Gas phase deposition method for passivating contact structures, solar cells and solar modules

Abstract

The present invention provides a vapor deposition method of a passivation contact structure, a solar cell and a solar module, and relates to the field of crystal growth technology. The vapor deposition method of a passivation contact structure comprises: after exhausting the air in the vapor deposition furnace tube, maintaining a first temperature, introducing a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stopping ventilation; maintaining the first temperature for a time greater than or equal to the time for introducing the gas including oxygen; lowering the temperature to a second temperature to obtain the tunneling oxide layer; the growth rate of the tunneling oxide layer during the time of maintaining the first temperature is greater than the growth rate during the time of lowering the temperature to the second temperature. The present invention can reduce production costs, reduce safety risks, save process time, and improve production efficiency. The tunneling oxide layer has good compactness and uniformity, and reduces passivation performance fluctuations.

Description

Technical Field

[0001] The invention relates to the technical field of crystal growth, in particular to a vapor deposition method for a passivation contact structure, a solar cell and a solar module. Background Art

[0002] The passivation contact structure includes: a stacked tunnel oxide layer and a doping layer. The passivation contact structure can bring excellent silicon interface passivation performance, and therefore has a wide range of applications in solar cells. For example, the passivation contact structure is used in TOPcon (Tunnel Oxide Passivated Contact) solar cells.

[0003] The ultra-thin tunneling oxide layer in the passivation contact structure plays a vital role in the silicon interface passivation. However, the existing method of preparing the tunneling oxide layer has the problems of high cost, high safety risk, and large fluctuations in the passivation performance of the tunneling oxide layer. Summary of the invention

[0004] The present invention provides a vapor deposition method for a passivation contact structure, a solar cell and a solar module, aiming to solve the problems of high cost and high safety risk in preparing a tunneling silicon oxide layer and large fluctuation in passivation performance of the obtained tunneling oxide layer.

[0005] A first aspect of the present invention provides a vapor deposition method for a passivation contact structure, wherein the passivation contact structure comprises a tunneling oxide layer; the method comprises:

[0006] After exhausting the air in the vapor deposition furnace tube, maintaining the first temperature, introducing a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stopping introducing the gas including oxygen into the vapor deposition furnace tube; maintaining the first temperature for a time period greater than or equal to the time period for introducing the gas including oxygen;

[0007] The temperature is lowered to a second temperature to obtain the tunnel oxide layer; the growth rate of the tunnel oxide layer during the time period of maintaining the first temperature is greater than the growth rate during the time period of lowering the temperature to the second temperature.

[0008] In an embodiment of the present invention, during the growth of the tunneling oxide layer, the time for maintaining the first temperature is greater than or equal to the time for introducing the oxygen-containing gas, and after the volume of the introduced oxygen-containing gas is less than or equal to 90% of the volume of the vapor deposition furnace tube, the introduction of the oxygen-containing gas into the vapor deposition furnace tube is stopped. Then, the amount of the introduced oxygen-containing gas is small, and the oxygen in the introduced oxygen-containing gas can meet the amount of oxygen required for depositing the tunneling oxide layer. At the same time, the introduced oxygen-containing gas does not fill the vapor deposition furnace tube. Before the growth of the tunneling oxide layer is completed, the oxygen-containing gas is basically not discharged from the vapor deposition furnace tube. There is basically no waste of oxygen-containing gas, and there is basically no waste of oxygen, which can reduce production costs. Moreover, the amount of the introduced oxygen-containing gas is small, and the amount of oxygen introduced is also small. After the growth of the tunneling oxide layer is completed, the amount of the oxygen-containing gas entering the exhaust gas treatment device is small, and the amount of oxygen entering the exhaust gas treatment device is also small, which reduces the possibility of explosion of oxygen and other gases in the subsequent exhaust gas treatment process and reduces safety risks. Moreover, the growth rate of the tunneling oxide layer during the time of maintaining the first temperature is greater than the growth rate during the time of lowering the temperature to the second temperature. At the same time, the time of maintaining the first temperature is greater than or equal to the time of introducing the gas including oxygen. Then, before cooling, the thickness of the tunneling oxide layer has grown to a suitable thickness, and then at a lower temperature, the growth rate is slow, which can improve the density and uniformity of the tunneling oxide layer, so that the passivation performance of the tunneling oxide layer fluctuates little. That is to say, the present invention ensures the growth rate of the tunneling oxide layer at a higher temperature, saves process time, and has high production efficiency. After the thickness of the tunneling oxide layer grows to a suitable thickness, the temperature is lowered to improve the density and uniformity of the tunneling oxide layer. In summary, the present invention can reduce production costs, reduce safety risks, save process time, and improve production efficiency. At the same time, it improves the density and uniformity of the tunneling oxide layer, so that the passivation performance of the tunneling oxide layer fluctuates little.

