Drying device, alkali polishing process equipment and alkali polishing process optimization method

Abstract

The invention relates to the technical field of semiconductor manufacturing processes, and discloses a drying device, alkali polishing process equipment and an alkali polishing process optimization method.The drying device comprises a bottom plate and a side wall plate surrounding the peripheral side of the bottom plate; the first hot air unit is arranged in the drying groove and located on the bottom plate, and the first hot air unit extends in the second direction and is suitable for blowing air towards the surface of the bottom plate; the second hot air unit is arranged in the drying groove and installed on the flower basket frame, and the second hot air unit extends in the first direction and is suitable for blowing air towards the flower basket end plate of the flower basket; the third hot air unit is arranged in the drying groove and installed on the flower basket frame, and the second hot air unit extends in the second direction and is suitable for blowing air towards the flower basket bottom rod of the flower basket. According to the drying device, blowing in multiple directions is added, the drying effect is improved, and the problem that stubborn parts such as a flower basket bottom end plate, a flower basket bottom rod and the bottom of a groove body cannot be dried can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing process, and in particular to a drying device, alkali polishing process equipment and an alkali polishing process optimization method. Background Art

[0002] At present, the preparation process of TOPCon cells (TOPCon cells are tunnel oxide passivated contact solar cells with N-type silicon as substrate) mainly includes: cleaning and texturing - boron diffusion - oxidation - BSG removal (the process of removing borosilicate glass (BSG) on the edge of the silicon wafer) - alkali polishing - LPCVD (low pressure chemical vapor deposition method, using heating to make gaseous compounds react on the surface of the silicon wafer and deposit into a solid film under low pressure conditions) - phosphorus diffusion - PSG removal (the process of removing phosphorus silicon glass (PSG) on the edge of the silicon wafer) - RCA (wet chemical cleaning method, used to remove the front and edge polysilicon layers and front BSG) - ALD (atomic layer deposition) - front film - back film - screen printing - sorting. Among them, the alkali polishing process is mainly used for silicon wafer processing. The silicon wafer is corroded by high-concentration alkali solution, and the textured corner pyramid is polished flat by relying on the isotropy of the lattice atoms, and the back and surrounding BSG (borosilicate glass) in the boron diffusion are removed at the same time.

[0003] After the alkali polishing process, the silicon wafers need to be dried. In the related art, the commonly used drying method is: place the silicon wafers in a basket, and put the basket into a drying tank, rely on an external drying fan to heat it, and use a blower to pass hot air into the interior of the tank, and dry the silicon wafers through continuous circulation and heating of the hot air. The basket serves as a tool for carrying silicon wafers. The bottom rod of the basket, the bottom end plate of the basket, the bottom of the tank, and other positions are in the dead corners of drying, resulting in water droplets at these positions after drying. Water droplets affect the drying temperature, reduce the drying capacity, and cause the problem of liquid on the silicon wafer, which in turn causes EL failure (EL failure refers to various defects or quality problems found in photovoltaic panels during the EL detection process; EL detection can find many types of defects, mainly including but not limited to oxidation stains, burning, and black edges), such as Figure 4(A) to Figure 4(D) shown.

[0004] The stubborn parts such as the bottom plate of the flower basket, the bottom rod of the flower basket, and the bottom of the tank body cannot be completely dried. On the one hand, the drying capacity is limited due to the unreasonable design of the drying tank; on the other hand, from the analysis of the alkali polishing process, there are several reasons: ① The mismatch of the acid tank concentration and the slightly poor dehydration effect of the cold water slow extraction lead to the alkali polishing flower basket carrying liquid; ② The silicon wafer carries too much water stains before entering the drying tank, resulting in the temperature of the flower basket to be lower when entering the drying tank, which shortens the effective drying time and worsens the drying effect; ③ The bottom rod of the flower basket cannot be effectively dried due to its position in the drying tank. This causes water droplets to be carried in the drying tank and at the bottom of the end plate of the unloading flower basket, affecting the stability of the alkali polishing process and causing some EL yield problems. Summary of the invention

[0005] In view of this, the present invention provides a drying device, an alkali polishing process equipment and an alkali polishing process optimization method to solve the problem that after drying, water droplets are still carried in the drying tank, the bottom of the end plate of the unloading flower basket and other places, affecting the stability of the alkali polishing process and causing partial EL yield.

[0006] In a first aspect, the present invention provides a drying device, comprising:

[0007] A bottom plate, and a side wall plate surrounding the bottom plate; the bottom plate and the side wall plate together enclose a drying tank;

[0008] A flower basket rack is arranged in the drying tank; the flower basket rack is suitable for placing a flower basket, the flower basket contains silicon wafers, the silicon wafers are arranged parallel to the first direction, and multiple silicon wafers are placed in the flower basket and arranged parallel to and at intervals along the second direction;

[0009] A first hot air unit is disposed in the drying tank and located on the bottom plate, the first hot air unit extends along the second direction and is suitable for blowing air toward the surface of the bottom plate;

[0010] A second hot air unit is disposed in the drying tank and mounted on the flower basket frame, the second hot air unit extends along the first direction and is suitable for blowing air toward the flower basket end plate of the flower basket;

[0011] The third hot air unit is arranged in the drying tank and installed on the flower basket frame. The second hot air unit extends along the second direction and is suitable for blowing air toward the flower basket bottom rod of the flower basket.

[0012] In an optional embodiment, the third hot air unit and / or the second hot air unit is arranged at the bottom of the flower basket rack along the height direction.

[0013] In an optional embodiment, the number of the first hot air units is multiple;

[0014] At least one first hot air unit is arranged in the middle of the drying tank and is provided with a first air inlet for blowing air toward both sides along a first direction;

[0015] At least one first hot air unit is arranged at a position of the drying tank close to the side wall plate, and is provided with a first air inlet for blowing air along a first direction toward a side away from the side wall plate.

[0016] In an optional embodiment, the number of the second hot air units is multiple;

[0017] At least one second hot air unit is arranged in the middle of the drying tank and is provided with a second air inlet for blowing air toward both sides along a second direction;

[0018] At least one second hot air unit is arranged at a position of the drying tank close to the side wall plate, and is provided with a second air inlet for blowing air along a second direction toward a side away from the side wall plate.

[0019] In an optional embodiment, the number of the third hot air units is one or more;

[0020] One or more third hot air units are arranged in the middle of the drying tank and are provided with third air inlets for blowing air toward both sides along the first direction.

[0021] In an optional embodiment, the side wall plate is provided with an air outlet, and the air outlet blows air toward one side of the flower basket frame.

[0022] Beneficial effect: The drying device provided by the embodiment of the present invention improves the drying effect by adding air inlet diversion pipes on the sides and bottom of the drying tank and adding air blowing in multiple directions. It can solve the problem that stubborn parts such as the bottom end plate of the flower basket, the bottom rod of the flower basket, and the bottom of the tank body cannot be dried.

[0023] In a second aspect, the present invention further provides an alkali polishing process equipment, comprising: a drying device as described above.

[0024] Because the alkali polishing process equipment includes a drying device, it has the same effect as the drying device and will not be described in detail here.

