P-poly silicon, PECVD deposition method, silicon wafer and application

Abstract

The invention relates to the technical field of solar cells, and particularly provides p-poly silicon, a PECVD (Plasma Enhanced Chemical Vapor Deposition) deposition method, a silicon wafer and application. The method aims at solving the problems that in the prior art, a method for depositing P-poly silicon through PECVD can reduce the film forming rate, the adjustability of a film layer is limited, and film explosion is likely to happen. The p-poly silicon sequentially comprises a silicon wafer substrate, a SiOx film layer, an a-Si film layer, at least one p-a-Si film layer structure and at least one p +-a-Si film layer structure from bottom to top, wherein the at least one p-a-Si film layer structure and the at least one p +-a-Si film layer structure are arranged on the side, away from the SiOx film layer, of the a-Si film layer, and one p-a-Si film layer structure is arranged on the surface of the a-Si film layer; the p-a-Si film layer structure and / or the p < + >-a-Si film layer structure are / is a laminated structure. According to the method, the p-poly film layer can be rapidly deposited, the adjustability of the film layer is improved, film explosion can be avoided, and the contact resistance of a silicon wafer is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and specifically provides a p-poly silicon and a PECVD deposition method, a silicon wafer and applications. Background Art

[0002] With the development of the photovoltaic industry, TOPCON, HJT, and BC technologies have advanced in parallel. However, TOPCON and TBC, due to their long high-temperature coating times and poor diffusion uniformity, no longer meet the needs of major companies seeking to reduce costs and increase efficiency. While tubular PECVD deposition of n-poly has yielded extensive research, relatively little research has been conducted on tubular PECVD deposition of p-poly.

[0003] In addition, the industry usually adopts a combination of one or more process parameters including high temperature, high pressure, high power and low pulse switching ratio, and uses a mixed gas of SiH4, B2H6 and H2 (Ar) to prepare P-poly silicon. During the preparation process, a series of problems are very likely to occur, such as film explosion, dust, graphite boat furnace mouth burning and poor film color uniformity.

[0004] On the one hand, during the PECVD process for preparing P-poly silicon, SiH4 has ample time to react with B2H6 under high pressure and plasma electric field bombardment, making it very easy for SiH4 to agglomerate on the silicon wafer surface, ultimately leading to problems such as film explosion and dust. On the other hand, during the PECVD process for preparing P-poly silicon, the B2H6 gas decomposes and deposits too quickly at the furnace mouth under the conditions of high temperature, high power, and low pulse on-off ratio, preventing it from covering the furnace tail of the graphite boat. As a result, the B atoms in the ionized B2H6 agglomerate on the silicon wafer surface at the furnace mouth, leading to problems such as burning of the graphite boat furnace mouth and poor film color uniformity.

[0005] CN117721438A discloses a method for depositing P-poly silicon by PECVD. This method limits the deposition pressure to below a specific value, effectively eliminating problems such as film explosion and dust generation through low-pressure process conditions. Furthermore, the deposition temperature and power are limited to below specific values, while the deposition pulse on / off ratio is limited to above a specific value. This low temperature, low power, and high pulse on / off ratio process conditions prevent graphite boat furnace mouth burning, improve film color uniformity, and ultimately grow high-quality P-poly silicon on the surface of a silicon wafer. However, this method's low pressure, power, and temperature restrictions inevitably reduce the film formation rate and limit the film's adjustability.

[0006] Accordingly, this field requires a new technical solution to solve the above technical problems. Summary of the Invention

[0007] The present invention aims to solve the above technical problems, namely, to solve the problems in the prior art that the PECVD method for depositing P-poly silicon reduces the film forming rate, limits the adjustability of the film layer, and is prone to film explosion.

[0008] In a first aspect, the present invention provides a p-poly silicon, wherein:

[0009] From bottom to top, it includes a silicon wafer substrate 1, a SiOx film layer 2, and an a-Si film layer 3, as well as at least one pa-Si film layer structure 4 and at least one p+-a-Si film layer structure 5 provided on a side of the a-Si film layer 3 away from the SiOx film layer 2, and one of the pa-Si film layer structures 4 is provided on the surface of the a-Si film layer 3;

[0010] The pa-Si film layer structure 4 and / or the p+-a-Si film layer structure 5 is a stacked structure.

[0011] In the preferred technical solution of the above-mentioned p-poly silicon, the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are both stacked structures.

[0012] In the preferred technical solution of the above-mentioned p-poly silicon, the stacked pa-Si film structure 4 includes at least one hydrogen-doped pa-Si film layer 41 and at least one lightly boron-doped pa-Si film layer 42, and the at least one hydrogen-doped pa-Si film layer 41 and the at least one lightly boron-doped pa-Si film layer 42 are alternately stacked;

[0013] And / or, the p+-a-Si film layer structure 5 of the stacked structure includes at least one layer of hydrogen-doped p+-a-Si film layer 51 and at least one layer of heavily boron-doped p+-a-Si film layer 52, and the at least one layer of hydrogen-doped p+-a-Si film layer 51 and the at least one layer of heavily boron-doped p+-a-Si film layer 52 are alternately stacked.

[0014] In the preferred technical solution of the above-mentioned p-poly silicon, the at least one pa-Si film layer structure 4 is continuously arranged, and the at least one p+-a-Si film layer structure 5 is continuously arranged; or, the at least one pa-Si film layer structure 4 and the at least one p+-a-Si film layer structure 5 are alternately stacked.

[0015] In the preferred technical solution of the above-mentioned p-poly silicon, the at least one pa-Si film layer structure 4 is continuously arranged, and the at least one p+-a-Si film layer structure 5 is continuously arranged.

