A method for improving plasma processing uniformity and its application

Abstract

The present application provides a method for improving plasma processing uniformity, a solar cell manufacturing process, and a solar cell. In the method for improving plasma processing uniformity, a hydrogen-containing gas is used as an auxiliary gas in the plasma processing process. The method for improving plasma processing uniformity provided by the present invention can improve the uniformity of plasma processing. Incorporating a hydrogen-containing gas in the alumina coating process can significantly improve the coating thickness uniformity of alumina, expand the process parameter window, and maintain a high-level passivation characteristic of alumina to be applicable to device applications. Applying it in the battery manufacturing process can effectively ensure the battery conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a method for improving plasma treatment uniformity, a solar cell preparation process, and a solar cell. Background Art

[0002] With the development of requirements for product performance and refined processes, higher requirements are put forward for the uniformity of the vacuum plasma treatment system during the plasma treatment of products.

[0003] In the solar cell coating process, improving the coating uniformity can, to a certain extent, improve the conversion efficiency of solar cells. Alumina films for solar cells are often prepared by methods such as plasma-enhanced chemical vapor deposition (PECVD) and plasma-enhanced atomic layer deposition (PEALD). Plasma-enhanced chemical vapor deposition (PECVD) is a new preparation technology that generates plasma by means of glow discharge and other methods, causing chemical reactions in gas substances containing thin film components, thereby realizing the growth of thin film materials. Plasma-enhanced atomic layer deposition (PEALD) introduces plasma to generate a large number of active radicals. In a heated reactor, gas-phase precursors are alternately introduced above the substrate, and self-limiting growth of ultra-thin films is carried out through alternating surface saturation reactions, enhancing the active reaction of precursor substances, and enabling deposition at low temperature or even room temperature.

[0004] During the preparation of alumina films by plasma-enhanced chemical vapor deposition (PECVD) method and plasma-enhanced atomic layer deposition (PEALD) method, when using low-frequency batch-type equipment, it is found that on n-type silicon wafer substrates and p-type silicon wafer substrates with relatively high resistivity, the in-plane uniformity of the alumina film thickness is very poor, about 10 - 30%, and cannot meet the quality requirements of device products such as solar cells. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for improving plasma treatment uniformity, a solar cell preparation process, and a solar cell, which is beneficial to improving the in-plane uniformity of plasma treatment.

[0006] To achieve the above purpose, the technical solution of the present invention is a method for improving plasma treatment uniformity, which uses a hydrogen-containing gas as an auxiliary gas in the plasma treatment process.

[0007] The plasma treatment process described in the present invention is specifically as follows: One or more gases participating in the treatment are excited into a plasma state; during the process of exciting the gases participating in the treatment into a plasma state, a hydrogen-containing gas is added as an auxiliary gas. The auxiliary gas does not serve as a reaction gas. The content of the hydrogen-containing gas in the gases participating in the treatment is 5% to 60%, and the plasma treatment process is carried out on a semiconductor substrate, and the semiconductor substrate is selected from Si substrates.

[0008] In one embodiment, to excite the gases participating in the treatment into a plasma state, a plasma is used to perform an alumina coating process on the surface of a semiconductor substrate, and the semiconductor substrate is selected from Si substrates. The gases participating in the alumina coating process include a reaction gas, a carrier gas, and an auxiliary gas. Trimethylaluminum and an oxygen source gas are used as the reaction gas, H 2 is used as the auxiliary gas, and Ar or N 2 is used as the carrier gas. The content of H 2 in the gases participating in the treatment is 5% to 60%. In the present invention, H 2 is incorporated during the alumina coating process, and H 2 is not added as a reaction gas. After incorporating H 2 , the internal electric field strength in the plasma is redistributed, and the generation rate distribution of reactive group oxygen atoms becomes more uniform, which can microscopically improve the surface of the alumina film. H 2 and the oxygen source gas react and combine on the surface of the alumina to form H-O bonds, which can perform surface modification to improve the bonding strength between the film layer and the Si substrate and improve the thickness uniformity of the alumina film.

[0009] In one embodiment, the hydrogen element in the hydrogen-containing gas is in an excited state.

[0010] In one embodiment, the excited state is excited to an active state by microwave or radio frequency means.

[0011] In one embodiment, an excited state of hydrogen is provided by a remote plasma generator.

