Monocrystalline silicon wafer low-temperature cleaning method

Abstract

The invention discloses a monocrystalline silicon wafer low-temperature cleaning method, which comprises the following steps of: respectively preparing a first medicine washing liquid and a second medicine washing liquid in two medicine washing tanks, and putting pure water into an overflow rinsing tank; starting an ultrasonic switch, and setting ultrasonic cleaning parameters to perform primary rinsing on the monocrystalline silicon wafer; performing primary medicine washing and secondary medicine washing on the monocrystalline silicon wafer after primary rinsing based on the first medicine washing liquid; putting the monocrystalline silicon wafer subjected to secondary chemical washing into an overflow rinsing tank for secondary rinsing; performing third-time medicine washing on the monocrystalline silicon wafer after the second-time rinsing based on the second medicine washing liquid, and then performing third-time rinsing to obtain a cleaned monocrystalline silicon wafer; by optimizing an agent adding process, adjusting the adding proportion of a slotting agent, prolonging the medicine changing period, applying a gradient ultrasonic method and setting different ultrasonic currents, power consumption and water consumption are reduced, then the agent performance, the water changing period, the medicine changing period, the process temperature and the ultrasonic gradient of an existing cleaning process are optimized, and the single crystal dirty piece rate is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of single-crystal silicon wafer cleaning, and particularly relates to a low-temperature cleaning method for single-crystal silicon wafers. Background Art

[0002] Currently, the single-crystal cleaning silicon wafer process mainly includes loading → chemical tank → pure water rinsing → hydrogen peroxide tank → pure water rinsing → slow lift tank → drying → unloading. In the existing cleaning process, the temperature of the chemical tank is 55 - 60°C, and heating tubes need to work at high temperature continuously. Moreover, the chemicals need to be replaced every day, and the pure water in the rinsing tank needs to be replaced every 4 days. This makes the chemical consumption, power consumption, and water consumption in the cleaning process remain at a high level, and it also affects the improvement of production efficiency. In view of the drawbacks of the existing cleaning process, a low-temperature cleaning agent is developed and introduced, and the process parameters are optimized to make the cleaning process more green, energy-saving, and environmentally friendly.

[0003] The existing cleaning methods for single-crystal silicon wafers have the following problems:

[0004] High requirement for cleaning agent temperature: Currently, most cleaning agents are added with component A and component B of the cleaning agent in a ratio of 2:1. Since the esterification of strong base in component A is mainly used to remove dirt, the chemical temperature needs to be controlled at 55 - 60°C for the strong base to exert the maximum effect, resulting in relatively high power consumption.

[0005] Short chemical replacement cycle: As the number of silicon wafers to be cleaned increases, the chemicals gradually become ineffective and the dirt removal effect weakens, so the chemicals need to be replaced. The existing cleaning agent has a chemical replacement cycle of 160,000 wafers, and the chemicals need to be replaced every day, resulting in a high chemical consumption per unit.

[0006] Short water replacement cycle: The existing water replacement cycle is 4 days for all tank bodies to replace pure water once, resulting in high water consumption and high time consumption.

[0007] No difference in ultrasonic cleaning: Due to the difference in the cavitation effect of ultrasonic waves in different media, the ultrasonic cleaning effect is different. However, in the existing cleaning process, the ultrasonic current of all tank bodies is uniformly set to 6A, without distinguishing the gradient difference of ultrasonic waves. Summary of the Invention

[0008] The object of the present invention is to provide a low-temperature cleaning method for single-crystal silicon wafers, which includes the following steps:

[0009] Configure the first chemical solution and the second chemical solution in two chemical washing tanks respectively, and put pure water in the overflow rinsing tank;

[0010] Turn on the ultrasonic switch and set the ultrasonic cleaning parameters to perform a first rinsing on the single-crystal silicon wafer;

[0011] Perform a first chemical wash and a second chemical wash on the single-crystal silicon wafer after the first rinsing based on the first chemical solution;

[0012] Put the single-crystal silicon wafer after the second chemical wash into the overflow rinsing tank for a second rinsing;

[0013] The single-crystalline silicon wafer after secondary rinsing is subjected to three times of chemical cleaning with a second chemical cleaning solution, and then subjected to three times of rinsing to obtain a cleaned single-crystalline silicon wafer.

[0014] Further, the first chemical solution includes component A and component B, and the ratio of component A to component B is 1:1.