[0016] In a second aspect, the present invention provides a PECVD deposition method for p-poly silicon, comprising PECVD deposition, wherein the PECVD deposition comprises:

[0017] First, a SiOx film layer 2 and an a-Si film layer 3 are sequentially deposited on a silicon wafer substrate 1;

[0018] Then, at least one pa-Si film layer structure 4 and at least one p+-a-Si film layer structure 5 are deposited on the side of the a-Si film layer 3 away from the SiOx film layer 2, wherein one of the pa-Si film layer structures 4 is deposited on the surface of the a-Si film layer 3; the pa-Si film layer structure 4 and / or the p+-a-Si film layer structure 5 are prepared by layered deposition.

[0019] In the preferred technical solution of the above-mentioned PECVD deposition method, preparing the pa-Si film structure 4 by layered deposition includes performing the following step A1 at least once and the following step A2 at least once, and step A1 and step A2 are performed alternately:

[0020] Step A1: SiH4 is used as the process gas and H2 is used as the diluent gas. The diluent gas / process gas flow ratio is set to (1-10): 1. The pressure is 1500-3000 mTorr and the deposition time is 10-100 seconds to form a hydrogen-doped pa-Si film layer 41;

[0021] Step A2: SiH4 is used as the process gas, H2 is used as the dilution gas, and a mixture of TMB and H2 is used as the doping gas. The flow ratio of the dilution gas / process gas is set to (1-10):1, the flow ratio of the dilution gas / doping gas is set to (70-90):1, the pressure is 1500-3000 mTorr, and the deposition time is 10-100 s to form a lightly boron-doped pa-Si film layer 42.

[0022] In the preferred technical solution of the above-mentioned PECVD deposition method, preparing the p+-a-Si film structure 5 by layered deposition includes performing at least one of the following steps B1 and at least one of the following steps B2, with steps B1 and B2 being performed alternately:

[0023] Step B1: SiH4 is used as the process gas and H2 is used as the diluent gas. The diluent gas / process gas flow ratio is set to (1-10): 1. The pressure is 1500-3500 mTorr and the deposition time is 10-100 seconds to form a hydrogen-doped p+-a-Si film layer 51;

[0024] Step B2: SiH4 is used as the process gas, H2 is used as the dilution gas, and the mixed gas of TMB and H2 is used as the doping gas. The flow ratio of the dilution gas / process gas is set to (1-10):1, the flow ratio of the dilution gas / doping gas is set to (5-15):1, the pressure is 1500-3500 mTorr, and the deposition time is 10-100 s to form a heavily boron-doped p+-a-Si film layer 52.

[0025] In the preferred technical solution of the above PECVD deposition method, in the mixed gas of TMB and H2, the volume percentage of TMB in the mixed gas is 2-10%, preferably 9%.

[0026] In the preferred technical solution of the above-mentioned PECVD deposition method, the conditions for depositing the SiOx film 2 are: N2O flow rate of 7000-12000 sccm, deposition time of 50-150 s, and pressure of 1000-2000 mTorr.

[0027] In the preferred technical solution of the above-mentioned PECVD deposition method, the conditions for depositing the a-Si film layer 3 are: SiH4 flow rate is 1000-3000 sccm, H2 flow rate is 6000-13000 sccm, deposition time is 50-200 s, and pressure is 1000-3000 mTorr.

[0028] In the preferred technical solution of the above-mentioned PECVD deposition method, when performing the PECVD deposition, the gas is first evacuated after depositing the previous film layer and before depositing the next film layer.

[0029] In the preferred technical solution of the above-mentioned PECVD deposition method, the PECVD deposition method further includes pretreatment, sample delivery, temperature increase, vacuuming and high-temperature annealing.

[0030] In the preferred technical solution of the above PECVD deposition method, the target temperature of the heating is 380° C.; and / or the absolute pressure of the vacuum pumping is 0 mTorr.

[0031] In the preferred technical solution of the above-mentioned PECVD deposition method, the temperature of the high-temperature annealing treatment is 900-1000° C., and the time is 20-60 minutes.

[0032] In a third aspect, the present invention provides a silicon wafer, wherein the surface of the silicon wafer is covered with the above-mentioned p-poly silicon or the p-poly silicon obtained by the above-mentioned PECVD deposition method.

[0033] In a fourth aspect, the present invention provides an application of the above-mentioned silicon wafer, specifically, the silicon wafer is used to prepare solar cells.

[0034] The technical solution of the present invention has at least one or more of the following technical effects:

[0035] (1) The p-poly silicon of the present invention has a laminated film structure, is non-explosive, has adjustable properties between film layers, and reduces the contact resistance of the silicon wafer;

[0036] (2) The method of the present invention can not only quickly deposit the p-poly film layer without film explosion, but also increase the adjustability of the film layer and prevent B diffusion from damaging the tunneling oxide layer (SiOx film layer), thus acting as a barrier layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0038] Figure 1 is a process flow chart of PECVD deposition in the method for PECVD deposition of p-poly silicon of the present invention;

[0039] Figure 2 is a process flow chart of the method for depositing p-poly silicon by PECVD of the present invention;

[0040] Figure 3 is a schematic structural diagram of p-poly silicon according to Example 1 of the present invention;

[0041] Figure 4 is a schematic structural diagram of p-poly silicon according to Example 2 of the present invention;

[0042] Figure 5 is a schematic structural diagram of p-poly silicon according to Example 3 of the present invention;

[0043] Figure 6 is a schematic structural diagram of p-poly silicon according to Example 4 of the present invention;

[0044] Figure 7 is a schematic structural diagram of p-poly silicon according to Example 5 of the present invention;

[0045] Figure 8 is a schematic structural diagram of p-poly silicon according to Example 6 of the present invention;

[0046] Figure 9 is a schematic structural diagram of p-poly silicon according to Example 7 of the present invention;

[0047] Figure 10 This is a schematic structural diagram of p-poly silicon in Comparative Example 1;