[0012] In one embodiment, in a vacuum reaction chamber, using plasma-enhanced chemical vapor deposition, an alumina coating process is carried out on the surface of a semiconductor substrate. The temperature of the semiconductor substrate is 100 to 350 °C, the semiconductor substrate is selected from Si substrates, and the Si substrate can be an n-type silicon wafer substrate or a high-resistance p-type silicon wafer substrate. The gas pressure for the alumina coating process is 50 to 250 Pa, and a plasma power supply is used. The plasma power supply can be a low-frequency bipolar input power supply. The gases participating in the reaction are simultaneously introduced into the reaction chamber and excited into a plasma state. The gases participating in the reaction include a reaction gas, a carrier gas, and an auxiliary gas. The auxiliary gas uses H 2 , and the content of H 2The content of is 5% - 60%, H 2 The flow rate of is 500 - 4000 SCCM. The carrier gas is selected from Ar or N 2 , the Ar or N 2 The flow rate of is 1000 - 3000 SCCM. The reaction gas includes trimethylaluminum and an oxygen source gas, and the oxygen source gas is selected from O 2 , N 2 O, NO 2 , O 3 , CO or CO 2 One or more of, and the flow rate of the oxygen source gas is 500 - 5000 SCCM. The trimethylaluminum is carried into the reaction chamber by the carrier gas. Set the power and pulse duty cycle of the plasma power supply. The plasma power supply frequency is 40 kHz, the power is 3000 - 18000 W, the pulse is set with an on-pulse of 1 - 100 ms and an off-pulse of 10 - 500 ms, and an alumina film layer is deposited on the semiconductor surface.

[0013] In one embodiment, in a vacuum reaction chamber, an alumina coating process is carried out on the surface of a semiconductor substrate by plasma-enhanced atomic layer deposition. The temperature of the semiconductor substrate is 100 - 350 °C, and the semiconductor substrate is selected from Si substrates. The Si substrate can be an n-type silicon wafer substrate or a high-resistance p-type silicon wafer substrate. The gas pressure of the alumina coating process is 50 - 250 Pa. In the reaction chamber, the gases participating in the reaction are excited into a plasma state. The gases participating in the reaction include a reaction gas, a carrier gas, and an auxiliary gas. The reaction gas includes trimethylaluminum and an oxygen source gas. The trimethylaluminum and the oxygen source gas are alternately introduced into the reaction chamber. The trimethylaluminum is carried into the reaction chamber by the carrier gas. The oxygen source gas is selected from O 2 , N 2 O, NO 2 , O 3 , CO or CO 2 One or more of, and the flow rate of the oxygen source gas is 500 - 5000 SCCM. The carrier gas includes Ar or N 2 , Ar or N 2 The flow rate of is 1000 - 3000 SCCM. The auxiliary gas uses H 2 , and the content of H 2 in the gases participating in the reaction is 5% - 60%, and the flow rate of H 2 is 500 - 4000 SCCM. The oxygen source gas and the incorporated H 2It can be continuously introduced or introduced in a pulsed manner, and no limitation is made here. When the oxygen source gas is introduced into the reaction chamber, the plasma power supply is turned on. The plasma power supply can be a low-frequency bipolar input power supply, the plasma power supply frequency is 40 kHz, the power is 3000 - 30000 W, the pulse setting is on-pulse 1 - 100 ms, off-pulse 10 - 500 ms; the pulse time of trimethylaluminum is 0.5 - 5 s, the purge time is 1 - 10 s; the pulse time of plasma treatment is 0.5 - 5 s, the purge time is 1 - 10 s, and an alumina film layer is deposited on the semiconductor surface.

[0014] In other embodiments, the auxiliary gas can also be other hydrogen-containing gases, such as NH 3 , N 2 H 2 , one or more of gaseous alkanes, gaseous alkenes or gaseous alkynes. Among them, the gaseous alkanes can be methane, ethane, propane, propane; the gaseous alkenes can be ethylene, propylene, butene, etc.; the gaseous alkynes can be propyne, butyne, etc. The hydrogen-containing gas can release hydrogen under plasma conditions, thus achieving a similar effect to using hydrogen as the auxiliary gas, that is, redistributing the internal electric field strength of the plasma and making the reaction group oxygen atom generation rate distribution more uniform, and can microscopically improve the surface of the alumina thin film; H 2 and the oxygen source gas react and combine on the alumina surface to form H - O bonds, which can perform surface modification to improve the bonding strength between the film layer and the Si substrate and improve the thickness uniformity of the alumina thin film.