[0015] Further, component A includes strong base, chelating agent, low-temperature surfactant, dispersant and deionized water;

[0016] The strong base includes NaOH and KOH, the concentration ratio of the strong base is 20%-30%, PH>12, and the free alkalinity is 350pt;

[0017] The chelating agent is ethylenediaminetetraacetic acid and sodium carbonate, with a ratio of 3%-5%;

[0018] The low-temperature surfactant is 5%-9%, the dispersant is 3%-7%, and the deionized water is 50%-70%.

[0019] Further, component B includes 25%-35% surfactant, 2%-4% penetrant, 10%-15% solvent and 3%-5% dispersant, the surface tension of component B is 20-40N / m, and the conductivity is 27-30us / cm.

[0020] Further, the surfactant is a low-foam, low-temperature surfactant AEO-9, isomeric fatty alcohol hexyl ether and nonylphenol polyoxyethylene ether, the penetrant is primary alkyl sulfonate, and the solvent is diethyl ether.

[0021] Further, the second chemical solution includes 10-15L of hydrogen peroxide and 100-200g of potassium hydroxide.

[0022] Further, the temperature of the chemical cleaning tank is 55-60°C.

[0023] Further, the ultrasonic cleaning parameters include ultrasonic current, and the ultrasonic currents set in the overflow rinsing tank and the chemical cleaning tank are different, and the range of the ultrasonic current is 3.5A-5A.

[0024] Further, the initial amount of the chemical cleaning solution added to the chemical cleaning tank is 5L of component A and 5L of component B.

[0025] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0026] The present invention optimizes the chemical addition process, adjusts the proportion of chemical addition in the grooved tank and extends the chemical change cycle, applies the method of gradient ultrasound, sets different ultrasonic currents, reduces power consumption and water consumption, and further optimizes the chemical properties, water change cycle, chemical change cycle, process temperature, and ultrasonic gradient of the current cleaning process, reducing the single crystal dirty wafer rate. Brief Description of the Drawings

[0027] Figure 1 The cleaning process diagram of the low-temperature cleaning method for single crystal silicon wafers provided by the embodiment of the present invention is shown. Detailed Embodiments

[0028] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of this application.

[0029] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so as to describe the embodiments of this application here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or equipment.

[0030] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0031] As Figure 1 shown, the embodiment of the present invention provides a low-temperature cleaning method for single crystal silicon wafers, including the following steps:

[0032] Configure the first chemical solution and the second chemical solution in two chemical cleaning tanks respectively, and put pure water in the overflow rinsing tank;

[0033] Start the ultrasonic switch, set the ultrasonic cleaning parameters to perform a primary rinse on the single crystal silicon wafer;

[0034] Perform a first chemical wash and a second chemical wash on the single crystal silicon wafer after the primary rinse based on the first chemical solution;

[0035] The single-crystal silicon wafers after the second chemical cleaning are placed in an overflow rinsing tank for secondary rinsing;

[0036] Based on the second chemical cleaning solution, the single-crystal silicon wafers after secondary rinsing are subjected to a third chemical cleaning, and then a third rinsing is carried out to obtain the cleaned single-crystal silicon wafers.

[0037] It should be noted that by adjusting the overflow size, monitoring the conductivity and turbidity of the rinsing tank, the water change cycle is extended to 30 days, the single-machine water consumption is reduced by 17%, the temperature of the chemical agent tank is 55 - 60 °C, the heating tube continuously heats, and the power consumption is relatively high. By using a low-temperature cleaning agent, the power consumption is reduced, but at the same time, the cleanliness of the silicon wafer surface can be improved, and the stable defective wafer rate is 0.2% - 0.3%.

[0038] Furthermore, the main function of the overflow rinsing tank is to carry away substances such as foam and silicon powder in the tank body, and continuously circulate and replace a part of the new water source to ensure the circulating water outlet of the overflow rinsing tank, avoid the problem of dirt accumulation at the tank opening, and improve the rinsing effect of silicon wafer cleaning.

[0039] According to an embodiment of the present invention, the first chemical solution includes component A and component B, and the ratio of component A to component B is 1:1.

[0040] Specifically, the chemical agent is added in the way of component A + component B. The volume of the tank body is 700L, and the addition ratio of A:B is 1:1. For the first addition, 5L + 5L is added. For every 40,000 wafers cleaned, 1L + 1L of the cleaning agent is replenished. The replenishment amount and the chemical agent addition amount are calculated according to the tank body size and the PH value and free alkalinity measured by in-process sampling.