[0048] Figure 11 is a 3D microscope image of p-poly silicon obtained in Example 1;

[0049] Figure 12 is a 3D microscope image of p-poly silicon obtained in Comparative Example 1;

[0050] In the figures, the reference numerals are as follows:

[0051] 1——Silicon wafer substrate, 2——SiOx film layer, 3——a-Si film layer, 4——pa-Si film layer structure, 41——hydrogen-doped pa-Si film layer, 42——lightly boron-doped pa-Si film layer, 5——p+-a-Si film layer structure, 51——hydrogen-doped p+-a-Si film layer, 52——heavily boron-doped p+-a-Si film layer. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0053] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0054] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0055] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0056] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0057] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0058] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0059] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0060] Based on the problems noted in the background art, the prior art PECVD deposition method for P-poly silicon reduces film formation rate, limits film adjustability, and is prone to film explosion. The present invention first provides P-poly silicon and a PECVD deposition method for P-poly silicon. This method utilizes a layered deposition approach that not only rapidly deposits P-poly films without causing film explosion, but also increases film adjustability, reduces silicon wafer contact resistance, and prevents B diffusion from damaging the tunneling oxide layer (SiOx film), thereby acting as a barrier layer.

[0061] Specifically, in a first aspect, the present invention provides a p-poly silicon, which includes, from bottom to top, a silicon wafer substrate 1, a SiOx film layer 2 and an a-Si film layer 3, as well as at least one pa-Si film layer structure 4 and at least one p+-a-Si film layer structure 5 arranged on the side of the a-Si film layer 3 away from the SiOx film layer 2, and one of the pa-Si film layer structures 4 is arranged on the surface of the a-Si film layer 3; the pa-Si film layer structure 4 and / or the p+-a-Si film layer structure 5 are a stacked structure.

[0062] In the p-poly silicon provided by the present invention, the pa-Si film layer structure 4 and / or the p+-a-Si film layer structure 5 are configured as a stacked structure, which not only reduces the possibility of film explosion but also provides adjustability between film layers.

[0063] In some preferred embodiments, the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are both stacked structures.

[0064] In some specific embodiments, the stacked pa-Si film structure 4 includes at least one hydrogen-doped pa-Si film layer 41 and at least one lightly boron-doped pa-Si film layer 42, wherein the at least one hydrogen-doped pa-Si film layer 41 and the at least one lightly boron-doped pa-Si film layer 42 are alternately stacked.

[0065] And / or, the p+-a-Si film layer structure 5 of the stacked structure includes at least one layer of hydrogen-doped p+-a-Si film layer 51 and at least one layer of heavily boron-doped p+-a-Si film layer 52, and the at least one layer of hydrogen-doped p+-a-Si film layer 51 and the at least one layer of heavily boron-doped p+-a-Si film layer 52 are alternately stacked.

[0066] It is a preferred embodiment of the present invention that the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are both stacked structures.

[0067] When the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are both stacked structures, the stacked structure can reduce the thickness of each hydrogen-doped pa-Si film layer 41 and hydrogen-doped p+-a-Si film layer 51 while maintaining the total thickness of the hydrogen-doped film layer, thereby reducing the hydrogen content in the single film layer and effectively suppressing film explosion; under this structure, the lightly boron-doped pa-Si film layer 42 and the heavily boron-doped p+-a-Si film layer 52 can more effectively increase the doping amount and reduce the contact resistance, thereby making it possible to make battery cells with a larger doping amount and reduce the contact resistance while effectively preventing film explosion.

[0068] In some specific embodiments, the at least one pa-Si film layer structure 4 is continuously arranged, and the at least one p+-a-Si film layer structure 5 is continuously arranged; or, the at least one pa-Si film layer structure 4 and the at least one p+-a-Si film layer structure 5 are alternately stacked.

[0069] In some specific embodiments, n+1 pa-Si film layer structures 4 and n p+-a-Si film layer structures 5 are included, where n is an integer greater than or equal to 1; the n+1 pa-Si film layer structures 4 and the n p+-a-Si film layer structures 5 are alternately stacked.

[0070] In some specific embodiments, n pa-Si film layer structures 4 and n p+-a-Si film layer structures 5 are included, where n is an integer greater than or equal to 1; the n pa-Si film layer structures 4 and the n p+-a-Si film layer structures 5 are alternately stacked.

[0071] In some preferred embodiments, the at least one pa-Si film layer structure 4 is continuously disposed, and the at least one p+-a-Si film layer structure 5 is continuously disposed.

[0072] When the at least one pa-Si film layer structure 4 and the at least one p+-a-Si film layer structure 5 are arranged continuously, it is more conducive to reducing the contact resistance. The surface doping concentration is higher, and the area in contact with the metal has lower contact resistance.

[0073] In a second aspect, the present invention provides a PECVD deposition method for p-poly silicon, comprising PECVD deposition, wherein the PECVD deposition comprises:

[0074] First, a SiOx film layer 2 and an a-Si film layer 3 are sequentially deposited on a silicon wafer substrate 1;

[0075] Then, at least one pa-Si film layer structure 4 and at least one p+-a-Si film layer structure 5 are deposited on the side of the a-Si film layer 3 away from the SiOx film layer 2, wherein one of the pa-Si film layer structures 4 is deposited on the surface of the a-Si film layer 3, and the pa-Si film layer structure 4 and / or the p+-a-Si film layer structure 5 are prepared by layered deposition.

[0076] Currently, p-poly silicon typically has a non-laminated film structure. Depositing a thick layer of p-poly silicon all at once causes significant stress, which can lead to film bursting. In the present invention, the pa-Si film structure 4 and / or the p+-a-Si film structure 5 are broken down into multiple layers and deposited in layers, reducing stress and thus minimizing film bursting. This also prevents B diffusion from damaging the tunneling oxide layer (SiOx film), acting as a barrier.