[0009] Optionally, after exhausting the air in the vapor deposition furnace tube, maintaining the first temperature, introducing a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stopping introducing the gas including oxygen into the vapor deposition furnace tube, comprising:

[0010] After the air in the vapor deposition furnace tube is discharged, the first temperature is maintained, and gas including oxygen is introduced into the vapor deposition furnace tube so that the volume of the gas including oxygen occupies 80%-90% of the volume of the vapor deposition furnace tube. Then, the introduction of the gas including oxygen into the vapor deposition furnace tube is stopped, and the first temperature is maintained, and the temperature is kept constant for a preset period of time.

[0011] Optionally, the gas including oxygen is: oxygen, or a mixed gas of oxygen and filling gas.

[0012] Optionally, the filling gas is at least one of nitrogen and an inert gas.

[0013] Optionally, the gas including oxygen is a mixed gas of oxygen and filling gas; the flow rate ratio of the oxygen and the filling gas is: (1:2)-(2:1).

[0014] Optionally, the duration of introducing the gas including oxygen is: 4 to 10 minutes;

[0015] The preset time duration is less than or equal to the time duration for lowering the temperature to the second temperature.

[0016] Optionally, the preset duration is: 2 to 8 minutes;

[0017] The time for reducing the temperature to the second temperature is: 2 to 8 minutes.

[0018] Optionally, the difference between the first temperature and the second temperature is 10 to 40°C.

[0019] Optionally, the first temperature is 580 to 600°C; the second temperature is 560 to 570°C.

[0020] Optionally, the vapor deposition is chemical vapor deposition.

[0021] Optionally, after lowering the temperature to the second temperature to obtain the tunnel oxide layer, the method further comprises:

[0022] In the vapor deposition furnace tube, based on the second temperature, the doping layer is prepared by in-situ doping on the tunneling oxide layer; the first temperature is greater than the in-situ doping temperature, and the second temperature is greater than or equal to the in-situ doping temperature.

[0023] Optionally, after lowering the temperature to the second temperature to obtain the tunnel oxide layer, the method further comprises:

[0024] In the vapor deposition furnace tube, on the basis of the second temperature, an intrinsic amorphous silicon layer corresponding to the doping layer is prepared on the tunneling oxide layer; the second temperature is lower than the growth temperature of the intrinsic amorphous silicon layer.

[0025] A second aspect of the present invention provides a solar cell, wherein the solar cell comprises a passivation contact structure prepared by any of the above-mentioned passivation contact structures using a vapor deposition method.

[0026] A third aspect of the present invention provides a solar energy assembly, comprising a cell string formed by connecting a plurality of the aforementioned solar cells in series. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0028] Figure 1 A flow chart showing the steps of a vapor deposition method for a passivation contact structure in an embodiment of the present invention is shown;

[0029] Figure 2 A schematic diagram of the thickness measurement position of a tunnel oxide layer in a solar cell according to an embodiment of the present invention is shown.

[0030] Description of reference numerals:

[0031] 11 - the center of the tunneling oxide layer in the solar cell, 12 - the edge 1 of the tunneling oxide layer in the solar cell, 13 - the edge 2 of the tunneling oxide layer in the solar cell, 14 - the edge 3 of the tunneling oxide layer in the solar cell, 15 - the edge 4 of the tunneling oxide layer in the solar cell. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0033] The passivation contact structure includes: a stacked tunneling oxide layer and a doping layer. The passivation contact structure can bring excellent silicon interface passivation performance. The ultra-thin tunneling oxide layer in the passivation contact structure plays a vital role in silicon interface passivation.

[0034] Figure 1 FIG. 1 is a flow chart showing the steps of a vapor deposition method for a passivation contact structure in an embodiment of the present invention. Figure 1 As shown, the vapor deposition method of the passivation contact structure includes the following steps:

[0035] Step 101, after exhausting the air in the vapor deposition furnace tube, maintain the first temperature, and introduce a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stop introducing the gas including oxygen into the vapor deposition furnace tube; the time length for maintaining the first temperature is greater than or equal to the time length for introducing the gas including oxygen.

[0036] The purpose of exhausting the air in the vapor deposition furnace tube is to prevent the air in the vapor deposition furnace tube from having an adverse effect on the preparation of the passivation contact structure. The amount of air exhausted from the vapor deposition furnace tube is not specifically limited. For example, the air in the vapor deposition furnace tube can be completely exhausted.

[0037] Step 102, lowering the temperature to a second temperature to obtain the tunnel oxide layer; the growth rate of the tunnel oxide layer during the time of maintaining the first temperature is greater than the growth rate during the time of lowering the temperature to the second temperature.