[0025] In a third aspect, the present invention further provides an alkali polishing process optimization method, which is applied to the alkali polishing process equipment as described above; the alkali polishing process optimization method comprises:

[0026] For pre-cleaning, set the process temperature to 67℃-70℃, the cleaning time to 120S, the initial NaOH concentration to 1.1%, the initial H2O2 concentration to 6%, the self-supplementing NaOH concentration to 0.01%, and the self-supplementing H2O2 concentration to 0.09%; use a continuous circulation and basket bubbling mode;

[0027] Once through the water tank, use deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. Set the time to 120S, and use overflow with basket or overflow all the time;

[0028] For alkali polishing, the process temperature is set at 67℃-69℃, the time is set at 280±20S, the initial NaOH concentration is selected as 3.5%, the initial ADDI concentration is selected as 0.4%, the self-supplementing NaOH concentration is selected as 0.09%, the self-supplementing ADDI concentration is selected as 0.04%, and the continuous circulation and basket-free bubbling mode is adopted;

[0029] In the secondary water tank, deionized water is used to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with basket or overflow all the time.

[0030] For post-cleaning, the process temperature was set at 67°C-70°C, the cleaning time was 120S, the initial NaOH concentration was selected as 0.9%, the initial H2O2 concentration was selected as 5%, the self-supplementing NaOH concentration was selected as 0.01%, the self-supplementing H2O2 concentration was selected as 0.09%, and the continuous circulation and basket bubbling mode was adopted;

[0031] Three times of water trough, using deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer, the setting time is 120S, and the overflow mode uses overflow with basket or overflow all the time;

[0032] Mixed acid washing, set the process temperature to room temperature, the time to 130S, the initial HF concentration to 1.1%, and the self-supplement HF concentration to 0.11%;

[0033] Four times through the water tank, using deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with a basket;

[0034] For pulling, set the process temperature to 48℃-50℃, add pulling additives, select the initial concentration as 2%, the self-replenishing concentration as 0.06%-0.08%, control the pulling speed at 3mm / s-5mm / s, and use overflow with basket or overflow all the way;

[0035] Drying: set the process temperature to 95±3℃ and the time to 600S.

[0036] In an optional embodiment, the component of the pulling additive includes a surfactant; wherein the surfactant includes polyvinyl pyrrolidone;

[0037] The pulling additives also include: sodium polystyrene sulfonate and deionized water.

[0038] In an optional embodiment, the concentration of polyvinyl pyrrolidone is 7%; the concentration of deionized water is 85%; and the concentration of sodium polystyrene sulfonate is 8%.

[0039] Beneficial effect: The present invention reduces the problem of water on silicon wafers before they enter the drying tank by optimizing the alkali polishing process. The present invention solves the problem of liquid on the bottom rod of the flower basket, the bottom end plate of the flower basket, and the bottom of the drying tank by improving the mixed acid tank and the slow pulling process and adding an air intake shunt pipeline for the drying tank. The improvement effect is obvious, and there is no liquid on the alkali polishing material. After the liquid on the alkali polishing drying tank is effectively improved, the proportion of oxidation dirt caused by water on the bottom rod of the flower basket, the bottom end plate of the flower basket, the bottom of the drying tank, etc. is reduced to 0.04%, the proportion of black edges is reduced to 0.06%, and the proportion of burnt is reduced to 0%. After the yield is significantly improved, the difficulty of process control can be reduced, and the yield change points affected by the alkali polishing process can be better reduced to match the subsequent process, further improve the process window of the subsequent process, and reduce yield fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 Schematic diagram of the drying device of the present invention Figure 1 ;

[0042] Figure 2 Schematic diagram of the drying device of the present invention Figure 2 ;

[0043] Figure 3 A schematic diagram of a flower basket of the present invention with silicon wafers placed therein;

[0044] Figure 4 (A) is a schematic diagram of EL failure caused by liquid in the battery cell Figure 1 ;

[0045] Figure 4(B) is a schematic diagram of EL failure caused by liquid in the battery cell Figure 2 ;

[0046] Figure 4(C) is a schematic diagram of EL failure caused by liquid in the battery cell Figure 3 ;

[0047] FIG. 4(D) is a fourth schematic diagram of EL failure caused by liquid in the battery cell.

[0048] Description of reference numerals:

[0049] 11. Side wall panel; 111. Air outlet; 12. Bottom plate; 13. Flower basket stand;

[0050] 2. A first hot air unit; 21. A first air inlet;

[0051] 3. Second hot air unit; 31. Second air inlet;

[0052] 4. The third hot air unit; 41. The third air inlet;

[0053] 5. Flower basket; 51. Flower basket bottom bar; 52. Flower basket end plate; 6. Silicon wafer. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0055] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0056] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] Related Technology In the alkali polishing process, it is easy for stubborn parts such as the bottom end plate of the flower basket, the bottom rod of the flower basket, and the bottom of the trough to fail to be completely dried. On the one hand, this is due to the unreasonable design of the drying trough, which leads to limited drying capacity; on the other hand, the alkali polishing process is unreasonable.

[0059] From the perspective of drying, the commonly used drying method is: place the silicon wafers in a flower basket, and put the flower basket into a drying tank, rely on an external drying fan to heat the air, and use a blower to pass the hot air into the tank body, and dry the silicon wafers through continuous circulation and heating of the hot air. However, the inside of the machine mainly relies on the hole-shaped air outlets on both sides to supply air to the middle position of the tank body to continuously dry the silicon wafers and achieve the purpose of drying the silicon wafers. However, during the drying process, the bottom rod of the flower basket, the bottom end plate of the flower basket, the bottom of the tank body and other positions are in the drying dead corners, resulting in water droplets in these positions after the drying is completed. In addition, the drying tank body is made of PP material, and the drying effect is poor, resulting in the flower basket or the tank body carrying water droplets, which increases the difficulty of process control and front and back matching. In addition, water droplets affect the drying temperature. The temperature of the tank body drops by 20℃-30℃ the moment the flower basket enters the drying tank, reducing the drying capacity and greatly shortening the effective drying time, resulting in the problem of silicon wafer liquid, which in turn causes EL defects, and easily causes silicon wafers to burn, oxidize and stain, and have black edges. Such as Figure 4(A) to Figure 4(D) shown.

[0060] From the analysis of the alkali polishing process, there are several reasons: ① The mismatch of acid tank concentration and the poor dehydration effect of cold water slow extraction lead to liquid in the alkali polishing basket; ② The silicon wafer carries too much water stains before entering the drying tank, which causes the temperature of the basket to change when entering the drying tank, and the drying effect becomes worse; ③ The bottom rod of the basket cannot achieve effective drying due to its position in the drying tank. This causes water droplets to be carried in the drying tank and at the bottom of the end plate of the unloading basket, affecting the stability of the alkali polishing process and causing some EL yield problems.

[0061] This shows that the current conventional alkali polishing process and drying method cannot solve the current problems of alkali polishing unloading and liquid in the drying tank.

[0062] The present invention optimizes and improves the alkali polishing process and increases the air inlet pipeline of the drying tank, thereby improving the silicon wafer drying efficiency, reducing liquid carryover caused by insufficient drying, improving the problem of liquid carryover in the drying tank, and thus solving some EL abnormalities.

[0063] Combine the following Figures 1 to 3 , describing an embodiment of the present invention.

[0064] According to an embodiment of the present invention, on the one hand, a drying device is provided, comprising:

[0065] A bottom plate 12, and a side wall plate 11 surrounding the bottom plate 12; the bottom plate 12 and the side wall plate 11 together enclose a drying tank;

[0066] A flower basket rack 13 is arranged in the drying tank; the flower basket rack 13 is suitable for placing a flower basket 5, the flower basket 5 contains a silicon wafer 6, the silicon wafer 6 is arranged parallel to the first direction, and a plurality of silicon wafers 6 are placed in the flower basket 5 and are arranged parallel to and spaced apart from each other along the second direction;

[0067] A first hot air unit 2 is disposed in the drying tank and located on the bottom plate 12. The first hot air unit 2 extends along the second direction and is suitable for blowing air toward the surface of the bottom plate 12.