[0015] The method for improving the plasma treatment uniformity provided by the present invention can improve the plasma treatment uniformity. In the alumina coating process, it can also maintain a high level of passivation characteristics of alumina, and can ensure the battery conversion efficiency when applied in the battery preparation process.

[0016] The present invention also provides a solar cell preparation process, which uses plasma-enhanced chemical vapor deposition or plasma-enhanced atomic layer deposition to treat the surface of a semiconductor substrate; during the process of exciting the gas participating in the treatment into a plasma state, H 2 is added as an auxiliary gas.

[0017] The process of the present invention for treating the surface of a semiconductor substrate by using plasma-enhanced chemical vapor deposition or plasma-enhanced atomic layer deposition is carried out in a reaction chamber. The reaction chamber can be a batch-type low-frequency reaction chamber. The equipment of the batch-type low-frequency reaction chamber has the following characteristics: (1) It can be used for silicon wafers of various sizes with side lengths of 156 mm - 230 mm; (2) It can adopt a single-boat or multiple-boat form in one chamber; (3) The loading capacity of each chamber is 500 - 600 pieces.

[0018] The process of the plasma enhanced chemical vapor deposition method described in the present invention is specifically as follows: The semiconductor substrate is loaded into a carrier and sent into a vacuum reaction chamber for preheating treatment. The carrier can be a graphite boat. The temperature of the semiconductor substrate is 100 - 350 °C. The semiconductor substrate is selected from Si substrates, and the Si substrate can be an n-type silicon wafer substrate or a high-resistance p-type silicon wafer substrate.

[0019] After the temperature of the semiconductor substrate reaches the required value, the pressure in the reaction chamber is 50 - 250 Pa. A plasma power supply is used. The plasma power supply can be a low-frequency bipolar input power supply. The gases participating in the reaction are simultaneously introduced into the reaction chamber and excited into a plasma state. The gases participating in the reaction include reaction gases, carrier gases, and auxiliary gases. The auxiliary gas is H 2 , and the content of H 2 in the gases participating in the reaction is 5% - 60%, and the flow rate of H 2 is 500 - 4000 SCCM. The carrier gas is selected from Ar or N 2 , and the flow rate of Ar or N 2 is 1000 - 3000 SCCM. The reaction gases include trimethylaluminum and an oxygen source gas. The oxygen source gas is selected from one or more of O 2 , N 2 O, NO 2 , O 3 , CO or CO 2 . The flow rate of the oxygen source gas is 500 - 5000 SCCM, and the trimethylaluminum is carried into the reaction chamber by the carrier gas. The power and pulse duty ratio of the plasma power supply are set. The plasma power supply frequency is 40 kHz, the power is 3000 - 18000 W, the pulse is set with an on-pulse of 1 - 100 ms and an off-pulse of 10 - 500 ms. An alumina film layer is deposited on the semiconductor surface. After the coating is completed, the chamber is vented and the boat is removed to unload the wafer. Controlling the working time of the plasma power supply, i.e., the power generator, can control the thickness of the alumina thin film.

[0020] The process of the plasma enhanced atomic layer deposition method described in the present invention is specifically as follows: The semiconductor substrate is loaded into a carrier and sent into a vacuum reaction chamber for preheating treatment. The carrier can be a graphite boat. The temperature of the semiconductor substrate is 100 - 350 °C. The semiconductor substrate is selected from Si substrates, and the Si substrate can be an n-type silicon wafer substrate or a high-resistance p-type silicon wafer substrate.

