Preparation method of aluminum oxide film for solar cell processing

Abstract

The invention discloses a preparation method of an aluminum oxide film for solar cell processing, which comprises the following steps: S1, a precursor A is carried by a reaction gas and enters a reaction chamber, a substrate in the reaction chamber is exposed in an atmosphere with the precursor A, the precursor A is attached to the surface of the substrate in a chemical adsorption form until saturation, and a precursor B is obtained; a new functional group is formed on the surface of the matrix; and S2, water vapor is used for purging the interior of the reaction cavity, redundant gas in the reaction cavity is blown away, the reaction cavity is cleaned, and impurities on the surface of the base body are cleared away. Compared with the prior art, the preparation method of the aluminum oxide film for solar cell processing can solve the problem of CVD parasitism caused by reaction of trimethylaluminum and hydroxyl instead of hydrogen atoms or incomplete arrangement due to over-high process temperature or insufficient process time to a great extent, and avoids the situation that the passivation effect becomes poor as far as possible; the energy consumption for preparing the aluminum oxide film is reduced, and meanwhile, the preparation efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cell preparation, and in particular relates to a method for preparing an aluminum oxide film used for solar cell processing. Background Art

[0002] The ALD process is a vapor deposition technology based on chemical adsorption. It is a thin film preparation technology that grows layer by layer at the atomic level. The ALD growth process is as follows Figure 1 As shown, by selectively alternating, different precursors are exposed to the surface of the substrate, chemically adsorbed and reacted on the surface to form a deposited film.

[0003] In short, water vapor first neutralizes the dangling bonds on the surface of the silicon wafer to form hydroxyl groups, and then trimethylaluminum reacts with the hydroxyl groups to form an Al 2 O 3 The film and silane gas are repeatedly purged until a good passivation layer is formed. Figure 2 As shown, the molecules in the aluminum oxide layer are regularly and neatly arranged on the silicon substrate. However, in reality, the process temperature is too high or the time is insufficient, so that trimethylaluminum reacts with hydroxyl groups instead of hydrogen atoms, or the molecules are not completely arranged, resulting in CVD parasitic conditions, such as Figure 3 As shown, at this time not only the passivation effect becomes worse, but also there will be higher energy consumption and reduced efficiency.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing an aluminum oxide film for solar cell processing, which can solve the technical problems raised in the above-mentioned background technology.

[0006] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0007] A method for preparing an aluminum oxide film for solar cell processing comprises the following steps:

[0008] S1. Precursor A is carried by the reaction gas and enters the reaction chamber. The substrate in the reaction chamber is exposed to the atmosphere containing precursor A. Precursor A adheres to the surface of the substrate in the form of chemical adsorption until saturation, and forms new functional groups on the surface of the substrate;

[0009] S2, using water vapor to purge the reaction chamber, blow away the excess gas in the reaction chamber, clean the reaction chamber and clean the impurities on the surface of the substrate. At the same time, the water vapor combines with the hydroxyl group as a hydrogen radical, and the hydroxyl group with a negative bond combines with the free positively charged dangling bond on the silicon surface;

[0010] S3, the precursor B is carried by the reaction gas and enters the reaction chamber, and the precursor B reacts with the functional groups on the surface of the substrate until the surface functional groups are completely saturated;

[0011] S4. Trimethylaluminum is introduced in pulse form to generate an aluminum oxide film. This process is performed at least once until a passivation layer is formed on the cell.

[0012] In one or more embodiments of the present invention, in step S2, the water vapor pulse time is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

[0013] In one or more embodiments of the present invention, in step S4, the pulse time of trimethylaluminum is 5 to 7 s, the purge time is 14 to 18 s, and the process flow rate is 15 to 25 sccm.

[0014] In one or more embodiments of the present invention, in step S2, the water vapor pulse time is 6 s, the purge time is 16 s, and the process flow rate is 20 sccm.

[0015] In one or more embodiments of the present invention, in step S4, the pulse time of trimethylaluminum is 5 to 7 s, the purge time is 14 to 18 s, and the process flow rate is 15 to 25 sccm.