[0038] Specifically, the inventors found that the existing method of preparing the tunneling oxide layer has high cost and high safety risk. The main reason for the large fluctuation of the passivation performance of the obtained tunneling oxide layer is that: in the prior art, in the entire process of preparing the tunneling oxide layer, pure oxygen is continuously introduced, the volume of the vapor deposition furnace tube is constant, and the amount of oxygen required for depositing the tunneling oxide layer is also small. The pure oxygen continuously introduced is greater than the volume of the vapor deposition furnace tube, and most of it will be discharged from the vapor deposition furnace tube, resulting in a large waste of pure oxygen, resulting in high production costs. At the same time, a large amount of pure oxygen discharged from the vapor deposition furnace tube will enter the exhaust gas treatment device, and in the subsequent growth process of the doping layer of the passivation contact structure, gases such as methane will also enter the exhaust gas treatment device, making the safety risks such as explosion high. And in the prior art, the tunneling oxide layer is grown at a higher temperature. At a higher temperature, the continuous introduction of pure oxygen will make the growth rate of the tunneling oxide layer faster, but the density and uniformity are poor, resulting in large fluctuations in the passivation performance of the obtained tunneling oxide layer.

[0039] In view of the above problems, the inventors, in an embodiment of the present invention, during the growth of the tunneling oxide layer, keep the first temperature for a time longer than or equal to the time for introducing the oxygen-containing gas, and after the volume of the oxygen-containing gas introduced is less than or equal to 90% of the volume of the vapor deposition furnace tube, stop introducing the oxygen-containing gas into the vapor deposition furnace tube. Then, the amount of oxygen-containing gas introduced is small, and the oxygen in the oxygen-containing gas introduced can meet the amount of oxygen required for depositing the tunneling oxide layer. At the same time, the oxygen-containing gas introduced does not fill the vapor deposition furnace tube. Before the growth of the tunneling oxide layer is completed, the oxygen-containing gas is basically not discharged from the vapor deposition furnace tube. There is basically no waste of oxygen-containing gas, and there is basically no waste of oxygen, which can reduce production costs. Moreover, the amount of oxygen-containing gas introduced is small, and the amount of oxygen introduced is also small. After the growth of the tunneling oxide layer is completed, the amount of oxygen-containing gas entering the exhaust gas treatment device is small, and the amount of oxygen entering the exhaust gas treatment device is also small, which reduces the possibility of explosion of oxygen and other gases in the subsequent exhaust gas treatment process and reduces safety risks. Moreover, the growth rate of the tunneling oxide layer during the time of maintaining the first temperature is greater than the growth rate during the time of lowering the temperature to the second temperature. At the same time, the time of maintaining the first temperature is greater than or equal to the time of introducing the gas including oxygen. Then, before cooling, the thickness of the tunneling oxide layer has grown to a suitable thickness, and then at a lower temperature, the growth rate is slow, which can improve the density and uniformity of the tunneling oxide layer, so that the passivation performance of the tunneling oxide layer fluctuates little. That is to say, the present invention ensures the growth rate of the tunneling oxide layer at a higher temperature, saves process time, and has high production efficiency. After the thickness of the tunneling oxide layer grows to a suitable thickness, the temperature is lowered to improve the density and uniformity of the tunneling oxide layer. In summary, the present invention can reduce production costs, reduce safety risks, save process time, and improve production efficiency. At the same time, it improves the density and uniformity of the tunneling oxide layer, so that the passivation performance of the tunneling oxide layer fluctuates little.

[0040] More specifically, compared with the prior art, the vapor deposition method of the passivation contact structure of the present invention reduces the oxygen consumption by 50% or more.

[0041] It should be noted that the difference between the duration of maintaining the first temperature and the duration of introducing the gas including oxygen is not specifically limited. The duration of introducing the gas including oxygen is mainly limited by the volume of the gas including oxygen introduced being less than or equal to 90% of the volume of the vapor deposition furnace tube. The duration of maintaining the first temperature is mainly limited by the thickness of the tunneling oxide layer formed being more suitable. The specific reason is that the thickness of the tunneling oxide layer grown during the duration of maintaining the first temperature can occupy the vast majority of the thickness of the tunneling oxide layer finally prepared, and the duration of maintaining the first temperature is positively correlated with the thickness of the tunneling oxide layer grown during the duration of maintaining the first temperature. For example, the duration of maintaining the first temperature can be: the duration required for the thickness of the tunneling oxide layer grown at the first temperature to be 55% to 98% of the thickness of the tunneling oxide layer finally prepared. For another example, the duration of maintaining the first temperature can be: the duration required for the thickness of the tunneling oxide layer grown at the first temperature to be 70% to 98% of the thickness of the tunneling oxide layer finally prepared. For another example, the time period for maintaining the first temperature may be: the time period required for maintaining the first temperature so that the thickness of the tunnel oxide layer grown is 72% to 90% of the thickness of the tunnel oxide layer finally prepared.

[0042] The time for lowering the temperature to the second temperature is mainly limited by the uniformity and density of the tunneling oxide layer finally prepared. Lowering the temperature to the second temperature can be achieved by naturally cooling it at room temperature. The time for lowering the temperature to the second temperature can also be limited by room temperature. In the embodiment of the present invention, no specific limitation is made to this. It should be noted that, since in the aforementioned step 101, after the volume of the gas including oxygen introduced is less than or equal to 90% of the volume of the vapor deposition furnace tube, the gas including oxygen is stopped from being introduced into the vapor deposition furnace tube, and the gas including oxygen introduced does not fill the vapor deposition furnace tube. Therefore, from the time when the gas including oxygen is stopped from being introduced into the vapor deposition furnace tube, until the temperature is lowered to the second temperature, or until the tunneling oxide layer is prepared, the gas including oxygen introduced will basically not be discharged from the vapor deposition furnace tube.