[0021] After the temperature of the semiconductor substrate reaches a certain level, the gas pressure in the reaction chamber is 50 - 250 Pa. A plasma power supply is used, and the plasma power supply can be a low-frequency bipolar input power supply. When the plasma power supply is turned on, the plasma power supply can be a low-frequency bipolar input power supply. The frequency of the plasma power supply is 40 kHz, and the power is 3000 - 30000 W. The pulse settings are an on-pulse of 1 - 100 ms and an off-pulse of 10 - 500 ms, which excites the gases participating in the reaction into a plasma state. The gases participating in the reaction include reaction gases, carrier gases, and auxiliary gases. The reaction gases include trimethylaluminum and oxygen source gases. The trimethylaluminum and oxygen source gases are alternately introduced into the reaction chamber. The trimethylaluminum is carried into the reaction chamber by the carrier gas. The oxygen source gas is selected from O 2 、N 2 O、NO 2 、O 3 、CO or CO 2 and one or more of them. The flow rate of the oxygen source gas is 500 - 5000 SCCM. The auxiliary gas is H 2 . The content of H 2 in the gases participating in the reaction is 5% - 60%, and the flow rate of H 2 is 500 - 4000 SCCM. The carrier gas includes Ar or N 2 , and the flow rate of the Ar or N 2 is 1000 - 3000 SCCM. The oxygen source gas and the incorporated H 2 can be continuously introduced or pulsed, and this is not limited here. The pulse time of trimethylaluminum is 0.5 - 5 s, and the purge time is 1 - 10 s; the pulse time of plasma treatment is 0.5 - 5 s, and the purge time is 1 - 10 s. An alumina film layer is deposited on the semiconductor surface. After the film coating is completed, the chamber is evacuated and the boat is removed to unload the wafer. The thickness of the film is controlled by the number of cycles of depositing the alumina film layer. Experimental results show that the growth per cycle (GPC) of the plasma-enhanced atomic layer deposition process is 0.12 ± 0.01 nm, and the film coating rate is 2 - 3.5 nm / min, which is mainly proportional to the power. In the present invention, H 2 is incorporated during the alumina film coating process by plasma-enhanced chemical vapor deposition or plasma-enhanced atomic layer deposition. H 2 is not added as a reaction gas. After incorporating H 2 , the internal electric field intensity in the plasma is redistributed, and the generation rate distribution of the reactive group oxygen atoms becomes more uniform, which can microscopically improve the surface of the alumina film. H 2 and the oxygen source gas react and combine on the alumina surface to form H - O bonds, forming water molecules, which can perform surface modification, improve the bonding strength between the alumina film and the Si substrate, and improve the thickness uniformity of the alumina film.

[0022] In other embodiments, the auxiliary gas may also be other hydrogen-containing gases, such as NH 3 , N 2 H 2 , one or more of gaseous alkanes, gaseous alkenes or gaseous alkynes, wherein the gaseous alkanes may be methane, ethane, propane, etc.; the gaseous alkenes may be ethylene, propylene, butene, etc.; the gaseous alkynes may be propyne, butyne, etc. The hydrogen-containing gas can release hydrogen under plasma conditions, thus achieving a similar effect to using hydrogen as the auxiliary gas, that is, redistributing the internal electric field strength of the plasma and making the reaction group oxygen atom production rate distribution more uniform, and can microscopically improve the surface of the alumina film; H 2 and the oxygen source gas react and combine on the alumina surface to form H-O bonds, which can perform surface modification to improve the bonding strength between the film layer and the Si substrate and improve the thickness uniformity of the alumina film.

[0023] The hydrogen-containing gas can also be provided in the form of a mixed gas, selected from a mixed gas including H 2 , NH 3 , N 2 H 2 , one or more of gaseous alkanes, gaseous alkenes or gaseous alkynes and another inert gas, and the inert gas is, for example, N 2 , Ar.

[0024] In some possible implementation manners, during the preparation of the solar cell, it further includes: adding H 2 O during the process of exciting the gas participating in the treatment into a plasma state. Among them, H 2 O can be introduced into the reaction chamber simultaneously with the oxygen source gas and the auxiliary gas, and H 2 O can be used as the oxygen source gas or can be mixed with other oxygen source gases.

[0025] The solar cell treatment process provided by the present invention prepares an alumina film layer in a batch-type plasma-enhanced chemical vapor deposition and plasma-enhanced atomic layer deposition equipment. During the plasma treatment step, H 2 is incorporated, and the coating thickness uniformity of the alumina is significantly improved, the process parameter window is expanded, and at the same time, a high level of passivation characteristics of the alumina is maintained to be suitable for device applications.

[0026] The present invention also provides a solar cell, which is prepared by the method for improving plasma treatment uniformity described in the above technical solution, or is prepared by the solar cell preparation process described in the above technical solution, and will not be elaborated here.

[0027] The solar cell provided by the present invention has better in-chip uniformity, and at the same time maintains a high level of passivation characteristics to ensure the conversion efficiency of the battery.