[0016] In one or more embodiments of the present invention, in step S4, the pulse time of trimethylaluminum is 5.5 s, the purge time is 16 s, and the process flow rate is 15-25 sccm.

[0017] By increasing the purge time, the efficiency of the ALD process can be improved, and the aluminum oxide film thickness can be thicker. It can also largely avoid the occurrence of CAD parasitics, and avoid as much as possible the situation where the process temperature is too high or the time is insufficient, causing trimethylaluminum to react with hydroxyl groups instead of hydrogen atoms, or incomplete arrangement to cause CVD parasitics, and avoid as much as possible the situation where the passivation effect is deteriorated.

[0018] In one or more embodiments of the present invention, the method for preparing the aluminum oxide film for solar cell processing is completed in an atomic layer deposition device.

[0019] In one or more embodiments of the present invention, a pulse device is installed on one side of the atomic layer deposition device, and a pulse transmitting end matching the pulse device is installed on the atomic layer deposition device. The pulse device is used to receive the reaction gas and transport it into the atomic layer deposition device in a pulsed manner.

[0020] In one or more embodiments of the present invention, a first pump is installed on one side of the atomic layer deposition equipment, a gas input pipe is installed between the first pump and the atomic layer deposition equipment, a gas output pipe is installed on the first pump, a diversion shell is installed on the other end of the gas output pipe, a plurality of diversion tubes are arranged on the diversion shell, valves are installed in the plurality of diversion tubes, a first connecting tube is installed on the diversion tube, a gas storage bottle is installed on the other end of the first connecting tube, a second connecting tube is installed between the pulse emission end and the gas storage bottle, and a second pump is arranged on the second connecting tube.

[0021] The inert gas can be recycled, and the diversion shell has multiple diversion tubes. When multiple inert gases are used in the atomic layer deposition equipment, different inert gases can be transported to different gas storage bottles through the diversion shell and the diversion tubes. The inert gas can be fully automatically stored through the control of the valve.

[0022] In one or more embodiments of the present invention, a gas output branch pipe is installed on the gas output pipe, a heat exchange shell matching the gas output branch pipe is installed in the diversion shell, a third connecting pipe is installed at the lower end of the heat exchange shell, a water storage tank is installed at the other end of the third connecting pipe, and an observation window for observation is provided on the water storage tank.

[0023] Installing a heat exchange shell in the diversion shell can realize heat exchange between water vapor and inert gas, reduce the situation where the inert gas input into the atomic layer deposition equipment causes the space temperature in the atomic layer deposition equipment to drop, and the waste heat of water vapor can be utilized to reduce energy consumption. At the same time, the speed of water vapor liquefaction can be accelerated, and the liquefied water vapor can be stored. After treatment, the liquefied water vapor can be reused secondary to reduce the preparation cost of solar cells.

[0024] Compared with the prior art, the method for preparing aluminum oxide film for solar cell processing of the present invention can largely solve the problem that the process temperature is too high or the time is insufficient, causing trimethylaluminum to react with hydroxyl groups instead of hydrogen atoms, or the CVD parasitic situation that is not completely arranged, and avoids the situation where the passivation effect is deteriorated as a result as much as possible, reduces the energy consumption consumed in preparing the aluminum oxide film, and improves the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 The schematic diagram is a method for preparing an aluminum oxide film for processing a solar cell according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of an ideal structure of an aluminum oxide film used for processing solar cells in one embodiment of the present invention;

[0028] Figure 3 A schematic diagram of a non-ideal structure of an aluminum oxide film used for processing a solar cell in one embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the structure of an atomic layer deposition device in one embodiment of the present invention Figure 1 ;

[0030] Figure 5 Schematic diagram of the structure of an atomic layer deposition device in one embodiment of the present invention Figure 2 ;

[0031] Figure 6 for Figure 5 Schematic diagram of the structure at A in the middle;

[0032] Figure 7 It is a partial structural cross-sectional view of an atomic layer deposition device in one embodiment of the present invention.