[0043] Thousands of silicon wafers or silicon substrates are usually placed in a batch in a vapor deposition furnace tube. Gas including oxygen is introduced into the vapor deposition furnace tube so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube. This can ensure that the vacuum in the vapor deposition furnace tube will not be broken, and the silicon wafers and silicon substrates in the vapor deposition furnace tube will be evenly wrapped by the gas atmosphere, that is, the gas including oxygen does not fill the vapor deposition furnace tube, and the gas including oxygen will basically not be discharged from the vapor deposition furnace tube, and the oxygen introduced can meet the amount of oxygen required for depositing the tunneling oxide layer.

[0044] It should be noted that the growth rate of the tunnel oxide layer during the time period of maintaining the first temperature can be: the growth thickness of the tunnel oxide layer during the time period of maintaining the first temperature, divided by the time period of maintaining the first temperature. The growth rate of the tunnel oxide layer during the time period of reducing the temperature to the second temperature can be: the growth thickness of the tunnel oxide layer during the time period of reducing the temperature to the second temperature, divided by the time period of reducing the temperature to the second temperature.

[0045] Optionally, the above step 101 may include: after discharging the air in the vapor deposition furnace tube, maintaining the first temperature, introducing gas including oxygen into the vapor deposition furnace tube so that the volume of the gas including oxygen occupies 80%-90% of the volume of the vapor deposition furnace tube, stopping introducing gas including oxygen into the vapor deposition furnace tube, maintaining the first temperature, and keeping the temperature constant for a preset time. Specifically, a gas including oxygen is introduced into the vapor deposition furnace tube so that the volume of the gas including oxygen occupies 80%-90% of the volume of the vapor deposition furnace tube. On the one hand, it can ensure that the vacuum in the vapor deposition furnace tube will not be broken, that is, the gas including oxygen does not fill the vapor deposition furnace tube and is basically not discharged from the vapor deposition furnace tube. The gas including oxygen is basically not wasted, which can reduce production costs. Moreover, the amount of gas including oxygen introduced is small, and the amount of oxygen introduced is also small. After the growth of the tunneling oxide layer is completed, the amount of gas including oxygen entering the tail gas treatment device is small, and the amount of oxygen entering the tail gas treatment device is also small, which reduces the possibility of explosion of oxygen and other gases in the subsequent tail gas treatment process, and reduces safety risks. On the other hand, the amount of gas introduced can fully wrap the silicon wafer or silicon substrate, provide a suitable gas atmosphere for the growth of the tunneling oxide layer, and the oxygen introduced can just meet the amount of oxygen required for the deposition of the tunneling oxide layer. The amount of oxygen entering the tail gas treatment device is less, and the production cost is lower. The time period for maintaining the first temperature may be equal to the time period for introducing the gas including oxygen plus the preset time period for constant temperature standing.

[0046] For example, the volume of the gas including oxygen introduced may occupy 80%, 82%, 83%, 85%, 86%, 88%, 90% of the volume of the vapor deposition furnace tube, and the introduction of the gas including oxygen into the vapor deposition furnace tube is stopped. The volume of the gas including oxygen introduced can be determined by the product of the introduction time and the introduced flow rate.

[0047] Optionally, the gas including oxygen is oxygen, or a mixed gas of oxygen and a filling gas, and the gas including oxygen has more selectivity. For the gas including oxygen being a mixed gas of oxygen and a filling gas, on the one hand, the filling gas can act as a part of the gas atmosphere, which can further reduce the amount of oxygen introduced and reduce costs. On the other hand, since less oxygen is introduced, the amount of oxygen entering the exhaust gas treatment device after the tunnel oxide layer growth is completed is also less, which further reduces the possibility of explosion of oxygen and other gases during the subsequent exhaust gas treatment process, and further reduces the safety risk.

[0048] Optionally, the filling gas may be at least one of nitrogen or an inert gas. The filling gas is easy to obtain and will not adversely affect the growth of the tunnel oxide layer. If the filling gas includes nitrogen, nitrogen is easier to obtain and has a lower cost.

[0049] It should be noted that if the filling gas includes nitrogen, silicon oxynitride and silicon nitride will basically not be generated under the deposition conditions of the vapor deposition furnace tube. The specific reason is that the temperature at which nitrogen and silicon react is usually high, such as 1300 to 1400°C or even higher, while the temperature at which the tunneling oxide layer grows in the vapor deposition furnace tube is usually less than or equal to 630°C, and the temperature at which the tunneling oxide layer grows in the vapor deposition furnace tube does not reach the temperature required for the reaction between nitrogen and silicon.