[0041] According to an embodiment of the present invention, component A includes strong base, chelating agent, low-temperature surfactant, dispersant and deionized water;

[0042] The strong base includes NaOH and KOH. The concentration ratio of the strong base is 20% - 30%, PH > 12, and the free alkalinity is 350pt;

[0043] The chelating agent is ethylenediaminetetraacetic acid and sodium carbonate, with a ratio of 3% - 5%;

[0044] The low-temperature surfactant is 5% - 9%, the dispersant is 3% - 7%, and the deionized water is 50% - 70%.

[0045] Preferably, in component A, the strong base is NaOH and KOH, with a concentration ratio of 20% - 30%, PH > 12, and the free alkalinity is 350pt. The chelating agent is ethylenediaminetetraacetic acid and sodium carbonate, with a ratio of 3%. The low-temperature surfactant is 6%, the dispersant is 5%, and the rest is deionized water, with a ratio of 64%.

[0046] According to an embodiment of the present invention, component B includes 25%-35% surfactant, 2%-4% penetrant, 10%-15% solvent, and 3%-5% dispersant. The surface tension of component B is 20-40 N / m, and the conductivity is 27-30 us / cm.

[0047] Preferably, the surfactant in component B is a low-foaming and low-temperature surfactant AEO-9, isomeric fatty alcohol hexyl ether, or nonylphenol polyoxyethylene ether, accounting for 30%. The penetrant is sodium primary alkyl sulfonate, accounting for 3%. The solvent is diethyl ether, accounting for 10%-15%. The dispersant is 4%. The surface tension is 30 N / m, and the conductivity is 29 us / cm.

[0048] According to an embodiment of the present invention, the surfactant is a low-foaming and low-temperature surfactant AEO-9, isomeric fatty alcohol hexyl ether, and nonylphenol polyoxyethylene ether. The penetrant is sodium primary alkyl sulfonate, and the solvent is diethyl ether.

[0049] It should be noted that by introducing a low-temperature cleaning agent, the content of the low-temperature surfactant component is increased. The decontamination ability of the low-temperature surfactant in the cleaning process is improved, and the esterification decontamination of the high-temperature cleaning agent is mainly converted into emulsification decontamination mainly based on the low-temperature surfactant.

[0050] According to an embodiment of the present invention, the second liquid medicine includes 10-15 L of hydrogen peroxide and 100-200 g of potassium hydroxide.

[0051] According to an embodiment of the present invention, the temperature of the medicine washing tank is 55-60 °C.

[0052] According to an embodiment of the present invention, the ultrasonic cleaning parameters include ultrasonic current. The ultrasonic currents set in the overflow rinsing tank and the medicine washing tank are different, and the range of the ultrasonic current is 3.5 A-5 A.

[0053] According to an embodiment of the present invention, the initial amount of the medicine washing liquid added to the medicine washing tank is 5 L of component A and 5 L of component B.

[0054] According to an embodiment of the present invention, this application can optimize the dressing change cycle. As Figure 1 shown, 2, 3, and 5 are medicine tanks, 1, 4, and 6 are overflow tanks, and 7, 8, and 9 are overflow rinsing tanks. The cleaning process is formulated in the way of overflow rinsing - medicine washing - medicine washing - rinsing - medicine washing - overflow rinsing to ensure normal conductivity, improve the cleaning effect, and reduce dirt. For the first time, 5 + 5 L of cleaning agent is added to the medicine tanks 2 and 3, and for 40,000 tablets of medicine, it is supplemented to make up for the failure and attenuation of the monitored medicine tank and maintain the stable performance of the medicine. For the first time, 200 g of KOH and 10 L of H2O2 are added to tank 5, and 5 L of hydrogen peroxide is added for 40,000 tablets. Monitor the changes in PH, surface tension, conductivity, and turbidity as the number of dirty tablets cleaned increases, optimize the dressing change cycle, and under the condition of controllable cleaning of the medicine performance for dirty tablets, the dressing change cycle is increased from 210,000 tablets to 320,000 tablets.

[0055] Extend the replacement cycle of pure water in the rinsing tank. For the replacement cycle of pure water in tanks 6 - 9, it is adjusted from 4 days to 30 days and is replaced according to the monthly equipment maintenance. Time consumption decreased: from 15 hours / month to 2 hours / month; frequency decreased: from 7.5 times / month to 1 time / month, saving 52 h / month / machine. Online real-time conductivity monitoring is adopted, control values are set, and early warnings are given for exceeding the standard. The pollution source is locked in the first time, reducing the risk of secondary pollution of the water quality to the silicon wafers. Monitor the conductivity of tanks 8 and 9, with the conductivity of tank 9 < 0.7 us / cm; the conductivity of tank 8 < 2.0 us / cm. Water quality control: According to the foam residue situation in #8, adjust the normal overflow flow rate of #9 from 1.5 GPW to 2.0 GPW. Adjust the feeding and water replenishing time of #8 to the maximum process time of 160S - 180S or replace the pure water.