[0077] Specifically, if Figure 1 As shown, the PECVD deposition includes the following steps:

[0078] S1, depositing a SiOx film layer 2 on a silicon wafer substrate 1;

[0079] S2, depositing an a-Si film layer 3 on the SiOx film layer 2;

[0080] S3, depositing a pa-Si film layer structure 4 on the a-Si film layer 3;

[0081] S4. Depositing a p+-a-Si film layer structure 5 on the pa-Si film layer structure 4.

[0082] The pa-Si film layer structure 4 is deposited in layers, and / or the p+-a-Si film layer structure 5 is deposited in layers.

[0083] In some specific embodiments, preparing the pa-Si film structure 4 by layered deposition includes performing the following step A1 at least once and the following step A2 at least once, with step A1 and step A2 being performed alternately:

[0084] Step A1: SiH4 is used as the process gas and H2 is used as the diluent gas. The diluent gas / process gas flow ratio is set to (1-10): 1. The pressure is 1500-3000 mTorr and the deposition time is 10-100 seconds to form a hydrogen-doped pa-Si film layer 41;

[0085] Step A2: SiH4 is used as the process gas, H2 is used as the dilution gas, and a mixture of TMB and H2 is used as the doping gas. The flow ratio of the dilution gas / process gas is set to (1-10):1, the flow ratio of the dilution gas / doping gas is set to (70-90):1, the pressure is 1500-3000 mTorr, and the deposition time is 10-100 s to form a lightly boron-doped pa-Si film layer 42.

[0086] In the present invention, executing step A1 plays a buffering role, which can reduce the corrosion of boron on the SiOx film layer and improve the passivation of the silicon wafer surface; and executing step A2 can achieve a high boron doping concentration, reduce contact resistance, and improve conductivity.

[0087] It should be noted that there is no restriction on the order of execution of step A1 and step A2. Step A1 can be executed first, or step A2 can be executed first.

[0088] In some specific embodiments, preparing the p+-a-Si film structure 5 by layered deposition includes performing at least one of the following steps B1 and B2, wherein steps B1 and B2 are performed alternately:

[0089] Step B1: SiH4 is used as the process gas and H2 is used as the diluent gas. The diluent gas / process gas flow ratio is set to (1-10): 1. The pressure is 1500-3500 mTorr and the deposition time is 10-100 seconds to form a hydrogen-doped p+-a-Si film layer 51;

[0090] Step B2: SiH4 is used as the process gas, H2 is used as the dilution gas, and the mixed gas of TMB and H2 is used as the doping gas. The flow ratio of the dilution gas / process gas is set to (1-10):1, the flow ratio of the dilution gas / doping gas is set to (5-15):1, the pressure is 1500-3500 mTorr, and the deposition time is 10-100 s to form a heavily boron-doped p+-a-Si film layer 52.

[0091] In steps B1 and B2 of the present invention, by means of different gases and flow ratios, the destructiveness to the SiOx film layer is reduced, the contact resistance is reduced, and the conductivity is increased.

[0092] It should be noted that there is no restriction on the order of execution of step B1 and step B2. Step B1 can be executed first, or step B2 can be executed first.

[0093] In some embodiments, the volume percentage of TMB in the TMB and H2 gas mixture is 2-10%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range.

[0094] In some preferred embodiments, in the mixed gas of TMB and H2, the volume percentage of TMB in the mixed gas is 9%.

[0095] In some specific embodiments, the conditions for depositing the SiOx film 2 are: N2O flow rate of 7000-12000 sccm, deposition time of 50-150 s, and pressure of 1000-2000 mTorr.

[0096] In some specific embodiments, the conditions for depositing the a-Si film layer 3 are: SiH4 flow rate is 1000-3000 sccm, H2 flow rate is 6000-13000 sccm, deposition time is 50-200 s, and pressure is 1000-3000 mTorr.

[0097] In some specific embodiments, when performing the PECVD deposition, the gas is evacuated after depositing the previous film layer and before depositing the next film layer.

[0098] Because excess gas is introduced during the deposition of each film layer, if the gas is not evacuated after the previous film layer is deposited and before the next film layer is deposited, the unused gas will continue to accumulate, increasing the probability of film explosion. In the present invention, during the PECVD deposition, the gas is evacuated after the previous film layer is deposited and before the next film layer is deposited, which can significantly reduce the probability of film explosion.

[0099] In some specific embodiments, the PECVD deposition method further includes pretreatment, sample feeding, temperature increase, vacuuming and high-temperature annealing.

[0100] Specifically, if Figure 2 The PECVD deposition method of p-poly silicon provided by the present invention comprises the following steps:

[0101] Step 1: Pretreatment: Pretreatment of the silicon wafer to form a velvet surface or a polished surface on the surface of the silicon wafer;

[0102] Step 2: Sample delivery: Place the pre-treated silicon wafer into a graphite boat, and deliver the graphite boat into the furnace tube;

[0103] Step 3: Heating and vacuuming: heating the furnace tube to the target temperature and vacuuming it to provide a deposition environment;

[0104] Step 4: PECVD deposition;

[0105] Step 5: High-temperature annealing: After deposition is completed, the silicon wafer is sent to an annealing furnace for annealing at high temperature to obtain p-poly silicon.

[0106] In the present invention, the pretreatment includes: cleaning and texturing the silicon wafer to form a texturing surface on the surface of the silicon wafer; or cleaning and polishing the silicon wafer to form a polishing surface on the surface of the silicon wafer.

[0107] In some preferred embodiments, the pretreatment is performed using an alkali solution, and the alkali solution includes a KOH solution and / or a NaOH solution.

[0108] In some specific embodiments, the target temperature of the heating is 380° C.; and / or the absolute pressure of the vacuuming is 0 mTorr.