[0028] The present invention provides a method for improving the uniformity of plasma treatment, and H is used as an auxiliary gas in the plasma treatment process. 2 The method for improving the uniformity of plasma treatment provided by the present invention can improve the uniformity of plasma treatment. Incorporating a hydrogen-containing gas, especially H 2 , into the alumina coating process can significantly improve the coating thickness uniformity of alumina, while maintaining a high level of passivation characteristics of alumina. Applying it in the battery preparation process can effectively ensure the battery conversion efficiency. The present invention prepares an alumina film layer in a batch-type plasma-enhanced chemical vapor deposition and plasma-enhanced atomic layer deposition equipment, and incorporates a hydrogen-containing gas, especially H 2 , into the plasma treatment step. The coating thickness uniformity of alumina is significantly improved, the process parameter window is expanded, and a high level of passivation characteristics of alumina is maintained to be applicable to device applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. However, the present invention is not limited to the following embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Figure 1 It is an in-chip thickness contour map of the sample when hydrogen is doped;

[0031] Figure 2 It is an in-chip thickness contour map of the sample when hydrogen is not doped. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1:

[0034] Aluminum oxide film coating is carried out by plasma-enhanced atomic layer deposition (PEALD) process. The specific process is as follows: The silicon wafer substrate is loaded into a carrier and sent into a batch-type low-frequency vacuum reaction chamber equipment for preheating treatment. The temperature of the semiconductor substrate is 200 °C. After the temperature of the semiconductor substrate reaches, the air pressure in the reaction chamber is 75 Pa. The plasma power supply is turned on, and the plasma power supply power is 15000 W. The pulse is set with an on-pulse of 6 ms and an off-pulse of 60 ms to excite the reaction gas into a plasma state. The reaction gas includes reaction gas, carrier gas and auxiliary gas. The reaction gas includes trimethylaluminum and oxygen source gas. Trimethylaluminum and oxygen source gas are alternately introduced into the reaction chamber. Trimethylaluminum is carried into the reaction chamber by the carrier gas, and the flow rate of the oxygen source gas (O 2 ) is 2600 SCCM; the flow rate of the carrier gas (Ar) is 1500 SCCM; the flow rate of doped H 2 is 0; the pulse time of trimethylaluminum (TMA) is 4 s, and the purge time is 7 s; the pulse time of plasma treatment is 4 s, and the purge time is 7 s. An aluminum oxide film layer is deposited on the semiconductor surface. After the film coating is completed, the chamber is vented and the wafer is unloaded from the boat.

[0035] The in-wafer uniformity of the detected aluminum oxide film layer is calculated by the following formula:

[0036] Take 5 points in the silicon wafer, with the four points on the edge about 2 cm away from the edge, and take one point in the middle.

[0037] U%=(max - min) / (2*AVE);

[0038] The experimental results show that the in-wafer uniformity of the aluminum oxide film layer is 13%.

[0039] Example 2:

[0040] Aluminum oxide film coating is carried out according to the method of Example 1. Among them, the plasma power supply power is adjusted. The plasma power supply power is increased to 20000 w and decreased to 5000 w respectively, and the in-wafer uniformity of the aluminum oxide film layer when the plasma power supply power is increased to 20000 w and decreased to 5000 w is detected.

[0041] The experimental results show that when the plasma power supply power is increased to 20000 w, the in-wafer uniformity of the obtained aluminum oxide film layer increases to 10.10%. When the plasma power supply power is decreased to 5000 w, the in-wafer uniformity of the obtained aluminum oxide film layer decreases to 22.88%. Therefore, the process method of changing the plasma power supply power cannot effectively improve the film uniformity and cannot achieve the effect of significantly improving the in-wafer uniformity.

[0042] Example 3:

[0043] Perform alumina coating according to the method of Example 1. Among them, adjust the deposition pressure in the reaction chamber, reduce the deposition pressure in the reaction chamber to 45 Pa and increase it to 150 Pa respectively, and detect the in-chip uniformity of the alumina film layer when the deposition pressure in the reaction chamber is reduced to 45 Pa and increased to 150 Pa.

[0044] The experimental results show that when the deposition pressure in the reaction chamber is reduced to 45 Pa, the in-chip uniformity of the obtained alumina film layer increases to 12%. When the deposition pressure in the reaction chamber is increased to 150 Pa, the in-chip uniformity of the obtained alumina film layer is reduced to 21%. Therefore, the process method of changing the deposition pressure in the reaction chamber cannot effectively improve the film uniformity and cannot achieve the effect of significantly improving the in-chip uniformity.

[0045] Example 4:

[0046] Perform alumina coating according to the method of Example 1. Among them, adjust the plasma power supply pulse setting, set the plasma power supply pulse to a full-open pulse of 6 ms, and detect the in-chip uniformity of the obtained alumina film layer.