[0056] Adopt the method of gradient ultrasound. According to the silicon powder residue on the surface of the silicon wafers and the performance of the solution, reset the ultrasound intensity of each tank, and adjust it to a gradient ultrasound with an ultrasound current of 5A in the chemical agent tanks of tanks 2, 3, and 5, an ultrasound current of 4A in the overflow tanks of tanks 1, 4, and 6, and an ultrasound current of 3.5A in the overflow rinsing tanks of tanks 7 and 8. Control the generation of fragments while reducing power consumption.

[0057] Furthermore, apply the method of gradient ultrasound, set different ultrasound currents, reduce power consumption, and the power consumption can be reduced by 57.2 KWH (1A * 3 tanks + 2A * 3 tanks + 2.5A * 2 tanks = 14A * 220v * 12 / 1000 = 37 KWH), where 12 represents the effective working time t = 12 hours, P = UI, W = Pt, so W = UIt, and the unit of work is WH, divided by 1000 to be converted into KWH

[0058] In summary, the present invention optimizes the chemical agent addition process, adjusts the addition ratio of the chemical agent in the tank opening and extends the chemical agent replacement cycle, applies the method of gradient ultrasound, sets different ultrasound currents, reduces power consumption and water consumption, and further optimizes the chemical agent performance, water change cycle, chemical agent replacement cycle, process temperature, and ultrasound gradient of the current cleaning process, reducing the single crystal wafer contamination rate.

[0059] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0060] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A low-temperature cleaning method for single-crystalline silicon wafers, characterized in that, It includes the following steps: Configure the first medicated washing solution and the second medicated washing solution in two medicated washing tanks respectively, and put pure water in the overflow rinsing tank; Start the ultrasonic switch, set the ultrasonic cleaning parameters to perform a first rinsing on the monocrystalline silicon wafer; Perform a first medicated wash and a second medicated wash on the monocrystalline silicon wafer after the first rinsing based on the first medicated washing solution; Put the monocrystalline silicon wafer after the second medicated wash into the overflow rinsing tank for a second rinsing; Perform a third medicated wash on the monocrystalline silicon wafer after the second rinsing based on the second medicated washing solution, and then perform a third rinsing to obtain the cleaned monocrystalline silicon wafer.

2. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 1, wherein The first medicated solution includes component A and component B, and the ratio of component A to component B is 1:

1.

3. The low-temperature cleaning method for monocrystalline silicon wafers according to claim 2, wherein Component A includes strong base, chelating agent, low-temperature surfactant, dispersant and deionized water; The strong base includes NaOH and KOH, the concentration ratio of the strong base is 20%-30%, PH>12, and the free alkalinity is 350pt; The chelating agent is ethylenediaminetetraacetic acid and sodium carbonate, with a ratio of 3%-5%; The low-temperature surfactant is 5%-9%, the dispersant is 3%-7%, and the deionized water is 50%-70%.

4. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 2, wherein, Component B includes 25%-35% surfactant, 2%-4% penetrant, 10%-15% solvent and 3%-5% dispersant, the surface tension of component B is 20-40N / m, and the conductivity is 27-30us / cm.

5. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 4, wherein, The surfactant is a low-foaming, low-temperature surfactant AEO-9, isomeric fatty alcohol hexyl ether and nonylphenol polyoxyethylene ether, the penetrant is sodium primary alkyl sulfonate, and the solvent is diethyl ether.

6. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 1, characterized in that, The second medicated solution includes 10-15L of hydrogen peroxide and 100-200g of potassium hydroxide.

7. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 1, wherein, The temperature of the medicated washing tank is 55-60°C.

8. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 1, wherein, The ultrasonic cleaning parameters include ultrasonic current. The ultrasonic currents set in the overflow rinsing tank and the medicated washing tank are different, and the range of the ultrasonic current is 3.5A-5A.

9. The low-temperature cleaning method for single-crystalline silicon wafers according to claim 2, wherein, The initial amount of the medicated washing solution added to the medicated washing tank is 5L of component A and 5L of component B.

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