Process for improving the uniformity of the square resistance of a boron furnace mouth before a topcon cell

Abstract

The application discloses a process for improving the uniformity of the square resistance of a TOPcon cell before a boron furnace mouth, comprising the following steps: furnace pipe feeding, vacuum pumping, temperature rising, constant temperature, leak detection, temperature rising, diffusion / deposition, purging, distributed temperature reduction 1, distributed temperature reduction 2, vacuum breaking and boat discharging. Compared with the prior art, the application adds an empty running process, and a deposition / diffusion step is added in the empty running process, so that the temperature of the paddle, the boron source atmosphere of the furnace mouth and the process environment difference are reduced in a short time, the STD of the furnace mouth silicon wafer is improved, the single wafer square resistance uniformity is improved, the PL defective proportion is reduced, and the A-level proportion of the solar cell wafer is improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more particularly to a process for improving the sheet resistance uniformity of the front boron furnace opening in TOPcon cells. Background Technology

[0002] Currently, the photovoltaic industry is booming worldwide, but the development of photovoltaic technology still faces two major challenges: reducing costs and improving conversion efficiency. Photoluminescence (PL) defects are a significant factor affecting the yield of solar cells. PL is a method for detecting the quality of photovoltaic cells, which judges their quality by observing the emission of light from the cells under the excitation of incident photons.

[0003] After the existing boron diffusion production process is completed, the long idle time of the furnace tube will lead to paddle cooling, slow reheating, insufficient boron source atmosphere at the furnace mouth, high sheet resistance at the furnace mouth, excessive sheet resistance at single points, and STD (dispersion of sheet resistance at continuous test points within a boron cell) of the first quartz boat exceeding the control limit. The high STD of the cell after boron diffusion will lead to low carrier lifetime doping density, thereby increasing the proportion of half-sided blackening of PL. Half-sided blackening of PL is a manifestation of PL defects, which seriously affects the yield efficiency of photovoltaic cells entering the warehouse. Summary of the Invention

[0004] The purpose of this invention is to provide a process for improving the sheet resistance uniformity of the front boron furnace in TOPcon cells. By adding a dry run process and incorporating a deposition / diffusion step, the differences between the paddle temperature, the boron source atmosphere at the furnace inlet, and the process environment are reduced within a short period of time. This improves the STD of the silicon wafer at the furnace inlet, improves the sheet resistance uniformity of a single wafer, reduces the PL defect rate, and increases the proportion of Grade A solar cells, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A process for improving the sheet resistance uniformity of the front boron furnace opening in TOPcon cells includes the following steps: Step 1, Furnace tube entry: Place the empty paddle without the quartz boat into the furnace tube. Set the furnace tube temperature to 810℃±20℃ and the tube pressure to 980mbar. The time is 300 seconds.

[0006] Step 2, Vacuuming: After closing the furnace door, set the pressure inside the pipe to 700 mbar, which takes 120 seconds.

[0007] Step 3, Heating: Raise the temperature to 820℃, set the pressure inside the pipe to 120mbar, and take 540 seconds.

[0008] Step 4, Temperature control: Set the temperature consistently, set the pressure inside the pipe to 95 mbar, and take 180 seconds.

[0009] Step 5, Leak detection: With the temperature and pressure consistent with before, close the gas valve and diaphragm pump, check the airtightness of the furnace tubes (less than 2.5 mbar), which takes 60 seconds.

[0010] Step 6, Heating: Raise the temperature to 900℃, set the pressure to 130mbar, and set the N2 to 3500sccm to purge the environment inside the tube; take 400 seconds.

[0011] Step 7, Diffusion / Deposition: Temperature and pressure remain the same as before. Set BCL3 to 100 sccm, N2 to 2500 sccm, and O2 to 540 sccm for power supply, taking 360 seconds.

[0012] Step 8, Purging: Set the temperature to 890℃, set BCL3 to 300sccm to purge the BCL3 pipeline, and N2 to 500sccm, for 180 seconds.

[0013] Step 9, Distributed Cooling 1: Temperature drops to 800℃, pressure rises to 600mbar, oxygen is set to 10000sccm, N2 is set to 1000sccm to purge the pipeline, taking 900 seconds.

[0014] Step 10, Distributed Cooling 2: The temperature drops to 780℃, the pressure rises to 600mbar, N2 is set to 8000sccm back pressure and the pipeline is purged, taking 400 seconds.

[0015] Step 11, Vacuum Break: The temperature drops to 760℃, the pressure returns to normal, N2 is set to 18000sccm back pressure and the pipeline is purged, which takes 120 seconds.

[0016] Step 12, Unloading: When the temperature drops to 750℃, send the paddle out of the furnace tube. The process is complete, taking 400 seconds.

[0017] The beneficial effects of this invention are: This invention improves the STD of silicon wafers at the furnace mouth, enhances the uniformity of sheet resistance of single wafers, reduces the PL defect rate, and increases the proportion of Grade A solar cells by adding a dry run process and incorporating a deposition / diffusion step. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1: As Figure 1As shown, a process for improving the sheet resistance uniformity of the front boron furnace opening in TOPcon cells includes the following steps: Step 1, Furnace tube entry: Place the empty paddle without the quartz boat into the furnace tube. Set the furnace tube temperature to 810℃±20℃ and the tube pressure to 980mbar. The time is 300 seconds.