[0068] The second hot air unit 3 is disposed in the drying tank and mounted on the flower basket frame 13. The second hot air unit 3 extends along the first direction and is suitable for blowing air toward the flower basket end plate 52 of the flower basket 5.

[0069] The third hot air unit 4 is disposed in the drying tank and installed on the flower basket frame 13 . The second hot air unit 3 extends along the second direction and is suitable for blowing air toward the flower basket bottom rod 51 of the flower basket 5 .

[0070] In some embodiments, the third hot air unit 4 and / or the second hot air unit 3 are arranged at the bottom of the flower basket rack 13 along the height direction.

[0071] The drying device provided in the embodiment of the present invention can improve the drying effect by adding air inlet diversion pipelines on the sides and bottom of the drying tank and adding air blowing in multiple directions, thereby solving the problem that stubborn parts such as the bottom end plate of the flower basket, the bottom rod of the flower basket, and the bottom of the tank body cannot be dried.

[0072] In some embodiments, the number of the first hot air units 2 is multiple;

[0073] At least one first hot air unit 2 is disposed in the middle of the drying tank and is provided with a first air inlet 21 for blowing air in a first direction toward both sides, so as to achieve the purpose of drying the surface of the bottom plate 12 and fully improve the drying efficiency;

[0074] At least one first hot air unit 2 is disposed at a position of the drying tank close to the side wall plate 11 and is provided with a first air inlet 21 for blowing air along a first direction toward a side away from the side wall plate 11 .

[0075] In some embodiments, the number of the second hot air units 3 is multiple;

[0076] At least one second hot air unit 3 is disposed in the middle of the drying tank and is provided with a second air inlet 31 for blowing air toward both sides along a second direction, so as to achieve the purpose of drying the flower basket end plates 52 at both sides and the middle position, thereby fully improving the drying efficiency;

[0077] At least one second hot air unit 3 is disposed at a position of the drying tank close to the side wall plate 11 and is provided with a second air inlet 31 for blowing air along a second direction toward a side away from the side wall plate 11 .

[0078] In some embodiments, the number of the third hot air unit 4 is one or more;

[0079] One or more third hot air units 4 are arranged in the middle of the drying tank and are provided with third air inlets 41 for blowing air toward both sides along the first direction.

[0080] The drying device of the present invention adds a plurality of transverse and longitudinal hot air units at the bottom of the drying tank, wherein the hot air units can specifically be hot air pipes, thereby increasing the air intake diversion pipeline of the drying tank, making the air flow distribution more uniform during drying and improving the drying efficiency.

[0081] In this embodiment, there are three first hot air units 2; one first hot air unit 2 is arranged in the middle of the drying tank and has a first air inlet 21 blowing air in the first direction toward both sides; two first hot air units 2 are respectively arranged at positions of the drying tank close to the side wall plate 11 and have first air inlet 21 blowing air in the first direction toward the side away from the side wall plate 11. The three hot air pipes cooperate to fully cover the surface of the bottom plate 12, thereby achieving the purpose of drying the surface of the bottom plate 12 and fully improving the drying efficiency.

[0082] In this embodiment, there are three second hot air units 3; one second hot air unit 3 is arranged in the middle of the drying tank, and is provided with a second air inlet 31 blowing air along the second direction toward both sides; two second hot air units 3 are arranged in the drying tank near the side wall plate 11, and are provided with a second air inlet 31 blowing air along the second direction toward the side away from the side wall plate 11. The purpose of drying the flower basket end plates 52 at both sides and the middle position is achieved, and the drying efficiency is fully improved.

[0083] In this embodiment, the number of the third hot air unit 4 is one; the third hot air unit 4 is arranged in the middle of the drying tank, and is provided with a third air inlet 41 for blowing air toward both sides along the first direction, so as to achieve the purpose of drying the bottom rod 51 of the flower basket and fully improve the drying efficiency.

[0084] The first hot air unit 2 is mainly used to improve the liquid accumulation at the bottom of the tank body. This is because after the water droplets condense, the drying temperature cannot dry the water droplets. After adding the first hot air unit 2 on both sides and the middle part, when the water droplets drip to the bottom of the tank body, the two-way air intake diversion pipe in the middle part can immediately blow away the water droplets at the bottom of the tank body, and then completely dry the water droplets through the air intake diversion pipes on both sides.

[0085] Secondly, the third hot air unit 4 dries the accumulated liquid on the bottom rod 51 of the flower basket. Because the flower basket is placed in the tank, the conventional drying process of the bottom rod 51 of the flower basket has poor drying effect, and hot air drying cannot solve this problem. The two-way air intake shunt pipeline of the third hot air unit 4 can solve the problem of residual water droplets at this location. Adding this two-way air intake shunt device can effectively blow and dry the water droplets carried by the bottom rods on both sides of the flower basket.

[0086] Again, the second hot air unit 3 mainly performs diversion drying on the flower basket end plate 52. Because the flower basket end plate 52 is close to the base, the conventional drying method cannot dry this part, so after adding three diversion devices on both sides and in the middle, the flower basket end plate 52 is diverted and dried, and the middle part is a two-way air intake diversion, because the middle part is the common bearing area of ​​the flower basket, so as to ensure that all the flower basket end plates 52 are dried.

[0087] In some embodiments, in combination Figure 1 As shown, the side wall plate 11 is provided with an air outlet 111 , and the air outlet 111 blows air toward one side of the flower basket frame 13 .

[0088] According to an embodiment of the present invention, on the other hand, an alkali polishing process equipment is also provided, including: a drying device as described above.

[0089] In addition to increasing the drying efficiency of silicon wafers by increasing the air intake pipeline of the drying tank, the present invention can also enable the silicon wafers to have sufficient dehydration before entering the drying tank. At this time, it is necessary to reasonably optimize the acid tank concentration to clarify whether the dehydration of the acid concentration in a certain interval is optimal, and there is no negative gain on the efficiency. Secondly, because the silicon wafer is in a "hydrophobic" state after the acid tank, increasing the slow pulling temperature can effectively reduce the surface tension of water, so that it can reduce the water droplets carried when leaving the slow pulling. Finally, the air intake shunt pipeline of the drying tank is superimposed to make the drying airflow distribution more uniform, so that the water droplets at the bottom rod of the flower basket, the bottom of the flower basket end plate, the bottom of the drying tank, etc. can ensure complete drying, reducing the poor EL introduced by the water in the drying tank.

[0090] In the related technology, the alkali polishing process is mainly based on low-concentration acid tank and cold water slow pull process. However, the acid tank concentration can directly affect the dehydration of silicon wafers. Secondly, because the tension of water at room temperature is greater than that of warm water or hot water, cold water slow pull has no advantage in drying, resulting in serious water in the basket after slow pull. By optimizing the alkali polishing process, the dehydration of silicon wafers before entering the drying tank can be improved.

[0091] According to an embodiment of the present invention, on the other hand, an alkali polishing process optimization method is also provided, which is applied to the alkali polishing process equipment as described above; the alkali polishing process optimization method comprises:

[0092] For pre-cleaning, set the process temperature to 67℃-70℃, the cleaning time to 120S, the initial NaOH concentration to 1.1%, the initial H2O2 concentration to 6%, the self-supplementing NaOH concentration to 0.01%, and the self-supplementing H2O2 concentration to 0.09%; adopt a continuous circulation and basket bubbling mode.