[0047] Perform alumina coating according to the method of Example 1. Among them, set the plasma power supply pulse to an on-pulse of 2 ms and an off-pulse of 120 ms, and detect the in-chip uniformity of the obtained alumina film layer.

[0048] The experimental results show that when the plasma power supply pulse is set to a full-open pulse of 6 ms, the in-chip uniformity of the obtained alumina film layer increases to 11%. When the plasma power supply pulse is set to an on-pulse of 2 ms and an off-pulse of 120 ms, the in-chip uniformity of the obtained alumina film layer is reduced to 17.10%. Therefore, the process method of changing the plasma power supply pulse setting cannot effectively improve the film uniformity and cannot achieve the effect of significantly improving the in-chip uniformity.

[0049] Example 5:

[0050] Perform alumina coating according to the method of Example 1. Among them, adjust the flow rate of H 2 The flow rate of H is increased to 500 SCCM, increased to 2000 SCCM, and increased to 3000 SCCM respectively, and the in-chip uniformity of the alumina film layer obtained by increasing the flow rate of H to 500 SCCM, 2000 SCCM, and 3000 SCCM is detected respectively. 2 The flow rate of H 2 is increased to 500 SCCM, 2000 SCCM, and 3000 SCCM respectively, and the in-chip uniformity of the alumina film layer obtained by increasing the flow rate of H to 500 SCCM, 2000 SCCM, and 3000 SCCM is detected respectively.

[0051] The experimental results show that when the flow rate of H 2 is increased to 500 SCCM, the in-chip uniformity of the obtained alumina film layer increases to 6.70%. When the flow rate of H 2 is increased to 2000 SCCM, the in-chip uniformity of the obtained alumina film layer increases to 4.10%. When the flow rate of H2 The flow rate is increased to 3000 SCCM, and the in - wafer uniformity of the obtained alumina film layer is increased to 2.90%. Therefore, the incorporation of H 2 can significantly improve the in - wafer uniformity of the alumina film layer, and the degree of improvement in thickness uniformity is positively correlated with the amount of H 2 .

[0052] During the debugging of the H 2 flow rate, the change trend of the in - wafer thickness contour map of the sample is as shown in Figure 1 and Figure 2 . Figure 1 Figure Figure 2 is the in - wafer thickness contour map of the sample when doped with hydrogen, and 2 Figure 2 is the in - wafer thickness contour map of the sample without hydrogen doping. The results show that the in - wafer uniformity of the sample without the incorporation of H 2 is 15.87%, while the in - wafer uniformity of the sample with the incorporation of H 2 is 4.4%. The central thickness voids are quickly filled due to the incorporation of H

[0053] During the debugging of the H 2 flow rate, a 30 - nm alumina thin film is deposited on both sides of an n - type silicon wafer (resistivity 1.2 ohm / sqr, thickness 160 μm). After deposition, a conventional annealing treatment method is used. The minority carrier lifetime after alumina coating is shown in Table 1. Table 1 is the minority carrier lifetime after alumina coating, where PEALD - O 2 w / o H 2 is the alumina coating process without hydrogen incorporation, and PEALD - O 2 with H 2 is the alumina coating process with hydrogen incorporation.

[0054] Table 1 Minority carrier lifetime after alumina coating

[0055]

[0056] The experimental results show that whether H 2 is doped has no effect on the minority carrier lifetime. In addition, the experimental results show that the growth per cycle (GPC) of PEALD and the deposition rate of PECVD are not affected by whether H 2 is doped.

[0057] Example 6:

[0058] The alumina coating was carried out according to the method of Example 1, in which NH 3 was added, and the flow rate of NH 3 was increased to 500 SCCM, increased to 2000 SCCM, and increased to 3000 SCCM respectively. The in-chip uniformity of the alumina film layer obtained by increasing the flow rate of NH 3 to 500 SCCM, 2000 SCCM, and 3000 SCCM was detected respectively.

[0059] The experimental results show that when the flow rate of NH 3 is increased to 500 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 7.70%. When the flow rate of NH 3 is increased to 2000 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 5.30%. When the flow rate of NH 3 is increased to 3000 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 3.30%. Therefore, the incorporation of NH 3 can also significantly improve the in-chip uniformity of the alumina film layer, and the improvement degree of the thickness uniformity is positively correlated with the amount of NH 3 .