[0021] Step 2, Vacuuming: After closing the furnace door, set the pressure inside the pipe to 700 mbar, which takes 120 seconds.

[0022] Step 3, Heating: Raise the temperature to 820℃, set the pressure inside the pipe to 120mbar, and take 540 seconds.

[0023] Step 4, Temperature control: Set the temperature consistently, set the pressure inside the pipe to 95 mbar, and take 180 seconds.

[0024] Step 5, Leak detection: With the temperature and pressure consistent with before, close the gas valve and diaphragm pump, check the airtightness of the furnace tubes (less than 2.5 mbar), which takes 60 seconds.

[0025] Step 6, Heating: Raise the temperature to 900℃, set the pressure to 130mbar, and set the N2 to 3500sccm to purge the environment inside the tube; take 400 seconds.

[0026] Step 7, Diffusion / Deposition: Temperature and pressure remain the same as before. Set BCL3 to 100 sccm, N2 to 2500 sccm, and O2 to 540 sccm for power supply, taking 360 seconds.

[0027] Step 8, Purging: Set the temperature to 890℃, set BCL3 to 300sccm to purge the BCL3 pipeline, and N2 to 500sccm, for 180 seconds.

[0028] Step 9, Distributed Cooling 1: Temperature drops to 800℃, pressure rises to 600mbar, oxygen is set to 10000sccm, N2 is set to 1000sccm to purge the pipeline, taking 900 seconds.

[0029] Step 10, Distributed Cooling 2: The temperature drops to 780℃, the pressure rises to 600mbar, N2 is set to 8000sccm back pressure and the pipeline is purged, taking 400 seconds.

[0030] Step 11, Vacuum Break: The temperature drops to 760℃, the pressure returns to normal, N2 is set to 18000sccm back pressure and the pipeline is purged, which takes 120 seconds.

[0031] Step 12, Unloading: When the temperature drops to 750℃, send the paddle out of the furnace tube. The process is complete, taking 400 seconds.

[0032] This invention improves the STD of silicon wafers at the furnace mouth, enhances the uniformity of sheet resistance of single wafers, reduces the PL defect rate, and increases the proportion of Grade A solar cells by adding a dry run process and incorporating a deposition / diffusion step.

[0033] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A process for improving the sheet resistance uniformity of the front boron furnace opening in TOPcon batteries, characterized in that: Includes the following steps: Step 1, Furnace tube entry: Place the empty paddle, which does not contain the quartz boat, into the furnace tube; Step 2, Vacuuming: After closing the furnace door, set the pressure inside the pipe to 700 mbar, which takes 120 seconds; Step 3, Heating: Raise the temperature to 820℃, set the pressure inside the tube to 120mbar, and take 540 seconds; Step 4, Temperature control: Set the temperature consistently, set the internal pressure to 95 mbar, and take 180 seconds. Step 5, Leak detection: With the temperature and pressure consistent with before, close the gas valve and diaphragm pump, check the air tightness of the furnace tubes (less than 2.5 mbar), which takes 60 seconds. Step 6, Heating: Raise the temperature to 900℃, set the pressure to 130mbar, and set the N2 to 3500sccm to purge the environment inside the tube; time: 400s; Step 7, Diffusion / Deposition: Temperature and pressure remain the same as before. Set the flow rates of BCL3, N2, and O2 for power supply, taking 360 seconds. Step 8, Purging: Set the temperature to 890℃, set BCL3 to 300 sccm to purge the BCL3 pipeline, and N2 to 500 sccm, for 180 seconds; Step 9, Distributed Cooling 1: Temperature drops to 800℃, pressure rises to 600mbar, oxygen is set to 10000sccm, N2 is set to 1000sccm to purge the pipeline, taking 900 seconds; Step 10, Distributed Cooling 2: The temperature drops to 780℃, the pressure rises to 600mbar, N2 is set to 8000sccm back pressure and the pipeline is purged, taking 400 seconds; Step 11, Vacuum Break: The temperature drops to 760℃, the pressure returns to normal, N2 is set to 18000sccm back pressure and the pipeline is purged, which takes 120 seconds; Step 12, Unloading: When the temperature drops to 750℃, send the paddle out of the furnace tube. The process is complete, taking 400 seconds.

2. The process for improving the sheet resistance uniformity of the front boron furnace opening in a TOPcon battery as described in claim 1, characterized in that: In step 1, the furnace tube temperature is set to 810℃±20℃, the tube pressure is set to 980mbar, and the time is 300S.

3. The process for improving the sheet resistance uniformity of the front boron furnace opening in a TOPcon battery as described in claim 1, characterized in that: In step 7, BCL3 is set to 100 sccm, N2 to 2500 sccm, and O2 to 540 sccm for power supply.

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