[0093] Using the unique strong oxidizing property of hydrogen peroxide to clean the surface contamination, the pre-cleaning temperature of the conventional process is basically controlled at around 60℃-65℃. Hydrogen peroxide reacts with NAOH. When the temperature reaches 90℃-100℃, hydrogen peroxide can decompose 90%; but when the temperature is 60℃, the decomposition rate is only about 50%. Hydrogen peroxide decomposes slowly, resulting in poor cleaning effect, and the surface of the silicon wafer adsorbs dirt residues, making it more difficult to dehydrate the silicon wafer.

[0094] After repeated experiments, when the process temperature is lower than 67°C, the NaOH concentration is lower than 1.1%, the H2O2 concentration is lower than 6%, the self-replenishing NaOH concentration is lower than 0.01%, and the self-replenishing H2O2 concentration is lower than 0.09%, the hydrogen peroxide reaction rate will be too slow, the cleaning effect will be poor, and the surface adsorbed dirt cannot be cleaned. When the process temperature is higher than 70°C, the NaOH concentration is higher than 1.1%, the H2O2 concentration is higher than 6%, the self-replenishing NaOH concentration is higher than 0.01%, and the self-replenishing H2O2 concentration is higher than 0.09%, the hydrogen peroxide reaction rate is too fast, resulting in the replenishment of hydrogen peroxide exceeding the consumption, resulting in the complete consumption of hydrogen peroxide, and then the cleaning effect is poor, and the silicon wafer may directly react with the silicon wafer to destroy the surface structure, resulting in low efficiency and abnormal appearance, and the expected cleaning effect cannot be achieved. Only when the process temperature is between 67℃ and 70℃, the cleaning time is 120S, the initial NaOH concentration is 1.1%, the H2O2 concentration is 6%, the self-replenishing NaOH concentration is 0.01%, and the self-replenishing H2O2 concentration is 0.09%, can the best cleaning effect be achieved and the dirt adsorbed on the silicon wafer surface be completely removed because the hydrogen peroxide reaction and cleaning effect are the best.

[0095] In a single pass through the water tank, deionized water is used to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with basket or overflow all the time.

[0096] For alkali polishing, the process temperature was set at 67℃-69℃, the time was set at 280±20S, the initial NaOH concentration was selected as 3.5%, the initial ADDI concentration was selected as 0.4%, the self-supplementing NaOH concentration was selected as 0.09%, the self-supplementing ADDI concentration was selected as 0.04%, and a continuous circulation and basket-free bubbling mode was adopted.

[0097] Alkali polishing can improve the reflectivity and structure of the back side, enhance the long-wave response and reduce the back side recombination. The back side is polished with alkali, and the additives protect the front side from corrosion. The flatness of the back side of the silicon wafer also varies with the etching amount of the polishing groove. The higher the etching amount of the polishing groove, the higher the flatness of the back side of the silicon wafer. The smoother the surface, the less likely it is that water droplets will remain on the surface of the silicon wafer, which improves the dehydration of the silicon wafer.

[0098] After repeated experiments, when the process temperature is lower than 67°C, the time is lower than 260S, the initial NaOH concentration is lower than 3.5%, the ADDI concentration is lower than 0.4%, the self-replenishing NaOH concentration is lower than 0.09%, and the self-replenishing ADDI concentration is lower than 0.04%, the polishing effect will be reduced, the polishing surface etching amount will be low, and the flatness of the silicon wafer polishing surface will be reduced, which is not conducive to the subsequent dehydration of the silicon wafer. When the process temperature is higher than 69°C, the time is higher than 300S, the initial NaOH concentration is higher than 3.5%, the ADDI concentration is higher than 0.4%, the self-replenishing NaOH concentration is higher than 0.09%, and the self-replenishing ADDI concentration is higher than 0.04%, the polishing etching amount will be too high, the silicon wafer will become thinner, and the subsequent trough silicon wafer adsorption risk will be increased. In addition, the high etching amount of the silicon wafer will cause a large load on the printed finished product machine, which is easy to lead to inefficiency. Only when the process temperature is between 67℃ and 69℃, the time is set at 280±20S, the initial NaOH concentration is 3.5%, the ADDI concentration is 0.4%, the self-replenishing NaOH concentration is 0.09%, and the self-replenishing ADDI concentration is 0.04%, because the silicon wafer etching amount is at its best, the back side flatness is at the optimal level, which can improve the dehydration effect.

[0099] In the secondary water tank, deionized water is used to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with basket or overflow all the time.

[0100] For post-cleaning, the process temperature was set at 67°C-70°C, the cleaning time was 120S, the initial NaOH concentration was selected as 0.9%, the initial H2O2 concentration was selected as 5%, the self-supplementing NaOH concentration was selected as 0.01%, the self-supplementing H2O2 concentration was selected as 0.09%, and a continuous circulation and basket bubbling mode was adopted.

[0101] Using the unique strong oxidizing property of hydrogen peroxide to clean the surface contamination, the pre-cleaning temperature of the conventional process is basically controlled at around 60℃-65℃. Hydrogen peroxide reacts with NAOH. When the temperature reaches 90℃-100℃, hydrogen peroxide can decompose 90%; but when the temperature is 60℃, the decomposition rate is only about 50%. Hydrogen peroxide decomposes slowly, resulting in poor cleaning effect, and the surface of the silicon wafer adsorbs dirt residues, making it more difficult to dehydrate the silicon wafer.

[0102] After repeated experiments, in the post-cleaning stage, when the process temperature is lower than 67°C, the initial NaOH concentration is lower than 0.9%, the initial H2O2 concentration is lower than 5%, the self-replenishing NaOH concentration is lower than 0.01%, and the self-replenishing H2O2 concentration is lower than 0.09%, the hydrogen peroxide reaction rate will be too slow, and the cleaning effect is poor, so the surface adsorbed dirt cannot be cleaned. When the process temperature is higher than 70°C, the initial NaOH concentration is higher than 0.9%, the initial H2O2 concentration is higher than 5%, the self-replenishing NaOH concentration is higher than 0.01%, and the self-replenishing H2O2 concentration is higher than 0.09%, because the hydrogen peroxide reaction rate is too fast, the hydrogen peroxide replenishment is greater than the consumption, resulting in the complete consumption of hydrogen peroxide, and then the cleaning effect is poor, and the silicon wafer may directly react with the silicon wafer to destroy the surface structure, resulting in low efficiency and abnormal appearance, so the expected cleaning effect cannot be achieved. Only when the process temperature is: 67℃-69℃, the time is set to 120S, the initial NaOH concentration is 0.9%, the H2O2 concentration is 5%, the self-replenishing NaOH concentration is 0.01%, and the self-replenishing H2O2 concentration is 0.09%, because the hydrogen peroxide reaction and cleaning effect are the best, the best cleaning effect can be achieved, and the dirt adsorbed on the silicon wafer surface can be completely removed.

[0103] The water tank is passed three times, and deionized water is used to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with basket or overflow all the time.

[0104] For mixed acid washing, the process temperature was set to room temperature, the time was 130S, the initial HF concentration was selected to be 1.1%, and the self-supplementing HF concentration was selected to be 0.11%.