[0033] Description of main reference numerals:

[0034] 1. Atomic layer deposition equipment; 2. Pulse equipment; 3. Pulse emission end; 4. First pump; 5. Gas input pipe; 6. Gas output pipe; 601. Gas output branch pipe; 7. Diverter shell; 701. Diverter pipe; 8. First connecting pipe; 9. Second connecting pipe; 10. Second pump; 11. Heat exchange shell; 12. Third connecting pipe; 13. Water tank; 1301. Observation window; 14. Valve; 15. Gas cylinder. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] like Figure 1 to Figure 3 As shown, the method for preparing an aluminum oxide film for solar cell processing in one embodiment of the present invention is specifically a vapor deposition technology based on chemical adsorption, and its basic principle is as follows Figure 1 As shown, it can be divided into four steps and two "half reactions":

[0037] The first "half-reaction" is:

[0038] S1. Precursor A is carried by an inert gas and enters the reaction chamber in a pulsed form. The substrate in the reaction chamber is exposed to the atmosphere of precursor A. Precursor A adheres to the surface of the substrate in the form of chemical adsorption until saturation occurs, and new functional groups are formed on the surface.

[0039] S2. Inert gas enters the chamber to purge the reaction chamber and take the remaining unreacted precursor A and by-products out of the chamber to clean the reaction chamber. At this point, the first "half reaction" is completed.

[0040] The second "half-reaction" is:

[0041] S3, the precursor B is carried by the inert gas and enters the reaction chamber through a pulse, and reacts chemically with the functional groups on the surface of the substrate until the surface functional groups are completely saturated;

[0042] S4. The inert gas enters the chamber again to purge the reaction chamber and take the remaining unreacted precursor B and by-products out of the chamber to clean the reaction chamber. At this point, the second "half reaction" is completed.

[0043] Among them, the by-products include impurities present on the surface of the substrate.

[0044] In step S2, water vapor is used to purge the reaction chamber to blow away excess gas in the reaction chamber, clean the reaction chamber and remove impurities on the surface of the substrate. At the same time, water vapor combines with hydroxyl groups as hydrogen radicals, and the negatively bonded hydroxyl groups combine with the free positively charged dangling bonds on the silicon surface. Specifically, the water vapor pulse time is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

[0045] Preferably, the water vapor pulse time is 6 s, the purge time is 16 s, and the process flow rate is 20 sccm.

[0046] In step S4, trimethylaluminum is introduced in pulse form to form an aluminum oxide film, and at least one round is performed until a passivation layer is formed on the cell. The pulse time of trimethylaluminum is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

[0047] Preferably, the pulse time of trimethylaluminum is 5.5 s, the purge time is 16 s, and the process flow rate is 15-25 sccm.

[0048] This process can ensure that water vapor fully forms hydroxyl groups on the surface of the silicon wafer. When purging TMA, the purging is stopped after trimethylaluminum fully reacts with the hydrogen bonds in the hydroxyl groups, thereby avoiding the generation of CAD parasitic conditions as much as possible. TMA is trimethylaluminum.

[0049] By adopting the above process, the efficiency of the ALD process can be improved, and the thickness of the aluminum oxide film can be thicker. It can also avoid the occurrence of CAD parasitics to a large extent, and avoid as much as possible the situation where the process temperature is too high or the time is insufficient, causing trimethylaluminum to react with hydroxyl groups instead of hydrogen atoms, or the CVD parasitic situation caused by incomplete arrangement, so as to avoid as much as possible the situation where the passivation effect is deteriorated.

[0050] like Figures 4 to 7 As shown, the preparation method of the aluminum oxide film for solar cell processing is generally completed in an atomic layer deposition device 1, a pulse device 2 matched with the atomic layer deposition device 1 is arranged on one side of the atomic layer deposition device 1, and a pulse transmitting end 3 matched with the pulse device 2 is installed on the atomic layer deposition device 1. The pulse device 2 uses a pulse to allow the inert gas, precursor A, precursor B and water vapor to enter the atomic layer deposition device 1 in the form of pulses, so that the inert gas, precursor A, precursor B and water vapor react with the substrate.

[0051] The pulse device 2 mainly has the pulse principle of blowing into the reaction chamber, blowing away the gas from the previous time, and filling the entire furnace with this gas. For example, the pulse of TMA is to blow away water vapor, so that the entire chamber is filled with TMA.