[0050] Optionally, the gas including oxygen is a mixed gas of oxygen and filling gas, and the flow rate ratio of oxygen to filling gas is: (1:2)-(2:1). When the flow rate ratio of oxygen to filling gas is within this range, on the one hand, the growth rate of the tunnel oxide layer, the density and uniformity of the generated tunnel oxide layer are well balanced, and on the other hand, the process quality of the tunnel oxide layer is easy to control and easy to achieve mass production.

[0051] For example, the gas including oxygen is a mixed gas of oxygen and filling gas, and the flow rate ratio of oxygen to the filling gas is: 1:2, 1:1.5, 1:1.2, 1:1, 1.1:1, 1.4:1, 1.7:1, 2:1.

[0052] Optionally, the duration of introducing the gas including oxygen is 4 to 10 minutes. Within this time range, before the growth of the tunneling oxide layer is completed, the gas including oxygen will basically not be discharged from the vapor deposition furnace tube, and the gas including oxygen is basically not wasted, and the oxygen is basically not wasted, which can reduce production costs. Moreover, the amount of the gas including oxygen introduced is small, and the amount of oxygen introduced is also small. After the growth of the tunneling oxide layer is completed, the amount of the gas including oxygen entering the exhaust gas treatment device is small, and the amount of oxygen entering the exhaust gas treatment device is also small, which reduces the possibility of explosion of oxygen and other gases in the subsequent exhaust gas treatment process and reduces safety risks. The oxygen introduced can just meet the amount of oxygen required for the deposition of the tunneling oxide layer. At the same time, the ventilation time is short, and the production efficiency of the tunneling oxide layer is high.

[0053] For example, the duration of introducing the gas including oxygen is: 4 minutes, 5 minutes, 6 minutes, 7.5 minutes, 8 minutes, 9 minutes, and 10 minutes.

[0054] Optionally, after stopping the introduction of gas including oxygen, the first temperature is maintained, and the preset time of constant temperature stillness is less than or equal to the time of lowering the temperature to the second temperature. That is to say, at a lower temperature, the time of slow growth rate is relatively long, which can further improve the density and uniformity of the tunneling oxide layer, and make the passivation performance of the tunneling oxide layer fluctuate less.

[0055] Optionally, after stopping the introduction of gas including oxygen, the first temperature is maintained and the preset time for constant temperature standing is: 2 to 8 minutes. Within this time range, the thickness of the tunnel oxide layer has grown to an appropriate thickness, which is beneficial to improving the uniformity and density of the prepared tunnel oxide layer. At the same time, the production efficiency is also high.

[0056] For example, the preset duration may be: 2 minutes, 3.5 minutes, 4 minutes, 5 minutes, 6 minutes, 7.5 minutes, or 8 minutes.

[0057] Optionally, the time duration for lowering the temperature to the second temperature is 2 to 8 minutes. Within this time duration range, the uniformity and density of the prepared tunnel oxide layer are excellent, and the production efficiency is also high.

[0058] For example, the time length for lowering the temperature to the second temperature may be: 2 minutes, 3 minutes, 4.5 minutes, 5 minutes, 6 minutes, 7.5 minutes, 8 minutes.

[0059] Optionally, the difference between the first temperature and the second temperature is 10 to 40° C. When the difference between the two is within this range, the production efficiency of the tunnel oxide layer and the uniformity and density of the prepared tunnel oxide layer are well balanced.

[0060] For example, the difference between the first temperature and the second temperature is 10°C, 13°C, 19°C, 21°C, 26°C, 30°C, 33°C, or 40°C.

[0061] Optionally, the first temperature is 580 to 600° C., and the second temperature is 560 to 570° C., the production efficiency of the tunneling oxide layer, and the uniformity and density of the prepared tunneling oxide layer achieve a good balance, and mass production is easy to achieve.

[0062] Optionally, the above-mentioned vapor deposition is chemical vapor deposition (CVD). The CVD method is mature and easy to obtain a tunneling oxide layer with good density and uniformity, and is easy to mass produce. At the same time, this method can be compatible with the relevant preparation process of the subsequent doping layer to a large extent, so that the preparation process of the passivation layer contact structure is simple and easy to mass produce. For example, the tunneling oxide layer can be grown by low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (Atmospheric Pressure Chemical VaporDeposition), etc.

[0063] Optionally, after the above step 102, the method may further include: in the vapor deposition furnace tube, on the basis of the above second temperature, in-situ doping on the tunneling oxide layer to prepare a doping layer, the first temperature is greater than the in-situ doping temperature, and the second temperature is greater than or equal to the in-situ doping temperature. In the process of growing the tunneling oxide layer, the temperature in the vapor deposition furnace tube is reduced from the first temperature to the second temperature, and the temperature in the subsequent in-situ doping process to prepare the doping layer is less than or equal to the second temperature. Before the in-situ doping to prepare the doping layer, it may be necessary to cool down, or the temperature is just right, thereby reducing the time required for cooling down before the subsequent in-situ doping to prepare the doping layer, reducing the production time of the passivation contact structure, and improving the production efficiency of the passivation contact structure.