[0105] There are often organic contaminations on the surface of silicon wafers, such as grease and lubricants. These organic substances will adhere to the surface of silicon wafers, affecting the subsequent process steps. Hydrofluoric acid has excellent corrosiveness and solubility, and can effectively remove organic pollutants on the surface of silicon wafers. Secondly, there may be metal impurities on the surface of silicon wafers, such as iron and copper. These metal impurities will cause the electrical properties of the surface of silicon wafers to deteriorate, thereby affecting the performance of devices. Hydrofluoric acid can react with metal impurities and dissolve them to achieve the purpose of removing impurities. There may also be an attached layer of oxides (such as silicon dioxide) on the surface of silicon wafers. These oxides will weaken the purity and finish of the surface of silicon wafers. Hydrofluoric acid can react chemically with oxides, dissolve the oxide layer, and make the surface of silicon wafers clean and smooth. Under certain conditions, hydrofluoric acid can quickly dissolve a very thin layer of silicon on the surface of silicon wafers, thereby achieving the effect of purifying the surface. It can be concluded that the increase in acid concentration is positively correlated with the dehydration of silicon wafers. Improving the initial preparation and supplementation of HF can make the silicon wafer reach the best dehydration state.

[0106] After repeated experiments, in the mixed acid cleaning stage, when the initial HF concentration is less than 1.1% and the self-replenishing HF concentration is less than 0.11%, the surface metal impurities and oxide layer cannot be completely removed because of the low hydrofluoric acid concentration, so the silicon wafer has poor dehydration after the acid tank. When the initial HF concentration is higher than 1.1% and the self-replenishing HF concentration is higher than 0.11%, the overall hydrofluoric acid concentration is too high. Although the metal impurities and oxide layer can be completely removed, the high concentration will increase production costs, and the HF may be vaporized during the robot arm's basket lifting process, resulting in the introduction of other silicon wafers. Only when the initial HF concentration is 1.1% and the self-replenishing HF concentration is 0.11%, the hydrofluoric acid cleaning effect is the best, and no vaporization occurs during the robot arm's basket lifting process, thus achieving the best removal effect and completely removing the metal dirt and oxide layer on the silicon wafer surface.

[0107] The deionized water was used to wash the desorbed impurities and the chemicals remaining on the surface of the silicon wafer for four times through the water tank. The time was set to 120S, and the overflow mode used overflow with basket.

[0108] For pulling, set the process temperature to 48℃-50℃, add pulling additives, select the initial concentration as 2%, the self-replenishing concentration as 0.06%-0.08%, control the pulling speed at 3mm / s-5mm / s, and use overflow with basket or overflow all the way.

[0109] In the related art, no additives are used in the pulling step. The present invention adds a pulling additive in the pulling step, and the pulling additive acts on the slow pulling tank, mainly improving the wet basket print and improving the dehydration effect of the slow pulling. This further solves the dehydration problem of the silicon wafer after leaving the slow pulling, thereby further reducing the water droplets entering the drying tank while improving the surface dehydration, reducing the drying difficulty, and secondly, the better dehydration effect reduces the drying difficulty, thereby reducing the inconsistent oxide layer thickness caused by the liquid at the basket caliper position in disguise, and reducing the basket print ratio.

[0110] In some embodiments, the component of the lifting additive includes a surfactant; wherein the surfactant includes polyvinyl pyrrolidone;

[0111] The pulling additives also include: sodium polystyrene sulfonate and deionized water.

[0112] In some embodiments, the concentration of polyvinyl pyrrolidone is 7%; the concentration of deionized water is 85%; and the concentration of sodium polystyrene sulfonate is 8%.

[0113] As the surface tension of water decreases with increasing temperature, the water content of silicon wafers when they are separated from the slow-lifting basket is significantly improved by increasing the temperature, and there are no obvious large water droplets. When they are pulled into the drying tank by the robotic arm, the surface tension of water decreases when the water temperature increases, and the water droplets carried by silicon wafers and baskets when they are separated from the slow-lifting basket are reduced.

[0114] After repeated experiments, in the slow pulling step, when the temperature is lower than 48℃, the water surface tension will cause more water droplets to be carried when leaving the slow pulling, affecting the drying. When the slow pulling temperature is higher than 50℃, although the surface tension of water is small, the excessively high temperature will form water vapor, which will form new dirt or defects. Only when the temperature is between 48℃ and 50℃, the surface tension of water and the evaporation of water vapor are optimal, so the dehydration is the best.

[0115] Drying: set the process temperature to 95±3℃ and the time to 600S.

[0116] The drying step adopts the drying device provided by the embodiment of the present invention. By adding an air intake diversion pipeline, there are no water droplets on the bottom rod of the alkali-throwing flower basket, the bottom end plate of the flower basket, and the bottom of the drying trough, which is a significant improvement compared with before the addition. The bottom rod of the flower basket, the bottom end plate of the flower basket, and the bottom of the drying trough are continuously purged to achieve the optimal drying state.

[0117] The present invention reduces the problem of water on silicon wafers before they enter the drying tank by optimizing the alkali polishing process. The present invention solves the problem of liquid on the bottom rod of the flower basket, the bottom end plate of the flower basket, and the bottom of the drying tank by improving the mixed acid tank and the slow pulling process and adding an air intake shunt pipeline for the drying tank. The improvement effect is obvious, and there is no liquid on the alkali polishing material. After the liquid on the alkali polishing drying tank is effectively improved, the proportion of oxidation dirt caused by water on the bottom rod of the flower basket, the bottom end plate of the flower basket, the bottom of the drying tank, etc. is reduced to 0.04%, the proportion of black edges is reduced to 0.06%, and the proportion of burnt is reduced to 0%. After the yield is significantly improved, the difficulty of process control can be reduced, and the process change points of the alkali polishing section can be better reduced to match the subsequent process.

[0118] The present invention performs an alkali polishing process on the silicon wafer after BSG removal, reduces water droplets before entering the drying tank through process optimization, and increases the air inlet pipeline of the drying tank to improve the drying effect. The alkali polishing machines used in the tank-type alkali polishing process all use the alkali polishing process optimization method of the present invention, and basically make corresponding optimization adjustments to the acid tank concentration, slow pulling temperature, and air inlet pipeline of the drying tank during the alkali polishing process. By optimizing the alkali polishing process, the silicon wafer has better dehydration before entering the drying tank, reducing the difficulty of drying; and solving the problem of liquid carrying caused by insufficient drying in the alkali polishing machine during the process.

[0119] The specific effects of the drying device, alkali polishing process equipment and alkali polishing process optimization method provided by the present invention are verified through several embodiments and comparative examples.

[0120] Comparative Example 1:

[0121] After PSG, the silicon wafers are carried in a basket and sent to the alkaline polishing machine by a robotic arm for processing:

[0122] Pre-cleaning: process temperature: 60-65℃, time 90S, initial NaOH concentration 0.5%, H2O2 concentration 2%, self-replenishing NaOH concentration 0.005%, self-replenishing H2O2 concentration 0.04%, circulation / bubbling mode: always circulating, with basket bubbling. Step purpose: Use the strong oxidizing property of hydrogen peroxide to clean surface contamination.

[0123] Water tank: time 90S, overflow mode: overflow with basket or overflow all the time. Step purpose: Deionized water rinses the desorbed impurities and chemicals remaining on the surface of the silicon wafer.

[0124] Alkali polishing: process temperature: 62-64℃, time 220S, initial NaOH concentration 1.8%, ADDI concentration 0.15%, self-replenishing NaOH concentration 0.04%, self-replenishing ADDI concentration 0.02%, circulation / bubbling mode: always circulating, with basket bubbling, step purpose: alkali polishing improves the back reflectivity and structure, enhances the long-wave response and reduces the back recombination, uses alkali to polish the back, and protects the front from corrosion;

[0125] Sink: Time 90S, with basket overflow or always overflowing, step purpose: Deionized water rinses the residual chemicals on the surface of the silicon wafer;

[0126] Post-cleaning: process temperature: 60-65℃, time 90S, initial NaOH concentration 0.5%, H2O2 concentration 2%, self-replenishing NaOH concentration 0.008%, self-replenishing H2O2 concentration 0.04%, circulation / bubbling mode: always circulating, with basket bubbling. Step purpose: Use the strong oxidizing property of hydrogen peroxide to clean surface contamination.