[0060] Example 7:

[0061] The alumina coating was carried out according to the method of Example 1, in which N 2 H 2 was added, and the flow rate of N 2 H 2 was increased to 500 SCCM, increased to 2000 SCCM, and increased to 3000 SCCM respectively. The in-chip uniformity of the alumina film layer obtained by increasing the flow rate of N 2 H 2 to 500 SCCM, 2000 SCCM, and 3000 SCCM was detected respectively.

[0062] The experimental results show that when the flow rate of N 2 H 2 is increased to 500 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 7.30%. When the flow rate of N 2 H 2 is increased to 2000 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 5.10%. When the flow rate of N 2 H 2 is increased to 3000 SCCM, the in-chip uniformity of the obtained alumina film layer is increased to 2.90%. Therefore, the incorporation of N 2 H 2 can also significantly improve the in-chip uniformity of the alumina film layer, and the improvement degree of the thickness uniformity is positively correlated with N 2H 2 It is positively correlated with the amount.

[0063] Example 8:

[0064] Perform alumina coating according to the method of Example 1, wherein H 2 and NH 3 are added. Respectively increase the total flow rates of H 2 and NH 3 to 500 SCCM, increase to 2000 SCCM, and increase to 3000 SCCM, and respectively detect the in-chip uniformity of the obtained alumina film layer.

[0065] The experimental results show that when the flow rate is increased to 500 SCCM, the in-chip uniformity of the obtained alumina film layer increases to 6.30%. When the flow rate is increased to 2000 SCCM, the in-chip uniformity of the obtained alumina film layer increases to 4.20%. When the flow rate is increased to 3000 SCCM, the in-chip uniformity of the obtained alumina film layer increases to 3.80%. Therefore, doping with the mixed gas can also significantly improve the in-chip uniformity of the alumina film layer, and the degree of improvement in thickness uniformity is positively correlated with the amount.

[0066] Based on this embodiment, the contents of H 2 and NH 3 in the mixed gas gradually change. The initial content of NH 3 is 100%, and the content of NH 3 decreases to less than 20% over time. In this way, under the same total flow rate, the uniformity can be further improved. At a flow rate of 500 SCCM, the in-chip uniformity can reach 5.3%. It is speculated that the possible mechanism is that the reaction conditions on the film surface are different in the initial stage of the reaction, and the large molecule NH 3 can better adapt to the reaction on the initial surface. As the film grows, the small molecule H 2 is more conducive to the uniform distribution of oxygen source molecules during the interfacial interaction.

[0067] Other embodiments:

[0068] Replacing the hydrogen-containing gas with one or more of gas alkane, gas alkene, or gas alkyne can also achieve the effect of improving the in-chip uniformity of the alumina film layer. There are certain differences in the improvement of each gas, but there are obvious changes compared with not adding the hydrogen-containing gas.

[0069] In addition, add H 2 O during the process of exciting the gas involved in the treatment into a plasma state. Among them, H 2 O can be introduced into the reaction chamber simultaneously with the oxygen source gas and the auxiliary gas, where H 2O can be used as the oxygen source gas or can be mixed with other oxygen source gases. In the case of adding other oxygen elements, H 2 O is considered another auxiliary gas, and the purpose of adding it is not to introduce oxygen elements.

[0070] For hydrogen-containing gases, they can also be provided in the form of a mixed gas, selected from a mixture of one or more of H 2 , NH 3 , N 2 H 2 , gaseous alkanes, gaseous alkenes or gaseous alkynes, and another inert gas. The inert gas is, for example, N 2 , Ar. The mixed gas of hydrogen and nitrogen, as a commonly used hydrogen-containing gas, has better safety than pure hydrogen, and it can also be confirmed through experiments that using the mixed gas of hydrogen and nitrogen can play the same role as pure hydrogen in improving uniformity. When using this mixed gas, the amount of nitrogen introduced in the original process can be reduced at the same time.

[0071] The hydrogen element in the hydrogen-containing gas can also be directly introduced in the form of an excited state, and the excited state can be excited to an active state by microwave or radio frequency means.

[0072] For the specific formation method of the excited state, it can be carried out by a remote plasma generator or directly in the reaction chamber.

[0073] In summary, by only adding hydrogen-containing gas on the basis of the conventional process, the uniformity of the coating can be significantly improved. For the improvement of the existing production line, only minor modifications are required, or only the gas source is replaced without changing the equipment structure, and the obvious improvement of the coating uniformity can be achieved.

[0074] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for improving plasma processing uniformity, characterized in that, a hydrogen-containing gas is used as an auxiliary gas in the formation of an alumina coating by a plasma processing process; hydrogen elements are directly excited in the reaction chamber.