[0109] In some specific embodiments, the high temperature annealing treatment is performed at a temperature of 900-1000°C, for example, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, or 1000°C; and for a time of 20-60 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min. However, the temperature and time are not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable.

[0110] In some specific embodiments, the thickness of the pa-Si film layer structure 4 is 30 to 150 nm; and / or the thickness of the p+-a-Si film layer structure 5 is 10 to 120 nm.

[0111] In a third aspect, the present invention provides a silicon wafer, wherein the surface of the silicon wafer is covered with the above-mentioned p-poly silicon or the p-poly silicon prepared by the above-mentioned method.

[0112] In a fourth aspect, the present invention provides an application of the above-mentioned silicon wafer, specifically, the silicon wafer is used to prepare TOPCon cells, IBC cells or TBC cells.

[0113] The p-poly silicon and the p-poly silicon PECVD deposition method of the present invention are described in detail below through several specific embodiments.

[0114] Example 1

[0115] This embodiment provides a p-poly silicon, such as Figure 3 As shown, the p-poly silicon includes, from bottom to top, a silicon wafer substrate 1, a SiOx film layer 2, and an a-Si film layer 3, as well as a pa-Si film layer structure 4 and a p+-a-Si film layer structure 5 arranged on the side of the a-Si film layer 3 away from the SiOx film layer 2, wherein the pa-Si film layer structure 4 is arranged on the surface of the a-Si film layer 3.

[0116] Furthermore, if Figure 3 As shown, the pa-Si film layer structure 4 is a stacked structure, including two hydrogen-doped pa-Si film layers 41 and two lightly boron-doped pa-Si film layers 42. From bottom to top, the two hydrogen-doped pa-Si film layers 41 and the two lightly boron-doped pa-Si film layers 42 are alternately stacked.

[0117] The PECVD deposition method of p-poly silicon provided in this embodiment includes the following steps:

[0118] Step 1: Pretreatment: Clean and polish the n-type silicon wafer with a KOH solution to form a polished surface on the surface of the silicon wafer;

[0119] Step 2: Sample delivery: Place the pre-treated silicon wafer into the graphite boat, and then place the graphite boat into the furnace tube;

[0120] Step 3: Heating and vacuuming: The furnace tube is heated to 380°C, and N2 is passed to remove the air in the tube. The tube is then vacuumed to an absolute pressure of 0 mTorr to provide a deposition environment.

[0121] Step 4: PECVD deposition:

[0122] S1. Depositing a SiOx film layer 2 on a silicon wafer substrate 1: introducing 10,000 sccm of N2O into a furnace tube, maintaining the pressure inside the tube at 1800 mTorr, and depositing for 130 s to grow a SiOx film layer 2;

[0123] S2. Depositing an a-Si film layer 3 on the SiOx film layer 2: After evacuating the gases in the above steps, introduce 3000 sccm of SiH4 and 8000 sccm of H2, maintain the pressure in the tube at 3300 mTorr, and deposit for 50 seconds to grow an a-Si film layer 3;

[0124] S3, preparing a pa-Si film structure 4 by depositing four layers on the a-Si film layer 3:

[0125] A1. After evacuating the gases in the above steps, introduce 3000 sccm of SiH4 and 8000 sccm of H2, using SiH4 as the process gas and H2 as the dilution gas, maintaining the pressure in the tube at 3000 mTorr, and depositing for 50 seconds to grow a hydrogen-doped pa-Si film 41.

[0126] A2. After evacuating the gases in the above step, 3000 sccm of SiH4, 8000 sccm of H2, and 100 sccm of a mixture of TMB and H2 (TMB accounts for 9% by volume of the mixture) are introduced. SiH4 is used as the process gas, H2 is used as the dilution gas, and the mixture of TMB and H2 is used as the doping gas. The pressure in the tube is maintained at 3000 mTorr, and the deposition time is 50 seconds to grow a lightly boron-doped pa-Si film 42.

[0127] Step A1 and step A2 are repeated in sequence to grow another hydrogen-doped pa-Si film layer 41 and a lightly boron-doped pa-Si film layer 42 .

[0128] S4, preparing a p+-a-Si film layer structure 5 by non-layered deposition on the pa-Si film layer structure 4:

[0129] After the gases in the above steps are evacuated, 3000 sccm of SiH4, 8000 sccm of H2, and 800 scm of a mixed gas of TMB and H2 (TMB accounts for 9% by volume of the mixed gas) are introduced. SiH4 is used as the process gas, H2 is used as the dilution gas, and the mixed gas of TMB and H2 is used as the doping gas. The pressure in the tube is maintained at 3100 mTorr, and the deposition time is 200 s to grow a layer of p+-a-Si film structure 5.

[0130] Step 5: High-temperature annealing: After deposition is completed, the silicon wafer is sent to an annealing furnace and annealed at 950°C for 40 minutes to obtain p-poly silicon.

[0131] Example 2

[0132] This embodiment provides a p-poly silicon, which is different from the embodiment 1 in that Figure 4 As shown, the p+-a-Si film layer structure 5 is a stacked structure, including two layers of hydrogen-doped p+-a-Si film layers 51 and two layers of heavily boron-doped p+-a-Si film layers 52. From bottom to top, the two layers of hydrogen-doped p+-a-Si film layers 51 and the two layers of heavily boron-doped p+-a-Si film layers 52 are alternately stacked.

[0133] The PECVD deposition method for p-poly silicon provided in this embodiment is the same as that in Example 1. The difference from Example 1 is that the pa-Si film structure 4 in step S3 is deposited in a single layer; and the p+-a-Si film structure 5 in step S4 is deposited in four layers. The details are as follows:

[0134] S3, depositing a pa-Si film layer structure 4 on the a-Si film layer 3 without delamination:

[0135] After the gases in the above steps were evacuated, 3000 sccm of SiH4, 8000 sccm of H2, and 100 sccm of a mixed gas of TMB and H2 (the volume percentage of TMB in the mixed gas is 2%) were introduced. SiH4 was used as the process gas, H2 was used as the dilution gas, and the mixed gas of TMB and H2 was used as the doping gas. The pressure in the tube was maintained at 3000 mTorr, and the deposition time was 200 s to grow a pa-Si film structure 4.