[0127] Sink: Time 90S, basket overflow or overflow all the time. Step Purpose: Deionized water rinses the residual chemicals on the surface of the silicon wafer.

[0128] Mixed acid pickling: process temperature: room temperature, time 90S, initial HF concentration 0.5%, self-supplement HF concentration 0.04%.

[0129] Water tank: time 90S, basket overflow or overflow all the time, step purpose: deionized water to rinse the residual chemicals on the surface of the silicon wafer.

[0130] Slow pulling: process temperature: 20-35℃, pulling speed controlled at 3-5mm / s, with basket overflow or always overflowing, step purpose: rinse the residual chemicals on the surface of the silicon wafer with deionized water, and pull it into the drying tank through the robotic arm.

[0131] Drying: process temperature: 90±5℃, time 500S.

[0132] Embodiment 1:

[0133] After PSG, the silicon wafers are carried in a basket and sent to the alkaline polishing machine by a robotic arm for processing:

[0134] Pre-cleaning: process temperature: 66℃, time 100S, initial NaOH concentration 0.7%, H2O2 concentration 3%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.06%, circulation / bubbling mode: always circulating, with basket bubbling, step purpose: hydrogen peroxide has a unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is not significantly improved at this concentration.

[0135] Water tank: time 100S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0136] Alkali polishing: process temperature: 66℃, time 240-250S, initial NaOH concentration 2%, ADDI concentration 0.2%, self-replenishing NaOH concentration 0.06%, self-replenishing ADDI concentration 0.025%, circulation / bubbling mode: always circulating, no basket bubbling, step purpose: Alkali polishing improves the back reflectivity and structure, enhances long-wave response and reduces back recombination, uses alkali to polish the back, and the additive protects the front from corrosion. Effect: The etching amount increases slightly at this concentration, and the flatness improvement is not obvious.

[0137] Water tank: time 100S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0138] Post-cleaning: process temperature: 66℃, time 100S, initial NaOH concentration 0.7%, H2O2 concentration 3%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.06%, circulation / bubbling mode: always circulating, with basket bubbling, step purpose: hydrogen peroxide has a unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is not significantly improved at this concentration.

[0139] Water tank: time 100S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0140] Mixed acid pickling: process temperature: room temperature, time 90-100S, initial HF concentration 0.7%, self-supplement HF concentration 0.06%, step purpose: the increase of acid concentration is positively correlated with the dehydration of silicon wafers, improve the initial HF preparation and supplementation to make the silicon wafer reach the best dehydration state. Effect: at this concentration, the dehydration effect of the acid tank is slightly improved.

[0141] Water tank: time 100S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0142] Slow pulling: process temperature: 35-39℃, add slow pulling additives for initial preparation 1%, self-supplement 0.02%, pull speed controlled at 3-5mm / s, basket overflow or overflow all the time, step purpose: deionized water rinses the residual chemicals on the surface of the silicon wafer, pulls it into the drying tank through the mechanical arm, and the surface tension of the water is reduced after the water temperature is increased, reducing the water droplets carried by the silicon wafer and the basket when it is separated from the slow pulling. Effect: The water carrying situation of the silicon wafer when it is separated from the slow pulling basket is improved by increasing the temperature, and the water carrying situation is slightly improved at this temperature.

[0143] Drying: process temperature: 95℃, time 500S. Effect: After adding the air intake diversion pipeline, there are no water drops on the bottom rod of the alkali throwing basket, the bottom end plate of the basket, and the bottom of the drying tank, which is significantly improved compared with before the addition. The bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank are continuously purged, but under the condition of 500S drying, there is a slight liquid problem on the bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank.

[0144] Embodiment 2:

[0145] After PSG, the silicon wafers are carried in a basket and sent to the alkaline polishing machine by a robotic arm for processing:

[0146] Pre-cleaning: process temperature: 67℃, time 110S, initial NaOH concentration 0.7-0.9%, H2O2 concentration 4-5%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.07-0.09%, circulation / bubbling mode: always circulating, with basket bubbling, step purpose: hydrogen peroxide has a unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is slightly obvious at this concentration.

[0147] Water tank: time 110S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0148] Alkali polishing: process temperature: 67℃, time 260-270S, initial NaOH concentration 2.5%, ADDI concentration 0.3%, self-replenishing NaOH concentration 0.07-0.08%, self-replenishing ADDI concentration 0.02-0.03%, circulation / bubbling mode: always circulating, no basket bubbling, step purpose: Alkali polishing improves the back reflectivity and structure, enhances the long-wave response and reduces the back recombination, uses alkali to polish the back, and the additive protects the front from corrosion. Effect: The etching amount increases at this concentration, and the flatness is slightly obvious.

[0149] Water tank: time 110S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0150] Post-cleaning: process temperature: 67℃, time 110S, initial NaOH concentration 0.7-0.9%, H2O2 concentration 4-5%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.07-0.08%, circulation / bubbling mode: always circulating, bubbling with basket, step purpose: hydrogen peroxide has unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is slightly obvious at this concentration.

[0151] Water tank: time 110S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0152] Mixed acid pickling: process temperature: room temperature, time 110-130S, initial HF concentration 0.8-0.9%, self-supplement HF concentration 0.7-0.9%, step purpose: the increase of acid concentration is positively correlated with the dehydration of silicon wafers, improve the initial HF preparation and supplementation to make the silicon wafer reach the best dehydration state. Effect: at this concentration, the dehydration effect of the acid tank is significantly improved.

[0153] Water tank: time 110S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water.

[0154] Slow pulling: process temperature: 40-45℃, add slow pulling additives at an initial mix of 1.5%, self-supplementation 0.04%, pull speed controlled at 3-5mm / s, with basket overflow or always overflowing, step purpose: deionized water rinses the residual chemicals on the surface of the silicon wafer, pulls it into the drying tank through the mechanical arm, and the surface tension of the water is reduced after the water temperature is increased, reducing the water droplets carried by the silicon wafer and the basket when it is separated from the slow pulling. Effect: When the temperature is increased, the water carrying situation of the silicon wafer from the slow pulling basket is improved, and the water carrying situation is improved more significantly at this temperature, and the water droplets carried after slow pulling are reduced.

[0155] Drying: process temperature: 95℃, time 550S. Effect: After adding the air intake diversion pipeline, there are no water drops on the bottom rod of the alkali-throwing basket, the bottom end plate of the basket, and the bottom of the drying tank, which is significantly improved compared with before the addition. The bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank are continuously purged. Under the condition of 550S drying, there is only a little liquid on the bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank.