2. The method for improving plasma processing uniformity according to claim 1, characterized in that, the plasma processing process is specifically: exciting one or more gases participating in the processing into a plasma state; During the process of exciting the gas participating in the treatment into a plasma state, H is added 2 as an auxiliary gas.

3. The method for improving plasma processing uniformity according to claim 2, characterized in that, the plasma processing process is carried out on a semiconductor substrate, and the semiconductor substrate is selected from Si substrates.

4. The method for improving plasma processing uniformity according to claim 2, characterized in that, the content of the hydrogen-containing gas in the gases participating in the processing is 5% to 60%.

5. The method for improving plasma processing uniformity according to claim 1, characterized in that, the hydrogen elements in the hydrogen-containing gas are in an excited state.

6. The method for improving plasma processing uniformity according to claim 5, characterized in that, the excited state is excited to an active state by microwave or radio frequency means.

7. The method for improving plasma processing uniformity according to any one of claims 1 to 6, characterized in that, The hydrogen-containing gas is selected from one or more of H 2 , NH 3 , N 2 H 2 , gaseous alkanes, gaseous alkenes or gaseous alkynes, or the hydrogen-containing gas is selected from a mixed gas including one or more of H 2 , NH 3 , N 2 H 2 , gaseous alkanes, gaseous alkenes or gaseous alkynes, and another inert gas.

8. The method for improving plasma processing uniformity according to claim 7, characterized in that, The hydrogen-containing gas is selected from H 2 , NH 3 , N 2 H 2 , CH 4 or C 2 H 4 .

9. A solar cell manufacturing process, characterized in that, a plasma enhanced chemical vapor deposition method or a plasma enhanced atomic layer deposition method is used to perform processing on the surface of a semiconductor substrate to form an alumina coating; during the process of exciting the gases participating in the processing into a plasma state, a hydrogen-containing gas is added as an auxiliary gas; hydrogen elements are directly excited in the reaction chamber.

10. The solar cell manufacturing process according to claim 9, characterized in that, the content of the hydrogen-containing gas in the gases participating in the processing is 5% to 60%.

11. The solar cell manufacturing process according to claim 9, characterized in that, the semiconductor substrate is selected from Si substrates.

12. The solar cell manufacturing process according to claim 9, characterized in that, the plasma enhanced chemical vapor deposition method process is specifically: using a plasma power source, simultaneously introducing trimethylaluminum, an oxygen source gas, and an auxiliary gas into the reaction chamber, and depositing an alumina film layer on the semiconductor surface.

13. The solar cell manufacturing process according to claim 9, characterized in that, the plasma enhanced atomic layer deposition method process is specifically: alternately introducing trimethylaluminum and a mixed gas into the reaction chamber, the mixed gas includes an oxygen source gas and an auxiliary gas, and when the oxygen source gas is introduced into the reaction chamber, the plasma power source is turned on, and an alumina film layer is deposited on the semiconductor surface.

14. The solar cell manufacturing process according to claim 12 or 13, characterized in that, The auxiliary gas includes a hydrogen-containing gas; Ar or N 2 , the flow rate of the hydrogen-containing gas is 500 to 4000 SCCM, and the flow rate of the Ar or N 2 is 1000 to 3000 SCCM; The oxygen source gas is selected from one or more of O 2 , N 2 O, NO 2 , O 3 , CO or CO 2 , and the flow rate of the oxygen source gas is 500 to 5000 SCCM.

15. The solar cell manufacturing process according to claim 14, characterized in that, The hydrogen-containing gas is selected from one or more of H 2 , NH 3 , N 2 H 2 , gaseous alkanes, gaseous alkenes or gaseous alkynes, or the hydrogen-containing gas is selected from a mixture of one or more of H 2 , NH 3 , N 2 H 2 , gaseous alkanes, gaseous alkenes or gaseous alkynes, and another inert gas.

16. The solar cell manufacturing process according to claim 15, characterized in that, The hydrogen-containing gas is selected from H 2 , NH 3 , N 2 H 2 , CH 4 or C 2 H 4 .

17. The solar cell manufacturing process according to claim 9, characterized in that, further comprising: Add H 2 O during the process of exciting the gas to be processed into a plasma state. O.

18. A solar cell, characterized in that, Prepared by the method for improving plasma treatment uniformity according to any one of claims 1 to 8, or prepared by the solar cell manufacturing process according to any one of claims 9 to 17.

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