[0052] During the use of the atomic layer deposition device 1 and the pulse device 2, water vapor is required. After the reaction, the temperature of the water vapor will become low and it cannot be reused in the atomic layer deposition device 1. If the water vapor is directly discharged, it will cause certain energy loss and waste of energy. Figures 4 to 7As shown, a first pump 4 is installed on one side of the atomic layer deposition device 1, a gas input pipe 5 is installed between the first pump 4 and the atomic layer deposition device 1, a gas output branch pipe 601 is installed at the gas output end of the first pump 4, and a diversion shell 7 is installed at the end of the gas output branch pipe 601 away from the first pump 4. The inert gas in the atomic layer deposition device 1 is temporarily stored in the diversion shell 7 through the gas input pipe 5, the first pump 4 and the gas output branch pipe 601 respectively. A heat exchange shell 11 is installed inside the diversion shell 7, and a gas output pipe 6 is installed between the heat exchange shell 11 and the gas output branch pipe 601. The gas output branch pipe 601 is used to temporarily store water vapor in the heat exchange shell 11. The inert gas is stored between the outer wall of the heat exchange shell 11 and the inner wall of the diversion shell 7, and can exchange heat with water vapor, preheat the inert gas, recycle the remaining heat of water vapor, reduce the loss of water vapor energy consumption, and is beneficial to energy saving and environmental protection.

[0053] Furthermore, the lower end of the heat exchange shell 11 is fixedly connected with a third connecting pipe 12, and the other end of the third connecting pipe 12 is installed with a water tank 13. After the water vapor is heat exchanged, the water vapor will be liquefied, and the liquefied water vapor enters the water tank 13 through the third connecting pipe 12 for temporary storage. If necessary, the liquid in the water tank 13 can be processed and put into the atomic layer deposition device 1 for use after heating. The water tank 13 is also provided with an observation window 1301, through which the liquid level of the liquid in the water tank 13 can be observed, so as to facilitate timely processing of the liquid in the water tank 13.

[0054] like Figures 4 to 7 As shown, a plurality of shunt tubes 701 are provided on the shunt shell 7, and a plurality of valves 14 are installed on the shunt tubes 701. Output pipelines can be connected to different shunt tubes 701 according to the needs of use. A first connecting tube 8 is installed on the shunt tube 701, and a gas cylinder 15 is installed on the other end of the first connecting tube 8. The gas cylinder 15 can temporarily store the inert gas after heat exchange and can achieve a certain degree of heat preservation so that the heat is not lost as much as possible. There is a pulse tube between the pulse transmitting end 3 and the pulse device 2, and a second connecting tube 9 is installed between the pulse tube and the gas cylinder 15. The second connecting tube 9 transports the inert gas in the gas cylinder 15 to the pulse tube. The pulse tube cooperates with the pulse device 2 and the pulse transmitting end 3 to input the inert gas in the gas cylinder 15 into the atomic layer deposition device 1 again to achieve the secondary utilization of the inert gas.

[0055] The second connecting pipe 9 is provided with a second pump 10 , and the second pump 10 can pump the inert gas between the flow-dividing shell 7 and the heat-exchanging shell 11 into the gas storage bottle 15 for storage.

[0056] Preferably, a filter assembly may be further provided on the second connecting pipe 9 to filter impurities in the inert gas so that the inert gas entering the pulse tube can meet the process requirements.

[0057] like Figures 4 to 7 As shown, when in use, first, the first pump 4 pumps the inert gas to the space between the flow-dividing shell 7 and the heat exchange shell 11 through the gas input pipe 5 for storage. The first pump 4 delivers water vapor to the heat exchange shell 11 through the gas input pipe 5 to exchange heat with the inert gas. During the heat exchange process, the temperature of the inert gas can be increased, and the temperature of the water vapor can be reduced, and finally condensed into water, which flows into the water storage tank 13 through the third connecting pipe 12 for temporary storage. The inert gas after heat exchange enters the gas storage bottle 15 through the first connecting pipe 8 for temporary storage. When the inert gas is needed, the inert gas can be delivered to the pulse tube through the cooperation of the second pump 10 and the second connecting pipe 9, and then enters the atomic layer deposition device 1 in the form of pulses from the pulse emission end 3, reducing the temperature difference between the inert gas and the space inside the atomic layer deposition device 1, and minimizing the situation where the temperature of the space inside the atomic layer deposition device 1 is reduced due to the excessively low temperature of the atomic layer deposition device 1, thereby improving the quality of the prepared aluminum oxide film.