[0156] Embodiment 3:

[0157] After PSG, the silicon wafers are carried in a basket and sent to the alkaline polishing machine by a robotic arm for processing:

[0158] Pre-cleaning: process temperature: 67-70℃, time 120S, initial NaOH concentration 1.1%, H2O2 concentration 6%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.09%, circulation / bubbling mode: continuous circulation, bubbling with basket, step purpose: hydrogen peroxide has a unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is significantly improved at this concentration;

[0159] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0160] Alkali polishing: process temperature: 67-69℃, time 280±20S, initial NaOH concentration 3.5%, ADDI concentration 0.4%, self-replenishing NaOH concentration 0.09%, self-replenishing ADDI concentration 0.04%, circulation / bubbling mode: always circulating, no basket bubbling, step purpose: Alkali polishing improves the back reflectivity and structure, enhances the long-wave response and reduces the back recombination, uses alkali to polish the back, and the additive protects the front from corrosion. Effect: The etching amount increases at this concentration, and the flatness is significantly improved;

[0161] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0162] Post-cleaning: process temperature: 67-70℃, time 120S, initial NaOH concentration 0.9%, H2O2 concentration 5%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.09%, circulation / bubbling mode: always circulating, with basket bubbling, step purpose: hydrogen peroxide has a unique strong oxidizing property, cleans surface contamination. Effect: The cleaning effect is significantly improved at this concentration;

[0163] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0164] Mixed acid cleaning: process temperature: room temperature, time 130-140S, initial HF concentration 1.15%, self-supplement HF concentration 0.12%, step purpose: the increase in acid concentration is positively correlated with the dehydration of silicon wafers, improve the initial HF preparation and supplementation to make the silicon wafer reach the best dehydration state. Effect: at this concentration, the dehydration effect of silicon wafers is significantly improved;

[0165] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0166] Slow pulling: process temperature: 48-50℃, add slow pulling additives at an initial mix of 2%, self-supplementation 0.06-0.08%, the pulling speed is controlled at 3-5mm / s, there is basket overflow or overflow all the time, step purpose: deionized water rinses the chemicals remaining on the surface of the silicon wafer, and pulls it into the drying tank through the robotic arm. After the water temperature is increased, the surface tension of the water is reduced, and the water droplets carried by the silicon wafer and the flower basket when they are separated from the slow pulling are reduced; effect: at an increased temperature, the water carrying situation of the silicon wafer when it is separated from the slow pulling flower basket is improved, and there are no obvious large water droplets. At this temperature, the water carrying situation is significantly improved, and the water droplets carried after slow pulling are significantly reduced;

[0167] Drying: process temperature: 95±3℃, time 600S, effect: after adding the air inlet diversion pipeline, there are no water droplets on the bottom rod of the alkali-throwing basket, the bottom end plate of the basket, and the bottom of the drying tank, which is significantly improved compared with before the increase. The bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank are continuously purged to achieve the best drying state. Under the condition of 600S drying, the liquid on the bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank basically disappears, achieving a complete drying effect.

[0168] Embodiment 4:

[0169] After PSG, the silicon wafers are carried in a basket and sent to the alkaline polishing machine by a robotic arm for processing:

[0170] Pre-cleaning: Process temperature: 75-80℃, time 150S, initial NaOH concentration 2%, H2O2 concentration 6%, self-replenishing NaOH concentration 0.01%, self-replenishing H2O2 concentration 0.1%, circulation / bubbling mode: continuous circulation, bubbling with basket, step purpose: hydrogen peroxide has unique strong oxidizing property, cleans surface contamination. Effect: hydrogen peroxide decomposes quickly, occasional abnormal appearance of unloading;

[0171] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0172] Alkali polishing: process temperature: 73-78℃, time 280±20S, initial NaOH concentration 4%, ADDI concentration 0.6%, self-replenishing NaOH concentration 0.12%, self-replenishing ADDI concentration 0.06%, circulation / bubbling mode: continuous circulation, no basket bubbling, step purpose: Alkali polishing improves the back reflectivity and structure, enhances long-wave response and reduces back recombination, uses alkali to polish the back, and additives protect the front from corrosion. Effect: At this concentration, the etching amount increases significantly, and the flatness is significantly improved, but the silicon wafer is adsorbed in the subsequent tank;

[0173] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0174] Post-cleaning: process temperature: 67-70℃, time 120S, initial NaOH concentration 0.9%, H2O2 concentration 5%, self-supplementing NaOH concentration 0.01%, self-supplementing H2O2 concentration 0.09%, circulation / bubbling mode: continuous circulation, bubbling with basket, step purpose: hydrogen peroxide has unique strong oxidizing property, cleans surface contamination. Effect: hydrogen peroxide decomposes quickly, occasional material appearance abnormality;

[0175] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0176] Mixed acid cleaning: process temperature: room temperature, time 160S, initial HF concentration 1.25%, self-supplement HF concentration 0.2%, step purpose: the increase in acid concentration is positively correlated with the dehydration of silicon wafers, improve the initial HF preparation and supplementation to make the silicon wafer reach the best dehydration state. Effect: At this concentration, the dehydration effect of silicon wafers is significantly improved;

[0177] Water tank: time 120S, overflow mode: overflow with basket or overflow all the time, step purpose: to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer with deionized water;

[0178] Slow pulling: process temperature: 55-60℃, add slow pulling additives for initial preparation 4%, self-supplement 0.1-0.2%, pull speed controlled at 3-5mm / s, with basket overflow or always overflow, step purpose: deionized water rinses the residual chemicals on the surface of the silicon wafer, pulls it into the drying tank through the robotic arm, and the surface tension of the water is reduced after the water temperature is increased, reducing the water droplets carried by the silicon wafer and the basket when it is separated from the slow pulling. Effect: When the temperature is increased, the water carrying situation of the silicon wafer when it is separated from the slow pulling basket is improved, and there are no obvious large water droplets. The water carrying situation is significantly improved at this temperature, and the water droplets carried after slow pulling are significantly reduced;

[0179] Drying: Process temperature: 95±3℃, time 800S. Effect: After adding the air intake diversion pipeline, there are no water drops on the bottom rod of the alkali-throwing basket, the bottom end plate of the basket, and the bottom of the drying tank, which is significantly improved compared with before the addition. The bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank are continuously purged to achieve the best drying state. Under the condition of 800S drying, the liquid on the bottom rod of the basket, the bottom end plate of the basket, and the bottom of the drying tank basically disappears, achieving a complete drying effect.

[0180] Compared with Example 3, this group of experiments can still achieve the required drying purpose, but the overall process of pre-cleaning, alkali polishing, post-cleaning, too high concentration of pickling tank, too high temperature of slow pulling, and long drying time cannot meet the mass production conditions. The production capacity and energy consumption are too high, and the slow pulling and too high acid tank concentration are worse than Example 3 in terms of EL.

[0181] The comparative example is compared with the data of the four embodiments:

[0182] Table 1 Dehydration data statistics of various implementation schemes

[0183]

[0184] In summary, the dehydration results of the comparative example are average, with a drying effect of 70%, the dehydration results of Example 1 show a slight improvement, with a drying effect of 75%, the dehydration results of Example 2 show a relatively obvious drying effect of 85%, the dehydration results of Example 3 show a significant improvement, with a drying effect of 95%, and the dehydration results of Example 4 show a significant improvement, with a drying effect of 98%. From the tracking data, Example 3 is the best implementation scheme. Compared with the comparative example, the dehydration / drying effects of the acid tank, slow pulling, drying tank, and tank bottom of the example are improved to a certain extent, and the drying tank basically solves the problem of liquid on the bottom rod of the alkali-throwing basket, the bottom end plate, and the tank body after adding an air intake shunt pipeline, and all indicators in terms of yield are improved.