[0064] For example, in the prior art, the temperature of 600°C is maintained during the preparation of the tunnel oxide layer, and the temperature of the subsequent in-situ doping to prepare the doped layer is about 560°C. Therefore, after the tunnel oxide layer is prepared, the temperature needs to be reduced by 40°C to prepare the doped layer by in-situ doping. However, in the process of preparing the tunnel oxide layer in the present invention, the first temperature is first maintained at 580 to 600°C, and then the temperature is reduced to the second temperature of 560 to 570°C. Therefore, after the tunnel oxide layer is prepared, it is only necessary to reduce the temperature by 0 to 10°C to prepare the doped layer by in-situ doping. Moreover, under normal circumstances, the cooling is mostly carried out by natural cooling. Therefore, the present invention significantly reduces the cooling time. Compared with the prior art, the present invention can reduce the cooling time by at least 5 minutes.

[0065] The present invention does not specifically limit the subsequent in-situ doping. For example, the gas introduced during the in-situ doping may include: phosphine and silane.

[0066] Optionally, after the above step 102, the method may further include: in the vapor deposition furnace tube, on the basis of the above second temperature, preparing an intrinsic amorphous silicon layer corresponding to the doping layer on the tunneling oxide layer, and the second temperature is less than the growth temperature of the intrinsic amorphous silicon layer. That is to say, after the tunneling oxide layer is prepared, the intrinsic amorphous silicon layer corresponding to the doping layer continues to grow in the vapor deposition furnace tube. Then, the doping layer is prepared by ex situ doping, and the method for preparing the passivation contact structure is diverse, flexible, and has a wide range of applications. There is no specific limitation on the ex situ doping method, for example, it can be phosphorus diffusion, etc.

[0067] The present invention also provides a solar cell, which includes a passivation contact structure prepared by any of the aforementioned vapor deposition methods for the passivation contact structure. The solar cell has the same or similar beneficial effects as any of the aforementioned vapor deposition methods for the passivation contact structure, and will not be described in detail here to avoid repetition.

[0068] The present invention also provides a solar module, which includes a battery string formed by a plurality of the aforementioned solar cells connected in series. The solar module also has the same or similar beneficial effects as any of the aforementioned vapor deposition methods of the passivation contact structure, and will not be described again here to avoid repetition.

[0069] It should be noted that the vapor deposition method of the passivation contact structure, the solar cell, and the solar module can be referenced to each other.

[0070] The present application is further explained below with reference to specific embodiments.

[0071] Example

[0072] After polishing, the silicon wafer is vapor-deposited with a tunneling oxide layer and a doping layer in the LPCVD equipment to form a passivation contact structure. Specifically, the growth of the tunneling oxide layer is divided into the following steps: the first step: after exhausting the air in the vapor deposition furnace tube, maintain the first temperature of 580-600°C, introduce 10slm (standard cubic centimeter per minute) of O2 (oxygen) and 10slm of N2 (nitrogen), and the ventilation time is 7min (minutes), and then stop ventilation. The purpose of the first step is to introduce a nitrogen-oxygen mixed gas to allow oxygen to be more evenly distributed in the tube, and the amount of nitrogen-oxygen mixed gas introduced occupies 80%-90% of the volume of the vapor deposition furnace tube. The nitrogen-oxygen mixed gas does not fill the vapor deposition furnace tube, does not break the vacuum of the vapor deposition furnace tube, and does not cause excessive waste of oxygen. The second step: maintain the first temperature of 580-600°C unchanged, do not pass gas, and oxidize at a constant temperature for 5min. The purpose of this step is to allow the silicon wafer in the tube to be fully and evenly oxidized in a stable atmosphere. Step 3: Lower the temperature inside the tube from the first temperature to the second temperature of 560-570°C without passing gas. The time required to lower the temperature inside the tube from the first temperature to the second temperature is 6 minutes. The purpose of this step is, on the one hand, low-temperature oxidation to obtain a tunneling oxide layer with better uniformity and density. On the other hand, early cooling helps to shorten the cooling time required before the subsequent in-situ doping preparation of the doping layer, because the temperature of the subsequent in-situ growth doping layer is 560-570°C. After the growth of the tunneling oxide layer is completed, the doping layer is deposited in situ, and then crystallized by high-temperature annealing to form a passivation contact structure. Then it is patterned, the electrodes are printed, etc. to form the final solar cell.

[0073] Comparative Example

[0074] After the polished silicon wafer, a tunneling oxide layer and a doping layer are vapor-deposited in the LPCVD equipment to form a passivation contact structure. Specifically, the growth of the tunneling oxide layer is completed in one step, specifically: after the air in the vapor deposition furnace tube is exhausted, it is maintained at 600°C, 18slm of O2 is introduced, and the ventilation time is 13min. Since, according to the flow rate of 18slm of O2, the ventilation time is 13min, the total volume of O2 introduced is greater than the volume of the vapor deposition furnace tube, and the oxygen introduced will be discharged from the vapor deposition furnace tube. After the growth of the tunneling oxide layer is completed, the temperature in the vapor deposition furnace tube is first cooled from 600°C to 560-570°C, and the cooling time is 8min, and then the doping layer is deposited in situ, and then crystallized by high-temperature annealing to form a passivation contact structure. Then it is patterned, the electrodes are printed, etc., to form the final solar cell.