[0058] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing an aluminum oxide film for solar cell processing, characterized in that: The following steps are involved: S1. Precursor A is carried by the reaction gas and enters the reaction chamber. The substrate in the reaction chamber is exposed to the atmosphere containing precursor A. Precursor A adheres to the surface of the substrate in the form of chemical adsorption until saturation, and forms new functional groups on the surface of the substrate; S2, using water vapor to purge the reaction chamber, blow away the excess gas in the reaction chamber, clean the reaction chamber and clean the impurities on the surface of the substrate. At the same time, the water vapor combines with the hydroxyl group as a hydrogen radical, and the hydroxyl group with a negative bond combines with the free positively charged dangling bond on the silicon surface; S3, the precursor B is carried by the reaction gas and enters the reaction chamber, and the precursor B reacts with the functional groups on the surface of the substrate until the surface functional groups are completely saturated; S4. Trimethylaluminum is introduced in pulse form to generate an aluminum oxide film. This is performed for at least one round until a passivation layer is formed on the cell.

2. The method for preparing an aluminum oxide film for solar cell processing according to claim 1, characterized in that: In step S2, the water vapor pulse time is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

3. The method for preparing an aluminum oxide film for solar cell processing according to claim 2, characterized in that: In step S4, the pulse time of trimethylaluminum is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

4. The method for preparing an aluminum oxide film for solar cell processing according to claim 2, characterized in that: In step S2, the water vapor pulse time is 6 s, the purge time is 16 s, and the process flow rate is 20 sccm.

5. The method for preparing an aluminum oxide film for solar cell processing according to claim 1, characterized in that: In step S4, the pulse time of trimethylaluminum is 5 to 7 seconds, the purge time is 14 to 18 seconds, and the process flow rate is 15 to 25 sccm.

6. The method for preparing an aluminum oxide film for solar cell processing according to claim 5, characterized in that: In step S4, the pulse time of trimethylaluminum is 5.5 s, the purge time is 16 s, and the process flow rate is 15-25 sccm.

7. The method for preparing an aluminum oxide film for solar cell processing according to claim 1, characterized in that: The method for preparing the aluminum oxide film for solar cell processing is completed in an atomic layer deposition device.

8. The method for preparing an aluminum oxide film for solar cell processing according to claim 7, characterized in that: A pulse device is installed on one side of the atomic layer deposition device. A pulse transmitting end matching the pulse device is installed on the atomic layer deposition device. The pulse device is used to receive the reaction gas and transport it into the atomic layer deposition device in a pulsed manner.

9. The method for preparing an aluminum oxide film for solar cell processing according to claim 8, characterized in that: A first pump is installed on one side of the atomic layer deposition device, a gas input pipe is installed between the first pump and the atomic layer deposition device, a gas output pipe is installed on the first pump, and a flow splitting housing is installed at the other end of the gas output pipe; The diversion housing is provided with a plurality of diversion tubes, each of which is provided with a valve, a first connecting tube is provided on the diversion tube, a gas storage bottle is provided at the other end of the first connecting tube, and a second connecting tube is provided between the pulse transmitting end and the gas storage bottle; The second connecting pipe is provided with a second pump.

10. The method for preparing an aluminum oxide film for solar cell processing according to claim 9, characterized in that: A gas output branch pipe is installed on the gas output pipe, a heat exchange shell matching the gas output branch pipe is installed in the flow splitting shell, a third connecting pipe is installed at the lower end of the heat exchange shell, and a water storage tank is installed at the other end of the third connecting pipe; An observation window for observation is provided on the water storage tank.

Images