of taking out the silicon wafer generates new thermal stress defects.

The invention has the beneficial effects that the defects in the background technology are overcome, the normal pressure oxidation annealing is changed into the low pressure oxidation annealing, and the constant temperature annealing and the cooling annealing are adopted in the annealing process, so that the gas atmosphere in the process can be accurately controlled, the cleaning of the annealing environment is improved, and the efficiency of the battery piece is improved.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Detailed Description

The invention will now be described in further detail with reference to the drawings and preferred embodiments. These drawings are simplified schematic views illustrating only the basic structure of the present invention in a schematic manner, and thus show only the constitution related to the present invention.

After the etching process is finished, 800 silicon wafers are taken for testing, and because two adjacent silicon wafers have similar or similar characteristics, in order to ensure the fairness of data, 800 silicon wafers are alternately selected according to an odd number sequence and an even number sequence and are divided into 2 groups, each group comprises 400 silicon wafers, and a furnace pipe tail gas control valve is adjusted, so that one group uses the low-pressure oxidation annealing process, the other group uses a conventional oxidation annealing process, and the other processes are finished under the same conditions.

The oxidation annealing process of the high-efficiency monocrystalline silicon battery shown in figure 1 comprises the following steps,

1) feeding the furnace tube, setting the temperature of the furnace tube after feeding the furnace tube into the boat to be 550 ℃, introducing 10000sccm of nitrogen, keeping the pressure to be 1000mbar, and keeping the pressure for 3-8 min;

2) heating, setting the temperature at 700 deg.C, introducing nitrogen gas of 10000sccm, and maintaining the pressure at 1000mbar for 10 min;

3) vacuumizing a furnace tube and detecting leakage, wherein the temperature is 700 ℃, the pressure is 100mbar, the time is 3min, and the leakage rate is less than 5mbar/min under the condition that the initial pressure is 100 mbar;

4) oxidizing at 100mbar and 700 deg.C for 5min, introducing nitrogen gas of 5000sccm and oxygen gas of 500 sccm;

5) annealing at constant temperature, maintaining the annealing at 100mbar and 700 ℃ for 15min, and introducing nitrogen gas of 8000 sccm;

6) cooling and annealing, maintaining the annealing at the pressure of 100mbar and the temperature of 650 ℃ for 15min, and introducing 10000sccm of nitrogen;

7) charging nitrogen gas at 650 deg.C and normal pressure of 1000mbar, introducing nitrogen gas of 20000sccm for 5 min;

8) taking out the boat, introducing nitrogen gas of 20000sccm at 550 ℃ and 1000mbar for 5min, and finishing the process.

The test was performed 2 times in total and the results were as follows:

in conclusion, the efficiency of the cell after the low-pressure oxidation annealing is about 0.04% higher than that of the cell after the normal-pressure oxidation annealing.

While particular embodiments of the present invention have been described in the foregoing specification, various modifications and alterations to the previously described embodiments will become apparent to those skilled in the art from this description without departing from the spirit and scope of the invention.