[0075] It should be noted that the silicon wafers used in the embodiment and the comparative example are from the same batch and have the same process parameters. The LPCVD equipment used in the embodiment and the comparative example is the same, the number of silicon wafers placed in the vapor deposition furnace tube is also the same, both are 1000 pieces, and the placement position and placement method of the silicon wafers in the vapor deposition furnace tube are also the same. The difference between the embodiment and the comparative example is only the process of preparing the tunneling oxide layer.

[0076] The furnace mouth can be an entrance for placing silicon wafers into the furnace tube. The furnace tail is the end of the furnace tube opposite to the furnace mouth. The passivation contact structure or solar cell numbered 1 is located at the furnace mouth, and the passivation contact structure or solar cell numbered 6 is located at the furnace tail. Along the direction from the furnace mouth to the furnace tail, the passivation contact structures or solar cells numbered 2 to 6 are arranged in sequence, and the distances between adjacent passivation contact structures or solar cells are equal. That is, the distance between the passivation contact structure or solar cell numbered 2 and the passivation contact structure or solar cell numbered 1 is equal to the distance between the passivation contact structure or solar cell numbered 2 and the passivation contact structure or solar cell numbered 3. For the passivation contact structures or solar cells formed in the above-mentioned embodiments and comparative examples, the 6 passivation contact structures or solar cells numbered 1 to 6 are measured, and the process parameters and measurement parameters, etc. are specifically referred to the table below.

[0077] Comparison table of process parameters and measurement parameters of the passivation contact structure formed in the embodiment and the comparative example

[0078]

[0079]

[0080] Figure 2 FIG. 1 is a schematic diagram showing a thickness measurement position of a tunnel oxide layer in a solar cell in an embodiment of the present invention. Figure 2 As shown, 11 is the center of the tunneling oxide layer in the solar cell, and the center thickness in the table is the thickness at 11. 12 is the edge 1 of the tunneling oxide layer in the solar cell, and the thickness of edge 1 in the table is the thickness at 12. 13 is the edge 2 of the tunneling oxide layer in the solar cell, and the thickness of edge 2 in the table is the thickness at 13. 14 is the edge 3 of the tunneling oxide layer in the solar cell, and the thickness of edge 3 in the table is the thickness at 14. 15 is the edge 4 of the tunneling oxide layer in the solar cell, and the thickness of edge 4 in the table is the thickness at 15. The measurement positions and measurement tools of the thickness of the tunneling oxide layer of the passivation contact structure in the six solar cells are all the same.

[0081] In the table, the intra-sheet non-uniformity of the tunneling oxide layer in a solar cell is determined by: the maximum value of the thickness of the tunneling oxide layer corresponding to the center 11, edge 1, edge 2, edge 3, edge 4, 5 points of the tunneling oxide layer in a solar cell, minus the difference of the minimum value, divided by the sum of the maximum value and the minimum value, to obtain the quotient. The inter-sheet non-uniformity of the tunneling oxide layer in the 6 solar cells of the embodiment is determined by: the arithmetic mean of the thickness of the tunneling oxide layer corresponding to the center 11, edge 1, edge 2, edge 3, edge 4, 5 points of the tunneling oxide layer in each solar cell of the embodiment is calculated, and the arithmetic mean is used as the thickness of the tunneling oxide layer in the solar cell, and then the maximum value of the thickness of the tunneling oxide layer in the 6 solar cells in the embodiment is minus the difference of the minimum value, divided by the sum of the maximum value and the minimum value, to obtain the quotient. The method for determining the inter-sheet non-uniformity of the tunneling oxide layer in the 6 solar cells of the comparative example is the same as the method for determining the inter-sheet non-uniformity of the tunneling oxide layer in the 6 solar cells of the embodiment.

[0082] By comparing the above table, it can be seen that, compared with the comparative example, the oxygen consumption in the embodiment is less, the intra-sheet non-uniformity of the tunneling oxide layer in each solar cell is smaller, and the inter-sheet non-uniformity of the tunneling oxide layer in the 6 solar cells in the embodiment is smaller. At the same time, after the growth of the tunneling oxide layer is completed, the in-situ deposition is used to grow the doping layer. Before the in-situ deposition of the doping layer, the cooling time of the embodiment is shorter. The specific reason is that in the embodiment, the volume of the oxygen and nitrogen gas introduced is less than or equal to 90% of the volume of the vapor deposition furnace tube, the oxygen and nitrogen introduced do not fill the vapor deposition furnace tube, and the nitrogen can also serve as part of the gas atmosphere, which further reduces the amount of oxygen introduced. The oxygen introduced can meet the amount of oxygen required for the deposition of the tunneling oxide layer. Before the growth of the tunneling oxide layer is completed, the oxygen and nitrogen introduced will basically not be discharged from the vapor deposition furnace tube, and the oxygen and nitrogen gases introduced are basically not wasted. Therefore, there is basically no waste of oxygen, which can reduce costs. In the embodiment, at the lower second temperature, the growth rate of the tunnel oxide layer is slow, which can improve the compactness and uniformity of the tunnel oxide layer, thereby reducing the intra-sheet non-uniformity and inter-sheet non-uniformity, and improving the intra-sheet uniformity and inter-sheet uniformity. In the embodiment, during the process of growing the tunnel oxide layer, the temperature in the vapor deposition furnace tube is reduced from the first temperature to the second temperature, reducing the time required for cooling before the subsequent in-situ doping to prepare the doping layer.