[0136] S4, preparing a p+-a-Si film structure 5 by depositing four layers on the pa-Si film layer 4:

[0137] B1. After evacuating the gases in the above steps, 3000 sccm of SiH4 and 8000 sccm of H2 are introduced, with SiH4 as the process gas and H2 as the dilution gas. The pressure in the tube is maintained at 3100 mTorr, and the deposition time is 50 s to grow a hydrogen-doped p+-a-Si film 51.

[0138] B2. After evacuating the gases in the above step, 3000 sccm of SiH4, 8000 sccm of H2, and 800 scm of a mixture of TMB and H2 (TMB accounts for 2% by volume of the mixture) are introduced, with SiH4 as the process gas, H2 as the dilution gas, and the mixture of TMB and H2 as the doping gas. The pressure in the tube is maintained at 3100 mTorr, and the deposition time is 50 s to grow a heavily boron-doped p+-a-Si film 52.

[0139] Repeat step B1 and step B2 in sequence to grow another hydrogen-doped p + -a-Si film layer 51 and a heavily boron-doped p + -a-Si film layer 52 .

[0140] Example 3

[0141] This embodiment provides a p-poly silicon, which is different from the embodiment 1 in that Figure 5As shown, the pa-Si film layer structure 4 is a stacked structure, including a hydrogen-doped pa-Si film layer 41 and a lightly boron-doped pa-Si film layer 42; the p+-a-Si film layer structure 5 is a stacked structure, including a hydrogen-doped p+-a-Si film layer 51 and a heavily boron-doped p+-a-Si film layer 52.

[0142] The PECVD deposition method of p-poly silicon provided in this embodiment is the same as that in embodiment 1. The difference from embodiment 1 is that the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 in steps S3 and S4 are prepared by deposition in two layers, as follows:

[0143] S3, preparing a pa-Si film structure 4 by depositing two layers on the a-Si film layer 3:

[0144] A1. After evacuating the gases in the above steps, introduce 3000 sccm of SiH4 and 8000 sccm of H2, using SiH4 as the process gas and H2 as the dilution gas, maintaining the pressure in the tube at 3000 mTorr, and depositing for 50 seconds to grow a hydrogen-doped pa-Si film 41.

[0145] A2. After evacuating the gases in the above steps, 3000 sccm of SiH4, 8000 sccm of H2, and 100 sccm of a mixed gas of TMB and H2 (TMB accounts for 10% by volume of the mixed gas) are introduced. SiH4 is used as the process gas, H2 is used as the dilution gas, and the mixed gas of TMB and H2 is used as the doping gas. The pressure in the tube is maintained at 3000 mTorr, and the deposition time is 50 seconds to grow a lightly boron-doped pa-Si film layer 42.

[0146] S4. Prepare a p+-a-Si film structure 5 by depositing two layers on the pa-Si film structure 4:

[0147] B1. After evacuating the gases in the above steps, 3000 sccm of SiH4 and 8000 sccm of H2 are introduced, with SiH4 as the process gas and H2 as the dilution gas. The pressure in the tube is maintained at 3100 mTorr, and the deposition time is 50 s to grow a hydrogen-doped p+-a-Si film 51.

[0148] B2. After the gases in the above steps are evacuated, 3000 sccm of SiH4, 8000 sccm of H2, and 800 scm of a mixed gas of TMB and H2 (TMB accounts for 10% by volume of the mixed gas) are introduced, with SiH4 as the process gas, H2 as the dilution gas, and the mixed gas of TMB and H2 as the doping gas. The pressure in the tube is maintained at 3100 mTorr, and the deposition time is 50 s to grow a layer of heavily boron-doped p+-a-Si film 52.

[0149] Example 4

[0150] This embodiment provides a p-poly silicon, which is different from the embodiment 3 in that Figure 6 As shown, the pa-Si film layer structure 4 is a stacked structure, including two hydrogen-doped pa-Si film layers 41 and a lightly boron-doped pa-Si film layer 42. Along the bottom-up direction, the two hydrogen-doped pa-Si film layers 41 and the lightly boron-doped pa-Si film layer 42 are alternately stacked; the p+-a-Si film layer structure 5 is a stacked structure, including two hydrogen-doped p+-a-Si film layers 51 and a heavily boron-doped p+-a-Si film layer 52. Along the bottom-up direction, the two hydrogen-doped p+-a-Si film layers 51 and the heavily boron-doped p+-a-Si film layer 52 are alternately stacked.

[0151] The PECVD deposition method of p-poly silicon provided in this embodiment is the same as that in embodiment 3. The difference from embodiment 3 is that the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 in steps S3 and S4 are both prepared by three-layer deposition, as follows:

[0152] S3, preparing a pa-Si film structure 4 by three-layer deposition on the a-Si film layer 3:

[0153] On the basis of Example 3, after executing step A1 and step A2, step A1 is repeated to grow another hydrogen-doped pa-Si film layer 41.

[0154] S4, preparing a p+-a-Si film structure 5 by three-layer deposition on the pa-Si film layer 4:

[0155] On the basis of Example 3, after executing step B1 and step B2, step B1 is repeated to grow another hydrogen-doped p + -a-Si film layer 51 .