[0185] The electrical performance data of the comparative example and the four embodiments are compared as follows:

[0186] Table 2 Electrical performance data of various implementation schemes

[0187]

[0188]

[0189] The comparative example and the four examples E1 data are compared as follows:

[0190] Table 3 Statistics of EL ratios of various implementation plans

[0191] Improve the situation Oxidation stains Darken Burnt Other pollution Comparative Example 2.30％ 2.50％ 2.00％ 0.09％ Example 1 1.30％ 1.50％ 0.80％ 0.07％ Example 2 0.57％ 0.47％ 0.05％ 0.06％ Example 3 0.04％ 0.06％ 0.00％ 0.04％ Example 4 0.06％ 0.04％ 0.00％ 0.07％

[0192] Among them, Uoc is the open circuit voltage, Isc is the short circuit current, Rs is the series resistance, Rsh is the parallel resistance, FF is the fill factor, and Ncell is the conversion efficiency of the cell. The conversion efficiency of the cell of the comparative example is 26.28%, the conversion efficiency of the cell of Example 1 reaches 26.29%, the conversion efficiency of the cell of Example 2 reaches 26.30%, the conversion efficiency of the cell of Example 3 reaches 26.30%, and the conversion efficiency of the cell of Example 4 reaches 26.30%. Compared with the comparative example, the conversion efficiency of the cell of the four embodiments is improved by 0.01-0.02%. Generally speaking, the reason for the high conversion efficiency of the embodiments is mainly due to the improvement of Uoc and Isc. The fundamental reason comes from the optimization of the alkali polishing process and the superposition of the drying tank air inlet diversion device, which reduces EL pollution and brings about the improvement of yield, making the alkali polishing process more stable, and making the front-end and back-end processes more adaptable, thereby improving the open circuit voltage and short circuit current, so that the cell can improve the conversion efficiency. The EL defect ratio of the comparative example is about 2-2.5%, and the yield of the three examples is improved to a certain extent, but the other pollution of Example 4 increases slightly, which may be affected by the excessive slow pulling temperature causing some water vapor to evaporate. In summary, Example 3 is the best solution of 3. Example 3 not only solves the problem of liquid in the drying tank while optimizing the alkali polishing process, but also improves the process stability, reduces the EL defect problem, reduces the process change point of the alkali polishing section, and improves the conversion efficiency of the battery cell by 0.02%.

[0193] The production route adopted by the present invention is in accordance with the production route of topcon products. As a variation, the present invention is not limited to use in the production process of topcon products, but can also be used in the production process of other types of battery cells. It is mainly suitable for cleaning processes such as texturing, alkaline polishing, RCA, and rework cleaning machines.

[0194] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the present invention.

Claims

1. A drying device, characterized in that: include: A bottom plate (12), and a side wall plate (11) surrounding the bottom plate (12); the bottom plate (12) and the side wall plate (11) together enclose a drying tank; A flower basket rack (13) is arranged in the drying tank; the flower basket rack (13) is suitable for placing a flower basket (5), the flower basket (5) contains a silicon wafer (6), the silicon wafer (6) is arranged parallel to a first direction, and a plurality of silicon wafers (6) are placed in the flower basket (5) and are arranged parallel to and at intervals along a second direction; A first hot air unit (2) is arranged in the drying tank and located on the bottom plate (12), the first hot air unit (2) extending along the second direction and being suitable for blowing air toward the surface of the bottom plate (12); A second hot air unit (3) is disposed in the drying tank and mounted on the flower basket frame (13), wherein the second hot air unit (3) extends along a first direction and is suitable for blowing air toward a flower basket end plate (52) of the flower basket (5); The third hot air unit (4) is arranged in the drying tank and installed on the flower basket frame (13); the second hot air unit (3) extends along the second direction and is suitable for blowing air toward the flower basket bottom rod (51) of the flower basket (5).

2. The drying device according to claim 1, characterized in that: The third hot air unit (4) and / or the second hot air unit (3) are arranged at the bottom of the flower basket rack (13) along the height direction.

3. The drying device according to claim 1, characterized in that: The number of the first hot air units (2) is multiple; At least one of the first hot air units (2) is arranged in the middle of the drying tank and is provided with a first air inlet (21) for blowing air in a first direction toward both sides; At least one of the first hot air units (2) is arranged at a position of the drying tank close to the side wall plate (11), and is provided with the first air inlet (21) for blowing air along a first direction toward a side away from the side wall plate (11).

4. The drying device according to claim 1, characterized in that: The number of the second hot air units (3) is multiple; At least one of the second hot air units (3) is arranged in the middle of the drying tank and is provided with a second air inlet (31) for blowing air in the second direction toward both sides; At least one of the second hot air units (3) is arranged at a position of the drying tank close to the side wall plate (11), and is provided with the second air inlet (31) for blowing air along a second direction toward a side away from the side wall plate (11).

5. The drying device according to claim 1, characterized in that: The number of the third hot air units (4) is one or more; One or more third hot air units (4) are arranged in the middle of the drying tank and are provided with third air inlets (41) for blowing air in a first direction toward both sides.

6. The drying device according to any one of claims 1 to 5, characterized in that: The side wall plate (11) is provided with an air outlet (111), and the air outlet (111) blows air toward one side of the flower basket frame (13).

7. An alkali polishing process equipment, characterized in that: It comprises a drying device as described in any one of claims 1 to 6 above.

8. A method for optimizing alkali polishing process, characterized in that: Applicable to the alkali polishing process equipment as described in claim 7 above; the alkali polishing process optimization method comprises: For pre-cleaning, set the process temperature to 67℃-70℃, the cleaning time to 120S, the initial NaOH concentration to 1.1%, the initial H2O2 concentration to 6%, the self-supplementing NaOH concentration to 0.01%, and the self-supplementing H2O2 concentration to 0.09%; use a continuous circulation and basket bubbling mode; Once through the water tank, use deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. Set the time to 120S, and use overflow with basket or overflow all the time; For alkali polishing, the process temperature is set at 67℃-69℃, the time is set at 280±20S, the initial NaOH concentration is selected as 3.5%, the initial ADDI concentration is selected as 0.4%, the self-supplementing NaOH concentration is selected as 0.09%, the self-supplementing ADDI concentration is selected as 0.04%, and the continuous circulation and basket-free bubbling mode is adopted; In the secondary water tank, deionized water is used to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with basket or overflow all the time. For post-cleaning, the process temperature was set at 67°C-70°C, the cleaning time was 120S, the initial NaOH concentration was selected as 0.9%, the initial H2O2 concentration was selected as 5%, the self-supplementing NaOH concentration was selected as 0.01%, the self-supplementing H2O2 concentration was selected as 0.09%, and the continuous circulation and basket bubbling mode was adopted; Three times of water trough, using deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer, the setting time is 120S, and the overflow mode uses overflow with basket or overflow all the time; Mixed acid washing, set the process temperature to room temperature, the time to 130S, the initial HF concentration to 1.1%, and the self-supplement HF concentration to 0.11%; Four times through the water tank, using deionized water to rinse the desorbed impurities and chemicals remaining on the surface of the silicon wafer. The time is set to 120S, and the overflow mode uses overflow with a basket; For pulling, set the process temperature to 48℃-50℃, add pulling additives, select the initial concentration as 2%, the self-replenishing concentration as 0.06%-0.08%, control the pulling speed at 3mm / s-5mm / s, and use overflow with basket or overflow all the way; Drying: set the process temperature to 95±3℃ and the time to 600S.

9. The alkali polishing process optimization method according to claim 8, characterized in that: The components of the lifting additive include a surfactant; wherein the surfactant includes polyvinyl pyrrolidone; The pulling additive also includes: sodium polystyrene sulfonate and deionized water.

10. The alkali polishing process optimization method according to claim 9, characterized in that: The concentration of polyvinyl pyrrolidone is 7%; the concentration of deionized water is 85%; and the concentration of sodium polystyrene sulfonate is 8%.

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