[0083] It should be noted that, for the method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0084] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0085] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A vapor deposition method for a passivation contact structure, characterized in that: The passivation contact structure comprises: a tunneling oxide layer and a doping layer; the method comprises: After exhausting the air in the vapor deposition furnace tube, maintaining the first temperature, introducing a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stopping introducing the gas including oxygen into the vapor deposition furnace tube; maintaining the first temperature for a time period greater than or equal to the time period for introducing the gas including oxygen; The temperature is lowered to a second temperature to obtain the tunnel oxide layer; the growth rate of the tunnel oxide layer during the time period of maintaining the first temperature is greater than the growth rate during the time period of lowering the temperature to the second temperature.

2. The vapor deposition method of the passivation contact structure according to claim 1, after exhausting the air in the vapor deposition furnace tube, maintaining the first temperature, introducing a gas including oxygen into the vapor deposition furnace tube, so that the volume of the gas including oxygen is less than or equal to 90% of the volume of the vapor deposition furnace tube, and stopping introducing the gas including oxygen into the vapor deposition furnace tube, comprising: After the air in the vapor deposition furnace tube is discharged, the first temperature is maintained, and gas including oxygen is introduced into the vapor deposition furnace tube so that the volume of the gas including oxygen occupies 80%-90% of the volume of the vapor deposition furnace tube. Then, the introduction of the gas including oxygen into the vapor deposition furnace tube is stopped, and the first temperature is maintained, and the temperature is kept constant for a preset period of time.

3. The vapor deposition method of the passivation contact structure according to claim 1, characterized in that: The gas including oxygen is: oxygen, or a mixed gas of oxygen and filling gas.

4. The vapor deposition method of the passivation contact structure according to claim 3, characterized in that: The filling gas is at least one of nitrogen and an inert gas.

5. The vapor deposition method of the passivation contact structure according to claim 3 or 4, characterized in that: The gas including oxygen is a mixed gas of oxygen and filling gas; the flow rate ratio of the oxygen and the filling gas is: (1:2)-(2:1).

6. The vapor deposition method of a passivation contact structure according to claim 2, characterized in that: The duration of the introduction of gas including oxygen is: 4 to 10 minutes; The preset time duration is less than or equal to the time duration for lowering the temperature to the second temperature.

7. The vapor deposition method of a passivation contact structure according to claim 6, characterized in that: The preset duration is: 2 to 8 minutes; The time for reducing the temperature to the second temperature is: 2 to 8 minutes.

8. The vapor deposition method of the passivation contact structure according to any one of claims 1 to 4, 6 and 7, characterized in that: The difference of the first temperature minus the second temperature is 10 to 40°C.

9. The vapor deposition method of a passivation contact structure according to claim 8, characterized in that: The first temperature is 580 to 600°C; the second temperature is 560 to 570°C.

10. The vapor deposition method of a passivation contact structure according to any one of claims 1 to 4, 6 and 7, characterized in that: The vapor deposition is chemical vapor deposition.

11. The vapor deposition method of a passivation contact structure according to any one of claims 1 to 4, 6 and 7, characterized in that: After lowering the temperature to the second temperature to obtain the tunnel oxide layer, the method further comprises: In the vapor deposition furnace tube, based on the second temperature, the doping layer is prepared by in-situ doping on the tunneling oxide layer; the first temperature is greater than the in-situ doping temperature, and the second temperature is greater than or equal to the in-situ doping temperature.

12. The vapor deposition method of a passivation contact structure according to any one of claims 1 to 4, 6 and 7, characterized in that: After lowering the temperature to the second temperature to obtain the tunnel oxide layer, the method further comprises: In the vapor deposition furnace tube, on the basis of the second temperature, an intrinsic amorphous silicon layer corresponding to the doping layer is prepared on the tunneling oxide layer; the second temperature is lower than the growth temperature of the intrinsic amorphous silicon layer.

13. A solar cell, characterized in that: The solar cell comprises a passivation contact structure prepared by a vapor deposition method of the passivation contact structure according to any one of claims 1 to 12.

14. A solar panel, characterized in that: The invention comprises a battery string formed by connecting several solar cells according to claim 13 in series.

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