[0156] Example 5

[0157] This embodiment provides a p-poly silicon, which is different from the embodiment 3 in that Figure 7 As shown, the pa-Si film layer structure 4 is a stacked structure, including two hydrogen-doped pa-Si film layers 41 and a lightly boron-doped pa-Si film layer 42. From bottom to top, the two hydrogen-doped pa-Si film layers 41 and the lightly boron-doped pa-Si film layer 42 are alternately stacked; the p+-a-Si film layer structure 5 is a stacked structure, including a hydrogen-doped p+-a-Si film layer 51 and a heavily boron-doped p+-a-Si film layer 52.

[0158] The PECVD deposition method of p-poly silicon provided in this embodiment is the same as that in embodiment 3. The difference from embodiment 3 is that in step S3, after executing step A1 and step A2 on the basis of embodiment 3, step A1 is repeated to grow another hydrogen-doped pa-Si film layer 41.

[0159] Example 6

[0160] This embodiment provides a p-poly silicon, which is different from the embodiment 3 in that Figure 8 As shown, there are two pa-Si film layer structures 4, each of which is a stacked structure, including a hydrogen-doped pa-Si film layer 41 and a lightly boron-doped pa-Si film layer 42; there are two p+-a-Si film layer structures 5, each of which is a stacked structure, including a hydrogen-doped p+-a-Si film layer 51 and a heavily boron-doped p+-a-Si film layer 52; the pa-Si film layer structures 4 and the p+-a-Si film layer structures 5 are alternately stacked.

[0161] The PECVD deposition method for p-poly silicon provided in this embodiment is the same as that in Example 3. The difference from Example 3 is that the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are alternately stacked. The details are as follows:

[0162] On the basis of Example 3, after executing step A1, step A2, step B1 and step B2, step A1, step A2, step B1 and step B2 are executed in sequence.

[0163] Example 7

[0164] This embodiment provides a p-poly silicon, which is different from the embodiment 3 in that Figure 9 As shown, there are two pa-Si film layer structures 4, each of which is a stacked structure, including a hydrogen-doped pa-Si film layer 41 and a lightly boron-doped pa-Si film layer 42; there are two p+-a-Si film layer structures 5, each of which is a stacked structure, including a hydrogen-doped p+-a-Si film layer 51 and a heavily boron-doped p+-a-Si film layer 52; the pa-Si film layer structures 4 are continuously arranged, and the p+-a-Si film layer structures 5 are continuously arranged.

[0165] The PECVD deposition method of p-poly silicon provided in this embodiment is the same as that in embodiment 3. The difference from embodiment 3 is that the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are continuously arranged. The details are as follows:

[0166] On the basis of Example 3, after executing step A1, step A2, step A1 and step A2, step B1, step B2, step B1 and step B2 are executed in sequence.

[0167] Example 8

[0168] This embodiment is the same as embodiment 1, but different from embodiment 1 in that the high temperature annealing is performed at 900° C. for 20 minutes.

[0169] Example 9

[0170] This embodiment is the same as embodiment 1, but different from embodiment 1 in that the high temperature annealing is performed at 1000° C. for 60 minutes.

[0171] Comparative Example 1

[0172] This comparative example provides a p-poly silicon, which is different from Example 1 in that Figure 10 As shown, the pa-Si film layer structure 4 is not a stacked structure.

[0173] The PECVD deposition method of p-poly silicon provided in this comparative example is the same as that in Example 1. The difference from Example 1 is that the pa-Si film structure 4 in step S3 is not deposited in layers, as follows:

[0174] S3, depositing a pa-Si film layer structure 4 on the a-Si film layer 3 without delamination:

[0175] After the gases in the above steps were evacuated, 3000 sccm of SiH4, 8000 sccm of H2, and 100 sccm of a mixture of TMB and H2 (TMB accounts for 9% by volume of the mixture) were introduced. SiH4 was used as the process gas, H2 was used as the dilution gas, and the mixture of TMB and H2 was used as the doping gas. The pressure in the tube was maintained at 3000 mTorr, and the deposition time was 100 s to grow a pa-Si film structure 4.

[0176] Test Example 1

[0177] This test example tests the appearance and performance of the p-poly silicon obtained in Example 1 of the present invention and Comparative Example 1.

[0178] Detection method: The p-poly silicon obtained in Example 1 and Comparative Example 1 was observed using a 3D microscope. The detection results are shown in Figure 11 and Figure 12 .

[0179] from Figure 11 and Figure 12It can be seen that the 3D microscope image of p-poly silicon obtained in Example 1 ( Figure 11 ) No obvious film bursting phenomenon; 3D microscope image of p-poly silicon obtained in Comparative Example 1 ( Figure 12 ) There is a pink bulge, which means the film has burst.

[0180] Test Example 2

[0181] This test example tests the contact resistance of the p-poly silicon obtained in Examples 1-7 of the present invention and Comparative Example 1.

[0182] Testing method: The p-poly silicon obtained in the examples and comparative examples was screen-printed with silver-aluminum paste, and electrodes were formed by sintering. The contact resistance of the cell was tested using the TLM (transmission line model) method.

[0183] The test results are shown in Table 1 below:

[0184] Table 1. Resistance test results

[0185] It can be seen from the above results that, compared with Comparative Example 1, the contact resistance of the p-poly silicon provided in the embodiment of the present invention is lower.

[0186] Compared to Examples 1 and 2, the contact resistance of the p-poly silicon provided in the other embodiments of the present invention is relatively low. It can be seen that when both the pa-Si film layer structure 4 and the p+-a-Si film layer structure 5 are configured as a stacked structure, the resulting p-poly silicon contact resistance is lower than when only one of them is configured as a stacked structure.

[0187] Comparing Example 6 and Example 7, it can be seen that compared with the alternating arrangement of the pa-Si film layer structure 4 of the stacked structure and the p+-a-Si film layer structure 5 of the stacked structure, when the pa-Si film layer structure 4 of the stacked structure and the p+-a-Si film layer structure 5 of the stacked structure are arranged continuously, the contact resistance of the obtained p-poly silicon is lower.

[0188] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A p-poly silicon, characterized in that The present invention comprises, from bottom to top, a silicon wafer substrate (1), a SiOx film layer (2), and an a-Si film layer (3), as well as at least one pa-Si film layer structure (4) and at least one p+-a-Si film layer structure (5) arranged on a side of the a-Si film layer (3) away from the SiOx film layer (2), and one of the pa-Si film layer structures (4) is arranged on the surface of the a-Si film layer (3); The pa-Si film layer structure (4) and / or the p+-a-Si film layer structure (5) are a stacked structure; Preferably, the pa-Si film layer structure (4) and the p+-a-Si film layer structure (5) are both stacked structures.

2. The p-poly silicon according to claim 1, characterized in that The pa-Si film layer structure (4) of the stacked structure comprises at least one hydrogen-doped pa-Si film layer (41) and at least one lightly boron-doped pa-Si film layer (42), wherein the at least one hydrogen-doped pa-Si film layer (41) and the at least one lightly boron-doped pa-Si film layer (42) are alternately stacked. And / or, the p+-a-Si film layer structure (5) of the stacked structure includes at least one hydrogen-doped p+-a-Si film layer (51) and at least one heavily boron-doped p+-a-Si film layer (52), and the at least one hydrogen-doped p+-a-Si film layer (51) and the at least one heavily boron-doped p+-a-Si film layer (52) are alternately stacked.

3. The p-poly silicon according to claim 1 or 2, characterized in that The at least one pa-Si film layer structure (4) is continuously arranged, and the at least one p+-a-Si film layer structure (5) is continuously arranged; or, the at least one pa-Si film layer structure (4) and the at least one p+-a-Si film layer structure (5) are alternately stacked. Preferably, the at least one pa-Si film layer structure (4) is continuously arranged, and the at least one p+-a-Si film layer structure (5) is continuously arranged.

4. A PECVD deposition method for p-poly silicon according to any one of claims 1 to 3, comprising PECVD deposition, characterized in that: The PECVD deposition includes: First, a SiOx film layer (2) and an a-Si film layer (3) are sequentially deposited on a silicon wafer substrate (1); Then, at least one pa-Si film layer structure (4) and at least one p+-a-Si film layer structure (5) are deposited on the side of the a-Si film layer (3) away from the SiOx film layer (2), wherein one of the pa-Si film layer structures (4) is deposited on the surface of the a-Si film layer (3); the pa-Si film layer structure (4) and / or the p+-a-Si film layer structure (5) are prepared by layered deposition.

5. The PECVD deposition method according to claim 4, wherein: The layered deposition method for preparing the pa-Si film structure (4) includes performing at least one of the following steps A1 and A2, wherein the steps A1 and A2 are performed alternately: Step A1, using SiH4 as process gas and H2 as dilution gas, setting the dilution gas / process gas flow ratio to (1-10): 1, the pressure is 1500-3000 mTorr, the deposition time is 10-100 s, and a hydrogen-doped pa-Si film layer (41) is formed; Step A2, using SiH4 as process gas, H2 as dilution gas, and a mixture of TMB and H2 as doping gas, setting the dilution gas / process gas flow ratio to (1-10):1, the dilution gas / doping gas flow ratio to (70-90):1, the pressure to 1500-3000 mTorr, and the deposition time to 10-100 s to form a lightly boron-doped pa-Si film layer (42).

6. The PECVD deposition method according to claim 4, wherein: The layered deposition method for preparing a p+-a-Si film structure (5) includes performing at least one of the following steps B1 and B2, wherein the steps B1 and B2 are performed alternately: Step B1, using SiH4 as process gas and H2 as dilution gas, setting the dilution gas / process gas flow ratio to (1-10): 1, the pressure is 1500-3500 mTorr, the deposition time is 10-100 s, and a hydrogen-doped p+-a-Si film layer (51) is formed; Step B2, using SiH4 as process gas, H2 as dilution gas, and a mixture of TMB and H2 as doping gas, setting the dilution gas / process gas flow ratio to (1-10):1, the dilution gas / doping gas flow ratio to (5-15):1, the pressure to 1500-3500 mTorr, and the deposition time to 10-100 s to form a heavily boron-doped p+-a-Si film layer (52).

7. The PECVD deposition method according to claim 5 or 6, characterized in that: In the mixed gas of TMB and H2, the volume percentage of TMB in the mixed gas is 2-10%, preferably 9%.

8. The PECVD deposition method according to claim 7, wherein: The conditions for depositing the SiOx film (2) are: N2O flow rate of 7000-12000 sccm, deposition time of 50-150 s, and pressure of 1000-2000 mTorr; And / or, the conditions for depositing the a-Si film layer (3) are: SiH4 flow rate is 1000-3000sccm, H2 flow rate is 6000-13000sccm, deposition time is 50-200s, and pressure is 1000-3000mTorr.

9. The PECVD deposition method according to claim 8, characterized in that: When performing the PECVD deposition, the gas is evacuated after depositing a previous film layer and before depositing the next film layer.

10. The PECVD deposition method according to claim 9, wherein: The PECVD deposition method also includes pretreatment, sample feeding, temperature increase, vacuuming and high-temperature annealing; Preferably, the target temperature of the heating is 380°C; And / or, the absolute pressure of the vacuum pumping is 0 mTorr; And / or, the high temperature annealing treatment is performed at a temperature of 900-1000° C. and for a time of 20-60 minutes.

11. A silicon wafer, characterized in that: The surface of the silicon wafer is covered with the p-poly silicon according to any one of claims 1 to 3 or the p-poly silicon obtained by the PECVD deposition method according to any one of claims 4 to 10.

12. Use of the silicon wafer according to claim 11, characterized in that: The silicon wafer is used for preparing solar cells.

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